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Feature Ar t ic les 4>Special Emphasis: Welding in the Automotive industry

4>Lasers Continue to Penetrate Automotive Production Lines B. Irving Advocates for laser beam welding in the automotive industry see many applications for the process/33

4>Golf Cart Maker Masters Welding with Robotic System A well-planned robotic system, installed to weld aluminum frames, is showing distinct production advantagesd37

4>Remote Laser Beam Welding Shows Potential in the Body Shop T. Heston Lase~ with focal lengths in excess of 5 ft are now being perfected with the hope they will provide added flexibility to welding automotive bodies/39

¢Hnnovative Welding Technologies for the Automotive Industry M. Pezzutti Many different welding processes are finding a place in the fabrication of trucks, automobiles and sport utility vehicles/43

4>Projection Welding Helps Assemble a Redesigned SUV Part A lift gate, resesigned from a plastic part to steel, requires blemish-free welds on its surface/47

Welding Research S u p p l e m e n t Stress Relaxation Study of HAZ Reheat Cracking in Type 347 Stainless Steel L. Li, et al. In an effort to better understand reheat cracking, specimens were reheated to various postweld heat treatment temperatures and a strain to cause yielding was applied/137-s

Effect of High Gravity on Weld Fusion Zone Shape D. K. Aidun, et al. Research into the effect of high-gravity, buoyancy-driven flow on weld pool size and shape improves our understanding of weldability/145-s

Intelligent Methodology for Sensing, Modeling and Control of Pulsed GTAW: Part I m Bead- on-Plate Welding S. B. Chert, et al. A new sensing system that images the front and back of the weld pool was tested with bead-on-plate welding/151-s

Intelligent Methodology for Sensing, Modeling and Control of Pulsed GTAW: Part 2 m Butt Joint Welding S. B. Chen, et al. A predictive model and control scheme for gas tungsten arc welding of a butt joint were developed to control the width and shape of the weld pool/164-s

Welding Journal(ISSN 0043-2296) is the official monthly publication of the American Welding So- ciety. Editorial and advertising offices are located at 550 N.W. LeJeune Rd., Miami, FL 33126, telephone (305) 443-9353. Printed by R. R. Donnelley & Sons Co., Senatobia, Miss. Subscriptions: $90.00 per year in the United States and possessions, foreign countries $130.00. Single copies: members $6.00, nonmembers $8.00. Periodicals postage paid at Miami, Fla., and additional mailing offices. POSTMASTER: Send address corrections to Welding Journal, 550 N.W. LeJeune Rd., Miami, FL 33126. Starred (*) items excluded from copyright. Readers of the Welding Joumalmay make copies of articles for personal, archival, educational or research purposes, and which are not for sale or resale. Permission is granted to quote from articles, provided customary acknowledgment of authors and sources is made.

AWS Web site: ht tp : / /www.aws.org

Monthly Columns

Press -Time News . . . . . . . . . . . . . . 7

Wash ing ton W a t c h w o r d . . . . . . . . . 9

Editorial . . . . . . . . . . . . . . . . . . . . 10

C o m m e n t a r y . . . . . . . . . . . . . . . . . 12

CyberNotes . . . . . . . . . . . . . . . . . . 14

Confe rences . . . . . . . . . . . . . . . . . 16

News of the Indus t ry . . . . . . . . . . . 20

New Produc t s . . . . . . . . . . . . . . . . 26

Welding W o r k b o o k . . . . . . . . . . . 51

Coming Events . . . . . . . . . . . . . . . 54

Society News . . . . . . . . . . . . . . . . . 59

Guide to AWS Services . . . . . . . . . 77

Automat ion . . . . . . . . . . . . . . . . . . 81

Brazing Q&A . . . . . . . . . . . . . . . . . 85

Stainless Q&A . . . . . . . . . . . . . . . . 89

New Literature . . . . . . . . . . . . . . . 90

Navy Jo in ing Center . . . . . . . . . . . 91

P e r s o n n e l . . . . . . . . . . . . . . . . . . . 92

Classifieds . . . . . . . . . . . . . . . . . . 97

Advert iser I ndex . . . . . . . . . . . . . . 99

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Lincoln Electric Bids to Buy Charter, ESAB's Parent Company

Lincoln Electric Holdings, Inc., recently offered to acquire Charter plc, a London-based multinational industrial corporation, for approximately $750 million. Lincoln Electric has offered 500 pence ($7.91) for each of the 94.5 million outstanding shares of Charter plc.

The Charter plc Board of Directors has unanimously recommended the offer. The acquisition is pending approval of regulatory agencies in Europe, the United States and elsewhere.

Charter's core businesses include ESAB, a manufacturer of welding and cutting products, and Howden, a manufacturer of air and gas handling equipment. ESAB employs 8000 persons and has manufacturing facilities in 16 countries in North America, Europe, Latin America and Asia. Howden has 3400 employees and manufacturing facilities in Europe, North America, Africa and the Asia-Pacific region. Charter had sales in 1999 of £1.086 billion.

Lincoln Electric has operations, manufacturing alliances and joint ventures in 17 countries and a worldwide network of sales offices and distributors covering more than 160 countries. The company had 1999 sales of $1.086 billion.

"This transaction involves two exceptional companies with complementary technologies, products and geographic locations," Anthony A. Massaro, chairman and chief executive officer of Lincoln, said. "This arrangement represents an acceleration of our globalization strategy and continues our focus and commitment to increasing shareholder value."

Charter Chairman Jeffrey Herbert said, "We are very pleased with this proposed transaction. It is in the best interests of our shareholders, providing a significant premium over the current market value of our shares."

International Electron Beam Welding Company Formed

The formation of KS Electron Technologies (KSET) was announced during the recent AWS Welding and Fabricating Exposition in Chicago by company president Eugene Lawrie and director Ivan Lialko. KSET is an alliance between K+S Services, Southgate, Mich., and JSC Selmi of Sumy, Ukraine.

K+S is an 18-year-old company providing equipment management and repair; JSC Selmi manufactures low- and high-voltage electron beam welding equipment and analytical instruments such as electron microscopes, physical vapor deposition equipment and mass spectrometers. KSET will provide marketing, sales and service internationally, with Selmi providing the research, design and manufacturing. Selmi employs approximately 1500 persons.

Praxair and Genesis Systems Group Form Alliance

Praxair, Inc., Danbury, Conn., through its Praxair Distribution, Inc., subsidiary, and Genesis Systems Group, Davenport, Iowa, recently formed an alliance to help prevent their customers from having to deal with multiple suppliers with sometimes conflicting approaches.

"This alliance broadens each partner's offering to their existing customer base and allows each partner to offer best-of-class solutions," Genesis CEO Rich Litt said. "Genesis and Praxair can stay focused on what each company does best while at the same time allowing each to grow and effectively reach strategic objectives."

Praxair Distribution provides shielding gases, welding equipment and applications support to the metal fabrication industry. Genesis designs, manufactures and builds robotic systems for welding and cutting applications.

Fluor Donates $ 100,000 to University of Florida for Construction Safety

Fluor Corp. recently presented a $100,000 grant to the Uni- versity of Florida to be used for the expansion of the Rinker School of Building Construction. The expansion, named the Fluor Program for Construction Safety, will house the School of Safety and Loss Control.

"Fluor Corp. has a longstanding commitment to support education," J. Robert Fluor II, vice president of corporate and public affairs, said. "Through this partnership, Fluor has demonstrated its commitment to the safety of our employees, clients, shareholders and the entire engineering and construction industry."

WELDING JOURNAL [ 7

)RTION AGEMENT

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Arc Welding

Solid State Welding

Laser Processing

Microjoining

Plastics

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Brazing, Soldering

Materials

Engineering

Testing Services

Member Services

Contract Services

Assessments

Conferences

Training

BY HUGH K. WEBSTER AWS Washington Government Affaris Office

Wash r w atchword

Court Decision May Limit Regulatory Authority

Federal agencies have expressed concern over the potential scope of the recent U.S. Supreme Court decision that the Food and Drug Administration does not have authority to regulate the tobacco industry. Many observers predict the ruling could be a basis to challenge the regulatory authority of all federal agencies.

In ruling against the FDA, the court attempted to determine whether or not Congress intended to grant the FDA authority over tobacco and found Congress never made an explicit grant of such authority. This aspect could be used in the future to challenge regulations issued by other federal agencies.

The federal administrative agency system was originally created because Congress realized it did not have the time or expertise to continually focus on specific issues. The system has evolved to where federal agencies regularly take actions not specifically assigned by Congress. Sup- porters view this as an exercise of necessary flexibility. Opponents call it usurpation of legislation authority.

Regardless, federal agencies are now subject to increasing legal challenges to their authority to regulate certain industries or industry practices not specifically referenced in a federal statute passed by Congress. It remains to be seen, however, how lower federal courts will interpret this decision, and whether they will view it as unique to tobacco or, rather, a legitimate basis for challenging federal agency actions.

Engineering Education Bills Introduced

Federal regulatory agencies may face legal scrutiny in the future.

Congress as a whole, and the House of

Representatives in particular, have

indicated educational initiatives will be a major

priority this year.

Three new bills have been introduced by Representative Vernon Ehlers (R-Mich.), a leading proponent in Congress for science and engineering education.

The National Science Education Act would provide grants to public and private schools to hire so-called "master teachers" with strong backgrounds in math, science and engineering, who will provide K-8 teachers with professional development and support, plus hands-on science materials. This legislation also would fund National Science Foundation grants for teacher-professional development.

The National Science Education Enhancement Act likewise would assist teachers, primarily through expanding Department of Education activities that currently focus on science, math, engineering and technology education.

Finally, the National Science Education Incentive Act would amend the Internal Revenue Code to encourage math and engineering education. For example, prospective K-12 science, math, engineering and technology teachers would be provided a tax credit of 10% of their total college tuition.

Congress as a whole, and the House of Representatives in particular, have indicated educational initiatives will be a major priority this year.

Taxpayer Rights Legislation Passed

The U.S. House of Representatives unanimously passed new taxpayer rights legislation that would provide for the waiver, modification or reduction of penalties and interest owed by taxpayers under various circumstances, plus require the IRS to disclose a broader array of internal guidance containing IRS interpretations of tax laws.

In a related development, the IRS has delayed until January 1, 2001, implementation of its controversial proposed regulations that would require anyone engaged in a trade or business to issue the Form 1099 for all payments to his or her attorney.

Assistance Provided for Small Manufacturers

The National Institute of Standards and Technology has announced the availability of "lean manufacturing" training to smaller manufacturers, training previously available only to large companies. NIST has partnered with a commercial training company, Modernization Form and Productivity Inc., to train through

NIST's Manufacturing Extension Partnerships (MEPs), which has locations nationwide.

"Lean manufacturing," a concept popularized in the 1970s, eliminates manufacturing activities or actions adding no real value to the product or service.

For more information, contact MEP at its Web site, www.mep.nist.gov, or at (800) 637-4634.

EPA Keeps Focus on Utilities

Late last year, the Environmental Protection Agency filed suit against a number of utilities, al-

leging coal-fired power plants had illegally released massive amounts of air pollutants. By December, the EPA is expected to issue regulations requiring coal-fired power plants to install additional controls to reduce mercury emissions. Finally, the EPA recently took a first step toward regulating coal ash and other power plant wastes as "hazardous material." The agency has begun developing a standard that would be implemented by the states for regulating power plant waste. But the EPA has said it may revisit this issue in the future - - on a federal level - - to determine whether or not these wastes should be deemed hazardous material.

Contact the A WS Washington Government Affairs Office at 174 7 Pennsylvania Ave. N. W., Washington, DC 20006; telephone (202) 466-2976; FAX (202) 835-0243.

WELDING JOURNAL I 9

Our Three Steps to Growth

In 1995, when I decided to seek the AWS vice presidency, I included the following statement in my letter to the National Nominat ing Committee: "I have become convinced that the primary goal of our Society has to be the growth of our membership (national and worldwide) in numbers, knowledge and skill." I feel even stronger about that today, and if you were at the recent AWS Annual Meeting in Chicago, you heard me restate my position with one addition - - "recognition." Not only must the knowledge and skills of our members increase, but the world must be able to instantly recognize they possess those abilities.

So, how do we go about increasing and upgrading our membership? I believe the first step is career development through education. One way this can be accomplished is by taking advantage of the many excellent conferences, seminars and educational programs AWS offers. In addition, the Schools Excelling through National Standards Education (S.E.N.S.E.) program is offered at many schools and colleges to train welders. There also are generous scholarships and postgraduate research grants available through the AWS Foundat ion to assist those who want to further their education or training. And, keep in mind that, as an AWS member, you can directly benefit by participating in your local Sec- t ion meetings, where many speakers present the "latest and the greatest" processes and equipment available to the welding industry.

I see certification as the second step in the career development of our members. Through certification, we can provide the means for industry to be able to recognize our qualifications at a glance. Certification is one of the best ways to verify that an individual possesses the knowledge and skills necessary to perform the required tasks in a given field. AWS leads the way in third-party, com- petency-based certification at all levels, from frontline welders to inspectors to engineers. These certifications are recognized worldwide, which increases the prestige o f - - and the demand for - - those who hold them.

The third step to increasing and upgrading our membership is improving our image. AWS has participated with the U.S. Depar tment of Energy in developing a vision document that describes what our industry would like to be in 20 years. One of the primary concerns of this vision statement is the public's per- ception that our industry is not very high tech. The public also has a poor image of the quality, reliability and serviceability of welded joints. The result? Tal- ented young people are selecting careers in other fields.

As president of the American Welding Society this year, I will continue to support all of our current educational activities, as well as encourage their expansion and investigate new avenues for student recruitment. Another priority is to be vigilant in protecting the integrity of the AWS certification programs.

Improving our image is a public relations function in which we all have a stake. You can help by taking greater pride in your workmanship and in your profession, talking about them in positive terms and using every opportunity to encourage ta lented young people to consider the welding profession as a career. I know I plan to do my part, and I believe if we all work together to improve our image, the membership numbers will take care of themselves.

tO I JUNE 2000

L. W. Myers AWS President

A M E R I C A N W E L D I N G S O C I E T Y

Officers President - - L. W. Myers

Dresser-Rand, Inc., Olean Operations

Vice President - - R. L. Arn Glunt Industries

Vice President - - E. D. Levert Lockheed Martin Missiles and Fire Control

Vice President - -T . M. Mustaleski Lockheed Martin Energy Systems

Treasurer - - N. A. Hamers DaimlerChrysler

Executive Director - - E G. DeLaurier, CAE

Directors

J. M. Appledorn (Dist. 18), The Lincoln Electric Co. B. J. Bastian (At Large), Benmar Associates

H. J. Bax (Dist. 14), cee Kay Supply M. D. Bell (Dist. 22), Preventive Metallurgy

H. E. Bennett (Dist. 8), Bennett Sales Co. B. A. Bernstein (Dist. 5), TechniWeld Lab S. W. Bollinger (Past President), ESA8 Welding and Cutting Prod.

O. AI-Erhayem (At Large), JOM Institute C. E Burg (Dist. 16), Ames Laboratory

S. C. Chapple (Dist. 11), Midway Products Group G. R. Crawmer (Dist. 6), GE Power Generation Engineering

D. H. Delk (Dist. 19), Consultant

A. E Fleury (Dist. 2), A. E Fleury & Associates J. R. Franklin (At Large), Sellstrom Mfg. Co. J. D. Heikkinen (Dist. 15), Spartan Sauna Heaters, Inc.

J. L. Hunter (Dist. 13), Mitsubishi Motor Mfg. of America, Inc.

C. B. Kaufman (Dist. 3), Dressel Welding Supply, Inc. M. D. Kersey (Dist. 12), The Lincoln Electric Co.

N. R. Kirsch (Dist. 20), Sterling Correctional Facility D. J. Kotecki (At Large), The Lincoln Electric Co. R. C. Lanier (Dist. 4), Pitt Community College G. E. Lawson (At Large), ESAB Welding and Cutting Products V. Y. Matthews (Dist. 10), The Lincoln Electric CO.

G. H. Putnam (Dist. 1), Thermal Dynamics

O. E Reich (Dist. 17), Texas State Technical College at Waco E R. Schneider (Dist. 21), Bob Schneider Consulting Services T. A. Siewert (At Large), NIST R. J. Tabernik (Dist. 7), The Lincoln Electric Co.

O. J. Templet (Dist. 9), Templet N Templet Welding Supply

R. J. Teuscher (Past President), Airgas, Inc.

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What Do You Really Know about AWS? All of us here at AWS headquarters would like to think our members read

every word of the WeMing Journal, but we know that just isn't so. You're busy people. So you read the items that deal with your area of expertise, what you believe is pertinent to your job or what simply just catches your eye. And because you're busy people, you only have time to send us the occasional letter to the editor or e-mail. That makes it hard for us to know sometimes whether you're receiving the information or message we're trying to convey, especially with regard to departments such as this Commentary and the Editorial.

So I decided to come up with a little contest to help us get a better handle on how many of you take the time to read the Commentary. It will test your knowledge about the American Welding Society. But don't worry. It's an "open book" test. Feel free to call AWS headquarters and ask the staff. In fact, call as many departments as you wish. There are plenty of friendly folks here who'll help supply the answers. The prize is hotel accommodations and airline tickets for two people to attend next year's AWS Exposition in Cleveland on May 6-10. Good luck with the questions, which follow.

1) How many AWS Sections are there? 2) What was the first AWS standard ever published? 3) What was the most recently published new standard? 4) Name five awards presented annually at the AWS Awards Luncheon. 5) On average, how many people visit the AWS home page each day? 6) In total, how many dollars does the AWS Foundation provide annually

for scholarships and fellowships? 7) Name the last five AWS Past Presidents, including the most recent one. 8) How many AWS Fellows have been inducted to date? 9) How many active CWls are there? 10) What does S.E.N.S.E. stand for? 11) How many Welding Journal magazines are shipped each month? 12) How many members did AWS have in 1990? 13) How many members are there today? 14) Who is the current AWS President? 15) How many papers were published in the Welding Journal's Research

Supplement during the last calendar year? 16) How many welding machines are housed in the AWS Welding Lab at

headquarters? 17) When was AWS founded? 18) What is the next scheduled AWS conference? 19) How many people are employed full time at headquarters? 20) How many exhibitors were there for the 2000 Chicago Show? 21) Name eight Sections that have Section Agreements with the AWS

Foundation. 22) Which AWS Section was most recently chartered? 23) Which Section is the oldest? To send in your entry, put your answers on a separate sheet of paper and

send it here to AWS headquarters along with the form on page 25 of this issue of the Welding Journal. The deadline is July 1. The person with the most correct answers wins. In case of a tie(s), a drawing will be held to determine the winner.

I hope you enjoy the contest and that it gives you the chance to get acquainted with some of the AWS staff. Thanks for participating.

12 I JUNE 2000

Frank G. DeLaurier, CAE A IT'S Executive Director

WELDING JOURNAL Editorial Staff Publisher

Jeff Weber Editor

Andrew Cuilison Features Editor

Mary Ruth Johnsen Managing Editor

Christine Tarafa Assistant Editors

Susan Campbell Tim Heston

Production Coordinator Zaida Chavez

Peer Review Coordinator Doreen Kubish

Contributing Editor Bob Irving

Publications, Expositions, Marketing C o m m i t t e e G. D. Uttrachi R.G. Pali Committee Chairman J. E Nissen Co. ESAB Welding & Cutting

S. Roberts G. O. Wilcox Whitney Punch Press Vice Chairman Thermadyne Industries J.F. Saenger, Jr.

Edison Welding Institute N. Zapata Secretary R.D. Smith American Welding Society The Lincoln Electric Co.

P. Albert P.D. Winslow, Ex Off. Krautkramer Branson Hypertherm

R. L. Arn E.D. Levert, Ex Off. Olunt Industries Lockheed Martin

Missiles and Fire Control T. A. Barry Miller Electric Mfg. Co. L G. Kvidahl, Ex Off.

lngalls Shipbuilding C. E. Boyer ABB Robotics N. Hamers, Ex Off.

DaimlerChrysler T. C. Conard ABICOR Binzel S.W. Bollinger, Ex Off.

ESAB Welding & Cutting D. L. Doench Hobart Brothers Co. J.C. Lippold, Ex Off.

The Ohio State Univeristity J. R. Franklin Sellstrom Mfg. Co. J .E. Jenson, CAE, Ex Off.

Precision Metalforming Association N. R. Helton Pandjiris, Inc. R.J. Teuscher, Ex Off.

Airgas V. Y. Matthews The Lincoln Electric Co. F.G. DeLaurier, CAE, Ex Off.

American Welding Society T. C. Myers DovaTech Ltd.

G. M. Nally Consultant

Advertising Director of Sales

Rob Saltzstein Advertising Sales Representatives

Blake and Michelle Holton 1-800-644-5563

Advertising Production Manager Colleen Beem

Subscriptions Nancy Batista

American Welding Society 550 N.W. LeJeune Rd., Miami, FL 33126 (800) 443-9353 Copyright © 2000 by American Welding Society. The Society is not responsible for any statement made or opinion expressed herein. Data and information developed by the authors of specific articles are for informational purposes only and are not intended for use without independent, substantiating investigation on the part of potential users.

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BY MARY RUTH JOHNSEN, Features Editor

Orbital Welding Technology

Arc Machines, Inc., Pacoima, Calif. This manufacturer of orbital welding equipment has recently expanded its Web site. Among the items added are service and training sections, promotions for the company's latest products, trade show schedules and links to the company's worldwide offices and representatives. The Training Section includes photos of the training staff, class outlines and a copy of the certificate students can receive upon com- pletion of training. Other sections offer links to welding-related organizations and a partial list of the company's clients.

The site's Applications section includes photographs and brief summaries of technical articles and case studies. Viewers can e-mail to receive the complete articles. Recent offerings included a case study titled Installing an Orbitally Welded Hygienic Piping Sys- tem and Orbital Welding of WDI and WFI Piping Systems for a Bioprocess Ap- plication. The site offers information about the uses of orbital equipment. Or- bital pipe welding, for instance, is "for joining thick-wall pipes and fittings using [welding] wire. Most applications are for 'code' welds for power plants, refineries, offshore, boiler construction, shipbuilding and similar industries."

Large, sharp, color photographs abound. Viewers should keep in mind, however, the photographs add to the downloading time when moving from page to page.

http://www.arcmachines.com

Instrumentation and Machine Tool Measuring Equipment

Sony Precision Technology America, Inc., Lake Forest, Calif. The company provides instrumentation and measurement devices, machine tool products and

media analysis equipment for metal- working, aerospace, automotive, electronics engineering and other industries. The site includes a company history, product information, trade show listings and press releases.

Visitors can submit requests for product specifications or customer support with a simple mouse click. Scroll-down menus aid in quick selection of product categories.

http://www.sonypt.com

Workholding, Jig and Fixture Components

Carr Lane Mfg. Co., St. Louis, Mo. The company's newly designed Web site allows interactive searching of more than 100,000 workholding and jib and fixture components. The search button, which remains in a constant frame on each page, allows users to type in product names, numbers or perform a text search to reach the corresponding page of items that correlates to the company's 550- page print catalog. Each catalog page contains photographs, drawings, dimensions and technical specifications. The site also includes sales and service information, a listing of distributors, company history and copies of several magazine articles.

The Reference Materials section offers information on how to order a variety of handbooks and other reference materials, a library of downloadable CAD drawings and an article titled The 5 Steps of Fixture Design. The steps are "define requirements, gather/analyze in-

formation, develop several options, choose the best option and implement the design." Regarding choosing the best option, the article states: "To evaluate the cost of any workholding alternative, first estimate the initial cost of the fixture. To make this estimate, draw an accurate sketch of the fixture. Number and list each part and component of the fixture individually. Here it is important to have an orderly method for outlining this information." The next step is "calculating the cost of material and labor for each

tooling element." The article offers a formula for determining the total cost to manufacture a part: "Cost per part = Run Cost + Setup Cost/Lot Size + Tooling Cost/Total Quan- tity over Tooling Lifetime." It follows with a description and sample values for each variable in the formula.

http://www.carrlane.com

Welding Products

Welding-Supply.com. The URL for this Web site recently changed from

www.HooperSupply.com to www.Weld- ing-Supply.com. The site, which is owned by Hooper Welding Supply, Warr Acres, Okla., offers welding equipment and consumables for shielded metal arc welding, gas tungsten arc welding, gas metal arc welding, plasma arc cutting and oxyacety- lene welding and cutting. The site also offers safety-related products such as welding gloves, cape sleeves, welding jackets, helmets and filter plates. The listings include product descriptions, illustrations and price information.

http://www.Weiding-Supply.com

Induction Heating Services

TOCCO, Inc. The company's Web site describes its line of induction heating equipment and services for brazing, melting, heat treating, forging and forming. The company, which is based in Boaz, Ala., also offers monitoring systems and a coil repair program.

http://www.tocco.com

i4 I JUNE 2000

ISO 9 0 0 1 C E R T I F I E D • UL L ISTED PRODUCTS

:)UR M A I N E M P H A S I S IS ON VALUE

HE BEST W A R R A N T Y IN THE BUSINESS

~ROAD P R O D U C T SELECTIOI~

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GENERICO products are produced, assembled, and tested by an exper ienced and dedicated work force that is commi t ted to the highest standards of product integrity and excel lence consistent wi th our ISO 9001 cert i f ication and UL l isted products.

THE HIGHEST QUALITY AT THE LOW PRICES! Quality and price must speak for themselves, so we encourage your inquiry. See for yourself why - the wor ld over - more and more professionals are using GENERICO products.

TWO YEAR "OVER THE COUNTER REPLACEMENT" WARRANTY All GENERICO manufactured welding apparatus and equipment is warranted to be free from defect ive material and workmanship for a per iod of t w o years from the date of purchase.

Regulators • Single Stage • Two-Stage • Station • l ine • Manifold • Flowmeter & Flow Gauge • Piston • Balloon

Welding Apparatus • Torch Handles • Cutting Attachments • Cutting Torches • Machine Torches • Air Torches • Welding & Heating Nozzles • Cutting Tips • Flashback Arrestors • Check Valves

Welding Accessor ies • Electrode Holders • Ground Clamps • Cable Connectors,

Lugs & Splicers • Chipping Hammers • Magnetic Holders • Tip Cleaners & Drills • Spark Lighter • Welding Goggles

GENSTAR T E C H N O L O G I E S CO. , INC. PRODUCTS ALSO AVAILABLE FROM 4525 Edison Ave • Chino, CA 91710 THE FOLLOWING WHOLESALERS: Tel: (909) 606-2726 • Fax: (909) 606-6485 • United Amencan Sales, Inc. (U.A.S.) Wilmington, OH 800-421-7081 Websi te : www.gens ta r t ech . com • westgate Sales Corp., Oakland, NJ 201-337-0024

• Doyle's Supply, Inc., Decatur, AL 800-633-3959

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"Pros Who K n o w . . . Go G E N E R I C O "

Aws AWS D I.I Code Week

The #1 selling welding code now comes alive in a five-day seminar that begins with a roadmap of Dl.l:2000, Structural Welding Code - - Steel. This is your opportunity to learn from an expert AWS instructor and ask your toughest questions about DI.1.

Code Week continues with corresponding subjects geared to engineers, supervisors, planners, welding inspectors and welding technicians. Since your work is based on a reputation for reliability and safety, you want the latest industry consensus on prequalification. If you want to improve your competitive position by referencing the latest workmanship standards, inspection procedures and acceptance criteria, you won't want to miss this seminar! Each day will be in depth and intense.

(Day 1, Monday) D I. I Road Map Las Vegas, Nev. - - May 22 Chicago, I11. - - June 5 Philadelphia, Pa. - - July 10 Detroit, Mich. - - August 21

(Day 2, Tuesday) Design of Welded Connections

Las Vegas, Nev. - - May 23 Chicago, Ill. - - June 6 Philadelphia, Pa. - - July 11 Detroit, Mich.-- August 22

(Day 3, Wednesday) Qualifications Las Vegas, Nev. - - May 24 Chicago, I11. - - June 7 Philadelphia, Pa. - - July 12 Detroit, Mich. - - August 23

(Day 4, Thursday) Fabrication Las Vegas, Nev. - - May 25 Chicago, Ilk - - June 8 Philadelphia, Pa. - - July 13 Detroit, Mich. - - August 24

(Day 5, Friday) Inspection Las Vegas, Nev. - - May 26 Chicago, I11. - - June 9 Philadelphia, Pa. - - July 14 Detroit, Mich. - - August 25

Prices Member Nonmember

(One-day seminar) $345 $420 (Entire Week) $795 $870

Upcoming Conferences

Basic Cracking Problems and Solutions Conference

July 20-21 m Mi lwaukee, Wis . Hydrogen-induced cracking isn't the only culprit that engineers and QC professionals need to be on the alert against. AWS experts will identify other, often unknown or overlooked, cracking scenarios, along with the best use of counteroffensives, including preheat and peening, and the best use of ultrasonics and Charpy, plus the lowdown on new test options. This intense day-and-a-half program covers cracking in steels, aluminum, stainless steels and titanium.

H o w to Compet i t ive ly We ld the 21 st Century Ship

N o v e m b e r 8 -10 m Norfolk , Va. This three-day event will feature presentations on one-sided, single-pass, multiwire SAW, two-wire GMAW and plate cutting technologies; plasma vs. laser vs. water jet; robotic welding; panel line fitting; welding automation; laser butt-joint welding; weldable primers; line heating technology; laser mapping for accuracy control; low-carbon bainitic electrodes; carbon equivalent; double-sided arc welding; and more.

A W S / D V S Conference and Exhibit ion on Plastic We ld ing

O c t o b e r 24-25 m Orlando, Fla. This two-day event will feature presentations within each of the five scheduled sessions listed below: • Welding Methods, Welding Machines and Equipment • Testing of Welded Joints, Design Calculations for Containers

and Apparatus, Characteristic Values • Welding of Thermoplastics in Manufacturing • Education and Qualification of Welders • Investigations into the Latest Research in Pipe Welding

I C A W T 2000 (Gas Metal Arc Weld ing for the 21 ST Century

D e c e m b e r 6 -8 m Orlando, Fla. This is a landmark conference on the gas metal arc welding GMAW) process and the related flux cored arc welding FCAW) process, celebrating 50 years of GMAW and evaluating

ways in which the application of the latest developments in GMAW technology can assist users in increasing productivity and quality. International experts will give keynote papers, and the latest process developments will be discussed in five sessions over three days.

For further information, contact: Conferences, American Welding Society, 550 N.W LeJeune Road, Miami, FL 33126, Telephone: 800-443-9353 ext. 223 or 305-443-9353 ext. 223, Fax: 305-443-1552. Visit the Conference Department home page via http://www.aws.org for upcoming conferences and registration information.

16 I JUNE 2000

O

WORLD Q U A

CLASS L I T Y

FI RST 0LASS S E R V I C E We have the bus n e s s to prove t,

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ISA HEARTFELT EXPRESSION - "

NST:TtlAT MUCH OlF rrnr J

Like playing the Blues, welding is more than a process. If it's ehzne right, it s an exper ience, You d o ~ l -

just need a good eye and steady hands. You need a fire in your belly that's hotter than the arc on your •

power source. At Miller Electric we're always in'proving the design and technology that goes into our power ~ ~

sources. So y.,pu can consistently fee/Lhis type of passion in your work ~ - M i l ! e ~.~, .... every day ¥ojl., punch in. To see how our ideas can help you, give us a call / ~ , ~

at 1 -800-4 -A-MILLE~ ext. 303 or log on to our website at MillerWelds.com. ' ~ , ~ t T ~ . P o w ~ ~ • ~.

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ew t+ DaimlerChrysler Utilizes Mash Seam Welding for First Time in Door Components

The newly introduced PT Cruiser, described as a cross between a car and minivan, incorporates inner door components constructed with the mash seam welding process. Although DaimlerChrysler has used the process to produce gas tanks for years, this is the company's first use of mash seam welding for door components, according to Ray Hedding, the company's director of Advanced Engineering Manufacturing, Stamping.

The vehicle is being produced at the company's Toluca As- sembly Plant in Mexico. When it reaches full production some- time this summer, the plant will have the capacity to produce 180,000 Chrysler PT Cruisers per year.

Toluca Assembly's stamping plant includes two mash seam welding lines from Soudronic AG in Switzerland to produce the tailor-welded blanks needed for the four inner door assemblies. The fully automated system includes stacking areas, a robot for materials handling, the welding station, centering station and a dimpling station that compensates for the different thicknesses of the material and makes the blanks nest together.

The company evaluated both laser beam welding and mash seam welding systems before purchasing the equipment, Hed- ding said. The deciding factor in selection of mash seam welding was DaimlerChrysler 's familiarity with the process and

The mash seam welding line at the Toluca Assembly Plant in Mexico.

A P T Cruiser on the assembly line at Tohlca. The plant has the capacity to produce 180, 000 of the vehicles each year.

safety issues - - the mash seam welding equipment did not require shielding. Mash seam welding also had a small cost advantage, he said, primarily due to the low reject rate. "There really was no quality difference at all," he said. "There was no investment advantage either. Investment was not really an issue because they were very close. All you're talking about is a laser station or a (mash) seam welding station. The rest of the line remains basically the same."

In the past, DaimlerChrysler produced the inner door assemblies by welding into place a reinforcing piece for the door hinges called a doubler. Even though the tailor-welded blanks are individually more expensive, there's an overall system advantage because they eliminate the tooling required to make the doubler and weld it into place, Hedding explained. "You save that tooling investment," he said. "When we buy the blanks on the outside, then the cost equations are very close, but when we do it inside, we have a substantial advantage."

The other advantage to tailor-welded blanks is increased dimensional integrity and quality, Hedding said. "We would weld the tapping plate to this reinforcement for the door hinge area and then take the reinforcement and weld it to the door inner. When you do that in a series of steps, you're going to get some variation between steps because you don't nest completely perfectly," he said. "What we've found with tailor-welded blanks is when you draw that inner panel one time and you don't have to put that doubler or reinforcement in there, you get much higher repeatability for your doors."

The launch of the PT Cruiser and the mash seam welding line has gone very smoothly, Hedding said. DaimlerChrysler is considering using the technology in production door assemblies for other products. - - Mary Ruth Johnsen, Features Editor

T W B to Produce Laser Welded Blanks for Mexican Automotive Market

TWB Company, LLC, Monroe, Mich., recently announced the opening of TWB de Mexico, S.A. de C.V., a subsidiary formed to provide laser welded blanks to the Mexican automotive market.

TWB de Mexico is located in Saltillo. The plant's operations began in April in support of Oxford Automotriz, a tier one sup-

plier that provides door assemblies to General Motors of Mex- ico. TWB de Mexico will provide 100% of the laser welded door inner assemblies for the soon-to-be-released Pontiac Aztez and will also provide 100% of the welded blank requirements in Mex- ico for the next-generation DaimlerChrysler Ram pickup.

TWB is a joint venture between Worthington Industries, ThyssenKrupp Stahl of Germany, Bethlehem Steel, LTV Steel and Rouge Industries. It is a leading supplier of laser welded blanks in North America.

20 1 JUNE 2000

Thompson Delivers Two Friction Welding Machines to Automotive Component Maker

Automotive component maker TRW, Inc., recently took delivery of two new friction welding machines from Thompson Friction Welding, Sterling Heights, Mich. The two Model 15s will be used at TRW's plant in Mesa, Ariz., for friction welding the activator and end cap parts for passenger-side air bag canisters.

During the manufacturing process, twin grippers on a overhead gantry pick up the components from the loading tool nest and transfer them to the friction welding machine. Following

TRW, Inc., has added two new Thompson Friction Welding machines to its passenger-side air bag canisterproduction line in Mesa, Ariz. Inset are an air bag canister and components.

welding, the machine uses the turning method to remove the flash and then transfers the canister to the offioad position. The two new machines have been integrated into TRW's existing air bag canister manufacturing system, which is controlled by a state-of-the-art host computer. This allows TRW to monitor the quality of the friction welding process on a continuing basis.

Study Indicates Resistance Welding Electrode Life Can Be Increased

Early indications are resistance welding electrode life can be increased, certainly to the change of shift, according to a project on coated steels (hot-dip galvanized and galvanneal) being conducted by the Auto-Steel Partnership. Currently, a report on this project is being written and automotive plants are involved in validating the experiments on the plant floor.

Founded in July 1987, the Auto-Steel Partnership is a con- sortium of the Big Three automakers - - General Motors, Ford and DaimlerChrysler - - along with ten steel companies belonging to the American Iron and Steel Institute. One of its objectives is to increase the resistance welding knowledge base because resistance welding is the primary process for joining automotive steel structures.

For the current study, the Edison Welding Institute, Colum- bus, Ohio, was contracted to evaluate how various welding parameters affect the weldability of coated steels. Of the 73 welding factors considered, 15 critical factors were evaluated. These included weld current, electrode alignment, electrode angle, coating type, coating weight, electrode geometry, edge position,

- C


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WELDING JOURNAL I 21

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22 l JUNE 2000

force buildup, electrode material, welding force, electrode face thickness and general electrode characteristics. The experiment was based on maintaining a robust process where the aspect ratio (uniformity and size of the weld button) remains stable.

A final report should be available soon on another study regarding the weldability of automotive high-strength steels. Welding characteristics on 50X and 60X high-strength steels were studied. Both Columbian-treated (high-strength, low- alloy) and re-phosphorus high-strength steels of three thicknesses (1.0, 1.5 and 2.0 mm) were compared to aluminum killed drawing quality (AKDQ) material. Researchers used tensile shear, cross tension, coach peel, Charpy impact and microhardness and metallographic tests to evaluate the welds.

Once approved, these reports, along with previously released ones, will be available on the Internet at www.a-sp.org.

Electron Beam Welding Systems Ready for Delivery to DaimlerChrysler

PTR-Precision Technologies, Inc., Enfield, Conn., recently completed final assembly on five electron beam welding (EBW) systems to be used for joining transmission components at a DaimlerChrysler plant in the Midwest.

The five low-voltage, drop bottom/partial vacuum systems will replace several other units that have been used to produce similar parts in production for approximately 25 years. The new EBW units require 3.5 x 4.0 m of floor space, approximately half that of the older units. Each new unit will be dedicated to welding just one of five different transmission components, but each system can be quickly retooled for welding any of the other components, if needed.

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These electron beam welding systems from PTR-Precision Tech- nologies will be used to weld transmission components for Daim- lerChrysler.

The PLC units use conventional means of part transfer, such as pick and place or indexing, to automatically move parts through the weld area. Actual weld motion is performed via beam motion, rather than through part motion.

British Federal Opens North American Office to Service Automotive Clients

British Federal Ltd., a maker of resistance welding equipment and welding controls, recently opened a North American sales and service office in Auburn Hills, Mich. The company is based in Dudley, West Midlands, England.

The company, which has been selling its products in North America for a number of years, set up the office to market its products to U.S. and Canadian automotive and automotive components suppliers and to provide a base for local after-sales support.

Ed Vivian is director of the company's North American Op- erations; Mitch Yencha is manager, North American Sales; Tim McLaughlan is manager, North American Engineering.

Miller Electric Donates Equipment to Boys Ranch

Miller Electric Mfg. Co., Appleton, Wis., recently donated a welding generator to the Rawhide Boys Ranch, New London, Wis., for use in its About Face community service program. The teenaged boys in the program assist on tornado and flood cleanup projects, build homes for Habitat for Humanity and work on other volunteer projects throughout Wisconsin.

The company delivered a Bobcat T. 225 NT, which is a 225-A, 8000-W engine-driven welding machine. Rawhide Boys Ranch will use the power source on a trailer for portable power generation, as well as maintenance- and repair-type welding on automobiles.

Mary Felton, Mifler Electric director of human resources (left) and Joe Feldhausen, manager of Miller's portable engine-drive products (far right), present a new welding machine to John Dery, Rawhide director of development (far left) and other Rawhide staff and residents.

Rawhide Boys Ranch was founded in 1965 to assist boys 13 to 17 years old. The residents must be referred to the program by a social service agency or juvenile judge. While there, they receive vocational training and learn the importance of punctuality, maintaining a steady work pace and high standards of quality.

Nooter Fabricators Awarded for Production of Seven N A O Reactors

Chevron Corp. recently gave an award to Nooter Fabricators, Inc. (NFI), St. Louis, Mo., in recognition of its outstanding job in fabricating seven Normal Alpha Olefin (NAO) reactors for Bechtel of Houston, Tex., for installation at Chevron's Cedar Bayou, Tex., facility.

NFI, a subsidiary of Nooter Corp., received the order on Feb- ruary 11, 1998; shipped the first vessel March 11, 1999; and delivered the last vessel on June 26, 1999. Each reactor is 11 ft 3

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in. by 129 ft, weighs 550 tons and contains approximately 5 miles of 4.5-in.-diameter, heavy-wall, carbon-steel tubing.

Brett Brickman, project manager, said the overall size of the vessels made the job challenging. NFI had to devise fabrication sequences to allow for minimal handling of the tubing. It also had to coordinate fabrication of the tubing with the fabrication of the vessel in which it would be installed to minimize handling and storage of the tubing.

One of seven Normal Alpha Olefin reactors Nooter Fabricators built for Chevron's Cedar Bayou, Tex., facility. The vessels are 129 fi long, weigh 550 tons and contain approximately 5 miles of 4.5- in.-diameter, heavy-wall, carbon-steel tubing.

More than 42,000 in. of butt-joint welds on the tubing were welded and examined with ultrasonic testing. Weld rejection rate was 0.21%. Approximately one-third of the welds were performed using orbital gas tungsten arc welding heads inside the vessel.

Name

Test Your AWS Knowledge Contest

Address

Daytime Phone Number

E-mail address

Write your answers to the quest ions found in the Commenta ry on page 12 of this issue of the Weld ingJournaI on a separate sheet of paper and send them along with this entry form to Test Your AWS Knowledge Contest, Attn: Welding Journal Dept., 550 N.W. LeJeune Rd., Miami, FL 33126 Deadline for entries is July 1, 2000.

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WELDING JOURNAL I 2S

roducts For more information, circle number on Reader Information Card.

Highlighting Automation Automated System Welds Small- to Medium-Size Components

The System 20A combines the Power Wave® 450-A welding power source with FANUC's ARC Mate 50iL robotic arm and controller. The integrated arc welding robot cell with a pneumatic turntable is designed to achieve increased production efficiencies when welding small- to medium-size parts. The system features a 48-in.-di-

Fabrication Center Performs a Variety of Operations

The Metal Muncher MM Series five- station hydraulic fabrication center can perform punching, shearing, coping, notching and forming. The unit features two-cylinder/two-person operation, a

safety feature allowing the punch and shear end to be operated separately at full capacity and speed. Additional features on most models include adjustable stroke lengths up to 9 in., up to a 3-in. ram that accepts oversized and special tooling, swing-away stripper for punch changing, large throat design for special tooling and die sets, a table that accepts up to 48-in. brake sets and a foot-activated press cylinder. Accessories and options are available.

Clausing Industrial, Inc. 1819 N. Pitcher St., Kalamazoo, MI 49007

101

Deformation System Tests Material under Extreme Strain

The MAXStrain multi-axis hot deformation system is designed for ultra-fine-

ameter, 180-deg indexing turntable rated at 500-1b balanced loading. Safety devices include two door interlock switches, a load-zone safety mat, an e-stop braking mechanism for the table, two external e-stop buttons and perimeter metal safety barriers. The operator palm station is accessible from the front of the cell to provide quick, cycle-ready situations. The "drop in place" system can be mounted on a forklift for in-plant transportation and installation.

The Lincoln Electric Co. 22801 St. Clair Ave., Cleveland, OH 44117

I00 grained materials, such as steel, aluminum and titanium. It is capable of pro-

26 I JUNE 2000

ducing strain as high as 15 and beyond. To do so, it restrains up to a 25-mm- square x 185-mm-long bar-shaped specimen lengthwise while allowing unlim- ited deformat ion in the other two dimensions. It allows trials involving many different parameters to be examined. As a result, ultra-fine-grained materials can be produced under control led thermal and mechanical conditions.

Dynamic Systems Inc. 102 P.O. Box 1234, Rte. 355, Poestenkin, NY 12140

Miniature Sensor Measures Electrode Tip Force

The company's WeldThrough miniature sensor measures resistance welding electrode tip force. The 1.1-in.-diameter load washer has a 5A-in. through hole and can be mounted integral to existing spot

or projection welding tooling. The load washer measures positive and negative weld tip forces while withstanding high currents. The device is available with force levels from 100 to 10,000 lb.

Sensotec, Inc. 103 P.O. Box 1612, Deleware, OH 43015

Microwelding Station Can Be Configured by User

The WS4000 microwelding workstation can be configured by the user. It includes the power supply, weld heads, motion control, parts handling and other items making up fully and semiauto- mated platforms. The workstation can be built around a variety of high-

frequency inverter linear DC, AC or ca- pacitive discharge power supplies, connected to a head using various electrode configurations. Z-axis movement and force control is handled via precision pneumatic actuators, complemented by a wide range of stepper motor-driven X, Y and theta motion control capabilities. According to the manufacturer, the unit can deliver sustained rates of up to 3600 welds per hour.

Microjoin 104 13535 Danielson St., Poway, CA 92064

Automatic Torch Cleaner Removes Various Deposits

The AirEaseTM torch cleaner uses a torch-initiated reaming process designed to remove various deposits that can build up over time on robot torches and guns. The self-clamping and releasing device on the robotic torch reamer prevents the nozzle from rotating while the welding torch is cleaned, protecting the wire inside the torch from damage during the cleaning cycle. The reamer does not require robot I/O, is pneumatically driven

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WELDING JOURNAL 1 27

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• 30 models. Choice of chisel & cross chisel; cone & chisel; cone & cross chisel heads; and brush with chisel

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Automat ion Peripherals, 105 a Div. of Genesis Systems Group 8900 Harrison St., Davenport, IA 52806

Angle-Iron Kit Offers Punching Options

The Series 1000 CNC precision fabricating machine can be combined with the company's angle-iron assembly to add angle and channel punching options to flat sheet, along with plate forming

and fabricating capabilities. The angle- iron kit can be attached to all four models in the series, including the 1524. The 1524 is made for short runs and one-of- a-kind parts. Its forming capabilities produce louvers, countersinks, extrusions and other items.

W . A . W h i t n e y Co. 106 650 Race St., P.O. Box 1206, Rockford, IL 61105

C o n t r o l l e r D e s i g n e d for U l t r a s o n i c W e l d i n g M a c h i n e s

The ST 3000 Mark II controller provides automatic monitoring, measurement and control of key parameters in ultrasonic metal welding, including the compression of wires before welding,

28 I JUNE 2000 Circle No. 3 on Reader Info-Card

work I/F and remote control, and a Joint Tracking System W o r k s printer port. with Narrow Tolerances

final weld height and operating frequency. Both crimp and weld height settings can be adjusted in O.O01-in. incre- ments. Designed to provide menu- driven, eight-button control for the company's ultrasonic welding systems, the unit features a large LCD screen that dis- plays numerical settings and a 3-D diagram of key components to help operators set, store and retrieve up to 1000 settings for welding different electrical connectors and terminals, without repro- gramming or changing the applicator. Other key features include overload protection, support of Windows® 98/NT SPC software and an interactive maintenance clock. Interfaces include RS-232 serial link to a PC, a serial link for net-

Stapla Ultrasonics 375 Ballardvale St., Wi lmington, M A 01876

107

CNC-Based System Welds Tubes to Tube Sheets

This CNC-based system is for welding tubes to tube sheets. The torch is moved into position with horizontal and vertical slides, which are programmed to locate the torch rotation axis in line with the tube's centerline. The rotation axis then moves the torch around the joint for welding. All weld parameters are fully programmable and may be changed as many times as necessary during a weld. The system can be programmed to make up to 100 welds. The system does not use a mandrel in the tube for locating purposes, allowing the torch to occupy a position normally taken by the mandrel.

Weldline Automation 1201 N. I.as Brisas St., Anaheim, C A 92806

108

The SeamFinder TM 2 system is designed to assure optimum weld quality by providing accurate, rapid localization of most joints, working with narrow mechanical tolerances. It is designed to in-

terface with new or existing robot systems, reducing scrap and rework, as well as trimming and fixturing requirements. The system's noncontact sensor is compact to allow use in small work areas. Measurements are insensitive to ambient light, surface texture or color changes. The 0.8-1b sensor can be integrated to robot systems with standard analog, RS-232 or RS-422 interfaces.


WELDING JOURNAL 29

The system can search for fillets, butt, edge and lap joints. Distance measurement can also be given for real-time Z- height positioning.

LMI Measurement and Control 109 21666 Melrose Ave., Southfield, H I 48075

Robot Designed to W e l d Small Parts

The IRB 140 stands knee-high on a 400 x 450-mm footprint and weighs less than 100 kg. It has six axes and a 5-kg load capacity. The robot can be integrated into the company's FlexArc® Compact, a skid-mounted arc welding cell for the production of small components. It incorporates the robot, work- table and weld supplies together with a cell management system. With a 2.1 x 1.3-m footprint, the entire system is designed to fit into a small space on an existing production line. The plug-and-play unit can be transported from location to location on a standard forklift truck. The robot 's controller is the S4Cplus, which

is based on a 200-MHz Intel Pentium processor with 64 or 128 Mb of memory.

ABB Flexible Automation, Welding Systems Div. 4600 Innovation Dr,, Fort Collins, CO 80525

I I 0

Machine Senses Poorly Positioned W e l d Nuts

The Marksman 2000 senses if a weld nut is right side up. If it is positioned correctly, the weld is completed. If the nut is upside down, the machine will not complete the weld cycle, so the operator must reset the control box to continue.

Resistance Welding Machine & Accessory 255 Palladium Dr., St. Joseph, HI 49085

I I I

Beveling Machine Produces Parts Ready for Weld ing

The UKF automatic abrasive straight-edge beveling machine is for

parts and plates up to 2 in. thick; the KFS machine can bevel up to 5 in. Producing parts ready for welding, the machines can give 500-microinch or bet ter finishes. The unit is designed not to roll or pull the material. All operating steps are controlled by a Siemens 7 touch-panel control system.

CIMID Corp. 112 50 S, Center St., Orange, NJ 07050

Laser Offers Versati l i ty

The Lasercell 1005 has modular configuration, accommodating a variety of shop-tested CO2 or Nd:YAG lasers, and can be used either as a universal stand- alone laser processing machine for cutting and other applications or as part of an integrated laser processing center. It is also capable of welding a variety of materials at high speeds, imparting minimal warping to the parts. Because laser welding is a noncontact process, fixturing requirements are simplified and high-quality welds with narrow flanges are possible. With the "quick change" focus mod-

Made in U.S.A.

LA-CO INDUSTRIES, INC. 1201 PRATT BOULEVARD, DEPT. 262, ELK GROVE VILLAGE, IL 60007-5746 Phone: (847) 956-7600 • Fax: (847) 956-9885 Customer Service Line: (847) 956-3867 ° E-maih [email protected]

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ules, the user can switch from cutting to welding in less than 5 min. Also, the unit can harden a variety of steels, plus cast iron. Laser hardening features a steep temperature gradient in the beam zone with a simultaneously limited and controlled effective depth and a short temperature cycle.

TRUMPF Inc. I 13 47809 Galleon Dr., Plymouth Township, MI 48170

A C I n v e r t e r C o n t r o l Can Be Used wi th A C T r a n s f o r m e r

The MIB-200A AC inverter resistance welding control can be used with a conventional AC transformer, providing an upgrade of existing AC welding equipment. The controller allows an input signal from an external source, such as a displacement device, to automatically change the current setting. The inverter technology has no "off time," so weld times are shortened and throughput increased with the continuous flow of weld current. It increases temperature linearly, providing welding heat without

peaks. The unit measures 10.6 x 7.3 x 19.9 in. and weighs 33 lb.

Miyachi I 14 245 E. El Norte St., Monrovia, CA 91016

Cable C a r r i e r Faci l i tates Cab le Assembly

E-Z Triflex cable carriers are designed for robotic applications and other space-restricted multiple-axis applications where maximum freedom of movement and minimum assembly time are crucial. Designed for one-, two- or three- axis movement of automated cables, the

carriers, in effect, are able to "snake" in up to three different directions for complex motion. These carriers incorporate a crossbar design that consists of two engineered polymer pieces that allow cables and hoses to be pressed directly into the carrier without the need for any tools.

Igus, Inc. 115 P.O. Box 14349, E. Providence, RI 02914

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Lasers Cont inue to Penetrate A u t o m o t i v e Production Lines

Core components o f this automobile welding unit are a T m m p f laser head and beam arm attached to a Kuka robot. The system is set up so that a pressure roller clamps the sheet close to the weld point, minimizing the root opening.

Carbon dioxide, YA G, diode-pumped and hybrid lasers provide the auto industry with much to consider in its quest for lighter, stronger vehicles

BY BOB I R V I N G

A ctivity in high-power lasers has reached a fever pitch. Manufacturing engineers within the automotive industry

are especially interested in exploiting the technology as much as they can. But, in many instances, there is one more river to cross - - design engineers must also become conversant with these high-energy beams.

A good starting point for the automotive designer is the Au- tomotive Laser Applications Workshop, or ALAW. The 8th annual ALAW was held on March 14 and 15 in Ann Arbor, Mich. The Center for Professional Development of the University of Michigan's College of Engineering and 23 organizations from industry sponsored the meeting. A record 280 individuals turned out for this year's function. Of those, only two attendees were design engineers. The coordinators intend to do something about that at next year's meeting.

Yet, the design people have played a role in the use of lasers in several parts of the automobile already. For example, laser beam welding has been used for many years in the manufacture of transmission components. According to Frank A. DiPietro, retired manager of manufacturing engineering at General Mo- tors Corp. and a strong supporter of laser technology, a big r e a -

BOB IRVING is Contributing Editor to the Welding Journal.

son why is that the joints in transmissions were actually designed for laser processing to begin with.

Tailor-Welded Blanks

Lasers are also making great strides in tailor-welded blanks. "The progress in laser-welded blanks has been phenomenal," noted DiPietro. "The domestic auto companies are now using about 40 to 50 million blanks per year for both cars and trucks. Eventually, the figure will probably reach 100 million blanks per year."

But what about the sheet metal portion of the car, which is known familiarly in Detroit as the body in white? What kind of penetration has the laser made there? Not as much as many experts predicted. Resistance spot welding is still very much in the driver's seat. It is a big jump from resistance spot welded lap joints to laser welded joints, and the design engineers who were so instrumental years ago in designing transmission components so the joints lent themselves to laser welding have not yet tack- led the body in white. Still, great potential awaits. "By 2004," DiPietro predicted, "we will see a considerable amount of resistance spot welding replaced by laser welding in the body in white."

WELDING JOURNAL 133

Table 1 - - Capital Costs: Laser Beam Welding vs. Resistance Spot Welding

Equipment Actual Cost for Projected Cost for Resistance Spot Welding Laser Beam Welding

Robot $776,000 $388,000 Geometry Fixture $2,433,000 $811,000 Window Geometry/Hem Weld $811,000 $405,000 Press Hammer $ I, 198,000 $1,198,000 Adhesive Apply and Marriage $616,000 $308,000

Fixture Re-Spot Fixture $556,000 $278,000 Laser Robot $0 $ I, 134,000 Adhesive Robot $574,000 $287,000 Idle Fixture $420,000 $140,000 Unload Conveyor $43,000 $43,000

Totals $7,427,000 $4,992,000

Source: Lamb Technicon

Difference

($388,O00) ($1,622,000)

($406,000) $0

($3O8,00O)

($278,000) $1,134,O0O ($287,000) ($280,0O0)

$0

($2,435,000)

Table 2 - - Laser vs. Conventional Die Blanking

Operation Laser

Trim Time 5.4 s Total Cycle Time 6.4 s Downtime/Tool Change 60 s Production Time/Batch @ 80% Availability 16,075 s Press System Price $0 Laser System Price $I ,950,000 Price/Blanking Die $0 Variable Cost @ $I 5/h $67/batch Investment in 5 Years for 20 dies $I ,950,000 Total Investment in 5 years (including such $I ,950,000

intangibles as die storage, engineering changes, die maintenance)

Conventional Press Die

3s 6s 3600 s 19,500 s $1,966,000 $0 $100,000 $ 81/batch $3,966,0O0 $ 5,466,000

Note: This business case example is a comparison for blank-fed systems. It is based on the following: 1) 20 different parts/blanking 5 years of life = 20 dies, 2) 1 batch/tool change @ 2000 parts JIT/batch and 3) 20 batches/week = 1000 tool changes/year.

line/week over

Source: GE Fanuc Automation, Inc.

Jaideep Samant, project engineer, Research & Development Department, Lamb Technicon, discussed the results of a study comparing the relative costs of laser welding and resistance spot welding in body and assembly production lines. Surprisingly, the findings indicated laser welding was the cheaper of the two technologies.

To date, this technological replacement has been rather slow. But two things are now taking place that will spur this change more dramatically, according to DiPietro. One is Ford Motor Co.'s acquisition of Volvo. For about 14 years, Volvo has been a leader in 3-D laser welding in the body in white. Al Ver, vice president of Ford Motor Co., in his ALAW keynote address, said Ford is using Volvo expertise to bring forward the implementation of 3-D laser welding of the body in white in its plants. Also, the acquisition of Chrysler by Daimler Benz is expected to increase the use of the 3-D laser welding in the body in white.

In robotic resistance spot welding, production is about 15 to 20 spot welds per minute, or one every three seconds. Jack R. Nichols, senior manager, Advanced Stamping Manufacturing Engineering, DaimlerChrysler Corp., said the company is laser welding at a rate of five laser welds per second. Each laser weld in this instance is equivalent to a spot weld. Resistance spot welds will still be used, but probably no more than half of what is used now.

Another emerging application of lasers will be the use of hydroformed tubing as a part of vehicle body structure. Laser cutting will be used extensively to cut holes in hydroformed tubes. Ultimately, laser welding will attach bracketry to the hydro-

formed tubes. This is a tremendous growth market. One major tier one supplier just purchased 45 laser cutting machines for hydroformed equipment. These are signs that hydroformed tube structures might eventually replace the conventional automobile chassis frame.

The Sleeping Giant

Perhaps the sleeping giant in this entire scene is laser blanking. An enormous die blanking industry has supported the automotive industry for decades. It has been cost-effective. It has done its job. But the patterns of styles for automobiles are rapidly changing. No longer is it customary to see runs of one million vehicles based on one car style. The number of styles has greatly multiplied and the volume runs have plummeted as a re- suit. Thus, the demand has soared for different dies, and the cost of die blanking has risen dramatically-- ergo, the need for some kind of "die-less" blanking technology. The laser is showing signs of rising to that occasion. Automotive companies are already feeding sheet metal parts made by laser blanking machines into their production lines.

Mark Stephens, the man in charge of die management at GM, was big on laser blanking. This is very important because of die costs. Not too many years ago, a large auto company would produce millions of only a few models per year, and those models held up for five years or so. This has all changed. Now, the demand is for many different models with volumes down in

34 I JUNE 2000

the 50,000 car range, and the models change every three years. Unit die cost per model has become extremely high as a result.

Charles Mombo-Caristan, manager, Laser Business Development, GE Fanuc Automation, N. A., Inc., Cincinnati, Ohio, discussed the advantages of using laser blanking instead of die blanking (Table 1). When appropriate, laser blanking can result in the elimination of costly blanking dies, of such non-value-added blank handling operations as pallet flip-over to switch from left-hand-side to right-hand-side stacks, and of non-value-added coil slitting. In addition, this technology provides for just-in-time blanking flexibility, reduces engineering scrap through better nesting, increases steel material savings and provides no-cost blank changes in real time (Table 2).

Mombo-Caristan said there are as many as 400 panels in every automobile body. Because of technical and economic considerations, about 50% of these panels have to be die blanked. In high-volume runs especially, high-speed blanking can provide generous economies. For low- to medium-run panels, those calling for configurative designs are candidates for laser blanking. The auto companies are looking at dies for these panels that might range in cost from $40,000 up to $500,000 for the very largest dies. If laser blanking is found suitable for some of this work, generous cost savings can be realized through the elimination of many costly dies and the reduction of material utilization.

The Break-Even Point

What is the break-even point, that point in production when laser blanking can be considered as an economic alternative? "It is probably in annual production runs of less than 60,000 vehicles per year," Mombo-Caristan said.

The auto industry is starting to think in terms of laser blanking. This year, for example, four laser blanking production lines are being readied at various automotive and tier one supplier plants throughout the world.

Alabama Laser Systems (ALS), Munford, Ala., is a pioneer in the introduction of laser blanking to the automotive industry, and has already delivered thousands of laser-blanked parts to automotive production lines. ALS operates its own job shop containing three CO2 laser blanking machines, including units having power outputs of 2, 3 and 6 kW - - Fig. 1. According to Wayne M. Penn, the company president, a second 6-kW system, designed specifically for automotive production, is currently under construction. Penn hopes also to sell at least one such system this year. "It's a forgone conclusion here," Penn said, "that laser blanking will be widely used in the automotive industry. Its driver is its flexibility and its speed. The technology just has to find its niches."

With an eye on future systems, Alabama Laser Systems is also conducting research on diode-pumped and YAG lasers. In terms of equipment, the company's laser blanking technology is now in its fifth generation.

At the A L A W 2000 meeting, Penn cited production cutting speeds of up to 35 m/min (112 ft/min) for steel. On 1-mm-thick (0.03-in.) aluminum, he mentioned a feed rate of 1500 in./min (3810 cm/min). On 2-mm-thick (0.06-in.) aluminum, it is 1000 in./min (2540 cm/min).

A laser blanking press is installed at United Defense LP, Ground Systems Div., Aiken, S. C., where it is being used to produce both sheet metal and plate sections from steel and aluminum for various defense contractors.

Fig. 1 - -Alabama Laser ~" 6000- W laser pelforming high -speed blanking operations.

Car Exhaust Systems

Considerable progress is also being made in the laser welding of various car exhaust system components. At the ALAW, Frank Brennan, laser sales manager, Trumpf, Inc., Plymouth Township, Mich., discussed the roles of lasers in the welding of exhaust pipes, exhaust manifolds, catalytic converters and mufflers. The most widespread application for laser welding in car exhaust systems, he said, is for exhaust pipes. Here, stainless steel - - usually ferritic - - exhaust pipes are produced from rolled coil material. Inasmuch as catalytic converters place extremely high demands on the quality of the weld, the exhaust pipes between the motor and catalyzer must be free of spatter and oxide to prevent material splitter from breaking off and damaging the catalytic converter.

In production, Brennan said, the CO2 laser beam is routed to the desired working position with the aid of one or more bending mirrors. The welding optics integrated in the working position focus the beam onto the weld joint.

Because of the constantly changing position of the root opening of the stainless exhaust pipes, which is often a problem in laser welding applications, Trumpf has developed a joint tracking system whereby the deviation of the root opening is detected and then corrected with the aid of a tactile or optical system.

At the Hamburg, Germany, plant of DaimlerChrysler AG, four 5-kW CO2 lasers produce a new generation of exhaust manifolds. Two additional lasers operate at a subcontractor's plant. Results indicate laser welding provides a 30% increase in production over conventional welding techniques. Also, contami- nation through spatter and smoke is ten times lower.

Activity in Mufflers

The laser is also at the center of new approaches being taken in the design and production of mufflers-- Fig. 2. The basic idea envisioned by AP Automotive Systems Inc. for a new generation of mufflers was to produce them from simple and inexpensive deep-drawn and punched parts. The laser then joins the components.

"The material in this application is a ferritic stainless steel," Brennan said. '~_s an alternative, aluminum-coated steel is also used. The individual components are between 0.8 and 1.2 mm (0.0024 and 0.036 in.) thick. In successive joining operations, up to six layers are welded together as a lap joint. The biggest challenge in welding the multilayer joints is to obtain a seam that is gap-free, nonporous and free of spatter."


Equipment based on this technology is now commercially available from Plasma Laser Technologies.

Fig,. 2 - - A la ser -beam-we lded a u t o m o b i l e muJ]ler.

In the area of equipment design, Kuka Schweissanlagen GmbH is the system integrator of a concept wherein the muffler welding unit is comprised of the core components of laser, beam arm and articulated joint robot, as well as the clamping fixtures, materials supply and outfeed (see photo on page 33). One of the chief benefits of this concept, Brennan said, is that a pressure roller actively clamps the sheet close to the weld point, thereby minimizing the root opening. In this system, a key component for beam delivery from the laser to the welding optics is a Trumpf laser arm that is an extension of a standard robot. Thus, the working range is so designed that one robot and one laser can serve several workstations.

Such a system is now being used to weld the front and rear mufflers for the Ford Focus. Both mufflers are produced from deep-drawn blanks of ferritic stainless steel. The front muffler is welded in two steps. At the last weld, the finished muffler consists of six layers, with a total thickness of 4 mm (0.12 in.). The rear muffler, which is also 4 mm thick, has four layers in all.

An Unusual Hybrid System

Igor Dykhno, managing director, Plasma Laser Technolo- gies, Yoqne'am, Israel, discussed his company's Weldone TM

process, which combines the laser and the plasma arc in a single torch. Systems are available that will operate with ei ther Nd:YAG or CO2 lasers. When operated in conjunction with a Rofin-Sinar RF5500 CO2 laser on 1.2 + 0.7 mm (0.21 in.) zinc- coated steel, welding speeds of 7.5 m/min (24 ft/min) at 3-kW power were demonstrated. Welds made by the laser alone recorded speeds of 4 m/min (12.8 ft/min). Tolerance to root opening were also demonstrated. This technology is believed to offer a dramatic impact on the economics of tailor-welded blanking. According to Dykhno, this hybrid process has demonstrated superior formability and mechanical properties over the laser when used alone. In corrosion tests, the two welding processes are similar.

Dykhno said the process increases the operational window by allowing improvements in both processing speed and root openings. "By relaxing joint fitup requirements," he said, "edge preparation can be reduced, affecting part preparation costs and throughput."

How about Aluminum?

In connection with the laser welding of aluminum, Andreas Mertes, project engineer, Fraunhofer Center for Laser Tech- nology, Plymouth, Mich., noted Fraunhofer has been involved in an intense study on the subject in collaboration with the Big Three auto companies and the three major producers of aluminum. As all welding engineers who have been involved in the welding of aluminum are well aware, aluminum is not as easy to weld as steel. So, certain precautions have to be taken.

In the welding of 6061-T4 and nonheat-treated 5754-0 alloys, Mertes said, the YAG laser seems to provide more forgiveness than the CO2 laser. There can be a problem with solidification cracking in some of the 6000 series aluminum alloys when welding is performed at high speeds. On 1-mm-thick material, he ad- vised, it is best to maintain a welding speed of less than 5 m/min (16 ft/min). On 5000 series alloys, speed is less of a problem. The use of elliptical or oblong spot optics improves metal flow around the keyhole, thereby stabilizing the welding process.

In the joint development program involving the auto companies and aluminum producers, welding was done in simulated production environments with typical weld lengths of 700 mm (21 in.). Laser powers up to 6-kW COz and 3-kW Nd-YAG were applied. Based on mechanical tests, it was found laser welding was superior to gas metal arc (GMA) and gas tungsten arc (GTA) welding. In tensile and forming tests, in fact, all of the 5754 aluminum weld specimens failed in the base metal across the fusion zone. In the 6061 alloy, solidification and solution cracking occurred in autogenous welds at speeds ex- ceeding 4 m/min. The result was a significant loss in strength and formability.

Overseas and the Future

Overseas, Volkswagen appears to be the biggest implemen- tor of laser processing on steels. On aluminum bodies, Audi is producing 30 m of laser welds in each of its A2 car bodies.

One of the challenges for laser welding throughout the world is in hot-dip galvanized steels. When laser welded, the zinc from these coatings can cause porosity problems in the welds. This does not seem to be as much of a problem in Europe where the zinc coatings are either minimal or nonexistent. Various organizations are working on solutions to the problem.

Several engineers within the automotive industry itself see certain other shortcomings among present laser technologies. One comment is that laser systems need to be more robust to survive the enormous activity of a high-volume production line. Their outputs also need to be more reproducible. Beam quality and stability both need improvement. Another suggestion is that more needs to be done in the controls area.

Another automotive engineer said industry needs a better database for lasers. This is required, he added, to establish the repeatability of the process. Such a database has been available for many years for resistance spot welding.

Despite it all, the laser industry is still very young. It has made enormous strides since those early years when researchers were using ruby lasers to punch holes in razor blades. As the CO2 laser replaced the ruby laser, so might the diode laser replace the CO2 and perhaps even the Nd:YAG laser. Many experts see the diode laser as the process for tomorrow. •

g6 I JUNE 2000

A ugusta, Ga., home of The Augusta National Golf Club and the Mas-

ters golf tournament, is synonymous with golfing excellence, so it's an appropriate location for Club Car, a leader in the manufacture of golf carts, transportation and utility vehicles - - Fig. 1. As the company states on its Web page, "The manufacture of quality products is paramount to the employees of Club Car and has been the driving force behind the company for more than 35 years."

Two years ago, as part of its efforts to enhance quality and increase productivity, Club Car installed a robotic arc welding system from ABB Flexible Automa- tion, Welding Systems Div., Fort Collins,

Colo. The company manufactures aluminum golf cart frames in four different sizes, in both gas- and electric-powered versions. Project Manager Rusty John- son said the company decided in the early stages of automation planning that "we could have our best success" by using the robotic system to weld the gas- powered cart frames first. A cross-func- tional team spent two years designing and testing a new frame to make it ro- botically compatible before the system was installed. The team focused on designing stronger joints that would also be easier for the robot to access. It achieved both of these goals by using interlocking parts with lap and fillet joints. "The whole focus was to try to get as many

welds as possible completed with the robot," Johnson said. "On the final product we designed, there's about 130 welds that could be done by the robot, and, of the 130, we can get to about 128." (The robot operator manually produces the remaining two welds while the robot is welding.)

In designing the system configuration, floor space was a primary concern. Because of the company's growth, John- son said, it needed the ability to increase production without a corresponding increase in floor space. Much of the equipment, such as welding machines, robotic controls and water chillers, were placed overhead on a mezzanine, saving 500 sq ft (150 sq m) of floor space.

Based on a story from ABB Flexible Automation, Welding Systems Div., Fort Collins, Colo.

WELDING JOURNAL 137

The rest of the cell configuration is unusual, as well. "Our fixture was too large (about 8 ft [2.4 m] long and approximately 48 in. [121.9 cm] wide) to go with a standard rotating table, so ABB had to come up with a different scheme to get the part and fixturing in front of the robot," Johnson said. Instead, two positioners are mounted on a 50-ft (15- m) servo track, moving up and down the track as necessary to place the various parts in the correct position for welding by four robots (Fig. 2), which are bolted to risers on the floor and placed along the track. This setup allows workers to turn this large part and weld it on all sides.

The positioners can hold up to 1650 lb (750 kg) each. This capacity is necessary, even though the gas cart frame itself weighs only about 60 or 70 lb (27 or 31.5 kg), because each positioner must be able to accurately hold and support the weight of the large number of steel locators and pneumatic clamps required to hold in place the 30 different parts of the frame being welded.

The unusually large number of parts, along with all the locators and clamps, required a system of checks and balances to ensure all parts, part icularly small ones, are in the right location and correctly loaded before being clamped into place. Therefore, Club Car's system uses a flex input/output programmable logic controller (I/O PLC) on each fixture that communicates with an Allen-Bradley re-

mote I/O PLC on the robot system. An important advantage of the controller is its ability to interface directly with the Allen-Bradley system. No special wiring was required, but some additional software programming was necessary.

Along with the flexibility of the robotic welding system, two other features were important to Johnson and his team. First, an automatic torch alignment system was needed because, with each robot performing so many welds, the torch gets bumped and banged around. The system features the ABB BullsEye® automatic TCP calibration system that offers three-dimensional and angular calculation. The torch alignment system, Johnson said, adjusts the program to the torch, eliminating the need for touch- ups. "We needed to run the system for as many hours per day as possible and not be standing with the teach pendant in our hands touching up weld programs."

Secondly, the company wanted automatic error handling, a necessary feature because the robots complete approxsi- mately 130 welds on each frame. Special error handlers were developed for the company's robots. "We have four robots in the cell welding on the same part at the same time, so there has to be some communication between the robots," Johnson said. To accomplish this, robot I/O between all four robots is used. If one robot has an error, it communicates the problem to the other three. The other robots then complete the weld

they are working on, but will not move to the next weld until they receive a "clear to go" signal. In the meantime, the robot with the error turns on its error light and automatically goes to a service position for an operator to check the problem. "We have a robot technician on each shift, but with these error handlers, you don't have to be a robot technician to service the wire feeder or service the tip or do some minor service work on the robot," Johnson explained.

Programming four robots to weld simultaneously was a challenge. "It took us a while to balance the welding from one robot to another," he said. "Once in a while you see one robot sitting up in the air waiting because it finished its welding sequence before the one in front of it." Adding to the complexity was the need to program both the error handling and the welding. Each group of welds needed its own error handler program, so they had to keep in mind the path the robot was following and make sure it wouldn't cross the path of another robot. "It was like creating two separate programs for the same part." Johnson and other members of the team went to Fort Collins and spent about six weeks at ABB to write these programs. "It 's the most complex thing I've ever been involved with," he said, "and I've been in robotics since 1984." Fortunately, the company continues welding the same gas cart frames, so these programs haven't needed to be changed. The company also welds a second part, a skeleton frame for one of its carryall carts, by leaving off a couple of parts and changing out several others.

The system was delivered in October 1997 and began production in January 1998 in time for Club Car's peak season. Since that time, it has produced 25,000 to 30,000 gas frames per year, operating 24 hours a day, 6 days a week during peak season from January through June. The company also has a late shift on Sunday all year round. During the off- peak season, Club Car usually runs with one fixture and one person, producing half the output. Two people operate the system during peak season; one loads each fixture while the robot welds on the other. All of the operators are welders who have been trained to run the robots.

Cycle time for a complete frame is 12 min, including 6 rain for the operator to load the fixture and 6 rain for the robots to weld the part. This 12-min total compares to 27 min to manually weld the frame - - a savings of more than 50%.

Johnson said he is pleased with the robotic system and that, overall, it has worked smoothly. •

38 I JUNE 2000

Remote Laser Beam Welding Shows Potential

in the Body Shop This process, with its large work envelope, could help eliminate

operations and lower costs

A t a prominent auto manufacturing conference in Europe, Dan Gha-

rasim heard a high-level program manager say lasers may eventually totally eliminate conventional resistance welding in the body shop. Knowing how opin- ionated automotive engineers can be, "I thought, 'This guy's going to get nailed'" for making such a statement, Gharasim said. But, in fact, two program managers from two major European manufacturers actually stood and wholeheartedly supported his statement.

This delighted Gharasim, of DCT, Sterling Heights, Mich. Gharasim is or- ganizing system integration for Aetna Industries, Center Line, Mich. (Fig. 1), a tier one automotive supplier of underbody components. Aetna and its partners, including DCT and Rofin-Sinar Laser, Plymouth, Mich., are attempting to integrate a new variat ion of laser beam welding (LBW) into its production line. Unlike much cutting-edge LBW development, mainly led by Euro- pean companies, this one is being developed and championed by North Ameri- can companies.

This process, called remote laser beam welding (Figs. 2 and 3), has a work envelope of 1 x 1 m (3.28 x 3.28 ft), with a focal length up to 1.6 m (5.25 ft). Such a focal length became feasible when the necessary laser power and beam quality became possible, with the delivery of a Rofin diffusion-cooled, 3.5-kW slab laser to Aetna's laser lab at the beginning of 1999. "More power gives you the larger work envelope," Michael Bembenek, Aetna 's manager of advanced technologies, said. As a partner in developing the system, Aetna

BY T IM H E S T O N

has first rights to the product, meaning its direct competitors may not purchase the system until a later date.

Weld Savings

Aetna is attempting to remote laser beam weld the coated steel of automotive underbodies, no easy task. Though exact use is still to be determined, Aetna is heavily testing stitch welds, replicating resistance spot welding that would set underbody geometry - - essentially tack welding parts in place. The process could also replace re-spot welding, which, after geometry is set, adds welds that complete the drawing specifications for the part. Development work has been done on a rear seat cross-member welded to

the central floor plan. Currently, 34 resistance spot welds are placed for the part, 8 geometry spot welds and 26 re- spot welds. The company is looking to replace these two operations with one, with just 34 remote laser welds, each ~ in. long. Eliminating at least a percentage of re-spot welding operations would represent huge cost savings. This was made clear in a presentation David Thal, vice president of engineering at Aetna, gave at the annual Automotive Laser Appli- cations Workshop, which was held at the University of Michigan in Ann Arbor. Out of Aetna's 74 welding stations for the rear compartment module, 46 are re- spot welding stations; these stations make 76% of the welds, which cost $9.3 million or 44% of the total cost of welding the module.

TIM HESTON is Assistant Editor of the Weld- ing Journal.

Fig. 1 - - A e t n a Industries is hoping to integrate remote laser beam welding into its production line.


Fig. 2 - -Ae tna ' s &ser bib, housing Rojin-Sinar~" DC035 h/sel; which is on top oJthe platform.

Besides cost savings, the process reduces material usage, using narrower joint overlap. As with other laser processes, the remote laser is a noncontact joining method, resulting in less product distortion and smaller heat- affected zones, yielding greater weld integrity than its resistance counterpart. It also offers single-sided weld access - - no pinching required. So, joints that couldn't be reached with a resistance robot now can be welded.

Another big plus: the laser process can adapt to change. With manufacturers changing car designs more frequently and drastically than before, this is a valuable asset. Aetna's laser system takes less time to change the quantity and locations of welds.

Still, obstacles abound, especially concerning the outgassing of zinc, which creates weld porosity that is not up to manufacturer specifications.

Great Potential

If the process works satisfactorily during an actual application, the system could represent some important innovations. For one, an operator can program

different weld geometries for each location, including spot, continuous and extended weld lengths. A lens is available for 1000-, 1400- and 1600-mm focal lengths (3.28-, 4.6- and 5.25 ft). The system, with its 12 x 14- ft (3.6 x 4.2 -m) footprint, can make more than 85 welds per minute, doing the work of four to ten spot welding robots. The system can weld 18 mm (0.72 in.) at more than 30 mm/s, spending less than 0.6 s on each weld and about 0.1 s moving between welds at a speed of 2 m/s. In contrast, robotic resistance welding can take 2 to 3 s to clamp, weld and unclamp, and 1-4 s to reposition for the next weld.

The sealed-CO2 DC035 diffusion- cooled laser that makes such a large work envelope possible has nearly Gaussian power distribution, which means power is distributed as an almost perfect bell curve, with the highest power distribution in the center of the beam. No gas flows inside the unit. The beam has low divergence, which allows it to be focused to a small enough spot with sufficient energy for keyhole welding, even from 1 m away. A telescope maximizes power density (and, therefore, weld speed) at the workpiece. Two water-cooled, servo-driven copper mir-

rors with protective metal coatings redi- rect the beam for different geometries. In addition, the system has a linear stage with a linear motor capable of speeds up to 2000 m/s and accelerations of up to 5 Gs. Weld programming is through Vi- sual Basic.

According to sources, at least one manufacturer is conducting remote laser welding research using specially designed parts. So, what makes this project unique isn't the process, it's the fact the partnership is using an off-the-shelf product that will be commercially available once Aetna's first rights expire, a date still to be determined. Bembenek said this will lower equipment costs, make parts easily accessible and make the right people available for equipment service.

Challenges

Even with all the the power and cutting-edge technology, challenges still abound. '~Mthough the process is attractive, providing speed, access, a smaller footprint and eliminating operations, at the end of the day, you're still dealing with coated sheet metal, which is very difficult to control," Gharasim said. "You're dealing with the metallurgy of what you're welding and the tooling to ensure the right parts fit up."

The biggest problem is zinc outgassing. Aetna and its partners are testing lap joints, for maximum integrity. Unfortunately, with no root opening, outgassing becomes a problem. A fillet weld, a geometry more forgiving of outgassing, requires a higher degree of tracking to maintain a high-quality fillet.

To reduce outgassing for conventional laser beam weld ing- - with a short focal length - - others have tried using spacers to give a stable offset in the material to provide a very consistent root opening. "This doesn't seem to be very popular, though," Gharasim said, "because it 's another (costly) opera t ion that 's not really adding value to the product, other than the opportunity to do the weld with the quality sought" with a laser. So, the industry has moved on to other things, such as using twin beams. This adds volume to the weld, making the weld hotter for a longer period of time and allowing the zinc to escape, reducing or eliminating porosity.

"What we're trying to do is blend these techniques into the remote welding operat ion so we can possibly improve the weld quality," Gharasim said.

Another major challenge is the laser gas dynamics, finding an efficient way to deliver gas to the workpiece. "We're working on ways to make sure sufficient gas coverage is being flowed over the

40 J JUNE 2000

weldment itself," he said. A possible solution is adding helium shielding gas delivery points.

"We can use shielding gas if the customer requires it," David Havrilla, senior product engineer at Rofin-Sinar, said. "But, this is a little involved because you have to build [gas delivery points] into the tooling."

Tooling and fixturing also present obstacles. Because the beam is a meter away, objects can easily get in the way.

The partnership is working on several distinct solutions for all of these problems, but, because these may be up for patents, they are not ready to be made public.

"All we can say now is there are some promising characteristics about a laser with a long focal length," Havrilla said.

Responsibilities To overcome these problems, each

project participant is focusing on a specific issue. To tackle the process itself, Aetna has signed an agreement with the University of Michigan's Center for Laser Aided Intelligent Manufacturing, led by Jyotirmoy Mazumder, to develop both the best techniques for welding galvanized material used for the targeted products and the most effective process monitoring system. Rofin-Sinar is engineering the product and delivering the required power to the workpiece (now at 3.5 kW). Finally, DCT and Aetna are responsible for the design, building and integration of the work cell, and for ensuring the final product meets manufacturer specifications. (For competitive reasons, which auto manufacturer these remote laser welded underbodies are going to was not disclosed.) The partners hope this kind of cooperation will help research in the lab quickly move to on the factory floor.

The partners are also privately funding research and development - - there's no grant money or any kind of direct government funding. Because of the process's huge potential, the partners are willing to take the financial risk.

j '

f

S

!

u , ~ , , -" ~ ~

Fig. 3 - - Remote laser beam welding with a Jocal length oJ'up to 1.6 m. The invisible beam, seen here marking sheet metal, is being emitted from the platform above.

Implementation DCT has set its own deadline - - the

end of 2000. Implementation will occur in at least three phases. Phase one began when DCT came on board at the beginning of the year, and focuses on concept feasibility. Here, the key is understanding the process and its variables. Gha- rasim is working with Bembenek at Aetna, troubleshooting the process and flushing out problems with equipment and tooling. To complete the first phase,

Fig. 4 - - Resistance welding robots at Aetna, capital that cottld one day be eliminated by lasers.

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42 l JUNE 2000


the process, equipment, tooling and weld joints must meet appropriate specs and gain approval from the auto manufacturer.

Phase two is called "concept readi- ness." "This is when everything will be elevated," Gharasim said. Here, the remote laser process will be tested with the actual parts and equipment antici- pated for production. With the actual parts in place, engineers will know whether laser optics need improvement or if any ancillary device needs upgrading. "We will also improve the process specification and the specific details of the process," Gharasim said. The phase ends with a successful failure mode effects analysis, ensuring everything is par with specifications.

The final phase involves actual production. "This is when we will actually develop, build and deliver the pilot production system on Aetna's floor, and we will run actual product with the equipment," he said.

The welding system could be put into an enclosed, light-tight work cell, and an indexing table or other part-del ivery method will be used to comply with safety standards. No humans could enter the cell during normal operation, when an invisible 3.5-kW beam will be shooting through the work area.

Envisaging

Still in the concept feasibility phase, the partners haven't determined exact joints and assemblies to be welded. And yet, they have high hopes this process could one day replace or help eliminate conventional resistance welding in the body shop - - Fig. 4.

The remote process could possibly complement other laser processes. For example, the remote laser could set the geometry for a body in white, then a CW:YAG laser could add subsequent welds, completing the drawing specs. (Europeans have conducted such CW:YAG research during the last few years.) Or, geometry could be set with resistance welding, and the remote laser could finish the welding. The goal here is to el iminate operations. Typically, geometry is set, then remaining welds are added during two or three operations. With the remote laser, geometry tack welds and remaining welds could potentially be done in one work cell.

' ~ t the end of the day, eliminating operations reduces your product costs," Gharasim said, "because you're lower- ing your capital investments."

And that, of course, is the ultimate goal. •

30% DCEN, 50 Hz

70% DCEN, 50 Hz

/ 10% DCEN, 50 Hz

50% DCEN, 50 Hz

90% DCEN, 50 Hz

Although resistance spot welding is

still the major player in the automotive

industry, other processes are gaining

attention for a variety of applications BY MARK P E Z Z U T T I

Fig. 1 - - Cross sections of

wehl beads deposited using

VP-GMA W (50 tlz switching

fi'equencv 300 in./min wire fi, ed

~weed, 20 in.lnzhl travel .weed,

98~ At-2% 02).

MARK PEZZUTTI is Market

Development Manager,

Automotive & Light

Manufacturing, Edison Welding

Institute, Columbus, Ohio.

resistance spot welding has been the process the automotive industry. This still holds true tany applications, especially when joining ~ut there are newer technologies now finding ~tomotive welding. The use of laser welding d rapidly over the past decade to join various • omponents. Tailor-welded blanks and trans- tke up a large portion of the laser-welded

. . . . . v . . . . . . . . within a typical car or truck. The gas metal arc welding (GMAW) process has also been used for many years to manufacture truck and sport utility vehicle (SUV) frames, as well as dozens of structural components.

As automakers redesign vehicles for reduced weight and higher performance, several welding technologies have captured their attention. Some have already been introduced into production or will be used for the next model year's components. Five of these technologies will be discussed, including their potential automotive applications.

W E L D I N G J O U R N A L I 43

10 ga. Lap Weld Travel Speed

Tandem MIG

Twin Sub-Arc

Twin MIG

Single Wire MG

Travel Speed

Fig. 2 - - Process comparisons.

Variable Polarity Gas Metal Arc Welding

GMAW has been used extensively to weld truck and SUV frames and is very common in seat manufacture. Automakers continually struggle with controlling weld penetration, especially with large root openings, but a hybrid GMAW technology, variable polarity gas metal arc welding (VP-GMAW), helps overcome the quality issues associated with the welding of thinner sheet materials. A VP-GMAW power supply has the ability to vary the welding polarity between direct current electrode positive (DCEP) and direct current electrode negative (DCEN). Electrode negative GMAW offers extremely high deposition rates at low heat input but suffers from unstable globular metal transfer and incomplete fusion. Microprocessor-controlled solid-state (inverter) power supplies now permit the metal transfer control of conventional pulsed GMAW with the high deposition, low heat input of DCEN GMAW. The net effect is a pulse globular transfer that can weld thin materials at high speeds while accommodating a large root opening. The VP-GMAW waveform can be modified to fit the thickness of parts and potential root openings, optimizing weld penetration-- Fig. 1.

Early attempts at VP-GMAW were made in the 1950s, but arc re-ignition and arc instability plagued the process. Power supplies of that period were limited to sinusoidal AC waveforms where the transition between polarities was too slow, and the proportion of electrode negative (EN) and electrode positive (EP) power was fixed. Inverter power supplies produce square waveforms and can be pulsed between polarities at an almost infinite rate. Closed loop control algorithms now allow for improved arc stability. With proper proportion of EN and EP power, the resulting welds have acceptable bead appearance and the desired weld penetration.

With VP-GMAW, the variety of arc welded automotive components can be increased. Aside from the typical applications, seats and truck frames, as well as hydroformed tubular components, are ideal candidates for welding with this process.

Fig. 3 - - Tandem-GMAWgun (photo courtesy of CLOOS).

Two-Wire Gas Metal Arc Welding

The limitation of the single-wire GMAW process at high deposition rates is the onset of weld melt through or plasma-jet-induced process instability. At high welding currents, single-wire processes develop significant plasma jet forces that tunnel into the weld pool, inducing humping and porosity, or extreme penetration causing melt through. In the 1990s, two-wire GMAW technology was developed offering significant improvements in productivity by modifying the arc condition and the arc interaction with the weld pool.

In two-wire GMAW, the welding electrodes are positioned so the attractive forces induced by the magnetic fields interact and change the arc pressure on the weld pool. Essentially, a common arc is formed where a portion of the arc force developed in each wire is directed toward each other. This produces a lower and more uniform arc pressure on the weld pool. The net effect is a deposition rate more than twice the rate achievable with single- wire GMAW. Higher welding travel speeds are now possible on both sheet and plate welding applications - - Fig. 2.

There are two basic systems: twin-wire same potential and tandem-wire separate potential. Both systems use two power supplies, but with twin-wire, the power supplies are connected in parallel, whereas the power supplies with tandem-wire are completely

Fig. 4 - -Ax l e diffetz, ntial cover (photo courtesy of CLOOS). Fig. 5 - - Magnetic pulse weld interface (copper to aluminum).

44 [ J U N E 2000

separate. The typical machine setup feeds two welding electrodes through a common welding gun body into a single weld pool - - Fig. 3. Limitations to broad use of the method are higher equipment cost and reduced accessibility due to the larger physical size of the welding gun.

Currently, two-wire GMAW is being used to weld automotive truck frames, wheel rims, suspension systems, axle differential covers (Fig. 4) and strut towers. The process is well suited to applications that have long, linear welds that can be automated (robotic or mechanized systems), and where welding gun access is not an issue. The process is also effective at improving welding productivity with aluminum alloys.

Magnetic Pulse Welding

Magnetic pulse welding has recently gained the attention of automakers due to its ability to join dissimilar materials within very short cycle times. Although not a recently developed technology, its use for automotive and high-volume applications is relatively new.

Magnetic pulse welding has been in use for several years in the former Soviet Union, where it is typically used for military applications (such as joining projectiles to artillery shell casings). The technology today is well suited for joining cylindrical components and dissimilar metals• The technology uses a magnetic field to rapidly collapse one component onto another, forming a metallurgical bond. The weld interface has characteristics similar to an explosion bond - - Fig. 5. Some process advantages include an extremely short welding cycle (typically less than one second), and the process does not require filler material• A limitation to magnetic pulse welding is that the materials being joined must be conductive, and the best results are obtained when one of the materials is highly conductive, such as aluminum or copper.

A typical magnetic pulse welding system includes a power supply, which contains a bank of capacitors, a high-speed switching system and a coil. The parts to be joined are inserted into the coil, the capacitor bank is charged and the high-speed switch is activated. As current is applied to the coil, a magnetic field is created, and the outer component is collapsed over the inner component• Highly conductive materials, such as copper and aluminum, are readily joined with this process. The welding of steel and titanium alloys is being investigated• Development is under way to refine the process to allow for joining of noncylindrical components, and nonclosed coils are being developed to allow for opening of the coil to increase part accessibility•

Potential automotive applications for magnetic pulse welding include air conditioning tubing, tubular space frames, struts, shocks and electrical connections•

¢ ¢:

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Fig,. 6 - Dual-beam laser intensi O' at focus position (CO> 3 kW).

• - ':~'~ ~'~:v: ~ ~ "~!;:~d'~

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Fig,. 7 - - Dual-beam laser weld in gah'anized steel.

Lo~er Ste~ Cover Loyer CBuC¢ J~n~ Con~gur~n)

f Upp¢~ ~¢¢~1 Cover L~yer 7

Fig. 8 - - Conduct ive / teat resistance seam welding process.

. . ;..:~,,i,L.~-; - . . ,. ......." , . ~ -.;- .:, , ".:,~

• • . ~.. • . . . , , ,,., • . , . ,?.~ -'~

Fig. 9 - - Conduc t ive / tea t resi,s'laltce st'ant weldit g c r o s s st'clioH, 2-ntm

7075 alloy Fig. 10 - - C'omhtclive /teat resistance seam welding cro.~,s-st'ction, l m m to 2 mm, 5754 allo~:

W E L D I N G J O U R N A L ] 45

Dual-Beam Laser Welding

The Edison Welding Institute (EWI) has been investigating the use of dual-beam laser welding for approximately two years. This technology splits a single laser beam into two separate beams with a desired spacing-- Fig. 6. The two beams are oriented to the weld joint based on the application - - transverse to the joint to fill root openings or longitudinal to the joint to improve weld quality. Stud- ies by EWI have shown a marked improvement in weld quality with aluminum, high-carbon steels and coated/galvanized steels. Galva- nized steel has been successfully welded with this technology in a lap joint configuration without a root opening and with little or no weld porosi ty-- Fig. 7.

The use of dual-beam laser welding to compensate for uneven fitup with tailor welded blanks is well documented. The ability to weld coated steels in a lap configuration without the need for a root opening will open the door to numerous body applications (such as hoods, door inners and deck lids). The success with welding of aluminum and high-strength steels places the dual-beam laser in an advantageous position for future lightweight vehicle programs.

Conductive Heat Resistance Seam Welding

Conductive heat resistance seam welding (CHRSW) is a relatively new process that has shown promising results joining aluminum sheet stock. The process utilizes conventional resistance welding equipment, but the method used to melt and produce a weld is unique. With CHRSW, aluminum sheet is positioned in a butt-joint configuration. Top and bottom steel cover sheets are placed over the joint (Fig. 8), and resistance seam welding wheels pass over the assembly. As current is supplied to the wheels, heat

is generated at the higher resistance steel cover sheets. This heat is conducted into the aluminum work-pieces from the cover sheets, resulting in melting at the joint. The weld, formed under a constrained condition, produces favorable metallurgical results, namely the absence of hot cracks in some difficult-to-weld alloys (such as 7075, 6061 and 2219). The constrained weld also exhibits less internal porosity than arc or other resistance welding processes.

Figure 9 illustrates a weld produced using the CHRSW process on 2-mm-thick (0.08-in.) 7075 alloys sheet; note the absence of cracks and internal porosity. Good results have also been obtained on dissimilar-thickness weld joints. Figure 10 shows a cross section of a weld made with 1- and 2-mm (0.04- and 0.08- in.) 5754 aluminum sheet stock. This promising new process has several advantages, including high travel speeds (less than laser welding but faster than resistance seam or arc welding), moder- ate equipment cost (CHRSW uses off-the-shelf resistance welding equipment), no need for filler metal or shielding gas, high process robustness and high resulting weld integrity. Due to the newness of this process, it has not yet been used in a commercial application, but it is an ideal candidate for tailor-welded aluminum blanks.

Summary

Five new technologies - - variable polarity GMAW, two-wire GMAW, magnetic pulse welding, dual-beam laser welding and conductive heat resistance seam welding - - offer promising al- ternatives to the methods used to manufacture automotive components. These technologies offer such benefits as improved productivity, higher tolerance to joint root openings and fewer weld defects. Continuing development efforts will increase the practical applications for these processes and will ultimately lower their cost and improve their feasibility. •

I Dedicated to the pipe fobrinotion industry I

Setting PAt:t' he" C - . . . .

all AROUND the world

AUTOMATION LT|E

1321 Hocquart Street, St- Bruno, QC Canada J3V 6B5 Tel.: (450) 461-1221 Fax: (450) 461-0808

www.tecnar-automation.com

Projection Welding Helps Assemble a

Redesigned SUV Part The special welding

process causes

minimal disruption to

protective coatings

l ' t was an unusual opportunity: Take a . sport utility vehicle's lift gate, origi-

nally plastic, and make it steel. It was unusual because many auto

parts once made from steel are now going to fiberglass, aluminum or plastic to save weight or protect against corrosion. However, there were structural stiffness and consistency problems with this plastic lift gate, prompting a redesign to steel.

Tower Automotive, Elkton, Mich., is a tier one automotive supplier and one of the largest contract stamping companies in the country. It also produces the final assembly from the stampings.

For the assembly of the finished parts, the company uses a unique manufacturing line utilizing robots, noncontact laser gauging and a special resistance projection welding line to maintain a class-A surface finish on the metal. Since the part was new, Tower developed the line to produce 112 parts per hour - - Fig. 1.

The Assembly Process

To develop the needed structural integrity, two stampings are used: the outer lift gate and an inner panel. Be- fore they are joined, several reinforcement brackets are welded to the inner panel across several stations. Sharp dimple projections for the projection welding are also added. At the same time, the outer panel is loaded onto the line and picked up by a robot. The robot holds the part and maneuvers it while a second robot applies a bead of two-part

Based on a story from Newcor, Bay City Div., Bay City, Mich.

Fig. 1 - - The lift gate line, utilizing resistance projection welding, at Tower Ataomotive's Elkton plant.

epoxy adhesive in various areas around the panel - - Fig. 2. The part-manipulation robot twists it in four different axes, keeping it level to the floor to reduce adhesive sag. The robot then presents the panel for the application of anti-flutter adhesive dollops.

A Perceptron laser system from Newcor, Bay City, Mich., is mounted on the adhesive-dispensing robot to measure the bead's thickness and quality, ensuring there are no gaps. The joint is measured for both height and width to a tolerance of at least --. 1 mm (0.04 in.). If a bead has a problem, an alarm is trig- gered to alert the operator to make corrections.

After the sealant is applied to the outer panel, it is placed in a setup jig where an operator manually joins the inner panel. The part is then transferred with an overhead pick-and-place unit through the rest of the system, where the inner and outer panels are hemmed together and welded using a conventional

spot welding system in areas that don't require a critical surface finish.

In critical surface finish areas, Tower uses a resistance projection welding system called HY-PAK®, from Newcor, to achieve a nonblemished surface. After welding, the part is unloaded to an operator for visual inspection and then placed in a shipping rack.

The entire dedicated line encom- passes 15 different stations. Galvanneal 1010 and 1008 steels are used for the parts.

The line offers some flexibility to produce components with minor tool modification. However, the system is intended to serve long-term part production requirements.

Projection Welding

The HY-PAK projection welding system is a resistance welding process, patented by Newcor, that uses a combi-


nation of a high-energy, short-duration, unidirectional pulse with a rapid electrode follow-up. The duration of the weld current pulse is so short, the high current is concentrated at the weld point and minimal heating is transmitted to the adjacent component and electrode material.

The fast process is designed to cause minimal disruption of protective coatings while reducing coating pickup on electrodes. It eliminates component damage for lightweight materials by using lower welding forces. Because the process does not build up heat in base materials and electrodes during welding, protective material coatings are not melted off and a class-A (show, unblem- ished) surface is left for immediate painting or coating without any secondary finishing.

To use the welding process on the panels, a sharp linear projection is produced on one of the panels where the weld takes place. With a very sharp projection, the resistance weld occurs very quickly, localizing the heat. The sharper the projection, the easier it is to weld quickly.

The projections for projection welding

Fig. 2 - - The lift gate outerpanel is loaded onto the line and picked up by a robot that maneuvers it while a second robot applies a bead o f two-part epoxy adhesive in various areas around the panel.

are put in the parts just prior to welding, instead of adding them during stamping. By doing it this way, the location of the

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projection can be adjusted and the dimensions of the projection can be easily controlled. Also, if the punch and die set needs changing, it's easier to do it on the assembly line. If one of the punches breaks, it can be detected quickly because the weld quality is immediately noticeable. On a stamping line, thousands of parts can be made with poor or miss- ing projections before they are noticed.

According to Chief Engineer Merlin Farver, without the projection weld, the inner and outer panels would shift no matter how tightly they squeeze the hems together in the hemming process.

Development of the Line

Tower worked with Newcor through the design and development of the line. The line primarily runs on demand, but if needed can run around the clock, depending on component parts or Tower's schedule. "Normally we'll produce around 15,000 to 20,000 parts a month," Farver said.

What's important with the part is repeatability, Farver said. Panel tolerance is 0.5 to 0.75 mm (0.02 to 0.03 in.). All aspects of the panel itself are checked. "We collect dimensional data and provide it to the customer. We track the dimensional tolerances of the part so we know if there is a problem with consistency. We can identify the problem during manufacturing and make the appropriate adjustments to maintain proper specifications."O

48 [ JUNE 2000

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Since then, machine rental has become a major aspect of the business. Chris Jennings, President, tells the story "In the past year we have purchased more than 20 MQ Power Welders for retail and rental purposes. Our customers love them! The machines are very reliable. The safety shutdowns, thickness of the sheet metal, and even the paint color exude quality. We feel a great sense of pride when towing the equipment through town to the jobsite and 'Ramsey Welding' is boldly painted on the side?

q'he only problem we've had with the machines is their popularity - - sometimes ifs difficult keeping them in stocki' Chris adds.'Our customers are loyal, and like the MQ Power units so much that they'll wait for one to come back from rental, rather than looking for a competitive welder from someone else:'

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Atlanta. Boise. Dallas. Houston ° Newark Montreal, Canada. Manchester, UK ° Rio De Janiero, Brazil. Guadalajara, Mexico

C i r c l e No. 54 on Reader Info-Card

D a t a s h e e t 241 a We, o oo Practical information for welders and others involved in welding

and its allied processes.

Resistance Spot Welding Terms and Definitions

Terms listed below are used when evaluating resistance spot weld integrity and require definition for correct interpretation of the test instructions. Many of these terms are unique to testing methods and are not contained in ANSI/AWS A3.0-94, Standard Welding Terms and Definitions.

anchor weld. The first of two welds made on a peel-test sample. average weld-but ton size. The mean of all weld-button sizes (peel sample test welds) determined at a given checkpoint. checkpoint . The location in the test sequence where specific weld-button size or weld-button-size/fracture-mode criteria are determined. c o m p o s i t e t ip imprint . A carbon-paper impression produced on a piece of white paper that shows the combined contact pattern of the top and bottom electrode faces when the electrodes are brought into direct (without the presence of any test coupon) contact with each other under full welding force. coupon. A single, small piece of test material with specified dimensions that is used to make up test samples. cross-tension tes t . A destructive test to measure spot weld strength and button size, with the test weld in the plane perpendicular (direct tension) to the applied load. cross-tension-test coupon. A coupon cut from a coupon strip according to specifications, with its length parallel to the direction of rolling, and used to make up a cross-tension test sample. cross-tension-test sample . A lap-joint test sample, composed of two cross-tension test coupons having a specified overlap and standard size, that is used to determine the direct tension strength of the test weld and its fracture mode. current. The effective (RMS) welding current of a spot weld that is measured at the secondary side of the welding transformer and is calculated by an integrating current meter. current level. The current required to produce a specific weld size or expulsion criteria in one or more spot welds. current range. The difference in welding current between the IMI N and IMA X currents. current setting. The programmed welding current (in kA) of an electronic spot weld controller that is capable of constant-current control, or the percent heat or percent current setting that is used to set the welding current on some constant-voltage-type welding controllers. dressed e lectrode-face d iameter . The mean diameter of the electrode surface (that which contacts the sheet surface) after the electrode faces are paralleled and adjusted (dressed) to size. This dimension is calculated by subtracting the tip-imprint correction factor (CF) from their individual tip-imprint diameters.

effective (RMS) welding current. The integrated current (amperage) of a weld that is equivalent in its heating or power capability to pure DC (direct current). electrode-face d iameter , The mean diameter of the electrode surface (that which contacts the sheet surface) before the electrode is dressed. This dimension is the as-ordered or as- machined diameter measured prior to electrode installation. electrode-face d iameter weld size (FDWS). The mean diameter of a weld button that is equal to the specified dressed electrode-face diameter of the electrodes being used. e lec trode sticking criterion. The condition at which severe sticking between the electrode and the peeI-test sample is noted so that pressure applied with a finger at the farthest end of the stuck sample results in permanent deformation (bending) of the peel-test sample before breaking free from the electrode. endurance limit. The total number of acceptable welds made during the endurance test. This number does not include welds made during the weld-size stabilization procedure or welds made as part of the initial IMI N and IMA X determinations. endurance test terminat ion criterion. When all five weld buttons fall below the specified minimum weld size at two consecu- tive checkpoints. expulsion. The ejection of molten metal from the laying interface (interface between the two test coupons) of the sample. Expulsion may be verified by destructive peel testing of the sample and observing whether metal "whiskers" or "fingers" are evident at the interface. fracture or pul lout mode . The appearance of the weld button after peel testing. full interracial fracture (FIF). A fracture mode of a spot weld where all of the weld nugget (fused area of a spot weld) separates through the plane of the weld. hold-time sensitivity (HTS) panel sample. A stackup of two HTS panel coupons used for making test welds in the HTS test. ho ld- t ime sensit ivity (HTS) tes t . A test that determines the behavior or properties of spot welds made on the test material under different weld cooling rates. This test is accomplished by making a series of seven welds on HTS panel samples at short and long hold times for MWS and FDWS weld button sizes. The welded HTS panel samples are then sectioned into individual samples that are destructively peeled. Weld-button size and fracture modes are then determined. IFDWS cur ren t . The lowest current that produces weld buttons that meet the electrode-face diameter (FDWS) button-size criterion and the full or oval button fracture-mode criterion. The current measured for the test weld of any sample is used when deter-

Exce rp t ed f rom the A N S I / A W S / S A E D8.9-97 Recommended Practices for Test Methods for Evaluating the Resistance Spot Welding Behavior of Automotive Sheet Metal Materials.

WELDING JOURNAL J 51

Datasheet 241 b

mining the IFDWS current. The IFDWS current is the mean of the test weld currents for the three peel samples that meet the IFDWS criteria. IMA X cur ren t . The lowest current (from a peel sample's test weld) that meets either the IMA X expulsion criterion (severe sticking on both anchor and test welds). The current measured for the second weld (test weld) of the appropriate peel-test sample is the IMA X current. IMi N cur ren t . The lowest current that produces weld buttons that meet the minimum button size (MWS) criterion and the full or oval button fracture-mode criterion. The current measured for the test weld of any sample is used when determining the IMI N current. The IMI N current is the mean of the test weld currents for the three peel sample that meet the IMI N criteria. l o p current . The fixed welding current at which the endurance test is run. The magnitude of I o p is approximately 200 A below IMA X. If the difference between IMA X and the current at the next lower setting is greater than 200 A, then I o p is the current that corresponds to the closest setting below IMA X. individual tip imprint. A carbon-paper impression produced under full welding force on a piece of white paper that shows the individual contact pattern of each electrode face (top and bottom electrodes) separately. microhardnesslmetallographic sample. A test sample (taken from one of the HTS panels) that is sectioned across the centerline of the weld (perpendicular or parallel to the length of the sample from which it is extracted), mounted, polished and etched for metallographic examination and microhardness testing. material characterization panel (MCP). A steel panel that is used in determining sheet thickness, coating weight, coating composition and substrate composition. Mechanical properties and surface roughness may also be determined from this panel if so desired. panel coupon. A coupon, cut in accordance with specifications, used to make up a panel sample. The direction of rolling is unim- portant. panel sample. A stackup of two panel coupons used for making rows of welds during the endurance test. partial interfacial fracture (PIF). A fracture mode of a spot weld where a part of the weld nugget (fused area of a spot weld) separates through the plane of the weld and some portion of the weld pulls out as a partial button. peel tes t . A destructive test for determining a spot weld's pullout mode and button size. The test involves mechanically separating the lap joint by peeling. peel-test coupon. A coupon cut in accordance with specifications, with its length parallel to the direction of rolling, and used to make up a peel-test sample. peel-test sample. A lap-joint test sample composed of two peel- test coupons having a specified overlap and standard size, which is used to determine the weld-button size and fracture mode of a resistance spot weld. percent current. The designation for the control used to set the welding current on some constant-voltage welding controllers.

percent heat. The designation for the control used to set the welding current on some constant-voltage welding controllers. rolling direction (RD) mark. A mark made prior to coil edge removal along the coil edge of a steel sheet that identifies the rolling direction. Also see the definition of transferred RD mark. secondary edge. The edge of peel coupon strips or the material characterization panel that is perpendicular to the rolling direction. shear tension test . A destructive test to measure spot weld strength and button size with the test weld in the same plane (shear orientation) as the applied load. shear tension test coupon. A coupon cut from a coupon strip in accordance with specifications, with its length parallel to the direction of rolling and used to make up a shear tension test sample. shear tension test sample. A lap-joint test sample composed of two shear-test coupons having a specified overlap and standard size, which is used to determine the shear strength of the test weld and its fracture mode. t e s t weld. The weld made on any sample that is to be used to determine weld size, weld strength, button fracture mode, or a combination of these. tip-imprint correction factor (CF). The average difference between the individual tip-imprint diameters and the actual electrode-face diameters of the top and bottom electrodes before dressing. These differences (the tip imprints always being larger than the actual electrode-face diameters if the electrode face is flat) are caused by the compression of the white and carbon papers. tip-imprint diameter. The mean of the maximum and minimum diameters of composite or individual tip imprints. top surface. For sheets with nominally equal coating weight on both sides, the top surface is the surface facing up (toward the viewer) in a stack of sheets. For differentially coated sheets, this is the side having the heavier coating weight. top surface identification (ID) mark. A mark used to indicate the top surface of an untrimmed sheet. This mark should be made long enough so that after trimming the sheet the mark is still visible. transferred rolling direction (RD) mark. An RD mark that is transferred to all coupon strips and the material characterization panel in subsequent shearing operations. Individual coupons do not need to be marked with an RD mark. transferred top surface identification (ID) mark. A mark placed along the secondary edge of the top surface of peel coupon strips, panel coupon strips or the material characterization panel. weld bu t ton . The part of a spot weld, including all or part of the nugget, that tears out during destructive testing of welded sam- pies. we ld -bu t ton size. The average of the minor and major dimensions of the weld button. welding rate. The frequency, expressed in welds per minute, at which welds are made on the panel samples.

52 I JUNE 2000

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Offshore Newfoundland Petroleum Show. June 21-22, St. John's Memorial Stadium, Newfoundland, Canada. Contact: Southex Exhibitions Inc., #605, 999 - 8 St. SW, Calgary, AB, Canada T2R 1J5, (403) 209-3566 or (888) 799-2545, FAX: (403) 245-8649.

• Basic Cracking Problems and Solutions Conference. July 20-21, Holiday Inn Milwaukee-City Centre, Milwaukee, Wis. Sponsored by the American Welding Society. Contact: AWS Conference Dept., 550 NW LeJeune Rd., Miami, FL 33126, (800) 443-9353 ext. 223, FAX: (305) 443-1552.

• Materials Joining in the New Millennium. August 21-23, The Inn at Aspen Resort and Conference Hotel, Aspen, Colo. Sponsored by the American Welding Society. Contact: AWS Conference Dept., 550 NW LeJeune Rd., Miami, FL 33126, (800) 443-9353 ext. 223, FAX: (305) 443-1552.

EPRI Cooling Tower Conference. August 23-24, Snow King Resort, Jackson Hole, Wyo. Contact: Brent Lancaster, CCM, Conference Manager, EPRI, 1300 W. T. Harris Blvd., Charlotte, NC 28262, (704) 547-6017.

4th Conference on Aerospace Materials, Processes and Environmental Technology. September 18-20, Von Braun Center, Huntsville, Ala. Contact: Dawn Cross, Marshall Space Flight Center, (256) 544-1835.

• I C A L E O ® 2000, International Congress on Applications of Lasers and Electro-Optics. October 2-5, Hyatt Regency-Dearborn, Dearborn, Mich. Sponsored by the Laser Institute of America (LIA) and the American Welding Society. Contact: LIA, 13501 Ingenuity Dr., Ste. 128, Orlando, FL 32826, (407) 380-1553, FAX: (407) 380-5588.

Materials Solutions 2000. October 9-12, Cervantes Convention Center, St. Louis, Mo. Contact: ASM International, (440) 338-5151.

Aluminum Association Annual Meeting. October 12-13, The Drake Hotel, Chicago, Ill. Contact: Pamela Dorsey, The Aluminum Association, 900 19th St. NW, Washington DC 20006, (202) 862-5153.

• Second International Conference on Education in Welding. October 15-17, Denmark. Cosponsored by the Institute for the Joining of Materials (JOM Institute) and the American Welding Society. Contact: JOM Institute, Klinteh~j, Va~nge 21, 3460 Birker~d, Denmark, +45 45 82 80 95, FAX: +45 45 94 08 55.

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• Conference and Exposition on Plastics Welding. October 24-25, Grosvenor Resort, Orlando, Fla. Sponsored by the American Welding Society. Contact: AWS Conference Dept., 550 NW LeJeune Rd., Miami, FL 33126, (800) 443-9353 ext. 223, FAX: (305) 443-1552.

FOND-EX 2000, Industry Foundry Trade Fair. October 24-27, Brno Exhibition Center, Brno, Czech Republic. Contact: Messe Dfisseldorf North America, 150 N. Michigan Ave., Ste. 2920, Chicago, IL 60601, (312) 781-5180, FAX: (312) 781-5188.

• How to Competitively Weld the 21st Century Ship. November 9-10, Quality Inn Lake Wright Resort and Convention Center, Norfolk, Va. Sponsored by the American Welding Society. Contact: AWS Conference Dept., 550 NW LeJeune Rd., Miami, FL 33126, (800) 443-9353 ext. 223, FAX: (305) 443-1552.

FABTECH International 2000. November 14-16, I-X Center, Cleveland, Ohio. Cosponsored by the Fabricators and Manufacturers Association, International, and the Society of Manufacturing Engineers. Contact: SME Customer Service, One SME Dr., Dearborn, MI 48121, (800) 733-4763 or (313) 271-1500, FAX: (313) 271-2861.

ICOMES 2000 I 6th International Conference of Mechanical Engineering Societies. November 18-22, Shanghai, China. Organized by the Chinese Mechanical Engineering Society (CMES). Contact: CMES, 46 Sanlihe Rd., Beijing 100823, E R. China, 010 68511753, FAX: 010 68533613.

EuroBLECH 2000: 16th International Sheet Metal Working Technology Exposition. December 5-9, Hannovcr,

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56 1 JUNE 2000

Germany. Contact: Mack-Brooks Exhibitions Ltd., Forum Place, Hatfield Herts ALl0 0RN, U.K., +44 (0)1707 275641, FAX: +44 (0)1707 275544.

Second EPRI Corrosion and Degradat ion Conference. December 11-14, Wyndham's Casa Marina Resort & Beach House, Key West, Fla. Cosponsored by EPRI and NACE. Contact: Brent Lancaster, CCM Conference Manager, EPRI, 1300 W. T. Harris Blvd., Charlotte, NC 28262, (704) 547-6017, FAX: (704) 547-6168.

Educational Opportunities

Laser Safety Off icer Course. June 5-9, St. Louis, Mo. Sponsored by the Laser Institute of America. Contact: LIA, 13501 Ingenuity Dr., Ste. 128, Orlando, FL 32826, (407) 380- 1553, FAX: (407) 380-5588.

Industrial Ventilation Courses. June 12-15, Tropicana Hotel, Las Vegas, Nev.; October 2-6, University of Alabama at Birmingham (UAB) Continuing Education Center, Birmingham, Ala. Conducted by the UAB School of Engineering. Contact: UAB School of Engineering, Professional Development, 1075 13th St. S., Birmingham, AL 35294, (205) 934-8994, FAX: (205) 934-8437.

ESAB A l u m i n u m 2000, Seminar on A l u m i n u m Welding. June 29-30, Quality Hotel 11, GOteborg, Sweden. Held in English. Sponsored by ESAB and TWI. Contact: ESAB AB, +46 31 509 479, FAX: +46 31 509 436.

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\

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By Susan Campbell

0 AWS R e l e a s e s S ix P u b l i c a t i o n s

• Two Updated P u b l i c a t i o n s in the AWS Welding Inspec t ion Series

The A m e r i c a n Weld ing Soc ie ty r ev i sed two va luable gu ides for eva lua t ing welds , Guide f o r the Nondes truc- t ive E x a m i n a t i o n o f Welds (AWS B1.10:1999) and Guide

f o r Visual Inspec t ion o f Welds (AWS B1.11:2000) . Each was d e v e l o p e d by the AWS C o m m i t t e e on Methods of In- spec t i on and is a p p r o v e d by the Amer i can Nat ional Stan- dards Ins t i tu te (ANSI).

Guide f o r the Nondes truc t ive E x a m i n a t i o n o f Welds d e s c r i b e s t h e va r ious NDE m e t h o d s c o m m o n l y u s e d to e x a m i n e w e l d s . T h e gu ide also ind ica tes w h i c h m e t h o d s are best for d e t e c t i n g var ious types of d i scont inu i t i es . It i nc ludes sec t ions on n u m e r o u s types of examina t ion , in- c l u d i n g visual , p e n e t r a n t , m a g n e t i c , r a d i o g r a p h i c , ultra- son ic , e l e c t r o m a g n e t i c and leak t e s t ing . Guide f o r the N o n d e s t r u c t i v e E x a m i n a t i o n o f Welds is 42 pages and lists for $72; $54 for AWS m e m b e r s .

Guide f o r Visual I n spec t i on o f Welds c o n t a i n s de- t a i l ed i n f o r m a t i o n on t h e v i sua l e x a m i n a t i o n o f we lds , i n c l u d i n g s e c t i o n s on i n s p e c t i o n p r e r e q u i s i t e s , funda- men ta l s , su r f ace c o n d i t i o n s and e q u i p m e n t . The g u i d e also c o n t a i n s s k e t c h e s and fu l l -co lor p h o t o g r a p h s to il- lus t ra te c o m m o n l y f o u n d w e l d p r o b l e m s . Guide f o r Vi- s u a l In spec t ion o f Welds is 36 p a g e s and also l ists for $72; $54 forAWS m e m b e r s .

• Safe Pract ices for Cutt ing and Weld ing Pipes and Containers Now Available

T h e la tes t ed i t i on o f R e c o m m e n d e d Safe Pract ices f o r the Prepara t ion f o r Welding a n d Cut t ing Contain- ers a n d Pip ing (AWS F4:1 :1999) has b e e n p u b l i s h e d by AWS.This ANSI-approved s tandard c o v e r s the n e c e s s a r y p r a c t i c e s to safely w e l d and cu t p i p i n g and c o n t a i n e r s . T h e r e c o m m e n d a t i o n s also c o v e r t h e v a r i o u s m e t h o d s for c l ean ing and p r e p a r i n g mater ia ls p r i o r to we ld ing o r cut t ing.

R e c o m m e n d e d Safe Pract ices f o r the Prepara t ion f o r Welding a n d Cutt ing Containers and Piping is e ight pages , m e a s u r e s 8~ x 11 in. and is s o f t b o u n d . T h e list p r ice is $32; $24 forAWS member s .

• New Spec i f i ca t ion for the Qual i f i cat ion o f Robotic Arc Welding P e r s o n n e l

The Amer ican Welding Socie ty has c o m p l e t e d a n e w Specif ication f o r the Qual i f icat ion o f Robot ic Arc Weld- ing Per sonne l (AWS D 16.4: 1999). This A N S I - a p p r o v e d pub l i ca t ion p rov ides the guide l ines for f ive levels o f qual- i f i ca t ion and i n c l u d e s i n f o r m a t i o n on p e r s o n n e l exc lu- s ions and l imi t a t i ons , as w e l l as de ta i l s on safe ty and hea l th c o n s i d e r a t i o n s . T h i s spec i f i c a t i on was d e v e l o p e d u n d e r t he g u i d a n c e o f t he AWS D16 C o m m i t t e e on Ro- bo t i c and A u t o m a t i c Welding, w h i c h i n c l u d e s r e p r e s e n - t a t ives f r o m a d i v e r s e g r o u p of c o m p a n i e s i n c l u d i n g T o w e r A u t o m o t i v e , Caterpi l lar , ABB Flex ib le A u t o m a t i o n and many others .

Speci f ica t ion f o r the Qual i f i ca t ion o f Robot ic Arc Welding Per sonne l is t en pages l o n g and i n c l u d e s o n e a n n e x and f ive t a b l e s . T h e s p e c i f i c a t i o n is ava i lab le for $16;$12 for AWS member s .

• R e c o m m e n d e d Practices for Local Heating o f Welds in P ip ing and Tubing

In its c o n t i n u i n g e f fo r t to r e s p o n d to t h e n e e d s o f t he w e l d i n g industry , t he A m e r i c a n Weld ing Soc ie ty has r e l e a s e d the l a tes t e d i t i o n o f R e c o m m e n d e d Pract ices f o r Local Hea t ing o f Welds in Piping a n d Tubing (AWS D 10 .10 /D 10.10M: 1999). T h e r e c o m m e n d e d p r a c t i c e s t ake in to c o n s i d e r a t i o n t h e v a r i o u s f ac to r s a s s o c i a t e d w i t h the local hea t ing o f welds , and t h e y speci f ica l ly address the app l ica t ion o f con t ro l l ed hea t to the we ld metal , t he hea t -a f fec ted zone (HAZ) and to a l imi ted v o l u m e of meta l ad jacen t to the weld .

T h e r e c o m m e n d e d p r a c t i c e s w e r e d e v e l o p e d for t h o s e i n s t a n c e s w h e n it is no t p r a c t i c a l to h e a t t h e en- t i re c o m p o n e n t o f e i t h e r a p i p i n g o r a t u b i n g sys t em. An A N S I - a p p r o v e d s t a n d a r d , R e c o m m e n d e d Prac t i ces f o r Local H e a t i ng o f Welds in Pip ing a n d Tubing gen- e r a l l y a d d r e s s e s i s s u e s a s s o c i a t e d w i t h c i r c u m f e r e n - t ia l bu t t j o in t w e l d s , bu t also p r o v i d e s i n f o r m a t i o n on loca l s p o t hea t ing .

R e c o m m e n d e d Practices f o r Local Heat ing o f Welds in Piping and Tubing is 116 pages and inc ludes sec t ions

-- continued on page 60

WELDING JOURNAL [ 59

• AWS R e l e a s e s S i x P u b l i c a t i o n s

-- continued from page 59

on terminology, tempera ture measurement , various types of heating, eight annexes, 16 tables and 23 figures.The list price is $32; $24 for AWS members.

• The 2000 AWS Catalog

With hundreds of t i t les for welding, cut t ing, brazing, so lder ing and more, the 2 0 0 0 A m e r i c a n Weld ing Soc ie ty Cata log is the ult imate source for mater ia ls jo ining p roduc t s .The upda ted catalog features 40 pages of eve ry th ing a welder , s tudent , engineer , des igner or r e sea rcher needs to know about welding.

Hundreds of titles are featured, including many ANSI-approved codes that are the vital part of any welding project . Order discounts are available for AWS members, educational institutions and some bulk o rde r s . •

Copies can be o rdered by ca l l i ng AWS C u s t o m e r Serv ice a t ( 8 0 0 ) 334- 9353, (305) 334-9353 ou ts ide the Uni ted States, M o n d a y th rough Friday, 8 a.m. to 5 p. m. EST, or t h r o u g h the AWS Web s i te a t www.aws.org . Addi - t iona l i n f o r m a t i o n on AWS's p r o g r a m s a n d p u b l i c a t i o n s can also be f o u n d on the Web site.

• N o r t h e r n Pla ins Sec t ion H o l d s Weld ing Contes t

o n March 9,Alexandria Technical College,Alexandria, Minn., was the site for the Nor thern Plains Sect ion 's 5th Annual Behind the Mask Welding Compet i t ion . Professional we lde r s from local indust r ies

and welding Students from North Dakota State College of Science (NDSCS), Wahpeton; Nor thwest Technical College, Moorhead; and Ridge Water Tech- nical College, Wilmar, compe ted in SMA or GMA welding divisions.

Welders f rom Ridge Water Technica l Col lege took all honor s in the SMAW division. Placing first was J e r emy Hall; Ryan Lipper t was second; Dave Willems took third and Allen Reiman was awarded honorab le mention. In the GMAW div is ion ,Jus t in Hynnek of Alexandria won first place; Derek Berge, also of Alexandria, p laced second;Travis Ripplinger of Moor- head p laced third; and Dustin Har tman of Alexandria r ece ived an honor- able mention.

The top three winner s in each divis ion chose f rom a large se lec t ion of prizes including two Smith welding torch sets valued at $500 each, two weld ing helmets wi th autodarkening lenses valued at $400 each, e lec t r ic hand grinders, tools and other prizes.All compet i tors were awarded a prize. Prize sponsors inc luded the Amer ican Welding Society 's Nor the rn Plains Section; Praxair of Grand Forks and Fargo;Airgas of Grand Forks;American Welders Supply, Fargo and Wi lmar ;Acme Electr ic , Grand Forks; Home of Economy, Grand Forks; Miller Elect r ic Mfg. Co, Apple ton , Wis; Arcsmi th Welding Torches, Water town, S.Dak.; Alexandria Technical College, Alexan- dria, Minn.

Serving as judges for the con tes t were Dan Emberland, Amer ican Welders Supply; Mike Gillispie, Protainer Co.,Alexandria;A1 Barney, Supe- r ior Industries, Morris, Minn. ;Joshua Heibel, Innovat ive Engr. Co.,Alexan- d r i a ; John Cox and Bob Mracek f rom NDSCS; Dennis Wilkins, Nor th land Communi ty and Technica l College, Th ie f River Falls; Tim Schwanz, AWS Nor thern Plains Section chairman, Grand Forks Public Schools; and Ralph Williams, Praxair, Grand Forks.

Each year, the Sect ion rotates the Behind the Mask weld ing compet i - t ion throughout the valley and the Northern Plains Section area. •

• T e n n e s s e e G o v e r n o r H o n o r s W e l d e r s

Tennessee Governor Don

Sundquist honored the welding pro-

fession in his state by proclaimingApril

23-29 as Welding Week.

The proclamation reads:

"Whereas, welding is a profession requiring considerable training

and specialized study; further, the

application of that training and spe-

cialized study is critical to the general

well-being for the country and calls for

a constant stream of operators, design-

ers, inspectors, engineers, teachers,

and scientists from our schools and

universities; and

"Whereas , the Sections and

Districts of the American Welding

Society wish to remind the public of

the critical importance of welding; and

"Whereas, the American Welding

Society's District 8 encourages the par-

ticipation in a public service program,

Welding for Communities, that follows

in the tradition of other profession's

service for the common good; and

"Now, Therefore, I, Don

Sundquist, Governor of the state of

Tennessee, do hereby proclaim April

23-29, 2000, as Welding Week in

Tennessee, and encourage all citizens

to recognize Welding for Communities

as the annual public service campaign

of the American Welding Society." •

• D i s t r i c t 6 Director P r e s e n t s A w a r d s

The District DirectorAward provides a means for District Directors to recognize individuals who have con- tributed their time and effort to the affairs of their local Section and/or Dis- trict.

District 6 Director Gerald R. Crawmer presented the following in his District with this award:

• Guy Mulee, Rochester

• Members o f the A l f r e d S ta te

College AWS S t u d e n t Chapter,

Olean-Bradford •

60 I JUNE 2000

• Northwest Holds Welding Contest and Scholarship Night

The Northwest Section recently held its Annual Behind the Mask Welding contest at the Hennepin Technical College in Brooklyn Park, Minn.

The contest consisted of three processes - - GTAW, SMAW and GMAW. Contestants could sign up for only one process. Prizes were $100, $50 and $25.The following are the winners in each category.

GTAW 1. Bob Ecks te in 2. Kjel l Plath 3. Nate B r e n i n g

GMAW 1. Paul P e t e r s o n 2. Greg Worthey 3. Chad Luedke

SMAW 1. Steve B a c k m a n 2. Ryan Lipper t 3. A n d r e w Sakry

Northwest Section scholarship recipients, f rom left to right, Eric Back- man;Jason Dannen; Richard Kooy, back; Brandon Bauer;Justin Kopp; Randy Mortland, back;Tyson Gerry, Kale Pribnow, Jeremiah Daniels; and Timothy Haraldson.

The same evening, the Section, along with six local companies, awarded $14,500 in education scholarships for the 2000-2001 school year. Donating companies include Kurt Manufacturing, which gave $500, along with Airgas North Central's $500 in equipment and supplies; Produc- tion Engineering Corp. gave $1000; Determan Brownie Inc. gave $1000 for the second year; Phillips &Temro Industries donated $1000; and Tennant awarded a $1500 scholarship.

The recipients of these scholarships are as follows: Tyson Gerry received the Tennant award, Jenny Norman

was selected for the Determan Brownie scholarship, Eric Backman won the Production Engineering scholarship,Je- remiah Daniels was picked for the Phillips Temro award, Brandon Bauer was chosen to receive the Airgas Central and Kurt Mfg. award and Nathan Sandvig, Kale Pribnow, Jason Dannen, Shaun Syverson,Justin Kopp, Chris Dahline, Randy Mortland,Timothy Haraldson and Richard Kooy received Northwest Section scholarships of $1000 each.

Northwest Section Chairman Bob Sands said,"I want to thank industry for their generosity.Without their help, these scholarships would not be possible."0

• A W S / W E M C O L a u n c h e s M a n u f a c t u r e r ' s S h o w c a s e

The American Welding Society and the Welding Equipment Manufac- turers Committee are proud to present the WEMCO Manufacturer's Showcase on the AWS Web site.This showcase is stocked by WEMCO members and presented to the general viewing public. Inside the showcase WEMCO members show their newest and most innovative products.

This new capability brings advantages not only to the WEMCO members but also to the welding industry as innovation and invention is brought to the industry's attention with colorful product pictures, information, product descriptions and easy-access e-mail and URL links.

You can visit the "Showcase" at www. aws. org/wemco/man_show. If you have already visited, we hope you return often for all the latest products available to enhance your job performance. •

• L o u i s i a n a G o v e r n o r H o n o r s W e l d e r s

Louisiana Governor M.J. "Mike"Foster, Jr., cente< presenting District 9 Director O.J. Templet, left, and Baton Rouge Past Section Chairman Jeff Knight with a plaque officiaUy proclaiming the week o f Apri123-29 as Welding Week in the state o f Louisiana.

Foster issued this Proclamation in recognition o f the hard work and dedication o f the welders in his state. This is something Foster really knows about, he once worked as a professional welder. •


• Sustaining Member Company

H - e n d e r s o n Manufactur ing is a

privately owned manufacturer , of dump bodies and ice con-

trol equ ipment .The company 's products include a wide range of dump bodies, a full l ine of snowplows (in-

cluding a reversible plow, front-mount wing, mid-mount wing and a one-way p low and wet and dry spreading equipment for the highway-ice-control market. Models are offered for both heavy- and medium-duty trucks.

Henderson manufactures most of its products internally at its plant in Manchester, Iowa.This plant is a well-equipped metal fabrication and manufactur ing facility wi th mode rn cutt ing, weld ing and paint ing capabil i t ies. Henderson 's manufacturing engineering and support ing design capabilities are highly regarded with the industry, and the company has introduced several product innovations in recent years.

The company's customers include a variety of construction-related seg- ments, along with state and local gove rnmen t markets .The company sells nat ionwide through a growing network of truck dealers and on a direct bid basis.

Henderson Manufacturing is commit ted to providing its customers with the highest quality products available. •

• Sus ta in ing C o m p a n y M e m b e r D u e s Update

Effective June 1,2000, the fo l lowing adjustments have been implemented forAWS Sustaining Company Members:

Dues: The annual dues are $750, domest ic ; $850, internat ional ; plus a $500 initiation fee.

B e n e f i t s : The enhanced AWS Sustaining Company Member benef i ts package includes one of the fol lowing pr imary offerings: 1) the c o m p l e t e l i b r a r y o f AWS p u b l i c a t i o n s ($ 5600 value), including 130+ codes, specifications and r e c o m m e n d e d pract ices, wi th compl imen ta ry publ ica t ion up- dates included; or 2) a discount p r o m o t i o n a l package , including a 5% discount on ads in the Welding Journal and a $4 per sq ft discount on booth space at the AWS/PMA Show; or 3) t e n addi t ional AWS I n d i v i d u a l Mem- berships for company employees or customers

• In addition,AWS Sustaining Company Members enjoy • Ten free Individual Memberships for company employees or customer. • Publicity of the company's name and product /service offerings in

the Welding Journal and on the AWS Web site. • Company recognit ion at the annual AWS/PMA Show. • Usage of the AWS Sustaining Company Member logo on company

letterhead and promotional material. • AWS Sustaining Company engraved wall plaque. • Free hyperlink from the AWS Web site to the member company's site.

For information on becoming an AWS Sustaining Company Member, contact the AWS Membership Dept. at (800) 443-9353 ext. 418, FAX (305) 443- 5647 or write AWS, 550 N.W. LeJeune Rd., Miami, FL 33126. •

OAnnounce Your Section's Activities

Increase attendance at your Section's meetings and training programs with free listings in the Section Meeting Calendar column of Society News.

Useful information includes your Section name; activity date, time and location; speaker's name, title, affiliation and subject; and notices of golf outings, seminars, contests and other special Section activities.

If some of your meeting plans are sketchy, send the name and phone number of a person to contact for more information.

Send your new calendar to Susan Campbell,Assistant Editor, Welding Jour- nal Dept.,AWS, 550 N.W. LeJeune Rd., Miami, FL 33126; FAX: (305) 443-7404. •

AWS WELCOMES

N E W S U P P O R T I N G C O M P A N I E S

N e w S u p p o r t i n g C o m p a n i e s

Thompson Friction Welding 6600 Center Drive Sterling Heights, MI 48312

Roth Manufacturing Corp. 21 North Main Street Milan, OH 44846

N e w E d u c a t i o n a l I n s t i t u t i o n s

NWCCD Gillette Campus Welding Dept. 720 West 8th Street Gillette,WY 82716

• Member Dues Adjustment

The AWS Board of Directors, acting on the recommendations made by the Membership Committee, approved a dues adjustment to $75 for the "Regular Member" classification effective June 1, 2000.

Upon joining and every third membership year, Regular Members dues will include an expanded publication choice of ei ther the latest Welding Handbook, Welding Metal- lurgy,Jefferson's Welding Encyclope- dia, Soldering Handbook or the De- sign and Planning Manual for Cost- Effective Welding upon request. In addition, AWS members receive a monthly subscript ion to the award- winning Welding Journal, as well as bimonthly issues of The American Welder supplement . AWS-certified personnel also receive quarterly issues of Inspection Trends magazine.

AWS members enjoy access to widely respected technical information in the materials-joining industry at d iscounted rates. Members-only discounts apply to AWS technical publications, as well as to top-notch certifications, conferences and other educational offerings. Members also benefit from networking opportunities at local Section meetings and at the AWS Exposition. Beginning June 1, AWS members will be able to choose be tween two value-added membership package offerings, the Gold and the Platinum Membership Packages, for modest fees. And, in the near future,AWS members will enjoy members-only access to special information and services on the AWS Web site, www.aws.org. •

62 I JUNE 2000

S A F E T Y A N D H E A L T H T O P I C S

• L o c k o u t / T a g o u t Fact S h e e t No . 18

Introduction

e r a b l e , p r o c e e d to t h e n e x t s t ep . If t h e y are o p e r a b l e , c h e c k w h e r e t h e locks s h o u l d b e p l a c e d , or, if n e e d e d , p l a c e a d d i t i o n a l l o c k s to e n s u r e e q u i p m e n t o r va lves are no t ope rab le . C h e c k t he e q u i p m e n t or valves for op- e r a t i on again.

S o m e t i m e s w o r k m u s t b e p e r f o r m e d o n e q u i p m e n t , p i p e l i n e s and m a c h i n e r y t ha t m ay c o n t a i n m o v i n g par t s , p r e s s u r i z e d g a s s e s o r l iqu ids , e l e c t r i c i t y o r o t h e r hazards. C o n t a c t w i t h any of t h e s e may r e s u l t in i n j u r y o r dea th .

• Star t t h e work . If t h e e m p l o y e e s ' sh i f t e n d s b e f o r e t h e w o r k is c o m p l e t e d , t h e y m u s t r e m o v e t h e i r l o c k s a n d t h e n e x t sh i f t ' s e m p l o y e e s m u s t ins ta l l t h e i r l ocks b e f o r e c o n t i n u i n g t h e w o r k a n d b e f o r e t h e p r e v i o u s sh i f t ' s locks are r e m o v e d .

Definitions

"Lockout" m e a n s to instal l a lock ing dev ice tha t k e e p s t he swi tch , valve or o t h e r m e c h a n i s m f rom b e i n g t u r n e d o n o r o p e n e d . "Tagout" m e a n s to p u t a tag o n t h e lock- ing d e v i c e . T h e t ag i n d i c a t e s DANGER or WARNING, a long w i t h a b r i e f message . It has a p l ace to p u t t he da te a n d p e r s o n ' s n a m e w h o l o c k e d o u t t h e e q u i p m e n t so t ha t h e or she may b e easily l oca t ed or not i f ied .

Steps to Follow

• W h e n t h e w o r k is c o m p l e t e d , e n s u r e all e m p l o y - e e s are c l ea r b e f o r e r e m o v i n g t h e locks a n d tags, ene r - g iz ing e q u i p m e n t or o p e n i n g valves.

I n f o r m a t i o n S o u r c e s

Occupa t iona l Safety and Hea l thAdmin i s t r a t ion (OSHA). Code o f Federal Regulat ions,Ti t le 29 Labor, C h a p t e r XVII, Par ts 1901.1 to 1910 .1450 , O r d e r No. 869-O19-OOll 1-5. Avai lable f rom S u p e r i n t e n d e n t of D o c u m e n t s , U.S. Gov- e r n m e n t Pr in t ing Off ice ,Washington , DC 20402.

• T ra in e m p l o y e e s in t h e p u r p o s e a n d m e t h o d s o f l o c k o u t / t a g o u t .

• I n f o r m the job s u p e r v i s o r a b o u t t he p r o p o s e d w o r k and o b t a i n p e r m i s s i o n to l o c k o u t and t agou t t he equ ip - m e n t .

• Shut d o w n the e q u i p m e n t .

Mine Safety and Hea l th A d m i n i s t r a t i o n (MSHA). Code o f Federal Regula t ions ,T i t l e 30 Minera l Resources , Parts 1 - 199. Ava i l ab le f r o m S u p e r i n t e n d e n t o f D o c u m e n t s , U.S. G o v e r n m e n t P r in t ing Of f i ce ,Wash ing ton , DC 20402.

For s p e c i f i c i n f o r m a t i o n o n r e c o m m e n d e d l o c k o u t p o i n t s for e q u i p m e n t , m a c h i n e r y and valves, c o n t a c t t he manufac tu re r . •

• P lace locks and tags o n t he s w i t c h e s and valves to p r e v e n t t h e i r use. Note: I f more than one p e r s o n is per- f o r m i n g w o r k on the e q u i p m e n t , i t is r e c o m m e n d e d they h a v e t h e i r o w n locks a n d tags on the l o c k o u t po in t .

• Have t h e o p e r a t o r t r y to s t a r t t h e e q u i p m e n t o r o p e n t he valves. If t he e q u i p m e n t and valves are n o t op-

The Safety and Health Fact Sheets, 2nd ed., cover all aspects of safety and health applicable to welding and cutting. The Fact Sheets include 20pages on subjects such as f u m e s and gases, radiation, noise and electrical hazards. Compiled in 1998. Price for AWS members is $24; nonmembers, $32. Copies of Safety and Health Fact Sheets can be ordered by calling AWS Customer Service at (800) 334-9353, or (305) 443- 9353 ext. 280 outside the United States, Monday through Fri- day, 8 a.m. to 5p.m. Eastern Standard Time.

• AWS O f f e r s W e l d C r a c k i n g C o n f e r e n c e

i n July of th i s year, t h e A m e r i c a n W e l d i n g Soc ie ty wil l b r i n g t o g e t h e r e x p e r t s f r o m a r o u n d t h e w o r l d to s h o w c a s e t h e l a t e s t m e t h o d s o f d e a l i n g w i t h w e l d

c r a c k i n g . W e l d c r a c k p r e v e n t i o n s c e n a r i o s r a n g e f r o m p r e h e a t i n g to u l t r a s o n i c s , w i t h m a n y m o r e in b e t w e e n . A t t e n d e e s of t h e "Weld C r a c k i n g : Basic P r o b l e m s - - Ad- v a n c e d So lu t ions" c o n f e r e n c e wil l s p e n d an i n t e n s e half- day l e a r n i n g a b o u t w e l d c r a c k i n g in s t ee l s , a l u m i n u m , s t a in less s tee l s and t i t a n i u m . A p a n e l of e x p e r t s wil l iden- t i fy m a n y o f t h e o f t e n o v e r l o o k e d s o u r c e s o f c r a c k i n g a n d i l l u s t r a t e t h e b e s t w ay to so lve th i s s e r i o u s w e l d i n g p r o b l e m .

C h a i r e d by AWS Weld ing J o u r n a l C o n t r i b u t i n g Edi-

t o r Bob I rv ing , t h e c o n f e r e n c e wil l f e a t u r e e x p e r t s f r o m T h e L i n c o l n E l e c t r i c Co. , E d i s o n W e l d i n g I n s t i t u t e , Dy- n a m i c Sys tems , t h e Nava l Su r face War f a r e Cen t e r , NIST, Fleet T e c h n o l o g y and o t h e r s . "Weld Cracking: Basic Prob- l ems - - A d v a n c e d So lu t ions" wil l b e h e l d July 20 a n d 21 at t he Hol iday I n n - M i l w a u k e e City C e n t e r in M i l w a u k e e , W i s . T h e fee is $550; $480 forAWS m e m b e r s .

W e l d i n g p r o f e s s i o n a l s c a n r e g i s t e r fo r t h e c o n f e r - e n c e by ca l l i ng t h e AWS C o n f e r e n c e Dep t . a t ( 8 0 0 ) 334- 9353 ext . 223 or, o u t s i d e t h e U n i t e d States , at ( 3 0 5 ) 443- 9353 ext . 223. R e g i s t r a t i o n is a lso ava i l ab le t h r o u g h t h e AWS Web s i te at w w w . a w s . o r g . •


E I N E W

Boston Section First Vice Chair- m a n Glenn Myrick , left, presen t - ing speaker's g i f t to Rick Moody.

New York Section Chairman Do- minick Colasanto, right, presenting a speaker's gift to Lou Gunther

D I S T R I C T I D i r e c t o r : G e o f f r e y H. P u t n a m

P h o n e : ( 8 0 2 ) 4 3 9 - 5 9 1 6

• BOSTON APRIL 10 Speaker: Rick Moody , quali ty assurance manager. Af f i l ia t ion: Artisan Industr ies, Waltham, Mass. Topic: Fabricat ion and welding of ASME pressure vessels, vacuum chambers, water clarification tanks, rotary thin film evaporators and associated piping systems using various processes. Activi ty: Ballots were collected for next year's execut ive board members.

Phi lade lph ia Section m e m b e r s in a se l f -conta ined d e m o n s t r a t i o n t ruck watching bevel mach in ing o f plate.

New Jersey Section Chairman Bob Bartley, left, present ing a speaker's gift to Mike Brace.

D I S T R I C T 2 D i r e c t o r : A l f r e d F. F l e u r y

P h o n e : ( 7 3 2 ) 8 6 8 - 0 7 6 8

• PHILADELPHIA MARCH 13 Speaker: T o m Bel l iz ia , regional manager. Affiliation: Jancy Corp. Topic: Magnetic drills and metal- working tools.

• NEW YORK MARCH 20 Speaker: Lou G u n t h e r , supervisor

AWS Past President Shirle}, Bollinger wi th Lehigh Valley Section Chair- man Steve Whitney

of materials engineering. Affil iation: Keyspan Energy Power, Engineering Department. Topic: Qualifications of procedures for welding underwater in a dry hy- perbaric chamber.

• NEW JERSEY MARCH 21 Speaker: Mike Brace, welding specialist. Affil iation: Miller Electric Mfg. Co., Appleton, Wis.

64 I JUNE 2000

Guest speaker Bruce Grone,, left, accepting a speaker's gift f rom Lehigh Valley Section Vice Chairman Rich Gallagher.

District 3 Director Claudia Kauf- man, r@t , presenting Lehigh Valley Section Chairman Steve Whitney.

Lehigh Valle~ Past Chairman Dave Schnalzer, left, wi th gues t speaker John S t i n s m e n a t the Apr i l meeting.

Long I s land Sect ion C h a i r m a n Don Scarcel la t h a n k i n g gues t speaker Mahesh M o h a n t y f o r his presentat ion.

Topic: Engine welding machines - - from the past to the future.

• DELAWARE MARCH 14 Act iv i ty : The Sect ion toured the Dodge Durango plant and wit- nessed how the Durango is built from start to finish. The robot ic weld ing systems used for the Du- rango were r ev iewed by the Sec- tion.

• LONG ISLAND MARCH 9 Speaker: M a h e s h Mohan ty , Ph.D. Affil iation: Sulzer Metco. Act iv i ty: The Section visi ted the Sulzer Metco plant where Mohanty discussed thermal spraying for wear or protect ion of different metals.

D I S T R I C T 3 D i r e c t o r : C l a u d i a B. K a u f m a n

P h o n e : ( 8 0 0 ) 2 2 6 - 9 9 3 9

• LEHIGH VALLEY SEPTEMBER 15 Speaker: S h i r l e y W. B o l l i n g e r , AWS past president.

Lehigh Valley Sect ion Vice Chair- m a n Rich Gallagher, left, t hank- ing gues t speaker Bob Reinhardt , Jr, f o r his presentat ion.

Affi l iation:AWS. Topic: Educat ion and h o w AWS is perceived in other countries.

JANUARY 4 Speaker: Bob R e i n h a r d t , Jr . , vice president of sales engineering. Aff i l iat ion:J. A. Reinhardt & Co., Inc., Mountainhome, Pa. Topic: Aluminum dip brazing.

FEBRUARY 1 Speaker: D a v i d U r e v i c h , applications engineer. Aff i l iat ion:Advanced Surface Coat- ings, Inc.,Allentown, Pa. Topic: Fundamentals of thermal spray coatings.

MARCH 7 Speaker: B r u c e G r o n e r , ch ief executive officer. Af f i l ia t ion: Wilson Products, Eas- ton, Pa. Topic: Life is a river. A c t i v i t y : T h e Sec t ion he ld its annual Vocational Educat ion Awards banquet .

APRIL 4 Speaker :John S t i n s m e n . Affiliation: Stinsmen Racing. Topic: Specialty bicycles for track and road competit ion.

Lehigh Valley Section Chairman Rich Gallagher, right, with gues t speaker David Urevich.

One o f the contestants at tDe Read- ing Section's welding contest.

Ac t iv i ty : The Sect ion held Past Chairman's Night. At tending past chairmen included Ed Becke t , Leo Maier, Bruce S o m e r s , J o h n J o h n - son , D o n D e b u s , D a v e Marks , Dave S c h n a l z e r and Chr i s Kipp.

• READING MARCH 11 Activi ty:The Section hosted a welding contes t b e t w e e n five area vo- tech schools.The compet i t ion was made of 500-hour level, lO00-hour level and 1500-hour level divisions.

WELDING JOURNAL 67

Florida West Coast Section Chair- man A1 Sedory, left, present ing a speaker's gift to Ted Toth.

Atlanta Section members at tlwir March meetiJzg.

Ted Alberts, left, associate profi, ssor o f welding, accepting a donation fi~r New River Communi ty College f rom Southwes t Virginia Section Chair- man Claude Holcomb.

• NORTHEAST NORTH CAROHNA FEBRUARY 29 Act iv i ty : The Sect ion toured the Kinston Neuse Corp. plant and saw how a forklift is built.

MARCH 22 Act iv i ty: The Section held an officer ' s mee t ing to plan for the upcoming year's meetings and events.

MARCH 28 Speaker: Tye Rober t s , president Af f i l ia t ion: Roberts Welding Co., Winterville, N.C. Activity: Roberts led the Section on a tour of the Roberts Welding Com- pany plant.

D I S T R I C T 4 D i r e c t o r : R o y C. L a n i e r P h o n e : ( 9 1 9 ) 3 2 1 - 4 2 8 5

• SOUTHWEST VIRGINIA MARCH 29 Speaker: Rob Col l ins .

Welding supervisor Jody Peaty during the North Central Florida Sec- tion's tour o f the Ring Power plant.

Affi l iation: Watson-Hegner Corp. Topic: Water jet cutting processes. Act iv i ty:The Section donated $500 to New River Communi ty College to p romote and advert ise welding as a career.

• TIDEWATER APRIL 20 Act iv i t y : The Sect ion toured the Ford Motor Company plant.

D I S T R I C T 5 D i r e c t o r : B o r i s A. B e r n s t e i n

P h o n e : ( 7 8 " / ) 8 8 3 - 8 3 8 3

• FLORIDA WEST COAST MARCH 8 Speaker: Ted Toth, metallurgist. A~//a//xTn: Applied Metals Science, Inc.

Holston Vall¢:l, Section Chairman Bob Thomas, left, thanking speaker John Abbitt f o r his presentation.

Topic:Weld failure analysis. Act iv i ty : The Sect ion toured the welding facility at the Pinellas Edu- cation Center.

• NORTH CENTRAL FLORIDA MARCH 14 Speaker: J o h n D u n c a n , O c a l a branch manager. Aff i l ia t ion: Ring Power Corp. Act iv i ty : The Sect ion toured the Ocala maintenance facility and observed submerged arc welding re- pairs.

• ATLANTA MARCH 16 Speaker: K e i t h S h a v e r , R o b e r t Bi tzky and B r a n C r a n f o r d . Affil iation: ESAB Group. Topic:Welding in NASCAR. Activi ty: T o m F l y n n was awarded a Certificate of Appreciation.

68 I JUNE 2000

AWS Vice President Bill Myers, left, with AWS Vice President Ernest Lev- err, center, and Olean-Bradford Sec- tion Chairman Rich DePue.

Registration at the Baton Rouge Section's Open Vendor Night.

Northeast Tennessee Chairman Dan Mobley, right, presenting Mark Richey with a speaker's gift.

APRIL 20 Speaker: Ben Howe. Affiliation: Kemper, Norcross, Ga. Topic: Air quali ty and smoke removal.

D I S T R I C T 6 Director: Gerald R. Crawmer

Phone: ( 5 1 8 ) 3 8 5 - 0 5 7 0

• OLEAN-BRADFORD MARCH 21 Speaker: E r n e s t D. Levert . Affiliation: Lockheed Martin Mis- siles and Fire Control. Topic:Welding of the International Space Station thermal control units.

D I S T R I C T 7 Director : R o b e r t J . T a b e r n i k

Phone: (614) 488-7913

• COLUMBUS MARCH 9 Speaker: Mike Madsen . Affiliation: Miller Electric Mfg. Co.

Topic:The d e v e l o p m e n t of GTAW inverter power sources.

APRIL 13 Speaker: D o u g l a s K e t r o n , senior eng inee r in arc welding and automation. Affiliation: Edison Joining Technol- ogy Center. Topic: Twin-wire GMAW systems.

D I S T R I C T 8 D i r e c t o r : H a r r e l l E. B e n n e t t

Phone: ( 4 2 3 ) 4 7 8 - 3 6 2 4

• HOLSTON VALLEY DECEMBER 7, 1999 Speaker: J o h n Abbit t . Affiliation:Thermal Dynamics. Topic: Plasma arc cutting processes.

MARCH 7 Speaker: Jerry Sullivan, welding instructor. Affiliation: Tennessee Technical Center. Topic:Welding Education in North- east Tennessee and Southwest Vir- ginia.

APRIL 4 Speaker: L o r e n T h o m a s , production manager. Affiliation: Shot-Doc, Inc. Topic: Lean manufac tur ing processes.

• CHATTANOOGA MARCH 16 Activity: The Sect ion hos ted Stu- dents ' Night for s tudents in welding programs in 12 area vocational

and high schools.Approximately 90 students from schools inTennessee, Georgia and Alabama at tended the event.

• NORTHEAST TENNESSEE MARCH 21 Speaker: D o u g J o h n s o n , recruiter, and M a r k R i c h e y , Sect ion education commit tee chairman. Affiliation: Hobart Inst i tute of Welding Technology and Northeast Tennessee Section, respectively. Topic: Educational opportunit ies in welding.

APRlL 18 Speaker: Steve Mize. Affiliation:Air Products. Topic:Advances in industrial shielding gases.

• NORTHEAST MISSISSIPPI MARCH 23 Activity:The Section held a dinner mee t ing and toured the Kerr- McGee facility in Hamilton, Miss.

APRIL 20 Activity: The Sect ion toured the Taylor Machine plant.

D I S T R I C T 9 D i r e c t o r : O . J . T e m p l e t

P h o n e : ( 2 2 5 ) 3 4 3 - 4 8 0 6

• BATON ROUGE FEBRUARY 24 Activity: The Sect ion held Open Vendor Night, wh ich was spon-


Laura Rilev, &ft, and Jonathan Gib- bon& VICA gold medal winners f o r the Florida Regionals, at the Mobile Section's March meeting.

New Orleans Section Chairman John Bruskotte< left, First Vice Chairman Damon Gerretts, right, and Q&C Chairman Bruce Hallila, second f rom right, with six welding students a t the Section's Students'Night in March.

at tended the meeting.The Mobile Sec- t ion donated $500 toward their trip to the state VICA contest.

New Orleans Section First Vice Chairman Damon Gerrets, left, present ing a speaker's award to Bree Allen.

sored by the American Welding So- ciety Baton Rouge Section, the American Society of Metals and the American Society for Nondestruc- tive Testing.

MARCH 16 Speaker: Larry H e n d e r s o n . Af f i l ia t ion: Weld Testing Labora- tory. Topic: Code review.

• MOBILE MARCH 16 Speaker: Kirk Brownlee . Affil iation: Exxon Mobil. Topic: Special requi rements for welding and materials in equipment in sour service in the p roduc t ion and processing of natural gas. Act iv i ty : Laura Ri ley, postsec- ondary gold w i n n e r in the Florida VICA Regionals, and J o n a t h a n G i b b o n s , high school gold winner,

• NEW ORLEANS MARCH 21 Speaker: Todd Dud- ley, national account manager. Affil iation: C & G Systems. Topic: Automated cutting machines. Activi ty: The meeting was designated Students ' Night. C a l v i n N o r t o n won the 50/50 drawing.

Posing j b r a photo at the Mahoning Valley Section's February meet ing are, f r o m left to right, Chairman Chuck Moore, Dave Hughes, guest speaker Steve Slone, Treasurer Alex Benyo and guest speaker Dave Eick.

APRIL 18 Speaker: Bree Allen, sales manager. Af f i l ia t ion: Niton Corp., Billerica, Mass. Topic:The Niton alloy analyzer.

• PASCAGOULA APRIL 13 Speaker: G r e g o r y Cain, vine president of technical service. Affil iation: Oxylance Corp. Topic: Underwater welding.

D I S T R I C T I 0 Direc tor : Vic tor Y. M a t t h e w s

P h o n e : ( 2 1 6 ) 3 8 3 - 2 6 3 8

• MAHONING VALLEY FEBRUARY 17 Speakers: Steve S lone , district manager, and Dave Eick, distribution manager. Affiliation: Donaldson/Torit. Topic: Dust, fume and mist collec- t ion methods employed in today's workplace.

70 I JUNE 2000

Guest speakers Edwin L. WolJ~ left, and Matthew Fekete, right, at the Clet,e- land Section's March meeting.

Northwestern Pennsylt,ania Secliott Chairman Israel Shabtai, left, present ing a speaker's g i f t to Brian Fowler.

• CLEVELAND MARCH 14 Speakers: E d w i n L. Wolf , CWI/CWE and technical specialist; Matthew Fekete , general manager; and E r n e s t A. Benway , CWI/CWE and technical specialist. Affil iation: Swageok. Topic: Orbital pipe welding and inspection.

• NOKIIiWESrERN PENNSYLVANIA MARCH 21 Speaker: B r i a n F o w l e r , distr ict manager. Affil iation:ABB Inc. Topic: How to find applications for automated welding equipment.

D I S T R I C T I I D i r e c t o r : S c o t t C. C h a p p l e

P h o n e : ( 9 1 3 ) 2 4 1 - 7 2 4 2

• DETROIT APRIL 13 Act iv i ty : The Sect ion hos ted the District 1 1 Quiz the Experts event at the Lansing Michigan Conference Center. The Detroi t Sect ion re- tained the Experts Cup for the third year running. Detroi t Technical Chairman D i c k D u C h a r m e and Sect ion Chairman J i m D o l f i presented quest ions and coached the teams. Special "Expert Certificates," commemora t ive coins and dinners were awarded to the par t ic ipants compliments of the Detroit Section.

Milwaukee Section scholarship u,inners, f r o m left, Shawn Howard, David Freitag and James Klug with instructor Tom Wagner, right.

D I S T R I C T 1 2 Director: Michael D. Kersey

Phone: ( 2 6 2 ) 6 5 0 - 9 3 6 4

• MILWAUKEE MARCH 16 Speakers: Paul Schulz , Rob Stein- s o n and Bob Fe rn i co l a . Aff i l ia t ions: Miller Electric Mfg. Co., The Lincoln Electric Co. and ESAB Welding and Cutt ing Prod- ucts, respectively. Topic:Ask the manufacturer. Act iv i t ies:A vendor panel answered members ' questions regarding their GMAW products. Scholarships were awarded to J o h n S c h w a r t z IV, Pat H u t c h i n s o n , A n g e l Fuen tes , J e f f Beach,James Klug, Shawn Howard and David Freitag.

• UPPER PENINSULA APRIL 1 1 Activities: The Section toured

Bill Mumford preparing to present the trophy for winning the Quiz-the- Experts event to the Detroit Section.

Marinette Casting, Peshtigo,Wis.Vern B lomberg hosted the tour of the custom foundry.The Section also held a Careers in Welding program at NWTC Marinette. Seventy-six students took part in hands-on welding with SMAW, GTAW,, GMAW, oxyfuel cutting and brazing, as well as computer numerically controlled PAC, plastic welding and metallurgy. Officers were elected for the upcoming year, and a presentation was made to Chairman Dale Lang.

D I S T R I C T 1 3 D i r e c t o r : J . L. H u n t e r

( 3 0 9 ) 8 8 8 - 8 9 5 6

D I S T R I C T 14 D i r e c t o r : H i l B a x

Phone : (314) 6 4 4 - 3 5 0 0 , ext. 105

• INDIANA FEBRUARY 8 Speaker: D e n n i s N a n c e , weld ing


Attending the Northern Plain Section's April meeting are, f rom left, David Ly- ness, Joe Johnson, Lee Larson, Blake English, Mick Tronson and Bob Mrack.

Indiana Section guest speaker Den- nis Nance, left, discussing waveform control technology with students.

A r r o w h e a d Section m e m b e r s at the March tour District 15 Direc- tor Jack Heikk inen is at left wi th back fac ing the camera.

instructor. Affiliation: Ivy Tech. Activities: Students ' Night. Section awards were passed out.

• MISSISSIPPI VALLEY MARCH 16 Speaker: Les Ke lehe r , group facili- tator. Affiliation:Wilson Trailers, Moberly, Miss. Activity: The Sect ion rece ived a tour of the Wilson Trailers plant f rom Keleher and Plant Manager C l a r e n c e Dahl .

• ST. LOUIS MARCH 16 Speakers: S u s a n H u r c u l e s , J o e H e l m and Mike Eye. Affiliation: Boeing Aircraft. Topic: Titanium and aluminum alloy welding.

Members of the East Texas Section during the March tour are, First Vice Chair- man Fred Klerekoper, host Don Davis, Just in Hopwood, Andrew Rypkema, Matthew Noel, Larry Lankford, Michael Hildebrant, Raul Gonzalez and Ladd Sheets.

Activity: The Sect ion toured the Boeing facility.

Contest . See s tory on page 60 for details.

D I S T R I C T 1 5 D i r e c t o r : J . D . H e i k k i n e n

P h o n e : ( 2 1 8 ) 7 4 1 - 9 6 9 3

• ARROWHEAD MARCH 15 Speaker: M a r v i n Gus t a f son , president. Aff i l iat ion: North land Machine Inc., Grand Rapids, Minn. Activity: The Sect ion toured the Northland Machine facility and rece ived a special demons t ra t ion of a three-unit GMA welding lathe.

• NORTHERN PLAINS MARCH 16 Activity: The Sect ion held its 5th annual Behind the Mask Welding

APRIL 6 Speaker:Je f f J o h n s t o n , distr ict sales manager. Affiliation: Hypertherm, New Rich- mond, Wis. Topic:The history, development and future of plasma arc cut t ing technology. Activity: Blake E n g l i s h and Mick T r o n s o n were both honored with Section Appreciation Awards, which were p re sen ted by Chairman T i m Schwartz .

D I S T R I C T 16 Direc tor : C. F. B u r g

P h o n e : ( 5 1 5 ) 2 9 4 - 5 4 2 8

• EASTERN IOWA FEBRUARY 1 Topic: Pulse welding from Miller Electric Mfg. Co.

72 I JUNE 2000

Facing the camera are Sa&ine Sectiott members Je f f Fawvor, left, and James A m y at the Section's Ca{fish Fry.

Sacramento Vallel' members Steve Hunter, left, and Dale Rogers, right, taking par t in hands-on welding with guest speaker Richard Lund.

MARCH 7 Speaker: Steve Black. Affiliation: Quad City Testing Lab. Topic: Welding inspection.

D I S T R I C T 1 7 D i r e c t o r : O r e n P. R e i c h P h o n e : ( 2 5 4 ) 8 6 7 - 2 2 0 3

• EAST TEXAS MARCH 23 Act iv i t y : The Sect ion toured the Vertex Communicat ions 'Vertex An- tenna Products Division. D o n Davis hosted the group.

• CENTRAL ARKANSAS APRIL 11 Speaker: Bob Hlass. Affi l iat ion :The Lincoln Electric Co. Topic:Aluminum wire welding. Act iv i ty : Demonst ra t ions of the company's MAG SG Spool Gun.

D I S T R I C T 18 D i r e c t o r : J . M. A p p l e d o r n P h o n e : ( 2 8 1 ) 8 4 7 - 9 4 4 4

• SAN ANTONIO MARCH 9 Speaker: Bil l B r y a n t , safety consultant. Affiliation:Texas Workers' Compen- sation Commission. Topic: OSHA welder safety.

District 19 Director Rich Kellum, left, accepting a speaker's p laque f r o m Puget Sound Section First Vice Chair- man Ken L.Johnson.

• SABINE APRIL 20 Speaker: Mike T o m p l a i t , fabrication manager. Af f i l ia t ion: Newtron Mechanical Contractors. Ac t i v i t y : The Sec t ion toured the Newtron Mechanical Contrac tors ' new fabrication facilities.A catfish fry was held at Weeks Labs af ter the t o u r . J e f f F a w v o r received the Sec t ion ' s Golden Roll Award .The award is the resul t of an ongo ing con t e s t b e t w e e n Fawvor and J a m e s A m y to see w h o cou ld ga the r the most d inne r ro l l s .The members had a lot of fun with the con t e s t and fo resee it b e c o m i n g an annual compet i t ion .

San Francisco Section Treasurer Sharon Jones wi th gues t speaker Simon Engel at the April meeting.

D I S T R I C T 19 D i r e c t o r : D. H. D e l k

P h o n e : ( 9 0 7 ) 5 5 2 - 6 9 7 4 • PORTLAND APRIL 4 Speaker: P h i l l i p M. F o r m e n t o , territory sales manager. Aff i l iat ion: ESAB Welding and Cut- ting Products. Topic: Advantages of n e w f lux cored welding wires and how they affect welding production. Activi ty: District 19 Director R i c h K e l l u m presented the AWS Merito- r ious Award to R i c k R ice for outstanding contr ibutions of time and effort for the Section.

• PUGET SOUND APRIL 6 Speaker: Rich K e l l um , owner and District 19 director. Affi l iat ion:Willamette Welding Sup- ply and AWS, respectively. Topic:The care and maintenance of welding machines.


Activity: Kel lum p r e s e n t e d Dis t r ic t C e r t i f i c a t e A w a r d s to S h a w n Mc- D a n i e l , M i k e W e a v e r a n d C h r i s S u n d b e r g .

DISTRICT 20 Director: Nei l R. Kirsch

P h o n e : ( 9 7 0 ) 8 4 2 - 5 6 9 5

DISTRICT 21 D i r e c t o r : F. R . S c h n e i d e r P h o n e : ( 6 1 9 ) 6 9 3 - 1 6 5 7

• HAWAII APRIL 19 Act i v i t y :The S e c t i o n h e l d a soc ia l m e e t i n g .

DISTRICT 22 D i r e c t o r : M a r k B e l l

P h o n e : ( 2 0 9 ) 3 6 7 - 1 3 9 8

• SACRAMENTO VALLEY FEBRUARY 17 Speaker: R i c h a r d L u n d , t e c h n i c a l r e p r e s e n t a t i v e . Aff i l iat ion :The Linco ln Elect r ic Co. Topic: GMAW, FCAW - - v a r i o u s m o d e s of t r a n s f e r a n d f e r r o u s a n d n o n f e r r o u s base meta ls . Act i v i t y :The t e c h n i c a l d i s c u s s i o n was f o l l o w e d by h a n d s - o n w e l d i n g o p p o r t u n i t i e s w i t h t h e l a t e s t Lin- co ln Elect r ic w i r e f eed e q u i p m e n t .

• SAN FRANCISCO APRIL 5 Speaker: S i m o n L. E n g e l , p r e s i - den t . Affi l iat ion: HDE Techno log ie s , Inc. Topic: Prec i s ion laser sys tems.

S E C T I O N E V E N T S

C A L E N D A R

• COLUMBUS JUNE 8 Act iv i t y :Annual G o l f O u t i n g w i t h ASM. For f u r t h e r i n f o r m a t i o n or r e s e r v a t i o n s , c o n t a c t T o m K u n t z - m a n , C o l u m b u s Sec t ion Cha i rman , at (614) 274-1128.

S T U D E N T A C T I V I T I E S

M e m b e r s o f the Madison Area Technical College S tuden t Chapter dur ing their tour o f the John Deere Horicon Works plant.

:E' 77 Tmam mm

D a v i d Lapinsky, left, a s s i s tan t director o f Lehigh Career and Techni- cal Ins t i tu te , w i th contes t w i n n e r s Will Henninger , center, a n d Troy Heiser

D I S T R I C T 3 D i r e c t o r : C l a u d i a B . K a u f m a n

P h o n e : ( 8 0 0 ) 2 2 6 - 9 9 3 9

• LEHIGH CAREER AND T E C H N I C A L INSTITUTE MARCH 7 Act iv i t ies : L e h i g h C a r e e r a n d Tech- n i c a l I n s t i t u t e s t u d e n t m e m b e r s w o n t h e AWS a n d VICA w e l d i n g con- t e s t s . T r o y H e i s e r w o n t h e g o l d m e d a l in Dis t r i c t 11 VICA Skills USA a n d W i l l H e n n i n g e r w o n t h e L e h i g h Val ley S e c t i o n 2 0 0 0 W e l d i n g C o n t e s t . T h e S t u d e n t C h a p t e r fabr i - c a t e d a b i c y c l e r a c k fo r S h e r w o o d Park in Hanover , Pa.

Lehigh Valley Section Foundation Rep- resentative John Johnston's grand- daughter p lays on the bicycle rack made by the Student Chapter f o r Sher- wood Park in Hanover, Pa.

DISTRICT 12 D i r e c t o r : M i c h a e l D . K e r s e y

Phone: ( 2 6 2 ) 6 5 0 - 9 3 6 4

• MADISON AREA T E C H N I C A L COLLEGE FEBRUARY 22 Act iv i t y : T h e C h a p t e r t o u r e d t h e J o h n D e e r e H o r i c o n Works . G a r y R u d e n a n d t h e p l a n t ' s V i s i to r ' s Ser- v i ces Off ice g u i d e d t he tour .

74 I JUNE 2000

• 1999-2000 Member-Get-A-Member Campaign The f o r m a t f o r r ec ogn i z i ng p a r t i c i p a n t s in the A WS M e m b e r - G e t - A - M e m b e r c a m p a i g n h a s c h a n g e d f r o m a p o i n t s s y s t e m to t h a t o f

a s y s t e m w h e r e m e m b e r s are recogn i zed f o r the a c t u a l n u m b e r o f m e m b e r s they sponsor. C a m p a i g n categor ies are o u t l i n e d on p a g e 65

o f this issue. I f y o u h a v e a n y q u e s t i o n s r e gar d ing y o u r m e m b e r p r o p o s e r p o i n t s , p l e a s e cal l the M e m b e r s h i p D e p a r t m e n t a t ( 8 0 0 ) 4 4 3 - 9 3 5 3

ext. 269.

Winner's Circle ( I n d i v i d u a l s s p o n s o r i n g 2 0 o r m o r e n e w m e m b e r s b e g i n n i n g J u n e 1, 1999 . )

J. Compton, S a n F e r n a n d o Val ley - - 44 N. C.WaI1, S o u t h F l o r i d a - - 42 E. H. Ezell, M o b i l e - - 31

B.A. Mikeska, H o u s t o n - - 24 W. L. Shreve, F o x V a l l e y - - 22 R.Wray, N e b r a s k a - - 21

President's Guild ( I n d i v i d u a l s s p o n s o r i n g 2 0 o r m o r e n e w m e m b e r s b e t w e e n J u n e 1, 1999 , a n d M a y 31, 2 0 0 0 . )

J. C o m p t o n , S a n F e r n a n d o Val ley - - 44 N. C.Wall, S o u t h F l o r i d a - - 42 E. H. Ezell, M o b i l e - - 31

B.A. Mikeska, H o u s t o n - - 24 W. L. Shreve, F o x V a l l e y - - 22 R.Wray, N e b r a s k a - - 21

President's Roundtable ( I n d i v i d u a l s s p o n s o r i n g 1 1 - 1 9 n e w m e m b e r s b e t w e e n J u n e 1, 1999 , a n d M a y 31, 2 0 0 0 . )

R. L. Peaslee, D e t r o i t B & S - - 16 W. R. Beck, R o c h e s t e r - - 12

G.W.Taylor, P a s c a g o u l a - - 11

President's Club ( I n d i v i d u a l s s p o n s o r i n g 6 - 1 0 n e w m e m b e r s b e t w e e n J u n e 1, 1999 , a n d

M a y 31, 2 0 0 0 . )

J. M. D e D e a u x , M o b i l e - - 10 W. S t u r g e , N e w Y o r k - - 10 R.J. Davis, N e w O r l e a n s - - 8

P. Baldwin, P e o r i a - - 8

R. Morgan, N o r t h w e s t O h i o - - 8

J.J. Daugherty, L o u i s v i l l e - - 7

E A . J u c k e m , M a d i s o n - B e l o i t - 7

J.T. Merzthal, P e r u - - 7

R. Purvis, S a c r a m e n t o - - 7

E. S. Ruiz, P u e r t o R i c o - - 7

P. G. Childers, O k l a h o m a C i t y - - 6

R. L. Fidge, B a t o n R o u g e - - 6

J.Jones, N o r t h T e x a s - - 6

E. D. Levert, N o r t h T e x a s - - 6

J. H. Neal, E a s t e r n C a r o l i n a s - - 6

H.T.Timmerman, C e n t r a l T e x a s - - 6

S. O. Ufuah, N e w Y o r k - - 6

S. R. Zwilling, L o u i s v i l l e - - 6

President's H o n o r Roll ( I n d i v i d u a l s s p o n s o r i n g 1 - 5 n e w m e m -

bers b e t w e e n J u n e 1, 1999, a n d M a y 31, 2000 . O n l y t h o se s p o n s o r i n g 2 or m o r e A W S R e g u l a r M e m b e r s are l is ted.)

K. M.Ali, S a u d i A r a b i a - - 5

S.Anderson, C o l u m b u s - - 5

R.J.Auciello, W o r c e s t e r - - 5

R. Bergeron, M o r g a n C i t y - - 5

E E. Blake, S a g i n a w V a l l e y - - 5

C. L. Graves, D e l a w a r e - - 5

P. O'Lear~,Eastern I d a h o / M o n t a n a - - 5

J. G. Pierce, C o l u m b u s - - 5

J. Saucier, P a s c a g o u l a - - 5

M. R.Tryon, U t a h - - 5

EJ.Wernet, L e h i g h V a l l e y - - 5

G. W o o m e r , J o h n s t o w n - A l t o o n a - - 5

C. Burrell, S o u t h F l o r i d a - - 4

W. M. Engeron, S r . , A t l a n t a - - 4

D. Fairchild, H o u s t o n - - 4

H.Jackson, L A . / I n l a n d E m p i r e - - 4

C. Lauridsen, H o r i d a S p a c e C o a s t - 4

R. L. Ledford, Jr., B i r m i n g h a m - - 4

H. R. M a d r o n , M a r y l a n d - - 4

W. L. Shreve, N o r t h w e s t O h i o - - 4

R. Zabel, S o u t h e a s t N e b r a s k a - - 4

A. M.Ali, C o l u m b u s - - 3

B.A. Bernstein, P u e r t o R i c o - - 3

C.A. C a s t i l l e , J r . , A c a d i a n a - - 3

A. L. Castro, P u e r t o R i c o - - 3

C.T. Corey, N o r t h e r n N Y - - 3

L. DeFreitas, S a n t a C l a r a V a l l e y - - 3

W. G a k v t y Jr.,Long B c h / O r a n g e Cn ty - - 3

G. Gavela, L . A . / I n l a n d E m p i r e - - 3

R. Grays, K e r n - - 3

P.T.Jacques, P o r t l a n d - - 3

W. H. Kielhorn, E a s t T e x a s - - 3

J. Knapp, T u l s a - - 3

O. C. Kooi, M a l a y s i a - - 3

E. H. Ley, P i t t s b u r g h - - 3

G. E. Mayfield, T u l s a - - 3

W. P. Mi l ler , J r . , N e w J e r s e y - - 3

J.W. Morris, M o b i l e - - 3

S. L. Petty, P e o r i a - - 3

J. D. Sanders, H o u s t o n - - 3

R.J. Samanich, N e v a d a - - 3

C. E Schiner, W e s t e r n M i c h i g a n - - 3

A.T. Sheppard, C l e v e l a n d - - 3

G. Sinkule, N o r t h e r n M i c h i g a n - - 3

J. H. S m i t h , J r . , M o b i l e - - 3

J. K. Smith, T r i - R i v e r - - 3

B. H. Suckow, N o r t h e r n P l a i n s - - 3

M. Uddin, P a k i s t a n - - 3

R.Worden,Jr., W a s h i n g t o n , D . C . - 3

T. R.Alberts, S o u t h w e s t V i r g i n i a - - 2

J. N. Carney, W e s t e r n M i c h i g a n - - 2

J. Chaparro, M e x i c o - - 2

B.A. Chin, B i r m i n g h a m - - 2

D.V. Day, C o r p u s C h r i s t i - - 2

H.W. Ebert, N e w J e r s e y - - 2

J.A. Grantham, C o l o r a d o - - 2

A. D. Grayson, N o r t h w e s t - - 2

D. L. Hatfield, T u l s a - - 2

J. P. Hennessy, F o x V a l l e y - - 2

D. L. Horsman, T u l s a - - 2

J.W.Jaeger, S o u t h e r n C o l o r a d o - - 2

K. E.Johnson, O l e a n - B r a d f o r d - - 2

R. S.Johnson, D e t r o i t - - 2

S. E.Johnson, C e n t r a l T e x a s - - 2

D. Klingman, C l e v e l a n d - - 2

J. Koster, W e s t e r n M i c h i g a n - - 2

S. K. C. Liu, C o l o r a d o - - 2

J.A. Livesay, N a s h v i l l e - - 2

H.V. McRae, N e w Y o r k - - 2

M.V. Medrano, S a n D i e g o - - 2

G.Menser , L o n g B c h . / O r a n g e C n ~ - - 2

P. Mulville, S o u t h e r n C o l o r a d o - - 2

T.J. Murphy, C a n a d a - - 2

N. Nakwek, T h a i l a n d - - 2

D.A. Nance, I n d i a n a - - 2

T. L. Newman, T r i - R i v e r - - 2

E. E. Norman, O z a r k - - 2

J. Norris, S a n g a m o n V a l l e y - - 2

R. Norris, M a i n e - - 2

T. S. Nottingham, P u g e t S o u n d - - 2

D.W. Parker, I d a h o / M o n t a n a - - 2

J. L. Padilla, M e x i c o - - 2

J. Pelster, S o u t h e a s t N e b r a s k a - - 2

J. E. Pernell, L . A . / I n l a n d E m p i r e - - 2

M. D. Pittman, S h r e v e p o r t - - 2

M. R. Pointer, S i e r r a N e v a d a - - 2

G.A. Rubino, V e n e z u e l a - - 2

T. Searcy, S a n F e r n a n d o V a l l e y - - 2

O. G. Shair-Ali, S a n F r a n c i s c o - - 2

C. D. Smith, M o b i l e - - 2

A.W. Steven, M e m p h i s - - 2

M. D. Swigart, D a y t o n - - 2

M.Tait, L . A . / I n l a n d E m p i r e - - 2

C.-L.Tsai, T a i w a n - - 2

E.Wells, P a s c a g o u l a - - 2

D.J.Wohfeil, D e t r o i t - - 2

D.A.Wright, K a n s a s C i t y - - 2

Student S p o n so rs ( I n d i v i d u a l s s p o n s o r i n g 3 or m o r e A W S S t u d e n t M e m b e r s are l is ted.)

H.Jackson, L . A . / I n l a n d E m p i r e - - 53 D. M. Boldt, P o r t l a n d - - 41 K. R. Geist, P u g e t S o u n d - - 31 R. E. Durham, L o u i s v i l l e - - 24 J. G. Owens, B a t o n R o u g e - - 24 P. Blaldwin, P e o r i a - - 22 D.A. Ketler, W i l l a m e t t e V a l l e y - - 21

- - continued oll page 76

WELDING JOURNAL 175

T E C H N I C A L C O M M I T T E E M E E T I N G S

All A W S technical c o m m i t t e e mee t ings are open to the public . Persons w i s h i n g to

a t t e n d a m e e t i n g s h o u l d c o n t a c t the s t a f f secre tary o f the c o m m i t t e e , as l is ted

below, a t AWS, 5 5 0 N. W. LeJeune Rd., M i a m i , FL 3 3 1 2 6 , t e l e p h o n e ( 3 0 5 ) 443-

9353.

June 7, Safety and Health Committee. Pittsburgh, Pa. Standards preparat ion meeting. Staff contact: S. P. Hedrick.

June 13-14,A9B Subcommit tee on the Exchange of Welding Information. Boulder, Colo. Standards preparation meeting. Staff contact:J. L. Gayler.

June 15, B5C Subcommit tee on Welding Engineers. Miami, Fla. Standards preparation and general meeting. Staff contact: J. L. Gayler.

June 16-17, B5 Committee on Qualification. Miami, Fla. Standards preparation and general meeting. Staff contact:J. L. Gayler.

June 22- 23, A 10C Subcommittee on Resistance Welding Processes. Boulder, Colo. Standards preparation meeting. Staff contact: C. B. Pollock.

N O T I C E S A W S w a s a p p r o v e d as a n accred i t ed s t a n d a r d s - p r e p a r i n g o r g a n i z a t i o n by the

A m e r i c a n N a t i o n a l S t a n d a r d s Ins t i t u t e (ANSI) in 1 9 7 9 . A WS rules, as a p p r o v e d

by ANSI, requ ire t ha t all s t a n d a r d s be open to p u b l i c r e v i e w f o r c o m m e n t during the a p p r o v a l process . This c o l u m n also a d v i s e s o f A N S I a p p r o v a l o f docu-

m e n t s . The f o l l o w i n g s t a n d a r d s are s u b m i t t e d f o r p u b l i c r e v i e w . A copy m a y

be o b t a i n e d by s e n d i n g the a m o u n t s h o w n to A W S Techn ica l Dept. , 5 5 0 N. W.

LeJeune Rd., M i a m i , FL 33126 , or by cal l ing (800 ) 334-9353.

ISO S t a n d a r d s f o r P u b l i c R e v i e w

ISO/DIS 9013, T h e r m a l Cu t t ing - - Classi f icat ion o f T h e r m a l Cuts - - Geomet r i - cal P r o d u c t Speci f icat ion a n d Q ua l i t y Tolerances. Standard. $6.75. ]ANSI Public Review expires June 30, 2000.]

ISO/DIS 17653, Des t ruc t i ve Tests on Welds in Metal l ic M a t e r i a l s - - Torsion Test

o f Res i s t ance Spo t Welds. Standard. $2.00. [ANSI Public Review expires June 30, 2000.]

ISO/DIS 17654, D e s t r u c t i v e Tests o n Welds in M e t a l l i c M a t e r i a l s - - I n t e r n a l Pressure Test on C o n t i n u o u s S e a m Welds. Standard. $1.75. [ANSI Public Review expires June 30, 2000.]

N e w S t a n d a r d s A p p r o v e d b y ANSI:

B5.9:2000, Speci f icat ion f o r the Qua l i f i ca t ion o f Weld ing Supervisors . Approval date:April 13, 2000. •

• 1 9 9 9 - 2 0 0 0 M e m b e r - G e t - A - M e m b e r C a m p a i g n

--cont inued f rom page 75

D. Serrano, P u e r t o R ico - - 21 K. S. Sabo, T r i S t a t e - - 20 M. R.Anderson, I n d i a n a - - 19 P. G.Walker, O z a r k - - 18 A. Reis, P i t t s b u r g h - - 16 K.A. Ellis, M a r y l a n d - - 15 T. C. Murrow, A r i z o n a - - 15 D.J. Roskiewich, P h i l a d e l p h i a - - 15 A.J. Badeaux, W a s h i n g t o n D.C. - - 14 T. Geisler, P i t t s b u r g h - - 14 E Mong, P i t t s b u r g h - - 14 D. Marks, L e h igh Valley - - 13

J. H. Smith, Jr., M o b i l e - - 13 E. Spalding, W i l l a m e t t e Valley - - 14 C. E. Kipp, L eh igh Valley - - 11 S. Mackenzie,Northern Michigan - - 11

W. P. Miller, Jr., N e w J e r s e y - - 11 J. Pelster, S o u t h e a s t N e b r a s k a - - 11 J. R. Cox , N o r t h e r n P l a i n s - - 10 A. P.Joseph, C o l u m b u s - - 10 R. Zabel, S o u t h e a s t N e b r a s k a - - 10 A. Baughman, S t a r k Cen t ra l - - 9 T. Storey, Utah - - 9 S. C.Tarnow, N e w J e r s e y - - 9 B. Huff, S a n g a m o n Valley - - 8 W. Sturge, L o n g I s l a n d - - 8 M. E.Tait, L . A . / I n l a n d E m p i r e - - 8

J. Compton , San Fernando Valley - - 7 J.A. Livesay, N a s h v i l l e - - 6 K. E. Sameulson, A l b u q u e r q u e - - 6 S. P. Siviski, M a i n e - - 6 R. Grays, K e r n - - 5 S. Green, N o r t h Texas - - 5 R. L. Ledford,Jr., B i r m i n g h a m - - 5 A. H. Price, H o u s t o n - - 5 T. Searcy, S a n F e r n a n d o Valley - - 4 S.Tennant, L a k e s h o r e - - 4 S. L. Belles, D e l a w a r e - - 3 J. N. Carney, Western M i c h i g a n - - 3 H. Elton, W y o m i n g - - 3 H. Erb, Chicago - - 3 S. E. Hall, R i c h m o n d - - 3 C.A. Hobson, O l y m p i c - - 3 A. Honegger, L A . / In land Empire - - 3

EA. J u c k u m , M a d i s o n - B e l o i t - 3 A. O. Ochoa, S a n Franc i sco - - 3 J. Pernell, L . A . / I n l a n d E m p i r e - - 3 R~ Shook, Eastern Idaho/Montana - - 3 T. Schwanz, N o r t h e r n P l a i n s - - 3

R. E.Tupta,Jr., M i l w a u k e e - - 3 D.Vinson, P h i l a d e l p h i a - - 3 Ricky Walburn, T w i n Tiers - - 3

E. J. Warren, Colorado - - 3 C.Wesley, N o r t h w e s t e r n Pa. - - 3 •

CTotal AWS Members as o f M a y 1, 2 0 0 0

50,809

76 I JUNE 2000

G U I D E T O A W S S E R V I C E S

P h o n e ( 8 0 0 ) 4 4 3 - 9 3 5 3 ; T e l e x 5 1 - 9 2 4 5 ; FAX ( 3 0 5 ) 4 4 3 - 7 5 5 9 I n t e r n e t : w w w . a w s . o r g

P h o n e e x t e n s i o n s a p p e a r i n p a r e n t h e s e s .

AWS PRESIDENT

L.William Myers,Welding Engineer Dresser-Rand

Olean Operations PO. Box 560, Paul Clark Dr.

Olean, NY 14760

ADMINISTRATION

Executive Director Frank G. DeLaurier, CAE (210)

Deputy Executive Directors Richard D. French (218) Jeffrey R. Hufsey (264)

John J. McLaughlin (235)

Assistant Executive Director Debbie A. Cadavid (222)

Director of Quality Systems Linda K.Williams (298)

Corporate Director of Finance/Comptroller Frank R.Tarafa (252)

INFORMATION SERVICES

Corporate Director Joe Cilli (258)

HUMAN RESOURCES

Director Luisa Hernandez (266)

INTERNATIONAL INSTITUTE OF WELDING

Information (294)

Provides l ia ison act ivi t ies involv ing o the r profess ional soc ie t i es and s tandards orga- nizat ions, nat ional ly and internationally.

GOVERNMENT LIAISON SERVICES

Hugh K. Webster Webster, Chamberlain & Bean

Washington, D.C. (202) 466-2976

FAX (202) 835-0243

Ident i f ies sources of funding for we ld ing e d u c a t i o n and r e sea rch & d e v e l o p m e n t . Monitors legis la t ive and regula tory issues impor tan t to the industry.

WELDING EQUIPMENT MANUFACTURERS COMMITTEE

Associate Executive Director Richard L.Alley (217)

INDUSTRY ACTION COMMITTEE

Associate Executive Director Charles R. Fassinger (297)

COMMUNICATIONS

Corporate Director, Communications Nannette M. Zapata (308)

Corporate Director of Administrative Services Jim Lankford (214)

Corporate Director of Marketing Technical Services Division

Debrah C.Weir (279)

P romotes Socie ty p r o g r a m s and act ivi t ies to AWS m e m b e r s , t h e w e l d i n g c o m m u - n i ty and the genera l publ ic .

CONVENTION & E X P O S m O N S Exhibiting Information (221, 256)

Managing Director Tom L. Davis (231)

Organizes the week-long annualAWS Inter- na t iona l Weld ing and Fabr ica t ing Exposi- t ion and Conven t ion . Regula tes space as- s ignments , registrat ion materials and o ther Expo activities.

PUBLICATION SERVICES Division Information (348)

Managing Director Jeff Weber (246)

WELDING JOURNAL

Publisher Jeff Weber (246)

Editor Andrew Cullison (249)

National Sales Director Rob Saltzstein (243)

WELDING HANDBOOK

Welding Handbook Editor Annette O'Brien (303)

Pub l i shes AWS's m o n t h l y magaz ine , the Welding Journal, w h i c h provides informa- t ion on the s ta te of the w e l d i n g industry, its t e c h n o l o g y and Society act ivi t ies . Pub- l i shes the Welding H andbook and books on general weld ing subjects.

MEMBER/CUSTOMER SERVICES Department Information (261)

Managing Director Cassie R. Burrell (253)

Assistant Director Rhenda A. Mayo (260)

Serves as a liaison between Section members and AWS headquarters. Informs members about AWS benefits and other activities of interest.

CERTIFICATION PROGRAMS/ BUSINESS DEVELOPMENT

Director Anna Petroski (481)

Director of Int'l Business Development Walter Herrera

For customized certification and educational programs to industry and government.

EDUCATION

Director James R. Cunningham (219)

Information on education products, projects and programs. CWI, SCWI and other seminars designed for assistance in Certification. Re- sponsible for the S.E.N.S.E. beginning welder program and dissemination of education information on the Web.

CONFERENCES

Director GiseUe I. Rodriguez (278)

Responsible for national and local conferences, seminars, individual corporate programs and home study courses on industry topics rang- ing from the basics to the leading edge of technology.

CERTIFICATION Information and application materials on cer- tifying welders, welding inspectors and edu- cators. (273)

Managing Director Wendy S. Reeve (215)

Awards & Fellows

Managing Director Wendy S. Reeve (215)

Coordinates awards and AWS Fellow nominees

TELEWELD

FAX: (305) 443-5951

For information about AWS technical publications, contact the Technical Services personnel listed below.

TECHNICAL SERVICES

Department Information (340)

Managing Director William R. Oates (299)

Leonard P. Connor (302) Standards Activities Director, Qualification, Inspection, Food

Processing Equipment

Andrew R. Davis (466) International Standards Program Manager, Welding in Marine

Construction

Stephen P. Hedrick (305) Safety and Health Manager, SylrdDols and Definitions

Engineers

Hardy H. Campbell III (300) Structural

Rakesh Gupta (301) Filler Metals

(~lristopher B. Pollock (304) Brazing, Soldering, Testing, Railroads, Computerization,

Instrumentation

Tim Potter (309) Robotics,Joining of Metals and Alloys, Piping and Tubing,

Friction Welding

Melvin O. Kulp (314) Oxyfuel GasWelding & Cutting,Arc Welding and Cutting, Machinery

and Equipment,Welding Iron Castings

John L Gayler (472) Metric Practices, Sheet Metal, Plastics and Composites, Personnel Qualification


ORDER DEPARTMENT (800) 334-9353 (305) 443-9353

Publication orders. Seminar and conference registrations.

Ed E Mitchell (254)Thermal Spray, High- Energy Beam Welding and Cutting, Re-

sistance Welding, Automotive, Aerospace

Senior Publ icat ions Coordinator

Rosalinda O'Neill (451)

AWS publishes more than 160 volumes of material, including standards that are used throughout the industry.

With regard to technical inquiries, oral opinions on AWS standards may be rendered. However, such opinions represent only the personal opinions of the particular individuals giving them.These individuals do not speak on behalf of AWS, nor do these oral opinions constitute official or unofficial opinions or interpretations of AWS. In addition, oral opinions are informal and should not be used as a substitute for an official interpretation.

It is the intent of the American Welding Society to build the Society to the highest quality standards possible. We welcome any suggestions you may have.

Please contact any of the staff listed on the previous page or AWS President L. William Myers, Welding Engineer, Dresser- Rand, Olean Operations P.O. Box 560, Paul Clark Dr., Olean, NY 14760.

AWS FOUNDATION, INC.

550 N.W. L e J e u n e Rd. Miami , FL 3 3 1 2 6 (305) 4 4 5 - 6 6 2 8

(800) 443-9353 , ext . 293 Or e-mail: b o b w @ a w s . o r g

C h a i r m a n , Board o f T r u s t e e s R o n a l d C. P i e rce

E x e c u t i v e D i r e c t o r F rank G. DeLaur ier , CAE

D i r e c t o r o f D e v e l o p m e n t R o b e r t B .Wi the re l l

T h e A W S F o u n d a t i o n is a n o t - f o r - p r o f i t c o r p o r a t i o n

e s t a b l i s h e d t o p r o v i d e s u p - p o r t f o r e d u c a t i o n a l a n d

s c i e n t i f i c e n d e a v o r s o f t h e A m e r i c a n W e l d i n g S o c i e t y .

I n f o r m a t i o n o n g i f t - g i v i n g p r o g r a m s is a v a i l a b l e

u p o n r e q u e s t .

• N o m i n e e s for N a t i o n a l Of f i ce Only Susta ining Members , Members , Honora ry Members , Life M e m b e r s or Ret ired

M e m b e r s w h o have b e e n m e m b e r s for a pe r i od o f at leas t t h r ee years shall be eligible for e lec t ion as a Direc tor o r National Officer.

It is the duty of the National Nominat ing Commi t t ee to nomina te candidates for national off ice.The commi t t ee shall hold an open meet ing , preferably at the Annual Meet- ing, at which members may appear to present and discuss the eligibility of all candidates.

To be cons idered a candidate for pos i t ions of President ,Vice Pres ident ,Treasurer or Director-at-Large, the following qualifications and condit ions apply:

P res iden t :To be el igible to ho ld t he off ice o f P res iden t , an ind iv idua l m u s t have se rved as a Vice Pres iden t for at least one year.

Vice P re s iden t :To be e l ig ible to ho ld t h e off ice o f Vice P re s iden t , an ind iv idua l m u s t have s e r v e d at leas t o n e year as a Director , o t h e r t h a n Execu t ive Di rec to r an d Secretary.

T reasu re r :To be el igible to h o l d t h e of f ice o f Treasurer , an ind iv idua l m u s t b e a m e m b e r o f t he Society, o t h e r t h a n a S tudent Member , m u s t be f requen t ly available to t h e Nat iona l Off ice and s h o u l d be o f e x e c u t i v e s t a tu s in b u s i n e s s o r i n d u s t r y w i t h e x p e r i e n c e in f inancial affairs.

Director-at-Large:To be eligible for elect ion as a Director-at-Large, an individual shall previous ly have he ld office as Cha i rman of a Section; as Cha i rman or Vice Cha i rman of a standing, technical or special commi t t e e of the Society; or as District Director.

In te res ted par t ies are to s end a let ter s ta t ing w h i c h par t icular office t hey are seek- ing, i n c l u d i n g a s t a t e m e n t o f qua l i f ica t ions , t he i r w i l l i n g n e s s and abi l i ty to s e rv e if n o m i n a t e d and e lec ted and 20 cop ies o f the i r b iographical sketch.

Th i s mate r ia l s h o u l d be s en t to Rober t J .Teuscher , Cha i rman , Nat iona l Nomin a t - ing C o m m i t t e e , A m e r i c a n Welding Society, 550 N.W. LeJeune Rd., Miami, FL 33126.

The n e x t m e e t i n g o f t he Nat ional N o m i n a t i n g C o m m i t t e e is cu r r en t ly s c h e d u l e d for May 1 ,2001, in Cleveland, O h i o . T h e t e r m s of office for cand ida t e s n o m i n a t e d at this m e e t i n g will c o m m e n c e June 1 ,2002. •

• H o n o r a r y - M e r i t o r i o u s Awards

The Honorary-Meritorious Awards Commit tee has the duty to make recommendat ions regarding nominees presented for Honorary Membership, National Meritorious Certificate, William Irrgang Memorial and the George E. Willis Awards. These awards are presented in conjunction with the AWS Exposition and Convention held each spring. The descriptions of these awards follow, and the submission deadline for consideration is July 1 prior to the year of presentation. All candidate material should be sent to the attention of John J. McLaughlin, Secretary, Honorary-Meritorious Awards Committee, 550 N.W. LeJeune Road, Miami, FL 33126.

N a t i o n a l M e r i t o r i o u s Cer t i f ica te Award: This award is g iven in r e c o g n i t i o n o f t he cand ida te ' s counse l , loyalty and devo t ion to t he affairs o f t h e Society, a s s i s t ance in p r o m o t i n g cordial relat ions wi th indus t ry and o t h e r o rganiza t ions , and for t he con- t r i bu t ion o f t ime and effor t on b e h a l f o f the Society.

W i l l i a m I r r g a n g M e m o r i a l A w a r d : This award is administered by the American Weld- ing Society and sponsored by The Lincoln Electric Company to hono r the late William Irrgang. It is awarded each year to the individual w h o has done the m o s t to e n h a n c e the Amer ican Welding Society's goal o f ad- vanc ing t he s c i ence and t e c h n o l o g y o f welding over the past five-year period.

George E. W i l l i s A w a r d : This award is a d m i n i s t e r e d by t h e A m e r i c a n W e l d i n g Soc ie ty a n d s p o n s o r e d by T h e L inco ln Elec t r ic C o m p a n y to h o n o r G e o r g e E. Willis. It is awa rded each year to an indi- v idua l for p r o m o t i n g t h e a d v a n c e m e n t o f w e l d i n g i n t e r n a t i o n a l l y by f o s t e r i n g c o o p e r a t i v e p a r t i c i p a t i o n in a reas s u c h as t e c h n o l o g y t ransfe r , s t a n d a r d s rat iona l i z a t i on a n d p r o m o t i o n o f i n d u s t r i a l goodwil l .

International Meritorious Certificate Award: This award is given in recogni t ion of the candidate 's significant cont r ibut ions to the wor ldwide we ld ing industry. This award shou ld ref lect "Service to the Inter- national Welding Communi ty" in the broad- est t e r m s . T h e awardee is no t r equ i red to be a m e m b e r of the Amer ican Welding So- ciety. Multiple awards can be given pe r year as the situation dictates.The award consists o f a cer t i f icate to be p r e s e n t e d at t h e award 's l u n c h e o n or at ano the r t ime as appropriate in conjunct ion wi th theAWS Pres- ident 's travel itinerary, and, if appropriate, a one-year m e m b e r s h i p to AWS.

Honorary M e m b e r s h i p Award: An H o n o r a r y M e m b e r shal l be a p e r s o n o f a c k n o w l e d g e d e m i n e n c e in t h e w e l d i n g profess ion , or w h o is acc red i t ed w i t h ex- cep t iona l a c c o m p l i s h m e n t s in t he devel- o p m e n t o f t h e w e l d i n g art , u p o n w h o m t h e A m e r i c a n Weld ing Socie ty sees fit to c o n f e r an h o n o r a r y d i s t i n c t i o n . A n Hon- o r a r y M e m b e r sha l l h a v e full r i g h t s o f m e m b e r s h i p . •

78 I JUNE 2000

EDUCATION INDUSTRIAL TECHNOLOGY TECHNICAL I

AUTHOR APPLICATION FORM

82nd Annual AWS Convention, Cleveland, Ohio May 6.10, 2001

Please complete both front and back of this form legibly This completed form is to accompany the 300-500 word summary described on the back.

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PROPOSED TITLE (10 words or less):

P l e a s e c h e c k a p p r o p r i a t e c l a s s i f i c a t i o n : Research -Or ien ted - - n e w sc ience or n e w research. This pape r p resents new, unpub l i shed work in sc ience or eng inee r ing in jo in ing or a l l ied p rocesses .

_ A p p l i e d Techno logy - - n e w or un ique appl ica t ion. This pape r app l ies known pr inc ip les of jo in ing sc ience or eng inee r ing in a un ique, unpub l i shed appl icat ion. Educa t ion - - we ld ing educa t ion - re la ted topic. For, about , or per ta in ing to we ld ing educa to rs and t ra iners at al l levels, the i r me thods , and the i r successes.

Is this pape r an or ig inal cont r ibu t ion? Yes Is this paper a p rogress repor t? Yes Is this paper a rev iew? Yes Is this paper a tutor ia l? Yes Wha t are the we ld ing process(es) used? Wha t are the mater ia ls used?

No No No No

The main emphas i s is more [3 p rocess o r ien ted or [3 mater ia ls or ien ted The industr ies this paper mos t app l ies to are

KEY WORDS: Please rank the top four in order of importance (i.e., 1 = most important; 2 = second most important, etc.): _ _ GTAW _ _ Hard fac ing _ _ P ip ing/Tub ing _ _ G M A W _ _ The rma l Spray ing _ _ Pressure Vesse ls

S M A W C-Mn Stee ls Weld Process S imu la t ion _ _ SAW _ _ Cr -Mo Stee ls _ _ Process Cont ro l /Mon i to r ing _ _ PAW _ _ H igh-St rength Stee ls _ _ Weld Des ign Adv isors _ _ FCAW _ _ Sta in less Stee ls _ _ Numer ica l Ana lys is _ _ ESW _ _ AI-AIIoys _ _ Res idua l St ress/Dis tor t ion _ _ EBW _ _ Ni-AIIoys _ _ Frac tu re /Fa t igue _ _ LBW _ _ Ti-AIIoys _ _ Au toma t i on _ _ Res is tance Weld ing _ _ Cu-AI Ioys _ _ Robot ics _ _ Forge Weld ing _ _ A d v a n c e d Mater ia ls _ _ Sensors _ _ Frict ion Weld ing _ _ Po lymer i c Mater ia ls _ _ Arc Phys ics _ _ Dif fusion Weld ing _ _ Ceramics _ _ Cor ros ion _ _ Braz ing /So lder ing _ _ C o n s u m a b l e s / F l u x e s _ _ NDE _ _ Sur fac ing /C ladd ing _ _ Weldab i l i t y Test ing _ _ Other

for AWS use: I T E

Author(s) of Proposed Paper:

Paper Title:

Summary Code: (for AWS use only)

I N T E N D E D AUDIENCE: (please check) Q Technical/Research-Oriented (3 Applied Technology - Industrially-Oriented (3 Welding Education-Oriented

GUIDELINES FOR SUMMARY: TECHNICAL PAPERS

Each summary for a technical paper should be divided into four main sections: • Introduction/Background Section (100 words max.)

Why the work was done, e.g. build on previous work, test/validate previous work; what is the "starting point;" how it relates to previous work and by whom; list key references.

• Procedure Section (100 words max.) Detailed (data base) description of approach and why this approach was taken.

• Results and Discussion Section (200-300 words max.) Detailed description of results with emphasis on

* what was found * why the results are "new" or original; what is added or what is corrected * why the results are of value

Inclusion of up to two pages of tables, graphs or diagrams is encouraged. • Conclusion Section (100 words max.) Summary of main conclusions and recommendations for continuing work. Compare results with premise or hypothesis; if premise was proven wrong, say so!

GUIDELINES FOR SUMMARY: OTHER PAPERS ( INCLUDING TUTORIALS) Summaries for other types of papers should be divided into two main sections:

• Introduction/Background Section (400 words max.) This section should begin with a description of why a paper or tutorial in this field is of value to the welding community, highlighting specific communities (if appropriate) for which this work is targeted. Once this has been established, the author should describe key work in this field including a brief description of the results obtained and the conclusions drawn for each reference (if appropriate) and provide the audience with an integration of these separate activities into a "continuum."

• Conclusion Section (100 words max.) This section should reiterate the key areas of value for this paper and provide guidance on the usage of this information - - how and by whom.

_ Type, 1.5 spaced, using a 12-pitch element or a minimum 10 point font. The summary must not be less than 300, but not more than 500, words. Please attach to this completed form and return to the address below. Email submissions must include the information requested on this form.

Be sure to give enough information to enable the review committee to get a clear idea of the content of the proposed paper. Please remember your intended audience. Technical papers will be judged on technical merit. A paper should not emphasize product names; use eeneric terms after the first mention of a trade-named product.

_ Application Form and Summary MUST be postmarked no later than July 17, 2000 to ensure consideration for inclusion in the Professional Program of the 82nd Annual AWS Convention in Cleveland.

Recognizing that the audience will be largely American, the use of "customary U.S. units" is recommended for the presentation; the written version of the paper should report in units used in the work, but should consider including the "customary U.S. equivalents" to facilitate understanding.

_ Applications may also be by fax (305-442-7451). An application may also be obtained by visiting our website at <www.aws.org>.

PRESENTATION AND PUBLICATION OF PAPERS: _ Has material in this paper ever been previously published or presented in a meeting? Yes __ No __

When and where? _ Papers accepted for presentation become the property of the Society with original publication rights assigned to the

Welding Journal. You may elect to submit your paper to Peer Review for publication in the Welding Journal Research Supplement.

Author's signature Date

Return this form, completed on both sides, with the 300--500 word summary to Technical Papers Editor, AWS Headquarters, 550 N. W LeJeune Road, Miami, FL 33126. MUST BE POSTMARKED NO L A T E R T H A N J U L Y 17, 2 0 0 0 .

Aut

Moving to Robotics, a Company Attains the Productivity It Needs

F or more than 20 years, Metex Corp. in Edison,

N.J., has been supplying exhaust system parts to automakers and tier two and three suppliers. Re- cently, the company won a new contract to manufacture exhaust system joints. Getting this business required the company to produce several hundred thousand of these new joints per year. Not only were production volumes high but so were the stringent quality requirements from the customer. So, the company turned to robotics.

"When we first looked into this project, we knew welding would be an important parameter to produce the final part," Kurry Emmons, the company's director of research and development, said. "We hadn't done this type of gas metal arc welding in any high volumes in the past. Also, because the component is part of the emissions control system, we had tight standards to adhere to in terms of leakage and durability."

Fig. 1 - - The coupling, which is composed of 304 stainless steel, consists of a 1.5-mm-wall pipe with a 2.0-mm flange welded around it.

To start, Metex identified several key characteristics that had to be present in the finished weld. The first was to create a leak- free weld - - something vital, considering how this new part fits into the design.

This new part is a unique flexible coupling that allows the exhaust system to flex with body vibration and engine torque without damage throughout the life of the vehicle. The part, which is composed of 304 stainless steel, consists of a 1.5-mm-wall pipe with a 2.0-mm flange welded around it - - Fig. 1. When later assembled with a proprietary seal, springs, nuts and bolts, the finished joint attaches the front and rear sections of the exhaust system.

Traditionally, the majority of leakage from the exhaust system comes from this sealed flange interface or other flex points in the system that this design eliminates. Therefore, if there were any imperfections in the weld, it could easily account for leakage. For this reason, the consistency and integrity of the weld were critical.

On one sport utility vehicle application, the height of the vehicle made portions of the exhaust system exposed, so the man-

Based on a story from The Lincoln Electric Co., Cleveland, Ohio.

ufacturer required good weld aesthetics.

Another challenge in welding this part was heat input. The weld is near the spherical sealing surface, so any excess heat put into the weld could distort the two flanges that form the sealing surfaces. This distortion could impact the sealing ability of the joint. In addition, excessive heat input from the weld on this type of stainless exhaust component can contribute to carbide precipi tat ion in the heat-affected zone (HAZ) and eventual failure of the part. For these reasons, the company knew it had to minimize the amount of heat input during welding, without sacrificing bead appearance.

Finally, the weld had to be free of spatter. Any spatter on the bearing surface on which the shoulder bolt and spring rest would interfere with the ability of the bolt and spring to seat properly.

After reviewing the requirements, Metex officials narrowed the options to either a robotic system or a fixturing system and began to call on potential suppliers.

The company chose a tabletop robotic welding unit from Lin- coln Electric and FANUC Robotics: the ARC Mate 50iL in combination with an inverter power source that utilizes surface tension transfer (STF), a variation of the gas metal arc welding (GMAW) process. The ARC Mate 50iL is a six-axis, electric servo-driven robot with a 3-kg-payload arm. The power source's STT capability is designed to reduce spatter, which suits the spatter-free welding needed for the new exhaust system part.

The robot has two identical sets of tooling, each able to hold six parts, mounted on a high-speed indexing table. This means the operator can unload and load six parts while the machine is welding six parts, increasing production volumes. There is also a zero defect rate.

Before installing the robot, the company sent three people to attend a two-day training course at Lincoln's Automation Di- vision in Cleveland, Ohio.

"Initially we had a learning curve because this was a brand- new process to us," said Sal Pizzi, manager of manufacturing engineering. "But after we made some adjustments, the robot now runs 16 hours per day on two shifts, enabling the company to achieve its production volumes."


Industr ial Robots: N u m b e r s and A t t i t u d e s

According to the Handbook of Industrial Robotics, recently published by John Wiley and Sons, between 1980 and 1996 the number of robots per 10,000 manufacturing employees sky- rocketed - - from 8.3 to 265 in Japan, 2 to 79 in Germany, 3 to 38 in the United States and 0 to 98 in Singapore. In roughly the same time frame, the world robot population surged, from about 35,000 in 1982 to 677,000 in 1996 and an estimated 950,000 in 2000. From 1992 to 1997, the North American robot population shot up 78%, from 46,000 to 82,000.

With more and more robots in industry, people's attitudes toward them are changing, according to Shimon Nof, the Hand- book's editor and engineering professor at Purdue University. "The fear that robots would replace workers has completely dis- appeared," he said. Instead of displacing large numbers of employees, robots have brought about a more highly trained work force better capable of running robots and computers.

And, for welding, that work force running robots also needs welding knowledge on top of computer and electronics skills, according to Lou DeFreitas, director of training at the Arc Gas Training Institute, Redwood City, Calif. "Let's face it. A computer programmer who only knows computers is not going to be able to program a robot as well as a welder" trained in programming, he said.

If robots are to continue to increasingly benefit industry, researchers have some obstacles to overcome. "Some new challenges for robotics researchers are better human-robot collaboration interfaces, robot mobility and navigation in unknown surroundings and better robot intelligence for services and for public transportation," Nof said.4

Diode -Pumped Laser Has Mult ip le Modes

The 100-W multimode and 20-W single-transverse-mode Q- switch, 1-micron Scimitar T M laser is diode pumped. It is a candi-

date for micromachining, welding, cutting, ablating, drilling, fast laser marking, engraving, sintering and other machining needs. The unit outputs approximately 40 W of green light. With laser beam welding, no working parts come in contact with the material--just a beam of light. It also offers improved weld penetration. Laser cuts usually do not require postprocessing.

Cutting Edge Optronics, inc. 20 Point West Blvd., St. Char les, M O 63301

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82 I JUNE 2000


I

Updated to meet today's tough quality requirement,, AWS Committee on Methods of Inspection

P.A. Grimm, Chair R. D. McGuire, I stVice Chair

E. D. Levert, 2nd Vice Chair

L. P. Connor, Secretary W. Borges* C. R. Brashears* W.A. Bruce E. L. Crisculo* C.J. Hellier* R. L. Holdren D. L. Isenhour*

J.W. OverT* K. Zerkle

Modern Welding Company National Board of Boiler

& PressureVessel Inspectors Lockheed Martin Missiles

and Fire Control American Welding Society Consultant Alyeska Pipeline Service Co. Edison Welding Institute Consultant Rockwood Service Corp. Edison Welding Institute Newport News Shipbuilding

& Dry Dock Co. Babcock & Wilcox Construction Hobart Institute

This Committee, along with these Team members, also produced Guide for the Visual Examination of Welds.

Guide ~ tire . . . . ViSUal E ~ m l n a t w " d welds

R. Brosilow Welding Design and Fabrication P. E. Deeds, Jr.* Consolidated Edison Co. of

New York L. Laime* Consultant W. C. Minton* Consultant M. N. Pfeiffer* Consultant A. G. Portz* Consultant S.J.Walmsley* S.J.Walmsley and Associates

*Advisor

Guide for the Nondest ruct ive Examinat ion of We lds Tells you which NDE method is best for detecting categories of discontinuities and defects. ANSI approved. 48 pages.

B1.10:1999 . . . . . . . . . . $72 AWS Members . . . . . . . $54

Guide for the Visual Examinat ion of We lds Hem's the first update of this AVVS guidebook in a decade with 48 photos and figures that sharply focus the characteristics of porosity, incomplete fusion, undercut, laminations, cracks, spatter, melt-through and other discontinuities. ANSI approved. 33 pages.

B I. I 1:2000 . . . . . . . . . .$72 AWS Members . . . . . . . $54

ORDER TODAY! CALL (800) 334-WELD. HAVE YOUR AWS MEMBER NUMBER, CREDIT CARD OR P.O. NUMBER READY. CREDIT CARD ORDERS ARE SECURE ON WWW.AWS.ORG

American Welding Society 550 NW LeJeune Rd., Miami, FL 33126 http://www.aws.org

Call (800) 334-9353 or use the secured server at www.aws.org to order ANSI-approved standards

Recommended Practices for Automotive Weld Quality Resistance Spot Welding Developed through the AWS/SAE Joint Committee on Automotive Welding to assist automotive parts suppliers using bare and coated low carbon steels. Tables provide minimum spot weld spacing, contact overlap and minimum weld diameter. Concise 6 pages serve as a quality checklist. Rearmed 1994. ANSI Approved. D8.7-88R .............................. $32 AWS Members ...................... $24

Specification for Automotive and Light Truck Weld Quality: Arc Welding The AWS/SAE Joint Committee on Automotive Welding defines the practical tolerances needed to

achieve satisfactory weld quality for production volumes associated with automotive structural parts. Includes welding of uncoated carbon steels (including HSLA) that do not require preheat or postheat. Limits are set for various types of discontinuities along with an illustrative schematic example. 13 figures, 10 pages. Published in 1997. ANSI Approved. D8.8-97 ................................ $32 AWS Members ...................... $24

Recommended Practices for Test Methods for Evaluating the Resistance Spot Welding Behavior of Automotive Sheet Steel Materials This publication will help predict the performance of all kinds of sheet steel when resistance spot welded for use in auto manufacturing. Mso addresses equipment setup, electrode installation and dressing, electrode endurance testing, and current level and range assessment. 56 pages, with 12 tables, 31 figures and 3 annexes 8 1/2" x 11", and softbound. Published in 1997. ANSI Approved. 08.9-97 .................................. $44 AWS Members ........................ $33

HEW Specification for Resistance Welding of Carbon and Low-Alloy Steels Provides for a quality program covering the minimum shear strength and weld button diameter requirements for carbon

and low-alloy steel sheet resistance and projection welds. Produced by the AWS Committee on Resistance Welding and the Task Group on Resistance Welding of Coated and Uncoated Carbon and Low-Alloy Steels, it is intended to replace MIL-W-12332A, MIL-W-45223A and MIL-W- 46154. Covers surface conditions, part fit-up, welding procedure and welding equipment requirements, pre- and production requirements, and safety and health. 6 tables, 5 figures, 20 pages. ANSI Approved. C1.4M/C1.4:1999 . . . . . . . . . . . . . . . . . . . . . $32 AWS Members . . . . . . . . . . . . . . . . . . . . . . . . $24

~, ~ . ~ = . , r , ~ The Resistance I Professional's Welding 1 Advisor @ : on Resistance

Welding This 5 1/2" x 8 1/2" spiral-bound book accompanies the busiest professionals on resistance welding worksites. 9 chapters address welding definitions, resistance welding electrodes, spot and seam welding parameters, multiple thickness combinations, projection and flash welding, defects and their causes in resistance welding, testing, and safety/health precautions for resistance welding, and more. Chapters are tabbed for quick access. 73 pages. Published in 1998. PARW .................................... $52 AWS Members ........................ $39

HEW Recommended Practices for Resistance Welding New release --just issued. First complete update in 30 years. 114 pages. Cl.IM/CI.I:2000 . .$52 AWS Members . . . . . $39

Order today. Call (800 ) 3 3 4 - 9 3 5 3 m have your AWS number, PO or credi t card ready. Credit card orders are secure on www.aws.org.

< ~ A.__mericanWelding Society 550 NW LeJeune Rd., Miami, FL 33126

Q: w e are beginninga program on brazing of aircraft parts of d i f ferent sizes and masses in a furnace wi th a vacuum a tmosphere . H o w fast can parts be heated within the furnace?

A : Since you will be brazing different parts of different sizes and masses, it is not possible to give a definitive answer. Each part is a beast unto itself and goes its own way, regardless of what it is told it should like. Therefore, you must take cues from each part i t s e l f - - its dimensions, mass, complexity; also, how much difference is there in metal thickness in various locations of the assembly? The answer to each of these questions will have a bearing on the allowable heating and cooling rate of the part.

The first thing to look at is distortion. We often hear people say the part will distort in the furnace because there are many welding, machining or forming

stresses. While there may be a lot of stress on the part, if the part is heated and cooled using the proper furnace cycle, there will be little or no distortion of the part. The main cause of distort ion is the differential temperatures throughout the part. First, look at the part and try to understand from its shape what differential tempera ture it can tolerate. If brazing a stator assembly consisting of heavy inner and outer bands, with very lightweight veins in between and the blades tacked in place, the part must be heated much slower than, for example, a small 2-in. round fuel nozzle assembly. Being small and fairly uniform in thickness, the fuel noz-

Fig. 1 Temperature, "C

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oy ?roducts N I C R O B R A Z ® Filler Metals

• T h e s e are the o r ig ina l and bes t k n o w n nickel- a l based brazing filler metals. A variety of c ompos i t i ons are ava i l ab l e to m e e t ~ i n d u s t r y spec i f i ca t ions , _.~ inc luding AMS, AWS, and ~-~__, (~. " ~"" ~+ G.E. Our Nicrobmz products are a v a i l a b l e in p o w d e r , pas t e , r o d a n d t ape .

Nicrobraz products from atttomotive to aerospace.

F o r i n f o r m a t i o n o n C o l m o n o y o r N i c r o b r a z , c i r c l e t h e r e a d e r c a r d n u m b e r o r c a l l 2 4 8 - 5 8 5 - 6 4 0 0



zle assembly can be heated as fast as the furnace can go up to heat. The heating rate will depend on the size and shape of the part.

When in doubt as to how the part is going to respond to heating, put thermocouples on the areas that will be the hottest and the coolest. The coolest part is going to be the heaviest section, most likely where it is sitting on the support- ing fixture. The hottest part is going to be the thinnest area, near the elements of the furnace, where the radiant heat

can strike the thin section. The next problem is how to thermocouple parts.

Thermocoupling of parts to get the proper information feedback is more difficult than one might suspect. Fre- quently, the thermocouple is made by twisting the two ends of an alumel/chromel couple together, then melting the end into a bead and placing it at the work area. Unfortunately, when the leads are twisted, the temperature is not read at the bead end but instead at the last twist away from it. It is therefore

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desirable to butt-joint weld the two ends of the thermocouple together with as small a bead as possible, making this the only area where the thermocouple wires touch. This junction can then be wired to the part and a small piece of insulat- ing material placed on top of it. This way, the junction does not see the radiant heat from the elements, but gets the heat directly from the part.

If the separate wires of the thermocouple can be welded to the part, making the part the junction of the thermocouple, this will give the best results for many applications. In other parts where there are drilled holes, it may be possible to put the thermocouple in the hole, not allowing the leads to touch the sidewalls but allowing the junction to touch the bottom of the hole. When this is not possible, it may be necessary to use blocks of metal simulating the thickest and thinnest sections and tack weld thermocouples to each of these pieces for use as an indicator.

Another technique for obtaining more uniform heating of a complicated shape part is to put a heat shield around, and sometimes cover the top of the part, so the part cannot see the direct radiant heat from the elements. This will tend to slow the heating and provide more uniformity of temperature throughout the part. In heating of stainless steel parts, the problems are less than when heating alloys such as 410 stainless steel and the carbon steels, as those base metals can be hardened and have a transformation with a change in volume around the 1300-1400°F (704-760°C) range. For example, if brazing a 410 stainless steel to a thick, heavy flange on the inside of a tube, the thin stainless steel tube can start to transform and shrink, while the heavier material on the inside is still expanding, causing a stretching of the outer tube during the heating cycle. When the part gets up to the brazing temperature, the outer thin tube is going to be larger than when it was assembled, so the clear- ance is now excessive. This is particularly true if the part is 12 in. in diameter. The braze may pull the thin tube into the flange, for most of the circumference, but at some point there will be an un- brazed area that is some distance away from the flange. In such a case, a heat shield is definitely in order. It may also be necessary to hold off just before the transformation temperature, go through the transformation more slowly and then speed up heating to get to the brazing temperature in a reasonable time.

While the heating must be considered in the brazing cycle, the most critical portion of the cycle, as far as distortion is concerned, would be the cooling cycle.

86 I JUNE 2000

If a complex part, such as the stator assembly mentioned earlier, with a nickel filler metal is being brazed at 1950°F (1051°C) and the fan is turned on while the filler metal is still molten, the blades will cool very rapidly compared to the heavy inner and outer band, which can cause cracking at the braze joint by liquid metal embrit t lement. Therefore, in such a case, it is necessary to furnace cool the part to below the solidus temperature of the brazing filler metal to ensure the part is not highly stressed before the filler metal is solid. If the fan is turned on at this point, again the blade is going to cool much more rapidly than the heavy section and will therefore get shorter as it cools down. While the big bands are hot and the joint solid brazed, the blade would be stretched. When the part gets down to room tempera ture and all the parts are the same temperature , the blade being stretched has to bow or it will rotate the inner band so the blades are no longer perpendicular to the sidewalls of the band. Again, a heat shield with a cover may be the best method of han-

dling it, or it may be that the part is so complex that it will be necessary to program the furnace to cool the part down below 1500 or 1000°F, depending on the hardness requirements.

As you can see, the part controls the heating and cooling cycle, the material it is made from, the size, the shape, the difference in thickness of the metals, etc., all have a profound effect on the cycle that must be developed. Unfortunately, it is very hard to think like a part in the furnace. Going up and coming down in temperature , the thermocouples will have to give a better idea of how the part is actually responding to the furnace cycle used.

To help understand the effect of the differential temperature , Fig. 1 shows the differential tempera ture allowable at various temperatures during the heating or cooling cycle. The curve for each base metal indicated is the point at which the yield strength of the base metal is reached, and, if exceeded, the part will be stretched, thus resulting in distortion when the part is cooled to room temper-

ature. Unfortunately, we do not have data for all base metals and, specifically, there is less data available at the higher temperatures. This is because the steel companies obtain data only up to the highest service temperature the base metal will see, and brazing often exceeds this temperature , sometimes by hundreds of degrees.

Unfortunately, after sitting down and trying to outguess the part and program a cycle, one must run a part and see if the cycle developed is acceptable. In many cases for complex parts, the part does not agree with the engineering selected; thus, to braze the part without distortion, the cycle must be corrected, either at the high- temperature area or at the transformation. As is often pointed out, if the part distorts, the proper furnace cycle for that specific part was not provided. Then, it's back to the drawing board to correct it and provide a cycle the part will accept with an extremely small amount or no distortion of the assembly. •

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I

N E W S T A N D A R D O N R E S I S T A N C E W E L D I N G

Specification for Resistance Welding of Carbon and Low-Alloy Steels A brand new AWS standard, Specification for Resistance Welding of Carbon and Low-Alloy Steels, provides

for a quality program covering the minimum shear strength and weld button diameter requirements for

carbon and low-alloy steel sheet resistance and projection welds. Produced by the AWS Committee on

Resistance Welding and the Task Group on Resistance Welding of Coated and Uncoated Carbon

and Low-Alloy Steels it is intended to replace MIL-W-12332A, MIL-W-45223A and MIL-W-46154. Covers

surface conditions, part fit-up, welding procedure and welding equipment requirements, pre- and

production requirements, and safety and health. ANSI Approved.

AWS Committee on Resistance Welding

P. G. Harris, Chair W. H. Brafford, I stVice. Chair B.J. Bastian, 2nd Vice Chair T. R. Potter, Secretary J. C. Bohr R. K. Cohen S.A. D'Angelo D. E. Destefan* P. Dent R.J. Gasser* J. M. Gerken R. C. Gill P. Howe* R.W.Jud M. Kimchi J.W. Lee D. L. OIson* J. P. Osborne M. Prager* W. E Quails WT. Shieh

Centerline Welding, Limited CMW, Inc. Benmar Associates American Welding Society General Motors Corp. WeldComputer Corp. Mercury Aircraft, Inc. High Current Technologies, Inc. Northrop Grumman Corp. Consultant Consultant General Motors Corp. Bethlehem Steel Corporation Chrysler Corp. Edison Welding Institute Allied Signal Aerospace Colorado School of Mines Ford Motor Company Welding Research Council Valiant International, Inc. Lockheed Martin Corp.

AWS Task Group on Resistance Welding of Coated and Uncoated Carbon and Low-Alloy Steels

Specification for Resistance Welding of Carbon and Low-Alloy Steels C 1.4/C 1.4M: 1999

Nonmember . . . . . . . . . . . $32

AWS Members . . . . . . . $24

W H. Brafford, Chair T. R. Potter, Secretary J. C. Bohr R.A. Bonneau S.A. D'Angelo P. Dent W. E Quails

CMW, Inc. American Welding Society General Motors Corp. US Army Research Laboratory Mercury Aircraft, Inc. Northrop Grumman Corp. Valiant International, Inc.

*Advisor

If you'd like to serve on an AWS Committee, go to www.aws.org/technical/comm_form.html to electronically complete an application or call (800) 443-9353 ext. 340

ORDER TODAY! CALL (800) 334-WELD. HAVE YOUR AWS MEMBER NUMBER, CREDIT CARD OR P.O. NUMBER READY. CREDIT CARD ORDERS ARE SECURE ON WWW.AWS.ORG

~ American Welding Socioty 550 NW LeJeune Rd., Miami, FL 33126 http://www.aws.org

Q&A Q: I 'm trying to qualify several procedures to repair weld C A - 6 N M valve body castings with 4 1 0 N i M o f i l l e r m e t a l . A hardness requirement of 22 Rockwell C m a x i m u m in the weld meta l and H A Z must be met . This hardness l imit is turning out to be a serious problem. I 've tr ied a n u m b e r of stress-relief t empera - tures, f rom I I00°F to as high as 1350°F, but I can't get the hardness down. In fact, stress rel ief at the higher temperatures seems to make the weld harder than stress relief at lower temperatures . W h a t can be done to get the hardness down?

A : The 22 Rockwell C hardness limitation probably means the casting is intended for corrosive service. The Na- tional Association of Corrosion Engi- neers (NACE) recommends such hardness limits for corrosive service, such as sour gas or sour crude oil. The CA-6NM casting and the 410NiMo filler metal are compositionally very similar and are often selected for sour service. See ASTM A743 for composition limits for the CA-6NM casting, AWS A5.4 for composition limits for 410NiMo covered electrodes, AWS A5.9 for limits for bare wires and AWS A5.22 for limits for flux cored wires. It will be instructive to compare these sets of limits, as shown in Table 1.

The main problem, as regards softening by postweld heat treatment (PWHT), is the nickel content of the casting and

the filler metals. The approximately 4% nickel in the casting and filler metals reduces the temperature at which austenite begins to form during heating. In an ordinary carbon steel, austenite begins to form when the temperature rises to about 1330°F (720°C). In a nickel-free 12% chromium martensitic stainless steel, such as 410 or CA-15, chromium raises the temperature at which austenite begins to form to about 1440°F (780°C). Therefore, these 12% chromium steels can be postweld heat treated at temperatures of 1350°F (730°C) or even a bit higher, and they are easily softened to below 22 Rockwell C.

But the 4% nickel in the CA-6NM or 410NiMo changes everything. Nickel is a powerful promoter of austenite. It reduces the temperature at which austen- ire begins to form at slightly above 1150°F (620°C). If tempered at a higher temperature, some austenite will form. The higher the temperature, the more austenite will form. Then, when the "stress-relieved" weldment is cooled back to ambient temperature, this austenite transforms to fresh, untem- pered martensite, which is hard. If you choose a "stress-relief" temperature at which the weldment is partially austenite and partially martensite, only the portion of the microstructure that remains martensite will be softened. Then the measured macroscopic hardness at ambient temperature is a composite of the softer tempered martensite and the harder fresh martensite.

The solution lies in a double temper- ing heat treatment. The first temper is done at a temperature at which the weld-

Table 1 - - Composition Limits

Material ASTM A743 AWS A5.4 AWS A5.9 AWS A5.22 CA-6NM E410NiMo-XX ER410NiMo E410N iMoTX-X

C, % 0.06 0.06 0.06 0.06 max. max. max. max.

Mn, % 1.00 1.0 0.6 1.0 max. max. max. max.

P, % 0.04 0.04 0.03 0.04 max. max. max. max.

S, % 0.03 0.03 0.03 0.03 max. max. max. max.

Si, % 1.00 0.90 0.5 1.0 max. max. max. max.

Cr, % 11.5 to 14.0 11.0 to 12.5 11.0 to 12.5 11.0 to 12.5 Ni, % 3.5 to 4.5 4.0 to 5.0 4.0 to 5.0 4.0 to 5.0 Mo, % 0.40 to 1.0 0.40 to 0.70 0.4 to 0.7 0.40 to 0.70

ment microstructure is approximately half austenite and half martensite, 1250°F (675°C), for two hours at temperature. This tempers the martensite portion of the microstructure. Cooling to ambient temperature causes the austenite portion of the microstructure to transform to fresh martensite. This cooling is essential to complete the transformation of the austenite - - in fact, refrigeration to dry ice or even liquid nitrogen temperature has been used in some cases to complete the transformation. After cooling, a second temper, at l140°F (615°C), will soften the fresh martensite. Since the temperature is lower for this second temper, a longer time is needed, typically four hours.

There are some composition effects worthy of consideration. Note the silicon limits for the various filler metals in Table 1. ER410NiMo has a lower silicon limit than the covered electrodes and flux cored wires. Silicon is known to increase resistance to softening in PWHT. Achievement of the 22 Rock- well C limit may hinge on keeping the silicon low (_< 0.4%). The silicon in the covered electrodes and flux cored wire may or may not be low. This should be discussed with your electrode supplier.

Another consideration is tramp elements in the weld metal. Slag systems in the welding electrode based on titanium dioxide produce residual titanium in the weld metal. Also, titanium dioxide, as the mineral rutile, generally contains vanadium as an impurity. Both vanadium and titanium in the weld metal make the softening of the weld metal in PWHT more difficult. If shielded metal arc or flux cored arc welding, try to select electrodes with slag systems that are metallurgically basic (low in TiO2). For gas metal arc or gas tungsten arc welding, the ER410NiMo does not normally contain significant Ti and V tramp elements. If ER410NiMo is to be used in submerged arc welding, choose a flux low in TiO 2 and discuss this flux selection with the technical department of your flux supplier.

Q: I 'm planning a field repair that will involve both 304L-to-304L joints and 304L-to-structural -steel joints. To avoid mix-ups, I'd like to have only one e lectrode on the job site. Can 309L electrodes be used for both joints?

W E L D I N G J O U R N A L I 8 9

iterature For more information, circle number on Reader Information Card.

Literature Presents Cut- Resistant Gloves and Sleeves

The literature features the company's cut-resistant product lines for applications where the user requires dexterity and tactile feel, yet needs protect ion from cuts and lacerations. The literature also includes the company's complete line of steel gloves and sleeves. Built to be comfortable and flexible, yet ex- t remely cut-resistant, these FDA- accepted gloves offer an advanced construction of double stainless steel fila- ments wrapped around a tough polyester core, with no exposed steel ends to irri- tate the user.

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117

Datasheet Presents Inverters

A four-page datasheet provides complete information and specifications on the company's family of six inverter resistance welding controls, suitable for both spot and seam applications. Fea- tured are the two newest additions to the product range - - one features forging, chaining and successive capabilities, and the other features three different feedback modes: constant power, constant voltage and constant current. The datasheet also offers a comprehensive section on the use of inverter technology and an explanation of the closed-loop feedback process utilized by this family of controls. Selection considerations, models and breakdown comparisons are specified on an easy-to-read chart.

Miyachi Corp. 245 E. El Notre St., P.O. Box 5039 Monrovia, CA 91016

118

Brochure Addresses Industrial Design and Application

Industrial Personal Computers - - De- signed and Bui l t f o r the Plant Floor is a brochure that addresses industrial computer design and application. The brochure provides information on how and why the company's rugged, high-per-

formance industrial PCs are designed for manufacturing environments. Included is an industrial computer checklist that identifies various industrial requirements and how the company's products meet those requirements. Some requirements identified in the checklist are resistance to foreign contaminant penetration, use in hazardous locations (explosion protection) and vibration and shock-loading resistance.The brochure also addresses the evolution of soft logic, which has enabled the growth of runtime and control development tools for open PC-based systems.

Xycom Automation, Inc. 750 N. Maple Rd., Saline, MI 48176-1292

119

Brochure Highlights Portable Machine Tools

A ten-page, full-color brochure covers the company's wide range of standard por table machine tools for flange facing, milling, drilling, boring and valve

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Global Machine Technology 10123 Tanner Rd., Houston, TX 77041

120

Brochure Features Earmuff Hearing Protection

An eight-page, ful l-color brochure details the features and benefits of the company's line of earmuffs for versatile and effective hearing protection. High- lighted is the company's radio earmuff,

c o n ~ n u e d o n p a g e 9 4

A: The potential mix-up problem lies in using the 308L filler metal, which is normally used for 304L-to-304L joints, on a 304L-to-structural steel joint. The 308L filler metal is not rich enough in alloy content to compensate for normal dilution from the structural steel side. As noted in a previous column, such a weld is likely to contain no ferrite, with resulting hot-cracking tendencies, and/or may contain martensite, which makes the weld metal brittle. So 308L filler metal is not recommended for joining 304L to structural steel.

Type 309L filler metal is usually chosen for joining 304L to structural steel. The real question here is whether or not it is also suitable for the 304L-to-304L joints. The only concern would be exposure to temperatures above 1000°F (540°C). A single-pass deposit of 309L on 304L would probably be okay. But I would caution against using the 309L filler metal for multipass welding of 304L if the weldment is to see such high temperatures. The potential problem is that the combinat ion of higher chromium and ferrite content in the 309L filler metal makes the weld metal susceptible to embri t t lement at high temperatures, due to formation of sigma phase (an iron-chromium intermetallic compound) where the ferrite was.

On the other hand, if the weldments are not to experience high-temperature exposure, then 309L filler metal should be quite acceptable for the 304L-to-304L joints. In fact, the AWS D1.6:1999 Struc- tural Welding Code - - Stainless Steel con- siders 309L filler metal to be prequalified for use in 304L-to-304L joints that are to be exposed to normal atmospheric corrosion. This prequalification is based upon the filler metal at least matching the mechanical properties of the base metal and having adequate resistance to normal atmospheric corrosion. Further- more, since the chromium and nickel con- tents of the 309L are higher than those of the 304L, service of the 309L filler metal in aqueous environments should also be more than adequate. •

DAMIAN J. KOTECKI is Technical Director for Stainless and High-Alloy Product Development for The Lincoln Electric Co., Cleveland, Ohio. He is a member of the AWS A5D Subcommittee on Stainless Steel Filler Metals; A W S D1 Structural Welding Committee, Subcommittee on Stainless Steel Welding; and a member and past chair of the Welding Research Council Subcommittee on Welding Stainless Steels and Nickel Base Alloys. Questions may be sent to Mr. Kotecki c/o Welding Journal, 550 N. IV.. LeJeune Rd., Miami, FL 33126.

90 l JUNE 2000

A MANTECH Center Of Execellence

I Center Operated bY ~I['~E

White Named A W S Congressional Fellow

T he American Welding Society (AWS), partnering with the Navy Joining Center, continues its efforts to provide the government with advice on engineering matters and

policies affecting the public interest. This helps to maintain a climate of understanding and credibility that fosters continuing dialogue with the government. As part of these efforts, AWS has named Matthew W. White as its Congressional Fellow for fiscal year 2001.

As a Congressional Fellow, White will assist legislators and officials of Congress in deliberations on engineering matters and policies affecting the public interest. Public policy issues affecting a broad constituency are increasingly based on technological factors and require input from the engineering profession, among others.

A native of Worthington, Ohio, White has more than 15 years of experience in the welding industry and an M.S. degree in welding engineering from The Ohio State University. He currently manages business development for the Edison Weld- ing Institute's (EWI) Government Programs Office. In this role, he is liaison with various government agencies, including the Departments of Defense, Energy, Transportation and Com- merce. He has also worked on a variety of efforts between AWS and EWI to launch projects to raise awareness of welding issues and develop and launch approaches by which the cause of welding can be advanced.

"It has become clear to me that welding is an underappreci- ated discipline, requiring its own representation," White said. White said the Congressional Fellow program offers a unique opportunity for him to work at a national level to create a greater understanding of the importance of welding and joining to U.S. industry, ultimately leading to increased public interest. White will serve a one-year term beginning in September.

The program's objective is to provide assistance to Congress while representing the welding engineering profession. As part

of the Congressional Science and Engineering Fellowship Pro- gram of the American Association for the Advancement of Sci- ence (AAAS), the AWS and AWS/ASM Congressional Fel- lowship programs will continue the advances made by other as- sociations in educating members of Congress to the over- whelming need for scientific research and investment.

For additional information on White's appointment, please contact Matt White at (614) 688-5241 or by e-mail at [email protected]; for additional information on the AWS Congressional Fellowship program, please contact Richard French, AWS, at (800) 443-9353 ext. 218 or by e-mail at [email protected].

NJC Rapid Response Project Results The Navy Joining Center (NJC) de-

veloped a unique welding procedure for Nitinol in response to a request from the Navy Surface Warfare Center (NSWC), Carderock Div., for technical assistance in welding this unusual alloy. The request was part of an NSWC In- dian Head Division program to improve the performance of the M66, 2.75-in., air-to-ground rocket, a weapon used by all the armed services.

Nitinol is a nickel-titanium shape- memory alloy used in ring form in the rocket motor assembly. It enables fire sating of the rocket motor during shipping and after the warhead is attached.

The Nitinol rings are difficult to weld and prone to solidification cracking.

NJC provided technical assistance, developed welding procedures and fab- ricated prototype rings that were tested in rocket adapters at NSWC facilities. The rings activated at specification temperatures and released simulated war- heads, proof that the welds met the required stress levels. There were no fail- ures in any of the tests. The NSWC has asked EWI to prepare additional prototype rings for further testing.

Special welding procedures developed under this NJC Rapid Response Project used foil strips to overcome the

in a Patented Fabrication solidification cracking problem with the Nitinol alloy. Cognizant staff members from the Edison Welding Institute and the NSWC are named as co-inventors of the entire ring fabrication process in a patent disclosure.

The Navy Joining Center 1250 Arthur E. Adams Dr.

~ d ~ Columbus, OH 43221 Phone: (614) 688-5010

Operated by FAX: (614) 688-5001 E ~ i e-mail: [email protected]

www: hltp:llwww.ewi.or,g Contact: Harvey Castner


ArcOne Names Director

ArcOne, a division of A.C.E. Interna- tional, Taunton, Mass., has named Richard Connelly [AWS] director of domestic sales for the Welding Products Market. His background includes having served in district and regional manager sales positions at Harris Calorific, Kemppi and Avesta Welding Products and, most recently, as national sales manager for ABICOR Binzel.

Piranha Announces Promotions and Additions

Piranha, a division of Mega Manufac- turing, Hutchinson, Kan., announced the following personnel promotions and additions.

Dean Dick, regional manager in the Great Lakes region, has been promoted to national sales manager. He will work across the company's dealer distribution network, focusing on training and dealer development.

Brian Griffith, formerly territory manager for the Western region, has been promoted to sales manager for bending rolls. He will oversee all aspects of the corn- paw's newest product line.

Dean Phillips, who has more than eight years of experience in the press brake and shear industry, joined the company as product manager for press brakes and

F

shears.

Phillips Giesbrecht

Terry Gieshrecht has been hired as a technical service specialist. With more than 15 years of press brake and shear experience, Giesbrecht will focus on service issues and further development of the product line.

Welding Services Appoints Sales Manager

Welding Services Inc. (WSI), Pearland, Tex., appointed Greg Whitaker as regional

92 l JUNE 2000

sales manager in the Southwest region. Prior to his employment with WSI, he was in sales at AWC in Houston, Tex., with the instrumental and mechanical division. Whitaker is a graduate of Texas A & M University.

Addison Machine Engineering Adds Staff

Addison Machine Engineering, Inc., Addison, II1., has appointed Dan Ventura as vice president of the Tube, Pipe and Roll Form Division and Mike Pacholik as design engineer of roll tooling. Ventura comes from T&H Machine Inc., where he served as vice president for the last 6 years. Pacholik also comes from T&H Machine, where he spent the past 15 years designing roll tooling.

Genesis System Group Adds to Sales Force

Genesis Systems Group (GSG), Dav- enport, Iowa, announced the hiring of Jon Grugel [AWS] as sales engineer for the

i/ Grugel

company's regional office in Michigan. In this position, Grugel is charged with nonautomotive business development in the state of Michigan. Prior to joining the company, Grugel was vice president of Ac- cubilt Automated Systems of Jackson, Mich., from 1994 to 1999.

Matheson Names Director

Matheson Tri-Gas, Montgomeryville, Pa., named Judy Long director of cus-

Long

tomer service. She joins the company after serving 30 years at Calgon Corp. in various positions in R&D, quality management, product management and, most recently, as director of customer service.

Tempil* Appoints General Manager

Tempil °, Inc., South Plainfield, N.J., has appointed Raymond C. Wiese general manager. Prior to joining the company, he served in various sales, marketing and management capacities for the Air Compressor

Wiese

Group of Ingersoll-Rand Co. Most recently, he was regional manager responsible for distribution in the Northeast region of the United States. Wiese has a B.S. degree in commerce and engineering from Drexel University, Philadelphia, Pa.

GSI Makes Additions to Its Sales Team

GSI Lumonics TM, Livonia, Mich., has announced the addition of Carl Bryant and Bill Reid to its Advanced Manufac- turing sales team.

Bryant, who was assigned to the South- east region, previously handled the De- troit auto market for the company. He holds a bachelor of science degree in electrical engineering from Austin Peay State University.

Reid, who has been assigned to the North Central region, has many years of capital equipment sales and account development experience with laser, robotic and automation market sectors, including eight years with Rofin-Sinar. He earned a bachelor of science degree in mechanical engineering from Bradley University.

Radyne Names Sales Engineer

Radyne, Milwaukee, Wis., has named Michael Santine district sales engineer for Michigan and Ontario. He has worked in commercial heat treating and failure analysis since 1991, most recently serving

as a metallurgist for ACR Industries, Ma- comb, Mich. Santine a t tended Western Michigan University and Macomb Com- munity College.

Jackson Products Names Vice President

Jackson Products, Inc., St. Louis, Mo., has named Mike Beavers vice president of operations for the Personal Safety Group. He will oversee operations of certain sites, as well as quality assurance, new product development and safety/environmental compliance for the group. Beavers joined the company in May 1999 as director of lo- gistics.

Stillwater Adds Engineer

Stillwater Technologies, Inc., announced the addition of Dewayne l teck as sales engineer covering southern Ohio. He brings more than 21 years of experience to

Heck

his new position. Heck most recently served as district sales account manager with Savair Inc. He holds an associate's degree in electronic engineering technology from I.T.T. Technical Insti tute and is presently working toward an associate of science degree in business management.

DovaTech AppointsVice Presidents

DovaTech, Ltd., Beecher, Ill., recently appointed two vice presidents.

Greg ltarrod was appointed vice president of sales. He oversees North American and Asian sales markets for the Bernard, Weldcraft and PlazCraft brands of welding and cutting products, as well as the DovaT- ech, Ltd., customer service department . Harrod joined DovaTech in 1998 as director of sales. Prior to that, he spent 21 years in the diesel and marine engine market

Shah Hartvd

with Mercury Marine and Cummins En- gine Co.

ltarshad Shah was named vice president of engineering. He leads Dova-Tech's product engineering group and the development of the Bernard, Weldcraft, PlazCraft and K&K product lines. Shah received his master 's degree in mechanical engineering from Cornell University, Ithaca, N.Y., followed by an MBA from the State University of New York. He has more than 25 years of experience in the machine tool and welding industries. Shah worked at Strippit and Clearing - Niagra, among other companies, prior to joining Dova Tech in 1997 as director of engineering.

Jerry Fry Retires From OKI

After a distinguished and successful career of more than 41 years with OKI Bering, Group Vice President of Sales and National Accounts Jerry Fry has decided to take some time off from his full-time du- ties. He will, however, continue to be involved in the company by serving on the Board of Directors and heading up special projects. Fry began his career with OKI at the age of 18, learning the wholesale welding supply business from OKI founder Ed Caluwaert and his father, Sam Fry, who was the company's chief financial officer.

,o

Take the road to t e c h n o l o g y w i t h the ADVENT --,- C o m p u t e r Contro l ler

The ADVENT Computer Controller brings the u l t i m a t e tn :. / t echno logy to the cont ro l of hard a u t o m a t i o n ~,~ a p p l i c a t i o n s . The system not on ly cont ro ls al l the

w e l d i n g paramete rs bu t also prov ides c o o r d i n a t e d cont ro l of the va r ious axes of mo t i on .

Eight w e l d i n g p a r a m e t e r control - s imu l t aneous l y . Coord ina ted contro] of s ix axes of m o t i o n .

Current p u l s i n g w i t h wave shap ing c a p a b i l i t i e s . Closed loop control and ful l data a c q u i s i t i o n f a c i l i t i e s .

Ful ly i n t eg ra ted f i x t u r i n g for a l l a p p l i c a t i o n s . User - f r iend ly opera tor i n te r face w i t h h igh level g raph i cs .

ADVENT Computer Contro l led hard a u t o m a t i o n w e l d i n g systems are a p roduc t of the Techno log ica l A l l i ance

be tween Jet l ine Eng inee r i ng and AMET.

j e .t;!ine=. I 5 G O O D Y E A R S T R E E T , I R V I N E , C A 9 2 {

9 5 1 - 1 5 1 5 • F A X : { g 4 9 } 9 5 ]

E M A I L : S A L E S @ d E T L I N E . COlM

W W W . d E T L I N E . P - O M

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Circle No. 22 on Reader Info-Card WELDING JOURNAL I 93

which combines FM stereo reception with electronic impact and amplification. The brochure also provides information on the company's other popular over- the-head and cap-mounted electronic earmuffs.

Dalloz Safety 12 I 2nd & Washington Sts., Reading, PA 19603-0622

Abrasives Video Offered

A ten-min video announces the company's complete abrasives line. The video is intended to help customers better understand the benefits of the company's abrasives line. It outlines the details of the abrasives manufacturing process from tests performed on raw materials to the speed and performance eval- uations completed on all the company's finished products. These tests ensure the wheels meet or exceed ANSI B7.1 standards.

Metabo Corp. P.O. Box 2287, West Chester, PA 19380

122

Catalog Features Tools for Pipe Weld ing and Fabrication

This eight-page catalog describes 14 economical guidance and positioning tools for pipe welding and general fabrication. Pictured with descriptions are the company's pipe-flange aligner, multi- purpose cutting guide, cutting attachment for small- to medium-sized holes, magnetic circle layout and cutting guide, plasma arc cutting guide, self-leveling magnetic marker for pipe fabrication, centering head tool for establishing and marking a centerline around the circumference on pipes or tanks, magnetic blocks, magnetic torch guides and others.

Flange Wizard Tools 2140 S. Santa Fe St., Santa Aria, CA 92705

123

Li terature Details G T A W Power Sources for Orbital Weld ing

An eight-page, full-color brochure describes the company's family of orbital GTAW power sources. The product family includes four power sources in a variety of current ranges. The brochure details user-friendly features such as multi- language programming, integrated program library for quick welding parameter research, a real-time monitoring system, integrated printers for documenta- tion of welds according to the ISO 9000 standard and inverter-based power source technology. The brochure also features a matrix of technical specifications for the product line as well as a grid of industrial applications and power source/head combinations.

Messer, Astro Arc Plysoude 124 WI33 N5138 Campbell Dr., Menomonee Falls, WI 53051

94 I JUNE 2000


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De:mands ,. .-t

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Tnday's y)uth are often fitced "~vith presstn'e and frustration when selecting

a career path? Friends suggest getting any job, just for a fe~ bucks to go out and

have a good time. Parents urge flleir kids to become the fit.st or next family

doctor or laxwer. How about having the best of both worlds? - - a job with

immediate income and a re~arding filture career:

Our industn.--the x~elding industry--offers tndav's vunth an equal-opportunig;

rewarding, and engaging career. They have an opportunity to develop their

interests and build upon them by becoming a welder, a certified inspector, an

educatou a welding engineer, or they can pursue welding research as a degreed

professional, all while earning a colnpetitive s:dary.

But who will offer tbem welding as a possible, dable career in light of escalating

education costs? At the stone time ~bo will fill more than 50,00{I welding

positions that will become mailable by the }cal" 2006?

A$S and its members have recognized this critic~d ~oid. That is why we have

elnbarked on Campaign 2000 to establish 100 new scholarships and attract the

next generalinn nf welding professionals. Let's give youth a chance to explore

their career options.

For a Campaign 2000 brochure explaining how you can help, please call the Foundation at 1-800-443-9353 ext. 689.

Foundation,Inc. A Foundation of the American Welding Society

550 X~; LeJeune Road, Miami, FI 3312(~ (800) -H.-;-9353, ext. 293 or (305) -H5-(~628 F V\: (30"~) +@'559 e-mail: [email protected],- ww~.a~ s.or,jfoundation/index.html

Save big when you sign up for more than one seminar or for the entire week.

AWS D I. ! Code Week The #1 selling welding code now comes alive in a five-day seminar that begins with a roadmap of the one and only D I,I:2000 Structural Welding Code-Steel. This is your opportunity to learn from an expert AWS instructor and ask your toughest questions about DI.I.

Code Week continues with corresponding subjects geared co engineers, supervisors, planners, welding inspectors, and welding technicians. Since your work is based on a reputation for reliability and safety, you want the latest industry consensus on prequalification and qualification. If you want to improve your competitive position by referencing the latest workmanship standards, inspection procedures and acceptance criteria - - you won't want to miss this seminar! Each day will be in-depth, intense,and more than interesting!

- .: - • L ' " -

J

~ p As art of the

registration fee, participants will

receive a copy of the new D I. 1:2000

,,Structural Welding Code-Steel.

. . . . . ~ , . - i

A W S D I. I Code Week Price List

Seminar C ~ t i o n Date

(Day l-Monday) DIWI05: Las Vegas, NV May 22, 2000 DI.I Road Map D1WI03: Chicago, IL June 5, 2000 Member $345 DtW106: Philadelphia, PA July 10, 2000 Non-Member $420 nlWl07: Detroit, MI August 21, 2000

(Day 2-Tuesday) D1W205: Las Vegas, NV May 23, 2000 Design of Welded Connections D1W203: Chicago, IL June 6, 2000 Member $345 D1W206: Philadelphia, PA July 11, 2000 Non-Member $420 DlW207: Detroit, MI August 22, 2000

(Day 3-Wednesday) D1W305: Las Vegas, NV May 24, 2000 Qualifications D1W303: Chicago, IL June 7, 2000 Member $345 D1W306: Philadelphia, PA July 12, 2000 Non-Member $420 DIW307: Detroit, ml August 23, 2000

(Bay 4-Thursday) D1W405: Las Vegas, NV May 25, 2000 Fabrication DlW403: Chicago, IL June 8, 2000 Member $345 D1W406: Philadelphia, PA July 13, 2000 Non-Member $420 D1W407: Detroit, MI August 24, 2000

(Day 5-Friday) DIW505: Las Vegas, NV May 26, 2000 Inspection D1W503: Chicago, IL June 9, 2000 Member $345 nlW506: Philadelphia, PA July 14, 2000 Non-Member $420 nlW507: Detroit, mI August 25, 2000

Take advantage of great savings by registering for any one-day seminar at original cost, and add any additional one-day event for only $150.

(Monday-Friday) DIWO05: Las Vegas, NV May 22-26, 2000 DI.I Code Week DIWOO3: Chicago, IL June 5-9, 2000 Member $795 D1W006: Philadelphia, PA July 10-14, 2000 Non-Member $870 DIW007: Detroit, MI August 21-25, 2000

C l a s s i f i e d s

SALES MANAGER COMPANY: Polymet Corporation is a Cincinnati based-manufacturer of high- performance wires for hardfacing, thermal spray and welding applications. The company has a strong track record of stability and growth. Benefits include annual bonus, company-paid pension, 401K savings program and full medical in- surance. ROLE: Market and sell Polymet's iron-, nickel- and colbolt-based cored and solid welding and thermal spray wire products. EXPERIENCE: Proven track record in sales with a minimum of 5 years of experience in sales of cored welding and thermal spray wire products and demonstrated ability to achieve closure.Significant experience in the hardfacing industry with a strong knowledge of the power generation and mining industries preferred. Practical experience with parameter development and process troubleshooting of the GMAW, FCAW and SAW processes. SKILLS: Strong interpersonal skills with ability to develop and maintain positive customer relationships. Results-oriented self starter. Will ingness to travel. LOCATION:The position may be based out of Cincinnati or the candidate's current residence. Candidates located in the Midwest and Southwest preferred. Please contact the General Manager of Polymet for further information at 513-874-3586 or Fax: 513-874-2880

CHICAGO BRIDGE & IRON WELDING & QA TECHNOLOGY

Available to develop timely, practical solutions for your technical problems

• Welding, Metallurgical, NDE and QA Consultation

• Laboratory Testing and Analysis • On-Site Inspection Analysis • Specialized Training

INDUSTRY LEADING EXPERTISE IN: • Welding and Metallurgical Engineering • Heat Treatment Engineering • Vacuum Technology • Leak Testing Systems • Failure Analysis

8900 Fairbanks N. Houston Rd., Houston,TX 77064 (713) 896-2940 Fax: (713) 466-4259

Visit our website at: www.cbiwelding.com

• ~ HORIZON PERSONNEL

Weld/Quality Eng., QS9000/FMEA$55K Application Eng., resistance weld $70K Mfg. Engrg. Mgr., metal fab/JIT/ISO $65K Stamping Mgr., welded assemblies $62K Weld Eng., start-up/layout/robotics $64K Mfg. Eng., welded tubing . . . . . . . $60K

Companies pay all costs. Send resume in confidence to

Joe Micksch, ASM Life Member 683 Fox Meadow Road Princeton, KY 42445

Phone 270-365-9165 or Fax 270-365-2248 www.micksch.com

WELDING ENGINEERS CAREER OPPORTUNITIES

PRI is a Recruitment Coordinator for 350 Search Firms Nationwide. High demand for Junior through Advanced Levels in variety of industries. Top companies, $40-80K. Fee PD. Contact Jerry or Mark.

Professional Recruiters, Inc. P.O. Box 24227

Omaha, NE 68124 800-999-8237 or Fax: 402-397-7357

[email protected] or www.jobteam.com

Machine & Welding Supply Company has been a leading distributor of gases and welding supplies throughout the Carolinas since 1954. We are interested in attracting Sales Representatives and Managers with experience in the welding supply industry and a desire to excel. If you wish to work for a growing company with career opportunities in sales and management with a willingness to invest in its employees, ~lease send a resume to Machine & Welding Supply Company, Department of Human Resources, P.O. Box 1708, Dunn, NC 28335, or send e-mail to bb @ mwsc.com, or call 800-571-1583 ext. 206 and ask for Jimmy Blalock. We are an Equal Opportunity Employer.

W E L D I N G JOURNAL I 97

WELDING JOBS.corn

Leading job site for all Welding Jobs. Top 10 l is~g on major search engines.

250 total visitors/day and growing. Site has Mailing Lists,

AD Stats, Job Links. Cmmmuimm/Ranu'uitm Pimcm ADS

http://www.WeldmgJobn.com

WELDING SALESMAN We Pay You!

For f inding us good used positioners, manipulators, turning rolls,

we ld ing machines, etc,

Weld Plus, Inc. Cincinnati, Ohio Jack Schroeder 1-800-288-9414

AS A NATIONWIDE WELDING ENGINEERING SPECIALIST Numerous client companies hove engaged me to recruit welding pros at various levels of experience. If your expertise is Welding Engineering, Coil, Moil, Fox resume to BILL ELIAS Dept WE, PO Box 396, East Brunswick, NJ 08816.

Phone 732-390-4600 Fax 732-390-9769 ELIAS ASSOCIATES

"Annually a National Award Winning Search firm"

I 800-523-2791 • PA: 6 t 0-82.5-1250 I FAX: 6 t 0 - 8 2 5 . 1 5 5 3

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S E E K I N G S U R P L U S E X C E S S W E L D I N G

R O D & W I R E D O N ' T G I V E IT A W A Y C A L L U S - - W E P A Y !

CALIFORNIA T R A D I N G I N T E R N A T I O N A L i

www.catradingint.com ] 8 0 0 - 7 3 5 - 9 3 5 3 - FAX: 805-523-918~

l i ~ l ~ Company of Texas, Inc. V V w~t~,,..~,i,,t~q~p,.~ts~;,~..z~

POSITIONERS -/MANIPULATORS - TANK TURNING ROLLS - SEA/MERS

New 24" to 240" Seam Welders New 2,500 to 120,000# Turntables

New 1 to 200 Ton Tank Turning Rolls New 2,500 to 240,000# Head and

Tailstocks " New 4' X 4' to 20' X 20' Welding Head

Manipulators

We also sell and rent used weld positioning equipment.

6620 Fulton Street, Houston, TX 77022 Phone (800) 877-6381

Fax (713) 691-4210 www.weldwire-tx.com - -

U S E D 1 ROBOTS I

We buy and sell all types. I f--,w0 in, o s since J I / I l - loo-s2s-Hss I I ! I ' [ '~ ' ] I : i -~ - - www.antenen.com

L , , , , o - , J ,NRTO

. . . . . . ~ ° V I ~ ~ P L A T E N S ! | ~ Re-Ground Tops | J FOB: Shipping Point • Call for Detai ls |

I ~ | Weldsale Company 1215) 739-7474 | L _ _ _ _ ~w~.w~ij.~le...com~ _ _ _ _ j

A robots%welding.com

(Guess what we sell :)

\\\\I DOS AND w,RE WANTED \ \ I l l All types and sizes / I l l

EXCESS I I I I fding Alloys, Inc. I I i !

//11 ,x,,o,.,.y//Ai We buy excess WELDING ROD & WIRE All types s Quantities large & small

C xford VALLOYS. Inc

2632 Tee Dr, Baton Rouge, LA 70814 800-562-3355

225-273-4800/FAX 225-273-4814

Cool Down Whit~tone Corp.

Douse off with refrigerated air or use long lasting HeatShield technology

www.whi testonedi rect .com ,! ',. (800) 266-54

98 I JUNE 2000

PIPE W E L D I N G VIDEOS

Acquire difficult pipe welding skills and techniques through easy-to-follow instruction. Six different videos are available at $39.95 each: SMAW 2G, 5G and 6G. Techniques are demonstrated, including walking the cup, tungsten extension, welding 1/4" gap, etc. Call today for more info. Visa and M.C. accepted.

Quality School of Pipe Welding 600 Great SW Pkwy Atlanta, GA 30336

phone 404-629-9909 fax 404-629-1229 pipewelding.com

Accredited AWS test facility.

REAL EDUCATIONAL SERVICES, INC.

pascagou~a. M~s~s/pp/ CWl PREPARATORY

or Repeat FREE/ June 12-16 Aug 21-15 Oct 16-20

Test follows o n Saturday @ same facility ADVANCED VISUAL

WELDING INSPECTION H a n d s - O n Class Using " R ~ " p~ojects

Great for Eugineers & Inspectors June5-9 Aug14-18 0ct9-13

ASMEINBIC QUALITY CONTROL

July 19-22 Sept 11-14 Ph 800-489-2890: Fax 228- 769-5219

w w w . datasync, com/techwdd

A D V E R T I S E R I N D E X

RECONDITIONED & NEW WELDING POSIT IONERS-

MANIPULATORS -SEAMERS - TURNTABLES - CIRCULAR

W E L D E R S - T U R N I N G ROLLS

JUST IN! Arc Machines #215 Programmable Internal Cold Wire Tig System w/Camera.

Many Aronson, Pandjiris, Ransome Weld Posit ioners, Manipulators, Turning Rolls.

Jetline, Pandjiris Seamers to 16 ft. Jetline, Cyclomatic Controls, Arc Lengths, Cold Wire Feeders, Seam Trackers. Lincoln, Miller

Sub-Arcs, Heads, Feeders, Osci l lators.

WE BUY AND SELL!! Web site: www.weldplus.com

e-mail: [email protected]

WELD PLUS, INC. Cincinnati, Ohio

Jack Schroeder 1-800-288-9414 Fax: 1-513-467-3585

ABICOR Binzel .................................................................. 53 Air Products ....................................................................... 49 At las Weld ing .................................................................... 28 Amer ican Torch Tip ........................................................... 17 Amer ican Weld ing Society ....................... 58,83,84,88,95,96 Amer ican Weld ing Society Detroit Sect ion ........................ 57 ArcSmith/Smi th Equ ipment ............................................... 82 Bernard Weld ing Equ ipment ........................................... IFC Bluco ................................................................................. 28 Bug-O Sys tems ....................................................... 21,23,25 Center l ine (Windsor) Limited ............................................. 21 Compute r Weld Techno logy .............................................. 42 Cor-Met ........................................................................ 55,86 D iamond Ground Products ................................................ 42 Edison Weld ing Institute ...................................................... 8 Enerpro ............................................................................. 56 ESAB Weld ing & Cutt ing Sys tems ................................ OBC F&M Marco Inc .................................................................... 3 G.A.L. Gage ...................................................................... 24 Gener ico ............................................................................ 15 Hobart Institute .................................................................. 22 Jet l ine Engineer ing ............................................................ 93 J.P. Nissen ........................................................................ 55 Kobe lco Weld ing Co. of Amer ica ........................................ 6 Koike Aronson Inc ............................................................. 56 La-Co Markal ..................................................................... 30 Lincoln Electr ic Co .............................................................. 1 Mack Products .................................................................. 27 Meridian ............................................................................ 56 Mil ler Electr ic Mfg. Co ................................................. 18&19 MQ Power ......................................................................... 50 Nat ional Standard ............................................................. 13 Nippert Co ......................................................................... 54

OTC Daihen ........................................................................ 4 Radyne ................................................................................ 2 Schaff Internat ional ........................................................... 48 Select -Arc ........................................................................ IBC SME .................................................................................. 32 Stave ley Instruments, Inc .................................................. 94 Stress Relief Engineer ing Co ............................................ 48 Super ior Glove Works ....................................................... 86 Tecnar ............................................................................... 46 The Caldwel l Group .......................................................... 23 Thermal Dynamics, a Div. of The rmadyne Industr ies ....... 31 Thermco ............................................................................ 57 T.J. Clark ........................................................................... 87 Tweco, a Div. of The rmadyne Industr ies ........................... 29 Ve lmex .............................................................................. 25 Wall Co lmonoy Corp ......................................................... 85 WeldersMal l .Com .............................................................. 11

IFC = Inside Front Cover IBC = Inside Back Cover OBC = Outside Back Cover

W E L D I N G J O U R N A L I 99

AWS Peer Review Panel All papers published in the Welding Journal's Welding Research Supplement undergo Peer Review before publication for: 1) originality of the contribution; 2) technical value to the welding community; 3) prior publication of the material being reviewed; 4) proper credit to others working in the same area; and 5) justification of the conclusions, based on the work performed. The following individuals serve on the AWS Peer Review Panel and are experts in specific technical areas. All are volunteers in the program.

D. Abson R.T. Hemzacek D. K. Aidun M.J. Higgins G. A. Andreano T. Hikido D. G. Atteridge J.E. Hinkel R. E. Avery J.F. Hinrichs S. S. Babu T.P. Hirthe D. J. Ball P. Hochanadel W. L. Ballis D.G. Howden P. Banerjee P. Howe T. S. Bannos C. Hsu R. E. Beal J.P. Hurley F. R. Beckman D.L. Isenhour S. S. Bhargava J.R. Jachna B. Bjorneklett J. Jaeger O. Blodgett M.Q. Johnson R. J. Bowers B.A. Jones J. E. M. Braid J.E. Jones K. L. Brown W. Kanne S. B. Brown B. Kapadia J. Bundy A. Kar S. N. Burchett D.D. Kautz M. L. Callabresi H.W. Kerr D. A. Canonico D.S. Kim K. W. Carlson J.F. King N. M. Carlson S. Kolli C. L. Chan P.J. Konkol C. C. Chen S. Kou J. C. Chennat J.J. Kozelski B. A. Chin H.G. Kraus G. E. Cook K.W. Kramer R. E. Cook J.J. Kwiatkowski R. A. Daemen F. Lake S. Daniewicz J.D. Landes J. C. Danko J.W. Lee V. R. Dav6 A. Lesnewich J. DeLoach G.K. Lewis G. den Ouden M.V. Li X. Deng T.J. Lienert P. J. Ditzel M.J. Lucas R. J. Dybas R.O. Lund H. W. Ebert K.A. Lyttle G. M. Evans B. Madigan R. G. Fairbanks M.C. Maguire D. A. Fink A.K. Majumdar D. W. Fitting M. Manohar W. R. Frick A.F. Manz E. Friedman K. Masubuchi J. A. Gianetto J. Mazumder F. E. Gibbs V.E. Merchant D. L. Hallum M.T. Merlo I. D. Harris J .O. Milewski D. A. Hartman W.C. Mohr

Principal Reviewers

Y. Adonyi W. E Gale K.W. Mitchiner C. E. Albright J .M. Gerken T.M. Mustaleski J. A. Brooks D.D. Harwig D.L. Olson H. R. Castner D. Hauser B.M. Patchett M. J. Cieslak G.K. Hicken T.P. Quinn C. E. Cross J .E. Indacochea A. Rabinkin C. B. Dallam J.L. Jellison B. Radhakrishnan B. Damkroger R.R. Kapoor W G. Reuter S. A. David T.J. Kelly R. W Richardson T. DebRoy G.A. Knorovsky S.I. Rokhlin J. H. Devletian D.J. Kotecki J. E Saenger R. D. Dixon R. Kovacevic M.L. Santella P. Dong E V. Lawrence, Jr. S.D. Sheppard J. N. DuPont W. Lin H.B. Smartt T. W. Eagar J.C. Lippold B.R. Somers G. R. Edwards S. Liu C.L. Tsai J. W. Elmer H.W. Ludewig G.D. Uttrachi D. E Farson R.P. Martukanitz D.R. White Z. Feng R. Menon T. Zacharia S. R. Fiore S.J. Merrick L. H. Flasche R.W. Messler, Jr. P. W. Fuerschbach D.W. Meyer

A. J. Moorhead D.J. Rybicki T. Morrissett E.F. Rybicki L. W. Mott K. Sampath C. G. Mukira J.M. Sawhill, Jr. K. Mundra A.P. Seidler O. Myhr L.R. Shockley K. Nagarathnam L.E. Shoemaker P. Nagy M. Sierdzinski S. Nasla T.A. Siewert T. W. Nelson S.D. Smith J. L. Novak T.M. Sparschu A. Ortega W.J. Sperko M. Parekh D.E. Spindler R. A. Patterson J.E. Stallmeyer R. L. Peaslee R.J. Steele D. D. Peter P.L. Sturgill E. Pfender D.W. Trees M. Piltch A.J. Turner L. E. Pope J.J. Vagi N. Potluri T.L. VanderWert M. Prager I. Varol D. D. Rager P.T. Vianco K. P. Rao K.K. Wang W. Ridgway D.K. Watney A. Ritter P.D. Watson M. N. Ruoff M.M. Weir

C. E. Wirsing C. E. Witherell W. E. Wood J. Xie Y. P. Yang H. Zhang J. Zhang Y. M. Zhang Y. Zhou

I00 l JUNE 2000

WELDING R E S E A R C H

SUPPLEMENT TO THE WELDING JOURNAL, JUNE 2000 Sponsored by the American Welding Society and the Welding Research Council

Stress Rel axation Study of HAZ Reheat Cracking in Type 347 Stainless Steel

GleebleTM-based stress relaxation tests evaluate a material's susceptibility to weld HAZ reheat cracking

BY L. LI AND R. W. MESSLER, JR.

ABSTRACT. Four different compositions of Type 347 austenitic stainless steel were studied using GleebleTM-based stress relaxation tests to evaluate susceptibility to weld HAZ reheat cracking. Coupons extracted from plate were thermally cycled to reproduce the coarse- grained region of the HAZ known to be most prone to such cracking. These samples were then reheated to various PWHT temperatures, and a strain com- parable to 70% of the strain to cause yielding at the temperature was applied. Force in the specimens was recorded for up to 3 h while this total strain was kept constant. Force vs. time curves for all samples exhibited an increase attributed to volumetric shrinkage upon precipitation of Nb-rich particles as confirmed by constant-stress tests. Formation of Nb- rich precipitates strengthens the alloy, and stress buildup due to volumetric shrinkage in the age-hardening matrix leads to cracking along grain boundaries when stress cannot relax fast enough by yielding or creep.

Introduction

Type 347 stainless steel, as well as

L. LI is a doctoral candidate and R. W. MESSLER, JR., is Professor in Materials Science and Engineering at Rensselaer Polytechnic In- stitute, Troy, N. Y.

Based on a paper presented at the 79th Annual AWS Convention in Detroit, Mich., Apri l 26-30,1998.

other Nb-containing Fe- and Ni-based austenitic alloy weldments, have been and continue to be plagued by cracking. Such cracking occurs frequently in the weld fusion zone (FZ) and/or the heat- affected zone (HAZ) during welding, oc- casionally in the HAZ during postweld heat treatment (PWHT) and, as found more and more with increasing experience, in HAZs following extended service at elevated temperatures (Ref. 1 ). This article reports the results of a study on the role of base metal composition and microstructure on HAZ reheat cracking.

Factors affecting reheat or strain-age cracking susceptibility during PWHT of ferrous and nonferrous alloys exhibiting precipitation of strengthening second- phase particles have been identified as 1 ) development of coarse grain size and dis- solution of second-phase particles in the HAZ during welding, 2) reheating that causes re-precipitation of fine particles

KEY WORDS

Austenitic Stainless Steel

Type 347

Reheat Cracking

Stress Relaxation

Gleeble TM

within grains and grain boundaries to cause hardening and loss of ductility, and 3) joint geometry and thermal history that determine the amount and rate of stress relaxation during reheating (Ref. 2). Post- weld stress-relief cracking is generally limited to thick-walled vessels made from higher-alloy, high-temperature, creep-resistant grades such as austenitic stainless and Cr-Mo-V steels (Ref. 3). Cracking occurs early in the reheat cycle and can be located in the coarse-grained weld metal, but is more commonly located in the less strain-tolerant, coarse- grained region of the HAZ (Ref. 4). It has been postulated that NbC and Nb(C,N) precipitates strengthen the matrix to the extent that most of the relaxation of stress takes place along grain boundaries (Refs. 3, 5). When the strain from welding or heat treatment or service-induced thermal cycles exceeds a critical value, in- tergranular cracking occurs.

Stress relaxation as a means for study- ing reheat cracking in austenitic alloys has been employed by numerous researchers (Refs. 6-10). In an as-welded joint, there are multi-axial stresses and elastic strains. No change in the physical size of the weld joint occurs as weld- induced stresses are relieved by postweld thermal cycles, at least for heavy-section weldments. Thus, the total strain in the weld joint remains constant. This condition of constant total strain is the principal factor that must be present in any test to study cracking during postweld heat treatment (Ref. 6).

WELDING RESEARCH SUPPLEMENT I 137-s

A 150

! "' DI

0 • D2

B 60O

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1(0 DI

D 2

est Te erature Test Temperature C

Fig. 1 - - Yield strength (A) and ultimate tensile strength (B) o f test Type 347 at different temperatures.

In a stress relaxation test, total strain (E T) remains constant. Plastic strain (Ep) accu- mu la tes at the expense of elastic strain (%), so the relation £T = £e + l~p holds true for the test. Stress relaxation i's a straight- forward and sensitive method for providing a guide to metallurgical events such as recrystall ization and precipitation (Ref. 1 I). During a stress relaxation test, stress or force vs. hold time can provide information on susceptibility to reheat cracking during postweld heat treatment or other thermal exposure.

Exper imenta l Procedure

Samples of commercial ly available Type 347 stainless steel plates with four different compositions within the specification for standard or nuclear grades (Table I ) were tested and compared. The experimental procedure involved the following: I) Instron-based hot tensile tests of base materials, 2) Gleeble weld thermal cycle simulation to develop susceptible HAZ microstructure, 3) notching of test specimens to facilitate cracking, 4) Gleeble-based stress relaxation tests, 5) data analysis, 6) metallographic observa- tions and 7) correlation of test results and microstructure.

Hot tensile tests were conducted on as-received materials to determine appro-

priate initial stresses and strains for stress relaxation tests. Ten- sile stress-strain behavior was measured with smooth samples for temperatures between 550 and 950°C. All tensile tests were performed using an In- stron Model 8562 Electro-Mechanical Testing System with self-aligning grips and a computer- based data acquisition system, along with a split, resistance-heated furnace. The samples were uniformly heated at 50°C/min from room temperature to test temperatures, and loading was started 1 min after arriving at the test temperature. The strain rate for tests was 0.04/rain. Results obtained are plotted in Fig. 1 as yield and tensile strength vs. test temperature.

An upgraded Model 1500 Gleeble TM (produced by DSI, Poestenkill, N.Y.) was

F f

3/16" ~ ~ ( ~ i.~ I"R 1/4" ,I- .ol

Y _ • '

_3_ I I I III I ! I 114"(.om.)

Fig. 2 - - Sample geometry for the Gleeble stress relaxation tests.

used to simulate key weld thermal cycles in coupons with a 6.4 x 6.4-mm square section. A 1300°C peak temperature with 1.1 kJ/mm (28 kJ/in.) heat input was employed in the Gleeble simulations to produce the structure found in the coarse- grained HAZ (CGHAZ) of welds, where

Table I - - Four Different Compositions of Type 347 Stainless Steel

Code C Si Mn P S Cr Ni Mo N Nb Co Cu

A1 0.022 0.32 1.51 0.025 0.004 17.68 10.48 0.24 0.036 0.4 N/A N/A (347NG) C2 0.05 0.59 1.57 0.025 0.025 17.75 9 . 5 3 0 . 3 3 0.032 0.59 0.09 0.23 (T347) D1 0.023 0.48 1.66 0.031 0.007 17.74 10.27 0.35 0.021 0.367 0.1 0.32 (T347) D2 0.044 0.57 1.42 0 .03 0.001 18 .2 10.63 0.27 0.044 0.48 0.19 0.33 (T347)

AI Ti Sn Nb/C PN measured

N/A N/A N/A 18.2 1.3

N/A 0.003 N/A 11.8 1.6

0.001 0.005 0.022 16 3.2

0.001 0.007 0.018 10.9 0.7

138-s I JUNE 2000

A 2O3O

1500

1000

500

' ' ' I ' ' ' 1 ' ' ' 1 ' ' ' 1 ' ' ' 1 ' ' ' I ' " "

, . , I . . . I . + , I . . + I . , , I , i , I . .

0 m 4o 00 8o 100 120 140

Time. minutes

B aOQ0

1GQO

1000

000

0

0

" ' ' I ' ' ' I ' ' ' 1 ' ' ' 1 ' ' ' 1 ' ' ' 1 ' ' "

7 8 0 ~ "

, 1 1 I i 1 1 1 m , l I l l i I l l 1 1 l l I I , 1 1

40 ~0 80 10O 120 140

Time, minutes

C =0

tmm

I.[.

5 0 O

" ' " I ' ' ' l ' ' ' l ' ' ' l ' ' ' l ' ' " I ' ' ' I

i i , I , , , I , , , I , l , l , , , I I , , I , , ,

~0 40 00 00 100 100 140

Time, minutes

D =o

1000

000

i i i I I i i I , , , I , , , I , , I 1 i 1 , 1 , , ,

0 ~ 40 00 m 100 100

Time, minutes

Fig. 3 - - Force vs. t i m e cu rves f r o m the stress r e l a x a t i o n tests: A - - A 1; B - - C2 ; C - - D 7 ; D - - D 2 .

140

tolerance to strain from any source (external or internal) is known to be lowest (Ref. 4).

Gleeble-based stress relaxation tests were performed by bringing the square- section samples to test temperatures in the range of 550 to 950°C at a heating rate of 50°C/min, then applying a strain (via the Gleeble's stroke control) to 70% of the strain at yield at the test temperature. The selection of 70% yield-strain level was somewhat arbitrary because, qualitatively, any initial residual stress level (assumed to be at the yield stress) in actual welds would decrease during the heating process (Refs. 6, 10). However, 70% yield-stress (equivalent to 70% strain within the elastic region) is widely used as a design allowable for yield- limited designs (Ref. 12). Once the strain level was adjusted to the predetermined value, sample extension was kept constant throughout testing while force was recorded vs. time over a period typically of 3 h. The 3-h time period was employed because of the convenience of testing and because long stress-relief cycles are economically burdensome. The resulting force-time curves were analyzed, and tested samples were metallographically examined for cracks.

Preliminary tests with Type 347

showed smooth bars did not produce cracks during relaxation. Previous work by others also confirmed stress concentration as one of the conditions exacer- bating reheat cracking (Ref. 8). In fact, smoothing the joint by grinding after welding was found effective for prevent- ing reheat cracking in Type 347 (Ref. 9). Thus, all thermally cycled specimens were notched to give a nominal stress concentration factor of K = 3.3. The final geometry for stress relaxation specimens, including notch dimensions, is shown in Fig. 2. Note that notch dimensions are not the same as for a standard Charpy V- notch specimen.

Results and Discussion

Force vs. time curves, as shown in Fig. 3A-D, generally exhibited a small decrease during the initial relaxation stage, lasting 1 to 5 min, with force then gradu- ally increasing. Force eventually decreases when relaxation time is extended sufficiently at any exposure temperature, with the time required being dependent upon the relaxation mechanism kinetics. Complete fracture of the sample seemed to be associated with force-time curves exhibiting a distinct peak (within the 3-h maximum test period). Crack initiation

was always observed in those samples in which force-time curves exhibited such a peak (again, within the 3-h test period).

Specimen examination showed cracking at the root of notches after testing over a range of temperatures. The deepest cracks occurred in all test alloy compositions after exposure to relaxation temperatures that produced a peak in the force-time curve (again, within the study's 3-h period). The decrease in force was related to cracking that produced a decrease in cross section.

Figure 4A-D compares cracking among the tested alloys. Specimens with composition D2 exhibited complete fracture, indicating D2 is the most susceptible among the tested compositions to reheat cracking during PWHT. Lower temperatures than what produced a peak in the force-time curve (e.g., 750 vs. 800°C for D2), resulted in less severe cracking for all tested compositions. The highest temperature tests (>850°C) were characterized by a low peak load and a short failure time. Here, specimens necked during testing, and failure was by a stress-rupture mode characterized by dynamic recrystallization, wedge-type cracking and formation of cavities at grain boundaries - - Fig. 5.

The as-received optical microstruc-


Fig. 4 - - Cracking at root o f notches (50X) after 3-h stress relaxation tests at temperatures that produced peaks in the force-time curves: A - - A 1 tested at 850°C; B - - C2 at 850°C; C - - D1 at 800°C; D - - D2 at 800°C

Fig. 5 - - Cross-sectional view of the fractured region in D2 after a 3- h stress relaxation at 950°C (25X).

ture of test alloys shows an austenite matrix with some Nb-containing particles in the matrix. As an example, the microstructure of D2 before and after a 1300°C peak thermal cycle is shown in Fig. 6. Note in Fig. 6B the virtual absence

of particles of Nb compounds at grain boundaries after the thermal cycle. This microstructure of as- cycled D2 before reheat testing was similar to the as-welded condition for the HAZ near the zero ductility temperature (ZDT). After a 550°C relaxation test, the microstructure was nearly the same as that of the as-cycled sample. The microstructure of D2 after a 700°C relaxation test showed sparse precipitates decorating

grain boundaries-- Fig. 7. Under higher- magnification SEM, smaller precipitates are abundantly distributed inside grains as well. The microstructure of D2 after a 750°C relaxation test showed more prevalent precipitates at grain bound-

aries, with some grain growth of the austenite matrix - - Fig. 8. The microstructure of D2 after an 800°C relaxation test showed small, newly formed austenite grains and wedge-type grain boundary openings for force-time curves that peaked within the 3-h test. Some grain boundaries were free of the precipitates observed after lower temperature exposure, though the intragranular precipitates were readily seen optically - - Fig. 9.

Precipitate-free grain boundaries were also observed in other alloy compositions tested - - Figs. 10-12. Com- pared with the precipitate-strengthened matrix, precipitate-free grain boundaries may experience more deformation and crack initiation through grain boundary sliding (Ref. 13). Such grain boundary sliding is suggested by the presence of both w-type (at grain corners, Fig. 9) and r-type (at grain edges, Fig. 12) cavities in the tested samples. The definitions for w- type and r-type cavities and their being indicative to grain boundary sliding are discussed in Ref. 14.

The reason for a force increase during

140-s I JUNE 2000

Fig. 6 - - Microstructure of (A) as-received and (B) after 1300°C-peak thermal cycle for D2 composition (400X). Note virtual absence of particles of Nb compounds at grain boundaries.

Fig. 7 - - Microstructure of D2 after 700°C relaxation test (400X) showing sparse, fine precipitates at grain boundaries. Fig. 8 - - Microstructure of D2 after 750°C relaxation test (400X) show-

ing larger, but still sparse, precipitates at some grain boundaries.

initial relaxation has been suggested to be due to shrinkage in a Gleeble stress relaxation study of a N i-based al Ioy (Ref. 7). To confirm this shrinkage mechanism in Type 347, a constant stress test was employed. If the sample became shorter during constant-strain stress relaxation, then, for a constant-stress condition at the same temperature and stress level, the strain in the sample should exhibit a negative change, i.e., volumetric shrinkage was occurring.

Verification tests were conducted on an Instron Model 8562 mechanical testing machine with a precise high-temperature extensometer and computer- controlled loading system. The gauge length of the test coupon was 25 mm. During tests, samples of the same notch geometry and microstructure as used in Gleeble stress relaxation tests were heated at 50°C/min to 750°C. When temperature equilibrated, stress of 70% yield

strength (equivalent to 70% strain at yield) at 750°C was applied in 30 s and kept constant throughout a 3-h test, while strain was recorded.

A typical strain-vs.-time curve obtained from this constant-load test is shown in Fig. 13. The curve clearly shows a small (15%) but definite decrease of strain with time at the test temperature, indicating the specimen shortened during a hold at 750°C. From these confirming tests, shrinkage during reheating of Type 347 has been identified and the force- time behavior from relaxation tests can readily be understood. Incidentally, this dimensional change is different from dimensional changes that are solely temperature dependent and completely reversible arising from normal thermal expansion and contraction. The shrinkage under discussion is of metallurgical origin, involving phase or other structural changes, such as carbide precipitation.

The cause of confirmed shrinkage is believed to be a decrease in the specific volume of the alloy during the precipitation process. An EDS analysis (Fig. 14) of precipitates in relaxation-tested samples shows precipitates are Nb-rich phases, likely Nb-carbides and nitrides. Accom- panying the precipitation, there are changes in specific volume of the solid solution matrix and contributions from concurrent appearance of carbide phases.

To understand the kinetics of stress relaxation and precipitation, the relaxation results are plotted as stress vs. logarithmic time. As in Fig. 15, all curves show an initial linear portion lasting up to 5 min with a slightly negative slope. This portion can be regressed to the following form:

=~o - kin(8

WELDING RESEARCH SUPPLEMENT[ 141-s

-,i i?!

Fig. 9 - - Microstructure o lD2 after 800°C relaxation test (400X) showing clean grain boundaries again after migration by growth.

• . ~--~.,;%.,.. . ~ "." : . . . ~ ; . ~ . . . .

• . f ::..-,~,./

I.¢'.'l • • L'._.: ,.:..., ...... . i'.;" .

r,. / " "",",;~S " " ; ' " ~ " "e¢" "

~ >v/~. .,£f'.",: :~'%'o~,'--~" I "Z ; . ..... "

~:{.~ ..... ..~- .... ..,:,.Y ~, .. ....... ....

Fig. I0 - - Microstructure of A1 after 850°C relaxation test (400X) showing grain boundaries free of precipitates.

, . .

Fig. I I - - Microstructure of C2 after 850°C relaxation test (400X) showing austenitic grain boundaries free of precipitates

Fig. 72 - - Microstructure o lD1 after 800°C relaxation test (400X) showing austenitic grain boundaries free of precipitates.

0,30'

0,25'

0.20.

0.15'

0.10'

0.0~'

0.00 o

0 0 0 0 0 0 0 0 0 0 0

0 0 O°ooO°°OOOoooooOoOoooo O

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Fig. 13 -- A strain vs. time curve from constant stress tests of C2 at 750°C (reproduced from representative strain vs. time strip chart recording) showing shrinkage with aging.

E

B . I B - ~ V F S * ~ 4 e

S . ~ EXEC ¢ ? " D ) ~

II.Z~

Fig. 14 - - ED5 analysis of an intragranular precipitate in C2 after 750°C relaxation test, showing strong presence of Nb.

142-s I JUNE 2000

d

A1 Stress Relaxation Data F i ' : ! : i

f i : i : i

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10 0,2 lO 0.4 100.0 10 0.8 101 103

Time, s e c

3 10=

2.5 10=

2 10=

_~ 1.510=

o~

. . . . . . . r ' ' C2 Stress Relaxation Data

1 10=

51o =

0100

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. . . . . i . . . . . . . . . . . # ; • ! :

: i ! i =o

$: ~ $ e0== )

: ' ~! 05o

: i

10 0.4 10 0.0 10 0.8 101 10 0

Time, s e c

3104 T - - ~ - - ~ - - 7 i D1 Stress Relaxation Data

2.510' " " " ' 700

510 ~ 050

0100 ~ i 10 0.2 10 0'4 10 0.8 10 0.8 101 10 3

Time, sec

.E

3104 L E D2 Stress Relaxation Data I

~.~10. ~ . . . . . . . . i ~

1.5 10 d i

010° L 100.2 100.4 100.6 1 ~ "8 1(~ 103

Time, sec

Fig. 15 - - Stress re laxat ion curves p l o t t ed as stress vs. logar i thmic t ime: A - - Hea t A 1; B - - heat C2; C - - heat D1 ; D - - heat D2.

where a is the engineering stress at the notch, ao is the initial stress level at the start of relaxation, k is the slope of the line (which can be considered as the relaxation modulus) and t is time. This equation shows stress relaxation seems to occur according to a logarithmic relationship observed in other studies (Refs. 15, 16).

Precipitation of Nb carbides is believed to start at the point where the relaxation curve loses linearity by bending upward. From the curves shown in Fig. 15, precipitation start times are obtained and plotted as precipitation-time-temperature (PTT) curves - - Fig. 16. These PTT curves exhibit a C-shape, which is typical for precipitation kinetics (Ref. 16). Test material D2, which is the most susceptible to reheat cracking, shows the shortest nose time in its precipitation C- curve. It is known that the closer the Nb:C ratio is to 7.7, the stoichiometric composition of niobium carbide, the greater the potential for precipitation (Ref. 17). In the present study, the Nb:C ratio for A1, C2, D1 and D2 (Table 1 ) are 18.2, 11.8, 16 and 10.9, respectively, with D2 being the closest to 7.7. When C2 and D2 are compared, it is noticeable they have almost the same Nb:C ratio, yet

C2 is more slug- gish in precipitation kinetics than D2. This result shows other chemical effects also influence precipitation kinetics. Since C2 contains 25 times more sul- fur than D2, it seems reasonable to suggest that sul- fur, which strongly segregates to interfaces, may have caused a slower precipitation reac- tion in C2. How- ever, further investigation is needed

1111113

o d

)

o

i Precipitation Start Times

!

~- . . . . . . . . . . i -

I . . . . . . . . . .

ld lO 2 lO 3 Time, SO(:

Fig. 16 - - Prec ip i ta t ion start t imes p l o t t ed in the fo rmat o f p rec ip i ta t ion -

t ime- tempera tu re (PTT) d iagram.

to positively identify these chemical factors. Nitrogen content and ferrite potential may also affect the precipitation kinetics.

From the preceding, it is reasonable to assume that reheat cracking during postweld heat treatment is driven by the precipitation behavior of the alloy. Ap- proaches to circumventing the reheat cracking problem should be considered

in light of factors affecting such precipitation. For example, compositional adjustments and control of thermal- mechanical treatment may allow reheat cracking to be circumvented.

C o n c l u s i o n s

1 ) A Gleeble-based test was employed

WELDING RESEARCH SUPPLEMENT[ 143-s

to evaluate reheat cracking during PWHT of Type 347 stainless steel, with considerations taken for microstructure, change of strength with temperature, and stress levels to simulate reheat cracking conditions. This test has been used by others as well (Refs. 7, 10).

2) The increase of force (stress) vs. relaxation time observed for all test compositions was attributed to volumetric shrinkage upon precipitation of Nb-rich particles; this increase is believed to contribute to reheat cracking in the presence of a precipitate-hardened matrix under rigid restraint.

3) A verification test under constant- load conditions produced a small but definite decrease in strain vs. time, sup- porting the contention that a volume (or density) change occurs during a complicated precipitation and stress-relaxation process.

Acknowledgments

The authors would like to thank the WRC High Alloys Committee and Stain- less Steel Welding Subcommittee for financial and technical support of the work reported here. Discussions with Dr. H. Ferguson and Dr. W. Chen, DSI, Inc., and technical assistance from D. Van

Steele, manager of the mechanical testing lab at RPI, are also gratefully ac- knowledged.

References

1. Messier, R. W., Jr., and Li, L. 1997. Weld heat-affected zone liquation cracking in Type 347 stainless steel. Science and Technology of Welding andJoining 2(2): 43-52.

2. Easterling, K. 1992. Introduction to the Physical Metallurgy of Welding, Second ed. Boston, Mass., Butterworth-Heinemann.

3. Cordea, J. N. 1975. Niobium- and vanadium-containing steels for pressure vessel service. Bulletin 203. New York, N.Y., Welding Research Council, pp. 33-34.

4. Thomas, R. D., Jr. 1984. HAZ cracking in thick sections of austenitic stainless steels - - part II. Welding Journal63(12): 355-s to 368-s.

5. Younger, R. N., and Baker, R. G. 1961. Heat-affected zone cracking in welded austenitic steels during heat treatment, Report B5/11/61, British Welding Research Associa- tion, pp. 579-587.

6. Christoffel, R. J. 1962. Cracking in Type 347 heat-affected zone during stress relaxation. Welding Journa141 (6): 251 -s to 256-s.

7. Franklin, J. E., and Savage, W. F. 1974. Stress relaxation and strain-age cracking in Rene 41 weldments. Welding Journal 53(9): 380- s to 387-s.

8. Widgery, D. J., Howard, R. D., McKeown, D., and Gooch, T. G. 1972. The development of criteria for the assessment of welding characteristics of high temperature materials:

progress in general applicability evaluation. TWl Final Report no. 3270/13/72, pp. 1-33.

9. Ishii, J., Kaihara, S., and Kume, R. 1995. Reheat cracking sensitivity of the welded joint of austenitic stainless steel, IIW Doc. IX-1787-94.

10. Lin, W., and Lippold, J. C. 1995. Eval- uation of postweld heat treatment cracking in nickel-based alloys and stainless steels. Paper presented at 76th AWS Annual Meeting, Cleveland, Ohio.

11. Karjalainen, L. P. 1995. Stress relaxation methods for investigation of softening kinetics in hot deformed steels. Materials Sci- ence and Technology 11 (6): 557-565.

12. ASM Handbook, Vol. 20, Materials Se- lection and Design. 1997. Materials Park, Ohio, ASM International, pp. 510-511.

13. Yue, M. S., and Jonas, J. J. 1991. Hot ductility of steels and its relationship to the problem of transverse cracking during continuous casting. International Materials Reviews 36(5): 187-217.

14. Dieter, G. E. 1976. Mechanical Metal- lurgy, New York, N.Y., McGraw Hill, pp. 473476.

15. Gibbs, G. B. 1966. Creep and stress relaxation studies with polycrystalline magne- sium. Phil. Mag. 13: 317-329.

16. Liu, W. J., and Jonas, J. J. 1988. A stress relaxation method for following carbonitride precipitation in austenite at hot working temperatures. Met. Trans. A: 19A(6): 1403-1413.

17. Keown, S. R., and Pickering, F. B. 1981. Niobium in stainless steels. Niobium, Pro- ceedings of the International Symposium, San Francisco, Calif., pp. 1113-1141.

Use of Low-Carbon 1-1/4Cr-lhMo Weld Metal for Fabrication of Cr-Mo Components

WRC Bulletin 439 (February 1999)

C. D. Lundin, P. Liu, G. Zhou and K. Kahn

This bulletin reports a two-phase project on the use of low-carbon 1 -V~Cr-'~Mo fil ler metal to provide a basis for the use of lower hardenabil i ty characteristic deposits to enhance weld repair and to evaluate the weld deposit elevated temperature properties with and wi thout PWHT. In Phase I, the efficacy was proven for repair of service exposed components as the testing of jumbo transverse weld specimens did not show rupture in the repair fi l ler metal and rupture times exceeded the ASTM DS50 minimum times when the weld coupons were tested in the creep regime. A Phase II program on fi l ler metal development to enhance the creep properties of the low-carbon 1 -V~Cr-V~Mo deposited weld metal by incorporating tungsten, niobium and vanadium additions. The program was successful in that weld metal creep behavior was improved to a level in excess of that of the base metal and no fabrication difficulties were evident. Thus, the basic work has been accomplished to permit the commercial development of Cr-Mo fil ler metals, which are fabrication fr iendly and have elevated temperature properties.

ISSN: 0043-2326 ISBN: 1-58145-446-5

Library of Congress Number 85-6471 16 Number of Pages: 99

Publication sponsored by the Pressure Vessel Research Counci l of the Welding Research Council, Inc.

The price of WRC Bulletin 439 is $135 per copy, plus $5 for postage and handl ing in the United States and Canada or $10 postage and handl ing for locations elsewhere. (All prices are in U.S. dollars.)

Orders should be sent with payment to the Welding Research Council , 3 Park Avenue, 27th Floor, New York, NY 10016-5902. Phone (212) 591-7956; Fax (212) 591-7183: e-mail [email protected]. Visit our Web site http : / /www. forengineers, org/wrc.

144-s I JUNE 2000

Effect of High Gravity on Weld Fusion Zone Shape

With an increase in gravitational acceleration, the depth-to-width ratio of the weld fusion zone tends to decrease

BY D. K. A IDUN, J. J. DOMEY AND G. A H M A D I

ABSTRACT. Understanding the physical phenomena involved in arc welding is of substantial value to improving the weldability of materials. One major factor affecting the motion within the weld pool is the gravity-driven buoyancy force. This force opposes the electromagnetic force- induced flow and opposes or enhances the Marangoni convective flow within the weld pool depending on the sign of the surface tension gradient (dy/dT). Physical experiments for spot GTA welding of commercially pure nickel (N i-270) in the high-gravity condition (1 g = 9.8 m/s2 to 10 g = 98 m/s2) were conducted in the Multi-Gravity Research Welding System at Clarkson University. It was found the depth-to-width ratio (d/w) of the weld fusion zone decreases as the net acceleration increases to 10 g. In addition, a trace element of iron (Fe) was added to the spot GTA welds at various g levels to better visualize the weld fusion zone. This case also showed the d/w ratio of the fusion zone decreases with the increase in gravitational acceleration.

Introduction

In light of the safety, economic and environmental factors concerned, we need to pay more attention to the advancement of manufacturing and fabrication processes such as welding (Ref. 1 ).

Whether the welding processes are used on earth or in space, they have the same common objective: to obtain defect-free welds. A defect can be defined as a discontinuity that inhibits a weldment from meeting the desired specifications/code requirements and includes such items as porosity, hot cracking and incomplete penetration. To achieve this objective, reliable science-based corre-

D. K. AIDUN, J. J. DOMEY and G. AHMADI are with the Mechanical & Aeronautical Engi- neering Department, Clarkson University, Potsdam, N. Y.

lations between the environment, welding process/technique, microstructure and properties of weldments, as well as models to predict such relations, must be developed.

To quantitatively understand the mechanisms behind defects in welds, one first has to examine and characterize the convection and heat transfer in weld pools and their effects on the overall weld integrity. Buoyancy, Marangoni and electromagnetic forces have been found to have significant effect on the fluid flow in arc weld pools (Refs. 2-14). In spite of the significant need for metal joining in different gravitational fields, the effect of gravity, especially high gravity, on the weld pool dynamics is not understood.

Keanini and Rubinsky (Ref. 15) studied plasma arc welding (PAW) of steel in a reduced-gravity environment. They reported that, for PAW, gravity did not have a significant effect on weld shape for their full-penetration welds. The major observed effect was pulling the weld down- ward, which widened the bottom of the pool. The authors also reported their results for the effects of gravity were independent of the mass flow rate of the plasma, initial temperature of the base metal and surface tension of the molten weld pool. Russell, et al. (Ref. 16), reviewed various weld processes being

KEY WORDS

Gravitational Acceleration Buoyancy Force Electromagnetic Force Marangoni Convective Flow GTAW Ni-270 Fusion Zone

considered for use in the construction, repair and fabrication of metal structures for space applications. Kaukler and Workman (Ref. 17) proposed that laser welding can be a viable joining process for space construction. They conducted simulations using a laser beam welding system on board a NASA KC-135 aircraft. The specimen was kept in a vacuum chamber to more closely represent the space environment. They reported an increase in penetration on the welds performed in a microgravity environment at 0.1 g = 0.98 m/s2 over those performed in the normal environment of 1 g = 9.8 m/s2. Wang and Tandon (Ref. 18) studied the microstructure changes of laser beam welding thin sheets of 316 stainless steel in a reduced-gravity environment. They reported that reduced gravity caused both the width and depth of the weld pool to increase over similar welds performed at 1 g. They also noticed an increase in porosity and suspended weld particles in microgravity conditions, which may lead to a weaker weld joint. Domey, etal. (Ref. 19), numerically simulated spot GTA welds onto aluminum under different gravitational fields. They found the convective flow field in the weld pool in a low-gravity environment (<1 g) is governed by a combination of the electromagnetic force and the Marangoni force, while for normal 1-g and high-gravity 2-g environments, the weld pool convection is driven by the buoyancy force. Recently, Singh, Kang, Lambrakos and Marsh (Ref. 20) reported the weld pool geometry changes consid- erably depending on gravity and the width of the weld pool was observed to increase by about 10% at 1.8 g compared with the width at -1.2 g.

The general scope of this work is to provide a better understanding of the role of enhanced buoyancy-driven flow at high g on the weld pool size and shape of GTA welds. A series of physical spot GTA welding of commercially pure

WELDING RESEARCH SUPPLEMENT [ 145-s

Fig. I - - The Mult i-Gravity Research Welding System (MGRWS) during rotation.

Net Acceleration vs. Beam Rotation

/ /

/ /

J f /

/ /

. . . . . . . . . Rotation ~l~mdS~of B~am ;rpm) ~ . . . . . . . . .

Fig. 2 - - Net acceleration o f the MGRWS as a function o f the rotation rate (rpm).

Table 1 - - Mill Composition of Ni-270

Element Wt-%

Ni 99.95 min. C 0.02 max. Fe 0.005 max. Mn, Cr, Ti, Mg, Co, 0.001 max. Cu, Si, and S

nickel for a range of high-gravity conditions in the Multi-Gravity Research Welding System (MGRWS) was performed. The variation of depth-to-width ratio as a function of gravity was studied. The effect of a trace element of iron was also analyzed.

High-Grav i ty Environment

To examine the effect of increased gravity (>1 g) on weld pool size and shape, a high-gravity environment was created using a centrifuge called the Multi-Gravity Research Welding System (MGRWS), which was designed and built at Clarkson University (Ref. 21). The MGRWS has a 1.15-m beam (arm) length and is capable of rotating at speeds in excess of 86 rpm (>12 g). Pictures of the MGRWS are shown in Figs. 1 and 2. The MGRWS is also capable of being outfit- ted with both the gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes. The welding box shown in Fig. 3 is pivoted so the net acceleration experienced is parallel to the torch and perpendicular to the bottom of the box at all times, as shown schematically in Fig. 4.

Regel and Wilcox (Ref. 22) discussed the changes that occur to a fluid when it is placed into a centrifuge with an arm length of r rotating at an angular velocity of co. They noted that three major

Table 2 - - Spot GTA Welding Parameters for Ni-270 at 1, 5 and 10 g

Arc Voltage Arc Current Shielding Gas and Flow Rate Arc Length Electrode Extension Electrode, Size, Tip Angle and Orientation

Weld or Arc Time Preheat

16 volts 1 oo amps (DCEN) 75Ar-25He and 1.0 m,/h 1.0 mm 2.0 mm W+2%ThO2; 3.18 mm, 60 deg

and 90 deg to the workpiece 10 seconds None

changes occur: 1 ) The net radial acceleration of the fluid is increased by c02r, where r is the radial distance; 2) a Corio- lis acceleration of the form 2co x v is introduced, where x represents the vector cross product and v is the local fluid velocity in the rotating frame; and 3) the acceleration vector varies in both direction and magnitude throughout the fluid due to the variation of r in the c02r term. These terms are related to the net acceleration, Coriolis acceleration and acceleration gradient, respectively. The Coriolis force in this case acts perpendicular to the plane of Fig. 4, and its magnitude varies because of the change in the fluid velocity in the weld pool.

Experimental Procedures

Base Material

It is well known small variations in chemical composition can have dramatic effects on resulting welds. There- fore, commercially pure nickel (Ni-270) was chosen as the base metal for this investigation. The Ni-270 stock was provided in a 25.4-mm-diameter swaged bar. The composition of the nickel is shown in Table 1. Samples of nickel were sliced from the base stock to the final dimensions of 25.4 mm diameter

by 3.18 mm thick. The "to be welded" surface was subjected to 320 SiC paper to provide a consistent surface finish for all of the samples.

Welding Parameters/Procedures

The samples were subjected to a spot GTA welding process using the MGRWS with the parameters shown in Table 2. The MGRWS was brought up to the desired speed (rpm) by remote control to obtain the specific g level. Once at the desired g level, the arc was turned on and the weld was performed for the predetermined arc time of 10 s. After completing the weld, the centrifuge was allowed to continue spinning for 60 s to allow for the initial cooling. Then the MGRWS was slowly brought to a stop using a foot brake.

The welded samples were then sectioned, polished and etched for metallographic analysis. The welds were pho- tographed using a stereomicroscope with a magnification of 19.5X. The resulting photographs were digitally scanned using a 600 x 600 dots-per-inch scanner, producing accuracy to within 5 pixels or + 5 microns. This technique was used for all the welds for determi- nation of the depth (d) and width (w) of the fusion zones.

146-s I JUNE 2000

Fig. 3 - - Welding box o f the MGRWS.

Results and Discussions

Figures 5-7 show photomacrographs of spot GTA welds performed on the MGRWS at accelerations of 1 (no rotation), 5 and 10 g, respectively. These macrographs are a cross section through the center of the weld fusion zone. To examine the effect of centrifugation on the weld fusion zone shape/profile, the depth and the width were measured, as outlined in the previous section. Table 3 shows the average depth, the average width and the average depth-to-width ratio of the fusion zone of the welds at various g levels. The data indicate that as g level (or rotation rate) increases, the average depth-to-width ratio of the weld fusion zones decreases (in the range of 1 to 10 g). To understand the reason for this trend of behavior, one should examine the controlling forces for an autogenous arc welding process during centrifugation. As was indicated earlier, Marangoni, electromagnetic and buoyancy are the dominant forces in an autogenous arc welding process at low arc currents. Once a metal is subjected to an arc welding process during centrifugation, not only does the buoyancy force increase, but also the Coriolis force is introduced in the weld pool of the form 20) x v, which in this case acts perpendicular to the plane of Fig. 4. The Coriolis acceleration does not necessarily influence the magnitude of the local fluid velocity, but it may alter the fluid flow pattern, which could affect the weld fusion zone shape. In this study, the effect of Coriolis force was not considered.

The effect of an increase in buoyancy acceleration in decreasing the d/w ratio of the weld fusion zone can be explained based on the three major forces; namely, the Marangoni, the electromagnetic and the buoyancy. Ni-270 has a negative surface tension gradient (dT/dT) of -0.38 x 10-3N/m°C, a reference density of 8900

kg/m~ (Ref. 23) and a magnetic permeability of 0.251 x 10 3H/m (Ref. 24). Observed from the top, for the case of Ni-270, the fluid flow pattern in the weld pool due to surface

Welding Box

Welding Torch ~r Net g

V Weld Pool J

Base Material

Fig. 4 - - The orientation o f the net acceleration with respect to the weld ing torch and the workpiece (see arrows).

tension gradient (or Marangoni), the buoyancy and the electromagnetic are outward, outward and inward, respectively. Figure 8 shows the schematic of flow patterns due to Marangoni, buoyancy, electromagnetic and the overall resultant flow pattern. This figure shows an increasing buoyancy- driven flow results in a stronger outward flow, which results in an overall smaller in- flow pattern and causes a shallower but wider weld fusion zone. This wil l decrease the depth-to- width ratio.

The relative importance between the surface-tension- driven flow and the buoyancy-driven

BM

Fig. 5 - - The shape o f the fusion zone o f a N i -270 GTA weld at 1 g (no rotation).

Fig. 6 - - The shape o f the fusion zone o f a Ni-27~) GTA weld at 5 g.

Table 3 - - Average,+~ d/w Ratio of the Weld Fusion Zone of Ni-270

g Level Average Depth (d), mm Average Width (w), mm d/w Ratio

1.0 2.68 7.64 0.351 5.0 1.44 7.08 0.203 10.0 1.20 6.89 0.174

(a) Two welds per g level.


Fig. 7 - - The shape of the fusion zone of a Ni-270 GTA weld at log .

Schematic showing iron arc bridge

Stando~ Fixture

Weldlnq

Work

Insulation [ ~ ]

Schematic outline of competing forces within the weld pool

Marangoni Buo~ncy FJectromzgnltlc Ovlmll

Forcu Forces For(ms RIIul l

Fig. 8 - - Schematic outl ine of the competing forces within the weld pool.

Fig. 9 - - Schematic showing the addition of Fe to the Ni-270 weld pool. Fig. 10 - - The shape of the fusion zone of Ni-270 (with Fe) GTA weld at

l g .

Fig. 11 - - The shape of the fusion zone of Ni-270 (with Fe) GTA weld atSg.

Fig. 12 - - The shape of the fusion zone of Ni-270 (with Fe) GTA weld at 10g.

148-s l JUNE 2000

flow can be studied by examination of the Bond number (Bo). The Bond number, which is the ratio of buoyancy force to the surface tension force, is defined as Bo = gApU/y, where g, Ap, L and y, respectively, are the gravitational acceleration, change in density, characteristic length (1-3 mm) and surface tension (1.778 N/m) (Ref. 23). Using the appropriate values for each of the terms, the Bo numbers at 1 and 10 g are 0.29 and 2.9, respectively. These values of Bo number indicate that for this system (Ni-270), as the acceleration increases from 1 to 10 g, the buoyancy force becomes more significant than the surface tension.

The Atthey's number (At) is the ratio of the buoyancy force over the electromagnetic force (Ref. 25) and is defined as At = gAp/[BI2/~aJ], where B, I and a are the magnetic permeability, the arc current (100 A) and the length scale (1-3 mm), respectively. Using the appropriate values for the terms, the At numbers at 1 and 10 g are 0.047 and 0.47, respectively. This dimensionless number shows that, even at 10-g acceleration, the electromagnetic force is stronger than the buoyancy force. Table 4 shows the relative magnitude of the three major forces for the Ni-270 weld. For this system, the electromagnetic force is the dominant force over the surface tension and buoyancy force even at 10 g. However, the net sum of the three forces as the g level increases results in a shallower and wider weld fusion zone, which decreases the depth-to-width ratio of the fusion zone.

To better visualize the shape of the spot GTA fusion zone of Ni-270 welds at various g levels, a trace element of iron (Fe, less than 0.01 grams) was added to the weld pool, as shown in Fig. 9. The addition of the Fe into the weld pool is the only parameter that was varied from previous welding experiments. Figures 10 through 12 show photomacrographs of the spot GTA welds of Ni-270 at 1,5 and 10 g, respectively. The fusion zone in these macrographs is well defined. Table 5 shows the depth, the width and the depth-to-width ratio of the fusion zone of the spot GTA welds at various g levels. Figure 13 shows the depth-to-width ratio of the fusion zone as a function of g level with and without the trace element iron. These indicate that as the acceleration (g) increases the d/w decreases similarly to the welds without the trace element.

The shape of the fusion zone of the welds with the trace element indicates the fluid flow pattern was made of two opposing circulation patterns due to a maximum that exists in the y-T relationship, as schematically shown in Fig. 14. In addition, the slope of d/w with the

Table 4 - - The Magnitude of the Forces (N/m 3) in the Ni-270 Weld Pool

Electromagnetic Force Surface Tension Buoyancy force @ 1 g Buoyancy force @ 10 g

9 x 10 s N/m 3 4 x 103N/m 3 1.2 x 10 4 N/m 3 1.2 x 105 N/m 3

Table 5 - - Depth (d), Width (w) and d/w Ratio for Welds with Fe Addition

g level d (mm) w (mm) d/w ratio

1 g 1.20 5.98 0.201 5 g 0.97 5.6 0.173 10 g 0.71 6.01 0.120

dW Ratio vs g - l e ~

0.403

0.3OO I ̧~i i ̧ i~ ! !

0.100

ao5o ~

o . i x l o . . . . .

(3.0 2-5 5.0

g-le~l (1.0:eartlYs gravity)

7.5 10.0

Fig. 13 - - The depth-to-width ratio of the fusion zone of the Ni-270 with and without Fe addition vs. the g level.

trace element is less than that without the trace element. These are due to the effect of added Fe on the three major forces that control the pattern of the convective flow in the weld pool mentioned earlier. It should be emphasized the addition of the trace of iron could have a significant effect on the electromagnetic and the surface tension of the weld pool. The addition of iron to Ni-270 changes the magnetic permeability of the weld pool, thus affecting the magnitude of the electromagnetic force but not the direction of the convective flow. It also changes the surface tension gradient of the weld pool surface, but it has a small effect on the buoyancy force. This is because the shape of the fusion zone in this case did not change as the g level increased.

What needs to be determined now is how significantly and in what way does the Coriolis force affect the overall convection pattern in the weld pool. Its sig- nificance is another interesting research topic. This, however, is left for a future study.

T ~

T T'

Fig. 14 - - The f luid f low in the weld pool re- suiting from Marangoni convection (Heiple- Roper Theory) for the case of high levels of surface-active elements where a maximum exists in the y-T relationship.


Conclusions

The present study shows the high gravity in the Ni-270 weld pool wi l l no- ticeably reduce the depth-to-width ratio of the fusion zone. It is clear that an increase in buoyancy-driven flow induced by the high gravity wi l l produce a wider, but shallower, weld fusion zone in metals such as Ni-270 with and without Fe as the trace element. It is conjectured that the addition of iron to Ni-270 produces a ~'-T relationship similar to that shown in Fig. 14 that causes the two opposing flow patterns. This is because the addition of the trace of iron is not expected to significantly change the flow pattern due to electromagnetic and buoyancy forces.

References

1. David S. A., and DebRoy, T. 1992. Cur- rent issues and problems in welding science. Science 257: 497-502.

2. Kou, S., and Sun, D. K. 1985. ASM Met. Trans. A 16A (2): 203.

3. Kou, S. 1987. Welding Metallurgy. New York, N.Y., John Wiley & Sons, p. 91.

4. Correa, S. M., and Sundell, R. E. 1986. Proceedings of the AIME Metallurgical Soci- ety.

5. Oreper, G. M., Szekely, J., and Eager, T. W. 1986. The role of transient convection in

the melting and solidification in arc weld pools. ASM Met. Trans. B 17B: 735-744.

6. Chan, C. L., Mazumder, J., and Chen, M. M. 1987. Material Science Technology, 3.

7. Matsunawa, A., Yokoya, S., and Asako, Y. 1987. Trans. JWRI, 16.

8. Thompson, M. E., and Szekely, J. 1989. Intl. Journal of Fluid and Mass Transfer, 32.

9. Tsotridis, G., Rother, H., and Hondros, E. D. 1989. Marangoni flow and the shapes of laser-melted pools. Naturwissensch 76: 216-218.

10. Pardo, E., and Weckman, D. C. 1989. Prediction of weld pool reinforcement dimensions of GMA welds using finite-element model. ASM Meta. Trans. B 20B: 937-947.

11. Zacharia, T., David, S. A., Vitek, J. M., and DebRoy, T. 1989. Weld pool development during GTA and laser beam welding of type 304 stainless steel. Welding Journal 68(12): 499-s to 519-s.

12. Kim, S. D., and Na, S.J. 1992. Effect of weld pool deformation on weld penetration in stationary gas tungsten arc welding. Welding Journal 71 (5): 171 -s to 178-s.

13. Shirali, A. A., and Mills, K. C. 1993. The effect of welding parameters on penetration in GTA welds. Welding Journal 72(7): 347-s to 353-s.

14. Zacharia, T., Eraslan, A. H., and Aidun, D. K. 1988. Modeling of autogeneous welding process. Welding Journal 67(3): 53-s to 62-s.

15. Keanin, R. G., and Rubinsky B. 1990. Plasma arc welding under normal and zero gravity. Welding Journal 69(6): 41-50.

16. Russel, C., Poorman, R., Jones, C.,

Nunes, A., and Hoffman, D. 1991.23rd Inter- national SAMPE Technical Conference.

17. Kaukler, W. F., and Workman G. L. 1991. Welding in Space and the Construction of Space Vehicles. Welding technical conference.

18. Wang, G., and Tandon, K. N. 1993. The microstructure changes during laser welding of stainless steel under reduced gravity environment. Microgravity Science Technology Vl/2.

19. Domey, J., Aidun, D. K., Ahmadi, G., Regel, L. L., and Wilcox, W. R. 1995. Numer- ical simulation of the effect of gravity on weld pool shape. Welding Journal 74(8): 263-s to 268-s.

20. Singh, J., Kang, N. H., Lambrakos, S. G., and Marsh, S. P. 1998. Gravity effects on the microstructural behavior and the development of weld pool. Microgravity Materials Sci- ence Conference. Huntsville, Ala.

21. Centrifuge designed for welding and casting in high Gs. 1997. News of Industry, Welding Journal (76)6:18.

22. Centrifugal Materials Processing. 1997. L. L. Regel and W. R. Wilcox, eds. New York, N.Y., Plenum Press.

23. UIIman's Encyclopedia of Industrial Chemistry, 5th ed., Vol. A1 7. 1991. Cam- bridge, N.Y.

24. Kirk-Othmer. 1983, Encyclopedia of Chemical Technology, 3rd edition. New York, N.Y., John Wiley & Sons.

25. Atthey, D. R. 1980. Journal of Fluid Me- chanics 98(4).

Fatigue Strength Reduction and Stress Concentration Factors for Welds in Pressure Vessels and Piping

1. Interpret ive Review of Weld Fatigue-Strength-Reduction and Stress-Concentration Factors By C. E. Jaske

2. Fatigue-Strength-Reduction Factor Based on NDE By J. L. Hechmer

1. Interpretive Review of Weld Fatigue-Strength-Reduction and Stress-Concentration Factors: The objectives of this report are to 1 ) clarify the current procedures for determining values of fatigue-strength-reduction factors (FSRFs), 2) collect relevant published data on weld-joint FSRFs, 3) interpret existing data on weld-joint FSRFs, 4) facilitate the development of a future database of FSRFs for weld joints and 5) facilitate the development of a standard procedure for determining the values of FSRFs for weld joints. The main focus of this report is on weld joints in Class 1 nuclear pressure vessels and piping. However, relevant fatigue data on similar weld joints for other applications, such as bridges and offshore structures, also are reviewed and interpreted.

2. Fatigue-Strength-Reduction Factors Based on NDE: This report addresses applying a fatigue-strength-reduction factor (FSRF) to a weld surface, based on the nondestructive examination (NDE) that is performed. The development is focused on Class 1, pressure vessels of the ASME Boiler and Pressure Vessel Code, Section III, NB and NC-3200 and Section VIII Division 2 (ASME Code, 1997). It is the position of this report that the fatigue life is a function of the quality of the material and the NDE gives an assessment of this quality. This leads to the conclusion that weld metal wi l l have a fatigue life consistent with the prediction of the ASME Code S-N curves and equivalent to that of base metal provided a full NDE is applied. With reduced NDE, the application of an FSRF in the analysis maintains consistency.

The report develops and defines the basis for each FSRF. For example, it explains why one NDE technique has a greater impact on fatigue life than another technique, i.e., its omission requires a higher FSRF.

Publication of this document - - WRC Bulletin No. 432 - - was sponsored by the Pressure Vessel Research Council of the Welding Research Council.

The Price of WRC Bulletin 432 (June 1998, 55 pages) is $85.00 per copy plus $5.00 for U.S. and Canada and $10.00 for overseas postage and handling. Orders should be sent with payment to the Welding Research Council, 3 Park Avenue, 27th Floor, New York, NY 10016-5902. Phone (212) 591-7956: Fax (212) 591-7183; e-maih [email protected] or visit our homepage http://www.forengineers.org/wrc.

150-s I JUNE 2000

Intelligent Methodology for Sensing, Modelin and Control of Pulsed GTAW:

Part l Bead-on-Plate Welding

g

Computer vision for sensing, neural networks for modeling, fuzzy logic and neuron self-learning for control of pulsed GTAW are described

BY S. B. CHEN, Y. J. LOU, L. WU A N D D. B. Z H A O

ABSTRACT. This study addresses intelligent techniques for fulfilling quality control of bead-on-plate welding. A new visual double-sided sensing system capable of imaging the weld pool topside and backside simultaneously in a frame was provided to determine the weld pool geometry parameters. The imaging principle was analyzed with spectrum distribution, in which the weld pool was illuminated by arc light emission to receive a clear image under base current. Dou- ble-sided size parameters describing weld pool geometry were defined and determined in real time with the developed image processing algorithm. The influences of welding parameters such as pulse duty ratio and travel speed on weld bead geometry were identified by step response. Based on the analysis, a neural network model of the dynamic process was established for predicting the backside width with the welding parameters and topside size parameters. The simulation results indicated the accuracy of the model, and the characteristics of the welding process were analyzed carefully. Aiming at the bead-on-plate pulsed GTAW process, conventional and intelligent control methods of single input and single output were investigated, and the neuron self-learning PSD control was verified with better performance for practical application through comparisons.

Introduction

As is well known, weld quality control is a complicated problem in arc welding

s. B. CHEN, previously with the Harbin Insti- tute of Technology, Harbin, P.R. China, is now with Shanghai Jiao Tong University, Shanghai, P.R. China. Y. J. LOU, L. WU and D. B. ZHAO are with the National Key Laboratory of Ad- vanced Welding Production Technology, Harbin Institute of Technology.

processes. Backside weld width and penetration depth are major factors in the final weld quality for full penetration. The sensing and control of backside width are critical and challenging issues in automated welding, including robotic welding. Although extensive research has been done to find feasible approaches for sensing these parameters using topside sensors, more practical solutions are still strongly needed for different cases.

In principle, backside weld width and penetration depth can be monitored by embedding thermocouples into the weld piece or by acoustic emission sensing (Ref. 1). However, their practical applications are limited because of the contact between the sensors and the workpiece. In the case of full penetration, the backside weld width can be detected by measuring the light intensity from the backside of the workpiece (Refs. 2-4). However, it is difficult or impossible to conveniently locate backside sensors for many configurations, for instance, during the welding of pressure containers. Also, the motion match between the torch and sensor can be difficult if the torch moves. Hence, the sensor should be attached to and move with the torch to conduct the so-called topside sensing of the weld penetration.

KEY WORDS

Bead-on-Plate Welding Control Algorithms Computer Vision Double-Sided Sensing Fuzzy Logic Neural Network Model Pulsed GTAW

Among the many proposed topside sensing techniques, pool oscillation methods have been extensively studied. The pioneering work was done by Richardson (Ref. 5), Hardt (Ref. 6) and their coworkers. Wang, et al. (Ref. 7), found that, for full penetration, the width of a stationary weld pool could be determined by the resonance frequency. An interesting discovery was the distinction of weld pool oscillation frequency between the partial joint penetration and full joint penetration. Xiao and Ouden (Refs. 8, 9) found a drop in the oscillation frequency occurs as the penetration state changes from partial to full penetration. Richardson and Yoo (Ref. 10) have also observed this frequency drop. For the measurement of the pool oscillation, both arc voltage and arc light fluctuations have been used.

Ultrasonic testing has become a standard technique for locating cracks, incomplete fusion, porosity and other discontinuities in fusion welds. Hardt and Katz (Ref. 11) utilized reflection ultrasound methods to measure the size of the stationary weld pool. Ultrasonic measurements of the weld pool were extensively studied at the Idaho National Engi- neering Laboratory (Refs. 12, 13). Different weld geometries were distinguished. Contact transducers were used. When the ultrasound was generated by a pulsed Nd:YAG laser, the contact trans- ducer could be eliminated (Ref. 14).

Modern infrared thermograph equipment provides a feasible means to measure the temperature field of the weld pool. At Auburn University, the infrared sensing of arc welding has been extensively investigated by Chin, et al. (Reg. 15, 16). The temperature distribution is measured in GMAW. It was found the depth of joint penetration can be determined using the characteristics of the temperature profiles. Beardsley, et al.

WELDING RESEARCH SUPPLEMENT J 151-S

I SCMmotion l centre i board ,~II~L

[ M i l't°r I

I Power

Travel L ~ °'°;°i. Work piece

Work

_C~., r ct_.~

~orch

n e - ~ ' l f Monitor Q /

LBackside Topside)

CCD c a l n c r a

tC•SCM Composed filter system

: Single-~hip Microcomputer

A Narrow band fdter

(566,0 566) / Neutraldensityfiltem ~ "CCDoan~ra Z 01" ' ' //

I u , 2,54.2 )I i

t / w3 (-56.6, O, -56.6)

Fig. 1 - - Structural diagram of the experimental system.

(Ref. 17), found the root surface bead width of the full-joint-penetration welds can be determined in GTAW using a ratio between the area of the 600°C isotherm surrounding the weld pool and the weld pool area.

Despite the above achievements in the topside sensing of weld joint penetration, more accurate information can still be determined from the weld pool itself. It is known the weld pool contains abundant information about the welding process. By viewing the weld pool, a skilled operator can estimate the weld joint penetration. Thus, visual sensing systems have been developed to view the weld pool. The visual sensing systems can be divided into two classifications according to the imaging light source: the active method (imaging with another high-intensity light source) and the passive method (imaging with arc light illumination).

The image sensing of the weld pool surface in GTAW has been extensively investigated by Kovacevic, Zhang and coworkers (Refs. 18-20). In their investigation, a high-shutter-speed camera as- sisted with a pulsed laser was used. The pulse of the laser lasted only 3 ns, and the shutter of the camera was synchronized with the laser pulse. Although the average power of the laser was only 7 mW, its peak power reached 70 kW. During the pulse duration, the intensity of the laser illumination was much stronger than that of the arc and molten metal. Thus, clear images of the weld pool surface could be captured in the GTAW process.

In the passive sensing method, the weld pool images can be illuminated by the arc light emission; therefore, this method has few pieces of hardware, a simple light path of imaging and low application cost. Elementary principle has

been carried out to map the visible light emissions in GTAW (Ref. 21). Spectral windows where the external sensors have the least radiance disturbance were proposed and a clear weld pool image was captured. To eliminate the disturbance of unnecessary arc light, Pietrzak (Ref. 22), R. W. Richard- son (Ref. 23), D. Brzakovic (Ref. 24) and their coworkers developed a coaxial arc weld pool viewing system, using the electrode tip to block the bright core of the arc from overpowering exposure on the CCD target. Investiga- tions concentrated on a more clear weld pool image, and the intensity of the arc light was found to change from strong to weak when the welding current transformed from pulse peak value to the base value in pulsed GTAW (Ref. 25). The illuminated image of the weld pool was the clearest for determining the weld pool geometry easily.

It should be pointed out the dynamic identification and control of arc welding processes have been explored through a number of studies. The conventional PID control system using current as a control variable was designed (Ref. 26). Advanced control techniques such as adaptive control have also been used to generate sound welds (Refs. 3, 19, 27).

Arc welding is characterized as inher- ently variable, nonlinear, time varying and having a strong coupling among welding parameters. So, it is very difficult to find a reliable mathematical model and to design an effective control scheme for arc welding by conventional modeling and control methods.

Artificial intelligence methodology was developed for modeling and con- troling the welding process because it

Fig. 2 - - The light path of the simultaneous double-sided visual image sensing system of the weld pool in a frame. A - - The schematic diagram; B - - photograph of sensing system.

could derive the control performance re- lying not on the mathematical process model but on human experience, knowledge and logic. Numerous exciting con- trois with perfect performance have been achieved. K. Andersen (Ref. 28) studied the application for modeling and control of arc welding. T. G. Lim, eta l . (Ref. 29), proposed an artificial neural network (ANN) model for predicting welding depth, and topside and backside width on-line from the detected surface temperature during GMAW (Ref. 29). During GTAW, the relation between welding current, arc voltage, travel speed, wire feed rate and weld bead geometry such as width, depth, reinforcement and cross

152-s I JUNE 2000

area was established from an ANN model and trained by experimental data (Ref. 30). Based on weld pool geometrical appearance, Zhang (Refs. 18, 31 ) developed a control system to simultaneously control the topside and backside pool widths using a neurofuzzy model. A self-learning fuzzy neural network control system of topside width enabled adaptive altering of welding parameters to compensate for changing environments (Refs. 25, 32). Therefore, the control of arc welding seems to be an intelligent and practical application.

In this study, a novel visual sensing system was established to image the topside and backside of the weld pool simultaneously in the same frame. A real- time image processing algorithm was developed to acquire topside and backside sizes of the weld pool. To investigate the dynamic character of arc welding, positive and negative step responses were used to identify the correlation between weld pool geometry and welding parameters. In addition, an artificial neural network model of pulsed GTAW was established. The simulation and analysis of bead-on-plate welds were conducted in pulsed GTAW based on this model. A conventional PID controller, an intelligent fuzzy logic controller and a neuron self-learning PSD controller were designed and compared by simulation results and verified through experiments.

Experimental Systems

Experimental Setup

This study addressed the image processing and quality control of pulsed GTAW. The experimental setup included a welding power source, cooling water pump and other auxiliary equipment. The welding current was computer controlled. A diagram of the system is shown in Fig. 1.

Double-Sided Visual Sensing System

Weld joint penetration has a direct influence on weld strength. Although sensors are available to monitor the back of the weld, it is not possible for many applications to access the back face of the weld. Experience of skilled operators suggests the geometry of the weld pool can provide accurate and instantaneous information about the weld penetration. Topside width of the weld pool can be sensed clearly by a CCD camera and a composite filter and controlled accurately (Ref. 25). For further accurate control of weld penetration, the correlation between topside geometry and backside width of the weld pool should be estab-

T c

3

molten 3

solidified 1

Fig. 3 - - A frame o f a complete we ld poo l image o f pulsed GTAW.

A 5OO

400

~ 3 0 0

~ 200

~ 1 0 0

0 '

350

Mild steel, 50A Arc length: 3mm

400 450 500 550 600 650 700 750 Wavelength, nm

B

~1ooo

/ ~ Mild steel, 50A

| i • I • i • i • i • i I I I

350 400 4 ~ 500 550 600 650 700 750

Wavelenglh, nm

Fig. 4 - - Arc l ight radiat ion o f GTAW with m i l d steel anode. A - - The spectral distr ibut ion; B - - arc l ight radiat ion flux.

lished so that the backside width can be predicted with the determined topside geometry in real time. To correlate the backside width to the topside geometry, both sides of the weld pool need to be imaged simultaneously.

The main parts of the visual sensing system were a composite filter system,

CCD camera, recorder, frame grabber and monitor, as shown on the right in Fig. 1. The schematic diagram of the visual sensing system is shown in Fig. 2A, with a photograph in Fig. 2B.

In Fig. 2A, O_XYZ is the workpiece coordinate system and point O is the center point of the weld pool image. M1, M2,


Table 1 - - Experimental Conditions of Pulsed GTAW

Welding Pulse Pulse duty Base Electrode Angle Conditions frequency ratio current diameter of tip

Unit f (Hz) ~ (%) Ib (A) ~ (ram) 0 (deg) Value 1 45 60 3.2 30

Arc length

1 (mm) 3.5

Flow Specimen rate dimension

L (L/rain) mm x mm x mm 8.0 280 x 50 x 2

Y y

o x o [ ~ I 7 r" ~ x

(A) 03)

Fig. 5 - - The definition of feature size parameters of a fully penetrated weld pool. A - - Topside; B - - backside.

Cazae~a ~..t~

D a D

lw.T

W , _ L~

Fig. 6 - - Signal flow chart of processing images of the weld pool.

M 3 and M 4 are reflectors, the centers of which are O1, 02 ,0 3 and 0 4. O1A, O2B, O3C and O4D represent the normal line of the reflectors, respectively, denoted as the angles with each single axis in the coordinate system.

Along with a video recorder and monitor system, the visual sensing system consisted of the following parts.

Light Path of Double-Sided Imaging Simultaneously in a Frame

The light path was composed of topside and backside imaging light paths. Figure 2B shows the photograph of the double-sided visual sensing system, and Fig. 2A shows its schematic diagram. The light from the weld pool reached the re- flector 01 at a 45-deg angle with the X

axis, and is reflected to pass the composite filter, then reflected by 02 , and finally focused on the target of the CCD camera. The backside light path is shown in the downside of Fig. 2A. The light path system was mounted behind the weld pool to avoid the pollution caused from spatter, fume and smoke.

The composite filter system included topside and backside light paths. The topside image of the weld pool was formed by the illumination from arc emission in the spectral window of 600-700 nm. The topside light path consisted of a neutral density filter (2 mm depth, and the attenuation ratio of the lens was 1%) and a narrow band filter. (The center band was 661 nm, half-width 10 nm and peak attenuation ratio of the lens, 28.8%.) The backside image was formed by the radi-

ance of the backside hot metal. Two neutral density filters were used in the backside light path with lens attenuation ratios of 10 and 50%. Both the topside and backside images concentrated on the same target of the CCD camera through the above double-sided visual sensing light path system.

CCD Imaging System Transferring the Optical Signal to Video Signal

The CCD imaging system included a CCD camera, optical lens and frame grabber. The focal distance of the lens was 50 mm. The sensitivity of the camera was 0.4 Lux, its area of target 5.24 x 6.4 mm, and the shutter was set at '/,000 s.

Initial Experiment

Bead-on-plate experiments were conducted on low-carbon steel during pulsed GTAW using the double-sided visual sensing system, and the experiment conditions are tabulated in Table 1. Peak current was set at 120 A and travel speed was 2.5 mm/s.

A complete weld pool image in a frame is shown in Fig. 3, in which the left is the backside image and the right is the topside image. The image contrast is high. Nozzle, arc center, topside molten portion and topside solidified portion can be clearly seen in the topside image. The bright arc around the weld pool was effectively eliminated, and the shape of the tungsten tip emerged from the background. The backside weld pool image is also distinguishable from the background.

Analysis of the Visual Sensing Principle

Arc light emission is complex. The intensity of spectral distribution of the arc light is shown in Fig. 4A (Ref. 33). It includes a continuous spectrum with low intensity and line spectrums with high intensity (metal line, Ar atom and Ar ion spectrum).

The principle behind imaging the weld pool is to illuminate the weld pool with the continuous spectrum of the arc light emission. This is because the radiation flux of the metal-line spectrum is much weaker than that of the continuous

1 5 4 - s I JUNE 2000

10

E 8

i 6

4

vw I l 3

l I I I l n i 0

0 20 40 60 80 100 T ime, s

E

1=i

Fig. 7 - - Transient response o f backside width with travel speed.

arc spectrum. Figure 4B shows the arc the weld pool light radiation flux of the whole spectrum and the back- through the narrow band filter, ground was im-

In the range of 600-700 nm, there is proved. The mainly a continuous spectrum, with a welding direc- few kinds of line spectrum, and the radi- tion was de- ation flux is low and flat. So the spectral noted as f k w a n d window 600-700 nm is suitable for light- ing the weld pool.

Image Processing for the Weld Pool

For controlling the backside width, the correlation between topside maximum width and backside width is often adopted (Ref. 25). Experiments have shown the length of the topside weld pool changes more distinctly than the topside width with the variation of the heat-sinking condition. Also, the shape of the front part of the weld pool always keeps semicircle with the half-maximum-width as the radius, but the shape of the rear part of the weld pool changes significantly.

Thus, in this study, the topside geometry was specified by the maximum width Wfmax,and the maximum half-length L~nax - - Fig. 5A. The backside geometry parameters included the maximum width Wbmax, the length Lbmax and the area S b - - Fig. 5B.

According to the different characteristics of the topside and backside images, different image processing algorithms were developed. The flowchart of processing is shown in Fig. 6. In the figure, EBS is the exponential base-smoothing algorithm (Ref. 34); CE is the contrast-enhancement algorithm (Refs. 35-37); TD is the image-threshold algorithm of the backside weld pool; and ETG and EBG are the algorithm for determining topside geometry and backside geometry, respectively.

In topside image processing, after EBS and CE, the contrast between the edge of

A 9

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the vertical direction as fkv.The distribution of grayness

Fig. 8 - - Transient response o f backside width with pulse duty ratio. A - - Positive step; B - - negative step.

along with f kv was like a mountain, which provided a feasible method for edge detection. The ETG algorithm included the following steps: finding the center, obtaining the gray value along with fkv, judging the edges, calculating the width, achieving the maximum width from comparison and deriving the maximum half-length.

In the backside image processing, the gray histogram of the filtered image with EBS showed the double-hump-shape prominently; therefore, the thresholding algorithm was suitable for image seg- ment. The BTG algorithm included the following steps: finding the center, obtaining the gray value along with fkv, judging the edges, calculating the width, achieving the maximum width from comparison and deriving the maximum length and area.

On a PC-486 computer, the topside image processing algorithm lasted less than 50 ms, and the time of the backside algorithm was less than 30 ms. The pulse frequency of pulsed GTAW was 1 Hz and the time of base current was not less than 350 ms. So, the algorithms of the image processing were fast enough to fulfill the requirement of closed-loop control in real time.

Neural Network Model for the Dynamic Process

Weld pool geometry is a crucial fac-

tor in determining welding quality. In a previous study, the topside width of the weld pool was sensed and controlled (Ref. 25). To control the weld quality better, the correlation between the topside geometry and the backside width of the weld pool should be identified and modeled first.

Conventional Identification of the Dynamic Process

To design a suitable control system, the dynamic characteristics of the welding process must be known, and the correlation between weld pool geometry and welding parameters must be established. In this study, step inputs were used to identify the transfer function. Generally, the welding process is considered as a first-order system with a given structure. The identification was thus simplified by estimating the model parameters. In pulsed GTAW, a skilled operator can make a near-perfect weld by regulating welding parameters such as pulse duty ratio and travel speed. Therefore, pulse duty ratio (~) and travel speed (V W) were adopted as the step inputs. Other conditions of the experiments were the same as in Table 1. Through experiment data, transient response of weld pool sizes with welding parameters (~ and V w) were derived using the algorithm-of-area method developed with the Matlab program.

The designed step inputs and the step


response are shown in Figs. 7 and 8. The model parameters of the topside and backside geometry parameters were identified. Both the initiation and steady welding periods were considered. The feasibility of each model was verified by comparing the simulation results with the Matlab program and actual outputs.

The transfer functions of the backside maximum width-to-pulse duty ratio are exemplified as follows: 1) Initial period:

(s)=Wbmax(S) 0.101 .e_ ~ Gwb max ~(S) 1.483s +1

~=ls

2) Positive step in steady period:

Wbmax(S) 0.101 Gwbma x (S) ~ (S) 2.068s +1

(1)

(2)

3) Negative step in steady period:

Wb max (s) 0.097 Gwb m a x ( S ) = ~ ( S ) 2 . 7 8 5 S + 1

(3)

The transfer functions of the backside maximum width to travel speed are exemplified as follows: 1 ) Positive step in steady period:

Wbmax(S) -2.911 Gwbma x (S)= Vw(S) ='3.328S +1 (4)

2) Negative step in steady period:

Wb max (s) -3.242 GWb ma× (S) Vw(S) 4.108s +1

(5)

Other transfer functions were identified between other size parameters (Wfmax , L~nax , Lbmax and S b) to pulse duty ratio and travel speed. From the identification results, the characteristics of the welding process were derived as follows:

• The three backside parameters respond to the variation in either ~ or V w at different speeds. Wbmax reaches the steady state faster than Lbmax and S~ but slower than topside geometrical parameters.

• W~a x and Wbmax respond to V w more quickly than to 5, while Lfmax, Lbmax and S b are just opposite.

• During the steady-state period, the transfer functions of negative and positive step responses were different, which indicated nonlinearity of the process.

• The effects of ~ and V w on geometry were coupled with each other.

To investigate the complicated relationships between the weld penetration and welding parameters, neural networks were used because of their capabil i ty for modeling complicated nonlinear processes.

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Experiments and Results for Neural Network Models

Variation in weld joint penetration could be influenced by welding parameters, experiment conditions and welding conditions. Welding parameters included pulse duty ratio, peak current, base current, arc voltage and welding speed, etc. Experiment conditions in-

cluded the root opening or geometry of the groove, material, thickness, workpiece size, electrode tip angle and the rate of the shielding gas flow, etc. The welding conditions contained the heat- sinking condit ion. To form a valid method to monitor the weld joint penetration, the major parameters that may vary during welding were considered in the experiment design. Based on the

156-s I JUNE 2000

analysis about the welding process, 8 and V w were selected as the input signal for exciting the characteristics of the welding process. Random and step signals were considered as the optimal input signals to the welding process. The weld pool size parameters were measured on-line during the experiments with the double- sided visual sensing system.

Twenty-four experiments were performed, and 2350 data pairs were obtained. The first ten results of each experiment were eliminated to avoid the effect of the transition process during the initial period, so 2110 samples were actually used. The results are shown in Fig. 9, arranged according to their serial number in the experiments.

Note the backside maximum width of weld pool varied widely, from 2 to 7.5 mm. The topside maximum width varied from 3.5 to 8.5 mm and the topside maximum half-length is from 3.5 to 9.5 mm. The variations of size parameters were caused by the different welding parameters or conditions.

Neural Network Model Architecture

An artificial neural network (ANN) provided a uniform model frame for almost all types of nonlinear functions. The actual inputs and outputs were taken as the training samples for the determina- tion of the neurons' weight with the back propagation algorithm. In this study, a topside neural network model (TNNM),

TWP

\ I TNNM I

i l

Yt

Fig. 10 - - The principle of weld pool topside sizes modeling with a neural network.

for describing the correlation between welding parameters and topside weld pool geometry, and a backside neural network model (BNNM), for predicting the backside width, were established.

Welding parameters, such as pulse duty ratio, peak current, base current, arc voltage and welding speed, were the major factors affecting heat input; the factors were also included in the model inputs. Because of the heat inertia of the welding process, size parameters re- sponded to welding parameters with a time delay. Hence, the history information was included. For example, Vw(t) meant the value of current pulse, Vw(t-1) meant the value of last pulse and Vw(t-2) meant the value of last before last pulse.

The principle of the ANN model is

shown in Fig. 10. In the figure, TWP represents the topside welding process, TMS represents the topside measuring system, u is actual input variable of the system, Yt is actual output and Ytm is the output of TNNM. The error etwas used for adjusting neuron weight in off-line training.

The general architecture of the TNNM is shown in Fig. 11A.

For most applications, one hidden layer was sufficient. The number of elements in the hidden layer was selected based on the principle of minimum root- mean-square error (RMS). In TNNM, the number was selected from 12 to 25, and 14 BP networks were established. At last, by contrasting the root-mean-square error, it was determined the best number in the hidden layer was 23.

The training was performed using the

A Hidden layer B Hidden layer

Fig. 11 - - The arch i tecture o f a neura l ne twork dynam ic mode l . A - - T N N M ; B - - B N N M .

WELDING RESEARCH SUPPLEMENT ] 157-s

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Fig. 12 - - The dynamic output o f TNNM and BNNM A - - Topside maximum width with variation of welding speed; B - - topside maximum half- length with variation of welding speed; C - - backside maximum width with variation of welding speed; D d the relationship between weld pool size and pulse duty ratio; E - - the relationship between weld pool size and welding speed; F - - the relationship between weld pool size and arc

voltage.

commercial neural network software, Professional Plus II. The sigmoid function was selected as the nonlinear function of the neuron. Delta-bar-delta (DBD) was selected as the learning algorithm, which could overcome the slow convergence associated with the conventional back- propagation algorithm. The learning coefficient and momentum ratio was automatically determined by the algorithm for each 5000 training cycle. The total training cycle was selected to be 20,000.

The RMS decreased to attain stable value with the increase of training numbers. The RMS of Wf~ax was 3.97%, the RMS of Lbmax was 6.09% and the network was thought to be convergent and feasible. A total of 178 samples without training were used to verify the accuracy with good results: the RMS of Wfmax was 4.97% and the RMS of Lbmax was 3.42%.

BNNM was used for predicting the backside width. The architecture is shown in Fig. 11B. The inputs of the model included not only the input variables of TNNM but also the topside maximum width W~ax(t) and maximum half-

length Lfmax(t) of current pulse. The model principle was similar to TNNM. The number of elements in the hidden layer selected was 24. The RMS of Wbmax was 3.04%, and the network was thought to be convergent and feasible. A total of 178 samples without training were used to verify the accuracy with good results: the RMS of Wbmax was 4.01%.

Simulation and Discussion of Neural Network Models

The structure and parameters of TNNM and BNNM could be translated into C program, with which the output characteristic of the welding process could be simulated conveniently. Both static and dynamic output of TNNM and BNNM were analyzed with the simulation results. Figure 12 shows the outputs of TNNM and BNNM with the variations of ~ and V W during pulsed GTAW. The travel speed was 2.5 mm/s, the arc length 3.5 mm/s, the pulse peak current 120 A and the pulse base current 60 A. Other welding parameters and conditions were

not changed. Therefore, the following can be con-

cluded: 1) At different V w, size parameters

such as Wfmax, Lfmax and Wbmax vary at different speeds with the increase of 5. When 8 is small, the three size parameters increase slowly with the increase of 5, and even more slowly if V w is large. When ~ is large, the changes of the three parameters become complicated.

2) At constant Vwand U a, the changes of W~a x, Lfmax and Wbmax depend on differently. This indicates nonlinearity existing in the process.

3) At constant 8 and U a, Wf~ax, Lfmax and Wbmax decrease with the increase of Vw.

4) At constant 8 and V w, W~a x, Lfmax and Wbmax increase with the increase of arc voltage.

The above analysis shows welding parameters are coupled in determining the geometry parameters of the weld pool. Wbmax cannot be determined accurately by only Wfmax. The influence of Lfmax must be considered.

158-S I JUNE 2000

Contrast of Conventional and Intelligent Controllers

Under the variation of welding conditions, the present automatic welding machine could hardly produce the feasible control rules. Based on the complete analysis of the dynamic process, conventional and intelligent controls were designed and compared with each other, given the backside width as the control output and pulse duty ratio as the control variable.

Open-Loop Experiment

To verify the effectiveness of the developed control system, open-loop experiments were conducted for comparison. The specimens were mild steel plate 2 mm thick, and dumbbell shaped for im- itating sudden changes in heat-sinking conditions during welding. From the test results shown in Fig. 13, the transition of weld pool size was distinguishable at 35 pulses and 70 pulses. From the photograph shown in Fig. 14, the weld sizes became larger when the size of the workpiece became narrower and the backside weld became poor.

PI D Control

The PID control is the most widely used control algorithm. The increment algorithm was adopted because of the following characteristics: taking the increment variable as output, its calculation without sum and little impulse with hindrance. The increment algorithm with a four-point difference was denoted as follows:

Au(k) = qoe(k) + qTe(k- l ) + q2e(k-2) + q3e(k-3) + q4e(k-4)

qo = Kp ( I + T/2Ti+ Td/6T) ql Kp (- I+T/2Ti+Td/3T)

q2 -K,. T ~

6=45%; ]=3.0mm; L=8l/min; --13--Wb,,= • l • l • I • I , I • l • l • I I I I

10 20 30 40 50 60 70 80 Time, s

90 100

Fig. 13 - - The weld pool sizes of the dumbbell-shaped workpiece under constant welding parameters.

q3 = .~K • Td/3 T q4 = Kp Td/6T (6)

where Kp is the proportional coefficient, T i is the integral constant, T d is the differential constant and T is the sampling cycle.

To complete different control effects with the given output value, the coefficients of the controller, such as K , T/and T d, were determined first. With t~e backside width at 5.0 mm and a method of finding optimum multivariables, the coefficients of the controller were set with Kp = 24.45, T i = 0.585 and T d = 0.795.

Fuzzy Control

Unlike the conventional control scheme, fuzzy logic control is based not on a mathematical or physical model but on skilled workers' experience. It is a suitable method for the complex system. Generally, fuzzy control design includes determining the structure of fuzzy control, designing control rules, establishing fuzzy correlation and calculating the defuzzier.

The inputs of fuzzy control were the error and error change and the output was the pulse duty ratio. The accurate set of

error was defined as e = [-2 mm, 2 mm]. The set of error change was ce =[-1.5 mm, 1.5 mm] and the set of pulse duty ratio change cu =[-15%, 15%].

Fuzzy variable sets of error and error change were denoted as Eand CEand its region was {-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6}. The fuzzy variable set of pulse duty ratio change CU was {-7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7}. Then, the quantitized factors were K e = 3.00, Kce = 4.00 and K u = 2.143.

The word sets of CU and CEwere defined as {NB, NM, NS, O, PS, PM, PB} and E was {NB, NM, NS, NO, PO, PS, PM, PB}. A bell-shaped normal function was selected as the subordinate function. Control rules were selected with the general rules of hot forming, with a sum of up to 56 rules.

The control rules can be described as fuzzy correlation for obtaining the set of control variables u. The method of gravity center was selected as the defuzzier method.

Then, the fuzzy control reference table could be derived (Table 2). During actual welding, the sampled e and ce were multiplied with Keand KcetO derive the column and row value. The output value was attained by looking up the

Fig. 14 - - Photographs of dumbbell-shaped workpiece under constant conditions. A - - Topside; B - - backside.


Table 2 - - The Reference Table for the Fuzzy Controller

U•CE -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6

E

-6 7 6 7 6 7 6 6 5 3 2 1 0 0 -5 6 6 6 6 6 6 5 5 3 2 1 0 0 -4 7 6 7 6 7 6 5 4 3 2 1 0 0 -3 5 5 5 5 5 5 4 3 2 1 0 -1 -1 -2 4 4 4 4 4 4 3 2 1 0 0 -2 -2 -1 4 4 3 3 2 2 2 1 -1 -2 -3 -3 -3 -0 4 4 4 3 2 1 0 0 -1 -3 -3 -4 -4 +0 4 4 3 3 1 0 0 -1 -2 -3 -4 -4 -4 +1 3 3 3 2 1 -1 -2 -2 -2 -3 -3 -4 -4 +2 2 2 0 0 -1 -2 -3 -4 -4 -4 -4 -4 -4 +3 1 1 0 -1 -2 -3 -4 -5 -5 -5 -5 -5 -5 +4 0 0 -1 -2 -3 -4 -5 -6 -7 -6 -7 -6 -7 +5 0 0 -1 -2 -3 -5 -5 -6 -6 -6 -6 -6 -6 +6 0 0 -1 -2 -3 -5 -6 -6 -7 -6 -7 -6 -7

Table 3 - - The Control Accuracy of Three Controllers

10 ~ 30 pulses 31 - 70 pulses 71 - 100 pulses Time A v e r a g e Maximum A v e r a g e Maximum A v e r a g e Maximum Errors error error error error error error Unit mm mm mm mm mm mm

PID 0.14 0.32 0.21 0.40 0.17 0.36 control Fuzzy 0.13 0.38 0.25 0.51 0.12 0.42 control PSD 0.07 0.25 0.12 0.27 0.09 0.30 control

J ~ , _ . ~ [ A a + ~ 8 . wb.., _1 Pulsed GTAW L _ _ _ _ ;~ - I Process ~

. . . . . Wrm.xl I

I I I I I I ~

Fig. 15 - - The schematic diagram o f a single neuron self- learning PSD contro l system dur ing pu lsed GTAW.

value in the table, then mul t ip ly ing it with a proportional factor Kcu to receive the actual variation of pulse duty ratio.

Neuron Self-Learning PSD Control

Aiming at the characteristics of changing structure and coefficients, a neuron self-learning PSD (proportional, sum and differential) control was proposed based on a single neuron. Only the desired output and the real output detected on-line

were needed to form the neuron self- learning closed- loop control system, wi thout on- l ine ident i f icat ion of the process coefficients. The weights of the neuron were corrected on-line with the improved BP algorithm and the error was minimized for optimizing the output of the control system.

The schematic of the neuron self- learning PSD control system is shown in Fig. 15. The output parameters of the weld ing process are size parameters,

such as Wfmax, Lfmax and Wbmax; Wbmax is the controlled variable. MS is the measuring system for detecting topside size parameters (W~a x and Lffnax) and welding parameters such as welding current, arc voltage, travel speed, etc.

These variables, combined with the values of the last two pulses, totaling 17 values, were as the input of BNNM. W m b m a x was the predicted backside with BNNM, inputted to the signal converter with the given backside width R. The output variables X = {X 1, X 2, X 3} generated by the signal converter were inputted into the neuron self-learning PSD controller. The controller summed the variables X and determined A(5 with the nonlinear transfer function. At the same time, the input weights of the neuron were adjusted on-l ine with a BP algorithm by the error of backside width, to keep the control within the optimized state.

The input variables X = [X 1, X 2, X 3} of the controller were error, error of first- order differential and error of second- order differential respectively, between the desired backside width and BNNM output, as follows:

x 7 = o~Te(t) = o~l[R - W m b m a x ( t ) ]

x 2 = o~2Ae(t) = ot2[e(t) - e(t - 1)] x 3 = o~3A2e(t) = o~3[e( t ) - 2 e ( t - 1 ) + e ( t - 2) ]

(7)

where c~ 1, (7.2 and 13/. 3 are constant weights, selected as o~ I = 1.0, c~ 2 = 0.3 and o~ 3 = 0.1.

Weight normalization is to avoid the saturation of weights during the learning process, as follows:

w T = w w (8)

The weight sum of the neuron's inputs is 3

s = ~_~ w , • x i (9) i=1

F(s) is a nonlinear transfer function, selected as hyperbolic tangent function,

A6 = F(s) = 7(1 - e 2~5)/(I + e -2~s) (10)

where 7and ~ are two constants. The sat- urated value of the control variable is determined by Y, and ~ determines the linear degree of the control variable. The larger the Y, the more possible it is to attain the desired value. The smaller the ~, the wider the linear work region to re- strain the fluctuation of the stable state. Y was selected as 300 and ~ as 0.135.

Object function was minimized by the fol lowing cost function:

160-s I JUNE 2000

1 2 E ( w ) = ~ , ~ [ R - W m b m a x ( k ) ]

k (11)

The derived corrected formula of weight was as follows:

A w i = qCx i wi (k + 1) = wi(k) + A w i , i = 1,2,3

(12)

where q =1.0 is the learning rate. is the equalized output error of neuron, resembling the actual output error.

= [ R - W m b m a x ( k ) J • [1 - AS(k)/y] • [1 + A~(k)/y]

(13)

Simulations of control performance were conducted with the developed neuron self-learning PSD controller. The desired outputs of the backside maximum width were set as 4.0, 4.5 and 5.0 mm.

Figure 16A shows the simulation results based on BNNM with R = 5.0 mm. The maximum overshoot was 2.81%, the regulating time 2 s, the steady-state error 0.04 mm and the pulse duty ratio stabilized at 42%.

Figure16C shows the simulation results with R = 4.5 mm. The maximum overshoot was 2.71%, the regulating time 2 s, the steady- state error 0.02 mm and the pulse duty ratio stabilized at 36%.

Figure16E shows the simulation results with R = 4.0 mm. The maximum overshoot was 2.25%, the regulating time 2 s, the steady-state error 0.01 mm and pulse duty ratio stabilized at 27%.

Figures 16B, D and F show the weights. Similar simulations were conducted with the PID controller and fuzzy controller.

Results show the maximum overshoot of the neuron self-learning PSD is similar to the PID and fuzzy control, but the regulating time and steady-state error is smaller. Furthermore, the coefficients of the neuron can be adjusted on-line to make it capable of controlling the nonlinear process.

To test the feasibility of the neuron self-learning PSD control, experiments during pulsed GTAW were conducted. The control variable was the pulse duty ratio and its minimum regulating unit was 1%.

Figure 17 shows the neuron self-learning PSD control effect with R = 5.0 mm.

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2 I - - simulation output I J L . . . . . . preset value ]

O ~ 0 10 20 30

Time I s

C

5O

40

3 0 ~

20

10 40

=: 2 ]j - - s i m u l a t i o n output I ] . . . . . . . preset value ]

• 1.0 - 4 0

0.8

30 0.6

20 • ~: 0.4

10 0.2

0 0.0 40 0

40 1.0

0.8 30

0.6 2 0 ~ m

~ 0.4

10 0.2

0 0.0

1.0 w]

0.8

~ 0 . 6 "6 w2

0.4

0.2

0.0 0 10 20 30 40

"nrrm, s

B

W]

w2

J e , w | | | i | K | i . | .

10 20 30 4O T i I~ , s

D

w!

w2

0

• w 3 O ~ . . . . . .

0 10 20 30 40 10 20 30 40 "Nme, s "lime, s

E F

Fig. 16 - - The s imulat ion curve o f the neuron self- learning PSD controller. A - - Wbmax = 5.0 rnrn; B - - the weight o f Wbmax =5.0 rnm; C - - Wbmax=4.5 mm; D - - the weight o f Wbmax = 4.5 rnm; E - - Wbma× = 4.0 turn; F - - the weight o f Wbmax = 4.0 rnrn.

8 50

6 . . . . ~ _- : / r h . 40

3 O

20 ,~ i ~ pulse duty ratio Vw,,2.Smm/s; Ip.,120A; Ib-60A; I - - actual output 10

l"3.0mm; L=81/min; | - BNNM output . . . . . , . . . . . . : T : : ; T T 0

10 20 30 40 S0 60 70 80 90 100 Time, s

Fig. 1 7 - The neuron self- learning PSD closed-loop control curves o f the dumbbel l -shaped workpiece dur ing pulsed GTAW.

WELDING RESEARCH SUPPLEMENT I 161-S

A

Fig. 18 - - Photographs o/dumbbel l-shaped workpiece with neuron, self-learning PSD control. A - - Topside; B - -backside.

50

EE j4

2 pulse duty ratio

11=3.0mm; L=81/min; I I BNNM output I 0 . . . . . . . . . . . . . . . . . . . 10

0 10 20 30 40 50 60 70 80 90 100 Time, s

40

3o~ oO

20

Fig. 19 - - The PID closed-loop control curves.

8 ~ , 45

l - -o- - pulse duty ratio IVw=2.Smm/s, Ip-120A, Ib=60A, I - actual output I i=3.0mm; L=8Vmin; I [ - BNNM output " n I ' ' ' ' ' ' ' ' ' ' " : ~ ;' ~ • ~ ;

Jm

35

25 ~

15

5

10 20 30 40 50 60 70 80 90 100 Time, s

Fig. 20 - - The fuzzy closed-loop control curves.

The control variable decreased with the heat-sinking conditions turning poor and increased with the condition reversing. The difference between BNNM output and set value R caused the variation of pulse duty ratio to keep the backside width maintained at 5.0 mm. The statistic results verified the feasibility of BNNM and neuron self-learning PSD control. The maximum error of BNNM output and test data was 0.26 mm. Test data were compared with the set value, the maximum error was 0.30 mm, the average error 0.10 mm and the root-mean- square deviation was 0.08 mm. The control results also verified the consistence

with the simulation results. The perfect results of topside and backside photographs are shown in Fig. 18.

Discussion - - Controls

Welding experiments with a conventional PID controller and fuzzy controller were conducted on a dumbbell-shaped specimen during bead-on-plate pulsed GTAW. The control curves are shown in Figs. 19 and 20. The statistic results of the three controllers are tabulated in Table 3. The initial ten pulses were omitted because the ignition period was not considered.

Results showed the accuracy of the PID and the fuzzy control are similar, with the maximum error less than 0.5 mm. The effect of the neuron self-learning PSD control was better, with the maximum error less than 0.3 mm. The errors of the middle period (31-70 pulses) were larger than that of both the start period (10-30 pulses) and the end period (71-100 pulses). This indicated the welding process becomes more complicated as the heat-sinking conditions turn worse.

The controllers designed were successfully implemented for pulse GTAW process control, but each PID control coefficient was limited to each desired backside width. Fuzzy control simulated the worker's experience, but did not possess the adaptive regulation with varied conditions. The neuron self-learning PSD control, however, attained a perfect control effect with different set values and conditions, and was suitable for the varied structure and coefficients of the welding process.

Conclusions

1) A new visual sensing system of imaging the topside and backside of the weld pool simultaneously in the same frame was established. The principle of obtaining a clear image of the weld pool with arc light illumination was analyzed.

2) A real-time algorithm of image processing was developed to acquire topside and backside sizes of the weld pool.

3) The dynamic characteristics of arc welding were investigated with positive and negative step responses. Further- more, a more accurate model of pulsed GTAW was established by an artificial neural network.

4) Conventional and intelligent single-input and single-output control schemes were investigated. By careful comparison of the three controls, it was found that, under certain conditions, the PID controller and basic fuzzy controller can achieve good performance, and, in

162-s I JUNE 2000

most cases, the neuron self-learning PSD controller can achieve better, more robust control performance.

Intelligent methodology provided in this paper can be easily transplanted into other arc welding processes.

Acknowledgment

This work was supported by the Na- t ional Natural Science Foundation of China, No. 59575057 and No. 59635160. The authors would like to thank the editor and anonymous referees for their careful review and constructive comments on the earlier versions of this article.

References

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9. Xiao, Y. H., and Ouden, G. den. 1990. A study of GTA weld pool oscillation. Weld-

ingJourna169(8): 289-s to 293-s. 10. Yoo, C. D., and Richardson, R. W.

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12. Lott, L. A. 1984. Ultrasonic detection of molten/solid interfaces in weld pools. Ma- terials Evaluation 42(3): 337-341.

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14. Carlson, N. M. 1992. Ultrasonic NDT methods for weld sensing. Materials Evalua- tion 50(11): 1338-1343.

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Weld pool edge detection for automated control of welding. IEEE Transactions on Robotics and Automation 7(3): 397-403.

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W E L D I N G RESEARCH SUPPLEMENT I 163-s

Intelligent Methodology for Sensing, Modeling and Control of Pulsed GTAW Part 2 Butt Joint Welding

Double variable intelligent control incorporated with a fuzzy neural network and expert system is proposed for bead shape control during butt joint welding

BY S. B. CHEN, D. B. ZHAO, L. WU AND Y. J. LOU

ABSTRACT. This paper addresses intelligent techniques for the quality control of the pulsed gas tungsten arc welding process for butt joints, and it is a development to Ref. 1. Because there exist some important differences in butt joint welding and bead-on-plate welding, the modeling and control scheme in Ref. 1 does not completely fit for butt joint welding. In this paper, the differences between the two were investigated. The shape and size parameters for the weld pool were used to describe the weld pool geometry. A new real-time algorithm was developed for the size and shape parameters. A size and shape neural network model (SSNNM) was established to predict the maximum backside width. The model accuracy was verified. Further- more, a self-learning fuzzy neural network controller (FNNC) was designed for control of the maximum backside width and the fuzzy rules were modified on- line. Based on the FNNC, and combined with an expert system, a double-input and double-output (DIDO) intelligent controller was developed for controlling the maximum backside width and the shape of the weld pool. Experiment results showed the DIDO intelligent controller could form a better butt joint weld.

Introduction

As is well known, quality control of weld penetration and weld shape is a

S. B. CHEN, previously with the Harbin Insti- tute of Technology, Harbin, PR. China, is now with Shanghai Jiao Tong University, Shanghai, P.R. China. D. B. ZHAO, L. WU and Y. J. LOU are with National Key Laboratory of Advanced Welding Production Technology, Harbin Insti- tute of Technology, Harbin, P.R. China.

complicated problem in arc welding. When using the GTAW process on thin- plate mild steel, full joint penetration is an essential factor for ensuring weld quality. Weld bead width, especially backside bead width, is a main factor for evaluating weld quality. In a previous investigation (Ref. 1), the existing sensing and control methods for penetration control were reviewed. Examples of the visual sensing systems reviewed are infrared (Refs. 2, 3), laser-strobe (Refs. 4, 5), laser-structured light (Ref. 6) and coaxial viewing (Refs. 7-9). These sensing systems paved the way for sensing and control of the welding process.

During bead-on-plate welding, the backside width of the weld pool can be predicted and controlled by the heat balance of the weld pool, or the weld pool geometry. Weld shape is ensured by the heat balance between the input and output of the welding process. A nonlinear first-order model was obtained for relating the input welding current to the output weld pool radius. Both the time constant and gain of the first order transfer function have resulted from some simpli-

KEY WORDS

Bead Size Bead Width Expert System Fuzzy Logic GTAW-P Intelligent Controller Neural Networks Weld Geometry

fication (Ref. I 0). Because of the plasma impact, the surface of the arc weld pool is depressed. The average depression of the solidified weld was found to have a good linear correlation with the backside bead width. The arc welding process was modeled and an adaptive control system was completed to achieve the desired backside width (Ref.1 1 ).

With butt joint welding, the welding parameters are more complex and the correlations among the welding parameters and the geometry of the weld pool become more nonlinear. The weld pool geometry, incorporating size parameters, such as width and length, and shape parameters, such as rear angles, can be used to characterize the shape of the weld pool. Accurate estimation of the backside width can be generated by a neural network model (Ref. 12). Intelli- gent methodology, such as fuzzy inference, neural network and expert system, is used for modeling and controlling the nonlinear welding process (Refs. 13, 14). A self-learning fuzzy neural control scheme was presented for real-time control of the bead width during pulsed GTAW (Ref. 15).

In a previous investigation (Ref. I), the backside width was predicted and controlled accurately by the topside size parameters during bead-on-plate welding. However, when the same experiments were carried out for butt joint welding, the shape of the weld pool became much more complicated. This shape made it difficult to characterize the backside width using the bead-on- plate welding information. Based on the previous investigation (Ref. I ), the differences between the two welding approaches are reported in this paper. Ef- fective intelligent techniques for an

164-s I JUNE 2000

image processing algorithm, modeling method and control scheme are proposed for butt joint welding.

Neural Network Model for Welding Butt Joints

Based on the visual sensing method developed in the bead-on-plate welding approach (Ref. 1 ), butt joint welding experiments were carried outon mild steel. The model relating welding parameters and topside size parameters to backside width was also established from the welding data. Results showed the two size parameters (the maximum width Wfmax and the maximum half-length Lfmax) varied in a narrow range, while the shape of the weld pool and backside width changed significantly. Thus, the models with the size parameters of the weld pool as the inputs could not accurately predict the backside width. The geometry of the weld pool should be characterized as the size and shape parameters.

Size and Shape Parameters of the Weld Pool

The geometry of the weld pool should be characterized as the size and shape parameters. In this study, the rear width of the weld pool is proposed as the shape parameter, with the definition shown in Fig. 1A. The definition of the backside size parameter is the same as in Ref. 1 and shown in Fig. lB. The shape parameter is represented by the rear width because the rear shape of the weld pool is sensitive, while the front portion of the weld pool maintains nearly a half circle despite different welding conditions.

In Fig. 1A, the maximum topside width of the weld pool is denoted as Wfmax. The center of the maximum width is point a. The topside half-length Lfmax is defined as the distance between the rear point b of the weld pool and point a. The rear area of the weld pool Sfmid is defined as the area surrounded by the maximum width and the rear boundary. Ten rear widths Wfi (i = 1, 2...10) are defined as the shape parameters of the weld pool, shown in Fig. 1A. Wil 0 is also Wfmax.

Image Processing for Determining Size and Shape Parameters of the Weld Pool

For determining the size and shape parameters on-line, a new image-processing algorithm was developed based on the previous work. The algorithm consists of the following steps: filter, edge detection, edge recognition, regression of edge points and parameter calculation.

Figure 2A shows the direction definitions of the topside image in the image

.+

Y

, ,

o : b

(A)

~ X 0

Y

~ x

(B)

Fig. 1 - - Definitions of the topside size and shape parameters of the weld pool. A - - Topside; B - - backside.

o

y A

xo-2

yo-I

Y,

fo+:

:%-1 Xo Xo+l Xo+2

,B

Fig. 2 - - Topside image and image processing template. A - - The direction definition in the image coordinates; B - - the definition of the direction template in the calculating window.

coordinates. The image is smoothed with the similar method used in bead-on-plate welding (Ref. 1).

The edge of the weld pool causes the most concern. It is characterized by the change of grayness. The grayness changes smoothly along the edge, but rapidly along its normal line. The edge types can be described as step style, slope style and roof style. Different edge calculation templates, such as gradient template, directional template and regression template, are used to determine different edge styles. The directional template was used to determine edge points for consideration in real-time control. The angle between the welding direction (fkw) and the axis y was 28 deg. The directional template was along the welding direction, and the definition is shown in Fig. 2B. The direction template points 1-9 were calculated by the interpolation algorithm with the surrounding image points printed in circles. To reduce on- line computation, a reference table was established for the interpolation calcula-

tion. To eliminate the disturbance from arc center on detecting the edge points, the directional template is selected as

001 h ( m , n ) = o

L2° 2o 20j (1)

The complete image processing results are shown in Fig. 3. Figure 3C shows the threshold image after the edge detection with the directional template. The boundary of the weld pool appears distinguishable, and the arc center and other noise points are effectively re- moved.

The rear point D, the central point C and the maximum width points A and B can be derived by scanning along f kw and the vertical welding direction fkv. All the edge points can be derived with the same method. However, the edge curve was not smooth and some disturbance points still exist. Two separate four order multinominals were adopted to fit the left and right edges of the weld pool and the

WELDING RESEARCH SUPPLEMENT [ 165-s

Fig. 3 - - Processing of the topside image of the weld pool. A - - Original image; B - - the smoothed image with EBS; C - the threshold image after edge detection; D - - the original edge points; E - - the fitted edge points; F - - the size and shape parameters.

A 80

~20

20

B ~15

3 s

13 c,1 i

t0

D 8

| ,

2

8O E

~eo E4o ,Q

tn 20

0 500 1000 1500 2000 2500 Sample number

500 1000 1500 2000 2500 Sample number

4.5

500 1000 1500 2000 2500 Sample number

4

I I I I I I • " • ' • • • J • • • J • • • ' • ' •

0 500 1000 1500 2000 2500 Sample number

0 500 1000 1500 2000 2500 Sample number

results are shown in Fig. 3E. Based on the regression result, the

size and shape parameters, such as Lfma×, Wfmax , Sfmid and Wfi, can be calculated. The backside image-processing algorithm was the same as that for bead-on- plate welding.

The frequency of the pulsed GTAW was 1 Hz and the pulse base time was not less than 350 ms. All the image processing algorithm and control scheme was done during the pulse base time. The double-side image processing algorithm was less than 80 ms, running on a PC486- 100 MHz computer. The following control scheme was less than 30 ms, making the selected algorithms adequate for the requirements of real-time control.

Experiments and Results on the Neural Net- work Model

The heat and force influences on the welding process were determined by the variations of welding parameters such as peak current (Ip), base current (Ib), duty ratio (8), travelspeed (Vw), arc voltage !Up) and so on. Therefore, different weld- mg parameters were related to differences in weld pool geometry. To establish a valid process model, all kinds of welding conditions should be considered during the experiment design. The major welding parameters, such as I., 8, Vw, were taken as the input signals ol~the model. To incorporate all the characteristics of a dynamic welding process, the inputs were designed with white noise signals because of the widespread spectrum and noncorrelation on time.

Butt joint welding experiments were conducted on a 2-mm-thick mild steel specimen without any surface preparation. A satisfactory weld shape was obtained with the following welding parameters: Ipo = 140 A, S o = 45%, Vwo -- 2.5 mm/s. The maximum variations for all the inputs were Alp = +25 A, AS = +20%, AV w = +0.83mm/s. The corresponding unit step variations were: dip = +5 A, d~ = -+5%, dV w = +0.167mm/s. Input welding parameters were generated with the

166-s l JUNE 2000

pseudo-random sequence method, using a total of 2800 numbers. Other welding conditions are tabulated in Table 1.

Welding experiments were conducted with the designed input signals, and the size and shape parameters were determined. Figure 4 shows the curves of double-side, typical-size and shape parameters, all of which varied by a wide range under the designed welding parameters. The maximum of Wfmax w a s approximately 8 mm, the maximum of Lfmax was approximately 10 mm and the maximum of Sfmid w a s approximately 45 mm 2. The maximum of Wbmax was approximately 7.5 mm, the maximum of Lbmax w a s approximately 9.0 mm and the maximum of S b was approximately 40.0 mm 2. When partial penetration occurred, the backside size parameters decreased to zero. Therefore, multiple welding states were activated and the experimental data could be thought as covering all the penetration situations. The experimental curves also showed that each group of topside size and shape parameters, and backside size parameters, varied in a similar manner.

The Neural Network Modeling Architecture

As is well known, neural networks are suitable for modeling a nonlinear process. A size and shape neural network model (SSNNM) for a dynamic welding process was established to relate the welding parameters, and the topside size and shape parameters, to the backside size parameters. To establish a dynamic process model, the input variables of the SSNNM included the welding parameters, the topside size and shape parameters and their last two history values, a total of 48 numbers. The number of elements in the hidden layer was 30. The output variable of the model was each of the backside size parameters (Wbmax, Lbmax and Sb), so three models for the process were established. The model structure is shown in Fig. 5. At the same time, a single-size neural network model (SNNM) with the welding parameters and the topside size parameters as the inputs was established for comparison.

Based on the test data, the three models for Wbmax , Lbmax and S b were trained. The training was performed using the commercial neural network software, Professional II plus. Sigmoid function was selected as the nonlinear function of the neuron. Delta-bar-delta (DBD) was selected as the learning algorithm. The learning coefficients and momentum ratio were automatically determined by the algorithm for each 5000 training cycles. The total training cycle was 20,000.

Simulation tests were carried out with

4 •

i '

12 E E 9

3

0 0 500 1000 1500 2000 2500

Sample number

G E 16 E 12

j. _1

4

0 500 1000 1500 2000 2500 Sample number

Fig. 4 - - The typical double-side size and shape parameters o f the weld pool. A - - Srmid; B - -

Lfmax; C - - Wfmax; D - - Wfl, E - - Sb; F - - Wbmax; G - - Lbrna x.

Table I - - Experimental Conditions of Pulsed GTAW

Welding Pulse Base Electrode Angle of Arc Flow Conditions Frequency Cur ren t Diameter Tip Length of Ar

Unit f (Hz) Ib (A) 4) (mm) e (deg) 1 (mm) L (L/min) Value 1 60 3.2 30 3.5 8.0

the models SSNNM and SNNM. The error statistic results between the outputs of the models and the test data are tabulated in Table 2. The results indicate the SSNNM can predict the backside size parameters more accurately than the SNNM.

Characteristic Comparison between Bead- on-Plate and Butt Joint Welding

Simulation and experimental results showed the following:

1) The geometry parameters of the weld pool during butt joint welding become more complex than that during bead-on-plate welding. There are some similar geometry parameters, as well as some very different parameters. There- fore, more information on weld pool geometry should supplement the estimating of backside width during butt joint welding.

2) When the pulse peak current and the pulse duty ratio are great and the travel speed is small, the double-side length-to-width ratios in butt joint welding become smaller than that in bead-on- plate welding. When the travel speed increases, the geometry parameters in the length direction become great, while the

geometry parameters in the width direction do not change a lot. This phenome- non is not found during bead-on-plate welding.

3) The causes for the variations in the geometry parameters may include an ir- regular root opening and the arc force acting on the weld pool surface. For example, the root opening may play a significant role in determining the depression of the weld pool.

4) The above analysis concludes that the backside width cannot be accurately predicted by the size parameters. The shape parameters should be considered as the model inputs to predict the backside width.

Single-Variable, Self-Learning Fuzzy Neural Network Control

Fuzzy Control Rules Determined from the Experiment Data

Fuzzy control rules express the fuzzy relationship between the inputs and the outputs of the control system. To achieve the fuzzy control rules for pulsed gas tungsten arc welding of a butt joint, a C- mean dynamic polymerizing algorithm was used to determine the fuzzy rules

WELDING RESEARCH SUPPLEMENT [ 1 6 7 - s

1

I m . i

a s . i

iJ.i i

m i

t i l l

t U l 2 1 i i

t ~ l

u l i

tu I

m i

b i

t i l l

a . I O l t t l l

t l J I

m m i

f J I

t i l l t / ) l u J I

Table 2 - - The Comparison between S N N M and SSNNM Statistic Results

SNNM SSNNM

Backside Maximum Width W~ ..... Maximum A v e r a g e Root-Mean-

Error Error Square Error (mm) (ram) (ram)

2.95 0.44 0.57 1.54 0.15 0.19

Backside Maximum Length L b~,, Backside Area .~, Maximum Average Root-Mean- Maximum Average Root-Mean-

Error Error Square Error Error Error Square Error (ram) (mm) (ram) (mm~) (mm-9 (mm*')

3.46 0.54 0.71 9.40 3.48 3.04 1.38 O. 16 0.21 4.03 0.59 0.72

Input layer Hidden layer

P121

P(31 • utput layer

: " V / " \..__ f . : :

• "

P1471

P1481

P(1)=Ip (t-2) P(2)=Ip (t-l) P(3)=Ip(t) P(4)=8(t-2) P(5.)-~(t-1) P(6)=4i(t) P(7)=Vw(t-2) P(S)=Vw(t-1) P(9)=Vw(t) V(lO)=U~(t-2) P(11)=Up(t-I) P(12)=Up (t)

P(17)=Lfm~(t-1) P(18)=Lf~x(t) P(19)=Wn(t-2) P(20)=Wn(t-1) P(E1)=Wn(t) P(E2)=Wf2 (t-2) P(Ea)=Wf~(t-1) P(24)=Wf~(t) P(ES)=W.(t-2) P(26)=Ws (t-l) P(27)=Ws (t) P(28)=Wf4 (t-2)

: P(13)=Sf~d(t-2) P(29)=Wf4 (t-l) P(14)=Sf~d(t-1) POO)=Wf4 (t) V(15)=Sfn~d (t) V(31)=Wfs(t-2) P(16)=14m~(t-2) P(32)=Wfs(t-1)

PO3)=Wfs(t) PO4)=Wfe(t-2) P(35)=Wf6 (t-l) P(36)=wr,(t) PO7)=wfz(t-2) POg)=Wn(t-1) P(39)=Wr,(O P(40)=W~(t-2) P(41)=Ws(t-1) P(42)=W~ (t) P(43)=W~9 (t-E) P(44)=We~(t-1) P(45)=W~(t) P(46)=Wno (t-2) P(47)=Wn0(t-1) P(48)=Wno(t)

Fig. 5 - - The structure of the size and shape neural network model (SSNNM).

III I

I from the welding experiment data. As a I~.1 O I result of actual arc welding, the maxi- - - , mum backside width WbmaxWaS defined uJ I i as the controlled variable and the pulse MJ I duty ratio 8 of the welding current was

I the control variable. To identify the dy- ', namic characteristic of pulsed gas tung-

r~l I sten arc welding of a butt joint, experi- ~[ I ments were undertaken using a uJ I pseudo-random sequence of 6 as the

I input of the actual welding system, and i i i I I 2109 normalizing sample data pairs {5,

~_ ', Wbmax} were achieved. Z I The error E of Wbmax and the change I.M I in error CE were chosen as the input n I fuzzy variables of the fuzzy control sys- O I tem, and ~ was chosen as the output - , , fuzzy variable, described as U of the m iI fuzzy control system. The fuzzy subsets m I of these fuzzy linguistic variables can be

I described as {NB, NM, NS, ZO, PS, PM, ~- ', PB}, where N, ZO and P mean negative, o I zero and positive, and B, M and S mean ,~ I big, medium and small. IJ.I I To determine the fuzzy control rules ¢/J I of the pulsed gas tungsten arc welding MJI X I process, the C-mean dynamic polymer-

izing algorithm is described as follows: Step 1. The initial centers of each fuzzy

subset of E and CE are chosen as shown

in Table 3. We define the polymerizing center of i th fuzzy subset of Eas ZEi(I), the polymerizing center o f j th fuzzy subset of CE as ZCEj(I) and I means iterating number of the algorithm, with a rise from 1.

Step 2. The Euclidean distance between a sample data pair and a polymerizing center of the fuzzy subset is

D (e k ,ZE i (I),ce k ,ZCE j (I))

=l(ek -ZE i (I))2+(cek -ZCE j (1))2 (2)

where ek denotes k th sample value of E, and ce k denotes k th sample value of CE. Calculating the Euclidean distance between each sample data pair and each polymerizing center of the fuzzy subset of E and CE, if

D(e k, ZEI(I ), ce , ZCE (/))= min m i = 1 . . . , 7

j= l . . . , 7

{o(o, ce ,

Then e k belongs to ZE I, and Cek belongs to ZCE m.

Step 3. I = I +1, calculating new polymerizing center of the fuzzy subset of E and CE as follows:

n i

lk~__~ i z~, (,)= n, k J =1,2, . . . ,7

(4)

nj

ZCEj (,)=n-~, ZceJ j =1,2,...,7 l k=l (5)

Where n i is the sample number of the i th fuzzy subset of E, nj is the sample number of the jth fuzzy subset of CE, elk is the k th sample of the i th fuzzy subset of E, and ce/k is the k th sample of the jth fuzzy subset of CE.

Step 4. Calculating the sum of square- error Jc(I) as follows:

7 n i ,~ i

~ nj .

Step 5. If I]c(I) - ] c d - l ) I <_ e, where c denotes the preset polymerizing precision, and if the polymerizing results con- verge, the algorithm stops, otherwise, return to Step 2, and the algorithm continues.

Using the above C-mean dynamic polymerizing algorithm, the final polymerizing centers of the fuzzy subsets of E and CE were derived, as shown in Table 4. We defined the centers of the fuzzy subset of the output fuzzy variable U as {-0.87, -0.58, -0.29, 0.00, +0.29, +0.58,

168-s I JUNE 2 0 0 0

( A ). p.~B). .~-(C3 . . . . , . . (D) . . . . . ~ , . - ~ . . . ~ . . - ~ - (03 . . . . . . P-CH)

Fig. 6 - - The structure of the fuzzy neural network controller (FNNC).

Table 3 - - The Initial Polymerizing Centers

NB NM NS ZO PS PM PB

E -0.95 -0.75-0.15 0.00 0.25 0.65 0.85 CE -0.80 -0.60-0.25 0.00 0.30 0.60 0.90

Table 4 - - The Final Polymerizing Centers

NB NM NS ZO PS PM PB

E -0.80-0.54~0.29-0.03 0.21 0.50 0.80 CE ~0.85 -0.58-0.32 0.04 0.30 0.55 0.82

Table 5 - - The Fuzzy Control Rules for Pulsed Gas Tungsten Arc Butt Joint Welding

E•E NB

NB PB NM PB NS PB ZO PM PS PS PM ZO PB ZO

NM NS ZO PS PM PB

PB PB PM PS ZO ZO PB PM PM PS ZO ZO PM PM PS ZO NS NS PM PS ZO NS NM NM PS ZO NS NM NM NB ZO NS NM NM NB NB ZO NS NM NB NB NB

+0.87}. On the basis of the polymerizing results of E and CE, the fuzzy control rules for welding a butt joint were obtained by the principle of the nearest distance, as tabulated in Table 5.

Based on the analysis of the welding process for a butt joint, using fuzzy inference technology and artificial neural network methodology, a self-learning fuzzy neural network controller for welding a butt joint is presented.

Fuzzy Neural Network Controller (FNNC)

Each layer and each node of the fuzzy neural network is related to a part of the fuzzy system. According to the membership function and inference process, all the nodes and weights have certain physical meanings. The jth fuzzy control rule of the fuzzy control system is denoted as

Rule j: IF (E is EJ) and (CE is CEJ) THEN (CU is CUJ), j = 1,2,...m (7)

Where EJ ~{E1,E2,...E7}, CEJ ~{CE], CE 2, -..CE7}, CUJ ~{CU 1, CU2, ""CU7}.

The output of the fuzzy system can be calculated as

cu (~j=l hj CU j

(~?=1 hj (8)

where cu is the crisp value of the output variable of the control system, (9 means algebraic sum and h, is the matched de- ] .

gree between the current input and t h e j th fuzzy control rule, described as

hj = pL ~ (e) • PCEJ(Ce) (9)

where pEJ (e) is the membership of e belonging to the fuzzy subset E J, and pc~(e) is the membership of ce belonging to the fuzzy subset CEJ.

The structure of the fuzzy system can be expressed by a forward neural network. The whole system is denoted as the fuzzy neural network controller (FNNC), shown in Fig. 6, in which the unmarked weights are one. The network includes eight layers, where A -D layers transform the input crisp value to the membership of the fuzzy subsets of E and CE, where E-F layers carry out fuzzy inference, G layer fulfills fuzzy synthesis, H layer acts as fuzzy judging, from which then the crisp output value is acquired.

Supposing the input of the jth node of the I th layer of the FNNC is I1~, the output is O/j, then the relationship [~etween the input, the output of each layer of the FNNC is described as

A layer: laj = xj,Oaj = laj, j= 1,2, x I = e, x 2 = ce (10)

B layer: Ib: = Wsj • Oaj , Obj -- Ibj, J= 1,2 (11)

C layer: IC k = (oh i - Wck), OCk = ICk, J = [(k-1 )/7] + 1, k = 1,2 .--14 (12)

D layer: Idi = Oci • Wdi, odi = e-(Idi )2, i = 1,2,...1 4

E layer: le k -- Odi • odj, Oek = lek, i = 1,2"',7, j = 8,9""14, k = 7 i + j - 1 4

(13)

(14)

F layer: If 1 = (t)49k= 10ek, o f 1 = (1/Ifl) , Ilk = O%_1, Ofk = Ilk, k = 2,3---,50 (15)

G layer: Ig k = Of 1 - Ofk+l, Og k = Igk, k = 1,2,...,49 (16)

H layer: Ihl = (~49k= 10g k " Wbk, oh1 = Ihl (1 7)

Learning Algorithm of the Fuzzy Neural Network Controller

The learning process of the FNNC consists of off-line and on-line learning. The off-line learning of the FNNC is to get the initial membership of the fuzzy subsets of input fuzzy variables Eand CE, determine the initial weights between the nodes in the G-H layer and reduce the on-line learning time of the FNNC. The

WELDING RESEARCH SUPPLEMENT[ 1 6 9 - s

1

I L J I =El

rill

iii I

m |

w .

i1[ I IL l I f,/'J I ILl I

-= : ILl I

"1 u J l

Ima I

h I

lUl

=El

ILl +I

lUl

ILl I

I~I UJ I

W I

m !

i l l I

m i

: ~ I : I U J I

:~0') I ~ II,,I I

1 . 0

~ 0 . 5

i ~ .0o=

- 1 . . !

0.0 -1.0 c e . .

1.0 e

Fig. 7 - - The init ial relationship surface between the inputs and outputs o f the FNNC.

on-line learning of the FNNC is to mod- ify the membership of the fuzzy subsets and fuzzy control rules during butt joint welding, so that the FNNC can adapt to the varying conditions.

The learning sample of the FNNC is provided with the fuzzy control rules, shown in Table 5. The initial quantifica-

tion factor Wsi of Eand CE is 6. The initial center Wci of the membership function of the fuzzy subsets in E is {-4.80, -3.24, -1.72, 0.00, 1.24, 3.00, 4.80}. The initial distributing parameters Wdi of the membership function of the fuzzy subsets in E is {1.068, 1.082, 1.029, 1.126, 1.111, 0.936, 0.926]. The initial centers Wci of the membership function of the fuzzy subsets in CE are {-5.07, -3.45, -1.90, 0.00, 1.79, 3.28, 4.93}, and initial distributing parameters Wdi of the membership function of the fuzzy subsets in CEis {1.029, 1.052, 0.966, 0.903, 1.01 6, 1.062, 1.010}. The initial value of the weights Wbi can be acquired by the off- line learning of the FNNC. By training the FNNC for 500 times using a back-propagation algorithm, the initial membership of the fuzzy subsets of E and CE were obtained. The relationship surface between the input and output of the FNNC after off-line learning is shown in Fig. 7.

The goal of the on-line learning of the FNNC is to minimize the output error of the controlled object. The error function is defined as

2

* l ~ ( y i - Y d ) E = 2 i =I (18)

where n is the number of the learning sample, Yi denotes the output of the controlled object and Yd denotes the desired output of the controlled object.

The weights of the FNNC are adjusted by error back-propagation learning algorithms. The formulations are shown as

H layer: OE* n

6~ - ~l h - ~_~(Yi-Yd)i=l

Ou

ao~ = - - = 1, k = 1, 2,-.., 49

Wbk(t + 1)= Wbk(t ) + rl" a2

of + [wb,(t)- wb,(t- 1)] G layer:

(19)

(20)

A 7

6

E 5 E 4

K

3

F N N C /

Ip=140A l Vw=2.50nan/s I

Up=12.3V I • II •

0 10 20 30 40 50 Time, s

B 65

55

. < 4 5

"°'35

25

15

% F+c

I I I I I • • a •

10 20 30 40 Time, s

50

C

5

[3 2 r 1 r

0 10 20 30 40 50 Time, s

D 60

50 ~ ~ N C

4O

30 ]1~

20

10

0 I ' '

0 10 20 30 Time, s

I i

40 50

Fig. 8 - - 5imulation curves of the FNNC. A - - Wbmax with Wmbma x : 6 mm; B - - d with Wmbma x = 6 mm; C - - Wbmax with Wmbma x = 5 mm; D - - d with Wmbrnax = 5 ram.

170-S I JUNE 2000

28O

Fig. 9 - - Geometry of the dumbbell-shaped workpiece.

80 lo

8 E E 6

o | • . • . | , | • | . • . • . | • • .

0 10 20 30 40 50 60 70 80 Time, s

60

4o e s

2O

o

90 1 O0

Fig. 10 - - Weld pool sizes for the dumbbell-shaped workpiece using constant welding parameters.

_ _ ~ E * _ ~ h 6g - - ~k w~k(t) r'(,~),

8/kg

~, ( /g l - ao~ _ ~kj-~-k -1, k=1,2,...,49

(21) F layer:

_- (o() (22)

= - OE * = 63 . Ofl ~ ~,~ ,

~,ll~ ~,l~ ao~ . =-~-7-f =1,

~j, ~ kJ a/k I = k - 1 , k =2,3,...,50 (23)

E layer:

_ ~ E * _ [ x f

• = - - = 1 ,

I = k + l , k=1,2,-. . ,49 (24)

D layer:

~)E* _ ~,/67(k-1)+/

ao~

• 0 d, k = 1,..., 7 (25)

oy

a/~ o~,k:8, ,14 ~26~

w~k(t ÷ 1)= w~k(t) + ~

c w~k(t) 1 ok + 5 -w~k(t-1)' k =1,2...14 (27)

C layer:

a'~ ~ w~k

~O~ _

w~ (t +~)=Wck (~ )+~ ~ o~ ÷ . [Wck (t ) -w~ (t -~)] /29/

B layer:

c~E * 7

=1, k =1,2 (30)

Wsk (t + 1)=W sk (t )+ FI.~ b

. 0 ~ +o~.[Wsk (t ) -Wsk (t -1)] (31)

where 81; denotes the back propagating error of the jth node in the I th layer of the FNNC, q is the learning coefficient and (x is the momentum factor. The regulation of the FNNC weights can be realized with Equations 19-31, which make up a one-step learning algorithm of the FNNC.

Simulation of the Fuzzy Neural Network Controller

Given the maximum backside width Wmbma x of 5.0 and 6.0 mm, the FNNC simulations for butt joint welding were accomplished. The learning coefficient q was 0.45 and the momentum factor c~ was 0.20. We defined the error e as

[-2.0 mm, +2.0 ram], the change in error ceas ~ [-1.5 mm, +1.5 mm] and the change in the pulse duty ratio cu as

[-12%, +12%]. Given Wmbma x as 6.0, the simulation

results are shown in Fig. 8A, 13. The overshoot of Wbmax was 3.26%, the regulating time was 3 s and 6 stabilized at 51%. The simulation results of Wmbma x = 5.0 are shown in Fig. 8C, D. The overshoot of Wbmax was 4.51%, the regulating time was 2 s and 6 stabilized at 43%. All the simulation results showed the overshoot was small and the regulating time was fast, indicating the FNNC can adapt to the variations in butt joint welding.

Control Experiments by the Fuzzy Neural Network Controller

To investigate the practical use of the FNNC, experiments were conducted with pulsed gas tungsten arc welding of a butt joint. The specimen for the test was mild steel plate of 2-mm thickness, shown in Fig. 9. The dumbbell-shaped specimen imitated the gradual changes in heat-transfer or heat-sink conditions during welding. Figure 10 shows the variations of the backside size parameters, as well as the stable welding parameters. The backside size fluctuated greatly with the different sizes of specimens. The tran- sitions of the weld pool size were distinguished at 35 and 70 pulses.

The FNNC closed-loop control experiments were performed on specimens with a Wmbma×Of 6.0 mm. The schematic of the control system is shown as Fig. 11. The output variable was (3 and the mini-


~ Learning Algorithm I

\ ~ _ ~ FNNC

Controller

W=b,., I SSNNM

H Pulsed GTAW Process

±

MS

Wb.= r

Fig. 71 - - Schematic of the FNNC closed-loop control system for pulsed gas tungsten arc welding of a butt joint.

A 10 80

8

|6

2

I I I I ' ' , , I ,

0 10 20 30 40 50 60 Time, s

! | I | 0

70 80 90 100

s° E

2o ~

B 6O

50 40

~ 20

10

0

Vw--2.Smmls; Ip:145A; Ib:60A; I I l:3.0mm; L:811min;

' ' ' " ' ' ' " ' I I I I I I I

0 10 20 30 40 50 60 70 80 90 100 Time, s

Fig. 12 - - FNNC closed-loop control curves of the dumbbell-shape workpiece. A - - Backside sizes of the weld pool; B --pulse duty ratio.

mum regulating unit of ~3 was 1%. Wbmax was the control variable. MS sensed the topside size and shape parameters, such as Wfmax, Lfmax, Sfmid , the rear widths Wfi and the welding parameters. The weights of the network were modified based on the above algorithm for self-learning on- line. Figure 12 A shows the variations in the backside size parameters, and Fig.12B shows the regulation curve of (3 with the variation in heat transfer. The shape of the curve is similar to a skilled operator's manipulation, which verifies a

capacity for self-learning. With the Wbmax maintained at a given value on the whole, the statistical results showed the maximum error was 0.46 ram, the average error was 0.07 mm and the root- mean-square error was 0.2 mm. This indicates that the size parameters in the width direction can be controlled.

Figure 13 shows the final relationship between input and output of the FNNC, which contains the fuzzy control rules. The differences between the initial and final surface relationship indicated the

surface control rules were modified automatically during welding, and the intelligent control function was realized. The surface relation changed more in- tensely than the initial relation surface (Fig. 7), which indicated a nonlinear function existed in the butt joint welding.

Double Variables in Intelligent Control

The backside maximum width of the weld pool can be controlled by the single variable controller, but the backside weld may not always be satisf actory. Through these investigations, the topside half-length and area were found to increase when the backside weld was unsatisfactory. This indicated the regulation of the single pulse duty ratio did not guarantee good weld geometry. More- over, the step impulse showed the travel speed had an important role with the size parameters in the welding direction. Therefore, the effect from travel speed adjustment should be considered.

Design of the Double-Input and Double- Output Intelligent Controller

An expert system for weld geometry control was applied to adjust welding speed. The double-input and double-output intelligent control system consisted of an expert system and a single-variable fuzzy neural network control.

To some extent, the expert system translates the expert experiences of solv- ing some problems into the generated rules represented by the knowledge base. Basically, an expert system consists of a knowledge base and a ratiocination machine. The knowledge base provides the expert knowledge in problem regions, and the ratiocination machine yields the control strategy from the knowledge base according to the current status. The generated rule is often represented as, "If A then B."

The schematic diagram of the closed- loop control system is shown in Fig. 14, where the top dashed-line frame represents the fuzzy neural network for controlling the backside width by adjusting the pulse duty ratio and the underside dashed-line frame represents the expert system to adjust the travel speed. The inputs of the expert system are Lfmax and 5fmid, which are combined and transferred to a shape factor 7through the signal converter. The error between y and the given value % matches the generated rules in the know~edge base of the expert system, yielding the travel speed V w. V w with 8 are regulating variables of the welding process for fulfilling the control.

When the weld shape is perfect, the

172-s I JUNE 2000

1.0 e

• 1 . 0

4o.5

o . o

~ - 1 . 0 -0.5 -1.0

Fig. 13 - - The final relationship surfaces between the inputs and outputs of the FNNC.

~ 8 i w..._ W, ~ ~ Pulsed GTAW ~ -

L I 'oo.-

.................................. v .

Fig. 14 - - Schematic of the closed-loop double-input and double-output intell i- gent control system for pulsed gas tungsten arc welding of a butt joint.

geometry parameters can be derived from the welding experiment curves. For example, the Lfmax is approximately 7.40 mm, and the Sfmid iS approximately 37.5 mm 2. Whi le the weld shape is not satis- fied, Lfmax increases to 8.95 mm and Sfmid increases to 45.0 mm 2. Based on the above experiences, the input ranges of the expert control ler are defined wi th Lfinax = [6.40 ram, 8.40 mm] and Slb~i d = [30.0 mm 2, 45.0 mm2]. The center values are 7.40 mm and 37.5 mm 2, respectively. To avoid the effect from the different units and ranges, normalization of the values as shown below is necessary.

-- x L - x L min XL =

XL max -XL min (32)

-- xs - x s min xS

xS max-xs min (33) where ~'L and ~s are the normalization results. The shape factor y is determined by the two factors, and defined as

7 = 0.~--L +O.~s (34) The generated rules of the expert con-

troller are the summarized experiences of specialists and skilled operators. The rules represent human behavior for adjusting travel speed to ensure weld shape. The generated rules for butt joint welding are as follows:

R I : I F7<0 .00 THEN AV w = -0 .50 mm/s

R2: IF 0.00 <7<0.20 THEN AV w = -0 .33 mm/s

R3: IF 0.20 _<7<0.45 THEN AV w = -0.17 mm/s

R4: IF 0.45 <7<0.55 THEN AV w = 0.00 mm/s

R5: IF 0.55<7<0.80 THEN AV w -- 0.17 mm/s

R6: IF 0.80 _<7<1.00 THEN AV w = 0.33 mm/s

R7 : IF?> I .00 THEN AV w = 0.50 mm/s

A 8

E6 E ~4 >-

/

0 0 0 10 20 30 40 50 60 70 80 90 100

Time, s

60

4 0 E =_"

20U)

B 10 ~ 50 8 I 40,,

. l.,~x

I i I I I I I I I I I 0

0 10 20 30 40 50 60 70 80 90 100 "Rme, S

C 60 50 40

~ 3o ~ 20

10 0

5.0

3 .0~

"lip =145A; Ib:50A; I 2.01.0 ;:~ -li=3.0mm; L=811min; I ~"- - - - Vw "" 0.0

10 20 30 40 50 50 70 80 90 100 Time, s

4.0

Fig. 15 - - The double-input and double-output intell igent control curves of the dumbbell-shaped workpiece during pulsed gas tungsten arc welding. A - - Topside sizes of the weld pool; B - - backside sizes of the weld pool; C - control variables.

W E L D I N G RESEARCH SUPPLEMENT I 173-s

A B

Fig. 16 - - The dumbbell-shaped workpiece with the double-input and double-output intelligent controller. A - - Topside; B - backside.

The Controlled Welding Experiments Using the DIDO Intelligent Controller

To verify the performance of the DIDO intelligent controller, welding experiments were conducted on dumbbell-shaped specimens. The minimum regulating unit of 6 was 1% and the minimum regulating unit of V w was 0.17 mm/s. Given Wmbma X was 6.0 mm, the control curve was derived as shown in Fig. 15, and the topside and backside are shown in Fig. 16. From the control results, the size parameters in both the width direction and the length direction are controlled perfectly. The geometry parameters are more stable than the results generated with the single variable controller. The results can be seen in the figures.

Statistical results showed the maximum error of Wbmax was 0.34 ram, the average error was 0.09 mm and the root- mean-square error was 0.11 mm. Other statistical results of Lfmax, Sfmi~ Lbmax and S b were smaller than that of the single variable controller. All the results testify to the feasibi l i ty and accuracy of the DIDO intelligent controller.

Conclusions

Intelligent techniques that incorporated computer vision, neural networks modeling, a self-learning fuzzy neural network controller, and a double-input and double-output intelligent controller were investigated and applied successfully to the pulsed gas tungsten arc welding of butt joints.

1) The shape parameters proposed in this paper along with the size parameters of the weld pool developed in a previous bead-on-plate welding investigation were combined to characterize the weld pool geometry. A new real-time algorithm was developed to determine the size and shape parameters.

2) The neural network model with both size and shape parameters as the inputs predicted the backside width more accurately than with single-size parameters as the model inputs.

3) The single-input and single-output fuzzy neural network controller was developed for control l ing the backside width. Experiment results from butt joint welding a 2-mm-thick mild steel dumbbell-shaped specimen showed the backside width was successfully controlled.

4) A double-input and double-output intelligent controller incorporated with a single-variable fuzzy neural network controller and expert system was developed. The capability for controlling the geometry parameters in the length and width directions by regulating the pulse duty ratio and the travel speed was verified. A good weld shape was obtained with the double-input and double-output control system.

The intelligent methodology provided in this paper can be fully or partially implemented in other arc welding processes.

Acknowledgments

This work was supported by the Na- tional Natural Science Foundation of China No. 59575057 and No. 59635160. The authors would like to thank the editor and anonymous referees for their careful review and constructive comments on this article.

References

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11. Zhang, Y. M., Wu, L., Walcott, B., and Chen, D. H. 1993. Determining joint penetration in GTAW with vision sensing of weld face geometry. Welding Journal 72(10): 463-s to 469-s.

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174-s I JUNE 2000

FIRST ANNOUNCEMENT AND CALL FOR PAPERS

ICAWT 2000 m The International Conference on Advances in Welding Technology

GAS METAL ARC WELDING FOR THE 21 sT CENTURY

December 6-8, 2000, Orlando, Florida

This is a landmark conference on the Gas Metal Arc Welding Process (GMAW) and the related Flux Cored Arc Welding (FCAW) process, celebrating 50 years of GMAW, and evaluating ways in which application of the latest developments in GMAW technology can assist users in increasing productivity and quality. International experts will give keynote papers, and the latest process developments will be discussed in five sessions over 3 days. An exhibition will be held in conjunction with the conference. Authors from around the world are invited to submit abstracts. The conference is sponsored by the American Welding Society and the Edison Welding Institute.

Authors should submit the Author Application Form (on reverse side) with an abstract of no more than 500 words by June 15, 2000, preferably by electronic mail ([email protected]). Authors will be notified of acceptance by June 30, 2000. Papers for the program will be selected by a technical committee. Completed manuscripts in camera-ready format will be required by October 1,2000. Companies interested in exhibiting at the conference should contact the AWS Conference Department at (800) 443-9353 ext. 449.

Authors are requested to offer papers appropriate for the theme of the conference, the application of the latest developments in GMAW technology to enhance productivity and quality. Session topics will include the following:

• GMAW power supplies. DC, AC and pulsed welding, process stability, adaptive power supplies, transfer modes, stability, spatter

• Process characterization and optimization. Optimization methods, gas mixtures, defects, modeling, neural nets.

• Process variants. Narrow groove welding, combined laser/GMA welding. • Flux core and metal core welding. Process selection, weld properties, hydrogen

control. • High productivity welding. Extended stickout, twin and tandem welding, rotated arc

welding. • Robotics and automation. Off-line programming, cost benefit, implementation of

automated systems, case studies. • Sensors and process monitoring. Data acquisition and signal analysis, through-the-

arc sensors, optical and other sensors, joint tracking, adaptive welding. • Safety. Fume generation, fume extraction. • Applications. Underwater welding, pipeline welding. Novel applications. • Materials. Galvanized and aluminized steel, high-strength steel, stainless steel,

aluminum, titanium, and nickel alloys.

A U T H O R A P P L I C A T I O N F O R M

I C A W T 2000 : G a s Me ta l Arc Welding for the 21 st Century December 6 - 8 , 2000 , Orlando, Florida

Abstract Title:

Author's Name:

How addressed: (Mr., Ms., Dr., Prof., Other):

Title or Position

Organization:

Mailing Address: City: State: Zip/Code: Country: Telephone: Fax: e-mail address:

Coauthors: Name: Organization: Address:

ABSTRACT; • Typed, double spaced, 250-500 words, transmitted with this form. • Application form and abstract must be provided to AWS no later than June 15, 2000.

PAPERS: • Manuscripts in camera-ready format will be required no later than October 1, 2000. • Guidelines for submission of manuscripts will be provided to authors selected for the program. • The offer of a paper is taken to imply that an author will be fully funded and available to attend and

present the work. • The bound conference proceedings will be provided to conference 15articipants at the commencement

of the conference.

Wherever possible, the abstract and author application form should be sent by electronic mail to [email protected]. Alternatively, the abstract can be provided on disc in Microsoft Word (6.0 or 7.0 or rich text format), and may also be faxed or mailed to the following address: Conference Department American Welding Society 550 N.W. LeJeune Rd. Miami, Florida, 33126, USA (800) 443-9353 or (305) 443-9353, ext. 278. FAX (305) 443-7559.

A R C

In the battle to provide the welding industry with the champion in metal- cored electrode quality and performance, Select-Arc has emerged victorious.

Hov,' can this four year old company triumph over the heawweights of the welding electrode industry?

First, Select-Arc designs and manufactures only tubular welding electrodes. This single-minded dedication to specialization sets Select-Arc apart.

Second, the company was founded with the commitment to providing the highest quality metal-cored products, the best service and the most value- added to the customer.

Third, Select-Arc offers a complete line of metal-cored electrodes to meet )'our specific welding application.

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Finall}; Select-Arc metal-cored electrodes have earned their outstanding reputation where it counts - in the vcelding arena. These unique wires deliver a solid one-two combination - the efficiencies of solid wire and the high productivity of flux-cored - resulting in these significant hencfits:

• Very smooth spray transler • Virtually no spatter enfission


• Low furne generation • Superb bead geometry • Enhanced sidewall fusion • Faster travel speeds for

greater productivity

Call us today at 1-800-341-5215 and discover for yourself what makes Select-Arc the unquestioned metal-cored electrode champion.

600 Enterprise Drive, PO. Box 259 Fort Loramic, OH 45845-0259 Phone: (937) 295-5215 Fax: (937~ 295-5217

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