tungsten inert gas welding - techav.co.za · page 3 o all ppe designed for use with arc-welding...

TUNGSTEN INERT GAS WELDING

(TIG)

Facilitator Guide

TABLE OF CONTENTS INTRODUCTION PAGE 1 THE LEARNING PROCEDURE PAGE 2 OUTCOMES / ASSESSMENT CRITERIA PAGE 4 MODEL ANSWERS TO SELF-TEST (THEORY) PAGE 6 PRACTICAL EXERCISES CRITERIA PAGE 12

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INTRODUCTION This programme, Tungsten Inert Gas-Welding, or TIG, has been designed to introduce Learners to the basic skills involved in the use of TIG equipment. The emphasis of this series is geared toward "safety" and "practical techniques" in basic (core) skills. No attempt has been made to include "advanced techniques" in this programme. Learners are guided through the learning process via a Learning-Guide and it is in this sense that the programme is "Learner Driven". A competent "Facilitator / Mentor", skilled in the techniques of using TIG equipment, is an essential factor in the "learning process". IMPORTANT Please be aware that TECH AV programmes are designed as "Training Aids", not "courses". The producers do not hold themselves responsible for accreditation of this or any other material produced under the Tech AV trade name. Any tests, exercises and assessments provided in the "Learning Guides" are offered as "suggestions" and do not necessarily conform to the criteria set by the authoritative SETA PRE-REQUISITES (LEARNING ASSUMED TO BE IN PLACE) It is assumed that those participating in this programme have successfully achieved competency / proficiency in the following:

o General Industrial safety. o Use of Basic Engineering Hand-Tools. o Basic measuring skills. o Gas welding basics (OXY). o Shielded metal arc welding basics (SMAW).


THE LEARNING PROCEDURE LEARNERS GUIDE (WORKBOOK)

o Each Learner should be supplied with a copy of the Learners' Guide. This should be retained in the possession of the Learner for future reference.

o The Learners' Guide serves to direct the Learner through the programme. EXERCISES AND SELF-TESTS

o Exercises and Self-Tests normally accompany each section of learning. The Learner performs these after having read the relevant "resource notes" and viewed the relevant section of video (where applicable).

o "Model Answers" to the theoretical tests are provided in this manual. o Practical exercises are assessed upon the "output criteria" and upon "safe working

practices". VIDEO PROGRAMMES

o A Learner will request the relevant video for the section he or she is attempting. o Learners must be permitted to view a video as many times as deemed necessary in

order to grasp a concept or observe a demonstration. o Each video is divided into sections. Learners should stop the video at the end of each

section and perform any exercise suggested before continuing. LEARNING ENVIRONMENT The primary requisites for a suitable learning environment are:

o A work area where practical exercises can be conducted. LEARNING AIDS

o TIG welding machines to maximum 250 amp current output. o Relevant "Operators Manuals" for TIG machines. o All PPE designed for use with arc-welding processes. o Mild steel, stainless steel and aluminium work-pieces for practice. o Assorted consumables - Filler wire relative to metal type and shielding gas. o Manufacturers wall charts or instructional material if available.

RECOMMENDED PROCEDURE FOR LEARNING

o Learner is provided with a copy of the Learning Guide. o Learner reads through the guide to familiarise himself / herself with content and

instructions. o Learner views the relevant video section (where applicable) as directed by the

instructions in the guide.


o Learner attempts the suggested exercise, or practices a skill in the workplace. o Learner performs a "self-evaluation" of the work.

EVALUATION Assessment of competencies must be made in accordance with the relevant unit standards applicable to your industrial sector. In broad based terms the following training objectives should be achieved by the Learner:

o Identify by name all equipment associated with TIG processes. o Prepare work area in terms of safety. o Set up work-pieces and equipment in preparation for welding. o Produce acceptable welding runs in the flat or "down-hand position".

MODULE STRUCTURE This module has been divided into (4) main programmes. It is recommended that Learners work through these sections in "numerical order". The first programme is considered to be "essential" for all processes involving the use of TIG Equipment.


OUTCOMES / ASSESSMENT CRITERIA PROGRAMME - 1 "TIG PROCESS AND EQUIPMENT" - (TIG-1) Observe: (Leaner will perform the following)

o Describe the principles of TIG welding. o Identify by name all the major components in a typical TIG system. o Describe welding currents in terms of "polarity" and heat distribution. o Describe PPE requirements for TIG processes. o Learner completes Self-Test No.1 (or company test) with 100% result.

Confirm:

o Learner completes Self-Test No. 1 (or company test) with 100% result. PROGRAMME - 2 “BASIC TIG EQUIPMENT” - (TIG-2) Observe: (Leaner will perform the following) Describe purpose and function of:

o Standard power source designed for TIG operation. o TIG torches and tungsten electrodes. o Shielding gas (Argon) and allied equipment. o Filler wires.

Confirm:

o Learner successfully completes Self-Test 2. PROGRAMME - 3 “EQUIPMENT PREPARATION” - (TIG-3) Observe: (Learner will demonstrate the following processes) Prepare the following for a given task:

o A TIG power source (welding machine). o Shielding gas supply and accessories. o The TIG welding torch and electrode

Confirm:

o Learner successfully completes Self-Test 3. PROGRAMME - 4 “TIG WELDING PROCEDURES AND PROCESSES” - (TIG-4) Observe: (Learner demonstrates)

o Preparation of metal surfaces for applying the TIG processes. o Methods of striking an arc. o Methods of breaking an arc. o Running a fusion weld on mild steel plate in down-hand position. o Running a stringer-bead on mild steel plate in down-hand position. o Weld a straight butt-joint on mild steel plate.


o Weld outside corner joint on stainless steel plate. o Weld an inside corner joint on stainless steel plate. o Weld a lap-joint on aluminium plate.

Confirm:

o All work to meet the criteria as provided in check-lists 1 - 5.


MODEL ANSWERS TO SELF-TEST EXERCISES 1 - 3 SELF-TEST NO. 1

TIG PRINCIPLES AND SAFETY

QUESTIONS YES NO

1. What do the letters “TIG” mean? Tungsten Inert Gas.

2. What other letters also describe the TIG process? GTAW – Gas Tungsten Arc Welding.

3. For which metal type is TIG particularly useful? Aluminium.

4. Which component in the TIG system contains the metal "Tungsten"? The Electrode.

5. What does the "Inert Gas" do in the process? It “shields” the hot metals / weld from the atmosphere and prevents “oxidising”.

6. What type of gas is most commonly used in the TIG process? Argon.

7. List those units required to make up a full TIG welding system: i) Power Source or Welding Machine. ii) Shielding Gas supply. iii) TIG Torch. iv) Welding Leads.

8. The electrons in an arc move in which direction? (tick applicable answer) a) From negative to positive pole. b) From positive to negative pole. c) In both directions.


9. Approximately how much of the "arc-heat" is deposited by electrons onto the pole? (Tick applicable answer) a) 30%. b) 70%. c) 100%.

10. Straight Polarity (DCSP) means what? (Tick applicable answer) a) Electrode positive. b) Electrode negative. c) Alternating current.

11. Reverse Polarity (DCRP) means what? (Tick applicable answer) a) Electrode negative. b) Electrode positive. c) Alternating current.

12. Which DC polarity would you use for maximum cleaning action? Reverse polarity, DCRP, DCEP.

13. What factor in the TIG arc is responsible for the "cleaning action"? The gas ions.

14. What "desirable features" does AC welding current provide? Good penetration of weld and good cleaning action.

15. What are considered "essential" items of PPE when using TIG? i) Welding mask / Hood visor. ii) Welding gloves. iii) Overalls.

16. What makes the TIG process “hazardous" in a confined space? The GAS which displaces oxygen.

17. What "General Safety rule" applies when using TIG? All rules applicable to your plant.


SELF-TEST NO. 2 TIG EQUIPMENT

QUESTIONS YES NO

1. What two features must a welding machine have if you want to use it with TIG? i) AC and DC welding current. ii) High frequency stabilising on the AC.

2. When connecting the welding leads to a DC machine to which "output connection" would you "normally" connect the "electrode lead"? To the negative of “minus” terminal.

3. When you have connected the electrode lead as answered in question 2 then you have set the welding current to what? (Tick the answers that relate) a) DCRP. b) DCSP. c) DCEN. d) DCEP.

4. Which type of welding current is normally used when welding Aluminium? AC with high frequency.

5. What are the 4 main functions of a TIG welding-torch? a) Hold and secure the electrode. b) Provide an electrical connection to the electrode. c) Direct shielding gas to the work. d) Insulate the operator.

6. Name the main parts of a typical TIG torch. a) Torch body. b) Nozzle or Cup also known as a “ceramic”. c) Collet Body. d) Collet or “split collet”. e) End Cap also called a Black-Cap. f) End Seal or “O-ring”.


7. In this country (South Africa) you will usually obtain electrodes colour coded red or white. What do these colours indicate? a) White electrodes are used with(AC Welding Current). b) Red electrodes are used with(DC Welding Current).

8. What is the purpose of a "regulator / flow-meter"? To reduce cylinder-pressure to working-pressure and to control the flow of gas to the torch.

9. Filler rods (or wires) suitable for TIG welding can be identified how? (give 2 answers) a) By markings stamped at one end. b) By length of approximately 1 meter.


SELF-TEST NO. 3 EQUIPMENT PREPARATION

QUESTIONS YES NO

1. If you discover any fault with your welding equipment during the "pre-inspection", what must you do? Notify your Supervisor.

2. Before you fit or swap the welding-cables what must you be sure to do? Make sure that the power is off, or the machine is isolated.

3. Why must "pin type connectors" be fully turned or twisted into their sockets? To ensure a good electrical connection.

4. What is important when connecting the work-lead clamp to the work or a welding-bench? That the clamp is attached to "bright metal".

5. When "reading" a floating-ball type flow-meter the reading must be taken where? At the top of the ball.

6. What "rule of thumb" is used when setting the "post-flow"? Allow 1 second for every 10 amps of welding current.

7. What type of electrode must you fit when you are using DC welding current? Thoriated or red electrode.

8. What type of electrode must you fit when you are using AC welding current? Zirconium or white electrode.

9. How do you determine the nozzle-size for a weld? The inside diameter must be approximately 3 - 4 mm wider than the bead width or 4 times the electrode size.


10. Why must you not fit or use a nozzle that is cracked or has slag" inside it? Because a proper gas-envelope will not be formed around the weld-pool.

11. How much protrusion, normally, must you allow the electrode beyond the nozzle? 3 mm Minimum or never more than the diameter of the nozzle.


CRITERION CHECK LIST #1 (FOR A "FUSION RUN")

INSTRUCTIONS When you have made a "successful" fusion run (bead) on 3 mm mild steel plate use the checklist below in order to assess the quality of your work.

CRITERIA YES NO 1. The run(s) follows the marked lines. 2. Runs are “clean” in appearance – no inclusions of oxide. 3. Uniform width (approximately 6 mm wide). 4. “Ripples” are uniformly spaced along the run. 5. Beads follow the scribed lines.

The above check-list does not take into account your "method" of producing the run, in other words it simply assesses the "finished work". If however you find that you cannot produce a bead meeting the "standard" required then perhaps your method requires looking at. Use the check-list below to assess your operating method and other criteria that will affect the bead.

CRITERIA YES NO

1. Are the “optimum settings” of the welding equipment correct?

2. Is the metal sufficiently clean for TIG welding?

3. Is the electrode tip clean and the correct shape?

4. Are you able to maintain a “consistent” arc-length?

5. Is the torch angle correct at 60 - 75 degrees?

6. Is the gas flowing?

7. Are you moving at the correct travel speed?

8. Are you following the scribed lines?


CRITERION CHECK LIST #2 (FOR STRINGER BEAD)

INSTRUCTIONS When you have made a "successful" stringer-bead on 3 mm mild steel plate, use the checklist below in order to assess the quality of your work.

CRITERIA YES NO

1. The bead is of uniform width @ approximately 6 mm wide.

2. The bead is of uniform height.

3. The ‘ripples’ are consistent (evenly spaced).

4. The beads are on the line (straight).

5. Beads are free of contamination (oxide). The above check-list does not take into account your "method" of producing the run, in other words it simply assesses the "finished work". If however you find that you cannot produce a bead meeting the "standard" required then perhaps your method requires looking at. Use the check-list below to assess your operating method and other criteria that will affect the bead.

CRITERIA YES NO

1. Metal has been sufficiently “cleaned” for TIG process?

2. Torch and filler wire angles correctly maintained?

3. Consistent arc-length maintained?

4. Filler wire tip always kept within the gas-shield?

5. Filler wire kept clear of the electrode?

6. Filler material added “consistently” (results in even ripples)?

7. Adequate gas-flow provided?

8. Post flow gas held over during arc break?


CRITERION CHECK LIST #3 (FOR "BUTT-JOINT")

INSTRUCTIONS When you have welded your butt-joint on 3 mm mild steel plate use the checklist below in order to assess the quality of your work.

CRITERIA YES NO

1. The weld-bead is ‘uniform’ in width and height along the joint?

2. The ‘ripples’ are consistent (uniform) in shape and spacing?

3. The plates are ‘level’ (owing to the pre-set)? 4. Penetration (root bead) can be seen along the full-length

(reverse side)?

5. Penetration bead is uniform in width and protrusion. The above check-list does not take into account your "method" of producing the run, in other words it simply assesses the "finished work". If however you find that you cannot produce a bead meeting the "standard" required then perhaps your method requires looking at. Use the check-list below to assess your operating method and other criteria that will affect the bead.

CRITERIA YES NO

1. Metal plates are properly cleaned for TIG process?

2. Root gap is set to filler wire width?

3. A pre-set was allowed after tracking?

4. Torch and wire angles maintained correctly?

5. Weld pool maintained evenly across the root gap?

6. Travel speed of torch and wire maintained correctly?

7. Arc-length maintained steady (consistent)?

8. Allowance made for heat build-up toward end of run?


CRITERION CHECK LIST #4.1 (FOR S/S OUTSIDE CORNER JOINT)

INSTRUCTIONS When you have welded your Outside Corner on 2 mm stainless steel then use the checklist below in order to assess your work.

CRITERIA YES NO

1. The weld is straight and neat in appearance.

2. The weld is free of contamination, craters etc.

METHOD

1. Metal has been sufficiently “cleaned” for TIG process?

2. Torch angle correctly maintained?



5. Post flow gas held over pool during arc break?


CRITERION CHECK LIST #4.2 (FOR S/S INSIDE CORNER-JOINT)

INSTRUCTIONS When you have welded your Inside Corner on 2 mm stainless steel then use the checklist below in order to assess your work.

CRITERIA YES NO

1. The weld is straight and neat in appearance.

2. The weld is free of contamination, craters etc.

METHOD

1. Metal and filler-wire has been sufficiently “cleaned” for TIG process?

2. Torch and filler-wire angle correctly maintained?

3. Filler-wire not removed from the gas shield?



6. Post flow gas held over pool during arc break?


CRITERION CHECK LIST 5.1 (FOR ALUMINIUM-BEADS)

INSTRUCTIONS When you have completed the exercise on your practice plates, check your work against the checklist below.

CRITERIA YES NO

1. Fusion beads are straight and clean. (No holes or contamination).

2. Stringer beads are straight and ‘uniform’ in width.

3. Ripples are consistent and uniform along the bead.

4. Beads are free of contamination and craters.

METHOD

1. Weld zone has been properly sanded and cleaned?

2. Torch angle and arc length correctly maintained?

3. Weld pool size maintained during the weld process?


CRITERION CHECK LIST 5.2 (FOR ALUMINIUM-LAP JOINT)

INSTRUCTIONS When you have completed the running of fusion beads and stringer beads on your practice plates, check your work against the checklist below.

CRITERIA YES NO

5. The weld is free of contamination and craters.

6. The weld-bead is evenly distributed between the plates.

METHOD

4. Weld zone has been thoroughly cleaned?

5. Correct electrode selected.

6. Current setting to AC. HF

7. Filler wire has been cleaned.

THIS EXERCISE COMPLETES THE "BASIC TRAINING MODULE" ON THE TOPIC OF TIG WELDING.

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