High Deposition Submerged Arc Welding

March 12-14, 2019Charleston, SC

DCN# 43-5026-19

Distribution A. Approved for public release: distribution unlimited.Prepared under ONR Contract # N0014-14-D-0377 as part of the Navy ManTech Program

• To support NNS' welding infrastructure improvement effort by identifying and recommending a high deposition rate submerged arc welding (SAW) process

• Deposition rates for state-of-the-art SAW technologies have approached 100 lbs/hr.

• Original estimate (CY 2015) was a potential savings of 30,000 hours per CVN hull.

• Issue: Acquiring equipment to use non-standard SAW has an inherent risk.

• What if you acquire the equipment with a process variant to increase productivity but never get qualified?

Purpose and Objective

• Phase I: Determine Requirements for SAW Welding Technology Improvements• Task 1 – Project Initiation and Technical Requirements Definition• Task 2 – Screen Candidate SAW Processes• Task 3 – Define Test Plans and Obtain Tech Warrant Holder Concurrence• Task 4 – Procure Plate Materials for Test Plan A Execution*• Task 5 – Weld Specimens for Test Plan A• Task 6 – Execute Test Plan A*• Task 7 – Refined Business Case Analysis• Task 8 – Phase I Reporting

• Phase II: Conduct Shipyard Evaluations to Determine Preferred Process• Task 9 – Shipyard evaluations• Task 10 – Execute Test Plan B**• Task 11 – Phase II Final Reporting

* Test Plan A = test plan to guide data generation to assist in selecting (1) process for Test Plan B ** Test Plan B = test plan to develop path to qualification and to evaluate process for meeting the

requirements

Project Plan

• Wanted a high deposition rate SAW process.• Not constrained by legacy processes• Executing within existing heat input ranges but with significant

deposition increase.• Goals

• 45-85 kJ/in (feasible to increase rate?)• ≥26 lbs/hr (can we increase deposition rate?)

• Design of Experiment • Multiple vendors• Different processes• Varying base materials

Process Requirements

• Task 2 goal was to identify three HIGH POTENTIAL processes• Develop & use a weighted matrix to compare processes

• Issues: • Too many candidates (20+) & literature data can only narrow it so much (7

candidates);• Physical examples & work was requested from the vendors to narrow the field and

identify the top (3) processes• But NDT & mechanicals all met requirements & deposition rates were great! 61%-175%

better than legacy;

Market Survey

• Issues continued: • Originally proposed this as process + equipment + consumable solution but evaluated

the consumables later.• Diffusible hydrogen testing was needed earlier to complete assessments• Part of the Weighted Matrix assessment

Market Survey Continued…

Diffusible Hydrogen allowed Weighted Matrix to identify (3) HIGH POTENTIALS

• Tests needed to compare baseline and candidate processesTest Plan A

• Tested (3) processes but (4) different sets of equipment• Test Plan A provided to vendors to guide test weldment

fabrication for final selection.• Witnessed by IPT members

• Weldments were shipped to NNS for evaluation• NDT showed all passed UT and RT• Mechanical Results were all good.

Test Plan A Execution

• Test Plan B was created to define the testing required for NAVSEA procedure qualification

• Based on results, NNS recommended the Twin Wire Variable Wave AC process for Test Plan B

Test Plan B

• NNS testing was needed to evaluate the transition of the process from the vendor lab environment to the shipyard environment.

• Five (5) tests were to be conducted• Maximum Deposition Rate Analysis• Root Pass Analysis• Capping Pass Analysis• Tractor Modularity Assessment• Field Application Assessment

Shipyard Evaluation Testing

• During Test Plan A, vendors fabricated test plates witnessed by NNS & IPT personnel

• During the fabrication, NNS observed that deposition rate was being sacrificed to ensure quality

• Testing by NNS technician performed to determine true maximum welding deposition rates while maintaining a stable arc

• Used:

Maximum Deposition Rate Analysis

ESO (in.)

WireFeed

Speed (ipm)

Current (A)

Voltage (V)

Travel Speed (ipm)

Heat Input (kJ/in)

Avg. Deposition

Rate (lbs/hr)

Freq (Hz)

Balance (%

)

Offset (V)

1.25 590 max

900 max 40 max. ≤30 <85 56.8 60 45 -2

• During Maximum Deposition Rate Evaluation, Weld Technician evaluated process for root and capping pass deposition

• Qualitative assessment by operator• Many variables exist affecting the operator’s selection of root and

capping passes parameters to achieve the desired result• Technician found root and capping passes could be deposited

using the process…more on this later• Little slag entrapment issues

Root and Capping Pass Analysis

• Intent was:• Collect actual production data – i.e., deposition rates (NNS weld lab

to field)• Operational assessment – Can the process be used as intended?

• Fabricated 4 assemblies. Components were 20-in. x 120-in. x 1.5-in. HSLA-100

• Two B2V.1 joints. (1) using legacy twin-wire DC and (1) using TWVW-AC

• Two B2V.3 joints. (1) using legacy twin-wire DC and (1) using TWVW-AC

• Had to run two rounds based on Round 1 resulting lessons learned

Field Application Assessment

• Recommend all root beads to be placed in using DC process• Improved ground. Ground assembly to machine and then to

Earth• Uncoil all supply-side power cables.• Consistent CTWD – 1 inch minimum

Field Applications – Lessons Learned

AC is highly sensitive to grounding. Need to ground back to the power supply.

AC is sensitive to the amount of coiled wire due to increases in induction

• From the B2V.1 joints:• Overall (global) processing time was 50% less with the TWVW-AC SAW • Arc-on time was 48% less

• DC SAW was 105 minutes• TWVW-AC SAW = 66 minutes

• From the B2V.3 joints• Overall (global) processing time was 42% less with the TWVW-AC SAW.• Arc-on time was 50% less

• DC SAW process was 88 minutes• TWVW-AC SAW was 44 minutes

• From the B2V.3 joints• Reduction in process-induced distortion of approximately 10%

Field Applications – Findings

DC

DC

AC

AC

• B2V.1 Joints

• B2V.3 Joints

• Plan to evaluate the capability of the process to obtain qualification for general usage for aircraft carrier construction

Test Plan B

• Review the market using literature and empirical testing methods• Identified and recommended a three processes for further testing using developed methods

• Advanced testing identified one particular process for use at NNS – Twin Wire Variable Wave AC SAW

• Twin Wire Variable Wave AC SAW was then investigated under Shipyard Evaluation and Test Plan B efforts

• Shipyard Evaluation Test Execution• Maximum deposition rate is 56.8 lbs/hr. (laboratory) with a stable arc• Maximum deposition rate is 51 lbs/hr. (field) for a quality production weld.• Root and Capping passes are possible with the TWVW-AC SAW process.

• TWVW-AC not recommended to install production root passes• Operator must control ground quality, impedance conditions, and contact-to-tip-distance to ensure a

quality weld.• Tractor modularity allowed additional applications to be available to the process.

• Test Plan B Execution• Process can Capable of meeting qualification requirements for general welding with standard preheat and

interpass temperatures for all thicknesses• Capable of meeting the reduced preheat and reduced angle joint for material less than 1-5/8-inch thick

and 2-inch thick respectively

Summary of Project

• An implementation plan has been developed and delivered.• Equipment acquisition has already started. All 31 systems are

received. Alternative designs for SAW tractors and equivalent arcs (power supplies) are being finalized.

• Procedure Qualification Request Letter has been written. • Submitted November 2018 to Supervisor of Shipbuilding –

Newport News.• Naval Surface Warfare Center – Carderock has pulled this forward –

January 2019.• Waiting for acceptance letter to allow usage

Final

Questions?