Hybrid Laser Arc Welding Process Verification

1. Hybrid Laser Arc Welding Process Verification and ImplementationNSRP All Panel Meeting March 12-14, 2019 Charleston, SC DCN# 43-4908-19 • Distribution Statement A: Approved for public release: distribution unlimited.

2. Legacy Processes • Ingalls Panel Line used the tandem submerged arc welding process for seaming plates from a single side • Two 5/32” diameter wires • Required 45 degree included bevel angle with varying land and root opening dimensions depending on material thickness • Could create single sided, full penetration welds in a single pass on material up to 5/8” thick • Process has a wide range of parameters and heat inputs for varying thicknesses • High heat input for thin material, ½” and less, would lead to increased distortion

3. Legacy Processes • ½” Plate • 112.2 kJ/in • 3/16” Plate • 37.4 kJ/in

4. Legacy Process • Ingalls began to redesign the Panel Line, and began to explore options for single sided seamers that would help reduce heat input • Hybrid Laser Arc Welding, abbreviated HLAW, was seen as a viable option for thin material

5. Hybrid Laser Capabilities • It was determined that HLAW could be successfully used on material ½” and less to create full penetration welds from a single side in a single pass • Heat inputs could be greatly reduced when compared to the legacy tandem SAW process • Reduction or elimination of welding consumables could be seen

6. Hybrid Laser Limitations • Would require extensive qualification efforts and altered upstream and downstream processes to successfully implement • Qualification efforts would be limited to carbon steel ½” and less • Cooling rates created toughness issues for high strength steels • Ingalls uses very little stainless steel or aluminum for ship structure • Large capital investment would be required • Laser power supply • Seamer with HLAW capabilities • Laser safety implemented into the system

7. Hybrid Laser Process Verification • NAVSEA and Naval Surface Warfare Center – Carderock Division were notified of Ingalls intention to implement an HLAW seamer on the new panel line • NSWCCD began to prepare a process verification test plan • Tech Pub 248 does not cover HLAW; therefore, this became a special qualification • Test plan requirements included destructive and nondestructive testing of HLAW weldments, as well as extensive fatigue and dynamic impact testing on HLAW and SAW weldments, on both the thinnest and thickest material types to be used • Production verification testing at Ingalls on HLAW seamer

8. Hybrid Laser Test Plan • Phase I • Similitude Document • Welding parameter development at EWI • Non-destructive testing at Ingalls • Destructive testing at EWI • Parameter Development report and Mechanical Testing report generated at EWI • Phase II • Welding of HLAW and SAW test plates for fatigue and dynamic impact testing • Fatigue testing at EWI and NSWCCD • Dynamic impact testing at NSWCCD • Production verification at Ingalls

9. Phase I, Similitude Document • Test plan required that all testing be performed on the system that was to be used in production • If this requirement was not satisfied, a document must be generated to show that the production system and the system used to produce the test welds were similar in all essential categories • Similitude Document was produced to include over 25 attributes of an HLAW system • In any instance where the EWI system varied from the Ingalls system, a justification was provided to show they two were still similar • Examples • Laser power supply and optics, process orientation • EWI used a Kuka robot, Ingalls system is a welding gantry • EWI created a fixture to simulate the Ingalls seamer

10. Phase 1, EWI Test Cell

11. Phase I, EWI Test Cell

12. EWI Test Cell

13. Phase I, EWI Test Cell EWI laser power supply was the same manufacturer, IPG, as the Ingalls system • Ingalls laser supply is only 16 kW, while EWI’s is capable of 20 kW so all tests were limited to 16 kW and less • Lincoln Electric welding machines and wire feeders were installed to match the Ingalls system • HLAW uses GMAW-P and the Similitude Document required the same pulse program to be used • Test fixture matched the hold down pressure and distance from the weld joint as the Ingalls System

14. Phase I, Test Matrix • Two materials were used • DH-36 and HSLA-65 • Thickest and thinnest of each used in production application at Ingalls were tested • 5/32” and ½” for DH-36 • 3/16” and ½” for HSLA-65 • Nondestructive testing performed at Ingalls by certified NDT personnel • Visual Inspection, Magnetic Particle Inspection, Radiographic Inspection, and Ultrasonic Inspection • Destructive testing performed at EWI • Transverse tensile testing, Charpy Impact testing, root and face bends for thin material, side bends for thick material, macro-etch specimens, micro hardness testing

15. Phase 1, Test Results • All NDT was successful to MIL-STD-2035 Class 1 requirements • All destructive testing met the minimum requirements of the base material and filler material

16. Phase I, Reporting and Decision • Parameter Development report and Weld Quality report were generated at EWI • Reports showed that HLAW was capable of producing sound joints that could meet all requirements for mechanical properties and nondestructive testing • Heat input could be drastically reduced when switching from the SAW process to the HLAW process • 60% to 80% reduction depending on material thickness • Travel speeds and GMAW parameters could remain constant as material thicknesses increased, laser power had to be increased to ensure full penetration • Go Decision was recommended

17. Phase II • HLAW test plates were welded at EWI and SAW test plates were welded at Ingalls to support fatigue and dynamic testing • All test plates were subjected to NDT as required in Phase I • Test welds were shipped to EWI for machining of fatigue and dynamic test coupons

18. Phase II, Fatigue Testing • Fatigue testing was performed at two different stress levels and was split between EWI and NSWCCD • Fatigue testing was to be until failure or 2 million cycles, whichever came first • Low stress level, 10 ksi, was tested at EWI • Low stress level test had the possibility of reaching 2 million cycles and EWI can run fatigue machines constantly • High stress level, 25 ksi, was tested at NSWCCD • NSWCCD can only run when operators are present, high stress level not expected to reach the 2 million cycle mark

19. Phase II, Fatigue Testing

20. Phase II, Fatigue Testing

21. Phase II, Fatigue Testing • For each comparable category of the test matrix, the HLAW weldments outperformed the SAW weldments • Initial concern of joint geometry was not realized • Many of the low stress level specimens reached 2 million cycles • Results were also compared to ABS fatigue curves • SAW and HLAW fatigue results exceeded industry standards for fatigue life

22. Phase II, Dynamic Testing • Dynamic testing was required to ensure adequate impact toughness in HLAW specimens • Specimens were machined at EWI and sent to NSWCCD for final preparations of the samples • Testing requires a fatigue pre-crack to be placed into the specimen at the bottom of the machine notch • This gives a precise location for a failure point and fracture path through the weldment

23. Phase II, Dynamic Testing

24. Phase II, Dynamic Testing • Fatigue pre-cracking of HLAW weldments has been unsuccessful to this point • ASTM E-1921 requires a tapering of stress intensity as the crack grows to help minimize plastic deformation at the root of the fatigue crack • Fatigue pre-crack has blunted and will not propagate as the stress tapers, which is being attributed to the high strength of the HLAW weld metal • Alternate methods are being tested to determine if pre-crack can be obtained • SAW specimens have shown that they are capable of producing a pre-crack within ASTM limits, however pre-cracking of these specimens is taking longer than anticipated • Alternate dynamic testing is being explored that would not require tapering of stress levels during fatigue pre-cracking

25. Phase II, Production Verification • Ingalls was required to prove that the HLAW system installed could meet the same requirements as the system at EWI • This is typical of standards that recognize HLAW • The thickest and thinnest of each material was welded using the Ingalls seamer • All non-destructive and destructive testing as required in Phase I was repeated • All test results met the minimum requirements • Approved test plan required welding of a ½” thick, 20’ test plate to ensure process stability over extended distances • Class 1 ultrasonic inspection required for entire length • Mechanical test specimens taken from the end of the joint

26. Phase II, Production Verification • Requirement to ultrasonically inspect the first 500’ of weld equal to or greater than 3/8” to show process tracking and stability • This requirement has been accomplished • Requirement that the first seam of at least 50’ be ultrasonically inspected • This requirement has been accomplished • Ingalls has submitted final welding procedures to NAVSEA and is using the seamer for limited applications until dynamic impact testing can be completed

27. Process Comparison Above: Single pass tandem SAW weld on ½” plate Right: Single pass HLAW weld on ½” plate

28. Process Pictures

29. Process Pictures

30. Process Pictures