NSRP Welding Technology Panel Meeting Miami, FL 8 – 9 April 2014 Controlled Waveform, Low Heat Input GMAW for Reduced Distortion in Shipbuilding Applications Jeff Farren Naval Surface Warfare Center Carderock Division Code 611 [email protected] 1 Introduction • Objective: Investigate the new generation of power supplies and arc control software that have been developed to replace conventional short-arc welding technology • Potential Benefits: – Sound welds at lower heat inputs – Smaller weld sizes – Reduced distortion • Candidates: – Lincoln: Surface Tension Transfer (STT) – Fronius: Cold Metal Transfer (CMT) – Miller: Regulated Metal Deposition (RMD) 2 Lincoln Power Wave S500 Advanced Process Welder with a Power Feed 10M wire feeder and STT (Surface Tension Transfer) module S500 STT Standard GMAW torch Dual torches and wire feeders STT is a separate module from the standard S500 power supply 3 Fronius • CMT 2700 with an integrated wire feeder and CMT (Cold Metal Transfer) capabilities CMT and wire feeder integrated into a suit case style power supply CMT torch is a push/pull style and there is a mechanical buffer in the cable to promote smooth feeding and droplet detachment 4 Miller • Axcess 300 power supply with integrated RMD (Regulated Metal Deposition) capabilities RMD capabilities integrated into the Axcess 300 power supply Standard GMAW torch 5 Part 1 – Preliminary Investigation 6 Experimental Design for Preliminary Investigation • STT/CMT/RMD are best suited for thin materials, open root welds, and gap filling • NSWCCD proposed tee and single V welds on ¼” thick DH-36 using a 3/16” root opening – Each power supply manufacturer agreed that this was a reasonable trial – Lee Kvidahl agreed as the shipyard partner 7 Preliminary Investigation Trial # Joint Type IT1 Tee IB1 Butt IT2 Tee IB2 Butt IT3 Tee IB3 Butt Weld Pass Root (1) Fill (2) Root (1) Fill (2) Root (1) Fill (2) Root (1) Fill (2) Root (1) Fill (2) Root (1) Fill (2) Power Supply Program Wire Feed (ipm) Voltage Notes Lincoln STT (#328) 186 16.9 Fusion line defects Lincoln STT (#328) 186 16.9 Excessive convex/concave CMT 200 12 Pulse 130 11.5 CMT 150 12 Pulse 130 11.5 Excessive convex/concave 14.5 Fusion line defects 14.5 Excessive convex/concave Fronius Fronius Miller Miller RMD (#3) RMD (#3) 189 189 189 189 Fusion line defects • 0.045” ER-70S-6 wire on DH-36 Plate, vertical down • Welds made by Ingalls welders at NSWCCD 8 Tee Weld Macros Defects Defects IT1 - Lincoln IT2 - Fronius Defects IT3 - Miller • All three tee welds contain defects at the fusion lines • Parameters were not optimized 9 Butt Weld Macros IB1 - Lincoln IB2 - Fronius IB3 - Miller • Parameters and bead placements need to be optimized • Concavity / convexity issues to be addressed • By parameter optimization • Next set of trials will be volumetrically inspected to ensure sound welds 10 Microhardness Traces • No significant differences observed between the three power supplies 11 Part 2 – Follow On Investigation 12 Follow-On Investigation • Shipyard feedback was received after the preliminary investigation was presented and it was decided that: – Use of a tee joint was not desirable since the attachment of stiffeners to plate is performed using fillet welds without an appreciable gap • Tee joint abandoned • Fillet configuration utilized – Initial idea was to use CWLHI process in the root of butt joint and then use pulsed GMAW for fill passes • Shipyard feedback indicated that switching back and forth between processes was not desired • Single process used for both root and fill 13 Experimental Matrix Joint/ Weld Type Gap Root Fill Power Supply Program ID Butt 3/16" CSA CSA Lincoln Power Wave S500 Program 5 Fillet none CSA CSA Lincoln Power Wave S500 Program 5 CWLHI-3 Pulsed GMAW Butt 3/16" P-GMAW P-GMAW Lincoln Power Wave S500 Program 12 CWLHI-4 Pulsed GMAW Fillet none P-GMAW P-GMAW Lincoln Power Wave S500 Program 12 CWLHI-5 STT Butt 3/16" STT STT Lincoln Power Wave S500 Program 325 CWLHI-6 STT Fillet none STT STT Lincoln Power Wave S500 Program 325 CWLHI-7 CMT Butt 3/16" CMT CMT Fronius CMT 2700 CMT CWLHI-8 CMT Fillet none CMT CMT Fronius CMT 2700 CMT CWLHI-9 RMD Butt 3/16" RMD RMD Miller Axcess 300 Program 3 CWLHI-10 RMD Fillet none RMD RMD Miller Axcess 300 Program 3 CWLHI-11 Combo Butt 3/16" STT Plate # CWLHI-1 CWLHI-2 • • Process Conventional Short Arc (CSA) Conventional Short Arc (CSA) P-GMAW Lincoln Power Wave S500 Program 325 (root) Program 12 (fill) ER-70S-6 filller metal; C-25 shielding gas Duplicates of CWLHI 5, 7, and 9 were produced by two different welders to determine the potential influence of the welder 14 Joint Configurations Butt Fillet 30° typical 1/16” – 3/32” land .0625 - .0938 land 30 ty p o 0~3/16” 0.1875 in. root ¼” ¼” 0.25in 0 2 2 1 1 ¼” 3 1 2 ¼” 15 Butt Weld Parameters- Welder 1 • In general, short arc produced lowest heat input, pulsed GMAW was the highest heat input, and the CWLHI processes fell between them 16 Butt Weld Parameters- Welder 2 • • Arc data monitor was not available to record for the CMT weld Welder 2 produced average heat inputs that were much lower than welder 1 – Welder 2 had previous experience with CWLHI processes and was more comfortable working with these processes at lower heat inputs 17 Butt Weld Heat Input • Voltage and amperage were very similar between Welder 1 and Welder 2 – Welder 2 was able to travel significantly faster than Welder 1 – Higher travel speed led to significantly lower heat input – Most likely a function of previous experience with CWLHI processes 18 Butt Weld Distortions • Maximum distortion recorded for each butt weld 19 Ultrasonic Testing • All of the butt welds received UT conducted IAW Tech Pub 271 • Results evaluated against MIL-STD-2035A Class 1 acceptance criteria • All butt welds passed UT to Class 1 except for the CMT weld fabricated by Welder 1 – Contained two small rejectable indications – Most likely caused by workmanship • Fillet welds did not receive UT 20 Butt Weld Macros – Welder 1 Welder 1 CSA Welder 1 CMT Welder 1 Pulsed GMAW Welder 1 RMD Welder 1 STT Welder 1 STT/Pulse • • • Bead profiles are all pretty similar across the machines/processes Convexity/concavity issues significantly reduced compared to Part 1 All welds passed UT to class 1 except the CMT – Two small rejectable defects, most likely workmanship 21 Butt Weld Macros – Welder 2 Welder 2 STT Welder 2 CMT • Bead Profiles are slightly different than those achieved by Welder 1 – Welder 1 used a light grind to clean up the surface – Welder 2 ground the root pass smooth before welding the 2nd pass • Still no significant convexity/concavity issues • All welds passed UT Welder 2 RMD 22 Fillet Weld Parameters • • • All weld passes made in the horizontal position All heat inputs fell between 18 – 28 kJ/in CMT and Short Arc had the lowest heat input and pulsed GMAW had the 23 highest Fillet Weld Heat Inputs • CMT fillet weld had a lower average heat input than short arc • Pulsed GMAW still had the highest heat input 24 Fillet Weld Macros CSA Pulse GMAW CMT • • • STT RMD Bead profiles very consistent across each of the five processes Minimal penetration/fusion at intersection of web and flange CWLHI processes visually produce very similar results to both short arc and pulsed GMAW 25 Summary and Conclusions • A series of butt welds was made using short arc, pulsed GMAW, STT, CMT, RMD, and a combination of STT and Pulsed GMAW – A second welder produced an additional set of butt welds using the STT, CMT and RMD processes – For Welder 1, pulsed GMAW exhibited the highest heat input, short arc generally exhibited the lowest heat input, and the CWLHI processes fell in the middle • As expected the distortion measurements followed the same trend – Welder 2, had previous experience with CWLHI processes which enabled him to produce welds with higher travel speeds and significantly lower heat inputs – Only minor convexity and concavity issues were observed and all of the butt welds passed Class 1 UT with the exception of the CMT butt weld • Believed to be the result of a workmanship issue 26 Summary and Conclusions Continued • A series of fillet welds was made using short arc, pulsed GMAW, STT, CMT, and RMD – The heat inputs were fairly consistent across each of the 5 processes with CMT having the lowest heat input followed by short arc – The bead profiles were consistent – Very minimal penetration/fusion at intersection of web and flange • Overall the results show that CWLHI welding processes are capable of producing sound welds at lower heat inputs than pulsed GMAW welding – Results in lower distortion – Further improvement would be possible through mechanization of the CWLHI processes 27 Acknowledgments • Funding – National Shipbuilding Research Program • Power Supplies – Lincoln Electric; Harry Sadler and Wyatt Mann – Fronius; Mike Ludwig – Miller; Rick Scharenbroch and Jim Wynegar • Shipyard Support – Lee Kvidahl – Mike Sullivan 28 Backups 29 STT Technology 30 CMT Technology During the arcing period the filler metal is moved towards the weld pool When the filler metal dips into the weld pool, the arc is extinguished. The welding current is lowered The rearward movement of the wire assists droplet detachment during the short circuit. The shortcircuit current is kept small. The wire motion is reversed and the process begins all over again. 31 RMD Technology 32
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