Elimination of Backing Gas in Austenitic and Duplex Stainless Steel Welds (HDMTGTAW)
Using High Deposition Metal Transfer Gas Tungsten-Arc Welding (HDMTGTAW)
Open root welding of austenitic and duplex stainless steel with gas tungsten-arc welding (GTAW) is typically performed using an inert backing gas for purging, such as argon, to protect the root pass from atmospheric contamination and oxidation. In many cases, using a backing gas for purging is impractical due to system design, access limitations, personnel safety, schedule and various economic factors. Until recently the only options available for open root welding of austenitic and duplex stainless steel that eliminated the need for backing gas were: flux agents, flux coated/flux cored rods and gas metal-arc welding using the short-circuiting transfer (GMAW-S). Each of these options have been used successfully, to some degree, in diverse service environments. Now after extensive application research, development and testing the need for backing gas has been eliminated for open root welding of austenitic and duplex stainless steel using a semiautomatic GTAW hot wire welding system technically known as High Deposition Metal Transfer Gas Tungsten-Arc Welding (HDMTGTAW), combined with stainless steel or duplex flux cored wires (AWS/ASME A/SFA-5.22 and A/SFA-5.22M) and argon shielding. The HDMTGTAW system when combined with flux cored wire for the root pass and solid wire for the remainder of the weldment is a complete, cost effective system for welding the entire weld from root to cap that is capable of producing quality welds with high integrity.
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