Microstructure and mechanical properties of welding metal with high Cr-Ni austenite wire through Ar-He-N₂ gas metal arc welding

A high Cr-Ni austenite wire with 0.1% nitrogen was developed for gas metal arc welding of high strength low alloy (HSLA) steel (10Ni5CrMoV) to prevent hydrogen induced crack. The austenite weld joint without visible defects can be obtained using Ar + He + N₂ shielding gas. When N₂ content of shielding gas increased from 0% to 8%, the nitrogen content of weld metal rose from 0.10% to 0.19%, and other alloy content kept unchanged. The increasing of nitrogen content in weld metal made weld grains refined. It can improve mechanical properties of weld metal in different degrees including yield strength, tensile strength, elongation and impact toughness. However, with 8% N₂ content of shielding gas, the massive microspores appeared in weld metal will decrease the welded joint properties. Therefore, 50%Ar + 45%He + 5%N₂ was selected for welding of 10Ni5CrMoV HSLA steel using high Cr-Ni austenite wire.