The Synergistic Enhancement Effect of H2 in the Shielding Gas on High Welding Efficiency and Corrosion Resistance in TIG Welding of Stainless Steel

Tungsten inert gas welding is widely used in marine engineering and petrochemical industries. Stainless steel is the main welding material, and its welding efficiency and corrosion resistance are key indicators. While previous research has predominantly focused on welding parameters, this study investigates the effect of H2 content in shielding gas on arc characteristics, macrostructure and corrosion behaviors in tungsten inert gas welding of stainless steel. The results indicate that increasing H2 content leads to greater arc contraction and energy density, significantly enhancing welding efficiency and corrosion resistance of the welded joints. Specifically, compared to Pure Ar, using Ar + 6 pct H2 as a shielding gas results in a 28.4 pct increase in maximum welding depth, a 137 pct increase in melting area, and a 32.9 pct reduction in corrosion rate within salt spray environments. The addition of H2 effectively suppresses ferrite formation in the weld metal (from 5.25 to 3.37 pct) and promotes precipitation of skeletal and vermicular ferrite. These microstructural changes, along with grain refinement, contribute to improved corrosion resistance. Moreover, the transition from Pure Ar to Ar + 6 pct H2 increases Ni content in the weld metal from 6.03 to 7.61 pct and decreases microhardness from 203 to 174 HV, further elucidating the mechanism underlying enhanced corrosion resistance.