A study of the behavior and effects of nitrogen take-up from protective gas shielding in laser welding of stainless steel

In this study, the SUS301l austenitic stainless steel plates were welded under different protective conditions with different percentages of N2/Ar. The welded joints, that were produced using fiber laser welding and CO2 laser welding, showed good shape and there were no significant differences in microstructure under different protective conditions. The welds consisted of γ-austenite and small amounts of δ-ferrite, and the welded joints were of approximately equal to the base metal in terms of their tensile strength and micro-hardness. The nitrogen that was absorbed by the molten pool mainly was concentrated around the surface of the weld and was present in the form Cr2N, CrN and FeN. With an increase of the N2 percentages in the protective gas, the anti-corrosion performance of the welds was improved. Compared with the fiber laser welding, the weld after CO2 laser welding had a slightly higher nitrogen content and better corrosion resistance.