Effect of Ar-N2 mixture on chemical composition of austenitic stainless steel welds

In order to verify the effect of argon-nitrogen mixture on the content of each element and FN value in the weld, the author carried out four ratios of argon-nitrogen mixture GTAW multi-layer multi-pass welding test on austenitic stainless steel SS304L, and the effects of four argon-nitrogen ratios on the content of each element in the weld metal and the changing trend of the content of each element in each weld with the number of bead layers were studied.The results show that among the 11 chemical elements of welds with different types of shielding gas, only N element increases significantly with the increase of nitrogen ratio in shielding gas, and other elements have no obvious effect; After a summary analysis, the author believes that the dilution rate induce the regularity of the content of each element in the weld of the same shielding gas: The C content decreases with the increase of the number of layers; The content of Si, P, S and Nb does not increase or decrease significantly with the increase of the number of layers; The content of Mn, Ni, Cr, Mo and Cu increase with the increase of the number of layers; The content of N element in pure argon protection SG-A decreased slightly with the increase of the number of layers, while in SG-AN-0.5, SG-AN-1, SG-AN-1.5, the N content in the three shielding gases increases with the increase of the number of layers; The analysis results also show that the Creq/Nieq value and the FN value of the weld ferrite have the same trend of change , are inversely proportional to the nitrogen content.Highlights: Due to step-by-step multi-pass welding is adopted, the original information of each layer of welds is retained, so a large amount of data so succeed to obtained to verify the effect of adding nitrogen to the shielding gas in GTAW welding process on various chemical compositions of austenitic stainless steel welds, which provides indispensable test data for the further engineering application of argon-nitrogen mixed gas GTAW welding of austenitic stainless steel.