Comparative studies on microstructure evolution and corrosion resistance of 304 and a newly developed high Mn and N austenitic stainless steel welded joints

Welding has a negative effect on the corrosion resistance of both 304 and newly developed steel (QN1803). Microstructure observation and element distribution analysis found that, due to the existence of nitrogen loss and the retardation of manganese on phase transition, the fusion zone (FZ) of the QN1803 has more δ-ferrite residual than that of 304, causing more serious element segregation. Therefore, QN1803 FZ has lower pitting corrosion resistance than base metal. In terms of intergranular corrosion, nitrogen promotes the formation of precipitates, so the weight loss rate of QN1803 weldments is higher than that of 304 weldments in immersion tests.