Microstructure, mechanical properties and sensitization of ultra-low nickel Cr–Mn austenitic stainless steels

The present study deals with the effect of SMAW and GMAW process with different welding speeds on microstructural, mechanical and intergranular corrosion properties of ultra-low nickel Chrome-Manganese austenitic stainless steel. The microstructural analysis was performed by optical microscope. The Fisher Ferritscope was used for determining ferrite content in the weldment. The microstructural analysis shows that size of dendrites of δ ferrite and width of HAZ decreases in order to increase in welding speed. It was found that more δ-ferrite in weldment of SMAW weld as compared to weld metal of GMAW weld. It was also found that when welding speed increases, tensile strength, impact strength and hardness values decrease for both the welding processes. From, U-bend test it was found that the welded joints are strong enough to withstand bend at 1800 without any cracks for both the welding processes. It was also found that Cr-Mn SS weld becomes susceptible to intergranular corrosion on welding. For both the welding processes, the degree of sensitisation value decreases with respect to increase in welding speed for both the welding processes as evaluated by DLEPR test. It was also found that the weld joint of GMAW process is more susceptible to intergranular corrosion than that of SMAW process.