Gas Tungsten Arc Welding of Low Carbon Steel with Ni-Cr and Medium Mn Stainless Steels

This research conducted a comparative analysis of dissimilar butt joints of low carbon steel (LCS) with low-Ni medium-Mn austenitic stainless steel (MMn-SS), and LCS with Ni-Cr austenitic stainless steel (NiCr-SS), utilizing gas tungsten arc welding. The welding process employed ER309MoL filler metal. The microstructural analysis, tensile strength, and hardness properties were conducted using optical microscopy, uniaxial tensile tests, and Vickers hardness testing, respectively. Findings revealed the formation of a duplex microstructure consisting of an austenite matrix and a minor δ-ferrite fraction < 9.5 %, in the fusion zone (FZ) processed at heat inputs of 0.697 kJ/mm for LCS/MMn-SS and 0.741 kJ/mm for LCS/NiCr-SS joints. The FZ of the welded specimens, LCS/MMn-SS and LCS/NiCr-SS exhibited hardness values (166.8 HV and 155.5 HV, respectively) lower than the corresponding stainless-steel sides yet higher than the LCS side. The tensile properties of the joints closely approximate those of the LCS base metal, with deformation and fracture primarily localized at the LCS side. Furthermore, the welded joints exhibited characteristic dimple features indicative of ductile fracture behavior, as revealed by scanning electron microscopy (SEM).