Optimization of resistance spot welding parameters and investigation of the effect of heat treatment on the mechanical properties and microstructure of AISI 631 stainless steel sheets

In this study, the Resistance Spot Welding (RSW) of 0.8 mm thick AISI 631 precipitation-hardening stainless steel sheets was investigated. By optimizing key welding parameters including welding current, welding time and electrode force, the maximum weld nugget diameter and mechanical strength of the joint were achieved. The maximum weld nugget diameter and mechanical strength of the joint were obtained at a welding current of 5 kA, an electrode force of 2.9 kN, and a welding time of five cycles, in which case the weld failure mode was the desired interfacial failure. After precipitation hardening heat treatment, the effect of this process on the microstructure, hardness and tensile-shear strength of the weld was examined. The results showed that after heat treatment, the hardness became uniform in all weld regions, but the tensile-shear load-bearing capacity decreased, and the failure mode changed. This study, while providing solutions for optimizing the RSW process, significantly contributes to improving the quality and performance of stainless steel joints, which is crucial for sensitive applications.