Optimization of resistance spot welding process parameters and microstructural examination for dissimilar welding of AISI 316L austenitic stainless steel and 2205 duplex stainless steel

Resistance spot welding (RSW) involves joining of contacting surfaces by heat generated by resistance to electric current. The process is swift and finds demand in automobile industries for mass production. In spite of all the assets of the process, it yields a poor quality welds and inferior weld strength at the inner region of the joint interface. This may be improved by accurate setting of control parameters. The objective of this study is to determine the effect of various control parameters like electrode tip diameter, welding current, and heating cycle on the nugget size and tensile shear strength of dissimilar metal spot welding of 2-mm-thick AISI 316L austenitic stainless steel and 2205 Duplex Stainless Steel sheets. The Taguchi's L27 orthogonal array (OA) design is selected to conduct the experimental spot welding trials on the dissimilar materials. Subsequently, the specimens are examined usinganalysis of variance (ANOVA) technique to customize optimal parameter setting to obtain high tensile strength and favorable weld quality characteristics. The results reveal that welding current is the most dictating factor to achieve highest tensile strength with superior weld quality. Also, weld samples are prepared for metallographic examination from cross section areas of resistance spot welds to examine microstructure changes and ferrite content measurement in different regions of weld nugget. The microstructure examination shows that the weld nugget consists of ferrite and austenite and ferrite and there is no precipitate of detrimental phases in the weldment.