Indentation-Free Resistance Spot Welding of SUS301L Stainless Steel

Paint-free bodywork has become an attractive alternative for rail vehicles, in the direction of easy maintainability and low manufacturing costs. However, conventional resistance spot welding inevitably leaves indentation marks to detrimentally reduce the optical homogeneity of the paint-free bodywork. In light of this, indentation-free resistance spot welding is proposed for joining SUS301L stainless steel sheets in order to achieve superior surficial integrity. A tiny SUS301L steel ball with a diameter of 1.5 mm was chosen as the intermediate filler between two steel sheets to avoid the formation of surficial indentation. The influence of welding current and welding time on the mechanical properties of joints was studied. The optimal parameters of the mechanical properties were obtained when the welding current was 8.0 kA, the welding time was 150 ms, the electrode pressure was 0.35 MPa, and the electrodes were cylindrical planar electrodes, which was determined by comparing the tensile shear test results. The surficial indentation depth was less than 1% of the plate thickness, and no observable indentations were seen on the surface of the optimized welding spots.