Research on the performance of cold rolled martensite ultrahigh-strength resistance spot welding process for 1300MPa class carriage structures

This work used resistance spot welding method to weld cold-rolled martensitic steel for 1300MPa level carriage structure. Conducted welding current window, microstructure, microhardness, tensile test, and spot welding consistency test.Within the standard parameters of SEP 1220-2, the weldability current of 1.2mm SCR1300 is 6.0kA-7.8kA, the welding current window is 1.8kA, and it has good adaptability to resistance spot welding. The shear force of welded joint is 24773N, the structure of nugget zone is lath martensite. The hardness in the critical zone and the supercritical zone is softened. After 50 times of welding point consistency tests, the diameter of nugget still reaches the standard of d ≥4.38mm.