Analysis of microstructure and mechanical properties of resistance spot welded 22MnB5 hot stamping steel

22MnB5 hot stamping steel was resistance spot welded using different welding procedures. The effects of welding parameters on weldability were investigated, and the microstructural evolution of spot weld and the relation of microstructure-mechanical performance were studied. The results show that there is a positive correlation between nugget diameter and tensile shear load. Compared to electrode force, welding current displays a more critical effect on mechanical performance of spot weld. The difference in micro-hardness across the whole weld is determined by the microstructural evolution. Fully martensitic microstructure appears in the whole weld, except for inter-critical heat affected zone(IC-HAZ), which has the lowest hardness due to a duplex microstructure of ferrite and martensite. This softening phenomenon improves load-carrying capacity and energy absorption of spot weld in mechanical failure condition, leading to the occurrence of pullout failure mode.