Characterization of resistance spot welded transformation induced plasticity (TRIP) steels with different silicon and carbon contents

Abstract This research work examines the influence of chemical composition and microstructure of 6 different transformation induced plasticity (TRIP) steels on the mechanical behavior of resistance spot weldments. The microstructure of the spot welds was characterized by means of scanning electron microscopy and X-ray diffraction techniques. The mechanical properties were assessed under lap-shear tensile and hardness testing. Results indicated that the nugget width is strongly correlated with the type of failure mode of the spot welds. The mechanical properties exhibited by the spot weldments are related with the partitioning behavior of chemical elements specially Si and C present in the steels during the cooling stage of the resistance spot welding process. X-ray diffraction study indicated traces of retained austenite in the heat affected zones of the spot welds of those steels with Si-enriched chemical composition where intercritical annealing temperatures were closer to Ac 1 .