Effects of process parameters on spot welding of TRIP and quenching and partitioning steels

This study investigates the resistance spot welding between a quenching and partitioning (Q&P) steel and a transformation-induced plasticity (TRIP) steel. The effects of welding current, electrode force, and welding time on microstructure and mechanical properties have been assessed by shear tension and hardness tests. Welding electrical parameters have been monitored to detect metal expulsion. An adequate shear strength of lap-joint Q&P/TRIP spots is observed, with the best mechanical strength (14kN) being obtained with a 7.5kA current. Metal expulsion is detected for the highest current (9kA), which limits the shear strength and nugget size of spot welds. The lap-joint samples mainly break by partial thickness with button pull; interfacial fractures only occur in the samples with the smallest nuggets.