Similar and dissimilar resistance spot welding of martensitic advanced high strength steel and low carbon steel: metallurgical characteristics and failure mode transition

Safety, emissions and fuel economy of vehicles have always been of great importance to automakers. Advanced high strength steels (AHSSs) have proved to be effective in fulfilling these needs of the industry, and this has led to great opportunities for increasing usage of AHSSs. The present work aimed to investigate the resistance spot welding characteristics of martensitic steel (M130) having the thickness of 2 mm, utilising metallographic observation, microhardness and tensile–shear testing. The results were compared for different combinations of martensitic steel and low carbon steel (LCS). In the study of interfacial to pull-out failure mode transition, dissimilar M130/LCS welds exhibited the lowest tendency to fail in the interfacial failure mode. Weld nugget diameter is proposed as a main variable controlling the peak load and energy absorption of the welds along with other factors such as electrode indentation and hardness/strength of the failure location.