Evaluation of resistance spot weldability and weld performance of zinc-coated martensitic steels

Abstract

This paper explores the resistance spot weldability of three martensitic (MS) steels of 1500 MPa tensile strength. A weld diameter versus current plot was developed for the three MS steels to investigate their weldable current range and expulsion characteristics. The mechanical performance of the welds was investigated using cross-tension, tensile-shear and hardness tests. It was found that the differences in electrical resistivity during the nugget growth period influenced the expulsion limit and, consequently, the weldable current range. The three MS steels failed in pullout failure mode but exhibited different plug ratios. Finally, the mechanical strength of the three MS steels was observed to be better than the other advanced high-strength steels (AHSS) such as DP600, TRIP1000 and PHS1500 steels.