Effect of Copper Electrode Pressure on Nugget Diameter and Mechanical Performance of Resistance Spot Welded Thin Dp800 Steel Sheets

Abstract

DP800 is an advanced high strength steel containing duplex microstructure of ferrite and martensite phases. It is broadly used in automotive structural frame applications owing to its high strength to weight ratio. DP steel is mainly joined by resistance spot welding (RSW) to avoid the problems of solidification cracking and severe HAZ softening. In this study, the effect of copper electrode pressure on nugget diameter and mechanical performance of resistance spot welded 1.2 mm thick DP800 steel sheets are investigated. The tensile shear strength (TSS) properties were evaluated in straight lap (SL-TSS) and cross lap (CL-TSS) joint configuration. Results showed that the DP-800 steel spot joints developed using the electrode pressure of 4.0 MPa exhibited superior SL-TSS of 830 MPa and CL-TSS of 684 MPa. It is attributed to the evolution of finer martensitic needles in nugget zone.