Residual stress evaluation during RSW of DP600 sheet steel

In this study, resistance spot welding (RSW) process has been used on DP600 automotive steel at pressures of 2, 3, 4, 5 and 6 bar at a welding current of 7 kA. Microstructure, hardness and residual stress were examined to evaluate the effect of the welding pressure. An experiment at 5 kA and 6 bar was also conducted to investigate the effect of welding current on this behavior of steel sheet. The results show that microhardness values were higher in the welding region than in any other parts. There was no considerable change in the hardness behavior versus the welding pressure applied except for the sample welded at 7 kA and 4 bar. When the welding current changed from 7 to 5 kA, hardness improved. Residual stress evaluation reveals that compression stress was found in the specimens, and the specimen welded at 5 kA and 6 bar exhibited the highest residual stress.