Optimization of Resistance Spot Welding Parameters for HSLA 340 Steel Using Response Surface Methodology and Finite Element Simulation

Abstract

Resistance spot welding (RSW) is used widely in the manufacturing of automotive body-in-white steels, in which high strength low alloy materials (HSLA) require the welding properties to be effectively established for integrity and reliability of joints. This study investigated the resistance spot welding process of HSLA 340 automotive steel sheets with dimensions of 100 × 25 × 3 mm by combined experimental, statistical and numerical approaches. To obtain a perfect welding current ratio, weld time and electrode force were identified as process parameters and optimized for RSM with a central composite design. Analysis of variance (ANOVA) indicated that welding current was the most important variable affecting the quality of the welds, then weld time and electrode force, and an interaction effect of process parameters was also statistically significant. Ideal welding parameters were established as 8.2 kA welding current, 13 cycles (0.26 s) weld time, and 3.2 kN electrode force. Due to the predicted dimensions, in particular the weld nugget diameter and maximum temperature and residual stress levels predicted in these scenarios were 6.25 mm, 1480 °C and 310 MPa. The proposed coupled electro-thermal-mechanical finite element model was synthesized in ANSYS to simulate the growth of the nuggets, the temperature distribution and the residual stress evolution during welding. The simulated findings exhibited significant agreement with RSM predictions, with deviations less than 3%. The experimental-numerical combined framework is proposed in the present work and it proves to be an efficient method to develop better resistance spot welding parameters of HSLA 340 steel as well as to enhance weld quality and process reliability in automotive applications.