Multi-objective Optimization of Resistance Spot Welding of AISI 409M Ferritic Stainless Steel

Abstract

Resistance spot welding is a widely used sheet metal joining process in automobile and rail car manufacturing industries. One of the most important quality characteristics of a spot welded joint is its tensile shear strength, as it is crucial in improving the crashworthiness of the vehicle. Amount of indentation made by the electrode on the surface of the sheet during spot welding, is another quality characteristic that needs to be minimized, to improve the surface finish and aesthetic value. Ensuring maximum strength of the spot weld joint, while keeping indentation at the minimum level is one of the major challenges in spot welding. In this work, multi-objective Taguchi method has been applied for optimization of various input parameters in resistance spot welding of AISI 409M ferritic stainless steel sheets, to maximize the tensile shear strength of the weld joint and minimize the surface indentation simultaneously. Furthermore, a linear response surface model has been developed to correlate tensile shear strength and indentation values with process parameters. The optimum values of control parameters were 11.5 KA for current, 14 cycles for weld time and 3.5 KN for electrode force. Current was found to be the most influential parameter affecting tensile shear strength and indentation. Results of the optimization process were validated by confirmation test.