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

271-275Resistance 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

Effect of process parameters on the mechanical performance of resistance spot welded joints of AISI 409M ferritic stainless steel

11-18In this study, the effect of process parameters on mechanical performance of the resistance spot welded joints of AISI 409M ferritic stainless steel sheets is investigated. Mechanical performance of the spot weld is evaluated in terms of output quality characteristics, such as load carrying capacity and energy absorption capacity. Important process variables, such as current, time, electrode force and holding time were varied separately and corresponding output parameters, which decide the mechanical performance of the spot welded joint have been analysed. Weld nugget geometrical parameters such as nugget size and surface indentation have also been analysed with respect to various process variables. It has been found that peak load and energy absorption capacity are in direct relationship with welding current as well as welding time, in expulsion free welds. Surface indentation increases with increase in current and welding time. It has also been observed that increasing electrode force results in slight reduction of both tensile shear strength and energy absorption capacity. The effect of holding time on mechanical performance of the resistance spot welded joint is found to be almost insignificant. Regression-based relations are developed to correlate the mechanical performance of the spot welds with nugget size