Parametric study of the nugget growth in spot welding of 304L stainless steel sheets having equal and unequal thicknesses

Abstract

In this paper, an experimental and analytical study of the weld nugget development in resistance spot welding process of 304L stainless steel sheets having equal and unequal thickness is presented. Experimentally, the metallographic technique has been used to determine the size and location of different weld nuggets realized under a given welding parameters which varies from no nugget formation to expulsion. Two stainless steel sheet thicknesses (1 mm and 1.5 mm) were investigated. The effects of welding current intensity and time on nugget growth are studied. Moreover, the influence of the electrode applied load in weld nugget displacement has been also investigated. Analytically, a two dimensional thermal model was developed with ability to predict the electrical contact resistance and nugget size during spot welding of equal sheet thicknesses. The maximum nugget thicknesses are reached when the electrical contact resistance becomes maximal, contrary to nugget diameter which is less influenced by the electrical contact resistance. For a given sheet thickness ratio (1/1.5), the nugget displacement induced during spot welding of unequal sheet thicknesses remains not influenced by the variation of the welding parameters.