Optimized designing of generalized electrodes for aluminum/steel resistance spot welding process based on numerical calculation

Abstract

This work focused on the effects of using different electrode combinations on the welding process and welding quality during aluminum/steel resistance spot welding (RSW) process. The electrodes used during the RSW process can be classified into two catalogues, planar type (P type) and sphere type(S type). An effective two dimensional (2D) numerical calculation model using finite element method (FEM) was developed. In the model, the friction effects between different contact surfaces were seriously considered, and the accuracy and reliability of the model were verified by means of actual welding experiments. Subsequently, the numerical calculation model was used to determine which type of electrode combination was the best one for welding quality by analyzing corresponding RSW processes using four different electrode combination schemes: PP type, SS type, PS type and SP type for upper and lower electrodes. To guarantee scientific nature of the comparisons and analyses, a constant energy regulation method was introduced for each process. The heat energy generation analyses, intermetallic compound formation and growth analyses, and current density analyses were conducted. Combining with actual experiments, the results showed that the welded joint obtained from RSW process using SP type electrode combination scheme had the best comprehensive performance, not only in the double nugget sizes, but also in the deformations of two types of parent metal sheets. In addition, the optimum sizes of the electrodes in this combination were determined through numerical calculations and experiments. Final result showed that the optimum diameter for S type and P type were respectively 9 mm and 60 mm. The work can supply important references for the dissimilar metal RSW process improvement.