Spot welding of aluminum alloy and different materials (e. g., high tensile steel/mild steel) attracts increasing attention from automobile industry. However, there are some problems in these welding. In case of aluminum alloy spot welding, large current and long machining time which raise cost of welding are required. In case of spot welding for dissimilar materials, often unbalanced nugget is formed, which is not desirable from joint strength point of view. One of the methods to solve these problems is the spot welding introducing process tape between the electrode and the work. In this study, the effectiveness of the process tape in spot welding of aluminum alloy A6063-T5 and that of dissimilar materials HT980/SS400 are studied using two dimensional axisymmetric FEM analysis. In the analyses, the material properties of the process tape such as the electric resistance are systematically changed and their influence on the nugget formation is examined. As a result, in case of aluminum alloy, large nugget can be obtained by low current when tape with high electric resistance is used.
