Friction stir spot welding of aluminum alloy/steel plate with position-controlled joining equipment

Research is progressing on multi-material car bodies that take advantage of the features of various structural materials with the aim of reducing the weight of cars. To achieve this, there is an increasing need for dissimilar material joining between aluminum alloy and steel plate. It is known that the joint strength of aluminum alloy/steel plate friction stir spot welding depends on the tool insertion amount (aluminum remaining thickness). Therefore, in this study, instead of the conventionally common load-controlled welding equipment, position-controlled welding equipment that can precisely control the amount and speed of tool insertion used, and the effects of welding parameters and steel plate plating on joint strength investigated. As a result, the relationship between tensile shear strength and aluminum remaining thickness can be approximated by an upwardly convex quadratic curve, and by controlling the aluminum remaining thickness, the tensile shear strength exceeded JIS Z3140 aluminum alloy resistance spot welding A grade. From the above, it is believed that this joining technology has the potential to be applied to vehicle body frame members that require strength.