Capacitor Discharge Spot Welding of Aluminum, Part 1: Weldability Assessments

A key aspect of integrating automotive sheet into automotive production are the costs associated with joining. While the majority of sheet steel assembly is done with resistance spot welding, that has not readily translated to aluminum. Resistance spot welding of aluminum sheet is challenged by high current demand as well as reduced electrode life. In the latter case, direct current (DC) power supplied by state-of-the-art systems has exacerbated the problem. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is a first effort in examining the response of resistance spot welding on aluminum sheet to polarity-switching CD power. In this paper, the current range response between medium-frequency DC (MFDC) and polarity-switching CD was investigated. It was found that polarity-switching CD welding offered improved current ranges over MFDC. In addition, replicate mechanical testing cross-tension results were similar, but tensile shear strengths improved nominally 20–25%. Finally, some limited tests were done to assess the suitability of CD resistance spot welding in the presence of an adhesive. Current range tests with and without a prepulse were done, and both showed excellent weldability.