Development of Resistance Spot Welding Processes of Metal-Plastic Composites

Metal-plastic composites (MPCs) are gaining importance mainly due to high strength to weight ratio. They consist of three layers, two outer metallic cover sheets, and a plastic core. The presence of that inner plastic layer makes them rather unsuitable for joining by means of any conventional welding processes, which significantly reduces the application range of MPC. In this work, three various resistance spot welding (RSW)-based concepts were developed to overcome that limitation and join Litecor to DP600 steel. In all cases, a dedicated initial stage was implemented to RSW, which was aimed at removing the non-conductive polymer layer from the welding zone and creating the proper electrical contact for the resistance welding. These were, namely: (i) shunt current-assisted RSW; (ii) induction heating-assisted RSW; and (iii) ultrasonic-assisted RSW. The development of each concept was supported by finite element modeling, which was focused on setting the proper process parameters for polymer layer removal. Finally, the macro- and microstructure of exemplary RSW joints are shown and the most common spot weld features as well as the further development possibilities are discussed.