Effect of Process Variables on Weldability in Ultra-High Strength Steel (SPFC 980Y) Nut Projection Welding

As the importance of safety performance for reducing the weight of automobiles and protecting drivers in case of vehicle collision emerges, the application rate of high-strength steel materials is increasing. In this study, high-strength steel nut projection welding was performed on the reinforcements mounted on the tailgate of the vehicle. Then, torque tightening force and pull-out measurements were performed to understand the mechanical characteristics of the joint. After the pull-out test, the fracture surface was analyzed in three modes: interfacial fracture, button fracture, and partial interface fracture. In the case of interfacial fracture, the joint was formed by corona bonding rather than melt welding, resulting in the lowest strength in the pull-out test.