Novel projection welding technology for joining of steel-aluminum hybrid components-part 1: technology and its potential for industrial use

Multi-material design offers cost-efficient lightweight solutions for automotive body-in-white production. Ultra-high strength steels remain an essential part of the lightweight construction and are increasingly used in combination with components made of aluminum alloys in multi-material body designs. For these applications, the commonly used joining processes (riveting, clinching, resistance spot welding, etc.) have been pushed to their technological limits and a further technological development is needed. The present research describes a new joining technology based on resistance welding process for joining ultra-high strength steel 22MnB5 (AS150) with aluminum sheets AW 6016. The technology consists of a two-stage resistance spot welding process with an additional simple cost-effective joining element. Its implementation allows joining aluminum and steel on extremely short flanges of 10 mm using short time projection welding with high-energy concentration. Joining elements-cylinders made of Cu- and Fe-based wires with diameter 1.6 mm and length 10 mm - were welded using the common resistance spot welding equipment. Experimental results have shown that all tested materials for joining dissimilar steel-aluminum compounds can be successfully used and the weld current ranges are sufficient for industrial application.