Laser roll welding of dissimilar metal joint of zinc coated steel to aluminum alloy

There is a subject to reduce the weight of car body by replacing steel to aluminum alloys as some structural body parts for improving fuel consumption and suppressing CO2 generation. As one of the solutions, the hybrid body structure concept using aluminum alloys and high strength steels is proposed recently. However, it is well known that fusion welding of steel and aluminum is difficult due to the formation of brittle intermetallic compounds at the joint interface. Therefore, new welding processes by which these dissimilar materials can be joined in high reliability and productivity are demanded. “Laser roll welding” has been developed for joining of dissimilar metals by Kutsuna, Rathod, and Tsuboi in 2002 (Japanese Patent No. 3535152 and No. 3692135). Controlling the formation of the brittle imtermetallic compounds was tried by application of laser roll welding to get a sound joint. In the present work, laser roll welding of zinc coated steel and aluminum alloy was fundamentally investigated, and the process parameters were studied. Furthermore, the influences of process parameters on the weldability, the formation of intermetallic compound layer, and the joint properties have been investigated to get a sound joint. When intermetallic compound layer thickness was less than 10 μm, failure of tensile shear test specimen occurred in the base metal of the zinc coated steel.