Friction stir welding (FSW) has become an important joining process of aluminum alloys in various industries. Conventional FSW process, however, is difficult to apply to the welding in dissimilar metals. In our series of research, the welding between aluminum alloy and steel has achieved by means of friction stirring. This is a promising way to realize a high performance joint in dissimilar metals. In the present study, the weldability between 6063 and S45C by means of friction stirring was investigated. By optimizing the welding conditions, such as a tool configuration and a rotating speed, higher welding speed more than 1000 mm/min was achieved. The mechanical properties of the weld joints fabricated were evaluated with the normal tensile test and hardness test. The specimens were fractured in the portion of the lowest hardness area in aluminum alloy. In the microstructure observation with SEM, thick intermetallic compound layer on the interface region was not detected.
