Characteristics of Friction Welding Between Solid Bar of 6061 Al Alloy and Pipe of Al-Si12CuNi Al Cast Alloy

Abstract

This paper describes the characteristics of friction welding between a solid bar of 6061 Al alloy and a pipe of Al-Si12CuNi (AC8A) Al cast alloy. When the joint was made by a continuous drive friction welding machine (conventional method), the AC8A portion of the joint showed heavy deformation and the AA6061 showed minimal deformation. In particular, the joint could not be successfully made with following conditions, because AC8A pipe side crushed due to insufficient friction heat or high pressure: a short friction time such as 0.3 s, high friction pressure such as 100 MPa, or high forge pressure such as 150 MPa. The heavy deformation of AC8A side was caused by increasing friction torque during braking. To prevent braking deformation until rotation stops, a joint was made by a continuous drive friction welding machine that has an electromagnetic clutch. When the clutch was released, the relative speed between both specimens simultaneously decreased to zero. When the joint was made with friction pressure of 25 MPa, friction time of 0.3 s, and forge pressure of 125 MPa, the joining could be successfully achieved and that had approximately 16% efficiency. In addition, when the joint was made with friction pressure of 25 MPa, friction time of 0.7 s, and forge pressure of 125 MPa, it had approximately 54% efficiency. However, all joints showed the fracture between the traveled weld interface and the AC8A side, because the weld interface traveled in the longitudinal direction of AC8A side from the first contacted position of both weld faying surfaces. Hence, it was clarified that the friction welding between a solid bar of AA6061 and a cast pipe of AC8A was not desirable since the traveling phenomena of the weld interface were caused by the combination of the shapes of the friction welding specimens.