Relationship between the Friction Time, Friction Torque, and Joint Properties of Friction Welding for the Low Heat Input Friction Welding Method -Study of Joining Mechanism of Friction Welding (Report 3)-

摘要

In the previous reports l and 2, the authors have clarified the joining mechanism in the first phase of friction stage during friction welding process.　The present paper describes the relationship between the friction time， friction torque， and joint properties of friction welding for a low heat input friction welding method. The materials joined were mild steels (same materials)，and a brake type friction welding machine was used for joining. In actual experiment, I.e., the low heat input friction welding method (LHI method)，the electromagnetic clutch was used in order to exclude braking deformation at rotation stopping. The following are concluded. (1) The joints obtained only in the first stage (up to initial peak torque) had 100％ joint efficiency and 90 degrees bend ductility with no crack. It was determined that friction welded joints with 100％ joint efficiency and good bend ductility could be obtained by using only the friction stage up to initial peak torque and without the need for the forging (upsetting) stage. (2) The fracture occurred at the substrates (not at the welded interface) in welded joints when friction torque was close to initial peak torque. It was clarified that those joints has less width of heat affected zone and less width of hardening. (3) It was clarified that the friction welded joints without using the forging stage (the friction welded joints by using the LHI method) have same mechanical properties as those welded by the conventional friction welding process including that stage. The LHI method has more advantages, I.e., less burn-off and less burr.