2018 Volume 36 Issue 2 Pages 135-144
This paper describes the joint strength of low carbon steel joints and the selection guide of friction welding conditions for low force requirements, which was made by friction stud welding. When joints were made at a friction pressure of 30MPa with a forge pressure of 30MPa, all joints did not have the fracture on the base metal. All joints, which were made with a friction time of 1.5s (just after the initial peak) and a forge pressure of 60MPa, had the fracture on the base metal. However, all joints with a long friction time such as 5.0s did not have the fracture on the base metal. Furthermore, when joints were made with a friction pressure of 10MPa, the joint efficiency of 100% was not successfully achieved regardless of increasing forge pressure. The cause of the joint with the fracture between the initial weld interface and the base metal was that the peripheral portion of that interface of the stud side (small diameter side) was not completely joined with low friction pressure such as 10MPa. On the other hand, the fracture on the base metal and the joint efficiency of 100% were successfully achieved when joints were made at a friction pressure of 60MPa, a friction time of 0.6s (just after the initial peak), and a forge pressure of 60MPa. All those joints with flash at the initial weld interface had the fracture on the base metal, and it also had the bend ductility of over 15 degrees with no cracking at the initial weld interface by impact shock bending test. However, all joints with a long friction time such as 5.0s in this friction pressure did not also have the fracture on the base metal. Hence, to obtain the joint possessing the fracture on the base metal with no cracking at the initial weld interface, the joint should be made with a friction pressure of 60MPa and a friction time of 0.6s, i.e. an optimum friction pressure and friction time such as the friction torque reached to just after the initial peak. By setting to this condition, the forge pressure will be able to set up the identical friction pressure.
