In the previous reports1-4), the authors had clarified the joining mechanism during the first phase of the friction stage during friction welding process. The present paper describes the effect of friction pressure and friction speed on initial seizure portion at the welded interface of mild carbon steels joint.
The following are concluded.
(1) When the substrates were welded under high friction pressure and high friction speed, i.e., 90MPa and 27.5s-1, almost no wearing existed during the first phase of the friction stage. The friction torque rapidly increased and reached to the initial peak torque immediately after both weld faying surfaces contacted each other.
(2) The friction torque have included wear and seizure stages during the first phase when the substrates were welded under the welding conditions of (a) high friction pressure and low friction speed, i.e., 90MPa and 8.8s-1, and (b) low friction pressure and high friction speed, i.e., 30MPa and 27.5s-1.
(3) The wear of both surfaces started at the periphery portion (outer surface), and it extended toward the center portion (center axis) of the welded interface. When the substrates were welded under high friction pressure and high friction speed, the initial seizure and the joining began at the periphery portion, and they extended toward the center portion. The initial seizure and the joining randomly began on the weld faying surface and extended toward whole surface with high friction pressure and low friction speed. On the other hands, they began at center portion and extended toward periphery portion with low friction pressure and high friction speed.
(4) The initial seizure portion was described by using the relationship between the temperature and the relative speed of the welded interface, and seizure temperature of them.
(5) The modeling was presented for the phenomena of the first phase of the friction stage.
