Abstract
This report deals with the effect of faying face condition on welding phenomena and mechanical properties of the welded joint in friction welding. The experiments were carried out by a continuous drive type friction welding machine. The base material used was 0.25% carbon steel.
Conditions of faying face are labelled as,
A: Clean face degreased with benzine.
B: Greased face.
C: Face covered with oxide film, which is made by keeping the specimen at 370°C for 1 hour.
D: Face with a drilled hole of 1 mm in diameter and 3 mm in depth.
Main results are as follows,
(1) The joints made under conditions A, B, C and D break at base metal in both tensile and fatigue tests, and have sufficient ductility in bending test.
(2) In case of condition B, grease on the faying faces is extruded from weld interface within 0.5s after base metals contact.
(3) The existence of oxide film, having about 0.1 μm in thickness, on faying face does not affect welding phenomena and weldability. However, when the oxide film becomes thicker, it decreases coefficient of friction and forbids the rise of initial torque. In this case the oxide film causes delay in starting burn off, and the delay time is proportional to the square of thickness of oxide film.
(4) In case of condition D, the dark layer is observed at weld interface and is vicinity, i.e., track of air from drilled hole. It is considered that the layer is shaded by the finely distributed oxide particles.
