1999 Volume 85 Issue 5 Pages 399-404
The effect of a silica-base lubricant film on sliding property and spot weldability of galvannealed steel sheet was investigated by using hat channel drawing with bead and electrode tip life under the SiO2 coating weight of 10-100 mg/m2 in the silica-base lubricant film. (1) Sliding property is improved largely by coating the silica-base film of 10-20 mg/m2 as SiO2 on the galvannealed steel sheet. The reason seems to be that the direct contact between galvannealed coating layer and die is prevented by coating silica-base film, then the adhesion at interface between the coating layer and the die is prevented, which decreases the true contact area between the coating layer and die, and consequently improves the sliding property. (2) The spot weldability evaluated by electrode tip life is improved largely by coating silica-base film, because protective layer which is composed of SiO2 and Fe-Zn alloy is formed on the surface of the electrode tip. (3) The silica-base lubricant film has no effect on phosphatability.
