表面処理鋼板のプレス成形における皮膜の耐加工性

抄録

The behavior of coating films during the press forming are investigated on some kinds of surface treated steel sheets for autobody panels. It is observed that the plastic deformation causes the damages of the film such as the cracking or the flaking and the corrosion resistance decreases. The mechanisms of these phenomena are also systematically investigated.
It has been found that the flaking depends on the deformation modes such as a stretch forming or a shrink flanging and its dependency is unique to the type of the coating. "Flaking Limit-Strain Diagram" was presented for a expression of coating characteristics.
The decrease of corrosion resistance after forming is generally due to the loss of coating weight or the surface damage during the deformation. In the galvanized coating which has the sacrificial corrosion effect, the lowering of corrosion resistance is dominated by the loss of coating weight, and it is concluded that the severity of the forming can be evaluated by the reduction in thickness. In the paint coating, that lowering is mainly dominated by the cracking or the flaking of the film. In the material for this experiment, the severity is evaluated by the equivalent strain occurring on the surface.