The Peeling-Off Resistance of Zinc and Iron-Zinc Coated Steel Sheets in Stamping

The effects of working mode, coating weight, thickness of substrate and iron content of coating on the peeling-off resistance of zinc and iron-zinc coatings have been investigated using a draw bead tester, which was designed to evaluate the peeling-off phenomena of coated materials. In the test, specimens are subjected to both bending-unbending deformation and the slide caused by the bead tip. The test was conducted under several working modes; i.e., proportion of the deformation to the slide was changed by altering draw bead conditions.

The draw bead results showed that Fe-Zn coating were mainly peeled off by the deformation, while Zn coatings were removed chiefly by the slide. It was also revealed that the amount of peeling-off of the coatings was considerably affected by the working mode.

The peeling-off resistance of galvannealed steel sheets was then investigated by the test. The results indicated that the amount of peeling-off was a function of coating weight, thickness of substrate and iron content.