51 巻 (2010) 593 号 p. 592-596
A mechanical clinching process for zinc-aluminum alloy coated steel sheets was developed to improve the corrosion resistance of joined sheets. In this process, the sheets are joined by local hemming with a punch and a die without heating; thus, problems with reductions in electrode life and the thickness of the coating layer in resistance welding are solved. The shaving of the coating layer on the side wall of the depression by the punch was prevented by increasing the corner radius of the punch. The stretching of the coating layer on the top of the projection was minimized by flattening the bottom of the die. The thickness of the coating layer and the corrosion resistance of the joined sheets were improved by optimizing the shapes of the punch and die. Although the corrosion resistance of the joined sheets was 55% of that of the initial coated sheet, the resistance became threefold the resistance of the welded sheets.