2007 年 48 巻 552 号 p. 41-45
A cold deep drawing process for commercial magnesium alloy (AZ31) sheets was developed. The commercial sheets were successfully formed into circular cups using cold deep drawing by optimizing the annealing temperature of the sheets, i.e. a limiting drawing ratio of 1.7 was attained for an annealing temperature of 500 °C. The increases in elongation, n-value and r-value, and the decrease in flow stress effective in the improvement of drawability were obtained for the annealing. The apparatus for cold deep drawing operation without heating becomes much simpler than that for the conventional warm operation. The effects of the lubricant, the clearance between the die and the punch and the corner radius of the punch on the drawability were examined. The limiting drawing ratio was increased by applying force onto the edge of a blank through the die corner. In addition, cold deep drawing of magnesium alloy square cups was performed. It was found that comparatively shallow magnesium alloy cups are satisfactorily formed at room temperature without heating.