| 摘要 |
<p>A method of producing seamless cans wherein a blank holder (2) is inserted in a metal cup (5) coated with an organic film (12), a punch (1) is advanced into a cavity (7) in a die (3) while pushing the bottom (5a) of the metal cup onto the flat surface portion (3a) of the die by the blank holder (2), so that the side wall (5b) of the metal cup (5) is brought into intimate contact with the flat surface portion (3a) of the die and with the working corner (3b) having a small radius of curvature, thereby to reduce the thickness of the side wall (5b) by bend-elongation. Moreover, the portion to be subjected to the necking is ironed at an ironing ratio of not smaller than 5% by the punch (1) in cooperation with the front end (3b1) of the working corner (3b), or by the front end (3b1) and an ironing portion of a short cylindrical portion in front thereof, or by the punch (1) in cooperation with the ironing portion (3g) of the die (3) by advancing the side wall (5b) slightly toward the inside in the cavity (7), thereby to obtain a seamless can (20) having a reduced thickness in the side wall (5b). This method makes it possible to control the thickness distribution in the side wall and, hence, to produce seamless cans having reduced thickness in the side wall permitting the organic film to be least whitened during the necking working. <IMAGE></p> |
