| 摘要 |
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.
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