| 摘要 |
PURPOSE:To improve the material flow of a hollow article and to eliminate the difference in the directivity of strength in an upsetting stage by specifying the relation of the extruding length at the front end thereby obtaining the hollow article. CONSTITUTION:A blank material 14 which is a solid round bar is disposed in a hollow die 11 in an upsetting stage and thereafter a punch 12 is advanced into the die 11 to upset the material 14 thereby forming a semielliptical hole 14a and forming a backward laterally drawn part 15b; at the same time, the front end of the material 14 is extruded to the extruding length thereof designated as l1. A punch 22 is advanced to form an intermediate hole 14b and to form a forward laterally drawn part 15a in a punching stage. The punch 22 is further advanced to form a deep hole 14c, and the front end part 14d of the material 14 of which the extruding length is designated as l3 is formed by the end face of the die 11, in a punching and extruding stage, wherein the relation of the extruding lengths l1, l3 is determined at l3/(l1+l3)<0.55. The front end part 14d is thereafter blanked in a blanking stage whereby a hollow article is obtd. |
