| 摘要 |
<p>Provided is a method of manufacturing an automobile door hinge having high strength from a round steel bar at low cost through a process including hot forging and punching. The method includes hot forging a round steel bar to form a forged workpiece 33a including a mounting portion, an arm portion, and a column portion 7a that has a horizontal cross section having a circular shape; and forming a shaft hole 6, into which a hinge pin is to be inserted, by punching the column portion 7a so that the shaft hole 6 extends through an axial center of the column portion 7a by using a special die 52a and a punch 51. The die 52a has a gap formed therein so that, during punching, a slug is not generated and the column portion 7a expands outward when the punch 51 is pressed into the column portion 7a from a punching start point to a predetermined dimension, and a slug is generated and discharged when the punch 51 is pressed into the column portion 7a from the predetermined dimension to a punching end point. Thus, the shaft hole 6 can be formed so as to have a height that is twice the diameter thereof or larger. Therefore, with the manufacturing method, an automobile door hinge having high strength can be manufactured at low cost.</p> |
