Patent ID: 7013696

Claim:
A method of making a flanged tubular metallic part by cold forging, comprising: a depression forming step of forming an axial depression that is concentric and cylindrical, in a cylindrical blank of ferrite-system stainless steel; and a flange forming step of making the depression axially deeper while causing a metal of the blank to flow radially outward thereby forming the blank into an intermediate product having an annular flange on an outer circumferential surface thereof; wherein the flange forming step is executed by using a flange forming die assembly including an inner punch, an annular outer punch disposed concentrically around and axially movable relative to the inner punch so as to provide a predetermined space therebetween, a die having a cylindrical hole surrounding the outer punch and a counter punch unit disposed opposite to the inner punch and cooperating with the outer punch and the die so as to define a cavity for forming the flange; wherein assuming that the direction in which the inner punch is moved for subjecting the blank to the flange forming step is referred to as forward, the flange forming step includes axially moving the inner punch so as to allow a leading end of the inner punch to be position more forward than a backward side surface of the flange thereby causing the intermediate product to be formed with a concentric sleeve portion that is of a predetermined axial length and that is positioned backward of the flange while allowing the outer punch to apply an axial biasing force to the backward side surface of the flange during formation of the flange within the cavity; and wherein the counter punch unit comprises an inner counter punch disposed so as to be concentric with and axially opposed to the inner punch, and an outer counter punch disposed concentrically around and axially movable relative to the inner counter punch so as to axially opposed to the outer punch, and wherein the flange forming step comprises allowing the outer counter punch to apply an axial biasing force to a forward side surface of the flange during formation of the flange.