52 巻 (2011) 601 号 p. 277-281
A hot spline forming process of an ultra high strength steel gear drum was developed to manufacture high tensile strength steel spur gears. Since the cross-sectional area of a side wall of a cup formed by cold deep drawing and ironing was uniform, the side wall formed put between the upper and lower electrodes was uniformly heated by the electrification in the axial direction. The uniformity of the temperature was improved by inserting a copper foil between the electrode and the side wall, and by decreasing the area of contact. Although the high strength steel cup was fractured by cold spline forming, a spur gear was successfully manufactured by the hot spline forming. The load for a hot spline forming of the high strength steel gear drum is similar to that for the cold forming of a mild steel gear drum, and the accuracy of teeth was improved. In addition, the formed gear drum was hardened by die quenching.