| 摘要 |
<p>A method for manufacturing a universal joint yoke that exhibits good yield in terms of material utilisation through obtainment of a universal joint yoke preform whose excess metal to be trimmed is diminished and whose cup portion (41) is of uniform height, includes a forging step for forming a universal joint yoke preform from a workpiece (6) placed in a die including an upper die (103) and a lower die (65) which are to define a closed space. The forging step is performed such that, while a back pressure not lower than 0.5 kg/mm2 is applied to an end of a prospective universal joint yoke cup portion (41) of the workpiece via a ring knock (67), material of the workpiece is allowed to flow into a pin-boss-forming cavity adapted to form a pin boss portion (43) extending opposite the prospective cup portion (41) until a filling rate not lower than 75% is reached, and that the ring knock (67) is then moved in a direction opposite a regular forming direction of the upper (103) or lower die in which the ring knock (67) is disposed so as to initiate flow of the workpiece material toward the prospective cup portion (41).</p> |
