To manufacture a lightened light metal wheel with a low cost by casting a preform of a wheel, then forging a disc part of the preform at the next step, and spinning a rim part.
A disc part 1a is pressed and held by a pair of dies 5, 6 in a rocking forging process of the disc part 1a, one of dies 5 is rocked relative to the other die 6, and a rocking surface is rotated about an axle shaft center. In this rocking forging process, the disc part 1a is partially pressed in the peripheral direction, so that the pressure force can be reduced in comparison with the ordinary forging where the disc part 1a is pressed over entire area of its peripheral direction. To reduce the pressure force, the forging preform is heated to a hot area. In a spinning process of the rim part 1b, the preform is heated to the hot area. The final shape of the rim part 1b is formed by the spinning process. Whereby the lightened wheel free from the excess thickness can be manufactured with the low cost.
MIZUSHIMA YOSHIHARU
ONO TADASHI
NAKA MASAYUKI
