Abstract: A punch 1 includes a forming land portion 2 formed in parallel with a punch axis 7, a forming R-portion 3 having an arc-shaped cross-section and formed continuously with the forming land portion 2 on a tip end side with respect to the forming land portion 2, and a recess portion 5 formed on a base end side with respect to the forming land portion 2 and having a diameter smaller than a diameter of the forming land portion 2. A Rockwell hardness HRF of the blank 20 is within a range of 65 to 105. The curvature radius R of the forming R-portion 3 of the punch 1 is set to be larger than the thickness L of a cylindrical peripheral wall portion 21 of the forged product 25. The length B of the forming land portion 2 of the punch 1 is set within a range of 0.05 to 0.15 mm. The recess width C of the recess portion 5 with respect to the forming land portion 2 of the punch 1 is set within a range of 0.15 to 1.0 mm.

Abstract: A closed forging method for producing a forged product includes preparing as a forging material a cylindrical cast ingot that has a volume the same as the volume of a forged product and assumes a shape having an upper surface, a lower surface and a side surface and containing no angular portion; and applying pressure to the side surface of the forging material. The shape has a ratio of the lateral length of a projection profile of the forging material as viewed in the direction perpendicular to the direction of pressure application to a length of the forging material as measured in the direction of pressure application is 1 or less. The forged product obtained is a preform of an upper arm or a lower arm with a plurality of branches that is a suspension part for a vehicle or a yoke with a plurality of branches that is a joint part employed in a vehicle suspension. The preform or yoke has metal flow lines along each branch and exhibits enhanced mechanical strength.

Abstract: A closed forging method for producing a forged product includes preparing as a forging material a cylindrical cast ingot that has a volume the same as the volume of a forged product and assumes a shape having an upper surface, a lower surface and a side surface and containing no angular portion; and applying pressure to the side surface of the forging material. The shape has a ratio of the lateral length of a projection profile of the forging material as viewed in the direction perpendicular to the direction of pressure application to a length of the forging material as measured in the direction of pressure application is 1 or less. The forged product obtained is a preform of an upper arm or a lower arm with a plurality of branches that is a suspension part for a vehicle or a yoke with a plurality of branches that is a joint part employed in a vehicle suspension. The preform or yoke has metal flow lines along each branch and exhibits enhanced mechanical strength.