Metal forged product, upper or lower arm, preform of the arm, production method for the metal forged product, forging die, and metal forged product production system

摘要

A method for producing a metal forged product having a plurality of branches includes a preliminary forging step of forming a preform by closed forging from a cylindrical material ( 301 ) having a surface layer ( 302 ) on a circumferential surface thereof such that the surface layer is contained in a surface region of the preform; an intermediate forging step of subjecting the preform to forging to thereby extrude the surface layer in the form of flash outside a periphery of a forged product corresponding to a target product; a final forging step of forging the forged product into a product assuming a target product shape; and a flash removal step of removing the flash containing the surface layer from the product assuming a target product shape to thereby produce a target forged product. The forged product is enhanced in mechanical characteristics and has no flash removal mark. Since the cylindrical material having a surface layer on a circumferential surface thereof is used, the power required for the steps can be reduced to enhance the yield of the products on the basis of the forging material.