| 摘要 |
PROBLEM TO BE SOLVED: To improve productivity and yield of an external joint member.SOLUTION: A method is used for manufacturing an external joint member 1 which has a cup portion 2 opening at one end and in which a plurality of track grooves 5 extending in an axial direction are formed on an inner diameter surface 4 of the cup portion 2. The external joint member 1 is manufactured through a pre-forging step of obtaining an intermediate forging 1" having a cup-shaped portion 2" in which track grooves 5' are roughly molded on an inner diameter surface from a bar-shaped material using a forging device in which a plurality of forging molds are consecutively provided, and an ironing step of obtaining a final forging 1' from the intermediate forging 1". In the pre-forging step, an intermediate product which finally becomes the intermediate forging 1", here, a third intermediate product M3 is molded, and at the same time, by molding portions 31b and 32b provided on a punch 31 and a die 32 forming a forging mold for molding the intermediate product, an end face mark portion 11 and an outer diameter mark portion 12 are molded at the third intermediate product M3 as mark portions which enables visual determination of pass or fail of the cup-shaped portion 2" of the intermediate forging 1". |
