Forged products are often employed in members of, for example, steam turbines and aircraft. The size of such products has been increasing in recent years. A large amount of plastic deformation has to be imparted to produce such forged products, necessitating upsetting of elongated material. For example, in the hot upset forging method disclosed in Japanese Patent Application Laid-Open (JP-A) No. H07-171650 (see Patent Document 1), for elongated material with an axial length (equivalent to height in upset forging)/bottom face diameter exceeding 3, for which there would normally be concerns regarding buckling, such issues are resolved by partially employing a specific mold.
Specifically, the hot upset forging method disclosed has the following features:
(1) deformation of an axial direction portion of shaft shaped material toward the outer side in the radial direction is blocked by the mold, such that the ratio of axial length/diameter of a free deformation portion is 3 or less; and
(2) forging is started in the state described in (1), and the free deformation portion, other than the deformation-blocked portion of the material, is made to undergo plastic deformation so as to bulge out toward the outer side in the radial direction.