Nippon Steel Corporation

Yukihiro Ota

Kenji Tamura

Junichi Okubo

Kunihiro Yoshida

Masao Hori

Sam Soo Hwang

Ryusuke Nakano

Provided is a production method, including a first preforming process for obtaining a first preform from a billet, a second preforming process for obtaining a final preform from the first preform, and a finish forging process for forming the final preform into a finishing dimension of a forged crankshaft. In the first preforming process, a plurality of flat parts are formed by pressing pin-corresponding parts and journal-corresponding parts in a direction perpendicular to an axial direction of the billet. The second preforming process includes: a process of pressing regions to be a plurality of journals with a width direction of the flat part as a pressing direction by using a pair of first dies; and a process of, after starting pressing by the first dies, decentering regions to be a plurality of pins with the width direction of the flat part as a decentering direction by using second dies.

Method for producing forged crankshaft

Provided is a production method, including a first preforming process, a second preforming process, and a finish forging process. In the first preforming process, while a plurality of flat parts are formed, a region to be a second pin is decentered. The second preforming process includes: a process of pressing each region to be a plurality of journals in a pressing direction corresponding to a width direction of the flat part by using a pair of second dies; and a process of, after starting the pressing by the second dies, decentering a region to be a first pin and to be disposed in a first position and a region to be a third pin and to be disposed in a third position from each other in opposite directions with a width direction of the flat part being as a decentering direction by using third dies.

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Tokyo, Japan

Yukihiro Ota