| 摘要 |
A production method for a forged crank shaft, including a die-forging step, a burr-removal step, and an excess thickness section-squashing step. In the die-forging step, a finished forged material having burrs thereon and having a crankshaft shape formed therein is molded, said crank shaft shape having excess thickness sections (Aaa, Aba) in the outer perimeter of both side sections (Aa, Ab) in the vicinity of a pin section (P) of a crank arm section (A), said excess thickness sections (Aaa, Aba) protruding from said outer perimeter. The burr-removal step removes burrs from the finished forged material molded in the die-forging step. In the excess thickness section-squashing step, the excess thickness sections (Aaa, Aba) of the crank arm are squashed by pressing downward, using a pair of first dies (10A, 10B), on to the crank shaft having the burrs removed therefrom during the burr-removal step. As a result, a forged crank shaft that is lighter and has rigidity ensured can be easily obtained. |
