| 摘要 |
PURPOSE:To reduce the cost of a forging equipment, and to decrease the generation of burr by performing partially forging to at least a crank arm corresponding part of a crank shaft stock. CONSTITUTION:In a forging process, when a temperature of a crank shaft stock 1a made of steel, etc. is 1,000-1,200 deg.C, a release is executed, and immediately, the stock is inserted and pressed between the upper and lower dies for forging. In this case, each crank arm corresponding part 4a is pressed from the upper and lower directions by freely slidable pressure punches 111, 112 and each crank arm corresponding part 4a is formed. This forging is executed easily because the crank stock 1a is in a high temperature state. To each crank pin corresponding part 3a and each crank journal corresponding part 2a of the crank shaft stock 1a, as well, forging is executed in the same way. In such a way, the cost of a forging equipment can be reduced, and the generation of burr can be decreased.
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