| 摘要 |
PROBLEM TO BE SOLVED: To provide a process of manufacture of forged crank shaft capable of attaining the forged crank shaft attaining simultaneously both light weight formation and a rigidity assurance.SOLUTION: This invention comprises the steps for die forging to get a burred forging member in which a shape of a crank shaft is formed; removing burrs for getting non-burred forging member 30 from a burred forging material; and pushing-in the second die 22 into a pin side surface after drafting the non-burred forging member 30 with a pair of first dies [11, 12] to form a recess part Au. At the die forging stage, the first pads [Aca, Ada] protruded from outer peripheries of both sides [Ac, Ad] near a journal part J is further formed; and when the non-burred forging member is drafted at the push-in stage, the first pads [Aca, Ada] are bent toward the pin part side surface by the first dies [11, 12] so as to increase a thickness of both side parts [Ac, Ad] near the journal part J and at the same time the recess Au is formed between both sides [Ac, Ad] near the journal part J at the pin part side surface.SELECTED DRAWING: Figure 11 |
