MANUFACTURING METHOD OF FORGED CRANK SHAFT

摘要

PROBLEM TO BE SOLVED: To provide a manufacturing method of a forged crank shaft integrally having a weight part which reduces the weight of the crank shaft without largely increasing manufacturing steps.SOLUTION: A manufacturing method of a forged crank shaft comprises: a mold forging step obtaining a forged material with burrs in which a shape of a forged crank shaft and an excess thickness part Ea protruding from an outer peripheral surface Wa of a weight part W to a fan-shaped radial direction are formed by a die-forging; a deburring step obtaining a forged material 40 without burrs by removing burrs from the forged material with burrs; and a bending step in which a first metal mold 11 is moved from the outer peripheral surface Wa side to a journal part J side to bend the excess thickness part Ea by pressing the first metal mold 11 against the excess thickness part Ea so that thickness is increased at an edge part Wb of the outer peripheral surface in the weight part W.SELECTED DRAWING: Figure 6A