| 摘要 |
PROBLEM TO BE SOLVED: To provide a crank shaft in which outer circumferential surfaces of a pin part and of a journal part can be used as rolling contact surfaces of a rolling bearing.SOLUTION: The crank shaft has a chemical component containing, by mass%, C:0.70% to 1.10%, Si:0.01% to 2.00%, Mn:0.03% to 0.20%, S:0.015% to 0.048%, Cr:0.01 to 2.00%, Al:0.001 to 0.050%, N:0.0200% or less, satisfying the formula 1 and the formula 2 and the balance Fe with inevitable impurities. In rolling contact surfaces 510 and 520, when observing a cross section parallel to the rolling contact surface at a position directly under the rolling contact surface, MnS having equivalent circle diameter of 10 μm or more among MnS present in an observation face of 10 mmis 5 or less, the rolling contact surfaces 510 and 520 has been subjected to an induction hardening treatment and has a hardness of 700 HV or more in the range of at least 1.5 mm depth from an outermost surface.SELECTED DRAWING: Figure 1 |
