| 摘要 |
PROBLEM TO BE SOLVED: To propose a case hardened steel suitable as a material of a machine structural component which is obtained at a relatively inexpensive production cost and has a high flexural fatigue strength and a high surface pressure fatigue strength.SOLUTION: There is provided a case hardened steel having a chemical composition which comprises, by mass%, 0.15% or more and 0.25% or less of C, more than 1.10% and 1.50% or less of Si, 0.40% or more and 1.20% or less of Mn, 0.010% or more and 0.030% or less of S, 0.05% or more and 0.50% or less of Cu, 0.80% or more and 1.80% or less of Cr, 0.10% or less of Mo, 0.020% or more and 0.060% or less of Al, 0.0060% or more and 0.0200% or less of N and 0.0015% or less of O under a predetermined relation, wherein the hardness at a position at a depth of 200 μm from the surface obtained after carburizing quenching and tempering is adjusted to be HV730 or more. |
