| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a case-hardened steel which has all of superior grain coarsening resistance, fatigue characteristics and excellent machinability, and to provide a preferable manufacturing method therefor. <P>SOLUTION: The case-hardened steel comprises, by mass%, 0.10-0.35% C, 0.03-1.0% Si, 0.20-2.0% Mn, 0.030% or less P, 0.010-0.10% S, 0.2% or less Al, 0.03-0.30% Ti, 0.020% or less N, and the balance Fe with unavoidable impurities; has Ti-based carbonitrides finely dispersed in the steel; and contains Ti-based sulfides with an average diameter of 1.0 to 5.0 μm existing at a density of 10 pieces/mm<SP>2</SP>or more, and Ti-based sulfides with an average diameter of larger than 5.0 μm existing at a density of 10 pieces/mm<SP>2</SP>or less. <P>COPYRIGHT: (C)2007,JPO&INPIT |
