| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a case hardening steel having a crystal grain size property at high temperature when carburized which is required when an automobile shaft or a power transmission component is obtained from a steel material of steel for machine structural use.SOLUTION: There is provided the case hardening steel which contains, by mass%, C:0.12 to 0.35%, Si:0.30 to 1.20%, Mn:0.10 to 0.85%, P:≤0.030%, S:≤0.030%, Cr:1.0 to 2.5%, Mo:≤0.1%, Al:0.020 to 0.50%, Nb:0.02 to 0.1%, Ti:≤0.20%, N:≤170 ppm, B:≤0.0050% as main components and the balance Fe with inevitable impurities and which has a pinning grain. The pinning grain contains Ti(CN), NbTi(CN), Nb(CN) and AlN, and has a diameter of 10 to 50 nm, the number of the pinning grain is 1×10/mmto 10×/mmand percentage of the number of the pinning grain satisfies Ti(CN)+NbTi(CN)+Nb(CN)≥3AlN.</p> |
