| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material for case hardening making pitching resistance or abrasion resistance good as one excellent in surface fatigue strength, and excellent in cold forgeability after spheroidizing.SOLUTION: The steel material for case hardening contains C:0.15 to 0.25%, Si:0.40 to 0.6%, Mn:0.20 to 0.49%, P:0.015% or less (excluding 0%), S:0.02% or less (excluding 0%), Cr:1.25 to 1.6%, Mo:0.40 to 0.80%, Al:0.01 to 0.050% and N:0.008 to 0.025% and the balance iron with inevitable impurities, and has an area fraction of ferrite:37 to 65%, the area fraction of bainite:30 to 60%, the area fraction of perlite:3 to 10% and a ferrite grain size number of 7 to 9. |
