| 摘要 |
PROBLEM TO BE SOLVED: To provide case hardening steel excellent in the characteristics of preventing coarse grains, in which cold workability is excellent, and also, heat treating strain is small and to provide its producing method. SOLUTION: This case hardening steel excellent in the characteristics of preventing coarse grains has a composition containing, by mass, 0.1 to 0.35% C, 0.02 to 0.5% Si, 0.3 to 1.8% Mn, 0.005 to 0.15% S, 0.02 to 0.05% Al and 0.005 to 0.015% N, furthermore containing one or more kinds selected from 0.4 to 1.8% Cr, 0.02 to 1.0% Mo and 0.1 to 3.5% Ni, in which the content of P is limited to <=0.025%, Ti to <=0.01%, and O to <=15 ppm, respectively, and the balance Fe with inevitable impurities, and in which the quantity of AlN to be precipitated after hot working is limited to <=0.004%, and the grade of a ferritic band in a cross-sectional structure parallel to the hot rolling direction is 1 to 3.
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