| 摘要 |
PURPOSE:To provide a case hardening steel consisting of specified amounts of C, Si, Mn, Ni and Mo and the balance Fe with impurities and having superior properties of preventing the formation of an abnormal surface layer during carburizing or carbonitriding. CONSTITUTION:This case hardening steel consists of, by weight, 0.1-0.4% C, 0.02-0.15% Si and <=2% Mn as essential components, 0.3-5% Ni and/or 0.05- 0.5% Mo and the balance Fe with impurities. The steel has superior properties of preventing the formation of an abnormal surface layer during carburizing or carbonitriding, and case hardened parts having high quality and high fatigue strength can be obtd. In order to improve the cold workability or to increase the strength furthermore, it is preferable to regulate the amounts of said impurities to <= about 0.015% S, <= about 0.015% P, <= about 0.01% N and <= about 0.002% O.
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