| 摘要 |
PURPOSE: To produce a bearing member in which instantaneous destruction can be prevented by the increase of its toughness without deteriorating the hardness of the core part and capable of obtaining excellent rolling fatigue life characteristics. CONSTITUTION: This is an Fe-base martensitic steel having a compsn. contg., by weight, <=0.4% C, <=2% Si, <=2% Mn, 5% Ni, 3.5 to 7.0% Cr, one or two kinds of W and Mo by 3 to 15% as W equivalent (W+2Mo) and 0.5 to <1.1% V and is a steel for carburizing in which, in the case the carbon equivalent Cv of V=0.2[V] and the carbon equivalent Ceq of carbide forming elements =0.063[Cr]+0.06[Mo]+0.033[W]+0.2[V], Cv/Ceq<=0.3 is satisfied. By regulating Cv/Ceq<=0.3, the precipitation of MC carbides is suppressed, and M2 C type carbides having a form bigger than theat of MC type carbides are suitably dispersed to improve its fracture toughness value.
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