| 摘要 |
PURPOSE:To provide a material for parts of an engine moving valve system having excellent resistance to wear and scuffing by subjecting a steel material contg. C, Mn, Si, and Cr respectively at prescribed ratios to a soft nitriding treatment and specifying the thickness of a surface compd. layer. CONSTITUTION:A steel material consisting, by weight %, of 0.80-1.40% C, <=1.50% Mn, <=1.0% Si, 6.0-9.0% Cr, and the balance Fe and impurities is prepd. The steel material is subjected to a soft nitriding treatment to regulate the thickness of the surface compd. layer consisting of the steel material to >=5mu. The hardness of the surface layer is thus made to 600-900Hv and the area rate of the carbide (the best result is obtd. if the grain size is adjusted to <=10mu) of the base is made 0.5-4.0. The resultant steel material has the excellent above- described characteristics and since the material has a low attacking property to the mating part, said material is suitable as a material for parts of an engine moving valve for which said characteristics are simultaneously required.
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