| 摘要 |
PROBLEM TO BE SOLVED: To facilitate high frequency hardening and to obtain a high hardness, in an alloy steel containing a specified weight % C, by making the number of carbide grains, which has a specified major diameter, existing within an observation visual field of a specified area of a cross-sectional high frequency hardened part of the steel a specified number. SOLUTION: In the steel, in which a chemical composition is, by weight, 0.4-1.20% C, preferably 0.50-0.75%, more preferably 0.60-0.70%, a number of the carbide grains having a major diameter of >=10μm, which exist within an observation visual field of an arbitrary 1 mm<2> of a cross-sectional high frequency hardened part of the steel, are <=60 pieces, and further, an area ratio of the carbide grains of <=5μm major diameter to a total area of the remaining carbide grains of <=10μm major diameter exceeds 70%. Cr of 9.00-20.00 wt.%, preferably 11.00-13.50 wt.% is added for forming an inactive film on a steel surface and improving corrosion resistance. Si of 0.01-1.50 mass %, preferably 0.31-1.00 mass % is added for a deoxidizer for the steel.
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