| 摘要 |
PROBLEM TO BE SOLVED: To provide a quenched and tempered nitrocarburized crankshaft having excellent bending straightening properties and further having high fatigue strength, and to provide a rough shaped article for a quenched and tempered nitrocarburized crankshaft suitable as the stock therefor. SOLUTION: (1) The rough shaped article for a quenched and tempered nitrocarburized crankshaft has a chemical composition comprising 0.30 to 0.55% C, 0.05 to 0.30% Si, 0.20 to <0.80% Mn, 0.005 to 0.05% P, 0.005 to 0.10% S, >0.01 to 0.30% V and 0.005 to 0.030% N, and the balance Fe with impurities satisfying <0.10% Cr and≤0.05% Al, wherein the microstructure at the part of≥2% depth from the surface is composed of pearlite or ferrite-pearlite satisfying ferrite<10%. (2) The quenched and tempered nitrocarburized crankshaft using the rough shaped article as the stock, and obtained by machining the rough shaped article in at least 2 mm at a depth from the surface, and then subjecting the same to nitrocarburization treatment. The chemical composition may comprise one or more kinds among elements of at least one element of a group selected from (a) one or more kinds selected from≤0.15% Mo and≤0.030% Ti and (b)≤0.020% Ca. COPYRIGHT: (C)2009,JPO&INPIT
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