| 摘要 |
PROBLEM TO BE SOLVED: To obviate a drawing stage and an annealing stage and to obtain carbonized axial parts small in heat treating distortion by allowing the parts to contain elements in a specified compsn. and dispersing specified value (piece/100μm<2> or above) of composite precipitates composed of components having a specified value or above of diameter into a matrix after carurizing quenching to form a structure in which the austenite grain size lies in a specified range. SOLUTION: The compsn. of elements are composed of the one contg., by weight, 0.10 to 0.35% C, 0.02 to 0.50% Si, 0.30 to 1.80% Mn, 0.005 to 0.15% S, 0.015 to 0.040% Al, 0.005 to 0.040% Nb and 0.0060 to 0.0200% N, furthermore contg. one or more kinds among Cr, Mo, Ni and V, in which the contents of P, Ti and O are limited, and the balance Fe with inevitable impurities. Then, into the matrix after decarburizing quenching, Nb(CN), AlN or composite precipitates of Nb(CN) and AlN having <=0.1μm diameter are dispersed by 80 pieces/100μm<2> ) in total to form a structure in which austenite grain size is regulated to No. >=8.
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