STEEL FOR VACUUM CARBURIZING, AND METHOD FOR PRODUCING VACUUM CARBURIZED COMPONENT

PROBLEM TO BE SOLVED: To securely prevent abnormal grain growth in the surface part generated in the case a carburizing gas is introduced into an evacuated atmosphere so as to be a pulse shape, and high temperature carburizing treatment is performed. SOLUTION: The steel in which a carburizing gas is introduced so as to be a pulse shape and which is subjected to vacuum carburizing has a composition comprising, by weight, 0.10 to 0.30% C, 0.05 to 0.50% Si, 0.30 to 1.50% Mn, 0.30 to 2.00% Cr, 0.005 to 0.050% Al, 0.01 to 0.10% Nb, 0.0080 to 0.0250% N and ≤0.01% V, and, if required, comprising ≤0.80% Mo, and the balance Fe with impurity elements. The amount of AlN to be precipitated is ≤100 ppm, the number of Nb(C, N) to be precipitated is 1 to 10 pieces/μm2, and among the Nb(C, N) precipitates within 0.5 mm from the surface, the precipitated grains with a size of 10 to 50 nm are present by ≥1 piece/μm2, and the precipitated grains of >50 nm are present by ≤1 piece/μm2. COPYRIGHT: (C)2005,JPO&NCIPI