| 摘要 |
PROBLEM TO BE SOLVED: To provide a high carbon steel member exhibiting excellent impact strength satisfying an impact value of≥25 J/cm<SP>2</SP>while maintaining its hardness of 600 to 900 HV. SOLUTION: The high carbon steel member is composed of a high carbon steel comprising, by mass, 0.60 to 1.30% C,≤1.0% Si, 0.2 to 1.5% Mn,≤0.02% P and≤0.02% S, and, if required, comprising one or more kinds selected from≤1.8% Ni,≤2.0% Cr,≤0.5% V,≤0.5% Mo,≤0.3% Nb,≤0.3% Ti,≤0.01% B and≤0.01% Ca, and in which undissolved carbide remains at a volume fraction Vf (volume%) satisfying the inequality (1) of 8.5<15.3×C%-Vf<10.0 in the matrix after quenching/tempering, and the number of undissolved carbide with a grain size of≥1.0μm is regulated to≤2 pieces per 100μm<SP>2</SP>in an observed area. In a production method therefor, a steel in which carbide with a mean minor axis length of 0.3 to 1.1μm is dispersed is used as a starting material, and is subjected to quenching/tempering heat treatment in such a manner that it is subjected to solution treatment so as to be held in the temperature range of 760 to 850°C for 3 to 30 min, is then subjected to quenching so as to be rapidly cooled with a cooling medium in the range of room temperature to 200°C, and is next held in the temperature range of 150 to 350°C for 10 to 180 min. COPYRIGHT: (C)2006,JPO&NCIPI
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