| 摘要 |
PROBLEM TO BE SOLVED: To provide a tool steel used for the material of a tool for cold working, which has both high hardness and high toughness, and to provide a method of producing a tool for precision working using the same. SOLUTION: The tool steel has an alloy composition comprising, by weight, 0.45 to 0.90% C, 0.1 to 2.0% Si, 0.1 to 1.5% Mn, 3.0 to 8.0% Cr and 0.02 to 0.5% V, and further comprising Mo and W so as to satisfy Mo+0.5W: 0.1 to 2.5%, and the balance Fe with impurities, and in which, provided that L=15.5C(%)+Cr(%), 14≤L≤20 is satisfied. In the tool steel, the number of carbides with a size of≥10μm expressed in terms of diameter is≤10 pieces in a field of 0.5 mm<SP>2</SP>, and, when A-based, B-based and C-based inclusions are measured in accordance with the method of JIS G0555, (dA+dB+dC)60×400≤0.01% is satisfied. The tool steel is held at≥1,150°C for≥5 hr, thereafter, the shape of a tool is imparted thereto, then, quenching is performed from 1,000 to 1,060°C, and subsequently, tempering is performed at 500 to 65°C. COPYRIGHT: (C)2007,JPO&INPIT
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