| 摘要 |
PURPOSE:To obtain a pre-hardened steel for specula finishing excellent in machinability, by specifying a composition and by uniformly dispersing fine Pb grains having a specific grain size or below. CONSTITUTION:The pre-hardened steel for specular finishing has a composition which consists of, by weight, 0.1-0.35% C, 0.05-0.3% Si, 0.5-2% Mn, <0.03% P, <0.01% S, 0.5-2.0% Cr, 0.05-1% Mo, 0.01-0.1% V, 0.005-0.03% Al, 0.0005-0.003% B, <0.006% N, <0.005% O, 0.03-0.1% Pb, and the balance Fe with inevitable impurities and in which fine Pb grains with a grain size of <=5 microns are uniformly dispersed.
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