| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-carbon sulfur free-cutting steel which has a smaller roughness of a finished surface than that of a conventional low-carbon free-cutting steel containing no Pb and also shows excellent chip treatability, when the steel is finished with a turning process using a hard metal tool. SOLUTION: The low-carbon sulfur free-cutting steel comprises: 0.02% or more but less than 0.20% C, more than 0.10% but 1.5% or less Si, 0.8 to 2.2% Mn, 0.005 to 0.25% P, more than 0.40% but 0.8% or less S, less than 0.010% O, 0.025% or less N, 0.0003 to 0.005% Ca and the balance Fe with impurities, while controlling the contents of impurities to less than 0.005% Al, less than 0.0003% Mg, 0.002% or less Ti, 0.002% or less Zr and less than 0.0003% REM, and making the components satisfy the expressions of 2.0<Mn/S<4.0 and 0.0005≤10Ca×Si≤0.050. The free-cutting steel may further include one or more elements of Te≤0.05%, Bi≤0.15% and Sn≤0.5%, and/or one or more elements of Cr≤2.0%, Mo≤0.5%, V≤0.3% and Nb≤0.3%. COPYRIGHT: (C)2009,JPO&INPIT
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