| 摘要 |
A steel excellent in machinability, characterized in that it has a chemical composition, in mass %: C: 0.005 to 0.2 %, Si: 0.001 to 0.5 %, Mn: 0.2 to 3.0 %, P: 0.001 to 0.2 %, S: 0. 03 to 1.0 %, B: 0.005 to 0.05, T.N: 0.002 to 0.02 %, T.O: 0.005 to 0.035 %, the balance: Fe and inevitable impurities, with the proviso that Mn/S in the steel is 1.2 to 2.8 and/or it has a microstructure wherein the area % of the pearlite having a grain size exceeding 1 mum is 5 % or less. |
