| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for machine structures, which is excellent in machinability, in particular, in tool wear resistance in lathe turning and drilling process.SOLUTION: A steel for machine structures includes, by mass, 0.15-0.65% of C, 0.10-1.50% of Si, 0.5-2.0% of Mn, ≤0.05% of P, >0.030% and ≤0.15% of S, 0.02-2.0% of Cr, ≤0.005 of Al, >0.0005% and ≤0.0040% of Ca, 0.0001-0.0010% of Mg, ≤0.030% of N and >0.0020% and ≤0.0060% of O, with the balance comprising Fe and impurities, wherein the average composition of oxide-based inclusions is in the range of CaO: 10.0-50.0%, SiO: 20.0-50.0%, AlO: 20.0-45.0%, MgO: 1.0-10.0%, and MnO: 0-2.0%, each by mass, and CaO×O×10≥550 is satisfied. The steel may include one kind or more elements of ≤0.30% of V, <0.040% of Ti, ≤0.05% of Nb and ≤0.50% of Mo in place of a portion of Fe. |
