| 摘要 |
PURPOSE:To improve machinability (tool life, machining crushability) of the titled steel to be obtained particularly in a low-speed working region, by adding B and Pb in combination and by controlling B/O. CONSTITUTION:The titled steel has a composition consisting of, by weight, <=0.60% C, <=0.50% Si, <=2.0% Mn, 0.01-0.40% Pb, 0.0030-0.0200% B, <=0.020% N, 0.0020-0.0300% O, and the balance essentially Fe and satisfying B/O=0.1-1.0. If necessary, one or more kinds among <=0.40% S, <=0.20% P, <=0.40% Bi, <=0.40% Se, and <=0.20% Te are further added to the above composi tion. Owing to this composition, machinability in the low-speed working region can be improved.
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