| 摘要 |
PROBLEM TO BE SOLVED: To provide steel for a machine structure, which does not substantially contain Pb, and is superior in machinability, especially in a chip parting property and the tool life in cutting work with the use of the hard metal tool. SOLUTION: The steel for the machine structure includes C, Si, Mn, S, P, Ca, N, Al, and the balance Fe with impurities, and has a value of [Ca]e expressed by [Ca]e=T.[Ca]-(T.[O]/(O)OX)×(Ca)OX of 5 ppm or less, where [Ca]e is an effective Ca concentration index (mass ppm); T.[Ca] and T.[O] are contents of Ca and O by mass ppm; and (O)OX and (Ca)OX are the ratios of O and Ca included in the oxide-based inclusions, and/or has a ratio of MnO included in oxide-based inclusions, of 0.05 or less, and the value of Ca/O, of 0.8 or less. The steel may include one or more of Ti, Cr, V, Mo, Nb, Cu, and Ni, and/or, one or more of Se, Te, Bi, Mg, and REM (rare earth metals), as needed. COPYRIGHT: (C)2003,JPO
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