| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel which has the adequate fatigue life and superior sound characteristics, by resolving the adverse effect of oxide-based inclusions. SOLUTION: A steel with finely dispersed inclusions superior in the fatigue life includes, by wt.%, 0.05% or less (including 0%) Al, 0.005% or less T.O, and REM in such an amount as to satisfy expression (1): -30<REM (ppm)-T.O (ppm)×280/48<50; includes REM-containing inclusions (oxides, sulfides, oxysulfides, nitrides and composite inclusions thereof ) by such a number proportion with respect to all inclusions (oxides, sulfides, oxysulfides, nitrides and composite inclusions thereof ) having a grain size of 1μm or larger by an equivalent circle diameter, as to satisfy expression (2): (REM-containing inclusions number)/(all inclusions number)>0.8; and satisfies a condition that the concentration of Al<SB>2</SB>O<SB>3</SB>contained in the REM-containing inclusions is 30 wt.% or lower (including 0%). COPYRIGHT: (C)2005,JPO&NCIPI
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