| 摘要 |
PROBLEM TO BE SOLVED: To provide steel for machine structural use free from the anxiety about the occurrence of the problem of environmental contamination, moreover widely applicable without being provided with machining conditions and using limitation and particularly excellent in the partibility of chips extremely important for automating machining operation. SOLUTION: As to this steel for machine structural use in steel for machine structures containing, by mass, C of 0.1 to 0.6%, Si of 2.5% or less (not inclusive of 0%), Mn of 0.2 to 3.0%, S of <0.150% (not inclusive of 0%) and O of 0.001 to 0.015%, the number of inclusions with a length of 1μm or more appearing in the longitudinal section is 50 to 1,000 pieces per mm2 of the cross section, the ratio of the number of oxides occupying in the total content if the inclusions is 10% or more, and also, in the oxides, the ratio of the number of the oxide of at least one kind of element selected from the group consisting of Na, Li and B or the multiple oxide of at least two kinds of elements selected from the group consisting of Na, Li, B and Si is 5% or more, and the method for producing the same is provided.
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