| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel as hot-rolled for machine structural in which the thickness of a decarburizing layer on the surface is suppressed, and which has cold workability equal to that of the conventional steel subjected to softening annealing after hot rolling, and to provide a production method therefor. SOLUTION: The steel has a composition comprising, by mass, 0.1 to 1.2% C, 0.01 to 2.5% Si, 0.1 to 1.5% Mn,≤0.04% P, 0.0005 to 0.05% S,≤0.2% Al, 0.0005 to 0.05% Te or/and 0.0005 to 0.05% Se and 0.0005 to 0.03% N, and in which the total content of S and Te or/and Se is 0.005 to 0.05%, and the balance Fe with inevitable impurities, and has a structure essentially consisting of ferrite and pearlite, and in which ferrite grain size number prescribed in JIS G 0552 is≥11. COPYRIGHT: (C)2004,JPO&NCIPI
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