| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot-rolled non-thermally refined bar steel capable of stably obtaining a tensile strength of≥700 Mpa and an impact value<SB>U</SB>E20 of≥100 J/cm<SP>2</SP>, and to provide a manufacturing method therefor. SOLUTION: The hot-rolled non-thermally refined bar steel has a componential composition comprising, by mass, 0.040 to 0.150% C,≤0.5% Si, 0.5 to 3.0% Mn,≤0.1% Al, 0.03 to 0.35% Ti and 0.05 to 0.8% Mo, and the balance Fe with inevitable impurities, in which the segregation ratio R of Mn is≤1.5, the structure is composed of a ferrite single phase with a crystal grain size of≤35μm, and fine precipitates with a grain size of <10 nm are dispersed into the ferrite. COPYRIGHT: (C)2007,JPO&INPIT
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