| 摘要 |
PURPOSE:To manufacture the titled steel plate, by hot rolling a steel slab having a specified compsn. to plate material, then cooling acceleratedly at the first step, successively cooling acceleratedly at the second step, then air cooling said plate. CONSTITUTION:The steel contg. by weight, 0.005-0.20% C, 0.05-0.50% Si, 0.5-2.0% Mn, 0.005-0.08% Al, <0.01% S, <0.008% N, or further at least one kind among <0.04% Ti, <0.10% V, <0.5% Cu, <1.0% Ni, <0.5% Cr, <0.5% Mo, and one kind among <0.010% Ca, <0.01% REM is manufactured. The steel slab is hot rolled at Ar3+70 deg.C-Ar3 point range at >=30% draft to plate material. Immediately thereafter, the plate is cooled to ferrite transformation stopping temp. - 500 deg.C range by 4-30 deg.C/sec rate, further cooled from the temp. to 500-200 deg.C at 1-3 deg.C/sec rate, then air cooled to room temp.
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