| 摘要 |
PROBLEM TO BE SOLVED: To obtain a steel plate having good flatness by reducing the temp. unevenness and deformation generated during cooling and then cooling. SOLUTION: The hot rolled steel plate rolled by a rolling mill is cooled by a frontstage cooling device 8, after that cooling is once stopped midway, successively the plate is hot straightened and then is cooled down to a target stop temp. by a poststage cooling device 9. A steel plate temp. in hot straightening is set to the value higher than (Ar3-150) deg.C to that lower than (Ar3-20) deg.C and a steel plate transformation ratio to >=5% to <=75%. By this method, the temp. unevenness generated at frontstage cooling is reduced by heat recovery, at the same time, the deformation generated at frontstage cooling is removed by hot straightening, successive poststage cooling is uniformly done, the temp. unevenness of the steel plate after final cooling is suppressed, thus, the steel excellent in flatness is obtained.
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