| 摘要 |
PROBLEM TO BE SOLVED: To provide a controlled cooling apparatus of a thick steel plate with the generation of hardness difference between the surface and the center of the steel plate is suppressed to small without bringing about the fall of rolling efficiency and the efficient mass production of the low yield ratio thick steel plate having low yield ratio is made possible. SOLUTION: This controlled cooling apparatus of the thick steel plate has a slow cooling zone for partially performing ferritic transformation in the steel structure on the outlet side of a rolling mill and a rapid cooling zone for transforming the balance austenite into perlite, bainite and martensite on the rear side of it. That is, the slow cooling zone and the rapid cooling zone which are independently controllable are provided in that order in this controlled cooling apparatus of the thick steel plate. COPYRIGHT: (C)2006,JPO&NCIPI
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