| 摘要 |
The present invention provides: a cooling apparatus, a cooling method, a manufacturing apparatus, and a manufacturing method of a hot-rolled steel sheet which are capable of manufacturing a hot-rolled steel sheet having ultra fine crystal grains. In the cooling apparatus of a hot-rolled steel sheet, when defining as L1, a length in a transporting direction of a steel sheet, of a zone from a rolling reduction point in a final stand to an exit side of a housing post; defining as L2, a length in the transporting direction of the steel sheet, of an area in which high-pressure water is continuously sprayed over the steel sheet, within the zone; and defining a ratio of L2/L1 as X, an average value Ps [kPa], in the transporting direction of the steel sheet, of an impact pressure of the high-pressure water on a surface of the steel sheet in the area of the length L2 satisfies Ps ‰¥ 2.5X (-1/0.6) on the above upper surface and lower surface of the steel sheet. The cooling method uses the cooling apparatus. The manufacturing apparatus of a hot-rolled steel sheet comprises a final stand of a row of hot finish rolling mills and the cooling apparatus in the mentioned order in the transporting direction of the steel sheet. And the manufacturing method of a hot-rolled steel sheet comprises a process to treat the steel sheet rolled in the final stand of the row of hot finish rolling mills by using the manufacturing apparatus. |
