| 摘要 |
The present invention provides a cooling apparatus of a hot-rolled steel sheet capable of manufacturing a hot-rolled steel sheet having ultra fine crystal grains. In the cooling apparatus, 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 where 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. |
