Water-blocking apparatus and water-blocking method for cooling water for hot-rolled steel sheet

1. A water-blocking apparatus for cooling water for a hot-rolled steel sheet, which blocks cooling water sprayed onto the hot-rolled steel sheet at a sprayed water density of higher than 4 m 3 /m 2 /min and equal to or less than 10 m 3 /m 2 /min when the hot-rolled steel sheet is cooled after finish rolling of a hot-rolling process, the water-blocking apparatus comprising:

a plurality of water-blocking nozzles which are flat spray nozzles spraying water-blocking water onto the hot-rolled steel sheet, wherein

the plurality of the water-blocking nozzles are arranged so that impact areas of the water-blocking water respectively sprayed from the water-blocking nozzles are continuously lined up in a straight line in a width direction of the hot-rolled steel sheet on a surface of the hot-rolled steel sheet and the adjacent impact areas partially overlap,

the plurality of the water-blocking nozzles are configured to form a water wall continuously extending along the width direction on the impact areas, and

a momentum F A of the water-blocking water that flows in the sheet-threading direction of the hot-rolled steel sheet on the surface of the hot-rolled steel sheet is 1.0 to 1.45 times a momentum F B of the cooling water that flows in the sheet-threading direction of the hot-rolled steel sheet.

2. The water-blocking apparatus for cooling water for a hot-rolled steel sheet according to claim 1 , wherein a height at which sprays of the water-blocking water which are adjacent to each other in the width direction of the hot-rolled steel sheet join is higher than 400 mm from the surface of the hot-rolled steel sheet in a side view as viewed from a sheet-threading direction of the hot-rolled steel sheet.

3. The water-blocking apparatus for cooling water for a hot-rolled steel sheet according to claim 1 , wherein the plurality of water-blocking nozzles are lined up and arranged in the width direction of the hot-rolled steel sheet so that a distance between the water-blocking nozzle and the surface of the hot-rolled steel sheet in a spraying direction of the water-blocking water is 2000 mm or less.

4. The water-blocking apparatus for cooling water for a hot-rolled steel sheet according to claim 1 , wherein a spray angle of the water-blocking water sprayed from the water-blocking nozzle with respect to a vertical direction is 20 to 65 degrees.

5. The water-blocking apparatus for cooling water for a hot-rolled steel sheet according to claim 1 , wherein the plurality of water-blocking nozzles are arranged on each of an upstream side and a downstream side of a cooling water nozzle which sprays the cooling water onto the hot-rolled steel sheet.

6. A water-blocking method for cooling water for a hot-rolled steel sheet, in which cooling water sprayed onto the hot-rolled steel sheet at a sprayed water density of higher than 4 m 3 /m 2 /min and equal to or less than 10 m 3 /m 2 /min when the hot-rolled steel sheet is cooled after finish rolling of a hot-rolling process is blocked by water-blocking water sprayed from a plurality of water-blocking nozzles which are flat spray nozzles, the water-blocking method comprising:

spraying the water-blocking water from the plurality of the water-blocking nozzles onto the hot-rolled steel sheet so that a plurality of impact areas of the water-blocking water are continuously lined up in a straight line in a width direction of the hot-rolled steel sheet on a surface of the hot-rolled steel sheet and the adjacent impact areas partially overlap; and

forming a water wall continuously extending along the width direction on the impact areas,

wherein a momentum F of the water-blocking water that flows in the sheet-threading direction of the hot-rolled steel sheet on the surface of the hot-rolled steel sheet is 1.0 to 1.45 times a momentum F B of the cooling water that flows in the sheet-threading direction of the hot-rolled steel sheet.

7. The water-blocking method for cooling water for a hot-rolled steel sheet according to claim 6 , wherein a height at which sprays of the water-blocking water which are adjacent to each other in the width direction of the hot-rolled steel sheet join is higher than 400 mm from the surface of the hot-rolled steel sheet in a side view as viewed from a sheet-threading direction of the hot-rolled steel sheet.

8. The water-blocking method for cooling water for a hot-rolled steel sheet according to claim 6 , wherein the plurality of water-blocking nozzles are lined up and arranged in the width direction of the hot-rolled steel sheet so that a distance between the water-blocking nozzle and the surface of the hot-rolled steel sheet in a spraying direction of the water-blocking water is 2000 mm or less.

9. The water-blocking method for cooling water for a hot-rolled steel sheet according to claim 6 , wherein a spray angle of the water-blocking water sprayed from the water-blocking nozzle with respect to a vertical direction is 20 to 65 degrees.

10. The water-blocking method for cooling water for a hot-rolled steel sheet according to claim 6 , wherein the plurality of water-blocking nozzles are arranged on each of an upstream side and a downstream side of a cooling water nozzle which sprays the cooling water onto the hot-rolled steel sheet, and the cooling water on the upstream side and the downstream side of the cooling water nozzle is blocked by the water-blocking water sprayed from the water-blocking nozzles disposed on the upstream side and the downstream side of the cooling water nozzle.