EP1935522A1

EP1935522A1 - Cooling facility and cooling method of steel plate

Info

Publication number: EP1935522A1
Application number: EP06783167A
Authority: EP
Inventors: Naoki Nakata; Takashi Kuroki; Akio Fujibayashi; Shogo Tomita; Masayuki Horie; Shunichi Nishida; Naoto Hirata; Michio Sato; Kyohei Ishida
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2005-08-30
Filing date: 2006-08-29
Publication date: 2008-06-25
Anticipated expiration: 2026-08-29
Also published as: KR20080034965A; WO2007026906A1; EP1935522A4; KR100973691B1; CN101253009B; CN101253009A; EP1935522B1

Abstract

There are provided cooling equipment and a cooling method for a steel plate or sheet which can properly cool a steel plate or sheet with a compact size on a hot rolling line, for example, during controlled rolling of the steel plate or sheet.

Specifically, steel-plate or sheet cooling equipment supplies cooing water onto upper and lower surfaces of a steel plate or sheet 10 while the steel plate or sheet 10 is passing during hot rolling, and includes nozzles 22a and 22b that obliquely supply the cooling water onto the upper surface of the steel plate or sheet 10 from above. The nozzles 22a and 22b are arranged so that jets of cooling water oppose each other in the transferring direction of the steel plate or sheet 10 on the steel plate or sheet 10.

More specifically, pass-type cooling equipment 20 has a high water flow rate of 4 m³/m²min or more.

Description

Technical Field

The present invention relates to cooling equipment and a cooling method for a steel plate or sheet.

Background Art

In recent hot rolling for steel plates or sheets, there is a demand to produce steel plates or sheets that are excellent in strength and toughness. As an example, thick steel plates having high quality are produced by subjecting a rolled material to controlled rolling (CR). That is, a slab heated to 1000°C or more is rolled to a predetermined thickness, and is then rolled again to a final thickness in a state in which the temperature of the rolled material is in a non-recrystallization temperature range or a temperature range close thereto. For example, a slab having a thickness of 200 to 300 mm is heated to about 1100 to 1200°C, and is rolled to about 1.5 to 2 times the final thickness. When the temperature thereof reaches 850°C or less, where is within the non-recrystallization range, controlled rolling is started, and the slab is rolled to the final thickness (e.g., 15 mm).
In this case, when the temperature at which controlled rolling is performed (controlled rolling start temperature) is low and the thickness with which controlled rolling is performed (controlled rolling start thickness) is large, much time is taken for the temperature of the rolled material to reach the controlled rolling start temperature. Therefore, the rolled material should wait in air cooling state or shower cooling state on a rolling line near a rolling mill (reversing rolling mill) until the material temperature reachs controlled rolling start temperature. As a result, waiting time is caused in the rolling mill by waiting for cooling, and this reduces the rolling productivity.
In order to prevent reduction of the rolling productivity due to waiting for cooling, a technique has been proposed in which a steel plate that needs to wait for cooling is moved to a waiting position provided outside the rolling line and is cooled thereat, other steel plates are rolled during cooling, and the steel plate cooled at the waiting position is returned from the waiting position into the rolling line so as to be subjected to controlled rolling when the temperature of the steel plate reaches a predetermined controlled rolling start temperature (e.g., see Japanese Unexamined Patent Application Publication Nos. 53-146208 and 60-180604 ).
However, in the techniques described in Japanese Unexamined Patent Application Publication Nos. 53-146208 and 60-180604 , it is necessary to provide a space that allows the waiting position to be set outside the rolling line, and equipment for moving the steel plate between the rolling line and the waiting position. This increases cost of the equipment.
Further, in order to prevent reduction of the rolling productivity due to waiting for cooling, for example, Japanese Unexamined Patent Application Publication No. 55-106615 discloses a controlled rolling method in which a shower-type cooling device is disposed at each of the front and rear sides of a reversing rolling mill and a rolled material is rolled by the reversing rolling mill in each rolling path while being cooled by water in the cooling device.
Japanese Unexamined Patent Application Publication No. 2005-000979 discloses a technique in which water cooling equipment(temperature adjustment cooling equipment) is provided, and a material rolled to a predetermined thickness by a reversing rolling mill is cooled by water to the predetermined controlled rolling start temperature in the water cooling equipment, and is rolled again to the final thickness by reversing rolling mill. This water cooling equipment is placed at a distance of about 20 m from the reversing rolling mill in order to avoid interference of rolling of another.
While the steel plate is cooled by the shower-type cooling devices in the technique disclosed in Japanese Unexamined Patent Application Publication No. 55-106615 , no consideration is taken of draining of cooling water (damming of remaining water). Therefore, if a high flow rate of cooling water is supplied onto the upper surface of the steel plate in order to obtain a predetermined temperature drop, remaining water freely moves on the upper surface of the steel plate. As the water cooling area of the steel plate is not constant, and cooling becomes nonuniform. This adversely affects the mechanical properties and shape of the products.
A damming rolls can be used as a method for damming cooling water remaining on the upper surface of the steel plate. However, there is a fear that conveyance trouble will occur, for example, a conveyed steel plate will collide with the damming rolls. Another method is flashing by use of air jet. However, this is not effective for a high flow rate of cooling water.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-000979 , temperature adjustment cooling to the predetermined controlled rolling start temperature is performed by the water cooling equipment disposed at a distance of about 20 m from the rolling mill. Therefore, much time is taken to perform cooling including conveyance of the steel plate, and it is impossible to sufficiently prevent the reduction in rolling productivity.
In a process for producing a steel plate by hot rolling, normally, cooling water is supplied or air cooling is performed in order to control the rolling temperature. In recent years, techniques of increasing the cooling rate for a finer structure and a greater strength of the steel plate have been developed vigorously.
For example, Japanese Unexamined Patent Application Publication No. 62-260022 discloses a technique of cooling a steel plate by supplying cooling water thereto. According to the statement made by this publication, a slit nozzle unit for ejecting jets of cooling water opposing in the transferring direction of the steel plate is moved up and down, and is used together with laminar nozzles and spray nozzles provided separately. This ensures a wide range of cooling rates.
Japanese Unexamined Patent Application Publication No. 59-144513 discloses another technique of cooling a steel plate by supplying cooling water thereto. This publication states that a high cooling rate can be obtained by ejecting cooling water films from obliquely opposing headers having slit-shaped nozzles, and by filling the space between the steel plate and partition plates with the cooling water.
Japanese Unexamined Patent Application Publication No. 2001-286925 discloses a further technique of cooling a steel plate by supplying cooling water thereto. According to the statement made by this publication, slit-shaped nozzles or flat spray nozzles are respectively disposed on the upstream and downstream sides of the steel plate and above the steel plate, and cooling water is ejected from these nozzles at a jet angle (an angle with respect to the normal to the steel plate) within the range of 20 to 60° such that the jets of cooling water oppose each other. Consequently, the cooling water on the steel plate can uniformly flow, and nonuniform cooling can be prevented.
However, the techniques disclosed in Japanese Unexamined Patent Application Publication Nos. 62-260022 and 59-144513 have serious problems in cooling uniformity and equipment cost.
That is, in the technique disclosed in Japanese Unexamined Patent Application Publication No. 62-260022 , since the slit nozzle unit needs to be disposed close to the steel plate, when a steel plate warped at the leading end or the tail end is cooled, it sometimes collides with the slit nozzle unit and damages the slit nozzle unit, or it cannot move. This sometimes stops the production line and reduces the yield. Accordingly, it is conceivable to cause the slit nozzle unit to recede upward by operating an lifting equipment during the passage of the leading or tail end. In this case, however, the leading or tail end is not sufficiently cooled, and a target material quality cannot be achieved. Further, the equipment cost increases because the lifting equipment is provided.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 59-144513 , the space between the steel plate and the partition plate is filled with cooling water only when the nozzles are disposed close to the steel plate. This arrangement of the nozzles close to the steel plate causes trouble when cooling the steel plate warped at the leading or tail end, in a manner similar to that in the technique disclosed in Japanese Unexamined Patent Application Publication No. 62-260022 .
Further, the techniques disclosed in Japanese Unexamined Patent Application Publication Nos. 62-260022 , 59-144513 , and 2001-286925 are based on the assumption that slit-shaped nozzles are used. Cooling water can be shaped into films only when the jet openings are always maintained in a clean state. For example, when a jet opening of a slit nozzle 52 is clogged by a foreign substance 60 adhering thereto, as shown in Fig. 15, a cooling water film or curtain 53 is broken. Further, the cooling water needs to be jet with a high pressure so as to be dammed in a jet area (cooling area). However, if the cooling water film 53 is jetted with a high pressure, it is easily broken because the balance of jet pressure is thrown off. When the cooling water film is obliquely jetted, if the distance between the steel plate and the nozzle is large, the thickness of the water film decreases near the steel plate, and the water film is broken more easily. In Japanese Unexamined Patent Application Publication Nos. 62-260022 , 59-144513 , and 2001-286925 , only one row of slit nozzles are provided on each of the upstream and downstream sides of the steel plate in the transferring direction. For this reason, if the cooling water film 53 is not formed well, the cooling water leaks out upstream and downstream of the jet area, remains on the steel plate 10, and partly cools the steel plate 10. This causes temperature differences. While there is a technique of removing the cooling water remaining on the upper surface of the steel plate 10, for example, by a side spray, this technique cannot completely remove the water when the amount of cooling water is large. This also causes temperature differences.
The present invention has been made with view of the above-described circumstances, and aims to provide cooling equipment and a cooling method for a steel plate or sheet which can properly cool the steel plate or sheet with a compact size on a hot rolling line.
The present invention also aims to provide hot rolling equipment and a hot rolling method for a steel plate or sheet in which the steel plate or sheet is uniformly cooled during controlled rolling and a high product quality is achieved, and in which the reduction in rolling productivity due to, for example, waiting for cooling can be prevented.
The present invention also aims to provide cooling equipment and a cooling method for a steel plate or sheet in which the steel plate or sheet can be uniformly and stably cooled at a high cooling rate when cooling water is supplied onto an upper surface of the steel plate or sheet.

Disclosure of Invention

In order to overcome the above-described problems, the present invention has the following features:

1. Steel-plate or sheet cooling equipment characterized in that cooling water is supplied onto upper and lower surfaces of a steel plate or sheet that is passing during hot rolling, in that nozzles are provided to obliquely supply the cooling water onto the upper surface of the steel plate or sheet from above, and in that a plurality of rows of the nozzles are provided so as to eject jets of the cooling water opposing each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
Herein, the supply of cooling water during hot rolling of the steel plate or sheet means that hot rolling is performed once or more after cooling, or that cooling is performed once or more by supplying the cooling water after the cooling and rolling.
2. The steel-plate or sheet cooling equipment according to the above 1, wherein cooling equipment is provided close to a reversing rolling mill for subjecting the steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, and the cooling equipment supplies the cooling water onto the upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling.
3. The steel-plate or sheet cooling equipment according to the above 1 or 2, wherein the nozzles eject rodlike jets of cooling water.
4. The steel-plate or sheet cooling equipment according to the above 3, wherein a header to which the nozzles for ejecting the rodlike jets of cooling water are connected is provided above the steel plate or sheet, and the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the steel plate or sheet is 30° to 60°.
5. The steel-plate or sheet cooling equipment according to the above 4, wherein three or more rows of the nozzles, preferably, five or more rows of the nozzles are arranged in each of the transferring direction of the steel plate or sheet and a direction opposite the transferring direction, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
6. The steel-plate or sheet cooling equipment according to any of the above 3 to 5, wherein jet directions of the rodlike jets of cooling water are set so that 0 to 35% of jet velocity components of the rodlike jets of cooling water head outward in a steel-plate or sheet width direction perpendicular to the transferring direction.
7. The steel-plate or sheet cooling equipment according to the above 6, wherein the jet directions of the rodlike jets of cooling water are set so that jet velocity components of the same number of rodlike jets of cooling water as 40 to 60% of the total number of nozzles that eject the rodlike jets of cooling water head in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction.
8. The steel-plate or sheet cooling equipment according to the above 6, wherein the jet directions of the rodlike jets of cooling water are set so that the number of rodlike jets of cooling water having components heading in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction is equal to the number of rodlike jets of cooling water having components heading in the other direction
9. The steel-plate or sheet cooling equipment according to the above 6, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction gradually increase as positions of the nozzles are shifted outward from the center in the steel-plate or sheet width direction.
10. The steel-plate or sheet cooling equipment according to the above 6, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction are fixed and so that positions where the rodlike jets of cooling water strike the steel plate or sheet are equally spaced in the steel-plate or sheet width direction.
11. The steel-plate or sheet cooling equipment according to any of the above 3 to 8, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other, and/or above remaining cooling water.
12. The steel-plate or sheet cooling equipment according to the above 11, wherein the lowermost end of the shield provided above the innermost rows of rodlike jets of cooling water opposing each other is disposed 300 to 500 mm above from the upper surface of the hot rolled steel plate or sheet.
13. The steel-plate or sheet cooling equipment according to the above 2, wherein a cooling area of the cooling equipment is provided at a position close to the reversing rolling mill, the position excluding a portion between the reversing rolling mill and a side guide provided on the entrance side and/or the exit side of the reversing rolling mill.
14. The steel-plate or sheet cooling equipment according to the above 13, wherein the cooling area of the cooling equipment is provided at a position on an upstream side of a side guide disposed on the entrance side of the reversing rolling mill and close to the reversing rolling mill, and/or at a position on a downstream side of a side guide disposed on the exit side of the reversing rolling mill and close to the reversing rolling mill.
15. A steel-plate or sheet cooling method for supplying cooling water onto upper and lower surfaces of a steel plate or sheet while the steel plate or sheet is passing during hot rolling, wherein the cooling water is obliquely supplied onto the upper surface of the steel plate or sheet from above by nozzles arranged so as to eject jets of cooling water opposing each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
16. The steel-plate or sheet cooling method according to the above 15, wherein cooling equipment is provided on an entrance side and/or an exit side of a reversing rolling mill for subjecting the steel plate or sheet to hot rolling and close to the reversing rolling mill, and the cooling water is supplied from the cooling equipment onto the upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling.
17. The steel-plate or sheet cooling method according to the above 15 or 16, wherein the nozzles eject rodlike jets of cooling water.
18. The steel-plate or sheet cooling method according to the above 17, wherein a header to which the nozzles for ejecting the rodlike jets of cooling water are connected is provided above the steel plate or sheet, and cooling is performed while the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the hot rolled steel plate or sheet is 30° to 60°.
19. The steel-plate or sheet cooling method according to the above 18, wherein three or more rows of the nozzles, preferably, five or more rows of the nozzles are arranged in each of the transferring direction of the hot rolled steel plate or sheet and a direction opposite the transferring direction, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
20. The steel-plate or sheet cooling method according to any of the above 15 to 19, wherein jet directions of the rodlike jets of cooling water are set so that 0 to 35% of jet velocity components of the rodlike jets of cooling water head outward in a steel-plate or sheet width direction perpendicular to the transferring direction.
21. The steel-plate or sheet cooling method according to the above 20, wherein the jet directions of the rodlike jets of cooling water are set so that jet velocity components of the same number of rodlike jets of cooling water as 40 to 60% of the total number of nozzles that eject the rodlike jets of cooling water head in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction.
22. The steel-plate or sheet cooling method according to the above 20, wherein the jet directions of the rodlike jets of cooling water are set so that the number of rodlike jets of cooling water having components heading in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction is equal to the number of rodlike jets of cooling water having components heading in the other direction.
23. The steel-plate or sheet cooling method according to the above 20, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction gradually increase as positions of the nozzles are shifted outward from the center in the steel-plate or sheet width direction.
24. The steel-plate or sheet cooling method according to the above 20, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction are fixed and so that positions where the rodlike jets of cooling water strike the steel-plate or sheet are equally spaced in the steel-plate or sheet width direction.
25. The steel-plate or sheet cooling method according to any of the above 15 to 19, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other, and/or above remaining cooling water.
26. The steel-plate or sheet cooling method according to the above 25, wherein the lowermost end of the shield provided above the innermost rows of rodlike jets of cooling water opposing each other is disposed 300 to 500 mm above from the upper surface of the steel plate or sheet.
27. The steel-plate or sheet cooling method according to the above 16, wherein a cooling area of the cooling equipment is provided at a position close to the reversing rolling mill, the position excluding a portion between the reversing rolling mill and a side guide provided on the entrance side and/or the exit side of the reversing rolling mill.
28. The steel-plate or sheet cooling method according to the above 27, wherein the cooling area of the cooling equipment is provided at a position on an upstream side of a side guide disposed on the entrance side of the reversing rolling mill and close to the reversing rolling mill, and/or at a position on a downstream side of a side guide disposed on the exit side of the reversing rolling mill and close to the reversing rolling mill.
29. Steel-plate or sheet hot rolling equipment characterized in that cooling equipment is provided close to a reversing rolling mill for subjecting a steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, and the cooling equipment supplies cooling water onto upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling, in that the cooling equipment provided above the upper surface includes nozzles for obliquely supplying the cooling water onto the steel plate or sheet from above, and in that the nozzles are arranged so that jets of the cooling water oppose each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
30. The steel-plate or sheet hot rolling equipment according to the above 29, wherein the nozzles eject rodlike jets of cooling water.
31. The steel-plate or sheet hot rolling equipment according to the above 29 or 30, wherein a cooling area of the cooling equipment is provided between the reversing rolling mill and a side guide disposed on the entrance side and/or the exit side of the reversing rolling mill.
32. A steel-plate or sheet hot rolling method characterized in that cooling equipment is provided close to a reversing rolling mill for subjecting a steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, in that cooling water is supplied by the cooling equipment onto upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling, and in that the cooling water is obliquely supplied onto the upper surface of the steel plate or sheet from above by nozzles arranged so as to eject jets of cooling water opposing each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
33. The steel-plate or sheet hot rolling method according to the above 32, wherein the nozzles eject rodlike jets of cooling water.
34. The steel-plate or sheet hot rolling method according to the above 32 or 33, wherein a cooling area of the cooling equipment is provided between the reversing rolling mill and a side guide disposed on the entrance side and/or the exit side of the reversing rolling mill.
35. Steel-plate or sheet cooling equipment characterized in that a header to which nozzles for ejecting rodlike jets of cooling water at a water flow rate of 4 m³/m²min or more are connected is provided above a hot rolled steel plate or sheet, and in that the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the hot rolled steel-plate or sheet is 30° to 60° and so that the nozzles oppose each other in a transferring direction of the hot rolled steel plate or sheet.
36. The steel-plate or sheet cooling equipment according to the above 35, wherein five or more rows of the nozzles are arranged in the transferring direction of the hot rolled steel plate or sheet, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
37. The steel-plate or sheet cooling equipment according to the above 35 or 36, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other.
38. The steel plate or sheet cooling equipment according to the above 37, wherein the lowermost end of the shield is disposed 300 to 500 mm above from an upper surface of the hot rolled steel plate or sheet.
39. A steel plate or sheet cooling method characterized in that a header to which nozzles for ejecting rodlike jets of cooling water at a water flow rate of 4 m³/m²min or more are connected is provided above a hot rolled steel plate or sheet, and in that the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the hot rolled steel plate or sheet is 30° to 60° and so that the nozzles oppose each other in a transferring direction of the hot rolled steel plate or sheet.
40. The steel plate or sheet cooling method according to the above 39, wherein five or more rows of the nozzles are arranged in the transferring direction of the hot rolled steel plate or sheet, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
41. The steel plate or sheet cooling method according to the above 39 or 40, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other.
42. The steel plate or sheet cooling method according to the above 41, wherein the lowermost end of the shield is disposed 300 to 500 mm above from an upper surface of the hot rolled steel plate or sheet.

Since the cooling water is supplied onto the upper and lower surfaces of the steel plate or sheet while the steel plate or sheet is passing in the present invention, the length of the equipment is short. Moreover, since the nozzles are arranged so that jets of cooling water oppose each other on the steel plate or sheet in the transferring direction, the supplied cooling water itself dams remaining cooing water on the steel plate or sheet, and draining can be performed without an additional device such as a damming rolls. As a result, for example, during controlled rolling of a steel plate or sheet, the steel plate or sheet can be properly cooled with a compact size on the hot rolling line.
In the present invention, since the pass-type cooling equipment having a high water flow rate of 4 m³/m²min or more is disposed close to the reversing rolling mill, the predetermined controlled rolling start temperature can be efficiently obtained by simultaneously rolling and cooling the steel plate or sheet, and this avoids the decrease in rolling productivity due to, for example, waiting for cooling. Further, the nozzles are arranged so that the jets of cooling water oppose each other in the transferring direction on the steel plate or sheet, and the cooling water is supplied at a high water flow rate of 4 m³/m²min or more. Therefore, the supplied cooling water itself dams the remaining cooling water on the steel plate or sheet and properly performs draining. This achieves a stable cooling area.
As a result, the steel plate or sheet is uniformly cooled during controlled rolling, and a high product quality is obtained. In addition, the reduction in rolling productivity due to, for example, waiting for cooling can be prevented.
The present invention allows the steel plate or sheet to be uniformly cooled to the target temperature at a high cooling rate. As a result, a high-quality steel plate or sheet can be produced.

Brief Description of the Drawings

Fig. 1 is a layout view of hot rolling equipment for a steel plate or sheet according to a first embodiment of the present invention.
Fig. 2 is an explanatory view of the cooling equipment in the first embodiment of the present invention.
Fig. 3 is a detailed view of the cooling equipment in the first embodiment of the present invention.
Fig. 4 includes views showing layout examples of nozzles in an upper header in the first embodiment of the present invention.
Fig. 5 is an explanatory view of another cooling equipment in the first embodiment of the present invention.
Fig. 6 is an explanatory view of cooling equipment for a steel plate or sheet according to a second embodiment of the present invention.
Fig. 7 is an explanatory view of another cooling equipment for a steel plate or sheet according to the second embodiment of the present invention.
Fig. 8 is an explanatory view showing the jet direction in the second embodiment of the present invention.
Fig. 9 is an explanatory view of cooling equipment according to a third embodiment of the present invention.
Fig. 10 is a view, as viewed from the direction of arrow A-A in Fig. 4.
Fig. 11 is an explanatory view of another cooling equipment according to the third embodiment of the present invention.
Fig. 12 is a view explaining splashed cooling water.
Fig. 13 is a comparative graph of the rolling time in an example of the present invention.
Fig. 14 is an explanatory view showing a hot rolling line for a thick steel plate and conveyance patterns in the example of the present invention.
Fig. 15 is a view showing a problem of the related art.
Fig. 16 is a detailed view of cooling equipment according to another embodiment of the present invention.
Fig. 17 is an explanatory view of another cooling equipment according to the third embodiment of the present invention.

(Reference Numerals)

10: steel plate or sheet, 13: table roller, 21: upper header unit, 21a: first upper header, 21b: second upper header, 22a, first upper nozzle, 22b: second upper nozzle, 23a: rodlike jet of cooling water, 23b: rodlike jet of cooling water, 24: remaining cooling water, 31: lower header, 32: lower nozzle, 33: rodlike jet of cooling water, 25: splashed cooling water, 26a: shielding plate, 26b: shielding plate, 27a: cylinder, 27b: cylinder, 28a; shielding curtain, 28b: shielding curtain, 29: shielding plate, 40: cooling unit, 51: cooling header, 52: slit nozzle, 53: cooling water film, 60: deposit, 61: side guide, 20: cooling equipment

(cooling unit)

Best Mode for Carrying Out the Invention

Embodiments of the present invention will be described with reference to the drawings.

(First Embodiment)

Fig. 1 is a layout view of hot rolling equipment for a steel plate or sheet according to an embodiment of the present invention. As shown in Fig. 1, a reheating furnace 11, a reversing rolling mill 12, and cooling equipment 20 are arranged in this embodiment. The cooling equipment 20 is provided close to each of the entrance side (upstream side) and the exit side (downstream side) of the reversing rolling mill 12. The cooling equipment (also referred to as a cooling unit) 20 is pass-type cooling equipment, and includes an upper header unit 21 for supplying cooling water onto an upper surface of a steel plate or sheet 10 and a lower header 31 for supplying cooling water onto a lower surface of the steel plate or sheet 10, as shown in Fig. 2. In Figs. 1 and 2, reference numeral 13 denotes a table roller.
Figs. 3 and 16 are detailed views of the cooling equipment 20. The cooling equipment 20 is provided between the reversing rolling mill 12 and a side guide 14 in Fig. 3, and is provided on the upstream side (a reheating furnace side) of the side guide 14 and near the reversing rolling mill 12 in Fig. 16. In any case, the cooling equipment 20 includes the upper header unit 21 and the lower header 31, as described above.
The upper header unit 21 includes a pair of upper headers 21a and 21b. Herein, an upper header close to the reversing rolling mill 12 is referred to as a first upper header 21a, and an upper header remote from the reversing rolling mill 12 is referred to as a second upper header 21b.
The first upper header 21a and the second upper header 21b are respectively provided with cylindrical nozzles 22a and 22b arranged in the width direction of the steel plate or sheet. The cylindrical nozzles 22a and 22b are also arranged in a plurality of rows in the transferring direction (herein, six rows in the transferring direction of the steel plate or sheet 10). The cylindrical nozzles (first upper nozzles) 22a of the first upper header 21a and the cylindrical nozzles (second upper nozzles) 22b of the second upper header 21b are arranged so that rodlike jets of cooling water supplied from the nozzles 22a and rodlike jets of cooling water supplied from the nozzles 22b oppose each other in the transferring direction of the steel plate or sheet 10. That is, the first upper nozzles 22a eject rodlike jets of cooling water 23a at an inclination θ1 (jet angle) from the side of the reversing rolling mill 12, and the second upper nozzles 22b eject rodlike jets of cooling water 23b at an inclination θ2 (jet angle) toward the reversing rolling mill 12.
Incidentally, a rodlike jet of cooling water (also referred to as a columnar jet of cooling water) in the present invention refers to cooling water jetted from a nozzle opening having a circular shape (including elliptical and polygonal shapes). Further, the rodlike jet flow of cooling water in the present invention does not refer to a spray jet, but refers to a continuous and straight flow of cooling water having a cross section kept substantially circular while the flow heads from the nozzle opening to the steel plate or sheet.
Therefore, a region provided between the positions where rodlike jets of cooling water from the cylindrical nozzles in the rows (outermost rows) farthest from the opposite upper headers strike the steel plate or sheet 10 serves as a cooling area.
In this case, the remaining cooling water 24 shown in Figs. 3 and 16 is stably formed by preventing the jet lines of rodlike jets of cooling water 23a from the first upper nozzles 22a from intersecting the jet lines of rodlike jets of cooling water 23b from the second upper nozzle 22b. Consequently, rodlike jets of cooling water are ejected from the cylindrical nozzles in rows (innermost rows) closest to the opposite upper headers toward the film of remaining cooling water 24. This is preferable because the rodlike jets of cooling water from the nozzles do not break the rodlike jets of cooling water from the nozzles in the opposite upper header. In a case in which the distance between the positions where rodlike jets of cooling water from the cylindrical nozzles in the innermost rows strike the steel plate or sheet 10 is referred to as a remaining region length, when the remaining region length is 1.5 m or less, the effect of the remaining water 24 will be relatively low in cooling of the steel plate or sheet 10. Therefore, it is possible to prevent non-uniform cooling at the leading or tail end of the steel plate or sheet 10, on which remaining water is unsteady.
Figs. 4A and 4B show layout examples of the cylindrical nozzles 22a and 22b attached to the upper headers 21a and 21b. As described above, the cylindrical nozzles 22a are arranged in six rows in the transferring direction of the steel plate or sheet 10, and the cylindrical nozzles 22b are arranged in six rows in the transferring direction. A plurality of rows are arranged in the transferring direction because only one row of nozzles can not dam the remaining cooling water between the jet collision spots on the steel plate or sheet 10. Therefore, it is preferable that three or more rows be arranged in the transferring direction. It is more preferable that five or more rows be arranged. The cylindrical nozzles are arranged in the plate or sheet width direction so that cooling water can be supplied over the entire width of the passing steel plate or sheet 10. While two upper headers are provided herein, they may be combined into one header, and the cylindrical nozzles 22a and 22b may be arranged in the header.
Two lower headers 31 are arranged. Cylindrical nozzles 32 are attached to each lower header 31 so as to eject rodlike jets of cooling water 33 from between the table rollers 13 and to supply the cooling water over the entire width of the passing steel plate or sheet 10.
In the cooling equipment 20, cooling water is supplied from the upper headers 21a and 21b onto the upper surface of the steel plate or sheet 10 so that the water flow rate on the steel plate or sheet surface is 4 m³/m²min or more. Similarly, cooling water is supplied from the lower headers 31 onto the lower surface of the steel plate or sheet 10 so that the water flow rate on the steel plate or sheet surface is 4 m³/m²min or more.
A description will be given of the reason why the water flow rate is set at 4 m³/m²min or more. The remaining cooling water 24 shown in Figs. 3 and 16 is formed by being dammed by the supplied rodlike jets of cooling water 23a and 23b. In this case, when the water flow rate is low, damming is impossible. When the water flow rate exceeds a certain rate, the amount of remaining cooling water 24 can be dammed and drained from the widthwise edge of the plate or sheet smoothly. Generally, a steel plate or sheet steel plate or sheet has a width of 2 to 5 m. By cooling the steel plate or sheet at a water flow rate of 4 m³/m²min or more, a volume of remaining cooling water can be constant, and a desired temperature drop can be obtained uniformly over the whole part of the steel plate or sheet 10 in passing during rolling.
As the water flow rate increases above 4 m³/m²min, the total waiting time for controlled rolling becomes shorter. For example, when the water flow rate is low, waiting for cooling can be avoided only in a thin plate rolling. By increasing the water flow rate, waiting for cooling can be avoided even in thicker plate rolling. The effect of reducing the total waiting time for controlled rolling becomes smaller at a higher water flow rate increases. Therefore, it is preferable to determine the water flow rate in consideration of the effect of reducing the total waiting time for controlled rolling and the equipment cost. A more preferable water flow rate is 4 to 10 m³/m²min.
In order to provide the cooling equipment 20 with a compact size and to cool the steel plate or sheet at the position close to the reversing rolling mill 12, the cooling equipment 20 is located so that the remaining region length is 1.5 m or less, the cooling area is 3 m or less, and the cooling equipment 20 is disposed at a position close to the reversing rolling mill 12, excluding the side guide provided on the entrance side and/or the exit side of the reversing rolling mill 12. In general, this position is set at a distance of 20 m or less from a work roll center 12a of the reversing rolling mill 12. By forming the cooling area outside the side guide so as not to overlap with the side guide, cooling water remaining on the upper surface of the steel plate or sheet 10 is smoothly drained from the widthwise edges of the steel plate or sheet 10 without being obstructed by the side guide 14.
In this case, as shown in Fig. 3, it is preferable, in effectively improving the rolling productivity, to place the cooling equipment 20 so that the cooling area is provided between the work roll center 12a of the reversing rolling mill 12 and the side guide (at a distance of about 2 to 4 m from the work roll center 12).
In contrast, the cooling area of the cooling equipment 20 may be provided close to the reversing rolling mill 12 on the upstream side of the side guide 14 disposed on the entrance side of the reversing rolling mill 12, or close to the reversing rolling mill 12 on the downstream side of the side guide 14 disposed on the exit side of the reversing rolling mill 13, as shown in Fig. 16. In this case, a large cooling equipment with a long cooling area can be set in a wide space.
It is needless to say that the cooling area can be provided between the work roll center 12a of the reversing rolling mill 12 and the side guide 14, and on the upstream side of the side guide 14 shown in Fig. 16.
In the cooling equipment 20, the rodlike jets of cooling water 23a ejected from the first upper nozzles 22a oppose the rodlike jets of cooling water 23b ejected from the second upper nozzles 22b in the transferring direction of the steel plate or sheet 10. Therefore, the ejected rodlike jets of cooling water 23a and 23b dam the remaining cooling water 24 on the upper surface of the steel plate or sheet 10 that attempts to flow out of water cooling area. Consequently, even when the cooling water is supplied at a high water flow rate of 4 m³/m²min or more, a stable cooling area can be obtained, and uniform cooling can be performed.
The cooling water ejected from the upper nozzles 22a and 22b is not in a film shape obtained by using slit nozzles or the like, but is in a rod shape because the rodlike jet of cooling water can form a more stable flow and has a stronger force for damming the remaining cooling water.
In a case in which a cooling water film is obliquely jetted, when the distance from the steel plate or sheet to the nozzle is long, the thickness of a water film near the steel plate or sheet becomes small, and the film is more easily broken.
In this case, it is preferable that the jet angle θ1 of the first upper nozzles 22a and the jet angle θ2 of the second upper nozzles 22b be 30° to 60°. If the jet angle θ1 and the jet angle θ2 are less than 30°, it is necessary to place the first upper nozzles 22a and the second upper nozzles 22b far apart from each other, and the length of the equipment increases. Moreover, vertical velocity components of the rodlike jets of cooling water 23a and 23b decrease, the rodlike jets of cooling water 23a and 23b do not strike the steel plate or sheet 10 hard, and the cooling ability is reduced. If the jet angle θ1 and the jet angle θ2 are more than 60°, the velocity components of the rodlike jets of cooling water 23a and 23b in the transferring direction decrease, and the force for damming the remaining cooling water 24 decreases. The jet angle θ1 and the jet angle θ2 do not always need to be equal to each other. More preferably, the jet angle θ1 and the jet angle θ2 are set at 40° to 50°.
In order to obtain a desired cooling ability and a desired draining ability, it is preferable that five or more rows of upper nozzles 22a and five or more rows of upper nozzles 22b be arranged in the transferring direction of the steel plate or sheet and the direction opposite the transferring direction, and that the jet velocity of the rodlike jets of cooling water 23a and 23b from the upper nozzles 22a and 22b be 8 m/s or more.
In order to achieve perfect draining, it is preferable that a plurality of rows, at least three rows of nozzles for jetting the cooling water be provided in the transferring direction and the direction opposite the transferring direction. More preferably, at least five rows are provided. The upper limit of number of rows can be appropriately determined in accordance with the size of the steel plate or sheet to be cooled, the transferring speed, and the target temperature drop.
When the jet velocity exceeds 30 m/s, pressure loss increases, and wear of the nozzle inner surface increases. Further, the pump capacity and the outer diameter of the pipes increase, and the equipment cost becomes too high. For this reason, it is preferable that the jet velocity be 30 m/s or less.
In order to suppress nozzle clogging and to ensure the jet velocity of cooling water, it is satisfactory as long as the nozzle inner diameter is within the range of 3 to 8 mm. Further, in order to prevent the cooling water from flowing out from between the rodlike jets of cooling water, the distance between the nozzles adjacent on an imaginary line drawn in the plate width direction is set to be ten times the nozzle inner diameter or less.
Fig. 4A shows a layout example in which six rows of nozzles are provided in the transferring direction while the distance between the adjacent nozzles is 40 mm, and Fig. 4B shows a layout example in which four rows of nozzles are provided in the transferring direction while the distance between the adjacent nozzles is 40 mm and two rows of nozzles are provided in the transferring direction while the distance between the adjacent nozzles is 20 mm.
In order to prevent the upper nozzles 22a and 22b from being damaged, for example, by warping of the steel plate or sheet 10, it is preferable that the leading ends of the upper nozzles 22a and 22b be apart from the pass line. However, if the leading ends are too apart, cooling water is dispersed. Therefore, it is preferable that the distance between the leading ends of the upper nozzles 22a and 22b and the pass line be 500 to 1800 mm.
When controlled rolling is performed with the steel-plate or sheet hot rolling equipment having the above-described configuration, a steel plate or sheet, which passes through the cooling area of the cooling equipment 20 before and/or during and/or after rolling, is rolled by the reversing rolling mill 12 while being cooled by the cooling equipment 20 so that a predetermined controlled rolling start temperature (e.g. 850°C or less) is achieved at a predetermined controlled rolling start thickness (e.g., 1.5 to 2 times the final thickness). After the predetermined controlled rolling start temperature is achieved at the predetermined controlled rolling start thickness, the steel plate or sheet is further rolled to the final thickness (e.g., 15 mm) without being cooled by the cooling equipment 20.
It is unnecessary to perform cooling by the cooling equipment 20 on the entrance and exit sides in all rolling paths until the controlled rolling start temperature is obtained. The cooling equipment (also referred to as a cooling unit) 20 is appropriately turned on and off so that the predetermined controlled rolling start temperature is obtained at the predetermined controlled rolling start thickness.
While at least one cooling equipment (cooing units) 20 including a pair of upper headers 21a and 21b, as shown in Fig. 2, is provided in the above-described embodiment, an intermediate header 21c can be provided between the upper headers 21 and 21b, as shown in Fig. 5, in order to obtain a higher cooling ability by combining the cooling units to some extent. Any number of upper headers can be adopted.
While the cooling equipment 20 is provided on each of the entrance side and the exit side of the reversing rolling mill 12, it may be provided on one of the sides.
Since the cooling water is thus supplied to the upper and lower surfaces of the passing steel plate or sheet 10 in this embodiment, the length of the equipment is short. Further, since the upper nozzles 22a and 22b are arranged so that the jets of cooling water oppose each other in the transferring direction on the steel plate or sheet 10, the supplied rodlike jets of cooling water 23a and 23b themselves dam the remaining cooling water 24 on the steel plate or sheet 10, thus performing draining. Draining is properly performed without any additional device such as a damming rolls. As a result, the steel plate or sheet can be properly cooled with a compact structure on the hot rolling line, for example, during controlled rolling.
In this embodiment, the pass-type cooling equipment 20 having a high water flow rate of 4 m³/m²min or more is disposed close to the reversing rolling mill 12, the predetermined control temperature can be efficiently obtained by simultaneously rolling and cooling the steel plate or sheet 10, and this avoids the reduction in rolling productivity due to, for example, waiting for cooling. Further, the cylindrical nozzles 22a and 22b are arranged so that the jets of cooling water therefrom oppose each other in the transferring direction on the steel plate or sheet 10, and the cooling water is supplied at a high water flow rate of 4 m³/m²min or more. Therefore, the rodlike jets of cooling water 23a and 23b themselves dam the remaining cooling water 24 on the steel plate or sheet 10 and properly perform draining. This achieves a stable cooling area.
As a result, the steel plate or sheet is uniformly cooled during controlled rolling, and a high product quality can be obtained. Moreover, the rolling productivity is prevented from being reduced by, for example, waiting for cooling.
While the rodlike jets of cooling water having a water flow rate of 4 m³/m²min or more on the steel plate or sheet surface is supplied onto the lower surface of the steel plate or sheet in the above-described embodiment, the present invention is not limited thereto. The cooling water may have any shape that can be supplied at the water flow rate of 4 m³/m²min or more on the steel plate or sheet surface, for example, a cooling water film ejected from a slit nozzle, or cooling water sprayed by a spray nozzle.
In this embodiment, the upper headers 21a and 21b are provided above the steel plate or sheet 10, and the upper nozzles 22a and 22b that eject rodlike jets of cooling water at a water flow rate of 4 m³/m²min or more are connected to the upper headers 21a and 21b. The inclinations θ1 and θ2 formed by the rodlike jets of cooling water 23a and 23b and the steel plate or sheet 10 are 30° to 60°, the upper nozzles 22a and 22b are disposed so as to oppose each other in the transferring direction of the steel plate or sheet 10, and cooling water is supplied onto the upper surface of the passing steel plate or sheet 10. Therefore, by installing the cooling equipment in the hot rolling line for a thick steel plate or sheet or a thin steel plate or sheet, the steel plate or sheet can be uniformly and stably cooled to the target temperature at a high cooling rate. As a result, a high-quality steel plate or sheet can be produced.

(Second Embodiment)

In steel-plate or sheet cooling equipment according to a second embodiment of the present invention, the jet directions of rodlike jets of cooling water 23a and 23b are set so that 0 to 35% of the velocity components in the jet directions of the rodlike jets of cooling water 23a and 23b in the first embodiment shown in Fig. 2 head outward in the steel-plate or sheet width direction.
As shown in Figs. 6 and 7, when the jet directions of rodlike jets of cooling water 23a and 23b are set so that 0 to 35% of the velocity components in the jet directions of the rodlike jets of cooling water 23a and 23b head outward in the steel-plate or sheet width direction, the cooling water jetted from the upper nozzles 22a and the cooling water ejected from 22b onto the upper surface of the steel plate or sheet 10 merge together and promptly drop from the widthwise edges of the steel plate or sheet 10, as shown by arrows A in Figs. 6 and 7. Therefore, remaining cooling water 24 can be dammed with a smaller amount of water for draining than when there are not velocity components heading outward in the steel plate or sheet width direction. This is preferable in energy cost reduction. A more preferable range of ratio of the velocity components is 10 to 35%. Incidentally, when the ratio exceeds 35%, the equipment cost increases so as to prevent splash of the cooling water, and the vertical components of the rodlike jets of cooling water decrease. This reduces the cooling ability.
It is preferable that the jet directions of the rodlike jets of cooling water be set so that the jet velocity components of the rodlike jets of cooling water from 40 to 60% of all nozzles that eject the rodlike jets of cooling water include components that head in one of the two directions pointing outward in the steel-plate width direction perpendicular to the transferring direction. More specifically, if the number of nozzles pointing in one outward direction is 60% or more of the total number of nozzles and the cooling water is not uniformly drained from the plate or sheet ends, the rodlike jets of cooling water cannot dam the remaining cooling water at a position where the layer of the remaining cooling water is thick, and the temperature may vary in the width direction. Moreover, if the amount of splashed water extremely increases on the one outer side, the equipment cost for preventing the increase rises.
Even when jet nozzles that do not point outward in the width direction are placed at the widthwise center, as shown in Fig. 6, the remaining cooling water is smoothly drained by setting the number of nozzles at 20% or less of the total number of nozzles, and setting the number of nozzles pointing in one outward direction, of the remaining nozzles, so as to be substantially equal to the number of nozzles pointing in the other outward direction. This is most suitable for damming and draining of the remaining cooling water.
A specific description will now be given of the above-described setting of the jet directions of the rodlike jets of cooling water.

That is, Fig. 8 shows the jet direction of a rodlike jet of cooling water. The angle (substantial inclination) formed between the jet line of the rodlike jet of cooling water and the steel plate or sheet is designated as β, the inclination with respect to the transferring direction is designated as θ, and the angle (outward angle) at which the cooling water heads outward in the steel-plate or sheet width direction is designated as α. To cause 0 to 35% of the jet velocity components of the rodlike jets of cooling water to head outward in the steel-plate or sheet width direction means that the ratio Lw/L (width-direction velocity component ratio) of the widthwise component of the steel plate or sheet to the jet length L of the cooling water is set at 0 to 35%. Table 1 shows the calculation results obtained when the height h of the nozzle opening is 900 mm and the inclination θ with respect to the transferring direction is 45° and 50°. The width-direction velocity component ratio is 0 to 35% when the inclination θ with respect to the transferring direction is 45° and the outward angle α is 0 to 25°, and when the inclination θ with respect to the transferring direction is 50° and the outward angle α is 0 to 30°. A preferable ratio of the jet velocity component in the steel-plate or sheet width direction is 10 to 25%.

Table 1

Nozzle Height h		mm		900	900	900	900	900	900	900	900	900	900	900	900
Inclination θ	Transferring Direction	deg	45	45	45	45	45	45	50	50	50	50	50	50
β	Substantial	deg	45	44.56	44.01	43.22	42.19	40.89	50	49.57	49.02	48.24	47.21	45.9
Outward Angle α	Outward Direction	deg		0	10	15	20	25	30	0	10	15	20	25	30
Jet Length Lv	Transferring-Direction Component	mm		900	900	900	900	900	900	755.2	755.2	755.2	755.2	755.2	755.2
Lw	Steel-Plate or Sheet Width-Direction Component	mm		0	158.7	241.2	327.6	419.7	519.6	0	133.2	202.4	274.9	352.2	436
Lp	Projection Length on Steel Plate or Sheet Surface	mm		900	913.9	931.7	957.8	993	1039	755.2	766.8	781.8	803.7	833.3	872
L	Substantial Length	mm	1273	1283	1295	1314	1340	1375	1175	1182	1192	1207	1227	1253
Steel-Plate or Sheet Width-Direction Velocity Component Ratio (Lw/L)		%	0	12.4	18.6	24.9	31.3	37.8	0	11.3	17.0	22.8	28.7	34.8
Transferring-Direction Velocity Component Ratio (Lv/L)		%	70.7	70.1	69.5	68.5	67.2	65.5	64.3	63.9	63.4	62.6	61.5	60.3

Fig. 6 described above is a plan view showing an example when the upper nozzles 22a and 22b are arranged according to the above. Herein, the outward angle α of a rodlike jet of cooling water from the center nozzle in the steel-plate or sheet width direction is 0°, and the outward angle α gradually increases as the nozzle setting position is shifted outward in the steel-plate or sheet width direction. The nozzles are disposed so that the positions where the rodlike jets of cooling water strike the steel plate or sheet are equally spaced (e.g., a pitch of 60 mm) in the steel-plate or sheet width direction.
Fig. 7 described above is a plan view showing another example in which the upper nozzles 22a and 22b are arranged according to the above. Herein, the outward angle α of rodlike jets of cooling water is fixed (e.g., 20°), and the nozzles are disposed so that the positions where the rodlike jets of cooling water strike the steel plate or sheet are equally spaced (e.g., a pitch of 60 mm) in the steel-plate or sheet width direction. In this case, nozzles that eject cooling water in both the rightward and leftward directions need to be disposed near the center in the steel-plate or sheet width direction. Therefore, in order that holes in which the nozzles are mounted can be bored, rows of nozzles that eject cooling water outward in one steel-plate or sheet width direction (e.g., rows of nozzles having an upward jet component in Fig. 7) and rows of nozzles that eject cooling water outward in the other steel-plate or sheet width direction (e.g., rows of nozzles having a downward jet component in Fig. 7) are alternately arranged so as to be shifted by a predetermined distance (e.g., 20 mm) in the transferring direction. Further, the number of rodlike jets of cooling water having components heading in one of the two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction is equal to the number of rodlike jets of cooling water having components heating in the other direction. More specifically, the number of nozzles that eject rodlike jets of cooling water having components heading toward one outer side in the steel-plate or sheet width direction perpendicular to components in the steel-plate or sheet width direction is equal to the number of nozzles that eject rodlike jets of cooling water having components heading toward the other outer side.
Although draining can be performed with less water by increasing the outward angle α, the range in which the nozzle density is high is increased near the center in the steel-plate or sheet width direction, as shown in Figs. 6 and 7. The outward angle α is determined in consideration of the ability of a pump that supplies water to the headers and the thickness of pipes so as to obtain a uniform flowrate distribution in the steel-plate or sheet width direction.
Preferably, a wall and a drain hole are provided on each outer side of the above-described cooling equipment. This is effective in preventing the cooling water from leaking out of the equipment and splashing inside the equipment to form remaining water.
It is not preferable that the outward angle α exceed 30°. This is because the equipment cost rises in order to prevent splash of the cooling water, the vertical components of the rodlike jets of cooling water decrease, and this reduces the cooling ability.

(Third Embodiment)

In the above-described first embodiment, when the jet velocity of the rodlike jets of cooling water 23a and 23b from the opposing upper nozzles 22a and 22b is high, for example, 10 m/s or more, the rodlike jets of cooling water 23a and 23b strike the steel plate or sheet 10, and then splash upward while striking each other. When splashed cooling water drops on the remaining cooling water 24, there is no problem. However, when the splashed cooling water 25 splashes in the obliquely upward direction and drops on the rodlike jets of cooling water 23a and 23b, as shown in Fig. 7, it leaks from between the rodlike jets of cooling water 23a and 23b, and complete draining is sometimes impossible. This problem easily occurs particularly when the remaining region length L is 200 mm or less. Further when the jet velocity of cooling water is high, the splashed cooling water 24 sometimes drops onto the steel plate or sheet 10 beyond the upper headers 21a and 21b.
In contrast, in cooling equipment according to a third embodiment, a cooling unit 40 is adopted instead of the cooling unit 20 adopted in the first embodiment shown in Fig. 1. In the cooing unit 40, shielding plates 26a and 26b are added above the innermost rows of rodlike jets of cooling water, as shown in Fig. 9 as a side view and Fig. 10 as a view taken from the direction of arrow A-A in Fig. 9.
In this case, even when splashed cooling water 25 splashes in the obliquely upward direction and drops, it is shielded by the shielding plates 26a and 26b, and drops on remaining cooling water 24 without dropping on the rodlike jets of cooling water 23a and 23b. Therefore, draining can be performed accurately.
The shielding plates 26a and 26b can be respectively moved up and down by cylinders 27a and 27b. The shielding plates 26a and 26b can be used only during product manufacturing, and can be raised to upper retracted positions in other cases.
Incidentally, when the shielding plates 26a and 26b are used, it is preferable that the lowermost edges of the shielding plates 26a and 26b be disposed 300 to 500 mm above from an upper surface of a steel plate or sheet 10. That is, when the lowermost edges are disposed 300 mm or more above from the upper surface of the steel plate or sheet 10, even if a steel plate or sheet that is warped upward at the leading or tail end enters, it does not collide with the shielding plates 26a and 26b. However, when the height from the upper surface of the steel plate or sheet 10 exceeds 500 mm, it is impossible to sufficiently shield the splashed cooling water 25.
The shielding plates 26a and 26b shown in Fig. 9 may be replaced with light shielding curtains 28a and 28b having a smooth surface, as shown in Fig. 11. The shielding curtains 28a and 28b normally stand by in a hanging manner. When ejection of rodlike jets of cooling water 23a and 23b starts, the shielding curtains 28a and 28b are raised along the innermost rows of rodlike jets of cooling water. In this case, the rodlike jets of cooling water 23a and 23b are violently ejected, and therefore, they are not disturbed.
When the jet velocity of cooling water is high and the splashed cooling water attempts to drop onto the steel plate or sheet 10 beyond the upper headers 21a and 21b, as described above, a shielding plate 29 shown in Fig. 17 may be used. The shielding plate 29 extends between the upper headers 21a and 21b and above the remaining cooling water 24. By using this shielding plate 29, the splashed cooling water that attempts to drop onto the steel plate or sheet 10 beyond the upper headers 21a and 21b can be shielded accurately. Moreover, this is effective because the splashed cooling water striking the shielding plate 29 drops onto the remaining cooling water 24 while catching splashed cooling water that attempts to splash laterally.

First Example

A first example of the present invention will be described below.
Fig. 14 is a view showing the hot rolling line for a thick steel plate adopted in the first embodiment of the present invention, and conveyance patters.
The hot rolling line for a thick steel plate includes a reheating furnace 11, a reversing rolling mill 12, first cooling equipment 14, a hot leveler 15, and second cooling equipment 16.
In a conveyance pattern A, accelerated cooling is performed after finish milling. A slab extracted from the reheating furnace 11 is subjected to rough rolling and finish rolling by the reversing rolling mill 12 so as to have a thickness of 25 mm, is passed through the hot leveler 15, and is subjected to accelerated cooling by a temperature drop of 150°C in the second cooling equipment 16.
In a conveyance pattern B, temperature adjustment cooling is performed before controlled rolling. A slab extracted from the reheating furnace 11 is roughly rolled to a thickness of 60 mm by the reversing rolling mill 12, is subjected to adjustment cooling by a temperature drop of 80°C in first cooling equipment 14, and is then subjected to low-temperature finish rolling, that is, controlled rolling.
According to the above, as a first invention example, conveyance was performed in the conveyance pattern A and the conveyance pattern B while one cooling unit of the same type as the cooling unit 20 shown in Fig. 2 was provided in the first cooling equipment 14, six cooling units were provided in the second cooling equipment 16. In this case, the height of the leading ends of upper nozzles 22a and 22b from the table rollers was 1.2 m, the upper nozzles 22a and 22b were arranged in the layout shown in Fig. 4A, the nozzle inner diameter was 6 mm, the water flow rate was 6 m³/m²min, the jet angles θ1 and θ2 of rodlike jets of cooling water were 45°, and the jet velocity was 8 m/s.
As a second invention example, one unit was provided in the first cooling equipment 14 in which the nozzle layout shown in Fig. 7 was adopted, the height of the leading ends of the nozzles, the nozzle inner diameter, the water flow rate, the jet angles θ1 and θ2, and the jet velocity were the same as those in the first invention example, and the outward angle α of the rodlike jets of cooling water was fixed at 20°. Six units of the same type were provided in the second cooling equipment 16. Conveyance was performed in the conveyance pattern A and the conveyance pattern B.
In the first and second invention examples, the position where the rodlike jets of cooling water strike the steel plate or sheet were spaced at a pitch of 60 mm in the steel-plate or sheet width direction.
As a first comparative example, conveyance was performed in the conveyance pattern A and the conveyance pattern B while each of the first cooling equipment 14 and the second cooling equipment 16 was formed by a known popular shower cooling device.
As a second comparative example, conveyance was performed in the conveyance pattern A and the conveyance pattern B while each of the first cooling equipment 14 and the second cooling equipment 16 was formed by the cooling device that eject cooling water films opposing each other, as shown in the above-described Patent Document 2.
In these cases, a temperature distribution on the upper surface of the steel plate or sheet was found by continuously measuring the temperature of the steel plate or sheet in the width direction with a radiation thermometer after cooling (after sufficient recuperation). Temperature variations in a stationary portion excluding the leading end, the tail end, and the widthwise edges (difference between the highest temperature and the lowest temperature) was defined as a temperature difference, and the temperature differences in the cases were compared. The temperature difference substantially corresponded to variations in mechanical characteristics of the product such as the tensile strength. The production efficiency and yield were compared with reference to those in the first comparative example.

Table 2 shows the comparison results.

Table 2

Conveyance Pattern	Cooling Water Supply Method	Outward Angle	Temperature Difference	Equipment Damage	Production Efficiency	Yield	Equipment Cost	Remarks
	Shower	-	80°C	○ None	Standard	Standard	○ Low	First Comparative Example
A	Cooling Water Film	-	80°C	× Sporadic	Reduced by 15%	Reduced by 10%	× High	Second Comaparative Example
A	Rodlike Jet of Cooling Water	0°	15°C	○ None	Improved by 10%	Improved by 1%	○ Low	First Invention Example
	Rodlike Jet of Cooling Water	20°	12°C	○ None	Improved by 10%	Improved by 1%	○ Low	Second Invention Example
	Shower	-	40°C	○ None	Standard	Standard	○ Low	First Comparative Example
B	Cooling Water Film	-	40°C	× Sporadic	Reduced by 6%	Reduced by 4%	× High	Second Comparative Example
B	Rodlike Jet of Cooling Water	0°	8°C	O None	Improved by 25%	Improved ○ by 1%	Low	First Invention Example
	Rodlike Jet of Cooling Water	20°	6°C	O None	Improved by 25%	Improved 0 by 1%	Low	Second Invention Example

First, shower cooling was performed in the first comparative example. By the influence of cooling water remaining on the steel plate or sheet, the temperature difference was 80°C in the conveyance pattern A (accelerated cooling after finish rolling), and 40°C in the conveyance pattern B (temperature adjustment cooling before controlled rolling). Moreover, the product strength greatly varied.
In the second comparative example, it was necessary to place the nozzles close to the steel plate or sheet, and therefore, the equipment was sometimes damaged when the steel plate or sheet was warped. Since the steel plate or sheet striking the equipment is defective as a product, the product yield was lower than in the first comparative example. Further, since much time was taken to repair the damaged equipment, the production efficiency also decreased. Since the cooling water films were supplied, deposits adhered to the nozzle openings and cooling water films were not formed. In this case, the cooling water could sometimes not be dammed within the jet area (within the cooling area). For this reason, by the influence of cooling water remaining on the steel plate or sheet, the temperature difference was 80°C in the conveyance pattern A (accelerated cooling after finish rolling), and 40°C in the conveyance pattern B (temperature adjustment cooling before controlled rolling). The product strength greatly varied.
In contrast, in the first invention example, the height of the nozzle leading ends was set high at 1.2 m. Therefore, the equipment was not damaged even when the steel plate or sheet was warped, the yield was not reduced by trouble, and the production efficiency was improved. Further, since rodlike jets of cooling water were ejected at high speed while opposing each other, the cooling water could be completely dammed within the cooling area, and the temperature difference could be limited to an extremely low value of 8 to 15°C.
In the second invention example, cooling water ejected from the upper nozzles 22a and 22b onto the upper surface of the steel plate or sheet 10 merged and promptly dropped from the widthwise edges of the steel plate or sheet 10, as shown by arrows A in Fig. 7. The remaining cooling water 24 could be dammed and draining was performed with less water than when there is no outward angle α. The temperature difference could be limited to an extremely low value of 6 to 12°C, and uniform cooling could be performed. In addition, since the cooling water could be dammed even when the flow rate and pressure were slightly decreased, a high pressure and much water were not necessary for the equipment. This allowed economical equipment design.
According to the above results, it was verified that the present invention was effective.

Second Example

A second example of the present invention will be described below.
Herein, the rolling time in this invention example and the rolling time in the related art were compared when manufacturing thick steel plates having a thickness of 18.5 mm, a width of 2560 mm, and a length of 35 m by controlled rolling.
In this invention example, the hot rolling equipment according to the above embodiment was used, and one cooling unit 20 of the same type as that shown in Fig. 2 was provided in the first cooling equipment 14, and six cooling units 20 of the same type were provided in the second cooling equipment 16. In this case, the height of the leading ends of the upper nozzles 22a and 22b from the table rollers was 1.2 m, the upper nozzles 22a and 22b were arranged in the layout shown in Fig. 4A, the nozzle inner diameter was 6 mm, the water flow rate was 6 m³/m²min, the jet angles θ1 and θ2 of rodlike jets of cooling water were 45°, and the jet velocity was 8 m/s. Further, a steel plate was rolled while being cooled by the cooling equipment 20 so that a predetermined controlled rolling start temperature (820°C) was obtained at a predetermined controlled rolling start thickness (34 mm). Subsequently, cooling by the cooling equipment 20 was stopped, and the steel plate was rolled to a final thickness of 18.5 mm.
In the related art, as in the technique disclosed in Japanese Unexamined Patent Application Publication No. 2005-000979 , after rolling to the predetermined controlled rolling start thickness (34 mm) is performed, rolling was temporarily stopped, and temperature adjustment cooling to the predetermined controlled rolling start temperature (820°C) was performed by the temperature adjustment cooing equipment. Subsequently, rolling to the final thickness of 18.5 mm was performed.
Fig. 13 shows the results. In the figure, a white circle and a black circle respectively show rolling paths in both cases. In this way, the time from extraction from the reheating furnace to completion of rolling was 205 seconds in the related art. In contrast, in this invention example, the time was reduced by 40 seconds to 165 seconds. The product quality in the invention example was not inferior to that in the related art.
This verifies that the present invention is effective.

Third Example

As an example of the present invention, according to the above-described second embodiment, one cooling unit 20 of the same type of that shown in Fig. 2 was provided in the first cooling equipment 14, and six cooling units 20 of the same type were provided in the second cooling equipment 16. In this case, the height of the leading ends of the upper nozzles 22a and 22b from the table rollers was 1.2 m, the upper nozzles 22a and 22b were arranged in the layout shown in Fig. 4A, the nozzle inner diameter was 6 mm, and the water flow rate was 6 m³/m²min. Further, a steel plate or sheet was cooled by the cooling equipment shown in Fig. 6 or 7. In this case, the inclination θ of rodlike jets of cooling water with respect to the transferring direction was 45°, and the jet velocity was 8 m/s.
As a first invention example, the cooling equipment shown in Fig. 6 was used, the outward angle α of rodlike jets of cooling water at the center in the steel-plate or sheet width direction was 0°, and the outward angle α of outermost rodlike jets of cooling water was 25°. The positions where the rodlike jets of cooling water strike the steel-plate or sheet were spaced at a pitch of 60 mm in the steel-plate or sheet width direction.
As a second invention example, the cooling equipment shown in Fig. 7 was used, the outward angle α of rodlike jets of cooling water was fixed at 20°, and the positions where the rodlike jets of cooling water strike the steel-plate or sheet were spaced at a pitch of 60 mm in the steel-plate or sheet width direction.
As a result, in both the first and second invention examples, the jets of cooling water ejected from the upper nozzles 22a and 22b onto the upper surface of the steel-plate or sheet 10 merged and promptly dropped from the widthwise edges of the steel plate or sheet 10, as shown by arrows A in Figs. 6 and 7. The remaining cooling water 24 could be dammed and draining could be performed with less water than when there is no outward angle α.

Fourth Example

In the hot rolling line for thick steel plates shown in Fig. 14, according to the above-described second embodiment, a steel plate was cooled while one cooling unit of the same type as that of the cooling unit 40 shown in Fig. 9 or 11 was provided in the first cooling equipment 14 and six units of the same type were provided in the second cooling equipment 16. In this case, the jet angles θ1 and θ2 of rodlike jets of cooling water were 45°, and the jet velocity was 12 m/s. The remaining region length L was 0 mm.
In a second invention example, the cooling unit 40 including the shielding plates 26a and 26b shown in Fig. 9 was used. In this case, the shielding plates 26a and 26b were positioned 50 mm above the innermost rodlike jets of cooling water. The distance in the transferring direction (δ in Fig. 9) from the lowermost ends of the shielding plates 26a and 26b to the positions where the outermost rows of rodlike jets of cooling water strike the steel plate 10 was 300 mm.
In a third invention example, the cooling unit 40 including the shielding curtains 28a and 28b shown in Fig. 11 was used. In this case, the distance in the transferring direction (δ in Fig. 11) from the lowermost ends of the shielding curtains 28a and 28b raised by ejection of the rodlike jets of cooling water to the positions where the outermost rows of rodlike jets of cooling water strike the steel plate 10 was 300 mm.
As a result, both the second and third invention examples could accurately prevent splashed cooling water 25 striking the steel plate 10 and splashing upward from dropping onto the rodlike jets of cooling water 23a and 23b. Consequently, cooling uniformity can be maintained.

Industrial Applicability

In the present invention, since cooling water is supplied onto the upper and lower surfaces of the steel plate or sheet while the steel plate or sheet is passing, the length of the equipment is short. Moreover, since the nozzles are arranged so that jets of cooling water oppose each other in the transferring direction on the steel plate or sheet, the supplied cooling water itself dams remaining cooling water on the steel plate or sheet, thus performing draining. Therefore, draining is properly performed without an additional device such as a damming rolls. As a result, for example, in controlled rolling, the steel plate or sheet can be properly cooled with a compact size on the hot rolling line.
In the present invention, since the pass-type cooling equipment having a high water flow rate of 4 m³/m²min or more is disposed close to the reversing rolling mill, the predetermined controlled rolling start temperature can be efficiently obtained by simultaneously rolling and cooling the steel plate or sheet. This prevents the rolling productivity from being reduced by waiting for cooling. Further, the nozzles are arranged so that the jets of cooling water oppose each other in the transferring direction on the steel plate or sheet, and the cooling water is supplied at a high water flow rate of 4 m³/m²min or more. Therefore, the supplied cooling water itself properly dams the remaining cooling water, and a stable cooling area can be obtained.
As a result, when the steel plate or sheet is subjected to controlled rolling, it is uniformly cooled, and a high product quality can be obtained. Moreover, the rolling productivity can be prevented from being reduced by waiting for cooling.
According to the present invention, the steel plate or sheet can be uniformly cooled to the target temperature at a high cooling rate. Consequently, a high-quality steel plate or sheet can be produced.

Claims

Steel-plate or sheet cooling equipment characterized in that cooling water is supplied onto upper and lower surfaces of a steel plate or sheet while the steel plate or sheet is passing during hot rolling, in that nozzles are provided to obliquely supply the cooling water onto the upper surface of the steel plate or sheet from above, and in that a plurality of rows of the nozzles are provided so as to eject jets of the cooling water opposing each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
The steel-plate or sheet cooling equipment according to claim 1, wherein cooling equipment is provided close to a reversing rolling mill for subjecting the steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, and the cooling equipment supplies the cooling water onto the upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling.
The steel-plate or sheet cooling equipment according to claim 1 or 2, wherein the nozzles eject rodlike jets of cooling water.
The steel-plate or sheet cooling equipment according to claim 3, wherein a header to which the nozzles for ejecting the rodlike jets of cooling water are connected is provided above the steel plate or sheet, and the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the steel plate or sheet is 30° to 60°.
The steel-plate or sheet cooling equipment according to claim 4, wherein three or more rows of the nozzles are arranged in each of the transferring direction of the steel plate or sheet and a direction opposite the transferring direction, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
The steel-plate or sheet cooling equipment according to any of claims 3 to 5, wherein jet directions of the rodlike jets of cooling water are set so that 0 to 35% of jet velocity components of the rodlike jets of cooling water head outward in a steel-plate or sheet width direction perpendicular to the transferring direction.
The steel-plate or sheet cooling equipment according to claim 6, wherein the jet directions of the rodlike jets of cooling water are set so that jet velocity components of the same number of rodlike jets of cooling water as 40 to 60% of the total number of nozzles that eject the rodlike jets of cooling water head in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction.
The steel-plate or sheet cooling equipment according to claim 6, wherein the jet directions of the rodlike jets of cooling water are set so that the number of rodlike jets of cooling water having components heading in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction is equal to the number of rodlike jets of cooling water having components heading in the other direction.
The steel-plate or sheet cooling equipment according to claim 6, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction gradually increase as positions of the nozzles are shifted outward from the center in the steel-plate or sheet width direction.
The steel-plate or sheet cooling equipment according to claim 6, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction are fixed and so that positions where the rodlike jets of cooling water strike the steel plate or sheet are equally spaced in the steel-plate or sheet width direction.
The steel-plate or sheet cooling equipment according to any of claims 3 to 8, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other, and/or above remaining cooling water.
The steel-plate or sheet cooling equipment according to claim 11, wherein the lowermost end of the shield provided above the innermost rows of rodlike jets of cooling water opposing each other is disposed 300 to 500 mm above from the upper surface of the steel plate or sheet.
The steel-plate or sheet cooling equipment according to claim 2, wherein a cooling area of the cooling equipment is provided at a position close to the reversing rolling mill, the position excluding a portion between the reversing rolling mill and a side guide provided on the entrance side and/or the exit side of the reversing rolling mill.
The steel-plate or sheet cooling equipment according to claim 13, wherein the cooling area of the cooling equipment is provided at a position on an upstream side of a side guide disposed on the entrance side of the reversing rolling mill and close to the reversing rolling mill, and/or at a position on a downstream side of a side guide disposed on the exit side of the reversing rolling mill and close to the reversing rolling mill.
A steel-plate or sheet cooling method for supplying cooling water onto upper and lower surfaces of a steel plate or sheet while the steel plate or sheet is passing during hot rolling, wherein the cooling water is obliquely supplied onto the upper surface of the steel plate or sheet from above by nozzles arranged so as to eject jets of cooling water opposing each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
The steel-plate or sheet cooling method according to claim 15, wherein cooling equipment is provided on an entrance side and/or an exit side of a reversing rolling mill for subjecting the steel plate to hot rolling and close to the reversing rolling mill, and the cooling water is supplied from the cooling equipment onto the upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling.
The steel-plate or sheet cooling method according to claim 15 or 16, wherein the nozzles eject rodlike jets of cooling water.
The steel-plate or sheet cooling method according to claim 17, wherein a header to which the nozzles for ejecting the rodlike jets of cooling water are connected is provided above the steel plate or sheet, and cooling is performed while the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the steel plate or sheet is 30° to 60°.
The steel-plate or sheet cooling method according to claim 18, wherein three or more rows of the nozzles are arranged in each of the transferring direction of the steel-plate or sheet and a direction opposite the transferring direction, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
The steel-plate or sheet cooling method according to any of claims 15 to 19, wherein jet directions of the rodlike jets of cooling water are set so that 0 to 35% of jet velocity components of the rodlike jets of cooling water head outward in a steel-plate or sheet width direction perpendicular to the transferring direction.
The steel-plate or sheet cooling method according to claim 20, wherein the jet directions of the rodlike jets of cooling water are set so that jet velocity components of the same number of rodlike jets of cooling water as 40 to 60% of the total number of nozzles that eject the rodlike jets of cooling water head in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction.
The steel-plate or sheet cooling method according to claim 20, wherein the jet directions of the rodlike jets of cooling water are set so that the number of rodlike jets of cooling water having components heading in one of two directions pointing outward in the steel-plate or sheet width direction perpendicular to the transferring direction is equal to the number of rodlike jets of cooling water having components heading in the other direction.
The steel-plate or sheet cooling method according to claim 20, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction gradually increase as positions of the nozzles are shifted outward from the center in the steel plate or sheet width direction.
The steel-plate or sheet cooling method according to claim 20, wherein the nozzles are arranged so that the jet velocity components of the rodlike jets of cooling water heading outward in the steel-plate or sheet width direction are fixed and so that positions where the rodlike jets of cooling water strike the steel plate or sheet are equally spaced in the steel-plate or sheet width direction.
The steel-plate or sheet cooling method according to any of claims 15 to 19, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other, and/or above remaining cooling water.
The steel-plate or sheet cooling method according to claim 25, wherein the lowermost end of the shield provided above the innermost rows of rodlike jets of cooling water opposing each other is disposed 300 to 500 mm above from the upper surface of the steel plate or sheet.
The steel-plate or sheet cooling method according to claim 16, wherein a cooling area of the cooling equipment is provided at a position close to the reversing rolling mill, the position excluding a portion between the reversing rolling mill and a side guide provided on the entrance side and/or the exit side of the reversing rolling mill.
The steel-plate or sheet cooling method according to claim 27, wherein the cooling area of the cooling equipment is provided at a position on an upstream side of a side guide disposed on the entrance side of the reversing rolling mill and close to the reversing rolling mill, and/or at a position on a downstream side of a side guide disposed on the exit side of the reversing rolling mill and close to the reversing rolling mill.
Steel-plate or sheet hot rolling equipment characterized in that cooling equipment is provided close to a reversing rolling mill for subjecting a steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, and the cooling equipment supplies cooling water onto upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling, in that the cooling equipment provided above the upper surface includes nozzles for obliquely supplying the cooling water onto the steel plate or sheet from above, and in that the nozzles are arranged so that jets of the cooling water oppose each other on the steel plate or sheet in a transferring direction of the steel plate or sheet.
The steel-plate or sheet hot rolling equipment according to claim 29, wherein the nozzles eject rodlike jets of cooling water.
The steel-plate or sheet hot rolling equipment according to claim 29 or 30, wherein a cooling area of the cooling equipment is provided between the reversing rolling mill and a side guide disposed on the entrance side and/or the exit side of the reversing rolling mill.
A steel-plate or sheet hot rolling method characterized in that cooling equipment is provided close to a reversing rolling mill for subjecting a steel plate or sheet to hot rolling and on an entrance side and/or an exit side of the reversing rolling mill, in that cooling water is supplied by the cooling equipment onto upper and lower surfaces of the steel plate or sheet at a water flow rate of 4 m³/m²min or more while the steel plate or sheet is passing before and/or after rolling, and in that the cooling water is obliquely supplied onto the upper surface of the steel plate or sheet from above by nozzles arranged so as to eject jets of cooling water opposing each other on the steel plate in a transferring direction of the steel plate or sheet.
The steel-plate or sheet hot rolling method according to claim 32, wherein the nozzles eject rodlike jets of cooling water.
The steel-plate or sheet hot rolling method according to claim 32 or 33, wherein a cooling area of the cooling equipment is provided between the reversing rolling mill and a side guide disposed on the entrance side and/or the exit side of the reversing rolling mill.
Steel-plate or sheet cooling equipment characterized in that a header to which nozzles for ejecting rodlike jets of cooling water at a water flow rate of 4 m³/m²min or more are connected is provided above a hot rolled steel plate or sheet, and in that the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the hot rolled steel plate or sheet is 30° to 60° and so that the nozzles oppose each other in a transferring direction of the hot rolled steel plate or sheet.
The steel-plate or sheet cooling equipment according to claim 35, wherein five or more rows of the nozzles are arranged in the transferring direction of the hot rolled steel plate or sheet, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
The steel-plate or sheet cooling equipment according to claim 35 or 36, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other.
The steel-plate or sheet cooling equipment according to claim 37, wherein the lowermost end of the shield is disposed 300 to 500 mm above from an upper surface of the hot rolled steel plate or sheet.
A steel-plate or sheet cooling method characterized in that a header to which nozzles for ejecting rodlike jets of cooling water at a water flow rate of 4 m³/m²min or more are connected is provided above a hot rolled steel plate or sheet, and in that the nozzles are arranged so that an inclination formed by the rodlike jets of cooling water and the hot rolled steel plate or sheet is 30° to 60° and so that the nozzles oppose each other in a transferring direction of the hot rolled steel plate or sheet.
The steel-plate or sheet cooling method according to claim 39, wherein five or more rows of the nozzles are arranged in the transferring direction of the hot rolled steel plate or sheet, and the rodlike jets of cooling water are ejected at a speed of 8 m/s or more.
The steel-plate or sheet cooling method according to claim 39 or 40, wherein a shield shaped like a plate or a curtain is provided above the innermost rows of rodlike jets of cooling water opposing each other.
The steel-plate or sheet cooling method according to claim 41, wherein the lowermost end of the shield is disposed 300 to 500 mm above from an upper surface of the hot rolled steel plate or sheet.