JP3546264B2 - High-temperature steel plate cooling apparatus and high-temperature steel plate cooling method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a cooling method for cooling a hot-rolled high-temperature steel sheet, and relates to a cooling apparatus and a cooling method for preventing C warpage of a steel sheet being cooled and enabling uniform cooling of the high-temperature steel sheet. is there.
[0002]
[Prior art]
Generally, a hot-rolled high-temperature steel sheet is likely to have cooling unevenness during water cooling immediately after rolling. The cooling unevenness causes deformation of the steel sheet, residual stress, and variation in material after cooling, and also causes deformation of the steel sheet, which easily causes trouble in operation. Further, the deformed steel sheet requires a refining process for removing the deformation by a press or a straightening machine later, which is disadvantageous in cost. Therefore, various so-called uniform cooling methods have been conventionally proposed in order to eliminate cooling unevenness.
[0003]
When cooling a hot steel sheet after rolling online, it is common to apply cooling water from above and below in a horizontal state to perform cooling. In particular, in recent years, technologies related to controlled rolling, which combines cooling and rolling, and controlled cooling, which cools steel sheets online, have been developed.With the advancement of these technologies, high-precision temperature control, especially cooling stop temperature control, has been developed. Is becoming increasingly important.
[0004]
However, a thick steel plate may have a large product size and a width of as much as 5 m. Further, since the plate is thick, a large amount of cooling water is required for cooling. Therefore, in order to use this cooling water efficiently, it is necessary to determine how to stop the cooling water on the outlet side of the cooling device and to drain the water, and how to quickly discharge the stopped cooling water from the plate edge. It is an important issue.
[0005]
In order to solve these problems, various studies have been made on a steel plate drainer, and for example, the following techniques have been proposed.
[0006]
Japanese Utility Model Application Laid-Open No. 53-39508 discloses a technique in which an air nozzle is vertically movable toward the upper surface of a steel plate to drain water by jetting air.
[0007]
Japanese Unexamined Patent Publication No. 7-9023 discloses that high-pressure spray water is sprayed in the width direction of a steel sheet from an injection nozzle provided on one side of a steel sheet transferred on a table roller, and the remaining water remaining on the steel sheet is sprayed. A method is disclosed for excluding water from the other side edge of the steel sheet.
[0008]
Further, Japanese Utility Model Application Laid-Open No. 58-125611 and Japanese Utility Model Application Laid-Open No. 59-161062 disclose methods of draining water by sandwiching a steel plate between rubber rolls provided above and below.
[0009]
Further, in Japanese Patent Application Laid-Open No. 60-206516 and Japanese Utility Model Application Laid-Open No. 7-33406, a draining roll is arranged, and an injection nozzle is provided downstream of the roll in the width direction of the steel sheet. A technique for injecting water toward both ends and toward a draining roll to drain the water is disclosed.
[0010]
[Problems to be solved by the invention]
However, as disclosed in Japanese Unexamined Utility Model Publication No. 53-39508, an air nozzle is arranged so as to be movable up and down to drain water with jet air, and as disclosed in Japanese Patent Application Laid-Open No. 7-9023. In the method of spraying high-pressure spray water from the side to remove the remaining cooling water from the plate edge, the cooling water remaining on the wide steel plate is damped and pushed to the plate edge to remove it It was difficult to do.
[0011]
The techniques described in Japanese Utility Model Laid-Open Nos. 58-125611 and 59-161062, the techniques described in Japanese Patent Laid-Open No. 60-206516 and Japanese Utility Model Laid-Open No. 7-33406 are as follows. There were serious problems.
[0012]
That is, when the steel sheet is rapidly cooled, as in the case of cooling a thick steel sheet, since the cooling of the upper surface and the lower surface of the steel sheet is not always the same, a deformation called so-called C-warpage is likely to occur in the sheet width direction. The amount of warping and the direction of warping are determined by the C width, the thickness, the temperature difference between the upper and lower surfaces, the difference in temperature history between the upper and lower surfaces, and the like.
[0013]
This is shown in FIG. In FIG. 5, 1 is a steel plate, 2 is an upper constraining roll, and 3 is a lower constraining roll. In general, if the upper surface is strongly cooled, a downwardly convex C-warp tends to occur in the cooling device as shown in FIG. 5A, and conversely, if the lower surface is strongly cooled, as shown in FIG. A convex C warpage occurs.
[0014]
In addition to the inventions disclosed in the above patent publications, when cooling a steel sheet in an online-pass type, the steel sheet is passed through a plurality of rolls also serving as draining rolls for stopping cooling water, and the rolls are rolled. In general, a method of cooling the steel sheet by pouring cooling water in between. In the cooling device of this type, when the above-described C warpage occurs, a gap is generated between the draining roll (restraining roll) and the steel sheet, and the cooling water leaks from the gap to supercool the non-cooled portion, thereby causing the cooling. This causes a problem.
[0015]
In particular, as shown in FIG. 5 (a), when a downwardly convex C warpage occurs, the cooling water leaks from the gap between the drain roll and the steel plate at the central portion of the steel plate, so that the cooling water stays at the central portion of the steel plate. As a result, overcooling of this portion was caused, and uneven cooling in the sheet width direction was inevitable.
[0016]
Further, since the cooling water staying in the central portion cools the upper central portion of the steel plate, there is a problem that C warpage is promoted.
[0017]
As described above, none of the conventional methods of draining by providing the draining rolls on the upper and lower sides have been able to achieve a sufficient effect due to the C warpage.
[0018]
The present invention has been made to solve such a problem, and a cooling device and a cooling method that prevent generation of C warpage in a cooling device for a high-temperature steel sheet, perform effective drainage, and do not generate cooling unevenness. The purpose is to provide.
[0019]
[Means for Solving the Problems]
The above-described problem is a cooling device for a high-temperature steel sheet that conveys a high-temperature steel sheet while constraining the high-temperature steel sheet with a plurality of upper and lower restraining rolls, injects cooling water into the steel sheet from above and below during the conveyance, and cools the high-temperature steel sheet. The problem is solved by a cooling device for a high-temperature steel plate (Claim 1), wherein a pass line of the steel plate at the position of the constraining roll is alternately shifted vertically within a range of elastic deformation of the high-temperature steel plate.
Patent Document 1 describes a cooling device for a steel sheet in which a plurality of roll surfaces of an upper roll unit and a lower roll unit are arranged so as to face each other.
, 2).
[0020]
If the pass lines of the steel sheet are alternately shifted in the vertical direction at the position of the lower constraining roll, the rigidity increases because the steel sheet passes between the constraining rolls while bending up and down around the constraining rolls. Therefore, even if the C warpage is generated due to the cooling imbalance, the generation of the C warp in the plate width direction can be suppressed due to the large rigidity.
[0021]
As a result, there is no gap between the constraining roll (water draining roll) and the steel sheet, and reliable draining is possible.
[0022]
Further, when a backup roll is provided on the upper constraining roll (claim 2), it is possible to prevent the upper constraining roll from bending due to the pressing force and forming a gap between the upper constraining roll and the steel plate, and it is possible to drain the water reliably.
[0023]
The shift amount of the pass line at the position of the lower constraining roll may be appropriately determined so that the passing of the steel sheet 1 is not hindered and the occurrence of the C warpage can be prevented. Normally, assuming that the distance (roll pitch) between adjacent lower constraining rolls 3 is L, it is desirable that the amount of vertical displacement is about Δh ≧ 0.005 L (claim 3). If Δh <0.005 L, it is not possible to sufficiently prevent the occurrence of C warpage.
[0024]
Further, by providing a draining spray device for purging cooling water staying on the steel sheet from one end to the other end of the steel sheet downstream of the upper constraining roll (claim 4) , When the upper constraining roll is bent and a gap is formed between the steel sheet and the steel sheet, even when the cooling water flows into another zone, the flowing cooling water can be purged to prevent the cooling water from staying on the steel sheet.
[0025]
A plurality of sets of upper and lower restraining rolls convey a high-temperature steel sheet while constraining it, pouring cooling water into the steel sheet from above and below during conveyance, and cooling the high-temperature steel sheet, pass the steel sheet pass line at the position of the lower constraining roll, A method for cooling a high-temperature steel sheet, wherein cooling is performed while restraining the high-temperature steel sheet alternately vertically within the elastic deformation range of the high-temperature steel sheet (Claim 5) ; the backup roll is provided in a roll, it is also expected that the same effect in the method of cooling hot steel plate for cooling while holding the above restraint roll (claim 6) by a backup roll.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of an embodiment of the present invention. In FIG. 1, 1 is a steel plate, 2 is an upper constraining roll (water draining roll), 3 is a lower constraining roll (water draining roll), 4 is a slit nozzle, 5 is a circular nozzle, and 6 is a hydraulic cylinder. In this cooling device, the steel sheet 1 immediately after rolling is transported between the 20 sets of the upper constraining rolls 2 and the lower constraining rolls 3, while the upper side is cooled by the cooling water from the slit nozzle 4, and the lower side is formed by the circular nozzle 5. Is cooled online by the cooling water. In the figure, three upper constraining rolls and two cooling zones are shown. The pitch of each roll is 1 m.
[0027]
On the upper surface between the rolls 2 and 3, from the upper constraining roll 2 on the upstream side in the sheet conveying direction to the upper constraining roll 2 on the downstream side, 2 m per 1 m of the sheet width from the slit nozzle 4 in the traveling direction of the steel sheet 1. ³ / min of cooling water is flowing along the steel sheet 1. On the other hand, the lower surface is jetted with water from a circular tube nozzle 5 provided at a pitch of 100 mm and submerged in water, and is cooled by a water flow generated by the accompanying flow.
[0028]
In these 20 sets of constraint rolls 2 and 3, the lower constraint roll 3 also serves as a transport roll and is a fixed type. The upper constraining roll 2 has a diameter of 200 mm, can be moved up and down, and can be controlled at a pitch of 0.5 mm.
[0029]
Further, the gap between the upper constraining roll 2 and the lower constraining roll 3 is set to be equal to or less than the thickness of the steel plate 1, and when the steel plate 1 passes, the upper constraining roll 2 resists the pressing force of the hydraulic cylinder 6. The steel plate 1 is lifted, and a pressing force is applied to the steel plate 1 by the reaction force, so that the steel plate 1 is restrained.
[0030]
FIG. 2 schematically shows a positional relationship between the upper constraining roll 2 and the lower constraining roll 3. In the following drawings, the same components as those shown in the preceding drawings are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 2, the heights of the fixed lower constraining rolls 3 are alternately different by Δh = 10 mm. That is, the heights of the pass lines at the positions of the constraining rolls 2 and 3 are alternately different by 10 mm.
[0031]
In this embodiment, Δh is set to 10 mm, but the amount of this deviation may be appropriately determined so as not to hinder the passing of the steel sheet 1 and to prevent the occurrence of C warpage. Normally, assuming that the distance (roll pitch) between adjacent lower constraining rolls 3 is L, it is desirable that Δh ≧ 0.005 L, and it is particularly desirable that Δh be about 0.01 L. If Δh <0.005 L, it is not possible to sufficiently prevent the occurrence of C warpage.
[0032]
Since the distortion in the plate longitudinal direction applied to the steel sheet 1 due to the displacement between the upper constraining roll 2 and the lower constraining roll 3 is within the elastic deformation range, the distortion due to this does not remain after cooling.
[0033]
FIG. 3 shows an example of another embodiment of the present invention. 3 differs from FIG. 1 in that a backup roll 7 is provided at the center of the upper constraining roll 2 in contact with the upper constraining roll 2; Roll 2 is provided. That is, the roll pitch of the upper constraining roll 2 is 2 m, and the roll pitch of the lower constraining roll 3 is 1 m.
[0034]
The backup roll 7 is well known in a rolling mill. In this case, the backup roll 7 serves to prevent the upper constraining roll 2 from being bent by receiving a reaction force from the steel plate 1 by pressing the roll from above. In this embodiment, the back roll has a body length of 500 mm and a diameter of 250 mm.
[0035]
In this embodiment, since the roll pitch of the upper constraining roll 2 is increased to 2 m, the constraining force to be applied by the upper constraining roll 2 is larger than that in the embodiment shown in FIG. For example, when a pressing force of 8 T each, a total of 16 T, is applied from the two hydraulic cylinders 6 located at both ends of the upper constraining roll 2, the upper constraining roll having a diameter of 200 mm is bent, and a gap of 5.6 mm is formed between the upper restraining roll and the steel plate 1. It was confirmed by calculation that the occurrence of.
[0036]
In order to eliminate this gap, in the present embodiment, a backup roll 7 is provided at the center of the upper constraining roll 2.
[0037]
The necessity / unnecessity of the backup roll 7 is determined by the plate width, the required restraining force, the diameter of the upper restraint roll 2 and the like. The amount of deflection of the roll when a load is applied from both ends of the upper restraint roll 2 is determined by elastic dynamics. If the number is several mm or more, it is necessary to provide a backup roll 7.
[0038]
In the cooling device shown in FIG. 3, while the steel sheet 1 immediately after rolling is conveyed between the ten upper restraining rolls 2 and the twenty lower restraining rolls 3, the upper side is cooled by the cooling water from the slit nozzle 4 to the lower side. Is cooled on-line by cooling water from the circular tube nozzle 5. FIG. 3 shows two upper constraining rolls 2, three lower constraining rolls 3, an upper cooling zone for one zone, and a lower cooling zone for two zones.
[0039]
Cooling water of 2 m ³ / min per 1 m of sheet width is fed from the slit nozzle 4 in the traveling direction of the steel sheet from the upper constraining roll 2 on the upstream side to the upper constraining roll 2 on the downstream side in the sheet conveying direction. Is flowing along the steel plate. On the other hand, the lower surface is jetted with water from a circular tube nozzle 5 provided at a pitch of 100 mm and submerged in water, and is cooled by a water flow generated by the accompanying flow.
[0040]
In the constraining rolls 2 and 3, the lower constraining roll 3 also serves as a transport roll and is a fixed type. The upper constraining roll 2 has a diameter of 200 mm, can be moved up and down, and can be controlled at a pitch of 0.5 mm.
[0041]
Further, the gap between the upper constraining roll 2 and the lower constraining roll 3 is set to be equal to or less than the thickness of the steel plate 1, and when the steel plate 1 passes, the upper constraining roll 2 resists the pressing force of the hydraulic cylinder 6. The steel plate 1 is lifted, and a pressing force is applied to the steel plate 1 by the reaction force, so that the steel plate 1 is restrained.
[0042]
Next, a third embodiment of the present invention will be described with reference to FIG. 4 is different from the embodiment shown in FIG. 3 in that a header 8 is provided immediately after the upper constraining roll, and an angle of 45 degrees A mechanism is provided for injecting 100 l / min of draining water from two draining spray nozzles 9 provided on the header 8 from the plate edge to the other plate edge in the opposite direction to the conveying direction of 1. It is being done.
[0043]
This embodiment is effective when the upper constraining roll 2 bends even if a backup roll is provided, and a gap is formed between the upper constraining roll 2 and the steel plate 1. For example, in order to cool a 3.3 m-long, 30 m-long and 40 mm-thick steel plate immediately after rolling, a maximum restraining force of 20 T is applied, and the bending of the upper restraining roll 2 is suppressed by the backup roll 7. A gap is formed between the upper confining roll 2 and the upper confining roll 2, from which cooling water flows into a downstream zone.
[0044]
The flowing cooling water is purged by draining water from the spray nozzle 9 and discharged from the end surface of the steel plate 1. Therefore, the steel sheet does not stay in the next zone to overcool the steel sheet.
[0045]
【Example】
(Example 1)
Using the cooling equipment shown in FIG. 1, a high-temperature steel plate having a width of 4.3 m, a length of 30 m, and a thickness of 25 mm immediately after rolling was cooled by passing at a conveying speed of 40 mpm. The difference between the pass lines at the upper and lower restraining roll positions (Δh in FIG. 2) was 10 mm. In this embodiment, the cooling water between the rolls is turned on and off every other zone in order to obtain a required cooling rate. That is, the cooling water of the slit nozzle 4 was stopped every two, and the cooling water of the circular pipe nozzle 5 was also stopped every other zone to perform intermittent cooling. The gap between the upper and lower restraining rolls 2 and 3 was set to a sheet thickness of -1.5 mm, that is, 23.5 mm.
[0046]
As a result, no phenomenon was observed in which the cooling water leaked to the rear side of the downstream roll of the cooling zone in which each cooling water was flowing. That is, the C warpage was suppressed.
[0047]
At this time, the temperature distribution of the steel sheet on the entry side was measured at 850 ° C. ± 15 ° C. by a scanning radiation thermometer. When the temperature distribution was measured by a scanning radiation thermometer at a position 20 m downstream of the cooling device, the temperature distribution was 500 ° C. ± 10 ° C., and no cooling unevenness occurred.
[0048]
At this time, there was no large C warpage deformation in the width direction of the sheet, no particularly large deformation occurred even after cooling in the cooling floor, and the product was obtained without performing any special correction. When the hardness distribution in the sheet width direction was examined after cooling, there was no particularly large difference in hardness distribution. From this, it is determined that there was no large cooling unevenness.
[0049]
(Example 2)
A high-temperature steel plate having a width of 3.3 m, a length of 30 m and a thickness of 25 mm immediately after rolling was cooled by the cooling device shown in FIG. In this example, in order to obtain a required cooling rate, the cooling water above the steel plate between the rolls was turned on and off every other zone. That is, the cooling water of the slit nozzle 4 was stopped one by two. As for the cooling water at the lower part of the steel plate, the cooling water from the circular pipe nozzle 5 is stopped and jetted every two zones so that the cooling from the circular pipe nozzle 5 is performed at the place where the cooling by the slit nozzle 4 is performed. The upper and lower surfaces of the steel plate were cooled in the same zone. The gap between the upper and lower restraining rolls was -1.5 mm in plate thickness, that is, 23.5 mm. The difference between the pass lines at the position of the constraining roll (Δh in FIG. 2) was 10 mm.
[0050]
At this time, the temperature distribution of the steel sheet on the entry side was measured at 850 ° C. ± 10 ° C. by a scanning radiation thermometer. When the temperature distribution was measured by a scanning radiation thermometer at a position 20 m downstream of the cooling device, the temperature distribution was 500 ° C. ± 10 ° C., and no cooling unevenness occurred.
[0051]
At this time, there was no large C warpage deformation in the width direction of the sheet, no particularly large deformation occurred even after cooling in the cooling floor, and the product was obtained without performing any special correction. When the hardness distribution in the sheet width direction was examined after cooling, there was no particularly large difference in hardness distribution. From this, it is determined that there was no large cooling unevenness.
[0052]
(Example 3)
Using the apparatus shown in FIG. 4, a high-temperature steel sheet having a width of 3.3 m, a length of 30 m and a thickness of 40 mm immediately after rolling was cooled. The cooling conditions were the same as those shown in Example 2, and the gap between the upper and lower restraining rolls was -1.5 mm in plate thickness, that is, 38.5 mm. The difference between the pass lines at the position of the constraining roll (Δh in FIG. 2) was 10 mm.
[0053]
In this case, even if the backup roll 7 was used, the bending of the upper constraining roll 2 could not be suppressed, and a phenomenon that the cooling water leaked from the space between the upper constraining roll 2 and the steel plate 1 to the adjacent zone occurred. However, the leaked water was quickly purged from above the steel plate 1 by the drainage water sprayed from the drainer spray nozzle 9, and did not stay on the steel plate 1.
[0054]
The temperature distribution of the steel sheet on the entry side was measured at 850 ° C. ± 10 ° C. by a scanning radiation thermometer. When the temperature distribution was measured by a scanning radiation thermometer at a position 20 m downstream of the cooling device, the temperature distribution was 500 ° C. ± 10 ° C., and no cooling unevenness occurred.
[0055]
At this time, there was no large C warpage deformation in the width direction of the sheet, no particularly large deformation occurred even after cooling in the cooling floor, and the product was obtained without performing any special correction. When the hardness distribution in the sheet width direction was examined after cooling, there was no particularly large difference in hardness distribution. From this, it is determined that there was no large cooling unevenness.
[0056]
(Comparative example)
Using the same cooling equipment as in FIG. 1, cooling was performed with the center axes of the upper constraining roll 2 and the lower constraining roll 3 aligned. That is, in this comparative example, the center positions of the upper constraining roll 2 and the lower constraining roll 3 are not shifted in the pass line direction. Other conditions were the same as those of Example 1.
[0057]
That is, a high-temperature steel plate having a width of 4.3 m, a length of 30 m, and a thickness of 25 mm immediately after rolling was cooled at a conveying speed of 40 mpm. Also in this comparative example, in order to obtain a required cooling rate, the cooling water between the rolls was turned on and off every other zone. That is, the cooling water of the slit nozzle 4 was stopped every two, and the cooling water of the circular pipe nozzle 5 was also stopped every other zone to perform intermittent cooling. The gap between the upper and lower restraining rolls was set to a thickness of −1.5 mm, that is, 23.5 mm.
[0058]
In addition to this, a header 8 is provided at the end of the plate in the same manner as shown in FIG. 4 on the downstream side in the transport direction of the roll, and 100 l / min is supplied from a drainer spray nozzle 9 attached to the header. Drain water was sprayed.
[0059]
In this cooling device, the cooling water leaked from the gap between the upper constraining roll 2 and the steel plate 1 in the central portion in the plate width direction, and flowed into the adjacent zone. The amount of the leaked cooling water was large, and it was impossible to completely remove the water from the draining spray nozzle 9 placed on the downstream side of the roll. Therefore, since this cooling water was always present at the center of the steel sheet, the center of the steel sheet 1 was selectively supercooled.
[0060]
At this time, the temperature distribution of the steel sheet on the entry side was measured at 850 ° C. ± 15 ° C. by a scanning radiation thermometer. When the temperature distribution was measured by a scanning radiation thermometer at a position 20 m downstream of the cooling device, the temperature distribution was 400 ° C. to 510 ° C., and large cooling unevenness occurred. At this time, C warpage deformation was observed in the plate width direction. When the plate was conveyed to a cooling floor and cooled to room temperature, a shape defect occurred. Therefore, a refining process for removing this deformation with a leveler and a press straightening machine was required. In addition, when the hardness distribution in the width direction of the plate was examined after cooling, a so-called baking unevenness having high hardness was observed at the center of the plate.
[0061]
【The invention's effect】
As described above, in the present invention, since the pass line of the steel sheet at the position of the lower constraining roll is alternately shifted up and down within the elastic deformation range of the high-temperature steel sheet , the steel sheet is bent up and down. While passing between the constraining rolls, the rigidity increases, and C warpage is prevented.
[0062]
Therefore, in an online cooling device that continuously cools a thick steel plate, uniform cooling without cooling unevenness is possible. Therefore, it is possible to stably produce a homogeneous steel sheet with little variation in the material inside the steel sheet. In addition, since there is no large deformation of the steel sheet during and after cooling and no trouble in passing the steel sheet, continuous operation is not hindered.
[0063]
Furthermore, since a large thermal distortion does not occur even after cooling, there is no need for a refining step using a leveler or a press, and low-cost production of a thick steel plate is possible.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an embodiment of the present invention.
FIG. 2 is a view schematically showing a positional relationship between an upper constraining roll 2 and a lower constraining roll 3;
FIG. 3 is a diagram showing another example of the embodiment of the present invention.
FIG. 4 is a diagram showing another example of the embodiment of the present invention.
FIG. 5 is a diagram schematically showing the warpage of a plate generated during cooling of the steel plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steel plate 2 Upper constraining roll 3 Lower constraining roll 4 Slit nozzle 5 Circular tube nozzle 6 Hydraulic cylinder 7 Backup roll

Claims (8)

A high-temperature steel plate cooling device that conveys a high-temperature steel sheet while constraining it with a plurality of upper and lower restraining rolls and injects cooling water into the steel sheet from above and below during the transfer, thereby cooling the high-temperature steel sheet. 2. The cooling device for hot steel sheets according to claim 1, wherein the pass lines of the steel sheets are alternately shifted vertically within a range of elastic deformation of the high-temperature steel sheets. The cooling device for a high-temperature steel sheet according to claim 1, wherein a backup roll is provided on the upper constraining roll. 2. The method according to claim 1, wherein when the interval (roll pitch) between adjacent lower constraining rolls is L, the pass lines of the steel sheet at the positions of the lower constraining rolls are alternately shifted by 0.005 L or more in the vertical direction. The cooling device for a high-temperature steel sheet according to claim 2. The downstream side of the upper restraining rolls, toward the other end from the one end portion of the steel plate, claims 1, characterized in that a draining spray device for purging the cooling water staying on the steel sheet according to claim 3 The cooling device for a high-temperature steel sheet according to any one of the above. A plurality of sets of upper and lower restraining rolls convey a high-temperature steel sheet while constraining it, pouring cooling water into the steel sheet from above and below during conveyance, and cooling the high-temperature steel sheet, pass the steel sheet pass line at the position of the lower constraining roll, A method for cooling a high-temperature steel sheet, wherein cooling is performed while restraining the high-temperature steel sheet by alternately shifting the high-temperature steel sheet vertically within the elastic deformation range of the high-temperature steel sheet. The method for cooling a high-temperature steel sheet according to claim 5 , wherein a backup roll is provided on the upper constraining roll, and cooling is performed while the upper constraining roll is pressed by the backup roll. 6. The cooling method according to claim 5 , wherein when the interval (roll pitch) between adjacent lower constraining rolls is L, cooling is performed by alternately shifting the pass line of the steel sheet at the position of the lower constraining roll in the vertical direction by 0.005 L or more. Alternatively, the method for cooling a high-temperature steel sheet according to claim 6 . By draining spraying device provided on the downstream side of the upper restraining rolls, toward the other end from the one end portion of the steel plate, claims 5 to 7, characterized in that purging the cooling water staying on steel The method for cooling a high-temperature steel sheet according to any one of the above.

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