JP4398898B2 - Thick steel plate cooling device and method - Google Patents

Description

  The present invention relates to a method and apparatus for cooling a thick steel plate, which is applied when cooling a hot-finished thick steel plate when producing a thick steel plate by hot rolling.

  A method of transporting a high-temperature thick steel plate constrained by a restraint roll and cooling it by using a spray nozzle from the upper and lower parts has been conventionally performed, but generally, when the plate width is widened, there is only a water discharge portion between the restraint rolls. Therefore, water easily collects in the upper part of the steel plate (hereinafter, the water accumulated on the steel plate is referred to as plate water). This water on the plate flows in the plate width direction because the water is discharged from the end of the restraint roll. At this time, if the thickness of the plate water in the plate width direction is different, the cooling capacity distribution is distributed in the plate width direction. There is a problem that the temperature difference occurs. In order to solve this problem, measures such as adjusting the amount of water in the plate width direction have been taken, but since the height distribution of the water on the plate is different if the plate width is different, it was not effective control. .

  Therefore, Document 1 discloses a method in which a nozzle box is installed at a distance of 50 mm from a steel plate and cooled by a columnar jet in order to keep the water on the plate at a certain height. Further, in Document 2, as a method of changing the water spraying method, it is disclosed that the top surface is cooled by a slit-like water flow that is uniform in the width direction.

JP 61-84318 A JP 11-347629 A

  However, in the cooling method of Document 1, when used to cool a thick steel plate, the distance between the nozzle box and the steel plate is too short, and there is a risk of damage to equipment. In addition, the columnar jet has the disadvantage that the area of jet impingement on the steel sheet is small, it cannot sufficiently pass through the vapor film, and the cooling capacity is not sufficient.

  In the invention of the cooling method of Document 2 above, when the plate width is wide, the water that has flowed on the steel plate is discharged after colliding with the restraint roll. Therefore, there is a problem that a cooling capacity deviation occurs between the center and the end of the steel plate. Thus, there has been no cooling method that effectively uses the water on the plate.

  The present invention advantageously solves the above-described problem of water on a plate, which is a problem of the prior art, and particularly in the case of cooling by pouring water on the upper and lower surfaces of a thick steel plate between restraining rolls that bite the thick steel plate being conveyed. An object of the present invention is to provide a thick steel plate cooling method and a cooling device capable of uniformly cooling the upper surface to reduce the temperature difference in the width direction of the upper surface, improving the flatness of the steel plate shape, and making the material uniform. It is what.

The present invention is summarized as follows in order to solve the above problems.
That is, according to the present invention, the thickness of water poured between the constraining rolls on the upper and lower surfaces of the thick steel sheet while biting and transporting the high-temperature thick steel sheet with a plurality of sets of constraining rolls formed by upper and lower rolls. The steel plate cooling device has a nozzle box in which a plurality of flat spray nozzles are arranged on the upper surface side, the arrangement of the impinging portion of the nozzle jet is symmetric with respect to the center line in the steel plate width direction, and between the restraining rolls in the steel plate traveling direction. Thick steel plate characterized in that the arrangement of the nozzle jet impingement shape is different from the center line, and the nozzle jet impingement shape is arranged approximately radially from the center point between the restraining rolls in the width direction and the traveling direction of the steel plate. A cooling device is provided.

  The twist angle of the axis of the collision part of the nozzle jet flow by the flat spray nozzle may form an angle of 20 to 45 degrees with respect to the steel plate traveling direction. Further, the spread angle of the nozzle jet of the flat spray nozzle may be 30 to 80 degrees. Furthermore, the distance from the steel plate on the bottom surface facing the steel plate of the nozzle box may be 220 mm or less, and the tip of the flat spray nozzle arranged in the nozzle box may be installed 5 mm or more away from the steel plate from the bottom surface of the nozzle box.

  Further, according to the present invention, in the cooling method using the cooling device described above, the method for cooling a thick steel plate that controls the cooling capacity by changing the height of water staying on the steel plate by changing the height of the nozzle box. Is provided.

  According to the present invention, it is possible to cope with various cooling conditions that vary depending on the type and thickness of the steel plate for creating the material of the steel plate, and it is possible to manufacture a steel plate having a uniform and good shape in the width direction of the steel plate. A cooling device and method can be presented.

  The thick steel plate cooling device of the present invention is, for example, as shown in FIG. 1, a hot rolled steel plate cooling device arranged at the subsequent stage of a hot rolling mill, and obtained by hot rolling with a hot rolling mill. This is particularly effective when a high-temperature steel plate (thick steel plate) having a surface temperature of 750 to 950 ° C. is rapidly cooled to 700 ° C. to room temperature by water injection during conveyance. Below, the structural example of the cooling apparatus of the hot-rolled steel plate of this invention is demonstrated. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is an example of a steel plate manufacturing facility in which a cooling device 4 according to an embodiment of the present invention is arranged. In this example, the finishing mill 1, the descaling device 2, the hot straightening device 3, and the cooling device 4 are arranged in sequence, and the steel plate 6 coming out of the finishing mill 1 is converted into the descaling device 2, the hot straightening device 3, It passes continuously in the order of the cooling device 4. The cooling device 4 includes a plurality of restraining rolls that form a pair of upper and lower rolls 5a and 5b. In this embodiment, the two restraining rolls 5 ₁ and 5 ₂ are spaced apart from each other in the front-rear direction. Has been placed. Further, between these constraining rolls ₅ 1, _{5 2} includes nozzle boxes 4a, 4b are vertically. The rolls 5a are disposed vertically, while conveying bite the steel plate 6 in a high temperature state across 5b, to water injection from each nozzle box 4a, 4b on the upper and lower surfaces of the steel plate 6 between the constraining rolls 5 _1, 5 ₂ Thus, the steel plate 6 is cooled while being conveyed. In addition, as shown with the dashed-dotted line in FIG. 1, three or more restraining rolls (for example, 5 ₃ , 5 ₄ ) including upper and lower rolls 5a, 5b are provided, and nozzle boxes 4a, 4b are also provided between them. May be. That is, the combination of the nozzle boxes 4a and 4b may be one stage or two or more stages.

  A plurality of flat spray nozzles 7 for injecting cooling water toward the upper surface of the steel plate 6 are arranged in the upper nozzle box 4a, and cooling water is blown downward from the plurality of flat spray nozzles 7 respectively. Water is poured on the upper surface of the steel plate 6. FIG. 2 is an arrangement view of the collision portion shape 9 of the nozzle jet 8 ejected from each flat spray nozzle 7. 3A and 3B are explanatory diagrams of the flat spray nozzle 7, in which FIG. 3A shows a state in which the nozzle jet 8 is viewed from the side, and FIG. 3B shows a state in which the nozzle jet 8 is viewed from above.

  As shown in FIG. 3, the nozzle jet 8 ejected from the flat spray 7 flows along the surface of the steel plate 6 and is discharged after colliding with the surface of the steel plate 6. In this case, the larger the spray angle θ, the more flat the flow in the spreading direction 10 is. Further, in the flat spray nozzle 7, the central portion of the nozzle jet 8 for ejecting the water flow in a fan shape is a wall shape, and a pseudo partition wall of the nozzle jet 8 can be formed on the surface of the steel plate 6. Then, the nozzle jets 8 of the flat spray nozzles 7 as shown in FIG. 3 are arranged adjacent to each other so as not to collide with each other as shown in FIG.

As shown in FIG. 2, each of the linear collision portion shapes 9 formed by the nozzle jets 8 ejected from the flat spray nozzles 7 colliding with the surface of the steel plate 6 is converted into a twist angle with respect to the traveling direction of the steel plate 6. α (the twist angle α of the axis of the collision portion of the nozzle jet 8 by the flat spray nozzles 7 on the surface of the steel plate 6) is arranged so as to form an angle of 20 to 45 degrees. At that time, with respect to the center line L in the width direction of the steel plate 6, the respective collision part shapes 9 located on the left side in FIG. 2 and the respective collision part shapes 9 located on the right side in FIG. Deploy. Further, the boundary of the center line M between the traveling direction of the constraining rolls 5 _1, 5 ₂ of the steel plate 6, and become a region above (constraining rolls 5 ₁ side) in a 2, lower (constraining rolls in a 2 5 the ₂ side) and a region, the arrangement of the collision portion shape 9 causes differently. In the upper right region in FIG. 2, the respective collision portion shapes 9 are arranged such that the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the clockwise direction in FIG. In the upper left region, each of the collision portion shapes 9 is arranged such that the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the counterclockwise rotation direction in the figure. Further, in the lower right region in FIG. 2, the respective collision portion shapes 9 are arranged such that the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the counterclockwise direction in the drawing. In the lower left region in FIG. 2, the respective collision portion shapes 9 are arranged such that the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the clockwise direction in the drawing. In this way, any of the collision portion shapes 9 are arranged substantially radially from the center point O between the restraining rolls in the width direction and the traveling direction of the steel plate 6.

Further, in this embodiment, as described above with reference to FIG. 4, the water jets of the flat spray nozzles 7 are disposed adjacent to each other without colliding with each other. Each of the collision part shape columns 9 _{1 to} 9 ₆ and the collision part shape columns 9 ₁ ′ to 9 ₆ ′ in which one or two or more collision part shapes 9 are arranged in a substantially straight line is formed. At that time, relates centerline L in the width direction of the steel sheet 6, and the collision portion shape columns 91 _to 93 ₃ and the collision portion shape column 9 ₁ 'to 9 _3' located on the left side in the figure 2, the right side in the figure 2 collision portion shape train ₉ located 4 to 9 ₆ and the collision portion shape column _{9 4} 'to 9 _6' is symmetrical, also border the center line M between the constraining rolls ₅ 1, _{5 2} traveling direction of the steel sheet 6 a manner, a collision portion shape columns 91 _to 93 ₆ and a region above (constraining rolls 5 ₁ side) in a 2, the collision portion shape of a region lower (constraining rolls 5 ₂ side) in a 2 In the columns 9 ₁ ′ to 9 ₆ ′, the arrangement is different. In each of the collision part shape rows 9 _{4 to} 9 ₆ in the upper right region in FIG. 2, the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the clockwise direction in FIG. None of the collision portion shape columns 91 _to 93 _3, the angle of twist angle α is 20 to 45 degrees counter clockwise direction in the drawing with respect to the traveling direction of the steel plate 6 of the upper left area in the middle, lower in the figure 2 Each collision part shape row 9 ₄ ′ to 9 ₆ ′ in the right region has a twist angle α of 20 to 45 degrees in the counterclockwise direction in the drawing with respect to the traveling direction of the steel plate 6. In each of the collision portion shape rows 9 ₁ ′ to 9 ₃ ′ in the region, the twist angle α with respect to the traveling direction of the steel plate 6 forms an angle of 20 to 45 degrees in the clockwise direction in the drawing. Thus, any of the collision part shape rows 9 _{1 to} 9 ₆ and the collision part shape rows 9 ₁ ′ to 9 ₆ ′ are arranged substantially radially from the center point O between the restraining rolls in the width direction and the traveling direction of the steel plate 6. It will be.

In this way, each impingement portion is formed substantially radially from the center point O between the restraining rolls in the width direction and the traveling direction of the steel plate 6 while forming a pseudo partition wall by the nozzle jet 8 of each flat spray nozzle 7 on the surface of the steel plate 6. By placing the shapes 9 (each of the collision portion shape rows 9 _{1 to} 9 ₆ and the collision portion shape rows 9 ₁ ′ to 9 ₆ ′) and performing water injection, the water on the steel plate 6 becomes as shown in FIG. constraining rolls 5 _1, at most between 5 ₂ flows in the traveling direction of the steel sheet 6, to be discharged from the restrained roll 5 _1, 5 ₂ near the ends of the steel plate 6 in. As described above, in the present invention, the pseudo partition wall formed by the nozzle jet 8 of the flat spray nozzle 7 suppresses the discharge flow of the jet refrigerant from the flat spray nozzle 7 from both ends of the steel plate 6, so It is possible to form a plate-like water having a height that does not depend much on the plate width for each of the collision portion shape rows 9 _{1 to} 9 ₆ and the collision portion shape rows 9 ₁ ′ to 9 ₆ ′.

  In addition, as shown in FIG. 5, when the present inventors investigated the relationship between board water height and cooling capacity, it turned out that cooling capacity is increasing with the board water height increasing. Therefore, for example, when the plate width of the steel plate 6 is narrowed, the water height on the plate is lowered with the conventional nozzle arrangement, but in the present invention, the water height on the plate is reduced due to the partition wall effect in the width direction. The margin is small and it is possible to maintain a high cooling capacity.

  In other words, the nozzle arrangement as shown in FIG. 2 makes it possible to increase the water height on the plate uniformly in the width direction in the width direction of the steel plate 6 and to improve the cooling capacity uniformly in the width direction. Cost can be reduced. In addition, by forming the pseudo partition, it becomes possible to reduce the change in the plate water direction in the plate width direction regardless of the plate width, and the shape of the steel plate 6 can be reduced by reducing the temperature deviation in the plate width direction. Properties and material properties can be homogenized. In addition, since the on-plate water tends to escape from the end of the steel plate 6, the cooling capacity is slightly lowered, and the supercooling state generated at the end of the steel plate 6 can be prevented.

  At this time, the twist angle α with the traveling direction of the steel plate 6 of each linear collision portion shape 9 formed by the nozzle jet 8 injected from the flat spray nozzle 7 (the surface of the steel plate 6 of the nozzle jet 8 by the flat spray nozzle 7) The twist angle α) of the axis of the collision part is preferably 20 to 45 degrees. If this angle α is smaller than 20 degrees, a vertical stripe pattern may be formed on the surface of the steel plate 6 and it is not preferable in appearance, and a portion with strong cooling is locally generated, which causes material variation. . On the other hand, when the angle α is larger than 45 degrees, the steel plate 6 flows in the width direction, the on-board water deterring force due to the pseudo partition effect is reduced, and the uniformity in the width direction is lowered.

Further, as described above with reference to FIG. 4, it is preferable that the nozzle jets 8 ejected from the flat spray nozzles 7 are arranged adjacent to each other so as not to collide with each other. As shown in FIG. 6, when the nozzle jets 8 ejected from the adjacent flat spray nozzles 7 do not overlap each other, the respective collision part shapes 9 formed on the surface of the plate 6 are separated from each other, and the respective collision part shapes are formed. The rows 9 _{1 to} 9 ₆ and the collision part shape rows 9 ₁ ′ to 9 ₆ ′ also do not become continuous linear shapes. In that case, there is almost no partition effect, and the effect of the present invention cannot be fully enjoyed.

  Further, as shown in FIG. 7, it has been experimentally confirmed that when the distance b between the flat spray nozzle 7 and the steel plate 6 is 220 mm or more, the cooling capacity is remarkably lowered, and below this distance (220 mm). The nozzle box 4a is installed. However, this is the case when the nozzle discharge pressure is constant at a maximum of 0.3 MPa. When the nozzle discharge pressure increases, the distance b between the nozzle and the steel plate 6 may be further increased. Is possible. In order to reduce the cooling capacity, the water discharge pressure may be reduced. If the distance is 220 mm or less, the cooling capacity is increasing. However, when the distance b between the flat spray nozzle 7 and the steel plate 6 is reduced, the collision width c of the nozzle jet is reduced, and the partition effect is generated. Therefore, it is necessary to increase the number of nozzles, and the amount of processing of the nozzle box 4a for installing a large number of flat spray nozzles 7 is large, which is economically disadvantageous. From this viewpoint, the distance b between the flat spray nozzle 7 and the steel plate 6 is preferably about 100 mm. Since the steel plate 6 being conveyed may collide with the nozzle tip, it is necessary to retract 5 mm or more so that the tip of the flat spray nozzle 7 is hidden in the nozzle box 4a as shown in FIG.

  Furthermore, as shown in FIG. 9, by changing the height of the flat spray nozzle 7 (distance b between the flat spray nozzle 7 and the steel plate 6), the height of the pseudo partition wall can be adjusted, Capability control is also possible. Thereby, cooling according to various board thickness and the kind of steel plate 6 is attained. By changing the height of the nozzle box 4a, it is possible to control the cooling capacity by changing the height of the water staying on the steel plate 6.

  This is the effect of the spread angle θ of the nozzle jet 8 injected from the flat spray nozzle 7 and the distance b between the flat spray nozzle 7 and the steel plate 6. Generally, when the spread angle θ increases, it greatly contributes to cooling when the steel plate collides. As shown in FIG. 10, the velocity component in the direction perpendicular to the steel plate 6 is reduced, and the length of passage through the plate water 11 is increased, so that the jet velocity attenuation is increased and the cooling capacity is reduced. . Further, when the distance b between the flat spray nozzle 7 and the steel plate 6 is increased, the attenuation of the jet flow in the on-board water 11 is increased and the cooling capacity is lowered.

  FIG. 4 shows the relationship between the distance a between the flat spray nozzles 7, the distance b between the flat spray nozzle 7 and the steel plate 6, and the spread angle θ of the nozzle for causing the partition effect by the flat spray nozzle 7. It was. In FIG. 4, it is desirable that the relationship 0.5 <a / {b · tan (θ / 2)} <1.8 be satisfied in order to produce the partition wall effect. This equation shows a ratio of the distance a between the flat spray nozzles 7 and a half of the spread of the jet, and serves as an index indicating the overlap of the jets. FIG. 11 shows the relationship between the partition wall height c / b and a / {b · tan (θ / 2)}. The spread angle θ of the jet flow of the flat spray nozzle 7 is preferably 30 to 80 degrees.

  When 1.8 <a / {b · tan (θ / 2)}, the partition wall effect is reduced, and the flow of plate water in the steel plate width direction cannot be suppressed. Further, when 0.5> a / {b · tan (θ / 2)}, the distance a between the flat spray nozzles 7 becomes small, and the efficiency becomes poor. Table 1 shows the range (mm) of a (distance between nozzles) when 0.5 <{b · tan (θ / 2)} <1.8.

  When the cooling capacity is adjusted by changing the height of the nozzle box 4a, a / {b · tan (θ / 2)} is 0.5 to 1.8 within the height control range of the nozzle box 4a. To enter.

Examples of the thick steel plate cooling apparatus and method according to the present invention will be specifically described below.
[Example 1]
In the steel plate manufacturing facility in which the steel plate cooling device according to the embodiment of the present invention described above is disposed, 15 sets of restraining rolls arranged at a distance of 900 mm in the front and rear are arranged, and each restraining roll is described above. A nozzle box comprising a plurality of flat spray nozzles arranged in the width direction of the steel plate is arranged on the upper surface side of the thick steel plate that is intercalated and conveyed. The nozzle box was arranged between 15 sets of restraining rolls. Moreover, 13 units | sets were operated (water injection) among 14 nozzle boxes each arrange | positioned between those 15 sets of restraint rolls. The flat spray nozzle has a spread angle of 30 degrees, uses a flat spray nozzle that discharges 15 L / min at 0.3 MPa, sets the distance between the nozzle and the steel plate to 220 mm, the width direction nozzle pitch is 75 mm, and the nozzle row in the steel plate traveling direction The interval pitch was 60 mm. As a result, the distance between adjacent nozzles causing the partition effect is 96 mm, and a / {b · tan (θ / 2)} = 1.63, c / b = 0.185. At this time, the twist angle formed by the axis of the impinging portion of the nozzle jet ejected from the flat spray nozzle with the traveling direction of the steel sheet was 25 degrees. Here, the nozzle box on the lower surface side is also arranged in the same manner as the upper surface side.

In this Example 1, a steel plate having a thickness of 25 mm and a width of 4000 mm obtained by finish rolling was hot-corrected after descaling and then bitten into 15 sets of constraining rolls, with a conveyance speed of 70 m. Water was injected at a water density of 1.0 m ³ / m ² / min from the six rows of water injection nozzles on the upper surface side while cooling at a rate of / min. The amount of water from each flat spray nozzle of the water injection nozzle row on the upper surface side was 11 L / min. On the other hand, the lower surface side was cooled by injecting water with a water density of 1.3 m ³ / m ² / min.

  When the temperature of the thick steel plate after being cooled for 10 seconds by this cooling was measured, the steel plate temperature was 500 ° C at the center in the width direction, and the uniformity was as high as ± 10 ° C in the width direction. We were able to obtain a sufficiently satisfying thick steel plate with excellent uniformity in both shape and material. The measurement of the steel plate temperature here was performed by excluding the edge region corresponding to twice the plate thickness from the end of the steel plate surface.

[Example 2]
In Example 2, the nozzle is a flat spray nozzle that discharges 18 L / min at a spread angle of 80 degrees, 0.3 MPa, the distance between the nozzle and the steel plate is 100 mm, the nozzle width in the width direction is 75 mm, and the nozzle in the steel plate traveling direction The pitch between rows was 60 mm. As a result, the distance between adjacent nozzles causing the partition effect is 96 mm, and a / {b · tan (θ / 2)} = 1.14, c / b = 0.43. At this time, the twist angle formed by the axis of the impinging portion of the nozzle jet ejected from the flat spray nozzle with the traveling direction of the steel sheet was 25 degrees. Here, the cooling row 4b on the lower surface side is also arranged in the same manner as the upper surface side.

In this Example 2, a thick steel plate having a thickness of 25 mm and a width of 4000 mm obtained by finish rolling was hot-corrected after descaling and then bitten into 15 sets of restraining rolls as in Example 1. Then, water was injected at a water density of 1.0 m ³ / m ² / min from the six water injection nozzle rows on the upper surface side and cooled while being conveyed at a conveyance speed of 70 m / min. The amount of water from each flat spray nozzle of the water injection nozzle row on the upper surface side was 11 L / min. On the other hand, the lower surface side was cooled by injecting water with a water density of 1.3 m ³ / m ² / min.

  When the temperature of the thick steel plate after being cooled for 10 seconds by this cooling was measured, the steel plate temperature at the central portion in the width direction was 515 ° C, and the uniformity was as high as ± 10 ° C in the width direction. We were able to obtain a sufficiently satisfying thick steel plate with excellent uniformity in both shape and material.

[Example 3]
In Example 3, the nozzle is a flat spray nozzle that discharges 18 L / min at an expansion angle of 80 degrees, 0.3 MPa, the distance between the nozzle and the steel plate is 100 mm, the nozzle width in the width direction is 75 mm, and the nozzle in the steel plate traveling direction The pitch between rows was 60 mm. As a result, the distance between adjacent nozzles causing the partition effect is 96 mm, and a / {b · tan (θ / 2)} = 1.14, c / b = 0.43. At this time, the twist angle formed by the nozzle jet sprayed from the flat spray nozzle and the steel plate traveling direction was 40 degrees. Here, the cooling row on the lower surface side is also arranged in the same manner as the upper surface side.

In this Example 3, a steel plate having a thickness of 25 mm and a width of 4000 mm obtained by finish rolling was hot-corrected after descaling and then bitten into 15 sets of restraining rolls as in Example 1. Then, water was injected at a water density of 1.0 m ³ / m ² / min from the six water injection nozzle rows on the upper surface side and cooled while being conveyed at a conveyance speed of 70 m / min. The amount of water from each flat spray nozzle of the water injection nozzle row on the upper surface side was 11 L / min. On the other hand, the lower surface side was cooled by injecting water with a water density of 1.3 m ³ / m ² / min.

  When the temperature of the thick steel plate after being cooled for 10 seconds by this cooling was measured, the uniformity was as high as ± 12 ° C in the width direction compared to the steel plate temperature of 517 ° C in the center in the width direction. We were able to obtain a sufficiently satisfying thick steel plate with excellent uniformity in both shape and material.

[Comparative Example 1]
In Comparative Example 1, the nozzle is a flat spray nozzle that discharges 18 L / min at an expansion angle of 80 degrees and 0.3 MPa, the distance between the nozzle and the steel plate is 100 mm, the nozzle pitch in the width direction is 75 mm, and the nozzle in the steel plate traveling direction The pitch between rows was 60 mm. As a result, the distance between adjacent nozzles causing the partition effect is 96 mm, and a / {b · tan (θ / 2)} = 1.14, c / b = 0.43. At this time, the twist angle formed by the nozzle jet sprayed from the flat spray nozzle with respect to the steel plate traveling direction is set to 25 degrees. However, unlike the requirements of the present invention, as shown in FIG. Rows 9 _{1 to} 9 ₇ were arranged. Here, the cooling row on the lower surface side is also arranged in the same manner as the upper surface side here.

In Comparative Example 1, a steel plate having a thickness of 25 mm and a width of 4000 mm obtained by finish rolling was hot-corrected after descaling and then bitten into 15 sets of restraining rolls as in Example 1. Then, water was injected at a water density of 1.0 m ³ / m ² / min from the six water injection nozzle rows on the upper surface side and cooled while being conveyed at a conveyance speed of 70 m / min. The amount of water from each flat spray nozzle of the water injection nozzle row on the upper surface side was 11 L / min. On the other hand, the lower surface side was cooled by injecting water with a water density of 1.3 m ³ / m ² / min.

  When the temperature of the thick steel plate after being cooled for 10 seconds by this cooling was measured, the steel plate temperature at the center in the width direction was 520 ° C, and the uniformity in the width direction was ± 30 ° C. It became a thick steel plate with problems. As a cause of this non-uniform cooling, when the flow of the on-board water in the case of FIG. 12 was observed, as shown in FIG. This is considered to have caused non-uniformity.

[Comparative Example 2]
In Comparative Example 2, the nozzle is a flat spray nozzle that discharges 18 L / min at a spread angle of 60 degrees and 0.3 MPa, the distance between the nozzle and the steel plate is 100 mm, the nozzle width in the width direction is 85 mm, and the nozzle in the steel plate traveling direction The pitch between rows was 75 mm. As a result, the distance between adjacent nozzles causing the partition effect is 113 mm, and a / {b · tan (θ / 2)} = 1.95, c / b = 0.02 (FIG. 6). At this time, the twist angle formed by the nozzle jet injected from the flat spray nozzle with the steel plate traveling direction was set to 25 degrees. Here, the cooling row on the lower surface side is also arranged in the same manner as the upper surface side.

In Comparative Example 2, a steel plate having a thickness of 25 mm and a width of 4000 mm obtained by finish rolling was hot-corrected after descaling and then bitten into 15 sets of restraining rolls as in Example 1. Then, water was injected at a water supply density of 1.0 m ³ / m ² / min from the six water injection nozzle rows on the upper surface side and cooled while being conveyed at a conveyance speed of 70 m / min. The amount of water from each flat spray nozzle of the water injection nozzle row on the upper surface side was 11 L / min. On the other hand, the lower surface side was cooled by injecting water with a water density of 1.3 m ³ / m ² / min.

  When the temperature of the thick steel plate after being cooled for 10 seconds by this cooling was measured, the steel plate temperature at the center in the width direction was 530 ° C, and the uniformity was low at ± 20 ° C in the width direction. It became a thick steel plate with problems. As a cause of this non-uniform cooling, it is considered that the partition wall effect is not sufficient as shown in FIG.

  The present invention can be used for cooling a hot-finished thick steel plate.

It is explanatory drawing of the thick steel plate manufacturing equipment which has arrange | positioned the cooling device concerning embodiment of this invention. It is an arrangement drawing of the shape of the collision part of the nozzle jet injected from each flat spray nozzle. It is explanatory drawing of the jet state of a flat spray nozzle, Comprising: (a) shows the state which looked at the nozzle jet from the side, (b) has shown the state which looked at the nozzle jet from the top. It is explanatory drawing of the nozzle jet injected from each flat spray nozzle. It is a figure which shows the relationship between board water height and cooling capacity. It is explanatory drawing when the nozzle jets injected from the adjacent flat spray nozzle do not mutually overlap. It is a figure which shows the relationship between the distance between a flat spray nozzle and a steel plate, and cooling capacity. It is a figure which shows the positional relationship of a flat spray nozzle and a nozzle box. It is explanatory drawing which shows the change of the pseudo partition when changing the distance between a flat spray nozzle and a steel plate. It is a schematic diagram at the time of a jet passing water on a board. It is a figure which shows the relationship between the distance between a flat spray nozzle and a steel plate, and the height of a pseudo partition. It is explanatory drawing of the comparative example of this invention. It is a schematic diagram which shows the flow of the on-plate water in the comparative example of FIG.

Explanation of symbols

1 finishing mill 2 descaling device 3 hot straightening unit 4 cooling device 4a, 4b nozzle box 5a, 5b roll 5 _{1, 5 2} constraining rolls 6 7 steel flat spray nozzles 8 nozzles jets 9 colliding part shape 91 _to 93 ₆ , 9 ₁ ′ to 9 ₆ ′ Colliding portion shape row 10 Nozzle jet spreading direction 11, 12 Surface water 13 Surface water retention portion

Claims (5)

  In the thick steel plate cooling device that injects water into the upper and lower surfaces of the thick steel plate between the constraining rolls while the high-temperature thick steel plate is bitten and transported by a plurality of pairs of constraining rolls that form a set of upper and lower rolls. The nozzle box has a plurality of flat spray nozzles, and the arrangement of the impingement shape of the nozzle jet is symmetric with respect to the center line in the width direction of the steel sheet. An apparatus for cooling a thick steel plate, characterized in that the shape of the collision portion is different and the shape of the collision portion of the nozzle jet is arranged substantially radially from the center point between the restraining rolls in the steel plate width direction and the traveling direction.   The cooling device according to claim 1, wherein the twist angle of the axis of the impinging portion of the nozzle jet by the flat spray nozzle forms an angle of 20 to 45 degrees with the steel plate traveling direction.   3. The apparatus for cooling a thick steel plate according to claim 1 or 2, wherein a spread angle of the nozzle jet of the flat spray nozzle is 30 to 80 degrees.   The distance from the steel plate on the bottom surface facing the steel plate of the nozzle box is 220 mm or less, and the tip of the flat spray nozzle arranged in the nozzle box is installed 5 mm or more away from the steel plate from the bottom surface of the nozzle box. The cooling apparatus of the thick steel plate in any one of Claims 1-3.   In the cooling method using the cooling device in any one of Claims 1-4, the thickness of the steel plate which controls the cooling capacity by changing the height of the water which stagnates on a steel plate by changing the height of a nozzle box. Cooling method.

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