JP2006212666A - Apparatus and method for cooling thick steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling apparatus and a cooling method of a thick steel plate by which supercooling in both end parts in the thickness direction is prevented and the thick steel plate is uniformly cooled without generating irregular cooling when cooling a high-temperature thick steel plate which is hot-rolled. <P>SOLUTION: Because cooling water to the both end parts in the width direction of a thick steel plate 1 of the cooling water jetted from an upper slit nozzle 4 is collided with a masking plate 6 and its jet angle is turned upward without disturbing the water stream, the water landing position is moved to the downstream side of the water landing position of the cooling water to the middle part in the width direction of the thick steel plate 1. In this way, the quantity of cooling in the both end parts in the width direction of the thick steel plate can correspond to the quantity of cooling in the middle part in the width direction of the thick steel plate and, as a result, the thick steel plate having a uniform temperature distribution in the width direction is manufactured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a thick steel plate cooling apparatus and cooling method, and more specifically, a thick steel plate cooling apparatus and cooling method capable of uniformly cooling by eliminating temperature deviation in the thick steel plate width direction after controlled cooling. About.

  In recent years, hot-rolled high-temperature (700 to 900 ° C.) thick steel plates are controlled and cooled online after hot rolling in order to obtain predetermined material properties or improve production efficiency. By this method, material properties such as high strength and high toughness can be obtained without increasing various additive elements, and a thick steel plate having excellent weldability can be produced at low cost because it is a low alloy component.

  As a means to cool hot rolled steel plates after being rolled online, cooling water nozzles are arranged in the plate width direction on the upper and lower surfaces of the thick steel plates that are transported into the cooling device, and cooling water is injected. The method of cooling is generally used.

  At this time, if the temperature deviation in the steel plate after controlled cooling is large, the occurrence of steel plate distortion, residual stress, material variation, etc., and operational troubles due to steel plate distortion may occur. When the thick steel plate is deformed, it is inevitable that the cost is increased because a forming operation using a press, a straightening machine, or the like is required in the refining process. In addition, the thick steel plate that has become a product may be cut as a secondary processing step, but if there is residual stress in the plate, the amount of deformation in the width direction of the steel plate after cutting (the cut camber) will increase. Even in the secondary processing step, such as the need for a correction process again, handling becomes a heavy burden.

  As a cooling water supply method for strongly cooling a thick steel plate, (a) a circular pipe jet, (b) a flat spray, and (c) a slit laminator shown in FIG. 14 are generally used. In the case of (a) a circular pipe jet and (b) a flat spray, the cooling capacity of the cooling water collision part is very high, but in order to uniformly cool a thick steel plate having a wide width of 2 m to 5 m, a large number of nozzles are used. It is necessary to arrange with high density. Therefore, a large amount of water is required and maintenance is poor. On the other hand, in the case of (c) slit laminar, the uniformity in the width direction is easy to control. In particular, when cooling the top surface, as shown in (d), by injecting the slit nozzle at a predetermined angle with respect to the thick steel plate, it is possible to perform strong cooling uniformly over a wide range even with a small amount of water. is there. Features of this cooling method include that the slit nozzle and the thick steel plate are brought close to each other and that the collision force at the collision point is very large.

  However, even when a cooling method capable of uniformly and strongly cooling, such as slit laminar, is used, a phenomenon in which the temperature is lower than that at the center portion of the thick steel plate is observed at the end portion in the width direction of the thick steel plate. The following three causes are considered for the overcooling phenomenon at the end in the width direction of the thick steel plate.

(1) Thing due to air cooling during rolling When a thick steel plate is manufactured by a general rolling process, in addition to air cooling from the top and bottom surfaces of the thick steel plate at the four circumferences of the thick steel plate during the rolling stage, Therefore, the temperature is lower than that of the central part of the thick steel plate. Also, when such a thick steel plate is controlled and cooled, even if it is cooled with a uniform cooling capacity over the entire surface of the thick steel plate, the four circumferences of the thick steel plate are already supercooled compared to the center of the thick steel plate before cooling. Therefore, this temperature distribution is maintained even after cooling.

(2) Thing caused by boiling phenomenon during water cooling When a thick steel plate is cooled in a state where there is a temperature deviation in the steel plate before cooling, the temperature deviation may increase. FIG. 15 shows the surface temperature of the thick steel plate and the heat flux (the amount of heat removed per unit area and unit time: cooling capacity) when the high temperature thick steel plate having a surface temperature of 700 ° C. or higher is cooled. Film boiling occurs when the steel plate surface temperature is high, nucleate boiling occurs when the steel plate surface temperature is low, and transition boiling occurs in the middle region. In the state of nucleate boiling or film boiling, the higher the thick steel plate surface temperature, the higher the heat flux, and the lower the thick steel plate surface temperature, the lower the heat flux. Therefore, even if there is a temperature deviation in the steel sheet, the portion having a high surface temperature is likely to be cooled, and the portion having a low surface temperature is difficult to be cooled. On the contrary, in the state of transition boiling, it can be seen that the temperature deviation is increased because the part with the high surface temperature is difficult to cool and the part with the low surface temperature is easy to cool. The relation between the steel plate surface temperature and the heat flux can be increased and decreased depending on the cooling water density, but in general control cooling, cooling is often performed at a cooling water density at which transition boiling occurs in such a boiling state. For this reason, the temperature deviation in the thick steel plate after cooling is often increased.

(3) Thing caused by drainage on the upper surface of the thick steel plate When the thick steel plate is cooled in a horizontal state, the cooling water flows in the outer peripheral direction and falls from the end of the steel plate at the upper part of the thick steel plate. Therefore, at the end of the upper surface of the thick steel plate, in addition to the cooling water sprayed from the nozzle installed on the upper portion of the thick steel plate, cooling is performed by the cooling water drained to the thick steel plate. The amount of water increases and the cooling rate increases. It should be noted that such a phenomenon does not occur on the lower surface of the thick steel plate because the collided cooling water quickly drops.

  From the three mechanisms as described above, the temperature of the end portion of the thick steel plate after the controlled cooling is lower than that of the central portion. Various apparatuses and methods for solving this problem and uniformly cooling a high-temperature thick steel plate have been proposed in the past, and are disclosed as follows.

  In the method disclosed in Patent Document 1, as shown in FIG. 16, in the vicinity of the injection nozzle of the slit nozzle 64 toward the upper surface of the hot-rolled steel plate 61, a predetermined interval is provided from the slit nozzle 64 in the steel plate width direction. The positioned water flow control body 66 is provided so as to move in the length direction of the slit nozzle 64, and since this water flow control body 66 has a streamline shape, the water flow is not disturbed, and the both ends of the steel plate are not disturbed. Cooling water is excluded.

  As shown in FIG. 17, the method disclosed in Patent Document 2 uses air jet slit nozzle 77 provided at the lower part of the jet nozzle of coolant water slit nozzle 74 facing the upper surface of hot-rolled steel sheet 71. 79 is jetted, the cooling water 78 is lifted and carried by the jet air 79, and the section L ′ where the cooling water stays is shortened by moving the landing position of the cooling water 78 on the upper surface of the steel plate away from the nozzle position. The cooling capacity is controlled.

  The method disclosed in Patent Document 3 is intended for preliminary cooling before controlled cooling using a spray nozzle as shown in FIG. 18, but hot rolling was performed on the upper and lower surfaces of the steel plate pass line on the upstream side of the cooling device. The width of the spray header 88 in which cooling water is jetted onto the surface of the steel plate 81, and the trapezoidal masking plate 87 having a flat shape provided between the spray header 88 and the steel plate 81 at the center in the width direction, After adjusting the relative position between the spray header 88 and the shielding plate 87 in the sheet passing direction so that the cooling area W at both ends in the direction becomes a desired width, both ends in the width direction of the hot rolled steel sheet It is to be cooled.

In the method disclosed in Patent Document 4, as shown in FIG. 19, a masking plate 92 in which a flowing water speed-reducing member or a brush 93 is attached to the upper and lower surfaces of the steel plate 91 is disposed at the position of the plate width direction end of the steel plate 91. The amount of cooling at the end in the width direction of the steel plate is reduced by slowing the flow rate of flowing water that enters the gap between the steel plate 91 and the masking plate 92 and using the masking plate 92 intermittently during cooling. Is to control.
JP-A-10-216824 JP-A-10-291019 JP 2000-192146 A JP 2002-263724 A

  However, in the method disclosed in Patent Document 1, whether or not the water flow control body has a streamline shape, only the section shielded by the water flow control body can be drained. Don't be. Therefore, there have been many structural problems such as the weight of the masking portion becoming very heavy, a member having high rigidity is required, and maintenance is frequently required. Further, even if the water flow control body is formed into a streamline shape, a part of the cooling water colliding with the water flow control body is scattered as it is directly on the upper surface of the steel plate, and the meaning of shielding the water flow is lost.

  In the method disclosed in Patent Document 2, the flow of the cooling water is disturbed by the jet air from the gas injection slit nozzle provided in the lower part of the cooling water slit nozzle, and the uniformity in the steel sheet width direction is deteriorated. In addition, it was found that the landing position range of the cooling water that can be controlled by the economical injection air amount is very narrow. Further, when cooling with a slit nozzle provided at a certain angle with respect to the thick steel plate, it is necessary to bring the nozzle close to the upper surface of the thick steel plate, so that there is a problem that it is very difficult to insert the nozzle for gas injection.

  In the method disclosed in Patent Document 3, although the direct collision of the cooling water sprayed from the spray nozzle can be avoided by the masking plate, the cooling water riding on the upper surface of the high-temperature steel plate enters the gap between the masking plate and the masking plate. Since it penetrates and flows out from both ends in the width direction of the steel sheet and cools the side surface in the width direction, it does not prevent the end portion from overcooling. In addition, since the masking plate receives a collision jet pressure from the spray nozzle over a large area, if deformation is taken into consideration, it must be a device with considerable rigidity, and the distance between the spray nozzle and the steel plate must be increased. It is disadvantageous from the viewpoint of nozzle proximity that is generally performed for the purpose of uniformly cooling the high-temperature steel sheet in the width direction.

  In the method disclosed in Patent Document 4, in order to solve the problems described in Patent Documents 1 and 2, etc., a flowing water moderation member such as a brush is introduced on the steel plate side surface of the masking plate, and this masking plate is intermittently cooled. By using this, the temperature drop amount control at the end in the width direction of the steel sheet is performed. When using flowing water moderators such as brushes for these purposes, we are striving to protect the surface of the steel sheet in various ways, but since these are installed so as to be in contact with the steel sheet, the scale on the surface of the steel sheet is unavoidable. It is not difficult to imagine that the surface appearance of the steel sheet deteriorates due to partial peeling. Furthermore, the surface property (scale thickness and roughness) in the width direction of the steel sheet varies, so that the cooling characteristics of the steel sheet also change, and instead of making the temperature distribution in the width direction uniform, a temperature deviation tends to occur. In addition, when steam is generated by a flowing water moderation member such as a brush, even if this masking plate is used intermittently during cooling, the end in the width direction of the steel plate is always in a boiling state where a steam film exists, and the temperature in the width direction after cooling is reduced. Controllability is much worse.

  As described above, in the prior art, it is not possible to properly prevent overcooling at both ends in the width direction of the steel sheet, and in some cases, the surface property of the thick steel sheet as a product may be further deteriorated. . Therefore, it has not been possible to prevent occurrence of deformation, residual stress, material variation, operational troubles due to deformation of the thick steel plate, etc. in the thick steel plate after cooling.

  The object of the present invention is to solve the above-mentioned problems, and when cooling a hot-rolled high-temperature thick steel plate, it prevents overcooling at both ends in the width direction of the plate, and makes the thick steel plate uniformly without causing cooling unevenness. An object of the present invention is to provide a cooling apparatus and cooling method for a thick steel plate that can be cooled.

  In order to solve the above problems, the present invention has the following features.

  [1] In a cooling apparatus for a thick steel plate provided with a slit nozzle having a predetermined injection angle with respect to the upper surface of the thick steel plate as a cooling water nozzle on the upper surface side of the thick steel plate, with respect to the injection direction from the injection port of the slit nozzle A shielding member that shields a predetermined distance in the width direction of the slit nozzle is provided in a predetermined direction, and the cooling water sprayed from the slit nozzle is collided with the shielding member to change the injection angle of the cooling water. Thus, a cooling device for a thick steel plate, wherein the landing position of the cooling water sprayed from the slit nozzle on the thick steel plate is different in the width direction of the thick steel plate.

  [2] The injection angle θ1 of the slit nozzle with respect to the upper surface of the thick steel plate is 5 ° ≦ θ1 ≦ 50 °, and the angle θ3 formed by the injection direction of the slit nozzle and the collision surface of the shielding member with which cooling water collides is 0 ° <θ3 <40 °, the thick steel plate cooling device according to [1].

  [3] The thick steel plate cooling device according to [1] or [2], wherein the shielding member is capable of changing a shielding distance in a width direction of the slit nozzle.

  [4] The cooling apparatus for thick steel plates according to any one of [1] to [3], wherein an angle θ3 formed by a collision surface of the shielding member and an injection direction of the slit nozzle is variable.

  [5] Thick steel plate longitudinal length of the shielding member is not less than 10 times the slit thickness of the slit nozzle. Cooling of the thick steel plate according to any one of [1] to [4] apparatus.

  [6] A plurality of pairs of restraining rolls for restraining the thick steel plate at the top and bottom are provided, and each of the cooling zones configured to be partitioned by a pair of front and rear restraining rolls includes a slit nozzle and the shielding member. The apparatus for cooling a thick steel plate according to any one of the above [1] to [5].

  [7] The thick steel plate cooling apparatus according to [6], wherein the angle of the collision surface of the shielding member is set to a predetermined angle so that the cooling water does not get over the restraining roll.

  [8] Using the thick steel plate cooling device according to any one of [1] to [7], the landing position of the cooling water sprayed from the slit nozzle on the thick steel plate by the shielding member Thick steel plate characterized by controlling the amount of cooling at both ends in the width direction of the steel sheet so that the landing position at both ends in the width direction is on the downstream side of the landing position at the central portion in the width direction of the steel plate Cooling method.

  [9] In the thick steel plate cooling apparatus according to [6], the distance that the shielding member shields in the width direction of the slit nozzle can be changed, and the width direction temperature distribution of the thick steel plate before cooling is measured. Then, from the temperature distribution in the width direction, the amount of temperature drop and the temperature drop range at the end in the width direction of the steel sheet relative to the central part in the width direction of the steel sheet are calculated. A method for cooling a thick steel plate, characterized in that a shielding distance is set in the width direction.

  According to this invention, since it has the said means, the temperature direction both-ends temperature fall after the control cooling of a high-temperature thick steel plate can be prevented, and the width direction temperature can be cooled uniformly. Therefore, it is possible to reduce the shape, residual stress, material variation, and the like, and to greatly reduce the load of the finishing process due to the deformation of the thick steel plate, and at the same time, it can be expected to produce a product with high added value.

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

  In FIG. 1, the schematic of the cooling device of the thick steel plate which concerns on one Embodiment of this invention is shown.

  In this cooling device, a plurality of pairs of restraining rolls 2 and 3 are provided on the upper and lower sides of the thick steel plate 1 transported in the cooling device after hot rolling, and a pair of front and rear restraining rolls 2 are provided. 3, each cooling zone is configured. For each cooling zone, on the upper surface side of the thick steel plate, a cooling water slit nozzle 4 is provided from the upstream roll to the downstream roll in the direction of transporting the thick steel plate, and the circular tube nozzle 5 is provided on the lower surface side of the thick steel plate. A plurality are provided at a constant pitch in the plate width and longitudinal direction. A shielding member (masking plate) 6 that shields a predetermined distance at both end portions in the width direction of the slit nozzle 4 is provided at a position at a predetermined interval from the injection port of the slit nozzle 4 at the lower end portion of the slit nozzle 4. . The masking plate 6 can be moved in the width direction of the thick steel plate by a masking plate driving device 7, and the shielding distance can be appropriately changed.

  Thereby, the upper surface of the thick steel plate 1 is uniformly cooled in the width direction by injecting the cooling water from the upper slit nozzle 4 toward the transport direction with respect to the thick steel plate 1 which has been transported into the cooling device, and the lower circle The lower surface of the thick steel plate 1 is uniformly cooled in the width direction by the circular tube jet injected from the tube nozzle 5. At that time, the cooling water on the lower surface side falls immediately after contacting the thick steel plate 1 by gravity, so that the drainage does not adversely affect the cooling. On the other hand, most of the cooling water supplied to the upper surface of the thick steel plate 1 is drained from the end portions in the width direction of the steel plate, but the cooling water sprayed toward both end portions in the width direction of the thick steel plate 1 collides with the masking plate 6. Since the spray angle is changed upward without disturbing the water flow, the landing position moves downstream from the landing position of the cooling water to the central portion in the width direction of the thick steel plate 1. Accordingly, the cooling amount at both ends of the thick steel plate in the width direction can be matched with the cooling amount at the center portion in the width direction of the thick steel plate, and as a result, a thick steel plate having a uniform temperature distribution in the width direction can be manufactured.

  FIG. 2 is a diagram showing an outline of the positional relationship among the upper restraint roll 2, the upper slit nozzle 4, and the masking plate 6 in each cooling zone of this cooling device.

  The slit nozzle 4 has an injection port provided at a distance L from the front upper restraining roll 2 b and is inclined by θ 1 with respect to the thick steel plate 1. On the other hand, the collision surface of the masking plate 6 on which the cooling water provided close to the injection port of the upper slit nozzle 4 collides is inclined with respect to the thick steel plate 1 by θ2. It is desirable that the cooling water after jetting collide with the masking plate 6 before spreading, and the distance from the jet port of the upper slit nozzle 4 to the masking plate 6 is preferably within 20 times the slit thickness.

  And with respect to the thick steel plate center part cooled by the cooling water flow 9 which does not collide with the masking plate 6, both ends of the thick steel plate are cooled by the cooling water flow 8 which collides with the masking plate 6 and the landing position has moved downstream. Therefore, the range in the longitudinal direction of the steel plate to be cooled can be greatly narrowed. If the angle θ2 of the masking plate 6 can be changed, the landing position can be adjusted and the control range of the cooling capacity becomes very wide.

  In FIG. 3, the schematic of the water flow at the time of the cooling water sprayed from the jet nozzle 10 of the slit nozzle 4 colliding with a thick steel plate is shown. In order to flow the cooling water uniformly in one direction, it is desirable that the inclination angle (spray angle) θ1 of the slit nozzle 4 is as small as possible. When the angle θ1 is increased (the inclination angle of the slit nozzle approaches vertical), the water flow (water amount Q) injected from the injection port 10 is a water flow (flow rate Q1) in a direction in which the cooling water flows down after colliding with the steel plate. ) And the water flow in the opposite direction (flow rate Q2). In order to make the flow rate Q2 as small as possible, the optimum setting method of the inclination angle θ1 of the slit nozzle 4 was experimentally studied. As a result, it was found that it follows the generally known law of fluid momentum. That is, the flow rate Q2 can be expressed by the following formula (1).

Q2 = Q (1-cos θ1) / 2 (1)
Further, the horizontal distance S from the tip of the injection nozzle 10 of the slit nozzle 4 to the collision point on the thick steel plate can be expressed by the following equation using the height h from the thick steel plate of the tip of the injection nozzle 10 of the slit nozzle 4.

S = h / tan θ1 (2)
FIG. 4 shows the relationship between the inclination angle θ1 of the upper slit nozzle 4 obtained by the equation (1) and the flow rate ratio Q2 / Q after the diversion, and h = 20 mm and 50 mm obtained by the equation (2). It is a figure which shows distance S from the nozzle tip to the collision point on a thick steel plate. The flow rate ratio Q2 / Q after the diversion has a relation that increases as θ1 increases, and considering that the steel plate is transported in the cooling water injection direction, Q2 / Q is 20% or less. It is desirable to set θ1 to 50 ° or less. On the other hand, the distance S increases as θ1 decreases, but it is not realistic that θ1 is less than 5 ° no matter how close the slit nozzle 4 is to the thick steel plate. Therefore, it is desirable to set 5 ° ≦ θ1 ≦ 50 °. Further, in order to stabilize the water flow, it is desirable to set 10 ° ≦ θ1 ≦ 40 °.

  In order to shield the cooling water without disturbing the water flow, it is important to set the angle θ3 formed by the jet direction of the upper slit nozzle 4 and the collision surface of the masking plate 6 on which the cooling water collides as shown in FIG. is there. That is, as shown in FIG. 6, when the angle θ2 is set to 90 ° as shown in FIG. 6, θ3 becomes very large, and the cooling water that collides with the masking plate 6 is diverted to the central portion of the thick steel plate. It is not difficult to imagine that the cooling water falls on the upstream side of the landing position of the cooling water at this point and causes uneven cooling.

  After collision with the masking plate 6, the flow rate Q2 of the water flow diverted in the direction opposite to the direction in which the cooling water is desired to flow can be expressed by the following equations (3) and (4), as in the equation (1). .

Q2 = Q (1-cos θ3) / 2 (3)
θ3 = θ1 + θ2 (4)
FIG. 7 is a diagram showing the relationship between the angle θ3 formed by the upper slit nozzle 4 and the masking plate 6 obtained by the equation (3) and the flow rate ratio Q2 / Q after the flow separation. As shown in FIG. 7, Q2 / Q increases as θ3 increases, and it can be seen that a flow rate Q2 is generated in a range of θ3> 0 °. The influence of Q2 on cooling varies depending on the form of the upper slit nozzle 4 and the amount of cooling water, but when the masking plate 6 has a simple flat plate shape as shown in FIG. 5, the flow rate Q2 is at most 10% of the input water amount Q. In order to achieve the following, it is desirable that 0 ° <θ3 <40 °.

  However, depending on the configuration of the cooling device, θ3 may not be set in the above range, or the flow rate Q2 may have to be further reduced. Accordingly, in this case, the distance between the lower end of the upper slit nozzle injection port 10 and the masking plate 6 (the distance from the lower end of the upper slit nozzle injection port to the masking plate directly below in the vertical direction) as shown in FIG. The masking plate 6 can be installed as short as possible, such as the masking plate 2 in FIG. 9, or the masking plate can be shaped to guide the cooling water sprayed from the upper slit nozzle to the collision surface, as in the masking plate 6 in FIG. As shown in FIG. 10, a thick steel plate is provided on one side of the masking plate 6 by providing a trough that escapes only the water flow Q2 after the diversion, inclining it in the width direction of the steel plate and draining it outside the cooling device. It is desirable to prevent unnecessary cooling water from dropping onto 1.

Further, as shown in FIG. 11, when the masking plate is provided and the cooling water injection angle is changed, the flying height y [m] from the upper surface of the thick steel plate of the water flow of the cooling water injected from the upper slit nozzle 4 and The flight distance x [m] of the water flow is the average discharge velocity V0 [m / s], the height H [m] of the masking plate (cooling water collision surface) from the top surface of the thick steel plate, and the flight time t [sec] of the water flow. The inventors experimentally confirmed that the following expressions (5) and (6) can be expressed by the gravitational acceleration g [m / sec ² ].

^{y = -gt 2/2 + V0sinθ2} · t + H ······ (5)
x = V0 cos θ2 · t (6)
Here, as shown in FIG. 1, the cooling device is provided with a plurality of pairs of restraining rolls 2, 3 in the transport direction across the thick steel plate 1, and is partitioned by a pair of front and rear restraining rolls 2, 3. If each cooling zone is configured and upper and lower cooling nozzles are provided for each cooling zone, the cooling in each cooling zone must be completed within that cooling zone. The cooling water stream 8 whose landing position has been moved by 6 must not pass over at least the front restraining roll 2b. For this purpose, when the water stream 8 is directly landed on the restraining roll 2b, its landing The position (water landing height) must be less than or equal to the radius (D / 2) of the restraining roll 2b. That is, as the range of the angle θ2 of the masking plate 6, the flight time t0 of the water flow when y = 0 is obtained from the equation (5), and the flight distance x0 at the flight time t0 obtained from the equation (6) is x0. When ≧ L, the flight time t1 of the water flow where x = L is obtained from Equation (6), and the water flow height y1 at the flight time t1 obtained from Equation (5) satisfies y1 ≦ D / 2. It is desirable. The flight distance xm to the landing position of the water flow does not have to be xm = L, and the cooling capacity is controlled by adjusting the flight distance xm of the water flow by changing the angle θ2 of the masking plate 6. It is possible.

  Further, as shown in FIG. 8, in the masking plate 6, if the length from the collision point of the cooling water to the end in the water flow direction is defined as the masking plate length, the masking plate length is the turbulence of the injected cooling water. In order to eliminate the rectification, the slit thickness (jetting thickness) of the slit nozzle 4 is preferably 10 times or more from the property of the fluid.

  Further, in the case of the cooling device having a plurality of cooling zones shown in FIG. 1, in order to limit the amount of water at the end in the width direction of the thick steel plate, the number of cooling zones shielded by the masking plate 6 (number of shielding zones) From the viewpoint of determining the distance (shielding distance) from the outermost end in the width direction of the thick steel plate at the time of shielding, the definition as shown in FIG. 12 is made for information on the end portion in the width direction of the thick steel plate before cooling. The temperature drop distance is defined as the distance from the position where the temperature gradient in the thick steel plate width direction becomes zero to the end of the thick steel plate in the width direction, and the temperature drop amount is zero in the thick steel plate width direction. It is defined by the difference between the temperature at the position where it becomes and the temperature at the extreme end in the width direction of the thick steel plate. The temperature drop distance and the temperature drop amount vary depending on the plate thickness of the raw material before rolling, the heating conditions, the plate width, the rolling completion temperature, and the like. The temperature drop distance is about 100 to 400 mm. The temperature drop amount and the temperature drop distance at the end of the thick steel plate may be tabulated by analyzing measured values in advance, or may be sequentially measured by installing a scanning thermometer or the like before the cooling device.

  And the shielding distance by the masking board 6 is made to become the temperature fall distance of the thick steel plate width direction edge part shown in FIG. In addition, the masking plate 6 of each cooling zone is retracted in advance to a position where the cooling water is not shielded, and when the number of shielding zones using the masking plate 6 is determined, the masking plate 6 of the corresponding cooling zone is moved, It sets so that it may become a predetermined shielding distance.

  The number of shielding zones using the masking plate 6 is determined by the following procedure.

  (S1) From the temperature difference DT between the number N of cooling zones used in the cooling device and the target cooling start temperature and cooling end temperature, the cooling amount ΔT per zone is calculated by the following equation (7).

ΔT = DT / N (7)
(S2) A cooling zone n in which the central portion in the width direction of the thick steel plate can be cooled by the temperature drop ET at the end portion in the width direction of the thick steel plate before cooling is obtained from the cooling amount ΔT per zone.

n = ET / ΔT / α (8)
Here, α is a cooling coefficient. Even if the masking plate 6 is used as in this embodiment, the cooling water sprayed to the thick steel plate width direction central portion is drained in the thick steel plate width direction, so that the temperature drop distance portions at both ends of the thick steel plate are thick steel plates. It is cooled α times in the center in the width direction. It is desirable to actually measure the cooling coefficient α in advance. It is also possible to adjust the cooling water landing position by setting the angle θ2 of the masking plate 6 to continuously control the cooling coefficient α in the range of α = 0.1-1.

  (S3) The masking plate 6 is used in the cooling zones corresponding to the number n of cooling zones obtained in the above (S2) in order from the first cooling zone (the cooling zone on the most upstream side) of the cooling device.

  At this time, it is desirable to set the cooling coefficient α so that n is an integer, and the angle θ2 of the masking plate 6 is changed so that the cooling coefficient α is adjusted by adjusting the landing position of the cooling water. It is desirable to have a possible structure. However, if the structure is difficult and the angle θ2 is fixed and n is not an integer, it is desirable to operate with the rounded number of cooling zones.

  Examples of the present invention are shown below.

  Using the cooling device of the present invention using the masking plate shown in FIG. 1, the high-temperature thick steel plates after hot rolling are cooled to high temperature after hot rolling without using a masking plate. What cooled the thick steel plate was made into Comparative Examples 1 and 2.

  In addition, the specification of the used cooling device is as follows.

There are 11 sets of 1m pitch restraint rolls (10 cooling zones), the distance L from the upper slit nozzle outlet to the front restraint roll is 0.7m, the upper slit nozzle jet thickness is 5mm, and the upper slit nozzle angle θ1 is 25. °, the cooling water density of the upper slit nozzle is 1.8 m ³ / min · m ² , the cooling water density of the lower circular pipe nozzle is 1.8 m ³ / min · m ² , and the conveying speed in the cooling device is 120 m / min. .

(Invention Example 1)
A hot steel plate after hot rolling with a plate thickness of 25 mm, a plate width of 4.0 m, and a plate length of 15 m is 750 ° C. at the center surface temperature in the target steel plate width direction when entering the cooling device, and the target steel plate width direction during reheating after cooling. Control cooling was performed at a central surface temperature of 500 ° C. At that time, the temperature drop at the end in the width direction of the thick steel plate before cooling is 40 ° C. and the temperature drop distance is 300 mm. The temperature distribution before and after cooling was measured with a scanning radiation thermometer installed before and after the cooling device.
The masking plate used is a simple flat plate as shown in FIG. 5, with a masking plate length of 60 mm, a masking plate angle θ2 = 10 °, and an angle θ3 = 35 ° between the upper slit nozzle and the masking plate (the cooling water landing position is the front In the vicinity of the contact portion between the roll and the thick steel plate, α = 0.55). Further, since the temperature drop per zone ΔT = 250 ° C./10=25° C. and the number of cooling zones used n = 40 ° C./25° C./0.55≈3 zones, the cooling zone using the masking plate is upstream. The first cooling zone to the third cooling 3 zone on the side.

(Invention Example 2)
The shape of the masking plate has a two-step slope as shown in FIG. 9, the masking plate angle θ2 = 10 °, the angle between the upper slit nozzle and the masking plate θ3 = 10 ° (the cooling water landing position is the front restraint roll) The high-temperature thick steel plate after hot rolling was cooled under the same conditions as Example 1 except that the contact portion was in the vicinity of the contact portion between the steel plate and the thick steel plate.

(Invention Example 3)
The thickness of the thick steel plate is 25 mm, the width of the plate is 4.0 m, and the length of the plate is 15 m, which is the same as the first example of the present invention. The target cooling start temperature is 800 ° C. The temperature drop at the end in the width direction is 35 ° C., and the temperature drop distance is 400 mm.
The shape of the masking plate is a shape having a two-step inclination similar to Example 2 of the present invention, the masking plate angle θ2 = 10 °, the angle between the upper slit nozzle and the masking plate θ3 = 10 ° (the cooling water landing position is the front roll As the temperature drop amount per cooling zone ΔT = 300 ° C / 10 = 30 ° C, the number of cooling zones used n = 35 ° C / 30 ° C / 0.55≈2 zones. The cooling zones using the masking plate were the first cooling zone and the second cooling zone on the upstream side. Other than that, it cooled on the same conditions as Example 1 of this invention.

(Invention Example 4)
The high-temperature thick steel plate was cooled under the same conditions as Example 1 except that the length of the masking plate was 30 mm.

(Comparative Example 1)
Cooling was performed under the same conditions as in Example 1 without using a masking plate.

(Comparative Example 2)
Instead of the masking apparatus of the present invention, the same cooling as in Example 1 of the present invention was performed using the method disclosed in Patent Document 2 above. Specifically, an air slit nozzle having a slit width of 3 mm was provided immediately below the upper slit nozzle and in a range of 500 mm at both ends, and factory air was jetted.

  Table 1 shows the cooling results (temperature results) in Examples 1 to 4 of the present invention and Comparative Examples 1 and 2.

  As shown in Table 1, in Examples 1 to 3 of the present invention, the steel plate width direction end portion overcooling was prevented by the masking plate, so the steel plate width direction temperature deviation that occurred before cooling was in the range of −2 to 5 ° C. It has been clarified that sufficient temperature uniformity in the width direction of the steel sheet can be secured. These thick steel plates also had good plate shape and surface condition after cooling.

  Further, in Example 4 of the present invention, since the masking plate length was short, the rectifying effect of the cooling water after the collision of the masking plate was small and the water flow was widened. Although it became a little large compared with 15 degreeC and this invention 1-3, the steel plate shape after cooling was favorable.

  On the other hand, in Comparative Example 1, the temperature drop at the end of the thick steel plate reached 60 ° C. at the end, and the temperature deviation appeared significantly. Since this thick steel plate had a poor shape after cooling, it had to be re-corrected.

  Further, in Comparative Example 2, it is very difficult to control the water flow, and if the air injection pressure is increased until the landing position of the cooling water is changed, the cooling water is atomized and cooling cannot be stabilized. The temperature distribution and the steel plate shape were both bad.

  Next, FIG. 13 shows the amount of cut camber (cut width 400 mm) of the thick steel plates cooled in Invention Examples 1 to 4 and Comparative Examples 1 and 2.

  The amount of cut camber and the temperature deviation in the width direction of the steel sheet are very correlated. The thick steel plates of Examples 1 to 4 of the present invention had a small cut camber and passed. In particular, the thick steel plate of Example 2 of the present invention produced almost no cut camber. On the other hand, the thick steel plates of Comparative Examples 1 and 2 had a camber amount significantly exceeding the acceptance line, and had to be corrected again.

  From the above results, in the present invention, it is confirmed that the steel sheet width direction temperature uniformity after cooling is improved by improving the steel sheet width direction end supercooling, and that high value-added products are manufactured. did it.

It is a figure which shows the cooling device of one Embodiment of this invention. It is the schematic explaining the masking apparatus of this invention. It is the schematic explaining the flow of the cooling water injected from an upper surface cooling nozzle. It is the schematic explaining the optimal setting range of the injection angle of an upper surface cooling nozzle. It is the schematic of the positional relationship of an upper surface cooling nozzle and a masking board. It is a figure which shows disturbance of the water flow from an upper surface nozzle when not installing a masking board optimally. It is a figure which shows the relationship between angle (theta) 3 which an upper slit nozzle and a masking plate make, and the shunt Q2 / Q after a collision. It is a figure for demonstrating the distance and masking board length of a slit nozzle lower end and a masking board. It is a figure which shows an example of the masking board of this invention. It is a figure which shows an example of the masking board of this invention. It is a figure for demonstrating the flight height y and the flight distance x of a water flow. It is a figure explaining the definition of the temperature fall amount and temperature fall distance in a thick steel plate width direction temperature distribution. It is a figure which shows the amount of cutting | disconnection camber of the thick steel plate after cooling in the example of this invention and a comparative example. It is a figure which shows the kind of general cooling system (cooling nozzle). It is a figure explaining the relationship between the surface temperature of a steel plate when a high temperature thick steel plate is water-cooled, and a heat flux. It is a figure which shows the technique of patent document 1. FIG. It is a figure which shows the technique of patent document 2. FIG. It is a figure which shows the technique of patent document 3. FIG. It is a figure which shows the technique of patent document 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Upper restraint roll 2a The upper slit nozzle is used as a base point, the restraint roll is located behind it 2b The upper surface cooling nozzle is used as the base point, the restraint roll located in front thereof 3 Table roll (lower restraint roll)
4 Upper slit nozzle 5 Lower circular pipe nozzle 6 Masking plate 7 Masking plate driving device 8 Water flow of cooling water moved by the masking plate 9 Water flow of cooling water not hitting the masking plate 10 Upper slit nozzle injection port

Claims (9)

  As a cooling water nozzle on the upper surface side of a thick steel plate, in a cooling apparatus for a thick steel plate provided with a slit nozzle having a predetermined injection angle with respect to the upper surface of the thick steel plate, a predetermined direction with respect to the injection direction from the injection port of the slit nozzle In the direction, by providing a shielding member that shields a predetermined distance in the width direction of the slit nozzle, by colliding the cooling water sprayed from the slit nozzle to the shielding member, by changing the injection angle of the cooling water, A cooling apparatus for a thick steel plate, wherein the landing position of the cooling water sprayed from the slit nozzle on the thick steel plate is different in the width direction of the thick steel plate.   The injection angle θ1 of the slit nozzle with respect to the upper surface of the thick steel plate is 5 ° ≦ θ1 ≦ 50 °, and the angle θ3 formed by the injection direction of the slit nozzle and the collision surface of the shielding member with which the cooling water collides is 0 °. The thick steel plate cooling device according to claim 1, wherein <θ3 <40 °.   The cooling apparatus for a thick steel plate according to claim 1 or 2, wherein the shielding member is capable of changing a shielding distance in a width direction of the slit nozzle.   The cooling apparatus for a thick steel plate according to any one of claims 1 to 3, wherein an angle θ3 formed by a collision surface of the shielding member and an injection direction of the slit nozzle is variable.   The steel plate cooling device according to any one of claims 1 to 4, wherein a length of the shielding member in a longitudinal direction of the steel plate is 10 times or more a slit thickness of the slit nozzle.   A plurality of pairs of restraining rolls for restraining a thick steel plate at the top and bottom are provided, and each of the cooling zones configured to be partitioned by a pair of front and rear restraining rolls includes a slit nozzle and the shielding member. The apparatus for cooling a thick steel plate according to any one of claims 1 to 5.   The apparatus for cooling a thick steel plate according to claim 6, wherein the angle of the collision surface of the shielding member is set to a predetermined angle so that the cooling water does not get over the restraining roll.   Using the thick steel plate cooling device according to any one of claims 1 to 7, the landing position of the cooling water sprayed from the slit nozzle on the thick steel plate is applied to both ends in the steel plate width direction by the shielding member. A cooling method for a thick steel plate, wherein the amount of cooling at both ends in the steel plate width direction is controlled by making the water landing position downstream of the water landing position at the center portion in the steel plate width direction. The apparatus for cooling a thick steel plate according to claim 6, wherein the distance that the shielding member shields in the width direction of the slit nozzle can be changed, and the temperature distribution in the width direction of the thick steel plate before cooling is measured. From the directional temperature distribution, the amount of temperature drop and the temperature drop range at the end in the width direction of the steel sheet with respect to the central part in the width direction of the steel sheet are calculated. A cooling method for a thick steel plate, characterized in that a shielding distance is set.