JP2006192455A - Method and apparatus for cooling steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cooling steel sheets, which method can manufacture the distortion-less steel sheets by controlling the rolling condition after hot-rolling the steel sheets such that the cooling speed is large as a whole and is uniform over the range of the steel sheets from the leading edge to the longitudinally intermediate portion of the steel sheet, and the temperature distribution is symmetric in the direction of the thickness of the steel sheet. <P>SOLUTION: In the method for cooling the steel sheets after hot rolling while passing the steel sheets 1 through a cooling zone partitioned by water squeezing rolls, a flow rate of the cooling water from a slit jet nozzle 13 for jetting the cooling water on the upper surface of the steel sheet 1 is regulated by means of a flow control valve 22 so as to be larger at the leading edge portion of the steel sheet than the intermediate portion in the longitudinal direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cooling method and a cooling apparatus for a steel plate in which hot-rolled high-temperature steel plates are confined by a roll while being constrained by a roll. The present invention relates to a steel plate cooling method and a cooling device capable of producing a steel plate.

  In the production of a steel plate, controlled cooling is performed on the rolled steel plate in order to ensure mechanical properties required for the steel plate, particularly strength and toughness. In this controlled cooling, it is necessary to increase the cooling rate in order to ensure the material properties required for the steel sheet, but at the same time, it ensures the uniformity of the material and suppresses the occurrence of distortion during cooling. Therefore, it is necessary that cooling be performed uniformly over the entire plate surface.

  Correspondingly, in the current controlled cooling of high-temperature steel plates, a method of constraining a steel plate by a plurality of rolls and arranging a cooling nozzle between the constraining rolls for cooling while passing is widely performed. Manufactures steel plates with less distortion.

  This is the reason why the control cooling is performed by such a method. Since the control cooling can be performed with a short equipment length by using the passing cooling, it is possible to suppress the initial investment cost. In addition, the restraining roll suppresses the distortion generated due to uneven upper and lower surfaces and in-plane temperature during cooling, and disposes the cooling water outside the cooling device by disposing the nozzle between the rolls and draining with the outlet roll. This prevents the cooling water from staying on the steel plate.

  On the other hand, although it has become possible to produce a steel plate with less distortion by such a method, it has a drawback that warped distortion tends to occur at the leading end of the steel plate. This phenomenon will be described with reference to FIGS.

  Here, the state of the water pool on the upper surface of the steel sheet is considered separately for the front end and the tail end of the steel sheet. FIG. 1 is a diagram for explaining the state of water pooling at the tip portion. First, the state from when the tip of the steel plate 1 enters the inlet side draining roll 3 to the outlet side draining roll 4 after entering the cooling zone. In FIG. 1 (a), in addition to drainage from both ends of the steel plate 1, the cooling water also drops from the tip of the steel plate under the steel plate. Since the tip enters the outlet side draining roll 4, the liquid level of the cooling water (plate water) collected on the upper surface of the steel plate 1 is not so high, but the tip of the steel plate 1 becomes the cooling zone outlet side draining roll 4. From the time of entry (FIG. 1 (b)), the drop of cooling water from the tip of the steel plate 1 is blocked by the draining rolls 3 and 4, so that the on-plate water 5 is formed and the liquid level rises. Further, as time passes, the amount of water drained from both ends of the steel plate 1 and the amount of water flowing in are balanced, and the on-board water 5 is stabilized at a constant liquid level as shown in FIG. Become.

  In addition, in the longitudinal center part of the steel plate 1 after that, the on-board water 5 continues a full water state as it is.

  On the other hand, in FIG. 2, although the figure explaining the water pool situation of a tail end part is shown, until the tail end of the steel plate 1 approachs into the entrance side draining roll 3 of a cooling zone first (FIG. 2 (a)), The liquid level of the on-board water 5 is almost full and stable. In the state from when the tail end of the steel plate 1 passes through the entry side draining roll 3 to the entrance side draining roll 4 (FIG. 1 (b)), in addition to drainage from both sides of the steel plate 1, the tail end portion The cooling water also falls below the steel plate 1, but if the plate passing speed is high, it enters the outlet draining roll 4 before the on-board water 5 is drained. Thus, compared with the longitudinal center part, the liquid level height of the on-board water 5 changes at the leading end of the upper surface of the steel plate 1, and the cooling capacity also changes accordingly. Details of the cooling capacity will be described later.

  On the other hand, the cooling water quickly falls under the influence of gravity on the lower surface of the steel plate 1, so that the cooling water does not stay in the steel plate 1 and the cooling capacity is uniform over the entire length of the steel plate 1.

  Therefore, for example, when the water / water ratio is adjusted so that the cooling capabilities of the upper and lower surfaces coincide with each other at the longitudinal center portion of the steel plate 1, an unbalance of the cooling capabilities of the upper and lower surfaces occurs at the leading end, and warpage occurs.

  Moreover, qualitatively, the state of the liquid surface height of the on-board water 5 at the tail end of the steel plate is maintained higher than that at the tip. In addition, the liquid level at the tail end of the steel plate 1 is changed only by the distance between the inlet side draining roll 3 and the outlet side draining roll 4, while the on-board water 5 is full at the tip. The cooling capacity changes between the distances that have passed by the amount of time. Therefore, the warp is greater at the tip of the steel plate. Therefore, in this invention, it aims at equalizing the cooling capability of the steel plate front-end | tip part and longitudinal center part which are especially a problem.

  In the cooling state as described above, the influence of the amount of water on the plate on the cooling varies depending on the cooling type.

  For example, when a cooling method with a low momentum such as spray cooling is used, the state is as shown in FIG. When there is no water on the plate, the cooling water directly collides with the high-temperature steel plate in the form of droplets 12 from the spray 11, so that the cooling capacity is increased. On the other hand, when the on-board water 5 is present, the velocity of the liquid droplet is attenuated by the on-board water 5 and the collision force is lowered. In this case, a vapor film is generated between the on-board water and the high-temperature steel plate. Heat is transferred by heat conduction in the vapor film, and the cooling capacity is low.

  Further, when the slit jet nozzle is a cooling type, according to Patent Document 1, the state is as shown in FIG. The cooling by the jet water flow is (1) cooling in the collision area A where the jet water flow collides with the steel plate 1 and takes the heat of the steel plate 1, and (2) the heat of the steel plate 1 while the jet water flow flows along the steel plate 1 after the collision. (3) Cooling in the flow zone B where the jet water flow is blocked by the draining roll 4 to form the on-board water 5 and cooling in the stirring zone C that takes the heat of the steel plate in the stirred state. . Until the tip of the steel sheet enters the draining roll 4, the on-board water is not formed, and there is no cooling due to the stirring state of the on-board water 5 in (3), so the cooling capacity is lowered.

  From the above mechanism, the cooling capacity is different only at the top surface of the high-temperature steel sheet at the leading edge and the longitudinal center. As a result, when the upper surface side longitudinal center and the lower surface side are adjusted to have the same cooling capacity, a temperature deviation occurs on the upper and lower surfaces at the leading end of the steel sheet, resulting in warped distortion.

  In order to solve such a problem, Patent Document 1 discloses that a jet water flow is jetted from a jet slit nozzle onto the upper and lower surfaces of a hot-rolled hot steel plate that is being transported, and the steel plate is continuously cooled on one side. Then, in the cooling method in which the jet water flow is interrupted by a pair of draining rolls provided on the downstream side of the jet slit nozzle, the tip of the steel plate is cooled in consideration of the cooling efficiency difference between the steel plate tip and other parts. There has been proposed a method for cooling a high-temperature steel sheet, in which the conveyance speed at the time of turning is slower than the conveyance speed at which the portion other than the tip is cooled.

In Patent Document 2, in a method of injecting and cooling while pressing a hot steel sheet from above and below with a roll, control means for the amount of coolant passing is provided above and / or below between the rolls, and further, the passing position of the hot steel sheet is detected. There has been proposed a method for cooling a hot steel sheet that includes a means and a cooling calculation control means, and controls the amount of coolant that passes through the position where the leading end and / or rear end of the moving hot steel sheet is about to pass.
JP 62-161415 A JP 60-043435 A

  The means disclosed in Patent Document 1 is that the jet water flow in the jet slit nozzle changes the cooling speed by changing the cooling capacity due to the change in the cooling capacity due to the difference in the flow state between the leading end and the longitudinal direction of the steel plate. This is a technique for making the longitudinal temperature uniform after cooling by adjusting the temperature. However, in the first place, a decrease in cooling capacity due to a change in the flow state of the steel plate leading end means that the cooling rate is different between the steel plate leading end and the longitudinal central portion, which is problematic from the viewpoint of material control. In addition, the cooling capacity changes only at the top surface of the steel sheet where the water on the plate is formed, and the temperature deviation due to the difference in cooling capacity between the top and bottom surfaces occurs and the steel sheet is warped. To do. Therefore, in this case, even if the temperature of the upper surface in the longitudinal direction of the steel plate after cooling can be made uniform, a difference in cooling capacity between the upper and lower surfaces occurs, so that the plate shape cannot be improved.

  The means disclosed in Patent Document 2 is provided with a means for detecting the passing position of the hot steel plate and a shield on the nozzle outlet side, blocking a part of the cooling water sprayed from the nozzle, and at the position of the leading end. This is a technique to change the cooling capacity of the tail end and the central part in the longitudinal direction, but it is necessary to secure a space for installing the shielding mechanism, and the cooling nozzle must be installed at a distance away from the steel plate. It is limited to cooling devices such as laminar cooling and cannot be applied to slit jet cooling or the like that is installed close to a steel plate in order to increase the striking force as shown in FIG. Moreover, the shielding rate of the flow rate is determined by the structure of the shielding object and cannot be made variable. For this reason, it is not possible to cope with the case where an appropriate shielding rate changes depending on the amount of cooling water or the plate size.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and when cooling the steel sheet after hot rolling, the cooling rate is high as a whole, and the steel sheet is uniform from the front end to the longitudinal center of the steel sheet. The present invention provides a steel plate cooling method and a cooling device capable of producing a steel plate free from strain with a symmetrical temperature distribution in the plate thickness direction.

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

  [1] In a method for cooling a steel sheet, the upper and lower surfaces of the steel sheet are cooled with cooling water while passing the steel sheet after hot rolling through a cooling zone partitioned by an inlet side draining roll and an outlet side draining roll at a constant speed. The nozzle that injects the cooling water toward the upper surface of the nozzle is a continuous flow injection nozzle that injects a continuous flow, and the cooling water amount from the continuous flow injection nozzle is the amount of cooling water when the tip of the steel plate passes through the cooling zone. A cooling method for a steel sheet, characterized in that the central portion in the longitudinal direction of the steel sheet is larger than the amount of cooling water when passing through the cooling zone.

  [2] In the method for cooling a steel sheet according to [1], the amount of cooling water from the continuous flow injection nozzle is set between the time when the leading end of the steel sheet enters the entry side draining roll and the entry side draining roll. The amount of cooling water is greater than the amount of cooling water when the central portion of the steel plate passes through the cooling zone, and after the tip of the steel plate enters the outlet side draining roll, the amount of cooling water from the continuous flow spray nozzle is changed to the longitudinal direction of the steel plate. A method for cooling a steel sheet, characterized by adjusting the amount of cooling water when the central portion passes through the cooling zone.

[3] In the method for cooling a steel plate according to [2], the amount of cooling water from the continuous flow injection nozzle when the steel plate width is W (m) and the front end of the steel plate enters the outlet side draining roll of the cooling zone. Is adjusted to Q (T / min · m ² ), the adjustment of the amount of cooling water from the continuous flow injection nozzle is started when the tip of the steel sheet enters the outlet side draining roll of the cooling zone, and the tip of the steel sheet is the outlet side of the cooling zone. continuous flow ejection nozzles when the elapsed time from when entering the draining roll t (sec) is, becomes ^{0.57 (1.12W + 1.93) Q -0.35} ≦ t ≦ (1.12W + 1.93) Q -0.35 The method for cooling a steel sheet, characterized in that the adjustment of the amount of cooling water from is finished.

  [4] In the method for cooling a steel sheet according to the above [2] or [3], regarding the amount of cooling water from the continuous flow injection nozzle, the front end of the steel sheet enters the entry side draining roll and then enters the exit side draining roll. A cooling method for a steel sheet, characterized in that the amount of the cooling water is up to 1.2 to 1.8 times the amount of cooling water when the longitudinal central portion of the steel sheet passes through the cooling zone.

  [5] In the method for cooling a steel plate according to any one of [1] to [4], a flow rate adjustment valve between the continuous flow injection nozzle and a cooling water supply device that supplies cooling water to the continuous flow injection nozzle. And adjusting the flow rate adjustment valve so that the amount of cooling water when the front end of the steel plate passes through the cooling zone is larger than the amount of cooling water when the longitudinal center portion of the steel plate passes through the cooling zone. A method for cooling a steel sheet, comprising:

  [6] The method for cooling a steel sheet according to [5], wherein two or more flow rate adjustment valves are provided in parallel between the continuous flow spray nozzle and the cooling water supply device.

  [7] In the method for cooling a steel plate according to any one of [1] to [4], between the continuous flow injection nozzle and a cooling water supply device that supplies cooling water to the continuous flow injection nozzle, cooling water is provided. A relief valve is provided to prevent a part of the water from being fed to the continuous flow injection nozzle, and by adjusting the relief valve, the amount of cooling water when the tip of the steel plate passes through the cooling zone is the center in the longitudinal direction of the steel plate. A method for cooling a steel sheet, characterized in that the amount of cooling water is greater than that when the section passes through the cooling zone.

  [8] The method for cooling a steel sheet according to [7], wherein two or more relief valves are provided in parallel between the continuous flow spray nozzle and the cooling water feeder.

  [9] In the method for cooling a steel plate according to any one of [1] to [8], the continuous flow injection nozzle may be one or more of a slit jet nozzle, a circular pipe jet nozzle, and a laminar nozzle. A method for cooling a steel sheet, comprising:

  [10] In a steel plate cooling apparatus for cooling the upper and lower surfaces of a steel sheet with cooling water while passing the steel sheet after hot rolling through a cooling zone partitioned by an inlet side draining roll and an outlet side draining roll at a constant speed. The nozzle that injects the cooling water toward the upper surface of the nozzle is a continuous flow injection nozzle that injects a continuous flow, and the cooling water amount from the continuous flow injection nozzle is the amount of cooling water when the tip of the steel plate passes through the cooling zone. A steel plate cooling apparatus, wherein a central portion in a longitudinal direction of the steel plate is larger than a cooling water amount when passing through a cooling zone.

  [11] In the steel sheet cooling apparatus according to [10], one or two in parallel are arranged between the continuous flow injection nozzle and the cooling water supply apparatus that supplies cooling water to the continuous flow injection nozzle. The amount of cooling water when the tip of the steel plate passes through the cooling zone is adjusted by adjusting the flow rate adjusting valve, so that the amount of cooling water when the longitudinal center of the steel plate passes through the cooling zone A steel sheet cooling device characterized by having more.

  [12] In the steel sheet cooling device according to [10], a part of the cooling water is continuously flow injected between the continuous flow injection nozzle and the cooling water supply device that supplies the cooling water to the continuous flow injection nozzle. The amount of cooling water when the tip of the steel sheet passes through the cooling zone by adjusting one of the relief valves to prevent water from being fed to the nozzle. Is a steel plate cooling device characterized in that the central portion in the longitudinal direction of the steel plate is larger than the amount of cooling water when passing through the cooling zone.

  [13] In the steel sheet cooling device according to any one of [10] to [12], a continuous flow is performed from the time when the front end of the steel sheet enters the entry side draining roll to the entry side draining roll. The amount of cooling water from the injection nozzle is set to be larger than the amount of cooling water when the longitudinal center of the steel plate passes through the cooling zone, and after the tip of the steel plate enters the outlet draining roll, the cooling from the continuous flow injection nozzle A steel sheet cooling apparatus characterized in that the amount of water is adjusted toward the amount of cooling water when the central portion in the longitudinal direction of the steel sheet passes through the cooling zone.

[14] In the cooling apparatus for a steel sheet according to [13], the amount of cooling water from the continuous flow injection nozzle when the sheet width is W (m) and the leading end of the steel sheet enters the outlet side draining roll of the cooling zone. Is adjusted to Q (T / min · m ² ), the adjustment of the amount of cooling water from the continuous flow injection nozzle is started when the tip of the steel sheet enters the outlet side draining roll of the cooling zone, and the tip of the steel sheet is the outlet side of the cooling zone. continuous flow ejection nozzles when the elapsed time from when entering the draining roll t (sec) is, becomes ^{0.57 (1.12W + 1.93) Q -0.35} ≦ t ≦ (1.12W + 1.93) Q -0.35 The cooling device for a steel sheet, characterized in that the adjustment of the amount of cooling water from the end is finished.

  [15] In the steel sheet cooling device according to any one of [10] to [14], the continuous flow injection nozzle may be one or more of a slit jet nozzle, a circular pipe jet nozzle, and a laminar nozzle. A cooling device for steel sheet, characterized in that there is.

  According to the present invention, when cooling a steel plate that has been hot-rolled, the temperature distribution in the plate surface from the front end to the tail end in the longitudinal direction of the steel plate can be made uniform, and a steel plate without tip warp can be produced. become.

  In the present invention, a slit jet nozzle, a circular pipe jet nozzle, or a laminar nozzle is employed from the viewpoint of obtaining material characteristics. As described above, the nozzle in which cooling water is sprayed from the nozzle in a droplet state, such as a spray nozzle, is a part where the on-plate water is formed like the longitudinal center of the steel plate, Although the droplets are attenuated by the water on the plate and the cooling capacity is lowered, the temperature distribution in the longitudinal direction must be made uniform by lowering the amount of cooling water at the leading end for this purpose. Has to lower the cooling capacity. On the other hand, in a nozzle (continuous flow injection nozzle) that injects a continuous flow such as a slit jet nozzle, heat transfer capacity can be improved by stirring the water on the plate at the site where the water on the plate is formed. By increasing the amount of cooling water as compared with the central portion in the longitudinal direction, the overall cooling capacity can be increased. Hereinafter, a case where a slit jet nozzle is employed will be described as an example.

  In the present invention, the flow rate of the cooling water injected from the nozzle in order to make the longitudinal temperature distribution of the steel sheet passing through the cooling zone partitioned by the inlet side draining roll and the outlet side draining roll at a constant speed uniform. (Cooling water amount) is changed at the tip of the steel plate. Specifically, since the on-plate water is not formed at the front end portion of the steel plate, the amount of cooling water is increased as compared with the longitudinal center portion of the steel plate. As this method, a method using a flow rate adjusting valve and a method using a relief valve are adopted.

  FIG. 5 shows a piping system diagram of a system using a flow rate adjusting valve as the first embodiment of the present invention. After the flow rate of the cooling water supplied from the cooling pump 20 is measured by the flow meter 21, the flow rate is adjusted by adjusting the opening of the flow rate adjustment valve 22 based on the measured flow rate value. Sprayed from the slit jet nozzle 13 for cooling.

  FIG. 6 shows a piping system diagram of a system using a relief valve as a second embodiment of the present invention. The cooling water supplied from the cooling pump 20 passes through a flow rate adjusting valve type piping system 27 including a flow meter 21 and a flow rate adjusting valve 22, and then is supplied to a piping system 25 and a relief valve piping 26 supplied to the upper nozzle. Branch off. The relief valve pipe 26 includes a relief valve composed of a shut-off valve 23 and a regulating valve 24. The shut-off valve 23 can only be adjusted to be fully closed or fully opened, and the regulating valve 24 can be opened manually or automatically. Can be adjusted. With such a configuration, the shut-off valve 23 of the relief valve pipe 26 is closed at the front end of the steel plate, and the shut-off valve 23 is opened at a certain point in time so that the top surface of the steel plate and the longitudinal center portion onward The amount of cooling water sprayed from the nozzle is changed.

  By such 1st Embodiment or 2nd Embodiment of this invention, the amount of cooling water is changed in a steel plate longitudinal direction. If it does in this way, it is not necessary to install a structure in the nozzle exit side like patent documents 2, for example, even if it is a cooling device which installs a nozzle and a steel plate near, it is to the steel plate in the longitudinal direction of a steel plate. It becomes possible to change the amount of water of the cooling water.

  Next, a specific flow rate control method in the first embodiment and the second embodiment of the present invention will be described.

  First, a method using the flow rate adjusting valve according to the first embodiment of the present invention shown in FIG. 5 will be described with reference to the piping system diagram of FIG. 5 and the flow rate control flowchart of FIG. As described above, the cooling capacity changes due to the formation of the on-board water 5, but the formation of the on-board water starts when the front end of the steel sheet enters the cooling zone outlet side draining roll 4 in FIG. Then, after a certain period of time, the on-board water 5 becomes full and the liquid level is stabilized. Therefore, the flow rate adjustment is started when the front end of the steel sheet enters the cooling zone outlet side draining roll 4, and the flow rate adjustment valve 22 is moved to control the flow rate so that the flow rate adjustment is completed when the water on the plate is full. There is a need.

  Next, a method using the relief valve according to the second embodiment of the present invention shown in FIG. 6 will be described with reference to the piping system diagram of FIG. 6 and the flow rate control flowchart of FIG. Similarly to the first embodiment, the flow rate adjustment is started when the steel sheet tip enters the cooling zone exit side draining roll 4, and the flow rate adjustment is completed when the water on the plate is full. The shutoff valve 23 of the relief pipe 26 is fully opened, and the closing operation is started when the front end of the steel sheet enters, and the shutoff valve 23 is fully closed when the on-board water is full. The flow rate is controlled by adjusting the operation speed (opening degree).

And about the setting of the flow volume of a cooling water, it carries out as follows.
(1) Calculate the cooling capacity required for material design at the longitudinal center of the steel plate.
(2) The amount of cooling water Qa that can obtain this cooling capacity is calculated in the presence of water on the plate.
(3) The amount of cooling water Qb at which this cooling capacity is obtained is calculated in the absence of on-plate water.
(4) The amount of cooling water required at the front end of the steel plate is set as the cooling water amount Qb in the state where there is no on-board water, and the amount of cooling water required in the longitudinal center is set as the cooling water amount Qa in the state where there is on-plate water. To do.

  This flow rate setting may be performed by adjusting the flow rate adjusting valve 22 by feedback with reference to the instruction value of the flow meter 21 in the flow valve control system according to the first embodiment. In the relief valve system according to the second embodiment, when the shutoff valve 23 of the relief pipe 26 is fully closed, the flow rate Qb required at the front end of the steel plate is reached, and the shutoff valve 23 is fully opened. Adjusts the opening degree of the regulating valve 24 of the relief pipe 26 so that the cooling water flows through the nozzle by the required flow rate Qa at the central portion in the longitudinal direction of the steel plate.

Here, the relationship between the cooling water amount and the cooling capacity in the state where the on-board water is formed and the state where the on-board water is not formed must be grasped in advance. FIG. 9 shows the heat flux at 500 ° C. (the amount of heat lost to the cooling water per unit area and unit time) when the steel sheet is cooled by the slit jet nozzle of the type shown in FIG. 4 (water draining roll pitch 1 m, 5 mm gap). . It can be seen that the heat flux (cooling capacity) is higher by about 20% when there is water on the plate than when there is no water on the plate. Further, in the figure, for example, when the flow rate at the longitudinal center with water on the plate is cooled at 1.2 T / min · m ² , in order to match this cooling capacity with the cooling capacity without water on the plate, Without clean water, a cooling water amount of about 1.7 T / min · m ² is required. Therefore, in this case, it is necessary to inject about 1.4 times as much cooling water as the central portion in the longitudinal direction at the leading end of the steel plate. Since this changes depending on the type of cooling and the installation position of the nozzle, it is necessary to investigate in advance according to various cooling nozzles. The inventors investigated with pipe laminator, slit laminar, slit jet nozzle in the range of cooling water amount 1.0-3.0 T / min · m ² and draining roll pitch 0.7-1.2 m. The flow rate when there is no on-board water required to match the cooling capacity when there is no on-board water is 1.2 to 1.8 of the flow rate when there is on-board water. It was found that it exists in the double range. Therefore, the pipe diameter and the flow rate adjusting valve may be selected so that the flow rate can be adjusted within this range.

  Next, as described above, regarding the adjustment time of the cooling water amount, it is necessary to start the flow rate adjustment when the steel sheet enters the outlet side draining roll of the cooling device, and to complete the flow rate adjustment when the water on the plate is full. There is. The time until the water on the plate is full varies depending on the cooling water amount and the plate width, but this can be obtained analytically.

  The change in the liquid level height per unit time is expressed by equation (1).

液面が満水になる時、液面高さの時間変化は無くなる。この時、式（１）の左辺はゼロになるので、満水になった場合の液面高さｈ∞は式（２）のようになる。

When the liquid level becomes full, the time change of the liquid level disappears. At this time, since the left side of the formula (1) becomes zero, the liquid level height h∞ when the water is full is given by the formula (2).

また、式（１）の微分方程式を解くと、液面高さの時間推移が計算できる。式（１）の微分方程式を解いて、得られた液面高さをｈ／ｈ∞と無次元化すると板上水が満水時となった時に対する液面高さになる（以後無次元液面高さと呼ぶ）。

Moreover, if the differential equation of Formula (1) is solved, the time transition of the liquid level can be calculated. Solving the differential equation of equation (1) and making the obtained liquid level height dimensionless as h / h∞ gives the liquid level height when the water on the plate is full (hereinafter referred to as dimensionless liquid level). Called surface height).

FIG. 10 shows a temporal transition of the liquid level height when the water density (cooling water amount) is 2.0 T / min · m ² , the cooling zone length is 1 m, and the plate width is 5 m. It can be seen that the liquid level height increases rapidly until the dimensionless liquid level height reaches about 0.80, but thereafter the liquid level height increases gradually. In particular, it can be considered that the substantial liquid level does not change when the dimensionless liquid level exceeds 0.95. In actual operation, if the dimensionless liquid level is 0.80 or more, the cooling capacity does not change much. Therefore, when the dimensionless liquid level height is 0.80 as a state in which the cooling capacity is substantially stabilized and the dimensionless liquid level height is 0.95 as a state in which the liquid level is steady, The time to reach the state is as follows.

  Time until the dimensionless liquid level reaches 0.95 (time until the water on the plate is full)

無次元液面高さが０．８０になる状態までの時間（板上水による冷却能力がほぼ安定するまでの時間）

Time until the dimensionless liquid level reaches 0.80 (time until the cooling capacity by the water on the plate is almost stabilized)

したがって、鋼板先端が冷却ゾーンの出側水切りロールに進入してから、式（４）よりも長く、式（３）より短い時間の間で流量変更（流量調整）を完了するのが望ましい。

Therefore, it is desirable to complete the flow rate change (flow rate adjustment) within a time longer than the equation (4) and shorter than the equation (3) after the front end of the steel sheet enters the outlet side draining roll of the cooling zone.

FIG. 11 shows, as an example of calculation, the time until the water level on the plate stabilizes and accumulates when cooling water is poured between draining rolls arranged at intervals of 1 m (dimensionless liquid level height). Time is 0.80). It can be seen that the narrower the plate width and the greater the amount of water, the shorter the stabilization time. When the amount of cooling water is 2.0 T / min · m ² , the time until the water on the plate accumulates is about 3 seconds, and it is necessary to change the flow rate at a very high speed.

  By the method as described above, it is possible to change the amount of cooling water at the front end portion and the longitudinal center portion of the steel sheet and to make the cooling capacity in the longitudinal direction uniform.

  In general valves, the moving speed cannot be changed greatly. Therefore, the larger the aperture, the longer the moving distance from the opening limit to the closing limit of the valve, and the response speed tends to decrease. In controlled cooling of thick steel plates, a large flow rate is injected, but in order to reduce pressure loss that occurs in the piping, there are many cases where a large pipe diameter is selected, and the flow rate injected from the nozzle within a predetermined time may not be adjusted. .

  For this reason, if the flow rate is relatively small and it takes a long time to collect the water on the plate, there is no problem with the control method using the flow adjustment valve. When the time is short, the method using a relief valve is preferable. In the method using the relief valve, since the relief amount is smaller than the supply amount of the cooling water, the diameter of the relief valve pipe can be made smaller than that of the cooling supply pipe, and a high response speed can be obtained. Further, since a valve having a simple structure that can be simply opened and closed can be employed, the valve can be opened and closed at a higher speed than the valve used for the flow rate adjustment valve.

  Furthermore, as a method of stabilizing the flow rate, there is a method of installing a flow meter 28 in the escape piping system as shown in FIG. In this case, the opening degree of the flow rate adjustment valve 29 of the relief piping system is set in advance so as to obtain the relief flow rate that has been calculated in advance. Fine adjustment of the opening may be necessary. In that case, if the flow meter 28 is in the relief valve piping system 26 in this way, the flow meter 28 can be used to finely adjust the amount of water to be released as shown in FIG. .

  In addition, there is a case where it is necessary to change the flow rate at a high speed in large flow injection. At that time, for example, as shown in FIG. 14, a flow meter 21 and a flow rate adjustment valve 22 are provided in a pipe between the pump and the nozzle. There are also a method of arranging a plurality of relief piping systems 26 in parallel as shown in FIG. In this way, a small-diameter type with a fast response speed can be selected as the diameter of the flow regulating valve, so that the flow rate can be changed at high speed even with a large flow rate injection.

  If the method described above is used, finer flow rate control becomes possible, and the cooling uniformity in the longitudinal direction can be further improved.

  FIG. 16 is a conceptual diagram of a steel sheet cooling device used in the examples of the present invention. The steel plate material slab 42 is rolled to a predetermined thickness by a thick plate mill 41, transferred to the steel plate 1 on the roller table 43, and cooled to a cooling stop temperature at a predetermined cooling rate by passing cooling by a control cooling device 44. Is done. In the control cooling device 44, an upper header 45 and a lower header 46 are arranged with the pass line of the steel plate 1 being sandwiched up and down, and a slit jet nozzle 13 for ejecting high-pressure water is attached to the control header 44. It has a function of rapidly cooling the steel sheet 1 with very high pressure jet water colliding with the surface. Further, thermometers 47 and 48 are installed before and after the control cooling device 44 so that the temperature of the steel sheet 1 can be measured before and after cooling. Reference numeral 43 denotes a table roll.

  FIG. 17 shows a detailed view of the control cooling device. The control cooling device is composed of a plurality of cooling zones, each of which is partitioned by a draining roll 49, and the amount of cooling water can be adjusted individually. This cooling zone is provided with a total of 10 zones having a zone length of 1 m, and is called 1 zone, 2 zone,.

  The nozzles of the respective cooling zones have a piping system as shown in FIG. Note that a slit jet nozzle with a gap of 5 mm is attached to the upper surface header, and a circular pipe jet of 20 mmΦ is attached to the lower surface header at a pitch of 200 mm.

  Then, the flow rate adjustment valve 22 on the upper surface detects the tip of the steel plate by the steel plate detector (photocell) 61, calculates the timing at which the steel plate tip enters the zone exit side draining roll 4 by the timer 62, and at that timing The flow rate adjustment is started, and the flow rate is controlled so that the flow rate adjustment is completed in a predetermined time. As a result, it is possible to perform the cooling control by the system using the flow rate adjustment valve according to the first embodiment of the present invention.

  Further, a shutoff valve 23 and a regulating valve 24 are provided downstream of the flow rate adjusting valve 22, and instead of the method using the flow rate adjusting valve, the method using the relief valve according to the second embodiment of the present invention is used. Cooling control can also be performed.

  In the example of the present invention, the plate was rolled to a size of a plate thickness of 25 mm, a plate width of 4000 m, and a plate length of 25 m at a finishing temperature of 800 ° C. It is necessary to control the cooling start temperature to 750 ° C. and the cooling end temperature to 550 ° C. due to material requirements.

Top nozzle has a heat transfer characteristic as shown in FIG. 9, given the cooling rate of the material requirements, as a heat flux definitive 500 ° C. is ^{1.7 × 10 6 kcal / m 2} hr ℃, reads from 9 The amount of cooling water at the tip must be 1.7 T / min · m ² , and the center of the longitudinal portion must be 1.2 T / min · m ^{2. The} amount of cooling water at the tip is 1.4 times that of the center of the longitudinal portion. There is a need to do more. The plate passing speed at this time is constant at 100 mpm. The change time (adjustment time) of the cooling water amount was 3 sec obtained by substituting the cooling water amount of 1.7 T / min · m ² and the plate width of 4000 m at the tip into the above-described equation (4). Regarding the lower surface side of the steel sheet, the lower surface water amount balanced with the upper surface water amount in the longitudinal central portion of the present invention example was investigated by another experiment, and found to balance at 1.6 T / min · m ^2. Carried out.

  Here, as Example 1 of the present invention, the above-described parameters were controlled by the method using the flow rate adjustment valve according to the first embodiment of the present invention.

  FIG. 19 shows the result of measuring the temperature in the longitudinal direction of the steel sheet after cooling with the thermometer 48. In Invention Example 1, the target temperature of 550 ° C. was satisfied over the entire length of the steel sheet. Moreover, the temperature of the upper and lower surfaces was almost the same value, and the steel plate shape was also flat.

  Next, as Example 2 of the present invention, the above-described parameters were controlled by a system using a relief valve according to the second embodiment of the present invention.

  FIG. 20 shows the result of measuring the temperature in the longitudinal direction of the steel sheet after cooling with the thermometer 48. In Invention Example 2, the target temperature of 550 ° C. was satisfied over the entire length of the steel plate. Moreover, the temperature of the upper and lower surfaces was almost the same value, and the steel plate shape was also flat.

In Comparative Example 1, showing the upper surface 1.2T / min · m ² without changing the amount of cooling water of the tip portion, an example of cooling the lower surface 1.6T / min · m ² in Figure 21. The lower surface side of the steel plate could be cooled to 550 ° C. over the entire length almost as aimed, but at the most advanced portion of the upper surface of the steel plate, it became 585 ° C., 35 ° C. higher than the target temperature of 550 ° C. On the upper surface of the steel plate, a region having a high temperature of about 7 m from the tip of the steel plate was generated. Moreover, since the upper surface side temperature was higher than the lower surface side temperature at the front end of the steel plate, warping occurred.

Further, as Comparative Example 2, cooling by the method of Patent Document 1 was performed. The amount of cooling water is the same as in Comparative Example 1. Further, from FIG. 9, when the cooling water amount is 1.2 T / min · m ² , the heat flux when there is water on the plate is 1.8 × 10 ⁶ kcal / m ² hr, and when there is no cooling water, it is 1.5 × 10 ⁶ kcal. / M ² hr. Therefore, the steel plate front end without water on the plate is (1.5 × 10 ⁶ kcal / m ² hr) / (1.8 × 10 ⁶ kcal / m ² hr) = 0. The cooling capacity is low by 833. Therefore, in order to correct this, the plate was passed at a plate-passing speed (83 mpm) that is 0.833 times the longitudinal center of the tip only. Further, in Comparative Example 1, since the upper surface temperature was high up to about 7 m from the front end of the steel plate, the initial speed of the steel plate was set to 83 mpm, which was accelerated to 100 mpm when the front end of the steel plate entered the 7 m cooling device. Cooling was performed. FIG. 22 shows the temperature distribution in the longitudinal direction after cooling as a result of this. As a result of slowing the plate passing speed by the amount that the cooling capacity on the upper surface side becomes lower at the front end of the steel plate, the temperature distribution in the longitudinal direction on the upper surface side extends over the entire length. As expected, the temperature reached 550 ° C, but on the bottom side, the cooling ability was originally uniform in the longitudinal direction, but as a result of slowing the plate passing speed only at the tip, the cooling time became longer and 505 ° C than the target temperature. It became low. Moreover, since the upper surface side temperature was higher than the lower surface side temperature at the front end of the steel plate, warping occurred.

なお、本発明例として、図５に示した流量調整弁を使う方式と図６に示した逃し弁を使う方式で実施したが、その応用例である図１２〜１５の配管系統としても同様の効果が得られることは言うまでも無い。

In addition, although it implemented by the system which uses the flow regulating valve shown in FIG. 5 and the system which uses the relief valve shown in FIG. 6 as an example of this invention, it is the same also as a piping system of FIGS. Needless to say, an effect can be obtained.

It is a figure explaining formation of the on-board water of the steel plate front-end | tip part at the time of cooling a high temperature steel plate. It is a figure explaining formation of the on-plate water of the steel plate tail end part at the time of cooling a high temperature steel plate. It is the figure explaining the influence which the board water in spray cooling exerts on cooling capacity. It is the figure explaining the influence which the water on a board in slit jet nozzle cooling has on cooling capacity. It is a figure explaining the piping system of the 1st Embodiment of this invention. It is a figure explaining the piping system of the 2nd Embodiment of this invention. It is a figure explaining the flow control method of a 1st embodiment of the present invention. It is a figure explaining the flow control method of the 2nd Embodiment of this invention. It is a figure explaining the relationship between the amount of cooling water at the time of slit jet cooling, and a heat flux. It is an example of the time transition of the liquid level height of water on a board. It is the figure which showed time until water on a board was collected stably. It is an example of the piping system which applied the 2nd Embodiment of this invention. It is a figure explaining the flow control method at the time of operating concretely the piping system of FIG. It is an example of the piping system which applied the 1st Embodiment of this invention. It is an example of the piping system which applied the 2nd Embodiment of this invention. It is the figure explaining the layout of the thick plate manufacturing equipment used in the Example of this invention. It is the figure explaining the detail of the cooling equipment used in the Example of this invention. It is a figure explaining the cooling zone in the example of the present invention. It is a steel plate longitudinal direction temperature distribution after the cooling in Example 1 of this invention. It is the steel plate longitudinal direction temperature distribution after the cooling in Example 2 of this invention. It is a steel plate longitudinal direction temperature distribution after the cooling in the comparative example 1. FIG. It is a steel plate longitudinal direction temperature distribution after the cooling in the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel plate 2 Cooling nozzle 3 Cooling zone entrance side draining roll 4 Cooling zone exit side draining roll 5 Plate water 11 Spray nozzle 12 Spray droplet water 13 Slit jet nozzle 20 Cooling water pump 21 Flow meter 22 Flow control valve 23 Shutoff valve 24 Adjustment valve 25 Upper surface nozzle water supply piping system 26 Relief valve system piping system 27 Flow rate adjustment valve system piping system 28 Flow meter for relief valve piping system 29 Flow control valve for relief valve piping system 41 Thick plate mill 42 Slab 43 Table roll 44 Cooling Equipment 45 Upper surface nozzle 46 Lower surface slip 47 Cooling device entry side thermometer 48 Cooling device exit side thermometer 49 Draining roll 61 Steel plate detector (photocell)
62 Timer

Claims (15)

  In the method for cooling a steel sheet, the upper and lower surfaces of the steel sheet are cooled with cooling water while passing the cooling zone divided by the inlet side draining roll and the outlet side draining roll at a constant speed after the hot rolling. The nozzle that injects the cooling water toward the continuous flow injection nozzle that injects a continuous flow, and the amount of cooling water from the continuous flow injection nozzle is the amount of cooling water when the tip of the steel plate passes through the cooling zone A cooling method for a steel sheet, characterized in that the central portion in the direction is larger than the amount of cooling water when passing through the cooling zone.   In the cooling method of the steel plate according to claim 1, the amount of cooling water from the continuous flow spray nozzle is set to the length of the steel plate until the tip of the steel plate enters the outlet side draining roll after entering the inlet side draining roll. The cooling water amount is larger than the cooling water amount when the central part of the steel plate passes through the cooling zone. A method for cooling a steel sheet, characterized by adjusting the amount of cooling water when passing through a zone. 3. The method for cooling a steel sheet according to claim 2, wherein the width of the steel sheet is W (m), and the amount of cooling water from the continuous flow injection nozzle when the front end of the steel sheet enters the outlet side draining roll of the cooling zone is Q (T / Min · m ² ), the adjustment of the amount of cooling water from the continuous flow injection nozzle starts when the tip of the steel sheet enters the outlet side draining roll of the cooling zone, and the tip of the steel sheet enters the outlet side draining roll of the cooling zone. elapsed time from when the t (sec) is, 0.57 (1.12W + 1.93) cooling water from the continuous flow ejection nozzles when a ^{Q -0.35 ≦ t ≦ (1.12W +} 1.93) Q -0.35 The steel sheet cooling method is characterized in that the adjustment of the steel sheet is finished.   In the cooling method of the steel plate of Claim 2 or 3, about the amount of cooling water from a continuous flow injection nozzle, the amount of cooling water from when the front-end | tip of a steel plate enters into an entrance side draining roll until it enters into an exit side draining roll Is increased by 1.2 to 1.8 times the amount of cooling water when the central portion in the longitudinal direction of the steel plate passes through the cooling zone.   In the cooling method of the steel plate in any one of Claims 1-4, a flow rate adjustment valve is provided between a continuous flow injection nozzle and the cooling water water supply apparatus which supplies cooling water to a continuous flow injection nozzle, The flow rate adjustment By adjusting the valve, the amount of cooling water when the tip of the steel plate passes through the cooling zone is made larger than the amount of cooling water when the central portion in the longitudinal direction of the steel plate passes through the cooling zone. Cooling method.   6. The method for cooling a steel sheet according to claim 5, wherein two or more flow rate adjusting valves are provided in parallel between the continuous flow injection nozzle and the cooling water feeding device.   In the cooling method of the steel plate in any one of Claims 1-4, a part of cooling water is continuously flowed between the continuous flow injection nozzle and the cooling water supply apparatus which supplies cooling water to a continuous flow injection nozzle. By providing a relief valve to prevent water from being delivered to the injection nozzle and adjusting the relief valve, the amount of cooling water when the tip of the steel plate passes through the cooling zone passes through the cooling zone at the center in the longitudinal direction of the steel plate. A method for cooling a steel sheet, characterized in that the amount of cooling water is larger than the amount of cooling water when   The method for cooling a steel sheet according to claim 7, wherein two or more relief valves are provided in parallel between the continuous flow spray nozzle and the cooling water feeding device.   In the cooling method of the steel plate in any one of Claims 1-8, a continuous flow injection nozzle is any 1 type, or 2 or more types of a slit jet nozzle, a circular pipe jet nozzle, and a laminar nozzle. A method for cooling steel sheets.   In a steel sheet cooling apparatus that cools the upper and lower surfaces of a steel sheet with cooling water while passing the steel sheet after hot rolling through a cooling zone partitioned by an inlet side draining roll and an outlet side draining roll at a constant speed, on the upper surface of the steel sheet The nozzle that injects the cooling water toward the continuous flow injection nozzle that injects a continuous flow, and the amount of cooling water from the continuous flow injection nozzle is the amount of cooling water when the tip of the steel plate passes through the cooling zone A steel sheet cooling device characterized in that the central portion in the direction is larger than the amount of cooling water when passing through the cooling zone.   11. The steel sheet cooling device according to claim 10, wherein one or two or more flow rates arranged in parallel between the continuous flow injection nozzle and the cooling water supply device for supplying cooling water to the continuous flow injection nozzle. By providing an adjustment valve and adjusting the flow rate adjustment valve, the amount of cooling water when the tip of the steel sheet passes through the cooling zone is greater than the amount of cooling water when the longitudinal center of the steel sheet passes through the cooling zone. A steel sheet cooling device characterized by that.   11. The steel sheet cooling device according to claim 10, wherein a part of the cooling water is not supplied to the continuous flow injection nozzle between the continuous flow injection nozzle and the cooling water supply device that supplies the cooling water to the continuous flow injection nozzle. The amount of cooling water when the tip of the steel sheet passes through the cooling zone is adjusted by adjusting the relief valve so that the amount of cooling water is the longitudinal length of the steel sheet. A steel sheet cooling device characterized in that the central portion in the direction is larger than the amount of cooling water when passing through the cooling zone.   The cooling device for a steel sheet according to any one of claims 10 to 12, wherein the amount of cooling water from the continuous flow injection nozzle is from the time when the leading end of the steel sheet enters the entry side draining roll until it enters the exit side draining roll. The amount of cooling water is greater than the amount of cooling water when the longitudinal center of the steel plate passes through the cooling zone, and after the tip of the steel plate enters the outlet draining roll, the amount of cooling water from the continuous flow spray nozzle is A steel sheet cooling apparatus characterized by adjusting the amount of cooling water when the central portion in the direction passes through the cooling zone. 14. The steel sheet cooling device according to claim 13, wherein the steel sheet width is W (m), and the cooling water amount from the continuous flow injection nozzle when the front end of the steel sheet enters the outlet side draining roll of the cooling zone is Q (T / Min · m ² ), the adjustment of the amount of cooling water from the continuous flow nozzle is started when the tip of the steel sheet enters the outlet draining roll of the cooling zone, and the tip of the steel sheet enters the outlet draining roll of the cooling zone. elapsed time from when the t (sec) is, 0.57 (1.12W + 1.93) cooling water from the continuous flow ejection nozzles when a ^{Q -0.35 ≦ t ≦ (1.12W +} 1.93) Q -0.35 The steel sheet cooling device is characterized in that the adjustment of the steel sheet is finished.   The steel sheet cooling device according to any one of claims 10 to 14, wherein the continuous flow injection nozzle is one or more of a slit jet nozzle, a circular pipe jet nozzle, and a laminar nozzle. Steel sheet cooling device.

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