JP2010023066A - Method and equipment for cooling hot-rolled steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and equipment for cooling a hot-rolled steel sheet by which the winding temperature of the hot-rolled sheet is accurately controlled to a target winding temperature. <P>SOLUTION: This cooling equipment 100 is provided with: a plurality of cooling systems 1 which are switchable to water cooling and air cooling; a plurality of thermometers 2, 2A which are respectively arranged on the inlet side and the outlet side of each cooling system; a heat transfer coefficient calculating means 3 for calculating the heat transfer coefficients at the water cooling and the air cooling on the basis of the temperature difference between the inlet side and the outlet side of the cooling system; a winding temperature predicting means 4 for predicting the winding temperature of the hot-rolled steel sheet about a plurality of cooling patterns by performing the heat transfer calculation by using the heat transfer coefficients at the water cooling and at the air cooling which are calculated by the heat transfer coefficient calculating means; and a cooling control means 5 for selecting the cooling pattern by which the predicted winding temperature of the hot-rolled steel sheet becomes a prescribed temperature from among the plurality of the cooling patterns and switching the water cooling and the air cooling performed by each cooling system according to a selected cooling pattern by selecting the cooling pattern. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for cooling a hot-rolled steel sheet and a cooling facility. In particular, the present invention relates to a method for cooling a hot-rolled steel sheet capable of accurately controlling the temperature of the hot-rolled steel sheet (winding temperature) when being wound by a winding device to a target temperature (target winding temperature), and It relates to cooling equipment.

  The hot-rolled steel sheet is rolled by a hot rolling mill, then conveyed to a winding device by a conveyance table, and wound in a coil shape by the winding device. A cooling device is installed on the transfer table. With this cooling device, the hot-rolled steel sheet is cooled before being wound by the winding device. The temperature (winding temperature) of the hot-rolled steel sheet when being wound by the winding device is important for obtaining a hot-rolled steel sheet of good quality by keeping the mechanical properties of the hot-rolled steel sheet within a predetermined range. It is a management item. Therefore, it is desired to accurately control the winding temperature of the hot-rolled steel sheet to the target temperature (target winding temperature).

FIG. 4 is a schematic diagram illustrating a schematic configuration example of a conventional general cooling facility.
As shown in FIG. 4, the conventional cooling facility 100 ′ has a coiling temperature of the hot-rolled steel sheet S that is rolled by the hot rolling mill 20 and conveyed by the conveying table 40 toward the winding device 30. It arrange | positions between the hot rolling mill 20 and the winding device 30, and it is comprised so that the hot-rolled steel plate S may be cooled with the predetermined | prescribed cooling pattern which consists of a combination of water cooling or air cooling.

  Specifically, the cooling equipment 100 ′ is arranged along the conveying direction of the hot-rolled steel sheet S, and a plurality of cooling devices 1 (11 to 1 n) capable of switching between water cooling and air cooling, and the hot rolling mill 20. The thermometer (radiation thermometer) 2 for measuring the temperature of the hot-rolled steel sheet S, which is arranged on the outlet side (the inlet side of the cooling device 11 arranged on the most upstream side in the conveying direction of the hot-rolled steel sheet S), and each cooling Assuming a plurality of cooling patterns in which the apparatus 1 performs either water cooling or air cooling, the heat transfer calculation is performed for the plurality of cooling patterns, thereby predicting the winding temperature of the hot-rolled steel sheet S for each cooling pattern. The winding temperature of the hot-rolled steel sheet S predicted by the winding temperature prediction means 4 and the winding temperature prediction means 4 among the plurality of assumed cooling patterns is a predetermined temperature (the difference from the target winding temperature is less than a predetermined value). Select the cooling pattern to be And a cooling control unit 5 for switching the water cooling or air the cooling device 1 is carried out according to the cooling pattern the selected.

  Each cooling device 1 includes a pair of upper and lower cooling headers, and each cooling header is provided with a plurality of water cooling nozzles that inject cooling water toward the hot-rolled steel sheet S. Whether or not the cooling water is supplied to the water cooling nozzle is controlled by opening and closing valves provided in each cooling device 1. In other words, when the valve provided in the cooling device 1 is opened, the cooling water is supplied to each water cooling nozzle provided in the cooling device 1, and the cooling water is jetted toward the hot-rolled steel sheet S from each water cooling nozzle. That is, the hot rolled steel sheet S is water cooled. On the other hand, when the valve provided in the cooling device 1 is closed, the supply of the cooling water to each water cooling nozzle provided in the cooling device 1 is stopped, and the injection of the cooling water from each water cooling nozzle toward the hot-rolled steel sheet S is performed. Stopped. That is, the hot-rolled steel sheet S is air-cooled (cooled).

In addition, the cooling facility 100 ′ is disposed on the exit side of the hot rolling mill 20, and is disposed on the exit side of the hot rolling mill 20 and a thickness gauge 6 that measures the thickness of the hot rolling steel sheet S, and the hot rolling steel sheet S. And a speedometer 7 for measuring the speed of
Furthermore, the cooling facility 100 ′ reduces the occurrence of a temperature measurement error in the thermometer 2 by the cooling water from the cooling device 1 splashing on the hot-rolled steel sheet S in the field of view of the thermometer 2. A draining device 8 for injecting high-pressure purge water is provided. Moreover, cooling equipment 100 'is arrange | positioned at the entrance side (outside of the cooling device 1n arrange | positioned in the conveyance direction most downstream side of the hot-rolled steel sheet S) of the winding apparatus 30, and takes up the winding temperature of the hot-rolled steel sheet S. A thermometer (radiation thermometer) 9 to be measured and a drainer 10 for reducing the occurrence of temperature measurement errors in the thermometer 9 are provided.

  In the cooling facility 100 ′ having the above configuration, when the hot-rolled steel sheet S rolled by the hot rolling mill 20 passes below the thermometer 2, the temperature and thickness of the hot-rolled steel sheet S are set at a predetermined sampling period. These are measured by the thermometer 2 and the thickness gauge 6, respectively. Since the thermometer 2 and the thickness meter 6 are close to each other, the part of the hot-rolled steel sheet S whose temperature is measured and the part of the hot-rolled steel sheet S whose thickness is measured are the same part (hereinafter, this part is sampled). There is no problem even if it is considered to be a point. Further, when the temperature at each sampling point is measured by the thermometer 2, the speed at each sampling point is measured by the speedometer 7. The temperature, thickness, and speed measured for each of these sampling points are input to the winding temperature prediction means 4.

  The coiling temperature predicting means 4 is not only the temperature, thickness and speed for each sampling point measured and inputted as described above, but also the specific heat, density, water cooling and air cooling of the hot rolled steel sheet S inputted in advance. A plurality of cooling patterns (a plurality of patterns with different opening / closing states of the valves included in each cooling device 1) are used using parameters such as heat transfer rate, water density of cooling water when the cooling device 1 is water-cooled, water temperature, and air temperature. ) To estimate the coiling temperature at each sampling point for each cooling pattern. The prediction of the coiling temperature is executed before each sampling point reaches the cooling device 11 arranged on the most upstream side in the transport direction of the hot-rolled steel sheet S.

  The cooling control means 5 is configured such that the winding temperature at each sampling point predicted by the winding temperature prediction means 4 among the plurality of assumed cooling patterns is a predetermined temperature (the temperature at which the difference from the target winding temperature is a predetermined value or less). ) Is selected, and water cooling or air cooling actually performed by each cooling device 1 is switched according to the selected cooling pattern. That is, the cooling control means 5 switches the open / close state of the valves included in each cooling device 1 in accordance with the selected cooling pattern. The valve switching operation by the cooling control means 5 is executed before each sampling point reaches each cooling device 11. Each sampling point is cooled by each cooling device 11 according to the selected cooling pattern.

The cooling facility 100 ′ described above switches the open / close state of the valves included in each cooling device 1 so that the winding temperature of the hot-rolled steel sheet S predicted by heat transfer calculation is equal to or close to the target winding temperature. Therefore, in order for the actual winding temperature of the hot-rolled steel sheet S to be equal to or close to the target winding temperature, it is necessary to predict the winding temperature of the hot-rolled steel sheet S with high accuracy.
However, in order to predict the coiling temperature of the hot-rolled steel sheet S with high accuracy, in addition to predicting the amount of heat taken from the hot-rolled steel sheet S during water cooling and the amount of heat taken from the hot-rolled steel sheet S during air cooling, Although it is necessary to predict the calorific value generated by transformation, it is difficult to accurately predict all of these.
In other words, it is difficult to predict the winding temperature of the hot-rolled steel sheet S with high accuracy by using empirically determined fixed values as the heat transfer coefficients during water cooling and air cooling.

For this reason, for example, as described in Patent Document 1, a method of correcting (learning) the heat transfer coefficient using the measured temperature of the hot-rolled steel sheet has been proposed. The method described in Patent Document 1 measures the temperature of a hot-rolled steel sheet on the outlet side of a hot rolling mill and the inlet side of a winding device, and uses a sequential least-squares method based on the measurement results to perform water cooling and air cooling. It is a method of learning the heat transfer coefficient at the time.
JP-A 64-62206

  However, in the method described in Patent Document 1, when learning the heat transfer coefficient during water cooling and air cooling, the measured temperature of the hot-rolled steel sheet on the outlet side of the hot rolling mill, the hot rolling mill and the winding device, Only the measured temperature of the hot-rolled steel sheet on the inlet side of the winding device affected by both water cooling and air cooling in the cooling facility located between the No consideration is given to temperature. Therefore, in the method described in Patent Document 1, it is not possible to separately learn the heat transfer coefficient at the time of water cooling and air cooling in the cooling facility, and the learning accuracy is low, that is, the actual accuracy at the time of water cooling and air cooling. The heat transfer coefficient cannot be calculated with high accuracy. As a result, there is a problem that the winding temperature of the hot-rolled steel sheet cannot be accurately predicted, and the winding temperature of the hot-rolled steel sheet cannot be accurately controlled to the target winding temperature.

  The present invention has been made in view of the problems of the prior art, and a hot-rolled steel sheet cooling method and cooling equipment capable of accurately controlling the coiling temperature of a hot-rolled steel sheet to a target coiling temperature. It is an issue to provide.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, in the cooling zone (cooling equipment) located between the hot rolling mill and the winding device, the temperature of the hot-rolled steel sheet before and after water cooling and before and after air cooling. It was found that the actual heat transfer coefficient at the time of water cooling and air cooling can be calculated with high accuracy by individually measuring the heat transfer coefficient at the time of water cooling and air cooling using this measured temperature. Then, by using this heat transfer coefficient, the coiling temperature of the hot-rolled steel sheet can be predicted with high accuracy, and consequently the coiling temperature of the hot-rolled steel sheet can be accurately controlled to the target coiling temperature, and the present invention has been completed. .

That is, the present invention provides the hot rolling mill and the winding device so that the winding temperature of the hot rolled steel sheet rolled by the hot rolling mill and conveyed toward the winding device becomes a predetermined temperature. A method of cooling a hot-rolled steel sheet with a predetermined cooling pattern consisting of a combination of water cooling or air cooling performed in each of the sections in a cooling zone located between and divided into a plurality of sections along the conveying direction of the hot-rolled steel sheet And the cooling method of the hot rolled sheet steel characterized by including each step of the following (1)-(4) is provided.
(1) Measure the temperature of the hot-rolled steel sheet on the inlet side and the outlet side of the section where the hot-rolled steel sheet is water-cooled in the cooling zone, and based on the measured temperature difference of the hot-rolled steel sheet, heat transfer during water cooling Calculating the rate (heat transfer rate from hot-rolled steel sheet to water).
(2) The temperature of the hot-rolled steel sheet on the inlet side and the outlet side of the section where the hot-rolled steel sheet is air-cooled in the cooling zone is measured, and the heat transfer during air-cooling is based on the measured temperature difference of the hot-rolled steel sheet. Calculating the rate (heat transfer rate from hot-rolled steel sheet to air).
(3) Assuming a plurality of cooling patterns in the cooling zone, each of the plurality of cooling patterns is subjected to heat transfer calculation using the calculated heat transfer coefficient during water cooling and air cooling. Predicting the winding temperature of the hot rolled steel sheet.
(4) A step of selecting a cooling pattern in which the predicted coiling temperature of the hot-rolled steel sheet is a predetermined temperature among the plurality of assumed cooling patterns, and cooling the hot-rolled steel sheet with the selected cooling pattern.

  Moreover, in order to solve the said subject, this invention is the said hot rolling mill so that the winding temperature of the hot rolled steel plate rolled with a hot rolling mill and conveyed toward a winding apparatus may turn into predetermined | prescribed temperature. And the winding device, and is a facility for cooling the hot-rolled steel sheet with a predetermined cooling pattern consisting of a combination of water cooling or air cooling, each arranged along the conveying direction of the hot-rolled steel sheet, A plurality of cooling devices capable of switching between air cooling, a plurality of thermometers arranged on the inlet side and the outlet side of each of the cooling devices, respectively, for measuring the temperature of the hot-rolled steel sheet, and hot rolling of the plurality of cooling devices Heat transfer rate during water cooling (heat transfer rate from hot-rolled steel plate to water) based on the temperature difference of hot-rolled steel plate measured by the thermometers placed on the inlet side and the outlet side of the cooling device for water cooling the steel plate And the hot-rolled steel sheet is emptied of the plurality of cooling devices. Based on the temperature difference between the hot-rolled steel sheets measured by the thermometers arranged on the inlet side and the outlet side of the cooling device, the heat transfer coefficient at the time of air cooling (heat transfer coefficient from the hot-rolled steel sheet to the air) is calculated. Assuming a plurality of cooling patterns in which the heat transfer coefficient calculating means and each of the cooling devices perform either water cooling or air cooling, water cooling and air cooling calculated by the heat transfer coefficient calculating means for the plurality of cooling patterns. A winding temperature predicting means for predicting the winding temperature of the hot-rolled steel sheet for each cooling pattern by performing heat transfer calculation using the heat transfer coefficient, and the winding temperature among the plurality of assumed cooling patterns. A cooling control unit that selects a cooling pattern in which the coiling temperature of the hot-rolled steel sheet predicted by the prediction unit becomes a predetermined temperature, and switches between water cooling and air cooling performed by each of the cooling devices according to the selected cooling pattern. Are provided as cooling equipment for a hot rolled steel sheet, characterized in that it comprises and.

  In the present invention, “calculating the heat transfer coefficient” means calculating the correction coefficient for multiplying the heat transfer coefficient given as a fixed value in addition to calculating the heat transfer coefficient given as a variable itself. It is a concept that includes.

  According to the present invention, since the heat transfer coefficient at the time of water cooling and air cooling can be calculated with high accuracy, the winding temperature of the hot-rolled steel plate can be accurately predicted, and consequently the winding temperature of the hot-rolled steel plate can be accurately targeted. It is possible to control the coiling temperature.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.

<1. Configuration of cooling equipment>
FIG. 1 is a schematic diagram illustrating a schematic configuration example of a cooling facility according to an embodiment of the present invention.
As shown in FIG. 1, the cooling facility 100 according to the present embodiment has a predetermined winding temperature of the hot-rolled steel sheet S that is rolled by the hot rolling mill 20 and transported by the transport table 40 toward the winding device 30. It arrange | positions between the hot rolling mill 20 and the winding device 30 so that it may become temperature, and it is comprised so that the hot-rolled steel plate S may be cooled with the predetermined cooling pattern which consists of a combination of water cooling or air cooling.

  Specifically, the cooling equipment 100 is arranged along the conveying direction of the hot-rolled steel sheet S, and a plurality of cooling devices 1 (11 to 1n) capable of switching between water cooling and air cooling, and the input of each cooling device 1 are provided. The plurality of thermometers (radiation thermometers) 2 and 2A (21 to 2n) that are arranged on the side and the outlet side and measure the temperature of the hot-rolled steel sheet S, and the water-cooled hot-rolled steel sheet S among the plurality of cooling devices 1 are water-cooled. Based on the temperature difference of the hot-rolled steel sheet S measured by the thermometers arranged on the inlet side and the outlet side of the cooling device 1 that performs cooling, the heat transfer coefficient during heat cooling (heat transfer coefficient from the hot-rolled steel sheet to water) is calculated. (Specifically, a heat transfer coefficient correction coefficient is calculated), and heat measured by thermometers respectively disposed on the inlet side and the outlet side of the cooling device 1 that cools the hot-rolled steel sheet S among the plurality of cooling devices 1. Based on the temperature difference of the rolled steel sheet S, the heat transfer coefficient during air cooling (heat from the hot rolled steel sheet to the air) Assuming a plurality of cooling patterns in which each cooling device 1 performs either water cooling or air cooling, and a heat transfer coefficient calculating means 3 that calculates (specifically a heat transfer coefficient correction coefficient). About this cooling pattern, by performing heat transfer calculation using the heat transfer coefficient at the time of water cooling and air cooling calculated by the heat transfer coefficient calculating means 3, the winding temperature of the hot rolled steel sheet S for each cooling pattern is set. The coiling temperature predicting means 4 to predict and the coiling temperature of the hot-rolled steel sheet S predicted by the coiling temperature predicting means 4 among the plurality of assumed cooling patterns are set to a predetermined temperature (the difference from the target coiling temperature is predetermined). A cooling control means 5 that selects a cooling pattern that is equal to or lower than the value and switches between water cooling and air cooling performed by each cooling device 1 in accordance with the selected cooling pattern.

Each cooling device 1 includes a pair of upper and lower cooling headers, and each cooling header is provided with a plurality of water cooling nozzles that inject cooling water toward the hot-rolled steel sheet S. Whether or not the cooling water is supplied to the water cooling nozzle is controlled by opening and closing valves provided in each cooling device 1. In other words, when the valve provided in the cooling device 1 is opened, the cooling water is supplied to each water cooling nozzle provided in the cooling device 1, and the cooling water is jetted toward the hot-rolled steel sheet S from each water cooling nozzle. That is, the hot rolled steel sheet S is water cooled. On the other hand, when the valve provided in the cooling device 1 is closed, the supply of the cooling water to each water cooling nozzle provided in the cooling device 1 is stopped, and injection of the cooling water from each water cooling nozzle toward the hot-rolled steel sheet S is performed. Stopped. That is, the hot-rolled steel sheet S is air-cooled (cooled).
In FIG. 1, for convenience of illustration, there is a gap between the cooling devices 11 to 1n in the conveying direction of the hot-rolled steel sheet S, but actually, the cooling devices 11 to 1n are continuous without a gap. Is arranged.
Moreover, the whole area | region where the cooling devices 11-1n are arrange | positioned corresponds to the "cooling zone" in this invention, and the area | region where each cooling device 11-1n is each arrange | positioned in the "section" in this invention. Equivalent to.

Each thermometer 2 </ b> A is arranged on the exit side of each cooling device 1. For example, the thermometer 21 is a thermometer disposed on the exit side of the cooling device 11 and also corresponds to a thermometer disposed on the entry side of the cooling device 12. The thermometer arranged on the outlet side of the cooling device 11 and the thermometer arranged on the inlet side of the cooling device 12 can be made as separate thermometers, but securing a space for installing the thermometer From the viewpoint of equipment costs, it is desirable to use one thermometer 21 as a thermometer arranged on the outlet side of the cooling device 11 and a thermometer arranged on the inlet side of the cooling device 12. The same applies to the other thermometers 2 </ b> A disposed between the cooling devices 1.
As each thermometer 2A, a so-called water column thermometer is used in order to reduce the occurrence of temperature measurement errors due to the cooling water for the transport roll 41 constituting the transport table 40 being scattered or the water vapor stagnating. It has been. That is, by forming a water column as an optical waveguide between the back surface of the hot-rolled steel sheet S and the radiation thermometer, and receiving the emitted light from the back surface of the hot-rolled steel sheet S through the water column with the radiation thermometer. The temperature of the hot-rolled steel sheet S is measured. A more detailed configuration of the thermometer 2A will be described later.

Moreover, the cooling facility 100 is disposed on the exit side of the hot rolling mill 20, and is disposed on the exit side of the hot rolling mill 20 and a thickness meter 6 that measures the thickness of the hot rolling steel sheet S. A speedometer 7 for measuring the speed.
Furthermore, the cooling facility 100 reduces the occurrence of temperature measurement errors in the thermometer 2 due to splashing of the cooling water from the cooling device 1 on the hot-rolled steel sheet S in the field of view of the thermometer 2. A draining device 8 for injecting purge water is provided. Further, the cooling facility 100 is disposed on the entrance side of the winding device 30, and a thermometer (radiation thermometer) 9 that measures the winding temperature of the hot-rolled steel sheet S and a temperature measurement error occur in the thermometer 9. And a draining device 10 for reduction.

  Hereinafter, the winding temperature prediction method performed by the winding temperature prediction unit 4 of the cooling facility 100 having the above-described configuration, the water cooling or air cooling switching operation performed by the cooling unit 5, and the heat transfer performed by the heat transfer coefficient calculation unit 3. The method of calculating the rate (specifically, calculating the correction coefficient of the heat transfer coefficient) will be specifically described.

<2. Winding temperature prediction method using winding temperature prediction means>
When the hot-rolled steel sheet S rolled by the hot rolling mill 20 passes below the thermometer 2, the temperature of the hot-rolled steel sheet S and the temperature of the hot-rolled steel sheet S are determined at a predetermined sampling period (for example, a period of 0.4 to 2.0 seconds). The thickness is measured by the thermometer 2 and the thickness meter 6, respectively. Since the thermometer 2 and the thickness meter 6 are close to each other, the part of the hot-rolled steel sheet S whose temperature is measured and the part of the hot-rolled steel sheet S whose thickness is measured are the same part (hereinafter, this part is sampled). There is no problem even if it is considered to be a point. Further, when the temperature at each sampling point is measured by the thermometer 2, the speed at each sampling point is measured by the speedometer 7. The temperature, thickness, and speed measured for each of these sampling points are input to the winding temperature prediction means 4.

  The coiling temperature predicting means 4 is not only the temperature, thickness and speed for each sampling point measured and inputted as described above, but also the specific heat, density, water cooling and air cooling of the hot rolled steel sheet S inputted in advance. A plurality of cooling patterns (a plurality of patterns with different opening / closing states of the valves included in each cooling device 1) are used using parameters such as heat transfer rate, water density of cooling water when the cooling device 1 is water-cooled, water temperature, and air temperature. ) To estimate the coiling temperature at each sampling point for each cooling pattern. The prediction of the coiling temperature is executed before each sampling point reaches the cooling device 11 arranged on the most upstream side in the transport direction of the hot-rolled steel sheet S.

Specifically, in the assumed cooling pattern, when the i-th cooling device 1 counted from the upstream side in the conveying direction of the hot-rolled steel sheet S is water-cooled (the valve is opened), the following formula (1) Thus, the temperature drop amount ΔT _Wi at each sampling point of the hot-rolled steel sheet S by the i-th cooling device is calculated. On the other hand, in the assumed cooling pattern, when the i-th cooling device 1 is air-cooled (the valve is closed), each sampling of the hot-rolled steel sheet S by the i-th cooling device is performed by the following equation (2). The temperature drop amount ΔT _ai at the point is calculated. And as shown in following formula (7), the thermometer 2 arrange | positioned at the exit side (entrance side of the cooling device 11 arrange | positioned in the conveyance direction uppermost stream side of the hot-rolled steel sheet S) of the hot rolling mill 20 the temperature T _F of each sampling point measured by subtracting the temperature drop due to all the cooling apparatus 1 predicts the winding temperature T _C of each sampling point.

In addition, the meaning of each parameter shown to said Formula (1)-(7) is as follows.
i: Subscript indicating the order of the cooling device 1 counted from the upstream side in the conveying direction of the hot-rolled steel sheet S ΔT _Wi : A temperature drop amount at each sampling point of the hot-rolled steel sheet S when the i-th cooling device 1 is water-cooled ( ℃)
α _Li : Heat transfer coefficient (kcal / m ² hr ° C.) at the time of water cooling of the i-th cooling device 1
Z _Li : Heat transfer coefficient correction coefficient (dimensionalless amount) at the time of water cooling of the i-th cooling device 1
c: Specific heat of hot-rolled steel sheet S (kcal / kg ° C.)
ρ: density of the hot-rolled steel sheet S (kg / m ³ )
h: thickness of hot-rolled steel sheet S (m)
T _i : Temperature (° C.) of each sampling point of the hot-rolled steel sheet S on the entry side of the i-th cooling device 1
T _L : Water temperature of the cooling water of the cooling device 1 (° C.)
t _i : Time for each sampling point of the hot-rolled steel sheet S to pass through the i-th cooling device 1 (hr)
ΔT _ai : Temperature drop amount (° C.) at each sampling point of the hot-rolled steel sheet S when the i-th cooling device 1 is air-cooled.
σ: Stefan-Boltzmann constant ε: Emissivity (dimensionless quantity)
T _E : Air temperature (° C)
α _Ei : Heat transfer coefficient (kcal / m ² hr ° C.) of the i-th cooling device 1 during air cooling
Z _Ei : Heat transfer coefficient correction coefficient (dimensionalless amount) at the time of air cooling of the i-th cooling device 1
a, b: Constant (dimensionless amount)
W _i : Water volume density (m ³ / m ² hr) of cooling water when the i-th cooling device 1 is water-cooled
L _i : length of the i-th cooling device 1 (m)
v _i : Speed when each sampling point of the hot-rolled steel sheet S passes through the i-th cooling device 1 (m / sec)
T _F : Outlet temperature (° C.) of the hot rolling mill 20 at each sampling point of the hot-rolled steel sheet S
T _C : Predicted winding temperature (° C.) at each sampling point of the hot-rolled steel sheet S
n: Number of cooling devices 1

The heat transfer coefficient α _Li during water cooling of the i-th cooling device 1 in the above equation (1) is calculated by the above equation (3).
The time t _i of the i-th cooling device 1 in the above formula (1) and (2) of the sampling points of the hot-rolled steel sheet S passes is calculated by the above equation (4). Note that the speed v _i when each sampling point of the hot-rolled steel sheet S passes through the i-th cooling device 1 in the above formula (4) is not an actually measured value when predicting the coiling temperature, A value calculated based on the speed of each sampling point measured by the speedometer 7 (speed when each sampling point passes under the thermometer 2) is used. For example, based on the speed measured by the speedometer 7, the conveyance acceleration of the hot-rolled steel sheet S previously input to the winding temperature prediction means 4, and the distance between the thermometer 2 and the i-th cooling device 1, The speed v _i is calculated.
Further, as the temperature T _i of each sampling point of the hot-rolled steel sheet S in the i-th cooling device 1 of the inlet side in the above equation (1) and (2), in predicting coiling temperature, first except for temperatures T ₁ in the inlet side of the cooling device 11, rather than the measured values, the values calculated by the above equation (5) and (6) are used. That is, as the temperature T ₁ on the entry side of the _first cooling device 11, the temperature _TF actually measured by the thermometer 2 disposed on the entry side of the cooling device 11 is used. Further, the temperature T _{2 on} the entry side of the second cooling device 12 is obtained by substituting T ₁ = _TF into the above equation (1) when the first cooling device 11 is water-cooled. the _w1 is calculated by substituting the [Delta] T ₁ of formula (5). Further, when the first cooling system 11 is air cooling, by substituting [Delta] T _a1 obtained by substituting _T 1 = _{T F} in the above formula (2) as [Delta] T ₁ of formula (5) Thus, the temperature T _{2 on} the entry side of the second cooling device 12 is calculated. Hereinafter, similarly, temperatures T _{3 to} Tn of the respective sampling points of the hot-rolled steel sheet S on the entry side of the third to n-th cooling devices 1 are calculated.

  The coiling temperature predicting unit 4 executes the above-described prediction of the coiling temperature at each sampling point for a plurality of assumed cooling patterns. Specifically, for example, for the cooling pattern in which all the valves included in each cooling device 1 are all closed (that is, all the cooling devices 1 are air-cooled), the winding temperature at each sampling point is set. Predict. When the predicted winding temperature is higher than a predetermined temperature (a temperature at which the difference from the target winding temperature is equal to or less than a predetermined value), the winding temperature prediction unit 4 performs any cooling according to a predetermined order. The winding temperature at each sampling point is predicted for another cooling pattern in which the valve of the apparatus 1 is opened. The order is not particularly limited, but is determined empirically in consideration of the quality of the hot-rolled steel sheet S after cooling, operational stability, and the like. The coiling temperature predicting unit 4 repeats the coiling temperature prediction by changing the cooling pattern used for the heat transfer calculation until the predicted coiling temperature reaches the predetermined temperature. Then, the cooling pattern when the predicted winding temperature reaches the predetermined temperature is transmitted to the cooling control means 5.

<3. Switching operation of water cooling or air cooling by cooling control means>
As described above, the cooling control unit 5 determines that the winding temperature at each sampling point predicted by the winding temperature prediction unit 4 among a plurality of assumed cooling patterns is a predetermined temperature (the difference from the target winding temperature is a predetermined value). The cooling pattern to be the following temperature) is selected, and water cooling or air cooling actually performed by each cooling device 1 is switched according to the selected cooling pattern. In the present embodiment, as described above, since the cooling pattern when the predicted winding temperature reaches the predetermined temperature is transmitted from the winding temperature prediction unit 4 to the cooling control unit 5, the cooling control unit 5 The water cooling or the air cooling actually performed by each cooling device 1 is switched in accordance with the transmitted cooling pattern (this corresponds to the cooling pattern selected by the cooling control means 5). However, the present invention is not limited to this, and all of the plurality of cooling patterns assumed by the winding temperature prediction unit 4 are transmitted to the cooling control unit 5 together with the winding temperature predicted by the winding temperature prediction unit 4. It is also possible to adopt a configuration in which the cooling control means 5 selects a cooling pattern in which the winding temperature is a predetermined temperature among the plurality of transmitted cooling patterns.

  Specifically, the cooling control unit 5 switches the open / close state of the valves included in each cooling device 1 in accordance with the selected cooling pattern (transmitted from the winding temperature prediction unit 4). The valve switching operation by the cooling control means 5 is executed before each sampling point reaches each cooling device 11. Each sampling point is cooled by each cooling device 11 according to the selected cooling pattern.

<4. Calculation of heat transfer coefficient by heat transfer coefficient calculation means (calculation of heat transfer coefficient correction coefficient)>
When each sampling point of the hot-rolled steel sheet S passes below the thermometer 2, the temperature of each sampling point measured by the thermometer 2 and the thickness of each sampling point measured by the thickness meter 6 are Input to the transmission rate calculation means 3.
Further, when each sampling point passes through each cooling device 1, the speed of each sampling point measured by the speedometer 7 and the temperature of each sampling point measured by the thermometer 2 </ b> A on the exit side of each cooling device 1. And the open / closed state of the valve included in each cooling device 1 are input to the heat transfer coefficient calculating means 3.
The above parameters input to the heat transfer coefficient calculating means 3 are accumulated in an appropriate buffer as necessary, and then cooling of each sampling point is completed (each sampling point passes above the thermometer 2n). Every time or after cooling of all the sampling points of the hot-rolled steel sheet S is completed (the last sampling point has passed above the thermometer 2n), the heat transfer coefficient calculation means 3 inputs the data.

Here, on the exit side of the i-th cooling device 1 counted from the upstream side in the transport direction of the hot-rolled steel sheet S, the j-th sampling point counted from the downstream side in the transport direction of the hot-rolled steel sheet S measured by the thermometer 2A. T _{mj, i} (° C.), and the time for the j-th sampling point to pass through the i-th cooling device 1 is t _{j, i} (hr). Here, the time t _{j, i} is the length of the i-th cooling device 1 and the speed at which the j-th sampling point passes through the i-th cooling device 1 in the same manner as the equation (4) described above. It is calculated by dividing. However, as the speed at which the j-th sampling point passes through the i-th cooling device 1, an actual measurement value measured by the speedometer 7 is used, unlike when the coiling temperature is predicted.

If the i-th cooling device 1 is in a state where the i-th cooling device 1 is water-cooled (the valve is open) when the j-th sampling point passes through the i-th cooling device 1, the heat transfer coefficient calculating means 3 Based on the following equation (8) derived from (1), a heat transfer coefficient correction coefficient Z _{Lj, i} of the i-th cooling device 1 for the j-th sampling point during water cooling is calculated. On the other hand, when the j-th sampling point passes through the i-th cooling device 1, if the i-th cooling device 1 is in an air-cooled state (valve closed), it is derived from the above-described equation (2). Based on the following formula (9), the heat transfer coefficient correction coefficient Z _{Ej, i} during air cooling of the i-th cooling device 1 at the j-th sampling point is calculated.

In the above formulas (8) and (9), Tm _{j, 0} (when i = 1 of Tm _{j, i−1} ) means the temperature of the j th sampling point measured by the thermometer 2. To do.
In addition, in the above formulas (8) and (9), the parameters represented by the same symbols as the parameters shown in the above formulas (1) to (7) are described above with respect to the formulas (1) to (7). Are the same meaning as those in FIG.

The heat transfer coefficient calculation means 3 repeats the above calculation for all sampling points, and the heat transfer coefficient correction coefficient Z _{Lj, i} obtained for each sampling point is expressed by the following equation (10). The average value Z _Li ^A of the heat transfer coefficient correction coefficient during water cooling of the i-th cooling device 1 is calculated. Similarly, the correction coefficient Z _{Ej, i} of the heat transfer coefficient at the time of air cooling obtained for each sampling point is averaged as shown in the following equation (11), and the air cooling of the i-th cooling device 1 is performed. The average value Z _Ei ^A of the heat transfer coefficient correction coefficient is calculated.

In the above equations (10) and (11), when the j-th sampling point passes through the i-th cooling device 1 in a water-cooled state (valve is open), u _{j, i} = 1, v _{j, i} = 0. When the j-th sampling point passes through the i-th cooling device 1 in the air-cooled state (valve is closed), u _{j, i} = 0 and v _{j, i} = 1. m means the number of sampling points.

The average value Z _Li ^A of the heat transfer coefficient correction coefficient at the time of water cooling of the i-th cooling device 1 calculated by the heat transfer coefficient calculating means 3 as described above is used as the i-th equation shown in the above-described equation (1). As the heat transfer coefficient correction coefficient Z _Li of the cooling device 1 at the time of water cooling, the hot-rolled steel sheet to be transported next time (the heat transported next to the hot-rolled steel sheet whose temperature is measured in order to calculate the above Z _Li ^A) It can be used for prediction of the coiling temperature by the coiling temperature predicting means 4 for the rolled steel sheet S. Similarly, the average value Z _Ei ^A of the heat transfer coefficient correction coefficient at the time of air cooling of the i-th cooling device 1 calculated by the heat transfer coefficient calculating means 3 is directly used as the i-th cooling device shown in the above-described equation (2). As the heat transfer coefficient correction coefficient Z _Ei at the time of 1 air cooling, it can be used for the prediction of the coiling temperature by the coiling temperature predicting means 4 for the hot rolled steel sheet S to be conveyed next time.

In addition, the correction coefficient of the heat transfer coefficient at the time of water cooling used for predicting the winding temperature of the hot rolled steel sheet S conveyed this time (that is, the water cooling calculated by the temperature measured for the hot rolled steel sheet S conveyed last time) Correction coefficient of heat transfer coefficient at the time) Z _Li and the average value Z _Li ^A of the heat transfer coefficient correction coefficient at the time of water cooling calculated by the temperature measured for the hot-rolled steel sheet S conveyed this time, As shown in the equation (12), the weighted average value Z _Li ^AW of the correction coefficient of the heat transfer coefficient during the water cooling obtained by the weighted averaging process is used to correct the heat transfer coefficient during the water cooling shown in the above equation (1). The coefficient Z _Li may be used for predicting the coiling temperature of the hot-rolled steel sheet S to be conveyed next time. Similarly, the heat transfer coefficient correction coefficient Z _Ei at the time of air cooling used for predicting the coiling temperature of the hot-rolled steel sheet S conveyed this time and the temperature measured for the hot-rolled steel sheet S conveyed this time are calculated. The average value Z _Ei ^A of the heat transfer coefficient correction coefficient during air cooling and the weighted average value of the heat transfer coefficient correction coefficient during air cooling obtained by weighted averaging as shown in the following equation (13) Z _Ei ^AW may be used for predicting the coiling temperature of the hot rolled steel sheet S to be conveyed next time, as the correction coefficient Z _Ei of the heat transfer coefficient during air cooling shown in the above-described equation (2). Note that β shown in the following equations (12) and (13) is a constant of 0 <β <1.

Moreover, all the correction coefficients Z _{Lj, i} , Z _{Ej, i} of the heat transfer coefficient at the time of water cooling and air cooling obtained for each sampling point of a plurality of (for example, about 100 coils) hot rolled steel sheets S are collected, Averaging treatment is performed as shown in the above formulas (10) and (11), and average values Z _Li ^A and Z _Ei ^A of heat transfer coefficient correction coefficients at the time of water cooling and air cooling are calculated and transported after the next time. You may use for prediction of the coiling temperature about the hot-rolled steel sheet S to be performed.

In addition, the heat transfer coefficient correction coefficients Z _{Lj, i} , Z _{Ej, i} at the time of water cooling and air cooling are sequentially calculated using the parameters for the sampling points where the cooling of one hot-rolled steel sheet S has been completed. It is also possible to use the hot-rolled steel sheet S for predicting the coiling temperature for the subsequent sampling points that have not yet been predicted for the coiling temperature.

  As described above, according to the cooling facility 100 and the cooling method using the same according to the present embodiment, the temperatures of the hot-rolled steel sheets S before and after water cooling and before and after air cooling are measured, and the water cooling is performed using the measured temperatures. Since the heat transfer coefficient during heat and air cooling (correction coefficient of heat transfer coefficient) is calculated separately, the actual heat transfer coefficient during water cooling and air cooling can be calculated with high accuracy. And if this heat transfer rate is used, the coiling temperature of the hot-rolled steel sheet S can be predicted with high accuracy, and the coiling temperature of the hot-rolled steel sheet S can be accurately controlled to the target coiling temperature.

<5. Preferred configuration of water column thermometer>
Hereinafter, a preferable configuration of the water column thermometer used as the thermometer 2A will be described.
FIG. 2 is a diagram illustrating a schematic configuration example of the thermometer 2A included in the cooling facility 100 illustrated in FIG.
As shown in FIG. 2, the thermometer 2 </ b> A includes a radiation thermometer 61, an optical fiber 62 whose front end is disposed at a position facing the hot-rolled steel sheet S and whose rear end is connected to the radiation thermometer 61, and hot rolling. In order to form a water column W as an optical waveguide between the steel sheet S and the tip of the optical fiber 62, a nozzle 63 for injecting water toward the lower surface of the hot-rolled steel sheet S, and water for supplying water to the nozzle 63 And a supply pipe 64. The thermometer 2A receives the heat radiation light from the lower surface of the hot-rolled steel sheet S through the water column W, a part of the water in the water supply pipe 647 and the optical fiber 62, and receives the heat from the lower surface of the hot-rolled steel sheet S. It is configured to measure temperature.

  A tip optical system 80 including an optical window 81 and, if necessary, a condensing lens 82 is attached to the tip of the optical fiber 62. As the optical window 81 and the condensing lens 82, for example, those made of quartz can be applied.

Next, the wavelength of the thermal radiation light to be detected by the radiation thermometer 61 will be described.
When measuring the temperature of the hot-rolled steel sheet S using the thermometer 2A, the temperature measurement error due to absorption / attenuation of thermal radiation by the water column W and disturbance water (cooling water for the transport roll 41, etc.) is suppressed. There is a need to. This temperature measurement error depends on the conditions of the cooling water, the pass line fluctuation of the hot-rolled steel sheet S (position fluctuation in the vertical direction of the lower surface of the hot-rolled steel sheet S), the presence or absence of steam due to changes in ambient temperature and humidity, etc. The thickness of the water column W and disturbance water existing between the rolled steel sheet S and the radiation thermometer 61 changes, and along with this, the degree of absorption / attenuation of thermal radiation by the water column W and disturbance water changes and is detected. This is caused by fluctuations in the amount of heat radiation light.

  The present inventors investigated the spectral transmittance of water on the assumption that thermal radiation light is detected through a water column W formed between the hot-rolled steel sheet S and the radiation thermometer 61. FIG. 5 shows the spectral transmission of water in the wavelength band of about 0.7 to 1.9 μm when the thickness of the water column interposed between the black body furnace and the radiation thermometer is 3, 11, 50, 100 mm. It is a graph which shows a rate. As shown in FIG. 5, it was found that the water transmittance was highest in the wavelength band of 0.85 μm or less, and then the water transmittance was increased in the wavelength band of 1.00 to 1.20 μm.

  On the other hand, the heat radiation light from the black body has a long wavelength and extremely high intensity of the heat radiation light, and is strongly emitted at a long wavelength as compared with a wavelength shorter than 0.9 μm. Therefore, the light energy detected by the radiation thermometer is largely influenced by the long wavelength light, and is strongly influenced by the absorption of water. Therefore, it is preferable to detect the heat radiation light having the shortest wavelength.

  FIG. 6 shows the measurement (temperature measurement error) of the temperature measurement value when the effective thickness of water existing between the radiation thermometer and the hot-rolled steel sheet varies by 30 mm in a hot-rolled steel sheet at about 700 ° C. Results are shown. In the cooling facility 100 for the hot-rolled steel sheet S, the pass line fluctuation of the hot-rolled steel sheet S (the position fluctuation in the vertical direction of the lower surface of the hot-rolled steel sheet S) may be about 30 mm at maximum.

  Here, the horizontal axis of FIG. 6 plotted the thickness of water existing between the radiation thermometer and the hot-rolled steel sheet, and the vertical axis plotted the temperature measurement error. As shown in FIG. 6, in the case of “no filter” (when detecting thermal radiation light in the entire wavelength band without blocking the long wavelength component), for example, 30 mm with respect to a reference thickness of 200 mm. When the thickness fluctuates only, a temperature measurement error of about 14 ° C. occurs (the temperature measurement value changes by about 14 ° C.). In addition, when the long wavelength component is not cut off, if the thickness of the reference water is increased, the temperature measurement error is reduced. However, in order to obtain a temperature measurement error of 10 ° C. or less, for example, a water thickness of 400 mm or more is necessary. It becomes. Note that when the temperature of the hot-rolled steel sheet increases, the temperature measurement error increases, and it is necessary to further increase the thickness of water. However, since the device for increasing the thickness of water becomes unnecessarily large, there is a problem in greatly restricting the installation conditions.

  On the other hand, as shown in FIG. 6, in the case of a “cutoff wavelength of 0.85 μm” (when light having a wavelength longer than the wavelength of 0.85 μm is detected by detection), regardless of the thickness of the reference water, Even if the thickness varies by 30 mm, it is possible to suppress the temperature measurement error to about 6 ° C.

  However, as shown in FIG. 7, it was found that when the measured temperature is 600 ° C. or lower, the temperature measurement value fluctuates greatly, and the temperature cannot be measured with high accuracy. This is considered to be caused by an increase in the long wavelength component of the emitted thermal radiation when the object to be measured becomes low temperature. Therefore, it has been found that in order to measure the temperature in a low temperature region of 600 ° C. or less, it is necessary to shift the wavelength of the thermal radiation light to be detected to the longer wavelength side.

  Therefore, the inventors made a prototype of a radiation thermometer that detects thermal radiation in the wavelength band of 1.00 to 1.20 μm, which has the second highest water transmittance, and used a black body furnace for its temperature characteristics. And evaluated. FIG. 8 is a graph showing an example of the evaluation result. As shown in FIG. 8, in the case of a radiation thermometer in which the wavelength band of the thermal radiation light to be detected is 1.00 to 1.20 μm, if the variation (3σ) of the temperature measurement value is 3 ° C., the allowable range is assumed. It was found that measurement was possible up to 310 ° C.

  From the above test results, in the high temperature range where the temperature of the hot rolled steel sheet S is 600 ° C. or higher, the wavelength band of the heat radiation light detected by the radiation thermometer 61 is 0.85 μm or less, and the temperature of the hot rolled steel sheet S is 600. In a low temperature range where the temperature is below ℃, it is desirable that the wavelength band of the thermal radiation detected by the radiation thermometer 61 is 1.00 μm or more and 1.20 μm or less.

  The optical fiber 62 can be used in various forms as long as it is an optical fiber that sufficiently transmits thermal radiation in the wavelength band determined as described above. For example, an optical fiber made of quartz can be used. Is possible. Moreover, in addition to the use of a single-core optical fiber, if the optical path length in water (see Fig. 2) needs to be relatively long due to installation restrictions, etc., the effect of attenuation by water In order to relax, a bundle fiber in which a plurality of optical fibers are bundled may be used as necessary. Moreover, there is no restriction | limiting in particular in the core diameter of an optical fiber.

  In addition, the nozzle 63 and the water supply pipe 64 positioned in front of the nozzle 63 are preferably designed so as to avoid sudden changes in the diameter and shape of the water channel as much as possible in order to suppress the generation of bubbles. Further, it is preferable to determine the shape and the like of the nozzle 63 so that a so-called potential core of the water column W discharged from the nozzle 63 becomes large.

  Hereinafter, the features of the present invention will be further clarified by describing examples and comparative examples.

<Example>
The test which cools the hot-rolled steel sheet S was conducted on condition of following (1)-(8) using the cooling equipment 100 which shows schematic structure in FIG.
(1) Steel type: 440 MPa class high strength hot-rolled steel sheet (2) Thickness: 3.5 mm
(3) Target winding temperature: 500 ° C
(4) Conveying speed: 570 mpm to 650 mpm (accelerated rolling)
(5) Number of cooling devices: 20
(6) Length of each cooling device: 5m
(7) Cooling water volume density of each cooling device: 1.0 m ³ / m ² hr
(8) Detection wavelength band of thermometer (water column thermometer) 2A:
0.85μm or less (1-10th cooling device outlet side)
1.00-1.20 μm (11th to 20th cooling device outlet side)

<Comparative example>
Using the cooling facility 100 ′ shown schematically in FIG. 4, the conditions (1) to (7) of the above-described embodiment and the conditions for not correcting the heat transfer coefficient during water cooling and air cooling (heat transfer) The rate was fixed), and a test for cooling the hot-rolled steel sheet S was performed.

<Test results>
Fig.3 (a) is a graph which shows the test result (The hot rolling mill delivery side temperature, coiling temperature estimated value, and coiling temperature actual value) of the said Example. FIG.3 (b) is a graph which shows the test result (The hot rolling mill delivery side temperature, coiling temperature prediction value, and coiling temperature actual value) of the said comparative example.
As shown in FIG. 3, it can be seen that the cooling device is controlled so that the estimated coiling temperature approaches the target coiling temperature of 500 ° C. in both the example and the comparative example.
However, as shown in FIG. 3 (a), in the embodiment, cooling is performed so that the actual winding temperature value is substantially equal to the target winding temperature, whereas as shown in FIG. 3 (b). In the comparative example, the actual winding temperature value deviates from the target winding temperature. This is due to the fact that in the example, the prediction accuracy of the winding temperature is higher than in the comparative example.

FIG. 1 is a schematic diagram illustrating a schematic configuration example of a cooling facility according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a schematic configuration example of a thermometer (water column thermometer) 2A included in the cooling facility 100 illustrated in FIG. FIG. 3 is a graph showing test results of Examples and Comparative Examples. FIG. 4 is a schematic diagram illustrating a schematic configuration example of a conventional general cooling facility. FIG. 5 is a graph showing the spectral transmittance of water in a wavelength band of about 0.7 to 1.9 μm. FIG. 6 is a graph showing the relationship between water thickness and temperature measurement error. FIG. 7 is a graph showing an example of a result of evaluating a temperature measurement variation of a radiation thermometer in which a wavelength band of detected thermal radiation light is 0.85 μm or less. FIG. 8 is a graph showing an example of a result of evaluating a temperature measurement value variation of a radiation thermometer in which a wavelength band of detected thermal radiation light is set to 1.00 to 1.20 μm.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 (11-1n) ... Cooling device 2 ... Thermometer 2A (21-2n) ... Thermometer 3 ... Heat transfer coefficient calculation means 4 ... Winding temperature prediction means 5 ... Cooling control means 6 ... thickness meter 7 ... speedometer 8 ... draining device 9 ... thermometer 10 ... draining device 20 ... hot rolling mill 30 ... winding device 100 ..Cooling equipment S ... Hot rolled steel sheet

Claims (2)

It is located between the hot rolling mill and the winding device so that the winding temperature of the hot rolled steel sheet rolled by the hot rolling mill and conveyed toward the winding device becomes a predetermined temperature. In the cooling zone divided into a plurality of sections along the conveying direction of the steel sheet, a method of cooling the hot-rolled steel sheet with a predetermined cooling pattern consisting of a combination of water cooling or air cooling performed in each of the sections,
Measure the temperature of the hot-rolled steel sheet on the inlet side and outlet side of the section where the hot-rolled steel sheet is water-cooled in the cooling zone, and calculate the heat transfer coefficient during water cooling based on the measured temperature difference of the hot-rolled steel sheet And steps to
Measure the temperature of the hot-rolled steel sheet on the inlet side and outlet side of the section where the hot-rolled steel sheet is air-cooled in the cooling zone, and calculate the heat transfer coefficient during air-cooling based on the measured temperature difference of the hot-rolled steel sheet And steps to
Assuming a plurality of cooling patterns in the cooling zone, each of the plurality of cooling patterns is subjected to heat transfer calculation using the calculated heat transfer coefficient at the time of water cooling and air cooling. Predicting the coiling temperature of the steel sheet;
Selecting a cooling pattern in which the predicted coiling temperature of the hot-rolled steel sheet is a predetermined temperature among the plurality of assumed cooling patterns, and cooling the hot-rolled steel sheet with the selected cooling pattern. A method for cooling a hot-rolled steel sheet. It is arranged between the hot rolling mill and the winding device so that the winding temperature of the hot-rolled steel sheet rolled by the hot rolling mill and conveyed toward the winding device becomes a predetermined temperature, and is water-cooled. Or a facility for cooling a hot-rolled steel sheet with a predetermined cooling pattern comprising a combination of air cooling,
A plurality of cooling devices that are arranged along the conveying direction of the hot-rolled steel sheet, and capable of switching between water cooling and air cooling,
A plurality of thermometers arranged on the inlet side and outlet side of each cooling device, respectively, for measuring the temperature of the hot-rolled steel sheet;
Based on the temperature difference between the hot-rolled steel sheets measured by the thermometers respectively disposed on the inlet side and the outlet side of the cooling apparatus that water-cools the hot-rolled steel sheets among the plurality of cooling apparatuses, the heat transfer coefficient during water cooling is calculated. The heat transfer coefficient at the time of air cooling is calculated based on the temperature difference between the hot rolled steel sheets measured by the thermometers respectively arranged on the inlet side and the outlet side of the cooling apparatus for cooling the hot rolled steel sheet among the plurality of cooling apparatuses. Heat transfer coefficient calculating means for
Assuming a plurality of cooling patterns in which each of the cooling devices performs either water cooling or air cooling, using the heat transfer coefficients at the time of water cooling and air cooling calculated by the heat transfer coefficient calculation means for the plurality of cooling patterns. Winding temperature prediction means for predicting the winding temperature of the hot-rolled steel sheet for each cooling pattern by performing heat transfer calculation,
Among the plurality of assumed cooling patterns, a cooling pattern in which the coiling temperature of the hot-rolled steel sheet predicted by the coiling temperature predicting means becomes a predetermined temperature is selected, and the water cooling performed by each of the cooling devices according to the selected cooling pattern Or the cooling control means which switches air cooling, The cooling equipment of the hot-rolled steel plate characterized by the above-mentioned.

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