JP2023125249A - Correction device and correction method for slab temperature model, furnace temperature control device and furnace temperature control method for heating furnace and manufacturing method of steel plate - Google Patents

Abstract

To provide a correction device and a correction method, etc. for a slab temperature model capable of accurately predicting a temperature distribution including a lengthwise direction and a thickness direction in at least a width central part of a slab at extraction of a heating furnace.SOLUTION: A correction device 10 for a slab temperature model corrects, at a model correction part 14, a heat release amount Qskd at a heating furnace skid included in a thermal conduction equation composing a slab temperature model, to be used in an extraction temperature calculation part 12, so that a deviation e is below a threshold value ε, the deviation e between: a temperature difference Tcal_diff of a temperature Tcal_skid at a position in a lengthwise direction corresponding to a heating furnace skid of a slab S and a temperature Tcal at a position in a lengthwise direction corresponding to an interval between heating furnace skids, outputted from a crude temperature calculation part 13; and a temperature difference Tact_diff of a temperature Tact_skid at the position in the lengthwise direction corresponding to the heating furnace skid of the slab S and a temperature Tact at the position in the lengthwise direction corresponding to the interval between heating furnace skids, acquired at a crude temperature acquisition part 11.SELECTED DRAWING: Figure 2

Description

The present invention provides a slab temperature model correction device, correction method, and heating method used for predicting the slab temperature at the time of extraction from the heating furnace when a slab is heated in a heating furnace and the slab extracted from the heating furnace is roughly rolled. The present invention relates to a furnace temperature control device, a furnace temperature control method, and a steel plate manufacturing method.

At a steelworks, slabs cast during the steelmaking process are stored in a slab yard as cold pieces, or sent directly to the heating furnace of the hot rolling process as DHCR (Direct Hot Charge) hot pieces. and heated to a predetermined temperature (approximately 1200 degrees). Then, the slab extracted from the heating furnace is rough rolled in a rough rolling process, and then finished rolled in a finish rolling process to become a thin steel plate. After the steel plate is cooled through a runout cooling process, it is wound into a coil in a winding process.

Here, in a walking beam type heating furnace, the slab is supported by a plurality of (for example, eight) skid beams. There are two types of skid beams, a fixed type and a movable type, and the movable skid beam repeatedly ascends, moves, and descends to transport the slab to the extraction side. The slab has a rectangular parallelepiped shape with predetermined dimensions in the width direction, length direction, and thickness direction, and is placed on a skid beam in the heating furnace so that the width direction of the slab is the conveyance direction of the slab. , the slab is conveyed to the extraction side by the movable skid beam repeatedly rising, moving, and descending.

At this time, heat is removed from the slab being heated via the skid beam, resulting in a low temperature at the contact point of the skid beam, resulting in temperature fluctuations in the length direction of the slab called skid marks. The skid marks extend across the slab in the width direction of the slab and are formed at predetermined pitches along the length of the slab. The inside of the heating furnace is a high-temperature environment and scale on the surface of the slab is generated, so it is difficult to accurately measure the surface temperature of the slab with a radiation thermometer. It is not possible to directly measure the temperature of skid marks, and temperature fluctuations in skid marks can generally be confirmed by measuring the temperature at the exit side of the roughing mill.

When operating a heating furnace, it is required to control the extraction temperature within a specified range from the viewpoint of the material of the hot-rolled coil. In particular, it is essential to raise the temperature of the contact area of the skid beam (hereinafter referred to as skid part), which tends to be insufficiently heated, to a specified temperature before extraction. However, if the extraction temperature is increased excessively, the fuel consumption rate (GJ/ton-steel) will deteriorate, so it is necessary to perform the heating operation appropriately.

BACKGROUND ART Conventionally, methods for operating a heating furnace are known, for example, as shown in Patent Document 1 and Patent Document 2.
The rolling heating furnace combustion control method disclosed in Patent Document 1 uses a one-dimensional heat conduction difference equation in the thickness direction of the slab between the skids, and a two-dimensional heat conduction difference equation in the longitudinal direction of the slab that is simplified by introducing coefficients for the skid portion. By solving the heat conduction difference equation (slab thickness direction x slab longitudinal direction), the future temperature distribution between the skids and the skid part of the slab in the furnace is predicted, and the set furnace temperature is calculated by evaluating the baking quality of the slab. It is something to do.

According to the rolling heating furnace combustion control method disclosed in Patent Document 1, the temperature distribution between skids and in the skid portion can be predicted for all slabs in the furnace with a small amount of calculation.

In addition, the slab temperature prediction method in a continuous heating furnace shown in Patent Document 2 is based on the "slab temperature measurement value at the extraction port" of the continuous heating furnace and the "slab extraction temperature calculated from the furnace temperature, furnace time, etc." The error is measured for each slab extraction, and the overall heat absorption rate of multiple zones in the furnace is sequentially estimated online by sequentially performing least squares estimation on the influence coefficient obtained by separately calculating the slab temperature. By updating the overall heat absorption rate of each zone based on the estimated value, the temperature prediction accuracy of the furnace slab is improved.

Japanese Patent Application Publication No. 7-258752 Japanese Patent Application Publication No. 6-264153

However, the rolling heating furnace combustion control method shown in Patent Document 1 and the slab temperature prediction method in a continuous heating furnace shown in Patent Document 2 have the following problems.
That is, in the case of the rolling heating furnace combustion control method shown in Patent Document 1, the one-dimensional heat conduction difference equation in the thickness direction of the slab is simplified between the skids, and the heat conduction in the longitudinal direction of the slab is simplified by introducing coefficients for the skid part. By solving the two-dimensional heat conduction difference equation, the future temperature distribution between the skids and the skid part of the furnace slab is predicted. It has not been verified whether or not it is truly correct. Therefore, the actual temperature distribution between the skids and the skid part of the slab in the furnace may deviate from the predicted temperature distribution between the skids and the skid part of the slab in the furnace. It is not possible to ensure the accuracy of the predicted value of the temperature at least in the width center of the slab during extraction in the furnace, including the length and thickness directions.

In addition, in the case of the slab temperature prediction method in a continuous heating furnace shown in Patent Document 2, the slab temperature measurement value at the extraction port of the continuous heating furnace and the slab extraction temperature calculated from the furnace temperature, furnace time, etc. ” error is measured every time a slab is extracted, but it is generally difficult to measure the temperature immediately after extraction from the heating furnace due to the influence of scale on the slab surface. "slab temperature measurements" cannot be obtained. For this reason, it is not possible to ensure the accuracy of the predicted value of the temperature including the length direction and thickness direction at least in the width center portion of the slab at the time of extraction in the heating furnace using the slab temperature model.

Therefore, the present invention has been made to solve these conventional problems, and its purpose is to modify the slab temperature model so that the temperature at least in the longitudinal direction of the slab during extraction in the heating furnace is To provide a slab temperature model correction device and correction method, a heating furnace furnace temperature control device, a furnace temperature control method, and a steel plate manufacturing method, which can accurately predict the temperature distribution including the thickness direction. be.

In order to solve the above problems, a slab temperature model correction device according to one aspect of the present invention heats a slab in a heating furnace, and when rough rolling the slab extracted from the heating furnace in a rough rolling mill. , a slab temperature model correction device used for predicting the temperature distribution including the length direction and thickness direction in at least the width center portion of the slab during extraction in the heating furnace, the device comprising: a rough temperature acquisition unit that acquires the temperature distribution in the longitudinal direction at the width center portion of the back surface of the slab after rough rolling measured by an installed rough temperature measuring meter; Using the input temperature as an initial value, and using the operating conditions while the slab is in the heating furnace, calculate the temperature distribution including the length direction and thickness direction at least at the width center of the slab at the time of extraction from the heating furnace. , an extraction temperature calculation unit that calculates and outputs the calculation based on a heat conduction equation constituting the slab temperature model; and a length of the slab at least in the width center portion at the time of extraction of the heating furnace, which is output from the extraction temperature calculation unit. Using the temperature distribution including the width direction and the thickness direction as an initial value, and using the operating conditions when rough rolling the slab extracted from the heating furnace, the length of the slab after rough rolling at least at the center width A rough-out side temperature calculation unit that calculates and outputs the temperature distribution including the width direction and the thickness direction based on a heat conduction equation, and the width center of the back side of the slab output from the rough-out side temperature calculation unit. The temperature at the longitudinal position corresponding to the heating furnace skid part in the heating furnace skid part, and the temperature at the longitudinal position corresponding to the heating furnace skid part at the width center part of the back surface of the slab, which is output from the raw side temperature calculation part. temperature, the temperature at a longitudinal position corresponding to the heating furnace skid part at the width center of the back surface of the slab, acquired by the rough temperature acquisition unit, and the temperature at the longitudinal position corresponding to the heating furnace skid part, acquired by the rough temperature acquisition unit. , used in the extraction temperature calculation unit so that the magnitude of the deviation of the temperature difference between the width center part of the back surface of the slab and the temperature at the longitudinal position corresponding between the heating furnace skids is less than a threshold value, The present invention further comprises a model correction section for correcting the amount of heat removed in the heating furnace skid section included in the heat conduction equation constituting the slab temperature model.

Further, a furnace temperature control device for a heating furnace according to another aspect of the present invention uses a slab temperature model corrected by the above-mentioned slab temperature model correction device to control the temperature at least in the width center portion of the slab during extraction of the heating furnace. A slab temperature prediction unit that predicts temperature distribution including the length direction and thickness direction, and a length corresponding to the heating furnace skid portion at the width center of the slab at the time of extraction of the heating furnace predicted by the slab temperature prediction unit The present invention further comprises a furnace temperature control section that controls the furnace temperature in the heating furnace so that the temperature in the thickness direction at the direction position exceeds the minimum extraction temperature.

Further, in a method for correcting a slab temperature model according to another aspect of the present invention, a slab is heated in a heating furnace, and the slab extracted from the heating furnace is roughly rolled in a rough rolling mill. A method for correcting a slab temperature model used for predicting temperature distribution including length direction and thickness direction in at least the center width of the slab during extraction, the method comprising: a rough temperature model installed at the exit side of the rough rolling mill; a rough temperature acquisition step of acquiring the temperature distribution in the length direction at the width center of the back surface of the slab after rough rolling measured by a measuring meter; and setting the charging temperature of the slab charged to the heating furnace to an initial value. Using the operating conditions of the slab while it is in the heating furnace, the temperature distribution including the length direction and thickness direction at least in the width center of the slab at the time of extraction in the heating furnace is determined by the slab temperature model. an extraction temperature calculation step that calculates and outputs the extraction temperature based on a heat conduction equation that constitutes the heating furnace; Using the operating conditions when rough rolling the slab extracted from the heating furnace, with the temperature distribution including the direction as an initial value, the length direction and thickness of the slab after rough rolling at least at the center width thereof. a rough output side temperature calculation step of calculating and outputting the temperature distribution including the direction based on a heat conduction equation; The temperature difference between the temperature at the longitudinal position corresponding to the part and the temperature at the longitudinal position corresponding to between the heating furnace skids at the width center part of the back surface of the slab, which is output in the raw side temperature calculation step. , the temperature at the longitudinal position corresponding to the heating furnace skid part in the width center of the back surface of the slab, obtained in the rough temperature obtaining step, and the back surface of the slab, obtained in the rough temperature obtaining step. The slab temperature model used in the extraction temperature calculation step is adjusted such that the temperature difference between the temperature at the longitudinal position corresponding to between the heating furnace skids at the width center of the slab is less than a threshold value. The gist of the present invention is to include a model modification step of modifying the amount of heat removed from the heating furnace skid part included in the heat conduction equation.

Further, a furnace temperature control method for a heating furnace according to another aspect of the present invention uses a slab temperature model corrected by the above-described slab temperature model correction method to A slab temperature prediction step that predicts the temperature distribution including the length direction and the thickness direction, and a length corresponding to the heating furnace skid portion at the width center of the slab at the time of extraction of the heating furnace predicted in the slab temperature prediction step. The method further comprises a furnace temperature control step of controlling the furnace temperature in the heating furnace so that the temperature in the thickness direction at the direction position exceeds the minimum extraction temperature.

Moreover, the gist of the method for manufacturing a steel plate according to another aspect of the present invention includes a furnace temperature control step of controlling the furnace temperature in the heating furnace by the above-mentioned furnace temperature control method for the heating furnace.

According to the slab temperature model correction device, correction method, heating furnace furnace temperature control device, furnace temperature control method, and steel plate manufacturing method according to the present invention, by correcting the slab temperature model, A slab temperature model correction device, correction method, furnace temperature control device for a heating furnace, and furnace temperature control method that can accurately predict the temperature distribution including the length direction and thickness direction in at least the central width of a slab. , and a method for manufacturing a steel plate.

1 is a schematic configuration diagram of a hot rolling line to which a slab temperature model correction device and a heating furnace furnace temperature control device according to an embodiment of the present invention are applied. FIG. 2 is a block diagram showing the internal configuration of the slab temperature model correction device in FIG. 1. FIG. FIG. 2 is a block diagram showing the internal configuration of the furnace temperature control device of the heating furnace in FIG. 1. FIG. It is a graph which shows an example of the temperature distribution of the length direction in the width center part of the back surface of the slab after rough rolling measured by the rough temperature meter. It is a graph which shows an example of the temperature distribution in the length direction in the width center part of the back surface of the slab after rough rolling, which is output from the rough rolling side temperature calculation unit. It is a flowchart for explaining the flow of processing in the slab temperature model correction device. 7 is a flowchart showing details of the process flow in step S4 (model modification step) in the flowchart shown in FIG. 6. FIG. It is a flowchart for explaining the flow of processing in the furnace temperature control device of the heating furnace. It is a figure for explaining the shape of a slab. 2 is a graph showing the temperature distribution in the vicinity of the longitudinal position corresponding to the heating furnace skid portion at the width center portion of the back surface of the slab after rough rolling in an example. In the example, the heating furnace skid portion at the width center of the back side of the slab after rough rolling, which is output from the rough-rolling side temperature calculation unit before and after the slab temperature model (correction coefficient η) is corrected. It is a graph showing a comparison of temperature distributions in the vicinity of corresponding longitudinal positions.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments shown below illustrate devices and methods for embodying the technical idea of the present invention. It is not limited to the embodiments described below. Furthermore, the drawings are schematic. Therefore, it should be noted that the relationships, ratios, etc. between thickness and planar dimensions are different from those in reality, and the drawings also include portions where the relationships and ratios of dimensions are different.

FIG. 1 shows a schematic configuration of a hot rolling line to which a slab temperature model correction device and a heating furnace furnace temperature control device according to an embodiment of the present invention are applied.
At a steelworks, the slab S cast during the steelmaking process is temporarily stored in a slab yard as a cold piece, or directly delivered as a hot piece of DHCR (Direct Hot Charge), as shown in Figure 1. Then, it is charged into a heating furnace 2 in a hot rolling line 1 and heated to a predetermined temperature (approximately 1200 degrees). Then, the slab S transported through the heating furnace 2 and extracted is rough rolled by a plurality of (n units in this embodiment) rough rolling mills 4 ₁ to 4 _n , and then finished by a finishing mill (not shown). It is rolled into a thin steel plate. After this steel plate is cooled in the cooling equipment 5, it is wound up into a coil shape by the winding device 6.

The heating furnace 2 includes a plurality of (n in this embodiment) combustion control zones 2 ₁ to 2 _n extending from the upstream side to the downstream side in the conveyance direction of the slab S. A combustion burner 3 for heating the slab S is installed in each combustion control zone 2 ₁ to 2 _n . The combustion burners 3 of each combustion control zone 2 ₁ to 2 _n are connected to a fuel flow rate control section 23, and each fuel flow rate control section 23 is connected to a furnace temperature control device 20 of the heating furnace.

Here, the heating furnace 2 is a walking beam type heating furnace, and the slab S is supported by a plurality of (for example, eight) skid beams. There are two types of skid beams, a fixed type and a movable type, and the slab S is conveyed to the extraction side by repeating rising, moving, and lowering of the movable skid beam. As shown in FIG. 9, the slab S has a width w, a length l, and a thickness t in the length direction indicated by an arrow x, the width direction indicated by an arrow y, and the thickness direction indicated by an arrow z. It has a rectangular parallelepiped shape. Inside the heating furnace 2, the slab S is placed so that its front surface Sa is on the upper side and its back surface Sb is on the lower side, and the width direction of the slab S is the conveying direction of the slab S, as shown in FIG. The slab S is placed on a skid beam, and the movable skid beam repeats raising, moving, and lowering, thereby conveying the slab S to the extraction side.

When the slab S is conveyed through the heating furnace 2, heat is removed from the slab S through the skid beam, so that the contact point of the skid beam becomes low temperature, and the lengthwise direction of the slab S, called a skid mark, is Temperature fluctuations occur. The skid marks extend across the slab in the width direction of the slab S and are formed at predetermined pitches along the length of the slab.
In operation in the heating furnace 2, it is required to control the extraction temperature of the slab S within a specified range from the viewpoint of the material of the hot-rolled coil. In particular, it is essential to raise the temperature of the contact point of the skid beam (hereinafter referred to as the heating furnace skid section), which tends to be insufficiently heated, to a specified temperature for extraction.

Therefore, in this embodiment, the charging temperature of the slab S charged into the heating furnace 2 is measured by the charging temperature meter 7 that measures the temperature of the slab S when charging the heating furnace 2, and the charging temperature of the slab S charged into the heating furnace 2 is measured. In the furnace temperature control device 20 of the furnace, the charging temperature of the slab S charged into the heating furnace 2 is set as an initial value, and the operating conditions (operating conditions include the furnace time, The temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 is calculated using the heat conduction equation that constitutes the slab temperature model. The thickness at the heating skid part of the slab S at the time of extraction in the heating furnace 2, obtained from the calculated temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2. Each fuel flow control unit 23 is controlled to control the fuel flow rate to each combustion burner 3 so that the temperature in the horizontal direction exceeds the minimum extraction temperature (for example, 1200° C.), and the furnace temperature in the heating furnace 2 is controlled. I try to do that.

Here, the heat conduction equations constituting the slab temperature model are the same as equations (1) to (7) used in the extraction temperature calculating section 12, which will be described later.
However, in the furnace temperature control device 20 of the heating furnace, the temperature distribution in the length direction and thickness direction of the central width of the slab S at the time of extraction in the heating furnace 2 is calculated based on the heat conduction equation that constitutes the slab temperature model. The predicted value deviates from the actual value, and there is a problem that the temperature distribution in the length direction and thickness direction of the width center portion of the slab S at the time of extraction in the heating furnace 2 cannot be accurately predicted.

Therefore, in this embodiment, as shown in FIG. By modifying the slab temperature model, it is possible to accurately predict the temperature distribution in the longitudinal and thickness directions at the central width of the slab during extraction in the heating furnace.

As shown in FIG. 1, this slab temperature model correction device 10 is connected to a furnace temperature control device 20 of a heating furnace. The slab temperature model correction device 10 also includes a charging temperature measuring meter 7 installed at the entrance side of the heating furnace 2 and measuring the charging temperature of the front surface Sa and the back surface Sb of the slab S charged into the heating furnace 2. and a rough temperature measuring meter 8 which is installed on the exit side of the rough rolling mills 4 ₁ to 4 _n and measures the temperature distribution in the length direction at the width center of the back surface Sb of the slab S after rough rolling. There is. The charging temperature meter 7 and the crude temperature meter 8 are constituted by radiation thermometers.

The internal configuration of the slab temperature model correction device 10 is shown in FIG. It includes an extraction temperature calculation section 12, a crude extraction temperature calculation section 13, a model correction section 14, and an output section 15.

The slab temperature model correction device 10 is a computer system having an arithmetic processing function, and the rough temperature acquisition unit 11 (step S1 described later) performs extraction temperature calculation based on instructions from various dedicated computer programs stored in advance in the hardware. The functions of the section 12 (step S2), the raw temperature calculation section 13 (step S3), the model correction section 14 (step S4), and the output section 15 (step S5) are executed on software.

The rough temperature acquisition unit 11 of the correction device 10 calculates the length at the width center of the back surface Sb of the slab S after rough rolling, which is measured by the rough temperature measuring meter 8 installed on the exit side of the rough rolling mills 4 ₁ to 4 _n . Obtain the temperature distribution in the direction. The rough temperature measuring meter 8 periodically measures the temperature of the back surface Sb of the slab S on the outlet side of the rough rolling mills 4 ₁ to 4 _n , and the results are recorded in a recording section (not shown). Get the result.

An example of the temperature distribution in the length direction at the width center of the back surface Sb of the slab S after rough rolling measured by the rough temperature measuring meter 8 is shown in FIG.
In addition, the extraction temperature calculation unit 12 sets the charging temperature of the slab S to be charged into the heating furnace 2 as an initial value, and calculates operating conditions for the slab S while it is in the heating furnace (operating conditions include time in the furnace, temperature, skid contact temperature, etc.), the temperature distribution in the length direction and thickness direction at the center of the width of the slab S at the time of extraction in the heating furnace 2 is expressed in the heat conduction equation that constitutes the slab temperature model. Calculate and output based on

The charging temperature of the front surface Sa and back surface Sb of the slab S when charging into the heating furnace 2 is measured by the charging temperature measuring meter 7, and the charging temperature of the front surface Sa and back surface of the slab S when charging into the heating furnace 2 is measured. The Sb charging temperature is input to the extraction temperature calculation section 12. Then, the extraction temperature calculation unit 12 uses the charging temperature of the slab S as an initial value and the width center of the slab S at the time of extraction in the heating furnace 2, using the above-mentioned operating conditions while the slab S is in the heating furnace. The temperature distribution in the length direction and thickness direction in the section is calculated and output based on the heat conduction equation expressed by the following equations (1) to (7) that constitute the slab temperature model.

Here, ρ: specific gravity [kg/ ³ ], C: specific heat [kcal/(kg・K)], λ: thermal conductivity [kcal/(m・hr・K)], θ: temperature [℃], x : Length direction coordinate [m], y: Thickness direction coordinate [m].

In calculating the temperature distribution using the heat conduction equation of equation (1), the slab temperature is calculated in time increments by setting the boundary conditions on the front surface Sa and the back surface Sb of the slab S by differentiating them in the time and space directions. Calculates up to the time of extraction each time and outputs it. Thereby, temperature fluctuations in the length direction of the slab S caused by the heating furnace skid portion can be obtained.
The boundary conditions set in this heat conduction equation include the radiant heat input from the heating furnace 2 to the slab S and the amount of heat removed at the heating furnace skid portion.
The radiant heat input from the surface (upper surface) Sa is expressed by the following equations (2) and (3).

Further, the radiant heat input from the back surface (lower surface) Sb is expressed by the following equations (4) and (5).

Furthermore, the amount of heat removed at the heating furnace skid portion is expressed by the following equations (6) and (7).

Here, to explain the variables in the boundary conditions, q _ui and q _Li are the upper surface heat load [kcal/(m ²・hr], the lower surface heat load [kcal/(m ²・hr]), Φ _CGUi and Φ _CGLi are the top surface overall heat absorption rate [-], the bottom surface overall heat absorption rate [-], θ _gU and Φ _gL are the top furnace temperature [℃], and θ _si is the slab temperature of the top or bottom surface before one calculation step. [°C], V _i is the shadow factor (correction due to skid shadow), Q _skd is the amount of heat removed at the skid part of the heating furnace (skid heat load) [kcal/(m ² · hr]), α _skd is the skid contact heat transfer coefficient [kcal/(m ² ·hr·K], θ is the slab temperature [°C], and θ _w is the water temperature in the heating furnace skid part [°C].

The information of equations (1) to (7) representing the heat conduction equation is recorded in a recording section (not shown), and the extraction temperature calculation section 12 reads the information of equations (1) to (7) representing the heat conduction equation from the recording section. 7) Obtain expression information.

In addition, the crude extraction side temperature calculation unit 13 uses the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 as an initial value, which is output from the extraction temperature calculation unit 12. Using the operating conditions (operating conditions include rolling load, rolling speed, cooling, etc.) when rough rolling the slab S extracted from the heating furnace 2, the width center of the slab S after rough rolling is Temperature distribution in the length direction and thickness direction is calculated based on the heat conduction equation and output.
The heat conduction equation is expressed by the following equation (8).

Here, ρ: specific gravity [kg/ ³ ], C: specific heat [kcal/(kg・K)], λ: thermal conductivity [kcal/(m・hr・K)], θ: temperature [℃], x : Length direction coordinate [m], y: Thickness direction coordinate [m].
The boundary conditions set in this heat conduction equation are set as follows according to each of the air-cooled section, water-cooled section, and rolling section.
The heat load q _air [kcal/(m ² ·hr]) in the air-cooled section is expressed by the following equation (9).

Here, ε: emissivity [-], θ _S : surface temperature of slab S [°C], θ _air : atmospheric temperature [°C].
Further, the heat load q _water [kcal/(m ² ·hr]) in the water cooling section is expressed by the following equation (10).

Here, α _w : water cooling heat transfer coefficient [kcal/(m ² ·hr·K)], θ _S : surface temperature of slab S [°C], θ _Water : water temperature [°C].
In addition, regarding the rolling section, three types of heat balance are considered: process heat generation, roll contact heat removal, and friction heat generation.
Regarding the processing heat generation ΔQ [kcal/(m ³ ·hr]), the following equation (11) is used.

Here, P _m : rolling pressure [kgf/mm ² ], h _in : inlet side plate thickness [mm], h _out : outlet side plate thickness [mm], A: heat work equivalent 427 [kgfm/kcal], τ: The rolling contact time is [hr].
Further, the roll contact heat removal q _r [kcal/(m ² ·hr)] is given by the following equation (12).

Here, λ _S : Thermal conductivity of slab S [kcal/(m・hr・K)], α _rS : Temperature diffusion coefficient of slab S [m ² /hr], τ : Contact temperature of slab S [°C] , T _m : Equilibrium temperature [°C]. The equilibrium temperature T _m is calculated by the following equation (13).

Here, α _rS = λ _S /(ρ _S・C _S ), α _rR = λ _R /(ρ _R・C _R ), and λ _S : Thermal conductivity of the slab S [kcal/(m・hr・K)], ρ _S : Specific gravity of slab S [kg/m ³ ], C _S : Specific heat of slab S [kcal/(kg・K)], λ _R : Thermal conductivity of roll [kcal/(m・hr・K)], ρ _R : Specific gravity of roll [kg/m ³ ], C _R : Specific heat of roll [kcal/(kg・K)], T _R0 : Roll temperature [°C], α _rR : Temperature diffusion of roll The rate is [m ² /hr].
Further, frictional heat generation q _μ [kcal/(m ² ·hr)] is given by the following equation (14).

Here, μ: coefficient of friction [-], P _m : rolling pressure [kgf/mm ² ], V _RM : relative speed between roll and slab S [m/hr], A: work equivalent of heat 427 [kgfm/kcal ].
The rolling pressure P _m is expressed by the following equation (15).

Here, P: rolling load [tonf], R': flat roll diameter [mm], h _in : inlet side plate thickness [mm], h _out : outlet side plate thickness [mm], B: plate width of slab S [mm] ].
Further, the relative speed _VRM is expressed by the following equation (16).

Here, V _R is the roll speed [m/hr], f is the forward rate [-], and b is the reverse rate [-], and the reverse rate b is expressed by the following equation (17).

FIG. 5 shows an example of the temperature distribution in the length direction at the width center of the back surface of the rough-rolled slab S, which is output from the rough-rolling side temperature calculation unit 13.
In addition, the model correction unit 14 calculates the temperature T cal_skid at a longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, which is output from the rough side temperature calculation unit 13, and the rough side temperature T _{cal_skid} . The temperature difference T _{cal_diff = T cal - T cal_skid between the} temperature T _cal at the longitudinal position corresponding to between the heating furnace skids at the width center portion of the back surface Sb of the slab S, which is output from the temperature calculation unit 13, and the rough temperature Temperature _{Tact_skid} at a longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the acquisition unit 11, and the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. The magnitude of the deviation e=T cal_diff - T act_diff of the temperature difference T _{act_diff} = T _act - T _{act_skid} from the temperature T _{act at} the longitudinal position corresponding to between the heating furnace skids at the center _width of is the threshold value ε(1 ℃), the amount of heat removed from the heating furnace skid part included in the heat conduction equation expressed by equations (1) to (7) that constitute the slab temperature model used in the extraction temperature calculation unit 12. Correct Q _skd .

Here, there are a plurality of temperatures at the longitudinal position corresponding to the heating furnace skid part in the width center portion of the back surface Sb of the slab S, which are output from the roughing side temperature calculating section 13, and the roughing side temperature calculating section There are also a plurality of temperatures outputted from 13 at longitudinal positions corresponding to between the heating furnace skids at the width center portion of the back surface Sb of the slab S. Here, the model correction unit 14 selects a specific temperature among the plurality of temperatures at the longitudinal position corresponding to the heating furnace skid part in the width center of the back surface Sb of the slab S, which is output from the raw side temperature calculation unit 13. The temperature T _{cal_skid} at the longitudinal position corresponding to the heating furnace skid portion, the above-mentioned specific heating furnace skid portion at the width center portion of the back surface Sb of the slab S, and this identification, which is output from the raw side temperature calculation unit 13. The temperature difference T cal_diff = T cal - T _{cal_skid} between the temperature T _cal at the longitudinal position corresponding to the heating furnace skid part adjacent to the heating _{furnace skid part} is calculated.

In addition, there are multiple temperatures at the longitudinal position corresponding to the heating furnace skid part in the width center of the back surface Sb of the slab S, which are acquired by the rough temperature acquisition unit 11. , there are also a plurality of temperatures at longitudinal positions corresponding to between the heating furnace skids at the width center portion of the back surface Sb of the slab S. Here, the model correction unit 14 selects the above-mentioned specific temperature among the plurality of temperatures at the longitudinal position corresponding to the heating furnace skid part in the width center portion of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. The temperature T _{act_skid} at the longitudinal position corresponding to the heating furnace skid portion, the above-mentioned specific heating furnace skid portion at the width center of the back surface Sb of the slab S, and this specific heating acquired by the rough temperature acquisition unit 11. A temperature difference T _{act_diff = T act - T act_skid} between the temperature T _act at a corresponding longitudinal position between the furnace skid part and the adjacent heating furnace _{skid part} is calculated.

Then, the model correction unit 14 determines that the magnitude of the deviation e=T cal_diff -T act_diff between the calculated temperature difference T _{cal_diff = T cal} -T _{cal_skid} and the temperature difference T _{act_diff} =T _act -T _{act_skid} is a threshold value ε(1 ℃), the amount of heat removed from the heating furnace skid part included in the heat conduction equation expressed by equations (1) to (7) that constitute the slab temperature model used in the extraction temperature calculation unit 12. Correct Q _skd .
As mentioned above, the amount of heat removed in the heating furnace skid part is expressed by equation (7), but it is possible to find an appropriate η in the following equation (18) by introducing the correction coefficient η into equation (7). This is an appropriate correction for the amount of heat removed _Qskd at the heating furnace skid section.

A method for determining an appropriate η in equation (18) will be described later based on a flowchart showing details of the process flow in step S4 (model modification step) shown in FIG.
Then, the output unit 15 of the correction device 10 outputs heat conduction equations (Equations ( ₁ ) to (7), (Equations (1) to (7), The information in equation 18) is output to the slab temperature prediction unit 21 of the furnace temperature control device 20 of the heating furnace.

Further, the furnace temperature control device 20 for the heating furnace includes a slab temperature prediction section 21 and a furnace temperature control section 22, as shown in FIG. The furnace temperature control device 20 is a computer system having an arithmetic processing function, and operates a slab temperature prediction section 21 (step S11 described later) and a furnace temperature control section according to instructions from various dedicated computer programs stored in advance in hardware. 22 (step S12) are executed on software.

The slab temperature prediction unit 21 acquires information on the slab temperature model corrected by the slab temperature model correction device 10 from the output unit 15 of the correction device 10, and uses that information to estimate the value of the slab S at the time of extraction in the heating furnace 2. Predict the temperature distribution in the length direction and thickness direction at the width center.

Specifically, the slab temperature prediction unit 21 uses the charging temperatures of the front surface Sa and back surface Sb of the slab S at the time of charging the heating furnace 2 measured by the charging temperature measuring meter 7 as initial values, and calculates the charging temperature of the slab S. Using the above-mentioned operating conditions while the heating furnace is in use, the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 is obtained from the output unit 15 of the correction device 10. The calculated value is calculated based on the heat conduction equations (Equations (1) to (7), and Equation (18)) constituting the revised slab temperature model, and this calculated value is used as the predicted value.

The furnace temperature control unit 22 also controls the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S at the time of extraction of the heating furnace 2, which is predicted by the slab temperature prediction unit 21. The furnace temperature in the heating furnace 2 is controlled so that the temperature exceeds the minimum extraction temperature.

Specifically, the furnace temperature control unit 22 controls the thickness at the longitudinal position corresponding to the heating furnace skid portion in the width center of the slab S at the time of extraction of the heating furnace 2, which is predicted by the slab temperature prediction unit 21. Each fuel flow control unit 23 is controlled to control the fuel flow rate to each combustion burner 3 so that the temperature in the horizontal direction reaches a target temperature exceeding the minimum extraction temperature (for example, 1200°C), and the fuel flow rate in the heating furnace 2 is controlled. Control the furnace temperature.

As a result, when the slab S is extracted from the heating furnace 2, the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S exceeds the minimum extraction temperature, which tends to result in insufficient temperature rise. This means that the contact point of the skid beam can be raised to a specified temperature for extraction.

As described above, according to the slab temperature model correction device 10 according to the present embodiment, the rough temperature acquisition unit 11 calculates the rough temperature measured by the rough temperature measuring meters 8 installed on the outlet sides of the roughing mills 4 ₁ to 4 _n . The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S after rolling is acquired, and the extraction temperature calculation unit 12 calculates the temperature distribution of the slab S by using the charging temperature of the slab S charged into the heating furnace 2 as an initial value. Using the operating conditions of S during heating furnace 2, the temperature distribution in the length direction and thickness direction at the width center of slab S at the time of extraction in heating furnace 2 is calculated using the heat conduction equation ( Calculate based on equations (1) to (7) and output. Then, in the crude extraction side temperature calculation unit 13, the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2, which is output from the extraction temperature calculation unit 12, is set as an initial value. Using the operating conditions when rough rolling the slab S extracted from the heating furnace 2, the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling is calculated using the heat conduction equation ((8 ) to (17)) and output. Then, in the model correction unit 14, the temperature T cal_skid at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S, which is output from the rough side temperature calculation unit 13, and the rough side temperature T _{cal_skid} The temperature difference T _{cal_diff = T cal - T cal_skid between the} temperature T _cal at the longitudinal position corresponding to between the heating furnace skids at the width center portion of the back surface Sb of the slab S, which is output from the temperature calculation unit 13, and the rough temperature Temperature _{Tact_skid} at a longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the acquisition unit 11, and the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. The magnitude of the deviation e=T cal_diff - T act_diff of the temperature difference T _{act_diff} = T _act - T _{act_skid} from the temperature T _{act at} the longitudinal position corresponding to between the heating furnace skids at the center _width of is the threshold value ε(1 ℃), the amount of heat removed from the heating furnace skid part included in the heat conduction equation expressed by equations (1) to (7) that constitute the slab temperature model used in the extraction temperature calculation unit 12. Correct Q _skd (formula (18)).

As a result, when predicting the temperature distribution in the length direction and thickness direction in the width center of the slab S at the time of extraction in the heating furnace 2 using the slab temperature model, by correcting the slab temperature model, the heating furnace It is possible to accurately predict the temperature distribution in the length direction and thickness direction at the width center portion of the slab during extraction in step 2.

In addition, through the correction of this slab temperature model, the model correction unit 14 uses the information output from the rough delivery side temperature calculation unit 13 and the rough temperature measurement meters installed on the exit sides of the rough rolling mills 4 ₁ to 4 _n . Since the slab temperature model is corrected based on the information acquired by the rough temperature acquisition unit 11 measured in step 8, the radiation thermometer installed immediately after the exit side of the heating furnace 2 measures the temperature immediately after the extraction of the heating furnace 2. There is no need to measure the temperature of the slab S. Immediately after extraction from the heating furnace 2, temperature measurement itself is difficult due to the influence of scale on the surface of the slab S, but according to the repair device 10 according to the present embodiment, there is no such fear.

According to the furnace temperature control device 20 of the heating furnace according to the present embodiment, the slab temperature prediction unit 21 uses the slab temperature model corrected by the slab temperature model correction device 10 to The temperature distribution in the length direction and the thickness direction at the width center of the slab S is predicted, and the width center of the slab S at the time of extraction of the heating furnace 2 predicted by the slab temperature prediction unit 21 is calculated in the furnace temperature control unit 22. The furnace temperature in the heating furnace 2 is controlled so that the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid exceeds the minimum extraction temperature.

As a result, when the slab S is extracted from the heating furnace 2, the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S exceeds the minimum extraction temperature, which tends to result in insufficient temperature rise. It is possible to raise the contact point of the skid beam to a specified temperature and extract it, preventing material defects in the hot-rolled coil due to insufficient temperature rise of the skid part of the heating furnace, and reducing the heating unit consumption due to overheating operation. can.

Next, a method for correcting a slab temperature model according to an embodiment of the present invention will be explained by a flowchart for explaining the process flow in the slab temperature model correction apparatus shown in FIG. 6, and a diagram shown in FIG. This will be explained with reference to a flowchart showing the flow of processing in step S4 (model modification step) in the flowchart shown in FIG.

First, in step S1, the rough temperature acquisition unit 11 of the correction device 10 measures the back surface Sb of the slab S after rough rolling, which is measured by the rough temperature measuring meter 8 installed on the outlet side of the rough rolling mills 4 ₁ to 4 _n . Acquire the temperature distribution in the length direction at the center width (rough temperature acquisition step).

Next, in step S2, the extraction temperature calculation unit 12 of the correction device 10 sets the charging temperature of the slab S charged into the heating furnace 2 as an initial value, and calculates the operating conditions (operating conditions) while the slab S is in the heating furnace. The temperature distribution in the length direction and the thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 is calculated using Calculate and output based on the heat conduction equation that constitutes the model (extraction temperature calculation step).

The charging temperature of the front surface Sa and back surface Sb of the slab S when charging into the heating furnace 2 is measured by the charging temperature measuring meter 7, and the charging temperature of the front surface Sa and back surface of the slab S when charging into the heating furnace 2 is measured. The Sb charging temperature is input to the extraction temperature calculation section 12. Then, the extraction temperature calculation unit 12 uses the charging temperature of the slab S as an initial value and the width center of the slab S at the time of extraction in the heating furnace 2, using the above-mentioned operating conditions while the slab S is in the heating furnace. The temperature distribution in the length direction and thickness direction in the section is calculated based on the heat conduction equations expressed by the above-mentioned equations (1) to (7) that constitute the slab temperature model, and is output.

In calculating the temperature distribution using the heat conduction equation of equation (1), the slab temperature is calculated in time increments by setting the boundary conditions on the front surface Sa and the back surface Sb of the slab S by differentiating them in the time and space directions. Calculates up to the time of extraction each time and outputs it. Thereby, temperature fluctuations in the length direction of the slab S caused by the heating furnace skid portion can be obtained.
The boundary conditions set in this heat conduction equation include the radiant heat input from the heating furnace 2 to the slab S and the amount of heat removed at the heating furnace skid portion.
The radiant heat input from the surface (upper surface) Sa is expressed by equations (2) and (3) as described above.
In addition, the radiant heat input from the back surface (lower surface) Sb is expressed by equations (4) and (5) as described above.
Furthermore, the amount of heat removed in the heating furnace skid portion is expressed by the above-mentioned equations (6) and (7).

Next, in step S3, the raw temperature calculation unit 13 of the correction device 10 calculates the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2, which is output in step S2. As an initial value, using the operating conditions (operating conditions include rolling load, rolling speed, cooling, etc.) when rough rolling the slab S extracted from the heating furnace 2, the slab S after rough rolling is The temperature distribution in the length direction and the thickness direction at the center width of is calculated based on the heat conduction equation and output (raw side temperature calculation step).
The heat conduction equation is expressed by equation (8) as described above.
Further, the boundary conditions set in the heat conduction equation of equation (8) are set according to each of the air-cooled section, water-cooled section, and rolling section, as described above.
The heat load q _air [kcal/(m ² ·hr]) in the air-cooled section is expressed by the above-mentioned equation (9).

Further, the heat load q _water [kcal/(m ² ·hr]) in the water-cooled section is expressed by the above-mentioned equation (10).
In addition, regarding the rolling section, three types of heat balance are considered: process heat generation, roll contact heat removal, and friction heat generation.
Regarding the processing heat generation ΔQ [kcal/(m ³ ·hr]), the above-mentioned equation (11) is used.
Further, the roll contact heat removal q _r [kcal/(m ² ·hr)] is given by the above-mentioned equation (12).
Equilibrium temperature [°C]. The equilibrium temperature T _m is calculated by the above-mentioned equation (13).
Furthermore, the frictional heat generation q _μ [kcal/(m ² ·hr)] is given by the above-mentioned equation (14). The rolling pressure P _m is expressed by the above-mentioned equation (15). Further, the relative speed _VRM is expressed by the above-mentioned equation (16). Further, the backward movement rate b is expressed by the above-mentioned equation (17).

Next, in step S4, the model correction unit 14 calculates the temperature T cal_skid at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S, which was output in step S3, and the temperature T _{cal_skid} output in step S3. The temperature difference T _{cal_diff} = T _cal - T _{cal_skid} between the temperature T _cal at the longitudinal position corresponding to between the heating furnace skids at the width center of the back surface Sb of the slab S, and the temperature difference between the slab S obtained in step S1 The temperature T act_skid at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S corresponds to the temperature T _{act_skid} at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, which is obtained in step S1. The magnitude (absolute value) of the temperature difference T _{act_diff} = T _act - T _{act_skid} from the temperature T _act at the longitudinal position, e = T _{cal_diff} - T _{act_diff} , is less than the threshold ε (1°C). As _shown in FIG. step).

As mentioned above, the amount of heat removed in the heating furnace skid section is expressed by equation (7), but it is possible to find an appropriate η in equation (18), which introduces the correction coefficient η into equation (7). This is an appropriate correction for the amount of heat removed _Qskd at the heating furnace skid section.

The process in step S4 will be explained in detail with reference to FIG.
First, in step S41, the model correction unit 14 calculates the temperature T _{cal_skid} at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S, which was output in step S3, and The temperature difference T _{cal_diff} = T _cal - T _{cal_skid} between the temperature T _cal at the longitudinal position corresponding to between the heating furnace skids at the width center of the back surface Sb of the slab S, and the temperature difference between the slab S obtained in step S1 The temperature T act_skid at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S corresponds to the temperature T _{act_skid} at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, which is obtained in step S1. The deviation e _{=T cal_diff - T act_diff of the temperature difference T act_diff = T act - T act_skid from the temperature T act at the longitudinal position is} calculated.

Here, the model correction unit 14 selects a specific heating furnace skid portion from among the plurality of temperatures at a longitudinal position corresponding to the heating furnace skid portion in the width center portion of the back surface Sb of the slab S, output in step S3. The temperature T _{cal_skid} at the corresponding longitudinal position, the above-mentioned specific heating furnace skid portion at the width center of the back surface Sb of the slab S, and the heating furnace adjacent to this specific heating furnace skid portion, output in step S3. The temperature difference T _{cal_diff} = T _cal - T _{cal_skid} between the temperature T _cal at the longitudinal position corresponding to the skid part is calculated.

In addition, the model correction unit 14 selects the above-mentioned specific heating furnace skid portion from among the plurality of temperatures at the longitudinal position corresponding to the heating furnace skid portion in the width center portion of the back surface Sb of the slab S, acquired in step S1. The temperature T _{act_skid} at the longitudinal position corresponding to the above-mentioned specific heating furnace skid portion at the width center of the back surface Sb of the slab S and the heating adjacent to this specific heating furnace skid portion obtained in step S1. The temperature difference T _{act_diff} = T act - T _{act_skid} between the temperature T _act at the corresponding longitudinal position between the furnace skid portion and the temperature T _act is calculated.
Then, the model correction unit 14 calculates the deviation e=T _{cal_diff} - T _{act_diff} (magnitude of absolute value) between the calculated temperature difference T cal_diff = _{T cal} - T _{cal_skid} and the temperature difference T _{act_diff} = T _act - T _{act_skid} . calculate.

Next, in step S42, the model correction unit 14 determines whether the deviation e (magnitude of absolute value) calculated in step S41 is less than a threshold value ε (=1° C.).
If the determination result in step S42 is NO (the deviation e is not less than the threshold ε), the process moves to step S43, and if the determination result in step S42 is YES (the deviation e is less than the threshold ε), the process moves to step S49. .
In step S43, the model correction unit 14 sets the correction coefficient η in the above-mentioned equation (18) to the correction coefficient η+δ after the slight change.

Next, in step S44, the model correction unit 14 uses the amount of heat removed from the heating furnace skid part Q _skd in equation (18), where the correction coefficient η is the correction coefficient η+δ after the slight change, to improve the heating furnace in step S2. The temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in step S3 is recalculated, and based on this, the length at the width center of the slab S after rough rolling in step S3 is calculated. The temperature distribution in the direction and the thickness direction is recalculated, and the temperature T _{cal_skid} ' at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S and the back surface of the slab S in step S41 is calculated. The temperature difference T _{cal_diff} ′=T _{cal ′} −T _{cal_skid} ′ between the temperature T _cal ′ at the longitudinal position corresponding to between the heating furnace skids at the center width of Sb is calculated.

Next, in step S45, the model correction unit 14 calculates, from the temperature difference T _{cal_diff} calculated in step S41, the temperature difference T _{cal_diff} ' calculated in step S44, and the minute change amount δ of the correction coefficient set in step S43, An influence coefficient ∂e/∂η=(T _{cal_diff} '−T _{cal_diff} )/δ is calculated.

Next, in step S46, the model correction unit 14 updates the correction coefficient η in the above-mentioned equation (18) to the updated correction coefficient η−e/(∂e/∂η).

Next, in step S47, the model correction unit 14 uses the amount of heat removed Q _skd in the heating furnace skid part of equation (18) where the correction coefficient η is the updated correction coefficient η−e/(∂e/∂η). Then, the temperature distribution in the length direction and the thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 in step S2 is recalculated, and the temperature distribution in the width center of the slab S after rough rolling in step S3 is calculated again. The temperature distribution in the length direction and the thickness direction is recalculated, and the temperature T _{cal_skid} '' at the longitudinal position corresponding to the heating furnace skid part in the width center of the back surface Sb of the slab S in step S41 and the slab The temperature difference T _{cal_diff} '' between the temperature T _cal '_' at the longitudinal position corresponding to between the heating furnace skids at the center width of the back _surface Sb of S is calculated.

Next, in step S48, the model correction unit 14 updates the deviation e calculated in step S41 to deviation e=T _{cal_diff} ''-T _{act_diff} .
Then, the process returns to step S42, and in step S42, the model correction unit 14 determines whether the deviation e updated in step S48 is less than the threshold value ε (=1° C.).
Then, steps S42 to S48 are repeated until the determination result in step S42 becomes YES.
If the determination result in step S42 is YES, the process moves to step S49, and the correction coefficient η when the deviation e becomes less than the threshold value ε (=1° C.) is set as the correction coefficient.

Thereby, the process in step S4 is completed, and an appropriate correction coefficient η in the above-mentioned equation (18) is determined, and the amount of heat removed Q _skd in the heating furnace skid portion is appropriately corrected.
Then, in step S5, the output unit 15 of the correction device 10 outputs heat _conduction equations (Equations (1) to (7) ) and (18) are output to the slab temperature prediction unit 21 of the furnace temperature control device 20 of the heating furnace (output step).

This completes the processing in the slab temperature model correction device 10.

As described above, according to the slab temperature model correction method according to the present embodiment, in the rough temperature acquisition step (step S1), the rough temperature measurement meter 8 installed on the outlet side of the roughing mills 4 ₁ to 4 _n The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the rough-rolled slab S is obtained, and in the extraction temperature calculation step (step S2), the charging temperature of the slab S to be charged into the heating furnace 2 is calculated. As an initial value, a slab temperature model is constructed using the operating conditions of the slab S while it is in the heating furnace, and the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2. Calculate based on the heat conduction equation (Equations (1) to (7)) and output. Then, in the crude extraction side temperature calculation step (step S3), the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2, which was output in the extraction temperature calculation step, is set to an initial value. Using the operating conditions when rough rolling the slab S extracted from the heating furnace 2, the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling is calculated using the heat conduction equation ( Calculate based on equations (8) to (17) and output. Then, in the model correction step (step S4), the temperature T _{cal_skid} at the longitudinal position corresponding to the heating furnace skid part in the width center of the back surface Sb of the slab S, which was output in the rough output side temperature calculation step, and the rough The temperature difference T _{cal_diff} = T _cal - T _{cal_skid} between the temperature T _cal at the longitudinal position corresponding to between the heating furnace skids at the width center portion of the back surface Sb of the slab S, which is output from the outlet temperature calculation unit 13; The temperature T act_skid at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11, and the temperature T _{act_skid} of the slab S acquired by the rough temperature acquisition unit 11. The size of the deviation e=T cal_diff - T act_diff of the temperature difference T _{act_diff} = T _act - T _{act_skid} between the temperature T _act at the longitudinal position corresponding to between the heating _{furnace skids} at the center width of the back surface Sb is the threshold value ε. (1°C) or less at the heating furnace skid, which is included in the heat conduction equation expressed by equations (1) to (7) that constitute the slab temperature model used in the extraction temperature calculation step. Correct the amount of heat Q _skd (formula (18)).

As a result, when predicting the temperature distribution in the length direction and thickness direction in the width center of the slab S at the time of extraction in the heating furnace 2 using the slab temperature model, by correcting the slab temperature model, the heating furnace It is possible to accurately predict the temperature distribution in the length direction and thickness direction at the width center portion of the slab during extraction in step 2.

In addition, through the correction of this slab temperature model, in the model correction step, the information output from the rough delivery side temperature calculation step and the rough temperature measurement meter 8 installed on the exit side of the roughing mills 4 ₁ to 4 _n are used. Since the slab temperature model is corrected based on the information acquired in the measured crude temperature acquisition step, the radiation thermometer installed immediately after the exit side of the heating furnace 2 can be used to determine the temperature of the slab S immediately after extraction from the heating furnace 2. There is no need to measure temperature. Immediately after extraction from the heating furnace 2, temperature measurement itself is difficult due to the influence of scale on the surface of the slab S, but according to the correction method according to the present embodiment, there is no such fear.

Next, a method for controlling the furnace temperature of a heating furnace according to an embodiment of the present invention will be described with reference to a flowchart for explaining the flow of processing in the furnace temperature control device for a heating furnace shown in FIG.

First, in step S11, the slab temperature prediction unit 21 of the furnace temperature control device 20 acquires information on the slab temperature model corrected by the slab temperature model correction method from the output unit 15 of the correction device 10, and uses the information. The temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 is predicted (slab temperature prediction step).

Specifically, the slab temperature prediction unit 21 uses the charging temperatures of the front surface Sa and back surface Sb of the slab S at the time of charging the heating furnace 2 measured by the charging temperature measuring meter 7 as initial values, and calculates the charging temperature of the slab S. Using the above-mentioned operating conditions while the heating furnace is in use, the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 is obtained from the output unit 15 of the correction device 10. The calculated value is calculated based on the heat conduction equations (Equations (1) to (7), and Equation (18)) constituting the revised slab temperature model, and this calculated value is used as the predicted value.

Next, in step S12, the furnace temperature control unit 22 of the furnace temperature control device 20 determines the longitudinal position corresponding to the heating furnace skid portion at the width center of the slab S at the time of extraction in the heating furnace 2 predicted in step S11. The furnace temperature in the heating furnace 2 is controlled so that the temperature in the thickness direction at is higher than the minimum extraction temperature (furnace temperature control step).

Specifically, the furnace temperature control unit 22 controls the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S at the time of extraction of the heating furnace 2 predicted in step S11. Each fuel flow control unit 23 is controlled to control the fuel flow rate to each combustion burner 3 so that the temperature reaches a target temperature exceeding the minimum extraction temperature (for example, 1200° C.), and the furnace temperature in the heating furnace 2 is controlled. Control.

As a result, when the slab S is extracted from the heating furnace 2, the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S exceeds the minimum extraction temperature, which tends to result in insufficient temperature rise. This means that the contact point of the skid beam can be raised to a specified temperature for extraction.

As described above, according to the furnace temperature control method for a heating furnace according to the present embodiment, in the slab temperature prediction step (step S11), the slab temperature model corrected by the slab temperature model correction method is used to control the temperature of the heating furnace 2. The temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction is predicted, and in the furnace temperature control step (step S12), the temperature distribution of the slab S at the time of extraction of the heating furnace 2 predicted in the slab temperature prediction step is calculated. The furnace temperature in the heating furnace 2 is controlled so that the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid portion in the width center of S exceeds the minimum extraction temperature.

As a result, when the slab S is extracted from the heating furnace 2, the temperature in the thickness direction at the longitudinal position corresponding to the heating furnace skid part in the width center of the slab S exceeds the minimum extraction temperature, which tends to result in insufficient temperature rise. It is possible to raise the contact point of the skid beam to a specified temperature and extract it, preventing material defects in the hot-rolled coil due to insufficient temperature rise of the skid part of the heating furnace, and reducing the heating unit consumption due to overheating operation. can.

Further, the method for manufacturing a steel plate according to an embodiment of the present invention includes a furnace temperature control step of controlling the furnace temperature in the heating furnace 2 by the above-mentioned method for controlling the furnace temperature of the heating furnace. The slab S that is heated by the temperature-controlled heating furnace 2 and extracted from the heating furnace 2 is rough rolled in a rough rolling process by a plurality of (n units in this embodiment) rough rolling mills 4 ₁ to 4 _n . After that, in a finish rolling process, the steel plate is finish rolled by a finish rolling mill (not shown) to become a thin steel plate. This steel plate is manufactured by being cooled in a cooling facility 5 in a cooling process, and then wound into a coil shape by a winding device 6 in a winding process.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various changes and improvements can be made.

For example, the extraction temperature calculation unit 12 (step S2) calculates the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2. It is sufficient to calculate the temperature distribution including the length direction and the thickness direction in the width center of the slab S. The temperature distribution in the horizontal direction may also be calculated.

In addition, in the rough-rolling side temperature calculation unit 13 (step S3), the temperature distribution in the length direction and thickness direction at the width center part of the slab S after rough rolling is calculated. It is sufficient to calculate the temperature distribution including the length direction and the thickness direction at least in the width center part, and is not limited to the length direction and thickness direction in the width center part of the slab S. The temperature distribution in the width direction and the thickness direction may be calculated.

In addition, the slab temperature prediction unit 21 (step S11) predicts the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2. What is necessary is to predict the temperature distribution including the length direction and the thickness direction at least at the width center of the slab S, and is not limited to the length direction and thickness direction at the width center of the slab S. The temperature distribution in the direction, length direction, and thickness direction may be predicted. It may be calculated.

In order to verify the effects of the present invention, in the hot rolling line ₁ shown in _FIG . The temperature distribution in the length direction at the center of the width was measured.

As a result, as shown in FIG. 10, the temperature _{Tact_skid} at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, and the heating furnace skid at the width center portion of the back surface Sb of the slab S. The temperature difference T _{act_diff} = T _act - T _{act_skid} between the temperature T _act at the corresponding longitudinal position in between was 26°C.

On the other hand, based on the heat conduction equation in which the correction coefficient η of the amount of heat removed Q _skd at the heating furnace skid portion is 0.20 (correction coefficient before correction), the extraction temperature calculation unit 12 of the correction device 10 calculates the Using the charging temperature of the slab S charged in the heating furnace 2 as an initial value, and using the operating conditions of the slab S while it is in the heating furnace, the length direction and thickness at the width center of the slab S at the time of extraction in the heating furnace 2 are determined. The temperature distribution in the horizontal direction was calculated and output. Then, the rough-out side temperature calculation unit 13 of the correction device 10 uses the outputted temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction in the heating furnace 2 as an initial value, and performs heating. Using the operating conditions when rough rolling the slab S extracted from the furnace 2, the temperature distribution in the length direction and thickness direction at the width center of the rough rolled slab S is calculated based on the heat conduction equation. , outputted.

As _a result, as shown by the broken line in FIG. The temperature difference between the temperature T _cal at the corresponding longitudinal position between the furnace skids, T _{cal_diff} = T _cal - T _{cal_skid} , was 19°C.

Therefore, the model correction unit 14 of the correction device 10 calculates the deviation e=T cal_diff -T between the temperature difference T _{cal_diff} = T _cal - T _{cal_skid} = 19°C and the temperature difference T _{act_diff} = T _act - T _{act_skid} = 26° _C . _{act_diff} =-7°C was calculated.

The model correction unit 14 of the correction device 10 judges whether the calculated deviation e=-7°C (absolute value magnitude) is less than the threshold value ε (=1°C), and as a result, the judgment result is NO. Therefore, the correction coefficient η=0.20 was set to the correction coefficient 0.20+0.05=0.25 after the slight change.

Then, the model correction unit 14 extracts the heating furnace 2 using the amount of heat removed Q _skd at the heating furnace skid portion with η = 0.20 as the correction coefficient 0.20 + 0.05 = 0.25 after the slight change. The temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of rough rolling is recalculated, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling is calculated. The distribution is recalculated, and the temperature T _{cal_skid} ' at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S and the temperature T cal_skid ' at the length direction position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S is calculated. The temperature difference T _{cal_diff} ′=T _cal ′−T _{cal_skid} ′ with respect to the temperature T _{cal ′} at the corresponding longitudinal position was calculated. As a result, the temperature difference T _{cal_diff} ' was 22°C.

Then, the model correction unit ₁₄ calculates the influence coefficient ∂e/∂η ₌ ( T _{cal_diff} ′−T _{cal_diff} )/δ=(22−19/0.05=60) was calculated.

Next, the model correction unit 14 updates the correction coefficient η for the amount of heat removed Q _skd in the heating furnace skid part by updating the correction coefficient η-e/(∂e/∂η)=0.20-(-7)/60= Updated to 0.31.

Next, the model correction unit 14 adjusts the heating furnace 2 by using the amount of heat removed Q _skd at the heating furnace skid portion with the correction coefficient η updated as the correction coefficient η−e/(∂e/∂η)=0.31. Recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction, and calculate the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling. The temperature T _{cal_skid} '' at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface Sb of the slab S, and the length corresponding to the length between the heating furnace skids at the width center of the back surface Sb of the slab S. The temperature difference T _{cal_diff} '' from the temperature T _cal '' at the horizontal position was calculated: T _cal '' - T _{cal_skid} ''. As a result, as shown by the solid line in FIG. 11, the temperature difference T _{cal_diff} '' was 26°C.

Then, the model correction unit 14 updated the aforementioned deviation e=-7°C to the deviation e=T _{cal_diff} ''-T _{act_diff} =26°C-26°C=0°C.
Then, the model correction unit 14 determines whether the updated deviation e=0°C is less than the threshold value ε (=1°C), and since the determination result is YES, update when the determination result is YES. The post-correction coefficient η-e/(∂e/∂η)=0.20-(-7)/60=0.31 was set as the correction coefficient η.
As a result, the processing in the model correction unit 14 is completed, and an appropriate correction coefficient η = 0.31 for the amount of heat removed from the heating furnace skid Q _skd (Equation (18)) is obtained, and the This resulted in an appropriate correction for the amount of heat removed _Qskd .

Therefore, according to this example, it was confirmed that the amount of heat removed Q _skd in the heating furnace skid part could be adjusted to match the crude temperature measurement value.
Further, the material quality in the longitudinal direction of the hot rolled coil manufactured by the method for manufacturing a steel plate according to the example of the present invention was more uniform than that in the case where the method of the present invention was not applied, confirming the effect of the present invention.

1 Hot rolling line 2 Heating furnace 2 ₁ ~ 2 _n combustion control zone 3 Combustion burner 4 ₁ ~ 4 _n rough rolling mill 5 Cooling equipment 6 Winding device 7 Charging temperature meter 8 Rough temperature meter 10 Slab temperature model Correction device 11 Crude temperature acquisition unit 12 Extraction temperature calculation unit 13 Crude side temperature calculation unit 14 Model correction unit 15 Output unit 20 Furnace temperature control device for heating furnace 21 Slab temperature prediction unit 22 Furnace temperature control unit 23 Fuel flow rate control unit S Slab Sa front side Sb back side

Claims (5)

When a slab is heated in a heating furnace and the slab extracted from the heating furnace is roughly rolled in a rough rolling mill, the length direction and the thickness direction of the slab at least in the width center portion at the time of extraction from the heating furnace. A slab temperature model correction device used for predicting temperature distribution including
a rough temperature acquisition unit that acquires the temperature distribution in the length direction at the width center portion of the back surface of the slab after rough rolling, measured by a rough temperature measuring meter installed on the exit side of the rough rolling mill;
Using the charging temperature of the slab charged into the heating furnace as an initial value, and using the operating conditions of the slab while it is in the heating furnace, the length of the slab at least in the center width at the time of extraction from the heating furnace is determined. an extraction temperature calculation unit that calculates and outputs a temperature distribution including a width direction and a thickness direction based on a heat conduction equation forming the slab temperature model;
The temperature distribution extracted from the heating furnace, with the temperature distribution including the length direction and thickness direction in at least the width center portion of the slab at the time of extraction from the heating furnace, which is output from the extraction temperature calculation unit, as an initial value. Using the operating conditions when rough rolling the slab, calculate the temperature distribution including the length direction and the thickness direction at least at the center width of the slab after rough rolling based on the heat conduction equation, and output the rough rolling temperature distribution. An outlet temperature calculation section;
The temperature at the longitudinal position corresponding to the heating furnace skid portion at the width center portion of the back surface of the slab, which is output from the rough output side temperature calculation unit, and the temperature of the slab, which is output from the rough output side temperature calculation unit. The temperature difference between the temperature at the longitudinal position corresponding to between the heating furnace skids at the width center of the back surface of the slab and the temperature at the heating furnace skid portion at the width center of the back surface of the slab, which is obtained by the rough temperature acquisition section. the temperature difference between the temperature at the corresponding longitudinal position and the temperature at the longitudinal position corresponding between the heating furnace skids at the width center portion of the back surface of the slab, which is acquired by the rough temperature acquisition unit; and a model correction unit that corrects the amount of heat removed in the heating furnace skid part included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation unit so that the size is less than a threshold value. A slab temperature model correction device characterized by: A slab whose temperature distribution including the length direction and thickness direction at least in the width center portion of the slab at the time of extraction in a heating furnace is predicted using the slab temperature model corrected by the slab temperature model correction device according to claim 1. The temperature prediction unit and the temperature in the thickness direction at a longitudinal position corresponding to the heating furnace skid portion in the width center of the slab at the time of extraction of the heating furnace predicted by the slab temperature prediction unit exceed the minimum extraction temperature. A furnace temperature control device for a heating furnace, comprising a furnace temperature control section that controls the furnace temperature in the heating furnace. When a slab is heated in a heating furnace and the slab extracted from the heating furnace is roughly rolled in a rough rolling mill, the length direction and the thickness direction of the slab at least in the width center portion at the time of extraction from the heating furnace. A method for modifying a slab temperature model used for predicting temperature distribution including
a rough temperature acquisition step of acquiring a temperature distribution in the length direction at the width center portion of the back surface of the slab after rough rolling, measured by a rough temperature measuring meter installed on the exit side of the rough rolling mill;
Using the charging temperature of the slab charged into the heating furnace as an initial value, and using the operating conditions of the slab while it is in the heating furnace, the length of the slab at least in the center width at the time of extraction from the heating furnace is determined. an extraction temperature calculation step of calculating and outputting a temperature distribution including a width direction and a thickness direction based on a heat conduction equation constituting the slab temperature model;
The temperature distribution extracted from the heating furnace, with the temperature distribution including the length direction and thickness direction in at least the width center portion of the slab at the time of extraction from the heating furnace, which is output in the extraction temperature calculation step, as an initial value. Using the operating conditions when rough rolling the slab, calculate the temperature distribution including the length direction and the thickness direction at least at the center width of the slab after rough rolling based on the heat conduction equation, and output the rough rolling temperature distribution. Outlet temperature calculation step;
The temperature at the longitudinal position corresponding to the heating furnace skid part at the width center of the back surface of the slab, which is output in the rough output side temperature calculation step, and the temperature of the slab, which is output in the rough output side temperature calculation step. The temperature difference between the temperature at the longitudinal position corresponding to between the heating furnace skids at the width center of the back surface of the slab and the temperature at the heating furnace skid portion at the width center of the back surface of the slab obtained in the rough temperature acquisition step. The temperature difference between the temperature at the corresponding longitudinal position and the temperature at the longitudinal position corresponding between the heating furnace skids at the center width of the back surface of the slab, which is obtained in the rough temperature acquisition step. and a model modification step of modifying the amount of heat removed from the heating furnace skid part included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation step so that the magnitude is less than a threshold value. A method for modifying a slab temperature model featuring . A slab whose temperature distribution including the length direction and thickness direction at least in the width center portion of the slab at the time of extraction in a heating furnace is predicted using the slab temperature model modified by the slab temperature model modification method according to claim 3. The temperature prediction step and the temperature in the thickness direction at a longitudinal position corresponding to the heating furnace skid portion in the width center of the slab during extraction of the heating furnace predicted in the slab temperature prediction step exceed the minimum extraction temperature. A furnace temperature control method for a heating furnace, comprising a furnace temperature control step of controlling the furnace temperature in the heating furnace. A method for manufacturing a steel sheet, comprising a furnace temperature control step of controlling a furnace temperature in a heating furnace by the furnace temperature control method for a heating furnace according to claim 4.

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