Slab temperature model correction device, correction method, furnace temperature control device for heating furnace, furnace temperature control method, and steel plate manufacturing method

Abstract

To provide a correction device and a correction method 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 through correcting a slab temperature model, a furnace temperature control device and a furnace temperature control method for a heating furnace and a manufacturing method of a steel plate.SOLUTION: A correction device 10 for a slab temperature model corrects, at a model correction part 14, a calculation parameter 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, the deviation e between: a temperature Tcal at a position in a lengthwise direction corresponding to an interval between heating furnace skids at a width central part of a front face Sa or a rear face Sb of a slab S outputted from a crude temperature calculation part 13; and a temperature Tact at the position in the lengthwise direction corresponding to the interval between heating furnace skids at the width central part of the front face Sa or the rear face Sb of the slab S acquired at a crude temperature acquisition part 11.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a device and method for correcting a slab temperature model used to predict the slab temperature at the time of extraction from a heating furnace when a slab is heated in the heating furnace and the slab extracted from the heating furnace is rough rolled, a furnace temperature control device for a heating furnace, a furnace temperature control method, and a method for manufacturing a steel plate. [Background technology]

[0002] In steelworks, slabs cast in the steelmaking process are temporarily stored in a slab yard and cooled as cold slabs, or directly shipped as hot slabs (DHCRs), which are then charged into a heating furnace for the hot rolling process and heated to a specified temperature (approximately 1200 degrees). The slabs removed from the heating furnace are then roughly rolled in a rough rolling process and finish rolled in a finish rolling process to become thin steel plates. The steel plates are then cooled in a runout cooling process and then wound into coils in a winding process.

[0003] Here, in a walking beam type heating furnace, the slab is supported by multiple skid beams (e.g., eight). There are two types of skid beams: fixed and movable, and the slab is transported to the extraction side by the movable skid beam repeatedly rising, moving, and lowering. The slab has a rectangular shape with a predetermined size in the width, length, and thickness directions, and is placed on the skid beam in the heating furnace so that the width direction of the slab is the transport direction of the slab, and the slab is transported to the extraction side by the movable skid beam repeatedly rising, moving, and lowering.

[0004] During this process, heat is removed from the slab during heating through the skid beam, causing the temperature at the contact points of the skid beam to drop, resulting in temperature fluctuations in the longitudinal direction of the slab called skid marks. Skid marks extend across the slab in the width direction and are formed at a certain pitch along the longitudinal direction of the slab. Note that the inside of a heating furnace is a high-temperature environment, and scale is also generated on the surface of the slab, making it difficult to accurately measure the surface temperature of the slab with a radiation thermometer. Therefore, the above-mentioned skid marks cannot be directly measured in a heating furnace, and temperature fluctuations in skid marks can generally be confirmed by measuring the temperature at the exit side of a roughing mill.

[0005] In the operation of a heating furnace, it is necessary 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 point of the skid beam (hereinafter referred to as the skid section), which tends to be insufficiently heated, to the specified temperature for extraction. However, if the extraction temperature is raised excessively, it will lead to a deterioration in the fuel consumption rate (GJ / ton-steel), so it is necessary to perform heating operation appropriately. Conventionally, methods for operating a heating furnace are known, for example, as shown in Patent Documents 1 and 2.

[0006] The rolling heating furnace combustion control method shown in Patent Document 1 predicts the future temperature distribution between the skids and in the skid section of the slab in the furnace by solving a one-dimensional heat conduction difference equation in the thickness direction of the slab between the skids, and a two-dimensional (slab thickness direction × slab longitudinal direction) heat conduction difference equation in the skid section, which is simplified by introducing coefficients to account for heat conduction in the longitudinal direction of the slab, and calculates the set furnace temperature by evaluating the baking quality of the slab. According to the rolling heating furnace combustion control method shown in Patent Document 1, it is possible to predict the temperature distribution between the skids and in the skid section for all slabs in the furnace with a small amount of calculation.

[0007] In addition, the method for predicting the slab temperature in a continuous heating furnace shown in Patent Document 2 measures the error between the "slab temperature measured at the extraction port" of the continuous heating furnace and the "slab extraction temperature calculated from the furnace temperature, time in furnace, etc." every time a slab is extracted, and sequential least squares estimation is performed on this and an influence coefficient obtained by a separate slab temperature calculation to sequentially estimate the overall heat absorptivity of multiple zones in the furnace online, and the overall heat absorptivity of each zone is updated based on this estimated value, thereby improving the accuracy of predicting the temperature of the slab in the furnace. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 7-258752 [Patent Document 2] Japanese Patent Application Publication No. 6-264153 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the rolling reheating furnace combustion control method disclosed in Patent Document 1 and the slab temperature prediction method in a continuous reheating furnace disclosed 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 future temperature distribution between the skids and the skid part of the slab in the furnace is predicted by solving a one-dimensional heat conduction difference equation in the thickness direction of the slab for between the skids and a two-dimensional heat conduction difference equation in which the heat conduction in the longitudinal direction of the slab is simplified by introducing coefficients for the skid part, but it is not verified whether the predicted future temperature distribution between the skids and the skid part of the slab in the furnace is truly correct. In other words, when the actual temperature distribution between the skids and the skid part of the slab in the furnace deviates from the predicted temperature distribution between the skids and the skid part of the slab in the furnace, the slab temperature model (the above-mentioned heat conduction difference equation) is not corrected to improve the accuracy of the predicted value. For this reason, it is not possible to guarantee the accuracy of the predicted value of the temperature including the length direction and thickness direction at least in the width center part of the slab when it is removed from the heating furnace using the slab temperature model.

[0010] In addition, in the case of the method for predicting the slab temperature in a continuous heating furnace shown in Patent Document 2, the error between the "slab temperature measured at the extraction port" of the continuous heating furnace and the "slab extraction temperature calculated from the furnace temperature, time in furnace, etc." is measured every time a slab is extracted, but generally, it is difficult to measure the temperature itself immediately after extraction from the heating furnace due to the influence of scale on the slab surface, and it is not possible to obtain an appropriate "slab temperature measured at the extraction port" of the continuous heating furnace. For this reason, it is not possible to guarantee the accuracy of the predicted value of the temperature including the length direction and thickness direction at least in the width center part of the slab when it is extracted from the heating furnace using a slab temperature model.

[0011] Therefore, the present invention has been made to solve these conventional problems, and its object is to provide a slab temperature model correction device, correction method, furnace temperature control device, furnace temperature control method, and steel plate manufacturing method that can accurately predict the temperature distribution including the length direction and thickness direction at least in the width center part of the slab when it is extracted from the heating furnace by correcting the slab temperature model using temperature measurements by a rough temperature measuring device installed between adjacent roughing mills or on the outlet side of multiple roughing mills. [Means for solving the problem]

[0012] In order to solve the above problems, a slab temperature model correction device according to one aspect of the present invention is a slab temperature model correction device used to predict a temperature distribution including the length direction and thickness direction at least in the width center of the slab when the slab is extracted from the heating furnace when the slab is heated in a heating furnace and the slab extracted from the heating furnace is rough rolled by a plurality of rough rolling mills. The device includes a rough temperature acquisition unit that acquires a longitudinal temperature distribution at the width center of the front or back surface of the slab measured by a rough temperature measuring device installed between adjacent rough rolling mills or on the outlet side of the plurality of rough rolling mills, and an extraction temperature calculation unit that calculates and outputs the temperature distribution including the length direction and thickness direction at least in the width center of the slab when the slab is extracted from the heating furnace based on a heat conduction equation constituting the slab temperature model, using the operating conditions while the slab is in the heating furnace, with the charging temperature of the slab charged into the heating furnace as an initial value, and The present invention also includes a coarse temperature calculation unit that calculates and outputs a temperature distribution including the length and thickness directions at least in the width center of the slab corresponding to the position where the coarse temperature gauge is installed, based on a heat conduction equation, using the operating conditions for rough rolling the slab extracted from the heating furnace, using the temperature distribution including the length and thickness directions at least in the width center of the slab at the time of extraction from the heating furnace output from the extraction temperature calculation unit as an initial value, and a model correction unit that corrects calculation parameters included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation unit so that the magnitude of deviation between the temperature at the length direction position corresponding to the heating furnace skids at the width center of the front or back surface of the slab output from the coarse temperature calculation unit and the temperature at the length direction position corresponding to the heating furnace skids at the width center of the front or back surface of the slab acquired by the coarse temperature acquisition unit is less than a threshold value.

[0013] In addition, a furnace temperature control device for a heating furnace according to another aspect of the present invention is characterized in that it includes a slab temperature prediction unit that predicts a temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace using a slab temperature model corrected by the above-mentioned slab temperature model correction device, and a furnace temperature control unit that controls the furnace temperature in the heating furnace so that the temperature of the temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace predicted by the slab temperature prediction unit exceeds the minimum extraction temperature.

[0014] In addition, a method for correcting a slab temperature model according to another aspect of the present invention is a method for correcting a slab temperature model used to predict a temperature distribution including a length direction and a thickness direction at least in a width center portion of the slab at the time of extraction from the heating furnace when the slab is heated in a heating furnace and the slab extracted from the heating furnace is rough rolled by a plurality of rough rolling mills, the method including the following steps: a rough temperature acquisition step for acquiring a length direction temperature distribution at the width center portion of the front or back surface of the slab measured by a rough temperature measuring device installed between adjacent rough rolling mills or on the outlet side of the plurality of rough rolling mills; an extraction temperature calculation step for calculating and outputting a temperature distribution including a length direction and a thickness direction at least in a width center portion of the slab at the time of extraction from the heating furnace based on a heat conduction equation constituting the slab temperature model, using an operating condition while the slab is in the heating furnace, with the charging temperature of the slab charged into the heating furnace as an initial value; a rough temperature calculation step of calculating and outputting a temperature distribution including the length and thickness directions at least in the width center of the slab corresponding to the position where the rough temperature gauge is installed, based on a heat conduction equation, using the operating conditions for rough rolling the slab extracted from the heating furnace, using the temperature distribution including the length and thickness directions at least in the width center of the slab at the time of extraction from the heating furnace outputted in the rough temperature calculation step as an initial value; and a model correction step of correcting calculation parameters included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation step, so that the magnitude of deviation between the temperature at the length direction position corresponding to the heating furnace skids at the width center of the front or back surface of the slab outputted in the rough temperature calculation step and the temperature at the length direction position corresponding to the heating furnace skids at the width center of the front or back surface of the slab acquired in the rough temperature acquisition step is less than a threshold value.

[0015] In addition, a furnace temperature control method of a heating furnace according to another aspect of the present invention includes a slab temperature prediction step of predicting a temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace using a slab temperature model corrected by the above-mentioned slab temperature model correction method, and a furnace temperature control step of controlling the furnace temperature in the heating furnace so that the temperature of the temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace predicted in the slab temperature prediction step exceeds a minimum extraction temperature. A method for producing a steel sheet according to another aspect of the present invention is characterized in that it includes a furnace temperature control step of controlling a furnace temperature in a heating furnace by the above-mentioned method for controlling a furnace temperature of a heating furnace. Effect of the Invention

[0016] According to the slab temperature model correction device, correction method, furnace temperature control device for a heating furnace, furnace temperature control method, and steel plate manufacturing method of the present invention, by correcting the slab temperature model using temperature measurements from a rough temperature gauge installed between adjacent roughing mills or on the outlet side of multiple roughing mills, it is possible to provide a slab temperature model correction device, correction method, furnace temperature control device for a heating furnace, furnace temperature control method, and steel plate manufacturing method that can accurately predict the temperature distribution including the length and thickness directions at least in the width center of the slab when it is extracted from the heating furnace. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a hot rolling line to which a slab temperature model correction device and a furnace temperature control device for a heating furnace according to an embodiment of the present invention are applied. [Diagram 2] FIG. 2 is a block diagram showing an internal configuration of a correction device for a slab temperature model in FIG. [Diagram 3] 2 is a block diagram showing an internal configuration of a furnace temperature control device of the heating furnace in FIG. 1. [Figure 4] 1 is a graph showing an example of temperature distribution in the longitudinal direction at the center of the width of the back surface of a slab, measured by a coarse temperature measuring device. [Diagram 5] 1 is a graph showing an example of a longitudinal temperature distribution at the width center of the back surface of a slab corresponding to the position on the exit side of a roughing rolling mill where a rough temperature measuring device is installed, output from a rough temperature calculation unit. [Figure 6] 10 is a flowchart for explaining a process flow in a slab temperature model correction device. [Figure 7] 7 is a flowchart showing details of the process flow in step S4 (model correction step) in the flowchart shown in FIG. 6. [Figure 8] 4 is a flowchart for explaining a process flow in a furnace temperature control device of a heating furnace. [Figure 9] FIG. 2 is a diagram for explaining the shape of a slab. [Figure 10] 13A and 13B are diagrams for explaining processing by a modified example of the model correction unit. [Figure 11] 13 is a flowchart illustrating a process flow according to a modified example of the model correction unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not specify the materials, shapes, structures, arrangements, etc. of the components to the embodiments described below. In addition, the drawings are schematic. Therefore, it should be noted that the relationship and ratio between thickness and planar dimensions are different from the actual ones, and the drawings include parts where the relationship and ratio of dimensions differ from each other.

[0019] FIG. 1 shows a schematic configuration of a hot rolling line to which a slab temperature model correction device and a heating furnace temperature control device according to one embodiment of the present invention are applied. In a steelworks, a slab S cast in a steelmaking process is temporarily stored in a slab yard and cooled, or is directly delivered as a hot slab (DHCR), which is then charged into a heating furnace 2 in a hot rolling line 1 as shown in FIG. 1 and heated to a predetermined temperature (about 1200°C). The slab S is then transported through the heating furnace 2 and extracted, and is then passed through a plurality of roughing mills 41-4 (n in this embodiment) to be heated. n After being roughly rolled by a rolling mill (not shown), the steel sheet is finish-rolled by a finishing rolling mill (not shown) to become a thin steel sheet. This steel sheet is then cooled by a cooling facility 5 and wound into a coil by a winding device 6.

[0020] The heating furnace 2 has a plurality of (n in this embodiment) combustion control zones 21-2 from the upstream side to the downstream side in the conveying direction of the slab S. n Each of the combustion control zones 21-2 n A combustion burner 3 for heating the slab S is installed in each of the combustion control zones 21-2. n The combustion burners 3 are connected to fuel flow rate control units 23, and each fuel flow rate control unit 23 is connected to a furnace temperature control device 20 of the heating furnace.

[0021] Here, the heating furnace 2 is a walking beam type heating furnace, and the slab S is supported by multiple (e.g., eight) skid beams. There are two types of skid beams: fixed and movable. The slab S is transported to the extraction side by the movable skid beam repeatedly rising, moving, and lowering. As shown in FIG. 9, the slab S has a rectangular parallelepiped shape having a width w, a length l, and a thickness t in the length direction indicated by the arrow x, the width direction indicated by the arrow y, and the thickness direction indicated by the arrow z. In the heating furnace 2, the slab S is placed on the skid beam in the heating furnace 2 so that its front surface Sa is the upper side and its back surface Sb is the lower side, and as shown in FIG. 1, the width direction of the slab S is the transport direction of the slab S. The slab S is transported to the extraction side by the movable skid beam repeatedly rising, moving, and lowering.

[0022] When the slab S is transported through the heating furnace 2, heat is removed from the slab S through the skid beam, causing the temperature at the contact points of the skid beam to become low, resulting in temperature fluctuations in the longitudinal direction of the slab S, called skid marks. The skid marks extend across the slab in the width direction of the slab S and are formed at a certain pitch along the longitudinal direction of the slab. In the operation of 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 heated insufficiently, to the specified temperature before extraction.

[0023] Therefore, in this embodiment, the charging temperature of the slab S loaded into the heating furnace 2 is measured using a charging temperature measuring meter 7 that measures the temperature of the slab S when it is loaded into the heating furnace 2, and in the heating furnace furnace temperature control device 20, the charging temperature of the slab S loaded into the heating furnace 2 is used as the initial value, and the operating conditions while the slab S is in the heating furnace (operating conditions include the residence time, furnace temperature, skid contact temperature, etc.) are used to calculate the temperature distribution in the length and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2 based on the heat conduction equation that constitutes the slab temperature model, and each fuel flow control unit 23 is controlled to control the fuel flow rate to each combustion burner 3 so that the furnace temperature in the heating furnace 2 is controlled so that the thickness direction temperature at the heating skid portion of the slab S when it is removed from the heating furnace 2, obtained from the calculated temperature distribution in the length and thickness directions at the center of the width of the slab S when it is removed from the heating furnace, exceeds the minimum extraction temperature (e.g., 1200°C).

[0024] Here, the heat conduction equations constituting the slab temperature model are the same as the equations (1) to (7) used in the extraction temperature calculation unit 12 described later.

[0025] However, in the heating furnace temperature control device 20, the predicted values ​​of the temperature distribution in the length and thickness directions of the center of the width of the slab S when removed from the heating furnace 2, calculated based on the heat conduction equation that constitutes the slab temperature model, deviate from the actual measured values, resulting in a problem that it is not possible to accurately predict the temperature distribution in the length and thickness directions of the center of the width of the slab S when removed from the heating furnace 2. Therefore, in this embodiment, as shown in Figure 1, a slab temperature model correction device 10 is connected to the furnace temperature control device 20 of the heating furnace, and this correction device 10 corrects the slab temperature model used in the furnace temperature control device 20, making it possible to accurately predict the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2.

[0026] Here, when correcting the slab temperature model, it is also possible to measure the temperature of the front surface Sa or back surface Sb of the slab S immediately after it is removed from the heating furnace 2, and use the measured value to correct the slab temperature model. However, in general, immediately after removal from the heating furnace 2, it is difficult to measure the temperature using a radiation thermometer due to the influence of scale on the front surface Sa or back surface Sb of the slab S. Therefore, in the slab temperature model correction device 10 according to the present embodiment, a plurality of roughing mills 41 to 4 n By utilizing the temperature measurements taken by a rough temperature gauge 8 installed on the exit side of the furnace, the slab temperature model is modified to accurately predict the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2.

[0027] The slab temperature model correction device 10 is connected to a furnace temperature control device 20 of the heating furnace as shown in Fig. 1. The slab temperature model correction device 10 also includes a charging temperature measuring device 7 that is installed on the inlet side of the heating furnace 2 and measures the charging temperatures of the front surface Sa and the back surface Sb of the slab S charged into the heating furnace 2, and a plurality of roughing mills 41 to 45. n and a rough temperature gauge 8 which is installed on the outlet side of the slab S and measures the temperature distribution in the longitudinal direction at the center of the width of the back surface Sb of the slab S. The charging temperature gauge 7 and the rough temperature gauge 8 are composed of radiation thermometers.

[0028] The internal configuration of the slab temperature model correction device 10 is shown in Figure 2, and the correction device 10 includes a rough temperature acquisition unit 11 connected to the rough temperature measuring device 8, an extraction temperature calculation unit 12 connected to the charging temperature measuring device 7, a rough temperature calculation unit 13, a model correction unit 14, and an output unit 15. The slab temperature model correction device 10 is a computer system with calculation processing capabilities, and executes each of the functions of a rough temperature acquisition unit 11 (step S1 described later), an extraction temperature calculation unit 12 (step S2), a rough temperature calculation unit 13 (step S3), a model correction unit 14 (step S4), and an output unit 15 (step S5) on software in accordance with the instructions of various dedicated computer programs pre-stored in the hardware.

[0029] The rough temperature acquisition unit 11 of the correction device 10 is a plurality of rough rolling mills 41 to 4 n The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S is measured by a rough temperature measuring device 8 installed on the delivery side of the rough rolling mill 41-4. n The temperature of the back surface Sb of the slab S is periodically measured at the exit side, and the results are recorded in a recording unit (not shown), and the rough temperature acquisition unit 11 acquires the results. FIG. 4 shows an example of the temperature distribution in the longitudinal direction at the center of the width of the back surface Sb of the slab S measured by the rough temperature measuring device 8.

[0030] In addition, the extraction temperature calculation unit 12 uses the charging temperature of the slab S loaded into the heating furnace 2 as an initial value, and calculates and outputs the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S at the time of extraction from the heating furnace 2 based on the heat conduction equation that constitutes the slab temperature model, using the operating conditions while the slab S is in the heating furnace (operating conditions include the time it is in the furnace, furnace temperature, skid contact temperature, etc.). The charging temperatures of the front surface Sa and back surface Sb of the slab S when it is charged into the heating furnace 2 are measured by the charging temperature gauge 7, and these measured charging temperatures of the front surface Sa and back surface Sb of the slab S when it is charged into the heating furnace 2 are input to the extraction temperature calculation unit 12. Then, the extraction temperature calculation unit 12 uses the charging temperature of the slab S as an initial value, and calculates and outputs the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 based on the heat conduction equations represented by the following equations (1) to (7) constituting a slab temperature model, using the above-mentioned operating conditions while the slab S is in the heating furnace.

[0031]

number

[0032] Where, ρ: specific gravity [kg / 3 ], C: specific heat [kcal / (kg K)], λ: thermal conductivity [kcal / (m hr K)], θ: temperature [°C], x: length direction coordinate [m], y: thickness direction coordinate [m].

[0033] When calculating the temperature distribution using the heat conduction equation (1), the temperature is differentiated in the time and spatial directions, and boundary conditions are set on the front surface Sa and back surface Sb of the slab S, so that the slab temperature is calculated and output at each time step up to the time of extraction. The boundary conditions set for this heat conduction equation consist of the radiant heat input from the heating furnace 2 to the slab S and the amount of heat removed at the heating furnace skid. The radiative heat input from the surface (upper surface) Sa is expressed by the following equations (2) and (3).

[0034]

number

[0035] The radiant heat input from the back surface (lower surface) Sb is expressed by the following equations (4) and (5).

[0036]

number

[0037] Furthermore, the amount of heat removed from the heating furnace skid is expressed by the following equations (6) and (7).

[0038]

number

[0039] Here, we explain the variables in the boundary conditions: q ui and q Li Each of the upper surface heat loads [kcal / (m 2 ·hr], bottom heat load [kcal / (m 2 ·hr], Φ CGUi and Φ CGLi are the upper surface total heat absorptivity [-], the lower surface total heat absorptivity [-], and θ gU and Φ gL are the upper furnace temperature [℃], θ si is the slab temperature on the top or bottom surface one calculation step before [℃], V i is the shadow factor (correction for skid shadows), Q skd is the amount of heat removed from the skid 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 [℃], θ w is the water temperature in the heating furnace skid [℃]. The information of equations (1) to (7) showing the heat conduction equations is recorded in a recording unit (not shown), and the extraction temperature calculation unit 12 acquires the information of equations (1) to (7) showing the heat conduction equations from the recording unit.

[0040] In addition, the rough temperature calculation unit 13 uses the temperature distribution in the length and thickness directions at the center of the width of the slab S at the time of extraction from the heating furnace 2 output from the extraction temperature calculation unit 12 as an initial value, and calculates and outputs the temperature distribution in the length and thickness directions at the center of the width of the slab S corresponding to the position where the rough temperature measuring device 8 is installed based on the heat conduction equation 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 heat conduction equation is expressed by the following equation (8), which considers only the heat conduction in the thickness direction of the slab S, or by a two-dimensional heat conduction equation that includes the thickness and length directions.

[0041]

number

[0042] Where, ρ: specific gravity [kg / 3 ], C: specific heat [kcal / (kg K)], λ: thermal conductivity [kcal / (m hr K)], θ: temperature [°C], and x: thickness coordinate [m]. The boundary conditions set in this heat conduction equation are set as follows for the air-cooling section, the water-cooling section, and the rolling section. Heat load q in air-cooled section air [kcal / (m 2 ·hr] is expressed by the following equation (9).

[0043]

number

[0044] Here, ε is emissivity [-], θ S : Surface temperature of slab S [℃], θ air :Atmospheric temperature [℃]. In addition, the heat load q of the water-cooled section water [kcal / (m 2 ·hr] is expressed by the following equation (10).

[0045]

number

[0046] Here, α w : Water cooling heat transfer coefficient [kcal / (m 2 ·hr·K)], θ S : Surface temperature of slab S [℃], θ Water :Water temperature [℃]. In addition, for the rolling section, the heat balance of three factors, namely, heat generated by processing, heat removal from roll contact, and heat generated by friction, is taken into consideration. Processing heat generation ΔQ[kcal / (m 3 For [·hr], the following equation (11) is used.

[0047]

number

[0048] Here, P m : Rolling pressure [kgf / mm 2 ], h in : Entrance side plate thickness [mm], h out : exit plate thickness [mm], A: thermal work equivalent 427 [kgfm / kcal], τ: rolling contact time [hr]. In addition, roll contact heat removal q r [kcal / (m 2 ·hr)] is given by the following equation (12).

[0049]

number

[0050] Here, λ S : Thermal conductivity of slab S [kcal / (m hr K)], α rS : Thermal diffusion coefficient of slab S [m 2 / hr], τ: contact temperature of slab S [℃], T m : Equilibrium temperature [℃]. Equilibrium temperature T m is calculated using the following equation (13).

[0051]

number

[0052] Here, α rS = λ S / (ρ S C S ), α rR = λ R / (ρ R C R ), and λ S : Thermal conductivity of 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 [℃], α rR : Thermal diffusivity of the roll [m 2 / hr].

[0053] In addition, frictional heat q μ [kcal / (m 2 ·hr)] is given by the following equation (14).

[0054]

number

[0055] where μ is the friction coefficient [-], P m : Rolling pressure [kgf / mm 2 ], V RM : relative speed between roll and slab S [m / hr], A: heat work equivalent 427 [kgfm / kcal]. Rolling pressure P m is expressed by the following equation (15).

[0056]

number

[0057] Where, P: rolling load [tonf], R': flat roll diameter [mm], h in : Entrance side plate thickness [mm], h out : exit plate thickness [mm], B: plate width of slab S [mm]. Also, the relative velocity V RM is expressed by the following equation (16).

[0058]

number

[0059] Here, V R : roll speed [m / hr], f: forward rate [-], b: reverse rate [-], and the reverse rate b is expressed by the following equation (17).

[0060]

number

[0061] FIG. 5 shows an example of temperature distribution in the longitudinal direction at the widthwise center of the back surface Sb of the slab S, which corresponds to the position where the coarse temperature gauge 8 is installed and is output from the coarse temperature calculation unit 13. The model correction unit 14 also calculates the temperature T cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equations represented by the formulas (1) to (7) constituting the slab temperature model used in the extraction temperature calculation unit 12 is set so that the magnitude (absolute value) of the deviation e from the threshold value ε (1 ° C.) is less than the threshold value ε. CG (Top surface overall heat absorption rate Φ CGUi and the overall heat absorption rate of the bottom surface Φ CGLi The overall heat absorption rate Φ CG is the overall heat absorption rate of the upper surface Φ CGUi and the overall heat absorption rate of the bottom surface ΦCGLi Each of the above means:

[0062] Here, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough temperature calculation unit 13 is cal The model correction unit 14 calculates the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, which is output from the rough temperature calculation unit 13. cal The temperature T at a longitudinal position corresponding to a portion between a specific heating furnace skid section and a heating furnace skid section adjacent to the specific heating furnace skid section cal Select. In addition, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, which is acquired by the rough temperature acquisition unit 11, act The model correction unit 14 calculates the temperature T at the longitudinal position corresponding to the space between the heating furnace skids at the width center of the back surface Sb of the slab S, which is acquired by the rough temperature acquisition unit 11. act The temperature T at a longitudinal position corresponding to the portion between the specific heating furnace skid section and the adjacent heating furnace skid section is act Select.

[0063] Then, the model correction unit 14 calculates the selected temperature T cal and the selected temperature T act Deviation from e=T cal -T act The overall heat absorptance Φ as a calculation parameter included in the heat conduction equations represented by the formulas (1) to (7) constituting the slab temperature model, which are used in the extraction temperature calculation unit 12, is set so that the magnitude (absolute value) of is less than the threshold value ε (1°C). CG Fix. Overall heat absorptivity Φ as a calculation parameter CG A specific method of making the correction will be described later with reference to the flowchart showing the details of the process flow in step S4 (model correction step) shown in FIG. The output unit 15 of the correction device 10 outputs the overall heat absorptance Φ CGThe information on the heat conduction equations (equations (1) to (7)) constituting the modified slab temperature model is output to the slab temperature prediction unit 21 of the furnace temperature control device 20 of the heating furnace.

[0064] 3, the furnace temperature control device 20 of the heating furnace includes a slab temperature prediction unit 21 and a furnace temperature control unit 22. The furnace temperature control device 20 is a computer system having a calculation function, and executes the functions of the slab temperature prediction unit 21 (step S11 described later) and the furnace temperature control unit 22 (step S12) on software in accordance with the commands of various dedicated computer programs pre-stored in the hardware. The slab temperature prediction unit 21 obtains information about 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 predict the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2.

[0065] 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 into the heating furnace 2 measured by the charging temperature measuring instrument 7 as initial values, and uses the operating conditions described above while the slab S is in the heating furnace to calculate the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S at the time of removal from the heating furnace 2 based on the heat conduction equations (equations (1) to (7)) that constitute the corrected slab temperature model obtained from the output section 15 of the correction device 10, and uses this calculated value as a predicted value. In addition, the furnace temperature control unit 22 controls the furnace temperature in the heating furnace 2 so that the temperature distribution in the length and thickness directions at the center of the width during extraction from the heating furnace 2 predicted by the slab temperature prediction unit 21 exceeds the minimum extraction temperature (e.g., 1200°C).

[0066] Specifically, the furnace temperature control unit 22 controls each fuel flow rate control unit 23 to control the fuel flow rate to each combustion burner 3 and controls the furnace temperature in the heating furnace 2 so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion and between the heating furnace skids at the center of the width of the slab S at the time of extraction from the heating furnace 2 predicted by the slab temperature prediction unit 21 becomes a target temperature that exceeds the minimum extraction temperature (e.g., 1200°C).

[0067] As a result, when the slab S is extracted from the heating furnace 2, the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid section and between the heating furnace skids at the center of the width exceeds the minimum extraction temperature, and the contact points of the skid beam, which tend to be insufficiently heated, can be raised to the specified temperature and extracted.This prevents poor material properties of the hot-rolled coil due to insufficient heating of the heating furnace skid section and reduces the heating unit consumption due to overheating operation.

[0068] In this way, according to the slab temperature model correction device 10 of this embodiment, the rough temperature acquisition unit 11 acquires the rough temperature of the plurality of rough rolling mills 41 to 4 n The longitudinal temperature distribution at the width center of the back surface Sb of the slab S measured by the rough temperature gauge 8 installed on the outlet side of the heating furnace 2 is acquired, and in the extraction temperature calculation unit 12, the charging temperature of the slab S charged into the heating furnace 2 is set as an initial value, and the temperature distribution in the longitudinal and thickness directions at the width center of the slab S at the time of extraction from the heating furnace 2 is calculated based on the heat conduction equations (Equations (1) to (7)) constituting the slab temperature model, using the operating conditions during the time the slab S is in the heating furnace, and output. Then, in the rough temperature calculation unit 13, the longitudinal and thickness direction temperature distribution at the width center of the slab S at the time of extraction from the heating furnace 2 outputted from the extraction temperature calculation unit 12 is set as an initial value, and the temperature distribution in the longitudinal and thickness directions at the width center of the slab S corresponding to the position where the rough temperature gauge 8 is installed is calculated based on the heat conduction equations (Equations (8) to (17)), using the operating conditions during rough rolling of the slab S extracted from the heating furnace 2, and output. Then, in the model correction unit 14, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough temperature calculation unit 13 is calculated. caland the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equations (Equations (1) to (7)) constituting the slab temperature model used in the extraction temperature calculation unit 12 is set so that the deviation e from the threshold value (1°C) is less than the threshold value (1°C). CG Fix.

[0069] As a result, when using the slab temperature model to predict the temperature distribution in the length and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2, by modifying the slab temperature model, it is possible to accurately predict the temperature distribution in the length and thickness directions at the center of the width of the slab when it is removed from the heating furnace 2.

[0070] In addition, in the correction of the slab temperature model, the model correction unit 14 corrects the slab temperature model by using a plurality of roughing mills 41 to 4 n Since the slab temperature model is corrected using temperature measurements taken by a rough temperature gauge 8 installed at the exit of the heating furnace 2, there is no need to measure the temperature of the slab S immediately after it is removed from the heating furnace 2 by a radiation thermometer installed immediately after the exit of the heating furnace 2. Immediately after it is removed from the heating furnace 2, it is difficult to measure the temperature due to the effect of scale on the surface of the slab S, but this is not a problem when using the correction device 10 according to this embodiment. According to the furnace temperature control device 20 of the heating furnace of this embodiment, the slab temperature prediction unit 21 predicts the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S at the time of extraction from the heating furnace 2 using the slab temperature model corrected by the slab temperature model correction device 10, and the furnace temperature control unit 22 controls the furnace temperature in the heating furnace 2 so that the temperature of the temperature distribution in the longitudinal and thickness directions at the center of the width of the heating furnace 2 at the time of extraction predicted by the slab temperature prediction unit 21 exceeds the minimum extraction temperature.

[0071] As a result, when the slab S is extracted from the heating furnace 2, the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid section and between the heating furnace skids at the center of the width exceeds the minimum extraction temperature, and the contact points of the skid beam, which tend to be insufficiently heated, can be raised to the specified temperature and extracted.This prevents poor material properties of the hot-rolled coil due to insufficient heating of the heating furnace skid section and reduces the heating unit consumption due to overheating operation.

[0072] Next, a method for correcting a slab temperature model in one embodiment of the present invention will be described with reference to a flowchart for explaining the processing flow in the slab temperature model correction device shown in Figure 6, and a flowchart showing the processing flow in step S4 (model correction step) in the flowchart shown in Figure 6, shown in Figure 7.

[0073] First, in step S1, the rough temperature acquisition unit 11 of the correction device 10 acquires the temperature of the rough rolling mills 41 to 4 n The temperature distribution in the length direction at the width center of the back surface Sb of the slab S is measured by a rough temperature measuring device 8 installed on the exit side of the slab S (rough temperature acquisition step).

[0074] Next, in step S2, the extraction temperature calculation unit 12 of the correction device 10 uses the charging temperature of the slab S loaded into the heating furnace 2 as an initial value, and calculates and outputs the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S at the time of extraction from the heating furnace 2 based on the heat conduction equation that constitutes the slab temperature model, using the operating conditions while the slab S is in the heating furnace (operating conditions include the residence time, furnace temperature, skid contact temperature, etc.) (extraction temperature calculation step). The charging temperatures of the front surface Sa and back surface Sb of the slab S when it is charged into the heating furnace 2 are measured by the charging temperature gauge 7, and these measured charging temperatures of the front surface Sa and back surface Sb of the slab S when it is charged into the heating furnace 2 are input to the extraction temperature calculation unit 12. Then, the extraction temperature calculation unit 12 uses the charging temperature of the slab S as an initial value, and calculates and outputs the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 based on the heat conduction equations represented by the above-mentioned equations (1) to (7) constituting the slab temperature model, using the above-mentioned operating conditions while the slab S is in the heating furnace.

[0075] When calculating the temperature distribution using the heat conduction equation (1), the temperature is differentiated in the time and spatial directions, and boundary conditions are set on the front surface Sa and back surface Sb of the slab S, so that the slab temperature is calculated and output at each time step up to the time of extraction. The boundary conditions set for this heat conduction equation consist of the radiant heat input from the heating furnace 2 to the slab S and the amount of heat removed at the heating furnace skid. The radiant heat input from the surface (upper surface) Sa is expressed by the above-mentioned formulas (2) and (3). Moreover, the radiant heat input from the back surface (lower surface) Sb is expressed by the above-mentioned formulas (4) and (5). Furthermore, the amount of heat removed from the skid of the heating furnace is expressed by the above-mentioned formulas (6) and (7).

[0076] Next, in step S3, the rough temperature calculation unit 13 of the correction device 10 uses the temperature distribution in the length and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2, output in step S2, as an initial value, and calculates and outputs the temperature distribution in the length and thickness directions at the center of the width of the slab S corresponding to the position where the rough temperature measuring device 8 is installed, based on the heat conduction equation, using the operating conditions (operating conditions include rolling load, rolling speed, cooling, etc.) when rough rolling the slab S removed from the heating furnace 2 (rough temperature calculation step). The heat conduction equation is expressed by the aforementioned equation (8), which only considers heat conduction in the thickness direction of the slab S, or by a two-dimensional heat conduction equation that includes the thickness and length directions. Moreover, the boundary conditions set in the heat conduction equation (8) are set according to the air-cooling section, the water-cooling section, and the rolling section, as described above. Heat load q in air-cooled section air [kcal / (m 2 ·hr] is expressed by the above-mentioned equation (9). In addition, the heat load q of the water-cooled section water [kcal / (m 2 ·hr] is expressed by the above-mentioned equation (10). In addition, for the rolling section, the heat balance of three factors, namely, heat generated by processing, heat removal from roll contact, and heat generated by friction, is taken into consideration. Processing heat generation ΔQ[kcal / (m 3 For [·hr], use the above-mentioned equation (11). In addition, roll contact heat removal q r [kcal / (m 2 ·hr)] is given by the above equation (12). Equilibrium temperature [℃]. Equilibrium temperature T m is calculated using the above formula (13). In addition, frictional heat q μ [kcal / (m 2 ·hr)] is given by the above-mentioned equation (14). Rolling pressure P m is expressed by the above-mentioned equation (15). Also, the relative velocity V RM is expressed by the above-mentioned equation (16). Also, the backward rate b is expressed by the above-mentioned equation (17).

[0077] Next, in step S4, the model correction unit 14 calculates the temperature T cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, obtained in step S1. act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equations represented by equations (1) to (7) constituting the slab temperature model used in step S2 is set so that the magnitude (absolute value) of the deviation e from the threshold value ε (1°C) is less than the threshold value ε. CG (Top surface overall heat absorption rate Φ CGUiand the overall heat absorption rate of the bottom surface Φ CGLi ) (model correction step).

[0078] The process in step S4 will be described in detail with reference to FIG. First, in step S41, the model correction unit 14 calculates the temperature T cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, obtained in step S1. act Calculate the deviation e from this.

[0079] Here, the model correction unit 14 calculates the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output in step S3. cal The temperature T at a longitudinal position corresponding to a portion between a specific heating furnace skid section and a heating furnace skid section adjacent to the specific heating furnace skid section cal Select. In addition, the model correction unit 14 calculates the temperature T at the longitudinal position corresponding to the space between the heating furnace skids at the width center of the back surface Sb of the slab S, which is obtained in step S1. act The temperature T at a longitudinal position corresponding to the portion between the specific heating furnace skid section and the adjacent heating furnace skid section is act Select. Then, the model correction unit 14 calculates the selected temperature T cal and the selected temperature T act Deviation from e=T cal -T act Calculate.

[0080] Next, in step S42, the model correction unit 14 determines whether or not the magnitude (absolute value) of the deviation e calculated in step S41 is less than a threshold value ε (=1° C.).

[0081] If the determination result in step S42 is NO (deviation e is not less than threshold value ε), the process proceeds to step S43, and if the determination result in step S42 is YES (deviation e is less than threshold value ε), the process proceeds to step S49. In step S43, the model correction unit 14 calculates the upper surface overall heat absorptance Φ CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi are the overall heat absorption rates Φ CG and the overall heat absorption rate Φ CG The total heat absorption rate Φ after a small change CG '=Φ CG Set to +δ.

[0082] Next, in step S44, the model correction unit 14 calculates the overall heat absorptance Φ after the small change. CG ' is used to recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 in step S2, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 was installed in step S3 is recalculated, and the temperature T cal ' is calculated.

[0083] Next, in step S45, the model correction unit 14 corrects the temperature T cal and the temperature T calculated in step S44 cal From the small change amount δ set in step 43, the influence coefficient ∂T cal / ∂Φ CG =(T cal '-T cal ) / δ.

[0084] Next, in step S46, the model correction unit 14 calculates the overall heat absorption rate Φ CG (The upper surface total heat absorption coefficient Φ in the above formula (3) CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi (each of these) is Φ CG ''=ΦCG -e / (∂T cal / ∂Φ CG ) to update.

[0085] Next, in step S47, the model correction unit 14 calculates the updated overall heat absorption rate Φ CG ''(=Φ CG -e / (∂T cal / ∂Φ CG ) is used to recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 in step S2, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 was installed in step S3 is recalculated, and the temperature T cal '' is calculated.

[0086] Next, in step S48, the model correction unit 14 calculates the deviation e calculated in step S41 as deviation e=T cal ''-T act to update. Then, the process returns to step S42, where the model correction unit 14 determines whether the deviation e updated in step S48 is less than the threshold value ε (=1° C.) or not. Then, steps S42 to S48 are repeated until the determination result in step S42 becomes YES. If the result of the determination in step S42 is YES, the process proceeds to step S49, and the overall heat absorptance when the deviation e becomes less than the threshold value ε (=1° C.) is calculated as the overall heat absorptance Φ CG (The upper surface total heat absorption coefficient Φ in the above formula (3) CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi (respectively).

[0087] This completes the process in step S4, and the overall heat absorption rate Φ CG This would be an appropriate correction. Then, in step S5, the output unit 15 of the correction device 10 calculates the overall heat absorptance ΦCG The information on the heat conduction equations (equations (1) to (7)) constituting the modified slab temperature model is output to the slab temperature prediction unit 21 of the furnace temperature control device 20 of the heating furnace (output step). This completes the process in the slab temperature model correction device 10.

[0088] As described above, according to the method for correcting the slab temperature model according to the present embodiment, in the rough temperature acquisition step (step S1), n The temperature distribution in the length direction at the width center of the back surface Sb of the slab S measured by the rough temperature measuring device 8 installed on the outlet side of the heating furnace 2 is acquired, and in an extraction temperature calculation step (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 from the heating furnace 2 is calculated based on the heat conduction equations (equations (1) to (7)) constituting the slab temperature model, using the operating conditions during the time when the slab S is in the heating furnace, and output. Then, in a rough 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 from the heating furnace 2 outputted in the extraction temperature calculation step (step S2) is calculated based on the heat conduction equations (equations (8) to (17)), using the operating conditions during rough rolling of the slab S extracted from the heating furnace 2, as the initial value, and output. Then, in the model correction step (step S4), the temperature T at the longitudinal position corresponding to the space between the heating furnace skids at the width center of the back surface Sb of the slab S output in the rough temperature calculation step (step S3) is calculated. cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, which is acquired in the rough temperature acquisition step (step S1). act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equations (Equations (1) to (7)) constituting the slab temperature model used in the extraction temperature calculation step (step S2) is set so that the deviation e from the threshold value (1°C) is less than the threshold value (1°C). CG Fix.

[0089] As a result, when using the slab temperature model to predict the temperature distribution in the length and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2, by modifying the slab temperature model, it is possible to accurately predict the temperature distribution in the length and thickness directions at the center of the width of the slab when it is removed from the heating furnace 2.

[0090] In addition, in the correction of the slab temperature model, in the model correction step (step S4), n Since the slab temperature model is corrected using temperature measurements taken by a rough temperature gauge 8 installed at the exit of the heating furnace 2, there is no need to measure the temperature of the slab S immediately after it is removed from the heating furnace 2 by a radiation thermometer installed immediately after the exit of the heating furnace 2. Immediately after it is removed from the heating furnace 2, it is difficult to measure the temperature due to the effect of scale on the surface of the slab S, but this is not a problem when using the correction device 10 according to this embodiment.

[0091] Next, a method for controlling the temperature of a heating furnace according to one embodiment of the present invention will be described with reference to a flowchart shown in FIG. 8 for explaining the flow of processing in a furnace temperature control device for a heating furnace.

[0092] First, in step S11, the slab temperature prediction unit 21 of the furnace temperature control device 20 acquires information of 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 to predict the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S when it is removed from the heating furnace 2 (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 into the heating furnace 2 measured by the charging temperature measuring instrument 7 as initial values, and uses the operating conditions described above while the slab S is in the heating furnace to calculate the temperature distribution in the longitudinal and thickness directions at the center of the width of the slab S at the time of removal from the heating furnace 2 based on the heat conduction equations (equations (1) to (7)) that constitute the corrected slab temperature model obtained from the output section 15 of the correction device 10, and uses this calculated value as a predicted value.

[0093] Next, in step S12, the furnace temperature control unit 22 of the furnace temperature control device 20 controls each fuel flow control unit 23 to control the fuel flow rate to each combustion burner 3 and control the furnace temperature in the heating furnace 2 so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion and between the heating furnace skids at the center of the width of the slab S at the time of extraction from the heating furnace 2 predicted in the slab temperature prediction step (step S11) becomes a target temperature higher than the minimum extraction temperature (e.g., 1200°C).

[0094] Thus, according to the furnace temperature control method of this embodiment, in a slab temperature prediction step (step S11), the longitudinal and thickness direction temperature distributions at the width center of the slab S at the time of extraction from the heating furnace 2 are predicted using the slab temperature model corrected by the slab temperature model correction method, and in a furnace temperature control step (step S12), each fuel flow rate control unit 23 is controlled to control the fuel flow rate to each combustion burner 3 so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion and between the heating furnace skids at the width center of the slab S at the time of extraction from the heating furnace 2 predicted in the slab temperature prediction step (step S11) exceeds the minimum extraction temperature, thereby controlling the furnace temperature in the heating furnace 2.

[0095] As a result, when the slab S is extracted from the heating furnace 2, the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid section and between the heating furnace skids at the center of the width exceeds the minimum extraction temperature, and the contact points of the skid beam, which tend to be insufficiently heated, can be raised to the specified temperature and extracted.This prevents poor material properties of the hot-rolled coil due to insufficient heating of the heating furnace skid section and reduces the heating unit consumption due to overheating operation.

[0096] Next, a process performed by a modified example of the model correction unit 14 will be described with reference to FIGS.

[0097] In the model correction unit 14, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough temperature calculation unit 13 is caland the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equations (Equations (1) to (7)) constituting the slab temperature model used in the extraction temperature calculation unit 12 is set so that the deviation e from the threshold value (1°C) is less than the threshold value (1°C). CG has been fixed.

[0098] In this model correction unit 14, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough temperature calculation unit 13 is calculated. cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act When the magnitude (absolute value) of the deviation e from the specified value α is larger than the specified value α as shown in FIG. 10, the magnitude (absolute value) of the deviation e (corrected deviation e') exceeding the specified value α is set to be less than the above-mentioned threshold value. CG Fix.

[0099] The processing by this modified example of the model correction unit 14 will be described with reference to FIG. 11. First, in step S401, the model correction unit 14 calculates the temperature T cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, obtained in step S1. act Calculate the deviation e from this.

[0100] Next, in step S402, the model correction unit 14 converts the deviation e calculated in step S401 into a corrected deviation e'. The corrected deviation e' is expressed as e'=f(e)=deviation e-prescribed value α.

[0101] Next, in step S403, the model correction unit 14 determines whether or not the magnitude (magnitude of the absolute value) of the corrected deviation e' converted in step S402 is less than a threshold value ε (=1° C.). If the determination result in step S403 is NO (the corrected deviation e' is not less than the threshold value ε), the process proceeds to step S404, and if the determination result in step S403 is YES (the corrected deviation e' is less than the threshold value ε), the process proceeds to step S410. In step S404, the model correction unit 14 calculates the upper surface overall heat absorptance Φ CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi are the overall heat absorption rates Φ CG and the overall heat absorption rate Φ CG The total heat absorption rate Φ after a small change CG '=Φ CG Set to +δ.

[0102] Next, in step S405, the model correction unit 14 calculates the overall heat absorptance Φ after the small change. CG ' is used to recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 in step S2, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 was installed in step S3 is recalculated, and the temperature T cal ' is calculated.

[0103] Next, in step S406, the model correction unit 14 corrects the temperature T cal and the temperature T calculated in step S405 cal From the small change amount δ set in step 404, the influence coefficient ∂T cal / ∂Φ CG =(T cal '-T cal ) / δ.

[0104] Next, in step S407, the model correction unit 14 calculates the overall heat absorption rate ΦCG (The upper surface total heat absorption coefficient Φ in the above formula (3) CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi (each of these) is Φ CG ''=Φ CG -e / (∂T cal / ∂Φ CG ) to update.

[0105] Next, in step S408, the model correction unit 14 calculates the updated overall heat absorption rate Φ CG ''(=Φ CG -e / (∂T cal / ∂Φ CG ) is used to recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 in step S2, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 was installed in step S3 is recalculated, and the temperature T cal '' is calculated.

[0106] Next, in step S409, the model correction unit 14 calculates the deviation e calculated in step S401 as deviation e=T cal ''-T act to update. Then, returning to step S402, in step S402, the model correction unit 14 converts the deviation e updated in step S409 into a corrected deviation e', and in step S403, it is determined whether the magnitude (absolute value) of the corrected deviation e' is less than the threshold value ε (=1°C). Then, steps S402 to S409 are repeated until the determination result in step S403 becomes YES. If the result of the determination in step S403 is YES, the process proceeds to step S410, and the overall heat absorptance when the corrected deviation e' becomes less than the threshold value ε (=1° C.) is calculated as the overall heat absorptance Φ CG (The upper surface total heat absorption coefficient Φ in the above formula (3) CGUi and the overall heat absorption coefficient Φ on the bottom surface in Eq. (5) CGLi(respectively).

[0107] This completes the process according to the modified example of the model correction unit 14, and the overall heat absorption rate Φ CG This would be an appropriate correction.

[0108] According to this modified example of the model correction unit 14, the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough temperature calculation unit 13 is cal and the temperature T at the longitudinal position corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act When the magnitude (absolute value) of the deviation e from the specified value α is greater than the specified value α, the magnitude (absolute value) of the deviation e (corrected deviation e') that exceeds the specified value α is less than the threshold value. CG Fix. This results in an overall heat absorption rate of Φ CG This can absorb the error contained in

[0109] In addition, the method for producing a steel sheet 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 furnace temperature control method for the heating furnace. The slab S is heated by the heating furnace 2 whose furnace temperature is controlled by this furnace temperature control step, and extracted from the heating furnace 2. The slab S is then subjected to rolling by a plurality of (n in this embodiment) rough rolling mills 41 to 42. n After being rough-rolled in a rough rolling process by a rolling mill (not shown), the steel sheet is finish-rolled in a finish rolling process by a finishing mill (not shown) to become a thin steel sheet. This steel sheet is then cooled in a cooling facility 5 in a cooling process, and wound into a coil by a winding device 6 in a winding process to be manufactured.

[0110] Although the embodiment of the present invention has been described above, the present invention is not limited to this and various modifications and improvements can be made. For example, in the extraction temperature calculation unit 12 (step S2), the temperature distribution in the length and thickness directions at the center of the width of the slab S when it is extracted from the heating furnace 2 is calculated, but it is sufficient to calculate a temperature distribution including the length and thickness directions at least at the center of the width of the slab S, and it is not limited to the length and thickness directions at the center of the width of the slab S, and it is also possible to calculate the temperature distribution in the width, length and thickness directions of the slab S, for example.

[0111] Furthermore, in the coarse temperature calculation unit 13 (step S3), the temperature distribution in the length and thickness directions at the center of the width of the slab S corresponding to the position where the coarse temperature measurement device 8 is installed is calculated. However, it is sufficient to calculate a temperature distribution including the length and thickness directions at least at the center of the width of the slab S corresponding to the position where the coarse temperature measurement device 8 is installed, and it is not limited to the length and thickness directions at the center of the width of the slab S, but it is also possible to calculate the temperature distribution in the width, length and thickness directions of the slab S, for example.

[0112] Furthermore, in the slab temperature prediction unit 21 (step S11), the temperature distribution in the length direction and thickness direction at the width center of the slab S when it is removed from the heating furnace 2 is predicted, but it is sufficient to predict the temperature distribution including the length direction and thickness direction at least at the width center of the slab S when it is removed from the heating furnace 2 using the corrected slab temperature model, and it is also possible to predict the temperature distribution in the width direction, length direction and thickness direction of the slab S, for example, without being limited to the length direction and thickness direction at the width center of the slab S. In other words, the slab temperature model correction device 10 heats the slab S in the heating furnace 2, and passes the slab S removed from the heating furnace 2 through multiple rough rolling mills 41-4. n The present invention modifies a slab temperature model used to predict the temperature distribution including the length direction and thickness direction at least in the width center portion of the slab S when it is removed from the heating furnace 2 during rough rolling at 300° C.

[0113] The rough temperature measuring device 8 is connected to a plurality of rough rolling mills 41 to 4 n The roughing mills 41-4 are installed at the exit side of the rolling mill. n Adjacent roughing mills 41-4 nIn this case, the rough temperature acquisition unit 11 may be installed between the rough rolling mills 41 to 4. n Adjacent roughing mills 41-4 n The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S is measured by a coarse temperature measuring device 8 installed between the slab S and the back surface Sb.

[0114] The coarse temperature gauge 8 may measure the temperature distribution in the longitudinal direction at the center of the width of the front surface Sa of the slab S, instead of the back surface Sb of the slab S. In this case, the coarse temperature acquisition unit 11 acquires the temperature distribution in the longitudinal direction at the center of the width of the front surface Sa of the slab S measured by the coarse temperature gauge 8. In this case, the model correction unit 14 calculates the temperature T cal and the temperature T at the longitudinal position corresponding to the heating furnace skid at the width center of the slab surface Sa acquired by the rough temperature acquisition unit 11. act The overall heat absorption rate Φ as a calculation parameter included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation unit 12 is set so that the deviation e from the threshold value is less than the threshold value. CG Fix.

[0115] In addition, the calculation parameters included in the heat conduction equation corrected by the model correction unit 14 (model correction step: step S4) are the overall heat absorption rate Φ CG Calculation parameters other than, for example, the skid contact heat transfer coefficient α skd [kcal / (m 2 ·hr·K] may also be used. EXAMPLES

[0116] In order to verify the effect of the present invention, in the hot rolling line 1 shown in FIG. 1, a slab S having a thickness of 215 mm was heated to about 1100° C. in a heating furnace 2, and then, the slab S was rolled by a plurality of rough rolling mills 41 to 4. n The steel sheets were then rolled into 35 mm thick steel plates (slabs S) by multiple rough rolling mills 41-44. nThe temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S was measured by a rough temperature measuring instrument 8 installed on the outlet side of the slab S.

[0117] As a result, the temperature T at a longitudinal position corresponding to a specific heating furnace skid portion at the width center of the back surface Sb of the slab S and a heating furnace skid portion adjacent to this specific heating skid portion, which is measured by the rough temperature measuring device 8 and acquired by the rough temperature acquisition unit 11, is act The temperature T at the longitudinal position corresponding to the area between the specific heating furnace skid portion and the heating furnace skid portion adjacent to the specific heating skid portion at the width center portion of the back surface Sb of the slab S, which was output from the rough temperature calculation unit 13, was 900°C. cal was 888.9.

[0118] For this reason, the model correction unit 14 of the correction device 10 calculates the temperature T cal = 888.9°C and the temperature T acquired by the rough temperature acquisition unit 11 act = 900℃ deviation e=T cal -T act =-11.1℃ was calculated.

[0119] Then, the model correction unit 14 calculates the overall heat absorption rate Φ CG (Top surface overall heat absorption rate Φ CGUi and the overall heat absorption rate of the bottom surface Φ CGLi Although the values ​​of are different, they are collectively called the overall heat absorption rate Φ CG (a method of correcting the deviation e was adopted), it was determined whether the magnitude (absolute value) of the calculated deviation e was less than a threshold value ε (=1° C.).

[0120] The magnitude (absolute value) of the deviation e is 11.1° C., which is greater than the threshold value of 1° C., and the judgment result is NO. Therefore, the model correction unit 14 corrects the overall heat absorption rate Φ CG The total heat absorption rate Φ after a small change CG '=Φ CG Set it to +0.1.

[0121] Then, the model correction unit 14 calculates the overall heat absorption rate Φ CG' = Φ CG +0.1, the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of removal from the heating furnace 2 is recalculated, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 is installed is recalculated, and the temperature T cal As a result, the temperature T cal ' was 895.6°C.

[0122] Then, the model correction unit 14 calculates the temperature T cal = 888.9℃ and temperature T cal '=895.6℃ and the small change in the overall heat absorption rate δ=0.1, the influence coefficient ∂T cal / ∂Φ CG =(T cal '-T cal ) / δ=67.

[0123] Next, the model correction unit 14 calculates the overall heat absorption rate Φ CG Φ CG ''=Φ CG -e / (∂T cal / ∂Φ CG )=Φ CG Updated to -11.1 / 67.

[0124] Next, the model correction unit 14 calculates the updated overall heat absorption rate Φ CG ''(=Φ CG -11.1 / 67) was used to recalculate the temperature distribution in the length direction and thickness direction at the width center of the slab S when it was removed from the heating furnace 2, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S corresponding to the position where the rough temperature measuring device 8 was installed was recalculated, and the temperature T cal The calculated temperature was 899.7°C.

[0125] Next, the model correction unit 14 corrects the deviation e=-11.1°C to deviation e=T cal ''-T act =899.7℃-900℃=-0.3℃.

[0126] Then, the model correction unit 14 judges whether the updated deviation e=-0.3 (absolute value is 0.3) is less than the threshold value ε (=1°C) or not. Since the judgment result is YES, the updated overall heat absorption rate Φ CG ''(=Φ CG -11.1 / 67) is the overall heat absorption rate Φ CG It was decided. This completes the process in the model correction unit 14, and the appropriate overall heat absorption rate Φ CG was required.

[0127] Furthermore, the material quality in the longitudinal direction of the hot-rolled coil manufactured by the manufacturing method of the steel sheet according to the present invention was more uniform than when the method of the present invention was not applied, confirming the effect of the present invention. [Explanation of symbols]

[0128] 1. Hot rolling line 2 heating furnace 21~2 n Combustion Control Zone 3 Combustion burner 41~4 n rough rolling mill 5 Cooling equipment 6 Winding device 7 Charging temperature meter 8 Crude temperature meter 10. Slab temperature model correction device 11 Rough temperature acquisition section 12 Extraction temperature calculation section 13 Crude temperature calculation section 14 Model Modification Section 15 Output section 20 Furnace temperature control device 21 Slab temperature prediction section 22 Furnace temperature control unit 23 Fuel flow control unit S slab Sa surface Sb back side

Claims

1. A slab temperature model correction device used to predict a temperature distribution including a length direction and a thickness direction at least in a width center portion of a slab when the slab is extracted from the heating furnace, when the slab is heated in the heating furnace and the slab extracted from the heating furnace is rough rolled by a plurality of rough rolling mills, A rough temperature acquisition unit that acquires a longitudinal temperature distribution at a width center portion of the front or back surface of the slab measured by a rough temperature measuring device installed between adjacent rough rolling mills or at the exit side of the rough rolling mills; an extraction temperature calculation unit that calculates and outputs a temperature distribution including the length direction and the thickness direction at least in the width center part of the slab when the slab is extracted from the heating furnace based on a heat conduction equation constituting the slab temperature model, using the operation conditions of the slab while it is in the heating furnace, with the charging temperature of the slab being an initial value when the slab is charged into the heating furnace; A rough temperature calculation unit that calculates and outputs a temperature distribution including the length direction and the thickness direction at least in the width center of the slab corresponding to the position where the rough temperature measuring device is installed based on a heat conduction equation using the operating conditions when rough rolling the slab extracted from the heating furnace, using the temperature distribution including the length direction and the thickness direction at least in the width center of the slab at the time of extraction from the heating furnace outputted from the extraction temperature calculation unit as an initial value. a model correction unit that corrects calculation parameters included in a heat conduction equation constituting the slab temperature model used in the extraction temperature calculation unit so that the magnitude of deviation between the temperature at the longitudinal position corresponding to the heating furnace skids at the width center of the front or back surface of the slab output from the rough temperature calculation unit and the temperature at the longitudinal position corresponding to the heating furnace skids at the width center of the front or back surface of the slab acquired by the rough temperature acquisition unit is less than a threshold value; The apparatus for correcting a slab temperature model is characterized in that the calculation parameter is an overall heat absorption rate.

2. The slab temperature model correction device of claim 1, characterized in that, when the magnitude of the deviation between the temperature at the longitudinal position corresponding to the heating furnace skids at the center of the width of the front or back surface of the slab output from the rough temperature calculation unit and the temperature at the longitudinal position corresponding to the heating furnace skids at the center of the width of the front or back surface of the slab acquired by the rough temperature acquisition unit is greater than a specified value, the model correction unit corrects the calculation parameters included in the heat conduction equation that constitutes the slab temperature model used in the extraction temperature calculation unit so that the magnitude of the deviation exceeding the specified value is less than the threshold value.

3. A furnace temperature control device for a heating furnace, characterized in that it comprises: a slab temperature prediction unit that predicts a temperature distribution including the length and thickness directions at least in the width center of the slab when removed from the heating furnace using a slab temperature model corrected by the slab temperature model correction device described in claim 1 or 2; and a furnace temperature control unit that controls the furnace temperature within the heating furnace so that the temperature of the temperature distribution including the length and thickness directions at least in the width center of the slab when removed from the heating furnace predicted by the slab temperature prediction unit exceeds a minimum extraction temperature.

4. A method for correcting a slab temperature model used to predict a temperature distribution including a length direction and a thickness direction at least in a width center portion of a slab when the slab is extracted from the heating furnace, in which the slab is heated in a heating furnace and the slab extracted from the heating furnace is rough rolled by a plurality of rough rolling mills, A rough temperature acquisition step of acquiring a longitudinal temperature distribution at a width center portion of the front or back surface of the slab measured by a rough temperature measuring device installed between adjacent rough rolling mills or at the exit side of the rough rolling mills; an extraction temperature calculation step of calculating a temperature distribution including a length direction and a thickness direction of the slab at least in the width center part of the slab when the slab is extracted from the heating furnace based on a heat conduction equation constituting the slab temperature model, using the operation conditions of the slab while it is in the heating furnace, with the charging temperature of the slab being an initial value; and A rough temperature calculation step of calculating and outputting a temperature distribution including the length direction and thickness direction at least in the width center of the slab corresponding to the position where the rough temperature measuring device is installed based on a heat conduction equation using the operating conditions for rough rolling the slab extracted from the heating furnace, using the temperature distribution including the length direction and thickness direction at least in the width center of the slab when extracted from the heating furnace outputted in the extraction temperature calculation step as an initial value; and a model correction step of correcting a calculation parameter included in a heat conduction equation constituting the slab temperature model used in the extraction temperature calculation step so that the magnitude of deviation between the temperature at the longitudinal position corresponding to the space between the heating furnace skids at the width center of the front or back surface of the slab output in the rough temperature calculation step and the temperature at the longitudinal position corresponding to the space between the heating furnace skids at the width center of the front or back surface of the slab acquired in the rough temperature acquisition step is less than a threshold value; A method for correcting a slab temperature model, wherein the calculation parameter is an overall heat absorption rate.

5. The slab temperature model correction method described in claim 4, characterized in that in the model correction step, when the magnitude of the deviation between the temperature at the longitudinal position corresponding to the heating furnace skids at the center of the width of the front or back side of the slab output in the rough temperature calculation step and the temperature at the longitudinal position corresponding to the heating furnace skids at the center of the width of the front or back side of the slab acquired in the rough temperature acquisition step is greater than a specified value, the calculation parameters included in the heat conduction equation constituting the slab temperature model used in the extraction temperature calculation step are corrected so that the magnitude of the deviation exceeding the specified value is less than the threshold value.

6. A furnace temperature control method for a heating furnace, comprising: a slab temperature prediction step of predicting a temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace using a slab temperature model corrected by the slab temperature model correction method described in claim 4 or 5; and a furnace temperature control step of controlling the furnace temperature in the heating furnace so that the temperature of the temperature distribution including the length and thickness directions at least in the width center of the slab when extracted from the heating furnace predicted in the slab temperature prediction step exceeds a minimum extraction temperature.

7. A method for manufacturing a steel sheet, comprising: a furnace temperature control step of controlling a furnace temperature in a heating furnace by the method for controlling a furnace temperature of a heating furnace according to claim 6.

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