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

Description

[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.

[0006] Conventionally, methods for operating a heating furnace are known, for example, as shown in Patent Documents 1 and 2. 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.

[0007] 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.

[0008] 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]

[0009] [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]

[0010] 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. Therefore, the actual temperature distribution between the skids and the skid part of the slab in the furnace may deviate from the predicted temperature distribution between the skids and the skid part of the slab in the furnace, and 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.

[0011] 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.

[0012] Therefore, the present invention has been made to solve these conventional problems, and its object is to provide a slab temperature model correction device, a correction method, a furnace temperature control device for a heating furnace, a furnace temperature control method, and a manufacturing method of steel plate, which are capable of accurately predicting the temperature distribution including the longitudinal and thickness directions at least in the width center portion of the slab when it is removed from the heating furnace by correcting the slab temperature model. [Means for solving the problem]

[0013] In order to solve the above-mentioned 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 a length direction and a thickness direction in at least a width center portion of the slab at the time of removal from the heating furnace when a slab is heated in a heating furnace and the slab extracted from the heating furnace is rough rolled in a rough rolling mill, the device comprising: a rough temperature acquisition unit that acquires a length direction temperature distribution in the width center portion of the back surface of the slab after rough rolling, measured by a rough temperature measurement device installed on the outlet side of the rough rolling mill; an extraction temperature calculation unit that calculates and outputs the temperature distribution including the length direction and the thickness direction in at least a width center portion of the slab at the time of removal from the heating furnace based on a heat conduction equation constituting the slab temperature model, using an initial value of the charging temperature of the slab charged into the heating furnace and operating conditions while the slab is in the heating furnace; The present invention relates to a rough discharge side 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 after rough rolling based on a heat conduction equation using operating conditions when rough rolling the slab extracted from the heating furnace, and a model correction unit that corrects the amount of heat extracted at the heating furnace skid portion 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 skid portion in the width center of the back side of the slab output from the rough discharge side temperature calculation unit and the temperature at the length direction position corresponding to the heating furnace skid portion in the width center of the back side of the slab output from the rough discharge side temperature calculation unit, and the temperature at the length direction position corresponding to the heating furnace skid portion in the width center of the back side of the slab acquired by the rough temperature acquisition unit and the temperature at the length direction position corresponding to the heating furnace skid portion in the width center of the back side of the slab acquired by the rough temperature acquisition unit is less than a threshold value.

[0014] 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 removed 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 thickness direction temperature at the length direction position corresponding to the heating furnace skid portion in the width center of the slab when removed from the heating furnace predicted by the slab temperature prediction unit exceeds the minimum extraction temperature.

[0015] Further, a method of correcting a slab temperature model according to another aspect of the present invention is a method of correcting a slab temperature model used for predicting a temperature distribution including a length direction and a thickness direction in at least a width center portion of the slab at the time of removal from the heating furnace when the slab is heated in a heating furnace and the slab extracted from the heating furnace is rough rolled in a rough rolling mill, the method including the following steps: a rough temperature acquisition step of acquiring a length direction temperature distribution in the width center portion of the back surface of the slab after rough rolling, measured by a rough temperature measurement device installed on the outlet side of the rough rolling mill; an extraction temperature calculation step of calculating and outputting the temperature distribution including the length direction and the thickness direction in at least a width center portion of the slab at the time of removal from the heating furnace based on a heat conduction equation constituting the slab temperature model, using an initial value as the charging temperature of the slab charged into the heating furnace and operating conditions while the slab is in the heating furnace; and a slab temperature model of the slab extracted from the heating furnace, using the temperature distribution including the length direction and the thickness direction in at least a width center portion of the slab at the time of removal from the heating furnace, outputted in the extraction temperature calculation step, as an initial value. The method includes a rough discharge side temperature calculation step of calculating and outputting a temperature distribution including the length direction and the thickness direction at least in the width center of the slab after rough rolling based on a heat conduction equation using operating conditions when rough rolling the slab obtained by ...

[0016] 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 longitudinal and thickness directions at least in the widthwise center of the slab when removed 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 thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion in the widthwise center of the slab when removed from the heating furnace predicted in the slab temperature prediction step exceeds the minimum extraction temperature.

[0017] A method for producing a steel sheet according to another aspect of the present invention 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

[0018] 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, 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 removed from the heating furnace by correcting the slab temperature model. [Brief description of the drawings]

[0019] [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 a temperature distribution in the longitudinal direction at the width center of the back surface of a slab after rough rolling, measured by a rough temperature measuring device. [Diagram 5]1 is a graph showing an example of a temperature distribution in the longitudinal direction at the width center of the back surface of a slab after rough rolling, output from the rough delivery side 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] 1 is a graph showing a temperature distribution in the vicinity of a longitudinal position corresponding to a heating furnace skid portion at the center of the width of the back surface of a slab after rough rolling in an embodiment. [Figure 11] This is a graph showing a comparison of the temperature distribution near the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface of the slab after rough rolling, output from the rough output side temperature calculation unit, before and after correcting the slab temperature model (correction coefficient η) in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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, which 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 time it is in the furnace, 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).

[0026] 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. 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.

[0027] 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 slab's width when it is removed from the heating furnace.

[0028] 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 is also connected to 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 roughing mills 41 to 45. n and a rough temperature gauge 8 which is installed on the delivery side of the slab S and measures the temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S after rough rolling. The charging temperature gauge 7 and the rough temperature gauge 8 are composed of radiation thermometers.

[0029] 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 measurement device 8, an extraction temperature calculation unit 12 connected to the charging temperature measurement device 7, a rough discharge side temperature calculation unit 13, a model correction unit 14, and an output unit 15.

[0030] The slab temperature model correction device 10 is a computer system with calculation processing capabilities, and executes each of the functions of the rough temperature acquisition unit 11 (step S1 described later), extraction temperature calculation unit 12 (step S2), rough outlet side temperature calculation unit 13 (step S3), model correction unit 14 (step S4), and output unit 15 (step S5) on software in accordance with the instructions of various dedicated computer programs pre-stored in the hardware.

[0031] The rough temperature acquisition unit 11 of the correction device 10 is n The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S after rough rolling 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.

[0032] FIG. 4 shows an example of the temperature distribution in the longitudinal direction at the widthwise center of the back surface Sb of the slab S after rough rolling, measured by the rough temperature measuring device 8. 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.).

[0033] 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.

[0034]

number

[0035] 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].

[0036] In calculating the temperature distribution using the heat conduction equation (1), the boundary conditions at the front surface Sa and back surface Sb of the slab S are set by differentiating the temperature distribution in the time and space directions, and the slab temperature is calculated and output at each time step until the time of extraction. This allows the temperature fluctuation in the length direction of the slab S caused by the heating furnace skid to be obtained. 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).

[0037]

number

[0038] The radiant heat input from the back surface (lower surface) Sb is expressed by the following equations (4) and (5).

[0039]

number

[0040] Furthermore, the amount of heat removed from the heating furnace skid is expressed by the following equations (6) and (7).

[0041]

number

[0042] 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 [℃].

[0043] 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.

[0044] In addition, the rough discharge side 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 after rough rolling 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).

[0045]

number

[0046] 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]. 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).

[0047]

number

[0048] 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).

[0049]

number

[0050] 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.

[0051]

number

[0052] 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).

[0053]

number

[0054] 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).

[0055]

number

[0056] 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 ], CR : Specific heat of roll [kcal / (kg K)], T R0 : Roll temperature [℃], α rR : Thermal diffusivity of the roll [m 2 / hr]. In addition, frictional heat q μ [kcal / (m 2 ·hr)] is given by the following equation (14).

[0057]

number

[0058] 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).

[0059]

number

[0060] 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).

[0061]

number

[0062] 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).

number

[0063] FIG. 5 shows an example of the temperature distribution in the longitudinal direction at the widthwise center of the back surface of the slab S after rough rolling, which is output from the rough delivery side temperature calculation unit 13. The model correction unit 14 also calculates the temperature T cal_skid 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 output from the rough discharge side temperature calculation unit 13. cal Temperature difference T cal_diff =T cal -T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act_skid 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 Temperature difference T act_diff =T act -T act_skid , deviation e=T cal_diff -T act_diff The amount of heat extracted Q at the skid of the heating furnace included in the heat conduction equations expressed by the formulas (1) to (7) constituting the slab temperature model used in the extraction temperature calculation unit 12 is less than the threshold value ε (1°C). skd Fix.

[0064] Here, there are multiple temperatures at the longitudinal positions corresponding to the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough discharge side temperature calculation unit 13, and there are also multiple temperatures at the longitudinal positions corresponding to the spaces between the heating furnace skids at the width center of the back surface Sb of the slab S output from the rough discharge side temperature calculation unit 13. Here, the model correction unit 14 calculates a temperature T cal_skidand 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 furnace skid portion at the width center portion of the back surface Sb of the slab S output from the rough discharge side temperature calculation unit 13. cal Temperature difference T cal_diff =T cal -T cal_skid Calculate.

[0065] Furthermore, there are a plurality of temperatures at longitudinal positions corresponding to the heating furnace skid portions at the width center of the back surface Sb of the slab S, which are acquired by the rough temperature acquisition unit 11, and there are also a plurality of temperatures at longitudinal positions corresponding to between the heating furnace skids at the width center of the back surface Sb of the slab S, which are acquired by the rough temperature acquisition unit 11. Here, the model correction unit 14 corrects the temperature T act_skid and the temperature T at a longitudinal position corresponding to the area between the specific heating furnace skid portion and the heating furnace skid portion adjacent to the specific heating furnace skid portion at the width center portion of the back surface Sb of the slab S, which is acquired by the rough temperature acquisition unit 11. act Temperature difference T act_diff =T act -T act_skid Calculate.

[0066] Then, the model correction unit 14 calculates the temperature difference T cal_diff =T cal -T cal_skid and temperature difference T act_diff =T act -T act_skid Deviation from e=T cal_diff -T act_diff The amount of heat extracted Q at the skid of the heating furnace included in the heat conduction equations expressed by the formulas (1) to (7) constituting the slab temperature model used in the extraction temperature calculation unit 12 is less than the threshold value ε (1°C). skd Fix. The amount of heat removed from the heating furnace skid is expressed by equation (7) as mentioned above. The amount of heat removed from the heating furnace skid Q can be calculated by calculating the appropriate η in the following equation (18) by introducing the correction coefficient η into equation (7). skd This would be an appropriate correction.

[0067]

number

[0068] A method for determining an appropriate η in equation (18) 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 is outputted from the model correction unit 14 as the heat extraction amount Q skd The information on the heat conduction equations (equations (1) to (7) and (18)) 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.

[0069] 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 an arithmetic processing 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 commands of various dedicated computer programs pre-stored in the hardware.

[0070] 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.

[0071] 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), (18)) 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.

[0072] In addition, the furnace temperature control unit 22 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 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 exceeds the minimum extraction temperature.

[0073] 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 thereby 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 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).

[0074] 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 portion at the center of the width exceeds the minimum extraction temperature, and the contact point of the skid beam, which tends to be insufficiently heated, can be raised to the specified temperature and extracted.

[0075] In this way, according to the slab temperature model correction device 10 of this embodiment, the rough temperature acquisition unit 11 acquires the temperature of the rough rolling mills 41 to 4 nThe temperature distribution in the length direction at the width center of the back surface Sb of the slab S after rough rolling measured by the rough temperature measuring device 8 installed on the delivery side of the heating furnace 2 is acquired, and in the extraction temperature calculation unit 12, 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, with the charging temperature of the slab S charged into the heating furnace 2 as an initial value, and output. Then, in the rough delivery temperature calculation unit 13, the temperature distribution in the length direction and thickness direction at the width center of the slab S at the time of extraction from the heating furnace 2 outputted from the extraction temperature calculation unit 12 is calculated based on the heat conduction equations (Equations (8) to (17)), using the operating conditions when rough rolling the slab S extracted from the heating furnace 2, with the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling as an initial value, and output. Then, in the model correction unit 14, the temperature T at the longitudinal position corresponding to the heating furnace skid part at the width center part of the back surface Sb of the slab S output from the rough discharge side temperature calculation unit 13 is calculated. cal_skid 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 output from the rough discharge side temperature calculation unit 13. cal Temperature difference T cal_diff =T cal -T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act_skid 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 Temperature difference T act_diff =T act -T act_skid , deviation e=T cal_diff -T act_diff The amount of heat extracted Q at the skid of the heating furnace included in the heat conduction equations expressed by the formulas (1) to (7) constituting the slab temperature model used in the extraction temperature calculation unit 12 is less than the threshold value ε (1°C). skd is modified (equation (18)).

[0076] 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.

[0077] In addition, in the process of correcting the slab temperature model, the model correction unit 14 uses the information output from the rough delivery side temperature calculation unit 13 and the rough rolling mills 41 to 4 n Since the slab temperature model is corrected based on information acquired by the crude temperature acquisition unit 11 measured by the crude temperature measurement meter 8 installed on the exit side 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 side 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 concern when using the correction device 10 according to this embodiment.

[0078] According to the furnace temperature control device 20 of the heating furnace of this embodiment, the slab temperature prediction unit 21 predicts the longitudinal and thickness temperature distributions at the width center 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 thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion at the width center of the slab S at the time of extraction from the heating furnace 2 predicted by the slab temperature prediction unit 21 exceeds the minimum extraction temperature.

[0079] As a result, when the slab S is extracted from the heating furnace 2, the thickness-wise temperature at the longitudinal position corresponding to the heating furnace skid section at the center of the width exceeds the minimum extraction temperature, and the contact point of the skid beam, which tends 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.

[0080] 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.

[0081] 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 longitudinal direction at the width center of the back surface Sb of the slab S after rough rolling is measured by a rough temperature measuring device 8 installed on the delivery side of the rolling mill (rough temperature acquisition step).

[0082] 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 time in the furnace, furnace temperature, skid contact time, etc.) (extraction temperature calculation step).

[0083] 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.

[0084] In calculating the temperature distribution using the heat conduction equation (1), the boundary conditions at the front surface Sa and back surface Sb of the slab S are set by differentiating the temperature distribution in the time and space directions, and the slab temperature is calculated and output at each time step until the time of extraction. This allows the temperature fluctuation in the length direction of the slab S caused by the heating furnace skid to be obtained. 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).

[0085] Next, in step S3, the rough discharge side 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 at the time of extraction 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 after rough rolling 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 (rough discharge side temperature calculation step). The heat conduction equation is expressed by equation (8) as described above. 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).

[0086] 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).

[0087] Next, in step S4, the model correction unit 14 calculates the temperature T cal_skid 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 output in step S3. cal Temperature difference T cal_diff =T cal -T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, obtained in step S1. act_skid 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 Temperature difference T act_diff =T act -T act_skid , deviation e=T cal_diff -T act_diff The amount of heat transferred from the heating furnace skid part Q included in the heat conduction equations expressed by Equations (1) to (7) constituting the slab temperature model used in step S2 is set so that the magnitude (absolute value) of is less than the threshold value ε (1°C). skd (model correction step).

[0088] The amount of heat removed from the heating furnace skid is expressed by equation (7) as mentioned above. The amount of heat removed from the heating furnace skid Q can be calculated by finding the appropriate η in equation (18) by introducing the correction coefficient η into equation (7). skd This would be an appropriate correction.

[0089] 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_skid 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 output in step S3. cal Temperature difference T cal_diff =T cal -T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, obtained in step S1. act_skid 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 Temperature difference T act_diff =T act -T act_skid , deviation e=T cal_diff -T act_diff Calculate.

[0090] Here, the model correction unit 14 selects a temperature T at a specific position in the length direction corresponding to a specific heating furnace skid portion among the multiple temperatures at the longitudinal positions corresponding to the heating furnace skid portion at the width center portion of the back surface Sb of the slab S output in step S3. cal_skid and 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 furnace skid portion at the width center portion of the back surface Sb of the slab S output in step S3. cal Temperature difference T cal_diff =T cal -T cal_skid Calculate.

[0091] In addition, the model correction unit 14 corrects the temperature T at the longitudinal position corresponding to the specific heating furnace skid portion among the multiple temperatures at the longitudinal positions corresponding to the heating furnace skid portion at the width center portion of the back surface Sb of the slab S acquired in step S1. act_skid and 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 furnace skid portion at the width center portion of the back surface Sb of the slab S, which is obtained in step S1. act Temperature difference T act_diff =T act -T act_skid Calculate. Then, the model correction unit 14 calculates the temperature difference T cal_diff =T cal -T cal_skid and temperature difference T act_diff =T act -T act_skid Deviation from e=T cal_diff -T act_diff Calculate the absolute value.

[0092] Next, in step S42, the model correction unit 14 determines whether or not the deviation e (magnitude of the absolute value) calculated in step S41 is less than a threshold value ε (=1° C.). 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 sets the correction coefficient η in the above-mentioned equation (18) to the correction coefficient η+δ after the small change.

[0093] Next, in step S44, the model correction unit 14 corrects the amount of heat removed Q at the skid of the heating furnace in the equation (18) by changing the correction coefficient η to the correction coefficient η+δ after the small change. skdUsing the above, 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 is recalculated, and based on this, the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling in step S3 is recalculated, and the temperature T cal_skid ' and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. cal ' and temperature difference T cal_diff '=T cal '-T cal_skid ' is calculated.

[0094] Next, in step S45, the model correction unit 14 corrects the temperature difference T cal_diff and the temperature difference T calculated in step S44 cal_diff From the small change amount δ of the correction coefficient set in step 43, the influence coefficient ∂e / ∂η = (T cal_diff '-T cal_diff ) / δ.

[0095] Next, in step S46, the model correction unit 14 updates the correction coefficient η in the above-mentioned equation (18) to an updated correction coefficient η-e / (∂e / ∂η).

[0096] Next, in step S47, the model correction unit 14 calculates the amount of heat removed Q from the skid of the heating furnace in the equation (18) by using the correction coefficient η as the updated correction coefficient η-e / (∂e / ∂η). skd Using the above, 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 is recalculated, and the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling in step S3 is recalculated. In step S41, the temperature T cal_skid '' and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. cal '' and the temperature difference T cal_diff ''=Tcal ''-T cal_skid '' is calculated.

[0097] Next, in step S48, the model correction unit 14 calculates the deviation e calculated in step S41 as deviation e=T cal_diff ''-T act_diff 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 determination result in step S42 is YES, the process proceeds to step S49, and the correction coefficient η when the deviation e becomes less than the threshold value ε (=1° C.) is set as the correction coefficient.

[0098] This completes the process in step S4, and the appropriate correction coefficient η in the above-mentioned equation (18) is obtained, and the amount of heat removed from the heating furnace skid Q skd This would be an appropriate correction. Then, in step S5, the output unit 15 of the correction device 10 calculates the amount of heat removed Q from the heating furnace skid section by the model correction unit 14. skd The information of the heat conduction equations (equations (1) to (7) and (18)) 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).

[0099] This completes the process in the slab temperature model correction device 10.

[0100] 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), nThe longitudinal temperature distribution at the width center of the back surface Sb of the slab S after rough rolling measured by the rough temperature measuring device 8 installed on the delivery side of the heating furnace 2 is obtained, and in an extraction temperature calculation step (step S2), the charging temperature of the slab S charged into the heating furnace 2 is set as an initial value, and the temperature distributions in the longitudinal and thickness directions at the width center of the slab S at the time of extraction from the heating furnace 2 are 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 a rough delivery side temperature calculation step (step S3), the longitudinal and thickness direction temperature distributions at the width center of the slab S after rough rolling are 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, using the temperature distributions in the longitudinal and thickness directions 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 as an initial value, and outputted. Then, in the model correction step (step S4), the temperature T at the longitudinal position corresponding to the heating furnace skid part at the width center part of the back surface Sb of the slab S output in the rough discharge side temperature calculation step is cal_skid 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 output from the rough discharge side temperature calculation unit 13. cal Temperature difference T cal_diff =T cal -T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid portion at the width center of the back surface Sb of the slab S, acquired by the rough temperature acquisition unit 11. act_skid 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 Temperature difference T act_diff =T act -T act_skid , deviation e=T cal_diff -T act_diff The amount of heat transferred from the skid of the heating furnace Q included in the heat conduction equations expressed by Equations (1) to (7) constituting the slab temperature model used in the extraction temperature calculation step is calculated so that the magnitude of is less than the threshold value ε (1°C). skd is modified (equation (18)).

[0101] 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.

[0102] In addition, in the correction of the slab temperature model, in the model correction step, the information output from the rough exit side temperature calculation step and the rough rolling mills 41 to 4 n Since the slab temperature model is corrected based on information acquired in a rough temperature acquisition step measured by a rough temperature measuring device 8 installed on the exit side 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 side 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 concern according to the correction method of this embodiment.

[0103] 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.

[0104] 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).

[0105] 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), (18)) 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.

[0106] Next, in step S12, the furnace temperature control unit 22 of the furnace temperature control device 20 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 at the center of the width of the slab S at the time of extraction from the heating furnace 2 predicted in step S11 exceeds the minimum extraction temperature (furnace temperature control step).

[0107] 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, thereby controlling 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 at the center of the width of the slab S at the time of extraction from the heating furnace 2 predicted in step S11 becomes a target temperature that exceeds the minimum extraction temperature (e.g., 1200°C).

[0108] 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 portion at the center of the width exceeds the minimum extraction temperature, and the contact point of the skid beam, which tends to be insufficiently heated, can be raised to the specified temperature and extracted.

[0109] Thus, according to the furnace temperature control method of this embodiment, in a slab temperature prediction step (step S11), 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 is predicted using a slab temperature model corrected by the slab temperature model correction method, and in a furnace temperature control step (step S12), the furnace temperature in the heating furnace 2 is controlled so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion 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 exceeds the minimum extraction temperature.

[0110] As a result, when the slab S is extracted from the heating furnace 2, the thickness-wise temperature at the longitudinal position corresponding to the heating furnace skid section at the center of the width exceeds the minimum extraction temperature, and the contact point of the skid beam, which tends 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] In addition, in the rough delivery side temperature calculation unit 13 (step S3), the temperature distribution in the length and thickness directions at the width center of the slab S after rough rolling is calculated, but it is sufficient to calculate a temperature distribution including the length and thickness directions at least at the width center of the slab S after rough rolling, and it is not limited to the length and thickness directions at the width center of the slab S, but for example, the temperature distribution in the width, length and thickness directions of the slab S may be calculated.

[0115] 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 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 removed from the heating furnace 2, and it is not limited to the length direction and thickness direction at the width center of the slab S, but it is also possible to predict the temperature distribution in the width direction, length direction and thickness direction of the slab S, for example. It may also be calculated. EXAMPLES

[0116] In order to verify the effect of the present invention, in the hot rolling line 1 shown in FIG. n The temperature distribution in the longitudinal direction at the width center of the back surface Sb of the slab S after rough rolling was measured by a rough temperature measuring device 8 installed on the delivery side of the slab S.

[0117] As a result, as shown in FIG. 10, the temperature T act_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. actTemperature difference T act_diff =T act -T act_skid was 26°C.

[0118] On the other hand, the amount of heat removed from the heating furnace skid Q skd Based on the heat conduction equation in which the correction coefficient η was 0.20 (correction coefficient before correction), the extraction temperature calculation unit 12 of the straightening device 10 calculated and output 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, using the operation conditions while the slab S was in the heating furnace, with the charging temperature of the slab S charged into the heating furnace 2 as an initial value. Then, the rough discharge side temperature calculation unit 13 of the straightening device 10 calculated and output the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling, based on the heat conduction equation, with the output 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 as an initial value, using the operation conditions when rough rolling the slab S extracted from the heating furnace 2.

[0119] As a result, as shown by the dashed line in FIG. 11, the temperature T cal_skid and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. cal Temperature difference T cal_diff =T cal -T cal_skid was 19°C.

[0120] For this reason, the model correction unit 14 of the correction device 10 detects the temperature difference T cal_diff =T cal -T cal_skid = 19℃ and the temperature difference T act_diff =T act -T act_skid = Deviation from 26℃ e=T cal_diff -T act_diff =-7℃ was calculated.

[0121] The model correction unit 14 of the correction device 10 judged whether the calculated deviation e = -7°C (absolute value) was less than the threshold value ε (=1°C), and since the judgment result was NO, the correction coefficient η = 0.20 was set to the correction coefficient after the small change, 0.20 + 0.05 = 0.25.

[0122] Then, the model correction unit 14 corrects the amount of heat removed Q at the skid of the heating furnace by making the correction coefficient 0.20+0.05=0.25 after a small change from η=0.20. skd Using the above, 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 after rough rolling is recalculated, and the temperature T cal_skid ' and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. cal ' and temperature difference T cal_diff '=T cal '-T cal_skid As a result, the temperature difference T cal_diff ' was 22°C.

[0123] Then, the model correction unit 14 calculates the temperature difference T cal_diff '=22℃ and the temperature difference T cal_diff = 19℃ and the small change in the correction coefficient δ = 0.05, the influence coefficient ∂e / ∂η = (T cal_diff '-T cal_diff ) / δ=(22-19 / 0.05=60.

[0124] Next, the model correction unit 14 calculates the amount of heat dissipated in the heating furnace skid Q skd After updating the correction coefficient η in the above, the correction coefficient η-e / (∂e / ∂η) was updated to 0.20-(-7) / 60 = 0.31.

[0125] Next, the model correction unit 14 updates the correction coefficient η to obtain the heat extraction amount Q in the heating furnace skid section with the correction coefficient η-e / (∂e / ∂η)=0.31. skdUsing the above, 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 the temperature distribution in the length direction and thickness direction at the width center of the slab S after rough rolling is recalculated, and the temperature T cal_skid '' and the temperature T at the longitudinal position corresponding to the heating furnace skid at the center of the width of the back surface Sb of the slab S. cal '' and the temperature difference T cal_diff ''=T cal ''-T cal_skid As a result, as shown by the solid line in Figure 11, the temperature difference T cal_diff ''=26℃.

[0126] Then, the model correction unit 14 changes the deviation e=-7°C to deviation e=T cal_diff ''-T act_diff =26℃-26℃=0℃. Then, the model correction unit 14 judged whether the updated deviation e = 0 °C is less than the threshold value ε (= 1 °C), and since the judgment result was YES, the updated correction coefficient η-e / (∂e / ∂η) = 0.20-(-7) / 60 = 0.31 when the judgment result was YES was set as the correction coefficient η. This completes the processing in the model correction unit 14, and the amount of heat removed from the heating furnace skid Q skd The appropriate correction coefficient η = 0.31 in (Eq. (18)) is obtained, and the amount of heat removed from the heating furnace skid Q skd This was an appropriate fix.

[0127] Therefore, according to this embodiment, the amount of heat removed from the heating furnace skid Q skd It was determined that can be adjusted to match the crude temperature measurement. 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 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 Rough output side 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 walking beam heating furnace, when the slab is heated in the walking beam heating furnace and the slab extracted from the walking beam heating furnace is rough rolled in a rough rolling mill, A rough temperature acquisition unit that acquires a longitudinal temperature distribution at the width center of the back surface of the slab after rough rolling, measured by a rough temperature measurement device installed on the exit side of the rough rolling mill; an extraction temperature calculation unit that calculates and outputs the 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 walking beam type heating furnace based on a heat conduction equation including a calculation formula for the amount of heat extracted in the heating furnace skid part constituting the slab temperature model, using the operating conditions while the slab is in the heating furnace and the charging temperature of the slab to be charged into the walking beam type heating furnace as an initial value; A rough exit temperature calculation unit calculates and outputs a temperature distribution including the length direction and thickness direction at least in the width center of the slab after rough rolling based on a heat conduction equation using the operating conditions for rough rolling the slab extracted from the walking beam 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 walking beam heating furnace as an initial value, the temperature distribution including the length direction and thickness direction at least in the width center of the slab after rough rolling output from the extraction temperature calculation unit; A temperature difference between a temperature at a longitudinal position corresponding to a specific heating furnace skid section among a plurality of temperatures at longitudinal positions corresponding to the heating furnace skid section, which is the contact point of the skid beam at the width center of the back surface of the slab, output from the rough discharge side temperature calculation unit, and a temperature at a longitudinal position corresponding to a heating furnace skid between the specific heating furnace skid section at the width center of the back surface of the slab and a heating furnace skid section adjacent to the specific heating furnace skid section, output from the rough discharge side temperature calculation unit, and a temperature difference between a temperature at a longitudinal position corresponding to a heating furnace skid section, which is the contact point of the skid beam at the width center of the back surface of the slab, output from the rough discharge side temperature calculation unit, and a temperature difference between a temperature at a longitudinal position corresponding to a heating furnace skid section, which is between the specific heating furnace skid section at the width center of the back surface of the slab ... output from the rough discharge side temperature calculation unit, and a temperature difference between a temperature at a longitudinal position corresponding to a heating furnace skid section, which is the contact point of the skid beam at the width center of the back surface of the slab, output from the rough discharge side temperature calculation unit, a model correction unit that corrects the amount of heat dissipated at the heating furnace skid section included in a heat conduction equation including a formula for calculating the amount of heat dissipated at the heating furnace skid section constituting the slab temperature model, used in the extracted temperature calculation unit, so that the magnitude of deviation between the temperature at a longitudinal position corresponding to the specific heating furnace skid section among multiple temperatures of the slab and the temperature at a longitudinal position corresponding to a space between the specific heating furnace skid section and a heating furnace skid section adjacent to the specific heating furnace skid section, acquired by the rough temperature acquisition unit, is less than a threshold value.

2. A furnace temperature control device for a heating furnace, characterized in that it comprises a slab temperature prediction unit that predicts the temperature distribution including the longitudinal and thickness directions at least in the width center of the slab when extracted from a walking beam type heating furnace using a slab temperature model corrected by the slab temperature model correction device described in claim 1, and a furnace temperature control unit that controls the furnace temperature in the walking beam type heating furnace so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion, which is the contact point of the skid beam at the width center of the slab when extracted from the walking beam type heating furnace, predicted by the slab temperature prediction unit exceeds the minimum extraction temperature.

3. 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 a walking beam heating furnace, in which the slab is heated in the walking beam heating furnace and the slab extracted from the walking beam heating furnace is rough rolled in a rough rolling mill, comprising: A rough temperature acquisition step of acquiring a longitudinal temperature distribution at a width center portion of the back surface of the slab after rough rolling, measured by a rough temperature measuring instrument installed on the exit side of the rough rolling mill; an extraction temperature calculation step of calculating and outputting 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 walking beam type heating furnace based on a heat conduction equation including a calculation equation for the amount of heat extracted in the heating furnace skid part constituting the slab temperature model, using the operation conditions of the slab while it is in the heating furnace and the charging temperature of the slab to be charged into the walking beam type heating furnace as an initial value; A rough exit 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 after rough rolling based on a heat conduction equation using the operating conditions for rough rolling the slab extracted from the walking beam 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 walking beam heating furnace as an initial value, which is output in the extraction temperature calculation step; A temperature difference between a temperature at a longitudinal position corresponding to a specific heating furnace skid section among a plurality of temperatures at longitudinal positions corresponding to the heating furnace skid section which is the contact point of the skid beam at the width center of the back surface of the slab, outputted in the rough discharge side temperature calculation step, and a temperature at a longitudinal position corresponding to a furnace skid between the specific heating furnace skid section at the width center of the back surface of the slab and a heating furnace skid section adjacent to the specific heating furnace skid section, outputted in the rough discharge side temperature calculation step, and a temperature difference between a temperature at a longitudinal position corresponding to a furnace skid between the specific heating furnace skid section at the width center of the back surface of the slab and a furnace skid section adjacent to the specific heating furnace skid section, outputted in the rough discharge side temperature calculation step, and a temperature difference between a temperature at a longitudinal position corresponding to the heating furnace skid section which is the contact point of the skid beam at the width center of the back surface of the slab, outputted in the rough discharge side temperature calculation step, and a temperature difference between a temperature at a longitudinal position corresponding to a furnace skid between the specific heating furnace skid section ... and a furnace skid section adjacent to the specific heating furnace skid section, outputted in the rough temperature acquisition step a model correction step of correcting the amount of heat dissipated at the heating furnace skid section included in a heat conduction equation including a formula for calculating the amount of heat dissipated at the heating furnace skid section constituting the slab temperature model, used in the extraction temperature calculation step, so that the magnitude of deviation between the temperature at a longitudinal position corresponding to the specific heating furnace skid section among multiple temperatures at different positions and the temperature at a longitudinal position corresponding to the heating furnace skid section between the specific heating furnace skid section at the center of the width of the back surface of the slab and a heating furnace skid section adjacent to the specific heating furnace skid section, acquired in the rough temperature acquisition step, is less than a threshold value.

4. A furnace temperature control method for a heating furnace, comprising: a slab temperature prediction step of predicting a temperature distribution including the longitudinal and thickness directions at least in the widthwise center of the slab when extracted from a walking beam type heating furnace using a slab temperature model corrected by the slab temperature model correction method described in claim 3; and a furnace temperature control step of controlling the furnace temperature in the walking beam type heating furnace so that the thickness direction temperature at the longitudinal position corresponding to the heating furnace skid portion, which is the contact point of the skid beam at the widthwise center of the slab when extracted from the walking beam type heating furnace, predicted in the slab temperature prediction step, exceeds the minimum extraction temperature.

5. A method for manufacturing a steel plate, comprising a furnace temperature control step of controlling the furnace temperature in a walking beam type heating furnace by the method for controlling the furnace temperature of a heating furnace according to claim 4.

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