Induction heating system

Abstract

The induction heating system comprises a plurality of transverse induction heating devices installed along the conveying direction of the rolled material, and a computer that calculates a heating pattern, which is a combination of the power supplied to the inductor of each induction heating device and the position of each inductor that can move in the width direction of the rolled material, based on information about the rolled material and actual values ​​of the widthwise temperature distribution at the input and output sides of the induction heating devices, and sets the heating pattern for each induction heating device. The computer is configured to define an evaluation function that includes a term for the deviation between the target value and the predicted value of the widthwise temperature distribution of the rolled material at the output side of each induction heating device, and a term for the power supplied to each inductor, and to calculate a heating pattern candidate, which is the heating pattern when the evaluation function is minimized.

Description

Technical Field

[0001] The present disclosure relates to an induction heating system installed in a hot rolling line to inductively heat a rolled material.

Background Art

[0002] The temperature of a rolled material rolled in a hot rolling line (hereinafter also referred to as "rolling line") affects the mechanical properties of the rolled material. Therefore, temperature control of the rolled material is very important. An induction heating device for inductively heating a rolled material is installed, for example, between a roughing mill and a finishing mill of a rolling line. Since the induction heating device can heat the rolled material with a high current density depending on the current and the number of turns of the induction coil, it can rapidly heat the rolled material conveyed in one direction in the rolling line. In addition, it has the advantages of good heating efficiency, the energy source being electric power, so it does not directly emit CO2 like gas heating, and by appropriately designing the shape of the induction coil and the core, it also has the advantage of being able to locally heat a desired portion of the rolled material.

[0003] The purposes of introducing such an induction heating device into a rolling line include, in addition to reducing thermal rundown and skid marks, equalizing the temperature and quality in the width direction of the rolled material. Thermal rundown is the temperature drop from the tip to the tail end in the longitudinal direction of the rolled material. A skid mark is a periodic temperature unevenness in the longitudinal direction of the rolled material due to heat extraction to the support (skid) that supports the slab in the heating furnace.

[0004] Induction heating devices are broadly classified into two types, solenoid type and transverse type, depending on the direction of the main magnetic flux (alternating magnetic flux generated from the induction heating device) linked to the rolled material. In the solenoid type, the direction of the main magnetic flux coincides with the longitudinal direction (conveying direction) of the rolled material. The current induced by the main magnetic flux (hereinafter also called "eddy current") flows in a circular manner near the surface within the thickness-to-width cross-section of the rolled material. Therefore, the heat generated by the eddy current has a distribution in the thickness direction and is almost uniform in the width direction. On the other hand, in the transverse type, the direction of the main magnetic flux coincides with the thickness direction of the rolled material. The eddy current flows in a circular manner around the main magnetic flux within the width-to-conveying cross-section of the rolled material. Therefore, the heat generated by the eddy current is almost uniform in the thickness direction, while in the width direction it changes significantly depending on the shape and position of the induction coil and iron core.

[0005] Here, the thickness of the rolled material is very short compared to its width. Therefore, the temperature distribution in the thickness direction becomes uniform relatively quickly after heating, while the temperature distribution in the width direction does not become uniform in a short time. Consequently, transverse induction heating devices, which generate a temperature increase distribution in the width direction, tend to be more complex to control than solenoid-type devices.

[0006] Incidentally, when using induction heating equipment, it is desirable to supply the minimum necessary power to the rolled material. On the other hand, if the power supply (inverter power supply) of the induction heating equipment is turned on while the rolled material is passing through the induction heating equipment, sudden load fluctuations may cause instability in the inverter startup. For this reason, it is common practice to decide in advance the number of induction heating equipment to be used for heating and to start the inverter power supply before the rolled material enters the induction heating equipment. The inverter power supply must always output power above the lower limit power (standby power) while running. In other words, even in positions along the longitudinal direction of the rolled material where heating is not actually necessary, the standby power will cause the temperature to rise, and this standby power is wasted power consumption. This wasted power consumption increases as the number of induction heating equipment used for heating increases. For this reason, from an energy saving perspective, it is desirable to heat the rolled material with the minimum necessary number of induction heating equipment.

[0007] Patent Document 1 below discloses a plurality of induction heating devices arranged in the conveying direction of a rough bar, which is a rolled material. Energy saving is achieved by determining the number of inductors used to heat the rolled material based on the target temperature at the exit side of the induction heating device and the temperature of the rolled material (rough bar) at the input side of the induction heating device.

[0008] Patent Document 2 below discloses an induction heating device having multiple inductors (heating units) arranged in the direction of conveyance of the rolled material. The rough rolling mill exit temperature is measured and sampled along the entire length of the rolled material, and the number of inductors used is reduced by not using some of the inductors, provided that the set maximum power is satisfied at each sampling point. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent No. 3960204 [Patent Document 2] Japanese Patent No. 3801154 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, neither Patent Document 1 nor 2 mentions the temperature distribution in the width direction of the rolled material. In other words, it is assumed that multiple positions obtained by dividing the rolled material along its length each have a representative temperature, and the power and number of induction heating devices used are determined according to the representative temperature of each position.

[0011] In the solenoid method, the rolling material is heated uniformly in the width direction, so no particular problems arise under the above premise. On the other hand, in the transverse method, the inductor moves along the width direction of the rolling material, so the amount of heating may differ depending on the position in the width direction of the rolling material. For example, as shown in Figure 9, the distribution of heating amount in the width direction changes as shown by D1 to D3 depending on the position of the inductor along the width direction of the rolling material. In this case, it is necessary to determine the optimal heating pattern of the induction heating device (number of induction heating devices used, power, and width direction position) according to the temperature target at the width direction position of the rolling material.

[0012] This disclosure is made to solve the problems described above, and aims to provide an induction heating system that can achieve energy savings while satisfying the target value of the temperature distribution in the width direction of the rolled material, even when the amount of heating differs depending on the position in the width direction of the rolled material. [Means for solving the problem]

[0013] The first aspect of this disclosure relates to an induction heating system installed in a hot rolling line for induction heating of the rolled material. The induction heating system comprises a plurality of transverse induction heating devices installed along the direction of transport of the rolled material, and based on information about the rolled material and actual values ​​of the widthwise temperature distribution at the inlet and outlet of the induction heating devices, Guidance The system includes a computer that calculates a heating pattern, which is a combination of the power supplied to the inductors of the heating device and the position of each inductor that is movable in the width direction of the rolled material, and sets the heating pattern for each induction heating device. The computer defines an evaluation function that includes a term for the deviation between the target value and the predicted value of the width direction temperature distribution of the rolled material at the exit side of each induction heating device, and a term for the power supplied to each inductor. Linear approximation of the predicted values ​​of the widthwise temperature distribution in the evaluation function, The system is configured to calculate a candidate heating pattern, which is the heating pattern that minimizes the evaluation function.

[0015] The 2 The perspective is, 1In addition to the above, it further has the following features: The computer is configured to recalculate the predicted values ​​of the temperature distribution in the width direction using the heating pattern candidates, and to verify the heating pattern candidates based on the deviation between the recalculated predicted values ​​and the target values.

[0016] The 3 This viewpoint, in addition to the first viewpoint, has the following further features: A pair of edge heaters are installed on the upstream or downstream side of the induction heating device in the conveying direction, to locally heat both ends of the rolled material in the width direction. The pair of edge heaters have inductors that are movable to different widthwise positions, and are configured to be supplied with the same power to the inductor of each edge heater. The computer is configured to set the power supply term in the evaluation function to a common value for the inductors of the edge heaters.

[0017] The 4 This perspective, in addition to the first perspective, further has the following features: The induction heating system further includes an inlet width thermometer that measures the actual value of the widthwise temperature distribution on the inlet side of the induction heating device. The computer is configured to use a corrected value learned from the actual value measured when the measurement conditions are good, instead of the actual value measured by the inlet width thermometer, when the measurement conditions of the inlet width thermometer are poor. [Effects of the Invention]

[0018] According to this disclosure, the evaluation function includes not only a term for the temperature deviation of the rolled material but also a term for the power supplied to the induction heating device. By controlling each induction heating device based on the heating pattern obtained by solving this evaluation function, it is possible to achieve energy savings while making the temperature distribution in the width direction of the rolled material uniform. Therefore, even if the amount of heating differs depending on the width direction position of the rolled material, it is possible to achieve energy savings while satisfying the target value for the temperature distribution in the width direction of the rolled material.

[0019] Furthermore, by linearly approximating the predicted values ​​of the temperature distribution in the width direction in the evaluation function, the evaluation function can be solved analytically, significantly reducing processing time compared to solving it numerically, and consequently lowering the processing load on the computer. For this reason, it can be suitably applied when the computer is a process control computer. Moreover, by performing transient heat conduction calculations using the heating pattern candidates and calculating the predicted values ​​of the temperature distribution in the width direction, the heating pattern candidates obtained by analytically solving the evaluation function can be verified. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic diagram showing the configuration of a hot rolling line to which the induction heating system according to the embodiment is applied. [Figure 2] This is a schematic diagram showing an example of the configuration of an induction heating device. [Figure 3] This is a schematic diagram illustrating the functions of a process control computer. [Figure 4] This is a flowchart to explain how to calculate the heating pattern. [Figure 5] This figure shows an example of a table that manages the combinations of initial values ​​included in the initial heating pattern. [Figure 6] This figure shows an example of the hardware configuration of a process control computer. [Figure 7] This is a schematic diagram showing another configuration of a hot rolling line to which an induction heating system is applied. [Figure 8] This is a schematic diagram showing an example of an edge heater configuration. [Figure 9] This figure shows the change in the temperature increase distribution in the width direction of the rolled material, depending on the position of the inductor along the width direction. [Modes for carrying out the invention]

[0021] The control device for an induction heating device according to an embodiment will be described below, with reference to the drawings, using as an example its application to an induction heating device installed between the roughing mill and the finishing mill in a hot rolling line. In each figure, common elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0022] Figure 1 is a schematic diagram showing the configuration of a hot rolling line RL to which the induction heating system according to the embodiment is applied. In the hot rolling line RL, the rolled material Mr is rolled to the desired thickness and width. The hot rolling line RL is equipped with the following main components: a heating furnace 1, a roughing mill 2, an induction heating device 3, a finishing mill 4, a cooling table 5, and a winding machine 6.

[0023] The heating furnace 1 heats the slab, which will be used as the rolled material Mr, to a predetermined temperature (for example, 1200°C). Immediately after being extracted from the heating furnace 1, the rolled material Mr is a rectangular parallelepiped metal material (for example, steel) having a thickness of 200 mm to 280 mm, a width of 800 mm to 2000 mm, and a length of 5 m to 12 m.

[0024] The roughing mill 2 is equipped with one to three stands 21. The roughing mill 2 rolls the rolled material Mr multiple times while reversing the conveying direction.

[0025] Figure 2 is a schematic diagram showing an example of the configuration of the induction heating device 3. As shown in Figure 2, the transverse induction heating device 3 consists of multiple units N arranged along the rolling direction of the rolled material Mr. IH The inductor 31 and each inductor 31j(1 <j≦N IHThe induction heating device 3 further comprises a power supply 32 for supplying power to the rolled material Mr. The inductor 31 has an iron core 311 and an induction coil (heating coil) 312 wound around the iron core 311. For example, an inverter power supply can be used as the power supply 32. When power is supplied to the induction coil 312 from the power supply 32, a flux linkage is generated in the thickness direction of the rolled material Mr, and eddy currents are induced in the rolled material Mr. These eddy currents generate Joule heat, and the rolled material Mr is heated. The induction heating device 3 further comprises a housing 33 that houses the inductor 31, a moving mechanism 34 provided in the housing 33, and a position controller 35. The moving mechanism 34 is not shown in detail, but can be made up of a trolley or slider that can move in the width direction. The position controller 35 can change the position of the moving mechanism 34, thereby changing the position of the inductor 31 in the width direction. Note that in Figure 2, for the sake of simplicity, only the upper inductor 31 positioned above the rolled material Mr is shown. However, a lower inductor with the same configuration as the upper inductor 31 can also be positioned below the rolled material Mr. In this case, the lower inductor is configured to be able to move independently of the upper inductor 31 in the width direction. That is, a housing 33 and a moving mechanism 34 are provided corresponding to the lower inductor. The power supply 32 and the position controller 35 may be shared between the upper inductor 31 and the lower inductor, or they may be provided independently.

[0026] The finishing rolling mill 4 is equipped with multiple (for example, seven) stands 41. The cooling table 5 has multiple cooling device groups (cooling bank groups) arranged along the conveying direction of the rolled material Mr. The cooling table 5 cools the rolled material Mr to a target temperature by pouring cooling water into it after it has passed through the finishing rolling mill 4. The rolled material Mr that has passed through the cooling table 5 is wound into a coil by the winding machine 6. The winding temperature (CT) is, for example, 600°C.

[0027] A width thermometer (hereinafter referred to as the "inlet width thermometer") 71 is positioned between the roughing mill 2 and the induction heating device 3 on the upstream side in the conveying direction. This inlet width thermometer 71 can measure the widthwise temperature of the rolled material Mr on the inlet side of the upstream induction heating device 3. A width thermometer (hereinafter referred to as the "outlet width thermometer") 72 is positioned between the induction heating device 3 on the downstream side in the conveying direction and the finishing mill 4. This outlet width thermometer 72 can measure the widthwise temperature of the rolled material Mr on the outlet side of the downstream induction heating device 3. The rolled material Mr is divided into multiple sections (hereinafter also referred to as "nodes") in the width direction. The inlet width thermometer 71 and the outlet width thermometer 72 measure the widthwise temperature distribution of each node.

[0028] The hot rolling line RL is operated by a computer-based control system. The computer system includes a host computer 10 and a process control computer 11, which are connected to each other via a network. An interface screen 12, which is the operator's control screen, is connected to the process control computer 11 via the network. The operator can perform input operations, including manual intervention operations, on the interface screen 12.

[0029] The higher-level computer 10 determines hot rolling command information, which includes information necessary for rolling, such as the specifications of the rolled material Mr (steel type and dimensions) and rolling targets (target product thickness, product width, and temperature (including the finishing mill exit temperature (FDT) and winding temperature (CT)), according to the operation plan, and transmits (outputs) the hot rolling command information to the process control computer 11.

[0030] The process control computer 11 calculates the heating pattern for the induction heating device 3 using the hot rolling command information (including rolled material information) input from the rolling computer 10, manual intervention information performed by the operator on the interface screen 12, actual values ​​of the widthwise temperature distribution measured by width thermometers 71 and 72, and process model parameters extracted from the database 114, and sends the calculated heating pattern to the induction heating device 3 as a set value. The functions of the process control computer 11 will be described below.

[0031] Figure 3 is a schematic diagram showing the functions of the process control computer 11. As shown in Figure 3, the process control computer 11 has a function 110 for controlling the induction heating device 3. The process control computer 11 comprises a temperature calculation unit (temperature calculation function) 111, an optimization calculation unit (heating pattern optimization calculation function) 112, a learning unit (learning function) 113, and a database 114.

[0032] The temperature calculation unit 111 uses a process model (physical model) to calculate predicted values ​​for the widthwise temperature distribution of each segment (points obtained by dividing the rolled material longitudinally) of the rolled material Mr at the entrance position of the induction heating device 3, and predicted values ​​for the widthwise temperature distribution of each segment of the rolled material Mr at the location of the exit thermometer 72, based on rolling information such as the thickness and width of the rolled material and the rolling material speed pattern calculated in the process control computer 11, actual values ​​of the widthwise temperature distribution of the rolled material Mr measured by the entrance thermometer 71, and actual values ​​of the rolled material Mr measured by the exit thermometer 72, and sends the calculated predicted values ​​to the optimization calculation unit 112. Furthermore, based on the heating pattern candidates calculated by the optimization calculation unit 112, it recalculates the predicted values ​​for the widthwise temperature distribution of each segment of the rolled material Mr at the entrance position of the induction heating device 3 and predicted values ​​for the widthwise temperature distribution of each segment of the rolled material Mr at the location of the exit thermometer 72, and sends the recalculated predicted values ​​to the optimization calculation unit 112. Since the process model (physical model) used to calculate the predicted values ​​is publicly known, a detailed explanation will be omitted here.

[0033] The optimization calculation unit 112 calculates candidate heating patterns to achieve the target value of the widthwise temperature distribution at the position of the outlet thermometer 72, based on the predicted value of the widthwise temperature distribution on the inlet side of the induction heating device 3 received from the temperature calculation unit 111, and sends the calculated candidate heating patterns to the temperature calculation unit 111. The candidate heating patterns are those that minimize (converge) the evaluation function described later, and the power p supplied to each inductor 31j. j and the position x in the width direction of each inductor 31j j This is the combination. Also, the supplied power p j Since induction heating device 3, which has a value of zero, is not used, the number of induction heating devices 3 used is effectively included in the heating pattern candidates.

[0034] The learning function unit 113 sends a correction value of the prediction error of the process model (physical model) to the temperature calculation unit 111. Further, after heating by the induction heating device 3, the correction value in the heating section is updated from the heating performance data. In the learning function unit 113, after heating by the induction heating device 3, the prediction error of the process model is learned based on the measured actual temperature by the outlet width thermometer 72 and the actual power of the induction heating device 3. The prediction error of the process model is stored in a learning table classified based on the actual number of induction heating devices used. The learning table is stored in, for example, the database 114. Note that the classification of the learning table is not limited to the actual number of induction heating devices 3 used. When heating by the induction heating device 3 is performed under the conditions corresponding to a certain classification of the learning table, the learning value of that classification is updated. The learning value corresponding to the learning table classification is sent to the temperature calculation unit 111 and used at the time of design calculation. The model parameters to be learned may be either the rolled material temperature or the heating efficiency of the induction heating device. Also, the learning value may be an additive type or a multiplicative type with respect to the model parameter.

[0035] FIG. 4 is a flowchart for explaining the calculation method of the heating pattern. According to the routine shown in FIG. 4, first, calculation conditions are acquired (step S1). In step S1, as the calculation conditions, in addition to the rolled material information and the basic information related to process control, the predicted temperature on the inlet side of the induction heating device, the target temperature on the outlet side of the induction heating device, and the status information of the induction heating device are acquired. The rolled material information includes, for example, the steel type and size. The basic information related to process control includes, for example, the speed pattern.

[0036] Next, an initial heating pattern is set (step S2). The initial heating pattern is a combination of the initial value p in of the power supplied to each inductor and the initial value x in of the position in the width direction of each inductor. These initial values p in , x in are managed by a table classified by the steel type and size of the rolled material Mr. FIG. 5 shows the initial values p in , x inThis figure shows an example of a table for managing combinations. In step S2 above, the initial values ​​for the optimization calculation described later are read by referring to the table shown in Figure 5. Note that the method of categorizing the table is not limited to the steel type and size of the rolled material Mr.

[0037] Next, an optimization calculation is performed to calculate candidate heating patterns (step S3). In step S3, the evaluation function (also called the "objective function") f defined by equation (1) below is used. obj To minimize the inductor 31j(1 <j≦N IH ) Power p j and width direction position x j This will be determined. The optimization calculation will be performed on the segment of the rolled material in which the sum of the errors between the target temperature and the predicted temperature at each widthwise target position is the largest when the induction heating device is not used. This is because if the number of induction heating devices 3 to be used is underestimated, it will not be possible to increase the number of devices used during heating, so the maximum number of devices to be used is estimated in advance.

[0038]

number

[0039] In the above formula (1), N node w is the number of widthwise divisions (widthwise target positions) i of the rolled material Mr. i This is the widthwise target position i (1 ≤ i ≤ N node This is the weight given to T. i tgt This is the target temperature at the widthwise target position i on the outlet side of the induction heating device 3, and T i pred x is the predicted temperature at the widthwise target position i on the outlet side of the induction heating device. j min This is the constraint value (minimum value) for the widthwise position of the j-th inductor 31j from the upstream side in the transport direction, and x j max This is the constraint value (maximum value) for the widthwise position of the j-th inductor 31j. j minThis is the constraint value (minimum value) of the power (supply power) of the j-th inductor 31j, and p j max is the power constraint value (maximum value) of the j-th inductor 31j. Also, λ(|p|) is a regularization term for Lasso regression, and λ is a regularization parameter that represents the weight of the regularization term. The regularization parameter λ is a predetermined arbitrary value greater than or equal to 0. The larger the regularization parameter λ, the greater the effect of reducing the number of inductors 31 used, while the smaller the regularization parameter λ, the greater the effect of reducing the temperature deviation (T i tgt -T i pred The reduction effect of ) becomes greater. Note that the inductor 31 may be a mixture of transverse type and solenoid type, and may include inductors whose width direction position cannot be changed. Note that the inductor 31 may be composed of an upper inductor on the upper side in the thickness direction and a lower inductor on the lower side in the thickness direction. If the upper and lower inductors can move their width direction positions independently, the width direction position x in equation (1) above becomes larger. j The upper and lower inductors can be treated as independent variables.

[0040] Equation (1) above can be solved using general optimization methods. Solving equation (1) above yields power p. j The threshold p j,th (=p j min +ε p ) Determine whether or not there is an inductor 31j that is less than or equal to (step S4). That is, the supplied power p j It is determined whether or not there is an inductor 31j that is small and can be set to not be used. If there is, the inductor 31j is set to not be used (step S5), and the process returns to step S3. This reduces the number of inductors 31 used, thereby saving energy. On the other hand, if there is no inductor 31, the process proceeds to step S6.

[0041] By the way, the predicted temperature T in equation (1) above i predSince this is a nonlinear function, in order to perform optimization including accurate prediction, it is necessary to calculate transient heat conduction considering the velocity patterns of the rolled material Mr at the inlet and outlet of the induction heating device 3. For this reason, the evaluation function f in equation (1) above obj It is difficult to solve this analytically, and it needs to be solved numerically. Evaluation function f obj Numerically solving this would significantly increase the solving time and the processing load on the process control computer. When the performance of the process control computer 11 is high, the evaluation function f obj It is also possible to solve this numerically. Since the process control computer 11 performs various controls on the rolling line RL, it is desirable to minimize the processing load on the process control computer 11. Therefore, the nonlinear function T i pred The linear function T is expressed as shown in equation (2) below. i pred‘ It approximates this.

[0042]

number

[0043] Here, in equation (2) above, T i 0 ΔT is the temperature at the input side of the induction heating device 3 at the target position i in the width direction. ij (x) is the predicted temperature increase at the target position i in the width direction of the rolled material at a certain reference power using the induction heating device 3j. Predicted temperature increase ΔT ij (x) is, for example, the widthwise position x as in equation (3) below. j This can be prepared in advance as an M-degree polynomial relating to .

[0044]

number

[0045] By approximating using equation (2) above, the evaluation function f of equation (1) above can be obtained. objThis allows for analytical solving, significantly reducing processing time compared to numerical solutions, and consequently lowering the processing load on the process control computer 11.

[0046] By repeating the processes in steps S3 to S5 described above, the optimal power value p supplied to each inductor 31j is determined. j And the optimal value x of the widthwise position of each inductor 31j j A candidate heating pattern is obtained by combining the following. These steps S3 to S5 are performed from the viewpoint of widthwise temperature distribution and energy saving, and the power p of each inductor 31j j and widthwise position x j This is a process to optimize the heating pattern. Using the heating pattern candidates obtained in this way, transient heat conduction calculations are performed to predict the widthwise temperature distribution T at the target location (for example, the output of the induction heating device 3). i pred Calculate (Step S6). The heating pattern candidates are evaluated using the approximation of equation (2) above, and the evaluation function f obj Since this is an analytical solution, the predicted value T of the temperature distribution in the width direction is obtained in step S6 above. i pred It is calculated and verified.

[0047] Next, the termination determination is performed (step S7). In step S7, the predicted value T of the calculated widthwise temperature distribution is determined. i pred and target value T i tgt Compare the two and the difference (T i tgt -T i pred It is determined whether the value is smaller than the threshold, that is, whether the termination condition is met. If it is determined in step S7 that the termination condition is not met, the process proceeds to step S8. In step S8, based on the above deviation, the target temperature (target value T) in the optimization calculation of step S3 is determined. i tgt ) is corrected. That is, the evaluation function f of equation (1) above is modified using the offset target temperature. objThe problem is solved again. The processes in steps S3 to S8 above are repeated until the termination condition is met. Note that the termination condition is not limited to the above deviation, but may also include other factors, such as the number of times the optimization calculation in step S3 is repeated. In other words, the process can be configured so that when the optimization calculation in step S3 is repeated a predetermined number of times, the process proceeds to step S6.

[0048] If the processing conditions are determined to be met in step S7 above, the candidate heating pattern is designated as the final heating pattern, and this routine is terminated. At the same time, the final heating pattern is determined by the supplied power p j and width direction position x j This combination is set for each induction heating device 3 and, consequently, for each inductor 31j.

[0049] There are no specific limitations on the structure of the process control computer 11, but as an example, it may be as follows. Figure 6 shows an example of the hardware configuration of the process control computer 11. The functions of the process control computer 11 can be realized by the processing circuit shown in Figure 6. This processing circuit may be dedicated hardware 11a. This processing circuit may also include a processor 11b and memory 11c. This processing circuit may be partially formed as dedicated hardware 11a and further include a processor 11b and memory 11c. In the example in Figure 6, part of the processing circuit is formed as dedicated hardware 11a, and the processing circuit also includes a processor 11b and memory 11c.

[0050] At least a portion of the processing circuit may be at least one dedicated hardware 11a. In this case, the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. The processing circuit may also include at least one processor 11b and at least one memory 11c. In this case, each function of the process control computer 11 is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 11c. The processor 11b realizes each function by reading and executing the programs stored in the memory 11c. The processor 11b is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 11c may be, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM. The memory 11c can also serve as a database 114. In this way, the processing circuit can realize each function of the process control computer 11 through hardware, software, firmware, or a combination thereof.

[0051] As explained above, according to this embodiment, the evaluation function f obj Because this evaluation function f includes not only the term for the temperature deviation of the rolled material Mr but also the term for the power supplied to the induction heating device 3, obj By controlling each induction heating device 3 based on the heating pattern obtained by solving the equation, it is possible to achieve energy savings while making the temperature distribution in the width direction of the rolled material Mr uniform. Therefore, as shown in Figure 9, even when the amount of heating differs depending on the width direction position of the rolled material Mr, it is possible to achieve energy savings while satisfying the target value of the temperature distribution in the width direction of the rolled material Mr.

[0052] Also, the evaluation function f obj The nonlinear function T i pred Linear function T ipred‘ By approximating, the evaluation function f obj can be solved analytically, and the processing time can be significantly shortened compared with the case of solving numerically, and as a result, the processing load on the process control computer 11 can be reduced. Moreover, by performing an unsteady heat conduction calculation using the heating pattern candidates and calculating the predicted value T i pred of the widthwise temperature distribution, the heating pattern candidates obtained by analytically solving the evaluation function f obj can be verified.

[0053] As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. In the above-described embodiments, when referring to the number of each element, quantity, amount, range, etc., the present invention is not limited to the mentioned number, except when specifically stated or clearly specified by the principle. Also, the structures and the like described in the above-described embodiments are not necessarily essential to the present invention, except when specifically stated or clearly specified by the principle.

[0054] As shown in Figures 7 and 8, a pair of edge heaters 8 are installed on the upstream or downstream side (downstream side in the example shown in Figure 7) of the induction heating device 3 in the transport direction to locally heat both ends in the width direction of the rolled material Mr (work side: WS, drive side: DS). Figure 7 is a schematic diagram showing another configuration of the hot rolling line RL to which the induction heating system is applied. Figure 8 is a schematic diagram showing an example of the configuration of the edge heater 8. The edge heater 8 is configured longitudinally in the transport direction. The edge heater 8, like the induction heating device 3, has an inductor 81 and a power supply 82 for supplying power to the inductor 81. The inductor 81 has an iron core 811 and an induction coil (heating coil) 812 wound around the iron core 811. The iron core 811 has a C-shaped cross-section so as to surround the width direction ends WS, DS. For the power supply 82, for example, an inverter power supply can be used. When power is supplied to the induction coil 812 from the power supply 82, flux linkage is generated on the work side WS and drive side DS of the rolled material Mr, inducing eddy currents in the rolled material Mr. These eddy currents generate Joule heat, heating both sides WS and DS of the rolled material Mr. The edge heater 8 further comprises a moving mechanism 84 provided on the iron core 811 and a position controller 85. mechanism 84, like the moving mechanism 34, can be composed of a trolley or slider that can move in the width direction. The position controller 85 changes the position of each moving mechanism 84, so that the pair of inductors 81 can be moved to different width directions. Furthermore, the pair of inductors 81 are configured to be supplied with the same power from the power supply 82. That is, the pair of inductors 81 are configured so that they cannot be supplied with different power. In such a case, the power supply term in equation (1) above is set to a common value p_j for the edge heater 8, and the width direction position of the edge heater 36 is set to separate variables such as x_(j_WS) and x_(j_DS), so that the evaluation function f can be used even when the edge heater 8 is provided. obj This can be applied.

[0055] Incidentally, depending on the conditions of the rolling line RL, such as the heating conditions of the heating furnace 1 or the waiting time of the rolled material Mr extracted from the heating furnace 1, the scale (oxide film) formed on the surface of the rolled material Mr may become thicker, potentially leading to poor measurement conditions of the entry-side width thermometer 71. In this case, when calculating the heating pattern described above, it is preferable not to use the measured value of the entry-side width thermometer 71 as the widthwise temperature distribution on the entry side of the induction heating device 3, but rather to use the measured value (measurement result) when the measurement conditions of the entry-side width thermometer 71 are good, i.e., when the measurement conditions of the entry-side width thermometer 71 are good. Specifically, it is possible to correct the predicted value of the widthwise temperature distribution of the process model using a correction value, which is the prediction error of the process model (physical model) learned by the learning unit 113 after rolling, and use this as the widthwise temperature distribution on the entry side of the induction heating device 3. The learned correction value can be stored and managed in a learning table (not shown) categorized based on the steel type and size of the rolled material Mr. The learning table is updated when rolling is performed under the same conditions.

[0056] In the above embodiment, the example was given in which the process control computer 11 executes the induction heating device control function 110, that is, the functions of each part 111, 112, and 113, but it may be executed on a different computer. In this case, the evaluation function f can be calculated without approximating using the above equation (2). obj It is also possible to solve this numerically.

[0057] In the above embodiment, a transverse induction heating device 3 was described as an example, but if there are multiple transverse induction heating devices, a mix of transverse and solenoid induction heating devices may be used. [Explanation of symbols]

[0058] RL…Hot rolling line, Mr…Rolled material, 1…Heating furnace, 2…Roughing mill, 21…Stand, 3…Induction heating device, 31…Inductor, 311…Iron core, 312…Induction coil, 32…Power supply, 33…Housing, 34…Moving mechanism, 35…Position controller, 4…Finishing rolling mill, 41…Stand, 5…Cooling table, 6…Winding machine, 71…Inlet width thermometer, 72…Outlet width thermometer, 8…Edge heater, 81…Inductor, 811…Iron core, 812…Induction coil, 82…Power supply, 83…Housing, 84…Moving mechanism, 85…Position controller, 11…Process control computer, 110…Induction heating device control function, 111…Temperature calculation unit, 112…Optimization calculation unit, 113…Learning unit, 114…Database

Claims

1. An induction heating system installed in a hot rolling line to induce heating of rolled material, Multiple transverse induction heating devices are installed along the conveying direction of the rolled material, A computer calculates a heating pattern, which is a combination of the power supplied to the inductor of each induction heating device and the position of each inductor that can move in the width direction of the rolled material, based on the information of the rolled material and the actual values ​​of the width direction temperature distribution on the inlet and outlet sides of the induction heating device, and sets the heating pattern to each induction heating device. Equipped with, The aforementioned computer is Define an evaluation function that includes a term representing the deviation between the target value and the predicted value of the widthwise temperature distribution of the rolled material at the exit of each induction heating device, and a term representing the power supplied to each inductor. The predicted values ​​of the widthwise temperature distribution in the evaluation function are linearly approximated, An induction heating system configured to perform the following: calculate a candidate heating pattern, which is the heating pattern that minimizes the evaluation function.

2. In the induction heating system according to Claim 1, The aforementioned computer is Recalculating the predicted values ​​of the temperature distribution in the width direction using the aforementioned heating pattern candidates, An induction heating system configured to perform the following: verify the candidate heating pattern based on the deviation between the recalculated predicted value and the target value.

3. In the induction heating system according to claim 1, A pair of edge heaters are installed on the upstream or downstream side of the conveying direction of the induction heating device to locally heat both ends of the rolled material in the width direction, and the pair of edge heaters have inductors that can move to different width direction positions from each other, and are configured to be supplied with the same power to the inductors of each edge heater. The aforementioned computer is An induction heating system configured such that the power supply term in the evaluation function is set to a common value for the inductor of the edge heater.

4. In the induction heating system according to claim 1, The induction heating device is further equipped with an inlet width thermometer for measuring the actual value of the widthwise temperature distribution on the inlet side, The aforementioned computer is configured to use a corrected value learned from actual values ​​measured when the measurement conditions are good, instead of the actual value measured by the inlet width thermometer, when the measurement conditions of the inlet width thermometer are poor.

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