Induction heating system

Abstract

An induction heating system is provided with: a plurality of transverse induction heating devices provided along the conveyance direction of a rolled material; and a computer that calculates a heating pattern, which is a combination of the electric power supplied to the inductors of the induction heating devices and the positions of the inductors movable in the width direction of the rolled material, on the basis of the information of the rolled material and the actual values of the temperature distributions in the width direction of the inlet side and the outlet side of the induction heating devices. The calculation unit is configured to: define an evaluation function including a term of a deviation between a target value and a predicted value of a temperature distribution in the width direction of the rolled material on the exit side of each induction heating device, and a term of power supplied to each inductor; a heating mode candidate, which is a heating mode for which the evaluation function is minimized, is calculated.

Description

Technical Field

[0001] This disclosure relates to an induction heating system installed on a hot rolling line for induction heating of rolled materials. Background Technology

[0002] The temperature of rolled material in a hot rolling line (hereinafter also referred to as a "rolling line") affects its mechanical properties. Therefore, temperature control of the rolled material is very important. Induction heating devices, which induction heat the rolled material, are installed, for example, between the roughing mill and the finishing mill of the rolling line. These induction heating devices can heat the rolled material at a high current density based on the current and number of turns of the induction coil, thus enabling rapid heating of the rolled material transported in one direction within the rolling line. Furthermore, they offer advantages such as good heating efficiency, and because the energy source is electricity, they do not directly emit CO2 as with gas heating. By appropriately designing the shape of the induction coil and the core, they also have the advantage of being able to locally heat desired areas of the rolled material.

[0003] The purpose of introducing such induction heating devices into the rolling line, in addition to reducing thermal disorder and sprue marks, is to achieve uniformity of temperature and quality along the width of the rolled material. Thermal disorder refers to the temperature drop from the front end to the back end of the rolled material along its length. Sprue marks refer to the periodic temperature unevenness along the length of the rolled material caused by heat dissipation into the supports (sprues) that support the slab in the heating furnace.

[0004] Induction heating devices are broadly classified into two types based on the direction of the main magnetic flux (AC flux generated by the induction heating device) linking with the rolled material: solenoid type and transverse type. In the solenoid type, the direction of the main magnetic flux is aligned with the length direction (transport direction) of the rolled material. The current induced by the main magnetic flux (hereinafter also referred to as "eddy current") flows in a manner that surrounds the surface within the thickness-width cross-section of the rolled material. Therefore, the heat generated by the eddy current is distributed in the thickness direction and is approximately uniform in the width direction. On the other hand, in the transverse type, the direction of the main magnetic flux is aligned with the thickness direction of the rolled material. Eddy currents flow in a manner that surrounds the main magnetic flux within the width-transport direction cross-section of the rolled material. Therefore, the heat generated by the eddy current is approximately uniform in the thickness direction, but varies significantly in the width direction depending on the shape and position of the induction coil / core.

[0005] Here, the thickness of the rolled material is very short compared to its width. Therefore, the temperature distribution in the thickness direction is homogenized within a short time after heating, while the temperature distribution in the width direction is not homogenized within a short time. Consequently, the control of an induction heating device that generates a transverse temperature distribution in the width direction becomes more complex compared to a solenoid-type device.

[0006] However, when using induction heating devices, it is preferable to supply the minimum required power to the rolled material. On the other hand, if the power supply to the induction heating device (inverter power supply) is turned on while the rolled material is passing through the induction heating device, the rapid load fluctuations may cause instability in the inverter startup. Therefore, typically, the number of induction heating devices to be used for heating is determined in advance, and the inverter power supply is started before the rolled material enters the induction heating device. During startup, the inverter power supply needs to always output power above the lower limit power (standby power). That is, even in positions along the length of the rolled material that do not require heating, the amount of standby power will be increased, and this standby power becomes wasted power consumption. This wasted power consumption increases as the number of induction heating devices used for heating increases. Therefore, from an energy-saving point of view, it is preferable to use the minimum required number of induction heating devices to heat the rolled material.

[0007] Patent Document 1 discloses a plurality of induction heating devices arranged in the transport direction of a rough bar, which is a rolled material. The number of inductors used for heating the rolled material is determined based on the target temperature at the outlet of the induction heating device and the temperature of the rolled material (rough bar) at the inlet of the induction heating device, thereby achieving energy saving.

[0008] Patent Document 2 discloses an induction heating device having multiple inductors (heating units) arranged in the transport direction of the rolled material. The temperature at the exit side of the roughing mill is measured and sampled along the entire length of the rolled material. By using a portion of the inductors while ensuring the maximum power is set at each sampling point, the number of inductors used is reduced.

[0009] Existing technical documents Patent documents Patent Document 1: Japanese Patent No. 3960204 Patent Document 2: Japanese Patent No. 3801154 Summary of the Invention

[0010] The problem that the invention aims to solve However, neither Patent Documents 1 nor 2 mentions the temperature distribution along the width of the rolled material. That is, they assume that the rolled material is divided into multiple locations along its length, each with a representative temperature, and determine the power of the induction heating device and the number of units used based on the representative temperature of each location.

[0011] In the solenoid method, the temperature rises uniformly along the width of the rolled material, so no particular problem arises under the aforementioned conditions. On the other hand, in the transverse method, since the inductor moves along the width of the rolled material, the amount of temperature rise sometimes varies depending on the position of the inductor along the width of the rolled material. For example, as... Figure 9As shown, the temperature rise distribution along the width of the rolled material varies as shown in D1 to D3, depending on the position of the inductor along the width of the rolled material. In this case, the optimal heating mode of the induction heating device needs to be determined based on the target temperature along the width of the rolled material (number of induction heating devices used, power consumption, and width-direction position).

[0012] This disclosure was made to solve the aforementioned problems, and its purpose is to provide an induction heating system that can achieve energy saving while meeting the target value of the temperature distribution in the width direction of the rolled material, even when the amount of temperature rise varies depending on the position of the rolled material in the width direction.

[0013] Methods for solving problems The first aspect of this disclosure relates to an induction heating system for induction heating of rolled material installed on a hot rolling line. The induction heating system includes: multiple transversely arranged induction heating devices positioned along the transport direction of the rolled material; and a computer that, based on information about the rolled material and actual values ​​of the width-direction temperature distribution at the inlet and outlet sides of the induction heating devices, calculates a combination of the power supplied to the inductors of each induction heating device and the position of each inductor movable in the width direction of the rolled material, i.e., a heating mode, and sets the heating mode for each induction heating device. The computer is configured to: define an evaluation function including 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 outlet side of each induction heating device, and a term for the power supplied to each inductor; and calculate the heating mode, i.e., a heating mode candidate, when the evaluation function is minimized.

[0014] The second viewpoint, building upon the first, also possesses the following characteristics: The computer is configured to perform a linear approximation of the predicted value of the temperature distribution in the width direction within the evaluation function.

[0015] The third perspective, building upon the second perspective, also possesses the following characteristics. The computer configuration is designed to perform: recalculate the predicted value of the temperature distribution in the width direction using the heating mode candidate; and verify the heating mode candidate based on the deviation between the recalculated predicted value and the target value.

[0016] The fourth viewpoint, building upon the first, also possesses the following characteristics. It is configured such that a pair of edge heaters are provided on the upstream or downstream side of the conveying direction of the induction heating device, for locally heating both ends of the rolled material in the width direction. Each pair of edge heaters has inductors capable of moving to different positions in the width direction, and the inductors of each edge heater are supplied with the same power. The computer is configured to set the power supply term in the evaluation function to a common value in the inductors of the edge heaters.

[0017] The fifth point, building upon the first point, also possesses the following characteristics: The induction heating system further includes an inlet-side width thermometer that measures the actual value of the temperature distribution in the width direction on the inlet side of the induction heating device. The computer is configured to, in the event of a malfunction in the inlet-side width thermometer, use a correction value obtained by learning from the actual value measured when the inlet-side width thermometer is functioning well, instead of the actual value measured by the inlet-side width thermometer.

[0018] Invention Effects 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 supply to the induction heating device. Therefore, if each induction heating device is controlled based on the heating mode obtained by solving this evaluation function, energy saving can be achieved while ensuring a uniform temperature distribution in the width direction of the rolled material. Thus, even when the temperature rise varies depending on the position of the rolled material in the width direction, energy saving can be achieved while meeting the target value for the temperature distribution in the width direction of the rolled material.

[0019] Furthermore, by linearly approximating the predicted value of the temperature distribution in the width direction within the evaluation function, the evaluation function can be solved analytically. Compared to numerical solutions, this significantly reduces processing time and consequently decreases the computational load on the computer. Therefore, it can be appropriately applied to cases where the computer is a process control computer. Moreover, by calculating the predicted value of the temperature distribution in the width direction using heating mode candidates for unsteady heat conduction calculations, the heating mode candidates obtained by analytically solving the evaluation function can be validated. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the structure of a hot rolling line using an induction heating system implemented in this way.

[0021] Figure 2 This is a schematic diagram illustrating an example of the structure of an induction heating device.

[0022] Figure 3 It is a schematic diagram showing the functions of a process control computer.

[0023] Figure 4 This is a flowchart illustrating the calculation method for the heating mode.

[0024] Figure 5 This is a diagram of an example of a table that manages the combination of initial values ​​contained in the initial heating mode.

[0025] Figure 6 This is a diagram illustrating an example of the hardware structure of a process control computer.

[0026] Figure 7This is a schematic diagram showing other structures of a hot rolling line that utilizes an induction heating system.

[0027] Figure 8 This is a schematic diagram illustrating an example of the structure of an edge heater.

[0028] Figure 9 It is a graph showing the change in the temperature rise distribution along the width direction corresponding to the position of the inductor along the width direction of the rolled material. Detailed Implementation

[0029] Hereinafter, with reference to the accompanying drawings, the control device of the induction heating device according to the embodiment will be described as an example, taking an induction heating device installed between the roughing mill and the finishing mill in a hot rolling line. Furthermore, common elements in all figures are labeled with the same reference numerals, and repeated descriptions are omitted.

[0030] Figure 1 This is a schematic diagram showing the structure of a hot rolling line RL using an induction heating system implemented in this way. In the hot rolling line RL, the rolled material Mr is rolled to the desired thickness and width. The hot rolling line RL has a heating furnace 1, a roughing mill 2, an induction heating device 3, a finishing mill 4, a cooling worktable 5, and a coiler 6 as its main equipment.

[0031] Heating furnace 1 heats the slab, which is to be rolled material Mr, to a specified temperature (e.g., 1200°C). The rolled material Mr, which has just been pulled out of heating furnace 1, is, for example, a cuboid metal (e.g., steel) with 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.

[0032] The roughing mill 2 has one to three stands 21. The roughing mill 2 performs multiple rolling operations on the rolled material Mr while reversing the transport direction.

[0033] Figure 2 This is a schematic diagram illustrating an example of the structure of the induction heating device 3. (See diagram for example.) Figure 2 As shown, the transverse induction heating device 3 includes multiple N units arranged along the rolling direction of the rolled material Mr. IH Inductor 31 and for supplying each inductor 31j (1<j≦N) IHThe inductor 31 has an iron core 311 and an induction coil (heating coil) 312 wound around the iron core 311. An inverter power supply can be used as the power source 32, for example. When power is supplied from the power source 32 to the induction coil 312, a linked magnetic flux is generated in the thickness direction of the rolled material Mr, inducing eddy currents in the rolled material Mr. Joule heating is generated by these eddy currents, heating the rolled material Mr. The induction heating device 3 also includes a housing 33 housing the inductor 31, a moving mechanism 34 disposed in the housing 33, and a position controller 35. Although detailed illustrations are omitted, the moving mechanism 34 can be composed of a trolley, slider, etc., capable of moving in the width direction. By changing the position of the moving mechanism 34 using the position controller 35, the position of the inductor 31 in the width direction can be changed. Furthermore, in Figure 2 For simplicity, only the upper inductor 31, positioned above the rolled material Mr, is shown in the diagram. However, a lower inductor with the same structure as the upper inductor 31 can also be positioned below the rolled material Mr. In this case, the lower inductor is configured to move its width direction independently of the upper inductor 31. 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 can be shared by the upper inductor 31 and the lower inductor, or they can be provided independently.

[0034] The finishing mill 4 has multiple (e.g., 7) stands 41. The cooling table 5 has multiple cooling unit groups (cooling unit groups) arranged along the transport direction of the rolled material Mr. The cooling table 5 injects cooling water into the rolled material Mr that has passed through the finishing mill 4, thereby cooling the rolled material Mr to the target temperature. The rolled material Mr that has passed through the cooling table 5 is wound into a coil by the coiler 6. The coiling temperature (CT) is, for example, 600°C.

[0035] A width thermometer (hereinafter referred to as the "entry-side width thermometer") 71 is installed between the roughing mill 2 and the induction heating device 3 on the upstream side of the conveying direction. The entry-side width thermometer 71 measures the width-direction temperature of the rolled material Mr entering the upstream induction heating device 3. A width thermometer (hereinafter referred to as the "exit-side width thermometer") 72 is installed between the downstream induction heating device 3 and the finishing mill 4. The exit-side width thermometer 72 measures the width-direction temperature of the rolled material Mr exiting 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 entry-side width thermometer 71 and the exit-side width thermometer 72 measure the width-direction temperature distribution of each node.

[0036] The hot rolling line RL is operated using a computer-controlled system. The computer includes a host computer 10 and a process control computer 11 interconnected via a network. The process control computer 11 is connected via a network to an interface screen 12, which serves as the operator's screen. The operator can perform input operations, including manual intervention, on the interface screen 12.

[0037] According to the operation plan, the host computer 10 determines the hot rolling command information, which includes the specifications (steel type, size) of the rolled material Mr, the rolling target (target product thickness, product width, temperature (including finishing mill exit temperature (FDT) and coiling temperature (CT)) and other information required for rolling, and sends (outputs) the hot rolling command information to the process control computer 11.

[0038] The process control computer 11 uses hot rolling command information (including rolled material information) input from the rolling computer 10, manual intervention information from the operator on the interface screen 12, actual values ​​of the temperature distribution in the width direction measured by the width thermometers 71 and 72, and parameters of the process model extracted from the database 114 to calculate the heating mode of the induction heating device 3, and sends the calculated heating mode as a setpoint to the induction heating device 3. The functions of the process control computer 11 will be described below.

[0039] Figure 3 This is a schematic diagram illustrating the functions of the process control computer 11. For example... Figure 3 As shown, the process control computer 11 has the function of controlling the induction heating device 3 110. The process control computer 11 includes a temperature calculation unit (temperature calculation function) 111, an optimization calculation unit (heating mode optimization calculation function) 112, a learning unit (learning function) 113, and a database 114.

[0040] The temperature calculation unit 111 calculates the predicted values ​​of the width-direction temperature distribution of each segment of the rolled material (the point that divides the rolled material in the length direction) at the inlet position of the induction heating device 3 and the predicted values ​​of the width-direction temperature distribution of each segment of the rolled material Mr at the outlet position of the outlet thermometer 72, based on rolling information such as the thickness and width of the rolled material and the rolling speed mode calculated in the process control computer 11, the actual values ​​of the width-direction temperature distribution of the rolled material Mr at the inlet position of the induction heating device 3 and the predicted values ​​of the width-direction temperature distribution of each segment of the rolled material Mr at the outlet position of the outlet thermometer 72, using the process model (physical model), and sends the calculated predicted values ​​to the optimization calculation unit 112. Furthermore, based on the heating mode candidates calculated by the optimization calculation unit 112, the predicted values ​​of the width-direction temperature distribution of each segment of the rolled material Mr at the inlet side of the induction heating device 3 and the predicted values ​​of the width-direction temperature distribution of each segment of the rolled material Mr at the outlet side thermometer 72 are calculated again, and the recalculated predicted values ​​are sent to the optimization calculation unit 112. Moreover, the process model (physical model) used for calculating the predicted values ​​is well-known, therefore a detailed description is omitted here.

[0041] The optimization calculation unit 112 calculates heating mode candidates to achieve the target value of the width-direction temperature distribution at the location of the outlet thermometer 72 based on the predicted value of the width-direction temperature distribution received from the temperature calculation unit 111 on the induction heating device 3. The calculated heating mode candidates are then sent to the temperature calculation unit 111. The heating mode candidate refers to the power p supplied to each inductor 31j that minimizes (converges) the evaluation function described later. j The position x in the width direction of each inductor 31j j The combination. Additionally, since no power supply p is used. j The number of induction heating devices 3 is zero, therefore the heating mode candidates actually include the number of induction heating devices 3 in use.

[0042] The learning function unit 113 sends the correction value of the prediction error of the process model (physical model) to the temperature calculation unit 111. Additionally, after heating by the induction heating device 3, the correction value of the heating zone is updated based on the actual heating 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 actual temperature measured by the output 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 partitioned based on the actual number of induction heating devices used. The learning table is stored, for example, in a database 114. Furthermore, the partitioning of the learning table is not limited to the actual number of induction heating devices 3 used. If heating is performed by the induction heating device 3 under conditions that conform to a certain partition of the learning table, the learning value for that partition is updated. The learning values ​​conforming to the partition of the learning table are sent to the temperature calculation unit 111 for use during design calculations. The model parameters learned can also be either the rolled material temperature or the heating efficiency of the induction heating device. In addition, the learning values ​​can be additive or multiplicative, applied to the model parameters.

[0043] Figure 4 This is a flowchart illustrating the calculation method for the heating mode. According to... Figure 4 The example shown first obtains the calculation conditions (step S1). In step S1, in addition to rolled material information and basic information related to process control, the calculation conditions also include the predicted temperature at the induction heating device input, the target temperature at the induction heating device output, and the status information of the induction heating device. Rolled material information includes, for example, steel grade and dimensions. Basic information related to process control includes, for example, the speed mode.

[0044] Next, the initial heating mode is set (step S2). The initial heating mode is the initial value p of the power supplied to each inductor. in The initial value x of the position of each inductor in the width direction in The combination of these initial values ​​p. in x in It is managed by a table that is partitioned by the steel type, size, etc. of the rolled material Mr. Figure 5 This represents the initial value p included in the initial heating mode. in x in A diagram illustrating an example of a table managed through a combination of elements. In step S2 above, refer to... Figure 5 The table shown is used to read the initial values ​​for the optimization calculations described later. Furthermore, the table's partitioning method is not limited to the steel grade or size of the rolled material Mr.

[0045] Next, heating mode candidates are calculated by performing optimization calculations (step S3). In step S3, the evaluation function (also known as the "objective function") f, defined by the following equation (1), is used. objThe method of minimization determines the inductors 31j of each induction heating device 3 (1 < j ≦ N). IH The electricity p j and width direction position x j Furthermore, the optimization calculation is performed on the section of the rolled material where the sum of the errors between the target temperature and the predicted temperature at each width direction target position is the largest when the induction heating device is not used. This is because if the number of induction heating devices 3 used is underestimated, the number of devices used cannot be increased during heating, so the maximum number of devices used is estimated in advance.

[0046] In equation (1) above, N node It represents the number of width-direction partitions (target positions in the width direction) i of the rolled material Mr. i This refers to the target position i (1 ≦ i ≦ N) in the width direction. node The weight of T. i tgt The target temperature T is the target position i in the width direction of the output side of the induction heating device 3. i pred It is the predicted temperature at the target position i in the width direction of the output side of the induction heating device. j min The constraint value (minimum value) for the width-direction position of the j-th inductor 31j, starting from the upstream side of the transport direction, is x. j max p is the constraint value (maximum value) for the position of the j-th inductor 31j in the width direction. j min p is the minimum value (constraint) of the power supply to the j-th inductor 31j. j max This is the constraint value (maximum value) of the power of the j-th inductor 31j. Additionally, λ(|p|) is the regularization term used for Lasso regression, and λ is the regularization parameter representing the weight of the regularization term. The regularization parameter λ is any value above 0 that is predetermined. The larger the regularization parameter λ, the greater the reduction in the number of inductors 31 used; conversely, the smaller the value, the greater the temperature deviation (T... i tgt -T i pred The greater the reduction effect, the better. Furthermore, inductor 31 can also be a combination of lateral and solenoid configurations, and may include inductors whose width direction position cannot be changed. Additionally, inductor 31 can also be composed of an upper inductor on the upper side of the thickness direction and a lower inductor on the lower side of the thickness direction. When the upper and lower inductors can move independently in the width direction, the width direction position x in equation (1) for the upper and lower inductors... jThese can be independent variables.

[0047] Equation (1) above can be solved using a general optimization method. The result of solving equation (1) is used to determine whether there is an electric current p. j For threshold p j，th (=p) j min +ε p The following inductor 31j (step S4). That is, determining whether there is a power supply p. j A small inductor 31j that can be set to be unused. If present, this inductor 31j is set to be unused (step S5), and the process returns to step S3. This reduces the number of inductors 31j used, achieving energy savings. On the other hand, if it is not present, the process proceeds to step S6.

[0048] In addition, the predicted temperature T in equation (1) above i pred Since it is a nonlinear function, in order to perform optimization that includes accurate prediction, it is necessary to calculate the unsteady heat conduction considering the velocity patterns of the rolled material Mr on both the inlet and outlet sides of the induction heating device 3. Therefore, it is difficult to analytically solve the evaluation function f of equation (1) above. obj This requires numerical solutions. If the evaluation function f is solved numerically... obj This significantly increases the solution time or the processing load on the process control computer. However, with a high-performance process control computer 11, the evaluation function f can be solved numerically. obj In the process control computer 11, since various controls related to the rolling line RL are performed, it is preferable to minimize the processing load on the process control computer 11. Therefore, as shown in equation (2), the nonlinear function T is... i pred Approximately a linear function T i pred‘ .

[0049] In this equation (2), T i 0 ΔT is the temperature at the input of the induction heating device 3 at the target position i in the width direction. ij (x) is the predicted temperature rise at the target position i in the width direction of the rolled material under a certain reference power caused by the induction heating device 3j. The predicted temperature rise ΔT ij (x) For example, it can be represented as the position x in the width direction, as in equation (3). j The relevant M-degree polynomials are prepared in advance.

[0050] Here, in the above equation (3), a ij，k These are the coefficients of an approximate M-degree polynomial.

[0051] By using the above equation (2) as an approximation, the evaluation function f of the above equation (1) can be solved analytically. obj Compared to numerical solutions, the processing time is significantly reduced, which in turn reduces the processing load on the process control computer 11.

[0052] By repeating steps S3 to S5 above, the optimal value p of the power supplied to each inductor 31j is obtained. j The optimal value x of the position of each inductor 31j in the width direction j The combination of these constitutes the heating mode candidate. These steps S3 to S5 are based on the perspectives of temperature distribution along the width and energy saving, aiming to reduce the power p of each inductor 31j. j and the position x in the width direction j Optimization processing. Using the resulting heating mode candidates, unsteady heat conduction calculations are performed to calculate the predicted value T of the width-direction temperature distribution at the target location (e.g., the outlet side of the induction heating device 3). i pred (Step S6). The heating mode candidate is obtained by analytically solving the evaluation function f using the approximation of equation (2) above. obj Therefore, in step S6 above, the predicted value T of the temperature distribution in the width direction is calculated and verified. i pred .

[0053] Next, the termination determination is performed (step S7). In step S7, the calculated predicted value T of the temperature distribution in the width direction is... i pred With target value T i tgt Compare and determine the deviation (T) between the two. i tgt -T i pred Whether the temperature is less than the threshold, i.e., whether the termination condition is met. If the termination condition is not met in step S7, proceed to step S8. In step S8, based on the above deviation, correct the target temperature (target value T) calculated in step S3. i tgt That is, using the target temperature with applied bias, the evaluation function f of equation (1) above is solved again. objRepeat steps S3 to S8 until the termination condition is met. Furthermore, the termination condition is not limited to the aforementioned deviation; it may also include other factors such as the number of times the optimization calculation in step S3 is repeated. That is, as long as the process is configured such that if the optimization calculation in step S3 is repeated a predetermined number of times, the process proceeds to step S6.

[0054] If the processing conditions are met in step S7 above, the heating mode candidate is set as the final heating mode, and the routine ends. Simultaneously, the power supply p for each induction heating device 3 and even each inductor 31j is set as the final heating mode. j Position x in the width direction j The combination of .

[0055] Furthermore, the specific construction of the process control computer 11 is not limited; for example, it could be constructed as follows. Figure 6 This diagram illustrates an example of the hardware structure of a process control computer 11. The functions of the process control computer 11 can be achieved through... Figure 6 The processing circuit shown is used to implement this. This processing circuit can also be dedicated hardware 11a. This processing circuit can also include a processor 11b and a memory 11c. Alternatively, this processing circuit can be partially configured as dedicated hardware 11a, and also include a processor 11b and a memory 11c. Figure 6 In the example, a portion of the processing circuit is formed as dedicated hardware 11a, and the processing circuit also includes a processor 11b and a memory 11c.

[0056] At least a portion of the processing circuitry can also be at least one dedicated hardware 11a. In this case, the processing circuitry may be equivalent to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. The processing circuitry may also include at least one processor 11b and at least one memory 11c. In this case, the functions of the process control computer 11 are implemented through software, firmware, or a combination of software and firmware. The software and firmware are described as programs and stored in the memory 11c. The processor 11b implements the functions by reading and executing the programs stored in the memory 11c. The processor 11b is also referred to as a CPU (Central Processing Unit), central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 11c may be equivalent to non-volatile or volatile semiconductor memories such as RAM, ROM, flash memory, EPROM, or EEPROM. The memory 11c can also be used as a database 114. Thus, the processing circuitry can implement the functions of the process control computer 11 through hardware, software, firmware, or a combination thereof.

[0057] As explained above, according to this embodiment, in the evaluation function f obj The evaluation function f includes not only the temperature deviation of the rolled material Mr, but also the term for the power supply to the induction heating device 3. Therefore, if the evaluation function f is obtained by solving this evaluation function... obj The obtained heating mode, used to control each induction heating device 3, enables uniform temperature distribution across the width of the rolled material Mr while simultaneously achieving energy savings. Therefore, as Figure 9 As shown, even when the temperature rise varies depending on the width direction position of the rolled material Mr, energy saving can be achieved while meeting the target value of the width direction temperature distribution of the rolled material Mr.

[0058] In addition, by using the evaluation function f obj nonlinear function T i pred Approximately a linear function T i pred‘ It can analytically solve the evaluation function f obj Compared to numerical solutions, the processing time is significantly reduced, thereby decreasing the processing load on the process control computer 11. Furthermore, by using heating mode candidates to perform unsteady heat conduction calculations, the predicted value T of the temperature distribution in the width direction is calculated. i pred It can be verified that the evaluation function f is solved analytically. obj The resulting heating mode candidates.

[0059] The embodiments of this disclosure have been described above, but this disclosure is not limited to the above-described embodiments, and various modifications can be made to implement it without departing from the spirit of this disclosure. When numerical values ​​such as the number, quantity, amount, and range of each element are mentioned in the above embodiments, the present invention is not limited to the mentioned numerical values, except where specifically stated or explicitly determined in principle. Furthermore, the structures described in the above embodiments are not essential to the present invention, except where specifically stated or explicitly determined in principle.

[0060] like Figure 7 and Figure 8 As shown, on the upstream or downstream side of the conveying direction of the induction heating device 3 (in Figure 7 In the example shown, a pair of edge heaters 8 are provided on the downstream side to locally heat both ends (workpiece side: WS, drive side: DS) of the rolled material Mr in the width direction. Figure 7 This is a schematic diagram showing other structures of the hot rolling line RL using an induction heating system. Figure 8This is a schematic diagram showing an example of the structure of the edge heater 8. The edge heater 8 is configured to be longer in the transport direction. Like the induction heating device 3, the edge heater 8 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 surrounding the ends WS and DS in the width direction. As the power supply 82, for example, an inverter power supply can be used. When power is supplied from the power supply 82 to the induction coil 812, a linkage magnetic flux is generated on the workpiece side WS and the drive side DS of the rolled material Mr, inducing eddy currents in the rolled material Mr. Joule heating is generated by these eddy currents, and the two sides WS and DS of the rolled material Mr are heated. The edge heater 8 also includes a moving mechanism 84 and a position controller 85 provided on the iron core 811. The moving mechanism 84 can be configured in the same way as the moving mechanism 34 as a trolley, slider, etc., that can move in the width direction. The position controller 85 is configured to move a pair of inductors 81 to different width-direction positions by changing the positions of each moving mechanism 84. Furthermore, it is configured to supply the same power to the pair of inductors 81 from the power supply 82. That is, it is configured to prevent the supply of different power to the pair of inductors 81. In this case, the term for power supply in equation (1) above is set to a common value p_j in the edge heater 8, and the width-direction positions of the edge heater 36 are set to different variables such as x_(j_WS) and x_(j_DS). Therefore, even with the edge heater 8, the evaluation function f can still be applied. obj .

[0061] However, under conditions such as the heating status of furnace 1 and a long waiting time for the rolled material Mr extracted from furnace 1, the oxide scale (oxide film) formed on the surface of the rolled material Mr may thicken depending on the state of the rolling line RL, potentially leading to poor measurement conditions of the inlet width thermometer 71. In this case, during the calculation of the heating mode described above, it is preferable not to use the measured value of the inlet width thermometer 71 as the inlet width direction temperature distribution of the induction heating device 3, but rather to use the measured value (measurement result) obtained when the inlet width thermometer 71 is functioning well. Specifically, the predicted value of the width direction temperature distribution of the process model can be corrected using the prediction error, i.e., the correction value, of the process model (physical model) learned by the learning unit 113 after rolling, and used as the width direction temperature distribution of the induction heating device 3. The learned correction value can be stored and managed in a learning table (illustration omitted) partitioned based on the steel grade and size of the rolled material Mr. The learning table is updated during rolling under the same conditions.

[0062] In the above embodiment, the example described is the case where the process control computer 11 performs the control function 110 of the induction heating device, that is, the functions of each part 111, 112, and 113. However, it can also be performed by other computers. In this case, it is also possible to solve the evaluation function f numerically without using the above equation (2) for approximation. obj .

[0063] In the above embodiment, the induction heating device 3 in the horizontal manner was used as an example for explanation, but if there are multiple horizontal induction heating devices, the horizontal and solenoid induction heating devices can also coexist.

[0064] Explanation of reference numerals in the attached figures RL…Hot rolling line, Mr…Rolled material, 1…Heating furnace, 2…Roughing mill, 21…Rack, 3…Induction heating device, 31…Inductor, 311…Core, 312…Induction coil, 32…Power supply, 33…House, 34…Moving mechanism, 35…Position controller, 4…Finishing mill, 41…Rack, 5…Cooling table, 6…Coiler, 71…Inlet width thermometer, 72…Outlet width thermometer, 8…Edge heater, 81…Inductor, 811…Core, 812…Induction coil, 82…Power supply, 83…House, 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 on a hot rolling line, for induction heating of rolled materials, comprising: Multiple transverse induction heating devices are arranged along the transport direction of the rolled material; and The computer, based on information about the rolled material and actual values ​​of the temperature distribution in the width direction on the inlet and outlet sides of the induction heating device, calculates the combination of the power supplied to the inductors of each induction heating device and the position of each inductor that can move in the width direction of the rolled material, i.e., the heating mode, and sets the heating mode for each induction heating device. The computer is configured to execute: Define an evaluation function that includes a term for the deviation between the target value and the predicted value of the temperature distribution in the width direction of the rolled material on the output side of each induction heating device, and a term for the power supply to each inductor; and calculate the heating mode, i.e., the heating mode candidate, when the evaluation function is minimized.

2. The induction heating system according to claim 1, wherein, The computer is configured to perform a linear approximation of the predicted value of the temperature distribution in the width direction in the evaluation function.

3. The induction heating system according to claim 2, wherein, The computer is configured to execute: The predicted value of the temperature distribution in the width direction is recalculated using the heating mode candidate; and The heating mode candidate is verified based on the deviation between the recalculated predicted value and the target value.

4. The induction heating system according to claim 1, wherein, A pair of edge heaters are provided 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. The pair of edge heaters have inductors that can be moved to different positions in the width direction, and the inductors of each edge heater are supplied with the same power. The computer is configured to set the power supply term in the evaluation function to a common value in the inductor of the edge heater.

5. The induction heating system according to claim 1, wherein, It also includes an inlet-side width thermometer for measuring the measured value of the temperature distribution in the width direction on the inlet side of the induction heating device. The computer is configured to, in the event of a malfunction in the inlet width thermometer, use a correction value obtained by learning from the actual value measured when the inlet width thermometer is functioning well, instead of the actual value measured by the inlet width thermometer.

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