Method for determining the number of leveling cycles

Abstract

To efficiently manufacture thick steel plates with a high yield. [Solution] The method for determining the number of leveling cycles includes the steps of: calculating the rolling time, which is the time it takes for the trailing steel sheet to be processed in the rolling mill after the trailing steel sheet reaches the hot straightening equipment; calculating the accelerated cooling time, which is the time it takes for the trailing steel sheet to be processed in the accelerated cooling device after the trailing steel sheet reaches the hot straightening equipment; calculating the arrival time, which is the time it takes for the trailing steel sheet to reach the hot straightening equipment from the present time, based on the rolling time and the accelerated cooling time; and determining the number of leveling cycles in the hot straightening equipment so as to maximize the number of leveling cycles performed in the hot straightening equipment, within a range where the leveling time is shorter than the arrival time.

Description

Technical Field

[0001] The present disclosure relates to a method for determining the number of leveling passes.

Background Art

[0002] Conventionally, when manufacturing thick steel plates, it has been required to manufacture them efficiently with a high yield.

[0003] In order to efficiently manufacture thick steel plates, for example, it is important to accurately estimate the rolling time of the steel plate. For example, Patent Document 1 discloses a method for accurately calculating the rolling time using the partial least squares regression method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a rolling line for manufacturing thick steel plates, hot leveling equipment is widely used. In hot leveling equipment, the more the number of leveling passes is increased, the more the distortion of the steel plate can be removed.

[0006] If the distortion of the steel plate can be well removed, the yield of the thick steel plate can be increased. Therefore, in order to increase the yield of the thick steel plate, it is desirable to increase the number of leveling passes in the hot leveling equipment.

[0007] However, if the number of leveling passes in the hot leveling equipment is increased too much, a situation may occur where even when the steel plate transported to the hot leveling equipment next reaches the hot leveling equipment, the leveling of the current steel plate has not ended. Then, a waiting time occurs for the steel plate that reaches the hot leveling equipment next, and the thick steel plate cannot be efficiently manufactured.

[0008] The purpose of this disclosure is to provide a method for determining the number of leveling cycles that can efficiently manufacture thick steel plates with a high yield. [Means for solving the problem]

[0009] [1] A method for determining the number of leveling operations to be performed in a hot straightening equipment in a rolling line comprising a rolling mill, an accelerated cooling device, and a hot straightening equipment, When the first steel sheet to be processed reaches the hot straightening equipment, the rolling time is calculated, which is the time it takes for the subsequent steel sheet to be processed in the rolling mill. When the preceding steel sheet reaches the hot straightening equipment, the step is to calculate the accelerated cooling time, which is the time it takes for the succeeding steel sheet to be processed in the accelerated cooling device. A step of calculating the arrival time, which is the time it takes for the subsequent steel sheet to reach the hot straightening equipment from the present time, based on the rolling time and the accelerated cooling time. The steps include determining the number of leveling operations performed in the hot straightening equipment so that the leveling time, which is the time it takes for the preceding steel sheet to be processed in the hot straightening equipment, is shorter than the time required to reach the target, and the number of leveling operations performed in the hot straightening equipment is maximized; A method for determining the number of leveling steps, including the steps mentioned above.

[0010] [2] The step of calculating the rolling time is: A step of calculating the one-pass rolling time based on parameters including the gripping speed, gripping release speed, and maximum rolling speed of the rolling mill, and the length of the subsequent steel sheet. A step of calculating the rolling time based on the first-pass rolling time, the number of subsequent passes to be performed by the rolling mill, and the temperature control time for adjusting the temperature of the subsequent steel sheet, A method for determining the number of leveling cycles as described in [1] above, including the above.

[0011] [3] The method for determining the number of leveling cycles according to [1] or [2] above, wherein the step of calculating the rolling time is to calculate the temperature control time based on the specifications of the subsequent steel sheet and the thickness of the sheet during temperature adjustment and the target temperature of the subsequent steel sheet during temperature adjustment.

[0012] [4] The leveling count determination method according to any one of the above [1] to [3], wherein the step of calculating the rolling time is to determine whether or not it is necessary to add the temperature control time based on a comparison of the target thickness of the subsequent steel sheet during temperature adjustment and the thickness of each pass of the subsequent steel sheet.

[0013] [5] The step of calculating the accelerated cooling time involves inputting parameters including the target or actual finish temperature at the time of completion of processing by the rolling mill, the start temperature instruction for the accelerated cooling device, and the stop temperature instruction for the accelerated cooling device into a machine learning model constructed based on actual data, and calculating the accelerated cooling time. The aforementioned machine learning model, The explanatory variables are parameters including the target finishing temperature, the actual finishing temperature, the start temperature instruction, and the stop temperature instruction. A method for determining the number of leveling cycles according to any one of the above [1] to [4], wherein the output is the required time for accelerated cooling. [Effects of the Invention]

[0014] According to the leveling cycle determination method described herein, thick steel plates can be manufactured efficiently with a high yield. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows an example of a rolling line to which a leveling cycle determination method according to one embodiment of this disclosure is applied. [Figure 2] This figure schematically shows an example of the configuration of a control device according to one embodiment of the present disclosure. [Figure 3] This figure shows an example of a speed chart for the second rolling mill. [Figure 4] It is a diagram showing an example of a flowchart of a process for determining whether it is necessary to add the temperature adjustment time. [Figure 5] It is a diagram showing an example of an explanatory variable of a machine learning model. [Figure 6] It is a diagram showing an example of a speed chart of hot leveling equipment. [Figure 7] It is a diagram showing an example of a flowchart of a process for determining the number of leveling times. [Figure 8] It is a diagram showing an example of a scatter diagram of the estimated value and the actual value of the required rolling time.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0017] FIG. 1 is a diagram showing an example of a rolling line 1 to which a leveling number determination method according to an embodiment of the present disclosure is applied.

[0018] The rolling line 1 is a production line for producing a thick steel plate by rolling a steel plate 2.

[0019] The rolling line 1 includes a control device 10, a heating furnace 20, a first rolling mill 30, a shower 40, a second rolling mill 50, an accelerated cooling device 60, a thermometer 70, and hot leveling equipment 80. The steel plate 2, which is a material for producing a thick steel plate, is conveyed through the rolling line 1 along the conveyance direction shown in FIG. 1.

[0020] In FIG. 1, the rolling line 1 is configured to include two rolling mills, namely, a first rolling mill 30 and a second rolling mill 50. However, the rolling line 1 is not limited to a configuration including two rolling mills. The rolling line 1 may include only one rolling mill or may include three or more rolling mills. In the present embodiment, a case where the rolling line 1 includes two rolling mills, namely, a first rolling mill 30 and a second rolling mill 50, will be described as an example.

[0021] The control device 10 is a general-purpose computer such as a workstation or personal computer. Alternatively, the control device 10 may be a dedicated computer configured to function as the control device 10 for the rolling line 1.

[0022] Figure 2 is a schematic diagram showing an example of the configuration of a control device 10 according to one embodiment of the present disclosure.

[0023] The control device 10 comprises a control unit 11, an input unit 12, an output unit 13, a storage unit 14, and a communication unit 15.

[0024] The control unit 11 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0025] The control unit 11 reads programs, data, etc., stored in the memory unit 14 and executes various functions.

[0026] The input unit 12 includes one or more input interfaces that detect user input and acquire input information based on user operations. The input unit 12 includes, for example, physical keys, capacitive keys, a touchscreen integrated with the display of the output unit 13, or a microphone that accepts voice input.

[0027] The output unit 13 includes one or more output interfaces for outputting information and notifying the user. The output unit 13 includes, for example, a display for outputting information as an image, a speaker for outputting information as sound, etc. The display included in the output unit 13 may be, for example, an LCD (Liquid Crystal Display), a CRT (Cathode Ray Tube) display, etc.

[0028] The storage unit 14 is, for example, a flash memory, a hard disk, or an optical memory. Part of the storage unit 14 may be located outside the control device 10. In this case, part of the storage unit 14 may be a hard disk, memory card, or the like, connected to the control device 10 via any interface.

[0029] The memory unit 14 stores programs for the control unit 11 to execute various functions, data used by those programs, and so on.

[0030] The communication unit 15 includes at least one of a communication module that supports wired communication and a communication module that supports wireless communication. The control device 10 can communicate with other devices via the communication unit 15.

[0031] Referring again to Figure 1, let's describe the rolling line 1.

[0032] The heating furnace 20 is a device for heating the steel plate 2. The steel plate 2 heated by the heating furnace 20 is transported to the first rolling mill 30.

[0033] The first rolling mill 30 is a device for rolling the steel sheet 2. The first rolling mill 30 may be, for example, a reverse rolling mill. The first rolling mill 30 may be, for example, a device for rough rolling the steel sheet 2. Note that "rough rolling" is a term used in conjunction with "finish rolling," and the steel sheet 2 is usually rough-rolled before being finish-rolled.

[0034] The steel plate 2, rolled by the first rolling mill 30, is transported to the second rolling mill 50 by passing under the shower 40.

[0035] The shower 40 cools the steel plate 2 with water to control its temperature. However, it is not mandatory to cool the steel plate 2 with water to control its temperature. For example, if the steel plate 2 is CR material (controlled-rolled material), the shower 40 will cool the steel plate 2 with water. CR material is a material that requires temperature control to reach a specific temperature at a specific plate thickness.

[0036] The shower 40 may cool the steel plate 2 with water while it is being transported from the first rolling mill 30 to the second rolling mill 50, or it may cool the steel plate with water between passes while rolling is being performed in the second rolling mill 50. When rolling is repeated several times in the second rolling mill 50, each rolling operation is referred to as a "pass," and the time between rolling operations is referred to as "between passes."

[0037] The second rolling mill 50 is a device for rolling the steel plate 2. The second rolling mill 50 may be, for example, a reverse rolling mill. The second rolling mill 50 may be, for example, a device for finish rolling the steel plate 2.

[0038] The steel sheet 2, rolled by the second rolling mill 50, is transported to the accelerated cooling device 60.

[0039] The accelerated cooling device 60 accelerates the cooling of the steel plate 2 to adjust its temperature. However, accelerating the cooling of the steel plate 2 to adjust its temperature is not mandatory. The accelerated cooling device 60 accelerates the cooling of the steel plate 2 as needed.

[0040] The steel plate 2, which has been accelerated-cooled by the accelerated cooling device 60, is transported to the hot straightening equipment 80.

[0041] The thermometer 70 measures the temperature of the steel plate 2 immediately before the hot straightening equipment 80. While Figure 1 shows an example where the thermometer 70 is installed immediately before the hot straightening equipment 80, the installation location of the thermometer 70 is not limited to this. The thermometer 70 may be installed in a location other than immediately before the hot straightening equipment 80. Furthermore, the thermometer 70 may be installed in two or more locations.

[0042] The hot straightening equipment 80 is a device that performs hot straightening treatment on the steel plate 2 by performing leveling. The hot straightening equipment 80 performs leveling on the steel plate 2 at least once. The hot straightening equipment 80 may be, for example, a reverse-type hot straightening equipment.

[0043] The hot straightening equipment 80 performs leveling on the steel plate 2 for a number of leveling cycles determined by the control device 10. Generally, the more leveling cycles there are, the less distortion there is in the steel plate 2, and the higher the yield of thick steel plates produced by the rolling line 1.

[0044] Next, we will explain in more detail the process by which the control device 10 determines the number of leveling operations to be performed in the hot straightening equipment 80.

[0045] In the rolling line 1, the steel sheet 2 is subjected to rolling by the first rolling mill 30 and the second rolling mill 50, accelerated cooling by the accelerated cooling device 60, and hot straightening by the hot straightening equipment 80, in that order.

[0046] In the rolling line 1, rolling, accelerated cooling, and hot straightening processes are performed sequentially on multiple steel sheets 2. For example, if a steel sheet 2 to be processed first (hereinafter also referred to as the "first steel sheet") and a steel sheet 2 to be processed next to the first steel sheet (hereinafter also referred to as the "second steel sheet") are processed sequentially in the rolling line 1, when the hot straightening process is started on the first steel sheet, in most cases the second rolling mill 50 is performing the rolling process on the second steel sheet. This embodiment will be explained using such a case as an example.

[0047] When the leading steel sheet reaches the hot straightening equipment 80, the control device 10 calculates the time required for the trailing steel sheet to be processed in the second rolling mill 50. Hereafter, the time required for the trailing steel sheet to be processed in the second rolling mill 50 will also be referred to as the "rolling time". Details of the process for calculating the rolling time will be described later.

[0048] Furthermore, when the leading steel sheet reaches the hot straightening equipment 80, the control device 10 calculates the time required for the trailing steel sheet to be processed in the accelerated cooling device 60. Hereafter, the time required for the trailing steel sheet to be processed in the accelerated cooling device 60 will also be referred to as the "accelerated cooling time." Details of the process for calculating the accelerated cooling time will be described later.

[0049] The control device 10 calculates the rolling time and the accelerated cooling time, and then calculates the time it takes for the subsequent steel sheet to reach the hot straightening equipment 80 from the current time based on the rolling time and the accelerated cooling time. Hereafter, the time it takes for the subsequent steel sheet to reach the hot straightening equipment 80 from the current time will also be referred to as the "arrival time".

[0050] The control device 10 may calculate the arrival time by, for example, adding the rolling time, the accelerated cooling time, and the inter-device transport time. The inter-device transport time may be, for example, the sum of the transport time from the second rolling mill 50 to the accelerated cooling device 60 and the transport time from the accelerated cooling device 60 to the hot straightening equipment 80.

[0051] The control device 10 determines the number of leveling cycles performed in the hot straightening equipment 80 so as to maximize the number of leveling cycles performed in the hot straightening equipment 80, within a range where the time it takes for the lead steel sheet to be processed in the hot straightening equipment 80 is shorter than the calculated required time to reach the target. Hereafter, the time it takes for the lead steel sheet to be processed in the hot straightening equipment 80 will also be referred to as the "leveling required time".

[0052] For example, the control device 10 determines the number of leveling cycles in the hot straightening equipment 80 to be 3 if the leveling time required is 3, and if the leveling time required is 4, it will be 3 if the leveling time required is 4.

[0053] As a result, the control device 10 can complete the hot straightening process on the preceding steel sheet using the hot straightening equipment 80 before the succeeding steel sheet reaches the hot straightening equipment 80, preventing a situation where the hot straightening process on the preceding steel sheet is not completed when the succeeding steel sheet reaches the hot straightening equipment 80, resulting in a waiting time. Furthermore, the control device 10 can maximize the number of leveling cycles on the preceding steel sheet within a range where no waiting time occurs, thereby further reducing the distortion of the preceding steel sheet.

[0054] (Calculation of rolling time) Next, we will explain the details of how to calculate the rolling time.

[0055] The control device 10 calculates the rolling time based on, for example, the rolling time for the i-th pass, the number of passes from the current pass to the final pass, and the temperature control time, as shown in equation (1) below.

number

[0056] In equation (1) above, the 1-pass rolling time is the time required for one rolling operation performed by the second rolling mill 50. The 1-pass rolling time for the i-th pass is the time required for one rolling operation in the i-th pass. The number of passes from the current pass to the final pass is the number of rolling operations to be performed by the second rolling mill 50 thereafter. The temperature control time is the time required to adjust the temperature of the subsequent steel sheet.

[0057] The one-pass rolling time may be calculated based on parameters including, for example, the gripping speed, release speed, and maximum rolling speed of the second rolling mill 50, and the length of the trailing steel sheet. The one-pass rolling time may also be calculated based on a speed chart of the second rolling mill 50, for example, as shown in Figure 3.

[0058] If the speed chart of the second rolling mill 50 is as shown in the example in Figure 3, the one-pass rolling time may be calculated, for example, as shown in equation (2) below.

number

[0059] In equation (2) above, T1 to T8 correspond to the interval T1 to T8 in Figure 3. T1 to T8 are the following times, respectively. T1: Off-road time T2: Bite speed acceleration time T3: Bite speed and time T4: Maximum speed acceleration time T5: Maximum speed time T6: Grip release speed deceleration time T7: Bite-release speed and time T8: Stopping speed time

[0060] Furthermore, in equation (1) described above, the number of passes until the final pass may be calculated by the control device 10 based on the actual thickness, target plate thickness, mill load, target temperature, target plate width, etc. The number of passes until the final pass may be changed as appropriate based on the actual thickness. The number of passes until the final pass may also be changed, for example, by an operator performing an input operation to the input unit 12 of the control device 10.

[0061] Furthermore, in equation (1) above, the control device 10 calculates the temperature control time based on the specifications and thickness of the subsequent steel plate during temperature adjustment, and the target temperature of the subsequent steel plate during temperature adjustment. Whether or not the steel plate 2 is a temperature-controlled material is determined based on the specifications. The target thickness and target temperature for temperature adjustment of the steel plate 2 are also determined based on the specifications. The method for calculating the target thickness and target temperature may be, for example, a method based on a physical model (heat transfer model), a table based on past performance, a statistical model, etc.

[0062] Furthermore, in equation (1) above, there are cases where the temperature control time needs to be added and cases where it does not. The control device 10 determines whether or not the temperature control time needs to be added based on a comparison between the target thickness of the subsequent steel plate during temperature adjustment and the thickness of each pass of the subsequent steel plate. Figure 4 shows an example of a flowchart for the process of determining whether or not the temperature control time needs to be added.

[0063] Step S101: The control device 10 determines whether the thickness of the steel sheet 2 in the pass in the second rolling mill 50 is equal to or greater than the target thickness during temperature control, and whether the thickness of the steel sheet 2 in the pass is closest to the target thickness during temperature control.

[0064] If the answer to step S101 is No, proceed to step S102. If the answer to step S101 is Yes, proceed to step S103.

[0065] Step S102: The control device 10 determines that no temperature control time is required to cool the steel plate 2, and sets the temperature control time to zero in equation (1).

[0066] Step S103: The control device 10 determines that if the thickness of the steel plate 2 in the pass is equal to or greater than the target thickness during temperature control, and the thickness of the steel plate 2 in the pass is closest to the target thickness during temperature control, then a temperature control time is required to cool the steel plate 2, and adds the temperature control time in equation (1).

[0067] If the second rolling mill 50 is a reverse rolling mill, the final pass of rolling in the second rolling mill 50 may be completed upstream of the second rolling mill 50. In this case, the control device 10 may calculate the rolling time as shown in, for example, equation (3) below.

number

[0068] In equation (3) above, the final empty pass time is the time it takes to pass the steel plate 2 through the second rolling mill 50 without applying any load, after the rolling process has been completed upstream of the second rolling mill 50.

[0069] The final empty pass time can be calculated, for example, using the following formula (4). Final empty pass time [s] = board length [m] / (180 [mpm] / 60) (4)

[0070] Equation (4) above is an example where the speed at which the steel plate 2 passes through the second rolling mill 50 is 180 [mpm].

[0071] (Calculation of the required time for accelerated cooling) Next, we will explain the details of how to calculate the accelerated cooling time. For materials that do not undergo accelerated cooling, the accelerated cooling time is the time it takes for the material to pass through the accelerated cooling device 60. For materials that undergo accelerated cooling, the accelerated cooling time is usually calculated based on a heat transfer model that reflects the cooling conditions, after predicting or measuring the temperature at the entrance of the accelerated cooling device 60. However, for materials being rolled, the temperature at the entrance of the accelerated cooling device 60 is uncertain, so in this embodiment, for example, it is estimated using a machine learning model as follows.

[0072] The control device 10 inputs parameters, for example, the target or actual finishing temperature at the completion of processing by the second rolling mill 50, the start temperature instruction for the accelerated cooling device 60, and the stop temperature instruction for the accelerated cooling device 60 into a machine learning model to calculate the required accelerated cooling time.

[0073] The machine learning model is a model constructed based on past performance data from the rolling line 1. The machine learning model may be stored in the memory unit 14 of the control device 10.

[0074] The explanatory variables input to the machine learning model may include parameters such as the target finishing temperature, the actual finishing temperature, the start temperature setting for the accelerated cooling unit 60, and the stop temperature setting for the accelerated cooling unit 60. The output of the machine learning model is the accelerated cooling time.

[0075] Figure 5 shows an example of explanatory variables for a machine learning model. In the example shown in Figure 5, the explanatory variables include the target finishing temperature, the start temperature setting for the accelerated cooling system, the actual finishing temperature, the composition, the steel grade, the product thickness, the product length, the carbon equivalent, the transformation temperature, the specifications, the cooling pattern, and the stop temperature setting for the accelerated cooling system. Note that the explanatory variables shown in Figure 5 are just an example, and the explanatory variables for a machine learning model are not limited to these.

[0076] The explanatory variables shown in Figure 5 are data that show a strong correlation with the accelerated cooling processing time in the accelerated cooling device 60.

[0077] In the explanatory variables shown in Figure 5, "Target Finish Temperature" is the target temperature of the steel sheet 2 at the time the rolling process in the second rolling mill 50 is completed. "Start Temperature Indication in Accelerated Cooling Unit" is the target temperature of the steel sheet 2 when the accelerated cooling process is started in the accelerated cooling unit 60. "Actual Finish Temperature" is the temperature measured at the time the rolling process in the second rolling mill 50 is completed. "Steel Type" categorizes the steel sheet 2 according to the manufacturing method, including whether or not cooling is performed, whether or not temperature adjustment is performed, and the timing of temperature adjustment. "Cooling Pattern" categorizes the flow rate of the cooling water and the location of the cooling water ejection in the accelerated cooling process for each steel sheet 2. "Stop Temperature Indication in Accelerated Cooling Unit" is the target temperature of the steel sheet 2 when the accelerated cooling process is completed in the accelerated cooling unit 60.

[0078] (Determining the number of leveling sessions) Next, we will explain the details of how to determine the number of leveling sessions.

[0079] The control device 10 calculates the required leveling time based on the one-pass leveling time and the number of leveling cycles, for example, as shown in equation (5) below. Leveling time required = Leveling time per pass × Number of leveling attempts (5)

[0080] In equation (5) above, the 1-pass leveling time is the time required for one leveling process performed by the hot straightening equipment 80. The number of leveling cycles is the number of leveling cycles performed by the hot straightening equipment 80.

[0081] The one-pass leveling time may be calculated based on the speed chart of the hot straightening equipment 80, for example, as shown in Figure 6.

[0082] If the speed chart of the hot straightening equipment 80 is as shown in the example in Figure 6, the one-pass leveling time may be calculated, for example, using the following formula (6).

number

[0083] The intervals t1 to t8 in equation (6) above correspond to the intervals t1 to t8 in Figure 6. The times t1 to t8 are as follows: t1: Off-road time t2: Off-road time t3: Biting speed and time t4: Leveling speed acceleration time t5: Leveling speed time t6: Grip release speed deceleration time t7: Biting speed and time t8: Off-road time

[0084] The control device 10 calculates the leveling time per pass and, based on the above equation (5), determines the number of leveling passes to maximize the number of passes within a range where the leveling time required for the preceding steel plate is shorter than the arrival time required for the following steel plate.

[0085] An example of the process for determining the number of leveling cycles will be explained using the flowchart shown in Figure 7. Note that the flowchart in Figure 7 shows an example where the hot straightening equipment 80 is a reverse-type hot straightening equipment. Therefore, it is assumed that the number of leveling cycles is odd. This is because, when the hot straightening equipment 80 is a reverse-type hot straightening equipment, if the number of leveling cycles is odd, the hot straightening process is completed when the steel plate 2 reaches the downstream side of the hot straightening equipment 80. Furthermore, the flowchart in Figure 7 is explained using the example where the maximum number of leveling cycles is 3.

[0086] Step S201: When the control device 10 finds that the leading steel sheet has reached the hot straightening equipment 80, it calculates the time required for the trailing steel sheet to reach the hot straightening equipment 80.

[0087] Step S202: The control device 10 calculates the leveling time required when the number of leveling cycles is 3.

[0088] Step S203: The control device 10 determines whether the leveling time required when the number of leveling cycles calculated in step S202 is 3 is shorter than the arrival time calculated in step S201.

[0089] If the leveling time required for 3 leveling cycles is shorter than the time required to reach the destination (Yes in step S203), the control device 10 proceeds to step S204. If the leveling time required for 3 leveling cycles is greater than or equal to the time required to reach the destination (No in step S203), the control device 10 proceeds to step S205.

[0090] Step S204: The control device 10 determines the number of leveling cycles to be 3.

[0091] Step S205: The control device 10 determines the number of leveling cycles to be 1.

[0092] Step S206: The control device 10 calculates the leveling time required when the number of leveling cycles is 1.

[0093] Step S207: The control device 10 determines whether the leveling time required when the number of leveling cycles calculated in step S206 is 1 is shorter than the arrival time calculated in step S201.

[0094] If the leveling time required for one leveling cycle is shorter than the time required to reach the destination (Yes in step S207), the control device 10 terminates the process. If the leveling time required for one leveling cycle is greater than or equal to the time required to reach the destination (No in step S207), the process proceeds to step S208.

[0095] Step S208: The control device 10 makes a change to increase the leveling speed in the hot straightening equipment 80. For example, if the original leveling speed is 60 [mpm], the control device 10 changes the leveling speed to 120 [mpm].

[0096] As a result, the control device 10 can determine the number of leveling steps to be 3 if the leveling time required is shorter than the time required to reach the destination, even if the number of leveling steps is 3. Also, if setting the number of leveling steps to 3 would result in a leveling time equal to or greater than the time required to reach the destination, the control device 10 can determine the number of leveling steps to be 1.

[0097] Furthermore, if the leveling time exceeds the time required to reach the destination even with only one leveling attempt, increasing the leveling speed can shorten the leveling time below the time required to reach the destination.

[0098] (Examples) The leveling cycle determination method according to this embodiment calculates the rolling time, and a comparison was made between the estimated rolling time calculated using the leveling cycle determination method according to this embodiment and the actual rolling time.

[0099] The comparison between estimated and actual rolling times was performed based on rolling data from 1759 steel plates 2. Figure 8 shows a scatter plot of estimated and actual rolling times in this embodiment.

[0100] In Figure 8, if a point lies on a straight line, it means that the estimated value and the actual value are in agreement. In the example shown in Figure 8, the correlation coefficient was 0.766. The standard deviation was 22.69 seconds. From this, it was confirmed that the leveling cycle determination method according to this embodiment can accurately calculate the rolling time.

[0101] Furthermore, by applying the leveling count determination method according to this embodiment, it was possible to change the leveling count of 11% of the 1759 steel plates 2 from 1 to 3.

[0102] As described above, the method for determining the number of leveling cycles according to this embodiment includes the steps of: calculating the rolling time, which is the time it takes for the trailing steel sheet to be processed in the second rolling mill 50 from the time the trailing steel sheet reaches the hot straightening equipment 80; calculating the accelerated cooling time, which is the time it takes for the trailing steel sheet to be processed in the accelerated cooling device 60 from the time the trailing steel sheet reaches the hot straightening equipment 80; calculating the arrival time, which is the time it takes for the trailing steel sheet to reach the hot straightening equipment 80 from the present time, based on the rolling time and the accelerated cooling time; and determining the number of leveling cycles in the hot straightening equipment 80 such that the number of leveling cycles performed in the hot straightening equipment 80 is maximized, within a range where the leveling time, which is the time it takes for the trailing steel sheet to be processed in the hot straightening equipment 80, is shorter than the arrival time. Thus, the leveling cycle determination method according to this embodiment can maximize the number of leveling cycles for the preceding steel sheet within a range where no waiting time occurs for the subsequent steel sheet. Therefore, the distortion of the preceding steel sheet by hot straightening in the hot straightening equipment 80 can be further reduced, and the yield can be increased. Accordingly, the leveling cycle determination method according to this embodiment can efficiently manufacture thick steel sheets with a high yield.

[0103] This disclosure is not limited to the embodiments described above. For example, multiple blocks described in the block diagram may be combined, or a single block may be divided. Instead of executing multiple steps described in the flowchart in chronological order as described, they may be executed in parallel or in a different order, depending on the processing capacity of the device performing each step, or as necessary. Other modifications are possible without departing from the spirit of this disclosure.

[0104] For example, in the above embodiment, when calculating the rolling time, an example was shown in which the time required for the rolling process in the second rolling mill 50 is calculated. However, if the subsequent steel sheet is before or during the rolling process in the first rolling mill 30, the time required for the rolling process in the first rolling mill 30 and the time required for the rolling process in the second rolling mill 50 may be added together to calculate the rolling time. [Explanation of Symbols]

[0105] 1. Rolling line 2 steel plate 10 Control device 11 Control Unit 12 Input section 13 Output section 14 Storage section 15 Communications Department 20 Furnace 30 First Rolling Mill 40 showers 50 Second Rolling Mill 60 Accelerated cooling device 70 Thermometer 80 Hot straightening equipment

Claims

1. A method for determining the number of leveling operations to be performed in a hot straightening facility in a rolling line comprising a rolling mill, an accelerated cooling device, and a hot straightening facility, wherein the method determines the number of leveling operations to be performed in the hot straightening facility. When the first steel sheet to be processed reaches the hot straightening equipment, the rolling time is calculated, which is the time it takes for the subsequent steel sheet to be processed in the rolling mill. When the preceding steel sheet reaches the hot straightening equipment, the step is to calculate the accelerated cooling time, which is the time it takes for the succeeding steel sheet to be processed in the accelerated cooling device. A step of calculating the arrival time, which is the time it takes for the subsequent steel sheet to reach the hot straightening equipment from the present time, based on the rolling time and the accelerated cooling time. The steps include determining the number of leveling operations in the hot straightening equipment such that the number of leveling operations performed in the hot straightening equipment is maximized, within a range where the leveling time, which is the time it takes for the preceding steel sheet to be processed in the hot straightening equipment, is shorter than the time required to reach the target; A method for determining the number of leveling steps, including the steps mentioned above.

2. The step of calculating the rolling time is: A step of calculating the one-pass rolling time based on parameters including the gripping speed, gripping release speed, and maximum rolling speed of the rolling mill, and the length of the subsequent steel sheet. A step of calculating the rolling time based on the first-pass rolling time, the number of subsequent passes to be performed by the rolling mill, and the temperature control time for adjusting the temperature of the subsequent steel sheet, A method for determining the number of leveling cycles according to claim 1, including the method described in claim 1.

3. The method for determining the number of leveling cycles according to claim 2, wherein the step of calculating the rolling time is to calculate the temperature control time based on the specifications and thickness of the subsequent steel sheet and the target temperature of the subsequent steel sheet during temperature control.

4. The leveling cycle determination method according to claim 2, wherein the step of calculating the rolling time is to determine whether or not it is necessary to add the temperature control time based on a comparison of the target thickness of the subsequent steel sheet during temperature adjustment and the thickness of each pass of the subsequent steel sheet.

5. The step of calculating the accelerated cooling time involves inputting parameters including the target or actual finishing temperature at the time of completion of processing by the rolling mill, the start temperature instruction for the accelerated cooling device, and the stop temperature instruction for the accelerated cooling device into a machine learning model constructed based on actual data, and calculating the accelerated cooling time. The aforementioned machine learning model, The explanatory variables are parameters including the target finishing temperature, the actual finishing temperature, the start temperature instruction, and the stop temperature instruction. The method for determining the number of leveling cycles according to claim 1, wherein the output is the required time for accelerated cooling.

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