Method for calculating thickness schedule for tandem rolling mill and rolling plant

Abstract

The present disclosure provides a thickness schedule calculation method and a rolling plant that make it possible to calculate and set a limit value for a limit check that is preferable for maintaining a stable rolling and operating state with reduced rolling troubles. The thickness schedule computing method comprises a computing step of computing a thickness schedule by using a rolling model formula including a forward slip model and a rolling load model, on the basis of a rolling load or motor power. The computing step includes a calculating step of calculating at least one of an upper limit value and a lower limit value of the rolling reduction ratio in each rolling stand on the basis of past rolling data, for each product specifications including a steel type category for rolling and a thickness category, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculating step as a limit value for a limit check with respect to the rolling reduction ratio.

Description

[Technical Field]

[0001] The present disclosure relates to a method for calculating a thickness schedule for a tandem rolling mill in which a plurality of rolling stands are arranged in parallel, and to a rolling plant. [Background technology]

[0002] In the method for calculating a thickness schedule for a tandem rolling mill disclosed in Patent Document 1 below, a thickness schedule is calculated using a group of mathematical formulas for predicting the material temperature, rolling load, rolling torque, etc. of each rolling stand in order to achieve a target thickness given as a rolling command.

[0003] The load ratio allocation method is used to calculate the thickness schedule, and the thickness schedule is calculated based on the allocation ratio γi of the load Pi at each rolling stand. Furthermore, the delivery thickness hi and roll peripheral speed Vi of each rolling stand must satisfy the law of constant volumetric velocity (also known as the "law of constant mass flow") in order to maintain uniformity between the rolling stands. Here, i is an identifier used to distinguish between multiple rolling stands, and the rolling stand number (i = 1 to N) is substituted for i.

[0004] In the above calculation method, the relational equations obtained from both the relationship between the rolling load and load ratio of each stand and the constant mass flow law, as well as the same number of unknowns as the relational equations, are numerically solved using the Newton-Raphson method or the like. Furthermore, in the above calculation method, limit checks (also called "parameter restrictions") are performed on parameters such as the reduction, rolling load, and rolling torque of each rolling stand. If the limit value of the limit check is exceeded, the target load ratio value of the rolling stand is lowered, thereby automatically correcting the thickness schedule. This thickness schedule calculation method has a problem in that calculation performance deteriorates depending on the number of rolling stands to be corrected or the amount of correction. Here, deterioration in calculation performance includes, for example, an increase in calculation load or difficulty in convergence of iterative calculations when a majority of rolling stands to be corrected exist or when the amount of correction is relatively large.

[0005] The following Patent Document 2 discloses a technique for appropriately correcting the calculation content by changing the function used in the calculation when a parameter related to rolling exceeds a limit value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2000-167612 [Patent Document 2] International Publication No. 2021-084636 Summary of the Invention [Problem to be solved by the invention]

[0007] However, neither Patent Document 1 nor Patent Document 2 clearly describes the limit values ​​used in the limit check, including how to set them. If a sufficiently large value is set as the limit value, the limit check itself will not function. On the other hand, if a relatively small value is set as the limit value, the limit value will be exceeded more frequently, and the thickness schedule calculation will not converge. In either case, there is a risk of rolling problems, a decrease in yield, and increased downtime. Furthermore, the limit values ​​are currently common (same) for all materials, regardless of steel type or size, and this common value cannot be said to be a limit value suitable for rolled materials.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a method for calculating a thickness schedule and a rolling plant that are capable of calculating and setting limit values ​​suitable for limit checks in order to maintain stable rolling and operating conditions with few rolling troubles. [Means for solving the problem]

[0009] The first aspect relates to a method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by multiple rolling stands. The thickness schedule calculation method includes a calculation step of calculating a thickness schedule based on rolling load or motor power using a rolling model equation including a forward ratio model and a rolling load model. The calculation step includes a calculation step of calculating at least one of an upper limit and a lower limit of the reduction rate for each rolling stand for each product specification including the steel grade classification and the thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit and the lower limit calculated in the calculation step as a limit value for limit check on the reduction rate.

[0010] The second aspect has the following characteristics in addition to the first aspect: The calculation step includes a step of extracting rolling data from past rolling data when rolling was possible without causing any rolling trouble, and is configured to calculate at least one of the upper limit value and the lower limit value by statistical analysis from at least one of the set calculated value and the actual value of the reduction ratio of the extracted rolling data.

[0011] The third aspect has the following characteristics in addition to the first aspect: The calculation step includes a step of extracting, from past rolling data, rolling data when the deviation between the set calculated value of the reduction rate and the actual value is smaller than a reference value, and is configured to calculate at least one of the upper limit value and the lower limit value by statistical analysis from at least one of the set calculated value and the actual value of the reduction rate of the extracted rolling data.

[0012] The fourth aspect has the following characteristics in addition to the first aspect: In the calculation step, at least one of a past set calculated value and an actual value when rolling was possible without rolling trouble among past rolling data is used as an input, and a rolling reduction is sequentially calculated using machine learning that outputs the rolling reduction, and at least one of an upper limit value and a lower limit value is calculated by adding or subtracting a certain numerical value to or from the calculated rolling reduction.

[0013] The fifth aspect has the following characteristics in addition to the first aspect: In the calculation step, at least one of a past calculated value and an actual value of the rolling reduction when the deviation between the calculated value and the actual value of the rolling reduction is smaller than a reference value is used as an input, and machine learning is used to sequentially calculate the rolling reduction as an output, and at least one of an upper limit value and a lower limit value is calculated by adding or subtracting a certain numerical value to the calculated rolling reduction.

[0014] The sixth aspect has the following characteristics in addition to the first aspect: In the calculation step, rolling data in a category in which a rolling trouble occurred is extracted from past rolling data, and an average value of the reduction ratio in the set calculation is calculated using rolling data when rolling was possible without any rolling trouble, and a percentile value is calculated from the reduction ratio in the set calculation using rolling data when a rolling trouble occurred, and at least one of an upper limit value and a lower limit value is calculated by adding or subtracting a certain numerical value to or from the calculated average value and percentile value.

[0015] The seventh aspect has the following feature in addition to the first aspect: When at least one of the upper limit value and the lower limit value calculated in a downstream rolling stand is larger than the upper limit value of the rolling stand immediately upstream, the upper limit value of the downstream rolling stand is replaced with the upper limit value of the rolling stand immediately upstream, or the upper limit value of the downstream rolling stand is replaced with a value obtained by subtracting a certain numerical value from the upper limit value of the stand immediately upstream.

[0016] An eighth aspect has the following features in addition to the first aspect. When the number of past rolling data is less than a first threshold, a pre-calculated rolling reduction is set as the limit value. When accumulation of rolling data progresses and the number of past rolling data is equal to or greater than the first threshold and less than a second threshold, at least one of an upper limit value and a lower limit value calculated by statistical analysis from at least one of a set calculated value and an actual value of the rolling reduction of the rolling data calculated by statistical analysis is set as the limit value. When accumulation of rolling data further progresses and the number of past rolling data is equal to or greater than a second threshold, at least one of an upper limit value and a lower limit value calculated by adding or subtracting a certain numerical value to the rolling reduction calculated using machine learning is set as the limit value.

[0017] A ninth aspect of the present invention provides a rolling mill comprising a plurality of rolling stands, a reduction device provided in each of the plurality of rolling stands, an electric motor for rotating rolls of each rolling stand, a process computer configured to calculate a thickness schedule for each rolling stand based on one of the rolling load ratio of the reduction device and the motor power ratio of the electric motor, and a database for storing past rolling data. The process computer is configured to execute a process of performing a limit check on the reduction rate of each rolling stand, a process of calculating at least one of an upper limit and a lower limit of the reduction rate for each rolling stand for each product specification including the steel grade classification and the plate thickness classification to be rolled based on the past rolling data stored in the database, and a process of setting at least one of the calculated upper limit and lower limit as a limit value for the limit check on the reduction rate. [Effects of the Invention]

[0018] According to the first and ninth aspects, by setting at least one of the upper and lower limits of the reduction rate calculated using past rolling data for each product specification as the limit value, it is possible to set a limit value suitable for the material to be rolled and to avoid rolling troubles, thereby realizing an improvement in yield and a reduction in downtime.

[0019] According to the second and fourth aspects, by using rolling data that did not cause rolling trouble, it is possible to reduce the possibility of rolling trouble occurring, and more stable operation becomes possible.

[0020] According to the third and fifth aspects, by using rolling data in which the deviation between the set calculated value and the actual value is small, at least one of the upper limit and the lower limit of the reduction rate can be determined with high accuracy.

[0021] According to the sixth aspect, even when using rolling data for a section in which a rolling trouble has occurred, it is possible to calculate at least one of the upper limit and the lower limit of the reduction rate.

[0022] According to the seventh aspect, by preventing the reversal of the rolling reduction, it is possible to prevent the rolling balance from being lost and rolling troubles from occurring.

[0023] According to the eighth aspect, the limit value can be set in stages according to the number of rolling data. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing a configuration of a rolling plant according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a process computer provided in a rolling plant. [Figure 3] 1 is a flowchart for explaining the flow of plate thickness schedule calculation in the first embodiment. [Figure 4] 10 is a flowchart for explaining the flow of plate thickness schedule calculation in the second embodiment. [Figure 5] 10 is a flowchart for explaining the flow of plate thickness schedule calculation in the third embodiment. [Figure 6] 10 is a flowchart for explaining the flow of plate thickness schedule calculation in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that elements common to the various drawings will be assigned the same reference numerals and redundant explanations will be omitted.

[0026] [System configuration of the embodiment] Fig. 1 is a schematic diagram showing the configuration of a rolling plant 1 according to an embodiment. The rolling plant 1 uses steel or other metallic material as a material to be rolled 10 and hot rolls the material 10 into a plate. The material 10 is a raw material to be rolled in the rolling plant 1. The rolling plant 1 may also be configured to cold roll the material 10 into a plate.

[0027] The rolling plant 1 includes a heating furnace 2, a roughing mill 3, a finishing mill 4, a cooling device 5, a winder 6, and a roller table (not shown) that transports the material 10 to be rolled between them.

[0028] The heating furnace 2 heats and raises the temperature of the material to be rolled 10. The roughing mill 3 has one or more rolling stands. Each rolling stand has a plurality of rolls 31, a reduction device 32, and an electric motor 33 for rotating the rolls.

[0029] The finishing mill 4 is a tandem rolling mill equipped with a plurality of rolling stands F1 to F5 arranged in series in the conveying direction of the rolled material 10. Each of the rolling stands F1 to F5 is equipped with a plurality of rolls 41, a screw down device 42, and an electric motor 43 for rotating the rolls. In the following description, the rolling stands may be designated as i or i-1.

[0030] Furthermore, the number of rolling stands of the heating furnace 1, winder 6, roughing mill 3 and finishing mill 4 is not particularly limited, and in this embodiment, a rolling plant 1 having one heating furnace 1, one rolling stand of the roughing mill 3, five rolling stands F1 to F5 of the finishing mill 4, and one winder 6 is given as an example.

[0031] In the following description, the screw down devices 32, 42 and electric motors 33, 43 of the rolling mills 3, 4 described above may be referred to as "equipment" of the rolling plant 1 for convenience. In addition to the screw down devices 32, 42 and electric motors 33, 43, the equipment may include various other components such as actuators (not shown) depending on the specific structure of the rolling mills 3, 4.

[0032] Various sensors serving as measuring instruments are installed at key points in the rolling plant 1. Key points in the rolling plant 1 include, for example, the outlet side of the heating furnace 2, the outlet side of the roughing mill 3, the outlet side of the finishing mill 4, and the inlet side of the coiler 6. Various sensors may also be installed between rolling stands F1 to F5 of the finishing mill 4. The various sensors include a pyrometer 71 that measures the surface temperature of the material 10 to be rolled at the inlet side of the finishing mill 4, a thickness and width meter 72 that measures the thickness and width of the material 10 to be rolled, a thermometer 73 that measures the surface temperature of the material 10 to be rolled at the outlet side of the finishing mill 4, a rolling load sensor 74 that measures the rolling load at each of the rolling stands F1 to F5, and a thermometer 75 that measures the surface temperature of the material 10 to be rolled at the inlet side of the coiler 6. The various sensors successively measure the condition of the material 10 to be rolled and the conditions of each piece of equipment.

[0033] The rolling plant 1 is operated (commissioned) by a control system using a computer. The computer includes a host computer 20 and a process computer 21, which are connected to each other via a network. An interface screen 21a, which is an operation screen, and a database 23 are connected to the process computer 21 via the network. Past rolling data is sequentially stored in the database 23. The past rolling data includes set values ​​and actual values ​​of the reduction rates of each of the rolling stands F1 to F5.

[0034] The host computer 20 issues rolling commands to the process computer 21 based on a preset production plan. The rolling commands include, for example, the target dimensions and target temperatures of each rolled material 10. The target dimensions include, for example, the target thickness, target width, and target crown. The target temperatures include, for example, the outlet temperature of the roughing mill 3, the outlet temperature of the finishing mill 4, and the inlet temperature of the winder 6.

[0035] When the material 10 to be rolled is extracted from the heating furnace 2, the process computer 21 calculates the setting values ​​for each device of the rolling plant 1 in accordance with a rolling command from the host computer 20. The process computer 21 outputs the calculated setting values ​​to the controller 22. The setting values ​​include the reduction position of the screw down device 42, the roll rotation speed, the bending force, the work roll shift amount, the amount of cooling water for the cooling device 5, etc.

[0036] When the material 10 to be rolled is transported to a predetermined position in front of each piece of equipment, the controller 22 operates, based on set values, the actuators (not shown) of each piece of equipment in the rolling plant 1. When rolling begins, the controller 22 operates each actuator sequentially based on measurement values ​​from sensors such as a radiation thermometer, an X-ray thickness gauge, and a load cell, so that the target dimensions, target temperature, etc. of the material 10 to be rolled conform to the rolling command.

[0037] There is no limitation on the specific structure of the process computer 21, and the following may be used as an example. Fig. 2 is a diagram showing an example of the hardware configuration of the process computer 21 provided in the rolling plant 1. The arithmetic processing function of the process computer 21 can be realized by the processing circuit shown in Fig. 2. This processing circuit may be dedicated hardware 20a. This processing circuit may include a processor 20b and a memory 20c. This processing circuit may be partly formed as dedicated hardware 20a, and further include the processor 20b and the memory 20c. In the example of Fig. 2, part of the processing circuit is formed as dedicated hardware 20a, and the processing circuit also includes the processor 20b and the memory 20c.

[0038] At least a portion of the processing circuitry may be at least one dedicated hardware 20a, such as a single circuit, multiple circuits, programmed processors, parallel programmed processors, ASICs, FPGAs, or any combination thereof.

[0039] The processing circuit may include at least one processor 20b and at least one memory 20c. In this case, each function of the process computer 21 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 20c. The processor 20b realizes the functions of each part by reading and executing the programs stored in the memory 20c.

[0040] The processor 20b is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 20c is, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM. The memory 20c can also be configured to function as the database 23.

[0041] In this way, the processing circuit can realize each function of the process computer 21 by using hardware, software, firmware, or a combination of these. The functions of the process computer 21 also include a machine learning function, which will be described later.

[0042] In the rolling plant 1, the material 10 to be rolled is heated in a heating furnace 2 and then extracted onto a roller table (not shown) of the rolling line. At this stage, the material 10 is, for example, a steel billet. When the material 10 reaches the roughing mill 3, it is repeatedly rolled while changing the rolling direction. At this stage, the material 10 is, for example, a bar having a thickness of about several tens of millimeters. Next, the material 10 is rolled while being sequentially fed into the rolling stands F1 to F5 of the finishing mill 4, until it reaches the desired thickness. At this stage, the material 10 is also called a strip. Thereafter, the material 10 is cooled in a cooling device 5. The cooled material 10 is wound by a winder 6 to obtain a coiled product.

[0043] [Method for calculating plate thickness schedule according to the embodiment] Before the rolling process in the finishing mill 4, the process computer 21 calculates the thickness schedule to be executed in the finishing mill 4. The thickness schedule is calculated using a mathematical model. The thickness schedule includes the delivery thickness of each of the rolling stands F1 to F5. This mathematical model is a group of mathematical formulas for predicting the temperature, rolling load, rolling torque, etc. of each of the rolling stands F1 to F5. In thickness schedule calculation based on the load ratio allocation method, the load ratio γ i is used. Load ratio γ i is the load P in each rolling stand F1 to F5 i This is the allocation ratio.

[0044] As described in the prior art, the rolling load in the "load ratio allocation method" is one of the factors that change the sheet crown. The higher the rolling load of a rolling stand, the larger the sheet crown at the exit of that rolling stand. Therefore, to minimize crown ratio changes and maintain good flatness, it is desirable for the rolling load to change in the same way at each stand. However, the rolling load changes from moment to moment for each rolled strip and stand due to fluctuations in the rolled strip temperature, which can lead to deterioration of flatness. Therefore, a thickness schedule calculation method has been devised that automatically adjusts the delivery thickness of each stand and keeps the rolling load ratio (i.e., the rolling load ratio) as constant as possible, even when fluctuations in the rolled strip temperature occur. With this calculation method, when the rolling load fluctuates due to some external disturbance, the tendency for the rolling load to increase or decrease is approximately the same for all rolling stands, thereby suppressing deterioration of flatness. This type of thickness schedule calculation method is called the "load ratio allocation method." The method of calculating the thickness schedule, excluding the calculation and setting of the limit values ​​for the limit check described later, is publicly known as described in the prior art, and therefore further explanation will be omitted here.

[0045] [Limit Check] In the calculation of the thickness schedule described above, known limit checks are performed on various parameters such as the reduction rate, rolling load, and rolling torque.

[0046] In this embodiment, the upper and lower limit values ​​that are limit values ​​that are thresholds for the reduction ratio in the limit check are calculated as follows. The set value or actual value of each rolling stand F1 to F5 is extracted and used from the database 23 that stores past rolling data. In the following, unless otherwise specified, either the set value or the actual value may be used. Furthermore, calculations may be performed using both the set value and the actual value, in which case the amount of data handled will be twice as much as when using either one alone.

[0047] [Calculation and setting of upper and lower limits of rolling reduction rate according to Example 1] 3 is a flowchart for explaining the flow of thickness schedule calculation in Example 1. FIG. 3 shows the flow of calculation of the upper limit and lower limit values ​​of the reduction rate in Example 1.

[0048] 3 is started, past rolling data stored in the database 23 is extracted as target data (step S1). There are two types of target data extracted in step S1:

[0049] <Target data (part 1)> The first target data is rolling data that shows rolling without any rolling trouble. This reduces the probability of rolling trouble, enabling stable operation. The presence or absence of rolling trouble is limited to cases where the rolled material 10 has been wound into a coil by the winder 6, and where actual data can be measured.

[0050] <Target data (part 2)> The second target data is rolling data with little deviation between the set value and the actual value. This makes it possible to calculate high-precision upper and lower limit values. "Low deviation" means that the deviation (error ratio) between the set calculated value and the actual value is small, and is expressed by the following formula (1).

number

[0051] where ri SET is the reduction rate setting value (%) in rolling stand i, and r i ACT represents the actual reduction rate (%) in rolling stand i. Deviation ε i r can be set arbitrarily, but for example, a value of about 10% can be used.

[0052] It is preferable to further narrow down the above two types of target data into more detailed target data, taking into account the characteristics of the material. For example, the target data is classified by product specifications including steel type classification AAA and plate thickness classification bb (hereinafter, this hierarchical classification will be referred to as "classification (AAA, bb)"). In addition, additional classifications may be added, such as a hierarchical classification (AAA, bb, cc) that adds plate width classification cc, to further subdivide the target data.

[0053] Next, the upper and lower limit values ​​of the rolling reduction are calculated (step S2). In step S2, the calculation is performed for each rolling stand using the following statistical analysis or machine learning.

[0054] <Calculating upper and lower limits (part 1)> A combination of the average value and standard deviation can be used for statistical analysis. In this case, the average value and standard deviation of the reduction rate of the target data are calculated. For example, the average value r of the reduction rate of each rolling stand i of the target data category (AAA, bb) and the number of data n is i AVE and standard deviation r i STD is calculated using the following formulas (2) and (3).

number

number

[0055] When calculating the upper limit, the standard deviation is added to the average value by the constant β as shown in the following formula (4). i Add the multiplied numbers.

number

[0056] When calculating the lower limit, the standard deviation from the average value is multiplied by the constant β i Subtract the multiplied number.

number

[0057] At this time, the constant β i is a common value for calculating the upper and lower limits, for example, β i = 2, but a different constant β is used for each rolling stand. i may be set.

[0058] <Calculating upper and lower limits (part 2)> Percentile values ​​can be used for statistical analysis. In this case, N of the target data (number of data n) in the target category (AAA, bb) pct,i (50 <N pct,i <100)% percentile was calculated as the upper limit, and (100-N pct,i )% is calculated as the lower limit. For example, N pct,i If N = 95, the upper limit is the 95th percentile and the lower limit is the 5th percentile. pct,i may be a common value regardless of the rolling stand.

[0059] The upper limit of the 95th percentile reduction rate r i 95% is calculated using the following formula (6).

number

[0060] In this case, (n+1)×0.95(=N pct,i / 100) is q and the decimal part is s, then the qth data is r i q is.

[0061] As with the upper limit, the lower limit of the 5th percentile reduction rate r i 5% is calculated using the following formula (7).

number

[0062] In this case, when the number of data is n, it is (n+1) × 0.05 (= 1-N pct,i / 100) is k, and the decimal part is l. i k is.

[0063] <Calculating upper and lower limits (part 3)> Quartiles can be used for statistical analysis. In this case, the first and second quartiles and interquartile range are calculated from the target data (number of data points n) in the target category (AAA, bb).

[0064] The first quartile r of the reduction rate for the number of data n i Q1 and the third quartile r i Q3 is the percentile value calculation formula above, N pct,i =25 or 75. r i Q1 =r i 25% r i Q3 =r i 75%

[0065] Interquartile range of reduction rate r i IQR is the third quartile r i Q3 and the first quartile r i Q1 This is the difference.

number

[0066] Therefore, the third quartile r i Q3 , the interquartile range r calculated using the above formula (8) i IQR a constant multiple N of Q,i The upper limit is calculated by adding the above (see formula (9) below).

number

[0067] In addition, as shown in the following equation (10), the first quartile r i Q1 The interquartile range r i IQR a constant multiple N of Q,i The lower limit is calculated by subtracting the above value.

number

[0068] At this time, the constant multiplication factor N Q,i is common to the calculation of the upper and lower limits, for example, N Q,i A value such as =1.5 is used, but it may be set for each rolling stand.

[0069] <Calculating upper and lower limits (part 4)> The input data are rolling commands including the slab's steel type, target dimensions, chemical composition, etc., read from a database 23 storing past rolling data, actual data on the surface temperature of the material 10 to be rolled before the finishing rolling mill 4, setting calculation data such as the material speed, rolling load, reduction rate, material temperature, etc. at each rolling stand F1 to F5, and actual rolling data such as the material speed, rolling load, reduction rate, plate thickness and plate thickness deviation at the exit side of the finishing rolling mill, material temperature, etc. at each rolling stand F1 to F5, and a machine learning-based rolling reduction rate calculation model is generated using this input data, with the reduction rate of each rolling stand F1 to F5 as output data.

[0070] As a machine learning method, for example, a known machine learning method such as random forest may be used. Other examples of the machine learning method include decision tree learning, neural networks, and support vector regression.

[0071] As shown in the following equation (11), the reduction rate r i ML For a certain value c i ML Add (%) to determine the upper limit.

number

[0072] In addition, as shown in the following equation (12), the reduction rate r i ML For a certain value c i ML Subtract (%) to obtain the lower limit.

number

[0073] This constant value c i ML (%) is common to the calculation of the upper and lower limits, for example, c i ML A value such as (%)=5 is used. However, it may be set for each rolling stand.

[0074] Furthermore, each time the number of rolled pieces (number of rolled materials 10) increases, the latest set values ​​and actual value data may be used as inputs to update the data as appropriate.

[0075] At least one of the upper limit and lower limit of the reduction rate calculated in step S2 is set as a limit value (limit range) that is a threshold value for limit check in thickness schedule calculation (step S3).

[0076] [Calculation and setting of upper and lower limits of rolling reduction rate according to Example 2] Fig. 4 is a flowchart for explaining the flow of calculation of the plate thickness schedule in Example 2. Fig. 4 shows the flow of calculation of the upper limit and lower limit values ​​of the rolling reduction rate in Example 2. In the above-mentioned Example 1, data without rolling trouble or data in which the deviation between the set value and the actual value is smaller than the reference value is extracted as the target data, whereas in Example 2, rolling data when a rolling trouble occurs in the leading end threading of the plate is also taken into consideration.

[0077] When the routine shown in FIG. 4 is run, rolling data of the stratification division (TTT, bd) (number of data N) in which rolling troubles occurred (relatively many rolling troubles) from the past rolling data stored in the database 23 is extracted as target data (step S11). The target data extracted in step S11 is then converted into data in which rolling was performed without any rolling troubles (number of data N OK ) and data with rolling trouble (number of data N NG ) and determine which data it is (step S12).

[0078] Next, data N, which was rolled without any rolling trouble OK For each roll, the average value of the reduction ratio in the setting calculation of each rolling stand is calculated using the following formula (13) (step S13).

number

[0079] On the other hand, data N, which had rolling trouble, NG For each rolling stand, set the reduction ratio for calculation. pct,i NG Percentile value r in % i Npct,i NG and (100-N pct,i NG )% percentile value r i 100-Npct,i NG (Step S14). pct,i NG <50. The percentile value is calculated using formula (6) above.

[0080] Next, the upper and lower limit values ​​are calculated based on the numerical values ​​that are close to the average value of the rolling reduction (step S15).

[0081] For example, r i OK,AVE <r i Npct,i NG In this case, if the rolling reduction is larger than the average value, it means that there is a high possibility of rolling trouble, so the upper limit is calculated using the following formula (14).

number

[0082] On the other hand, r i OK,AVE >r i 100-Npct,i NG In this case, if the rolling reduction is smaller than the average value, it means that there is a high possibility of rolling trouble, so the lower limit is calculated using the following formula (15).

number

[0083] This constant value c i OK (%) is common to the calculation of the upper and lower limits, and any numerical value can be used, but (r i Npct,i NG -r i OK,AVE ) or (r i OK,AVE -r i 100-Npct,i NG ) is desirable. i OK (%) may be set for each rolling stand.

[0084] At least one of the upper limit and lower limit of the reduction rate calculated in step S15 is set as a limit value (limit range) that is a threshold value for limit check in thickness schedule calculation (step S16).

[0085] [Calculation and setting of upper and lower limits of rolling reduction rate according to Example 3] 5 is a flowchart for explaining the flow of thickness schedule calculation in Example 3. FIG. 5 shows the flow of calculation of the upper limit and lower limit values ​​of the reduction rate in Example 3.

[0086] The routine shown in Fig. 5 is started when the upper and lower limit values ​​of the reduction ratio are calculated in the above-mentioned Examples 1 and 2. Here, if the calculated upper or lower limit value of the reduction ratio of a certain rolling stand is larger than the upper limit value of the reduction ratio of an upstream rolling stand, a reversal of the reduction ratio will occur, the rolling balance in the finishing mill 4 will be lost, and there is a risk of rolling trouble occurring.

[0087] Therefore, in this embodiment, a process is defined for the case where the calculated upper limit of the rolling reduction is larger than that of the upstream rolling stand. In this case, although both are based on past data and have proven results, it is desirable that the rolling reduction of the downstream rolling stand be smaller than that of the upstream rolling stand, so the process shown in Fig. 5 is executed.

[0088] When the routine shown in FIG. 5 is started, it is determined whether the upper limit value of the reduction ratio calculated in a certain rolling stand i is greater than the upper limit value of the reduction ratio calculated in the rolling stand i-1 one upstream, that is, whether the following equation (16) is satisfied (step S17).

number

[0089] If the relational expression (16) is satisfied, the upper limit value of the downstream rolling stand i is substituted as in the following expression (17) (step S18).

number

[0090] In step S18, a constant value α is calculated as shown in the following formula (18) so that the upper limit value is smaller than that of the rolling stand one upstream. i You can also subtract (%).

number

[0091] This constant value α i For example, α i = 3, where the value α i may be set.

[0092] In this way, the new upper limit value of the reduction ratio substituted by the above formula (17) or calculated by the above formula (18) is set as the limit value (limit range) which is the threshold value for limit check in the plate thickness schedule calculation.

[0093] [Calculation and setting of upper and lower limits of rolling reduction rate according to Example 4] 6 is a flowchart for explaining the flow of thickness schedule calculation in Example 4. FIG. 6 shows the flow of calculation of the upper limit and lower limit values ​​of the reduction rate in Example 4.

[0094] In the fourth embodiment, the method of calculating the upper and lower limit values ​​of the reduction rate is switched in stages according to the number N of past rolling data stored in the database 23.

[0095] 6, it is determined whether the number N of rolling data stored in the database 23 is smaller than the threshold value Nb1 (step S21). If the number N of rolling data is smaller than the threshold value Nb1, the upper and lower limit values ​​of the reduction ratio calculated in advance as in the conventional method are set as limit values ​​(step S22).

[0096] If the number of rolling data N is equal to or greater than the threshold value Nb1 in step S21, it is determined whether the number of rolling data N is less than the threshold value Nb2 (>Nb1) (step S23). If the number of rolling data N is less than the threshold value Nb2, i.e., if the number of accumulated rolling data N is small, the upper and lower limit values ​​of the rolling reduction are calculated using the statistical analysis <Calculation of upper and lower limit values ​​(any one of steps 1 to 3)> described in the first embodiment above (step S24). If the number of accumulated rolling data N increases and reaches or exceeds the threshold value Nb2, the upper and lower limit values ​​of the rolling reduction are calculated using the machine learning <Calculation of upper and lower limit values ​​(part 4)> described in the first embodiment above (step S25). Thereafter, at least one of the upper and lower limit values ​​of the rolling reduction calculated in step S24 or step S25 above is set as a limit value (limit range) (step S26).

[0097] According to this embodiment, at least one of the upper limit and lower limit of the reduction rate calculated by stepwise calculation according to the number of rolling data stored in the database 23 can be used as the limit value.

[0098] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. When the numbers, quantities, amounts, ranges, etc. of each element are mentioned in the above embodiments, the present invention is not limited to the mentioned numbers unless otherwise specified or clearly specified in principle. Furthermore, the structures, etc. described in the above embodiments are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle. [Explanation of symbols]

[0099] 1...Rolling plant, 4...Finishing rolling mill (tandem rolling mill), 21...Process computer, 23...Database, 41...Roll, 42...Screw reduction device, 43...Electric motor, F1 to F5...Rolling stands

Claims

1. A method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by a plurality of rolling stands, A calculation step of calculating a thickness schedule based on a rolling load or a motor power using a rolling model formula including a forward rate model and a rolling load model, The calculation step includes a calculation step of calculating at least one of an upper limit value and a lower limit value of a reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculation step as a limit value for a limit check on the reduction rate, The calculation step includes a step of extracting rolling data when rolling was possible without causing any rolling trouble from the past rolling data, and calculating at least one of the upper limit value and the lower limit value by statistical analysis from at least one of a set calculation value and an actual value of the reduction rate of the extracted rolling data.

2. A method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by a plurality of rolling stands, A calculation step of calculating a thickness schedule based on a rolling load or a motor power using a rolling model formula including a forward rate model and a rolling load model, The calculation step includes a calculation step of calculating at least one of an upper limit value and a lower limit value of a reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculation step as a limit value for a limit check on the reduction rate, The calculation step includes a step of extracting rolling data from the past rolling data when a deviation between a set calculation value of a rolling reduction rate and an actual value is smaller than a reference value, and calculating at least one of the upper limit value and the lower limit value by statistical analysis from at least one of the set calculation value and the actual value of the rolling reduction rate of the extracted rolling data.

3. A method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by a plurality of rolling stands, A calculation step of calculating a thickness schedule based on a rolling load or a motor power using a rolling model formula including a forward rate model and a rolling load model, The calculation step includes a calculation step of calculating at least one of an upper limit value and a lower limit value of a reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculation step as a limit value for a limit check on the reduction rate, In the calculation step, at least one of a past set calculation value and an actual value when rolling was possible without rolling trouble among the past rolling data is input, and a rolling reduction is sequentially calculated using machine learning as an output, and at least one of the upper limit value and the lower limit value is calculated by adding or subtracting a certain numerical value to the calculated rolling reduction.

4. A method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by a plurality of rolling stands, A calculation step of calculating a thickness schedule based on a rolling load or a motor power using a rolling model formula including a forward rate model and a rolling load model, The calculation step includes a calculation step of calculating at least one of an upper limit value and a lower limit value of a reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculation step as a limit value for a limit check on the reduction rate, In the calculation step, at least one of the past set calculation value and the past actual value of the rolling reduction when the deviation between the set calculation value and the actual value of the rolling reduction is smaller than a reference value is used as an input, and the rolling reduction is sequentially calculated using machine learning as an output, and at least one of the upper limit value and the lower limit value is calculated by adding or subtracting a certain numerical value to the calculated rolling reduction.

5. A method for calculating a thickness schedule for a tandem rolling mill in which rolling is performed continuously by a plurality of rolling stands, A calculation step of calculating a thickness schedule based on a rolling load or a motor power using a rolling model formula including a forward rate model and a rolling load model, The calculation step includes a calculation step of calculating at least one of an upper limit value and a lower limit value of a reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled based on past rolling data, and a setting step of setting at least one of the upper limit value and the lower limit value calculated in the calculation step as a limit value for a limit check on the reduction rate, In the calculation step, rolling data for a category in which rolling trouble occurred is extracted from the past rolling data, and an average value of the reduction ratio for the set calculation is calculated using rolling data when rolling was possible without any rolling trouble, and a percentile value is calculated from the reduction ratio for the set calculation using rolling data when a rolling trouble occurred, and at least one of the upper limit value and the lower limit value is calculated by adding or subtracting a certain numerical value from the calculated average value and percentile value.

6. 6. A plate thickness schedule calculation method according to claim 1, wherein, when at least one of the upper limit value and the lower limit value calculated in the downstream rolling stand is greater than the upper limit value of the rolling stand immediately upstream, the upper limit value of the downstream rolling stand is replaced with the upper limit value of the rolling stand immediately upstream, or the upper limit value of the downstream rolling stand is replaced with a value obtained by subtracting a certain numerical value from the upper limit value of the stand immediately upstream.

7. The rolling mill comprises a plurality of rolling stands, a reduction device provided in each of the plurality of rolling stands, an electric motor for rotating the rolls of each of the rolling stands, a process computer configured to calculate a plate thickness schedule for each of the rolling stands based on one of the rolling load ratio of the reduction device and the motor power ratio of the electric motor, and a database for storing past rolling data, The process computer a process of performing a limit check on the reduction rate of each rolling stand; a calculation process for calculating at least one of an upper limit value and a lower limit value of a rolling reduction rate in each rolling stand for each product specification including a steel type classification and a plate thickness classification to be rolled, based on the past rolling data accumulated in the database; a process of setting at least one of the calculated upper limit value and the calculated lower limit value as a limit value for the limit check for the reduction rate; Run The calculation process includes a process of extracting rolling data from the past rolling data when rolling was possible without causing any rolling trouble, and the rolling plant is configured to calculate at least one of the upper limit value and the lower limit value by statistical analysis from at least one of a set calculated value and an actual value of the reduction rate of the extracted rolling data.

Images