A thickness control compensation method for acceleration and deceleration process of cold continuous rolling of ultra-high strength steel

Abstract

A kind of thickness control compensation method for ultra-high strength steel cold continuous rolling acceleration and deceleration process, by the evaluation model based on strip outlet thickness out-of-tolerance rate set, in combination with the actual value of each rack rolling force, each rack inlet speed, each rack outlet speed, each rack inlet thickness, each rack outlet thickness, the optimization evaluation of set front tension and set rear tension is completed, according to the evaluation result, the optimization of front tension and rear tension set value is completed, and the thickness control compensation of ultra-high strength steel cold continuous rolling acceleration and deceleration process is completed accordingly.A kind of thickness control compensation method for ultra-high strength steel cold continuous rolling acceleration and deceleration process according to actual multidimensional data and in combination with the evaluation model set, establishes the thickness control compensation optimization based on multiple factors.

Description

Technical Field

[0001] This invention belongs to the field of cold continuous rolling technology, specifically relating to a thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel. Background Technology

[0002] With the rapid development of my country's automotive, home appliance, and aerospace industries, the demand for sheet and strip products is constantly increasing. As competition in the domestic and international markets intensifies, the quality requirements for sheet and strip products are also rising. During the rolling process, thickness is one of the most important indicators for measuring the dimensional quality of strip steel, directly affecting the quality and economic benefits of the product. With the rapid development of industries such as aerospace-specific sheet and strip components, precision instruments, and canned food, customers have higher requirements for the thickness accuracy of cold-rolled strip steel. Automatic thickness control is a crucial method in the sheet and strip production process. Currently, the main automatic thickness control methods include feedforward control, feedback control, and metal flow rate control. The strip rolling process is a coupled process involving thickness control, tension control, speed control, and speed control; therefore, the accuracy of thickness control depends not only on the thickness control algorithm but also on the tension and speed control.

[0003] Before the head of the strip is successively bitten into each stand, it is rolled without pre-tension. Similarly, after the tail of the strip is successively ejected from each stand, it is rolled without post-tension. In both cases, tension disappears, resulting in thickness differences between the head and tail of the strip. Furthermore, fluctuations in factors affecting the mill exit thickness, such as incoming material thickness, material properties, rolling speed, and tension, also cause fluctuations in the mill exit thickness, resulting in thickness deviations in the longitudinal direction of the strip.

[0004] Currently, based on literature reviews, the main research directions both domestically and internationally fall into several categories. Some researchers analyze the strip thickness difference data measured during the rolling process to calculate the thickness compensation value during the strip's acceleration and deceleration. Others adjust the roll gap of the current stand based on the deviation between the thickness data at the current stand entrance and the corresponding target thickness. This method only analyzes and calculates data related to the head and tail thickness to achieve thickness control. However, numerous and complex factors influence the head and tail thickness fluctuations in the field, thus limiting the effectiveness of this method. Other researchers obtain actual tension data between stands and adjust the roll gap of the corresponding stands based on the tension deviation between the actual tension data and the preset target tension. Still others use speed measuring instruments on different stands to obtain the strip speed of the corresponding stands in real time and control the reduction and / or speed of each stand in the cold continuous rolling mill in real time through feedback control to achieve thickness control. Like the aforementioned methods, these only consider a single factor to achieve thickness control and have certain limitations. Some researchers have also used measured parameters such as strip thickness, tension, and rolling force to perform regression calculations on deformation resistance, and then calculated deformation resistance model parameters for on-site model technicians to set parameters and achieve thickness control. This method only considers a few factors in the rolling process to achieve thickness control. However, in addition to some factors in the rolling process affecting the thickness difference between the beginning and end of the strip, the incoming material factors or other important process factors have a significant impact on the thickness difference between the beginning and end of the strip. That is, the influence of incoming material factors, rolling factors, and other process factors on the thickness difference between the beginning and end of the ultra-high strength steel cold continuous rolling acceleration and deceleration process is not considered simultaneously.

[0005] The invention application with application number CN200910175208.6 discloses "a thickness control method for rolling die copper plates". The rolling process of the method is that the first few passes are rolled according to conventional rectangular copper plate rolling technology. In the last pass, the height of the oil column in the hydraulic cylinder of the rolling mill is controlled by the TDC controller to continuously change the gap distance and realize the continuous change of the longitudinal thickness of the copper plate. The oil column height model hoil input to the TDC controller is a function of time t, where t is in ms. The oil column height model is composed of two parts: the linear oil column height model hoil 1 and the oil column height bounce compensation oS t.

[0006] The invention application with application number CN202110928103.4 discloses "a method to improve the thickness hit rate of high alloy steel plates", including: measure 1, optimizing the roll gap compensation and bounce compensation of steel biting during the rolling process to reduce the thickness difference between the beginning and end of the steel plate; measure 2, adopting target thickness compensation to reduce the thickness loss during heat treatment.

[0007] The invention application with application number CN202010366335.0 discloses "a tension control method for the dynamic specification change stage of a five-stand cold rolling mill", which includes the following steps: all stands decelerate in advance when the weld seam approaches the rolling mill, all stands accelerate after a delay after the weld seam has completely passed through the rolling mill, and the tension set value of each stand is appropriately adjusted during the acceleration and deceleration stages; the stands whose tension set values ​​need to be adjusted when passing through the wedge zone are determined according to the specification change of the two strips before and after, and the tension set values ​​are adjusted when passing through each stand in the wedge zone; the tension set values ​​are smoothed and limited to obtain the final tension set value, and the work roll rotation frequency signal in the tension meter measurement value is filtered out using a band-stop filter to obtain the final actual tension value; based on the final tension set value and the actual tension value, the roll gap adjustment amount of each stand is calculated using a PI controller.

[0008] The paper "Slab Shape Change and Tension Compensation Technology in Cold Continuous Rolling Speed ​​Increase / Decrease Process" published in "Iron and Steel Journal" on February 20, 2021, is a scheme to complete the optimization calculation of the tension speed compensation model based on the evaluation of rolling force, and completes all calculations based on set values; its essence is to establish the optimization of the single factor of rolling speed. Summary of the Invention

[0009] To address the above problems, this invention provides a thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel, the specific technical solution of which is as follows:

[0010] A thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel, characterized in that:

[0011] By setting an evaluation model based on the strip exit thickness deviation rate, and combining the historical actual values ​​of each stand's rolling force, each stand's inlet speed, each stand's outlet speed, each stand's inlet thickness, and each stand's outlet thickness, the optimization evaluation of the set pre-tension and set post-tension is completed. Based on the evaluation results, the set values ​​of the pre-tension and post-tension are optimized, thereby completing the thickness control compensation of the acceleration and deceleration process of ultra-high strength steel cold continuous rolling.

[0012] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0013] The evaluation model is established based on two dimensions: the root mean square error of the deviation rate and the distribution of extreme values. The thickness control compensation method specifically includes the following steps:

[0014] S1: Divide the closed interval from 0 to the maximum value allowed by the process into N equal parts to form each specific speed value discrete on the interval.

[0015] S2: Starting from their respective set values, the back tension and front tension are iteratively calculated with a set step size under the constraints of their respective limits allowed by the process, until the iteration ends when both values ​​exceed the constraints.

[0016] S3: Calculate the corresponding strip exit thickness of each rack at each discrete speed value after each iteration before the iteration terminates.

[0017] S4: Calculate the corresponding strip exit thickness deviation rate based on the strip exit thickness of each rack at each discrete speed value after each iteration.

[0018] S5: The evaluation model for the strip steel exit thickness deviation rate is based on the strip steel exit thickness deviation rate after each iteration, and the evaluation calculation is performed after each iteration.

[0019] S6: Select the value with the lowest evaluation value among all iterations, and determine the set tension optimization value based on this value.

[0020] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0021] In step S4, after each iteration, after calculating the corresponding strip exit thickness and the corresponding strip exit thickness deviation rate for each rack at each discrete speed value, the strip exit thickness deviation rate of each rack is compared with the critical deviation rate of its respective rack. If the strip exit thickness deviation rate of any rack at any discrete speed value is greater than its corresponding critical deviation rate, then reverse optimization iteration is performed according to the set step size, and steps S2, S3, and S4 are re-executed until any discrete speed value of all racks is less than or equal to the critical deviation rate of its respective rack, then the inner loop is exited and step S5 is executed.

[0022] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0023] In step S2, when only one tension value iterates to exceed its process limit, the iteration of that tension value is terminated in the next iteration, and the iteration of another tension value continues.

[0024] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0025] The pre-tension and post-tension in step S2 are iterated according to the following set of equations, wherein the iteration is performed on the tension compensation coefficient in the formula.

[0026]

[0027] In the above formula,

[0028] T 0ik : The post-tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0029] T 0i : The set back tension of the i-th frame, in MPa;

[0030] ΔT 0ik Additional back tension in the current iteration, unit: MPa;

[0031] T 1ik : The front tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0032] T 1i : The set pretension of the i-th frame, in MPa;

[0033] ΔT 1ik Additional pretension in the current iteration, unit: MPa;

[0034] v ik : The set rolling speed for the k-th discrete speed value of the i-th stand, in m / s;

[0035] The rolling speed is set for the i-th stand, in m / s.

[0036] c1, c2: Tension compensation coefficients;

[0037] v imax : The maximum permissible rolling speed for the i-th stand, in m / s;

[0038] i: Number of racks;

[0039] k: the sequence number of discrete velocity values, k = 1, 2, 3…n;

[0040] n: The n equal divisions between the strip speed from 0 to the maximum value allowed by the process.

[0041] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0042] When an iteration is triggered because both the current values ​​of the front and back tensions are within the limits allowed by the process, the iteration is performed according to the following formulas:

[0043] c1=c1+0.05l1, c2=c2+0.05l2;

[0044] When a reverse iteration is triggered because the strip exit thickness deviation rate at any discrete speed value for any stand exceeds the critical deviation rate for the corresponding stand, the iteration is performed according to the following formula:

[0045] c1=c1-0.01, c2=c2-0.01.

[0046] According to the present invention, a thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel is characterized in that: the strip exit thickness in step S3 is determined according to the following formula:

[0047]

[0048] In the formula,

[0049] h ik ': Strip exit thickness at the k-th discrete speed value of the i-th frame, unit: mm;

[0050] H i : The average historical strip entry thickness of the i-th frame, in mm;

[0051] P i : The historical average actual rolling force of the i-th stand, in N;

[0052] ν: Poisson's ratio;

[0053] E: Elastic modulus of strip steel, unit: MPa;

[0054] σ s Yield strength of strip steel, unit: MPa;

[0055] h i : The historical average strip exit thickness of the i-th frame, in mm;

[0056] T 1ik : The front tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0057] T 0ik : Post-tension after tension compensation for the k-th discrete velocity value of the i-th frame, unit: MPa

[0058] B: Strip width, unit: mm;

[0059] R i : Radius of the working roller of the i-th frame, in mm;

[0060] Q Fi : External friction influence coefficient.

[0061] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0062]

[0063] In the formula,

[0064] Q Fi External friction influence coefficient;

[0065] r i : The pass reduction rate of the i-th rack;

[0066] μ i : The coefficient of friction for strip steel produced on the i-th stand under typical working conditions;

[0067] R i : Radius of the working roller of the i-th frame, in mm;

[0068] h i : The historical average strip exit thickness of the i-th frame, in mm

[0069] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0070] The reduction rate per pass is determined by the following formula:

[0071] r i =(H i -h i ) / H i ,

[0072] In the formula,

[0073] r i : The pass reduction rate of the i-th rack;

[0074] H i : The average historical strip entry thickness of the i-th frame, in mm;

[0075] h i : The average historical strip exit thickness of the i-th frame, in mm.

[0076] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0077] The strip exit thickness deviation rate in step S4 is determined according to the following formula:

[0078]

[0079] In the formula,

[0080] e ik : The strip exit thickness deviation rate for the k-th discrete speed value of the i-th frame;

[0081] V Hi : The average historical strip entry velocity of the i-th rack, in m / s;

[0082] V hi : The average historical strip exit speed of the i-th rack, in m / s;

[0083] h ik ': Strip exit thickness at the k-th discrete speed value of the i-th frame, unit: mm;

[0084] H i : The average historical strip entry thickness of the i-th frame, in mm.

[0085] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0086] The evaluation model in step S5 is as follows:

[0087]

[0088] In the formula,

[0089] γ: Weighting coefficient;

[0090] M: Total number of racks.

[0091] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0092] The weighting coefficient γ is determined based on four factors: the actual tension setting range, yield strength, tensile strength, and elongation.

[0093] A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to the present invention is characterized in that:

[0094] Step S6 is as follows:

[0095] First, sort all the calculated evaluation values ​​to determine the lowest evaluation value;

[0096] Then, based on this minimum assessment value, the corresponding compensation coefficients c1 and c2 are determined;

[0097] Then, the maximum strip exit thickness deviation rate at this iteration number is found, and the rolling speed v is determined based on the maximum strip exit thickness deviation rate. ik Then, the corresponding front and back tensions are determined.

[0098] This invention discloses a thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel. Based on considerations of multiple factors including rolling force, inlet speed, outlet speed, inlet thickness, outlet thickness, and tension, a thickness control optimization scheme based on tension optimization is established. This results in a technical solution aimed at optimizing tension, taking into account actual historical data on rolling force, inlet speed, outlet speed, inlet thickness, and outlet thickness. Specifically, it aims to optimize tension by calculating the deviation rate and establishing an evaluation system for the deviation rate, reflecting optimization based on a comprehensive consideration of multiple factors. Specifically, when calculating the deviation rate and outlet thickness, the rolling force, inlet speed, outlet speed, and outlet thickness are substituted into their respective calculation formulas. Speed, inlet thickness, and outlet thickness are all obtained based on historical data processing. The calculation formulas for outlet thickness and external friction influence coefficient are optimized expressions. Tension optimization is achieved by distributing the optimization process across two factors: the supplementary coefficient and the discrete division of rolling speed. Finally, an evaluation model is established based on the fundamental idea of ​​considering the root mean square error of the deviation rate and the distribution of extreme values. Through the construction and implementation of the above technical solutions, the thickness control compensation optimization of this technical solution is formed, further ensuring and improving the accuracy of the strip outlet thickness. This improves strip steel production efficiency and quality, bringing significant economic benefits to the on-site ultra-high strength steel unit. Attached Figure Description

[0099] Figure 1 This is a schematic diagram of the steps of the present invention;

[0100] Figure 2 This is a schematic diagram of the overall process of the working principle of this invention. Detailed Implementation

[0101] The following is a detailed description of a thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel, based on the accompanying drawings and specific embodiments of the present invention.

[0102] A thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel is proposed. By setting an evaluation model based on the strip exit thickness deviation rate, and combining the historical actual values ​​of rolling force, entry speed, exit speed, entry thickness, and exit thickness of each stand, the method completes the optimization evaluation of the set pre-tension and post-tension. Based on the evaluation results, the set values ​​of pre-tension and post-tension are optimized, thereby completing the thickness control compensation for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel.

[0103] The evaluation model is established based on two dimensions: the mean square error of the deviation rate and the distribution of extreme values. The thickness control compensation method specifically includes the following steps (see...). Figure 1 ):

[0104] S1: Divide the closed interval from 0 to the maximum value allowed by the process into N equal parts to form each specific speed value discrete on the interval.

[0105] S2: Starting from their respective set values, the back tension and front tension are iteratively calculated with a set step size under the constraints of their respective limits allowed by the process, until the iteration ends when both values ​​exceed the constraints.

[0106] S3: Calculate the corresponding strip exit thickness of each rack at each discrete speed value after each iteration before the iteration terminates.

[0107] S4: Calculate the corresponding strip exit thickness deviation rate based on the strip exit thickness of each rack at each discrete speed value after each iteration.

[0108] S5: The evaluation model for the strip steel exit thickness deviation rate is based on the strip steel exit thickness deviation rate after each iteration, and the evaluation calculation is performed after each iteration.

[0109] S6: Select the value with the lowest evaluation value among all iterations, and determine the set tension optimization value based on this value.

[0110] in,

[0111] In step S4, after each iteration, after calculating the corresponding strip exit thickness and the corresponding strip exit thickness deviation rate for each rack at each discrete speed value, the strip exit thickness deviation rate of each rack is compared with the critical deviation rate of its respective rack. If the strip exit thickness deviation rate of any rack at any discrete speed value is greater than its corresponding critical deviation rate, then reverse optimization iteration is performed according to the set step size, and steps S2, S3, and S4 are re-executed until any discrete speed value of all racks is less than or equal to the critical deviation rate of its respective rack, then the inner loop is exited and step S5 is executed.

[0112] in,

[0113] In step S2, when only one tension value iterates to exceed its process limit, the iteration of that tension value is terminated in the next iteration, and the iteration of another tension value continues.

[0114] in,

[0115] The pre-tension and post-tension in step S2 are iterated according to the following set of equations, wherein the iteration is performed on the tension compensation coefficient in the formula.

[0116]

[0117] In the above formula,

[0118] T0ik : The post-tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0119] T 0i : The set back tension of the i-th frame, in MPa;

[0120] ΔT 0ik Additional back tension in the current iteration, unit: MPa;

[0121] T 1ik : The front tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0122] T 1i : The set pretension of the i-th frame, in MPa;

[0123] ΔT 1ik Additional pretension in the current iteration, unit: MPa;

[0124] v ik : The set rolling speed for the k-th discrete speed value of the i-th stand, in m / s;

[0125] The rolling speed is set for the i-th stand, in m / s.

[0126] c1, c2: Tension compensation coefficients;

[0127] v imax : The maximum permissible rolling speed for the i-th stand, in m / s;

[0128] i: Number of racks;

[0129] k: the sequence number of discrete velocity values, k = 1, 2, 3…n;

[0130] n: The n equal divisions between the strip speed from 0 to the maximum value allowed by the process.

[0131] in,

[0132] When an iteration is triggered because both the current values ​​of the front and back tensions are within the limits allowed by the process, the iteration is performed according to the following formulas:

[0133] c1=c1+0.05l1, c2=c2+0.05l2;

[0134] When a reverse iteration is triggered because the strip exit thickness deviation rate at any discrete speed value for any stand exceeds the critical deviation rate for the corresponding stand, the iteration is performed according to the following formula:

[0135] c1=c1-0.01, c2=c2-0.01.

[0136] in,

[0137] The strip exit thickness in step S3 is determined according to the following formula:

[0138]

[0139] In the formula,

[0140] h ik ': Strip exit thickness at the k-th discrete speed value of the i-th frame, unit: mm;

[0141] H i : The average historical strip entry thickness of the i-th frame, in mm;

[0142] P i : The historical average actual rolling force of the i-th stand, in N;

[0143] ν: Poisson's ratio;

[0144] E: Elastic modulus of strip steel, unit: MPa;

[0145] σ s Yield strength of strip steel, unit: MPa;

[0146] h i : The historical average strip exit thickness of the i-th frame, in mm;

[0147] T 1ik : The front tension after tension compensation for the k-th discrete velocity value of the i-th frame, in MPa;

[0148] T 0ik : Post-tension after tension compensation for the k-th discrete velocity value of the i-th frame, unit: MPa

[0149] B: Strip width, unit: mm;

[0150] R i : Radius of the working roller of the i-th frame, in mm;

[0151] Q Fi : External friction influence coefficient.

[0152] in,

[0153]

[0154] In the formula,

[0155] Q Fi External friction influence coefficient;

[0156] r i: The pass reduction rate of the i-th rack;

[0157] μ i : The coefficient of friction for strip steel produced on the i-th stand under typical working conditions;

[0158] R i : Radius of the working roller of the i-th frame, in mm;

[0159] h i : The historical average strip exit thickness of the i-th frame, in mm

[0160] in,

[0161] The reduction rate per pass is determined by the following formula:

[0162] r i =(H i -h i ) / H i ,

[0163] In the formula,

[0164] r i : The pass reduction rate of the i-th rack;

[0165] H i : The average historical strip entry thickness of the i-th frame, in mm;

[0166] h i : The average historical strip exit thickness of the i-th frame, in mm.

[0167] in,

[0168] The strip exit thickness deviation rate in step S4 is determined according to the following formula:

[0169]

[0170] In the formula,

[0171] e ik : The strip exit thickness deviation rate for the k-th discrete speed value of the i-th frame;

[0172] V Hi : The average historical strip entry velocity of the i-th rack, in m / s;

[0173] V hi : The average historical strip exit speed of the i-th rack, in m / s;

[0174] h ik ': Strip exit thickness at the k-th discrete speed value of the i-th frame, unit: mm;

[0175] Hi : The average historical strip entry thickness of the i-th frame, in mm.

[0176] in,

[0177] The evaluation model in step S5 is as follows:

[0178]

[0179] In the formula,

[0180] γ: Weighting coefficient;

[0181] M: Total number of racks.

[0182] in,

[0183] The weighting coefficient γ is determined based on four factors: the actual tension setting range, yield strength, tensile strength, and elongation.

[0184] in,

[0185] Step S6 is as follows:

[0186] First, sort all the calculated evaluation values ​​to determine the lowest evaluation value;

[0187] Then, based on this minimum assessment value, the corresponding compensation coefficients c1 and c2 are determined;

[0188] Then, the maximum strip exit thickness deviation rate at this iteration number is found, and the rolling speed v is determined based on the maximum strip exit thickness deviation rate. ik Then, the corresponding front and back tensions are determined.

[0189] Working principle and process

[0190] To achieve the above objectives, the present invention adopts the following technical solution (for further understanding, please refer to...). Figure 1 , 2 ):

[0191] (A) Collect equipment and process parameters of the ultra-high strength steel cold rolling mill: diameter d of the work rolls of each stand wi (i = 1, 2, ..., 5, the range of i is the same for the following i) The rolling force P of the i-th stand i The set values ​​T for the back tension and front tension of the i-th stand when the rolling speed is the set rolling speed of the unit. 0i T 1i The coefficient of friction μ of the i-th stand producing strip steel under typical working conditions i The i-th stand is set with a rolling speed The actual inlet velocity of the i-th rack is V. Hi The actual exit speed of the i-th rack is V.hi The critical tolerance rate is set for the i-th rack. and all rolling forces P i All inlet velocities V Hi All exit speeds V hi Perform their respective mean calculations;

[0192] (B) Collect relevant parameters of the strip: strip elastic modulus, Poisson's ratio E, ν, and strip entry thickness H of the i-th stand. i Export thickness setting h i Strip width B, strip yield strength σ s And each inlet thickness and outlet thickness is averaged separately.

[0193] (C) Define the stand number i (i = 1, 2, ..., 5), and the strip rolling speed of each stand ranges from 0 to the maximum v. imax Divided into n average segments, the maximum back tension and maximum front tension of the i-th frame. Minimum back tension and minimum front tension of the i-th frame Additional back tension and additional front tension ΔT of segment k of frame i 0ik ΔT 1ik The thickness deviation rate e of the k-th discrete velocity value of the i-th frame ik The objective function values ​​g3(x) and g4(x) are combined. The objective function g3(x) is mainly based on the idea of ​​mean square error, while the objective function g4(x) is mainly based on the idea of ​​maximum and minimum difference. The comprehensive optimization objective function value F(x) reflects the consideration of both g3(x) and g4(x).

[0194] (D) Initialize the tension compensation optimization coefficient c 1i =0, c 2i =0, then proceed to step (E);

[0195] (E) Calculate the initial tension compensation value and the compensated tension value required for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel:

[0196]

[0197] In the formula: T 0ik T 1ik These are the back tension and front tension of the k-th segment of the i-th frame after tension compensation, respectively, T 0i T 1i These are the set values ​​for the back tension and front tension of the i-th stand when the rolling speed is the set rolling speed of the unit, respectively. ik The set rolling speed for the k-th discrete speed value of the i-th stand;

[0198] (F) Judgment Are all true; if only If this holds true, let l1 = 1, l2 = 0, if only If this holds true, let l1 = 0, l2 = 1, then... If both are true, let l1 = 1, l2 = 1, and simultaneously let c1 = c1 + 0.05l1, c2 = c2 + 0.05l2, proceed to step (E) to begin the next iteration calculation, and simultaneously calculate step (G) to calculate the exit thickness under the current iteration; if If none of the above conditions are met, the iteration terminates.

[0199] (G) Calculate the exit thickness h′ of the strip in the i-th frame. ik :

[0200]

[0201] In the formula: r i Let Q be the pass reduction rate of the i-th rack. Fi R is the coefficient of influence of external friction. i The working roll radius of the i-th frame;

[0202] (H) Calculate the strip exit thickness deviation rate for the i-th frame:

[0203] In the formula: when h ik ′ <h i That is, when the outlet thickness is less than the set value, l = 1; when h ik ′>h i That is, when the outlet thickness is greater than the set value, l = -1, V Hi For rolling exit thickness h ik The inlet velocity of ultra-high strength steel at ′ time, V hi For rolling exit thickness h ik The export speed of ultra-high strength steel at ′ time;

[0204] (I) Judgment Does the condition hold true? If it does, proceed to step (J) to perform the evaluation calculation for the current iteration; otherwise, let c1 = c1 + 0.01l1 and c2 = c2 + 0.01l2, proceed to step (E), and repeat steps (E) to (I) until the condition is met. Only then does it exit the inner loop and enter step (J);

[0205] (J) Calculate the comprehensive optimization objective function value of the tension compensation coefficient:

[0206] In the formula: γ is the weighting coefficient, and γ∈(0,1), f1(x) is the average value of the comprehensive objective function of all racks, and f2(x) is the maximum difference of the comprehensive objective function of all racks;

[0207] (K) Output optimal tension compensation coefficient Front and rear tension compensation values ​​of each frame under optimal thickness control during acceleration and deceleration of ultra-high strength steel. The front and rear tension compensation values First, the rolling speed v needs to be determined. ik Completed, and this v ik e represents the iteration number where the tension compensation value is located under optimal thickness control. ik The Kth discrete velocity value corresponding to the maximum value.

[0208] Example

[0209] Below, we take the thickness control compensation during the acceleration and deceleration process of cold continuous rolling of a certain specification of ultra-high strength steel as an example, combined with... Figure 1 The present invention provides a detailed description of the comprehensive optimization flowchart for thickness control compensation in the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel.

[0210] Example 1: The steel grade is AP0961E1, and the specifications are 2500mm × 2.50mm (width × thickness).

[0211] First, in step (A), collect the equipment and process parameters of the ultra-high strength steel cold rolling mill: the diameters of the work rolls for each stand are d1 = 560mm, d2 = 520mm, d3 = 480mm, d4 = 440mm, d5 = 400mm; the rolling forces for each stand are P1 = 20,000,000N, P1 = 22,000,000N, P1 = 24,000,000N, P1 = 25,000,000N, P1 = 26,000,000N; and the back tension T for each stand at the set rolling speed of the mill. 01 =35MPa, T 02 =40MPa, T 03 =45MPa, T 04 =50MPa, T 05 =60MPa, tension setpoint T for each frame 11 =110MPa, T 12 =115MPa, T 13 =120MPa, T 14 =125MPa, T 15 =135MPa, the friction coefficients for strip production on each stand under typical operating conditions are μ1=0.055, μ2=0.029, μ3=0.02, μ4=0.012, μ5=0.013, and the rolling speeds set for each stand are v1 and v2 respectively. * =4m / s, v2 * = 4.9 m / s, v3 * =5.5m / s, v4 * =5.6m / s, v5* =6m / s, the actual inlet velocity of each rack is V H1 = 3.5 m / s, V H2 = 3.98 m / s, V H3 = 4.87 m / s, V H4 = 5.56 m / s, V H5 = 5.63 m / s, the actual exit velocity is V h1 = 3.98 m / s, V h2 = 4.87 m / s, V h3 = 5.56 m / s, V h4 = 5.63 m / s, V h5 =5.98m / s, with the same critical deviation rate e set for each rack. i * =0.05;

[0212] Subsequently, in step (B), relevant strip parameters are collected: strip elastic modulus, Poisson's ratio E = 210000 MPa, v = 0.3, strip inlet thickness for each stand H1 = 2.5 mm, H2 = 2.14 mm, H3 = 1.78 mm, H4 = 1.58 mm, H5 = 1.51 mm, outlet thickness set values ​​h1 = 2.14 mm, h2 = 1.78 mm, h3 = 1.58 mm, h4 = 1.51 mm, h5 = 1.47 mm, strip width B = 2500 mm, and strip yield strength σ. s =1050MPa;

[0213] Subsequently, in step (C), the stand number i (i = 1, 2, ..., 5) is defined, and the strip rolling speed of each stand ranges from 0 to the maximum v. imax =12m / s is divided into n=2 segments, and the maximum back tension and maximum front tension of each frame are set to be equal. The minimum back tension and minimum front tension of each frame are set to be equal values.

[0214] Then in step (D), it is assumed that after the p-th iteration, the tension compensation optimization coefficients c1 = 0.2 and c2 = 0.8, and then proceed to step (E);

[0215] Subsequently, in step (E), the required initial tension compensation value and the compensated tension value for the acceleration and deceleration process of ultra-high strength steel cold rolling are calculated: T was calculated 011 =30.06MPa, T 012 =42MPa, T 021 =40.07MPa, T 022 =48MPa, T 031 =45.07MPa, T032 =54MPa, T 041 =50.08MPa, T 042 =60MPa, T 051 =60.10MPa, T 052 =72MPa, T 111 =110.18MPa, T 112 =132MPa, T 121 =115.19MPa, T 122 =138MPa, T 131 =120.2MPa, T 132 =144MPa, T 141 =125.21MPa, T 142 =150MPa, T 151 =135.22MPa, T 152 =162MPa;

[0216] Subsequently, in step (F), after judgment, If successful, proceed to step (G);

[0217] Subsequently, in step (G), the exit thickness h′ of the strip in the i-th frame is calculated. ik : The exit thickness h′ of each rack was calculated. 11 =2.145mm, h′ 21 =1.778mm, h′ 31 =1.579mm, h′ 41 =1.516mm, h′ 51 =1.424mm, h′ 12 =2.148mm, h′ 22 =1.783mm, h′ 32 =1.575mm, h′ 42 =1.507mm, h′ 52 =1.423mm;

[0218] Then, in step (H), the strip exit thickness deviation rate for each stand is calculated: Calculate e 11 =0.025, e 12 =0.024, e 21 =0.016, e 22 =0.016, e 31 =0.013, e 32 =0.012, e 41 =0.029, e 42 =0.027, e 51 =0.002, e52 =0.003;

[0219] Subsequently, in step (I), it is determined that for all racks, If all conditions are met, proceed to step (J);

[0220] Subsequently, in step (J), let γ = 0.4, and calculate the comprehensive optimization objective function value of the tension compensation coefficient: The calculations yielded g3(x)1 = 0.365, g4(x)1 = 0.028, g3(x)2 = 0.476, g4(x)2 = 1.31e-6, g3(x)3 = 0.534, g4(x)3 = 0.015, g3(x)4 = 0.311, g4(x)4 = 0.049, g3(x)5 = 0.677, g4(x)5 = 0.019, and F(x) = 0.218.

[0221] Subsequently, in step (K), the optimal tension compensation coefficient is output. Rolling speed Average front and rear tension compensation of each frame under optimal thickness control during acceleration and deceleration of ultra-high strength steel.

[0222] This invention establishes a comprehensive optimization model for thickness control compensation of ultra-high strength steel by studying the influence of key equipment and process parameters on thickness compensation control during the acceleration and deceleration process of ultra-high strength steel cold continuous rolling. Through optimization of these parameters, the thickness control accuracy during the acceleration and deceleration process of ultra-high strength steel cold continuous rolling is ensured, improving the production efficiency and quality of ultra-high strength steel on-site and bringing long-term economic benefits to the unit.

[0223] Example 2: The steel grade is AP1055E5, and the specifications are 2100mm × 1.50mm (width × thickness).

[0224] First, in step (A), collect the equipment and process parameters of the ultra-high strength steel cold rolling mill: the diameters of the work rolls for each stand are d1 = 560mm, d2 = 520mm, d3 = 480mm, d4 = 440mm, d5 = 400mm; the rolling forces for each stand are P1 = 25,000,000N, P1 = 25,500,000N, P1 = 26,000,000N, P1 = 26,500,000N, P1 = 27,000,000N; and the back tension T for each stand at the set rolling speed of the mill. 01 =35MPa, T 02 =40MPa, T 03 =45MPa, T 04 =50MPa, T 05 =60MPa, tension setpoint T for each frame 11=125MPa, T 12 =130MPa, T 13 =135MPa, T 14 =140MPa, T 15 =150MPa, the friction coefficients for strip production on each stand under typical operating conditions are μ1=0.055, μ2=0.029, μ3=0.02, μ4=0.012, μ5=0.013, and the rolling speeds set for each stand are v1 and v2 respectively. * =5.3m / s, v2 * =6.8m / s, v3 * =8.6m / s, v4 * =10.4m / s, v5 * =11.3m / s, the actual inlet velocity of each rack is V H1 = 4.2 m / s, V H2 = 5.31 m / s, V H3 = 6.81 m / s, V H4 = 8.60 m / s, V H5 =10.38m / s, the actual exit velocity is V h1 = 5.31 m / s, V h2 = 6.81 m / s, V h3 = 8.60 m / s, V h4 =10.38m / s, V h5 =11.33m / s, with the same critical deviation rate set for each rack.

[0225] Subsequently, in step (B), relevant strip parameters are collected: strip elastic modulus, Poisson's ratio E = 210000 MPa, v = 0.3, strip inlet thickness for each stand H1 = 1.5 mm, H2 = 1.22 mm, H3 = 0.93 mm, H4 = 0.72 mm, H5 = 0.61 mm, outlet thickness set values ​​h1 = 1.22 mm, h2 = 0.93 mm, h3 = 0.72 mm, h4 = 0.61 mm, h5 = 0.55 mm, strip width B = 2100 mm, and strip yield strength σ. s =1150MPa;

[0226] Subsequently, in step (C), the stand number i (i = 1, 2, ..., 5) is defined, and the strip rolling speed of each stand ranges from 0 to the maximum v. imax =12m / s is divided into n=2 segments, and the maximum back tension and maximum front tension of each frame are set to be equal. The minimum back tension and minimum front tension of each frame are set to be equal values. Maximum value of the overall objective function g 3max (x)=1, g4max (x) = 1, the minimum value of the comprehensive objective function is g. 3min (x)=0, g 4min (x) = 0;

[0227] Then in step (D), it is assumed that after the p-th iteration, the tension compensation optimization coefficients c1 = 0.3 and c2 = 0.7, and then proceed to step (E);

[0228] Subsequently, in step (E), the required initial tension compensation value and the compensated tension value for the acceleration and deceleration process of ultra-high strength steel cold rolling are calculated: T was calculated 011 =35.08MPa, T 012 =40.21MPa, T 021 =40.09MPa, T 022 =45.96MPa, T 031 =45.10MPa, T 032 =51.70MPa, T 041 =50.11MPa, T 042 =57.45MPa, T 051 =60.13MPa, T 052 =68.94MPa, T 111 =125.28MPa, T 112 =143.62MPa, T 121 =130.29MPa, T 122 =149.37MPa, T 131 =135.30MPa, T 132 =155.11MPa, T 141 =140.31MPa, T 142 =160.86MPa, T 151 =150.34MPa, T 152 =172.35MPa;

[0229] Subsequently, in step (F), after judgment, If successful, proceed to step (G);

[0230] Subsequently, in step (G), the exit thickness h′ of the strip in the i-th frame is calculated. ik : The exit thickness h′ of each rack was calculated. 11 =1.219mm, h′ 21 =0.934mm, h′ 31 =0.721mm, h′ 41 =0.608mm, h′ 51 =0.552mm, h′12 =1.217mm, h′ 22 =0.931mm, h′ 32 =0.723mm, h′ 42 =0.605mm, h′ 52 =0.553mm;

[0231] Then, in step (H), the strip exit thickness deviation rate for each stand is calculated: Calculate e 11 =0.027, e 12 =0.020, e 21 =0.018, e 22 =0.021, e 31 =0.021, e 32 =0.011, e 41 =0.019, e 42 =0.022, e 51 =0.012, e 52 =0.002;

[0232] Subsequently, in step (I), it is determined that for all racks, If all conditions are met, proceed to step (J);

[0233] Subsequently, in step (J), let γ = 0.6, and calculate the comprehensive optimization objective function value of the tension compensation coefficient: The calculations yielded g3(x)1 = 0.305, g4(x)1 = 0.178, g3(x)2 = 0.363, g4(x)2 = 0.050, g3(x)3 = 0.435, g4(x)3 = 0.271, g3(x)4 = 0.341, g4(x)4 = 0.098, g3(x)5 = 0.587, g4(x)5 = 0.260, and F(x) = 0.352.

[0234] Subsequently, in step (K), the optimal tension compensation coefficient is output. Rolling speed Average front and rear tension compensation of each frame under optimal thickness control during acceleration and deceleration of ultra-high strength steel.

[0235] For Unit C502, due to the downstream units not accepting thickness variations exceeding 30m, closed rolls require rework at the finishing unit. Statistics from January to October 2020 show that the cumulative rework volume for Unit C502 due to longitudinal thickness deviations was 17,600 tons, with an average monthly rework volume of 1,765 tons. Considering the equipment and process characteristics of Unit C50, and applying the aforementioned model to the on-site units, analysis of recent on-site tracking data shows that the average monthly rework volume for Unit C502 is approximately 975 tons, a decrease of nearly 800 tons compared to before the model application, significantly reducing the monthly rework volume on-site. The specific deviations at the site are as follows: Head thickness deviation is 3% with an average of 4.8388 meters, and 5% with an average of 3.3486 meters; Tail thickness deviation is 3% with an average of 5.9141 meters, and 5% with an average of 2.6088 meters. The head and tail thickness deviation data and images at the site are shown below:

[0236] Table 1. Strip thickness deviation data after thickness control compensation during acceleration and deceleration of ultra-high strength steel.

[0237]

Claims

1. A thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel, characterized in that: By establishing an evaluation model based on the strip exit thickness deviation rate, and combining historical actual values ​​of rolling force, entry speed, exit speed, entry thickness, and exit thickness for each stand, the optimal evaluation of the set pre-tension and post-tension is completed. Based on the evaluation results, the set values ​​of pre-tension and post-tension are optimized, thereby completing the thickness control compensation during the acceleration and deceleration process of ultra-high strength steel cold continuous rolling. The evaluation model is established based on two dimensions: the root mean square error of the deviation rate and the distribution of extreme values. The thickness control compensation method specifically includes the following steps: S1: Divide the closed interval from 0 to the maximum value allowed by the process into N equal parts to form each specific speed value discrete on the interval. S2: Starting from their respective set values, the back tension and front tension are iteratively calculated with a set step size under the constraints of their respective limits allowed by the process, until the iteration ends when both values ​​exceed the constraints. S3: Calculate the corresponding strip exit thickness of each rack at each discrete speed value after each iteration before the iteration terminates; S4: Calculate the corresponding strip exit thickness deviation rate based on the strip exit thickness of each rack at each discrete speed value after each iteration. S5: The evaluation model for the strip steel exit thickness deviation rate is based on the strip steel exit thickness deviation rate after each iteration, and the evaluation calculation is performed after each iteration. S6: Select the value with the lowest evaluation value among all iterations, and determine the optimal tension value based on this value. The pre-tension and post-tension in step S2 are iterated according to the following set of equations, wherein the iteration is performed on the tension compensation coefficient in the formula. ， In the above formula, : No. rack number The post-tension after tension compensation for discrete velocity values, unit: MPa; : No. The set tension of the frame, in MPa; Additional back tension in the current iteration, unit: MPa; : No. rack number The front tension after tension compensation for discrete velocity values, unit: MPa; : No. The set tension of the frame, in MPa; Additional pretension in the current iteration, unit: MPa; : No. rack number The set rolling speed is a discrete speed value, in m / s; : No. The stand is set to the rolling speed, in m / s; , Tension compensation coefficient; : No. Maximum permissible rolling speed for stand-up rolling processes, in m / s; Number of racks; : The number of discrete velocity values ​​in a sequence, k=1, 2, 3…n; The strip speed is divided into n equal parts from 0 to the maximum value allowed by the process.

2. The thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel according to claim 1, characterized in that: In step S4, after each iteration, after calculating the corresponding strip exit thickness and the corresponding strip exit thickness deviation rate for each rack at each discrete speed value, the strip exit thickness deviation rate of each rack is compared with the critical deviation rate of its respective rack. If the strip exit thickness deviation rate of any rack at any discrete speed value is greater than its corresponding critical deviation rate, then reverse optimization iteration is performed according to the set step size, and steps S2, S3, and S4 are re-executed until the strip exit thickness deviation rate of all racks at any discrete speed value is less than or equal to the critical deviation rate of its respective rack. Then, the inner loop is exited and step S5 is executed.

3. The thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel according to claim 1, characterized in that: In step S2, when only one tension value iterates to exceed its process limit, the iteration of that tension value is terminated in the next iteration, and the iteration of another tension value continues.

4. The thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 3, characterized in that: When an iteration is triggered because both the current values ​​of the front and back tensions are within the limits allowed by the process, the iteration is performed according to the following formulas: ； When a reverse iteration is triggered because the strip exit thickness deviation rate at any discrete speed value for any stand exceeds the critical deviation rate for the corresponding stand, the iteration is performed according to the following formula: ， judge Are they all true? If only Established, Order , If only Established, Order , if All are established, therefore , They are respectively: the Maximum back tension and maximum front tension of the frame They are respectively: the Minimum back tension and minimum front tension of the frame.

5. The thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel according to claim 4, characterized in that: The strip exit thickness in step S3 is determined according to the following formula: In the formula, h ik ＇ : No. rack number The exit thickness of the strip at discrete velocity values, in mm; H i : No. The historical average thickness of the strip at the entrance of the frame, in mm; P i : No. The historical average actual rolling force of the mill stand, in N; Poisson's ratio; E: Elastic modulus of strip steel, unit: MPa; σ s Yield strength of strip steel, unit: MPa; h i : No. The historical average thickness of the strip steel exiting the frame, in mm; : No. rack number The front tension after tension compensation for discrete velocity values, unit: MPa; : No. rack number The post-tension after tension compensation for discrete velocity values, unit: MPa; B: Strip width, unit: mm; R i : No. The radius of the working rollers on the frame, in mm; Q Fi : External friction influence coefficient.

6. The thickness control compensation method for the acceleration and deceleration process of cold continuous rolling of ultra-high strength steel according to claim 5, characterized in that: ， In the formula, Q Fi External friction influence coefficient; : No. The pass reduction rate of the rack; : No. The coefficient of friction for strip steel produced on the machine frame under typical working conditions; R i : No. The radius of the working rollers on the frame, in mm; h i : No. The historical average thickness of the strip steel exiting the frame, in mm.

7. The thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 6, characterized in that: The reduction rate per pass is determined by the following formula: ， In the formula, : No. The pass reduction rate of the rack; H i : No. The historical average thickness of the strip at the entrance of the frame, in mm; h i : No. The historical average thickness of the strip steel exiting the frame, in mm.

8. The thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 7, characterized in that: The strip exit thickness deviation rate in step S4 is determined according to the following formula: ， In the formula, e ik : No. rack number Out-of-tolerance rate of strip exit thickness at discrete speed values; V Hi : No. The average historical strip entry velocity of each rack, in m / s; V hi : No. The average historical strip exit speed of each stand, in m / s; h ik ＇ : No. rack number The exit thickness of the strip at discrete velocity values, in mm; H i : No. The historical average thickness of the strip at the entrance of the frame, in mm; in style That is, when the outlet thickness is less than the set value, ;when That is, when the outlet thickness is greater than the set value, .

9. A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 8, characterized in that: The evaluation model in step S5 is as follows: ， In the formula, Weighting coefficients ∈(0,1), f1(x) is the average of the combined objective function for all racks. f2(x) is the maximum difference in the combined objective function for all racks. Total number of racks e ik : No. rack number Out-of-tolerance rate of strip exit thickness at discrete speed values e i * The critical deviation rate is set for the i-th rack.

10. A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 9, characterized in that: Weighting coefficients The setting is determined based on four factors: actual tension range, yield strength, tensile strength, and elongation.

11. A thickness control compensation method for acceleration and deceleration processes in cold continuous rolling of ultra-high strength steel according to claim 10, characterized in that: Step S6 is as follows: First, sort all the calculated evaluation values ​​to determine the lowest evaluation value; Then, the corresponding compensation coefficient is determined based on this minimum assessment value. , ; Then, the maximum strip exit thickness deviation rate at that iteration number is found, and the rolling speed is determined based on the maximum strip exit thickness deviation rate. Then, the corresponding front and back tensions are determined.

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