A method for dynamically controlling the finish rolling temperature in a finish rolling threading process

Abstract

The application discloses a kind of final-rolling temperature dynamic control method in finishing threading process, belong to metallurgical automation control technical field.The method obtains the entry strip thickness and outlet strip thickness of finishing mill set to calculate threading reduction, and the preset rolling force preset value of each rack is determined in combination with preset rolling speed initial value;After strip head enters finishing mill set, real-time acquisition actual rolling force and actual rolling speed, according to the first correction of actual rolling speed according to rolling force deviation;According to the inter-rack heat loss compensation value of one-time correction rolling speed and strip instantaneous deformation resistance calculation, and the target value is obtained after compensating to final-rolling temperature preset value;Again, the difference between target value and actual final-rolling temperature is calculated to calculate the dynamic adjustment amount of rolling speed, and after the second correction, it is issued to drive control system.The method uses rolling force deviation speed correction and heat loss dynamic compensation, realizes the closed-loop accurate control of final-rolling temperature.

Description

Technical Field

[0001] This invention relates to the field of metallurgical automation control technology, specifically a method for dynamic control of final rolling temperature during the finishing rolling strip threading process. Background Technology

[0002] The control of the final rolling temperature during the strip threading process directly affects the uniformity of the strip's microstructure and the final product performance. In existing technologies, the final rolling temperature mainly relies on a pre-set model for feedforward control, supplemented by feedback adjustment after exit temperature measurement. The pre-set model calculates the rolling speed and inter-stand cooling strategy based on initial process parameters; once strip threading begins, the model parameters remain fixed. During actual threading, factors such as roll thermal expansion, fluctuations in incoming material thickness, and changes in deformation resistance cause significant deviations between the actual rolling force of each stand and the pre-set value. These deviations alter deformation heat and rolling power, leading to drift in the final rolling temperature. Traditional feedback adjustment only intervenes after the strip head reaches the exit temperature measurement point, resulting in a long lag time and failing to effectively suppress temperature deviations in the initial threading stage. Furthermore, calculations of inter-stand heat loss mostly rely on empirical formulas, assuming a constant rolling speed and uniform deformation resistance, without considering the impact of real-time speed adjustments during the threading stage on running time variations and instantaneous deformation resistance fluctuations on heat dissipation. This rough estimation of heat loss leads to insufficient accuracy in predicting the exit temperature of the preceding stands. Errors accumulate across each stand, ultimately resulting in a lack of real-time performance and accuracy in the final rolling temperature control. Therefore, it is necessary to promptly capture rolling force deviations and quickly correct the rolling speed during the strip threading process, and to accurately calculate the inter-stand heat loss compensation value based on the actual speed and deformation state, in order to solve the problems of delayed response and inaccurate heat loss compensation in the final rolling temperature control. Summary of the Invention

[0003] The purpose of this invention is to provide a dynamic control method for the final rolling temperature during the strip threading process of finishing rolling, which solves the problems of temperature drift caused by the lack of real-time compensation for rolling force deviation and the accumulation of temperature prediction errors caused by the rough calculation of heat dissipation loss between stands in the prior art, and realizes dynamic and accurate control of the final rolling temperature during the strip threading process.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for dynamic control of final rolling temperature during the finishing rolling strip threading process, comprising the following: The entry and exit strip thicknesses of the finishing mill are obtained, and the strip-threading reduction rate of the finishing mill stand is calculated based on these thicknesses. The preset rolling force value for each stand during the strip-threading process is determined based on the strip-threading reduction rate and a pre-set initial rolling speed value. After the strip head enters the finishing mill, the actual rolling force and actual rolling speed of each stand are collected in real time. The actual rolling speed is corrected for the first time based on the deviation between the actual rolling force and the preset rolling force value, resulting in a corrected rolling speed. This quickly compensates for rolling force fluctuations caused by changes in deformation conditions in the early stages of strip-threading, maintaining the stability of the rolling process.

[0005] Based on the first-corrected rolling speed and the inter-stand heat loss compensation value of the strip's instantaneous deformation resistance, the preset value of the final rolling temperature is compensated using this inter-stand heat loss compensation value to obtain the compensated target value of the final rolling temperature. Based on the difference between the compensated target value of the final rolling temperature and the actual final rolling temperature of the strip at the exit, the dynamic adjustment amount of the rolling speed for each stand is calculated. The first-corrected rolling speed is then corrected a second time based on this dynamic adjustment amount to obtain the second-corrected rolling speed, which is then sent to the corresponding stand's drive control system. By introducing heat loss compensation that matches the real-time deformation conditions and rolling rhythm, combined with dynamic speed adjustment based on closed-loop feedback of the final rolling temperature, the control accuracy of the strip's full-length final rolling temperature can be significantly improved, and the temperature deviation between the head and the body can be reduced.

[0006] Preferably, when determining the preset rolling force value for each stand, the inlet strip temperature and the target outlet strip temperature of the finishing mill are obtained. The total temperature drop during the strip threading process is calculated based on these temperatures. A temperature drop coefficient is allocated to each stand based on the total temperature drop and the strip threading reduction rate. The average deformation rate of each stand is calculated based on the temperature drop coefficient and the preset initial rolling speed. The predicted deformation resistance value for each stand is determined based on the average deformation rate and the chemical composition of the strip. This predicted deformation resistance value is then substituted into the rolling force formula to calculate the preset rolling force value for each stand. The rolling force formula is either the Hill formula or the Sims formula, and the calculation process considers the elastic flattening effect of the rolls, making the preset rolling force value closer to the actual rolling state and providing an accurate comparison benchmark for subsequent speed correction.

[0007] As a technical solution of the present invention, when making the first correction to the actual rolling speed, the deviation between the actual rolling force and the preset rolling force value is calculated. When the deviation exceeds a preset dead zone threshold, a speed correction program is triggered to avoid unnecessary speed adjustments caused by minor fluctuations. The speed correction direction is determined according to the sign of the deviation. When the actual rolling force is greater than the preset rolling force value, the speed correction direction is to decrease the rolling speed; when the actual rolling force is less than the preset rolling force value, the speed correction direction is to increase the rolling speed. The speed correction step size is determined according to the absolute value of the deviation and the width of the strip. The speed correction step size is superimposed with the actual rolling speed to obtain the first corrected rolling speed, thereby achieving precise speed compensation that matches the strip specifications and actual load.

[0008] When calculating the inter-stand heat loss compensation value, the running time of the strip between two adjacent stands is calculated based on the first modified rolling speed. A baseline value for natural heat loss is calculated based on the running time and the specific heat capacity of the strip. The deformation heat addition value is determined based on the instantaneous deformation resistance of the strip, and this value is superimposed on the baseline value for natural heat loss to obtain the total heat loss value. The actual spray density of cooling water between stands is obtained, and the total heat loss value is corrected based on this density to obtain the inter-stand heat loss compensation value. The instantaneous deformation resistance is calculated in real-time using a deformation resistance model based on the actual strain, strain rate, and deformation temperature of the current stand. This method comprehensively considers the changes in running time caused by variations in the strip threading speed, the deformation heat effect, and the actual fluctuations in cooling conditions between stands, enabling the heat loss compensation value to dynamically reflect the actual heat exchange state of the rolling line.

[0009] Furthermore, when compensating for the preset value of the final rolling temperature, the measured temperature of the strip at the entrance of the finishing mill is obtained. Based on the measured temperature of the strip at the entrance and the rolling deformation heat of each stand, the predicted exit temperature of each stand is calculated. The predicted exit temperature of each stand is passed sequentially along the rolling direction, and the predicted exit temperature of the final finishing mill is iteratively calculated by equating the entrance temperature of the next stand with the exit temperature of the previous stand minus the heat loss compensation value between stands. The difference between the target exit temperature of the strip and the predicted exit temperature of the final finishing mill is calculated, and the difference is added to the preset value of the final rolling temperature to obtain the compensated target value of the final rolling temperature. Thus, the heat loss distributed along the rolling line is fed back to the target value of the final rolling temperature in real time, making the target value more reasonable and achievable, fundamentally reducing steady-state control deviation.

[0010] When calculating the dynamic adjustment of the rolling speed, the actual final rolling temperature of the strip at the exit is subtracted from the compensated target final rolling temperature to obtain the final rolling temperature deviation. This deviation is then input into a proportional-integral controller (PIC). A speed adjustment coefficient is determined based on the PIC output and the instantaneous thickness of the strip. This coefficient is then allocated to the first few stands of the finishing mill, with the coefficient decreasing progressively according to the stand number. The dynamic adjustment of the rolling speed for each stand is multiplied by a reference speed adjustment to obtain the corresponding dynamic adjustment for that stand. This strategy of concentrating speed adjustments in the first few stands and decreasing them sequentially effectively utilizes the significant temperature influence of the first stands to quickly correct final rolling temperature deviations while avoiding large speed fluctuations in the later stands that could affect the exit thickness accuracy.

[0011] Preferably, the proportional-integral controller further includes an anti-integral saturation mechanism. When the dynamic adjustment of the rolling speed reaches a limit value, the output of the integral term is frozen to prevent control performance deterioration due to actuator saturation. More preferably, the integral time constant of the proportional-integral controller is set in segments according to the stages of the strip threading process. Specifically, the bite signal of the strip head reaching the final stand of the finishing mill is detected, and the strip threading process is divided into a head bite stage and a stable threading stage based on the bite signal. In the head bite stage, the integral time constant of the proportional-integral controller is set to a first integral time constant value. In the stable threading stage, the integral time constant of the proportional-integral controller is set to a second integral time constant value, which is greater than the first integral time constant value. When the absolute value of the final rolling temperature deviation is detected to be less than a preset stable threshold and the duration exceeds a preset time window, the integral time constant of the proportional-integral controller is switched back to the first integral time constant value. By setting the integral time constant in segments, it can quickly respond to eliminate the initial temperature deviation during the head-gripping stage, and avoid speed jitter caused by high-frequency disturbances during the stable threading stage, thus balancing dynamic response and steady-state smoothness.

[0012] As another improvement of the present invention, after the secondary correction rolling speed is sent to the transmission control system of the corresponding stand, the rolling speed of adjacent stands is also cascadedly corrected. Specifically: the speed change between the secondary correction rolling speed of the i-th stand and the previous correction rolling speed of the i-th stand is obtained; the speed change is multiplied by the cascade transmission coefficient to obtain the speed correction feedforward of the i-th+1 stand; the speed correction feedforward is superimposed on the secondary correction rolling speed of the i-th+1 stand to obtain the cascaded correction rolling speed of the i-th+1 stand; the speed correction feedforward is transmitted sequentially in the direction of increasing stand number, and the speed correction feedforward of each stand comes from the speed change of its predecessor stand, until the speed cascade correction of all stands of the finishing mill is completed. This cascaded correction can pre-coordinate the speed matching between upstream and downstream stands, reducing the adverse effects on the strip tension between adjacent stands caused by the speed adjustment of this stand.

[0013] In the first correction process, the cascade transfer coefficient is dynamically adjusted based on the strip width and thickness. Specifically, this involves: obtaining the strip width and entry thickness values; calculating the strip's cross-sectional area based on these values; determining a baseline value for the cascade transfer coefficient based on the cross-sectional area and the strip's yield strength; increasing the baseline value when the cross-sectional area increases and decreasing it when the yield strength increases; and multiplying the baseline value by a weighting factor related to the frame number to obtain the cascade transfer coefficient for each frame, with the weighting factor of the preceding frame being greater than that of the following frame. This allows for automatic adjustment of the speed cascade compensation strength based on the strip's stiffness and specifications, making the cascade control more adaptable to different products.

[0014] Before making a second correction to the first-corrected rolling speed, the rolling speed dynamic adjustment amount is also limited. Specifically, the rated speed and current load rate of the main motor of the finishing mill are obtained, and the maximum allowable speed adjustment range for each stand is calculated based on the rated speed and current load rate. The calculated rolling speed dynamic adjustment amount is compared with the maximum allowable speed adjustment range. When the absolute value of the rolling speed dynamic adjustment amount exceeds the maximum allowable speed adjustment range, the rolling speed dynamic adjustment amount is limited to the maximum allowable speed adjustment range. The sign of the limited rolling speed dynamic adjustment amount is inverted and added to the speed adjustment reserve of the adjacent stand, and the adjacent stand undertakes the speed adjustment task exceeding the limit. This limiting and redistribution mechanism, under the premise of meeting the motor drive capability and process constraints, maximizes the achievement of the final rolling temperature target by having adjacent stands collaboratively share the adjustment task, avoiding control lag or inadequate adjustment caused by insufficient capacity of a single stand.

[0015] The technical effects and advantages provided by the present invention in the above technical solution are as follows: The actual rolling speed is first corrected based on the deviation between the actual rolling force and the preset rolling force value. When the actual rolling force exceeds the preset value, the rolling speed is actively reduced; when the actual rolling force is below the preset value, the rolling speed is increased. This correction directly applies to each stand during the strip threading stage, completing speed intervention based on load changes before the strip reaches the exit temperature measurement point. This timely suppresses deformation heat changes caused by rolling force fluctuations and avoids further accumulation of the initial deviation in the final rolling temperature. The speed correction step size is determined by the absolute value of the deviation and the strip width, ensuring that different strip specifications receive matched adjustment ranges to prevent over-adjustment from causing rolling instability. A triggering mechanism with a dead zone threshold is employed, initiating correction only when the rolling force deviation exceeds a reasonable range, reducing unnecessary speed fluctuations from interfering with the rolling rhythm. The first-corrected rolling speed is used in the calculation of the inter-stand heat loss compensation value. Based on this speed, the actual running time between adjacent stands is obtained, and then combined with the specific heat capacity of the strip to obtain the baseline value of natural heat loss. At the same time, the deformation heat added value is determined based on the instantaneous deformation resistance of the strip and superimposed on the baseline value of natural heat loss. The actual spray density of cooling water between stands is also introduced to correct the total heat loss, forming a comprehensive heat loss compensation value that includes the effects of speed, deformation heat, and cooling intensity. This compensation value is used to correct the preset value of the final rolling temperature, so that the temperature target value can follow the changes in heat dissipation conditions during strip threading in real time. Based on the difference between the compensated final rolling temperature target value and the actual final rolling temperature of the exit strip, the dynamic adjustment amount of the rolling speed of each stand is calculated and a second correction is performed. Since the target value has fully compensated for the heat loss, and the speed adjustment coefficient is distributed according to the stand number, the speed of the preceding stand is mainly adjusted to control the temperature. The response path is consistent with the direction of temperature change propagation, and the lag effect of closed-loop correction is effectively reduced. This method achieves cascaded dynamic control from rolling force to temperature, and then from temperature to speed, reducing the fluctuation range of the final rolling temperature throughout the strip threading process and improving control accuracy. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 This is a flowchart of a dynamic control method for final rolling temperature during the finishing rolling strip threading process; Figure 2 This is a flowchart for calculating the heat loss compensation value between racks; Figure 3This is a flowchart of the final rolling temperature control based on inter-stand heat loss compensation and segmented integral speed regulation; Figure 4 It is the curve showing the change between the actual rolling speed and the first-stage corrected rolling speed; Figure 5 It is the dynamic change curve of the heat loss compensation value between racks; Figure 6 It is a curve comparing the target value of the compensated final rolling temperature with the actual final rolling temperature of the exit strip. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] See Figure 1 This invention provides a method for dynamic control of the final rolling temperature during the strip threading process in finishing mills, comprising: acquiring the entry and exit strip thicknesses of the finishing mill; calculating the strip threading reduction rate of the finishing mill stand based on the entry and exit strip thicknesses; determining a preset rolling force value for each stand during the strip threading process based on the strip threading reduction rate and a preset initial rolling speed value; after the strip head enters the finishing mill, collecting the actual rolling force and actual rolling speed of each stand in real time; and performing a first correction on the actual rolling speed based on the deviation between the actual rolling force and the preset rolling force value to obtain a first correction. The rolling speed is corrected; based on the first corrected rolling speed and the instantaneous deformation resistance of the strip, the inter-stand heat loss compensation value is used to compensate the preset value of the final rolling temperature, thus obtaining the compensated target value of the final rolling temperature; based on the difference between the compensated target value of the final rolling temperature and the actual final rolling temperature of the exit strip, the rolling speed dynamic adjustment amount for each stand is calculated, and the first corrected rolling speed is corrected a second time based on the rolling speed dynamic adjustment amount, thus obtaining the second corrected rolling speed, which is then sent to the drive control system of the corresponding stand.

[0020] Example 1: In practice, the preset rolling force value for each stand during the threading process is determined based on the threading reduction rate and the preset initial rolling speed value, which is achieved through the following steps.

[0021] Obtain the inlet strip temperature and the target outlet strip temperature of the finishing mill. Calculate the total temperature drop during the strip threading process based on the inlet strip temperature and the target outlet strip temperature. The total temperature drop is the difference between the inlet strip temperature and the target outlet strip temperature.

[0022] The temperature drop coefficient for each stand is allocated based on the total temperature drop and the strip threading reduction rate. The temperature drop coefficient represents the proportion of the temperature drop during the strip threading process to the total temperature drop for each stand. For the i-th stand of the finishing mill, the temperature drop coefficient is allocated according to the ratio of the strip threading reduction rate of the i-th stand to the sum of the strip threading reduction rates of all stands. After obtaining the allocated temperature drop coefficient for each stand, the average deformation rate of each stand is calculated in conjunction with the preset initial rolling speed value. The average deformation rate is calculated as follows: using the preset initial rolling speed value of the i-th stand, the strip threading reduction rate of the i-th stand, the work roll radius of the i-th stand, and the inlet and outlet thicknesses of the i-th stand, the initial value of the contact arc length of the deformation zone of the i-th stand is obtained through the geometric relationship of the deformation zone. Then, the average deformation rate of the i-th stand is calculated from the initial rolling speed value, inlet thickness, reduction, and the initial value of the contact arc length of the deformation zone.

[0023] The predicted deformation resistance value for each stand is determined based on the average deformation rate and the chemical composition of the strip. The determination of the predicted deformation resistance value relies on a pre-stored deformation resistance prediction model. The model's inputs include the carbon, manganese, and silicon content in the strip's chemical composition, the average deformation rate, and the deformation temperature of the i-th stand, calculated from the temperature drop coefficient and the inlet strip temperature. The deformation resistance prediction model outputs the predicted deformation resistance value for the i-th stand.

[0024] The predicted deformation resistance value is substituted into the rolling force formula to calculate the preset rolling force value for each stand. The rolling force formula adopts the Sims formula, and the elastic flattening effect of the rolls is considered in the calculation process. The rolling force formula used is:

[0025] in, This represents the preset rolling force value for the i-th stand. Indicates the width of the strip. This represents the contact arc length of the deformation zone of the i-th frame after considering the elastic flattening effect of the rolls. This represents the stress state coefficient of the i-th frame. This represents the predicted deformation resistance value of the i-th frame.

[0026] In determining In the process, firstly, the initial deformation zone contact arc length, without considering elastic flattening, is calculated based on the geometric relationship using the work roll radius of the i-th stand and the reduction amount of the i-th stand. Then, the elastic flattening amount of the roll is calculated using the Hitchcock formula. The initial deformation zone contact arc length is then superimposed with the elastic flattening amount to obtain the first corrected deformation zone contact arc length. The corrected deformation zone contact arc length is then substituted back into the Hitchcock formula for iteration until the deformation zone contact arc length meets the convergence condition. The deformation zone contact arc length obtained at this point is the deformation zone contact arc length considering the elastic flattening effect of the roll. Stress state coefficient According to Sims theory, the reduction rate of the i-th frame and the shape factor of the deformation zone of the i-th frame are used as inputs, and the shape factor is obtained from a pre-stored database of stress state coefficient curves through interpolation. The shape factor of the deformation zone is determined by... Determined by the ratio of the arithmetic mean of the inlet and outlet thicknesses of the i-th frame. Predicted deformation resistance value. Obtained from the deformation resistance prediction model. The width of the strip. The measured strip width is taken at the entrance of the finishing mill. Substituting these values ​​into the Sims formula, the preset rolling force for the i-th stand is calculated.

[0027] Alternatively, the rolling force formula can also be based on the Hill formula. When using the Hill formula, the stress state coefficient... The determination method follows the stress state coefficient calculation method corresponding to the Hill formula. When using the Hill formula, it is also necessary to iteratively calculate the contact arc length of the deformation zone after considering the elastic flattening effect of the roll. The iterative method is consistent with the method described above in this embodiment.

[0028] In some implementations, the deformation resistance prediction model is an empirical model obtained by regression of a large amount of experimental data. The model contains coefficient terms corresponding to the chemical composition of the strip steel, which are automatically retrieved from the material database according to the steel grade code of the strip steel.

[0029] Example 2: In practice, the actual rolling speed is first corrected based on the deviation between the actual rolling force and the preset rolling force value, resulting in a first corrected rolling speed, which is achieved through the following steps.

[0030] The deviation between the actual rolling force and the preset rolling force value is calculated. The actual rolling force is acquired in real time by rolling force sensors installed on each stand. The preset rolling force value is determined by the strip reduction rate and the preset initial rolling speed. The deviation is defined as the difference between the actual rolling force and the preset rolling force value. When the absolute value of the deviation exceeds a preset dead zone threshold, a speed correction program is triggered. The dead zone threshold is set based on the preset rolling force value, taking 5% of the preset rolling force value as the dead zone threshold. When 5% of the preset rolling force value is less than a preset minimum dead zone limit, the dead zone threshold is taken as the preset minimum dead zone limit. The preset minimum dead zone limit is determined based on the measurement accuracy and noise level of the rolling force sensor.

[0031] The direction of speed correction is determined by the sign of the deviation. When the actual rolling force is greater than the preset rolling force value, the deviation is positive, and the speed correction direction is to decrease the rolling speed. When the actual rolling force is less than the preset rolling force value, the deviation is negative, and the speed correction direction is to increase the rolling speed.

[0032] The speed correction step size is determined based on the absolute value of the deviation and the strip width. The speed correction step size is calculated as follows: divide the absolute value of the deviation by the strip width to obtain the rolling force deviation per unit width; then multiply the rolling force deviation per unit width by the speed correction coefficient to obtain the speed correction step size. The formula for calculating the speed correction step size is:

[0033] in, This represents the speed correction step size for the i-th rack. represents the actual rolling force of the i-th stand, and represents the preset rolling force value of the i-th stand. Indicates the width of the strip. This represents the speed correction factor for the i-th rack.

[0034] strip width The width is measured in real time by a width measuring instrument at the entrance of the finishing mill. Speed ​​correction coefficient. The speed correction coefficient is obtained by linear interpolation from a preset speed correction coefficient table based on the force value interval where the preset rolling force value of the i-th stand falls. The preset speed correction coefficient table stores multiple force value interval endpoints and the corresponding speed correction coefficient value for each interval endpoint. The endpoints of the force value intervals in the speed correction coefficient table are set based on the design range of the rolling force for each stand of the finishing mill. The design range is divided into ten force value intervals according to an equal division principle. The difference between the endpoints of adjacent force value intervals is one-tenth of the difference between the upper and lower limits of the rolling force design range. The speed correction coefficient value corresponding to each force value interval endpoint is determined through on-site calibration tests. The calibration test conditions are: under the same steel grade and specifications, recording the rolling force variation data at different rolling speeds; the ratio of the rolling force variation to the speed correction value is used as the speed correction coefficient value for the stress value interval endpoint.

[0035] The speed correction step size is superimposed on the actual rolling speed to obtain the first corrected rolling speed. The superposition method is determined according to the speed correction direction: when the speed correction direction is to decrease the rolling speed, the first corrected rolling speed is equal to the actual rolling speed minus the speed correction step size; when the speed correction direction is to increase the rolling speed, the first corrected rolling speed is equal to the actual rolling speed plus the speed correction step size.

[0036] In some implementations, when the primary correction rolling speed exceeds the speed limit range of the i-th stand drive control system, the primary correction rolling speed is limited to either the upper or lower limit of the speed limit range. The upper limit of the speed limit range is the rolling line speed corresponding to the highest speed of the i-th stand main motor, and the lower limit is the rolling line speed corresponding to the lowest stable operating speed of the i-th stand main motor. The highest and lowest stable operating speeds of the i-th stand main motor are read from the parameter table of the drive control system.

[0037] Optionally, the dead zone threshold can also be set as 3% of the preset rolling force value. When 3% of the preset rolling force value is less than the preset minimum dead zone limit, the dead zone threshold is taken as the preset minimum dead zone limit. The preset minimum dead zone limit is a fixed value calculated based on the range and accuracy class of the rolling force sensor.

[0038] See Figure 4 In the graph, the horizontal axis represents time, ranging from 0 to 10 seconds, and the vertical axis represents rolling speed, in meters per second, ranging from approximately 4.4 to 5.8 meters per second. The solid curve represents the actual rolling speed, and the dashed curve represents the first-stage correction rolling speed. The two curves generally show a close synchronous fluctuation trend, indicating that the actual rolling speed and the first-stage correction rolling speed are closely tracked during dynamic adjustments.

[0039] The curves show that both the actual rolling speed and the first-correction rolling speed fluctuate between 4.8 and 5.4 meters per second, indicating that after the first correction, the actual rolling speed remains basically within the preset range. Compared to the solid-line actual speed curve, the dashed first-correction speed curve exhibits more frequent and slightly larger fluctuations, reflecting the response characteristics when speed correction is performed based on the deviation between the actual rolling force and the preset rolling force value.

[0040] In several time periods shown in the figure, especially between 1 and 2 seconds, 4 and 5 seconds, and 7 and 9 seconds, the corrected rolling speed exhibited significant peak-to-valley variations. The peak value was generally slightly higher than the actual rolling speed, while the trough value was slightly lower, indicating overshoot and adjustment behavior during the speed correction process. This aligns with the adjustment mechanism described in Example 2, which calculates the speed correction step size based on the rolling force deviation and adds it to the actual speed.

[0041] Overall, the data curves in the figure reflect the dynamic control process described in Example 2, which involves the first correction of the actual rolling speed based on the deviation between the actual rolling force and the preset rolling force value. This verifies the real-time adjustment effect of the method on the rolling speed during the finishing rolling strip threading stage, enabling the actual rolling speed to respond promptly to the rolling force deviation and remain within a reasonable fluctuation range, thereby providing a stable speed basis for the subsequent dynamic control of the final rolling temperature.

[0042] Example 3: In specific implementation, please refer to Figure 2 The compensation for heat loss between the rolling mill and the instantaneous deformation resistance of the strip is achieved through the following steps, based on the computer-compensated value for heat loss between the rolling mill and the instantaneous deformation resistance of the strip.

[0043] The running time of the strip between two adjacent stands is calculated based on the first-correction rolling speed. The running time between two adjacent stands is defined as the time it takes for the strip to travel from the exit of the previous stand to the entrance of the next stand. For the running time between the i-th stand and the i+1 stand, the calculation method is as follows: obtain the stand spacing between the exit side of the i-th stand and the entrance side of the i+1 stand, divide the stand spacing by the first-correction rolling speed of the i-th stand, and obtain the running time between the i-th stand and the i+1 stand. The first-correction rolling speed of the i-th stand is the rolling speed value of the i-th stand obtained after the first correction. The stand spacing is a finishing mill equipment layout parameter, stored in the equipment parameter database of the process control system, and retrieved as a fixed value.

[0044] The baseline value for natural heat loss is calculated based on the running time and the specific heat capacity of the strip. The baseline value for natural heat loss characterizes the temperature drop of the strip between two adjacent stands due to radiation alone. The baseline value for natural heat loss is calculated using the following formula:

[0045] in, This represents the baseline value of natural heat loss between the i-th rack and the i+1-th rack, in degrees Celsius. The emissivity of the strip surface is determined based on the state of the iron oxide scale on the strip surface. For hot-rolled strip, The value is taken between 0.70 and 0.85. When the iron oxide scale on the strip surface is thick, the larger value in the range is taken, and when the iron oxide scale is thin, the smaller value in the range is taken. The specific emissivity value is obtained by interpolation from the preset emissivity table according to the iron oxide scale thickness level. This represents the Stefan-Boltzmann constant. Values The unit is watts per square meter per Kelvin to the power of 4. The temperature of the strip at the exit of the i-th stand is expressed in Kelvin. It is calculated by combining the rolling deformation heat calculation model of the i-th stand with the inlet temperature, or by real-time measurement by a pyrometer installed on the exit side of the i-th stand. This indicates the ambient temperature between the stands, measured in Kelvin, and is acquired in real time by ambient temperature sensors installed on the side of the finishing mill stand. This represents the rack spacing between the exit side of rack i and the entrance side of rack i+1, in meters, and is read from the equipment parameter database. This represents the corrected rolling speed of the i-th stand, expressed in meters per second. The thickness of the strip at the exit of the i-th frame is represented in meters and is calculated from the bounce equation of the i-th frame. This indicates the density of the strip steel, expressed in kilograms per cubic meter. The corresponding density value is retrieved from the material density database based on the steel grade code. The specific heat capacity of the strip is expressed in joules per kilogram per kelvin. It is obtained by linear interpolation from the specific heat capacity temperature curve based on the exit temperature of the strip at the i-th stand. The specific heat capacity temperature curve is pre-stored in the material thermophysical property database with the steel grade code as the index.

[0046] The deformation heat surcharge is determined based on the instantaneous deformation resistance of the strip. The deformation heat surcharge characterizes the temperature rise of the strip due to the conversion of plastic work into heat energy during rolling deformation. The deformation heat surcharge is calculated as follows: obtain the instantaneous deformation resistance of the i-th stand, multiply the instantaneous deformation resistance by the deformation heat conversion efficiency factor, and then divide by the product of the strip density and the strip specific heat capacity to obtain the deformation heat surcharge. The deformation heat conversion efficiency factor represents the proportion of plastic deformation work converted into heat. The deformation heat conversion efficiency factor is a constant between 0.90 and 0.95, and is uniformly taken as 0.92 for all stands of the finishing mill.

[0047] The total heat loss value is obtained by superimposing the deformation heat added value onto the natural heat loss baseline value. The superposition method is that the total heat loss value equals the natural heat loss baseline value minus the deformation heat added value. The natural heat loss baseline value is the temperature decrease of the strip due to heat loss by radiation, the deformation heat added value is the temperature increase of the strip due to heat gain by plastic deformation, and the total heat loss value represents the actual temperature change of the strip after comprehensively considering natural heat loss and deformation heat.

[0048] The actual spray density of the cooling water between stands is obtained, and the total heat loss value is corrected based on the actual spray density to obtain the inter-stand heat loss compensation value. The actual spray density of the cooling water between stands is calculated by converting the signals from the flow meter and pressure sensor installed on the cooling water manifold between stands. The calculation method is to divide the total cooling water flow rate by the surface area of ​​the strip being sprayed. The method for correcting the total heat loss value is as follows: multiply the actual spray density of the cooling water between stands by the cooling water heat transfer coefficient, then multiply by the difference between the strip temperature and the cooling water temperature, and divide by the product of the strip density, the specific heat capacity of the strip, the first correction rolling speed of the i-th stand, and the exit strip thickness of the i-th stand to obtain the forced convection temperature drop of the cooling water; add the total heat loss value to the forced convection temperature drop of the cooling water to obtain the inter-stand heat loss compensation value. The inter-stand heat loss compensation value represents the net change in strip temperature between the i-th stand and the i+1 stand after comprehensively considering radiation heat dissipation, deformation heat, and forced cooling by the cooling water. This net change provides a basis for the final rolling temperature compensation.

[0049] The instantaneous deformation resistance is calculated in real time using a deformation resistance model based on the actual strain, strain rate, and deformation temperature of the current frame. The deformation resistance model adopts the Zhou Jihua-Guan Kezhi deformation resistance model structure, and its expression is as follows:

[0050] In the formula, This represents the instantaneous deformation resistance, measured in megapascals (MPA). This represents the baseline deformation resistance, expressed in megapascals (MPa). The value is set to 100 MPa; This indicates the deformation temperature, measured in Kelvin. It is obtained by subtracting the temperature rise in the deformation zone from the current strip temperature at the inlet of the frame; This represents the strain rate, measured in seconds. Determined based on the current average deformation rate calculation formula of the rack; Indicates actual strain. The thickness is calculated using the logarithmic strain formula based on the current inlet and outlet thicknesses of the frame. to These are the model coefficients. to The values ​​are retrieved from the model coefficient database based on the steel grade code. The model coefficient database stores the coefficient values ​​for each steel grade obtained through regression analysis of experimental data. (Base deformation resistance) The value is set to 100 MPa, which serves as the benchmark reference value for the deformation resistance of steel under reference deformation conditions. The deformation resistance model operates as a function module in the process control system, updating the instantaneous deformation resistance value once per control cycle based on the collected actual strain, strain rate, and deformation temperature.

[0051] See Figure 5 In the figure, the horizontal axis represents time in seconds, and the vertical axis represents the heat loss compensation value between racks in degrees Celsius. The figure shows the variation curves of heat loss compensation values ​​between four adjacent racks: racks 1-2, racks 2-3, racks 3-4, and racks 4-5, represented by solid lines, dashed lines, dotted lines, and dotted lines, respectively.

[0052] Observing the curve trends, during the 8-second strip threading process, the heat loss compensation values ​​between the four sets of stands all exhibited fluctuations, reflecting the impact of dynamic changes in parameters such as the inter-stand cooling water spray density, the instantaneous deformation resistance of the strip, and the first-stage correction rolling speed on the heat loss compensation values. The heat loss compensation values ​​between stands 1 and 2 generally remained in the range of approximately 180℃ to 210℃, with the highest amplitude and the most drastic fluctuations, indicating that the heat loss compensation between these stands was significantly affected by various factors. The compensation values ​​between stands 2 and 3 were mostly distributed in the range of 160℃ to 190℃, which were lower than those between stands 1 and 2 and had slightly smaller fluctuations. The compensation values ​​between stands 3 and 4 were concentrated in the range of 150℃ to 170℃, with further reduced fluctuations. The compensation values ​​between stands 4 and 5 were the lowest among the four groups, concentrated in the range of 130℃ to 160℃, and the fluctuation trend was stable.

[0053] The progressively decreasing compensation values ​​described above conform to the calculation logic for heat loss compensation between stands in Example 3, reflecting the net temperature change of the strip steel under the combined effects of multiple factors such as radiative heat dissipation, additional deformation heat, and forced convection of cooling water between continuous stands. The dynamic fluctuations in the heat dissipation compensation values ​​demonstrate that the real-time collected data on the strip steel's primary correction rolling speed and instantaneous deformation resistance are effectively coupled with the cooling water spray state, ensuring the accuracy and timeliness of the compensation calculation.

[0054] The data in this figure is a real-time change curve of the inter-stand heat loss compensation value in Example 3. It reflects the process of dynamic computer inter-stand heat loss compensation value based on the rolling speed and the instantaneous deformation resistance of the strip. It verifies the effective operation and real-time adjustment capability of the heat loss compensation module in the dynamic control method of the present invention.

[0055] Example 4: In specific implementation, please refer to Figure 3The final rolling temperature preset value is compensated based on the heat loss compensation value between stands to obtain the compensated final rolling temperature target value, which is achieved through the following steps.

[0056] The measured temperature of the strip at the inlet of the finishing mill is obtained. Based on the measured temperature of the strip at the inlet and the rolling deformation heat of each stand, the predicted exit temperature of each stand is calculated. The measured temperature of the strip at the inlet is obtained in real time by a temperature measuring instrument installed on the inlet side of the finishing mill. The measured temperature value of the strip at the inlet collected by the temperature measuring instrument is updated once in each control cycle. The rolling deformation heat of each stand is the heat generated by plastic deformation of the strip during the rolling process of the corresponding stand. The rolling deformation heat is calculated as follows: the predicted value of the deformation resistance of the i-th stand and the actual strain of the i-th stand are obtained. The predicted value of the deformation resistance is multiplied by the actual strain and then multiplied by the deformation heat conversion efficiency factor to obtain the rolling deformation heat of the i-th stand. The actual strain of the i-th stand is calculated according to the logarithmic strain formula based on the inlet thickness and outlet thickness of the i-th stand. The deformation heat conversion efficiency factor represents the proportion of plastic deformation work converted into heat, and the deformation heat conversion efficiency factor is set to 0.92. The base value for the predicted outlet temperature of the i-th stand is obtained by adding the temperature rise corresponding to the rolling deformation heat to the inlet temperature of the i-th stand. The temperature rise corresponding to the rolling deformation heat is equal to the rolling deformation heat of the i-th stand divided by the product of the strip density and the strip specific heat capacity. The strip density of the i-th stand is retrieved from the material density database based on the steel grade code, and the strip specific heat capacity of the i-th stand is obtained by linear interpolation from the specific heat capacity temperature curve based on the deformation temperature of the i-th stand.

[0057] The predicted exit temperature of each stand is passed sequentially along the rolling direction. The predicted exit temperature of the final finishing stand is calculated iteratively by equating the inlet temperature of the next stand with the exit temperature of the previous stand minus the inter-stand heat loss compensation value. For the first stand of the finishing mill, the inlet temperature is taken as the measured temperature of the inlet strip; the predicted exit temperature of the first stand is calculated by adding the temperature rise corresponding to the rolling deformation heat of the first stand to the measured temperature of the inlet strip. For the second stand, the inlet temperature is equal to the predicted exit temperature of the first stand minus the inter-stand heat loss compensation value between the first and second stands; the predicted exit temperature of the second stand is calculated by adding the temperature rise corresponding to the rolling deformation heat of the second stand to the inlet temperature of the second stand. Following the same transfer method, the predicted inlet and exit temperatures of the third stand to the final finishing stand are calculated sequentially. The inter-stand heat loss compensation value is calculated by adjusting the rolling speed and the instantaneous deformation resistance of the strip.

[0058] The difference between the target exit temperature of the strip and the predicted exit temperature of the final stand in the finishing mill is calculated. This difference is then added to the preset final rolling temperature to obtain the compensated target final rolling temperature. The target exit temperature of the strip is the required final rolling temperature of the finished strip specified in the production order, retrieved from the production management system. The preset final rolling temperature is the target value pre-calculated by the process control system based on the initial process parameters of the strip. The compensated target final rolling temperature is used for subsequent calculations of final rolling temperature deviation and dynamic adjustment of the rolling speed.

[0059] In practice, the rolling speed of each stand is dynamically adjusted based on the difference between the compensated target final rolling temperature and the actual final rolling temperature of the exit strip. This is achieved through the following steps.

[0060] The final rolling temperature deviation is obtained by subtracting the actual final rolling temperature of the strip at the exit from the compensated target final rolling temperature. The actual final rolling temperature of the strip at the exit is measured in real time by a temperature measuring instrument installed on the exit side of the finishing mill stand. The actual final rolling temperature value collected by the temperature measuring instrument is updated once in each control cycle. The final rolling temperature deviation is then input into the proportional-integral controller.

[0061] The output value of the proportional-integral controller is calculated according to the following formula:

[0062] in, Indicates the proportional-integral controller in time The output value is in meters per second. This represents the proportional gain of the proportional-integral controller. The value of is a constant determined based on the speed adjustment sensitivity and final rolling temperature response characteristics of the finishing mill. The value ranges from 0.5 to 2.0, and the specific value is obtained by linear interpolation from the proportional gain parameter table based on the specifications of the strip steel by the process control system. This indicates the final rolling temperature deviation, in degrees Celsius. This represents the integral time constant of the proportional-integral controller, in seconds. The process of threading the straps is divided into segments. This indicates the final rolling temperature deviation value from time zero to time... The integral value.

[0063] The speed adjustment coefficient is determined based on the output value of the proportional-integral (PI) controller and the instantaneous thickness of the strip. The speed adjustment coefficient is the ratio of the PI controller output value to the strip flow rate reference value per second. The strip flow rate reference value is calculated by multiplying the instantaneous thickness of the strip, the strip width, and the actual rolling speed of the exit strip. The instantaneous thickness of the strip is the exit strip thickness of the finishing mill stand, calculated in real-time using the springback equation of the finishing mill stand. The strip width is the measured value of the strip width at the entrance of the finishing mill unit. The actual rolling speed of the exit strip is the actual rolling speed of the finishing mill stand, acquired by a speed sensor installed on the drive control system of the finishing mill stand.

[0064] Speed ​​adjustment coefficients are allocated to the first few stands of the finishing mill. The speed adjustment coefficient allocated to each stand is set in a manner that increases and decreases according to the stand number. The allocation method of the speed adjustment coefficient is as follows: Let the total number of the first few stands participating in speed adjustment of the finishing mill be N, where N is 3. The speed adjustment coefficient allocated to the i-th stand is the speed adjustment coefficient multiplied by the allocation weight of the i-th stand. The allocation weight of the i-th stand decreases according to the stand number from the first stand to the Nth stand, and the sum of the allocation weights is 1. The formula for calculating the allocation weight of the i-th stand is: the allocation weight of the i-th stand is equal to twice the difference between N and i plus one divided by the square of N. When N is 3, the allocation weight of the first stand is 5 / 9, the allocation weight of the second stand is 3 / 9, and the allocation weight of the third stand is 1 / 9.

[0065] The dynamic adjustment amount of the rolling speed for each stand is obtained by multiplying the speed adjustment coefficient assigned to each stand by the base speed adjustment amount. The base speed adjustment amount is taken as one percent of the actual rolling speed of the final finishing stand. When the speed adjustment coefficient assigned to the i-th stand is positive, the dynamic adjustment amount of the rolling speed for the i-th stand is positive, indicating an increase in the rolling speed; when the speed adjustment coefficient assigned to the i-th stand is negative, the dynamic adjustment amount of the rolling speed for the i-th stand is negative, indicating a decrease in the rolling speed.

[0066] In practical implementation, the proportional-integral controller also includes an anti-integral saturation mechanism. When the dynamic adjustment of the rolling speed reaches a limit, the output of the integral term is frozen. The limit is five percent of the rolling line speed corresponding to the rated speed of the main motor of the i-th stand. When the absolute value of the dynamic adjustment of the rolling speed of the i-th stand reaches the limit, the accumulated value of the integral term in the proportional-integral controller remains at its current value and does not increase further until the absolute value of the dynamic adjustment of the rolling speed falls below the limit, at which point the normal accumulation of the integral term resumes.

[0067] In practice, the integral time constant of the proportional-integral controller is set in segments according to the stages of the tape-threading process.

[0068] The strip threading process is divided into a head biting stage and a stable threading stage based on the bite signal as the strip head reaches the finishing mill's final stand. The bite signal is identified by a metal detector installed at the entrance side of the finishing mill's final stand or by the sudden change in rolling force signal from the finishing mill's final stand's rolling force sensor. The head biting stage is defined as a duration of 0.5 seconds following the triggering of the bite signal. The stable threading stage is defined as the period from the end of the head biting stage until the strip head reaches the underground coiler.

[0069] During the head-biting stage, the integral time constant of the proportional-integral controller (PIC) is set to a first integral time constant value of 0.3 seconds. This value is chosen because a rapid response to final rolling temperature deviations is required during the head-biting stage, and a shorter integral time allows the PIC to quickly eliminate these deviations. During the stabilization threading stage, the integral time constant of the PIC is set to a second integral time constant value of 1.0 second. This value is chosen to avoid excessive adjustment and oscillation of the rolling speed due to excessive integral action during the stabilization threading stage, and a longer integral time is used to smooth out short-term fluctuations. The second integral time constant value is greater than the first integral time constant value.

[0070] When the absolute value of the final rolling temperature deviation is detected to be less than a preset stability threshold and the duration exceeds a preset time window, the integral time constant of the proportional-integral controller is switched back to the first integral time constant value. The preset stability threshold is 5 degrees Celsius, which is based on the allowable deviation range defined in the accuracy requirements for final rolling temperature control of the finishing mill. The preset time window is 3 seconds, which is based on the need for delayed judgment to avoid erroneous switching due to instantaneous disturbances. The absolute value detection of the final rolling temperature deviation is performed by the process control system once in each control cycle. When the absolute value of the final rolling temperature deviation is less than 5 degrees Celsius for several consecutive control cycles and the duration of the corresponding cycle exceeds 3 seconds, the integral time constant switching operation is performed.

[0071] See Figure 6 In the graph, the horizontal axis represents time in seconds, and the vertical axis represents temperature in degrees Celsius. The solid line represents the compensated target final rolling temperature, and the dashed line represents the actual final rolling temperature of the strip at the exit. Starting from 0 seconds, the actual final rolling temperature rapidly rises from its initial fluctuating state and stabilizes at a level close to the compensated target final rolling temperature within approximately 1 second. The compensated target final rolling temperature remains essentially constant throughout the entire time interval, stabilizing at around 870℃, demonstrating the dynamic adjustment effect of the preset final rolling temperature based on the compensation value for heat loss between stands.

[0072] The actual final rolling temperature fluctuated significantly within a period of approximately 0 to 1 second, ranging from roughly 835°C to 855°C, reflecting the unstable temperature state of the strip head as it entered the finishing mill. Subsequently, the actual final rolling temperature rapidly responded to the compensated target value, exhibiting a steep and smooth upward curve, stabilizing after 1 second with a significantly reduced fluctuation amplitude, closely oscillating around the target value. This demonstrates the effective regulation of the final rolling temperature deviation by the proportional-integral controller.

[0073] This figure illustrates how, in Example 4, the rolling speed is dynamically adjusted using a proportional-integral controller based on the difference between the compensated target final rolling temperature and the actual final rolling temperature of the strip at the exit. This adjustment drives the rolling speed regulation to achieve rapid and stable control of the final rolling temperature. Especially in the initial stage of strip threading, the control system adjusts quickly, ensuring that the actual final rolling temperature rapidly tracks the compensated target value, avoiding the impact of excessive temperature deviation on product quality. The overall trend shows that the control algorithm effectively suppresses temperature fluctuations, achieving stability and accuracy in dynamic final rolling temperature control.

[0074] Example 5: In practice, after the secondary correction rolling speed is sent to the transmission control system of the corresponding stand, the rolling speed of adjacent stands is also cascadedly corrected.

[0075] Obtain the speed change between the second-correction rolling speed of the i-th stand and the first-correction rolling speed of the i-th stand. The first-correction rolling speed of the i-th stand is defined as the effective rolling speed setpoint of the i-th stand most recently calculated before this second correction. The speed change equals the second-correction rolling speed of the i-th stand minus the first-correction rolling speed of the i-th stand. Multiply the speed change by the cascade transfer coefficient to obtain the speed correction feedforward for the i+1 stand. The speed correction feedforward is calculated as follows:

[0076] in, This represents the speed correction feedforward for the i-th frame plus one, in meters per second. This represents the cascade transfer coefficient from rack i to rack i+1, and is dimensionless. This represents the second-correction rolling speed of the i-th stand, in meters per second; This indicates the previous correction rolling speed of the i-th stand, in meters per second.

[0077] The speed correction feedforward is superimposed on the secondary correction rolling speed of the i-th stand to obtain the cascaded correction rolling speed of the i-th stand. The superposition method is that the cascaded correction rolling speed of the i-th stand equals the secondary correction rolling speed of the i-th stand plus the speed correction feedforward. When the speed correction feedforward is positive, the rolling speed of the i-th stand increases; when the speed correction feedforward is negative, the rolling speed of the i-th stand decreases.

[0078] The speed correction feedforward is passed sequentially in ascending order of stand number. The speed correction feedforward for each stand originates from the speed change of the previous stand, until the speed cascade correction for all stands in the finishing mill is completed. For the i+1 stand, after completing the cascade correction, the speed change between the cascade correction rolling speed of the i+1 stand and the previous correction rolling speed of the i+1 stand is multiplied by the cascade transfer coefficient to obtain the speed correction feedforward for the i+2 stand, and this feedforward is then passed sequentially to the next stand.

[0079] In practice, during the first correction of the actual rolling speed based on the deviation between the actual rolling force and the preset rolling force, the cascade transfer coefficient is dynamically adjusted according to the width and thickness of the strip.

[0080] The strip width and entry thickness are obtained, and the cross-sectional area of ​​the strip is calculated based on these values. The strip width is measured in real-time by a width gauge at the entrance of the finishing mill. The strip entry thickness is the incoming strip thickness measured at the entrance of the finishing mill, which is indirectly calculated by subtracting the reduction amount of the roughing mill from the slab thickness data at the furnace exit using a thickness gauge installed on the entrance side of the finishing mill. The cross-sectional area of ​​the strip is equal to the strip width multiplied by the strip entry thickness.

[0081] The baseline value of the cascade transfer coefficient is determined based on the cross-sectional area and the yield strength of the strip. The yield strength of the strip is retrieved from a material mechanical property database based on the steel grade code. This database stores reference values ​​for the yield strength of each steel grade under the strip-threading temperature condition. The baseline value of the cascade transfer coefficient increases when the cross-sectional area increases and decreases when the yield strength increases. The baseline value of the cascade transfer coefficient is determined according to the following relationship: it is directly proportional to the cross-sectional area and inversely proportional to the yield strength. Specifically, the baseline value of the cascade transfer coefficient is equal to the cross-sectional area multiplied by a scaling factor and then divided by the yield strength. The scaling factor is a pre-calibrated constant, with a value of 0.015, expressed in units of per square millimeter per megapascal. This value is determined by reverse calculation based on the constraint that the baseline value of the cascade transfer coefficient remains between 0.3 and 0.7 under typical strip specifications and steel grades.

[0082] The cascading transfer coefficient for each rack is obtained by multiplying the baseline value by the weighting factor associated with the rack number. The weighting factors are a pre-defined sequence of constants based on the rack number, with the weighting factor of the preceding rack being greater than that of the following rack. For a cascading transfer from rack i to rack i+1, the weighting factors... The weighting factor is extracted from the weighting factor sequence according to the i-th stand number. The length of the weighting factor sequence is one less than the total number of stands in the finishing mill. The value of each element in the weighting factor sequence decreases monotonically in the direction of increasing stand number, and the decrease is linear. The first element of the weighting factor sequence has a value of 1.0, and the last element has a value of 0.2. The cascade transfer coefficient corresponding to the i-th stand is equal to the base value of the cascade transfer coefficient multiplied by the weighting factor of the i-th stand. .

[0083] In practice, before making a second correction to the first-correction rolling speed based on the dynamic adjustment amount of the rolling speed, the process also includes limiting the dynamic adjustment amount of the rolling speed.

[0084] The rated speed and current load rate of the main motor of the finishing mill are obtained. Based on these parameters, the maximum allowable speed adjustment range for each stand is calculated. The rated speed of the main motor is read from the motor parameter table of the transmission control system, in revolutions per minute (rpm). The current load rate is the ratio of the main motor output torque to the rated torque at the current moment, calculated and provided in real time by the transmission control system. The rated speed of the main motor is converted to the rated rolling line speed by multiplying the rated speed by the reduction ratio, then by the work roll radius, and finally dividing by sixty. The maximum allowable speed adjustment range is equal to the rated rolling line speed multiplied by the absolute value of the difference between the rated speed and the current load rate, then multiplied by the speed margin coefficient. The speed margin coefficient is set to 0.15, which is based on reserving a 15% speed control margin for the main motor under rated operating conditions to meet transient speed control requirements.

[0085] The calculated dynamic adjustment amount of the rolling speed is compared with the maximum allowable speed adjustment range. When the absolute value of the dynamic adjustment amount is less than or equal to the maximum allowable speed adjustment range, no limiting is applied to the dynamic adjustment amount. When the absolute value of the dynamic adjustment amount exceeds the maximum allowable speed adjustment range, the dynamic adjustment amount is limited to the maximum allowable speed adjustment range. The limiting method is as follows: if the dynamic adjustment amount is positive and exceeds the maximum allowable speed adjustment range, the dynamic adjustment amount is set to the maximum allowable speed adjustment range; if the dynamic adjustment amount is negative and its absolute value exceeds the maximum allowable speed adjustment range, the dynamic adjustment amount is set to the negative maximum allowable speed adjustment range.

[0086] The sign of the dynamic adjustment amount of the rolling speed after the limit is inverted and then added to the speed adjustment reserve of the adjacent stand. The adjacent stand then undertakes the speed adjustment task for the portion exceeding the limit. The portion exceeding the limit is defined as the difference between the original dynamic adjustment amount of the rolling speed and the dynamic adjustment amount of the rolling speed after the limit. The inversion operation means that when the portion exceeding the limit is positive, the speed adjustment reserve added to the adjacent stand is negative; when the portion exceeding the limit is negative, the speed adjustment reserve added to the adjacent stand is positive. The adjacent stand is defined as the downstream stand immediately adjacent to the current stand. The speed adjustment reserve is the cumulative amount of speed adjustment to be processed that each stand reserves in advance in each control cycle, with an initial value of zero. In each control cycle, after a stand adds the portion exceeding the limit to the speed adjustment reserve of the adjacent stand, when the adjacent stand calculates its own rolling speed dynamic adjustment amount, it algebraically sums the speed adjustment reserve amount with the dynamic adjustment amount of the rolling speed calculated by the current stand, and uses this sum as the new dynamic adjustment amount of the rolling speed of the adjacent stand for the second correction. After summing, the speed adjustment allowance for adjacent racks is reset to zero.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for dynamic control of final rolling temperature during the finishing rolling strip threading process, characterized in that, include: Obtain the inlet strip thickness and outlet strip thickness of the finishing mill, and calculate the strip reduction rate of the finishing mill stand based on the inlet strip thickness and the outlet strip thickness; The preset rolling force value for each stand during the threading process is determined based on the threading reduction rate and the preset initial rolling speed value. After the strip head enters the finishing mill, the actual rolling force and actual rolling speed of each stand are collected in real time. The actual rolling speed is corrected for the first time based on the deviation between the actual rolling force and the preset rolling force value, and a corrected rolling speed is obtained. Based on the first-time corrected rolling speed and the instantaneous deformation resistance of the strip, the inter-stand heat loss compensation value is used to compensate the preset value of the final rolling temperature, thereby obtaining the compensated target value of the final rolling temperature. Based on the difference between the compensated final rolling temperature target value and the actual final rolling temperature of the exit strip, the rolling speed dynamic adjustment amount for each stand is calculated. The first-corrected rolling speed is then corrected a second time based on the rolling speed dynamic adjustment amount to obtain the second-corrected rolling speed. The second-corrected rolling speed is then sent to the transmission control system of the corresponding stand.

2. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 1, characterized in that, The preset rolling force value for each stand during the threading process is determined based on the threading reduction rate and the preset initial rolling speed value, specifically as follows: Obtain the inlet strip temperature and the target outlet strip temperature of the finishing mill, and calculate the total temperature drop during the strip threading process based on the inlet strip temperature and the target outlet strip temperature; The temperature drop coefficient of each stand is allocated according to the total temperature drop and the strip reduction rate, and the average deformation rate of each stand is calculated according to the temperature drop coefficient and the preset initial value of rolling speed. The predicted deformation resistance value for each stand is determined based on the average deformation rate and the chemical composition of the strip. The predicted deformation resistance value is then substituted into the rolling force formula to calculate the preset rolling force value for each stand.

3. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 2, characterized in that, The rolling force formula is either the Hill formula or the Sims formula, and the elastic flattening effect of the rolls is taken into account during the calculation.

4. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 1, characterized in that, The actual rolling speed is first corrected based on the deviation between the actual rolling force and the preset rolling force value, resulting in a first corrected rolling speed, specifically: Calculate the deviation between the actual rolling force and the preset rolling force value. When the deviation exceeds the preset dead zone threshold, trigger the speed correction program. The speed correction direction is determined based on the sign of the deviation. When the actual rolling force is greater than the preset rolling force value, the speed correction direction is to reduce the rolling speed. When the actual rolling force is less than the preset rolling force value, the speed correction direction is to increase the rolling speed. The speed correction step size is determined based on the absolute value of the deviation and the width of the strip. The speed correction step size is then superimposed with the actual rolling speed to obtain the first corrected rolling speed.

5. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 1, characterized in that, Based on the aforementioned corrected rolling speed and the computer-compensated inter-row heat loss value for the instantaneous deformation resistance of the strip, specifically: The running time of the strip between two adjacent stands is calculated based on the first modified rolling speed, and the reference value of natural heat loss is calculated based on the running time and the specific heat capacity of the strip. The deformation heat added value is determined based on the instantaneous deformation resistance of the strip, and the deformation heat added value is superimposed on the natural heat loss benchmark value to obtain the total heat loss value. The actual spray density of cooling water between racks is obtained, and the total heat loss value is corrected based on the actual spray density to obtain the heat loss compensation value between racks.

6. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 5, characterized in that, The instantaneous deformation resistance is calculated in real time based on the actual strain, strain rate and deformation temperature of the current frame through the deformation resistance model.

7. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 1, characterized in that, The preset value of the final rolling temperature is compensated based on the heat loss compensation value between stands to obtain the compensated target value of the final rolling temperature, specifically: Obtain the measured temperature of the inlet strip of the finishing mill, and calculate the predicted temperature of the outlet of each stand based on the measured temperature of the inlet strip and the rolling deformation heat of each stand. The predicted exit temperature of each stand is passed sequentially in the rolling direction. The predicted exit temperature of the finishing mill stand is calculated iteratively by taking the inlet temperature of the next stand as equal to the exit temperature of the previous stand minus the heat loss compensation value between the stands. Calculate the difference between the target temperature of the exit strip and the predicted temperature of the exit of the finishing mill stand, and add the difference to the preset value of the final rolling temperature to obtain the compensated target value of the final rolling temperature.

8. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 1, characterized in that, Based on the difference between the compensated target final rolling temperature and the actual final rolling temperature of the exit strip, the dynamic adjustment of the rolling speed for each stand is calculated, specifically as follows: Subtract the actual final rolling temperature of the exit strip from the compensated final rolling temperature target value to obtain the final rolling temperature deviation value, and input the final rolling temperature deviation value into the proportional-integral controller. The speed adjustment coefficient is determined based on the output value of the proportional-integral controller and the instantaneous thickness of the strip. The speed adjustment coefficient is then allocated to the first few stands of the finishing mill. The speed adjustment coefficient allocated to each stand is set in a manner that increases and decreases according to the stand number. Multiply the speed adjustment coefficient assigned to each stand by the base speed adjustment amount to obtain the dynamic adjustment amount of the rolling speed corresponding to each stand.

9. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 8, characterized in that, The proportional-integral controller is also equipped with an anti-integral saturation mechanism, which freezes the output of the integral term when the dynamic adjustment of the rolling speed reaches the limit value.

10. The method for dynamic control of final rolling temperature during the finishing rolling process according to claim 8, characterized in that, Based on the difference between the compensated target final rolling temperature and the actual final rolling temperature of the exit strip, the dynamic adjustment of the rolling speed for each stand is calculated. The integral time constant of the proportional-integral controller is set in segments according to the stages of the strip threading process, specifically as follows: The bite signal of the strip head reaching the finishing mill stand is detected, and the strip threading process is divided into the head bite stage and the stable threading stage based on the bite signal. During the head-biting steel stage, the integral time constant of the proportional-integral controller is set to a first integral time constant value. During the stable belt-threading stage, the integral time constant of the proportional-integral controller is set to a second integral time constant value, where the second integral time constant value is greater than the first integral time constant value. When the absolute value of the final rolling temperature deviation is detected to be less than the preset stability threshold and the duration exceeds the preset time window, the integral time constant of the proportional-integral controller is switched back to the first integral time constant value.

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