A control method for correcting rolling mill load in a hot continuous rolling process

Abstract

The application discloses a control method for correcting rolling mill load in a hot continuous rolling process, which calculates a correction rolling mill load reference value in the rolling process according to the predicted rolling forces of two rolling mills in front and back, calculates a rolling force deviation in real time after the two rolling mills bite the steel, sets a correction rolling mill load reference value dead zone, judges a thickness correction mark according to the calculated real-time rolling force deviation, sets a thickness correction speed, corrects an exit thickness lock value of a previous rack in real time according to the thickness correction mark, sets a correction previous rack thickness lock value amplitude limit, and clears the correction previous rack exit thickness lock value after the previous rack throws the steel. The control method is simple and easy to implement, is favorable to optimizing the rolling force intersection problem of the rolling mill in the roll gap adjustment process caused by the changes of the strip temperature, the rolling mill stiffness, the rolling piece plasticity, the second flow and other factors, and has a positive significance for improving the strip thickness quality, improving the roll wear and prolonging the service life of the rolling mill.

Description

Technical Field

[0001] This invention relates to the field of metallurgical automation control technology, and in particular to a control method for correcting mill load during hot continuous rolling. Background Technology

[0002] In the field of metal rolling, the initial load of a hot strip mill finishing mill is preset by the process control model based on data such as the type and specifications of the rolled steel, and is roughly distributed from large to small according to the gradient. However, due to factors such as the automatic thickness control system of the mill adjusting the mill roll gap according to the target thickness lock value of each stand, as well as factors such as the strip temperature of each stand, the flow rate between stands, the mill stiffness, and the plasticity of the rolled piece, the rolling forces of each stand may overlap or not be adjusted according to the predicted load. Therefore, reasonably adjusting the load distribution of each stand of the finishing mill during the rolling process plays a key role in stabilizing strip rolling and improving strip shape quality, and is of great significance for improving roll wear and increasing the service life of the mill.

[0003] Currently, the common methods for load distribution in rolling mills include the following: The method, device, electronic equipment and medium for load distribution of finishing mill stands proposed in announcement number CN114406015B monitors the measured tension value of the looper during strip threading and corrects the measured tension value based on the preset tension value of the looper, updates the strip rolling parameters of the finishing mill, and redistributes the load of each stand of the finishing mill. This method can make the load distribution of each stand of the finishing mill more reasonable, effectively ensure the smoothness of the finishing mill load distribution, and greatly improve the stability of on-site rolling. The announcement CN108856305B proposes a load distribution method for non-oriented silicon steel production mills. In the process of non-oriented silicon steel production, the original distributed load of the production mill is obtained, and the load of the downstream stand is reduced according to a preset rule. This method improves strip shape and extends the rolling cycle by reducing the load of the downstream stand.

[0004] However, the above methods mainly target load distribution in the finishing rolling process and cannot be fully applied to load correction in the hot strip rolling process. There are currently no other effective control methods for correcting mill load in the hot strip rolling process, especially when the temperature and rolling speed of the strip vary greatly along its entire length. In summary, there is currently a lack of strategies for optimizing the uniform distribution of mill load during the rolling process in the metal rolling field. A control method for correcting mill load during the rolling process is needed that can effectively correct the mill roll gap adjustment amount by combining automation with the thickness correction of each mill exit, thereby controlling the stability of the strip during the rolling process. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the mill load during hot continuous rolling.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for controlling the load of a rolling mill during hot continuous rolling includes the following steps: S1. Calculate the corrected mill load reference value during the rolling process based on the predicted rolling force of the two mills before and after; S2. After the two rolling mills bite each other, calculate the rolling force deviation in real time; S3. Set the dead zone of the mill load reference value and determine the thickness correction flag based on the calculated real-time rolling force deviation; S31. Set the dead zone of the modified mill load reference value to Dead. St The unit is ton, and the value range is [10, 100]. S32. Based on the modified mill load reference value and the dead zone of the modified mill load reference value obtained during the rolling process, calculate the rolling force reference value for determining the increase of the thickness locking value of the previous stand and the rolling force reference value for determining the decrease of the thickness locking value of the previous stand, respectively. The formula for determining the rolling force reference value for increasing the thickness lock value of the previous stand is as follows: Pri Add This represents the rolling force reference value for determining the thickness locking value added in the previous stand, in tons (tons). St This indicates the corrected mill load reference value during the rolling process, in tons. The formula for determining the rolling force reference value for reducing the thickness lock value of the previous stand is as follows: Pri Sub This represents the rolling force reference value used to determine the thickness lock value of the previous stand, in tons (tons). St This indicates the corrected mill load reference value during the rolling process, in tons. S33. The thickness correction flag is determined by comparing the rolling force reference value for determining the increase of the thickness lock value of the previous stand and the rolling force reference value for determining the decrease of the thickness lock value of the previous stand with the actual rolling force deviation. S4. Set the thickness correction speed, obtain the correction amount of the previous rack exit thickness lock value in real time according to the thickness correction flag, and correct the previous rack exit thickness lock value. S5. Set the limit of the thickness lock value of the previous frame for correction. After the previous frame throws steel, clear the thickness lock value of the previous frame for correction to zero.

[0007] Preferably, the formula for calculating the corrected mill load reference value in step S1 is: Among them, Pri St Pri indicates the correction of the mill load reference value during the rolling process. Fx-1 This indicates the predicted rolling force of the previous stand, single Pri. Fx This indicates the predicted rolling force for the current stand.

[0008] Preferably, the formula for calculating the rolling force deviation in step S2 is: Among them, For dev This indicates the actual rolling force deviation, in tons. Fx-1 This indicates the measured rolling force of the previous stand, in tons. Fx This indicates the actual rolling force of the current stand, measured in tons.

[0009] Preferably, in step S33, if the actual rolling force deviation is greater than the rolling force reference value for determining the thickness lock value of the previous stand, a correction flag for increasing the thickness lock value of the previous stand is generated; if the actual rolling force deviation is less than the rolling force reference value for determining the thickness lock value of the previous stand, a correction flag for decreasing the thickness lock value of the previous stand is generated.

[0010] Preferably, in step S4, the speed S of increasing the thickness lock value of the previous frame is defined. add The unit is mm / s, and the value range is [0.01, 0.1]. The speed S is defined as the rate at which the thickness of the previous frame is reduced to lock at the corrected value. sub The unit is mm / s, and the value range is [0.01, 0.1]. The formula for correcting the thickness lock value at the outlet of the previous frame is: Among them, h cor This indicates the correction amount for the previous frame thickness lock value, in mm, S add This indicates the speed at which the thickness locking value is increased in the previous frame, expressed in mm / s (s). sub This indicates the rate at which the thickness lock value of the previous stand is reduced, in mm / s, and t represents the strip rolling time, in seconds. When the correction flag for increasing the thickness lock value of the previous stand is generated, S... sub If it is 0, then S is 0; otherwise, when the previous frame thickness reduction lock value correction flag is generated, S is 0. add It is 0.

[0011] Preferably, in step S5, the limit h of the previous frame correction thickness locking value is defined. limThe unit is mm, and the value range is [0.2, 2]. When the correction amount of the previous frame thickness lock value is greater than the limit of the previous frame thickness lock value, the previous frame thickness lock value limit remains unchanged. Otherwise, the correction amount of the previous frame thickness lock value is executed. After the previous frame throws steel, the previous frame outlet thickness lock value is cleared to zero.

[0012] The beneficial effects of the method for controlling the load of the rolling mill during hot strip milling as described in this invention are as follows: The control method is simple and easy to implement, which is conducive to optimizing the rolling force crossover problem that occurs during the roll gap adjustment process of the finishing mill due to the changes in strip temperature of each stand, mill rigidity, workpiece plasticity, flow rate and other factors. It also helps to address the uneven adjustment of each stand when the temperature change range is large. This method is beneficial to improving the rolling stability of the finishing mill and has positive significance for improving strip thickness quality, reducing roll wear and extending the service life of the mill. Attached Figure Description

[0013] Figure 1 The execution flowchart of the control method for correcting mill load during hot strip rolling provided by the present invention; Figure 2 A schematic diagram of the load of each stand before correction in the control method for correcting the load of the rolling mill during hot strip rolling provided by the present invention; Figure 3 The control method for correcting mill load during hot strip milling provided by the present invention includes a schematic diagram of the load of each stand after correction. Figure 4 This is a schematic diagram of the load correction amount for each stand in the control method for correcting the mill load during hot continuous rolling provided by the present invention. Detailed Implementation

[0014] 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, and 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.

[0015] like Figure 1-4 As shown, the present invention provides a method for controlling the load of a rolling mill during hot strip rolling, comprising the following steps: S1. Calculate the corrected mill load reference value during the rolling process based on the predicted rolling forces of the two mills before and after. The formula for calculating the corrected mill load reference value is as follows: Among them, PriSt This indicates the corrected mill load reference value during the rolling process, in tons (tons). Fx-1 This indicates the predicted rolling force of the previous stand, in tons. This value is set by the process control model. Fx This indicates the predicted rolling force for the current stand, in tons. This value is set by the process control model. S2. After the steel bites between the two rolling mills, the rolling force deviation is calculated in real time. The formula for calculating the rolling force deviation is as follows: Among them, For dev This indicates the actual rolling force deviation, in tons. Fx-1 This indicates the measured rolling force of the previous stand, in tons. Fx This indicates the actual rolling force of the current stand, in tons. S3. Set the dead zone of the mill load reference value and determine the thickness correction flag based on the calculated real-time rolling force deviation; The dead zone of the modified mill load reference value is set to Dead. St The unit is ton, and this value is given empirically, with a range of [10, 100]. The method of determining the thickness correction flag based on the calculated real-time rolling force deviation includes: Based on the obtained mill load reference value Pri during the rolling process... St and the dead zone of the modified mill load reference value St The rolling force reference values ​​for determining whether the thickness locking value of the previous stand is increased and the rolling force reference values ​​for determining whether the thickness locking value of the previous stand is decreased are calculated respectively. The formula for determining the rolling force benchmark value for increasing the thickness lock value of the previous stand is as follows: Pri Add This represents the rolling force reference value for determining the thickness locking value added in the previous stand, in tons (tons). St This indicates the correction of the mill load reference value during the rolling process, in tons. St This indicates the dead zone of the corrected mill load reference value, in tons. The formula for determining the rolling force reference value for reducing the thickness lock value of the previous stand is as follows: Pri Sub This represents the rolling force reference value used to determine the thickness lock value of the previous stand, in tons (tons). St This indicates the correction of the mill load reference value during the rolling process, in tons. StThis indicates the dead zone of the corrected mill load reference value, in tons. By judging the rolling force reference value of the previous stand increasing the thickness lock value and judging the rolling force reference value of the previous stand decreasing the thickness lock value, respectively, the deviations from the actual rolling force are determined. dev By comparing the values, the thickness correction mark can be determined. If the actual rolling force deviation is... dev The rolling force reference value Pri, which is greater than the thickness locking value of the previous stand, is used to determine the rolling force reference value. Add This will generate a correction flag indicating an increase in the thickness lock value of the previous stand. If the actual rolling force deviation is For dev The rolling force reference value Pri is less than the thickness locking value of the previous stand. Sub Then a correction flag for reducing the thickness lock value of the previous frame will be generated; S4. Set the thickness correction speed, obtain the correction amount of the previous rack exit thickness lock value in real time according to the thickness correction flag, and correct the previous rack exit thickness lock value. The specific thickness correction speed is as follows: Define the speed S of increasing the thickness lock value of the previous rack. add The unit is mm / s. This value is empirically given and ranges from [0.01, 0.1]. The speed S for reducing the thickness lock value of the previous frame is defined as... sub The unit is mm / s, and this value is given empirically, with a range of [0.01, 0.1]. The thickness lock value at the exit of the previous rack is adjusted in real time according to the thickness correction flag. The formula for adjusting the thickness lock value of the previous rack is as follows: Among them, h cor This indicates the correction amount for the previous frame thickness lock value, in mm, S add This indicates the speed at which the thickness locking value is increased in the previous frame, expressed in mm / s (s). sub This indicates the rate at which the thickness lock value of the previous stand is reduced, in mm / s, and t represents the strip rolling time, in seconds. When the correction flag for increasing the thickness lock value of the previous stand is generated, S... sub If it is 0, then S is 0; otherwise, when the previous frame thickness reduction lock value correction flag is generated, S is 0. add =0; S5. Set the limit of the thickness lock value of the previous frame to be corrected. After the steel is thrown from the previous frame, clear the thickness lock value of the previous frame to zero. Define the previous frame correction thickness lock value limit h lim The unit is mm. This value is given empirically and ranges from [0.2, 2].

[0016] The implementation process of the present invention will be described below with reference to embodiments, taking the last stand and the penultimate stand in a conventional hot continuous rolling mill as examples (such as stands F7 and F8 in an eight-stand rolling mill). The specific process is as follows: S1. Calculate the corrected mill load reference value during the rolling process based on the rolling force predicted by the two mills before and after; The formula for calculating the corrected mill load reference value during the rolling process is as follows: The predicted rolling force for the penultimate stand is 1200 tons, and the predicted rolling force for the last stand is 1050 tons. The corrected mill load reference value Pri during the rolling process can be calculated. St It is 150 tons; S2. After the two rolling mills bite each other, calculate the rolling force deviation in real time; The formula for calculating the rolling force deviation is: Monitor the actual rolling force of the second-to-last stand and the last stand from time t1 to t7, and record and calculate the rolling force deviation, as shown in Table 1 below: Table 1 S3. Set the dead zone of the mill load reference value and determine the thickness correction flag based on the calculated real-time rolling force deviation; The setting of the mill load reference value dead zone Dead St Set at 50 tons, the rolling force benchmark value based on the formula for determining the thickness locking value of the previous stand is: The rolling force benchmark value Pri, used to determine the thickness locking value of the previous stand, was calculated. Add It is 200 tons; The formula for determining the rolling force reference value based on the previous stand's reduction in thickness locking value is as follows: The rolling force reference value Pri, which determines the thickness locking value of the previous stand, is calculated. Sub 100 tons; The actual rolling force deviation and the rolling force benchmark value Pri used to determine the thickness lock value added in the previous stand are combined. Add 1. Determine the rolling force reference value Pri for reducing the thickness lock value of the previous stand Sub The following table shows the comparisons: Table 2 Through actual rolling force deviation For devCompared with the rolling force reference value Pri for determining the thickness locking value of the previous stand Add And the rolling force reference value Pri for determining the thickness lock value of the previous stand. Sub The comparison shows that the rolling force deviation is greater than Pri during the time intervals from t1 to t7. Add Therefore, a correction flag is generated for increasing the thickness lock value of the previous rack.

[0017] S4. Set the thickness correction speed and correct the thickness lock value at the exit of the previous rack in real time according to the thickness correction flag; wherein, the speed at which the thickness lock value of the previous rack is increased is S add The value is 0.01 mm / s. The formula for real-time correction of the previous frame's exit thickness lock value based on the thickness correction mark is as follows: Because time intervals from t1 to t7 all involve adding thickness lock value correction flags to the previous rack, S sub If the value is 0, the formula for calculating the actual pre-correction frame exit thickness lock value is as follows: Assuming the time interval t1-t7 is 5 seconds, then the correction amount h for the thickness lock value of the previous frame is... cor It is 0.05mm.

[0018] S5. Set the limit for correcting the thickness lock value of the previous stand. After the previous stand throws steel, clear the thickness lock value of the previous stand to zero. Set the previous frame thickness lock value limit h. lim The value is 0.2mm. If the thickness lock value correction amount h of the previous stand is at a certain moment during the rolling process... cor The limit h is greater than the previous frame thickness locking value. lim If the width is too large, the limit of 0.2mm will remain unchanged; otherwise, the correction amount h will be based on the previous frame thickness locking value. cor Once the steel is ejected from the previous stand, the exit thickness lock value of the previous stand will be reset to zero.

[0019] Specific reference Figure 2-4 The above-described method for controlling the mill load during hot strip rolling can be applied in actual production by adjusting the exit thickness lock value of each stand. A comparison before and after shows that the adjustment amount is significant. This method solves the problem of rolling force crossover during roll gap adjustment caused by changes in strip temperature, mill stiffness, workpiece plasticity, and flow rate, as well as the problem of uneven adjustment amount of each stand when the temperature change range is large. It has positive significance for improving the rolling stability of finishing mills, improving strip thickness quality, reducing roll wear, and extending the service life of mills.

[0020] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the load of a rolling mill during hot continuous rolling, characterized in that, Includes the following steps: S1. Calculate the corrected mill load reference value during the rolling process based on the predicted rolling force of the two mills before and after; S2. After the two rolling mills bite each other, calculate the rolling force deviation in real time; S3. Set the dead zone of the mill load reference value and determine the thickness correction flag based on the calculated real-time rolling force deviation; S31. Set the dead zone of the modified mill load reference value to Dead. St The unit is ton, and the value range is [10, 100]. S32. Based on the modified mill load reference value and the dead zone of the modified mill load reference value obtained during the rolling process, calculate the rolling force reference value for determining the increase of the thickness locking value of the previous stand and the rolling force reference value for determining the decrease of the thickness locking value of the previous stand, respectively. The formula for determining the rolling force reference value for increasing the thickness locking value of the previous stand is as follows: Pri Add This represents the rolling force reference value for determining the thickness locking value added in the previous stand, in tons (tons). St This indicates the corrected mill load reference value during the rolling process, in tons. The formula for determining the rolling force reference value for reducing the thickness lock value of the previous stand is as follows: Pri Sub This represents the rolling force reference value used to determine the thickness lock value of the previous stand, in tons (tons). St This indicates the corrected mill load reference value during the rolling process, in tons. S33. The thickness correction flag is determined by comparing the rolling force reference value for determining the increase of the thickness lock value of the previous stand and the rolling force reference value for determining the decrease of the thickness lock value of the previous stand with the actual rolling force deviation. S4. Set the thickness correction speed, obtain the correction amount of the previous rack exit thickness lock value in real time according to the thickness correction flag, and correct the previous rack exit thickness lock value. S5. Set the limit of the thickness lock value of the previous frame for correction. After the previous frame throws steel, clear the thickness lock value of the previous frame for correction to zero.

2. The method for controlling the load of a rolling mill during hot continuous rolling as described in claim 1, characterized in that, The formula for calculating the corrected mill load reference value in step S1 is as follows: Among them, Pri St Pri indicates the correction of the mill load reference value during the rolling process. Fx-1 This indicates the predicted rolling force of the previous stand, single Pri. Fx This indicates the predicted rolling force for the current stand.

3. The method for controlling the load of a rolling mill during hot continuous rolling as described in claim 1, characterized in that, The formula for calculating the rolling force deviation in step S2 is as follows: Among them, For dev This indicates the actual rolling force deviation, in tons. Fx-1 This indicates the measured rolling force of the previous stand, in tons. Fx This indicates the actual rolling force of the current stand, measured in tons.

4. The method for controlling the load of a rolling mill during hot continuous rolling as described in claim 1, characterized in that: In step S33, if the actual rolling force deviation is greater than the rolling force reference value for determining the thickness lock value of the previous stand, a correction flag for increasing the thickness lock value of the previous stand is generated; if the actual rolling force deviation is less than the rolling force reference value for determining the thickness lock value of the previous stand, a correction flag for decreasing the thickness lock value of the previous stand is generated.

5. The method for controlling the load of a rolling mill during hot continuous rolling as described in claim 1, characterized in that: In step S4, the speed S of increasing the thickness lock value of the previous frame is defined. add The unit is mm / s, and the value range is [0.01, 0.1]. The speed S is defined as the rate at which the thickness of the previous frame is reduced to lock at the corrected value. sub The unit is mm / s, and the value range is [0.01, 0.1]. The formula for correcting the thickness lock value at the exit of the previous frame is as follows: Among them, h cor This indicates the correction amount for the previous frame thickness lock value, in mm, S add This indicates the speed at which the thickness locking value is increased in the previous frame, expressed in mm / s (s). sub This indicates the rate at which the thickness lock value of the previous stand is reduced, in mm / s, and t represents the strip rolling time, in seconds. When the correction flag for increasing the thickness lock value of the previous stand is generated, S... sub If it is 0, then S is 0; otherwise, when the previous frame thickness reduction lock value correction flag is generated, S is 0. add It is 0.

6. The method for controlling the load of a rolling mill during hot continuous rolling as described in claim 1, characterized in that: In step S5, the limit h of the previous frame correction thickness locking value is defined. lim The unit is mm, and the value range is [0.2, 2]. When the correction amount of the previous frame thickness lock value is greater than the limit of the previous frame thickness lock value, the previous frame thickness lock value limit remains unchanged. Otherwise, the correction amount of the previous frame thickness lock value is executed. After the previous frame throws steel, the previous frame outlet thickness lock value is cleared to zero.

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