A dynamic self-adaptive correction control method for tail end of hot continuous rolling finishing mill

Abstract

The present application belongs to the field of automatic control technology in metallurgical industry, a kind of hot continuous rolling finishing tail dynamic self-adapting correction control method, it is applied to the hot continuous rolling finishing unit of multiple continuous rolling stands, the hot continuous rolling finishing unit has tail correction function, rack steel throwing signal acquisition function, rack strip in situ detection function, including function start-stop and function interlock: start-stop by manual start-stop or intelligent start-stop determination logic module;After tail correction function is put into use, the real rolling pressure deviation and real roll gap level deviation of the transmission side and the operation side of each rack of the hot continuous rolling finishing unit are monitored in real time, when the absolute value of the rolling pressure deviation of any one rack is greater than the set pressure deviation value or the absolute value of the roll gap level deviation is greater than the set roll gap level deviation value, automatic correction adjustment is immediately put into by hydraulic AGC system.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology in the metallurgical industry, specifically relating to a dynamic adaptive correction control method for the tail of hot continuous rolling mill finishing. Background Technology

[0002] The hot strip finishing mill consists of multiple continuous rolling stands. The rolling and strip ejection stages at the tail end of the strip are the most unstable conditions in the rolling process. After the strip tail ends out of the constraints of the upstream stands, the tension between the stands decreases rapidly, the looper support torque becomes unbalanced, and factors such as the original camber of the intermediate billet, asymmetrical rolling forces of the stands, uneven wear of the roll system, and uneven temperature distribution can easily lead to quality defects such as strip tail deviation, unilateral tail swing, head and edge curling, and edge tearing. In severe cases, it can cause production accidents such as tail stacking, impact with guide equipment, and roll scratches, significantly increasing the scrap rate and equipment maintenance costs.

[0003] To avoid the above problems, the industry generally uses tail-end correction technology for correction. In the existing technology, tail-end correction of the finishing mill adopts a single feedforward control or a single visual feedback control, which has the problems of poor adaptability to working conditions and weak anti-interference ability, and cannot completely solve the problem of stubborn tail-end deviation and tail-wagging in the finishing mill. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of persistent deviation and tail-wagging at the tail of the finishing mill.

[0005] The technical solution adopted in this invention is: a dynamic adaptive deviation correction control method for the tail end of a hot continuous rolling mill, applied to a multi-stand hot continuous rolling mill, wherein the hot continuous rolling mill has a tail deviation correction function, a stand strip ejection signal acquisition function, and a stand strip in-situ detection function, comprising the following steps: Step 1, Function Start-up and Function Interlock: The logic module is started or stopped manually or intelligently. After the function is started, the tail correction function is put into use. After the tail correction function is put into use, the finishing mill one-key monotonic reset function is automatically put into use. When the finishing mill one-key monotonic reset function is put into use, the rolling pre-leveling state of each mill in the hot continuous rolling finishing mill unit is automatically restored before rolling. Step 2: After the tail correction function is put into use, the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand of the hot continuous rolling mill are monitored in real time. When the absolute value of the rolling pressure deviation of any stand is greater than the set pressure deviation value or the absolute value of the roll gap horizontal deviation is greater than the set roll gap horizontal deviation value, the automatic correction adjustment is immediately put into use through the hydraulic AGC system.

[0006] Manual start and stop are achieved through the tail correction function start and stop button set on the finishing mill control panel; the intelligent start judgment logic module assigns sequential numbers to all stands of the hot strip mill finishing unit along the strip conveying direction, taking the stand corresponding to the first entry of the strip into the hot strip mill finishing unit as the first stand, and collects the strip throwing signal and strip presence signal of each stand in real time; when the second stand is detected to have a strip throwing action, and there is strip in the last three stands, it is determined that the strip has entered the tail rolling stage, and the tail correction function is automatically started; when the last stand is detected to have a strip throwing action, it is determined that the strip has completely left the finishing mill, and the tail correction function is automatically stopped.

[0007] Real-time monitoring of the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand in the hot strip mill finishing unit refers to collecting the rolling pressure deviation of each of the n points with deviation at each rated time interval, and then taking the average value of the n points as the reference rolling pressure deviation. Similarly, collecting the roll gap horizontal deviation of each of the m points with deviation at each rated time interval, and then taking the average value of the m points as the reference roll gap horizontal deviation, using the reference rolling pressure deviation as the actual rolling pressure deviation, and using the reference roll gap horizontal deviation as the actual reference roll gap horizontal deviation.

[0008] n is 20, m is 10, and the average is the arithmetic mean.

[0009] During automatic correction adjustment, automatic correction adjustment should be carried out at intervals between racks, and simultaneous correction adjustment of adjacent racks is prohibited.

[0010] For a hot strip mill with 7 continuous rolling stands, the pressure deviation is set at 150 kN and the roll gap horizontal deviation is set at 3 mm.

[0011] The beneficial effects of this invention are as follows: Improved production line operating efficiency: This invention effectively avoids severe tail-wagging accidents, reduces roll wear and replacement frequency, minimizes unplanned downtime, and ensures continuous and efficient production line operation. Reduced production and equipment costs: Tail-wagging accidents are significantly reduced, extending roll lifespan and lowering equipment maintenance and component replacement costs associated with malfunctions; simultaneously, it reduces the probability of scrap steel generation at the tail end, achieving cost reduction and efficiency improvement. Lowered operating threshold and stable rolling rhythm: This invention features a one-button operation mode that automatically determines operating conditions, automatically corrects deviations, and automatically resets the roll gap, reducing reliance on operator experience; the interlocking logic avoids secondary faults caused by deviation correction, ensuring a stable rolling rhythm. Strong adaptability to operating conditions: This invention combines steel ejection timing determination, multi-point average benchmark filtering to eliminate signal disturbances, and a stand-alone deviation correction strategy to adapt to different steel grades and strip thicknesses at the tail end of the rolling process, achieving millimeter-level precise deviation correction at the strip tail end, reducing tail-end edge breakage and steel piling accidents, and improving the coil shape quality at the coil tail end. Detailed Implementation

[0012] This embodiment uses a hot continuous rolling mill with 7 continuous rolling stands as an example for illustration.

[0013] The roll gap level of a hot strip mill is a core process parameter that determines the transverse thickness uniformity, strip straightness, and the elimination of defects such as single-sided waviness, camber, and deviation. During actual rolling, problems such as uneven stiffness between the drive and operating sides of the mill, hydraulic cylinder zero-position deviation, assembly clearance differences, asymmetrical rolling loads, uneven roll wear, and thermal expansion deviations can lead to inconsistent roll gap openings on both sides of the stand, resulting in roll gap level deviation. This deviation directly causes transverse thickness differences in the strip, excessive edge thinning, and strip shape distortion. In severe cases, it can cause production failures such as strip deviation, scraping, and breakage, significantly reducing the quality of finished strip and the stability of the production line.

[0014] As the core auxiliary control module of the hydraulic AGC system, the automatic roll gap leveling system for finishing mills can detect the rolling pressure and roll gap displacement deviation on both sides of the mill in real time. Relying on the mechanical balance model and closed-loop adjustment algorithm, it dynamically corrects the difference in roll gap between the transmission side and the operation side, ensuring that the roll gap is always in a horizontal balance state during the rolling process. It is a key technology for achieving high-precision transverse quality control of strip steel and ensuring rolling stability.

[0015] The essence of automatic leveling of the finishing mill roll gap is to eliminate asymmetric elastic deformation and roll gap deviation on both sides of the mill, achieving mechanical balance and geometric roll gap horizontal uniformity during the rolling process. Under ideal rolling conditions, the roll gap opening and elastic deformation on the drive side (DS) and operating side (OS) of the finishing mill are completely consistent, resulting in uniform transverse force on the strip and symmetrical reduction. In actual operating conditions, imbalance of parameters on both sides can cause roll gap tilting. The automatic leveling system independently adjusts the stroke of the hydraulic reduction cylinders on both sides to counteract asymmetric deformation and deviation, maintaining the horizontal attitude of the roll gap.

[0016] The core objective of leveling control is to ensure that the roll gap horizontal deviation approaches zero under steady-state conditions through dynamic adjustment. Roll gap tilt directly causes uneven rolling loads on both sides, and pressure deviation is the core detection basis of the leveling system. When the roll gap is level and there is no deviation, and the rolling alignment is good, the rolling pressure deviation on both sides (drive side and operating side) approaches zero. When the roll gap is tilted and the strip is unevenly loaded, the pressure deviation increases significantly, providing feedback signals for leveling adjustment.

[0017] A dynamic adaptive deviation correction control method for the tail end of a hot strip finishing mill is applied to a 7-stand hot strip finishing mill. The hot strip finishing mill has tail deviation correction function, stand strip ejection signal acquisition function, and stand strip in-situ detection function. The method includes the following steps: Step 1: Function Start-up and Function Interlocking: The start-up and stop are determined by the logic module through manual start-up or intelligent start-up. After the function is started, the tail correction function is put into use. After the tail correction function is put into use, the finishing mill one-key monotonic reset function is automatically put into use. When the finishing mill one-key monotonic reset function is put into use, the rolling pre-leveling state of each mill in the hot continuous rolling finishing mill unit is automatically restored before rolling.

[0018] Manual start / stop is achieved via the tail correction function start / stop button on the finishing mill control panel. Rolling mill operators can use a one-button start button on the control panel to flexibly and in real-time enable or disable the function based on different steel grades and rolling plans, eliminating the need for cumbersome operations. Simultaneously, this function is linked to the finishing mill one-button leveling and reset function, establishing a strong interlock: when correction is activated, the single-adjustment reset function is automatically activated synchronously, ensuring that any deviation caused by excessive correction can automatically return to the pre-leveling state of the mill before rolling, avoiding adverse effects on the next strip threading.

[0019] The intelligent start-up judgment logic module assigns sequential numbers to all stands of the hot strip mill along the strip conveying direction, with the stand corresponding to the first entry of the strip into the hot strip mill as the first stand. It collects the strip throwing signals and strip presence signals of each stand in the hot strip mill in real time. When a strip throwing action is detected in the second stand (F2) and there is strip in the last three stands (F5, F6, F7), it is determined that the strip has entered the tail rolling stage, and the tail correction function is automatically started. When a strip throwing action is detected in the last stand, it is determined that the strip has completely left the mill, and the tail correction function is automatically stopped. The centering control is completed before the strip completely leaves the mill.

[0020] Step 2: After the tail-end correction function is put into use, the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand in the hot continuous rolling mill are monitored in real time. When the absolute value of the rolling pressure deviation of any stand is greater than the set pressure deviation value or the absolute value of the roll gap horizontal deviation is greater than the set roll gap horizontal deviation value, automatic correction adjustment is immediately activated through the hydraulic AGC system. For a 7-stand hot continuous rolling mill, the set pressure deviation value is 150kN and the set roll gap horizontal deviation value is 3mm.

[0021] Real-time monitoring of the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand in the hot strip mill finishing unit involves collecting the rolling pressure deviation at each of the 20 points with deviations on each stand every 0.3 seconds, and then taking the average of the 20 points as the benchmark rolling pressure deviation, effectively eliminating the interference of drastic fluctuations during steel ejection. At rated intervals, the roll gap horizontal deviation is collected at each of the 10 points with deviations on each stand, and then the average of the 10 points is taken as the benchmark roll gap horizontal deviation. The benchmark rolling pressure deviation is used as the actual rolling pressure deviation, and the benchmark roll gap horizontal deviation is used as the actual benchmark roll gap horizontal deviation. This locks in the actual benchmark under stable rolling conditions, ensuring the accuracy of correction adjustments.

[0022] In practical applications, it was found that simultaneously adjusting the strip alignment on all stands can easily exacerbate unidirectional strip misalignment. To address this issue, we developed and adopted an innovative "alternating stand adjustment" strategy to improve the stability of the alignment process. During automatic alignment adjustment, alternating stands are used to prevent simultaneous alignment adjustments on adjacent stands.

[0023] When a "steel throwing" action is detected on the Fn-2 stand in the finishing mill line, the tail correction function of the Fn stand is automatically triggered to achieve precise timing control. For example, after the F5 stand completes the steel throwing, only the F7 stand is adjusted, effectively preventing the amplification effect of deviation caused by continuous adjustment and ensuring the stability of the steel throwing process.

[0024] To ensure that the function automatically intervenes at the most needed moment, this invention incorporates a set of intelligent start-up judgment logic that requires no manual intervention: when a steel throwing action is detected in real time on the finishing mill F2 stand, and it is simultaneously determined that there is still strip steel in the downstream stands F5, F6, and F7, the system automatically determines to enter the tail rolling stage. At the instant the determination is made, the system will initiate the automatic tail-end correction function of the finishing mill within milliseconds, completing the centering control before the strip steel completely leaves the finishing mill unit.

[0025] In this invention, after the automatic tail adjustment function is activated, sometimes the adjustment amount is too large, which can affect the threading of the next piece of steel. To address this, the program automatically binds the "automatic recovery function for single-roll gap adjustment after steel throwing". After the rolling of a piece of steel is completed, the roll gap is automatically restored to the preset state, effectively solving the roll gap reversal problem, simplifying the operation, and ensuring the rolling rhythm and stability.

[0026] The tail-end correction control technology for hot strip mill finishing has been implemented and put into use on the 2250 production line of Taiyuan Iron & Steel's hot strip mill. The entire implementation process is automated within a computer program. During daily production on the 2250 hot rolling line, when the rolling operator determines that the tail-end correction function is required for the steel grade being rolled, they can activate it with a single button on the control panel. The L1 program automatically identifies the finishing mill process and, after the strip is ejected at the F2 tail end, initiates the dynamic adaptive correction control function at the tail end of the finishing mill stands F4-F7. After the strip is ejected at the F7 tail end, the mill returns to its pre-rolling leveling state. This technology is currently operating stably and will continue to provide stable support for the operation of the hot coil box bending roll equipment.

Claims

1. A dynamic adaptive deviation correction control method for the tail end of a hot continuous rolling mill, applied to a multi-stand hot continuous rolling mill finishing unit, wherein the hot continuous rolling mill finishing unit has tail deviation correction function, stand strip ejection signal acquisition function, and stand strip in-situ detection function, characterized in that... Includes the following steps: Step 1, Function Start-up and Function Interlock: The logic module is started or stopped manually or intelligently. After the function is started, the tail correction function is put into use. After the tail correction function is put into use, the finishing mill one-key monotonic reset function is automatically put into use. When the finishing mill one-key monotonic reset function is put into use, the rolling pre-leveling state of each mill in the hot continuous rolling finishing mill unit is automatically restored before rolling. Step 2: After the tail correction function is put into use, the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand of the hot continuous rolling mill are monitored in real time. When the absolute value of the rolling pressure deviation of any stand is greater than the set pressure deviation value or the absolute value of the roll gap horizontal deviation is greater than the set roll gap horizontal deviation value, the automatic correction adjustment is immediately put into use through the hydraulic AGC system.

2. The dynamic adaptive deviation correction control method for the tail section of hot continuous rolling mill according to claim 1, characterized in that: In step one, manual start and stop are achieved through the tail correction function start and stop button set on the finishing mill control panel; the intelligent start judgment logic module assigns sequential numbers to all stands of the hot strip mill finishing unit along the strip conveying direction, taking the stand corresponding to the first entry of the strip into the hot strip mill finishing unit as the first stand, and collects the strip throwing signal and strip presence signal of each stand in real time; when the second stand is detected to have a strip throwing action, and there is strip in the last three stands, it is determined that the strip has entered the tail rolling stage, and the tail correction function is automatically started; when the last stand is detected to have a strip throwing action, it is determined that the strip has completely left the finishing mill, and the tail correction function is automatically stopped.

3. The dynamic adaptive deviation correction control method for the tail section of hot continuous rolling mill according to claim 1, characterized in that: In step two, real-time monitoring of the actual rolling pressure deviation and actual roll gap horizontal deviation of each stand in the hot strip mill means that the rolling pressure deviation of each of the n points with deviations in each stand is collected at rated time intervals, and the average value of the n points is taken as the reference rolling pressure deviation. The roll gap horizontal deviation of each of the m points with deviations in each stand is collected at rated time intervals, and the average value of the m points is taken as the reference roll gap horizontal deviation. The reference rolling pressure deviation is taken as the actual rolling pressure deviation, and the reference roll gap horizontal deviation is taken as the actual reference roll gap horizontal deviation.

4. The dynamic adaptive deviation correction control method for the tail section of hot continuous rolling mill according to claim 3, characterized in that: In step two, n is 20, m is 10, and the average is the arithmetic mean.

5. The dynamic adaptive deviation correction control method for the tail section of hot continuous rolling mill according to claim 1, characterized in that: In step two, during automatic correction and adjustment, automatic correction and adjustment should be carried out at intervals between racks, and simultaneous correction and adjustment should not be carried out on adjacent racks.

6. The dynamic adaptive correction control method for the tail section of hot continuous rolling mill according to claim 1, characterized in that: For a hot strip mill with 7 continuous rolling stands, the pressure deviation is set at 150 kN and the roll gap horizontal deviation is set at 3 mm.