A method for pre-tilting the roll gap of a finishing rolling mill

Abstract

The present application relates to the technical field of rolling mill roll gap adjustment, and particularly relates to a method for pre-adjusting roll gap of a finishing mill set. For the first roll period, copper bars are placed at the positions of the strip width on both sides of the rolling mill, and the pressure of the hydraulic cylinders on both sides of each rolling mill is given to simulate the rolling process of the strip, so as to realize the pre-adjustment of the roll gap of the first roll period. For the second and third roll periods, the roll gap pre-adjustment value of the current roll period is calculated according to the rolling force difference of each stand during the stable rolling of the previous roll period. For the third roll period and the subsequent roll periods, the roll gap pre-adjustment value of the current roll period is calculated according to the rolling force difference of each stand during the stable rolling of the previous three roll periods. The present application has the following advantages: different roll gap pre-adjustment strategies are adopted in different stages (the first roll period, the second / third roll period, and the subsequent roll period), and the roll gap adjustment is combined with the rolling force difference calculation and copper bar calibration, so that the roll gap adjustment has a theoretical basis, the dependence on manual experience is reduced, and the control precision is improved; and the differentiated adjustment strategies for different roll periods can adapt to dynamic factors such as the change in the rigidity of the rolling mill and the wear of the rolls.

Description

Technical Field

[0001] This invention relates to the field of rolling mill roll gap adjustment technology, and in particular to a pre-swing method for the roll gap of a finishing mill. Background Technology

[0002] In steel production, hot strip rolling technology is one of the core processes for manufacturing high-quality steel plates. With the rapid development and high-end transformation of the manufacturing industry, users have increasingly stringent requirements for steel quality, especially the precision of plate shape control, which has become a key indicator for measuring the competitiveness of steel companies. Currently, hot strip rolling has achieved a high level of control over symmetrical plate shapes (such as crown), but there are still significant challenges in controlling asymmetrical plate shapes (such as wedges and edge waviness).

[0003] The causes of asymmetric plate shapes are complex and mainly include:

[0004] 1. Stiffness difference between the two sides of the rolling mill:

[0005] Due to mechanical structure, wear, or assembly errors, the stiffness of the operating side (OS) and drive side (DS) of the rolling mill may be inconsistent, resulting in uneven distribution of rolling force, which in turn affects the strip shape.

[0006] 2. Reliance on human experience:

[0007] Currently, many steel mills still rely on operators' experience to manually adjust the roll gap pre-sway value, which lacks scientific basis, resulting in low control accuracy and poor stability.

[0008] 3. Dynamically changing factors:

[0009] During the rolling process, factors such as roll wear and temperature changes can further exacerbate the problem of asymmetric plate shape, which traditional methods cannot adapt to in real time.

[0010] Existing roll gap pre-swaying methods typically employ fixed compensation values ​​or simple linear adjustments, which cannot effectively adapt to the dynamic requirements of different rolling stages (such as the initial stage after roll change and the stable rolling stage).

[0011] Therefore, there is an urgent need for a scientific and precise method for pre-positioning the roll gap, which combines rolling force difference analysis and historical data optimization to reduce manual intervention and improve production efficiency and product quality. Summary of the Invention

[0012] The purpose of this invention is to provide a pre-swing method for the roll gap of a finishing mill, which achieves precise control of the asymmetric shape of the finished strip through a phased dynamic adjustment strategy.

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] A method for pre-positioning the roll gap of a finishing mill includes:

[0015] S1, First pre-swing roll gap in the first rolling period:

[0016] Copper bars are placed on both sides of the strip width within the roll gap of each rolling mill's work rolls, and the hydraulic cylinders on both sides are simultaneously pressed down to the same rolling force;

[0017] After lifting the roll gap, remove the copper rod to measure the thickness difference and obtain the pre-swing roll gap value of the first piece of steel;

[0018] S2. Obtain the rolling force deviation during stable rolling:

[0019] The first to nth steel blocks are rolled in the first rolling period, n≤5. After the rolling process stabilizes, the rolling force deviation of each stand is recorded.

[0020] S3, second and third roll pre-swing roll gap:

[0021] Manually adjust the rolling force deviation on both sides of each stand of the rolling mill to the rolling force deviation recorded in the previous rolling period, and obtain the pre-sway roll gap of the current rolling period;

[0022] S4, fourth and subsequent pre-sway roll gap:

[0023] Based on the rolling force deviation of each stand during the first three rolling periods, the pre-swing rolling force difference is obtained by weighted calculation, and the roll gap is manually adjusted to this pre-swing rolling force difference to obtain the pre-swing roll gap for this rolling period.

[0024] In S4, the pre-swing rolling force difference in the fourth and subsequent roll periods is calculated using the following formula:

[0025] ①;

[0026] In formula ①,

[0027] The calculated pre-swing rolling force difference is expressed in kN.

[0028] , , The deviation of rolling force on both sides of each stand during the first three roll periods of stable rolling is expressed in kN.

[0029] , , This is the weighting coefficient for the difference in rolling force during the first three rolling periods;

[0030] This is the rolling period number. =4,5,6,……; For rack number, =1,2,……,7.

[0031] It also includes anomaly handling: when the operator reports an anomaly in the pre-sway rolling force deviation calculation value for a certain roll period based on the on-site rolling conditions, the pre-sway roll gap value of each stand for each roll period is recalculated according to S1, and at this time, the roll period becomes the new first roll period.

[0032] The rolling force deviation on both sides of each stand is read from the PLC.

[0033] In S1, the thickness difference of the copper rod is: the thickness difference between the copper rod on the operating side and the transmission side.

[0034] The anomaly includes measurement deviation of the copper rod.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1. By adopting different roll gap pre-swing strategies in stages (first roll period, second / third roll period, and subsequent roll periods), combined with rolling force difference calculation and copper bar calibration, roll gap adjustment has a theoretical basis, reduces reliance on manual experience, and improves control accuracy.

[0037] 2. Differentiated adjustment strategies are adopted for different roll stages (initial roll change and stable rolling stage) to adapt to dynamic factors such as changes in mill stiffness and roll wear, ensuring continuous optimization of asymmetric shape;

[0038] 3. Weighted calculations are performed using stable rolling data (rolling force deviation) from the first three rolling periods to make the pre-sway value closer to the actual working conditions, thereby improving the adaptability and reliability of the model.

[0039] 4. By automatically calculating the pre-swing rolling force difference and guiding the roll gap adjustment, the reliance on operator experience is reduced, human adjustment errors are minimized, and production efficiency is improved.

[0040] 5. When the pre-swing value is abnormal, the system can automatically switch to the initial calibration mode (first roll period method) to recalibrate the data, ensure the stability of the rolling process, and avoid batch quality problems caused by the accumulation of errors;

[0041] 6. Combining on-site rolling experience with theoretical models, we can quickly respond to asymmetric plate shape problems during the rolling process, shorten debugging time, and improve yield and product qualification rate. Attached Figure Description

[0042] Figure 1 This is a flowchart of the roll gap pre-swing method for finishing mill units. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0044] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0045] Example 1:

[0046] See Figure 1 Taking the F3 stand as an example, a method for pre-swinging the roll gap of a finishing mill includes:

[0047] Step S1, First Pre-Swing Roll Gap in the First Rolling Period:

[0048] A copper bar is placed on each side of the strip width within the roll gap of the F3 rolling mill, and the hydraulic cylinders on both sides are simultaneously pressed down to the same rolling force of 50kN.

[0049] Lift the roll gap and remove the two copper bars to measure the thickness difference. The thickness of the copper bar on the operating side is 6.24 mm, and the thickness of the copper bar on the drive side is 5.78 mm. The roll gap value of the first steel piece is the difference between the thickness of the copper bar on the operating side and the copper bar on the drive side. .

[0050] Step S2: Obtain the rolling force deviation during stable rolling:

[0051] The rolling process of the first five strips in the first rolling period tends to be stable. After multiple leveling adjustments of each stand, the rolling force difference array of stand F3 read from the PLC is shown in the table below:

[0052] Table 1: Rolling force difference of F3 stand in the first rolling period.

[0053]

[0054] The rolling force difference is obtained from the PLC, so the rolling force deviation of the F3 stand during stable rolling is... It is 97kN.

[0055] Step S3, the pre-swing roll gap during the second and third rolling periods:

[0056] When the work roll calibration for the second rolling period is successful, manually adjust the F3 stand rolling mill until the rolling force deviation on both sides is 97kN, which is the F3 stand rolling force deviation recorded in the first rolling period. The difference between the roll gap values ​​on the operating side and the drive side of the current rolling period is 0.57mm. Therefore, the pre-swing roll gap of the F3 stand in the second rolling period is 0.57mm.

[0057] When rolling in the second rolling period, the F3 rolling force difference array is shown in the table below:

[0058] Table 2: Rolling Force Difference of F3 Stand in the Second Rolling Period

[0059]

[0060] The rolling force difference is obtained from the PLC, so the rolling force deviation of the F3 stand during stable rolling is... It is 159kN;

[0061] Similarly, when the work roll calibration of the third roll period is successful, manually adjust the F3 stand rolling mill until the rolling force deviation on both sides is 159kN, which is the F3 stand rolling force deviation recorded in the second roll period. The difference between the roll gap values ​​of the operating side and the drive side of the current roll period is 0.98mm. Then the pre-swing roll gap of the F3 stand in the second roll period is 0.98mm.

[0062] When rolling in the third rolling period, the F3 rolling force difference array is shown in the table below:

[0063] Table 3: Rolling Force Difference of F3 Stand in the Third Rolling Period

[0064]

[0065] The rolling force difference is obtained from the PLC, so the rolling force deviation of the F3 stand during stable rolling is... It is 81kN.

[0066] Step S4, fourth and subsequent roll pre-swing roll gap:

[0067] The pre-swing rolling force difference is calculated in the fourth rolling period based on the rolling force deviation of the F3 stand during the stable rolling of the first three rolling periods. The calculation formula is as follows:

[0068] ①;

[0069] In formula ①, The pre-swaying rolling force difference calculated for the F3 stand in the fourth rolling period, in kN, is obtained through calculation; , , The rolling force difference weighting coefficients for the previous three roll periods are dimensionless. During the rolling process, the rolling conditions of the most recent roll period (such as roll wear state and rolling temperature stability) are closer to the current roll period, and their impact on the current roll gap pre-sway is more significant. Therefore, following the principle of "larger weight for closer periods and smaller weight for farther periods," the weighting coefficients of the preceding roll periods closer to the current roll period are larger. The initial values ​​were determined to be K1=0.2, K2=0.3, and K3=0.5. Then, a large amount of stable rolling data for consecutive roll periods was collected, including the rolling force deviation ΔF on both sides of each stand during stable rolling in different roll periods, as well as the actual roll gap adjustment amount and the final strip shape quality inspection results for the corresponding roll periods. Correlation analysis was performed on the collected data, focusing on exploring the mapping relationship between the rolling force deviation of the previous three roll periods and the optimal roll gap adjustment amount for the current roll period. By statistically analyzing different weight combinations, the K, K2, and K3 values ​​with the highest degree of agreement with the actual production process that can achieve stable rolling and meet the strip shape standards were calculated.

[0070] Based on on-site rolling experience , , ; , , The values ​​are the rolling force deviations on both sides of the F3 stand during stable rolling in the first, second, and third rolling stages, respectively, in kN. These values ​​are read from the PLC by S2 and S3.2 and are 97kN, 159kN, and 81kN, respectively. The specific calculation results are as follows:

[0071] ②;

[0072] At this point, manually adjust the F3 stand rolling mill until the rolling force deviation on both sides reaches the pre-swing rolling force difference. The difference between the roll gap on the operating side and the drive side is 0.73 mm, which is the pre-swing roll gap of the F3 frame in this roll period;

[0073] During the stabilization rolling process, the rolling force deviation on both sides of the F3 stand is taken. It is 73kN, used for calculating the pre-swing rolling force difference in subsequent rolling stages.

[0074] Step S5, Exception Handling:

[0075] When the operator reports an abnormality in the calculated value of the pre-sway rolling force deviation for a certain roll period based on the on-site rolling conditions (abnormality includes a copper bar measurement deviation greater than 2mm), the pre-sway roll gap value of each stand for each roll period is recalculated according to step S1. At this time, the roll period becomes the new first roll period.

[0076] After applying this pre-alignment method of the finishing mill roll gap to the automatic deviation correction system of a 1580mm hot strip mill for large-scale industrial application, it achieved very significant control results. According to daily reports and monthly quality inspection logs, the manual operation rate was reduced by more than 60% after adopting this control method, greatly improving the control effect of asymmetric plate shape.

[0077] This invention employs different roll gap pre-swing methods for different rolling stages. For the first rolling stage, copper bars are placed at the strip width position on both sides of the mill. By applying a pressure of 50kN to the hydraulic cylinders on both sides of the mill, the strip reduction process is simulated, achieving roll gap pre-swing for the first rolling stage. For the second and third rolling stages, the roll gap pre-swing value is calculated using the rolling force difference between the stands during stable rolling in the previous rolling stage. After the third rolling stage, the roll gap pre-swing value is calculated using the rolling force difference between the stands during stable rolling in the previous three rolling stages. Using different roll gap pre-swing methods for different rolling stages is supported by scientific theoretical basis while also taking into account practical rolling experience. It utilizes the rolling force difference of the previous rolling stages, reducing operator intervention and improving the efficiency of strip shape control. Furthermore, it allows for handling of anomalies based on operator feedback on the rolling situation, improving the stability of the rolling process.

[0078] This invention employs different roll gap pre-swaying strategies in stages (first roll stage, second / third roll stage, and subsequent roll stages), combined with rolling force difference calculation and copper bar calibration, to provide a theoretical basis for roll gap adjustment, reduce reliance on manual experience, and improve control accuracy. Differentiated adjustment strategies are used for different roll stages (initial roll change and stable rolling period) to adapt to dynamic factors such as changes in mill stiffness and roll wear, ensuring continuous optimization of asymmetric shape. Weighted calculations using stable rolling data (rolling force deviation) from the first three roll stages make the pre-swaying value closer to actual rolling conditions. Furthermore, it improves the adaptability and reliability of the model; by automatically calculating the pre-swing rolling force difference and guiding roll gap adjustment, it reduces reliance on operator experience, minimizes human adjustment errors, and improves production efficiency; when the pre-swing value is abnormal, the system can automatically switch to the initial calibration mode (first roll period method) to recalibrate the data, ensuring the stability of the rolling process and avoiding batch quality problems caused by error accumulation; combining on-site rolling experience with theoretical models, it can quickly respond to asymmetric plate shape problems in the rolling process, shorten debugging time, and improve yield and product qualification rate.

Claims

1. A method for pre-positioning the roll gap in a finishing mill, characterized in that, include: S1, First pre-swing roll gap in the first rolling period: Copper bars are placed on both sides of the strip width within the roll gap of each rolling mill's work rolls, and the hydraulic cylinders on both sides are simultaneously pressed down to the same rolling force; After lifting the roll gap, remove the copper rod to measure the thickness difference and obtain the pre-swing roll gap value of the first piece of steel; S2. Obtain the rolling force deviation during stable rolling: The first to nth steel blocks are rolled in the first rolling period, n≤5. After the rolling process stabilizes, the rolling force deviation of each stand is recorded. S3, second and third roll pre-swing roll gap: Manually adjust the rolling force deviation on both sides of each stand of the rolling mill to the rolling force deviation recorded in the previous rolling period, and obtain the pre-sway roll gap of the current rolling period; S4, fourth and subsequent pre-sway roll gap: Based on the rolling force deviation of each stand during the first three rolling periods, the pre-swing rolling force difference is obtained by weighted calculation, and the roll gap is manually adjusted to this pre-swing rolling force difference to obtain the pre-swing roll gap for this rolling period.

2. The pre-positioning method for the roll gap of a finishing mill according to claim 1, characterized in that, In S4, the pre-swing rolling force difference in the fourth and subsequent roll periods is calculated using the following formula: ①； In formula ①, The calculated pre-swing rolling force difference is expressed in kN. , , The deviation of rolling force on both sides of each stand during the first three roll periods of stable rolling is expressed in kN. , , This is the weighting coefficient for the difference in rolling force during the first three rolling periods; This is the rolling period number. =4,5,6,……; For rack number, =1,2,……,7.

3. The pre-positioning method for the roll gap of a finishing mill according to claim 1, characterized in that, It also includes anomaly handling: when the operator reports an anomaly in the pre-sway rolling force deviation calculation value for a certain roll period based on the on-site rolling conditions, the pre-sway roll gap value of each stand for each roll period is recalculated according to S1, and at this time, the roll period becomes the new first roll period.

4. The pre-positioning method for the roll gap of a finishing mill according to claim 2, characterized in that, The rolling force deviation on both sides of each stand is read from the PLC.

5. The pre-positioning method for the roll gap of a finishing mill according to claim 1, characterized in that, In S1, the thickness difference of the copper rod is the difference between the thickness of the copper rod measured on the operating side and the transmission side.

6. The pre-positioning method for the roll gap of a finishing mill according to claim 3, characterized in that, The aforementioned anomalies include deviations in the measurement of the copper rod.

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