Pre-swing method for roll gap of finishing mill group

Abstract

The invention relates to the technical field of rolling mill roll gap adjustment, in particular to a rolling mill group roll gap pre-swing method, which comprises the following steps of: for a first roll period, placing copper bars at the width positions of strip steel on two sides of a rolling mill, simulating the pressing process of the strip steel by applying pressure to hydraulic cylinders on two sides of each rolling mill, and realizing roll gap pre-swing in the first roll period; the roll gap pre-swing value of the roll period is calculated according to the rolling force difference of all racks during stable rolling of the previous roll period in the second roll period and the third roll period; and after the third roll period, the roll gap pre-swing value of the roll period is calculated according to the rolling force difference of the racks during stable rolling of the first three roll periods. The method has the advantages that different roll gap pre-swing strategies are adopted in stages (the first roll period, the second / third roll period and the subsequent roll period), rolling force difference calculation and copper bar calibration are combined, roll gap adjustment has a theoretical basis, dependence on artificial experience is reduced, and control precision is improved; differential adjustment strategies are adopted for different roller periods, and the method can adapt to dynamic factors such as rolling mill rigidity changes and roller abrasion.

Description

Technical Field

[0001] The invention relates to the technical field of rolling mill roll gap adjustment, and in particular to a finishing mill roll gap pre-swing method. Background Art

[0002] In the steel industry, hot rolling is a core process for producing high-quality steel plates. With the rapid development and shift toward high-end manufacturing, customers are placing increasingly stringent demands on steel quality. Shape control, in particular, has become a key indicator of steel companies' competitiveness. While hot rolling has achieved a high level of control over symmetrical shape (such as crown), controlling asymmetric shapes (such as wedges and edge waves) remains a significant challenge.

[0003] The causes of asymmetric plate shape are complex, mainly including:

[0004] 1. Difference in stiffness on both sides of the rolling mill:

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

[0006] 2. Dependence on manual experience:

[0007] At present, many steel mills still rely on the operator's experience to manually adjust the roll gap pre-swing value, which lacks scientific basis and leads to low control accuracy and poor stability.

[0008] 3. Dynamic change factors:

[0009] During the rolling process, factors such as roll wear and temperature changes will further aggravate the problem of asymmetric plate shape, and traditional methods are difficult to adapt in real time.

[0010] Existing roll gap pre-swing methods usually use 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 accurate roll gap pre-swing method that 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 the present invention is to provide a method for pre-swinging the roll gap of a finishing mill, which can realize precise control of the asymmetric plate shape of the finishing strip through a staged dynamic adjustment strategy.

[0013] To achieve the above object, the present invention is implemented through the following technical solutions:

[0014] A finishing mill roll gap pre-swing method, comprising:

[0015] S1, the first pre-swing roll gap of the first roll period:

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

[0017] After lifting the roll gap, take out 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 rolling force deviation during stable rolling:

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

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

[0021] Manually adjust and press down the rolling mills of each stand until the rolling force deviation on both sides is equal to the rolling force deviation recorded in the previous rolling period, and obtain the pre-swing roll gap of the current rolling period;

[0022] S4, the fourth and subsequent roll period pre-swing roll gap:

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

[0024] In S4, the pre-swing rolling force difference of the fourth and subsequent roll periods is calculated as follows:

[0025] ①;

[0026] In formula ①,

[0027] is the calculated pre-swing rolling force difference, in kN;

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

[0029] , , is the rolling force difference weight coefficient of the first three rolling periods;

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

[0031] It also includes exception handling: when the operator reports that the calculated value of the pre-swing rolling force deviation of a certain roll period is abnormal based on the on-site rolling conditions, the pre-swing roll gap value of each frame of 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 copper rod thickness difference is measured as follows: the thickness difference between the copper rods on the operating side and the transmission side is measured.

[0034] Anomalies include deviations in copper rod measurements.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0038] 3. Use the stable rolling data (rolling force deviation) of the first three rolls for weighted calculation to make the pre-swing 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, it reduces the dependence on operator experience, reduces human adjustment errors, and improves production efficiency;

[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 to ensure the stability of the rolling process and avoid batch quality problems caused by error accumulation;

[0041] 6. Combining on-site rolling experience with theoretical models, quickly respond to asymmetric plate shape problems during the rolling process, shorten commissioning time, and improve yield rate and product qualification rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flow chart of the roll gap pre-swing method of the finishing mill. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below 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 examples are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating processes, but the scope of protection of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0045] Example 1:

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

[0047] Step S1, first pre-swing of the roll gap in the first roll phase:

[0048] A copper rod is placed on each side of the strip width position in the roll gap of the F3 rolling mill work rolls, and the hydraulic cylinders on both sides are pressed down simultaneously to the same rolling force of 50kN;

[0049] Lift the roller gap and take out the two copper bars to measure the thickness difference. The thickness of the copper bar on the operating side is 6.24mm, and the thickness of the copper bar on the transmission side is 5.78mm. The pre-swing roller gap value of the first piece of steel is the difference in thickness between the copper bar on the operating side and the copper bar on the transmission side: .

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

[0051] The first rolling period, the first to fifth steel strip rolling positions tend to be stable rolling process. After multiple leveling adjustments of each stand, the rolling force difference array of F3 stand is read from PLC as shown in the following table:

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

[0053]

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

[0055] Step S3, pre-swing the gap between the second and third rollers:

[0056] When the working rolls of the second rolling period are calibrated successfully, the F3 stand rolling mill is manually adjusted and pressed down until the rolling force deviation on both sides is the F3 stand rolling force deviation of 97kN recorded in the first rolling period. The difference in the roll gap between the operating side and the transmission side of the F3 in the current rolling period is 0.57mm, and the pre-swing roll gap of the F3 stand in the second rolling period is 0.57mm.

[0057] When the second roll is rolling, the F3 rolling force difference array is as shown in the following table:

[0058] Table 2: Rolling force difference of F3 stand in the second rolling period

[0059]

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

[0061] Similarly, when the working roll calibration of the third rolling period is successful, the rolling force deviation of the F3 stand is manually adjusted and pressed down until the rolling force deviation on both sides is the F3 stand rolling force deviation of 159kN recorded in the second rolling period. The difference in the roll gap between the operating side and the transmission side of the F3 in the current rolling period is 0.98mm, and the pre-swing roll gap of the F3 stand in the second rolling period is 0.98mm.

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

[0063] Table 3: Rolling force difference of F3 stand during the third rolling period

[0064]

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

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

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

[0068] ①;

[0069] In formula ①, is the pre-swing rolling force difference calculated for the fourth roll stage F3 stand, in kN, obtained by calculation; , , The dimensionless weight coefficient for the rolling force difference in the first three roll periods is K1, which is a weighted coefficient. During rolling, the rolling conditions (such as roll wear and rolling temperature stability) of the most recent roll period are closer to the current roll period, and thus have a more significant impact on the current roll gap pre-swing. Therefore, the weight distribution principle of "larger near, smaller far" is followed: the closer the previous roll period is to the current roll period, the larger the weight coefficient. Initial values ​​are initially determined to be K1=0.2, K2=0.3, and K3=0.5. A large amount of stable rolling data for consecutive roll periods is then collected, including the rolling force deviation ΔF on both sides of each stand during stable rolling at different roll periods, as well as the actual roll gap adjustment values ​​for the corresponding roll periods and the final plate shape quality test results. Correlation analysis is performed on this data, focusing on the mapping relationship between the rolling force deviations in the first three roll periods and the optimal roll gap adjustment value for the current roll period. By statistically analyzing different weight combinations, the K, K2, and K3 values ​​that best match the actual production results for stable rolling and plate shape compliance are calculated.

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

[0071] ②;

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

[0073] When rolling is stable, take the rolling force deviation on both sides of F3 stand It is 73kN, which is used to calculate the pre-swing rolling force difference in the subsequent rolling period.

[0074] Step S5: Exception handling:

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

[0076] This finishing mill roll gap pre-swing method was applied to the finishing rolling measurement, control, and automatic deviation correction system of a 1580mm hot-rolling mill on a large-scale industrial scale, achieving remarkable control results. Daily reports and monthly quality inspection records indicate that this control method has reduced the manual operation rate by over 60%, significantly improving the control of asymmetric flatness.

[0077] The present invention adopts different roll gap pre-swing methods for different roll periods. For the first roll period, copper bars are placed at the strip width position on both sides of the rolling mill. By applying 50kN pressure to the hydraulic cylinders on both sides of each rolling mill, the strip pressing process is simulated to achieve roll gap pre-swing for the first roll period. For the second and third roll periods, the roll gap pre-swing value for the current roll period is calculated using the rolling force difference of each stand during stable rolling in the previous roll period. After the third roll period, the roll gap pre-swing value for the current roll period is calculated using the rolling force difference of each stand during stable rolling in the first three roll periods. Using different roll gap pre-swing methods for different roll periods is supported by scientific theoretical basis and takes into account actual rolling experience. The rolling force difference of the first few roll periods is utilized to reduce the degree of operator intervention and the efficiency of plate shape control. Abnormal processing is performed based on the operator's response to the on-site rolling situation, thereby improving the stability of the rolling process.

[0078] The present invention adopts different roll gap pre-swing strategies in different stages (first roll period, second / third roll period, subsequent roll period), combines rolling force difference calculation and copper bar calibration, so that the roll gap adjustment has a theoretical basis, reduces reliance on manual experience, and improves control accuracy; adopts differentiated adjustment strategies for different roll periods (initial roll change period, stable rolling period), can adapt to dynamic factors such as rolling mill stiffness changes and roll wear, and ensure continuous optimization of asymmetric plate shape; uses stable rolling data (rolling force deviation) of the first three roll periods for weighted calculation, so that the pre-swing value is closer to the actual working condition. By automatically calculating the pre-swing rolling force difference and guiding the roll gap adjustment, the system reduces the reliance on operator experience, reduces 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) and recalibrate the data to ensure the stability of the rolling process and avoid batch quality problems caused by accumulated errors. 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 the yield rate and product qualification rate.

Claims

1. A finishing mill roll gap pre-swing method, characterized in that: include: S1, the first pre-swing roll gap of the first roll period: Copper bars are placed on both sides of the strip width position in the roll gap of each rolling mill, and the hydraulic cylinders on both sides are pressed down simultaneously to the same rolling force; After lifting the roll gap, take out the copper rod to measure the thickness difference and obtain the pre-swing roll gap value of the first piece of steel; S2. Obtain rolling force deviation during stable rolling: During the first rolling period, the first to nth steel pieces are rolled, where n≤5. After the rolling process stabilizes, the rolling force deviation of each stand is recorded. S3, the second and third roller pre-swing roller gap: Manually adjust and press down the rolling mills of each stand until the rolling force deviation on both sides is equal to the rolling force deviation recorded in the previous rolling period, and obtain the pre-swing roll gap of the current rolling period; S4, the fourth and subsequent roll period pre-swing roll gap: According to the rolling force deviation of each stand during stable rolling in the first three roll periods, the pre-swing rolling force difference is obtained by weighted calculation, and the pressure is manually adjusted to the pre-swing rolling force difference to obtain the pre-swing roll gap of this roll period.

2. A finishing mill roll gap pre-swing method according to claim 1, characterized in that: In S4, the pre-swing rolling force difference of the fourth and subsequent roll periods is calculated as follows: ①； In formula ①, is the calculated pre-swing rolling force difference, in kN; , , The rolling force deviation on both sides of each stand during the first three rolling periods is in kN. , , is the rolling force difference weight coefficient of the first three rolling periods; is the roll period number, =4,5,6,……; is the rack number, =1,2,……,7.

3. A finishing mill roll gap pre-swing method according to claim 1, characterized in that: It also includes exception handling: when the operator reports that the calculated value of the pre-swing rolling force deviation of a certain roll period is abnormal based on the on-site rolling conditions, the pre-swing roll gap value of each frame of each roll period is recalculated according to S1, and at this time the roll period becomes the new first roll period.

4. A finishing mill roll gap pre-swing method according to claim 2, characterized in that: The rolling force deviations on both sides of each stand are read from the PLC.

5. A finishing mill roll gap pre-swing method according to claim 1, characterized in that: In S1, the copper rod thickness difference is measured by measuring the thickness difference between the copper rods on the operating side and the transmission side.

6. A finishing mill roll gap pre-swing method according to claim 3, characterized in that: The anomalies mentioned include copper rod measurement deviations.

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