Speed balance optimization control method in finish rolling threading process

Abstract

The invention discloses a speed balance optimization control method in a finish rolling threading process, which comprises the following steps of: acquiring actual-performance rolling mill rotating speed, rolling force, roll gap and loop angle data of a finish rolling mill through a finish rolling setting model after threading of a strip steel head is finished, calculating a rotating speed ratio change condition between racks by combining a preset rotating speed, and judging whether the rotating speed of the rolling mill has deviation or not; whether the incoming material speed unbalance exists or not is judged by combining the offset of the loop angle; calculating the speed variation of the strip steel caused by the change of the roll gap of each rack, and judging whether the speed is unbalanced or not caused by the change of the roll gap; and comprehensively calculating the unbalance speed ratio for optimizing the rotating speed of a subsequent strip steel set rolling mill. The method is used for improving the stability of the head threading process of the hot continuous rolling strip steel.

Description

Technical Field

[0001] The present invention relates to steel rolling control technology, and more specifically, to an optimized control method for speed balance during the threading process of finish rolling. Background Art

[0002] Before the strip threading in the finish rolling area, aiming at the speed balance of the strip between the finish rolling stands, the roll gaps and forward slips of each stand are calculated, and the rotational speeds of the work rolls and the loop angles are set. During the threading process, the loop is used to dynamically adjust the speed imbalance state between the stands caused by setting deviations such as roll gaps and rotational speeds. However, excessive control of the loop is likely to cause abnormal conditions such as steel pulling, loop formation, and unstable rolling.

[0003] In the existing patent examination, for example, Patent Publication No. CN104801548B discloses a method for automatically adjusting the strip second flow rate balance during the threading process of hot continuous rolling. Since the "post facto" interventions of the operators are basically correct, the second flow rate balance changes in a more reasonable direction. Therefore, by analyzing the loop amount during the threading process and the manual intervention amount of the operators, the ideal stand speed matching value of this piece of steel can be calculated and used to correct the setting of the next piece of steel of the same specification. This patented technology is also for automatically adjusting the strip second flow rate balance, but in terms of the specific implementation method, it is different from the implementation method of the present invention in aspects such as the calculation of the speed change rate, the calculation of the loop amount, the calculation of the influence of the roll gap on the speed, and the rotational speed adjustment method.

[0004] Another example is Patent Publication No. 104874613B, which discloses a method for achieving the second flow rate balance between the stands of hot continuous rolling through mill speed compensation. According to the adjustment process of the roll speeds of each finish rolling stand due to loop control during the threading process, the actual roll speeds of each finish rolling stand and the roll speed adjustment amount required due to loop control are collected from the first-level computer. The change rate of the roll speed required due to loop control is adaptively learned according to the steel type × thickness × stand for specification classification. When calculating the setting of the next coil of strip, the latest learning coefficient is used to correct the roll speed, so as to make the second flow rate between the finish rolling stands tend to be balanced. However, this patented technology uses a genetic management method. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide an optimized control method for speed balance during the threading process of finish rolling, so as to improve the stability of the strip head threading process in hot continuous rolling.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An optimized control method for speed balance during the threading process of finish rolling:

[0008] After the strip threading at the head of the strip is completed through the finish rolling setting model, the actual rolling mill speed, rolling force, roll gap, and loop angle data of the finish rolling mill are collected. By combining with the preset speed, the change of the speed ratio between stands is calculated to determine whether there is a deviation in the rolling mill speed.

[0009] Combined with the offset of the loop angle, it is judged whether there is an incoming material speed imbalance.

[0010] Calculate the strip speed change caused by the roll gap change of each stand, and judge whether there is a speed imbalance caused by the roll gap change.

[0011] Comprehensively calculate the imbalance speed ratio and use it for subsequent strip setting and rolling mill speed optimization.

[0012] Preferably, there are 7 stands on the finish rolling mill, namely F1 stand, F2 stand, F3 stand, F4 stand, F5 stand, F6 stand, and F7 stand.

[0013] After the threading of the strip through the F1 stand to the F7 stand is completed, the actual rolling mill speed, rolling force, roll gap, and loop angle data of the finish rolling mill collected are sent from L1 (basic automation level) to L2 (process control level). L2 performs basic processing on the measurement data, determines whether the data is valid, and performs filtering processing on the abnormal data.

[0014] Preferably, the rolling mill speed includes the rotational linear speed of the work rolls of the rolling mill.

[0015] The rolling force includes the rolling force on the working side of the rolling mill and the rolling force on the drive side of the rolling mill.

[0016] The roll gap includes the roll gap on the working side of the rolling mill and the roll gap on the drive side of the rolling mill.

[0017] Preferably, the calculation of the speed ratio specifically includes:

[0018] Taking the speed of the F7 stand as the reference, calculate the speed ratio Vr of the F1 stand to the F6 stand to the F7 stand.

[0019] Preferably, judging whether there is a deviation in the rolling mill speed specifically includes:

[0020] By calculating the deviation amount between the actual speed ratio and the set speed ratio, it is judged whether there is a speed abnormality, and the calculation is as follows:

[0021] According to the actual rolling speed of the strip at the stable position of the strip head threading, calculate the actual speed Vr during the rolling process ponst and the set speed Vr pre The deviation ratio ΔVr:

[0022]

[0023] Preferably, in combination with the offset of the loop angle, determining whether there is an incoming material speed imbalance specifically includes:

[0024] Calculate the loop quantity adjustment amount based on the set and actual loop angles. When the change in the loop angle is consistent with the speed control target, calculate the loop quantity brought about by the change in the loop angle, and then calculate the incoming material speed deviation ratio ΔV loop , the loop quantity ΔL between each stand is calculated according to the loop angle α and the inherent parameters of the equipment:

[0025]

[0026] In the formula, R is the loop arm length, H is the horizontal height of the loop shaft point, and L is the distance between stands;

[0027]

[0028] In the formula, Δt is the time taken from the rear stand biting the steel to the loop completing the loop quantity adjustment;

[0029] Determine whether the control targets of the loop angle adjustment and the rotational speed adjustment are consistent to judge whether there is an incoming material speed imbalance:

[0030] vFlay = ΔVr × ΔV loop

[0031]

[0032] When vFlay < 0, it means that the direction of the incoming material speed deviation is opposite to the direction of the actual rotational speed change;

[0033] When -0.2 < vDiff < 0.2, it is determined that the control targets are consistent.

[0034] Preferably, calculating the strip speed change amount caused by the roll gap change of each stand specifically includes:

[0035] When there are differences between the set values and the actual values of the roll gap and the rolling force, the actual exit thickness changes accordingly. Calculate the actual exit thickness newh based on the actual rolling force and roll gap exit 、the front slip coefficient newSlip forward 、the exit speed change rate ΔV gap :

[0036] newh exit = DeliveryThink(gap, force)

[0037] In the formula, DeliveryThink is the exit thickness calculation method, gap is the actual roll gap, and force is the actual rolling force;

[0038] newslip forward= FSlip(R, h entry , newh exit )

[0039] ΔV gap = newslip forward - slip forward 。

[0040] Preferably, it is determined whether the speed imbalance is caused by the roll gap change, and the calculation of the imbalance amount specifically includes:

[0041] When the following four conditions are simultaneously satisfied, it is determined that the set rotational speed is imbalanced:

[0042] 1) The deviation of the actual rotational speed ratio is greater than 3%;

[0043] 2) The difference between the actual loop angle and the set angle is greater than 5 degrees;

[0044] 3) The rotational speed change is consistent with the loop control target;

[0045] 4) The amplitude of the speed change caused by the roll gap is less than 1%;

[0046] The calculation of the imbalance ratio is to calculate the ratio of the speed imbalance amount to the target exit speed:

[0047]

[0048] Preferably, the comprehensive calculation of the imbalance speed ratio and its use for subsequent strip steel setting and mill rotational speed optimization specifically includes:

[0049] Adopt the method of forward proportional drive to use the speed imbalance ratio to adjust the mill rotational speeds of all previous stands, and complete the speed balance optimization control;

[0050] Correction of the stand rotational speed:

[0051]

[0052] In the formula, i is the current stand number, n is the number of the last stand, and newV circle is the corrected rotational speed.

[0053] A speed balance optimization control method for the threading process in finish rolling provided by the present invention makes full use of the actual rotational speed, roll gap, rolling force, and loop angle of the strip steel during the finish rolling process, improves the speed imbalance phenomenon caused by the finish rolling setting deviation, and effectively enhances the threading stability of the head in the finish rolling area. This technical method is applied in the hot rolling preset calculation process, reducing the width blockage caused by the flow imbalance between stands and decreasing the scrap steel amount caused by the imbalance. Brief Description of the Drawings

[0054] Figure 1It is a schematic diagram of the principle of the speed balance optimization control method during the finishing mill threading process of the present invention;

[0055] Figure 2 It is a schematic diagram of the process flow of the speed balance optimization control method during the finishing mill threading process of the present invention. Specific embodiments

[0056] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0057] A speed balance optimization control method during the finishing mill threading process provided by the present invention utilizes the set and actual data of each stand on the finishing mill, including roll gap, rotational speed, and loop angle data, calculates the set rotational speed ratio and actual rotational speed ratio between stands, combines the loop angle change and roll gap change to evaluate and quantify the set deviation of the work roll rotational speed, and develops a speed balance optimization control technology for the threading process to improve the rolling stability during the finishing mill threading process.

[0058] Under the given equipment state, the finishing mill setting model first completes the load distribution of the roll gap for each stand according to the thickness of the intermediate billet and the finishing mill target thickness, then calculates the threading speed of each stand with the finishing mill final rolling temperature as the target, and finally calculates the forward slip coefficient, backward slip coefficient, and mill rotational speed in sequence in combination with the roll gap load and threading speed of each stand. During the threading process, the strip steel flow state between stands is sensed through the loop tension and angle. When the flow is too large, the loop angle is increased in a timely manner, and when the flow is too small, the loop angle is decreased, so as to achieve the balance adjustment of the flow between stands through this feedback control means. The feedback control means cannot improve the threading stability of the strip steel head and cannot complete the threading stability optimization before rolling.

[0059] Combined with Figure 1 As shown, after the strip steel head threading is completed by the finishing mill setting model of the present invention, the actual mill rotational speed, rolling force, roll gap, and loop angle data of the finishing mill are collected, the change of the rotational speed ratio between stands is judged in combination with the preset rotational speed, and whether there is a deviation in the mill rotational speed is judged; combined with the offset of the loop angle, whether there is an incoming material speed imbalance is judged; the strip steel speed change amount caused by the roll gap change of each stand is calculated, and whether there is a speed imbalance caused by the roll gap change is judged; the imbalance speed ratio is comprehensively calculated and used for the subsequent optimization of the set mill rotational speed of the strip steel. The specific steps are as follows:

[0060] S1. Processing of rolling measured value data;

[0061] There are 7 stands on the finishing mill, namely F1 stand, F2 stand, F3 stand, F4 stand, F5 stand, F6 stand, and F7 stand;

[0062] After threading is completed from the F1 stand to the F7 stand, the actual measured data of the rolling mill speed, rolling force, roll gap, and loop angle of the finishing mill are sent from L1 (basic automation level) to L2 (process control level). L2 performs basic processing on the measurement data, determines whether the data is valid, and filters the abnormal data.

[0063] The actual data collected by L1 includes the rolling mill speed, rolling force, and roll gap, where:

[0064] The rolling mill speed includes the linear velocity of the rotation of the work rolls of the rolling mill; the rolling force includes the rolling force on the working side of the rolling mill and the rolling force on the drive side of the rolling mill; the roll gap includes the roll gap on the working side of the rolling mill and the roll gap on the drive side of the rolling mill.

[0065] S2. Calculation of speed ratio; specifically including:

[0066] Based on the speed of the F7 stand, calculate the set speed ratio Vr of the F1 stand to the F6 stand and the F7 stand pre and the actual speed ratio Vr post .

[0067] S3. Calculation of speed ratio deviation;

[0068] Calculate the deviation ratio ΔVr of the set speed ratio Vr pre and the actual speed ratio Vr post to determine whether there is an abnormal speed situation.

[0069] S4. Calculation of loop quantity and incoming material speed deviation;

[0070] Calculate the loop quantity adjustment amount according to the set and actual loop angles, and calculate the incoming material speed deviation ratio that causes the change in loop quantity.

[0071] S5. Consistency analysis;

[0072] Analyze whether the actual speed change and the incoming material speed deviation are in the opposite direction and have similar absolute values.

[0073] S6. Calculation of the influence amount of reduction deviation on the exit speed;

[0074] Calculate the forward slip and the change rate of the exit speed caused by the deviation between the actual roll gap, rolling force and the set values.

[0075] S7. Judgment of speed imbalance state and calculation of imbalance ratio;

[0076] Judge whether the speed ratio difference reaches the specified threshold and is consistent with the loop angle adjustment control target. Calculate the influence of the reduction deviation on the speed, determine whether there is a real speed imbalance, and calculate the imbalance ratio.

[0077] S8. Optimization of speed control;

[0078] Optimize the rotational speed setting by using the speed imbalance ratio during the setting calculation process.

[0079] The calculation principle of the finish rolling setting model is as follows:

[0080] 1) Threading speed calculation:

[0081] The finish rolling threading speed calculation is based on the theory of speed balance and flow balance to calculate the running speeds of the strip at the inlet and outlet of each stand in the finish rolling area.

[0082] Flow balance means that the volume of the strip at the inlet of each stand should be equal to the volume of the strip at the outlet of the stand. Since the width spread caused by the horizontal reduction in the finish rolling area is small, after ignoring the width change, the inlet and outlet speeds of the strip should be inversely proportional to the strip thickness.

[0083] V entry ×h entry =V exit ×h exit (1)

[0084] In the formula, V entry is the inlet speed, h entry is the inlet thickness, V exit is the outlet speed, h exit is the outlet thickness.

[0085] Speed balance means that the outlet strip speed of the previous stand between adjacent stands should be equal to the inlet strip speed of the next stand.

[0086] V entry (i)=V exit (i - 1) (2)

[0087] 2) Relationship between mill rotational speed and threading speed:

[0088] The threading speed is the speed at which the strip flows out of the mill after horizontal reduction, with frictional sliding and internal sliding occurring during rolling.

[0089] The forward sliding speed of the strip during rolling is related to the work roll diameter, inlet strip thickness, and outlet strip thickness. It is a relative ratio with respect to the mill rotational speed, called the forward slip coefficient slip forward .

[0090] slip forward =FSlip(R, h entry , h ecit ) (3)

[0091] In the formula, FSlip is the calculation method for the forward slip coefficient (calculating the forward slip coefficient based on the work roll diameter, inlet thickness, and outlet thickness), and R is the work roll diameter of the mill.

[0092] Rotational speed V circle Refers to the linear speed of the working roll rotation that the rolling mill should set to achieve the target strip speed at the outlet.

[0093] V circle = V exit / slip forward (4)

[0094] 3) Rotational speed ratio in the finishing rolling area:

[0095] Taking the finishing rolling mill consisting of 7 stands as an example, from front to back are F1 stand to F7 stand. Based on the speed of F7 stand, calculate the rotational speed ratio Vr of each previous stand to F7.

[0096] 4) Calculation of actual rotational speed deviation:

[0097] Calculate the set rotational speed ratio Vr based on the actual rolling rotational speed at the stable position of the strip head threading. pre and the actual rotational speed ratio Vr post of the deviation ratio ΔVr.

[0098]

[0099] 5) Conduct control target consistency analysis by combining the loop angle:

[0100] The loop between stands plays a function of strip flow regulation. When the flow between stands is too large, the loop will raise the angle to increase the loop amount. When the flow between stands is too small, the loop will lower the angle to reduce the loop amount.

[0101] Judge whether it is in the same direction as the speed regulation control target according to the change direction of the loop angle.

[0102] Looper angle Increase Increase Decrease Decrease Front stand speed Reduce speed Reduce speed Increase speed Increase speed Control target Consistent Inconsistent Consistent Inconsistent

[0103] When the change of the loop angle is consistent with the speed control target, calculate the loop amount brought by the change of the loop angle, and then calculate the incoming material speed deviation ratio ΔVr loop , the loop amount ΔL between stands is calculated according to the loop angle α and the inherent parameters of the equipment:

[0104]

[0105] In the formula, R is the loop arm length, H is the horizontal height of the loop shaft point, and L is the distance between stands.

[0106]

[0107] In the formula, Δt is the time spent from the back stand biting the steel to the loop completing the loop amount adjustment.

[0108] Then make the following calculations to determine whether the control targets of the loop angle adjustment and the rotational speed adjustment are consistent:

[0109] vFlay = ΔVr × ΔV loop (8)

[0110]

[0111] When vFlay < 0, it means that the deviation of the incoming material speed is opposite to the direction of the actual rotational speed change;

[0112] When -0.2 < vDiff < 0.2, it is determined that the control targets are consistent.

[0113] 6) Strip speed changes caused by actual roll gap and rolling force changes:

[0114] When there are differences between the set values and the actual values of the roll gap and the rolling force, the actual exit thickness changes accordingly. Calculate the actual exit thickness and the forward slip coefficient newslip based on the actual rolling force and roll gap forward and the exit speed change rate ΔV gap .

[0115] newh exit = DeliveryThink(gap, force) (10)

[0116] In the formula, DeliveryThink is the method for calculating the exit thickness (calculating the strip thickness at the exit of the stand based on the actual roll gap and rolling force), gap is the actual roll gap, and force is the actual rolling force.

[0117] newslip forward = FSlip(R, h entry , newh exit ) (11)

[0118] ΔV gap = newslip forward - slip forward (12)

[0119] 7) Judgment of rotational speed imbalance state and calculation of imbalance amount:

[0120] When the following four conditions are simultaneously met, it is determined that the set rotational speed is imbalanced:

[0121] 1) The deviation of the actual rotational speed ratio is greater than 3%;

[0122] 2) The difference between the actual loop angle and the set angle is greater than 5 degrees;

[0123] 3) The rotational speed change is consistent with the loop control target;

[0124] 4) The amplitude of the speed change caused by the roll gap is less than 1%;

[0125] The unbalance ratio calculation is to calculate the ratio of the speed imbalance amount to the target outlet speed:

[0126]

[0127] 8) Optimization of rotational speed control:

[0128] During the speed optimization setting process, the rotational speed of the previous stand needs to consider the rotational speed change of the subsequent stand to ensure the speed balance between the previous stands. Therefore, the forward proportional drive method is used to adjust the rolling mill rotational speed of all previous stands with the speed imbalance ratio to complete the speed balance optimization control.

[0129] Correction of stand rotational speed:

[0130]

[0131] In the formula, i is the current stand number, n is the number of the last stand, and newV circle is the corrected rotational speed.

[0132] Embodiment

[0133] This embodiment provides a method for optimizing the speed balance control during the finishing mill threading process, which specifically includes the following steps:

[0134] S1. Processing of rolling measured data

[0135] L1 collects the head rolling performance data and calculates the rolling force, rolling mill rotational speed, roll gap, and loop angle as follows:

[0136]

[0137] S2. Calculation of rotational speed ratio

[0138] The preset rotational speed and the actual performance rotational speed are as follows:

[0139]

[0140] The calculation of the preset rotational speed ratio and the actual performance rotational speed ratio is as follows:

[0141]

[0142] S3. Calculation of rotational speed ratio deviation

[0143]

[0144] It can be seen from the rotational speed ratio deviation that the F5 stand has an obvious speed reduction behavior, and the speed reduction ratio is greater than 3%.

[0145] S4. Calculation of loop amount and incoming material speed deviation

[0146] Calculate the loop quantity compensation value based on the preset loop angle and the actual loop angle, and then calculate the incoming material speed deviation and the incoming material speed deviation ratio based on the loop quantity compensation value and the loop action time (Δt).

[0147]

[0148] The loop angle behind the F5 stand is on the large side. Calculate the compensation loop quantity and the incoming material speed. The incoming material speed is also the strip speed at the F5 outlet. Therefore, the strip speed at the F5 outlet is on the fast side.

[0149] S5. Consistency analysis

[0150] The deviation of the rolling mill speed ratio of F5 is in the opposite direction to the "incoming material speed deviation ratio" calculated based on the loop quantity, indicating that the control directions are consistent. Both are to reduce the strip flow between F5 and F6, and the absolute value deviation between the two is equal to 6.699%, which is less than 20%, meeting the requirements for judging the consistency of the control target.

[0151]

[0152] S6. Calculate the influence amount of the screwdown deviation on the outlet speed

[0153] Calculate the actual outlet thickness using the actual rolling force, roll gap, and roll diameter through the DeliveryThink model, and then calculate the actual reduction ratio, actual forward slip, forward slip deviation, and the speed deviation caused by the forward slip.

[0154]

[0155] S7. Determine the speed imbalance state and calculate the imbalance ratio

[0156] vFlay = ΔVr × ΔV loop = -3.369 * 3.5947185 = -12.1106066

[0157]

[0158] The calculation results show that the ΔVr speed regulation ratio is greater than 3.5%, meeting the further calculation conditions; vFlay < 0 indicates that the control directions of the speed adjustment and the loop angle adjustment for speed balance are consistent; the absolute value of Diff < 0.2 indicates that the control targets of the speed adjustment and the loop angle adjustment are consistent.

[0159] 1) The actual speed deviation is -3.369%, and the absolute value is greater than 3%;

[0160] 2) The difference between the actual loop angle and the set angle is 6.86, which is greater than 5 degrees;

[0161] 3) The speed change is consistent with the loop control target;

[0162] 4) Caused by roll gap. When the speed change range is -0.00027712199%, which is less than 1%.

[0163] In summary, it is determined that there is a speed imbalance in the F5 stand.

[0164] Calculate the imbalance ratio (%):

[0165]

[0166] Other stands do not meet the imbalance determination, and the imbalance ratio is 0. The imbalance ratios of each stand in the finishing area are as follows:

[0167]

[0168] S8. Optimization of speed control

[0169] In the subsequent setting calculation process, use the speed imbalance ratio to adjust the mill speed to complete the optimization control of speed balance.

[0170] Correction of the set speed for the new coil of strip steel:

[0171]

[0172] Conclusion

[0173] Using the rolling performance of the previous strip steel, after analysis and determination, the speed imbalance ratio is quantified and used to optimize the subsequent strip steel speed setting. In this case, it is calculated from the previous rolling performance that the speed of F5 is too fast, providing a basis for speed optimization for the subsequent strip steel speeds of F1 - F5. The speed optimization and actual rolling data are as follows:

[0174]

[0175] It is verified that the ratio of the subsequent coil setting speed to the actual speed is basically the same, indicating that there is no obvious speed adjustment behavior during threading. Therefore, the balance of the optimized set speed is effectively improved, and the threading stability is enhanced.

[0176] Those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as it is within the scope of the essential spirit of the present invention, changes and modifications to the above - described embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for optimizing the speed balance control during the finishing mill threading process, characterized in that: After the threading of the strip head is completed through the finishing mill setting model, the actual mill rotational speed, rolling force, roll gap, and loop angle data of the finishing mill are collected, and the change in the rotational speed ratio between stands is calculated in combination with the preset rotational speed to determine whether there is a deviation in the mill rotational speed; Combined with the offset of the loop angle, it is judged whether there is an incoming material speed imbalance; Calculate the strip speed change caused by the roll gap change of each stand to judge whether there is a speed imbalance caused by the roll gap change; Comprehensively calculate the imbalance speed ratio and use it for optimizing the subsequent strip setting mill rotational speed.

2. The method for optimizing the speed balance control during the finishing mill threading process according to claim 1, characterized in that: There are 7 stands on the finishing mill, namely F1 stand, F2 stand, F3 stand, F4 stand, F5 stand, F6 stand, and F7 stand; After the threading of the F1 stand to the F7 stand is completed, the actual mill rotational speed, rolling force, roll gap, and loop angle data of the finishing mill collected are sent from L1 to L2, and L2 performs basic processing on the measurement data, determines whether the data is valid, and filters the abnormal data.

3. The method for optimizing the speed balance control during the finishing mill threading process according to claim 2, characterized in that: The mill rotational speed includes the circumferential speed of the work roll of the mill; The rolling force includes the rolling force on the working side of the mill and the rolling force on the drive side of the mill; The roll gap includes the roll gap on the working side of the mill and the roll gap on the drive side of the mill.

4. The method for optimizing the speed balance control during the finishing mill threading process according to claim 3, characterized in that, The specific calculation of the rotational speed ratio includes: Taking the rotational speed of the F7 stand as the reference, calculate the rotational speed ratio Vr of the F1 stand to the F6 stand to the F7 stand.

5. The method for optimizing the speed balance control during the finishing mill threading process according to claim 4, characterized in that, Judging whether there is a deviation in the mill rotational speed specifically includes: By calculating the deviation between the actual rotational speed ratio and the set rotational speed ratio, judge whether there is an abnormal rotational speed situation, and the calculation is as follows: According to the actual rolling speed at the stable position of the strip head, calculate the actual rolling speed Vr post With the set speed Vr pre Deviation ratio ΔVr:

6. The method for optimizing the speed balance control during the finishing mill threading process according to claim 5, characterized in that, Combined with the offset of the loop angle, judging whether there is an incoming material speed imbalance specifically includes: Calculate the loop quantity adjustment based on the set and actual loop angles. When the change in the loop angle is consistent with the speed control target, calculate the loop quantity caused by the change in the loop angle, and then calculate the incoming material speed deviation ratio ΔV loop , and the loop quantity ΔL between each stand is calculated according to the loop angle α and the inherent parameters of the equipment: In the formula, R is the loop arm length, H is the horizontal height of the loop shaft point, and L is the distance between stands; In the formula, Δt is the time taken for the rear stand to bite the steel until the loop completes the loop amount adjustment; Judge whether the control objectives of the loop angle adjustment and the rotational speed adjustment are consistent to judge whether there is an incoming material speed imbalance: vFlay = ΔVr × ΔV loop When vFlay < 0, it means that the incoming material speed deviation is opposite to the direction of the actual rotational speed change; When -0.2 < vDiff < 0.2, it is judged that the control objectives are consistent.

7. The method for optimizing the speed balance control during the finishing mill threading process according to claim 3, characterized in that, Calculating the strip speed change caused by the roll gap change of each stand specifically includes: When there are differences between the set values and actual values of the roll gap and rolling force, the actual exit thickness changes accordingly. Calculate the actual exit thickness newh based on the actual rolling force and roll gap exit , the forward slip coefficient newSlip forward , and the exit speed change rate ΔV gap : newh exit = DeliveryThink(gap, force) In the formula, DeliveryThink is the calculation method of the exit thickness, gap is the actual roll gap, and force is the actual rolling force; newslip forward = FSlip(R, h entry , newh exit ) ΔV gap = newslip forward - slip forward 。 8. The speed balance optimization control method for the rough rolling threading process according to claim 7, characterized in that, it is judged whether the speed imbalance is caused by the roll gap change, and the calculation of the imbalance amount specifically includes: when the following four conditions are simultaneously satisfied, it is determined that the set rotational speed is imbalanced: 1) The deviation of the actual rotational speed ratio is greater than 3%; 2) The difference between the actual loop angle and the set angle is greater than 5 degrees; 3) The rotational speed change is consistent with the loop control target; 4) The amplitude of the speed change caused by the roll gap is less than 1%; The calculation of the imbalance ratio is to calculate the ratio of the speed imbalance amount to the target exit speed:

9. The speed balance optimization control method for the rough rolling threading process according to claim 8, characterized in that, the comprehensive calculation of the imbalance speed ratio and its use for the subsequent strip mill set rotational speed optimization specifically includes: adopting the method of forward proportional drive to use the speed imbalance ratio to adjust the mill rotational speeds of all previous stands to complete the speed balance optimization control; Roll stand rotational speed correction: Where i is the current rack number, n is the last rack number, and newV circle is the corrected rotational speed.

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