Method for optimizing tension setting of cold continuous rolling mill stand

Abstract

The present application relates to a kind of cold continuous rolling mill set rack tension optimization setting method, sequentially include the following steps: obtaining strip parameters and the equipment parameters and rolling process parameters of each rack;Setting the tension optimization coefficient of each rack, load roll gap optimization objective function, iteration calculation number;Unit tension of rack is obtained by calculation;The strip equivalent tension influence coefficient of different sections of each rack is obtained by calculation;According to rolling force calculation model, the rolling force of different sections of each rack is obtained;According to the front slip calculation model, the front slip value of different sections of each rack is obtained;Front slip value, rolling force are sequentially judged, and optimization objective function is calculated, and the optimal tension parameter is determined.The present application can optimize the tension between each rack of cold continuous rolling mill set, thereby reducing the rolling force fluctuation in rolling direction, ensuring the stability of load roll gap in the process of cold continuous rolling production process, thereby realizing the effective control of strip shape.

Description

TECHNICAL FIELD

[0001] The present application relates to a cold continuous rolling production process, in particular to a method for optimizing tension setting of a cold continuous rolling mill stand. BACKGROUND

[0002] In the cold continuous rolling production process, the thickness reduction of the strip is realized by the loaded roll gap between the upper and lower rolls. If the elastic deformation of the strip is ignored, the shape of the contact part of the strip is actually the cross-sectional shape of the strip at the exit of the rolling mill, i.e. the shape of the plate. In short, the control of the shape of the plate and the crown of the plate during cold rolling is actually the control of the shape of the loaded roll gap between the upper and lower rolls.

[0003] During rolling, the deformation heat and friction heat generated during rolling increase with the increase of the rolling pressure, which leads to the increase of the thermal crown, thereby affecting the shape of the loaded roll gap. When the front and rear tensions of the strip change, the rolling force also changes, which causes the change of the thermal crown, and further leads to the instability of the loaded roll gap and the relative instability of the plate shape at the exit of the rolling mill. Therefore, the change of the tension indirectly affects the change of the loaded roll gap in the cold continuous rolling production process. At the same time, the relationship among the rolling force, the rolling speed and the tension is very complex. With the increase of the rolling speed, the rolling force changes differently, and the tension and the rolling force are negatively correlated. Therefore, in the rolling process, the specific influence law of the tension and the rolling speed on the rolling force should be fully considered. Since the rolling speed is of great significance to the yield, adjustment measures are generally not taken. Therefore, in the cold continuous rolling process, it is extremely critical to optimize the tension setting between the stands in the cold continuous rolling mill.

[0004] At present, most of the cold continuous rolling related technologies are based on the role of tension in the cold continuous rolling production process, and propose the basic principles of tension control and the influencing factors of tension. According to the specifications and steel grades of the products, the additional tension under different speeds is calculated to reduce the change of the rolling force in the production process, thereby ensuring the stability of the thickness control. In addition, there are also some technologies that optimize the additional tension method for the instability of the emulsion flow. However, these technologies mainly target the change of the friction force during the speed change, and increase a part of the tension on the basis of the tension, which are mainly aimed at thickness control as the main target, and do not explicitly propose a basic tension optimization method that considers the factors of rolling force, bending force, tension, etc. on the loaded roll gap and front slip. SUMMARY

[0005] The present application aims to provide a cold continuous rolling mill rack tension optimization setting method, which can effectively reduce the rolling force fluctuation along the rolling direction, stabilize the rolling process parameters in the cold continuous rolling production process, effectively control the loaded roll gap of each rack, ensure the strip shape quality, and improve the actual production efficiency and economic benefits by establishing a corresponding optimization tension calculation model, taking the shape control as the target, and comprehensively considering the rolling force, bending force, tension and other factors.

[0006] The present application is implemented as follows:

[0007] A cold continuous rolling mill rack tension optimization setting method, the cold continuous rolling mill set includes several racks; the method comprises the following steps:

[0008] Step one, obtain the strip parameters and the equipment parameters and rolling process parameters of each rack, and divide the strip into N segments along the rolling direction, divide the loaded roll gap into n segments along the roll axis direction, and the number of racks is P;

[0009] Step two, set the tension optimization coefficient of each rack, the optimization target function of the loaded roll gap, the weighting coefficient and the constraint value, the initial value and the limit value of the iteration calculation number;

[0010] Step three, calculate the rack unit tension according to the following formula:

[0011]

[0012] In the formula, 0 x1 is the unit tension at the outlet of the xth rack, σ x1min is the minimum value of the unit tension at the outlet of the xth rack, σ x1max is the maximum value of the unit tension at the outlet of the xth rack, k x is the iteration calculation number of the xth rack, Δδ x is the tension optimization coefficient of the xth rack, σ (x+1)0 is the unit tension at the inlet of the x+1th rack;

[0013] Step four, calculate the strip equivalent tension influence coefficient of each rack segment according to the following formula:

[0014]

[0015] In the formula, ψ xj is the strip equivalent tension influence coefficient of the jth segment of the xth rack, σ0 xj is the unit tension at the inlet of the jth segment of the xth rack, σ1 xj is the unit tension at the outlet of the jth segment of the xth rack, km xjThe average deformation resistance of the strip steel of the jth section of the xth stand, and the calculation coefficients α1, α2 and α3 are different according to the material properties of the strip steel;

[0016] Step five, the rolling force of each section of each stand is obtained according to the rolling force calculation model;

[0017] Step six, the front slip value of each section of each stand is obtained according to the front slip calculation model;

[0018] Step seven, the loaded roll gap of each section of each stand is calculated according to the following formula:

[0019] Gap xjw

[0020] =f(P xj ,crIStp xjw ,crOStp xjw ,σ0 xj ,σ1 xj ,wrshp x ,imrshp x ,brshp x ,wrFb x ,imrFb x ,imrSht x ,B,n)

[0021] In the formula, Gap xjw is the loaded roll gap of the wth section of the jth section of the xth stand, P xj is the rolling force of the jth section of the xth stand, crIStp xjw is the incoming crown of the wth section of the jth section of the xth stand, crOStp xjw is the target crown of the wth section of the jth section of the xth stand, σ0 xj is the inlet unit tension of the jth section of the xth stand, σ1 xj is the outlet unit tension of the jth section of the xth stand, wrshp x is the work roll profile distribution curve of the xth stand, imrshp x is the intermediate roll profile distribution curve of the xth stand, brshp x is the backup roll profile distribution curve of the xth stand, wrFb x is the work roll bending force of the xth stand, imrFb x is the intermediate roll bending force of the xth stand, imrSht x is the intermediate roll displacement of the xth stand, B is the width of the strip steel, and n is the number of transverse sections;

[0022] Step eight, it is judged whether the front slip value is within the numerical constraint range, if yes, step nine is entered, and if not, the tension is adjusted, the number of iteration calculations is accumulated, and step three is entered;

[0023] Step nine, judging whether the rolling force of each stand longitudinal different section is in the numerical constraint range, if yes, entering step ten, if no, adjusting the tension, accumulating the iteration calculation times and entering step three;

[0024] Step ten, calculating the optimization target function value of each stand according to the loaded roll gap optimization target function, and judging whether the optimization target function value is less than the constraint value, if yes, taking the tension value of each stand of this calculation as the optimal tension parameter and ending the calculation, if no, then judging whether the optimization target function value of this time is the minimum value, if yes, recording the optimization target function value and the corresponding unit tension value of each stand, if no, not recording and judging whether the iteration calculation times reaches the limit value, if the iteration calculation times does not reach the limit value, adjusting the tension, accumulating the iteration calculation times and entering step three, if the iteration calculation times reaches the limit value, taking the recorded optimization target function value and the corresponding unit tension value of each stand as the optimal tension parameter.

[0025] In the step two, the formula of the loaded roll gap optimization target function is as follows:

[0026]

[0027] In the formula, G(X) is the optimization target function, G(X)1 is the average value of the extreme difference of the loaded roll gap in each longitudinal section of each transverse section of each stand, G(X)2 is the average value of the standard deviation of the loaded roll gap in each longitudinal section of each transverse section of each stand, ξ is the weighting coefficient of the optimization target function, Gap xjw is the loaded roll gap of the jth section of the xth stand.

[0028] In the step five, the formula of the rolling force calculation model is as follows:

[0029]

[0030] In the formula, P xj is the rolling force of the jth section of the xth stand, km xj is the average deformation resistance of the strip of the jth section of the xth stand, ψ xj is the equivalent tension influence coefficient of the strip of the jth section of the xth stand, B is the width of the strip, R′ xj is the flattening radius of the work roll of the jth section of the xth stand, Δh xj is the thickness variation of the strip of the jth section of the xth stand, μ x is the friction coefficient of the xth stand, ε xj is the deformation of the jth section of the xth stand, h xj is the exit thickness of the strip of the jth section of the xth stand.

[0031] In the step six, the formula of the forward slip calculation model is as follows:

[0032]

[0033] In the formula, S xj is the front slip value of the xth stand jth section, h xj is the strip outlet thickness of the xth stand jth section, Δh xj is the strip thickness change of the xth stand jth section, μ x is the friction coefficient of the xth stand, P xj is the rolling force of the xth stand jth section, R' xj is the work roll flattening radius of the xth stand jth section, σ0 xj is the inlet unit tension of the xth stand jth section, σ1 xj is the outlet unit tension of the xth stand jth section.

[0034] In the step two, the cumulative value of the iteration calculation times is 1.

[0035] The cold rolling mill group stand tension optimization setting method of the present application is based on the strip parameters and the equipment parameters and rolling process parameters of each stand of the cold rolling mill group, fully considers the reason that the rolling force inter-roll distribution fluctuation of the cold rolling mill group leads to insufficient plate shape quality, studies the influence of rolling speed, rolling force, bending force, tension and other factors on the dynamic roll gap and the plate shape, establishes a corresponding optimized tension calculation model, and makes the on-load roll gap fluctuation very small. Thus, the inter-stand tension of the cold rolling mill group is optimized through the inter-stand tension optimization model of the cold rolling mill group, thereby reducing the rolling force inter-roll distribution fluctuation, ensuring the stability of the dynamic roll gap in the cold rolling process and the plate shape quality. The present application realizes the optimization of the cold rolling mill group tension based on the theoretical analysis and in combination with the actual production situation, can accurately control the on-load roll gap, thereby further improving the strip plate shape quality and helping the stable production of the cold rolling mill group.

[0036] Compared with the prior art, the present application has the following beneficial effects: the rolling force and the on-load roll gap fluctuation are reduced by optimizing the cold rolling mill group tension, the plate shape quality of the strip in the cold rolling production process is ensured, and the production efficiency, product quality and economic benefit are improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The figure is a flow chart of the cold rolling mill group stand tension optimization setting method of the present application. DETAILED DESCRIPTION

[0038] The present application will be further described below in combination with specific embodiments.

[0039] Referring to Figure 1 A cold rolling mill group stand tension optimization setting method, comprising the following steps:

[0040] Step one, obtaining the strip parameters and the equipment parameters and rolling process parameters of each stand.

[0041] The tandem cold rolling mill can adopt four to six stands, i.e. P = 4-6, and divide the strip into N segments along the longitudinal direction (i.e. the rolling direction) and divide the loaded roll gap into n segments along the transverse direction (i.e. the work roll axis direction). Thus, x = 1, 2, …, P, j = 1, 2, …, N, w = 1, 2, …, n.

[0042] The strip parameters mainly include the strip width and the strip crown.

[0043] The equipment parameters mainly include the work roll diameter, the intermediate roll diameter, the backup roll diameter, the work roll profile distribution curve, the intermediate roll profile distribution curve, the backup roll profile distribution curve, the work roll barrel length, the intermediate roll barrel length, and the backup roll barrel length.

[0044] The rolling process parameters mainly include the friction coefficient of the xth stand, the average deformation resistance of the strip in the jth segment of the xth stand, the inlet thickness and the outlet thickness of the strip in the jth segment of the xth stand, the stand tension parameters, the maximum rolling force, the maximum critical value of the forward slip, the flattening radius of the work roll, and the thickness variation of the strip in the jth segment of the xth stand. The friction coefficient of the stand is related to the rolling speed, and the thickness variation of the strip in the jth segment of the xth stand is obtained from the difference between the inlet thickness and the outlet thickness of the strip in the jth segment of the xth stand.

[0045] Specifically, the stand tension parameters include the maximum value of the outlet unit tension, the minimum value of the outlet unit tension, the maximum value of the inlet unit tension, and the minimum value of the inlet unit tension.

[0046] Step two, setting the tension optimization coefficient of each stand, establishing the loaded roll gap optimization objective function, setting the weighting coefficient and the constraint value of the optimization objective function, and setting the initial value and the limit value of the iteration calculation number.

[0047] Specifically, the formula of the loaded roll gap optimization objective function is as follows:

[0048]

[0049] In the formula, G(X) is the optimization objective function, G(X)1 is the average value of the extreme value difference of the loaded roll gap of each segment in the transverse direction and each segment in the longitudinal direction of each stand, G(X)2 is the average value of the standard deviation of the loaded roll gap of each segment in the transverse direction and each segment in the longitudinal direction of each stand, ξ is the weighting coefficient of the optimization objective function, Gap xjw is the loaded roll gap of the jth segment and the wth segment of the xth stand.

[0050] Step three, the stand unit tension is calculated according to the following formula:

[0051]

[0052] wherein 0 < x < (P-1), σ x1 is the unit tension at the exit of the xth stand, σ x1min is the minimum value of the unit tension at the exit of the xth stand, σ x1max is the maximum value of the unit tension at the exit of the xth stand, k x is the iteration number of the xth stand, Δδ x is the tension optimization coefficient of the xth stand, σ (x+1)0 is the unit tension at the entrance of the x+1th stand.

[0053] Step four, the strip equivalent tension influence coefficient of each stand is calculated according to the following formula:

[0054]

[0055] wherein ψ xj is the strip equivalent tension influence coefficient of the jth segment of the xth stand, σ0 xj is the unit tension at the entrance of the jth segment of the xth stand (i.e. the unit tension at the entrance of the xth stand), σ1 xj is the unit tension at the exit of the jth segment of the xth stand (i.e. the unit tension at the exit of the xth stand), km xj is the average deformation resistance of the strip of the jth segment of the xth stand, and α1, α2, α3 are calculation coefficients which are different according to the material properties of the strip.

[0056] Step five, the rolling force of each segment of the stand is obtained according to the rolling force calculation model, and the formula of the rolling force calculation model is as follows:

[0057]

[0058] wherein P xj is the rolling force of the jth segment of the xth stand, km xj is the average deformation resistance of the strip of the jth segment of the xth stand, ψ xj is the strip equivalent tension influence coefficient of the jth segment of the xth stand, B is the width of the strip, R ′ xj is the flattening radius of the work roll of the jth segment of the xth stand, Δh xj is the thickness variation of the strip of the jth segment of the xth stand, μ x is the friction coefficient of the xth stand, ε xj is the deformation of the jth segment of the xth stand, h xj is the exit thickness of the strip of the jth segment of the xth stand. Wherein Δh xj is obtained from the difference between the entry thickness of the strip and the exit thickness of the strip, ε xj is the proportional value, i.e. the ratio of Δh xj and the entry thickness of the strip.

[0059] Step six, according to the front slip calculation model of each rack different segment of the front slip value, the formula of the front slip calculation model is as follows:

[0060]

[0061] In the formula, S xj is the front slip value of the x rack j segment, h xj is the strip outlet thickness of the x rack j segment, Δh xj is the strip thickness change of the x rack j segment, μ x is the friction coefficient of the x rack, P xj is the rolling force of the x rack j segment, R ′ xj is the flattening radius of the work roll of the x rack j segment, σ0 xj is the inlet unit tension of the x rack j segment, σ1 xj is the outlet unit tension of the x rack j segment.

[0062] Step seven, according to the incoming crown of the strip, the target crown and the roll deformation principle, the load roll gap of each rack different segment is calculated, and the calculation formula is as follows:

[0063] Gap xjw

[0064] = f (P xj , crIStp xjw , crOStp xjw , σ0 xj , σ1 xj , wrshp x , imrshp x , brshp x , wrFb x , imrFb x , imrSht x , B, n)

[0065] In the formula, Gap xjw is the load roll gap of the x rack j segment w segment, P xj is the rolling force of the x rack j segment, crIStp xjw is the incoming crown of the strip x rack j segment w segment, crOStp xjw is the target crown of the strip x rack j segment w segment, σ0 xj is the inlet unit tension of the x rack j segment, σ1 xj is the outlet unit tension of the x rack j segment, wrshp x is the work roll profile distribution curve of the x rack, imrshp xis the roll shape distribution curve of the intermediate roll in the xth stand, brshp x is the roll shape distribution curve of the support roll in the xth stand, wrFb x is the bending force of the work roll in the xth stand, imrFb x is the bending force of the intermediate roll in the xth stand, imrSht x is the shifting amount of the intermediate roll in the xth stand, B is the strip width, and n is the number of transverse sections.

[0066] Step eight, it is judged whether the front slip value is within the numerical constraint range. If yes, step nine is entered. If no, the tension is adjusted, the number of iteration calculations is accumulated, and step three is entered.

[0067] Step nine, it is judged whether the rolling force of each stand in different longitudinal sections is within the numerical constraint range. If yes, step ten is entered. If no, the tension is adjusted, the number of iteration calculations is accumulated, and step three is entered.

[0068] Step ten, the optimization objective function value of each stand is calculated according to the loaded roll gap optimization objective function, and it is judged whether the optimization objective function value is less than the constraint value. If the optimization objective function value is less than the constraint value, the tension value of each stand in this calculation is taken as the optimal tension parameter, and the calculation is ended. If the optimization objective function value is greater than or equal to the constraint value, it is then judged whether the optimization objective function value in this calculation is the minimum value. If the optimization objective function value in this calculation is the minimum value (if it is the first calculation, the optimization objective function value obtained in this calculation is recorded), the optimization objective function value and the corresponding unit tension value of each stand are recorded. If the optimization objective function value in this calculation is greater than the minimum value recorded, no recording is performed, and it is judged whether the number of iteration calculations reaches the limit value. If the number of iteration calculations does not reach the limit value, the tension is adjusted, the number of iteration calculations is accumulated, and step three is entered. If the number of iteration calculations reaches the limit value, the optimization objective function value (i.e., the minimum value of the optimization objective function) and the corresponding unit tension value of each stand recorded are taken as the optimal tension parameter.

[0069] Example one

[0070] A five-stand cold continuous rolling mill is adopted, the first three stands are four-roll rolling mills, and the last two stands are six-roll rolling mills. The steel grade is AP1060A1, the outlet width is 1015 mm, the outlet thickness is 306 mm, the inlet thickness is 2260 mm, the head part convexity of the strip is 38 μm, the middle part convexity of the strip is 32 μm, and the tail part convexity of the strip is 34 μm.

[0071] According to step one, the strip is divided into N=100 sections along the longitudinal direction, and the loaded roll gap is divided into n=5 sections along the transverse direction.

[0072] The device parameters of each stand are obtained, specifically:

[0073] The work roll diameters d of the five standsw = 430 mm, middle roll diameter d of rear 2 stands c = 505 mm, support roll diameter d of 5 stands b = 1295 mm, maximum rolling force P max = 18000 KN, work roll body length of front 3 stands 1510 mm, work roll body length of rear 2 stands 1350 mm, middle roll body length of rear 2 stands 1510 mm, support roll body length 1350 mm.

[0074] Obtain the rolling process parameters of each stand, specifically:

[0075] Stand number x = 1, 2, 3, 4, 5;

[0076] The entry thickness of the strip is {2.268, 1.452, 0.877, 0.557, 0.386} mm;

[0077] The exit thickness of the strip is {1.452, 0.877, 0.557, 0.386, 0.306} mm;

[0078] The reduction is thus {0.816, 0.575, 0.32, 0.171, 0.08} mm;

[0079] The average deformation resistance of the strip is {619, 766, 850, 967, 998} MPa;

[0080] The numerical constraint range of the front slip value is

[0081] {(0.01, 0.12), (0.005, 0.12), (0.003, 0.10), (0.003, 0.08), (0.001, 0.05)};

[0082] The minimum value of the entry unit tension σ x0min = {50, 110, 120, 135, 144} MPa;

[0083] The maximum value of the entry unit tension σ x0max = {100, 210, 220, 270, 180} MPa;

[0084] The minimum value of the exit unit tension σ x1min = {110, 120, 135, 144, 40} MPa;

[0085] The maximum value of the exit unit tension σ x1max = {210, 220, 270, 180, 100} MPa;

[0086] friction coefficient μ x ={0.055,0.029,0.02,0.012,0.013}.

[0087] Take j=1, that is, the average deformation resistance km of the strip in the first longitudinal segment during the rolling process. x1 ={619,766,850,967,998}, unit is MPa; the flattening radius R′ of the work roll in the first longitudinal section. x1 ={217.4,216.6,215.95,216.65,215.8}, in mm.

[0088] According to step two, the model compensation coefficient is initialized to 0.05, the initial value of the number of iterations is set to 1, the limit value is 5000 and the cumulative value is 1, the weighting coefficient ξ of the loaded roll gap optimization objective function is 0.3, and the constraint value of the optimization objective function G(X) is 0.001.

[0089] Based on step three, the calculation results of the unit tension for each frame are as follows:

[0090] The inlet unit tension is σ x0 ={50.05,110.05,120.05,135.05,144.05}, unit is MPa;

[0091] The unit tension at the outlet is σ x1 ={110.05,120.05,135.05,144.05,40.05}, in MPa.

[0092] According to step four, the calculation results of the equivalent tension influence coefficient of the strip in the first longitudinal segment of each frame are as follows:

[0093] ψ x1 ={0.944,0.864,0.856,0.863,0.831}.

[0094] Based on step five, the calculation results of the rolling force in the first longitudinal segment of each stand are as follows:

[0095] P x1 ={9906,10103,7773,7902,6431}, unit is kN.

[0096] Based on step six, the calculation results of the forward slip value of the first longitudinal segment of each frame are as follows:

[0097] S xj ={0.023,0.0178,0.016,0.009,0.0031}.

[0098] According to step seven, the calculation results of the loaded roll gap of each stand in the different segments (i.e. w = 1 ~ 5) of the first segment in the longitudinal direction are as follows:

[0099]

[0100] Thus, all the loaded roll gap values are sequentially calculated, i.e. the loaded roll gap values of 100 segments in the longitudinal direction and 5 segments in the transverse direction.

[0101] According to steps eight to ten, it is firstly judged whether the forward slip value is within the numerical constraint range, and then it is judged whether the rolling force of each stand in the different segments in the longitudinal direction is within the numerical constraint range, and then the optimization objective function of each stand is calculated, i.e. G(X) = 1.395. Since G(X) is greater than the constraint value 0.001 and it is the first calculation, the calculation result is recorded as the minimum value and the corresponding unit tension value of each stand is recorded. Then, it is judged whether the iteration calculation number reaches the limit value and the result is no, and then the iteration calculation number is accumulated and step three is entered for the second calculation, and the following results are obtained:

[0102] The inlet unit tension is σ0 x = {50.1, 110.1, 120.1, 135.1, 144.1} in MPa;

[0103] The outlet unit tension is σ1 x = {110.1, 120.1, 135.1, 144.1, 40.1} in MPa.

[0104] According to step four, the calculation results of the strip equivalent tension influence coefficient of each stand in the first segment in the longitudinal direction are as follows:

[0105] ψ x1 = {0.944, 0.860, 0.863, 0.863, 0.830}.

[0106] According to step five, the calculation results of the rolling force of each stand in the first segment in the longitudinal direction are as follows:

[0107] P x1 = {9902, 10099, 7770, 7899, 6429} in KN.

[0108] According to step six, the calculation results of the forward slip value of each stand in the first segment in the longitudinal direction are as follows:

[0109] S xj = {0.024, 0.0178, 0.016, 0.010, 0.0031}.

[0110] According to step seven, the calculation results of the loaded roll gap of each stand in the different segments (i.e. w = 1 ~ 5) of the first segment in the longitudinal direction are as follows:

[0111]

[0112] Thus, all the loaded roll gap values are calculated in turn, i.e. the loaded roll gap values of 100 segments in the longitudinal direction and 5 segments in the transverse direction.

[0113] According to steps eight to ten, it is firstly judged whether the front slip value is within the numerical constraint range, and then it is judged whether the rolling force of each stand in different longitudinal segments is within the numerical constraint range, and then the optimization objective function of each stand is calculated, i.e. G(X) = 1.392. Since G(X) is greater than the constraint value 0.001 and less than the previously saved optimization objective function value, the calculation result is recorded as the minimum value and the corresponding unit tension value of each stand is recorded. Then, it is judged whether the iteration calculation number reaches the limit value, and the result is no, then the iteration calculation number is accumulated and step three is entered, and the following results are obtained through multiple loop calculations:

[0114] The optimal inlet unit tension of each stand is {53.3, 121.7, 135.1, 140.7, 169.2}, unit: MPa;

[0115] The optimal outlet unit tension of each stand is {121.7, 135.1, 140.7, 169.2, 44.2}, unit: MPa.

[0116] Example two

[0117] A five-stand cold continuous rolling mill is adopted, the first three stands are four-roll mills, and the last two stands are six-roll mills. The steel grade is AQ0510B1, the outlet width is 841 mm, the outlet thickness is 0.688, the inlet thickness is 2.71 mm, the head part crown of the strip is 43 μm, the middle part crown of the strip is 41 μm, and the tail part crown of the strip is 39 μm.

[0118] According to step one, the strip is divided into N = 100 segments along the longitudinal direction, and the loaded roll gap is divided into n = 5 segments along the transverse direction.

[0119] The device parameters of each stand are obtained, specifically:

[0120] The work roll diameter d of the five stands w = 430 mm, the intermediate roll diameter d of the last two stands c = 505 mm, the support roll diameter d of the five stands b = 1295 mm, the maximum rolling force P max = 194000 KN, the work roll body length of the first three stands is 1510 mm, the work roll body length of the last two stands is 1350 mm, the intermediate roll body length of the last two stands is 1510 mm, and the support roll body length is 1350 mm.

[0121] Obtain the rolling process parameters of each stand, specifically:

[0122] The stand number x = 1, 2, 3, 4, 5;

[0123] The entry thickness of the strip is {2.707, 1.961, 1.331, 0.953, 0.702} mm;

[0124] The exit thickness of the strip is {1.961, 1.3311, 0.953, 0.702, 0.688} mm;

[0125] Thus, the reduction is {0.746, 0.63, 0.378, 0.251, 0.014} mm;

[0126] The average deformation resistance of the strip is {582, 701, 774, 825, 839} MPa;

[0127] The numerical constraint range of the front slip value is

[0128] {(0.01, 0.12), (0.005, 0.12), (0.003, 0.10), (0.003, 0.08), (0.001, 0.05)};

[0129] The minimum value of the entry unit tension σ x0min = {50, 110, 120, 135, 144} MPa;

[0130] The maximum value of the entry unit tension σ x0max = {100, 210, 220, 270, 180} MPa;

[0131] The minimum value of the exit unit tension σ x1min = {110, 120, 135, 144, 40} MPa;

[0132] The maximum value of the exit unit tension σ x1max = {210, 220, 270, 180, 100} MPa;

[0133] The friction coefficient μ x = {0.053, 0.024, 0.014, 0.013, 0.173}.

[0134] Take j = 1, that is, the average deformation resistance km x1 = {582, 701, 774, 825, 839} MPa of the strip in the longitudinal first section during rolling; the working roll flattening radius R′ of the longitudinal first section x1= {215.84, 216.8, 215.95, 216.85, 215.8} in mm.

[0135] According to Step Two, the model compensation coefficient is initialized as 0.05, the initial value of the iteration calculation times is set as 1, the limit value is set as 4000 and the cumulative value is set as 1, the weighting coefficient of the loaded roll gap optimization objective function is set as 0.4, and the constraint value of the optimization objective function G(X) is set as 0.05.

[0136] According to Step Three, the calculation results of the unit tension of each stand are as follows:

[0137] The inlet unit tension is σ x0 = {50.05, 110.05, 120.05, 135.05, 144.05} in MPa.

[0138] The outlet unit tension is σ x1 = {110.05, 120.05, 135.05, 144.05, 40.05} in MPa.

[0139] According to Step Four, the calculation results of the strip equivalent tension influence coefficient of the first segment in the longitudinal direction of each stand are as follows:

[0140] ψ x1 = {0.941, 0.846, 0.849, 0.839, 0.799}.

[0141] According to Step Five, the calculation results of the rolling force of the first segment in the longitudinal direction of each stand are as follows:

[0142] P x1 = {6843, 6599, 5521, 4799, 4930} in KN.

[0143] According to Step Six, the calculation results of the front slip value of the first segment in the longitudinal direction of each stand are as follows:

[0144] S xj = {0.028, 0.019, 0.007, 0.012, 0.0024}.

[0145] According to Step Seven, the calculation results of the loaded roll gap of each stand in the different segments (i.e. w = 1-5) in the first segment in the longitudinal direction are as follows:

[0146]

[0147] Thus, all the loaded roll gap values are sequentially calculated, including the loaded roll gap values of 100 segments in the longitudinal direction and 5 segments in the transverse direction.

[0148] According to steps eight to ten, first, it is determined whether the forward slip value is within the numerical constraint range, then it is determined whether the rolling force of each stand longitudinal different section is within the numerical constraint range, and then the optimization objective function of each stand is calculated, i.e. G(X) = 1.518. Since G(X) is greater than the constraint value and is the first calculation, the calculation result is recorded as the minimum value and the corresponding unit tension value of each stand is recorded. Then, it is determined whether the iteration calculation number reaches the limit value, and the result is no, then the iteration calculation number is accumulated and step three is entered for the second calculation, and the following results are obtained:

[0149] The inlet unit tension is σ0 x = {50.1, 110.1, 120.1, 135.1, 144.1} MPa;

[0150] The outlet unit tension is σ1 x = {110.1, 120.1, 135.1, 144.1, 40.1} MPa.

[0151] According to step four, the calculation results of the strip equivalent tension influence coefficient of each stand longitudinal first section are as follows:

[0152] ψ x1 = {0.941, 0.847, 0.850, 0.839, 0.799}.

[0153] According to step five, the calculation results of the rolling force of each stand longitudinal first section are as follows:

[0154] P x1 = {6846, 6601, 5523, 4802, 4932} KN.

[0155] According to step six, the calculation results of the forward slip value of each stand longitudinal first section are as follows:

[0156] S xj = {0.028, 0.019, 0.006, 0.011, 0.0024}.

[0157] According to step seven, the calculation results of the loaded roll gap of each stand in the longitudinal first section (i.e. w = 1-5) are as follows:

[0158]

[0159] Thus, all the loaded roll gap values are calculated in turn, i.e. the loaded roll gap values of 100 longitudinal sections and 5 transverse sections.

[0160] According to steps eight to ten, firstly, it is judged whether the front slip value is in the numerical constraint range, then it is judged whether the rolling force of each stand longitudinal different section is in the numerical constraint range, and then the optimization objective function of each stand is calculated, i.e. G(X)=1.408. Since G(X) is greater than the constraint value 0.001 and less than the previously saved optimization objective function value, the calculation result is recorded as the minimum value and the corresponding unit tension value of each stand is recorded. Then, it is judged whether the iteration calculation number reaches the limit value and the result is no, then the iteration calculation number is accumulated and step three is entered, and the following results are obtained through multiple loop calculations:

[0161] The optimal inlet unit tension of each stand is {59.3, 118.1, 125.6, 135.5, 145.3}, unit: MPa;

[0162] The optimal outlet unit tension of each stand is {118.1, 125.6, 135.5, 145.3, 45.8}, unit: MPa.

[0163] The cold continuous rolling mill stand tension optimization setting method optimizes the inlet unit tension and outlet unit tension of the stand for the purpose of controlling the loaded roll gap, so that the shape of the loaded roll gap in the cold continuous rolling process is effectively controlled, the rolling process is more stable, and the strip shape quality is significantly improved, which has a positive effect on the cold continuous rolling process production and its on-site economic benefits.

[0164] The above is only a preferred embodiment of the present application, and is not used to limit the protection scope of the present application, therefore, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for optimizing tension setting of stands of a tandem cold rolling mill, the tandem cold rolling mill comprising a plurality of stands; characterized in that: The method comprises the following steps: Step one, obtaining the strip steel parameters and the equipment parameters and rolling process parameters of each stand, and dividing the strip steel into N segments along the rolling direction and dividing the load roll gap into n segments along the roll axis direction, and the number of stands is P; Step two, setting the tension optimization coefficient of each stand, the load roll gap optimization objective function and its weighting coefficient and constraint value, the initial value and limit value of the iteration calculation number; Step three, calculating the stand unit tension according to the following formula: where 0 < x < (P-1), σ x1 is the unit tension at the exit of the xth stand, σ x1min is the minimum value of the unit tension at the exit of the xth stand, σ x1max is the maximum value of the unit tension at the exit of the xth stand, k x is the number of iterations for the xth stand, Δδ x is the tension optimization coefficient for the xth stand, σ (x+1)0 is the unit tension at the entrance of the x+1th stand; Step four, calculating the strip equivalent tension influence coefficient of each stand segment according to the following formula: In the formula, ψ xj is the equivalent tension influence coefficient of the jth section of the xth stand, σ0 xj is the inlet unit tension of the jth section of the xth stand, σ1 xj is the outlet unit tension of the jth section of the xth stand, km xj is the average deformation resistance of the jth section of the xth stand, α1, α2, α3 are calculation coefficients which are different according to the material properties of the strip Step five, obtaining the rolling force of each stand segment according to the rolling force calculation model; Step six, obtaining the forward slip value of each stand segment according to the forward slip calculation model; Step seven, calculating the load roll gap of each stand segment according to the following formula: Gap xjw = f(P xj , crIStp xjw , crOStp xjw , σ0 xj , σ1 xj , wrshp x , imrshp x , brshp x , wrFb x , imrFb x , imrSht x , B, n) In the formula, Gap xjw is the load roll gap of the xth stand jth section wth section, P xj is the rolling force of the xth stand jth section, crIStp xjw is the incoming crown of the strip xth stand jth section wth section, crOStp xjw is the target crown of the strip xth stand jth section wth section, σ0 xj is the inlet unit tension of the xth stand jth section, σ1 xj is the outlet unit tension of the xth stand jth section, wrshp x is the working roll profile distribution curve of the xth stand, imrshp x is the intermediate roll profile distribution curve of the xth stand, brshp x is the backup roll profile distribution curve of the xth stand, wrFb x is the bending force of the working roll of the xth stand, imrFb x is the bending force of the intermediate roll of the xth stand, imrSht x is the intermediate roll displacement of the xth stand, B is the strip width, and n is the number of transverse sections. Step eight, judging whether the forward slip value is within the numerical constraint range, if yes, entering step nine, and if not, adjusting the tension, accumulating the iteration calculation number and entering step three; Step nine, judging whether the rolling force of each stand longitudinal segment is within the numerical constraint range, if yes, entering step ten, and if not, adjusting the tension, accumulating the iteration calculation number and entering step three; Step ten, calculating the optimization objective function value of each stand according to the load roll gap optimization objective function, and judging whether the optimization objective function value is less than the constraint value; if the optimization objective function value is less than the constraint value, taking the tension value of each stand in this calculation as the optimal tension parameter and ending the calculation; if the optimization objective function value is greater than or equal to the constraint value, then judging whether the optimization objective function value is the minimum value; If the optimization objective function value is the minimum value, recording the optimization objective function value and the corresponding unit tension value of each stand; if the optimization objective function value is not the minimum value, not recording and judging whether the iteration calculation number reaches the limit value; if the iteration calculation number does not reach the limit value, adjusting the tension, accumulating the iteration calculation number and entering step three; if the iteration calculation number reaches the limit value, taking the recorded optimization objective function value and the corresponding unit tension value of each stand as the optimal tension parameter.

2. The method for optimizing tension setting of a cold tandem mill stand according to claim 1, characterized in that: In the step two, the formula of the load roll gap optimization objective function is as follows: In the formula, G(X) is an optimization objective function, G(X)1 is an average value of the extreme difference of the loaded roll gap in each section in the transverse direction and in each section in the longitudinal direction of each stand, G(X)2 is an average value of the standard deviation of the loaded roll gap in each section in the transverse direction and in each section in the longitudinal direction of each stand, ξ is a weighting coefficient of the optimization objective function, Gap xjw is the loaded roll gap of the xth stand, the jth section and the wth section.

3. The method of tension optimization setting for a cold tandem mill stand according to claim 1, characterized in that: In the step five, the formula of the rolling force calculation model is as follows: wherein P xj is the rolling force of the xth stand jth segment, km xj is the average deformation resistance of the strip of the xth stand jth segment, ψ xj is the equivalent tension influence coefficient of the strip of the xth stand jth segment, B is the strip width, R' xj is the flattening radius of the work roll of the xth stand jth segment, Δh xj is the thickness variation of the strip of the xth stand jth segment, μ x is the friction coefficient of the xth stand, ε xj is the deformation of the xth stand jth segment, h xj is the strip exit thickness of the xth stand jth segment.

4. The method of tension optimization setting for a cold tandem mill stand according to claim 1, characterized in that: In the step six, the formula of the forward slip calculation model is as follows: where S xj is the front slip value of the jth segment of the xth stand, h xj is the strip exit thickness of the jth segment of the xth stand, Δh xj is the strip thickness change of the jth segment of the xth stand, μ x is the friction coefficient of the xth stand, P xj is the rolling force of the jth segment of the xth stand, R' xj is the work roll flattening radius of the jth segment of the xth stand, σ0 xj is the entry unit tension of the jth segment of the xth stand, σ1 xj is the exit unit tension of the jth segment of the xth stand.

5. The method of tension optimization setting for a cold tandem mill stand according to claim 1, characterized in that: In the step two, the accumulated value of the iteration calculation number is 1.

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