A method for setting rolling force and rolling torque in the full deformation zone of cold rolling of steel strip

Abstract

The present invention belongs to the technical field of rolling production, and particularly relates to a method for setting rolling force and rolling torque in the full deformation zone of strip cold rolling. The method mainly includes the following steps: S1: Determine rolling parameters; S2: Divide the deformation zone; S3: Calculate the entrance thickness of the plastic deformation zone and the exit thickness of the plastic deformation zone; S4: Calculate the neutral angle parameter; S5: Calculate the total rolling force per unit width in the rolling deformation zone; S6: Calculate the torque per unit width; S7: Set the rolling force and rolling torque in the rolling process according to the finally obtained calculated values of the total rolling force per unit width in the rolling deformation zone and the calculated value of the torque per unit width. In the calculation process of the method of the present invention, the difference in rolling pressure between the plastic deformation zone and the elastic deformation zone is considered and distinguished, the influences of the rolling plastic zone and the elastic deformation zone are comprehensively considered, and the calculation error value of the rolling force setting is within 8%.

Description

Technical Field

[0001] The present invention belongs to the technical field of rolling production, and particularly relates to a method for setting rolling force and rolling torque in the whole deformation zone of cold rolling of steel strips. Background Art

[0002] Rolling force is an important parameter for formulating rolling processes during the steel strip rolling process. It is particularly important to quickly and accurately predict the rolling force during the steel strip rolling process. The rolling process automation system realizes the setting and control of the roll gap and rolling speed during the rolling process according to the set value of the rolling force. With the development of strip production technology and the improvement of product thickness accuracy and shape quality requirements, as the key and fundamental requirements for producing qualified steel strips, a reasonable rolling force calculation model and a high-precision model directly affect the steel strip thickness control and shape quality, and are the basis for the automatic control of steel strips.

[0003] The Chinese invention patent with the application number 201510423680.2 discloses "a calculation method for mutual iteration of rolling force and rolling temperature". This invention comprehensively considers the coupling effects among rolling force, rolling temperature, and flattening radius, and aims to simultaneously improve the prediction performance of the rolling force and rolling temperature models through numerical iteration. The Chinese invention patent with the application number 201911045319.5 discloses "a calculation method for cold rolling strip rolling force". By using on-site actual data, the parameters of the deformation resistance model and the friction model are optimized by the least square method to achieve the purpose of improving the prediction effect of the rolling force model and accurately guiding production. The Chinese invention patent with the application number 202011284055.1 discloses "a method for predicting the rolling force and the thickness of each layer of a cold-rolled metal composite plate". The rolling force and the thickness of each layer of the bimetal composite plate are calculated by calculating the rolling force when the soft metal and hard metal slabs are rolled separately as equivalent single plates.

[0004] The Chinese invention patent with the application number 201811435556.8 discloses "A rolling force optimization method and device". Aiming at the problem that the deviation of the rolling force setting value is relatively large for some specifications of steel strips due to the small amount of rolling samples, the expected correction coefficient of the actual value and the setting value of the rolling force and the neural network coefficient are re-corrected to obtain the final target rolling force setting. The Chinese invention patent with the application number 201911331771.8 discloses "A control method based on an offline adaptive optimized rolling force model". By adjusting the relevant parameters of the deformation resistance and the rolling force compensation coefficient, etc., this method keeps the rolling force adaptive coefficient Zp near 1.0, providing a new idea for the optimization of the rolling force model. The Chinese invention patent with the application number 202110070446.1 discloses a "rolling force prediction method integrating theoretical model and big data model". This method establishes a BP neural network model based on actual production data to compensate for the prediction error of the rolling force theoretical model, inheriting both the structure of the theoretical model and the accuracy of the neural network model.

[0005] The rolling force setting in the above patents is based on the traditional Hill model and the adaptive correction model, ignoring the influence of the elastic zone, or simplifying the elastic zone using the Ford model. At present, no method for setting the rolling force and rolling torque in the full deformation zone of the plastic and elastic zones of steel strip rolling has been seen. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention proposes a method for setting the rolling force and rolling torque in the full deformation zone of cold rolling of steel strips. The rolling force and rolling torque models established in the present invention for the full cold rolling deformation zone adopt the following basic assumptions:

[0007] (1) The width of the steel strip is much larger than the contact arc length. Except for the narrow areas near both edges, it can basically be regarded as a plane deformation problem.

[0008] (2) After elastic deformation, the roll still remains circular, and the flattened radius is denoted as R'.

[0009] (3) The friction coefficient μ is a constant within the entire contact arc and conforms to Coulomb's friction law.

[0010] (4) The normal compressive stress is approximately equal to the compressive stress in the vertical direction.

[0011] (5) For a point on the contact arc between the steel strip and the roll, let the radian between it and the roll center line on the contact arc (contact arc radian) be Because The value is usually small, so there is

[0012] Such as Figure 1As shown in the figure, R′ is the flattened radius of the roll. Taking the center line of the two rolls as the y-axis and the rolling direction as the x-axis to establish a coordinate system, the rolling inlet direction is the positive direction of the x-axis; the steel strip deformation zone is divided into three regions along the x-axis. From x = -l o to x = 0 is the outlet elastic recovery zone, and from x = 0 to x = l p is the plastic deformation zone, and from x = l p to x = l p +l i is the inlet elastic compression zone. Among them, the plastic deformation zone is further divided into a forward slip zone near the outlet side and a backward slip zone near the inlet side with the position of the neutral angle γ as the dividing line. The inlet elastic compression zone and the outlet elastic recovery zone are collectively called the elastic deformation zone.

[0013] At x = l p +l i , that is, at the rolling inlet, the steel strip thickness is the steel strip inlet thickness h i ; at x = l p , that is, at the junction of the inlet elastic compression zone and the plastic deformation zone, the steel strip thickness is the inlet thickness of the plastic deformation zone At x = 0, that is, at the junction of the outlet elastic recovery zone and the plastic deformation zone, the steel strip thickness is the outlet thickness of the plastic deformation zone At x = -l o , that is, at the rolling outlet, the steel strip thickness is the steel strip outlet thickness h o ;

[0014] As Figure 1 shown by the dotted shaded part, taking a micro-element in the deformation zone and analyzing its force in the horizontal direction, the general form of the Karman unit rolling pressure differential equation can be obtained:

[0015]

[0016] In the formula, p x is the unit rolling pressure at any point x in the deformation zone (corresponding to the specific coordinates of the above x-axis), that is, the rolling pressure per unit area, and the unit can be MPa; σ x is the horizontal stress at point x, and the unit is also MPa; h is the steel strip thickness corresponding to point x, in mm; for the last term of the equation, the “+” sign is taken for the forward slip zone and the “-” sign is taken for the backward slip zone.

[0017] (I) Calculation of the unit rolling pressure in the elastic deformation zone

[0018] According to Hooke's elastic theory, the stress-strain relationship of the steel strip in the inlet and outlet elastic deformation zones can be expressed as:

[0019]

[0020] In formula (3), is the true strain in the elastic deformation zone at the entrance (exit); υ s is the Poisson's ratio of the steel strip, generally taken as 0.3; E s is the elastic modulus of the steel strip, MPa; σ i(o) is the tensile stress at the entrance (exit), MPa. Obviously, in the elastic compression zone at the entrance, Equation (4) takes σ i and h i , and in the elastic recovery zone at the exit, it takes σ o and h o .

[0021] Taking the derivative of both sides of Equation (2) with respect to x and combining it with Equation (1), we get:

[0022]

[0023] Since p x +σ x << E s , and in the elastic zone, the change in the thickness of the steel strip is very small compared to the whole, so the last term of the equation can be ignored, and the differential equation of the unit rolling pressure in the elastic zone is expressed as:

[0024]

[0025] The relationship between the variables h and x in the differential equation of Equation (6) can be determined by the radian (the radian of the contact arc) between the point x on the contact arc and the center line of the roll. Since the contact arc in actual rolling is much smaller than the roll radius (the contact angle in cold rolling usually does not exceed 4 - 8°), using the following parabola to replace the contact curve also has sufficient accuracy:

[0026]

[0027] The thickness h of the steel strip corresponding to each point x in the deformation zone on the x-axis of the established coordinate system can be calculated from Equation (7). Substituting Equation (7) into Equation (6):

[0028]

[0029] For the convenience of writing and calculation, new variables u and m are introduced:

[0030]

[0031] Substituting u and m in Equation (9) into Equation (8), we get:

[0032]

[0033] The boundary conditions on the entrance side and exit side of the elastic deformation zone can be expressed as:

[0034] When x = -l o the value of variable u

[0035] When x = l p +l i the value of variable u

[0036] where are respectively the relative reduction rate values at several key positions of x = -l o , x = l p +l i , x = l p .

[0037] According to the standard solution of the first-order linear differential equation, for any x point (corresponding to a related u value) in the outlet elastic recovery zone, solve the unit rolling pressure in the outlet elastic recovery zone as follows:

[0038]

[0039] For any x point (corresponding to a u value) in the inlet elastic compression zone, the unit rolling pressure in the inlet elastic compression zone is as follows:

[0040]

[0041] The integral terms in equations (13) and (14) are approximated as follows:

[0042]

[0043] Substituting the approximation in equation (15) into equations (13) and (14) gives equations (16) and (17), both of which are functions with u as the single variable:

[0044]

[0045]

[0046] When x = 0, u = 0. This position is the junction where the outlet elastic recovery zone starts to enter the plastic deformation zone. Substituting it into equation (14), the unit rolling pressure p at this position o is as follows:

[0047]

[0048] When x = l p the corresponding value of variable u is This position is the junction where the inlet elastic compression zone starts to enter the plastic deformation zone. Substituting it into equation (15), the unit rolling pressure p at this positioni is:

[0049]

[0050] Substituting Eqs. (20) and (21) into Eqs. (18) and (19) respectively, we can obtain:

[0051]

[0052]

[0053] (2) Calculation of unit rolling pressure in plastic deformation zone

[0054] In the plastic deformation zone, the unit rolling pressure p x and the horizontal stress σ x satisfy the Mises yield criterion, that is:

[0055]

[0056] where k is the yield shear stress, MPa; 2k is the deformation resistance.

[0057] Substituting Eq. (24) into Eq. (1), the Karman differential equation can be rewritten as:

[0058]

[0059] Continuing to adopt the parabolic approximation of Eq. (7) and introducing the variables u and m defined by Eq. (9), and after arrangement, we get:

[0060]

[0061] Substituting the boundary conditions of Eqs. (20) and (21) and solving the differential equation (26), the unit rolling pressure at a certain point x (corresponding to u) in the forward slip zone can be obtained is:

[0062]

[0063] The unit rolling pressure at a certain point x (corresponding to u) in the back slip zone is:

[0064]

[0065] where 2k o is the deformation resistance in the exit elastic recovery zone, 2k i is the deformation resistance in the entrance elastic compression zone, and the horizontal stress σ′ p at the entrance of the plastic deformation zone (x = l i ) is σ′ i = 2k i, the horizontal stress σ′ at x = 0 at the exit of the plastic deformation zone o = 2k o - p o ; 2k is the deformation resistance of the plastic deformation zone.

[0066] Similarly, the following approximate conditions are introduced:

[0067]

[0068] Substituting into Eqs. (27) and (28) gives:

[0069]

[0070]

[0071] From the above analysis, it can be seen that to calculate the unit pressure distribution in the elastic zone and the plastic deformation zone, it is necessary to determine the strip thickness p at the entrance (x = l and and the exit (x = 0) of the plastic deformation zone.

[0072]

[0073] Substituting Eq. (32) into Eq. (2) gives the following relationship:

[0074]

[0075] Combining the first equation of Eq. (29) with Eq. (16) It is not difficult to find that when the deformation resistance 2k o , the exit tensile stress σ o , the exit strip thickness h o and the elastic modulus and Poisson's ratio of the strip are all known, there is only one unknown, so the calculation result of this unknown can be obtained.

[0076] Similarly, combining Eq. (17) with the second equation of Eq. (29) and substituting the obtained can be used to calculate

[0077] (III) Neutral angle parameter

[0078] The unit rolling pressure distribution curves in the forward slip zone and the backward slip zone at the neutral point intersect here, that is, the position of the maximum rolling pressure, and it is also the boundary between the forward slip zone and the backward slip zone. The contact arc corresponding to the neutral point is the neutral angle γ.

[0079] Let the u value (neutral angle parameter) corresponding to the coordinate of the neutral point on the x-axis be u γ , at the neutral point, the unit rolling pressure calculated according to the unit rolling pressure formulas of the forward slip zone and the backward slip zone should be equal. According to Eqs. (30) and (31), it can be known that:

[0080]

[0081] The neutral angle parameter u can be easily obtained from Eq. (34) by using the bisection method γ .

[0082] (IV) Calculation of the total rolling force

[0083] The total unit-width rolling force in the entire rolling deformation zone is the sum of the total pressures in the plastic deformation zone and the elastic deformation zone, that is

[0084]

[0085] In the formula, F is the total unit-width rolling force; F p is the unit-width rolling force in the plastic deformation zone; is the unit-width rolling force in the exit elastic recovery zone; is the unit-width rolling force in the entrance elastic compression zone.

[0086] According to the geometric relationship of the rolling deformation zone, the unit-width rolling force acting on the roll can be expressed as:

[0087]

[0088] In the formula α and γ are the contact arc radian (with the roll center line as 0 degrees) at the rolling exit (x = -l o ), the rolling entrance (x = l p + l i ), and the neutral point (u = u γ ), respectively. p is the unit rolling pressure corresponding to the corresponding contact arc radian. The vertical component of the frictional force in the brackets in the above formula makes a very small contribution to the total rolling force and can be ignored. Therefore, the unit-width rolling force in the plastic deformation zone is the integral of Eqs. (30) and (31) over the entire plastic deformation zone, and its value is related to the four values of r, m, :

[0089]

[0090] It is not difficult to understand that the upper limit of integration α in Eq. (33) p is x = l pThe arc of contact at the junction of the entrance elastic compression zone and the plastic deformation zone, i.e., at the position, represents the starting point of the plastic deformation zone; the lower limit of integration 0 is the arc of contact at the junction of the exit elastic recovery zone and the plastic deformation zone, i.e., at x = 0, representing the end point of the plastic deformation zone; the intermediate integration point γ represents the neutral angle, which is the boundary between the forward slip zone and the backward slip zone.

[0091] Similarly, integrating Equation (22) in the exit elastic recovery zone, the rolling force per unit width in the exit elastic recovery zone is obtained as:

[0092]

[0093] Integrating Equation (23), the rolling force per unit width in the entrance elastic compression zone is obtained as:

[0094]

[0095] (V) Calculation of rolling torque

[0096] According to the Bland-Ford theory, the torque per unit width T can be expressed as:

[0097]

[0098] According to Equation (40), the rolling torque can be decomposed into the rolling torque reference term caused by the rolling force and the tension influence term added together. The rolling torque reference term can be further expressed as:

[0099]

[0100] In the formula, is the rolling torque reference term in the plastic deformation zone; is the rolling torque reference term in the exit elastic recovery zone; is the rolling torque reference term in the entrance elastic compression zone. The above three terms can be expressed respectively as:

[0101]

[0102]

[0103]

[0104] Thus, the total rolling force per unit width and the torque per unit width in the rolling process are obtained. After multiplying them by the strip width respectively, the set values of the rolling force and the rolling torque in the rolling process can be obtained.

[0105] In most of the parameters in the above calculation process (such as the entrance and exit thicknesses h of the strip i 、h o, the friction coefficient μ of the working roll, the roll diameter R of the working roll, and the unit tension or tensile stress σ at the inlet and outlet of the steel strip i 、σ 0 etc.) can all be determined according to the actual rolling situation.

[0106] For the cold rolling process of the steel strip, the deformation resistance 2k at a certain point x in the plastic deformation zone x can be calculated by the following formula:

[0107]

[0108] where h x is the thickness of the steel strip at point x (Equation (5)), h init is the incoming thickness of the steel strip, k m is the reference constant of the deformation resistance considering material properties, ε and n are the deformation resistance model parameters. This formula is a mature formula in this field of the prior art, and these parameters can be obtained through regression experiments and other methods, and the obtaining methods are all prior art.

[0109] 2k i is the deformation resistance at the inlet, 2k o is the deformation resistance at the outlet, and h i 、h o are respectively substituted into h in the above formula x for calculation. In the elastic deformation zone, the deformation resistance can be regarded as unchanged. Therefore, 2k i and 2k o are also the deformation resistances in the inlet elastic compression zone and the outlet elastic deformation zone respectively. In the plastic deformation zone, the deformation resistance changes with the x value and the u value. In the calculation, the average deformation resistance 2k in the plastic deformation zone can be used in Equation (33). Specifically, the average deformation resistance 2k can be the definite integral average value of the deformation resistance in the plastic deformation zone.

[0110] There is a mutually coupled relationship between the rolling force and the flattened radius of the roll. The rolling force can be numerically solved by an iterative method until the relative error of the flattened radius between the previous and the current calculations meets a certain accuracy requirement before the iteration can be terminated. The iteration convergence condition in this article is set as:

[0111]

[0112] where R′ 0 is the calculated value of the flattened radius this time, in mm; R′ is the calculated value of the flattened radius in the previous time, that is, the value of the flattened radius used in this calculation, in mm; ε R is the iteration calculation accuracy, and generally taking 10 -3 can meet the requirements. At the same time, to prevent the calculation from falling into an infinite iteration loop, the maximum number of iteration loops can be given, such as giving 5 iteration loops to ensure the model calculation time.

[0113] For the tandem rolling process, the above method can be used for the setting calculation of the rolling force and rolling torque in a certain cold rolling pass.

[0114] The overall idea of the calculation of the present invention is introduced above. Next, the specific steps of the present invention will be introduced. The method of the present invention includes the following basic steps:

[0115] S1: Determine the rolling parameters:

[0116] The rolling parameters mainly include: the incoming strip thickness h init , the incoming strip thickness h i , the outgoing strip thickness h o , the elastic modulus E of the strip s , the elastic modulus E of the working roll wr , the inlet unit tension σ i , the outlet unit tension σ o , the friction coefficient μ between the roll and the strip, the roll radius R;

[0117] S2: Establish a coordinate system and divide the deformation zone:

[0118] Taking the center line of the two rolls as the y-axis and the rolling direction as the x-axis to establish a coordinate system, with the rolling inlet direction as the positive direction of the x-axis; divide the strip deformation zone along the x-axis into three regions. From x = -l o to x = 0 is the outlet elastic recovery zone, from x = 0 to x = l p is the plastic deformation zone, and from x = l p to x = l p +l i is the inlet elastic compression zone;

[0119] x = l p +l i The strip thickness at is the incoming strip thickness h i , x = l p The strip thickness at is the inlet thickness of the plastic deformation zone The strip thickness at x = 0 is the outlet thickness of the plastic deformation zone x = -l o The strip thickness at is the outgoing strip thickness h o ;

[0120] The strip thickness corresponding to any x value on the x-axis in the deformation zone R′ is the roll flattening radius;

[0121] S3: Calculate the inlet thickness of the plastic deformation zone and the outlet thickness

[0122] Introduce variables u and m related to x:

[0123]

[0124] Exit thickness of the plastic deformation zone Calculate using the following formula:

[0125]

[0126] Where 2k o Is the deformation resistance of the exit elastic recovery zone, and p o Is the unit rolling pressure starting from the exit elastic recovery zone and entering the plastic deformation zone. The calculation formula is as follows:

[0127]

[0128] In the formula, x = -l o The relative reduction at this point Is the value of variable u when x = -l o ;

[0129] Entry thickness of the plastic deformation zone Calculate using the following formula:

[0130]

[0131] Where 2k i Is the deformation resistance of the entry elastic compression zone, and the unit rolling pressure p at the start of the entry elastic compression zone entering the plastic deformation zone i The calculation formula is as follows:

[0132]

[0133] In the formula, x = l p +l i The relative reduction at this point Is the value of variable u when x = l p +l i The value of variable u at this point, u r Is the value of variable u when x = l p The value of variable u at this point:

[0134]

[0135] Where x = l p The relative reduction at this point

[0136] S4: Calculate the neutral angle parameter:

[0137] Neutral angle parameter u γThe variable u value corresponding to the neutral angle γ is calculated using the following formula:

[0138]

[0139] S5: Calculate the total rolling force per unit width F in the rolling deformation zone:

[0140] The total rolling force per unit width F in the entire rolling deformation zone is the sum of the rolling forces per unit width in the plastic deformation zone and the elastic deformation zone, that is

[0141]

[0142] In the formula, F is the total rolling force per unit width, F p is the rolling force per unit width in the plastic deformation zone, is the rolling force per unit width in the exit elastic recovery zone, F i e is the rolling force per unit width in the entrance elastic compression zone;

[0143] Among them:

[0144]

[0145] Among them, 2k is the deformation resistance in the plastic deformation zone, and the horizontal stress σ′ at the entrance of the plastic deformation zone i = 2k i - p i , and the horizontal stress σ′ at the exit of the plastic deformation zone o = 2k o - p o ;

[0146]

[0147]

[0148] S6: Calculate the torque per unit width T:

[0149] The torque per unit width T is expressed as:

[0150]

[0151] Among them, the rolling torque reference term can be further expressed as:

[0152]

[0153] In the formula, is the rolling torque reference term in the plastic deformation zone; is the rolling torque reference term in the exit elastic recovery zone; is the rolling torque reference term in the entrance elastic compression zone; the above three items can be expressed respectively as:

[0154]

[0155]

[0156]

[0157] S7: Set the rolling force and rolling torque during the rolling process according to the calculated value F of the total rolling force per unit width and the calculated value T of the torque per unit width in the finally obtained rolling deformation zone.

[0158] In the above method, for the cold rolling process, the deformation resistance 2k of the entrance elastic compression zone i is calculated as follows:

[0159]

[0160] The deformation resistance 2k of the exit elastic recovery zone o is calculated as follows:

[0161]

[0162] The deformation resistance 2k at a certain point with abscissa x in the plastic deformation zone x is calculated as follows:

[0163]

[0164] where h x is the thickness of the steel strip at point x, h init is the incoming thickness of the steel strip, k m is the reference constant of the deformation resistance considering the material properties, and ε, n are the deformation resistance model parameters.

[0165] In the plastic deformation zone, the deformation resistance 2k can adopt the average deformation resistance in the whole plastic deformation zone. For example, the average value of the deformation resistance calculated by definite integral can be adopted.

[0166] Due to the mutual coupling relationship between the rolling force and the flattening radius, in the above method, the flattening radius R′ needs to correspond to the calculated value of the rolling force. For this reason, an iterative method can be used to obtain the values of the flattening radius R′, the total rolling force F per unit width, and the torque T per unit width in the rolling deformation zone, as Figure 2 shown. The specific method is as follows:

[0167] After calculating the current calculated values of F and T according to the above steps S2 to S6 using the current flattening radius R′, recalculate the flattening radius R′ according to the current F value o, and determine whether the current iterative calculation process meets the iterative convergence condition: If the iterative convergence condition is met, the calculation ends, and the calculated values F and T obtained in steps S5 and S6 of the current iterative calculation process are the final values and are used for step S7; if the iterative convergence condition is not met, the newly calculated flattened radius R′ obtained currently o is iterated back to step S2 and used as the new flattened radius R′ for the next iterative calculation from step S2 to S6.

[0168] The initial value of the flattened radius R′, that is, in the first calculation, the flattened radius adopts the roll radius R.

[0169] The iterative convergence condition is ε R is the iterative calculation accuracy, taking a value not greater than 10 -3 of the numerical value.

[0170] A method for recalculating the flattened radius R′ according to the current F value o is as follows:

[0171]

[0172] In the formula, E wr is the elastic modulus of the roll.

[0173] Advantages of the present invention: The present invention provides a method for setting and calculating the rolling force and rolling torque in the entire deformation zone of strip steel rolling. During the calculation process, the differences in rolling pressure between the plastic deformation zone and the elastic deformation zone are considered and distinguished, comprehensively considering the influences of the rolling plastic zone and the elastic deformation zone. The setting calculation error value of the rolling force is within 8%. Description of the Drawings

[0174] Figure 1 : Schematic diagram of the division of the rolling deformation zone of the present invention.

[0175] Figure 2 : Flow chart of the iterative calculation of the present invention. Detailed Embodiments

[0176] Example 1

[0177] Taking the 1740mm five-stand six-high cold tandem rolling mill as an example, the working roll diameter of this mill is 430 - 480mm, the intermediate roll diameter is 510 - 580mm, the backup roll diameter is 1315 - 1465mm, and the maximum rolling force of the mill is 32000kN. The thickness before rolling (i.e., the thickness of the strip steel at the inlet of the rolling / thickness before rolling), the thickness after rolling (the thickness of the strip steel at the outlet of the rolling / thickness after rolling), the front and back tensions, and the rolling force calculated by using the method of the present invention and the measured rolling force of each rolling pass of the DP590 strip steel with a width of 1358mm are shown in Table 1.

[0178] Table 1 Thickness of steel strip, front and rear tensions, calculated rolling force and measured rolling force in Example 1

[0179]

[0180]

[0181] As can be seen from Table 1, the error between the cold rolling force of DP590 steel strip calculated by using the present invention and the measured rolling force is within 7.6%, and the error between the calculated value and the measured value of the rolling torque is within 19.8%, with relatively high accuracy.

[0182] Example 2

[0183] Taking a 1740 mm five-stand six-high cold tandem mill as an example, the work roll diameter of this mill is 430 - 480 mm, the intermediate roll diameter is 510 - 580 mm, the backup roll diameter is 1315 - 1465 mm, and the maximum rolling force of the mill is 32000 kN. The thickness before rolling (i.e., the thickness of the incoming rolled steel strip / thickness before rolling), thickness after rolling (the thickness of the outgoing rolled steel strip / thickness after rolling), front and rear tensions, and the rolling force and measured rolling force calculated by using the method of the present invention for each rolling pass of W780QX steel strip with a width of 1223 mm are shown in Table 2.

[0184] Table 2 Thickness of steel strip, front and rear tensions, calculated rolling force and measured rolling force in Example 2

[0185]

[0186] As can be seen from Table 2, the error between the cold rolling force of W780QX steel strip calculated by using the present invention and the measured rolling force is within 7.8%, and the error between the calculated value and the measured value of the rolling torque is within 15.7%, with relatively high accuracy.

[0187] Example 3

[0188] Taking a certain 1340 mm six-high cold tandem mill as an example, the work roll diameter of this mill is 420 - 460 mm, the intermediate roll diameter is 440 - 490 mm, the backup roll diameter is 1000 - 1090 mm, and the maximum rolling force of the mill is 15000 kN. The thickness before rolling (thickness of the incoming rolled steel strip / thickness before rolling), thickness after rolling (i.e., the thickness of the outgoing rolled steel strip / thickness after rolling), front and rear tensions, and the rolling force and measured rolling force calculated by using the method of the present invention for each rolling pass of 16Mn steel strip with a width of 919.0 mm are shown in Table 3.

[0189] Table 3 Thickness of steel strip, front and rear tensions, calculated rolling force and measured rolling force in Example 3

[0190]

[0191] As can be seen from Table 3, the error between the cold rolling force of the 16Mn steel strip calculated using the present invention and the measured rolling force is within 7.4%, and the error between the calculated value and the measured value of the rolling torque is within 16.6%, with relatively high accuracy.

[0192] Example 4

[0193] Taking a 1340 mm six-high tandem cold rolling mill as an example, the work roll diameter of this mill is 420 - 460 mm, the intermediate roll diameter is 440 - 490 mm, the backup roll diameter is 1000 - 1090 mm, and the maximum rolling force of the mill is 15000 kN. The thickness before rolling (inlet thickness of the rolled steel strip / thickness before rolling), thickness after rolling (outlet thickness of the rolled steel strip / thickness after rolling), front and back tensions, and the rolling force and measured rolling force calculated using the method of the present invention for each rolling pass of the Q215 steel strip with a width of 1044.0 mm are shown in Table 4.

[0194] Table 4 Thickness, front and back tensions, calculated rolling force and measured rolling force of the steel strip in Example 4

[0195]

[0196] As can be seen from Table 4, the error between the cold rolling force of the Q215 steel strip calculated using the present invention and the measured rolling force is within 4%, and the error between the calculated value and the measured value of the rolling torque is within 18.1%, with relatively high accuracy.

Claims

1. A method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip, characterized in that, it includes the following steps: S1: Determine rolling parameters; The rolling parameters mainly include: the incoming strip thickness h init , the strip inlet thickness h i , the strip outlet thickness h o , the strip elastic modulus E s , the elastic modulus E of the working roll wr , the inlet unit tension σ i , the outlet unit tension σ o , the friction coefficient μ between the roll and the strip, the roll radius R; S2: Divide the deformation zone; S3: Calculate the thickness at the entrance of the plastic deformation zone and the thickness at the exit of the plastic deformation zone S4: Calculate neutral angle parameters; S5: Calculate the total rolling force F per unit width in the rolling deformation zone; The total rolling force F per unit width in the entire rolling deformation zone is the sum of the rolling forces per unit width in the plastic deformation zone and the elastic deformation zone, that is Wherein, F is the total rolling force per unit width, F p is the rolling force per unit width in the plastic deformation zone, is the rolling force per unit width in the exit elastic recovery zone, F i e is the rolling force per unit width in the entrance elastic compression zone; where: where 2k is the average deformation resistance of the plastic deformation zone, and the horizontal stress σ i ′ = 2k i - p i at the entrance of the plastic deformation zone, and the horizontal stress σ o ′ = 2k o - p o at the exit of the plastic deformation zone; S6: Calculate the torque T per unit width; The torque T per unit width is expressed as: Among them, the rolling torque reference term can be further expressed as: In the formula, is the rolling torque reference term in the plastic deformation zone; is the rolling torque reference term in the exit elastic recovery zone; is the rolling torque reference term in the entrance elastic compression zone; the above three terms can be expressed respectively as: S7: Set the rolling force and rolling torque in the rolling process according to the finally obtained calculated value F of the total rolling force per unit width in the rolling deformation zone and the calculated value T of the torque per unit width.

2. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 1, characterized in that, the specific steps included are as follows: S2: Establish a coordinate system and divide the deformation zone: Taking the center connection line of the two rolling rolls as the y-axis and the rolling direction as the x-axis to establish a coordinate system, with the rolling inlet direction being the positive direction of the x-axis; dividing the steel strip deformation zone into three regions along the x-axis, from x = -l o to x = 0 is the exit elastic recovery zone, from x = 0 to x = l p is the plastic deformation zone, from x = l p to x = l p +l i is the inlet elastic compression zone; x = l p +l i The thickness of the steel strip at this point is the inlet thickness h of the steel strip i and at x = l p the thickness of the steel strip is the inlet thickness of the plastic deformation zone The thickness of the steel strip at x = 0 is the outlet thickness of the plastic deformation zone x = -l o the thickness of the steel strip at this point is the outlet thickness h of the steel strip o ; The thickness of the steel strip corresponding to any x value on the x-axis within the deformation zone R′ is the flattened radius of the roll; S3: Calculate the thickness at the entrance of the plastic deformation zone and the thickness at the exit of the plastic deformation zone Introduce variables u and m related to x: Thickness at the exit of the plastic deformation zone It is calculated by the following formula: where 2k o is the deformation resistance of the outlet elastic recovery zone, and p o is the unit rolling pressure starting from the outlet elastic recovery zone and entering the plastic deformation zone. The calculation formula is as follows: where x = -l o relative reduction rate at x = -l o is the value of variable u Entrance thickness of the plastic deformation zone It is calculated by the following formula: Among which 2k i is the deformation resistance of the entrance elastic compression zone, and the unit rolling pressure p when the entrance elastic compression zone begins to enter the plastic deformation zone i The calculation formula is as follows: where x = l p + l i is the relative reduction ratio at x = l p + l i is the value of variable u at x = l r where x = l p is the value of variable u at this point: where x = l p relative reduction ratio S4: Calculate neutral angle parameters: Neutral angle parameter u γ is the value of variable u corresponding to the neutral angle γ and is calculated using the following formula: S7: Set the rolling force and rolling torque in the rolling process according to the finally obtained calculated value F of the total rolling force per unit width in the rolling deformation zone and the calculated value T of the torque per unit width.

3. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 2, characterized in that, the values of the flattened radius R′, the total rolling force F per unit width in the rolling deformation zone, and the torque T per unit width are obtained by an iterative method, and the specific method is as follows: After calculating the current calculated values of F and T according to the steps S2 to S6 using the current flattening radius R', recalculate the flattening radius R according to the current F value o ', and determine whether the current iterative calculation process meets the iterative convergence condition: if the iterative convergence condition is met, the calculation ends, and the calculated values F and T obtained in steps S5 and S6 of the current iterative calculation process are the final values and are used in step S7; if the iterative convergence condition is not met, the currently recalculated flattening radius R o ' is iterated back to step S2 and used as the new flattening radius R' for the next iterative calculation.

4. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 3, characterized in that, The iterative convergence condition is ε R is the iterative calculation accuracy.

5. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 4, characterized in that, The iterative calculation accuracy ε R is not greater than 10 -3 .

6. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 3, characterized in that, The method for recalculating the flattening radius R o ′ is as follows: In the formula, E wr is the elastic modulus of the roll.

7. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 3, characterized in that, the initial value of the flattened radius R′ adopts the roll radius R.

8. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 2, characterized in that, The deformation resistance 2k of the entrance elastic compression zone i is calculated as follows: The deformation resistance 2k of the described outlet elastic recovery area o is calculated as follows: The deformation resistance 2k of a certain point with the abscissa x in the plastic deformation zone x is calculated as follows: where h x is the thickness of the steel strip at point x, h init is the incoming thickness of the steel strip, k m is the reference constant of the deformation resistance considering material properties, and ε and n are the deformation resistance model parameters.

9. The method for setting rolling force and rolling torque in the entire deformation zone of cold rolling of steel strip according to claim 8, characterized in that, the average deformation resistance 2k in the plastic deformation zone is the definite integral average value of the deformation resistance in the plastic deformation zone.

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