Forecasting method for section shape and plate shape of finished strip of hot rolling unit

Abstract

The invention relates to the technical field of hot rolling, in particular to a hot rolling unit finished strip section shape and strip shape forecasting method which comprises the following steps: carrying out transverse unit distribution division on a roll system; the rolling pressure borne by the working roller is segmented; analyzing roller system stress and calculating roller deflection; calculating transverse distribution values of the inter-roller pressure and the rolling force; calculating a section shape distribution value of the finished strip according to a roll gap equation; calculating a front tension transverse distribution value; and calculating the strip shape distribution of the finished strip. The method has the advantages that the metal deformation model and the roll shape elastic deformation model in the hot rolling process are established, the section shape and the plate shape of the finished strip are calculated by coupling the two models, and forecasting of the section shape and the plate shape of the finished strip of the hot rolling unit is completed; the forecasting result obtained by adopting the scheme of the invention conforms to the quality of the product real object produced in an industrial batch mode, and the provided theoretical calculation model can be directly applied to an industrial production line, so that the purposes of simplifying the production process and reducing the production cost are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hot rolling, and particularly relates to a method for predicting the cross-sectional shape and strip shape of the finished strip of a hot rolling mill. Background Art

[0002] Hot-rolled sheet and strip play an important role in the development of the national economy, and their applications in industry, agriculture, national defense, and civilian products are extremely extensive. In particular, hot-rolled strip can not only be directly used as thin sheet and medium plate, but also serve as the raw material for cold-rolled sheet, welded pipe, and cold-formed section steel.

[0003] The strip shape and cross-sectional shape of hot-rolled strip are two extremely important quality indicators. Poor strip shape and defects in the cross-sectional shape have a great impact on rolling operations. In severe cases, it will lead to accidents such as strip breakage and tearing, making the rolling operation unable to proceed normally and causing serious negative impacts on subsequent further processing.

[0004] The control of the cross-sectional shape and strip shape during the hot rolling process is mainly completed in the finishing rolling stage. Rolling technologies such as accelerated rolling, micro-tension control, and large reduction are adopted in the finishing rolling process. However, the non-uniform change of the rolled piece during the hot rolling finishing process becomes greater as the thickness of the rolled piece becomes thinner, resulting in difficulties in controlling the cross-sectional shape and strip shape of the rolled piece.

[0005] In the prior art, the publication number is CN109871590A, which discloses a method for reproducing the cross-sectional profile of hot-rolled strip, belonging to the technical field of strip cross-sectional shape control. This method uses a piecewise quadratic function to reproduce the overall cross-sectional profile of hot-rolled strip. The function uses fewer characteristic coefficients and only needs three index parameters with actual physical meanings to solve, namely the measurement indexes C40 and W40 in the hot-rolled strip control standard, and C25 representing the outermost edge index of the cold-rolled strip finishing coiling. The cross-sectional profile of the strip reproduced by this method has high accuracy and fast reproduction speed. At the same time, the introduction of the constraint equation ensures that the reproduced cross-sectional profile of the strip is smooth and continuous, and more in line with the actual situation. The method for reproducing the cross-sectional profile of hot-rolled strip proposed by this invention is of great significance for controlling the cross-sectional shape of the strip and improving the strip quality. The scheme reproduces the cross-sectional profile in the form of a piecewise quadratic function, does not consider metal deformation and tension distribution, and does not consider subsequent strip shape prediction based on the reproduction result.

[0006] Publication number CN113333474A discloses a strip hot rolling shape control method and system based on digital twin. The method includes: collecting historical production data of different steel grades to establish a production database; the data includes rolling process parameters of each stand, slab state parameters, and finish rolling exit shape data; establishing a physical model of various shape influencing factors in the rolling process through historical production data, on-site test data, and experimental data; and solving the input parameters of the finite element simulation model through the physical model; establishing a finite element simulation result database; based on the production database and the finite element simulation result database, establishing a digital twin body, and adjusting the rolling process parameters of each stand through the digital twin body to control the shape. In this invention, data interaction is carried out between the rolling mill and the twin body, and shape prediction can be realized. According to the shape prediction result and the measured result of the rolling mill exit shape, the shape control means are adjusted to improve the shape quality. This solution needs to perform finite element simulation for the physical model to achieve shape prediction. However, it is difficult to apply in practice for finite element simulation of a large amount of production practice data, and modeling needs to be carried out separately according to the steel grade characteristics and product specifications, with great application difficulty.

[0007] Publication number CN109821903A discloses a control method for hot rolling shape of high-strength steel with simple process control and low cost, including the following steps: a. Heating; b. Rolling; c. Two-stage cooling after rolling: cooling the rolled steel plate to ensure uniform cooling in the thickness direction, controlling the final cooling temperature to be 580 - 620 °C, and controlling the roller table speed to be 1.0 - 1.5 m / s; d. The number of coils entering the pit is 30 - 140 coils, the time in the pit is ≥ 72 hours, and the temperature when leaving the pit is ≤ 200 °C; e. The hot-rolled high-strength steel is leveled and straightened on a seven-roll leveler, and the thick-specification high-strength steel plate finished product is obtained after leveling. This invention can simplify the production process, shorten the production cycle, reduce the transfer of the steel plate in the intermediate process, and save energy consumption; at the same time, it reduces the increase of unplanned quantity, can obtain good shape, and has obvious economic benefits; it is especially applicable to the production of high-strength steel with a yield strength value greater than 550 MPa and a thickness specification greater than or equal to 10 mm. It mainly controls the shape for the production process and does not mention the related technology content of prediction. At the same time, this solution is mainly applicable to thick plate products rather than thin plate products. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for predicting the cross-sectional shape and shape of the finished strip of a hot rolling mill. Based on the hot rolling mill as the research object, a corresponding control model for the cross-sectional shape and shape of the finished strip is set to realize the prediction of the cross-sectional shape and shape of the finished strip of the hot rolling mill, so as to better ensure the quality of the cross-sectional shape and shape of the hot rolled finished strip steel.

[0009] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0010] A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill unit, comprising:

[0011] S1. Collect the characteristic parameters of the key equipment of the hot rolling mill unit and the rolling process parameters;

[0012] S2. Divide the roll system into transverse unit distributions;

[0013] S3. Segment the rolling pressure received by the work roll;

[0014] S4. Analyze the force on the roll system and calculate the roll deflection;

[0015] S5. Calculate the inter-roll pressure and the transverse distribution value of the rolling force;

[0016] S6. Calculate the cross-sectional shape distribution value of the finished strip according to the roll gap equation;

[0017] S7. If the difference between the cross-sectional shape distribution value of the current finished strip and the target value is greater than 0.01, return to step S2;

[0018] S8. Calculate the transverse distribution value of the front tension;

[0019] S9. Calculate the flatness distribution of the finished strip;

[0020] S10. Output the cross-sectional shape and flatness of the finished strip.

[0021] In S1, the characteristic parameters of the key equipment of the hot rolling mill unit collected include the diameter D w , mm, the diameter D b , mm of the backup roll; the roll body length L w , mm, the roll body length L b , mm of the backup roll, the rolling speed V, m / s, the safety factor η. The rolling process parameters collected include the maximum inlet tension σ0, MPa, the outlet tension σ1, MPa, the inlet thickness H, mm, the outlet thickness h, mm of the strip, the strip width B, mm, the initial strength σ s0 , MPa, the elastic modulus E, MPa, the Poisson's ratio v, and the initial temperature t, °C of the rolled piece.

[0022] In S2, the division of the roll system into transverse unit distributions is as follows: Calculate the transverse distribution value σ1(j) of the front tension stress under the current inlet thickness H and outlet thickness h of the strip through the metal deformation model. The formula is as follows:

[0023]

[0024] In formula ①, T1 represents the set front tension, MPa; h(j) represents the exit thickness in the j-th section, MPa; L(j) represents the inlet length of the j-th section, mm; u′(j) represents the lateral displacement in the j-th section, mm; Δb represents the absolute spread of the rolled piece, mm; b represents the width of the rolled piece, mm; two certain sections among the set number of sections are i, j {1, 2, …, 2n + 1}.

[0025] In S3, the rolling pressure on the work roll is segmented, and the formula is as follows:

[0026]

[0027] In formula ②, q′ j represents the rolling pressure on the j-th section of the work roll, kN, q j represents the inter-roll pressure in the j-th section, kN; 2n + 1 represents the expansion of the number of segments of the rolling pressure; m represents the number of segments of the strip without rolling pressure; q′ j = 0.

[0028] In S4, analyze the force on the roll system and calculate the roll deflection, including:

[0029] S41. Bending deflection equation of the work roll in the vertical direction

[0030] 1) Deflection equation of the left side of the upper work roll, and the formula is as follows:

[0031]

[0032] In formula ③, a ij represents the influence coefficient of the load in the j-th section on the deflection of the work roll in the i-th section; represents the inter-roll pressure in the j-th section of the upper work roll, kN; q' j represents the rolling pressure on the j-th section of the work roll, kN; represents the influence coefficient of the left bending roll force S1 in the i-th section on the deflection of the j-th section; S1 represents the left bending roll force of the upper work roll, kN; α 上 represents the rigid rotation angle of the upper work roll relative to the backup roll, rad; x i represents the displacement from the i-th unit to the rolling center line;

[0033] 2) Deflection equation of the right side of the upper work roll, and the formula is as follows:

[0034]

[0035] In formula ④, represents the influence coefficient of the right bending roll force in the i-th section on the deflection of the j-th section; S2 represents the right bending roll force of the upper work roll, kN;

[0036] 3) Deflection equation of the left side of the lower work roll, and the formula is as follows:

[0037]

[0038] In Equation ⑤, represents the inter-roll pressure of the j-th section of the lower work roll, in kN; represents the influence coefficient of the left backup roll force S1 of the i-th section of the work roll on the deflection of the j-th section; S1 represents the left backup roll force of the lower work roll, in kN; β 下 represents the rigid rotation angle of the lower work roll relative to the backup roll, in rad;

[0039] 3) Deflection equation of the right side of the lower work roll, the formula is as follows:

[0040]

[0041] In Equation ⑥, represents the influence coefficient of the right backup roll force of the i-th section of the work roll on the deflection of the j-th section; S2 represents the right backup roll force of the lower work roll, in kN;

[0042] S42. Bending deflection equation of the backup roll in the vertical direction

[0043] 1) Deflection equation of the left side of the upper backup roll, the formula is as follows:

[0044]

[0045] In Equation ⑦, b ij represents the influence coefficient of the load of the j-th section on the deflection of the i-th section of the backup roll; b p1i represents the influence coefficient of the backup roll bending force of the i-th section on the deflection of the j-th section.

[0046] 2) Deflection equation of the right side of the upper backup roll, the formula is as follows:

[0047]

[0048] In Equation ⑧, b ij represents the influence coefficient of the load of the j-th section on the deflection of the i-th section of the backup roll; b p2i represents the influence coefficient of the right backup roll bending force of the i-th section on the deflection of the j-th section;

[0049] 3) Deflection equation of the left side of the lower backup roll, the formula is as follows:

[0050]

[0051] In Equation ⑨, b ij represents the influence coefficient of the load of the j-th section on the deflection of the i-th section of the backup roll; b p1i represents the influence coefficient of the backup roll bending force of the i-th section on the deflection of the j-th section;

[0052] 4) Deflection equation for the right side of the lower backup roll, the formula is as follows:

[0053]

[0054] In formula ⑩, b ij represents the influence coefficient of the deflection of the i-th backup roll caused by the load in the j-th section; b p2i represents the influence coefficient of the right bending force of the i-th backup roll on the deflection of the j-th section;

[0055] S43. Calculate the deformation coordination relationship between the work roll and the backup roll

[0056] 1) Deformation coordination relationship between the left work roll and the backup roll, the formula is as follows:

[0057]

[0058] In formula f lwi represents the deflection of the left work roll in the i-th section, μm; f lbi represents the deflection of the left backup roll in the i-th section, μm; K represents the coefficient of mutual flattening between the work roll and the backup roll; ΔD i represents the crown of the work roll in the i-th section, mm;

[0059] 2) Deformation coordination relationship between the right work roll and the backup roll, the formula is as follows:

[0060]

[0061] In formula f Rwi represents the deflection of the right work roll in the i-th section, μm; f Rbi represents the deflection of the right backup roll in the i-th section, μm; K represents the coefficient of mutual flattening between the work roll and the backup roll; ΔD i represents the crown of the work roll in the i-th section, mm.

[0062] In S5, calculate the inter-roll pressure and the transverse distribution value of the rolling force, including:

[0063] S51. Supplement the force balance equation according to the force and moment balance of the rolls

[0064] 1) Force balance equation of the upper backup roll, the formula is as follows:

[0065]

[0066] In formula where represents the inter-roll force of the i-th section of the upper backup roll, kN; P1 上 represents the supporting force received on the left side of the upper backup roll, kN; Denotes the supporting force received on the right side of the upper supporting roll, kN;

[0067] 2) Force balance equation of the lower supporting roll, the formula is as follows:

[0068]

[0069] Formula In, Denotes the force between the i-th segments of the lower supporting roll, kN; P1 下 Denotes the supporting force received on the left side of the lower supporting roll, kN; Denotes the supporting force received on the right side of the lower supporting roll, kN;

[0070] 3) The (n + 1)-th equation, rolling force balance equation, the formula is as follows:

[0071]

[0072] Formula In, q i ′ Denotes the rolling pressure of the i-th segment, kN; P denotes the total rolling pressure, kN;

[0073] 4) The (2n + 2)-th equation, upper supporting roll balance equation, the formula is as follows:

[0074]

[0075] Formula In, denotes the pressure between the upper supporting roll segments kN; P1 上 Denotes the supporting force received on the left side of the upper supporting roll, kN; L P1 Denotes the arm of force of the supporting force received on the left side of the upper supporting roll, mm; Denotes the supporting force received on the right side of the upper supporting roll, kN; L P2 Denotes the arm of force of the supporting force received on the right side of the upper supporting roll, mm;

[0076] 5) The (2n + 3)-th equation, lower supporting roll balance equation, the formula is as follows:

[0077]

[0078] Formula In, the pressure distribution value between the lower supporting roll segments kN; P1 下 Denotes the supporting force received on the left side of the lower supporting roll, kN; L P1 Denotes the arm of force of the supporting force received on the left side of the lower supporting roll, mm; Denotes the supporting force received on the right side of the lower supporting roll, kN; L P2 Denotes the arm of force of the supporting force received on the right side of the lower supporting roll, mm;

[0079] S52. Calculate the inter-roll pressure and the transverse distribution value of the rolling force as follows:

[0080]

[0081] Formula In represents the inter-roll pressure of the upper work roll, kN; represents the inter-roll pressure of the lower work roll, kN; represents the inter-roll pressure of the upper backup roll, kN; represents the inter-roll pressure of the lower backup roll, kN; q j ′ represents the rolling pressure of the i-th section, kN;

[0082] S53. According to the obtained inter-roll pressure and the transverse distribution value of the rolling pressure, calculate the deflections of the upper and lower work rolls

[0083] represents the deflections of the left and right sides of the upper work roll in the i-th section, μm; represents the deflections of the left and right sides of the lower work roll in the i-th section, μm.

[0084] In S6, calculate the cross-sectional shape distribution value of the finished strip according to the roll gap equation. The formula is as follows:

[0085]

[0086] Formula In h i represents the cross-sectional shape distribution value of the i-th section of the strip, mm; h1 represents the average exit thickness, mm; represents the deflections of the left and right sides of the upper work roll in the i-th section, μm; represents the deflections of the left and right sides of the lower work roll in the i-th section, μm; K represents the coefficient of mutual flattening of the work roll and the backup roll; q n +1 represents the rolling pressure of the (n + 1)-th section, kN; q i ′ represents the rolling pressure of the i-th section, kN; ΔD wi represents the work roll crown of the i-th section, mm.

[0087] S8. Calculate the transverse distribution value of the front tension. The formula is as follows:

[0088]

[0089] In S9, calculate the shape distribution of the finished strip. The formula is as follows:

[0090]

[0091] Formula where v represents the Poisson stress; E represents the elastic modulus, in MPa; σ 1j represents the calculated transverse distribution value of the front tension in the j-th section, in MPa; T1 represents the set front tension, in MPa.

[0092] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0093] 1. Combine the theoretical model with on-site actual data to establish a metal deformation model and a roll profile elastic deformation model during hot rolling. Calculate the cross-sectional shape and flatness of the finished strip by coupling the two models to complete the prediction of the cross-sectional shape and flatness of the finished strip of the hot rolling mill.

[0094] 2. The prediction results obtained by adopting the solution of the present invention are consistent with the physical quality of the products in industrial mass production. The proposed theoretical calculation model can be directly applied to the industrial production line, achieving the purpose of simplifying the production process and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 is the force diagram of the roll system of the hot rolling mill.

[0096] Figure 2 is the flow chart for predicting the cross-sectional shape and flatness of the finished strip of the hot rolling mill.

[0097] Figure 3 is the cross-sectional shape of the finished strip at the outlet of the hot rolling mill in Example 1.

[0098] Figure 4 is the flatness distribution value of the finished strip at the outlet of the hot rolling mill in Example 1.

[0099] Figure 5 is the cross-sectional shape of the finished strip at the outlet of the hot rolling mill in Example 2.

[0100] Figure 6 is the flatness distribution value of the finished strip at the outlet of the hot rolling mill in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0101] The present invention will be described in detail below with reference to the accompanying drawings of the specification, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0102] The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments. The methods used in the following embodiments are all conventional methods unless otherwise specified.

[0103] Example 1

[0104] The method for predicting the cross-sectional shape and flatness of the finished strip of the hot rolling mill, for the flow chart, seeFigure 2 , taking the steel type with the specification of 16.62mm×1500mm as an example for calculation, the content is as follows:

[0105] (a) Collect the characteristic parameters of the key equipment of the hot rolling mill, mainly including: the diameter D of the work roll w = 800mm, the diameter D of the backup roll b = 1200mm, the roll body length L of the work roll w = 2000mm, the roll body length L of the backup roll b = 2050mm, the rolling speed V = 10.59m / s, and the safety factor η = 0.9.

[0106] (b) Collect the rolling process parameters, mainly including: the maximum inlet tension σ0 of the rolling mill = 5MPa, the outlet tension σ1 = 5MPa, the inlet thickness H of the strip = 16.22mm, the outlet thickness h = 3.60mm, the strip width B = 1500mm, the initial strength σ of the strip s0 = 150MPa, the elastic modulus E = 2.1×10 5 MPa, the Poisson's ratio v = 0.3, and the initial temperature t of the rolled piece = 1050℃.

[0107] (c) Calculate the transverse distribution value σ1(j), MPa of the front tension stress at the current inlet thickness H and outlet thickness h of the strip through the metal deformation model. The formula is as follows:

[0108]

[0109] In formula ①, please note that in formula ①, T1 represents the set front tension, MPa; h(j) represents the outlet thickness in the j-th section, mm; L(j) represents the inlet length in the j-th section, mm; u′(j) represents the transverse displacement in the j-th section, mm; Δb represents the absolute spread of the rolled piece, mm; b represents the width of the rolled piece; and i and j in the set number of segments are {1, 2, …, 2n + 1}.

[0110] (d) Express the rolling pressure on the work roll as q′ j , expand the number of segments of the rolling pressure to 2n + 1, and q j = 0 for the parts outside the strip width, that is:

[0111] In formula ②, q′ j represents the rolling pressure on the j-th section of the work roll, kN, and q j represents the roll gap pressure in the j-th section, kN; 2n + 1 represents the expansion of the number of segments of the rolling pressure; m represents the number of segments of the strip without rolling pressure; and q′ j = 0 for the parts outside the strip width.

[0112] (e) Combine the mechanical analysis of the roll system and calculate the expression of roll deflection:

[0113] 1) The bending deflection equation of the work roll in the vertical direction

[0114] The deflection equation of the upper work roll on the left side The formula is as follows:

[0115]

[0116] In formula ③, a ij represents the influence coefficient of the load in the j-th segment on the deflection of the i-th segment of the work roll; represents the inter-roll pressure in the j-th segment of the upper work roll, kN; q' j represents the rolling pressure on the j-th segment of the work roll, kN; represents the influence coefficient of the left roll bending force S1 in the i-th segment on the deflection of the j-th segment; S1 is the left roll bending force of the upper work roll, kN; β 上 represents the rigid rotation angle of the upper work roll relative to the backup roll, rad; x i The displacement from the i-th unit to the rolling center line;

[0117] The deflection equation of the upper work roll on the right side The formula is as follows:

[0118]

[0119] In formula ④, represents the influence coefficient of the right roll bending force in the i-th segment on the deflection of the j-th segment; S2 represents the right roll bending force of the upper work roll, kN.

[0120] The deflection equation of the lower work roll on the left side The formula is as follows:

[0121]

[0122] In formula ⑤, represents the inter-roll pressure in the j-th segment of the lower work roll, kN; represents the influence coefficient of the left roll bending force S1 in the i-th segment on the deflection of the j-th segment; S1 represents the left roll bending force of the lower work roll, kN; β 下 represents the rigid rotation angle of the lower work roll relative to the backup roll, rad;

[0123] The deflection equation of the lower work roll on the right side The formula is as follows:

[0124]

[0125] In formula ⑥, It represents the influence coefficient of the right bending roll force of the i-th segment of the work roll on the deflection of the j-th segment; S2 represents the right bending roll force of the lower work roll, in kN;

[0126] 2) The bending deflection equation of the backup roll in the vertical direction

[0127] The deflection equation of the left side of the upper backup roll The formula is as follows:

[0128]

[0129] In formula ⑦, b ij represents the influence coefficient of the load of the j-th segment on the deflection of the i-th segment of the backup roll; b p1i represents the influence coefficient of the bending roll force of the i-th segment of the backup roll on the deflection of the j-th segment;

[0130] The deflection equation of the right side of the upper backup roll The formula is as follows:

[0131]

[0132] In formula ⑧, b ij represents the influence coefficient of the load of the j-th segment on the deflection of the i-th segment of the backup roll; b p2i represents the influence coefficient of the right bending roll force of the i-th segment of the backup roll on the deflection of the j-th segment;

[0133] The deflection equation of the left side of the lower backup roll The formula is as follows:

[0134]

[0135] In formula ⑨, b ij represents the influence coefficient of the load of the j-th segment on the deflection of the i-th segment of the backup roll; b p1i represents the influence coefficient of the bending roll force of the i-th segment of the backup roll on the deflection of the j-th segment;

[0136] The deflection equation of the right side of the lower backup roll The formula is as follows:

[0137]

[0138] In formula ⑩, b ij represents the influence coefficient of the load of the j-th segment on the deflection of the i-th segment of the backup roll; b p2i represents the influence coefficient of the right bending roll force of the i-th segment of the backup roll on the deflection of the j-th segment.

[0139] (f) Calculate the deformation coordination relationship between the work roll and the backup roll:

[0140] The deformation coordination relationship between the left work roll and the backup roll, the formula is as follows:

[0141]

[0142] Formula In it, f lwi represents the deflection of the work roll on the left side of the i-th section; f lbi represents the deflection of the backup roll on the left side of the i-th section, μm; K is the coefficient of mutual flattening of the work roll and the backup roll; ΔD i represents the crown of the work roll in the i-th section, mm;

[0143] The deformation coordination relationship between the work roll and the backup roll on the right side is as follows: The formula is as follows:

[0144]

[0145] Formula In it, f Rwi represents the deflection of the work roll on the right side of the i-th section, μm; f Rbi represents the deflection of the backup roll on the right side of the i-th section, μm; K represents the coefficient of mutual flattening of the work roll and the backup roll; ΔD i represents the crown of the work roll in the i-th section, mm.

[0146] (g) According to the force and moment balance of the rolls, supplement the force balance equation

[0147] 1) Force and moment balance equations of each roll

[0148] The force balance equation of the upper backup roll is as follows:

[0149]

[0150] Formula In it, represents the inter-roll force of the i-th section of the upper backup roll, kN; P1 上 represents the supporting force received on the left side of the upper backup roll, kN; represents the supporting force received on the right side of the upper backup roll, kN;

[0151] The force balance equation of the lower backup roll is as follows:

[0152]

[0153] Formula In it, represents the inter-roll force of the i-th section of the lower backup roll, kN; P1 下 represents the supporting force received on the left side of the lower backup roll, kN; represents the supporting force received on the right side of the lower backup roll, kN;

[0154] The (n + 1)-th equation, the rolling force balance equation, is as follows:

[0155]

[0156] Formula In which, q i ′ represents the rolling pressure of the i-th section, kN; P represents the total rolling pressure, kN;

[0157] The (2n + 2)-th equation, the upper backup roll balance equation, is as follows:

[0158]

[0159] Formula In which, the inter-roll pressure of the upper backup roll kN; P1 上 represents the supporting force received by the left side of the upper backup roll, kN; L P1 represents the lever arm of the supporting force received by the left side of the upper backup roll, mm; represents the supporting force received by the right side of the upper backup roll; L P2 represents the lever arm of the supporting force received by the right side of the upper backup roll, mm;

[0160] The (2n + 3)-th equation, the lower backup roll balance equation, is as follows:

[0161]

[0162] Formula In which, represents the inter-roll pressure of the upper work roll, kN; represents the inter-roll pressure of the lower work roll, kN; represents the inter-roll pressure of the upper backup roll, kN; represents the inter-roll pressure of the lower backup roll, kN; q j ′ represents the rolling pressure of the i-th section, kN.

[0163] (h) Calculate the inter-roll pressure and the transverse distribution value of the rolling force from the simultaneous equations in (h) to (i):

[0164]

[0165] Formula In which, represents the inter-roll pressure of the upper work roll, kN; represents the inter-roll pressure of the lower work roll, kN; represents the inter-roll pressure of the upper backup roll, kN; represents the inter-roll pressure of the lower backup roll, kN; q j ′ represents the rolling pressure of the i-th section, kN.

[0166] (i) Calculate the deflections of the upper and lower work rolls based on the obtained inter-roll pressure and the transverse distribution value of the rolling pressure represents the deflection of the left and right working rolls of the upper working roll in the i-th section, μm; represents the deflection of the left and right working rolls of the lower working roll in the i-th section, μm.

[0167] (j) Taking the loaded roll gap as a bridge, coupling the metal deformation model and the roll system elastic deformation model, the cross-sectional shape distribution value of the strip after rolling can be calculated:

[0168] Formula In, h i represents the cross-sectional shape distribution value of the i-th section of the strip, mm; h1 represents the average exit thickness, mm; represents the deflection of the left and right working rolls of the upper working roll in the i-th section, μm; represents the deflection of the left and right working rolls of the lower working roll in the i-th section, μm; K represents the coefficient of mutual flattening of the working roll and the backup roll; q′ n+1 represents the rolling pressure of the (n + 1)-th section, kN; q′ i represents the rolling pressure of the i-th section, kN; ΔD wi represents the convexity of the working roll in the i-th section, mm.

[0169] (k) Judge Whether it holds (where P represents the rolling pressure, h i represents the calculated cross-sectional shape distribution value of the finished strip, H i represents the target value of the cross-sectional shape of the finished strip. If it does not hold, go to step (e); otherwise, go to step (l);

[0170] (l) Calculate the transverse distribution value of the front tension stress σ1(j), MPa from the front tension model.

[0171] (m) According to the relationship between the shape of the strip and the transverse distribution value of the front tension stress, the shape distribution of the strip at the exit of the hot rolling mill can be expressed as:

[0172]

[0173] Formula In, v represents the Poisson stress; E represents the elastic modulus, MPa; σ 1j represents the calculated transverse distribution value of the front tension in the j-th section, MPa; T1 represents the set front tension, MPa.

[0174] (n) Output the cross-sectional shape h of the finished strip i and the shape of the strip L j , see Figure 3 , see Figure 4 .

[0175] Example 2

[0176] Prediction method for cross-sectional shape and strip shape of finished strip in hot rolling mill. Taking a steel grade with specifications of 13.58 mm × 1350 mm as an example, the calculations are as follows:

[0177] (a) Collect key equipment characteristic parameters of the hot rolling mill, mainly including: the diameter D of the work roll w = 800 mm, the diameter D of the backup roll b = 1200 mm, the roll body length L of the work roll w = 2000 mm, the roll body length L of the backup roll b = 2050 mm, the rolling speed V = 10.59 m / s, and the safety factor η = 0.9.

[0178] (b) Collect rolling process parameters, mainly including: the maximum inlet tension σ0 of the rolling mill = 5 MPa, the outlet tension σ1 = 5 MPa, the inlet thickness H of the strip = 13.58 mm, the outlet thickness h = 3.28 mm, the strip width B = 1350 mm, the initial strength σ s0 = 150 MPa, the elastic modulus E = 2.1×10 5 MPa, the Poisson's ratio v = 0.3, and the initial temperature t of the rolled piece = 1050 °C.

[0179] (c) Obtain the transverse distribution value σ1(j) of the front tension stress under the current inlet thickness H and outlet thickness h of the strip through the metal deformation model, in MPa.

[0180] (d) Represent the rolling pressure on the work roll as q′ j , expand the number of segments of the rolling pressure to 2n + 1, and q′ j = 0 for the parts outside the strip width, that is:

[0181] (e) Combine the mechanical analysis of the roll system to calculate the expression of the roll deflection:

[0182] The bending deflection equation of the work roll in the vertical direction is: the deflection equation of the left side of the upper work roll The deflection equation of the right side of the upper work roll The deflection equation of the left side of the lower work roll The deflection equation of the right side of the lower work roll

[0183] The bending deflection equation of the backup roll in the vertical direction is: the deflection equation of the left side of the upper backup roll The deflection equation of the right side of the upper backup roll The deflection equation of the left side of the lower backup roll The deflection equation of the right side of the lower backup roll

[0184] (f) Calculate the deformation coordination relationship between the work roll and the backup roll:

[0185] Left side:

[0186] Right side:

[0187] (g) According to the force and moment balance of the rolls, supplement the force balance equations, namely the force balance equations of the upper and lower backup rolls, the (n + 1)-th equation, the rolling force balance equation, the (2n + 2)-th equation, the balance equation of the upper backup roll, the (2n + 3)-th equation, and the balance equation of the lower backup roll.

[0188] (h) Calculate the inter-roll pressure and the transverse distribution value of the rolling force from the simultaneous equations in (h) to (i):

[0189] q j ′.

[0190] (i) Calculate the deflections of the upper and lower work rolls according to the obtained inter-roll pressure and the transverse distribution value of the rolling pressure

[0191] (j) Taking the loaded roll gap as a bridge, couple the metal deformation model and the roll system elastic deformation model to calculate the cross-sectional shape distribution value of the strip after rolling:

[0192] (k) Judge Is it established? If not, go to step (e); otherwise, go to step (l).

[0193] (l) Calculate the transverse distribution value of the front tension stress σ1(j), MPa from the front tension model.

[0194] (m) According to the relationship between the strip shape and the transverse distribution value of the front tension stress, the strip shape distribution at the outlet of the hot rolling mill can be expressed as:

[0195]

[0196] (n) Output the cross-sectional shape h of the finished strip i and the strip shape L j , see Figure 5 , see Figure 6 .

[0197] The present invention combines a theoretical model with on-site actual data to establish a metal deformation model and a roll profile elastic deformation model during the hot rolling process. By coupling the two models, the cross-sectional shape and flatness of the finished strip are calculated to complete the prediction of the cross-sectional shape and flatness of the finished strip of the hot rolling mill. The prediction results obtained by the solution of the present invention are consistent with the actual quality of the products in industrial mass production. The proposed theoretical calculation model can be directly applied to industrial production lines, achieving the purpose of simplifying the production process and reducing production costs.

Claims

1. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill, characterized in that, Including: S1. Collect the characteristic parameters of key equipment of the hot rolling mill and the rolling process parameters; S2. Divide the roll system into transverse unit distributions; S3. Segment the rolling pressure on the work rolls; S4. Analyze the forces on the roll system and calculate the roll deflection; S5. Calculate the inter-roll pressure and the transverse distribution values of the rolling force; S6. Calculate the cross-sectional shape distribution values of the finished strip according to the roll gap equation; S7. If the difference between the cross-sectional shape distribution value of the current finished strip and the target value is greater than 0.01, return to step S2; S8. Calculate the transverse distribution value of the front tension; S9. Calculate the shape distribution of the finished strip; S10. Output the cross-sectional shape and shape of the finished strip.

2. The cross-sectional shape and flatness prediction method for the finished strip of a hot rolling mill set according to claim 1, characterized in that, In S1, the characteristic parameters of the key equipment of the hot rolling mill are collected, including the working roll diameter D w , mm, the diameter D b of the backup roll, mm; the roll body length L w of the working roll, mm, the roll body length L b of the backup roll, mm, the rolling speed V, m / s, the safety factor η. The rolling process parameters are collected, including the maximum inlet tension σ0 of the rolling mill, MPa, the outlet tension σ1, MPa, the inlet thickness H of the strip, mm, the outlet thickness h, mm, the strip width B, mm, the initial strength σ s0 of the strip, MPa, the elastic modulus E, MPa, the Poisson's ratio v, and the initial temperature t of the rolled piece, °C.

3. A method for predicting the cross-sectional shape and strip shape of the finished strip of a hot rolling mill unit according to claim 1, characterized in that, In S2, the dividing the roll system into transverse unit distributions is as follows: Obtain the transverse distribution value σ1(j) of the front tension stress under the inlet thickness H and the outlet thickness h of the current strip through the metal deformation model. The formula is as follows: In formula ①, T1 represents the set front tension, in MPa; h(j) represents the outlet thickness in the j-th segment, in mm; L(j) represents the inlet length of the j-th segment, in mm; u′(j) represents the transverse displacement amount in the j-th segment, in mm; Δb represents the absolute spread amount of the rolled piece, in mm; b represents the width of the rolled piece, in mm; Let two segments in the set number of segments be i, j {1, 2,..., 2n + 1}.

4. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill assembly according to claim 1, characterized in that In S3, the segmenting the rolling pressure on the work rolls is as follows: The formula is as follows: In formula ②, q′ j represents the rolling pressure on the j-th section of the work roll, in kN, and q j represents the inter-roll pressure on the j-th section, in kN; 2n + 1 represents the expansion of the number of segments of the rolling pressure; m represents the number of segments of the strip without rolling pressure; q′ j = 0 for the parts outside the strip width.

5. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill assembly according to claim 1, characterized in that, In S4, the analyzing the forces on the roll system and calculating the roll deflection includes: S41. The bending deflection equation of the work roll in the vertical direction 1) The deflection equation of the left side of the upper work roll is as follows: In formula ③, a ij represents the influence coefficient of the deflection of the working roll in the i-th section caused by the load in the j-th section; represents the inter-roll pressure in the j-th section of the upper working roll, kN; q' j represents the rolling pressure on the j-th section of the working roll, kN; represents the influence coefficient of the left bending roll force S1 in the i-th section on the deflection in the j-th section; S1 represents the left bending roll force of the upper working roll, kN; α 上 represents the rigid rotation angle of the upper working roll relative to the backup roll, rad; x i represents the displacement from the i-th unit to the rolling center line; 2) The deflection equation of the right side of the upper work roll is as follows: In Formula ④, represents the influence coefficient of the right bending roll force in the i-th segment on the deflection in the j-th segment; S2 represents the right bending roll force of the upper work roll, kN; 3) The deflection equation of the left side of the lower work roll is as follows: In Formula ⑤, represents the inter-roll pressure of the j-th segment of the lower work roll, in kN; represents the influence coefficient of the left bending force S1 of the i-th segment of the work roll on the deflection of the j-th segment; S1 represents the left bending force of the lower work roll, in kN; α 下 represents the rigid rotation angle of the lower work roll relative to the backup roll, in rad; 3) The deflection equation of the right side of the lower work roll is as follows: In Formula ⑥, represents the influence coefficient of the right bending force of the working roll in the i-th section on the deflection of the j-th section; S2 represents the right bending force of the lower working roll, kN; S42. The bending deflection equation of the backup roll in the vertical direction 1) The deflection equation of the left side of the upper backup roll is as follows: In formula ⑦, b ij represents the influence coefficient of the load in the j-th segment on the deflection of the support roll in the i-th segment; b p1i represents the influence coefficient of the bending roll force of the support roll in the i-th segment on the deflection in the j-th segment. 2) The deflection equation of the right side of the upper backup roll is as follows: In formula ⑧, b ij represents the influence coefficient of the load in the j-th segment on the deflection of the support roll in the i-th segment; b p2i represents the influence coefficient of the right bending force of the support roll in the i-th segment on the deflection in the j-th segment. 3) The deflection equation of the left side of the lower backup roll is as follows: In Equation ⑨, b ij represents the influence coefficient of the load in the j-th segment on the deflection of the support roll in the i-th segment; b p1i represents the influence coefficient of the bending roll force of the support roll in the i-th segment on the deflection in the j-th segment. 4) The deflection equation of the right side of the lower backup roll is as follows: In formula ⑩, b ij represents the influence coefficient of the deflection of the support roll in the i-th segment caused by the load in the j-th segment; b p2i represents the influence coefficient of the right bending roll force of the support roll in the i-th segment on the deflection in the j-th segment; S43. Calculate the deformation coordination relationship between the work roll and the backup roll 1) The deformation coordination relationship between the left-side work roll and the backup roll is as follows: Formula In the formula lwi , $f_{i}^{w}$ represents the deflection of the work roll on the left side of the $i$-th segment, in μm; $f_{i}^{b}$ lbi represents the deflection of the backup roll on the left side of the $i$-th segment, in μm; $K$ represents the coefficient of mutual flattening of the work roll and the backup roll; $\Delta D_{i}$ i represents the crown of the work roll in the $i$-th segment, in mm. 2) The deformation coordination relationship between the right-side work roll and the backup roll is as follows: Formula where f Rwi represents the deflection of the i-th work roll section on the right side, in μm; f Rbi represents the deflection of the i-th backup roll section on the right side, in μm; K represents the coefficient of mutual flattening between the work roll and the backup roll; ΔD i represents the crown of the i-th work roll section, in mm.

6. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill assembly according to claim 1, characterized in that, In S5, the calculating the inter-roll pressure and the transverse distribution values of the rolling force includes: S51. According to the force and moment balance of the roll, supplement the force balance equation 1) The force balance equation of the upper backup roll is as follows: Formula In represents the force between the i-th segments of the upper backup roll, kN; P1 上 represents the supporting force received on the left side of the upper backup roll, kN; represents the supporting force received on the right side of the upper backup roll, kN; 2) The force balance equation of the lower backup roll is as follows: Formula In represents the force between the i-th segments of the lower backup roll, kN; P1 下 represents the supporting force received on the left side of the lower backup roll, kN; represents the supporting force received on the right side of the lower backup roll, kN; 3) The (n + 1)-th equation, the rolling force balance equation, is as follows: Formula where q i ′ represents the rolling pressure of the i-th section, in kN; P represents the total rolling pressure, in kN; 4) The (2n + 2)-th equation, the upper backup roll balance equation, is as follows: Formula represents the inter-roll pressure of the upper backup roll kN; P1 上 represents the supporting force received on the left side of the upper backup roll, kN; L P1 represents the arm of force of the supporting force received on the left side of the upper backup roll, mm; represents the supporting force received on the right side of the upper backup roll, kN; L P2 represents the arm of force of the supporting force received on the right side of the upper backup roll, mm; 5) The (2n + 3)-th equation, the lower backup roll balance equation, is as follows: Formula In the formula, the pressure distribution value between the lower support rolls kN; P1 下 represents the supporting force received on the left side of the lower support roll, kN; L P1 represents the lever arm of the supporting force received on the left side of the lower support roll, mm; represents the supporting force received on the right side of the lower support roll, kN; L P2 represents the lever arm of the supporting force received on the right side of the lower support roll, mm; S52. Calculate the inter-roll pressure and the transverse distribution values of the rolling force as follows: Formula In represents the inter-roll pressure of the upper work roll, kN; represents the inter-roll pressure of the lower work roll, kN; represents the inter-roll pressure of the upper backup roll, kN; represents the inter-roll pressure of the lower backup roll, kN; q j ' represents the rolling pressure of the i-th section, kN; S53. Calculate the deflections of the upper and lower work rolls based on the obtained inter-roll pressure and the lateral distribution value of the rolling pressure. represents the deflection of the i-th section of the left and right working rolls of the upper working roll, μm; represents the deflection of the i-th section of the left and right working rolls of the lower working roll, μm.

7. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill set according to claim 1, characterized in that, In S6, the calculating the cross-sectional shape distribution values of the finished strip according to the roll gap equation is as follows: The formula is as follows: Formula In which, h i represents the cross-sectional shape distribution value of the i-th strip section, in mm; h1 represents the average exit thickness, in mm; represents the deflection of the i-th section of the upper work roll on the left and the right work rolls, in μm; represents the deflection of the i-th section of the lower work roll on the left and the right work rolls, in μm; K represents the coefficient of mutual flattening of the work roll and the backup roll; q′ n+1 represents the rolling pressure of the (n + 1)-th section, in kN; q′ i represents the rolling pressure of the i-th section, in kN; ΔD wi represents the convexity of the i-th work roll, in mm.

8. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill assembly according to claim 1, characterized in that S8. Calculate the transverse distribution value of the front tension. The formula is as follows:

9. A method for predicting the cross-sectional shape and flatness of the finished strip of a hot rolling mill set according to claim 1, characterized in that, In S9, the calculating the shape distribution of the finished strip is as follows: The formula is as follows: Formula where ν represents the Poisson stress; E represents the elastic modulus, in MPa; σ 1j represents the calculated transverse distribution value of the front tension in the j-th segment, in MPa; T1 represents the set front tension, in MPa.

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