A method for controlling the shape of hot-rolled high-grade oriented silicon steel sheets

Abstract

The present invention discloses a plate shape control method for hot-rolled high-grade oriented silicon steel plate, comprising: heating the ingot to 1250°C-1320°C, the total heating time in the preheating section is 3.5h-4h, the time in the soaking section is 1.5h-2h, and the total furnace time is 5h-5.5h; the rough rolling process adopts 1+1+3 passes, the first three passes adopt a large reduction rate, and the reduction rate of each pass is ≥20%; the cooling water of the rolling roll is not turned on, and the final rolling temperature is >1140°C; during the finishing rolling process, each stand follows the equal-proportional convexity Control principle: F1~F3 stands are CVC rolls, F4~F7 stands are flat rolls, and the optimal bending roll force of each stand and the shifting roll setting value of the CVC roll are solved to optimize the plate shape control parameters of the silicon steel finishing rolling process; the starting rolling temperature during finishing rolling is 1040℃~1070℃, the final rolling temperature is 890℃~930℃, and the target convexity is 20um~40um; the silicon steel strip coming out of the finishing rolling unit is laminar cooled; the silicon steel after laminar cooling is curled, and the curling temperature is not lower than 550℃.

Description

Technical Field

[0001] The invention belongs to the technical field of hot continuous rolling and relates to a plate shape control method for hot-rolled high-grade oriented silicon steel plates. Background Art

[0002] Silicon steel is an excellent soft magnetic functional material, widely used in the fields of electricity, electronics, electromechanical, post and telecommunications, and military industries. In production, silicon steel requires high magnetic stress strength and low iron loss performance, and also has very strict requirements on the dimensional accuracy of the plate shape. Among all the plate shape indicators, silicon steel has very demanding requirements on the edge drop after rolling. Since the main purpose of downstream customers using silicon steel is to manufacture compressors and motors, multiple sheets need to be stacked, so the plate shape of cold-rolled silicon steel directly affects its yield rate and production cost. Hot-rolled silicon steel incoming materials are the basic raw materials for cold-rolled products, and the plate shape quality of hot-rolled products directly affects the improvement of cold-rolling production efficiency and quality. In hot-rolling production, the edge drop of hot-rolled silicon steel strip is too large, which is prone to problems such as large convexity and edge waves, which seriously restricts the yield rate of the product. Under the existing technology, reducing the large trimming amount of cold-rolled incoming materials and improving the yield rate of hot-rolled silicon steel mainly involves the plate shape control technology of the hot rolling process. Summary of the invention

[0003] To solve the above technical problems, the purpose of the present invention is to provide a plate shape control method for hot-rolled high-grade oriented silicon steel plates, which improves the hot-rolled silicon steel yield by optimizing the plate shape control parameters of the silicon steel finishing rolling process and meets the raw material requirements of the downstream process.

[0004] The present invention provides a method for controlling the shape of a hot-rolled high-grade oriented silicon steel sheet. The production process of the silicon steel sheet includes heating of the ingot, rough rolling, finish rolling, cooling and curling, which specifically includes:

[0005] Step 1: Heat the ingot to 1250℃~1320℃, the total heating time in the preheating section is 3.5h~4h, the time in the soaking section is 1.5h~2h, and the total time in the furnace is 5h~5.5h;

[0006] Step 2: The rough rolling process adopts 1+1+3 passes, the first three passes adopt a large reduction rate, and the reduction rate of each pass is ≥20%; the roller cooling water is not turned on, and the final rolling temperature is >1140℃;

[0007] Step 3: To ensure that the strip shape is within the required range, each stand follows the principle of proportional crown control during the finishing rolling process. The F1~F3 stands in the finishing mill are CVC rolls, and the F4~F7 stands are flat rolls. The optimal bending roll force of each stand and the shifting roll setting value of the CVC roll are solved to optimize the strip shape control parameters of the silicon steel finishing rolling process;

[0008] Step 4: During the finishing rolling process, the starting rolling temperature is 1040℃~1070℃, the final rolling temperature is 890℃~930℃, the target convexity is 20um~40um, and the wedge shape is within the range of ±15um;

[0009] Step 5: laminar cooling of the silicon steel strip coming out of the finishing mill;

[0010] Step 6: Curl the laminar cooled silicon steel, with the curling temperature being no less than 550°C.

[0011] The plate shape control method of a hot-rolled high-grade oriented silicon steel plate of the present invention has the following beneficial effects:

[0012] 1. The present invention adopts a relatively high heating temperature and ensures the furnace time of the soaking section and the heating section at the same time, thereby avoiding softening caused by phase change during the finishing rolling process and ensuring the thickness control accuracy.

[0013] 2. The present invention adopts a method of mixed configuration of CVC and ordinary flat rolls, so that the proportional convexity of each stand is constant during the finishing rolling process.

[0014] 3. The present invention starts with solving the problem of high-grade silicon steel plate shape, formulates the process requirements in the finishing rolling process and the calculation method of bending and shifting rolls, effectively solves the problems of large convexity and edge waves of hot-rolled high-grade silicon steel, and provides a strong guarantee for the hot-rolled materials in the downstream process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart for solving the bending roll force and the CVC roll shifting set value. DETAILED DESCRIPTION

[0016] The present invention discloses a method for controlling the shape of a hot-rolled high-grade oriented silicon steel sheet. The production process of the silicon steel sheet includes heating of the ingot, rough rolling, finish rolling, cooling and curling, and specifically includes:

[0017] Step 1: Heat the ingot to 1250℃~1320℃, the total heating time in the preheating section is 3.5h~4h, the time in the soaking section is 1.5h~2h, and the total time in the furnace is 5h~5.5h;

[0018] Step 2: The rough rolling process adopts 1+1+3 passes, the first three passes adopt a large reduction rate, and the reduction rate of each pass is ≥20%; the roller cooling water is not turned on, and the final rolling temperature is >1140℃;

[0019] Step 3: To ensure that the strip shape is within the required range, each stand follows the principle of proportional crown control during the finishing rolling process. The F1~F3 stands in the finishing rolling unit are CVC rolls, and the crown control range of the CVC rolls is -500um~800um. The F4~F7 stands are flat rolls. The optimal bending roll force of each stand and the shifting roll setting value of the CVC roll are solved to optimize the plate shape control parameters of the silicon steel finishing rolling process, such as Figure 1 As shown, specifically:

[0020] Step 3.1: Determine the target convexity of the current strip according to the convexity measurement value of the previous strip. The calculation formula is:

[0021] ;

[0022] ;

[0023] in, C old is the target convexity of the previous strip, in um; C self_coe is the convexity deviation self-learning coefficient read from the convexity self-learning table, with a value range of [-1, 1] and a unit of μm; C corr_coe It is the self-learning correction value read from the self-learning table of plate shape according to steel type and width and thickness layering. The value range is [-0.02, 0.02], and the unit is um; C curr It is the target convexity of the current strip, with a value range of [20, 40] and a unit of um.

[0024] Step 3.2: Calculate the absolute convexity of the roll gap of each stand according to the roll bending force and roll shifting amount. The calculation formula is as follows:

[0025] ;

[0026] in, It is i Roller gap crown of the stand, in um, i The value range is 1~7; It is in i The original crown of the roll gap measured when the frame is unloaded has a value range of [115, 160] and the unit is um; is the first value read from the plate shape efficiency coefficient table i The bending roll force sensitivity coefficient of the frame has a value range of [-0.51, -0.02], and the unit is um / kN; F i For the i The bending roll force of the frame has a value range of [300, 1800] and the unit is kN; No.i The sensitivity coefficient of the roll shifting of the frame is i When the value is 1~3, the CVC roller shifting sensitivity coefficient is read from the plate shape efficiency coefficient table. i When the value is 4 to 7, the sensitivity coefficient of the flat roller shifting is 0; S i For the i The amount of roller shifting on the rack, when i When the value is 1~3, the range of the CVC roller shifting amount is [-150, 150], in mm. i When the value is 4~7, the amount of roller shifting of the flat roller is 0.

[0027] Step 3.3: Convert the absolute convexity of the roll gap of each stand into the relative convexity according to the following formula:

[0028] ;

[0029] in, h i For the i The strip steel exit thickness of the rack, the value range is [1.8, 28], the unit is mm.

[0030] Step 3.4: Calculate the influence coefficient of the relative convexity of the roll gap of each stand on the strip shape according to the following formula:

[0031] ;

[0032] Among them, γ i For the i The relative convexity of the roll gap of the stand, R i For the i The working roller radius of the frame, the value range is [300, 360], the unit is mm; W i For the i The outlet thermal width of the rack, the value range is [1000, 1500], the unit is mm; c 1 and c 2 are -7.394 and 0.327 respectively.

[0033] Step 3.5: Correct the influence coefficient of the relative convexity of the roll gap on the strip shape. The calculation formula is as follows:

[0034] ;

[0035] ;

[0036] ;

[0037] Among them, γ i-1 For the i- 1. Relative convexity of the roll gap of the stand, γ i+1 For the i+ 1. Relative convexity of the roll gap of the frame; α is the correction factor, α The value range is 0~1; A i For the i The correction factor of the frame shape transfer coefficient is in the range of [0.87, 1.21]; B is the comprehensive correction factor of the shape transfer coefficient, in the range of [0.9, 1]; γ i_corr For the i The influence coefficient of the relative convexity of the roll gap after frame correction on the strip shape.

[0038] Step 3.6: Calculate the relative convexity of the intermediate blank to the i Influence of relative convexity of strip at the exit of the rack , the calculation formula is as follows:

[0039] ;

[0040] in, C Trb is the convexity of the intermediate blank, the value range is [-363.79, 940.92], the unit is um; H Trb is the intermediate billet thickness, the value range is [-363.79, 940.92], the unit is mm; For the intermediate blank i The influence coefficient of the relative convexity of the strip at the rack outlet ranges from [-0.08665, -0.39695].

[0041] Step 3.7: Calculate the relative convexity of the strip at the exit of each rack. The calculation formula is as follows:

[0042] ;

[0043] in, For the i Relative convexity of the strip at the rack outlet, For the j The relative convexity of the roll gap of the stand, j < i ; γ j_corr For the j The influence coefficient of the relative convexity of the roll gap after the frame correction on the strip shape, j < i .

[0044] Step 3.8: Calculate the strip convexity at the exit of each rack. The calculation formula is as follows:

[0045] ;

[0046] ;

[0047] in, For the i The crown of the strip at the rack exit.

[0048] Step 3.9: In order to ensure that the proportional crown between the stands is constant and the final outlet crown is as close to the target crown as possible, the gradient descent method is used to solve the optimal solution of the bending and shifting rolls of the finishing mill. The objective function is as follows:

[0049] ;

[0050] In the formula, It is i The optimal solution for the bending roll of the stand is in the range of [300, 1800], in kN; No. i The optimal solution for the roller shifting of the frame, the value range is [-150, 150], the unit is mm; λ and β is the weight coefficient.

[0051] Step 4: During the finishing rolling process, the starting rolling temperature is 1040℃~1070℃, the final rolling temperature is 890℃~930℃, the target convexity is 20um~40um, and the wedge shape is within the range of ±15um;

[0052] In specific implementation, the cooling water volume of the rollers during the finishing rolling process is controlled at 40m 3 / h~60m 3 / h; the load distribution during rolling follows the principle of decreasing in sequence. The first three passes adopt a large reduction rate, with a reduction rate of 45%~50% for each pass, the fourth pass has a reduction rate of 28%~32%, the fifth to sixth passes have a reduction rate of 20%~24%, and the last pass has a reduction rate of less than 10%; the rolling speeds of each stand are 0.95m / s, 1.92m / s, 3.62m / s, 5.43m / s, 6.97m / s, 8.89m / s, and 10.29m / s respectively.

[0053] Step 5: laminar cooling of the silicon steel strip coming out of the finishing mill;

[0054] Step 6: Curl the laminar cooled silicon steel, with the curling temperature being no less than 550°C.

[0055] The chemical composition and mass percentage of the silicon steel strip obtained by the above steps are:

[0056] C: 0.034%~0.038%, Mn: 0.213%~0.215%, Si: 3.12%~3.22%, Nb: 0.0012%~0.008%, Ti: 0.0019%~0.0021%, V: 0.029%~0.03%, Cu: 0.48%~0.5%, Ni: 0.005%~0.006%, Cr: 0.038%~0.041%, Als: 0.0174%~0.0196%, P: 0.011%~0.015%, S: 0.048%~0.05%, N: 0.091%~0.094%, and the rest are Fe and unavoidable impurities.

[0057] The finished silicon steel sheet has a thickness range of 2mm~3mm and a width range of more than 1000mm~1250mm.

[0058] The implementation of the present invention is carried out on a hot rolling production line. The chemical composition of the embodiment is shown in Table 1, the process parameters of the heating furnace are shown in Table 2, the roll shifting amount in the finishing rolling process is shown in Table 3, the bending roll force in the finishing rolling process is shown in Table 4, and the quality of the finished strip steel plate shape obtained in the embodiment is shown in Table 5.

[0059] Table 1 Chemical composition of hot-rolled silicon steel in Example Mass percentage (%).

[0060]

[0061] Table 2 Process parameters of the heating furnace for hot-rolled silicon steel in Example

[0062]

[0063] Table 3 Roll shifting amount of hot-rolled silicon steel in Example

[0064]

[0065] Table 4 Bending roll force of hot-rolled silicon steel in Example

[0066]

[0067] Table 5 Plate quality of hot-rolled silicon steel products in Example.

[0068]

[0069] As can be seen from Table 5, the method of the present invention solves the plate shape problem of hot-rolled high-grade silicon steel with a thickness of 2.0 mm to 3.0 mm and a width of 1000 mm to 1250 mm, and the convexity, flatness and wedge shape of the silicon steel all meet the quality requirements.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the concept of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the shape of a hot-rolled high-grade oriented silicon steel sheet, characterized in that: The production process of silicon steel sheets includes heating of ingots, rough rolling, finishing rolling, cooling and curling, specifically including: Step 1: Heat the ingot to 1250°C to 1320°C, the total heating time in the preheating section is 3.5h to 4h, the time in the soaking section is 1.5h to 2h, and the total time in the furnace is 5h to 5.5h; Step 2: The rough rolling process adopts 1+1+3 passes, the first three passes adopt a large reduction rate, and the reduction rate of each pass is ≥20%; the roller cooling water is not turned on, and the final rolling temperature is >1140℃; Step 3: To ensure that the strip shape is within the required range, each stand follows the principle of proportional crown control during the finishing rolling process. The F1-F3 stands in the finishing mill are CVC rolls, and the F4-F7 stands are flat rolls. The optimal bending roll force of each stand and the shifting roll setting value of the CVC roll are solved to optimize the strip shape control parameters of the silicon steel finishing rolling process. Step 4: During the finishing rolling process, the starting rolling temperature is 1040℃~1070℃, the final rolling temperature is 890℃~930℃, the target convexity is 20um~40um, and the wedge shape is within the range of ±15um; Step 5: laminar cooling of the silicon steel strip coming out of the finishing mill; Step 6: Curling the laminar cooled silicon steel, with the curling temperature being not less than 550°C; The step 3 is specifically as follows: Step 3.1: Determine the target convexity of the current strip according to the convexity measurement value of the previous strip. The calculation formula is: C new =C old +C self_coe ; C curr =C new +C corr_coe ; Among them, C old is the target convexity of the previous strip, in um; C self_coe is the convexity deviation self-learning coefficient read from the convexity self-learning table, with a value range of [-1,1] and a unit of um; C corr_coe It is the self-learning correction value read from the self-learning table of the plate shape according to the steel type and width and thickness layer. The value range is [-0.02, 0.02], and the unit is um; C curr is the target convexity of the current strip, the value range is [20,40], and the unit is um; Step 3.2: Calculate the absolute convexity of the roll gap of each stand according to the roll bending force and roll shifting amount. The calculation formula is as follows: in, is the roll gap crown of the i-th stand, in um, i ranges from 1 to 7; is the original roll gap convexity measured when the i-th frame is in the no-load state, with a value range of [115,160] and a unit of um; F is the bending roll force sensitivity coefficient of the i-th frame read from the plate shape efficiency coefficient table, with a value range of [-0.51, -0.02] and a unit of um / kN; i is the bending roll force of the i-th frame, with a value range of [300,1800] and a unit of kN; The roll shifting sensitivity coefficient of the i-th frame, when i is 1-3, that is, the roll shifting sensitivity coefficient of the CVC roll is read from the plate shape efficiency coefficient table; when i is 4-7, that is, the roll shifting sensitivity coefficient of the flat roll is 0; S i is the roller shifting amount of the i-th frame. When i is 1 to 3, the roller shifting amount of the CVC roller is in the range of [-150, 150], in units of mm. When i is 4 to 7, the roller shifting amount of the flat roller is 0. Step 3.3: Convert the absolute convexity of the roll gap of each stand into the relative convexity according to the following formula: Among them, h i is the strip outlet thickness of the i-th stand, with a value range of [1.8,28], in mm; Step 3.4: Calculate the influence coefficient of the relative convexity of the roll gap of each stand on the strip shape according to the following formula: Among them, γ i is the relative convexity of the roll gap of the i-th stand, R i is the radius of the working roller of the i-th frame, the value range is [300,360], the unit is mm; W i is the outlet thermal width of the i-th rack, with a value range of [1000,1500], in mm; c1 and c2 are -7.394 and 0.327 respectively; Step 3.5: Correct the influence coefficient of the relative convexity of the roll gap on the strip shape. The calculation formula is as follows: c i_α =(1-a)×c i +α×γ′ i ; c i_corr =c i_α ×A i ×B; Among them, γ i-1 is the relative convexity of the roll gap of the i-1th stand, γ i+1 is the relative convexity of the roll gap of the i+1th stand; α is the correction factor, and α ranges from 0 to 1; A i is the correction factor of the plate transfer coefficient of the i-th frame, and its value range is [0.87, 1.21]; B is the comprehensive correction factor of the plate transfer coefficient, and its value range is [0.9, 1]; γ i_corr is the influence coefficient of the relative convexity of the roll gap after correction of the i-th stand on the strip shape; Step 36: Calculate the influence of the relative convexity of the intermediate billet on the relative convexity of the strip at the exit of the i-th stand The calculation formula is as follows: Among them, C Trb H is the convexity of the intermediate blank, with a value range of [-363.79,940.92], in um; Trb is the intermediate billet thickness, the value range is [-363.79,940.92], the unit is mm; is the influence coefficient of the intermediate billet on the relative convexity of the exit strip of the i-th stand, and its value range is [-0.08665,-0.39695]; Step 3.7: Calculate the relative convexity of the strip at the exit of each rack. The calculation formula is as follows: in, is the relative convexity of the strip at the exit of the i-th rack, is the relative convexity of the roll gap of the j-th stand, <i;γ j_corr is the influence coefficient of the relative convexity of the roll gap after correction on the strip shape of the j-th stand, <i; Step 3.8: Calculate the strip convexity at the exit of each rack. The calculation formula is as follows: in, is the strip crown at the exit of the i-th rack; Step 3.9: In order to ensure that the proportional crown between the stands is constant and the final outlet crown is as close to the target crown as possible, the gradient descent method is used to solve the optimal solution of the bending and shifting rolls of the finishing mill. The objective function is as follows: In the formula, F i * is the optimal solution for the bending roll of the i-th stand, with a value range of [300,1800] and a unit of kN; S i * The optimal solution for the roller shifting of the i-th frame has a value range of [-150, 150], in mm; λ and β are weight coefficients.

2. The method for controlling the shape of a hot-rolled high-grade oriented silicon steel sheet according to claim 1, characterized in that: During the finishing rolling process of step 4, the cooling water volume of the rolls is controlled at 40m 3 / h~60m 3 / h; the load distribution during rolling follows the principle of decreasing in sequence. The first three passes adopt a large reduction rate, with a reduction rate of 45% to 50% for each pass, the fourth pass has a reduction rate of 28% to 32%, the fifth to sixth passes have a reduction rate of 20% to 24%, and the last pass has a reduction rate of less than 10%; the rolling speeds of each stand are 0.95m / s, 1.92m / s, 3.62m / s, 5.43m / s, 6.97m / s, 8.89m / s, and 10.29m / s respectively.

3. The method for controlling the shape of hot-rolled high-grade oriented silicon steel sheet according to claim 1, characterized in that: The chemical composition and mass percentage of the silicon steel sheet are as follows: C: 0.034% ~ 0.038%, Mn: 0.213% ~ 0.215%, Si: 3.12% ~ 3.22%, Nb: 0.0012% ~ 0.008%, Ti: 0.0019% ~ 0.0021%, V: 0.029% ~ 0.03%, Cu: 0.48% ~ 0.5%, Ni: 0.005% ~ 0.006%, Cr: 0.038% ~ 0.041%, Als: 0.0174% ~ 0.0196%, P: 0.011% ~ 0.015%, S: 0.048% ~ 0.05%, N: 0.091% ~ 0.094%, the rest is Fe and unavoidable impurities.

4. The method for controlling the shape of hot-rolled high-grade oriented silicon steel sheet according to claim 1, characterized in that: The finished product thickness of the silicon steel sheet ranges from 2mm to 3mm, the width ranges from greater than 1000mm to 1250mm, the convexity is close to the target convexity of 30um, the straightness is within 0 to 30I-Unit, and the wedge shape is controlled within the range of ±15um.

5. The method for controlling the shape of hot-rolled high-grade oriented silicon steel sheet according to claim 1, characterized in that: The crown control range of the CVC rollers used in the F1 to F3 stands during the finishing rolling process is -500um to 800um.

Images