A method for distributing and controlling the crown of a stand of a PC+WRS hot continuous rolling finishing mill train

Abstract

The application discloses a kind of PC+WRS hot continuous rolling finishing mill set frame crown distribution and control method, first from process control computer obtains the data set of strip steel to be produced, including finishing mill outlet strip steel width, target crown and the like data, then the upper and lower limits of proportion crown in the range of equipment capacity allowed is calculated, and the upper and lower limits of proportion crown allowed under the stable production condition of strip steel are calculated, finally according to the optimal capacity and production stability, the proportion crown distribution value of each frame is determined, for determining the PC angle and bending roll force used by each frame, the capacity of front frame PC angle can be fully utilized, and the production stability between frames is guaranteed, ideal crown control is realized.The application can fully exert the crown regulation and control capacity of upstream frame PC angle, while ensuring the stability of strip steel between frames, improving the crown pass rate of product and production stability.

Description

Technical Field

[0001] This invention relates to the field of hot strip rolling technology, and more particularly to a method for stand crown distribution and control of a PC+WRS hot continuous rolling mill. The PC+WRS mill (Pair Crossed rolling mill, Work Roll Shifting) is a mill with paired crossed rolling mills and lateral work roll shifting. Background Technology

[0002] For hot-rolled strip steel, the two main indicators reflecting the strip shape are crown and straightness. Crown reflects the difference between the thickness in the middle of the strip and the average thickness on both sides, while proportional crown refers to the ratio of the strip crown to its thickness. For traditional hot continuous rolling mills, the basic principle of production is to ensure that the crown and straightness of the strip after passing through the last stand meet the planned target values. As the strip passes through each stand, the unevenness caused by the change in crown between stands must not exceed the straightness dead zone. To achieve this, the crown of each stand in the finishing mill must follow a certain distribution method; ideally, it should be a proportional crown distribution method, meaning that the proportional crown of each stand in the finishing mill is equal.

[0003] To control the crown and straightness of strip steel, there are currently two main types of hot strip finishing mills: CVC mills (Continuously Variable Crown) and PC+WRS mills (Pair Crossed rolling mills, Work Roll Shifting). The basic form of a PC+WRS mill is to divide the finishing mill into upstream and downstream stands. The upstream stands (generally F1 to F4) are PC mills, which have strong crown control capabilities. The downstream stands (generally F5 to F7) are WRS mills, which lack crown control capabilities and can only rely on bending roll force for small-scale crown adjustments. For PC+WRS mills, due to the limited crown control capability of the downstream stands, to achieve the target values ​​for strip crown and straightness, it is necessary to fully utilize the control capabilities of the upstream stands; existing crown allocation methods are not suitable.

[0004] The existing crowning distribution technology has two main problems: First, it is easy for the upstream stand to still have the ability to adjust, but the crowning at the finishing mill exit cannot meet the product target, especially for strip steel with small crowning requirements, which leads to a decrease in the product yield. Second, it is easy for inconsistent wave trends to occur between stands, such as the wave trend at the exit of the previous stand being central and the wave trend at the exit of the next stand being edge, which has an adverse effect on production stability and may even lead to scrap steel accidents in severe cases.

[0005] Chinese patent CN112122357A discloses a method for distributing the crown of hot-rolled strip in finishing mills. This invention belongs to the technical field of strip shape control. The invention obtains the strip process data from the roughing mill exit and the strip thickness and width at the exit of each finishing mill stand. It calculates the target proportional crown of the strip exiting stand F7, then determines the strip crown at the exits of stands F4, F5, and F6 based on the principle of equal proportional crown distribution for downstream stands, calculates the adjustable proportional crown for stands F1, F2, and F3, and finally calculates the strip crown at the exits of stands F1, F2, and F3 based on the principle of minimizing changes in equivalent proportional crown. This completes the distribution of the finishing strip crown. This invention achieves the goal of setting the crown of hot-rolled strip in finishing mills while ensuring adjustment margins for each stand, providing a theoretical basis for optimizing the proportional crown setting on-site. This patent falls under the category of equal proportional crown distribution methods, requiring downstream stands to have significant crown adjustment capabilities. This patent is not applicable to PC+WRS mills.

[0006] Chinese Patent CN107626750A discloses a method for allocating the proportional crown of hot-rolled strip, belonging to the field of hot-rolled strip technology. The method includes the following steps: calculating the entrance proportional crown C0 of the finishing mill's F1 stand; obtaining the target proportional crown C6 of the finishing mill's last stand F6; calculating the total proportional crown change ΔC* of the finishing mill; calculating the proportional crown allocation coefficient λn of each stand in the finishing mill; calculating the proportional crown allocation amount ΔCn of each stand in the finishing mill; and calculating the strip exit proportional crown Cn of each stand in the finishing mill. This invention maximizes the strip shape control capability of the hot-rolled strip mill while ensuring good straightness and target crown of each stand. This patent is similar to the previous one, and also falls under the category of proportional crown distribution methods. It is not applicable to PC+WRS mills. This patented method will cause inconsistent wave patterns between stands, which will affect production stability.

[0007] Therefore, for PC+WRS mills, how to fully utilize the front stand crown adjustment capability while ensuring stability between stands is the key issue that the crown distribution and control method needs to address. Summary of the Invention

[0008] The purpose of this invention is to provide a method for the distribution and control of stand crown in a PC+WRS hot continuous rolling mill. This method can fully utilize the crown adjustment capability of the PC angle of the upstream stand, while ensuring the stability of the strip between stands, and improving the crown yield and production stability of the product.

[0009] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0010] A method for stand crown distribution and control in a PC+WRS hot continuous rolling mill finishing unit, comprising the following steps:

[0011] Step 1: Obtain strip steel process data by acquiring the dataset of the strip steel to be produced from the process control computer;

[0012] Step 2: Calculate the proportional crown of the mechanical capacity. Assume the upstream stands of the PC+WRS mill are F1-F4, and the downstream stands are F5-F7. F1-F4 represent the PC mill, and F5-F7 represent the WRS mill. Calculate the maximum proportional crown C achievable for the produced strip under the conditions of maximum equipment capacity (maximum allowable PC angle and maximum allowable bending roll force) and minimum capacity (minimum allowable PC angle and minimum allowable bending roll force). pmax(i) and minimum proportional convexity C pmin(i) , where i represents the rack number;

[0013] Step 3: Calculate the proportional convexity under stable production conditions, specifically the maximum proportional convexity C under stable production conditions. λpmax(i) and minimum value C λpmin(i) ;

[0014] Step 4: Calculate the upper and lower limits of the proportional convexity, and determine the upper limit C of the proportional convexity that simultaneously satisfies both equipment capacity and production stability conditions. pU(i) and lower limit C pL(i) ;

[0015] Where the upper limit value of proportional convexity is C pU(i) The maximum proportional convexity C λpmax(i) and maximum proportional convexity C pmax(i) The minimum of the two, the lower limit of proportional convexity C pL(i) The minimum value of proportional convexity C λpmin(i) and minimum proportional convexity C pmin(i) The maximum value of the two;

[0016]

[0017] Step 5: Allocate the proportional convexity of each rack. For downstream racks, the convexity should not exceed the proportional convexity C of each rack. pU(i) Under the upper limit conditions, the proportional convexity distribution value remains approximately equal between the front and rear racks, and the F7 rack simultaneously meets product target C. p_target Requirements: For upstream racks, the convexity should not exceed the upper limit C of the F5 rack's proportional convexity. pU(5) Under these conditions, the F1 frame takes the minimum permissible proportional convexity C. p_min and C pU(5) The minimum value is allocated to racks F2, F3, and F4 according to a decreasing principle, and the proportional convexity of each rack is calculated.

[0018] Step 6: Allocate the target crown of each frame. Determine the target value of the exit crown of each frame according to the proportional crown allocation value of each frame and calculate it according to formula (5). Send this target value to the process computer plate shape control system to determine the PC angle and bending roller force used by each frame to achieve ideal crown control.

[0019] C (i) =C p_F(i) Thick (i) (5)

[0020] In the formula: C (i) The target value for the outlet convexity of the i-th rack is given in mm and C. p_F(i) The proportional convexity allocation value for the i-th rack is dimensionless and Thick. (i) The thickness at the outlet of the i-th rack is in mm.

[0021] The maximum proportional convexity C pmax(i) The roll crossing angle PC of the finishing mill is calculated using formula (1). (i) Minimum PC value is allowed for PC angle. min(i) The bending force F of the finishing mill roll (i) The maximum value F is allowed for the bending roller force. max(i) 0.3 to 0.4 times;

[0022] The minimum proportional convexity C pmin(i) The roll crossing angle PC of the finishing mill is calculated using formula (1). (i) The maximum PC value is allowed for the PC angle. max(i) The bending force F of the finishing mill roll (i) The maximum value F is allowed for the bending roller force. max(i) 0.8 to 0.9 times;

[0023] Formula (1) is as follows:

[0024]

[0025] In the formula: C p(i) C represents the proportional crown of the strip, in mm / mm; p(0) The proportional crown of the intermediate billet, with a value ranging from 0.008 to 0.012; Thick (0) Thickness of intermediate billet rough A 1(i) The transverse stiffness coefficient of the rolling mill, in kN / mm, ranges from 6.0E+5 to 9.0E+6; A 2(i) The conversion factor for the bending roll force crown is in mm / KN, and its value ranges from 8.8E-7 to 9.5E-6; A 3(i) For PC convexity conversion factor, in mm / mm, the value ranges from 0.083 to 0.87; A4(i) The work roll type conversion factor, in mm / mm, ranges from 0.12 to 1.2; A 5(i) The genetic influence coefficient of the frame is expressed in mm / mm, with a value ranging from 0.08 to 0.98; A 6(i) _t_ is a constant affecting convexity, in mm, with a value ranging from -0.04 to 0.06; FixPos is the location of the convexity characteristic value, with a value of 25 or 40, in mm; PC (i) The PC angle of the finishing mill, in degrees; F (i) The bending force of the finishing mill rolls is expressed in kN.

[0026] The maximum proportional convexity C λpmax(i) The allowable value of the frame outlet unevenness λ is calculated using formula (2). (i) The value is set according to the upper limit allowed by the trend of the edge wave, ranging from 3.7 to 98.7;

[0027] The minimum value of the proportional convexity C λpmin(i) The allowable value of the frame outlet unevenness λ is calculated using formula (2). (i) According to the allowed lower limit value based on the mid-wave trend, the value ranges from -98.7 to -3.7;

[0028]

[0029] In the formula: C λp(i) Proportional convexity under stable production conditions, unit: mm / mm; C λp(0) λ represents the proportional crown of the intermediate billet, with a value ranging from 0.008 to 0.012. (i) B represents the permissible unevenness at the rack exit, in units of IU. 1(i) This is the unevenness conversion factor, with no unit, and a value ranging from 0.01 to 0.68.

[0030] The decreasing coefficients for racks F2, F3, and F4 in step 5 are 0.128, 0.618, and 0.872, respectively.

[0031] Calculate the proportional convexity of each frame according to formula (4);

[0032]

[0033]

[0034] In the formula: C p_F(1) ~C p_F(7) These represent the proportional convexity of the exits of racks 1 through 7, in units not specified; C p_target Target proportional convexity, unitless; C p_min The minimum permissible proportional convexity ranges from 0.001 to 0.003; C targetTarget convexity of strip steel (known value), unit: mm; Thick target Thickness of finished strip at the exit (known value), unit mm.

[0035] The stand crown allocation and control method of the PC+WRS hot strip finishing mill of this invention first obtains the dataset of the strip to be produced from the process control computer, including the strip width at the finishing mill exit, target crown, and other data. Then, it calculates the upper and lower limits of proportional crown within the allowable range of equipment capacity for each stand, and calculates the upper and lower limits of proportional crown under stable strip production conditions. Finally, it determines the proportional crown allocation value of each stand according to optimal capacity and production stability, which is used to determine the PC angle and bending roll force used by each stand. This method can fully utilize the PC angle capacity of the preceding stand and ensure production stability between stands, achieving ideal crown control.

[0036] Compared with the prior art, the beneficial effects of this invention are:

[0037] (1) For the upstream racks, namely racks F1 to F4, the present invention adopts a control method based on the principle of optimal capacity utilization. Under the condition that the proportional convexity of rack F5 does not exceed the upper limit, the capacity of rack F1 is maximized and the capacity of racks F2, F3 and F4 is gradually reduced. In this way, the equipment capacity is combined with the product constraints, and the equipment capacity can be fully utilized.

[0038] (2) For the downstream racks, namely F5 to F7 racks, the present invention adopts a control method based on the principle of production stability. Under the condition of not exceeding the upper limit of proportional convexity, the proportional convexity is distributed according to the principle of keeping the front and rear racks approximately equal, thereby providing a rack convexity control method with consistent edge wave trend between racks, which can improve the stability of production, especially for the production of thin-specification products.

[0039] The stand crown distribution and control method of the present invention, tailored to the characteristics of PC+WRS rolling mills, can fully leverage the strong crown adjustment capability of the front stand PC angle, thereby improving the crown yield of products. This is especially true for products with high precision requirements, where the advantages of the rolling mill can be further utilized. At the same time, the method of the present invention rolls in the same direction as the edge wave trend between stands, which is more conducive to improving production stability, especially for the production of thin-gauge products, and avoiding the occurrence of production accidents. Attached Figure Description

[0040] Figure 1 This is a flowchart of the stand crown distribution and control method of the PC+WRS hot continuous rolling mill finishing unit of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0042] See Figure 1A method for stand crown distribution and control in a PC+WRS hot strip finishing mill, comprising the following steps:

[0043] Step 1: Obtain strip process data. Retrieve the dataset of the strip to be produced from the process control computer, including the strip width (in mm) at the finishing mill exit and the target crown (C). target (unit: mm), thickness of finished strip at export (Thick) target (unit: mm) and intermediate billet thickness (Thick) rough (unit: mm), strip thickness at the exit of each finishing mill stand (Thick) (i) (Unit: mm), calculated rolling force for each stand (P) (i) (unit: kN), diameter of each frame work roll (D) w(i) (unit: mm), length of each work roll (L) w(i) (unit: mm), original roll type of each frame work roll (C) R(i) (unit: mm), equivalent wear calculation value of each frame work roller (C) W(i) (unit: mm), calculated equivalent thermal crown of each frame work roll (C) T(i) (Unit: mm), maximum allowable PC angle for each rack (PC) max(i) (Unit: °), minimum allowable PC angle for each rack (PC) min(i) (Unit: °), maximum allowable bending roll force for each frame (F) max(i) , KN), where i represents the rack number, which is generally 6 or 7. In this embodiment, the number of racks is 7.

[0044] Step 2: Calculate the proportional crown of the mechanical capacity. The upstream stands of the PC+WRS mill are typically F1-F4 for the PC mill, and the downstream stands are typically F5-F7 for the WRS mill. The WRS mill does not have crown control capability and can only rely on the bending roll force for small-scale crown adjustments. Based on the characteristics of the mill, this step calculates the maximum proportional crown C achievable for the produced strip under the conditions of the equipment's maximum capacity (maximum allowable PC angle and maximum allowable bending roll force) and minimum capacity (minimum allowable PC angle and minimum allowable bending roll force). pmax(i) and minimum proportional convexity C pmin(i) .

[0045] Maximum proportional convexity C pmax(i) The roll crossing angle PC of the finishing mill is calculated using formula (1). (i) Minimum PC value is allowed for PC angle. min(i) The bending force F of the finishing mill roll (i) The maximum value F is allowed for the bending roller force. max(i) 0.3 to 0.4 times that.

[0046] Minimum proportional convexity C pmin(i) The roll crossing angle PC of the finishing mill is calculated using formula (1). (i) The maximum PC value is allowed for the PC angle. max(i) The bending force F of the finishing mill roll (i) The maximum value F is allowed for the bending roller force. max(i) 0.8 to 0.9 times that.

[0047] Formula (1) is as follows:

[0048]

[0049] In the formula: C p(i) C represents the proportional crown of the strip, in mm / mm; p(0) The proportional crown of the intermediate billet, typically ranging from 0.008 to 0.012; Thick (0) Thickness of intermediate billet rough A 1(i) This is the transverse stiffness coefficient of the rolling mill, in kN / mm, typically ranging from 6.0E+5 to 9.0E+6; A 2(i) The conversion factor for the bending roll force crown is in mm / KN, and its value ranges from 8.8E-7 to 9.5E-6; A 3(i) For PC convexity conversion factor, in mm / mm, the value ranges from 0.083 to 0.87; A 4(i) The work roll type conversion factor, in mm / mm, ranges from 0.12 to 1.2; A 5(i) The genetic influence coefficient of the frame is expressed in mm / mm, with a value ranging from 0.08 to 0.98; A 6(i) The convexity influence constant is expressed in mm and ranges from -0.04 to 0.06; FixPos is the convexity characteristic value position, typically 25 or 40 mm; convexity is the difference between the center thickness and the edge thickness of the strip. The selection of the edge position is defined as the convexity characteristic value position. For hot rolling, the edge position is usually selected as 25 mm or 40 mm; PC (i) The PC angle of the finishing mill, in degrees; F (i) The bending force of the finishing mill rolls is expressed in kN.

[0050] Step 3: Calculate the proportional convexity for stable production. To ensure stability of the strip steel during production across different stands, the unevenness at the exit of each stand must be within the allowable range. This step calculates the maximum proportional convexity C under stable production conditions based on formula (2). λpmax(i) and minimum value C λpmin(i) .

[0051] C λpmax(i)The allowable value of the frame outlet unevenness λ is calculated using formula (2). (i) The upper limit of the allowable value is determined according to the trend of the edge wave, and is generally taken as 3.7 to 98.7.

[0052] C λpmin(i) The allowable value of the frame outlet unevenness λ is calculated using formula (2). (i) According to the allowed lower limit value based on the mid-wave trend, the value is generally -98.7 to -3.7.

[0053]

[0054] In the formula C λp(i) Proportional convexity under stable production conditions, unit: mm / mm; C λp(0) λ represents the proportional crown of the intermediate billet, typically ranging from 0.008 to 0.012. (i) B represents the permissible unevenness at the rack exit, in units of IU. 1(i) This is the unevenness conversion factor, with no unit, and generally a value of 0.01 to 0.68.

[0055] Step 4: Calculate the upper and lower limits of the proportional convexity, and find the upper limit value C of the proportional convexity that simultaneously satisfies the conditions of equipment capacity and production stability. pU(i) and lower limit C pL(i) C pU(i) C λpmax(i) and C pmax(i) The minimum of the two, C pL(i) C λpmin(i) and C pmin(i) The maximum of the two.

[0056]

[0057] Step 5: Allocate the proportional convexity of each rack. Within the allowable upper and lower limits of proportional convexity, determine the proportional convexity allocation value for each rack based on optimal capacity utilization and production stability. For downstream racks, typically F5 to F7 racks, the allocation value should not exceed the proportional convexity C of each rack, following the principle of production stability. pU(i) Under the upper limit conditions, the proportional convexity distribution value is kept approximately equal between the front and rear racks, and the F7 rack must simultaneously meet product target C. p_target Requirements: For upstream racks, based on the principle of optimal capacity utilization, the convexity should not exceed the upper limit C of the F5 rack's proportional convexity. pU(5) Under the condition that the F1 frame can achieve its maximum capacity, the minimum permissible proportional convexity C is taken. p_min and C pU(5)The minimum value of F2, F3, and F4 is allocated according to the principle of gradually decreasing capacity, with decreasing coefficients of 0.128, 0.618, and 0.872 respectively. The proportional convexity allocation value obtained according to this method is the minimum allowable value. The smaller the proportional convexity, the larger the corresponding PC angle, which means the optimal capacity is achieved. The proportional convexity of each rack is calculated according to formula (4).

[0058]

[0059]

[0060] In the formula C p_F(1) ~C p_F(7) These represent the proportional convexity of the exits of racks 1 through 7, in units not specified; C p_target Target proportional convexity, unitless; C p_min The minimum permissible proportional crown is typically taken as 0.001 to 0.003. Target crown C of the strip. target Unit: mm; Thickness of finished strip at export target , unit mm.

[0061] Step 6: Allocate the target convexity of each frame. Determine the target value of the exit convexity of each frame according to the proportional convexity allocation value of each frame, and calculate according to formula (5). Send this target value to the process computer plate shape control system to determine the PC angle and bending roller force used by each frame. This can give full play to the PC angle capability of the front frame and ensure the production stability between frames, so as to achieve ideal convexity control.

[0062] C (i) =C p_F(i) Thick (i) (5)

[0063] In the formula: C (i) The target value for the outlet convexity of the i-th rack is given in mm and C. p_F(i) The proportional convexity allocation value for the i-th rack is dimensionless and Thick. (i) The thickness at the outlet of the i-th rack is in mm.

[0064] The proportional convexity is the ratio of convexity to thickness. Here, the convexity value can be obtained by multiplying the proportional convexity allocation value by the thickness, which serves as the target for the convexity of each rack exit.

[0065] According to the rack convexity allocation and control method of the present invention, step 4 can obtain the upper and lower limits of the proportional convexity that simultaneously meet the conditions of equipment capacity and production stability. Step 5 uses the constraints of step 4 to separate the upstream and downstream racks. The downstream rack maintains a similar proportional convexity to the front and rear racks to ensure production stability. The upstream rack utilizes its capacity according to the principle that rack F1 utilizes its full capacity, and racks F2, F3, and F4 gradually decrease their capacity. The target convexity of each rack obtained in this way ensures that the calculated PC angle operates within the maximum allowable range, achieving optimal capacity utilization. Under stable conditions between racks, the target product convexity is guaranteed, achieving ideal convexity control.

[0066] Example

[0067] The stand crown allocation and control method of the present invention will be further illustrated below with an example of stand crown allocation and control in a hot continuous rolling mill (7 stands for finishing, stands 1 to 4 are PC mills, and stands 5 to 7 are WRS mills). The example is the 38th piece of steel from a certain plan on a certain day in December 2021.

[0068] Step 1: Obtain the dataset for the 38th steel piece from the process control computer. This dataset includes the strip width at the finish mill exit, the target strip crown, the strip thickness at the finish mill exit, the intermediate billet thickness; the strip thickness at the finish mill exit for each stand, the calculated rolling force for each stand, the roll diameter of each stand's work rolls, the roll body length of each stand's work rolls, the original roll profile of each stand's work rolls, the calculated equivalent wear of each stand's work rolls, the calculated equivalent thermal crown of each stand's work rolls, the maximum allowable PC angle for each stand, the minimum allowable PC angle for each stand, and the maximum allowable bending force for each stand. The data is shown in Table 1.

[0069] Table 1. Data set of the 38th steel piece

[0070]

[0071]

[0072] Step 2, calculate the mechanical capacity proportional crown. Use formula (1) to calculate the maximum and minimum proportional crowns respectively. In formula (1), the proportional crown C of the intermediate billet... p(0) The value is 0.01; the convexity eigenvalue position FixPos is 40. Maximum proportional convexity C pmax(i) Calculation of the bending roll force F of the finishing mill (i) The maximum value F is allowed for the bending roller force. max(i) 0.3 times. Minimum proportional convexity C pmin(i) Calculation of the bending roll force F of the finishing mill (i) The maximum value F is allowed for the bending roller force. max(i) 0.8 times. A 1(i) ~A 6(i)The values ​​and calculation results Cp are shown in Table 2.

[0073] Table 2. Calculation results of mechanical capacity proportional convexity

[0074]

[0075] Step 3, Calculation of proportional convexity under stable production conditions: According to formula (2), calculate the maximum proportional convexity C under stable production conditions. λpmax(i) and minimum value C λpmin(i) The formula includes the allowable value for frame outlet unevenness and B. 1(i) The values ​​and calculation results are shown in Table 3.

[0076] Table 3. Calculation Results of Stable Production Proportional Convexity

[0077]

[0078] Step 4, Calculation of proportional convexity upper and lower limits: Find the upper limit value C of proportional convexity that simultaneously satisfies the conditions of equipment capacity and production stability according to formula (3). pU(i) and lower limit C pL(i) The calculation results are shown in the table below.

[0079] Table 4. Calculation results of proportional convexity upper and lower limits

[0080] i CpU CpL 1 0.006 -0.006 2 0.013 -0.016 3 0.014 -0.022 4 0.019 -0.025 5 0.019 -0.025 6 0.017 -0.026 7 0.015 -0.023

[0081] Step 5, proportional convexity allocation for each rack: Calculate the proportional convexity of each rack according to formula (4), where C p_min The minimum allowable proportional convexity is set to 0.003. The calculation results are shown in Table 5.

[0082] Table 5. Proportional convexity distribution results for each frame

[0083]

[0084] Step 6, Target Convexity Allocation for Each Stand: Calculate the target convexity of each stand according to formula (5), and the calculation results are shown in Table 6. Send this target value to the process computer strip shape control system, use this target as the result of formula (1), and solve for the PC angle as a variable. The actual control values ​​of the PC angle for stands 1 to 4 are 0.8, 0.7, 0.4, and 0.3, respectively, in degrees. Production is stable during the rolling process, and the actual convexity of the strip is 41, achieving the product control target.

[0085] Table 6. Target convexity allocation results for each rack

[0086]

[0087] In this embodiment, the design requirement for the strip steel product is a convexity target of 40μm (0.040mm) at the 40mm position on the edge (i.e., convexity characteristic value position 40). During the production process, the edge convexity needs to be controlled between 20 and 60μm. After adopting the frame convexity distribution and control method of the present invention, the actual convexity of the strip steel is 41μm, indicating that the product control target is well met.

[0088] The stand crown distribution and control method of the PC+WRS hot continuous rolling mill of this invention can give full play to the strong crown adjustment capability of the front stand PC angle. At the same time, rolling in the same direction as the edge wave trend between stands is more conducive to improving production stability, achieving ideal crown control, and improving the product crown qualification rate. It has a good effect, especially for products with strict requirements such as small crown, and can be widely used in PC+WRS hot continuous rolling mills.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for stand crown distribution and control in a PC+WRS hot continuous rolling mill finishing unit, characterized by: The steps are as follows: Step 1: Obtain strip steel process data by acquiring the dataset of the strip steel to be produced from the process control computer; Step 2: Calculate the proportional crown of the mechanical capacity. Assume the upstream stands of the PC+WRS mill are F1~F4, and the downstream stands are F5~F7. F1~F4 represent the PC mill, and F5~F7 represent the WRS mill. Calculate the maximum proportional crown of the strip that can be produced under the conditions of maximum equipment capacity (maximum allowable PC angle and maximum allowable bending roll force) and minimum capacity (minimum allowable PC angle and minimum allowable bending roll force). and minimum proportional convexity ,in Represents rack number; Step 3: Calculate the proportional convexity under stable production conditions, and calculate the maximum proportional convexity under stable production conditions respectively. and minimum value ; Step 4: Calculate the upper and lower limits of the proportional convexity, and determine the upper limit of the proportional convexity that simultaneously satisfies both equipment capacity and production stability conditions. and lower limit value ; The upper limit of proportional convexity Maximum proportional convexity and maximum proportional convexity The minimum of the two, the lower limit of proportional convexity Minimum of proportional convexity and minimum proportional convexity The maximum value of the two; (3) ； Step 5: Allocate the proportional convexity of each rack, ensuring that the convexity of the downstream rack does not exceed the upper limit of the proportional convexity of each rack. Under these conditions, the proportional convexity distribution value remains approximately equal between the front and rear racks, and the F7 rack simultaneously meets the product objectives. Requirements: For upstream racks, the proportional convexity should not exceed the upper limit of the F5 rack. Under these conditions, the F1 frame takes the minimum permissible proportional convexity. and The minimum value is allocated to racks F2, F3, and F4 according to a decreasing principle, and the proportional convexity of each rack is calculated. Step 6: Allocate the target crown of each frame. Determine the target value of the exit crown of each frame according to the proportional crown allocation value of each frame and calculate it according to formula (5). Send this target value to the process computer plate shape control system to determine the PC angle and bending roller force used by each frame to achieve ideal crown control. (5) In the formula: Here is the target value for the outlet convexity of the i-th frame, in mm; This represents the proportional convexity allocation value for the i-th rack, which is dimensionless. The thickness at the outlet of the i-th rack is in mm.

2. The stand crown distribution and control method of the PC+WRS hot continuous rolling mill unit according to claim 1, characterized in that: The maximum proportional convexity The roll crossing angle of the finishing mill is calculated using formula (1). Minimum value is allowed for PC angle. Bending roll force of finishing mill The maximum value is allowed for the bending roller force. 0.3 to 0.4 times; The minimum proportional convexity The roll crossing angle of the finishing mill is calculated using formula (1). Maximum value allowed for PC angle Bending roll force of finishing mill The maximum value is allowed for the bending roller force. 0.8 to 0.9 times; Formula (1) is as follows: （1） In the formula: The proportional crown of the strip, in mm / mm; The proportional crown of the intermediate billet, with a value of 0.008~0.012; For the thickness of the intermediate billet ; This is the transverse stiffness coefficient of the rolling mill, in kN / mm, with values ​​ranging from 6.0E+5 to 9.0E+6. The conversion factor for the bending roller force crown is in mm / KN and ranges from 8.8E-7 to 9.5E-6. The convexity conversion factor for PC angle is expressed in mm / mm and ranges from 0.083 to 0.

87. The working roll type conversion factor, in mm / mm, ranges from 0.12 to 1.

2. The genetic influence coefficient of the rack is expressed in mm / mm and ranges from 0.08 to 0.

98. For constants affecting convexity, in mm, with values ​​ranging from -0.04 to 0.06; This represents the location of the convexity characteristic value, which is either 25 or 40, in mm. The PC angle of the finishing mill is expressed in degrees. The bending force of the finishing mill rolls is expressed in kN. The calculated rolling force for each stand is expressed in kN. The width of the finished strip at the exit is in mm; The diameter of the working rollers for each frame is in mm; The length of the working rollers for each frame is in mm. The original roll type for each frame's work rolls, in mm; The equivalent wear calculation values ​​for the work rollers of each frame are in mm. The calculated equivalent thermal crown of the work rolls for each frame is in mm.

3. The stand crown distribution and control method of the PC+WRS hot continuous rolling mill unit according to claim 1, characterized in that: The maximum proportional convexity The allowable value of the frame outlet unevenness is calculated using formula (2). The upper limit of the allowable value is determined according to the trend of the edge wave, ranging from 3.7 to 98.7; The minimum value of proportional convexity The allowable value of the frame outlet unevenness is calculated using formula (2). According to the mid-wave trend, the lower limit value is allowed to be -98.7 to -3.7; (2) In the formula: The proportional convexity is measured in mm / mm to ensure stable production. The proportional crown of the intermediate billet, with a value of 0.008~0.012; This is the allowable unevenness value at the rack exit, in IU. This is the unevenness conversion factor, with no unit, and a value ranging from 0.01 to 0.

68.

4. The stand crown distribution and control method of the PC+WRS hot continuous rolling mill finishing unit according to claim 1, characterized in that: The decreasing coefficients for racks F2, F3, and F4 in step 5 are 0.128, 0.618, and 0.872, respectively.

5. The stand crown distribution and control method of the PC+WRS hot continuous rolling mill unit according to claim 4, characterized in that: Calculate the proportional convexity of each frame according to formula (4); （4） In the formula: ~ These represent the proportional convexity of the exits of racks 1 through 7, in units of none. Target proportional convexity, unitless; The minimum permissible proportional convexity is 0.001 to 0.

003. Target convexity of strip steel (known value), unit mm; Thickness of finished strip steel at the export (known value), unit mm.

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