Closed-loop control method, system and equipment for improving uniformity of strip steel edge zinc layer and medium

Abstract

The invention relates to the technical field of coating thickness control, in particular to a closed-loop control method, system and equipment for improving the uniformity of a strip steel edge zinc layer and a medium. The closed-loop control method comprises the following steps: step 1, at an air knife injection section, dividing 18 control points at equal intervals in the length of the whole body of an air knife lip, and arranging a thickness gauge behind the air knife; step 2, measuring the thickness of the zinc layer at each point in the width direction of the strip steel by a thickness gauge, and normalizing the width; 3, according to the zinc layer thickness data and the normalized plate width, the strip steel plate shape is fitted based on the Legendre polynomial, and the coefficient # imgabs0 # of the second-order Legendre polynomial is solved through fitting of the least square method; 4, the interval range of # imgabs1 # is judged, and corresponding operation is executed; and step 5, circularly executing the step 2 to the step 4. The method can effectively solve the problem of poor uniformity of zinc layers at the edges of strip steel of different specifications, so that the distribution of the zinc layers in the width direction of the strip steel is more consistent.

Description

Technical Field

[0001] The present invention relates to the technical field of coating thickness control, and in particular to a closed-loop control method, system, equipment and medium for improving the uniformity of zinc coating on the edge of a steel strip. Background Art

[0002] Hot-dip galvanized sheets are widely used in many industries such as construction and automobile manufacturing. With the gradual increase in the production capacity of hot-dip galvanized sheets, the current market supply and demand has become saturated, and downstream users have increasingly stringent requirements on the quality of hot-dip galvanized sheets.

[0003] Research has found that the uniformity of the coating thickness of hot-dip galvanized sheet has a crucial impact on its performance. First, the galvanized layer, as an anodic coating, protects the base metal through its own corrosion. If the coating thickness is uneven, the thinner coating cannot withstand sacrificial corrosion, which will cause the base metal to rust prematurely. Therefore, the uniformity of the coating thickness is directly related to the corrosion resistance of the hot-dip galvanized sheet. Secondly, the uneven coating thickness will cause differences in the mechanical properties of hot-dip galvanized steel coils in different parts. At the same time, for some application scenarios with high requirements on appearance, such as architectural decoration and home appliance casings, the uniformity of the coating thickness directly affects the appearance quality of the hot-dip galvanized steel coils. Thin coatings usually have poor gloss, and are easily exposed during subsequent treatments such as polishing and passivation, affecting the overall aesthetics. To this end, technicians start with improving the uniformity of the coating thickness to further enhance the performance of hot-dip galvanized sheet.

[0004] CN 110565039 A provides a method for controlling the zinc layer thickness of a hot-dip galvanizing unit. The method determines the operating condition changes, calculates all possible zinc layer thickness prediction values ​​corresponding to the current operating condition changes based on process parameters, finds a group of zinc layer thickness prediction values ​​closest to the zinc layer thickness set value, and adjusts and controls the corresponding parameters of the air knife based on the process parameters corresponding to the group of zinc layer thickness prediction values. The method is characterized by introducing a neural network model to optimize prediction and improve control accuracy by combining production big data. However, the neural network model requires a large amount of historical data training. If the production process is adjusted or the equipment ages, the model's generalization ability may decrease, resulting in control lag. In addition, the method requires the collection of multiple parameters such as strip speed, air knife height, distance from knife lip to strip, air knife pressure, knife lip gap, and strip thickness. The multi-parameter combination calculation may cause adjustment delays, affecting the uniformity of the coating.

[0005] CN 112899600 A provides a galvanizing method for high-strength hot-dip galvanized steel strip with an ultra-thick zinc layer. By optimizing the hot-dip galvanizing furnace control unit, zinc pot control unit, zinc layer control unit, and cooling control unit, the method can continuously and stably produce hot-dip galvanized thick-coated products. The disadvantages of this method are: ① It is only applicable to steel strips with a thickness of 2.5-3.0 mm and a zinc layer of ≥600 g / m 2②: The segmented knife lip opening must be pre-set, and no online dynamic adjustment is performed during the control process. There is a lack of closed-loop linkage between the real-time detection of the coating thickness and the air knife parameters.

[0006] CN 116949384 A discloses a closed-loop control method for edge thickness defects in ultra-thin, thick-zinc-coated hot-dip galvanized sheet. The method optimizes edge drop by optimizing the hot-rolling crown, the galvanizing line speed, the sheet temperature entering the zinc pot, the position of the air knife edge baffle, and the skin-passing process. Furthermore, the skin-passing rolling force is controlled based on the strip thickness profile detected by the exit thickness gauge. This method places high demands on the skin-passing mill's functionality, imposes stringent control conditions, and is difficult to manufacture. Furthermore, the closed-loop control based on the comparison of the thickness gauge's edge profile with the intermediate profile is inefficient. Summary of the Invention

[0007] To address the technical issues of existing methods for controlling the zinc coating thickness of hot-dip galvanized steel sheets, such as a lack of closed-loop control or low closed-loop control efficiency, the present invention provides a closed-loop control method, system, device, and medium for improving the uniformity of the zinc coating on the edges of steel strips. This method effectively addresses the issue of poor zinc coating uniformity on the edges of steel strips of varying specifications, significantly improving the uniformity and adjustment accuracy of zinc coating thickness control, and ensuring a more consistent zinc coating distribution across the width of the strip.

[0008] The technical solutions of the present invention are as follows: In a first aspect, the present invention provides a closed-loop control method for improving the uniformity of the zinc layer on the edge of a steel strip, comprising the following steps: Step 1: In the air knife blowing section, the air knife lip is divided into 18 control points at equal intervals along its entire length, and a thickness gauge is set behind the air knife; Step 2: After the strip passes through the air knife, the thickness of the zinc layer at each point in the width direction is measured by a thickness gauge, and the width is normalized to obtain the normalized plate width. y i , y i ∈[-1, 1]; Step 3: Based on the zinc layer thickness data and normalized plate width obtained in step 2 y i , based on the Legendre polynomial fitting of the strip shape, the coefficients of the second-order Legendre polynomial are solved by the least squares method , and calculate the coefficients The absolute value of , ∈[0,1); Step 4, judge and perform corresponding operations: like satisfy , maintain the current lip opening of each control point; like satisfy , the lip opening of all control points is uniformly set to 1.10 mm; like satisfy , the lip opening of the six control points in the middle is uniformly set to 1.15 mm, and the lip opening of each control point on both sides is increased by 0.03 mm until the lip opening reaches 1.30 mm and no longer increases; like satisfy , the lip opening of the six control points in the middle is uniformly set to 1.20 mm, and the lip opening of each control point on both sides is increased by 0.05 mm; Step 5: Repeat steps 2 to 4.

[0009] Furthermore, in step 1, the initial values ​​of the lip opening of the 18 control points are set as follows: The lip opening of all control points was uniformly set to 1.10 mm.

[0010] Furthermore, in step 3, the basic flatness mode selects the 1st to 4th order Legendre polynomials, which are expressed as: , Where, 、 、 and are coefficients, y i is the normalized plate width; Constructing the fitting function , according to the zinc layer thickness data and normalized plate width obtained in step 2 y i , the polynomial regression decomposition method based on the least squares principle is used to establish a pattern recognition model, and the coefficients are obtained. The numerical value of .

[0011] Furthermore, the air knife lip angle of the air knife blowing section is controlled as follows: The angle of the upper air knife is -0.7°~-0.8°, and the angle of the lower air knife is -0.9°~-1.1°. On the one hand, this setting ensures that the airflow blown out by the air knife is downward to avoid gravity interference. On the other hand, the air knife angles are staggered to avoid turbulence in the opposite direction of the airflow.

[0012] Furthermore, the air knife edge baffle distance of the air knife blowing section is controlled as follows: S=2h+1, Where, S is the distance between the air knife edge baffle, unit is mm, h is the thickness of the strip, in mm.

[0013] Furthermore, the air knife distance of the air knife blowing section is controlled to 7 mm~12 mm, the air knife pressure is controlled to 80 mbar~600 mbar, the air knife height is controlled to 180 mm~350 mm, the correction roller insertion amount is controlled to 15 mm~40 mm, and the air knife frame is controlled to ±10 mm, thereby improving the accuracy of zinc layer control.

[0014] Furthermore, the strip steel is hot-dip galvanized strip steel, and the galvanizing process of the hot-dip galvanized strip steel is controlled according to the following parameters: The zinc liquid temperature in the galvanizing section is 450℃~460℃, the aluminum content of the zinc liquid is 0.26%~0.28%, and the plate temperature entering the zinc pot is 455℃~480℃. By controlling the process parameters, rapid cooling or solidification of the edge zinc layer can be effectively avoided.

[0015] In a second aspect, the present invention provides a system for improving the uniformity of the zinc layer on the edge of a steel strip, the system being used to implement the above-mentioned closed-loop control method for improving the uniformity of the zinc layer on the edge of a steel strip, comprising: Data acquisition module, used to measure the zinc layer thickness of the strip and output it; The data preprocessing module is used to normalize the strip width and map the actual plate width to the [-1, 1] interval to obtain the normalized plate width. y i And output; Plate shape feature calculation module, used to obtain normalized plate width y i The strip shape is fitted based on Legendre polynomials and the zinc layer thickness data. The coefficients of the second-order Legendre polynomials are solved by the least squares method. , calculate the coefficient The absolute value of And output; Judgment and decision module, used to Output different air knife lip opening control commands: like ∈[0, 0.1), output the command to maintain the current lip opening of each control point; like ∈[0.1, 0.3), output the command to uniformly set the lip opening of all control points to 1.10 mm; like ∈[0.3, 0.6), output a command to uniformly set the lip opening of the six control points in the middle to 1.15 mm, and increase the lip opening of each control point on both sides by 0.03 mm until the lip opening reaches 1.30 mm and stops increasing; like ∈[0.6, 1), output the command to uniformly set the lip opening of the six control points in the middle to 1.20 mm, and increase the lip opening of each control point on both sides by 0.05 mm; The control execution module is used to adjust the lip opening degree of 18 control points along the entire length of the air knife.

[0016] The third invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor, wherein the processor is configured to implement the steps of the above-mentioned closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip when executing the computer program.

[0017] In a fourth aspect, the present invention further provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip.

[0018] The beneficial effects of the present invention are: The core of the closed-loop control method for improving the uniformity of the zinc coating on the strip edges provided by this invention lies in the application of fluid dynamics principles to precisely control the distribution of the gas jet flow rate at the air knife lip, effectively reducing the problem of excessive zinc coating thickness on the strip edges caused by airflow drop losses. Furthermore, by optimizing the galvanizing process parameters and air knife parameters, and based on the precise measurement results of a thickness gauge, a closed-loop control model for zinc coating uniformity was constructed to address challenges such as edge thickness and zinc spalling under complex operating conditions such as varying speeds, switching steel grades, and switching specifications.

[0019] Through the method of the present invention, precise closed-loop control of the uniformity of the zinc layer on the edge of the strip is achieved, defects such as the zinc layer being too thick or too thin on the edge are eliminated, zinc consumption and the amount of correction of thick edge defects and flying zinc defects are greatly reduced, so that the products meet higher quality standards and bring significant economic benefits to the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 This is the first measured curve of the zinc layer thickness in the width direction of the strip steel in Example 1 of the present invention.

[0022] Figure 2 This is the second measured curve of the zinc layer thickness in the width direction of the strip in Example 1 of the present invention.

[0023] Figure 3 This is the third measured curve of the zinc layer thickness in the width direction of the strip steel in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0025] The specific embodiment of the present invention partially provides a closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip, which is applicable to hot-dip galvanized strip or strip with a zinc layer obtained by other processes.

[0026] In a preferred embodiment of the present invention, the steel strip is hot-dip galvanized, the zinc bath temperature in the galvanizing section is 450°C to 460°C, the aluminum content of the zinc bath is 0.26% to 0.28%, and the plate temperature entering the zinc pot is 455°C to 480°C. By precisely controlling these key process parameters, the cooling rate of the zinc layer at the strip edge can be effectively slowed, preventing premature solidification of the zinc layer, thereby significantly improving the thickness uniformity and surface quality of the zinc layer at the edge.

[0027] The specific steps of the closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip provided by the present invention are as follows: Step 1: In the air knife blowing section, the entire length of the air knife lip is divided into 18 control points at equal intervals, and a thickness gauge is set behind the air knife.

[0028] Before starting the air knife spraying process, the air knife must be initially configured. The air knife lip angle determines the direction of the airflow. If the lip angle is not set properly, the airflows from the two air knives will easily form turbulence when they meet on the strip surface. This turbulent airflow will cause uneven distribution of the zinc liquid on the strip surface, reducing the uniformity of the zinc layer. A proper lip angle ensures smooth counterflow of the airflow from both sides, reducing turbulence and ensuring uniform adhesion of the zinc liquid.

[0029] Air knife parameters have a comprehensive and critical impact on the accuracy of zinc coating control. If the air knife is too close, the airflow impact is too strong, which can easily result in a thin zinc coating or even exposed iron defects. If the air knife is too far away, the airflow effect is weakened, resulting in a thicker and less uniform zinc coating. Air knife pressure directly affects the kinetic energy of the airflow. Excessively high or low pressure will deviate from the ideal zinc coating thickness control range. Air knife height determines the airflow action area, and height variations can alter the zinc deposition effect. The insertion distance of the straightening roller affects the flatness and running state of the strip, which in turn affects the interaction between the air knife airflow and the strip surface.

[0030] Based on this, as a preferred specific implementation of the technical solution of the present invention, the air knife can be initially set as follows: ① Set the lip opening of the air knife lip to a uniform value of 1.10 mm.

[0031] ②Optimize the air knife lip angle to avoid airflow turbulence: optimize the upper air knife angle to -0.7°~-0.8°, and optimize the lower air knife angle to -0.9°~-1.1°.

[0032] ③ Establish an air knife edge baffle control model: set the air knife edge baffle distance to S, the strip thickness to h, S=2h+1, unit mm.

[0033] ④ Control the air knife parameters to improve the accuracy of zinc layer control: control the air knife distance to 7 mm~12 mm, the air knife pressure to 80 mbar~600 mbar, the air knife height to 180 mm~350 mm, the correction roller insertion amount to 15 mm~40 mm, and the air knife frame to ±10 mm.

[0034] Step 2: After the strip passes through the air knife, the thickness gauge measures the zinc layer thickness at each detection point along the strip width in real time. To facilitate data analysis and control, the strip width coordinates are normalized: Taking the center line of the strip width direction as the reference (defined as 0 coordinate), the edge coordinate of one side of the strip is set to -1, and the edge coordinate of the other side is set to 1, thereby establishing the normalized plate width coordinate y i ,in y i ∈[-1, 1].

[0035] Through normalization processing, the influence of dimensional differences between strips of different widths is eliminated, and a unified mathematical model can be used to optimize the control of the uniformity of the edge zinc layer.

[0036] Step 3: According to the zinc layer thickness data and normalized plate width measured in step 2 y i, based on the Legendre polynomial fitting of the strip shape, the coefficients of the second-order Legendre polynomial are solved by the least squares method , and calculate the coefficients The absolute value of , ∈[0,1).

[0037] As a preferred specific implementation of the technical solution of the present invention, 1st to 4th order Legendre polynomials are used to fit the strip shape, and the 1st to 4th order Legendre polynomials are expressed as: , Where, 、 、 and are coefficients, y i is the normalized plate width.

[0038] The characteristics of the zinc layer of the steel strip can be decomposed into the flatness components of Legendre polynomials of different orders. The left and right waves correspond to the flatness components of the first-order Legendre polynomials, the double-sided waves and the middle waves correspond to the flatness components of the second-order Legendre polynomials, the left three-way waves and the right four-way waves correspond to the flatness components of the third-order Legendre polynomials, and the four-way waves and the side-center waves correspond to the flatness components of the fourth-order Legendre polynomials. The actual shape of the zinc layer of the steel strip can be represented by the linear combination of the above flatness components, that is, .

[0039] According to the zinc layer thickness data and normalized plate width obtained in step 2 y i , the polynomial regression decomposition method based on the least squares principle is used to establish a pattern recognition model, and the coefficients can be obtained 、 、 and The numerical value of .

[0040] Step 4, judge and perform the corresponding operations: (1) If satisfy , indicating that the thickness of the zinc layer in the width direction of the strip meets the uniformity standard, and there is no need to adjust the lip opening, and the current lip opening of each control point is maintained.

[0041] (2) If satisfy , the lip opening of all control points is uniformly set to 1.10mm.

[0042] (3) If satisfy The lip opening of the 6 control points in the middle is uniformly set to 1.15 mm, and the lip opening of each control point on both sides is increased by 0.03 mm in sequence until the lip opening reaches 1.30 mm and no longer increases. That is, the lip opening of the 18 control points along the length of the air knife lip from one end to the other is 1.30 mm, 1.30 mm, 1.27 mm, 1.24 mm, 1.21 mm, 1.18 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.18 mm, 1.21 mm, 1.24 mm, 1.27 mm, 1.30 mm, and 1.30 mm.

[0043] (4) If satisfy The lip opening of the 6 control points in the middle is uniformly set to 1.20 mm, and the lip opening of each control point on both sides is increased by 0.05 mm successively, that is, the lip opening of the 18 control points along the length of the air knife lip from one end to the other is 1.50 mm, 1.45 mm, 1.40 mm, 1.35 mm, 1.30 mm, 1.25 mm, 1.20 mm, 1.20 mm, 1.20 mm, 1.20 mm, 1.20 mm, 1.25 mm, 1.30 mm, 1.35 mm, 1.40 mm, 1.45 mm, and 1.50 mm respectively.

[0044] The opening of the air knife lip directly affects the edge drop effect of the airflow. When the opening of the air knife lip decreases, the airflow velocity at the air knife outlet increases, and the kinetic energy of the airflow increases, which reduces the diffusion of the airflow at the edge of the strip and weakens the edge drop effect, which can effectively inhibit the thickening of the zinc layer at the edge; conversely, when the opening of the air knife lip increases, the airflow velocity decreases, the airflow diffusion at the edge intensifies, and the edge drop effect is enhanced, which can easily lead to an excessively thick zinc layer at the edge.

[0045] exist Optimize the air knife lip opening, uniformly control the lip opening of the six control points in the middle of the air knife lip to 1.10 mm or 1.20 mm, and increase the lip opening of each control point on both sides by 0.03 mm to 0.05 mm, which can effectively reduce the airflow side drop effect.

[0046] Step 5, loop through steps 2 to 4 and enter a closed-loop control loop: the thickness gauge continuously detects the zinc layer thickness of the running strip, collects zinc layer thickness data at each point in the width direction in real time, and dynamically adjusts the lip opening of the air knife lip based on the latest detection data.

[0047] The above method can form a complete feedback closed loop, realize adaptive real-time control of the opening degree of the air knife lip and lip gap, ensure that the uniformity of the edge zinc layer remains stable throughout the production process, and continuously improve the quality consistency of the product.

[0048] The specific embodiment of the present invention provides a system for improving the uniformity of the zinc layer on the edge of the strip. The system is used to implement the above-mentioned closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip, including: Data acquisition module, used to measure the zinc layer thickness of the strip and output it; The data preprocessing module is used to normalize the strip width and map the actual plate width to the [-1, 1] interval to obtain the normalized plate width. y i And output; Plate shape feature calculation module, used to obtain normalized plate width y i The strip shape is fitted based on Legendre polynomials and the zinc layer thickness data. The coefficients of the second-order Legendre polynomials are solved by the least squares method. , calculate the coefficient The absolute value of And output; Judgment and decision module, used to Output different air knife lip opening control commands: like ∈[0, 0.1), output the command to maintain the current lip opening of each control point; like ∈[0.1, 0.3), output the command to uniformly set the lip opening of all control points to 1.10 mm; like ∈[0.3, 0.6), output a command to uniformly set the lip opening of the six control points in the middle to 1.15 mm, and increase the lip opening of each control point on both sides by 0.03 mm until the lip opening reaches 1.30 mm and stops increasing; like ∈[0.6, 1), output the command to uniformly set the lip opening of the six control points in the middle to 1.20 mm, and increase the lip opening of each control point on both sides by 0.05 mm; The control execution module is used to adjust the lip opening degree of 18 control points along the entire length of the air knife.

[0049] A specific embodiment of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and runnable on the processor, wherein the processor is configured to implement the steps of the above-mentioned closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip when executing the computer program.

[0050] The specific embodiment of the present invention provides a storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the closed-loop control method for improving the uniformity of the zinc layer on the edge of the strip are implemented.

[0051] Example 1 Producing a strip with a thickness of 1.2 mm and a strip width of 1600 mm, with a target zinc layer thickness of 50 g / m 2 This product adopts hot-dip galvanizing process, the zinc liquid temperature is controlled at 450℃~460℃, the aluminum content of the zinc liquid is controlled at 0.26%~0.28%, and the plate temperature entering the zinc pot is controlled at 455℃~480℃.

[0052] The air knife blowing section of the product is closed-loop controlled. The closed-loop control is carried out in the following steps: Step 1: In the air knife blowing section, the entire length of the air knife lip is divided into 18 control points at equal intervals. From one end of the air knife lip to the other end, the lip opening of the 18 control points is uniformly controlled to be 1.10 mm. The upper air knife angle is -0.7°, and the lower air knife angle is -0.9°; The distance between the air knife edge baffle is 3.4 mm; The air knife distance is 12 mm, the air knife pressure is 80 mbar, the air knife height is 350 mm, the correction roller insertion is 15 mm, and the air knife frame is ±10 mm; A thickness gauge is set up 180 m behind the air knife.

[0053] Step 2: After the strip passes through the air knife, the thickness gauge measures the zinc layer thickness at each detection point in the strip width direction in real time, and normalizes the strip width coordinates. Taking the center line of the strip width direction as the reference (defined as the 0 coordinate), the edge coordinates on one side of the strip are set to -1, and the edge coordinates on the other side are set to 1, thereby establishing the normalized plate width coordinates. y i , with the normalized plate width coordinate y i Plotting the zinc layer thickness with the strip width direction, the first measured curve of the zinc layer thickness is obtained (e.g. Figure 1 As shown in Figure 2), the zinc layer thickness on both sides of the strip is higher than that in the middle.

[0054] Step 3: According to the zinc layer thickness data and normalized plate width measured in step 2 yi , fitting the strip shape based on 1st to 4th order Legendre polynomials: , The coefficient values ​​of Legendre polynomials of order 1 to 4 are obtained by fitting and solving with the least square method. =-6.45, =0.99, =-0.006, =0.0002, coefficient A positive value indicates that the strip has a C-shaped zinc layer thickness distribution characteristic toward the upper surface.

[0055] Calculate the coefficient The absolute value of =0.99.

[0056] Step 4, judgment coefficient The absolute value of The range of the coefficient satisfy Therefore, the lip opening of the 18 control points was adjusted to 1.5 mm, 1.45 mm, 1.4 mm, 1.35 mm, 1.3 mm, 1.25 mm, 1.2 mm, 1.2 mm, 1.2 mm, 1.2 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, and 1.5 mm.

[0057] Step 5: Repeat steps 2 to 4.

[0058] During the first cycle of step 2 to step 4 in step 5, the second measured curve of the zinc layer thickness in the strip width direction obtained by thickness gauge detection and normalization in step 2 is as follows: Figure 2 As shown, step 3 calculates =-0.87, =-0.33, =-0.052, =-0.0016, =0.33, step 4 judge It belongs to the interval of [0.3, 0.6), and the lip opening adjustment command is executed. After the adjustment, the lip openings of the 18 control points are 1.30 mm, 1.30 mm, 1.27 mm, 1.24 mm, 1.21 mm, 1.18 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.15 mm, 1.18 mm, 1.21 mm, 1.24 mm, 1.27 mm, 1.30 mm, and 1.30 mm.

[0059] During the second cycle of step 2 to step 4 in step 5, the third measured curve of the zinc layer thickness in the strip width direction obtained by thickness gauge detection and normalization in step 2 is as follows: Figure 3 As shown, step 3 calculates =-0.26, =0.0004, =-0.0002, =-0.00005, =0.0004, step 4 judge It belongs to the interval [0, 0.1), indicating that the zinc layer thickness in the width direction of the strip meets the uniformity standard. There is no need to adjust the lip opening, and the command to maintain the current lip opening is executed.

[0060] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A closed-loop control method for improving the uniformity of the zinc layer on the edge of a steel strip, characterized in that: The steps include: Step 1: In the air knife blowing section, the air knife lip is divided into 18 control points at equal intervals along its entire length, and a thickness gauge is set behind the air knife; Step 2: After the strip passes through the air knife, the thickness of the zinc layer at each point in the width direction is measured by a thickness gauge, and the width is normalized to obtain the normalized plate width. y i , y i ∈[-1, 1]; Step 3: Based on the zinc layer thickness data and normalized plate width obtained in step 2 y i , based on the Legendre polynomial fitting of the strip shape, the coefficients of the second-order Legendre polynomial are solved by the least squares method , and calculate the coefficients The absolute value of , ∈[0,1); Step 4, judge and perform the corresponding operations: like satisfy , maintain the current lip opening of each control point; like satisfy , the lip opening of all control points is uniformly set to 1.10 mm; like satisfy , the lip opening of the six control points in the middle is uniformly set to 1.15 mm, and the lip opening of each control point on both sides is increased by 0.03 mm until the lip opening reaches 1.30 mm and no longer increases; like satisfy , the lip opening of the six control points in the middle is uniformly set to 1.20 mm, and the lip opening of each control point on both sides is increased by 0.05 mm; Step 5: Repeat steps 2 to 4.

2. The closed-loop control method according to claim 1, wherein: In step 1, the initial values ​​of the lip opening of the 18 control points are set as follows: The lip opening of all control points was uniformly set to 1.10 mm.

3. The closed-loop control method according to claim 1, wherein: In step 3, the basic flatness mode selects the 1st to 4th order Legendre polynomials, which are expressed as: ， Where, 、 、 and are coefficients, y i is the normalized plate width; Constructing the fitting function , according to the zinc layer thickness data and normalized plate width obtained in step 2 y i , the polynomial regression decomposition method based on the least squares principle is used to establish a pattern recognition model, and the coefficients are obtained. The numerical value of .

4. The closed-loop control method according to any one of claims 1 to 3, characterized in that: The air knife lip angle of the air knife blowing section is controlled as follows: The upper air knife angle is -0.7°~-0.8°, and the lower air knife angle is -0.9°~-1.1°.

5. The closed-loop control method according to any one of claims 1 to 3, characterized in that: The distance between the air knife edge baffles in the air knife blowing section is controlled as follows: S=2h+1, Where, S is the distance between the air knife edge baffle, unit is mm, h is the thickness of the strip, in mm.

6. The closed-loop control method according to any one of claims 1 to 3, wherein: The air knife distance of the air knife blowing section is controlled to be 7 mm~12 mm, the air knife pressure is controlled to be 80 mbar~600 mbar, the air knife height is controlled to be 180 mm~350 mm, the correction roller insertion amount is controlled to be 15 mm~40 mm, and the air knife frame is controlled to be ±10 mm.

7. The closed-loop control method according to any one of claims 1 to 3, characterized in that: The strip steel is hot-dip galvanized strip steel, and the galvanizing process of the hot-dip galvanized strip steel is controlled according to the following parameters: The zinc liquid temperature in the galvanizing section is 450℃~460℃, the aluminum content of the zinc liquid is 0.26%~0.28%, and the plate temperature entering the zinc pot is 455℃~480℃.

8. A system for improving the uniformity of the zinc layer on the edge of a steel strip, characterized in that: The system is used to implement the closed-loop control method according to claim 1, comprising: Data acquisition module, used to measure the zinc layer thickness of the hot-dip galvanized strip at the current position and output it; The data preprocessing module is used to normalize the strip width and map the actual plate width to the [-1, 1] interval to obtain the normalized plate width. y i And output; Plate shape feature calculation module, used to obtain normalized plate width y i The strip shape is fitted based on Legendre polynomials and the zinc layer thickness data. The coefficients of the second-order Legendre polynomials are solved by the least squares method. , calculate the coefficient The absolute value of And output; Judgment and decision module, used to Output different air knife lip opening control commands: like ∈[0, 0.1), output the command to maintain the current lip opening of each control point; like ∈[0.1, 0.3), output the command to uniformly set the lip opening of all control points to 1.10 mm; like ∈[0.3, 0.6), output a command to uniformly set the lip opening of the six control points in the middle to 1.15 mm, and increase the lip opening of each control point on both sides by 0.03 mm until the lip opening reaches 1.30 mm and stops increasing; like ∈[0.6, 1), output the command to uniformly set the lip opening of the six control points in the middle to 1.20 mm, and increase the lip opening of each control point on both sides by 0.05 mm; The control execution module is used to adjust the lip opening degree of 18 control points along the entire length of the air knife.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: The processor is configured to implement the steps of the closed-loop control method according to claim 1 when executing the computer program.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the closed-loop control method according to claim 1 are implemented.

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