A method for controlling the uniformity of a coating in the width direction of a cold-rolled hot-galvanizing unit

Abstract

This invention discloses a method and apparatus for controlling the uniformity of the coating width direction in a cold-rolled hot-dip galvanizing unit, comprising the following steps: A1: Collecting zinc coating thickness data; instantaneous zinc coating thickness data is collected using a zinc coating thickness gauge, and the detection trajectory of the zinc coating thickness gauge is set, with the measuring point of the zinc coating thickness gauge moving in a Z-shaped trajectory on the surface of the strip steel; A2: Calculating the curvature of the strip steel; the surface curvature of the strip steel is calculated based on the collected zinc coating thickness data to obtain the curvature data of each sampling point on the strip steel surface; A3: Quantifying the curve arc; the curvature of each sampling point is processed to obtain the average curvature value; A4: Surface correction; the obtained average curvature value of the strip steel is compared with a standard curvature range. After calculating the average curvature of the strip steel, this invention evaluates the uniformity of the zinc coating thickness in the width direction of the strip steel. If the average curvature is within a specific range, the strip steel is considered to require no adjustment; otherwise, the position of the correction roller is adjusted according to the curvature to optimize the zinc coating thickness distribution of the strip steel.

Description

Technical Field

[0001] This invention relates to the field of strip steel production technology, and in particular to a method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit. Background Technology

[0002] The uniformity of zinc coating thickness in continuous hot-dip galvanizing units is a crucial standard for evaluating product quality. During production, the zinc coating thickness of the strip steel is primarily controlled by air knife equipment. Air knives are typically positioned above the zinc pot, and under a certain pressure, nitrogen gas is sprayed from nozzle slits onto the strip steel surface. Their main function is to control the thickness and uniformity of the zinc coating after galvanizing. In most domestic steel mills, zinc coating thickness control in hot-dip galvanizing lines requires operators to manually adjust various parameters of the air knife based on zinc coating thickness data fed back by thickness gauges to ensure the correct thickness. In recent years, air knife control models have seen rapid development, and many fields are gradually developing automated air knife control systems.

[0003] Patent application CN201910999806.9 discloses a method for controlling the zinc layer thickness of a hot-dip galvanizing unit. The method includes: collecting process parameters of the hot-dip galvanizing unit used to calculate the predicted zinc layer thickness, wherein the process parameters include strip speed, air knife height, distance from the cutter lip to the strip, air knife pressure, cutter lip gap, and strip thickness; determining the current operating condition changes; calculating all possible predicted zinc layer thickness values ​​corresponding to the current operating condition changes based on the process parameters; finding the set of predicted zinc layer thickness values ​​closest to the set zinc layer thickness value; and adjusting and controlling the corresponding air knife parameters based on the process parameters corresponding to this set of predicted zinc layer thickness values. However, this technology has significant limitations in prediction accuracy, especially when dealing with special process parameters, where the prediction error is relatively large.

[0004] Patent application CN201710064818.3 discloses an automatic control method for the blowing pressure of a continuous hot-dip galvanizing air knife. In the preset control, the system adjusts the target thickness based on a long-term adaptive model of the coating thickness. When the air knife distance and strip speed remain constant, control is performed according to the preset input model PPRESET for the blowing pressure. When the strip speed changes, the air knife blowing pressure is controlled online using the feedforward control model PFFC. When unpredictable variables occur, feedback control is performed using the air knife blowing pressure feedback control model PFBC. The triggering conditions of this method depend on changes in coating thickness and speed, but when the target coating thickness of the current roll changes, the model cannot provide corresponding adjustment parameters.

[0005] Patent application number CN202210078686.0 discloses an automatic control method for air knife parameters in a continuous hot-dip galvanizing unit, including the following steps: S1, collecting actual production data of the hot-dip galvanizing production line; S2, monitoring production line tracking data, reading PLC data from the field control, and triggering step S3 when the weld position of the next coil of strip and the current strip is about to reach the air knife; S3, calculating the air knife parameter values ​​corresponding to the upper and lower surfaces of strips of different specifications, the specific process of setting the air knife parameters depends on the calculation of the neural network N, and after the air knife setting parameters are calculated by the neural network, proceeding to step S4; S4, storing the calculated air knife parameters in the PLC data block, triggering a judgment when the weld position of the next coil of strip and the current strip reaches the air knife, at which time the specific execution logic is selected according to the strip production requirements. If the target zinc layer thickness of the upper and lower surfaces of the strip is the same, the air knife parameters for both the upper and lower surfaces are set according to the upper surface of the strip; if the target zinc layer thickness of the upper and lower surfaces of the strip is different, the air knife parameters for the upper and lower surfaces are adjusted accordingly. The settings are configured separately. At this point, a new coil of strip enters the air knife area, proceeding to step S5. S5: Detect any changes in the speed of the hot-dip galvanizing unit's production line. If the production line speed changes, adjust the air knife parameters accordingly. Based on different zinc bath types, calculate the adjustment amount of the air knife parameters using a random forest model. S6: Monitor in real-time whether the zinc layer thickness meets the requirements. If the zinc layer thickness does not meet the requirements, immediately adjust the corresponding air knife parameters using a PID algorithm based on the zinc bath type. The target value of the PID algorithm is the target zinc layer thickness, and the adjustment amounts are the air knife distance and air knife pressure, respectively. This step is executed in parallel with step S5. After adjustment, monitoring continues, leading to step S7. S7: Finally, the tail of the strip leaves the air knife area, completing the control process for this coil of strip, and simultaneously executing the air knife parameters for the next coil of strip. This model has a deficiency in real-time adjustment capability; it cannot promptly adjust the parameters of the strip currently in the air knife area, especially when the actual zinc layer thickness changes, the model cannot detect and provide corrective parameters in a timely manner.

[0006] Existing methods have limited prediction and control accuracy, leading to discrepancies between predicted and actual values. When the actual zinc layer thickness deviates from the set value, they cannot effectively adjust for the prediction deviation in a timely manner. Therefore, it is necessary to improve this structure to overcome these shortcomings. Summary of the Invention

[0007] The purpose of this invention is to provide a method for controlling the uniformity of the coating width in a cold-rolled hot-dip galvanizing unit. By collecting zinc layer thickness data, fitting zinc layer curves, calculating curvature, and adjusting the position of straightening rollers, the strip shape is effectively improved, resulting in a more uniform distribution of the galvanized layer in the strip width direction. The zinc layer thickness on the strip surface is monitored in real time, and possible thickness deviations are detected and corrected in a timely manner, avoiding quality problems caused by uneven thickness. The production process is optimized, and the equipment such as straightening rollers and guide rollers can be adjusted flexibly and operated efficiently.

[0008] The above-mentioned technical objective of this invention has been achieved by the following technical solutions:

[0009] A method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit includes the following steps:

[0010] A1: Collect zinc layer thickness data. Instantaneous zinc layer thickness data is collected using a zinc layer thickness gauge. The detection trajectory of the zinc layer thickness gauge is set. The measuring point of the zinc layer thickness gauge moves in a zigzag trajectory on the surface of the strip steel to collect the zinc layer thickness swept by the measuring point. The collected zinc layer thickness data is used to reflect the variation law of zinc layer thickness in the width direction of the strip steel.

[0011] A2: Strip curvature calculation: The surface curvature of the strip is calculated based on the collected zinc layer thickness data to obtain the curvature data of each sampling point on the strip surface;

[0012] A3: Quantify the curvature of the curve by processing the curvature of each sampling point and taking the average value to obtain the average curvature value;

[0013] A4: Surface straightening. The average curvature value of the strip is compared with the standard curvature range. If the average curvature value of the strip does not meet the standard curvature range, the position of the straightening roller is adjusted, and the surface of the strip is flattened by the straightening roller. If the average curvature value of the strip meets the standard curvature range, it indicates that the uniformity of the zinc layer thickness in the width direction of the strip meets the requirements, and there is no need to perform uniformity correction on the strip.

[0014] The calculation of strip curvature in step A2 includes the following steps;

[0015] B1: The zinc layer thickness at each point on the strip surface is calculated by fitting the zinc layer curve using the least squares method.

[0016] B2: After fitting the zinc layer curve, the thickness quadratic polynomial in the width direction of the zinc layer is obtained, and the curvature of the points on the strip surface is calculated.

[0017] The expression for the zinc layer thickness in step B1 is as follows:

[0018] y = ax 2 +bx+c;

[0019] Where a, b, and c are constants, x is the strip width direction coordinate with the width center as the zero point, and y is the zinc layer thickness at the alignment position.

[0020] The expression for the surface curvature of the strip in step B2 is as follows:

[0021]

[0022] Where a and b are constants, x is the coordinate of the strip width direction, and k is the curvature at the corresponding position, used to represent the curvature of the point on the strip surface.

[0023] The expression for the average curvature value in step A3 is as follows:

[0024]

[0025] in, The average curvature at each point is used to represent the average curvature of the strip surface, where n is the number of points and K is the average curvature. i It is the curvature at the i-th point.

[0026] The insertion depth of the straightening roller for surface straightening in step A4 is calculated according to the following formula:

[0027]

[0028] in, The average curvature of each point is taken, p1 is the insertion depth, and p0 is the initial position depth.

[0029] An apparatus for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit, comprising:

[0030] A zinc pot is used to hold and heat zinc raw materials until the zinc is molten, so that strip steel can be immersed in it and an adhesive zinc coating can be formed.

[0031] Guide rollers are mounted on the zinc pot. One end of the guide rollers is connected to an external transmission mechanism. The guide rollers are used to provide driving force, guide the strip steel, and direct the strip steel to move.

[0032] The straightening roller is located above the guide roller. There are two straightening rollers, and a channel is left between the two straightening rollers for the strip steel to pass through. The straightening roller is used to straighten the galvanized strip steel. One end of the straightening roller is connected to an external adjustment unit. The position of the straightening roller is adjusted by the external adjustment unit, thereby changing the straightening effect on the strip steel.

[0033] An air knife controls the thickness of the galvanized layer by blowing air. Multiple air knives are set up and distributed at both ends of the strip. The output end of the air knife is set towards the two end faces of the strip. The air knife lip is parallel to the strip and maintains a consistent left-right spacing, so that the galvanized sheet can obtain an accurate and uniform coating along the width direction.

[0034] A thickness gauge is used to detect the thickness of the zinc layer on the surface of a steel strip. The thickness gauge emits rays, which pass through the zinc layer being measured and are received by a detector. Based on the intensity of the rays passing through the material being measured and the signal received by the detector, the zinc layer thickness gauge can calculate the thickness of the zinc layer.

[0035] In summary, the present invention has the following beneficial effects:

[0036] 1. Improve product quality: By precisely controlling the uniformity of the galvanized layer in the width direction of the strip, ensure product consistency and quality stability.

[0037] 2. Enhance production efficiency: Real-time monitoring and feedback mechanisms enable deviations in the production process to be detected and corrected in a timely manner, reducing scrap and rework rates and improving production efficiency.

[0038] 3. High flexibility: The position of the straightening roller can be flexibly adjusted to adapt to the processing needs of strip steel of different specifications and materials, thus improving the versatility and adaptability of the equipment.

[0039] 4. Intelligent control: By using mathematical methods such as least squares fitting of zinc layer curve and calculation of curvature, combined with an automated control system, intelligent and precise control of the galvanizing process is achieved. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the present invention.

[0041] Figure 2 This is a schematic diagram of the structure of the present invention.

[0042] Numbering: 1. Zinc pot; 2. Air knife; 3. Strip steel; 4. Thickness gauge; 5. Galvanized layer; 6. Guide roller; 7. Straightening roller. Detailed Implementation

[0043] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to the figures and specific embodiments.

[0044] like Figures 1 to 2 As shown, the present invention proposes a method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit, which includes the following steps:

[0045] Zinc layer thickness data is collected by using a zinc layer thickness gauge to collect instantaneous zinc layer thickness data. The detection trajectory of the zinc layer thickness gauge is set, and the measuring point of the zinc layer thickness gauge moves in a zigzag trajectory on the surface of the strip steel to collect the zinc layer thickness swept by the measuring point. The collected zinc layer thickness data is used to reflect the variation law of zinc layer thickness in the width direction of the strip steel.

[0046] The distribution characteristics of zinc layer thickness are affected by the shape of the strip. According to the data, the zinc layer thickness is thinner in the middle of the strip and thicker at both ends. By fitting the zinc layer curve using the least squares method, a quadratic polynomial of the zinc layer thickness in the width direction is obtained, and its expression is as follows:

[0047] y = ax 2 +bx+c;

[0048] Where a, b, and c are constants, x is the width direction coordinate with the width center as the zero point, and y is the zinc layer thickness at the corresponding position;

[0049] The curvature of the fitted quadratic polynomial curve is calculated using the following formula:

[0050]

[0051] Where a, b, and c are constants, x is the width-direction coordinate, and k is the curvature at the corresponding position. Curvature describes the degree of bending of the strip at that point; the larger the absolute value of the curvature, the greater the bending of the curve at that point. To quantify the curvature of the curve, the average curvature at each point in the width direction is taken to obtain...

[0052] By obtaining To determine the surface uniformity of the strip, if If the strip does not conform to the range of [-0.1, 0.1], the strip surface is leveled using straightening rollers. The position of the straightening rollers is adjusted according to the curvature value to improve the strip shape and make the zinc layer thickness distribution in the width direction of the strip more uniform. If the value falls within the range of [-0.1, 0.1], it indicates that the uniformity of the zinc layer thickness in the width direction of the strip meets the requirements, and no uniformity correction is required for the strip.

[0053] The expression for the average curvature value in step A3 is as follows:

[0054]

[0055] in, The curvature at each point is taken as the average value, where n is the number of points and K is the average value. iIt is the curvature at the i-th point. The average curvature provides an indicator that quantifies the overall curvature of a curve or surface. Compared with the curvature at a single point, the average curvature better reflects the characteristics of the entire shape.

[0056] The insertion depth of the straightening roller for surface straightening in step A4 is calculated according to the following formula:

[0057]

[0058] in, The average curvature at each point is taken, p1 is the insertion depth, and p0 is the initial position depth. By measuring the curvature at different depths and calculating the average value, the relationship between the average curvature and the insertion depth can be obtained.

[0059] In summary, improving the sampling frequency and accuracy of the zinc layer thickness gauge to more accurately reflect changes in zinc layer thickness, and using a quadratic polynomial for curvature calculation to more accurately describe these changes, are crucial. Furthermore, real-time monitoring and adjustment of the insertion depth of the straightening rollers during adjustment are essential to ensure the flatness of the strip surface and the uniformity of the zinc layer thickness.

[0060] An apparatus for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit, comprising:

[0061] A zinc pot is used to hold and heat zinc raw materials until the zinc is molten, so that strip steel can be immersed in it and an adhesive zinc coating can be formed.

[0062] Guide rollers are mounted on the zinc pot. One end of the guide rollers is connected to an external transmission mechanism (omitted in the figure). The guide rollers are used to provide driving force, guide the strip steel, and direct the strip steel to move.

[0063] The straightening roller is located above the guide roller. There are two straightening rollers, and a channel is left between the two straightening rollers for the strip steel to pass through. The straightening roller is used to straighten the galvanized strip steel. One end of the straightening roller is connected to an external adjustment unit (omitted in the figure). The position of the straightening roller is adjusted by the external adjustment unit, thereby changing the straightening effect on the strip steel.

[0064] An air knife controls the thickness of the galvanized layer by blowing air. Multiple air knives are set up and distributed at both ends of the strip. The output end of the air knife is set towards the two end faces of the strip. The air knife lip is parallel to the strip and maintains a consistent left-right spacing, so that the galvanized sheet can obtain an accurate and uniform coating along the width direction.

[0065] A thickness gauge is used to detect the thickness of the zinc layer on the surface of a steel strip. The thickness gauge emits rays, which pass through the zinc layer being measured and are received by a detector. Based on the intensity of the rays passing through the material being measured and the signal received by the detector, the zinc layer thickness gauge can calculate the thickness of the zinc layer.

[0066] The zinc raw material in the zinc pot is heated to a molten state. The strip steel is immersed in the zinc liquid under the drive of the guide rollers to form an adhesive zinc coating. After galvanizing, the strip steel passes through the channel between two straightening rollers. The straightening rollers straighten the strip steel to ensure its flatness. Multiple air knives are distributed at both ends of the strip steel. The thickness of the zinc coating is controlled by blowing airflow, thereby ensuring the uniformity of the zinc coating in the width direction of the strip steel. The thickness gauge emits rays that pass through the zinc layer being measured. The intensity of the rays passing through the measured material is received by the detector. Based on the received signal intensity, the thickness gauge can calculate the thickness of the zinc layer and monitor and record it in real time.

[0067] In summary, this device ensures an accurate and uniform galvanized coating across the width of the strip, improving product quality and consistency. The position of the straightening rollers can be flexibly adjusted via an external adjustment unit, thereby altering the straightening effect on the strip and adapting to the processing needs of strips of different specifications and materials. The guide rollers provide stable driving force, ensuring smooth movement of the strip during the galvanizing process and improving production efficiency. The thickness gauge can monitor the zinc layer thickness on the strip surface in real time, promptly identifying and correcting potential thickness deviations to ensure product quality.

[0068] Example 1

[0069] In this embodiment, the strip thickness to be corrected is 976 mm, the strip width is 887 mm, the strip running speed is 120 m / min, and the target zinc layer thickness is set to 144 g / m. 2 The air knife height is 400mm, the distance between the upper and lower surfaces of the air knife is 14.00mm, the stabilizing roller pressure is 220MPa, and the straightening roller position is 0, -22 (operating side, transmission side).

[0070] The collected instantaneous zinc layer thickness data can reflect the variation law of zinc layer thickness in the width direction of the strip. Here, the least squares method is used to fit the zinc layer curve, and the quadratic polynomial of the zinc layer thickness in the width direction is obtained as follows:

[0071] y = -0.7318x 2 -0.2859x+175.94;

[0072] Calculate the curvature of the fitted quadratic polynomial curve and take the average value. Record the instantaneous values ​​in units of 100 mm in the width direction and finally take the average value.

[0073]

[0074] The strip at this point does not meet the requirement for uniform zinc layer thickness in the width direction. The calculation expression is as follows:

[0075]

[0076]

[0077] After the strip has advanced 220 meters, proceed to step one for a new cycle of judgment, including zinc layer thickness and uniformity assessment.

[0078] The zinc coating curve was fitted using the least squares method on the next 220 meters of strip, and the fitting equation is as follows:

[0079] y = 0.0558x 2 +0.6585x+145.55;

[0080] Next, the curvature of the fitted quadratic polynomial curve is calculated, and the average value is taken. At this point, This indicates that the zinc layer thickness uniformity in the width direction of the strip has met the requirements. Continue to monitor the zinc layer thickness uniformity in the width direction of this coil of strip. If the uniformity is found to be non-compliant, the zinc layer of the strip is corrected by straightening rollers until the strip leaves the air knife area.

[0081] In summary, instantaneous zinc layer thickness data of the strip surface is collected using a zinc layer thickness gauge. This data reflects the variation pattern of zinc layer thickness in the width direction of the strip. The collected zinc layer thickness data is fitted using the least squares method to obtain a quadratic polynomial of the zinc layer thickness in the width direction. This polynomial describes the distribution of zinc layer thickness in the width direction of the strip. The curvature of the fitted quadratic polynomial curve is calculated, and the average value is taken to quantify the curve's arc. By comparing the average curvature value with a preset range, the uniformity of zinc layer thickness in the width direction of the strip can be assessed. When the average curvature value exceeds the preset range, it indicates that the uniformity of zinc layer thickness in the width direction of the strip does not meet the requirements. At this time, the strip is straightened by adjusting the position of the straightening roller to improve the uniformity of strip shape and zinc layer thickness. The insertion depth of the straightening roller is calculated and set based on the relationship between curvature and insertion depth. Throughout the galvanizing process, the zinc layer thickness gauge continuously monitors the zinc layer thickness on the strip surface and feeds the data back to the control system. The control system analyzes and judges based on real-time data, and adjusts production parameters and straightening roller positions in a timely manner to ensure the uniformity of the galvanized layer in the width direction of the strip.

[0082] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connect" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0083] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit, characterized in that, Includes the following steps, A1: Collect zinc layer thickness data. Instantaneous zinc layer thickness data is collected using a zinc layer thickness gauge. The detection trajectory of the zinc layer thickness gauge is set. The measuring point of the zinc layer thickness gauge moves in a zigzag trajectory on the surface of the strip steel to collect the zinc layer thickness swept by the measuring point. The collected zinc layer thickness data is used to reflect the variation law of zinc layer thickness in the width direction of the strip steel. A2: Strip curvature calculation: The surface curvature of the strip is calculated based on the collected zinc layer thickness data to obtain the curvature data of each sampling point on the strip surface; A3: Quantify the curvature of the curve by processing the curvature of each sampling point and taking the average value to obtain the average curvature value; A4: Surface straightening. The average curvature value of the strip is compared with the standard curvature range. If the average curvature value of the strip does not meet the standard curvature range, the position of the straightening roller is adjusted, and the surface of the strip is flattened by the straightening roller. If the average curvature value of the strip meets the standard curvature range, it indicates that the uniformity of the zinc layer thickness in the width direction of the strip meets the requirements, and there is no need to perform uniformity correction on the strip.

2. The method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit according to claim 1, characterized in that, The calculation of strip curvature in step A2 includes the following steps; B1: The zinc layer thickness at each point on the strip surface is calculated by fitting the zinc layer curve using the least squares method. B2: After fitting the zinc layer curve, the thickness quadratic polynomial in the width direction of the zinc layer is obtained, and the curvature of the points on the strip surface is calculated.

3. The method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit according to claim 2, characterized in that, The expression for the zinc layer thickness in step B1 is as follows: y=ax 2 +bx+c; Where a, b, and c are constants, x is the strip width direction coordinate with the width center as the zero point, and y is the zinc layer thickness at the alignment position.

4. The method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit according to claim 2, characterized in that, The expression for the surface curvature of the strip in step B2 is as follows: Where a and b are constants, x is the coordinate of the strip width direction, and k is the curvature at the corresponding position.

5. The method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit according to claim 1, characterized in that, The expression for the average curvature value in step A3 is as follows: in, The curvature at each point is taken as the average value, where n is the number of points and K is the average value. i It is the curvature at the i-th point.

6. The method for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit according to claim 1, characterized in that, The insertion depth of the straightening roller for surface straightening in step A4 is calculated according to the following formula: in, The average curvature of each point is taken, p1 is the insertion depth, and p0 is the initial position depth.

7. An apparatus for controlling the uniformity of coating width in a cold-rolled hot-dip galvanizing unit, characterized in that, include, A zinc pot is used to hold and heat zinc raw materials until the zinc is molten, so that strip steel can be immersed in it and an adhesive zinc coating can be formed. Guide rollers are mounted on the zinc pot. One end of the guide rollers is connected to an external transmission mechanism. The guide rollers are used to provide driving force, guide the strip steel, and direct the strip steel to move. The straightening roller is located above the guide roller. There are two straightening rollers, and a channel is left between the two straightening rollers for the strip steel to pass through. The straightening roller is used to straighten the galvanized strip steel. One end of the straightening roller is connected to an external adjustment unit. The position of the straightening roller is adjusted by the external adjustment unit, thereby changing the straightening effect on the strip steel. An air knife controls the thickness of the galvanized layer by blowing air. Multiple air knives are set up and distributed at both ends of the strip. The output end of the air knife is set towards the two end faces of the strip. The air knife lip is parallel to the strip and maintains a consistent left-right spacing, so that the galvanized sheet can obtain an accurate and uniform coating along the width direction. A thickness gauge is used to detect the thickness of the zinc layer on the surface of a steel strip. The thickness gauge emits rays, which pass through the zinc layer being measured and are received by a detector. Based on the intensity of the rays passing through the material being measured and the signal received by the detector, the zinc layer thickness gauge can calculate the thickness of the zinc layer.

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