A method for improving the thickening defect of the edge portion of a thick zinc layer galvanized product

Abstract

The application discloses a method for improving edge thickening defects of thick zinc layer galvanized products, and belongs to the field of pickling and galvanizing plate production, and specifically comprises the following steps: Step 1, generation of a misaligned edge curling command; Step 2, calculation of a misaligned edge position; and Step 3, transverse movement of a coiler core shaft to realize misaligned edge curling of the strip steel. The application realizes misaligned layer coiling in the coiling process of the strip steel, alleviates the wave-shaped defects caused by the overlapping of the steel coils in the edge thickening area, and does not increase the hardware modification cost.

Description

Technical Field

[0001] This invention relates to a steel production method, and more particularly to a method for improving the edge thickening defect of thick zinc-plated products based on a hot-plate pickling and galvanizing continuous production line. Background Technology

[0002] Galvanized steel sheets have excellent corrosion resistance, and the thicker the zinc layer, the stronger the corrosion resistance, extending the service life of the steel substrate. However, ultra-thick zinc layer products are more difficult to produce and are prone to edge waviness. The paper "A Method and Device for Controlling Edge Waviness of Galvanized Steel Sheets During Rolling" (CN201410077506.2) achieves control through the spray valve of the precision cooling equipment in the cold rolling and pickling mill production line.

[0003] However, the urgent demand from downstream users for lower steel costs has spurred the rapid development of hot-rolling technology. The successful development of thin-gauge hot-rolled plates has enabled the replacement of cold-rolled finished products with hot-rolled ones, with a large number of thin-gauge hot-rolled substrate pickled and galvanized products replacing traditional cold-rolled galvanized products. Therefore, controlling edge waviness in galvanized products using a continuous hot-rolled substrate pickling and galvanizing production line has become a major challenge in the industry.

[0004] The production of ultra-thick zinc-coated products is challenging, partly due to edge bulging, which causes edge waviness defects that render the product unusable. Another reason is the abnormal cross-sectional shape of the hot-rolled substrate, with high points or severe wedge-shaped sections at the edges. During the cold rolling and coiling process, these localized high points or wedge-shaped areas accumulate and bulge, creating edge waviness defects that render the galvanized product unusable. Abnormal process parameters such as raw material edge ribs and waviness, raw material edge quality, air knife pressure, and the distance between the air knife and the strip contribute to strip edge thickening. During the coiling process, as the number of coil layers increases, the thickened edge areas accumulate and bulge, causing deformation and waviness defects in the overlapping areas of the strip.

[0005] To address this, various enterprises have conducted relevant research, with control methods primarily focusing on adjusting the air knife gap and reducing the baffle distance. The former, exemplified by "A Method for Eliminating Zinc Wavy Defects in Alloyed Hot-Dip Galvanized Steel Sheets" (CN202110598871.8), addresses zinc wavy quality by controlling the temperature of the zinc bath and the strip's entry temperature, controlling the percentage of aluminum in the zinc bath, and the strip's running speed, increasing the air knife purging pressure, widening the air knife gap, and increasing the unit finishing rolling force. The latter, exemplified by "A Method for Production and Surface Quality Control of Cold-Rolled Thick Zinc-Coated Hot-Dip Pure Zinc Steel Strip" (CN202010938210.0), controls the distance between the baffles on the drive and operating sides of the zinc bath and the strip edge to be 1-5 mm. However, in actual production, most air knives can only have their gap adjusted offline, which cannot meet the production needs of multi-specification strips. Furthermore, simply reducing the distance between the baffle and the strip increases the risk of slag adhesion to the baffle, which, once accumulated, can clog the air knife and cause other defects.

[0006] Therefore, there is an urgent need for a method that can be used in real-world industrial continuous production to improve the edge thickening defect of thick zinc-plated products. Summary of the Invention

[0007] The technical objective of this invention is to address the shortcomings of the prior art by providing a method for improving the edge thickening defect of thick zinc-coated products. This method utilizes the correction function of the galvanizing coiler to achieve staggered coiling during the strip coiling process, thereby alleviating the waviness defect caused by the overlapping of steel coils in the edge thickening area.

[0008] The technical solution of this invention to solve its technical problem is: a method for improving the edge thickening defect of thick zinc-plated products, characterized in that: the specific method includes: Step 1. Generation of the misalignment curling command: When the exit slitting shear cuts the strip head length to zero, the automated system automatically calculates the strip head position value during the threading process. When the system detects that the strip head position is greater than the target length L, it generates a misalignment curling command and sends it to the EPC correction device. Step 2. Calculation of misalignment position: After receiving the misalignment curling command, the EPC automatically saves the current strip edge position value as the reference position S1 for the misalignment curling position; during the strip curling process, the EPC detects the strip edge position in real time and calculates the deviation value ΔS based on the current strip edge position S2 and the reference position S1. Step 3. Lateral movement of the coiler mandrel to achieve staggered edge curling of the strip: The opening degree K of the hydraulic cylinder servo valve of the coiler mandrel is automatically calculated and adjusted, and the staggered edge curling of the strip is achieved by the lateral movement of the mandrel.

[0009] Furthermore, the formula for calculating the target length L is as follows: L = L1 + n × d × π Where: L1 is the distance from the slitting shear to the tangent point between the strip and the coiler drum; n is the number of turns of the strip on the coiler; d is the outer diameter of the coiler mandrel.

[0010] Furthermore, the formula for calculating the above deviation value ΔS is: ΔS=S2-S1, where: S1 is the reference position; S2 is the current position.

[0011] Furthermore, the formula for calculating the opening degree K is: K = k1 × f(t) × ΔS, where: f(t) is the analytical expression of the misaligned side model; k1 is the conversion coefficient; and ΔS is the deviation value.

[0012] Furthermore, the formula for calculating the analytical expression f(t) of the above-mentioned staggered edge model is as follows: , Where: A is the amplitude, i.e. the depth of the misalignment; T is the misalignment period time; t is the time during the misalignment process.

[0013] Compared with the prior art, the present invention has the following outstanding advantages: 1. This invention enables staggered winding during strip steel winding, alleviating the waviness defect caused by overlapping steel coils in the thickened edge area; 2. The misalignment winding function of the galvanizing coiler is used to achieve the winding without increasing the cost of hardware modification; 3. It can be used in real-world continuous industrial production to reduce edge waviness defects in hot-dip pickled zinc-plated products. Attached Figure Description

[0014] Figure 1 is a schematic diagram of the staggered edge winding operation in Embodiment 1 of the present invention.

[0015] Figure 2 is a dynamic curve of the strip cross-sectional profile thickness in Embodiment 2 of the present invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] For the purposes of the following detailed description, it should be understood that the invention may take various alternative variations and sequences of steps unless explicitly stated otherwise. Furthermore, except in any operational instance or where otherwise indicated, all figures representing quantities of ingredients as used, for example, in the specification and claims, should in all cases be understood to be modified by the term “about.” At least, and without attempting to limit the application of the principle of equivalents to the scope of the claims, each numerical parameter should be understood at least according to the number of significant figures reported and by applying common rounding techniques.

[0018] Although the numerical ranges and parameters illustrating the broad scope of the invention are approximate, the values ​​described in the specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that is necessarily caused by the standard deviation found in its corresponding test measurement.

[0019] It should also be understood that any range of values ​​stated herein is intended to include all subranges included therein. For example, the range “1 to 10” is intended to include all subranges between (and including) the stated minimum value of 1 and the stated maximum value of 10, that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10.

[0020] In this application, unless otherwise specified, the use of the singular includes the plural and the plural encompasses the singular. Additionally, in this application, unless otherwise expressly stated, the use of "or" means "and / or," even if "and / or" may be explicitly used in certain circumstances. Furthermore, in this application, unless otherwise specified, the use of "a" or "an" means "at least one / a." For example, "an" first material, "an" coating composition, etc., refer to one or more of any of these items.

[0021] This invention relates to a method for improving edge thickening defects in thick zinc-coated products. By utilizing the EPC (Enhanced Participation Control) correction device of the galvanizing coiler, it achieves regular edge-misalignment during coiling, preventing the bulging areas at the galvanized edges from continuously accumulating stress and causing edge waviness defects, thus solving the edge waviness defect problem in galvanized products. The EPC correction device is an existing structure in current galvanizing coilers used for correction; its hardware and software are not described in detail here.

[0022] The following is the operation plan for Example 1, where the target zinc layer thickness is ≥300 / m2, and staggered edge winding is performed.

[0023] Step 1. Generating the Misaligned Curl Command The formula for calculating the target length L is: L = L1 + n × d × π Where: L1 is the distance from the slitting shear to the tangent point between the strip and the coiler drum; n is the number of turns of the strip on the coiling machine; d is the outer diameter of the winding mechanism shaft.

[0024] like Figure 1 As shown, when the exit slitting shear cuts the strip head length to zero, the automated system automatically calculates the strip head position value during the threading process. When the system detects that the strip head position is greater than the target length L, it generates a misalignment curling command and sends it to the EPC correction device.

[0025] Step 2. Calculation of the position of the misaligned side After receiving the misalignment curling command, the EPC automatically saves the current strip edge position value as the reference position S1 for the misalignment curling position. During the strip curling process, the EPC monitors the strip edge position in real time and calculates the deviation value ΔS based on the current strip edge position S2 and the reference position S1. The formula for calculating the deviation value ΔS is as follows: ΔS = S2 - S1 Where: S1 is the reference position; S2 represents the current position.

[0026] Step 3. The winding machine spindle moves laterally to achieve staggered coiling of the strip. The opening degree K of the hydraulic cylinder servo valve of the coiler mandrel is automatically calculated and adjusted, and the strip is rolled up by the lateral movement of the mandrel.

[0027] K = k1 × f(t) × ΔS Where: f(t) is the analytical expression of the staggered edge model; k1 is the conversion factor; ΔS is the deviation value.

[0028] In this invention, a sinusoidal wave model with an initial phase angle of zero degrees is selected for on-site winding. The formula for calculating the analytical expression f(t) of the staggered-side model is as follows: , Where: A is the amplitude, i.e. the depth of the misalignment; T represents the staggered cycle time; t represents the time at which the layering process occurs.

[0029] In the optimized scheme, the period T is the actual torque setpoint period T of the winding machine. Because the mandrel moves continuously and repeatedly, to ensure a stable winding effect, the EPC will detect the mandrel's lateral position value in real time and feed it back to the automation system. The automation system automatically calculates the winding machine torque setpoint compensation value ΔT based on the detected position value. The formula for the actual torque setpoint period T of the winding machine is: T = T0 + ΔT1 + ΔT2 + ΔT3 Where: T0 is the motor torque value corresponding to the tension of the coiled strip; ΔT1 is the torque compensation amount for the motor overcoming rotational inertia; ΔT2 is the torque compensation amount of the motor to overcome the friction between the roller surface and the strip surface; ΔT3 is the torque compensation amount for the motor to overcome spindle position deviation.

[0030] With the solution of this invention, during the winding process of galvanized coils, the edge thickening area no longer exhibits wavy defects caused by overlapping and bulging as the number of coil layers increases. The original edge wavy occurrence rate of galvanized products is reduced from 0.6% to 0.4%.

[0031] During the ESP rolling process, due to temperature differences at the strip edge or wear of the rolls, local high points exist at the edge of the strip cross-section. These high points accumulate during galvanizing and coiling, causing edge bulging of the entire coil and resulting in strip shape issues. Example 2 addresses this problem by incorporating a cross-sectional shape assessment of the hot-pressed substrate. Raw materials potentially prone to bulging due to local high points or severely wedge-shaped areas are preemptively removed, overcoming the problem of strip edge thickening caused by abnormal raw material edge quality and further reducing the possibility of strip deformation in the overlapping areas.

[0032] Example 2: Before entering the galvanizing process, the cross-sectional shape of the hot-dip substrate is evaluated. During the winding process, the staggered winding pattern from Example 1 is used. Specific methods include: 1. Classification and setting of local high points at the edge of the cross-section profile The production line's thickness profile inspection equipment measures the thickness variation of the strip in the width direction in real time, generating a dynamic curve of the strip's cross-sectional profile thickness (e.g., ...). Figure 2 (As shown), and the software automatically generates the 0-point straight line and the L-shaped simulated line. For example... Figure 2 As shown in the figure, the upper straight line is the 0-point straight line (the target thickness curve of the strip), the lower straight line is the L-simulation line, and the dynamic line is the thickness profile of the strip cross section.

[0033] Select warning high points, within a range of 40mm to 200mm from the longitudinal edge.

[0034] Point a is the highest point on the side of the line above 0, and it is also higher than the highest point in the middle of the convexity of the steel plate. Da represents the distance from point a to the simulated line L.

[0035] Point b is the lowest edge high point of the line below 0, and Db represents the distance from point b to the simulated line L.

[0036] 2. Set early warning standards Based on the thickness specifications, the warning standards for point a, point b, convexity, and wedge value are set as follows: 0.8≤t＜1.2 ≥1 ≥16 ≤6 wedge value > convexity value 1.2≤t＜2.0 ≥5 ≥21 ≤9 wedge value > convexity value 2.0≤t＜3.0 ≥7 ≥26 ≤11 wedge value > convexity value Among them, the crown C of hot-rolled strip steel, also known as the transverse thickness difference of strip steel, refers to the thickness difference of the strip along the width direction.

[0037] 3. Judgment After galvanizing on the galvanizing line, the high points on the edge of the raw material still exist. After being coiled by the coiler on the galvanizing line, the high points on the edge of the strip steel overlap. At the same time, due to the effect of the galvanizing air knife, this overlapping effect is aggravated, resulting in more pronounced waviness in the galvanized product.

[0038] Therefore, if a wedge value warning occurs, or if any two of the warning standards (point a, point b, and convexity) are present, the raw material is deemed defective and will not be produced on the galvanizing line to avoid edge waviness defects.

[0039] By controlling the raw materials, the edge waviness rate of galvanized products was reduced from 0.6% to 0.1% in a continuous hot-plate pickling and galvanizing production line.

[0040] Besides the high points at the edges of the raw materials, there are two other main reasons for the edge thickening and overlapping waviness of galvanized products. Firstly, the edge effect of the steel strip causes changes in the airflow of the air knife at the edges, reducing the airflow's ability to scrape zinc. Secondly, after the air knife scrapes away excess zinc from the steel strip surface during galvanizing, the zinc on the surface is not completely solidified. Due to the surface tension of the zinc, the zinc layer accumulates from other areas towards the edges, resulting in edge thickening and overlapping waviness defects. The thicker the zinc layer, the lower the blowing pressure of the air knife, the more severe the decrease in the edge airflow's ability to scrape zinc, and the more zinc accumulates from the center towards the edges. These two factors increase the probability of edge thickening and overlapping waviness.

[0041] In addition to the measures mentioned above, the following controls can also be implemented: 1. Quality requirements for cold rolling rolls In galvanized steel production lines, worn rubber rollers may develop a conical shape or form noticeable steps. When the strip comes into contact with these worn rollers, uneven deformation and edge waviness defects occur at the edges. Therefore, there are specific requirements for roller wear on production lines: the wear of polyurethane rubber rollers on galvanized steel production lines should be ≤2mm. Rollers with wear greater than 2mm must be replaced. Production line engineers will schedule roller wear assessments twice a month during maintenance periods.

[0042] 2. Distance between the air knife baffles on both sides and the strip: The air knife baffle is 2-3mm away from the edge of the strip. This can effectively prevent the baffle from being too close to the edge of the strip (<2mm), which would cause slag to stick to the baffle. Once the slag accumulates to a certain amount, it is very easy for the slag to stick to the strip, which would cause other defects. At the same time, it can also prevent the baffle from being too far away, which would reduce its effectiveness.

[0043] The factors that affect the thickening of the galvanized edge and cause edge waviness, such as air knife gap, blowing angle, zinc liquid temperature, and aluminum content in the zinc pot, are all conventional processes and will not be discussed in this invention.

[0044] Alternatively, a high-definition camera can be installed at the galvanized coil exit. If a local bulge is found on the edge of the galvanized coil during the winding process, the coil can be temporarily detained and then unwound at the rewinding unit to verify the edge waviness. The quality can then be judged based on the waviness standard.

[0045] It should be noted that the specific embodiments of the present invention have been described in detail. For those skilled in the art, various obvious changes made to it without departing from the spirit and scope of the present invention are within the protection scope of the present invention.

Claims

1. A method for improving the edge thickening defect of thick zinc-plated products, characterized in that: Specific methods include: Step 1. Generation of the misalignment curling command: When the exit slitting shear cuts the strip head length to zero, the automated system automatically calculates the strip head position value during the threading process. When the system detects that the strip head position is greater than the target length L, it generates a misalignment curling command and sends it to the EPC correction device. Step 2. Calculation of Misalignment Position: After receiving the misalignment curling command, the EPC automatically saves the current strip edge position value as the reference position S1 for the misalignment curling position; during the strip curling process, the EPC monitors the strip edge position in real time and calculates the deviation value ΔS based on the current strip edge position S2 and the reference position S1; the formula for calculating the deviation value ΔS is as follows: ΔS = S2 - S1, Where: S1 is the reference position; S2 is the current position; Step 3. Lateral movement of the coiler mandrel to achieve staggered edge curling of the strip: The opening degree K of the hydraulic cylinder servo valve of the coiler mandrel is automatically calculated and adjusted, and the staggered edge curling of the strip is achieved by the lateral movement of the mandrel. The formula for calculating the opening degree K is: K = k1 × f(t) × ΔS, Where: f(t) is the analytical expression of the misaligned model; k1 is the transformation coefficient; ΔS is the deviation value; The formula for calculating the analytical expression f(t) of the staggered edge model is as follows: ， Where: A is the amplitude, i.e. the depth of the misalignment; T is the misalignment period time; t is the time during the misalignment process.

2. The method for improving the edge thickening defect of thick zinc-plated products according to claim 1, characterized in that: The formula for calculating the target length L is: L = L1 + n × d × π Where: L1 is the distance from the slitting shear to the tangent point between the strip and the coiler drum; n is the number of turns of the strip on the coiler; d is the outer diameter of the coiler mandrel.

3. The method for improving the edge thickening defect of thick zinc-plated products according to claim 1, characterized in that: The staggered layer cycle time T is the actual torque given cycle T of the winding machine, and its calculation formula is as follows: T = T0 + ΔT1 + ΔT2 + ΔT3 Where: T0 is the motor torque value corresponding to the tension of the coiled strip; ΔT1 is the motor torque compensation amount for overcoming rotational inertia; ΔT2 is the motor torque compensation amount for overcoming the friction between the roller surface and the strip surface; ΔT3 is the motor torque compensation amount for overcoming the mandrel position deviation.

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