Zinc layer thickness control method based on plate shape correction

Abstract

The invention discloses a zinc layer thickness control method based on strip shape correction. The zinc layer thickness control method comprises the following steps that S1, the warping amount delta of strip steel C is obtained; s2, according to the warping amount delta of the strip steel C, the biting amount IM of the stabilizing roller is obtained through calculation; and S3, the stabilizing roller is controlled to move to the position of the nip amount IM obtained through calculation. The method can effectively improve the C warping defect of the hot-dip galvanized strip steel and reduce the strip shape error of the strip steel at the air knife, so that the uniformity of a galvanized layer of the strip steel is improved.

Description

Technical Field

[0001] This invention relates to hot-dip galvanizing technology, and more specifically, to a method for controlling zinc layer thickness based on plate shape correction. Background Technology

[0002] During the hot-dip galvanizing process, the strip steel is affected by various factors, and when it enters the air knife after passing through the zinc pot, it will exhibit a transverse warping deformation, abbreviated as C-warping (see...). Figure 1 (a) Furthermore, depending on the direction of the C-curve, it can be further divided into reverse C-curve (see Figure 1 (b) and positive C-curve (see Figure 1 (c) Due to the presence of the reverse C-curve, the distance between the middle of the strip and the front air knife nozzle is greater than the distance between the edge and the air knife nozzle. The farther the nozzle is from the strip, the lower the airflow pressure and the greater the zinc layer thickness. For example, the presence of the reverse C-curve ultimately results in a zinc layer thickness distribution on the upper surface of the strip that is "thinner in the middle and thicker at the edges," while the lower surface shows the opposite (see [reference]). Figure 2 (See illustration). The thickness and uniformity of the galvanized layer greatly affect the quality of galvanized sheet products. Unstable thickness and uniformity will affect the performance of the zinc sheet, reduce the yield of the product, and cause significant economic losses to the unit. Summary of the Invention

[0003] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a zinc layer thickness control method based on plate shape correction, which can effectively improve the C-curve defect of hot-dip galvanized strip steel, reduce the plate shape error of strip steel at the air knife, and thus improve the uniformity of the zinc layer of strip steel.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A zinc layer thickness control method based on plate shape correction includes the following steps:

[0006] S1, obtain the strip C-curvature δ;

[0007] S2, the bite amount IM of the stabilizing roll is calculated based on the strip C warp amount δ;

[0008] S3, control the stabilizing roller to move to the calculated bite amount IM position.

[0009] Preferably, step S1 specifically includes:

[0010] A position sensor is installed at the center of the channel line between the front air knife and the rear air knife. The position sensor uses the eddy current detection principle to detect the distance between the center of the strip and the air knife.

[0011] The strip warp amount δ is calculated based on the distance between the strip center and the air knife obtained by the position sensor.

[0012] Preferably, in step S2, the bite amount IM of the stabilizing roller is calculated as follows:

[0013] δ=-18*(t / w)*IM 2 -(0.0056*d)*IM+0.06*L

[0014] In the formula, t is the strip thickness, w is the strip width, d is the difference in diameter between the two stabilizing rolls, and L is the vertical distance between the centers of the two stabilizing rolls.

[0015] Preferably, the diameter difference d between the two stabilizing rollers is ≥80mm;

[0016] The vertical distance L between the centers of the two stabilizing rollers is between 150 and 220 mm.

[0017] Preferably, the diameter of one of the stabilizing rollers is 300-350 mm;

[0018] The diameter of the other stabilizing roller is 200-250 mm.

[0019] The present invention provides a zinc layer thickness control method based on plate shape correction, which obtains plate shape data based on position sensors and uses zinc pot stabilizing rollers to control C-warping defects in hot-dip galvanized strip steel. This method can effectively improve C-warping defects in hot-dip galvanized strip steel, reduce plate shape error at air knife, and thus improve the uniformity of the zinc layer of strip steel. Attached Figure Description

[0020] Figure 1 These are schematic diagrams of C-curves: (a) is a typical C-curve, (b) is a reverse C-curve, and (c) is a normal C-curve.

[0021] Figure 2 This is a schematic diagram of the zinc layer thickness when the C-shaped curve is reversed;

[0022] Figure 3 This is a flowchart illustrating the zinc layer thickness control method of the present invention;

[0023] Figure 4 This is a schematic diagram of step S1 in the zinc layer thickness control method of the present invention;

[0024] Figure 5 This is a schematic diagram of the existing stabilizing rolls arranged on the left and right sides of the strip, (a) is PSJ, (b) is SJP;

[0025] Figure 6 This is a schematic diagram of the SJP-D arrangement in the zinc layer thickness control method of the present invention;

[0026] Figure 7This is a schematic diagram of the relationship between the bite amount IM and the C-curve correction amount δ in Embodiment 1 of the zinc layer thickness control method of the present invention;

[0027] Figure 8 This is a schematic diagram of the relationship between the bite amount IM and the C-curve correction amount δ in Embodiment 2 of the zinc layer thickness control method of the present invention. Detailed Implementation

[0028] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] Combination Figure 3 As shown, the zinc layer thickness control method based on plate shape correction provided by the present invention includes the following steps:

[0030] S1, obtain the strip C-curvature δ;

[0031] S2, the bite amount IM of the stabilizing roll is calculated based on the strip C warp amount δ;

[0032] S3, control the stabilizing roller to move to the calculated bite amount IM position.

[0033] Combination Figure 4 As shown, step S1 specifically includes:

[0034] A position sensor 3 is installed at the center of the channel line between the front air knife 1 and the rear air knife 2. The position sensor 3 uses the eddy current detection principle to detect the distance between the center of the strip and the air knife (front air knife 1 and rear air knife 2).

[0035] The strip warping amount δ is calculated based on the distance between the strip center and the air knife obtained by the position sensor 3.

[0036] Combination Figure 5 As shown, zinc pot stabilizing rolls of the same diameter are used to straighten the strip shape. One stabilizing roll is used as a guide roll to ensure the strip is on the correct guide line; this stabilizing roll is called the P roll and does not require adjustment during production. Another stabilizing roll can move back and forth to adjust the wrap angle between the strip and the stabilizing roll, thereby achieving the purpose of straightening the strip shape; this stabilizing roll is called the J roll. The last submerged roll is called the S roll. In current production, operators visually observe the C-curve and manually adjust the bite depth IM of the J roll to improve the strip shape.

[0037] According to the arrangement of the stabilizing rolls on the left and right sides of the strip, they are respectively called: PSJ (e.g., Figure 5 (a) and SJP (e.g.) Figure 5 (b)

[0038] Generally, the PSJ type is effective for adjusting positive C-curve, but less effective for adjusting negative C-curve. The SJP type can adjust both positive and negative C-curve. However, when the C-curve is large, the bite depth (IM) adjustment is limited by the travel of the moving mechanism, typically only reaching 30-40mm, thus limiting its ability to correct plate shape.

[0039] Combination Figure 6 As shown, the zinc coating thickness control method of this invention uses unequal-diameter stabilizing rollers to correct strip shape. The P roller and J roller have different diameters and are arranged in an SJP-D configuration. The diameter difference d between the P roller and the J roller is ≥ 80 mm. The diameter of the P roller ranges from 300 to 350 mm, and the diameter of the J roller ranges from 200 to 250 mm. The diameter of the submerged roller (S roller) ranges from 750 to 800 mm. The centerline height difference L between the P roller and the J roller is between 150 and 220 mm. Theoretically, a smaller L is better, but if L is less than 150 mm, the roller surfaces of the two stabilizing rollers will come into contact when adjusting the bite depth IM. If L is too large, the wrap angle between the strip and the stabilizing roller decreases, and the strip shape correction capability deteriorates.

[0040] The stabilizing roll configuration in this invention allows for a smaller bite depth IM to achieve better strip shape correction. Theoretically, a larger bite depth IM results in stronger strip shape correction. However, due to equipment structure limitations, an infinitely large bite depth IM cannot be obtained. Furthermore, an excessively large bite depth IM can cause zinc dross to be pressed into the strip, resulting in roll marks and quality defects. Therefore, the purpose of this invention (SJP-D) is to achieve greater strip shape correction with the same bite depth IM as the SJP configuration with the same diameter, while using a different diameter stabilizing roll configuration. In other words, with the same strip shape correction capability, the bite depth IM of the SJP-D is smaller, which is more beneficial to strip quality and prevents zinc dross from being pressed into the strip, causing roll marks.

[0041] To avoid discrepancies in manual plate shape adjustments due to differences in operator skills and experience, and to achieve faster and more accurate plate shape adjustments, the bite amount IM of the stabilizing roller is calculated in step S2 above as follows:

[0042] δ=-18*(t / w)*IM 2 -(0.0056*d)*IM+0.06*L

[0043] In the formula, t is the strip thickness, w is the strip width, d is the difference in diameter between the two stabilizing rolls, and L is the vertical distance between the centers of the two stabilizing rolls.

[0044] Theoretically, the target C-curve δ is best when it is zero. However, a completely straight strip will produce vibration marks when running at high speed. Generally, maintaining a slight positive (negative) C-curve is actually beneficial for high-speed strip passage. Therefore, the target C-curve δ should be set according to the actual strip passage speed to obtain a strip shape that is as close to a straight strip as possible, so as to obtain a uniform zinc layer thickness on the upper and lower surfaces of the strip.

[0045] Example 1

[0046] The specifications of the strip steel produced by a certain hot-dip galvanizing unit are: thickness 0.6~2.5mm, width 1000~1750mm.

[0047] During production, the specific strip specifications are: strip thickness t = 1.0 mm, strip width w = 1700 mm, the C-curve detected by position sensor 3 is positive C-curve, δ = 14, the target control C-curve amount δ = ±1 mm, which can obtain the zinc layer thickness accuracy required by the user.

[0048] Production is carried out using stabilizing rollers of different diameters, as detailed below:

[0049] Scheme 1 (Example of the invention): The diameter of roller P is 315mm, the diameter of roller J is 235mm, the difference in roller diameter between the two stabilizing rollers is d = Dp - Dj = 80mm, and the vertical distance between the centers of the two stabilizing rollers is L = 220.

[0050] Scheme 2 (Comparative Example 1): The diameter of roller P is 300mm, the diameter of roller J is 270mm, the difference in roller diameter between the two stabilizing rollers is d = Dp - Dj = 30mm, and the vertical distance between the centers of the two stabilizing rollers is L = 220.

[0051] Scheme 3 (Comparative Example 2): The diameter of roller P is 250mm, the diameter of roller J is 250mm, the difference in diameter between the two stabilizing rollers is d = Dp - Dj = 0mm, and the vertical distance between the centers of the two stabilizing rollers is L = 220.

[0052] The relationship between bite depth IM and C-curve correction δ satisfies the following equation:

[0053] δ=-18*(t / w)*IM 2 Substituting the known data into -(0.0056*d)*IM+0.06*L:

[0054] δ=-0.0106*IM 2 -(0.0056*d)*IM+13.2

[0055] Based on this relationship, curves showing the relationship between bite depth IM and C-curve correction δ under different diameter differences can be plotted as follows: Figure 7 As shown, from Figure 7As can be seen from this, the correction ability of Scheme 1 in this embodiment 1 is significantly higher than that of Scheme 2 and Scheme 3.

[0056] The table below shows the comparative data between the inventive example and the comparative example in Embodiment 1:

[0057] As can be seen from the invention, the greater the difference d between the two stabilizing rollers, the stronger the correction ability of the invention at the same bite amount IM. When IM = 20mm, the invention can correct C warp to near zero, satisfying δ = ±1mm.

[0058] The comparative examples could only be corrected to 5.6mm and 8.9mm.

[0059] δ t w d L IM Invention Examples 0.004705882 1 1700 80 220 25 Comparative Example 1 5.604705882 1 1700 30 220 25 Comparative Example 2 8.964705882 1 1700 0 220 25

[0060] Example 2

[0061] The specifications of the strip steel produced by a certain hot-dip galvanizing unit are: thickness 0.6~2.5mm, width 1000~1750mm.

[0062] During production, the specific strip specifications are: strip thickness t = 2.0 mm, strip width w = 1500 mm, the C-curve detected by position sensor 3 is positive C-curve, δ = 6, the target control C-curve amount δ = ±1.5 mm, which can obtain the zinc layer thickness accuracy required by the user.

[0063] Production is carried out using stabilizing rollers of different diameters, as detailed below:

[0064] Scheme 1 (Example of the invention): The diameter of roller P is 315mm, the diameter of roller J is 235mm, the difference in roller diameter between the two stabilizing rollers is d = Dp - Dj = 80mm, and the vertical distance between the centers of the two stabilizing rollers is L = 180.

[0065] Scheme 2 (Comparative Example 1): The diameter of roller P is 315mm, the diameter of roller J is 235mm, the difference in roller diameter between the two stabilizing rollers is d = Dp - Dj = 80mm, and the vertical distance between the centers of the two stabilizing rollers is L = 250.

[0066] Scheme 3 (Comparative Example 2): The diameter of roller P is 315mm, the diameter of roller J is 235mm, the difference in roller diameter between the two stabilizing rollers is d = Dp - Dj = 80mm, and the vertical distance between the centers of the two stabilizing rollers is L = 300.

[0067] The relationship between bite depth IM and C-curve correction δ satisfies the following equation:

[0068] δ=-18*(t / w)*IM 2 -(0.0056*d)*IM+0.06*L

[0069] Based on this relationship, curves showing the relationship between bite depth IM and C-curve correction δ under different diameter differences can be plotted as follows: Figure 8 As shown, from Figure 8 As can be seen from this, the correction capabilities of schemes 1 and 2 in this embodiment 2 are significantly higher than those of scheme 3.

[0070] The table below shows the comparative data between the inventive example and the comparative example in Embodiment 2:

[0071] As can be seen from the inventive examples, when the center distance L of the two stabilizing rollers is within the range of the present invention, the inventive examples have a stronger corrective ability at the same bite amount IM. When IM = 13 mm, the inventive examples can correct C-warping to near zero, satisfying δ = ±1.5 mm. In contrast, the comparative examples can only correct to 5.12 mm and 8.12 mm.

[0072] δ t w d L IM Invention Examples 0.92 2 1500 80 180 13 Comparative Example 1 5.12 2 1500 80 250 13 Comparative Example 2 8.12 2 1500 80 300 13

[0073] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A zinc layer thickness control method based on plate shape correction, characterized in that, Includes the following steps: S1, obtain the strip C-curvature δ; S2, the bite amount IM of the stabilizing roll is calculated based on the strip C warp amount δ; S3, control the stabilizing roller to move to the calculated bite amount IM position.

2. The zinc layer thickness control method based on plate shape correction according to claim 1, characterized in that, Step S1 specifically includes: A position sensor is installed at the center of the channel line between the front air knife and the rear air knife. The position sensor uses the eddy current detection principle to detect the distance between the center of the strip and the air knife. The strip warp amount δ is calculated based on the distance between the strip center and the air knife obtained by the position sensor.

3. The zinc layer thickness control method based on plate shape correction according to claim 1, characterized in that, In step S2, the bite amount IM of the stabilizing roller is calculated as follows: δ=-18*(t / w)*IM 2 -(0.0056*d)*IM+0.06*L In the formula, t is the strip thickness, w is the strip width, d is the difference in diameter between the two stabilizing rolls, and L is the vertical distance between the centers of the two stabilizing rolls.

4. The zinc layer thickness control method based on plate shape correction according to claim 3, characterized in that: The diameter difference d between the two stabilizing rollers is ≥80mm; The vertical distance L between the centers of the two stabilizing rollers is between 150 and 220 mm.

5. The zinc layer thickness control method based on plate shape correction according to claim 4, characterized in that: The diameter of one of the stabilizing rollers is 300-350 mm; The diameter of the other stabilizing roller is 200-250 mm.

Images