A control method for preventing flat diagonal lines of a tinned substrate

Abstract

This invention discloses a method for controlling diagonal lines on tin-plated substrates. For controlling localized diagonal lines: utilizing the characteristics of the leveling mill's roller system, the method increases the leveling mill inlet tension and the height of the anti-wrinkle rollers to reduce the corrugation index of the incoming strip, ensuring that the corrugation index entering the leveling mill is less than 15I. For controlling diagonal lines across the entire surface: the method reduces the difference in levelness between the anti-wrinkle rollers and the surface, reduces the rolling inlet tension Q1, reduces the anti-wrinkle roller height, and reduces the incoming material width W. Furthermore, the method evaluates the inlet strip offset index N and the overall diagonal line occurrence index E, ensuring that N < 40I and E < 0.15. This invention, by increasing the leveling mill inlet tension and the height of the anti-wrinkle rollers, can reduce the corrugation index of the incoming strip and avoid the generation of localized diagonal lines.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for controlling the flatness of tin-plated substrates with diagonal lines. Background Technology

[0002] When tin-plated substrates enter the leveling machine at a speed greater than 500 m / min on a high-speed continuous annealing line, the strip surface is highly susceptible to flatness diagonal lines. These defects form an angle with the rolling direction and can occur locally across the strip width or throughout the entire strip surface. Figure 1 As shown.

[0003] Regarding research on leveling diagonal lines, previous researchers have summarized their experience in producing cold-rolled plain plates and high-strength steel with a thickness of 0.4mm or more, proposing that leveling diagonal lines are caused by differences in transverse rolling force across the plate width, differences in longitudinal rolling force, or fluctuations in rolling force. CN104226696B argues that leveling diagonal lines occur when the cross-sectional area of ​​the steel does not match the leveling roll gap. Based on the plate shape data after leveling, a wedge shape matching with the roll gap is determined by quantifying the single-sided waviness coefficient. A predictive model for diagonal line occurrence based on rolling force difference, width, and single-sided waviness coefficient is presented. The key control point is to regulate leveling diagonal lines by matching the roll gap and reducing the rolling force difference in the plate width direction. Furthermore, adjustments based on the plate shape after leveling constitute a feedback mechanism. CN107511400B introduces a method for controlling diagonal lines defects caused by significant differences in the flatness and elongation of the upper and lower surfaces on a whole plate. The method addresses the diagonal lines resulting from the difference in flatness and elongation caused by the lower support drive leveling machine. By adjusting process parameters such as rolling force, tension, upper wrap angle, roughness, and belt speed, the method aims to reduce the difference in flatness and elongation between the upper and lower surfaces. CN113699326B introduces a method to avoid surface diagonal lines caused by fluctuations in rolling force during leveling due to uneven steel strip properties. This is achieved through the stability of the composition, annealing process, and leveling process. The aim is to avoid surface diagonal lines and other defects caused by insufficient recrystallization annealing of the steel strip, resulting in uneven internal structure and properties, which can lead to fluctuations in rolling force during leveling. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a method for controlling the oblique lines on the flatness of tin-plated substrates. By increasing the inlet tension of the flattening machine and the height of the anti-wrinkle roller, the corrugation index of the board entering the flattening machine is reduced, thus avoiding the generation of local oblique lines.

[0005] Technical solution: A method for controlling the oblique lines on the flatness of tin-plated substrates. For the control of local oblique lines: by utilizing the characteristics of the roller system of the flattening machine, the inlet tension of the flattening machine and the height of the anti-wrinkle roller are increased to reduce the wave shape index of the board entering the flattening machine, ensuring that the board shape index of the board entering the flattening machine is less than 15I.

[0006] For controlling the slab surface slant: reduce the difference between the anti-wrinkle roller and the levelness S, reduce the rolling inlet tension Q1, reduce the height of the anti-wrinkle roller, and reduce the incoming material width W; and evaluate according to the inlet strip offset evaluation index N and the slab surface slant occurrence evaluation index E, ensuring that N < 40I and E < 0.15.

[0007] Furthermore, the specific steps to reduce the corrugation index of the plate entering the leveling machine are as follows:

[0008] S1, Determine the shape index I of the incoming wave of the tin-plated substrate. ０ ;

[0009] ,

[0010] Where ∆L / L represents the relative length difference of the waves, L is the wavelength of the original tensionless wave, and R is the wave amplitude;

[0011] S2, Determine the shape index of the plate entering the leveling machine under tension. ;

[0012] According to Hooke's Law, the elastic strain rate The relationship with the inlet tension Q1 of the leveling machine is as follows:

[0013] ,

[0014] Therefore, the shape index of the plate entering the leveling machine under tension for:

[0015] ,

[0016] Where E is the elastic modulus of the tin-plated substrate;

[0017] S3, determine the tension Q1 of the tin-plated sheet entering the leveling machine inlet;

[0018] According to the principles of mechanics and Euler's formula, the tension relationship between the strip and the roll before and after forming a wrap angle is as follows:

[0019] ,

[0020] Among them, Q ０ This refers to the initial tension at the leveling machine inlet;

[0021] f is the coefficient of friction between the tin-plated substrate and the rolling mill rolls and anti-wrinkle rolls;

[0022] The angle between the strip and the anti-wrinkle roll varies depending on the height of the anti-wrinkle roll.

[0023] The wrap angle between the strip and the rolling mill rolls varies depending on the height of the anti-wrinkle rolls.

[0024] Furthermore, based on the characteristics of the roller system, after the tinplate enters the leveling mill and comes into contact with the tension meter roller, rolling mill roller, and straightening roller, the measures to increase the inlet tension Q1 of the leveling mill are as follows: Increase the overall inlet tension Q by using the tension meter roller before the leveling mill roller system. ０ Alternatively, this can be achieved by increasing the height of the anti-wrinkle roller or increasing the wrap angle between the strip and the anti-wrinkle roller. Increase the wrap angle between the strip and the rolling mill rolls. .

[0025] Furthermore, the inlet strip offset evaluation index N is the ratio of half the parallelism difference between the two tooling rolls within the strip width range to the horizontal distance between the two tooling components, expressed as follows:

[0026] ,

[0027] In the formula, To enter the rolling mill angle, and >10°;

[0028] Overall board diagonal grain occurrence assessment index E g The expression is as follows:

[0029] ,

[0030] Where H is the distance between the anti-wrinkle roller and the work roller.

[0031] Furthermore, measures to reduce the height of the anti-wrinkle rolls are as follows: reduce the angle of entry into the rolling mill. Alternatively, increase the distance H between the anti-wrinkle roller and the work roller.

[0032] Compared with the prior art, the significant advantages of this invention are as follows:

[0033] 1. This invention utilizes the characteristics of the roller system of the leveling machine unit. By increasing the inlet tension of the leveling machine and the height of the anti-wrinkle roller, the corrugation index of the incoming plate can be reduced, thus avoiding the generation of local diagonal lines.

[0034] 2. This invention controls the generation of diagonal lines on the entire plate surface by reducing the difference between the anti-wrinkle roller and the levelness, reducing the rolling inlet tension, reducing the entry angle of the rolling mill, increasing the distance between the anti-wrinkle roller and the work roller, and reducing the incoming material width. Attached Figure Description

[0035] Figure 1 Schematic diagrams showing partial diagonal patterns and diagonal patterns across the entire board surface;

[0036] Figure 2 This is a side view of the flat frame;

[0037] Figure 3 The wave enters the side view of the leveling machine;

[0038] Figure 4 Top view of the steel strip entering the leveling machine. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0040] Tin-plated substrates are relatively thin, typically between 0.17 and 0.55 mm. Even without significant abnormal fluctuations in rolling force, diagonal lines can still occur. These diagonal lines can be localized or spread across the entire board. Figure 1 As shown. During the tin-plated substrate leveling process, the steel plate, in addition to being rolled by the work rolls, also comes into contact with the front and rear anti-wrinkle rolls, tension gauge rolls, and rolling mill rolls of the leveling machine. The steel plate does not enter the rolls horizontally, but rather passes through the anti-wrinkle rolls and the upper roll of the work rolls, forming a certain wrap angle before entering the leveling machine rolls, as shown. Figure 2 The image shown is a side view of the flattened frame.

[0041] Based on the production conditions described above, this invention proposes a method to prevent flatness diagonal lines on cold-rolled tin-plated substrates under steady-state conditions without abnormal rolling force differences. This method aims to prevent both localized and full-surface diagonal lines. Depending on the underlying mechanism, the diagonal lines are categorized as localized or full-surface diagonal lines, and the control methods are as follows:

[0042] I. Mechanism of Local Diagonal Texture Generation

[0043] like Figure 3 As shown, the incoming plate shape (wavy) is abnormal before leveling. The steel plates entering the leveling machine have varying lengths in the width direction, with the longer sections bulging. When the bulging reaches a certain extent and is subjected to tensile stress perpendicular to the rolling direction, microscopic local folds occur on the plate surface during the leveling process, forming diagonal lines after rolling. If there is no tensile stress perpendicular to the rolling direction, the bulging steel plate will be eliminated by leveling. However, objective conditions such as the horizontality and parallelism of the tooling rollers, the installation accuracy, and the difference in rolling force on both sides will cause tension differences on both sides, resulting in local diagonal lines.

[0044] Factors influencing localized diagonal lines include: inlet raw material shape, inlet tension, leveling machine shape control strategy (roller type, bending roll), and inlet anti-wrinkle roll setting height (strip wrapping angle). Control measures include: reducing the raw material shape index I. ０ Rolling control strategies to increase inlet tension Q and suppress raw material shape (exit shape index I) １ ), Ensure a certain angle of entry into the rolling mill Reduce the parallelism difference between the anti-wrinkle roller and the work roller.

[0045] The strip shape index refers to the cross-sectional shape and straightness of raw strip steel, mainly including crown and strip profile. Crown refers to the thickness variation across the strip's cross-section, while strip profile refers to the straightness of the strip. Crown and strip profile are two independent but interrelated indicators that jointly affect the quality of the strip steel and the ease of subsequent processing.

[0046] To achieve precise control of the tension difference between the inlet and outlet of the leveling machine, firstly, the tension difference can be changed by adjusting the tension control system of the equipment, including adjusting the position of the tension sensor and calibrating the parameters of the tension controller; secondly, the tension difference can also be affected by changing the process parameters, such as adjusting the processing speed and temperature, which can indirectly affect the material's flowability and tension distribution.

[0047] Under normal circumstances, when the leveling machine roller system is adjusted to near zero deviation and the parallelism accuracy S≤0.05mm / m, the waves enter the leveling machine and undergo approximately two-dimensional deformation. During leveling, the waves will not fold, and the leveling elongation can cover the length difference of the waves to eliminate defects.

[0048] However, effective adjustment of equipment precision usually requires major or medium-sized overhauls, and daily production often faces poor precision. In this embodiment, the characteristics of the leveling machine's roller system are utilized to reduce the corrugation index of the incoming plate by increasing the leveling machine inlet tension and the height of the anti-wrinkle rollers. <15I (1 I unit represents a relative length difference of 10) -5 To avoid this defect, the specific steps are as follows:

[0049] Step 1: Determine the shape index I of the incoming tin-plated substrate waviness. ０ ;

[0050] Plate shape index I ０ The relative length difference ∆L / L of the waves is represented by the wavelength L and amplitude R of the original tensionless wave, measured using tools such as offline feeler gauges and rulers. Based on metallurgy, the plate shape index I... ０ The physical relationship between wavelength L and amplitude R is as follows:

[0051] (1)

[0052] Step 2: Determine the shape index of the plate entering the leveling machine under tension. ;

[0053] The yield strength of tin-plated sheets is generally greater than 300 N / mm². 2 The inlet tension of the leveling machine is increased to Q1 to increase the elastic deformation rate, as the tension is higher than the inlet tension. This prevents plastic deformation before the material enters the leveling process. The relative length difference of the waves is eliminated through elastic deformation, and the plate shape index is increased when the plate enters the leveling machine under tension. Equal to the original plate shape index I ０ Subtract the elastic strain rate from the base .

[0054] According to Hooke's Law, the elastic strain rate The relationship with tension Q1 is as follows:

[0055] (2)

[0056] Therefore, the shape index of the plate entering the leveling machine under tension for:

[0057] (3)

[0058] Where E is the elastic modulus of the tinplate, which is measured based on a tensile test.

[0059] Step 3: Determine the tension Q1 of the tin-plated sheet entering the leveling machine inlet;

[0060] Based on the characteristics of the roller system, after the tinplate comes into contact with the tension meter roller, rolling mill roller, and leveling roller before entering the leveling mill, the following measures are taken to increase the inlet tension Q1 of the leveling mill:

[0061] First, the overall inlet tension Q can be increased by using the tension gauge roller before the leveling mill roller system. ０ This tension can be measured by the tension gauge roller;

[0062] Secondly, the height of the anti-wrinkle roller can be increased, and the wrap angle between the strip and the anti-wrinkle roller can be increased. Roll wrap angle This could further improve Q1.

[0063] According to the principles of mechanics and Euler's formula, the tension relationship between the strip and the roll before and after forming a wrap angle is as follows:

[0064] (4)

[0065] Among them, Q ０ The initial tension at the leveling machine inlet is measured by a tension gauge roller.

[0066] f is the coefficient of friction between the tinplate and the rolling mill rolls and anti-wrinkle rolls;

[0067] α is the wrap angle between the strip and the anti-wrinkle roll, and its variation is determined by the height of the anti-wrinkle roll; different anti-wrinkle roll heights correspond to wrap angle data. The data of the front and rear roll systems of the leveling machine are entered into CAD for drawing and measurement.

[0068] β is the wrap angle between the strip and the rolling mill rolls, and its variation is determined by the height of the anti-wrinkle rolls; the wrap angle data corresponding to different anti-wrinkle roll heights are entered into CAD for drawing and measurement.

[0069] Substituting formulas (1) and (4) into (3), we can obtain the plate shape index when the plate enters the leveling machine under tension. as follows:

[0070] (5)

[0071] Therefore, based on the measurement of incoming material wave, the adjustment of the tension of the leveling machine and the wrap angle of the anti-wrinkle roller can be guided according to formula (5); based on adjustment experience, the sheet shape index of the tinplate strip before entering the leveling machine can be adjusted. ,when A value <15I can prevent the formation of localized diagonal lines.

[0072] II. Diagonal grain on the entire board surface

[0073] Mechanism and definition of diagonal strip texture: The inclined inlet tooling roller causes the strip to enter the leveling machine at an overall inclination. During the leveling process, microscopic folds are generated throughout the strip, resulting in diagonal strip texture. The reason for the strip entering the leveling machine at an inclination is the excessive difference in horizontality between the anti-wrinkle roller and the rolling roller.

[0074] The probability of diagonal strip occurrence is assessed by defining the entry strip offset evaluation index and the diagonal strip occurrence evaluation index.

[0075] The inlet strip offset assessment index N is defined as the ratio of half the parallelism difference between two tooling rolls within the strip width to the horizontal distance between the two tooling components. Figure 4 As shown.

[0076] This defect can be controlled by reducing the difference in levelness between the anti-wrinkle roll and the roll, lowering the rolling inlet tension Q1, reducing the height of the anti-wrinkle roll (reducing the entry angle θ of the mill and increasing the distance H between the anti-wrinkle roll and the work roll), and reducing the feed width W. The relationship between these process parameter adjustments and the occurrence of the defect is as follows:

[0077] The expression for the inlet strip offset evaluation index N is as follows:

[0078] (6)

[0079] In the formula, the applicable scope is: >10°.

[0080] Overall board diagonal grain occurrence assessment index E g The expression is as follows:

[0081] (7)

[0082] Based on experience, N < 40I and E g When the value is less than 0.15, no diagonal grain will occur on the entire board.

[0083] The technical solution of the present invention will be further described below with reference to the embodiments.

[0084] The production conditions for flattening tin-plated substrates are as follows: work roll diameter 400–440 mm, anti-wrinkle roll diameter 210 mm, strip thickness 0.17–0.55 mm, rolling force 2000–7000 KN, and flattening elongation 0.5–2.0%. Examples of local diagonal pattern control parameters are shown in Table 1, and examples of whole-surface diagonal pattern control parameters are shown in Table 2.

[0085] Table 1. Parameter Table for Local Diagonal Pattern Control Cases

[0086]

[0087] Table 2 Parameter Table for Diagonal Grating Control of the Entire Board Surface

[0088]

[0089] Table 1 shows that, as in Case C1, localized diagonal lines occur when the strip shape I1 entering the leveling machine under tension is 22.4 I-unit. Measure one, without adjusting the strip shape, eliminates the localized diagonal lines by adjusting the parallelism S of the rolling mill rolls, anti-wrinkle rolls, and work rolls from 0.16 mm / m to 0.05 mm / m or less through maintenance, as shown in Case C2. Measure two, by adjusting the leveling machine inlet tension and anti-wrinkle roll height to reduce the strip shape I1 entering the leveling machine to <15 I-unit, suppresses the generation of localized diagonal lines.

[0090] Table 2 shows that reducing the difference between the anti-wrinkle roll and the horizontality S, reducing the rolling inlet tension Q1, and reducing the height of the anti-wrinkle roll (reducing the angle of entry into the mill) can help. Increase the distance H between the anti-wrinkle roller and the work roller, reduce the incoming material width W, and adjust the inlet strip offset evaluation index N < 40IU and the overall strip diagonal pattern occurrence evaluation index E. g When the value is less than 0.15, no diagonal grain will occur on the entire board.

Claims

1. A method for controlling unevenness lines on a tin-plated substrate, characterized in that, For the control of local slant: Utilize the characteristics of the leveling machine's roller system, by increasing the leveling machine's inlet tension and the height of the anti-wrinkle roller, reduce the shape index of the sheet entering the leveling machine, and ensure that the shape index of the sheet entering the leveling machine is less than 15I; To control the overall strip surface diagonal lines: reduce the parallelism difference S between the anti-wrinkle roller and the work roller, reduce the inlet tension Q1 of the leveler, reduce the height of the anti-wrinkle roller, and reduce the incoming material width W; and based on the inlet strip offset evaluation index N and the overall strip diagonal line occurrence evaluation index E. g Conduct an evaluation to ensure that N < 40I and E g <0.15; The specific steps to reduce the shape index of the plate entering the leveling machine are as follows: S1, determine the shape index I0 of the incoming wave of the tin-plated substrate; I0=ΔL / L=(πR / 2L) 2 , Where ΔL / L represents the relative length difference of the waves, L is the wavelength of the original tensionless wave, and R is the wave amplitude; S2, determine the plate shape index I1 for entering the leveling machine; According to Hooke's Law, the relationship between the elastic strain rate ε and the inlet tension Q1 of the leveler is as follows: ε=Q1 / E, Therefore, the shape index I1 entering the leveling machine is: I1 = I0 - Q1 / E, Where E is the elastic modulus of the tin-plated substrate; S3, determine the tension Q1 of the tin-plated substrate entering the flattening machine inlet; According to the principles of mechanics and Euler's formula, the tension relationship between the strip and the roll before and after forming a wrap angle is as follows: Q1=Q0e f(α+β) , Where Q0 is the initial tension at the leveler inlet; f is the coefficient of friction between the tin-plated substrate and the rolling mill rolls and anti-wrinkle rolls; α is the wrap angle between the strip and the anti-wrinkle roll, and its variation is determined by the height of the anti-wrinkle roll. β is the wrap angle between the strip and the rolling mill rolls, and its variation is determined by the height of the anti-wrinkle rolls; By adjusting the inlet tension and wrap angle process parameters of the leveling machine, the strip shape index I1 of the tin-plated substrate entering the leveling machine is adjusted to ensure that I1 < 15I, where 1 I unit represents a relative length difference of 10. -5 ; The expression for the inlet strip offset evaluation index N is as follows: In the formula, θ is the angle at which the strip enters the work roll, and θ > 10°; Overall board diagonal grain occurrence assessment index E g The expression is as follows: Where H is the distance between the anti-wrinkle roller and the work roller.

2. The method for controlling unevenness lines on a tin-plated substrate according to claim 1, characterized in that, Based on the characteristics of the roller system, after the tin-plated substrate comes into contact with the tension meter roller, rolling mill roller, and straightening roller before entering the leveling mill, the following measures are taken to increase the inlet tension Q1 of the leveling mill: increase the initial inlet tension Q0 of the leveling mill by using the tension meter roller before the leveling mill roller system, or increase the wrap angle α between the strip and the anti-wrinkle roller, or increase the wrap angle β between the strip and the rolling mill roller.

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