Control method for preventing tinned substrate from flat twill

Abstract

The invention discloses a control method for preventing a tinned substrate from flattening inclined grains, which comprises the following steps of: controlling local inclined grains by utilizing the characteristics of a unit roll system of a temper mill, increasing the inlet tension of the temper mill and the height of an anti-wrinkling roll, and reducing the index of a wavy plate entering the temper mill to ensure that the index of the plate entering the temper mill is less than 15I; the method comprises the following steps of: reducing the difference S between a crease-resistant roller and the levelness, reducing the tension Q1 of a rolling inlet, reducing the height of the crease-resistant roller and reducing the width W of an incoming material by reducing the difference S between the crease-resistant roller and the levelness; and evaluation is carried out according to an inlet strip steel deviation evaluation index N and a whole plate twill occurrence evaluation index E, and it is ensured that N is smaller than 40I and E is smaller than 0.15. By means of increasing the inlet tension of the temper mill, the height of the anti-wrinkling roller and the like, the index of a wave plate entering the temper mill can be reduced, and generation of local twill can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a control method for preventing flat diagonal lines on a tin-plated substrate. Background Art

[0002] When the tin-plated substrate enters the flattening machine at a speed of more than 500m / min on the high-speed continuous annealing line, the strip surface is very likely to produce flat twill defects. This defect forms a certain angle with the rolling direction and occurs in part of the plate width or the entire plate surface, such as Figure 1 shown.

[0003] Regarding the research on flat twill, predecessors have summarized their experience in producing cold-rolled common plates and high-strength steels with a width of more than 0.4 mm, and proposed that the difference in rolling force across the plate width, the difference in rolling force in the longitudinal direction of the steel plate, or the rolling force fluctuation mechanism produces flat twill. CN104226696B believes that flat twill will be produced when the cross-sectional area of ​​the steel does not match the flattening roll gap, and based on the flatness data of the flatness meter after flattening, it is determined whether the wedge shape matches the roll gap by quantifying the single-sided wave coefficient, and a twill occurrence prediction model based on rolling force difference, width, and single-sided wave coefficient is given. The key control point is to control the flat twill by matching the roll gap and reducing the rolling force difference in the plate width direction, and making adjustments based on the plate shape after flattening is a feedback mechanism. CN107511400B introduces a method for controlling the twill defects of the upper and lower surfaces of the whole plate, which is characterized by the difference in the flat elongation of the upper and lower surfaces caused by the lower support transmission flattening machine, which leads to a twill. By adjusting the process parameters such as rolling force, tension, upper wrap angle, roughness, belt speed, etc., the purpose is to reduce the difference in the flat elongation of the upper and lower surfaces. CN113699326B introduces a method for avoiding the surface twill caused by the fluctuation of rolling force during flattening due to uneven performance of steel strips, which is ensured by the stability of composition, annealing process, and flattening process; the purpose is to avoid the defects such as surface twill caused by insufficient recrystallization annealing of steel strips, uneven internal organization and performance, and fluctuation of rolling force during flattening. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a control method for preventing flat twill lines on tin-plated substrates. By increasing the entrance tension of the flattening machine, the height of the anti-wrinkle roller, etc., the wave shape index entering the flattening machine can be reduced to avoid the generation of local twill lines.

[0005] Technical solution: A control method to prevent flat twill on tin-plated substrates. For the control of local twill, the roller system characteristics of the leveling machine are utilized to increase the tension at the leveling machine entrance and the height of the anti-wrinkle roller, thereby reducing the wave shape index entering the leveling machine and ensuring that the shape index entering the leveling machine is less than 15I.

[0006] For the control of the whole plate surface twill: by reducing the difference S between the anti-wrinkle roller and the horizontality, reducing the rolling entrance tension Q1, reducing the anti-wrinkle roller height, reducing the incoming material width W; and evaluating according to the entrance strip deviation evaluation index N and the whole plate twill occurrence evaluation index E, ensure that N < 40I and E < 0.15.

[0007] Furthermore, the specific steps to reduce the wave shape index entering the flattening machine are as follows:

[0008] S1, determine the plate shape index I0 of the incoming wave of the tin-plated substrate;

[0009] I0=ΔLL=(πR2L) 2

[0010] Among them, ΔL / L represents the relative length difference of the waves, L is the wavelength of the original tension-free wave, and R is the amplitude;

[0011] S2, determines the strip tension entering the flatness index I1 of the flatness mill;

[0012] According to Hooke's law, the relationship between the elastic strain rate ε and the leveling machine entrance tension Q1 is as follows:

[0013] ε=Q1 / E

[0014] Therefore, the flatness index I1 with tension entering the flattening machine is:

[0015] I1=I0-Q1 / E

[0016] Where, E is the elastic modulus of the tinplate;

[0017] S3, determine the entrance tension Q1 of the tinplate entering the skin-pass mill;

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

[0019] Q1=Q0e f(α+β)

[0020] Among them, Q0 is the initial tension at the entrance of the leveling machine;

[0021] f is the friction coefficient between the tinplate and the rolling line roller and the anti-wrinkle roller;

[0022] α is the wrap angle between the strip and the anti-wrinkle roller, and its change is determined by the height of the anti-wrinkle roller;

[0023] β is the wrap angle between the strip and the rolling line roller, and its change is determined by the height of the anti-wrinkle roller.

[0024] Furthermore, according to the characteristics of the roller system, after the tinplate enters the leveling mill and contacts the tension meter roller, the rolling line roller and the straightening roller, the measures to increase the leveling mill entrance tension Q1 are as follows: increase the overall entrance tension Q0 through the tension roller before the leveling mill roller system, or by increasing the height of the anti-wrinkle roller, increasing the wrap angle α between the strip and the anti-wrinkle roller, and the wrap angle β between the rolling line roller.

[0025] Furthermore, the inlet strip deviation evaluation index N is the ratio of half of the difference in parallelism between the two tooling rollers within the strip width to the horizontal distance between the two tooling parts, and the expression is as follows:

[0026]

[0027] Where θ is the angle of entering the rolling mill, and θ>10°;

[0028] The expression of the evaluation index E of the whole board twill occurrence is as follows:

[0029]

[0030] Wherein, H is the distance between the anti-wrinkle roller and the working roller.

[0031] Furthermore, measures to reduce the height of the anti-wrinkle roller are as follows: reducing the angle θ entering the rolling mill, or increasing the distance H between the anti-wrinkle roller and the working roller.

[0032] Compared with the prior art, the present invention has the following significant effects:

[0033] 1. The present invention utilizes the roller system characteristics of the leveling machine unit, and reduces the wave plate index entering the leveling machine by increasing the entrance tension of the leveling machine, the height of the anti-wrinkle roller, etc., and can avoid the generation of local twill;

[0034] 2. The present invention reduces the difference between the anti-wrinkle roller and the horizontality, reduces the rolling entrance tension, reduces the angle of entry into the rolling mill, increases the distance between the anti-wrinkle roller and the working roller, and reduces the incoming material width, thereby controlling the generation of twill on the entire plate surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of local twill and whole board twill;

[0036] Figure 2 It is the side view of the leveling rack;

[0037] Figure 3 It is a side view of the wave entering the leveling machine;

[0038] Figure 4 Top view of the steel strip entering the leveling machine. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0040] The thickness of the tin-plated substrate is relatively thin, generally 0.17-0.55mm. When there is no significant abnormal fluctuation in rolling force, twill will also be produced. Twill is divided into local twill and whole plate twill, such as Figure 1 In the flattening process of tinned substrate, the steel plate not only passes through the working roll, but also contacts with the front and rear anti-wrinkle rolls, tension rolls, and rolling line rolls of the flattening mill. The steel plate does not enter the roll horizontally, but passes through the anti-wrinkle roll and the upper roll of the working roll, forming a certain wrap angle before entering the flattening mill roll, such as Figure 2 Shown is a side view of the leveling frame.

[0041] Based on the production conditions, the present invention cold-rolls the tin-plated substrate. Under the condition of no abnormal rolling force difference in a steady state, in order to prevent local twill and whole-plate twill, a control method for preventing flat twill of the tin-plated substrate is proposed. According to the different mechanisms of generation, it is divided into local twill and whole-plate twill, and the control methods are as follows:

[0042] 1. The mechanism of local twill production

[0043] like Figure 3 As shown in the figure, the incoming material has an abnormal shape (wave) before leveling. The length of the steel plate entering the leveling machine is different in the width direction. The long part of the steel plate bulges. When the bulge reaches a certain degree and under the tensile stress in the vertical rolling direction, the plate surface produces microscopic local folds during the leveling process, and diagonal lines are formed after rolling. If there is no tensile stress in the vertical rolling direction, the bulging steel plate will be leveled and eliminated, but the objective conditions such as the horizontality of the tooling rollers, the parallelism installation accuracy and the rolling force difference on both sides lead to the tension difference on both sides, resulting in local diagonal lines.

[0044] The influencing factors of local twill include: the plate shape of raw materials at the entrance, the entrance tension, the plate shape control strategy of the leveler (roller shape, bending roll), and the setting height of the entrance anti-wrinkle roll (strip steel wrap angle). The control measures include: reducing the raw material plate shape index I0, increasing the entrance tension Q, suppressing the rolling control strategy of the raw material plate shape (exit plate shape index I1), ensuring a certain entry angle θ into the rolling mill, and reducing the parallelism difference S between the entrance anti-wrinkle roll and the working roll.

[0045] The raw material flatness index refers to the cross-sectional shape and flatness of the raw material strip, which mainly includes crown and flatness. Crown refers to the thickness variation on the cross section of the strip, while flatness refers to the flatness of the strip. Crown and flatness are two independent but interrelated indicators that jointly affect the quality of the strip and the difficulty of subsequent processing.

[0046] In order to achieve precise control of the tension difference at 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, calibrating the parameters of the tension controller, etc.; secondly, the tension difference can also be affected by changing the process parameters. For example, adjusting the processing speed, temperature and other parameters can indirectly affect the fluidity and tension distribution of the material.

[0047] Generally, the leveling and parallelism accuracy of the roller system of the leveling machine is adjusted to close to zero deviation. When the parallelism accuracy S≤0.05mm / m, the waves enter the leveling machine with approximately two-dimensional deformation. The waves will not fold during leveling, and the leveling elongation can cover the length difference of the waves to eliminate the defects.

[0048] However, effective adjustment of equipment accuracy generally requires major repairs, and daily production often faces poor accuracy. In this embodiment, by utilizing the characteristics of the roller system of the leveling machine, by increasing the entrance tension of the leveling machine, the height of the anti-wrinkle roller, etc., the wave plate index entering the leveling machine is reduced to I1<15I (1 I unit represents a relative length difference of 10 -5 ) To avoid this defect, the specific steps are:

[0049] Step 1, determining the plate shape index I0 of the incoming wave of the tin-plated substrate;

[0050] The plate index I0 represents the relative length difference of the wave ΔL / L. The wavelength L and amplitude R of the original tension-free wave are measured by offline feeler gauges, rulers and other tools. According to metallurgy, the physical relationship between the plate index I0 and the wavelength L and amplitude R is as follows:

[0051] I0=ΔLL=(πR2L) 2 (1)

[0052] Step 2, determine the flatness index I1 of the belt tension entering the flattening machine;

[0053] The yield strength of tinplate is generally greater than 300N / mm 2 , which is higher than the entrance tension. No plastic deformation occurs before entering the leveling machine. In order to reduce the abnormal plate shape index, the entrance tension Q1 of the leveling machine is increased to increase the elastic deformation rate ε. The relative length difference of the waves is eliminated through elastic deformation. The plate shape index I1 with tension entering the leveling machine is equal to the original plate shape index I0 minus the elastic strain rate ε.

[0054] According to Hooke's law, the relationship between elastic strain rate ε and tension Q1 is as follows:

[0055] ε=Q1 / E (2)

[0056] Therefore, the flatness index I1 with tension entering the flattening machine is:

[0057] I1=I0-Q1 / E (3)

[0058] Wherein, E is the elastic modulus of the tinplate, which is measured by tensile test.

[0059] Step 3, determine the entrance tension Q1 of the tinplate entering the leveling machine;

[0060] According to the characteristics of the roller system, after the tinplate enters the leveling mill and contacts the tension meter roller, the rolling line roller, and the straightening roller, the measures to increase the leveling mill entrance tension Q1 are as follows:

[0061] First, the overall entrance tension Q0 can be increased by the tension roller before the leveler roller system, and this tension can be measured by the tension meter roller;

[0062] Secondly, the height of the anti-wrinkle roller can be increased, and the wrap angle α between the strip and the anti-wrinkle roller and the wrap angle β between the rolling line roller can be increased to further improve Q1.

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

[0064] Q1=Q0e f(α+β) (4)

[0065] Where Q0 is the initial tension at the leveling mill entrance, measured by the tension meter roller;

[0066] f is the friction coefficient between the tinplate and the rolling line roller and the anti-wrinkle roller;

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

[0068] β is the wrap angle between the strip and the rolling line roller, and its change is determined by the height of the anti-wrinkle roller; different anti-wrinkle roller heights correspond to the wrap angle data, and the front and rear roller system data of the leveling mill are entered into the CAD for drawing measurement.

[0069] Substituting formulas (1) and (4) into (3), the flatness index I1 of the belt tension entering the flattening machine can be obtained as follows:

[0070]

[0071] Therefore, according to the incoming material wave measurement, the tension of the leveling machine and the anti-wrinkle roller wrap angle process parameters can be adjusted according to formula (5); based on the adjustment experience, the plate shape index I1 before the tinplate strip tension enters the leveling machine is adjusted. When I1 < 15I, the occurrence of local twill defects can be avoided.

[0072] 2. Twill on the entire board

[0073] The mechanism and definition of the whole plate twill: The inclination of the entry tooling roller drives the strip to tilt as a whole into the leveling machine. The leveling process produces micro-folding of the whole plate, resulting in the whole plate surface twill. The reason why the strip tilts into the leveling machine is that the horizontality of the anti-wrinkle roller is too different from that of the rolling roller.

[0074] The probability of occurrence of whole plate twill is evaluated by defining the entry strip deviation assessment index and the whole plate twill occurrence assessment index.

[0075] The entry strip deviation evaluation index N is defined as the ratio of half of the difference in parallelism between the two tooling rolls within the strip width to the horizontal distance between the two tooling parts, such as Figure 4 shown.

[0076] This defect can be controlled by reducing the difference S between the anti-wrinkle roller and the horizontality, reducing the rolling entrance tension Q1, reducing the height of the anti-wrinkle roller (reducing the angle of entry into the rolling mill θ, increasing the distance H between the anti-wrinkle roller and the working roller), and reducing the incoming material width W; the relationship between these process parameter adjustments and the occurrence of defects is as follows:

[0077] The expression of the entry strip deviation evaluation index N is as follows:

[0078]

[0079] Wherein, the applicable range is θ>10°.

[0080] The expression of the evaluation index E of the whole board twill occurrence is as follows:

[0081]

[0082] According to experience, when N<40I and E<0.15, no twill will occur on the whole board.

[0083] The technical solution of the present invention is further described below in conjunction with embodiments.

[0084] The production conditions for flattening the tinned substrate are: working roll diameter 400-440 mm, anti-wrinkle roll diameter 210 mm, strip thickness 0.17-0.55 mm, rolling force 2000-7000 KN, flattening elongation 0.5-2.0%. The example of local twill control parameters is shown in Table 1, and the example of whole plate twill control parameters is shown in Table 2.

[0085] Table 1 Parameters of each case of local twill control

[0086]

[0087] Table 2 Parameters of various cases for controlling the twill on the entire board

[0088]

[0089]

[0090] It can be concluded from Table 1 that, as shown in Case C1, local diagonal lines will occur when the strip enters the leveler under tension with a plate shape I1 of 22.4I-unit. Taking measure 1, without adjusting the plate shape, the local diagonal lines can be eliminated by adjusting the parallelism S of the rolling line roller, anti-wrinkle roller and working roller from 0.16mm / m to 0.05mm / m or below through maintenance, as shown in Case C2. Taking measure 2, by adjusting the plate shape I1 of the strip entering the leveler to <15I-unit through the tension at the leveler entrance and the height of the anti-wrinkle roller, the local diagonal lines can be suppressed.

[0091] It can be concluded from Table 2 that by reducing the difference S between the anti-wrinkle roller and the horizontality, reducing the rolling entrance tension Q1, reducing the height of the anti-wrinkle roller (reducing the angle θ entering the rolling mill, increasing the distance H between the anti-wrinkle roller and the working roller), reducing the incoming material width W, adjusting the entrance strip deviation evaluation index N < 40IU and the whole plate twill occurrence evaluation index E < 0.15, no whole plate twill will occur.

Claims

1. A control method for preventing flat twill on tin-plated substrates, characterized in that: Control of local twill: Utilize the roller system characteristics of the leveling machine, increase the inlet tension of the leveling machine and the height of the anti-wrinkle roller, reduce the wave shape index entering the leveling machine, and ensure that the shape index entering the leveling machine is less than 15I; For the control of the whole plate surface twill: by reducing the difference S between the anti-wrinkle roller and the horizontality, reducing the rolling entrance tension Q1, reducing the anti-wrinkle roller height, reducing the incoming material width W; and evaluating according to the entrance strip deviation evaluation index N and the whole plate twill occurrence evaluation index E, ensure that N < 40I and E < 0.

15.

2. The control method for preventing flat twill on tin-plated substrate according to claim 1, characterized in that: The specific steps to reduce the wave shape index entering the flattening machine are as follows: S1, determine the plate shape index I0 of the incoming wave of the tin-plated substrate; I0=ΔLL=(πR2L) 2 Among them, ΔL / L represents the relative length difference of the waves, L is the wavelength of the original tension-free wave, and R is the amplitude; S2, determines the strip tension entering the flatness index I1 of the flatness mill; According to Hooke's law, the relationship between the elastic strain rate ε and the leveling machine entrance tension Q1 is as follows: ε=Q1 / E Therefore, the flatness index I1 with tension entering the flattening machine is: I1=I0-Q1 / E Where, E is the elastic modulus of the tinplate; S3, determine the entrance tension Q1 of the tinplate entering the skin-pass mill; According to the principles of mechanics and Euler's formula, the tension relationship between the strip and the roller before and after the wrap angle is: Q1=Q0e f(α+β) Among them, Q0 is the initial tension at the entrance of the leveling machine; f is the friction coefficient between the tinplate and the rolling line roller and the anti-wrinkle roller; α is the wrap angle between the strip and the anti-wrinkle roller, and its change is determined by the height of the anti-wrinkle roller; β is the wrap angle between the strip and the rolling line roller, and its change is determined by the height of the anti-wrinkle roller.

3. The control method for preventing flat twill on tin-plated substrate according to claim 2, characterized in that: According to the characteristics of the roller system, after the tinplate enters the leveling mill and contacts the tension meter roller, rolling line roller and straightening roller, the measures to increase the leveling mill entrance tension Q1 are as follows: increase the overall entrance tension Q0 through the tension roller before the leveling mill roller system, or by increasing the height of the anti-wrinkle roller, increasing the wrap angle α between the strip and the anti-wrinkle roller, and the wrap angle β between the rolling line roller.

4. The control method for preventing flat twill on tin-plated substrate according to claim 1, characterized in that: The entry strip deviation evaluation index N is the ratio of half of the difference in parallelism between the two tooling rollers within the strip width to the horizontal distance between the two tooling parts, and is expressed as follows: Where θ is the angle of entering the rolling mill, and θ>10°; The expression of the evaluation index E of the whole board twill occurrence is as follows: Wherein, H is the distance between the anti-wrinkle roller and the working roller.

5. The control method for preventing flat twill on tin-plated substrates according to claim 4, characterized in that: The measures to reduce the height of the anti-wrinkle roller are as follows: reduce the angle θ entering the rolling mill, or increase the distance H between the anti-wrinkle roller and the working roller.

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