Method for reducing interlayer defects of cold-rolled steel coil

Abstract

A method for reducing interlayer defects of a cold-rolled steel coil comprises the following steps of: obtaining the change influence relationship of strip steel with different thicknesses t, the residual length L of the strip steel and the included angle alpha between the strip steel between an uncoiler and an inlet turning roller and the horizontal direction on tension component F through multiple times of test measurement and the change relationship among various values when the steel coil is uncoiled; and the relationship between the control range of the residual length L of the strip steel and the control range of the corresponding uncoiling tension T is obtained, so that the generation of interlayer defects is reduced through segmented control of the uncoiling tension. According to the method, the generation rate of strip steel interlayer defects is reduced, and the production quality and the yield of the strip steel are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of cold-rolled strip steel production, and particularly relates to a method for reducing interlayer defects generated during the uncoiling process of cold-rolled steel coils. Background Art

[0002] During the strip steel production process, the problem of interlayer defects has always been a major technical problem plaguing the quality and yield of cold-rolled products. Especially when the strip steel is uncoiled in a continuous annealing unit, it is extremely easy to occur. When the uncoiling tension remains constant, as the strip steel continues to thin, the horizontal component of the uncoiling tension of the strip steel gradually increases. When the horizontal component is greater than the maximum static friction force between the strip steel layers, the force balance is broken, and relative sliding occurs between the layers of the steel coil. The surface of the relatively sliding strip steel then generates interlayer scratches. Especially when the remaining length of the steel coil is small, it is easier for the strip steel layers to slide, and when the horizontal component of the tension is too large, tensile strain marks are also likely to occur, seriously affecting the yield of the strip steel production line. The traditional method mostly uses reducing the uncoiling tension to control the generation of interlayer scratches, but it is not perfect. Its control force is insufficient, quantitative control is not achieved, and it mostly relies on workers to control according to experience. And manual control often requires long-term accumulation. Moreover, when facing strip steel of different lengths, blindly controlling by experience is extremely likely to generate control errors, which in turn cause other problems such as loose coils or tearing, thus making it impossible to avoid the generation of interlayer defects. The trial-and-error process of manual experience accumulation greatly affects the production cost of strip steel. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for precisely controlling the full-uncoiling tension of strip steel and thereby reducing interlayer defects generated during the uncoiling process of cold-rolled steel coils, so as to solve the technical problems that interlayer defects are easily generated in the existing strip steel production, and the existing control methods mostly rely on manual experience, with insufficient control force and high trial-and-error costs.

[0004] To achieve the above purpose, the specific technical solution of the present invention is as follows:

[0005] 1. A method for reducing interlayer defects of cold-rolled steel coils, the steps of which include:

[0006] S1. Clearly define the main generation mechanism of interlayer defects of strip steel: Interlayer defects are mainly caused by the tension component F of the uncoiling tension T in the horizontal direction increasing to be greater than the interlayer static friction force f of the strip steel as the steel coil gradually thins. Thus, it can be known that controlling the uncoiling tension T can reduce the generation probability of interlayer defects of strip steel;

[0007] S2. According to the mechanism of S1, determine the relationship between the tension component F and the uncoiling tension T during the uncoiling process as: F = Tcosα (where T represents the uncoiling tension of the uncoiler, α represents the angle between the strip steel between the uncoiler and the inlet deflector roll and the horizontal direction, and F represents the tension component);

[0008] S3. Further determine the relationship between the tension component force F and various changing quantities of the steel coil during the uncoiling process according to S2 as: D = 2(tan(α1 - α2)R + d / 2) (where D represents the outer diameter of the steel coil, d represents the inner diameter of the steel coil, α1 represents the angle between the strip steel between the outer diameter D of the steel coil and the inlet turning roll and the horizontal direction, α2 represents the angle between the strip steel between the inner diameter of the steel coil and the inlet turning roll and the horizontal direction, and R represents the distance between the axis of the steel coil and the axis of the turning roll);

[0009] S4. According to the critical value of the critical frictional force f of the steel coil (1), combined with the relationship between the critical frictional force f and the tension component force F in S1, obtain the control range that the tension component force F needs to be controlled;

[0010] S5. Combine the strip steel thickness t to determine the relationship between the outer diameter D of the steel coil, the inner diameter d of the steel coil, and the strip steel length L as:

[0011] L = π(D² - d²) / 4t - π(D - d) / 2 (where L represents the remaining length and t represents the strip steel thickness)

[0012] S6. Combine S2 - S5 to obtain the influence relationship of the remaining length L of the strip steel with different thicknesses t and the angle α between the strip steel between the uncoiler and the inlet turning roll and the horizontal direction on the change of the tension component force F, and then obtain the control range of the remaining length L of the strip steel with different thicknesses and the corresponding control range of the uncoiling tension T, so as to reduce the generation of interlayer defects through segmented control of the uncoiling tension.

[0013] Furthermore, when the strip steel thickness is between 0.5 - 2 mm, the strip steel on the steel coil will have interlayer relative sliding when the α angle is in the range of 15 - 20°, and the maximum critical frictional force f is 1690 daN. At this time, it is necessary to control the uncoiling tension T of the uncoiler to be less than 1750 dN.

[0014] Furthermore, for the strip steel with a thickness of 0.5 mm, when its remaining length is no more than 391 m, start to control the uncoiling tension T of the uncoiler to be no more than 1750 dN.

[0015] Furthermore, for the strip steel with a thickness of 1 mm, when its remaining length is no more than 195 m, start to control the uncoiling tension of the uncoiler.

[0016] Furthermore, for the strip steel with a thickness of 1.5 mm, when its remaining length is no more than 130 m, start to control the uncoiling tension of the uncoiler.

[0017] Furthermore, for the strip steel with a thickness of 2 mm, when its remaining length is no more than 98 m, start to control the uncoiling tension of the uncoiler.

[0018] The method for reducing interlayer defects of cold-rolled steel coils in the present invention realizes precise control of the balance between the uncoiling tension and the interlayer friction force of the strip steel by means of segmented control of the uncoiling tension, improves the stability between the layers of the strip steel during uncoiling, reduces the incidence of interlayer sliding, decreases the generation rate of interlayer defects, improves the production quality of the strip steel without increasing equipment investment, reduces the production waste rate, and expands the economic benefits of strip steel production. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the steps of the present invention;

[0020] Figure 2 It is a schematic diagram when the steel coil of the present invention is uncoiled;

[0021] Explanation of the markings in the figure: 1. Steel coil; 11. Strip steel; 2. Deflection roller. Detailed Embodiments

[0022] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail a method for reducing interlayer defects of cold-rolled steel coils of the present invention with reference to the accompanying drawings.

[0023] As Figure 1-2 shown, the steps of the method for reducing interlayer defects of cold-rolled steel coils in the present invention include:

[0024] S1. The main generation mechanism of interlayer defects of the strip steel 11 is clarified: From the reasons for the generation of interlayer defects during the uncoiling process of the strip steel 11, it is mainly because the tension component force F of the uncoiling tension T of the uncoiler in the horizontal direction increases as the steel coil 1 gradually thins. When it is greater than the interlayer static friction force f of the strip steel 11, interlayer sliding will occur, and then abrasion will be generated. Even if the tension component force F is too large, the steel will be pulled and deformed, resulting in tensile deformation marks. Thus, it can be seen that the force directly acting on the interlayer abrasion of the strip steel 11 during uncoiling is the tension component force F of its uncoiling tension T in the horizontal direction. Controlling the tension component force F can reduce the generation probability of interlayer defects of the strip steel 11;

[0025] S2. According to the mechanism in S1, the relationship between the tension component force F and the uncoiling tension T during the uncoiling process is determined: As Figure 2 shown, the relationship between the strip steel 11, the uncoiling tension T and the tension component force F is:

[0026] F = Tcosα (where T represents the uncoiling tension of the uncoiler, α represents the angle between the strip steel 11 between the uncoiler and the inlet deflection roller 2 and the horizontal direction, and F represents the tension component force);

[0027] S3. According to S2, the relationship between the tension component force F and the various changing quantities of the steel coil 1 during the uncoiling process is further determined. As Figure 2As shown in the figure, the relationships among the outer diameter D, inner diameter d, the distance R between the axes of the steel coil 1, and the angles α1 and α2 are as follows:

[0028] D = 2(tan(α1 - α2)R + d / 2) (where D represents the outer diameter of the steel coil 1, d represents the inner diameter of the steel coil 1, α1 represents the angle between the strip 11 between the outer diameter D of the steel coil 1 and the entrance turning roll 2 and the horizontal direction, α2 represents the angle between the strip 11 between the inner diameter of the steel coil 1 and the entrance turning roll 2 and the horizontal direction, and R represents the distance between the axis of the steel coil 1 and the axis of the turning roll 2);

[0029] S4. Monitor the change of the critical friction force f of the steel coils 1 with different thicknesses through multiple tests, measure the critical values of the change, and then obtain the range of the tension component force F that needs to be controlled according to the relationship between the critical friction force f and the tension component force F in S1;

[0030] S5. Combine the strip thickness t to determine the relationship among the outer diameter D of the steel coil, the inner diameter d of the steel coil, and the strip length L as follows:

[0031] L = π(D² - d²) / 4t - π(D - d) / 2 (where L represents the remaining length and t represents the strip thickness);

[0032] S6. Combine S2 - S5 to obtain the influence relationship of the change of the remaining length L and the angle α between the strip between the uncoiler and the entrance turning roll and the horizontal direction on the change of the tension component force F during the uncoiling process of the strip with different thicknesses t, and then obtain the control range of the remaining length L of the strip with different thicknesses and the corresponding control range of the uncoiling tension T, so as to reduce the generation of interlayer defects through the segmented control of the uncoiling tension.

[0033] In this embodiment, the thickness of the strip is 1.5 mm, the initial tension of the uncoiler is 1800 dN, the distance between the axes of the steel coil 1 and the entrance turning roll 2 is 1900 mm, and the change range of the α angle is 15 - 30°, that is, α1 is at most 30° and α2 is 15°. The control data measured through tests are as shown in the following table. It can be seen that the maximum critical friction force f is 1690 daN, and when the horizontal component force is 1690, the α angle is 20°. When the initial force remains unchanged, the strip 11 on the steel coil 1 will have interlayer relative sliding within the range of the α angle from 15° to 20°, resulting in interlayer abrasion. Therefore, after it is less than 20°, the remaining length of the strip 11 is 269 m, and the uncoiling tension needs to be controlled within the range of less than 1750 dN to avoid interlayer abrasion.

[0034] The specific control data table is as follows:

[0035]

[0036]

[0037] Furthermore, the strip steel 11 with different thicknesses was tested, and the specific control range data of the strip steel remaining length L and the unwinding tension T corresponding to the critical friction force f were obtained as follows:

[0038]

[0039]

[0040] As can be seen from the above, for the uncoiling of the strip steel 11 with a thickness of 0.5-2 mm, when the remaining length of the strip steel 11 makes its angle with the horizontal direction no more than 20°, its critical friction force f is not sufficient to balance the demand of the original tension component F, and the tension of the uncoiling machine needs to be optimally controlled within the range of less than 1750dN.

[0041] The method for reducing the interlayer scratches of cold-rolled steel coils of the present invention, without increasing the equipment investment, is based on the generation mechanism of interlayer scratches and controls the unwinding tension in sections, thereby accurately controlling the balance between the horizontal component force and the critical friction force between the layers of the steel strip 11, thereby reducing the generation of relative sliding between the layers of the steel strip 11 when the steel strip 11 is unwinded, improving the curling stability between the layers, greatly reducing the generation rate of defects between the layers of the steel strip 11, improving its production quality and yield rate, reducing its waste rate, thereby reducing its production cost, and improving the economic benefits of the production of the steel strip 11.

[0042] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for reducing interlayer defects of a cold-rolled steel coil 1, characterized in that: The steps include: S1. The main mechanism of interlayer defects of the steel strip (11) is clarified: interlayer defects are mainly caused by the fact that the tension component F of the unwinding tension T in the horizontal direction increases to be greater than the interlayer static friction f of the steel strip (11) as the steel coil (1) gradually becomes thinner. It can be seen that controlling the unwinding tension T can reduce the probability of interlayer defects of the steel strip (11); S2. According to the mechanism of S1, determine the relationship between the tension component F and the unwinding tension T during the unwinding process; S3, further determining the relationship between the tension component F and the values ​​of the change of the steel coil (1) during the uncoiling process according to S2; S4, according to the critical value of the critical friction force f of the steel coil (1), combined with the relationship between the critical friction force f and the tension component force F in S1, the control range of the tension component force F to be controlled is obtained; S5. Determine the relationship between the outer diameter D of the steel coil (1), the inner diameter d of the steel coil (1) and the length L of the steel coil (11) in combination with the thickness t of the steel strip (11); S6. Combining S2-S5, the influence relationship between the remaining length L of the strip (11) with different thicknesses t and the angle α between the strip (11) and the horizontal direction between the uncoiler and the entrance steering roller (2) on the tension component F is obtained, and then the control range of the remaining length L of the strip (11) with different thicknesses and the corresponding control range of the uncoiling tension T are obtained, so as to reduce the generation of interlayer defects through segmented control of the uncoiling tension.

2. The method for reducing interlayer defects of a cold-rolled steel coil 1 according to claim 1, characterized in that: When the thickness of the steel strip (11) is between 0.5 and 2 mm, relative sliding between layers will occur when the steel strip (11) on the steel coil (1) is within the range of 15-20°, and the critical friction force f is at most 1690 daN. At this time, it is necessary to control the uncoiling tension T of the uncoiling machine to be less than 1750 dN.

3. The method for reducing interlayer defects of a cold-rolled steel coil 1 according to claim 2, characterized in that: The 0.5 mm thick steel strip (11) starts to control the uncoiling tension T of the uncoiling machine to be no more than 1750 dN when the remaining length of the steel strip (11) is no more than 391 m.

4. The method for reducing interlayer defects of a cold-rolled steel coil 1 according to claim 2, characterized in that: The uncoiling tension of the uncoiling machine begins to be controlled when the remaining length of the 1 mm thick steel strip (11) is no more than 195 m.

5. The method for reducing interlayer defects of a cold-rolled steel coil 1 according to claim 2, characterized in that: The uncoiling tension of the uncoiling machine begins to be controlled when the remaining length of the 1.5 mm thick steel strip (11) is no more than 130 m.

6. The method for reducing interlayer defects of a cold-rolled steel coil 1 according to claim 2, characterized in that: The uncoiling tension of the uncoiling machine begins to be controlled when the remaining length of the 2 mm thick steel strip (11) is no more than 98 m.

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