A method of skin passing hot rolled strip

Abstract

The application relates to the field of steel rolling technology, in particular to a flattening method of hot-rolled strip steel. The tensile strength of the strip steel is 800 MPa, and the method comprises the following steps: flattening the hot-rolled strip steel under the condition of a set speed, and controlling rolling force and bending roller force in the flattening process to obtain hot-rolled strip steel with regular plate shape; wherein the insertion amount of the tension roller after the flattening machine is controlled to reduce the front tension of the flattening. Under the premise of eliminating the wave defect in the flattening process of the 800 MPa grade hot-rolled high-strength wide strip steel, the application effectively reduces the generation of internal residual stress in the flattening process and the degree of steel coil layering after coiling, improves the quality level of the product after flattening, and solves the phenomena of cutting leakage, cutting redundancy and warping in the user processing process.

Description

Technical Field

[0001] This application relates to the field of steel rolling technology, and more particularly to a method for leveling hot-rolled strip steel. Background Technology

[0002] The leveling process involves uncoiling, leveling, rolling, and coiling the steel coil. While this eliminates visible waviness defects, it also introduces new quality problems.

[0003] Due to the high content of alloying elements in their composition, 800MPa grade hot-rolled high-strength steel products are highly sensitive to temperature during the phase transformation process in the cooling stage of hot rolling. However, under current hot continuous rolling equipment technology, it is impossible to guarantee completely uniform temperature, which easily leads to edge waviness defects. Therefore, a hot rolling leveling process is necessary to further eliminate waviness defects in order to meet the user's quality requirements. Summary of the Invention

[0004] This application provides a method for leveling hot-rolled strip steel to solve the technical problem of waviness defects in existing 800MPa grade hot-rolled strip steel.

[0005] In a first aspect, this application provides a method for leveling hot-rolled strip steel, wherein the strip steel has a tensile strength of 800 MPa, the method comprising:

[0006] Under a set speed, the hot-rolled strip is leveled, and the rolling force and bending of the rolls are controlled during the leveling process.

[0007] Force is applied to obtain hot-rolled strip steel with a regular shape; wherein, the insertion amount of the tension roller after the leveling machine is controlled to reduce the pre-tension of the leveling.

[0008] Optionally, the expression for the rolling force during leveling is:

[0009]

[0010] In the formula, F represents the leveling rolling force, B represents the strip width, and F s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

[0011] Optionally, the reference leveling rolling force F s The reference strip thickness H is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.3. The reference strip thickness H is 5000kN to 5500kN.

[0012] Optionally, the expression for the bending roller force during leveling is:

[0013]

[0014] In the formula, Indicates the bending force of the roller. B represents the reference leveling bending roll force, B represents the strip width, and F represents the reference leveling bending roll force. s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

[0015] Optionally, the reference flattening bending roller force The range is -200kN to -150kN, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.3.

[0016] Optionally, the expression for the insertion amount of the tension roller is:

[0017]

[0018] In the formula, I represents the insertion amount of the tension roller, I s denoted by , b represents the thickness influence index of the tension roll insertion, h represents the strip thickness, and H represents the reference strip thickness.

[0019] Optionally, the reference tension roller insertion amount I s The thickness of the reference strip is 30mm to 40mm, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index b of the tension roller insertion amount is -0.45 to -0.55.

[0020] Optionally, the set speed is 100m / min to 150m / min.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] The hot-rolled strip steel leveling method provided in this application optimizes the leveling rolling force, leveling bending roll force, pre-coiling tension roll insertion amount, and leveling process speed during the leveling process. Under the premise of eliminating waviness defects during the leveling process of 800MPa grade hot-rolled high-strength wide strip steel, it effectively reduces the generation of internal residual stress and the degree of steel coil misalignment after coiling during the leveling process, improves the quality level of the product after leveling, and also solves the problems of missed cutting, over-cutting, and warping that occur during the user's processing. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic flowchart illustrating a method for leveling hot-rolled strip steel provided in this application embodiment;

[0026] Figure 2 An image of a hot-rolled strip steel provided in Embodiment 1 of this application;

[0027] Figure 3 The image shown here is of a hot-rolled strip steel that was not used in Embodiment 1 of this application.

[0028] Figure 4 Images showing the post-processing of hot-rolled strip steel, both using and not using the embodiments provided in Example 1 of this application;

[0029] Figure 5 An image of a hot-rolled strip provided in Embodiment 2 of this application;

[0030] Figure 6 The image shown here is of a hot-rolled strip steel that was not used in Embodiment 2 of this application.

[0031] Figure 7 Images showing the post-processing of hot-rolled strip steel, both with and without the adoption of Embodiment 2 provided in this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0034] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0035] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] Firstly, this application provides a method for leveling hot-rolled strip steel; please refer to [link to relevant documentation]. Figure 1 The tensile strength of the strip steel is 800 MPa, and the method includes:

[0037] S1. Under a set speed, the hot-rolled strip is leveled, and the rolling force during the leveling process is controlled.

[0038] The bending roller force is used to obtain hot-rolled strip steel with a regular shape; wherein, the insertion amount of the tension roller after the leveling machine is controlled to reduce the pre-tension of the leveling.

[0039] The leveling process involves uncoiling, leveling rolling, and coiling of the steel coil. While this eliminates visible waviness defects, it also introduces new quality problems. Firstly, high rolling forces are required during leveling rolling to deform the strip and eliminate waviness. However, this increased rolling force leads to the formation of intermediate waviness defects and increased internal residual stress. Intermediate waviness defects require close observation to detect, while internal residual stress cannot be detected through online monitoring, making them easily overlooked and manifesting as warping during user processing. Secondly, the presence of the original camber in the strip or slight deviations in alignment during leveling can cause significant layering faults in the coil, resulting in missed or excessive cuts during user processing, impacting material utilization. All these issues are related to the processing methods used in the leveling process.

[0040] Therefore, it is necessary to address the problems exhibited during the leveling process of 800MPa-grade hot-rolled high-strength steel, and to design a set of key leveling process usage methods that take into account the high strength characteristics of the material, the deformation mechanism of the strip during the leveling process, and the equipment conditions of the hot-rolled leveling production line. This would solve the technical problem of wavy defects in existing 800MPa-grade hot-rolled strip steel, avoid excessive residual stress inside the material and severe layering faults in the steel coil during the leveling process, thereby improving product quality and user satisfaction.

[0041] In this embodiment, by controlling the leveling rolling force, leveling bending roll force, pre-coiling tension roll insertion amount, and leveling process speed during the leveling process, while ensuring the elimination of waviness defects during the leveling process of 800MPa grade hot-rolled high-strength wide strip steel, the generation of internal residual stress during the leveling process and the degree of steel coil misalignment after coiling are effectively reduced, thereby improving the quality level of the product after leveling. It also solves the problems of missed cutting, over-cutting, and warping that occur during the user's processing.

[0042] In the embodiments of this application, the width of the hot-rolled strip can be 900mm to 1800mm, and the thickness of the hot-rolled strip can be 2mm to 7mm.

[0043] In some embodiments, the expression for the rolling force during leveling is:

[0044]

[0045] In the formula, F represents the leveling rolling force, B represents the strip width, and F s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

[0046] Based on the relationship between deformation rate and rolling force of strip with different thicknesses, the relationship between strip width and rolling force, and the optimal rolling force for eliminating waviness in strip with reference thickness, an algorithm for setting rolling force under different thickness conditions is established.

[0047] In some embodiments, the reference leveling rolling force F s The reference strip thickness H is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.3. The reference strip thickness H is 5000kN to 5500kN.

[0048] Set the benchmark leveling rolling force F s The positive effect of a 5000kN to 5500kN range is that it ensures sufficient deformation of the strip through leveling rolling to eliminate waviness without causing significant warping. If the benchmark leveling rolling force F... s Excessive pressure can lead to excessive warping of the strip after leveling; if the benchmark leveling rolling force F is too high, it will cause excessive warping of the strip after leveling. s If the value is too low, the deformation of the strip will be insufficient to eliminate waviness. Specifically, the benchmark leveling rolling force can be 5000kN, 5200kN, 5500kN, etc.

[0049] The advantages of setting a reference strip thickness H of 4mm to 5mm are: this thickness is the median value for this type of strip thickness specification, and using it as a reference can balance the accuracy of the rolling force calculation for both thicker and thinner strip specifications. If the reference strip thickness H is too high, it will cause a significant deviation in the rolling force setting for thinner strip specifications; if the reference strip thickness H is too low, it will cause a significant deviation in the rolling force setting for thicker strip specifications. Specifically, the reference strip thickness H can be 4mm, 4.5mm, 5mm, etc.

[0050] The positive effects of setting the thickness influence index 'a' to 0.2–0.3 are as follows: Given a fixed reference thickness and reference rolling force, the rolling force is adjusted according to the strip thickness to ensure sufficient deformation during leveling rolling to eliminate waviness without causing significant warping. If the thickness influence index 'a' is too high, it may lead to excessive leveling rolling force and significant strip warping; conversely, if the thickness influence index 'a' is too low, it may lead to insufficient leveling rolling force and inadequate strip deformation to eliminate waviness. Specifically, the thickness influence index 'a' can be 0.2, 0.25, 0.3, etc.

[0051] In some embodiments, the expression for the bending roller force during leveling is:

[0052]

[0053] In the formula, Indicates the bending force of the roller. B represents the reference leveling bending roll force, B represents the strip width, and F represents the reference leveling bending roll force. s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

[0054] Based on the relationship between the bending force and the rolling force on the roll gap crown and the rolling force setting algorithm, the above bending force setting algorithm is established.

[0055] In some embodiments, the reference flattening bending roller force The range is -200kN to -150kN, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.3.

[0056] Set the benchmark leveling bending roller force The positive effects of a reference leveling force of -200kN to -150kN include: preventing new waviness defects in the strip during the leveling process; if the reference leveling bending roll force is too high, it will increase the risk of medium waviness in the strip during the leveling process to some extent; if the reference leveling bending roll force is too low, it will increase the risk of edge waviness in the strip during the leveling process to some extent. Specifically, the reference leveling bending roll force... It can be -200kN, -180kN, -150kN, etc.

[0057] In some embodiments, the expression for the tension roller insertion amount is:

[0058]

[0059] In the formula, I represents the insertion amount of the tension roller, I s denoted by , b represents the thickness influence index of the tension roll insertion, h represents the strip thickness, H represents the reference strip thickness, and a represents the thickness influence index.

[0060] Based on the influence of tension roll insertion on tension under different strip thickness conditions, the degree of strip bending deformation, and the optimal value of tension roll insertion under the reference strip thickness conditions, the above tension roll insertion setting algorithm is established.

[0061] In some embodiments, the reference tension roller insertion amount I s The thickness of the reference strip is 30mm to 40mm, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index b of the tension roller insertion amount is -0.45 to -0.55.

[0062] Set the reference tension roller insertion amount I sThe positive effects of a 30mm to 40mm insertion depth are: ensuring sufficient tension from the tension roller without causing plastic bending deformation of the strip; if the insertion depth of the reference tension roller is too high, it may cause plastic bending deformation of the strip to some extent, resulting in new warping defects; if the insertion depth of the reference tension roller is too low, it may cause insufficient tension from the tension roller to adjust the tension before the leveling machine. Specifically, the insertion depth of the reference tension roller can be 30mm, 34mm, 38mm, 40mm, etc.

[0063] The positive effects of setting the thickness influence index b of the tension roller insertion amount to -0.45 to -0.55 are as follows: Given a fixed reference thickness and insertion amount, setting the insertion amount according to the strip thickness satisfies the requirement of ensuring sufficient tension from the tension roller without causing plastic bending deformation of the strip. If the thickness influence index of the tension roller insertion amount is too high, it may lead to plastic bending deformation due to an excessively large insertion amount set according to the strip thickness, given a fixed reference thickness and insertion amount. Conversely, if the thickness influence index of the tension roller insertion amount is too low, it may lead to insufficient tension due to an excessively small insertion amount set according to the strip thickness, given a fixed reference thickness and insertion amount. Specifically, the thickness influence index b of the tension roller insertion amount can be -0.45, -0.50, -0.55, etc.

[0064] In some embodiments, the set speed is 100m / min to 150m / min.

[0065] "Set speed" refers to the leveling speed. Controlling this leveling speed to 100m / min to 150m / min has the following advantages: it ensures accurate coil alignment control without significantly impacting production efficiency. If the leveling speed is too high, it can affect control accuracy and cause steel coil lamination defects; if the leveling speed is too low, it can affect the production efficiency of the leveling line. Specifically, the leveling speed can be 100m / min, 120m / min, 150m / min, etc.

[0066] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0067] Table 1 Leveling process parameter settings

[0068]

[0069] Table 1 shows the setting parameters in the hot-rolled strip leveling method of this application embodiment. The above-mentioned leveling process parameters, based on Embodiment 1 of this application, indicate the coil layer misalignment and warping state during user processing before and after application. Figure 2 , 3 As shown in the figure, the stacking fault phenomenon in the steel coil is significantly improved, such as... Figure 2 As shown; the warping phenomenon during the user's processing is improved, such as Figure 4 (Green) As shown. The above describes the steel coil layer misalignment and warping state during user processing before and after applying the leveling process parameters of Embodiment 2 of this application. Figure 4 , 5 As shown in the figure, the stacking fault phenomenon in the steel coil is significantly improved, such as... Figure 4 As shown; the warping phenomenon during the user's processing is improved, such as Figure 6 (Green) is shown. The method described in the application embodiment was not used. Figure 3 , Figure 5 There is a layering fault in the steel coil. Figure 4 (red), Figure 6 (Red) Warping occurs during the user's processing. Therefore, the flattening method of this application effectively reduces the generation of internal residual stress during the flattening process and the degree of misalignment of the steel coil after winding, improves the quality level of the product after flattening, and solves the problems of missed cutting, over-cutting and warping that occur during the user's processing.

[0070] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for leveling hot-rolled strip steel, characterized in that, The tensile strength of the strip steel is 800 MPa, and the method includes: Under a set speed, hot-rolled strip steel is leveled, and the rolling force and bending roll force during the leveling process are controlled to obtain hot-rolled strip steel with regular shape; wherein, the insertion amount of tension rolls after the leveling machine is controlled to reduce the pre-leveling tension; The expression for the rolling force during the leveling process is: In the formula, F represents the leveling rolling force, B represents the strip width, and F s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

2. The method according to claim 1, characterized in that, The benchmark leveling rolling force F s The reference strip thickness H is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.

3. The reference strip thickness H is 5000kN to 5500kN.

3. The method according to claim 1, characterized in that, The expression for the bending roller force during leveling is: In the formula, Indicates the bending force of the roller. B represents the reference leveling bending roll force, B represents the strip width, and F represents the reference leveling bending roll force. s The value represents the reference leveling rolling force, h represents the strip thickness, H represents the reference strip thickness, a represents the thickness influence index, and A represents the reference strip width of 1500mm.

4. The method according to claim 3, characterized in that, The reference leveling bending roller force The range is -200kN to -150kN, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index a is 0.2 to 0.

3.

5. The method according to claim 1, characterized in that, The expression for the insertion amount of the tension roller is: In the formula, I represents the insertion amount of the tension roller, I s denoted by , b represents the thickness influence index of the tension roll insertion, h represents the strip thickness, H represents the reference strip thickness, and a represents the thickness influence index.

6. The method according to claim 5, characterized in that, The insertion amount of the reference tension roller I s The thickness of the reference strip is 30mm to 40mm, the thickness H of the reference strip is 4mm to 5mm, and the thickness influence index b of the tension roller insertion amount is -0.45 to -0.

55.

7. The method according to claim 1, characterized in that, The set speed is 100m / min to 150m / min.

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