A control method for reducing the warpage of hot-rolled steel strip

Abstract

The application discloses a control method for reducing the warping degree of hot-rolled strip steel, which comprises the following steps: step one, formula calculation; step two, plate convexity setting; step three, model calculation; step four, coiling degree adjustment; step five, convexity adjustment; step six, water spraying proportion adjustment; and step seven, flatness change. The application improves the phenomenon that the unwinding warping degree of the strip steel is too large at room temperature by reducing the coiling convexity, standardizing the water spraying proportion of the upper and lower surfaces and controlling the intermediate wave, simultaneously avoids the serious warping defects in the first half of the unwinding of the steel coil, eliminates the occurrence of the serious wrinkle defects on the surface after flattening, solves the problem that the head and tail welding is difficult when the cold-rolled material is continuously rolled on the pickling and rolling unit of the subsequent cold rolling mill, influences the rolling rhythm, and improves the quality of the products subjected to working operation by using the strip steel.

Description

A method for reducing the warpage of hot-rolled strip steel Technical Field

[0001] This invention relates to the field of hot-rolled strip steel production technology, specifically to a method for controlling the warpage of hot-rolled strip steel. Background Technology

[0002] The shape control of hot-rolled strip steel mainly involves controlling the strip's convexity. This is achieved by controlling the metal flow through the deformation of the strip during rolling. The flatness and convexity indicators are fed back by the multi-functional instrument at the finishing mill exit. The released steel coils are judged by curves to determine whether they meet the standard requirements. However, after the steel coils are uncoiled by the users, serious shape defects such as warping, single-sided wavy, double-sided wavy, and middle wavy appear, which seriously affect the users' use. Therefore, a control method to reduce the warping of hot-rolled strip steel is needed to adjust the degree of transverse warping during the production operation.

[0003] Currently, there is an unavoidable problem of warping defects occurring in the first half of the uncoiling process when processing hot-rolled steel. This makes it difficult to eliminate wrinkles on the surface after leveling. Furthermore, this defect makes it difficult to weld the head and tail ends when using cold-rolled material in subsequent pickling and rolling mills, affecting the rolling rhythm and reducing the quality of processing strip steel. Therefore, it is necessary to invent a method to control the warping of hot-rolled strip steel. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the warpage of hot-rolled strip steel, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling the warpage of hot-rolled strip steel, comprising: step one, formula calculation; step two, plate crown setting; step three, model calculation; step four, coiling degree adjustment; step five, crown adjustment; step six, water spray ratio adjustment; and step seven, changing the flatness.

[0006] In step one above, to quantitatively represent the degree of transverse warpage of the strip and facilitate transverse comparison of strips with thicknesses of 2.0-5.0 mm, a concept of warpage, denoted by the symbol ζ, is proposed, and its expression is as follows: The value represents the degree of warpage. δ, B, and H are the bending deflection, strip width, and strip thickness of the strip in the width direction, respectively. By substituting the data collected from the steel strip into the formula, it is easier to calculate the degree of transverse warpage of the steel in the subsequent calculation, thus ensuring the scientific rigor of the subsequent calculation of the degree of transverse warpage of the steel.

[0007] In step two above, as the winding length increases, the winding diameter increases, and the cumulative winding warpage also increases. To avoid this, the crown setting is changed twice during winding to achieve step crown control of the entire coil of steel. However, the adjustment range cannot be too large, and the total reduction should be within 40% of the initial target crown to prevent poor straightness due to excessive adjustment, which would affect the subsequent levelness of the steel strip.

[0008] In step three above, the target board convexity in the PDI data is sent to the secondary model for calculation. The secondary model then uses the PCFC calculation result based on the target convexity estimation model and calculates the expected target convexity based on equipment status, product specifications, production cycle, and other conditions. Using the secondary model for calculation ensures the scientific reliability of the calculation results.

[0009] In step four above, the predetermined target crown is automatically controlled on site by means of rolling force, water spraying on the frame, and bending roll force. When the winding reaches a certain distance, about 1 / 3 of the position is occupied, the target crown is changed based on the original setting and reduced by a certain percentage.

[0010] In step five above, when the coil is wound to 2 / 3 position, the target convexity is changed again based on the original setting and reduced by a certain percentage. This avoids metal fatigue of the steel strip caused by excessive coiling value and facilitates the reduction of steel strip warping in the future.

[0011] In step six above, for strip steel with a thickness of 2.0-5.0mm, under the same bottom-to-top water ratio, the temperature gradient in the thickness direction will increase with the increase of thickness, and the warping height will also increase. Therefore, in actual production, it is necessary to determine the cooling water volume and bottom-to-top water ratio according to the thickness of the strip steel. By strictly controlling the amount of cooling water used, it can be ensured that the strip steel is cooled down slowly in the subsequent process, and the deformation of the strip steel after cooling can be avoided.

[0012] In step seven above, the target flatness of the strip after rolling is changed in the rolling settings to make the strip have a slight waviness tendency, which can suppress the influence of uneven cooling. Although the strip has a certain amount of waviness after rolling, it will return to flatness when it reaches room temperature.

[0013] Preferably, step six changes the winding state by adjusting the plate convexity online to prevent excessive coil convexity. At the same time, by strictly controlling the water spray ratio, stress deformation of the steel coil can be avoided during the subsequent cooling process, thus ensuring a stable cooling effect for the steel coil.

[0014] Preferably, step seven improves the excessive warpage of strip steel uncoiling at room temperature by reducing coil convexity, standardizing the water spray ratio of the upper and lower surfaces, and controlling the intermediate waves. This solves the problem of poor strip shape after uncoiling, reduces the proportion of flatness repairs, saves costs, reduces the objection rate, and ensures the warpage of subsequent strip steel uncoiling.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention discloses a method for controlling the warpage of hot-rolled strip steel. By reducing coil convexity, standardizing the water spray ratio on the upper and lower surfaces, and controlling the intermediate wave, it improves the excessive warpage of strip steel at room temperature, solves the problem of poor strip shape after uncoiling, reduces the proportion of force leveling repairs, saves costs for subsequent strip processing, and improves the economic efficiency of production using strip steel. It also avoids severe warpage defects in the first half of the uncoiling process and eliminates severe wrinkle defects on the surface after leveling. This solves the problem of difficulty in welding the head and tail ends when using cold-rolled material in subsequent pickling and rolling mills, which affects the rolling rhythm. Furthermore, it avoids the problem of transverse crease defects easily appearing in the middle part of the upper surface when used for commercial applications, which seriously affects the appearance quality and improves the quality of products processed from strip steel. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the plate crown data table of the control method for reducing the warpage of hot-rolled strip steel according to the present invention, in Example 1.

[0018] Figure 2 is a schematic diagram of the water spray ratio data table of the control method for reducing the warpage of hot-rolled strip steel according to the present invention, in Example 1;

[0019] Figure 3 is a schematic diagram of Embodiment 1 of the calculation formula of the control method for reducing the warpage of hot-rolled strip steel according to the present invention;

[0020] Figure 4 is a schematic diagram of the water spraying method of the control method for reducing the warpage of hot-rolled strip steel according to the present invention;

[0021] Figure 5 is a schematic diagram of Example 1 of the two-level model calculation flowchart of the control method for reducing the warpage of hot-rolled strip steel according to the present invention;

[0022] Figure 6 is a schematic diagram of Embodiment 1 of the two-level model calculation flowchart of the control method for reducing the warpage of hot-rolled strip steel according to the present invention;

[0023] Figure 7 is a schematic diagram of the construction process of the method for controlling the warpage of hot-rolled strip steel according to the present invention, which is a schematic diagram of Embodiment 2.

[0024] Figure 8 is a schematic diagram of the construction process of the method for controlling the warpage of hot-rolled strip steel according to the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Please refer to Figures 1, 2, 3, 4, 5, 6, 7, and 8 for an embodiment provided by the present invention:

[0029] Example 1

[0030] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling the warpage of hot-rolled strip steel, comprising: step one, formula calculation; step two, plate crown setting; step three, model calculation; step four, coiling degree adjustment; step five, crown adjustment; step six, water spray ratio adjustment; and step seven, changing the flatness.

[0031] Please refer to Figures 1, 2, 3, 4, 5, and 6.

[0032] In Figure 3, to quantitatively represent the degree of transverse warpage of the strip and facilitate transverse comparison of strips with thicknesses ranging from 2.0 to 5.0 mm, a concept of warpage, denoted by the symbol ζ, is proposed, and its expression is as follows: The values ​​represent warpage, where δ, B, and H represent the bending deflection of the strip in the width direction, the strip width, and the strip thickness, respectively.

[0033] As the winding length increases, the winding diameter increases, and the cumulative winding warpage also increases. To avoid this, the crown setting is changed twice during winding to achieve step crown control of the entire coil of steel. However, the adjustment range cannot be too large, and the total reduction should be within 40% of the initial target crown to prevent poor straightness due to excessive adjustment. Straightness refers to the measurement index of the degree of conformity between the rail and the horizontal plane.

[0034] In Figures 5 and 6, the target board convexity in the PDI data is sent to the secondary model for calculation. Then, the secondary model calculates the expected target convexity based on the PCFC calculation result of the target convexity estimation model, and calculates the expected target convexity based on the equipment status, product specifications, and production cycle.

[0035] On-site, the predetermined target crown is automatically controlled by means of rolling force, water spraying on the stand, and bending roll force. When the winding reaches a certain distance, about 1 / 3 of the position is occupied, the target crown is changed based on the original setting and reduced by a certain percentage.

[0036] In Figure 1, when the coil is wound to 2 / 3 position, the target convexity is changed again based on the original setting and reduced by a certain percentage. This avoids metal fatigue of the steel strip caused by excessive coiling value and facilitates the reduction of steel strip warping in the future. The winding tension is set to the lower limit control of this specification.

[0037] To avoid defects such as loose coiling or misalignment;

[0038] In Figure 2, under the same bottom-to-top water ratio, the temperature gradient in the thickness direction increases with the increase of thickness, and the warping height also increases accordingly. Therefore, in actual production, it is necessary to determine the cooling water volume and bottom-to-top water ratio according to the thickness of the strip. Different water spray ratios are summarized for different thickness specifications of Q235B. The water spray ratio of laminar flow cooling will be appropriately adjusted according to the original situation. The adjustment range will be appropriately adjusted according to the actual coiling state of different specifications and steel grades to avoid the occurrence of "ship-shaped" plates.

[0039] In Figure 4, the rolling settings are adjusted to change the target flatness of the strip after rolling, giving it a slight waviness tendency. This suppresses the effects of uneven cooling, ensuring that although the strip has some waviness after rolling, it will return to flatness at room temperature. Therefore, the slight waviness rolling strategy is applied in actual production. For thin strips less than 3mm thick, taking Q235B as an example, the slight waviness setting values ​​(target flatness values) are: 15I for 2.0~2.5mm; 12I for 2.5~2.75mm; and 6I for 2.76~3.0mm. This strategy has shown good results in actual control.

[0040] Example 2:

[0041] Please refer to Figures 7 and 8.

[0042] By adjusting the plate crown online, the winding state can be changed to prevent excessive crowning. At the same time, by strictly controlling the water spray ratio, stress deformation of the steel coil can be avoided during the subsequent cooling process, thus ensuring a stable cooling effect for the steel coil.

[0043] By reducing the coil crown, standardizing the water spray ratio on the upper and lower surfaces, and controlling the intermediate waves, the excessive warpage of strip steel at room temperature was improved. This solved the problem of poor strip shape after uncoiling for users, reduced the proportion of flattening rework, saved costs, reduced the objection rate, and ensured the warpage of subsequent strip steel uncoiling.

[0044] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0045] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications and equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for controlling the warpage of hot-rolled strip steel, comprising: Step 1, formula calculation; Step 2, strip crown setting; Step 3, model calculation; Step 4, coiling degree adjustment; Step 5, crown adjustment; Step 6, water spray ratio adjustment; Step 7, changing flatness; characterized in that: In step one above, to quantitatively represent the degree of transverse warpage of the strip and facilitate transverse comparison of strips with thicknesses of 2.0-5.0 mm, a concept of warpage, denoted by the symbol ζ, is proposed, and its expression is: The warpage is represented by δ, B, and H, which are the bending deflection of the strip in the width direction, the strip width, and the strip thickness, respectively. In step two above, as the winding length increases, the winding diameter increases, and the cumulative winding warpage also increases. To avoid this, the crown setting is changed twice during winding to achieve step crown control of the entire coil. However, the adjustment range should not be too large, and the total reduction should be within 40% of the initial target crown to prevent poor straightness due to excessive adjustment. In step three above, the target board convexity in the PDI data is sent to the secondary model for calculation. Then, the secondary model calculates the expected target convexity based on the PCFC calculation result of the target convexity estimation model, and calculates the expected target convexity based on the equipment status, product specifications, production cycle and other conditions. In step four above, the predetermined target crown is automatically controlled on site by means of rolling force, water spraying on the frame, and bending roll force. When the winding reaches a certain distance and occupies 1 / 3 of the position, the target crown is changed based on the original setting, reducing the set proportion. In step five above, when the coil is wound to 2 / 3 position, the target convexity is changed again based on the original setting, and the set ratio is reduced again. This avoids metal fatigue of the steel strip caused by excessive winding value, and provides convenience for reducing the degree of steel strip warping in the future. In step six above, for strip steel with a thickness of 2.0-5.0mm, under the same bottom-to-top water ratio, the temperature gradient in the thickness direction increases with the increase of thickness, and the warping height also increases accordingly. Therefore, in actual production, it is necessary to determine the cooling water volume and bottom-to-top water ratio based on the strip steel thickness. In step seven above, in the rolling settings, the target straightness of the strip steel after rolling is changed to make the strip steel have a slight waviness tendency, which can suppress the influence of uneven cooling. Although the strip steel has a certain amount of waviness after rolling, it is easy for the strip steel to return to straightness when it reaches room temperature.

2. The method for controlling the warpage of hot-rolled strip steel according to claim 1, characterized in that: By adjusting the crown of the 2.0-5.0mm thick plate online, the winding state can be changed to prevent excessive crowning. At the same time, by strictly controlling the water spray ratio, stress deformation of the steel coil can be avoided during the subsequent cooling process, thus ensuring the stable cooling effect of the steel coil.

3. The method for controlling the warpage of hot-rolled strip steel according to claim 1, characterized in that: By reducing the thickness of the coil crown by 2.0-5.0mm, standardizing the water spray ratio on the upper and lower surfaces, and controlling the intermediate waves, the problem of excessive warpage of strip steel at room temperature has been improved. This has solved the problem of poor strip shape after uncoiling for users, reduced the proportion of flatness rework, saved costs, reduced the objection rate, and ensured the warpage of subsequent strip steel uncoiling.

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