A method for improving the flared edge shape defect of hot-rolled thin strip

Abstract

This invention relates to the field of hot strip milling technology, specifically disclosing a method for improving the flared edge shape defect of hot-rolled thin strip, comprising the following steps: Step 1, tracking the hot-rolled thin strip production process to determine the location of the flared edge shape defect; Step 2, analyzing the wear state of the finishing mill work rolls and adjusting the work roll shifting interval according to the wear state; Step 3, analyzing the deviation of the strip's finishing mill exit centerline and optimizing the strip deviation direction; Step 4, tracking the optimized flared edge condition of the hot-rolled thin strip and further optimizing the work roll shifting interval and strip deviation. This invention, by optimizing the work roll shifting interval and adjusting the strip head deviation direction, avoids strip deviation during the strip threading process that causes the strip edge to exceed the roll wear step, resulting in a flared edge shape defect. This is beneficial for improving the continuity and stability of hot rolling, extending the planned total number of strips, reducing the rework rate of flared edge shape defects and flattening losses, and improving the overall yield of hot-rolled thin strip.

Description

Technical Field

[0001] This invention belongs to the field of hot strip rolling technology, specifically relating to a method for improving the flared edge shape defect of hot-rolled thin strip. Background Technology

[0002] Strip shape is a crucial quality indicator for hot-rolled strip steel products. The thinner the strip, the more difficult it is to control strip shape defects, and the more severe these defects become, significantly impacting hot-rolling yield and downstream production stability. Strip shape defects in hot-rolled strip steel generally refer to flatness defects. During hot rolling, varying thickness reductions at different locations along the width direction cause uneven elongation along the length direction, resulting in internal stresses exceeding the strip's yield strength and ultimately forming visible waviness defects.

[0003] Common strip shape defects include central waviness, single-sided waviness, double-sided waviness, and quarter-sided waviness, which can be improved by reducing bending roll force, adjusting mill roll gap inclination, increasing bending roll force, and optimizing work roll shape, respectively. However, there is currently no detailed research or specific improvement method for the lobed edge shape defect of hot-rolled thin strip.

[0004] Wavy edge defects refer to localized plate shape defects that appear at the edge of hot-rolled thin strips. Their wavy appearance is characterized by large wave height, narrow wave width, and short wave period.

[0005] Once the lobed edge shape defect appears during the rolling process, conventional measures such as bending rolls, shifting rolls, and roll gap leveling cannot improve it. The coil must be reworked and removed during the leveling process, which seriously affects the rework rate and overall yield of hot-rolled strip. Replacing the finishing work rolls in advance can improve the lobed edge shape defect of hot-rolled strip, but this operation not only affects the continuity and stability of hot rolling, but also significantly increases the workload of roll grinding in the grinding workshop. Therefore, this application proposes a method for improving the lobed edge shape defect of hot-rolled thin strip. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the flared edge shape defect of hot-rolled thin strip, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the flared edge shape defect of hot-rolled thin strip, comprising the following steps:

[0008] Step 1: Track the hot-rolled thin strip production process to determine the location of the lobed edge shape defect;

[0009] Step 2: Analyze the wear condition of the finishing mill work rolls and adjust the roll shifting range according to the wear condition;

[0010] Step 3: Analyze the deviation of the strip steel exit centerline and optimize the deviation direction;

[0011] Step 4: Track the condition of the rolled edge of the hot-rolled thin strip after optimization, and further optimize the work roll shifting interval and strip deviation.

[0012] Preferably, the method for determining the location of defects in the leaf-shaped plate mentioned in step one involves recording, viewing, analyzing, and comparing multiple sets of cold exit plate shape diagrams of hot-rolled thin strip layers.

[0013] Preferably, the location of the leaf-shaped defect mentioned in step one is the operating side of the strip.

[0014] Preferably, the method for analyzing the wear state of the finishing mill work rolls mentioned in step two is as follows: the finishing mill work rolls on the F7 stand have a CVC roll shape. The upper and lower work rolls in the F7 stand are removed from the F7 stand respectively. Then, the roll shape curves of the upper and lower work rolls are plotted, and the roll shape curves of the upper and lower work rolls after the work rolls on the F7 stand are compared with those of the lower work rolls after the work rolls on the F7 stand are removed.

[0015] Preferably, the operation steps for adjusting the work roll shifting range mentioned in step two are as follows: in the early and middle stages of finishing milling, the negative shifting value of the work roll at the F7 stand is limited to within -100mm, thereby limiting the degree of increased load on the leaf edge caused by positive shifting of the work roll.

[0016] Preferably, the method for analyzing the deviation of the center line at the exit of the strip finishing mill mentioned in step three is as follows: record the data of the position of the center line at the exit of the finishing mill and draw the deviation curve of the center line at the exit of the finishing mill.

[0017] Preferably, the method for optimizing the strip deviation direction mentioned in step three is to reduce the roll gap on the working roll operating side of the F5 frame and the F6 frame, limit the area of ​​the strip operating side, and place the strip operating side inside the wear step of the working roll in the F7 frame.

[0018] Preferably, the method for tracking the condition of the flared edge of the hot-rolled thin strip mentioned in step four is as follows: record the number of flared edge shape defects requiring repair before and after the improvement, calculate the corresponding ratio, and compare the ratios.

[0019] Preferably, the method for further optimizing the work roll slippage range and strip deviation mentioned in step four is as follows: limit the slippage range, adjust the frame leveling value, restrict the strip head, and prevent the strip head from entering the F7 frame and deviating to the operating side.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention optimizes the working roll misalignment interval and adjusts the strip head deviation direction to avoid strip deviation during the strip threading process, which causes the strip edge to exceed the roll wear step and result in strip flared edge defects. This is beneficial to improving the continuity and stability of hot rolling, extending the planned total number of blocks, reducing the rework rate of flared edge defects and flattening losses, and improving the overall yield of hot-rolled thin strip. Attached Figure Description

[0022] Figure 1 This is a cloud diagram of the cold exit plate shape defect of the hot-rolled thin strip in this invention.

[0023] Figure 2 This is the morphology of the leaf-shaped edge of the hot-rolled thin strip under the surface inspection camera in this invention.

[0024] Figure 3 This is a diagram showing the wear condition of the work rolls on the finishing mill F7 stand in this invention.

[0025] Figure 4 This shows the wear condition of the work rolls under the finishing mill F7 stand in this invention.

[0026] Figure 5 This is the deviation curve of the center line of the finishing mill exit in this invention.

[0027] Figure 6 This is to optimize the repair rate of defects in the leaf edge plate shape before and after the present invention.

[0028] Figure 7 This is a flowchart of the method for improving the flared edge shape defect of hot-rolled thin strip in this invention. Detailed Implementation

[0029] 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.

[0030] Reference Figure 7 A method for improving the flared edge shape defect of hot-rolled thin strip includes the following steps:

[0031] Step 1: Track the hot-rolled thin strip production process to determine the location of the flared edge shape defect. The flared edge of the strip is a shape defect at the edge of the strip, which can appear on either side of the strip. Determine whether the flared edge defect occurs on the operating side or the drive side of the strip during production, and analyze and compare the frequency of flared edge defects on the operating and drive sides. The method mentioned in Step 1 for determining the location of the flared edge shape defect involves recording, viewing, analyzing, and comparing multiple sets of cold exit shape diagrams of the hot-rolled thin strip. After analyzing multiple sets of data, it is confirmed that the flared edge shape defect occurs on the operating side of the strip.

[0032] like Figure 1 The image shown is a cold exit plate shape diagram of several consecutive hot-rolled thin strip layers at the end of the planned phase. (From...) Figure 1 It is evident that hot-rolled thin strip shape control is challenging. All five coils of strip exhibited quarter-wave defects on the drive side after cooling. Coils 3 and 4 showed flared edges, with coil 3 exhibiting a more severe flared edge. The flared edge defects in both coils were located on the operating side of the strip. Production data from the past two months indicates that, due to variations in the rolling conditions of each coil, flared edge defects generally do not occur continuously. However, once a flared edge defect appears, it is always located on the operating side. The morphology of the flared edge defect captured by the inspection camera is as follows. Figure 2 As shown, the area with alternating light and dark areas is a wavy area resembling the edge of a lotus leaf.

[0033] Step 2: Analyze the wear condition of the finishing work rolls and adjust the roll shifting range based on the wear condition. During the production of hot-rolled thin strip, the finishing rolling load is high, leading to severe wear of the work rolls. This wear further affects the shape control of the hot-rolled thin strip, resulting in most flared edge defects appearing in the middle and later stages of the finishing rolling process. Therefore, for hot-rolled thin strip projects with flared edge shape defects, it is necessary to review the wear curves of the work rolls after they leave the mill to determine the wear condition of the work rolls and optimize the roll shifting range based on the wear status.

[0034] The method for analyzing the wear state of the finishing mill work rolls is as follows: The finishing mill work rolls on the F7 stand have a CVC roll shape. The upper and lower work rolls in the F7 stand are removed from the F7 stand respectively. Then, the roll shape curves of the upper and lower work rolls are plotted. The roll shape curves of the upper work rolls after they are removed from the F7 stand and the roll shape curves of the lower work rolls after they are removed from the F7 stand are compared to confirm the wear state of the upper and lower work rolls.

[0035] The steps for adjusting the work roll shifting range are as follows: In the early and middle stages of finishing milling, the negative shifting value of the work roll of F7 stand is limited to within -100mm to limit the degree of aggravation of the camber edge caused by positive shifting of the work roll, leaving enough space for negative shifting of the work roll in the later stage of finishing milling. Throughout the entire production process, the work rolls gradually shift negatively to avoid aggravating the camber edge defect due to positive shifting.

[0036] The wear curves of the work rolls after the rolling mill runs exhibiting wavy edges are checked retrospectively. Figure 3 The roll profile curve of the work roll after it leaves the F7 frame. Figure 4 The image shows the roll profile after the work rolls on the F7 stand have exited the mill. The finishing work rolls on the F7 stand have a CVC roll profile. Both upper rolls used in the wide and thin strip steel projects exhibit severe localized wear after operation. Figure 3 As shown. Localized wear also exists on the drive side of the lower work roll, but the extent of this wear is less than on the operating side of the upper work roll, such as... Figure 4 As shown, during the hot rolling production of wide and thin strip steel, there is severe localized wear on the operating side of the upper roll. When the work roll moves forward, the wear step moves towards the strip steel. When the edge of the strip steel exceeds the wear step, it is more likely to cause a flared edge plate shape defect.

[0037] Step 3: Analyze the deviation of the strip steel centerline at the finishing mill exit and optimize the deviation direction. The lobed edge shape defect appears in the middle to late stages of a single hot-rolled thin strip rolling plan. For rolling plans with lobed edge shape defects, analyze the deviation of the centerline at the finishing mill exit for coils with and without lobed edge defects. Especially for several consecutive coils where lobed edge defects and non-lobed edge defects appear alternately, analyze the deviation of the strip steel centerline at the finishing mill exit for both types of coils, study the impact of the deviation on the lobed edge shape defect, and optimize the deviation direction.

[0038] The method for analyzing the deviation of the center line at the exit of the strip finishing mill is as follows: record the data of the position of the center line at the exit of the finishing mill, and draw the deviation curve of the center line at the exit of the finishing mill. In the drawn figure, the positive value of the vertical axis represents the operating side of the deviation at the exit of the strip finishing mill, and the negative value represents the transmission side of the deviation at the exit of the strip finishing mill.

[0039] Figure 5 For steel coils exhibiting flared edge defects, the centerline of the finishing mill exit deviates, which is related to... Figure 1 The five consecutive coils of strip steel are respectively represented on the vertical axis. Positive values ​​on the vertical axis indicate deviation on the operating side of the strip steel finishing mill exit, while negative values ​​indicate deviation on the transmission side of the strip steel finishing mill exit. Figure 5It is known that the center lines of the finishing mill exits of coils 1, 2, and 5 are all deviated by more than 20mm towards the drive side at the strip head. The center lines of the finishing mill exits of coils 3 and 4 are less deviated towards the drive side at the strip head. In particular, the center line of coil 3 has a deviated area towards the operating side at the strip head, where the operating side has the most severe camber edge. Therefore, when a camber edge defect appears on the operating side of the strip, the finishing mill leveling value must be adjusted to prevent the strip from deviating from the operating side. The method to optimize the strip deviation direction is as follows: adjust the leveling values ​​of stands F5 and F6 to reduce the roll gap between the working rolls on the operating side of stands F5 and F6, limiting the strip deviation on the operating side and ensuring that the operating side of the strip is inside the wear step of the working rolls in stand F7. This limits the deviation of the strip before it enters stand F7, preventing the operating side from exceeding the wear step of the working rolls in stand F7 and causing severe camber edge defects on the operating side.

[0040] Step 4: Track and optimize the edge curling of hot-rolled thin strip, and further optimize the work roll shifting range and strip deviation. During hot-rolled thin strip production, optimize the work roll shifting range and strip deviation direction of the finishing mill stand, track the edge curling defects of the hot-rolled thin strip after adjustment, and further optimize the roll shifting and strip deviation control based on the edge curling defects of the hot-rolled thin strip after adjustment.

[0041] The method for tracking the condition of the flared edge of the hot-rolled thin strip after optimization is as follows: record and compare the number of flared edge shape defects that need to be repaired before and after the improvement, calculate the corresponding ratio, and compare the ratios.

[0042] The method for further optimizing the work roll slippage range and strip deviation is as follows: limit the slippage range, adjust the stand leveling value, adjust the strip head deviation, and prevent the strip head from entering the slippage operation side in front of the F7 stand. This significantly reduces the flared edge shape defect in the precision rolling of a certain grade of wide and thin strip. Figure 6 As shown, this avoids batch rework and flattening losses, and improves the continuity and overall yield of hot-rolled thin strip production.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the flared edge shape defect of hot-rolled thin strip, characterized in that, Includes the following steps: Step 1: Track the hot-rolled thin strip production process to determine the location of the lobed edge shape defect; Step 2: Analyze the wear condition of the finishing mill work rolls and adjust the roll shifting range according to the wear condition; Step 3: Analyze the deviation of the strip steel exit centerline and optimize the deviation direction; Step 4: Track the condition of the rolled edge of the hot-rolled thin strip after optimization, and further optimize the work roll shifting range and strip deviation; The method for determining the location of defects in the lotus leaf edge plate mentioned in step one involves recording, viewing, analyzing, and comparing multiple sets of cold exit plate shape diagrams of hot-rolled thin strip layers. The location of the leaf-shaped defect mentioned in step one is the operating side of the strip steel; The operation steps for adjusting the work roll slippage range mentioned in step two are as follows: In the early and middle stages of finishing milling, the negative slippage value of the work roll at F7 stand is limited to within -100mm to limit the degree of increased load on the leaf edge caused by positive slippage of the work roll. The method for analyzing the deviation of the center line at the exit of the strip finishing mill mentioned in step three is as follows: record the data of the position of the center line at the exit of the finishing mill and draw the deviation curve of the center line at the exit of the finishing mill. The method for optimizing the strip deviation direction mentioned in step three is to reduce the roll gap on the working roll operating side of the F5 and F6 frames, limit the area of ​​the strip operating side, and place the strip operating side inside the wear step of the working roll in the F7 frame.

2. The method for improving the flared edge shape defect of hot-rolled thin strip according to claim 1, characterized in that, The method for analyzing the wear state of the finishing mill work rolls mentioned in step two is as follows: The roll shape of the finishing mill work rolls on the F7 stand is CVC roll shape. The upper and lower work rolls in the F7 stand are removed from the F7 stand respectively. Then, the roll shape curves of the upper and lower work rolls are plotted. The roll shape curves of the upper work rolls after they are removed from the F7 stand are compared with those of the lower work rolls after they are removed from the F7 stand.

3. The method for improving the flared edge shape defect of hot-rolled thin strip according to claim 1, characterized in that, The method for tracking the condition of the flared edge of the hot-rolled thin strip mentioned in step four is as follows: record the number of flared edge defects requiring repair before and after the improvement, calculate the corresponding ratio, and compare the ratios.

4. The method for improving the flared edge shape defect of hot-rolled thin strip according to claim 3, characterized in that, The method for further optimizing the work roll slippage range and strip deviation mentioned in step four is as follows: limit the slippage range, adjust the frame leveling value, restrict the strip head, and prevent the strip head from entering the F7 frame and deviating to the operation side.

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