Edge crack elimination method for ultrathin copper plate strip

Abstract

The invention discloses a method for eliminating edge cracks of an ultrathin copper plate strip. Aiming at the edge crack problem in the ultrathin copper strip production, the invention provides an efficient elimination method, and the process comprises the following steps of: balancing the internal stress of a casting blank and optimizing the material performance by a multiple annealing process; a machine vision technology is utilized to accurately determine crack positions, and defect areas are automatically cut and removed; carrying out local edge heating treatment; and in the rolling process, the rolling speed is dynamically regulated and controlled according to the actually measured edge stress, cracks are prevented, and the production rate is optimized. According to the method, the belt breakage risk and raw material waste are remarkably reduced, and the product percent of pass and the production efficiency are improved.

Description

Technical Field

[0001] The invention relates to the field of copper plate and strip production, in particular to a method for eliminating edge cracks of an ultra-thin copper plate and strip. Background Art

[0002] Ultra-thin copper sheet and strip is a high-precision, high-performance metal material, the main feature of which is its very thin thickness, usually referring to copper alloy sheets or strips with a thickness between 0.05 mm and 0.1 mm. This material has a wide range of applications in electronics, communications, electrical appliances, new energy, precision instruments, aerospace and other fields due to its unique physical and chemical properties and good processability.

[0003] When the copper strip is melted and cast, cracks may appear on the edges due to factors such as stress. The cracks may cause the ultra-thin copper strip to break during rolling and cause the upper and lower rollers to come into direct contact, causing great damage to the rolling mill. The current solution is to uniformly cut off a part of both sides of the entire copper strip before rolling. This method causes a large loss of raw materials for the casting, greatly increases production costs, and still cannot completely solve the problem of breaking caused by cracks on the edges of the raw materials. Summary of the invention

[0004] In order to solve the above technical problems, a method for eliminating edge cracks of an ultra-thin copper strip adopted by the present invention comprises the following steps: S1: subjecting the initial copper strip casting to multiple annealing treatments; The multiple annealing method comprises: In the preheating stage, the copper strip casting embryo is slowly heated to a preset value below the recrystallization temperature so that the internal stress of the copper strip casting embryo is evenly distributed; In the first stage of annealing, the copper strip casting continues to be heated to the first preset temperature, which is 650 degrees Celsius. This temperature is sufficient to restore the lattice distortion produced during the cold working process and promote the regrowth of grains, thereby reducing the hardness of the material and improving the plasticity. This temperature is maintained for 20 to 30 minutes to ensure sufficient recrystallization.

[0005] Rapid cooling: After the first stage of annealing is completed, forced air cooling is used for a rapid cooling strategy to fix the new grain structure. Rapid cooling can prevent the grains from growing too fast, resulting in performance degradation. Rapid cooling also helps reduce oxidation and improve production efficiency.

[0006] The second stage of annealing is to heat the copper strip casting to a second preset temperature of 400 degrees Celsius and maintain this temperature for 10 to 15 minutes to further refine the grains, homogenize the structure or achieve specific mechanical properties. The copper strip casting is then naturally cooled to the preset rolling temperature.

[0007] Inert gas protection, such as nitrogen or argon, is used during the annealing process to avoid oxidation and ensure the surface quality of the copper material. At the same time, the composition and pressure of the furnace atmosphere are precisely controlled to further optimize material properties and reduce the possibility of crack formation.

[0008] S2: Use machine vision to detect cracks on the edge of the copper strip casting after processing, mark the location and length of the cracks, calculate the minimum width that needs to be cut, and automatically adjust the cutting equipment based on the calculation results to remove the cracked part of the copper strip casting; S3: Locally heating the edge of the copper strip casting embryo after the treatment, wherein the local heating position is 20 mm on the left and right of the copper strip casting embryo; S4: During the rolling process of the copper strip cast into ultra-thin copper strip, the edge stress of the copper strip is monitored in real time. The rolling speed is dynamically adjusted based on the detected stress. A model of stress and rolling speed is constructed to predict and adjust the feed speed of the copper strip rolling mill.

[0009] The specific steps for real-time monitoring of the edge stress of the copper strip include: Step 1: Install a temperature sensor at the edge of the copper strip before and after rolling, and record the temperature of the copper strip before and after rolling; Step 2: Comparing the temperature change rate before and after rolling reflects the stress inside the copper strip. The calculation formula for the stress inside the copper strip and the temperature change rate is: + ,in is the stress, E is the elastic modulus, is the coefficient of thermal expansion, is the temperature change, k is the thermal conductivity, is the specific heat capacity, is the rate of temperature change; Step 3: Based on the analysis results of temperature changes, draw the internal stress distribution diagram of the copper strip and adjust the processing parameters according to the stress distribution.

[0010] As a further solution of the present invention, in step S2, the specific steps of using machine vision to perform crack detection are: S21: using a high-definition camera to continuously photograph the copper plate and strip cast embryo to be rolled, and segmenting the image into the edge portion of the copper plate and strip cast embryo according to a preset size, wherein the preset size of the copper plate and strip cast embryo edge is 10 mm on each side; S22: De-noise and enhance the image, use Canny to extract feature values, and mark this area as a crack area; S23: Use contour detection in the crack area to identify the contour of the crack, and determine the starting and ending coordinates P1 (x1, y1) and P2 (x2, y2) of the crack, and calculate the pixel width of the crack based on the starting and ending coordinates , the formula is: ; S24: Calculate the real crack width based on the pixel width of the crack. The calculation formula is: , where R is the pixel resolution of the camera; S25: Based on the calculated true crack width The control system automatically adjusts the blade position and cutting path to accurately cut out the crack area.

[0011] As a further solution of the present invention, in step S4, the step of dynamically adjusting the rolling speed according to the detected stress magnitude is: S41: According to the internal stress value of the copper strip obtained in step S4, the speed, temperature, and roller pressure during rolling are collected simultaneously; S42: cleaning the data, removing outliers and missing values, normalizing the data, and extracting the characteristic value of stress change rate from the processed data; S43: Based on the goal of edge stress control, the following model can be established to predict the risk factor R of copper strip breakage: ,in is the stress value at the edge of the ultra-thin copper strip after rolling, is the stress value of the edge of the copper strip casting before rolling, P is the roller pressure, V is the current rolling speed, , , is a constant coefficient; when R is greater than the predetermined threshold, it means that the risk of copper strip breaking during rolling is high, and the rolling speed needs to be reduced to reduce the R value; when R is less than the predetermined threshold, it means that the risk of copper strip breaking during rolling is low, and the rolling speed can be increased to achieve the optimal production rate.

[0012] The sudden increase of edge stress is one of the main causes of cracks. By slowing down the rolling speed, the material can be given more time to adapt to deformation, thereby reducing stress concentration and avoiding crack formation. The speed adjustment is to maintain or improve production efficiency as much as possible while ensuring product quality. Excessive speed reduction will reduce production efficiency, while moderate adjustment can find the optimal production speed point while ensuring product quality.

[0013] Beneficial effects: The invention adopts multiple annealing strategies to improve material shaping, introduces machine vision to detect cracks, and automatically and accurately cuts, reducing the loss of raw materials. The local heating strategy and dynamic adjustment of rolling speed effectively control the edge stress of the copper strip, greatly reducing the generation of cracks and the risk of strip breakage, ensuring equipment safety, and improving production flexibility and capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a schematic flow chart of a method for eliminating edge cracks of an ultra-thin copper strip. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below in conjunction with the embodiments.

[0016] See also Figure 1 As shown, the specific steps of a method for eliminating edge cracks of an ultra-thin copper strip are as follows: S1: subjecting the initial copper strip casting to multiple annealing treatments; The multiple annealing method comprises: In the preheating stage, the copper strip casting embryo is slowly heated to a preset value below the recrystallization temperature so that the internal stress of the copper strip casting embryo is evenly distributed; In the first stage of annealing, the copper strip casting continues to be heated to the first preset temperature, which is 650 degrees Celsius. This temperature is sufficient to restore the lattice distortion produced during the cold working process and promote the regrowth of grains, thereby reducing the hardness of the material and improving the plasticity. This temperature is maintained for 20 to 30 minutes to ensure sufficient recrystallization.

[0017] Rapid cooling: After the first stage of annealing is completed, forced air cooling is used for a rapid cooling strategy to fix the new grain structure. Rapid cooling can prevent the grains from growing too fast, resulting in performance degradation. Rapid cooling also helps reduce oxidation and improve production efficiency.

[0018] The second stage of annealing is to heat the copper strip casting to a second preset temperature of 400 degrees Celsius and maintain this temperature for 10 to 15 minutes to further refine the grains, homogenize the structure or achieve specific mechanical properties. The copper strip casting is then naturally cooled to the preset rolling temperature.

[0019] Inert gas protection, such as nitrogen or argon, is used during the annealing process to avoid oxidation and ensure the surface quality of the copper material. At the same time, the composition and pressure of the furnace atmosphere are precisely controlled to further optimize material properties and reduce the possibility of crack formation.

[0020] S2: Use machine vision to detect cracks on the edge of the copper strip casting after processing, mark the location and length of the cracks, calculate the minimum width that needs to be cut, and automatically adjust the cutting equipment based on the calculation results to remove the cracked part of the copper strip casting; S3: Locally heating the edge of the copper strip casting embryo after the treatment, wherein the local heating position is 20 mm on the left and right of the copper strip casting embryo; S4: During the rolling process of the copper strip cast into ultra-thin copper strip, the edge stress of the copper strip is monitored in real time. The rolling speed is dynamically adjusted based on the detected stress. A model of stress and rolling speed is constructed to predict and adjust the feed speed of the copper strip rolling mill.

[0021] The specific steps for real-time monitoring of the edge stress of the copper strip include: Step 1: Install a temperature sensor at the edge of the copper strip before and after rolling, and record the temperature of the copper strip before and after rolling; Step 2: Comparing the temperature change rate before and after rolling reflects the stress inside the copper strip. The calculation formula for the stress inside the copper strip and the temperature change rate is: + ,in is the stress, E is the elastic modulus, is the coefficient of thermal expansion, is the temperature change, k is the thermal conductivity, is the specific heat capacity, is the rate of temperature change; Step 3: Based on the analysis results of temperature changes, draw the internal stress distribution diagram of the copper strip and adjust the processing parameters according to the stress distribution.

[0022] Furthermore, in step S2, the specific steps of using machine vision to perform crack detection are: S21: using a high-definition camera to continuously photograph the copper plate and strip cast embryo to be rolled, and segmenting the image into the edge portion of the copper plate and strip cast embryo according to a preset size, wherein the preset size of the copper plate and strip cast embryo edge is 10 mm on each side; S22: De-noise and enhance the image, use Canny to extract feature values, and mark this area as a crack area; S23: Use contour detection in the crack area to identify the contour of the crack, and determine the starting and ending coordinates P1 (x1, y1) and P2 (x2, y2) of the crack, and calculate the pixel width of the crack based on the starting and ending coordinates , the formula is: ; S24: Calculate the real crack width based on the pixel width of the crack. The calculation formula is: , where R is the pixel resolution of the camera; S25: Based on the calculated true crack width The control system automatically adjusts the blade position and cutting path to accurately cut out the crack area.

[0023] Furthermore, in step S4, the step of dynamically adjusting the rolling speed according to the detected stress magnitude is: S41: According to the internal stress value of the copper strip obtained in step S4, the speed, temperature, and roller pressure during rolling are collected simultaneously; S42: cleaning the data, removing outliers and missing values, normalizing the data, and extracting the characteristic value of stress change rate from the processed data; S43: Based on the goal of edge stress control, the following model can be established to predict the risk factor R of copper strip breakage: ,in is the stress value at the edge of the ultra-thin copper strip after rolling, is the stress value of the edge of the copper strip casting before rolling, P is the roller pressure, V is the current rolling speed, , , is a constant coefficient; when R is greater than the predetermined threshold, it means that the risk of copper strip breaking during rolling is high, and the rolling speed needs to be reduced to reduce the R value; when R is less than the predetermined threshold, it means that the risk of copper strip breaking during rolling is low, and the rolling speed can be increased to achieve the optimal production rate.

Claims

1. A method for eliminating edge cracks of ultra-thin copper strips, characterized in that: The following steps are involved: S1: subjecting the initial copper strip casting to multiple annealing treatments; The multiple annealing method comprises: In the preheating stage, the copper strip casting embryo is slowly heated to a preset value below the recrystallization temperature so that the internal stress of the copper strip casting embryo is evenly distributed; The first stage annealing is to continue heating the copper strip casting to a first preset temperature, which is 650 degrees Celsius, and maintain this temperature for 20 to 30 minutes; Rapid cooling: After the first stage of annealing, forced air cooling is used for rapid cooling to fix the new grain structure; The second stage annealing is to heat the copper strip cast embryo to a second preset temperature, which is 400 degrees Celsius, and maintain this temperature for 10 to 15 minutes; then the copper strip cast embryo is naturally cooled to a preset rolling temperature; S2: Use machine vision to detect cracks on the edge of the copper strip casting after processing, mark the location and length of the cracks, calculate the minimum width to be cut, and adjust the cutting equipment according to the calculation results to remove the cracked part of the copper strip casting; S3: heating the edge of the copper strip casting embryo after the treatment, wherein the heating position is 20 mm to the left and right of the copper strip casting embryo; S4: During the rolling process of copper strip casting into ultra-thin copper strip, the edge stress of the copper strip is monitored in real time. The rolling speed is dynamically adjusted according to the detected stress. A stress and rolling speed model is constructed to predict and adjust the feed speed of the copper strip rolling mill. The specific steps of real-time monitoring of the edge stress of the copper strip include: Step 1: Install a temperature sensor at the edge of the copper strip before and after rolling, and record the temperature of the copper strip before and after rolling; Step 2: Comparing the temperature change rate before and after rolling reflects the stress inside the copper strip. The calculation formula for the internal stress and temperature change rate of the copper strip is: + ,in is the stress, E is the elastic modulus, is the coefficient of thermal expansion, is the temperature change, k is the thermal conductivity, is the specific heat capacity, is the rate of temperature change; Step 3: Based on the analysis results of temperature changes, draw the internal stress distribution diagram of the copper strip and adjust the processing parameters according to the stress distribution.

2. The method for eliminating edge cracks of an ultra-thin copper strip according to claim 1, characterized in that: In step S2, the specific steps of using machine vision to perform crack detection are: S21: using a high-definition camera to continuously photograph the copper plate and strip cast embryo to be rolled, and segmenting the image into the edge portion of the copper plate and strip cast embryo according to a preset size, wherein the preset size of the copper plate and strip cast embryo edge is 10 mm on each side; S22: De-noise and enhance the image, use Canny to extract feature values, and mark this area as a crack area; S23: Use contour detection in the crack area to identify the contour of the crack, and determine the starting and ending coordinates P1 (x1, y1) and P2 (x2, y2) of the crack, and calculate the pixel width of the crack based on the starting and ending coordinates , the formula is: ; S24: Calculate the true crack width based on the pixel width of the crack. The calculation formula is: , where R is the pixel resolution of the camera; S25: Based on the calculated true crack width The control system automatically adjusts the blade position and cutting path to accurately cut out the crack area.

3. The method for eliminating edge cracks of an ultra-thin copper strip according to claim 1, characterized in that: In step S4, the step of dynamically adjusting the rolling speed according to the detected stress magnitude is as follows: S41: According to the internal stress value of the copper strip obtained in step S4, the speed, temperature, and roller pressure during rolling are collected simultaneously; S42: cleaning the data, removing outliers and missing values, normalizing the data, and extracting the characteristic value of stress change rate from the processed data; S43: Based on the goal of edge stress control, the following model can be established to predict the risk factor R of copper strip breakage: ,in is the stress value at the edge of the ultra-thin copper strip after rolling, is the stress value of the edge of the copper strip casting before rolling, P is the roller pressure, V is the current rolling speed, , , is a constant coefficient; when R is greater than the predetermined threshold, it means that the risk of copper strip breaking during rolling is high, and the rolling speed needs to be reduced to reduce the R value; when R is less than the predetermined threshold, it means that the risk of copper strip breaking during rolling is low, and the rolling speed can be increased to achieve the optimal production rate.

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