Metal copper bar bending method

Abstract

The invention discloses a metal copper bar bending method. The method comprises the following steps: firstly, preferentially selecting annealed soft T2 red copper (the hardness is HV50) with the oxygen content of less than or equal to 0.02%; then the copper bar is subjected to recrystallization annealing softening treatment, and the annealing temperature is 260 + / -10 DEG C; and after the annealed copper bar is cooled to room temperature (25 + / -5 DEG C), the copper bar with scratches, oxide skin, mechanical internal damage or rolling defects on the surface is removed in a visual inspection or ultrasonic flaw detection mode. T2 red copper with the oxygen content being smaller than or equal to 0.02% is adopted as a raw material to machine the metal copper bar, recrystallization annealing softening treatment is conducted, and therefore the ductility of the copper bar is improved. And then the bending radius of the copper bar is optimized, so that the included angle between the bending line of the copper bar and the rolling direction of the copper plate is 45-90 degrees, bending in the parallel rolling direction is avoided, the cracking risk is reduced, the risk of severe plastic deformation of the inner side and the outer side of the copper bar is reduced, and the conductivity of the copper bar is prevented from being influenced.

Description

Technical Field

[0001] This invention relates to the field of metal copper busbar processing technology, specifically a method for bending metal copper busbars. Background Technology

[0002] Copper busbars, also known as copper busbars or current busbars, are solid copper conductors with a large cross-section and rectangular shape. They are mainly used for the efficient and reliable transmission of large currents and are commonly used in various power systems such as distribution cabinets, transformers, switchgear, bus trunking, electric vehicle battery packs, and industrial equipment.

[0003] In the processing of copper busbars, straight busbars often need to be bent. This is mainly because the internal space of electrical cabinets is usually very limited and the layout is complex, so the connection points of the copper busbars are often not on the same plane or a straight line. Bending the copper busbars allows them to bypass obstacles and change direction within the internal space of the electrical cabinet, thereby accurately reaching the target connection point. Secondly, copper busbars generate heat when operating under high current, and this increased temperature causes them to expand and elongate. If the busbar is rigidly straight, this expansion will generate significant internal stress and thrust at the bolts, insulators, and other fixing points, potentially leading to breakage or loosening of the insulators and connecting bolts, as well as deformation or even breakage of the busbar itself. However, by appropriately bending the copper busbar, the bent corners can undergo slight elastic deformation when the busbar expands due to heat, absorbing most of the thermal stress and preventing destructive forces from being transmitted to the fixing points.

[0004] However, when the bending radius of existing copper busbars is too small, the tensile stress on the outer side of the busbar can easily exceed the material's tensile limit, leading to cracking or even breakage on the outer side. Furthermore, the inner side will also be subjected to strong compressive forces, causing the inner wall metal of the busbar to yield and deform, forming wavy wrinkles. This is especially prone to occur when the copper busbar itself has undergone severe cold work hardening or has excessively high hardness, resulting in insufficient ductility. This severe plastic deformation can damage the original grain structure of the copper busbar, particularly at the bends, leading to localized embrittlement or affecting the busbar's conductivity.

[0005] To address this problem, a method for bending metal copper busbars is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for bending copper busbars, which solves the problem that when the bending radius of copper busbars is too small and the copper busbars themselves are severely cold-worked or have too high hardness, resulting in insufficient ductility, the outer side of the copper busbar is prone to stretching and cracking, and the inner side is prone to compression and wrinkling, causing severe plastic deformation of the copper busbars, thereby destroying the original grain structure of the copper busbars, leading to local embrittlement or affecting conductivity.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for bending a metal copper busbar, comprising the following steps: Step 1: Material selection: First, prioritize soft T2 copper (hardness HV50) with oxygen content ≤0.02% and annealed. Step 2: Pretreatment: Then, the copper busbar is subjected to recrystallization annealing softening treatment at a temperature of 260±10℃. After the copper busbar is cooled to room temperature (25±5℃) after annealing, copper busbars with scratches, oxide scale, mechanical damage or rolling defects are removed by visual inspection or ultrasonic testing. Step 3: Optimize bending radius: Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and standardize the minimum bending radius. For static bending, R≥1.0×plate thickness (T), and for dynamic rolling bending, R≥1.5×T. Dynamic rolling bending refers to the process of bending by continuous rolling of rollers, which is suitable for bending scenarios with large curvature radii. At the same time, optimize the bending direction so that the bending line is at an angle of 45°-90° with the rolling direction of the copper plate to avoid bending parallel to the rolling direction. Step 4: Springback Dynamic Compensation: Subsequently, a CNC bending machine with angle feedback is used to correct the downward pressure in real time. The pre-bending angle is calculated as follows: pre-bending angle = theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. At the same time, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away from the bending line. The distance between the center of the hole and the edge of the copper busbar is ≥2 times the hole diameter, to buffer stress. Step 5: Defect Handling: When surface cracks ≤0.1mm appear on the outer side of the copper busbar after bending, local repair welding can be performed using copper-based brazing filler metal with conductivity ≥80% IACS. The repaired or shaped copper busbar should then undergo low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, grind until Ra≤6.3μm. If cracks >0.1mm deep appear on the outer side of the copper busbar, the entire section should be cut off and reprocessed. Simultaneously, when wrinkles appear on the inner side of the copper busbar, mild wrinkles (height ≤0.2T) can be gently flattened by tapping along the bending line with a copper shaping hammer. Severe wrinkles (height >0.2T) require first low-temperature annealing (180±10℃, 20-30 minutes, furnace cooling to 150℃ followed by air cooling), and then gradually shaped by applying pressure along the wrinkle direction using a hydraulic shaping machine.

[0008] Preferably, the copper busbar is cut to the required length according to the unfolded length of the copper busbar, and the cut end face of the copper busbar is deburred to ensure that the edge is smooth and without sharp corners, so as to prevent scratches and tip discharge.

[0009] Preferably, during copper busbar annealing, the temperature should be kept below 300°C to avoid grain coarsening. For copper busbars with a thickness ≤ 5 mm, the holding time is 8 minutes per millimeter; for copper busbars with a thickness > 5 mm, the holding time is 10 minutes per millimeter. The cooling method is to cool the busbar to 150°C in the furnace and then air cool it.

[0010] Preferably, use a non-woven cloth or clean cotton cloth to wipe the surface of the copper busbar to remove oil and dust. If necessary, a special copper cleaner can be used, but ensure that the cleaner has completely evaporated and leaves no residue.

[0011] Preferably, the bending line should be clearly drawn on the surface of the copper busbar before bending to facilitate subsequent positioning. A scribing needle or an easily erasable marker can be used to ensure that it does not affect subsequent tin plating or use.

[0012] Preferably, a suitable V-shaped bending die is selected based on the thickness of the copper busbar. Specifically, for copper busbars with a thickness ≤3mm, the width of the lower die V-groove is 6-8 times the copper busbar thickness (T); for copper busbars with a thickness of 3-10mm, the width of the V-groove is 8-10 times the copper busbar thickness (T); and for copper busbars with a thickness >10mm, the width of the V-groove is 10-12 times the copper busbar thickness (T). This prevents an excessively small V-groove from increasing the bending force, which could lead to damage to the copper busbar or the die. An excessively large V-groove can affect the bending accuracy, resulting in larger or unstable fillet radius. At the same time, the upper die adopts an R-angle die, and the tip angle of the upper die must match the V-shape of the lower die, ensuring that the upper die tip is intact and free of chipping.

[0013] Preferably, the lower die is securely mounted on the bending machine's worktable, ensuring it is level, and the upper die is mounted on the bending machine's slide block, ensuring it is secure and reliable. A level is used for calibration, adjusting the upper die's descent limit and the lower die's height so that when the upper die reaches its lowest point, the distance between its tip and the bottom of the lower die's V-groove maintains an appropriate copper busbar thickness. The upper and lower dies are then ensured to be parallel using a level.

[0014] Preferably, the copper busbar to be bent is positioned on the bending machine's worktable, ensuring the drawn bending line is precisely aligned with the center line of the lower die's V-groove. The upper die's cutting edge contacts the copper busbar and applies pressure, causing the copper busbar to begin plastic bending deformation around the shoulder of the lower die's V-groove. The hydraulic system continuously and steadily applies pressure until the slider reaches the preset position. After reaching the preset position, the hydraulic system maintains pressure for a few seconds, thereby helping the copper busbar to undergo more complete plastic deformation, reducing springback, and stabilizing the angle.

[0015] Preferably, if the measured angle of the springback after the copper busbar is bent is less than the target angle, the target angle setting on the machine needs to be increased. If the measured angle is greater than the target angle, the target angle setting needs to be decreased, and repeated bending adjustments should be made until the target angle is reached.

[0016] Preferably, the bent copper busbars should be carefully inspected, especially the inner and outer edges of the bend and the original cut end face. All burrs and sharp edges should be removed with a file, scraper, sandpaper or special deburring tool. For critical conductive components, it is necessary to measure the DC resistance of the bent and unbent sections to ensure that the bending has not caused a significant deterioration in conductivity.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention patent utilizes T2 copper with an oxygen content ≤0.02% as raw material to process copper busbars, followed by recrystallization annealing softening treatment. Then, by optimizing the bending radius of the copper busbar and simultaneously performing springback dynamic compensation to real-time adjust the bending die's downward pressure, the elongation of the copper busbar is improved. This ensures the bending line of the copper busbar forms a 45°-90° angle with the rolling direction of the copper plate, avoiding bending parallel to the rolling direction, reducing the risk of cracking, minimizing the risk of severe plastic deformation on the inner and outer sides of the copper busbar, and preventing any impact on the conductivity of the copper busbar. This invention patent addresses the issue of surface cracks ≤0.1mm appearing on the outer side of a bent copper busbar by localized soldering with copper-based brazing filler metal. Simultaneously, when wrinkles appear on the inner side of the copper busbar, minor wrinkles can be smoothed out by gently tapping along the bending line with a copper shaping hammer, while severe wrinkles are directly annealed and then hydraulically shaped. This allows for targeted defect repair even in copper busbars with minor, severe deformation after optimizing the bending radius, further improving the bending quality of the copper busbar. Detailed Implementation

[0018] The present invention will now be described in more detail by way of examples. These examples are merely illustrative and do not limit the scope of the present invention in any way.

[0019] This invention provides a technical solution: a method for bending metal copper busbars, comprising the following steps: Step 1: Material selection: First, prioritize soft T2 copper (hardness HV50) with oxygen content ≤0.02% and annealed. Step 2: Pretreatment: Then, the copper busbar is subjected to recrystallization annealing softening treatment at a temperature of 260±10℃. After the copper busbar is cooled to room temperature (25±5℃) after annealing, copper busbars with scratches, oxide scale, mechanical damage or rolling defects are removed by visual inspection or ultrasonic testing. Step 3: Optimize bending radius: Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and standardize the minimum bending radius. For static bending, R≥1.0×plate thickness (T), and for dynamic rolling bending, R≥1.5×T. Dynamic rolling bending refers to the process of bending by continuous rolling of rollers, which is suitable for bending scenarios with large curvature radii. At the same time, optimize the bending direction so that the bending line is at an angle of 45°-90° with the rolling direction of the copper plate to avoid bending parallel to the rolling direction. Step 4: Springback Dynamic Compensation: Subsequently, a CNC bending machine with angle feedback is used to correct the downward pressure in real time. The pre-bending angle is calculated as follows: pre-bending angle = theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. At the same time, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away from the bending line. The distance between the center of the hole and the edge of the copper busbar is ≥2 times the hole diameter, to buffer stress. Step 5: Defect Handling: When surface cracks ≤0.1mm appear on the outer side of the copper busbar after bending, local repair welding can be performed using copper-based brazing filler metal with conductivity ≥80% IACS. The repaired or shaped copper busbar should then undergo low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, grind until Ra≤6.3μm. If cracks >0.1mm deep appear on the outer side of the copper busbar, the entire section should be cut off and reprocessed. Simultaneously, when wrinkles appear on the inner side of the copper busbar, mild wrinkles (height ≤0.2T) can be gently flattened by tapping along the bending line with a copper shaping hammer. Severe wrinkles (height >0.2T) require first low-temperature annealing (180±10℃, 20-30 minutes, furnace cooling to 150℃ followed by air cooling), and then gradually shaped by applying pressure along the wrinkle direction using a hydraulic shaping machine.

[0020] Example 1: First, prioritize the use of soft T2 copper (hardness HV50) with an oxygen content ≤0.02% and after annealing. Then, perform recrystallization annealing softening treatment on the copper busbar at 260±10℃. After annealing, cool the copper busbar to room temperature (25±5℃), and remove any surface scratches, oxide scale, mechanical damage, or rolling defects using visual inspection or ultrasonic testing. Next, select an appropriate hydraulic bending machine tonnage based on the thickness and width of the copper busbar and the required bending force, and standardize the minimum bending radius. For static bending, R≥1.0×plate thickness (T), and for dynamic roll bending, R≥1.5×T. Dynamic roll bending refers to a bending process achieved through continuous rolling of rollers, suitable for bending scenarios with large radii of curvature. Simultaneously, optimize the bending direction to ensure the bending line forms a 45°-90° angle with the copper plate rolling direction, avoiding flat bending. The bending process begins with bending along the rolling direction. A CNC bending machine with angle feedback is then used to correct the downward pressure in real time. The pre-bending angle is calculated as the theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. Simultaneously, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away. The center of the hole is at least twice the hole diameter from the edge of the copper busbar to buffer stress. Finally, if a surface crack ≤0.1mm appears on the outer side of the bent copper busbar, it can be locally repaired using copper-based brazing filler metal with a conductivity ≥80% IACS. The repaired or shaped copper busbar is then subjected to low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, it is ground to Ra≤6.3μm. If a crack >0.1mm deep appears on the outer side of the copper busbar, the entire section is cut off and reprocessed. Meanwhile, when wrinkles appear on the inside of the copper busbar, for slight wrinkles (height ≤ 0.2T), a copper shaping hammer can be used to gently flatten them along the bending line. For severe wrinkles (height > 0.2T), low-temperature annealing is required first (temperature 180±10℃, hold for 20-30 minutes, cool with the furnace to 150℃ and then air cool), and then a hydraulic shaping machine can be used to gradually apply pressure and shape them along the wrinkle direction.

[0021] Example 2: In Example 1, the following steps are added: In step 1, the copper busbar is cut to the required length according to the unfolded length of the copper busbar, and the cut end face of the copper busbar is deburred to ensure that the edge is smooth and without sharp corners, so as to prevent scratches and tip discharge.

[0022] In step 2, during copper busbar annealing, the temperature should be kept below 300℃ to avoid grain coarsening. For copper busbars with a thickness ≤ 5mm, the holding time is 8 minutes per millimeter; for copper busbars with a thickness > 5mm, the holding time is 10 minutes per millimeter. The cooling method is to cool the busbar in the furnace to 150℃ and then air cool it. Wipe the surface of the copper busbar with a non-woven cloth or clean cotton cloth to remove oil and dust. If necessary, a special copper cleaning agent can be used, but it must be ensured that the cleaning agent has completely evaporated and left no residue.

[0023] First, prioritize the use of soft T2 copper (hardness HV50) with an oxygen content ≤0.02% and after annealing. Cut the copper busbar to the required length according to its unfolded length, and deburr the cut ends to ensure smooth edges without sharp corners, preventing scratches and tip discharge. Then, perform recrystallization annealing softening treatment on the copper busbar at a temperature of 260±10℃. After annealing, cool the copper busbar to room temperature (25±5℃), and remove any copper busbars with scratches, oxide scale, mechanical damage, or rolling defects by visual inspection or ultrasonic testing. During annealing, avoid temperatures exceeding 300℃ to prevent grain coarsening. For copper busbars with a thickness ≤5mm, hold for 8 minutes per millimeter; for copper busbars with a thickness >5mm, hold for 10 minutes per millimeter. Cool in the furnace to 150℃ and then air cool. Wipe the surface of the copper busbar with a non-woven cloth or clean cotton cloth to remove oil and dust. Specialized copper cleaning agents can be used if necessary, but it must be ensured that the cleaning agent completely evaporates and leaves no residue. Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and specify the minimum bending radius. For static bending, R ≥ 1.0 × plate thickness (T); for dynamic roll bending, R ≥ 1.5 × T. Dynamic roll bending refers to a bending process achieved through continuous rolling of rollers, suitable for bending scenarios with large radii of curvature. Simultaneously, optimize the bending direction to ensure the bending line forms a 45°-90° angle with the copper plate rolling direction, avoiding bending parallel to the rolling direction. Subsequently, use a CNC bending machine with angle feedback to correct the downward pressure in real time. The pre-bending angle = theoretical angle + (0.03 × material hardness HV)°, for example, H... When bending a V60 copper busbar at 90°, it needs to be pre-bent to 91.5°. Simultaneously, pre-drill one φ3-5mm stress relief hole at each end of the bending line, 5-10mm away from the bending line. The center of the hole should be at least twice the hole diameter from the edge of the copper busbar to buffer stress. Finally, if a surface crack ≤0.1mm appears on the outer side of the copper busbar after bending, it can be locally repaired using copper-based brazing filler metal with a conductivity ≥80% IACS. The repaired or reshaped copper busbar should then undergo low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, grind to Ra≤6.3μm. If a crack >0.1mm deep appears on the outer side of the copper busbar, the entire section should be cut off and reprocessed. Meanwhile, when wrinkles appear on the inside of the copper busbar, for slight wrinkles (height ≤ 0.2T), a copper shaping hammer can be used to gently flatten them along the bending line. For severe wrinkles (height > 0.2T), low-temperature annealing is required first (temperature 180±10℃, hold for 20-30 minutes, cool with the furnace to 150℃ and then air cool), and then a hydraulic shaping machine can be used to gradually apply pressure and shape them along the wrinkle direction.

[0024] Example 3: In Example 2, the following additional steps are added: In step 3, before bending the copper busbar, the bending line must be clearly drawn on the surface of the copper busbar for easy positioning later. A scribing needle or an easily erasable marker can be used to ensure that it does not affect subsequent tin plating or use. Select a suitable V-shaped bending die according to the thickness of the copper busbar. For copper busbars with a thickness ≤3mm, the V-groove width of the lower die is 6-8 times the copper busbar thickness (T); for copper busbars with a thickness of 3-10mm, the V-groove width is 8-10 times the copper busbar thickness (T); for copper busbars with a thickness >10mm, the V-groove width is 10-12 times the copper busbar thickness (T). This prevents the V-groove from being too small, which would increase the bending force and cause damage to the copper busbar or the die. An excessively large V-groove will affect the bending accuracy, resulting in larger or unstable corner radii. At the same time, the upper die should use an R-angle die. The tip angle of the upper die must match the V-shape of the lower die, and the upper die tip must be intact and free of chips. Securely install the lower die on the bending machine's worktable, ensuring it is level, and install the upper die on the bending machine's slider, ensuring it is secure and reliable. Using a level for calibration, adjust the upper die's descent limit and the lower die's height to ensure that when the upper die reaches its lowest point, the tip of the upper die maintains a distance appropriate to the copper busbar thickness from the bottom of the lower die's V-groove. Ensure the upper and lower dies are parallel using the level. Position the copper busbar to be bent on the bending machine's worktable, ensuring the drawn bending line is precisely aligned with the center line of the lower die's V-groove. Open the upper die's blade to contact the copper busbar and apply pressure. The copper busbar begins to undergo plastic bending deformation around the shoulder of the lower die's V-groove. The hydraulic system continuously and steadily applies pressure until the slider reaches the preset position. After reaching the preset position, the hydraulic system maintains pressure for a few seconds to help the copper busbar undergo more complete plastic deformation, reduce springback, and stabilize the angle.

[0025] First, prioritize the use of soft T2 copper (hardness HV50) with an oxygen content ≤0.02% and after annealing. Cut the copper busbar to the required length according to its unfolded length, and deburr the cut ends to ensure smooth edges without sharp corners, preventing scratches and tip discharge. Then, perform recrystallization annealing softening treatment on the copper busbar at a temperature of 260±10℃. After annealing, cool the copper busbar to room temperature (25±5℃), and remove any copper busbars with scratches, oxide scale, mechanical damage, or rolling defects by visual inspection or ultrasonic testing. During annealing, avoid temperatures exceeding 300℃ to prevent grain coarsening. For copper busbars with a thickness ≤5mm, hold for 8 minutes per millimeter; for copper busbars with a thickness >5mm, hold for 10 minutes per millimeter. Cool in the furnace to 150℃ and then air cool. Wipe the surface of the copper busbar with a non-woven cloth or clean cotton cloth to remove oil and dust. Specialized copper cleaning agents can be used if necessary, but it must be ensured that the cleaning agent completely evaporates and leaves no residue. Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and specify the minimum bending radius. For static bending, R ≥ 1.0 × plate thickness (T), and for dynamic roll bending, R ≥ 1.5 × T. Dynamic roll bending refers to a bending process achieved through continuous rolling of rollers, suitable for bending scenarios with large radii of curvature. Simultaneously, the bending direction should be optimized so that the bending line forms a 45°-90° angle with the copper plate rolling direction, avoiding bending parallel to the rolling direction. Before bending the copper busbar, the bending line must be clearly drawn on the surface of the copper busbar for easy subsequent positioning. Use a scribing needle or an easily erasable marker to ensure it does not affect subsequent tinning or use. Select a suitable V-shaped bending die according to the thickness of the copper busbar. For copper busbars with a thickness ≤3mm, the V-groove width of the lower die should be 6-8 times the copper busbar thickness (T); for copper busbars with a thickness of 3-10mm, the V-groove width should be 8-10 times the copper busbar thickness (T); and for copper busbars with a thickness >10mm, the V-groove width should be 10-12 times the copper busbar thickness (T). This prevents an excessively small V-groove from increasing bending force, causing damage to the copper busbar or the die. An excessively large V-groove will affect bending accuracy, resulting in larger or unstable fillet radius. At the same time, the upper die should use an R-angle die, and the tip angle of the upper die must match the V-shape of the lower die, ensuring that the upper die tip is intact and free of chips. Securely install the lower die on the bending machine's worktable, ensuring it is level, and install the upper die on the bending machine's slide block, ensuring it is firm and reliable. Using a level, adjust the stroke limit of the upper die and the height of the lower die to ensure that when the upper die descends to its lowest point, the blade tip and the bottom of the V-groove of the lower die maintain a distance of appropriate copper busbar thickness. Also, use a level to ensure that the upper and lower dies are parallel. Position the copper busbar to be bent on the bending machine's worktable, ensuring that the drawn bending line is precisely aligned with the center line of the V-groove of the lower die. Open the upper die blade to contact the copper busbar and apply pressure. The copper busbar will then begin to undergo plastic bending deformation around the shoulder of the V-groove of the lower die.The hydraulic system continuously and steadily applies pressure until the slider reaches the preset position. After reaching the preset position, the hydraulic system maintains pressure for a few seconds, thereby helping the copper busbar to undergo more complete plastic deformation, reducing springback, and stabilizing the angle. Subsequently, a CNC bending machine with angle feedback is used to correct the downward pressure in real time. The pre-bending angle is calculated as the theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. Simultaneously, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away from the line. The center of the hole is at least twice the hole diameter from the edge of the copper busbar to buffer stress. Finally, if a surface crack ≤0.1mm appears on the outer side of the bent copper busbar, it can be locally repaired using copper-based brazing filler metal with a conductivity ≥80% IACS. The repaired or shaped copper busbar is then subjected to low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, it is then ground to Ra≤6.3μm. If a crack >0.1mm deep appears on the outer side of the copper busbar, the entire section is cut off and reprocessed. Meanwhile, when wrinkles appear on the inside of the copper busbar, for slight wrinkles (height ≤ 0.2T), a copper shaping hammer can be used to gently flatten them along the bending line. For severe wrinkles (height > 0.2T), low-temperature annealing is required first (temperature 180±10℃, hold for 20-30 minutes, cool with the furnace to 150℃ and then air cool), and then a hydraulic shaping machine can be used to gradually apply pressure and shape them along the wrinkle direction.

[0026] Example 4: In Example 3, the following steps are added: In step 4, if the measured angle of the springback after the copper busbar is bent is less than the target angle, the target angle setting on the machine needs to be increased. If the measured angle is greater than the target angle, the target angle setting needs to be decreased, and repeated bending and adjustment should be performed until the target angle is reached.

[0027] In step 5, carefully inspect the bent copper busbar, especially the inner and outer edges of the bend and the original cut end face. Remove all burrs and sharp edges with a file, scraper, sandpaper or special deburring tool. For critical conductive components, it is necessary to measure the DC resistance of the bent and unbent sections to ensure that the bending has not caused a significant deterioration in conductivity.

[0028] First, prioritize the use of soft T2 copper (hardness HV50) with an oxygen content ≤0.02% and after annealing. Cut the copper busbar to the required length according to its unfolded length, and deburr the cut ends to ensure smooth edges without sharp corners, preventing scratches and tip discharge. Then, perform recrystallization annealing softening treatment on the copper busbar at a temperature of 260±10℃. After annealing, cool the copper busbar to room temperature (25±5℃), and remove any copper busbars with scratches, oxide scale, mechanical damage, or rolling defects by visual inspection or ultrasonic testing. During annealing, avoid temperatures exceeding 300℃ to prevent grain coarsening. For copper busbars with a thickness ≤5mm, hold for 8 minutes per millimeter; for copper busbars with a thickness >5mm, hold for 10 minutes per millimeter. Cool in the furnace to 150℃ and then air cool. Wipe the surface of the copper busbar with a non-woven cloth or clean cotton cloth to remove oil and dust. Specialized copper cleaning agents can be used if necessary, but it must be ensured that the cleaning agent completely evaporates and leaves no residue. Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and specify the minimum bending radius. For static bending, R ≥ 1.0 × plate thickness (T), and for dynamic roll bending, R ≥ 1.5 × T. Dynamic roll bending refers to a bending process achieved through continuous rolling of rollers, suitable for bending scenarios with large radii of curvature. Simultaneously, the bending direction should be optimized so that the bending line forms a 45°-90° angle with the copper plate rolling direction, avoiding bending parallel to the rolling direction. Before bending the copper busbar, the bending line must be clearly drawn on the surface of the copper busbar for easy subsequent positioning. Use a scribing needle or an easily erasable marker to ensure it does not affect subsequent tinning or use. Select a suitable V-shaped bending die according to the thickness of the copper busbar. For copper busbars with a thickness ≤3mm, the V-groove width of the lower die should be 6-8 times the copper busbar thickness (T); for copper busbars with a thickness of 3-10mm, the V-groove width should be 8-10 times the copper busbar thickness (T); and for copper busbars with a thickness >10mm, the V-groove width should be 10-12 times the copper busbar thickness (T). This prevents an excessively small V-groove from increasing bending force, causing damage to the copper busbar or the die. An excessively large V-groove will affect bending accuracy, resulting in larger or unstable fillet radius. At the same time, the upper die should use an R-angle die, and the tip angle of the upper die must match the V-shape of the lower die, ensuring that the upper die tip is intact and free of chips. Securely install the lower die on the bending machine's worktable, ensuring it is level, and install the upper die on the bending machine's slide block, ensuring it is firm and reliable. Using a level, adjust the stroke limit of the upper die and the height of the lower die to ensure that when the upper die descends to its lowest point, the blade tip and the bottom of the V-groove of the lower die maintain a distance of appropriate copper busbar thickness. Also, use a level to ensure that the upper and lower dies are parallel. Position the copper busbar to be bent on the bending machine's worktable, ensuring that the drawn bending line is precisely aligned with the center line of the V-groove of the lower die. Open the upper die blade to contact the copper busbar and apply pressure. The copper busbar will then begin to undergo plastic bending deformation around the shoulder of the V-groove of the lower die.The hydraulic system continuously and steadily applies pressure until the slider reaches the preset position. After reaching the preset position, the hydraulic system maintains pressure for a few seconds to help the copper busbar undergo more complete plastic deformation, reduce springback, and stabilize the angle. Subsequently, a CNC bending machine with angle feedback is used to correct the downward pressure in real time. The pre-bending angle is calculated as the theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. At the same time, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away from the bending line. The distance between the center of the hole and the edge of the copper busbar is ≥2 times the hole diameter, to buffer stress. If the measured springback angle of the copper busbar after bending is less than the target angle, the target angle setting on the machine needs to be increased. If the measured angle is greater than the target angle, the target angle setting needs to be decreased, and repeated trial bending and adjustment are performed until the target angle is reached. Finally, if surface cracks ≤0.1mm appear on the outer side of the copper busbar after bending, local repair soldering can be performed using copper-based brazing filler metal with conductivity ≥80% IACS. The repaired or reshaped copper busbar should then undergo low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After soldering, the busbar should be ground to Ra≤6.3μm. If cracks >0.1mm deep appear on the outer side of the copper busbar, the entire section should be cut off and reprocessed. Meanwhile, when the inner side of the copper busbar wrinkles, for slight wrinkles (height ≤ 0.2T), a copper shaping hammer can be used to gently flatten them along the bending line. For severe wrinkles (height > 0.2T), low-temperature annealing is required first (temperature 180±10℃, hold for 20-30 minutes, cool with the furnace to 150℃ and then air cool), and then a hydraulic shaping machine is used to gradually apply pressure and shape along the wrinkle direction. Carefully inspect the bent copper busbar, especially the inner and outer edges of the bend and the original cut end face. Use a file, scraper, sandpaper or special deburring tool to remove all burrs and sharp edges. For critical conductive components, it is necessary to measure the DC resistance of the bent and unbent sections to ensure that the bending does not cause significant deterioration of conductivity.

[0029] 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 bending a metal copper busbar, characterized in that: Includes the following steps: Step 1: Material selection: First, select soft T2 copper (hardness HV50) with an oxygen content ≤0.02% and after annealing. Step 2: Pretreatment: Then, the copper busbar is subjected to recrystallization annealing softening treatment at a temperature of 260±10℃. After the copper busbar is cooled to room temperature (25±5℃) after annealing, copper busbars with scratches, oxide scale, mechanical damage or rolling defects are removed by visual inspection or ultrasonic testing. Step 3: Optimize bending radius: Then, based on the thickness and width of the copper busbar and the required bending force, select the appropriate hydraulic bending machine tonnage and standardize the minimum bending radius. For static bending, R≥1.0×plate thickness (T), and for dynamic rolling bending, R≥1.5×T. Dynamic rolling bending refers to the process of bending by continuous rolling of rollers, which is suitable for bending scenarios with large curvature radii. At the same time, optimize the bending direction so that the bending line is at an angle of 45°-90° with the rolling direction of the copper plate to avoid bending parallel to the rolling direction. Step 4: Springback Dynamic Compensation: Subsequently, a CNC bending machine with angle feedback is used to correct the downward pressure in real time. The pre-bending angle is calculated as follows: pre-bending angle = theoretical angle + (0.03 × material hardness HV)°. For example, when bending an HV60 copper busbar to 90°, it needs to be pre-bent to 91.5°. At the same time, a φ3-5mm stress relief hole is pre-drilled at each end of the bending line, 5-10mm away from the bending line. The distance between the center of the hole and the edge of the copper busbar is ≥2 times the hole diameter, to buffer stress. Step 5: Defect Handling: When surface cracks ≤0.1mm appear on the outer side of the copper busbar after bending, local repair welding can be performed using copper-based brazing filler metal with conductivity ≥80% IACS. The repaired or shaped copper busbar should then undergo low-temperature annealing (150±10℃, 30 minutes) to eliminate processing stress and prevent deformation or cracking due to stress release during subsequent use. After welding, grind until Ra≤6.3μm. If cracks >0.1mm deep appear on the outer side of the copper busbar, the entire section should be cut off and reprocessed. Simultaneously, when wrinkles appear on the inner side of the copper busbar, mild wrinkles (height ≤0.2T) can be gently flattened by tapping along the bending line with a copper shaping hammer. Severe wrinkles (height >0.2T) require first low-temperature annealing (180±10℃, 20-30 minutes, furnace cooling to 150℃ followed by air cooling), and then gradually shaped by applying pressure along the wrinkle direction using a hydraulic shaping machine.

2. The method for bending a copper busbar according to claim 1, characterized in that: In step 1, the copper busbar is cut to the required length according to the unfolded length of the copper busbar, and the cut end face of the copper busbar is deburred to ensure that the edge is smooth and without sharp corners, so as to prevent scratches and tip discharge.

3. The method for bending a metal copper busbar according to claim 1, characterized in that: In step 2, during the annealing of the copper busbar, it is necessary to avoid the temperature from exceeding 300°C to prevent grain coarsening. For copper busbars with a thickness ≤ 5 mm, the holding time is 8 minutes per millimeter; for copper busbars with a thickness > 5 mm, the holding time is 10 minutes per millimeter. The cooling method is to cool the busbar to 150°C in the furnace and then air cool it.

4. The method for bending a metal copper busbar according to claim 1, characterized in that: In step 2, wipe the surface of the copper busbar with a non-woven cloth or clean cotton cloth to remove oil and dust. If necessary, a special copper cleaning agent can be used, but it must be ensured that the cleaning agent has completely evaporated and leaves no residue.

5. The method for bending a copper busbar according to claim 1, characterized in that: In step 3, before bending the copper busbar, a bending line must be clearly drawn on the surface of the copper busbar to facilitate subsequent positioning. A scribing needle or an easily erasable marker can be used to ensure that it does not affect subsequent tin plating or use.

6. The method for bending a metal copper busbar according to claim 3, characterized in that: In step 3, a suitable V-shaped bending die is selected according to the thickness of the copper busbar. Specifically, for copper busbars with a thickness ≤3mm, the width of the lower die V-groove is 6-8 times the thickness of the copper busbar (T); for copper busbars with a thickness of 3-10mm, the width of the V-groove is 8-10 times the thickness of the copper busbar (T); and for copper busbars with a thickness >10mm, the width of the V-groove is 10-12 times the thickness of the copper busbar (T). This prevents an excessively small V-groove from increasing the bending force, which could lead to damage to the copper busbar or the die. An excessively large V-groove can affect the bending accuracy, resulting in larger or unstable fillet radius. At the same time, the upper die adopts an R-angle die, and the tip angle of the upper die must match the V-shape of the lower die, ensuring that the tip of the upper die is intact and free of chipping.

7. The method for bending a metal copper busbar according to claim 1, characterized in that: In step 3, the lower die is securely installed on the bending machine's worktable, ensuring it is level. The upper die is installed on the bending machine's slide block, ensuring it is secure and reliable. A level is used for calibration, and the stroke limit of the upper die's descent and the height of the lower die are adjusted so that when the upper die descends to its lowest point, there is a proper gap between the tip of the upper die and the bottom of the lower die's V-groove, maintained by the appropriate copper busbar thickness. The upper and lower dies are then ensured to be parallel using a level.

8. The method for bending a copper busbar according to claim 1, characterized in that: In step 3, the copper busbar to be bent is positioned on the bending machine's worktable, ensuring the drawn bending line is precisely aligned with the center line of the lower die's V-groove. The upper die's cutting edge contacts the copper busbar and applies pressure, causing the copper busbar to begin plastic bending deformation around the shoulder of the lower die's V-groove. The hydraulic system continuously and steadily applies pressure until the slider reaches the preset position. After reaching the preset position, the hydraulic system maintains pressure for a few seconds, thereby helping the copper busbar to undergo more complete plastic deformation, reducing springback, and stabilizing the angle.

9. The method for bending a metal copper busbar according to claim 1, characterized in that: In step 4, if the measured angle of the springback after the copper busbar is bent is less than the target angle, the target angle setting on the machine needs to be increased. If the measured angle is greater than the target angle, the target angle setting needs to be decreased, and repeated bending and adjustment should be performed until the target angle is reached.

10. A method for bending a metal copper busbar according to claim 1, characterized in that: In step 5, carefully inspect the bent copper busbar, especially the inner and outer edges of the bend and the original cut end face. Remove all burrs and sharp edges with a file, scraper, sandpaper or special deburring tool. For critical conductive components, it is necessary to measure the DC resistance of the bent and unbent sections to ensure that the bending has not caused a significant deterioration in conductivity.