Busbar multi-material resistance welding process and gradient current sharing electrode structure

Abstract

The application discloses a bus multi-material resistance welding process and a gradient current-distribution electrode structure and belongs to the technical field of resistance welding.The application integrates an electrode quick-change mechanism in a single welding station, can automatically switch a chromium-zirconium-copper inlaid tungsten-copper electrode and a graphite electrode, respectively completes two types of welding procedures of copper braided wire-copper plate and copper plate-L-shaped copper bent plate, adopts a gradient current-distribution electrode with a waist-shaped through groove on a working surface in a matched mode, realizes uniform distribution of current in a large-area welding area with a size of 21*15 mm or above, simultaneously constructs a full-process automatic production line of "welding-air knife cleaning-CCD visual detection-automatic sorting", and effectively solves problems of uneven welding current of large-area copper workpieces, low electrode change efficiency, easy interference of detection by cooling water and the like, electrode switching time is less than or equal to 5 s, the welding point drawing force is stable, the bus welding full-process unmanned operation can be realized, and production efficiency and product consistency are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of resistance welding technology, specifically relating to a multi-material resistance welding process for busbar processing, an electrode adaptive fast switching method, and a matching gradient current equalization electrode structure. Background Technology

[0002] Busbars are core conductive connectors in power transmission, new energy storage, and industrial automated power distribution systems. They are typically assembled by welding copper braided wire to copper plates, copper plates to L-shaped bent copper plates, or other copper components of the same material or various shapes. With the rapid development of the new energy and power industries, the requirements for welding quality, production efficiency, and consistency of busbars are constantly increasing.

[0003] The existing busbar resistance welding process suffers from the following technical defects: First, poor uniformity of current distribution in large-area welding areas. For copper welding surfaces of 21×15mm and above, conventional planar electrodes tend to concentrate the current towards the center, leading to overmelting at the center and insufficient fusion at the edges, resulting in defects such as incomplete welds and copper leakage, and making it difficult to guarantee the stability of pull-out force. Second, poor electrode compatibility with different welding objects and low changeover efficiency. Welding copper braided wire to copper plate requires tungsten-copper electrodes to ensure bonding strength, while welding copper plate to L-shaped bent plate requires graphite electrodes to ensure weld quality. Existing production equipment requires manual disassembly and replacement of electrodes, resulting in long changeover times, poor positioning consistency, and inability to meet the needs of continuous production at the same station. Third, low reliability of online inspection after welding. Cooling water generated during electrode water cooling during resistance welding remains on the surface of the weld, leading to a high rate of missed inspections during manual visual inspection and making full inspection impossible, easily resulting in defective products being released. Fourth, low degree of automation integration throughout the entire process. Clamping, welding, testing, and sorting rely heavily on manual processes, resulting in high labor intensity for operators. Furthermore, the intense light and heat from resistance welding can easily cause occupational injuries to the human body.

[0004] Therefore, there is a need to develop a busbar resistance welding solution that is compatible with multi-object welding, has stable weld quality, and is fully automated. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings of the prior art, the present invention aims to provide a busbar multi-material resistance welding process that enables a single workstation to be compatible with two types of welding objects, ensures uniform and stable weld quality, and achieves fully automated production. At the same time, it provides a matching gradient current equalization electrode structure to solve the problem of uneven current distribution during welding of large-area copper workpieces.

[0006] This invention is achieved through the following scheme:

[0007] 1. Busbar multi-material resistance welding process

[0008] Includes the following steps:

[0009] S1. Clamping and conveying: Position and clamp the copper braided wire, copper plate and L-shaped copper bent plate of the busbar in the tooling, and send them into the welding station through the conveyor line;

[0010] S2, First welding process: Using a chromium zirconium copper-tungsten copper upper electrode and a pure tungsten lower electrode, the tooling is moved by the XY platform to complete all resistance welding points of the copper braided wire and the copper plate in sequence.

[0011] S3. Automatic electrode switching: The upper electrode is automatically switched to a graphite electrode through the electrode quick-change mechanism integrated into the welding head, and the entire switching process is done without manual intervention.

[0012] S4. Second welding process: Using a graphite upper electrode and a pure tungsten lower electrode, the tooling is moved by the XY platform to complete all resistance welding points of the copper plate and the L-shaped copper bent plate in sequence.

[0013] S5. Cleaning and Inspection: Grab the completed busbar, first use an air knife to blow away residual cooling water and impurities on the surface of the weld joint, and then use machine vision to inspect for weld joint defects.

[0014] S6. Sorting and unloading: Based on the machine vision detection results, the busbars are automatically sorted into the good product area and the defective product area.

[0015] In step S2, the welding working surface of the chromium zirconium copper inlaid tungsten copper upper electrode has a through-groove hollow structure. The welding current is diverted through the groove and diffuses to the edge of the welding area before converging to the center, so that the current is evenly distributed in the welding area of ​​21×15mm and above, avoiding overmelting in the center and poor welding at the edge.

[0016] The specific process of automatic electrode switching in step S3 is as follows: after the upper electrode is lifted and reset, the electrode quick-change mechanism descends and unlocks the current upper electrode, then moves horizontally to the graphite electrode storage position, lifts the graphite electrode into the upper electrode seat and locks it, and finally the quick-change mechanism is reset. The time for a single electrode switching is ≤5 seconds.

[0017] In step S5, the air knife blowing time is 2-3 seconds; machine vision inspection identifies two types of solder joint defects: exposed copper and blackening, and the inspection results are transmitted to the unloading execution unit in real time to achieve 100% online full inspection.

[0018] The welding processes in steps S1 to S4 are completed in a closed welding machine. The machine integrates a resistance welding head, an electrode quick-change mechanism, and an XY moving platform. An external circulating water pump is installed on the side of the machine. The external circulating water pump is connected to the resistance welding head through an internal circulating pipeline to provide circulating cooling for the electrodes.

[0019] The electrode quick-change mechanism includes a horizontally arranged electrode exchange moving cylinder, a vertically arranged double-ended stroke cylinder, and an electrode gripper; the electrode exchange moving cylinder is connected to the electrode gripper in a transmission manner, driving the electrode gripper to move horizontally between the two work positions of the first electrode and the second electrode; the double-ended stroke cylinder is connected to an electrode locking and fixing mechanism on its side, which is used to realize the unlocking and locking actions of the electrode.

[0020] The cleaning and inspection process in step S5 is implemented by a cleaning and inspection mechanism, which includes a fixed frame on which three CCD cameras are arranged horizontally side by side. Each CCD camera is equipped with a strip light source. An air knife is arranged below the strip light source. The air knife blowing station is located upstream of the CCD camera inspection station.

[0021] 2. Gradient current sharing electrode structure

[0022] The electrode assembly includes an electrode body and a welding contact head. The top of the electrode body is integrally connected to the welding contact head. A through waist-shaped groove is provided on the side of the welding contact head along its length. The waist-shaped groove diverts the welding current, allowing the current to flow preferentially through both sides of the electrode and converge in the middle of the welding area, forming a progressive energizing path extending from the periphery to the center.

[0023] Furthermore, the electrode structure is made of chromium-zirconium copper inlaid with tungsten copper or graphite; wherein the chromium-zirconium copper inlaid with tungsten copper electrode is suitable for welding copper braided wire and copper plate, and the graphite electrode is suitable for welding copper plate and L-shaped copper bent plate. Furthermore, the working surface size of the welding contact head is suitable for welding areas of 21×15mm or larger. When used with a pure tungsten lower electrode, the pull-out force of a single-point weld between copper braided wire and copper plate is ≥1000N, and the pull-out force of a double-point weld between copper plate and L-shaped copper bent plate is ≥7000N.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. The quality and stability of the solder joints are greatly improved. The gradient current equalization electrode structure with waist-shaped through grooves effectively improves the current distribution during the welding of large-area copper workpieces, avoiding overmelting in the center and poor welding at the edges. With the matching electrode combination of corresponding materials, the single-point pull-out force of copper braided wire and copper plate can reach 1050-1200N, and the double-point pull-out force of copper plate and L-shaped bent plate can reach 7800N. There are no defects such as protrusions, copper leakage, or blackening on the surface of the solder joints, and the batch consistency is good.

[0026] 2. High process flexibility and significantly improved changeover efficiency. A single workstation integrates dual-material electrode storage and an automatic quick-change mechanism, which can automatically adapt to two different welding objects. Electrode switching time is ≤5 seconds, eliminating the need for manual disassembly and adjustment, eliminating positioning errors caused by manual changeover, and meeting the needs of continuous production.

[0027] 3. The online inspection is highly reliable. It adopts a linkage scheme of air knife pre-blowing cleaning + CCD vision inspection to completely eliminate the interference of cooling water residue on vision inspection, realize 100% online full inspection of weld defects, replace manual visual inspection, and significantly reduce the missed inspection rate.

[0028] 4. The entire process is unmanned, improving both production efficiency and safety. The entire line achieves fully automated operation of clamping and conveying, welding, electrode switching, cleaning and inspection, sorting and unloading. The number of operators has been reduced from 4 to 1, and they only need to complete the loading in the safe area. The welding and inspection processes are carried out in a closed manner, realizing human-machine isolation and eliminating occupational hazards to operators from the strong light and high heat of resistance welding. The production cycle of the entire line can reach 140 seconds / piece. Attached Figure Description

[0029] Figure 1 This is a three-dimensional structural diagram of a multi-material resistance welding device for busbars according to the present invention.

[0030] Figure 2 This is a three-dimensional schematic diagram of the electrode quick-change mechanism of a multi-material resistance welding device for busbars according to the present invention.

[0031] Figure 3 This is a three-dimensional schematic diagram of the cleaning and testing mechanism of a multi-material resistance welding device for busbars according to the present invention.

[0032] Figure 4 This is a schematic diagram of the formal structure of the cleaning and inspection mechanism of the multi-material resistance welding device for busbars according to the present invention.

[0033] Figure 5 This is a three-dimensional structural diagram of a multi-material resistance welding gradient current equalization electrode structure for a busbar according to the present invention.

[0034] In the diagram: 100, resistance welding head; 200, electrode quick-change mechanism; 201, electrode exchange moving cylinder; 202, double-end stroke cylinder; 203, first electrode; 204, second electrode; 205, electrode gripper; 206, fixing mechanism; 300, XY moving platform; 400, external circulating water pump; 401, internal circulating pipeline; 500, cleaning and inspection mechanism; 501, fixing frame; 502, light source; 503, CCD camera; 504, air knife; 1, electrode body; 2, welding contact head; 3, waist-shaped through groove. Detailed Implementation

[0035] The following is combined with Figure 1-5 The present invention will be further described, but the scope of protection of the present invention is not limited to the contents described herein.

[0036] This embodiment provides a complete automated resistance welding device and supporting process for busbar products containing copper braided wire, copper plate, and L-shaped copper bent plate. The whole device consists of four core units: welding host, electrode quick change mechanism, cleaning and inspection mechanism, and gradient current equalization electrode. The structure and implementation process are described below with reference to the accompanying drawings.

[0037] I. Overall Device Structure

[0038] like Figure 1 As shown, the multi-material resistance welding device of the present invention mainly consists of a welding host unit, a cooling unit, a cleaning and inspection unit, and a material sorting unit. All welding processes are carried out within a closed protective cover, achieving human-machine isolation. The welding host unit is set on the machine table and includes a resistance welding head 100, an electrode quick-change mechanism 200, and an XY moving platform 300. The resistance welding head 100 is vertically arranged and is used to output welding pressure and welding current. The electrode quick-change mechanism 200 is integrated and installed on the side of the resistance welding head 100 to achieve fully automatic switching between electrodes of two materials. The XY moving platform 300 is set directly below the welding head and is used to support the welding fixture and move the workpiece precisely between each welding point. An external circulating water pump 400 is set on the side of the machine table. The external circulating water pump 400 is connected to the internal cooling channel of the resistance welding head 100 through an internal circulating pipeline 401 to provide circulating water cooling for the upper and lower electrodes, reducing the electrode wear rate caused by high welding temperatures. The machine entrance connects to the tooling conveyor line, and the exit side is equipped with a six-axis robot, which connects to the 500 cleaning and inspection mechanism and the good and bad product bins to realize the automatic transfer and sorting of workpieces.

[0039] II. Electrode Quick-Change Mechanism Structure

[0040] like Figure 2As shown, the electrode quick-change mechanism 200 specifically includes an electrode exchange moving cylinder 201, a double-ended stroke cylinder 202, a first electrode 203, a second electrode 204, an electrode gripper 205, and a fixing mechanism 206. The electrode exchange moving cylinder 201 is horizontally fixed, and its moving end is connected to the electrode gripper 205, allowing the electrode gripper 205 to reciprocate horizontally between the first electrode 203 storage position and the second electrode 204 storage position. In this embodiment, the first electrode 203 is a chromium zirconium copper-tungsten copper electrode, suitable for welding copper braided wire and copper plate; the second electrode 204 is a graphite electrode, suitable for welding copper plate and L-shaped copper bent plate. The double-ended stroke cylinder 202 is vertically disposed on the side of the upper electrode holder, and its side is connected to the fixing mechanism 206. Through the extension and retraction of the double-ended stroke cylinder 202, the fixing mechanism 206 is driven to unlock and lock the electrodes within the electrode holder. When switching electrodes, the electrode gripper 205 holds the electrode to complete the picking, placing and repositioning. With the locking action of the fixing mechanism 206, the switching between two types of electrodes can be achieved automatically without manual intervention. The time for a single switch is ≤5 seconds.

[0041] III. Structure of Cleaning Testing Organization

[0042] The structure of the cleaning testing agency is viewed from a three-dimensional perspective. Figure 3 ) and facing the perspective ( Figure 4 The cleaning and inspection mechanism 500 includes a mounting frame 501, a strip light source 502, a CCD camera 503, and an air knife 504. As shown in Figure 3, the mounting frame 501 is a vertical gantry frame structure, serving as the mounting base for the entire inspection unit. Three CCD cameras 503 are horizontally mounted side-by-side on the upper part of the mounting frame 501, with a set of strip light sources 502 corresponding to the lower part of each CCD camera 503, providing a uniform and stable lighting environment for weld joint inspection and improving the accuracy and stability of defect identification. Figure 3 and Figure 4 As can be seen, an air knife 504 is installed below the bar light source 502 and at the entrance of the inspection station. The air outlet of the air knife 504 is directly facing the workpiece transfer path. When the workpiece is picked up by the robot and passes through the inspection area from bottom to top, it is first blown away by the air knife 504 to remove residual cooling water and metal debris from the surface of the weld joint, and then enters the field of view of the CCD camera 503. This can completely eliminate the interference of liquid residue on visual inspection and avoid false detection and missed detection.

[0043] IV. Gradient Current Equalizing Electrode Structure

[0044] like Figure 5As shown, the gradient current equalization electrode of this invention includes an electrode body 1 and a welding contact head 2. The upper part of the electrode body 1 and the welding contact head 2 are integrally formed. The tail of the electrode body 1 is provided with a standard tapered mounting interface, which can be quickly embedded into the electrode seat of the welding head to achieve precise positioning and reliable conductivity. The welding contact head 2 has through waist-shaped grooves 3 on both sides along its length. The waist-shaped grooves 3 extend along the length of the working surface, hollowing out the middle solid of the welding contact head 2 and retaining only the symmetrical conductive paths on both sides. When the electrode is pressed down and energized, the welding current cannot pass directly from the center of the electrode and is forced to split to both sides of the electrode. It is conducted to the edge of the welding area through the conductive paths on both sides and then converges back to the center of the welding area, forming a current path that gradually advances from the periphery to the center. This results in a uniform current density distribution within the 21×15mm welding area, avoiding overmelting and erosion caused by current concentration in the center, while ensuring sufficient fusion in the edge area and eliminating defects such as incomplete welding. This electrode structure can be made of two materials: chromium zirconium copper inlaid with tungsten copper and graphite. It is used with a unified pure tungsten bottom electrode and is suitable for two different welding processes.

[0045] V. Complete Process Implementation Steps

[0046] Based on the above apparatus, the complete welding process flow of this embodiment is as follows:

[0047] Step 1: Clamping and Conveying

[0048] Operators place copper braided wire, copper plate, and L-shaped copper bent plate into the tooling groove in the loading area outside the safety gate according to the positioning requirements. They then start the clamping cylinder. After the cylinder is ventilated, the pressure is maintained by the induction check valve to prevent the workpiece from shifting during the conveying process. The conveyor line then automatically sends the tooling onto the XY moving platform 300 in the enclosed welding station.

[0049] Step 2: Welding copper braided wire to copper plate

[0050] The XY moving platform 300 moves the tooling directly beneath the first welding point. The pure tungsten lower electrode rises, while the chromium-zirconium-copper tungsten-inlaid copper upper electrode presses down with the welding head, pressing the copper braided wire and the copper plate together to the set welding pressure. Resistance welding is then performed, with welding current, energizing time, and electrode pressure all optimized and matched through pre-testing. After each welding point is completed, the XY moving platform 300 moves to the next welding point along a preset path, repeating the welding action until all connections between the copper braided wire and the copper plate are completed.

[0051] Step 3: Automatic switching of upper electrode

[0052] After all braided wire welding points are completed, the welding head is raised and reset; the electrode quick-change mechanism 200 is activated: the double-end stroke cylinder 202 drives the fixing mechanism 206 to unlock the current chromium zirconium copper inlaid tungsten copper electrode, the electrode gripper 205 descends to hold the electrode, and the electrode exchange moving cylinder 201 drives the gripper to move horizontally to the graphite electrode storage position; after the gripper puts down the original electrode, it holds the graphite electrode, moves horizontally back to directly below the upper electrode seat, lifts up to embed the graphite electrode into the electrode seat, the fixing mechanism 206 locks, the quick-change mechanism resets, and the electrode material switching is completed. The entire switching process takes about 4 seconds.

[0053] Step 4: Welding the copper plate to the L-shaped bent plate

[0054] After the electrode switching is completed, the XY moving platform 300 moves the tooling to the welding point position of the L-shaped bending plate, the lower electrode is lifted, the upper graphite electrode is pressed down to clamp the workpiece, and the resistance welding of the copper plate and the L-shaped copper bending plate is completed by powering on. After all welding points are processed, the XY moving platform 300 moves the tooling to the unloading station.

[0055] Step 5: Cleaning and Visual Inspection

[0056] A six-axis robot picks up the welded busbar and moves it to the area below the cleaning and inspection unit 500. The robot then moves the product at a constant speed in front of the air knife 504, blowing for approximately 2.5 seconds to thoroughly remove residual cooling water and metal debris from the weld joint surface. Next, the robot moves the product upwards at a constant speed through the inspection field of view of the CCD camera 503. Three cameras, each corresponding to a different area of ​​the weld joint, simultaneously acquire images and identify two types of defects: exposed copper (abnormal metallic luster) and blackening (excessive oxidation). The inspection data is transmitted in real time to the robot control system, recording the quality assessment result for each product.

[0057] Step 6: Automatic sorting and unloading

[0058] Based on the inspection results, the robot discharges the products judged as good into the good product bin and puts the products judged as defective into the defective product bin, thus completing the entire process of processing a single product.

[0059] VI. Process Validation Results

[0060] After batch trial production verification, the process of this embodiment achieves the following effects:

[0061] Welding strength: The measured single-point pull-out force between the copper braided wire and the copper plate is 1050N-1200N, which meets the requirement of ≥1000N; the measured double-point pull-out force between the copper plate and the L-shaped bent plate is 7800N, which meets the requirement of ≥7000N.

[0062] Solder joint appearance: The solder joint surface is flat, without defects such as central overmelting protrusion, edge copper leakage, oxidation and blackening, and the batch consistency is good.

[0063] Production cycle time: The processing cycle time for a single piece on the entire line is approximately 140 seconds. A single workstation can accommodate two types of welding processes without requiring manual changeovers during downtime.

[0064] Personnel and Safety: The entire line requires only one operator to be responsible for material loading. Welding, inspection and sorting are all unmanned, realizing human-machine isolation and effectively eliminating occupational hazards caused by strong welding light and high heat.

[0065] Although the technical solutions of the present invention have been described and enumerated in detail, it should be understood that modifications to the above embodiments or the adoption of equivalent alternatives are obvious to those skilled in the art. Such modifications or improvements made without departing from the spirit of the present invention are all within the scope of protection claimed by the present invention.

Claims

1. A multi-material resistance welding process for busbars, characterized in that, include: S1. Clamping and conveying: Position and clamp the copper braided wire, copper plate and L-shaped copper bent plate of the busbar in the tooling, and send them into the welding station through the conveyor line; S2, First welding process: Using a chromium zirconium copper inlaid tungsten copper upper electrode and a pure tungsten lower electrode, the tooling is moved by the XY platform to complete all resistance welding points of the copper braided wire and the copper plate in sequence. S3. Automatic electrode switching: The upper electrode is automatically switched to a graphite electrode through the electrode quick-change mechanism integrated into the welding head, and the entire switching process is done without manual intervention. S4. Second welding process: Using a graphite upper electrode and a pure tungsten lower electrode, the tooling is moved by the XY platform to complete all resistance welding points of the copper plate and the L-shaped copper bent plate in sequence. S5. Cleaning and Inspection: Grab the completed busbar, first use an air knife to blow away residual cooling water and impurities on the surface of the weld joint, and then use machine vision to inspect for weld joint defects. S6. Sorting and unloading: Based on the machine vision detection results, the busbars are automatically sorted into the good product area and the defective product area.

2. The multi-material resistance welding process for busbars according to claim 1, characterized in that, In step S2, the welding working surface of the chromium zirconium copper inlaid tungsten copper upper electrode has a through-groove hollow structure. The welding current is diverted through the groove and diffuses to the edge of the welding area before converging to the center, so that the current is evenly distributed in the welding area of ​​21×15mm and above, avoiding overmelting in the center and poor welding at the edge.

3. The multi-material resistance welding process for busbars according to claim 2, characterized in that, The specific process of automatic electrode switching in step S3 is as follows: after the upper electrode is lifted and reset, the electrode quick-change mechanism descends and unlocks the current upper electrode, then moves horizontally to the graphite electrode storage position, lifts the graphite electrode into the upper electrode seat and locks it, and finally the quick-change mechanism is reset. The time for a single electrode switching is ≤5 seconds.

4. The multi-material resistance welding process for busbars according to claim 2, characterized in that, In step S5, the air knife blowing time is 2-3 seconds; machine vision inspection identifies two types of solder joint defects: exposed copper and blackening, and the inspection results are transmitted to the unloading execution unit in real time to achieve 100% online full inspection.

5. The multi-material resistance welding process for busbars according to claim 2, characterized in that, The welding processes in steps S1 to S4 are completed in a closed welding machine. The machine integrates a resistance welding head (100), an electrode quick-change mechanism (200), and an XY moving platform (300). An external circulating water pump (400) is provided on the side of the machine. The external circulating water pump (400) is connected to the resistance welding head (100) through an internal circulating pipeline (401) to provide circulating cooling for the electrode.

6. The multi-material resistance welding process for busbars according to claim 2, characterized in that, The electrode quick-change mechanism (200) includes a horizontally arranged electrode exchange moving cylinder (201), a vertically arranged double-ended stroke cylinder (202), and an electrode gripper (205). The electrode exchange moving cylinder (201) is connected to the electrode gripper (205) in a transmission manner, driving the electrode gripper (205) to move horizontally between the two work positions of the first electrode (203) and the second electrode (204). The double-ended stroke cylinder (202) is connected to an electrode locking and fixing mechanism (206) on its side, which is used to realize the unlocking and locking action of the electrode.

7. The multi-material resistance welding process for busbars according to claim 2, characterized in that, The cleaning and inspection process in step S5 is implemented by a cleaning and inspection mechanism (500). The cleaning and inspection mechanism (500) includes a fixed frame (501). Three CCD cameras (503) are arranged horizontally side by side on the fixed frame (501). Each CCD camera (503) is equipped with a strip light source (502). An air knife (504) is arranged below the strip light source (502). The air knife blowing station is located upstream of the CCD camera (503) inspection station.

8. A gradient current-equalizing electrode structure for resistance welding of multi-material busbars, characterized in that, It includes an electrode body (1) and a welding contact head (2). The top of the electrode body (1) is integrally connected to the welding contact head (2). The welding contact head (2) has a through waist-shaped groove (3) on its side along the length direction. The waist-shaped groove (3) allows the welding current to form a power path that gradually progresses from the edge to the center.

9. A gradient current-equalizing electrode structure for multi-material resistance welding of busbars according to claim 8, characterized in that, The electrode structure is made of chromium zirconium copper inlaid with tungsten copper or graphite; wherein the chromium zirconium copper inlaid with tungsten copper electrode is suitable for the welding process of copper braided wire and copper plate, and the graphite electrode is suitable for the welding process of copper plate and L-shaped copper bent plate.

10. A gradient current-equalizing electrode structure for multi-material resistance welding of busbars according to claim 8, characterized in that, The working surface size of the welding contact head (2) is adapted to welding areas of 21×15mm and above. When used with a pure tungsten lower electrode, the pull-out force of a single-point welding between the copper braided wire and the copper plate is ≥1000N, and the pull-out force of a double-point welding between the copper plate and the L-shaped copper bent plate is ≥7000N.

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