Aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite tape and preparation method thereof

Abstract

A copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strip and its preparation method are disclosed, relating to the field of cable connector manufacturing technology. The method includes material preparation, cutting, forming, and post-processing steps. Using a copper-aluminum composite strip prepared with eutectic technology as the substrate, an integrated copper-aluminum transition terminal is directly fabricated using forming processes such as rolling and bending. This replaces the traditional separate copper-aluminum friction-welded structure, greatly simplifying the manufacturing process and reducing equipment investment, lowering the unit manufacturing cost to 50%~60% of that of friction-welded terminals. This aluminum alloy cable copper-aluminum transition terminal has no welding interface, completely eliminating electrochemical corrosion. The process is simplified, costs are controllable, and the connection is reliable with a long service life, making it highly valuable for applications.

Description

Technical Field

[0001] This invention relates to the field of cable connector manufacturing technology, and more specifically, to an aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite strip and its manufacturing method. Background Technology

[0002] With the price of electrolytic copper remaining high, the copper-aluminum price ratio has exceeded 4.3:1, far surpassing the critical threshold of 3.8:1 for large-scale substitution. Aluminum alloy cables, with their significant cost advantages and excellent conductivity, are experiencing accelerated large-scale adoption in power distribution networks, new energy projects, and other fields. This large-scale promotion of aluminum alloy cables has created an urgent demand for their matching connectors.

[0003] Aluminum alloy cable connections must use copper-aluminum transition terminals to avoid problems such as electrochemical corrosion and thermal expansion mismatch that occur with direct copper-aluminum connections. Currently available copper-aluminum transition terminals use aluminum for the aluminum alloy cable connector and copper for the copper connector, with the two ends connected using a friction welding process. However, existing friction-welded copper-aluminum transition terminals have the following technical drawbacks: The process is complex and costly: friction welding requires specialized welding equipment and strict process control, especially for large cross-sections (120mm²). 2 (Above) Terminals, due to limitations in the power of friction welding equipment and the difficulty of process control, have a low yield; S2 Welding surface is prone to failure: During long-term service, the copper-aluminum welding interface is subject to the dual effects of thermal cycling stress and electrochemical corrosion, which poses a risk of corrosion cracking. In particular, the difference in the thermal expansion coefficients of copper and aluminum (the thermal expansion coefficient of aluminum is about 36% higher than that of copper) can cause stress concentration at the interface, affecting service life; S3 Stamping process affects welding quality: Traditional copper-aluminum transition terminals require stamping after friction welding. During the stamping process, micro-cracks that are not easily detected may occur on the welding surface, reducing conductivity.

[0004] On the other hand, breakthroughs have been made in eutectic technology for copper-aluminum composite plates / strips / tubes in recent years. Using a solid-liquid casting and rolling process, precise control of the eutectic structure at the copper-aluminum interface has been achieved, forming a eutectic structure with a thickness of 300-500 nm. Its peel strength can reach over 100 MPa, conductivity is close to that of pure copper, and density is only 45% of pure copper. Copper-aluminum eutectic plates / strips combine the good conductivity of copper with the lightweight and low-cost advantages of aluminum, and have already seen initial applications in fields such as power busbar trunking and overhead conductors. For example, Chinese patent CN115764346A discloses a copper-aluminum eutectic transition clamp and its preparation method. It uses induction brazing to form a joint structure of Cu-Al eutectic and CuAl2 brittle phases between the copper and aluminum plates, achieving high joint strength and corrosion resistance. However, this solution uses a flat-to-flat welding structure and does not involve a technical solution for manufacturing terminals from copper-aluminum eutectic composite strips through rolling, bending, or other forming processes.

[0005] It is worth noting that when copper-aluminum eutectic composite strips are rolled into tubular structures with an aluminum layer on the inner surface and a copper layer on the outer surface, a key technical problem that has not been addressed in existing technologies is encountered: due to the significant differences in the elastic modulus (approximately 110 GPa for copper and approximately 69 GPa for aluminum) and yield strength between the copper and aluminum layers, during the rolling and bending process, the copper layer is on the outer side and the aluminum layer is on the inner side. The different deformation along the arc length leads to interlaminar shear stress and radial delamination tendency at the eutectic interface. If the interfacial bonding strength is insufficient to resist this stress, or if the rolling process parameters are inappropriate, the rolling process may induce microcracks at the interface, which can then expand into macroscopic delamination failure during subsequent pressing deformation and thermal cycling. Therefore, not any copper-aluminum composite plate can be simply "rolled" into a reliable terminal—interfacial mechanical compatibility is a crucial prerequisite for success. Existing technologies (including CN115764346A) do not address the interfacial shear control problem in this bending and forming scenario.

[0006] In conclusion, developing a copper-aluminum transition terminal for aluminum alloy cables that is simple to manufacture, low in cost, reliable in connection, and can effectively solve the problem of stress at the coiling interface has significant engineering application value and market prospects. Summary of the Invention

[0007] The purpose of this invention is to provide a copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strip and its preparation method. The process is simple, the cost is low, and it also has good connection reliability.

[0008] The embodiments of the present invention are implemented as follows: A method for preparing a copper-aluminum transition terminal for an aluminum alloy cable based on a eutectic copper-aluminum composite strip, comprising the following steps: S1. Material preparation: Select copper-aluminum composite strip prepared by eutectic technology. One surface of the composite strip is a copper layer and the opposite surface is an aluminum layer. The copper layer and the aluminum layer are metallurgically bonded by a continuous Cu-Al eutectic structure with a thickness of 200~800nm, and the interface peel strength is not less than 100MPa. S2. Cutting: Cut the copper-aluminum composite strip into blanks according to the preset size of the required terminals; S3. Forming: The cut blank is rolled into a tubular structure using a rolling die; S4. Post-processing: Trim and deburr the formed terminals.

[0009] A copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strip is prepared by the above-mentioned preparation method. The terminal is formed by rolling the copper-aluminum composite strip into at least one tubular structure, the inner surface of which is an aluminum layer and the outer surface is a copper layer.

[0010] The beneficial effects of the embodiments of the present invention are: This invention provides an aluminum alloy cable copper-aluminum transition terminal based on a eutectic copper-aluminum composite strip and its preparation method. The method includes material preparation, cutting, forming, and post-processing steps. Using a copper-aluminum composite strip prepared with eutectic technology as the substrate, an integrated copper-aluminum transition terminal is directly fabricated using forming processes such as rolling and bending. This replaces the traditional separate copper-aluminum friction-welded structure, greatly simplifying the manufacturing process and reducing equipment investment, lowering the unit manufacturing cost to 50%~60% of that of friction-welded terminals. This aluminum alloy cable copper-aluminum transition terminal has no welding interface, completely eliminating electrochemical corrosion. The process is simplified, costs are controllable, and the connection is reliable with a long service life, making it highly valuable for applications. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the copper-aluminum transition terminal of the aluminum alloy cable provided in Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view from a first perspective of the copper-aluminum transition terminal of the aluminum alloy cable provided in Embodiment 1 of the present invention. Figure 3 This is a cross-sectional view from a second perspective of the copper-aluminum transition terminal of the aluminum alloy cable provided in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the composite tape provided in an embodiment of the present invention.

[0013] Icons: 100 - Aluminum alloy cable copper-aluminum transition terminal; 101 - Composite strip; 102 - Copper layer; 103 - Aluminum layer; 104 - Eutectic structure layer; 110 - Tubular structure; 111 - Inner hole; 120 - Flat strip structure; 121 - Connection hole. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0015] The following is a detailed description of a method for preparing a copper-aluminum transition terminal for an aluminum alloy cable based on a eutectic copper-aluminum composite strip, according to an embodiment of the present invention.

[0016] This invention provides a method for preparing a copper-aluminum transition terminal for an aluminum alloy cable based on a eutectic copper-aluminum composite strip, comprising the following steps: S1. Material preparation: Select copper-aluminum composite strip prepared by eutectic technology. One surface of the composite strip is a copper layer and the opposite surface is an aluminum layer. The copper layer and the aluminum layer are metallurgically bonded by a continuous Cu-Al eutectic structure with a thickness of 200~800nm, and the interface peel strength is not less than 100MPa. S2. Cutting: Cut the copper-aluminum composite strip into blanks according to the preset size of the required terminals; S3. Forming: The cut blank is rolled into a tubular structure using a rolling die; S4. Post-processing: Trim and deburr the formed terminals.

[0017] Currently available copper-aluminum transition terminals use aluminum for the aluminum alloy cable connector and copper for the copper connector, with the two ends connected via friction welding. This method is not only complex and costly, but also prone to weld failure and has a short lifespan.

[0018] This invention achieves integrated connection of copper and aluminum transition parts by using an integral structure formed by rolling copper-aluminum composite strip in one piece and without separate welding interfaces. This eliminates the inherent defects of friction welding terminals, such as easy corrosion and cracking of the welding interface and unstable contact resistance.

[0019] Furthermore, the interface of the copper-aluminum composite strip used features a continuous Cu-Al eutectic structure of 200~800nm, ensuring that the copper and aluminum are metallurgically bonded rather than mechanically interlocked. The eutectic structure possesses a uniform microstructure and excellent interfacial bonding force; a peel strength ≥100MPa means that even under shear stress generated by rolling and bending, the interface will not separate. Simultaneously, this nanoscale thickness ensures the toughness of the interface layer itself, preventing interface cracking caused by excessively thick brittle phases (such as CuAl2). Subsequent cutting, shaping, and post-processing steps constitute a complete process chain, ensuring full controllability from material to finished product.

[0020] Further, in step S3, the forming includes: rolling one end of the blank into a tubular cable connector and bending and flattening the other end to form a flat copper terminal connector and machining a connection hole, or cutting the blank into strip blanks according to the required pipe diameter and then directly rolling it into a tubular terminal body.

[0021] The two forming processes described above are applicable to both crimp-type and insert-type terminal structures, respectively. The first approach (rolling one end of the tube + bending and flattening the other end + punching) utilizes the flexibility of the copper-aluminum composite strip. With simple mold changes, two functional parts can be processed from the same blank, and the inner aluminum and outer copper layer structure is maintained after bending and flattening, ensuring that both sides are in contact with the same metal. The second approach (directly rolling the tube after cutting to the diameter) controls the tube diameter by adjusting the cutting width; the rolled product is the finished product, making the process simpler. Both approaches share the same material preparation and post-processing steps, demonstrating the versatility and flexibility of the methods.

[0022] Further, in step S3, the rolling process includes: preheating the billet to 60~180℃ before rolling, and completing the rolling in at least two passes using a progressive rolling process, ensuring that the pipe diameter D and the total thickness t of the composite strip after rolling satisfy D / t≥8. Due to the difference in elastic modulus between copper and aluminum (copper≈110GPa, aluminum≈69GPa), the neutral layer shifts during bending, causing the outer side of the copper layer to elongate and the inner side of the aluminum layer to compress, generating shear stress along the arc direction at the eutectic interface. If not controlled, this stress may exceed the interfacial bonding strength, initiating microcracks. Preheating can reduce the yield strength of copper and aluminum, especially softening the aluminum layer in advance, reducing bending springback force, thereby reducing the peak shear value at the interface. Preheating also promotes the homogenization of residual stress at the interface. The progressive rolling process in at least two passes avoids stress concentration caused by a single sharp bend. Each pass only produces partial bending deformation, allowing the interface to gradually adapt to the curvature change, releasing and redistributing stress. D / t≥8 is a geometric compatibility constraint. The larger the tube diameter D relative to the total thickness t of the composite strip, the smaller the bending curvature and the lower the shear strain at the interface. A D / t ≥ 8 effectively limits the maximum bending strain within the material's tolerance range, ensuring no plastic damage occurs at the interface. This process effectively suppresses interlaminar shear stress and radial peeling at the copper-aluminum interface during rolling, prevents micro-cracks at the interface, and improves product quality.

[0023] Further, in step S3, after rolling and forming, the joints of the tubular structure are reinforced by welding or riveting, and / or subjected to low-temperature stress relaxation treatment at 120~180℃ for 15~30 minutes. After rolling and forming, the tubular structure has two potential weak points: first, the longitudinal joint (the butt joint of the blank edge) may open during pressing; second, the residual stress from rolling may slowly release during long-term service, leading to interfacial creep separation. By reinforcing the joints by welding or riveting, the open edge of the tubular structure can be fixed into a closed ring shape. During subsequent pressing, the circumferential tension is borne by the joint, and the eutectic interface is no longer under tension but under compression (the radial pressure generated by pressing is converted into circumferential compression).

[0024] It should be noted that the temperature of the aforementioned low-temperature stress relaxation treatment is much lower than the copper-aluminum eutectic temperature and will not change the interfacial microstructure. At this temperature, the residual bending stress inside the material is gradually released through atomic diffusion and dislocation movement, allowing the tubular structure to reach a more stable stress state. After treatment, the terminals are less prone to deformation or interfacial separation due to stress release during use.

[0025] Furthermore, in step S3, when the tube is rolled into a tubular terminal body, axial slots are machined on its wall, and / or axial ribs or knurling are machined on its outer surface. Insert-type terminals rely on the frictional contact between the outer wall of the tube and the inner hole of the device for conductivity and fixation. If the tube is a rigid cylinder, insertion may be too loose or too tight due to dimensional deviations; if the outer surface is smooth, the contact resistance may be too high and the vibration resistance poor. Therefore, it is necessary to increase elastic compensation and micro-interlocking structure by machining axial slots, ribs, or knurling.

[0026] This invention also provides a copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strip, which is prepared by the above-described preparation method. The terminal is formed by rolling the copper-aluminum composite strip into at least one tubular structure, the inner surface of which is an aluminum layer and the outer surface is a copper layer.

[0027] This product is a one-piece rolled molding component without any welding marks. The inner aluminum and outer copper layer structure determines its connection method: when the cable is inserted into the conduit, the aluminum layer contacts the aluminum conductor, forming a homogeneous metal press-fit; the copper layer on the outer wall of the conduit contacts the copper equipment terminal, forming a homogeneous metal fastening. This "double homogeneous metal contact" design completely eliminates the driving force of electrochemical corrosion (galvanic cell effect) and avoids stress concentration caused by differences in thermal expansion coefficients. Because there is no welding interface, there is no welding heat-affected zone or welding defects, resulting in overall mechanical strength and conductivity uniformity superior to traditional friction-welded terminals.

[0028] Furthermore, the copper layer thickness of the copper-aluminum composite strip accounts for 10% to 40% of the total thickness of the composite strip. The proportion of copper layer thickness directly affects the conductivity, cost, and rolling processability of the terminals. If the proportion is too low, the contact resistance of the copper terminals will be too high; if the proportion is too high, the cost will increase and bending will be difficult. At the above proportion, a better balance can be achieved in terms of conductivity, cost, and processability.

[0029] Furthermore, one end of the tubular structure is integrally connected to a flat strip structure. This flat strip structure is formed by bending and flattening the other end of a copper-aluminum composite strip, and has at least one connecting hole. The outer surface of the flat strip structure is a copper layer, and the inner surface is an aluminum layer. One end of the copper-aluminum composite strip is rolled into a tube (cable connection part), and the other end is bent and flattened into a flat shape (copper terminal connection part), with the two naturally connected through a transition area. After bending and flattening, the flat part still maintains the "outer copper, inner aluminum" layered structure: the outer copper layer faces the copper busbar, forming copper-copper contact when the bolt is tightened; the inner aluminum layer faces inward and does not contact any conductor, thus avoiding the introduction of dissimilar metals. The connecting hole is used for bolts to pass through, achieving mechanical fastening and electrical connection with the copper busbar. This design allows a single part to perform both connection functions without the need for additional adapters.

[0030] Furthermore, after the tubular structure is rolled into shape, its joints are sealed by welding or riveting. This sealing structure simultaneously restrains the radial peeling tendency of the copper-aluminum interface that occurs during the rolling process. This sealing structure acts as a mechanical constraint: when radial pressure is applied by the crimping clamps, the tube tends to expand outward, but the sealing point at the joint restricts this expansion, causing circumferential tensile stress in the tube. This circumferential tensile stress is mainly borne by the joint, while the eutectic interface is almost unaffected by tensile stress and mainly bears compressive stress (from radial compression). Since the compressive strength of the interface is much higher than its tensile strength, this stress conversion greatly reduces the risk of interface failure.

[0031] Furthermore, the tubular structure is an integral tubular terminal body. The outer diameter of this tubular terminal body matches the inner hole or insertion interface diameter of the terminal wiring end. Its inner hole is used to accommodate and connect the aluminum alloy cable conductor. An axial slot is formed on the wall of the tubular terminal body, and / or one or more axial ribs or knurling are provided on the copper layer of its outer surface. Insertion terminals need to simultaneously meet the contradictory requirements of easy insertion and reliable contact after insertion. Rigid tubular bodies are difficult to satisfy both simultaneously, therefore, elastic deformation capacity and surface microstructure need to be introduced through the above processing methods.

[0032] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0033] Example 1

[0034] This embodiment provides a copper-aluminum transition terminal 100 for aluminum alloy cables based on eutectic copper-aluminum composite strip. The structure of the aluminum alloy cable copper-aluminum transition terminal 100 is as follows: Figures 1-3 As shown, one end has a cylindrical tubular structure 110, with an aluminum layer 103 on the inner surface and a copper layer 102 on the outer surface. The diameter of the inner hole 111 of the tubular structure 110 matches the outer diameter of the aluminum alloy cable conductor to be connected. The other end is a flat strip structure 120, which also maintains the layered distribution of the aluminum layer 103 on the inside and the copper layer 102 on the outside. A circular connecting hole 121 is located at the center of the flat strip structure 120, with a diameter matching the specifications of the fastening bolt for the terminal copper connector. The transition area between the flat strip structure 120 and the tubular structure 110 must be smooth to avoid stress concentration.

[0035] Its preparation method is as follows: S1. Material Preparation The copper-aluminum eutectic composite strip (model SM-CuAl-E202) produced by Ningbo Shenma Group was selected and prepared using a solid-liquid casting and rolling process. Figure 4As shown, the total thickness of the composite strip 101 is 2.0 mm, of which the copper layer 102 is 0.4 mm thick (accounting for 20%) and the aluminum layer 103 is 1.6 mm thick (accounting for 80%). A continuous Cu-Al eutectic layer 104 is formed between the copper and aluminum layers. The average thickness of the eutectic layer is 350 nm as measured by scanning electron microscopy, and the interfacial peel strength is 128 MPa as tested by the T-peel method, which meets the requirement of ≥100 MPa.

[0036] S2. Cutting Cut the composite tape 101 into rectangular blanks with dimensions of 80mm in length and 30mm in width (adjusted according to the required terminal specifications; in this embodiment, 185mm is used). 2 Aluminum alloy cable).

[0037] S3. Molding (3a) Preheating: Place the billet in an oven and heat it to 120°C. Keep it warm for 10 minutes to preheat the billet evenly.

[0038] (3b) Rolling the tubular cable connector: One end of the preheated blank is fed into a three-point progressive rolling die, and the rolling is completed in two passes: the first pass bends at an angle of approximately 45°, and the second pass bends to close the connection. After rolling, the inner diameter of the tubular structure 110 is 18.5 mm (matching the outer diameter of the 185 mm² cable conductor), and the outer diameter is 22.5 mm. The calculated D / t = 18.5 / 2.0 = 9.25 satisfies D / t ≥ 8. The inner surface of the tubular structure 110 is an aluminum layer 103, and the outer surface is a copper layer 102.

[0039] (3c) Bending and flattening to form a flat connecting part: The other end of the blank is pressed into a flat strip structure 120 in a bending die, with an inner corner radius of 4mm (≥2 times the total thickness of the composite strip), keeping the inner surface as an aluminum layer 103 and the outer surface as a copper layer 102. A connecting hole 121 with a diameter of 10.5mm is punched at the center of the flat part.

[0040] (3d) Joint welding: The longitudinal joints of the tubular structure 110 are sealed by resistance spot welding with a weld spacing of 5mm and a weld diameter of 2mm. After welding, the joints are checked to ensure they are firm and free of cracks.

[0041] S4. Post-processing The formed terminals were placed in an oven for low-temperature stress relaxation treatment: the temperature was 150℃, the temperature was maintained for 20 minutes, and then the terminals were allowed to cool naturally to room temperature. Subsequently, deburring and trimming were performed, and a conductive anti-corrosion coating (approximately 5μm thick) was applied to the surface of the terminals.

[0042] S5. Finished Product Structure The resulting terminals are of a single, integrated structure with no solder joints. The cable connector is tubular, with an inner aluminum and an outer copper casing; the copper terminal connector is a flat strip, with an outer copper casing and an inner aluminum casing, and includes a connection hole; the two are smoothly connected via a transition area.

[0043] Example 2

[0044] This embodiment provides a copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strips, and its preparation method is as follows: S1. Material Preparation The same copper-aluminum eutectic composite strip as in Example 1 was used, with a total thickness of 1.5 mm, a copper layer thickness of 0.3 mm (accounting for 20%), and an aluminum layer thickness of 1.2 mm. The average thickness of the eutectic structure layer was 380 nm, and the interfacial peel strength was 132 MPa.

[0045] S2. Cutting Cut the composite tape into strip blanks according to the required pipe diameter, with a width of 62mm (corresponding to the calculated unfolded width of the tubular terminal with an outer diameter of 20mm and an inner diameter of 17mm). The blank length is 40mm.

[0046] S3. Molding (3a) Preheating: Heat the strip billet to 100°C and keep it warm for 5 minutes.

[0047] (3b) Rolling the tubular terminal body: A roller-type rolling die is used for progressive rolling in three passes: the first pass rolls to a semicircle (bending angle of approximately 180°), the second pass rolls to approximately 300°, and the third pass rolls to a closed shape. After rolling, the outer diameter of the tubular terminal body is 20.0 mm, and the inner diameter is 17.0 mm. The calculated D / t = 17.0 / 1.5 = 11.3, which satisfies D / t ≥ 8. The outer surface of the tubular terminal body is a copper layer, and the inner surface is an aluminum layer.

[0048] (3c) Processing axial gap: Cut a gap with a width of 0.3mm and a length of 30mm on one side of the tube wall of the tubular terminal body to give the tube body the ability to elastically shrink.

[0049] (3d) Machining axial ribs: On the copper layer on the outer surface of the tubular terminal body, three axial ribs are uniformly machined in the circumferential direction. The ribs are 0.2mm high, 0.5mm wide, and 25mm long.

[0050] (3e) Joint treatment: Since this embodiment is an insert-type terminal, the joint is not welded and sealed, and the gap structure is retained to maintain elasticity.

[0051] S4. Post-processing The terminals were placed in an oven for low-temperature stress relaxation treatment: temperature 160℃, held for 15 minutes. After cooling, the burrs were removed, the surface was trimmed, and an anti-oxidation coating was applied.

[0052] S5. Finished Product Structure The resulting terminal is a monolithic tubular structure with a copper outer surface and three axial ribs, and an aluminum inner surface. An axial slit is cut into one side of the tubular wall. In use, the aluminum alloy cable conductor is inserted into the inner hole (aluminum-aluminum contact), and then the monolithic tubular terminal body is inserted into the inner hole of the terminal copper connector (copper-copper contact, with the ribs embedded in the inner hole wall) to achieve an insertion connection.

[0053] Test case The terminal block provided in Embodiment 1 of the present invention was compared with the existing friction-welded copper-aluminum transition terminal (control example) in a comparative test, and the results are shown in Table 1.

[0054] Table 1. Product Performance Comparison Number of manufacturing process steps 3-4 (Cutting → Rolling → Bending → Punching) 5-6 (Machining copper parts → Machining aluminum tubes → Friction welding → Stamping → Finishing → Protective treatment) Required special equipment Ordinary stamping / rolling equipment Friction welding machine + stamping equipment Unit manufacturing cost Approximately 50% to 60% of the control group. Peel strength of copper-aluminum interface ≥120MPa (Original manufacturer specification) The yield rate of large-section products is low due to significant fluctuations caused by welding processes. Electrical performance The DC resistance meets the requirements of GB / T14315-2008. The DC resistance meets the requirements of GB / T14315-2008. Electrochemical corrosion resistance The copper-aluminum interface has a eutectic structure, resulting in a dense bond that is resistant to moisture. The yield rate of large-section products is low due to significant fluctuations caused by welding processes. Temperature rise test (1.2 times rated current) ≤55K ≤60K As shown in Table 1, the manufacturing of traditional friction-welded copper-aluminum transition terminals requires 5-6 steps, including separate processing of copper parts and aluminum tubes, friction welding, stamping, finishing, and protective treatment. Furthermore, a dedicated friction welding machine is required, resulting in significant equipment investment and complex process control, especially for 120mm... 2 The yield rate of the above large-section products is low due to limitations in welding power and process difficulty. In addition, the friction-welded interface is subject to both thermal cycling stress and electrochemical corrosion during long-term service, posing a risk of corrosion cracking. The stamping process may also introduce microcracks, affecting conductivity and service life.

[0055] In contrast, this invention uses eutectic copper-aluminum composite strip as the substrate and directly manufactures integrated terminals through conventional forming processes such as rolling and bending, requiring only 3-4 steps and no specialized welding equipment, significantly reducing equipment barriers and investment costs. More importantly, this invention employs an "inner aluminum, outer copper" layered structure design, creating an aluminum-aluminum homometallic contact on the aluminum alloy cable connection side and a copper-copper homometallic contact on the copper terminal side, structurally eliminating the risk of electrochemical corrosion. Simultaneously, the copper-aluminum interface exhibits a metallurgical bond with a continuous eutectic structure of 200-800nm, with a peel strength ≥100MPa, far superior to the consistency and reliability of friction-welded interfaces. Through process control measures such as preheating before rolling, progressive two-pass rolling, geometric constraints of D / t≥8, and low-temperature stress relaxation after rolling, the shear stress problem at the copper-aluminum interface during rolling is effectively solved, ensuring interface integrity.

[0056] This invention provides an aluminum alloy cable copper-aluminum transition terminal based on a eutectic copper-aluminum composite strip and its preparation method. The method includes material preparation, cutting, forming, and post-processing steps. Using a copper-aluminum composite strip prepared with eutectic technology as the substrate, an integrated copper-aluminum transition terminal is directly fabricated using forming processes such as rolling and bending. This replaces the traditional separate copper-aluminum friction-welded structure, greatly simplifying the manufacturing process and reducing equipment investment, lowering the unit manufacturing cost to 50%~60% of that of friction-welded terminals. This aluminum alloy cable copper-aluminum transition terminal has no welding interface, completely eliminating electrochemical corrosion. The process is simplified, costs are controllable, and the connection is reliable with a long service life, making it highly valuable for applications.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-aluminum transition terminal for an aluminum alloy cable based on a eutectic copper-aluminum composite strip, characterized in that, Includes the following steps: S1. Material preparation: Select copper-aluminum composite strip prepared by eutectic technology. One surface of the composite strip is a copper layer and the opposite surface is an aluminum layer. The copper layer and the aluminum layer are metallurgically bonded by a continuous Cu-Al eutectic structure with a thickness of 200~800nm, and the interface peel strength is not less than 100MPa. S2. Cutting: Cut the copper-aluminum composite strip into blanks according to the preset size of the required terminals; S3. Forming: The cut blank is rolled into a tubular structure using a rolling die; S4. Post-processing: Trim and deburr the formed terminals.

2. The preparation method according to claim 1, characterized in that, In step S3, the forming includes: rolling one end of the blank into a tubular cable connector and bending and flattening the other end into a flat copper terminal connector and machining a connection hole, or cutting the blank into strip blanks according to the required pipe diameter and then directly rolling it into a tubular terminal body.

3. The preparation method according to claim 1 or 2, characterized in that, In step S3, the rolling process includes: preheating the blank to 60~180℃ before rolling, using a progressive rolling process to complete the rolling in at least two passes, and ensuring that the pipe diameter D and the total thickness t of the composite strip after rolling satisfy D / t≥8.

4. The preparation method according to claim 1 or 2, characterized in that, In step S3, after the tubular structure is rolled into shape, the joints are reinforced by welding or riveting, and / or subjected to low-temperature stress relaxation treatment at 120~180℃ for 15~30 minutes.

5. The preparation method according to claim 1 or 2, characterized in that, In step S3, when the tube is rolled into a tubular terminal body, an axial gap is processed on its tube wall, and / or an axial rib or knurling is processed on its outer surface.

6. A copper-aluminum transition terminal for aluminum alloy cables based on eutectic copper-aluminum composite strip, characterized in that, The terminal is prepared by the preparation method described in any one of claims 1 to 5, and the terminal is formed by rolling the copper-aluminum composite strip into at least one tubular structure, wherein the inner surface of the tubular structure is an aluminum layer and the outer surface is a copper layer.

7. The aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite strip according to claim 6, characterized in that, The copper layer thickness of the copper-aluminum composite strip accounts for 10% to 40% of the total thickness of the composite strip.

8. The aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite strip according to claim 6, characterized in that, One end of the tubular structure is integrally connected to a flat strip structure, which is formed by bending and flattening the other end of the copper-aluminum composite strip. At least one connecting hole is provided on the flat strip structure. The outer surface of the flat strip structure is a copper layer and the inner surface is an aluminum layer.

9. The aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite strip according to claim 8, characterized in that, After the tubular structure is rolled into shape, its joints are sealed by welding or riveting. The sealing structure also restrains the radial peeling tendency of the copper-aluminum interface generated during the rolling process.

10. The aluminum alloy cable copper-aluminum transition terminal based on eutectic copper-aluminum composite strip according to claim 6, characterized in that, The tubular structure is an integral tubular terminal body. The outer diameter of the tubular terminal body matches the inner hole or plug diameter of the terminal wiring terminal. Its inner hole is used to accommodate and connect the aluminum alloy cable conductor. An axial slot is opened on the tube wall of the tubular terminal body, and / or one or more axial ribs or knurling are provided on the copper layer on its outer surface.

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