Preparation method of copper-clad aluminum conductive part and copper-clad aluminum conductive part obtained thereby

Abstract

The present invention discloses a preparation method of a copper-clad aluminum conductive part and the obtained copper-clad aluminum conductive part, including continuous extrusion. The continuous extrusion includes the following process: simultaneously subjecting an aluminum blank and more than two copper blanks to continuous extrusion to respectively obtain an aluminum extrusion material and more than two copper extrusion materials. Each copper extrusion material is extruded through a copper extrusion cavity into a first welding cavity to form a copper coating layer; the aluminum extrusion material is extruded through an aluminum extrusion cavity; the aluminum extrusion cavity is located in the middle, the first welding cavity is arranged around the aluminum extrusion cavity, and more than two copper extrusion materials respectively enter the first welding cavity from the periphery of the aluminum extrusion material; the copper coating layer is extruded from the first welding cavity, contacts the aluminum extrusion material extruded from the aluminum extrusion cavity, enters a second welding cavity, and completes the coating and welding to obtain the copper-clad aluminum conductive part. The present invention has remarkable effects of energy saving, environmental protection, short process, low cost, high welding strength and high conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of processing conductive parts of new energy electric vehicles, and more specifically, to a method for preparing a copper-clad aluminum conductive part and the prepared copper-clad aluminum conductive part. Background Art

[0002] Conductive parts are the components with the highest cost in the high-voltage connector harness of electric vehicles. The traditional conductor materials used are mainly copper and copper alloys. Copper has good electrical and mechanical properties and is an ideal material for electrical conduction. In the context of the development of charging power towards high-power charging, the current charging technology standards have increased the maximum allowable charging current to 800 A, and will develop towards 1000 A and higher in the future. In the absence of additional cooling measures on the vehicle side, when the current increases, according to Joule's law (Q=I 2 Rt), the conductor resistance needs to be reduced to prevent the vehicle from thermal failure and other problems. An effective measure to reduce resistance is to increase the conductor cross-sectional area. Generally, 120 mm 2 The maximum current carrying capacity of copper conductive bars / rows is 500 A. To obtain a higher current carrying capacity, the cross-sectional area of ​​the conductive bars / rows should be larger than 120 mm. 2 Such a large size will lead to problems such as overweight of the conductive rod / row and excessive bending radius. Therefore, lightweight conductors such as aluminum bars or aluminum rods will have an opportunity to be applied.

[0003] Pure aluminum has the highest conductivity, about 62% IACS, but it is too soft to meet the strength requirements. In order to meet the strength requirements, pure aluminum is doped with alloy elements to increase its strength. However, the doped alloy elements will reduce the conductivity of pure aluminum. Therefore, aluminum alloy conductive parts doped with alloy elements are difficult to break through the bottleneck of 62% IACS conductivity.

[0004] The copper clad layer with better conductivity is coated on the outer layer of the aluminum core, that is, the copper-clad aluminum conductor, which has the high conductivity of copper and the light weight of aluminum. The conductivity can exceed 62% IACS, which can meet the needs of high voltage, high power, light weight and low cost conductors. Copper-clad aluminum conductors are called the third generation of new conductors after copper and aluminum.

[0005] The preparation methods of copper-clad aluminum conductive parts in the prior art include the following: 1) Solid-solid combination method: A finished hollow copper tube is sleeved outside a finished aluminum core, and then through compression and drawing, the gap between the copper tube and the aluminum core is eliminated. The disadvantage of this method is that the aluminum core and the copper tube are mechanically combined, the copper-aluminum interface resistance is large, and the overall conductivity of the copper-clad aluminum conductive part is low. 2) Liquid-liquid combination method: Copper and aluminum are respectively melted into liquid state, and then the two liquid flows flow out and converge through the core cavity channel and the shell cavity channel respectively, and then are cooled and drawn repeatedly to obtain the copper-clad aluminum conductive part. The copper and aluminum are metallurgically combined, which can significantly improve the conductivity. However, the disadvantages of this method are: high energy consumption in melting casting, large volume of the melting furnace, serious environmental pollution, long process flow, and high production cost. 3) Liquid-solid combination method: One of the copper cladding layer and the aluminum core is heated and melted into liquid state, and the other is a finished product. The liquid aluminum material is filled into the copper cladding layer, or liquid copper material is poured outside the finished aluminum core, and then cooled and drawn repeatedly to obtain the copper-clad aluminum conductive part. The disadvantages of this method are: still need the melting process, high energy consumption, serious environmental pollution, long process due to repeated drawing, high cost, and large liquid-solid combination interface resistance. 4) Liquid-semi-solid combination method: The semi-solid aluminum is obtained by continuously extruding aluminum, and then the molten copper is coated on the surface of the extruded semi-solid aluminum, and then cooled and drawn repeatedly to obtain the copper-clad aluminum conductive part. The disadvantage of this method is also: still need the melting process, high energy consumption, serious environmental pollution, long process due to repeated drawing, and high cost. 5) Semi-solid-solid combination method: The aluminum core is passed into a cavity and moves forward at a certain speed. The semi-solid copper is obtained by continuously extruding copper, and the semi-solid copper is extruded onto the aluminum core, and then compressed and extruded and cooled to obtain the copper-clad aluminum conductive part. The disadvantage of this method is that only the copper is extruded through the closed high-pressure cavity of the continuous extrusion device, the extrusion pressure between the copper and the aluminum is small when they are combined, the bonding strength at the copper-aluminum interface is insufficient, it is easy to delaminate, and the aluminum core is not semi-solid, and there is still room for improvement in the resistivity at the copper-aluminum interface. 6) Semi-solid-semi-solid combination method: The semi-solid copper cladding blank is obtained by continuously extruding method, and the semi-solid aluminum core blank is obtained by continuously extruding method. The copper cladding blank is longitudinally and evenly coated on the surface of the aluminum core blank, and the copper cladding blanks are welded to form a closed ring. There are two kinds of weldings in this method. One is the welding between the copper cladding blanks, and the other is the welding between the copper cladding blank and the aluminum core blank. The disadvantages of this method are: First, the above two weldings are carried out under normal pressure, and the bonding strengths of both copper-copper welding and copper-aluminum welding are insufficient. Second, although the welding interface between the copper cladding blanks is smooth on the surface, internal welds are easy to generate, resulting in increased resistance. Third, after the coating is completed, repeated drawing is still required, and the process is long.7) One-round double-groove continuous extrusion technology, that is, the clad billet and the core billet respectively enter two extrusion grooves arranged side by side in the same extrusion wheel for continuous extrusion, and at the same time, the core extruded material and the clad extruded material are obtained. The core extruded material is extruded from the middle die cavity, and the clad extruded material is extruded from the annular die cavity surrounding the middle die cavity to obtain a metal-clad metal conductive part. In this preparation method, there are also two types of welding. One is that the clad material is continuously extruded to form a closed annular clad layer, and there is welding between the clad layers. The other is the welding between the clad layer and the core. However, there are also gaps inside the welding interface between the clad layers, and these gaps will destroy the skin effect and seriously affect the conductivity.

[0006] In the prior art, the copper clad layer in the copper-clad aluminum conductive part is also formed by surface coating technology, mainly including laser cladding, high-velocity oxy-fuel spraying, electroless plating, electroplating, physical vapor deposition (PVD), and chemical vapor deposition (CVD). However, they all have significant defects. Laser cladding relies on a high-cost silver transition layer (450 - 850 μm), and thermal stress is likely to cause deformation of the core substrate; high-velocity oxy-fuel spraying has a low bonding strength (≤50 MPa) due to the mechanical biting of semi-molten particles, and the high-temperature flame flow (3000°C) damages the core substrate; electroless plating requires acid etching activation and complex pretreatment, the coating is loose (porosity > 10%), and the waste liquid pollution is serious; the electroplating process produces heavy metal wastewater, has a poor bonding force (≤20 MPa), and is gradually phased out; PVD is limited by the deposition rate (13 μm / h) and the coating thickness (<5 μm), and it is difficult to meet industrial requirements; the CVD process temperature (800 - 1000°C) far exceeds the melting point of the aluminum alloy, and an intermediate layer is required to inhibit the melting of the core substrate, and the equipment is complex and the cost is high. Although the existing surface coating technologies can also achieve the coating of copper on the surface of the aluminum substrate, they generally have problems such as high cost, low efficiency, or environmental protection. Summary of the Invention

[0007] The object of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide a preparation method of a copper-clad aluminum conductive part and the obtained copper-clad aluminum conductive part, which have the remarkable effects of energy saving, environmental protection, short process, low cost, high welding strength, and high conductivity.

[0008] To achieve the above object, the first technical solution of the present invention is as follows:

[0009] A preparation method of a copper-clad aluminum conductive part, including continuous extrusion, and the continuous extrusion includes the following processes:

[0010] Provide an aluminum billet and two or more copper billets;

[0011] Simultaneously perform continuous extrusion on the aluminum billet and each copper billet to obtain an aluminum extruded material and two or more copper extruded materials respectively;

[0012] Each of the copper extrusion materials is extruded into the first welding cavity through the copper extrusion cavity. In the first welding cavity, the copper extrusion materials are welded to each other to form a closed copper-coated layer extrusion material.

[0013] The aluminum extrusion material is extruded through the aluminum extrusion cavity. The aluminum extrusion cavity is located in the middle, and the first welding cavity is arranged around the aluminum extrusion cavity. Each of the copper extrusion materials enters the first welding cavity from the periphery of the aluminum extrusion material.

[0014] The copper-coated layer extrusion material is extruded from the first welding cavity, contacts the aluminum extrusion material extruded from the aluminum extrusion cavity, enters the second welding cavity, and completes the coating welding to obtain the copper-clad aluminum conductive part.

[0015] The second technical solution of the present invention is as follows:

[0016] A copper-clad aluminum conductive part is prepared by the above preparation method.

[0017] Implementing the embodiments of the present invention will have the following beneficial effects:

[0018] In the embodiments of the present invention, the closed annular copper-coated layer is divided into two parts and regarded as formed by welding two or more copper-coated layer extrusion materials to each other. Since the copper-coated layer is formed by welding two or more copper-coated layer extrusion materials to each other, the extension distance of each copper-coated layer extrusion material in the circumferential direction is short, which can significantly improve the welding quality between the copper-coated layer extrusion materials, increase the width of the welding joint interface, avoid defects such as gaps at the welding interface as much as possible, improve the conductivity of the copper-coated layer, and enhance the improvement of the overall conductivity of the conductive part by the skin effect.

[0019] At the same time, two or more copper-coated layer extrusion materials are extruded around the aluminum extrusion material at the same time, and the extrusion forces formed by the copper-coated layer extrusion materials on the aluminum core can be symmetric about the center of the aluminum core, thereby avoiding the eccentricity of the aluminum core and ensuring the concentricity of the aluminum core and the copper-coated layer. Therefore, a copper-coated layer with uniform thickness can be obtained, further enhancing the improvement of conductivity by the skin effect.

[0020] The copper-coated layer is formed by welding two or more copper-coated layer extrusion materials to each other in the first welding cavity, which can reduce the extension distance of the copper-coated layer extrusion material in the circumferential direction. Then, the length of the first welding cavity in the extrusion direction can be significantly reduced, the welding time can be reduced, and the occurrence of complex metal dislocations at the welding interface caused by too long welding time can be avoided, which has an adverse effect on conductivity. Reducing the length of the first welding cavity in the extrusion direction can also reduce the frictional loss of extrusion energy, making it easier to ensure that the extrusion speed of the copper-coated layer extrusion material is basically the same as that of the aluminum extrusion material, reducing the dislocation of the welding interface caused by the frictional resistance between the copper-coated layer and the aluminum core, and reducing the equivalent resistance of the welding interface between the copper-coated layer and the aluminum core, thereby further improving the overall conductivity of the copper-clad aluminum conductive part.

[0021] The present invention simultaneously performs continuous extrusion on the copper coating layer and the aluminum core to respectively obtain a fresh and non-oxidized semi-solid copper coating layer extrusion material and an aluminum extrusion material. This not only significantly reduces impurities at the welding interface, but also the extrusion materials are in a high-temperature and high-pressure state, enabling the welding between the copper coating layer extrusion materials and between the copper coating layer extrusion material and the aluminum extrusion material to be full metallurgical welding. This not only improves the welding strength, but also minimizes defects such as bubbles and pores, further enhancing the electrical conductivity of the copper coating layer and the aluminum core, which cannot be achieved by other existing processes.

[0022] The present invention uses a continuous extrusion method to respectively form the copper coating layer and the aluminum core. It not only has the remarkable effects of energy conservation, environmental protection, short process, high production efficiency, and reduced production costs, but also continuous extrusion can fully homogenize and densify the metal materials, making the organizational structures of the two metals more uniform and the atomic arrangements more compact, significantly improving the strength of the two metal materials. Therefore, the method of the present invention can not only enhance the electrical conductivity of the conductive part, but also improve the strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Among them:

[0025] Figure 1 is a schematic flow chart of a method for continuously extruding a copper-clad aluminum conductive part according to a specific embodiment of the present invention.

[0026] Figure 2 is a schematic flow chart of forming a copper coating layer by an existing one-round double-groove continuous extrusion method.

[0027] Figure 3 is a schematic cross-sectional structure diagram of a copper-clad aluminum conductive part obtained by an existing semi-solid to semi-solid bonding method.

[0028] Figure 4 is a schematic flow chart of forming a copper coating layer according to the present invention.

[0029] Figure 5 is a schematic diagram of an extrusion device for a copper-clad aluminum conductive part according to a specific embodiment of the present invention.

[0030] Figure 6 is Figure 5 a schematic assembly diagram of an extrusion wheel boot and an extrusion die in the shown extrusion device.

[0031] Figure 7 is Figure 6 an exploded structural schematic diagram of the structure shown.

[0032] Figure 8 is Figure 6 a cross-sectional structural schematic diagram of the structure shown.

[0033] Figure 9 a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity in a specific embodiment of the present invention.

[0034] Figure 10 a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity in another specific embodiment of the present invention.

[0035] Figure 11 a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity in another specific embodiment of the present invention.

[0036] Figure 12 a schematic flow diagram of the preparation method of the copper-clad aluminum conductive part in a specific embodiment of the present invention.

[0037] Figure 13 a schematic flow diagram of the preparation method of the copper-clad aluminum conductive part in another specific embodiment of the present invention.

[0038] Figure 14 a schematic flow diagram of the preparation method of the copper-clad aluminum conductive part in another specific embodiment of the present invention.

[0039] Figure 15 a SEM micrograph of the copper-aluminum welded bonding interface of the copper-clad aluminum conductive part obtained in Example 1 of the present invention. Detailed Embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0041] Referring to Figure 1 , the present invention discloses a preparation method of a copper-clad aluminum conductive part, including continuous extrusion, and the continuous extrusion includes the following processes:

[0042] S1: Provide an aluminum billet and two or more copper billets, and simultaneously perform continuous extrusion on the aluminum billet and each copper billet to obtain an aluminum extrusion and two or more copper extrusions respectively.

[0043] S2: The copper extrusion materials are extruded through the copper extrusion cavity into the first welding cavity respectively, and in the first welding cavity, the copper extrusion materials are welded to each other to form a closed copper cladding layer extrusion material;

[0044] S3: The aluminum extrusion material is extruded through the aluminum extrusion cavity; the aluminum extrusion cavity is located in the middle, and the first welding cavity is arranged around the aluminum extrusion cavity, and each copper extrusion material enters the first welding cavity from the periphery of the aluminum extrusion material;

[0045] S4: The copper clad layer extrusion material is extruded from the first welding chamber, contacts with the aluminum extrusion material extruded from the aluminum extrusion chamber, enters the second welding chamber, completes the cladding welding, and obtains the copper clad aluminum conductive part.

[0046] In the above technical scheme, the closed annular copper cladding layer is divided into two parts, which are regarded as formed by welding two or more copper cladding extrusions to each other. Since the copper cladding layer is formed by welding two or more copper cladding extrusions to each other, the extension distance of each copper cladding extrusion along the circumferential direction is short, which can significantly improve the welding quality between the copper cladding extrusions and the copper cladding extrusions, increase the width of the welding interface, avoid defects such as gaps at the welding interface as much as possible, improve the conductivity of the copper cladding, and enhance the improvement of the overall conductivity of the conductive part due to the skin effect.

[0047] At the same time, more than two copper cladding layer extrudates are extruded around the aluminum extrudate at the same time, and the extrusion thrusts formed by each copper cladding layer extrudate on the aluminum core can be symmetrical about the center of the aluminum core, thereby avoiding eccentricity of the aluminum core and ensuring the concentricity of the aluminum core and the copper cladding layer. Therefore, a copper cladding layer with uniform thickness can be obtained, further enhancing the improvement of conductivity due to the skin effect.

[0048] The copper cladding layer is formed by welding two or more copper cladding layer extrusion materials to each other in the first welding cavity, which can reduce the extension distance of the copper cladding layer extrusion material in the circumferential direction, and can significantly reduce the length of the first welding cavity in the extrusion direction, reduce the welding time, and avoid the generation of more complex metal dislocations at the welding interface due to excessive welding time, which has an adverse effect on conductivity. Reducing the length of the first welding cavity in the extrusion direction can also reduce the friction loss of extrusion energy, and it is more convenient to ensure that the extrusion speed of the copper cladding layer extrusion material is basically the same as the extrusion speed of the aluminum extrusion material, reduce the dislocation of the welding interface caused by the friction resistance between the copper cladding layer and the aluminum core, and reduce the equivalent resistance of the welding interface between the copper cladding layer and the aluminum core, thereby further improving the overall conductivity of the copper clad aluminum conductive part.

[0049] The present invention simultaneously performs continuous extrusion on the copper cladding layer and the aluminum core to respectively obtain a newly formed and non-oxidized semi-solid copper cladding layer extrusion and an aluminum extrusion. This not only significantly reduces the impurities at the welding interface, but also the extrusion materials are in a high-temperature and high-pressure state, enabling the welding between the copper cladding layer extrusions and between the copper cladding layer extrusion and the aluminum extrusion to be full metallurgical welding. This not only improves the welding strength, but also minimizes defects such as bubbles and pores, further enhancing the electrical conductivity of the copper cladding layer and the aluminum core, which cannot be achieved by other existing processes.

[0050] The present invention uses a continuous extrusion method to form the copper cladding layer and the aluminum core respectively. It not only has the remarkable effects of energy conservation, environmental protection, short process, high production efficiency, and reduced production costs, but also continuous extrusion can fully homogenize and compact the metal materials, making the organizational structures of the two metals more uniform and the atomic arrangements more compact, significantly improving the strength of the two metal materials. Therefore, the method of the present invention can not only enhance the electrical conductivity of the conductive part, but also improve the strength.

[0051] In the present invention, the aluminum blank and the copper blanks can respectively select blanks formed by casting, continuous casting and rolling, forging, etc. The cross-sectional dimensions of the aluminum blank and each copper blank can be calculated from the specified dimensions of copper and aluminum in the copper-clad aluminum conductive part. The ratio of the sum of the cross-sectional areas of each copper blank to the cross-sectional area of the aluminum blank is equal to the ratio of the cross-sectional areas of copper and aluminum on the cross-section of the copper-clad aluminum conductive part, so as to form a copper-clad aluminum conductive part with a specified material ratio.

[0052] In a specific embodiment, the aluminum blank and more than two copper blanks are arranged in parallel in sequence and respectively enter different extrusion grooves arranged in parallel in the same extrusion wheel for continuous extrusion respectively. The extrusion cavity is provided with a core die orifice for extruding the aluminum extrusion and each cladding layer die orifice for extruding each copper extrusion respectively. That is, this embodiment uses a continuous extrusion method with more than three grooves in one wheel to form a conductive part composed of two metal materials, having the remarkable effects of energy conservation, environmental protection, short process, high production efficiency, and reduced production costs. In this embodiment, the number of copper blanks can specifically be two, three, or more than three, etc.

[0053] Reference Figure 2When the copper-clad aluminum conductive parts are prepared by the existing one-round double-slot continuous extrusion technology, only one copper billet is used. The copper billet and the aluminum billet enter different extrusion slots for continuous extrusion. When the copper extrusion enters the first welding cavity, as the copper extrusion is extruded, the cross-sectional width W of the copper extrusion gradually increases, and the thickness D gradually decreases, until the two ends of the cross-sectional width W are surrounded by a closed annular shell. In this way, the extension deformation in the width W direction is too large, and it is easy to have a gap at the welding interface between the copper extrusion and the copper extrusion. When the strength of the copper material of the cladding layer is greater than the strength of the core aluminum, due to the poor fluidity of the material with high strength, more gap defects will be generated at the welding interface between the copper material of the cladding layer and the core aluminum material.

[0054] from Figure 2 It can also be seen that in the process of the copper extrusion material forming a closed ring, the extrusion force of the copper extrusion material on the aluminum extrusion material can easily cause the core material to be eccentric and the thickness of the coating layer to be uneven.

[0055] refer to Figure 3 , which is a schematic diagram of the cross-sectional structure of a copper-clad aluminum conductive part made by a semi-solid-semi-solid combination method in the prior art. The semi-solid-semi-solid combination method is: a semi-solid copper-clad blank is obtained by a continuous extrusion method, a semi-solid aluminum core blank is obtained by a continuous extrusion method, the copper-clad blank is uniformly coated on the surface of the aluminum core blank in the longitudinal direction, and the copper-clad blank and the copper-clad blank are welded to form a closed ring. Figure 3 It can be seen that there is a copper-copper welding interface, holes can be seen on the copper-copper welding interface, and there are gaps at the copper-aluminum welding interface where the bonding is not tight.

[0056] refer to Figure 4 In a specific embodiment of the present invention, the closed annular copper cladding layer is formed by welding two copper extrusions, the cross-sectional width W direction of the two copper extrusions gradually increases, and the thickness D direction gradually decreases, and then the two ends of the cross-sectional width W direction of the two copper extrusions are respectively welded close to each other to form a closed annular shell, and the deformation amount in the width W direction is reduced. Figure 2 The existing technology can avoid defects such as gaps or holes at the welding interface between copper extrusion materials as much as possible. Figure 4 It can also be seen that when two or more copper extrusions extend from the periphery of the aluminum core in a circumferential direction at the same time, eccentricity of the aluminum core can be avoided.

[0057] Since more than two copper billets are welded to each other to form a coating layer, preferably, the cross-sectional areas of the copper billets are the same. In the first welding cavity, the copper extrusions are evenly distributed around the aluminum extrusions, and the extrusion speeds of the copper extrusions are the same, so that the extrusion thrusts of the copper extrusions on the aluminum core can be symmetrically distributed about the center of the aluminum core, thereby avoiding eccentricity of the aluminum core and ensuring the concentricity of the aluminum core and the copper coating layer. Therefore, a copper coating layer with uniform thickness can be obtained, which improves the consistency and stability of the copper-clad aluminum conductive part structure, thereby further enhancing the improvement of conductivity due to the skin effect.

[0058] Further preferably, the extrusion speed of the copper extrusion material is the same as that of the aluminum extrusion material, which reduces the dislocation of the welding interface caused by the friction resistance between the copper cladding and the aluminum core, and reduces the equivalent resistance of the welding interface between the copper cladding and the aluminum core, thereby further improving the overall conductivity of the copper-clad aluminum conductive part.

[0059] Further specifically, in a specific embodiment, the width of the welding interface between the copper extrusion material and the copper extrusion material is 5μm~60μm; the number of welding interfaces between the copper extrusion material and the copper extrusion material is more than 2, and the welding interface between the copper extrusion material and the copper extrusion material extends along the axial direction of the copper-clad aluminum conductive part, and the width of the bonding interface between the copper extrusion material and the aluminum extrusion material is 5μm~40μm. The above-mentioned welding interface width is large enough to achieve true metallurgical bonding, which not only improves the welding strength and the structural stability of the overall structure of the conductive part, but also avoids the formation of defects such as gaps or holes as much as possible, thereby improving conductivity.

[0060] In a specific embodiment, reference Figure 5 The copper billet includes a first copper billet and a second copper billet. The first copper billet, the aluminum billet and the second copper billet are arranged in parallel in sequence and enter three parallel extrusion wheel grooves 11 of the same extrusion wheel 10 for continuous extrusion at the same time.

[0061] refer to Figures 5 to 8 In a specific embodiment, the extrusion equipment includes: an extrusion wheel 10, an extrusion wheel shoe 20 and an extrusion die 30. The extrusion wheel 10 is provided with three parallel extrusion wheel grooves 11, which are used to feed the first copper billet, the aluminum billet and the second copper billet in turn. The extrusion wheel shoe 20 is provided with a plug 21 at the position corresponding to each extrusion wheel groove 11. The extrusion wheel groove 11, the plug 21 and the extrusion wheel shoe 20 constitute an extrusion cavity. The three billets are continuously extruded in three independent extrusion cavities to obtain extrusion materials. Each extrusion cavity is provided with a first cladding layer die 24, a core die 25 and a second cladding layer die 26. The first copper extrusion material enters the first copper extrusion cavity 31 through the first cladding layer die 24, the aluminum extrusion material enters the aluminum extrusion cavity 32 through the core die 25, and the second copper extrusion material enters the second copper extrusion cavity 33 through the third cladding layer die 26.

[0062] refer toFigure 7 And Figure 8 The extrusion die 30 includes a first die 36 and a second die 37 which are stacked. The extrusion die 30 is provided with a first copper extrusion cavity 31, an aluminum extrusion cavity 32, a second copper extrusion cavity 33, a first welding cavity 34 and a second welding cavity 35. The aluminum extrusion cavity 32 is located in the middle. The first copper extrusion cavity 31 and the second copper extrusion cavity 33 are respectively located on both sides of the aluminum extrusion cavity 32. The first welding cavity 34 is located behind the first copper extrusion cavity 31 and the aluminum extrusion cavity 32, and is located outside the periphery of the aluminum extrusion cavity 32. The second welding cavity 35 is located behind the aluminum extrusion cavity 32. The second welding cavity 35 is coaxially arranged with the aluminum extrusion cavity 32. The inlets of the first copper extrusion cavity 31, the aluminum extrusion cavity 32 and the second copper extrusion cavity 33 are respectively communicated with the corresponding die openings. The outlets of the first copper extrusion cavity 31 and the second copper extrusion cavity 33 are respectively communicated with the first welding cavity 34. The outlets of the first welding cavity 34 and the aluminum extrusion cavity 32 are respectively communicated with the second welding cavity 35.

[0063] The first copper blank, the second copper blank and the aluminum blank respectively undergo plastic deformation in the corresponding extrusion cavities to obtain the corresponding extruded materials. The first copper blank enters the first copper extrusion cavity 31 through the first cladding layer die opening 24. The aluminum blank enters the aluminum extrusion cavity 32 through the core die opening 25. The second copper blank enters the second copper extrusion cavity 33 through the second cladding layer die opening 26. Thus, the continuous production of the copper-clad aluminum conductive part can be realized in one step by using one extrusion device. Of course, in other embodiments, two or more extrusion devices can also be used.

[0064] In a specific embodiment, the temperature difference between the copper extruded material at the cladding layer die opening and the aluminum extruded material at the core die opening does not exceed 100 °C. Further preferably, it does not exceed 50 °C. If the temperature difference between the copper extruded material and the aluminum extruded material is too large, it will cause a large dimensional error at the copper-aluminum interface when the copper and aluminum come into contact, affecting the concentricity. Specifically, in a specific embodiment, the temperature difference between the first copper extruded material at the first cladding layer die opening 24 or the second copper extruded material at the second cladding layer die opening 26 and the aluminum extruded material at the core die opening 25 does not exceed 100 °C.

[0065] Since the copper extruded materials together form a closed annular copper cladding layer, preferably, the temperatures of the copper extruded materials at their corresponding cladding layer die openings are the same.

[0066] Preferably, in a specific embodiment, the temperature of the aluminum extruded material at the core die opening 25 is 350 °C to 550 °C. Within this temperature range, the structure of the aluminum extruded material will be fully refined, improving the conductivity of the aluminum core.

[0067] The temperature of the copper extruded material at the cladding layer die opening is preferably 450 °C to 650 °C.

[0068] Preferably, the rotation speed of the extrusion wheel is 5 rpm to 40 rpm, which can make the temperature of the aluminum extrusion material at the die orifice reach 350°C to 550°C.

[0069] Since the melting point of copper material is higher than that of aluminum material, therefore, preferably, the copper blank is preheated and then continuously extruded simultaneously with the aluminum blank.

[0070] In a specific embodiment, a first sizing belt 321 is provided at the outlet of the aluminum extrusion cavity 32, and the first sizing belt 321 is used to shape the external contour of the aluminum core. A second sizing belt 351 is provided at the inlet of the second welding cavity 35, and the second sizing belt 351 is used to shape the external contour of the coating layer. The shapes of the first sizing belt 321 and the second sizing belt 351 can be any shape, for example, they can be circular, square, triangular, polygonal, and irregular shapes, etc.

[0071] In addition to ensuring the shape and size of the product, the sizing belt is also used to ensure the surface quality of the extruded product. The length of the sizing belt has different effects on the quality, size, accuracy, etc. of the product. The effect of the sizing belt on the composite of the composite material is mainly achieved by affecting the flow of the composite metal.

[0072] In this patent, the second sizing belt 351 is used to achieve the welding between the surface metal copper and the core metal aluminum. Preferably, the length of the second sizing belt 351 along the extrusion direction is preferably 5 mm to 20 mm. If the length of the second sizing belt 351 is too long, the contact area between the surface metal and the die outlet is too large, the resistance is large and the flow rate is slow, and more defects are likely to occur at the interface of the two metals. If the length of the second sizing belt 351 is too short, defects such as waves are likely to appear on the product surface, and at the same time, the metallurgical bonding between the two metals is insufficient.

[0073] Preferably, the length of the first sizing belt 321 along the extrusion direction is equal to or close to the length of the second sizing belt 351 along the extrusion direction to ensure that the extrusion speeds of the two metal materials are the same or close. The length of the first sizing belt 321 along the extrusion direction is preferably 5 mm to 20 mm.

[0074] Reference Figures 9 to 11 , when the hardness of the copper coating extrusion material is greater than the hardness of the aluminum extrusion material, that is, when it is hard wrapping soft, preferably, the outlet end of the aluminum extrusion cavity can protrude into the inlet of the second welding cavity to prevent the aluminum core extrusion material from being cut off by the copper coating extrusion material during the extrusion process. When the hardness of the copper coating extrusion material is close to the hardness of the aluminum extrusion material, preferably, the outlet end of the aluminum extrusion cavity is flush with the inlet end of the second welding cavity. When the hardness of the copper coating extrusion material is less than the hardness of the aluminum extrusion material, the outlet end of the aluminum extrusion cavity can be located above the inlet of the second welding cavity, the outlet end of the aluminum extrusion cavity can also be flush with the inlet end of the second welding cavity, or the outlet end of the aluminum extrusion cavity can also protrude into the inlet of the second welding cavity.

[0075] Further, in a specific embodiment, the length of the first welding cavity 34 along the extrusion direction is 10 mm to 50 mm. If the length of the first welding cavity 34 is too small, the copper extrusion materials cannot be completely welded together, and defects such as gaps or holes are likely to exist. If the length of the first welding cavity 34 is too large, it is easy to increase the atomic misalignment at the welding interface between the cladding extrusion materials, affecting the conductivity.

[0076] Preferably, in a specific embodiment, the angle between the outlet direction of the first welding cavity 34 and the outlet direction of the aluminum extrusion cavity 32 is less than 60°, so that the radial extrusion stress of the copper cladding on the aluminum core is appropriate, which not only strengthens the welding but also avoids breaking the core material.

[0077] In a specific embodiment, the length of each copper extrusion cavity along the extrusion direction is 10 mm to 50 mm; the length of the aluminum extrusion cavity along the extrusion direction is 10 mm to 50 mm. Preferably, the lengths of the copper extrusion cavity and the aluminum extrusion cavity along the extrusion direction are the same, which is convenient for synchronously extruding multiple extrusion materials.

[0078] In a specific embodiment, the aluminum billet can be 1-series aluminum or 6-series aluminum. In the present invention, 1-series aluminum refers to aluminum materials with an aluminum element mass content exceeding 99%, including undoped pure aluminum. 6-series aluminum refers to aluminum alloys with magnesium and silicon as the main alloying elements, such as 6061, 6063, etc. When the aluminum billet is 6-series aluminum, preferably, the aluminum billet is selected as the T4 state aluminum alloy. The T4 state aluminum alloy refers to the state that has naturally aged to a basically stable state after solution heat treatment. In this state, the hardening phase in the aluminum alloy has not been completely precipitated. Therefore, it has low strength but good toughness, is suitable for large deformations of continuous extrusion, and high-conductivity aluminum cores can be obtained through subsequent cooling and heat treatment.

[0079] In a specific embodiment, the area of the copper cladding layer on the cross-section of the copper-clad aluminum conductive part accounts for 10% to 40%, preferably 20% to 30%. It can not only play a skin effect to improve the conductivity but also save the consumption of copper.

[0080] The continuous extrusion of the present invention can be radial continuous extrusion or tangential continuous extrusion. When it is radial continuous extrusion, the die orifices of the extrusion materials are located on the extrusion boots. When it is tangential continuous extrusion, the die orifices of the extrusion materials are located on the plugs.

[0081] In a specific embodiment, the preparation method of the copper-clad aluminum conductive part further includes one or more of the following processes a to h:

[0082] a. Drawing, which is used to draw the conductive part obtained by continuous extrusion to obtain a copper-clad aluminum conductive wire;

[0083] b. Online cooling, which is used to cool the conductive parts obtained by continuous extrusion or the conductive wires obtained by wire drawing online;

[0084] c. Rewinding, which is used to wind and collect the cooled conductive parts or conductive wires;

[0085] d. Heat treatment, which is used to heat-treat the rewound conductive parts or conductive wires. The heat treatment includes the processes of heating up and holding. The main purpose of the heat treatment is to make the atomic diffusion at the welded joint interface more sufficient, and at the same time release the stress concentration caused by continuous extrusion, improving the performance and stability of the material;

[0086] e. Blank rewinding, which is used to wind and collect the aluminum blanks and each copper blank respectively;

[0087] f. Traction, which is used to traction the wound aluminum blanks and each copper blank respectively;

[0088] g. Online straightening, which is used to straighten the tractioned aluminum blanks and each copper blank respectively; and

[0089] h. Online cleaning, which is used to clean the straightened aluminum blanks and each copper blank respectively, removing surface impurities to prevent the influence on the performance of the welded joint interface; the aluminum blanks and each copper blank after online cleaning are continuously extruded simultaneously.

[0090] Reference Figure 12 , in a specific embodiment, the preparation method of the copper-clad aluminum conductive part includes the following processes:

[0091] Continuous extrusion, as described above, to obtain the copper-clad aluminum conductive part;

[0092] Online cooling, which is used to cool the copper-clad aluminum conductive part obtained by continuous extrusion online;

[0093] Rewinding, which is used to wind and collect the cooled copper-clad aluminum conductive part; and

[0094] Heat treatment, which is used to heat-treat the rewound copper-clad aluminum conductive part.

[0095] In another embodiment, the above preparation method may not include the heat treatment process. Not all metals require heat treatment. For example, the copper coating layer and the pure aluminum core may not require the heat treatment process after continuous extrusion.

[0096] In the above preparation method, continuous extrusion can produce a copper-clad aluminum conductive part with fine and uniform crystal grains. Then, through on-line cooling, the crystal grains are further refined into secondary microcrystals, and the crystal grain structure is solidified in a timely manner to inhibit the excessive growth of crystal grains. Crystal grain refinement can improve strength and hardness, making it have better mechanical properties. Heat treatment can fully release the residual stress caused by continuous extrusion and on-line cooling, and obtain a copper-clad aluminum conductive part with stable structure and high conductivity. In the above preparation method, the obtained copper-clad aluminum conductive part can be a conductive rod or a conductive busbar.

[0097] Through continuous extrusion and on-line cooling, the above preparation method can produce a continuous and long enough copper-clad aluminum conductive part, and then through winding and collection, it is convenient for storage and transportation. The wound copper-clad aluminum conductive part can be directly placed in a heat treatment chamber for heat treatment. The above preparation method can achieve continuous on-line production with high production efficiency.

[0098] Reference Figure 13 , in another specific embodiment, a preparation method of a copper-clad aluminum conductive part includes the following processes:

[0099] Continuous extrusion, which is as described above, to produce a copper-clad aluminum conductive part;

[0100] Drawing, which is used to draw the copper-clad aluminum conductive part produced by continuous extrusion to obtain copper-clad aluminum wire;

[0101] On-line cooling, which is used to cool the copper-clad aluminum wire on-line;

[0102] Winding, which is used to wind and collect the cooled copper-clad aluminum wire; and

[0103] Heat treatment, which is used to heat-treat the wound copper-clad aluminum wire.

[0104] In this specific embodiment, copper-clad aluminum wire can be obtained through drawing. The on-line cooling, winding, and heat treatment are the same as those in the Figure 9 illustrated embodiment and will not be elaborated here.

[0105] Reference Figure 13 and Figure 14 , in another specific embodiment, before continuous extrusion, the preparation method of the copper-clad aluminum conductive part further includes:

[0106] Blank winding, which is used to wind and collect the aluminum blank and each copper blank respectively;

[0107] Traction, which is used to traction the wound aluminum blank and each copper blank respectively;

[0108] On-line straightening, which is used to straighten the traction aluminum blank and each copper blank on-line; and

[0109] Online cleaning, where the online cleaning is used to perform online cleaning on the straightened aluminum billets and each copper billet respectively; the aluminum billets and each copper billet after online cleaning are simultaneously subjected to the continuous extrusion.

[0110] The above preparation method can realize the automatic continuous feeding of each billet in the continuous extrusion process, further improving the production efficiency.

[0111] The present invention also discloses a copper-clad aluminum conductive part prepared by the above preparation method, which has both high strength and high conductivity.

[0112] It should be noted that the equality or sameness in the descriptions of the above embodiments is not equality or sameness in an absolute sense, but equality or sameness allowing a certain error, because it is impossible to achieve absolute equality or sameness in actual production.

[0113] The following are specific embodiments.

[0114] Example 1

[0115] To prepare a copper-clad aluminum conductive part, the following process is included:

[0116] 1) Continuous extrusion: Provide the first pure copper billet, the second pure copper billet and the 6101 aluminum billet after cleaning and drying. The cross-sectional areas of the first pure copper billet and the second pure copper billet are the same. Arrange the first pure copper billet, the 6101 aluminum billet and the second pure copper billet in parallel in sequence and enter three sequentially arranged extrusion grooves of the same extrusion wheel respectively for continuous extrusion. The structure of the extrusion equipment is as Figures 5 to 11 shown. To prepare a copper-clad aluminum conductive part, the cross-sectional area ratio of the copper coating layer on the cross-section of the copper-clad aluminum conductive part is 25%. Among them, the rotation speed of the extrusion wheel is 10 rpm, the lengths of the first sizing belt and the second sizing belt are the same, both being 10 mm, and the length of the first welding cavity is 10 mm.

[0117] 2) The copper-clad aluminum conductive part obtained by continuous extrusion enters the water bath for cooling within 3 s, then is coiled, and is heat-treated at 250 °C for 5 h to obtain the final finished copper-clad aluminum conductive part.

[0118] Examples 2 - 3

[0119] The differences between Examples 2 - 3 and Example 1 are only that the copper billets are preheated to 200 °C and 300 °C respectively, and the rest are the same.

[0120] Examples 4 - 5

[0121] The differences between Examples 4 - 5 and Example 2 are only that the lengths of the first sizing belt and the second sizing belt are changed, and the length of the first sizing belt is still equal to that of the second sizing belt.

[0122] Examples 6 - 7

[0123] The differences between Examples 6 - 7 and Example 4 are only that the length of the first welding cavity is changed.

[0124] Comparative Example 1

[0125] Comparative Example 1 was prepared by a one - round double - groove continuous extrusion method, and the rest were the same as those in Example 1.

[0126] Comparative Examples 2 - 3

[0127] The differences between Comparative Examples 2 - 3 and Comparative Example 1 are only that the length of the first welding cavity is changed.

[0128] The preparation parameters of Examples 1 - 7 and Comparative Examples 1 - 3 are shown in Table 1.

[0129] Table 1: Preparation parameters of Examples 1 - 7 and Comparative Examples 1 - 3

[0130]

[0131] Test Example 1

[0132] The tensile strength, yield strength, and conductivity per unit area of the conductive parts prepared in Examples 1 - 7 and Comparative Examples 1 - 3 were tested respectively, and the results are shown in Table 2.

[0133] Table 2: Performance indexes of the conductive parts prepared in Examples 1 - 7 and Comparative Examples 1 - 3

[0134]

[0135] It can be seen from Table 1 that: 1) Comparing Examples 1 - 7 with Comparative Examples 1 - 3, it can be seen that the copper - clad aluminum conductive parts prepared by the one - round three - groove continuous extrusion method of the present invention can significantly improve the conductivity. This is because there are many defects such as gaps or bubbles at the copper - copper welding interface of the copper - clad aluminum conductive parts prepared by the one - round double - groove continuous extrusion method used in Comparative Example 1, which seriously affect the conductivity.

[0136] 2) Comparing Example 1 with Examples 2 - 3, the difference is that in Examples 2 - 3, the copper is pre - heated to 200 °C and 300 °C. It can be seen that pre - heating the copper can improve the processing performance and welding performance of the copper extrusion material. Therefore, the conductivity and strength of the overall copper - clad aluminum conductive parts are both improved.

[0137] 3) Compared with Example 2, the difference between Examples 4 and 5 is that the length of the sizing tape is increased in Examples 4 and 5 respectively. It can be seen that when the length of the sizing tape is increased from 5 mm to 10 mm, the conductivity increases. However, when the length of the sizing tape is increased from 10 mm to 20 mm, the conductivity decreases instead. It can be seen that the length of the sizing tape should not be too long, otherwise, the extrusion pressure of the sizing tape will cause an increase in dislocations at the copper-aluminum interface and increase the interface equivalent resistance.

[0138] 4) Comparing Example 6-7 with Example 4, the difference is that the length of the first welding cavity is increased. It can be seen that the conductivity first increases and then decreases with the increase of the length of the first welding cavity. It can be seen that the length of the first welding cavity cannot be too long. This is because the friction resistance of the copper coating layer in the first welding cavity can increase the dislocation of the welding interface and improve the equivalent resistance of copper-copper welding.

[0139] 5) Compared with Comparative Examples 1 to 3, in the one-round double-groove continuous extrusion method, as the length of the first welding cavity increases, the conductivity first increases and then decreases, but the conductivity still does not increase significantly. It can be seen that a high-performance copper-copper welding interface cannot be obtained by using a one-round double-groove connection extrusion method.

[0140] 6) The strength of the conductive parts obtained in Comparative Examples 1 to 3 is also much worse than that of the present invention. The reason may be that there are many gaps or holes in the copper-copper welding interface, which makes copper and aluminum easy to delaminate.

[0141] Test Example 2

[0142] The conductive member prepared in Example 1 was subjected to SEM test to observe the microstructure of the copper-aluminum welding interface. Figure 15 As shown, it can be seen that the width of the copper-aluminum welding interface exceeds 10μm, which is a sufficient metallurgical bond, and the copper and aluminum are evenly distributed at the bonding interface.

[0143] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A preparation method of a copper-clad aluminum conductive part, characterized in that, Including continuous extrusion, the continuous extrusion includes the following processes: Providing an aluminum billet and two or more copper billets; simultaneously subjecting the aluminum billet and each of the copper billets to continuous extrusion to respectively obtain an aluminum extrudate and two or more copper extrudates; during the continuous extrusion process, arranging the aluminum billet and two or more of the copper billets side by side and respectively entering different extrusion grooves arranged side by side in the same extrusion wheel for continuous extrusion respectively. The extrusion cavity is provided with a core die orifice for the aluminum extrudate to be extruded and each cladding layer die orifice for each of the copper extrudates to be extruded respectively. The copper extrudate enters the copper extrusion cavity through the cladding layer die orifice, and the aluminum extrudate is extruded through the core die orifice into the aluminum extrusion cavity; Each of the copper extrudates is respectively extruded through the copper extrusion cavity into the first welding cavity. In the first welding cavity, each of the copper extrudates is welded to each other to form a closed copper cladding layer extrudate; The aluminum extrudate is extruded through the aluminum extrusion cavity. The aluminum extrusion cavity is located in the middle, and the first welding cavity is arranged around the aluminum extrusion cavity. Each of the copper extrudates enters the first welding cavity from the periphery of the aluminum extrudate respectively; The copper cladding layer extrudate is extruded from the first welding cavity, contacts the aluminum extrudate extruded from the aluminum extrusion cavity, enters the second welding cavity, completes the cladding welding, and obtains the copper-clad aluminum conductive part.

2. The preparation method according to claim 1, characterized in that, The copper billet includes a first copper billet and a second copper billet. The first copper billet, the aluminum billet, and the second copper billet are arranged side by side in sequence and respectively enter three extrusion grooves arranged side by side in sequence in the same extrusion wheel for continuous extrusion respectively to obtain a first copper extrudate, the aluminum extrudate, and a second copper extrudate respectively. The extrusion cavity is sequentially provided with a first cladding layer die orifice, the core die orifice, and a second cladding layer die orifice. The first copper extrudate enters the first copper extrusion cavity through the first cladding layer die orifice, the aluminum extrudate enters the aluminum extrusion cavity through the core die orifice, and the second copper extrudate enters the second copper extrusion cavity through the second cladding layer die orifice.

3. The preparation method according to claim 1, characterized in that, The temperature difference between the temperature of the copper extrudate at the cladding layer die orifice and the temperature of the aluminum extrudate at the core die orifice does not exceed 100 °C.

4. The preparation method according to claim 1, characterized in that, The temperature of the copper extrudate at the cladding layer die orifice is 450 °C to 650 °C; The temperature of the aluminum extrudate at the core die orifice is 350 °C to 550 °C.

5. The preparation method according to claim 1, characterized in that, The rotation speed of the extrusion wheel is 5 rpm to 40 rpm.

6. The preparation method according to claim 1, wherein The cross-sectional areas of each of the copper billets are the same; In the first welding cavity, each of the copper extrudates is evenly distributed around the aluminum extrudate; The extrusion speeds of each of the copper extrudates are the same; The extrusion speeds of the copper extrudate and the aluminum extrudate are the same.

7. The preparation method according to claim 1, characterized in that, A first sizing belt is arranged at the outlet of the aluminum extrusion cavity, and a second sizing belt is arranged at the inlet of the second welding cavity; The length of the first sizing belt along the extrusion direction is 5 mm to 20 mm; The length of the second sizing belt along the extrusion direction is 5 mm to 20 mm.

8. The preparation method according to claim 1, characterized in that, The included angle between the outlet direction of the first welding cavity and the outlet direction of the aluminum extrusion cavity is less than 60°.

9. The preparation method according to claim 1, wherein When the hardness of the copper-coated layer extrusion material is greater than that of the aluminum extrusion material, the outlet end of the aluminum extrusion cavity protrudes into the inlet of the second welding cavity; When the hardness of the copper-coated layer extrusion material is equal to that of the aluminum extrusion material, the outlet end of the aluminum extrusion cavity is flush with the inlet end of the second welding cavity; When the hardness of the copper-coated layer extrusion material is less than that of the aluminum extrusion material, the outlet end of the aluminum extrusion cavity is located above the inlet end of the second welding cavity, or the outlet end of the aluminum extrusion cavity is flush with the inlet end of the second welding cavity, or the outlet end of the aluminum extrusion cavity protrudes into the inlet of the second welding cavity.

10. The preparation method according to claim 1, wherein, The length of the first welding cavity in the extrusion direction is 10 mm to 50 mm; The length of the copper extrusion cavity in the extrusion direction is 10 mm to 50 mm; The length of the aluminum extrusion cavity in the extrusion direction is 10 mm to 50 mm.

11. The preparation method according to claim 1, characterized in that, The percentage of the cross-sectional area of the coating layer of the copper-clad aluminum conductive part in the total cross-sectional area of the copper-clad aluminum conductive part is 10% to 40%.

12. The preparation method according to claim 1, characterized in that, The aluminum billet is 1-series aluminum or 6-series aluminum.

13. According to the preparation method described in claim 1, wherein The width of the welding joint interface between the copper extrusion materials is 5 μm to 60 μm; The number of the welding interfaces between the copper extrusion materials is more than 2, and the welding interfaces extend along the axial direction of the copper-clad aluminum conductive part; The width of the joint interface between the copper extrusion material and the aluminum extrusion material is 5 μm to 40 μm.

14. The preparation method according to any one of claims 1 to 13, characterized in that, Preheat each of the copper billets and then continuously extrude them simultaneously with the aluminum billet.

15. The preparation method according to claim 1, wherein It further includes online cooling, winding, and heat treatment; or, it further includes online cooling and winding: The online cooling is used to cool the copper-clad aluminum conductive part obtained by the continuous extrusion online; The winding is used to wind and collect the cooled copper-clad aluminum conductive part; and The heat treatment is used to heat-treat the wound copper-clad aluminum conductive part.

16. The preparation method according to claim 1, characterized in that, It further includes: Drawing, the drawing is used to draw the copper-clad aluminum conductive part obtained by the continuous extrusion to obtain copper-clad aluminum wire; Online cooling, the online cooling is used to cool the copper-clad aluminum wire online; Winding, the winding is used to wind and collect the cooled copper-clad aluminum wire; and Heat treatment, the heat treatment is used to heat-treat the wound copper-clad aluminum wire.

17. The preparation method according to claim 15 or 16, characterized in that, Before the continuous extrusion, it further includes: Billet winding, the billet winding is used to wind and collect the aluminum billet and each of the copper billets respectively; Traction, the traction is used to traction the wound aluminum billet and each of the copper billets respectively; Online straightening, the straightening is used to straighten the traction aluminum billet and each of the copper billets online respectively; and Online cleaning, the online cleaning is used to clean the straightened aluminum billet and each of the copper billets online respectively; and then simultaneously perform the continuous extrusion on the online-cleaned aluminum billet and each of the copper billets.

18. A copper-clad aluminum conductive part, characterized in that, Obtained by the preparation method according to any one of claims 1 to 17.

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