Preparation method of copper-clad aluminum conductive part and prepared copper-clad aluminum conductive part

Abstract

The invention discloses a preparation method of a copper-clad aluminum conductive part and the prepared copper-clad aluminum conductive part, and the preparation method comprises the following steps: continuously extruding an aluminum blank and more than two copper blanks at the same time to respectively obtain an aluminum extruded material and more than two copper extruded materials, each copper extrusion material is extruded through the copper extrusion cavity and enters the first welding cavity to form a copper coating layer; the aluminum extrusion material is extruded through the aluminum extrusion cavity; the aluminum extrusion cavity is located in the middle, the first welding-on cavity is arranged around the aluminum extrusion cavity, and more than two copper extrusion materials enter the first welding-on cavity from the periphery of the aluminum extrusion material; and the copper cladding layer is extruded out of the first welding cavity, makes contact with the aluminum extrusion material extruded out of the aluminum extrusion cavity and enters the second welding cavity, cladding welding is completed, and the copper-clad aluminum conductive part is obtained. The method has the remarkable effects of energy conservation, 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 bonding method, in which the finished hollow copper tube is placed outside the finished aluminum core, and then the gap between the copper tube and the aluminum core is eliminated by compression and drawing. The disadvantage of this method is that the aluminum core and the copper tube are mechanically bonded, the copper-aluminum interface resistance is large, and the overall conductivity of the copper-clad aluminum conductive parts is low. 2) Liquid-liquid bonding method, in which copper and aluminum are melted into liquids respectively, and then the two liquid fluids flow out through the core cavity channel and the shell cavity channel respectively and merge, and then cooled and repeatedly drawn to obtain copper-clad aluminum conductive parts. Copper and aluminum are metallurgically bonded, which can significantly improve conductivity, but the disadvantages of this method are: high energy consumption of melting casting, large volume of melting furnace, serious environmental pollution, long process steps, and high production costs. 3) Liquid-solid combination method: one of the materials in the copper cladding and the aluminum core is heated and melted into a liquid state, and the other is a finished product. The liquid aluminum material is filled into the copper cladding layer, or the liquid copper material is poured outside the finished aluminum core, and then cooled and repeatedly drawn to obtain a copper-clad aluminum conductive part. The disadvantages of this method are: it still requires a melting process, high energy consumption, and serious environmental pollution. In addition, repeated drawing has a long process and high cost, and the liquid-solid bonding interface resistance is large. 4) Liquid-semi-solid combination method: aluminum is extruded by continuous extrusion to obtain semi-solid aluminum, and then the copper melt is coated on the surface of the extruded semi-solid aluminum, and then cooled and repeatedly drawn to obtain a copper-clad aluminum conductive part. The disadvantages of this method are: it still requires a melting process, high energy consumption, and serious environmental pollution. In addition, repeated drawing has a long process and high cost. 5) Semi-solid-solid bonding method: the aluminum core is passed into a cavity and moves forward at a certain speed. The copper is extruded by continuous extrusion to obtain semi-solid copper. The semi-solid copper is extruded onto the aluminum core, and then compressed, extruded and cooled to obtain a copper-clad aluminum conductive part. The disadvantage of this method is that only copper is extruded through the closed high-pressure cavity of the continuous extrusion device. The extrusion pressure between copper and aluminum is small when they are combined. The bonding strength at the copper-aluminum interface is insufficient and it is easy to delaminate. In addition, the aluminum core is not semi-solid, and the resistivity at the copper-aluminum interface still has room for improvement. 6) Semi-solid-semi-solid combination method, a semi-solid copper-clad billet is obtained by a continuous extrusion method, a semi-solid aluminum core billet is obtained by a continuous extrusion method, the copper-clad billet is uniformly coated on the surface of the aluminum core billet along the longitudinal direction, and the copper-clad billet and the copper-clad billet are welded to form a closed ring. There are two types of welding in this method, one is the welding between the copper-clad billet and the copper-clad billet, and the other is the welding between the copper-clad billet and the aluminum core billet. The disadvantages of this method are: first, the above two types of welding are carried out under normal pressure, and the bonding strength of copper-copper welding and copper-aluminum welding is insufficient. Second, although the welding interface between the copper-clad billet and the copper-clad billet has a smooth surface, a weld is easily generated inside, resulting in increased resistance. Third, after the coating is completed, repeated drawing is still required, and the process is long.7) One-wheel double-groove continuous extrusion technology, that is, the coating layer blank and the core material blank enter the two extrusion grooves arranged in parallel in the same extrusion wheel for continuous extrusion, and the core material extrusion material and the coating layer extrusion material are obtained at the same time. The core material extrusion material is extruded from the middle mold cavity, and the coating layer extrusion material is extruded from the annular mold cavity surrounding the middle mold cavity to obtain a metal-clad metal conductive part. In this preparation method, there are also two types of welding. One is that the coating layer material is continuously extruded to form a closed annular coating layer, and there is welding between the coating layers, and the other is welding between the coating layer and the core material. However, there is also a gap inside the welding interface between the coating layers, which will destroy the skin effect and seriously affect the conductivity.

[0006] In the prior art, the copper cladding layer in copper-clad aluminum conductive parts is also formed by surface coating technology, mainly including laser cladding, supersonic flame spraying, chemical plating, electroplating, physical vapor deposition (PVD) and chemical vapor deposition (CVD), but all of them have significant defects. Laser cladding relies on a high-cost silver transition layer (450~850 μm), and thermal stress easily causes deformation of the core substrate; supersonic flame spraying has low bonding strength (≤50 MPa) due to mechanical bite of semi-molten particles, and high-temperature flame flow (3000℃) damages the core substrate; chemical plating requires acid etching activation and complex pretreatment, the coating is loose (porosity>10%), and the waste liquid is seriously polluted; the electroplating process produces heavy metal wastewater, has poor bonding strength (≤20 MPa), and is gradually eliminated; PVD is limited by deposition rate (13 μm / h) and coating thickness (<5 μm), which is difficult to meet industrial needs; the CVD process temperature (800~1000℃) is far higher than the melting point of aluminum alloy, and an intermediate layer is required to suppress the melting of the core substrate. The equipment is complex and costly. Although the existing surface coating technology can also achieve copper coating on the surface of aluminum substrate, it generally has high cost, low efficiency or environmental protection problems. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing a copper-clad aluminum conductive part and the prepared copper-clad aluminum conductive part, which has 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: A method for preparing a copper-clad aluminum conductive part includes continuous extrusion, wherein the continuous extrusion includes the following processes: Provide an aluminum billet and two or more copper billets; The aluminum billet and the copper billets are simultaneously and continuously extruded to obtain an aluminum extrusion material and two or more copper extrusion materials respectively; Each of the copper extrusion materials is extruded through the copper extrusion cavity into the first welding cavity, and in the first welding cavity, each of the copper extrusion materials is welded to each other to form a closed copper cladding layer extrusion material; The aluminum extrusion material is extruded through the aluminum extrusion cavity; the aluminum extrusion cavity is located in the middle, the first welding cavity is arranged around the aluminum extrusion cavity, and each of the copper extrusion materials enters the first welding cavity from the periphery of the aluminum extrusion material respectively; The copper clad layer extrusion material is extruded from the first welding cavity, contacts with the aluminum extrusion material extruded from the aluminum extrusion cavity, enters the second welding cavity, completes the cladding welding, and obtains the copper clad aluminum conductive part.

[0009] The second technical solution of the present invention is as follows: A copper-clad aluminum conductive part is prepared by the above preparation method.

[0010] Implementing the embodiments of the present invention will have the following beneficial effects: In the embodiment of the present invention, the closed annular copper cladding layer is divided into two parts, which are regarded as being formed by welding two or more copper cladding layer extrusion materials to each other. Since the copper cladding layer is formed by welding two or more copper cladding layer extrusion materials to each other, the extension distance of each copper cladding layer extrusion material along the circumferential direction is short, which can significantly improve the welding quality between the copper cladding layer extrusion materials and the copper cladding layer extrusion materials, 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 layer, and enhance the improvement of the overall conductivity of the conductive part due to the skin effect.

[0011] 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.

[0012] 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.

[0013] The present invention simultaneously and continuously extrude the copper cladding layer and the aluminum core to obtain newly formed, non-oxidized semi-solid copper cladding layer extrusion material and aluminum extrusion material respectively, which can not only significantly reduce impurities at the welding interface, but also the extrusion materials are in a high temperature and high pressure state, so that the welding between the copper cladding layer extrusion materials and the welding between the copper cladding layer extrusion materials and the aluminum extrusion materials are both sufficient metallurgical welding, which not only improves the welding strength, but also avoids defects such as bubbles and pores as much as possible, and further improves the conductivity of the copper cladding layer and the aluminum core, which cannot be achieved by other existing processes.

[0014] The present invention adopts a continuous extrusion method to form the copper cladding layer and the aluminum core respectively, which not only has the remarkable effects of energy saving, environmental protection, short process, high production efficiency and reduced production cost, but also the continuous extrusion can make the metal materials fully homogenized and compacted, making the organizational structures of the two metals more uniform and the atomic arrangement more compact, which can significantly improve the strength of the two metal materials. Therefore, the method of the present invention can not only enhance the conductivity of the conductive part, but also improve the strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] in: Figure 1 It is a schematic flow chart of a continuous extrusion preparation method of a copper-clad aluminum conductive part according to a specific embodiment of the present invention.

[0017] Figure 2 The invention is a schematic diagram of the process of forming a copper cladding layer by an existing one-round double-slot continuous extrusion method.

[0018] Figure 3 The present invention 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.

[0019] Figure 4 It is a schematic diagram of the process of forming a copper cladding layer according to the present invention.

[0020] Figure 5 It is a schematic diagram of an extrusion device for a copper-clad aluminum conductive part according to a specific embodiment of the present invention.

[0021] Figure 6 yes Figure 5 Schematic diagram of the assembly of the extrusion wheel shoe and the extrusion die in the extrusion equipment shown.

[0022] Figure 7 yes Figure 6 Schematic diagram of the exploded structure of the structure shown.

[0023] Figure 8 yes Figure 6 Schematic diagram of the cross-sectional structure of the structure shown.

[0024] Fig. 9 It is a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity according to a specific embodiment of the present invention.

[0025] Fig.10 It is a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity according to another specific embodiment of the present invention.

[0026] Fig.11 It is a schematic diagram of the positions of the outlet end of the aluminum extrusion cavity and the inlet end of the second welding cavity according to another specific embodiment of the present invention.

[0027] Fig.12 It is a schematic flow chart of a method for preparing a copper-clad aluminum conductive part according to a specific embodiment of the present invention.

[0028] Fig.13 It is a schematic flow chart of a method for preparing a copper-clad aluminum conductive part according to another specific embodiment of the present invention.

[0029] Fig.14 It is a schematic flow chart of a method for preparing a copper-clad aluminum conductive part according to another specific embodiment of the present invention.

[0030] Fig.15 This is a SEM image of the microstructure of the copper-aluminum welding interface of the copper-clad aluminum conductive part prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] refer to Figure 1 The present invention discloses a method for preparing a copper-clad aluminum conductive part, comprising continuous extrusion, wherein the continuous extrusion comprises the following processes: S1: providing an aluminum billet and two or more copper billets, and simultaneously and continuously extruding the aluminum billet and the copper billets to obtain an aluminum extrusion material and two or more copper extrusion materials, respectively.

[0033] 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; 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; 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The present invention simultaneously and continuously extrude the copper cladding layer and the aluminum core to obtain newly formed, non-oxidized semi-solid copper cladding layer extrusion material and aluminum extrusion material respectively, which can not only significantly reduce impurities at the welding interface, but also the extrusion materials are in a high temperature and high pressure state, so that the welding between the copper cladding layer extrusion materials and the welding between the copper cladding layer extrusion materials and the aluminum extrusion materials are both sufficient metallurgical welding, which not only improves the welding strength, but also avoids defects such as bubbles and pores as much as possible, and further improves the conductivity of the copper cladding layer and the aluminum core, which cannot be achieved by other existing processes.

[0038] The present invention adopts a continuous extrusion method to form the copper cladding layer and the aluminum core respectively, which not only has the remarkable effects of energy saving, environmental protection, short process, high production efficiency and reduced production cost, but also the continuous extrusion can make the metal materials fully homogenized and compacted, making the organizational structures of the two metals more uniform and the atomic arrangement more compact, which can significantly improve the strength of the two metal materials. Therefore, the method of the present invention can not only enhance the conductivity of the conductive part, but also improve the strength.

[0039] In the present invention, the aluminum billet and the copper billet can be respectively selected from billets formed by casting, continuous casting and rolling or forging. The cross-sectional dimensions of the aluminum billet and each copper billet can be calculated based on the specified dimensions of copper and aluminum of the copper-clad aluminum conductive member, and the ratio of the sum of the cross-sectional areas of each copper billet to the cross-sectional area of ​​the aluminum billet is equal to the ratio of the cross-sectional areas of copper and aluminum on the cross-sectional area of ​​the copper-clad aluminum conductive member, so as to form a copper-clad aluminum conductive member with a specified material ratio.

[0040] In a specific embodiment, an aluminum billet and two or more copper billets are arranged in parallel in sequence, and are respectively entered into different extrusion slots arranged in parallel in sequence of the same extrusion wheel for continuous extrusion, and the extrusion cavity is provided with a core die for extruding the aluminum extrusion material and each cladding layer die for extruding each copper extrusion material. That is, this embodiment adopts a continuous extrusion method of one round with three or more slots to form a conductive part composited with two metal materials, which has the significant effects of energy saving, environmental protection, short process, high production efficiency, and reduced production cost. In this embodiment, the number of copper billets can be two, three, or more than three.

[0041] refer to 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] refer to Figure 5~Figure 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.

[0050] refer to Figure 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 at 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 connected to the corresponding die openings. The outlet of the first copper extrusion cavity 31 and the outlet of the second copper extrusion cavity 33 are respectively connected to the first welding cavity 34. The outlet of the first welding cavity 34 and the outlet of the aluminum extrusion cavity 32 are respectively connected to the second welding cavity 35.

[0051] The first copper billet, the second copper billet and the aluminum billet are plastically deformed in the corresponding extrusion cavities to obtain corresponding extrusion materials. The first copper billet enters the first copper extrusion cavity 31 through the first cladding layer die 24, the aluminum billet enters the aluminum extrusion cavity 32 through the core die 25, and the second copper billet enters the second copper extrusion cavity 33 through the second cladding layer die 26. In this way, the continuous production of copper-clad aluminum conductive parts can be achieved in one step using one extrusion device. Of course, in other embodiments, more than two extrusion devices can also be used.

[0052] In a specific embodiment, the temperature difference between the copper extrusion material at the cladding layer die and the aluminum extrusion material at the core die does not exceed 100°C. More preferably, it does not exceed 50°C. If the temperature difference between the copper extrusion material and the aluminum extrusion material is too large, the copper-aluminum interface dimensional error will be large when the copper and aluminum contact, affecting the concentricity. Specifically, in a specific embodiment, the temperature difference between the first copper extrusion material at the first cladding layer die 24 or the second copper extrusion material at the second cladding layer die 26 and the aluminum extrusion material at the core die 25 does not exceed 100°C.

[0053] Since the copper extrudates together form a closed annular copper cladding layer, preferably, the temperatures of the copper extrudates at their corresponding cladding layer die openings are the same.

[0054] Preferably, in a specific embodiment, the temperature of the aluminum extrusion material at the core die opening 25 is 350° C. to 550° C. Within this temperature range, the structure of the aluminum extrusion material will be fully refined, thereby improving the electrical conductivity of the aluminum core.

[0055] The temperature of the copper extrudate at the cladding layer die is preferably 450°C to 650°C.

[0056] Preferably, the rotation speed of the extrusion wheel is 5 rpm~40 rpm, which can make the temperature of the aluminum extrudate at the core die mouth reach 350℃~550℃.

[0057] Since the melting point of copper material is higher than that of aluminum material, it is preferred that the copper billet is preheated and then continuously extruded simultaneously with the aluminum billet.

[0058] 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 outer contour of the aluminum core. A second sizing belt 351 is provided at the entrance of the second welding cavity 35, and the second sizing belt 351 is used to shape the outer 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, irregular, etc.

[0059] 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, precision, etc. of the product. The effect of the sizing belt on the composite material is mainly achieved by affecting the flow of the composite metal.

[0060] In this patent, the second sizing belt 351 is used to achieve 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 it is easy to produce more defects at the interface of the two metals. If the length of the second sizing belt 351 is too short, defects such as waves are prone to appear on the surface of the product, and the metallurgical bonding between the two metals is insufficient.

[0061] 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, ensuring 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.

[0062] refer to Figure 9~Figure 11 When the hardness of the copper clad extrudate is greater than that of the aluminum extrudate, that is, hard-covered-soft, preferably, the outlet end of the aluminum extrusion cavity may protrude into the inlet of the second welding cavity to prevent the aluminum core extrudate from being squeezed off by the copper clad extrudate during the extrusion process. When the hardness of the copper clad extrudate is close to that of the aluminum extrudate, 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 clad extrudate is less than that of the aluminum extrudate, the outlet end of the aluminum extrusion cavity may be located above the inlet of the second welding cavity, the outlet end of the aluminum extrusion cavity may also be flush with the inlet end of the second welding cavity, or the outlet end of the aluminum extrusion cavity may also protrude into the inlet of the second welding cavity.

[0063] Furthermore, 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 extrusions 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 dislocation at the welding interface between the cladding layer extrusions and the cladding layer extrusions, thereby affecting the conductivity.

[0064] 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 prevents the core material from being squeezed off.

[0065] 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, so as to facilitate the simultaneous extrusion of multiple extrudates.

[0066] In a specific embodiment, the aluminum billet may be 1 series aluminum or 6 series aluminum. In the present invention, 1 series aluminum refers to an aluminum material with an aluminum content of more than 99% by mass, including undoped pure aluminum. 6 series aluminum refers to an aluminum alloy 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 a T4 state aluminum alloy. T4 state aluminum alloy refers to a state in which the aluminum alloy naturally fails to a basically stable state after solution heat treatment. In this state, the hardened phase in the aluminum alloy has not yet completely precipitated, so the strength is low but the toughness is good, which is suitable for large deformation of continuous extrusion, and a high conductivity aluminum core can be obtained through subsequent cooling and heat treatment.

[0067] In a specific embodiment, the area of ​​the copper coating layer on the cross section of the copper-clad aluminum conductive part accounts for 10% to 40%, preferably 20% to 30%, which not only can produce a skin effect and improve conductivity, but also save copper usage.

[0068] The continuous extrusion of the present invention can be radial continuous extrusion or tangential continuous extrusion. When it is radial continuous extrusion, the die opening of each extrusion material is located on the extrusion shoe, and when it is tangential continuous extrusion, the die opening of each extrusion material is located on the plug.

[0069] In a specific embodiment, the method for preparing a copper-clad aluminum conductive member further includes one or more of the following processes a to h: a. Wire drawing: Wire drawing is used to draw the conductive parts obtained by continuous extrusion to obtain copper-clad aluminum conductive wire; b. Online cooling: Online cooling is used to cool conductive parts made by continuous extrusion or conductive wires made by wire drawing; c. Winding: Winding is used to wind and collect the cooled conductive parts or conductive wires; d. Heat treatment: Heat treatment is used to heat the conductive parts or conductive wires after winding. The heating treatment includes heating and heat preservation processes. The purpose of heat treatment is mainly to make the atoms at the welding interface diffuse more fully, release the stress concentration caused by continuous extrusion, and improve the performance and stability of the material; e. Billet coiling: Billet coiling is used to coil and collect aluminum billets and copper billets respectively; f. Traction, which is used to separately haul the aluminum billets and copper billets collected by winding; g. Online straightening, which is used to straighten the aluminum billet and the copper billet being pulled online respectively; and h. Online cleaning: Online cleaning is used to clean the straightened aluminum billet and each copper billet separately to remove surface impurities and prevent the influence on the welding interface performance; the aluminum billet and each copper billet after online cleaning are continuously extruded at the same time.

[0070] refer to Fig.12 In a specific embodiment, the method for preparing the copper-clad aluminum conductive member includes the following steps: Continuous extrusion, the continuous extrusion is as described above to produce a copper-clad aluminum conductive part; Online cooling, wherein the online cooling is used to cool the copper-clad aluminum conductive parts obtained by continuous extrusion; Coiling, wherein the coiling is used to coil and collect the cooled copper-clad aluminum conductive member; and Heat treatment, the heat treatment is used to heat the copper-clad aluminum conductive part after winding.

[0071] In another embodiment, the above preparation method may not include the heat treatment process. Not all metals require heat treatment. For example, the copper cladding layer and the pure aluminum core may not require heat treatment after continuous extrusion.

[0072] In the above preparation method, continuous extrusion can produce a copper-clad aluminum conductive part with fine and uniform grain structure, and then the grains are further refined into secondary microcrystals through online cooling, and the grain structure is solidified in time to inhibit excessive growth of the grains. Grain refinement can improve strength and hardness, so that it has better mechanical properties. Heat treatment can fully release the residual stress caused by continuous extrusion and online 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 bar.

[0073] The above preparation method can produce a continuous and sufficiently long copper-clad aluminum conductive part through continuous extrusion and online cooling, and then collect it by winding, which is convenient for storage and transportation. The rolled copper-clad aluminum conductive part can be directly placed in a heat treatment chamber for heating treatment. The above preparation method can realize continuous online production with high production efficiency.

[0074] refer to Fig.13 In another specific embodiment, the method for preparing the copper-clad aluminum conductive member includes the following steps: Continuous extrusion, the continuous extrusion is as described above to produce a copper-clad aluminum conductive part; Wire drawing, wherein the wire drawing is used to draw the copper-clad aluminum conductive parts obtained by continuous extrusion to obtain copper-clad aluminum wire; Online cooling, wherein the online cooling is used to cool the copper-clad aluminum wire online; Coiling, wherein the coiling is used to coil and collect the cooled copper-clad aluminum wire; and Heat treatment, the heat treatment is used to heat the copper-clad aluminum wire after winding.

[0075] This specific embodiment can produce copper-clad aluminum wire by wire drawing, online cooling, winding and heat treatment Fig. 9 The embodiments shown are the same and will not be described again.

[0076] refer to Fig.13 and Fig.14 In another specific embodiment, the method for preparing the copper-clad aluminum conductive member further comprises, before continuous extrusion: Billet coiling, the billet coiling is used to coil and collect the aluminum billet and the copper billet respectively; Traction, the traction is used to respectively haul the aluminum billet and the copper billet collected by winding; Online straightening, wherein the straightening is used to perform online straightening on the pulled aluminum billet and each copper billet respectively; and Online cleaning, the online cleaning is used to clean the straightened aluminum billet and each copper billet online respectively; the aluminum billet and each copper billet after online cleaning are simultaneously subjected to the continuous extrusion.

[0077] The above preparation method can realize the automatic and continuous feeding of each billet in the continuous extrusion process, further improving the production efficiency.

[0078] The invention also discloses a copper-clad aluminum conductive part made by the preparation method, which has both high strength and high conductivity.

[0079] It is worth noting that the equality or sameness described in the above embodiments is not equality or sameness in an absolute sense, but equality or sameness allowing a certain error, because absolute equality or sameness cannot be achieved in actual production.

[0080] The following are specific embodiments.

[0081] Example 1 Preparation of copper-clad aluminum conductive parts includes the following processes: 1) Continuous extrusion: providing a first pure copper billet, a second pure copper billet and a 6101 aluminum billet after cleaning and drying, wherein the first pure copper billet and the second pure copper billet have the same cross-sectional area, arranging the first pure copper billet, the 6101 aluminum billet and the second pure copper billet in parallel in sequence, and respectively entering three extrusion slots arranged in parallel in sequence on the same extrusion wheel for continuous extrusion. The extrusion equipment is as follows: Figure 5~Figure 11 The structure shown is used to prepare a copper-clad aluminum conductive part, in which the cross-sectional area of ​​the copper cladding layer accounts for 25% of the cross-sectional area of ​​the copper-clad aluminum conductive part, wherein 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, namely 10 mm respectively, and the length of the first welding cavity is 10 mm.

[0082] 2) The copper-clad aluminum conductive part obtained by continuous extrusion is cooled in a water bath within 3 seconds, then rolled up and heat treated at 250°C for 5 hours to obtain the final copper-clad aluminum conductive part.

[0083] Embodiment 2-3 The only difference between Examples 2 and 3 and Example 1 is that the copper blanks are preheated to 200° C. and 300° C. respectively, and the rest are the same.

[0084] Embodiment 4-5 The difference between Examples 4 and 5 and Example 2 is 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 the length of the second sizing belt.

[0085] Embodiment 6-7 The difference between Embodiments 6 and 7 and Embodiment 4 is only that the length of the first welding cavity is changed.

[0086] Comparative Example 1 Comparative Example 1 was prepared by a one-round double-groove continuous extrusion method, and the rest was the same as Example 1.

[0087] Comparative Examples 2~3 The difference between Comparative Examples 2 and 3 and Comparative Example 1 is only that the length of the first welding cavity is changed.

[0088] The preparation parameters of Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1.

[0089] Table 1: Preparation parameters of Examples 1 to 7 and Comparative Examples 1 to 3 Test Example 1 The tensile strength, yield strength and conductivity per unit area of ​​the conductive members prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were tested respectively. The results are shown in Table 2.

[0090] Table 2: Performance indicators of the conductive parts obtained in Examples 1 to 7 and Comparative Examples 1 to 3 It can be seen from Table 1 that: 1) By comparing Examples 1 to 7 with Comparative Examples 1 to 3, it can be seen that the copper-clad aluminum conductive parts prepared by the one-round three-slot continuous extrusion method of the present invention can significantly improve the conductivity. This is because, for the copper-clad aluminum conductive parts prepared by the one-round double-slot continuous extrusion method adopted in Comparative Example 1, there are many defects such as gaps or bubbles on the copper-copper welding interface on the copper cladding layer, which seriously affect the conductivity.

[0091] 2) Comparing Example 1 with Examples 2-3, the difference is that in Examples 2-3, the copper is preheated to 200°C and 300°C in advance. It can be seen that preheating the copper can improve the processing performance and welding performance of the copper extrusion material. Therefore, the overall conductivity and strength of the copper-clad aluminum conductive parts are improved.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] Test Example 2 The conductive member prepared in Example 1 was subjected to SEM test to observe the microstructure of the copper-aluminum welding interface. Fig.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.

[0097] 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 method for preparing a copper-clad aluminum conductive part, characterized in that: Comprising continuous extrusion, the continuous extrusion comprising the following processes: Providing an aluminum billet and two or more copper billets; simultaneously and continuously extruding the aluminum billet and each of the copper billets to obtain an aluminum extrusion material and two or more copper extrusion materials respectively; Each of the copper extrusion materials is extruded through the copper extrusion cavity into the first welding cavity, and in the first welding cavity, each of the copper extrusion materials is welded to each other to form a closed copper cladding layer extrusion material; The aluminum extrusion material is extruded through the aluminum extrusion cavity, the aluminum extrusion cavity is located in the middle, the first welding cavity is arranged around the aluminum extrusion cavity, and each of the copper extrusion materials enters the first welding cavity from the periphery of the aluminum extrusion material respectively; The copper clad layer extrusion material is extruded from the first welding cavity, contacts with the aluminum extrusion material 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: During the continuous extrusion process, the aluminum billet and two or more copper billets are arranged in parallel and respectively enter different extrusion grooves arranged in parallel on the same extrusion wheel for continuous extrusion. The extrusion cavity is provided with a core die opening for extruding the aluminum extrudate and each cladding layer die opening for extruding each copper extrudate.

3. The preparation method according to claim 2, characterized in that: The copper billet comprises a first copper billet and a second copper billet. The first copper billet, the aluminum billet and the second copper billet are sequentially arranged in parallel and respectively enter three sequentially arranged extrusion grooves of the same extrusion wheel for continuous extrusion to obtain a first copper extrusion material, the aluminum extrusion material and the second copper extrusion material respectively. The extrusion cavity is sequentially provided with a first cladding layer die opening, the core die opening and the second cladding layer die opening. The first copper extrusion material enters the first copper extrusion cavity through the first cladding layer die opening, the aluminum extrusion material enters the aluminum extrusion cavity through the core die opening, and the second copper extrusion material enters the second copper extrusion cavity through the second cladding layer die opening.

4. The preparation method according to claim 2, characterized in that: The temperature of the copper extrusion material at the cladding layer die port is less than 100° C. from the temperature of the aluminum extrusion material at the core die port.

5. The preparation method according to claim 2, characterized in that: The temperature of the copper extrudate at the coating layer die is 450°C to 650°C; The temperature of the aluminum extrudate at the core die opening is 350° C. to 550° C.

6. The preparation method according to claim 2, characterized in that: The rotation speed of the extrusion wheel is 5 rpm~40 rpm.

7. The preparation method according to claim 1, characterized in that: The cross-sectional areas of the copper blanks are the same; In the first welding cavity, each of the copper extrusions is evenly distributed around the aluminum extrusion; The extrusion speeds of the copper extrudates are the same; The copper extrusion material and the aluminum extrusion material are extruded at the same speed.

8. The preparation method according to claim 1, characterized in that: A first sizing belt is provided at the outlet of the aluminum extrusion cavity, and a second sizing belt is provided 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.

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

10. The preparation method according to claim 1, characterized in that: When the hardness of the copper cladding extrusion material is greater than the hardness 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 cladding layer extrusion material is equal to the hardness 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 clad layer extrusion material is less than the hardness 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.

11. The preparation method according to claim 1, characterized in that: The length of the first welding cavity along the extrusion direction is 10 mm to 50 mm; The length of the 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.

12. 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 to the total cross-sectional area of ​​the copper-clad aluminum conductive part is 10% to 40%.

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

14. The preparation method according to claim 1, characterized in that: The width of the welding interface between the copper extrusion materials is 5 μm to 60 μm; The number of 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 member; The width of the bonding interface between the copper extrusion material and the aluminum extrusion material is 5 μm to 40 μm.

15. The preparation method according to any one of claims 1 to 14, characterized in that: After each of the copper billets is preheated, they are continuously extruded simultaneously with the aluminum billet.

16. The preparation method according to claim 1, characterized in that: Also includes online cooling, winding and heat treatment; or, Also includes online cooling and winding: The online cooling is used to perform online cooling on the copper-clad aluminum conductive part obtained by continuous extrusion; The coiling is used to coil and collect the cooled copper-clad aluminum conductive member; and The heat treatment is used to heat the copper-clad aluminum conductive part after winding.

17. The preparation method according to claim 1, characterized in that: Also includes: Wire drawing, the wire drawing is used to draw the copper-clad aluminum conductive part obtained by continuous extrusion to obtain copper-clad aluminum wire; Online cooling, the online cooling is used to perform online cooling on the copper-clad aluminum wire; Coiling, the coiling is used to coil and collect the cooled copper-clad aluminum wire; and Heat treatment, the heat treatment is used to heat the copper-clad aluminum wire after winding.

18. The preparation method according to claim 16 or 17, characterized in that: Before the continuous extrusion, the method further comprises: Billet coiling, the billet coiling is used to coil and collect the aluminum billet and the copper billets respectively; Traction, the traction is used to respectively haul the aluminum billet and each copper billet collected by winding; Online straightening, the straightening is used to perform online straightening on the pulled aluminum billet and each copper billet respectively; and Online cleaning, the online cleaning is used to clean the straightened aluminum billet and each copper billet online respectively; the aluminum billet and each copper billet after online cleaning are simultaneously subjected to the continuous extrusion.

19. A copper-clad aluminum conductive part, characterized in that: Prepared by the preparation method described in any one of claims 1 to 18.

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