Preparation method of metal-clad metal conductive part and prepared metal-clad metal conductive part

Abstract

The invention discloses a preparation method of a metal-clad metal conductive part and the prepared metal-clad metal conductive part, the preparation method comprises continuous extrusion, and the continuous extrusion comprises the following processes: respectively carrying out continuous extrusion on a core blank and more than two coating layer blanks to respectively obtain a core extruded material and more than two coating layer extruded materials; more than two coating layer extruded materials are respectively extruded by the coating layer extrusion cavities to enter the first welding cavity, and the coating layer extruded materials are mutually welded to form a closed coating layer extruded material; the core extrusion material is extruded from the core extrusion cavity; and the cladding layer extrusion material is extruded out of the first welding cavity, makes contact with the core extrusion material extruded out of the core extrusion cavity and enters the second welding cavity, cladding welding is completed, and the metal-clad metal conductive part is obtained. The conductive part 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 metal-clad metal conductive part and the prepared metal-clad metal 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 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 800A, and will develop towards 1000A and higher in the future. In the absence of additional cooling measures on the vehicle end, 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, 120mm 2 The maximum current carrying capacity of copper conductive rods / rows is 500A. To obtain a higher current carrying capacity, the cross-sectional area of ​​the conductive rods / rows should be larger than 120mm. 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] The conductivity of pure aluminum is the highest, about 62% IACS, but pure aluminum is too soft to meet the strength requirements. In order to meet the strength requirements, pure aluminum is doped with alloy elements to increase the strength of pure aluminum. However, the doped alloy elements will reduce the conductivity of pure aluminum. Therefore, strength and conductivity are usually mutually restricted in aluminum alloy conductive parts. 6 series aluminum alloy has excellent conductivity and is widely used in conductive parts such as conductive bars or rods of electric vehicles. The conductivity of conductive bars or rods made of 6 series aluminum alloy can be increased to 60% IACS, but its yield strength is only 90MPa to 150MPa. How to break the restrictive relationship between strength and conductivity and prepare high-strength and high-conductivity conductive parts is a very important scientific and industrial problem.

[0004] The generator of new energy electric vehicles outputs alternating current, and the alternating current transmission process has the characteristic of "skin effect", that is, the current will be concentrated on the surface of the conductor during the AC transmission process, which provides theoretical support for the preparation of high-strength and high-conductivity conductive parts. Applying the above theory, using high-conductivity metal as the cladding metal and using high-strength metal as the core metal to prepare conductive parts can not only improve the strength of conductive parts, but also improve the conductivity of conductive parts.

[0005] Copper-clad aluminum composite conductive parts and aluminum-clad aluminum composite conductive parts are typical representatives of the above theory application. Limited by materials, the conductivity of aluminum-clad aluminum composite conductive parts is difficult to exceed 62% IACS, but its advantages are light weight and low cost. The cost of copper-clad aluminum composite conductive parts is higher than that of aluminum alloy, but its conductivity is between that of pure copper and pure aluminum, that is, between 62% IACS and 99% IACS, and there is a large room for improvement in conductivity. Therefore, copper-clad aluminum composite conductive parts are also known as the third-generation new conductors after copper and aluminum.

[0006] However, due to the existence of a bonding interface between the clad metal and the core metal, the quality of the bonding interface will seriously affect the interface resistance, thereby affecting the conductivity.

[0007] In the prior art, the preparation methods of metal-clad metal conductive parts include the following: 1) Solid-solid bonding method: A finished hollow cladding sleeve is sleeved outside a finished core material, and then through compression and drawing, the gap between the sleeve and the core material is eliminated. The disadvantage of this method is that the sleeve and the core material are mechanically bonded, the bonding interface resistance is large, the conductivity is low, and at the same time, it is difficult to keep the cross-sections of the core part and the cladding layer of the conductive part prepared by this method in regular shapes, resulting in uneven distribution of charges in the cladding layer during the skin effect and increasing the equivalent resistance of the conductor. 2) Liquid-liquid bonding method: The cladding metal and the core metal are respectively melted into liquids, 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 conductive part. Although the cladding material and the core material are metallurgically bonded, which can significantly improve the conductivity, the disadvantages of this method are: high energy consumption for melting and casting, large volume of the melting furnace, serious environmental pollution, long process steps, and high production cost. 3) Liquid-solid bonding method: One of the materials of the cladding layer and the core material is heated and melted into a liquid, and the other is a finished product. The liquid core material is filled into the cladding sleeve, or the liquid cladding metal material is poured outside the finished core material, and then cooled and drawn repeatedly to obtain the conductive part. The disadvantages of this method are: First, the melting process is still required, with high energy consumption and serious environmental pollution. Coupled with repeated drawing, the process is long and the cost is high. Second, the difference between the liquid-solid bonding interfaces is large and the resistance is high. 4) Liquid-semi-solid bonding method: The core material is extruded to obtain a semi-solid core material by a continuous extrusion method, and then the molten copper is coated on the surface of the extruded semi-solid core material, and then cooled and drawn repeatedly to obtain the conductive part. The disadvantages of this method are also: the melting process is still required, with high energy consumption and serious environmental pollution. Coupled with repeated drawing, the process is long and the cost is high, and the difference between the liquid-semi-solid bonding interfaces is also large. 5) Semi-solid-solid bonding method: The core material is passed into a cavity and moves forward at a certain speed. The cladding metal is extruded by a continuous extrusion method to obtain a semi-solid cladding layer. The semi-solid cladding layer is extruded onto the core material, and then compressed, extruded and cooled to obtain the conductive part. The disadvantages of this method are: Only the cladding layer is extruded through the closed high-pressure cavity of the continuous extrusion device, and the extrusion pressure between the copper and aluminum of the cladding layer 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) The semi-solid and semi-solid combination method involves obtaining a semi-solid copper-coated blank by continuous extrusion, obtaining a semi-solid aluminum core blank by continuous extrusion, uniformly wrapping the copper-coated blank longitudinally on the surface of the aluminum core blank, and forming a closed ring by welding the copper-coated blanks together. There are two types of welding in this method. One is the welding between the copper-coated blanks, and the other is the welding between the copper-coated blank and the aluminum core blank. The disadvantages of this method are as follows: First, both of the above-mentioned weldings are carried out under normal pressure, and the bonding strengths of copper-copper welding and copper-aluminum welding are insufficient. Second, although the welding interface between the copper-coated blanks is smooth on the surface, weld seams are likely to occur inside, resulting in an increase in resistance. Third, after the wrapping is completed, repeated drawing is still required, and the process is long. 7) The one-round double-groove continuous extrusion technology means that the coated blank and the core blank enter two extrusion grooves arranged side by side in the same extrusion wheel in sequence for continuous extrusion, and at the same time, the core extrusion material and the coated extrusion material are obtained. The core extrusion material is extruded from the middle die cavity, and the coated extrusion 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 the welding between the continuously extruded coated materials to form a closed ring-shaped coating layer, and there is welding between the coating layers. The other is the welding between the coating layer and the core material. However, there are also gaps inside the welding interface between the coating layers, and these gaps will damage the skin effect and seriously affect the conductivity. Summary of the Invention

[0008] An object of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide a preparation method of a metal-clad metal conductive part and the obtained metal-clad metal conductive part, which have the remarkable effects of energy conservation, environmental protection, short process, low cost, high welding strength, and high conductivity.

[0009] To achieve the above object, the first technical solution of the present invention is as follows:

[0010] A preparation method of a metal-clad metal conductive part includes continuous extrusion, and the continuous extrusion includes the following processes:

[0011] Provide a core blank and two or more coated blanks;

[0012] Carry out continuous extrusion on the core blank and two or more of the coated blanks respectively to obtain a core extrusion material and two or more coated extrusion materials respectively;

[0013] Two or more of the coated extrusion materials are respectively extruded into the first welding cavity through the coated extrusion cavity, and in the first welding cavity, the coated extrusion materials are welded together to form a closed coated extrusion material;

[0014] The core extrusion material is extruded from the core extrusion cavity; the core extrusion cavity is located in the middle, the first welding cavity is arranged around the core extrusion cavity, and each of the coating layer extrusion materials enters the first welding cavity from the periphery of the core extrusion material;

[0015] The coating layer extrusion material is extruded from the first welding cavity, contacts the core extrusion material extruded from the core extrusion cavity, enters the second welding cavity, and completes the coating welding to obtain the metal-clad metal conductive part.

[0016] The second technical solution of the present invention is as follows:

[0017] A metal-clad metal conductive part is obtained by the above preparation method.

[0018] Implementing the embodiments of the present invention will have the following beneficial effects:

[0019] In the embodiments of the present invention, the closed annular coating layer is divided into two or more parts, which is regarded as being formed by welding two or more coating layer extrusion materials to each other. Since the coating layer is formed by welding two or more coating layer extrusion materials to each other, the extension distance of each coating layer extrusion material in the circumferential direction is short, which can significantly improve the welding quality between the coating 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 coating layer, and enhance the improvement of the overall conductivity of the conductive part by the skin effect.

[0020] At the same time, two or more coating layer extrusion materials are extruded around the core extrusion material at the same time, and the extrusion forces formed by each coating layer extrusion material on the core material can be symmetric about the center of the core material, thereby avoiding core eccentricity and ensuring the concentricity of the core material and the coating layer. Therefore, a coating layer with uniform thickness can be obtained, further enhancing the improvement of conductivity by the skin effect.

[0021] The coating layer is formed by welding two or more coating layer extrusion materials to each other in the first welding cavity, which can reduce the extension distance of the coating 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 generation 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 coating layer extrusion material is basically the same as that of the core extrusion material, reducing the dislocation of the welding interface caused by the frictional resistance between the coating layer and the core material, and reducing the equivalent resistance of the welding interface between the coating layer and the core material, thereby further improving the overall conductivity of the metal-clad metal conductive part.

[0022] The present invention simultaneously performs continuous extrusion on the cladding layer and the core material to respectively obtain a newly formed and non-oxidized semi-solid cladding layer extrusion material and a core extrusion material. This not only significantly reduces impurities at the welding interface, but also, since the extrusion materials are in a high-temperature and high-pressure state, the welding between the cladding layer extrusion materials and the welding between the cladding layer extrusion material and the core extrusion material are both full metallurgical welds. This not only improves the welding strength, but also minimizes defects such as bubbles and pores, further enhancing the conductivity of the cladding layer and the core material, which cannot be achieved by other existing processes.

[0023] The present invention uses a continuous extrusion method to form the cladding layer and the core material 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 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 conductivity of the conductive part, but also improve the strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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 drawings in the following description 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.

[0025] Wherein:

[0026] Figure 1 is a schematic flow chart of a method for continuously extruding a metal-clad metal conductive part according to a specific embodiment of the present invention.

[0027] Figure 2 is a schematic flow chart of forming a hollow copper cladding layer by an existing one-round double-groove continuous extrusion method.

[0028] 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 combination method.

[0029] Figure 4 is a schematic flow chart of forming a copper cladding layer according to the present invention.

[0030] Figure 5 is a schematic diagram of an extrusion device for a metal-clad metal conductive part according to a specific embodiment of the present invention.

[0031] Figure 6 is Figure 5 a schematic assembly diagram of an extrusion wheel shoe and an extrusion die in the shown extrusion device.

[0032] Figure 7 is Figure 6 the explosion structure schematic diagram of the shown structure.

[0033] Figure 8 is Figure 6 the cross-section structure schematic diagram of the shown structure.

[0034] Figure 9 is the process schematic diagram of the preparation method of the metal-clad metal conductive part in a specific embodiment of the present invention.

[0035] Figure 10 is the process schematic diagram of the preparation method of the metal-clad metal conductive part in another specific embodiment of the present invention.

[0036] Figure 11 is the process schematic diagram of the preparation method of the metal-clad metal conductive part in another specific embodiment of the present invention.

[0037] Figure 12 is the SEM micrograph of the copper-aluminum welded joint interface of the copper-clad aluminum conductive part obtained in Example 1 of the present invention.

[0038] Figure 13 is the SEM micrograph of the aluminum-aluminum welded joint interface of the aluminum-clad aluminum conductive part obtained in Example 2 of the present invention. Specific Embodiments

[0039] 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0040] Refer to Figure 1 , the present invention discloses a preparation method of a metal-clad metal conductive part, including continuous extrusion, and the continuous extrusion includes the following processes:

[0041] S1: Provide a core blank and two or more cladding layer blanks; continuously extrude the core blank and two or more cladding layer blanks respectively to obtain a core extruded material and two or more cladding layer extruded materials.

[0042] S2: Two or more cladding layer extruded materials are respectively extruded into the first welding cavity through the cladding layer extrusion cavity. In the first welding cavity, the cladding layer extruded materials are welded together to form a closed cladding layer extruded material.

[0043] S3: The core extruded material is extruded from the core extrusion cavity; the core extrusion cavity is located in the middle, the first welding cavity is arranged around the core extrusion cavity, and each cladding layer extruded material enters the first welding cavity from the periphery of the core extruded material.

[0044] S4: The extruded material of the coating layer is extruded from the first welding cavity, contacts the extruded material of the core extruded from the core extrusion cavity, enters the second welding cavity, and completes the coating welding to obtain a metal-clad metal conductive part.

[0045] In the above technical solution, the closed annular coating layer is divided into more than two parts, regarded as being formed by welding more than two extruded materials of the coating layer with each other. Since the coating layer is formed by welding more than two extruded materials of the coating layer with each other, the extension distance of each extruded material of the coating layer in the circumferential direction is short, which can significantly improve the welding quality between the extruded materials of the coating layer, increase the width of the welding joint interface, and avoid defects such as gaps at the welding interface as much as possible, improve the conductivity of the coating layer, and enhance the improvement of the overall conductivity of the conductive part by the skin effect.

[0046] At the same time, more than two extruded materials of the coating layer are extruded simultaneously around the extruded material of the core, and the extrusion forces formed by each extruded material of the coating layer on the core material can be symmetrically distributed about the center of the core material, thereby avoiding the eccentricity of the core material and ensuring the concentricity of the core material and the coating layer. Therefore, a coating layer with uniform thickness can be obtained, further enhancing the improvement of the conductivity by the skin effect.

[0047] The coating layer is formed by welding more than two extruded materials of the coating layer with each other in the first welding cavity, which can reduce the extension distance of the extruded material of the coating layer 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 generation of complex metal dislocations at the welding interface due to too long welding time can be avoided, which has an adverse effect on the conductivity. Reducing the length of the first welding cavity in the extrusion direction can also reduce the frictional loss of the extrusion energy, making it easier to ensure that the extrusion speed of the extruded material of the coating layer is basically the same as that of the extruded material of the core, reducing the dislocation of the welding interface caused by the frictional resistance between the coating layer and the core material, and reducing the equivalent resistance of the welding interface between the coating layer and the core material, thereby further improving the overall conductivity of the metal-clad metal conductive part.

[0048] In the above technical solution, the coating layer and the core material are continuously extruded simultaneously to obtain fresh and non-oxidized semi-solid extruded materials of the coating layer and the core extruded material respectively. This can not only significantly reduce the impurities at the welding interface, but also the extruded materials are in a high-temperature and high-pressure state, enabling the welding between the extruded materials of the coating layer with each other and the welding between the extruded material of the coating layer and the extruded material of the core to be full metallurgical welding, which not only improves the welding strength, but also avoids defects such as bubbles and pores as much as possible, further improving the conductivity of the coating layer and the core material, which cannot be achieved by other existing processes.

[0049] In the above technical solution, the cladding layer and the core material are respectively formed by the continuous extrusion method, which not only has the remarkable effects of energy saving, environmental protection, short process, high production efficiency and reduction of production costs, but also can make the metal material fully homogenized and compacted by continuous extrusion, 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.

[0050] In the above technical solution, the core blank and each cladding layer blank can respectively select blanks formed by casting, continuous casting and rolling or forging, etc. The cross-sectional dimensions of the core blank and each cladding layer blank can be calculated from the specified dimensions of the cladding layer and the core material of the metal-clad metal conductive part. The ratio of the sum of the cross-sectional areas of each cladding layer blank to the cross-sectional area of the core blank is equal to the ratio of the cross-sectional areas of the cladding layer and the core material on the cross-section of the metal-clad metal conductive part, so as to form a metal-clad metal conductive part with a specified material ratio.

[0051] In a specific embodiment, the core blank and more than two cladding layer blanks are arranged side by side in sequence and respectively enter 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 extruding the core extrudate and each cladding layer die orifice for extruding each cladding layer extrudate respectively. That is, this embodiment adopts a continuous extrusion method with more than three grooves in one wheel to form a conductive part composed of two metal materials, which has the remarkable effects of energy saving, environmental protection, short process, high production efficiency and reduction of production costs. In this embodiment, the number of the cladding layer blanks can specifically be two, three, or more than three, etc.

[0052] Reference Figure 2 When preparing a metal-clad metal conductive part by the existing continuous extrusion technology with two grooves in one wheel, the number of the cladding layer blanks used is only one. The cladding layer blank and the core blank enter different extrusion grooves for continuous extrusion respectively. When the cladding layer extrudate enters the first welding cavity, as the cladding layer extrudate is extruded, the cross-sectional width W of the cladding layer extrudate gradually increases and the thickness D gradually decreases until the two ends in the cross-sectional width W direction enclose a closed annular shell. In this way, the extension deformation amount in the cross-sectional width W direction is too large, and it is easy to have gaps at the welding interface between the cladding layer extrudates. When the strength of the cladding layer material is greater than that of the core material, due to the poor fluidity of the material with high strength, more gap defects will be generated at the welding interface between the cladding layer extrudates.

[0053] From Figure 2 It can also be seen that during the process of the cladding layer extrudate forming a closed ring, the extrusion force of the cladding layer extrudate on the core extrudate easily causes the core material to be eccentric and the thickness of the cladding layer to be uneven.

[0054] Reference Figure 3, which is a schematic cross-sectional structure diagram of a copper-clad aluminum conductive part obtained by the semi-solid / semi-solid combination method in the prior art. The semi-solid / semi-solid combination method is as follows: 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 longitudinally and uniformly coated on the surface of the aluminum core blank, and the copper-clad blanks are welded to form a closed ring. From Figure 3 it can be seen that it includes a welding interface between copper and copper, and holes can be seen on the welding interface between copper and copper, and there are also gaps with poor bonding on the copper-aluminum welding interface.

[0055] Reference Figure 4 , in a specific embodiment of the present invention, the closed annular coating layer is formed by welding two coating layer extrudates. The cross-sectional width W of the two coating layer extrudates gradually increases, and the thickness D gradually decreases. Then, the two ends of the cross-sectional width W of the two coating layer extrudates approach each other and are welded into a closed annular shell, and the deformation amount in the width W direction decreases. Compared with Figure 2 the prior art, it is possible to avoid defects such as gaps or holes at the welding interface between the coating layer extrudates as much as possible. At the same time, from Figure 4 it can also be seen that when two or more coating layer extrudates extend circumferentially from around the core material at the same time, the eccentricity of the core material can be avoided.

[0056] Since two or more coating layer blanks are welded to form a coating layer, preferably, the cross-sectional areas of the coating layer blanks are the same. In the first welding cavity, the coating layer extrudates are evenly distributed around the core extrudate, and the extrusion speeds of the coating layer extrudates are the same, so that the extrusion forces of the coating layer extrudates on the core material can be symmetrically distributed about the center of the core material, thereby avoiding the eccentricity of the core material and ensuring the concentricity of the core material and the coating layer. Therefore, a coating layer with uniform thickness can be obtained, and the skin effect on the improvement of conductivity can be further enhanced.

[0057] More preferably, the extrusion speeds of the coating layer extrudate and the core extrudate are the same, which reduces the dislocation of the welding interface caused by the frictional resistance between the coating layer and the core material, and reduces the equivalent resistance of the welding interface between the coating layer and the core material, thereby further improving the overall conductivity of the metal-clad metal conductive part.

[0058] Further specifically, in a specific embodiment, the width of the welding interface between the cladding extrusion material and the cladding extrusion material is 5μm to 100μm; the number of welding interfaces between the cladding extrusion material and the cladding extrusion material is more than 2, and the welding interface between the cladding extrusion material and the cladding extrusion material extends along the axial direction of the metal-clad metal conductive part, and the width of the bonding interface between the cladding extrusion material and the core extrusion material is 5μm to 80μm. 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.

[0059] In a specific embodiment, reference Figure 5 The cladding layer blank includes a first cladding layer blank and a second cladding layer blank. The first cladding layer blank, the core blank and the second cladding layer blank are sequentially arranged in parallel and enter three parallel extrusion wheel grooves 11 of the same extrusion wheel 10 for continuous extrusion at the same time.

[0060] refer to Figures 5 - 8 In a specific embodiment, the extrusion equipment includes: an extrusion wheel 10, an extrusion wheel boot 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 cladding layer blank, the core blank and the second cladding layer blank in sequence. The extrusion wheel boot 20 is provided with plugs 21 at positions corresponding to each extrusion wheel groove 11. The extrusion wheel groove 11, the plug 21 and the extrusion wheel boot 20 constitute an extrusion cavity. The three blanks are continuously extruded in three independent extrusion cavities to obtain extrusion materials. Each extrusion cavity is provided with a first cladding layer die opening 24, a core die opening 25 and a second cladding layer die opening 26. The first cladding layer extrusion material enters the first cladding layer extrusion cavity 31 through the first cladding layer die opening 24, the aluminum extrusion material enters the core extrusion cavity 32 through the core die opening 25, and the second cladding layer extrusion material enters the second cladding layer extrusion cavity 33 through the second cladding layer die opening 26.

[0061] refer to Figure 7 and Figure 8, the extrusion die 30 includes a first die 36 and a second die 37 arranged in a stacked manner. The extrusion die 30 is provided with a first cladding layer extrusion cavity 31, a core extrusion cavity 32, a second cladding layer extrusion cavity 33, a first welding cavity 34 and a second welding cavity 35. The core extrusion cavity 32 is located in the middle, the first cladding layer extrusion cavity 31 and the second cladding layer extrusion cavity 33 are respectively located on both sides of the core extrusion cavity 32. The first welding cavity 34 is located behind the first cladding layer extrusion cavity 31 and the core extrusion cavity 32, and is located outside the periphery of the core extrusion cavity 32. The second welding cavity 35 is located behind the core extrusion cavity 32. The second welding cavity 35 is coaxially arranged with the core extrusion cavity 32. The inlets of the first cladding layer extrusion cavity 31, the core extrusion cavity 32 and the second cladding layer extrusion cavity 33 are respectively communicated with corresponding die orifices. The outlets of the first cladding layer extrusion cavity 31 and the second cladding layer extrusion cavity 33 are respectively communicated with the first welding cavity 34. The outlets of the first welding cavity 34 and the core extrusion cavity 32 are respectively communicated with the second welding cavity 35.

[0062] The first cladding layer blank, the second cladding layer blank and the core blank respectively undergo plastic deformation in the corresponding extrusion cavities to obtain corresponding extruded materials. The first cladding layer blank enters the first cladding layer extrusion cavity 31 through the first cladding layer die orifice 24, the core blank enters the core extrusion cavity 32 through the core die orifice 25, and the second cladding layer blank enters the second cladding layer extrusion cavity 33 through the second cladding layer die orifice 26. Thus, the continuous production of the metal-clad metal conductive part can be realized in one step by using one extrusion device. Of course, in other embodiments, more than two extrusion devices can also be used.

[0063] In a specific embodiment, a first sizing band 321 is provided at the outlet of the core extrusion cavity 32. The first sizing band 321 is used to shape the external contour of the core material. A second sizing band 351 is provided at the inlet of the second welding cavity 35. The second sizing band 351 is used to shape the external contour of the cladding layer. The shapes of the first sizing band 321 and the second sizing band 351 can be any shape, for example, they can be circular, square, triangular, polygonal and irregular shapes, etc.

[0064] In addition to ensuring the shape and size of the product, the sizing band is also used to ensure the surface quality of the extruded product. The length of the sizing band has different effects on the quality, size, accuracy, etc. of the product. The effect of the sizing band on the composite of the composite material is mainly achieved by affecting the flow of the composite metal.

[0065] In this patent, the second sizing belt 351 is used to achieve the welding between the surface coating metal and the core metal. 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 coating metal and the die outlet is too large, resulting in large resistance and slow flow rate, and it is easy to generate 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 likely to appear on the product surface, and at the same time, the metallurgical bonding between the two metals is insufficient.

[0066] 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.

[0067] 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 extrusion materials of each coating layer cannot be completely welded, 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 extrusion materials of the coating layers, affecting the conductivity.

[0068] Preferably, in a specific embodiment, the angle between the outlet direction of the first welding cavity 34 and the outlet direction of the core extrusion cavity 32 is less than 60°, so that the radial extrusion stress of the coating layer on the core material is appropriate, which not only strengthens the welding but also avoids the core material from being squeezed off.

[0069] In a specific embodiment, the length of each coating layer extrusion cavity along the extrusion direction is 10 mm to 50 mm; the length of the core extrusion cavity along the extrusion direction is 10 mm to 50 mm. Preferably, the lengths of each coating layer extrusion cavity and the core extrusion cavity along the extrusion direction are the same, which is convenient for synchronously extruding each extrusion material.

[0070] 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 each extrusion material are located on the extrusion boots. When it is tangential continuous extrusion, the die orifices of each extrusion material are located on the plugs.

[0071] In a specific embodiment, the method for preparing the metal-clad metal conductive part further includes one or more of the following processes a to h:

[0072] a. Wire drawing, which is used to draw the metal-clad metal conductive part obtained by continuous extrusion to obtain a metal-clad metal conductive wire;

[0073] b. Online cooling, which is used to perform online cooling on the metal-clad metal conductive part obtained by continuous extrusion or the metal-clad metal conductive wire obtained by wire drawing;

[0074] c. Rewinding, which is used to wind and collect the cooled conductive parts or conductive wires, facilitating transfer and storage;

[0075] d. Heat treatment, which is used to heat-treat the rewound conductive parts or conductive wires. The heat treatment includes a heating-up process and a heat-preservation process. The main purpose of the heat treatment is to make the atomic diffusion at the welding 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;

[0076] e. Blank rewinding, which is used to wind and collect the core blank and each cladding layer blank respectively;

[0077] f. Traction, which is used to traction the wound core blank and each cladding layer blank respectively;

[0078] g. On-line straightening, which is used to straighten the tractioned core blank and each cladding layer blank respectively; and

[0079] h. On-line cleaning, which is used to clean the straightened core blank and each cladding layer blank respectively, removing surface impurities to prevent the influence on the performance of the welding joint interface; and continuously extruding the core blank and each cladding layer blank after on-line cleaning at the same time.

[0080] Reference Figure 9 , in a specific embodiment, the preparation method of the metal-clad metal conductive part includes the following processes:

[0081] Continuous extrusion, as described above, to obtain the metal-clad metal conductive part;

[0082] On-line cooling, which is used to cool the metal-clad metal conductive part obtained by continuous extrusion on-line;

[0083] Rewinding, which is used to wind and collect the cooled metal-clad metal conductive part; and

[0084] Heat treatment, which is used to heat-treat the rewound metal-clad metal conductive part.

[0085] In the above preparation method, continuous extrusion can obtain a metal-clad metal conductive part with fine and uniform tissue grains. Then, through on-line cooling, the grains are further refined into secondary microcrystals, and the grain structure is solidified in time, inhibiting the excessive growth of grains. 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, obtaining a metal-clad metal conductive part with stable structure and high conductivity. In the above preparation method, the obtained metal-clad metal conductive part can be a conductive rod or a conductive bar.

[0086] The above preparation method can produce continuous and long enough metal-clad metal conductive parts through continuous extrusion and on-line cooling, and then collect them by winding, which is convenient for storage and transportation. The wound metal-clad metal conductive parts 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.

[0087] Reference Figure 11 , in another specific embodiment, a method for preparing a metal-clad metal conductive part includes the following processes:

[0088] Continuous extrusion, which is as described above, to produce a metal-clad metal conductive part;

[0089] Drawing, which is used to draw the metal-clad metal conductive part obtained by continuous extrusion to obtain a metal-clad metal wire;

[0090] On-line cooling, which is used to cool the metal-clad metal wire on-line;

[0091] Winding, which is used to wind and collect the cooled metal-clad metal wire; and

[0092] Heat treatment, which is used to heat-treat the wound metal-clad metal wire.

[0093] In this specific embodiment, a metal-clad metal wire can be obtained through drawing. The on-line cooling, winding, and heat treatment are the same as those in the Figure 8 illustrated embodiment and will not be elaborated here.

[0094] Reference Figure 10 and Figure 11 , in another specific embodiment, before continuous extrusion, the method for preparing a metal-clad metal conductive part further includes:

[0095] Blank winding, which is used to wind and collect the first cladding layer blank, the core blank, and the second cladding layer blank respectively;

[0096] Traction, which is used to traction the wound first cladding layer blank, the core blank, and the second cladding layer blank respectively;

[0097] On-line straightening, which is used to straighten the tractioned first cladding layer blank, the core blank, and the second cladding layer blank respectively; and

[0098] On-line cleaning, which is used to clean the straightened first cladding layer blank, the core blank, and the second cladding layer blank respectively; and the first cladding layer blank, the core blank, and the second cladding layer blank after on-line cleaning are simultaneously subjected to the continuous extrusion.

[0099] The above preparation method can achieve automatic continuous feeding of each blank in the continuous extrusion process, further improving production efficiency.

[0100] The present invention also discloses a metal-clad metal conductive part prepared by the above preparation method, which has high strength and high conductivity.

[0101] The cladding layer metal can specifically be copper, copper alloy, aluminum, aluminum alloy, silver, silver alloy, gold or gold alloy, etc., and the core metal can specifically be copper, copper alloy, aluminum, aluminum alloy, silver, silver alloy, gold or gold alloy, etc. Preferably, the conductivity of the cladding layer metal is greater than that of the core metal, and the skin effect is utilized to improve the conductivity. Preferably, one of the cladding layer metal and the core metal has greater strength to improve the strength of the conductive part. Of course, the cladding layer metal and the core metal can also be metal materials other than those listed above.

[0102] It should be noted that the equality or sameness expressed in 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.

[0103] The following are specific embodiments.

[0104] Example 1

[0105] Prepare a copper-clad aluminum conductive part, including the following process:

[0106] 1) Continuous extrusion: Provide the first pure copper blank, the second pure copper blank and the 6101 aluminum blank after cleaning and drying. The cross-sectional areas of the first pure copper blank and the second pure copper blank are the same. Arrange the first pure copper blank, the 6101 aluminum blank and the second pure copper blank in parallel in sequence and enter three sequentially arranged extrusion grooves of the same extrusion wheel respectively for continuous extrusion. The extrusion equipment is as Figures 5 - 8 shown in the structure to prepare a copper-clad aluminum conductive part. The cross-sectional area ratio of the copper cladding 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 are 10 mm, and the length of the first welding cavity is 10 mm.

[0107] 2) The copper-clad aluminum conductive part obtained by continuous extrusion enters the water bath for cooling within 3 s, and then is wound up and heat-treated at 250 °C for 5 h to obtain the final finished copper-clad aluminum conductive part.

[0108] Example 2

[0109] Prepare an aluminum-clad aluminum conductive part, including the following process:

[0110] 1) Continuous extrusion is carried out to provide the first 1060 aluminum billet, the second 1060 aluminum billet, and the 6101 aluminum billet after cleaning and drying. The cross-sectional areas of the first 1060 aluminum billet and the second 1060 aluminum billet are the same. The first 1060 aluminum billet, the 6101 aluminum billet, and the second 1060 aluminum billet are arranged side by side in sequence and enter three extrusion grooves arranged side by side in the same extrusion wheel respectively for continuous extrusion. The extrusion equipment is as Figures 5 - 8 shown in the structure, and an aluminum-clad aluminum conductive part is prepared. The cross-sectional area ratio of the aluminum cladding layer in the cross-section of the aluminum-clad aluminum conductive part is 25%. Among them, the rotation speed of the extrusion wheel is 20 rpm, the lengths of the first sizing belt and the second sizing belt are the same, both are 10 mm, and the length of the first welding cavity is 10 mm.

[0111] 2) The aluminum-clad aluminum conductive part obtained by continuous extrusion enters the water bath for cooling within 3 s, then is wound up, and heat-treated at 250 °C for 5 h to obtain the final finished aluminum-clad aluminum conductive part.

[0112] Comparative Example 1

[0113] Comparative Example 1 is prepared by a one-round double-groove continuous extrusion method, and the rest are the same as those in Example 1.

[0114] Comparative Example 2

[0115] Comparative Example 2 is prepared by a one-round double-groove continuous extrusion method, and the rest are the same as those in Example 2.

[0116] Comparative Example 3

[0117] Comparative Example 3 is prepared by a continuous extrusion cladding method to prepare a copper-clad aluminum conductive part with the same size as that in Example 1, including the following process:

[0118] 1) The copper cladding layer is continuously extruded from a pure copper billet. A 6101 aluminum alloy finished core material is provided, and the 6101 aluminum alloy finished core material passes through a cavity, and then the copper cladding layer is extruded and coated on the 6101 aluminum alloy finished core material, and then the copper-clad aluminum conductive part is extruded.

[0119] 2) The copper-clad aluminum conductive part obtained by continuous extrusion is cooled within 3 s, then is wound up, and heat-treated at 250 °C for 5 h to obtain the final finished copper-clad aluminum conductive part.

[0120] Comparative Example 4

[0121] Comparative Example 4 is prepared by the method of Comparative Example 3 to prepare an aluminum-clad aluminum conductive part with the same size as that in Example 2.

[0122] Comparative Example 5

[0123] Comparative Example 5 is a commercially available copper-clad aluminum conductive member prepared by a solid-solid combination method, that is, a finished hollow cladding sleeve is sleeved outside a finished core material, and then the gap between the sleeve and the core material is eliminated by compression and drawing.

[0124] Test Example 1

[0125] The tensile strength, yield strength and conductivity per unit area of the conductive members prepared in Examples 1-2 and Comparative Examples 1-5 were tested respectively, and the results are shown in Table 1.

[0126] Table 1: Performance indexes of the conductive members prepared in Examples 1-2 and Comparative Examples 1-4

[0127]

[0128]

[0129] It can be seen from Table 1 that: 1) Comparing Example 1 with Comparative Examples 1 and 3, it can be seen that the copper-clad aluminum conductive member prepared by the preparation method of the present invention has not only significantly improved conductivity but also improved strength compared with the prior art one-round double-groove continuous extrusion method and continuous extrusion cladding method.

[0130] 2) Comparing Example 2 with Comparative Examples 2 and 4, it can be seen that the aluminum-clad aluminum conductive member prepared by the preparation method of the present invention has not only significantly improved conductivity but also improved strength compared with the prior art one-round double-groove continuous extrusion method and continuous extrusion cladding method.

[0131] 3) Comparing Example 1 with Comparative Example 5, it can be seen that the copper-clad aluminum conductive member prepared by the preparation method of the present invention has significantly improved conductivity compared with the prior art solid-solid combination method.

[0132] Test Example 2

[0133] For the conductive members prepared in Examples 1 and 2, SEM tests were respectively carried out to observe the microstructures of the copper-aluminum welded joint interface and the aluminum-aluminum welded joint interface, as Figures 12 - 13 shown.

[0134] From Figure 12 it can be seen that: the width of the copper-aluminum welded joint interface exceeds 10 μm, which is a sufficient metallurgical bond, and the copper and aluminum are evenly distributed at the joint interface.

[0135] From Figure 13 it can be seen that: the width of the aluminum-aluminum welded joint interface exceeds 10 μm, which is a sufficient metallurgical bond, the two aluminum materials are evenly distributed at the joint interface, and the materials of the aluminum core and the aluminum cladding layer are also evenly distributed.

[0136] Test Example 3

[0137] Compression fatigue tests were carried out on the conductive parts of Examples 1-2 and Comparative Examples 1-5. The specimens were fixed in the fixture of the compression fatigue testing machine, and the maximum load (usually 70% of the material ultimate strength), loading frequency (10 Hz) and preset number of cycles (10 4 times) were set. After starting the equipment, a periodic axial pressure was continuously applied until the specimen broke or reached the set number of cycles.

[0138] The conductivity per unit area of the conductive parts after the fatigue test was measured, and the results are shown in Table 1.

[0139] As can be seen from Table 1: For the metal-clad metal conductive parts prepared by the present invention, the bonding strength between the cladding layer and the core material is more excellent, and after long-term use, the loss of conductivity is the smallest.

[0140] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a metal-coated metal conductive component, characterized in that, Including continuous extrusion, and the continuous extrusion includes the following processes: Providing a core blank and more than two cladding layer blanks; Continuously extruding the core blank and more than two of the cladding layer blanks respectively to obtain a core extrudate and more than two cladding layer extrudates respectively; The more than two cladding layer extrudates are respectively extruded into a first welding cavity through a cladding layer extrusion cavity. In the first welding cavity, the cladding layer extrudates are welded to each other to form a closed cladding layer extrudate; The core extrudate is extruded from a core extrusion cavity. The core extrusion cavity is located in the middle. The first welding cavity is arranged around the core extrusion cavity. The cladding layer extrudates respectively enter the first welding cavity from around the core extrudate; The cladding layer extrudate is extruded from the first welding cavity, contacts the core extrudate extruded from the core extrusion cavity, enters a second welding cavity, and completes cladding welding to obtain the metal-clad metal conductive part.

2. The preparation method according to claim 1, characterized in that, During the continuous extrusion process, the core blank and more than two of the cladding layer blanks are arranged side by side and respectively enter different extrusion grooves arranged side by side of the same extrusion wheel for continuous extrusion respectively.

3. The preparation method according to claim 1, wherein, The cross-sectional areas of the cladding layer blanks are the same; In the first welding cavity, the cladding layer extrudates are evenly distributed around the core extrudate; The extrusion speeds of the cladding layer extrudates are the same.

4. The preparation method according to claim 1, characterized in that, The extrusion speed of the cladding layer extrudate is the same as that of the core extrudate.

5. The preparation method according to claim 1, characterized in that, The width of the welded joint interface between the cladding layer extrudates is 5 μm to 100 μm; The number of the welding interfaces between the cladding layer extrudates is more than 2, and the welding interfaces extend along the axial direction of the metal-clad metal conductive part; The width of the joint interface between the cladding layer extrudate and the core extrudate is 5 μm to 80 μm.

6. The preparation method according to claim 1, wherein A first sizing belt is arranged at the outlet of the core 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.

7. 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 core extrusion cavity is less than 60°; 8. 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 each cladding layer extrusion cavity along the extrusion direction is 10 mm to 50 mm; The length of the core extrusion cavity along the extrusion direction is 10 mm to 50 mm.

9. The preparation method according to any one of claims 1 to 8, characterized in that, It further includes one or more of the following processes a to h: a. Drawing, which is used to draw the metal-clad metal conductive part obtained by continuous extrusion to obtain a metal-clad metal conductive wire; b. Online cooling, which is used to cool the metal-clad metal conductive part obtained by continuous extrusion or the metal-clad metal conductive wire obtained by drawing online; c. Rewinding, which is used to wind and collect the cooled conductive part or conductive wire; d. Heat treatment, which is used to heat-treat the rewound conductive part or conductive wire; e. Blanking coil winding, where the blanking coil winding is used to wind and collect the core blank and each of the cladding layer blanks respectively; f. Traction, where the traction is used to traction the wound and collected core blank and each of the cladding layer blanks respectively; g. On-line straightening, where the on-line straightening is used to straighten the tractioned core blank and each of the cladding layer blanks respectively; and h. On-line cleaning, where the on-line cleaning is used to clean the straightened core blank and each of the cladding layer blanks respectively; The core blank and each of the cladding layer blanks after on-line cleaning are simultaneously subjected to the continuous extrusion.

10. A metal-clad metal conductive member, characterized in that, Obtained by the preparation method according to any one of claims 1 to 9.

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