A copper-clad aluminum composite wire, a preparation method thereof and application thereof

Abstract

The present application relates to the technical field of metal composite material processing, and discloses a copper-clad aluminum composite wire and a preparation method and application thereof, the preparation method of the copper-clad aluminum composite wire comprises the following steps: using high-frequency induction welding to clad a copper strip concentrically on the outer layer of an aluminum core wire, so that the aluminum core wire is accommodated in a space enclosed by the copper strip, to obtain a composite material; and sequentially performing three continuous warm drawings of rough drawing, medium drawing and fine drawing on the composite material, to obtain the copper-clad aluminum composite wire. The present application realizes local melting in seconds by using high-frequency induction welding, and the interface bonding uniformity is good, and the interface bonding strength is greater than or equal to 80 MPa, so that the tensile strength, electrical conductivity and other key performance indicators of the copper-clad aluminum composite wire are improved; and then, three continuous warm drawings of rough drawing, medium drawing and fine drawing are sequentially performed on the composite material, to obtain a more fine and uniform structure, to realize better mechanical properties and high conductivity, and to improve the qualified rate of the copper-clad aluminum composite wire.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal composite material processing, in particular to a copper-clad aluminum composite wire and a preparation method and application thereof. BACKGROUND

[0002] The copper-clad aluminum composite wire is a copper layer concentrically coated on the outer surface of an aluminum core wire, so that the two metals form a whole metal wire through atomic interfacial metallurgical bonding. The copper-clad aluminum composite wire has the advantages of both copper and aluminum while ensuring signal transmission quality, greatly reduces material cost, and meets the demand for light-weight high-conductivity (>70% IACS) conductor materials in the fields of high-frequency signal transmission and transportation.

[0003] The preparation method of the traditional copper-clad aluminum composite wire includes solid / solid composite method, liquid / solid phase composite method and electroplating method. The solid / solid composite method mainly includes the following process: copper strip cleaning → copper strip coating aluminum rod → argon arc welding / laser welding → multi-pass cold drawing + multiple intermediate annealing, which is the most widely used preparation process. However, there are still many problems that restrict its application in precision electronics, such as high energy density of traditional argon arc welding / laser welding, which is easy to form oxide inclusions, resulting in poor interfacial bonding uniformity and bonding strength ≤50 MPa, which cannot withstand large deformation drawing stress, leading to an interfacial cracking rate >18% of the wire with a diameter of >1.0 mm; at the same time, the heat-affected zone of melting welding is large, and the high temperature in the welding process will affect the aluminum core wire through heat conduction, leading to grain growth of the aluminum core wire and poor microstructure uniformity, reducing the tensile strength and conductivity of the copper-clad aluminum alloy wire; in addition, the yield strengths of copper and aluminum during cold drawing work hardening at room temperature are about 250-330 MPa and 80-140 MPa, respectively, with a large difference in yield strength, and the deformation resistance of the double-layer metal is too large, leading to easy breakage of the aluminum core during cold drawing, poor consistency of the coordinated deformation of the copper-aluminum bimetallic material, and uneven flow of the two metals, which easily leads to poor thickness uniformity of the copper layer material; and the cold drawing passes reach dozens of times, and multiple intermediate annealing (annealing temperature 400-500℃) is also required, resulting in high process cost, low efficiency and unstable process.

[0004] Therefore, how to prepare a copper-clad aluminum composite wire with good interfacial bonding, high tensile strength, good conductivity, high product qualification rate, simple preparation process and high production efficiency is one of the technical problems to be solved in the field. SUMMARY

[0005] Therefore, the present application provides a preparation method of a copper-clad aluminum composite wire with good interfacial bonding uniformity, high tensile strength, good conductivity, high product qualification rate, simple preparation process and high production efficiency.

[0006] In a first aspect, the present invention provides a method for preparing copper-clad aluminum composite wire, comprising the following steps:

[0007] (1) A copper strip is concentrically wrapped around an aluminum core wire by high-frequency induction welding, so that the aluminum core wire is contained within the space enclosed by the copper strip, thus obtaining a composite material.

[0008] (2) The composite material is subjected to three consecutive warm drawing processes: coarse drawing, medium drawing, and fine drawing, to obtain copper-clad aluminum composite wire.

[0009] In some optional embodiments, during the high-frequency induction welding step, the welding temperature is 900℃-1050℃, the AC operating frequency is 100kHz-400kHz, and the power density is 3kW / cm². 2 -5kW / cm 2 The welding speed is 10m / min-30m / min, the extrusion pressure of the extrusion roller is 0.5KN-1.2KN, and the high-frequency induction welding is carried out under inert gas.

[0010] In some optional embodiments, in the rough drawing step, the temperature of the rough drawing is 320℃-350℃, the holding time is 15min-30min, the total deformation is 40%-70%, the drawing speed is 3m / min-5m / min, the number of drawing passes is 3-5, the deformation per pass is 15%-25%, and the rough drawing step is carried out under an inert atmosphere.

[0011] In some optional embodiments, in the intermediate drawing step, the drawing temperature is 320℃-350℃, the holding time is 15min-30min, the total deformation is 50%-80%, the drawing speed is 4m / min-8m / min, the number of drawing passes is 3-6, the deformation per pass is 15%-30%, and the intermediate drawing step is carried out under an inert atmosphere.

[0012] In some optional embodiments, in the fine drawing step, the drawing temperature is 280℃-320℃, the holding time is 5min-15min, the total deformation is 40%-60%, the drawing speed is 5m / min-12m / min, the number of drawing passes is 3-5, the deformation per pass is 10%-20%, and the fine drawing step is carried out under an inert atmosphere.

[0013] In some alternative embodiments, after the fine drawing, an annealing process is further included, wherein the annealing temperature is 150°C-200°C and the time is 10 min-20 min, and the annealing process is carried out under an inert atmosphere.

[0014] In some optional embodiments, the aluminum core wire comprises the following mass fractions of alloying elements: Al > 99.5wt%, Ag 0.05wt%-0.15wt%, rare earth elements 0.02wt%-0.08wt%, and the rest is inevitable impurities.

[0015] In some optional embodiments, the rare earth elements comprise at least one of Ce, La, and Yb.

[0016] In some optional embodiments, the aluminum core wire comprises the following mass fractions of alloying elements: Al > 99.9wt%, Fe ≤ 0.05wt%, Si ≤ 0.04wt%, and the rest is inevitable impurities.

[0017] In the second aspect, the application provides a copper-clad aluminum composite wire prepared by the preparation method of the first aspect, wherein the copper-clad aluminum composite wire comprises an aluminum core wire and a copper layer wrapped outside the aluminum core wire.

[0018] In some optional embodiments, the volume ratio of the copper layer is 10%-40%.

[0019] In some optional embodiments, the diameter of the copper-clad aluminum composite wire is 1mm-2.5mm.

[0020] In the third aspect, the application provides an application of the copper-clad aluminum composite wire prepared by the preparation method of the first aspect or the copper-clad aluminum composite wire of the second aspect in the field of new energy technology, transportation equipment, and high-frequency signal transmission.

[0021] Compared with the prior art, the technical scheme of the application has the following advantages:

[0022] 1. The preparation method of the copper-clad aluminum composite wire provided by the application comprises the following steps: (1) wrapping a copper strip concentrically outside an aluminum core wire by high-frequency induction welding, so that the aluminum core wire is contained in a space enclosed by the copper strip, to obtain a composite material; and (2) performing three continuous warm drawings of rough drawing, medium drawing, and fine drawing on the composite material in sequence, to obtain a copper-clad aluminum bimetal composite wire.

[0023] The traditional argon arc welding or laser welding belongs to fusion welding, high temperature generated by the fusion welding has great heat influence on the aluminum core wire, causes the problems of grain growth and uneven structure of the aluminum core wire, and damages the strength and conductivity of the copper-clad aluminum composite wire; on this basis, the high-frequency induction welding of the present application belongs to solid-phase welding, realizes local melting in seconds, has good interface bonding uniformity, and realizes interface bonding strength of 80MPa or more; and the welding temperature is low, avoids burning through, and the heat is mainly concentrated on the surface layer of the copper strip, reduces the heat influence of high temperature generated by the solid-phase welding on the aluminum core wire, so that the aluminum core wire can basically keep the cold working state, controls the grain size of 20um or less, and is beneficial to further improve the key performance indicators such as tensile strength and conductivity of the copper-clad aluminum composite wire; in summary, the high-frequency induction welding of the present application can improve the welding quality of the weld, ensure the reliability and stability of the production process, and ensure the uniform and small structure of the aluminum core before rough drawing.

[0024] The composite material is subjected to three times of continuous warm drawing of rough drawing, medium drawing and fine drawing in sequence, so that the composite material is always in a uniform flow state in the process of realizing large deformation, thereby obtaining a copper layer with uniform thickness; at the same time, the warm drawing process significantly improves the processing plasticity of the composite material, realizes large deformation processing, and fully breaks the grains of the composite wire; at the same time, through the control of the drawing temperature (slightly higher than the recrystallization temperature), dynamic recrystallization occurs in the drawing process to realize the control of the uniformity and grain size of the structure, obtain a more fine and uniform structure, realize better mechanical properties (high tensile strength) and high conductivity, and improve the qualified rate of the copper-clad aluminum composite wire.

[0025] 2、The preparation method of the copper-clad aluminum composite wire provided by the application controls the temperature of rough drawing, medium drawing and fine drawing to be 320-350 DEG C, 320-350 DEG C and 280-320 DEG C respectively, and the holding time is 15-30 min, 15-30 min and 5-15 min respectively, which on the one hand reduces the yield strength of copper and aluminum to about 30-70 MPa and 20-50 MPa, reduces the yield strength difference, ensures that the two kinds of metals have similar deformation resistance, reduces the problem of aluminum core wire breakage or fragmentation caused by too large deformation resistance difference, breaks through the barrier of poor consistency of copper and aluminum plastic deformation, ensures that the double-layer metal is in a uniform flow state during the deformation process, and the obtained copper layer has uniform thickness distribution, thereby improving the qualified rate of the copper-clad aluminum composite wire; on the other hand, it is helpful for the slight diffusion of copper and aluminum atoms at the interface, controls the thickness of the brittle phase layer to be less than 1 micron, further improves the bonding strength of the copper layer and the aluminum core, avoids the growth of copper layer and aluminum core grains and the formation of an excessively thick brittle intermetallic compound layer at the copper-aluminum bonding interface caused by excessively high temperature or excessively long holding time, and reduces the bonding strength, tensile strength and conductivity; in addition, the rough drawing, medium drawing and fine drawing are carried out in an inert gas protection atmosphere (such as high-purity nitrogen N2 or argon Ar), which isolates air, ensures that the copper layer, the aluminum core and the bonding interface are free of oxidation, inclusions and other defects, ensures the conductivity of the copper layer and the aluminum core, improves the bonding strength of the composite wire, and ensures the brightness of the copper layer.

[0026] 3、The preparation method of the copper-clad aluminum composite wire provided by the application further comprises annealing treatment after fine drawing, and the annealing temperature is controlled to be 150-200 DEG C, which eliminates the internal stress generated in the drawing process, effectively avoids the delamination problem of the composite wire caused by stress concentration, reduces the lattice distortion and residual stress generated in the processing process, thereby stabilizing the conductivity of the copper-clad aluminum composite wire. In addition, the intermediate high-temperature annealing step is omitted, which has little effect on the aluminum core grain, and further improves the tensile strength of the aluminum core.

[0027] 4、The copper clad aluminum composite wire provided by the present application, the selection of the aluminum core wire has two kinds, one is to control the aluminum core wire to include the following mass fraction of alloy elements: Al > 99.5wt%, Ag 0.05wt%-0.15wt%, rare earth elements 0.02wt%-0.08wt%, and the rest is inevitable impurities, Ag element fills the lattice vacancy, the electron mobility is improved by about 18%, the rare earth elements purify the grain boundary, and the grain boundary resistance is reduced by 30%, so that the conductivity of the aluminum core wire is ≥65.2% IACS; the second is to directly select a high-purity aluminum core wire (Al > 99.9wt%, Fe ≤0.05wt%, Si ≤0.04wt%), the impurity element content of Fe, Si and the like in the high-purity aluminum core wire is low, the purity of the aluminum core wire is high, and a more fine and uniform structure can be obtained, so that the tensile strength, elongation and high conductivity of the copper clad aluminum composite wire are improved.

[0028] 5、The copper clad aluminum composite wire provided by the present application, the volume ratio of the copper layer is controlled to be 10%-40%, and the conductivity is >70% IACS, and the cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0030] Figure 1 is the optical microscope photo of the copper clad aluminum composite wire prepared in Example 1 of the present application after being enlarged 300X;

[0031] Figure 2 is the copper layer thickness uniformity detection point position of the copper clad aluminum composite wire of the present application. DETAILED DESCRIPTION

[0032] The following examples are provided to better further understand the present application, and do not limit the best embodiments described, and do not constitute a limitation on the content and protection scope of the present application, and any person under the enlightenment of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application.

[0033] The specific experimental steps or conditions are not specified in the examples, and can be operated according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments used are not specified by the manufacturer, and are conventional reagent products that can be obtained by market purchase.

[0034] In the prior art, the preparation methods of copper-clad aluminum composite wire mainly include: solid / solid composite method, liquid / solid phase composite method and electroplating method. The main process flow of the solid / solid composite method includes: copper strip cleaning, copper strip cladding aluminum rod, argon arc welding, multi-pass cold drawing + multiple intermediate annealing, etc. The welding interface bonding strength of this method is low (≤50 MPa); the argon arc welding is seriously oxidized, and there are oxide inclusions such as CuO at the interface, which leads to easy cracking during large deformation drawing; multiple intermediate annealing (≥400℃) is required to eliminate work hardening, the cold drawing pass is as many as dozens of times, the linear speed is ≤2m / min, the efficiency is low, and the annealing temperature is relatively high (≥400℃), the aluminum grain coarsening leads to the attenuation of the electrical conductivity (≤60% IACS); the yield strength difference between copper and aluminum is large, and the cold drawing is prone to deformation mismatch to cause core breakage, and stress concentration occurs at the copper-aluminum interface, resulting in a high wire breaking rate. The main process flow of the liquid / solid phase composite method includes: copper tube filling aluminum, pressure casting composite, hot extrusion and cold drawing. In this method, the aluminum liquid forms an oxidized interface at high temperature (680℃-720℃), penetrates into the copper layer, forms a brittle intermetallic compound layer (such as CuAl2) and the brittle intermetallic compound layer is relatively thick, the thickness of the intermetallic compound (IMC) layer is difficult to control, which affects the bonding strength and electrical conductivity of the composite material; the pressure casting porosity leads to a breaking rate of >10%, and it is difficult to realize stable production; the high-temperature aluminum liquid leads to abnormal grain growth of the copper layer, resulting in local non-uniformity of the structure, and the electrical conductivity of the finished product is less than 70% IACS. The electroplating method is to electrolytically deposit an ultra-thin copper layer (1-20μm) on the surface of the aluminum core wire, and the thickness is controlled by current density and time. It is suitable for high-frequency precision applications, but the current transmission capacity of the copper layer is weak and the environmental protection pressure is large; the electroplating solution is highly toxic, and the wastewater treatment cost increases by 30%; the pure copper consumption is still 70% of that of the traditional cladding process.

[0035] In order to solve the problems in the related art, according to a first aspect of the present application, a preparation method of copper-clad aluminum composite wire is provided, comprising the following steps:

[0036] (1) straighten the copper strip and the aluminum core wire respectively, and then peel the aluminum core wire after straightening;

[0037] (2) surface texturing treatment is performed on the straightened copper strip and the peeled aluminum core wire respectively, the roughness Ra of the copper strip is 1-4μm, and the roughness Ra of the aluminum rod is 4-8μm; then the copper strip and the aluminum core wire after surface texturing treatment are cleaned, the cleaning time is 1-5min, and the cleaning speed is 1-5m / min, so as to remove the dirt on the surface; then the cleaned copper strip and aluminum core wire are dried and wound;

[0038] (3) using high-frequency induction welding to clad copper band concentrically on the outer layer of the aluminum core wire, so that the aluminum core wire is contained in the space enclosed by the copper layer to obtain a composite material; in the high-frequency induction welding step, the welding temperature is 900-1050 DEG C, the working frequency of alternating current is 100-400 kHz, the power density is 3-5 kW / cm 2 -5kW / cm 2 , the welding speed is 10-30 m / min, the extrusion force of the extrusion roller is 0.5-1.2 KN; the welding seam area is always in an inert gas protection atmosphere, and the oxygen content is ≤0.005%;

[0039] (4) using a helium mass spectrometry leak detection device (leak rate <1*10 -9 pa*m 3 / s) to withstand 0.6 MPa pressure leak detection;

[0040] (5) the composite material is subjected to three continuous warm drawing of rough drawing, medium drawing and fine drawing in sequence, and then annealing treatment is carried out to obtain a copper-clad aluminum composite wire; the rough drawing, medium drawing and fine drawing are all carried out in an inert atmosphere, in the rough drawing step, the drawing temperature is 320-350 DEG C, the holding time is 15-30 min, the total deformation is 40-70%, the drawing speed is 3-5 m / min, the drawing pass is 3-5 times, and the single pass deformation is 15-25%; in the medium drawing step, the drawing temperature is 320-350 DEG C, the holding time is 15-30 min, the total deformation is 50-80%, the drawing speed is 4-8 m / min, the drawing pass is 3-6 times, and the single pass deformation is 15-30%; in the fine drawing step, the drawing temperature is 280-320 DEG C, the holding time is 5-15 min, the total deformation is 40-60%, the drawing speed is 5-12 m / min, the drawing pass is 3-5 times, and the single pass deformation is 10-20%; the annealing temperature is 150-200 DEG C, the time is 10-20 min, and the annealing atmosphere is inert gas.

[0041] The present application utilizes the skin effect of high-frequency current to make the edge of the copper band melt instantaneously and press together, the welding speed is controlled to be 10-30 m / min to reduce the heating of the aluminum core wire, the extrusion force of the extrusion roller is controlled to be 0.5-1.2 KN to press the molten pool and remove the oxides, and the welding temperature is controlled to be 900-1050 DEG C, which is lower than the melting point of copper, so that the problems such as burning through are avoided.

[0042] The temperature of the rough drawing is 320-350 DEG C, the temperature of the medium drawing is 320-350 DEG C, and the temperature of the fine drawing is 280-320 DEG C, the copper-clad aluminum composite wire cannot obtain sufficient plasticity to realize large deformation drawing when the drawing temperature is too low, which can easily lead to surface cracks or even breakage during the drawing process; when the temperature is too high, the crystal grains will be coarse, which can affect the mechanical properties, electrical properties and other properties of the copper-clad aluminum composite wire, and also can cause energy waste.

[0043] In some optional embodiments, the aluminum core wire comprises the following mass fractions of alloy elements: Al > 99.5wt%, Ag 0.05wt%-0.15wt%, rare earth elements 0.02wt%-0.08wt%, and the rest is inevitable impurities.

[0044] In some optional embodiments, the aluminum core wire comprises the following mass fractions of alloy elements: Al > 99.9wt%, Fe ≤ 0.05wt%, Si ≤ 0.04wt%, and the rest is inevitable impurities.

[0045] In some optional embodiments, the rare earth elements include at least one of Ce, La and Yb.

[0046] In the second aspect, the application provides a copper-clad aluminum composite wire prepared by the preparation method of the first aspect, which comprises an aluminum core wire and a copper layer coated outside the aluminum core wire.

[0047] In some optional embodiments, the volume ratio of the copper layer is 10%-40%.

[0048] In some optional embodiments, the diameter of the copper-clad aluminum composite wire is 1-2.5mm.

[0049] In the third aspect, the application provides the copper-clad aluminum composite wire prepared by the preparation method of the first aspect, or the application of the copper-clad aluminum composite wire of the second aspect in the field of new energy technology, transportation equipment and high-frequency signal transmission.

[0050] In the application, the purity of copper in the copper strip is > 99.90wt%, and the rest is inevitable impurities.

[0051] The warm drawing process is adopted, good processing plasticity is obtained in the drawing process, large deformation processing deformation can be realized, and the grains of the material are fully broken; meanwhile, the heating temperature is in the range of the recrystallization temperature, the dynamic recrystallization (fine and uniform equiaxed structure is obtained) of the double-layer metal can fully occur in the process of processing deformation; through reasonable control of the heating process, uniform and coordinated deformation of the copper layer and the aluminum layer can be realized, and the grain growth caused by too high drawing temperature can also be avoided; finally, the copper layer with good uniformity, more fine and uniform structure can be obtained, so that better mechanical properties (high tensile strength) and high conductivity and the like can be realized.

[0052] The application will be further described in detail below in combination with specific embodiments, and these embodiments cannot be understood as limiting the scope of the application.

[0053] In the application, the deformation amount = (1-(d f / d0) 2 ) × 100%, wherein d f represents the target diameter, and d0 represents the initial diameter. The copper layer volume ratio = ((d0+2t) 2 -d0 2 ) / (d0+2t) 2 × 100%, and t is the initial copper strip thickness.

[0054] In the application, the 1050 aluminum alloy is an industrial pure aluminum with an aluminum content of more than 99.5%.

[0055] In the application, the mass fraction of the alloying elements is: the aluminum core wire with Al > 99.9wt%, Fe ≤ 0.05wt%, and Si ≤ 0.04wt% is commercially available.

[0056] In the application, the mass fraction of the alloying elements of the aluminum core wire with Al > 99.5wt%, Ag 0.05wt%-0.15wt%, and rare earth elements 0.02wt%-0.08wt% includes the following steps:

[0057] (1) high-purity primary aluminum (such as ≥99.85% remelted aluminum ingot) is used as the basic raw material to ensure that the initial impurity content is extremely low; silver (Ag) and rare earth elements (RE) are usually added in the form of aluminum-silver intermediate alloy and aluminum-rare earth intermediate alloy;

[0058] (2) the high-purity primary aluminum is added to an induction melting furnace and heated to 720-750℃, so that the aluminum is completely melted into clear aluminum liquid, and electromagnetic stirring is adopted in the heating process to facilitate subsequent composition uniformity; high-purity argon (Ar) or a mixed gas of nitrogen (N2) and chlorine (Cl2) is introduced into the aluminum liquid for rotary degassing treatment;

[0059] (3) When the temperature of the molten aluminum is stabilized at 730-750℃, first add the preheated aluminum-silver intermediate alloy, fully stir to make it completely dissolved; then add the preheated aluminum-rare earth intermediate alloy, immediately fully stir using a mechanical stirring or electromagnetic stirring device, fully stir the melt for a long time, and ensure that the silver and rare earth elements are uniformly distributed in the molten aluminum;

[0060] (4) Perform static slag removal in the furnace, perform refining and filtration to ensure the purity of the melt, then continuously cast and roll to obtain aluminum alloy round rods of a specific size, quickly cool, then perform homogenization heat treatment, and then cold draw the rod blanks after heat treatment through a series of gradually smaller dies to reduce the diameter to the size required for the copper-clad aluminum composite process.

[0061] Example 1

[0062] This example provides a copper-clad aluminum composite wire, which includes an aluminum core wire and a copper layer cladded on the outside of the aluminum core wire, the diameter of the copper-clad aluminum composite wire is φ 1.75 mm, and the volume ratio of the copper layer is 13%; the aluminum core wire includes the following mass fractions of alloy elements: Al 99.8wt%, Ag 0.1wt%, Yb 0.05wt%, and the rest is unavoidable impurities;

[0063] This example provides a method for preparing a copper-clad aluminum composite wire, which includes the following steps:

[0064] (1) Straighten the copper strip and the aluminum core wire respectively, then perform skinning treatment on the straightened aluminum core wire (the diameter of the skinned aluminum core wire is φ 8.2 mm); perform surface roughening treatment on the straightened pure copper strip with a thickness of 0.3 mm and a width of 26 mm and the skinned aluminum core wire respectively, the roughness Ra of the copper strip is 3.2 μm, and the roughness Ra of the aluminum rod is 6 μm;

[0065] (2) Clean the copper strip and the aluminum core wire after the surface roughening treatment, the cleaning time is 2 min, and the cleaning speed is 2.5 m / min to remove the dirt on the surface; then dry and wind the cleaned copper strip and the aluminum core wire;

[0066] (3) Clad the copper layer on the surface of the aluminum core wire, use high-frequency induction welding to concentrically clad the copper strip on the outer layer of the aluminum core wire, so that the aluminum core wire is contained in the space enclosed by the copper layer to obtain a composite material; in the high-frequency induction welding step, the welding temperature is 900-1050℃, the working frequency of the alternating current is 100 kHz, the power is 120 kW, the power density is 4 kW / cm 2 , the welding speed is 20 m / min, the extrusion force of the extrusion roller is 1 KN, the output cladded rod has a diameter of about 8.8 mm, and the high-frequency induction welding is performed under inert gas;

[0067] (4) Use a helium mass spectrometry leak detection device (leak rate <1×10-9 pa·m 3 ( / s) Withstands 0.6MPa air pressure leak test with no leaks;

[0068] (5) The composite material with a diameter of 8.8 mm was subjected to rough drawing under an inert atmosphere. The drawing temperature was 320℃, the holding time was 20 min, the drawing speed was 3 m / min, the total deformation was 64.408%, the drawing passes were 4, the deformation of the first pass was 24.429%, the deformation of the second pass was 23.294%, the deformation of the third pass was 22.455%, and the deformation of the fourth pass was 20.820%, resulting in a composite material with a diameter of 5.25 mm.

[0069] (6) The composite material with a diameter of 5.25 mm was drawn under an inert atmosphere. The drawing temperature was 340℃, the holding time was 25 min, the drawing speed was 6 m / min, the total deformation was 78.22%, the drawing passes were 5, the deformation of the first pass was 28.154%, the deformation of the second pass was 27.080%, the deformation of the third pass was 26.852%, the deformation of the fourth pass was 23.101%, and the deformation of the fifth pass was 26.100%, thus obtaining the composite material with a diameter of 2.45 mm.

[0070] (7) Fine drawing of composite material with φ 2.45mm was performed. The drawing temperature was 280℃, the holding time was 8min, the drawing speed was 8m / min, the total deformation was 48.98%, the drawing passes were 4, the deformation of the first pass was 19.367%, the deformation of the second pass was 17.355%, the deformation of the third pass was 14.438%, the deformation of the fourth pass was 10.519%, and finally annealed at 175℃ for 15min to obtain copper-clad aluminum composite wire with φ 1.75mm.

[0071] Example 2

[0072] This embodiment provides a copper-clad aluminum composite wire, including an aluminum core wire and a copper layer covering the outside of the aluminum core wire. The diameter of the copper-clad aluminum composite wire is φ2.05mm, and the volume ratio of the copper layer is 19%. The aluminum core wire contains the following alloying elements by mass fraction: Al 99.95wt%, Fe 0.03wt%, Si 0.01wt%, with the remainder being unavoidable impurities.

[0073] This embodiment provides a method for preparing copper-clad aluminum composite wire, including the following steps:

[0074] (1) Straighten the copper strip and the aluminum core wire respectively, and then perform skinning treatment on the straightened aluminum core wire (the diameter of the skinned aluminum core wire is φ9.0 mm); perform surface roughening treatment on the straightened pure copper strip with a thickness of 0.5 mm and a width of 29 mm and the skinned aluminum core wire respectively, the roughness Ra of the copper strip is 3.2 μm, and the roughness Ra of the aluminum rod is 6 μm;

[0075] (2) Clean the copper strip and the aluminum core wire after the surface roughening treatment, the cleaning time is 2 min, and the cleaning speed is 2.5 m / min, so as to remove the dirt on the surface of the copper strip and the aluminum core wire; then dry and wind the cleaned copper strip and the aluminum core wire;

[0076] (3) Coat a copper layer on the surface of the aluminum core wire, and concentrically coat the copper strip on the outer layer of the aluminum core wire by high-frequency induction welding, so that the aluminum core wire is contained in the space enclosed by the copper layer to obtain a composite material; in the high-frequency induction welding step, the welding temperature is 900-1050 °C, the working frequency of the alternating current is 400 kHz, the power is 120 kW, the power density is 5 kW / cm 2 , the welding speed is 10 m / min, the extrusion force of the extrusion roller is 1.2 KN, the output coated rod has a diameter of about 10 mm, and the high-frequency induction welding is performed in an inert gas;

[0077] (4) Use a helium mass spectrometry leak detection device (leak rate <1×10 -9 pa·m 3 / s) to withstand a gas pressure of 0.6 MPa for leak detection without leakage;

[0078] (5) Coarsely draw the composite material with a diameter of φ10 mm in an inert atmosphere, the drawing temperature is 335 °C, the holding time is 30 min, the drawing speed is 4 m / min, the total deformation is 66.360%, the drawing pass is 4, the first pass deformation is 23.438%, the second pass deformation is 24.558%, the third pass deformation is 23.438%, and the fourth pass deformation is 23.930%, to obtain a composite material with a diameter of φ5.8 mm;

[0079] (6) Medium-draw the composite material with a diameter of φ5.8 mm in an inert atmosphere, the drawing temperature is 320 °C, the holding time is 30 min, the drawing speed is 4 m / min, the total deformation is 79.125%, the drawing pass is 5, the first pass deformation is 28.627%, the second pass deformation is 29.988%, the third pass deformation is 27.127%, the fourth pass deformation is 26.531%, and the fifth pass deformation is 21.972%, to obtain a composite material with a diameter of φ2.65 mm;

[0080] (7) The φ 2.65 mm composite material is fine-drawn under inert atmosphere, the drawing temperature is 320℃, the holding time is 5 min, the drawing speed is 5 m / min, the total deformation is 40.157%, the drawing pass is 3, the first pass deformation is 17.978%, the second pass deformation is 15.972%, the third pass deformation is 13.171%, and finally the φ 2.05 mm copper-clad aluminum composite wire is obtained by annealing under inert atmosphere at 150℃ for 20 min.

[0081] Example 3

[0082] The embodiment provides a preparation method of a copper-clad aluminum composite wire, which is basically same as the steps of the example 1, and the difference is that the volume ratio of the copper layer is 25%, and the aluminum core wire comprises alloy elements with the following mass fractions: Al 99.82wt%, Ag 0.05wt%, La 0.08wt%, and the rest is inevitable impurities.

[0083] Example 4

[0084] The embodiment provides a preparation method of a copper-clad aluminum composite wire, which is basically same as the steps of the example 1, and the difference is that the volume ratio of the copper layer is 30%, and the aluminum core wire comprises alloy elements with the following mass fractions: Al 99.7wt%, Ag 0.15wt%, Ce 0.08wt%, and the rest is inevitable impurities.

[0085] Example 5

[0086] The embodiment provides a copper-clad aluminum composite wire, which comprises an aluminum core wire and a copper layer wrapped outside the aluminum core wire, the diameter of the copper-clad aluminum composite wire is φ 1.05 mm, the volume ratio of the copper layer is about 38.6%, and the aluminum core wire comprises alloy elements with the following mass fractions: Al 99.98wt%, Fe 0.002wt%, Si 0.008wt%.

[0087] The embodiment provides a preparation method of a copper-clad aluminum composite wire, which comprises the following steps:

[0088] (1) The copper strip and the aluminum core wire are straightened respectively, and then the straightened aluminum core wire is subjected to peeling treatment (the diameter of the peeled aluminum core wire is φ 4.7 mm); then the straightened pure copper strip with a thickness of 0.65 mm and a width of 15 mm and the peeled aluminum core wire are subjected to surface roughening treatment, the roughness Ra of the copper strip is 2 μm, and the roughness Ra of the aluminum rod is 4 μm;

[0089] (2) The copper strip and the aluminum core wire subjected to the surface roughening treatment are cleaned, the cleaning time is 5 min, and the cleaning speed is 5 m / min, so as to remove dirt on the surfaces of the copper strip and the aluminum core wire; and then the cleaned copper strip and the aluminum core wire are dried and wound;

[0090] (3) The copper layer is coated on the surface of the aluminum core wire, and the copper band is concentrically coated on the outer layer of the aluminum core wire by high-frequency induction welding, so that the aluminum core wire is contained in the space enclosed by the copper layer to obtain a composite material; in the high-frequency induction welding step, the welding temperature is 900-1050°C, the working frequency of the alternating current is 300 kHz, the power is 120 kW, the power density is 3 kW / cm 2 , the welding speed is 30 m / min, the extrusion force of the extrusion roller is 0.5 KN, the output coated rod φ is 6 mm, and the high-frequency induction welding is carried out under inert gas;

[0091] (4) The helium mass spectrometry leak detection equipment (leak rate <1x10 -9 pa·m 3 / s) is used to withstand 0.6 MPa air pressure leak detection without leakage;

[0092] (5) The φ 6 mm composite material is coarsely drawn under inert atmosphere, the drawing temperature is 350°C, the holding time is 15 min, the drawing speed is 5 m / min, the total deformation is 65.190%, the drawing pass is 5 times, the first pass deformation is 21.972%, the second pass deformation is 19.678%, the third pass deformation is 19.945%, the fourth pass deformation is 17.938%, and the fifth pass deformation is 15.456%, to obtain a φ 3.54 mm composite material;

[0093] (6) The φ 3.54 mm composite material is medium-drawn under inert atmosphere, the drawing temperature is 350°C, the holding time is 15 min, the drawing speed is 8 m / min, the total deformation is 79.6%, the drawing pass is 6 times, the first pass deformation is 25.768%, the second pass deformation is 26.209%, the third pass deformation is 25.593%, the fourth pass deformation is 23.244%, the fifth pass deformation is 21.883%, and the sixth pass deformation is 16.408%, to obtain a φ 1.6 mm composite material;

[0094] (7) The φ 1.6 mm composite material is finely drawn under inert atmosphere, the drawing temperature is 300°C, the holding time is 15 min, the drawing speed is 12 m / min, the total deformation is 56.9%, the drawing pass is 5 times, the first pass deformation is 17.871%, the second pass deformation is 15.867%, the third pass deformation is 15.857%, the fourth pass deformation is 14.210%, the fifth pass deformation is 13.658%, and finally annealed at 200°C for 10 min, to obtain a φ 1.05 mm copper-coated aluminum composite wire.

[0095] Comparative Example 1

[0096] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the temperature of rough drawing is 400°C.

[0097] Comparative example 2

[0098] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the temperature of rough drawing is 250°C.

[0099] Comparative example 3

[0100] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the temperature of medium drawing is 420°C.

[0101] Comparative example 4

[0102] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the temperature of medium drawing is 240°C.

[0103] Comparative example 5

[0104] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the annealing temperature is 450°C.

[0105] Comparative example 6

[0106] The comparative example provides a preparation method of a copper-clad aluminum composite wire, which is basically the same as the steps of example 1, and the only difference is that the aluminum core wire is replaced by 1050 aluminum alloy.

[0107] Comparative example 7

[0108] The comparative example provides a copper-clad aluminum composite wire, the diameter of the copper-clad aluminum composite wire is φ 2.05 mm, and the volume ratio of the copper layer is 20%.

[0109] The comparative example adopts a solid / solid phase composite method, and provides a preparation method of a copper-clad aluminum composite wire, including the following steps:

[0110] (1) straighten, surface roughening treatment, and cleaning the copper strip and the aluminum core wire, respectively;

[0111] (2) copper strip and aluminum core wire are simultaneously sent into the covering box, vertical forming wheels and horizontal forming wheels in the covering box make the copper strip uniformly cover the surface of the aluminum rod, air is introduced into the covering box through the air inlet to prevent the two kinds of metal materials from being oxidized during the covering process; the copper strip enters the welding area, argon gas is used as protective gas at the welding gun of the welding area, and the metal material is continuously welded by tungsten pulse arc welding, and then enters the cooling area after welding, air is introduced into the cooling area as protective gas, and finally the covered copper-clad aluminum wire is obtained; after covering is completed, the diameter of the covered rod is about 15 mm, and the volume ratio of the copper layer of the copper-clad aluminum is 20%;

[0112] (3) the covered copper-clad aluminum is directly sent into the continuous drawing equipment for drawing, the first continuous drawing process draws the copper-clad aluminum wire to 9.2 mm, each die is reduced by 0.40 mm, and annealing is performed in a 450°C annealing furnace; the second continuous drawing process draws the copper-clad aluminum wire to 5.1-5.6 mm, each die is reduced by 0.30 mm, and annealing is performed in a 450°C annealing furnace; the third process draws the copper-clad aluminum wire to 3.2-4.7 mm, each die is reduced by 0.20 mm, and annealing is performed in a 450°C annealing furnace; the fourth process draws the copper-clad aluminum wire to 2.05 mm, each die is reduced by 0.20 mm, and φ2.05 mm copper-clad aluminum composite wire is obtained.

[0113] Comparative Example 8

[0114] The present comparative example provides a copper-clad aluminum composite wire, the diameter of the copper-clad aluminum composite wire is φ2.05 mm, and the volume ratio of the copper layer is 19%.

[0115] The present comparative example adopts a liquid / solid phase composite method, and provides a preparation method of a copper-clad aluminum composite wire, which comprises the following steps:

[0116] (1) a copper pipe with an outer diameter of φ9 mm and a wall thickness of 0.5 mm is selected, the inner wall of the copper pipe is deoiled and pickled to remove the oxide film, one end of the copper pipe is closed in the form of a pressing plate under gas protection, and molten aluminum (the temperature of the molten metal is 680°C) is cast into the other end of the copper pipe by pressure casting (the pressure is 0.3 MPa) to prepare a composite blank;

[0117] (2) the composite blank is heated to 500°C, then put into the extrusion cylinder of the extruder for extrusion, then the surface of the blank is cleaned with dilute hydrochloric acid, and φ3m copper-clad composite aluminum wire is prepared by roll die drawing, the reduction of the cross section of each pass is 15%-30%, and the deformation amount of each pass is gradually reduced;

[0118] (3) the φ3m composite wire is annealed at an annealing temperature of 400°C for 0.5h;

[0119] (4) The copper-clad aluminum wire material is stretched by single die to 2.05 m, the lubricant is vegetable oil, the cross-sectional shrinkage rate of each pass is 10%-25%, and the pass deformation gradually decreases.

[0120] Experimental Example 1

[0121] The copper-clad aluminum composite wire materials prepared in the above Examples 1-5 and Comparative Examples 1-8 are subjected to interface bonding strength test according to ASTM D1002, electrical conductivity test according to IEC 60228, tensile strength test according to ISO 6892-1, and wire breaking rate test according to the number of broken points per kilometer, and the results are shown in Table 1.

[0122] Table 1: Performance test results of copper-clad aluminum composite wire materials prepared in each example and comparative example

[0123]

[0124] As can be seen from Table 1, the copper-clad aluminum composite wire materials prepared in Examples 1-5 have good electrical conductivity, high tensile strength, high elongation, and low wire breaking rate. The high rough drawing temperature of Comparative Example 1 and the high intermediate drawing temperature of Comparative Example 3 cause the grains of the copper layer and the aluminum core to grow and excessively diffuse to form a thick brittle intermetallic compound layer at the copper-aluminum bonding interface, resulting in poor tensile strength, electrical conductivity, and elongation of the copper-clad aluminum composite wire material. The low rough drawing temperature of Comparative Example 2 and the low intermediate drawing temperature of Comparative Example 4 significantly enhance the work hardening effect, resulting in a decrease in elongation and an increase in wire breaking rate. The high annealing temperature of Comparative Example 5 causes the grains of the copper layer and the aluminum core to excessively diffuse to form brittle intermetallic compounds, which reduces the tensile strength and electrical conductivity of the copper-clad aluminum composite wire material. In Comparative Example 6, the aluminum core wire is replaced by 1050 aluminum alloy, which has a low purity and cannot obtain a finer and more uniform structure, resulting in poor tensile strength, elongation, and electrical conductivity of the copper-clad aluminum composite wire material. In Comparative Example 7, the copper-clad aluminum composite wire material is prepared by a traditional cold drawing method, which causes severe argon arc welding oxidation and the presence of oxide inclusions such as CuO at the interface, resulting in easy cracking during large deformation drawing and poor elongation. The high temperature during welding can affect the aluminum core wire through heat conduction, causing the grains of the aluminum core wire to grow and the structure to be less uniform, which reduces the tensile strength and electrical conductivity of the copper-clad aluminum alloy wire. At the same time, a high annealing temperature (> 400°C) causes the aluminum grains to coarsen, further reducing the electrical conductivity. During cold drawing, the copper / aluminum yield strength difference is large, and the cold drawing process is prone to deformation mismatch, which can cause the core to break. In Comparative Example 8, the copper-clad aluminum composite wire material is prepared by a liquid / solid phase composite method, which causes the aluminum liquid to form an oxidized interface at high temperature, penetrate into the copper layer, and form a thick brittle intermetallic compound layer, resulting in poor electrical conductivity of the copper-clad aluminum composite wire material. At the same time, the high-temperature aluminum liquid causes the copper layer grains to abnormally grow, resulting in a locally uneven structure, which further reduces the electrical conductivity of the copper-clad aluminum composite wire material. The gas holes in the die casting cause the breaking rate to be > 10%.

[0125] Experimental Example 2

[0126] The cross section of the copper-clad aluminum composite wire prepared in Example 1 above was subjected to metallographic detection analysis, and the results are shown in FIG. 2. Figure 1 As can be seen from the figure, the copper-clad aluminum composite wire prepared in Example 1 has a good interface bonding, and the copper layer has a uniform thickness distribution.

[0127] Experimental Example 3

[0128] The copper-clad aluminum composite wire prepared in Example 2 and Comparative Example 7 above was subjected to thickness uniformity test, and the results are shown in Table 2; wherein, the copper-clad aluminum composite wire copper layer thickness uniformity test point position is shown in FIG. 3. Figure 2

[0129] Table 2 Thickness uniformity test results of the copper-clad aluminum composite wire prepared in Example 2 and Comparative Example 7

[0130]

[0131] As can be seen from Table 2, the copper-clad aluminum composite wire prepared in Example 2 has a good uniformity of copper tape thickness, copper tape diameter and aluminum core wire diameter; in Comparative Example 7, the copper / aluminum yield strength difference is large during cold drawing, and the cold drawing is prone to deformation mismatch, resulting in uneven copper tape thickness of the copper-clad aluminum composite wire, etc.

[0132] Obviously, the above examples are merely examples for the purpose of clear illustration, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.​

Claims

1. A method for preparing a copper-clad aluminum composite wire, characterized in that, Includes the following steps: (1) A copper strip is concentrically wrapped around an aluminum core wire by high-frequency induction welding, so that the aluminum core wire is contained within the space enclosed by the copper strip, thus obtaining a composite material. (2) The composite material is subjected to three consecutive warm drawing processes: coarse drawing, medium drawing, and fine drawing, without intermediate high-temperature annealing, to obtain copper-clad aluminum composite wire. In the high-frequency induction welding step, the welding temperature is 900℃-1050℃, the AC operating frequency is 100kHz-400kHz, and the power density is 3kW / cm². 2 -5kW / cm 2 The welding speed is 10m / min-30m / min, the extrusion pressure of the extrusion roller is 0.5KN-1.2KN, and the high-frequency induction welding is carried out under an inert gas atmosphere. In the rough drawing step, the temperature is 320℃-350℃, the holding time is 15min-30min, the total deformation is 40%-70%, the drawing speed is 3m / min-5m / min, the number of drawing passes is 3-5, and the deformation per pass is 15%-25%. The rough drawing step is carried out under an inert atmosphere. In the intermediate drawing step, the drawing temperature is 320℃-350℃, the holding time is 15min-30min, the total deformation is 50%-80%, the drawing speed is 4m / min-8m / min, the number of drawing passes is 3-6, and the deformation per pass is 15%-30%. The intermediate drawing step is carried out under an inert atmosphere. In the fine drawing step, the drawing temperature is 280℃-320℃, the holding time is 5min-15min, the total deformation is 40%-60%, the drawing speed is 5m / min-12m / min, the number of drawing passes is 3-5, and the deformation per pass is 10%-20%. The fine drawing step is carried out under an inert atmosphere.

2. The method for preparing copper-clad aluminum composite wire according to claim 1, characterized in that, After the fine drawing, an annealing process is also included. The annealing temperature is 150℃-200℃ and the time is 10min-20min. The annealing process is carried out under an inert atmosphere.

3. The method for preparing copper-clad aluminum composite wire according to claim 1, characterized in that, The aluminum core wire comprises the following alloying elements by mass fraction: Al > 99.5 wt%, Ag 0.05 wt% - 0.15 wt%, rare earth elements 0.02 wt% - 0.08 wt%, with the remainder being unavoidable impurities; the rare earth elements include at least one of Ce, La, and Yb. Alternatively, the aluminum core wire may contain alloying elements in the following mass fractions: Al > 99.9 wt%, Fe ≤ 0.05 wt%, Si ≤ 0.04 wt%, with the remainder being unavoidable impurities.

4. A copper-clad aluminum composite wire, characterized in that, The copper-clad aluminum composite wire is prepared by any one of the preparation methods described in claims 1-3, and includes an aluminum core wire and a copper layer covering the outside of the aluminum core wire.

5. The copper-clad aluminum composite wire according to claim 4, characterized in that, The volume ratio of the copper layer is 10%-40%; And / or, the diameter of the copper-clad aluminum composite wire is 1mm-2.5mm.

6. The application of the copper-clad aluminum composite wire prepared by the preparation method according to any one of claims 1-3 or the copper-clad aluminum composite wire according to any one of claims 4-5 in the fields of new energy technology, transportation equipment, and high-frequency signal transmission.

Images