A copper-aluminum composite wire and a method for manufacturing the same

Abstract

The application provides a copper-aluminum composite wire and a preparation method thereof, and belongs to the technical field of metal composite materials. After the total reduction rate of drawing reaches 60 %, on-line current annealing is started to eliminate internal stress, restore the plasticity of the material, avoid the reduction of the strength of the wire after thinning and the breakage under the influence of internal stress; the annealing mode of gradually increasing the temperature is adopted to gradually enhance the diffusion of copper-aluminum atoms while eliminating the internal stress generated in the drawing process, form a diffusion layer at the interface, gradually realize the diffusion combination of the copper-aluminum interface, make the copper-aluminum evolve from mechanical combination to metallurgical combination, reduce the problems of interface defects and cracking, improve the strength of the wire and reduce the wire breakage rate; the short on-line current annealing time can avoid the excessive growth of the diffusion layer to form coarse intermetallic compounds, which are not conducive to the interface combination.

Description

Technical Field

[0001] This invention belongs to the field of metal composite materials technology, specifically relating to a copper-aluminum composite wire and its preparation method. Background Technology

[0002] Copper and copper alloys are the most commonly used conductive materials. At 20°C, the conductivity of pure copper is approximately 58.5 × 10⁻⁶. 6 S / m (100% of the International Standard for Annealed Copper, IACS) is second only to silver (61.1 × 10⁻⁶) among metals. 6 (S / m). Furthermore, copper has good chemical stability, is not easily oxidized at room temperature, and maintains stable performance over long-term use. However, copper has a high density and high cost. In many applications, using aluminum or aluminum alloys to replace copper can achieve cost reduction, weight reduction, and optimized resource utilization. However, the electrical conductivity of aluminum or aluminum alloys is only 61% IACS, which is insufficient to meet high conductivity requirements.

[0003] Copper-clad aluminum composite wire is a new type of composite material formed by combining a copper layer and an aluminum core through a composite process. Its core advantage lies in the complementary properties of copper and aluminum, significantly reducing material cost and weight while retaining the excellent electrical conductivity of copper. The density of copper is 8.9 g / cm³. 3 Aluminum content is only 2.7 g / cm³. 3 Copper-clad aluminum has a density between that of pure copper and aluminum, making it particularly advantageous in applications requiring weight reduction. Through its structure of encasing an aluminum core in copper layers, copper-clad aluminum achieves high conductivity using the "skin effect." For the same specifications, copper-clad aluminum composite wires cost only 30-50% of pure copper wires, significantly reducing material costs.

[0004] Currently, the main manufacturing processes for copper-clad aluminum composite wires include cladding welding, continuous extrusion, and drawing, all of which are solid-solid composite processes. These solid-solid composite processes require applying deformation forces such as drawing and rolling to the copper-aluminum composite material. However, due to the large difference in thermal expansion coefficients between copper and aluminum (copper approximately 17 × 10⁻⁶), these processes are difficult to implement. -6 / ℃, aluminum approximately 23×10 -6 After deformation (at / ℃), the copper-aluminum composite wire will have significant internal stress, especially at the interface, where residual stress is even greater. Heating and annealing are necessary to eliminate this stress before proceeding to the next deformation stage; otherwise, problems such as breakage or rolling breakage are likely to occur. Furthermore, the interfacial bonding between copper and aluminum is extremely difficult to control. In existing solid-solid bonding methods, the copper and aluminum layers in copper-clad aluminum composite wires often only exhibit mechanical bonding or discontinuous diffusion bonding (also known as metallurgical bonding), resulting in low interfacial bonding strength. This makes them prone to cracking or defects during deformation (drawing). Therefore, conventional solid-solid bonding processes for preparing copper-clad aluminum composite wires have a high wire breakage rate and a low yield of approximately 70% per 500,000 meters. Summary of the Invention

[0005] The purpose of this invention is to provide a copper-aluminum composite wire and its preparation method. The preparation method provided by this invention can form a continuous diffusion layer at the copper-aluminum interface, reducing wire breakage rate and improving yield.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing copper-aluminum composite wire, comprising:

[0008] Copper-clad aluminum composite billet is drawn to obtain copper-aluminum composite wire.

[0009] During the drawing process, when the total reduction in surface area of ​​the material reaches 60%, online current annealing is performed during the next drawing pass; then, when the total reduction in surface area of ​​the material increases by 10-15%, online current annealing is performed during the next drawing pass, and online current annealing is performed during the last drawing pass.

[0010] The temperature of each online current annealing is independently 300-400℃, and the temperature of each online current annealing increases gradually; the temperature of the last online current annealing is 350-400℃.

[0011] Preferably, except for the last online current annealing, the temperature difference between two adjacent online current annealings is 15 to 25°C.

[0012] Preferably, the current density for each online current annealing is independently 10–25 A / mm. 2 .

[0013] Preferably, the wire drawing speed during each online current annealing is independently 150-200 m / min, and the length of each online current annealing is independently 1-2 m.

[0014] Preferably, the current for each online current annealing is either a direct current or a pulse current.

[0015] Preferably, the frequency of the pulse current is 0.5 to 1.5 kHz, and the duty cycle is 15 to 25%.

[0016] Preferably, the drawing is cold drawing or warm drawing.

[0017] Preferably, the single-time reduction rate of the cold drawing is not higher than 30%.

[0018] Preferably, the temperature of the warmer is 100–250°C.

[0019] The present invention also provides a copper-aluminum composite wire prepared by the preparation method described above, wherein the copper-aluminum composite wire has a continuous diffusion layer at the copper-aluminum interface, and the thickness of the diffusion layer is 1 to 5 μm.

[0020] This invention provides a method for preparing copper-aluminum composite wire, comprising: drawing a copper-clad aluminum composite billet to obtain a copper-aluminum composite wire; during the drawing process, when the total reduction in surface area of ​​the material reaches 60%, in-line current annealing is performed during the next drawing pass; then, when the total reduction in surface area of ​​the material increases by 10-15%, in-line current annealing is performed during the next drawing pass, and in-line current annealing is performed during the final drawing pass; the temperature of each in-line current annealing is independently 300-400℃, and the temperature of each in-line current annealing increases progressively; the temperature of the final in-line current annealing is 350-400℃. This invention initiates online current annealing after the total reduction in surface area during drawing reaches 60%, eliminating internal stress, restoring the material's plasticity, and preventing strength reduction and breakage due to internal stress after wire thinning. A progressively increasing temperature annealing method gradually enhances copper-aluminum atom diffusion while eliminating internal stress generated during drawing, forming a diffusion layer at the interface. This gradually achieves diffusion bonding at the copper-aluminum interface, transforming the mechanical bond into a metallurgical bond, reducing interface defects and cracking, improving wire strength, and lowering the breakage rate. The short online current annealing time avoids excessive diffusion layer growth, forming coarse intermetallic compounds that are detrimental to interface bonding. Online current annealing also promotes atomic diffusion under the combined effects of drawing stress and current heating, facilitating the formation of a continuous diffusion layer. By limiting the annealing temperature, drawing stress is eliminated, a diffusion layer is formed, and material recrystallization is avoided, preventing strength reduction. Limiting the temperature of the final online current annealing ensures the continuity of the diffusion layer. The results of the examples show that the preparation method provided by the present invention achieves a yield of 95%, and the tensile strength of the obtained copper-aluminum composite wire reaches 320 MPa, with an electrical conductivity of 92.5% IACS. Attached Figure Description

[0021] Figure 1 This is a cross-sectional SEM image of the copper-aluminum composite wire prepared in Example 1 of the present invention;

[0022] Figure 2 This is a cross-sectional SEM image of the copper-aluminum composite wire prepared in Example 2 of the present invention;

[0023] Figure 3 This is a cross-sectional SEM image of the copper-aluminum composite wire prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0024] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0025] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses raw materials with purity commonly used in the field of metal wire.

[0026] This invention provides a method for preparing copper-aluminum composite wire, comprising:

[0027] Copper-clad aluminum composite billet is drawn to obtain copper-aluminum composite wire.

[0028] During the drawing process, when the total reduction in surface area of ​​the material reaches 60%, online current annealing is performed during the next drawing pass; then, when the total reduction in surface area of ​​the material increases by 10-15%, online current annealing is performed during the next drawing pass, and online current annealing is performed during the last drawing pass.

[0029] The temperature of each online current annealing is independently 300-400℃, and the temperature of each online current annealing increases gradually; the temperature of the last online current annealing is 350-400℃.

[0030] In one embodiment of the present invention, the volume fraction of copper in the copper-clad aluminum composite billet can be 15-25% or 18-22%.

[0031] As one embodiment of the present invention, the preparation method of the copper-clad aluminum composite billet is as follows: the copper strip is spirally wound on the aluminum rod at a certain angle to form an overlap edge. The overlap between the aluminum rod and the copper strip is heated to 600-650°C by induction heating or high frequency welding machine so that the aluminum reaches a semi-molten state and the copper and aluminum are partially fused. Then, the surface of the weld is water-cooled and polished.

[0032] In one embodiment of the present invention, the copper-aluminum composite billet is straightened and surface scratches and protrusions are removed before drawing.

[0033] In this invention, when the total reduction in surface area of ​​the material reaches 60% during drawing, in-line current annealing is performed before the next drawing pass. This invention initiates in-line current annealing after the total reduction in surface area reaches 60% to eliminate internal stress, restore the material's plasticity, and prevent the wire from breaking due to reduced strength caused by internal stress after thinning.

[0034] In this invention, after the total reduction in surface area of ​​the material reaches 60% during drawing, in-line current annealing is performed for every 10-15% increase in the total reduction in surface area before the next drawing pass. Performing in-line current annealing at the above frequency can promptly eliminate internal stress in the material and reduce the wire breakage rate.

[0035] In one embodiment of the present invention, the initial diameter of the material before drawing can be 8-10 mm.

[0036] In this invention, in-line current annealing is performed during the final drawing pass. The in-line current annealing temperature is 350–400°C, preferably 380–400°C. As one embodiment of this invention, the in-line current annealing temperature during the final drawing pass can be 360°C, 370°C, 380°C, 390°C, or 400°C. The in-line current annealing temperature during the final drawing pass is within the above range, which ensures the formation of a continuous diffusion layer, improves the tensile strength and conductivity of the wire, and reduces the wire breakage rate.

[0037] In this invention, the current density for each online current annealing is preferably 10–25 A / mm². 2 More preferably, it is 15–20 A / mm 2 As one embodiment of the present invention, the current density of the online current annealing can be 12A / mm². 2 14A / mm 2 16A / mm 2 18A / mm 2 20A / mm 2 22A / mm 2 Or 24A / mm 2 When the current density of in-line current annealing is within the above range, it is beneficial to promote the diffusion of copper and aluminum atoms, form a diffusion layer, and further reduce the wire breakage rate.

[0038] In one embodiment of the present invention, the voltage of the online current annealing can be 25-45V.

[0039] In this invention, the length of the online current annealing is preferably 1 to 2 m, more preferably 1.5 to 2 m; as one embodiment of this invention, the length of the online current annealing can be 1.5 m, 1.6 m, 1.7 m, 1.8 m, 1.9 m, or 2 m. The length of the online current annealing within the above range is beneficial for controlling the annealing time, further promoting the formation of the diffusion layer, and reducing the wire breakage rate.

[0040] In this invention, the wire drawing speed during each online current annealing is preferably 150–200 m / min, more preferably 160–180 m / min. As one embodiment of this invention, the wire drawing speed during online current annealing can be 150 m / min, 160 m / min, 170 m / min, 180 m / min, 190 m / min, or 200 m / min. During online annealing, a faster wire drawing speed results in higher production efficiency but also a higher wire breakage rate. A wire drawing speed within the above range is beneficial for balancing production speed and wire breakage rate. Furthermore, the wire drawing speed directly affects the online current annealing time; a wire drawing speed within the above range helps control the online current annealing time, further promoting the formation of the diffusion layer and reducing the wire breakage rate.

[0041] In this invention, the temperature of each online current annealing is independently 300-400°C, and the temperature of each online current annealing increases progressively.

[0042] In this invention, except for the final online annealing, the temperature difference between two adjacent online current annealings is preferably 15–25°C, more preferably 18–22°C; as one embodiment of this invention, the temperature difference between two adjacent online current annealings can be 15°C, 20°C, or 25°C. A temperature difference between two adjacent online current annealings within the above range is beneficial for the gradual formation of a diffusion layer, further reducing the wire breakage rate.

[0043] In one embodiment of the present invention, the temperature of each online current annealing can be 300℃, 320℃, 340℃, and 380℃ sequentially, or it can be 300℃, 320℃, 340℃, and 400℃ sequentially. Annealing within the above range and employing a progressively increasing temperature annealing method can gradually enhance the diffusion of copper and aluminum atoms while eliminating the internal stress generated during drawing, forming a diffusion layer at the interface, and gradually achieving diffusion bonding at the copper-aluminum interface. This transforms the mechanical bonding of copper and aluminum into a metallurgical bonding, reducing interface defects and cracking, improving wire strength, and lowering the wire breakage rate.

[0044] In this invention, the current for each online current annealing is preferably a direct current or a pulse current, more preferably a pulse current.

[0045] In this invention, the frequency of the pulse current is preferably 0.5–1.5 kHz, more preferably 0.8–1.2 kHz; as one embodiment of this invention, the frequency of the pulse current can be 0.5 kHz, 0.7 kHz, 0.9 kHz, 1.0 kHz, 1.1 kHz, or 1.5 kHz. A pulse current frequency within the above range is beneficial for further improving the stress relief effect.

[0046] In this invention, the duty cycle of the pulse current is preferably 15-25%, more preferably 18-22%; as one embodiment of this invention, the duty cycle of the pulse current can be 16%, 17%, 19%, 20%, 21%, or 23%. A duty cycle within the above range is beneficial for further improving the elimination of internal stress.

[0047] In this invention, the drawing is preferably cold drawing or warm drawing. Both cold drawing and warm drawing are common drawing methods, and using cold drawing helps to reduce the cost of drawing.

[0048] In this invention, the single-pass reduction rate of the cold drawing is preferably no higher than 30%, more preferably 20-25%; as one embodiment of this invention, the single-pass reduction rate of the cold drawing can be 20%, 21%, 22%, 23%, or 24%. The lower the single-pass reduction rate, the lower the wire breakage rate and the lower the processing efficiency; a single-pass reduction rate within the above range is beneficial for balancing processing efficiency and wire breakage rate.

[0049] In this invention, the temperature of the warming process is preferably 100–250°C, more preferably 150–200°C; as one embodiment of this invention, the temperature of the warming process can be 160°C, 180°C, 190°C, 210°C, 220°C, or 230°C. A warming temperature within the above range can balance the strength and electrical conductivity of the material.

[0050] As one embodiment of the present invention, the single reduction rate of the surface area of ​​the Winra may not exceed 50%, or may be 20-40%.

[0051] This invention initiates online current annealing after the total reduction in surface area during drawing reaches 60%, eliminating internal stress, restoring the material's plasticity, and preventing strength reduction and breakage due to internal stress after wire thinning. A progressively increasing temperature annealing method gradually enhances copper-aluminum atom diffusion while eliminating internal stress generated during drawing, forming a diffusion layer at the interface. This gradually achieves diffusion bonding at the copper-aluminum interface, transforming the mechanical bond into a metallurgical bond, reducing interface defects and cracking, improving wire strength, and lowering the breakage rate. The short online current annealing time avoids excessive diffusion layer growth, forming coarse intermetallic compounds that are detrimental to interface bonding. Online current annealing also promotes atomic diffusion under the combined effects of drawing stress and current heating, facilitating the formation of a continuous diffusion layer. By limiting the annealing temperature, drawing stress is eliminated, a diffusion layer is formed, and material recrystallization is avoided, preventing strength reduction. Limiting the temperature of the final online current annealing ensures the continuity of the diffusion layer.

[0052] The present invention also provides a copper-aluminum composite wire prepared by the preparation method described in the above technical solution.

[0053] In this invention, the copper-aluminum composite wire has a continuous diffusion layer at the copper-aluminum interface, and the thickness of the diffusion layer is 1 to 5 μm, preferably 2 to 4 μm.

[0054] The copper-aluminum composite wire provided by this invention has good tensile strength and electrical conductivity.

[0055] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0056] Example 1

[0057] A method for preparing copper-aluminum composite wire includes the following steps: cold drawing a copper-clad aluminum composite billet (initial diameter 9mm) with a volume content of 15% and a single reduction in surface area of ​​20%; and applying three online DC current annealing processes at a current density of 20A / mm² when the total reduction in surface area is 60%, 75%, and 90%. 2 The voltages were 25V, 30V, and 35V, the drawing speed was 150m / min, the length of the in-line current annealing was 1.4m, and the temperatures of the three in-line current annealings were 300℃, 320℃, and 340℃, respectively. When the wire diameter reached 1.2mm, the final drawing and in-line current annealing were performed. The length of the in-line current annealing was 2m, the voltage was 45V, the drawing speed was 200m / min, and the annealing temperature was 380℃.

[0058] Example 2

[0059] A method for preparing copper-aluminum composite wire includes the following steps: cold drawing a copper-clad aluminum composite billet (initial diameter 9mm) with a volume fraction of 25% and a single reduction in surface area of ​​20%; applying three in-line pulsed current annealing processes at total reductions in surface area of ​​60%, 75%, and 90%, with a frequency of 1kHz, a duty cycle of 20%, and a current density of 20A / mm². 2 The voltages were 25V, 30V, and 35V, the drawing speed was 150m / min, the length of the in-line current annealing was 1.5m, and the temperatures of the three in-line current annealings were 300℃, 320℃, and 340℃, respectively. When the wire diameter reached 1.0mm, the final drawing and in-line current annealing were performed. The length of the in-line current annealing was 2m, the voltage was 45V, the drawing speed was 200m / min, and the annealing temperature was 400℃.

[0060] Comparative Example 1

[0061] A method for preparing copper-aluminum composite wire is the same as in Example 1, except that the temperature for each online current annealing is 300°C.

[0062] Comparative Example 2

[0063] A method for preparing copper-aluminum composite wire is the same as in Example 2, except that the temperature for each online current annealing is 300°C.

[0064] Test Example 1

[0065] The copper-aluminum composite wires prepared in Examples 1 and 2, and Comparative Example 1, were observed using a scanning electron microscope (SEM), and SEM images were obtained, as shown below. Figures 1-3 As shown. From Figure 1 It can be seen that the wire prepared in Example 1 formed a diffusion layer of 2–5 μm at the copper-aluminum interface; from Figure 2 It can be seen that the diffusion layer formed at the copper-aluminum interface in the wire prepared in Example 2 is more uniform, with a thickness of 2–3 μm; from Figure 3 It can be seen that the wire prepared in Comparative Example 1 did not form a significant diffusion layer.

[0066] Test Example 2

[0067] The density, tensile strength (GB / T228.1-2021), and electrical conductivity (GB / T29197-2012) of the copper-aluminum composite wires prepared in Examples 1 and 2, and Comparative Examples 1 and 2 were tested and recorded in Table 1.

[0068] Table 1 Performance Test Record of Copper-Aluminum Composite Wire

[0069] Example 1 3.5 280 85.4 Comparative Example 1 3.5 240 84.1 Example 2 4.0 320 92.5 Comparative Example 2 4.0 283 91.3

[0070] As can be seen from Table 1, the preparation method of the present invention can improve the tensile strength and electrical conductivity of the wire, indicating that the formation of the diffusion layer improves the tensile strength and electrical conductivity of the wire.

[0071] Test Example 3

[0072] The fiber breakage rate of Examples 1 and 2, and Comparative Examples 1 and 2 was statistically analyzed (with a 500,000-meter fiber drawing cycle as one period, the probability of fiber breakage during the drawing process was recorded). The results showed that the fiber breakage rate of Examples 1 and 2 was 5% (the number of fiber breakages was 5 times in 100 500,000-meter fiber drawing cycles), while the fiber breakage rate of Comparative Examples 1 and 2 reached 30%. This indicates that the method of the present invention can significantly reduce the fiber breakage rate.

[0073] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-aluminum composite wire, comprising: Copper-clad aluminum composite billet is drawn to obtain copper-aluminum composite wire. During the drawing process, when the total reduction in surface area of ​​the material reaches 60%, online current annealing is performed during the next drawing pass; then, when the total reduction in surface area of ​​the material increases by 10-15%, online current annealing is performed during the next drawing pass, and online current annealing is performed during the last drawing pass. The temperature of each online current annealing is independently 300-400℃, and the temperature of each online current annealing increases gradually; the temperature of the last online current annealing is 350-400℃.

2. The preparation method according to claim 1, characterized in that, Except for the last online current annealing, the temperature difference between two adjacent online current annealings is 15 to 25°C.

3. The preparation method according to claim 2, characterized in that, The current density for each online current annealing is independently 10–25 A / mm. 2 .

4. The preparation method according to any one of claims 1 to 3, characterized in that, The wire drawing speed during each online current annealing is independently 150-200 m / min, and the length of each online current annealing is independently 1-2 m.

5. The preparation method according to claim 1, characterized in that, The current for each online current annealing is either a direct current or a pulse current.

6. The preparation method according to claim 5, characterized in that, The frequency of the pulse current is 0.5 to 1.5 kHz, and the duty cycle is 15 to 25%.

7. The preparation method according to claim 1, characterized in that, The drawing process is either cold drawing or warm drawing.

8. The preparation method according to claim 7, characterized in that, The single-time reduction rate of the cold drawing shall not exceed 30%.

9. The preparation method according to claim 7, characterized in that, The temperature of the Winra is 100–250°C.

10. The copper-aluminum composite wire prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The copper-aluminum composite wire has a continuous diffusion layer at the copper-aluminum interface, and the thickness of the diffusion layer is 1 to 5 μm.

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