Copper-aluminum composite special-shaped enameled wire and manufacturing method thereof

Abstract

The invention belongs to the technical field of electromagnetic wire materials and manufacturing, and particularly relates to a copper-aluminum composite special-shaped enameled wire and a preparation method thereof.The enameled wire comprises a copper-clad aluminum composite conductor and an insulating paint layer coated on the outer surface of the copper-clad aluminum composite conductor; the composite conductor is composed of a copper layer and an aluminum core, and the volume ratio of the copper layer to the aluminum core is 60%: 40%-70%: 30%. The thickness of the composite conductor is 0.5-2.0 mm, the width of the composite conductor is 2.0-10.0 mm, and the width-to-thickness ratio of the composite conductor is 2-8; the eccentricity of the copper layer is less than or equal to 2.5. The enameled wire has high conductivity, light weight and high reliability, and is especially suitable for high-frequency power electronic devices such as new energy automobile motors, high-frequency transformers and photovoltaic inverters, and application scenarios with high requirements for space utilization rate, heat dissipation performance and long-term stability such as spaceflight and deep sea equipment in extreme environments.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wire materials and manufacturing technology, specifically relating to a copper-aluminum composite shaped enameled wire and its preparation method. The enameled wire has high conductivity, lightweight and high reliability, and is especially suitable for high-frequency power electronic devices such as new energy vehicle motors, high-frequency transformers, photovoltaic inverters and aerospace and deep-sea equipment in extreme environments, where space utilization, heat dissipation performance and long-term stability are required. Background Technology

[0002] With the development of industries such as new energy, electric vehicles, and 5G communications, power electronic equipment is moving towards higher frequencies, smaller sizes, and higher power densities, which places higher demands on winding conductors. Although traditional round pure copper enameled wire has excellent conductivity (conductivity ≥100% IACS), it suffers from problems such as heavy weight, high cost, significant skin effect, and easy heat accumulation due to high temperature rise, which limits its application efficiency in high-frequency scenarios.

[0003] To address these issues, existing technologies have employed irregularly shaped copper flat wires to improve slot fill factor and heat dissipation, but this still fails to overcome the inherent high density of copper (8.96 g / cm³). Furthermore, at high frequencies, copper current tends to distribute on the surface (skin effect), leading to a decrease in effective cross-sectional area, increased resistance, and intensified heat generation.

[0004] In recent years, copper-clad aluminum (CCA) wires have emerged, utilizing an aluminum core (density approximately 2.7 g / cm³) to reduce overall weight, while the copper layer ensures surface conductivity. However, existing CCA wires are mostly circular in structure, resulting in low filler ratios in complex windings; furthermore, during subsequent drawing or rolling processes, the difference in thermal expansion coefficients between copper and aluminum (copper: ~17×10⁻⁻⁻⁴) leads to problems. 6 / K, Aluminum: ~23×10⁻ 6 The stress concentration ( / K) and deformation stress make the product prone to problems such as interface peeling, cracks, and high eccentricity, which seriously affect product reliability.

[0005] Furthermore, traditional processes often use adhesive bonding or mechanical coating to combine copper and aluminum, resulting in insufficient interfacial bonding strength. During annealing, brittle intermetallic compounds (such as CuAl2) are easily generated, further weakening mechanical properties. For example, CN209657819U discloses a long-life copper-clad aluminum composite enameled wire, comprising an enameled wire body, an aluminum wire core, multiple adhesive grooves on the surface of the aluminum wire core, adhesive inside the adhesive grooves, a bonding block on one side of the adhesive grooves, a copper layer on the outside of the bonding block, multiple bonding grooves on the inner wall surface of the copper layer, a primer layer on the outside of the copper layer, an insulation layer on the outside of the primer layer, the insulation layer including a first insulation layer and a second insulation layer, and a wear-resistant layer on the outside of the insulation layer.

[0006] Therefore, there is an urgent need for a new type of composite electromagnetic wire that can achieve a synergistic optimization of lightweight and high conductivity, ensure high bonding strength and structural stability of the copper-aluminum interface after multiple plastic deformations, and meet the requirements of high-frequency applications. Summary of the Invention

[0007] The purpose of this invention is to provide a high-performance copper-aluminum composite irregular-shaped enameled wire and its preparation process, aiming to solve the problems of large weight of copper wire, severe skin effect, poor interface bonding of CCA wire, high deformation and cracking rate, and difficulty in forming irregular cross-sections in the prior art.

[0008] In a first aspect, the present invention provides a copper-aluminum composite profiled enameled wire, employing the following technical solution: A copper-aluminum composite shaped enameled wire includes a copper-clad aluminum composite conductor and an insulating varnish layer coated on its outer surface; the composite conductor is composed of a copper layer and an aluminum core, with the volume ratio of the copper layer to the aluminum core being 60%:40% to 70%:30%; The composite conductor has a thickness of 0.5-2.0 mm, a width of 2.0-10.0 mm, and a width-to-thickness ratio of 2-8. Copper layer eccentricity ≤ 2.5.

[0009] In this invention, the volume ratio of the copper layer to the aluminum core is set to 60%:40% to 70%:30% to ensure that the copper layer provides high conductivity (copper conductivity is approximately 5.96 × 10⁻⁶). 7 The aluminum core reduces weight (aluminum density is approximately 2.7 g / cm³) while preventing insufficient bonding strength. Too high a copper ratio increases weight and cost, while too low a ratio affects conductivity; a 30%-40% aluminum core reduces skin effect and heat buildup in high-frequency applications.

[0010] Preferably, the aluminum core contains 0.1 to 0.5 wt% magnesium or silicon to improve ductility and fatigue resistance.

[0011] In a second aspect, the present invention provides a method for preparing the above-mentioned copper-aluminum composite profiled enameled wire, employing the following technical solution: A method for preparing a copper-aluminum composite profiled enameled wire includes the following steps: S1. Copper strip cladding: Copper strip with a thickness of 0.2-0.8 mm is clad around an aluminum core material with a diameter of 8-16 mm to form a copper-clad aluminum composite rod; S2. Welding: Seamless connection is achieved through high-frequency induction welding or laser welding to obtain copper-clad aluminum round wires with an initial diameter of 1.0 mm-5.0 mm; S3. Gradual deformation process: The copper-clad aluminum round wire is sequentially pre-formed by a round die, rolled and thickened, and shaped by a flat die. The deformation rate of each pass is controlled at 10% to 30%, the total deformation is 60% to 80%, and the deformation rate is less than 0.5 mm / s. S4. Annealing treatment: Hold at 605-610℃ for 8-10 min, then water cool; S5. Coating and Curing: Coating is done using a mold, and the paint layer is cured at a peak temperature of 400-450℃. The take-up speed is 20-60m / min.

[0012] In the above scheme, copper strip is used to wrap the aluminum core by cold rolling or hot rolling, and then copper and aluminum are bonded by high-frequency induction welding or laser welding to ensure that there are no oxide residues at the interface, improve the bonding strength, and avoid delamination failure in high-frequency applications.

[0013] Gradual deformation is achieved by using a "round die, rolling, and flat die" sequence, which optimizes the process to avoid sudden stress changes. Round die pre-forming, rolling for thickness reduction, and flat die shaping ensure step-by-step control of deformation. The uniformity of the copper layer in the finished copper-clad aluminum enameled wire is improved: the copper layer eccentricity (uniformity) is reduced from above 3.5 to below 2.5.

[0014] The deformation rate is controlled at 10%–30% per step, causing plastic deformation at the copper-aluminum interface rather than brittle fracture. Grain reorganization occurs during rolling, with copper and aluminum atoms bonding through diffusion, increasing bond strength and preventing cracking caused by stress concentration. The low deformation rate (<0.5 mm / s) reduces frictional heat, and the flat wire design (increasing surface heat dissipation) ensures uniform heat dispersion. During operation (e.g., in high-frequency transformers), the current is uniformly distributed (the irregular cross-section increases the fill factor), minimizing the skin effect.

[0015] The final product design features a flat shape to increase surface area. Combined with deformation control, this reduces the skin depth of high-frequency current. The low deformation rate ensures uniform heat diffusion and avoids heat accumulation and melting.

[0016] As a preferred embodiment, the gradual deformation process in S3 specifically covers the following sections: Section I: Circular die drawing, temperature 150-200℃, deformation rate per pass ε1=10-20%, speed v1=0.3-0.8 m / min; Section II: Rolling, temperature 180-220℃, reduction rate ε2=15-25%, speed v2=0.5-1.0 m / min, real-time adjustment of the reduction to ensure that the resistance to weight per unit length fluctuates ≤±1%; Section III: Flat die shaping, temperature 160-200℃, deformation rate ε3=10-20%, speed v3=0.4-0.9 m / min; Section IV: Finishing cold drawing, temperature 20-80℃, deformation rate ε4=5-10%, speed v4=1.0-2.0 m / min.

[0017] Preferably, the rolling of section II is controlled by online resistance-weight closed loop control. The online resistance-weight closed loop control is achieved by resistance test rollers and laser thickness gauges set at the inlet and outlet of section II. The control algorithm is PID and the sampling frequency is ≥1 kHz.

[0018] Preferably, high-frequency induction welding is used, with a welding frequency of 200-400 kHz, a welding speed of 3-8 m / min, and an oxygen content of ≤30 ppm in the weld.

[0019] Preferably, the water cooling rate in the annealing step is ≥50℃ / s to suppress the growth of CuAl2 continuous films.

[0020] Preferably, the contact surfaces of the copper strip and the aluminum core are pretreated to make the surface roughness Rz of the copper 80-95 μm and the surface roughness Rz of the aluminum 95-115 μm, so as to enhance the mechanical interlocking force at the interface.

[0021] A third aspect of the present invention provides the application of the above-mentioned copper-aluminum composite irregular enameled wire in high-frequency transformers, new energy vehicle drive motors, photovoltaic inverters, or aerospace electrical equipment.

[0022] By implementing the above technical solution, the present invention has the following beneficial effects: 1. This invention achieves high conductivity while making the enameled wire lightweight.

[0023] 2. This invention ensures that there are no oxide residues at the interface, improves the bonding strength, and avoids delamination failure in high-frequency applications.

[0024] 3. This invention reduces the skin depth of high-frequency current, resulting in a low deformation rate that ensures uniform heat diffusion and avoids thermal accumulation and melting. Detailed Implementation

[0025] The present invention will be further described in detail below through specific embodiments.

[0026] It should be noted that the following embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0027] Example 1 This embodiment provides a copper-aluminum composite irregular enameled wire, which is prepared according to the following method: 1. Material preparation Aluminum core: 3003 aluminum alloy rod with a diameter of 12 mm (Al ≥ 99.5%, containing 0.3 wt% Mg), surface sandblasted to Rz = 105μm; Copper strip: 0.6 mm thick, 15.7 mm wide, pure copper (Cu ≥ 99.9%), surface Rz = 90 μm.

[0028] 2. Encapsulation welding Copper strip is spirally wrapped around an aluminum core, and the joint is welded using high-frequency induction welding (frequency 300 kHz, speed 5 m / min). The oxygen content of the weld is detected to be 25 ppm, forming a copper-clad aluminum round wire with an initial diameter of 4.5 mm and a copper-aluminum volume ratio of 60%:40%.

[0029] 3. Gradual deformation treatment The process is carried out according to the four-section procedure: Section I: Temperature 180℃, deformation rate ε1=15%, velocity v1=0.6 m / min; Section II: Temperature 200℃, reduction rate ε2=20%, speed v2=0.8 m / min, equipped with an online resistance-weight closed-loop control system (PID control, sampling frequency 1.2 kHz). Section III: Temperature 180℃, deformation rate ε3=18%, velocity v3=0.7 m / min; Section IV: room temperature 25℃, deformation rate ε4=8%, velocity v4=1.5 m / min.

[0030] 4. Annealing treatment The sample was held at 608°C for 9 minutes under nitrogen protection (O2 ≤ 5 ppm), followed by water cooling at a rate of 60°C / s.

[0031] 5. Paint curing Three coats of polyesterimide varnish were applied, with a peak curing temperature of 430℃, a take-up speed of 40 m / min, and a film thickness of 0.1 mm.

[0032] Example 2 This embodiment provides a copper-aluminum composite irregular enameled wire, which is prepared according to the following method: 1. Material preparation Aluminum core: 3003 aluminum alloy rod with a diameter of 12 mm (Al ≥ 99.5%, containing 0.3 wt% Mg), surface sandblasted to Rz = 105μm; Copper strip: 0.6 mm thick, 15.7 mm wide, pure copper (Cu ≥ 99.9%), surface Rz = 90 μm.

[0033] 2. Encapsulation welding Copper strip is spirally wrapped around an aluminum core, and the joint is laser welded (power 3.5 kW, speed 6 m / min). The oxygen content of the weld is measured to be 25 ppm, forming a copper-clad aluminum round wire with an initial diameter of 4.5 mm and a copper-aluminum volume ratio of 60%:40%.

[0034] 3. Gradual deformation treatment The process is carried out according to the four-section procedure: Section I: Temperature 200℃, deformation rate ε1=20%, speed v1=0.6 m / min; Section II: Temperature 180℃, reduction rate ε2=20%, speed v2=0.8 m / min, equipped with an online resistance-weight closed-loop control system (PID control, sampling frequency 1.2 kHz). Section III: Temperature 190℃, Deformation rate ε3=18%, Velocity v3=0.7 m / min; Section IV: Ambient temperature 60℃, deformation rate ε4=8%, velocity v4=1.5 m / min.

[0035] 4. Annealing treatment The sample was held at 608°C for 9 minutes under nitrogen protection (O2 ≤ 5 ppm), followed by water cooling at a rate of 60°C / s.

[0036] 5. Paint curing Three coats of polyesterimide varnish were applied, with a peak curing temperature of 430℃, a take-up speed of 40 m / min, and a film thickness of 0.1 mm.

[0037] Example 3 The difference from Example 1 is that the volume ratio of copper to aluminum in this example is adjusted to 70%:30% (copper strip with a thickness of 0.8 mm and 3003 aluminum core with a diameter of 8 mm are selected as materials).

[0038] Example 4 The difference from Example 1 is that the four-segment process of gradual deformation treatment in this example is as follows: Section I: Temperature 150℃, deformation rate ε1=15%, velocity v1=0.6 m / min; Section II: Temperature 180℃, reduction rate ε2=20%, speed v2=0.8 m / min, equipped with an online resistance-weight closed-loop control system (PID control, sampling frequency 1.2 kHz). Section III: Temperature 170℃, deformation rate ε3=18%, velocity v3=0.7 m / min; Section IV: room temperature 50℃, deformation rate ε4=8%, velocity v4=1.5 m / min.

[0039] Example 5 The difference from Example 1 is that the four-segment process of gradual deformation treatment in this example is as follows: Section I: Temperature 180℃, deformation rate ε1=18%, velocity v1=0.6 m / min; Section II: Temperature 200℃, reduction rate ε2=15%, speed v2=0.8 m / min, equipped with an online resistance-weight closed-loop control system (PID control, sampling frequency 1.2 kHz). Section III: Temperature 180℃, deformation rate ε3=20%, velocity v3=0.7 m / min; Section IV: room temperature 25℃, deformation rate ε4=5%, velocity v4=1.5 m / min.

[0040] Comparative Example 1 The only difference from Example 1 is that no gradual deformation process is performed, and a circular copper-aluminum composite enameled wire is finally obtained.

[0041] Comparative Example 2 The difference from Example 1 is that the deformation process in this comparative example is not gradual deformation, but is directly formed by a single flat mold, with a total deformation of 70%.

[0042] The enameled wires obtained in each embodiment and comparative example were subjected to relevant performance tests. The test items and results are as follows:

Claims

1. A copper-aluminum composite irregular-shaped enameled wire, characterized in that, It includes a copper-clad aluminum composite conductor and an insulating varnish layer coated on its outer surface; the composite conductor consists of a copper layer and an aluminum core, with a copper layer to aluminum core volume ratio of 60%:40% to 70%:30%; the composite conductor has a thickness of 0.5-2.0 mm, a width of 2.0-10.0 mm, and a width-to-thickness ratio of 2-8; the copper layer eccentricity is ≤2.

5.

2. The copper-aluminum composite shaped enameled wire according to claim 1, characterized in that, The aluminum core contains 0.1-0.5 wt% magnesium or silicon.

3. The method for preparing a copper-aluminum composite profiled enameled wire as described in claim 1 or 2, characterized in that, The steps are as follows: S1. Copper strip cladding: Copper strip with a thickness of 0.2-0.8 mm is clad around an aluminum core material with a diameter of 8-16 mm to form a copper-clad aluminum composite rod; S2. Welding: Seamless connection is achieved through high-frequency induction welding or laser welding to obtain copper-clad aluminum round wires with an initial diameter of 1.0 mm-5.0 mm; S3. Gradual deformation process: The copper-clad aluminum round wire is sequentially pre-formed by a round die, rolled and thickened, and shaped by a flat die. The deformation rate of each pass is controlled at 10%-30%, the total deformation is 60%-80%, and the deformation rate is less than 0.5 mm / s. S4. Annealing treatment: Hold at 605-610℃ for 8-10 min, then water cool; S5. Coating and Curing: Coating is done using a mold, and the paint layer is cured at a peak temperature of 400-450℃. The take-up speed is 20-60 m / min.

4. The preparation method according to claim 3, characterized in that, The gradual deformation processing in S3 is specifically arranged in the following sections: Section I: Circular die drawing, temperature 150-200℃, deformation rate per pass ε1=10-20%, speed v1=0.3-0.8 m / min; Section II: Rolling, temperature 180-220℃, reduction rate ε2=15-25%, speed v2=0.5-1.0 m / min, real-time adjustment of the reduction to ensure that the resistance to weight per unit length fluctuates ≤±1%; Section III: Flat die shaping, temperature 160-200℃, deformation rate ε3=10-20%, speed v3=0.4-0.9 m / min; Section IV: Finishing cold drawing, temperature 20-80℃, deformation rate ε4=5-10%, speed v4=1.0-2.0 m / min.

5. The preparation method according to claim 4, characterized in that, The rolling of section II is controlled by online resistance-weight closed loop control. The online resistance-weight closed loop control is achieved by resistance test rollers and laser thickness gauges set at the inlet and outlet of section II. The control algorithm is PID and the sampling frequency is ≥1 kHz.

6. The preparation method according to claim 4, characterized in that, Welding is performed using high-frequency induction welding, with a welding frequency of 200-400 kHz, a welding speed of 3-8 m / min, and an oxygen content of ≤30 ppm in the weld.

7. The preparation method according to claim 4, characterized in that, The water cooling rate in the annealing process is ≥50℃ / s.

8. The preparation method according to claim 4, characterized in that, The contact surfaces of the copper strip and the aluminum core are pretreated to make the surface roughness Rz of the copper 80-95μm and the surface roughness Rz of the aluminum 95-115μm.

9. The application of the copper-aluminum composite shaped enameled wire as described in claim 1 or 2, characterized in that, It is used in high-frequency transformers, drive motors for new energy vehicles, photovoltaic inverters, or aerospace electrical equipment.

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