Copper-clad aluminum wire cladding welding process

Abstract

The invention relates to the technical field of copper-clad aluminum wire processing, and discloses a copper-clad aluminum wire cladding welding process which comprises the following steps: firstly, providing a functional reaction sleeve formed by a matrix alloy and a metastable reaction precursor; assembling the end part of the copper-clad aluminum wire in the functional reaction sleeve to form an assembly body; and heating the assembly to melt the matrix alloy of the functional reaction sleeve, and after the matrix alloy is melted, applying a dynamic frequency conversion ultrasonic wave to the assembly. By applying low-frequency and high-power ultrasonic waves in the welding process, a compact oxide film (Al2O3) on the surface of the aluminum core can be effectively and physically broken, so that a fresh metal matrix is exposed, good wetting and reliable metallurgical bonding of brazing filler metal are achieved, the problem that high-corrosivity scaling powder must be used in traditional brazing is thoroughly solved through the mechanism, and the service life of the brazing filler metal is prolonged. And the hidden danger of long-term corrosion of the soldering flux residues to the cladding welding joint is fundamentally eliminated.

Description

Technical Field

[0001] This invention relates to the field of copper-clad aluminum wire processing technology, specifically a copper-clad aluminum wire cladding and welding process. Background Technology

[0002] Copper-clad aluminum (CCA) wires have been increasingly widely used in fields such as radio frequency cables, power cables, motor windings, and electronic components due to their combination of the good conductivity of copper and the lightweight and low cost of aluminum. However, achieving reliable, long-lasting, and low-resistance connections for copper-clad aluminum wires, especially multi-strand wire harnesses, has always been a key technical challenge in industry applications.

[0003] The technical difficulty stems primarily from the chemical properties of the aluminum core in copper-clad aluminum wire. Aluminum is a highly reactive metal, and its exposed surface instantly forms a dense, high-melting-point (approximately 2015 °C), electrically insulating aluminum oxide (Al2O3) film in the air. The presence of this oxide film severely hinders the diffusion and bonding between metal atoms during welding or brazing. To remove this oxide film, traditional aluminum brazing processes (soft brazing or hard brazing) must rely on highly chemically active corrosive fluxes (such as fluoride-based or chloride-based fluxes). Although these fluxes can effectively remove the oxide film, their highly corrosive residues are extremely difficult to clean completely, especially for the "cladding welding" structure or complex gaps in multi-strand wire harnesses targeted by this invention. These residues can rapidly trigger electrochemical corrosion of the joints in humid environments.

[0004] To avoid flux corrosion, existing technologies employ fluxless joining methods such as laser welding and resistance welding. However, copper-clad aluminum wire, as a dissimilar metal composite material, faces another fatal flaw when heated to high temperatures. Copper (Cu) and aluminum (Al) undergo a violent metallurgical reaction under heating conditions (especially in the liquid phase), inevitably forming a series of hard and brittle intermetallic compounds (IMCs), such as CuAl2 and Cu9Al4. At the high temperatures of welding, this reaction is extremely difficult to control. A thick, continuous brittle IMC layer severely degrades the mechanical properties of the joint, making it highly susceptible to cracking under vibration or thermal cycling stress, leading to connection failure. To simultaneously avoid both flux corrosion and IMC embrittlement... Currently, the most mainstream industrial solution is solid-state ultrasonic welding. This technology utilizes high-frequency mechanical vibration and pressure to physically break down the oxide film through friction and plastic deformation in the solid state of the non-melting or essentially non-melting base material, thereby achieving metal bonding. Although this method can effectively suppress the formation of IMC, the joint interface formed by solid-state ultrasonic welding is not a completely fused metallurgical structure. It cannot achieve the dense, non-porous, and airtight coating effect required in cladding welding for the wire harness. The interface strength and long-term environmental stability (such as resistance to moisture penetration) of this solid-state connection are still limited. Therefore, this invention designs a copper-clad aluminum wire cladding welding process to address the proposed technical problem. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a copper-clad aluminum wire cladding welding process, which solves the problem that existing copper-clad aluminum wire welding processes are unable to effectively remove the oxide film without corrosive flux, while simultaneously inhibiting the growth of brittle intermetallic compounds (IMC) and forming a dense metallurgical cladding.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a copper-clad aluminum wire cladding and welding process, comprising the following steps: S1. First, a functional reaction sleeve composed of a matrix alloy and a metastable reaction precursor is provided; the end of a copper-clad aluminum wire is assembled into the functional reaction sleeve to form an assembly; S2. Heating the assembly to melt the base alloy of the functional reactive sleeve, and applying dynamic frequency-converting ultrasound to the assembly after the base alloy has melted. S3. The dynamic frequency-converting ultrasonic wave is used to trigger the metastable reaction precursor to undergo an in-situ metallurgical reaction, and then cools and solidifies under the continuous action of the dynamic frequency-converting ultrasonic wave to finally form a cladding welded joint.

[0007] Preferably, the functional reaction sleeve is made of composite powder, which comprises, by weight percentage: the matrix alloy: 95.0~99.0 wt%; the metastable reaction precursor: 1.0~5.0wt%.

[0008] Preferably, the matrix alloy is composed of the following components by weight percentage: tin (Sn): 40.0~60.0wt%; bismuth (Bi): 30.0~50.0wt%; zinc (Zn): 1.0~8.0wt%.

[0009] Preferably, the metastable reaction precursor is specifically a mixture of nano-titanium (Ti) powder and amorphous boron (B) powder.

[0010] Preferably, the step of providing the functional reaction sleeve specifically includes: preparing the functional reaction sleeve by mechanically mixing and cold pressing a composite powder containing the matrix alloy and the metastable reaction precursor.

[0011] Preferably, the heating method described in step S2 is high-frequency induction heating, with a heating rate of 150~300℃ / s and a target peak temperature of 250~350℃.

[0012] Preferably, the application of dynamic frequency-converting ultrasound in step S3 specifically includes the following stages performed in a time sequence: Cleaning and reaction triggering phase: Applying low-frequency, high-power ultrasound; Interface control and solidification refinement stage: After the previous stage is completed, immediately switch to high frequency, low power ultrasound.

[0013] Preferably, the low frequency in the cleaning and reaction triggering phase is 18-22kHz, the high power is 300-800W, and the duration is 100-400ms.

[0014] Preferably, the high frequency in the interface control and solidification refinement stage is 40~60kHz, the low power is 50~150W, and the duration is 400~1000ms.

[0015] Preferably, the cooling and solidification under the continuous action of dynamic frequency-converting ultrasonic waves in step S3 specifically includes: simultaneously with the start of the interface control and solidification refinement stage, the assembly is subjected to forced synchronous cooling, which is achieved by injecting Ar gas or N2 gas.

[0016] This invention provides a copper-clad aluminum wire welding process. It has the following advantages: 1. This invention utilizes low-frequency, high-power ultrasonic waves applied during the welding process to generate a strong cavitation effect in the liquid brazing filler metal. The mechanical impact force effectively and thoroughly breaks down the dense oxide film (Al) on the surface of the aluminum core. 2 O 3 This exposes the fresh metal substrate, enabling good wetting of the brazing filler metal and reliable metallurgical bonding. This mechanism completely avoids the problem of using highly corrosive flux in traditional brazing, fundamentally eliminating the long-term corrosion risk of flux residues on the coated weld joint.

[0017] 2. This invention generates a controllable acoustic flow effect by immediately switching to high-frequency, low-power ultrasound in the later stages of the welding cycle. This acoustic flow effect creates intense micro-stirring at the interface of copper-aluminum-liquid phase brazing filler metal, preventing long-term interdiffusion and reaction between copper and aluminum atoms at the interface. This dynamic physical intervention mechanism can effectively control the thickness of the brittle intermetallic compound (IMC) layer to an extremely low level, thereby ensuring the excellent mechanical strength and electrical conductivity of the coated weld joint.

[0018] 3. This invention utilizes the extreme local high temperature and high pressure generated during the low-frequency and high-power stages of dynamic frequency-converting ultrasound as a "mechanical catalyst" to instantaneously trigger in-situ metallurgical reactions in these metastable precursors. This mechanism generates nanoscale dispersed reinforcing phases in-situ in the liquid phase before the solder joint solidifies. These reinforcing phases work synergistically with the ultrafine brazing filler metal structure to significantly improve the overall strength and creep resistance of the final coated weld joint.

[0019] 4. This invention achieves precise matching and optimization of different metallurgical stages of the welding process by seamlessly switching between low-frequency high-power and high-frequency low-power according to the time sequence. This collaborative control mechanism ensures that the CCA line end can achieve both thorough metallurgical bonding and have an extremely fine structure and a minimum of brittle phase, thereby guaranteeing the high reliability of the cladding weld joint.

[0020] 5. The functional reactive sleeve used in this invention completely encapsulates and penetrates the entire welding area of ​​the CCA wire harness in the form of molten liquid. Combined with the auxiliary effect of ultrasound in the liquid phase, the molten base alloy can fully wet and fill all gaps between the wire harness strands. The final solidified joint forms a dense, non-porous metallurgical connection structure, which not only completes the conductive function, but also provides a complete airtight protective layer, greatly enhancing the resistance of the encapsulated welded joint to the external environment (such as moisture and chemicals) and improving its service life. Attached Figure Description

[0021] Figure 1 is one of the process flow diagrams of the present invention; Figure 2 is a second schematic diagram of the process flow of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please refer to Figure 1-Appendix Figure 2 This invention provides a copper-clad aluminum wire cladding welding process, comprising the following steps: S1. First, a functional reactive sleeve composed of a matrix alloy and a metastable reaction precursor is provided; the end of a copper-clad aluminum wire is assembled into the functional reactive sleeve to form an assembly. The functional reactive sleeve is made of composite powder, which comprises, by weight percentage: matrix alloy: 95.0~99.0 wt%; metastable reaction precursor: 1.0~5.0 wt%. The matrix alloy is composed of the following components by weight percentage: Tin (Sn): 40.0 ~60.0 wt%; Bismuth (Bi): 30.0 ~50.0 wt%; Zinc (Zn): 1.0 ~8.0 wt%. The metastable reaction precursor is specifically a mixture of nano-titanium (Ti) powder and amorphous boron (B) powder. The step of providing a functional reaction sleeve specifically includes: preparing a functional reaction sleeve by mechanically mixing and cold pressing a composite powder containing a matrix alloy and a metastable reaction precursor. Specifically, the functional reactive sleeve is made of composite powder, which, by weight percentage, includes: a matrix alloy (95.0~99.0 wt%) and a metastable reaction precursor (1.0~5.0 wt%). The matrix alloy is preferably a low-melting-point eutectic or near-eutectic alloy composed of tin (Sn), bismuth (Bi), and zinc (Zn). This Sn-Bi-Zn alloy has a low melting point (e.g., below 250°C), and the addition of Zn helps to improve wettability with the Al matrix. The reaction precursor is preferably a nanoscale powder so that it can be ultrasonically activated in a subsequent step. In one embodiment, the precursor is a mixture of nano-titanium (Ti) powder and amorphous boron (B) powder.

[0024] "Metastable state" means that the two precursors (Ti and B) will not undergo or will only undergo an extremely slow metallurgical reaction (Ti+B→TiB2) at the target peak temperature (e.g., 250~350℃) after the matrix alloy melts, relying solely on thermal energy. They require an additional, non-thermal energy input to provide local activation energy, thereby being "triggered" to react.

[0025] The matrix alloy powder (e.g., average particle size 20-75 μm) and metastable reaction precursor powder (e.g., average particle size 50-300 nm) are mechanically mixed under an inert atmosphere (e.g., in a planetary ball mill). The uniformly mixed composite powder is loaded into a mold, and a holding pressure of 300-600 MPa is applied. The mixture is then cold-pressed into a sleeve structure with a predetermined inner diameter and wall thickness. Subsequently, copper-clad aluminum wire (CCA) harnesses are selected, and the insulation layer at the ends (e.g., 5-10 mm) is mechanically stripped. The exposed wire ends are then ultrasonically cleaned in acetone and anhydrous ethanol (e.g., for 3-5 minutes each) to remove oil and impurities. Finally, the wires are dried. This step does not require removing the natural oxide film (Al) on the surface of the aluminum core. 2 O 3 The oxide film will be removed in a subsequent step. The pretreated CCA wire harness end is inserted into the prepared functional reaction sleeve. The assembly is fixed on the welding station using a high-temperature resistant ceramic or alloy clamp. The clamping pressure (e.g., 0.5-2.0 MPa) should be sufficient to ensure positioning, but avoid plastic deformation of the wire harness, thus completing the preparation work before welding.

[0026] S2. The assembly is heated to melt the base alloy of the functional reactive sleeve. After the base alloy melts, dynamic frequency-converting ultrasonic waves are applied to the assembly. The heating method is high-frequency induction heating, with a heating rate of 150~300℃ / s and a target peak temperature of 250~350℃. Specifically, the purpose of this step is to create a liquid phase environment for subsequent ultrasonic treatment. High-frequency induction heating (e.g., 100-300 kHz) is preferred due to its rapid heating speed and concentrated energy, which reduces the heat-affected zone. The heating rate is controlled at 150-300℃ / s to quickly heat the assembly to the target peak temperature, preferably 250-350℃. At this temperature, the base alloy (Sn-Bi-Zn) in the functional reactive sleeve rapidly melts, forming a liquid phase molten pool that impregnates and wraps the CCA wire harness. However, due to the Al... 2 O 3 The oxide film hinders the reaction and the Ti / B reactants have not yet been activated. At this time, it is only physical wetting and no metallographic bond has been formed. A short holding time of 0.1 to 0.5 seconds can be set to ensure uniform melting.

[0027] S3. Dynamic frequency-converted ultrasound is used to trigger in-situ metallurgical reactions in metastable reaction precursors, which then cool and solidify under the continuous action of dynamic frequency-converted ultrasound, ultimately forming a cladding welded joint. The application of dynamic frequency-converted ultrasound specifically includes the following stages executed in sequence: Cleaning and reaction triggering phase: Applying low-frequency, high-power ultrasound; Interface control and solidification refinement stage: After the previous stage is completed, immediately switch to high frequency, low power ultrasound. The low frequency in the cleaning and reaction triggering stage is 18~22kHz, the high power is 300~800W, and the duration is 100~400ms. The high frequency in the interface control and solidification refinement stage is 40~60kHz, the low power is 50~150W, and the duration is 400~1000ms. The cooling and solidification under the continuous action of dynamic frequency-converting ultrasound in step S3 specifically includes: at the same time as the interface control and solidification refinement stage is started, the assembly is subjected to forced synchronous cooling. Forced synchronous cooling is achieved by spraying Ar gas or N2 gas. Specifically, by precisely controlling the ultrasonic wave mode, oxide film removal, in-situ reaction triggering, interfacial IMC suppression, and microstructure grain refinement are completed synergistically in a very short time. "Dynamic frequency conversion ultrasound" refers to the dynamic variation of the ultrasonic wave frequency and power according to a predetermined program within a welding cycle. This step is initiated immediately after induction heating reaches its peak temperature or after the holding period ends, and executes the following two stages sequentially: a) Cleaning and reaction triggering phase Objective: To physically break down Al 2 O 3 Oxide film; triggers the in-situ reaction of Ti + B.

[0028] Parameters: Apply low-frequency (18~22kHz), high-power (300~800W) ultrasound.

[0029] Duration: 100~400ms.

[0030] Principle: Low-frequency, high-power ultrasonic waves generate a strong acoustic cavitation effect in a liquid-phase molten pool. The instantaneous collapse of the cavitation bubbles produces a huge mechanical impact force, physically breaking down and peeling off the Al on the surface of the CCA wire aluminum core. 2 O 3The insulating layer, exposing the fresh Al matrix, and the extreme local high temperature and pressure (thousands of K, hundreds of MPa) generated when the cavitation bubble collapses, act as a "mechanical catalyst," providing sufficient activation energy for the "metastable" Ti + B precursors in step S1, instantaneously triggering them to undergo an in-situ metallurgical reaction (Ti + B → TiB2), generating a nanoscale TiB2 dispersion-reinforced phase in situ in the molten pool.

[0031] b) Interface control and solidification refinement stage Objective: To inhibit the growth of Cu-Al brittle IMC and refine the solidification structure.

[0032] Switching: After the cleaning and reaction triggering phase ends, the ultrasonic system immediately and seamlessly switches to high-frequency, low-power mode.

[0033] Parameters: Apply high-frequency (40~60kHz), low-power (50~150W) ultrasound.

[0034] Duration: 400~1000ms.

[0035] Principle: High-frequency, low-power ultrasound primarily generates a gentle, high-frequency acoustic flow effect. This intense "micro-stirring" action creates a vigorous mass exchange at the interface between Cu / Al and the liquid solder, inhibiting the long-term interdiffusion of Cu and Al atoms, thereby reducing the brittleness of IMC (such as CuAl2). The growth thickness of the layer is controlled at an extremely low level (e.g., submicron level). Meanwhile, the TiB2 nanoparticles generated in situ during the cleaning and reaction triggering stages act as heterogeneous nucleation cores. High-frequency vibration breaks up the growing solder dendrites, achieving ultra-fine solidification structure. In order to "freeze" the "crystal control" and "phase suppression" effects in the interface control and solidification refinement stages, the assembly must be forced to be synchronously cooled at the same time as this stage is started.

[0036] Method: High-purity Ar gas or N2 gas flow (e.g., flow rate 20~40L / min) is injected into the welding area through a nozzle; Process: Cooling gas and high-frequency ultrasound work together until the end of this stage, the molten pool is completely solidified, and after the ultrasound stops, continue to blow air to cool to room temperature (e.g., below 50°C). Finally, release the fixture to obtain the cladding welded joint.

[0037] In summary, this invention provides a copper-clad aluminum wire welding process. By applying low-frequency, high-power ultrasonic waves during the welding process, a strong cavitation effect is generated in the liquid brazing filler metal. The mechanical impact force can effectively and thoroughly physically break the dense oxide film (Al) on the surface of the aluminum core. 2 O3 This exposes the fresh metal matrix, enabling good wetting of the brazing filler metal and reliable metallurgical bonding. This mechanism completely avoids the problem of using highly corrosive flux in traditional brazing, fundamentally eliminating the long-term corrosion risk of flux residues on the coated weld joint. Furthermore, by immediately switching to high-frequency, low-power ultrasound in the later stages of the welding cycle, a controllable acoustic flow effect can be generated. This acoustic flow effect creates intense micro-stirring at the interface of the copper-aluminum-liquid phase brazing filler metal, preventing long-term interdiffusion and reaction of copper and aluminum atoms at the interface. This dynamic physical intervention mechanism can effectively control the thickness of the brittle intermetallic compound (IMC) layer to an extremely low level, thereby ensuring the excellent mechanical strength and electrical conductivity of the coated weld joint.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A copper-clad aluminum wire welding process, characterized in that, Includes the following steps: S1. First, a functional reaction sleeve composed of a matrix alloy and a metastable reaction precursor is provided; the end of a copper-clad aluminum wire is assembled into the functional reaction sleeve to form an assembly; S2. Heating the assembly to melt the base alloy of the functional reactive sleeve, and applying dynamic frequency-converting ultrasound to the assembly after the base alloy has melted. S3. The dynamic frequency-converting ultrasonic wave is used to trigger the metastable reaction precursor to undergo an in-situ metallurgical reaction, and then cools and solidifies under the continuous action of the dynamic frequency-converting ultrasonic wave to finally form a cladding welded joint.

2. The copper-clad aluminum wire welding process according to claim 1, characterized in that, The functional reaction sleeve is made of composite powder, which comprises, by weight percentage: the matrix alloy: 95.0~99.0 wt%; and the metastable reaction precursor: 1.0~5.0 wt%.

3. The copper-clad aluminum wire welding process according to claim 1, characterized in that, The base alloy is composed of the following components by weight percentage: tin (Sn): 40.0 ~ 60.0 wt%; bismuth (Bi): 30.0 ~ 50.0 wt%; zinc (Zn): 1.0 ~ 8.0 wt%.

4. The copper-clad aluminum wire welding process according to claim 2, characterized in that, The metastable reaction precursor is specifically a mixture of nano-titanium (Ti) powder and amorphous boron (B) powder.

5. The copper-clad aluminum wire welding process according to claim 1, characterized in that, The step of providing the functional reaction sleeve specifically includes: preparing the functional reaction sleeve by mechanically mixing and cold pressing a composite powder containing the matrix alloy and the metastable reaction precursor.

6. The copper-clad aluminum wire welding process according to claim 1, characterized in that, The heating method described in step S2 is high-frequency induction heating, with a heating rate of 150~300℃ / s and a target peak temperature of 250~350℃.

7. The copper-clad aluminum wire welding process according to claim 1, characterized in that, The application of dynamic frequency-converting ultrasound in step S3 specifically includes the following stages performed in a time sequence: Cleaning and reaction triggering phase: Applying low-frequency, high-power ultrasound; Interface control and solidification refinement stage: After the previous stage is completed, immediately switch to high frequency, low power ultrasound.

8. The copper-clad aluminum wire welding process according to claim 7, characterized in that, The low frequency in the cleaning and reaction triggering phase is 18~22kHz, the high power is 300~800W, and the duration is 100~400ms.

9. The copper-clad aluminum wire welding process according to claim 7, characterized in that, The high frequency in the interface control and solidification refinement stage is 40~60kHz, the low power is 50~150W, and the duration is 400~1000ms.

10. The copper-clad aluminum wire welding process according to claim 7, characterized in that, The cooling and solidification under the continuous action of dynamic frequency-converting ultrasonic waves in step S3 specifically includes: while the interface control and solidification refinement stage is started, the assembly is subjected to forced synchronous cooling, which is achieved by spraying Ar gas or N2 gas.

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