Brazing flux pre-embedded aluminum-based composite material, preparation method thereof and heat exchanger component

Abstract

The invention discloses a brazing flux pre-embedded aluminum-based composite material, a preparation method thereof and a heat exchanger component, and the preparation method of the brazing flux pre-embedded aluminum-based composite material comprises the steps that brazing flux powder, inorganic filler, an organic binder and a solvent are mixed, and brazing flux slurry is prepared; coating the brazing flux slurry on the surface of a brazing filler metal layer aluminum alloy base material, and drying and curing to form a brazing flux composite film layer on the surface; the brazing filler metal layer aluminum alloy base material with the brazing flux composite film layer formed on the surface and the structural core layer aluminum alloy base material with the high solidus temperature are oppositely placed, so that the brazing flux composite film layer is located on the side, away from the structural core layer aluminum alloy base material, of the brazing filler metal layer aluminum alloy base material, and casting-rolling compounding is conducted; and the brazing filler metal layer aluminum alloy base material wraps the structural core layer aluminum alloy base material. According to the preparation method, complex procedures in a traditional process can be avoided, soldering flux flying and pollution can be avoided, and the distribution uniformity and the interface bonding strength of the soldering flux are improved. The obtained composite material is good in brazing filler metal spreadability, low in porosity and high in joint strength in the brazing process.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to a flux-embedded aluminum-based composite material and its preparation method, and a heat exchanger component. Background Technology

[0002] Aluminum alloys, with their low density, excellent thermal conductivity, and good resistance to atmospheric corrosion, have become a core material in the manufacture of key heat exchangers such as automotive radiators, air conditioning condensers, aero-engine thermal management components, and heat exchangers for new energy fuel cells / power batteries. However, the dense oxide film that naturally forms on their surface constitutes a major obstacle to the brazing process. This oxide film severely hinders the spread and wetting of the brazing filler metal, leading to defects such as incomplete welds, porosity, and insufficient bond strength in the brazed joints, directly affecting the reliability and service life of the heat exchanger.

[0003] Currently, vacuum brazing is the primary technology used in the industrial sector to connect aluminum heat exchanger components. This technology suppresses oxide film regeneration under high vacuum and utilizes the low surface tension of the brazing filler metal for good spreading, resulting in high-quality joints. However, it relies on large-scale vacuum equipment, has a long production cycle, and is only suitable for small-batch, high-value-added products, making it difficult to meet the needs of large-scale continuous production. Controlled atmosphere brazing (CAB) is another feasible technical approach. This process requires flux spraying or coating under a protective atmosphere, utilizing the chemical reaction between fluoride flux and the oxide film to disrupt its structure. However, this technology has inherent drawbacks: coating uniformity is significantly affected by spraying parameters and substrate condition, easily leading to localized excessive thickness or thinness; flux residues may induce corrosion, reacting with the aluminum substrate in high-temperature or humid environments to generate corrosion products, reducing system cleanliness and increasing coolant conductivity, thereby inducing localized galvanic corrosion and shortening component service life; furthermore, the spraying process lacks flexibility and is difficult to integrate efficiently with subsequent forming processes.

[0004] With the rapid development of the new energy vehicle and fuel cell industries, heat exchangers need to meet requirements for high reliability, long lifespan, and low maintenance. Flux residue must be extremely low and uniformly distributed, and they must be compatible with continuous production lines to achieve high production capacity. Therefore, it is necessary to provide a brazing technology that can overcome the limitations of spraying processes, achieve precise and uniform flux application, and minimize harmful residues. This will improve joint reliability, adapt to efficient continuous production, and meet the requirements of long-life systems. Summary of the Invention

[0005] In view of this, this application provides a flux-embedded aluminum-based composite material and its preparation method, as well as a heat exchanger component, to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for preparing a flux-embedded aluminum-based composite material. The method includes: mixing flux powder, inorganic filler, organic binder, and solvent to prepare a flux slurry; coating the flux slurry onto the surface of a solder layer aluminum alloy substrate, drying and curing it to form a flux composite film layer on the surface; placing the solder layer aluminum alloy substrate with the flux composite film layer on its surface opposite to a structural core layer aluminum alloy substrate, such that the flux composite film layer is located on the side of the solder layer aluminum alloy substrate away from the structural core layer aluminum alloy substrate, and performing casting and rolling composite bonding, so that the solder layer aluminum alloy substrate covers the structural core layer aluminum alloy substrate, wherein the solidus temperature of the solder layer aluminum alloy is lower than the solidus temperature of the structural core layer aluminum alloy, thus preparing the flux-embedded aluminum-based composite material.

[0007] Based on the first aspect, in some embodiments, based on the total mass of the flux slurry, the mass percentages of each component are as follows: flux powder 40wt% to 60wt%, inorganic filler 8wt% to 18wt%, and organic binder 1wt% to 8wt%.

[0008] Based on the first aspect, in some embodiments, the flux powder includes fluoroaluminate.

[0009] Based on the first aspect, in some embodiments, the inorganic filler includes at least one of aluminum silicate and aluminum silicate.

[0010] Based on the first aspect, in some embodiments, the organic binder includes at least one of carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and hydroxypropyl methyl cellulose.

[0011] Based on the first aspect, in some embodiments, the coating method includes at least one of blade coating, extrusion coating, and spray coating.

[0012] Based on the first aspect, in some embodiments, drying and curing includes multiple drying steps at different temperatures.

[0013] Based on the first aspect, in some embodiments, the casting and rolling temperature is 680 °C to 720 °C.

[0014] Based on the first aspect, in some embodiments, in the multi-stage drying step, the temperature of the first stage drying is 50 ℃ to 70 ℃, the temperature of the second stage drying is 80 ℃ to 100 ℃, and the temperature of the third stage drying is 150 ℃ to 260 ℃.

[0015] Secondly, this application provides a flux-embedded aluminum-based composite material, which is prepared by the above-mentioned preparation method. The flux-embedded aluminum-based composite material includes a structural core aluminum alloy substrate and a solder layer aluminum alloy substrate located outside the structural core layer. Flux powder is embedded in the surface layer of the solder layer aluminum alloy substrate away from the structural core layer.

[0016] Based on the second aspect, in some embodiments, the aluminum alloy substrate of the solder layer includes an aluminum-silicon alloy, and the aluminum alloy substrate of the structural core layer includes an aluminum-manganese alloy.

[0017] Based on the second aspect, in some embodiments, the areal density of the flux composite film is 3 g / m². 2 Up to 10 g / m 2 .

[0018] Thirdly, this application provides a heat exchanger component comprising the above-mentioned flux-embedded aluminum-based composite material.

[0019] Based on the third aspect, in some embodiments, the heat exchanger components include at least one of an evaporator tube, a condenser fin, and a battery cooling plate.

[0020] In the preparation method of the flux-embedded aluminum-based composite material of this application, flux powder, inorganic filler and organic binder are prepared into a uniform slurry by wet process. The flux is pre-embedded in the internal structure in situ and uniformly during the material manufacturing stage, which reduces flux flying and pollution, and promotes the high dispersion and stability of flux components. This is conducive to the formation of a uniform coating in the future. It fundamentally overcomes the defects of flux agglomeration and uncontrollable distribution in traditional dry powder spraying or physical mixing processes. It also effectively avoids the complicated powder metallurgy and hot isostatic pressing processes in traditional processes, and reduces production energy consumption and manufacturing costs. By coating the flux layer substrate with slurry and then drying and curing it to form a continuous flux composite film, the flux is transformed from discrete particles into a dense and firmly adhered film. This facilitates the uniform distribution of flux at the nano / micro level in a two-dimensional plane and promotes a strong physicochemical bond between the film and the substrate. This solves the problems of uneven coating thickness and poor adhesion in traditional controlled atmosphere brazing (CAB), as well as the weak bonding and easy peeling of flux at the metal interface in pre-embedded technologies such as powder metallurgy. The flux-coated flux layer and the higher-melting-point structural core layer are placed in a predetermined direction and composited using casting and rolling, while controlling the difference in solidus temperature between the two. On the one hand, casting and rolling enables efficient and continuous metallurgical bonding, which improves production efficiency and reduces costs, adapting to large-scale continuous production. Simultaneously, while forming a high-strength composite interface, it also solidifies the pre-embedded structure of the flux on the surface of the flux layer. On the other hand, the difference in melting points between the flux layer and the core layer ensures that the flux layer melts and connects during brazing while the core layer maintains its structural integrity. The flux-embedded aluminum-based composite material prepared by the method of this application has excellent surface cleanliness, consistent brazing performance and good mechanical integrity. During the brazing process, it exhibits excellent properties such as excellent filler metal spreading, dense and high-strength joints and low flux residue. It is highly suitable for mass production and high-efficiency industrial applications, and helps to meet the requirements of new energy vehicle battery cooling systems for long life, high reliability and low corrosion risk. Attached Figure Description

[0021] Figure 1 Images showing the surface morphology and surface element distribution of the composite brazed aluminum alloy substrate provided in Embodiment 1 of this application.

[0022] Figure 2 Image showing the casting-rolling composite interface morphology of the flux-embedded aluminum-based composite material provided in Example 1 of this application.

[0023] Figure 3 This is a microscopic image of the flux-embedded aluminum-based composite material provided in Example 1 of this application after brazing. Detailed Implementation

[0024] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions of this application will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the technical solutions of this application. However, the technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and comprehensive understanding of the disclosure of the technical solutions of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] To overcome the limitations of spray coating processes, achieve precise and uniform flux application, and minimize harmful residues, related technologies have proposed a "flux pre-embedding" strategy. For example, flux can be embedded into the aluminum substrate using powder metallurgy or hot isostatic pressing (HIP) technology. Powder metallurgy involves mixing flux with aluminum alloy powder, pressing it into shape, and sintering it; HIP utilizes high temperature and pressure to promote diffusion bonding. While these methods avoid coating uniformity issues, they have significant limitations: insufficient interfacial bonding strength, making them prone to peeling under thermal cycling or mechanical stress; low production efficiency, complex powder metallurgy processes, and limited single-pass throughput in HIP; and high cost, with material costs significantly higher than traditional processes.

[0027] Against this backdrop, developing novel pre-embedded flux aluminum alloy materials and their preparation technologies, characterized by ease of processing, adaptability to continuous production, uniform flux distribution, and low residue, has become a key approach to overcoming the performance bottlenecks of aluminum heat exchangers. Addressing the shortcomings of existing technologies and the demands of industrial upgrading, there is an urgent need to innovate the microstructure and preparation process of pre-embedded flux to achieve low-cost, high-efficiency, and low-residue large-scale production while ensuring brazing quality. This will provide high-performance, high-reliability heat exchanger material solutions for the new energy vehicle and fuel cell sectors.

[0028] Based on this, one embodiment of this application provides a method for preparing a flux-embedded aluminum-based composite material, the method comprising:

[0029] Step 1: Mix flux powder, inorganic filler, organic binder and solvent to prepare flux slurry.

[0030] In the above steps, by using a wet process to prepare a uniform slurry from flux powder, inorganic filler, and organic binder, the flux is pre-embedded in situ and uniformly in the internal structure during the material manufacturing stage. This reduces flux dispersion and pollution, and promotes the high dispersion and stability of flux components, which is beneficial for the subsequent formation of a uniform coating. This fundamentally overcomes the defects of flux agglomeration and uncontrollable distribution in traditional dry powder spraying or physical mixing processes. It also effectively avoids the complex powder metallurgy and hot isostatic pressing processes in traditional processes, reducing production energy consumption and manufacturing costs.

[0031] In some embodiments, based on the total mass of the flux slurry, the mass percentages of each component are as follows: flux powder 40wt% to 60wt%, inorganic filler 8wt% to 18wt%, and organic binder 1wt% to 8wt%. For example, the mass percentage of flux powder can be 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, or any value within the range of any two of the above values. The mass percentage of inorganic filler can be 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, or any value within the range of any two of the above values. The mass percentage of organic binder can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or any value within the range of any two of the above values. It is understood that the balance is solvent. It is understood that the solvent includes, but is not limited to, water. This application controls the solid content, viscosity and dispersibility of flux slurry by controlling the mass ratio of the above components, and formulates a highly stable slurry containing fine flux powder, which is conducive to promoting uniform suspension of flux particles, thereby further promoting the high dispersion and stability of flux components.

[0032] In some embodiments, the flux powder comprises fluoroaluminate. For example, fluoroaluminate includes, but is not limited to, potassium fluoroaluminate. Understandably, potassium fluoroaluminate, as a flux, has a good cleaning effect on oxide films.

[0033] In some embodiments, the inorganic filler includes at least one of aluminum silicate and aluminum silicate. The aforementioned inorganic filler helps to regulate rheological properties, prevent slurry sedimentation, promote uniform subsequent coating, and reduce film shrinkage stress during subsequent drying and sintering, thereby lowering the risk of film cracking. Furthermore, it maintains a stable structure at brazing temperatures, providing a high-temperature framework for the flux and aiding in the regulation of flux release.

[0034] In some embodiments, the organic binder includes at least one selected from carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and hydroxypropyl methyl cellulose. The aforementioned organic binders help provide the slurry viscosity and the adhesion between the dried film and the substrate.

[0035] Step 2: Apply flux slurry to the surface of the aluminum alloy substrate of the solder layer, and dry and cure it to form a flux composite film layer on the surface.

[0036] In the above steps, by coating the slurry onto the surface of the solder layer substrate and drying and curing it to form a continuous flux composite film, the flux is transformed from discrete particles into a dense and firmly attached film. This is beneficial for promoting the uniform distribution of flux at the nano / micro level in a two-dimensional plane, and also helps the film to form a strong physicochemical bond with the substrate. This solves the problems of uneven coating thickness and poor adhesion in traditional controlled atmosphere brazing (CAB), as well as the weak bonding and easy peeling of flux to the metal interface in pre-embedded technologies such as powder metallurgy.

[0037] In some embodiments, the coating method includes at least one of blade coating, extrusion coating, and spray coating. Precision coating equipment helps achieve uniform coating of the slurry, promoting the formation of a wet film with controllable thickness.

[0038] In some embodiments, drying and curing includes multiple drying steps at different temperatures. By using a multi-stage drying process, such as sequentially passing through low-temperature pre-drying, medium-temperature curing, and final-temperature sintering stages, the solvent is gradually removed and the arrangement of flux particles is controlled, which is beneficial for promoting the formation of a continuous, dense, and structurally stable film layer between particles through interfacial forces.

[0039] In some embodiments, in the multi-stage drying process, the temperature of the first stage drying is 50°C to 70°C, the temperature of the second stage drying is 80°C to 100°C, and the temperature of the third stage drying is 150°C to 260°C. For example, the temperature of the first stage drying can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, or any value within the range of any two of the above values. The temperature of the second stage drying can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, or any value within the range of any two of the above values. The temperature for the third drying stage can be 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, or any value within the range of any two of the above values. Controlling the temperatures of these multiple drying stages allows for low-temperature pre-drying, medium-temperature curing, and final-temperature sintering processes. This helps to precisely regulate the changes in the film layer at each stage, promoting the formation of a continuous, dense, and structurally stable film layer between particles through interfacial forces.

[0040] Step 3: Place the aluminum alloy substrate with the flux composite film formed on its surface opposite the aluminum alloy substrate of the structural core layer, so that the flux composite film is located on the side of the aluminum alloy substrate away from the aluminum alloy substrate of the structural core layer, and perform casting and rolling composite to make the aluminum alloy substrate of the solder layer cover the aluminum alloy substrate of the structural core layer. The solidus temperature of the aluminum alloy of the solder layer is lower than that of the aluminum alloy of the structural core layer, thus preparing the flux-embedded aluminum matrix composite material.

[0041] In the above steps, the solder layer coated with flux film and the structural core layer with a higher melting point are placed in a preset direction and composited by casting and rolling. The difference in solidus temperature between the two is controlled. On the one hand, casting and rolling can achieve efficient and continuous metallurgical bonding, which is conducive to improving production efficiency and reducing costs, and is suitable for large-scale continuous production. At the same time, while forming a high-strength composite interface, the pre-embedded structure of flux on the surface of the solder layer is also solidified. On the other hand, the design of the melting point difference between the solder layer and the core layer ensures that the solder layer melts and connects during the brazing process while the core layer maintains structural integrity.

[0042] In some embodiments, the casting temperature is between 680°C and 720°C. For example, the casting temperature is 680°C, 685°C, 690°C, 695°C, 700°C, 705°C, 710°C, 715°C, 720°C, or any value within the range of any two of the above values. Controlling the casting temperature within the above range helps to further improve the bonding strength of the formed composite interface and regulate the pre-embedded structure of the flux on the surface of the solder layer.

[0043] In some embodiments, after casting-rolling composite to obtain a composite plate, the above preparation method further includes: hot rolling or cold rolling the composite plate. Hot rolling or cold rolling helps to control the thickness of the composite plate.

[0044] In some embodiments, after casting-rolling composite to obtain a composite plate, the above preparation method further includes annealing the composite plate. Annealing helps to eliminate processing stress and stabilize the microstructure.

[0045] An embodiment of this application also provides a flux-embedded aluminum-based composite material, which is prepared by the above-described preparation method. The flux-embedded aluminum-based composite material includes a structural core aluminum alloy substrate and a solder layer aluminum alloy substrate located outside the structural core. Flux powder is embedded in the surface layer of the solder layer aluminum alloy substrate away from the structural core.

[0046] The flux-embedded aluminum-based composite material prepared by the method of this application has excellent surface cleanliness, consistent brazing performance and good mechanical integrity. During the brazing process, it exhibits excellent properties such as excellent filler metal spreading, dense and high-strength joints and low flux residue. It is highly suitable for mass production and high-efficiency industrial applications, and helps to meet the requirements of new energy vehicle battery cooling systems for long life, high reliability and low corrosion risk.

[0047] In some embodiments, the aluminum alloy substrate of the solder layer includes an aluminum-silicon alloy, and the aluminum alloy substrate of the structural core layer includes an aluminum-manganese alloy. When the above-mentioned aluminum alloy substrates are selected for the solder layer and the structural core layer, the flux-embedded aluminum matrix composite material of this application can use its own solder layer as a source of solder and flux to braze the entire flux-embedded aluminum matrix composite material to the target part.

[0048] In some embodiments, the areal density of the flux composite film is 3 g / m². 2 Up to 10 g / m 2 For example, the areal density of the flux composite film can be 3 g / m². 2 3.5 g / m 2 4 g / m 2 4.5 g / m 2 5 g / m 2 5.5 g / m2 6 g / m 2 6.5 g / m 2 7g / m 2 7.5 g / m 2 8 g / m 2 8.5 g / m 2 9 g / m 2 9.5 g / m 2 10 g / m 2 Or any value within the range formed by any two of the above values.

[0049] One embodiment of this application also provides a heat exchanger component, including the above-described flux-embedded aluminum-based composite material.

[0050] During the brazing process, the flux slurry used in the flux-embedded aluminum matrix composite material of this application exhibits excellent chemical and thermal stability, maintaining component uniformity and preventing decomposition or volatilization at high temperatures, thereby achieving a uniform and dense coating. Through optimized rheological properties and wetting performance, this slurry ensures the formation of a continuous and controllable-thickness film on the substrate surface, promoting good solder spreading and forming a strong metallurgical interface with the substrate, effectively suppressing potential defects caused by localized powder accumulation, porosity, or lack of fusion. Simultaneously, during brazing, the flux achieves a highly uniform distribution within the solder layer with extremely low residual levels, avoiding corrosion or electrochemical problems caused by flux accumulation. This helps maintain the long-term stability of the coolant conductivity, thereby improving the corrosion resistance of the brazed joint and the overall process reliability. Therefore, this technology is suitable for fields with stringent requirements for material durability, sealing, and electrochemical environment, such as advanced manufacturing scenarios like new energy vehicle battery cooling systems, fuel cell bipolar plate connections, and electronic power modules.

[0051] In some embodiments, the heat exchanger components include at least one of an evaporator tube, a condenser fin, and a battery cooling plate.

[0052] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0053] Example 1:

[0054] (1) A flux-embedded aluminum-based composite material, the preparation method of which includes:

[0055] Step 1: Material and substrate pretreatment. 3003 aluminum-manganese alloy (1.2 mm thick) was selected as the core layer material, and 4045 aluminum-silicon alloy foil (0.12 mm thick) was selected as the solder layer material. The surface of the solder foil was wiped with ethanol to remove grease contaminants and surface impurities, and then placed in a room temperature environment to air dry for later use.

[0056] Step 2: Flux Slurry Preparation. Potassium fluoroaluminate-based flux powder (particle size D90≤50 μm) was selected, with the following composition: 52wt% flux powder, 12wt% aluminum silicate, 1.8wt% carboxymethyl cellulose (CMC), 0.3wt% dispersant, 0.2wt% defoamer, and the balance being deionized water. After mechanical stirring until uniformly mixed, the mixture was filtered through a 200-mesh sieve. The final viscosity of the slurry was adjusted to 100 mPa·s~180 mPa·s to obtain a flux slurry with good stability.

[0057] Step 3: Coating and drying to form a composite brazed aluminum alloy substrate. A blade coating machine was used to apply the slurry, with a blade gap of 80 μm and a substrate transfer rate of 6 m / min. After coating, the substrate was placed in a hot air drying line for segmented drying: the first stage was at 60 ℃ for 1.5 min; the second stage was at 90 ℃ for 3 min; and the pre-sintering stage was at 200 ℃ for 5 min. After drying, the surface density was approximately 3.5 g / m³. 2 A dense flux film layer.

[0058] Step 4: Casting and Rolling Composite and Post-treatment. The core layer and the brazing filler layer are composited in a twin-roll casting mill, with the casting and rolling temperature controlled within the range of 690 ℃ to 710 ℃ and the strip running speed within the range of 1.5 m / min to 2.0 m / min. The composite sheet obtained by casting and rolling is then thinned to a thickness of 0.3 mm by hot rolling and cold rolling. Subsequently, it is annealed at 350 ℃ for 1 h to eliminate processing stress and stabilize the microstructure, resulting in a flux-embedded aluminum matrix composite material.

[0059] The resulting flux-embedded aluminum matrix composite material exhibits a uniform microstructure and good interfacial bonding. The flux is evenly distributed and has low residual amount, which meets the requirements for subsequent brazing.

[0060] (2) An evaporator for use in an automotive air conditioning system, the preparation method of which includes: the flux-embedded aluminum-based composite material obtained in (1) is slit, stamped and formed and surface cleaned to make a multi-layer flat tube for the evaporator. Then, the flat tube is assembled with aluminum alloy fins, manifolds and other components to form an evaporator core. The assembled core is directly sent into a controlled atmosphere brazing furnace for brazing, and after cooling, the finished evaporator is obtained.

[0061] Example 2:

[0062] (1) A flux-embedded aluminum-based composite material, the preparation method of which includes:

[0063] Step 1: Material and substrate pretreatment. 3003 aluminum-manganese alloy (1.0 mm thick) was selected as the core layer material, and 4045 aluminum-silicon alloy foil (0.10 mm thick) was selected as the solder layer material. The surface of the solder foil was wiped with ethanol to remove grease contaminants and surface impurities, and then placed in a room temperature environment to air dry for later use.

[0064] Step 2: Flux Slurry Preparation. Potassium fluoroaluminate-based flux powder (particle size D90≤50 μm) was selected, with the following composition: 50wt% flux powder, 15wt% aluminosilicate, 2wt% carboxymethyl cellulose (CMC), 0.5wt% dispersant, 0.2wt% defoamer, and the balance being deionized water. After mechanical stirring until uniformly mixed, the mixture was filtered through a 200-mesh sieve. The final viscosity of the slurry was adjusted to 70 mPa·s~120 mPa·s to obtain a flux slurry with good stability.

[0065] Step 3: Coating and drying to form a composite brazed aluminum alloy substrate. A spray coating machine is used to apply the flux slurry, with the nozzle pressure set to 0.25 MPa and the substrate running speed at 8 m / min. After coating, segmented drying is carried out on a hot air drying line: initial drying temperature 55 ℃, time 2 min; middle drying temperature 85 ℃, time 3 min; pre-firing temperature 180 ℃, time 5 min. The resulting surface density is approximately 4.5 g / m³. 2 A dense flux film layer.

[0066] Step 4: Casting and Rolling Composite and Post-treatment. The core layer and the brazing filler layer were composited in a double-strip casting and rolling mill, with the casting and rolling temperature controlled within the range of 690 ℃~710 ℃ and the strip running speed at 1.8 m / min. The composite sheet obtained by casting and rolling was then thinned to a thickness of 0.5 mm by hot rolling and cold rolling. Subsequently, it was annealed at 350 ℃ for 1.5 h to eliminate processing stress and stabilize the microstructure, resulting in a flux-embedded aluminum-based composite material.

[0067] The resulting flux-embedded aluminum matrix composite material exhibits a uniform microstructure and good interfacial bonding. The flux is evenly distributed and has low residual amount, which meets the requirements for subsequent brazing.

[0068] (2) An internal chip for an automotive radiator, the preparation method of which includes: using the flux-embedded aluminum-based composite material obtained in (1), precision stamping and forming it into an internal chip with a complex flow channel structure. After stacking multiple internal chips with side plates, controlled atmosphere brazing is directly carried out, and the automotive radiator is obtained after cooling.

[0069] Example 3:

[0070] (1) A flux-embedded aluminum-based composite material, the preparation method of which includes:

[0071] Step 1: Material and substrate pretreatment. 3003 aluminum-manganese alloy (1.2 mm thick) was selected as the core layer material, and 4045 aluminum-silicon alloy foil (0.12 mm thick) was selected as the solder layer material. The surface of the solder foil was wiped with ethanol to remove grease contaminants and surface impurities, and then placed in a room temperature environment to air dry for later use.

[0072] Step 2: Preparation of flux slurry. Potassium fluoroaluminate-based flux powder (particle size D90≤50 μm) was selected, with the following composition: 52wt% flux powder, 12wt% aluminosilicate, 6wt% polyvinyl butyral (PVB), and 30wt% mixed organic solvent (propylene glycol methyl ether acetate and isopropanol in a volume ratio of 1:1). The flux powder, aluminosilicate, and PVB binder were added to a high-speed mixer and stirred at 800 r / min for 10 min to obtain a first mixture. The first mixture was then transferred to a two-roll mill and ground for 30 min. The mixed organic solvent was added to the ground mixture and stirred at 500 r / min for 20 min to obtain a flux slurry with a viscosity range of 250 mPa·s to 380 mPa·s, uniform dispersion, and no agglomeration. The slurry was then filtered through a 200-mesh sieve to remove large particles.

[0073] Step 3: Coating and drying to form a composite brazed aluminum alloy substrate. A doctor blade coater is used to coat the pretreated aluminum alloy brazed foil surface, with the substrate running speed (coating speed) controlled at 1 m / s. After coating, the foil is placed in an oven at a set temperature of 260 ℃ for 15 s to dry. After cooling, the areal density is measured to be approximately 6 g / m². 2 A dense flux film layer.

[0074] Step 4: Casting and Rolling Composite and Post-treatment. The core layer and the brazing filler layer are composited in a double-strip casting and rolling mill, with the casting and rolling temperature controlled within the range of 690 ℃ to 710 ℃ and the strip running speed within the range of 1.5 m / min to 2.0 m / min. The composite sheet obtained by casting and rolling is then thinned to a thickness of 0.45 mm by hot rolling and cold rolling. Subsequently, it is annealed at 350 ℃ for 1 h to eliminate processing stress and stabilize the microstructure, resulting in a flux-embedded aluminum-based composite material.

[0075] The resulting flux-embedded aluminum matrix composite material exhibits a uniform microstructure and good interfacial bonding. The flux is evenly distributed and has low residual amount, which meets the requirements for subsequent brazing.

[0076] (2) A water-cooled plate for heat dissipation of battery systems in new energy vehicles, the preparation method of which includes: using the flux-embedded aluminum-based composite material obtained in (1), and stamping it to make a flat plate and a flow plate component of the water-cooled plate respectively. After assembling the two, they are directly brazed in a controlled atmosphere, and after cooling, the water-cooled plate is obtained.

[0077] Example 4:

[0078] A flux-embedded aluminum-based composite material, the preparation method of which includes:

[0079] Step 1: Material and substrate pretreatment. 3003 aluminum-manganese alloy (1.5 mm thick) was selected as the core layer material, and 4045 aluminum-silicon alloy foil (0.15 mm thick) was selected as the solder layer material. The surface of the solder foil was wiped with ethanol to remove grease contaminants and surface impurities, and then placed in a room temperature environment to air dry for later use.

[0080] Step 2: Preparation of flux slurry. Potassium fluoroaluminate-based flux powder (particle size D90≤50 μm) was selected, with the following composition: 55wt% flux powder, 10wt% aluminosilicate, 5wt% polyvinyl butyral (PVB), and 30wt% mixed organic solvent (propylene glycol methyl ether acetate and isopropanol in a volume ratio of 1:1). The flux powder, aluminosilicate, and PVB binder were added to a high-speed mixer and stirred at 800 r / min for 10 min to obtain a first mixture. The first mixture was then transferred to a two-roll mill and ground for 30 min. The mixed organic solvent was added to the ground mixture and stirred at 500 r / min for 20 min to obtain a flux slurry with a viscosity range of 280 mPa·s to 450 mPa·s, uniform dispersion, and no agglomeration. The slurry was then filtered through a 200-mesh sieve to remove large particles.

[0081] Step 3: Coating and drying to form a composite brazed aluminum alloy substrate. An extrusion coating machine was used to coat the pretreated aluminum alloy brazing foil surface, controlling the substrate running speed (coating speed) at 10 m / s. After coating, the foil was placed in an oven set to 250 ℃ for drying for 20 s. After cooling, the areal density was measured to be approximately 7 g / m². 2 A dense flux film layer.

[0082] Step 4: Casting and Rolling Composite and Post-treatment. The core layer and the brazing filler layer were composited in a double-strip casting and rolling mill, with the casting and rolling temperature controlled within the range of 690 ℃~710 ℃ and the strip running speed at 2.0 m / min. The composite sheet obtained by casting and rolling was then thinned to a thickness of 0.6 mm by hot rolling and cold rolling. Subsequently, it was annealed at 350 ℃ for 1 h to eliminate processing stress and stabilize the microstructure, resulting in a flux-embedded aluminum-based composite material.

[0083] The resulting flux-embedded aluminum matrix composite material exhibits a uniform microstructure and good interfacial bonding. The flux is evenly distributed and has low residual amount, which meets the requirements for subsequent brazing.

[0084] Comparative Example 1:

[0085] Traditional dry powder coating processes include:

[0086] Substrate preparation: Pre-treatment of materials and substrates. 3003 aluminum-manganese alloy (1.0 mm thick) was selected as the core layer material, and 4045 aluminum-silicon alloy foil (0.15 mm thick) was selected as the solder layer material. The surface of the solder foil was wiped with ethanol to remove grease contaminants and surface impurities, and then placed in a room temperature environment to air dry for later use.

[0087] Powder preparation: A5001 powder and KAlF4 flux were mechanically mixed at a mass ratio of 9:1.

[0088] Spraying parameters: feeding temperature set at 400℃; feeding air pressure at 450 Psi; powder feeding speed at 20 g / min; coating speed at 0.15 m / s; coating step distance at 1 mm; spraying height at 15 mm, ultimately forming a flux coating.

[0089] Casting-rolling composite and post-treatment: The core layer and the brazing filler layer were composited in a double-strip casting and rolling mill, with the casting and rolling temperature controlled within the range of 690 ℃~710 ℃ and the strip running speed controlled within the range of 1.5 m / min~2.0 m / min. The composite sheet obtained by casting and rolling was thinned to a thickness of 0.5 mm by hot rolling and cold rolling. Subsequently, it was annealed at 350 ℃ for 1 h to obtain the flux-embedded aluminum matrix composite material.

[0090] This application conducted performance tests on the flux-embedded aluminum-based composite materials of Examples 1-4 and Comparative Example 1, including tensile strength, yield strength, elongation, and brazing performance.

[0091] Tensile mechanical property tests were conducted according to GB / T 228.1-2021. High-temperature brazing tests were conducted according to GB / T 11363-2008: a high-temperature brazing furnace was used to simulate actual process conditions; after polishing the substrate surface, brazing was performed at 610 ℃ for 12 minutes. Coating pre-application and brazing were completed under an inert atmosphere. Weld inspection involved taking weld samples, which were then sequentially inlaid, mechanically polished, and etched. The brazing quality was then observed and analyzed using a metallographic microscope (AxioObserver Z1m). The test results are shown in Table 1.

[0092] Table 1. Performance test results of flux-embedded aluminum matrix composite materials of Examples 1-4 and Comparative Example 1 of this application

[0093]

[0094] Please refer to Table 1. Examples 1-4 of this application employ a wet coating process, in which flux powder, inorganic filler, organic binder, and solvent are mixed to prepare a uniform slurry. This slurry is then coated onto the surface of the solder layer and dried and cured to form a continuous flux composite film. The flux is then pre-embedded through casting and rolling composite processes. This avoids the expensive plasma spraying equipment and inert gas consumables required by the traditional dry powder spraying process in Comparative Example 1, thus reducing production energy consumption and costs. Furthermore, Examples 1-4 of this application generally exhibit higher tensile strength and yield strength than Comparative Example 1, and some examples show better elongation. The brazing performance is also superior, with strong weld points and complete weld surfaces, while Comparative Example 1 suffers from incomplete welds and poor weld quality. The key difference lies in the fact that the embodiment forms a continuous film layer through slurry coating, with uniform flux distribution. The casting-rolling composite process achieves metallurgical bonding, resulting in high interfacial bonding strength. The raw material utilization rate is also significantly improved by reducing flux flying and waste. This solves the defects in Comparative Example 1, such as uneven coating, poor soldering, and raw material waste caused by powder splashing and limitations of the spraying process. It verifies the advantages of the wet coating technology of this patent in improving material performance and production efficiency.

[0095] This application analyzed the surface morphology and elemental distribution characteristics of the composite brazed aluminum alloy substrate treated with coating technology (obtained in the third step) using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) (GeminiSEM 300) under the conditions of accelerating voltage 10-20 kV, working distance 5-15 mm, and EDS acquisition time 5-10 min. Please refer to [link to relevant documentation]. Figure 1 Taking Example 1 as an example, the analysis results show that the flux particles on the substrate surface are densely and uniformly dispersed, with no obvious agglomeration or exposed areas. The particle spacing is uniform, and no large agglomerates are observed, indicating that the flux is uniformly spread on a macroscopic scale during the coating process. Magnification from (a) to (d) reveals that the high-magnification morphology images further reveal the microscopic dispersion state of the flux: the flux particles are irregular polygons with a narrow size distribution, and no abnormally large or ultrafine particle agglomeration is observed, confirming that the flux maintains high uniformity at the microscopic scale. Fluorine (F) and potassium (K), as characteristic elements of the flux KAIF4, show in their distribution diagrams that both elements are fully covered on the substrate surface with uniform signal intensity distribution, indicating that the flux is uniformly present and no elemental segregation occurs. The surface morphology and elemental distribution results fully verify the advantages of the preparation method of this application in terms of flux coating uniformity, providing uniform reaction conditions for oxide film removal and wetting promotion during subsequent brazing.

[0096] This application also analyzed the casting-rolling composite interface morphology of the obtained flux-embedded aluminum matrix composite material using a scanning electron microscope (GeminiSEM 300). Please refer to [link to relevant documentation]. Figure 2 Taking Example 1 as an example, the interface morphology under multiple fields of view A to H (a to h are magnified views of the corresponding fields of view) shows that a continuous and dense metallurgical interface is formed between the core layer and the solder layer, with no obvious gaps, pores, or oxide inclusions. Under high magnification, the interface transition zone shows a gentle gradient change without clear physical separation lines, indicating that the core layer and the solder layer achieve atomic-level diffusion under high temperature and pressure during the casting and rolling process, avoiding the risks of "mechanical bonding" or interface delamination commonly seen in traditional composite processes. No abnormal reaction products between the flux and the matrix were observed in the interface area. The flux particles are uniformly distributed in a discrete state in the near-interface region of the solder layer, i.e., on the surface away from the core layer, without diffusing or aggregating into the core layer. This feature ensures that the flux can be uniformly released during subsequent brazing, while maintaining the overall mechanical properties of the composite plate.

[0097] This application also analyzed the microstructure of the obtained flux-embedded aluminum matrix composite material after brazing using a scanning electron microscope (GeminiSEM 300). Please refer to [link to relevant documentation]. Figure 3 Taking Example 1 as an example, the red dashed line and its vicinity indicate the brazing area. The brazing area is continuous and uniformly distributed, with no obvious pores, cracks, or unbonded areas at the interface. A continuous transition zone is formed between the brazing filler metal and the aluminum alloy matrix, without macroscopic defects. Fine, dispersed granular second phases are visible in the matrix near the interface, showing no significant signs of detachment from the matrix, indicating sufficient atomic diffusion at the interface and the formation of a strong metallurgical bond.

[0098] Based on the above analysis results, in the preparation method of flux-embedded aluminum-based composite material in this application embodiment, flux powder, inorganic filler and organic binder are prepared into a uniform slurry by wet method. The flux is pre-embedded in situ and uniformly in the internal structure during the material manufacturing stage, which reduces flux flying and pollution, and promotes the high dispersion and stability of flux components. This is conducive to the formation of a uniform coating in the future. It fundamentally overcomes the defects of flux agglomeration and uncontrollable distribution in traditional dry powder spraying or physical mixing processes. It also effectively avoids the complex powder metallurgy and hot isostatic pressing processes in traditional processes, and reduces production energy consumption and manufacturing costs. By coating the flux layer substrate with slurry and then drying and curing it to form a continuous flux composite film, the flux is transformed from discrete particles into a dense and firmly adhered film. This facilitates the uniform distribution of flux at the nano / micro level in a two-dimensional plane and promotes a strong physicochemical bond between the film and the substrate. This solves the problems of uneven coating thickness and poor adhesion in traditional controlled atmosphere brazing (CAB), as well as the weak bonding and easy peeling of flux at the metal interface in pre-embedded technologies such as powder metallurgy. The flux-coated flux layer and the higher-melting-point structural core layer are placed in a predetermined direction and composited using casting and rolling, while controlling the difference in solidus temperature between the two. On the one hand, casting and rolling enables efficient and continuous metallurgical bonding, which improves production efficiency and reduces costs, adapting to large-scale continuous production. Simultaneously, while forming a high-strength composite interface, it also solidifies the pre-embedded structure of the flux on the surface of the flux layer. On the other hand, the difference in melting points between the flux layer and the core layer ensures that the flux layer melts and connects during brazing while the core layer maintains its structural integrity. The flux-embedded aluminum-based composite material prepared by the method of this application has excellent surface cleanliness, consistent brazing performance and good mechanical integrity. During the brazing process, it exhibits excellent properties such as excellent filler metal spreading, dense and high-strength joints and low flux residue. It is highly suitable for mass production and high-efficiency industrial applications, and helps to meet the requirements of new energy vehicle battery cooling systems for long life, high reliability and low corrosion risk.

[0099] Furthermore, since the preparation method of this application has highly controllable process parameters, including temperature profile, atmosphere conditions, coating rate and thickness, key variables can be precisely adjusted, thus providing a solid technical foundation for continuous and large-scale production. This not only ensures the consistency and repeatability of product performance in mass production, but also significantly improves material utilization and yield by reducing solder splashing, scrap rate and subsequent processing steps, thereby reducing overall production costs.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a flux-embedded aluminum-based composite material, characterized in that, The preparation method includes: A flux slurry is prepared by mixing flux powder, inorganic filler, organic binder and solvent. The flux slurry is coated onto the surface of the aluminum alloy substrate of the solder layer, and then dried and cured to form a flux composite film layer on the surface. The solder layer aluminum alloy substrate with the flux composite film formed on its surface is placed opposite to the structural core layer aluminum alloy substrate, such that the flux composite film is located on the side of the solder layer aluminum alloy substrate away from the structural core layer aluminum alloy substrate, and then cast and rolled to composite the solder layer aluminum alloy substrate with the structural core layer aluminum alloy substrate. The solidus temperature of the solder layer aluminum alloy is lower than that of the structural core layer aluminum alloy, thus preparing the flux-embedded aluminum-based composite material.

2. The preparation method according to claim 1, characterized in that, Based on the total mass of the flux slurry, the flux powder accounts for 40 wt% to 60 wt% of the mass, the inorganic filler accounts for 8 wt% to 18 wt% of the mass, and the organic binder accounts for 1 wt% to 8 wt% of the mass.

3. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (1) The flux powder includes fluoroaluminate; (2) The inorganic filler includes at least one of aluminum silicate and aluminum silicate; (3) The organic binder includes at least one of carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral and hydroxypropyl methyl cellulose.

4. The preparation method according to claim 1, characterized in that, The preparation method also satisfies at least one of the following conditions: (1) The coating method includes at least one of blade coating, extrusion coating and spray coating; (2) The drying and curing process includes multiple drying steps at different temperatures; (3) The casting and rolling temperature is 680 ℃ to 720 ℃.

5. The preparation method according to claim 4, characterized in that, In the multi-stage drying process, the temperature of the first stage is 50 ℃ to 70 ℃, the temperature of the second stage is 80 ℃ to 100 ℃, and the temperature of the third stage is 150 ℃ to 260 ℃.

6. A flux-embedded aluminum-based composite material, characterized in that, Prepared by the preparation method according to any one of claims 1 to 5; The flux-embedded aluminum-based composite material includes the structural core aluminum alloy substrate and the solder layer aluminum alloy substrate located outside the structural core layer, wherein the flux powder is embedded in the surface layer of the solder layer aluminum alloy substrate away from the structural core layer.

7. The flux-embedded aluminum-based composite material as described in claim 6, characterized in that, The aluminum alloy substrate of the brazing filler layer includes an aluminum-silicon alloy, and the aluminum alloy substrate of the structural core layer includes an aluminum-manganese alloy.

8. The flux-embedded aluminum-based composite material as described in claim 6, characterized in that, The areal density of the flux composite film is 3 g / m³. 2 Up to 10 g / m 2 .

9. A heat exchanger component, characterized in that, The flux-embedded aluminum-based composite material included in any one of claims 6 to 8.

10. The heat exchanger component as claimed in claim 9, characterized in that, The heat exchanger components include at least one of an evaporator flat tube, a condenser fin, and a battery cooling plate.

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