Composite aluminum plate with pre-embedded mixed melting layer microstructure and cast-rolling preparation method of composite aluminum plate

Abstract

The invention discloses a composite aluminum plate with an embedded mixed melting layer microstructure and a cast-rolling preparation method of the composite aluminum plate, and belongs to the technical field of aluminum alloy material preparation, the composite aluminum plate comprises a coating aluminum alloy, a matrix aluminum alloy and an embedded brazing flux mixed melting layer, the coating aluminum alloy is connected with the matrix aluminum alloy through the embedded brazing flux mixed melting layer, and the matrix aluminum alloy is connected with the embedded brazing flux mixed melting layer. The pre-embedded brazing flux mixed melting layer is a controllable mixed metal layer formed by mixing pre-embedded brazing flux metal and a fusion layer formed by a solid-liquid cast rolling process, the cast rolling preparation method is a coating-cast rolling combined preparation method, and the method has the advantages of being short in process, high in production efficiency, high in pre-embedded layer control precision and the like, and large-scale production of products is facilitated.

Description

Technical Field

[0001] This invention relates to the technical field of heat-transfer aluminum alloy materials, and in particular to a composite aluminum plate with a pre-embedded fusion layer microstructure and its casting and rolling preparation method. Background Technology

[0002] Heat transfer composite aluminum plates are widely used in the field of heat exchangers for new energy vehicles due to their excellent heat dissipation, corrosion resistance, and low density. The main difficulty in brazing aluminum alloys is the formation of a thin but mechanically strong oxide film on the surface, which hinders the metallurgical bonding of the alloy during welding. Applying flux to the brazing surface during the brazing process can effectively break down this oxide film. Traditional methods for preparing pre-embedded flux heat transfer composite aluminum plates involve first applying flux to the surface of the cladding aluminum alloy, followed by sintering and then multiple cold rolling and annealing processes with the base aluminum alloy. This process is not only lengthy but also inefficient. It is complex and requires extensive production facilities, such as flux spraying production lines and baking ovens. Traditional brazing fluxes often result in poor bonding between the flux and the aluminum alloy cladding, leading to low weld strength. This is particularly problematic in the production of high-performance products such as liquid-cooled plates and condensers, where conventional production processes struggle to meet the dual requirements of production efficiency and brazing performance.

[0003] Combining flux spraying and solid-liquid-solid casting and rolling processes, a dynamic interaction mechanism between solid-phase pre-embedded flux and liquid-phase molten aluminum alloy is employed to form a fused layer during high-temperature rolling. This reduces interface defects and enables in-situ removal of the oxide film and atomic diffusion of alloying elements. The unique porous microstructure of the pre-embedded flux fused layer, with its dispersed flux distribution, allows gas to escape during casting and rolling, effectively removing air and volatile substances trapped during cold spraying. This ensures a thorough metallurgical bond between the pre-embedded flux interface and the fused layer composite interface, significantly improving interface bonding quality. Heat-transfer aluminum plates with pre-embedded flux fused layers can greatly reduce production steps, meeting the market demand for efficient and stable production of aluminum alloy composite plates, making it a future application hotspot in the new energy vehicle industry. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a composite aluminum plate with a pre-embedded flux-coated microstructure and its casting and rolling preparation method. This improves upon the problems of long production cycles and complex processes associated with pre-embedded flux aluminum alloy composite plates, making it suitable for the production of high-performance heat exchangers such as liquid-cooled plates and condensers, and facilitating large-scale production.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a composite aluminum plate with a pre-embedded flux-mixed layer microstructure, characterized in that: the composite aluminum plate is a layered metal composite structure, including a cladding aluminum alloy, a base aluminum alloy, and a pre-embedded flux-mixed layer, wherein the cladding aluminum alloy and the base aluminum alloy are connected by the pre-embedded flux-mixed layer; the layered metal composite aluminum plate includes structural forms such as cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy, cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy-pre-embedded flux-mixed layer-cladding aluminum alloy, and cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy-cladding aluminum alloy.

[0006] A further improvement of the technical solution of the present invention is that: the cladding aluminum alloy is a 4-series aluminum alloy strip or a 7-series aluminum alloy strip, and its thickness is 8% to 16% of the total thickness of the composite aluminum plate; the pre-embedded flux melting layer is a flux-aluminum-silicon alloy melting microstructure formed after the interface is controllably mixed and melted in the solid-liquid casting and rolling joint preparation, and its thickness is 2% to 4% of the thickness of the composite aluminum plate; the base aluminum alloy is a 3-series aluminum alloy, and its thickness is 80% to 90% of the thickness of the composite aluminum plate.

[0007] A further improvement of the technical solution of the present invention is that: the pre-embedded flux-aluminum-silicon alloy mixed microstructure is a diffuse structure in which the flux is uniformly embedded in the microporous structure of the aluminum-silicon alloy; the aluminum-silicon alloy micropores are a novel aluminum-based porous microstructure in which the flux is diffusely distributed after the molten pre-embedded flux mixed layer melts and mixes with the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy and then solidifies for a second time.

[0008] A further improvement of the technical solution of the present invention is that the melting point, solidification point and other physical properties of the novel aluminum-based porous microstructure with flux dispersion can be customized by adjusting the ratio of aluminum and silicon elements in the aluminum-silicon alloy and the melting ratio of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy, thereby controlling the working characteristics of the pre-embedded flux during brazing.

[0009] A casting and rolling method for preparing a composite aluminum plate with a pre-embedded fusion layer microstructure includes the following specific steps: Step 1: Mix the flux with aluminum-silicon alloy powder in a specific ratio and apply the mixture to the surface of the coated aluminum alloy by adjusting the spraying process parameters to produce a coated aluminum alloy plate containing a pre-embedded flux coating layer. Step 2: Place the coated aluminum alloy sheet and strip containing the pre-embedded flux coating into an atmosphere-protected heating furnace, heat to 200~300℃ and hold for 1~2 hours to adjust the hardness of the coated aluminum alloy and diffuse the coating interface; after the heat treatment, grind to remove the surface oxide film on the side of the coated aluminum alloy containing the pre-embedded flux coating, and remove residual stains by chemical treatment. Step 3: After removing stains and impurities from the base aluminum alloy, place it in a melting furnace and heat it to melt. During the heating process, a protective atmosphere is introduced, and the uniformity of the structure is ensured by stirring. The treated coated aluminum alloy strip containing the pre-embedded flux coating is preheated to 60~80℃ under a protective atmosphere. Step 4: The preheated coated aluminum alloy containing the pre-embedded flux coating is simultaneously fed into the roll gap on both sides of the casting roll, and tension is applied to ensure the contact effect between the coated aluminum alloy and the casting roll; the molten base aluminum alloy is poured into the tundish and the front box after being controlled at the preset casting temperature, and enters the roll gap through the distribution device to form a molten pool, and is then cast and rolled together with the coated aluminum alloy strips on both sides to obtain a heat transfer aluminum plate with a microstructure of pre-embedded flux mixed layer under specific casting and rolling composite preparation process parameters; argon gas is continuously introduced during the casting and rolling process to prevent oxidation.

[0010] A further improvement of the technical solution of the present invention is that: in step 1, the spraying process includes thermal spraying, cold spraying and other methods; the flux is KAlF4 and other fluxes, and its powder particle size is 2-30μm; the aluminum-silicon alloy powder particle size is 30-50μm, and the silicon content is 10%~18%.

[0011] A further improvement of the technical solution of the present invention is that: in step 1, the specific ratio is the mass ratio, and the mass ratio of KAlF4 powder to Al-Si powder is controlled within the range of 1:1 to 1:9.

[0012] A further improvement to the technical solution of this invention lies in the following: In step 1, the spraying process includes a post-mixing spraying process and a mixing process during spraying. For applications requiring high strength, a mixing process during spraying is used, adjusting the Si content ratio in the Al-Si powder to 14%~18%, the KAlF4 powder particle size to 2-6μm, and employing a spraying temperature of 300~500℃. During casting and rolling, this forms well-connected, strongly supporting pores, creating a high-strength metallurgical bond between the Al-Si powder and the base aluminum alloy and cladding aluminum alloy. For applications requiring high toughness, a post-mixing spraying process is used, adjusting the Si content ratio in the Al-Si powder to 10%~14%, the KAlF4 powder particle size to 5-30μm, and employing a spraying temperature of 100~300℃. During casting and rolling, this forms a porous microstructure with a certain degree of plasticity.

[0013] A further improvement of the technical solution of the present invention is that: in step 1, the spraying process parameters are adjusted according to the mass ratio of KAlF4 powder to Al-Si powder and the coating thickness, the spraying pressure is 0.5~2.5MPa, the spraying distance is 100~250mm, the powder feeding speed is 30~250g / min, and the coating thickness is 0.05mm~2mm.

[0014] A further improvement of the technical solution of the present invention is that: in step 3, during the heating process of the base aluminum alloy and the cladding aluminum alloy plate containing the pre-embedded flux coating layer, an argon atmosphere is introduced for protection, with a purity of ≥99.99%, to ensure that the base is not oxidized during the heating process and to reduce impurities generated at the composite interface between the cladding and the base during casting and rolling.

[0015] A further improvement to the technical solution of this invention lies in: in step 4, the melting ratio η of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy is controlled by the casting-rolling composite preparation process parameters: η = K1·( T 浇铸 - T m )+K2·( T 预热 -T0)+K3·(S-S0)+K4·( δ / ν)+C, through synergistic adjustment of the aluminum-silicon element ratio S Coating thickness δ Casting temperature T 浇铸 Coating preheating temperature T 预热 and casting and rolling speed v This enables precise control of the shallow melting ratio η, where T0 is the ambient temperature. T m S0 represents the melting point of the aluminum-silicon alloy, and S0 represents the silicon content at the eutectic point. δ C represents the coating thickness and is a constant. Furthermore, the melting point, solidification point, and other physical properties of the pre-embedded flux-coated layer are customized to obtain a heat-transfer aluminum plate with a microstructure of the pre-embedded flux-coated layer. The casting and rolling process is affected by the thickness of the pre-embedded flux-coated layer, ensuring the preparation of a heat-transfer aluminum plate with a high-performance pre-embedded flux-coated layer microstructure.

[0016] The technological advancements achieved by this invention, due to the adoption of the above-mentioned technical solutions, are as follows: By preparing a pre-embedded flux fusion layer, the problem of difficult treatment of the oxide film on the coating surface during brazing is effectively solved, while simultaneously ensuring the brazing efficiency of the heat transfer aluminum plate. The production process is short, production costs are low, and it is conducive to large-scale production. By combining spraying and casting-rolling processes, a pre-embedded flux fusion layer is formed during high-temperature rolling. The spraying and casting-rolling processes avoid thermal decomposition of the flux, preserving its chemical activity. The unique porous microstructure of the pre-embedded flux fusion layer allows gas to escape smoothly along these channels under the driving force of rolling pressure, thereby obtaining a dense, defect-free metallurgical bonding interface, increasing the bonding strength of the bonding surface, and giving the heat transfer aluminum plate excellent brazing performance and mechanical properties. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the composite aluminum plate with a pre-embedded fusion layer microstructure according to the present invention; Figure 2 This is a schematic diagram of a pre-embedded flux-aluminum-silicon alloy mixed porous microstructure; Figure 3 This is a schematic diagram of the horizontal casting and rolling process of a composite aluminum plate with pre-embedded flux heat transfer. Figure 4 This is a schematic diagram of the vertical casting and rolling process of a composite aluminum plate with pre-embedded flux heat transfer. Figure 5 This is a schematic diagram of the production process of the casting and rolling preparation method of the composite aluminum plate with the microstructure of the pre-embedded fusion layer of the present invention.

[0018] Among them, 1. Unwinder, 2. Coated aluminum alloy including pre-embedded flux coating, 3. Smelting furnace, 4. Tundish, 5. Front box, 6. Nozzle, 7. Coiler, 8. Pinch roll, 9. Horizontal casting roll, 10. Double nozzle, 11. Vertical casting roll. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to embodiments: like Figure 1 The diagram shows a structural schematic of a composite aluminum plate with a pre-embedded flux-mixed layer microstructure according to the present invention. It is a layered metal composite structure, including a cladding aluminum alloy, a base aluminum alloy, and a pre-embedded flux-mixed layer. The cladding aluminum alloy and the base aluminum alloy are connected by the pre-embedded flux-mixed layer. The layered metal composite structure includes structural forms such as cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy, cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy-pre-embedded flux-mixed layer-cladding aluminum alloy, and cladding aluminum alloy-pre-embedded flux-mixed layer-base aluminum alloy-cladding aluminum alloy. The cladding aluminum alloy is a 4-series or 7-series aluminum alloy strip, with a thickness of 8% to 16% of the total thickness of the composite aluminum plate; the pre-embedded flux-mixed layer is a flux-aluminum-silicon alloy fused microstructure, with a thickness of 2% to 4% of the composite aluminum plate thickness; the base aluminum alloy is a 3-series aluminum alloy, with a thickness of 80% to 90% of the composite aluminum plate thickness. The pre-embedded flux-aluminum-silicon alloy fused microstructure is a dispersed structure in which the flux is uniformly embedded in the microporous structure of the aluminum-silicon alloy; such as Figure 2As shown, the micropores of the aluminum-silicon alloy are a novel aluminum-based porous microstructure formed by the secondary solidification of the melted pre-embedded flux mixture layer with the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy, resulting in a diffusely distributed flux distribution. The melting point, solidification point, and other physical properties of this novel aluminum-based porous microstructure can be customized by adjusting the aluminum-silicon element ratio in the aluminum-silicon alloy and the melting ratio of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy, thereby controlling the working characteristics of the pre-embedded flux during brazing.

[0020] like Figure 3 and Figure 4 The diagram illustrates the process of preparing composite aluminum plates using horizontal and vertical casting and rolling equipment. In horizontal casting and rolling, the molten pool is downwards due to gravity, and the rolls are horizontally arranged, suitable for high-speed production of thin plates. In vertical casting and rolling, gravity is perpendicular to the rolling force, enabling symmetrical feeding from both sides. The cladding strip is first released by the uncoiling machine 1, and after a spraying process, a flux mixture layer is sprayed onto the cladding surface through nozzles 6 or dual nozzles 10 to obtain a cladding aluminum alloy 2 containing a pre-embedded flux coating layer. It then enters the casting and rolling roll gap. The base aluminum alloy melts in the melting furnace 3 to form a molten liquid. This molten liquid flows sequentially through the tundish 4 for stable flow, and through the front box 5 for precise flow control, finally being injected into the casting and rolling roll gap via a distributor to form a molten pool. Under the rolling pressure of the casting and rolling rolls, the cladding strip and the core material achieve solid-liquid composite, forming a pre-embedded molten layer structure. The final composite aluminum plate is then wound up by the coiler 7 and pinch rolls 8. The steps are as follows: Figure 5 As shown, the details are as follows: Step 1: Release the coated tape roll using unwinder 1. KAlF4 powder and Al-Si powder are mixed in a specific ratio and bonded to the surface of the coated aluminum alloy plate by adjusting the spraying process parameters. The mass ratio of KAlF4 powder to Al-Si powder is controlled within the range of 1:1 to 1:9 to ensure a balance between flux activity and flowability. The particle size range of KAlF4 powder is 2-30 μm, and the Si content in the Al-Si powder is 10%-18%, with a particle size range of 30-50 μm. The spraying process includes both pre-mixing spraying and in-process mixing. For applications requiring high strength, a mixing process during spraying is used, adjusting the Si content in the Al-Si powder to 14%–18%, the KAlF4 powder particle size to 2–6 μm, and the spraying temperature to 300–500℃. For applications requiring high toughness, a post-mixing spraying process is used, adjusting the Si content in the Al-Si powder to 10%–14%, the KAlF4 powder particle size to 5–30 μm, and the spraying temperature to 100–300℃. The spraying process is adjusted according to the mass ratio of KAlF4 powder to Al-Si powder and the coating thickness, with a spraying pressure of 0.7–1.5 MPa, a spray distance of 30–100 mm, a powder feed rate of 30–250 g / min, and a coating thickness of 0.05 mm–2 mm.

[0021] Step 2: Place the coated aluminum alloy plate 2 containing the pre-embedded flux coating into a protective atmosphere heating furnace, heat to 200~300℃ and hold for 1~2 hours to eliminate internal stress in the coating; after heat preservation treatment, grind to remove the oxide film on the inner coating surface of the coated aluminum alloy plate and strip, and remove residual stains by chemical treatment.

[0022] Step 3: After removing stains and other impurities from the base aluminum alloy, place it in melting furnace 3 and heat it to melt. During the heating process, a protective atmosphere is introduced, and the uniformity of the structure is ensured by stirring. The treated coated aluminum alloy strip containing the pre-embedded flux coating is preheated to 60~80℃. Argon atmosphere is introduced for protection during the heating process of the base and the coating. The purity is ≥99.99% to ensure that the base is not oxidized during the heating process and to reduce impurities generated at the composite interface between the coating and the base during casting and rolling.

[0023] Step 4: The preheated coated aluminum alloy containing the pre-embedded flux coating is simultaneously fed into the roll gap of the casting rolls from both sides. Tension is applied to ensure effective contact between the coated aluminum alloy and the casting rolls. The coating tension is 10~20 N / mm² to prevent wrinkles. The molten base aluminum alloy is poured into the tundish 4 and the front box 5 after being controlled at the preset casting temperature. It enters the roll gap of the casting rolls through the distributor to form a molten pool. It is then combined with the coated aluminum alloy strips on both sides through casting and rolling to prepare a heat transfer aluminum plate with a microstructure of pre-embedded flux mixed layer by the coiler 7 and the pinch roll 8. Argon gas is continuously introduced during the casting and rolling process to prevent oxidation. The melting ratio η of the inner shallow layer of the coated aluminum alloy and the base aluminum alloy is controlled by the casting and rolling composite preparation process parameters: η=K1·( T 浇铸 - T m )+K2·( T 预热 -T0+K3·(S-S0)+K4·( δ / ν)+C, through synergistic adjustment of the aluminum-silicon element ratio S Coating thickness δ Casting temperature T 浇铸 Coating preheating temperature T 预热 and casting and rolling speed v This enables precise control of the shallow melting ratio η, where T0 is the ambient temperature. T m S0 represents the melting point of the aluminum-silicon alloy, and S0 represents the silicon content at the eutectic point. δ Where C represents the coating thickness, and C is a constant. Furthermore, the melting point, solidification point, and other physical properties of the pre-embedded flux-coated layer are customized and adjusted to obtain a heat-transfer aluminum plate with a microstructure of the pre-embedded flux-coated layer. Where H is the height of the K-value point. v For casting and rolling speed, T 浇铸 For casting temperature,T 预热 The preheating temperature is denoted by n, which is a constant. This ensures the fabrication of a heat-transfer aluminum plate with a well-developed microstructure for the embedded flux-coated layer.

[0024] The present invention will be further illustrated below through specific embodiments: Example 1 The heat transfer aluminum plate with a pre-embedded flux-mixed layer microstructure produced in this embodiment is suitable for applications requiring high toughness. It is applied using a single nozzle at a spraying temperature of 250℃. The Al-Si alloy powder has a Si content of 10%~12%; the ratio of KAlF4 powder to Al-Si powder is 10:90. The melting ratio η of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy is controlled by the casting-rolling composite preparation process parameters: η=K1·( T 浇铸 - T m )+K2·( T 预热 -T0)+K3·(S-S0)+K4·( δ / ν)+C, where K1=0.25, K2=0.40, K3=1.5, K4=-8000, C=15.0. A single-sided cladding of 4343 aluminum alloy is used, with a base of 3003 aluminum alloy. The preheating temperature is 100℃. The thickness of the 4343 aluminum alloy is 0.5mm, the exit thickness is 5mm, the heating and melting temperature is 700℃, the casting temperature is 660℃, and the casting and rolling speed is 1.2m / min.

[0025] S1: Powder mixing preparation: The raw material Al-Si alloy powder has a Si content of 10%~12%, and the mass percentages of each component of KAlF4 powder are: K: 27.52%, Al: 18.99%, F: 53.48%. The particle size of the aluminum-silicon alloy powder is 35-40μm, and the particle size of the KAlF4 powder is 25-30μm. The ratio of KAlF4 powder to Al-Si powder is 10:90, and the two powders are thoroughly mixed evenly.

[0026] S2: Milling: Take a 0.5mm thick clad 4343 aluminum alloy obtained by cold rolling and mill off the oxide on the clad surface using a milling machine.

[0027] S3: Heating: The cladding aluminum alloy is preheated at a temperature of 100°C, and a protective atmosphere is introduced during the preheating process; the base 3003 aluminum alloy is introduced into the melting furnace 3 and heated to obtain the base aluminum liquid after melting, at a temperature of 700°C, and a protective atmosphere is introduced during the heating process.

[0028] S4: Surface spraying: The mixed powder is sprayed onto the surface of the 4343 aluminum alloy coating through the nozzle 6 of the spraying machine. The powder spraying temperature is 250℃, the powder feeding pressure is 1.0MPa, the spraying distance is 100mm, and the powder feeding speed is 200g / min.

[0029] S5: Casting and rolling parameter adjustment: A horizontal twin-roll casting and rolling mill is adopted, the gap between the two casting and rolling rolls is adjusted to 5mm, the casting and rolling speed is 1.2m / min, and cooling water is introduced into the casting and rolling roll 9.

[0030] S6: Casting and rolling composite: The coated aluminum strip after surface spraying is fed into the roll gap from one side of the casting and rolling roll. The liquid matrix is ​​cooled to 660°C and then poured into the tundish 4 and the front box 5. It enters the roll gap of the casting and rolling roll through the distributor. A protective atmosphere is introduced during the casting and rolling process. The coiler 7 and the pinch roll 8 are used to coil the heat transfer aluminum plate with a thickness of 6mm and a microstructure with a pre-embedded flux fusion layer.

[0031] The performance of the composite aluminum plate obtained above was tested experimentally: Metallographic observation revealed a microporous composite structure at the composite interface. Measurements showed that the thickness of the 4343 aluminum alloy cladding after casting and rolling was 0.4 mm, the thickness of the fusion layer was 0.10 mm, the thickness of the intermediate matrix was 4.5 mm, the core flux coverage was 98%, and the porosity of the weld after brazing was <0.5%.

[0032] Subsequent mechanical property tests and brazing performance tests were conducted to compare the results. The brazing performance of the prepared heat transfer composite aluminum plate was higher than that of the traditional cast and rolled composite aluminum plate, and the mechanical properties met the performance requirements of the heat transfer composite aluminum plate.

[0033] Example 2 The heat transfer aluminum plate with a pre-embedded flux-coated microstructure produced in this embodiment is suitable for applications requiring high strength. KAlF4 powder and Al-Si powder are sprayed using a dual-nozzle system; the KAlF4 powder is sprayed at 400°C, and the Al-Si powder at 100°C. The Al-Si alloy powder has a Si content of 14%~16%. The melting ratio η of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy is controlled by the casting-rolling composite preparation process parameters: η = K1·( T 浇铸 - T m )+K2·( T 预热 -T0)+K3·(S-S0)+K4·( δ / ν)+C, where K1=0.25, K2=0.40, K3=1.5, K4=-8000, C=15.0. A double-sided cladding of 4343 aluminum alloy is used, with a 3003 aluminum alloy substrate in the middle. The preheating temperature is 150℃; the thickness of the 4343 aluminum alloy is 0.8mm, the exit thickness is 6mm, the heating and melting temperature is 700℃, the casting temperature is 660℃, and the casting and rolling speed is 1.2m / min.

[0034] S1: Powder preparation: The raw material Al-Si alloy powder has a Si content of 14%~16%, and the mass percentage of each component of KAlF4 powder is: K: 27.52%, Al: 18.99%, F: 53.48%. The particle size of aluminum-silicon alloy powder is 35-40μm, and the particle size of KAlF4 powder is 2-6μm.

[0035] S2: Milling: Take a 0.8mm thick clad 4343 aluminum alloy obtained by cold rolling and mill off the oxide on the clad surface using a milling machine.

[0036] S3: Heating: The cladding aluminum alloy is preheated at a temperature of 150°C, and a protective atmosphere is introduced during the preheating process; the base 3003 aluminum alloy is introduced into the melting furnace 3 and heated to obtain the base aluminum liquid after melting, at a temperature of 700°C, and a protective atmosphere is introduced during the heating process.

[0037] S4: Surface Coating: KAlF4 powder and AL-Si powder are respectively sprayed onto the surface of the 4343 aluminum alloy using a spraying machine with dual nozzles 11. The spraying temperature of KAlF4 powder is 400℃, the powder feeding pressure is 1.5MPa, the spraying distance is 100mm, and the powder feeding speed is 32g / min; the spraying temperature of AL-Si powder is 100℃, the powder feeding pressure is 0.8MPa, the spraying distance is 150mm, and the powder feeding speed is 168g / min.

[0038] S5: Casting and rolling parameter adjustment: A vertical twin-roll casting and rolling mill is adopted, the gap between the two casting and rolling rolls is adjusted to 6mm, the casting and rolling speed is 1.2m / min, and cooling water is introduced into the casting and rolling roll 10.

[0039] S6: Casting and rolling composite: The coated aluminum strip after surface spraying is simultaneously fed into the roll gap from both sides of the casting and rolling roll. After the liquid matrix is ​​cooled to 660°C, it is poured into the tundish 4 and the front box 5. It enters the center of the coated aluminum strip in the roll gap of the casting and rolling roll through the distributor. A protective atmosphere is introduced during the casting and rolling process. The coiler 7 and the pinch roll 8 are used to wind up the heat transfer aluminum plate with a thickness of 6mm and a microstructure with a pre-embedded flux fusion layer.

[0040] The performance of the composite aluminum plate obtained above was tested experimentally: Metallographic observation revealed a microporous composite structure at the composite interface. Measurements showed that the thickness of the 4343 aluminum alloy cladding after casting and rolling was 0.7 mm, the thickness of the fusion layer was 0.15 mm, the thickness of the intermediate matrix was 4.45 mm, the core flux coverage was 97%, and the porosity of the weld after brazing was <0.5%.

[0041] Subsequent mechanical property tests and brazing performance tests were conducted to compare the results. The brazing performance of the prepared heat transfer composite aluminum plate was higher than that of the traditional cast and rolled composite aluminum plate, and the mechanical properties met the performance requirements of the heat transfer composite aluminum plate.

[0042] This invention utilizes the melting point differences of its components to form a controllable pre-embedded flux fusion layer at the composite interface, pre-embedding the flux into the interface between the core material and the cladding. During subsequent brazing, the high temperature melts the flux, removing the oxide film on the base material surface and promoting wettability and diffusion bonding between the filler metal and the base material, forming a metallurgical interface. By adding this pre-embedded flux fusion layer, the liquid flux can rapidly and uniformly penetrate and transport through the microporous channels of the pre-embedded fusion layer using capillary force, ensuring sufficient and uniform coverage of the brazing surface. This avoids flux enrichment or area gaps caused by uneven spraying in traditional processes, thus achieving extremely high penetration and low porosity. Simultaneously, it effectively solves the problem of needing to add flux separately in traditional brazing, shortening the production process and avoiding secondary contamination from corrosive flux. Furthermore, the flux is pre-uniformly distributed in the interface layer, ensuring uniform contact between the filler metal and the base material during welding, reducing defects such as porosity and inclusions, and improving weld strength.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A composite aluminum plate with a pre-embedded fusion layer microstructure, characterized in that: The composite aluminum plate is a layered metal composite structure, including a cladding aluminum alloy, a base aluminum alloy, and a pre-embedded flux mixing layer; the cladding aluminum alloy and the base aluminum alloy are connected by the pre-embedded flux mixing layer; the layered metal composite structure includes various structural forms such as cladding aluminum alloy-pre-embedded flux mixing layer-base aluminum alloy, cladding aluminum alloy-pre-embedded flux mixing layer-base aluminum alloy-pre-embedded flux mixing layer-cladding aluminum alloy, and cladding aluminum alloy-pre-embedded flux mixing layer-base aluminum alloy-cladding aluminum alloy.

2. The composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 1, characterized in that: The cladding aluminum alloy is a 4-series aluminum alloy strip or a 7-series aluminum alloy strip, and its thickness is 8% to 16% of the total thickness of the composite aluminum plate; the pre-embedded flux fusion layer is a flux-aluminum-silicon alloy fusion microstructure, and its thickness is 2% to 4% of the thickness of the composite aluminum plate; the base aluminum alloy is a 3-series aluminum alloy, and its thickness is 80% to 90% of the thickness of the composite aluminum plate.

3. The composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 2, characterized in that: The pre-embedded flux-aluminum-silicon alloy mixed microstructure is a diffuse structure in which the flux is uniformly embedded in the microporous structure of the aluminum-silicon alloy; the aluminum-silicon alloy micropores are a novel aluminum-based porous microstructure in which the flux is diffusely distributed after the molten pre-embedded flux mixed layer melts and mixes with the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy and then solidifies for a second time.

4. A composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 3, characterized in that: the melting point and solidification point properties of the novel aluminum-based porous microstructure with flux dispersed in the brazing flux can be customized by adjusting the ratio of aluminum and silicon elements in the aluminum-silicon alloy and the melting ratio of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy, thereby controlling the working characteristics of the pre-embedded flux during brazing.

5. A casting and rolling method for preparing a composite aluminum plate with a pre-embedded fusion layer microstructure, used to prepare the composite aluminum plate according to any one of claims 1-4, characterized in that: The specific steps are as follows: Step 1: Mix the flux with aluminum-silicon alloy in a specific ratio and apply the mixture to the surface of the coated aluminum alloy by adjusting the spraying process parameters to produce a coated aluminum alloy plate containing a pre-embedded flux coating layer. Step 2: Place the coated aluminum alloy containing the pre-embedded flux coating into an atmosphere-protected heating furnace, heat it to 200~300℃ and hold it for 1~2 hours to adjust the hardness of the coated aluminum alloy and diffuse the coating interface. After heat preservation treatment, the surface oxide film on the side containing the pre-embedded flux coating layer of the coated aluminum alloy is removed by grinding, and residual stains are removed by chemical treatment. Step 3: After removing stains and impurities from the base aluminum alloy, place it in a melting furnace and heat it to melt. During the heating process, a protective atmosphere is introduced, and the uniformity of the structure is ensured by stirring. The treated coated aluminum alloy strip containing the pre-embedded flux coating is preheated to 60~80℃ under a protective atmosphere. Step 4: The preheated coated aluminum alloy containing the pre-embedded flux coating is simultaneously fed into the roll gap on both sides of the casting roll, and tension is applied to ensure the contact effect between the coated aluminum alloy and the casting roll; the molten base aluminum alloy is poured into the tundish and the front box after being controlled at the preset casting temperature, and enters the roll gap through the distribution device to form a molten pool, and is then cast and rolled together with the coated aluminum alloy strips on both sides to obtain a heat transfer aluminum plate with a microstructure of pre-embedded flux mixed layer under specific casting and rolling composite preparation process parameters; argon gas is continuously introduced during the casting and rolling process to prevent oxidation.

6. The casting and rolling preparation method of a composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 5, characterized in that: In step 1, the spraying process includes thermal spraying and cold spraying; the flux is KAlF4 flux with a powder particle size of 2-30μm; the aluminum-silicon alloy powder has a particle size of 30-50μm, and the silicon content is 10%-18%; the specific ratio is the mass ratio, and the mass ratio of KAlF4 powder to Al-Si powder is controlled within the range of 1:1 to 1:

9.

7. The casting and rolling preparation method of a composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 5, characterized in that: In step 1, the spraying process includes a post-mixing spraying process and a spraying-in-mixing process. In the spraying-in-mixing process, the Si content in the Al-Si powder is adjusted to 14%~18%, the KAlF4 powder particle size is 2-6μm, and a spraying temperature of 300~500℃ is used. In the post-mixing spraying process, the Si content in the Al-Si powder is adjusted to 10%~14%, the KAlF4 powder particle size is 5-30μm, and a spraying temperature of 100~300℃ is used.

8. The casting and rolling preparation method of a composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 5, characterized in that: In step 1, the spraying process parameters are adjusted according to the mass ratio of KAlF4 powder to Al-Si powder and the coating thickness. The spraying pressure is 0.5~2.5MPa, the spraying distance is 100~250mm, the powder feeding speed is 30~250g / min, and the coating thickness is 0.05mm~2mm.

9. The casting and rolling preparation method of a composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 5, characterized in that: In step 3, an argon atmosphere with a purity of ≥99.99% is introduced during the heating process of the base aluminum alloy and the cladding aluminum alloy plate containing the pre-embedded flux coating to ensure that the base is not oxidized during the heating process and to reduce impurities generated at the composite interface between the cladding and the base during casting and rolling.

10. The casting and rolling preparation method of a composite aluminum plate with a pre-embedded fusion layer microstructure according to claim 5, characterized in that: In step 4, the casting-rolling composite preparation process parameters control the melting ratio η of the inner shallow layer of the cladding aluminum alloy and the base aluminum alloy: η = K1·( T 浇铸 - T m )+K2·( T 预热 -T0)+K3·(S-S0)+K4·( δ / ν)+C, through synergistic adjustment of the aluminum-silicon element ratio S Coating thickness δ Casting temperature T 浇铸 Coating preheating temperature T 预热 and casting and rolling speed v This enables precise control of the shallow melting ratio η, where T0 is the ambient temperature. T m S0 represents the melting point of the aluminum-silicon alloy, and S0 represents the silicon content at the eutectic point. δ C represents the coating thickness, and C is a constant term. Furthermore, the melting point, solidification point, and other physical properties of the pre-embedded flux-coated layer are customized to obtain a heat transfer aluminum plate with a microstructure of the pre-embedded flux-coated layer.

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