Aluminum alloy composite brazing sheet and method of making

Abstract

This invention provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate includes a core layer and a brazing layer. The core layer is made of an aluminum-manganese alloy, with a manganese content of 0.5–1.5 wt%. In the alloy microstructure of the core layer, the R-Cube texture area accounts for 10–20%, and the P-texture area accounts for 10–20%. The core layer is in the O state. The brazing layer is made of an aluminum-silicon alloy. The method of this invention regulates the microstructure of the material through homogenization heat treatment, cold rolling, and two-stage annealing during the preparation of the composite brazing plate. This controls the area ratio of R-Cube and P-textures within the material microstructure, resulting in a lower recrystallization activation energy for the composite plate material, improving its corrosion resistance, ensuring its strength while avoiding excessive reduction in elongation, thus giving it good formability.

Description

Technical Field

[0001] This invention belongs to the field of metal composite materials technology, and relates to an aluminum alloy composite brazing plate and its preparation method. Background Technology

[0002] Currently used heat sink components, such as evaporator plates, intercooler plates, and oil cooler plates, typically require the plates themselves to have good formability to meet the necessary bending, stamping, and other forming requirements. The cooling core of an oil cooler has a stacked structure, consisting of multiple layers of chips and fins brazed together. During the forming process, the chips require stamping deformation, resulting in localized deformation. In the subsequent brazing process of assembling the oil cooler, the stamped deformation sites on the chips are prone to erosion, leading to a reduction in the oil cooler's lifespan. Therefore, the chip raw materials must possess good erosion resistance.

[0003] Erosion occurs during brazing when molten outer layer diffuses along the grain boundaries of the core material. For fully softened annealed sheet metal, a certain amount of deformation occurs during subsequent forming processes such as stamping. This processing deformation leads to dislocation. When the deformation amount of subsequent processing is within the critical deformation range for alloy recrystallization, the deformation energy stored within the material is low and insufficient to trigger the recrystallization process during brazing. As a result, the deformed portion does not easily recrystallize before the brazing filler metal melts. The molten brazing filler metal penetrates into the core material along the deformed location, altering the composition and microstructure of the core material, leading to brazing erosion. This severely reduces the material's corrosion resistance. Therefore, such sheet metal not only needs good formability but also good erosion resistance.

[0004] The existing approach to improving the corrosion resistance of materials involves using incomplete homogenization or applying a certain amount of processing after annealing. This results in more dispersed grain boundaries and a more complex diffusion path along the thickness direction after welding, thereby improving corrosion resistance. For example, CN 102554585A discloses an aluminum alloy brazing sheet and its manufacturing method. This method includes: casting an aluminum alloy ingot, homogenizing and cooling it, and then milling the surface. Then, a single-sided or double-sided aluminum-silicon brazing filler layer is applied to form a composite material. After heating, it is hot-rolled and then cold-rolled to obtain a cold-rolled material. The cold-rolled material is then fully annealed and softened before pre-stretching to obtain the aluminum alloy brazing sheet. This patent obtains the final sheet by pre-deforming the softened and annealed material. The deformation during the stamping process is superimposed to increase the deformation energy storage, allowing it to recrystallize during brazing to form coarse grains and improve corrosion resistance. However, pre-deformation will cause the material to enter a work-hardened state, which will limit the subsequent stamping processing performance.

[0005] CN 113198837A discloses a method for preparing an oil cooler chip material. The method includes: preparing a core material, a first sheath material, and a second sheath material; stacking the core material between the first and second sheath materials for composite processing; rolling the resulting aluminum alloy composite ingot to obtain an O-state foil; determining its critical deformation amount; subjecting the O-state foil to pre-deformation exceeding the critical deformation amount by 0.5–5%; and subsequently performing low-temperature stress-relief annealing. This method involves pre-deformation of the material exceeding the critical value, resulting in a large pre-deformation amount that alters the material's state to a non-O state, affecting its elongation and forming performance. Furthermore, the process path is complex, leading to high production costs.

[0006] In summary, the selection of the composition and processing technology of aluminum alloy composite plates also requires adjustment based on their composition and preparation process to ensure that they have a low recrystallization activation energy, can still recrystallize during the brazing heating process after stamping deformation, have good corrosion resistance, good formability, and high elongation. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention aims to provide an aluminum alloy composite brazing plate and its preparation method. The method regulates the microstructure of the material through homogenization heat treatment, cold rolling, and two-stage annealing during the preparation of the composite brazing plate. By controlling the area ratio of R-Cube texture and P texture within the material microstructure, the composite plate material has a lower recrystallization activation energy, improving its corrosion resistance. While ensuring its strength, it avoids excessive reduction in elongation, thus giving it better formability.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] On one hand, the present invention provides an aluminum alloy composite brazing plate, the composite brazing plate comprising a core layer and a brazing layer, wherein the core layer is made of an aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 0.5 to 1.5 wt%, for example 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, or 1.5 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable;

[0010] In the alloy microstructure of the core layer, the R-Cube texture area accounts for 10-20%, such as 10%, 12%, 14%, 15%, 16%, 18%, or 20%, and the P texture area accounts for 10-20%, such as 10%, 12%, 14%, 15%, 16%, 18%, or 20%, etc.; but it is not limited to the listed values, and other unlisted values ​​within their respective ranges are also applicable; the core layer is in the O state; the brazing layer is made of aluminum-silicon alloy.

[0011] In this invention, the structure of the aluminum alloy composite brazing plate is controlled by adjusting the material of its core layer, especially the microstructure of the alloy. The area ratio of R-Cube texture and P texture is controlled. R-Cube texture contributes to the formation of subgrains by accommodating dislocations generated during the stamping deformation of the O-state material. R-Cube oriented subgrains have a low recrystallization activation energy and are prone to recrystallization during brazing heating, forming recrystallized grains. If the R-Cube texture content is too high, it will lead to a decrease in the strength of the material. P texture contributes to the strength of the material. Using P texture can achieve texture strengthening and improve the strength of the material in the annealed state and after brazing. However, if the P texture content is too high, it will lead to a serious decrease in the elongation of the material. In this invention, the R-Cube texture and P texture in the core layer alloy form an antagonistic relationship during the development of the microstructure. By controlling the ratio range of the two, the O-state material can still recrystallize during the brazing heating process after stamping deformation, resulting in good anti-melting properties and high strength and elongation.

[0012] The O state of the core material is a fully annealed state, which allows the material to obtain the lowest strength and the highest elongation under the same alloy composition. When used as the core plate of an oil cooler, it can undergo plastic deformation such as stamping, punching, and flanging without cracking.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0014] As a preferred embodiment of the present invention, the aluminum-manganese alloy of the core layer further includes silicon and iron in its elemental composition.

[0015] Preferably, the silicon content in the aluminum-manganese alloy is ≤0.2wt%, for example 0.2wt%, 0.18wt%, 0.16wt%, 0.15wt%, 0.12wt%, 0.1wt%, or 0.08wt%, and the iron content is 0.1-0.5wt%, for example 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, or 0.5wt%, etc.; but it is not limited to the listed values, and other unlisted values ​​within their respective ranges are also applicable.

[0016] Preferably, the elemental composition of the aluminum-manganese alloy of the core layer also includes copper, and the copper content is 0.1 to 0.5 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In this invention, iron in the core alloy can improve the casting performance of the alloy, but too high iron content will lead to a decrease in the elongation of the alloy. At the same time, the silicon content should also be as low as possible, as excessive silicon can form a brittle second phase with iron, affecting the elongation and life of the alloy. Copper can improve the strength of the alloy and increase the corrosion potential of the alloy, but too high copper content will lead to a decrease in the alloy's resistance to intergranular corrosion.

[0018] As a preferred technical solution of the present invention, in the alloy structure of the core layer, the length of the ∑7 grain boundary accounts for 1.5% to 5%, such as 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In this invention, the ∑7 grain boundaries in the aluminum alloy include 35–45°. <111> Σ7 grain boundaries belong to low-Σ CSL grain boundaries, and their grain boundary energy is lower than that of ordinary grain boundaries, resulting in a lower slip rate during creep. Σ7 grain boundaries can also improve the corrosion resistance of materials from another perspective. In this invention, controlling the length ratio of Σ7 grain boundaries to 1.5-5% is effective in improving the corrosion resistance of materials. It is speculated that Σ7 grain boundaries have low wettability to the alloy liquid film of the brazing layer during the brazing process, which can effectively prevent the core material from being eroded, thereby improving the corrosion resistance of the material. In contrast, the annealing process used in the alloys of the prior art generally produces mostly Σ3 grain boundaries, with few or almost no Σ7 grain boundaries.

[0020] In this invention, the aluminum-silicon alloy of the brazing layer can be selected from conventional 4-series aluminum alloys such as AA4004, AA4043, AA4045, AA4047, and AA4343. These alloys are typically characterized by low liquidus temperatures and are commonly used as the solder layer for the core material. For example, the liquidus temperature of the aluminum-silicon alloy can be controlled to be 40–80°C lower than the solidus temperature of the aluminum-manganese alloy in the core layer, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.

[0021] The thickness of the composite brazing plate is designed according to specific application requirements and can be selected from 0.4 to 0.8 mm, such as 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm or 0.8 mm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] For example, the thickness of the core layer in the composite brazing board is 70% to 90%, such as 70%, 75%, 80%, 85%, or 90%, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The thickness of the brazing layer is 10% to 20%, such as 10%, 12%, 14%, 16%, 18%, or 20%, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] For example, the composite brazing plate further includes a water-contact layer located on the side of the core layer away from the brazing layer.

[0024] For example, the thickness of the water-contact layer is 0% to 10% of the thickness of the composite brazing plate, such as 0, 2%, 4%, 5%, 6%, 8% or 10%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In this invention, the alloy of the water-contact layer can be selected from 7-series aluminum alloys, such as AA7072 alloy, AA7772 alloy, etc., wherein the zinc content is relatively high, and can be selected from 0.5 to 5 wt%, for example 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, or 5.0 wt%.

[0026] Secondly, the present invention provides a method for preparing the above-mentioned composite brazing plate, the method comprising the following steps:

[0027] (1) According to the composition ratio, the raw materials of each structural layer of the composite brazing plate are melted and cast to obtain alloy ingots of the core layer and the brazing layer respectively.

[0028] (2) The core alloy ingot is subjected to homogenization heat treatment, and then each structural layer is milled.

[0029] (3) After processing in step (2), the structural layers are stacked in sequence and then hot rolled to obtain a primary composite plate;

[0030] (4) The primary composite plate obtained in step (3) is cold rolled to control the cold deformation rate to 82-92%, such as 82%, 84%, 86%, 88%, 90% or 92%, to obtain the secondary composite plate;

[0031] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing, and finally an aluminum alloy composite brazing plate is obtained.

[0032] In this invention, the P-texture and the deformed texture Copper have a 40° angle. <111> Regarding orientation relationships, the R-Cube texture and Brass texture also have a 40° < 111 > orientation relationship. The 40° < 111 > grain boundary has a high mobility. Therefore, during the annealing process, the Brass texture in the first-order low-temperature segment will transform into the R-Cube texture, and the Copper texture in the second-order high-temperature segment will transform into the P texture.

[0033] In this invention, the final proportion of the P-texture in the core layer is related to the control of the dissolved manganese content in the matrix after homogenization heat treatment, the cold deformation rate, and the coordination of the annealing process. Firstly, the P-texture is formed during high-temperature annealing, originating from both the transformation of the Copper texture into the P-texture during high-temperature annealing and the newly generated P-texture at this stage. Traditional processing methods tend to produce a large amount of P-texture, hindering the development of other textures and resulting in insufficient R-Cube texture area. This invention uses a two-stage annealing process to control the preferential generation of R-Cube texture before P-texture, meaning the P-texture is formed in the second-stage annealing. Secondly, it is necessary to control the dissolved manganese content in the early homogenization heat treatment to avoid excessive formation, otherwise it will promote the excessive generation of P-texture in the second-stage annealing. Finally, it is necessary to control the cold deformation rate to avoid excessively high rates, otherwise excessive Copper texture will be generated during the cold rolling stage, and the Copper texture will transform into P texture in the second stage of annealing, leading to an excessive P-texture area.

[0034] Meanwhile, the control of the above process should also avoid excessive suppression of the formation of P texture, which would result in insufficient P texture area. By controlling the cold deformation rate, it is helpful to obtain a certain amount of Copper texture and Brass texture during the cold deformation process. The Copper texture will be transformed into P texture in the second annealing stage, and the Brass texture will be transformed into R-Cube texture in the first annealing stage.

[0035] When using a conventional single-stage high-temperature annealing process, the P-texture preferentially and rapidly nucleates and grows, thus inhibiting the formation of the R-Cube texture to some extent. This invention proposes a two-stage annealing process. The first stage is a low-temperature annealing stage suitable for the formation of the R-Cube texture. In this stage, on the one hand, it is conducive to the nucleation and growth of the R-Cube texture, and on the other hand, the Brass texture formed during cold rolling will transform into the R-Cube texture.

[0036] As a preferred technical solution of the present invention, the structural layer of the composite brazing plate in step (1) further includes a water-contact layer.

[0037] Preferably, the raw materials described in step (1) are melted and stirred to ensure uniform mixing before casting.

[0038] Preferably, the homogenization heat treatment temperature in step (2) is 500 to 590°C, such as 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C or 590°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the homogenization heat treatment time in step (2) is 6 to 12 hours, such as 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] In this invention, the homogenization heat treatment time should be matched with the homogenization temperature so that the content of dissolved manganese in the core matrix after the homogenization heat treatment in step (2) is 0.2 to 0.5 wt%, for example, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, or 0.5 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In this invention, during the homogenization heat treatment process, supersaturated Mn elements precipitate from the aluminum matrix, forming a dispersed phase. The content of Mn still dissolved in the matrix is ​​called the dissolved Mn content. The homogenization heat treatment process determines the level of dissolved Mn content, which has a significant impact on the evolution of the P-texture in the Al-Mn alloy system during annealing. If the homogenization heat treatment temperature is too low, the dissolved Mn content is high, resulting in an excessively large P-texture area and a larger average grain size, leading to a decrease in elongation. If the homogenization heat treatment temperature is too high, the dissolved Mn content is low, resulting in an excessively small P-texture area after annealing, affecting the material strength.

[0042] Preferably, in step (2), each structural layer is first sawed and then milled.

[0043] As a preferred technical solution of the present invention, each structural layer in step (3) is hot-rolled separately before hot rolling, and the thickness ratio of each structural layer after hot rolling is consistent with the thickness ratio of each structural layer in the final composite brazed plate.

[0044] Preferably, when the structural layer in step (3) includes a water-contact layer, the stacking order is that the core layer is in the middle, and the two sides are the brazing layer and the water-contact layer, respectively.

[0045] The selection of the hot rolling temperature in step (3) shall be based on meeting the hot rolling requirements; for example, 460 to 500°C can be selected, such as 460°C, 465°C, 470°C, 475°C, 480°C, 485°C, 490°C, 495°C or 500°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the target thickness of hot rolling in step (3) is based on obtaining the desired cold deformation rate and cold rolled finished product thickness. For example, 4 to 6 mm can be selected, such as 4 mm, 4.5 mm, 5 mm, 5.5 mm or 6 mm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] As a preferred technical solution of the present invention, the target thickness of cold rolling in step (4) is 0.4 to 0.8 mm, such as 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm or 0.8 mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] In this invention, the microstructure of the alloy after annealing is adjusted by controlling the cold deformation rate. If the cold deformation rate is too low, the content of the deformation textures Copper and Brass textures formed in the microstructure during the cold deformation process is low, which affects the content of P texture and R-Cube texture after annealing. If the cold deformation rate is too high, too many Copper textures are formed in the microstructure, resulting in too many P textures in the high-temperature annealing stage.

[0049] As a preferred technical solution of the present invention, the temperature of the first-stage annealing in step (5) is 200-260°C, such as 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or 260°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The time of the first-stage annealing is 3-6h, such as 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the temperature of the second-stage annealing in step (5) is 350 to 400°C, such as 350°C, 360°C, 380°C, 380°C, 390°C, or 400°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The time of the second-stage annealing is 1 to 4 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] In this invention, since the transformation of different textures within the microstructure often occurs at different temperature stages during annealing, a lower-temperature first-stage annealing process is first used to promote the formation of R-Cube texture, followed by a higher-temperature second-stage annealing to promote the formation of P texture and other textures. Simultaneously, under the low-temperature + high-temperature annealing method, adjusting the specific holding time can increase the length ratio of ∑7 grain boundaries; during the holding stage at the low temperature, the length ratio of ∑7 grain boundaries increases with the extension of the first-stage holding time, and then reaches a constant value. If the holding time is too short, the proportion of ∑7 grain boundary length will be insufficient; if the first-stage holding time is too long, the proportion of R-Cube texture area will be too large. Therefore, the holding time for the low-temperature annealing stage is selected as 3 to 6 hours. However, if the holding time for the second-stage high-temperature stage is too long, it will still lead to an excessively high proportion of P texture area, which will affect the elongation of the material. The elongation shows a trend of first increasing, then stabilizing and finally decreasing as the second-stage holding time increases. The preferred second-stage holding time is 1 to 4 hours. If the second-stage holding time is too short, the proportion of P texture area will be insufficient, which will affect the strength of the material.

[0052] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0053] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer, brazing layer and water contact layer respectively.

[0054] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 500-590°C for 6-12 hours. After homogenization heat treatment, the content of dissolved manganese in the core matrix is ​​0.2-0.5 wt%. Then, each structural layer is sawed and milled in sequence.

[0055] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 460-500℃ and the target thickness of the hot rolling is 4-6mm to obtain a primary composite plate.

[0056] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled to be 82-92%, and the target thickness of the cold rolling is 0.4-0.8 mm, to obtain the secondary composite plate;

[0057] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 200-260℃ and the time is 3-6h. The temperature of the second-stage annealing is 350-400℃ and the time is 1-4h. Finally, an aluminum alloy composite brazing plate is obtained.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] (1) The method of the present invention regulates the microstructure of the material through homogenization heat treatment, cold rolling and two-stage annealing during the preparation of composite brazing plates, controls the area ratio of R-Cube texture and P texture in the microstructure of the material, so that the composite plate material has a lower recrystallization activation energy, improves its resistance to melting, and avoids excessive reduction of elongation while ensuring its strength, so that it has better forming performance.

[0060] (2) The tensile strength of the composite brazing plate material of the present invention is ≥100MPa, and the elongation is A 50 ≥30%, core layer erosion ratio ≤4%;

[0061] (3) The method described in this invention is simple to operate, has low raw material and process costs, and is widely applicable. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the structure of the aluminum alloy composite brazing plate provided in Embodiment 1 of the present invention;

[0063] Figure 2 This is a schematic diagram of the structure of the aluminum alloy composite brazing plate provided in Embodiment 4 of the present invention;

[0064] Among them, 1-core layer, 2-brazing layer, 3-water contact layer. Detailed Implementation

[0065] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0066] The present invention provides an aluminum alloy composite brazing plate and its preparation method in the specific embodiments section. The composite brazing plate includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 0.5-1.5 wt%. In the alloy microstructure of the core layer 1, the R-Cube texture area accounts for 10-20% and the P texture area accounts for 10-20%. The state of the core layer 1 is O state. The brazing layer 2 is made of aluminum-silicon alloy.

[0067] The preparation method includes the following steps:

[0068] (1) According to the composition ratio, the raw materials of each structural layer of the composite brazing plate are melted and cast to obtain alloy ingots of core layer 1 and brazing layer 2 respectively.

[0069] (2) The core layer 1 alloy ingot is subjected to homogenization heat treatment, and then each structural layer is milled.

[0070] (3) After processing in step (2), the structural layers are stacked in sequence and then hot rolled to obtain a primary composite plate;

[0071] (4) The primary composite plate obtained in step (3) is cold rolled to control the cold deformation rate to 82-92% to obtain the secondary composite plate;

[0072] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing, and finally an aluminum alloy composite brazing plate is obtained.

[0073] The following are typical but non-limiting embodiments of the present invention:

[0074] Example 1:

[0075] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. A schematic diagram of the composite brazing plate is shown below. Figure 1 As shown, it includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 1.5 wt%. The state of the core layer 1 is O state.

[0076] The elemental composition of the aluminum-manganese alloy of the core layer 1 also includes silicon, iron and copper;

[0077] The aluminum-manganese alloy contains 0.2 wt% silicon, 0.2 wt% iron, and 0.4 wt% copper.

[0078] The brazing layer 2 is made of aluminum-silicon alloy, specifically AA4045 alloy, wherein the silicon content is 10.0 wt%, the iron content is 0.3 wt%, the copper content is 0.25 wt%, the manganese content is 0.05 wt%, the magnesium content is 0.05 wt%, and the zinc content is 0.1 wt%.

[0079] The thickness of the composite brazing plate is 0.6 mm; the core layer 1 accounts for 90% of the thickness of the composite brazing plate, and the brazing layer 2 accounts for 10% of the thickness.

[0080] The preparation method includes the following steps:

[0081] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer 1 and brazing layer 2 respectively.

[0082] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 500°C for 6 hours, and then each structural layer is sawed and milled in sequence.

[0083] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 480℃ and the target thickness of the hot rolling is 5mm to obtain a primary composite plate.

[0084] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled at 88% and the target thickness of cold rolling is 0.6 mm to obtain the secondary composite plate.

[0085] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 200℃ and the time is 3h, and the temperature of the second-stage annealing is 350℃ and the time is 1h, and finally an aluminum alloy composite brazing plate is obtained.

[0086] Example 2:

[0087] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 1.2 wt%. The state of the core layer 1 is O state. The elemental composition of the aluminum-manganese alloy of the core layer 1 also includes silicon, iron and copper.

[0088] The aluminum-manganese alloy contains 0.2 wt% silicon, 0.5 wt% iron, and 0.2 wt% copper.

[0089] The brazing layer 2 is made of aluminum-silicon alloy, specifically AA4343 alloy, wherein the silicon content is 7.5wt%, the iron content is 0.4wt%, the copper content is 0.2wt%, the manganese content is 0.1wt%, the magnesium content is 0.05wt%, and the zinc content is 0.08wt%.

[0090] The thickness of the composite brazing plate is 0.4 mm; the core layer 1 accounts for 85% of the thickness of the composite brazing plate, and the brazing layer 2 accounts for 15%.

[0091] The preparation method includes the following steps:

[0092] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer 1 and brazing layer 2 respectively.

[0093] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 520°C for 10 hours, and then each structural layer is sawed and milled in sequence.

[0094] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 500℃ and the target thickness of the hot rolling is 4mm to obtain a primary composite plate.

[0095] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled at 90% and the target thickness of cold rolling is 0.4 mm to obtain the secondary composite plate.

[0096] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 220°C and the time is 3h. The temperature of the second-stage annealing is 360°C and the time is 2h. Finally, an aluminum alloy composite brazing plate is obtained.

[0097] Example 3:

[0098] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 1 wt%. The core layer 1 is in the O state.

[0099] The elemental composition of the aluminum-manganese alloy of the core layer 1 also includes silicon, iron and copper;

[0100] The aluminum-manganese alloy contains 0.1 wt% silicon, 0.4 wt% iron, and 0.1 wt% copper.

[0101] The brazing layer 2 is made of aluminum-silicon alloy, specifically AA4004 alloy, wherein the silicon content is 9.5wt%, the iron content is 0.5wt%, the copper content is 0.25wt%, the manganese content is 0.08wt%, the magnesium content is 1.5wt%, and the zinc content is 0.2wt%.

[0102] The thickness of the composite brazing plate is 0.5 mm; the core layer 1 accounts for 80% of the thickness of the composite brazing plate, and the brazing layer 2 accounts for 20%.

[0103] The preparation method includes the following steps:

[0104] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer 1 and brazing layer 2 respectively.

[0105] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 560°C for 8 hours, and then each structural layer is sawed and milled in sequence.

[0106] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 460℃ and the target thickness of the hot rolling is 6mm to obtain a primary composite plate.

[0107] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled at 92% and the target thickness of cold rolling is 0.5 mm to obtain the secondary composite plate.

[0108] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 240°C and the time is 4 hours. The temperature of the second-stage annealing is 380°C and the time is 3 hours. Finally, an aluminum alloy composite brazing plate is obtained.

[0109] Example 4:

[0110] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. A schematic diagram of the composite brazing plate is shown below. Figure 2 As shown, the composite brazing plate includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 0.5 wt%. The core layer 1 is in the O state.

[0111] The elemental composition of the aluminum-manganese alloy of the core layer 1 also includes silicon, iron and copper;

[0112] The aluminum-manganese alloy contains 0.1 wt% silicon, 0.3 wt% iron, and 0.5 wt% copper.

[0113] The brazing layer 2 is made of aluminum-silicon alloy, specifically AA4047 alloy, wherein the silicon content is 12.0 wt%, the iron content is 0.25 wt%, the copper content is 0.3 wt%, the manganese content is 0.05 wt%, the magnesium content is 0.05 wt%, and the zinc content is 0.1 wt%.

[0114] The composite brazing plate also includes a water-contact layer 3, which is located on the side of the core layer 1 away from the brazing layer 2.

[0115] The water-contact layer 3 is made of AA7072 alloy, which contains 1.2 wt% zinc, 0.4 wt% silicon, 0.3 wt% iron, 0.1 wt% copper, 0.1 wt% manganese, and 0.1 wt% magnesium.

[0116] The thickness of the composite brazing plate is 0.8 mm; the core layer 1 accounts for 70% of the thickness of the composite brazing plate, the brazing layer 2 accounts for 20% of the thickness, and the water-contact layer 3 accounts for 10% of the thickness.

[0117] The preparation method includes the following steps:

[0118] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer 1, brazing layer 2 and water contact layer 3 respectively.

[0119] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 590°C for 12 hours, and then each structural layer is sawed and milled in sequence.

[0120] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 490℃ and the target thickness of the hot rolling is 4.5mm to obtain a primary composite plate.

[0121] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled at 82% and the target thickness of cold rolling is 0.8 mm to obtain the secondary composite plate.

[0122] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 260°C and the time is 6 hours. The temperature of the second-stage annealing is 400°C and the time is 4 hours. Finally, an aluminum alloy composite brazing plate is obtained.

[0123] Example 5:

[0124] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate includes a core layer 1 and a brazing layer 2. The core layer 1 is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 0.8 wt%. The core layer 1 is in the O state.

[0125] The elemental composition of the aluminum-manganese alloy of the core layer 1 also includes silicon, iron and copper;

[0126] The aluminum-manganese alloy contains 0.1 wt% silicon, 0.3 wt% iron, and 0.3 wt% copper.

[0127] The brazing layer 2 is made of aluminum-silicon alloy, which is a non-standard 4-series aluminum alloy with a Si content of 10.0 wt%, an Fe content of 0.4 wt%, a Cu content of 0.3 wt%, a Mn content of 0.05 wt%, a Mg content of 0.05 wt%, and a Zn content of 2.5 wt%.

[0128] The composite brazing plate also includes a water-contact layer 3, which is located on the side of the core layer 1 away from the brazing layer 2.

[0129] The water-contact layer 3 is made of AA7772 alloy, which contains 4.8 wt% zinc, 0.8 wt% silicon, 1.0 wt% iron, 0.05 wt% copper, 0.05 wt% manganese, and 0.05 wt% magnesium.

[0130] The thickness of the composite brazing plate is 0.5 mm; the core layer 1 accounts for 80% of the thickness of the composite brazing plate, the brazing layer 2 accounts for 15% of the thickness, and the water-contact layer 3 accounts for 5% of the thickness.

[0131] The preparation method includes the following steps:

[0132] (1) According to the composition ratio, the raw materials are melted and stirred, and then cast to obtain alloy ingots of core layer 1, brazing layer 2 and water contact layer 3 respectively.

[0133] (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 580°C for 12 hours, and then each structural layer is sawed and milled in sequence.

[0134] (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 480℃ and the target thickness of the hot rolling is 4mm to obtain a primary composite plate.

[0135] (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled at 88%, and the target thickness of the cold rolling is 0.5 mm to obtain the secondary composite plate.

[0136] (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 220°C and the time is 6 hours. The temperature of the second-stage annealing is 350°C and the time is 2 hours. Finally, an aluminum alloy composite brazing plate is obtained.

[0137] Example 6:

[0138] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate is the same as the composite brazing plate in Embodiment 1, except that the silicon content in the aluminum-manganese alloy of the core layer 1 is 0.3 wt%.

[0139] Example 7:

[0140] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Embodiment 1, except that the first-stage annealing time in step (5) is 2 hours.

[0141] Example 8:

[0142] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Embodiment 1, except that the second-stage annealing time in step (5) is 6 hours.

[0143] Example 9:

[0144] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate is the same as the composite brazing plate in Embodiment 2, except that the iron content in the aluminum-manganese alloy of the core layer 1 is 0.6 wt%.

[0145] Example 10:

[0146] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate is the same as the composite brazing plate in Embodiment 3, except that the aluminum-manganese alloy of the core layer 1 does not contain copper.

[0147] Example 11:

[0148] This embodiment provides an aluminum alloy composite brazing plate and its preparation method. The composite brazing plate is the same as the composite brazing plate in Embodiment 4, except that the copper content in the aluminum-manganese alloy of the core layer 1 is 0.6 wt%.

[0149] Comparative Example 1:

[0150] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 1, except that the homogenization heat treatment temperature in step (2) is 400℃.

[0151] Comparative Example 2:

[0152] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 4, except that the homogenization heat treatment temperature in step (2) is 600℃.

[0153] Comparative Example 3:

[0154] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 1, except that the cold deformation rate is controlled at 70% in step (4).

[0155] Comparative Example 4:

[0156] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 1, except that the cold deformation rate is controlled at 96% in step (4).

[0157] Comparative Example 5:

[0158] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 1, except that the first-stage annealing is not disclosed in step (5), and the second-stage annealing is performed directly.

[0159] Comparative Example 6:

[0160] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 4, except that the first-stage annealing time in step (5) is 7 hours.

[0161] Comparative Example 7:

[0162] This comparative example provides an aluminum alloy composite brazing plate and its preparation method. The preparation method is the same as that in Example 1, except that the second-stage annealing time in step (5) is 0.8h.

[0163] The aluminum alloy composite brazed plates obtained in Examples 1-11 and Comparative Examples 1-7 were subjected to performance tests, including: determination of Mn content dissolved in the matrix; statistics of R-Cube texture area ratio, P texture area ratio, and ∑7 grain boundary ratio; evaluation of simulated brazing and post-weld recrystallization and erosion; and testing of tensile strength and elongation.

[0164] Its testing methods include:

[0165] 1. Determination of Mn content dissolved in the matrix:

[0166] The conductivity of the core matrix after homogenization heat treatment was tested using a Fischer-SIGMASCOPE conductivity meter. The dissolved Mn content (Mnss) was calculated using the following formula:

[0167] 1 / σ=0.0267+0.032Fess%+0.033Mnss%+0.0068Siss%+0.0032Cuss%.

[0168] 2. Statistics on the proportion of R-Cube texture area, P texture area, and ∑7 grain boundary length:

[0169] Five annealed samples with a thickness of 20 mm × 20 mm were taken, and the longitudinal sections were mounted and mechanically polished, followed by vibration polishing. EBSD (backscattered electron diffraction) analysis was performed using a ZEISS Sigma 300 electron microscope. Two regions (each region area approximately 1.1 mm × sample thickness) were randomly measured on each sample at 100x magnification. The acquired images were imported into AZCrystal software, and the system automatically performed analysis and statistics on texture type and area ratio, as well as ∑ grain boundary type and length ratio, to obtain relevant texture data and ∑7 length ratio data for the samples.

[0170] In this alloy system, grains with specific orientations, such as R-Cube texture, P texture, Cube texture, Goss texture, R texture, Q texture, Copper texture, and Brass texture, as well as some grains with arbitrary orientations, were found. However, statistical analysis revealed that only P texture and R-Cube texture have a significant impact on the recrystallization process and strength of the annealed material during subsequent stamping deformation and brazing. Therefore, only the statistical analysis results for P texture and R-Cube texture are published in the example data. ∑ grain boundaries include ∑1, ∑3, ∑5, ∑7, etc. Statistical analysis showed that ∑7 grain boundaries have a significant impact on resistance to erosion in the annealed material. Therefore, this invention only publishes the statistical analysis results for ∑7 grain boundaries.

[0171] 3. Evaluation of simulated brazing and post-weld recrystallization, and erosion:

[0172] The composite brazed plate was subjected to deformation amounts of 0.5% and 4% respectively to simulate brazing, and the recrystallization and post-weld erosion were measured. The simulated brazing conditions were set to heat to 610℃ within 25 minutes, hold at that temperature for 20 minutes, and then remove and cool.

[0173] Recrystallization: EBSD (backscattered electron diffraction) analysis was performed using a ZEISS Sigma 300 electron microscope. Two regions (approximately 1.1 mm in area per region) were randomly measured for each sample at 100x magnification. The acquired EBSD images were imported into Channel 5 software to analyze the area ratio of deformed, subgrained, and recrystallized structures. A deformed structure area ratio exceeding 0.5% was considered present; a deformed structure area ratio below 0.5% was considered fully recrystallized. Typically, approximately 0.5% deformed structure is unavoidably introduced during sample preparation.

[0174] Erosion: Metallographic examination was performed on the cross-sections of the composite brazed plates before and after brazing. The average thickness T1 of the core layer in the sample before brazing was measured, and the remaining thickness T2 of the core layer at the location with the largest erosion depth in the sample was measured. The degree of erosion was expressed by the following formula: Remaining core layer thickness ratio = T2 / T1 × 100%.

[0175] 4. Tensile strength and elongation tests:

[0176] Mechanical properties at room temperature were tested according to the method disclosed in GB / T228.1-2010 "Metallic Materials - Tensile Testing". The testing instrument was a ZWICK universal testing machine, and the test parameters were tensile strength Rm and elongation A. 50 .

[0177] The results of the determination of the solid solution Mn content and the statistical results of the R-Cube texture area ratio, P texture area ratio, and ∑7 grain boundary length ratio are shown in Table 1; the evaluation results of the simulated brazing and post-weld recrystallization and erosion are shown in Table 2; the tensile strength Rm and elongation A... 50 The test results are shown in Table 3.

[0178] Table 1

[0179]

[0180] Table 2

[0181]

[0182]

[0183] Table 3

[0184]

[0185]

[0186] As shown in Tables 1-3, the composite brazing plates prepared in Examples 1-11 exhibit well controlled area ratios of R-Cube and P-textures, strong resistance to erosion, and core layer erosion ratios all below 4%. Tensile strengths all exceed 100 MPa, and elongation exceeds 28%, preferably exceeding 30%. Higher elongation is more difficult to improve. Compared to Example 6, Example 1 further controls the silicon content at 0.2 wt%, which can further improve the material's elongation. Compared to Example 7, Example 1 incorporates a first-stage annealing process... Extending the annealing time from 2h to 3h significantly increased the proportion of ∑7 grain boundary length and further reduced the degree of erosion. Compared with Example 8, shortening the second-stage annealing time from 6h to 4h in Example 1 reduced the proportion of P texture from 22.3% to 19.5%, which was found to be more conducive to improving elongation. Compared with Example 9, further controlling the Fe content to within 0.5wt% in Example 2 was beneficial to further improving the elongation. Compared with Example 11, adjusting the Cu content in Example 4 could avoid intergranular corrosion without significantly affecting the strength.

[0187] Compared to Example 1, Comparative Example 1, due to the excessively low homogenization heat treatment temperature, resulted in an excessively high dissolved manganese content, an excessively large proportion of P-texture, and a reduced elongation of the material. Compared to Example 4, Comparative Example 2, due to the excessively high homogenization heat treatment temperature, resulted in a lower dissolved manganese content, an excessively small proportion of P-texture, and a lower strength of the material. Compared to Example 1, Comparative Example 3, due to the excessively low cold deformation rate, resulted in a lower proportion of both R-Cube and P-texture in the material, making it prone to forming deformed structures during brazing, leading to excessive erosion, poor erosion resistance, and a significant decrease in strength compared to Example 1. Compared to Example 1, Comparative Example 4, due to the excessively low cold deformation rate... In Comparative Example 5, compared to Example 1, excessive Copper texture was formed within the microstructure, resulting in excessive P texture and a significant decrease in elongation. In Comparative Example 6, compared to Example 4, the excessive first-stage annealing time led to an excessive proportion of R-Cube texture, which affected the formation of R-Cube texture, easily forming deformable structures, resulting in excessive melting degree, poor melting resistance, and a decrease in material elongation. In Comparative Example 7, compared to Example 1, the excessively short second-stage annealing time resulted in insufficient P texture proportion, leading to a decrease in material strength.

[0188] The applicant declares that the present invention is illustrated through the above embodiments to describe the detailed products and methods of the present invention, but the present invention is not limited to the detailed products and methods described above, that is, it does not mean that the present invention must rely on the detailed products and methods described above to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the products of the present invention, additions to auxiliary structures, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An aluminum alloy composite brazing plate, characterized in that, The composite brazing plate includes a core layer and a brazing layer. The core layer is made of aluminum-manganese alloy, and the manganese content in the aluminum-manganese alloy is 0.5~1.5wt%. In the alloy structure of the core layer, the R-Cube texture area accounts for 10~20%, the P texture area accounts for 10%~20%, and the state of the core layer is O state. The brazing layer is made of aluminum-silicon alloy.

2. The composite brazing plate according to claim 1, characterized in that, In the alloy microstructure of the core layer, the length of the ∑7 grain boundaries accounts for 1.5~5%.

3. The composite brazing plate according to claim 1, characterized in that, The aluminum-manganese alloy of the core layer also includes silicon and iron in its elemental composition.

4. The composite brazing plate according to claim 3, characterized in that, The aluminum-manganese alloy contains ≤0.2wt% silicon and 0.1~0.5wt% iron.

5. The composite brazing plate according to claim 1, characterized in that, The aluminum-manganese alloy of the core layer also includes copper, with a copper content of 0.1~0.5wt%.

6. The composite brazing plate according to any one of claims 1-5, characterized in that, The thickness of the composite brazing plate is 0.4~0.8mm.

7. The composite brazing plate according to claim 1, characterized in that, The core layer of the composite brazed plate accounts for 70-90% of the thickness, and the brazed layer accounts for 10-20% of the thickness.

8. The composite brazing plate according to claim 1, characterized in that, The composite brazing plate also includes a water-contact layer, which is located on the side of the core layer away from the brazing layer.

9. The composite brazing plate according to claim 8, characterized in that, The thickness of the water-contact layer accounts for 0 to 10% of the thickness of the composite brazing plate.

10. The method for preparing the composite brazing plate according to any one of claims 1-9, characterized in that, The preparation method includes the following steps: (1) According to the composition ratio, the raw materials of each structural layer of the composite brazing plate are melted and cast to obtain alloy ingots of the core layer and the brazing layer respectively; (2) The core alloy ingot is subjected to homogenization heat treatment, and then each structural layer is milled. (3) After processing in step (2), the structural layers are stacked in sequence and then hot rolled to obtain a primary composite plate; (4) The primary composite plate obtained in step (3) is cold rolled to control the cold deformation rate to 82~92% to obtain the secondary composite plate; (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing, and finally an aluminum alloy composite brazing plate is obtained.

11. The preparation method according to claim 10, characterized in that, The structural layer of the composite brazing plate in step (1) also includes a water-contact layer.

12. The preparation method according to claim 10, characterized in that, After the raw materials described in step (1) are melted, they are stirred to ensure that the raw materials are evenly mixed before casting.

13. The preparation method according to claim 10, characterized in that, The homogenization heat treatment in step (2) is performed at a temperature of 500~590℃.

14. The preparation method according to claim 10, characterized in that, The homogenization heat treatment in step (2) takes 6 to 12 hours.

15. The preparation method according to claim 10, characterized in that, The content of dissolved manganese in the core matrix after the homogenization heat treatment in step (2) is 0.2~0.5wt%.

16. The preparation method according to claim 10, characterized in that, Step (2) Each structural layer is first sawed and then milled.

17. The preparation method according to any one of claims 10 to 16, characterized in that, Before hot rolling each of the structural layers in step (3) is hot rolled separately, the thickness ratio of each structural layer after hot rolling is consistent with the thickness ratio of each structural layer in the final composite brazed plate.

18. The preparation method according to claim 17, characterized in that, When the structural layer in step (3) includes a water-contact layer, the stacking order is that the core layer is in the middle, and the brazing layer and the water-contact layer are on both sides.

19. The preparation method according to claim 10, characterized in that, The target thickness of the cold rolling in step (4) is 0.4~0.8 mm.

20. The preparation method according to claim 10, characterized in that, The temperature of the first-stage annealing in step (5) is 200~260℃, and the time of the first-stage annealing is 3~6h.

21. The preparation method according to claim 10, characterized in that, The temperature of the second-stage annealing in step (5) is 350~400℃, and the time of the second-stage annealing is 1~4h.

22. The preparation method according to claim 10, characterized in that, The preparation method includes the following steps: (1) According to the composition ratio, the raw materials of each structural layer of the composite brazing plate are melted and stirred, and then cast to obtain alloy ingots of core layer, brazing layer and water contact layer respectively. (2) The core alloy ingot is subjected to homogenization heat treatment at a temperature of 500~590℃ for 6~12h. After homogenization heat treatment, the content of dissolved manganese in the core matrix is ​​0.2~0.5wt%. Then, each structural layer is sawed and milled in sequence. (3) Each structural layer after step (2) is hot rolled separately, and then stacked in sequence and hot rolled. The hot rolling temperature is 460~500℃ and the target thickness of the hot rolling is 4~6mm to obtain a primary composite plate. (4) The primary composite plate obtained in step (3) is cold rolled, and the cold deformation rate is controlled to be 82~92%, and the target thickness of the cold rolling is 0.4~0.8mm, to obtain the secondary composite plate; (5) The secondary composite plate obtained in step (4) is subjected to two-stage annealing, wherein the temperature of the first-stage annealing is lower than that of the second-stage annealing. The temperature of the first-stage annealing is 200~260℃ and the time is 3~6h. The temperature of the second-stage annealing is 350~400℃ and the time is 1~4h. Finally, an aluminum alloy composite brazing plate is obtained.

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