Brazing flux-embedded aluminum alloy brazing filler metal plate blank and preparation method thereof, brazing flux-embedded composite aluminum alloy brazing plate strip and preparation process and application thereof

Abstract

The invention provides a pre-buried brazing flux aluminum alloy brazing filler metal plate blank and a preparation method thereof, a pre-buried brazing flux composite aluminum alloy brazing plate strip and a preparation process and application thereof. After the mixed powder of the aluminum-silicon alloy and the brazing flux is pressed into the cylinder, the cylinder is extruded into the aluminum alloy brazing filler metal plate blank with the pre-embedded brazing flux through the semi-continuous extruding machine, the production efficiency is high, the yield is high, and the prepared aluminum alloy brazing filler metal plate blank with the pre-embedded brazing flux is uniform in component and good in extensibility. The prepared pre-buried brazing flux aluminum alloy brazing filler metal plate blank and an aluminum alloy core material are easy to roll and compound, the obtained pre-buried brazing flux composite aluminum alloy brazing plate strip has a good compound interface, does not have obvious defects such as slag inclusion, bubbles, layering and peeling, has the mechanical property meeting the requirements, has excellent ductility and good brazing performance, and is suitable for large-scale production. And the brazing effect with other aluminum components is good, the surface of a workpiece is bright, and soldering flux traces are not left. The technology can greatly simplify the manufacturing process of the aluminum heat exchanger, and can be used for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aluminum alloy brazing, and particularly relates to a pre-embedded flux aluminum alloy brazing sheet and a preparation method thereof, a pre-embedded flux aluminum alloy composite brazing material and a preparation process and application thereof. The material prepared by the technology can greatly simplify the production process of an aluminum heat exchanger and improve the brazing quality. BACKGROUND

[0002] The brazing method is currently commonly used in the industry to produce aluminum alloy heat exchangers. However, aluminum and aluminum alloy materials are usually produced in an atmospheric environment, and a dense oxide film layer is formed on the surface thereof. The dense oxide film has poor wettability with aluminum filler during brazing, which hinders the flow of the filler melt and the fusion welding with the aluminum material. Therefore, the dense oxide film must be broken to enable the molten filler to contact and wet the fresh aluminum alloy surface.

[0003] Currently, two methods, i.e., a pre-spraying Nocolock flux method and a vacuum brazing method, are usually used in industrial production to eliminate the influence of the oxide film. However, the pre-spraying flux method can cause a large amount of flux residue to be left, which is difficult to completely remove in the subsequent cleaning process. In addition to affecting the appearance quality, the flux residue can accelerate the corrosion of the aluminum heat exchanger once it enters the cooling liquid, thereby affecting the service life thereof. The vacuum brazing method requires the entire brazing process to be completed in a vacuum furnace under a sub-atmospheric state (3.5 x 10 -3 Pa). The vacuum furnace equipment is expensive, which increases the production cost and causes the production to be intermittent and the production efficiency to be low.

[0004] Currently, aluminum heat exchangers are increasingly developed in the direction of small size, light weight, and long service life. The uniformity of the sprayed layer of the flux is increasingly required in the inert gas protection brazing process of high-performance aluminum heat exchangers. Therefore, it is necessary to further provide high-quality aluminum alloy composite brazing materials to meet the production needs. Currently, the brazing aluminum alloy composite material with pre-embedded flux is usually used to solve this problem.

[0005] The known manufacturing process of the brazing filler layer with pre-embedded flux is relatively complex and has many deficiencies. For example, CN113210608A and CN117381228A disclose that the brazing filler layer with pre-embedded flux is obtained by uniformly mixing flux powder and aluminum-silicon alloy powder, hot isostatic pressing (HIP) to press a blank, and then milling and rolling the obtained blank. Although this method can manufacture the aluminum brazing filler layer with pre-embedded flux, the hot isostatic pressing needs to be kept at high pressure for 3 to 6 hours after pressurization, the preparation time is long, and the production is intermittent, which is low in production efficiency. Moreover, the production cost is high due to the expensive hot isostatic pressing equipment, the small volume of the high-pressure container, the small volume of the pressed blank (about 100 kg per piece), the need to mill the periphery of the pressed blank, the low material yield due to the large amount of milling waste, and the difficulty in large-scale production.

[0006] For example, CN114473385A discloses that a frame structure is arranged on the surface of a core material aluminum alloy slab to form a recess, aluminum alloy powder and mixed powder mixed with a brazing agent are filled into the recess in three layers to form a powder layer, a cover plate is welded with the frame to seal the powder layer in the recess to obtain a pre-embedded brazing agent blank, and then heating and hot rolling are performed to obtain a pre-embedded brazing agent composite plate; although the process is simple, the powder layer sealed in the recess is in a natural accumulation state, there are gaps between the powder particles and a large amount of gas exists therein, and it is difficult to roll during subsequent rolling, and the gas sealed therein cannot be fully discharged, which will bubble during annealing and affect the quality of the material. SUMMARY

[0007] The present application aims to solve the above-mentioned problems of the prior art, and the purpose is to provide a pre-embedded brazing agent composite aluminum alloy brazing plate strip and its preparation method and application.

[0008] In view of the problems existing in the prior art for preparing a pre-embedded brazing agent composite aluminum alloy brazing plate strip, the applicant attempts to mix brazing powder and aluminum-silicon alloy powder, and then perform hot rolling or cold rolling to roll the mixture into a plate, and then perform annealing to obtain a self-contained brazing agent aluminum-silicon alloy brazing plate. Although a self-contained brazing agent aluminum-silicon alloy brazing plate with uniform density and uniform brazing agent distribution can be prepared, it is found that when the self-contained brazing agent aluminum-silicon alloy brazing plate is used as raw material to assemble a blank with a core material, and the blank is rolled into a pre-embedded brazing agent composite aluminum alloy brazing plate strip, there is a phenomenon of aluminum powder peeling off and falling off from the surface of the self-contained brazing agent aluminum-silicon alloy brazing plate, the self-contained brazing agent aluminum-silicon alloy brazing plate is easy to break and has poor ductility, which leads to the difficulty in preparing a qualified pre-embedded brazing agent composite aluminum alloy brazing plate strip in the subsequent process. In view of this phenomenon, the applicant has developed a new preparation method of a pre-embedded brazing agent aluminum alloy brazing plate blank and a preparation method of a pre-embedded brazing agent composite aluminum alloy brazing plate strip to overcome the above-mentioned defects.

[0009] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: In a first aspect, a preparation method of a pre-embedded brazing agent aluminum alloy brazing plate blank is provided, comprising: Mixing aluminum-silicon alloy powder and brazing agent powder to obtain mixed powder; Pressing the mixed powder into a cylinder, and then using a semi-continuous extruder to extrude the cylinder into a pre-embedded brazing agent aluminum alloy brazing plate blank.

[0010] Further, the pressing is normal temperature pressing, and the pressure of the pressing is 500 MPa or more.

[0011] Further, the extrusion is hot extrusion, and the extrusion temperature of the hot extrusion is 350-480 DEG C, preferably 380-450 DEG C.

[0012] Further, the pre-embedded flux aluminum alloy filler material slab has a length of 5-30 mm, a width of 100-400 mm, and a rectangular cross section.

[0013] Further, the aluminum-silicon alloy powder has a silicon content of 6.5wt%-12.5wt%, an oxygen content of not more than 800ppm, and a particle size D50 of 20-55μm.

[0014] Further, the flux powder is at least one of potassium fluoroaluminate powder and cesium fluoroaluminate powder, and has a particle size D50 of 10-40μm.

[0015] Further, the weight ratio of the aluminum-silicon alloy powder to the flux powder is (95-80):(5-20).

[0016] In a second aspect, a pre-embedded flux aluminum alloy filler material slab is provided, which is prepared by the method described above.

[0017] In a third aspect, a preparation process of a pre-embedded flux composite aluminum alloy brazing plate strip is provided, which comprises: The pre-embedded flux aluminum alloy filler material slabs described in the second aspect are arranged in a mutually abutting manner on the upper surface of the aluminum alloy core material, so that the pre-embedded flux aluminum alloy filler material slabs collectively form a continuous cladding layer that covers more than 85% of the upper surface of the aluminum alloy core material, preferably more than 90% of the upper surface of the aluminum alloy core material; an aluminum-silicon alloy slab is covered on the surface of the cladding layer of the pre-embedded flux aluminum alloy filler material slabs to form a sandwich-structured pre-assembled slab, and the pre-assembled slab is spot-welded along the periphery to obtain a pre-embedded flux composite aluminum alloy brazing assembly slab. After the assembly slab is heated, a hot-rolled composite plate is obtained through multi-pass hot rolling, and the hot-rolled composite plate is cold-rolled to obtain a pre-embedded flux composite aluminum alloy brazing plate strip with a target thickness.

[0018] In a fourth aspect, a preparation process of a pre-embedded flux composite aluminum alloy brazing plate strip is provided, which comprises: The pre-embedded flux aluminum alloy filler material slabs described in the second aspect are arranged in a mutually abutting manner on the first surface of the aluminum alloy core material, so that the pre-embedded flux aluminum alloy filler material slabs collectively form a continuous cladding layer that covers more than 85% of the first surface of the aluminum alloy core material, preferably more than 90% of the first surface of the aluminum alloy core material; an aluminum-silicon alloy slab is covered on the surface of the cladding layer of the pre-embedded flux aluminum alloy filler material slabs to form a sandwich-structured first pre-assembled slab, and the first pre-assembled slab is spot-welded along the periphery. The pre-embedded flux aluminum alloy filler material plate blanks of the second aspect are arranged in a mutually abutting manner on the second surface of the aluminum alloy core material of the first pre-assembled blank, so that the pre-embedded flux aluminum alloy filler material plate blanks collectively constitute a continuous cladding layer that covers more than 85%, preferably more than 90%, of the second surface of the aluminum alloy core material; and an aluminum-silicon alloy plate blank is covered on the surface of the pre-embedded flux filler material plate blank cladding layer to form a second pre-assembled blank with a sandwich structure, and the second pre-assembled blank is spot welded around the periphery. After heating the second assembled blank, a hot-rolled composite plate is obtained through multi-pass hot rolling, and the hot-rolled composite plate is cold-rolled to obtain a pre-embedded flux composite aluminum alloy brazing plate strip with a target thickness.

[0019] Further, the aluminum-silicon alloy plate blank is any one of 4343, 4045, 4047, 4A13, and 4104 aluminum alloy.

[0020] Further, in the aluminum-silicon alloy plate blank, the mass fraction of Si is 6.5-12.5wt%.

[0021] Further, the aluminum alloy core material is an aluminum alloy plate containing 0.6-1.5wt% Mn.

[0022] Further, in the pre-assembled blank and the first pre-assembled blank, the sum of the thicknesses of the pre-embedded flux aluminum alloy filler material plate blank and the aluminum-silicon alloy plate blank is 5-20% of the total thickness of the pre-assembled blank; the thickness of the pre-embedded flux aluminum alloy filler material plate blank is 25-50% of the total thickness of the pre-embedded flux aluminum alloy filler material plate blank and the aluminum-silicon alloy plate blank.

[0023] Further, in the second pre-assembled blank, the sum of the thicknesses of the pre-embedded flux aluminum alloy filler material plate blank and the aluminum-silicon alloy plate blank on each side of the aluminum alloy core material is independently 5-20% of the total thickness of the pre-assembled blank; the thickness of the pre-embedded flux aluminum alloy filler material plate blank on each side of the aluminum alloy core material is independently 25-50% of the total thickness of the pre-embedded flux aluminum alloy filler material plate blank and the aluminum-silicon alloy plate blank.

[0024] Further, the heating temperature is 450-600℃, preferably 500-550℃; and the holding time is 1-6h, preferably 2-5h.

[0025] Further, the hot rolling is multi-pass hot rolling; and the final rolling temperature of the hot rolling is not lower than 250℃, preferably not lower than 280℃.

[0026] Further, the single-pass reduction of the first to third passes of the hot rolling is 3% or less, preferably 0.5-2.5%; and the hot rolling is performed from the middle of the plate to both sides.

[0027] Further, the hot rolling is low-speed rolling, and the cooling liquid needs to be turned off for liquid-free rolling during the hot rolling process.

[0028] Further, the cold rolling is multi-pass cold rolling; the pass reduction of the cold rolling is 25-50%, preferably 25-40%; annealing is performed between adjacent passes of cold rolling or no annealing is performed.

[0029] Further, the thickness of the hot-rolled composite plate is 5-8 mm.

[0030] In a fifth aspect, a pre-embedded brazing flux composite aluminum alloy brazing sheet is provided, which is prepared by the method of the third aspect or the fourth aspect.

[0031] In a sixth aspect, the use of the pre-embedded brazing flux composite aluminum alloy brazing sheet of the fifth aspect in an aluminum heat exchanger is provided.

[0032] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: The preparation method of the pre-embedded brazing flux aluminum alloy filler sheet provided not only has high production efficiency, no cutting waste, high material yield, and can reduce production cost, but also has uniform composition, density and properties close to aluminum alloy, and good ductility, which can be used for subsequent preparation of pre-embedded brazing flux composite aluminum alloy brazing sheet with aluminum alloy core material. Compared with the prior art, the problems of hot rolling difficulty, delamination of composite material and difficulty in extrusion into one body caused by aluminum powder peeling, easy breakage and poor ductility can be avoided.

[0033] The preparation process of the pre-embedded brazing flux composite aluminum alloy brazing sheet is simple and easy to implement, the surface of the material finished product has a good composite interface due to hot rolling, and has no obvious defects such as slag inclusion, bubbles, delamination, peeling and the like for subsequent use of customers, and the mechanical properties of the finished product can meet the requirements, have excellent ductility and good brazing performance, and can be perfectly brazed with other aluminum components under the protection of inert atmosphere, the surface of the workpiece is bright, and no brazing flux traces are left, thereby improving the quality of the aluminum heat exchanger. Therefore, the technology can greatly simplify the manufacturing process of the aluminum heat exchanger, and the preparation process of the pre-embedded brazing flux composite aluminum alloy brazing sheet can be used for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 It is a process flow diagram for the preparation process of the pre-embedded brazing flux aluminum alloy composite brazing material.

[0036] Figure 2 Pictures of the oil press and the pressing die used for the oil press pressing in Example 1, wherein (a) corresponds to the oil press, and (b) corresponds to the pressing die.

[0037] Figure 3 Pictures of the cylinder pressed by the oil press and the rectangular cross-section long strip blank prepared by extrusion in Example 1, wherein (a) corresponds to the cylinder pressed by the oil press, and (b) corresponds to the rectangular cross-section long strip blank prepared by extrusion.

[0038] Figure 4 Assembly schematic diagram of the hot-rolled composite blank of the present application, wherein (a) is a top view schematic diagram, (b) is a side view schematic diagram, and (c) is a front view schematic diagram.

[0039] Figure 5 Metallographic structure diagram of the pre-embedded flux brazing filler metal blank obtained in Step (2) of Example 2.

[0040] Figure 6 Picture of the pre-embedded flux composite aluminum alloy brazing plate strip product obtained in Example 2.

[0041] Figure 7 Metallographic structure diagram of the cross section of the pre-embedded flux composite aluminum alloy brazing plate strip product obtained in Example 2.

[0042] Figure 8 Brazing test sample diagram of the pre-embedded flux composite aluminum alloy brazing plate strip product obtained in Example 2. BRIEF DESCRIPTION OF DRAWINGS 1, core material aluminum alloy; 2, pre-embedded flux blank; 3, aluminum-silicon alloy plate blank; 4, bundled steel strip. DETAILED DESCRIPTION

[0044] Some embodiments of the present application provide a preparation method of a pre-embedded flux aluminum alloy brazing filler metal plate blank, comprising: Mixing aluminum-silicon alloy powder and flux powder to obtain a mixed powder; Pressing the mixed powder into a cylinder, and then extruding the cylinder into a pre-embedded flux aluminum alloy brazing filler metal plate blank by using a semi-continuous extruder.

[0045] The preparation method of the pre-embedded flux aluminum alloy brazing filler metal plate blank provided not only has high efficiency, no cutting waste, high production efficiency, and high material yield, but also the density of the prepared pre-embedded flux aluminum alloy brazing filler metal plate blank is close to that of the aluminum alloy, and the properties are also close to those of the aluminum alloy, and the elongation type is good. However, the powder rolling is relatively more difficult, the forming density is relatively lower, and the gas content is relatively higher. In addition, when the aluminum alloy brazing filler metal plate is used to prepare subsequent products (such as a pre-embedded flux composite aluminum alloy brazing plate strip), various hot-rolling composite difficulties occur, the interface cannot be rolled into one body, and defects such as gas bubbles, peeling, and slag inclusion occur in the interface.

[0046] In some embodiments, the pressing is room temperature pressing; and the pressure of the pressing is 500 MPa or more.

[0047] In some preferred embodiments, the extrusion is hot extrusion; and the extrusion temperature of the hot extrusion is 350-480℃, further preferably 380-450℃, for example 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, etc. Before the hot extrusion, the aluminum powder cylinder (B) needs to be heated to 350-450℃ in a heating furnace and kept for 3-8h, preferably kept for 4-6h, for example 4h, 4.5h, 5h, 5.5h, 6h, etc.

[0048] In some embodiments, the pre-embedded brazing agent aluminum alloy filler material slab is a long strip slab with a rectangular cross section, with a thickness of 5-30mm (for example 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, etc.), a width of 100-400mm (for example 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, etc.), and no limitation on the length of the long strip slab.

[0049] In some preferred embodiments, the aluminum-silicon alloy powder is an aluminum-silicon alloy powder containing 6.5wt.%-12.5wt.% silicon, for example 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, etc.; the oxygen content of the aluminum-silicon alloy powder is not more than 800ppm, for example not more than 700ppm, not more than 600ppm, not more than 500ppm, not more than 400ppm, not more than 300ppm, not more than 200ppm, not more than 100ppm, etc.; and the particle size D50 of the aluminum-silicon alloy powder is 20-55μm, for example 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, etc.

[0050] In some preferred embodiments, the brazing agent powder is at least one of potassium fluoroaluminate powder and cesium fluoroaluminate powder; and the particle size D50 of the brazing agent powder is 10-40μm, for example 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, etc.

[0051] In some preferred embodiments, the weight ratio of the aluminum-silicon alloy powder to the brazing agent powder is (95-80):(5-20), for example 95:5, 92:8, 90:10, 88:12, 85:15, 82:18, 80:20, etc.

[0052] In some embodiments, the mixing is performed by a V-type mixer or a three-dimensional high-efficiency mixer, and the rotating speed is 2-12 rpm.

[0053] In some embodiments, the pre-embedded flux aluminum alloy filler plate blank is prepared by the above method, and has the advantages of uniform composition, good ductility, easy subsequent hot rolling with aluminum alloy, good hot-rolled composite interface, and no obvious defects such as slag inclusion, bubbles, delamination, and peeling.

[0054] In some embodiments, the preparation process of the pre-embedded flux composite aluminum alloy brazing plate strip material comprises the following steps: The pre-embedded flux aluminum alloy filler plate blanks are arranged on the upper surface of the aluminum alloy core material in a mutually adjacent manner, so that the pre-embedded flux aluminum alloy filler plate blanks collectively form a substantially continuous coating, which covers more than 85% of the upper surface of the aluminum alloy core material, preferably more than 90%, and an aluminum-silicon alloy plate blank is covered on the surface of the coating of the pre-embedded flux aluminum alloy filler plate blanks to form a sandwich structure pre-assembled blank. The pre-assembled blank is spot welded around the periphery to obtain a pre-embedded flux composite aluminum alloy brazing assembly blank. It is worth noting that after the continuous coating of the pre-embedded flux aluminum alloy filler plate blanks is formed on the upper surface of the aluminum alloy core material, the relative positions are fixed by spot welding, and then an aluminum-silicon alloy plate blank is covered on the upper surface of the continuous coating to form a sandwich structure pre-assembled blank, and then spot welding is performed to achieve overall fixation.

[0055] In some embodiments, the preparation process of the pre-embedded flux composite aluminum alloy brazing plate strip material comprises the following steps: The pre-embedded flux aluminum alloy filler plate blanks are arranged on the first surface of the aluminum alloy core material in a mutually adjacent manner, so that the pre-embedded flux aluminum alloy filler plate blanks collectively form a substantially continuous coating, which covers more than 85% of the first surface of the aluminum alloy core material, preferably more than 90%, and an aluminum-silicon alloy plate blank is covered on the surface of the coating of the pre-embedded flux aluminum alloy filler plate blanks to form a sandwich structure first pre-assembled blank. The first pre-assembled blank is spot welded around the periphery. The pre-embedded flux aluminum alloy filler plate blanks are arranged on the second surface of the aluminum alloy core material of the first pre-assembled blank in a mutually adjacent manner, so that the pre-embedded flux aluminum alloy filler plate blanks collectively form a substantially continuous coating, which covers more than 85% of the second surface of the aluminum alloy core material, preferably more than 90%, and an aluminum-silicon alloy plate blank is covered on the surface of the coating of the pre-embedded flux aluminum alloy filler plate blanks to form a sandwich structure second pre-assembled blank. The second pre-assembled blank is spot welded around the periphery. After the second assembly blank is heated, it is hot-rolled in multiple passes to obtain a hot-rolled composite plate. The hot-rolled composite plate is cold-rolled to obtain a pre-embedded flux composite aluminum alloy brazing plate strip material with a target thickness.

[0056] In assembling the first pre-assembled blank and the second pre-assembled blank, after forming the continuous coating layer of the pre-embedded fluxing agent aluminum alloy filler sheet blanks on the upper surface of the aluminum alloy core material, spot welding is used to fix the relative position, and then an aluminum-silicon alloy sheet blank is covered on the upper surface of the continuous coating layer to form a sandwich structure pre-assembled blank, and then spot welding is performed to realize overall fixation.

[0057] In some preferred embodiments, the aluminum-silicon alloy sheet blank is any one of 4343, 4045, 4047, 4A13, and 4104 aluminum alloy.

[0058] In some preferred embodiments, the mass percentage of Si in the aluminum-silicon alloy sheet blank is 6.5-12.5%, such as 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, 10wt%, 10.5wt%, 11wt%, 11.5wt%, 12wt%, 12.5wt%, etc.

[0059] In some preferred embodiments, the aluminum alloy core material is an aluminum alloy sheet containing 0.6-1.5wt% Mn, such as containing 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, etc.

[0060] In some preferred embodiments, in the pre-assembled blank, the first pre-assembled blank, and the second pre-assembled blank, the sum of the thicknesses of the pre-embedded fluxing agent aluminum alloy filler sheet blank and the aluminum-silicon alloy sheet blank is 5-20% of the total thickness of the pre-assembled blank, such as 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.; the thickness of the pre-embedded fluxing agent aluminum alloy filler sheet blank is 25-50% of the total thickness of the pre-embedded fluxing agent aluminum alloy filler sheet blank and the aluminum-silicon alloy sheet blank, such as 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, etc.

[0061] In some preferred embodiments, in the pre-assembled blank, the first pre-assembled blank, and the second pre-assembled blank, the sum of the thicknesses of the pre-embedded fluxing agent aluminum alloy filler sheet blank and the aluminum-silicon alloy sheet blank is 5-20% of the total thickness of the pre-assembled blank, such as 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.; the thickness of the pre-embedded fluxing agent aluminum alloy filler sheet blank is 25-50% of the total thickness of the pre-embedded fluxing agent aluminum alloy filler sheet blank and the aluminum-silicon alloy sheet blank, such as 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, etc.

[0062] In some preferred embodiments, the thickness of the pre-embedded brazing agent aluminum alloy filler sheet and the thickness of the aluminum-silicon alloy sheet on one side of the aluminum alloy core material in the second pre-assembled blank are each independently 5-20% of the total thickness of the pre-assembled blank, such as 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.; the thickness of the pre-embedded brazing agent aluminum alloy filler sheet on one side of the aluminum alloy core material is each independently 25-50% of the total thickness of the pre-embedded brazing agent aluminum alloy filler sheet and the aluminum-silicon alloy sheet, such as 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, etc.

[0063] It is worth noting that the pre-embedded brazing agent aluminum alloy filler sheet and the aluminum-silicon alloy sheet in the pre-assembled blank, the first pre-assembled blank, and the second pre-assembled blank have similar dimensions in the length and width directions.

[0064] In some preferred embodiments, the heating temperature is 450-600°C, preferably 500-550°C; the holding time is 1-6h, preferably 2-5h, such as 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.

[0065] In some preferred embodiments, the hot rolling is multi-pass hot rolling; the finish rolling temperature of the hot rolling is not lower than 250°C, such as not lower than 260°C, not lower than 280°C, not lower than 300°C, etc.

[0066] In some preferred embodiments, the single reduction of the first to third passes of the hot rolling is 3% or less, preferably 0.5-2.5%, such as 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, etc.; by performing hot rolling with small reduction in the first few passes, low-speed and small-reduction rolling can ensure that the composite surfaces of the layers are tightly pressed together and have good bonding strength, and also ensure that the air between the layers is fully exhausted. The subsequent hot rolling can be conventional hot rolling, and after the hot rolling to a thickness of 50-100mm, the head and tail of the rolled blank are removed for further conventional hot rolling.

[0067] In some preferred embodiments, the hot rolling is performed from the middle of the sheet to both sides.

[0068] In some preferred embodiments, the thickness of the hot-rolled composite sheet is 5-8mm, such as 5mm, 6mm, 7mm, 8mm, etc. After the hot rolling is completed, conventional coiling is performed to obtain a hot-rolled aluminum coil.

[0069] In some preferred embodiments, the hot rolling is low-speed rolling, and the cooling liquid needs to be turned off during the hot rolling process to prevent the cooling liquid from entering the composite interface and affecting the composite effect.

[0070] In some preferred embodiments, the cold rolling is multi-pass cold rolling; the pass reduction of the cold rolling is 25-50%, such as 25%, 30%, 35%, 40%, 45%, 50%, or the like, preferably 25-40%; annealing is performed between adjacent passes of cold rolling or no annealing is performed.

[0071] It is worth mentioning that the target thickness of the cold rolling can be determined according to actual needs.

[0072] In some embodiments, a pre-embedded flux composite aluminum alloy brazing sheet is provided, which is prepared by the above preparation method. The surface of the finished material has no obvious defects such as slag inclusion, bubbles, delamination, and peeling, which can be used by customers later. The mechanical properties of the prepared pre-embedded flux filler metal blank can meet the requirements, have excellent ductility and good brazing performance, can be perfectly brazed with other aluminum components under the protection of inert atmosphere, and the surface of the workpiece is bright without flux traces.

[0073] In some embodiments, the application of the pre-embedded flux composite aluminum alloy brazing sheet in an aluminum heat exchanger is also provided.

[0074] In order to facilitate the understanding of the present application, the present application will be described in more detail below in conjunction with the drawings and preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0075] Unless otherwise defined, all the professional terms used below have the same meaning as understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0076] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0077] Example 1 The preparation process of the pre-embedded flux composite aluminum alloy brazing sheet comprises: The flux powder and the aluminum-silicon alloy powder are mixed in a weight ratio of (5-20):(95-80) to form a mixed powder (A); the flux powder is potassium fluoroaluminate (or cesium fluoroaluminate) powder, and the powder particle size D50 is 10-40 μm; the aluminum-silicon powder contains 6.5-12.5 wt% of silicon (Si) and less than 800 ppm of oxygen, and the particle size D50 is 20-55 μm.

[0078] The mixing is performed by a V-shaped universal mixer or a 3-dimensional high-efficiency mixer, and the mixing speed is 2-12 revolutions per minute; the mixing time is 2-5 hours.

[0079] The mixed powder (A) is pressed into a cylinder (B) by an oil press, as shown in Figure 2 (a), and the pressing mold is shown in Figure 2 (b). The cylinder (B) is extruded into a rectangular-section long billet (C) with pre-embedded flux by a semi-continuous extruder, as shown in Figure 3 (a). The thickness of the billet (C) is 5-30 mm, and the width is 100-400 mm. The pressing can be normal temperature pressing, and the pressing pressure is above 500 MPa. The extrusion is hot extrusion, and the aluminum powder cylinder (B) is heated to 350-480°C in a heating furnace for 3-8 h before the hot extrusion. Figure 3

[0080] The pre-embedded flux filler metal billet (C) is tightly laid on the upper surface of the aluminum alloy billet as the core material (specifically, arranged on the upper surface of the aluminum alloy billet core material in a mutually adjacent manner, so that the pre-embedded flux aluminum alloy filler metal plate billet collectively constitutes a substantially continuous coating, which covers more than 85% of the upper surface of the aluminum alloy billet core material, preferably more than 90%, to form a pre-assembled billet. The pre-assembled billet is spot welded along the periphery to obtain a pre-embedded flux composite aluminum alloy brazing assembly billet. An aluminum-silicon alloy plate billet is then covered on the billet (C). The aluminum-silicon alloy plate billet is any one of 4343, 4045, 4047, 4A13, and 4104 aluminum alloys. The three-layer laminated composite billet (D) is welded and fixed to form a three-layer laminated composite billet (D), as shown in Figure 4 . The sum of the thicknesses of the pre-embedded flux aluminum alloy filler metal plate billet and the aluminum-silicon alloy plate billet is 5-20% of the total thickness of the pre-assembled billet. The thickness of the pre-embedded flux aluminum alloy filler metal plate billet is 25-50% of the total thickness of the pre-embedded flux aluminum alloy filler metal plate billet and the aluminum-silicon alloy plate billet. (a), (b), and (c) are top view, side view, and front view, respectively. The welded composite billet (D) is heated in a heating furnace at a temperature of 450-600°C for 1-6 h. The heated composite billet (D) is hot rolled in multiple passes to obtain an aluminum alloy composite brazing plate with a thickness of 5-8 mm. The final rolling temperature is greater than 250°C. The single-pass reduction of the first, second, and third passes of hot rolling is 4-8 mm, i.e., the single-pass reduction is less than 3%. The subsequent passes are conventional hot rolling. During the hot rolling process, the head and tail of the rolled billet can be removed when the hot rolled billet reaches a thickness of 50-100 mm, and the conventional hot rolling can continue. Each pass is rolled from the middle to both sides of the composite billet (D), and the emulsion cooling water needs to be closed. The liquid-free low-speed rolling process is adopted to prevent the emulsion from entering the composite interface and affecting the composite effect. After the hot rolling is completed, the conventional coiling is performed to obtain a hot-rolled aluminum coil. ​

[0081] After cooling the hot-rolled sheet, the pre-embedded flux composite aluminum alloy brazed strip is cold-rolled to the target thickness through multiple passes; the reduction per cold rolling pass is 25-50%, for example 25%, 30%, 35%, 40%, 45%, 50%, etc., preferably 25-40%; annealing may or may not be performed between adjacent cold rolling passes; depending on the user's requirements for material properties, an additional pre-annealing pass for the finished product can be added.

[0082] Example 2 The preparation process of pre-embedded flux composite aluminum alloy brazing strip includes: (1) Mix the flux powder and aluminum-silicon alloy powder in a weight ratio of 10:90 and mix them thoroughly to form a mixed powder; the flux powder is potassium fluoroaluminate powder with a particle size D50 of 25μm; the aluminum-silicon powder contains 10wt% silicon (Si), has an oxygen content of less than 800ppm, and a particle size D50 of 35μm; the mixing is carried out using a V-type universal mixer at a mixing speed of 7 rpm; the mixing time is 3.5 hours.

[0083] (2) The above-mentioned uniformly mixed powder is pressed into a cylinder using a hydraulic press, and then the cylinder is extruded into a rectangular cross-section pre-embedded flux strip blank with a thickness of 15 mm and a width of 200 mm using a semi-continuous extrusion press. The pressing is at room temperature with a pressing pressure of over 500 MPa. The extrusion is hot extrusion. Before hot extrusion, the aluminum powder cylinder (B) needs to be heated to 400℃ in a heating furnace and held for 5 hours. The hot extrusion temperature is 400℃. The SEM image of the obtained pre-embedded flux solder blank is shown below. Figure 5 As shown, by Figure 5 It can be seen that the solder and aluminum-silicon alloy components in the obtained pre-embedded flux solder blank are uniform. The density of the pre-embedded flux solder blank is measured to be 2.6 g / cm³. 3 .

[0084] (3) The pre-embedded flux filler blank is tightly laid on the upper surface of the aluminum alloy blank as the core material, and then an aluminum-silicon alloy plate blank (4045 aluminum alloy) is covered on the pre-embedded flux filler blank. The three-layer pre-assembled blanks are welded and fixed by spot welding along the perimeter to form a three-layer composite blank. The pre-embedded flux filler blank is then tightly laid on the other surface of the aluminum alloy blank core material of the three-layer composite blank. Then an aluminum-silicon alloy plate blank (4045 aluminum alloy) is covered on the pre-embedded flux filler blank. The pre-assembled blank is then welded and fixed by spot welding along the perimeter to form a five-layer composite blank. In the composite blank, the total thickness of the pre-embedded flux filler blank + aluminum-silicon alloy plate blank on both sides of the aluminum alloy blank core material is about 10% of the total thickness of the composite blank, and the thickness of the pre-embedded flux filler blank on one side / (thickness of the pre-embedded flux filler blank + thickness of the aluminum-silicon alloy plate blank) is about 35%. (4) The welded composite billet is heated in a heating furnace at a temperature of 500°C and held for 3.5 hours. The heated composite billet is hot-rolled in multiple passes into an aluminum alloy composite brazing plate with a thickness of 6 mm. The final rolling temperature is greater than 300°C. The single-pass reduction of the first, second, and third passes of hot rolling is 2%. Subsequent passes of hot rolling are conventional hot rolling. During hot rolling, when the hot-rolled billet reaches a thickness of 75 mm, the head and tail of the rolled billet can be removed before continuing conventional hot rolling. Each pass is rolled from the middle of the composite billet (D) to both sides and the emulsion cooling water must be turned off. A liquid-free low-speed rolling process is adopted to prevent the emulsion from entering the composite interface and affecting the composite effect. After hot rolling is completed, conventional coiling is performed to obtain hot-rolled aluminum coil. After the above hot-rolled plate is cooled, it is cold-rolled in 3 passes to the target thickness of the pre-embedded flux composite aluminum alloy brazing plate strip. The single-pass reduction of the cold rolling is 35%. An annealing is performed before the finished product pass. The attached image shows the finished product. Figure 6 As shown, this indicates that the production process of the pre-embedded flux composite aluminum alloy brazing plate and strip is feasible, and further shows that the pre-embedded flux brazing blank prepared in step (2) has excellent ductility.

[0085] The tensile strength of the obtained product was 116.3 MPa, the yield strength was 69.3 MPa, and the elongation was 36%. Metallographic analysis was performed on a sample of the product's cross-section, and the results are as follows: Figure 7 As shown, the field of view is circular. The gray areas on both sides represent the pre-embedded flux, solder, and aluminum-silicon alloy, while the gold areas represent the core material. Figure 7 It can be seen that the gray area has a clear boundary and is tightly bonded, indicating that the composite interface is good and there are no obvious defects in the interface.

[0086] Brazing experiment: Using a 100mm*100mm pre-embedded flux composite aluminum alloy brazing strip and a 100mm*100mm ZX303 tri-series aluminum alloy strip as experimental subjects, the contact surfaces of both were wiped clean with alcohol, and then the two were stacked together and held at 605℃ for 7 minutes in a muffle furnace. The resulting brazed product is shown below. Figure 8 As shown. By Figure 8 It can be seen that after brazing, the surface of the composite board shows obvious brazing layer melting, and there is solder accumulation on the edge of the bare board. The two layers of board are in close contact and the welding is firm.

[0087] Example 3 The preparation process of pre-embedded flux composite aluminum alloy brazing strip includes: (1) The flux powder and the aluminum-silicon alloy powder are mixed in a weight ratio of 15:85 to form a mixed powder; the flux powder is potassium fluoroaluminate powder with a powder particle size D50 of 10 μm; the aluminum-silicon powder contains 6.5 wt% of silicon (Si) and has an oxygen content of less than 800 ppm, and a particle size D50 of 50 μm; the mixing is performed by a V-shaped universal mixer at a mixing speed of 7 revolutions per minute; and the mixing time is 3.5 hours.

[0088] (2) The mixed powder is pressed into a cylinder by an oil press, and the cylinder is extruded into a rectangular section long strip blank with embedded flux by a semi-continuous extruder, the thickness of the rectangular section long strip blank with embedded flux is 15 mm, and the width is 200 mm; the pressing is normal temperature pressing, and the pressing pressure is above 500 MPa; the extrusion is hot extrusion, and the aluminum powder cylinder (B) needs to be heated to 380 ℃ in a heating furnace and kept for 6 hours before the hot extrusion, and the temperature of the hot extrusion is 380 ℃.

[0089] (3) The long strip blank with embedded flux is tightly laid on the upper surface of the aluminum alloy blank as a core material, and an aluminum-silicon alloy plate blank (4045 aluminum alloy) is covered on the long strip blank with embedded flux, the three-layer pre-assembled blank is welded and fixed by spot welding along the periphery, and the three-layer pre-assembled blank is assembled into a three-layer laminated composite blank, in the composite blank, the total thickness of the long strip blank with embedded flux and the aluminum-silicon alloy plate blank is 10% of the thickness of the composite blank, and the thickness of the long strip blank with embedded flux / (the thickness of the long strip blank with embedded flux + the thickness of the aluminum-silicon alloy plate blank) is 25%. (4) The composite blank after welding is heated in a heating furnace, the heating temperature is 450 ℃, and the holding time is 5 hours; the heated composite blank is hot-rolled into an aluminum alloy composite brazing plate with a thickness of 6 mm by multiple passes, the final rolling temperature is greater than 280 ℃, and the single pass reduction of the first pass, the second pass and the third pass of the hot rolling is 1.6%; the subsequent pass hot rolling is conventional hot rolling, during the hot rolling process, the head and tail of the rolled blank can be removed when the hot rolled blank reaches a thickness of 75 mm, and then the conventional hot rolling is continued; each pass is rolled from the middle to both sides of the composite blank (D) and needs to close the emulsion cooling water, and the liquid-free low-speed rolling process is adopted to prevent the emulsion from entering the composite interface and affecting the composite effect, and after the hot rolling is completed, the conventional coiling is carried out to obtain a hot-rolled aluminum coil; after the hot-rolled plate is cooled, the pre-embedded flux composite aluminum alloy brazing plate strip is obtained by cold rolling for 3 passes to the target thickness; the pass reduction of the cold rolling is 25%; and no annealing is performed between adjacent cold rolling passes.

[0090] Example 4 The preparation process of the pre-embedded flux composite aluminum alloy brazing plate strip includes: (1) The flux powder and the aluminum-silicon alloy powder are mixed in a weight ratio of 15:85 to form a mixed powder; the flux powder is potassium fluoroaluminate powder with a powder particle size D50 of 40 μm; the aluminum-silicon powder contains 12.5 wt% of silicon (Si) and has an oxygen content of less than 800 ppm, and a particle size D50 of 55 μm; the mixing is performed by a V-shaped universal mixer at a mixing speed of 7 revolutions per minute; and the mixing time is 3.5 hours.

[0091] (2) The mixed powder is pressed into a cylinder by an oil press, and the cylinder is extruded into a rectangular section long strip blank with embedded flux by a semi-continuous extruder, the thickness of the rectangular section long strip blank is 15 mm, and the width is 200 mm; the pressing is normal temperature pressing, and the pressing pressure is above 500 MPa; the extrusion is hot extrusion, and the aluminum powder cylinder (B) is heated to 420 ℃ in a heating furnace and kept for 4 hours before the hot extrusion, and the temperature of the hot extrusion is 450 ℃.

[0092] (3) The embedded flux filler metal blank is closely laid on the upper surface of the aluminum alloy blank as a core material, and an aluminum-silicon alloy plate blank (4045 aluminum alloy) is covered on the embedded flux filler metal blank, the three-layer pre-assembled blank is welded and fixed by spot welding along the periphery, and the three-layer laminated composite blank is assembled, in the composite blank, the total thickness of the embedded flux filler metal blank and the aluminum-silicon alloy plate blank is 10% of the thickness of the composite blank, and the thickness of the embedded flux filler metal blank / (thickness of the embedded flux filler metal blank + thickness of the aluminum-silicon alloy plate blank) is 30%; (4) The composite blank after welding is heated in a heating furnace, the heating temperature is 550 ℃, and the holding time is 2 hours; the heated composite blank is hot-rolled into an aluminum alloy composite brazing plate with a thickness of 6 mm by multiple passes, the final rolling temperature is greater than 280 ℃, and the single pass reduction of the first pass, the second pass and the third pass of hot rolling is 2.5%; the subsequent pass hot rolling is conventional hot rolling, during the hot rolling process, the head and tail of the rolled blank are removed when the hot rolling blank reaches a thickness of 75 mm, and then the conventional hot rolling is continued; each pass is rolled from the middle to both sides of the composite blank (D) and needs to close the emulsion cooling water, and the liquid-free low-speed rolling process is adopted to prevent the emulsion from entering the composite interface and affecting the composite effect, and after the hot rolling is completed, the conventional coiling is performed to obtain a hot-rolled aluminum coil; after the hot-rolled plate is cooled, the embedded flux composite aluminum alloy brazing plate strip with a target thickness is obtained by three passes of cold rolling; the pass reduction of the cold rolling is 40%; and annealing is performed between adjacent passes of cold rolling.

[0093] Comparative Example 1 (1) the brazing flux powder and the aluminum-silicon alloy powder are mixed in a weight ratio of 8:92 to form mixed powder; the brazing flux powder is potassium fluoroaluminate powder, the powder particle size D50 is 40 μm; the aluminum-silicon powder contains 12.5wt% of silicon (Si) and less than 800ppm of oxygen, and the particle size D50 is 55 μm; the mixing is performed by a V-shaped universal mixer at a mixing speed of 7 revolutions per minute; and the mixing time is 3.5 hours.

[0094] (2) the mixed powder is hot-rolled into a plate by a powder rolling mill, the powder rolling mill is a 2-roller rolling mill, the hot-rolling temperature is 470℃, and the rolling speed is 2m / min, to obtain a plate with a thickness of 6mm; the plate is heated at 500℃ for 3h in a nitrogen atmosphere to obtain a plate blank with pre-embedded brazing flux; (3) the pre-embedded brazing filler metal blank is tightly laid on the upper surface of an aluminum alloy blank as a core material, and an aluminum-silicon alloy plate blank is covered on the pre-embedded brazing filler metal blank, the three-layer pre-assembled blank is welded and fixed by spot welding along the periphery, and the three-layer pre-assembled blank is assembled into a three-layer laminated composite blank; (4) the composite blank after welding is heated in a heating furnace, the heating temperature is 500℃, and the holding time is 3.5h; the heated composite blank is hot-rolled, and it is found that the pre-embedded brazing filler metal blank has problems of aluminum powder peeling off, easy to break, poor ductility and the like, which leads to the failure of rolling the pre-embedded brazing filler metal blank into one body with the core material and the aluminum-silicon alloy plate blank.

[0095] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a pre-embedded flux aluminum alloy brazing filler blank, characterized in that, include: Aluminum-silicon alloy powder and brazing flux powder are mixed to obtain a mixed powder; The mixed powder is pressed into a cylinder, and then the cylinder is extruded into a pre-embedded flux aluminum alloy brazing filler blank using a semi-continuous extruder.

2. The method for preparing the pre-embedded flux aluminum alloy brazing filler blank as described in claim 1, characterized in that, The pressing is performed at room temperature; the pressing pressure is above 500 MPa. The extrusion is hot extrusion; the extrusion temperature of the hot extrusion is 350~480℃, preferably 380~450℃.

3. The method for preparing the pre-embedded flux aluminum alloy brazing filler blank as described in claim 1, characterized in that, The pre-embedded flux aluminum alloy brazing blank is a long strip blank with a thickness of 5~30mm, a width of 100~400mm, and a rectangular cross-section.

4. The method for preparing the pre-embedded flux aluminum alloy brazing filler blank as described in claim 1, characterized in that, The aluminum-silicon alloy powder is an aluminum-silicon alloy powder containing 6.5wt% to 12.5wt% silicon; the oxygen content of the aluminum-silicon alloy powder is not greater than 800ppm; the particle size D50 of the aluminum-silicon alloy powder is 20 to 55μm. The flux powder is at least one of potassium fluoroaluminate powder and cesium fluoroaluminate powder; the particle size D50 of the flux powder is 10~40μm; The weight ratio of the aluminum-silicon alloy powder to the flux powder is (80~95): (5~20).

5. Aluminum alloy brazing filler blank with pre-embedded brazing flux, characterized in that, Prepared using the preparation method described in any one of claims 1 to 4.

6. A process for preparing pre-embedded flux composite aluminum alloy brazing strip, characterized in that, include: The pre-embedded flux aluminum alloy brazing filler blanks of claim 5 are arranged adjacent to each other on the upper surface of the aluminum alloy core material, so that the pre-embedded flux aluminum alloy brazing filler blanks together form a continuous coating layer, which covers more than 85%, preferably more than 90%, of the upper surface of the aluminum alloy core material. An aluminum-silicon alloy blank is then covered on the surface of the pre-embedded flux aluminum alloy brazing filler blank coating layer to form a sandwich structure pre-assembled blank. The pre-assembled blank is spot-welded around the perimeter to obtain a composite aluminum alloy brazing assembly blank with pre-embedded flux. After heating the assembly blank, it is hot-rolled in multiple passes to obtain a hot-rolled composite plate. The hot-rolled composite plate is then cold-rolled to obtain a pre-embedded flux composite aluminum alloy brazing strip with the target thickness.

7. A process for preparing pre-embedded flux composite aluminum alloy brazing strip, characterized in that, include: The pre-embedded flux aluminum alloy solder blanks of claim 5 are arranged adjacent to each other on the first surface of the aluminum alloy core material, such that the pre-embedded flux aluminum alloy solder blanks together form a continuous coating layer, which covers more than 85%, preferably more than 90%, of the first surface of the aluminum alloy core material; and an aluminum-silicon alloy blank is covered on the surface of the pre-embedded flux aluminum alloy solder blank coating layer to form a first pre-assembled blank with a sandwich structure, and the first pre-assembled blank is spot-welded around the perimeter. The pre-embedded flux aluminum alloy solder blanks of claim 5 are arranged adjacent to each other on the second surface of the aluminum alloy core material of the first pre-assembled blank, so that the pre-embedded flux aluminum alloy solder blanks together form a continuous coating layer, which covers more than 85%, preferably more than 90%, of the second surface of the aluminum alloy core material; and an aluminum-silicon alloy blank is covered on the surface of the pre-embedded flux solder blank coating layer to form a sandwich structure of the second pre-assembled blank, and the second pre-assembled blank is spot welded around the perimeter. After heating the second assembly billet, it is hot-rolled through multiple passes to obtain a hot-rolled composite plate. The hot-rolled composite plate is then cold-rolled to obtain a pre-embedded flux composite aluminum alloy brazing strip with the target thickness.

8. The preparation process of the pre-embedded flux composite aluminum alloy brazing strip as described in claim 6 or 7, characterized in that, The aluminum-silicon alloy slab is any one of 4343, 4045, 4047, 4A13, and 4104 aluminum alloys; preferably, the mass percentage of Si in the aluminum-silicon alloy slab is 6.5~12.5 wt%. The aluminum alloy billet core material is an aluminum alloy plate containing 0.6~1.5wt% Mn; In the pre-assembled blank and the first pre-assembled blank, the sum of the thicknesses of the pre-embedded flux aluminum alloy solder blank and the aluminum-silicon alloy blank is 5-20% of the total thickness of the pre-assembled blank; the thickness of the pre-embedded flux aluminum alloy solder blank is 25-50% of the total thickness of the pre-embedded flux aluminum alloy solder blank and the aluminum-silicon alloy blank. In the second pre-assembled blank, the sum of the thicknesses of the aluminum alloy core material's pre-embedded flux aluminum alloy solder blank and the aluminum-silicon alloy blank is independently 5-20% of the total thickness of the pre-assembled blank; the thicknesses of the aluminum alloy core material's pre-embedded flux aluminum alloy solder blank are independently 25-50% of the total thickness of the pre-embedded flux aluminum alloy solder blank and the aluminum-silicon alloy blank.

9. The preparation process of the pre-embedded flux composite aluminum alloy brazing strip as described in claim 6 or 7, characterized in that, The heating temperature is 450~600℃, preferably 500~550℃; the heat preservation time is 1~6h, preferably 2~5h; The hot rolling is a multi-pass hot rolling; the final rolling temperature of the hot rolling is not lower than 250°C, preferably not lower than 280°C; The single-pass reduction in the first to third passes of the hot rolling is less than 3%, preferably 0.5% to 2.5%; the hot rolling process involves rolling from the middle of the sheet material outwards to both sides. The hot rolling is a low-speed rolling process, and the coolant needs to be turned off during the hot rolling process to achieve liquid-free emulsification; The cold rolling is a multi-pass cold rolling; the reduction per pass of the cold rolling is 25-50%, preferably 25-40%; annealing may or may not be performed between adjacent cold rolling passes; The thickness of the hot-rolled composite plate is 5~8mm.

10. A brazing strip of composite aluminum alloy with pre-embedded flux, characterized in that, It is prepared by the preparation method described in any one of claims 6 to 9.

11. The application of the pre-embedded flux composite aluminum alloy brazing plate and strip as described in claim 10 in aluminum heat exchangers.

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