Controllable atmosphere brazed composite aluminum plate and preparation method thereof

Abstract

The invention relates to a controlled atmosphere brazed composite aluminum plate and a preparation method thereof, the controlled atmosphere brazed composite aluminum plate comprises a filler layer and a non-filler layer which are sequentially arranged, the filler layer is fused during braze welding, the non-filler layer is not fused during braze welding, the non-filler layer comprises a core layer and a corrosion protection layer, and the filler layer comprises a brazing filler metal layer; the corrosion protection layer is arranged between the core layer and the brazing filler metal layer; a base body of the corrosion protection layer is a 1XXX series aluminum alloy; the thickness of the corrosion protection layer is smaller than or equal to 40 microns and larger than or equal to the corrosion thickness in the target brazing environment; the brazing filler metal layer is filler alloy; the ratio of the thickness of the filler layer to the thickness of the non-filler layer is at most 0.2; the preparation method of the controlled atmosphere brazed composite aluminum plate comprises the working procedures of raw material preparation, hot rolling compounding, cold rolling and annealing. According to the controlled atmosphere brazing composite aluminum plate, the corrosion protection layer is arranged between the brazing filler metal layer and the core layer and can prevent the brazing filler metal layer from melting to corrode the core layer during brazing; according to the method, the degree of brazing corrosion is reduced to a great extent, and the process is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of brazing composite aluminum plates, and relates to a method for preparing a composite aluminum plate for controlled atmosphere brazing. Background Art

[0002] In the brazing process, low-melting-point 4XXX series aluminum-silicon alloys are usually used as brazing filler metals. Such aluminum-silicon alloys contain a large amount of alloying element silicon, and generally the higher the silicon content, the lower the melting point of the aluminum alloy. The brazing temperature is generally higher than the liquidus temperature of the brazing filler metal, so that at this temperature, as the brazing filler metal melts, under the influence of capillary action, the brazing filler metal can wet the materials to be welded to form a welded joint. At the same time, the brazing temperature should be lower than the solidus temperature of the core layer so that the mechanical properties of the material can be basically maintained.

[0003] However, during brazing, the molten brazing material will inevitably cause brazing corrosion to the core layer, thereby reducing the mechanical properties of the core layer. Brazing corrosion is related to the suitability of the brazing temperature and the alloy composition of the core layer itself. To this end, there are several existing methods to reduce core corrosion:

[0004] First, lower the brazing temperature or shorten the brazing time. For example, literature 1 (Effects of brazing temperature and brazing filler metal coverage on aluminum alloy corrosion [J]. Metal Heat Treatment, 2005, (12): 13-15.) found that the higher the brazing temperature, the more complete the corrosion process, the deeper the brazing filler metal penetrates into the core material, and the greater the risk and harm of corrosion. Although lowering the brazing temperature can reduce the risk of brazing corrosion, it will lead to poor brazing quality and the occurrence of cold welds.

[0005] Secondly, by increasing the grain size and reducing the number of grain boundaries, the corrosion resistance of the core layer can be improved. The grain boundary is a high-speed channel for Si to diffuse and penetrate into the core material to form corrosion. The smaller the grain, the more grain boundaries there are, and the more serious the grain boundary penetration. However, changing the grain size generally requires complex processing technology, which is a long process and increases the cost. In addition, the larger the grain size, the better, but it must be controlled within a certain range. For example, Reference 2 (Effect of Processing Technology on the Corrosion Performance of Brazing Aluminum Alloy Fins for Radiators [J]. Nonferrous Metal Materials and Engineering, 2022, 43(03): 37-42.) Through high-temperature intermediate annealing, cold rolling, secondary intermediate annealing, cold finishing rolling and other complex processes, it was found that when the grain size is 100-400μm, the diffusion of Si can be more comprehensively and effectively hindered during the brazing process.

[0006] Therefore, it is of great significance to study a composite aluminum plate for controlled atmosphere brazing and a preparation method thereof to solve the problems existing in the prior art. Summary of the invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and to provide a composite aluminum plate for controlled atmosphere brazing and a preparation method thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A composite aluminum plate for controlled atmosphere brazing, comprising a filler layer and a non-filler layer arranged in sequence, wherein the filler layer melts during brazing, and the non-filler layer does not melt during brazing, the non-filler layer comprises a core layer and an ablation protection layer, and the filler layer comprises a brazing material layer; the ablation protection layer is arranged between the core layer and the brazing material layer;

[0010] The matrix of the ablation protection layer is a 1XXX series aluminum alloy; the material of the ablation protection layer can be prepared by any suitable method for obtaining a matrix of a 1XXX series aluminum alloy containing flux particles; including but not limited to hot isostatic pressing, cold isostatic pressing, vacuum hot pressing, spray forming or a direct powder mixing hot rolling forming method as disclosed in CN114473385A.

[0011] The thickness of the ablation protection layer is ≤40μm and is greater than or equal to the ablation thickness in the target brazing environment; this can help avoid core layer ablation without compromising the thickness ratio of the core layer. After brazing, the brazing material layer is melted, so the composite layer is composed of alloy layers such as the ablation protection layer and the core layer that still maintain a solid shape. These layers constitute the overall thickness of the composite layer after welding, and the core layer that is not ablated after welding is the main strength contributor. Therefore, in composite layers of the same thickness, the thinner the ablation protection layer, the relatively thicker the core layer, and the relatively higher the simulated tensile strength after welding; but the thickness of the ablation protection layer is at least greater than or equal to the ablation thickness in the target brazing environment to ensure that the core layer is not ablated.

[0012] The brazing material layer is a filler alloy; the term "filler alloy" refers to a filler alloy that can be completely melted at the brazing temperature and form a bond with the surface to be welded, generally set to a 4XXX series aluminum-silicon alloy; the ratio of the filler layer thickness to the non-filler layer thickness is at most 0.2; the filler layer melts to form a liquid phase during brazing, and the relatively excessive amount of liquid phase will cause more severe corrosion to the surface of the non-filler layer that contacts the liquid phase.

[0013] The brazing temperature should be higher than the liquidus temperature of the filler alloy and lower than the melting point of the non-filler alloy. Since the melting point of the non-filler alloy, such as the corrosion protection layer and / or core layer in the technical solution, is usually above 630°C, and the liquidus temperature of the 4XXX series aluminum-silicon filler alloy is generally around 570°C, a suitable brazing temperature can be selected between the two, and 610°C brazing is generally selected.

[0014] In order to reduce the core layer corrosion phenomenon, the present invention sets a corrosion protection layer between the brazing material layer and the core layer, and the corrosion protection layer can prevent the melting of the brazing material layer from corroding the core layer during brazing. The inventor found that the 1XXX series aluminum alloy has low corrosion characteristics, and it is introduced into the composite material as a corrosion protection layer to avoid the corrosion of the core layer. When brazing, the thickness of the brazing corrosion protection layer can be reduced to less than 40μm, or even 20μm, while the core layer corrosion depth is usually at least 60μm, and some are even as high as 100μm. The corroded core layer will lose its contribution to the mechanical strength of the aluminum alloy material. When a very thin corrosion protection layer is used to replace a part of the core layer close to the brazing material layer, the core layer material can be prevented from being corroded. This is because the aluminum matrix alloy of the corrosion protection layer is selected from an alloy with a melting point higher than the brazing temperature, so it will not melt during the brazing process, and plays a role in protecting the core layer, so that the corrosion phenomenon acts on the protective layer, and does not corrode the core layer. That is, the thickness of the core layer that has not been dissolved after brazing will be relatively increased, and the tensile strength after brazing will be increased simultaneously.

[0015] As the preferred technical solution:

[0016] In the controlled atmosphere brazing composite aluminum plate as described above, the filler layer also includes a pre-embedded flux layer, which is a filler alloy containing 2 to 10 wt% of inorganic flux, and the pre-embedded flux layer is arranged between the ablation protection layer and the brazing material layer.

[0017] In a composite aluminum plate for controlled atmosphere brazing as described above, the thickness of the pre-embedded flux layer is at most 60% of the thickness of the filler layer; the ratio of the thickness of the filler layer to the thickness of the non-filler layer is at least 0.1. Both the pre-embedded flux layer and the solder layer are filler alloys, and both will form a liquid phase during brazing, so the sum of the thickness of the two layers determines the amount of liquid phase. Since the alloy layer with the pre-embedded flux is extremely brittle, it is necessary to cover it with a solder layer, otherwise it will be difficult to process. The sum of the thickness of the pre-embedded flux layer and the solder layer is affected by the processability and the requirements for the pre-embedded flux amount.

[0018] In the above-mentioned controlled atmosphere brazing composite aluminum plate, the ablation protection layer contains 2 to 10 wt% of fluoride brazing flux, too little will not effectively break the film, and too much will deepen the dissolution depth; and the diffusion coefficient of the fluoride brazing flux is ≥3×10 -15 m 2 s -1 Compared with the conventional method of pre-embedding the brazing agent in the brazing material layer alloy, one of the advantages of the present invention is that the amount of brazing material is further reduced while ensuring the brazing quality, thereby slowing down the dissolution.

[0019] During the brazing process, as the temperature increases, part of the fluoride will enter the molten state and release part of the fluoride ions, among which the fluoride ions will enter the filler layer through the gap of the pre-embedded aluminum alloy of the film-breaking layer, helping the AlSi alloy of the filler layer to break the film and melt, and complete the brazing. Compared with the method of pre-embedded brazing flux using filler alloy, when the fluoride brazing flux is pre-embedded in the ablation protection layer, the filler alloy required for brazing is significantly reduced. The prior art generally pre-embeds fluoride in the Al-Si filler alloy. Under the same composite ratio, the present invention pre-embeds fluoride in the 1XXX series aluminum alloy that will not melt. During brazing, the content of the Al-Si filler alloy that forms the liquid phase will be relatively reduced, and the ablation will also be weakened. The inventor found that even under the condition of thinning the brazing material layer, when the brazing flux is pre-embedded in the brazing material, under the brazing temperature conditions, the wettability of the brazing material is aggravated, and the damage to the ablation protection layer will be aggravated.

[0020] The present invention creatively introduces fluoride flux into the ablation protection layer, which can reduce the degree of dissolution of the ablation protection layer during brazing. Since the melting point of the ablation protection layer is higher than the brazing temperature, it is still in a solid state compared to the brazing alloy during brazing, which is not conducive to the diffusion of the flux. Compared with the solution of pre-embedding the flux in the filler alloy, when the 1XXX series aluminum alloy is used as the pre-embedded matrix, there are certain requirements for the type of flux used, and a fluoride flux with a high diffusion coefficient needs to be used. During brazing, the fluoride flux can make use of the inevitable ablation surface formed during brazing of the ablation protection layer to smoothly diffuse to the material surface and break the film. Otherwise, during brazing, the flux may not be able to smoothly diffuse to the material surface to help break the film.

[0021] As the preferred technical solution:

[0022] In the above-mentioned controlled atmosphere brazing composite aluminum plate, when the fluoride brazing flux material is pre-embedded in the ablation protection layer, the thickness of the ablation protection layer is at least 20 μm. Insufficient thickness will lead to insufficient brazing flux. The thickness of the ablation protection layer and the concentration of the pre-embedded brazing flux should be matched so that the fluoride loading is 2 g / m 2 The ratio of the thickness of the filler layer to the thickness of the non-filler layer is at least 0.04. During brazing, the brazing material layer melts and flows to form a welded joint. If the thickness of the brazing material layer is too small, sufficient welding filler cannot be obtained. If the thickness is too large, the melting corrosion is aggravated, and even the melting corrosion breaks through the melting corrosion protection layer to the core layer.

[0023] As described above, in a composite aluminum plate for controlled atmosphere brazing, the core layer is an aluminum alloy with a tensile strength ≥140MPa, and the core layer alloy can be a 3XXX series alloy or a 3XXX series improved alloy or other high-strength alloy; the core layer selects an aluminum alloy modified by strengthening alloy elements, and its tensile strength is much greater than that of pure aluminum alloy; the total amount of alloy elements in the core layer is ≥1.0wt%, and the Mg element content is ≤0.2wt%; although the Mg element can be strengthened by aging, the Mg element in the core layer will react with the brazing flux in the ablation protective layer and consume the brazing flux, and when the Mg element content in the core layer is controlled to a concentration below 0.2wt%, it basically does not affect the brazing flux in the ablation protective layer.

[0024] The present invention also provides a method for preparing a composite aluminum plate for controlled atmosphere brazing as described in any one of the above items, comprising the steps of raw material preparation, hot rolling and composite, cold rolling and annealing;

[0025] (1) preparing a core layer slab, a melt protection layer slab and a brazing material layer slab;

[0026] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them to a target thickness;

[0027] (3) The composite aluminum plate is obtained through cold rolling and annealing.

[0028] As the preferred technical solution:

[0029] In the method for preparing a composite aluminum plate for controlled atmosphere brazing as described above, the hot rolling temperature in step (2) is 430-480° C.;

[0030] The cold rolling reduction in step (3) is ≥50%, the final thickness of the cold rolling is selected according to product requirements, and the annealing conditions are selected according to customer requirements to achieve the target state.

[0031] Beneficial Effects

[0032] (1) In the controlled atmosphere brazing composite aluminum plate of the present invention, a corrosion protection layer is provided between the brazing material layer and the core layer, and the corrosion protection layer can prevent the brazing material layer from melting and corroding the core layer during brazing.

[0033] (2) In the controlled atmosphere brazing composite aluminum plate of the present invention, fluoride brazing flux is introduced into the erosion protection layer, which can reduce the degree of dissolution of the erosion protection layer during the brazing process.

[0034] (3) The method for preparing a composite aluminum plate by controlled atmosphere brazing of the present invention greatly reduces the degree of brazing corrosion and has a simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1Schematic diagram of the preparation of composite aluminum plate for controlled atmosphere brazing;

[0036] Figure 2 This is a cross-sectional metallographic image of the sample prepared in Example 1 after simulated brazing;

[0037] Figure 3 This is a cross-sectional metallographic image of the sample prepared in Comparative Example 2 after simulated brazing;

[0038] Among them, 1 is the core layer, 2 is the ablation protection layer, 3 is the ablated part of the ablation protection layer, and 4 is the solder layer. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0040] The test methods involved in the performance indicators of the present invention are as follows:

[0041] Melting point: also known as solidus temperature. The melting point of the sample was tested using a DSC model STA449 from NETZSCH, Germany. The heating curve was from room temperature to 700°C at a rate of 10°C / min, and then cooled to 50°C in an argon atmosphere. The melting point of the sample was obtained by automatic analysis using the software.

[0042] Diffusion coefficient: The sample was placed in a muffle furnace, heated to 400°C, kept warm for 30 minutes, and then air-cooled. A line scan was performed on ten randomly selected sample sections using EPMA-1720 from Shimadzu Corporation, Japan, and the average diffusion distance was calculated using the formula x 2 =6D*t, where x is the diffusion distance, D is the diffusion coefficient, and t is the heat treatment time. The diffusion coefficients of different samples were calculated.

[0043] Corrosion depth: The cross-section of the sample after simulated brazing was photographed using a Zeiss optical microscope (model: ZeissAxio). The corrosion depth was measured using the Axio Vision SE64 (version: 4) software provided with the optical microscope. Ten positions were randomly selected for measurement on each sample, and the mathematical average was taken as the average corrosion depth of the sample.

[0044] Brazing performance (T-type brazing test): The sample prepared by the present invention is processed into a specification size of 23mm×58mm, and placed on the surface of a 3003 alloy with a thickness×width×length of 2mm×25mm×60mm. Then, a piece of 3003 alloy with a thickness×width×length of 1mm×25mm×55mm is vertically placed on the upper part of a single-layer brazable aluminum alloy material, and the other end is padded and fixed with a steel wire with a diameter of 1mm, so that the distance from the contact point between the vertical 3003 alloy and the sample to the steel wire is maintained at 50mm, and a "T"-shaped tooling sample with an inverted cross section is made, referred to as a T-type sample (the construction of the T-type sample refers to CN115927923A); the T-type sample is placed in a continuous furnace (CAB furnace) protected by a nitrogen atmosphere for brazing, and the target brazing temperature and time conditions are set. The belt speed is 350mm / min, and the formation of the weld is observed and counted, and the weld length is measured. The weld length is greater than or equal to 15mm, which means that the brazing is qualified.

[0045] Tensile strength after welding: The tensile strength test of the sample after simulated brazing adopts the standard method of GB / T 228.1-2021 "Room temperature tensile properties Part 1: Test method", and the tensile strength of the sample after simulated brazing is determined by a Zwick universal testing machine.

[0046] According to the current experimental results, it is believed that the corrosion protection layer of the present invention can avoid the dissolution of the core layer during the brazing process. The core layer mainly contributes to the mechanical properties of the composite plate. The mechanical properties of the core layer material and the thickness ratio in the composite plate determine the mechanical properties of the composite plate. Compared with the prior art solutions, the present invention can obtain better post-weld tensile strength under the condition of using the same core layer aluminum alloy. In order to better illustrate the problem, those skilled in the art can understand the inventive concept and the contribution made by the present invention on the basis of the prior art. The core layer aluminum alloy materials used in the embodiments of the present invention are all core layer aluminum alloys. The strength and toughness levels of the core aluminum alloy affect the strength and toughness levels of the composite material. Therefore, those skilled in the art can freely choose according to their needs.

[0047] Some raw material information of the present invention is as follows:

[0048] Core layer aluminum alloy: 3003 alloy, Mn 1.5wt%, Cu 0.2wt%, Zn 0.1wt%, Fe 0.3wt%, Si0.2wt%, Mg 0.05wt%; its tensile strength is 140MPa, and its elongation at break is 15%;

[0049] Ablation protection layer aluminum alloy I: 1050 series aluminum alloy, Si 0.18wt%, Fe 0.25wt%, total alloy element 0.5wt%, melting point 643℃;

[0050] Ablation protection layer aluminum alloy II: 1100 series aluminum alloy, Si 0.3wt%, Fe 0.4wt%, Cu 0.2wt%, total alloy element amount is 1.0wt%, melting point is 632℃;

[0051] Ablation protection layer aluminum alloy III: 1060 series aluminum alloy, Si 0.1wt%, Fe 0.1wt%, Mn 0.1wt%, total alloy element 0.4wt%, melting point 648℃;

[0052] Fluoride flux I: potassium hexafluoroaluminate, diffusion coefficient 3.1×10 -15 m 2 s -1 ;

[0053] Fluoride flux II: cesium fluoride, diffusion coefficient 7.6×10 -15 m 2 s -1 ;

[0054] Fluoride flux III: calcium fluoride, diffusion coefficient 7.4×10 -16 m 2 s -1 ;

[0055] Pre-embedded brazing flux layer aluminum alloy: 4XXX series filler alloy, AA4045, Si 10.2wt%;

[0056] Brazing filler layer aluminum alloy: 4XXX series filler alloy, AA4045, Si 10.2wt%.

[0057] Example 1

[0058] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0059] (1) Raw material preparation:

[0060] Core slab: core aluminum alloy, made of 3003 alloy, thickness 18mm;

[0061] Ablation protective layer slab: Ablation protective layer aluminum alloy I, made of 1050 series aluminum alloy, pre-embedded with 5wt% fluoride brazing flux I, with a thickness of 1.2mm;

[0062] Brazing material layer blank: material is AA4045, thickness is 0.8mm;

[0063] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 450° C. to a target thickness of 1500 μm;

[0064] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 60% and the target annealing state is 0 state.

[0065] like Figure 1 As shown, the composite aluminum plate for controlled atmosphere brazing finally obtained includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer 1 and an ablation protection layer 2, the filler layer is a brazing material layer 4, and the ablation protection layer 2 is located between the core layer 1 and the brazing material layer 4; the thickness of the composite aluminum plate for controlled atmosphere brazing is 600 μm; the ratio of the thickness of the filler layer to the thickness of the non-filler layer is 4:100; the thickness of the ablation protection layer is 36 μm, and the fluoride brazing flux loading amount of the composite aluminum plate for controlled atmosphere brazing is 5 g / m 2 .

[0066] The composite aluminum plate of controlled atmosphere brazing was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt during brazing. Figure 2 The cross section of the sample after simulated brazing is shown. Figure 2 The dissolution zone in Figure 1 The part of the corrosion protection layer that was melted was 3; after mathematical statistics, the average corrosion depth under the target brazing environment was 16μm; the tensile strength of the composite aluminum plate brazed in controlled atmosphere was 141.1MPa, and the T-type brazing test was qualified.

[0067] Comparative Example 1

[0068] A method for preparing a composite aluminum plate is basically the same as that in Example 1, except that the ablation protection layer slab does not contain fluoride brazing agent I, a pre-embedded brazing agent layer is arranged between the ablation protection layer and the brazing material layer, the filler layer comprises a brazing material layer and a pre-embedded brazing agent layer, the thickness of the pre-embedded brazing agent layer slab is 0.6 mm, the thickness of the brazing material layer slab is 0.2 mm, so that the total thickness of the filler layer is consistent with that in Example 1, the concentration of fluoride brazing agent I in the pre-embedded brazing agent layer slab is adjusted to 10 wt% to match the thickness of the ablation protection layer, so that the loading amount of fluoride brazing agent I is equal to that in Example 1; because the brazing material layer of Comparative Example 1 is too thin, the composite rolling fails and cracks occur.

[0069] Example 2

[0070] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0071] (1) Raw material preparation:

[0072] Core slab: core aluminum alloy, made of 3003 alloy, 36mm thick;

[0073] Ablation protection layer slab: Ablation protection layer aluminum alloy II, made of 1100 series aluminum alloy, pre-embedded with 10wt% fluoride brazing flux I, with a thickness of 1.34mm;

[0074] Brazing material layer blank: material is AA4045, thickness is 2.7mm;

[0075] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 430° C. to a target thickness of 1200 mm;

[0076] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 50% and the target annealing state is 0 state.

[0077] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a erosion protection layer, the filler layer is a brazing material layer, and the erosion protection layer is located between the core layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 600 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 7:100; the thickness of the erosion protection layer is 20 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 5.6 g / m 2 ; The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt during brazing. The corrosion depth under the target brazing environment was 19μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 147.3MPa, and the T-type brazing test was qualified.

[0078] Example 3

[0079] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0080] (1) Raw material preparation:

[0081] Core slab: core aluminum alloy, made of 3003 alloy, thickness 24mm;

[0082] Ablation protection layer slab: Ablation protection layer aluminum alloy III, made of 1060 series aluminum alloy, pre-embedded with 2wt% fluoride brazing flux II, with a thickness of 1.32mm;

[0083] Brazing material layer blank: material is AA4045, thickness is 4.3mm;

[0084] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 480° C. to a target thickness of 2000 mm;

[0085] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, the cold rolling reduction is 55%, and the target annealing state is 0 state.

[0086] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a erosion protection layer, the filler layer is a brazing material layer, and the erosion protection layer is located between the core layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 900 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 17:100; the thickness of the erosion protection layer is 40 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 2.2 g / m 2 The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt. The corrosion depth under the target brazing environment was 14μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 143.5MPa, and the T-type brazing test was qualified.

[0087] Example 4

[0088] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0089] (1) Raw material preparation:

[0090] Core slab: core aluminum alloy, made of 3003 alloy, thickness 18mm;

[0091] Ablation protection layer slab: Ablation protection layer aluminum alloy I, made of 1050 series aluminum alloy, pre-embedded with 5wt% fluoride brazing flux III, with a thickness of 1.2mm;

[0092] Brazing material layer blank: material is AA4045, thickness is 0.8mm;

[0093] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 450° C. to a target thickness of 1500 mm;

[0094] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 60% and the target annealing state is 0 state.

[0095] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a erosion protection layer, the filler layer is a brazing material layer, and the erosion protection layer is located between the core layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 600 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 4:100; the thickness of the erosion protection layer is 36 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 5 g / m2 The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt. The corrosion depth under the target brazing environment was 28μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 140.6MPa. It could not be directly brazed in the T-type brazing test. After applying flux on the surface, the T-type brazing test was qualified.

[0096] Example 5

[0097] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0098] (1) Raw material preparation:

[0099] Core slab: core aluminum alloy, made of 3003 alloy, thickness 18mm;

[0100] Ablation protective layer slab: Ablation protective layer aluminum alloy I, made of 1050 series aluminum alloy, with a thickness of 1.2 mm;

[0101] Brazing material layer blank: material is AA4045, thickness is 0.8mm;

[0102] (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 450° C. to a target thickness of 1500 mm;

[0103] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 60% and the target annealing state is 0 state.

[0104] The final controlled atmosphere brazing composite aluminum plate comprises a filler layer and a non-filler layer arranged in sequence, the non-filler layer comprises a core layer and a corrosion protection layer, the filler layer is the brazing material layer, and the corrosion protection layer is located between the core layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 600 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 4:100; the thickness of the corrosion protection layer is 36 μm; the controlled atmosphere brazing composite aluminum plate is simulated brazing under the brazing conditions of 610°C and 15 min, the filler layer melts during brazing, and the non-filler layer does not melt during brazing; the corrosion depth under the target brazing environment is 28 μm; the tensile strength of the controlled atmosphere brazing composite aluminum plate is 140.2 MPa, and it cannot be directly brazed in the T-type brazing test. After applying flux on the surface, the T-type brazing test is qualified.

[0105] Comparative Example 2

[0106] A method for preparing a composite aluminum plate is basically the same as Example 5, except that the ablation protective layer is not included and a core layer blank of the same thickness is used to replace the ablation protective layer blank.

[0107] The final clad aluminum plate has a melting depth of 72 μm under the target brazing environment; the tensile strength of the clad aluminum plate is 131.9 MPa. Figure 3 The figure shows the cross section after brazing simulation in Example 2. Figure 3 The dissolution zone in the figure is the part of the core layer that is dissolved. According to mathematical statistics, the average dissolution depth is 72 μm.

[0108] Comparing Comparative Example 2 with Example 5, it can be found that the ablation depth of Comparative Example 2 is larger and the tensile strength is smaller. This is because the filler layer melts and directly dissolves the core layer during the brazing process after the ablation protection layer is missing, resulting in a larger ablation depth of the core layer. The dissolved part cannot contribute to the tensile strength of the composite material, resulting in performance deterioration.

[0109] Example 6

[0110] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0111] (1) Raw material preparation:

[0112] Core slab: core aluminum alloy, made of 3003 alloy, thickness 18mm;

[0113] Ablation protective layer slab: Ablation protective layer aluminum alloy I, made of 1050 series aluminum alloy, with a thickness of 1.2 mm;

[0114] Pre-embedded flux layer slab: AA4045 filler alloy containing 5wt% fluoride flux I, thickness 1.2mm;

[0115] Brazing material layer blank: material is AA4045, thickness is 0.8mm;

[0116] (2) stacking the prepared core layer slab, the ablation protection layer slab, the pre-embedded flux layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 450° C. to a target thickness of 1590 mm;

[0117] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 60% and the target annealing state is 0 state.

[0118] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a corrosion protection layer, and the filler layer includes a brazing material layer and a pre-embedded brazing flux layer; the corrosion protection layer is located between the core layer and the brazing material layer, and the pre-embedded brazing flux layer is located between the corrosion protection layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 636 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 10:100; the thickness of the corrosion protection layer is 36 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 5 g / m 2 ; The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt during brazing. The corrosion depth under the target brazing environment was 21μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 140.8MPa, and the T-type brazing test was qualified.

[0119] Comparative Example 3

[0120] A method for preparing a composite aluminum plate is basically the same as Example 6, except that the ablation protective layer is not included and a core layer blank of the same thickness is used to replace the ablation protective layer blank.

[0121] The final composite aluminum plate has a target brazing environment and a dissolution depth of 65 μm; the tensile strength of the composite aluminum plate is 133.2 MPa.

[0122] By comparing Comparative Example 3 and Example 6, it can be found that the corrosion depth of Comparative Example 3 becomes larger and the tensile strength becomes smaller. This is because the filler layer melts during the brazing process in the absence of the corrosion protection layer and directly dissolves the core layer, resulting in a larger corrosion depth of the core layer. The dissolved part cannot contribute to the tensile strength of the composite material, resulting in performance deterioration.

[0123] Comparative Example 4

[0124] A method for preparing a composite aluminum plate is basically the same as Example 6, except that the thickness of the core layer slab is 16.2 mm and the thickness of the ablation protection layer slab is 3 mm.

[0125] The thickness of the corrosion protection layer of the final composite aluminum plate under the target brazing environment is 90 μm, and the corrosion depth under the target brazing environment is 21 μm; the tensile strength of the composite aluminum plate is 127 MPa.

[0126] By comparing Comparative Example 3 with Example 6, it can be found that in Comparative Example 3, because the corrosion protection layer is too thick, it exceeds the conventional core material corrosion loss thickness when no corrosion protection layer is set. Under the same non-filler layer thickness, the relative core material thickness is reduced, resulting in a decrease in tensile strength, and the significance of strength improvement is lost.

[0127] Example 7

[0128] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0129] (1) Raw material preparation:

[0130] Core slab: core aluminum alloy, made of 3003 alloy, 30mm thick;

[0131] Ablation protective layer slab: Ablation protective layer aluminum alloy II, made of 1100 series aluminum alloy, with a thickness of 1.8 mm;

[0132] Pre-embedded brazing flux layer slab: AA4045 filler alloy containing 10wt% fluoride brazing flux II, thickness 1.8mm;

[0133] Brazing material layer blank: material is AA4045, thickness is 2.3mm;

[0134] (2) stacking the prepared core layer slab, the ablation protection layer slab, the pre-embedded flux layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 430° C. to a target thickness of 1600 mm;

[0135] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 65% and the target annealing state is 0 state.

[0136] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a corrosion protection layer, the filler layer includes a brazing material layer and a pre-embedded brazing flux layer; the corrosion protection layer is located between the core layer and the brazing material layer, and the pre-embedded brazing flux layer is located between the corrosion protection layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 560 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 13:100; the thickness of the corrosion protection layer is 28 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 7.8 g / m 2 ; The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt during brazing. The corrosion depth under the target brazing environment was 24μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 143.1MPa, and the T-type brazing test was qualified.

[0137] Example 8

[0138] A method for preparing a composite aluminum plate for controlled atmosphere brazing, the specific steps are as follows:

[0139] (1) Raw material preparation:

[0140] Core slab: core aluminum alloy, made of 3003 alloy, 25mm thick;

[0141] Ablation protective layer slab: Ablation protective layer aluminum alloy III, made of 1060 series aluminum alloy, with a thickness of 1mm;

[0142] Pre-embedded brazing flux layer slab: AA4045 filler alloy containing 6wt% fluoride brazing flux II, thickness 1.4mm;

[0143] Brazing material layer blank: material is AA4045, thickness is 3.8mm;

[0144] (2) stacking the prepared core layer slab, the ablation protection layer slab, the pre-embedded flux layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them at a temperature of 480° C. to a target thickness of 1600 mm;

[0145] (3) A composite aluminum plate for controlled atmosphere brazing is obtained after cold rolling and annealing, wherein the cold rolling reduction is 50% and the target annealing state is 0 state.

[0146] The finally obtained controlled atmosphere brazing composite aluminum plate includes a filler layer and a non-filler layer arranged in sequence, the non-filler layer includes a core layer and a corrosion protection layer, the filler layer includes a brazing material layer and a pre-embedded brazing flux layer; the corrosion protection layer is located between the core layer and the brazing material layer, and the pre-embedded brazing flux layer is located between the corrosion protection layer and the brazing material layer; the thickness of the controlled atmosphere brazing composite aluminum plate is 800 mm; the ratio of the filler layer thickness to the non-filler layer thickness is 20:100; the thickness of the corrosion protection layer is 26 μm, and the fluoride brazing flux loading amount of the controlled atmosphere brazing composite aluminum plate is 6 g / m 2 The composite aluminum plate brazed by controlled atmosphere was simulated brazing under the brazing conditions of 610℃ and 15min. The filler layer melted during brazing, while the non-filler layer did not melt. The corrosion depth under the target brazing environment was 23μm. The tensile strength of the composite aluminum plate brazed by controlled atmosphere was 147.2MPa, and the T-type brazing test was qualified.

Claims

1. A composite aluminum plate for controlled atmosphere brazing, comprising a filler layer and a non-filler layer arranged in sequence, wherein the filler layer melts during brazing, and the non-filler layer does not melt during brazing, characterized in that: The non-filler layer includes a core layer and an ablation protection layer, and the filler layer includes a solder layer; the ablation protection layer is arranged between the core layer and the solder layer; The substrate of the ablation protection layer is a 1XXX series aluminum alloy; The thickness of the ablation protection layer is ≤40 μm and is greater than or equal to the ablation thickness under the target brazing environment; The solder layer is a filler alloy; the ratio of the thickness of the filler layer to the thickness of the non-filler layer is at most 0.

2.

2. The composite aluminum plate for controlled atmosphere brazing according to claim 1, characterized in that: The filler layer further comprises a pre-embedded brazing flux layer, which is a filler alloy containing 2-10 wt% of inorganic brazing flux, and the pre-embedded brazing flux layer is arranged between the ablation protection layer and the brazing material layer.

3. The composite aluminum plate for controlled atmosphere brazing according to claim 2, characterized in that: The thickness of the pre-embedded flux layer is at most 60% of the thickness of the filler layer; and the ratio of the thickness of the filler layer to the thickness of the non-filler layer is at least 0.

1.

4. The composite aluminum plate for controlled atmosphere brazing according to claim 1, characterized in that: The ablation protection layer contains 2-10 wt% of fluoride flux, and the diffusion coefficient of the fluoride flux is ≥3×10 -15 m 2 s -1 .

5. The composite aluminum plate for controlled atmosphere brazing according to claim 4, characterized in that: The thickness of the ablation protection layer is at least 20 μm, and the fluoride flux loading is 2 g / m 2 Above; the ratio of the thickness of the filler layer to the thickness of the non-filler layer is at least 0.

04.

6. A composite aluminum plate for controlled atmosphere brazing according to any one of claims 1 to 5, characterized in that: The core layer is an aluminum alloy with a tensile strength of ≥140 MPa; the total amount of alloy elements in the core layer is ≥1.0wt%, and the Mg element content is ≤0.2wt%.

7. The method for preparing a composite aluminum plate for controlled atmosphere brazing according to any one of claims 1 to 6, characterized in that: Including raw material preparation, hot rolling and laminating, as well as cold rolling and annealing processes; (1) preparing a core layer slab, a melt protection layer slab and a brazing material layer slab; (2) stacking the prepared core layer slab, the ablation protection layer slab and the brazing material layer slab in sequence, and hot rolling and laminating them to a target thickness; (3) The composite aluminum plate is obtained through cold rolling and annealing.

8. The method for preparing a composite aluminum plate for controlled atmosphere brazing according to claim 7, characterized in that: In step (2), the hot rolling temperature is 430-480° C.; The cold rolling reduction in step (3) is ≥50%.

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