A preformed aluminum piece brazing material, and a preparation method and application thereof

Abstract

The application discloses a preformed aluminum piece brazing material and a preparation method and application thereof, and belongs to the technical field of brazing. The product is combined with the composite aluminum powder and the magnesium net with the copper oxide shell protection structure, nickel powder is introduced for compounding, heat generated by igniting the magnesium net at a low temperature can initiate the aluminum thermal reaction to release a large amount of heat, and the aluminum powder, the nickel powder and copper generated by the aluminum thermal reaction are combined to form intermetallic compounds or solid solutions under a large amount of heat, so that brazing is realized. In use, the aluminum alloy connecting piece is not worried about being damaged due to overheating caused by high brazing temperature, the energy consumption is low during brazing, and the brazing quality is good.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, specifically to a brazing material for preformed aluminum parts, its preparation method, and its application. Background Technology

[0002] Aluminum alloys, due to their excellent thermal conductivity, electrical conductivity, and corrosion resistance, are frequently used in metal connectors. Brazing is required during connector fabrication; this involves heating a filler metal with a melting point lower than that of the connector, along with the connector itself, until the filler metal melts and rapidly fills the gaps in the connector, thus achieving interconnection. Currently, the primary brazing filler metal used for aluminum alloy connectors is aluminum-silicon filler metal, but its melting point reaches 577℃. To perform brazing, a brazing temperature of at least 600℃ is required. This temperature is very close to the melting point of the aluminum alloy connector. Unstable temperatures during brazing can easily cause overheating and damage to the aluminum alloy connector. Additional processes or equipment are needed to precisely control the heating temperature, increasing processing difficulty and resulting in high energy consumption at such high temperatures. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a pre-formed aluminum brazing material. By combining aluminum powder and magnesium mesh with a copper oxide shell protective structure, and simultaneously introducing nickel powder, the heat generated by the magnesium mesh can be ignited at a relatively low temperature to trigger an aluminothermic reaction that releases a large amount of heat. The aluminum powder, nickel powder, and copper generated by the aluminothermic reaction combine under a large amount of heat to form an intermetallic compound or solid solution, thereby achieving brazing. This product eliminates concerns about overheating damage to aluminum alloy connectors due to high brazing temperatures, while also exhibiting low energy consumption and high brazing quality.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A brazing material for preformed aluminum parts includes a magnesium mesh and a mixture filling the surface and pores of the magnesium mesh;

[0006] The mixture includes composite aluminum powder, nickel powder, and aluminum brazing flux;

[0007] The composite aluminum powder comprises a core and a shell from the inside out. The core comprises aluminum and the shell comprises copper oxide.

[0008] Existing common aluminum brazing materials have high melting points, and their brazing temperatures are very close to the melting points of aluminum alloy connectors. If the temperature is not properly controlled, it is very easy for the connectors to melt or even be damaged. To address this, people have considered adding aluminum powder and other powders that can undergo an aluminothermic reaction with aluminum powder to the brazing material. At a lower brazing temperature, a large amount of heat is released through the aluminothermic reaction to achieve brazing. However, aluminum powder itself is extremely prone to aging and deactivation, and the aluminothermic reaction releases heat at a very fast rate. This can easily lead to a large amount of heat concentrating locally in a short period of time, causing overheating and affecting the quality of the brazing. In this invention, the preformed aluminum brazing material uses magnesium mesh as the skeleton structure material, and fills its pores and surface with a brazing-functional mixture. This mixture contains aluminum powder with a core-shell structure, as well as nickel powder and aluminum flux. Through the coating of the copper oxide shell, the aging and deactivation probability of the aluminum powder in the core is significantly reduced. When heated, because the magnesium mesh has a low ignition point, it only needs to be ignited at less than 500°C. The heat generated will promote the aluminothermic reaction, while the copper oxide shell will slow down the exothermic rate of the aluminothermic reaction, allowing it to release heat at a relatively uniform rate and avoiding overheating. During the aluminothermic reaction, the heat released by the aluminothermic reaction further causes some aluminum to form intermetallic compounds or solid solutions with nickel powder and copper generated by the aluminothermic reaction. This substance can be directly used as a brazing material to achieve the purpose of brazing. At the same time, the aluminum flux can increase the activity of aluminum powder, break the oxide film on the surface of the joint during brazing, and push the oxide slag generated during the brazing process to the weld, ultimately improving the quality of brazing. When brazing with the pre-formed aluminum brazing material described in this invention, not only can low heating energy consumption and low heating temperature be guaranteed, eliminating concerns about overheating damage to the connectors, but the brazed connectors also exhibit high shear strength and excellent brazing quality. However, if aluminum powder without a core-shell structure is used, or if other powders such as cobalt are used instead of nickel powder, the above effects cannot be achieved, or the brazing temperature is too high, posing a risk of overheating damage, or the brazing quality is poor, resulting in aluminum parts that fail to meet usage requirements.

[0009] Preferably, the magnesium mesh content in the brazing material of the preformed aluminum part is 6-8% by mass.

[0010] More preferably, the magnesium mesh content in the brazing material of the preformed aluminum part is 6.2% to 7.4% by mass.

[0011] The inventors noted that magnesium's main function is to provide initial initiation heat for the aluminothermic reaction, but its addition cannot be excessive, otherwise sufficient intermetallic compounds and solid solutions for brazing cannot be formed. When introduced in conventional powder form, the product prepared under the same addition ratio and without the introduction of other combustion improvers has poor dispersibility, low air permeability, and is not easy to ignite. Even if the temperature is increased, it may only achieve partial ignition. If other combustion improvers are introduced, it may lead to overburning of the brazing, affecting the quality of the brazing. Therefore, using magnesium with a mesh structure as the skeleton support of the brazing functional mixture, this form of product has the best effect.

[0012] Preferably, the ratio of the average diameter of the core to the thickness of the shell of the composite aluminum powder is (5-20):1.

[0013] More preferably, the ratio of the average diameter of the core to the thickness of the shell of the composite aluminum powder is (5-18):1.

[0014] The role of copper oxide is to prevent the aging of aluminum powder and slow down the heat release rate of the aluminothermic reaction. Simultaneously, the copper produced by the reaction of aluminum powder and copper oxide forms a solid solution with nickel powder, and excess aluminum powder also forms intermetallic compounds with nickel powder. Therefore, when preparing composite aluminum powder, a larger core diameter, i.e., a higher aluminum content in the composite aluminum powder, is more beneficial to the brazing effect of the product. However, if the copper oxide coating thickness is too small, it will lead to insufficient heat in the aluminothermic reaction or an excessively rapid aluminothermic heat release rate, which is detrimental to the brazing quality. On the other hand, if the proportion of copper oxide is too large, and the coating layer is too thick, the adhesion of the shell to the core is reduced due to surface tension limitations, making it very easy to detach during processing and brazing, weakening its protective effect. Therefore, the thickness ratio of the core to the shell needs to be properly matched. When the above-mentioned moderate ratio range is optimally selected, the product further prepared from this composite aluminum powder has a better brazing effect.

[0015] More preferably, the average diameter of the core in the composite aluminum powder is 10–45 μm;

[0016] More preferably, the average diameter of the kernel is a value within the range of one or any two of the following: 10μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 36μm, 38μm, 40μm, 42μm, and 45μm.

[0017] The core is the key structure for the aluminothermic reaction of composite aluminum powder and the final brazing. The smaller its diameter, the larger the specific surface area of ​​the overall particles under the condition of a certain ratio of inner and outer layer thickness. This results in a higher probability of aluminum aging in the core and a tendency to reduce the uniformity of coating during the coating process. However, if the diameter is too large, the relative melting point of the overall particles will be too high, which will not be conducive to the full aluminothermic reaction and the mutual contact of materials forming intermetallic compounds or solid solutions. Therefore, it needs to be maintained within a moderate range.

[0018] Preferably, the brazing material for the preformed aluminum part satisfies the following requirements:

[0019] (M1-9M2 / 40):M3=(5~16):1;

[0020] Where M1 is the mass of aluminum in the core of the composite aluminum powder, M2 is the mass of copper oxide in the shell of the composite aluminum powder, and M3 is the mass of nickel powder, and M1, M2, and M3 have the same unit.

[0021] More preferably, the brazing material for the preformed aluminum part satisfies the following requirements:

[0022] (M1-9M2 / 40): M3=(6~10):1.

[0023] The introduction of nickel powder can improve the overall brazing effect, resulting in higher strength of the brazed product. It mainly reacts with the copper generated after the aluminothermic reaction and the remaining aluminum. Therefore, it is necessary to establish an appropriate addition ratio with the two components in the composite aluminum powder. The amount added should not be too small, otherwise it will weaken the brazing effect. On the other hand, nickel powder itself has a high melting point. If the addition ratio is too high, it is very easy for some nickel powder to fail to melt under the same heat release, which will also weaken the brazing effect and cause the brazing temperature of the product to be too high. When the ratio of the three materials is maintained within the above-mentioned preferred range, the nickel powder can fully react with the composite aluminum powder and achieve a better brazing effect.

[0024] More preferably, the nickel powder content in the brazing material of the preformed aluminum part is 1-8.4% by mass.

[0025] Preferably, the average particle size of the nickel powder is 200–1200 nm;

[0026] More preferably, the average particle size of the nickel powder is 200–1000 nm;

[0027] More preferably, the average particle size of the nickel powder is a range of one or any two of 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, and 1000nm.

[0028] Through experiments, the inventors discovered that when nickel powder is heated and reacts with copper or aluminum, the uniformity of heating and the degree of reaction are related to the average particle size of the nickel powder. When the average particle size of the nickel powder is large, its dispersibility decreases, and the uniformity of heating, as well as the uniformity of the subsequently formed intermetallic compounds and solid solutions, also decreases. The brazing temperature required increases, and the strength of the brazed product decreases. However, the smaller the particle size of the nickel powder, the larger its specific surface area, making it easier to oxidize, and the powder production cost is also high. Therefore, when the average particle size of the nickel powder is preferably within the above range, the brazing temperature and the strength of the brazed product can be maintained at a better level.

[0029] Preferably, the magnesium mesh is a two-dimensional magnesium mesh or a three-dimensional magnesium mesh.

[0030] It should be noted that the magnesium mesh described in this invention can be a planar two-dimensional mesh or a sponge-like three-dimensional magnesium mesh. As mentioned above, the main function of the magnesium mesh is to provide heat for the aluminothermic reaction, while requiring sufficient ignition space and a low mass ratio. Those skilled in the art will readily realize that the magnesium mesh can meet the above effects in both two-dimensional and three-dimensional structures. The magnesium mesh can be applied directly with commercially available products or can be a self-made product. For example, magnesium foil or magnesium blocks can be hollowed out using laser etching or chemical etching methods, with or without a mold, to obtain a two-dimensional or three-dimensional mesh structure.

[0031] More preferably, the magnesium mesh is a two-dimensional magnesium mesh with a thickness of 0.1 to 0.5 mm.

[0032] Preferably, the porosity of the magnesium mesh is 60-90%.

[0033] More preferably, the porosity of the magnesium mesh is 70-85%.

[0034] The porosity of magnesium mesh is related to the relative magnesium content, the ventilation of the magnesium mesh, the bonding degree between the magnesium mesh and the mixture, and even the ease of processing during product preparation and use. When the porosity is small, the mixture cannot fully fill the pores of the magnesium mesh, and the ventilation is low, resulting in incomplete combustion during ignition. Furthermore, the relative magnesium content is high, leading to a smaller amount of usable brazing material. However, if the porosity is too high, the processing difficulty of the product will increase, and the magnesium mesh is prone to tearing during processing, resulting in lower composite composition and reaction uniformity of the mixture. At the same time, the relative magnesium content is low, which cannot provide sufficient initiation heat for the aluminothermic reaction, requiring a higher brazing temperature. When a magnesium mesh with a porosity within the above-mentioned preferred range is selected, it can perform its optimal use and skeletal support functions.

[0035] Preferably, the aluminum flux is a fluoroaluminate aluminum flux.

[0036] More preferably, the aluminum flux is cesium fluoroaluminate aluminum flux.

[0037] More preferably, the brazing material for the preformed aluminum part contains 5-15% aluminum flux by mass.

[0038] The main function of aluminum flux is to remove the oxide film on the surface of aluminum parts. However, introducing too much flux will not further improve the brazing quality of the product. On the contrary, it will cause too much flux residue after brazing. Therefore, it is sufficient to mix the flux with an appropriate amount.

[0039] Another object of the present invention is to provide a method for preparing the brazing material for the preformed aluminum part, comprising the following steps:

[0040] (1) Micron-sized aluminum powder and nano-sized copper oxide powder are mixed in an organic solvent to prepare a slurry, which is then spray-granulated and dried to obtain a composite aluminum powder with a core-shell structure.

[0041] (2) The composite aluminum powder, nickel powder and aluminum flux are mixed in an organic solvent to form a paste, which is then applied to a magnesium mesh, left to stand, dried and cured, and cut to obtain the preformed aluminum brazing material.

[0042] In the preparation method of the product described in this invention, a slurry containing aluminum powder and copper oxide powder is granulated by spray drying. Due to the Venturi effect, the aluminum powder in the slurry will form highly dispersed small particles under the high shear force of the airflow during spraying. The nano copper oxide powder has a large specific surface area and high surface tension, so it will spontaneously adsorb onto the surface of the aluminum particles, ultimately forming a core-shell structured composite aluminum powder. Subsequently, the composite aluminum powder and raw materials such as nickel powder are directly coated onto a magnesium mesh and penetrate into the magnesium mesh. After drying and curing, the product can be obtained. The preparation method of this product is simple to operate, so it can be industrialized on a large scale.

[0043] Another object of the present invention is to provide the application of the preformed aluminum brazing material in the brazing of aluminum parts.

[0044] The beneficial effects of this invention are that it provides a pre-formed aluminum brazing material. By combining aluminum powder and magnesium mesh with a copper oxide shell protective structure, and simultaneously introducing nickel powder, the heat generated by the magnesium mesh can be ignited at a relatively low temperature to trigger an aluminothermic reaction that releases a large amount of heat. The aluminum powder, nickel powder, and copper generated by the aluminothermic reaction combine under a large amount of heat to form an intermetallic compound or solid solution, thereby achieving brazing. When using this product, there is no need to worry about the aluminum alloy connectors being damaged by overheating due to the high brazing temperature. At the same time, the energy consumption during brazing is low, and the brazing quality is good. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0046] Example 1

[0047] An embodiment of the brazing material for preformed aluminum parts, its preparation method, and its application according to the present invention, wherein the preparation method of the brazing material for preformed aluminum parts includes the following steps:

[0048] (1) 130g of aluminum powder with an average particle size of 45μm and 260g of copper oxide powder with an average particle size of 60nm are mixed in 90g of organic solvent and prepared into a slurry. The slurry is sprayed and granulated in a spray granulator at a flow rate of 1.9mL / s and dried to obtain a composite aluminum powder with a core and a shell. The average diameter of the core in the composite aluminum powder is 45μm and the ratio of the average diameter of the core to the thickness of the shell is 9:1. The organic solvent is a mixture of ethyl cellulose, polyvinyl ketone and isopropanol in a mass ratio of 4:4:2.

[0049] (2) A magnesium foil with a thickness of 0.2 mm was chemically etched to obtain a magnesium mesh with a porosity of about 80%.

[0050] (3) Mix 195g of composite aluminum powder, 6g of nickel powder with an average particle size of 200nm, 11.3g of cesium fluoroaluminate aluminum flux and 24g of anhydrous ethanol to prepare a paste, then apply it to the magnesium mesh (mass of 15.3g) obtained in step (2), let it stand for 5min, dry it with hot air at 80℃ and finally cut it into a size of 16*16*0.2mm to obtain the preformed aluminum brazing material; the mass content of magnesium mesh in this product is 6.7%, the mass content of nickel powder is 2.6%, and the mass content of cesium fluoroaluminate aluminum flux is 5%;

[0051] The brazing material for the preformed aluminum part meets the following requirements:

[0052] (M1-9M2 / 40):M3 = 6:1;

[0053] Where M1 is the mass of aluminum in the core of the composite aluminum powder, M2 is the mass of copper oxide in the shell of the composite aluminum powder, and M3 is the mass of nickel powder.

[0054] Example 2

[0055] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of copper oxide powder added is adjusted to 554.2g, and the ratio of the average diameter of the core to the thickness of the shell of the resulting composite aluminum powder is 5:1.

[0056] Example 3

[0057] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of copper oxide powder added is adjusted to 186.8g, and the ratio of the average diameter of the core to the thickness of the shell of the resulting composite aluminum powder is 12:1.

[0058] Example 4

[0059] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of copper oxide powder added is adjusted to 144.8g, and the ratio of the average diameter of the core to the thickness of the shell of the resulting composite aluminum powder is 15:1.

[0060] Example 5

[0061] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of copper oxide powder added is adjusted to 118g, and the ratio of the average diameter of the core to the thickness of the shell of the resulting composite aluminum powder is 18:1.

[0062] Example 6

[0063] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of copper oxide powder added is adjusted to 105.2g, and the ratio of the average diameter of the core to the thickness of the shell of the resulting composite aluminum powder is 20:1.

[0064] Example 7

[0065] This invention provides an embodiment of a preformed aluminum brazing material, its preparation method, and its application. The difference between this embodiment and Embodiment 1 is that the amount of nickel powder added is 5.1g, and the nickel powder content in the product is 2.3% by mass. The preformed aluminum brazing material satisfies the following requirements:

[0066] (M1-9M2 / 40):M3=7:1.

[0067] Example 8

[0068] This invention provides an embodiment of a preformed aluminum brazing material, its preparation method, and its application. The difference from Embodiment 1 lies only in that the amount of nickel powder added is 4g, and the nickel powder content in the product is 1.8% by mass. The preformed aluminum brazing material satisfies the following requirements:

[0069] (M1-9M2 / 40):M3=9:1.

[0070] Example 9

[0071] This invention provides an embodiment of a preformed aluminum brazing material, its preparation method, and its application. The difference between this embodiment and Embodiment 1 is that the amount of nickel powder added is 3.6g, and the nickel powder content in the product is 1.6% by mass. The preformed aluminum brazing material satisfies the following requirements:

[0072] (M1-9M2 / 40):M3=10:1.

[0073] Example 10

[0074] This invention provides an embodiment of a preformed aluminum brazing material, its preparation method, and its application. The difference between this embodiment and Embodiment 1 is that the amount of nickel powder added is 7.2g, and the nickel powder content in the product is 3.2% by mass. The preformed aluminum brazing material satisfies the following requirements:

[0075] (M1-9M2 / 40):M3=5:1.

[0076] Example 11

[0077] This invention provides an embodiment of a preformed aluminum brazing material, its preparation method, and its application. The difference between this embodiment and Embodiment 1 is that the amount of nickel powder added is 2.2g, and the nickel powder content in the product is 1% by mass. The preformed aluminum brazing material satisfies the following requirements:

[0078] (M1-9M2 / 40):M3=16:1.

[0079] Example 12

[0080] An embodiment of the preformed aluminum brazing material, its preparation method and application described in this invention differs from Embodiment 1 only in that the average particle size of the nickel powder is 400 nm.

[0081] Example 13

[0082] An embodiment of the preformed aluminum brazing material, its preparation method and application described in this invention differs from Embodiment 1 only in that the average particle size of the nickel powder is 600 nm.

[0083] Example 14

[0084] An embodiment of the preformed aluminum brazing material, its preparation method and application described in this invention differs from Embodiment 1 only in that the average particle size of the nickel powder is 800 nm.

[0085] Example 15

[0086] An embodiment of the preformed aluminum brazing material, its preparation method and application described in this invention differs from Embodiment 1 only in that the average particle size of the nickel powder is 1200 nm.

[0087] Example 16

[0088] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the etching degree of the magnesium mesh is adjusted so that the porosity of the magnesium mesh is approximately 70%, and the mass content of the magnesium mesh in this product is 7.4%.

[0089] Example 17

[0090] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the etching degree of the magnesium mesh is adjusted so that the porosity of the magnesium mesh is approximately 75%, and the mass content of the magnesium mesh in this product is 7.1%.

[0091] Example 18

[0092] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the etching degree of the magnesium mesh is adjusted so that the porosity of the magnesium mesh is approximately 85%, and the mass content of the magnesium mesh in this product is 6.2%.

[0093] Example 19

[0094] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the etching degree of the magnesium mesh is adjusted so that the porosity of the magnesium mesh is approximately 60%, and the mass content of the magnesium mesh in this product is 8%.

[0095] Example 20

[0096] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the etching degree of the magnesium mesh is adjusted so that the porosity of the magnesium mesh is approximately 90%, and the mass content of the magnesium mesh in this product is 6%.

[0097] Example 21

[0098] An embodiment of the brazing material for preformed aluminum parts, its preparation method, and its application according to the present invention, wherein the preparation method of the brazing material for preformed aluminum parts includes the following steps:

[0099] (1) 140g of aluminum powder with an average particle size of 10μm and 250g of copper oxide powder with an average particle size of 60nm are mixed in 90g of organic solvent and prepared into a slurry. The slurry is sprayed and granulated in a spray granulator at a flow rate of 2.3mL / s and dried to obtain composite aluminum powder. The average diameter of the core in the composite aluminum powder is 10μm and the ratio of the average diameter of the core to the thickness of the shell is 10:1. The organic solvent is a mixture of ethyl cellulose, polyvinyl ketone and isopropanol in a mass ratio of 7:5:3.

[0100] (2) A magnesium foil with a thickness of 0.2 mm was chemically etched to obtain a magnesium mesh with a porosity of about 80%.

[0101] (3) Mix 195g of composite aluminum powder, 7g of nickel powder with an average particle size of 200nm, 11.3g of cesium fluoroaluminate aluminum flux and 24g of anhydrous ethanol to prepare a paste, then apply it to the magnesium mesh (15.3g by mass) obtained in step (2), let it stand for 5 minutes, dry it with hot air at 80℃ and finally cut it into a size of 16*16*0.2mm to obtain the preformed aluminum brazing material; the magnesium mesh content in this product is 6.7% by mass, the nickel powder content is 3% by mass, and the cesium fluoroaluminate aluminum flux content is 5% by mass;

[0102] The brazing material for the preformed aluminum part meets the following requirements:

[0103] (M1-9M2 / 40):M3=6:1.

[0104] Example 22

[0105] An embodiment of the brazing material for preformed aluminum parts, its preparation method, and its application according to the present invention, wherein the preparation method of the brazing material for preformed aluminum parts includes the following steps:

[0106] (1) 264g of aluminum powder with an average particle size of 36μm and 114g of copper oxide powder with an average particle size of 60nm were mixed in 90g of organic solvent and prepared into a slurry. The slurry was sprayed and granulated in a spray granulator at a flow rate of 3.1mL / s and dried to obtain composite aluminum powder. The average diameter of the core in the composite aluminum powder is 36μm and the ratio of the average diameter of the core to the thickness of the shell is 18:1. The organic solvent is a mixture of ethyl cellulose, polyvinyl ketone and isopropanol in a mass ratio of 3:5:2.

[0107] (2) A magnesium foil with a thickness of 0.2 mm was chemically etched to obtain a magnesium mesh with a porosity of about 80%.

[0108] (3) Mix 189g of composite aluminum powder, 19.9g of nickel powder with an average particle size of 200nm, 11.8g of cesium fluoroaluminate aluminum flux and 24g of anhydrous ethanol to prepare a paste, then apply it to the magnesium mesh (15.3g by mass) obtained in step (2), let it stand for 5 minutes, dry it with hot air at 80℃ and cure it, and finally cut it into a size of 16*16*0.2mm to obtain the preformed aluminum brazing material; the magnesium mesh content in this product is 6.5% by mass, the nickel powder content is 8.4% by mass, and the cesium fluoroaluminate aluminum flux content is 5% by mass;

[0109] The brazing material for the preformed aluminum part meets the following requirements:

[0110] (M1-9M2 / 40):M3=6:1.

[0111] Example 23

[0112] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of cesium fluoroaluminate aluminum flux added is 38.2g, and its mass content in the preformed aluminum brazing material is 15%.

[0113] Example 24

[0114] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of cesium fluoroaluminate aluminum flux added is 4.4g, and its mass content in the preformed aluminum brazing material is 2%.

[0115] Example 25

[0116] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the amount of cesium fluoroaluminate aluminum flux added is 72.1g, and its mass content in the preformed aluminum brazing material is 25%.

[0117] Example 26

[0118] An embodiment of the preformed aluminum brazing material, its preparation method, and its application described in this invention differs from Embodiment 1 only in that the cesium fluoroaluminate aluminum flux is replaced with an equal mass of potassium fluoroaluminate aluminum flux.

[0119] Comparative Example 1

[0120] An embodiment of a preformed aluminum brazing material, its preparation method and application, differs from Embodiment 1 only in that the nickel powder is replaced by cobalt powder of the same size and mass.

[0121] Comparative Example 2

[0122] An embodiment of a preformed aluminum brazing material, its preparation method, and its application differs from Embodiment 1 only in that the magnesium mesh is replaced by a tin mesh with the same porosity.

[0123] Comparative Example 3

[0124] An embodiment of a preformed aluminum brazing material, its preparation method, and its application differs from Embodiment 1 only in that the composite aluminum powder is replaced with 65g of aluminum powder with an average particle size of 45μm and 130g of copper oxide powder with an average particle size of 60nm.

[0125] Comparative Example 4

[0126] An embodiment of a preformed aluminum brazing material, its preparation method, and its application differs from Embodiment 1 only in that the preformed aluminum brazing material is commercially available Al88Si12 (mass ratio Al:Si = 88:12) brazing filler metal, which is cut into samples of the same size as in Embodiment 1 (16*16*0.2mm) and coated with 5% cesium aluminum fluoroaluminate flux.

[0127] Example of effect

[0128] To verify the effectiveness of the brazing material for preformed aluminum parts described in this invention, brazing tests were conducted on the products of each embodiment and comparative example:

[0129] Two 6061 grade aluminum parts to be brazed were assembled together with the brazing filler metals used in the various embodiments and comparative examples (with the brazing filler metal sandwiched between the brazing areas of the two aluminum parts), and laser brazing was performed. The dimensions of the brazing filler metal were all 16*16*0.2mm, and the area of ​​the overlapping brazing area was also 16mm*16mm. The following tests were then conducted:

[0130] 1) Record the temperature required for brazing. The temperature required for brazing is measured using an infrared temperature detector. The lower the temperature, the less likely the aluminum parts are to burn out, and the more energy-efficient it is. The test results are shown in Table 1.

[0131] 2) After brazing, the shear strength of the lap brazed joints was tested using an electronic universal testing machine. A higher shear strength indicates better brazing strength. The test results are shown in Table 1.

[0132] The performance test results are shown in Table 1.

[0133] Table 1 Performance Test Results

[0134]

[0135]

[0136] The test results show that the preformed aluminum brazing material described in this invention has excellent performance. During brazing, the brazing temperature is low, below 570℃, and the shear strength of the brazed aluminum part is high, reaching over 80MPa, and even exceeding 108MPa. Its cost-effectiveness is far superior to the aluminum-silicon brazing material described in Comparative Example 4. The reason why the product of this invention can achieve such performance is mainly due to the magnesium mesh structure and design, as well as the compounding of aluminum powder and nickel powder. The magnesium mesh is ignited at a relatively low external temperature, and the heat released from the ignition triggers an aluminothermic reaction. The heat released from the aluminothermic reaction causes the materials to form intermetallic compounds or solid solutions, thus achieving brazing. However, if, as shown in Comparative Examples 1-3, nickel powder is replaced with cobalt powder, the magnesium mesh is replaced with tin mesh, or only aluminum powder and copper oxide powder are introduced as raw materials without constructing a core-shell structure, the product not only cannot guarantee a low brazing temperature, but even after brazing, its brazing strength is also low.

[0137] As can be seen from Examples 1 to 6, the composite aluminum powder of the present invention has a high correlation between the core aluminum powder and the outer copper oxide powder, and the interaction between the two is relatively complex. It is necessary to take into account the degree of the aluminothermic reaction, the rate of heat release, and the reaction probability of the intermetallic compound and solid solution after the aluminothermic reaction. If the content of either one is low, it will lead to a higher brazing temperature and a lower shear strength after brazing. The thickness of the core and the outer shell need to be maintained in a moderate ratio.

[0138] As can be seen from Examples 1 and 7-11, when nickel powder and composite aluminum powder are compounded, the addition ratio needs to be maintained at a suitable level with the composite aluminum powder. Otherwise, because nickel powder has a high melting point and is a key raw material for forming the brazing layer after the aluminothermic reaction, when the brazing material of the preformed aluminum part meets the following preferred range: the mass content of nickel powder is 1-8.4%, and (M1-9M2 / 40):M3 = (6-10):1, the product can be used at a lower brazing temperature and the brazing layer of the aluminum part can obtain higher shear strength.

[0139] The nickel powder particle size used in Examples 1 and 12-15 is not the same. It can be seen that as the particle size increases, the brazing temperature of the product gradually increases, indicating that more heat is needed to melt and react with aluminum and copper powder. At the same time, the shear strength of the brazed layer gradually decreases. Therefore, it is necessary to maintain the nickel powder size at a low level.

[0140] As can be seen from Examples 1 and 16-20, as the porosity of the magnesium mesh increases, the subsequent reaction effect after ignition is better, and the shear strength of the product after brazing is improved. However, the required brazing temperature also increases. If the porosity is too large, the brazing temperature will continue to increase. As in the product described in Example 21, the magnesium mesh will not be strong enough due to excessive porosity, and the magnesium mesh will be torn locally. This not only increases the processing difficulty but also reduces the uniformity of the composite material and reaction with the mixture, and the shear strength of the product after brazing will also decrease. Therefore, when the preferred porosity is 70-85%, the product has the best performance. The larger the porosity of the magnesium mesh, the lower the mass content of the magnesium mesh in the brazing material of the preformed aluminum parts. When the preferred mass content of the magnesium mesh in the brazing material of the preformed aluminum parts is 6.2-7.4%, the product has the best performance.

[0141] As can be seen from Examples 21 and 22, the composite aluminum powder in the product of the present invention does not have specific limitations on the size of the core aluminum powder during construction. Aluminum powder of other sizes can be used. In fact, the composite aluminum powder prepared using smaller aluminum powder has better dispersibility. Under other conditions that are not significantly different, the product has higher performance.

[0142] As can be seen from Examples 1 and 23-26, different amounts and types of aluminum flux have a certain impact on the brazing temperature and brazing effect of the product. The main reason is that the primary function of aluminum flux is to break down the oxide film on the surface of the aluminum part, push the oxide slag generated during brazing to the edge of the brazed layer, and activate the composite aluminum powder. If the aluminum flux content is too low, the product's performance will inevitably suffer, and the shear strength will decrease. However, if too much aluminum flux is added, as shown in Example 25, not only will the shear strength of the brazed aluminum part increase only slightly, but excessive flux residue will also worsen the product's appearance and may even leave flux residue in the brazed layer, further reducing the shear strength. Therefore, the optimal brazing effect is achieved when the mass content of aluminum flux in the preformed aluminum part brazing material is 5-15%.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A brazing material for preformed aluminum parts, characterized in that, Includes magnesium mesh and the mixture filling the surface and pores of the magnesium mesh; The mixture includes composite aluminum powder, nickel powder, and aluminum brazing flux; The composite aluminum powder comprises a core and a shell from the inside out. The core comprises aluminum, and the shell comprises copper oxide. The ratio of the average diameter of the core to the thickness of the shell of the composite aluminum powder is (5~20):

1. The brazing material for the preformed aluminum part meets the following requirements: (M1-9M2 / 40): M3= (5~16): 1; Where M1 is the mass of aluminum in the core of the composite aluminum powder, M2 is the mass of copper oxide in the shell of the composite aluminum powder, and M3 is the mass of nickel powder, and M1, M2, and M3 have the same unit.

2. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The magnesium mesh content in the brazing material of the preformed aluminum part is 6-8% by mass.

3. The brazing material for preformed aluminum parts as described in claim 2, characterized in that, The magnesium mesh content in the brazing material of the preformed aluminum part is 6.2-7.4% by mass.

4. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The ratio of the average diameter of the core to the thickness of the shell in the composite aluminum powder is (5~18):

1.

5. The brazing material for preformed aluminum parts as described in claim 4, characterized in that, The average diameter of the core in the composite aluminum powder is 10~45μm.

6. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The brazing material for the preformed aluminum part meets the following requirements: (M1-9M2 / 40): M3= (6~10):

1.

7. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The average particle size of the nickel powder is 200~1200nm.

8. The brazing material for preformed aluminum parts as described in claim 7, characterized in that, The average particle size of the nickel powder is 200~1000nm.

9. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The nickel powder content in the brazing material of the preformed aluminum part is 1~8.4% by mass.

10. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The porosity of the magnesium mesh is 60-90%.

11. The brazing material for preformed aluminum parts as described in claim 10, characterized in that, The porosity of the magnesium mesh is 70-85%.

12. The brazing material for preformed aluminum parts as described in claim 1, characterized in that, The aluminum flux is a fluoroaluminate aluminum flux; the mass content of the aluminum flux in the brazing material of the preformed aluminum part is 5-15%.

13. The method for preparing the brazing material for preformed aluminum parts according to any one of claims 1 to 12, characterized in that, Includes the following steps: (1) Micron-sized aluminum powder and nano-sized copper oxide powder are mixed in an organic solvent to prepare a slurry, which is then spray-granulated and dried to obtain a composite aluminum powder with a core-shell structure; (2) The composite aluminum powder, nickel powder and aluminum flux are mixed in an organic solvent to form a paste, which is then applied to a magnesium mesh, left to stand, dried and cured, and cut to obtain the preformed aluminum brazing material.

Images