Sintering type preform solder, its preparation method and application

Abstract

The present application relates to the technical field of brazing, in particular to a sintering type preformed filler metal, a preparation method and application thereof. The sintering type preformed filler metal comprises a magnesium film, aluminum powder, copper oxide powder and nickel powder attached to the same side of the magnesium film, and an aluminum flux attached to the other side of the magnesium film. The present application takes advantage of the low ignition point of magnesium, which is as low as 490 DEG C, to ignite the magnesium film at a lower temperature during brazing, and the heat generated causes the aluminum powder and copper oxide powder to produce an aluminothermic reaction. The high temperature released by the aluminothermic reaction further causes part of the aluminum powder and the nickel powder and the copper generated by the aluminothermic reaction to form intermetallic compounds or solid solutions, thereby achieving the purpose of brazing connection. Therefore, the present application only needs to apply a temperature of about 500 DEG C to the weld to achieve the purpose of brazing aluminum alloy connecting pieces. The present application solves the problem that the other heat-resistant parts are easily damaged by overheating when using aluminum-based filler metal to braze aluminum alloy connecting pieces, and further reduces the brazing temperature under the premise of ensuring the brazing strength.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, specifically to a sintered preformed brazing filler metal, its preparation method, and its application. Background Technology

[0002] Brazing uses an alloy with a melting point lower than that of the base metal as the filler metal. Upon heating, the filler metal melts and fills and holds the joint gap through wetting and capillary action, while the base metal remains solid. The brazed joint is formed by the mutual diffusion between the liquid filler metal and the solid base metal. Brazing has minimal impact on the physicochemical properties of the base metal, results in lower welding stress and deformation, allows for the welding of dissimilar metals with significantly different properties, can simultaneously complete multiple welds, produces aesthetically pleasing and neat joints, requires simple equipment, and involves low production investment.

[0003] The metallic joining material used in brazing is called brazing filler metal. Brazing filler metals are generally divided into two main categories based on their liquidus temperature: those with a liquidus temperature below 450°C are called soft filler metals, and those with a liquidus temperature above 450°C are called hard filler metals. Based on the matrix elements, they can also be classified as bismuth-based, indium-based, tin-based, lead-based, antimony-based, and zinc-based filler metals (these are also called soft filler metals); and aluminum-based, silver-based, copper-based, manganese-based, nickel-based, and palladium-based filler metals (these are also called hard filler metals). Generally, brazing filler metals should possess good fluidity, uniform composition, a narrow melting range, and good brazed joint strength. Furthermore, the melting point of the filler metal is an important physical property. The melting point refers to the temperature at which the filler metal completely liquefies; this temperature is also called the liquidus temperature. Except for pure metals and eutectic alloys, most filler metals have a corresponding interval between the initial melting and complete liquefaction. During brazing, the melting point of the filler metal is generally selected to be tens of degrees lower than that of the brazing metal. Otherwise, the brazing process is difficult to control, and it is easy to cause brazing metal grain growth, overheating, or even localized melting. Among the many types of filler metals, aluminum alloys are increasingly widely used in connectors due to their good thermal and electrical conductivity and corrosion resistance.

[0004] However, the aluminum-based brazing filler metals currently used for brazing aluminum alloys, such as the commonly used aluminum-silicon brazing filler metal, have a melting point of 577℃, while the brazing temperature usually needs to be 25℃ higher than the melting point of the filler metal, that is, the brazing temperature needs to be at least 600℃. This excessively high brazing temperature, and its proximity to the melting point of aluminum alloys, means that when heating the aluminum-based filler metal and the aluminum alloy connector to melt the aluminum-based filler metal for brazing, the excessively high temperature can easily cause other heat-sensitive parts of the aluminum alloy connector to overheat and be damaged, and it also results in high energy consumption. Summary of the Invention

[0005] In view of this, it is necessary to address the above-mentioned problems by providing a sintered preformed brazing filler metal, its preparation method, and its application. The sintered preformed brazing filler metal provided by this invention can initiate local brazing at a lower temperature, thereby solving the problem of overheating damage when using aluminum-based brazing filler metals to braze other heat-sensitive parts of aluminum alloy connectors. Furthermore, it further reduces the brazing temperature while ensuring brazing strength.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a sintered preformed brazing filler metal, comprising a magnesium film and aluminum powder, copper oxide powder and nickel powder attached to the same side of the magnesium film, and aluminum flux attached to the other side of the magnesium film.

[0008] Furthermore, the mass of the nickel powder is 1.7%-2.7% of the total mass of the sintered preformed brazing filler metal.

[0009] Furthermore, the mass ratio of the aluminum powder to the copper oxide powder is ≥9:40.

[0010] The mass ratio of aluminum to copper oxide that reacts completely is 9:40. Furthermore, the copper and nickel produced by the reaction of aluminum and copper oxide are infinitely soluble, which is beneficial for brazing. Moreover, if there is excess aluminum after the reaction, it can form intermetallic compounds with nickel, further enhancing brazing. Therefore, it is necessary to ensure that sufficient aluminum participates in the reaction; that is, the mass ratio of aluminum powder to copper oxide powder in this invention should be ≥9:40.

[0011] Furthermore, the mass of the aluminum powder is M1, the mass of the copper oxide powder is M2, and the mass of the nickel powder is M3, wherein (M1-9M2 / 40):M3=(6~10):1.

[0012] Nickel reacts with aluminum to form a nickel-aluminum alloy, which has excellent anti-aging properties and is beneficial for improving the strength of the solder joint. However, nickel has a high melting point. If too much nickel powder is added, some nickel may not be able to fully fuse with aluminum and copper effectively; but if too little nickel powder is added, it will not have the effect of improving the strength of the solder joint. Therefore, in this invention, the mass of aluminum powder M1, the mass of copper oxide powder M2, and the mass of nickel powder M3 should conform to the relationship (M1-9M2 / 40):M3=(6~10):1.

[0013] Furthermore, the particle size of the aluminum powder and copper oxide powder is 10μm to 50μm, and the particle size of the nickel powder is 200nm to 800nm.

[0014] Smaller aluminum powder particle sizes result in a larger specific surface area, making it more prone to oxidation. Furthermore, smaller particle sizes for both aluminum and copper oxide powders increase manufacturing costs. However, excessively large particle sizes hinder thorough mixing, impede the aluminothermic reaction during brazing, and impede the formation of intermetallic compounds or solid solutions from aluminum, copper, and nickel to achieve brazing. Nickel has a high melting point; to ensure sufficient fusion with aluminum and copper, nickel powder particle sizes must be as small as possible. However, smaller particle sizes also lead to a larger specific surface area, making it more prone to oxidation, and higher production costs. Therefore, in this invention, the particle sizes of aluminum and copper oxide powders are selected to be 10μm–50μm, and the particle size of nickel powder is 200nm–800nm. Powder particle sizes within this range save costs while ensuring thorough mixing for good brazing.

[0015] Furthermore, the thickness of the magnesium film is 1 / 25 to 1 / 20 of the total thickness of the sintered preformed brazing filler metal, and the mass of the magnesium film is 1.5% to 1.9% of the total mass of the sintered preformed brazing filler metal. Magnesium has a low ignition point of only about 490°C. During brazing, the heat generated by igniting the magnesium film at a relatively low temperature causes an aluminothermic reaction between the aluminum powder and copper oxide powder. The high temperature released by the aluminothermic reaction further causes a portion of the aluminum powder to undergo an aluminothermic reaction with the nickel powder, forming copper, which then forms an intermetallic compound or solid solution, achieving the purpose of brazing connection. If the magnesium film is too thin, the magnesium content is too low, and the heat generated is insufficient to initiate the aluminothermic reaction; if the magnesium film is too thick, the magnesium content is too high, resulting in excessive magnesium oxide slag after ignition, affecting the brazing quality. Therefore, in this invention, the thickness of the magnesium film is selected to be 1 / 25 to 1 / 20 of the total thickness of the sintered preformed brazing filler metal (excluding the aluminum flux portion), and the mass of the magnesium film is 1.5% to 1.9% of the total mass of the sintered preformed brazing filler metal.

[0016] Furthermore, in the sintered preformed brazing filler metal, the magnesium film side, which is not covered with aluminum powder, copper oxide powder, and nickel powder, is coated with aluminum flux. The aluminum flux can break the oxide film on the surface of the aluminum part, push the oxide slag generated during the brazing process to the vicinity of the weld, and also increase the activity of the aluminum powder, ensuring the brazing quality of the weld.

[0017] Preferably, the aluminum flux is a fluoroaluminate aluminum flux.

[0018] More preferably, the aluminum flux is cesium aluminate aluminum flux or potassium aluminate aluminum flux, with a content of 2%-8% of the total mass of the sintered preformed filler metal. If the flux content is too low, the removal of the oxide film on the surface of the aluminum part will be ineffective; if the flux content is too high, excessive flux residue will remain after brazing, affecting the brazing effect and appearance. Therefore, in this invention, the aluminum flux content is 2%-8% of the total mass of the sintered preformed filler metal.

[0019] Secondly, the present invention provides a method for preparing a sintered preformed solder, comprising the following steps:

[0020] S1. Mix aluminum powder, copper oxide powder and nickel powder evenly to obtain a mixed powder;

[0021] S2. Roll the magnesium strip into a magnesium film of the required thickness and cut it to the required size;

[0022] S3. The magnesium film prepared in step S2 is laid in the mold cavity of the die casting machine. Then the mixed powder prepared in step S1 is placed on the magnesium film in the mold cavity. Then die casting is performed so that the mixed powder is compacted on the magnesium film to form a brazing filler blank.

[0023] S4. Coat the magnesium film side of the brazing filler blank prepared in step S3, which is not covered with mixed powder, with aluminum flux to form a sintered preformed brazing filler.

[0024] Thirdly, the present invention provides the application of the above-mentioned sintered preformed brazing filler metal or the preparation method of sintered preformed brazing filler metal in brazing.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) The brazing temperature of commonly used aluminum-silicon brazing filler metal is as high as 600°C, which is energy-intensive and can cause overheating damage to other heat-sensitive parts of the aluminum alloy connector due to excessive temperature. This invention utilizes the advantage of magnesium's low ignition point of 490°C. During brazing, the magnesium film is ignited at a relatively low temperature. The heat generated causes the aluminum powder and copper oxide powder to undergo an aluminothermic reaction. The high temperature released by the aluminothermic reaction further causes some of the aluminum powder to form intermetallic compounds or solid solutions with nickel powder and copper generated by the aluminothermic reaction, thereby achieving the purpose of brazing. Therefore, this invention only requires applying a temperature as low as about 500°C to the weld to achieve the purpose of brazing aluminum alloy connectors.

[0027] (2) In this invention, the magnesium film side that is not covered with aluminum powder, copper oxide powder, and nickel powder is coated with aluminum flux. This can break the oxide film on the surface of the aluminum alloy brazed part and push the oxide slag generated during the brazing process to the vicinity of the weld. In addition, it can increase the activity of aluminum powder and further improve the brazing quality of the weld. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described clearly and completely below in conjunction with the embodiments of this invention. It should be noted that the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0030] Example 1

[0031] A sintered preformed brazing filler metal includes a magnesium film and aluminum powder, copper oxide powder, and nickel powder attached to the same side of the magnesium film; the side of the magnesium film without aluminum powder, copper oxide powder, and nickel powder is coated with aluminum flux; its dimensions (excluding flux) are 10*10*0.5mm, and its total mass is 4.736g; the particle size of the aluminum powder is 10μm, the particle size of the copper oxide powder is 10μm, and the particle size of the nickel powder is 200nm; the mass of the aluminum powder is 1.38g; the mass of the copper oxide powder is 2.76g, and the mass of the nickel powder is [missing information - likely a percentage]. The total mass of the alloy is 2.7%, or 0.127g; the mass ratio of the aluminum powder (M1), copper oxide powder (M2), and nickel powder (M3) is (M1-9M2 / 40):M3=6:1; the thickness of the magnesium foil is 25μm, and the mass is 0.09g, meaning the thickness of the magnesium film is 1 / 20 of the total thickness of the sintered preformed brazing filler metal, and the mass of the magnesium film is 1.9% of the total mass of the sintered preformed brazing filler metal; the aluminum flux is cesium fluoroaluminate aluminum flux, with a mass of 0.379g, and its content is 8% of the total mass of the sintered preformed brazing filler metal.

[0032] The above-mentioned sintered preformed solder was prepared using the following method:

[0033] S1. Preparation of mixed powder: Mix 1.38g of aluminum powder with a particle size of 10μm, 2.76g of copper oxide powder with a particle size of 10μm and 0.127g of nickel powder with a particle size of 200nm evenly to prepare mixed powder;

[0034] S2. Preparation of magnesium film: Magnesium strips are rolled into magnesium film with a thickness of 25μm and cut into 10mm*10mm sizes. The mass of the magnesium film of this size is 0.09g.

[0035] S3. Preparation of brazing filler blanks: The magnesium film prepared in step S2 is laid in the mold cavity of the die-casting machine. Then, 4.267g of the mixed powder prepared in step S1 (of which the mass of aluminum powder is 1.38g, the mass of copper oxide powder is 2.76g, and the mass of nickel powder is 0.127g) is placed on the magnesium film in the mold cavity. Then, die casting is performed to compact the mixed powder on the magnesium film, forming a brazing filler blank with a size of 10*10*0.5mm. The total mass of each brazing filler blank is 4.357g, of which the mass of magnesium film is 0.09g and the mass of mixed powder is 4.267g.

[0036] S4. Preparation of sintered preformed brazing filler metal: 0.379g of cesium aluminum fluoroaluminate flux is coated on the magnesium film side of the brazing filler metal blank prepared in step S3 before the mixed powder is attached, to form a sintered preformed brazing filler metal.

[0037] Example 2

[0038] A sintered preformed brazing filler metal differs from Example 1 in that the aluminum powder has a particle size of 50 μm.

[0039] Example 3

[0040] A sintered preformed brazing filler metal differs from Example 1 in that the copper oxide powder has a particle size of 50 μm.

[0041] Example 4

[0042] A sintered preformed brazing filler metal differs from Example 1 in that the particle size of both aluminum powder and copper oxide powder is 50 μm.

[0043] Example 5

[0044] A sintered preformed brazing filler metal differs from Example 1 in that the nickel powder has a particle size of 800 nm.

[0045] Example 6

[0046] A sintered preformed brazing filler metal differs from Example 1 in that the total mass of the mixed powder is 4.31g, of which the mass of aluminum powder is 1.43g, the mass of copper oxide powder is 2.8g, and the mass of nickel powder is 0.08g, i.e., the mass of nickel powder is 1.7% of the total mass of the sintered preformed brazing filler metal; the mass of cesium fluoroaluminate aluminum flux is 0.383g, i.e., its content is 8% of the total mass of the sintered preformed brazing filler metal; the mass of magnesium film is 0.09g, i.e., it is 1.9% of the total mass of the sintered preformed brazing filler metal; and the relationship between the mass of aluminum powder M1, the mass of copper oxide powder M2, and the mass of nickel powder M3 is (M1-9M2 / 40):M3=10:1.

[0047] Example 7

[0048] A sintered preformed brazing filler metal differs from Example 1 in that the magnesium film has a thickness of 20 μm and a mass of 0.072 g, meaning the thickness of the magnesium film is 1 / 25 of the total thickness of the sintered preformed brazing filler metal, and the mass of the magnesium film is 1.5% of the total mass of the sintered preformed brazing filler metal.

[0049] Example 8

[0050] A sintered preformed solder differs from Example 1 in that the mass of the cesium fluoroaluminate aluminum flux is 0.089 g, and the content is 2% of the total mass of the sintered preformed solder.

[0051] Example 9

[0052] A sintered preformed brazing filler metal, which differs from Example 1 in that the aluminum brazing flux is potassium fluoroaluminate aluminum brazing flux, which is a type of fluoroaluminate aluminum brazing flux.

[0053] Comparative Example 1

[0054] A sintered preformed brazing filler metal differs from Example 1 in that cobalt powder is used instead of nickel powder.

[0055] Comparative Example 2

[0056] A sintered preformed solder differs from Example 1 in that a tin film is used instead of a magnesium film.

[0057] Comparative Example 3

[0058] A sintered preformed brazing filler metal differs from Example 1 in that it does not contain a magnesium film; the filler metal blank size is also 10*10*0.5mm (excluding the aluminum flux portion), the mass of the filler metal blank is 4.492g, and one side of the upper and lower surfaces of the filler metal is coated with cesium fluoroaluminate aluminum flux, the mass of which is 0.391g, accounting for 8% of the total mass.

[0059] Comparative Example 4

[0060] A sintered preformed brazing filler metal differs from Example 1 in that the aluminum powder has a particle size of 100 μm.

[0061] Comparative Example 5

[0062] A sintered preformed brazing filler metal differs from Example 1 in that the copper oxide powder has a particle size of 100 μm.

[0063] Comparative Example 6

[0064] A sintered preformed brazing filler metal differs from Example 1 in that the nickel powder has a particle size of 1200 nm.

[0065] Comparative Example 7

[0066] A sintered preformed brazing filler metal differs from Example 1 in that the total mass of the mixed powder is 4.329g, of which the mass of aluminum powder is 1.339g, the mass of copper oxide powder is 2.75g, and the mass of nickel powder is 0.24g; the mass of the cesium fluoroaluminate aluminum flux is 0.384g, and its content is still 8% of the total mass of the sintered preformed brazing filler metal; the mass of the nickel powder is 5% of the total mass of the sintered preformed brazing filler metal; the thickness of the magnesium film is still 1 / 20 of the total thickness of the sintered preformed brazing filler metal, that is, the mass of the magnesium film is still 1.9% of the total mass of the sintered preformed brazing filler metal; the relationship between the mass of aluminum powder M1, the mass of copper oxide powder M2, and the mass of nickel powder M3 is (M1-9M2 / 40):M3=3:1.

[0067] Comparative Example 8

[0068] A sintered preformed brazing filler metal differs from Example 1 in that the mass of the aluminum powder is 1.406g, the mass of the copper oxide powder is 2.85g, and the mass of the nickel powder is 0.051g; the mass of the cesium aluminate flux is 0.382g, and its content remains 8% of the total mass of the sintered preformed brazing filler metal; the mass of the nickel powder is 1.1% of the total mass of the sintered preformed brazing filler metal; the thickness of the magnesium film remains 1 / 20 of the total thickness of the sintered preformed brazing filler metal, that is, the mass of the magnesium film remains 1.9% of the total mass of the sintered preformed brazing filler metal; the relationship between the mass of the aluminum powder M1, the mass of the copper oxide powder M2, and the mass of the nickel powder M3 is (M1-9M2 / 40):M3=15:1.

[0069] Comparative Example 9

[0070] A sintered preformed brazing filler metal differs from Example 1 in that the magnesium film has a thickness of 10 μm and a mass of 0.036 g, meaning the thickness of the magnesium film is 1 / 50 of the total thickness of the sintered preformed brazing filler metal, and the mass of the magnesium film is 0.8% of the total mass of the sintered preformed brazing filler metal.

[0071] Comparative Example 10

[0072] A sintered preformed brazing filler metal differs from Example 1 in that the magnesium film has a thickness of 50 μm and a mass of 0.18 g, meaning the thickness of the magnesium film is 1 / 10 of the total thickness of the sintered preformed brazing filler metal, and the mass of the magnesium film is 3.9% of the total mass of the sintered preformed brazing filler metal.

[0073] Comparative Example 11

[0074] A sintered preformed solder differs from Example 1 in that the mass of the cesium aluminate flux is 0.022 g, and the content is 0.5% of the total mass of the sintered preformed solder.

[0075] Comparative Example 12

[0076] A sintered preformed solder differs from Example 1 in that the mass of the cesium aluminate flux is 0.769 g, and the content is 15% of the total mass of the sintered preformed solder.

[0077] Comparative Example 13

[0078] Commercially available Al88Si12 solder measures 10*10*0.5mm (excluding flux) and weighs 0.133g. It is coated with 0.012g of cesium fluoroaluminate flux, which accounts for 8% of the total mass.

[0079] Performance testing

[0080] To further verify the performance of the sintered preformed brazing filler metal of this application, the brazing materials in Examples 1-9 and Comparative Examples 1-12 were used as the test group, and the brazing material in Comparative Example 13 was used as the control group. Brazing tests were conducted on each group. The aluminum parts to be brazed were assembled with the brazing filler metals from the test group and the control group, respectively, and laser brazing was performed. The dimensions of the brazing filler metals in both the test group and the control group were 10*10*0.5mm (excluding flux). The following tests were performed:

[0081] 1) Record the temperature required for brazing. The temperature required for brazing is measured with 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.

[0082] 2) After brazing is completed, shear strength test is performed on the lap brazed parts. The shear strength is tested by an electronic universal testing machine. The greater the shear strength, the better the brazing strength.

[0083] The test results are shown in Table 1.

[0084] Table 1 Performance Test Results

[0085]

[0086]

[0087] 1) Comparison of performance test results between Examples 1-9 and Comparative Example 13

[0088] As shown in Table 1, the shear strength of Example 1 was increased by approximately 45% compared to Comparative Example 13 (i.e., the control group), and the brazing temperature was reduced from over 600°C to close to 500°C, a decrease of approximately 110 degrees, resulting in a significant improvement in brazing performance. Other examples also showed significant improvements in increasing shear strength and reducing brazing temperature.

[0089] 2) The modification effect of nickel powder was compared using Example 1, Comparative Example 1, and Comparative Example 13.

[0090] As shown in Table 1, Comparative Example 13 uses commercially available common brazing filler metals, while Comparative Example 1 uses a different brazing filler metal modification material, cobalt, to replace nickel. The performance test results show that cobalt modification can effectively reduce the brazing temperature, but the relative shear strength is also reduced. Example 1, on the other hand, shows significant improvement in both increasing shear strength and reducing brazing temperature.

[0091] 3) The effects of magnesium film modification were compared using Example 1, Comparative Example 2, and Comparative Example 3.

[0092] As can be seen from the data in Table 1, Comparative Example 3 did not use magnesium film, and Comparative Example 2 used tin film instead of magnesium film. Tin film had no effect on reducing the brazing temperature and also reduced the shear strength. However, Example 1, which used magnesium film, showed significant improvement in both increasing the shear strength and reducing the brazing temperature.

[0093] 4) The effects of aluminum powder particle size modification were compared using Examples 1, 2, and 4.

[0094] As shown in Table 1, as the particle size of aluminum powder decreases from 100 μm to 10 μm, the shear strength increases and the brazing temperature decreases. The improvement in performance from reducing the particle size from 100 μm to 50 μm is greater than that from reducing it from 50 μm to 10 μm. Larger aluminum powder particle sizes hinder thorough mixing, impede the aluminothermic reaction during brazing, and impede the formation of intermetallic compounds or solid solutions from aluminum, copper, and nickel to achieve brazing. However, smaller particle sizes result in a larger specific surface area, making the powder more prone to oxidation. Furthermore, smaller particle sizes increase manufacturing costs. In summary, aluminum powder with a particle size in the range of 10 μm to 50 μm offers lower product costs and allows for use at lower brazing temperatures while achieving higher shear strength.

[0095] 5) The particle size modification effect of copper oxide powder was compared using Examples 1, 3, and 5.

[0096] As shown in Table 1, as the particle size of copper oxide powder decreases from 100 μm to 10 μm, the shear strength increases and the brazing temperature decreases. The improvement in performance from reducing the particle size from 100 μm to 50 μm is greater than that from reducing it from 50 μm to 10 μm. Larger copper oxide powder particle sizes hinder thorough mixing, impede the aluminothermic reaction during brazing, and impede the formation of intermetallic compounds or solid solutions from aluminum, copper, and nickel to achieve brazing. However, smaller particle sizes also increase manufacturing costs. In summary, a copper oxide powder particle size range of 10 μm to 50 μm results in lower product costs and allows for use at lower brazing temperatures while achieving higher shear strength.

[0097] 6) The effects of simultaneous modification with aluminum powder and copper oxide powder were compared through Examples 1, 2, 3, and 4.

[0098] As shown in Table 1, the particle size of both aluminum powder and copper oxide powder in Example 4 was 50 μm. Compared to Example 4, in Example 3, the particle size of aluminum powder was reduced to 10 μm, but the shear strength decreased slightly while the brazing temperature increased. This may be due to the larger specific surface area of ​​the aluminum powder, making it easier to oxidize during powder preparation. In Example 2, compared to Example 4, the particle size of copper oxide powder was reduced to 10 μm, resulting in a lower brazing temperature and improved brazing strength. In Example 1, compared to Example 4, simultaneously reducing the particle size of both aluminum powder and copper oxide powder to 10 μm significantly improved the shear strength and significantly reduced the brazing temperature, with a better modification effect than reducing the particle size of copper oxide powder alone.

[0099] 7) The effects of nickel powder particle size modification were compared using Examples 1, 5, and 6.

[0100] As shown in Table 1, as the particle size of nickel powder decreases from 1200 nm to 200 nm, the shear strength increases while the brazing temperature decreases. The improvement in shear strength from reducing the particle size from 1200 nm to 800 nm is less significant than that from reducing it from 800 nm to 200 nm, while the difference in the increase in brazing temperature is negligible. Nickel has a high melting point; to ensure sufficient fusion with aluminum and copper, the particle size of the nickel powder needs to be as small as possible. However, smaller particle sizes result in a larger specific surface area, making it more prone to oxidation, and also increasing the powder production cost. In summary, nickel powder with a particle size in the range of 200 nm to 800 nm offers lower product costs and allows for use at lower brazing temperatures while achieving higher shear strength.

[0101] 8) The modification effects of the mass ratios of aluminum powder, copper oxide powder, and nickel powder were compared using Examples 1, 6, 7, and 8.

[0102] As shown in Table 1, when the mass ratio of aluminum powder (M1), copper oxide powder (M2), and nickel powder (M3) is (M1-9M2 / 40):M3 within the range of (3-15):1, the improvement in shear strength and brazing temperature increases first and then decreases as the ratio increases. The improvement is greater in the (3-10):1 range and less in the (10-15):1 range. Furthermore, the improvement is more significant in the (3-6):1 range than in the (6-10):1 range. Therefore, when the mass ratio of aluminum powder (M1), copper oxide powder (M2), and nickel powder (M3) is (M1-9M2 / 40):M3 within the range of (6-10):1, the material can be used at a lower brazing temperature and achieve higher shear strength.

[0103] 9) The modification effects on magnesium film thickness and quality were compared using Examples 1, 7, 9, and 10.

[0104] As shown in Table 1, the magnesium film accounts for a proportional relationship between the total thickness and total mass of the sintered preformed brazing filler metal. When the magnesium film thickness percentage is in the range of 1 / 50 to 1 / 10 (i.e., the magnesium film mass percentage is in the range of 0.8% to 3.9%), the improvement in shear strength increases first and then decreases as the magnesium film percentage increases. When the magnesium film thickness percentage is in the range of 1 / 50 to 1 / 20 (i.e., the mass percentage is in the range of 0.8% to 1.9%), the improvement increases, while when the magnesium film thickness percentage is in the range of 1 / 20 to 1 / 10 (i.e., the mass percentage is in the range of 1.9% to 3.9%), the improvement decreases. Furthermore, the improvement in the effect is more significant when the magnesium film thickness percentage is in the range of 1 / 50 to 1 / 25 (i.e., the mass percentage is in the range of 0.8% to 1.5%) than when it is in the range of 1 / 25 to 1 / 20 (i.e., the mass percentage is in the range of 1.5% to 1.9%). The effect of brazing temperature modification increases with the increase of magnesium film thickness (i.e., the mass percentage). However, the increase is significantly lower in the magnesium film thickness range of 1 / 20 to 1 / 10 (i.e., mass percentage of 1.9% to 3.9%) compared to other ranges. Furthermore, the brazing results of Comparative Example 10 show that an excessively large magnesium film thickness (i.e., mass percentage) results in too much magnesium oxide slag, affecting brazing strength and appearance. Therefore, considering all factors, when the magnesium film proportion in the total thickness and mass of the sintered preformed brazing filler metal meets the required ratio, and the magnesium film thickness is in the range of 1 / 25 to 1 / 20 (i.e., mass percentage of 1.5% to 1.9%), it can be used at a lower brazing temperature while achieving higher shear strength without affecting appearance, resulting in the optimal overall effect.

[0105] 10) By comparing the modification effects of different mass ratios of nickel powder in sintered preformed brazing filler metals through Examples 1, 6, 7, and 8, the modification effects of nickel powder in sintered preformed brazing filler metals were compared.

[0106] As shown in Table 1, the improvement in shear strength and brazing temperature increases with the increase in the proportion of nickel powder. The improvement is initially seen when the nickel powder proportion is between 1.1% and 2.7%, but decreases when it is between 2.7% and 5%. Furthermore, the improvement is more significant between 1.1% and 1.7% nickel powder compared to the 1.7% to 2.7% range. Therefore, when the nickel powder content is 1.7%–2.7% of the total mass of the sintered preformed brazing filler metal, it can be used at a lower brazing temperature while achieving higher shear strength.

[0107] 11) The modification effect of the mass ratio of cesium fluoroaluminate aluminum flux was compared using Examples 1, 8, 11, and 12.

[0108] As shown in Table 1, when the proportion of cesium aluminate flux in the total mass of the sintered preformed filler metal is between 0.5% and 15%, the improvement in shear strength and brazing temperature increases first and then decreases with increasing flux proportion. Specifically, the improvement is greater in the 0.5%–8% range and less in the 8%–15% range, with a more significant improvement in the 0.5%–2% range compared to the 2%–8% range. In Comparative Example 12, excessive flux content resulted in excessive flux residue after brazing, affecting both the brazing effect and appearance. Therefore, this invention demonstrates that when the aluminum flux content is 2%–8% of the total mass of the sintered preformed filler metal, it can be used at a lower brazing temperature while achieving higher shear strength without affecting appearance, resulting in the optimal overall performance.

[0109] 12) By comparing the modification effects of the selected aluminum brazing flux in Examples 1 and 9.

[0110] As can be seen from the data in Table 1, the commonly used potassium fluoroaluminate aluminum flux is not as effective as the cesium fluoroaluminate aluminum flux in increasing shear strength and reducing brazing temperature.

[0111] In summary, the sintered preformed brazing filler metal provided by this invention not only ensures high shear strength but also effectively reduces brazing temperature.

[0112] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A sintered preformed brazing filler metal, characterized in that, It includes magnesium film and aluminum powder, copper oxide powder and nickel powder attached to the same side of the magnesium film, as well as aluminum flux attached to the other side of the magnesium film; The mass of the nickel powder is 1.7%-2.7% of the total mass of the sintered preformed brazing filler metal; The mass of the aluminum powder is M1, the mass of the copper oxide powder is M2, and the mass of the nickel powder is M3, wherein (M1-9M2 / 40):M3=(6~10):

1.

2. The sintered preformed brazing filler metal according to claim 1, characterized in that, The aluminum powder and copper oxide powder have a particle size of 10μm to 50μm, and the nickel powder has a particle size of 200nm to 800nm.

3. The sintered preformed brazing filler metal according to claim 1, characterized in that, The thickness of the magnesium film is 1 / 25 to 1 / 20 of the total thickness of the sintered preformed brazing filler metal; the mass of the magnesium film is 1.5% to 1.9% of the total mass of the sintered preformed brazing filler metal.

4. The sintered preformed brazing filler metal according to claim 1, characterized in that, In the sintered preformed brazing filler metal, the magnesium film side that is not covered with aluminum powder, copper oxide powder, and nickel powder is coated with aluminum flux.

5. The sintered preformed brazing filler metal according to claim 4, characterized in that, The aluminum flux is a fluoroaluminate aluminum flux.

6. The sintered preformed brazing filler metal according to claim 5, characterized in that, The aluminum flux is cesium fluoroaluminate aluminum flux or potassium fluoroaluminate aluminum flux, and its content is 2%-8% of the total mass of the sintered preformed solder.

7. The method for preparing the sintered preformed solder according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mix aluminum powder, copper oxide powder and nickel powder evenly to obtain a mixed powder; S2. Roll the magnesium strip into a magnesium film of the required thickness and cut it to the required size; S3. The magnesium film prepared in step S2 is laid in the mold cavity of the die casting machine. Then the mixed powder prepared in step S1 is placed on the magnesium film in the mold cavity. Then die casting is performed so that the mixed powder is compacted on the magnesium film to form a brazing filler blank. S4. Coat the magnesium film side of the brazing filler blank prepared in step S3, which is not covered with mixed powder, with aluminum flux to form a sintered preformed brazing filler.

8. The application of the sintered preformed brazing filler metal as described in any one of claims 1 to 6 or the brazing filler metal obtained by the preparation method of the sintered preformed brazing filler metal as described in claim 7 in brazing.

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