Synthesis method of nanoscale hydroxyl fluorine metal acid potassium / sodium brazing flux for aluminum brazing
By synthesizing nano-sized potassium/sodium hydroxyl fluoride metal brazing flux in an organic solvent/water mixture, the problems of uneven particle size and complex process of traditional brazing fluxes are solved, achieving low-cost and high-efficiency aluminum brazing, and improving the quality and stability of brazed joints.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG MINGRUI NEW MATERIAL TECHNOLOGY CO LTD
- Filing Date
- 2026-03-31
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional brazing fluxes suffer from poor particle size uniformity and stability, complex processes, and high costs during aluminum brazing. They are also difficult to precisely control the reaction process in non-aqueous environments, resulting in poor brazed joint quality.
Nanoscale potassium/sodium hydroxyl fluoride metal oxide brazing flux was synthesized by using aluminum hydroxide, potassium hydroxide/sodium hydroxide/calcium hydroxide/magnesium hydroxide, etc., and hydrofluoric acid aqueous solution in a mixed system of organic solvent/water. By controlling the pH value and temperature, a brazing flux with small particle size and high activity was prepared, which lowered the melting point and improved the wetting performance.
The prepared brazing flux has uniform particle size, stable dispersion, low melting point, low cost, and is easy to use. It produces a smooth surface after brazing, reduces brazing defects and residues, and improves the quality of brazed joints.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of brazing materials technology, specifically relating to a method for synthesizing a nano-scale potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing. Background Technology
[0002] The traditional soldering flux "Nokolock" is nominally composed of K 1.14 AlF 4.14 Potassium fluoroaluminate is used as a brazing flux in many industrial fields. Hundreds of thousands of tons are used annually in the manufacture of heat exchangers for air conditioning systems, automobiles, and refrigeration equipment. 1.14 AlF 4.14 It is actually a mixture of KAlF4 with small amounts of AlF3 and K2AlF5, and trace amounts of K3AlF6. In the chemical phase diagram of the KF-AlF3 system, a molar ratio of 1.14KF to 1AlF3 represents the eutectic composition, at which point the system has the lowest melting point. During the brazing of aluminum, a dense alumina film exists on its surface. This oxide film hinders the wetting and flow of the molten brazing filler metal, severely affecting the quality of the brazed joint. The main application of potassium fluoroaluminate brazing flux is its ability to react with the alumina film in the molten (liquid) state. The main reaction equation is as follows: Al₂O₃ + 6KAlF₄ → 8AlF₃ + 3K₂O (Equation 1a) Al₂O₃ + 3K₂AlF₅ → 5AlF₃ + 3K₂O (Formula 1b) Al2O3 + 2K3AlF6 → 4AlF3 + 3K2O (Formula 1c)
[0003] In practical applications, since the melting point of metallic aluminum is approximately 660.3℃, while the melting points of pure potassium fluoroaluminate (KAlF4, K2AlF5, and K3AlF6) are all higher than 660.3℃, it is impossible to use any one type of pure potassium fluoroaluminate in the brazing process. However, at the eutectic point, the melting points of 1.14KF and 1AlF3 are only about 565-572℃, therefore, nominally composed of K... 1.14 AlF 4.14 Potassium fluoroaluminate can be used as a brazing flux in aluminum brazing processes. However, in application, according to Formula 1, the powdered brazing flux must be suspended in water or an alcohol / water mixture, and usually a binder is added to adhere it to the aluminum surface. At this stage, Nokolock needs to be evenly applied to the aluminum surface to ensure brazing continuity.
[0004] The traditional synthesis process of potassium fluoroaluminate for soldering mainly includes the following two steps: 1. Aluminum hydroxide is dissolved in a 40% hydrofluoric acid solution, with a molar ratio of hydrofluoric acid to aluminum hydroxide of 4.14:1. After complete dissolution, fluorochloric acid is formed, and the reaction formula is as follows: 4.14HF + Al(OH)3 → H 1.14 AlF 4.14 +3H₂O (Equation 2); 2. After aluminum hydroxide is completely dissolved in hydrofluoric acid solution, add the required amount (quantitative) of potassium hydroxide aqueous solution according to chemical calculations to neutralize the system. The reaction formula is as follows: H 1.14 AlF 4.14 +1.14KOH→K 1.14 AlF 4.14 +1.14H2O (Equation 3). The above two steps of reaction form the total component K. 1.14 AlF 4.14 The product is cleaned, filtered, dried and crushed to obtain a white solid powder product. For example, Chinese patent application document with publication number CN106392383A discloses an aluminum-based flux-cored welding wire and its preparation method. The preparation steps are as follows: (1) After the aluminum-based alloy is smelted and purified, it is melted to obtain a molten liquid; the molten liquid is subjected to inert gas impact and falls, cooled, collected and sieved to obtain a brazing filler metal; (2) aluminum hydroxide is added to hydrofluoric acid, and then potassium hydroxide is added to perform co-precipitation. The product obtained from the co-precipitation is dried, crushed and sieved to obtain a brazing flux; (3) the brazing filler metal obtained in step (1) and the brazing flux obtained in step (2) are mixed evenly and then pressed to obtain a pressed blank. The pressed blank is heated and extruded at varying speeds to obtain the aluminum-based flux-cored welding wire. However, traditional synthesis processes suffer from the following problems: 1. In an aqueous reaction environment, even with the addition of surfactants or activators, powder particles are still prone to Ostwald ripening and agglomeration, making it difficult to obtain products with fine and uniform particle size distribution; 2. Complex steps such as washing are required after the reaction to remove impurity ions, making the process complicated; 3. The reaction products require filtration, drying, crushing, and grinding, resulting in high post-processing costs and environmental pollution. Therefore, a new reaction control strategy is needed to more precisely control the reaction process in a non-aqueous environment to synthesize a new type of aluminum brazing flux with more uniform particle size, better stability, and direct usability. Summary of the Invention
[0005] To address the technical problems of poor particle size uniformity and stability, complex processes, and high costs in the existing technologies, the present invention aims to provide a method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing. The present invention uses aluminum hydroxide, potassium hydroxide / sodium hydroxide / calcium hydroxide / magnesium hydroxide, and hydrofluoric acid aqueous solution as main raw materials, and prepares a novel aluminum brazing flux in the presence of an organic solvent / water mixture, which can be directly applied to the brazing process.
[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing includes the following steps: S1: Add aluminum hydroxide to hydrofluoric acid aqueous solution to dissolve, stir and react for 0.5-3 hours to obtain fluoroaluminic acid solution; S2: Add an organic solvent to the fluoroaluminate solution obtained in step S1, stir until homogeneous, and obtain an alcohol solution; S3: Add an aqueous solution of metal hydroxide to the alcohol solution obtained in step S2, stir until homogeneous, adjust the pH of the system to 5.0, stir the reaction, and concentrate by rotary evaporation to obtain nano-sized potassium / sodium hydroxyl fluoride metal brazing flux.
[0007] In the above scheme, the controllable synthesis of nano-sized potassium / sodium hydroxyl fluoride metal oxides under mild conditions is achieved through an alcohol-water mixed reaction system. The product has small particle size, high activity, and excellent brazing wetting performance. The pH value is precisely controlled at 5.0 during the reaction process to stably introduce hydroxyl groups, significantly reduce the melting point of the brazing flux, improve its ability to remove oxide film on aluminum surface, enhance spreadability and wettability, reduce brazing defects, and produce less residue. The addition of organic solvents in the reaction process reduces polarity, eliminating the need for high-temperature calcination and mechanical ball milling, avoiding particle agglomeration and the introduction of impurities, and resulting in a product with uniform particle size.
[0008] Furthermore, in step S1, the molar ratio of hydrofluoric acid to aluminum hydroxide in the hydrofluoric acid aqueous solution is (4-6):1.
[0009] Furthermore, in step S1, the molar ratio of hydrofluoric acid to aluminum hydroxide in the hydrofluoric acid aqueous solution is (4.1-4.2):1.
[0010] In the above scheme, the molar ratio of hydrofluoric acid to aluminum hydroxide is crucial in determining whether aluminum hydroxide dissolves, whether the system is clear and stable, the coordination morphology of the fluorine-aluminum complex particles, and the amount of hydroxyl groups retained in the product. A molar ratio that is too low will lead to incomplete dissolution of aluminum hydroxide, a turbid system, insufficient coordination of the formed fluorine-aluminum complex, and easy re-hydrolysis to form aluminum hydroxide colloid. A molar ratio that is also too low will result in excessive fluorine, excessively acidic system, and a product that is almost entirely perfluorinated, making it difficult to retain the hydroxyl structure and affecting the performance of the soldering flux. In this invention, a molar ratio of hydrofluoric acid to aluminum hydroxide of (4-6):1 is selected. Within this range, complete dissolution of aluminum hydroxide and stable formation of AlF4 are ensured. - AlF5 2- The fluorine-aluminum complex system, which is mainly composed of fluorine and aluminum, has moderate acidity, providing a basis for the subsequent introduction of hydroxyl groups.
[0011] Furthermore, the hydrofluoric acid aqueous solution in step S1 has a mass percentage of 5%-100%.
[0012] Furthermore, the hydrofluoric acid aqueous solution in step S1 has a mass percentage of 20%-50%.
[0013] In the above scheme, the mass percentage of hydrofluoric acid aqueous solution directly determines the acidity, fluoride ion activity, aluminum hydroxide dissolution rate, and fluorine-aluminum complexation degree of the system. If the concentration of hydrofluoric acid aqueous solution is too high, it will lead to increased fluoride ion activity, which will easily form transitional fluoride coordination at the aluminum center, making it difficult to retain structural hydroxyl groups. In addition, the local reaction is too fast, which can easily lead to a large number of nucleations in an instant, resulting in severe product agglomeration and uneven particle size. If the concentration of hydrofluoric acid aqueous solution is too low, it will lead to slow and incomplete dissolution of aluminum oxide, insufficient fluoride supply, insufficient fluorine-aluminum complexation, and the formation of colloidal aluminum hydroxide. At the same time, the reaction driving force will decrease, the crystallinity of the product will be poor, the brazing activity will be insufficient, and the wettability and oxide film removal ability will decrease.
[0014] Furthermore, the temperature of the stirring reaction in step S1 is 0-80℃, and the stirring reaction time is 1-3h.
[0015] Furthermore, the temperature of the stirring reaction in step S1 is 5-20°C.
[0016] In the above scheme, during the dissolution of aluminum hydroxide in hydrofluoric acid aqueous solution to form a fluorochloric acid complex, temperature directly affects the dissolution rate and degree of aluminum hydroxide, the coordination structure of the fluoroaluminate complex particles, the retention degree of hydroxyl groups in the subsequent alcohol-water system, and the particle size and dispersibility of the final product. Excessive temperature leads to significant fluorine loss, unstable product composition, and the easy formation of high coordination number fluoroaluminates during the complexation reaction, making it difficult to retain hydroxyl groups, resulting in high solution supersaturation. This leads to rapid agglomeration during subsequent neutralization, precipitation of coarse crystals, and difficulty in obtaining nanoscale products. Conversely, excessively low temperatures significantly slow down the dissolution rate of aluminum hydroxide, resulting in incomplete reactions. In this invention, a temperature range of 0-80℃ is selected to ensure the dissolution of aluminum hydroxide and the formation of a stable fluorochloric acid complex solution, while avoiding excessive volatilization of hydrofluoric acid and side reactions, providing a stable precursor for the preparation of nanoscale potassium / sodium hydroxyl fluoride metal brazing flux.
[0017] Furthermore, the organic solvent mentioned in step S2 is one or more of methanol, ethanol, ethylene glycol, propylene glycol, butanediol, and methylpentanediol; the amount of the organic solvent added is 2-6 times the mass of aluminum hydroxide.
[0018] Furthermore, the organic solvent mentioned in step S2 is methylpentanediol, and the amount of the organic solvent added is 3-5 times the mass of aluminum hydroxide.
[0019] In the above scheme, an alcohol-water reaction system is constructed by adding an alcohol organic solvent, which reduces the node constant of the reaction system and weakens the association between fluoroaluminate ions, making the product formation rate much greater than the crystal growth rate, thereby directly obtaining nanoscale fine crystals without the need for subsequent ball milling. At the same time, the addition of alcohol organic solvent can also improve the miscibility of the system, so that the alkaline solution can be quickly and evenly dispersed after addition, the pH fluctuation of the reaction system is small, the reaction is more uniform, the product phase purity is higher, the melting point is stable, and the brazing consistency is good. Moreover, the alcohol molecule contains hydroxyl groups, which can form hydrogen bonds with fluoroaluminate complexes, inhibit the excessive substitution of fluorine, and keep the structural hydroxyl groups in the product stably, thereby reducing the melting point of the brazing flux and improving the wetting and spreading ability of the aluminum oxide film.
[0020] Furthermore, the metal hydroxide mentioned in step S3 is one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, and magnesium hydroxide; the molar ratio of the metal hydroxide to hydrofluoric acid is (0.061-0.134):(0.41-0.42).
[0021] Compared with existing technologies, the method for synthesizing nano-scale potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing provided by this invention has the following technical advantages: (1) The present invention uses aluminum hydroxide, potassium hydroxide / sodium hydroxide / calcium hydroxide / magnesium hydroxide and hydrofluoric acid aqueous solution as the main raw materials, and prepares a new type of aluminum brazing flux with a melting point about 20°C lower than that of the traditional Nokolock in a mixed system of organic solvent / water. (2) The brazing flux prepared by the present invention has the characteristics of low melting point, small particle size, concentrated distribution and strong dispersion stability, and its comprehensive performance is significantly better than that of the brazing flux prepared by traditional methods. (3) The brazing flux prepared by the present invention has low cost, is easy to use, has good film-forming effect, low dosage and high surface smoothness after brazing. Detailed Implementation
[0022] The following will provide further details with reference to specific embodiments, but the present invention is not limited to these embodiments. Those skilled in the art can make various modifications based on the basic idea of the present invention, but as long as they do not depart from the basic idea of the present invention, they are all within the scope of the present invention. The raw materials described in this specific embodiment are all commercially available.
[0023] In this specific embodiment, the synthesis route of nano-sized potassium / sodium hydroxyl fluoride metal oxide for aluminum brazing is as follows: 4.14HF + Al(OH)3 → H 1.14 AlF 4.14 +3H2O formula 4a; H 1.14 AlF 4.14 +glycol→H 1.14 AlF4.14 (gly) Formula 4b; H 1.14 AlF 4.14 +(1.14+n)KOH→K (1.14+n) AlF 4.14 (OH)n+1.14H2O Equation 5a, where n=0-2; H 1.14 AlF 4.14 +xKOH + yNaOH → K x Na y AlF 4.14 (OH) (x+y-1.14) +1.14H2O, formula 5b, where x=0-2, y=0-2; H 1.14 AlF 4.14 +xKOH+yMg(OH)2→K x Mg y AlF 4.14 (OH) (x+2y-1.14) +1.14H2O, formula 5c, where x=0-2, y=0-2.
[0024] Example 1 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 41.4g of a 20% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Start stirring. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.385g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the above system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0025] Example 2 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 27.6 g of a 30% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath at 20°C and start stirring. Measure 7.8 g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2 g of methylpentanediol to the system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.385 g of potassium hydroxide in 9.58 ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40°C to a solid content of 35% to obtain liquid brazing flux.
[0026] Example 3 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.385g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the above system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0027] Example 4 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 16.56 g of a 50% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20°C. Start stirring. Measure 7.8 g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2 g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38 g of potassium hydroxide in 9.58 ml of deionized water and slowly add it dropwise to the above system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40°C to a solid content of 35% to obtain liquid brazing flux.
[0028] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 1-4 are shown in Table 1.
[0029] Table 1. Detection results of Examples 1-4
[0030] Example 5 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.5g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.16g of potassium hydroxide in 9.24ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ until the solid content is 35%, obtaining liquid brazing flux.
[0031] Example 6 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 21.0 g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20°C. Turn on the stirrer. Measure 7.8 g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2 g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.72 g of potassium hydroxide in 10.09 ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40°C to a solid content of 35% to obtain liquid brazing flux.
[0032] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 5 and 6 are shown in Table 2.
[0033] Table 2 Detection results of Examples 5-6
[0034] Example 7 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 5°C. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40°C to a solid content of 35% to obtain liquid brazing flux.
[0035] Example 8 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 10℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0036] Example 9 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 15℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0037] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 7-9 are shown in Table 3.
[0038] Table 3 Detection results of Examples 7-9
[0039] Example 10 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 48 minutes. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0040] Example 11 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 90 minutes. After the reaction system becomes clear and transparent, add 31.2g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0041] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 10 and 11 are shown in Table 4.
[0042] Table 4 Detection results of Examples 10-11
[0043] Example 12 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of ethanol to the reaction system and continue stirring for 0.5 hours until the ethanol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0044] Example 13 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of ethylene glycol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0045] Example 14 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 31.2g of propylene glycol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0046] Example 15 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add a mixture of 15.6g of ethylene glycol and 15.6g of propylene glycol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0047] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 12-15 are shown in Table 5.
[0048] Table 5. Detection results of Examples 12-15
[0049] Example 16 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 23.4g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0050] Example 17 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 39g of methylpentanediol to the reaction system and continue stirring for 0.5 hours until the alcohol and solution are completely mixed. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0051] The particle size and melting point test results of the liquid brazing fluxes prepared in Examples 16 and 17 are shown in Table 6.
[0052] Table 6 Detection results of Examples 16-17
[0053] Example 18 A method for synthesizing a nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, specifically comprising: Measure 20.7g of a 40% hydrofluoric acid aqueous solution and add it to a four-necked flask. Place the flask in a water bath and control the temperature at 20℃. Turn on the stirrer. Measure 7.8g of aluminum hydroxide powder and slowly add it to the flask. React at this temperature for 1 hour. After the reaction system becomes clear and transparent, add 39g of water to the reaction system and continue stirring for 0.5 hours. Dissolve 6.38g of potassium hydroxide in 9.58ml of deionized water and slowly add it dropwise to the system while stirring. Adjust the pH of the system to 5.0 with hydrofluoric acid solution or potassium hydroxide solution. React at room temperature for 2 hours. Concentrate the reaction solution by rotary evaporation at 40℃ to a solid content of 35% to obtain liquid brazing flux.
[0054] The particle size and melting point test results of the liquid brazing flux prepared in Example 18 are shown in Table 7.
[0055] Table 7 Detection Results of Example 18
[0056] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.
Claims
1. A method for synthesizing nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing, characterized in that, Includes the following steps: S1: Add aluminum hydroxide to hydrofluoric acid aqueous solution to dissolve, stir and react for 0.5-3 hours to obtain fluoroaluminic acid solution; S2: Add an organic solvent to the fluoroaluminate solution obtained in step S1, stir until homogeneous, and obtain an alcohol solution; S3: Add an aqueous solution of metal hydroxide to the alcohol solution obtained in step S2, stir until homogeneous, adjust the pH of the system to 5.0, stir the reaction, and concentrate by rotary evaporation to obtain nano-sized potassium / sodium hydroxyl fluoride metal brazing flux.
2. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 1, characterized in that, The molar ratio of hydrofluoric acid to aluminum hydroxide in the hydrofluoric acid aqueous solution in step S1 is (4-6):
1.
3. The method for synthesizing the nano-scale potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 2, characterized in that, The molar ratio of hydrofluoric acid to aluminum hydroxide in the hydrofluoric acid aqueous solution in step S1 is (4.1-4.2):
1.
4. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 1, characterized in that, The hydrofluoric acid aqueous solution in step S1 has a mass percentage of 5%-100%.
5. The method for synthesizing nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 4, characterized in that, The hydrofluoric acid aqueous solution in step S1 has a mass percentage of 20%-50%.
6. The method for synthesizing the nano-scale potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 1, characterized in that, The temperature of the stirring reaction in step S1 is 0-80℃, and the stirring reaction time is 1-3h.
7. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 6, characterized in that, The temperature of the stirring reaction in step S1 is 5-20℃.
8. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 1, characterized in that, The organic solvent mentioned in step S2 is one or more of methanol, ethanol, ethylene glycol, propylene glycol, butanediol, and methylpentanediol; the amount of organic solvent added is 2-6 times the mass of aluminum hydroxide.
9. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 8, characterized in that, The organic solvent mentioned in step S2 is methylpentanediol, and the amount of organic solvent added is 3-5 times the mass of aluminum hydroxide.
10. The method for synthesizing the nano-sized potassium / sodium hydroxyl fluoride metal brazing flux for aluminum brazing according to claim 1, characterized in that, The metal hydroxide mentioned in step S3 is one or more of potassium hydroxide, sodium hydroxide, calcium hydroxide, and magnesium hydroxide; the molar ratio of the metal hydroxide to hydrofluoric acid is (0.061-0.134):(0.41-0.42).