Highly active aluminum brazing agent

Abstract

The application discloses a high-activity aluminum brazing flux. The high-activity aluminum brazing flux is composed of 46.0-54.0% of cesium fluoride, 2.5-5.0% of nano aluminum hydroxide, 2.5-5.0% of nano aluminum oxide, 0.02-0.2% of nano rubidium fluoride, 0.0001-0.0002% of nano gallium fluoride, 0.0001-0.0002% of nano gallium oxide and the balance of aluminum fluoride. The spreading area of the brazing flux is increased by 200-280% compared with that of the existing commercially available cesium fluoroaluminate brazing flux, the spreading area of the brazing filler metal is increased by 100-140%, the high-activity aluminum brazing flux can meet the brazing requirements of 'aluminum-steel', 'aluminum-copper' and 'aluminum-aluminum' simultaneously.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of brazing materials of metal materials, and particularly relates to a high-activity aluminum flux. BACKGROUND

[0002] Aluminum and aluminum alloy are widely used in brazing, and the research and performance improvement of the flux for aluminum alloy brazing have been a hot topic in the field of aluminum alloy brazing, because the reliable brazing connection of aluminum and aluminum alloy can only be achieved with the aid of flux in the atmosphere environment during brazing. Generally, the flux residue needs to be cleaned up properly after the brazing connection is completed, so as to avoid the corrosion of the flux residue on the brazed joint metal or base material or other adverse effects.

[0003] Before the appearance of Nocolok flux (K3AlF6-KAlF4 flux), the brazing of aluminum and aluminum alloy has been a problem in the field of brazing. Since the melting point of Nocolok flux is high (about 580 DEG C), it needs to be protected by high-purity nitrogen to have high activity, therefore, although Nocolok flux has been put into the market in the 1970s, it has not been applied to the manufacture of automobile radiators until the late 1980s. Later, through continuous improvement by scientists, it is found that the pure KAlF4 flux has better performance than the K3AlF6-KAlF4 flux, and the reliable brazing connection of aluminum alloy can still be achieved without nitrogen, therefore, at present, the manufacturers of automobile radiators at home and abroad still widely use KAlF4 flux matched with 4047 filler metal (there are also cases of matching with 4043 filler metal) to braze aluminum automobile radiators and other aluminum alloy parts in a tunnel furnace.

[0004] In the past 20 years, there are more reports about the Nocolok flux and the similar CsAlF4 flux for brazing of aluminum and aluminum alloy, because the melting point of CsAlF4 flux is only about 450 DEG C, which is more than 100 DEG C lower than that of KAlF4 flux (about 560 DEG C), so that it is easier to use CsAlF4 flux to braze aluminum alloy and the process is simpler. Since Cs element is a rare element and expensive, the price of CsAlF4 flux is 10 times that of KAlF4 flux, which is a weakness that cannot be overcome by CsAlF4 flux. Therefore, it has great practical value to further improve the activity of CsAlF4 flux without significantly increasing the cost of flux materials, so that it can still meet the requirements of aluminum and aluminum alloy structure brazing while greatly reducing the amount.

[0005] The applicant found through literature retrieval that patent CN201410188273.3 discloses a high-activity non-corrosive aluminum brazing flux, which is mainly composed of the following components: KF 43-46.3%, AlF3 50-53.7%, NaO 0.5-4%, CoO 0.1-1%, and Al2O3 0.5-5%. NaO, Al2O3, and CoO are added to the base components KF and AlF3 of the brazing flux, which can reduce the melting point of the brazing flux and improve the activity of the brazing flux. However, the melting point of the brazing flux is still 539.2-547.5°C, which is much higher than the melting point of the CsAlF4 brazing flux (about 450°C).

[0006] Patent CN201610145455.1 discloses a brazing flux suitable for aluminum-steel brazing, which contains, by mass percentage, 0.001-0.01% of rubidium fluoride, 11.0-45.0% of cesium fluoride, 0.01-2.0% of aluminum hydroxide, 0.01-5.0% of potassium fluoride, 0.001-0.04% of zinc fluoride, and the balance of aluminum fluoride. The brazing flux can simultaneously meet the requirements of aluminum-steel, aluminum-copper, and aluminum-aluminum brazing and has high activity. However, the biggest disadvantage of the brazing flux is that zinc fluoride has hygroscopicity, so the brazing flux needs to be strictly sealed during use and storage, otherwise it is easy to harden and even lose brazing activity.

[0007] Document CN202110606723.6 discloses an aluminum brazing flux and a preparation method thereof. The aluminum brazing flux contains CsF, KF, and AlF3, and the mass ratio of CsF:KF:AlF3 is 1.0-4.0:40.3-48.5:50.5-55.7. The aluminum brazing flux with CsF, KF, and AlF3 as the main phase not only has the characteristics of non-corrosion, but also can effectively remove the oxide film on the surface of aluminum base material and brazing filler containing a high amount of magnesium, so that the aluminum brazing flux has good wettability, improves the effective welding point rate of the aluminum brazing flux, and reduces the leakage rate. From the formula, it belongs to the improvement of K3AlF6-KAlF4 brazing flux, and the matching brazing filler should belong to 4047 or 4043, so the melting point should also be about 550°C.

[0008] Document CN202111031957.9 discloses a rubidium cesium aluminum fluoroaluminate brazing flux and a preparation method thereof. The brazing flux contains 45-50% Rb, 9-10% Cs, 10-13% Al, 27-35% F, <0.01% Li, <0.01% K, <0.05% Na, <0.01% Ca, <0.005% Ba, and the balance of oxygen and other impurities. The Rb content in the brazing flux is as high as 45% or more, which makes the price cost too high and difficult to be widely applied (Rb also belongs to a rare element, and the current market price is higher than that of Cs).

[0009] The above brazing fluxes have respective advantages, but each has different problems: K3AlF6-KAlF4 brazing flux with KF-AlF3 as main chemical component has low price, its melting point is relatively high (about 560℃), but it is already widely used in brazing of Al-Si filler metal for automobile radiators; CsAlF4 brazing flux with CsF-AlF3 as main chemical component has low melting point (about 450℃), its price is about 10 times of K3AlF6-KAlF4 brazing flux, and its application is limited. Therefore, it is urgent to develop CsF-AlF3 brazing flux with high activity and low melting point, which can greatly reduce the amount of rare element Cs and Rb and meet the requirements of "aluminum-steel", "aluminum-copper" and "aluminum-aluminum" brazing. SUMMARY

[0010] The present application aims to provide a high-activity aluminum brazing flux with a melting point not higher than that of CsF-AlF3 brazing flux, but with higher activity to meet the requirements of "aluminum-steel", "aluminum-copper" and "aluminum-aluminum" brazing.

[0011] The technical solution to achieve the object of the present application is as follows:

[0012] A high-activity aluminum brazing flux, comprising, by mass percentage: 46.0-54.0% of cesium fluoride, 2.5-5.0% of nano-aluminum hydroxide, 2.5-5.0% of nano-aluminum oxide, 0.02-0.2% of nano-rubidium fluoride, 0.0001-0.0002% of nano-gallium fluoride, 0.0001-0.0002% of nano-gallium oxide, and the balance of aluminum fluoride.

[0013] Further, the particle size of the nano-aluminum hydroxide, nano-aluminum oxide, nano-rubidium fluoride, nano-gallium fluoride and nano-gallium oxide is 100-200 nm.

[0014] The high-activity aluminum brazing flux can be prepared by mixing the components in a stainless steel container in proportion.

[0015] According to GB / T11364-2008 "Brazing filler metal wettability test method", the spread area of the high-activity aluminum brazing flux of the present application on 6061 aluminum alloy plate, T2 red copper and Q235 steel plate is measured at 520℃ with Zn85-Al15 filler metal. The mass of the filler metal used in each test is 100 mg, and the mass of the brazing flux is 15 mg. The test results show that the spread area of the brazing flux of the present application is increased by 200%-280% compared with that of the existing commercially available cesium fluoroaluminate (CsAlF4) brazing flux, and the spread area of the filler metal is increased by 100%-140%, which indicates that the aluminum brazing flux of the present application has high activity and can meet the requirements of "aluminum-steel", "aluminum-copper" and "aluminum-aluminum" brazing. DETAILED DESCRIPTION

[0016] Compared with the existing commercially available cesium fluoroaluminate brazing agent (CsAlF4 brazing agent), the high-activity aluminum brazing agent of the present application creatively solves the following key technical problems:

[0017] 1) The synergistic effect of extremely small amounts of nanometer gallium fluoride and nanometer gallium oxide is discovered, i.e. the rule of significantly improving the wetting and spreading performance of CsF-AlF3 brazing agent. After composition optimization, it is determined that when the particle size of nanometer gallium fluoride and nanometer gallium oxide is controlled at 100 nm-200 nm, and the addition amount is controlled at 0.0001-0.0002% respectively, the spreading area of the brazing agent of the present application can be increased by 200%-280% compared with the spreading area of the commercially available CsAlF4 brazing agent, and the spreading area of the filler metal can be increased by 100%-180%. As can be seen from Comparative Example 1, the spreading area of the brazing agent and the filler metal is still significantly improved compared with the CsAlF4 brazing agent, but the performance is still far from that of the brazing agent of the present application, which fully shows the unexpected technical effect of the extremely small amounts of nanometer gallium fluoride and nanometer gallium oxide.

[0018] The brazing agent of the present application uses propane as the combustible gas for flame brazing, and cooperates with Zn85-Al15 filler metal to form Q235 steel plate+6061 aluminum alloy plate, T2 red copper+6063 aluminum alloy plate combination, and carries out tests according to GB / T11363-2008 "Brazed joint strength test method". The shear strength of the brazing seam is all 137 MPa±10 MPa (the fracture position is all at the interface between the brazing seam and the base material). The above results show that the brazing agent of the present application can save more than 50% of the brazing agent in actual brazing work, not only greatly reduces the production cost, but also greatly reduces the amount of "fluoride residue" after welding, and reduces the pollution of fluoride in CsAlF4 brazing agent to the environment.

[0019] 2) By adding 2.5-5.0% of nanometer aluminum hydroxide+2.5-5.0% of nanometer aluminum oxide+0.02-0.2% of nanometer rubidium fluoride (particle size controlled at 100 nm-200 nm), the same effect of reducing the melting temperature of the new brazing agent and improving the spreading area of the brazing agent and the filler metal is achieved.

[0020] The content of cesium fluoride (CsF) in the pure CsAlF4 flux agent is 64.4%, and the melting temperature range is 465-475°C. Although the "new combination" of the application adds the composition of "2.5-5.0% nano-aluminum hydroxide + 2.5-5.0% nano-aluminum oxide + 0.02-0.2% nano-rubidium fluoride" with higher melting temperature, the melting temperature of the flux agent of the application is reduced to 448-462°C, which is closer to the melting temperature of Zn85-Al15 filler metal, and is more conducive to the brazing operation of "aluminum-steel" and "aluminum-copper" dissimilar materials. As shown in Comparative Example 2, the addition of the compound combination of aluminum hydroxide, aluminum oxide and rubidium fluoride with ordinary particle size can significantly improve the spreading area of the flux agent and filler metal compared with the CsAlF4 flux agent, but the performance of the flux agent is still far from that of the flux agent of the application, which shows that the compound combination of nano-aluminum hydroxide, nano-aluminum oxide and nano-rubidium fluoride has more excellent performance.

[0021] The application will be further described in detail below with reference to specific examples.

[0022] Example 1

[0023] A high-activity aluminum flux agent, consisting of the following components in mass percentage: 46.0% cesium fluoride, 5.0% nano-aluminum hydroxide, 2.5% nano-aluminum oxide, 0.2% nano-rubidium fluoride, 0.0001% nano-gallium fluoride, 0.0002% nano-gallium oxide, and the balance being aluminum fluoride. The particle size of the nano-aluminum hydroxide, nano-aluminum oxide, nano-rubidium fluoride, nano-gallium fluoride and nano-gallium oxide is 100-200 nm.

[0024] The melting temperature range of the above flux agent is 448-462°C. According to GB / T11364-2008 "Test method for wettability of filler metal", the Zn85-Al15 filler metal is used to test the excellent wetting and spreading performance of the flux agent on 6061 aluminum alloy plate, T2 red copper and Q235 steel plate at 520°C (see Table 1, the spreading area of the commercially available CsAlF4 flux agent is increased by 200-280%, and the spreading area of the filler metal is increased by 100-180%). Propane is used as a combustible gas for flame brazing at 500-600°C, and the Zn85-Al15 filler metal is used to test the Q235 steel plate + 6061 aluminum alloy plate, T2 red copper + 6061 aluminum alloy plate and 6061 aluminum alloy + 6061 aluminum alloy plate combination according to GB / T11363-2008 "Test method for strength of brazed joint", and the shear strength of the brazing seam is 137 MPa ± 10 MPa (the fracture position is at the interface between the brazing seam and the base material).

[0025] Example 2

[0026] A high-activity aluminum brazing flux, consisting of the following components in percentage by mass: 54.0% cesium fluoride, 2.5% nano-aluminum hydroxide, 5.0% nano-aluminum oxide, 0.02% nano-rubidium fluoride, 0.0002% nano-gallium fluoride, 0.0002% nano-gallium oxide, and the balance being aluminum fluoride. The particle size of the nano-aluminum hydroxide, nano-aluminum oxide, nano-rubidium fluoride, nano-gallium fluoride, and nano-gallium oxide is 100-200 nm.

[0027] The melting temperature range of the above-mentioned brazing flux is 448-462°C. According to GB / T11364-2008 "Brazing Flux Wettability Test Method", in combination with Zn85-Al15 brazing filler metal, it has excellent wetting and spreading performance on 6061 aluminum alloy plate, T2 red copper, and Q235 steel plate at 520°C (see Table 1, the spreading area is increased by 200-280% compared with that of commercially available CsAlF4 brazing flux, and the spreading area of the brazing filler metal is increased by 100-180%).

[0028] Example 3

[0029] A high-activity aluminum brazing flux, consisting of the following components in percentage by mass: 50.0% cesium fluoride, 3.5% nano-aluminum hydroxide, 3.0% nano-aluminum oxide, 0.1% nano-rubidium fluoride, 0.0001% nano-gallium fluoride, 0.0001% nano-gallium oxide, and the balance being aluminum fluoride. The particle size of the nano-aluminum hydroxide, nano-aluminum oxide, nano-rubidium fluoride, nano-gallium fluoride, and nano-gallium oxide is 100-200 nm.

[0030] The melting temperature range of the above flux is 448-462°C. According to GB / T11364-2008 "Solder Wettability Test Method", with Zn85-Al15 solder, it is measured that it has excellent wetting and spreading performance on 6061 aluminum alloy plate, T2 red copper, Q235 steel plate at 520°C (see Table 1, the spreading area is increased by 200-280% compared with the commercially available CsAlF4 flux, and the spreading area of the solder is increased by 100-180%).

[0031] Comparative Example 1

[0032] An aluminum flux, consisting of the following components by mass percentage: 50.0% cesium fluoride, 3.5% nano-aluminum hydroxide, 3.0% nano-aluminum oxide, 0.1% nano-rubidium fluoride, and the balance being aluminum fluoride. The particle size of the nano-aluminum hydroxide, nano-aluminum oxide, and nano-rubidium fluoride is 100-200 nm.

[0033] The melting temperature range of the above flux is 455-462°C. According to GB / T11364-2008 "Solder Wettability Test Method", with Zn85-Al15 solder, it is measured that it has excellent wetting and spreading performance on 6061 aluminum alloy plate, T2 red copper, Q235 steel plate at 520°C (see Table 1, the spreading area is increased by 100-120% compared with the commercially available CsAlF4 flux, and the spreading area of the solder is increased by 50-80%). Flame brazing is carried out at 500-600°C using propane as a combustible gas, with Zn85-Al15 solder, with Q235 steel plate + 6061 aluminum alloy plate, T2 red copper + 6061 aluminum alloy plate, 6061 aluminum alloy + 6061 aluminum alloy plate combinations, and according to GB / T11363-2008 "Brazed Joint Strength Test Method", the shear strength of the brazing seam is 118 MPa ± 10 MPa (the fracture position is at the interface between the brazing seam and the base material, which is more than 13% lower than that of Example 1-3).

[0034] Comparative Example 2

[0035] An aluminum flux, consisting of the following components by mass percentage: 50.0% cesium fluoride, 3.5% aluminum hydroxide, 3.0% aluminum oxide, 0.1% rubidium fluoride, 0.0001% nano gallium fluoride, 0.0001% nano gallium oxide, and the balance being aluminum fluoride. The particle size of the aluminum hydroxide, aluminum oxide, and rubidium fluoride is the commonly used ordinary particle size, which is -100 mesh (particle size ≤0.15 mm).

[0036] The melting temperature range of the above flux is 455-470°C. According to GB / T11364-2008 "Test Method for Flux Wettability", in combination with Zn85-Al15 filler metal, it has excellent wetting and spreading performance on 6061 aluminum alloy plate, T2 red copper, and Q235 steel plate at 520°C (see Table 1, the spreading area is increased by 80-100% compared to commercially available CsAlF4 flux, and the spreading area of the filler metal is increased by 50-60%). Using propane as a combustible gas, flame brazing is carried out at 500-600°C, in combination with Zn85-Al15 filler metal, with Q235 steel plate + 6061 aluminum alloy plate, T2 red copper + 6061 aluminum alloy plate, and 6061 aluminum alloy + 6061 aluminum alloy plate combinations, according to GB / T11363-2008 "Test Method for Brazed Joint Strength", the brazed joint shear strength reaches 122 MPa ± 10 MPa (the fracture position is at the interface between the brazed joint and the base material, which is more than 10% lower than that of Example 1-3).

[0037] Table 1 Comparison of flux and filler metal spreading area

[0038]

Claims

1. A high-activity aluminum flux, characterized by comprising: According to mass percentage, the composition comprises: 46.0-54.0% of cesium fluoride, 2.5-5.0% of nano aluminum hydroxide, 2.5-5.0% of nano aluminum oxide, 0.02-0.2% of nano rubidium fluoride, 0.0001-0.0002% of nano gallium fluoride, 0.0001-0.0002% of nano gallium oxide, and the rest is aluminum fluoride.

2. The high activity aluminum flux according to claim 1, characterized by, The particle size of the nano aluminum hydroxide, the nano aluminum oxide, the nano rubidium fluoride, the nano gallium fluoride and the nano gallium oxide is 100-200 nm.

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