JPH054191B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a brazing flux used for brazing aluminum heat exchangers, automobile intake manifolds, etc. according to brazing specifications, and a method for brazing aluminum materials using the flux. In this specification, the term aluminum is used to include its alloys. Conventional technology For example, when manufacturing aluminum heat exchangers such as automobile radiators and condensers, and aluminum intake manifolds for automobiles with brazing specifications, each component is brazed using chloride-based flux. Many bonding methods are used. However, the above chloride flux
Because corrosive residue deteriorates corrosion resistance,
After brazing, it is necessary to thoroughly wash and remove flux by acid washing or the like, which is a complicated process, and also has the disadvantage that it is not possible to perform sufficient washing on bonded members having a complicated structure. Therefore, brazing has recently been carried out using fluoride flux, which is essentially non-corrosive, instead of chloride flux. Problems to be Solved by the Invention However, fluoride-based fluxes generally have a high melting point and have the problem of being inferior to chloride-based fluxes in their oxide film breaking action and covering action for preventing oxidation. For this reason, in order to avoid oxidation of the joining parts, the atmosphere in the furnace is generally
Brazing is performed in an inert atmosphere such as N ₂ gas, but this is not sufficient to prevent oxidation and break down the oxide film.
It has been difficult to braze aluminum-containing materials or aluminum casting materials to which a large amount of Si has been added. This invention was made in view of the above technical background, and is directed to Mg-containing aluminum materials and high-Si materials.
The object of the present invention is to provide a non-corrosive flux that makes it possible to braze aluminum-containing casting materials, and a method for brazing aluminum materials using the flux. Means for Solving the Problems For the above purpose, the present invention basically uses a fluoride-based flux which is a non-corrosive flux, while adding CuCl (cuprous chloride) in a predetermined range to the flux. The inventors have discovered that the weak flux action of fluoride fluxes can be compensated for by adding fluoride-based fluxes, and have completed the present invention based on this knowledge. That is, the present invention provides a fluoride flux:
Using a brazing flux in which 0.5 to 20 wt% of CuCl is added to 99.5 to 80 wt%, and a flux in which 99.5 to 80 wt% of fluoride flux and 0.5 to 20 wt% of CuCl are added, A method for brazing aluminum materials in which flux is suspended in an acidic solvent, the suspension is applied to a bonding member made of aluminum, dried, heated to a predetermined temperature, and a brazing filler metal for bonding is melted and brazed. The gist is: First, to explain the flux, fluoride-based flux refers to a flux containing fluoride as a component, but its composition is not particularly limited. As an example of a fluoride flux, AlF ₃ powder is dissolved in an aqueous KF solution so that KF and AlF ₃ are contained in a eutectic composition or in a composition range close to it, an exothermic reaction is generated, water is removed by evaporation, and then water is removed by evaporation. or by adding water to a mixture of KF and AlF ₃ to form a paste and drying it,
Or KAlF ₄ and KF 80~99.8wt%: 20~0.2wt
% mixture or K ₃
Examples include those containing AlF ₆ and KAlF ₄ as a composition. The CuCl prevents oxidation of the surface of the joining parts, compensates for the weak flux action of fluoride flux, improves the wettability of the brazing metal, and achieves good brazing even with Mg-containing aluminum materials. play a role. That is, when the flux according to the present invention is heated in a non-oxidizing atmosphere such as a normal _N2 atmosphere, the copper component in CuCl precipitates thinly and uniformly on the surface of the aluminum bonding member at a relatively low temperature of 400 to 450°C. At the same time, a so-called cut pearlizing reaction occurs, and the chlorine component in CuCl reacts with Al to form AlCl ₃
It scatters. This thin layer of copper deposited contributes to preventing oxidation of the joining member during subsequent heating. Moreover, there is no aluminum oxide film and the copper is used for pre-treatment (Pre-treatment) for wetting and spreading of the solder.
tinning), there is no need to take more brazing temperature and time than necessary, and good brazing can be achieved. Furthermore, adding CuCl has the advantage of lowering the melting point of the flux. In order to effectively exhibit the above-mentioned effects of CuCl, it is necessary to adjust its addition ratio to a fluoride-based flux.
It is necessary to set CuCl: 0.5 to 20 wt% to 99.5 to 80 wt%. If it is less than 0.5 wt%, the above effects will be poor and it will therefore be difficult to perform good brazing of Mg-containing aluminum materials, etc. On the other hand, if it is added in excess of 20wt%, the antioxidant effect will not work effectively. A particularly preferred blending ratio of fluoride flux and CuCl is 97 to 90wt.
%: 3 to 10 wt%. The flux according to the present invention is most commonly produced by adding and mixing CuCl powder to a fluoride flux powder. When performing brazing, the flux is suspended in a slurry form in a solvent such as water. Since CuCl powder is usually oxidized and covered with a blue-green surface of CuO, it is necessary to use an acidic solvent (usually nitric acid) for suspension. The suspension prepared in this way is uniformly applied to either one of the joining members made of aluminum. In order to facilitate suspension and application in the solvent and improve brazing properties, the powder particle size of the flux component is preferably approximately 200 μm or less. Although spraying or brushing can be used as the above-mentioned application method, it is recommended to use a dipping method as a uniform application method suitable for mass production. The joining member made of aluminum is dried after applying the above flux, and then using an aluminum brazing filler metal whose melting point is lower than that of the joining member, preferably in a non-oxidizing atmosphere such as N ₂ gas or other inert gas atmosphere. By heating at a temperature lower than the melting point of the joining member and higher than the melting point of the flux, the brazing material is melted and a brazed joint is achieved. From the viewpoint of workability, it is desirable that the brazing filler metal is used by being clad with at least one aluminum component of the members to be joined. The present invention is particularly effective when applied to brazing high Mg-containing aluminum materials, but it goes without saying that it may also be applied to brazing other aluminum materials. Effects of the Invention According to the flux according to the present invention as described above, the copper component contained in CuCl precipitates on the surface of the aluminum bonding member at a relatively low temperature stage during brazing heating, so that the bonding does not occur during subsequent heating. It is possible to prevent oxidation of the member and improve the wettability and spreadability of the brazing material, thereby supplementing the oxidation-preventing and oxide film-destroying effects of the fluoride-based flux. As a result, good brazing is possible not only with ordinary aluminum materials but also with Mg-containing aluminum materials such as 7003 and high-Si-containing aluminum casting materials.
Furthermore, by adding CuCl, the melting point of the flux can be lowered compared to a single fluoride flux, and the range of aluminum materials that can be brazed can be expanded. Since the main component is a non-corrosive fluoride flux, problems such as deterioration of corrosion resistance due to corrosive residues such as those caused by chloride fluxes do not occur. Example 54.1wt% of AlF ₃ and 45.9wt% of KF were uniformly dry-mixed, a small amount of water was added to make a paste, and this paste was dried and then crushed to form a powdered powder. A chemical flux was used. Various fluxes were prepared by mixing this fluoride flux and CuCl powder in the proportions shown in Table 1 below, and the melting points of each flux were examined.

[Table] Next, each flux obtained above was suspended in a 5% nitric acid aqueous solution, and each flux was 10%
A concentrated aqueous suspension was prepared and uniformly applied to the surface of the test aluminum assembly to be bonded using a dipping method. The aluminum material assembly for this joint test was made of A7003 alloy and had a length of 50 mm.
The first member is 50 mm wide and 1.5 mm thick, and the second member is 50 mm long, 25 mm wide, and 1.5 mm thick, which is made by cladding 4343 alloy brazing filler metal on both sides of an A3003 alloy core material.
A combination of letters was used. The assembly coated with the flux suspension was then dried and then heated at 605° C. for 5 minutes in an N ₂ gas atmosphere to perform brazing. Visual observation of the brazed state after brazing revealed that in all cases Nos. 1 to 4 using the flux according to the present invention, a sufficient fillet was formed at the joint, and excellent brazing performance was achieved. It was hot.
On the other hand, when flux No. 5 containing no CuCl was used, fillet formation was insufficient and good brazing was not achieved. Therefore, when using the flux according to the present invention, high
It was confirmed that Mg-containing aluminum materials can be brazed.

Claims (1)

[Claims] 1. Fluoride flux: 99.5 to 80 wt%
A brazing flux containing 0.5 to 20 wt% of CuCl. 2 Fluoride flux: 99.5-80wt%
Using a flux containing 0.5 to 20 wt% of CuCl, suspending the flux in an acidic solvent, applying the suspension to a bonding member made of aluminum, drying it, and heating it to a predetermined temperature. A brazing method for aluminum materials that involves melting and brazing the joining filler metal.