JPH054192B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention relates to brazing fluxes, particularly aluminum alloy castings, die castings, Al-Cu-Mg based fluxes,
The present invention relates to a brazing flux that is suitably used for brazing joining members including Al-Zn-Mg high-strength alloys. BACKGROUND ART When joining members made of aluminum or its alloy are brazed to each other, flux brazing using an Al-Si brazing material has been conventionally performed.
By the way, for example, aluminum intake manifolds for automobiles are formed by brazing wrought material and cast material, and various other parts used in automobiles, industrial machinery, home appliances, office equipment, etc. When materials such as metals, die castings, ternary high-strength alloys, etc. are included, it is necessary to use a material with a low melting point as a brazing material since the melting point of casting materials is generally low. Therefore, conventionally, in such flux brazing, a brazing material made by adding zinc and copper to an Al-Si alloy to lower the melting point has been used. 4245
Alloy (typical composition Al-10wt%Si-10wt%Zn-3wt
%Cu). Problems to be Solved by the Invention However, even when such a brazing material is used, the melting point of some casting materials is still too high, making it difficult to perform good flux brazing. Therefore, in order to further lower the melting point, Al
−Si− High Zn brazing filler metal (e.g. Al−10wt%Si−
Attempts have been made to use a 30 wt% Zn alloy brazing filler metal (melting point: approximately 530°C). But in this case, high Zn
The oxide film formed on the surface of the alloy brazing material contained therein was strong, and this oxide film caused a new problem in that it inhibited brazing properties. This invention was made in view of the above circumstances, and enables the brazing of members that were previously difficult to braze, such as cast materials such as AC4C, die-cast materials such as ADC12, and ternary high-strength alloys. The purpose is to Means for Solving the Problems For the above purpose, the present invention provides In, Sn, Bi
Focusing on the fact that Zn has the effect of weakening the surface oxide film of high Zn-containing alloy brazing filler metal during brazing, we have made it possible to put high Zn-containing alloy brazing filler metal into practical use by incorporating these components into chloride-based flux.
This also makes it possible to braze cast materials, etc. That is, in this invention, Si: 4 to 12 wt%, Zn: 15
~55wt%, with the remainder being aluminum and unavoidable impurities.The flux is based on a chloride flux, and one or two of In, Sn, and Bi components are added to the flux. In terms of content in the total amount of these components and chloride fluxes,
In: 0.2~2.0wt%, Sn: 0.5~3.0wt%, Bi: 0.5~
The gist is a brazing flux characterized by containing a flux of 3.0wt%. First, Al, which is the target of the flux of the present invention
-Si-To explain the significance of adding each component of the high Zn brazing material and the reason for limiting the composition range, Si is necessary to lower the melting point of the brazing material and to increase its fluidity. However, if the content is less than 4 wt%, these effects will be poor, and if the content exceeds 12 wt%, the melting point will rise sharply, making it impossible to use it as a brazing filler metal. A particularly preferred content of Si is 5 to 8 wt%. Zn is an extremely effective element for lowering the melting point of brazing filler metals. However, if the content is less than 15wt%, the effect is poor,
On the other hand, if it exceeds 55wt%, processability will deteriorate. A particularly preferable Zn content is 20 to 50 wt%. Next, explaining the flux according to the present invention, chloride-based flux was used as a base because chloride-based flux generally has a low melting point and is suitable for brazing casting materials etc. with low melting points. . The composition of this chloride-based flux is not particularly limited, and any conventionally used flux may be used, but preferably,
BaCl ₂ , KCl, and NaCl are the main components, and NaF,
It is better to use one to which NH ₄ F or the like is added.
As a specific composition, for example, BaCl ₂ : 45wt
%, KCl: 33wt%, NaCl: 20wt%, _NH4F :
It is 2wt%. In, Sn, Bi contained in chloride flux
is an effective element for making the strong oxide film formed on the surface of the high Zn-containing brazing material weak and defective when the melted brazing material spreads during brazing. All of these are evaluated as equivalent in terms of such effects, and it is sufficient that at least one of them is contained. These in flux
The content of each component of In, Sn, and Bi is In: 0.2 to 2.0 wt%, Sn: 0.5 to 3.0 wt%,
Bi: Must be contained at a ratio of 0.5 to 3.0 wt%. In is 0.2wt for the entire flux
%, Sn is less than 0.5 wt%, and Bi is less than 0.5 wt%, the above effects cannot be exhibited. On the other hand, In
More than 2.0wt%, Sn more than 3.0wt%, Bi 3.0wt
%, the effect reaches saturation, resulting in economic waste. Particularly preferred range is In: 0.3-1.5wt
%, Sn: 0.8 to 2.5 wt%, Bi: 0.8 to 2.5 wt%. In general, the production of the flux according to the present invention involves adding In, Sn, and Bi, which are weighed in the above proportions, to a base chloride flux powder.
This can be done by adding and mixing powders of one or more of the following, but it is not necessarily necessary to use powders of In, Sn, and Bi alone;
- It may be mixed in the form of Sn alloy powder or the like. When performing brazing, the flux is suspended in a slurry form in a solvent such as water. The suspension thus prepared is uniformly applied to either one of the aluminum bonding members. Although spraying or brushing can be used as a coating method, it is recommended to use a dipping method as a uniform coating method suitable for mass production. The bonding member made of aluminum is made by drying the above flux after applying it, and then applying Al-Si-
By heating a high Zn-containing alloy brazing material preferably in a non-oxidizing atmosphere such as N ₂ gas or other inert gas atmosphere at a temperature lower than the melting point of the joining member and higher than the melting point of the flux. to melt. When this molten brazing filler metal spreads, the oxide film on the surface of the filler metal is weakened by the action of In, Sn, and Bi in the flux, promoting wetting and spreading of the filler metal, achieving a good brazed joint. . Effects of the Invention According to the flux according to the present invention as described above, by containing a predetermined amount of one or more of In, Sn, and Bi, Al-4 to 12wt% Si-15 to 55wt%
When brazing using a Zn alloy brazing material, the strong oxide film formed on the surface of the brazing material can be weakened and become defective. As a result, it is possible to promote appropriate flow of the brazing material, form a sufficient fillet at the joint portion, and achieve good brazing. Therefore, although it has a low melting point, it has become possible to braze using a high Zn-containing alloy brazing filler metal, which was previously difficult due to its strong oxide film. In particular, it is possible to realize reliable and strong joining of cast materials, especially cast materials with low solidus temperature such as AC4C, die casting, high strength alloys, etc. Examples Next, examples of the present invention will be shown. Brazing filler metals made of extruded Al-Si-high Zn alloys with varying amounts of Si and Zn were prepared. On the other hand, based on chloride flux powder, In, Sn,
Various fluxes were produced with or without addition of one or more types of Bi powder. Then, the brazing filler metal and flux were combined as shown in Table 1. Here, In in the flux,
The content of Sn and Bi in the entire flux is
It was as shown in the table.

【table】

[Table] Next, brazing was performed using the above combination of brazing filler metal and flux, and its brazing properties were investigated. Brazing was performed in the following steps. That is, each flux was suspended in water to create a suspension with a concentration of 10%.
This was uniformly applied to the surface of an assembly of aluminum materials to be bonded for testing by a dipping method. The aluminum material assembly for this joint test was an aluminum casting block made of AC4C with a 6063 aluminum alloy pipe assembled, and each brazing filler metal was placed at the joint. The above assembly coated with the flux suspension is then dried and then
By brazing in a furnace in an _N2 gas atmosphere, the ambient temperature is 555
Heated at ~560°C. Visual observation of the state of the joints after brazing revealed that all of Nos. 1 to 5 had sufficient fillets formed in the joints and had excellent brazing properties. On the other hand, when flux No. 6 was used, fillet formation was insufficient and good brazing was not achieved. Therefore, by using the flux and high Zn-containing aluminum alloy brazing material according to the present invention,
We have confirmed that it is possible to braze aluminum casting materials.

Claims (1)

[Claims] 1 A flux for aluminum alloy brazing filler metal containing Si: 4 to 12 wt%, Zn: 15 to 55 wt%, and the balance consisting of aluminum and unavoidable impurities. , Sn, Bi, and the content of one or more of these components in the total amount of these components and chloride flux is In: 0.2 to 2.0wt.
%, Sn: 0.5 to 3.0 wt%, Bi: 0.5 to 3.0 wt%.