JPH01258866A - Manufacture of aluminum brazing part excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To form a thin film on the member surface and to obtain a brazing part excellent in corrosion resistance by sticking the flux contg. 0.05-15W% tin fluoride to one part of the surface at least of a aluminum member and brazing by melting an Al-Si brazing filler metal. CONSTITUTION:The fluoride flux contg. 0.05-15W% tin fluoride is heated at the specified temp. under nonoxidizing atmosphere after sticking it to one part of the surface at least of the joining member composed of an aluminum and brazed by melting the brazing filler metal consisting of an Al-Si alloy. At this time, the tin fluoride forms a tin coating layer as a sacrificing corrosion preventing layer on the surface of the aluminum joining member and an excellent corrosion resistance is given to the aluminum joining member without spoiling the brazing property.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing aluminum brazed products with excellent corrosion resistance, and in particular to manufacturing aluminum brazed products suitable for manufacturing aluminum heat exchangers according to brazing specifications. Regarding the method.

In this specification, the term aluminum is used to include its alloys.

Conventional technology Conventionally, when aluminum heat exchangers such as automobile radiators, car cooler evaporators, or condensers are manufactured using flux brazing specifications, the heat exchanger components are brazed using fluoride flux. things are being done. The reason why fluoride-based flux is used in this way is that fluoride-based flux is non-corrosive, so cleaning to remove flux residue after brazing is not necessary.

However, fluoride flux itself does not have the effect of actively improving the corrosion resistance of products such as heat exchangers. For this reason, in the past, in order to make aluminum products with excellent corrosion resistance, a zinc film was coated as a corrosion-preventing layer on the aluminum joining parts by plating, etc., and then zinc was added at the same time as joining the aluminum parts in the brazing heat process. It was being disseminated.

Problems to be Solved by the Invention However, with this method, since a zinc film must be formed on the aluminum bonding member by plating for soldering, the number of man-hours is large and productivity is poor.

Moreover, in order to obtain excellent corrosion resistance, it is necessary to form a uniform zinc film, which requires complicated pretreatment and strict liquid control, which is extremely troublesome.

The present invention was made in order to eliminate such drawbacks, and an object of the present invention is to provide a wax peritectic having the same corrosion resistance as that of a conventional zinc film formed by a simple process.

Means for Solving the Problems In order to achieve the above object, the method for producing aluminum brazing peritectics with excellent corrosion resistance according to the present invention uses a fluoride flux containing 0.05 to 15 vt% of tin fluoride. , after being attached to at least one surface of a joining member made of aluminum, it is heated to a predetermined temperature in a non-oxidizing atmosphere to melt and braze a brazing material made of an Al-5i alloy. It is something.

In the fluoride-based flux used in the present invention, tin fluoride forms a tin coating layer as a sacrificial corrosion protection layer on the surface of the aluminum bonding member through the flux attachment process and the subsequent heating process, thereby impairing brazing properties. This provides excellent corrosion resistance to aluminum bonded members. However, if the added content is less than 0.05vt%, the above effects are poor and excellent corrosion resistance cannot be imparted.
On the other hand, if it exceeds 15 wt%, the solderability of the flux is inhibited and a uniform bonding state cannot be obtained. A particularly preferable content range of tin fluoride is about 0.3 to 10 νt%.

The fluoride flux used in the present invention may be one containing tin fluoride within the above range (although other compositions are not limited), for example, potassium fluoride (
A complex mixture containing KF) and aluminum fluoride (AQF3) in a eutectic composition or a composition range close to it, or a complex mixture containing KAlF3 and KF in a weight ratio of 80 to
99.8720~0. A mixture of 2 parts,
Alternatively, KF is particularly preferable in terms of manufacturing simplicity, etc.
Examples include those in which tin fluoride is added to and mixed with a residue obtained by dissolving γ-AρF3 powder and/or β-AQF3 powder in an aqueous solution to cause an exothermic reaction to evaporate water.

When performing brazing, the above-mentioned flux is uniformly applied to at least one surface, preferably both surfaces, of the aluminum members to be joined. There are no particular limitations on the method of attaching flux to the joining parts, but - within the membrane, a suspension of flux in water or a solvent may be applied to the joining part by dipping, spraying, or showering. The flux is applied by a brush coating method or the like, but it is also possible to apply the flux directly to the joint part by electrostatic powder coating or the like without suspending the flux in water or the like.

Furthermore, the method of mixing tin fluoride and the base flux is not particularly limited, and fine powders of each may be mixed together, or when creating a suspension, both may be mixed separately. It may also be added to a suspension and mixed in the suspension.

After the above-mentioned flux is attached, the aluminum bonding member is dried if necessary, and then the melting point of the bonding member is reduced in a non-oxidizing atmosphere such as an inert gas atmosphere using an aluminum alloy brazing filler metal whose melting point is lower than that of the bonding member. By heating to about 600 to 610° C., which is lower and higher than the melting point of the flux, the brazing material is melted and a brazed joint is achieved. The above brazing filler metal has a Si content of approximately 6°8~13ν[
About % All! Although a -Si alloy is used, the brazing material may be constructed as a plating sheet clad with an aluminum material.

In the step of attaching the flux to the bonding member and the subsequent heating step, a tin coating layer is formed on the surface of the aluminum bonding member, and its sacrificial anticorrosion effect imparts excellent corrosion resistance to the aluminum bonding member.

By implementing the present invention, sufficient corrosion resistance can be imparted without forming a zinc film on the surface of the joining member; however, it is possible to provide sufficient corrosion resistance without forming a zinc film on the surface of the joining member. By carrying out the above, it becomes possible to impart even more excellent corrosion resistance due to the synergistic effect of both.

Effects of the Invention According to the present invention as described above, it is possible to provide a brazing peritectic with excellent corrosion resistance without impairing the excellent brazing properties of fluoride flux. In other words, through the flux adhesion process and heating process, a tin coating layer can be formed on the surface of the aluminum bonding member, and its sacrificial anti-corrosion effect creates an aluminum solder peritectic layer with excellent corrosion resistance similar to that of a conventional zinc coating. . Furthermore, such corrosion resistance can be easily imparted by simply using a fluoride flux containing tin fluoride within a predetermined range, and without any other special process for imparting corrosion resistance. Therefore, it is possible to eliminate the need for a zinc film coating process that was previously performed before the brazing process, and productivity can be improved by reducing the number of man-hours. Further, even when carrying out the present invention after forming a zinc film, sufficient corrosion resistance can be obtained without considering the uniformity of the zinc film, so pretreatment, liquid management, etc. can be facilitated.

Examples [Samples Nos. 1 to 7] As shown in Fig. 1, a tube (1) made of extruded Al100 aluminum alloy with a wall thickness of 0.8 was bent into a meandering shape, and a plate was placed between the parallel parts. Full gate fins (2
), and the inlet and outlet joints (4) and (5) were temporarily assembled and fixed to the inlet and outlet ports at both ends of the tube (1) to temporarily assemble a serpentine heat exchanger.

On the other hand, as the base flux, the purity is 99.9%.
In an aqueous solution of Nono KF5.5Kg dissolved in 6Q water,
6.58 g of industrial γ-A42F3 (average particle size approximately 10 μm) with a purity of 90% or higher was gradually added and stirred to generate an exothermic reaction, and after removing moisture, the residue was heated in the air for 20 minutes.
0'CX dried for 90 minutes and further ground to an average particle size of 15 μm.

And the above flux space and tin fluoride (SnF2)
Various fluxes were prepared by mixing the tin fluoride with the composition ratio shown in Table 1 or without mixing.

Next, each flux was suspended in water to create a suspension with a concentration of 5%, and the heat exchanger assembly was immersed in this suspension to uniformly apply the flux to the surface of the assembly. . In addition, the same flux was applied at a concentration of 30 at the joint between the inlet and outlet joints (4) and (5) and the tube (1).
% suspension was brushed on.

Next, the above heat exchanger assembly was dried in a drying oven, and then heated in a N2 gas atmosphere at a temperature of 600° C. for 5 minutes to obtain various heat exchangers.

[Sample Nos. 8 to 11] As the tube (1), a galvanized film with a thickness of 1 to 3 μm was formed on the surface of the extruded Al100 alloy material by a conventional method, and as the corrugated fin (2), B
A heat exchanger assembly was produced in the same manner as above except that a plating sheet containing lvt% zinc added to A12PC was used.

Next, brazing was performed under the same conditions as above except that the same four types of fluxes as those used in Sample Nos. 3.4.5 and 1 were used to obtain four types of heat exchangers.

For each heat exchanger of samples No. 1 to 11 obtained above,
While visually observing the brazed state,
-8681 was conducted to examine the corrosion resistance of each heat exchanger. The results are shown in Table 1.

[Blank below] As can be seen from the above results, according to the present invention, it is possible to impart corrosion resistance equivalent to that obtained by forming a conventional zinc film through a simple process without impairing brazability. I was able to confirm that.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a heat exchanger manufactured in an example. (1)...tube, (2)...corrugate fin, (3)...heat exchanger. that's all

Claims (1)

[Claims] A fluoride flux containing 0.05 to 15 wt% of tin fluoride is attached to at least one surface of a bonding member made of aluminum, and then heated to a predetermined temperature in a non-oxidizing atmosphere to form an Al-Si based flux. A method for manufacturing aluminum brazed products with excellent corrosion resistance, which is characterized by melting and brazing a brazing filler metal made of an alloy.