JPS6199569A - Brazing method of aluminum and its alloy - Google Patents

Abstract

PURPOSE:To achieve an extremely good brazing joining by mixing at the specified percentage one kind two kinds among KAlF4, KF and LiF, NaF and CaF2 as a flux. CONSTITUTION:The mixture mixing at the rate of 0.1-8wt% one kind or >=two kinds among LiF, NaF and CaF2, 73.6-99.7wt% KAlF4, 18.4-0.2wt% KF is used as a flux. The minute powder of the flux is suspended into the liquid of water, etc. and this suspension is coated on the joining member consisting of aluminum or its alloy. Then after drying it, it is heated to the prescribed temp. in a nonoxidizing atmosphere and brazing is performed with melting the brazing material for joining.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for brazing aluminum and its alloys,
In particular, the present invention relates to a method for brazing aluminum materials, which is suitably used for manufacturing aluminum heat exchangers according to brazing specifications.

In the following description, the term aluminum is used to include its alloy.

Conventional technology and problems Conventionally, when manufacturing aluminum heat exchangers such as automobile radiators, car cooler evaporators, or condensers using flux brazing specifications, chloride-based flux was used to braze the heat exchanger components. A method of joining is often used.

However, when using such a chloride-based flux, the flux used is essentially water-soluble and has strong hygroscopic properties, so it is necessary to quickly clean the flux residue after brazing. This requires removal, which increases equipment costs, complicates the process, and imposes a heavy workload. In addition, even if the above-mentioned cleaning is incomplete, or even if it is thoroughly cleaned, there is a risk that the aluminum parts will corrode relatively early due to residual flux components incorporated into the metal of the joint. was there.

Therefore, as a brazing method that basically eliminates the need for flux cleaning as described above, Fluoroaluminum 834! (
The advantage of a brazing method using a flux which is almost insoluble in water and whose composition is K, AρF6 and KAQF4) has been proposed. This flux-based brazing method is very effective for its intended purpose.

However, in the brazing method using this flux, the melting point of the flux that is actually industrially produced and used is relatively high, and the melting point of the aluminum material to be joined or the brazing material used is Due to the relationship with the melting point of the soil, there was a problem in that the applicable range of the practical soil was limited to υ. Moreover, when used for brazing aluminum materials containing Mg, the above-mentioned flux has the problem that it deteriorates the wetting and spreading properties of the brazing material, making it impossible to form a good joint. Furthermore, when the above flux is actually produced industrially,
Generally, AQFx and KF are used as starting materials, and the starting materials are mixed with KAρF4, which is a eutectic mixture thereof, to 3ΔρF6
are mixed in a dry state in an appropriate ratio so that the and A: Because it is made by coagulating,
There were also problems in that the number of manufacturing steps was large and preparation was troublesome.

In view of the above-mentioned problems, this invention eliminates the need for defluxing treatment after brazing, further lowers the melting point of the flanks, and can be suitably used for joining M9-containing aluminum materials. The object of the present invention is to develop a non-corrosive flux that can be easily prepared, and to provide a brazing method using the flux.

Means for Solving the Problems In order to achieve the above object, the inventor conducted various experiments and research on the combination of flux compositions, and found that KAlF4, KF, 1i F, Na F, Ca
By using a flux composed of one or more of F2, it was possible to create and complete a scale that achieves good brazing under more advantageous conditions.

That is, this invention adjusts KAρF4 to 73.6 to 99.7w.
t%, KF from 18.4 to Q, 2wt%.

It is characterized by using a mixture of one or more of LiF, NaF, and CaF2 at a ratio of 0.1 to 8 wt% as a flux, and adding fine powder of the flux to a liquid such as water. The suspension was applied to a bonding member made of aluminum or its alloy and dried by heating it to a predetermined temperature in a non-oxidizing atmosphere to melt the bonding brazing filler metal. It is to be brazed.

The above composition range of the flux used in this invention specifies the component ratio as close as possible to the eutectic point composition of each composition mixture, and the melting temperature range of the flux obtained within the composition range is approximately 530. ~565°C. Therefore,
It exhibits a sufficiently lower melting point than most aluminum materials that are usually subject to brazing, and also most brazing materials used for brazing,
The range of aluminum materials that can be brazed can be expanded.

KAρF4, KF, and LrF in flux,
The relative composition ratio of NaF or CaF2 is
If it deviates from the above-mentioned limited range, the melting point of the flux will be higher than the desired range, and the melting point of the flux will be higher than the desired range.
There is no difference from that of the AQFa-based flux, making it impossible to obtain suitable results. In particular, when uF, NaF, or CaF2 is not added, not only is it not possible to effectively lower the melting point of the flux, but also it becomes difficult to braze an aluminum material containing ~1 g.

It is desirable that the powder particle size of the flux component be approximately 150 μm or less. This is not only to facilitate suspension and application in a liquid as described below, but also to facilitate
This is because if the flux exceeds .mu.m, the melting point of the flux will rise even if the composition is the same, which may impair brazing properties.

When performing brazing, the above-mentioned flux is used by suspending it in the form of a slurry in a liquid such as water, and this suspension is uniformly applied to at least one of the joining members made of aluminum. 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.

After applying the above-mentioned flux, the bonding member made of aluminum is dried, and then, using an aluminum alloy material having a lower melting point than the bonding material, in a non-oxidizing atmosphere such as an inert gas atmosphere, Approximately 580 to 620, which is lower than the melting point of the joining member and higher than the melting point of the flux.
By heating to 0.degree. C., the brazing material is melted and a brazed joint is achieved. Furthermore, when brazing is performed in the atmosphere, the amount of flux required increases, which not only impairs the appearance and paint adhesion after brazing, but also makes it difficult to form anti-corrosion coatings such as chromic acid coatings. Become something. The upper brazing filler metal contains AQ-8i with a 3i content of approximately 4°5 to 13.5 wt%.
Generally, a brazing filler metal is used, and from the viewpoint of workability, it is preferable that the brazing filler metal is used as a cladding material on at least one aluminum component of the members to be joined.

Effects of the Invention According to the implementation of the present invention as described above, extremely good brazing joints of aluminum materials can be achieved. That is, the flux used exhibits excellent flux effects such as the effect of destroying oxides on the joint surface and the effect of promoting wetting and spreading of the brazing material, making it possible to form a sufficiently strong brazed joint. Furthermore, since the flux used in this invention is non-corrosive after brazing, there is no need to wash and remove flux residue after brazing, unlike when using conventional chloride-based fluxes. , while simplifying a series of brazing work processes, it is possible to manufacture perfectly bonded aluminum brazed products with even less risk of corrosion.

Furthermore, as is clear from the examples, the flux used in this invention is 3AρFs-KAΩF4 compared to the conventional flux.
Compared to system fluxes, it is possible to achieve a lower melting point, and aluminum materials containing M9,
In particular, for example, A3005, A3052'l:! Low M (such that the content of M (1) is approximately 8 wt% or less)
1-containing aluminum materials can be carried out without any problems while maintaining good wettability and spreadability of the brazing material, and the range of applications of brazingable aluminum materials can be expanded.

Further, the flux used in this invention is KARF4, KF
Since both are easily available as single products as commercial products, these are mixed as starting materials, and ci F, Na r
AQF3. :, ca F2 can be easily prepared by adding or blending one second or two or more of them. Conventional 3 AQ Fs-KAN F4 starting from KF
Does not require complicated FA manufacturing process like system flux,
It is easy to prepare and grow.

EXAMPLESNext, in order to clarify the advantages of the present invention, several examples thereof will be shown in comparison with various comparative examples.

A corrugated fin material with a thickness of 0.12 m made of A3005 alloy, which is a low M9 content aluminum alloy, and BAll
An ifa tube made of aluminum alloy with a thickness of 0.4M (the outer surface of an A3003 alloy core material is clad with an A4343 alloy skin material at a cladding rate of 12%) was prepared, and a pair of the above fin materials was placed on a degreased model. Noden 8! It was fixed in a manner that it was inserted between the tubes to form a heat exchanger assembly.

Then, water was added to the fluxes having various compositions shown in Samples Nos. 41 to 9 in Table 1 to form a suspension at a temperature of about 5%, and the heat exchanger assembly was immersed in this suspension and dried. Incidentally, the powder particle size of each Franks component was 50 μm or less.

[Left below] After that, each of the above assemblies was heated to a dew point of -30″C using N2 gas.
A heat exchanger was obtained by heating at 600″C for 2 minutes and brazing in a furnace adjusted to .

Then, while examining the brazing state of each heat exchanger obtained above, the melting start temperature (solidus temperature) of each flux
, the complete melting temperature (liquidus temperature) was measured. The results are shown in Table 2.

[Margin below] Table 2 Brazing condition: O...Good x...Poor As is clear from these results, in the case of samples No. 1 to 7 in the table using the flux in the limited composition range of the present invention The brazing condition was good, the fillet was large, and both the initial melting temperature σa and the complete melting temperature were low.

On the other hand, in the case of sample No. 8 using a flux that does not contain LiF, NaF, and CaF2, the fillet was small and a good bonding state could not be obtained, and both the melting start temperature and complete melting temperature were high. It was something. Therefore, L
It can be seen that the addition of one or more of iF, NaF, and CaF2 is effective in lowering the melting point of flux and brazing Mg-containing aluminum materials.

In addition, conventionally known 3. In the case of sample No. 9 using Fa-KAlF4-based flux, a good brazed state could not be obtained, and both the melting start temperature and complete melting temperature were high.

- From the second point, it was confirmed that the flux according to the present invention is more advantageous in terms of the selection range of aluminum materials that can be brazed and the brazability of M9-containing aluminum materials.

that's all

Claims (1)

[Claims] KAlF_4 73.6-99.7wt%, KF 18
．． 4-0.2wt%, and LiF, NaF, CaF_2
It is characterized by using a mixture of one or more of these at a ratio of 0.1 to 8 wt% as a flux, and suspending a fine powder of the flux in a liquid such as water, A method for brazing aluminum and its alloys, in which a liquid is applied to a joining member made of aluminum or its alloys, dried, and then heated to a predetermined temperature in a non-oxidizing atmosphere to melt and braze a joining brazing material. .