JPS6037294A - Brazing method of aluminum and alloy thereof - Google Patents

Abstract

PURPOSE:To obtain a brazed product having excellent resistance to corrosion without requiring flux removal by using a mixture composed of a specific ratio of K3AlF6 and AlF3 as a flux for brazing. CONSTITUTION:A mixture prepd. by mixing potassium hexafluoroaluminate K3AlF6 and aluminum fluoride AlF3 at 70-59:30-41 by weight is suspended into liquid such as water to obtain a suspension. Such suspension is coated on a joining member such as a heat exchanger formed of Al or Al alloy and after drying, the member is heated to a prescribed temp. in a nonoxidative atmosphere to melt the brazing material for joining, by which joining is accomplished. Since the flux is noncorrosive, the brazed product having excellent resistance to corrosion is obtd. by the simple operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for soldering aluminum and its alloys,
Especially for aluminum heat exchangers depending on the brazing properties!
This article deals with brazing methods for aluminum materials that are suitably used for I-structures.

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

Conventionally, when manufacturing aluminum heat exchangers such as automobile radiators, car cooler evaporators, or condensers by brazing properties, the heat exchanger components were brazed using a chloride-based flux containing zinc chloride. Many bonding methods are used. In this case, at the same time as each member is joined by brazing, zinc is precipitated on the surface of the component member due to the additional heat of the brazing, and diffuses into the member, and the sacrificial circle of the zinc diffusion layer causes heat exchange. It is possible to improve the corrosion resistance of the container.

However, in this method, the flux used is essentially water-soluble and has strong hygroscopic properties, so it is necessary to wash away any remaining flux immediately after brazing. However, there were drawbacks such as high equipment costs, complicated processes, and a heavy workload.

Of course, if the residual flux was not completely removed, there was a risk of corrosion.

On the other hand, as a brazing method that basically eliminates flux cleaning as described above, for example, British Patent No. 1055914
If aluminum fluoride (A
A method of brazing using a fluoride-based flux consisting of a mixture of ΩF3) and potassium fluoride (KF) has been proposed, but even in this case, the brazing flux residue may be corrosive. There was a drawback that some of the KF remained.

In view of the above, this invention aims to develop a completely non-corrosive flux, which makes it possible to manufacture brazed products such as aluminum heat exchangers with excellent corrosion resistance with the simplest possible operation. This is what I am trying to do.

However, this invention can be applied to aluminum fluoride (A) such as potassium aluminate (K3△ΩFa).
lF3), the small ratio is 70 to 59: 30=41
It is characterized by using a mixture mixed at a ratio of The present invention provides a method for brazing aluminum in which brazing is performed by heating to a predetermined temperature in an atmosphere and melting a joining brazing material.

The mixing ratio of 3△ρ'6 and 8ρ[3 in the flux is determined by selecting a ratio of 70 to 59:30-41 on a weight basis to lower the melting point of the flux during brazing heating. If the above-mentioned limited range is exceeded, the melting point of the flux will become high, making it impossible to perform a good soldering process, and even worse, the reaction temperature of the flux will become too high for the joining parts. (=l itself may become impossible.)

When performing brazing, the above-mentioned flux consisting of a mixture of 3AρF6 and ΔΩF3 is used by suspending it in the form of a slurry in a liquid such as water, and this suspension is applied to at least one of the joining members made of aluminum. Apply evenly to one side. In order to facilitate suspension and application in this liquid, the powder particle size of the flux component (approximately 15
It is preferable that the thickness be 0μ or less. Although spraying or gluing can be used as the above-mentioned coating method, it is highly recommended to use a dipping method as a uniform coating method suitable for mass production.

The bonding member made of aluminum is dried after applying the above-mentioned flux, and then the bonding member (J) is heated in a non-oxidizing atmosphere such as an inert gas atmosphere using an aluminum alloy brazing material with a low melting point. The brazing material is melted by heating to approximately 580 to 620° C., which is lower than the melting point of A and higher than the melting point of 3Au Fs and Δρ[':3.A brazed joint is achieved by melting the brazing material. Normally, a hemp Δρ-8L alloy with an S1 content of about 4.5 to 13.5% is used, and the brazing filler metal usually has at least one of the parts to be joined, from the point of production i+lJ. It is used by cladding one aluminum component.

According to the implementation of the present invention as described above, since a mixture of 3AρF6 and AQF3 at a predetermined ratio is used as the flux, not only can a good solder joint be achieved, but also the flux itself Essentially complete non-eclipse 1/
l, and J when using conventional chloride-based flux
:It eliminates the need to wash and remove residual flux after brazing, and reduces the hygroscopicity that is a concern when compared to the case of using a conventional fluoride flux made of a mixture of AlF2 and KF. There is no risk of KF remaining as residue, and this has the effect of simplifying the series of brazing work processes and making it possible to manufacture aluminum brazed products in a perfectly bonded state with little risk of corrosion. play.

Next, examples of this invention will be shown.

Example 3003 alloy 3 mm x 50 mm x
50 mm aluminum piece and 2 mm double-sided cladding made of 3003 alloy core and 4343 alloy skin.
Brazing sheets 1- and 25-m x 25-mm x 50-m x 50-m x 25-mm x 50-m x 25-mm x 50-m x 25-mm x 50-m x 25-mm x 50-m brazing sheets were divided into silks with an inverted Go-shape in cross section, and on these surfaces 1), suspensions in water (flux moisture content 30%) of various flux compositions shown in Table 1 were applied. Apply and dry. Thereafter, this assembly was heated for 60 minutes in a furnace adjusted to a dew point of -40°C using N2 gas.
The mixture was heated at 5°C for 5 minutes to perform waxing.

As a result, good brazing was achieved with the fluxes shown in Samples No. 1 and No. 2 in Table 1, but Sample 11
A good brazed state could not be obtained with No. 0.3 and No. 4.

Table 1

Claims (1)

[Claims] power 1 noful Δ[] Potassium aluminate and aluminum fluoride in a weight ratio of 70 to 59:30-41;
The mixture mixed in step 1 is used as a flux, and a suspension of this in a liquid such as water is applied to the surface of a joint made of aluminum or its alloy, dried, and non-oxidized. 1. A method for brazing aluminum and its alloys, which comprises heating to a predetermined temperature in a neutral atmosphere to melt and braze a joining brazing filler metal.