JPS619995A - Flux for brazing alminum and alminum alloy material - Google Patents

Abstract

PURPOSE:To provide a flux for brazing Al and Al alloy material consisting of substance is obtd. by crushing the mixture consisting of K3AlF6, AlF3 and PbF2 having the prescribed weight ratio or the melted and solidified substance of the mixture. CONSTITUTION:A flux for brazing Al and Al alloy material is formed of substance obtd. by crushing the mixture consisting of 60-70% K3AlF6, 27-37% AlF3 and 0.1-10% PbF2 (each wt%) or the melted and solidified substance of the mixture, actually. Accordingly the operating temp. is lower and braze is better than the conventional fluoride flux and a good joining part equivalent to the brazing method in fluxless inert gas atmosphere and the soldering method in furnace of chloride flux is obtainable, and yet a fluoride flux having insolubleness and nonhygroscopicity is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to the composition of a flux used for brazing aluminum (including aluminum alloys) materials.

``L Bold'' Flux brazing, in which a layer of aluminum brazing alloy with a melting point lower than that of the aluminum materials to be joined is interposed between the aluminum materials to be joined, generally uses chloride as the main component. The component flux is used in the atmosphere. These 7 luxes are inherently water soluble, generally omega-absorbing, and corrode aluminum, including aluminum braze alloys, in the presence of water. Therefore, such flux brazing residues must be removed by cleaning after the brazing process.

Vacuum brazing 1) method and inert atmosphere brazing method are already known as fluxless brazing methods that perform brazing without using flux. In addition to gas, it requires a special aluminum material for the welded material or braze alloy. Furthermore, it is inferior to the flux brazing method in that it requires stricter precision in the clearance of the brazed part.

Also known are fluoride fluxes that leave a residue on the brazing surface after brazing that is substantially insoluble in water, non-hygroscopic and non-corrosive to aluminum.

Specifically, British Patent No. 1,055,914 proposes a flux that is a mixture of AI F3 and KF. Furthermore, according to Japanese Patent Publication No. 58-27031, K was used as a flux that is non-hygroscopic before brazing and substantially water-insoluble after brazing.
A flux consisting of 3 AI F4 and 3 AI F6 has been proposed. This flux is obtained by melting the mixture using KF and At F3 as raw materials and then pulverizing the solidified product, and the solidified product contains KAI F4.
3AIF & is generated. KF and At of raw material components
It is recommended that the ratio of F3 be as close to the eutectic composition of both components as possible.

In this way, in the state before brazing, KF-△1[3 or
K3 AI F6 KAI F<Or! AI
These fluoride fluxes, which have the substantial chemical formula of F6 AI F3 or KAlF4, 3AI F6 KAI F4 or KAlF4 in the brazed state, or combinations thereof, have the advantages of conventional chloride-based fluxes as well as Moreover, since the residue is non-hygroscopic and non-corrosive to aluminum, it has the great advantage of not requiring cleaning of the brazing pad.

Furthermore, these fluxes can be applied in any form of brazing, and are particularly suitable for torch brazing and furnace brazing.

However, these 7luxes had the disadvantage that the operating temperature was slightly higher than that of chloride-based fluxes, making it difficult to obtain good joints.

Although the mechanism of action of flux used in brazing has not been fully elucidated, in general, as a flux,
Before the brazing alloy begins to melt, the flux melts and covers the brazing surfaces, removing the surface oxide film, increasing the wettability of the base metal, and inhibiting the flow of the brazing alloy to the brazing surfaces. There is a need for something that has the ability to help and also block contact with air to prevent re-oxidation. Therefore, it is significant in brazing to moderately lower the working temperature of flux.

Purpose The purpose of the present invention is to use a flux for brazing aluminum materials, which has a lower operating temperature than conventional fluoride-based fluxes, thereby making it possible to use fluxless inert gas atmosphere brazing methods and furnaces using chloride-based fluxes. The object of the present invention is to provide a fluoride-based flux that can form a good joint similar to that of the intermediate brazing method and is substantially water-insoluble and non-hygroscopic.

Composition The present invention substantially consists of 70% by weight of K3AlF660,
A flux for brazing aluminum and aluminum alloy materials, which is made of a mixture of 327 to 31% by weight of AlF and 20.1 to 10% by weight of PbF, or a product obtained by pulverizing a molten solidified product of the mixture.

The term "substantially" used here means that the fluoride used as raw material V1 does not necessarily have to be of high purity; impurities that are more mixed in than general commercially available fluoride are allowed; 3AI F6, AI
This is because only the weight ratio of the three substances when converted to F2 (F3, PI) is important for the function of the flux of the present invention.

Substantially 41 to 3Δ in PbFz-free flux
Preferred values for the weight ratio of IF6 and AlF3 are found in known literature (e.g. B, Phllips et al. J, Δmer, Ceram
, S oc.

Vol. 49 (1966) page 632)
This can be easily understood from the binary phase diagram of the l-△lF3 system, and as shown in this figure, the eutectic phase is formed, that is, KF45.8% by weight - △1F354,2% (KF55 mol% - AI).
F345 mol%> or a ratio around it.

In the present invention, in addition to PbF20 in addition to 99.9 to 90% by weight of the mixture or molten mixture having substantially this weight ratio,
．． When 1 to 10% by weight is added, the improvement is significant.

If the amount of PbF2 added is less than the specified lower limit, there will be no desired effect, and if it is added in a larger amount than the upper limit, the working temperature of the flux will become upper, making it unfavorable for brazing.

Note that PB dissociated above the working temperature has the effect of lowering the surface tension of the solder and improving the brazing properties.

Known fluoride fluxes can be prepared by mixing as is or by melting the mixture and pulverizing the solidified product, and the flux of the present invention can similarly be prepared by various methods.

Next, examples and effects thereof will be described.

Example 1 Using industrial 3AI F6 and industrial AI F3 and taking into account their respective purity, Ks AI F
667.87% by weight - AI F332.13% by weight, and melted the mixture with a flux prepared by melting (targeting the melting temperature at about 100°C above the eutectic temperature of 562°C). Similarly, by adding PbF2 to both components, substantially 3Δl F 667.75% by weight-A I
F 332.07 heavy width% - PbF20.18 heavy width%,
The working temperature of each of the PbFz-added fluxes prepared by mixing the mixture and melting the mixture so as to have a ratio of 1 to 1 was measured by the following method.

That is, both of the prepared fluxes were placed in a platinum crucible, heated and melted in an argon atmosphere, and then cooled at a cooling rate of 1°C/
Thermal analysis was carried out using the cooling method for 1 minute, and the liquidus temperature and solidus temperature were measured, and the working temperature was determined from these. The measurement results are shown in Table 1. As described above, by adding PbFz, a good result of lowering the common mode temperature was obtained, and a lowering of the operating temperature was confirmed.

Example 2 Using the PbFz-added flux and non-additive flux shown in Example 1, a brazing test was conducted in an inert atmosphere (in this atmosphere, brazing is not possible without flux), and in a standard inert atmosphere. 7 Luxless inert atmosphere brazing was performed. The bonding states of these were compared.

The figure shows a joint using a brazing test.

A 3003 with BΔ4045 aluminum alloy brazing material clad on both sides on Δ3003 aluminum alloy
A plating sheet 2 made of an aluminum alloy was fixed at a joint angle θ, and after heating at 600° C. for 3 minutes, the fillet length L was measured to determine the filling rate (L/LOX100).

The results are shown in Table 2. Comparing the filling ratios, in the case of PbF2-added flux, it shows a much higher value than additive-free flux brazing and flux brazing (B), indicating that excellent brazed parts can be obtained by using the flux of the present invention. .

This result is due to the lowering of the working temperature of the flux of the present invention and the lowering of the surface tension of the solder due to Pb dissociated above the working temperature.

Table 2 Example 3 The water solubility of the PbF2-added flux and non-additive flux shown in Example 1 was measured, and these were compared with the water solubility of the main components of the chloride flux (literature values). . The results are shown in Table 3, and in the case of PbFz-added flux, it is about the same as that of non-additive flux,
The chloride content is extremely low.

Table 3 Circle-1 The flux for brazing aluminum materials of the present invention has a lower operating temperature than conventional fluoride-based fluxes, and a temperature higher than the operating temperature (the surface tension of the solder decreases due to dissociated PB). By changing the condition of the joint to 7
It is as good as the flux-less inert gas atmosphere brazing method or the chloride flux furnace brazing method, and also has non-hygroscopicity and virtually water-insolubility, which are the characteristics of fluoride-based fluxes. be.

[Brief explanation of drawings]

The figure is an explanatory diagram showing the configuration of the joint used in the brazing test. 1...A 3003 aluminum alloy, 2...To Blazing Sea 1,

Claims (1)

[Claims] (1) Substantially K_3AlF_660-70% by weight, A
lF_327-31% by weight and PbF_20.1-10
A flux for brazing aluminum and aluminum alloy materials, comprising a mixture consisting of % by weight or a product obtained by pulverizing a molten solidified product of the mixture.