JPH0224626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an immersion brazing method for joining aluminum or its alloy members.

(B) Background Art Conventional immersion brazing generally involves melting a flux consisting of fluorides such as sodium chloride, potassium chloride, lithium chloride, and aluminum fluoride in a refractory tank, and then melting the assembled brazed parts into the refractory tank. This method joins joint members by immersing them in a liquid and melting the brazing filler metal that has been clad or placed in the joint area in advance.In addition to its original role as a flux effect, the molten flux also creates a non-oxidizing heating atmosphere. This constitutes a non-oxidizing heating medium.

For these reasons, the brazing joining method using immersion has the characteristics of a faster temperature rise rate, easier uniform heating, and higher brazing reliability than brazing methods using a heating furnace. .

However, fluxes (sodium chloride, potassium chloride, lithium chloride, fluoride, etc.) have strong deliquescent properties and strongly corrode metals such as steel and copper, and because they are conductive, they have the disadvantage of destroying the insulation of electrical equipment.

In addition, for the same reason as mentioned above, the strong corrosivity of conventional chloride flux is
Preventing immersion brazing with pots made of nickel or nickel alloys, for example, carbon electrode direct heating brazing furnaces have been used, typically melting the flux in a refractory bath as described above.

The deliquescent property of flux is from 580℃ to the brazing temperature.
Even at 620°C, moisture is present in the flux, severely oxidizing aluminum and inhibiting brazing.

For this reason, it is necessary to immerse an aluminum plate whose surface has been purified in advance in the molten flux to react with water and dehydrate it into hydrogen and aluminum oxide. Furthermore, the molten flux cannot avoid contact with air for a long period of time, and it is necessary to carry out dehydration operations repeatedly. Moreover, there were problems such as the necessity of removing precipitates such as aluminum oxide produced during dehydration.

(C) Disclosure of the Invention The present invention proposes an immersion brazing method using a non-deliquescent flux.

In particular, the present invention proposes a method of brazing in a practical metal pot, which has hitherto been impossible on a practical scale.

That is, the present invention mainly uses barium chloride (BaCl ₂ ), sodium chloride (NaCl), and potassium chloride (KCl) that do not have deliquescent properties, adds fluoride to these, and produces a chemically activated flux in a metal pot. It is used after being dissolved.

For example, the flux used in the present invention is
The weight ratio of BaCl ₂ , NaCl and KCl is 54.7:
The melting point of the 18.0:27.3 eutectic salt is 540°C. In addition, the melting temperature of the Al-Si base alloy of aluminum hard solder is 564-580℃, and the brazing work temperature is 580-580℃.
Since it is 615℃, the melting temperature of the above eutectic salt is
540°C is suitable as a brazing flux for aluminum or its alloys.

Furthermore, in order to chemically activate the flux, fluorides such as aluminum fluoride (AlF ₃ ) and sodium fluoride (NaF) are mixed, but in this case, the melting temperature of the flux due to mixing is 570°C.
℃Preferably, the temperature may be raised to 565℃, so since the temperature of the above eutectic salt is 540℃, the temperature is 30℃ (or 25℃)
This means that there is still room for this. This means that there is a wide range of selection in the type and amount of fluoride, and also in the mixing ratio of the eutectic salt.

In this case, the weight ratio ranges of barium chloride, sodium chloride, potassium chloride and fluoride are 55-47%, 18-22%, 27-33% and 1-20%, respectively.

Melting and brazing of aluminum brazing fluxes with electrically resistive or combustion heated metal pots is superior to brazing with electrode heated brazing furnaces using conventional refractory baths. In particular, it has the outstanding effect of greatly facilitating flux dissolution, precipitate removal, redissolution, etc.

(d) Example Powders of BaCl ₂ , NaCl and KCl were mixed in a weight ratio of 54.7.
%, 18.0%, 23.3%, and this with a weight ratio of 10% NaF
The powders are mixed and melted in a pure nickel (low carbon) pot using electric resistance heating at 610℃±3.
℃ and preheated to 560℃±5℃ in an air atmosphere electric furnace, an Al-Si based aluminum alloy brazing material was immersed in the molten flux, and heated to 610℃.
The temperature was raised to 1, and after holding for 3 minutes, the sample was taken out. Thereafter, the flux was removed by air cooling, hot water washing, and cleaning with a detergent to clean the surface of the member.

As a result of brazing, all joints formed sufficient fillets, and a strong joint member was obtained.

Furthermore, after 12 and 24 hours, immersion brazing was carried out in the same electric furnace as described above without performing the dehydration work in advance, and good joints were obtained as in the above.

It was also confirmed that the steam rising from the electric furnace was not sticky and non-deliquescent, and did not adversely affect the working environment.

This pot furnace has been in continuous operation for 6 months without any problems and continues to operate satisfactorily.

In this example, a pot made of nickel was used, but it was confirmed that the use of a nickel alloy (for example, an alloy of nickel and molybdenum) would have no problem in brazing performance and durability.

On the other hand, a flux having the same composition as that described above was melted in a pot made of iron, chromium, cobalt, titanium, or an alloy thereof, and the corrosivity of the pot and the brazing property of the flux were tested.

As a result, the pot corroded and the metal components of the pot dissolved into the flux, resulting in poor brazing properties and breakage of the pot.

(E) Effects of the Invention As described above, the present invention improves the chemical activity necessary for the brazing properties of aluminum or its alloys and the substitutability with molten solder by composing the flux with BaCl ₂ , NaCl, KCl and fluoride. , it is possible to use a metal pot with many advantages while satisfying the melting point of the flux corresponding to the brazing filler metal, it is possible to omit most of the dehydration work in conventional flux immersion brazing, and it is possible to It has many excellent effects, such as reducing the amount of sediment removed and reducing changes in flux composition due to water absorption.

Moreover, the use of a non-deliquescent flux according to the method of the present invention also has the advantage of preventing corrosion of equipment and jigs and reducing deterioration in electrical insulation.

As described above, it is an object of the present invention to provide an immersion brazing joining method that greatly improves workability and economical efficiency while maintaining highly reliable brazing performance.

Claims (1)

[Claims] 1. Aluminum or its alloy member with brazing material applied in advance is mixed with 55 to 47% by weight barium chloride.
A method of brazing by immersing in a molten flux consisting of 18 to 22% by weight of sodium chloride, 27 to 33% by weight of potassium chloride, and 1 to 20% by weight of fluoride, the molten flux being nickel or A method for immersion brazing of aluminum or its alloy parts, characterized in that the parts are melted in a nickel alloy pot.