Flux-impregnated Brazing Aluminium Filler Metal

Vacuum brazed heat exchangers have their inherent advantages, but their application is greatly limited due to cost and efficiency;

Conventional tunnel furnace brazing must use a certain amount of flux to remove surface oxide scale.

However, flux spraying and drying not only increase the process steps and costs, but also make it impossible to accurately control the spray volume and uniformity.

On the one hand, the spraying that cannot be precisely controlled will lead to a large amount of flux waste, and on the other hand, it will lead to a large amount of flux residue on the surface of the heat exchanger after brazing.

Adverse effects of flux residue:

1. The more residue, the more it affects the heat exchange performance of the heat exchanger;

2. The flux remaining on the inner surface will react with the lubricating oil, sealing ring or working oil medium under high temperature for a long time and peel off, which may cause equipment failure;

3. The flux residue in the new energy battery cooling system dissolves in the circulating cooling water and increases the conductivity. Once leaked, it may cause a short circuit in the system and cause a major accident;

Therefore, more and more heat exchanger manufacturers urgently need to control the amount of flux used in the heat exchanger production process to the lowest appropriate level.

Some forms of atomized spraying can significantly reduce the amount of flux used, and pre-embedded flux is another realistic option. 

Gränges' TRILLIUM process provides useful inspiration for this. Domestic manufacturers have taken a different approach to produce composite aluminum strips or solder strips with pre-embedded flux, which have also been put into actual small batch applications. The NOCOLOK brazing flux is impregnated into the clad/unclad material during the production with an amount of 3-5 g/M2, which is suitable for a normal aluminium brazing. This process removes the process of flux slurry application and drying before brazing. 

Trials conducted by our well-known European heat exchanger manufacturers showed that after brazing in CAB process, the products had a clean appearance and passed the pressure test; further tests were also approved.

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