Aluminium cladding / brazing sheet

Aluminium aluminum alloy cladding/brazing sheet is the key material of air separation equipment and heat exchanger. It is made of cladding alloy with single or double cladding matrix alloy, which is rolled by composite rolling.
Reference standard: YS/T69 Q/S 185
The common welding methods of heat exchanger are NOCOLOK brazing and vacuum brazing. Most of the brazing materials are 3221, 6061 and 6063.
As brazing filler metal of cladding base alloy, cladding alloy should have low melting point, good fluidity and good wettability. The cladding alloys for NOCOLOK brazing process are X414, 4343, 4045, 4047 and 4N43 alloys. LQ2 (old), Q616 (new)




The suitable cladding alloys for vacuum brazing are 4004, 4104 and 4N04 alloys.
The main elements in the alloy act as follows:
Zn: The corrosion potential of the alloy can be reduced. The larger the amount of additives, the more the potential decreases. The fins after punching are preferentially corroded as the anode to protect the medium passage, and the strength of oxide film on the surface of the alloy is reduced, so that the surface of the alloy is easy to peel off and corrode in an all-round way, so as to achieve the purpose of inhibiting pitting corrosion. However, if the content of Zn is too high and the corrosion rate of the fins is too fast, the heat transfer effect of the fins will be lost and the service life of the fins will be reduced.
The lowest melting point of Si:Al-Si alloy near eutectic point can reach 577 C, which is its advantage as brazing material. After compounding, the Si element diffuses to the matrix due to its concentration, and the Mn roundness solid solubility of the matrix decreases with the increase of Si content. At the same time, Si can change the fluidity of brazing filler metal, uniform and fine structure, and improve the brazing quality.
Mg: Mg in cladding alloy is an indispensable metal activator to ensure the quality of vacuum brazing. The corrosion test shows that the corrosion potential of the cladding alloy decreases and the corrosion rate increases with the increase of Mg element, which has a certain anti-pitting effect.