The functional part of the flux can be divided into three:
1, removal of the welding surface of the oxide, reducing the solder melting point and the surface tension as soon as possible to reach the brazing temperature.
To protect the weld metal in the liquid from the impact of harmful gases in the ambient atmosphere.
3, so that the liquid solder the appropriate flow rate to fill the brazing seam. Melting point of the Types Of Welding Electrode  should be lower than the melting point of brazing 10-30 ° C,

Flux melting point higher than the brazing also allows special circumstances. If the melting point of the flux too small solder premature melting of the Welding Fluxby

Flux in the solder melts, evaporation, and the role of parent material has lost activity.
The flux of choice usually depending on the nature of the oxide film. Alkaline oxide film such as: Fe, Ni and Cu oxides often

The use of acidic boron anhydride (B2O3) flux, the acidic oxide film such as to deal with cast iron containing high SiO2 oxide film used

With alkaline Na2CO3 flux makes it into the slag generated fusible Na2SiO3.
Fluoride gas used as a flux, their response is uniform, no residue after welding. Of BF3 often and N2 mix at high

Temperature brazing of stainless steel. Below 450 ℃ brazing flux as soft flux. Soft flux is divided into two, one water-soluble

Of usually hydrochloride and phosphate single or cable Lattice salt aqueous solution composition, activity, corrosive, and after welding needs clear

Wash. Another is water-insoluble organic matter flux, usually based on rosin or artificial resin, by adding organic acids, organic amines or

HCL or HBr salt, to film in order to improve capacity and activity.