General brazing flux FormReferenceTemperature applicable /℃Paste brazing fluxFB105G550～850fluid-paste brazing fluxQJ501Y650～850fluid-paste brazing flux/ Gas booster fluxQJ403>450 Flux has lower melting point than brazing filler metal, good surface activity. It can break or dissolve metallic oxides on the surface of work and brazing alloys during the process, which is good for the liquid brazing alloy wetting the surfaces to permit adequate migration of the filler metal in order to get good quality joint. Flux is used in most of cases. It is widely applied in brazing of copper-based and silver filler metals.