Effect of Ga₂O₃ on of microstructure and properties of brazed joints obtained by Ag30CuZnSn flux cored brazing filler metal and brass

The effect of Ga₂O₃ on the microstructure and properties of brazed joints formed by Ag30CuZnSn flux cored brazing filler metal brazed brass was studied when adding Ga₂O₃ into flux cored brazing powders. The results showed that the micro amount of Ga₂O₃ additions can significantly improve the wettability of Ag30CuZnSn flux cored brazing filler metal and reduce the flux additions. When the content of Ga₂O₃ was 0.4 %, the wettability of Ag30CuZnSn flux cored brazing filler metal and the shear strength of brazed joint was up to the optimum. This was attributed to the fact that Ga₂O₃ was a surfactant, which can significantly reduce the interfacial tension between the molten brazing filler metal and the base metal, to improve the effect of removing oxide film of flux powders. Finally, the wettability of Ag30CuZnSn flux cored brazing filler metal was improved. In the process of flame brazing, when Ga₂O₃ addition was 0.4 %, the shear strength of brazed joint was increased by more than 11% owing to the microstructure refinement of brazing seam and the increase of brazed rate (the brazed rate was increased to more than 95%). The fracture morphology of the brazed joint proved the above results.