Effect of trace silicon on properties of Cu-P-Sn powdery brazing filler metal

Cu-P-Sn powdery brazing filler metal was prepared by gas-water coupling atomization method,the sphericity andsize distribution were improved by adding 0. 5% mass fraction silicon. The basic properties of two kinds of powdery brazing filler metal were tested by powder material comprehensive tester,specific surface area tester,laser particle size tester and differential thermal analysis tester. The tensile specimen was prepared by flame brazing with the prepared powder filler. The tensile strength of weld was tested by mechanical testing machine. The micromorphology and microstructure of two kinds of powdery brazing filler metal were analyzed by electron microscope. The results showed that trace silicon could improve the comprehensive properties of Cu-P-Sn powders. The bulk density was increased by 17%,the compaction density by 15%,and the specific surface area by 60%. The particle size was reduced from 42. 93 to 30. 88 micron,and the melting point of alloy powder was decreased by 6 ℃ . The sphericity of Cu-P-Sn powdery brazing filler metal could be significantly improved by trace silicon element. A larger cellular alpha-Cu-based solid solution formed in brazing seam and silicon element diffused into the matrix,which slightly improved the tensile strength of the joint.