Effect of induction brazing process on microstructure and properties of brazing seam

Effects of brazing temperature,flux amount and holding time on quality of the brazing seam for hard alloy milling cutters were systematically researched through methods of scanning electron microscope and universal mechanical testing machine. The research results showed that the damage degree of high temperature to the strength of the brazing seam was significantly higher than that of low temperature. The main reason was that the flux began to fail at high temperature and did not effectively protect the brazed area. The internal oxidation phenomenon of the brazed seam was very obvious and the oxygen content was as high as more than 30%. The enrichment of oxygen occurred in the entire observation area,and the oxidation resistance of the copper-rich phase was significantly lower than that of the silver-rich phase. When extending the holding time to 5 ～ 6 s at the same brazing temperature,the wettability of brazing filler metal on the base metal was significantly improved and the tensile strength of the brazed joint reached above 410 MPa. However,if the holding time continued to increase,the flux would lose its protective ability and the strength of the joint would begin to decrease. When the amount of flux applied was larger,some flux slag appeared at the interface of the brazed joint,which would easily affect the performance of the joint. The amount of flux must be reasonably controlled.