The Effect Of Alloy Element And Brazing Process On Cu-P-Ag Brazing Performance

Copper base filler metal with different content of element Sn,P,X can be obtained by induction melting, which could be used for red copper brazing under various process conditions. To investigate the properties of Cu-P-Ag filler with different alloy element composition and the impacts of brazing process towards the red copper joints, DTA,XRD,SEM and tensile tests are adopted. To analysis the forming steps of joint at the first stage, then observe the impacts of joints mechanical properties with different temperatures, preservation time and various alloy elements content. The relationship between microstructure and mechanical properties should be acquired, heat treatment is utilized for strengthen the joint properties after brazing as final stage.The research efforts shows that:Copper-Tin compound molten during the heating process, then flow into the weld line due to capillary force and react, weld line are composed with interface layer, diffusion layer and residual layer. Liquid filler metal react with base metal first due to grain boundary diffusion followed by erosion effect with intracrystalline diffusion which finally form compound as metallurgical bonding. Diffusion layer consists of copper base solid solution which contain element of Sn and X, copper solid solution containing tin mainly distributed at interface area while brittle compound Cu3P mainly distributed at middle of residual layer on weld line which become the weak part.Element Sn effectively decrease the liquidus temperature and melting range of the filler metal while element X and P could hardly influence the reducing melting behaviour. Element X can modify the morphology of brittle phase Cu3P whereas proper content of element X could cause the shape transformation of phase Cu3P from petaloid to spherical. The brittle phase content in filler metal have close relationship to the content of element P. Extending heat preservation time and increasing brazing temperature make the diffusion layer become thicker, however, excessive heating temperature could lead profound loss of filler, as consequence, the brazing defects appear.Tempering treatment after brazing could eliminate residual stress of joint part as well as develop the tension resistance of joint. Preserve the sample for30minutes at300℃could effective remove residual stress while the tensile strength of joint increased from190.107MPa to211.065MPa.