Sil-fos™ is used to braze copper and copper alloys. When brazing copper, the phosphorus within the alloy imparts a metallurgical based self-fluxing capability. When Sil-fos™ is used to join copper alloys (such as brass, bronze or gun metal) a separate flux will be required because the self-fluxing action only occurs on copper. This filler metal should not be used to braze iron containing materials like carbon or stainless steels or nickel containing materials as the phosphorus within the filler metal will form brittle, intermetallic, phosphide compounds, at the joint interface. Sil-fos™ is not suitable for use in sulfurous atmospheres at elevated service temperatures. Sil-fos™ is the most ductile of the silver-copper-phosphorus brazing filler metals and is specified where a self-fluxing alloy must be used and joint ductility is a factor. It should be noted however that conventional silver brazing filler metals are considerably more ductile than Sil-fos™. Due to its ductility Sil-fos™ is the only filler metal of its type that can be fabricated into foil, tape, strip and fine wire. Consequently it is used to manufacture a wide range brazing filler metal pre-forms, rings and punched or pressed parts such as discs, washers and clips. The optimum joint gap for brazing is normally 0.05-0.2mm. Sil-fos™ finds extensive use in electrical engineering applications where it is used to make electrically conductive joints. The brazing of rotor bars to end rings in electric motors, the fabrication of bus bars and lightning conductors are common applications. The electrical conductivity of Sil-fos™ is approximately 11% I.A.C.S. It also finds use in heating and ventilation and refrigeration applications where it is used to join copper pipes. Information provided by Johnson Matthey Metal Joining |