| Copper-flo™ is a copper-phosphorus brazing filler metal containing a nominal 7.8% phosphorus. It is primarily used for the brazing of copper, although it can also be used for brazing copper alloys. When brazing copper the phosphorus within the alloy imparts a metallurgical based self-fluxing capability. Copper-flo™ does not contain a flux core or flux coating. If 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. Copper-flo™ is not suitable for use in sulfurous atmospheres at elevated service temperatures. When selecting a copper-phosphorus brazing filler metal it is necessary to understand about their flow properties and ductility. The level of phosphorus within the filler metal controls these two characteristics - the higher this is the more free flowing the filler metal and the lower its ductility. Copper-flo™ is the most free flowing copper-phosphorus filler metal. However, due to its high phosphorus content it is one of the least ductile. The low ductility of the alloy imparts it with glass like properties, making it both ‘notch’ sensitive and sensitive to impact type loadings. This filler metal should therefore not be used in applications involving exposure to strong vibration, impact loads or where some deformation of the joint might be expected in service. Copper-flo™ is best suited for making copper joints that are of the true capillary type and where tight joint clearances of 0.025-0.075 mm are used. The use of ‘bell mouthed’ type joints should be avoided. Copper-flo™ can be used to braze copper alloys, but its lack of ductility can be exposed in such applications. Copper-flo™ is widely used in the refrigeration, heating and ventilating and air conditioning industries for the brazing of copper pipe-work systems. Information provided by Johnson Matthey Metal Joining |
