The Harris Sil-Fos 15 (15% Silver) Brazing Alloy is the premier choice in the phos-copper family, designed for high-integrity joining of copper and copper alloys. With a composition of 15% silver, 5% phosphorus, and the balance copper, this alloy meets the rigorous AWS BCuP-5 classification. It is widely recognized in the industrial gas and HVAC\/R sectors as the standard for brazing refrigerant systems where joint integrity is paramount. The addition of 15% silver significantly enhances the ductility of the brazed joint, making it far more resistant to the stresses of vibration and thermal expansion\/contraction compared to lower silver alternatives like Sil-Fos 5 or Dynaflow.<\/p>\n
One of the key metallurgical advantages of Sil-Fos 15 is its wide melting range (Solidus 1190\u00b0F to Liquidus 1475\u00b0F). This “plastic range” allows the alloy to transition slowly from solid to liquid, giving the operator excellent control when bridging gaps or dealing with poor fit-ups. While it is fluid enough to penetrate tight capillaries, it can also be manipulated to cap joints effectively. For copper-to-copper applications, the phosphorus content acts as a self-fluxing agent, eliminating the need for separate flux and streamlining the brazing process. This reduces cleanup time and minimizes the risk of flux inclusion in the system.<\/p>\n
This 1 lb pack contains approximately 24 rods of 3\/32″ diameter, offering a convenient quantity for service technicians and fabricators. While primarily used on copper, Sil-Fos 15 can also be used to braze brass or bronze components; however, a white brazing flux (such as Stay-Silv White) is required for these base metals to remove oxides. It should strictly not be used on ferrous metals (steel, iron) or nickel alloys, as the phosphorus can form brittle intermetallic compounds that compromise joint strength.<\/p>\n