95086 - Sil-Fos 5 Brazing Alloy 5% Silver Flat Rods 25lb Box

Technical Overview of Harris Sil-Fos 5 Brazing Alloy

The Harris Sil-Fos 5 is a copper-phosphorus-silver brazing alloy designed for the rigorous demands of the HVAC and refrigeration industries. Classified as AWS BCuP-3, this alloy contains 5% silver, approximately 6% phosphorus, and the balance copper. The addition of silver significantly improves the ductility of the alloy compared to standard copper-phosphorus rods (like BCuP-2), making it more resistant to vibration and thermal cycling common in compressor and condenser lines.

One of the primary technical advantages of Sil-Fos 5 is its wide melting range. With a solidus of 1190°F and a liquidus of 1495°F, it provides a substantial plastic range that allows operators to cap or fill loose connections effectively. This "sluggish" flow characteristic is particularly beneficial when brazing vertical up joints or when fit-up tolerances are not precise. The flat profile of these 36-inch rods further aids in controlling the deposition rate and heat input.

Chemically, the phosphorus content acts as a fluxing agent when joining copper to copper, eliminating the need for external flux and reducing the risk of flux entrapment. However, when brazing brass or bronze fittings, a high-quality Stay-Silv white or black flux is required to dissolve the surface oxides. Note that this alloy should strictly not be used on ferrous metals or nickel-based alloys, as the phosphorus can form brittle intermetallic compounds that compromise joint integrity.