31130 - Sil-Fos 2 BCuP-6 Silver Brazing Alloy 1/8" (3.2mm) - 25lb Bulk

Harris Sil-Fos 2% Silver Brazing Alloy (BCuP-6)

The Harris Sil-Fos 2 is a premium copper-phosphorus-silver brazing alloy designed for the rigorous demands of the HVAC and refrigeration industries. Formulated with 2% silver, 7% phosphorus, and a copper balance, this alloy (AWS BCuP-6) serves as a superior alternative to standard copper-phosphorus rods. The addition of silver significantly enhances the ductility of the brazed joint, making it more resistant to the vibration and thermal cycling common in compressor lines and evaporator coils. This 3.2mm (1/8") diameter rod is an industry standard for joining copper tubing and fittings in both residential and commercial settings.

One of the primary technical advantages of Sil-Fos 2 is its self-fluxing property when used on copper-to-copper joints. The phosphorus content acts as a fluxing agent, reducing surface oxides at brazing temperatures and eliminating the need for additional chemical flux. This not only speeds up the workflow but also prevents flux entrapment inside the refrigeration system, which can lead to corrosion or system blockages. For applications involving brass or bronze fittings, a standard silver brazing flux (such as Stay-Silv white flux) is required to ensure proper wetting and adhesion.

Metallurgically, Sil-Fos 2 exhibits a medium plastic range with a solidus of 1190°F (643°C) and a liquidus of 1450°F (788°C). Unlike high-silver alloys that flow like water (capillary action), Sil-Fos 2 has a slightly more viscous flow characteristic. This "sluggish" nature is highly advantageous when dealing with joints that have wider clearances or poor fit-ups, as the alloy can bridge gaps that thinner fluids would run out of. Packaged in a substantial 25lb tube, this product is tailored for industrial fabricators and large-scale mechanical contractors requiring consistent, high-quality consumables for extensive piping projects.