95038 - Sil-Fos 2% Silver Phos-Copper Brazing Alloy - 2.4mm Rods (25lb Bulk)

Technical Overview of Sil-Fos 2% Silver Brazing Alloy

The Harris Sil-Fos 2 is a copper-phosphorus-silver brazing alloy designed to provide a cost-effective solution for joining copper and copper alloys. Classified under the American Welding Society (AWS) standard as BCuP-6, this alloy contains nominally 2% silver, 7% phosphorus, and the balance copper. The addition of silver, even at a modest 2%, significantly alters the metallurgical properties compared to standard phos-copper (BCuP-2) rods. It lowers the liquidus temperature slightly and improves the ductility of the brazed joint, making it more robust against thermal cycling and minor vibration than silver-free alternatives.

One of the primary technical advantages of the Sil-Fos 2 formulation is its self-fluxing property when applied to copper base metals. The phosphorus content acts as a deoxidizer, reacting with copper oxides at brazing temperatures to form a fluid slag that cleans the joint surface, thereby eliminating the need for a separate flux application. This characteristic streamlines the brazing process in high-volume industrial environments and reduces the risk of flux entrapment. However, when brazing brass or bronze fittings, the self-fluxing action is insufficient due to the presence of zinc and tin oxides; therefore, a high-quality paste flux, such as Stay-Silv white flux, is required to ensure proper wetting and adhesion.

The alloy exhibits a wide melting range, with a solidus of approximately 1190°F (643°C) and a liquidus of 1450°F (788°C). This 260°F plastic range provides operators with a "mushy" state, allowing for the capping of joints or bridging of slightly wider gaps that may occur in field fit-ups. While it flows more freely than 0% silver rods, it is less fluid than high-silver content alloys like Sil-Fos 15, offering a controllable deposition rate ideal for vertical and overhead positions found in complex piping assemblies.

This 25lb bulk tube packaging is specifically tailored for large-scale MRO operations, HVAC manufacturing facilities, and mechanical contractors who require a consistent supply of consumable material. The 2.4mm (approx. 3/32") diameter is a versatile size, suitable for a broad range of tubing diameters commonly found in refrigeration and air conditioning systems. It is critical to note that phosphorus-bearing alloys like Sil-Fos 2 must never be used on ferrous metals (steel, iron) or nickel alloys, as the formation of brittle iron phosphides can lead to catastrophic joint failure.