Sil-Fos 15 Silver-Copper-Phosphorus Brazing Alloy
Self-Fluxing Silver Alloy for Copper-Copper & Copper-Brass Brazing
Sil-Fos 15 is a silver-copper-phosphorus alloy designed for brazing copper to copper, and copper to brass (with flux). Phosphorus in the alloy acts as its own flux when used on clean copper surfaces, making Sil-Fos 15 ideal even when joint fit-up isn’t perfect. Commonly used in HVAC/R, refrigeration coils, and copper tube assemblies.
Features:
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15% silver content — boosts strength, fluid flow, and joint appearance
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Self-fluxing on copper — phosphorus element removes oxide without external flux when brazing clean copper
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Highest joint ductility among Sil-Fos alloys — bonds resist cracking or stress
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Good flow into long, thin joints, even when fit-up is marginal
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Supports fillet build-ups and brazing in less-than-ideal joint clearance
Applications:
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Brazing copper to copper (no flux needed)
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Brazing copper to brass (use flux recommended)
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HVAC systems & refrigeration coils
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Air conditioning units & evaporator/refrigerator coils
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Copper tube, piping, fittings, and copper assemblies
Specifications:
| Specification | Detail |
|---|---|
| Nominal Composition | ~ 15% Silver, ~ 5% Phosphorus, balance Copper |
| Alloy Classification | AWS BCuP-5 / ISO CuP 284 |
| Solidus Temperature | ~ 1190 °F (≈ 643 °C) |
| Liquidus Temperature | ~ 1300 °F (≈ 704 °C) |
| Maximum Recommended Brazing Temp | ~ 1500 °F (≈ 816 °C) |
| Material Compatibility | Clean Copper (self-fluxing); Copper-Brass (use flux) |
| Limitations | Do not use on iron or nickel base metals — brittle intermetallics may form |
Why Choose Sil-Fos 15?:
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Reduces need for external flux when brazing copper — cleaner job, less contamination
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Premium ductility gives stronger joints under stress
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Ideal for refrigeration and HVAC work with variable joint fit-up
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Trusted alloy made in USA with established specifications
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