Brazing & Soldering Products

Lucas-Milhaupt offers the most comprehensive inventory of alloys and forms in the industry and our expertise in brazing and soldering ensures that we can find the best-matched products for your needs.

Technical Documentation

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Silver/Copper/Phosphorus Alloys

SIL-FOS® Saves You Time and Money Before Brazing

SIL-FOS® alloys are Copper-based filler metals that are self-fluxing on copper by virtue of their phosphorous content. Because of their self-fluxing nature, you save time and money by eliminating the steps necessary to flux a joint before brazing. However, copper alloys such as brass and bronze should be fluxed with HANDY FLUX™ or Sure Flo Brazing Flux to assure a sound braze joint.

While this filler metal is widely used in the air conditioning and plumbing industries, it is not recommended for ferrous or nickel based materials because the joint will become brittle and may fail. The SIL-FOS® Alloys vary in silver content from 18% to 2% and the percentage of silver and phosphorous does change the melt and flow characteristics of the filler metal.

SIL-FOS® Available in the Following Materials

Our alloys are available in wire and rod, powder and paste, and preformed rings and shapes. Some SIL-FOS® alloys are available in strip as well.

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Product SolidusLiquidusNominal Composition, %AWS & International Standards Technical Documents* MSDS Safety Documents*
°F °C °F °C Ag Cu P
SIL-FOS® 15

(Formally SILVALOY® 15) For use where close fit-ups cannot be maintained and joint ductility is important. Recommended joint clearance: .002 to .005 (.051 mm to .127 mm). Slow flow. The only phos/copper silver filler metal available in strip or sheet form.


1190 645 1475 (1300) 805 (705) 15 80 5 BCuP-5
SIL-FOS® 18

A ternary eutectic filler metal for joints where good fit-up can be maintained and low melting point is of prime importance. Clearance: .001 to .003 (.025 mm to .076 mm). Very fast flow.


1190 645 1190 645 17.6 75.9 6.5  
SIL-FOS® 2

(Formally SILVALOY® 2) A filler metal with comparable characteristics to FOS-FLO® . Recommended joint clearance: .001 to .005 (.025 mm to .127 mm). Medium flow.


1190 645 1450 (1325) 785 (720) 2 91 7 BCuP-6
SIL-FOS® 2M
(Formally SILVALOY® 2M) Has ability to fill moderate gaps in poorly fitted joints. More ductile than FOS-FLO® or SIL-FOS® 2. Intended for use on copper tube headers and similar applications where a sleeve fit is not practical. Recommended joint clearance: .002 to .005 (.051 mm to .127 mm). Slow flow.
1190 645 1495 (1350) 815 (730) 2 91.4 6.6  
SIL-FOS® 5

(Formally SILVALOY® 5) Designed primarily for those applications where close fit-ups cannot be maintained. It has ability to fill gaps and form fillets without adversely affecting joint strength. Recommended joint clearance: .003 to .005 (.076 mm to .127 mm). Slow flow.


1190 645 1495 (1325) 815 (720) 5 89 6 BCuP-3
SIL-FOS® 6

(Formally SILVALOY® 6F) A very fluid filler metal for close fit-up work. Low melting range makes it ideal where temperature is a factor. Recommended joint clearance: .001 to .003 (.025 mm to .076 mm). Fast flow. Lowest melt and flow in the minimum silver class.


1190 645 1325 (1275) 720 (690) 6 86.75 7.25 BCuP-4
SIL-FOS® 6M

(Formally SILVALOY® 6) Recommended for use where close fit-up cannot be maintained. Has the ability to fill gaps and form fillets without affecting joint strength. Recommended joint clearance: .002 to .005 (.051 mm to .127 mm). Slow flow.


1190 645 1460 (1300) 795 (705) 6 88 6  

Note: NOTE: The SIL-FOS® and FOS-FLO® filler metals are for use with copper and copper alloy base metals. Do not use these materials to join ferrous materials as brittle phosphide compounds will be formed at the interface. The SIL-FOS® and FOS-FLO® filler metals have a unique characteristic called the "Flow Point" (listed in parentheses). The "Flow Point" is defined as the temperature at which the filler metal is fluid enough to capillary through a joint even though not completely liquid (i.e. above the liquidus temperature).

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