Copper Alloy C55181
UNS C55181
C55181 is the highest-phosphorus self-fluxing copper-phosphorus brazing filler and the most widely used copper-to-copper brazing alloy.
Reference datasheet — C55181 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the AB condition
C55181 tempers and conditions
C55181 is supplied in one standard condition, AB. AB is the default FabDigit quotes; the values on this page are for it.
Supply forms, finishes and certifications
Ways C55181 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FC | Flux-coated rod | Supply form |
PREFORM | Stamped/formed rings, washers and shaped preforms | Supply form |
ROD | ROD/WIRE | Supply form |
STRIP | Cast/rolled strip and shim stock | Supply form |
POWDER | POWDER/PASTE | Printing process |
What is C55181?
C55181 is the highest-phosphorus self-fluxing copper-phosphorus brazing filler and the most widely used copper-to-copper brazing alloy. It is chosen because it needs no flux on copper, flows into close-fitting tube joints, and is available as bare rod, strip, stamped preforms and powder; as-brazed values are about 250 MPa tensile strength, 2 % elongation, 105 HB, 10 % IACS conductivity and service to 200 °C. Elongation is low and the alloy is brittle on steel and nickel-base metals, and joints should not be used in H2S or SO2 atmospheres. For more ductile, better-wetting joints use a silver-bearing phos-copper such as C55280 or C55283. C55181 has a density of 7.95 g/cm³ (0.287 lb/in³), lighter than 88% of copper alloy grades. It melts at 710°C (1,310 °F). C55181 has a tensile strength of 250 MPa (36.3 ksi), weaker than 81% of copper alloy grades. Elongation at break is 2% and the elastic modulus is 110 GPa (16 Msi).
What is C55181 used for?
- HVAC/R copper tube brazing
- plumbing pipe joints
- electrical bus bar joints
- copper fitting assembly
Limitations
- Hard to polish — 40/100, worse than 100% of copper alloy grades
- Limited ductility — 2%, worse than 98% of copper alloy grades
- Difficult to weld — 15/100, worse than 94% of copper alloy grades
- Difficult to machine — 25/100, worse than 86% of copper alloy grades
- Poor heat conductor — 45 W/m·K (26 BTU/hr·ft·°F), worse than 76% of copper alloy grades
C55181 properties
Typical room-temperature values for C55181-AB; bars are the position among copper alloy grades.
Physical3
C55181 has a density of 7.95 g/cm³ (0.287 lb/in³), lighter than 88% of copper alloy grades. It melts at 710°C (1,310 °F).
Mechanical9
C55181 has a tensile strength of 250 MPa (36.3 ksi), weaker than 81% of copper alloy grades. Elongation at break is 2% and the elastic modulus is 110 GPa (16 Msi).
Thermal6
C55181 is rated for continuous service to 200°C (392 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), worse than 76% of copper alloy grades. Thermal expansion is 17 µm/m·K (9.44 µin/in·°F).
Electrical3
C55181 conducts electricity at 10 % IACS, worse than 74% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is good (58/100), worse than 76% of copper alloy grades.
Sustainability4
Producing a kilogram of C55181 takes about 55 MJ of energy and emits 3.8 kg of CO₂ — less than 72% of copper alloy grades. Typical recycled content is 30%.
Manufacturability7
C55181's machinability is poor (25/100, worse than 86% of copper alloy grades); weldability poor (15/100); formability poor (20/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the copper alloy family
Yield strength against density for every copper alloy grade FabDigit runs. C55181 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C55181
Is C55181 easy to machine?
Rarely machined; the Cu3P eutectic makes it brittle and chips crumble — cut rod with shears/abrasive wheel rather than turning.
Can C55181 be welded?
Not a weldable structural alloy; it is the filler itself — never use on steel, nickel or nickel alloys (brittle phosphides) or in H2S/SO2 service.
Can C55181 be formed, bent or molded?
Supplied continuous-cast then hot-extruded/warm-drawn to rod, strip or preforms; essentially no cold formability, so bend preforms warm.
C55181 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| PAWS A5.8 BCuP-2 / GB/T 6418 BCu93P | 7 – 7.5 | 7.25 |
| Other elements (total)residuals, total max per AWS A5.8 | ≤ 0.15 | |
| Curemainder, ~92.5–93.0 % | balance |
What surface finishes work on C55181?
Joints need no post-braze flux removal on copper (self-fluxing); wire-brush or 5 % citric/sulfuric pickle to remove phosphate film before plating or painting.
Surface treatments FabDigit runs on copper alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Equivalent designations
Standards and trade names that resolve to Copper Alloy C55181 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Phos-Copper
How much does C55181 cost?
C55181 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C55181 — frequently asked
What is C55181 used for?
C55181 is typically used for HVAC/R copper tube brazing, plumbing pipe joints, electrical bus bar joints and copper fitting assembly. In short: most used copper-to-copper filler; highest-phosphorus phos-copper; no flux needed on copper.
What is the tensile strength of C55181?
C55181 has a typical tensile strength of 250 MPa (36.3 ksi) — weaker than 81% of copper alloy grades.
Is C55181 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 86% of copper alloy grades). Rarely machined; the Cu3P eutectic makes it brittle and chips crumble — cut rod with shears/abrasive wheel rather than turning.
Can C55181 be welded?
Not readily — weldability is rated poor (15/100). Not a weldable structural alloy; it is the filler itself — never use on steel, nickel or nickel alloys (brittle phosphides) or in H2S/SO2 service.
What surface finishes work on C55181?
Joints need no post-braze flux removal on copper (self-fluxing); wire-brush or 5 % citric/sulfuric pickle to remove phosphate film before plating or painting.
Can C55181 be formed, bent or molded?
Supplied continuous-cast then hot-extruded/warm-drawn to rod, strip or preforms; essentially no cold formability, so bend preforms warm.
What is the maximum service temperature of C55181?
C55181 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C55181 cost?
C55181 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.8/A5.8M — Specification for Filler Metals for Brazing and Braze Welding (BCuP-2, UNS C55181) — American Welding Society (2019)
- GB/T 6418 — (BCu93P) — SAC / (2019)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering (copper-phosphorus filler metals) — ASM International (1993)
- Fos-Flo 7 / phos-copper brazing alloy datasheet — Lucas-Milhaupt (Handy & Harman) (2022)
- Harris Phos-Copper (BCuP-2) product data — The Harris Products Group / Lincoln Electric (2021)
- Copper alloy UNS C55181 designation data — Copper Development Association (copper.org) (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.