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C544
Free-Cutting Phosphor Bronze
C54400
Overview
C54400 is a free-machining phosphor bronze with a lead addition (3.5–4.5% Pb) that dramatically improves machinability to an 80 rating — compared to only 20 for standard C510. It retains the good corrosion resistance and moderate strength of phosphor bronze while enabling high-speed machining for screw machine products and precision parts. C544 is the material of choice when phosphor bronze properties are needed but high-volume machining is required.
Chemical Composition
| Element | Min | Max |
|---|---|---|
| Copper (Cu) | Balance (~87.7%) | — |
| Tin (Sn) | 3.50% | 4.50% |
| Lead (Pb) | 3.50% | 4.50% |
| Zinc (Zn) | 1.50% | 4.50% |
| Phosphorus (P) | 0.01% | 0.50% |
Alloy Designations
UNSC54400
ASTMB139
Common NameFree-Cutting Phosphor Bronze
Mechanical Properties
Tensile Strength (H04)55 ksi (379 MPa)
Yield Strength (H04)50 ksi (345 MPa)
Elongation (H04)15%
Hardness (H04)70 HRB
Machinability Rating80
Physical Properties
Density8.89 g/cm³ (0.321 lb/in³)
Melting Point843–999°C (1,550–1,830°F)
Electrical Conductivity19% IACS
Thermal Conductivity75.5 W/m·K
Typical Applications
- Screw machine products
- Precision electrical connectors
- Bearing cages and retainers
- Hydraulic and pneumatic fittings
- Clock and instrument parts
- Gear blanks
Fabrication & Joining
- Excellent machinability (80 rating)
- Good cold working
- Soldering: Good
- Brazing: Good
- Not recommended for welding (lead content)
- Available in rod, bar, and wire
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