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UNS C51000 (CW451K) Phosphor Bronze

C51000 bronze is a bronze formulated for primary forming into wrought products. CW451K is the EN numeric designation for this material. C51000 is the UNS number. Additionally, the EN chemical designation is CuSn5. And the British Standard (BS) designation is PB102. Older literature may refer to this material as ASTM Phosphor Bronze Grade A1, but this is now discouraged.

It has a moderately high base cost among the wrought bronzes in the database.

The properties of C51000 bronze include eight common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare C51000 bronze to: wrought bronzes (top), all copper alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

110 GPa 16 x 106 psi

Elongation at Break

2.7 to 64 %

Poisson's Ratio


Rockwell B Hardness

26 to 97

Rockwell Superficial 30T Hardness

42 to 80

Shear Modulus

42 GPa 6.1 x 106 psi

Shear Strength

250 to 460 MPa 36 to 66 x 103 psi

Tensile Strength: Ultimate (UTS)

330 to 780 MPa 47 to 110 x 103 psi

Tensile Strength: Yield (Proof)

130 to 750 MPa 19 to 110 x 103 psi

Thermal Properties

Latent Heat of Fusion

200 J/g

Maximum Temperature: Mechanical

190 °C 370 °F

Melting Completion (Liquidus)

1050 °C 1930 °F

Melting Onset (Solidus)

960 °C 1770 °F

Specific Heat Capacity

380 J/kg-K 0.090 BTU/lb-°F

Thermal Conductivity

77 W/m-K 44 BTU/h-ft-°F

Thermal Expansion

18 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

18 % IACS

Electrical Conductivity: Equal Weight (Specific)

18 % IACS

Otherwise Unclassified Properties

Base Metal Price

33 % relative


8.8 g/cm3 550 lb/ft3

Embodied Carbon

3.1 kg CO2/kg material

Embodied Energy

50 MJ/kg 21 x 103 BTU/lb

Embodied Water

350 L/kg 42 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

7.0 to 490 MJ/m3

Resilience: Unit (Modulus of Resilience)

75 to 2490 kJ/m3

Stiffness to Weight: Axial

7.0 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

10 to 25 points

Strength to Weight: Bending

12 to 21 points

Thermal Diffusivity

23 mm2/s

Thermal Shock Resistance

12 to 28 points

Alloy Composition

Among wrought copper alloys, the composition of C51000 bronze is notable for including phosphorus (P) and tin (Sn). Phosphorus is used as an alloy deoxidizer, and to reduce vulnerability to dezincification. Tin is used to improve strength, bearing properties, and corrosion resistance against certain types of media.

Copper (Cu)Cu 92.9 to 95.5
Tin (Sn)Sn 4.5 to 5.8
Phosphorus (P)P 0.030 to 0.35
Zinc (Zn)Zn 0 to 0.3
Iron (Fe)Fe 0 to 0.1
Lead (Pb)Pb 0 to 0.050
Residualsres. 0 to 0.5

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM B139: Standard Specification for Phosphor Bronze Rod, Bar, and Shapes

ASTM B103: Standard Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar

Copper: Its Trade, Manufacture, Use, and Environmental Status, Gunter Joseph, 2001