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UNS C51900 (CW452K) Phosphor Bronze

C51900 bronze is a bronze formulated for primary forming into wrought products. CW452K is the EN numeric designation for this material. C51900 is the UNS number. Additionally, the EN chemical designation is CuSn6. And the British Standard (BS) designation is PB103.

It has a moderately high base cost and a moderately low melting temperature among wrought bronzes.

The properties of C51900 bronze include three 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 C51900 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

14 to 29 %

Poisson's Ratio


Rockwell B Hardness

42 to 91

Rockwell Superficial 30T Hardness

45 to 76

Shear Modulus

42 GPa 6.0 x 106 psi

Shear Strength

320 to 370 MPa 47 to 54 x 103 psi

Tensile Strength: Ultimate (UTS)

380 to 620 MPa 55 to 89 x 103 psi

Tensile Strength: Yield (Proof)

390 to 570 MPa 57 to 82 x 103 psi

Thermal Properties

Latent Heat of Fusion

200 J/g

Maximum Temperature: Mechanical

180 °C 360 °F

Melting Completion (Liquidus)

1040 °C 1900 °F

Melting Onset (Solidus)

930 °C 1700 °F

Specific Heat Capacity

380 J/kg-K 0.090 BTU/lb-°F

Thermal Conductivity

66 W/m-K 38 BTU/h-ft-°F

Thermal Expansion

18 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

14 % IACS

Electrical Conductivity: Equal Weight (Specific)

14 % IACS

Otherwise Unclassified Properties

Base Metal Price

33 % relative


8.8 g/cm3 550 lb/ft3

Embodied Carbon

3.2 kg CO2/kg material

Embodied Energy

51 MJ/kg 22 x 103 BTU/lb

Embodied Water

360 L/kg 42 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

55 to 180 MJ/m3

Resilience: Unit (Modulus of Resilience)

680 to 1450 kJ/m3

Stiffness to Weight: Axial

7.0 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

12 to 19 points

Strength to Weight: Bending

13 to 18 points

Thermal Diffusivity

20 mm2/s

Thermal Shock Resistance

14 to 22 points

Alloy Composition

Among wrought copper alloys, the composition of C51900 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 91.7 to 95
Tin (Sn)Sn 5.0 to 7.0
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 B103: Standard Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar

ASM Specialty Handbook: Copper and Copper Alloys, J. R. Davis (editor), 2001