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UNS C18900 Silicon Copper

C18900 copper is a lightly alloyed grade of copper, formulated for primary forming into wrought products. It has a moderately low thermal conductivity among wrought coppers. In addition, it has a moderately low electrical conductivity and can have a moderately high ductility.

The properties of C18900 copper include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare C18900 copper to: wrought coppers (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

120 GPa 17 x 106 psi

Elongation at Break

14 to 48 %

Poisson's Ratio

0.34

Shear Modulus

43 GPa 6.2 x 106 psi

Shear Strength

190 to 300 MPa 27 to 44 x 103 psi

Tensile Strength: Ultimate (UTS)

260 to 500 MPa 38 to 73 x 103 psi

Tensile Strength: Yield (Proof)

67 to 390 MPa 9.8 to 56 x 103 psi

Thermal Properties

Latent Heat of Fusion

210 J/g

Maximum Temperature: Mechanical

200 °C 390 °F

Melting Completion (Liquidus)

1080 °C 1970 °F

Melting Onset (Solidus)

1020 °C 1860 °F

Specific Heat Capacity

390 J/kg-K 0.092 BTU/lb-°F

Thermal Conductivity

130 W/m-K 75 BTU/h-ft-°F

Thermal Expansion

17 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

30 % IACS

Electrical Conductivity: Equal Weight (Specific)

30 % IACS

Otherwise Unclassified Properties

Base Metal Price

31 % relative

Density

8.9 g/cm3 560 lb/ft3

Embodied Carbon

2.7 kg CO2/kg material

Embodied Energy

42 MJ/kg 18 x 103 BTU/lb

Embodied Water

310 L/kg 37 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

65 to 95 MJ/m3

Resilience: Unit (Modulus of Resilience)

20 to 660 kJ/m3

Stiffness to Weight: Axial

7.2 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

8.2 to 16 points

Strength to Weight: Bending

10 to 16 points

Thermal Diffusivity

38 mm2/s

Thermal Shock Resistance

9.3 to 18 points

Alloy Composition

Among wrought copper alloys, the composition of C18900 copper is notable for including aluminum (Al) and silicon (Si). Aluminum is used to add strength and oxidation resistance. Silicon is used to increase strength at the expense of ductility. It also lowers the melting temperature and raises the fluidity of the alloy.

Copper (Cu) 97.7 to 99.15
Tin (Sn) 0.6 to 0.9
Silicon (Si) 0.15 to 0.4
Manganese (Mn) 0.1 to 0.3
Zinc (Zn) 0 to 0.1
Phosphorus (P) 0 to 0.050
Lead (Pb) 0 to 0.020
Aluminum (Al) 0 to 0.010
Residuals 0 to 0.5

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

Followup Questions

Similar Alloys

Further Reading

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015