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.
| Cu | 97.7 to 99.15 | |
| Sn | 0.6 to 0.9 | |
| Si | 0.15 to 0.4 | |
| Mn | 0.1 to 0.3 | |
| Zn | 0 to 0.1 | |
| P | 0 to 0.050 | |
| Pb | 0 to 0.020 | |
| Al | 0 to 0.010 | |
| res. | 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