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UNS C93800 (Alloy 3D, SAE 67) Hard Bronze

C93800 bronze is a bronze formulated for casting. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 67 is the SAE designation for this material. C93800 is the UNS number. Additionally, the common industry name is 78-7-15. Older literature may refer to this material as ASTM Alloy 3D, but this is now discouraged.

It has a very low heat capacity among cast bronzes. In addition, it has a very low tensile strength and a moderately low ductility.

The graph bars on the material properties cards below compare C93800 bronze to: cast 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

96 GPa 14 x 106 psi

Elongation at Break

9.7 %

Poisson's Ratio


Shear Modulus

35 GPa 5.1 x 106 psi

Tensile Strength: Ultimate (UTS)

200 MPa 29 x 103 psi

Tensile Strength: Yield (Proof)

120 MPa 17 x 103 psi

Thermal Properties

Latent Heat of Fusion

170 J/g

Maximum Temperature: Mechanical

140 °C 280 °F

Melting Completion (Liquidus)

940 °C 1730 °F

Melting Onset (Solidus)

850 °C 1570 °F

Specific Heat Capacity

340 J/kg-K 0.081 BTU/lb-°F

Thermal Conductivity

52 W/m-K 30 BTU/h-ft-°F

Thermal Expansion

19 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

11 % IACS

Electrical Conductivity: Equal Weight (Specific)

11 % IACS

Otherwise Unclassified Properties

Base Metal Price

31 % relative


9.1 g/cm3 570 lb/ft3

Embodied Carbon

3.2 kg CO2/kg material

Embodied Energy

51 MJ/kg 22 x 103 BTU/lb

Embodied Water

380 L/kg 45 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

17 MJ/m3

Resilience: Unit (Modulus of Resilience)

70 kJ/m3

Stiffness to Weight: Axial

5.9 points

Stiffness to Weight: Bending

17 points

Strength to Weight: Axial

6.1 points

Strength to Weight: Bending

8.4 points

Thermal Diffusivity

17 mm2/s

Thermal Shock Resistance

8.1 points

Alloy Composition

Among cast copper alloys, the composition of C93800 bronze is notable for containing a comparatively high amount of lead (Pb). Lead is used to improve machinability and bearing properties, at the cost of toxicity. It also adds pressure tightness to castings.

Copper (Cu) 75 to 79
Lead (Pb) 13 to 16
Tin (Sn) 6.3 to 7.5
Phosphorus (P) 0 to 1.5
Nickel (Ni) 0 to 1.0
Zinc (Zn) 0 to 0.8
Antimony (Sb) 0 to 0.8
Iron (Fe) 0 to 0.15
Sulfur (S) 0 to 0.080
Silicon (Si) 0 to 0.0050
Aluminum (Al) 0 to 0.0050
Residuals 0 to 1.0

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

Followup Questions

Similar Alloys

Further Reading

ASTM B271: Standard Specification for Copper-Base Alloy Centrifugal Castings

ASTM B505: Standard Specification for Copper Alloy Continuous Castings

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