UNS C94300 (Alloy 3E) Soft Bronze
C94300 bronze is a bronze formulated for casting. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C94300 is the UNS number for this material. Additionally, the common industry name is 71-5-24. Older literature may refer to this material as ASTM Alloy 3E, but this is now discouraged.
It has a very low melting temperature among cast bronzes. In addition, it has the lowest heat capacity and a very low tensile strength.
The graph bars on the material properties cards below compare C94300 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
87 GPa 13 x 106 psi
Elongation at Break
9.7 %
Poisson's Ratio
0.36
Shear Modulus
32 GPa 4.6 x 106 psi
Tensile Strength: Ultimate (UTS)
180 MPa 25 x 103 psi
Tensile Strength: Yield (Proof)
120 MPa 17 x 103 psi
Thermal Properties
Latent Heat of Fusion
150 J/g
Maximum Temperature: Mechanical
110 °C 240 °F
Melting Completion (Liquidus)
820 °C 1520 °F
Melting Onset (Solidus)
760 °C 1390 °F
Specific Heat Capacity
320 J/kg-K 0.075 BTU/lb-°F
Thermal Conductivity
63 W/m-K 36 BTU/h-ft-°F
Thermal Expansion
20 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
9.0 % IACS
Electrical Conductivity: Equal Weight (Specific)
8.7 % IACS
Otherwise Unclassified Properties
Base Metal Price
28 % relative
Density
9.3 g/cm3 580 lb/ft3
Embodied Carbon
2.9 kg CO2/kg material
Embodied Energy
47 MJ/kg 20 x 103 BTU/lb
Embodied Water
370 L/kg 44 gal/lb
Common Calculations
Resilience: Ultimate (Unit Rupture Work)
15 MJ/m3
Resilience: Unit (Modulus of Resilience)
77 kJ/m3
Stiffness to Weight: Axial
5.2 points
Stiffness to Weight: Bending
16 points
Strength to Weight: Axial
5.2 points
Strength to Weight: Bending
7.4 points
Thermal Diffusivity
21 mm2/s
Thermal Shock Resistance
7.1 points
Alloy Composition
Among cast copper alloys, the composition of C94300 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.
| Cu | 67 to 72 | |
| Pb | 23 to 27 | |
| Sn | 4.5 to 6.0 | |
| P | 0 to 1.5 | |
| Ni | 0 to 1.0 | |
| Zn | 0 to 0.8 | |
| Sb | 0 to 0.8 | |
| Fe | 0 to 0.15 | |
| S | 0 to 0.080 | |
| Si | 0 to 0.0050 | |
| Al | 0 to 0.0050 | |
| res. | 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
CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015