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UNS C91700 Nickel Gear Bronze

C91700 bronze is a bronze formulated for casting. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C91700 is the UNS number for this material. Older literature may refer to this material as ASTM Gear Bronze Type B, but this is now discouraged.

It has a fairly high base cost among cast bronzes. In addition, it has a very high embodied energy and a moderately high thermal conductivity.

The graph bars on the material properties cards below compare C91700 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

Brinell Hardness

90

Elastic (Young's, Tensile) Modulus

110 GPa 16 x 106 psi

Elongation at Break

13 %

Poisson's Ratio

0.34

Shear Modulus

41 GPa 5.9 x 106 psi

Tensile Strength: Ultimate (UTS)

330 MPa 48 x 103 psi

Tensile Strength: Yield (Proof)

170 MPa 25 x 103 psi

Thermal Properties

Latent Heat of Fusion

190 J/g

Maximum Temperature: Mechanical

170 °C 340 °F

Melting Completion (Liquidus)

1020 °C 1860 °F

Melting Onset (Solidus)

850 °C 1560 °F

Specific Heat Capacity

370 J/kg-K 0.088 BTU/lb-°F

Thermal Conductivity

71 W/m-K 41 BTU/h-ft-°F

Thermal Expansion

18 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

10 % IACS

Electrical Conductivity: Equal Weight (Specific)

10 % IACS

Otherwise Unclassified Properties

Base Metal Price

36 % relative

Density

8.7 g/cm3 550 lb/ft3

Embodied Carbon

3.9 kg CO2/kg material

Embodied Energy

63 MJ/kg 27 x 103 BTU/lb

Embodied Water

400 L/kg 48 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

35 MJ/m3

Resilience: Unit (Modulus of Resilience)

140 kJ/m3

Stiffness to Weight: Axial

6.9 points

Stiffness to Weight: Bending

18 points

Strength to Weight: Axial

11 points

Strength to Weight: Bending

12 points

Thermal Diffusivity

22 mm2/s

Thermal Shock Resistance

12 points

Alloy Composition

Among cast copper alloys, the composition of C91700 bronze is notable for containing a comparatively high amount of tin (Sn) and including sulfur (S). Tin is used to improve strength, bearing properties, and corrosion resistance against certain types of media. It also places certain constraints on cast part design, so as to avoid porosity problems. Sulfur is used to improve machinability at the cost of a decrease in electrical conductivity.

Copper (Cu) 84.2 to 87.5
Tin (Sn) 11.3 to 12.5
Nickel (Ni) 1.2 to 2.0
Phosphorus (P) 0 to 0.3
Lead (Pb) 0 to 0.25
Zinc (Zn) 0 to 0.25
Iron (Fe) 0 to 0.2
Antimony (Sb) 0 to 0.2
Sulfur (S) 0 to 0.050
Silicon (Si) 0 to 0.0050
Aluminum (Al) 0 to 0.0050

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

Followup Questions

Similar Alloys

Further Reading

ASTM B427: Standard Specification for Gear Bronze Alloy Castings

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