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.
| Cu | 84.2 to 87.5 | |
| Sn | 11.3 to 12.5 | |
| Ni | 1.2 to 2.0 | |
| P | 0 to 0.3 | |
| Pb | 0 to 0.25 | |
| Zn | 0 to 0.25 | |
| Fe | 0 to 0.2 | |
| Sb | 0 to 0.2 | |
| S | 0 to 0.050 | |
| Si | 0 to 0.0050 | |
| 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