ASTM B631 Class B Silver-Tungsten Electrical Contact Alloy
ASTM B631 class B is a precious metal alloy formulated for use in electrical contacts.
The properties of ASTM B631 class B include three common variations. This page shows summary ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare ASTM B631 class B to: precious metal electrical contact alloys (top), all alloys in the same category (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
210 GPa 30 x 106 psi
Poisson's Ratio
0.31
Rockwell B Hardness
53 to 85
Shear Modulus
78 to 79 GPa 11 x 106 psi
Thermal Properties
Latent Heat of Fusion
150 J/g
Melting Completion (Liquidus)
2460 to 2480 °C 4470 to 4500 °F
Specific Heat Capacity
170 J/kg-K 0.040 to 0.041 BTU/lb-°F
Thermal Conductivity
450 W/m-K 260 BTU/h-ft-°F
Thermal Expansion
12 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
50 to 53 % IACS
Electrical Conductivity: Equal Weight (Specific)
32 to 34 % IACS
Otherwise Unclassified Properties
Density
14 g/cm3 880 lb/ft3
Embodied Carbon
49 kg CO2/kg material
Embodied Energy
760 MJ/kg 330 x 103 BTU/lb
Common Calculations
Stiffness to Weight: Axial
8.1 points
Stiffness to Weight: Bending
14 points
Thermal Diffusivity
190 mm2/s
Followup Questions
Further Reading
ASTM B631: Standard Specification for Silver-Tungsten Electrical Contact Materials
Tungsten: Properties, Chemistry, Technology of the Element, Alloys, and Chemical Compounds, Erik Lassner and Wolf-Dieter Schubert, 1999