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Contact Materials

Silver Carbon
Silver carbon (graphite) contact materials are used in a diverse range of applications.

Rheostatic devices, for instance, often use silver carbon primarily for its self-lubricating properties. Silver carbon is also used in circuit breaker and switching applications due to its excellent anti-welding properties and its relatively stable contact resistance. The carbon content can be varied from 0.5% to 8.0% of the contact mass. As carbon content increases, the resistance to sticking will improve, although conductivity will decease slightly. The disadvantages of silver carbon are its relatively high erosion rates, poor arc mobility, its limited ductility, and its relatively high cost.


Although silver carbon has limited ductility, it may be fabricated in strip and wire form when lower concentrations of carbon are specified. From this strip and wire, rivet contacts, discrete contacts, laminated products, and various contact assemblies can be produced. When more than 1% carbon is required, unit compaction processes are employed. Silver carbon contact materials are typically supplied with a silver rich surface on the face which will be attached to the contact support. Discrete contacts can be supplied with or without a solder alloy on the attachment surface. Resistance welded and brazed assemblies are available as well. 

The asterisks (*) in this table represent the fully annealed condition. The compositions listed are generally considered the industry standards. The listed values represent the typical properties of these materials. Modifications to meet special applications may be possible.

Composition Hardness Density Conductivity
(weight %) (R'well) (g/cc) (IACS %)
WSG.5 Ag99.5/C.5 15T 40* 10.2 95
WSG1 Ag99/C1 15T 35* 10 90
SG1 Ag99/C1 15T 32* 9.8 88
SG3 Ag97/C3 15T 27* 9.2 75
SG5PSR Ag95/C5 15T 22* 8.6 60
SG7PSR Ag93/C7 15T 15* 8.1 55

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