Silver-Carbon

Silver-Carbon Contact Materials


OVERVIEW

Silver-carbon (graphite) contact materials are used currently in a diverse range of applications. Use of silver-carbon in rheostatic devices is primarily due to the self-lubricating properties of these materials. In addition, the material is used in circuit breaker and switching applications due to its very good anti-welding properties and its relatively stable contact resistance. The carbon content can be varied from .5% to 8% of the contact mass. The resistance to sticking increases as the carbon content increases. The disadvantages of silver-carbon are its relatively high erosion rates, poor arc mobility, its limited ductility and its relatively high cost.

AVAILABILITY

The materials have limited ductility but may be fabricated in strip and wire form when lower concentrations of carbon are specified. From this strip and wire, rivet contacts, discrete contacts, including 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. 

MATERIALS

Composition

Hardness

Density

Conductivity

(weight %)

(R'well)

(g/cc)

(IACS %)

Silver-Carbon

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



Note
The asterisk (*) indicates the fully annealed condition. The compositions listed are generally considered the industry standards. The values listed above represent the typical average properties of the materials. Modifications to meet special applications may be possible.