Silver Refractory

Silver Refractory Contact Materials


OVERVIEW

These contact materials are used extensively in applications where high voltages generate extensive arcing, such as circuit breakers and switchgear. The refractory component (W, WC, Mo) provides durability to the contact, while the silver provides excellent thermal and electrical conductivity. Relative to many other contact materials, silver refractory materials are highly resistive. The use of silver refractory materials typically entails high contact pressures because of the high resistance of the refractory component. When selecting these materials, consideration must be given to the increasing contact resistances that are experienced during service life. The correct selection of compositions, refractory components and particle sizes can often overcome this phenomena.

AVAILABILITY

Silver Refractory

These dual phase materials are produced exclusively through powder metallurgy techniques, primarily through unit compaction. Compositions can range from 10% to 90% silver. The low ductility of these materials entails unit compaction. Consequently, the materials tend to involve more fabrication than many other contact materials. Refractory contact materials are supplied as discrete contacts with and without brazing alloys flushed to the attachment side. They are also available as furnace, torch and resistance brazed contact assemblies. 

MATERIALS

Composition

Hardness

Density

Conductivity

(weight %)

(R'well)

(g/cc)

(IACS %)

Silver-Tungsten

ST50PSI Ag50/W50

B65

13.2

62

ST65PSI Ag35/W65

B85

14.6

50

ST75PSI Ag25/W75

B95

15.4

45

Silver-Tungsten Carbide

STC50PSI Ag50/WC50

B80

12.1

47

STC65PSI Ag35/WC65

B98

12.8

36

Silver-Molybdenum

SM50PSI Ag50/Mo50

B75

10.1

50

SM60PSI Ag40/Mo60

B82

10.1

43

SM65PSI Ag35/Mo65

B87

10.0

40



Note
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.