The Tungsten Silver Elkonite® materials consist of a family of powder metals that range in tungsten content from 50% to 78% by weight. Tungsten has the highest strength and the highest melting temperature of the refractory metals. This is the principle factor in determining the material’s resistance to arc erosion and mechanical wear. The strength, erosion and weld resistance characteristics of the material increase with increasing tungsten content; the electrical and thermal characteristics decrease. In selecting a material composition for a given application, you should select the highest refractory content that will provide a satisfactory temperature rise and current interruption.
|Material||Composition % by Weight||Density gr/cc||Density lb/in3||Rockwell Hardness||Thermal Conductivity||Electrical Conductivity||Cross Breaking Strength|
|Note: “typical” values listed – Not Material Specifications||www.resistanceweldsupplies.com|
|Fine Silver||Pure Silver||10.49||0.379||30 F||245 Btu / hr.ft.F||104% IACS||38,000 psi|
|Elkonite® 50S||50W / 50Ag||13.48||0.487||55 B||190 Btu / hr.ft.F||65% IACS||80,000 psi|
|Elkonite® 45S||55W / 45Ag||14.01||0.506||65 B||185 Btu / hr.ft.F||62% IACS||100,000 psi|
|Elkonite® 40S||60W / 40Ag||14.28||0.516||70 B||180 Btu / hr.ft.F||58% IACS||110,000 psi|
|Elkonite® 35S||65W / 35Ag||14.77||0.534||82 B||170 Btu / hr.ft.F||55% IACS||120,000 psi|
|Elkonite® 30S||70W / 30Ag||15.28||0.552||85 B||165 Btu / hr.ft.F||50% IACS||125,000 psi|
|Elkonite® 20S||78W / 22Ag||15.56||0.562||95 B||160 Btu / hr.ft.F||49% IACS||130,000 psi|
Tungsten Silver Materials
These are infiltrated materials with strong sintered structure. They provide the greatest strength and excellent erosion characteristics for a given weight percentage of refractory metal. The Tungsten Silver Elkonite® materials consist of a family of powder metals that range in tungsten content from 50% to 78% by weight and are used in many electric applications from contacts to circuit breakers to medium duty switching devises.
Elkonite® 20S has a high refractory content and normally the greatest resistance to arc erosion. It is generally used for arcing contacts in large air and oil circuit breakers, line disconnects, reclosures, and in high current switches and contactors. Contact resistance is low enough to protect the higher conductivity current carrying contacts from arc damage. Its resistance to welding makes it a good shorting contact for bimetal protection in circuit breakers.
Elkonite® 30S and 35S have more silver which provides higher conductivity and a lower contact resistance. They are used extensively in a large variety of circuit breakers. In this application, a single pair of contacts provides the dual function of carrying the current without overheating, and interrupting the current without excessive arc erosion. They are also used in high current contactors where resistance to contact welding and arc erosion are required. In a variety of DC applications, they offer resistance to metal transfer.
Elkonite® 40S, 45S, and 50S contain still higher contents of silver and are used where higher conductivity and low contact resistance are needed. In some breakers, one pole tends to have greater erosion. In these cases Elkonite® 35S or 40S can be used on this pole and operated against Elkonite® 50S. Elkonite® 50S has the highest silver content of these materials. It exhibits good resistance to contact welding and is used for current carrying contacts in power circuit breakers that encounter high momentary currents.