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Silver Tungsten & Silver Tungsten Carbide Contacts

Silver Tungsten
The silver and tungsten composite group combines the high thermal and electrical conductivity of silver with the high erosion resistance of the high melting tungsten. These materials are also characterized by their high strength and their resistance to welding or sticking. They are principally made by infiltration and the nominal silver content varies from 20-50%. By increasing the amount of tungsten, the hardness and welding is reduced. This composite group of alloys is specially preferred for use in air.

On account of their excellent properties, silver tungsten materials have found a wide field of applications. They are used successfully with high tungsten content as burn-off contacts for large low-voltage circuit breakers and with lower contents as contacts carrying a steady line current for moulded case circuit breakers and in various protective circuit breakers. These contacts are also used in high current contactors where resistance to contact welding and arc erosion are required.

Silver Tungsten Carbide
The silver and tungsten carbide composites exhibit initial resistance to formation of surface films and possess good antiweld and arc erosion resistance. These are specially used for devices requiring more consistent millivolt drop as compare to silver tungsten.

Modison manufacture these composites by powder metallurgy. Pressed parts are sintered and infiltered by silver in liquid phase.

TYPICAL PROPERTIES

MATERIAL NOMINAL COMPOSITION	DENSITY g/cm³	HARDNESS HV10	ELECTRICAL CONDUCTIVITY
			%I.A.C.S	m/mm²

SILVER TUNGSTEN
W Ag 20	16.1 – 16.5	180 – 240	31 – 39	18 – 23
W Ag 25	15.1 – 15.9	170 – 220	32 – 43	19 – 25
W Ag 30	15.0 – 15.4	160 – 200	34 – 44	20 – 26
W Ag 35	14.5 – 14.9	150 – 190	38 – 46	22 – 27
W Ag 40	14.0 – 14.4	140 – 170	41 – 50	24 – 29
W Ag 50	13.2 – 13.6	120 – 150	45 – 55	26 - 32

SILVER TUNGSTEN CARBIDE
WC Ag 35	13.0 – 13.4	160 – 200	34 – 43	20 – 25
WC Ag 50	12.2 – 12.6	140 – 180	38 – 46	22 – 27
WC Ag 60	11.6 – 12.1	120 – 160	41 – 52	24 - 30

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