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RESISTANCE WELDING
A group of welding processes where joining of metal is accomplished by the heat produced from the resistance of the article to the flow of electrical current in a circuit of which the article is a part. This occurs when pressure is directed at the electrodes where the electrical circuit is initiated and concluded.
ELECTRICAL CONTACT MATERIALS
Neither copper nor silver will alloy appreciably with Molybdenum or Tungsten, but through a tightly controlled powder metallurgy process, Sherbrooke produces a homogeneous bi-metal for electrical contact use. These bi-metals afford the user superior chemical, mechanical and electrical properties.In addition, the high electrical and thermal conductivity of the silver or copper along with the arc-resistant and non-welding properties of Molybdenum or Tungsten, provide the customer with a wide range of bi-metals to best suit their needs. Because these bi-metals withstand the effects of the arcing incident to the interruption of large current they are often used for circuit breakers, relays, switches and heavy duty contractors. Sherbrooke Metals is a primary manufacturer of copper & silver tungsten discs, bars, rings, rods with special shapes available. We are a stocking distributor of tungsten & molybdenum rod & plate. We also offering access to Copper-Tungsten Carbide material.
Elkonite® is a trademark of Sherbrooke Metals Corporation.This family of unique composite materials consists of
Tungsten combined with Silver or Copper. They are excellent electrical contact materials for heavy duty switching applications. The high melting temperatures and high strengths of the refractory give them a high resistance to arc erosion, welding, mechanical wear and deformation. The high conductivity metals provide good electrical and thermal conduction and a low contact resistance. Because they have these unique properties,these Elkonite® materials are also used in many other applications. Some applications are: resistance welding, electrical discharge machining, electrochemical machining and semi-conductor bases. Special applications where their density, expansion, or strength is important characteristics include structural and inertial materials
The Elkonite® family consists of the following materials:
TUNGSTEN-SILVER
TUNGSTEN CARBIDE-SILVER
MOLYBDENUM-SILVER
TUNGSTEN-COPPER
TUNGSTEN CARBIDE-COPPER
The refractory metals are insoluble in silver and copper. They do not form alloys and cannot be made by the usual melting and casting methods. Instead they are made by powder metallurgy techniques. Elkonite® is made using the press-sinter-infiltration procedure whereby refractory powders are pressed and sintered to form strong bodies with a pre-determined amount of porosity. The pores are then filled with molten silver or copper to form essentially fully dense bodies. There is usually an excess of silver or copper on one of the surfaces which in most cases is removed by machining. With the press-sinter-infiltrate process, the refractory content of the materials can range from about 35% to 90% by weight. The materials made by the press-sinter-infiltration process normally have the greatest resistance to arc erosion. They are used for almost all of the larger switchgear contacts as well as for some of the lighter duty applications
Elkonite® materials are used for electrodes in electrical discharge machining (EDM) and electrochemical machining (ECM). The spark erosion resistance and good electron emission characteristics of Elkonites® make them good electron EDM electrode materials. They have excellent wear resistance, good metal removal rates and the ability to retain good detail. They are particularly good for machining tungsten carbides as other electrode materials may be inadequate. Elkonite® 3W3 is used where speed and wear resistance is important. Elkonites® 10W3 and 20S are especially outstanding on applications requiring high precision cutting and high quality surface finishes. Elkonite® 10W3 is used for ECM electrodes because it conducts high current and resists deformation and abrasion from high velocity movement of the electrolyte.
Elkonite® 20S has a high refractory content and normally the greatest resistance to arc erosion. It is generally used as 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® 35S has 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® 50S contains still higher contents of silver and is used where higher conductivity and low contact resistance is needed. In some breakers one pole tends to have greater erosion. In these cases Elkonite® 35S 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.
Manufacturer of copper & silver tungsten, refactory composites produced under strict processing guidelines using the powder metallurgy techniques of pressing, sintering & infiltrating with copper or silver. Decimals are plus 0.015 in., minus 0.000 in. for copper & silver tungsten. Distributor of molybdenum tungsten. All tungsten offered in special tolerances, odd sizes, rings & special flat forms shaped to meet specifications. Distributor of standard round bars, flat plates, & discs (inserts) also cut & tinned to meet specifications. Machinable high density tungsten alloys can be quoted upon request.
Product Information
Manufacturer of a wide range of contacts including welding rods, wire & electrodes & a variety of tungsten rods & tungsten alloys including heat treated copper alloy tungsten, silver alloy tungsten & special shaped tungsten. Standard tungsten density, hardness & electric conductivities vary & custom specifications can be met. Decimals are plus 0.015 in., minus 0.000 in. for copper & silver tungsten. Special tolerances, odd sizes, special flat forms shaped to meet specifications. Machinable high density tungsten alloys can be quoted upon request.
| Materials Accepted |
|---|
| Metal |
| 1 | Alloys |
| 2 | Silver |
| 3 | Steel |
| 4 | Tungsten |