Quality

Tungsten is a very hard metal with following physical properties:

• High melting and boiling point – highest of all the metals
• Excellent resistance to wear and tear
• Excellent resistance to welding , sticking and material transfer
• High electrical conductivity

Due to above properties, it is primarily used in applications which require high-frequency switching like automotive ignition system and horn contacts. On air-exposure, Tungsten Contacts form oxide layer, the thickness of which may reach up to 50Å (1Å = 1x10-10 meter). By use of high contact force, most of the oxide layers are broken, and current flow (electron tunneling) takes place with tungsten contacts and the device starts functioning. Force of 0.500 kgf or more is common for devices using tungsten contacts. During arcing, as in the case of other composite contact materials, the tungsten will be oxidized under the heat of arc.

Tungsten contacts are very popular for high frequency switching operations, like 100-500 cycles/second. It has low electrical erosion, but is not good for carrying high currents for long periods in the closed position. High heating in the current constriction area can leads to oxide build-up and without mechanical wiping movement of the contacts, high resistance can result with device overheating and/or device failure. Current range of 1 to 5 Ampere is common. Tungsten for contact application is generally made by powder metallurgical process.