Cemented Tungsten Carbide
Tungsten, the main component in Cemented Carbide is mined from the ground. This ore is processed chemically into what is known as Ammonium Paratungstate or APT. This is the raw material traded in “metric tonne units” or MTU on the world’s commodity markets. An MTU is a unit of measure defined as one tonne of ore concentrate containing 1 per cent of the desired product. So in essence, one ton of APT contains 10g of tungsten.
Most of the mined tungsten metal powder is converted to tungsten carbide by a reaction with pure carbon powder known as carbon black. It is combined in pusher or batch furnaces at 900-2000 deg C in a process called carburization. By melting the resulting mix of Tungsten Monocarbide (WC) with tungsten metal a eutectic
composition of WC and W2C is formed. The molten mix is poured into sheet castings and then rapidly quenched. This is a highly secretive process in which carbide manufacturer’s guard their exact process. The result of this quenching forms a very, hard material having a fine crystalline structure. After cooling this material is crushed and screened into various mesh sizes, into sub micro and nano grain sizes.
The resulting powder is mixed with a binder such as cobalt or chromium and formed into various shapes before going into a sintering furnace; the result is cemented tungsten carbide which is used by in various cutting tools for a number of industries.