The majority of our saws are tipped on the automatic tipper, however there are times when we are required to pretin the carbide ourselves. We start with metal plates and layout the carbide. It is necessary to keep a margin of space around the outside edges, as the silver solder on the outside carbide tips will melt, or “puddle” sooner than ones closer to the centre. Next we put a dab of black flux on the side of the carbide tip that will be brazed to the saw, then we apply a piece of silver solder. The tips are fired in a kiln until the silver solder puddles, once cooled they are tumbled in a rock tumbler to be cleaned , they are then ready to be brazed onto a saw by hand.
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.