Cemented Carbide Processing Facts

Cemented carbide is an extremely hard and durable metal that's used for everything from industrial applications to men's jewelry. A combination of the extremely hard metal tungsten and carbide mixed together with another metal binding agent, tungsten carbide can a hardness of up to 9.5 on the Moh's scale (not very far below diamond, which is the hardest on the scale). Cemented carbide is also chemically inert, and will not rust or react with other chemicals. Naturally a steel gray color and coming in a powdered form, tungsten carbide can be molded and shaped through extreme heat and pressure into a variety of shapes and forms.

The process for making cemented carbide is simple. Equal parts powdered tungsten and carbon are mixed together along with a metallic binder. The most common binders currently in use are cobalt and nickel. The mixture is compacted into a shape, and it's then heated to above the melting point of the binder. The cemented carbide, which is powdered, is then surrounded by the molten binder. As the slurry dries, the binder holds the cemented carbide in a matrix that's extremely hard and durable. Technically cemented carbide that uses a bonding agent is a composite metal, but it's rarely an issue.

Production process
1) Raw material
Sheelite or wolframite is the tungsten containing mineral. Ammonium-Para Tungsten is the beginning raw material of our production. The “Wet “process is the first step involving a sequence of dissolutions, precipitations and separations.?? ????????
2) Reduction
After a hot reduction of the APT in hydrogen we obtain pure tungsten powder (W). By varying the reduction process the grain size of the tungsten power can be controlled within ca.1-20um
3) Carburization
Tungsten and carbon is mixed in the proper proportions. The mixture is heated at a high temperature in hydrogen under formation of tungsten carbide powder (WC)
4) Weighing-in of the ingredients
Different WC powder and binder Cobalt (Co) powder are looked as the raw material for the manufacturing of cemented carbide. After weighing-in of WC, Co and other additives to prescribed composition and cemented carbide grade, the mixture is wet milled.
5) Milling
The milling has effect on both carbide grain and homogeneity of the slurry. The milling procedure is important for achieving homogeneous cemented carbide after sintering. ????
6) Spray-drying
After milling the slurry must be dried, for example, by spray-drying to powder form. This “Ready-To-Press“(RTP) powder consists of spheric agglomerates of the constituents.
7) Blending test
The pressing properties and the composition of the RTP-powder are important for the following process. The size and shape of the RTP-powder are measured. Furthermore the powder must have good flow behaviors in order to uniformly fill the cavities of a press tool.
8) Compaction
The production of cemented carbide starts to press RTP-powder into compacts. Different methods of compaction RTP-powder:
-Uniaxial die pressing: gives high reproducibility in shape, relatively high fixed and low variable costs.
-Cold isostatic pressing(CIP): For products with shapes unsuited for uniaxial pressing, low fixed and high variable costs.
-Extrusion: For cemented carbide rods: high fixed and low variable costs.
9) Soft Machining
In some cases the compacts are soft machined or green shaped into a proper shape prior to sintering
10) Sintering
The sintering is the final process step in which the cemented carbide get its properties as a high strength engineering material. The sintering process is performed at such high temperature so the molten binder could combine with the WC. The sintering could be done with or without high isostatic gas pressure (HIP)
11) Machining
After the sintering the compact has undergone shrinkage of ca.50 volume-%. Some CC-blanks are ready for dispatch after sintering. Most blanks are machined by different means, for example, EDM, turning, drilling, grinding, to make finished tool.
12) Quality Control
A quality control is performed of the cemented carbide pieces before shipment: dimension, shape and physical properties are checked before approval of the cemented carbide parts.