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Carbide (also known as Widia, Cemented Carbide or Tungsten Carbide) is a material used in mechanical machining consisting of hard Tungsten Carbide particles incorporated in a metal matrix (often Cobalt). Carbide is produced thanks to the sintering process; in other words, the fine powders of the components are mixed, pressed and then heated. Therefore, the pressure is kept high, so that the powder granules come together to form a single piece. This means that hard metals are not real metals but carbides bound by a metal. About 50% of the cemented carbides are produced with Tungsten Carbide (70-95%) and Cobalt.
It looks like a dark gray powder. Its molecular formula is WC. It is a very hard material, which ranks around 9 on the Mohs scale and around 2600 on the Vickers scale. It has a density of 15.63 g / cm3 as per the metal density table, so it requires too high melting or sintering temperatures to be used pure. For practical use it is combined with transition metals such as cobalt or nickel.
It is an excellent bond for hard metal. To improve the transverse breaking strength, hardness and density of the cemented carbide, a cobalt powder with very fine particles is used.
It has a high degree of hardness; and a high resistance to pressure, deformation and high temperatures. These are very useful physical characteristics in metal cutting applications. Widia tungsten carbide allows a long life to tools which, if made with other materials, would soon wear out. For more information, see the page on the technical characteristics of hard metal.
Among the hard metal producers is Nashira Hardmetals, a company with a long experience and committed to research and development. At Nashira, we offer many different grades of carbide to meet the requirements of every project and application. Contact us for more information
Since 1999 in Nashira we have been manufacturing components and semi-finished products in hard metal.
First we buy the raw materials: carbide, tungsten and cobalt powders. Their particles can have different characteristics and a degree of purity, depending on the process by which they are obtained. The combination of tungsten carbide and cobalt allows for the creation of a highly hard and wear-resistant alloy. Then we move on to the actual production.
The production starts from the mixing of the powders. This takes place in cylindrical or double cone drums; or in screw or paddle mixers. Depending on the use for which the hardmetal is intended, a particular compound is required. For example, using 10% cobalt we obtain a hardness of about 90 HRA, suitable for making semi-finished products for companies that produce finished tools for working wood. Instead, an 8% cobalt mixture is suitable for instruments dedicated to the metal sector.
When the mix is ready, we proceed to compaction. In this phase a high pressure value is applied to the powder, to reduce the spaces between the particles and obtain the desired shape. The most common method of compaction is pressing. In this case, two opposing motion punches compress the powder contained in a mold. It is possible to produce blocks of semi-finished products in the shapes requested by the customer; or you can press the powder into molds with defined geometry. Shaping and cutting follow.
The blocks are machined by machine tools to obtain the final shape and dimensions are increased by about 20%, to compensate for the effect of the shrinkage of the material that will occur during sintering. The obtained product is called green compact; this means that the process is not yet concluded. In fact, each particle has its own surface. And the material still lacks strength and hardness.
At the end the products are subjected to the sintering process. It is a heat treatment that welds the particles into an indivisible compound: the sintered metal. Thanks to the contribution of heat, porosities are eliminated and junctions and bridges are created between the particles; therefore the total surface of the material is reduced.
Usually in sintering the temperature is equal to 1400-1500 ° C. However it must be below the melting point. It is also defined as a function of the percentage of cobalt used. As a result of the sintering, the ceramic-metallic material called cemented carbide, hard metal or widia is obtained.
There are other technologies to obtain hard metal, also called cemented carbide, sintered widia metal or carboloy.
Isostatic compaction is among the techniques used in Nashira. In this case the pressure is exerted evenly by means of a liquid. The operation can take place:
Using this technology, the internal structure of the carbide will be homogeneous. Conversely, with conventional compaction techniques, the pressure is applied uniaxially; and the structure of the final product is uneven.
Applied to hardmetal, it is a recent processing technique. Is already used in Nashira. It consists in compressing a mixture with tungsten carbide and cobalt powders with a piston, through a shape called “matrix” or “die”. The section of the matrix can also be hollow; for example it is used to make pipes or cylinders.
The dough is pushed towards the extrusion head, producing the desired shape. Upon exiting the matrix, the material is cooled. The advantage is the possibility of creating constant section profiles of indefinite length; and the only limit is given by the size of the sintering furnaces. To manage this production method, considerable know-how is required. On the other hand, it is a versatile technique. And it allows the creation of shapes and sizes that would not be possible with other technologies.
It will soon integrate traditional production lines in Nashira. It is a similar process to that used to model plastic materials. The finely pulverized metal is mixed with binder material, creating a mixture; this is then modeled and solidified by injection molding.
The process allows you to shape complex and large-volume parts in a single step. After molding, the piece is subjected to conditioning operations to remove the binder and densify the powders. Finished products are small components used in many industries and applications.
While the world consumption of cemented carbide shows limited growth, in Italy the situation is different. Here there is a sharp growth trend for the use of sintered components. Today hardmetal is indispensable in various sectors and production processes. For example, it is used in the metallurgical, mechanical, mining, aeronautical and aerospace industries.
And it is used in the medical, agricultural, textile and food sectors. It is often the best choice for making valves, rollers, cylinders, plates, pins, blades, nozzles, gears, etc. In short, any type of device, component or tool. Indeed: It is wear resistant It has a high tenacity It guarantees long life and safer processes
We have the right solution for every technical application. While the big chains compete on prices and are oriented towards mass production, we at Nashira Hard Metals differentiate ourselves by focusing on quality and innovation. We have a sector dedicated to research and development. And we are able to make special products according to customer’s requests. Among the advantages we offer: Targeted solutions Technical expertise Constant quality Safety Assistance