Secondary Carbonization Method to Produce Tungsten Carbide

Tungsten carbide is an important raw material for the production of cemented carbide. The preparation technology of tungsten carbide is various, and the preparation of tungsten carbide powder from tungsten powder is the most widely used one.

The tungsten powder from which tungsten carbide is usually produced is generally a original tungsten powder. For the regenerated tungsten powder, the regenerated tungsten powder obtained by ball milling after the porous tungsten-based alloy obtained by acid-dissolving or electrochemically dissolving has the problem of large particle size, small specific surface area and poor chemical activity. When the tungsten carbide powder is prepared by the above carbonization method, the tungsten carbide powder obtained by the primary carbonization has problems of low carbon content, high free carbon content, and incomplete carbonization, and the obtained tungsten carbide has unstable performance and cannot directly satisfy the requirements of cemented carbide. However, it is said that there are processes in China that can use regenerated tungsten powder for the production of tungsten carbide, and the index is close to the original tungsten powder.

The preparation process is as follows:

1) Primary carbonization

5 kg of regenerated tungsten powder with a particle size of 10 μm and a purity of 99.5% is weighed, and 0.160 kg of carbon black having a purity of more than 99% was ball-milled in a ball mill. After fully mixing, the mixture is transferred into a graphite boat and slowly pushed into a high temperature zone of a graphite carbon tube furnace of Φ120 mm×1200 mm for carbonization. The carbonization temperature of the high temperature zone of the graphite carbon tube furnace is controlled to 1850 ° C, and the time of staying in the high temperature zone of the boat is controlled to be 50 min. After the end of primary carbonization, the boat was slowly pushed out of the high temperature zone of the graphite carbon tube furnace. After it was slowly cooled, the primary carbonized material is obtained, and the carbon content is 3.0%.

2) Secondary carbonization

Then, 0.165 kg of carbon black with a purity of more than 99% and a primary carbonized material, then the mixture is ball-milled in a ball mill, and the mixture is uniformly mixed and then subjected to carbonization for secondary carbonization. The carbonization temperature of the high temperature zone of the graphite carbon tube furnace is controlled to 1550 ° C, and the time of the boat staying in the high temperature zone is controlled to be 70 min. After the second carbonization, the boat is slowly pushed out of the high temperature zone of the graphite carbon tube furnace. After it is slowly cooled, the tungsten carbide material is obtained. After further ball milling and sieving, the final tungsten carbide powder product is obtained, and the carbonaceous product is sampled and analyzed. The content of carbon is 6.0%.

The advantages of the secondary carbonization method are as follows:

The regenerated tungsten powder with large particle size and poor chemical activity is once carbonized to form a three-layer structure in which the outer layer is WC, the intermediate layer is W₂C, and the inner layer is W. Therefore, a material with a finer particle size and a larger surface area is obtained, and finally a qualified tungsten carbide powder having stable performance and a satisfactory carbon content is obtained.

• < Prev
• Next >