Production Method of Tungsten Carbide Powder from Recycled Powder

Tungsten carbide (WC) is an important raw material for the production of cemented carbide. The preparation processes of tungsten carbide are various, and the preparation of tungsten carbide powder from tungsten powder is the most widely used method.

For the recycled tungsten powder, it is obtained by ball milling of the porous tungsten foam by acid-dissolving or electrochemically dissolving the waste tungsten-based alloy. It has large particle size, small specific surface area, and poor chemical activity; when the WC powder is prepared by the carbonization method, it 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 production requirements of cemented carbide.

In order to overcome the problems encountered in the carbonization of regenerated tungsten powder, some scholars have provided a method for preparing tungsten carbide powder suitable for the production of cemented carbide by using recycled tungsten powder as a raw material. The technical aspects of its adoption include the following two main steps:

1) Primary carbonization:

The regenerated tungsten powder having a purity greater than 99% and the carbon black having a purity greater than 99% are compounded according to the weight ratio of carbon black: tungsten powder = 3 to 3.5: 100, and then mixed in a ball mill. Until the material is not stratified, and then carbonized in a graphite carbon tube furnace, the carbonization temperature is 1800-2000 ° C, the carbonization time is controlled to 50-80 minutes by controlling the pushing speed, and the primary carbonized material is obtained;

2) Secondary carbonization:

After ball milling and sieving the primary carbonized material, the carbon content is analyzed, and then adds the carbon black material according to the carbon content requirement of the final tungsten carbide product. Then, the mixture is mixed in a ball mill until the material is not stratified, and then carbonized in a graphite carbon tube furnace, the carbonization temperature is 1500-1700 ° C, and the carbonization time is controlled to 60-90 minutes by controlling the pushing speed. The secondary carbonized product is ball milled and sieved to obtain a final tungsten carbide product.

The advantages of the above process are as follows:

1) By primary carbonization with high temperature, low carbon content and ball milling of carbonized products, a primary carbonized material with high chemical reactivity and easy carbonization is obtained;

2) A high temperature of 1800-2000 ° C is used in primary carbonization, which accelerates the carbonization reaction rate, promotes the decomposition of tungsten sub-carbide (W₂C), and makes the obtained primary carbonized product more susceptible to fragmentation. Finally, high-quality tungsten carbide powder with stable performance and qualified carbon content is obtained, and its performance is close to that of the original tungsten product.

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