How To Recycle Tungsten Carbide
How To Recycle Tungsten Carbide
Tungsten carbide (WC) is chemically a binary compound of tungsten and carbon in the stoichiometric ratio of 93.87% tungsten and 6.13% carbon. However, industrially the term usually implies cemented tungsten carbides; a sintered powdered metallurgical product consisting of very fine grains of pure tungsten carbide bound or cemented together in a cobalt matrix. The size of the tungsten carbide grains ranges from ½ to 10 microns. The cobalt content can vary from 3 to 30%, but will typically range from 5 to 14%. The grain size and cobalt content determine the application or end use of a finished product.
Cemented carbide is one of the most valuable metals, tungsten carbide products mainly be used for making cutting and forming tools, drills, abrasives, rock bits, dies, rolls, ordnance and wear surfacing materials. Tungsten carbide plays an important role in industry development. We all know that tungsten is a kind of material nonrenewable. These attributes make tungsten carbide scrap one of the best contenders for recycling.
How to recycle the tungsten from the tungsten carbide? There have three ways in China.
At present, there are mainly three kinds of cemented carbide recycling and regeneration processes commonly used in the world, it is zinc melting method, electro-dissolution method, and mechanical pulverization method.
1. Zinc melting method:
The zinc melting method is to add zinc at a temperature of 900 °C to form a zinc-cobalt alloy between cobalt and zinc in the waste cemented carbide. At a certain temperature, the zinc is removed by vacuum distillation to form a sponge-like alloy block and then crushed, batched, and ground into raw material powder. Finally, the cemented carbide products are prepared according to the conventional process. However, this method has large equipment investment, high production cost, and energy consumption, and it is difficult to completely remove zinc, resulting in unstable product quality (performance). In addition, the used dispersant zinc is harmful to the human body. There is also an environmental pollution problem using this method.
2. Dissolution method:
The electro-dissolution method is to use an appropriate leaching agent to dissolve the binder metal cobalt in the waste cemented carbide into the leaching solution under the action of an electric field and then chemically process it into cobalt powder, which will then be dissolved. The scrap alloy blocks of the binder are cleaned.
After crushing and grinding, tungsten carbide powder is obtained, and finally, a new cemented carbide product is made according to the conventional process. Although this method has the characteristics of good powder quality and low impurity content, it has the disadvantages of long process flow, complicated electrolysis equipment, and the limited processing of tungsten-cobalt waste cemented carbide with cobalt content greater than 8%.
3. Traditional mechanical crushing method:
The traditional mechanical pulverization method is a combination of manual and mechanical pulverization, and the waste cemented carbide that has been manually pulverized is put into the inner wall with a cemented carbide lining plate and a crusher equipped with large-sized cemented carbide balls. It is crushed into powder by rolling and (rolling) impact, and then wet-ground into a mixture, and finally made into cemented carbide products according to the conventional process. This kind of method is described in the article "Recycling, Regeneration, and Utilization of Waste Cemented Carbide". Although this method has the advantages of a short process and less equipment investment, it is easy to mix other impurities in the material, and the oxygen content of the mixed material is high, which has a serious impact on the quality of alloy products, and cannot meet the requirements of production standards, and has always been In addition, the crushing efficiency is extremely low, and it generally takes about 500 hours of rolling and grinding, and it is often difficult to achieve the required fineness. Therefore, the regeneration treatment method has not been popularized and applied.
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