How to Recycle Tungsten Carbide Tools

Tungsten carbide is also known as tungsten alloy, cemented carbide, hard alloy, and hard metal. Tungsten carbide tools have been increasingly popular in the modern industry since the 1920s. With the environment, recycling of the tungsten carbide products emerges which can induce cost and wasted energy. There can be a physical method or a chemical method. The physical method usually is to break down the scrapped tungsten carbide tools into pieces, which is hard to realize and costs a lot because of the great hardness of tungsten carbide tools. So, recycling tungsten carbide cutting tools are usually realized in chemical methods. And three chemical methods will be introduced---zinc recovery, electrolytic recovery, and extraction by oxidation.

Zinc Recovery

Zinc is a kind of chemical element with the atomic number 30, which has melting points of 419.5℃ and boiling points of 907℃. In the process of zinc recovery, tungsten carbide cutting tools are put into the molten zinc under an environment of 650 to 800℃ first. This process happens with inert gas in an electrical furnace. After the zinc recovery, the zinc will be distilled under a temperature of 700 to 950℃. As a result of the zinc recovery, the reclaimed powder is nearly the same as the virgin powder in proportion.

Electrolytic Recovery

In this process, the cobalt binder can be dissolved by electrolyzing the scrap of the tungsten carbide cutting tools to recover the tungsten carbide. By the electrolytic recovery, there will be no contamination in the reclaimed tungsten carbide.

Extraction by Oxidation

1. Tungsten carbide scrap should be digested by fusion with oxidizing agents to get the sodium tungsten;

2. Sodium tungsten can be treated with water and experience filtration and precipitation to remove impurities to get purified sodium tungsten;

3. Purified sodium tungsten can be reacted with a reagent, which can be dissolved in an organic solvent, to get the tungsten species;

4. Add aqueous ammonia solution and then re-extract, we can get the ammonium poly-tungstate solution;

5. It is easy to get the ammonium para-tungstate crystal by evaporating the ammonium poly-tungstate solution;

6. Ammonium para-tungstate can be calcined and then reduced by hydrogen to get the tungsten metal;

7. After carburizing the tungsten metal, we can get the tungsten carbide, which can be manufactured into different tungsten carbide products.

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