The Direct Reduction Carbonization Method to Prepare Ultra-Fine WC Powder

Tungsten carbide (WC) is the main raw material for the production of cemented alloy. The main production method is one-step method and two-step method. At present, the main method for producing WC powder is two-step method: Firstly reducing the tungsten oxide to tungsten powder with hydrogen. Then, tungsten powder is carbonized to form WC powder at a high temperature. In the production practice, the method is not suitable for producing ultrafine WC powder.

Considering the shortcomings of the two-step method, some scholars have proposed a direct reduction carbonization method to prepare ultra-fine WC powder. The main process of this method is as follows:

1) Preparation: Take a certain amount of tungsten oxide or tungsten oxide and cobalt oxide, the purity of which is 99%, and react with tungsten oxide to form carbonization theoretical carbon content of tungsten or tungsten carbide-metal cobalt is 70-125% with a carbon source. After ball milling for 2 hours, the mixture is loaded into a graphite boat. Among them, tungsten oxide is blue tungsten or purple tungsten, and cobalt is Cobalt tetraoxide, the carbon source is graphite powder

2) In-furnace reaction: Push the graphite boat containing the mixture into a high-temperature molybdenum wire tube furnace of 900～1850°C or a single-tube push boat high-temperature furnace, and react under a hydrogen or argon reducing atmosphere to 0.5~6 hour;

3) Outlet detection: the reactants are cooled in the furnace cooling zone for 0.5 to 1 hour, and the 80 mesh sieve is removed to remove some mechanical impurities, and the total carbon, free carbon and oxygen content thereof are detected, wherein the total carbon should be 6.12~ 6.25% by weight, free carbon should be between 0.1 and 0.2% by weight, and the oxygen content is less than or equal to 0.25% by weight;

4) Adjustment: When the produced product is WC powder and the test result does not meet the requirements, the product should be fine-tuned with carbon or tungsten oxide. When the product is tungsten carbide-metal cobalt powder, it is necessary to fine-tune. The alloying process requires a cobalt content of cobalt or an alloy of tungsten required for the alloying process, or an oxide of the cobalt to be reduced to be the amount of carbon required for the metal cobalt and the reduced tungsten oxide to be tungsten carbide. The adjusted material is further ball milled for 0.5 to 2 hours, and further reacted for 0.5 to 6 hours in a high temperature molybdenum wire tube furnace at 900 to 1850 ° C under gas protection. After cooling, ball milling and sieving, ultrafine WC is obtained.

The above method has the advantages of short process flow, good product quality, simple equipment and high efficiency, low power consumption, water consumption and low hydrogen consumption, and can be used for producing 1 μm, 0.8 μm, 0.6 μm, 0.4 μm, 0.2 μm, 0.1 μm or even Finer powder, suitable for large-scale production of ultra-fine WC powder.

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