One Step Reduction Method of Ultrafine Tungsten Carbide Powder
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- Category: Tungsten Information
- Published on Sunday, 07 January 2018 17:57
Ultrafine cemented carbide is a tool material developed in recent years, mainly based on ultrafine WC powder and adding appropriate binder and grain growth inhibitor to produce high hardness, high wear resistance and high toughness cemented carbide materials.
The preparation methods of WC powder are divided into two main categories: reduction carbonization two step method and reduction carbonization one step method. At present, in the industrial production, ultrafine tungsten carbide powder is produced by high temperature carbonization after the reduction carbonization one step is mixed with superfine tungsten powder and carbon powder precursor. However, because the ultrafine tungsten powder has large surface area and strong surface activity, it has a slight contact with air, that is, the phenomenon of oxidative spontaneous combustion affects the quality of products and causes the loss of materials.
Some scholars have proposed a preparation method of ultrafine tungsten carbide powder, with ultrafine tungsten powder and carbon black as raw materials. The following steps are as follows:
(1) Passivation of Ultrafine Tungsten Powder
The pure carbon dioxide gas is added into the ultrafine tungsten powder for more than 12 hours, which makes the surface of ultrafine tungsten powder passivating to reduce the surface activity of tungsten powder.
(2) Charcoal
The passivated Fisher particle size is 0.4 m, the specific surface area of 5m2/g, 300 ~ 500kg ultrafine tungsten powder loaded with carbon machine, adding carbon powder and additives, the cooling water is cooled, and the inert gas is protected. After mixing for 3~5 hours, the cooling water is naturally cooled for 10~14 hours. The additive can be a hard alloy grain growth inhibitor, such as chromium, vanadium and so on.
(3) Carbonization
The mixed ultrafine tungsten powder and carbon powder were mixed into the boat of the corresponding production specification. The molybdenum wire carbonization furnace at high temperature was reacted at 1000~1400 degree high temperature, and tungsten powder and carbon powder were made into lump tungsten carbide powder.
(4) Crushing and Sieving
The bulk tungsten carbide powder was crushed into a crusher for 2~4 hours, and then cooled by natural gas, then ultrafine tungsten carbide powder was obtained through 100~140 mesh stainless steel screen, and packaged into inert gas.
This method reduces the oxidation and spontaneous combustion reaction of the precursor, and the ultrafine tungsten carbide powder prepared is not easy to spontaneous combustion and low oxygen content. It has the advantages of more stable and better quality than the conventional one-step process.
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