How to Improve the Quality of Regenerated Tungsten

In view of the shortage of raw tungsten resources, it is of great significance to reuse the waste hard alloy products and reuse it after recycling, and it is very important to make full use of the protection resources. In the United States, 35% of tungsten products are derived from recycled tungsten.

There are mainly three technologies for recycling waste cemented carbide at home and abroad, namely, mechanical crushing, zinc melting and electro dissolution. At present, the common drawback of traditional recovery methods is that the structure and particle size distribution of regenerated tungsten carbide are unstable and low purity.

In view of the shortcomings of the existing technology, a new method of recycling high quality tungsten carbide from abandoned cemented carbide has been developed. The recycling method has the following advantages: fine grain structure and high recycling efficiency. The steps include magnetic separation, crushing, decarburization, alkali dissolution, ammoniation, calcination, reduction and carburization.

Tungsten carbide particles were obtained by electric dissolving. The tungsten carbide powder was obtained by magnetic separation and crushing. Tungsten carbide powder was placed in the kiln. The temperature of the kiln was set to 1600°C, and the oxygen of 0.5atm was maintained at high temperature to get tungsten oxide particles. Then the tungsten oxide particles were soaked in a 50% concentration of sodium hydroxide solution, and the temperature of the liquid was controlled at 180°C and was stirred. The soluble tungsten ions containing sodium tungstate (Na₂WO₄) solution containing soluble tungsten ions were obtained for 6 hours, and the residual Co, Ni, Fe and other impurities were hydrated and precipitated.

Separate precipitates from alkaline solutions for subsequent treatment. In the crude sodium tungstate solution after precipitation, acid solution is added to acidification, and the pH value is adjusted to 1~6. Then, the organic phase composed of 25% P507 and 75% sulfonated kerosene is added to further separate the impurities such as molybdenum, iron, zinc, calcium, copper and magnesium to obtain the high purity sodium tungstate solution. Then remove the sodium ion in the solution: first, the pH value of sodium tungstate solution is adjusted to 2.9, then the organic relative sodium tungstate solution composed of 10%N235 and 90% kerosene is added to extract, and then the organic phase is retained. Then, the ammonia crystals of para tungstate were obtained by adding organic ammonia, evaporation and concentration.

Tungsten oxide powder was obtained by calcining method of parotungstate crystallization, and tungsten powder was reduced by reducing carbon as reducing agent. Tungsten powder was obtained by reduction of tungsten oxide powder. Finally, the tungsten powder was carburized in sealed carburized box, the temperature of carburized box was controlled at 1100°C and the carburizing time was 6 minutes, the final product of high quality tungsten carbide powder was obtained.

The final product test shows that the regenerated tungsten carbide eliminates trace pollution and trace crystal change of the inherited crystal, thus ensuring the fine grain structure and low micro inclusions of the regenerated tungsten carbide, making the regenerated tungsten carbide powder performance comparable to the original tungsten carbide produced by the mineral, and the recovery efficiency is high. 

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