Tungsten carbide

       Tungsten carbide powder (WC) is the main raw material for the production of cemented carbide, chemical formula WC. The full name is Wolfram Carbide, also translated as tungsten carbide. It is a black hexagonal crystal with metallic luster and hardness similar to diamond. It is a good conductor of electricity and heat. The melting point is 2870℃, the boiling point is 6000℃, and the relative density is 15.63 (18℃). Tungsten carbide is insoluble in water, hydrochloric acid and sulfuric acid, but easily soluble in a mixed acid of nitric acid and hydrofluoric acid. Pure tungsten carbide is fragile, and if a small amount of titanium, cobalt and other metals are added, the brittleness can be reduced. Tungsten carbide used as a steel cutting tool is often added with titanium carbide, tantalum carbide or their mixture to improve the anti-knock ability. Tungsten carbide is chemically stable.



The tungsten carbide powder produced every year is mainly for domestic use, and some are exported to Japan, the United States, Germany, Italy, France, Sweden and other countries.



 

nature

 



Tungsten carbide powder is a dark gray powder, which can be dissolved in a variety of carbides, especially in titanium carbide, which has a high solubility, forming TiC-WC solid solution. Another compound of tungsten and carbon is tungsten carbide, the chemical formula is W2C, the melting point is 2860°C, the boiling point is 6000°C, and the relative density is 17.15. Its nature, preparation method and use are the same as tungsten carbide.



 

use

Tungsten carbide powder is mainly used to produce cemented carbide. In tungsten carbide, carbon atoms are embedded in the interstices of the tungsten metal lattice without destroying the original metal lattice, forming interstitial solid solutions, so it is also called interstitial (or intercalation) compound. Tungsten carbide can be made of a mixture of tungsten and carbon



It is made by heating at high temperature. The presence of hydrogen or hydrocarbons can accelerate the reaction. If the oxygen-containing compounds of tungsten are used for preparation, the product must be vacuum treated at 1500°C to remove the carbon and oxygen compounds. Tungsten carbide is suitable for mechanical processing at high temperatures, and can be used to make cutting tools, structural materials for kilns, jet engines, gas turbines, nozzles, etc.



 

Production system

Using metal tungsten powder and carbon black as raw materials, a mixture is prepared according to a certain proportion, and the mixture is placed in a graphite boat, placed in a carbon tube furnace or a high and medium frequency induction furnace, and carbonized at a certain temperature, and then Tungsten carbide powder can be obtained by ball milling and sieving.



 

Quality specification

The technical condition of tungsten carbide powder is GB/T4295-93, which generally implements the internal control standard of the enterprise, and the technical requirements of some enterprises are shown in Table 6-6-42 and Table 6-6-43.



Table 6-6-42 Quality specifications of tungsten carbide powder



 

Category Fisher average particle size (μ) Total carbon (%) Free carbon (%)



 

WC-1 ≤1.0 6.08～6.18 ≤0.08



 

WC-2 1～1.99 6.08～6.18 ≤0.08



 

WC-3 2～3.99 6.08～6.18 ≤0.08



 

WC-4 4～5.99 6.08～6.18 ≤0.08



 

WC-5 6～7.99 6.08～6.18 ≤0.08



 

WC-6 8～11.99 6.08～6.18 ≤0.08



 

WC-7 12～15.99 6.08～6.18 ≤0.08



 

WC-8 ≥16 6.08～7.18 ≤0.08



 

Table 6-6-43 Chemical composition index of tungsten carbide powder



 

Grade\Content% WC Fe Mo Al Si Ca Mn Mg Ni Na



 

FWC-1 ≥99.8 ≤0.04 ≤0.010 ≤0.001 ≤0.01 ≤0.005 ≤0.002 ≤0.002 ≤0.005 ≤0.003



 

FWC-2 ≥99.7 ≤0.06 ≤0.015 ≤0.002 ≤0.01 ≤0.008 ≤0.002 ≤0.004 ≤0.008 ≤0.005



 

Note: Customers have special requirements for the above specifications, and they can negotiate for details.



 

Package

Generally, it is sealed in inner plastic bag and packed in outer iron drum. The net weight of each drum does not exceed 50kg.



 

Inspection standards

The arbitration analysis method for the chemical composition of exported tungsten carbide powder is carried out according to GB4324-84, the Fisher average particle size is carried out according to GB3249-82, the sampling method is carried out according to GB5314-85, and the main content (WC) is calculated by the difference method. 

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