Frequently asked questions.

Frequently asked questions.

What is tungsten carbide?

Tungsten carbide is a compound composed of tungsten and carbon, the molecular formula is Wc, and the molecular weight is 195.85, tungsten carbide is a black hexagonal crystal, with metal gloss, hardness is similar to diamond, for electricity, and hot conductors. Tungsten carbide is insoluble in water, hydrochloric acid, and sulfuric acid, soluble in mixed acids of nitric acid-hydrofluoric acid. Pure tungsten carbide is fragile, if a small amount of titanium, cobalt is incorporated, it can reduce brittleness.

Tungsten carbide used as steel cutting tools often adds titanium carbide, tantalum carbide, or mixtures thereof to improve explosion resistance. The chemical properties of tungsten carbide are stable. Tungsten carbide powder is applied to cemented carbide production materials.

Name Chemical formula Molecular weight CAS number EINECS number Melting point MDL number
Tungsten Carbide WC 195.85 12070-12-1 235-123-0 2870℃ MFCD00011464
Boiling point Water solubility Density Appearance Security description Resistivity
6000℃ no 15.63g/cm³ Black hexagonal crystal with metallic luster S22,S24/25 19.2×10-6Ω·cm

Content

  1. Brief history
  2. Physical and chemical properties
    ▪ Physical properties
    ▪ Chemical properties
  3. Production method
  4. Application field
  5. Precautions
  6. Storage and transportation
  7. Safety information
    ▪ Safe terminology
    ▪ Risk terminology

Brief history

Since 1893, German scientists have removed tungsten carbide by using tridete and carbon to heat to high temperatures and attempt to use their high melting point, high hardness and other characteristics to substitute a diamond material. . However, industrial applications have been unable to obtain industrial applications due to the criticism of tungsten carbide, easy to crack and toughness.

In the 1920s, German scientist Karl Schroter found that pure tungsten carbide can not be adapted to the fierce stress changes formed during the draw, only the low melting point metal is added to the WC to make the blank without reducing the hardness. Has a certain toughness. Schroter first proposed a method of powder metallurgy in 1923, to mix tungsten carbide and a small amount of ferrous metal (iron, nickel, cobalt), then press molding and sintering over hydrogen at a temperature above 1300 ° C, Sintering. Patent.

Physical and chemical properties

Physical nature

Microhardness Elastic Modulus Compressive strength Thermal expansion coefficient
17 300 MPa 710GPa 56MP 6.9×10-6/K

 

Crystallize the black hexagonal crystal system. Soluble in alfluenzaic acid and hydrofluoric acid mixed with hydrofluoric acid, insoluble in cold water.

Gray with metal glossy powder. It belongs to the hexafang crystal system. Very hard, the elasticity is also large (72700kg / mm2).
Tungsten carbide powder particle size:

Chemical nature

The air is activated and oxidized, and the antioxidant capacity is weak.
Strong acid resistance.
Chemical Reaction: W + C = WC Note: Reaction at 1150°C.
It is less than 400°C without chlorine; at room temperature to be fiercely reacted with fluorine; oxidized into tungsten oxide when heated in air.

Tungsten carbide molecular formula

Production method

The metal tungsten and carbon are raw materials, and the average particle diameter of 3 to 5 μm is dry mixed with a carbon black ball mill, after sufficiently mixing, press molding and placed in graphite disc, then in graphite resistance furnace Or heating from 1400 to 1700℃ in the induction electric furnace, preferably 1550 to 1650℃.

In the hydrogen stream, W₂C was initially formed and continued to react at high temperatures to generate WC. Alternatively, hexacarbonyl tungsten is first decomposed in 650 to 1000℃, and the tungsten powder is thermally decomposed in the CO atmosphere, and then the WC is obtained from the carbon monoxide at 1150℃, and the temperature is higher than the temperature. W₂C.

Tungsten carbide metallographic