Tungsten carbideis 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 add 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.

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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
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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
  8. Calculate chemical data

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. [1]

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:

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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

Chemical reaction:

2W + C = W₂C
W + C = WC

The tungsten oxide WO₃ hydrotreated was reduced to prepare tungsten powder (average particle size 3 to 5μm). The tungsten powder is then pressing the mixture of the carbon black (mixed with a ball mill drying by a ball mill), and press molding at a pressure of around 1T / cm². The pressurized molded block is placed in a graphite disc or a crucible, and the graphite resistance furnace or the induction electric furnace is heated to 1400 to 1700℃ (preferably 1550 to 1650) with a graphite resistance furnace or induction electric furnace (pure hydrogen using a dew point of -35℃) (preferably 1550 to 1650)℃) so that the carbon is carburized to form a WC.

The reaction begins around tungsten particles because W₂C is generated in the initial stage of the reaction, since the reaction is not complete (mainly low in reaction temperature), except for unreacted W and intermediate product W₂C in addition to the WC. Therefore, it must be heated to the above high temperature. The highest temperature should be determined according to the size of the raw material tungs. If the average particle size is between 150μm, the reaction is carried out at a high temperature of 1550 to 1650℃.

Chemical reaction:

WO₃ + 3H₂ → W + 3H₂O
2WO₃ + 3C → 2W + 3CO₂
2W + C = W₂C
W + C = WC

The carbon tungsten carbide WC particle size is used according to the hard alloy of different purposes, using different particle size tungsten carbide; hard alloy cutter, such as cutting machine blade V-CUT knives, finishing alloy adopts superfine Dine particle tungsten carbide; coarse processing alloy adopts medium-granulated tungsten carbide; alloys in gravity cutting and heavy cutting of coarse particles do raw materials; mine tool rock hardness high impact load is large with crude particulate tungsten carbide; rock impact small impact load Small, using medium particulate tungsten carbide to do raw material wear parts; the Lord.

Tungsten carbide theory contains 6.128% (50% atom), and free carbonization (Wc + C) occurs in tungsten carbon tungsten carbon, and free carbon is sintered when carbonized carbon content is greater than the theoretical amount of carbon. The tungsten grain grew up, causing the hard alloy crystal grains uneven; tungsten carbonized carbon high (≥6.07%) free carbon (≤0.05%), the total carbon is determined in the production process and scope of use of cemented carbide.

Under normal circumstances, paraffin process vacuum sintered tungsten carbon tungsten carbon mainly decided that the compound oxygen content in the sintered front block contains a part of oxygen to increase by 0.75 parts of carbon, Tc total carbon = 6.13% + oxygen content% × 0.75 (assuming sinter In the furnace, the neutral atmosphere is actually the carbonized carbon tungsten carbon tungsten carbon tungsten carbon tungsten carbon carbon carbon carbon carbon atmosphere is less than the calculated value). China’s total carbon content is generally divided into three paraffinic process vacuum sintered with tungsten carbon tungsten carbon, about 6.18±0.03% (free carbon will increase) paraffin process hydrogen sintering tungsten carbonate total carbon content is 6.13 ± 0.03 % Rubber process hydrogen sintering Tungsten carbide total carbon = 5.90±0.03% The above process sometimes cross-proceeds, thus determining total carbon carbon tungsten carbon according to specific situations.

Different use ranges, different cobalt content, total carbon of WC used in different grain size alloys can do some small adjustments. Low cobalt alloy can be used for tungsten carbide of total carbon, and high cobalt alloy can be used for tungsten carbide with low carbon. In summary, the specific use requirements of the carbide use different requirements for tungsten tungsten tungsten particles.

Application field

  • Used as a tungsten carbide end mill, a tungsten carbide woodworking spiral cutter head, a high-speed cutting vehicle, a kiln structural material, a jet engine component, a metal-ceramic material, a resistance heating element, and the like.
  • For use in the manufacture of a cutting tool, a wear-resistant component, copper, cobalt, and a molten crucible, a wear semiconductor film.
  • Used as ultra-hard tool materials, wear-resistant materials. It can form solid solutions with many carbides. WC-TiC-Co hard alloy tool has been widely used. It can also be used as modified additives for NBC-C and TAC-C ternary systems, which can reduce sintering temperatures, and maintain excellent performance, and can be used as aerospace materials.
  • Tungsten carbide (WC) powder is synthesized with tungsten anhydride (WO₃) and graphite at a high temperature of 1400 to 1600°C in a reduced atmosphere. The dense ceramic article can be obtained by thermostat sintering or thermostatic sintering.
UKO's CNC Coated End Mill

Precautions

Health hazard: tungsten dust can cause bronchial periharmonitis, fine branch tracheitis, latching fine bronchitis and atrophic emblem. Tungsten carbide can cause hyperplasia reactions in lung lymphoid cells and gradually crash. The vessel wall thickened and uniform. In the work, the person who contacted tungsten carbide dust, the gastrointestinal dysfunction, the kidney was stimulated, and the upper respiratory tract appeared. The highest allowance concentration of tungsten carbide is 6mg/m³. The highest allowable concentration of 1mg/m³ in the US soluble tungsten compound (according to the tungsten meter), an insoluble tungsten compound (according to the tungsten meter) is 5mg /m³.

UKO's Coated Indexable Inserts

Safety: Use a gas mask, dust uniform, gloves, glasses that meet the requirements. Dust leakage should be prevented at all stages of production. Workers must do physical examination before employment, check once a year. When there is obvious symptom of the upper respiratory tract, it is temporarily mobilized, detached from tungsten contact. When the pulmonary hardening or external respiratory is disordered, it should be lowered.

Storage and transportation

Storage: Storage in a cool, dry warehouse, pay attention to the packaging container in the transportation, rain and anti-Japanese light exposure.

Packaging Storage and Transportation: The product uses a iron barrel (plastic bucket), the lined polyethylene plastic bag sealing package, the net weight of each bag must not exceed 50kg. There should be “moisture-proof” and “up” and other words on the outer packaging bucket. The product should be stored in a cool, dry warehouse, pay attention to the packaging container in the transportation, rain and anti-Japanese light exposure.

Safety information

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Security terminology

S22 Do not inhale dust.
S24 / 25 AVOID Contact with Skin and Eyes.

Risk terminology

R23 is inhaled toxic.

  • Calculation reference value (XLOGP): NO
  • Hydrogen bond donor quantity: 0
  • The number of hydrogen bond receptors: 1
  • Can rotate chemical bonds: 0
  • The number of tautomers: no
  • Topological molecular polar surface area: 0
  • Heavy momentum quantum: 2
  • Surface charge: 0
  • Complexity: 10
  • Isotope atom: 0
  • Determine the number of atomic integers: 0
  • Uncertain Atomic Center Number: 0
  • Determine the number of chemical key structure: 0
  • Uncertain chemical key structure center quantity: 0
  • Number of covalent keys: 1