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Tungsten characteristics

What is tungsten?

1High melting point

High melting point

With the highest melting point among metals, tungsten has low thermal expansion coefficient and extremely high shape stability even under a super high temperature environment.

2Large electric resistance

Large electric resistance

For its relatively large electric resistance, we offer tungsten rods for various discharge electrodes, which have improved discharge property and discharge consumption resistance.

3High hardness

High hardness

Although tungsten is a metal with high hardness, its hardness is enhanced by combining it with carbon; it is used for high-grade cutting tools.

Tungsten, meaning “heavy stone” in Swedish, is a very hard and heavy silver gray rare metal. With the highest melting point among metals, tungsten has a relatively large electric resistance as a metal, so it is used for heaters and reflectors and the like in furnaces exceeding 2000℃.

It also becomes a hard alloy when mixed with carbon, etc. Cemented carbide combined with cobalt is used for high-grade cutting tools.

In addition, tungsten, with extremely low environmental impact, has a very high radiation shielding capability compared to lead; it is also widely used as radiation shielding material in medical field such as X-ray CT.

Tungsten does not seem familiar to us in our daily life, but it is closely related to our lives for its industrial and medical uses.

Physical properties of tungsten
Atomic number 74
Density
(Mg/cm3
293K 19.26
Melting point(K) 3683
Boiling point(K) 5930
Vapor pressure(Pa) 2000K 2・10-10
Resistivity
(10-8Ωm)
300K 5.65
Specific heat
(J/kg・K)
273K~373K 138
Thermal conductivity(W/m・K) 300K 174
Linear expansion coefficient
(10-6/K)
293
293~2000K
4.5
5.2
Work function
(eV)
Single crystal
polycrystal
5.2
4.5
Thermal neutron capture cross section area
(10-28m2
300K 18.4

Chemical properties

  • Tungsten is stable at room temperature but oxidizes to the extent that surface gloss is lost. It reacts mainly with O2, CO2, N2, H2O and hydrocarbon at high temperature, but not with mercury vapor and hydrogen.
  • When reacting with oxygen or air, it produces elevated oxide (WO3) via lower oxides such as W3O, WO2, or W20O58 as the temperature rises.
  • Water does not corrode it, but vapor in the red heat state does, producing WO3.
  • It reacts vigorously and dissolves in a mixed solution of nitric acid and hydrofluoric acid.
  • It has reducing properties under extremely hot temperature. When heated at very high temperature with sulfur, it produces the compound (WS2); it produces the compound (W3P4) when phosphorus vapor is applied.
Tungsten: Reaction with gases
Substance Temperature Reaction
Air   Room
temperature
No reaction
400℃ Oxidation starts
700℃ Produces WO3 and rapidly oxidizes
Oxygen Room
temperature
No reaction
530℃ Produces WO3 even at low pressure
Vapor

≧700℃

Oxidation progresses rapidly
Nitrogen   No reaction up to  2,000℃
  Three stages of absorption up to 1,700°C
Carbon
monoxide
≧1,000℃ Produces W2C4
Carbon
dioxide
1,200℃ Oxidizes
Hydrocarbon 1,200℃ Produces carbides
2,430℃ Carbide decomposes
Dry chlorine 250℃ Produces 6 chloride
Fluorine Room
temperature
Produces sublimable fluoride
Bromine Red heat Produces bromide
Iodine Red heat Produces bromide
Hydrogen  

No reaction
Very small amount of absorption at ≦1,200°C

Hydrogen
sulfide
Red heat Surface reaction occurs
Sulfur
dioxide
≧700℃ Oxide formation
Tungsten: Reaction with liquids/dissolved salt
Substance Temperature Reaction
Water Room
temperature
No reaction
Hot liquid No reaction
Mercury   No reaction
Hydrochloric acid Room
temperature
No reaction for dilute/concentrated
Hot liquid A little corrodes
Dilute sulfuric acid Room
temperature
Doesn't corrode
Hot liquid Slightly corrodes
Concentrated
sulfuric acid
Room
temperature
Slightly corrodes
Hot liquid Gradually corrodes
Sulfuric acid Hot liquid Slightly corrodes
Hydrofluoric acid Hot liquid No reaction for dilute/concentrated

Sulfuric acid

+hydrofluoric acid
Hot liquid Rapidly corrodes
Aqua regia Hot liquid Slightly dissolves producing oxide film
Sodium
hydroxide
Room
temperature
Doesn't corrode
Dissolved
state
Rapidly corrodes
  Accelerated in air by oxidation
Sodium nitrite about 500℃ Melts while violently generating heat
Ammonium
hydroxide
  Not corrode
Liquid ammonia   Not corrode
Tungsten : Reaction with solids
Substance Temperature Reaction
Carbon, graphite 850 to 1,410℃ Absorbs carbon
1,410 to 1,600℃ Produces carbides
Magnesia up to 1,500℃ Stable
Zirconia up to 1,600℃ Stable
Thoria 2,200℃ Reduces thoria slightly
Alumina up to 1,900℃ Stable
Beryllia up to 2,200℃ Stable