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What is tungsten?

1High melting point

High melting point

With the highest melting point among metals, tungsten has a low thermal expansion coefficient and exceptional shape stability, even in extremely high-temperature environments.

2Large electric resistance

Large electric resistance

With their relatively high electrical resistance, our tungsten rods are designed for use in various discharge electrodes, offering enhanced discharge performance and improved resistance to discharge consumption.

3High hardness

High hardness

Although tungsten is a metal with high hardness, its hardness is further enhanced when combined with carbon, making it an ideal material 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, making it suitable for heaters and reflectors in furnaces exceeding 2000℃. It also forms a hard alloy when mixed with carbon, and cemented carbide combined with cobalt is used for high-grade cutting tools. Furthermore, tungsten, which has an extremely low environmental impact, provides very high radiation shielding capability compared to lead, making it widely used as a radiation shielding material in medical fields such as X-ray CT. While tungsten may not seem familiar in our daily lives, it is closely related to us through its industrial and medical applications.

Physical properties of tungsten
Atomic number  *1 74
Element symbol W
Density
(Mg/m3*2
293K 19.3
Melting point(K)*2 3653
Boiling point(K)*2 5800
Electrical Resistance
(10-8Ωm)*2
293K 5.4
Specific heat
(J/kgK)*2
273-373K 138
Thermal conductivity(W/mK)*2 273-373K 174
Coefficient of Linear Expansion
(10-6/K)*2
273-373K
293-2273K
4.5
5.4
Work function
(eV)*2
4.5
Thermal neutron capture cross section area
(barns/atom)*3
19.2±1.0
*1 Standard Atomic Weights (2017), The Chemical Society of Japan
*2 Fourth Edition of Metal Data Book, The Japan Institute of Metals and Materials
*3 Materials and techniques for electron Tubes,Walter H.Kohl (1960)

Chemical properties

  • Tungsten is stable at room temperature but oxidizes to the extent that surface gloss is lost. It mainly reacts with O₂, CO₂, N₂, H₂O, and hydrocarbons at high temperatures, but does not react with mercury vapor or hydrogen.
  • When reacting with oxygen or air, it forms elevated oxide (WO₃) through lower oxides such as W₃O, WO₂, or W₂₀O₅₈ as the temperature increases.
  • Water does not corrode tungsten, 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 exhibits reducing properties under extremely high temperatures. When heated at very high temperatures with sulfur, it forms the compound (WS₂), and it produces the compound (W₃P₄) when phosphorus vapor is present.
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