Tungsten, also known as wolfram, is a chemical element with the chemical symbol W and atomic number 74.
It has highest melting point of all elements except carbon - sources in scientific literature vary between 3387°C and 3422°C. It also has also excellent high temperature mechanical properties and the lowest expansion coefficient of all metals. A temperature of about 5700°C is needed to bring tungsten to boil - which corresponds approximately to the temperature of the sun’s surface. With a density of 19.25 g/cm3, tungsten is also among the heaviest metals. Its electrical conductivity at 0°C is about 28% of that of silver which itself has the highest conductivity of all metals.
Main Tungsten Properties
|
Atomic Number |
74 |
Atomic Weight |
183.86 |
Maximum Density @ 20°C (68°F) |
19.3 g/cc; 0.697 lb/cu.in. |
Melting Point |
3410°C (6170°F) |
Linear Coefficient of Expansion |
4.3 x 10E-6°C |
Thermal Conductivity @ 20°C |
0.40 cal/cm/°C/sec |
Specific Heat @ 20°C |
0.032 cal/g/°C |
Electrical Conductivity |
31% IACS |
Tensile Strength @ Room Temp. |
100,000 - 500,000 psi |
Tensile Strength @ 500°C (932°F) |
75,000 - 194,000 psi |
Tensile Strength @ 1000°C (1832°F) |
50,000 - 75,000 psi |
Poisson's Ratio |
0.284 |
Hardness (Mineral) |
7.5 |
Hardness (Vickers) |
3430 |
Hardness (Brinell) |
2570 |
Uses
Tungsten and its alloys are used extensively for filaments for electric lamps, electron and television tubes, and for metal evaporation work; for electrical contact points for automobile distributors; X-ray targets; windings and heating elements for electrical furnaces; and for numerous spacecraft and high-temperature applications. High-speed tool steels, Hastelloy(R), Stellite(R), and many other alloys contain tungsten. Tungsten carbide is of great importance to the metal-working, mining, and petroleum industries. Calcium and magnesium tungstates are widely used in fluorescent lighting; other salts of tungsten are used in the chemical and tanning industries. Tungsten disulfide is a dry, high-temperature lubricant, stable to 500C. Tungsten bronzes and other tungsten compounds are used in paints.
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