Tungsten has the highest melting point (3420 °C) and the lowest vapour pressure of all metals . Tungsten is an excellent material for high-vacuum technology up to the highest temperatures. Low thermal expansion combined with its high melting point and its perfect form stability make tungsten an excellent material for glass seals. The electric resistance of tungsten is important for its use as heater material for high-temperature furnaces. Thanks to its high density tungsten has a good absorption ability for ionising radiation.
At ambient temperature, ordinary tungsten is rather brittle and therefore difficult to process. At higher temperatures (between 200 and 500 °C), however, it changes to a ductile condition. Tungsten's high temperature strength and strain depends on deformation and annealing pre-treatment may vary significantly at certain temperatures.
Since the beginning of the 20th century, PLANSEE is one of the most important producers of tungsten. Thanks to many years of experience in the production and processing PLANSEE today offers a wide range of mill and final products made of tungsten and tungsten-alloys.
Tungsten: The advantages at a glance
- high melting temperature
- low vapour pressure
- sufficiently high electrical resistance
- low thermal expansion combined with good thermal conductivity
- high E-modulus
Mechanical properties of tungsten
The mechanical properties of tungsten can be influenced by the purity of the material, the type and amount of alloying elements, heat treatment (annealing condition) and microstructure. Tungsten has a body-centred cubic lattice structure and exhibits very low ductility at room temperature.
The ductile to-brittle transition temperature can be reduced by mechanical working and alloying. Strength increases with increasing degree of deformation. Different than most other metals, working also increases the ductility. Room-temperature ductility can be improved by alloying with rhenium.
The mechanical properties, especially creep strength, can be improved significantly by the addition of small quantities of oxides of cerium or lanthanum. Various tungsten alloys are used depending on specific customer requirements and areas of application.
Chemical properties of tungsten
Tungsten and its alloys have a similar corrosion behaviour (with the exception of tungsten-copper and the high-density alloys).
Below 60 % humidity tungsten is resistant to corrosion. In damper air surface staining occurs (coloured oxides), although to a lesser extent than with molybdenum. Rough surfaces are more susceptible than smoother ones.
In certain water-based media above 100 °C (373K), a lack of resistance to attack from alkaline and oxidizing substances is to be expected. Reactions can occur in the presence of oxidizing gases and elements in other states of matter at temperatures above 250 °C (523K). Molten glass, nitrogen, inert gases, molten metals and ceramic oxides attack tungsten only very slightly, even at very high temperatures, provided they do not contain additional oxidizing agents.
Typical fields of application
Since the early 20th century PLANSEE has developed various grades of tungsten for different applications
Tungsten and its alloys are used in the lighting industry and electronics, for medical applications and thin-film technology as well as for welding electrodes and in the construction of high-temperature furnaces. Additionally tungsten is the main component of tungsten-rhenium alloys, composite materials (tungsten-copper) and for high-density heavy-metal alloys (Densimet® and Inermet®).
Pure tungsten is used only in a few application fields such as the coating industry with crucibles and sputter targets and high-temperature furnace construction with heating elements and heat shields. For special applications, tungsten with a defined residual porosity of up to 35 volume percent is also produced.
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Symbol: W
Category: Transition metals
Atomic number: 74
Melting point: 3420°C
Boiling point: 5660°C
Density: 19.3 g/cm3
Chemical element of the VIth subsidiary
group of the periodic system of the
chromium group
In nature tungsten is found in more or less the same quantities as copper (average content of tungsten in the earth's crust is aprox. 70 g/t). It has a base-centered cubic lattice and with 3420 °C the highest melting point of all metals.
The discovery of tungsten is attributed to the brothers J.J. and F. Elhuyar, two Spanish chemists, who worked in Sweden. Its common English name, tungsten (in many other languages it is known as wolfram), is derived from a Swedish word meaning "dense stone".
 More information on tungsten
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