Thursday, May 7, 2009
Tungsten (pronounced /ˈtʌŋstən/), also known as wolfram (/ˈwʊlfrəm/), is a chemical element with the chemical symbol W and atomic number 74.
A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite. It is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon.Tungsten is often brittle and hard to work in its raw state; however, if pure, it can be cut with a hacksaw.The pure form is used mainly in electrical applications, but its many compounds and alloys are used in many applications, most notably in light bulb filaments, X-ray tubes (as both the filament and target), and superalloys. Tungsten is also the only metal from the third transition series that is known to occur in biomolecules.
In its raw form, tungsten is a steel-gray metal that is often brittle and hard to work. But, if pure, it can be worked easily. It is worked by forging, drawing, extruding, or sintering. Of all metals in pure form, tungsten has the highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure and (at temperatures above 1,650 °C) the highest tensile strength.Tungsten has the lowest coefficient of thermal expansion of any pure metal. Alloying small quantities of tungsten with steel greatly increases its toughness.