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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 incandescent 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 and is the
heaviest element known to be
used by living organisms.
Pure tungsten
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. Of all metals in
pure form, tungsten has the
highest melting point
(3,422 Deg C, 6,192 °F),
lowest vapour pressure and
(at temperatures above
1,650 °C, 3,002 °F) the
highest tensile strength.
Tungsten has the lowest
coefficient of thermal
expansion of any pure metal.
The low thermal expansion
and high melting point and
strength of tungsten are due
to strong covalent bonds
formed between tungsten
atoms by the 5d electrons.
Alloying small quantities of
tungsten with steel greatly
increases its toughness.
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AS PER THE NATIONAL
& INTERNATIONAL
STANDARD &
SPECIFICATIONS
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