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For filament in electric heaters.
(Gr. molybdos, lead) Before Scheele recognized molybdenite as a distinct ore of a new
element in 1778, it was confused with graphite and lead ore. The metal was prepared as an
impure form in 1782 by Hjelm. Molybdenum does not occur native, but is obtained
principally from molybdenite. Wulfenite, and Powellite are also minor commercial ores.
Molybdenum is also recovered as a by-product of copper and tungsten mining operations.
The metal is prepared from the powder made by the hydrogen reduction of purified molybdic
trioxide or ammonium molybdate.
The metal is silvery white, very hard, but is softer and more ductile than tungsten. It
has a high elastic modulus, and only tungsten and tantalum, of the more readily available
metals, have higher melting points. It is a valuable alloying agent, as it contributes to
the hardenability and toughness of quenched and tempered steels. It also improves the
strength of steel at high temperatures.
It is used in certain nickel-based alloys, such as the "Hastelloys(R)" which
are heat-resistant and corrosion-resistant to chemical solutions. Molybdenum oxidizes at
elevated temperatures. The metal has found recent application as electrodes for
electrically heated glass furnaces and foreheaths. The metal is also used in nuclear
energy applications and for missile and aircraft parts. Molybdenum is valuable as a
catalyst in the refining of petroleum. It has found applications as a filament material in
electronic and electrical applications. Molybdenum is an essential trace element in plant
nutrition. Some lands are barren for lack of this element in the soil. Molybdenum sulfide
is useful as a lubricant, especially at high temperatures where oils would decompose.
Almost all ultra-high strength steels with minimum yield points up to 300,000 psi(lb/in.2) contain molybdenum in
amounts from 0.25 to 8%.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.