Aluminum is the newest of the major metals in casting today.
Aluminum is the world’s third most abundant element after oxygen and silicon.
It makes up about 8.3% by weight of the Earths solid surface. Aluminum metal is
very reactive so native specimens are rare. It is found combined in over 270
different minerals. The major ore used in the production of primary aluminum is
bauxite.
The process for extracting aluminum was very complex and
expensive until in 1886 when Oberlin College student Charles Hall and French
engineer Paul Heroult separately and simultaneously developed a relatively
inexpensive electrolysis process by which aluminum is extracted from aluminum
oxide. Prior to that aluminum was considered a precious metal. During the reign
of Napoleon III (1852 to 1870) privileged guests at state dinners were served
on aluminum plates while less privileged guests were served on plates made of
gold and silver. When the Washington Monument was capped with a 100 ounce
aluminum casting in 1884, the cost was today’s equivalent of $300 per ounce or
$4,800 per pound. The 6-1/4” pound casting was the largest ever produced at
that time.
In 1919 the
Smithsonian Institute reported that 80 tons of aluminum was produced in 1889
and that grew to 80,000 tons in 1917. The major use of the increased production
was in the manufacture of aircraft and dirigibles. The development of low cost
electricity production, especially hydro-electric, drove the cost of producing
primary aluminum down to more reasonable levels. Production of primary aluminum
in 2013 was 4.527 million metric tons.
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