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Construction
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Operation
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electric arc furnace
eafh.com
An electric arc furnace is a system that heats charged material by means of an
electric arc. Arc furnaces range in size from small units of approximately one
ton capacity used in foundries for producing cast iron products, up to about 400
ton units used for secondary steelmaking. Arc furnaces used in research
laboratories and by dentists may have a capacity of only a few dozen grams.
Temperatures inside an electric arc furnace can rise to approximately 1,800
degrees Celsius.
History
The first electric arc furnaces were developed by Paul Héroult of France, with a
commercial plant established in the United States in 1907. Initially "electric
steel" was a specialty product for such uses as machine tools and spring steel.
Arc furnaces were also used to prepare calcium carbide for use in carbide lamps.
In the 19th century, a number of men had employed an electric arc to melt iron.
Sir Humphry Davy conducted an experimental demonstration in 1810; welding was
investigated by Pepys in 1815; Pinchon attempted to create an electrothermic
furnace in 1853; and, in 1878 - 79, Sir William Siemens took out patents for
electric furnaces of the arc type. The Stessano electric furnace is an arc type
furnace that usually rotates to mix the bath. The Girod furnace is similar to
the Héroult furnace.
Different from the arc type of electrothermic furnace is the induction type
furnace. The Kjellin furnace and the Röchling-Rodenhauser furnace are two. The
Grönwall furnace produced steel at Trollhattan, in Scandinavia.
While EAFs were widely used in World War II for production of alloy steels, it
was only afterwards that electric steelmaking began to expand. The low capital
cost for a mini-mill - around US$140-200 per ton of annual installed capacity,
compared with US$1,000 for an integrated steel mill - allowed mills to be
quickly set up in war-ravaged Europe, and also allowed them to successfully
compete with the big United States steelmakers, such as Bethlehem Steel and U.S.
Steel, for low-cost, carbon steel 'long products' (structural steel, rod and
bar, wire and fasteners) in the U.S. market. When Nucor decided to enter the
long products market in 1969, they chose to start up a mini-mill, with an EAF as
its steelmaking furnace, soon followed by other manufacturers. Whilst Nucor
expanded rapidly up and down the Eastern U.S., the companies that followed them
into mini-mill operations concentrated on local markets for long products, where
the use of an EAF allowed the plants to be flexible with production, according
to local demand. This pattern was also followed in countries around the world,
with EAF steel production primarily used for long products, while integrated
mills, using blast furnaces and basic oxygen furnaces, cornered the markets for
flat products - sheet steel and plate. In 1987, Nucor made the decision to
expand into the flat products market, still using the EAF production route. The
fact that an EAF uses scrap steel as feedstock, instead of raw iron, has
impacted on the quality of the flat product made from EAF steel, because of the
limited amount of control over the impurities that are contained within the
scrap.
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