d. Several processes exist for the conversion of iron to steel. The four most
common are the electric arc furnace, Bessemer converter, open-hearth furnace, and
basic oxygen furnace.
NOTE: Regardless of the steel process used, the steel manufacturing operation
involves four basic steps: producing the steel and pouring ingot; stripping
and soaking the ingot; rolling the ingot into blooms, billets, or slabs;
rolling a finished or semifinished product.
(1) Electric arc furnaces account for only a minute part of the steel produced
worldwide, but they produce the finest quality steel.
These furnaces are
relatively small facilities that have a minimum of imagery components, making it
hard to identify them from photography. Major recognition features of electric arc
furnace include:
Scrap steel pile
Transformer yard which supplies electric power
Vents or monitors on the building housing the furnace
Possibly a dust catcher.
(2) Bessemer converters are the oldest of the steel processes still in use.
Steel is produced quickly but is of a low quality.
Many of the phosphoric
impurities cannot be removed so the steel retains some brittleness.
(a) The Bessemer converter is a large, open-mouthed vessel pivoted on
trunnions (Figure 2-64).
Air ducts or pipes enter the converter through the
trunnions.
To charge the converter, it is tilted forward, and molten iron is
poured in.
The vessel is then returned to the vertical position, and a high
pressure stream of air is pumped through the air ducts and forced up through the
mass of molten iron.
As the air passes through the hot metal, carbon and other
impurities are burned off, creating a cloud of smoke and sparks that vent from the
open mouth of the converter vessel. The smoke and sparks escape through an opening
on the roof. The converter is often housed in the same building as the open-hearth
furnace or in a smaller, similar structure.
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