Characteristics and Benefits of Real Wrought Iron
Definition of Real Wrought Iron;
A two component metal consisting of high
purity iron and iron silicate -an inert, non-rusting glass like slag. These
two materials are merely mixed and not chemically joined as in an alloy.
Slag amount from 1% to 3% in the form of small fibers up to 200,00 per
inch of cross section. (1)
Hand Process
One or two workmen would take a bloom
of pig iron from a blast furnace to a reverberatory furnace and constantly
stir the 100 to 500 pound spongy lump to reduce the carbon, slag,
and impurities. At some point it would then be hammered to bring slag to
acceptable level. Because of the large amount of highly skilled labor required
to produce it, wrought iron was replaced in the late 1800's by steel which
could be produced much cheaper and faster.
Factory process
Started in 1930, pig iron is purified
in a Bessemer converter, poured into a processing machine with an exact
amount of iron silicate slag, and mixed. Then the 6000 pound bloom
is put in a large press to eject surplus slag and weld particles into a
uniform mass. This process was the result of many studies on the qualities
of wrought iron and steel. In 1905, about 15 years after the general use
of steel, a group of American farmers appealed to the Department of Agriculture
to investigate the cause of "fence wire corrosion". The conclusions
from the Dept. of Ag. were in part, "The modern Bessemer, or open hearth
steel rusts more rapidly than iron wire, and manganese, especially if it
is unevenly distributed in the steel, is at least in part the cause
of the trouble." (1)
Qualities of Real Wrought Iron
Principal Virtues of Wrought Iron-
Are its ability
to resist corrosion and fatigue failure. The slag fibers in wrought iron
are present in such great numbers that they serve in one capacity as an
effective mechanical barrier against corrosion and, under most conditions,
force it to spread over the surface of the metal rather than pit or penetrate.
Any film or layer of corrosion on the surface, although microscopic in
thickness in many cases, affords a high degree of protection to the underlying
metal in much the same way that a scab protects a wound. (1)
Real wrought iron has long been regarded
as the traditional material worked by the blacksmith, and its replacement
by mild steel is still a matter of regret amongst older craftsmen. Two
of the qualities possessed by wrought iron are its ability to be drawn
out - "ductility", and its ability to be hammered into shapes - "malleability".
It is these special characteristics which make wrought iron eminently suitable
for decorative iron work, for which it is still preferred by many blacksmiths.
The texture of wrought iron improves with careful forging and it can be
worked and welded into the most intricate, delicate, and graceful shapes
with greater ease than mild steel. (2)
Real Wrought
Iron Company - For more information on real wrought iron availability,
use, and restoration.
1- "Wrought Iron - Its Manufacture, Characteristics, and
Applications" by James Aston and Edward Story of The A. M. Byers
Company, 1936
2- "The Blacksmiths Craft" - Rural Development Commission,
U. K.
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Last updated October 22, 2001