Category: THE FORGING OF STEEL
Although it is possible to work steels cold, to an extent
depending upon their ductility, and although such operations are
commonly performed, forging usually means working heated steel.
Heating is therefore a vital part of the process.
Heating should be done slowly in a soaking heat. A soft lazy
flame with excess carbon is necessary to avoid burning the corners
of the bar or billet, and heavily scaling the surface. If the
temperature is not raised slowly, the outer part of the metal may
be at welding heat while the inner part is several hundred degrees
colder and comparatively hard and brittle.
The above refers to muffle furnaces. If the heating is done in
a small blacksmith's forge, the fire should be kept clean, and
remade at intervals of about two hours. Ashes and cinders should
be cleaned from the center down to the tuyere and oily waste and
wood used to start a new fire. As this kindles a layer of coke
from the old fire is put on top, and another layer of green coal
(screened and dampened blacksmiths' coal) as a cover. When the
green coal on top has been coked the fire is ready for use. As
the fuel burns out in the center, the coke forming around the edge
is pushed inward, and its place taken by more green coal. Thus the
fire is made up of three parts; the center where coke is burning
and the iron heating; a zone where coke is forming, and the outside
bank of green coal.
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