Ken Barraclough's book, Steelmaking before Bessemer (1985) remains the best
historical work on this subject. The raw material was bar iron, but this
needed to be particularly free of impurities. For this reason, the raw
material was usually oregrounds iron from a region north of Stockholm. This
was made by the Walloon forge process, the same one that was invariably used
in Britain (and America) in the 18th century. Accordingly your comment
about decarburising and recarburising is correct.
One inch by 2.5 inches is about a size that was commonly used in the 18th
century. If other conditions are right, there is no reason why the people
at Williamsburg should not have succeeded. However I presume there was some
reason why the furnaces were built in a particular way, and I suspect that a
common brick kiln is of a somewhat simpler construction.
It is apparent from Barraclough's book that steel burners, were able to work
out how far the carburisation process had gone by withdrawing a bar from the
coffin; this may have been by looking at the fracture. However this is
beyond me.
Peter King
-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
James Brothers
Sent: 19 November 2005 02:52
To: Peter King
Subject: Cementation
The blacksmiths at Colonial Williamsburg have taken advantage of a
brick kiln to run some cementation experiments. They have put
sandstone coffins filled with powdered charcoal and bar iron into the
brick kiln and left them in for the burn. They have gotten some
results that are not what I understand is the norm for cementation.
It is my understanding, from reading, that the reason the British
used cementation, rather than fining pig to steel (which was done in
Europe for a while and continued to be done in Germany), was that it
was much easier to control. Thus the British took pig iron and
decarburized in through fining and then recarburized in in the
cememtation furnace. The sources I remember reading, stated that
cementation resulted in a maximum of about 1.5%C. And that regardless
of how long you left bar iron in a cementation furnace that the
penetration of C was not very deep. I am looking at a 1/2" bar of
cast iron. At least the fracture sure looks like cast iron. The
people at Williamsburg told me that they have 1x2.5" bars that appear
to have almost completely carburized. It does produce a good spark
with flint. They do not have a means to test the carbon content.
anyone want to volunteer?
|