The folks at Williamsburg said that each coffin (both historic and
theirs) had an "access port" that was plugged with clay. This allowed
for bars to be withdrawn to check the level of carburization. They
also recognized that a brick kiln was not the same as a cementation
furnace, but wanted to see what would happen. The bar that I have was
snapped clean, with very little deformation of the bar (it is still
essentially straight). The break looks like the multifaceted breaks I
have seen associated with cast iron. They said that the cross section
of the larger bars is somewhat different. There is an area in the
center that does not have the multifaceted surface. but again the
majority of the bar appears to be carburized.
One of the smiths made the comment that they had managed to convert a
perfectly good piece of bar iron into a useless bar of cast iron. It
does not forge. The original bar iron was from a demolished bridge.
Unfortunately, and not surprizingly, none of the libraries in my area
have Barraclough.
On Nov 19, 2005, at 6:24, Peter King wrote:
> 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?
>
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