Thanks for your answer David.
I must precise that, in my case, even if we are in the 14th century, there
is no doubt that the forge is a direct process bloomery due to his location
in the Pyrennées, where the indirect process is not installed at this
period. Moreover, slags are typical of bloomery process.
I have to re-read you work .... but can you precise what to you mean by
"high Mn in metal" (how much ppm ?). Is that indicated in your paper of
Norberg ?
-----Message d'origine-----
De : Arch-Metals Group [mailto:[log in to unmask]] De la part de
David Starley
Envoyé : lundi 16 mai 2005 10:05
À : [log in to unmask]
Objet : Re: Manganese in bloomery process
Phillipe,
Manganese was one of the elements I used when trying to determine smelting
technology from the metallic and inclusion composition of Europen Armour -
seeing how particular elements partitioned between the two phases. Bodsworth
and Bell (1992 Physical chemistry of iron and steel manufacture) had
suggested that, all other factors being equal a rise from 1327 to 1525 oC in
the smelting temperature would increase the manganese recovery 11-fold.
Unfortunately, many of my samples had too little Mn in the metal to allow
these partition coefficients to be reliably determined. However, I was
struck by the extent to which material we believed to have originated in
Germany from about 1500 onwards had high Mn in metal contents generally, and
relative to their inclusions. From metallographically we also knew that this
was steel of good quality.
One of the suggestions to come out of these results was that this
(specialist?) source was using a process that ran hotter and under more
reducing conditions that most bloomeries - quite possibly the stuckofen,
which had a reputation for being able to produce steely blooms.
Of course with the intro of the blast furnace/finery process things start
getting complicated at this period.....
If you're working with earlier material so much the better.
David Starley PhD
Science Officer
Royal Armouries Museum
Conservation Department
Armouries Drive
Leeds LS10 1LT
United Kingdom
Tel. 0044 (0)113 220 1919
Fax 0044 (0)113 220 1917
-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
dillmann
Sent: 15 May 2005 10:31
To: [log in to unmask]
Subject: Manganese in bloomery process
Dear all,
For several month, I'm analysing ferrous artefacts coming from direct
process and that are made from an ore containing high levels of Manganese (a
14th c. forge in the French Pyrenees). The slag inclusions contain up to
30mass% of MnO and Mn is not detectable in the metal (<100ppm). Indeed, the
metal is highly carburised (over eutectoid).
Several authors talk about the carburising role of Mn and, indeed, several
historical zones of producing steel were associated with high Mn ores
(Italian alps, Pyrenees...)
Nevertheless, I have several questions about the exact metallurgical role of
this element in the carburising process during bloomery operating chain.
Indeed, in the thermodynamic conditions of the shaft furnace, the MnO oxide
can not be reduced into metallic Mn. Thus, this element can not play a role
in the metal. Moreover, even if this element were in the iron, it seems that
the influence of Mn on the diffusion coefficient of carbon is not proved.
So, I ask the questions: does anyone study the exact role of manganese on
the carburisation of iron in the direct process. Does Mn play a role indeed?
Can you help me?
Best regards
Philippe Dillmann
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