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Iron Age tool marks move to steel
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By Paul Rincon
BBC News Online science staff
A tiny Iron Age tool found in Holland is one of the
oldest objects unearthed in Europe made from the alloy
steel.
The 6cm-long punch has a carbon content (2%) rarely seen
in iron-based objects from the region at the time.
The 4th Century AD tool, which may have been used as a
nail, was probably made using the process of furnace
smelting.
The discovery, which occurred at the site of Heeten, is
reported in the Journal of Archaeological Science by
Evelyne Godfrey and Matthijs van Nie.
"We think it is the earliest ultra-high carbon steel
from Europe," Godfrey, of the University of Bradford,
UK, told BBC News Online.
"The punch was broken in use and then it was lost. But
it was a finished, functional tool. It was no accident."
Metal lump
The very first iron production may have occurred by
chance, perhaps with iron ore rocks in a camp fire.
At some stage, humans learnt how to improve the quality
of this basic metal product by raising temperatures,
reducing impurities and controlling the content of
carbon - to make the resilient alloy known as steel
(which generally has a carbon content of less than 2%).
The origins of ultra-high carbon steel production are
traditionally thought to lie in Asia.
In India, the production of a type of cast iron known as
crucible steel can be traced to the 3rd Century BC. And
Romans were demonstrating knowledge of cast iron
manufacture by the 5th or 6th Centuries AD.
But the 4th Century AD steel punch is evidence of an
indigenous steel-making tradition in northern Europe,
the authors argue.
The authors suggest that the steel punch from Heeten was
not made using iron casting, but with the traditional
bloomery furnace smelting process used throughout Iron
Age Europe.
This involved tapping molten slag out of the side of the
bloomery furnace. In the furnace, an iron "bloom" would
form, which would then be removed.
Welsh Steel
"There is thus far no evidence for crucibles or cast
iron processing remains of the Roman Iron Age in
northern Europe that might indicate Germanic
manufacturing of ultra-high carbon steel by
decarburisation from cast iron," Evelyne Godfrey and
Dutch archaeologist Matthijs van Nie write in their
journal paper.
The punch's 2% carbon content is at the limit of what
can be produced using the furnace smelting process.
But archaeometallurgist Dr Chris Salter, of University
of Oxford, told BBC News Online the find was nothing
unusual.
Dr Salter said he had recovered an example of a 2nd
Century steel object from Carmarthen in Wales.
He added that ultra-high carbon objects are often not
identified as such when they are found, partly because
they are more subject to corrosion than unalloyed iron
ones.
During the 4th Century AD, Heeten was occupied by a
Germanic-speaking tribe known as the Salian Franks. The
Frankish tribes of Europe would later give their name to
the country of France.
Story from BBC NEWS:
Published: 2004/05/12 11:14:28 GMT
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