Ancient Steel Production
A one thousand year old steel production site has been unearthed by an International research team in the remains of the ancient city of Gyaur Kala in Turkmenistan. The excavated remains of three furnaces, probably used to produce the steel used in ancient swords and tools, suggest an advanced production process that predates the next evidence of co-fusion steel (the Huntsman Process) by more than a millennium.
Dr Dafydd Griffiths, part of the international research team from University College London, says, "These remains give a fascinating glimpse from over 1,000 years ago of a process for making crucible steel using a sophisticated furnace design. We know of no ancient metallurgical furnaces of similar design."
The crucibles stood on a pad of clay with recycled crucible fragments between pads to help distribute the centrally supplied air. The 1cm-thick crucible lids with a central hole were able to withstand temperatures of up to 1500 degrees Celsius before starting to sag. The ancient steel makers showed considerable knowledge of the steel production process and the reactions deep within the furnace itself by placing the thick-walled crucible in the hottest zone of the 80 cm furnaces. "These features all suggest a mastery over the process", according to Griffiths.
The ancient city of Gyaur Kala stood in the Merv oasis on the "Silk Road" over-land trading route between China and the West. "Merv was thus a great meeting point of knowledge and trading goods from far and wide [but] in terms of nearby natural resources, Merv had no iron ore, no refractory clay and very little fuel". The steel makers thus had to conserve use of their raw materials and recycled spent refractory crucibles and maximised energy efficiency. Griffiths says, "It is fascinating to compare ancient and modern practice and to realise that the artisans of times past can still teach us a few things that may inspire improvements in modern processing technology".
This item is due to appear as "Thermal processing in the last millennium" by Dr Dafydd Griffiths, in the August issue of Materials World, Volume 7, Issue 8, p.472.
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