Wootz steel
Wootz, is a
steel alloy having a pattern of bands or sheets of micro carbides within a tempered
martensite or
pearlite matrix. Developed in
India around
300 AD, (although some say as early as
200 BC). the word
wootz may have been a mistranscription of
wook, an anglicised version of
ukku, the word for steel in many south Indian languages.
Wootz can be made in crucibles, e.g.,
crucible steel by combining a mixture of
wrought iron or
iron ore and
charcoal with
glass, which is then sealed and heated in a
furnace. The result is a mixture of impurities mixed with glass as slags, and "buttons" of steel. The buttons (with a typical
carbon content of 1.5%) were separated from the
slag and forged into
ingots. The ingots could be further forged out into blades/tools or welded to other ingots to increase the mass of the steel for larger items.
Wootz steel was widely exported throughout the region, and became particularly famous in the
Middle East, where it became known as
Damascus steel. The critical characteristic of wootz steel is the abundant ultrahard metallic
carbides in the steel matrix precipitating out in bands, making wootz steel display a characteristic banding on its surface. Wootz swords were renowned for their sharpness and
toughness.
The techniques for its making died out around 1700 AD after the principal sources of special ores needed for its production were depleted. Those sources contained trace amounts of
tungsten and/or
vanadium which other sources did not. Oral tradition in India maintains that a small piece of either white or black hematite (or old wootz) had to be included in each melt, and that a minimum of these elements must be present in the steel for the proper segregation of the micro carbides to take place.
Wootz was rediscovered in the mid 19th century by the Russian metallurgist
Pavel Petrovich Anosov, who refused to reveal the secret of its manufacture other than to write five one-sentence descriptions of different ways in which it could be made. Another method of wootz production, using modern technology, was developed around 1980 by
Dr. Oleg Sherby and
Dr. Jeff Wadsworth at Stanford University and Livermore National Laboratories. Master bladesmith
Alfred Pendray and
Dr. John Verhoeven re-discovered what may be the classic techniques in the early 1980's.
J.D. Verhoeven, A.H. Pendray, and W.E. Dauksch. (1998).
The Key Role of Impurities in Ancient Damascus Steel Blades. Journal of Metals. 50(9). pp.58-64. [
1]
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The key role of impurities in ancient damascus steel blades*
Wootz steel: an advanced material of the ancient world*
Indian heritage in metallurgy
