Wootz steel

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Wootz is a steel characterized by a pattern of bands or sheets of micro carbides within a tempered martensite or pearlite matrix. It was developed in India around 300 BC[1]. The word wootz[2] may have been a mistranscription of wook, an anglicised version of ukku, the word for steel in Kannada, Telugu and many other southern Indian languages.

Wootz steel was widely exported throughout the region, and became particularly famous in the Middle East, where it become known as Damascus steel after being locally forged into swords. 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, especially damascus blades, were renowned for their sharpness and toughness.

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[edit] Manufacture

While other methods may be used today, it is known that wootz was classically 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.

The techniques for its making died out around 1700 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 possibly rediscovered in the mid 19th century by the Russian metallurgist Pavel Petrovich Anosov (see Bulat steel), 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.

Master bladesmith Alfred Pendray re-discovered what may be the classic techniques in the early 1980s, as later verified by Dr. John Verhoeven. [3][4]

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. Even though this steel had the charactertistic bands of microcarbides, whether or not this could be considered wootz was disputed by Verhoeven since it was not made in a classical manner.

Recently, researcher Peter Paufler from Dresden University in Germany has discovered evidence of carbon nanotubes in Wootz steel[5], although this is disputed[citation needed].


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[edit] Trivia

[edit] References

  1. ^ IISC
  2. ^ p.108 -- Michael Faraday, as quoted by Peter Day, The Philosopher's Tree ISBN 0-7503-0571-1
  3. ^ 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): 58-64. 
  4. ^ Verhoeven, J. D. (1987). "Damascus Steel. I. Indian Wootz Steel". Metallography 20 (2): 145. doi:10.1016/0026-0800(87)90026-7. 
  5. ^ Reibold, M; Paufler P, Levin AA, Kochmann W, Pätzke N, Meyer DC (November 16, 2006). "Materials: Carbon nanotubes in an ancient Damascus sabre". Nature 444 (7117): 286. Nature Publishing Group. doi:10.1038/444286a. 

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