Wootz steel

Wootz steel 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.^[3][4]

History

According to traditional history Wootz steel originated in India before the beginning of the common era.^[5] Wootz steel was widely exported and traded throughout ancient Europe and the Arab world, and became particularly famous in the Middle East, where it became known as Damascus steel. Archaeological evidence suggests that this manufacturing process was already in existence in South India even before the Christian era.^[6][7]

Wootz steel and development of modern metallurgy

Legends of Wootz steel and Damascus swords aroused the curiosity of the European scientific community from the 17th to the 19th Century. The use of high carbon alloys were not known in Europe previously and thus the research into Wootz steel played an important role in the development of modern English, French and Russian metallurgy.^[8]

Western research

The British Occupation in the 1750s gave a fresh impetus into this research. By 1790, samples of wootz steel were received by Sir Joseph Banks, President of the British Royal society. These samples were subjected to scientific examination and analysis by several experts.^[9][10]

Manufacturing techniques

A 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.

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. ^[11][12]

Another method of wootz production, using modern technology, was developed around 1980 by Dr. Oleg Sherby and Dr. Jeff Wadsworth at Stanford University and Lawrence Livermore National Laboratory. Even though this steel had the characteristic 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 of Technology in Germany has discovered evidence of carbon nanotubes in Wootz steel^[13], although this is disputed^{[citation needed]}.

Cultural references

• An elaborate fictionalized description of Wootz steel manufacture is presented in Neal Stephenson's book The Confusion, part of Stephenson's three-volume work The Baroque Cycle.
• The manufacturing of Wootz steel is also detailed in Leo Frankowski's Conrad Stargard series.

See also

• Damascus steel
  • Bulat steel, a Russian crucible steel
  • Pattern welding
• Iron pillar of Delhi

Notes

1. ^ IISC
2. ^ p.108 -- Michael Faraday, as quoted by Peter Day, The Philosopher's Tree ISBN 0-7503-0571-1
3. ^ http://www.telegraphindia.com/1050415/asp/northeast/story_4588593.asp
4. ^ http://books.google.com/books?id=sDKBAAAAMAAJ&q=%22derived+from+kannada+word%22&dq=%22derived+from+kannada+word%22
5. ^ Srinivasan & Ranganathan
6. ^ Srinivasan 1994
7. ^ Srinivasan & Griffiths
8. ^ C. S. Smith, A History of Metallography, University Press, Chicago (1960)
9. ^ Philosophical Transactions of the Royal Society, Vol.85 (1795), ‘Experiments and Observations to investigate the Nature of a Kind of Steel, manu-factured at Bombay, and there called Wootz: with Remarks on the Properties and Composition of the different States of Iron’, by. George Pearson, M.D., F.R.S., pp.322-346
10. ^ D. Mushet: Experiments on Wootz or Indian Steel (British Museum 727. k.3), pp.650-62
11. ^ 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. http://www.tms.org/pubs/journals/JOM/9809/Verhoeven-9809.html. 
12. ^ Verhoeven, J. D. (1987). "Damascus Steel. I. Indian Wootz Steel". Metallography 20 (2): 145. doi:10.1016/0026-0800(87)90026-7. 
13. ^ Reibold, M; Paufler P, Levin AA, Kochmann W, Pätzke N, Meyer DC (November 16, 2006). "Materials: Carbon nanotubes in an ancient Damascus sabre". Nature (Nature Publishing Group) 444 (7117): 286. doi:10.1038/444286a. http://www.nature.com/nature/journal/v444/n7117/abs/444286a.html. Retrieved 2006-11-17. 

References

• Srinivasan, S. & Ranganathan, S. Wootz Steel: An Advanced Material of the Ancient World. Bangalore: Indian Institute of Science.
• Srinivasan,S. Wootz crucible steel: a newly discovered production site in South India. Institute of Archaeology, University College London, 5 (1994), pp. 49-61.
• Srinivasan, S. and Griffiths, D. South Indian wootz: evidence for high-carbon steel from crucibles from a newly identified site and preliminary comparisons with related finds. Material Issues in Art and Archaeology-V, Materials Research Society Symposium Proceedings Series Vol. 462.
• Hansson 2002, p 81 "Den skapande människan"
• urukku - from the Tamil Lexicon, University of Madras

External links

• The key role of impurities in ancient damascus steel blades
• Wootz steel: an advanced material of the ancient world
• Indian heritage in metallurgy
• Nanotubes present in Damascus Blades