Wootz steel

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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 BCE^[1]. 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 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. 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.^{[dubious — see talk page]} Master bladesmith Alfred Pendray and Dr. John Verhoeven re-discovered what may be the classic techniques in the early 1980s^[2].

Recently, reasercher Peter Paufler from Dresden University in Germany has discovered evidence of carbon nanotubes in Wootz steel, although this is disputed^[3].

[edit] Trivia

An elaborate fictionalized description of Wootz steel manufacture is presented in Neal Stephenson's historical science fiction The Confusion, part of Stephenson's three-volume work The Baroque Cycle.