Wootz steel

The term wootz is derived from anglicized forms of South Indian words for steel, including Tamil urukku, Kannada ukku, and Telugu ukku, meaning "steel" or "melted metal".Heyne, Benjamin (1814). Tracts, Historical and Statistical, on India.

Wootz steel originated in the mid-1st millennium BC in India. It was made in Golconda in Telangana, Karnataka, Tamilnadu and Sri Lanka.^[1][2][3][4] The steel was exported as cakes of steely iron that came to be known as "wootz".^[5] The method was to heat black magnetite ore in the presence of carbon in a sealed clay crucible inside a charcoal furnace to completely remove slag. An alternative was to smelt the ore first to give wrought iron, then heat and hammer it to remove slag. The carbon source was bamboo and leaves from plants such as Avārai.^[5][6] Locals in Sri Lanka adopted the production methods of creating wootz steel from the Cheras by the 5th century BC.^[7] In Sri Lanka, this early steel-making method employed a unique wind furnace, driven by the monsoon winds. Production sites from antiquity have emerged, in places such as Anuradhapura, Tissamaharama and Samanalawewa, as well as imported artifacts of ancient iron and steel from Kodumanal. Recent archaeological excavations (2018) of the Yodhawewa site (in Mannar District) discovered the lower half of a spherical furnace, crucible fragments, and lid fragments related to the crucible steel production through the carburization process.^[8] In the South East of Sri Lanka, there were some of the oldest iron and steel artifacts and production processes to the island from the classical period.^{[9][10][11][12]}

Trade between India and Sri Lanka through the Arabian Sea introduced wootz steel to Arabia. The term muhannad مهند or hendeyy هندي in pre-Islamic and early Islamic Arabic refers to sword blades made from Indian steel, which were highly prized, and are attested in Arabic poetry. Further trade spread the technology to the city of Damascus, where an industry developed for making weapons of this steel. This led to the development of Damascus steel. The 12th century Arab traveler Edrisi mentioned the "Hinduwani" or Indian steel as the best in the world.^[13] Arab accounts also point to the fame of 'Teling' steel, which can be taken to refer to the region of Telangana, the Golconda region of Telangana clearly being the nodal center for the export of wootz steel to West Asia.^[13]

Another sign of its reputation is seen in a Persian phrase – to give an "Indian answer", meaning "a cut with an Indian sword".^[7] Wootz steel was widely exported and traded throughout ancient Europe and the Arab world, and became particularly famous in the Middle East.^[7]

[Crucible steel]

Specimens of daggers and other weapons were sent by the Rajas of India to the Great Exhibition in London in 1851 and 1862 International Exhibition. Though the arms of the swords were beautifully decorated and jeweled, they were most highly prized for the quality of their steel. The swords of the Sikhs were said to bear bending and crumpling, and yet be fine and sharp.^[7]

Archaeological and metallurgical evidence indicates that crucible steel production associated with wootz steel originated in the Indian subcontinent by at least the mid-first millennium BCE.Craddock, Paul T. (2003). Early Metal Mining and Production. Edinburgh University Press. pp. 229–232.Srinivasan, Sharada; Ranganathan, S. (2004). India's Legendary Wootz Steel: An Advanced Material of the Ancient World. National Institute of Advanced Studies.

The earliest firmly documented crucible steel production sites have been identified in southern India, particularly in Tamil Nadu and Karnataka, where excavations have uncovered crucibles, furnaces, slag, and steel artifacts consistent with high-carbon crucible steel manufacture.Srinivasan, Sharada (1994). "Wootz crucible steel: a newly discovered production site in South India". Institute of Archaeology, University College London.

Excavations at the industrial settlement of Kodumanal in Tamil Nadu have yielded crucible fragments and metallurgical remains dating between approximately the 3rd century BCE and the early centuries CE. Metallographic analysis of excavated materials confirms the production of high-carbon steel consistent with crucible steel technology.

Additional early iron and steel production sites in southern India, including Hallur, Adichanallur, and Gattihosahalli, demonstrate advanced ironworking traditions dating to the early Iron Age (c. 1200–800 BCE), which preceded and likely contributed to the development of crucible steelmaking.Allchin, F. Raymond; Allchin, Bridget (1979). The Rise of Civilization in India and Pakistan. Cambridge University Press.Tripathi, Vibha (2001). "The Age of Iron in South Asia". Journal of World Prehistory. 15: 1–34.

In Sri Lanka, archaeological investigations have revealed early iron and steel production at sites such as Anuradhapura, with ironworking dating to at least 900 BCE.Juleff, Gillian (1998). Early Iron and Steel in Sri Lanka: A Study of the Samanalawewa Area. Archetype Publications. These early metallurgical traditions later developed into crucible steel production using advanced furnace systems.

Excavations at Samanalawewa and other Sri Lankan sites have revealed wind-powered furnaces dating between the 3rd century BCE and the first millennium CE, capable of producing high-carbon steel. These furnaces used natural monsoon winds to achieve temperatures exceeding 1200 °C, enabling crucible steel production without mechanical bellows.

Recent excavations at Yodhawewa in Sri Lanka’s Mannar District, conducted in 2018, uncovered crucible fragments, furnace remains, and metallurgical slag associated with crucible steel production.Juleff, Gillian (2018). "Iron and steel production in Sri Lanka: recent archaeological discoveries at Yodhawewa". South Asian Archaeology Reports. Radiocarbon dating indicates that steel production at the site occurred between the 7th and 11th centuries CE.

These archaeological discoveries confirm that crucible steel production in South Asia developed from earlier ironworking traditions and became established as a technologically sophisticated industry by the early historic period.

Metallurgical analyses of ancient crucible steel samples demonstrate that wootz steel was produced through controlled carburization and slow cooling, resulting in carbide banding microstructures responsible for its characteristic properties.Verhoeven, John D. (2001). "The metallurgy of Damascus steel". JOM. 53: 18–20.

The archaeological record demonstrates that crucible steel production associated with wootz steel originated in South Asia and was subsequently exported to the Middle East, where it was forged into Damascus steel blades.Pendray, Alfred (2006). "Reconstruction of Damascus steel". Materials Characterization.

Wootz is characterized by a pattern caused by bands of clustered Fe
₃C particles made by melting of low levels of carbide-forming elements.^[14] Wootz contains greater carbonaceous matter than common qualities of cast steel.^{[citation needed]}

The distinct patterns of wootz steel that can be made through forging are wave, ladder, and rose patterns with finely spaced bands. However, with hammering, dyeing, and etching further customized patterns were made.^[15]

The presence of cementite nanowires and carbon nanotubes has been identified by Peter Pepler of TU Dresden in the microstructure of wootz steel.^[16] There is a possibility of an abundance of ultrahard metallic carbides in the steel matrix precipitating out in bands. Wootz swords were renowned for their sharpness and toughness.

In the 19th century, Wootz steel was studied in depth by the Royal School of Mines in an attempt to reproduce it.^[18] Dr. Pearson was the first to chemically examine wootz in 1795 and he published his contributions to the Philosophical Transactions of the Royal Society.^[19]

Russian metallurgist Pavel Petrovich Anosov (see Bulat steel) was able to reproduce ancient wootz steel with nearly all of its properties and the steel he created was very similar to traditional wootz.^{[citation needed]} He documented four different methods of producing wootz steel that exhibited traditional patterns.^{[citation needed]} His work titled “On Bulat Steels” was published in the Mining Journal (ru:Горный журнал).^[20]

In the late 20th century, J.D Verhoeven and Alfred Pendray chemically analysed extant Damascus blades, reconstructed methods of production, proved the role of impurities of ore, specifically the inclusion of Vanadium (~0.005%) in carbide formation, along with the need for repeated thermal cycling of the forged blades in the pattern creation, to reproduce wootz steel blades with patterns microscopically and visually identical to ancient blade patterns.^[21][22]

Reibold et al.'s analyses spoke of the presence of carbon nanotubes enclosing nanowires of cementite, with the trace elements/impurities of vanadium, molybdenum, chromium etc. contributing to their creation, in cycles of heating/cooling/forging. This resulted in a hard high carbon steel that remained malleable.^[23]

There are smiths who are now consistently producing wootz steel blades visually identical to the old patterns.^[24] Steel manufactured in Kutch (in present-day India) particularly enjoyed a widespread reputation, similar to those manufactured at Glasgow and Sheffield.^[7]

With fellow experts, the Georgian-Dutch master armourer Gocha Laghidze developed a new method to reintroduce "Georgian Damascus steel". In 2010, he and his colleagues gave a masterclass on this at the Royal Academy of Fine Arts in Antwerp.^[25][26]

• Toledo steel
• Noric steel
• Bulat steel
• Tamahagane steel
• Ferrous metallurgy
• Iron pillar of Delhi
• Pattern welding