Wootz steel

Wootz steel, also known as Seric steel, is a crucible steel characterized by a pattern of bands and high carbon content. These bands are formed by sheets of microscopic carbides within a tempered martensite or pearlite matrix in higher carbon steel, or by ferrite and pearlite banding in lower carbon steels. It was a pioneering steel alloy developed in southern India in the mid-1st millennium BC and exported globally. Wootz steel originated in the mid-1st millennium BC in South India, in present-day Tiruchirappalli, Kodumanal, Erode, Tamil Nadu. There are several ancient Tamil, North Indian, Greek, Chinese and Roman literary references to high carbon Tamil steel. In later times, wootz steel was also made in Golconda in Telangana, Karnataka and Sri Lanka. The steel was exported as cakes of steely iron that came to be known as "Wootz". 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. The Chinese and locals in Sri Lanka adopted the production methods of creating wootz steel from the Chera Tamils by the 5th century BC. 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 a lower half-spherical furnace, crucible fragments, and lid fragments related to the crucible steel production through the carburization process. A 200 BC Tamil trade guild in Tissamaharama, in the South East of Sri Lanka, brought with them some of the oldest iron and steel artifacts and production processes to the island from the classical period.