The history of ferrous metallurgy in the Indian subcontinent began in the 2nd millennium BC. Archaeological sites in Gangetic plains have yielded iron implements dated between 1800 and 1200 BC. By the early 13th century BC, iron smelting was practiced on a large scale in India. In Southern India (present day Mysore) iron was in use 12th to 11th centuries BC. The technology of iron metallurgy advanced in the politically stable Maurya period and during a period of peaceful settlements in the 1st millennium BC.
Iron artifacts such as spikes, knives, daggers, arrow-heads, bowls, spoons, saucepans, axes, chisels, tongs, door fittings, etc., dated from 600 to 200 BC, have been discovered at several archaeological sites of India. The Greek historian Herodotus wrote the first western account of the use of iron in India. The Indian mythological texts, the Upanishads, have mentions of weaving, pottery and metallurgy, as well. The Romans had high regard for the excellence of steel from India in the time of the Gupta Empire.
Perhaps as early as 500 BC, although certainly by 200 AD, high-quality steel was produced in southern India by the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon. Iron chain was used in Indian suspension bridges as early as the 4th century.
Wootz steel was produced in India and Sri Lanka from around 300 BC. Wootz steel is famous from Classical Antiquity for its durability and ability to hold an edge. When asked by King Porus to select a gift, Alexander is said to have chosen, over gold or silver, thirty pounds of steel. Wootz steel was originally a complex alloy with iron as its main component together with various trace elements. Recent studies have suggested that its qualities may have been due to the formation of carbon nanotubes in the metal. According to Will Durant, the technology passed to the Persians and from them to Arabs who spread it through the Middle East. In the 16th century, the Dutch carried the technology from South India to Europe, where it was mass-produced.
Steel was produced in Sri Lanka from 300 BC by furnaces blown by the monsoon winds. The furnaces were dug into the crests of hills, and the wind was diverted into the air vents by long trenches. This arrangement created a zone of high pressure at the entrance, and a zone of low pressure at the top of the furnace. The flow is believed to have allowed higher temperatures than bellows-driven furnaces could produce, resulting in better-quality iron. Steel made in Sri Lanka was traded extensively within the region and in the Islamic world.
One of the world's foremost metallurgical curiosities is an iron pillar located in the Qutb complex in Delhi. The pillar is made of wrought iron (98% Fe), is almost seven meters high and weighs more than six tonnes. The pillar was erected by Chandragupta II Vikramaditya and has withstood 1,600 years of exposure to heavy rains with relatively little corrosion.