Technology, chronology and the role of crucible steel as inferred from iron objects of the ancient site at Junnar, India

Abstract

Ordinary iron objects from an ancient habitation site at Junnar in India, dating to the 2nd BC to AD 2nd century, were examined for their microstructure, chemical composition and age. The objects were mostly made of high carbon steel with a homogeneous microstructure consisting of fine spherical particles of carbide in the ferrite background, free of non-metallic inclusions. Their carbon concentration ranged from 0.7% to over 1.6% with one exception at 0.2%. Some of them contained trace amounts of silicon, manganese and sulfur while one object retained cavities due to volume contraction during solidification reactions. These features indicate that the objects examined constitute an early example of Indian steel making in crucibles. Evidence was found that basic techniques needed for the success of crucible steel technology were mostly available at Junnar at the time. The radiocarbon measurement on carbon samples extracted from one of the iron objects placed its date between 176 BC and AD 20, in agreement with the radiocarbon dates of three charcoal samples from the same site. The forgoing results support that crucible steel was produced in India at a much earlier date than previously supposed, to serve as a material for specific needs arising in daily life.