Ancient high carbon steel from South Tamil Nadu, India: microstructural and elemental analysis

Abstract

There have been claims of early use of high carbon steel in south India. Still, the antiquity, elemental composition, and steelmaking process have not been explored adequately. The high carbon steel was known in the iron age or early historic period. However, the large -scale use of such steel was practiced only in medieval times. This paper examines the presence of steel and its metallographic features in the iron artifacts retrieved from two archeological sites, namely, Ambal and Vallam, Tamil Nadu, India, with occupational evidence from the Iron Age to the Medieval period through a number of scientific tests. Metallographic as well as mechanical tests, were performed to identify the morphology and measure the strength, respectively. Similarly, the chemical compositions were measured to quantify the alloying elements in the material. The slag was exposed on the etched surface of the sample cut from axe. Microscopy and chemical composition analysis showed very fine bright dendrites of the wustite in the iron slag. The deterioration of samples was confirmed in microscopy and composition analysis. The result shows the occupants of ancient Ambal and the Vallam were equipped with iron smelting technology and had the knowledge of steelmaking in the iron age.