Novel Micro‐Scale Steel‐Making from Molten Cast Iron Practised in Medieval Nomadic Communities of East Mongolia

Evidence of novel steel‐making was found in a number of small cast‐iron fragments recovered by the Mongolia–American archaeological survey of eastern Mongolia. These iron artefacts come from medieval period habitation and manufacturing sites and they consistently display irregular surface features characteristic of a solidification reaction from a partially molten state. Their microstructure consists of large near‐spherical islands of pearlite spread on a background of fine white cast‐iron eutectic. Reflected in this peculiar structure is an extremely small‐scale steel‐making process where one or more small pieces of cast iron were heated above the eutectic temperature for rapid decarburization in the partially molten state. We provide a detailed account of the technological aspects of this micro‐scale steel‐making method as observed in the microstructure and chemical composition of the objects examined. This small‐scale technology was ideally suited to the pastoral nomadic way of life that characterized medieval eastern Mongolia; however, it probably would not have been appropriate for sedentary communities with access to large‐scale urban manufacturing centres. Based on this observation, we discuss the role of nomadic lifeways and associated political environments that likely influenced the development of this innovative steel‐making technique.