Steel making in the ancient Korean Kingdom of Koguryo

Five iron artifacts excavated from the same spot in a military fortress of the former Korean kingdom, Koguryo (37 BCE-668 CE), have been metallographically examined. The result shows that they comprise two pieces of white cast iron, one piece of wrought iron and two pieces with microstructures consisting of high C steel buried in white cast iron or white cast iron buried in high C steel. This provides direct material evidence of both white cast iron and wrought iron being combined to form steel. This article is to present the detailed account of metallurgical microstructures observed in the rare archaeological evidence of the unique ancient steel making process involving liquid cast iron.