The metal-manufacturing method and smelting temperature of ancient metal-production processes have been studied by analyzing the principal elements and microstructures of slag. However, the microstructure of slag varies according to the solidification cooling rate and types and relative amounts of various oxides contained within the smelting materials. Hence, there is a need for accurate analysis methods that allow slag to be distinguished by more than its composition or microstructure. In this study, the microstructures of slag discharged as a result of smelting iron sands collected from Pohang and Gyeongju, as well as the slag excavated from the Ungyo site in Wanju, were analyzed by using metalloscopy, scanning election microscopy-energy dispersine X-ray spectroscopy(SEM-EDS) and wavelength dispersive X-ray fluorenscence(WD-XRF). Furthermore, the microcrystals were accurately characterized by performing Raman micro-spectroscopy, which is a technique that can be used to identify the microcrystals of slags. SEM-EDS analysis of Pohang slag indicated that its white polygonal crystals could be Magnetite; however, Raman micro-spectroscopy revealed that these crystals were actually ulvöspinel. Raman micro-spectroscopy and SEM-EDS were also used to verify that the coarse white dendritic structures observed in the Gyeongju-slag were Wüstites. Additionally, the Wanju slag was observed to have a glassy matrix, which was confirmed by Raman micro-spectroscopy to be Augite. Thus, we have demonstrated that Raman micro-spectroscopy can accurately identify slag microcrystals, which are otherwise difficult to distinguish as solely based on their chemical composition and crystal morphology. Therefore, we conclude that it has excellent potential as a slag analysis technique.

This study analyzes six slags excavated from the iron making site in Gogi-ri, Namwon, Korea to understand the characteristics of the ruins, and to confirm the iron making process performed at the time. The chemical components of the iron making by-products from the Gogi-ri site were analyzed, and the findings indicate total Fe contents between 23.24% and 37.56%, which are lower than the typical total Fe content found in ancient iron making processes. The deoxidation agent contents of the slags ranged from 43.88% to 58.13%, which are higher than the typical deoxidation agent content of ancient iron making processes. The high content suggests smooth separation between iron and slags, and TiO2 detected from the site suggests the use of materials with high titanium content in the iron making in the region. As for the microstructures of the slags, some slags have long pillar-shaped fayalites, while others have pillar-shaped wüstite along with ulvöspinel. Slags from the forging furnace show hammer scales created by both the earlier stages and later stages of forging work. The findings suggest that the iron making site in Gogi-ri, Namwon, Korea used to be an iron making facility where a full range of iron making process was carried out ranging from smelting to forging, and the ironmakers used a wide array of technologies to manufacture iron products.