1. INTRODUCTION
2. SAMPLES AND METHODS
2.1. Samples for analysis
2.2. Analysis methods
3. ANALYTIC RESULTS
3.1. The archaeological sites of Cheongdangdong · Guryong-dong in Cheonan
3.1.1. A sword with a ring pommel excavated from a ditch-pit-tomb during the Proto–Three Kingdoms period (No. 1)
3.1.2. A sword with a ring pommel excavated from a pit-tomb during the Proto–Three Kingdoms period (No. 2)
3.2. The archaeological site of Galsan-ri in Asan (N0.3)
4. DISCUSSION
4.1. Comparison of production techniques applied to iron swords excavated from the Asan and Cheonan
4.2. Comparison of CaO ratios
5. CONCLUSIONS
The results of examining microstructures indicate that the target swords were formed by using hypoeutectoid steel with a high carbon content through repeated forging. Horizontally elongated nonmetallic inclusions caused by these processes were observed, whereas traces of specific heat treatment were not. Furthermore, it is analyzed that decarburization unintentionally occurred during the production processes.
The results of analyzing the components of nonmetallic inclusions indicate that most nonmetallic inclusions have the form of glassy slag. In some cases, wüstite or fayalite was observed. The existence of wüstite suggests that iron ores were smelted through a direct smelting technique.
The results of conducting the EDS analysis and EDS mapping based on the glassy matrices of nonmetallic inclusions exhibited a comparatively high Ca content, with exceptions in some cases. Based on these results, it is inferred that slag generation or fusing agents were intentionally added. There is also a possibility of the inclusion of fuel ashes or smelting using iron ores with a high Ca content.
The comparison results indicate that heat treatment techniques were not applied to base swords with ring pommels produced during the Mahan and Baekje periods despite the existence of such techniques. Thus, we analyze that the target swords were produced as ceremonial items rather than weapons.