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Microstructural Change by Hot Forging Process of Korean Traditional Forged High Tin Bronze

Currently, the fabrication of a high-tin bronze spoon by traditional manufacturing techniques involves 10 steps in the bronze ware workshop. Hot forging has a major influence on manufacturing and involves two to three steps. The dendritic α-phase in the microstructure of the high-tin bronze spoon is refined and finely dispersed through hot forging. In addition, twinning is observed in the α-phase of the hammered part, and the α-phase microstructure gradually transform from a polygon to a circular shape due to hammering. In this process, the adjacent α-phases overlap with each other and remain combined after quenching. The microstructure with the overlapping is also observed in bronze artifacts, and this shows the correlation with technical system. The results of the experimental hot forging of Cu-22%Sn alloys show that the decrease in in the amount of the dendritic microstructure, which forms during casting, is in proportion to the number of processing steps and that the refined grain obtained by hammering contributes to the improvement in the strength of the material. From the hammering marks, which are observed on both the bronze artifact excavated from archaeological 494 | 보존과학회지 Vol.34, No.6, 2018 sites and on the high-tin bronze spoon produced in the traditional workshop, it is presumed that the knowledge regarding the unrecorded manufacturing system of bronze ware in ancient times has been passed down in a traditional way up to the system used currently.