著者

桐野 文良 大野 直志 田口 智子 根津 暁充 横山 亮一

出版者

公益社団法人 日本金属学会

雑誌

日本金属学会誌 (ISSN:00214876)

巻号頁・発行日

2019

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<p>The production processes of old Japanese coins, <i>Genbun-koban</i>, <i>Akita-ginban</i> and <i>Morioka-ginban</i>, were studied. These coins were manufactured by a forging method in the <i>Edo</i>-era. <i>Genbun-koban</i>, manufactured at a gold mint of the <i>Tokugawa</i> shogunate called <i>Kinza</i>, in 1736, is made of Au-Ag alloy and its surface is not flat. The residual stress of this coin is compressive, and the residual stress in the stamped area is higher than that in the flat area. The <i>Iroage</i> method was used to color the coin; it is a thermal treatment, resulting in lows the residual stress is smaller at flat area. <i>Akita-ginban</i>, manufactured in the <i>Akita</i> domain in 1863 is made of pure Ag and its surface is also not flat. There is no residual stress in this coin. This result shows that the thermal treatment of this coin was carried out after processing. <i>Morioka-ginban</i>, manufactured in the <i>Morioka</i> domain in 1868, is made of pure Ag, and its surface is flat. The residual stress of this coin is compressive, and the residual stress in the stamped area is higher than that in the flat area. This result shows that the thermal treatment was not carried out after processing. These coins manufactured in the <i>Edo-</i>era thus had different thermal treatments.</p>