江戸元禄時代に国友鉄砲鍛冶により製造された火縄銃の金属組織

抄録

  The microstructure and mechanical properties of the steel barrel of a Japanese matchlock gun fabricated by the gunsmith Kunitomo Tokudayuu in the Edo Genroku period have been investigated. The purpose of this work is to obtain modern materials-science data for a Japanese matchlock gun fabricated by a noted Kunitomo gunsmith and to study the manufacturing technique of the steel barrel. Specimens are cut from the center, the muzzle, and the screw of the barrel. The carbon concentration is determined by chemical analysis. The microstructure and nonmetallic inclusions of the specimens are observed with an optical microscope and a scanning electron microscope (SEM). To evaluate the hardness, Vickers hardness (Hv) is used. The inner structure of the screw is observed by X-ray radiography. The carbon concentration is 0.007 mass% in the center of the barrel and 0.07-0.3 mass% in the muzzle. The distribution of nonmetallic inclusions in the center of the barrel indicates that the barrel was fabricated by joining two long edges of a steel sheet, a technique that is called Udonbari (seamed steel pipe in Japanese). The muzzle was reinforced with steel having a higher carbon content than that of the center of the barrel by rolling the steel over the Udonbari barrel. The female screw of the barrel was made of clad steel. Both male and female screws of the barrel were made by a cutting technique.