江戸時代に製造された火縄銃の金属組織

抄録

  The metallurgical microstructure and mechanical properties of the steel barrel of a Japanese matchlock gun fabricated in the Edo period have been investigated. The purpose of this work is to obtain modern materials-science data of the Japanese matchlock gun and to study the manufacturing technique of the steel barrel. Test pieces are cut from the center, the muzzle and the screw of the barrel. The carbon concentration is determined by chemical analysis. The metallurgical microstructure and nonmetallic inclusions of the barrel are observed using an optical microscope and a scanning electron microscope (SEM). Test pieces for measuring the mechanical properties are cut from the gun. To evaluate the hardness, Vickers hardness (Hv) is used. The stress-strain curve, tensile strength and elongation of the gun are obtained.
   The carbon concentration is 0.01∼0.1mass% for the center of the barrel, 0.04∼0.1 mass% for the muzzle of the barrel, 0.05∼0.5 mass% for the front sight (Saki-meate in Japanese) and 0.13∼0.3 mass% for the male screw. The distribution of nonmetallic inclusions in the center and in the muzzle of the barrel suggest that the barrel was fabricated by a manufacturing technique called Udonbari (in Japanese). The metallurgical microstructure of the specimen taken from the muzzle of the barrel in the vertical direction suggests that the barrel and a front sight were joined mechanically. Both male and female screws were made by a cutting technique. The tensile strength and elongation are 316∼366 MPa and 25.0∼31.4%, respectively.