736 論 文 鉄と鋼 Tetsu-to-Hagané Vol. 102 (2016) No. 12 加速器質量分析による日本刀の C 年代と暦年代 1 2 2 3 C Ages and Calendar Years of Japanese Swords Measured with Accelerator Mass Spectrometry Kazuhiro Nagata, Akihiro Matsubara, Yoko Saito-Kokubu and Toshio Nakamura Synopsis : Steel of Japanese swords has been produced with Tatara process from iron sand and charcoal. Carbon dissolved in steel was absorbed from wooden charcoal fuel during the production of the steel. From the decay of C activity in the steel, the C age of Japanese sword can be determined. The C ages of 4 Japanese swords were measured with accelerator mass spectrometry and calibrated to calendar years. Each C age provided plural calendar year periods with definite probabilities, and one of the periods agreed with the production year of each sword that was determined from the sword master s name cut in the grip of his sword after taking the age range of charcoal used for steel production and usage for several generations of the same names of sword masters into account. Key words: C age; calendar year; Japanese sword; accelerator mass spectrometry. 1. 緒言 C 5730 40 12 C 13 C Accelerator Mass Spectrometry, AMS C C 2. たたら製鉄と小鍛冶 6 9 12 19 52 1.2 m 19 12.8 13.5 30 3 3 72 1.5 2.1 40 3.0 3.5 mass% 28 5 10 28 7 7 Received on May 10, 2016 ; Accepted on Jul. 7, 2016 1 Professor Emeritus, Tokyo Institute of Technology, 3-1-13-401 Eda-higashi Tsuzuki-ku Yokohama 224-0006 2 Tono Geoscience Center, Japan Atomic Energy Agency 3 Center for Chronological Research, Nagoya University Corresponding author : E-mail : nagata-kr05@d08.itscom.net DOI : http://dx.doi.org/10.2355/tetsutohagane.tetsu-2016-036 76
C 737 1 1350 00 Fe FeO SiO 2 TiO 2 Table 1 2 1154 1.0 1.5 mass% 0.1 mass% 2 1528 3 FeO 4 3. 鋼に吸収された炭素 5 20 25 Table 1. Chemical compositions of pig iron (Zuku) and steel (Kera, Tamahagane) produced by Tatara furnaces at Ataidani and Tonami in 1891 2). Chem. comp (mass%) C Si Mn P S Ti Pig iron (Ataidani) 3.63 Trace Trace 0.100 0.003 Trace Steel* (Tonami) 1.33 0.04 Trace 0.0 0.006 Trace * Tamahagane (Best quality of steel in bloom) 4. 実験方法 4 1 測定試料 4 Fig.1 Fig.4 CO 2 Enami 6 mm 3 60 1.2NNaOH 1 60 1.2NHCl 5 10 LECO-502-231, LECO Corp., USA 1 g 1000 10 500 30 HF-10, LECO Corp., USA CO 0.1 ppm CO 2 0.1 ppm Total hydrocarbon 0.1 ppm 100 ml 4 CO 2 100 CO 2 CO 2 99.99% Aldrich USA 99.99999% 10 640 1 mm CO 2 CO 2 4 2 測定方法 C/ 12 C 13 C/ 12 C JAEA-AMS-TONO 7,8 National Institute for Standards and Technoligy NIST HOxII, SRM-4990C C/ 12 C 13 C/ 12 C 77
738 鉄と鋼 Tetsu-to-Hagané Vol. 102 (2016) No. 12 Fig. 1.Katana Okuizuminokami Tadashige (Satsuma, Edo period) Fig. 3.Katana Kawachinokami Fujiwara Kunisuke (Settsu, Momoyama period) Fig. 4.Katana Echizen-ju Harima Daijo Fujiwara Shigetaka (Echizen, Edo period) Fig. 2.Wakizashi Sukemune (suruga, Muromati last period) 78
C 739 C/ 12 C 1950 C C BP C 9 C C LECO-501-938, LECO Corp., USA CO 2 C CO 2 12 C 13 C C 0.989 0.011 1.2 10 12 C C C C C IntCal13 10 OxCal 4.2.4 11 3 4 6. 考察 6 1 C 年代と暦年代の再現性 1a 1b C 1a 133 19BP 1b 210 21BP 2 133 38BP 210 42BP C Fig.6 1a 1678 1940 4 1b 1648 1950 4 5. 結果 Table 2 C BP σ AD C Fig.5 1b C BP AD C C C 2σ Fig. 1 1648 1950 4 Fig.6 1a 1b 2 Fig. 5. Calibration of calendar year (cal AD) of the sample 1b from C age (BP) measured with AMS using IntCal13 data set 10) and OxCal 4.2.4 program 11) : (Left side) Normal distribution of BP of the sample, (Lower distribution) Probability density of calendar year within ±2σ of normal distribution of BP of the sample. Table 2. Calendar year (cal AD) of the samples from C age (BP) measured with AMS using IntCal13 data set 10) and OxCal 4.2.4 program 11). No. 1a Name of sample Okuizuminokami Tadashige C age (BP ± 1σ) 133 ± 19 1b 210 ± 21 2 3 4 Sukemune Kawachinokami Fujiwara Kunisuke Echizen-ju Harima Daijo Fujiwara Shigetaka σ: Standard deviation 404 ± 20 390 ± 20 306 ± 19 Calendar year (AD ± 2σ) 1678-1765 (34.9%) 1773-1776 (0.5%) 1800-1891 (43.9%) 1909-1940 (16.0%) 1648-1682 (31.1%) 1738-1750 (2.8%) 1762-1803 (44.4%) 1937-1950 (17.2%) 40-98 (88.5%) 1601-1616 (6.9%) 45-1516 (80.7%) 1597-1618 (.7%) 15-1600 (71.7%) 1616-1648 (23.7%) AMS ID JAEA-AMS-TONO Nagoya Univ. JAT-9367 SGTD-1 JAT-9368 SGTD-2 JAT-9370 SKMN-1 JAT-9371 KNSK-1 JAT-9372 SGTK-1 79
740 鉄と鋼 Tetsu-to-Hagané Vol. 102 (2016) No. 12 6 2 銘奥和泉守忠重の刀の制作年代 1704 1711 5 1720 63 12 Fig.1 2 1a 34.9% 1678-1765 0.5% 1773-1776 43.9% 1800-1891 16.0% 1909-1940 1b 31.1% 1648-1682 2.8% 1738-1750 44.4% 1762-1803 17.2% 1937-1950 1b1648-1682 1680 6 3 銘助宗の脇差の制作年代 3 92 1501 2 1558 1570 3 1555 1558 2 3 13 Fig.2 2 C 404 20BP 40 1500 88.9% 6 4 銘河内守藤原國助の刀の制作年代 4 1624 1644 4 1647 5 30 2 1673 1681 Fig.3 1615 1624 3 C 390 20BP 45 1516 81.12% 1598 1619.3% 2 6 5 銘越前住播磨大掾藤原重高の刀の制作年代 1624 1644 2 1661 1673 3 1688 1704 Fig. 6. Probability density of calendar year within ±2σ of normal distribution of BP of the samples. 80
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