日本金属学会誌

J. Japan Inst. Met. Mater, Vol. 81, No. 03 (2017),
pp. 101-108

Production techniques of coin-type medal rewarding contributions manufacturing in the Momoyama-era

Fumiyoshi Kirino 1, Naoshi Ohono 1, Satoko Taguchi 1, Akimitsu Nezu 2 and Ryouichi Yokoyama 2

1 Graduate School, Tokyo University of the Arts
2 Application Laboratories, Rigaku Corporation

Abstract:

Metal craft production techniques for coin-type medal rewarding contributions manufactured in the Momoyama-era were studied. Reward samples are separated into two types on the basis of production process. One process is casting, and the other is forging. An example of the composition of a casting sample is Ag-Cu alloy, and that of a forged sample is pure Ag. Many voids in cast cultural properties, called eirakutsuho, are observed using X-ray transmission imaging techniques, and indicate the production technique used during this era. Inner stress is measured by the sin2ψ method for identifying X-ray diffraction pattern changes. The inner stress of eirakutsuho manufactured by casting is compressive. This is a solidification contraction that occurs at the time of casting. The metal morphology of cast cultural properties, such as eirakutsuho is of the branch type. A thermal flaw is manufactured at the surface of such a cultural property. A creased metal morphology is formed in production by the forging method. Eirakutsuho manufactured by the forging method is stress free. This result indicates that thermal treatment is used in this manufacture process. A pure Ag is easy to process for forging. Test samples of cultural properties have been found to have been manufactured by forging methods. It is assumed that the jyotagane metal craft technique was used. The inner stress manufactured in this sample prepared by this method is compressive. After annealing, this sample becomes stress free. The result matches the results obtained by measuring the inner stress of cultural properties.

[doi:10.2320/jinstmet.J2016050]


(Received 2016/09/05)

Keywords:

casting, forging, manufacturing technique, Momoyama-era, inner stress


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