焼入れ時に生じる日本刀の反りの影響因子に関する数値解析的検討

抄録

In recent years, the Japanese sword is focused as the traditional craft. The unique curving and HAMON is characteristic of Japanese sword. these characteristics are made from unique quenching method. Swordsmith pasts the clay as called “YAKIBATSUTI” on the surface of sword before quenching to control the cooling speed. Due to the difference of this clay thickness, the sword transforms to martensite and pearlite, and the blade curving is occurred because of the different expansion between martensite and pearlite. It is known that the deformation like curving of the Japanese sword is occurred from transformation expansion and thermal contraction. However, there few particularity studies about the effect of these factors. In this study, the strain distribution which is occurred from phase transformation and thermal contraction was focused. Therefore, the setting area of high heat transfer coefficient at the edge part was changed and the effect of thermal contraction and transform expansion for the blade curving by numerical simulation was investigated. As the result, the martensitic transform area was expanded with expansion quenching area. Further, the negative curvature which was appeared in the Initial process also increased with expanding martensite area. The history of total strain at the edge part and ridge part was calculated to explain these phenomena. Plastic strain which changes with expanding martensite area affected to the negative curving in the initial process. Further, elastic strain which changes with expanding martensite area affected to the positive curving in the after quenching process. To summarize the result, it was indicated that the martensitic transformation area affects to the blade curving.