日本刀の焼入れにおける焼刃土の効果

概要

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The quenching process of a Japanese sword is simulated by a CAE system "HEARTS" developed by one of the authors. The system is available to consider the coupling effect among metallurgical change due to phase transformation, temperature and inelastic stress/strain. In the quenching process of the Japanese sword, a special kind of clay is pasted on the surface to control the heat transfer coefficient between metal and water. The dependence of the coefficient on the thickness of clay and also the surface temperature is experimentally evaluated first by using a cylindrical rod of silver. The results show a relatively higher value with thin-pasted clay than that without clay at a high temperature range. The data are then applied to simulate the variation of temperature coupled with the structural change from austenite to martensite and pearlite as well as the variation of stress. It gives an attractive result that the sword is bent two times to the direction opposite to the normal shape due to the complicated time difference between martensitic and pearlitic transformation and thermal contraction. The simulated results of residual stress distributions are compared with the measured data by X-ray diffraction technique.
1995-03-15