横型遠心鋳造プロセスにおける等軸晶挙動の直接観察

概要

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Centrifugal casting technique has been widely used to produce long products, such as pipes. In this casting, sometimes problems such as macroscopic segregation arise. However, we have not found effective countermeasures. This reason may be attributed to the fact that solidification under being applied centrifugal force itself has not been well understood. Therefore, in order to understand the solidification process in centrifugal casting, in-situ observations using transparent substance have been performed by an experimental equipment newly developed. One of the advantageous points of this equipment is that a video camera is installed on the rotating shaft enabling observation of predetermined area during whole period of solidification. Owing to the thermal gradient imposed, transparent substance solidifies inward.At the initial stage, columnar dendrites grew from the rim. Then, equiaxed grains formed in the liquid phase. Equiaxed grains oscillated not only in radial direction but tangential direction synchronized with the rotation. This movement became smaller as solidification proceeded. This change in oscillation with time is due to the increase of apparent viscosity as solidification proceeds.