| 摘要 |
PROBLEM TO BE SOLVED: To reduce the variation of product characteristics in cast slab unit, such as center segregation, center cross sectional crack and workability, by simply and accurately predicting the arbitrary equiaxed crystal ratio. SOLUTION: The position in the thickness direction of the cast slab in which the solid-phase ratio fs in a solid-liquid coexistent range of a metallic alloy is a equal to a specified solid-phase ratio fe is calculated over the casting direction. Further, the ratio G/Rn (n=1/2: (b) curve in the figure) of the temperature gradient G and an exponential function Rn of the solidification velocity R in the thickness direction of the cast slab at the position (curve (a) in the figure) obtained from the above calculation is calculated, and the sum of the lengths in the thickness direction of the cast slab in which the G/Rn is smaller than a prescribed threshold is calculated. It is judged that this obtained length d/(the thickness of the cast slab/2)×100% is the equiaxed crystal ratio, and the casting is performed.
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