1994 Volume 80 Issue 12 Pages 896-901
It is well known that solidification structure is made finer by reduction in semisolid state. The object of this research is to clarify the condition of occurrence of such a process quantitatively and to make it possible to estimate the size of the refined region in cast products. We made experiments in which cast pieces were reduced in semisolid state. We also analysed the distribution of temperature, fraction of solid and strain in the thickness direction of cast pieces. The results obtained from these experiments and/or analyses are as follows.
(1) The solidification structure of the region refined by reduction is equiaxed and transformed into globular austenite, while that of the other part, columnar dendritic or equiaxed with regular size, is transformed into columnar austenite.
(2) The portion of refined region becomes larger as average fraction of solid and/or reduction ratio increase. Precisely, the condition of refining is expressed with the following equation in terms of local solid fraction and local compressive strain.
fs≤0.75ε0.132
(3) By use of the above quantitative relations for refining, it becomes possible to estimate the fined region in cast pieces.
