In order to elucidate the effect of deformation of initial solidified layer on surface defects of continuously cast slabs, the deformation behavior of freely solidifying disc was observed with several non-ferrous metals and their alloys by the droplet method. The following results were obtained:
(1) After solidification and cooling to room temperature, the shape of the shell bottom of all the metals and alloys tested became parabolic.
(2) Deformation of pure metals was positive, i.e. convex toward chill and was attributed to thermal contraction after solidification. A model for the prediction of deformation of pure metals was proposed and a fair agreement with experimental results was obtained.
(3) Direction of deformation of alloys was either positive or negative, sometimes very large near eutectic, depending on the composition. This is because many alloys solidify to form supersaturated solid solution, from which a second phase precipitates causing expansion or contraction, depending on the difference of molar specific volumes of the two phases.