FREE DEFORMATION OF THE INITIAL SOLID LAY ER OF SOME NONFERROUS ALLOYS

In order to elucidate the effect of deformation of initial solidified layer on surface defects of continuously cast slabs, the deformation b ehavior of freely solidifying disc was observed with several non-ferro us metals and their alloys by the droplet method. The following result s were obtained : (1) After solidification and cooling to room tempera ture, the shape of the shell bottom of all the metals and alloys teste d became parabolic. (2) Deformation of pure metals was positive, i.e. convex toward chill and was attributed to thermal contraction after so lidification. A model for the prediction of deformation of pure metals was proposed and a fair agreement with experimental results was obtai ned. (3) Direction of deformation of alloys was either positive or neg ative, sometimes very large near eutectic, depending on the compositio n. This is because many alloys solidify to form supersaturated solid s olution, from which a second phase precipitates causing expansion or c ontraction, depending on the difference of molar specific volumes of t he two phases.