The expression of the solute distribution in columnar crystal zone was deduced when the solid-liquid inter- face bended periodically, and the quantitative calculations of macrosegregation were also made in the process of the continuous casting. The solute distribution along the thickness direction of the slabs was obtained, which verified the theoretical calculation. The effect of the bulge size, solidification speed, and solidification shrinkage speed on macro- segregation of the slabs was calculated.It can be concluded that normal segregation and negative segregation alterna- tively appear as a result of the bulge.The normal segregation exponentially depends on the bulge size, and the nega- tive segregation linearly depends on the bulge size. The extent of the normal segregation is greater than that of the negative segregation when the bulge size is the same. The macrosegregation of the same position along the thickness direction of the slabs changes in a sine wave with increasing the solidification rate, and the amplitude is larger at the casting blank center. The normal segregation linearly decreases with increasing the solidification shrinkage speed, and when the solidification shrinkage speed exceeds a critical value, the segregation appears negatively and increa- ses linearly.
The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.
In view of the periodic bending deformation of solid-liquid interface in the solidification process for continuous casting slab, the variation of temperature gradient and dendritic spacing in the front edge of the solid-liquid interface, and the nucleation and propagation process of crack were studied. It is shown that the bending deformation of the interface results in the temperature field change in the front edge of solid-liquid interface, and the occurrence of temperature gradient along drawing direction results in the growth of secondary dendrites. The initial crack formed during the middle and final stage of solidification may extend to the surface of the casting slab and become an internal crack. The results of the theoretical analysis are basically in agreement with that of the experiment.
