Investigation on Initial Shell Solidification and the Effect of Negative Strip Time on Oscillation Marks during Continuous Casting

The initial solidification of the shell and the effect of the negative strip on oscillation marks were studied during the oscillation of the mold. A two-dimensional model was established concerning mold oscillation, which was coupled with fluid flow, heat transfer, and solidification, and the validity of the model was verified. The results show that oscillation marks were formed at the negative strip stage and that the quality of the slabs can be improved by reducing the duration of the negative strip stage. During the negative strip stage, the shell was affected by the strong backflow of liquid slag and the pressure on the surface sharply increased, resulting in the formation of a depression oscillation mark on the shell. The effects of the negative strip stage on the initial solidified shell during each cycle were compared. As the depth of the oscillation mark decreased, the upward shear stress on the shell's surface increased, without the occurrence of a negative strip stage during one cycle. The results provided a new method for reducing oscillation marks and are of great significance for improving casting slabs' quality.