Mold Simulator Study on the Initial Solidification of Molten Steel Near the Corner of Continuous Casting Mold

Corner cracks are one of the most widespread surface defects of continuous casting slabs, and they are especially severe for peritectic steels and low-alloy steels. Therefore, a clear understanding of molten steel initial solidification around mold corner would be of great importance for the inhibition of corner cracks. This paper has been conducted with the aim to elucidate this understanding, by using a novel mold simulator equipped with a right-angle copper mold. The responding temperatures and heat fluxes across the mold hot-face and corner were firstly calculated through a 2D-inverse heat conduction program mathematical model, and the results suggested that the cooling ability and the fluctuation of heat fluxes around the mold corner are stronger than those for mold hot-face. With the help of power spectral density analysis and fast Fourier transformation, the four characteristic signals of heat fluxes were discussed in this paper. Next, the relation between the thickness of solidified shell and solidification time was fitted with the solidification square root law; as a result, the average solidification factor \( \bar{K} \) for the hot-face shell is 2.32 mm/s^1/2, and it is 2.77 mm/s^1/2 for the shell near-corner. For the same oscillation marks (OMs), it appeared that the OMs positions on the shell corner are lower than those on the shell hot-face along the casting direction, because the stronger shrinkage of shell at the corner allows the overflowing steel to penetrate deeper into the larger gap between the shell corner and mold, which is demonstrated through the heat transfer analysis and metallographic examination. Finally, the interrelation between shell profile, mold oscillation, variation rate of heat flux, high-frequency heat flux and high-frequency temperature was discussed for above two cases, and the results suggested that meniscus conditions (heat transfer and melt flow) around the mold corner are more unsteady.