Influence of External Physical Fields on Grain Distribution in Continuous Cast Round Blooms

The growth of columnar grains and the distribution of equiaxed grains in the continuous casting process of round blooms had a significant impact on the solute distribution properties of the product. External physical fields, including gravity, electromagnetic stirring (EMS), and temperature, directly affected the growth of the columnar grains and the nucleation, growth, and movement of the equiaxed grains, and thereby influenced the final distribution characteristics of the solidification structure and of the phase fractions. In this study, a model for the growth of the columnar grains, and the nucleation, growth, and movement of the equiaxed grains was developed. The control variable method was employed, and the effects of different mold electromagnetic stirring (M-EMS) parameters, casting temperatures, and casting speeds on the solidification structure were individually calculated and analyzed. The results indicated that under the influence of gravity, the equiaxed grains migrated from the inner arc side to the outer arc side, which resulted in asymmetry in the microstructure on both sides. By increasing the electromagnetic stirring current, reducing the casting temperature, and lowering the casting speed, the equiaxed grain ratio can be increased. The effect of reducing the casting temperature is most significant, with the equiaxed grain ratio raising from 51.2 to 65.5 pct when the casting temperature is reduced from 1519 °C to 1514 °C. Lowering the superheat, lowering the casting speed, and enhancing M-EMS all lower the overall temperature of the blooms, leading to more pronounced asymmetrical characteristics in the structure. This model can efficiently calculate the heat transfer behavior, evolution, and distribution characteristics of the solidification structure of continuous casting round blooms under different external field effects and casting process parameters, providing a theoretical basis for improving the internal quality of round blooms in production.