Solidification Structure, Compositional Segregation, and Banded Formation in High Magnetic Induction Grain-Oriented Silicon Steel during Continuous Casting and Rolling

The homogeneity of composition and microstructure of high magnetic induction grain-oriented silicon steel (denoted as Hi-B steel) critically influences the magnetic properties of the final product. This study investigated the solidification structure, elemental distribution, point segregation spots, and banded carbon (C)-rich microstructures of Hi-B steel under 0 A and 400 A current intensities during continuous casting and rolling. Results indicated that electromagnetic stirring increased the equiaxed zone fraction from 13.04% to 32.6%, refining the macroscopic solidification structure of the slab. However, central solidification defects were not eliminated. In rolled materials, banded C-rich structures appeared as narrow and wide bands, which corresponded spatially and dimensionally to segregate spots, central solidification defects, and positive segregation zones beneath the white bands in slabs. Elemental distribution analysis further revealed that electromagnetic stirring extended segregation throughout the equiaxed region, intensifying segregation in both the width and thickness directions of the slab. Although current heat treatment processes reduced segregation in rolled materials, C distribution remained uneven. In pursuit of efficient quality enhancement, Hi-B steel exhibited a dense columnar dendritic structure, with solidification defects and segregation spots localized within a narrow central region. Future enhancements should prioritize optimizing the cooling rate and increasing the extent of soft reduction to further refine the solidification structure and reduce segregation.