Industrial Investigation on Inclusions and Solidification Structure of Steel Continuous Casting Slabs Under Mold Electromagnetic Stirring

Abstract

In the current study, the quantity, size, and spatial distribution of non-metallic inclusions along the thickness direction of an ultralow carbon IF steel were detected employing an automatic SEM-EDS scanning system. And the distribution of the slab subsurface inclusions was mainly analyzed. In addition, the total oxygen content in the steel and the solidification structure of the slab were analyzed. Upon the application of M-EMS, the solidification front was flushed due to the stirring effect generated by the electromagnetic force, promoting the floating removal of inclusions, thereby improving the overall cleanliness of the slab. However, the probability of the collision and agglomeration of inclusions was increased by applying M-EMS, resulting in an increase in the size of inclusions. The influence of M-EMS on inclusions was primarily on the slab subsurface. Following the application of M-EMS, the inclusions in the slab subsurface were experienced a reduction in number density from 9.99 to 6.11 #/mm², and the area fraction was decreased from 69.51 × 10⁻⁶ to 57.31 × 10⁻⁶. However, the average size of inclusions was increased from 2.45 to 2.87 μm. With the application of M-EMS, the total oxygen content in the subsurface of the slab was reduced by 1–3 ppm, and the total oxygen content in the center of the slab was reduced by 0–1 ppm. These results indicated that the adoption of M-EMS contributed positively to the reduction of inclusions from the slab subsurface, thereby enhancing the surface quality of the slabs. Furthermore, the analysis revealed that the equiaxed crystal area comprised 12.06 pct of the total area without the consideration of M-EMS, while with the application of M-EMS, this proportion increased to 20.99 pct.