Three-Dimensional Spatial Distribution of Non-metallic Inclusions on the Entire Cross Section of a Steel Continuous Casting Slab

In the current study, the size, composition, and spatial distribution of non-metallic inclusions (NMIs) on the entire cross section of a low-carbon Al-killed steel continuous casting (CC) slab was detected using an automatic SEM-EDS scanning system. The total oxygen (T.O) content of the steel was measured to estimate the cleanliness of the CC slab and evaluate the effect of the Flow-Control Mold (FC-Mold) on the cleanliness. The average T.O content was reduced from 12.2 ppm to 10.6 ppm after the application of the FC-Mold. Besides, the FC-Mold was efficient to obtain a more symmetrical distribution of T.O along the width of the CC slab. A fitting formula between the number density and the diameter was proposed based on the current inclusion size distribution. There were four accumulation zones of NMIs along the thickness of the CC slab, including the 1/4 thickness and 3/4 thickness from the loose side, and the layer beneath the surface of the CC slab. The accumulation zones near the 1/4 thickness and 3/4 thickness from the loose side corresponded to the curved segment of the vertical-bending caster and the interaction between the NMI and solidification front. In addition, the accumulation near the 1/4 thickness from the loose side became more severe as the diameter of the NMIs increased. The other two accumulation zones were issued from the double-roll flow pattern and the high-temperature gradient in the mold. The spatial distribution of NMIs along the width of the CC slab was more uniform than the distribution along the thickness of the CC slab. The measured spatial distribution of NMIs provided a validation data for numerical predictions.