Abstract: In order to improve the surface quality of continuous casting bloom in a factory, the surface cracks and porosity defects of bloom were analyzed and the use of mold flux was tracked. The results show that obvious decarburization occurs around the defect, the original austenite grain size is larger than the normal position, and the thickness of the liquid slag layer of the mold flux is relatively thin. By adjusting the height of mold flux, the melting rate of mold flux is optimized to increase the thickness of liquid slag layer. After optimization, the thickness of liquid slag layer was higher than before, and the incidence of cracks was obviously reduced. Magnetic flux leakage testing was carried out on the rolled products, and the qualified ratio of the studied steel grades increased from 51.6% in the previous period to 94.0%.

Key words: bloom, surface quality, mold flux, thickness of liquid slag layer, melting rate