Abstract: The SEM and XRD were used to analyze the mineral compositions and crystallization ratio of the original mold flux after melting and cooling down and its agglomerates during continuous casting process in Xiangtan Iron and Steel Group Co., Ltd.. The results indicate that the three types of mold flux samples have high sphericity and smooth surfaces. The main crystalline phases of mold flux A are cuspidine, nepheline, and wollastonite. Those of mold flux B are cuspidine, wollastonite, and iron sodium potassium silicate. Those of mold flux C is cuspidine. The formation and growth of mold slag bars and agglomerates is due to the large amount of bonding in the sintered phase. In order to reduce the possibility of agglomerates, the Al₂O₃ content in the mold flux should be reduced, and the carbon content should be appropriately increased, so that the mold flux are capable of precipitating cuspidine well during the continuous casting process. Therefore, the heat transfer between the casting slab and mold becomes uniform and stable, thereby reducing the possibility of the destruction of dynamic equilibrium of the liquid slag layer due to slag bar sticking. The occurrence of mold slag agglomeration can be reduced.

Key words: ultra-thick slabs, slag bar, crystalline mineral phases, mold flux