Distribution of Large‐Size Inclusions in Transition Slabs for Automotive Exposed Panel Steel

In order to improve the quality of the transition slabs, the large‐size inclusions in 28 m‐long transition slabs are studied by large sample electrolysis and thermodynamic analysis. The results reveal that the length of transition slabs influenced by ladle exchange is 17 m, which is 4 m before the second steel ladle casting and 13 m after the casting. Large‐size inclusions in transition slabs can be divided into five kinds of Al2O3, Al2O3‐CaO, Al2O3‐CaO‐SiO2, Al2O3‐CaO‐MgO, and entrapment slag. The average contents of total inclusions, the inclusions in the range of 30–100 μm, those of 100–200 μm, and those larger than 200 μm in the transition slabs are 4.8, 19, 2.8, and 4.2 times higher than those in the normal slabs, respectively. For the large inclusions greater than 200 μm, the average contents of the Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags significantly increase in the transition slabs, being 9.4, 13.1, and 2.4 times higher than those in the normal slabs, respectively. The sources of Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags should be the secondary oxidation in tundish, entrapment of tundish flux, and entrapment of mold powders, respectively. The large‐size inclusions in 28 m long transition slabs are studied by large sample electrolysis and thermodynamic analysis. The results show that the length of transition slabs influenced by ladle exchange is 17 m. The sources of 5 kinds of large‐size inclusions are analyzed, and the solutions to improve the cleanliness of transition slabs are provided.