Study of Large Inclusions in Casting Slab of 45# Steel

Abstract

According to the production process of 45#steel(120t BOF→ slag refining →CC), some system analysis are introduced to research on the type, composition and quantity of large inclusions in casting slab under slag washing process, the effect of slag washing production process on the cleanliness of casting slab is evaluated. The results of the study show that: Under slag washing process, many of large inclusions are spherical inclusions，the main type of large inclusions is CaO-SiO2-Al2O3-MnO complex inclusion andSiO2-Al2O3 inclusion; the content of large inclusions in normal slab is 5.17mg/10kg, it is lower than that under un-slag washing process; the content of large inclusions in head slab is 108.82mg/10kg, it’s 21.05 times higher than that in normal slab; the content of large inclusions in compound casting slab is 15.94mg/10kg, it’s 3.08 times higher than that in normal slab; the content of large inclusions in casting slab is slightly higher under the condition of unsteady casting; the main inclusions with a size of between 140μm and 300μm in head slab, take up 70.13%, the inclusions with a size of more than 300μm is second, take up 29.24%, and the least is inclusions with a size of between 80μm and 140μm, only take up 0.63%. The level of the molten steel fluctuated remarkably, slag entrapment and secondary oxidation is serious at the casting start and compound casting, which cause the cleanliness of casting slab decreasing. Unsteady casting has great effect on the cleanliness of casting slab.