The study looked at how clean the first slab of IF steel is compared to a normal slab. They analyzed the oxygen and nitrogen levels, as well as the size and distribution of inclusions in the steel. The researchers found that the first slab had lower oxygen and nitrogen levels along its casting direction. Large-sized inclusions were more common in the first slab, but decreased along the casting direction. Inclusions were mainly from slag entrapment, reoxidation products, and stuffing sand. The inner arc of the slab had more inclusions than the outer arc.