Cleanliness of interstitial-free steel slabs produced in different casting stages

The cleanliness of IF steel slabs produced by the BOF-RH-CC process in different casting stages was investigated. Due to reoxidation at the casting beginning period, theC,O_T,N contents of the first slab are higher than those of the slabs in other stages, and a few big size Al₂O₃ clusters exist in the first slab. The non-metallic inclusions in the normal slabs at the casting middle period is mainly small size Al₂O₃ blocks (≤ 30μm) and a few small size Al₂O₃ clusters (≤ 40μm). The transition and end slabs have still mainly small size Al₂O₃ blocks, but appear few big size (≥ 100 μm) composite inclusions.