Investigation on Nonmetallic Inclusions of LCAK Steel in LF Secondary Refining

Investigation was made on non-metallic inclusions in LCAK liquid steel during LF secondary refining for thin slab casting. It was found that, in the refining when high basicity and reductive slag was used, transfer of inclusions of Al2O3 in liquid steel took place first to inclusions of MgO-Al2O3 system and then to inclusions of CaO-MgO-Al2O3 and CaO-CaS-Al2O3 system. At the end of refining, there had almost no Al2O3 inclusions in liquid steel. So, the amount of calcium used for modifying Al2O3 inclusions in later Ca treatment to ensure the castability of the steel could be reduced.