Effect of Oxygen at Basic Oxygen Furnace Endpoint on Control of Inclusions in a Si-Mn Killed Steel

The existence of the dissolved aluminum and other impurity elements in alloys would inevitably lead to the formation of the Al2O3 component of inclusions in Si-Mn killed steels. Herein, the effect of dissolved oxygen at the endpoint of basic oxygen furnace (BOF) on the control of inclusions in a Si-Mn killed steel is investigated. With the increase in the dissolved oxygen at the BOF endpoint, the (FeO + MnO) content in the refining slag increases and the dissolved aluminum in the steel decreases as a whole. Meanwhile, the proper increase in the dissolved oxygen hardly deteriorated the cleanliness of the steel. As the equilibrium dissolved oxygen at the BOF endpoint increased from 148 to 402 ppm, the Al2O3 content of inclusions could be lowered to <4 wt%. Both industrial trials and the thermodynamic consideration indicate that increasing the dissolved oxygen at the endpoint of BOF can be an efficient approach to achieve the ultralow Al2O3 content of inclusions in the Si-Mn killed steel due to the oxidation of the dissolved aluminum by the oxygen both in the molten steel and in the refining slag.