Controlling dissolved oxygen content in molten steel
AssigneeInland Steel Company
InventorsHoward M. Pielet, Larry A. Frank, William Edgar, Milan Alavanja
Life of this patent
Estimating the term…
Abstract
The dissolved oxygen content in a bath of molten steel is controlled, in one embodiment, by diluting a slag layer atop the bath with an oxide such as lime (CaO), to reduce the percentage of MnO and FeO in the slag, and stirring the bath of molten steel. In another embodiment, a gaseous mixture of an inert gas and carbon monoxide is disequilibrium with the carbon and dissolved oxygen content is bubbled through the bath.
Claims21
A method for treating, outside of a steel refining furnace, a bath of molten steel containing carbon and dissolved oxygen, said method comprising the steps of:
- preparing untreated molten steel in a steel refining furnace;
- pouring said untreated molten steel into a vessel to form therein a bath of molten steel;
- covering said bath in said vessel with a slag layer;
- diluting the slag in said slag layer with a diluent oxide;
- said slag layer comprising an oxide other than said diluent oxide which, in the percentage thereof existing in the undiluted slag, was in or was moving toward equilibrium with the dissolved oxygen in said bath;
- and stirring said bath;
- said diluting step comprising decreasing the percentage of said other oxide in said slag, thereby disrupting said equilibrium or said movement thereto, and causing to form, at the molten steel bath-slag layer interface, additional amounts of said other oxide which are absorbed into said slag layer as a result of the tendency to reestablish an equilibrium between said other oxide in the slag layer and the dissolved oxygen in the bath;
- whereby the dissolved oxygen content of said bath is decreased while the formation of oxides within said bath is avoided.
A method for treating, outside of a steel refining furnace, a bath of molten steel containing carbon and dissolved oxygen, said method comprising the steps of:
- preparing untreated molten steel in a steel refining furnace;
- pouring said untreated molten steel into a ladle;
- flowing said molten steel from said ladle into a tundish to form therein a bath of molten steel;
- covering said bath in said tundish with a slag layer;
- and diluting the slag in said slag layer with a diluent oxide;
- said slag layer comprising an oxide other than said diluent oxide which, in the percentage thereof existing in the undiluted slag, was in or was moving toward equilibrium with the dissolved oxygen in said bath;
- the area of the molten steel bath-slag layer interface in said tundish being substantially greater per unit mass of molten steel than the surface area per unit mass of molten steel in said ladle;
- said diluting step comprising decreasing the percentage of said other oxide in said slag, thereby disrupting said equilibrium or said movement thereto, and causing to form, at the molten steel bath-slag layer interface, additional amounts of said other oxide which are absorbed into said slag layer as a result of the tendency to reestablish an equilibrium between said other oxide in the slag layer and the dissolved oxygen in the bath;
- whereby the dissolved oxygen content of said bath is decreased while the formation of oxides within said bath is avoided.
A method for treating, outside of a steel refining furnace, a bath of molten steel containing carbon and dissolved oxygen, said method comprising the steps of:
- preparing untreated molten steel in a steel refining furnace;
- pouring said untreated molten steel into a vessel to form therein a bath of molten steel;
- covering said bath in said vessel with a slag layer;
- said slag layer comprising an oxide which is in or is moving toward equilibrium with the dissolved oxygen in said bath;
- stirring said bath;
- and changing the dissolved oxygen content of said bath to a predetermined desired level by changing, in said vessel, the percentage of said oxide in said slag, thereby disrupting said equilibrium or said movement thereto, whereby there is a change in the respective percentages in the molten steel of dissolved oxygen and of the cation of said oxide;
- continuing the change in percentage of said oxide in said slag until the percentage of said oxide in the slag layer is substantially in equilibrium with said predetermined desired level of dissolved oxygen in the bath;
- and avoiding the formation of oxides within said bath.
A method for changing the dissolved oxygen content of a bath of molten steel containing dissolved oxygen and carbon, said method comprising:
- determining the dissolved oxygen content and carbon content of said bath;
- introducing into said bath a gaseous mixture comprising an inert gas and carbon monoxide;
- mixing said gaseous mixture within said bath;
- providing said gaseous mixture with a percentage of carbon monoxide different than that which is in equilibrium with the dissolved oxygen content and carbon content of said bath;
- whereby there is a change in the proportion of carbon monoxide in said gas and a change in the proportion of dissolved oxygen and carbon in said molten steel bath toward the percentages of each at which equilibrium exists;
- and continuing said introducing and mixing steps until the dissolved oxygen content in said bath changes to the desired level.
Dependencies are inferred from the claim text.