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US 6,547,849 B2Granted
Ladle refining of steel
AssigneeNucor Corporation
InventorsClay Gross, Rama Ballav Mahapatra, Walter W. Blejde, Steve Leonard Wigman
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AssigneeNucor Corporation
InventorsClay Gross, Rama Ballav Mahapatra, Walter W. Blejde, Steve Leonard Wigman
Estimating the term…
A steel charge and slag forming material is heated in a ladle to form molten steel covered by a slag containing silicon, manganese and calcium oxides. The steel is stirred by injection of an inert gas such as argon or nitrogen to cause silicon/manganese-deoxidation and desulphurization to produce a silicon/manganese killed molten steel. Stirring of the molten steel by the inert gas injection while in contact with slag high in calcium oxide generates low free oxygen levels in the steel and desulphurization to sulphur levels below 0.009%. The slag may subsequently be thickened by lime addition to prevent reversion of sulphur back into the steel and oxygen may be injected into the steel to increase its free oxygen content to produce a steel that is readily castable in a twin roll caster.
A method of refining steel in a ladle, including heating a steel charge and slag forming material in a ladle to form molten steel covered by a slag containing silicon, manganese and calcium oxides, wherein the molten steel has a carbon content in the range 0.001% to 0.1% by weight, a manganese content in the range of 0.1% to 2.0% by weight and a silicon content in the range 0.1% to 10% by weight, and stirring the molten steel by injecting an inert gas into it to cause silicon/manganese deoxidation and desulphuization of the steel to produce a silicon/manganese killed molten steel having a sulphur content of less than 0.01% by weight.
A method of refining steel in a ladle, including heating a steel charge and slag forming material in a ladle to form molten steel covered by a slag containing silicon, manganese and calcium oxides, and stirring the molten steel by injecting an inert gas into it to cause silicon/manganese deoxidation and desulphuization of the steel to produce a silicon/manganese killed molten steel having a sulphur content of less than 0.01% by weight, wherein at the conclusion of desulphurization, the slag is thickened to prevent reversion of sulphur into the steel and oxygen is injected into the steel to increase the free oxygen content thereof.
Dependencies are inferred from the claim text.