A method for desulfurizing the molten steel in use for ultra low-sulfur steel

摘要

PURPOSE: A method for efficiently desulphurizing molten steel for manufacturing ultra low sulphur steel is provided to improve a desulphurization ratio of molten steel 20 to 30% more than an existing method, thereby stably manufacturing steel in which 10 ppm or less of sulphur content are required by deciding injection order and method of subsidiary raw materials and optimizing the operation pattern depending on a dissolved carbon level in molten steel and the tapping hole condition of a converter when terminating blowing in the converter process. CONSTITUTION: In a method for desulphurizing the molten steel after passing molten steel discharged from a converter through the bubbling process, the method comprises the steps of transferring the molten steel passing through the bubbling process to an LF (ladle furnace); preparing top slag having a superior sulphur distribution ratio £Ls=(%S)/(%S)|by dividedly injecting subsidiary raw materials into molten steel twice in the order of slag deoxidizer, CaO-Al2O3 flux, calcium oxide and silica (SiO2), and dolomite as increasing a temperature of the molten steel in the LF; and simultaneously carrying out top and bottom bubbling right after completing the temperature increasing operation of the molten steel so as to promote the reaction of the obtained top slag with the molten steel.