METHOD FOR MANUFACTURING HIGH CLEANLINESS STEEL CONTAINING LOW PHOSPHORUS AND LOW CARBON

摘要

PURPOSE: A method for manufacturing high cleanliness steel containing low phosphorus and low carbon is provided to secure cleanliness in molten steel of the steelmaking process and improve actual yield by adopting a process of reducing phosphorus in molten steel and preventing generation of lower oxides in molten steel. CONSTITUTION: In manufacturing low carbon steel containing phosphorus concentration of 0.017% or less and carbon concentration of 0.015 to 0.060% through converter tapping, ladle slag deoxidizing and RH processes, the method for manufacturing high cleanliness steel containing low phosphorus and low carbon comprises a step of dephosphorizing molten steel during tapping, wherein slag basicity is increased by injecting quicklime and fluorite into molten steel containing a converter finishing point oxygen of 400 ppm or more during tapping, and dephosphorizing efficiency is maximized by temperature drop; a step of deoxidizing slag by injecting slag deoxidizer into ladle slag to reduce lower oxides after the tapping is completed; and a step of reflux molten steel to flotation separate alumina that is a deoxidized product by deoxidizing molten steel using Al after lowering dissolved oxygen in molten steel before deoxidization by injecting manganese alloy iron into molten steel at the end of decarburizing in an RH degassing process of treating the molten steel in ladle passing through the slag deoxidizing step under the decreased pressure conditions.