METHOD FOR REFINING MOLTEN STEEL FOR ULTRA LOW CARBON STEEL

摘要

PURPOSE: A method for refining molten steel is provided which is capable of stably controlling concentration of carbon in molten steel to 15 ppm or less by optimizing reflux gas blowing patterns so as to improve decarburizing control capacity in vacuum facility. CONSTITUTION: In a method for refining molten steel for ultra low carbon steel using a vacuum degassing facility, the method comprises the steps of controlling reflux gas flow rate to 1.5 to 2.0 Nm¬3/min until an internal degree of vacuum of the vacuum degassing facility reaches 2 torr or less during the initial stage of decarburizing; controlling the flux gas flow rate to 1.5 to 3.0 Nm¬3/min until CO content in flue gas exhausted from the facility reaches 2% or less; and controlling the flux gas flow rate to 3.5 Nm¬3/min or more by decarburizing completion time point.