METHOD FOR MANUFACTURING ULTRA LOW CARBON STEEL

摘要

PURPOSE: Provided is a method for manufacturing an ultra low carbon steel with a carbon content of less than 70 ppm in steelmaking process by reducing the generation amount of non metallic inclusions in RH vacuum degasser. CONSTITUTION: The method includes the steps of measuring oxygen content in molten steel with a sampling device at a time when 2 to 3 minutes have passed after start of molten steel refining in RH vacuum degasser; calculating the amount of aluminum to be added to the molten steel during decarburization on the basis of measured oxygen content of the molten steel; adding aluminum to the molten steel in an amount of 0.04 to 0.08 kg/ton, wherein the aluminum pouring is started from a time when about 4 minutes have passed after start of molten steel refining at a time interval of 0.5 to 1 minute for 4 to 8 minutes; and refluxing the molten steel for a fixed time after adding the aluminum into molten steel.