METHOD FOR REFINING HIGH MANGANESE EXTRA-LOW CARBON STEEL

PROBLEM TO BE SOLVED: To adjust Al content in molten steel at only one time of Al-deoxidize-treatment without needing the plurality of times for Al component adjustments, when a high Mn extra-low carbon steel is refined by using Mn ore as Mn source and combining a converter and a vacuum-degassing facility. SOLUTION: When the high Mn extra-low carbon steel having 0.4-2.0 mass% Mn content is refined by applying a vacuum-decarburize-refining and an Al-deoxidizing treatment with the vacuum-degassing facility to the molten steel after steel-tapping off from the converter, in the converter, the decarburize-refining is performed by charging the Mn ore as the Mn source and in the Al-deoxidizing treatment after vacuum-decarburize-refining, Al-series deoxidizing agent of the quantity identical with the charging quantity calculated by formula (1): WAL=(A+α×[O]+β+γ×ΔMn)/B, is added. In the formula (1), WALis the charging quantity of the deoxidizing agent per the molten steel ton; A is the Al targeted value per 1 ton of the molten steel; [O] is an oxygen concentration in the molten steel; ΔMn is Mn concentrating variation (mass%) in the molten steel after vacuum-decarburize-refining just after steel tapping-off; B is an Al pure content in the deoxidizing agent; and α, β and γ are each a constant. COPYRIGHT: (C)2010,JPO&INPIT