METHOD FOR PRODUCING HIGH-CLEANNESS STEEL

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PURPOSE : A method for producing high-cleanliness steel is provided to reduce manufacturing costs and to produce steel products without defects by increasing the cleanliness of the steel with a circulation-type vacuum degassing device.CONSTITUTION : A method for producing high-cleanliness steel is as follows. In killed treatment, cold materials are added while circulating gas having 4 L(Normal)/min·t or more of flow rate circulates molten steel. While the temperature of the molten steel is adjusted, a circulating time (T) after the addition of the cold materials is set. The circulating time after the addition of the cold materials satisfies next equation. Equation : T (min) >= 0.25 W (kg/t) + 2 In the equation, W means an amount of the added cold materials per 1 ton of the molten steel.[Reference numerals] (AA) Backflow gas flow rate : 8L(Normal)/min·t; (BB) Backflow time after inserting a refrigerant(min); (CC) Rate of inclusion generation 0.01 piece /cm^2; (EE) Refrigerant input amountCOPYRIGHT KIPO 2013