Method for desulfurizing molten pig iron

Abstract

A method for the desulfurization of molten pig iron which comprises submerging a submersion-type free board and an injection lance in molten pig iron within a ladle and blowing an inert gas and CaO powder into the molten pig iron through the injection lance to desulfurize the molten pig iron, and which is provided with the step of adding metallic Al to the surface of the molten pig iron after theoxygen partial pressure within the submerged free board has been lowered to 0.1MPa or below by blowing the inert gas into the submerged free board and before 30mass% of the total CaO powder used has been blown into the molten pig iron.

Description

technical field [0001] The present invention relates to a method for desulfurizing molten iron by immersing a free board and a spray gun in molten iron in a molten iron tank, blowing inert gas and CaO powder from the spray gun, and in particular It relates to a molten iron desulfurization method in which metal Al is added to improve the reaction efficiency of CaO. [0002] This application is based on and claims priority to Japanese Patent Application Publication No. 2008-228502 filed on September 5, 2008, and the content thereof is incorporated herein. Background technique [0003] Since the molten iron from the blast furnace contains a lot of sulfur (S) that adversely affects the quality of the steel, desulfurization of the molten iron is performed as a process of the pretreatment of the molten iron. On the other hand, in recent years, the demand for the production of high-grade steel has increased, and the adoption of a cheaper low-sulfurization treatment method has been...

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Problems solved by technology

[0009] However, since the method described in this patent document 2 is treated in the atmosphere without using immersion free space, etc., the oxygen in the atmosphere reacts with the added Al, so the

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