Abstract: There is proposed a method for preliminary treatment of molten iron wherein heat source for dissolving scrap is ensured sufficiently to improve iron yield while decreasing phosphorus concentration efficiently by suppressing the amount of flux solvent used in the process of desiliconization, dephosphorization and decarburization. In the method for preliminary treatment of molten iron by conducting desiliconization and dephosphorization of molten iron with a converter type container, molten iron is first charged into the converter type container to conduct desiliconization and then intermediate slag removal is conducted, and subsequently a lime-based flux solvent is added to the container while blowing oxygen to conduct dephosphorization of the molten iron, and thereafter newly untreated molten iron is charged into the container to conduct desiliconization, and subsequently the above treatments are repeatedly conducted with the same container.

Abstract: In a molten iron refining method by charging molten iron and a cold iron source into a converter type refining vessel, supplying a material containing CaO with an oxygen source dissolving the cold iron source and conducting molten iron desiliconization, removing at least a part of the produced slag as an intermediate slag removal, and supplying a slag-forming agent and an oxygen source to the molten iron for dephosphorization, a silicon-containing material or a combination of it and carbonaceous material is added in the desiliconization then carried out under conditions such that the slag basicity (mass % CaO/mass % SiO2) in the desiliconization completion is more than 0.5 but less than 1.5 and a molten iron temperature in the desiliconization completion is more than 1280° C. but less than 1350° C. and more than 30 mass % of the slag produced in the desiliconization is removed from the vessel in the intermediate slag removal.

Abstract: There is proposed a method for preliminary treatment of molten iron wherein heat source for dissolving scrap is ensured sufficiently to improve iron yield while decreasing phosphorus concentration efficiently by suppressing the amount of flux solvent used in the process of desiliconization, dephosphorization and decarburization. In the method for preliminary treatment of molten iron by conducting desiliconization and dephosphorization of molten iron with a converter type container, molten iron is first charged into the converter type container to conduct desiliconization and then intermediate slag removal is conducted, and subsequently a lime-based flux solvent is added to the container while blowing oxygen to conduct dephosphorization of the molten iron, and thereafter newly untreated molten iron is charged into the container to conduct desiliconization, and subsequently the above treatments are repeatedly conducted with the same container.

Abstract: In a molten iron refining method by charging molten iron and a cold iron source into a converter type refining vessel, supplying a material containing CaO with an oxygen source dissolving the cold iron source and conducting molten iron desiliconization, removing at least a part of the produced slag as an intermediate slag removal, and supplying a slag-forming agent and an oxygen source to the molten iron for dephosphorization, a silicon-containing material or a combination of it and carbonaceous material is added in the desiliconization then carried out under conditions such that the slag basicity (mass % CaO/mass % SiO2) in the desiliconization completion is more than 0.5 but less than 1.5 and a molten iron temperature in the desiliconization completion is more than 1280° C. but less than 1350° C. and more than 30 mass % of the slag produced in the desiliconization is removed from the vessel in the intermediate slag removal.