STEEL MAKING METHOD

摘要

PURPOSE: To increase the utilizing ratio of inexpensive cold iron sources and to inexpensively produce low-phosphorus steel with excellent productivity by using two units of converter type refining furnaces and separately executing preliminary dephosphorization refining and decarburization steel making and refining of molten steel. CONSTITUTION: The molten iron 5 is charged into the converter type refining furnace 3 having an oxygen top blowing lance 1 and refractory lance 2 and a slag forming agent and dephosphorizing agent are blown from the lance 2 into the furnace to form molten slag 6. The prerefining including dephosphorizing is executed by blowing an oxygen gas jet 8 from the oxygen lance 1 and thereafter the molten iron subjected to the prerefining is transferred into another converter type refining furnace. The molten iron is refined to the molten steel by the decarburization reaction by oxygen blowing. The dephosphorization prerefining and the decarburization steel making and refining are executed by such two-stage refining method. The inexpensive iron sources, such as steel scrap 7, are respectively dividedly used, by which the dephosphorization defect by the excessive charging of the steel scrap and the decarburization reaction defect by an insufficient heat quantity are prevented. The use of a large amt. of the steel scrap is thus made possible and the low-phosphorus steel having excellent quality is stably produced.