PURPOSE: To collectively use a converter to a pre-treatment process and to improve the drastic heat tolerance by removing slag after executing desiliconizing and dephosphorizing refining to molten iron in the converter under a specific bottom-blowing gas stirring, and successively, executing the decarburizing blowing.
CONSTITUTION: In the converter having the bottom-blowing function, the desiliconizing and dephosphorizing refining of the molten iron is executed. At this time, the bottom-blowing gas flow rate is controlled so that the stirring energy defined by the equation becomes ≥0.5kw/T. Further, after this treatment, the refining is executed so as to become <2.0 slag basicity (CaO/SiO2) and ≥5% iron oxide content. After this refining, the blowing is temporarily stopped, and by tilting the furnace, the slag in the furnace is discharged. This slag becomes high in forming level by the bottom-blowing gas and is efficiently removed. After completing the slag-off, successively the decarburizing blowing is executed.
KOIZUMI FUMIO
MASUMITSU NORIYUKI
