PURPOSE: To improve the dephosphorization effect of molten steel with slag of less Fe content by controlling the basicity and T, Fe amounts of the slag to the specific value after ending of oxygen blowing and flushing at the time of performing steel smelting by an oxygen top blowing converter provided with bottom tuyeres.
CONSTITUTION: At the time of performing steel smelting by decarbonizing molten iron with an oxygen top blowing converter having a bottom blowing function, CaO- contg. flux is added to the molten iron in such a manner that the basicity of the molten slag i.e. CaO/SiO2 beomes 2 or more at the end of blowing. In addition, the FeO in the molten slag is so controlled as to become ≥10% in T, Fe equiv. by increasing the amount of oxygen blown or added iron ore, sintered ore, etc. Next, an inert gas such as Ar gas is blown at a rate of ≥5Nm3/hr per ton of the molten steel through the bottom tuyeres, whereby flushing is accomplished. While the amount of loss of Fe into the molten slag in the form of FeO is being reduced, the P in the molten steel is easily oxidized to P2O5 to form stable compound with CaO and slag, whereby dephosphorization reaction is accelerated.
HIRAI MASAZUMI
IIDA HIROSHI
MURAKAMI SHIYOUZOU
| JPS55164014A | 1980-12-20 |