HIGH SPEED BLOWING METHOD FOR CONVERTER

摘要

PROBLEM TO BE SOLVED: To secure an excellent dephosphorization function, while improving a slag formation rate of CaO and shortening blowing time.SOLUTION: A blowing method of an upper bottom blowing converter manufacturing a molten steel from a molten pig iron to which a molten pig iron preliminary dephosphorization treatment is not applied includes adjusting a charge basicity calculated by the formula (I)=3.0 to 4.0 with a molten pig iron having [Si] concentration in the molten pig iron=0.40% to 0.60% by mass% as a target, and adjusting an AlOmass concentration in a slag after the completion of blowing=4.0% to 6.0% by using CaO-AlOmultiple oxide as an AlOsource charged into a furnace and adjusting a [C] concentration in the molten steel=0.05 mass% or less and a molten steel temperature=1630°C to 1690°C after the completion of blowing. Charge basicity=(mass of CaO charged into the furnace)/(mass of Si in the molten steel charged into the furnace ×2.14+mass of SiOcharged into the furnace) (I)