| 摘要 |
PURPOSE:To melt extremely low sulfut content steel and lower the contents of other impurities at the same time, by applying strong desulfurization blowing at specified period during smelting time and promoting desulfurization by making desulfurization optimum condition of low O2 partial pressure, and consecutively maintaining strong reducing atmosphere in the furnace. CONSTITUTION:After desulfurizing S in molten pig iron to less than 0.10% preliminarily outside the furnace, the desulfurized slag is separated by keeping the temperature above 1200 deg.C. The desulfurized molten pig iron is charged in a bottom blown converter equipped with double tube tuyere, and oxidizing gas such as O2 is blown in to form a steel pit of more than 3.5% C concentration and more than 1200 deg.C bath temperature. Then, while blowing calcined plaster powder with inert gas, proective gas of HC compound base is blown in from the tuyere outer tube to maintain strong reducing atmosphere in the furnace, and the S content is reduced to less than 0.002%, in particular less than 0.002%. Next, refining gas such as O2 is blown in from the tuyere inner tube, and CaO powder is blown in from the tuyere inner tube at the same time to prevent return flow into the molten steel. Then, the steel is discharged from the furnace. |
