| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a dephosphorization treatment method capable of carrying out a dephosphorization treatment of molten pig iron with high efficiency and stably obtaining a low expansion slag while limiting use of a CaF<SB POS="POST">2</SB>source such as fluorite without positively using an Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>source. <P>SOLUTION: The dephosphorization treatment of molten pig iron is carried out by spraying a powdered CaO source together with a gaseous oxygen of 1.6 to 2.1 Nm<SP POS="POST">3</SP>/min per 1 ton of the molten pig iron from a top blowing lance onto the molten pig iron using the powdered CaO source and a massive CaO source in a smelting furnace having a top and bottom blowing function. The powdered CaO ratio is set to 20 to 40% to control a slag basicity after the dephosphorization treatment to 1.9 to 2.2 while limiting use of the CaF<SB POS="POST">2</SB>source such as fluorite to 0.8 kg or less per 1 ton of the molten pig iron without positively adding an Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>source. Simultaneously, during supplying the top blown oxygen, an atmospheric pressure in the smelting furnace is controlled to 15 to 35 Pa after 10% of a total top blown oxygen supply time passes from supply start of the top blown oxygen till 90% of the total top blown oxygen supply time passes. <P>COPYRIGHT: (C)2013,JPO&INPIT |
