| 摘要 |
<P>PROBLEM TO BE SOLVED: To remove phosphorus from molten iron at a dephosphorization ratio of 80% or higher without using a fluoride-containing sub raw material as a dephosphorizing agent and without causing spitting and slopping even for 5-8 min of supply time of top-blowing oxygen. <P>SOLUTION: There is provide a dephosphorization method for molten iron which uses a top and bottom-blowing converter, starts spray of 40% or more of CaO mass to be supplied as the dephosphorizing agent, to the molten iron concurrently with start of the supply of the top-blowing oxygen or by the time of elapse of 1 min, and sets a slag basicity at the completion time of the dephosphorization treatment to be 2.0-2.9. The method satisfies a first and a second condition. In the first condition, ladle slag or calcium ferrite is charged before supplying the top-blowing oxygen or just after starting this supply. In the second condition, the ladle slag is charged before supplying the top-blowing oxygen or before elapse of 21% of the whole supplying time of the top-blowing oxygen and the calcium ferrite is charged before supplying the top-blowing oxygen or before elapse of 28% of the supplying time, and Al<SB POS="POST">2</SB>O<SB POS="POST">3</SB>concentration in the slag at the completion time of the dephosphorization treatment, is adjusted to 6-12%. <P>COPYRIGHT: (C)2012,JPO&INPIT |
