| 摘要 |
<p>PURPOSE: To efficiently execute a dephosphorizing treatment while carburizing molten iron by inserting a lane into molten iron and injecting dephosphorizing flux and coke powder from different depths into the molten iron. CONSTITUTION: The molten iron is charged into a molten iron ladle PL provided with a free board F, and a triple-tube lance R is inserted into the molten iron from the upper part and coke powder having <=1mm grain diameter is blown into the molten iron together with gaseous nitrogen from a tuyere N2 arranged at the lower end part thereof. O2 gas and CaO base dephosphorizing flux are blown from a tuyere N1 at the upper part thereof and also, iron oxide powder as oxidizer of P is changed onto the molten iron. In this case, at the time of using Ho (mm) for the molten iron in a molten iron vessel PL, Hp (mm) and Hc (mm) for the depth position from the molten iron surface to the tuyeres N1 and N2 , respectively, these relations are made to Hc /Ho >=0.6 and Hc -Hp >=300 mm to oxidize P in the molten iron and P is formed to slag and the dephosphorization is executed. Further, the lowering of temp. of the molten iron is prevented with increase of C content as the heat source at the time of decarburize-refining in the following process by carburizing the molten iron and the using ratio of the steel scrap as cold material can be improved.</p> |
