PURPOSE: To efficiently execute the refining in a converter while generating less splash and dust with high secondary combustion rate by blowing gaseous oxygen from plural nozzles each having a specific size and shape toward molten steel surface at a specific distance.
CONSTITUTION: In the top-blowing or the top and bottom combined blowing converter, the gaseous oxygen is spouted from a top-blowing lance to execute a decarburize-refining of the molten steel. In the refining method, 2-20 pieces of top-blowing gas spouting nozzle in the top-blowing lance are provided. Further, this nozzle shape is made to be rectangle, ellips, circular arc or combined shape thereof. Further, at the time of using Y for the short side length of each nozzle, W for the area of opening hole part and X=W/Y, the top-blowing lance of X/Y=30-300 is used and the distance between the nozzle tip and the molten steel surface is made to be (10-30)×X0.9×Y0.1. By this method, the errosion of the refractory and the development of the dust are regulated less and the refining can be executed with high iron yield.
NAITO KENICHIRO
SASAGAWA SHINJI
KIKUCHI MAKOTO
