Method for Re-blowing Molten Steel in Converter Steel Making Process

摘要

PURPOSE: A method for re-blowing molten steel in converter steelmaking process is provided to lower content of£P|during re-blowing than target content of£P|and prevent injection quantity of deoxidizer and increase of inclusions due to oxygen increase at finishing point, prevent increase of dissolved nitrogen by air sucked during re-blowing and improve productivity. CONSTITUTION: In a molten steel re-blowing method performed in case that there is something wrong with£P|in constituents of molten steel(3) in converter steelmaking process. the method comprises a step of blowing molten steel by maintaining a lance at an elevation 10 to 50 cm higher than a standard lance height, lowering oxygen flow rate as much as 5 to 15% compared with a standard oxygen flow rate and blowing oxygen under the conditions that the total oxygen blowing amount is calculated by the following relational expression 2 if£C|content in molten steel at a time point corresponding to 70 to 80% of the total blowing time is 0.6 wt.% or more and temperature of molten steel is 1,560 deg.C or more in a blowing process in which deoxidizer is injected during tapping, or£C|content in molten steel at a time point corresponding to 70 to 80% of the total blowing time is 0.6 wt.% or more and temperature of molten steel is 1,600 deg.C or more in a blowing process in which deoxidizer is not injected during tapping:£Relational Expression 2|, total oxygen blowing amount=£C|content(wt.%)x40(Nm¬3)+300¯800 Nm¬3/min; a step of positioning the lance at an oxygen lance height (Y) obtained by the following relational expression 4 if K value is deviated from the range of 0.9 to 1.4 by substituting the measured oxygen amount for the following relational expression 3 after measuring oxygen amount at finishing point: £Relational Expression 3|, K=oxygen at finishing point/500, £Relational Expression 4|, Y=(L/2-i)/tan x, where Y is height of oxygen lance(2), L is diameter of furnace mouth(11), i is a distance between lance nozzle ports, and tan x is nozzle injection angle or inclination angle; and a step of performing re-blowing by blowing 1.0 to 1.8 Nm¬3/molten steel-ton of oxygen into converter(1) after positioning the lance at the oxygen lance height (Y).