FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy and can be used for secondary refining of molten steel. Method comprises forming slag containing CaO and Al2O3, by a combination of the step of introducing Al into the molten steel in the form of Al metal to obtain an Al-containing molten steel and the step of introducing CaO into the molten steel in the form of a material containing CaO, and then performing the process oxygen purging, including process of denitrogenation by blowing molten steel oxygen gas. Al concentration [Al]i (wt.%) in molten steel immediately before oxygen blowing is equal to or exceeds the value [Al]e, calculated by formula based on specific power ε (W/t) of mixing during slag formation. Concentration of aluminium [Al]f at the end of the oxygen blowing process is in range of 0.03 wt.% to 0.06 wt.%. In another method, slag containing CaO and Al2O3, and removing nitrogen and sulphur from the molten steel by blowing with oxygen gas, during the oxygen blowing process, the Al concentration in the molten steel is maintained from 0.05 wt.% to 0.48 wt.% and adjusting the ratio C/A (-) between the concentration of CaO (wt.%) and the concentration Al2O3 (wt.%) in slag in range from 1.8 to 2.2 inclusive.
EFFECT: efficient removal of nitrogen or nitrogen and sulphur from molten steel.
9 cl, 9 dwg, 2 tbl, 6 ex
