Abstract: The bottom blowing gas supply intensity of 120 t top and bottom combined blowing converter was increased from 0.026 m3/(t·min) to 0.103 m3/(t·min), which provides dynamic conditions for molten steel. At the same time, the bottom slag layer thickness was reduced from 200-300 mm to 50-100 mm, reducing gas supply resistance, increasing the dynamic conditions of molten steel, strengthening the stirring of molten steel, promoting the carbon oxygen reaction and reducing the end point oxygen content of molten steel. The [%C][·[%O] in the end-point of converter was reduced from 0.003 1 to 0.002 3, and the FeO mass fraction in the end-point slag was reduced from 18.64 % to 18.12 %, which effectively improves the cleanliness and quality of molten steel.

Key words: top and bottom combined blowing, [%C]·[%O], cleanliness