| 摘要 |
PURPOSE: A secondary refining method of molten steel is provided which secures high cleanliness of molten steel at low cost to manufacture ferrite stainless steel for deep drawing. CONSTITUTION: The secondary refining method of ferrite stainless steel comprises a step of discharging molten ferrite stainless steel together with slag having basicity (CaO/SiO2) of 1.6 to 2.2 from an argon oxygen decarburization refining furnace to a ladle formed of alumina; a step of injecting fluorite (CaF2) into the ladle in the state that slag is floated on an upper part of the molten ferrite stainless steel; and a step of performing bottom bubbling in the ladle, wherein slag before pouring the molten ferrite stainless steel to the ladle comprises 2.0 wt.% or less of Al2O3 and 1.0 wt.% or less of TiO2, wherein 1.0 to 3.0 tons of slag per 90 tons of ladle is floated on an upper part of the molten ferrite stainless steel in the ladle, wherein 20 to 40 kg of fluorite per ton of slag is fed into the ladle, wherein the molten steel is bottom bubbled to an agitation flux of 3.0 to 6.0 L/ton of the molten steel for 15 minutes or more in the bottom bubbling step, and wherein the ferrite stainless steel is a ferrite stainless steel for deep drawing comprising 16.0 to 18.0 wt.% of chromium (Cr), 0.12 wt.% or less of carbon (C) and 0.01 wt.% or less of sulfur (S).
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