PURPOSE: To execute vacuum treatment under good operability while reducing Cr oxidation loss due to low C content level and restrained metal scattering by blowing oxygen for decarburizing under vacuum and the specific flow rate of gas for stirring molten metal to intensely stir the molten metal.
CONSTITUTION: A cover 52 for vacuum seal is set to a ladle 51 for conveying molten metal charging the molten stainless steel 11 and inside of the ladle 51 is evacuated with a vacuum exhaust device 57 to the prescribed vacuum degree. Successively, the oxygen for decarburizing is supplied through a top blowing oxygen lance 53 and also the stirring gas is supplied from tuyeres 54 to stir the molten metal 11. In the vacuum treatment of the stainless steel, the gas for stirring molten metal is blown at the flow rate of 0.05W1Nm3/ min.ton of the molten steel. Further, the blowing flow rate F0 of the oxygen for decarburizing is decided with F0≤A.B.α.[C] (wherein, A, B: parameters, α: stirring force, [C]: carbon content in the molten steel, α: 0.1W0.5 of correction factor). Further, it is desirable to restrain sticking of the scattered metal to the cover 52, etc., by holding free board to 2W5m.
TAKAHASHI KENJI
INOUE SHIGERU
TANABE HARUYOSHI
KAWAKAMI MASAHIRO
TERADA OSAMU
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