PURPOSE: To prevent the sticking of a base metal to a lance and to increase a decarburization rate by adjusting the vacuum degree in a reduced pressure chamber according to the carbon concn. in a molten steel in the decarburization refining of the molten stainless steel by a vacuum degassing device.
CONSTITUTION: The decarburization refining of the molten stainless steel is executed by blowing a gaseous mixture composed of oxygen and argon to the surface of the molten stainless steel in the reduced pressure chamber by using the vacuum degassing device. The vacuum degree in the chamber is maintained at 5 to 20Torr if the carbon concn. in the molten steel is below a certain value in a 0.10 to 0.05wt.% range and the vacuum degree in the chamber is maintained at a high vacuum degree of ≤3Torr if the carbon concn. is below a certain value of a ≤0.03wt.% region. The decarburization rate is increased without generating the sticking of the base metal to the lance in this way and the loss of Cr is decreased.
SAKURATANI TOSHIKAZU
TADA MUTSUMI
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