| 摘要 |
<p>PURPOSE:To efficiently execute desulfurize-refining to molten steel by restraining metallic oxide quantity in molten slag on the surface of molten steel in a ladle, circulating the molten steel in a vacuum vessel in an RH vacuum degassing apparatus and injecting CaO-base flux after raising the molten steel temp. CONSTITUTION:The molten steel 3 is charged into the ladle 2 and the total content of FeO and MnO in the molten slag on the molten steel is restrained to <=5wt.% and oxidizing property of the molten slag 8 is made to be low. Immersion tubes 1a, 1b in the RH vacuum degas- refining apparatus are dipped into the molten steel 3 in the ladle, and the air is exhausted and the pressure is reduced in a vacuum vessel 5 and the molten steel 3 is sucked into the vacuum vessel 5 through the immersion tube 1a and returned back into the ladle 2 through the immersion tube 1b, while circulating the molten steel, oxygen-containing gas is blown into the molten steel in the vacuum vessel 5 through a top-blowing lance 6. Further, Al is charged and the molten steel temp. is raised by combustion heat of Al and also the flux 7 for desulfurizing mainly containing CaO as the desulfurizing agent is added from the top- blowing lance 6 at 1kg/ton of the molten steel, In this case, the depth of the molten steel in the vacuum vessel 5 is made to be shallow to make the contact between the flux 7 and the molten steel good and the extremely low steel is stably produced.</p> |
