| 摘要 |
The present invention provides a method for refining a molten chromium-containing steel by decarburization according to a combined-blown process, which contributes to an improvement in decarburization rate and realizes efficient decarburization while preventing [Cr] contained in the molten steel from being oxidized. The method is characterized in that, in a region where the [C] concentration of the molten chromium-containing steel is not less than 0.15%, oxygen or a gas mixture of oxygen with an inert gas is blown through a top-blown lance onto the surface of the molten steel under the following conditions: (1) the velocity of the gas immediately after spouting through one or at least two nozzle holes of the top-blown lance is not less than the velocity of sound; and (2) the ratio of the length h of a zone, in the vicinity of the surface of the molten steel, where the gas jet velocity is less than the velocity of sound, to the minimum hole diameter d0 of said nozzle, h/d0, is not more than 60, provided that when gas jets blown through a multihole nozzle overlap each other with a degree of overlap beta , a requirement represented by the formula h/d0x(1- beta )</=60 is met.
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