Steel making process
AssigneeNippon Steel Corporation
InventorsRyoji Arima, Kazushige Umezawa, Tokuzo Nisugi
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Abstract
Molten steel in desiliconized, dephosphorized and decarburized in a three-step sequence. In the first-two steps the melt is agitated. In the first step the temperature is also maintained at between 1480.degree.-1380.degree. C. while oxygen is introduced until the silicon content is reduced to 0.20%. In the second step a flux consisting essentially of CaO and 0.2-0.5 parts by weight of CaCl.sub.2 and/or KCl is introduced while maintaining the basicity of the slag at between 3.5-8.0 and the T.Fe value at between 3-10%. The third step involves blowing oxygen onto this melt without using a refining flux.
Claims16
A steelmaking process for desiliconizing, dephosphorizing, desulfurizing and decarburizing molten iron from a blast furnace, comprising the following sequence of steps:
- (1) a first step of agitating the molten iron in a vessel, supplying the molten iron with both gaseous oxygen and, an iron oxide contanitive material reducing the Si content in the iron to a value between 0.05 and 0.20% at a controlled bath temperature between 1480 and 1480.degree. C., and discharging the resulting slag;
- (2) a second step of agitating the molten iron from the first step having a bath temperature between 1380.degree. and 1380.degree. C., supplying the molten iron with a flux consisting essentially of CaO and 0.2 to 0.5 parts by weight of CaCl.sub.2 or KCl or both CaCl.sub.2 and KCl per part by weight of CaO and a source of oxygen, maintaining the basicity of the processing slag between 3.5 and 8.0 and the T.Fe value between 3 and 10%, desulfurizing and dephosphorizing the iron with the same slag to reduce the P, S and Si contents to no higher than 0.025%, 0.020% and a trace, respectively, and to hold the C content not lower than 3.8%, and discharging the resulting slag;
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- (3) a third step of decarburizing the molten iron from the second step by blowing oxygen onto the melt without using a refining flux.
Dependencies are inferred from the claim text.