Composition for reducing the oxygen potential of slag

Abstract

A slag composition containing steelmaking slag and from about 0.3 to about 10 weight percent of reducing agent. The steelmaking slag contains from about 20 to about 55 weight percent of calcium oxide, from about 8 to about 50 weight percent of ferrous oxide, from about 4 to about 20 weight percent of magnesium oxide, from about 8 to about 30 weight percent of silicon oxide, from 0.5 to about 10 weight per cent aluminum oxide, and from about 0.5 to about 10 weight percent of manganese oxide. The reducing agent contains from about 15 to about 70 weight percent of calcium carbide and from about 10 to about 50 weight percent silicon carbide, wherein the ratio of calcium carbide to silicon carbide is between 0.7 and 7.

Description

[0001]This invention relates in one embodiment to an additive for making a ladle slag composition used in steel making, and more particularly to an additive that that reduces the oxygen potential of slag.BACKGROUND[0002]1. Field of the Invention[0003]Additives used in steel making for improving the composition of slag disposed on molten steel during the steel making process.[0004]2. Description of Related Art[0005]Slag is a mixture of metal oxides and other non-metallic components, which is typically found in partially molten liquid form floating upon the surface of molten steel during a steel making process. During steel making, the molten steel and slag may be contained in an open vessel known as a ladle. The composition of the slag during steel making is critical in achieving the desired composition of the finished steel.[0006]Heretofore, a number of patents and publications have disclosed compositions for synthesizing and / or optimizing and / or treating ladle slag in steel making....

AI Technical Summary

Benefits of technology

[0016]It is therefore an object of this invention to provide an additive for treating ladle slag specifically for steel grades that are restricted from the use of aluminum as a reducing agent, which more readily facilitates the production of the desired ladle slag than prior art compositions.

Problems solved by technology

One problem with the Kemeny et al composition is that is takes a relatively long period of time for it to treat the slag in order to produce the desired slag composition.

The reaction of the Kemeny et al composition is endothermic and therefore the progress of the reaction is often limited by heat transfer to the reactants.

It is common that the rate limiting step in steel production is the treatment of slag in the ladle.

However, this reagent mixture can be used only for those grades of steel for which the process route allows for the use of aluminum as a reducing agent.

Many grades of steel are restricted from the use of aluminum as a reducing agent because this may cause processing problems with the steel in subsequent downstream operations such as casting.

Conversely, the addition of aluminum to the slag as a reducing agent may significantly decrease the fraction of solid in the slag, thereby requiring the addition of a slag thickening agent, such as lime, to counter the fluidizing effect.

In steel making, there is often a “see-saw” effect, in which reducing agent, is used, causing a high viscosity problem which halts the reducing reaction; then excessive fluidizer is used to lower the viscosity, which causes refractory erosion and heat loss.

Slag requiring a large amount of deoxidation often leads to breaks in the process flow due to the excessive time used up by this see-saw effect.

Extended cycle time and yield loss result from this effect.

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