Enhanced Alloy Recovery In Molten Steel Baths Utilizing Cored Wires Doped With Dispersants

Abstract

The present invention provides increased recovery in additive-enhanced or alloy-enhanced molten steel. This is accomplished by dispersing agents blended with the additive alloys. The dispersant powder reacts with the carbon in the steel forming carbon monoxide gas which provides kinetic energy to the additive alloy particle causing dispersion within the molten bath, resulting in greater dissolution of the particles in the molten bath. The alloy or additive region is enriched, thereby improving the recovery in the molten steel.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to U.S. provisional application No. 60 / 938,670, filed on May 17, 2007, the disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to adding alloys to molten steel. More particularly, this invention relates to adding alloys and dispersants to molten steel in order to increase recovery in the steel.BACKGROUND OF THE INVENTION[0003]It is well known to add alloys and other additives to molten steel in order to improve the material properties, including strength and toughness, of the finished steel.[0004]In the prior art, adding alloys and additives to molten steel is often accomplished by encasing powdered alloys and additives in a metal sheath to form a “cored wire” which is subsequently “injected” into the molten steel. U.S. Pat. No. 4,128,414 describes such an injection process. To ensure good mixing of the steel, many steel making companie...

AI Technical Summary

Benefits of technology

[0012]The present invention may be embodied as a method for providing an additive alloy to molten metal, wherein at least one dispersing agent is blended with at least one solid additive dissolvable alloy to provide a blended substance. Preferably, the additive alloy is dissolvable. The blended substance may be encapsulated in a metal jacket to provide an alloy delivery device. Molten metal may be produced and the alloy delivery device may be injected into the molten steel. The delivery device may be injected into the molten steel by a wire injector and guide tube arrangement. The delivery device may be fed into the molten metal and the metal jacket may be allowed to melt in the molten metal, and once the jacket melts, the additive alloy, in solid particle form is allowed to mix with the molten steel, and the dispersing agent facilitates such mixing. Depending on the alloy, the solid alloy particles may melt, or not, after having been acted on by the dispersing agent.

[0013]It is well known that ground additive alloys (typically ground to powders under 1 mm in diameter) encased in a steel jacketed cored wire that is injected deep into molten baths results in a significant improvement in recovery. In this invention, the recovery is enhanced by blending limestone powder in varying amounts (typically, but not limited to, 5% to 50% of the mixture by weight or volume) with the additive alloy that is, at least initially, introduced to the molten steel as a solid particle. The limestone has been shown to react with the carbon in the molten metal resulting in a reaction that generates CO2 gas. This CO2 gas expands rapidly in the hot molten metal generating considerable stirring energy which imparts kinetic energy to the fine additive alloy powder upon release from the cored wire deep within the molten bath. The extra kinetic energy causes these fine particles to be further dispersed in the bath, thus, enriching the molten metal with their chemical elements in additive alloy depleted areas of the molten bath that, under normal cored wire injection methods, would not be enriched. As a result of particles being kinetically driven to further reaches of the bath, more of the bath becomes enriched, thereby increasing the recovery of the additive alloy.

[0014]Thus, the present invention provides an additive-enhanced or alloy-enhanced molten steel with improved recovery.

Problems solved by technology

Often, the stirring generated by such devices is not sufficient to achieve good mixing and, as such, a portion of the additive alloys injected into the molten bath will rise to the steel surface.

This is especially true in steel making operations with insufficient stirring capabilities.

This method, however, increases the oxygen and hydrogen content of the steel (oxygen is generally undesired in steel and hydrogen is always undesired in steel).

Further, due to the larger size of these additive alloy particles (generally on the order of 5 mm to 100 mm in diameter) and the method of adding bulk alloys to molten baths (e.g., hand additions of cans, bags, boxes or adding loose additions by shovel or by chute to the surface of the bath) the effectiveness of this dispersing method is reduced.

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