Steelmaking additives are added to steel for several purposes. These include facilitating the removal of deleterious materials from the steel during the refining process. They also improve the basic steelmaking technology. The use of additives in these processes varies by steelmaker and the steelmaking method.
A steelmaking additive comprises a material with a melting point below 1600 degC. It is preferably a solid material comprising at least one oxide selected from the following classes: iron oxide, magnesium oxide, titanium dioxide, titanium oxyhydroxide, and manganese oxide. The addition of such a material to molten steel promotes the removal of deleterious materials and increases the formation of fluid basic slag. This enhances slag removal, which in turn increases the life of refractory linings. In addition, it may serve as a desulfurization additive.
Novel additive compositions have the potential to be added to tundish, ladle, furnace, or other steelmaking processes. These materials can be used to provide insulating blankets, increase reoxidation control, or remove undesired inclusions. Moreover, they can improve the desulfurization, solubilization, and cleanliness of molten steel.
Some of the known and commercially available additives have serious shortcomings. Hence, the invention is designed to provide a novel additive that possesses the properties to improve the art of making steel.
Novel compositions of the invention are also capable of enhancing the removal of unwanted inclusions in molten steel. Such compositions are added to tundish, furnace, or other steelmaking processes to provide an insulating blanket, to increase reoxidation control, to remove undesired inclusions, and to prevent recarburization. Other benefits include improved lining life and improved processing performance of steel.
One example of a preferred composition is a silicon manganese alloy, which is a strong deoxidizing agent and has good grain refining properties. Furthermore, it can be used to reduce the reoxidation rate of molten steel and to improve the hardness and wear resistance of cast iron.
Another preferred invention is the addition of a desulfurization additive during the manufacturing of a steel product. These additives can be used with other known or commercially available steelmaking additives to promote desulfurization of the molten steel.
A third preferred embodiment is the addition of a fluxing additive during the manufacturing of a steel product. This additive contains a mixture of at least 20 percent alumina and at least 10 percent metal oxides. The amount of such an additive in the tundish depends on the thickness of the blanket, the temperature profile, and the desulfurization requirements.
Other possible sources for the raw materials needed to produce novel compositions of the invention include slag material generated during the melting process of calcium metal and waste by-products from the production of other metals. The impurities of these materials can be used to make novel additives with lower melting points.
Preferred embodiments of the invention have been described, but modifications can be made by skilled artisans. In general, the additives of the invention are in the range of one part by weight for five to fifteen parts by weight of lime.
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