DIRECT STEEL ALLOYING BY MANGANESE UNDER RECENT CONDITIONS OF ELECTRIC STEEL-MAKING

Abstract

One of the directions of increasing production efficiency in ferrous metallurgy is reduction of expensive and scarce ferroalloy consumption. Great opportunities in that direction are provided by technology of direct steel alloying by oxide materials. Thermodynamic study of the process of direct steel alloying by manganese oxide materials (manganese ore) and industrial testing of that technology has been done in that work. Two options of direct alloying technology have been considered: during steel melting in modern 100-ton EAF in oxidative conditions and during processing of steel on ladle furnace (LF) in reductive conditions. Thermodynamic modeling of oxidative technology option by TERRA software package has shown that there is opportunity to increase content of manganese in metal by manganese ore injection. Key factor in that process is current carbon content in steel. Content of manganese can be raised up to 0.6 % and more in medium and high-carbon steel. Residual manganese in low-carbon steel is defined by value of carbon content in the end of oxygen lancing. Graphic dependence is provided. MnO + Si = Mn + SiO 2 is main reaction of the process of direct alloying under reductive conditions. Thermodynamic analysis gives very rough data. That is why semi-empirical analysis was performed, which was based on received industrial results of FeO and MnO proportion contained in slag in the end of steel processing at LF. That way of process estimation is considered reasonable, because of approximation to balance of metal-slag system during long processing of steel at LF. Using this proportion, and conditions of slag initial basicity retaining and maintaining of FeO content in slag at level around 1 %, balance equation describing process of direct steel alloying by manganese ore at ladle was derived. This equation helps to calculate basic technological parameters of the process of direct alloying by manganese ore as applied to specific conditions of production. Good convergence of theoretical calculation and practical data has been received.