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

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 + SiO₂ 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.

thermodynamic analysis, direct alloying, manganese oxide, ladle furnace, out-of-furnace processing, manganese ore, oxygen lancing, slag

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