Experiment Research On Oxidation Desilication In The Niobium-bearing Hot Metal

In strength, toughness and weldability of the steel，Niobium steel has favorableconditions than other steels. Moreover, Niobium alloy steels are developed rapidly in theentire world everywhere. Baogang molten irons have important Niobium. In order toproduce Niobium steel, our project team has brought forward the“Direct Alloying method”.one of content in the method is the research of Pre-Desiliconization in the Niobium-bearingHot Metal，which is my issue. In addition, it also provide a theoretical basis ondephosphorization and decarburization in following process.Through thermodynamic calculation analysis, Equilibrium and Kinetics of tests,double-film theory and coupled reaction, the oxidation process of the niobium-bearing hotmetal is accentually analyzed.The following results are obtained:（1） Carrying out Equilibrium test, the effect of adding CaO is very important for thepoint of desiliconization and Retain niobium. when slag containing CaO, Silicon has beenoxidized to0.1%, niobium is oxidized quickly。In the above condition, the point ofdesiliconization and Retain niobium has reduced0.7%than the case of without CaO.（2） Through thermodynamic calculation, we can known that the lower temperatureis, the better desiliconization and Retain niobium shows; when at the condition oftemperature1350℃and adding CaO and γ_Nb2O5=10^-10 in the slag, the point ofdesiliconization and Retain niobium is the lowest.（3） Designing desiliconization with sinter ore, we know that the silicon manganese andniobium in the molten iron are all oxidized，with a pity that the requirements of thedesiliconization and Retain niobium is not achieved; the smaller the sinter ore grain is,themore quickly the reaction rate;the lower the temperature is, the lower the equilibriumcontent in the iron is;when lower temperature、more slag and smaller grain,it is morebeneficial to reach the purpose of the desiliconization and Retain niobium.（4） Based on the double-film theory, we can conclude that in the case of slag containingCaO, the desiliconization and deniobium reaction is speeded remarkably. In the actualcondition, the calculation is based on the different controlling steps determined by therelative concentration of silicon in the iron and （FeO） in the slag.（5） The experiment process of desilication kinetics is simulated by coupling reactionmodel. The effects of the amount of slag,（FeO） ratio in slag, the initial silicon content andmass transfer coefficient on the dynamic process of desilication are analyzed and discussed.With the increase of the amount of slag, a higher （FeO） proportion in the slag, improvementof the initial silicon content, the oxidation rate of niobium with silicon is speeded up.