Thermodynamic Calculation And Experiment On Direct Alloying By Niobium Concentrate

Niobium is a very excellent steel alloying elements..Baotou Bayan Obo Multi-Metallic Resources is the largest Nb mineral resources in China,which has very important value in use.The content of niobium has reached5%in the niobium concentrate which after the processing of dressing.This kind of niobium concentrate has very low phosphorus and other impurity elements.In order to make full use of this part of niobium resources in the niobium concentrate, In this paper,combining the thermodynamic calculation and experiment method,make the thermodynamic studies of directly alloying with niobium concentrate instead of FeNb alloy in refining environment.By using the thermodynamic calculation software FactSage to make the thermodynamic calculation that effect of different (Nb2O5) activity coefficient、different content of slag、different reducing agent、temperature on distribution of niobium in the slag and steel;Using the Molecular ions coexistence theory make the calculation of the CaO-SiO2-Al2O3-FeO-Nb2O5slag system elements activity changes with basicity changes from1-5.Also make the calculation that the chang regulation of the reaction between [C] and [Si] with (Nb2O5)’s ΔG,which changes with temperature and basicity changes.By using the result of slag and steel equilibrium to make the preliminary estimation of the activity coefficient of (Nb2O5)’s order of magnitude range under the calculation of this slag system.The following conclusions are obtained:(1)Though the FactSage equilibrium’s calculation we can draw the conclusion:The value of [Nb]/(Nb2O5) increases with the activity coefficient of (Nb2O5) increases,which becomes one of the important thermodynamic factors that has an influence on directly alloying;Under high temperature,The reducer [C]’s ability is good,under high basicity, The reducer [Si]’s ability is great. The value of [Nb]/(Nb2O5) decreases with the content of (FeO) increases,(Al2O3) is good for reducer [Si].(TiO2) has no significant effect. (2)By using molecular ion coexistence model’s calculation indicates:The calculation of the activity of (Nb2O5) in this slag system decreases with the increaseof basicity;The activity coefficient of (Nb2O5) is about10-3-10-6range;The reaction of [C] and (Nb2O5)’s ΔG decreases as the temperature increase and increases as the basicity increase; The reaction of [Si] and (Nb2O5)’s ΔG decreases as the basicity increase and increases as the temperature increase.(3)The results of slag steel equilibrium experimental indicates:Steel-slag equilibrium’s time needs more than1and a half hours;With the increases of basicity from1-5,[Si] decreases obviously,and [Nb] increases a little.The slag basicity in equilibrium is lower than the prepared slag basicity.The recuction rate of (Nb2O5) is low relatively,the highest is10.3%.Make the estimation of the activity coefficient of (Nb2O5) in equilibrium decreases with the basicity increases from1-5,and changes in about10-3-10-6,and results of activity coefficient of (Nb2O5) which are in good agreement with the calculated by molecular ion coexistence model.