Numerical Calculation Of Thermodynamics-Kinetics For Inclusion Behavior On Aluminum And Titanium Deoxidation In Liquid Steel

Non-metallic inclusions are a key issue during the production of high performance steels,as they influence the microstructure and structural properties to a large extent.They are often considered as harmful to the final product quality and to the steel processing productivity,so researchers pay more attention on promoting inclusions removal.The development of oxide metallurgy,the high quality steel product depends on the fine inclusions.In both cases,the key issue is to control the characteristics of the inclusion distribution in the liquid steel,such as number density,composition,morphology,size and spatial distribution.Based on the previous experimental data and the existing thermodynamic data,the thermodynamic calculation was performed to analyze the chemical reaction product and the chemical reaction equilibrium constant in the Fe-Al-0 ternary system and the Fe-Ti-O ternary system.At first,the thermodynamic calculation was applied to analyze the critical Ti concentration where Ti3O5 coexisted with Ti2O3 in the Fe-Ti-O ternary system by Wagner's formalism and quadratic formalism with Redlich-Kister type polynomial.Then,the research about the size distribution of the inclusion after deoxidation with AI/Ti in the steel liquid was studied by the model of inclusion nucleation and growth.Numerical results are showed as follows:(1)The value of Itoh is recommended for the standard Gibbs free energy and the interaction parameters between dissolved Al and O.? G?(J·mol-1)=-867300+222.5T,eOO=0.76-1750/T,eOAl ?1.90-5750/T,eAlO =3.21-9720/T,eAlAl =80.5/T,rOAl<=0.0033-25.0/T,rAlO=-107+275000/T,rO(Al,O)=-127.3-327300/T,rAl(O,Al)=0.021-13.78/T.(2)With the increase of the value of w[Al]in the liquid,the value of w[O]decreases firstly and then increases,but the value of a[O]decreases and the value of a[Al]increases monotonically in liquid iron at 1873K.the trend of deoxidation equilibrium with Ti are generally similar to the with Al.the upward part of aluminum-oxygen equilibrium curve is caused by the first-order and the second-order interaction parameter,and the second-order interaction parameter affect the upward degree of the aluminum-oxygen equilibrium curve.(3)When a[O]<0.219,during the steelmaking process,the chemical reaction product is only titanium oxides in the Fe-Ti-O ternary system at 1873K.With the increase of the value of w[Al]in the liquid,the value of w[O]decreases firstly and then increases.(4)The value of Cha is recommended for the equilibrium constants and the interaction parameters between dissolved Al and O.lgKTi3O5=-68280/T+19.95,lgKTi2O3=-42940/T+12.94,eOO=0.76-1750/T,eOTi=0.0344-710/T,eTiO=2.994 eOTi-0.00867,eTiTi=212/T-0.0640.(5)The critical Ti concentration corresponding to coexistence of Ti3Os and Ti2O3 was 0.358 mass%by Wagner's formalism,meanwhile,0.526 mass%by quadratic formalism with Redlich-Kister type polynomial.(6)Second order interaction from the present experimental results due to the lack of experimental accuracy.The interaction parameters in Redlich-Kister type polynomial can be converted into Wagner's interaction parameters.(7)Under different stirring intensities,inclusion size distribution for alumina and titanium oxides is lognormal distribution.With the increase of turbulent energy dissipation rate,the inclusion size distribution curve is slimmer.With the increasing interfacial free energy,the peak-value diameter decreases and the maximum number density increases.As time goes on,the law on the contrary.(8)The inclusion size distribution for Ti2O3 is on the left curve of TibO5.