Effect of CaO on the ionic microstructure and properties in dephosphorization slag by molecular dynamics simulation.

• The intermediate state of P 2 O 5 dissolved in molten slags was studied by molecular dynamics simulation. • The influence of CaO content on the microstructure and properties of molten melt was studied. • The microstructure transformation mechanism of phosphate clusters was illustrated. The microstructure of dephosphorization slag determines its macroscopic properties. Dephosphorization process affects the dissolution of P 2 O 5 in the slag and changes the dephosphorization conditions. In this paper, molecular dynamics simulation was used to study the effect of composition on the microstructure and macroscopic properties of CaO-P 2 O 5 binary system, which have a significance effect on the dissolution mechanism of P 2 O 5 in slag in the steelmaking field. The microstructure of the melt was described by radial distribution function, cluster proportion, bond angle distribution and so on. The diffusion coefficient, viscosity, thermal conductivity and surface tension were calculated to describe the macroscopic properties of the molten slags. The results show that the P-O bond length changes from 1.45 to 1.55 as the content of CaO increases from 50 % to 70 %. The planar [PO 3 ]- anions gradually transform into tetrahedral [PO 4 ]3- anions with increasing X CaO , and finally the [PO 4 ]3- clusters occupy the majority. Ca exists as free cation and plays the role of charge complement in molten CaO-P 2 O 5 melt. The order of diffusion ability of elements is O2– > Ca2+ > P5+ as X CaO increases from 50 % to 70 %. The viscosity of the system tends to decrease. The dilution of P-O clusters is enhanced with the increase of X CaO. The thermal conductivity and surface tension shows an upward trend. [ABSTRACT FROM AUTHOR]