Multiscale Mechanisms of Ti(C,N) Precipitation Suppression in Oxygen Blast Furnace Smelting of Vanadium–Titanium Magnetite

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Abstract
The oxygen blast furnace (OBF) process provides a promising pathway for the efficient and low-carbon smelting of vanadium–titanium magnetite (VTM). In this study, Ti(C,N) precipitation in hot metal under OBF conditions was systematically investigated through thermodynamic analysis, in situ confocal scanning laser microscopy (CSLM), and molecular dynamics (MD) simulations. Thermodynamic calculations show that decreasing the N₂ mole fraction increases the critical Ti content required for Ti(C,N) precipitation while reducing the equilibrium amount of precipitated Ti(C,N). At an N₂ mole fraction of 1%, the theoretical equilibrium amount of precipitated Ti(C,N) decreases by 57%. CSLM observations further reveal that OBF conditions suppress the nucleation, growth, and agglomeration of Ti(C,N), thereby decreasing the average equivalent particle size compared with conventional blast furnace conditions. MD simulations reveal that the lower nitrogen content reduces Ti–N coordination and inhibits the formation and sustained growth of TiN clusters, resulting in smaller and less stable clusters with higher average atomic energies.

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