Quantitative Thermodynamic Criterion for TiC Precipitation in Molten Iron Under Industrial Blast Furnace Conditions

In this study, the thermodynamic conditions governing TiC formation were systematically investigated based on Gibbs free energy and interaction parameter theory. The effects of temperature and furnace atmosphere on interaction parameters were explicitly incorporated, enabling an improved thermodynamic description of TiC formation under realistic blast furnace conditions. Furthermore, compared with conventional two-dimensional equilibrium analyses, a three-dimensional Ti-C-temperature thermodynamic precipitation surface was established to quantitatively evaluate the effects of temperature, titanium content, and carbon content on TiC precipitation behavior. The results indicate that titanium is the dominant controlling factor for TiC formation, while carbon plays a secondary synergistic role. Compared with dissolved carbon, solid carbon provides more favorable thermodynamic conditions, suggesting that TiC preferentially forms via interactions with high-activity carbon sources such as coke or refractory materials. Based on the modified thermodynamic framework and boundary conditions, a quantitative precipitation criterion was established as 100 × w[Ti]% + w[C]% ≥ 10, which ensures TiC precipitation prior to molten iron solidification under representative blast furnace hearth conditions. The proposed criterion provides a practical guideline for titanium addition and carbon regulation in blast furnace ironmaking and improves the thermodynamic prediction capability for titanium-bearing protective phase formation in complex high-temperature metallurgical environments.