The precipitation of non‐metallic inclusions in Ti‐deoxidised steels is analysed with the multiphase equilibrium code CEQCSI which is based on the IRSID slag model. For that purpose, the slag model has been extended to systems containing titanium oxides, using data available in the literature, and validated with industrial results obtained on various steel grades. Applications concerning slag‐metal reactions in ladle metallurgy are described. 2 applications concerning inclusions in Ti‐deoxidised steels are also presented: (a) experimental study of the effect of steel contamination by magnesia refractory lining on the composition of oxide inclusions in a Ti‐deoxidised steel: there is a good correlation between analysed oxide compositions and compositions predicted by the model; (b) evaluation of the optimised steel composition to obtain Al2O3‐TiO2 inclusions during solidification for steels pertaining to the so‐called “metallurgy of oxides in steels”.

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A bibliographical review of the most recent developments in slag modelling approaches, published since the 5th International Conference on Molten Slags, Fluxes and Salts, is presented, and the trends in using this information in Computational Thermodynamics software/database packages are outlined. Industrial applications based on examples pertaining to various iron-and steelmaking reactors are discussed. These applications are made essentially with the IRSID slag model and the CEQCSI software. They concern metal refining or micro alloying by slag-metal reactions and inclusions control in steels.

In order to find a method to characterize the inclusion distribution of high-cleanliness materials, complementary techniques were tested, such as high-frequency (80 MHz) ultrasonic testing, X-ray tomography or Extreme Value Analysis (EVA). The micro-cleanliness was also characterized by standard methods based on observations of polished surfaces by light optical or scanning electronic microscopy. The combination of all these techniques, enhanced by metiS software, allows us to determine the complete 3D distribution of oxides or to estimate the probability of largest inclusion size by modelling virtual samples. At the end, fatigue testing was performed in order to try to link fatigue results to previous characterization outcomes.

A bibliographical review of the most recent developments in slag modelling approaches is presented. It covers the period posterior to the publication in the 2nd edition of Slag Atlas of the comprehensive review by Kowalski, Spencer and Neuschütz of thermodynamic models and databases for calculation of phase diagrams and thermodynamic properties of slags. The trends in using this information in computational thermodynamics software/database packages are outlined. Industrial applications based on examples pertaining to various iron‐and steelmaking reactors are discussed. These applications made essentially with the Irsid slag model and the CEQCSI software concern steel refining or microalloying by slag‐metal reactions in the ladle, steel‐refractories interactions, and inclusions control in steels.