Kinetics of inclusion precipitation during steel solidification

The precipitation of non-metallic inclusions (complex oxides, sulphides, ni trides.,,) during steel solidification is analysed using the multiphase equ ilibrium code CEQCSI and a nucleation and growth model. The CEQCSI code is based in part on the Irsid slag model, and it provides an evaluation of the composition of inclusions formed at equilibrium, as well as guidelines for industrial treatments in order to reach desirable compositions in semi-kil led steel grades. The nucleation and growth model can be applied to the for mation, during steel solidification, of stoichiometric compounds or liquid oxide inclusions. Two particularities of this kinetic model are that nuclea tion and growth are treated simultaneously, and they compete in consuming t he supersaturation at each moment, and that a mixed controlled growth model transport/interfacial kinetics at the precipitate/liquid steel interface i s considered. The predicted size distribution of TiN precipitates formed in two steel grades is in good agreement with the results of laboratory exper iments. In the case of liquid oxide precipitation, the first calculations i ndicate that the composition of inclusions can be significantly different f rom that of inclusions assumed to precipitate under equilibrium conditions.