Abstract: The size, number, morphology and type of inclusion particles are the key factors to estimate the quality of steel product. Although considerable efforts have been made in the mathematical modeling of inclusion growth, few papers were involved in inclusion0s nucleation and collision-growth, and all the existing researches about the behaviors of magnesia inclusion were based on the experiments. Thus, a mathematical model was developed to investigate the nucleation, Ostwald ripening and collision-growth of magnesia inclusion in the molten steel. Numerical results showed that the predicted particle size distributions are consistent with the previous experimental data. For the magnesia inclusions smaller than 100 nm, Brownian collision is the main
collision modes. For the inclusions ranging from 0.1 to 10 μm, Brownian collision and turbulent collision are the main collision modes. For the inclusions ranging from 10 to 100 μm, turbulent collision and Stokes collision are the main collision modes. Thus, the strong turbulent flow can decrease the peak-value diameter of the magnesia inclusion effectively.

Key words: Magnesia, Homogeneous nucleation, Ostwald ripening, Brownian collision, Stokes collision, Turbulent collision, Particle size distribution