Visualization of collision and aggregation behavior of particles simulating movement of inclusions in molten steel

Abstract

Inclusions with sizes less than 1 μm in molten steel are difficult to float up to the molten steel and slag interface owing to their slow terminal velocity. Thus, increasing the size of inclusion is essential for accelerating the removal of inclusions. Polystyrene particles simulating inclusions in molten steel were quantified by direct observation of the particle collision behavior in a turbulent flow in a water model. The box-counting fractal dimension of particles was calculated by processing the binary images of aggregated particles. The fractal dimension of the outer contours of the single plastic particles was smaller than that of the aggregated particles. The fractal dimension was varied from 1.14 to 1.35. When two or more monomer particles collide, the aggregates are separated more easily, as the temperature increases from 40 to 80 °C. The aggregated particles were loose and easy to separate in the high-temperature aqueous solution. The effect of temperature on the surface tension of liquid and the interfacial tension of solid and liquid is obvious. The particles are wetting in the water solution at a temperature more than 60 °C. The relationship between the velocity of the particles and the fractal dimension of the solid particles with the equivalent diameter was discussed.