INTERACTION FORCE BETWEEN PARTICLES SUSPENDED IN LIQUID METAL IN THE CASE OF TURBULENT AGGLOMERATION

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The mechanism of the agglomeration of inclusion particles in liquid metal is not made clear enough for achieving the highly clean metal products. In the previous studies on the agglomeration of inclusion particles, the hydrodynamic effect on the collision between particles is taken into account, however, the role of inter-particle force such as van der Waals force has been disregarded, which is important for the process of particle agglomeration. In the present study, the following investigations have been made to make clear the role of inter-particle force in the agglomeration of inclusion particles in turbulent flow of liquid metal.1. Experiment on the agglomeration of PSL particles in aqueous solution : Agglomeration curves of polystyrene-latex particles (PSL) which had a uniform size and spherical shape were measured in an agitated NaCl-aqueous solution. By applying the calculated curve obtained by the agglomeration theory composed of hydrodynamics and inter-particle force on the m … More easured agglomeration curves, the Hamaker constant, the characteristic of the van der Waals force, was determined. This value agreed well with the literature value of PSL. A mathematical model (grouping model) was newly developed to estimate the size distribution of agglomerated particles by a simple procedure.2. Experiment on the agglomeration of SiC particles in aqueous solution : SiC particle was used as the model of inclusion particle and agglomeration curves were measured in an agitated NaCi solution. It was found that the breakup of agglomerated particles took place in the later stage of agglomeration. The grouping model was modified to include the breakup phenomenon and adopted measured agglomeration curves, and as a result, the Hamaker constant of SiC was determined, which agreed with the literature value.3. Experiment on the agglomeration of SiC particles in molten aluminum : An ultrasonic homogenizer was constructed and adopted successfully to the dispersion of SiC particles in molten aluminum. Agglomeration of SiC particles in the molten aluminum under turbulent agitation was observed in some preliminary experiments. However, quantitative analysis of agglomeration was not carried out because of the problem of the reproducibility. The behavior of SiC particles in molten aluminum was investigated under the electromagnetic agitation and the separation of particles by the electromagnetic force was clearly observed. In the experiment, particles with 13μm and 23μm in average diameter were used, and in the case of larger particle, separation was found to proceed before agglomeration. On the contrary, the smaller particle was found to agglomerate first and then be separated.In conclusion, the importance of inter-particle force in the inclusion agglomeration was made clear and the measure for understanding the mechanism of inclusion particles in liquid metal was given in this study. Less