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

对金属液中夹杂物颗粒团聚的机理尚不清楚，无法获得高纯度的金属制品。在以往的包裹体颗粒团聚的研究中，考虑了流体动力对颗粒间碰撞的影响，忽略了颗粒间作用力如范德华力的作用，而这对颗粒团聚的过程是很重要的。在本研究中，为了弄清在金属液态湍流中颗粒间力在夹杂颗粒团聚中的作用，进行了以下研究。聚苯乙烯-乳胶颗粒在水溶液中的团聚实验：测定了粒径均匀的球形聚苯乙烯-乳胶颗粒（PSL）在nacl溶液中的团聚曲线。将由流体力学和质点间力组成的团聚理论计算得到的团聚曲线应用于颗粒上，得到了更多实测的团聚曲线，确定了范德华力特征的Hamaker常数。该值与PSL的文献价值吻合较好。本文提出了一种新的数学模型（分组模型），用一种简单的方法来估计团聚颗粒的大小分布。SiC颗粒在水溶液中的团聚实验：以SiC颗粒为夹杂颗粒模型，在搅拌nacl溶液中测量团聚曲线。研究发现，团聚颗粒的破碎发生在团聚的后期。对分组模型进行修正，加入破碎现象，并采用实测团聚曲线，得到SiC的Hamaker常数，与文献值一致。SiC颗粒在铝液中的团聚实验：构建了超声波均质机，并成功应用于SiC颗粒在铝液中的分散。初步实验发现，在湍流搅拌作用下，铝液中出现了碳化硅颗粒的团聚现象。但由于重现性问题，未能对团聚现象进行定量分析。研究了铝液中SiC颗粒在电磁搅拌作用下的行为，清楚地观察到电磁力对颗粒的分离作用。在实验中，平均粒径为13μm和23μm的颗粒被使用，当颗粒较大时，在团聚之前会进行分离。相反，发现较小的颗粒先凝聚后分离。综上所述，本研究明确了颗粒间力在夹杂物团聚中的重要性，并提出了进一步了解夹杂物颗粒在液态金属中团聚机理的措施。少

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