Abstract
In order to investigate the influence of the surface-active element on the interfacial phenomena between molten iron and molten Al2O3-CaO-SiO2 slag, a mildly surface-active element, nitrogen, was introduced, and the interfacial phenomena were directly observed using an X-ray sessile drop method. The multiphysics model was employed to calculate the velocity of the Marangoni convection caused by the surface/interfacial tension gradient along with the contour of the sessile drop. Movement of the sessile drop was observed in the experiment, and the driving force of the movement was discussed from the distribution of surface tension active element viewpoint. The calculated velocity of the Marangoni convection in the droplet was reasonably agreed with the literature data for the metal-gas system, and thus, the same model was applied for the metal-slag system. The velocity of the Marangoni convection for the metal-slag system becomes ten times lower compared to that of metal-gas system.Graphical abstract
Highlights
The Marangoni convection is a flow along with surface/interface caused by the surface tension gradient along with the surface/interface, and such surfaceinterfacial tension gradient is induced by (1) the temperature gradient, (2) the concentration gradient of surface-active elements and (3) the electrical potential gradient
The present study is a collaboration between the interfacial tension measurement project by the Japan Aerospace Exploration Agency (JAXA) and the project for the measurement of viscosity of molten slag, and interfacial tension measurement which is funded by Swedish National Space Agency (SNSA)
(2) Marangoni convection in the droplet, which is induced by the nitrogen concentration gradient between the bottom part and top part of the droplet
Summary
The Marangoni convection is a flow along with surface/interface caused by the surface tension gradient along with the surface/interface, and such surfaceinterfacial tension gradient is induced by (1) the temperature gradient, (2) the concentration gradient of surface-active elements and (3) the electrical potential gradient. Apart from above-mentioned phenomena, the dissolution and adsorption rate of nitrogen gas into molten iron and desorption rate of nitrogen from molten iron were studied by many researchers, and it is concluded that the experimental results can be explained so-called blocking mechanism [17, 18] and change in the surface tension gradient (surface activeness), i.e. Marangoni convection [19, 20]. Some researches on the effect of surface-active elements on the interfacial phenomena between molten slag and molten metal, including the movement and deformation of the sessile drop have been done [27,28,29,30,31]. In the present experiment, the nitrogen as a surfaceactive element was introduced to the molten iron droplet, which is immersed in the Al2O3-CaO-SiO2 molten slag, through the dissolution of boron nitride and the interfacial phenomena (movement and shape of the iron droplet) was observed using X-ray furnace. A recrystallised Al2O3 reaction tube, with an inner diameter of 60 mm, was positioned vertically in the furnace
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