Motion of small particles in solution with an interfacial tension gradient and engulfment of the particles by solidifying interface

Abstract

In order to clarify the behavior of small non-metallic inclusions and bubbles in liquid steel in front of an advancing solid-liquid interface, the force acting on a particle, and the velocity of the particle, due to the interfacial tension gradient between particle and solution, were investigated theoretically and experimentally. The force and the velocity are theoretically described as a function of particle radius, viscosity of solution and interfacial tension gradient. The velocity of small bubbles in a water solution with C18H29SO3Na concentration gradient was observed. The theoretical equation derived in this paper can describe experimental results of the velocity. The critical solidifying velocity from particle pushing to engulfment by the interface was evaluated qualitatively by combining the effect of interfacial tension gradient induced by concentration and temperature gradient formed in boundary layer in front of the solid-liquid interface with the treatments developed by the previous investigators based on the wettability of the particle with the solid and liquid.