Prediction of Behavior of Alumina Inclusion in Front of Solid–Liquid Interface in SPFH590 Steel

To predict the behavior of an alumina inclusion in front of the solid–liquid interface during solidification, the interfacial tension between SPFH590 micro-alloyed steel and alumina was experimentally determined. The surface tension of the micro-alloyed steel was measured by the constrained drop method, and the contact angle between the micro-alloyed steel and alumina was investigated by the sessile drop method. Temperature was controlled within the range of 1823 K to 1873 K, and the sulfur concentration in the steel was set in the range of 11 to 94 ppm. With increasing temperature, the surface tensions of steel samples decreased. Further, with increasing temperature, the contact angles of the samples containing 11 to 72 ppm sulfur decreased whereas that of the sample containing 94 ppm sulfur increased. The experimental data were then used to calculate the interfacial tension between the micro-alloyed steel and alumina according to Young’s equation. With increasing temperature, the interfacial tensions of the samples containing 11 to 72 ppm sulfur decreased whereas that of the sample containing 94 ppm sulfur increased. The behavior of an alumina inclusion in front of the solid–liquid interface in the SPFH590 steel was predicted using the calculated interfacial tension values. It was estimated that an increase in the sulfur concentration from 5 to 10 ppm caused a transition of the inclusion from being in an entrapped state to being pushed away from solid–liquid interface.