Observation and measurement of bubble separation at liquid steel–slag interfaces

The separation of bubbles at liquid steel–slag interfaces is interesting due to its importance in the formation of subsurface defects during casting. X‐ray fluoroscopy was used to observe argon bubbles separating at a carbon saturated liquid iron–slag interface. It was found that rest times at the interface are significant and range from 0.1 to 8 s depending upon the experimental conditions for bubble sizes ranging from 7 to 12 mm in diameter. Rest‐time distributions were found to be a function of slag chemistry and temperature (due to viscosity and interfacial tension changes), bubble size and reaction rate when there was a slag–metal reaction that occurred during the experiment. The phenomenon was highly variable and could only be studied statistically, indicating that current models of film drainage and rupture do not completely describe the key variables that affect the phenomena.