Dynamic Surface Tension Behavior of Liquid Iron during Carburization and Decarburization Processes

A new technique to study the kinetics of the carburization and decarburization processes of liquid iron is proposed. A liquid iron droplet was electromagnetically levitated in a CO–CO2 gas mixture during carburization and decarburization, and its surface oscillation was continuously recorded using a high-speed camera. The surface tension varied depending on each elementary step in the carburization and decarburization processes. This behavior was caused by transient adsorption and desorption of oxygen on the surface of the liquid iron accompanied by CO and CO2 gases. The kinetics of the carburization process were discussed and the conclusion was drawn that the desorption rate of oxygen adatoms in the form of CO2 was predominantly controlled by the gas-phase mass transfer.