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A mathematical model was developed to investigate the effect of snorkel shape on the recirculation rate and the erosion of the lining refractory during RH degassing process. A particle image velocimetry technique was used to measure the velocity distribution in a water modelling experiment. The calculated results were well validated with the measured ones. In the mathematical model, the interfaces between the molten steel and the gas phase, and the motion of argon bubbles were simulated and tracked using VOF + DPM model by which the argon bubbles were treated as the discrete phase in the molten steel and the top gas phase, and the top gas phase was treated as a second continuous phase. It was found that the recirculation rate of the molten steel with oval snorkels was significantly larger than that with round snorkels. For round snorkels, the optimum gas flow rate was 1800 L min −1 and it was 2800 L min −1 for oval snorkels. Furthermore, the volume distribution of the argon in the radial direction of the upsnorkel with oval snorkels was much more homogeneous than that with round snorkels. Meanwhile, the predicted maximum wall shear stress showed that the bottom and the sidewall of the ladle with round snorkels were more seriously eroded than that with oval snorkels. Therefore, the oval snorkel was beneficial to improve the service life of the RH degasser.

A kinetic model was developed to investigate the evolution of inclusions during the Ca treatment of Al-killed steels. Evolutions of steel chemistry and inclusion composition in Al-killed Ca-treated steels from previous experimental works were accurately predicted using the current kinetic model. The model was widely used to predict the evolution of inclusions during the Ca treatment of Al-killed steels with varying concentrations of Al, S, O and Ca. During the Ca injection of Alkilled steels, a large number of CaS and CaO inclusions are transiently generated in the Ca-rich zone due to the excessive Ca. Al 2 O 3 inclusions are gradually modified to calcium aluminates in the bulk steel with the addition of Ca. The superfluous Ca or S may lead to the formation of solid CaS in the liquid steel.

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