Effect of Inert Gas Flow Rate on Homogenization and Inclusion Removal in a Gas Stirred Ladle

Abstract

In the present study, the effect of gas flow rate on homogenization and inclusion removal in a gas stirred ladle was investigated. Both industrial trials and cold model experiments were conducted. CFD calculation was also carried out as an auxiliary tool. The mixing times predicted by CFD simulation agreed well with both the model experiments and industrial data. 99% mixing could be achieved in about 2–3 minutes. The increase of flow rate of inert gas would not improve the mixing substantially, while the mixing time decreased somewhat with the increase of gas flow rate. The water model study showed also that the gas flow rate had a negligible effect on the rate of inclusion removal. Both the experiments and CFD calculation strongly suggested that a low gas flow rate should be applied in the ladle treatment.

Effect of Stirring Practice on Sulphur and Nitrogen Refining as well as Inclusion Removal in Ladle Treatment

“…The removal of inclusion by gas bubbles has been the topic of modeling . Söder et al indicate that inclusion removal by bubble attachment is mainly seen for inclusions smaller than 25 μm.…”

“…The aims of ladle treatment are many, namely refining with respective to sulfur, nitrogen and hydrogen, fine adjustment of the steel composition, homogenization as well as heating of the melt to reach optimum casting conditions, and inclusion removal. While a number of studies have been performed on the removal of hydrogen, nitrogen, and sulfur, many research works have been carried out to acquire a deeper understanding of the inclusion removal mechanisms during ladle refining …”

“…Some industrial trials showing a decrease of the total amount of inclusions during degassing have been reported . Cold model experiments, computational simulations and mathematical models have suggested that bubble stirring contributes to inclusion removal. On the other hand, an increased argon flow has been reported not to enhance the removal efficiency .…”

“…Cold model experiments, computational simulations and mathematical models have suggested that bubble stirring contributes to inclusion removal. On the other hand, an increased argon flow has been reported not to enhance the removal efficiency . Soft argon stirring has been found to lead to a better inclusion removal efficiency than a strong stirring .…”

Physical modelling and industrial trials of CAS-OB refining process for low carbon aluminium killed steels

“…6 The maximum mixing time of three points was considered as the final mixing time of the model. For reproducibility the experiments were run three times at the same conditions.…”