Abstract: Based on a prototype of 180t RH vacuum refining equipment in a steel plant， the physical simulation experiment device was established according to the similarity criterion. The threelevel orthogonal experiments with the influence of two factors such as the gas blowing angle and gas flow rate were studied in the water model experiments， which revealed thorough understanding of the circulating flow conditions in RH vacuum refining process， and provided technical references for the decision of process and operating parameters. The results showed that both the gas flow rate and the gas blowing angle influenced the refining efficiency， of which the gas flow rate had more significant influence. The optimization argonblow scheme was that the minimum mixing time was obtained with the nozzle angle of 45°when the gas flow rate was 20m3/h. While for the different gas flow rates， the increased amplitude of the circulation flow rate decreased with the increase of the gas blowing angle， and the optimal gas blowing angle was between 25 ° and 35 °.

Key words: RH vacuum refining, circulation flow rate, mixing characteristics, mixing time, physical simulation