Fluid Flow Phenomena And Transition Of Inclusions During RH Refining Process

In the current study, water physical modeling, Particle Image Velocimetry (PIV) detection, mathematical modeling and industrial trials were used to investigate the metallurgical effect of a 210 ton RH refining using round shape snorkels and oval shape snorkels. In the water modeling, the mixing time was measured by detecting the electrical conductivity of KC1 solution, and 0.4%KMnO4 was injected into the model to show the flow pattern in the ladle. The velocity, turbulent energy and its dissipation rate of the fluid flow in the ladle and vacuum chamber were measured using PIV. The three-dimensional multiphase flow in the ladle and the vacuum chamber during RH refining was simulated using VOF-DPM models. In industrial trials of a non-oriented silicon steel and a ultra-low carbon steel were performed and inclusions and total oxygen in steel samples during RH refining were analyzed. The effects of detection position, gas flow rate and number of gas injection nozzles, vacuum degree in vacuum chamber on the mixing time, fluid flow and steel cleanliness were discussed, by which the metallurgical effect of round shape snorkels and oval shape snorkels was evaluated. The current study had a certain amount of novel findings. The mixing time depended seriously on the detection location and in the ladle the longest mixing time was 1.8 times of the shortest mixing time so that the detection location has to be clarified if it is reported. The gas flow rate had a great influence on the mixing time. The increase of the gas flow rate increased the fluid flow velocity so that the liquid recirculation rate was increased. The number of the gas injection nozzles also had an effect on the mixing phenomena but not as remarkable as the gas flow rate. With the same operation conditions, the fluid flow velocity of the liquid using oval shape snorkels was lager than that using round shape snorkels. The turbulent energy and its dissipation rate (namely the stirring power) was increased with increasing gas flow rate. The turbulent energy was 0.0001-0.00025 m2/s2 and the stirring power was 0.2-0.5 W/t when round snorkels were used, and the corresponding mixing time was 59s-32s. When the oval shape snorkels were used, the turbulent energy was 0.00015-0.0007 m2/s2 and the stirring power was 0.24-1.4 W/t, and the corresponding mixing time was 49s-22s. A relationship between mixing time and stirring power was derived as tm=28.1ε-0.4, where the tm is mixing time in seconds, and ε is stirring power in W/t. The mathematical modeling concluded that using round shape snorkels, the shear stress on the ladle bottom, side wall and the wall of the snorkels were two time higher than that using oval shape snorkels, so that the utilization life time of the lining refractory would be shorter. The industrial trials of the non-oriented silicon steel and the ultra-low carbon steel revealed that the total oxygen and the amount of inclusions in the steel samples using oval shape snorkels were lower than that using round shape snorkel and the ability of deoxidation, decarburization and removing inclusions was lower than using round shape snorkel. The final conclusion was that the metallurgical effect of the RH using oval shape snorkel was better than that using round shape snorkels.