Investigation On The Gas-Liquid Two-Phase Flow Phenomena In A Steel Slab Continuous Casting Strand

In the current study,the gas-liquid two-phase fluid flow phenomena in a steel slab continuous casting(CC)strand was investigated.Firstly,the size distribution of bubble sizes,the turbulent characteristic of the two-phase flow,and the critical casting parameter for slag entrainment were measured using water model experiments.Secondly,the variation of the speed,the level fluctuation at the top surface,and the flow pattern in the mold were analyzed using both industrial trails and numerical simulations.Finally,a software was developed to predict the flow pattern inside the mold.The motion of air bubbles and the fluid flow in the CC strand were simulated using a 0.5-scale water model.The effect of casting parameters on the size and spatial distribution of bubbles were studied using a high speed video camera.The mean diameter of bubbles decreased from 3.31 mm to 2.82 mm when the casting speed increased from 0.63 m/min to 1.05 m/min for the current 1300 mm × 230 mm CC mold.The mean diameter of bubbles increased from 2.24 mm to 3.55 mm when the gas flow rate increased from 1.11 NL/min to 2.58 NL/min.Besides,when the submergence depth of the SEN increased from 60 mm to 90 mm,the mean diameter of bubbles decreased from 3.24 mm to 2.54 mm.The turbulence characteristic of the gas-liquid two-phase flow inside the CC mold was investigated using a Particle Image Velocimetry(PIV).The turbulent kinetic energy and its dissipation rate reached the maxinmum value at both the jet zone and the lower recirculation zone near the narrow face.The vorticity was symmetrical at both sides of the SEN while with an opposite direction each side.Critical values of the casting speed and gas flow rate for slag entrainment in the CC mold with varied dimensions were proposed.Casting parameters were optimized,and the critical relationship between the argon volume fraction(?G,%)and the steel throughput(WSteel,ton/min)for the transition of the flow pattern in the steel CC mold with varied dimensions were obtained through nail board measurements.For the transition from the double roll flow to the complex flow,the critical relationship was ?G=5.97Wsteel-1.77.For the transition from the complex flow to the single roll flow,the critical relationship was ?G=5.1 WSteel+8.9.The effect of casting parameters on the motion of the molten steel and the distribution of argon bubbles in the CC mold were studied through the three-dimensional numerical simulation of the gas-liquid two-phase flow.The influence of the casting speed and the argon flow rate on the transition of the flow pattern in the CC mold was studied using the Euler-Euler approach with a constant bubble diameter,concluding that the higher casting speed and lower argon flow rate easily generated a double roll flow pattern,otherwise resulted a complex flow or single roll flow.The size and the spatial distribution of argon bubbles in the mold were studied using the numerical simulation of Euler-Euler-multiple-size-group approach,indicating that from the SEN to the narrow face,the mean diameter of argon bubbles decreased with a higher casting speed and increased with a larger argon flow rate.A software incorporated by a Graphical User Interface was developed to predict the flow pattern inside the mold and to optimize casting parameters.