Numerical And Physical Simulation Of Fluid Flow And Interfacial Behavior In Slab Continuous Casting Mold

Controlling the inclusion content in steel and increasing the purity of steel is main way to improve steel quality presently. Steel flow behavior in mold has an important effect on inclusion flotation, slag entrapment and shell growth, which is has directly related to steel quality. The steel flow in mold is mainly affected by the submersed nozzle structure and operating conditions. Therefore, optimizing the nozzle structure and the technical parameters are important for performance of continuous casting.In the present work, the effects of nozzle structure, immersion depths, casting speed and argon flow on the flow field and the temperature field of 1025mmx 180mm,1225mmx 180mm, and 1280mmx 180mm section slab continuous casting by numerical simulation and water modeling, and the nozzle structure and mold technical parameters were optimized. The conclusions are as follows:(1) The bigger downward port degree of nozzle, the less liquid level fluctuates, the stronger inhibition effect of slag entrapment, too great downward port angle of nozzle is not obvious to restrain slag entrapment. The critical velocity of entrapped slag rises from 1.2m/min to 1.4m/min with the downward port degree added from a-2.5° to a°, when the downward port degree is a+2.5°, the critical velocity is only 1.5m/min. Too big downward port angle results in too deep position of the under circulation region, and the high temperature region will move down, inclusions are difficult to float.(2) nozzle outlet shape and bottom structure has an influence on surface-free velocity, but little influence on the fluid field and temperature field in mold. The surface-free maximum velocity of 2# SEN is 0.325m/s, the surface-free maximum velocity of 4# SEN is 0.362m/s, the surface-free maximum velocity of 5# SEN is 0.334m/s, the maximum interface velocity of them is found about 1/3 of the mold from the width to the narrow face.(3) Casting speed has a strong influence on the fluid field in mold, too high speed will result in a strong fluctuation on the free surface. Within the range of casting speed from 0.8m/min to 2.2m/min, the maximum wave height is 3.24mm, the surface-free maximum velocity range from 0.22m/s to 0.767m/s.(4) Increasing immersion depth will decrease the free surface velocity and restrain interfacial oscillations. With the submergence depth added from 110mm to 180mm, the surface-free maximum velocity decline from 0.41m/s to 0.324m/s, wave height decline from 1.5mm to 1.25mm.(5) Blowing argon gas could reduce the free surface velocity of region in which the bubbles float up, but too much argon flowrate will result in the strong fluctuation, and the upper circulation region disappear. The upper circulation region is suppressed to smaller with argon gas flowrate of 2NL/min, the velocity near the submerged entry nozzle rises, the surface-free maximum velocity become small. The upper circulation region vanishes with the argon flowrate of 4NL/min, the liquid level fluctuates strongly near the nozzle.The numerical and physical results indicates that 2#SEN is the optimal nozzle structure, the optimal operating parameters are 150mm immersion depth and the argon flowrate of 2NL/min, the casting speed of 1225mm× 180mm section is under 1.4m/min as possible.