Numerical Simulation Of Bubble Behavior In Slab Continuous Casting Mold Under Combined Magnetic Field

The wide application of electromagnetic brake and electromagnetic stirring technology in continuous casting production has greatly improved the quality of steel products.Combining the advantages of the two,the flow field of the mold is controlled by the compound magnetic field(electromagnetic brake+electromagnetic stirring).The flow field,the temperature field and the bubble behavior under the pure flow field(no magnetic field)and the compound magnetic field are analyzed,and the position of the bubbles captured by the solidification front is predicted.In this paper,the finite element software ANSYS is used to calculate the magnetic field.The calculated magnetic field data is introduced into the FLUENT,and the corresponding modules are used in the FLUENT to calculate the flow field,temperature field and bubble.Finally,the TECPLOT and ORIGIN are used to analyze the images.According to the actual situation of a steel plant,this paper simulates the steel in a slab(1750mm x 230mm)with the casting speed of 1.0m/min,and the related electromagnetic parameters are:brake current 400A,600A and 800A,stirring current 500A,600A,700A and 800A,stirring frequency 2Hz.The results are as follows:Under the compound magnetic field,the main stream is restrained and the plug flow is more easily formed in the lower part of the mold,the low temperature region of the lower part completely disappeared;The electromagnetic stirring at the meniscus made the low temperature region near the wall and corner reduced or even disappeared,and the temperature distribution was even more uniform.In the no-magnetic field case,the bubbles come out from the nozzle,and some large bubbles float up fast next to the outer wall of the nozzle,and some of the bubbles float up at the 1/4 width of the slab.In the vicinity of the narrow surface,some small bubbles float up with the upper loop flow,and other small bubbles come into the lower circulation zone with the molten steel.Under the action of the compound magnetic field,the movement state of the bubbles has changed significantly.The electromagnetic stirring makes the movement of bubbles in the upper circulation region from vertical to spiral,which greatly increases the paths of bubbles.The electromagnetic brake can well reduce the number of bubbles reaching the lower circulation area.Among the bubbles captured by the solidification front,most of them are less than 0.4mm in diameter,and the bubbles captured are located in the shallow subcutaneous parts of the casting billet.Thanks to the scouring effect of electromagnetic stirring on the solidification front,the bubbles captured on the upper part of the mold under the compound magnetic field are significantly less than those under the no-magnetic field.