Experimental Research On Effect Of Process Parameters On Flow And Behavior Of Bubbles In Slab Continuous Casting With Swirling Flow

In continuous casting process of steel, the occurrence of uneven outlet flow from submerged entry nozzle (SEN) is unavoidable, which leads to uneven distribution of the flow field and temperature field and larger meniscus fluctuation in the mold and so on. It influences the surface and internal quality of the billet as well as the casting speed. Research results show that the swirling flow in SEN is effective to control the occurrence of the uneven outlet flow. A technology that set up a mechanical swirling blade in SEN for swirling flow has been extended to industrial applications. Electromagnetic swirling flow has been proposed by Northeastern University. This technology has the same effect of swirling flow as the mechanical swirling nozzle. But it is difficult to study the process parameters under electromagnetic swirling flow in some extend. On the other hand, the effect of the process parameters on water model experiment for mechanical swirling flow has not been reported, and the research results of mechanical swirling technology are also benefit and useful for electromagnetic swirling technology development.Therefore, in this paper, water model experiment for mechanical swirling flow was carried out based on the prototype continuous casting machine of certain steel company. In this paper, the effects of different process parameters (SEN immersion depth, structure of SEN) on the flow field and the bubble behavior in slab mold were studied. The velocity distribution was measured by a Ultrasonic Doppler Velocimetry (UDV), the effects of the immersion depth and the structure of SEN on flow field were analyzed; bubble behavior in mold was recorded by high-speed video camera. The main conclusions are summed up as follows:1. The effect of structure of SEN on flow field with swirling:In the case of convex bottom nozzle without swirling, the effect of optimizing the upper wall of the outlet of nozzle on the flow field in the mold is not obvious. It is similar with the conventional convex bottom nozzle; the effect of optimizing the upper wall of the outlet of nozzle on the flow field in the mold is obvious with swirling. It is similar to concave bottom nozzle which has diverging outlet. It indicates that the type of nozzle bottom has little effect on flow field.2. The effect of structure of nozzle on bubble behavior with swirling:For the convex bottom nozzle without swirling, the effect of optimizing the outlet of nozzle on the bubble distribution is not obvious. The effect is similar with conventional convex bottom nozzle; the effect of optimizing the outlet of nozzle on the flow field in the mold is obvious with swirling. The effect is similar to concave bottom nozzle which has diverging outlet. It indicates that the type of nozzle bottom has little effect on bubble distribution.3. The effect of immersion depth flow field with swirling:In this paper, the effect of immersion depth on the flow field is not obvious, e.g, the velocity at the meniscus in the mold. There is little effect of immersion depth on the stability of the flow field in practical production with swirling.4. The effect of immersion depth on bubble behavior with swirling:The effect of immersion depth on bubble distribution is not obvious. It indicates that it is not necessary to adjust argon blowing for immersion depth change.