Uniform velocity distribution can be obtained within a very short distance from the outlet of the nozzle.Heat and mass transfer near the meniscus can be remarkably activated comparedwith a conventional straight type immersion nozzle without swirl.Swirl helps the superheat in the melt dissipate,Penetration depth of nozz[e outlet flow is decreased remarkably by the application of swirling.Those findings mentioned above are very useful to control the flow pattern in the biliet and bloom continuous casters,

We began development of swirling-flow submerged entry nozzles in 1997 as a fundamental and effective measure for controlling the flow pattern in continuous casting molds. As a first step, we developed a swirling-flow submerged entry nozzle for round billet casting at the Wakayama works. We then began developing swirling-flow submerged entry nozzles for slab casting. The main purpose of the present work was to demonstrate that the formation of swirling flow in submerged entry nozzle improves productivity and the quality of products in continuous casting. We examined swirling-flow submerged entry nozzles with a swirl blade in these main bodies because such an arrangement is the easiest way to apply swirling flow to submerged entry nozzles in continuous casters without investment by facilities. We had only to change the submerged entry nozzle in the experiment. Swirling-flow submerged entry nozzles for slab casting were developed and their operation examined at the Wakayama and Kashima works. It was found that the proposed submerged entry nozzles increased the casting speed and improved the surface quality of slabs and steel sheets.

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In addition. the mechanism for obtaining the uniform velocity profile at the nozzle outlet was correlated with the flow pattern of the nozzle and the strength of the swirl. This is also done for a system in which swirl is generated by a rotating magnetic field imposed on the pouring tube. The model shows how the flow of steel from the nozzle may be modified using such a system. Such a swirling flow can provide a uniform, Iow velocity at the nozzle exit, which may be highly desirable for continuous casting purposes.

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A numerical analysis and a water model study of the mold region of a billet continuous caster was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold. The following results were found: A weak impinging flow can be observed near the corner of the mold wall, which results in the promotion of uniform heat and mass transfer all around across the plane, particularly at the casting corner. An upward flow directed from the vicinity of the nozzle outlet to the meniscus can be observed near the corner of the upper part of the mold, which leads to the active heat and mass transfer into the meniscus. A uniform velocity and heat distribution can be obtained within a short distance of 200 mm downward from the outlet of the nozzle. Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable than that using the straight nozzle.

Fig. 12.Predicted radial steel velocity at the surface at different steel heights during the mold filling. Data are given for the reference case and the three cases with swirl blade at 250, 500 and 750 mm distance to the inlet, for the velocity of 1 m/s. The radial velocity for the flared inlet is also shown.