Simulation of mould level velocities during continuous casting of round bloom strands with mould-electromagnetic stirring
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In modern continuous casting of round steel blooms rotating electromagnetic fields are commonly employed to improve the product quality. Mould-electromagnetic stirrers (M-EMS) are used to excite a rotary motion along the solidification front in the liquid core. These velocities lead to a better strand surface quality as well as enhancing the transition from columnar to equiaxed solidification. Although the usage of electromagnetic stirrers is widespread, not all effects are fully known or understood.
Due to harsh conditions at the plant, measurements are scarce and limited. Water model experiments ? an established alternative for investigating continuous casting of steel ? cannot be used due to the low electrical conductivity of water. Experiments with liquid metals like mercury, Galinstan or Wood?s metal are either expensive or difficult to perform. Thus numeric simulations are essential to gain a better understanding of the processes involved in continuous casting with electromagnetic stirring. However numeric simulations should always be validated with experiments and/or measurements. While the velocity field inside the liquid core of the bloom cannot be measured at the caster, the velocity at the mould level can be measured by dipping a nail into it. The skull forming at the tip of the nail is directly linked to the occurring surface velocity. These measurements can then be compared with numeric simulations of the nail dipping process. The numeric model is restricted to the upper part of the strand. The lower part of the strand is also taken into account through adjusted boundary conditions (velocity field etc. taken from a simulation of the whole strand). In this work the influence of the stirring field strength on the simulation results will be investigated.
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Supplement of Journal of Iron and Steel Research, International