Investigation and validation of mould-electromagnetic stirring for continuous casting of round steel blooms

At voestalpine Stahl Donawitz GmbH the continuous casting of round steel blooms is commonly enhanced by electromagnetically stirring the liquid steel flow in the mould region. The electromagnetic stirring provides a number of benefits, among them the enhanced transition from columnar to equiaxed solidification. Others are the homogenization of the liquid steel flow and the reduction of surface or subsurface defects. It is well known that the flow inside the liquid core of the strand plays a major role for all these phenomena. Although the positive effects of M-EMS can be clearly seen (e.g. in etchings) the mechanism is not sufficiently understood and hence probably not optimized. Plant measurements are often not possible or severely restricted due to the harsh environment or safety regulations. Theoretical considerations are often limited to general cases and cannot be applied to a real continuous casting geometry. In this work the steel flow in a round bloom caster is investigated by numeric simulations and experimental work. A specific test section has been built up which allows flow measurements to be carried out in a 1:3 scale Perspex model of a round bloom strand under the influence of a rotating magnetic field. The low melting point alloy, GaInSn, is used to substitute the liquid steel, as established water models cannot be used with M-EMS due to the far too low electrical conductivity of water. The implemented numeric model accounts for the full coupling between liquid steel flow and magnetic field and is split into two parts – the flow simulation and the electromagnetic calculation. By comparing the simulation results for the model strand geometry with experimental measurements, the numeric model can be validated. Simulations of the real caster are then conducted with this model, parameter influences are shown and conclusions for the real casting process can be drawn.