Electromagnetic flow control for casting and metallurgical applications: Model experiments and measuring techniques

The contactless handling of electrically conducting liquids by the application of magnetic fields makes this technology attractive for many industrial applications. The possibility to superimpose different kind of fields allows to generate a variety of flow structures being beneficial, for instance, to control the heat and mass transfer.
The further optimization of liquid metal flows in industrial technologies requires experimental data of the flow field to understand the process and the consequences of an intervention using electromagnetic fields. Numerical simulations alone are often of limited value. Realizing this situation, the motivation arises to perform laboratory studies using cold liquid metals as a model of realistic processes. The main feature of such cold (temperatures up to about 300°C) liquid metal models is the availability of measuring techniques allowing to analyse the local transport phenomena with a sufficient resolution. Some applications using the ultrasound Doppler velocimetry (UDV) will be presented showing the capability of this technique to measure velocity profiles in liquid metal flows. Note that water models of liquid metal processes are only meaningful if the melt flow Reynolds number represents the only determining parameter of the transport processes under consideration, which is seldom the case for real casting processes. As soon as temperature gradients, free-surface phenomena, two-phase flows or electromagnetic phenomena play a role, the water model is always of very limited value.
Some examples for model experiments will be presented showing the flow modelling of an investment casting process of aluminium alloys, the electromagnetic stirring of liquid metals and the solidification of metallic alloys affected by time-dependant magnetic fields, respectively.