Contactless inductive flow tomography: recent developments in its application to continuous casting with electromagnetic brakes

M. Ratajczak1, T. Wondrak1, R. Martin1,2, F. Stefani1, R. T. Jacobs2

1Helmholtz-Zentrum Dresden - Rossendorf, Institute of Fluid Dynamics, Bautzner Landstraße 400, 01328 Dresden, Germany

2TU Dresden, Faculty of Electrical and Computer Engineering, Chair of Electromagnetic Theory and

Compatibility, Helmholtzstraße 9, 01069 Dresden, Germany m.ratajczak@hzdr.de

ABSTRACT

Measuring the velocity in hot and/or aggressive melts is a challenging task. Many applications, like continuous casting of steel, would benefit even from a rough knowledge of the global flow structure of the melt, because the flow structure has a direct impact on the quality of the final product. In continuous casting, electromagnetic brakes (EMBrs) are widely used to influence the flow in the mold, as they are expected to damp undesired flow oscillations that are associated with multiple kinds of defects. Yet, without direct feedback from the mold flow, a tailored process control with EMBrs is hardly possible.

The contactless inductive flow tomography (CIFT) could help to circumvent these problems. The method relies on the induction of a secondary magnetic field if the moving fluid is exposed to a primary magnetic field. From the measurement of the induced magnetic outside the melt, the global flow structure of the melt can be inferred by solving the associated linear inverse problem. A successful application of CIFT to EMBr-influenced mold flows could enable steel producers to cast high quality steel with less rejects. In this paper we will outline the efforts to adapt CIFT to a laboratory liquid-metal mold under the influence of an EMBr.

Keywords Contactless inductive flow tomography, continuous casting, magnetic field measurement, gradiometric sensor, electromagnetic brake