Induction tomography is a new and emerging non-invasive imaging technique based on the principle of eddy current induction in conductive media. Induction tomography provides a contactless method to image the electrical conductivity (and magnetic permeability) of an object. A time varying electrical current is used as an excitation signal in transmitting coil(s), producing eddy currents in the conductive medium under test. This eddy current in turn produces a secondary magnetic field that is detected by receiving coils. An array of excitation and receiving coils provides multiple measurements of mutual inductances and will be used in the tomographic image reconstruction software to image the electrical conductivity distribution. Based on the electrical conductivity difference between the solid shell and the liquid core, the boundaries between the different domains can be identified.

SHELL-THICK project aims at developing an innovative induction tomography system for metal solidification process in order to provide a real-time and reliable measurement of the shell thickness at some cross-sections of the stand (located in the region after the secondary cooling and before the liquid cone closure) and the value of the metallurgical length for a better control of the process. The project also addresses the implementation of a tool for the on-line and non-destructive detection of different surface defects on the billet (e.g. rhombicity or depressions) and potential fails in the process (e.g. non-uniform cooling), based on the real-time monitoring and analysis of the shell thickness and external shape of the billet cross-section obtained through the tomography system.

This will introduce a step change in solidification process with significant benefits in terms of quality, safety, productivity, costs and ultimately of competitiveness.