NUMERICAL AND LABORATORY STUDY OF SEISMIC WAVES PROPAGATION, TEMPERATURE EFFECTS AND FLUID FLOWS IN MULTILAYERED MEDIA

Steel production by continuous casting is nowadays the most efficient method and the one that yields the best quality semi-finished products. The types of steel that can be produced varies greatly depending on the composition of the mixtures, the casting powders used to prevent oxidation and reduce heat loss, the cooling rate, and many other factors. During continuous casting, heat from the molten steel must be removed in large quantities and quickly to allow the first layer of solid skin to be created, so the continuous casting moulds, i.e. large hollow tubes generally made of copper alloys, are immersed in a conveyor with a closed water circuit where water circulates at high speed and pressure. In addition to water, there are also other parameters that can be monitored to increase production quality, such as powder deposition on the casting bath and steel level control. It would be useful to have automatic systems capable of replacing manual human control, to avoid the hazardous situations obviously present in steel mills, but also to increase knowledge of the production process through the acquisition of reliable data. This research aims to experimentally explore the possibility of measuring the level of molten steel in the mould by making time-of-flight measurements in the wall of the ingot using ultrasonic transducers similar the ones used for non-destructive testing of materials. These time-of-flight measurements are then converted to temperature and determine a thermal profile along the mould wall, from which the steel level is derived using an ad-hoc constructed algorithm. The research activity was divided into the realization of a real-time hardware and software system that was eventually adopted in real production systems as well. To understand how to design an initial prototype and how to choose the key parameters of the measurement system, a numerical model was implemented to simulate Gaussian beams, which are used to approximate the propagation of ultrasonic beams in even heterogeneous media, as in this case. The results obtained, both from numerical simulations and laboratory tests, made it possible to implement a first measurement tool that adopted a technique already known in the literature but innovative in the sense of application to an industrial context such as continuous casting