Run-out table bottom jet cooling

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There has been a tremendous development of advanced steels over the past few decades to provide steel products with improved properties for a wide range of applications including automotive, energy and construction. These advancements by steelmakers were critically enabled by design of innovative processing paths and better process control. Here, the development of process models has had a significant impact. For hot rolled steels cooling by water sprays on the run-out table is a key metallurgical tool to tailor the properties of the steel. During the cooling the phase transformation occurs from austenite with a face-centred cubic (FCC) crystal structure to ferrite with a body-centred cubic (BCC) crystal structure. In detail, depending on steel chemistry and processing path, different transformation products can be obtained to create complex multi-phase microstructures which offer new paradigms for the design of properties. To realize this potential it is critical to control the cooling path precisely as this determines the phase transformation kinetics and the resulting microstructures. Cooling of hot moving steel sheets by water is a complex transient heat transfer problem including nucleate, transition and film boiling regimes. Current run-out table cooling models are to a large degree empirical in nature. There is a need to develop more fundamentally based models. Research in this area has so far emphasized top surface cooling whereas bottom jet cooling studies have received far less attention. Thus, the proposed project is designed to provide a systematic bottom jet cooling study to develop a cooling model for bottom jets that rigorously accounts for the underlying boiling mechanisms. The project is conducted in collaboration with ArcelorMittal Dofasco - Canada's leader in the production of automotive steel sheets. Experimental studies will be carried on a pilot scale run-out table facility to provide guidance for the model development. The proposed heat transfer correlations will then be incorporated into an existing hot strip mill process model of ArcelorMittal Dofasco such that the model can be validated with industrial data. The project offers training opportunities for three graduate students.