Effect of pressurized spray cooling on microstructure gradients in thicker hot strip products

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The development of new steel products continues to play an important role in the economy and society. The ever increasing pace of steel development is driven by the demands of critical sectors like automobile manufacturing, construction and energy. Developing new steels requires to deepen the knowledge in the underlying metallurgy and constant modernization of steel production facilities. Accelerated cooling has become a key technology to produce thermo-mechanically controlled processed hot-rolled steels with fine grained and/or multi-phase microstructures and the mechanical properties that are now increasingly required for demanding applications. Using well-designed processing paths rather than alloying additions is an attractive approach to manufacture these high-performance steels. The cooling path on the runout table takes a critical role as it can be used to tailor the phase transformation 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. The Canadian steel industry, including ArcelorMittal Dofasco (AMD), is actively engaged in upgrading their runout table cooling capabilities. A particular challenge is here the production of thicker gage steels, e.g. line pipe, because the intense cooling, e.g. in a pressurized spray unit, may lead to through-thickness microstructure/property variations. The development of process models will have an increasing impact for making these value-added products with high quality and minimum variability. The proposed project is conductecd in collaboration with AMD to develop a next generation runout table model that combines heat transfer and phase transformation kinetics for line pipe steels. Experimental studies will be carried out on a pilot scale runout table facility and the thermo-mechanical processing laboratory to provide guidance for the model development. The proposed model will be validated with industrial data. The project offers training opportunities for three graduate students.