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SUMMARYThe explicit finite element method is applied in this work to simulate the coupled and highly non-linear thermo-mechanical phenomena that occur during steel solidification in continuous casting processes. Variable mass scaling is used to efficiently model these processes in their natural time scale using a Lagrangian formulation. An efficient and robust local-global viscoplastic integration scheme (Int. J. Numer. Meth. Engng 2006; 66:1955-1989) to solve the highly temperature-and rate-dependent elasticviscoplastic constitutive equations of solidifying steel has been implemented into the commercial software ABAQUS/Explicit (ABAQUS User Manuals v6.7. Simulia Inc., 2007) using a VUMAT subroutine. The model is first verified with a known semi-analytical solution from Weiner and Boley (J. Mech. Phys. Solids 1963; 11:145-154). It is then applied to simulate temperature and stress development in solidifying shell sections in continuous casting molds using realistic temperature-dependent properties and including the effects of ferrostatic pressure, narrow face taper, and mechanical contact. Example simulations include a fully coupled thermo-mechanical analysis of a billet-casting and thin-slab casting in a funnel mold. Explicit temperature and stress results are compared with the results of an implicit formulation and computing times are benchmarked for different problem sizes and different numbers of processor cores. The explicit formulation exhibits significant advantages for this class of contact-solidification problems, especially with large domains on the latest parallel computing platforms.

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Plant measurements and three-dimensional models are used to develop an accurate and efficient model of heat transfer in a thin-slab continuous casting mould, interface, and solidifying shell. A finite-element model of the complex-shaped mould, developed using ABAQUS, is applied to find offset correction factors that enable the efficient CON1D model to accurately predict temperature at thermocouple locations. Model interface parameters are calibrated using an extensive database of plant data obtained from the Corus Direct Sheet Plant in IJmuiden, The Netherlands, including measurements of mould heat removal, mould temperature, oscillation mark shape, mould-powder consumption, and mould thickness. The validated CON1D model is applied to quantify the combined effects of casting speed and mould plate thickness on mould heat transfer. Increasing casting speed causes a thinner solidified steel shell, higher heat flux, higher mould hot face temperature, a thinner slag layer and lower solid slag layer velocity. Increasing mould plate thickness increases hot face temperature, lowers solid slag layer velocity, increases slag layer thickness, and lowers mould heat flux.