Keywords: continuous casting, thermo-mechanical analysis, thin slab production, cyclic steady-state, mould oscillation.

The main topic of this paper deals with a modelling approach to thermo-mechanical analysis of a solidifying shell, as encountered in the thin slab continuous casting process. There is a general interest in building a three-dimensional numerical model capable of simulating the process conditions in this specific zone to ensure adequate technology design. The impossibility of a direct experimental inspection of the developed mechanical state is a motivation. Supported by a corresponding numerical model describing the physical process the level of induced stresses can be computationally determined and, as a consequence, a proper mould design is adequately controlled.

In the problem modelling with the Eulerian description assumed to keep the spatial location constant a special emphasis is given to the mechanical response of the solidified shell inside the mould, which is considered as cyclic steady-state because of the imposed mould oscillation. The thermo-mechanical problem is treated as uncoupled, with thermal analysis performed first to compute the steady-state temperature field. To take the loading history of the emerging shell which is pulled through the mould properly into account special modelling techniques are applied in the subsequent mechanical analysis to achieve a cyclic steady-state.

A specific thin slab continuous casting in the mould with a continuously varying cross-section in the withdrawal direction is required. The mould is designed to have a lens producing a gap at the top between the submerged entry nozzle and the inner mould surface, the gap having a function to guarantee melting of the lubrication and to avoid the appearance of the solidification bridges between the mould and the submerged entry nozzle. To prevent the loss of contact between the shell and the mould, thus establishing adequate cooling of the shell, the mould lateral walls are tapered due to shrinkage of the solidified shell. While in thick slab production with constant mould cross-section the shrinkage modelling is mainly a thermal problem, in thin slab production on the contrary, the circumference of the upper part of the mould is larger than the circumference of the lower part. Hence, since both shrinkage arising from the cooling and wedge due to the cross-section reduction must be taken into account, to design the mould interior shape adequately is a complex task.

The simulation results obtained on the basis of the numerical model developed confirm the great capability of the numerical modelling in achieving a better physical insight into the complex thermo-mechanical behaviour in continuous casting. Especially, such a numerical model is useful not only for direct analysis purposes, but above all for an advanced technology design involving the process parameters prescription and the mould's internal geometry determination, as well as the corresponding optimization tasks.

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