The development of reliable numerical models is vital to improve the quality of
continuously cast products and to increase the productivity of the casting
machine. In order to provide accurate predictions, these models must include
detailed descriptions of the physical phenomena occurring inside the mould, such
as metal flow, heat transfer and solidification. However, these topics are often
treated separately during modelling due to their complexity. This has a negative
impact on the accuracy of the predictions. To address this issue, a numerical
model capable of coupling the flow dynamics with both the heat transfer to the
mould walls and solidification has been developed.
The 2‐dimenional model is based on a commercial CFD code that solves the
Navier‐Stokes Equations coupled with a Volume of Fluid interface tracking
technique for the multiphase system slag‐steel‐air under transient conditions
within a conventional slab mould. The use of an extremely fine mesh in the
meniscus region (~50 μm) allows, for the first time, the explicit calculation of
liquid slag infiltration into the shell‐mould gap. Heat transfer through the solid
mould faces and mould oscillation were also included in the model to provide a
more realistic representation of the process.
The model developed was tested in two case studies. In the first case, the
predicted values were compared to prior numerical models and laboratory
experiments directed to casting of conventional slabs. Excellent agreement was
found for characteristics such as slag film development and heat flux variations
during mould oscillation.
Furthermore, predicted values for shell thickness, consumption and heat flux were
also found to be in good agreement with plant measurements. The findings of this
case study provided improved, fundamental understanding of the mechanisms
involved in slag infiltration and solidification inside the mould and how these
affect key process parameters, such as powder consumption and shell growth.
The second case study consisted of a sensitivity study, where casting conditions
(e.g. casting speed, mould cooling, steel/slag properties and oscillation settings)
were varied in the simulations to determine their effect on both powder
consumption and the formation of defects. The simulations predicted the initial
formation of typical casting defects known as oscillation marks, without the aid of
any external data fitting. The key result drawn from the sensitivity study was the
determination of simple rules for the calculation of consumption, heat flux and
defect formation as a function of the casting conditions. This opens the possibility
of using the model as a diagnostic tool and for process optimisation.