DC-casting Models

Mathematical modelling of DC-casting is used to understand the basic mechanisms of the process and to interpret casting experiments, and the models ALSIM and ALSPEN have been used in process design and development over a long period of time. Current topics of research are the coupled stress, thermal and fluid flow modelling of the start-up phase of the process as well as grid refinement and adaptivity applied on finite element grids.
Contact

Mortensen, Dag

Department Head

 

The mathematical model ALSIM is a FEM model for the time dependent heat and fluid flows in direct chill (DC) semicontinuous casting of aluminium ingots and billets. Thermal convection and turbulence are included in the model formulation, and in the mushy zone the momentum equations are modified with a Darcy type source term dependent on the liquid fraction. The boundary conditions involve calculations of the air gap along the mould wall as well as the heat transfer to the falling water film with forced convection, nucleate boiling and film boiling. The mould wall and the starting block is included in the computational domain. In the start-up period of the casting the ingot domain is expanding over the starting block level.

ALSPEN is a FEM model which, based on the temperature evolution from ALSIM, computes the evolution of the displacement, stress and strain fields. The metal is assumed to be an isotropic elasto-viscoplastic material with strongly temperature dependent properties. The mathematical formulation is based on the classical small deformation theory, implying that the total strain can be divided into an elastic, a viscoplastic and a thermal part. In the material description, the viscoplastic strain is treated in a "unified" manner, in which low-temperature time-dependent plasticity and creep at high temperatures occur as special cases.

Customers

  • Elkem Aluminium
  • Hydro Aluminium