Topic: Simulation of Continuous Casting of Steel

Speaker: Professor Božidar Šarle

          Laboratory for Simulation of Materials and Processes, Institute of Metals and Technology, Lepi pot 11, SI-1000 Ljubljana, Slovenia

          Laboratory for Multiphase Processes, University of Nova Gorica, Vipavska 13, SI-5000 Nova Gorica, Slovenia

Time: 10:00-11:30, (Mon.) Oct.26th , 2015

Venue: Room 468, Lee Hsun Building, IMR CAS

Welcome to attend!

Abstract

The presentation in the first part gives an overview on multiphysics, multiscale, and multiobjective simulations of solidification in continuous casting (CC) of steel.

A simple Lagrange-an traveling slice model is described next. The main advantage of the slice model is its very fast calculation time in comparison with the complete 3D models which might need calculation time, measured in days. The slice model can be, despite its simplicity, used for prediction of the relations between the process parameters and the temperature field as well as estimation of the grain structure, strain/stress field, and macrosegregation, as well as optimization of process parameters and calculation of caster regulation coefficients. The solution procedure is based on local collocation on influence domains with scaled multiquadrics radial basis functions, augmented with the first order polynomials. The node redistribution is based on transfinite interpolation and elliptic node generation. The microstructure model is based on the novel meshless point automata model. Several realistic industrial examples are shown. The slice model can be used in off-line and on-lined modes and extended also to hot rolling and heat treatment.

The presentation next gives a complete 3D macrosegregation model of CC process. The physical model is established on a set of macroscopic equations for mass, energy, momentum, species, turbulent kinetic energy, and dissipation rate. The mixture continuum model is used to treat the solidification system. The mushy zone is modeled as a Darcy-Forchheimer porous media with Kozeny-Karman permeability relation. The incompressible turbulent flow of the molten steel is described by the Low-Reynolds-Number k-ε turbulence model, closed by the Abe-Kondoh-Nagano closure coefficients and damping functions. Scheil microsegregation model is used. The numerical method is established on explicit time-stepping, collocation with scaled multiquadrics radial basis functions with adaptive selection of its shape on non-uniform five-nodded influence domains. The velocity–pressure coupling of the incompressible flow is resolved by the explicit Chorin’s fractional step method. The advantages of the method are its simplicity and efficiency, since no polygonisation is involved, easy adaptation of the nodal points in areas with high gradients, almost the same formulation in two and three dimensions, high accuracy and low numerical diffusion.

Finally, methods for verification on the modelling are described, based on infrared thermography, indentation techniques and microstructure characterisation.