Modelling and Simulation of Solidification of High Grade Steel Ingot Castings

Anton Ishmurzin

Research output: ThesisDoctoral Thesis

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Abstract

In the work presented an approach to simulate ingot solidication of highly alloyed steels was developed. It includes simplied simulation of initial mould lling with the melt, followed by a subsequent simulation of the solidication course within the framework of multiphase multicomponent computational fluid dynamics. The multiphase multicomponent solidication model was developed, based on the previous models for binary alloys. In order to allow the multicomponent capability, the governing multiphase ow equations were reconsidered, that include equations describing conservation of mass, momentum, energy as well as alloying components (species) and grain density transport. Source terms for the equations were reformulated to reect multicomponent kinetic and thermodynamic relations. An approach to couple multicomponent/multiphase thermodynamics and kinetics with multiphase/multicomponent ow model was developed. It has a formof a nonlinear algebraic equation system, relating temperature and composition of the bulk melt with solid and liquid compositions at the interface at the solid-liquid phase interface. A Newton-type iterative method was used for solving the equation system. The coupling approach was validated using alloys from Fe-C-Cr, Fe-C-Mn and Cu-Sn-P systems. The necessary thermodynamic functions, the liquidus temperature and tie-line relations were approximated as piecewise-linear as well as interpolated using bivariate splines. The implementation of the model for ternary alloys was used for carrying out simulations of solidication of Fe-C-Cr alloys in two different ingot geometries taking into account two- and three-phase ow. The thermal convection was found to be the predominant effect inuencing the course of solidication, solutal convection did not inuence the solidication signicantly. The modelling and simulation methods of multiphase multicomponent alloy solidication presented can be used for simulation of a wide range of multicomponent solidication processes.
Translated title of the contributionModellierung und Simulation der Erstarrung von Edelstählen
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Ludwig, Andreas, Assessor A (internal)
  • Brand, Clemens, Assessor B (internal)
Publication statusPublished - 2009

Bibliographical note

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Keywords

  • Computational Fluid Dynamics
  • Solidification
  • Modelling
  • Simulation
  • Ternary
  • Thermodynamics
  • multiphase

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