Numerical simulation of macrosegregation in steel ingots using a two-phase model

Abstract

A two-phase model for the prediction of macrosegregation formed during solidification is presented. This model incorporates the descriptions of heat transfer, melt convection, solute transport, and solid movement on the system scale with microscopic relations for grain nucleation and growth. Then the model is used to simulate the solidification of a benchmark industrial 3.3-t steel ingot. Simulations are performed to investigate the effects of grain motion and pipe shrinkage formation on the final macrosegregation pattern. The model predictions are compared with experimental data and numerical results from literatures. It is demonstrated that the model is able to express the overall macrosegregation patterns in the ingot. Furthermore, the results show that it is essential to consider the motion of equiaxed grains and the formation of pipe shrinkage in modelling. Several issues for future model improvements are identified.

Keywords

steel ingots / solidification / segregation / shrinkage / modeling

References

[1] Flemings M.C. Principles of control of soundness and homogeneity of large ingots. Scand. J. Metall., 1976, 5, 1.

[2] Flemings M.C. Our understanding of macrosegregation: Past and present. ISIJ Int., 2000, 40(9): 833

[3] Beckermann C. Modelling of macrosegregation: Applications and future needs. Int. Mater. Rev., 2002, 47(5): 243

[4] Lesoult G. Macrosegregation in steel strands and ingots: Characterisation, formation and consequences. Mater. Sci. Eng. A, 2005, 413–414, 19.

[5] Ni J., Beckermann C. A volume-averaged two-phase model for transport phenomena during solidification. Metall. Trans. B, 1991, 22, 349

[6] Wang C.Y., Beckermann C. Equiaxed dendritic solidification with convection: Part I. Multiscale/multiphase modeling. Metall. Mater. Trans. A, 1996, 27, 2754

[7] Ludwig A., Wu M. Modeling of globular equiaxed solidification with a two-phase approach. Metall. Mater. Trans. A, 2002, 33, 3673

[8] Wu M., Ludwig A. A three-phase model for mixed columnar-equiaxed solidification. Metall. Mater. Trans. A, 2006, 37, 1613

[9] Wu M., Ludwig A. Modeling equiaxed solidification with melt convection and grain sedimentation: I. Model description. Acta Mater., 2009, 57, 5621

[10] Wu M., Fjeld A., Ludwig A. Modelling mixed columnar-equiaxed solidification with melt convection and grain sedimentation: Part I. Model description. Comput. Mater. Sci., 2010, 50, 32

[11] Combeau H., Založnik M., Hans S., Richy P.E. Prediction of macrosegregation in steel ingots: Influence of the motion and the morphology of equiaxed grains. Metall. Mater. Trans. B, 2009, 40, 289

[12] Založnik M., Combeau H. An operator splitting scheme for coupling macroscopic transport and grain growth in a two-phase multiscale solidification model: Part I. Model and solution scheme. Comput. Mater. Sci., 2010, 48, 1

[13] Pardeshi R., Dutta P., Singh A.K. Modeling of convection and macrosegregation through appropriate consideration of multiphase/multiscale phenomena during alloy solidification. Ind. Eng. Chem. Res., 2009, 48(19): 8789

[14] Liu B.C., Xu Q.Y., Jing T., Shen H.F., Han Z.Q. Advances in multi-scale modeling of solidification and casting processes. JOM, 2011, 63(4): 19

[15] Combeau H., Kumar A., Založnik M. Modeling of equiaxed grain evolution and macrosegregations development in steel ingots. Trans. Indian Inst. Met., 2009, 62, 285

[16] Gidaspow D. Multiphase Flow and Fluidization, Continuum and Kinetic Theory Description, 1994, New York, Academic Press, 35.

[17] Ferziger J.H., Peric M. Computational Methods for Fluid Dynamics, 2002, New York, Springer, 101

[18] Patankar S.V. Numerical Heat Transfer and Fluid Flow, 1980, New York, Hemisphere, 113.

[19] Karema H., Lo S. Efficiency of interphase coupling algorithms in fluidized bed conditions. Comput. Fluids, 1999, 28, 323

[20] Liu B.C., Shen H.F., Li W.Z. Progress in numerical simulation of solidification process of shaped casting. J. Mater. Sci. Technol., 1995, 11, 313

[21] Gu J.P., Beckermann C. Simulation of convection and macrosegregation in a large steel ingot. Metall. Mater. Trans. A, 1999, 30, 1357

[22] Li W.S., Shen H.F., Liu B.C. Three-dimensional simulation of thermosolutal convection and macrosegregation in steel ingots. Steel Res. Int., 2010, 81(11): 994