Numerical Simulation of Solidification Structure of High Carbon Steel in Continuous Casting Using Cellular Automaton Method

Abstract

A combined cellular automaton-finite difference (CA-FD) model has been developed to simulate solute diffusion controlled solidification in continuous steel casting. Constitutional and curvature undercooling were both solved to determine the equilibrium temperature and growth velocity of the solid/liquid interface. Simulations were firstly performed for both the free dendritic growth from an undercooled melt and the columnar dendritic growth in unidirectional solidification. Finally, competitive dendritic growth and columnar to equiaxed transition (CET) occurring in solidification of continuous casting process were reproduced by the present CA-FD model. The effect of the fragmentation of dendrites due to fluid flow induced by EMS in mould on nuclei was taken into consideration by increasing the grain density. The comparison between the simulated and experimentally observed results shows that the present model can be used to simulate solidification structure formation during the continuous casting process of steel. The influence of superheat on solidification structure was also analyzed, and it was found that increasing superheat increases the columnar dendritic growth and reduces the equiaxed ratio, as it is empirical well known.

Analysis on the Deflection Angle of Columnar Dendrites of Continuous Casting Steel Billets Under the Influence of Mold Electromagnetic Stirring

“…[2,4,5,10,[17][18][19][20][21][22] However, only one previous research reported data on the deflection angle under the influence of M-EMS. In that work, [23] it is indicated that the deflection angle is effected by the solute and temperature gradients induced by fluid flow not by the EM force directly and 60 pct of the imposed electromagnetic force disappears due to the interaction of 3D flow, for example, from the submerged entry nozzle.…”

Numerical Simulation of Dendritic Growth of Continuously Cast High Carbon Steel

“…The temperature within a CA cell regarded to be uniform is determined through the bilinear interpolation according to the four temperature nodes around it. [4] The heat flux boundary conditions are applied at the bottom wall of the modeling domain, while the thermal isolation is used for other walls. The value of the heat flux is determined according to mold cooling conditions listed in Table I during SWRH82B steel billet continuous casting process, as expressed in Eq.…”

“…[1][2][3][4] According to the antiparallel relationship between the growth direction of columnar dendrites and the heat flow direction and the upstream growth characteristic, the cooling uniformity and the intensity of electromagnetic stirring (EMS) can be deduced from the growth direction of columnar dendrites in the transverse section of strands. Meanwhile, the dendritic solidification parameters reflecting the cooling intensity, such as primary and secondary dendrite arm spacings, are important to predict the crack susceptibility of steel [5] and the permeability of the mushy zone, [6] which is crucial to accurately investigate the formation and the development of central macrosegregation.…”

“…Accordingly, they investigated the growth behavior of equiaxed dendrites and micro-segregation between columnar dendrites of high carbon steel under low cooling conditions. Recently, Luo et al [4,24] successively used the Neumann ruler and the decentered square algorithm and simplified high carbon steels into Fe-C alloys to investigate the equiaxed dendritic morphology and growth behavior of columnar dendrites. Yin and Felicelli [25] used the decentered square algorithm to predict the primary and secondary dendrite arm spacings of Fe-0.13 wt pct C alloy during the laser-engineered net shaping (LENS) process.…”

“…Yin and Felicelli [25] used the decentered square algorithm to predict the primary and secondary dendrite arm spacings of Fe-0.13 wt pct C alloy during the laser-engineered net shaping (LENS) process. Since many researchers [4,15,19,20] neglected the release of the latent heat during the solidification of equiaxed dendrites, or applied cooling conditions directly [17,18,22] which causes the variation of the melt undercooling, the comparisons between the developed CA model and LGK analytical model [25] were not strictly appropriate.…”