2013 Volume 53 Issue 4 Pages 655-664
In order to investigate the compactness degree of longitudinal section of the outer columnar grain zone in continuous casting billet, a Cellular Automaton-Finite Element coupling model was first developed. After validation, the solidification structures of billet under different conditions were simulated. The compactness degree of longitudinal section of billet is evaluated by the grain number in the same area. Because the widths of the columnar grain zone of billet under different conditions are different, the same zone was chosen for comparison and the zone was named as outer columnar grain zone. Thereafter, the compactness degree of longitudinal section of the outer columnar grain zone is found to be decreased with the increase of superheat, and increased slightly with the increase of casting speed, and decreased slightly with the increase of mould cooling intensity. Meanwhile, the corresponding compactness degree is increased with the increase of maximum nucleation density, and decreased with the increase of mean nucleation undercooling, and also decreased with the increase of dendrite growth velocity. Moreover, it is shown that the compactness degree of longitudinal section of the outer columnar grain zone in continuous casting billet is closely related to the average temperature gradient of the solidification process of the outer columnar grain zone, i.e., the former will be decreased when increasing the latter. This phenomenon can be probably attributed to two features that the established model has considered the preferential growth direction and new nucleation cores in the solidification front of the columnar grains.
