Compactness Degree of Longitudinal Section of Outer Columnar Grain Zone in Continuous Casting Billet Using Cellular Automaton-Finite Element Method

Abstract

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.

Effect of Solidification Pressure on Compactness Degree of 19Cr14Mn0.9N High Nitrogen Steel Using CAFE Method

“…The compactness degree can be evaluated by the number of grains, for the same area, higher compactness degree means greater number of grains . Based on the simulation results of solidification structure (Figure ), the number of grains for central equiaxed grain zone and columnar grain zone under 0.5, 0.85, and 1.2 MPa were counted.…”

“…So the increment of solute diffusion coefficient can be ignored with solidification pressure according to Equation . In this simulation, Gibbs‐Thomson coefficient is 1.9 × 10 −7 m K, according to the value of literature and the value of solute diffusion coefficient is chosen based on literature report listed in Table .…”

“…The compactness degree can be evaluated by number of grains or grain size, i.e., larger number of grains or smaller grain size means higher compactness degree. Experimental and simulation methods are two very important ways to investigate the compactness degree of solidification structure . For high alloy steel, the dendrites of equiaxed crystals are more developed with more branches and firmly connect with each other.…”

“…In recent years, the cellular automaton‐finite element (CAFE) model has been successfully used to investigate the effect of casting conditions on the compactness degree . Hou used CAFE model to investigate the effect of superheat, mold cooling intensity, and casting speed on the compactness degree of continuous casting billet. Zeng investigated the relationship between secondary cooling water intensity and the compactness degree at equiaxed zone of continuously cast high‐carbon rectangular billet.…”

Numerical Study on Solidification Behavior and Structure of Continuously Cast U71Mn Steel

“…This CAFE model has been successfully applied in simulating the solidification behavior and structure [8][9][10]. In recent years, several published works have used the CAFE model to investigate the solidification structure during the continuous casting process [11][12][13][14][15]. However, most of them focus only on the structure during the continuous casting process and the heat transfer results associated with the solidification structure are ignored.…”