Investigation on the Effects of Ladle Change Operation and Tundish Cover Powder on Steel Cleanliness in a Continuous Casting Tundish

Abstract

The multiphase flows involving steel—slag—air phases in a two‐strand tundish during ladle change are investigated using mathematical modeling. Experimental results from water modeling are used to validate the simulated results. Tundish cover powder (TCP) and steel samples are taken from eight heats in one sequence to evaluate the effect of the multiphase flows during ladle change on the composition of the TCPs and steel cleanliness. Furthermore, the effect of the refilling time on the air entrainment and slag aperture during ladle change is analyzed and discussed. It is found that the strong turbulent flows in the tundish impact zone during ladle change promote the mix of the two‐layer cover powder, which consists of a basic TCP layer at the bottom and a top layer of rice hull balls. It results in a significant change in the composition of the TCPs and gradually deteriorates the steel cleanliness by the slag—steel reaction. Increasing the refilling time can effectively decrease the amount of entrained air and area of slag layer aperture in the tundish bath during ladle change. To reduce the steel reoxidation during ladle change, the refilling time should be larger than 184 s. Moreover, a new TCP is developed instead of the top layer of rice hull balls in industrial production. The use of the new TCP significantly improves the steel cleanliness in the tundish.

Mathematical and Physical Modelling of Transient Multi-Phase Flows in a Ladle Shroud during Start-Up

“…These, when exiting the Ladle Shroud, and rising to the liquid steel surface within the tundish, can be expected to disturb the overlaying 1.5-inch slag layer. This, in turn, can promote slag entrainment in the form of small inclusions, as demonstrated earlier experimentally and numerically [8,9,15].…”

“…and rising to the liquid steel surface within the tundish, can be expected to disturb the overlaying 1.5-inch slag layer. This, in turn, can promote slag entrainment in the form of small inclusions, as demonstrated earlier experimentally and numerically [8,9,15]. To complement the previous results for the different phases on the symmetry plane, 3D visualizations of the simulation were generated via Volume Rendering, where the volume is split in 100 planes parallel to the symmetry plane to obtain an inner view of the filling stage at different time steps for the steel volume fraction only.…”

“…Studies of different Ladle Shroud designs have mainly focused on the steadystate regime via physical [2] and mathematical models [3,6,7]. Only a few transient studies have been performed thus far [7][8][9], focusing on start-up and ladle change operations and their impact on fluid flows and steel quality. Mathematical modeling of Ladle Shroud-tundish systems has resulted in improved practices over the last few years.…”

Carbon Macrosegregation Pattern in 30Cr15Mo1N Ingot: Impact of Pouring Rate

“…With an increase in the pouring rate, the flow of molten steel becomes more intense and the flow rate increases. This intensified flow leads to further mixing of the solute‐enriched residual liquid steel along the solidification front in the lower part of the ingot with the unsolidified liquid steel in the upper part of the ingot, [ 46 ] which is beneficial to reduce the degree of macrosegregation above and below the ingot. Meanwhile, the increase in the pouring rate increases the cooling rate and thus the temperature gradient.…”