Effect of Ladle Changeover Condition on Transient Three-Phase Flow in a Five-Strand Bloom Casting Tundish
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The transient three-phase flow behavior in a five-strand bloom casting tundish during the ladle changeover process considering a constant casting speed was investigated by the VOF model, and the effect of ladle throughput rate, shroud immersion depth, turbulence inhibitor structure and ladle changeover time on the turbulent flow, and level fluctuations during the filling process were analyzed to optimize the flow pattern in the tundish during ladle changeover. The results showed that the exposed area of molten steel in the impact zone increases as the ladle throughput rate increases during the filling process and that the exposure of molten steel is eliminated when the ladle throughput rate is 1.5Qsteady. As the immersion depth of the shroud increases, a slight decrease in slag entrainment happens, while the exposed area of molten steel first decreases and then increases. The shroud immersion depth should be 310 mm. When the optimized turbulence inhibitor is used, the wave crests of the steel level are greatly reduced, the height of the level fluctuation is alleviated with the maximum value decreasing from 33 mm to approximately 10 mm, and the exposure of molten steel is eliminated. When the ladle changeover time is between 2 and 3 minutes, the exposed area of molten steel during the stable period of the filling process is in the range from 150 to 170 cm2, which is substantially less than the exposed area of 500 cm2 when the ladle changeover time is 4 minutes. Therefore, the ladle changeover time should be controlled within 3 minutes. The flaw detection disqualification rate caused by ladle changeover operation is decreased from 43.8 to 25.8 pct of the total disqualified steel rails after optimization.
The authors would like to express their gratitude for the financial support provided by the National Natural Science Foundation of China (51774217 and 51604201) and the Research Project of Hubei Provincial Department of Education (D20171104).