Abstract
The steel-slag-air multiphase flow in a bloom tundish with five strands during the transient casting of the ladle change was simulated using the Volume of Fluid (VOF) model, and the formation mechanisms of macro-inclusions and the behavior of the steel-slag-air interface during the filling process were investigated. Water model experiments were conducted to validate the multiphase model. The results showed that the numerical results of slag entrapment behavior and the exposed area of steel are basically consistent with the experimental results. The flow of molten steel in the tundish is weak except for the region around the stopper rods at the end of the emptying process. Strong fluctuations in liquid level were formed during the filling process, showing two wave crests in front of and behind the shroud in the impact zone, which intensified with the increase in filling time and then declined gradually. Entrapment phenomena and exposure of liquid steel could not be observed before the filling stage. While the entrapped slag droplets mostly float up and can be removed within 40 s during the filling process, the remainder enters the casting zone through the baffle. The maximum exposed area of molten steel is 252 cm2 when the filling time is 4.0 s.
Highlights
A transient casting process refers to a casting process in which the flow rates at the inflow and outflow differ [1], and has become a key method for obtaining high-quality clean steel in continuous casting
The simulation results the multiphase flow field were verified by the water model to represent the slag phase
A three-dimensional mathematical model was developed with Volume of Fluid (VOF) to track the interface between different phases in the transient casting period
Summary
A transient casting process refers to a casting process in which the flow rates at the inflow and outflow differ (e.g., a ladle change) [1], and has become a key method for obtaining high-quality clean steel in continuous casting. Re-oxidation and the entrapment of slag during transient-state casting are much more serious issues than in steady-state casting, and lead to the number of billet quality defects being significantly higher [2,3]. The ladle change operation between the previous and the ladle of steady casting occurs repeatedly in a complete casting process, which is detrimental to overall quality control of continuous casting. During the ladle change of the continuous casting process, minimizing the negative effects at the transient casting stage is a challenge faced by the world’s metallurgists [4,5]. Takahashi et al [7]
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