Numerical simulation of fluid flow and solidification in bloom continuous casting mould with electromagnetic stirring

Abstract

A three-dimensional mathematical model of bloom continuous casting with mould electromagnetic stirring (M-EMS) has been developed. Stirring current effects on induced flow characteristics, heat transfer and solidification were investigated numerically. The results indicate that the electromagnetic force has a circumferential distribution on the plane transverse to the bloom strand, with maxima at the bloom corners. Joule heating produced by M-EMS is very small and can be ignored in the heat transfer calculations. Under the influence of rotational M-EMS, the swirl flow velocity of the melt decreases significantly when solidification is considered. With increasing stirring current, swirl flow intensifies remarkably, which prevents the superheated jet from the submerged entry nozzle flowing downwards and thereby reduces jet penetration into the liquid core. This increases the temperature of the melt in the mould and the temperature gradient at the solidification front, promoting superheat dissipation in the mould and enhancing the percentage of equiaxed zone in the strand.

On an Anomaly in the Modeling of Electromagnetic Stirring in Continuous Casting

“…[11]. The above may be simplified in a self-consistent way by taking v r 0; [4], [11], and [16]. We find that [1] and [4] are satisfied automatically, whereas [2] and [3] become…”

“…Consequently, there appears to be some uncertainty as to what should be the correct boundary condition in this situation: indeed, McKee et al [10] followed Moffatt [11] in initially assuming that both the normal and tangential components of the magnetic flux density are required as boundary conditions, only to ultimately just use the latter. Moreover, the fact that the expressions for the components of the Lorentz force for round billets [2,7] and for rectangular strands [3] have been cited and used on numerous occasions since, even up to the present day, [9,[12][13][14][15][16][17][18][19] suggests that a resolution of the issue is timely.…”

Effects of EMS Induced Flow on Solidification and Solute Transport in Bloom Mold

“…Geng et al [4] and Yu et al [5] indicated that the EMS parameters affects the metallurgical behavior and the steel quality significantly, an optimum EMS parameter for a certain bloom should be proposed for a higher quality. Recently, numerous mathematical and experimental studies on the CC process involving M-EMS were conducted to investigate the flow field distribution of molten steel [6][7][8][9], and the heat transfer and initial solidification behaviors influenced by EMS induced fluid flow were also studied in past years [10][11][12][13]. Yang et al [10] and Ren et al [13] recently discussed the effects of EMS parameters on the flow pattern and initial solidification in the big bloom mold fed by a normal nozzle with a single outlet, and stated that M-EMS can promote superheat dissipation and enhance the percentage of the equiaxed zone, while the mutual effect between the EMS induced flow and the growth of the solidifying shell lacked discussion.…”

Large Eddy Simulation of Electromagnetic Three‐Phase Flow in a Round Bloom Considering Solidified Shell

“…The iron core is assumed to be magnetically with a constant permeability. The specific heat of molten steel has a permanent value. In continuous casting, the magnetic Reynolds number in CC is so small that the movement of steel can not affect the electromagnetic field The influence of Joule heat generated by currents is ignored in calculation of heat transfer and solidification because of its low frequency. The mushy zone is modeled as a porous medium, in which the flow obeys Darcy's law. The slag is assumed to be in a liquid state.…”

“…Due to the drag effect of solid dendrites in the mushy zone, a sink term is modeled by Darcy's law: where is the casting speed; is a mushy zone parameter, depending on the morphology of the solidifying alloy. In general, the value for is usually between and . However, an excessive large value may lead to iteration divergence, especially in multiphase flow considering solidification.…”