Modeling of Fluid Flow and Residence Time Distribution in a Four-strand Tundish for Enhancing Inclusion Removal

Abstract

The introduction of the appropriate size and precise location of flow control devices such as dam, turbulence inhibitor, etc., helps to modify the flow pattern and minimizing short circuiting and dead zone. Beside this, these also create the surface directed flow and maximize the residence time available for the flotation of inclusions and assimilation of the reaction products from the molten steel into the slag phase. These can be products of deoxidation, reoxidation, precipitation, emulsification and/or entrainment of refractory components into the melt and thus encompass both indigenous and exogenous inclusions. To this end, both the numerical and physical simulations were carried out mainly for three cases: a) in absence of flow control devices (i.e., bare tundish), b) in the presence of a dam, and c) with the application of turbulence inhibiting device (TID) and dam combination in the existing tundish configuration. The commercial CFD (computational fluid dynamics) package FLUENT ® was used to predict the flow field prevalent in the water model tundish at steady state, whereas in the experimental program, both Particle Image Velocimetry (PIV) techniques for flow measurements and tracer dispersion experiments for concentration measurements were applied in the present study. Among all types of configurations applied in the present study, a combination of TID with holesϩa dam work reasonably found to be an optimum configuration of the four-strand tundish regarding inclusion floatation. A superior strand similarity is also achieved in this configuration. Also the predicted time averaged horizontal and vertical components agreed withinϮ10 % with the experimentally derived ones.

Numerical and physical modelling of tundish slag entrainment in the steelmaking process

“…Numerical and physical modelling of tundish slag entrainment and Koria, 2008;Mazumdar and Guthri, 1999;Sahai and Emi, 2008). As a result there is little or no information on how the FCDs affect the slag layer.…”

“…These studies were aimed at improving the flow characteristics in the tundish (Chattopadhyay, Isac, and Guthri, 2010;Cloete, 2014;Jha, Dash, and Kumar, 2001;Jha, Rao, and Dewan, 2008;Kumar, Koria, and Mazumdar, 2007;Kumar, Mazumdar, and Koria, 2008;Mazumdar and Guthri, 1999;Sahai and Emi, 1996;Sahai and Burval, 1992; Tripathi and Ajmani, 2011). These studies have led to the use of flow control devices (FCDs) to increase the melt residence time in the tundish and provide surface-directed flow so as to assist with inclusion removal.…”

“…Figure 3 shows the dimensions of the FCD used in this study. The design is based on those used by Cloete (2014) and Kumar, Mazumdar, and Koria, (2008). The FCD was constructed from 15 mm thick grey PVC.…”

“…The design is based on a tundish used by Kumar, Mazumdar, and Koria (2008), but instead of a scale factor of 1/3 a scale factor of 1/2 was used. The model is constructed from clear 6 mm PVC.…”

“…This has been the norm for most researchers who have worked in the field. They specified the boundary condition at the top of the fluid layer (Cloete, 2014;Kumar, Mazumdar, and Koria, 2008;Mazumdar and Guthri, 1999;Sahai and Emi, 1996;Tripathi and Ajmani, 2011). It is worth mentioning, though, that this boundary condition was used without the presence of a slag phase.…”