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This
is a collaborative work between Prof. S. Kitamura’s research group
(Tohoku University, Institute of Multidisciplinary Research for
Advanced Materials, Sendai, Japan) and our research group (at IISc).
In recent times the demand of ultra-low carbon
steel (ULCS) with improved mechanical properties such as good ductility
and good workability has been increased as it is used to produce
cold-rolled steel sheets for automobiles. For producing ULCS
efficiently, it is necessary to improve the productivity of the vacuum
degasser such as RH, DH and tank degasser. Recently, it has been
claimed that using a new process, called REDA (Revolutionary Degassing Activator),
one can achieve the carbon content below 10ppm in less time. As such,
REDA process has not been studied thoroughly. Fluid flow phenomena
affect the decarburization rate the most besides the chemical reaction
rate. Therefore, in this study, momentum balance equations along with
k-eps turbulent model have been solved for gas and liquid phases in
two-dimension (2D) for REDA process. Similarly, computational fluid
dynamic studies have been made in 2D for tank degasser and RH processes
to compare them with REDA process. Computational results have been
validated with published experimental and theoretical data (Figure 1).
It is found that REDA process is the most efficient among all these
processes in terms of mixing efficiency. Fluid flow phenomena have been
studied in details for REDA process by varying gas flow rate, depth of
immersed snorkel in the steel, diameter of the snorkel and change in
vacuum pressure. It is found that design of snorkel affects the melt
circulation of the bath significantly. Typical contours of average
water velocity in REDA process at air flow rate of 6.1 x 10-4 Nm3/s are shown in Figure 2.
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