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ISIJ International, Vol. 44 (2004), No. 8, pp. 1358–1365

Effect of Entrance Nozzle Design on the Fluid Flow in an Ingot
Mold during Filling
Robert ERIKSSON, Lage JONSSON and Pär G. JÖNSSON
Division of Metallurgy, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
(Received on June 12, 2003; accepted in final form on May 27, 2004 )

Earlier studies have shown that the mold powderreacts with steel during filling of the mold during ingot
casting of ball-bearing and tool steels, which results in formation of inclusions. Since all inclusions are bad
for the material properties for these grades, this is a phenomenon that needs to be avoided. In this study,
fundamental mathematical modeling of the filling of an ingot has been used to predict the fluid flow characteristics. Aspecial effort has been made to model the effect of a modified inlet allowing for a larger volume
flow. Predictions made by the presently used numerical model, indicates that a successive increase in the
opening angle of the inlet nozzle leads to a gradual decrease in the disturbance of the free surface, during
mold filling. Furthermore, the horizontal velocities are lower, which results in lowervalues of the Weber
number which is an indication of less chances for mold powder entrapment into steel. It is concluded that
both these improvements leads to decreased possibilities for the creation of inclusions in the steel due to
interaction with the mold powder.
KEY WORDS: up-hill teeming; mold filling; fluid flow; CFD; inlet geometry; large eddy simulation.

1.

the filling of the molds.This could lead to the formation
of new non-metallic inclusions at a very late stage in the
process chain. Due to the late formation of these inclusions,
they could be very hard to remove from the liquid steel.
The size of these inclusions containing mold flux are quite
large,2) which makes them especially harmful to the quality
of the final product. Therefore, it is of the outmost interest
tofind ways to eliminate, or at least reduce, the risk of the
formation of inclusions that originates from the mold flux
in order to improve the product quality.
In this work numerical simulations have been carried out
in order to investigate the effect of the geometry of the inlet
on the velocity field during the early stages of the filling of
a 4.2 tonne ingot mold. In Fig. 1 a schematic diagramof
the up-hill teeming process is shown. Before casting, a
paper bag filled with approximately 5 kg of mold powder is

Introduction

Up-hill teeming only makes up a small fraction of today’s
steel production, but it is still used in the production of certain steel grades where the quality rather than the quantity
comes in the first room. Furthermore, up-hill teeming is
used for steel grades,such as ball-bearing and tool steels
that are hard to cast continuously with a good sound product quality. Therefore, it is more important than ever for
companies using up-hill teeming to pay attention to the
process and develop it further in order to remain competitive. Quality aspects concerning the up-hill teeming process
that have been addressed is yield and surface quality and in
recentyears the formation of unwanted non-metallic inclusions. Non-metallic inclusions are primarily formed as deoxidation products as a result of the addition of a metals
with strong affinity to oxygen during the ladle treatment operation. Entrained ladle slag or torn of refractory lining can
also be a source of non-metallic inclusions. The presence of
this type of inclusions is quite scarce butvery harmful
since they usually are quite large in size. At the end of the
ladle treatment operation, just before the casting, ball-bearing and tool steel grades contains very few non-metallic
inclusions and has a low total oxygen concentration.1)
Previous studies have shown that it is possible to find inclusions containing traces of mold flux in samples taken from
the steel during the filling...