FIELD OF THE INVENTION
The present invention relates to an improved submerged entry nozzle assembly for
delivering molten steel between a tundish and a mold in a continuous casting process.
BACKGROUND OF THE INVENTION
In a continuous casting process, a tundish is generally used as a buffer vessel where
the molten steel is continuously delivered from the ladle and injected to the mold. The
molten steel gets cooled and solidified in the mold to form continuously cast solid
lengths of metal. A submerged entry nozzle is disposed at the bottom of the tundish
and connected to the mold to discharge the molten metal from the tundish to the mold
without allowing any contact with the air since exposure of the cast solid lengths of
metal to air would cause oxidation of the steel, which adversely affects its quality. It is
highly desirable for the submerged entry nozzle to introduce the molten steel into the
mold smoothly and without any turbulence.
Many quality problems that originate during the continuous casting processes , can be
directly attributed to poor control of fluid flow conditions inside the mold. The quality of
final steel product and productivity of the cast steel substantially depends on liquid steel
flow and turbulence associated with gravity feeding of the liquid steel into the mold.
In a continuous slab caster, a mold slag sometimes get dragged down into the mold
(known as entrainment) due to vortexing, high-velocity flow that shears the slag from
the surface, and turbulence at the meniscus. The capture of large inclusions into the
solidifying shell leads to obvious line defects or slivers in the final product.
In addition, sometimes the thickness of the flux layer starts getting thinner due to
entrainment and vortexing, which interalia causes the meniscus to develop bald near

the narrow side wall of the mold. This leads to oxidation of the liquid steel at the
meniscus and increases oxide inclusions in the steel which is detrimental to the
produced steel product. Hence to deal with these instances, it becomes necessary to
control flow in the mold to avoid meniscus turbulence that could entrain air and slag.
The present inventors recognized that the prior art disadvantages can be avoided, or
their occurrence substantially reduced, by modifying the structure of distribution zone
located at the bottom of the prior art nozzle assembly. The conventional submerged
entry nozzle of prior art comprises a housing having an inlet for receiving an incoming
flow of molten steel from the tundish; a longitudinal body having a central bore
disposed at opposite ends and distribution zone for delivering molten steel to the mold.
The distribution zone of the nozzle assembly having two exit ports to deliver the molten
metal into mold.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an improved submerged
entry nozzle assembly for delivering molten steel between a tundish and a mold in a
continuous casting process.
Another object of the invention is to propose an improved submerged entry nozzle
assembly for delivering molten steel between a tundish and a mold in a continuous
casting process, which is configured to produce stable outflow and reduce meniscus
turbulence including asymmetrical flow patterns inside the casting mold by modifying
the delivery zone portion of the nozzle assembly.

SUMMARY OF THE INVENTION
Accordingly, there is providedan improved submerged entry nozzle assembly for use in
casting of molten metal. The submerged entry nozzle assembly includes at least one
exit port to provide stable and uniform outflow of the molten metal through and from
the exit port. Improved outflow of the molten metal ensures that the turbulence at the
meniscus is not increased to a point that slag particles get entrained into the liquid steel
stream and a symmetrical outflow is maintained. These benefits result in improved
finished products.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a vertical cross-sectional view of a conventional submerged entry nozzle
assembly.
Figure 2 is a three dimensional view of an embodiment of a submerged entry nozzle
assembly of the invention
Figure 3 is a vertical cross-sectional view of a submerged entry nozzle assembly
constructed in accordance with the present invention;
Figure 4 is a side elevational view of the nozzle assembly shown in Figure 3;
Figure 5 is a bottom view of the nozzle assembly shown in Figure 3;
Figure 6 is a cross-sectional view of the bottom end of the nozzle of Figure 3 showing
geometric features of rectangular rib
Figure 7 is a three dimensional view of the bottom of the nozzle assembly shown in
Figure 3;
Figure 8 is an experimental device of 0.4 scaled slab casting water model.

Figure 9 is an experimental device with vane anemometer to determine the sub
meniscus velocity
Figure 10 is a graph depicting the effect of casting speed on sub meniscus velocity for
conventional submerged entry
Figure 11 is a graphical representation of the effect of casting speed on sub meniscus
velocity for the novel submerged entry nozzle assembly of present invention
DETAIL DESCRIPTION OF THE INVENTION
Submerged entry nozzle has the form of an elongate conduit and generally has the
appearance of a rigid pipe or tube (refer Figure 2).
Figures 3-7 illustrate a submerged entry nozzle 1 for introducing molten steel into
continuous casting mold. The nozzle 1 is built of generally tubular-shaped refractory
material and includes a top end 2 (generally called inlet) adapted to connect to a
tundish and a bottom end (designated as exit ports of submerged entry nozzle) 4a & 4b
used to deliver the molten metal into casting mold. A generally circular central bore 3
extends vertically and concentrically through the nozzle 1, the centre of which is
defined by the geometric centre of the nozzle 1, indicated generally by the axis A.
Figure 3 illustrates a sectioned view of the submerged entry nozzle, showing the
rectangular exit ports, transporting molten metal from bore of submerged entry nozzle
to continuous casting mold ) 4a & 4b. 6 represent longitudinal body of submerged entry
nozzle tube. In the preferred embodiment, the two individual rectangular exit ports 4a,
4b are about 180 degrees apart (as shown in Figure 3, 4), situated transverse to central
bore at the end of submerged entry nozzle tube 3.

Exit ports 4a, 4b consist of upper regions which are defined by respective downwardly
slanted lips 8a, 8b and lower rectangular rib region 7. The slanted lips 8a, 8b emerge
from an interior wall 5 of the central bore 3 to the periphery or outer wall of the nozzle
1. The slanted lips 8a, 8b are negatively sloped at an angle alpha with respect to the
horizontal plane. According to the invention, the angle alpha can vary between 0 and 15
degrees. The desired angle may depend on such factors as the size of the nozzle, the
casting speed, the immersion depth of the nozzle. In a preferred embodiment, angle
alpha is 0 degrees from the horizontal. The exit port (4a) has a height (L) ranging from
80 mm to 140 mm, a width (B) ranging from 40 mm to 80 mm as shown in Figure 4.
In Figures 5 and 6, Rectangular cross section rib shape 7 appears at the bottom of the
nozzle tube to create the flow downward directed compared to the prior art. Figures 5
and 6 illustrate bottom view of submerged entry nozzle providing a deeper insight into
the design feature related to rectangular rib 7. According to the invention, width of the
rectangular rib 7 is 55- 85% of the inside bore diameter of cylindrical tube, 5.
Rectangular rib (ref. figure 5) is so designed that along its width, it conceals a portion
of inner bore area. Width of rectangular rib conceals between 50-90% of inner bore
area by subtending an angle (shown as B in figure 5) 45°-115° at the centre of cylinder
bore.
EXPERIMENTAL PROCEDURE
Experiments were conducted to demonstrate the advantages of the flow characteristics
of the submerged entry nozzle assembly of the present invention over the conventional
nozzle under various casting speeds. Specifically, water model simulations were
performed on a 0.4 scale water model caster (ref. Figure 8).

Water was used to model steel because it has a similar kinematic viscosity to molten
steel enabling the water to exhibit similar flow properties for modeling purposes. In
order to achieve the dynamic similarity between the water model and the steel
prototype system, the Froude similarity was used,

where m denotes model (water modeling), and p denotes prototype (molten steel
system), U is the characteristic velocity, L is the characteristic length.
For the current study, λ=Lm/Lp.=1:2.5, Eq.(l) gives

Thus, the flow rate ratio between the model and the prototype can be calculated by,

The flow rate used in the water modeling can be derived from the casting speed using
Eq.(3) and is shown in Table 1. Water modeling experiments were carried out for the
steel casting speed of 1.2-1.8 m/min.


Water was poured into the tundish and the flow entered the mold via the SEN and
finally recirculated back to the tundish by a pump. A flow meter was used to control the
outlet flow rate to simulate flow state in the mold at different casting speeds. The water
level in the tundish was controlled by adjusting the opening using stopper rod whereas
the water level in mold was controlled by the valves at the mold exit.
The time averaged fluid velocity distribution along the mold width direction just under
the meniscus was measured by impeller-velocity probes. (See Figure 8)
EXPERIMENTAL RESULTS
Referring now to Figures 10 and 11, it can be is seen that the steel velocity near the
meniscus is substantially lower for the novel SEN of the present invention than it is for
the conventional SEN. The lateral ports in the said SEN impinges liquid steel deep into
the mold. This would cause 'least disturbances to the meniscus. This reduces the
likelihood of entraining particles from the mold slag layer into the recirculating liquid
stream in the mold and later causing defects such as slivers in final products.
It can be also seen that near the meniscus, the velocity rises by almost double as the
casting speed is increased from 1.2 m/min to 1.8 m/min for conventional submerged
entry nozzle. But in case of the improved submerged entry nozzle assembly of present
invention, this velocity rise is much more less. It is therefore established that by use of
the submerged entry nozzle assembly of the present invention, casting of steel can be
performed at higher speeds than those attained by use of the conventional nozzle.
Consequently, the overall productivity of the caster is substantially increased.

With the improved submerged entry nozzle assembly of present invention, the stream
penetration is very deep, and recirculating flow travels a long distance before flowing
upward to the meniscus corners. With a quiet surface, slag entrainment is unlikely with
this condition.
Lateral exit ports in the submerged entry nozzle of present invention are proficient to
create double roll flow pattern inside the mold which is desired for an optimal flow. An
optimal flow pattern near the meniscus is always preferred to transport the inclusion
particles to the top surface so that they can be continuously absorbed by the molten
mold powder layer and encourage uniform solidification. Further, with the use of the
nozzle of the present invention, it is possible to improve the quality of a steel product
made by using the nozzle, and ensure a stabilized casting process operation.

WE CLAIM:
1. An improved submerged entry nozzle assembly for delivering molten steel
between a tundish and a mold in a continuous casting process, comprising:
a housing having an inlet (2), for receiving an incoming flow of molten steel from
the tundish;
a longitudinal body (6), having a central bore (3) disposed at opposite ends;
a distribution zone, for delivering molten steel to the mold, the distribution zone
having a bottom portion and an upper portion,
the bottom portion consisting of a rectangular rib (7), the rectangular rib width
being 55-85% of inside bore diameter of the longitudinal body (6),
the upper portion having downwardly slanted lips (8a, 8b) sloped at about an
angle of 0 to 15 degrees with respect to a plane perpendicular to the vertically
extending central bore (3).
2. The submerged entry nozzle as claimed in claim 1, wherein the distribution
zone has two lateral openings to pour the molten steel.
3. The submerged entry nozzle as claimed in claim 1, wherein the submerged
entry nozzle has a tubular shape.

4. The submerged entry nozzle as claimed in claim 1, wherein the angle of the
slanted lips (8a, 8b) is adjusted depending upon size of the nozzle, casting speed
and immersion depth of the nozzle.

ABSTRACT

Slag entrapment in the mold is one of the major causes of macro nonmetallic inclusions
in steel which arises from the disturbances at the melt free surface (meniscus) in the
mold. Again appropriate surface flow velocity in mold is required during the casting
process because the mold level should keep stable and the covering slag cover well.
There are continuous demands for the improvement of the submerged entry nozzle
structure to achieve a more desirable flow pattern in the mold. The novel submerged
entry nozzle design of the present invention is adapted to reduce turbulence and mold
disturbances, thereby producing a more stable, uniform outflow, which will play vital
role in reducing the nonmetallic content and inclusions in the casting.