FIELD OF THE INVENTION
The present invention relates to a submerged entry nozzle (SEN) for use in delivering the molten
steel from tundish to mold in the slab continuous casting process. The invention is related to
providing with a structural configuration of the submerged entry nozzle and in particular to a
SEN that minimizes mold flux related defects in subsequent steel processing by modifying the
fluid flow inside the caster mold cavity.
BACKGROUND OF THE INVENTION
In the continuous casting of steel, there had been continuous efforts to control the fluid flow
inside mold cavity by different SEN designs to garnish a better product quality along with
productivity. One such commonly used SEN is a bifurcated SEN (ref fig 1) where a central bore
terminates into two exit ports that extend almost horizontally to the central bore. However,
although such bifurcated port nozzles enables control on molten steel flow patterns within
casting molds, in the past such SEN designs are faced with certain limitations to maintain a calm
or still liquid reservoir of molten steel within the mold.
In the mold, a liquid slag layer is formed on the steel meniscus by adding or distributing mold
powder into the mold on top of the molten steel. This liquid slag layer acts as a lubricant between
the solidifying steel shell and the mold as the molten steel solidifies as well as an insulator to the
meniscus of the liquid steel.
To prevent the freezing of the steel near the meniscus and sufficiently melt mold flux, there must
continuous supply of heat from underneath steel current overcoming heat loss from the meniscus.
This is attained in conventional bifurcated nozzle by achieving a dual roll flow formation where
a part of port-exit flow is directed towards meniscus to do the job. However, upper roll stream
poses danger of dragging mold flux deep into mold through a higher velocity shear and vortex
formation, consequently, an increased risk that this can lead to the formation of surface defects
known as slivers. These undesirable side-effects can be avoided, or their occurrence is
substantially reduced, by appropriately modifying fluid flow on a scientific basis. There have
been attempts to design submerged entry nozzle to minimize the side effects as described and

patented in US6932250 and US6016941 however, the problems described above still remain
unsolved.
Objects of the Current Invention:
It is therefore an object of the present invention to provide an improved SEN that enable a
greater control of the fluid flow inside mold cavity thus achieving a better meniscus condition
conducive to reduce slivers in subsequent steel processing.
Another object of the invention is to design an improved SEN that can be integrated with
existing set-up and overcome the limitations of the prior art.
SUMMARY OF THE INVENTION: The SEN of the current invention includes a structure that
has a vertical straight bore extending to a point where it joins two bores attached at a
downwardly angle. Unlike in prior art where port angles face limitation in directing the flow at
chosen direction, present invention enables to modify SEN exit flow direction at a desired angle
by suitable deciding the angle of exit bores. According to a feature of the invention, exit bores
angle may vary from 10° to 60° from vertical axis. According to another feature of the invention,
the length of exit bores is sufficient to ensure that angle of the jet streaming out of exit-bores is
as close as exit-bore angle. Generally, it is 4 to 10 times of internal exit-bore diameter. It is yet
another feature of the invention that twice of one exit-bore cross section area is greater than cross
section area of vertical straight bore of incoming section of the SEN. According to another
feature of the invention, both exit-bores of the SEN may have a straight or divergent tube
opening. The opening may suitable be circular or oval so as to spread more flow vertically. The
divergence angle varies in the range from 0° to 20°. Range is to ensure a no boundary layer
separation condition inside the tube. According to the invention, the SEN generates sufficient
upwards flow in a manner that the temperature near the meniscus is sufficiently high as to
prevent the freezing of the steel and melts sufficient mold flux at the meniscus. The invention
also ensures that the turbulence at the meniscus is not increased to a point where steel overlying
phase is dragged into the mold.

BRIEF DESCRIPTlON OF THE ACCOMPANYING DRAWINGS
Figure 1 is a vertical cross-sectional view of a bifurcated submerged entry nozzle.
Figure 2a and 2b are three dimensional view of embodiment of the submerged entry nozzle of
current invention from different angle;
Figure 3 is a vertical front cross-sectional view of a submerged entry nozzle constructed in
accordance with the present invention;
Figure 4 is a side elevation view of the nozzle shown in Figure 2; and
Figure 5 compares water modeling results of the SEN as per the present invention with a prior art
SEN type having an angle of 15° downward ports.
DETAIL DESCRIPTION OF PREFFERED EMBODIMENT
A submerged entry nozzle as per the present invention is depicted in Fig. 2 to 4 for introducing
liquid steel into a slab continuous caster mold. The SEN has appearance of a rigid pipe or tube
and is made of refractory material 1 that has an entry 2 which is connected to a tundish (not
shown) at the top. The vertical bore 3 of the SEN extends downward and divides further into two
bores 4a and 4b attached to vertical bore 3 in a manner that twin bore axis has an angle alpha
with vertical bore 3. Twin bores 4 extends in a plane parallel to wide face of the mold and along
both the opposite side of vertical straight bore 3 axis. Twin bore has a length L and bottom end 5
is submerged into the slab continuous caster mold. The end of the vertical straight bore 3 and
starting of twin bore has a smoothened curved surface 6 to guide the flow from vertical bore 3 in
equal proportion into twin bores 4.
Fig, 2a illustrates an outer view of the submerged entry nozzle, as seen from a top angle. The
figure shows a circular entry of the SEN as per the disclosed invention where vertical section of
the SEN in form of a pipe or tubing leads twin-bore section in a manner so as to divide the

incoming flow of liquid steel through vertical bore equally into two downwardly twin-bore
nozzles.
Fig. 2b illustrates an outer view of the submerged entry nozzle, as seen from a down angle. The
figure shows a vertical section of the SEN in form of a pipe or tubing leads twin-bore section in a
manner so as to divide the incoming flow of liquid steel through vertical bore equally into two
downwardly twin-bore nozzles. Exit of the twin-bore nozzles can be seen as a circular cross
section where liquid steel leaves the SEN as per the invention into the caster mold. Though, exit
of the twin-bore nozzles may also have a shape other than circular like oval shaped so as to
ensure that liquid steel leaves the SEN as per the present invention in a vertically spreading
manner.Fig. 3 illustrates a vertically sectioned view of the submerged entry nozzle, showing a
vertical section 3 leading to twin-bores 4, transporting liquid steel from entry 2 of submerged
entry nozzle to continuous casting mold. The body of submerged entry nozzle pipe 1 is made of
refractory material well known to the makers of such SENs. In the preferred embodiment of the
invention, the two individual downwardly angled pipe shaped nozzles 4, henceforth called twin-
bore, connect to incoming vertical section 3 of the SEN. The surface 6 joining vertical section 3
of the SEN and twin-bore 4 is smoothen elevated curved made in a manner so as to divide the
incoming flow from vertical section of the SEN equally. The SEN has two exits 5a, 5b where
liquid steel leaves the SEN into the caster mold.
In Fig. 4, illustrates vertically side internal view of the SEN as per the invention providing a
deeper insight into the design feature. Here the twin-bores 4 are shown attached to the vertical
section 3. The body of submerged entry nozzle pipe 1 extends downwards. The surface 6 joining
vertical section 3 of the SEN and twin-bore 4 looks flat from this view. The SEN exit openings 5
are circular here but can also be non-circular like oval shaped in a manner that the liquid steel
leaves the SEN in vertically spreading manner.
Referring to the preferred embodiments (Fig. 2-4), downward twin-bores 4 are 60° apart i.e.
alpha 30°, but according to the present invention the angle may suitably have any angle from 20°
to 60° depending upon other parameters of the caster such as size of the nozzle, width of the

caster, casting speed, submergence depth of the SEN etc. The angle can also be computed based
on the heat transfer requirement at the meniscus to ensure enough supply of heat to sufficiently
melt mold flux for required lubrication during continuous casting inside the mold. A simplistic
method for computation of upward movement of the incoming liquid steel mass from twin-bore
nozzle is given as:

This Mu is suitably designed to give just required heat towards meniscus.The advantage of the
downwards twin-bore nozzles 4 attached to the vertical bore 3 is that it avoids sucking of
overlying mold flux in event of a vertex formation near vertical section of the SEN. It is well
known that a vortex forms near SEN vertical section as flow happens from narrow face of the
mold toward SEN along the meniscus. In the prior arts like bifurcated SENs having ports, molten
steel leaves the ports at high velocity. These ports falls in the vicinity of the occurrence of these
vortexes thus are susceptible to catch the overlying flux and subsequently form slivers in the
final product. As per the disclosed invention, exit-bores 4 takes molten steel away from the
vertical section of the SEN before leaving it into liquid pool in the mold thus reducing the
likelihood of molten flux being dragged into molten steel pool by an exit stream from the SEN.
In the preferred embodiments (Fig. 2-4), the bores of the twin nozzles 4 are shown to be straight
pipe like but as per the present invention the bores may also have a divergent bore towards exit
where the shape of the exit 5 may suitable be circular or oval so as to spread more flow

vertically. The divergent angle is from 0° to 20°. The divergent angle depends upon throughput
and nozzle size and can tie computed to ensure a no boundary layer separation condition within
the twin-bore nozzle 4. Such divergent bore will slowly retard the flow within the twin-bore
itself reducing effectively the velocity near meniscus so as to stabilize meniscus. This avoids
breaking the overlying molten flux layer to prevent catching of molten flux deep into the mold
and thus helping production of sliver free steel.
The length L of the SEN twin-bore nozzle 4 is sufficient to ensure that angle of the jet streaming
out of exit-bores is as close as exit-bore angle. For the experiment conducted in laboratory with
SEN as per preferred embodiment, L was kept 7 times of internal bore diameter. Though, 4 to 10
times of internal exit-bore diameter should be sufficient to ensure the angle condition.
Experiments were conducted to demonstrate the advantages the SEN as per the present invention
over those of the conventional nozzles having bifurcated ports. Water model simulations were
performed on a 0.4 scale-down water model caster as per the laws of physical modeling well
explained in the relevant literature. The experiments were carried out for a typical caster casting
speed of 1.2 m/min, slab caster dimension of 1500 x 210 mm2. The time averaged fluid velocity
distribution along the mold width direction just under the meniscus was measured. Figure 5
compares water modeling results of the SEN as per the present invention with a prior art SEN
type having a 150 downward ports. It was found that the steel velocity near the meniscus is
substantially lower for the SEN as per the present invention than it is for the prior art SEN. The
twin-bore nozzles in the disclosed invention are able to direct flow out of the SEN in a desired
ways. It can be seen from the graph that the peak velocity has shifted away from SEN. This
indicates less chances of molten flux being dragged into liquid steel pool due to the vortex
formation phenomena near SEN. A properly designed and controlled upward flow from the SEN
as per the present invention gives an optimized performance in terms of heat supply and
meniscus behavior. This minimizes disturbances to the meniscus thus reduces the likelihood of

entraining particles from upper lying mold molten flux layer into the recirculating liquid steel
stream in the mold to avoid defects such as slivers in final steel products.
Although the present invention has been described with a certain degree of particularity, it
should be understood that those skilled in the art can make various changes to it without
departing from the spirit or scope of the invention as hereinafter claimed.

WE CLAIM:
1. A submerged entry nozzle for transferring liquid steel into a continuous casting mold
from a tundish, the submerged entry nozzle comprising (figure 3 and figure 4):
nozzle structure having a central vertical bore 3 and two downward angled nozzle
bores 4a and 4b; down warded angled nozzles 4a and 4b being positioned at an angle
varying in the range of 10° to 60° from the central vertical bore axis extending to
curved bottom 6.
2. The submerged entry nozzle as per claim 1, wherein the nozzle structure is having an
inlet 2 for receiving an incoming flow of liquid steel from the tundish.
3. The submerged entry nozzle as per claim 1, wherein down warded nozzles 4a and 4b
have a length L equal to 4 to 10 times of internal bore diameter of the down warded
nozzles 4a and 4b nozzles.
4. The submerged entry nozzle as per claim 1, wherein down warded nozzles 4a and 4b
have a length L equal to preferably 7 times of internal bore diameter of the down
warded nozzles 4a and 4b nozzles.
5. The submerged entry nozzle as per claim 1, wherein cross section area of both exit-
bores added-up is greater than cross section area of vertical straight bore of incoming
section of the SEN.

6. The submerged entry nozzle as per claim 1, wherein the bores of the down warded
nozzles 4 are straight pipe or may also have a divergent bore at an angle in the range
of 0° to 20°towards exit where the shape of the exit 5 is circular or oval so as to
spread more flow vertically. The divergent angle is from
7. The submerged entry nozzle as per claim 1, wherein the submerged entry nozzle
vertical section has a tubular shape.
8. The submerged entry nozzle as per claim 1, wherein the downward angled nozzle
bores 4a and 4b directs flow of liquid steel such that the temperature near the
meniscus is sufficiently high as to prevent the freezing of the liquid steel and melts
mold flux at the meniscus.
9. The submerged entry nozzle as per claim 1, wherein the submerged entry nozzle
minimizes turbulence at the meniscus to a point where steel overlying phase is not
dragged into the continuous caster mold.