FIELD OF INVENTION
This invention relates to conical nozzle fitted in vessels containing molten metal
e.g. steel for teeming. In particular, the invention relates to outlet nozzles used
in a tundish for teeming of molten steel in continuous casting moulds such as
billet moulds. More particularly, the invention relates to an improved tundish
nozzle to substantially reduce the flickering of molten metal stream outletting via
the tundish nozzle.
BACKGROUND OF INVENTION
Cone-shaped open-metering nozzles are used normally for the teeming of molten
metal, such as steel, from a tundish into continuous casting moulds. While
teeming, the molten metal stream coming out of such a conical nozzle is prone
to generate flow-instability. Conical shape of the nozzle tends to amplify any
disturbance in the fluid flowing from upstream such as inlet stream into the
tundish from the ladle, including operational changes for example, change in
steel temperature etc. The flow-instability causes the outlet stream via the
tundish nozzle to flicker. Flickering of the molten metal stream is detrimental to
the downstream processes and thus is undesired. In contrast, a smooth molten
metal stream entrains less atmospheric air into the mould and consequently
creates less disturbance at the liquid surface in the mould.
A flickering and turbulent molten metal stream coming out of the nozzle impairs
the meniscus as it impacts the molten metal surface in the mould thus worsens
the metallurgical solidification conditions.

OBJECT OF INVENTION
It is therefore an object of the present invention to propose an improved tundish
nozzle to substantially reduce the flickering of molten metal stream outletting via
the tundish nozzle.
SUMMARY OF INVENTION
According to the invention there is provided an improved tundish nozzle to
substantially reduce the flickering of molten metal stream outletting via the
tundish nozzle. The improved nozzle is provided with an annular ring at the
bottom of the tundish. The edges of the annular ring is configured substantially
smooth and curved to minimize the erosion and to guide the fluid flow smoothy
into the nozzle. The annular ring may be a part of the nozzle itself as an
extended and integrated part or a part of the tundish bottom. The height and
width of the annular ring is configured corresponding to the size of the nozzle
and that of the tundish.
Accordingly, there is provided an improved tundish nozzle to substantially reduce
the flickering of molten metal stream outletting via the tundish nozzle, the
improvement comprises providing an annular ring having an inner diameter
identical to the entry diameter of the tundish nozzle disposed on the bottom of
the tundish so that the annular ring constitutes one of an integral part of the
nozzle and a part of the tundish bottom, the annular ring provided with edges
and corners configured to be smooth and rounded with refractory material
superimposed thereon, the annular ring designed with a height and width

corresponding to the size of the nozzle and that of the tundish such that the fluid
flow gets stabilized before it enters into a conical part of the nozzle.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In order that the invention may be more readily understood, an embodiment
thereof will now be described with reference to the drawing in which:
Fig. 1 shows side and top view schematic illustrating the improved tundish nozzle
in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
This invention is configured to overcome the problem of metal stream flickering,
in which a simple and effective modification of a known conical nozzle has been
incorporated. The existing conical nozzle as used in the tundish is not capable of
suppressing any perturbation coming from upstream in the tundish and thus
sometime leads to flickering of molten metal stream. Experimentions have
established that the fluid flow path that molten metal takes before entering into
the nozzle essentially makes the flow susceptible to flickering. The present
invention thus, modifies the fluid flow-before it enters into the nozzle (1) and
stabilizes the fluid flow so that effect of upstream perturbations on the flow
outletting from the nozzle (1) is reduced. It has been noticed during water
modeling experiments that the fluid flow in the nozzle (1) is of swirling type and
it is the fluctuations is side streams that come along the bottom wall of the
tundish which largely affects the molten metal stream out of the nozzle (1). The

present invention contemplates to curtail these side streams before they enter
into the nozzle (1). To curtail these side stream, an annular ring (2) is placed on
the nozzle (1) at the tundish bottom (3). The annular ring (2) is so configured
and disposed to be an integral part of the nozzle (1) itself or a part of the
tundish bottom(3). The edges and corners of the annular ring (2) whether
configured as a part of the existing nozzle (1) or a part of the tundish bottom
(3), is designed sufficiently smooth and rounded to enable the flow to be guided
over it and thus minimize the wear of the annular (2) ring. The refractory
material of the annular ring (2) can be suitably selected to resist the wear and
any impact at high temperature encountered in the corresponding condition. The
inner diameter of the annular ring (2) is to be chosen same as that of the entry
diameter of the nozzle (1). The height of the annular ring (2) is designed to
stabilize the flow before it enters into conical part of the nozzle (1).
It will be understood that the improved tundish nozzle in accordance with
present invention has many advantages.
1. It enables smooth and turbulence free molten metal stream coming out of
the nozzle (1).
2. The effect of any perturbation generated upstream to the nozzle (1) in the
tundish (3) on the molten metal stream is suppressed by the improved
tundish nozzle having the annular ring (2).
3. The annular ring (2) placed on the tundish nozzle reinforces the nozzle
(1), thus is expected to increase the life of the nozzle (1) itself.

Although particular embodiments of the invention have been shown and
described in full here, there is no intention to thereby limit the invention to the
details of such embodiments. On the contrary, the intention is to cover all
modifications, alternatives, embodiments, usages and equivalents as fall within
the sprit and scope of the present invention, specification and appended claims.

WE CLAIM:
1. An improved tundish nozzle to substantially reduce the
flickering of molten metal stream outletting via the tundish
nozzle, the improvement is characterized by:
- an annular ring (2) having an inner diameter identical to the
entry diameter of the tundish nozzle (1) disposed on the bottom
of the tundish nozzle (1) so that the annular ring (2) constitutes
one of an integral part of the nozzle (1) and a part of the tundish
bottom (3),
- the annular ring (2) provided with edges and corners
configured to be smooth and rounded with refractory material
superimposed thereon,
- the annular ring (2) designed with a height and width
corresponding to the size of the nozzle (1) and that of the
tundish (3) such that the fluid flow gets stabilized before it
enters into a conical part of the nozzle (1).

ABSTRACT

TITLE; 'A TUNDISH NOZZLE DESIGN FOR SMOOTH TEEMING OPERATION'
The invention relates to an improved tundish nozzle to substantially reduce the
flickering of molten metal stream outletting via the tundish nozzle, the
improvement is an annular ring (2) having an inner diameter identical to the
entry diameter of the tundish nozzle (1) disposed on the bottom of the tundish
nozzle (1) so that the annular ring (2) constitutes one of an integral part of the
nozzle (1) and a part of the tundish bottom (3). The annular ring (2) is provided
with edges and corners configured to be smooth and rounded with refractory
material superimposed thereon, the annular ring (2) designed with a height
and width corresponding to the size of the nozzle (1) and that of the tundish (3)
such that the fluid flow gets stabilized before it enters into a conical part of the
nozzle (1).