REFRACTORY IMMERSION NOZZLES

BUSES REFRACTAIRES D'IMMERSION

English Abstract

ABSTRACT
REFRACTORY IMMERSION NOZZLES
A refractory immersion nozzle for pouring molten steel
into ingot mounds of small cross-section e.g. from a con-
tinuous billet casting installation includes a pouring tube
of ceramic oxide material, e.g. stabilized ZrO2, at at least
that end of the nozzle which, in use, is immersed.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A refractory immersion nozzle in which at least that
end of the nozzle which, in use, is immersed comprises a
pouring tube of ceramic oxide material.
2. A nozzle as claimed in claim 1 in which the wall thick-
ness of the pouring tube is less than 10 mm.
3. A nozzle as claimed in claim 1 in which the pouring
tube comprises one or more oxides with a melting point above
1950°C.
4. A nozzle as claimed in claim 1 including a support
flange of refractory concrete mounded around the end of the
pouring tube remote from the end which, in use, is immersed.
5. A nozzle as claimed in claim 1, including a pre-
fabricated refractory support flange cemented to the end of
the pouring tube remote from the end which, in use, is
immersed.
6. A nozzle as claimed in claim 1, 2 or 3, including
a metal shell extending over at least part of its external
surface.

7. A nozzle as claimed in claim 4 or claim 5 in which
the support flange is substantially gas impermeable and a
porous ceramic ring or a space extends around the pouring tube
within the support flange and is connected to a gas connec-
tion, whereby gas may be introduced into the pouring tube.
8. A method of casting a billet in which molten metal
is permitted to flow through an immersion nozzle as claimed
in claim 1, 2 or 3 into an ingot mound, the length of at least
one of the sides of the cross-section of which is less than
125 mm.

Description

I Z
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REFRACTORY IMMERSION NOZZLES
The invention relates to refractory immersion nozzles,
particularly for pouring molten steel into ingot mounds of
small cross-section from continuous billet casting
installations.
5. With ingot mounds having a small pouring cross-section,
whose sides are less than 125 mm long, conventional immersion
nozzles manufactured from conventional refractory materials,
for instance, alumina-graphite or vitreous silica, have
only a short service life and thus do not permit a
10. continuous pouring operation thereby rendering the pouring
operation uneconomical. This is due to the fact that a
small cross-section of the ingot mound necessitates a
small cross-section for the immersion nozzle which projects
into it. Having regard to the requirement of providing a
15. sufficiently large flow cross-section for the molten stream
of metal this results in the wall thickness of the nozzle
being so small as to cause problems, particularly as
regards wear resistance. The wall thickness when using
conventional material is in any event in practice limited
20. to a lower limit of 10 mm due to the properties of the
materials. The closer the wall thickness comes to this
lower limit the shorter the service life of the immersion
nozzle. The manufacture of immersion nozzles with a small
wall thickness is extremely difficult and a relatively
25. high proportion of wastage and breakage occurs.
Having regard to these problems it is an object of the
present invention to provide an immersion nozzle for use with
ingot mounds having a small pouring cross-section, primarily
for casting billets the length of whose sides is less than
30. 125 mm, which has a relatively long service life and high
resistance to breakage and is simple to manufacture with a

39~22
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relatively small wall thickness.
According to the present invention there is provided a
refractory immersion nozzle, particularly for pouring molten
steel into ingot mounds of small cross-section from contain-
5. use billet casting installations, in which at least that end of the nozzle which, in use, is immersed comprises a
pouring tube of ceramic oxide material. The thickness of the
wall of the pouring tube is preferably less than 10 mm and
may be as low as 5 mm but the nozzle nevertheless has an
10. excellent service life which can as much as triple the
casting time whereby casting may be effected economically
even when the ingot mound is extremely small. The pouring
tube is preferably isostatically pressed or extruded and
may be simply manufactured with a mechanical stability
15- which is resistant even to rough handling.
The pouring tube preferably comprises one or more oxides
with a melting point above 1950C and preferably comprises
stabilized ZrO2. Such materials have a high resistance to
thermal shock.
20. The entire immersion nozzle may be constructed as a
single unit of ceramic oxide material. Alternatively, the
nozzle may be of two-part construction with a refractory
support flange extending around the end of the pouring tube
remote from the end which, in use, is immersed. The support
25- flange may be of refractory concrete mounded around the
pouring tube or it may be prefabricated and cemented to the
pouring tube. In both embodiments which are found to be
particularly suitable for practical use an external metal
shell is preferably provided which covers the whole or a
part of the external surface of the nozzle and serves to
reinforce and protect the nozzle when being handled. The
sheet metal shell can be used as a lost mound for mounding

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a support flange of refractory concrete around the pouring
tube.
In one embodiment of the invention the support flange
is substantially gas impermeable and a porous ceramic ring
5. or a space extends around the pouring tube within the
support flange and is connected to a gas connection, whereby
flushing or scaven~rg gas may be introduced into the pouring
tube at any time in accordance with requirements.
One exemplary embodiment of the invention will be
10. described below with reference to the single drawing which
is a longitudinal sectional view of an immersion nozzle.
The nozzle comprises a circular section ceramic oxide
pouring tube 1 whose upper end is received in a support
flange 2 for connection to a pouring vessel which is not
15- illustrated for the sake of simplicity. The free lower end
of the nozzle is shown extending into a continuous casting
ingot mound 3 which has a relatively small cross-section
and serves to cast steel billets, the length of the sides
of the cross-section of which is less than 125 mm. The
20- pouring tube 1 and the support flange 2 are surrounded by a
sheet metal shell 4 which reinforces and protects the
immersion nozzle.
In a modified embodiment which is not illustrated a
prefabricated pouring tube 1 is centrally set in a pro-
25- fabricated sheet metal shell 4 and concrete is poured into
the shell to form the support flange 2. This is found to
be a particularly simple method of manufacture.
If the pouring tube is cemented into a prefabricated
support flange 2 the sheet metal shell 4 may be applied
subsequently. The shell 4 may cover only part of the exterior
of the pouring tube 1, for instance that portion of the
pouring tube which extends out of the support flange 2 in

~39S~
which event the support flange 2 merely serves as a
securing basis for the sheet metal shell 4.
A porous ceramic ring 5 extends around the pouring
tube 1 within the support flange 2 and communicates with
5- a gas connection 6 and may be used to introduce a flushing
or scavenging gas into the pouring tube.