U.S. patent application number 10/258925 was filed with the patent office on 2003-05-15 for refractory component and assembly with improved sealing fo injection of an inert gas.
Invention is credited to Hanse, Eric, Richaud, Johan.
Application Number | 20030090043 10/258925 |
Document ID | / |
Family ID | 8175739 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030090043 |
Kind Code |
A1 |
Hanse, Eric ; et
al. |
May 15, 2003 |
Refractory component and assembly with improved sealing fo
injection of an inert gas
Abstract
The invention describes a refractory component (1, 4) provided
with means of injecting or conveying (5, 16) gas and means of
delivering said gas from an external wall of the component to said
means of injection (5, 16), the means of delivery of the gas
comprising a part of enlarged cross-section (7, 17) extending from
an external wall of the component and a part of reduced
cross-section (8, 18) communicating, at one end, with the inner end
of the part of enlarged cross-section (7, 17) and, at the other
end, with the means of injecting or conveying gas (5, 16), the said
component also comprising a seal (12, 22) fitted against the inner
end of the part of enlarged cross-section, said seal (12, 22),
comprising an orifice at least partially in register with the
communicating orifice (11, 21) between the parts of enlarged and
reduced cross-section, which is characterised in that the seal (12,
22) presents a cross-section substantially similar to the
cross-section of the enlarged part (7, 17). According to another of
its aspects, the present invention relates to an assembly including
a refractory component as described above and a gas delivery line
(9, 19), wherein one end of the gas delivery line is engaged in the
part of enlarged cross-section which holds a seal (12, 22) in
compression against the side walls of the part of enlarged
cross-section.
Inventors: |
Hanse, Eric; (Feignies,
FR) ; Richaud, Johan; (Ontario, CA) |
Correspondence
Address: |
Vesuvius
USA Corporation
27 Noblestown Road
Carnegie
PA
15106-1632
US
|
Family ID: |
8175739 |
Appl. No.: |
10/258925 |
Filed: |
October 28, 2002 |
PCT Filed: |
April 27, 2001 |
PCT NO: |
PCT/BE01/00076 |
Current U.S.
Class: |
266/217 |
Current CPC
Class: |
B22D 41/58 20130101 |
Class at
Publication: |
266/217 |
International
Class: |
C21C 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2000 |
EP |
00870089 |
Claims
1. Refractory component (1, 14) provided with means of injecting or
conveying (5, 16) gas and means of delivering said gas from an
external wall of the component to said means of injection (5, 16),
the means of delivery of the gas comprising a part of enlarged
cross-section (7, 17) extending from an external wall of the
component and a part of reduced cross-section (8, 18)
communicating, at one end, with the inner end of the part of
enlarged cross-section (7, 17) and, at the other end, with the
means of injecting or conveying gas (5, 16), the said component
also comprising a seal (12, 22) fitted against the inner end of the
part of enlarged cross-section, said seal (12, 22), comprising an
orifice at least partially in register with the communicating
orifice (11, 21) between the parts of enlarged and reduced
cross-section, the thickness of the seal (12, 22) exceeding not the
depth of the part of enlarged cross-section (7, 17), characterised
in that the seal (12, 22) presents a cross-section substantially to
the cross-section of the enlarged part (7, 17).
2. Refractory component according to claim 1, characterised in that
the inner end of the part of enlarged cross-section (7, 17) forms a
surface presenting an orifice (11, 21), the said parts of enlarged
(7, 17) and reduced (8, 18),cross-section communicating via this
orifice (11, 21).
3. Refractory component according to claim 1 or 2, characterised in
that part of enlarged cross-section (7, 17) consists of a bore of
substantially circular cross-section.
4. Refractory component according to claim 3, characterised in that
the surface forming the inner end of the part of enlarged
cross-section (7, 17) is flat and essentially orthogonal to the
axis of the bore.
5. Refractory component according to claim 1, characterised in that
the seal (12, 22) is constituted of one or more washer(s) in a
plastic material.
6. Assembly including a refractory component (1, 14) according to
any of claims 1 to 5 and a gas delivery line (9, 19), wherein one
end of the gas delivery line holds the seal (12, 22) in compression
against the side walls of the part of enlarged cross-section (7,
17).
7. Assembly according to claim 6, characterised in that the
refractory component is provided with a metal casing (10) or band
(20), in that the gas delivery line (9, 19) passes through or is
contiguous with said casing or band, and in that a solid connection
is made between the line and the casing or band.
8. Assembly according to one of claims 6 or 7, characterised in
that the end of the gas delivery line (9, 19) engaged in the
refractory component is configured so as to form a tight joint with
the seal (12, 22).
9. Assembly according to claim 8, characterised in that the end of
the gas delivery line (9, 19) engaged in the refractory component
comprises a thread which engages in the seal.
10. Assembly according to claim 8, characterised in that the end of
the gas delivery line (9, 19) engaged in the refractory component
is shaped as a cone or truncated cone which engages in the seal
(12, 22).
11. Assembly according to any of claims 6 to 10, characterised in
that the part of enlarged cross-section (7, 17) is sufficiently
deep so that, under the effect of expansion of the part of the gas
delivery line (9, 19) engaged in said part of enlarged
cross-section, the seal (12, 22) is compressed against the inner
end and against the side walls of the part of enlarged
cross-section (7, 17).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a refractory component used
in the processing of a metal in the molten state, for example
steel, fitted with a gas supply and providing improved sealing. In
particular, the invention relates to such a component used in
continuous casting of a metal in the molten state.
BACKGROUND OF THE INVENTION
[0002] It is known that casting of a liquid metal is generally
carried out by means of an installation comprising various
refractory components forming a channel between two successive
metallurgical vessels. These refractory components perform various
functions, namely conveyance of the liquid metal, protection of the
liquid metal against cooling and chemical attack from the
surrounding atmosphere and, where appropriate, regulation of the
rate of pouring of the liquid metal. These components may be, for
example, an inner nozzle supported on a well block integral with
the bottom of the upper metallurgical vessel, a submerged entry
nozzle or a pouring shroud, a collector nozzle, or the fixed or
mobile plates of a slide valve.
[0003] The joint surfaces between these various components forming
a pouring channel all constitute points of potential ingress for
the ambient air. In effect, by virtue of the flow of liquid metal
through the pouring channel, substantial negative pressure is
generated which is conducive to air ingress through these joint
surfaces. The detrimental effects of such air ingress (nitrogen and
oxygen) on the quality of the cast metal are known, and efforts
have been made over a long period of time to remedy this.
[0004] One of the known solutions in the current state of the art
involves injecting an inert gas, for example argon, into the joint
surface between two adjacent refractory components in the pouring
channel. This injection may be effected for example via a groove
made for this purpose in the surface of at least one of the
components. To be effective, this groove must as far as possible
encircle the pouring orifice so that the inert gas which is under
positive pressure can prevent any ingress of air into the pouring
channel. Recently, an improvement to this system was proposed in
international patent application WO 98/17421, involving the
additional injection of a sealing agent in suspension in a carrier
fluid (which may be an inert gas) so that any sealing defect liable
to appear between two adjacent surfaces during casting is
immediately eliminated.
[0005] Another known solution in the current state of the art
entails injecting an inert gas directly into the pouring channel so
as to form a protective barrier against pollution by the ambient
air along the entire length of the pouring channel. In this case,
the injection of inert gas into the liquid metal is generally
carried out by diffusion through a porous wall of the component
forming part of the pouring channel or, in another known variant,
via one or more orifices in form of holes or slots arranged around
the pouring channel.
[0006] Furthermore, a method is also known wherein an inert gas is
injected directly into the pouring channel in a manner such that
the inert gas cooperates mechanically with the liquid metal. The
purpose of this type of inert gas injection may be to protect
against erosion of certain refractory components located downstream
of the injection point and which are particularly susceptible to
the erosive action of the stream of liquid metal, such as for
example the edges of the pouring orifice of the mobile plate of a
slide valve designed to regulate the rate of flow. Another known
effect of injecting an inert gas into a pouring channel is that it
reduces problems of clogging of the pouring channel. In effect,
problems due to the formation of alumina deposits against the walls
of the pouring channel have been known for a long time,
particularly in the case of casting of aluminium-killed steels. The
inert gas thus injected downstream of a point where this type of
clogging can occur mechanically, or even thermally, isolates the
liquid metal from the pouring channel and, consequently, prevents
or reduces the formation of such deposits.
[0007] Finally, it is also possible to inject a gas for the purpose
of cooling the refractory component in question. It will be noted
that the invention also relates to components used for the
injection of gas into the bottom of a metallurgical vessel
containing a bath of metal in the molten state, such as for example
porous plugs.
[0008] For the purposes of the present patent application, the
expression "injection of gas" will therefore refer both to the
direct injection of an inert gas into a pouring channel or into the
bottom of a metallurgical vessel and to the injection of an inert
gas (or a sealing agent in suspension in a carrier fluid as
described in international patent application WO 98/17421) into the
joint surface between two adjacent refractory components of a
pouring channel via a groove encircling at least partially the
pouring orifice of the liquid metal, or to the injection of a
cooling gas.
[0009] The refractory components designed for the injection of an
inert gas generally include means of delivering the gas to the
means of injection (via a groove or the pouring channel). However,
assemblies of refractory components are known in which the means of
delivery and means of injection of the gas are provided by adjacent
inter-communicating components (possibly they may even be separated
by intermediate refractory components, the essential feature being
that the gas can be transferred from the means of delivery to the
means of injection). For the purposes of the present patent
application, where reference is made to a component equipped with
means of delivery and means of injection of gas, this will refer
equally to a component including both means of delivery and means
of injection of gas or a component fitted with means of delivering
gas and means of transfer and/or communication to means of
injection which may be provided by another refractory
component.
[0010] The means of delivery generally include an inlet aperture
opening on the outside wall of the refractory component and
connected to a gas delivery line. This delivery line is connected
to the fixed gas supply circuit of the casting installation,
possibly via flexible pipes protected against thermal radiation.
Conventionally, during the fabrication of said refractory
component, a metal connector is mounted in the inlet aperture; the
connector and the material then form an integral assembly upon
sintering of the constituent refractory material of the component.
The connector can then be connected to the gas delivery line by
screwing (either the connector is fitted with a male threaded part
projecting beyond the component onto which the female end of the
line is screwed, or the connector has a female thread into which
the male-threaded end of the line is screwed), by welding or by
various means of mechanical coupling. These means of gas delivery
are not entirely satisfactory in that, firstly, it is not obvious
that a threaded joint can be made airtight, and particularly a
joint that will remain airtight at the very high temperatures to
which the installation is subjected during casting operations and,
secondly, by virtue of the difference between the coefficients of
expansion of the metal of which the connector is made and the
refractory material, it is inevitable that the sealing tightness
between the connector and the refractory will gradually
deteriorate. The negative effects of this loss of sealing tightness
are three-fold: firstly, the quantities of gas to be injected are
that much greater (the high price of inert gases such as argon is
well known), secondly, as indicated above, given that the whole of
the pouring channel is under negative pressure relative to the
ambient environment, there is a risk that air will be drawn in
through these defective joints and, thirdly, in case of loss of
sealing tightness, precise control of the quantity of gas actually
injected into the system is lost and it becomes impossible to
establish a perfectly reproducible system.
[0011] Various attempts have been made to improve this situation,
such as for example "packing" the refractory component in a metal
casing incorporating an aperture at the connector, welding to
ensure mechanical retention of the connector and improve the gas
tightness. A number of drawbacks associated with this "improvement"
have already been reported. For instance, as the connector is
integral with the metal casing, it has a tendency to work loose
from the refractory material and to move about in its seating,
which gives rise to losses of inert gases and, as indicated above,
ingress of air into the liquid metal.
[0012] More recently, a very simple device was proposed in European
patent application EP 703,028 for the delivery of inert gas to an
inner nozzle, wherein the external surface of the refractory
component receiving the gas feed simply incorporates a gas inlet
aperture against which a connection fitting connected to an inert
gas delivery line is held in compression. Where appropriate, it may
even be possible to provide a seal between the fitting and the
inlet aperture.
[0013] Although this device greatly improves the situation, the
applicant observed that it as not yet wholly satisfactory in that
sealing tightness between the connection fitting and the gas inlet
aperture at the surface of the component was not totally assured,
even when a seal is engaged between the fitting and the
aperture.
[0014] A refractory component provided with means of injecting or
conveying gas and means of delivering said gas from an external
wall of the component to said means of injection, the means of
delivery of the gas comprising a part of enlarged cross-section
extending from an external wall of the component and a part of
reduced cross-section communicating, at one end, with the inner end
of the part of enlarged cross-section and, at the other end, with
the means of injecting or conveying gas, the said component also
comprising a seal fitted against the inner end of the part of
enlarged cross-section, said seal, comprising an orifice at least
partially in register with the communicating orifice between the
parts of enlarged and reduced cross-section is known from
FR-A-2,763,012.
[0015] By virtue of this particular arrangement of the refractory
component, the gas delivery line can be engaged more deeply into
said component so that, when an appropriate seal is fitted therein,
sealing tightness is assured not only at the communication between
the two parts of the means of delivery, but also at the walls of
the part of enlarged cross-section. A very substantial improvement
in sealing tightness compared with the device disclosed in European
patent application 703,028 (reduction of the consumption of inert
gas, reduction of air ingress, and precise control of the quantity
of gas injected) was observed. However, it is desirable to still
improve the sealing tightness.
SUMMARY OF THE INVENTION
[0016] According to the invention, the seal presents a
cross-section substantially similar to the cross-section of the
enlarged part. Thus, when the seal is placed in compression in an
appropriate manner, it bears not only on the end of the part of
enlarged cross-section, but also on the side walls of the latter,
thereby providing an even tighter seal.
[0017] It is advantageous that the thickness of the seal does not
exceed the depth of the part of enlarged cross-section, otherwise,
under the effect of compression by the gas delivery line, the
plastic seal will bear on the rim of the outer orifice of the means
of delivery as it deforms, and sealing tightness will no longer be
assured at the inner end of the part of enlarged cross-section.
[0018] According to a particular embodiment of the invention, the
inner end of the part of enlarged cross-section forms a surface
presenting an orifice, the said parts of enlarged and reduced
cross-section communicating via this orifice. In this way, it is
possible to use a gas delivery line of essentially tubular
form.
[0019] Advantageously, the part of enlarged cross-section consists
of a bore of substantially circular cross-section which is easy to
make.
[0020] Provision can also be made so that the surface forming the
inner end of the part of enlarged cross-section is flat and
essentially orthogonal to the axis of the bore. Not only is this
arrangement easy to achieve, but its sealing tightness will be
improved where it is made by the pressing of parallel elements.
[0021] According to a particular aspect of the invention. The
thickness of the seal does not exceed the depth of the part of
enlarged cross-section. It is to be noted that the seal can be made
integral with the component.
[0022] Advantageously, the seal presents a cross-section
substantially similar to the cross-section of the enlarged part.
Thus, when the seal is placed in compression in an appropriate
manner, it bears not only on the end of the part of enlarged
cross-section, but also on the side walls of the latter, thereby
providing an even tighter seal. It is essential that the thickness
of the seal does not exceed the depth of the part of enlarged
cross-section, otherwise, under the effect of compression by the
gas delivery line, the plastic seal will bear on the rim of the
outer orifice of the means of delivery as it deforms, and sealing
tightness will no longer be assured at the inner end of the part of
enlarged cross-section.
[0023] Preferably, the seal takes the form of a washer. Provision
may be made however for a stack of such washers depending on the
required thickness of the seal. The person skilled in the art will
readily determine the optimal thickness of the seal.
[0024] Advantageously, the seal is made of a plastic material so
that, at operating temperatures, it is able to deform sufficiently
when pressure is exerted on it to form a tight seal with the bottom
wall and with the side walls of the end of the part of enlarged
cross-section. Clay and graphite are materials potentially suitable
for such use, graphite being the preferred choice.
[0025] According to another of its aspects, the invention relates
to an assembly including a refractory component as described above
and a gas delivery line, wherein one end of the gas delivery line
is engaged in the part of enlarged cross-section which holds the
seal in compression at the inner end and against the side walls of
the part of enlarged cross-section. The advantages of such an
assembly have already been described above.
[0026] According to a particular embodiment of the invention, the
refractory component is fitted with a metal casing (in the case of
an inner nozzle for example) or band (in the case of a slide valve
plate for example) covering it at least partially in the area of
the gas delivery means. It is thus possible to form a solid
attachment between the delivery line (by welding or screwing) and
the casing or band, thereby avoiding accidental loss of sealing
tightness in case of vibration for example.
[0027] Advantageously, the end of the line engaged in the part of
enlarged cross-section is configured so as to form a tight joint
with the seal. For example, the end may be shaped as a cone or
truncated cone so that it "keys" into the joint. As a variant, the
end of the line may be threaded to enable the line to "screw" into
the joint. Provision may also be made for a self-tapping end so
that a perfectly fitting thread is formed in situ in the seal and
the line/seal joint is totally tight. According to this variant, it
is advantageously the action of screwing the end of the line into
the seal that compresses said seal towards the side walls of the
part of enlarged cross-section.
[0028] Finally, according to a most particular embodiment of the
invention, the part of enlarged cross-section is sufficiently deep
so that, under the effect of thermal expansion of the end of the
line engaged in the part of enlarged cross-section, the compression
of the seal increases. In effect, once the line is made solid with
the casing or band, its only possibility of expansion is towards
the end of the part of enlarged cross-section where the seal is
located.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to better explain the invention, two embodiments
given by way of a non-limitative example are described below with
reference to the attached diagrams in which:
[0030] FIG. 1 is an axial sectional view of an inner nozzle;
[0031] FIG. 2 is an enlarged view of the circle I in FIG. 1.
[0032] FIG. 3 is an axial sectional view of a slide valve
plate.
DETAILED DESCRIPTION OF THE INVENTION
[0033] FIG. 1 shows an inner nozzle 1 comprising a refractory body
2 forming a pouring channel 3 and a plate 4. The inner nozzle 1
also includes means of injecting gas, for example an inert gas such
as argon, into the pouring channel 3. These means of injecting gas
are formed for example by a sleeve 5 in porous material mounted in
a groove 6 formed in the refractory body 2. The groove 6 is
connected to means of delivery of gas (7, 8). As shown in FIG. 1,
these means of delivery may emerge at the upper surface of the
plate 4. Also shown is part of the gas delivery line 9, together
with a metal casing 10 surrounding the plate 4 of the inner
nozzle.
[0034] FIG. 2 shows the details of the connection between the gas
inlet and the means of delivery of the gas at the plate 4 of the
inner nozzle. These means of delivery of gas include a part of
enlarged cross-section 7 and a part of reduced cross-section 8
communicating via an orifice 11. The inner end of the part of
enlarged cross-section is fitted with a seal 12 for example in
graphite. Also shown is one end of the gas delivery line 9 engaged
in the part of enlarged cross-section 7. It can be seen that the
line 9 is made solid with the casing 10 by means of a circular weld
13.
[0035] FIG. 3 shows a refractory plate 14 of a slide valve
presenting an orifice 15 for the pouring of metal. The plate is
provided with a circular groove 16 circumscribing the pouring
orifice 15 and forming with the surface of the refractory part (not
shown) adjacent to the plate 14 a channel for the injection of a
gas between these adjacent parts. The groove 16 is connected to gas
delivery means including a portion of enlarged cross-section 17 and
a portion of reduced cross-section 18 communicating via an orifice
21. Also shown is the gas delivery line 19 engaged in the part of
enlarged cross-section and made solid with the metal band 20 of the
plate 14 by a spot weld 23. When the plate is in service, under the
effect of the temperature to which the assembly is raised, the part
of the line 19 between the spot weld 23 and its inner end expands
towards the inner end of the enlarged part 17 and compresses the
seal 22.
* * * * *