U.S. patent application number 14/009545 was filed with the patent office on 2014-03-06 for refractory element, assembly and tundish for transferring molten metal.
This patent application is currently assigned to VESUVIUS CRUCIBLE COMPANY. The applicant listed for this patent is Philippe Guillo, Dominique Janssen, Jose Simoes. Invention is credited to Philippe Guillo, Dominique Janssen, Jose Simoes.
Application Number | 20140061257 14/009545 |
Document ID | / |
Family ID | 47072676 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140061257 |
Kind Code |
A1 |
Janssen; Dominique ; et
al. |
March 6, 2014 |
REFRACTORY ELEMENT, ASSEMBLY AND TUNDISH FOR TRANSFERRING MOLTEN
METAL
Abstract
A refractory element is configured to prevent or limit steel
reoxidation in a steel casting process. The refractory element
contains a base surrounded by a periphery in a specified
geometrical arrangement. The refractory element is constituted of a
base surrounded by a periphery in a specified geometrical
arrangement.
Inventors: |
Janssen; Dominique; (McKees
Rocks, PA) ; Guillo; Philippe; (Paris, FR) ;
Simoes; Jose; (Saint Ghilsain, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Janssen; Dominique
Guillo; Philippe
Simoes; Jose |
McKees Rocks
Paris
Saint Ghilsain |
PA |
US
FR
BE |
|
|
Assignee: |
VESUVIUS CRUCIBLE COMPANY
Wilmington
DE
|
Family ID: |
47072676 |
Appl. No.: |
14/009545 |
Filed: |
February 28, 2012 |
PCT Filed: |
February 28, 2012 |
PCT NO: |
PCT/US2012/026856 |
371 Date: |
October 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61481136 |
Apr 29, 2011 |
|
|
|
Current U.S.
Class: |
222/590 ;
222/591 |
Current CPC
Class: |
B22D 41/50 20130101;
B22D 41/502 20130101 |
Class at
Publication: |
222/590 ;
222/591 |
International
Class: |
B22D 41/50 20060101
B22D041/50 |
Claims
1. A refractory element for transferring molten metal comprising: a
base having a bottom and a main surface, a main orifice passing
through the main surface, and a periphery surrounding the main
surface, wherein the main orifice has an interior face and a
longitudinal axis, wherein the periphery has an interior face, an
exterior face and an upper face, wherein the upper face of the
periphery is higher than the main surface of the refractory
element, wherein the periphery intersects the bottom of the base,
and wherein the exterior face of the periphery forms an angle other
than a right angle with the bottom of the base in at least one
point in their intersection.
2. The refractory element of claim 1, wherein the exterior face of
the periphery forms a right angle with the bottom of the base at
two points in their intersection.
3. The refractory element of claim 1, wherein the exterior face of
the periphery forms an acute angle with the bottom of the base at
all points in their intersection.
4. The refractory element of claim 1, wherein the exterior face of
the periphery forms an obtuse angle with the bottom of the base at
all points in their intersection.
5. The refractory element of claim 1, wherein the element partially
encloses a volume with a cross-section that decreases in size with
decreasing distance to the bottom surface.
6. The refractory element of claim 1, wherein the plane of the
upper face of the periphery and the plane of the bottom of the base
are not parallel.
7. The refractory element of claim 1, wherein the upper face of the
periphery comprises an upper level and a lower level joined by two
transitional non-vertical, non-horizontal portions.
8. The refractory element of claim 1, wherein the main surface has
a geometry selected from the group consisting of circular, oval,
truncated circular, truncated oval, and polygonal geometry.
9. The refractory element of claim 1, further comprising a vane
extending from the interior face of the periphery.
10. The refractory element of claim 1, further comprising a
plurality of vanes extending from the interior face of the
periphery.
11. The refractory element of claim 1, further comprising a vane
extending from the exterior face of the periphery.
12. The refractory element of claim 1, further comprising a
plurality of vanes extending from the exterior face of the
periphery.
13. The refractory element of claim 1, further comprising at least
one port passing from the exterior face to the interior face of the
periphery.
14. The refractory element of claim 1, further comprising a feature
located at a position selected from the group consisting of the
interior face of the main orifice and the bottom of the base,
wherein the feature is selected from the list consisting of a
marking, a recess, a protrusion, a groove, a lip, a peg, a bore, a
notch, a dimple, a mogul, a ridge, a threaded receiver, a key
receiver, a bayonet receiver, a bevel, and a non-circular
geometry.
15. An assembly for the transferring of molten metal comprising a
refractory element according to claim 1, and a refractory nozzle in
communication with the refractory element, wherein the nozzle has a
bore having a longitudinal axis, and wherein the nozzle has an
exterior radial surface configured to mate with the interior face
of the main orifice.
16. The assembly of claim 15, wherein the axis of the nozzle bore
is aligned with the axis of the main orifice.
17. The assembly of claim 15, wherein the main surface of the base
of the element has a lowest level, the lowest level being lower
than the top outer edge of the nozzle inlet portion.
18. The assembly of claim 15, wherein the refractory element and
the refractory nozzle together comprise a single piece.
19. The assembly of claim 15, wherein the refractory element
comprises a main orifice having a non-circular geometry, and
wherein the refractory nozzle comprises an exterior radial surface
having a non-circular geometry configured to mate with the
refractory element.
20. The assembly of claim 15, wherein the refractory element
comprises a main orifice interior face having a mating feature,
wherein the refractory nozzle comprises an exterior radial surface
having a corresponding mating feature configured to engage with the
main orifice interior face mating feature.
21. The assembly of claim 20, wherein the mating feature and the
corresponding mating feature, when engaged, prevent rotational
motion of the element around the longitudinal axis of the bore of
the nozzle.
22. A metallurgical vessel for the casting of molten metal
comprising an assembly of a refractory nozzle having an inlet
portion forming a passage through the bottom wall of the
metallurgical vessel and a refractory element according to claim 1
surrounding the inlet portion of the nozzle, wherein the inlet
portion of the nozzle has a top outer edge, wherein the inlet
portion of the nozzle has a longitudinal axis, wherein the main
orifice of the element is adapted for matching engagement with at
least a portion of the outer surface of the nozzle, wherein the
main surface of the base of the element has a lowest level, the
lowest level being lower than the top outer edge of the nozzle
inlet portion, and wherein at least a portion of the periphery of
the refractory element is higher than the surface of the bottom
wall of the tundish.
23. The assembly of claim 15, wherein the element comprises a gas
impervious refractory material.
24. The assembly of claim 15, wherein the nozzle comprises a gas
impervious refractory material.
25. The assembly of claim 15, further comprising gas impervious
mortar between the nozzle and the refractory element.
26. The element of claim 1, consisting essentially of a high
alumina material comprising at least 75 wt. % of Al.sub.2O.sub.3,
and less than 1.0 wt. % of SiO.sub.2, less than 5 wt. % of C.
27. Process for the continuous casting of steel comprising pouring
the molten steel from a ladle into a metallurgical vessel according
to claim 22, and from the metallurgical vessel into a casting
mold
28. The refractory element of claim 1, wherein the periphery of the
element has a thickness equal to or greater than 2 millimeters, and
equal to or less than 100 millimeters.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to the continuous casting of
steel and particularly to the problem of steel reoxidation. In
particular, the invention relates to a tundish comprising an
assembly comprising a nozzle and a surrounding refractory element
preventing or limiting steel reoxidation, and preventing oxidation
products from entering a casting channel. The invention also
relates to an assembly comprising a nozzle and a surrounding
refractory element preventing or limiting steel reoxidation, and
preventing oxidation products from entering a casting channel.
According to other of its aspects, the invention also relates to
such a surrounding refractory element and to a continuous steel
casting process.
[0003] With growing demands for quality and property control,
cleanliness of steel becomes more and more important. Issues like
controlling the chemical composition and the homogeneity have been
supplanted by concerns generated by the presence of non-metallic
inclusions. Especially the presence of aluminum oxide and spinel
inclusions is considered as harmful both for the production process
itself as for the steel properties. These inclusions are mainly
formed during the deoxidation of the steel in the ladle, which is
necessary for continuous casting. Incomplete removal of the
non-metallic inclusions during secondary metallurgy and reoxidation
of the steel melt cause nozzle clogging during continuous casting.
The layer of clogged material contains generally large clusters of
aluminum oxide. Its thickness is related to the amount of steel
cast as well as to the cleanliness of the steel. Nozzle clogging
results in a decreased productivity, because less steel can be cast
per unit of time (as result of the decreasing diameter) and due to
replacement of nozzles with concurrent casting interruptions.
Besides clogging, the presence of reoxidation products may give
rise to erosion of the nozzle and to the formation of inclusion
defects in the steel.
[0004] (2) Description of Related Art
[0005] Several solutions have been developed in the art to prevent
steel reoxidation. In particular, the molten metal stream is
generally shrouded with a pouring shroud during its transfer from a
casting vessel to a downstream vessel (or mold) to prevent direct
contacts between the poured steel and the surrounding atmosphere.
Argon is often injected directly at the surface of a pouring nozzle
so as to shield the molten metal stream. The surface of the steel
melt in a metallurgical vessel (for example a tundish) is generally
covered with a liquid slag layer so as to prevent direct contacts
between the steel and the surrounding atmosphere. Alternatively (or
in addition), the atmosphere above the tundish can be made inert
(by the use of an oxygen scavenger or of an inert gas such as
argon).
[0006] Further solutions have been developed in the art to remove
non-metallic inclusions and reoxidation products when they are
present in the tundish. These solutions consist generally in
facilitating the flotation of these inclusions and reoxidation
products so that these are captured by the floating slag layer. For
example, dams, weirs, baffles and/or impact pads can be used to
deflect upwardly the molten metal stream in the tundish. Inert gas
bubbling devices can also be used to float out inclusions and
reoxidation products.
[0007] Other solutions also exist for making the inclusions and
oxidation product harmless. For example calcium based alloys can be
used to eliminate some of the problems generated by the presence of
aluminum oxide inclusions.
[0008] All these prior art solutions have contributed to improve
the general cleanliness of the steel. However, some of the prior
art solutions can, in turn, generate new defects in the steel (as
in gas bubbling, or the use of a calcium-based alloy), can be
expensive (as in the use of an inert atmosphere) or environmentally
unacceptable. For these reasons, it would be desirable to propose
an alternative solution which would solve the above problem, which
would be economical and would not raise environmental problems.
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention is based on the hypothesis that, even
though the steel can be made relatively clean, it is impossible to
keep it clean up to the mold in normal conditions. In particular,
reoxidation of the steel by chemical reaction between the
refractory elements (generally metal oxide) used in the continuous
casting (vessel lining, slag, nozzles, stoppers, etc.) can also
generate reoxidation products. Another potential source of
reoxidation is the oxygen permeating through these refractory
elements or through a permeable joint between the bottom wall
lining and the nozzle inlet or even the oxygen desorbed from the
refractory element.
[0010] An object of the present invention is therefore to solve the
above problems by preventing the reoxidation products from reaching
a casting nozzle and/or from forming in the immediate vicinity of
or in the casting nozzle.
[0011] According to the invention, this object is achieved by the
use of a surrounding refractory element, an assembly of a nozzle
and a surrounding refractory element, or an assembly of a nozzle
and a surrounding refractory element housed in a tundish, in which
the element has a base having a main surface, a bottom and a
periphery surrounding the main surface, in which the periphery has
an exterior surface, and interior surface and an upper face, and
the intersection of the bottom of the base and the exterior surface
of the periphery contains at least one point at which the angle of
intersection is not a right angle.
[0012] It is already known in the art to provide a surrounding
element around the pouring orifice of a tundish. FR-A-2394348 for
example discloses a ring intended to retain the steel in the
tundish until a sufficient level and thereby a sufficient thermal
mass is reached in order to avoid the entry of "cold" steel into
the pouring orifice. The prior art however fails to disclose an
element with a base and a periphery, and the intersection of the
bottom of the base and the exterior surface of the periphery
contains at least one point at which the angle of intersection is
not a right angle.
[0013] JP-A1-2003-205360 discloses a tundish for the continuous
casting of steel. The well block of this tundish is comprised of
two elements. The nozzle is located inside the bottom part of the
well block. An additional refractory element is positioned above
the upper part of the nozzle to cover and protect the cement joint
between the nozzle and the well block. However, this document fails
to disclose a refractory element with a base and a periphery, and
the intersection of the bottom of the base and the exterior surface
of the periphery contains at least one point at which the angle of
intersection is not a right angle.
[0014] WO2007/009667 discloses an element for use in conjunction
with a nozzle in a metallurgical vessel. However, this document
does not disclose a refractory element with a base and a periphery
in which the intersection of the bottom of the base and the
exterior surface of the periphery contains at least one point at
which the angle of intersection is not a right angle.
[0015] Thanks to the particular arrangement according to the
present invention, the reoxidation products and/or inclusions
present in the metallurgical vessel and which tend to accumulate on
the bottom surface of the vessel and are carried down by the molten
steel stream cannot reach the inlet of the nozzle.
[0016] It must be understood that the element surrounding the
nozzle can be of any appropriate shape. In function of the
metallurgical vessel design; it can be circular, oval or polygonal;
its main orifice can be central or eccentric. In an alternate
embodiment of the invention, appropriate shapes for the element may
exclude circular shapes. The element surrounding the nozzle can
also be cut off so as to accommodate those cases when one or more
tundish walls are close to the pouring orifice. The main surface of
the element can be planar or not (it can be frusto-conical,
rippled, inclined). The nozzle can be an inner nozzle (for example
in case the molten steel flow is controlled with a slide gate valve
or if the installation is equipped with a tube or calibrated nozzle
changer) or a submerged entry nozzle or SEN (for example in the
case of stopper control). The metallurgical vessel or tundish can
be equipped with one or more of such assemblies. The assembly can
be supplied as a one-piece pre-assembled article (for example,
co-pressed) or as separated articles.
[0017] As the element surrounding the nozzle need not be circular,
and as the element may be placed in a vessel that does not have
circular symmetry, it may be important to align the element with
the nozzle, and therefore with the nozzle's surroundings, to
produce desired flow patterns in the vicinity of the nozzle.
Accordingly, the element and the nozzle may be constructed with
matching visual indicators or markings that, when aligned or placed
in contact, produce the desired geometrical arrangement of the
element and the nozzle. Alternatively, the element and the nozzle
may be constructed with mating geometries so that, when these
geometries are mated, the desired geometrical arrangement of the
element and nozzle, and of the combined element and nozzle with
their surroundings, is produced. The mating geometries may be a
matching recess and protrusion, a matching groove and lip, a
matching peg and bore, a matching notch and protrusion, a matching
dimple and mogul, a matching ridge and groove, aligned threaded
receivers, aligned key or bayonet receivers, or matching
non-circular surface geometries such as oval or polygonal faces.
The mating geometry of the element may be placed within its main
orifice or on the bottom of the base. The element, considered
alone, may contain, within its main orifice or on its base, one or
more orienting geometries, such as pegs, bores, protrusion,
recesses, notches, bevels, dimples, moguls, ridges, grooves,
housings for screw or bayonet fittings, or shaped or threaded
receiver portions. The bore of the element may be asymmetric, oval
or polygonal in shape.
[0018] In certain embodiments of the invention, the element and the
nozzle may constitute a single piece.
[0019] According to the present invention, the refractory element
comprises a base having a main surface and a periphery surrounding
the main surface; the upper face of the periphery being higher than
the main surface of the refractory element. Thereby, a kind of
deflecting trap is created in the area surrounding the nozzle. It
must be understood that the upper face of the periphery does not
need to be planar. It can be waved or have different heights along
the periphery (for example higher in area of the periphery close to
a vessel lateral wall and lower on the other side). The periphery
may contain one or more interruptions or openings. The periphery
may contain stepped changes in height, or may contain gradual
changes in height. The upper face of the periphery may have a
sawtooth configuration, a semicircular notch configuration, a
square notch configuration, a wave configuration, a semicircular
protrusion configuration or may contain one or more steps. The
upper face of the periphery may be in communication with an
outwardly protruding lip. The upper face of the periphery may be in
communication with an inwardly protruding lip. The upper face of
the periphery may be in communication with a plate or dome
structure containing at least one port. The periphery may contain
one or more ports; these ports may be circular, oval or polygonal
in shape, and the ports may have horizontal axes, axes directed
upwards and inwardly, axes directed downwards and inwardly, or axes
that are not perpendicular to the external surface of the
periphery. The ports may be configured to have axes that are
mutually tangent to a circle within the periphery. Pairs of ports
may be configured to have axes that intersect each other at a
circle within the periphery. The ports may be flared. In the
inventive combination of a tundish, a nozzle and a refractory
element, the level of at least one portion of the outer periphery
of the refractory element is higher than the surface of the bottom
wall of the tundish. Thereby, a second obstacle is created around
the nozzle tundish preventing the inclusions or reoxidation
products to reach its inlet. This type of arrangement is
particularly advantageous.
[0020] The periphery of the refractory element of the present
invention may take the form of a wall with measurements that are
related to other measurements of the element by particular ratios
or ranges of ratios. In certain embodiments, the maximum height of
the wall, measured from the bottom of the base, has a ratio of 1:1
to 6:1, or 1.1:1 to 6:1, to the minimum height of the wall,
measured from the bottom of the base. In certain embodiments, the
maximum height of the wall, measured from the bottom of the base,
has a ratio of 0.1:1 to 10:1, or 0.1:1 to 8.5:1, or 0.2:1 to 8.5:1,
or 0.5:1 to 8.5:1, to the maximum exterior diameter of the base. In
certain embodiments, the wall has a minimum thickness of 2 mm, 5
mm, or 10 mm. In certain embodiments, the wall has a maximum
thickness of 60 mm, 80 mm, or 100 mm. In certain embodiments, the
base has a maximum thickness of 100 mm or 200 mm.
[0021] The periphery of the refractory element of the present
invention may take the form of a wall that has an exterior surface
that has a portion that is not vertical. In certain embodiments,
the entire exterior surface of this wall is not vertical. In
certain embodiments, the entire wall forms an obtuse angle with the
main surface, as measured from the interior of the element. In
certain embodiments, the angle between the bottom surface of the
base and the exterior surface of the wall has an angle lying within
the ranges of 45 degrees to 89.5 degrees and 90.5 degrees to 135
degrees. In certain embodiments, the angle between the bottom
surface of the base and the exterior surface of the wall may vary
around the circumference of the element. In particular embodiments,
the element has non-vertical outer walls, and the element partially
encloses a volume with a cross-section that decreases in size with
decreasing distance to the nozzle or to a port in which the nozzle
may be located. The walls may take the form of a cylinder with an
axis that is not orthogonal to the horizontal plane. The walls may
take the form of the radial surface of a truncated cone with a
projected vertex below the plane of the main surface. The walls may
take the form of the radial surface of a truncated cone with a
projected vertex above the plane of the main surface. The upper
face of the periphery may form a circle, oval, or polygonal figure
in a plane that is not parallel to the plane of the main
surface.
[0022] The interior of the wall of the refractory element and the
base of the refractory element may communicate, separately or
together, with one or more vanes. A vane may be disposed so that a
projection of the plane of the vane intersects the axis of the
nozzle. A vane may also be disposed so that no projection of a
plane of the vane intersects the axis of the nozzle. The vanes may
have surfaces and edges; the surfaces may be planar, may be curved
in one or two dimensions, and may be smooth or have grooves. The
edges of the vanes may be chamfered or have a sawtooth
configuration, a semicircular notch configuration, a square notch
configuration, a wave configuration, a semicircular protrusion
configuration or may contain one or more steps.
[0023] The exterior of the wall of the refractory element may
communicate with one or more vanes. A vane may be disposed so that
a projection of the plane of the vane intersects the axis of the
nozzle. A vane may also be disposed so that no projection of a
plane of the vane intersects the axis of the nozzle. The vanes may
have surfaces and edges; the surfaces may be planar, may be curved
in one or two dimensions, and may be smooth or have grooves. The
edges of the vanes may be chamfered or have a sawtooth
configuration, a semicircular notch configuration, a square notch
configuration, a wave configuration, a semicircular protrusion
configuration or may contain one or more steps.
[0024] The surrounding refractory element may be made from a
gas-impervious material. To be regarded as gas-impervious, such
material has an open porosity (at the temperature of use) which is
lower than 20% (thus lower than the open porosity of conventional
lining material which is typically higher than 30%). For refractory
materials, the permeability is generally related to the porosity.
Therefore a low porosity material has a low permeability to gases.
Such a low porosity can be obtained by including oxygen scavenger
materials (e.g. antioxidants) in the material constituting the
surrounding element. Suitable materials are boron or silicon
carbide, or metals (or alloys thereof) such as silicon or aluminum.
In certain embodiments, they are used in an amount not exceeding 5
wt %. Alternatively (or in addition), products generating melting
phase (for example B.sub.2O.sub.3) can also be included in the
material constituting the surrounding element. In certain
embodiments, they are used in an amount not exceeding 5 wt. %.
Alternatively or (in addition), materials forming more voluminous
new phases (either upon reaction or the effect of the temperature)
and closing thereby the existing porosity can also be included in
the material constituting the preformed element. Suitable materials
include compositions of alumina and magnesia. Thereby, steel
re-oxidation in the area surrounding the nozzle is prevented. In
certain embodiments of the invention, the refractory material has a
permeability value less than 15cD, 20cD, 25cD or 30cD, according to
standard ASTM testing. A material that may be used contains 0.5-1%,
or 1-5% silica, 0.005% to 0.2% titania, 75% to 95% alumina, 0.1% to
0.5% iron (III) oxide, 0.5% to 1% magnesia, 0.1% to 0.5% sodium
oxide, 0.25% to 2% boron oxide, and 1% to 10% of zirconia+hafnia. A
suitable material may have a loss on ignition value of 0 to 5%.
[0025] The element, the nozzle or a layer of the element or the
nozzle may be made from a gas-impervious material. The nozzle or
element may be made from refractory oxides (alumina, magnesia,
calcia) and may be isostatically pressed. To be regarded as
gas-impervious in the sense of the present invention, a 100 g
sample of the candidate material is placed in a furnace under argon
atmosphere (a gentle stream of argon is continuously blown (about
11/min) into the furnace) and the temperature is raised to
1000.degree. C. The temperature is then raised progressively to
1500.degree. C. (in 1 hour) and is then left at 1500.degree. C. for
2 hours. The loss of weight of the sample between 1000.degree. C.
and 1500.degree. C. is then measured. This loss of weight must be
lower than 2% for qualifying the material as gas-impervious.
Thereby, not only the inclusion or reoxidation products cannot
reach the nozzle but, in addition, they cannot form in the nozzle
or the element. This particular combination provides thus a
synergistic effect according to which a perfectly inclusion- and
reoxidation product-free steel can be cast.
[0026] The material constituting the nozzle or element can be
selected from three different categories of materials:
a) materials which do not contain carbon; b) materials essentially
constituted of non reducible refractory oxides in combination with
carbon; or c) materials comprising elements which will react with
the generated carbon monoxide. Preferably, the selected material
will present two or three of the above categories.
[0027] Examples of suitable material of the first category are
alumina, mullite, zirconia or magnesia based material (spinel).
[0028] Suitable materials of the second category are for example
pure alumina carbon compositions. In particular, these compositions
should contain very low amounts of silica or of conventional
impurities which are usually found in silica (sodium or potassium
oxide). In particular, the silica and its conventional impurities
should be kept under 1.0 wt. %, preferably under 0.5 wt. %.
[0029] Suitable materials of the third category comprise for
example free metal able to combine with carbon monoxide to form a
metal oxide and free carbon. Silicon and aluminum are suitable for
this application. These materials can also or alternatively
comprise carbides or nitrides able to react with oxygen compound
(for example silicon or boron carbides).
[0030] In certain embodiments of the invention the selected
material will belong to the second or third categories; in certain
embodiments of the invention the selected material will belong to
the second and third categories.
[0031] A suitable material constituting the layer which will not
produce carbon monoxide at the temperature of use can comprise 60
to 88 wt. % of alumina, 10 to 20 wt. % graphite and 2 to 10 wt. %
of silicon carbide. Such a material contains oxygen getters such as
non-oxide species such as nitrides or carbides, or non-reducible
oxides, which can react with any oxygen present.
[0032] In a variant, only a liner present at the steel contacting
surface (inside and outside of the nozzle) is made from such a
material. In another variant, the nozzle and the surrounding
element are made integral (one-piece).
[0033] In case the joint between the surrounding element and the
nozzle is not perfectly tight, it might be advantageous to provide
a mortar joint which is made from a gas impervious mortar.
Conventional mortars have an open porosity of 30 to 50%. According
to this advantageous embodiment, the mortar should have an open
porosity of less than 20%. The mortar may be made of a composition
similar to, and processed in similar fashion to, the element or
nozzle.
[0034] According to another of its aspects, the invention relates
to a particular surrounding refractory element which is used in the
assembly according to the invention. This surrounding element
comprises a main orifice adapted for matching engagement with at
least a portion of the outer surface of the nozzle, a main surface
surrounding the main orifice and an outer periphery surrounding the
main surface, the level of the upper face of the periphery being
higher than that of the main surface. Advantageously, the
surrounding refractory element is made from a gas-impervious
material. Thereby, steel re-oxidation in the area surrounding the
nozzle is prevented. For example, a particularly suitable
composition to this end is essentially comprised of a high alumina
material comprising at least 75 wt. % of Al.sub.2O.sub.3, less than
1.0 wt. % of SiO.sub.2, less than 5 wt. % of C, the reminder being
constituted of refractory oxides or oxides compounds that cannot be
reduced by aluminum (particularly aluminum dissolved in molten
steel) at the temperature of use (for example calcia and/or spinel.
A particularly suitable material is the CRITERION 92SR castable
available from VESUVIUS UK Ltd. This material is a high alumina low
cement castable material reinforced with fused alumina-magnesia
spinel. A typical analysis of this product is the following:
TABLE-US-00001 Al.sub.2O.sub.3 92.7 wt. % MgO 5.0 wt. % CaO 1.8 wt.
% SiO.sub.2 0.1 wt. % Other 0.4 wt. %
[0035] According to yet another of its aspects, the invention is
directed to a process for the continuous casting of steel which
comprises pouring the molten steel through an element, or a
combination of a nozzle and an element, as above described.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0036] The invention will now be described with reference to the
attached drawings in which
[0037] FIG. 1 shows a cross-section of the bottom wall of a
metallurgical vessel provided with an assembly according to the
invention;
[0038] FIGS. 2 and 3 show respectively top and perspective views of
a surrounding element according to the invention;
[0039] FIGS. 4 and 5 show skulls collected at the end of the
casting operations in the upper part of the nozzle;
[0040] FIG. 6 is a cross-section of an element according to the
invention;
[0041] FIG. 7 is a cross-section of an element according to the
invention;
[0042] FIG. 8 is a cross-section of an element according to the
invention;
[0043] FIG. 9 is a perspective view of an element according to the
invention;
[0044] FIG. 10 is a cross-section of an element according to the
invention;
[0045] FIG. 11 is a cross-section of an element according to the
invention;
[0046] FIG. 12 is a cross-section of an element according to the
invention;
[0047] FIG. 13 is a perspective view of an element according to the
invention;
[0048] FIG. 14 is a cross-section of an element according to the
invention;
[0049] FIG. 15 is a perspective view of an element according to the
invention;
[0050] FIG. 16 is a cross-section of an element according to the
invention;
[0051] FIG. 17 is a cross-section of an element according to the
invention;
[0052] FIG. 18 is a cross-section of an element according to the
invention;
[0053] FIG. 19 is a cross-section of an element according to the
invention;
[0054] FIG. 20 is a perspective view of an element according to the
invention;
[0055] FIG. 21 is a perspective view of an element according to the
invention;
[0056] FIG. 22 is a perspective view of an element according to the
invention;
[0057] FIG. 23 is a perspective view of an element according to the
invention;
[0058] FIG. 24 is a perspective view of an element according to the
invention;
[0059] FIG. 25 is a perspective view of an element according to the
invention;
[0060] FIG. 26 is a perspective view of an element according to the
invention;
[0061] FIG. 27 is a perspective view of an element according to the
invention;
[0062] FIG. 28 is a perspective view of an element according to the
invention;
[0063] FIG. 29 is a perspective view of an element according to the
invention;
[0064] FIG. 30 is a cross-section of an element according to the
invention;
[0065] FIG. 31 is a cross-section of an element according to the
invention;
[0066] FIG. 32 is a schematic perspective view of an element
according to the invention;
[0067] FIG. 33 is a schematic perspective view of an element
according to the invention;
[0068] FIG. 34 is a top view of an element according to the
invention;
[0069] FIG. 35 is a top view of an element according to the
invention;
[0070] FIG. 36 is a cross section of an element and a metallurgical
vessel according to the invention;
[0071] FIG. 37 is an elevation of a portion of a raised outer
periphery of an element according to the invention;
[0072] FIG. 38 is an elevation of a portion of a raised outer
periphery of an element according to the invention;
[0073] FIG. 39 is an elevation of a portion of a raised outer
periphery of an element according to the invention;
[0074] FIG. 40 is an elevation of a portion of a raised outer
periphery of an element according to the invention;
[0075] FIG. 41 elevation of a portion of a raised outer periphery
of an element according to the invention; and
[0076] FIG. 42 is a perspective drawing of an element according to
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0077] The bottom wall 3 of a metallurgical vessel (here a tundish)
is generally constituted of a permanent lining 33 made from
refractory bricks or castable material. A working layer 32 of
castable material is generally present above the permanent lining
33. The surface 31 of the working layer will contact molten steel
during the casting operations. A layer of insulating material 34 is
normally present under the permanent lining 33 in order to protect
the metallic envelope 35 of the metallurgical vessel.
[0078] A nozzle 1 goes through the bottom of the tundish and serves
to the transfer of the molten steel from the tundish to the
continuous casting mold. The nozzle is provided with an inlet 11
opening into a bore defining thus a passage 2 for the molten steel.
The upper edge of the inlet is depicted as reference 12. FIG. 1
shows a submerged entry shroud or SES but, as explained above other
kind of nozzles (such as an inner nozzle) are also encompassed
within the scope of the present invention. In the case of a SEN,
the continuous casting operation is generally provided with a
guillotine 37 to break the nozzle 1 and terminate casting
operations. Generally, the SEN is maintained in position by a
ramming mass 36.
[0079] The surrounding refractory element 4 surrounds the inlet
portion 11 of the nozzle 1. The surrounding element 4 is comprised
of a main surface 41 surrounding a main orifice 40. The main
surface has been represented frusto-conical at FIG. 1 and planar at
FIGS. 2 and 3, but, as explained above, other arrangements are
possible. A raised outer periphery surrounds the main surface 41;
the raised outer periphery has an interior face 105. The upper face
42 of the periphery is higher than the level of the main surface
41.
[0080] As can be seen on FIG. 1, it is advantageous to have the
upper face 42 of the periphery rising higher than the surface 31 of
the tundish.
[0081] A mortar or cement joint at the junction 5 between the
refractory element 4 and the nozzle 1 can be provided for further
tightness improvement.
[0082] A trial has been performed to illustrate the effect of the
invention. The solidified steel skull remaining in the inner nozzle
at the end of casting operations has been collected and cut
vertically in the middle. FIG. 4 (given by way of comparison) shows
such a skull collected in a conventional installation (without the
surrounding refractory element) and FIG. 5 shows such a skull
collected in an installation according to the invention.
[0083] The skull 20 of FIG. 4 shows significant disturbance in the
region 21, 21' indicating the presence of alumina deposit on the
inner wall of the nozzle. This alumina deposit is responsible for
the clogging of the nozzle with all the detrimental consequences
explained above. The skull 20 of FIG. 4 shows also an enlarged
portion in the region 22, 22' indicating a severe erosion of the
nozzle inlet.
[0084] The skull 20 shown on FIG. 5 corresponds to the inner shape
of the nozzle indicating thereby that the nozzle has neither been
subjected to erosion nor to alumina clogging.
[0085] FIG. 6 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are obtuse angles. In this embodiment, the height of
the raised outer periphery is constant.
[0086] FIG. 7 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are obtuse angles. In this embodiment, the height of
the raised outer periphery varies around the course of the
element's circumference.
[0087] FIG. 8 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are obtuse angles. In this embodiment, portions of
the raised outer periphery with a fixed height are joined by height
transition segments 44.
[0088] FIG. 9 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, all angles
formed between the bottom face of the base of the element and the
exterior face of the raised outer periphery of the element are
obtuse. In this embodiment, the height of the raised outer
periphery varies around the course of the element's circumference.
The plane of the upper face of the raised outer periphery and the
plane of the bottom face of the base of the element are not
parallel.
[0089] FIG. 10 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are acute angles. In this embodiment, the height of
the raised outer periphery is constant.
[0090] FIG. 11 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are acute angles. In this embodiment, the height of
the raised outer periphery varies around the course of the
element's circumference.
[0091] FIG. 12 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, both of the angles shown in the cross-section
representation are acute angles. In this embodiment, portions of
the raised outer periphery with a fixed height are joined by height
transition segments 44.
[0092] FIG. 13 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, all angles
formed between the bottom face of the base of the element and the
exterior face of the raised outer periphery of the element are
acute. In this embodiment, the height of the raised outer periphery
varies around the course of the element's circumference. The plane
of the upper face of the raised outer periphery and the plane of
the bottom face of the base of the element are not parallel.
[0093] FIG. 14 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, one of the angles shown in the cross-section
representation is an acute angle; the other angle shown is an
obtuse angle. In this embodiment, the height of the raised outer
periphery is constant around the course of the element's
circumference. The plane of the upper face of the raised outer
periphery and the plane of the bottom face of the base of the
element are parallel.
[0094] FIG. 15 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are acute, obtuse
and, at two points, are right angles. In this embodiment, the
height of the raised outer periphery varies around the course of
the element's circumference. The plane of the upper face of the
raised outer periphery and the plane of the bottom face of the base
of the element are not parallel.
[0095] FIG. 16 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, one of the angles shown in the cross-section
representation is an acute angle; the other angle shown is an
obtuse angle. In this embodiment, the height of the raised outer
periphery varies around the course of the element's circumference.
The plane of the upper face of the raised outer periphery and the
plane of the bottom face of the base of the element are not
parallel.
[0096] FIG. 17 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, one of the angles shown in the cross-section
representation is an acute angle; the other angle shown is an
obtuse angle. In this embodiment, the height of the raised outer
periphery varies around the course of the element's circumference.
The plane of the upper face of the raised outer periphery and the
plane of the bottom face of the base of the element are not
parallel.
[0097] FIG. 18 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, one of the angles shown in the cross-section
representation is an acute angle; the other angle shown is an
obtuse angle. In this embodiment, the raised outer periphery has
two portions of constant height; these portions are joined by two
height transition segments 44. The planes of the constant height
portions of the upper face of the raised outer periphery and the
plane of the bottom face of the base of the element are
parallel.
[0098] FIG. 19 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40 and base
bottom face 104. A raised outer periphery is joined to the base;
the raised outer periphery has an exterior face 106 and an upper
face 42. Angles 108 are formed between element base bottom face 104
and exterior face 106 of the raised outer periphery. In this
embodiment, one of the angles shown in the cross-section
representation is an acute angle; the other angle shown is an
obtuse angle. In this embodiment, the raised outer periphery has
two portions of constant height; these portions are joined by two
height transition segments 44. The planes of the constant height
portions of the upper face of the raised outer periphery and the
plane of the bottom face of the base of the element are
parallel.
[0099] FIG. 20 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes from the interior face 105 of the raised outer
periphery of the element. The fin surface nearest main orifice 40
is at an angle from the vertical.
[0100] FIG. 21 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. Two
element fins 120 protrude from the interior face 105 of the raised
outer periphery of the element.
[0101] FIG. 22 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. Three
element fins 120 protrude from the interior face 105 of the raised
outer periphery of the element.
[0102] FIG. 23 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes from the interior face 105 of the raised outer
periphery of the element. The fin surface nearest main orifice 40
is vertical.
[0103] FIG. 24 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes from the interior face 105 of the raised outer
periphery of the element. The fin extends upwardly above the
maximum height of the upper face 42 of the raised outer periphery
of the element.
[0104] FIG. 25 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes inwardly from the interior face 105 of the raised
outer periphery of the element as well as outwardly from the
exterior face 106 of the raised outer periphery of the element. The
fin extends upwardly above the maximum height of the upper face 42
of the raised outer periphery of the element.
[0105] FIG. 26 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes outwardly from the exterior face 106 of the
raised outer periphery of the element.
[0106] FIG. 27 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery varies
around the course of the element's circumference. The plane of the
upper face of the raised outer periphery and the plane of the
bottom face of the base of the element are not parallel. An element
fin 120 protrudes inwardly from the interior face 105 of the raised
outer periphery of the element. The fin extends upwardly above the
maximum height of the upper face 42 of the raised outer periphery
of the element.
[0107] FIG. 28 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery is
constant around the course of the element's circumference. The
plane of the upper face of the raised outer periphery and the plane
of the bottom face of the base of the element are parallel. A
plurality of lateral ports 124 extends from interior face 105 of
raised outer periphery of the element to the exterior face 106 of
the raised outer periphery of the element. These ports may be
cylindrical, or may be flared at one end or at both ends.
[0108] FIG. 29 shows a perspective view of an element 4 of the
present invention having main orifice 40. A raised outer periphery
is joined to the base; the raised outer periphery has an exterior
face 106 and an upper face 42. In this embodiment, angles formed
between the bottom face of the base of the element and the exterior
face of the raised outer periphery of the element are obtuse. In
this embodiment, the height of the raised outer periphery is
constant around the course of the element's circumference. The
plane of the upper face of the raised outer periphery and the plane
of the bottom face of the base of the element are parallel. A
plurality of paired lateral ports 128 extends from interior face
105 of raised outer periphery of the element to the exterior face
106 of the raised outer periphery of the element. These ports may
be cylindrical, or may be flared at one end or at both ends. These
ports may be directed so that the longitudinal axes of each of a
pair of ports intersect at a circle within the volume partially
enclosed by the element, i.e., the volume partially enclosed by the
interior face 105 of the raised outer periphery of the element.
[0109] FIG. 30 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40. A raised
outer periphery 140 is joined to the base; the raised outer
periphery has an exterior face 106. In this embodiment an
externally directed rim 132 is in communication with the exterior
face 106 of the raised outer periphery of the element. In the
embodiment shown, externally directed rim 132 is horizontal; it may
be directed above or below the horizontal in other embodiments.
[0110] FIG. 31 shows a cross section of an element 4 of the present
invention, in which base 102 contains main orifice 40. A raised
outer periphery 140 is joined to the base; the raised outer
periphery has an interior face 105. In this embodiment an
internally directed rim 134 is in communication with the interior
face 106 of the raised outer periphery of the element. In the
embodiment shown, the internally directed rim takes a truncated
conical form; it may be horizontal in other embodiments.
[0111] FIG. 32 shows a schematic perspective view of an element 4
of the present invention, in which base 102 contains main orifice
40. A raised outer periphery 140 is joined to the base. In the
embodiment shown, the raised outer periphery has a gap.
[0112] FIG. 33 shows a schematic perspective view of an element 4
of the present invention, in which base 102 contains main orifice
40. A raised outer periphery 140 is joined to the base. In the
embodiment shown, the raised outer periphery has two gaps.
[0113] FIG. 34 shows a top view of an assembly of an element 4 of
the present invention with a nozzle 1. The top view depicts the
main surface 41 of the element and the outer periphery surrounding
the main surface of the element; the interior face 105 of the
raised outer periphery is visible, as is the upper face 42 of the
raised outer periphery. The interior of the main orifice 40 of the
element has a non-circular geometry configured to mate with the
exterior geometry of nozzle 1. In the embodiment shown, the
respective geometries are hexagonal. The corresponding geometries
constrain the positioning of the element 4 about the nozzle, so
that vertical and horizontal asymmetries of the element can be
properly positioned within a metallurgical vessel.
[0114] FIG. 35 shows a top view of an assembly of an element 4 of
the present invention with a nozzle 1. The top view depicts the
main surface 41 of the element and the outer periphery surrounding
the main surface of the element; the interior face 105 of the
raised outer periphery is visible, as is the upper face 42 of the
raised outer periphery. The interior of the main orifice 40 of the
element has a non-circular geometry configured to mate with the
exterior geometry of nozzle 1. In the embodiment shown,
indentations on the interior of main orifice 40 accept protrusions
on the surface of nozzle 1. The corresponding geometries constrain
the positioning of the element 4 about the nozzle, so that vertical
and horizontal asymmetries of the element can be properly
positioned within a metallurgical vessel.
[0115] FIG. 36 shows a cross section of an element 4 and the walls
152 of a metallurgical vessel according to the invention. The
nozzle and the floor of the metallurgical vessel have been omitted
for clarity. A stopper rod 154 is positioned to be moved vertically
to permit or interrupt flow through main orifice 40. The interior
face 105 and the exterior face 106 of the raised outer periphery of
the element are indicated. Gaps 162 between the element and the
metallurgical vessel wall are indicated. The distance 164 between
the interior face 105 and the main orifice 40 is also indicated.
The asymmetric design on the element embodiment shown permits gaps
of the same size between each metallurgical vessel wall 152 and the
top of the element, as well as permitting constant, or nearly
constant, distances between the interior face 105 and the main
orifice 40, while allowing the stopper rod 154 to be positioned
closer to one metallurgical vessel wall than to the other.
[0116] FIG. 37 shows a portion 170 of the raised outer periphery of
element 4. The upper face 42 of raised outer periphery of the
element contains a plurality of square notches.
[0117] FIG. 38 shows a portion 170 of the raised outer periphery of
element 4. The upper face 42 of raised outer periphery of the
element contains a plurality of semicircular protrusions.
[0118] FIG. 39 shows a portion 170 of the raised outer periphery of
element 4. The upper face 42 of raised outer periphery of the
element is formed in a sawtooth pattern.
[0119] FIG. 40 shows a portion 170 of the raised outer periphery of
element 4. The upper face 42 of raised outer periphery of the
element contains a plurality of semicircular notches.
[0120] FIG. 41 shows a portion 170 of the raised outer periphery of
element 4. The upper face 42 of raised outer periphery of the
element is formed in a wave pattern.
[0121] FIG. 42 is a perspective drawing of an element 4 of the
present invention, in which base 102 contains main orifice 40 and
in communication with raised outer periphery 140. Raised outer
periphery 140 houses upper face 42. The maximum external dimension
of the base of the element 202, the minimum external dimension of
the base of the element 204, the maximum external dimension of the
top of the element 206, the minimum external dimension of the top
of the element 208, the thickness of the base of the element 222,
the thickness of the raised outer periphery of the element 224, the
maximum exterior height of the element 232, the maximum interior
height of the element 234, the minimum exterior height of the
element 236, and the minimum interior height of the element 238 are
indicated.
[0122] A refractory element according to the present invention,
therefore, may comprise a base having a bottom and a main surface,
a main orifice passing through the main surface, and a periphery
surrounding the main surface, wherein the main orifice has an
interior face, wherein the periphery has an interior face, an
exterior face and an upper face, wherein the upper face of the
periphery is higher than the main surface of the refractory
element, wherein the periphery intersects the bottom of the base,
and wherein the exterior face of the periphery forms an angle other
than a right angle with the bottom of the base in at least one
point in their intersection. The exterior face of the periphery may
form a right angle with the bottom of the base at two points in
their intersection, may form an acute angle with the bottom of the
base at all points in their intersection, or may form an obtuse
angle with the bottom of the base at all points in their
intersection. The plane of the exterior face of the periphery and
the plane of the bottom of the base may be non-parallel planes. The
upper face of the periphery comprises an upper level and a lower
level joined by two transitional non-vertical, non-horizontal
portions. The main surface of the element may have a geometry
selected from the group consisting of circular, oval, truncated
circular, truncated oval, and polygonal geometry. The element may
also comprise one or more fins extending from the inner face of the
periphery, or one or more fins extending from the exterior face of
the periphery. The element may comprise one or more ports passing
from the exterior face to the interior face of the periphery. The
element may comprise a feature on its surface, for example on the
interior face of the main orifice or on the bottom of the base,
which may be a marking, a recess, a protrusion, a groove, a lip, a
peg, a bore, a notch, a dimple, a mogul, a ridge, a threaded
receiver, a key receiver, a bayonet receiver, a bevel, and a
non-circular geometry, or any other device or feature which would
constrain movement of the element around an axis. The refractory
element of the invention may be composed of single pieces or of
multiple pieces. The refractory element of the invention may be
produced from a high alumina material comprising at least 75 wt. %
of Al.sub.2O.sub.3, less than 1.0 wt. % of SiO.sub.2, and less than
5 wt. % of C. The refractory element may be constructed so that the
periphery of the element has a thickness equal to or less than 100
millimeters, and the base of the element has a thickness equal to
or less than 100 millimeters.
[0123] An assembly of a refractory element and a nozzle according
to the invention may be composed of a single piece or multiple
pieces. The refractory element may comprise a main orifice having a
non-circular geometry, and wherein the refractory nozzle comprises
an exterior radial surface having a non-circular geometry
configured to mate with the refractory element. The refractory
element comprises a main orifice interior face having a mating
feature, wherein the refractory nozzle comprises an exterior radial
surface having a corresponding mating feature configured to engage
with the main orifice interior face mating feature. The mating
feature of the nozzle and the mating feature of the element, when
engaged, may prevent rotational motion of the element around the
longitudinal axis of the bore of the nozzle.
[0124] An assembly of a refractory element and a nozzle according
to the present invention may be deployed in a metallurgical vessel
for the casting of molten metal. In a typical deployment, the
refractory nozzle may have an inlet portion forming a passage
through the bottom wall of the metallurgical vessel and a
refractory element as previously described surrounding the inlet
portion of the nozzle, wherein the inlet portion of the nozzle has
a top outer edge, wherein the inlet portion of the nozzle has a
longitudinal axis, wherein the main orifice of the element is
adapted for matching engagement with at least a portion of the
outer surface of the nozzle, wherein the main surface of the base
of the element has a lowest level, the lowest level being lower
than the top outer edge of the nozzle inlet portion, and wherein at
least a portion of the periphery of the refractory element is
higher than the surface of the bottom wall of the tundish. The
element may comprise a gas impervious refractory material. The
nozzle or the element may comprise a gas impervious refractory
material. A gas impervious mortar may be used between the nozzle
and the refractory element.
[0125] A process for the continuous casting of steel may comprise
pouring the molten steel from a ladle into a metallurgical vessel
housing an assembly of a refractory element and a nozzle as
described above, and thence into a casting mold.
[0126] Numerous modifications and variations of the present
invention are possible. It is, therefore, to be understood that
within the scope of the following claims, the invention may be
practiced otherwise than as specifically described.
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