FIELD OF THE INVENTION
[0001] The present invention relates to diffusers for tundishes as well as the use of such
diffusers in tundishes and the tundishes comprising said diffusers.
BACKGROUND OF THE INVENTION
[0002] An impact pad is commonly placed on the floor of a tundish to receive an incoming
stream of molten metal poured into the tundish from a source such as a metallurgical
ladle or the output of a high furnace. The tundish has a distribution and buffering
function for the molten metal, but also helps purifying and cleaning the melt.
[0003] Due to the high requirements for steel quality, cleanliness has become one of the
main concerns for steel makers. The tundish is considered an important tool in improving
the cleanliness of cast steel. Improving the liquid steel flow in the different stages
of the steelmaking chain is becoming essential. Uncontrolled flow severely impairs
the steel quality through atmosphere contamination with oxygen and nitrogen entrained
in the open slag areas around the feeding shroud.
[0004] Slag entrapment and refractory wear due to surface turbulence form large inclusions
in the steel product; skull formation zones are also sources of operational problems
and quality. Non-metallic inclusions, such as AlO
3, are removed from the steel melt as they float to the top of the melt and collect
at the liquid steel to metal-slag interface, due to their lower density compared to
the liquid steel. For this process to occur efficiently, convection streams in the
steel melt can be encouraged by installation of so-called tundish furniture such as
dams, weirs and baffles.
[0005] It is a common problem that the residence time of a steel melt in a tundish is too
short for this convection process to occur to a sufficient degree. The flow of the
dense and viscous steel melt through the tundish and the arrangement of the tundish
furniture lead to a complex dynamic system, the behaviour of which is inherently difficult
to predict. In particular, the occurrence of so-called "dead zones" where some liquid
metal accumulates and stagnates, and around which the flow of the melt is directed,
is problematic. On the one hand the flow of the melt is accelerated by the reduction
of the effective volume of the tundish, leading to a reduced residence time of the
melt in the tundish. On the other hand, the accumulated stagnating melt is exposed
to the atmosphere for prolonged time, leading to the formation of impurities through
reaction with atmospheric oxygen and nitrogen. These problems could be avoided by
directing the flow of the liquid metal such that a uniform flow velocity and temperature
distribution are ensured throughout the molten metal in the tundish during operation.
[0006] Impact pads are generally designed to protect the tundish interior surface from the
forces caused by the heavy and hot melt falling onto the tundish floor at the start
of the casting process. They are generally formed of a reinforced portion of refractory
material, and arranged such that minimal splashing of molten metal occurs upon impact.
[0007] US 5,169,591 discloses an impact pad designed to protect the tundish from said strain, and to
reduce the occurrence of surface turbulence on the melt which causes the supernatant
solid metal and slag to be dragged into the melt and to negatively affect the purity
and quality of the obtained product. The disclosed impact pad comprises a base for
receiving an incoming stream of liquid metal and upwardly extending sidewalls with
an inner surface having an undercut portion facing the incoming stream. This effectively
reduces splashing and surface turbulence within the tundish during operation, but
does not direct the flow of liquid metal such that residence time in the tundish may
be controlled or dead zones eliminated. Tundish furniture is still required for directing
the melt flow.
[0008] DE 197 26 540 A1 and
WO 03/061879 A1 propose further impact pad designs for protecting the tundish interior and improving
the serviceability or the stability of the impact pad, respectively. None of these
designs proposes a method for reducing effective flow velocity and therefore increasing
or stabilising the residence time of the melt and avoiding the formation of dead zones
in the tundish.
[0009] EP 1 397 221 B1 proposes impact pads for use in molten metal tundishes which help directing the flow
of molten metal. These impact pads consist of a base plate and sidewalls having multiple
protrusions, with a complex design. They are therefore difficult and expensive to
produce and maintain.
[0010] The state of the art therefore constitutes a problem.
SHORT DESCRIPTION OF THE INVENTION
[0011] The above mentioned problems are solved by the invention according to the appended
claims. In particular, the problem is solved by a diffuser for use in a tundish and
made of a refractory material, comprising (a) a base portion having a top surface
and a bottom surface, wherein said top surface is an impact surface suitable for withstanding
the impact of molten metal; and (b) an outer side wall entirely surrounding said base
portion and extending from said top surface of said base portion in order to from
a substantially bucket-like structure. The said outer side wall comprises two or more
flow outlets in the form of recesses extending from the edge of said side wall located
furthest from said base portion towards but not up to said base portion. The diffuser
may be further characterised in that the opening at the top of the diffuser has a
cross-sectional surface greater than or equal to the surface of said base portion
not covered by said side wall. The base portion of the diffuser according to the invention
may be substantially planar or raised towards its centre.
[0012] In one advantageous embodiment of the invention, the outer side wall of the diffuser
comprises exactly two flow outlets, which may be arranged at diametrically opposed
portions of said side wall, depending on the shape of the tundish. The flow outlets
extend from the edge of the side wall located furthest from the base portion towards
the base portion, and may extend for a distance which is substantially half the total
distance between said edge of the side wall and said base portion. Each flow outlet
may have a different length extension compared to any other of the two or more flow
outlets.
[0013] In one advantageous embodiment of the invention, the side wall extends in an outwardly
direction from said base portion, such that the top opening of the diffuser has a
larger section than the base portion of the diffuser, and the internal volume of the
diffuser is increased. For example, the side wall may form an angle of more than 90
degrees with the base portion, such as for example from 92 to 110 degrees, or from
95 to 105 degrees. In a further advantageous embodiment of the invention, said outer
side wall may have a varying extension, such that the edge of said side wall which
is furthest away from said base portion is at least partially sloped.
[0014] The diffuser according to the present invention may be made of a refractory material
which is a cast or pressed refractory material capable of withstanding prolonged contact
with molten metal, such as molten steel. In one embodiment, the refractory material
may have an alumina content between 55% and 85% by weight. The refractory material
may be an alumina-spinel or an alumina-magnesia refractory material. In an alternative
embodiment, the refractory material may be a basic refractory material with a magnesia
content of between 55% and 95% by weight.
[0015] The diffuser according to the present invention is adapted for use in a tundish for
transfer of molten metal. The tundish may be selected from the group consisting of
V-shaped tundishes, B-shaped tundishes, T-shaped tundishes, C-shaped tundishes and
H-shaped tundishes, and the shape and orientation of the diffuser adapted accordingly.
[0016] Further part of the invention is the use of a diffuser of the invention in the process
of pouring molten metal through a tundish.
SHORT DESCRIPTION OF THE FIGURES
[0017] The invention will be further illustrated using the following figures:
- Fig. 1a
- shows an impact pad according to the state of the art;
- Fig. 1b
- shows the flow of molten metal when pored into the impact pad according to the state
of the art of Fig. 1 a
- Fig. 2
- shows top views of different types of tundishes available;
- Fig. 3
- shows a cross-section of an exemplary base portion having a non-planar shape of the
diffuser according to the invention;
- Fig. 4
- shows a three-dimensional structure of a diffuser according to the invention in a
B-shaped tundish;
- Fig. 5a
- shows 3-dimensional image of a diffuser according to one embodiment of the present
invention;
- Fig. 5b
- shows 3-dimensional image of a diffuser according to a further embodiment of the present
invention;
- Fig. 6a
- shows the temperature distribution in a V-shaped tundish shortly after the start of
the pouring process when an impact pad according to the state of the art is used;
- Fig. 6b
- shows the temperature distribution in a V-shaped tundish shortly after the start of
the pouring process when an impact pad according to the present invention is used;
- Fig. 7a
- shows the temperature distribution in a V-shaped tundish one minute after the start
of the pouring process when an impact pad according to the state of the art is used;
- Fig. 7b
- shows the temperature distribution in a V-shaped tundish one minute after the start
of the pouring process when an impact pad according to the present invention is used;
- Fig. 8
- shows the velocity distribution of flowing molten metal in a B-shaped tundish at different
height levels of the tundish during casting;
- Fig. 9
- shows the temperature distribution of molten metal in a B-shaped tundish at different
height levels of the tundish during casting.
DETAILED DESCRIPTION OF THE INVENTION
[0018] According to the state of the art, impact pads have been used in order to reduce
the strain and forces borne by a tundish during operation, and in particular at the
start of the casting process. Tundish furniture, such as dams, weirs and baffles are
traditionally used for directing flow and avoiding dead zones of the molten metal
in the tundish during operation. In continuous casting, it is particularly important
that uniform flow and temperature are ensured during operation, and the strain caused
by prolonged exposure to high temperatures and abrasion caused by the constant flow
of dense and viscous liquid requires high stability and resilience of the equipment
used.
[0019] Tundishes for distributing and buffering metal melts are available in different configurations,
according to the requirements of the specific metals, processes and conditions. The
diffusers according to the present invention may be employed in tundishes for different
ferrous and non-ferrous metal melts. They are particularly useful in steel making.
Fig. 2 shows top views of a range of different tundishes available. Most commonly
used are the B-shaped (boat-shaped) tundish with a substantially rectangular base,
and the V-shaped tundish with a corresponding V-shaped base. Also available for different
applications are T-, C- and H-shaped versions. The tundishes may have varying numbers
of strands or outlets, such as for example 1, 2, 4, 6 or 8 strands, depending on the
size and shape of the tundish. Further to the shape of the tundishes, the insertion
zone of the molten material and the positions of the one or more strands may vary.
The flow characteristics of a metal melt in these different tundishes is of course
influenced by all these factors. As mentioned above, it is an object of the invention
to provide systems allowing the production of cast material of superior and uniform
quality by ensuring that the flow velocity and temperature within the tundish during
operation is as uniform as possible, with increased residence time, reduced surface
turbulence and avoidance of dead zones.
[0020] The diffusers according to the present invention act as both impact pads and flow
controllers for molten metal in the tundishes.
[0021] Impact pads according to the state of the art, such as described in
US 5,169,591 (see Fig. 1a and 1b), are very effective in reducing and distributing the forces
acting on the tundish during operation and in particular at the start of the casting
process, and in reducing surface turbulence. However, they are not suitable for directing
the flow of molten metal within the tundish during operation, in order to obtain controlled
residence times and flow velocities and to avoid dead zones. Various tundish furniture
items (dams, weirs and baffles) need to be used in order to control metal flow. The
actual flow obtained is difficult to predict prior to starting a casting operation,
and it is not convenient to change the positioning of the tundish furniture once installed,
since the process has to be stopped and the equipment cooled down before any adaptations
can be made.
[0022] The diffusers according to the present invention serve both as impact pads and for
directing flow in the tundish during operation. It has been found that diffusers having
the specific shapes according to the present invention are efficient and predictable
in their operation, in that they direct the flow of molten metal within a tundish
such that flow direction and velocity, as well as residence times in the tundish can
be controlled. Furthermore, surface turbulence is avoided.
[0023] The diffusers according to the present invention are made of a refractory material
and comprise (a) a base portion having a top surface and a bottom surface, wherein
said top surface is an impact surface suitable for withstanding the impact of molten
metal; and (b) an outer side wall entirely surrounding said base portion and extending
from said top surface of said base portion in order to from a substantially bucket-like
structure; and the said outer side wall comprises two or more flow outlets in the
form of recesses extending from the edge of said side wall which is furthest away
from said base portion towards but not up to said base portion. They may be characterised
in that the opening at the top of the diffuser has a cross-sectional surface greater
than or equal to the surface of said base portion not covered by said side wall. In
other words, there is no overhang at the top of the side wall, as is shown e.g. in
the prior art diffuser to of Figs. 1 a and 1 b.
[0024] Said base portion of the diffuser may be substantially planar or have a shape that
is slightly raised towards the centre of the base portion, as shown in Fig. 3. In
general, the shape of the base portion may be adapted to the overall shape of the
diffuser and tundish, in order to improve the flow characteristics in the tundish.
[0025] The size and exact configuration of the diffuser may be adapted to the tundish it
is to be used in, but always within the structural features as described above. In
most common applications, the diffuser has exactly two flow outlets, though diffusers
with more than two flow outlets may be considered for more complex applications.
[0026] In particular, the positioning of the flow outlets in the side wall depends on the
shape of the tundish. For example, in the case of a B- (boat)-shaped tundish with
a central insertion point for the melt and outlets along a central line parallel to
the longitudinal sides of the tundish, the two flow outlets of the diffuser may be
arranged at diametrically opposed ends of the side wall, in order to direct the flow
along said outlets in the tundish (see Fig. 4 and 5a). On the other hand, in tundishes
with non-symmetrical base shapes, such as V-shaped tundishes, the flow outlets of
the diffuser may be arranged also non-symmetrically along the side wall (see an exemplary
embodiment in Fig. 5b).
[0027] The flow outlets of the diffuser according to the invention may have different sizes
and shapes and need not be identical for the flow outlets in any given diffuser. They
may be rectangular or angled or have any other shape deemed suitable. The flow outlets
extend from the edge of the side wall furthest from the base portion of the diffuser
(the "top edge") down towards the base portion. They may however not extend all the
way down to the base portion of the diffuser, such as to form a gap in the side wall.
In that case, splashing of molten metal would occur outside of the diffuser at the
start of the casting process, and small puddles of molten metal would form in the
tundish in the initial stages of the process, and therefore increasing surface area
and exposure to the atmosphere of the molten metal, leading to the formation of further
impurities in the melt. Instead, the recesses may extend to substantially half the
distance between the top edge of the outer wall and the base portion of the diffuser,
such as a distance between 20% and 80% between the top edge of the outer wall and
the base portion of the diffuser, or a distance between one third and two thirds between
the top edge of the outer wall and the base portion of the diffuser. According to
the present invention however, any length of the flow outlets may be considered, as
long as they do not extend up to the base portion of the diffuser.
[0028] The flow outlets may furthermore have a total width at the top edge of the side wall
which is no more than 30% of the total width of the side wall, or a width which is
no more than 20, or no more than 10% of the total width of the side wall.
[0029] The side wall of the diffuser may be arranged such that it extends in an outwardly
direction from said base portion, meaning the side wall and the base portion form
an angle of 90 degrees or higher, such as 92 to 110 degrees, or 95 to 105 degrees
or 100 degrees or the like. This further reduces splashing of the molten metal at
the start of the pouring process and helps avoid the formation of reaction products
from unnecessary exposure to the atmosphere. Even if the side wall extends in an outwardly
direction from said base portion, according to the present invention, it need not
comprise an overhang at its top edge.
[0030] The outer wall of the diffuser according to the present invention may have varying
length, such that its edge furthest away from the base portion of the diffuser is
sloped in various portions. An exemplary embodiment of a diffuser with a sloped edge
is shown in Fig. 5b. The slope may help direct the flow of molten metal in the tundish
in the desired direction.
[0031] The diffusers may be formed from a cast or pressed refractory composition capable
of withstanding continuous contact with molten metal, in particular molten steel such
as is used in continuous casting operations. Usually a standard medium-to-high alumina
refractory with an alumina content in the range of about 55% to 85% by weight is desirable.
In case of long sequence or high aggressive steel grades, alumina-spinel or alumina
magnesia are suitable. Where a basic refractory is preferred because of steel chemistry,
a magnesia-based refractory composition may be utilised, with MgO in the range of
about 55% to 95% by weight. In general, any refractory material known by the skilled
person in the art may be used for the diffusers according to the invention.
[0032] The diffusers are installed in the tundishes simply by placing at the bottom of the
tundish in the designated position. Alternatively, a region may be provided in the
wear lining on the floor of the tundish, which is adapted to receiving the impact
pad. This may be in the form of an indentation corresponding to the shape of the base
of the impact pad. The mass of the impact pad is generally sufficient to hold it in
place at the bottom of the tundish.
[0033] The diffusers may have a total height (the distance between the base portion and
the end of the side wall furthest from said base portion) which is adapted to the
size and height of the tundish they are intended for use in. For example, the height
shall be sufficient to avoid splashing or spilling of the molten metal out of the
diffuser at the start of the pouring process. However, the impact pad shall not be
so high as to create turbulence at the surface of the liquid metal during operation,
since this could lead to the creation of vortexes in the liquid and the formation
of impurities therein. In general, the impact pad may have a height which is substantially
between 20% and 80% of the height of the tundish, or between one third and two thirds
of the height of the tundish.
EXAMPLE 1
[0034] A diffuser according to the present invention as shown in Fig. 5b was installed in
a V-shaped tundish and an impact pad according to the state of the art as shown in
Fig. 1 a was installed in an identical V-shaped tundish. Molten steel was poured into
both tundishes and the temperature distribution within the tundishes was recorded
using temperature imaging equipment. Figs. 6a (state of the art) and 6b (invention)
show the temperature distribution in the V-shaped tundishes shortly after the start
of the pouring, and Figs. 7a (state of the art) and 7b (invention) show the temperature
distribution in the same tundishes exactly 1 minute after the start of the pouring
process.
[0035] Figs. 6a and 6b clearly show that at the start of the process, the temperature dissipation
within the tundish occurs at a much faster rate when the diffuser according to the
invention is used, compared to the impact pad of the state of the art. Also, after
1 minute of operation, it is clearly apparent that a uniform temperature distribution
is established in the tundish using the diffuser according to the invention (Fig.
7b), while the temperature differences throughout the tundish are notably larger in
the tundish using the impact pad according to the state of the art (Fig. 7a).
[0036] These observations show two different advantages of the present invention. On the
one hand, the molten material flows more smoothly through the tundish, as is shown
by the wider distribution of the high-temperature zone shortly after the start of
the process, showing that that the cast material is distributed quicker throughout
the tundish, therefore creating more uniform flow and less surface turbulence caused
by pressure variations within the melt. Furthermore, as can be seen in Figs. 7a and
7b, the temperature distribution during operation is much more uniform, leading to
an overall flow of liquid that is not disturbed by temperature variations in different
parts of the tundish. A uniform flow of material may be easily controlled and avoid
the occurrence of dead zones and reduction of effective volume of the tundish.
EXAMPLE 2
[0037] Molten steel was poured at approximately 1510 to 1570°C through boat-shaped tundishes
and the distributions of velocity and temperature within the tundish at different
height levels was measured. The tundish had previously been equipped with a diffuser
according to Fig. 5a.
[0038] Figs. 8 and 9 show flow velocity and temperature distributions within the B- (boat)-shaped
tundish during operation, when a diffuser according to Fig. 5a is used. The different
section images in each figure describe the situation at different heights in the tundish
during operation (heights indicated in mm). As can be seen, the velocity and temperature
distributions are very uniform at all heights throughout the tundish, showing that
there is a uniform flow pattern of the molten metal through the tundish, avoiding
the creation of turbulences and vortexes at the liquid surface and of dead-zones where
there is stagnant liquid metal. This leads to an overall improvement of the efficiency
of the pouring process, and of the quality of the final product. Due to the reduced
splashing and surface turbulence of the liquid metal, as well as the uniform flow
and temperature pattern, a homogenous distribution of the metal between separate strands
(outflows) in the tundish is guaranteed. This leads to more consistent product quality
and reliability.
1. Diffuser for use in a tundish and made of a refractory material comprising
a base portion having a top surface and a bottom surface, wherein said top surface
is an impact surface suitable for withstanding the impact of molten metal; and
an outer side wall entirely surrounding said base portion and extending from said
top surface of said base portion in order to form a substantially bucket-like structure;
characterised in that
the side wall forms an angle of more than 92 degrees with said base portion, wherein
the side wall has no overhang at its top edge;
and in that
said outer side wall comprises two or more flow outlets in the form of recesses extending
from the edge of said side wall which is located furthest from said base portion towards
but not up to said base portion.
2. Diffuser according to claim 1, wherein the opening at the top of the diffuser has
a cross-sectional surface greater than or equal to the surface of said base portion
not covered by said side wall.
3. Diffuser according to claim 1 or claim 2, wherein the base portion is substantially
planar or wherein the base portion is raised towards its centre.
4. Diffuser according to any one of the previous claims, wherein the outer side wall
comprises exactly two flow outlets.
5. Diffuser according to claim 4, wherein the two flow outlets are arranged at diametrically
opposed portions of said side wall.
6. Diffuser according to any one of the previous claims, wherein the flow outlets each
extend to points between 20% to 80% the distance between said base portion and the
edge of said side wall which is located furthest from said base portion.
7. Diffuser according to any of the previous claims, wherein the side wall extends in
an outwardly direction from said base portion, such that the top opening of the diffuser
has a larger section than the base portion of the diffuser, and the internal volume
of the diffuser is increased.
8. Diffuser according to claim 7, wherein the side wall forms an angle of 92 to 110 degrees
with said base portion.
9. Diffuser according to any of the previous claims, wherein the extension of the outer
side wall varies such that the edge of said side wall which is furthest away from
said base portion is at least partially sloped.
10. Diffuser according to any of the previous claims, wherein the refractory material
is a cast or pressed refractory material capable of withstanding prolonged contact
with molten metal, such as molten steel.
11. Diffuser according to any of the previous claims, wherein the refractory material
has an alumina content between 55% and 85% by weight.
12. Diffuser according to any of the previous claims, wherein the refractory material
is an alumina-spinel or an alumina-magnesia refractory material.
13. Diffuser according to any of claims 1 to 10, wherein the refractory material is a
basic refractory material with a magnesia content of between 55% and 95% by weight.
14. Use of a diffuser according to any of the previous claims in the process of pouring
molten metal through a tundish.
15. Use according to claim 14, wherein the tundish is a tundish selected from the group
consisting of V-shaped tundishes, B-shaped tundishes, T-shaped tundishes, C-shaped
tundishes and H-shaped tundishes.
16. Use according to claim 13, wherein flow of molten metal in the tundish is directed
by the flow outlets in the diffuser.
17. Use according to claim 15 wherein the tundish does not include furniture items other
than the said diffuser to control metal flow.
1. Diffusor für die Verwendung in einer Gießwanne und hergestellt aus einem Feuerfeststoff,
umfassend
einen Basisabschnitt mit einer oberen Fläche und einer unteren Fläche, wobei die obere
Fläche eine Aufprallfläche ist, geeignet zum Aushalten des Aufschlags von geschmolzenem
Metall; und
eine äußere Seitenwand, die den Basisabschnitt ganz einkreist und sich von der oberen
Fläche des Basisabschnitts so erstreckt, dass sie eine im Wesentlichen Eimer-artige
Struktur bildet; dadurch gekennzeichnet, dass
die Seitenwand einen Winkel von mehr als 92 Grad mit dem Basisabschnitt bildet, wobei
die Seitenwand an ihrem oberen Rand keinen Überhang hat;
und dass
die äußere Seitenwand zwei oder mehr Auslassdurchflüsse umfasst, in der Form von Vertiefungen,
die sich von dem Rand der Seitenwand, der am weitesten vom Basisabschnitt entfernt
ist, zum Basisabschnitt hin, aber nicht bis daran, erstrecken.
2. Diffusor gemäß Anspruch 1, wobei die Öffnung oben am Diffusor eine Querschnittsfläche
hat, größer oder gleich der Oberfläche des Basisabschnitts, die nicht von der Seitenwand
bedeckt ist.
3. Diffusor gemäß Anspruch 1 oder Anspruch 2, wobei der Basisabschnitt im Wesentlichen
eben ist, oder wobei der Basisabschnitt zu seiner Mitte hin erhöht ist.
4. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei die äußere Seitenwand
genau zwei Auslassdurchflüsse umfasst.
5. Diffusor gemäß Anspruch 4, wobei die zwei Auslassdurchflüsse an zwei diametral gegenüberliegenden
Abschnitten der Seitenwand angeordnet sind.
6. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei die Auslassdurchflüsse
sich jeweils bis zu Punkten zwischen 20% und 80% der Entfernung zwischen dem Basisabschnitt
und dem Rand der Seitenwand, der am weitesten vom Basisabschnitt entfernt ist, erstrecken.
7. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei die Seitenwand sich
in einer Richtung nach außen vom Basisabschnitt aus erstreckt, so dass die obere Öffnung
des Diffusors einen größeren Querschnitt hat als der Basisabschnitt des Diffusors,
und das innere Volumen des Diffusors vergrößert wird.
8. Diffusor gemäß Anspruch 7, wobei die Seitenwand einen Winkel von 92 bis 110 Grad mit
dem Basisabschnitt bildet.
9. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei die Verlängerung der
äußeren Seitenwand so variiert, dass der Rand der Seitenwand, der am weitesten vom
Basisabschnitt entfernt ist, mindestens teilweise geneigt ist.
10. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei der Feuerfeststoff
ein gegossener oder gepresster Feuerfeststoff ist, der längerem Kontakt mit geschmolzenem
Metall, wie geschmolzenem Stahl, standhalten kann.
11. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei der Feuerfeststoff
einen Aluminiumoxydgehalt zwischen 55 Gew.-% und 85 Gew.-% hat.
12. Diffusor gemäß irgendeinem der vorhergehenden Ansprüche, wobei der Feuerfeststoff
ein Aluminiumoxyd-Spinell- oder ein Aluminiumoxyd-Magnesiumoxyd-Feuerfeststoff ist.
13. Diffusor gemäß irgendeinem der Ansprüche 1 bis 10, wobei der Feuerfeststoff ein basischer
Feuerfeststoff ist mit einem Magnesiumoxydgehalt von zwischen 55 Gew.-% und 95 Gew.-%.
14. Verwendung eines Diffusors aus irgendeinem der vorhergehenden Ansprüche im Verfahren
zum Gießen von geschmolzenem Metall durch eine Gießwanne.
15. Verwendung gemäß Anspruch 14, wobei die Gießwanne eine Gießwanne ist, ausgewählt aus
der Gruppe V-förmige Gießwannen, B-förmige Gießwannen, T-förmige Gießwannen, C-förmige
Gießwannen und H-förmige Gießwannen.
16. Verwendung gemäß Anspruch 13, wobei Durchfluss von geschmolzenem Metall in der Gießwanne
durch die Auslassdurchflüsse im Diffusor geleitet wird.
17. Verwendung gemäß Anspruch 15, wobei die Gießwanne außer dem Diffusor keine Ausstattungsgegenstände
umfasst, um den Metallfluss zu steuern.
1. Diffuseur pour l'utilisation dans un panier de coulée et construit d'un matériau réfractaire,
comprenant
une portion de base ayant une surface supérieure et une surface inférieure, où ladite
surface supérieure est une surface d'impact capable de résister à l'impact de métal
fondu ; et
une paroi latérale extérieure qui encadre totalement ladite portion de base et s'étend
de ladite surface supérieure de ladite portion de base pour former une structure essentiellement
en forme de seau ; caractérisé en ce que
la paroi latérale forme un angle supérieur à 92 degrés avec ladite portion de base,
où la paroi latérale n'a pas de surplomb sur son bord supérieur ;
et en ce que
ladite paroi latérale extérieure comprend deux ou plusieurs sorties de flux en forme
de cavités qui s'étendent du bord de ladite paroi latérale qui se trouve le plus éloigné
de ladite portion de base, vers ladite portion de base mais sans y arriver.
2. Diffuseur selon la revendication 1, dans lequel l'ouverture en haut du diffuseur a
une surface de section supérieure ou égale à la surface de ladite portion de base
qui n'est pas couverte par ladite paroi latérale.
3. Diffuseur selon la revendication 1 ou la revendication 2, dans lequel la portion de
base est essentiellement plate ou dans lequel la portion de base est élevée vers son
centre.
4. Diffuseur selon une quelconque des revendications précédentes, dans lequel la paroi
latérale extérieure comprend exactement deux sorties de flux.
5. Diffuseur selon la revendication 4, dans lequel les deux sorties de flux sont arrangées
dans des positions diamétralement opposées de ladite paroi latérale.
6. Diffuseur selon une quelconque des revendications précédentes, dans lequel les sorties
de flux chacune s'étendent vers un point entre 20% et 80% de la distance entre ladite
portion de base et le bord de ladite paroi latérale qui se trouve le plus éloigné
de ladite portion de base.
7. Diffuseur selon une quelconque des revendications précédentes, dans lequel la paroi
latérale s'étend en une direction vers l'extérieur de ladite portion de base, de façon
que l'ouverture supérieure du diffuseur ait une section plus grande que la portion
de base du diffuseur, et le volume interne du diffuseur est agrandi.
8. Diffuseur selon la revendication 7, dans lequel la paroi latérale forme un angle de
92 à 110 degrés avec ladite portion de base.
9. Diffuseur selon une quelconque des revendications précédentes, dans lequel l'extension
de la paroi latérale extérieure varie de façon que le bord de la paroi latérale qui
se trouve le plus éloigné de ladite portion de base soit au moins partiellement incliné.
10. Diffuseur selon une quelconque des revendications précédentes, dans lequel le matériau
réfractaire est un matériau réfractaire coulé ou comprimé capable de tolérer un contact
prolongé avec du métal fondu, comme de l'acier fondu.
11. Diffuseur selon une quelconque des revendications précédentes, dans lequel le matériau
réfractaire a un contenu en alumine entre 55% et 85% en poids.
12. Diffuseur selon une quelconque des revendications précédentes, dans lequel le matériau
réfractaire est un matériau réfractaire en spinelle d'alumine ou en alumine-magnésie.
13. Diffuseur selon une quelconque des revendications 1 à 10, dans lequel le matériau
réfractaire est un matériau réfractaire alcalin avec un contenu en magnésie entre
55% et 95% en poids.
14. Utilisation d'un diffuseur de l'une quelconque des revendications précédentes, dans
le procédé de couler du métal fondu à travers un panier de coulée.
15. Utilisation selon la revendication 14, dans laquelle le panier de coulée est un panier
de coulée sélectionné parmi le groupe constitué en paniers de coulée en forme de V,
paniers de coulée en forme de B, paniers de coulée en forme de T, paniers de coulée
en forme de C et paniers de coulée en forme de H.
16. Utilisation selon la revendication 13, dans laquelle le flux de métal fondu dans la
panier de coulée est dirigé par les sorties de flux dans le diffuseur.
17. Utilisation selon la revendication 15, dans laquelle le panier de coulé ne comprend
pas d'éléments de fournitures autres que ledit diffuseur pour contrôler le flux de
métal.