U.S. patent number RE37,214 [Application Number 09/215,429] was granted by the patent office on 2001-06-12 for device for continuous casting between rolls with applied side dams.
This patent grant is currently assigned to Thyssen Stahl Aktiengesellschaft, Usinor. Invention is credited to Jacques Barbe, Pierre Delassus, Luc Vendeville.
United States Patent |
RE37,214 |
|
June 12, 2001 |
Device for continuous casting between rolls with applied side
dams
Abstract
A side dam assembly for a continuous casting apparatus for
continuously casting thin steel strips between casting rolls. The
side dam assembly has a side dam for bearing directly against the
rolls of the casting apparatus for preventing leakage of molten
metal therebetween. The side dam is attached by a pair of belts to
an insulating refractory plate which is carried by a cooled panel.
To allow axial motion, one of the belts is not rigidly affixed to
either the insulating refractory plate or the side dam. The cooled
panel is carried by a thrust plate and is urged toward the rolls by
biasing elements which preferably comprise a plurality of pistons
urged outwardly from the thrust plate by springs. Preferably, the
biasing elements are constructed and arranged so that they are
distributed over a zone of shape corresponding to that of the side
dam and are capable of exerting on the side dam thrust forces
independently of one another.
Inventors: |
Barbe ; Jacques (Saint Etienne,
FR), Vendeville; Luc (Bethune, FR),
Delassus; Pierre (Bethune, FR) |
Assignee: |
Usinor (Puteaux, FR)
Thyssen Stahl Aktiengesellschaft (Duisburg,
DE)
|
Family
ID: |
9465040 |
Appl.
No.: |
09/215,429 |
Filed: |
December 17, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
497028 |
Jun 30, 1995 |
05584335 |
Dec 17, 1996 |
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Foreign Application Priority Data
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Jun 30, 1994 [FR] |
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94 08319 |
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Current U.S.
Class: |
164/428;
164/480 |
Current CPC
Class: |
B22D
11/066 (20130101); B27J 1/02 (20130101); B22D
11/0405 (20130101); D04C 1/00 (20130101) |
Current International
Class: |
B22D
11/06 (20060101); B22D 11/04 (20060101); B22D
011/06 () |
Field of
Search: |
;164/480,428 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0212423 |
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Mar 1987 |
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EP |
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0546206 |
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Jun 1993 |
|
EP |
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0556657 |
|
Aug 1993 |
|
EP |
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57-9566 |
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Jan 1982 |
|
JP |
|
63-026243 |
|
Feb 1988 |
|
JP |
|
63-177944 |
|
Jul 1988 |
|
JP |
|
64-83337 |
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Mar 1989 |
|
JP |
|
4224052 |
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Aug 1992 |
|
JP |
|
5253647 |
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Oct 1993 |
|
JP |
|
Other References
Patent Abstracts of Japan, vol. 12, No. 229; No. JP63026243; Jun.
1988. .
Patent Abstracts of Japan, vol. 6, No. 69; No. JP57009565; Apr.
1982. .
Patent Abstracts of Japan. vol. 13, No. 310; No. JP1099749; Jul.
1989..
|
Primary Examiner: Lin; Kuang Y.
Attorney, Agent or Firm: Nilles & Nilles, S.C.
Claims
We claim:
1. Device for continuous casting of thin metal products between
rolls, including two cooled counter-rotatory rolls, two side dams
and means for supporting and applying by pressure said side dams
against ends of said rolls, characterized in that said support
means include:
(a) a thrust plate which can be moved in an axial direction (A) of
said rolls and which is arranged generally perpendicular to said
axial direction;
(b) a panel, which supports one of said side dams and which is
carried by said thrust plate and is arranged facing the latter;
(c) at least three thrust members interposed between said thrust
plate and said panel, said thrust members being distributed over a
zone of shape corresponding to that of said side dam, and .[.being
capable of.]. exerting .Iadd.thrust forces .Iaddend.on said side
dam .[.thrust forces independently of one another.]. ;
(d) a support carriage for .Iadd.(i) .Iaddend.carrying said thrust
plate .[.and.]. .Iadd., (ii) .Iaddend.which can be moved in said
axial direction, and which includes.[.;.]. .Iadd.(iii) .Iaddend.a
means for displacing said carriage relative to said rolls for
enabling a force to be exerted on said rolls.Iadd.;
(e) said side dam comprises (i) a first plate of a thermally
insulating refractory material surrounded by a first belt with said
first plate of thermally insulating refractory material carried by
said first belt and said plate of a thermally insulating refractory
material displaceable in a direction generally parallel to an axis
of one of said rolls, and (ii) a second plate of a refractory
material surrounded by a second belt that is operably connected to
said first belt for axial movement substantially in unison with
said first plate of thermally insulating refractory material and
constructed and arranged such that said thrust forces are
transmitted through said first plate of thermally insulating
refractory material to said second plate of refractory
material;
(f) wherein said first plate of a thermally insulating refractory
material is disposed between said panel and said second plate of a
refractory material; and
(g) wherein each said second plate is of unitary construction and
bears against ends of said counter-rotatory rolls.Iaddend.. .[.
2. Device according to claim 1 wherein said side dam comprises:
(1) a plate of a thermally insulating refractory material
surrounded by a first belt with said first belt carried by said
plate for permitting displacement of said plate in a direction
generally parallel to an axis of one of said rolls; and
(2) a plate of a hard refractory material surrounded by a second
belt that is operably connected to said first belt for axial
movement in unison with said insulating refractory plate and
constructed and arranged such that thrust forces transmitted by
said panel to said insulating refractory plate are transmitted by
said insulating refractory plate to said hard refractory
plate..].
3. Device according to claim 1 wherein said means for displacing
said carriage relative to said rolls comprises a thrust jack.
4. Device according to claim 1 further comprising a rigid chassis,
a prepositioning carriage carried by said chassis and which carries
said support carriage, and a screw-nut assembly in operable
communication with said chassis and said prepositioning carriage
for enabling said side dam to be controllably moved toward or away
from said rolls.
5. Device according to claim 1, characterized in that said thrust
members are springs.
6. Device according to claim 5 wherein the stiffness of each said
spring and the distribution of said springs in said zone are
determined so that, for the same flexion of said springs, the
thrust force which they exert on the lower part of said side dam is
greater than the thrust force exerted on the upper part of said
side dam.
7. Device according to claim 1, characterized in that said thrust
members are controlled jacks.
8. Device according to claim 7, characterized in that said jacks
are pressure-regulated.
9. Device according to claim 1 wherein said panel is designed so
that the thrust force which it transmits is applied only on said
side dam..[.
10. Device according to claim 9 wherein said side dam consists of a
plate of hard refractory material surrounded by a metal belt to
which it is connected, and said metal belt is fixed on a cooled
belt surrounding a plate of thermally insulating refractory
material, with said cooled belt and said insulating refractory
plate constructed and arranged to allow relative movement
therebetween in a direction generally parallel to an axis of one of
said rolls, said cooled belt being supported by said panel, and
said insulating refractory plate being constructed and arranged so
that the thrust force transmitted by said panel to said insulating
refractory plate is retransmitted by said insulating refractory
plate only to said plate of hard refractory material..].
11. Device according to claim .[.10.]. .Iadd.1 .Iaddend.wherein
said .[.cooled.]. .Iadd.first .Iaddend.belt .Iadd.is cooled and
.Iaddend.surrounds .Iadd.the entire periphery of .Iaddend.said
.[.insulating refractory.]. .Iadd.first .Iaddend.plate .Iadd.of
insulating refractory material .Iaddend.and is not rigidly attached
to said .[.insulating refractory.]. .Iadd.first .Iaddend.plate to
allow relative movement between said .Iadd.cooled .Iaddend.belt and
said .[.insulating refractory.]. .Iadd.first .Iaddend.plate in a
direction generally parallel to an axis of one of said
rolls..Iadd.
12. Device according to claim 1 wherein said counter-rotatory rolls
have a casting space therebetween that is generally triangular and
said at least three thrust members are distributed over a zone of
triangular shape corresponding to said substantially triangular
shape of said casting space..Iaddend..Iadd.
13. Device according to claim 12 wherein each of said side dams are
substantially triangular..Iaddend..Iadd.
14. Device according to claim 13 wherein each of said side dams
have a first side edge is curved and has a portion that overlaps
part of one of said counter-rotatory rolls and a second side edge
that is curved and has a portion that overlaps part of the other
one of said counter-rotatory rolls..Iaddend..Iadd.
15. Device according to claim 12 wherein said at least three thrust
members comprises five spaced apart rows of pistons with each said
piston urged toward said side dam by a spring..Iaddend..Iadd.
16. Device according to claim 15 wherein three rows of thrust
members is comprised of eleven spaced apart pistons each urging
said side dam toward one of said counter-rotatory
rolls..Iaddend..Iadd.
17. Device according to claim 11 wherein said thrust forces from
said at least three thrust members are transmitted by said panel
through said first plate of a thermally insulating refractory
material only to said second plate of a refractory
material..Iaddend..Iadd.
18. Device according to claim 17 wherein said belts are made of
steel and said first belt is cooled by water..Iaddend..Iadd.
19. Device according to claim 17 wherein said first plate of
insulating refractory material has a thickness and said first belt
has a width that is less than said thickness of said first plate of
insulating refractory material..Iaddend..Iadd.
20. A device for continuously casting a thin metal product between
two rolls comprising two cooled counter-rotating rolls defining a
generally triangular shaped cross-sectional casting space
therebetween, a pair of side dams disposed adjacent a pair of ends
of said counter-rotating rolls and said side dams each being of one
piece construction, a pair of means for supporting and applying by
pressure each of said side dams against an end of each of said
rolls, wherein (a) each of said side dams comprises a first plate
of refractory material that contacts said pair of ends of said
counter-rotating rolls during casting and which is surrounded by a
first metallic belt that is operatively connected to said first
plate, and (b) each said supporting and pressure applying means
comprises at least three thrust members that urge one of said side
dams toward one of said pairs of ends of counter-rotating rolls,
said at least three thrust members distributed over a zone of shape
generally corresponding to that of said generally triangularly
shaped cross-sectional casting space defined between said
counter-rotating rolls with said thrust members applying a thrust
force against a lower part of said side dam that is greater than a
thrust force applied against an upper part of said side dam, said
at least three thrust members exerting thrust forces on said side
dam independently of one another, and each of said side dams
further comprises (a) a second plate of a thermally insulating
refractory material disposed interjacent said at least three thrust
members and said first plate of refractory material, and (b) a
second metallic belt that is operatively connected to said second
plate, said second metallic belt permitting relative movement
between said second plate and said second metallic belt in a
direction toward or away from said one of said pairs of ends of
said counter-rotating rolls..Iaddend..Iadd.
21. A device according to claim 20 wherein each of said supporting
and pressure applying means further comprises a support assembly
that urges said side dam against said ends of said
rolls..Iaddend..Iadd.
22. A device according to claim 20 wherein each of said supporting
and pressure applying means comprises a panel that carries said
side dam..Iaddend..Iadd.
23. A device according to claim 22 wherein for each of said
supporting and pressure applying means, said side dam has a
hook-shaped shaft that rests in a cradle in said panel attaching
said side dam to said panel..Iaddend..Iadd.
24. A device according to claim 22 wherein said supporting and
pressure applying means further comprises a support carriage
operatively connected to said panel..Iaddend..Iadd.
25. A device according to claim 24 further comprising a thrust jack
operatively connected to said support carriage for displacing said
support carriage toward or away from said ends of said rolls
thereby also displacing said side dam toward or away from said ends
of said rolls..Iaddend..Iadd.
26. A device according to claim 22 wherein said second plate of
refractory material is disposed between said panel and said first
plate of refractory material..Iaddend..Iadd.
27. A device according to claim 26 wherein said second belt
surrounds said second plate of refractory material and contains a
coolant..Iaddend..Iadd.
28. A device for continuously casting a thin metal product between
two rolls comprising two cooled counter-rotating rolls, two side
dams, a first support assembly that urges one of said side dams
against one end of each of said rolls, a second support assembly
that urges the other one of said side dams against another end of
each of said rolls, wherein each of said side dams comprises a
plate of refractory material that is surrounded about its entire
periphery by a metallic belt connected to a cooled metal
belt..Iaddend..Iadd.
29. A device according to claim 28 wherein each of said support
assemblies further comprises a movable support carriage that is
constructed and arranged to urge one of said side dams against one
of said ends of each of said rolls..Iaddend..Iadd.
30. A device according to claim 29 further comprising a thrust jack
operatively connected to said support carriage for displacing said
support carriage toward or away from said ends of said rolls
thereby also displacing said side dam toward or away from said ends
of said rolls..Iaddend..Iadd.
31. A device according to claim 28 wherein said metallic belt is
operatively connected both to said plate and to a corresponding one
of said support assemblies..Iaddend..Iadd.
32. A device according to claim 28, wherein the metallic belt
surrounds only the periphery of the plate of refractory
material..Iaddend..Iadd.
33. A device according to claim 28, wherein the metallic belt
surrounds substantially only the periphery of the plate of
refractory material..Iaddend..Iadd.
34. A device for the continuous casting of metal between a pair of
counter rotating rolls that define a generally triangular
cross-sectional casting space therebetween comprising:
a pair of side dams spaced apart by the counter rotating rolls;
means for urging each of said side dams and means for supporting
against ends of the counter rotating rolls, said means
including:
(a) a thrust plate that can be moved in an axial direction relative
to the counter rotating rolls and which is arranged generally
perpendicular to said axial direction;
(b) a panel that supports one of said side dams and which is
carried by said thrust plate and is arranged facing the latter;
(c) at least three thrust members interposed between said thrust
plate and said panel, said thrust members being distributed over a
zone of shape corresponding to that of the generally triangular
casting space cross section between the counter rotating rolls, and
being capable of exerting on said side dam thrust forces
independently of one another;
(d) a support carriage for carrying said thrust plate and which can
be moved in said axial direction; and
(e) wherein said side dam comprises (1) a plate of a thermally
insulating refractory material surrounded by a first belt with said
first belt carried by said plate for permitting displacement of
said plate in a direction generally parallel to an axis of one of
said rolls; and (2) a second plate of a refractory material
surrounded by a second belt that is attached to said first belt and
fixed to said second refractory plate for axial movement in unison
with said second refractory plate and wherein thrust forces
transmitted by said panel to said insulating refractory plate are
transmitted by said insulating refractory plate to said second
refractory plate..Iaddend..Iadd.
35. A device for continuously casting a thin metal product between
two rolls comprising two cooled counter-rotating rolls, a pair of
side dams, a pair of means for supporting and applying by pressure
each of said side dams against an end of each of said rolls,
wherein each of said side dams comprises a plate of refractory
materials surrounded by a metallic belt that is operatively
connected to said plate, and wherein each of said supporting and
pressure applying means comprises a panel that carries said side
dam, a second plate of refractory materials that is disposed
between said panel and said side dam, and a cooled belt surrounding
said second plate of refractory material..Iaddend..Iadd.
36. The device according to claim 35 wherein said second plate of
refractory material is movable relative to said cooled belt in a
direction toward or away from said end of one of said
rolls..Iaddend..Iadd.
37. A device for continuously casting a thin metal product between
two counter-rotating rolls, comprising:
a plate of a thermally insulating refractory material that has a
periphery that is surrounded by a first belt that permits movement
of said thermally insulating refractory plate relative to said
first belt in a direction generally parallel to an axis of rotation
of one of said rolls;
a support assembly that urges a side dam against one end of one of
both of said rolls with said side dam disposed between said plate
of a thermally insulating refractory material and said one end of
both of said rolls; and
a second belt surrounding the periphery of said side dam, said
second belt being operably connected to said first belt and said
side dam such that said second belt axially moves substantially in
unison with said side dam..Iaddend..Iadd.
38. A device for continuously casting a thin metal product between
two counter-rotating rolls, comprising:
(a) a side dam that comprises 1) a first plate of a refractory
material that bears against ends of said counter-rotating rolls
during casting and having a first belt disposed around said first
plate, and 2) a second plate of a refractory material disposed
adjacent said first plate and having a second belt disposed around
said second plate of a refractory material,
(b) at least three thrust members in operable cooperation with said
side dam that urge said side dam toward said ends of said
counter-rotating rolls, and
(c) wherein said second belt is carried by said second plate and
permits relative movement between said belt and said second plate
in a direction generally parallel to an axis of rotation of one of
said counter-rotating rolls..Iaddend..Iadd.
39. A device according to claim 38 wherein said second plate is an
insulating plate that has a thickness greater than a width of said
second belt and said second belt is hollow and contains a coolant
during casting..Iaddend..Iadd.
40. A device according to claim 39 wherein said first belt is
attached to 1) said first plate and 2) said second
belt..Iaddend..Iadd.
41. A device according to claim 38 further comprising a panel that
carries 1) said first and second plate and 2) said first and second
belts, and wherein said second plate is disposed between said panel
and said first plate..Iaddend..Iadd.
42. A device according to claim 41 wherein said panel further
comprises a cradle and said second belt further comprises a finger
received in said cradle such that 1) said second belt is suspended
from said panel, and 2) said second belt is movable in a direction
generally parallel to an axis of rotation of one of said
counter-rotating rolls..Iaddend..Iadd.
43. A device according to claim 41 further comprising a coolant in
said second belt..Iaddend..Iadd.
44. A device according to claim 43 wherein said panel is internally
cooled..Iaddend..Iadd.
45. A device according to claim 41 wherein 1) said counter-rotating
rolls define a generally triangularly-shaped cross-sectional
casting space therebetween, 2) said at least three thrust members
are distributed over a zone of shape that corresponds to said
generally triangularly-shaped cross-sectional casting space, and 3)
said at least three thrust members urge said panel, said first
plate and said second plate toward said ends of said
counter-rotating rolls during casting..Iaddend..Iadd.
46. A device according to claim 45 comprising a plurality of thrust
members that urge a lower part of said first refractory plate
against said ends of said counter-rotating rolls by applying a
first force, a plurality of thrust members that urge an upper part
of said first refractory plate against said ends of said
counter-rotating rolls by applying a second thrust force, and
wherein said first force is greater than said second
force..Iaddend..Iadd.
47. A device according to claim 38 wherein 1) said counter-rotating
rolls define a generally triangularly-shaped cross-sectional
casting space therebetween, 2) said at least three thrust members
are distributed over a zone of shape that corresponds to said
generally triangularly-shaped cross-sectional casting space, and 3)
said at least three thrust members urge said first plate against
said ends of said counter-rotating rolls during
casting..Iaddend..Iadd.
48. A device according to claim 38 comprising a plurality of thrust
members that urge a lower part of said first refractory plate
against said ends of said counter-rotating rolls by applying a
first force, a plurality of thrust members that urge an upper part
of said first refractory plate against said ends of said
counter-rotating rolls by applying a second thrust force, and
wherein said first force is greater than said second
force..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to continuous casting of thin metal
products, in particular thin steel strips, according to the
continuous casting technique between two cooled counter-rotatory
rolls. It more particularly relates to side dams applied against
the front ends of the rolls in order to delimit the casting space
defined between the rolls, as well as the means for supporting them
and applying them against the side front ends.
BACKGROUND OF THE INVENTION
It is known that installations for continuous casting between rolls
include two rolls with horizontal and parallel axes, vigorously
cooled internally by circulation of water driven in rotation in
opposite directions and spaced apart by a distance corresponding to
the desired thickness of the cast product.
During casting, molten metal poured into the casting space defined
between the rolls solidifies in contact with these rolls and is
extracted downwards, as the rolls rotate, in the form of a thin
strip. In order to contain molten metal, the side dams are pressed
flat against the front ends of the rolls. Such side dams are
commonly made of refractory material, at least in the part of the
dam which is brought into contact with the molten metal.
It is therefore necessary to ensure leaktightness between the rolls
and the side dams. For this purpose, these side dams are pressed
against the ends of the rolls and, in order to reduce the friction
induced during rotation of the rolls, lubrication of the interface
between the rolls and side dams is usually provided. Lubrication is
carried out by supplying a consumable lubricant or by using a
self-lubricating material at this interface.
However, actually producing this leaktightness and retaining it
throughout the casting still raises numerous difficulties, due in
particular:
to the geometrical deformations of the rolls and of the side dams,
in particular at the start of casting, which are caused by
expansions of the various elements of the installation,
to the forces exerted on these elements in particular the forces
exerted on the side dams by the cast metal in the axial direction
of the rolls, which forces tend to separate the side dams from the
rolls,
to wear of the side dams or of the edges of the cooled walls of the
rolls, which is not always uniform over the entire area of the
contact zones,
to the possible beginning of infiltration of cast metal between
side dam and roll, and solidification of these infiltrations which
tends to separate one from the other.
It has already been proposed to solve these problems by causing
controlled wear of the side dam, by friction of the rolls against
the latter, throughout the casting. The aim is thus to regenerate
the interface between rolls and side dams continuously, so as to
make the contact conditions over the entire area of this interface
as uniform as possible. Thus, document EP-A-546,206 describes a
method according to which, before the start of casting, the side
dams are pressed strongly against the rolls, in order to carry out
a sort of grinding-in of these side dams by abrasion by the edges
of the rolls. Then this pressure is reduced and, during casting,
the side dams are continued to be moved towards the rolls at a
predetermined speed in order continuously to ensure the progress of
intentional wear and thus to attempt to retain uniform contact over
the entire area of the interfaces.
However, this method leads to a significant wear of the refractory
material of the side dams, even when the contact conditions are
satisfactory.
If, instead of regenerating the interface as indicated above, the
side dam is merely applied with a predetermined force, stronger
wear may occur in certain zones of the interface, or in other zones
of localized infiltration between the edge of the rolls and the
side dam, which lead to local creation of play between the roll and
the side dam. For example, an infiltration of molten metal between
a roll and a side dam will tend, by solidifying, to separate the
side dam from the edge of the roll, and therefore also from the
edge of the second roll, since the entire side dam will then be
displaced backwards, with the risk of deteriorating the
leaktightness at the second roll. The same problem may occur if the
front end of the rolls are not perfectly orthogonal to the axes of
the rolls and/or are not exactly in the same plane; in this case,
the side dam is correctly applied against one roll but not against
the other.
SUMMARY OF THE INVENTION
The object of the present invention is to solve these problems, and
aims in particular to maintain the best possible leaktightness,
throughout casting, between a side dam and the two rolls against
which it is applied.
With these objects in mind, the subject of the invention is a
device for continuous casting of thin metal products between rolls,
including two cooled counter-rotatory rolls, two side dams and
means for supporting and applying by pressure the side dams against
the edges of the rolls, characterized in that the support means
include:
a thrust plate which can be moved in the axial direction of the
rolls and which is arranged perpendicular to this direction,
a panel, which supports the side dam and which is carried by the
thrust plate and arranged facing the latter,
at least three thrust members interposed between the thrust plate
and the said panel, these members being distributed over a zone of
shape corresponding to that of the side dam, and being capable of
exerting thereon thrust forces independently of one another.
The panel is only supported by the thrust plate, that is to say
that it is mechanically connected to it only in the vertical
direction and optionally horizontally, perpendicularly to the axes
of the rolls. On the other hand, the panel may be displaced with
respect to the thrust plate, on the one hand in the direction of
the axes of the rolls and, on the other hand, by pivoting with
respect to it about any axis located in the overall plane of the
panel, substantially orthogonal to the axial direction.
These various allowed displacements are, of course, limited in
amplitude, but are sufficient to allow the side dam to be applied
in the best possible manner against the front ends of the rolls,
even if the respective front ends of the rolls are not perfectly
coplanar. In addition, when the side dam is caused during casting
to be separated from the edge of a roll, for example following
passage of a parasitic solidification of the cast metal between
this roll and the side dam, the latter can pivot slightly on itself
and therefore retain the best possible contact with the second
roll. Without this freedom of movement, such a parasitic
solidification would lead to pushing back the side dam in its
entirety and to creating play between the latter and the second
roll.
Furthermore, during such pivoting, the thrust members located on
the side where the side dam moves away from the roll are more
greatly stressed and, by reaction, it is possible to act
preferentially or solely on them without substantially altering the
thrust on the side of the second roll.
The thrust members may be controlled jacks or springs.
In the case in which the thrust members are jacks, they can then be
controlled individually either in pressure or in displacement,
which makes it possible to apply a stronger thrust just at the
location where such an increase in thrust is required, for example
in the case indicated above, on the side where parasitic
solidification has taken place.
In the case in which the thrust members are springs, this increase
in thrust is actually generated automatically by the compression of
the springs, on the side where the side dam is moved away from the
rolls, and therefore by increasing the force exerted by the pressed
springs, insofar as the position of the thrust plate is fixed.
Preferably, the stiffness of each spring and the distribution of
the springs in the zone are determined so that, for the same
flexion of these springs, the thrust force which they exert in the
lower part of the side dam is greater than the thrust force exerted
in the upper part of the side dam. This arrangement makes it
possible to take into account the fact that the pressure exerted on
the side dam by the cast metal is stronger at the bottom of this
side dam than towards the top, on the one hand because of the
hydrostatic pressure of the liquid metal and, on the other hand
because of the rolling force exerted by the rolls on the metal
during solidification in proximity to the neck between the rolls,
which tends to widen the cast strip and therefore to push the side
dam downwards. In order to obtain this particular distribution of
the thrust force, it is possible to vary either the stiffness of
the springs or the positioning and distribution of the springs in
the plane of the thrust plate, which is easier to do since the
number of springs is sufficiently high, or vary both of these
parameters at the same time.
In the case of using jacks, the choice of their location will also
take into account the desired distribution of the forces applying
the side dam onto the rolls. This choice is, however, less
constraining, since this distribution of the forces can be produced
by a suitable pressure-control of the jacks.
In addition to the advantage, already indicated, of being capable
of distributing the thrust exerted on the side dam in a
predetermined configuration and of not causing backward
displacement of the entire dam in the event of parasitic
solidification, the invention also makes it possible to vary the
overall bearing force throughout casting, by displacing the said
thrust plate with respect to the rolls, while retaining
adaptability of the position of the side dam with respect to the
edges of the rolls. To this end, the thrust plate is carried by a
carriage which can be moved in the said axial direction, and the
device includes means for displacing the carriage with respect to
the rolls and for exerting thereon a force directed towards the
rolls. For example, by displacing the thrust plate towards the
rolls, the springs all undergo complementary compression, which is
added to that which they had before this displacement, but which
retains a similar distribution of the thrust over the surface of
the side dam, while more greatly accentuating the force in the
zones where the springs were already supplying a larger force.
Thus, for example, the position of the thrust plate can be
initially adjusted, when starting up, in order to compress the
springs fairly strongly, and thus to ensure a sort of grinding-in
of the side dam against the edges of the rolls; the overall bearing
force may then be reduced, in stabilized casting regime, in order,
in particular, to avoid excessively fast wear of the side dam, and
increased again in the event of an incident, for example
infiltration of liquid metal, in order to reestablish leaktightness
as quickly as possible.
Other characteristics and advantages will emerge from the following
description of a device for continuous casting of thin steel strips
between rolls.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to the attached drawings, in which:
FIG. 1 is a sectional view of the support assembly of the side dam,
in the case in which the thrust members are springs,
FIG. 2 is a sectional view along line II--II in FIG. 1, showing the
distribution of the springs in the plane of the thrust wall,
FIG. 3 is an enlarged partial view of FIG. 1.
In the figures, the same elements are designated by identical
references.
DETAILED DESCRIPTION OF THE INVENTION
In the drawing of FIG. 1, only one of the rolls 1 of the casting
installation has been represented, against the edge 2 of which roll
the side dam 3 carried by a support assembly 4 is applied by thrust
force.
This support assembly comprises a rigid chassis 5 which carries a
first carriage or prepositioning carriage 6, the position of which
can be adjusted on the chassis 5 in the axial direction A of the
rolls, for example by a screw-nut system 7.
The prepositioning carriage 6 carries a second carriage 8, guided
in translation in the axial direction A. The position of the second
carriage 8 is adjusted by a positioning and thrust jack 9.
The second carriage 8 supports a thrust plate 10 by means of two
support shafts 11. Preferably, as is shown in FIG. 1, the thrust
plate 10 hangs from the support shafts 11. Furthermore, the thrust
plate 10 is held against stops 12, connected to the carriage 8 and
is positionally adjustable, in a manner which is known per se, in
order to ensure verticality of the thrust plate 10.
The thrust plate 10 includes a plurality of bores 13, distributed
over a zone of triangular shape corresponding to the shape of the
side dam. A compression spring 14, bearing via one end on the
bottom of the bore and, via the other end, on a piston 15 sliding
in the bore and including tension means 16 for keeping the spring
and piston in the bore, is placed in each bore 13.
The thrust plate 10 also includes, at its upper part, bearing
blocks 17, 17', on which lugs 18, 18' of an internally cooled panel
19 rest, the rear face of which panel is in contact with the
pistons 15.
One of the bearing blocks 17 includes a rib 17B which engages with
small play in a corresponding groove in the lug 18, in order to
ensure lateral positioning of the panel along Ox (horizontal
direction) while leaving it free to rotate about Oz (vertical
direction). The other lug 18' rests simply on the bearing block
17'. In total, the planes 17A and 17'A formed by the bearing
surfaces on the bearing blocks 17 and 17' fix the altitude along Oz
of the side dam, the rib 17B fixes the position along Ox, and the
direction along Oy is free. Means 20 for lateral abutment of the
lower end of the panel 19 with respect to the thrust plate 10 are
also provided in order to avoid tilting on the bearing blocks 17,
17'.
A plate 21 of insulating refractory material is held against the
front face of the panel 19 by a cooled metal belt 22 which
surrounds it and which is suspended from the panel by a hook-shaped
shaft 23 which rests in a cradle 24 of the said panel, with some
freedom of movement in the axial direction Oy. The hook-shaped
shaft 23 extends outwardly from an offset leg 29 of the cooled
metal belt 22. To enable the insulating refractory plate 21 to be
displaced at least somewhat in an axial direction, it is not
restrained along its bottom edge and can bear against a lateral
abutment means 20', when urged against the rolls. So that the plate
21 can further be axially displaced, the plate 21 is not rigidly
secured to the cooled metal belt 22 and can therefore slide axially
relative to the belt 22. The insulating refractory plate 21 can
also be displaced in the axial direction relative to the cooled
belt 22, and has a thickness slightly greater than that of the said
belt 22. During operation, a coolant, such as water, can flow
through a channel 28 in the belt 22 to help regulate temperature of
the side dam 3.
A second metal belt 25 is screwed onto the cooled belt, which
second belt surrounds the side dam 3 which is connected to it by a
refractory cement, and the thickness of which is also greater than
that of the said second belt 25, so as to extend beyond it on the
roll side, in order to prevent contact between them and the belt
25, even after a maximum allowable wear.
The shapes and dimensions of the two refractory plates 3 and 21 and
of the belts 22 and 25 are such that, even when the second belt 25
is clamped onto the cooled belt 22, the insulating refractory plate
21 is in contact only with the side dam 3 and not with the said
second belt 25.
Since, furthermore, the thickness of the insulating refractory
plate 21 is greater than that of the cooled belt, the thrust force
transmitted by the panel 19 is retransmitted only to the side dam 3
and not to the belt 25, which avoids creating stresses between this
belt and the refractory material of the side dam, and therefore
risks of deformation of the latter or detachment of it from the
belt 25.
When fixing the second belt 25 onto the cooled belt 22, a
displacement of the latter towards the rolls may occur; this is why
the connection to the insulating refractory plate 21 is not rigid,
and the hook 23 also has some freedom of displacement in the axial
direction in the cradle 24. Taking into account that the plate 21
has a thickness greater than that of the belt 22, it is possible,
at the time of assembling the device, that the belt 22, as well as
the plate 21, will contact the panel 19 causing the plate 21 to
extend outwardly of the belt 22 toward the rolls. In this case,
when screwing the second belt 25 to the first belt 22, the first
belt 22 can, in some instances, move relative to the insulating
plate 21 until it contacts the second belt 25.
Preferably, the panel 19 is made of steel, as is the cooled belt
22, and the second belt 25 is made of a material which has good
thermal characteristics, such as steel or cast steel, its natural
cooling being assisted by contact with the cooled belt 22 via
internal circulation of water.
Before the start of casting, it is necessary to preheat the side
dam 3. For this purpose, the support assembly 4 is moved away from
the rolls, the chassis 5 being for this purpose provided with
means, known per se and not represented, making it possible to
displace it with respect to the structure of the casting
installation.
A radiation-preheating furnace is then brought in front of the side
dam in order to heat it to an elevated temperature, the insulating
refractory 21, the cooled plate 19 and the cooled belt 22 limiting
heating of the rest of the device.
Just before start-up, the furnace is removed and the chassis 5 is
returned into position and clamped onto the structure. The jack 9
is then actuated in order to bring the side dam into contact with
the edges of the rolls and, by continuing its movement, to displace
the thrust plate 10, which has the effect of compressing the
springs 14. The position of the jack 9 is adjusted. The force which
it supplied is transmitted to the thrust plate by the carriage 8
and its stops 12, and this force is then distributed over the panel
19 by the springs; the forces locally supplied by each of the said
springs 14 are therefore essentially a function of their
compression and therefore of the relative position of the panel and
of the thrust plate.
Thus, for a particular position of the jack 9, the side dam 3 is
applied against the rolls 1 in a position which ensures the best
possible contact. Even if, for example, the edges of the two rolls
are in fact slightly distorted or axially offset with respect to
one another, the side dam is applied against the two rolls with a
minimum of play. However, the thrust forces on the side of the roll
whose edge extends beyond the other are higher, which will lead to
more rapid wear on this side of the side dam 3 and therefore tend
to return its overall plane parallel to that of the thrust plate
10, lead to more homogeneous distribution of the forces supplied by
the springs 14 and obtain optimum contact for leaktightness between
the side dam 3 and the rolls 1.
During casting, if parasitic solidification appears between a roll
and the side dam, the latter is displaced backwards on the side of
that roll, but maintains the best possible contact with the second
roll. The backward displacement compresses the springs on the side
where it takes place and consequently spontaneously increases the
thrust force on this side; an increase in friction then results,
which leads relatively quickly to the elimination of the
solidification.
In the case in which accentuated wear occurs on one side of the
side dam, the springs 14 will act so that the side dam nevertheless
remains in contact with the roll located on this side. This
displacement can be detected either by a displacement sensor or by
a reduction in the thrust force, resulting from the fact that the
springs located on the worn side are thus less compressed. The jack
9 can then be actuated in order to advance the thrust plate towards
the rolls, until reestablishment of the desired force applying the
side dam against the edge of the roll on the side where the wear
has occurred. By doing this, the forces on the other side are
increased and will therefore lead to accelerated wear on this other
side, which will have the result of returning the side dam parallel
to the thrust plate and therefore recovering optimum
leaktightness.
Thus, the springs 14 make it possible not only to take up the
contact defects between side dam and roll but tend to provide
automatic and spontaneous correction of these defects. In contrast
to the prior technique indicated above, in which the refractory
wall is eroded continuously in order to ensure the best possible
contact with the rolls, by pushing it against them with a large
force, the invention makes it possible, on the one hand, to reduce
this thrust force, and on the other hand, to cause wear on the side
dam only when contact is disturbed.
In addition, even in the absence of such disturbances, the device
according to the invention makes it possible to adjust the bearing
force of the side dam against the edge of the rolls, in particular
as a function of each step of the casting, by simple control of the
jack 9. It is possible, for example, to exert a strong force when
starting casting, in order to carry out a sort of grinding-in of
the side dam against the edge of the rolls, then to reduce this
force in stabilized casting regime and increase it at will in the
event of incident, for example infiltration of liquid metal.
In an alternative embodiment, already indicated, of the device, the
springs may be replaced by controlled jacks which will fulfil the
same functions as the springs, on the basis of measurement of their
internal pressure, and of the position of the side dam. Each of the
jacks can be adjusted individually according to predefined laws, in
order to ensure, for example, either a force proportional to the
displacement, the jacks then acting as springs, or a constant
force, or else according to laws of the type F=K.multidot.x.sup.n
or F=K.multidot.e.sup.x, where F is the force, K and n are
predefined constants and x is the displacement of the rod of the
jack, measured, for example, indirectly by displacement sensors of
the side dam or of the panel.
In addition, synchronization adjustment of the wear of the side
dam, acting on all the jacks, may be combined with the individual
adjustment, for example by defining one of the jacks as the driver
enslaving the others to the driver jack.
The jack chosen as the driver jack will then preferably be the one
located towards the bottom of the side dam, that is to say in
proximity to the neck between the rolls, where wear on the side dam
is generally more accentuated.
* * * * *