Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LIQUID-COOLED PLATE MOLD
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid-cooled plate mold for
the continuous casting of metals, in particular, of steel
materials, comprising highly heat-conductive mold plates of
copper or copper alloys which are connected by means of
fastening bolts with a fastening support in the form of a
water box or a support plate, respectively.
2. Description of the Related Art
The plate attachment of mold plates of identical
thickness by means of welded-on bolts is known. As a result
of the plate expansion caused by temperature increase during
the casting operation, additional bending loads and tension
loads result, especially in the case of short bolts, and
this can cause failure of the welding connection.
The patent document DE 197 16 450 A1 describes a
liquid-cooled mold for continuous casting of thin steel slab
with two oppositely positioned wide sidewalls, each
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comprised of a copper plate and a steel support plate. The
copper plates, which delimit a cavity of the mold, are
detachably connected by means of metal bolts of a CuNiFe
alloy to the support plates. The metal bolts are welded
onto the copper plates. When doing so, a nickel ring is
additionally used as a welding additive. In the copper
plates cooling medium channels are provided, and cooling
medium bores are provided in the area of the transverse
section planes of the metal bolts. The gist of the
aforementioned mold is the feature that metal bolts of a
CuNiFe alloy are being used. As a result of using such,
especially hard drawn, metal bolts, a significant strength
increase with only minimal strength fluctuations in regard
to the welding connections with a copper plate is said to be
achievable. Expediently, bolt welding methods that are known
in the art are used for the attachment of the metal bolts on
the copper plates.
The patent document WO 95/21 036 describes an assembly
group of a mold for continuous casting of steel with a
support plate. A copper or copper alloy plate with
excellent heat conducting properties is screwed onto the
support plate and a relatively thin cover layer of copper or
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copper alloy is soldered onto the copper plate. If desired,
the plate with excellent heat conducting properties can be
omitted and the cover layer can be soldered directly onto
the support plate. The cover layer contacts and cools the
cast strand passing through when moving through the mold.
When the cover layer shows cracks or wear, the solder
connection is melted in order to remove it and a new layer
is soldered onto the thermally conductive layer or the
support plate.
The patent document DE 198 O1 728 C1 discloses a
continuous casting mold for casting strands of, preferably,
steel. The mold is comprised of mold plates and water boxes
which are connected to one another and between which a water
cooling system is provided with the aid of water guiding
channels. The water guiding channels are arranged at the
side of the water box facing the mold plate and not within
the mold plate. A continuous casting mold of this
configuration is improved in that the wide side of the mold
with its elements copper plate and/or water box with water
guiding channels or with a water box without water guiding
channels, but with a connecting plate having water guiding
channels, is secured by means of clamping bolts. They have
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substantially conical clamping bolt heads which are secured
in conical recesses of the copper plate.
In this configuration, the bolt head of the clamping
head should have a special conical shape or be conical-
lamella-shaped, and, advantageously, should be comprised of
the same material as the copper plate of the continuous
casting mold. In order to optimize the heat conductivity
between the clamping bolt/clamping bolt head and the copper ,
plate, the surfaces between the copper plate and the
clamping bolt/clamping bolt head can be provided with a
highly conductive layer of metal, preferably silver. A
further improvement of the connection of the copper plate
and clamping bolt is achieved when the connection is
provided on the cold side of the copper plate with a seal
against water passage across the surface in the direction of
the hot side.
The patent application DE 198 35 119.9, not yet
published, concerns a mold wall of a continuous casting
device for casting a metal strand, in particular, a steel
strand, with a water box and an inner mold plate connected
by bolts to the water box. The bolts have a bolt neck,
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respectively, penetrating the water box and having a bolt
neck cross-section, and a bolt head, secured in the inner
mold plate and having a bolt head cross-section. For
simplifying securing of the bolt in the inner mold plate, it
is suggested that the bolt head cross-section of at least
one of the bolts is greater than the bolt neck cross-section
of this bolt, and that the inner mold plate has a groove
which tapers in a direction toward the water box for
receiving the bolt head of this bolt.
Finally, the German published document 15 08 902
discloses a liquid-cooled plate mold for continuous casting
of high-melting metals in which a mold wall is connected by
fastening screws to a support frame. Round rods are
provided which are inserted into bores of the mold wall
transverse to the casting direction and are provided with
threaded bores for receiving fastening screws. The assembly
expenditure for this configuration is considerable.
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SUMMARY OF THE INVENTION
It is an object of the present invention to control or
minimize for a liquid-cooled plate mold of the
aforementioned kind the difficulties and problems in the
area of the connection of the inner mold plates, comprised
of copper or copper alloys, with bearing, supporting, or
shape-providing support plates or water box plates of copper
or steel during the temperature changes occurring during the
continuous casting operation and to provide a safe type of
attachment for tension-loaded as well as thermally loaded
fastening elements on inner mold plates of copper, which
attachment can be realized with economically feasible
expenditure of cost and labor and is suitable to provide a
longer and failure-free service life.
In accordance with the present invention, this is
achieved in that in the on the water side of each mold plate
shaped parts provided with threads are arranged and
connected by soldering connections or by welding connections
with the mold plates in a non-positive way as a fastening
piece.
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Such soldering connections and/or welding connections
can be produced easily, on the one hand, and have fatigue
strength under reversed stresses of, for example, 100 N/mmz,
on the other hand.
Advantageously, for this connection, the shaped parts
or fastening pieces are preferably produced of a material
with excellent conducting properties such as CuAg, CuCrZr,
CuNiBe, or CuNiFe.
The fastening pieces can be connected by a soft solder
layer with high shearing strength with the mold plates.
However, it is also possible to use the measure of
connecting the fastening pieces by a hard solder layer with
the mold plates, wherein preferably a silver-containing or
copper-containing hard solder is used as a solder metal.
It is furthermore possible to connect the fastening
piece with the mold plate by high-temperature soldering.
The heating of the soldering location can be realized in
this context by electron beam or by electric current.
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It is particularly advantageous to connect the
fastening piece with the mold plate by electron beam
welding.
For this purpose, the fastening piece can also be
inserted into a shallow, round recess of relatively minimal
depth at the backside of the mold plate. The welding
connection is then carried out annularly along the
separating location between the mold plate and the fastening
piece. The electron beam can impinge perpendicularly or at
an angle onto the surface of the mold. The fastening pieces
can be provided with a step or shoulder which is of such a
size that it is flush with the upper rim of the recess, as
illustrated in Fig. 2.
The fastening pieces, as described above, can be
produced of a metal material of good conducting properties
or a suitable steel alloy.
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BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
Fig. 1 is a section of a portion of an inner mold plate
with a shaped part attached by soldering and fastening bolts
of a support plate screwed into the shaped part;
Fig. 2 shows in section a\detail of Fig. 1 with the
shaped part attached by electron beam welding.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
The part of a liquid-cooled plate mold illustrated in
Fig. 1 for continuous casting of high-melting metals, such
as steel, comprises a highly heat-conductive mold plate 1 of
copper or copper alloy which is connected by means of
fastening elements in the form of fastening bolts 2 on a
fastening support. The fastening support can be a water box,
e.g., the backside of the water box, or a support plate 4
provided with channels 3 for the cooling water. The
channels for the cooling water can also be located within
the mold plate.
According to the invention, on the water side of the
mold plate 1 shaped parts 6 with threaded bores 5 for
screwing in the fastening bolts 2 are arranged and connected
by a non-positive connection with the mold plate 1 by means
of soldering connections 7, 7' in order to provide fastening
pieces. The shaped parts or fastening pieces 6 are
preferably produced of a metal material having good
conducting properties such as CuAg, CuCrZr, CuNiBe, or
CuNiFe. The fastening pieces 6 are connected by a soft
solder layer 7 with the mold plates 1. The soft solder
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layer 7 with a high shearing strength is preferably produced
of a solder material of the alloys L CdZn or L CdZnAg or L
SnCdZn.
However, it is also possible to employ the measure of
connecting the fastening pieces 6 by a hard soldering layer
7' with the mold plates 1, wherein the solder metal is
preferably copper solder alloy or a silver solder alloy.
It is moreover possible to connect the fastening pieces
6 by high-temperature soldering by means of an electron beam
or by means of electrical current with the mold plates 1.
The hard solder connection provides at soldering
temperatures above approximately 450' C a comparatively high
strength in comparison to a soft solder connection; however,
in comparison to the soft solder connection, it is somewhat
more prone to solder fractures when subjected to changing
temperatures and requires a higher expenditure during
manufacture and cannot be removed (by melting) without
affecting the surrounding material, in particular, copper,
in the case of repairs.
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One embodiment of the invention suggests that the
soldering surface of the mold plates for the fastening
pieces 6 is metallized for an exact positioning of the
fastening pieces 6.
An inventive embodiment also suggests that the
fastening pieces 6 are shaped parts with preferably annular
cross-section which are inserted into congruent shallow
recesses 8 of relatively minimal depth (see Fig. 1), for
example, up to 5 mm, in the backside of the mold plate 1 and
are soldered therein, and that the support plate 4 has a
cooling medium bore 9 having a spacing on all sides relative
to the fastening piece 6 positioned in the bore 9 and being
in flow communication with at least one cooling medium
channel 3. The cooling medium bore 9 can also be provided
in the plate of the water box.
This configuration of the bolt attachment has the
advantage that the fastening piece 6 as well as the shaft of
the bolt 2 are exposed to the flow of cooling water and are
therefore sufficiently cooled. Thus, the endangerment of
the solder connections is reliably prevented.
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For the same purpose, according to another embodiment
of the invention, it is suggested to provide the support
plate 4 with receiving bores 2' for receiving the fastening
bolts 2, which receiving bores 2' have a diameter that is
greater than the shaft diameter of the fastening bolts 2.
This results in the formation of annular gaps 10, and,
according to the invention, each of these annular gaps 10 is
connected with a cooling medium bore 9 supplying cooling
water.
The aforementioned embodiment has furthermore the
advantage that temperature-caused expansion differences
between the mold plate 1 and the support plate 4 can be
compensated easily.
Moreover, if desired, it is possible to use the measure
of arranging the cooling medium channels 3 either in the
mold plate 1 or in the support plate 4 or in a plate of the
water box contacting the mold plate.
Finally, the cooling medium channels 3 in the mold
plate 1 can be configured either as grooves or as channel
bores extending preferably in the casting direction.
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Fig. 2 shows in section a detail of Fig. 1 with the
shaped part 6, which, as an alternative solution of the
aforementioned object, is fixedly connected by an electron
beam welding seam 12 with the mold plate 1. The welding
seam is positioned at the exterior side of the shaped part
(fastening piece) 6. Before welding is carried out, the
outer diameter of the shaped part, which in cross-section is
annular, has a diameter which is greater by 1 to 8 mm in the
area of the welding seam 12. For the electron beam welding
step, the mold plate 1 can have in the area of the
attachment a minimal material projection which corresponds
approximately to the height of the welding seam depth. The
shaped part (fastening piece) 6 is provided with an inner
thread 5 for attachment of the fastening bolt 2 (Fig. 1).
The shaped part can also be in the form of a bolt with outer
thread.
The channels 3 of the support plate 4 for supplying
cooling water are indicated only partially, and the bore 9
supplying the cooling water is also only partially
indicated.
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While specific embodiments of the invention have been
shown and described in detail to illustrate the inventive
principles, it will be understood that the invention may be
embodied otherwise without departing from such principles.
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