Note: Descriptions are shown in the official language in which they were submitted.
213.~6~
Method of forming a gap, particularly
in the metallurgical field
Description
The invention relates to a method of forming a gap
between two materials deposited on or adhering to one
another, which wet one another on contact, particularly
in the metallurgical field.
In metallurgical technology there is frequently the
problem that metal melt freezes locally on components of
refractory, ceramic material or forms alumina-rich
deposits on the component, whereby the function of such
component~ is impaired. Such componente are, for
instance, gas flushing bricks, ~liding gate valve
components, ~leeves or immer~ion nozzles.
Such problems occur when casting thin strips close to
their final dimensions, for instance in the belt-roll or
twin-roll method. The steel melt can freeze on the
necessary enclosure bodies or form alumina-rich AL~03
deposits. This considerably impairs the quality of the
strip ~teel.
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Such methods are described in the periodical Stahl undEisen (Steel and Iron) 111 (1991) No. 6, p.37 to 43.
However, solutions to the said problem are not given.
In DE 41 41 50~ Al it is propo~ed to construct enclosure
bodies disposed laterally of the steel melt as metal
plates which are permeable to a magnetic field from an
inductor. The magnetic field induces currents in the
metal melt which result in additional warming of the
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metal melt. This is supposed to prevent the metal melt
freezing on the enclosure plates. The currents induced
in the melt can, however, lead to destruction of the
structure in the edge region of the thin strip which is
associated with a reduction in quality.
In the prior patent application P 41 43 049 a device is
described in which porous, ceramic inserts are arranged
on the enclosure bodies disposed laterally of the melt.
These are acted on by a liquid, which forms a film, which
is supposed to prevent freezing of the melt onto the
enclosure bodies. For the same purpose, it is proposed
in the prior patent application P ~2 3a 036.7 that
enclosure plates be provided of an inductively heatable,
refractory, ceramic material which couples into the
electromagnetic field of the inductor.
It is the object of the invention to propose a method in
which the adhering together of materials, particularly a
metal melt and a solid body, is avoided in order to
render relative movement of the materials possible.
The said object is ~olved by the features of Claim 1.
The vibrations imposed on the material or materials
~J 25 prevent the materials clogging on one another. The
vibrations are preferably ultrasonic vibration
Embodiments of the invention will be apparent from the
dependent claims and the description of exemplary
embodiments, exemplary embodiments being shown from the
metallurgical field. The invention is however not
limited hereto but may be used in other fields.
In the drawings:
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21~iO625
igure 1 is a schematic view of an immersion nozzle on
a metallurgical vessel,
igure 2 shows an apparatus for the twin-roll method,
Figure 3 shows an apparatus for the belt-roll method,
and
Figure 4 is a schematlc view of a further apparatus for
casting close to the final dimeni~iion~.
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, An immersion nozzle 1 of refractory, ceramic material i8
attached to the base of a metallurgical ves~el 2. A
passage 3 in the immersion nozzle 1 serves to conduct
citeel melt. Attached to the immersion nozzle 1 is an
ultrasonic generator 4. This imparts mechanical
vibrations with a frequency greater than 20 kHz to the
immersion nozzle 1 as a solid body. The vibrations
propagate within the immersion nozzle 1 to the wall 5 of
the passage 3. A gap thus forms between the melt flowing
through the passage 3 and the wall 5 because the high
frequency vibrations prevent the melt from remaining in
permanent contact with the wall 5. This gap prevents
solid materials, particularly Al203particles, solidifying
on the wall 5. Growing caked-on portion~, which could
result in the free cross-sectional area of the passage 3
decreasing, are thus prevented. ~s a result of the gap
the discharge characteristics of the melt are also
improved overall since the gap reduces the friction
between the wall 5 and the melt. The breadth of the gap
is of the order of fractions of a mm, for instance of the
order of a few ~m.
An ultrasonic generator 4 ii shown externally on the
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immersion nozzle 1 in Figure 1 (left). If necessary, a
plurality of such generators 4 can be arranged
distributed over the external periphery of the immersion
nozzle 1. The generator 4 can alsG annularly surround
the external periphery of the immersion nozzle 1. The
ultrasonic generator 4 or extensions connected to it can
also be built into the wall of the immersion nozzle (see
Fig. 1, right-hand side). It then induces the melt as a
liquid rnaterial to vibrate. The generator 4 is
preferably arranged at the height in the immersion nozzle
1 at which experience shows there is the tendency for
', Al2O3 deposits to form. The ultrasonic vibrations prevent
crystallisation nuclei for growing deposits being able to
become established on the wall 5.
Figure 2 shows the counter-rotated rol'ers 6, 7 of an
apparatus for carrying out the twin-roll method with
which casting of a thin steel strip close to the final
dimensions may be performed. The steel melt is applied
to the rollers 6, 7 and transferred downwardly in the
space between the rollers 6, 7. In order to prevent
lateral eacape of the steel melt, enclosure plates 8, 9
are disposed as solid bodies adjacent the rollers 6, 7.
~ Ultrasonic generators 4 are secured to the enclosure
- ~ 25 plates 8, 9 which comprise steel or refractory ceramic
material. These induce the enclosure platea 8, 9 to
vibrate. This vibration prevents the melt from freezing
on them or deposits forming, as is described above.
In the apparatus illustrated in Figure 3 for the belt-
roll method, two drive rollers 10, 11 are provided for a
transport belt 12. The melt is supplied onto the
transport belt 12 in a region 13 as a thin strip. The
steel melt cools on the tran~port belt 12 until it
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solidifies and is withdrawn from it.
In order to prevent lateral flowing away of the steel
! melt, enclosure strips 14, 15 are provided. Arranged on
¦ 5 the enclosure strips 14, 15 are ultra~onic generators 4
which impose vibrations on the enclosure strips 14, 15.
These result in gaps in the described manner between the
enclosure strips 14, 15 as solid bodie~ and the steel
melt as a liquid material so that the ~teel melt cannot
freeze on the enclosure strips 14, 15 and the
crystallisation nuclei contained in the steel melt cannot
deposit on the enclosure strips 14, 15 and thus no
deposits can grow on them.
In the exemplary embodiment of Figure 4 an apparatus is
shown which is similar as regards the casting of a thin
strip close to the final dimensions shown in Figure 3.
In the apparatus of Figure 4 a transport belt 12 driven
by the drive rollers 10, 11 is omitted. Instead of this
a receiving plate 16 of steel or refractory, ceramic
material is provided which is arranged on solid supports
17, 18. Arranged at the sides of the receiving plate 16
are the enclosure strips 14, 15. These can be integrally
constructed with the receiving plate 16 or secured to the
~J 25 receiving plate 16 as separate components.
Arranged on the underside of the receiving plate 16 is at
least one ultrasonic generator 4. Additionally,
ultrasonic generators 4 can be provided on the enclosure
strips 1~ . These can be omitted when the ultrasonic
generator 4 arranged on the receiving plate 16 also
imparts the desired ultrasonic vibrations to the
enclosure strips 1~
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The steel melt is supplied to the receiving plate 16 in
the region 13, for instance from a broad slit nozzle.
The receiving plate 16 is inclined to the horizontal H at
an angle of inclination W which is so dimensioned that
the melt flows away obliquely downwardly on the receiving
plate 16 towards the region 13. As a result of the
ultrasonic vibrations of the receiving plate 16 and the
enclosure strips 14, 15, a gap is produced between the
solid bodies and the steel melt which prevents freezing
or caking of the steel melt or particles from it on the
receiving plate 16 and the enclosure strips 14, 15, that
; is to say renders the desired movement possible of the
melt with respect to the receiving plate 16 and the
enclosure strips 14, 15.
; In the exemplary embodiment of Figure 4 the withdrawal of
the melt is achieved by the oblique position of the
receiving plate 16 at the angle W.
The withdrawal of the melt may be improved in a receiving
~ plate 16 arranged at an angle W to the horizontal H or
¦ achieved with the receiving plate 16 arranged in the
horizontal H if the ultrasonic vibrations imposed on the
receiving plate 16 are so aligned that they impart a
~J 25 guide component in the direction F directed away from the
region 13 on the melt.
I
The described arrangement of an ultrasonic generator 4
may also be used on other components, for instance gas
flushing bricks or sliding gate valve~ of metallurgical
vessels in order to prevent freezing of melt or caking on
of alumina-rich impurities.
The effect i.s promoted by the selection of refractory
materials which the steel only slightly wets.
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