U.S. patent application number 14/379918 was filed with the patent office on 2015-10-15 for stirring-roll for a continuous cast machine of metallic products of large cross section.
This patent application is currently assigned to ROTELEC. The applicant listed for this patent is Siebo Kunstreich. Invention is credited to Siebo Kunstreich.
Application Number | 20150290703 14/379918 |
Document ID | / |
Family ID | 46044614 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150290703 |
Kind Code |
A1 |
Kunstreich; Siebo |
October 15, 2015 |
STIRRING-ROLL FOR A CONTINUOUS CAST MACHINE OF METALLIC PRODUCTS OF
LARGE CROSS SECTION
Abstract
Stirring roll comprising: (a) a shell ring 1 made of nonmagnetic
steel in rotation of axis A-A and intended to come into contact
with the surface of a large face of the cast slab (6), (b)
mechanical-connection members, arranged on each side of the shell
ring to support the shell ring while leaving it free to rotate
axially, (c) support elements 4 which are offset on either side
beyond the limits of the shell ring and fixed to the rigid frame 5
of the casting machine, (d) internal electromagnetic equipment
consisting of at least one polyphase linear inductor 8 mounted
coaxially with respect to the shell ring so as to leave between the
two an annular space 11 through which a cooling liquid can
circulate, and which constitutes an axial shaft provided with
terminal extensions 20 that rest, without the ability to rotate
axially, on the fixed support elements 4 and which are hollow so as
to allow the passage of the cooling liquid and of the electrical
connections of the inductor, and (e) inlet/outlet casings 16 for
the cooling liquid which are provided with electrical connection
terminals 18a, 18b and mounted at the ends of the terminal
extensions 20 of the inductor beyond the fixed support elements 4;
this stirring roller, which is characterized in the shell ring
bears against said terminal extensions (20) of the inductor (8) via
rolling bearings (3), has been designed to be suitable also for the
casting of extra-wide slabs.
Inventors: |
Kunstreich; Siebo; (Paris,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kunstreich; Siebo |
Paris |
|
FR |
|
|
Assignee: |
ROTELEC
Bagnolet
FR
|
Family ID: |
46044614 |
Appl. No.: |
14/379918 |
Filed: |
March 27, 2012 |
PCT Filed: |
March 27, 2012 |
PCT NO: |
PCT/EP2012/001330 |
371 Date: |
August 20, 2014 |
Current U.S.
Class: |
164/504 |
Current CPC
Class: |
B22D 11/0651 20130101;
B22D 11/115 20130101; B22D 11/122 20130101 |
International
Class: |
B22D 11/115 20060101
B22D011/115; B22D 11/06 20060101 B22D011/06; B22D 11/12 20060101
B22D011/12 |
Claims
1. A stirring roll for a continuous casting machine of metallic
products having a broad cross section, such as a slab, comprising:
(a) at least one external axially rotating tubular body made of
non-magnetic steel intended to come into contact with the surface
of a wide face of the cast slab, (b) mechanical connection elements
that ensure the support of the tubular body while allowing it to
freely rotate axially, (c) support elements of the stirring roll
located on both sides beyond the limits of the tubular body and
fixed to the rigid frame of the casting machine, (d) internal
electromagnetic equipment consisting of at least one polyphasic
linear inductor with a sliding magnetic field, mounted coaxially
with the tubular body so as to provide an annular space between
them for the circulation of a cooling liquid, said equipment
forming an axial shaft equipped with end extensions that come to
rest blocked against axial rotation on said support elements, said
end extensions being hollow to allow the passage of cooling liquid
and the passage of the electrical connections of the inductor, and
(e) inlet/outlet boxes for cooling liquid equipped with electrical
connection terminals and mounted on the ends of the terminal
extensions of the inductor beyond said support elements; stirring
roll characterized in that the tubular body (1) bears on the
inductor (8) by means of said mechanical connecting elements formed
by the bearings (3) located between said tubular body and the
terminal extensions (20) of the inductor.
2. The stirring roll according to claim 1, characterized in that it
comprises two separate aligned half tubular bodies (1a, 1b)
equipped with mechanical connection elements with an intermediate
extension (20c) of the inductor without electric windings, and a
central support (21) connected to the rigid frame (5) of the
casting machine, said mechanical connection elements being formed
by at least one intermediate bearing (3c, 3d) carried by said
intermediate extension (20c) and the latter being supported by said
central support (21).
3. The stirring roll according to claim 2, characterized in that
each half tubular body (1a, 1b) incorporates its own inductor (8a,
8b).
4. The stirring roll according to claim 2, characterized in that
said intermediate bearing is a single bearing, common to the two
half tubular bodies (1a, 1b) and fixed on both of its sides to the
latters' ends.
Description
[0001] The present invention relates to electromagnetic equipment
with a sliding magnetic field for setting in motion the still
molten liquid metal within a large cross sectional metallic
product, such as a steel slab, during its solidification,
downstream of the ingot mold, in the secondary cooling zone of the
continuous casting unit that produces the slab.
[0002] More specifically, the invention concerns the manufacture of
this type of equipment, usually called "stirring roll" when it is
connected with a supporting and guide roll for the cast slab, and
made tubular for this purpose.
[0003] It should be stated that the electromagnetic part of this
type of equipment traditionally comprises a polyphase linear
inductor that generates a movable magnetic field directed
perpendicularly to the surface of the shell of the roll that
surrounds it and which slides along the rotational axis of said
roll.
[0004] A quick review of this technology that is widely used today
in the steel industry throughout the world for the continuous
casting of slabs, allows us to identify schematically three
periods.
[0005] The first, that of the principle, is represented by the
document FR 72/20546 published in December 1973 which describes a
polyphasic central linear inductor that is coaxially mounted with a
non-magnetic steel tubular body that surrounds it. This was the
birth of the stirring roll as an active piece of equipment capable
of replacing one or a plurality of pre-existing full-matter
supporting and guide rolls on the casting machine. The two
fundamental versions were already disclosed therein: an inductor
that turns with the shell of the roll (the tubular body) in contact
with the surface of one of the large sides of the cast slab, or a
fixed inductor.
[0006] The second period is that of the document FR 75/05623
published in August 1976 which states the basic technological
concept of the stirring roller with a turning inductor; the concept
is based on a tubular body and mechanical linking elements that
ensure the support of the tubular body while allowing it a free
axial rotation. These elements are schematically constituted by a
unit, formed, on each side of the tubular body, by a tubular
spindle in the shape of a truncated cone, mounted at the end of the
tubular body, and by a rolling bearing mounted on a supporting
element located beyond the limits of the tubular body and fixed to
the rigid frame of the caster, the small base of the spindle coming
to turn in said bearing. The central inductor is maintained and
centered in an internal space of the large base of each spindle. At
least one of the spindles (detachable to allow the inductor to be
mounted in the tubular body) extends past its support bearing to
allow the inductor to be electrically connected up to a polyphasic
external supply.
[0007] The third period is that of the document EP-A-0 043 315
published in January 1982. This document discloses in detail the
successful operational achievement of the stirring roll, this time
with a fixed inductor, which is still used today: again there is
the same general structure as that of the turning inductor, except
that the central inductor in this case is held by its own internal
core, on which are wound the electric phase windings. For this
purpose this core forms an axial shaft, whose ends of narrowed
diameter pass by the small bases of the spindles of the tubular
body to engage with the roller bearings supporting the tubular body
and fixed to the rigid frame of the caster machine by means of a
flange lock mounted on the external side of these bearings and
which blocks the inductor against axial rotation.
[0008] Moreover, this flange constitutes the floor of a sealed
water box equipped with water inlets/outlets for cooling the
tubular body and the inductor by circulation in the calibrated
annular space that separates the inductor from the tubular body.
The water box also acts as an electrical connection panel and on
the outside possesses electric terminals that connect the inductor
to the external electricity supply.
[0009] As can be seen from the right hand side of FIG. 1, such a
technology for a stirring roller of the prior art is essentially
characterized overall by the cooperation of two distinct coaxial
sub-assemblies, one free to rotate axially, the other fixed, and
both being carried by the supports 4 of the tubular body 7 which
are fixed to the rigid frame 5 of the casting machine: [0010] a
first assembly, fixed in axial rotation, formed by the central
inductor 8, whose terminal extensions 12 rest on the centering
cradles 14 that block it against axial rotation and which are
integral with the rigid frame 5 of the caster by means of the
supporting elements 4; [0011] and a second assembly, mobile in
axial rotation, formed by the tubular body 1 intended to come into
rolling contact with the cast slab 6 and by its two tubular
spindles 2 that lengthen it at each of its ends so as to turn by
their small base 13 in the projected roller bearings 3 mounted on
the supporting elements 4 fixed to the rigid frame 5 of the
caster.
[0012] For convenience, the water boxes 16, also acting as an
electrical connection panel 18 for the inductor, externally cover
and seal the cradles 14.
[0013] This type of stirring roll, which has proved to be perfectly
adapted to its dual function, support-stirring, is commonly used in
the majority of machines for the continuous casting of slabs of
standard width, i.e. up to about 1600-1700 mm, the width at which
the tubular body supported by two end bearings is still
sufficiently rigid so as not to sag unacceptably.
[0014] This type of stirring roll could also be used for very wide
slabs, namely with a width of more than 2400 mm, by means of
installing two half-rollers with an intermediate roller bearing in
order to ensure the rigidity and geometric straightness of such an
assembly under the thermo mechanical stresses imposed by the
presence at its contact of a very wide slab that is solidifying
(WO2011/117479).
[0015] On the other hand, this technology proves to be inapplicable
for slabs of intermediate width, for example from 2000 mm to
.+-.20% (therefore from 1600 to 2400 mm to be precise). The
presence of the end spindles makes the active part of the inductor
too short for considering the solution with two half-rollers with
an intermediate bearing, and the solution with a single roller
without an intermediate bearing would certainly lead to an
inacceptable sag, especially as the presence of the end spindles
separates the points of support on the rigid frame of the casting
machine far beyond the simple distance needed for covering the
whole width of the slab. For example, a stirring roll of 240 mm
diameter mounted at a distance of approximately 3 m below the level
of the metal cast into an ingot mold in a "standard" casting
machine with a width of 1600 mm, sags less than 1 mm under the
ferrostatic pressure of the slab, whereas in a machine with a width
of 2000 mm the sag would be about 4 mm, which is inacceptable.
[0016] In view of the above, and while retaining the functional and
operational qualities of the conventional stirring rolls in their
entirety, the object of the present invention is to propose a
technological concept for them without end spindles in order to
rigidify the tubular body, to permit a more economical production
both in acquisition and running costs and in addition to be able to
fulfil all requirements in terms of width of the slabs from 1600 mm
(or less) to 2400 mm (at most).
[0017] Accordingly, the subject matter of the invention is a
stirring roll for a continuous casting machine of metallic products
having a broad cross section, such as a slab, comprising: [0018]
(a) at least one external axially rotating tubular body made of
non-magnetic steel intended to come into contact with the surface
of a wide face of the cast slab, [0019] (b) mechanical connection
elements that ensure the support of the tubular body while allowing
it to freely rotate axially, [0020] (c) supporting elements of the
stirring roll located on both sides beyond the limits of the
tubular body and fixed to the rigid frame of the casting machine,
[0021] (d) internal electromagnetic equipment consisting of at
least one polyphasic linear inductor with a sliding magnetic field,
mounted coaxially with the tubular body so as to provide an annular
space between them for the circulation of a cooling liquid, said
equipment forming an axial shaft equipped with hollow end
extensions that provide support that is blocked against axial
rotation on said support elements, and [0022] (e) inlet/outlet
boxes for cooling liquid equipped with electrical connection ports
and mounted on the ends of the terminal extensions of the inductor
beyond said supporting elements; stirring roll characterized in
that the tubular body bears on said terminal extensions of the
inductor by means of said mechanical connecting elements formed by
the bearings located between the tubular body and said terminal
extensions (preferably at the ends of the tubular body).
[0023] Clearly, the invention is based on the idea of making the
inductor act as the support for the tubular body that turns around
it in close proximity. To this end the roller bearings of the
tubular body, or more generally its mechanical connecting elements
that leave it free for axial rotation, are separated from their
traditional supporting elements integral with the structure of the
casting machine. By doing so, the terminal extensions of the
inductor are exclusively received by the supporting elements, while
the roller bearings required to support the tubular body and
allowing it free for axial rotation, therefore become simple
bearings mounted on these terminal extensions of the inductor.
[0024] Among the principal advantages specific to the technology of
the stirring rolls according to the invention, and which will be
presented in more detail below, we can already mention the
elimination, or at least a major reduction, of the phenomenon of
"angular deflection" of the rollers in the bearings, because they
have disappeared.
[0025] The technological concept according to the invention
moreover opens particularly attractive possibilities for a
simplified embodiment of extra-long stirring rolls, intended, as
already emphasized, for machines for casting wide slabs (more than
1600 mm), whose trend is increasingly confirmed in the worldwide
steel industry driven by ever increasing productivity requirements
of steel works.
[0026] In fact it is known that tubular rolls of great unit length
can sag unacceptably from the ferrostatic pressure of the slab
resting on them. To provide a solution to this problem, in another
embodiment of the invention which is accordingly advantageously
applicable to the casting of wide slabs, such an extra-long
stirring roll (hereinafter called "split stirring roll") comprises
not one but two separate aligned tubular bodies. These two tubular
bodies preferably have the same length, and are equipped with two
additional intermediate bearings that bear on a central
intermediate extension of the axial core of the inductor. This
intermediate extension is itself supported by a supplementary
central support fixed to the rigid frame of the casting
machine.
[0027] It should be noted that an advantage that is specific to
this variant is the compactness of the central bearing zone of the
split stirring roll, compactness impossible to achieve with end
spindles and which naturally leads to a more extensive, therefore
better, mechanical support of the cast slab in the central zone of
its large faces.
[0028] Another interest of the split stirring roll is operational
in nature: in the case of very wide slabs, for example greater than
2000 mm, two inductors that are electrically and magnetically
independent of one another can be mounted on the same axial frame
for the inductors within the same stirring roll, while at the same
time adapting a central support fixed to the rigid frame of the
caster.
[0029] In all the embodiments, the stirring roll according to the
invention, compared with traditional stirring rolls of the prior
art, is characterized by the fact that the end rolling bearings and
the spindles are eliminated and replaced by simple supports for a
fixed, non-turning shaft represented by the terminal extensions of
the inductor and that the tubular body turns around said fixed
shaft by bearing on the latter by means of the bearings that hold
it.
[0030] This arrangement leads to a marked decrease in the distance
separating the fixed supports of the stirring roll, hence to a
corresponding reduction of the sag of the tubular body in
operation, and consequently reduces or obviates the phenomenon of
angular deflection.
[0031] Moreover, the strain imparted by the tubular body on its
connecting elements is no longer transmitted by the necessarily
tubular and thus deformable spindles, but is applied directly to a
central shaft that can be dimensioned as needed to avoid any
deformation. Furthermore, transposed to the intermediate bearings
in the version of the split stirring roll, this arrangement ensures
a minimum space between the two tubular bodies, and consequently a
maximized continuity of support for the slab across its width.
[0032] The invention will be well understood and other aspects and
advantages will appear when studying the following description that
gives an example of an embodiment of the stirring rolls according
to the invention with reference to the figures, in which:
[0033] FIG. 1 is a didactic representation, according to an axial
section, of a voluntarily hybrid stirring roll for the purpose of
comparison with the prior art, in the sense that the left extremity
(in the figure) is realized with the technology according to the
invention, whereas the right extremity is shown in the usual form
of the prior art;
[0034] FIG. 2 is an axial section of a stirring roll in its basic
version with a single tubular body (thus without central
support);
[0035] FIG. 3 is an axial section of a variant with two tubular
bodies and central support, named "split stirring roll".
[0036] Referring firstly as a reminder to the right hand side of
FIG. 1, it can be seen that a classic stirring roll is essentially
formed by an extended tubular body that turns about its principal
axis of symmetry A-A. This body consists of an envelope or tubular
body 1, made of non-magnetic stainless steel and by frustoconical
spindles 2 that maintain said tubular body at both of its ends, the
small base 2a of each spindle being engaged in a rolling bearing 3
incorporated into a support 4 fixed to the rigid frame 5 of the
continuous casting machine.
[0037] This casting machine can cast the metallic slabs 6 that
progress from an ingot in the top down to a lengthwise cutting tool
at the bottom of the machine. At the same time starting from the
periphery of the cast product 6 the molten metal progressively
solidifies under the effect of an intense cooling of its surface by
contact with the internal walls of the ingot mold, then by direct
application of water in the secondary cooling stages of the casting
machine, exactly there, where the stirring rolls that equip the
machines are located.
[0038] In fact at this location the cast slab is maintained and
guided in its slow movement toward the turning bearing rollers that
by a constantly renewed force generated by the rotation are pressed
into contact on each of the broad faces of the slab, such as the
broad face 7 of the figure.
[0039] As can be seen, the available volume inside the tubular body
1 is almost totally occupied by an electromagnetic inductor 8
intended to allow the still molten metal to be set in motion in a
controlled manner within the slab 6. For that purpose, the inductor
8 of the polyphasic linear type comprises a magnetic shell 9 that
serves as a winding support for the phase windings 10 that follow
one another along the inductor so as to be able to generate a
magnetic field that is directed on the whole perpendicularly to the
wide faces of the slab 6, but mobile, i.e. sliding along the axis
A-A of the inductor when said windings 10 are correctly connected
to the terminals of an external polyphasic (biphasic or triphasic)
power source (not shown).
[0040] This inductor 8 is also an axially symmetrical body on its
longitudinal axis which merges with the axis A-A of the tubular
body 1 in order to be able to be well centered on the latter while
leaving an annular space 11 between them for the circulation of a
cooling fluid that will ensure the thermal maintenance of the
stirring roll when in operation. This axial centering is achieved
with the help of cylindrical terminal extensions 12 of the inductor
of reduced diameter so as to be able to engage with a slight
clearance in the small base 2a of the spindle 2 and to exceed the
confines of the spindle past the bearing 3 by a projection 13 that
serves as a key to block the inductor against axial rotation at the
level of an end plate 14 equipped with the necessary cotter pins.
Each terminal extension 12, which is hollow (axial channel 24) is
provided with radial ducts 15 communicating with the annular space
11, emerges in a water box 16 mounted in a water-tight manner at
the extremity on the end plate 14 and provided with an inlet or
outlet pipe 17 for the cooling water (shown as an outlet in the
figure).
[0041] It can be seen that the water box 16 also serves as a panel
with terminals 18 for connecting the inductor 8 to an external
polyphasic electricity supply, the connecting wires 19 of the
inductor passing in the axial hollow of its extension 12 to reach
the terminals 18.
[0042] Referring now at will to FIG. 2 or to the left hand side of
FIG. 1, it can be seen that the stirring roll according to the
invention (whose component parts that are identical to those of the
just-described stirring roll of the prior art are designated with
identical reference numbers) differs from the classical technology
of the prior art in that the rolling bearing 3 as well as the
spindle on each end of the roll have been eliminated. This
singularity frees up space for the terminal extension 20 of the
inductor 8 that then, blocked from rotation by a wedge 31, comes to
rest in the cradle formed by this fixed support 4.
[0043] As can be seen, but without it being mandatory, this
extension 20 is planned to be more massive with a greater diameter
than that of the analogous extension 12 of the classical stirring
roll (right hand part of the figure); this is in order to reinforce
as needed its mechanical strength, because greater demands will be
placed on it at this point, as will be understood from the
following.
[0044] In fact, firstly the bearings 3 replace by themselves the
end spindles of the tubular body 1 (which are therefore eliminated)
in their retention and driving force functions when the body
rotates, and, secondly, these bearings 3 come to bear directly on
the terminal extension 20 of the inductor that accordingly serves
to support the tubular body 1.
[0045] It should be noted that by eliminating the end spindles, the
distance between the fixed supports 4 is consequently reduced by 25
to 40 cm, depending on the case, with respect to the technology of
the prior art, i.e. nearly 20% of the length of the stirring
roll.
[0046] A bearing 3 will therefore be fixed to each end of the
tubular body. This fixing can be achieved, in a manner known per
se, by means of a bolted ring (not shown in the figures so as not
to needlessly clutter them). Similarly, it will be advantageous to
provide an annular flange 32 mounted on the end of the tubular body
to act as a lubrication plate for the bearings 3 and which comes to
cover said bearings to protect them from dust and to improve the
water-tightness of the assembly.
[0047] However, it will be advantageous, as already stated at the
beginning, to opt, at least for one of the two ends, if not for
both, for a cage assembly for the bearings which is "openable" in
its mechanical design so as to facilitate the installation of the
inductor 8 inside the tubular body 1 in the workshop.
[0048] FIG. 3 illustrates the technological variant of the
invention applied in the case where the stirring roll no longer has
a single tubular body that extends over the whole width of the cast
slab, but has two half-tubular bodies 1a and 1b.
[0049] These two collinear half tubular bodies are held close to
their ends by intermediate bearings 3c and 3d and are separated
from one another by a short distance (say between 10 and 20 cm) due
to the presence between them of an intermediate extension 20c of
the inductor. As the end bearings 3a and 3b bear on the terminal
extensions 20a and 20b of the inductor, the intermediate bearings
3c and 3d bear on the intermediate extension 20c of the inductor
that for this reason is free of electrical windings and bears on a
central support 21 fixed to the rigid frame 5 of the casting
machine.
[0050] As already stated, a stirring roll of this type, called
"split" for a reason that is obvious from the above statement, and
formed in fact by two half tubular bodies, designated 1a and 1b, is
an adequate response to the growing demand--at least in the steel
industry--to be able to continuously cast slabs of greater width,
easily exceeding the limits of conventional stirring rolls of
1.6-1.7 m, even 2.4 m width and still more in a not too distant
future, because this split roll is protected against unacceptable
sagging by the central support 21.
[0051] The terminal extensions of the inductor 20a or 20b, located
at the ends of the roll, are hollow so as to be able to emerge,
[0052] on one side, by their free end, into a water-tight water box
16a or 16b, provided with an inlet/outlet pipe 17a or 17b for the
water and whose panel with the terminals 18a or 18b forms one of
the walls (the front panel in the figure), [0053] and on the other
side, into the annular space 11a or 11b, arranged between each half
tubular body 1a or 1b and the inductor 8 by means of radially
drilled ducts 15a or 15b.
[0054] The intermediate extension 20c is also hollow and provided
with radially drilled ducts 15c, 15d so as to form a water-tight
central duct communicating between the annular spaces 11a and
11b.
[0055] The cooling of the half tubular bodies 1a and 1b and the
inductor 8 is thus ensured by a common water circuit, comprising
the following elements, taken in the order corresponding to the
direction of flow of the cooling liquid, from left to right in FIG.
3: [0056] the water-supply box 16a into which the cooling water
enters by the supply pipe 17a, connected to a source of pressurized
water (not shown); [0057] the axial passage 24a of the left
external terminal extension 20a of the inductor 8 with its radial
ducts 15a that emerge at the extremity of the annular space 11a;
[0058] said annular space 11a arranged between the half tubular
body 1a and the concentric inductor 8 so as to be capable of
ensuring a circulation of water in the vicinity of the half tubular
body 1a and to cool it during and after its contact with the hot
slab 6 as well as to cool the left part of the inductor 8; [0059]
the radially drilled ducts 15c, the axial passage 26 and the
radially drilled ducts 15d of the intermediate extension 20c of the
inductor which connect the annular space 11a with the space 11b;
[0060] said annular space 11b arranged between the half tubular
body 1b and the inductor 8 so as to be capable of ensuring a
circulation of water in the vicinity of the half tubular body 1b
and to cool it during and after its contact with the hot slab 6 as
well as to cool the right part of the inductor 8; [0061] the
radially drilled ducts 15b and the axial passage 24b of the
external right extension 20b of the inductor which emerges into the
water discharge box 16b, [0062] and the water discharge box 16b
equipped with an outlet pipe 17b to recover the cooling water in a
circulating loop.
[0063] The intermediate extension 20c of the inductor implies of
course that the electric windings 10 be well away from this spot,
but the mechanical continuity between the left and right part of
the inductor is ensured by this extension that can be in steel or
in the same material as the axial frame of the inductor.
[0064] In accordance with one embodiment of the invention shown in
FIG. 3, said split stirring roll can comprise two separate and
distinct electromagnetic inductors, one in each half tubular body:
an inductor 8a in the left half tubular body 1a and an inductor 8b
in the right half tubular body 1b. According to a preferred variant
of the embodiment of the invention, the inductors 8a and 8b are
represented here as being identical to one another and similar to
the single inductor 8 of FIG. 1 or 2.
[0065] These inductors 8a and 8b can be firmly connected
mechanically by the intermediate extension 20c, or detachable so as
to facilitate the installation, but are reunited through the
central support 21. As is shown in the figure, a simple interlock
of the "male-female" kind in this respect would be sufficient to
ensure the mechanical connection of the two inductors.
[0066] However, it is clearly understood that a mechanical join of
this type between the two inductors 8a and 8b is required solely to
form a hold on the central support 21 when the support is a single
one. In contrast, the option in which each inductor comprises its
own central support on its inner end could very well be considered.
In such a case, two central supports would be juxtaposed, one
beside the other, each carried by the rigid frame of the casting
machine. In this case, however, a junction would be needed, even a
flexible one but water-tight, between these two linked inductors so
as to allow the cooling water to circulate.
[0067] Another aspect that could be disadvantageous for this
variant is that the distance between the two half tubular bodies
would be correspondingly greater and hence also the fraction of the
width of the cast slab 6 left free of any mechanical support and
uncooled in a dead zone at the level of the intermediate bearings.
However, the resulting unwanted effects on the slab could be
alleviated by providing sets of half tubular bodies of variable but
different lengths on the same roll. In this way, according to
already well-known principles, the dead zones would be shifted over
the width of the cast slab from one roll to another on the height
of the casting machine, with the aim of homogenizing by and large
the perturbation after the slab has progressed some meters in the
casting direction.
[0068] However, it is understood that, whatever the chosen variant
of the embodiment for the central support zone 21, one has
available a stirring roll consisting of two half-rolls with two
distinct inductors 8a and 8b generating sliding magnetic fields
that can be independently regulated both for power and for the
direction of slide along the axis of the inductors, providing that
one has available two electric supplies, or a single supply capable
of separately supplying each inductor. Moreover, that is why, for
practical reasons, the panel with electric connection terminals,
18a and 18b, respectively, is preferably selected that is the
closest to a given inductor 8a or 8b.
[0069] In order to better clarify the presentation, it should be
recalled here that the inductors 8a and 8b are of the linear
polyphase type (triphasic or more usually biphasic), each requiring
as many pairs of terminal connection as there are phases of its
electricity supply: two pairs for a biphase type, three pairs for a
triphase type (nevertheless with the remark that in the case of an
electric installation of the inductor "without neutral output", its
number of terminals will be three for a biphase type and three for
a triphase type).
[0070] This type of inductor produces a magnetic field, whose lines
of force are on the whole oriented perpendicular to the
longitudinal axis A-A of the inductor, and mobile, because the
field can be made to slide along this axis in one direction or the
other by simply reversing the phase of the electricity supply.
Consequently, if two electricity supplies are available, or what
amounts to the same thing, a duplicate supply, then the sliding
fields can be adjusted on the two inductors 8a and 8b of a same
stirring roll independently of one another, thereby opening
particularly interesting opportunities in regard to the
possibilities for setting in motion the molten metal within the
slab during the casting process.
[0071] It should be noted that such a stirring roll split into two
distinct stirrers does not look any different from a stirring roll
with a single inductor. Clearly, each inductor must have the
complete set of windings in order to generate a sliding magnetic
field (minimum four for biphasic inductors and six for triphasic
inductors), whereas the single inductor distributes its set of
windings between the left and right part; this can for example
allow the number of pairs of poles per phase to be increased.
[0072] On the other hand, the connections of the windings of an
inductor to the phases of the electricity supply will all be
guided, preferably, toward the same electrical connection panel
located at one end of the roll and the connections of the other
inductor will all be guided toward the other connection panel
installed at the other end of the roll (here the connections 18a
toward the nearest panel 19a and the connections 18b toward the
panel 19b), whereas with a single inductor, half of the connections
can be grouped together on the left and the other half on the
right.
[0073] It is evident that neither in the case of a split stirring
roll with a single inductor (FIG. 2), nor in the case of two
distinct inductors (FIG. 3), is it required to provide connections
through the intermediate central extension 20c of the inductor
which would otherwise complicate the design and the assembly of the
installation.
[0074] The stirring rolls according to the invention, in their
embodiment without a central support 21, can be integrated without
any particular difficulty to a segment of the structure of the
casting machine equipped with other customary support rolls and
guide rolls for the slab. This is also true for the split stirring
rolls according to the invention, because the customary support
rolls are likewise equipped with intermediate bearings or with
intermediate supports in the case of wide machines and the
structure of the segments is already designed with central
supports.
[0075] From this observation it can be deduced that the un-split
stirring rolls with a single tubular body, therefore without a
central support, in accordance with the invention, should rather be
reserved for the casting of slabs with a classical width, i.e. up
to about 1650 mm. Over and above, one would prefer split stirring
rolls with two half tubular bodies and a central support, although
it should be emphasized that there is no reason not to use them
even for casting slabs with a customary width.
[0076] As a non-limiting example for casting wide slabs of the
order for example of 2000 mm, use can be made of split stirring
rolls with two distinct inductors, each with a tubular body of
about 1000 mm in length, with a central support of about 10 mm
width. The diameter of the half tubular bodies can be about 240 mm
or more.
[0077] In a variant, for at least some of the split stirring rolls
with a central support which equip a machine for the continuous
casting of slabs, the lengths of the two half tubular bodies can be
unequal. In fact, that the cast slab is not guided on the width of
the central support, means that the part of the slab passing next
to this "hole" can swell up. Also, planning for split stirring
rolls having contiguous half tubular bodies of unequal length, by
therefore shifting their central support such that it is placed
between two successive split stirring rolls, will ensure that it
will not always be the same part of the width of the slab that will
swell up. Accordingly, this will avoid as needed any flaws in the
slab, such as cracks and porosities, caused by the swelling.
[0078] It can be seen that the bearings of the tubular body may be
exposed to the heat of the slab to a much greater extent during
casting than in the technology of the prior art of stirring rolls
with supporting spindles that are offset on both sides of the
tubular body. In a variant, it can consequently be advantageous to
select helicoidal thermal deformation bearings for the tubular
bodies. This type of mechanical bearing is commercially available.
In this regard, solely for informational purposes, mention may be
made of the bearings manufactured and commercialized by the German
company "Maschinenfabrik Joseph EICH KG Gmbh".
[0079] Obviously, the invention should not be limited to the
described examples, but should extend to a plurality of variants or
equivalents, in so far as they are as defined by the claims
presented below.
[0080] For example, it is understood that the term "spindle" used
to designate the supporting elements mounted at the ends of the or
the two tubular bodies that are constituents of a split stirring
roll, encompasses all transmission organs that are capable of
ensuring a water-tight, rigid connection between the tubular bodies
and the roller bearings that carry them in free axial rotation.
* * * * *