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.

Description

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.

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.

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.

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.

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.

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.

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.

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.

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:

• 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;
• 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.

For convenience, the water boxes 16, also acting as an electrical connection panel 18 for the inductor, externally cover and seal the cradles 14.

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.

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).

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.

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).

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:

• (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) 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,
• (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
• (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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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:

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;

FIG. 2 is an axial section of a stirring roll in its basic version with a single tubular body (thus without central support);

FIG. 3 is an axial section of a variant with two tubular bodies and central support, named “split stirring roll”.

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.

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.

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.

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).

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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,

• 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),
• 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.

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.

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:

• 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);
• 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;
• 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;
• 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;
• 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;
• 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,
• and the water discharge box 16b equipped with an outlet pipe 17b to recover the cooling water in a circulating loop.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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”.

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.

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.

Claims

1. A stirring roll for a continuous casting machine of metallic products having a broad cross section, such as a slab, comprising: 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.

(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;

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.