EP2550121B1 - Stirring roller for a continuous slab-casting machine - Google Patents

Description

The invention is in the field of continuous casting of metal slabs, in particular steel. More precisely, it relates to the controlled electromagnetic stirring of still molten metal in the solidification well by means of polyphase inductors with a sliding magnetic field coaxially housed in rollers for supporting and guiding the secondary cooling zone of the continuous casting machine, rolls made hollow for this purpose.

The first achievements of such rollers, known as "brewers-rollers", already date from the beginning of the years 1970 (FR 2 187 467 ).

• d'un élément en rotation axiale destiné à venir en contact roulant avec la surface d'une grande face de la brame en cours de coulée, constitué par une virole de diamètre en principe égal, en tous cas proche du diamètre du rouleau de soutien habituel qu'elle remplace. Cette virole est généralement maintenue à ses extrémités par deux fusées amovibles pour permettre le montage de l'inducteur, et de forme générale tronconique, dont les petites bases viennent se loger dans des paliers à roulement d'extrémité fixés aux structures rigides du châssis de la machine de coulée,
• d'un équipement de brassage électromagnétique constitué par un inducteur linéaire polyphasé apte à générer un champ magnétique glissant le long de son axe et occupant l'espace intérieur libre de la virole, coaxialement avec celle-ci, des moyens de blocage de l'inducteur en rotation axiale étant avantageusement prévus, comme le propose par exemple FR 2 485 412 ;
• et d'un circuit de refroidissement de l'ensemble par circulation d'un liquide de refroidissement, généralement de l'eau, pour assurer le maintien thermique de la virole au contact de la brame chaude et de l'équipement de brassage électromagnétique;

Schematically, a brewer roll consists mainly of:

• an element in axial rotation intended to come in rolling contact with the surface of a large face of the slab during casting, consisting of a ferrule of diameter in principle equal, in any case close to the diameter of the usual support roller it replaces. This shell is generally held at its ends by two removable rockets to allow the mounting of the inductor, and frustoconical general shape, the small bases are housed in end rolling bearings fixed to the rigid structures of the chassis of the casting machine,
• an electromagnetic stirring equipment consisting of a polyphase linear inductor capable of generating a magnetic field sliding along its axis and occupying the free inner space of the ferrule, coaxially with it, means for locking the inductor in axial rotation being advantageously provided, as proposed for example FR 2,485,412 ;
• and a cooling circuit of the assembly by circulating a cooling liquid, generally water, to ensure the thermal maintenance of the ferrule in contact with the hot slab and the electromagnetic stirring equipment;

It will be recalled that the inductor is of the three-phase or two-phase type, with one or more pairs of magnetic poles per phase of the external power supply to which its connection means connects it, and that it therefore generates a sliding mobile magnetic field. along the axis of the roller, either in one direction or the other, according to the order of connection of these coils to the phases of the supply. The sliding speed of the field depends on the polar pitch of the inductor (a parameter fixed by construction) and the frequency of the electric current which feeds it and which, it is the variable of adjustment of this speed.

The application of the stirring rollers to a continuous slab casting machine schematically involves subjecting the slab, in one or more zones of the casting machine located downstream of the mold, to one or more moving magnetic fields sliding horizontally along the width of the slab, each in a certain direction. The still liquid portion of the molten metal located in the core of the slab being The cooling is thus driven in a direction and a direction identical to those of the sliding of the magnetic field acting on it.

Thus, depending on the circulation movements that it is desired to print on the liquid metal, the stirring rollers may be arranged in groups, facing each other on either side of the large faces of the slab at the same level in height (see FIG. Fig. 1 coming from FR 2,185,467 above), or superimposed on the same side of the slab, or distributed on both sides of the slab on different stages of the machine, etc ...

Document is known FR 2,601,270 from 1988 a unique use of stirring rollers for long products of large format (blooms) poured continuously. This use proposes to bring the molten metal into axial rotation by succeeding in generating a generally rotating magnetic induction around the casting axis of the bloom. It would succeed, no longer with the aid of a rotary inductor usually reserved for this purpose, but with the aid of a brewing technology that can be considered as inspired by that used for flat products that are the slabs: linear inductors, but single-phase here, so inductive coils actually, remotely housed in hollow support rollers mounted on two opposite sides of the cast bloom. Thus, from two coils per roll, an architecture with four inductors "square" and whose overall electrical assembly from two single-phase power supplies can generate this quasi magnetic induction rotating around the axis casting.

We also know from the document Russian SU 1,168,321 of 1985 , a technology of single-phase inductive stirring rollers similar to that mentioned above, but for slabs. The slab is perceived as the juxtaposition of two adjacent sections, therefore of less individual squareness than that of the slab itself, and single-phase induction coils with protruding pole teeth housed in rollers cause the slab to pass locally through static magnetic inductions.

We still know from the document EP 0750958 of 1997 , an electromagnetic stirring technology for slabs, but within the mold this time, so other than by stirring rollers. It is then the large walls themselves of the mold that are equipped with polyphase electromagnetic equipment for acting magnetic fields sliding on selected portions only of the width of the cast slab according to the set adjustment modalities of their local actions, multiple and varied.

We still know, from the article of Parshing et al. Entitled "Effectiveness of electromagnetic stirring of steel in the continuous casting" published in "Steel in translation" Allerton Press, NY, USA, vol.23, No. 4, p. 14-16 published on 01/01/1993 , a technology of roll-stirrers, incorporating a single polyphase linear inductor sliding magnetic field, of the type mentioned at the beginning (cf. FR 2 187 467 ), and whose particularity is to present, in addition to the two conventional bearings supporting the ferrule at its ends, a central support bearing. This central bearing marks the physical separation of the inductor in two portions aligned and distant from each other, on either side of the bearing central, thus providing a "dead" inductive zone between them. The latter thus constitutes a geographical discontinuity of the sliding of the magnetic field along the axis of the roll all the more important, so penalizing for the stirring, that the dimension of the central landing is large, but this technology of rollers should allow to sink slabs extra large without risk of deformation thereof under the effect of the ferrostatic pressure.

A preferred use, however, still customary nowadays, such single polyphase linear inductor stirrer rollers incorporated, on a continuous steel slab casting machine is clearly exposed for example in EP-A-0 097 561 dating 1982. By appropriately distributing the stirring rollers on the metallurgical height of the slab, it is thus possible to create within it movement movements of the molten metal whose overall configuration, called "triple zero" shown on the figure 2 hereinafter, develops parallel to the large faces of the slab and tends to homogenize the liquid metal, both thermally and chemically, between the top and bottom of the casting machine by loops of metal currents which are established parallel to the large faces of the slab, with, along the two small lateral faces, an ascensional branch on one side, and a descending branch on the other side, on both sides of the brewer

It is now accepted that such a double homogenization of the molten metal (thermal and chemical) is the guarantor of obtaining a cast product having good internal health combined with a broader equiaxed solidification structure, favorable to a reduction. or even suppression, central porosity and central segregation.

However, it is now also known that this double homogenization of the metal cast between the top and the bottom of the machine can be substantially improved by installing a central main stream, rising or falling, located in the middle of the liquid metal, the slab or in this vicinity, rather than only along the small side faces where it is thwarted by the roughness of a solidification front of the cast product present almost everywhere on this spot (cf. FR 2 861 324 A ).

However, the current brewers-brewers do not allow: by their design, they only know metal circulation loops occupying the entire width of the slab, so with vertical branches that are only lateral, long and against small faces.

In addition, the known stirrer rollers conventionally have diameters of 30 cm and more. However, today more and more often used rollers of smaller diameter (of the order of 24 cm) can be easily used together with support rollers of small diameter which have the advantage of being more numerous on the same height portion of the machine and, therefore, better fulfill their function.

Usually, the continuous casting machines of steel slabs are designed to cast products whose width is typically between 0.9 and 1.6 m, sometimes up to 2.0 m. But, in a permanent search for increased productivity of steel mills, the current trend is to have machines that can run products of greater width, for example 2.4 m. This would imply to have correlatively longer brewers rollers (say 2.5 m and more to fix the ideas).

However, the structure of current brewers of relatively small diameter would not prevent the appearance, more or less quickly, a crippling boom due to the large distance between the support bearings, with regard to the efforts to which the rollers would be subject to contact with the cast product.

The question that arises is that of the realization of a new controlled electromagnetic stirring equipment of the liquid metal suitable for the casting of extra wide slabs and which can provide a vertical central circulation of the molten metal in the heart of the slab casting .

The present invention proposes to achieve this by converting a conventional brewer roll into a "double brewer" roll, or, otherwise, into a "split brewer roll".

• un élément en rotation axiale destiné à venir au contact roulant avec la surface de la brame coulée, ledit élément étant constitué par au moins une virole cylindrique maintenue à ses extrémités par deux fusées, de forme générale tronconique, dont les petites bases reposent dans deux paliers à roulements d'extrémité fixés aux structures rigides du châssis de la machine de coulée,
• un équipement de brassage électromagnétique à champ magnétique glissant constitué par deux inducteurs linéaires mis bout à bout et alignés et occupant l'espace intérieur libre de la virole, coaxialement avec celle-ci et à faible distance afin de ménager entre eux un espace annulaire;
• un circuit de refroidissement, incluant ledit espace annulaire, par circulation d'un liquide de refroidissement pour assurer le maintien thermique de ladite virole au contact de la brame et dudit l'équipement de brassage électromagnétique;
• et des bornes de connexion électrique pour assurer la liaison électrique dudit équipement de brassage électromagnétique à une alimentation électrique externe,

caractérisé en ce que ledit élément en rotation axiale, destiné à venir au contact roulant avec la surface de la brame coulée sur laquelle il est en appui, est constitué de deux viroles cylindriques distinctes alignées, en ce qu'il comporte un troisième palier à roulements intermédiaire entre lesdits deux autres paliers à roulements d'extrémité et délimitant avec ceux-ci deux demi rouleaux brasseurs, situés de part et d'autre dudit palier intermédiaire et formés chacun par l'une desdites deux viroles,
et en ce que lesdits deux inducteurs linéaires sont de type polyphasé, électriquement indépendants l'un de l'autre et aptes chacun à générer un champ magnétique glissant indépendamment de l'autre.Thus, the subject of the invention is a divided stirring roll for a continuous casting machine for flat products with a large cross section, such as a slab, in particular an extra wide slab, comprising:

• an element in axial rotation intended to come into rolling contact with the surface of the cast slab, said element being constituted by at least one cylindrical shell held at its ends by two fuses, of frustoconical general shape, whose small bases rest in two bearings with end bearings attached to the rigid structures of the casting machine frame,
• electromagnetic stirring equipment with sliding magnetic field consisting of two linear inductors placed end to end and aligned and occupying the free inner space of the ferrule, coaxially with it and at a short distance so as to provide an annular space between them;
• a cooling circuit, including said annular space, by circulation of a cooling liquid to ensure the thermal maintenance of said ferrule in contact with the slab and said electromagnetic stirring equipment;
• and electrical connection terminals for electrically connecting said electromagnetic stirring equipment to an external power supply,

characterized in that said element in axial rotation, intended to come into rolling contact with the surface of the cast slab on which it bears, consists of two distinct cylindrical rings aligned, in that it comprises a third bearing bearing intermediate between said two other end bearing bearings and defining therewith two half-stirrer rollers, located on either side of said intermediate bearing and each formed by one of said two ferrules,
and in that said two linear inductors are of polyphase type, electrically independent of each other and each able to generate a magnetic field sliding independently of the other.

As will have been understood, nothing visible will change on the continuous casting machine compared to an installation equipped with usual brewing rollers. However, simply by properly connecting the windings of the two internal inductors to the external power supply so that they produce sliding magnetic fields in opposite directions, for example convergent, will necessarily generate within the cast slab a main circulation rising from molten metal in the middle region of the slab initiating where the two inductors meet.

If the two inductors are identical in size, the desired recovery of the molten metal to the mold will naturally locate just in the middle of the large faces.

The versatility of the equipment in this respect must be emphasized here: the desired homogenization of the molten metal within the liquid well in the slab can be obtained in the same way if the two inductors are adjusted to produce magnetic fields sliding in the slab. divergent opposite directions, that is to say moving away from each other since the median junction of the inductors. The central main circulation of the liquid metal will then descend towards and to the junction point of the two inductors.

It should be understood that the term "half-roll" includes both the case where the two aligned rings constituting the brewer-roll as a whole are of equal lengths, that the case where they are of different lengths for stated reasons. further.

Each half-roll brewer has its own power supply terminals for feeding the polyphase inductor sliding magnetic field it encloses, preferably grouped all at the end of the relevant half-roll facing outward of the machine.

On the other hand, the circulation of the cooling fluid is common to the two half-rolls, and the means which ensure the circulation of the fluid in each half-roll are connected to each other inside the central support bearing.

These characteristics make it possible to produce a compact device that can easily fit into an existing casting machine, since it is not necessary to place electrical connections and fluid supply lines in the central zone of the segment carrying the rollers. and the usual rollers providing support and guidance of the slab as it descends into the casting machine.

• la figure 1 est une vue schématique illustrant l'art antérieur représenté par le document FR 2185467 déjà cité pour créer un brassage du métal liquide dans la zone de refroidissement secondaire de la machine de coulée de brames d'acier selon une configuration à double boucle, dite en "ailes de papillon";
• la figure 2 est une vue schématique analogue à la figure précédente, mais illustrant l'art antérieur représenté par le document EP-A- 0 097 561 également déjà cité pour installer un brassage du métal liquide selon une configuration à trois boucles, dite en "triple zéro";
• la figure 3 est une vue d'ensemble, dans un plan perpendiculaire aux grandes faces de la brame coulée, d'une réalisation d'un rouleau brasseur divisé selon l'invention à trois paliers support à roulements, dont un intermédiaire, et à deux viroles;
• la figure 4 illustre un premier mode de brassage à circulation centrale du métal en fusion au sein de la brame coulée réalisable avec le rouleau brasseur divisé selon l'invention, la partie 4a étant une vue dans un plan perpendiculaire aux grandes faces de la brame coulée, la partie correspondante 4b étant une vue dans le plan des grandes faces;
• la figure 5, dans ses deux parties 5a et 5b, est une représentation analogue à la figure 4 illustrant un second mode de brassage à circulation centrale de métal liquide coulé réalisable avec le rouleau brasseur divisé selon l'invention;
• la figure 6, dans ses deux parties 6a et 6b, est une représentation analogue aux figures 4 ou 5 illustrant un autre mode de brassage du métal liquide, de type rotatif autour de l'axe de coulée, pouvant être également réalisable avec le rouleau brasseur divisé selon l'invention.

The invention will be better understood on reading the description which follows, referring to the attached figure plates on which:

• the figure 1 is a schematic view illustrating the prior art represented by the document FR 2185467 already cited to create a stirring of the liquid metal in the cooling zone secondary of the steel slab casting machine in a double loop configuration, called "butterfly wings";
• the figure 2 is a schematic view similar to the previous figure, but illustrating the prior art represented by the document EP-A-0 097 561 also already cited to install a stirring of the liquid metal in a configuration with three loops, called "triple zero";
• the figure 3 is an overall view, in a plane perpendicular to the large faces of the cast slab, of an embodiment of a divided stirring roll according to the invention with three bearing bearings, one of which is intermediate, and two rings;
• the figure 4 illustrates a first central circulating stirring mode of the molten metal within the cast slab achievable with the divided stirring roll according to the invention, the part 4a being a view in a plane perpendicular to the large faces of the cast slab, the part corresponding 4b being a view in the plane of the large faces;
• the figure 5 , in its two parts 5a and 5b, is a representation similar to the figure 4 illustrating a second central circulation mode of poured liquid metal achievable with the divided stirring roll according to the invention;
• the figure 6 , in its two parts 6a and 6b, is a representation similar to Figures 4 or 5 illustrating another method of stirring the liquid metal, rotating type around the casting axis, which can also be achieved with the divided stirring roller according to the invention.

1. a) que la figure 1 montre les boucles de circulation (en pointillés) du métal en fusion brassé, avec des remontées et descentes principales le long des petites faces latérales 1 et 2 de la brame coulée 3 qui se forment sur toute la largeur de celle-ci sous l'action de deux rouleaux-brasseurs classiques 4 et 5 montés en regard l'un de l'autre, de part et d'autre des grandes faces 6 et 7 de la brame dans la zone du refroidissement secondaire de la machine de coulée, ces deux rouleaux-brasseurs produisant des champs magnétiques mobiles qui glissent longitudinalement dans le même sens, représenté par les flèches pleines horizontales 8 et 9;
2. b) et que la figure 2 montre les boucles de circulation (en pointillés) du métal en fusion brassé, avec des remontées et descentes principales le long des petites faces 1 et 2 qui se forment sur toute la largeur de la brame coulée 3 sous l'action de deux rouleaux-brasseurs classiques, écartés l'un de l'autre, sur une même grande face 6 de la brame (ici sur l'intrados) et représentés ici uniquement par les flèches pleines horizontales 10 et 11 exprimant que les champs magnétiques mobiles qu'ils produisent glissent longitudinalement dans des sens opposés.

The Figures 1 and 2 have already been mentioned in the introduction to this memo as representative of the prior art. We will limit ourselves here to indicate:

1. (a) that figure 1 shows the circulation loops (in dashed lines) of the molten molten metal, with main ascents and descents along the small lateral faces 1 and 2 of the slab 3 which are formed over the entire width thereof under the action two conventional rollers-brewers 4 and 5 mounted facing each other, on both sides of the large faces 6 and 7 of the slab in the secondary cooling zone of the casting machine, these two rollers breakers producing moving magnetic fields which slide longitudinally in the same direction, represented by the solid horizontal arrows 8 and 9;
2. (b) and that figure 2 shows the circulation loops (in dashed lines) of the molten molten metal, with main ascents and descents along the small faces 1 and 2 which are formed over the entire width of the slab 3 under the action of two rollers-brewers conventional, spaced from each other, on the same large face 6 of the slab (here on the intrados) and represented here only by the horizontal arrows 10 and 11 expressing that the moving magnetic fields they produce slip longitudinally in opposite directions.

On the figure 3 , to which reference is now made, the tubular divided brewing roll 1 is fixed to a rigid support 2 integrated in the frame of the continuous casting machine of continuous casting slabs and enclosing the usual support and guide rollers.

The slab 3 progresses perpendicularly to the plane of the figures from the mold (not shown) towards the bottom of the casting machine, and the divided stirring roll 1 covers the entire width of the slab while remaining in rolling contact with the surface of the slab. one of its large faces by a generatrix of the element in axial rotation which constitutes it.

This rotating element is formed by two aligned cylindrical shells 6 and 12 spaced apart from each other, thus constituting two half brewing rollers 4 and 5 tubular, contiguous and aligned, and of equal length in the example shown.

Three rolling bearings fixed to the support 2 ensure alignment and axial rotation of these two half-rollers: two end bearings, left 9 and right 15, and an intermediate bearing 10, in central position here, facing the middle of the slab 3.

Each half roll 4 or 5 incorporates a polyphase linear inductor (respectively 40 and 50), mounted coaxially with it, capable of generating a longitudinal sliding magnetic field. The left half roll 4 contains the polyphase inductor 40 on the left; the right half-roll 5 contains the right-hand polyphase inductor 50.

In the remainder of the description, the terms "left" and "right" will be used with reference to the equipment as seen on the figure 3 . In addition, it is specified that all that will be said about the left half brewer roller 4 and its annexes will be exactly transferable to the half brewer roller 5 right, the design, as the realization of one being identical to that on the other, even if in some cases we would opt for different lengths between them.

The cylindrical shell 6, constituting the left half brewing roll 4, is held at its ends by two rockets, of the same frustoconical general shape, a left rocket 7 and a right rocket 8. Each rocket is removably mounted at one end of the ferrule by its large base 7a, 8a, the small base 7b, 8b being itself engaged in an end bearing bearing, respectively left 9 and intermediate 10, integral with the support 2 of the rigid chassis of the casting machine .

As is usual, these rolling bearings 9 and 10 allow the brew roller 4 to rotate freely about its longitudinal axis B under the effect of the rolling contact of its ferrule 6 with the slab 3 progressing towards the lower part of the machine continuous casting.

On the other hand, the sliding magnetic field inductor 40, centered in the ferrule 6 and occupying almost all the available volume inside the roll (except for an annular space 60 which distances it from a few mm, say 4 or 5 mm, the ferrule to allow the circulation of cooling water) is itself blocked in rotation.

For this purpose, its left terminal extensions 40a and 40b, of reduced diameter relative to that of the inductor, constitute support pins that come to rest, one in a wedge flange 11, placed outside bearing left 9, so after having crossed this landing by the interior of the small base 7b of the rocket 7, and, the other, after have likewise crossed the small base 8b of the right rocket 8, in the intermediate bearing 10 to come forward on the opposite extension, coming from the right inductor 50, by a male-female coupling with flutes (no represented), therefore removable by simple translation.

Similarly, the right half brewer roller 5 comprises a cylindrical shell 12 engaged between two rockets, left 13 and right 14 (similar to the rockets 7 and 8) by their respective large bases 13a and 14a. The small base 14b of the right-hand rocket 14 is inserted into a right-end bearing bearing 15 secured to the support 2, and the small base 13b of the left-hand rocket 13 is inserted into the central intermediate-bearing bearing 10.

The inner rockets 8 and 13, engaged in the intermediate bearing 10, abut each other. But, this is not an absolute obligation, insofar as it ensures the sealing of their connection, because these parts are constitutive of the cooling circuit of the assembly, as will be seen later.

Each half-brewer roller 4, 5 has its own electrical circuit ensuring the power supply of its inductor. The left half-brewer roller 4 thus comprises, mounted at the end of the end bearing 9, a panel 16 with two pairs of connection terminals 16 'and 16 ", having two pairs of terminals for connection to the electrical network of the coils. of phases of the inductor 40.

It should be remembered that the polyphase linear inductor implemented by the invention, and which can be bi or three-phase, requires as many pairs of connection terminals as phases of its power supply: two pairs for a two-phase, three pairs for a three-phase, being nevertheless emphasized that in the case of a "delta" electrical mounting of the inductor, its number of terminals will be reduced by one.

It is also recalled that an inductor of this type is schematically constituted by an alternating series of coils 41, 51 and apparent circular magnetic poles 42, 52 coming from the internal magnetic framework of the inductor, which also serves as a support for winding for the windings in the receiving spaces between two contiguous magnetic poles. Only from this ordered set are the wires or cables of electrical connection 41a, 41b; 51a, 51b that come out and enter from each series of coils connected to each other in series-opposition (thus connected to the same phase), and run on the surface to reach the nearest terminals of the connection panel .

Note that, usually in the case of a single two-phase inductor covering the width of the slab, an inductor of 1.6 to 2.0 m, the number of windings connected in series-opposition is four or eight, either having two or four pole steps over the active length of the inductor.

It is also recalled that, in the known case of a single stirring roll covering the width of the slab, it comprises an electrical connection terminal board at each of its ends, one receiving the input wires of the interconnected phase windings, the other receiving the leads. On the other hand, in the case of a brewer divided according to the invention, it is preferable not to differentiate the input and output terminals at the connection panels 16 and 17, but to group within the same panel all the connection terminals relating to a and only one of the two inductors and dedicate a given panel to the inductor that is closest to him.

There is thus only one inductor connection panel. In the case represented by an intermediate split split stirring roller 10, thus with two distinct and distant inductors, it is understood that, in this way, it is not necessary to provide a connection through the central bearing 10, which would complicate the design and assembly of the installation.

The right half brewer roll 5 comprises, at the right end of the assembly, a connection panel 17 having two pairs of terminals 17 'and 17 ", similar to the one 16, which is dedicated to the left half brewing roll. 4, is on the left side of the installation.

• une première boite à eau d'entrée 18, montée (dans l'exemple représenté) extérieurement sur le palier à roulement de gauche 9 et dans laquelle l'eau de refroidissement des rouleaux brasseurs pénètre à travers une conduite d'alimentation 19 reliée à une source d'eau traitée sous pression non représentée;
• un passage axial 20 du palier 9 reliant la boîte à eau 18 au trou borgne 21 foré dans la prolongation terminale gauche 40a de l'inducteur de gauche 40, ce trou borgne foré comportant une conduite forée fille radiale 22 qui débouche dans l'espace annulaire 60 déjà mentionné, ménagé entre la virole 6 et son inducteur concentrique 40 pour être apte à assurer une circulation d'eau au voisinage de la périphérie rouleau brasseur 4 et la refroidir pendant et après son contact avec la brame chaude 3;
• une seconde conduite forée radiale 23 qui collecte l'eau ayant circulé dans l'espace annulaire 60 pour l'amener dans un second trou axial borgne 24, symétrique au trou borgne 21, mais prévu dans la prolongation terminale droite 40b de l'inducteur de gauche 40 en prise, comme déjà dit, via un emboîtement mâle-femelle étanche, avec la prolongation terminale gauche 50a de l'inducteur de droite 50 au sein du palier intermédiaire 10;
• un troisième trou borgne foré 25 ménagé axialement dans cette prolongation terminale gauche 50a et sur lequel est piqué une troisième conduite forée fille radiale 26, analogue aux conduites filles précédentes, et qui débouche dans l'espace annulaire 61 ménagé entre la virole 12 du rouleau brasseur de droite 5 et son inducteur intérieur concentrique 50 pour être apte à assurer une circulation d'eau au voisinage de la périphérie rouleau brasseur 5 et la refroidir pendant et après son contact avec la brame chaude 3;
• une quatrième conduite fille forée radiale 27 débouchant dans un quatrième trou axial foré borgne 28 dans la prolongation terminale droite 50b du rouleau brasseur 5, un second passage axial 29, équivalent au passage axial gauche 20, ménagé dans l'axe du palier d'extrémité droite 15 pour relier une boîte à eau de sortie 31 dotée d'une conduite d'évacuation de l'eau 30.

As for the cooling of the brewing half-rolls 4, 5, this is ensured, according to the invention, by a common circuit, comprising the following elements, taken in an order corresponding to the direction of circulation of the cooling water:

• a first inlet water box 18, mounted (in the example shown) externally on the left rolling bearing 9 and in which the cooling water of the stirring rollers enters a supply pipe 19 connected to a source of treated water not shown;
• an axial passage 20 of the bearing 9 connecting the water box 18 to the blind hole 21 drilled in the left terminal extension 40a of the left inductor 40, this drilled blind hole comprising a radial daughter bore 22 which opens into the annular space 60 already mentioned, formed between the ferrule 6 and its concentric inductor 40 to be able to ensure a flow of water in the vicinity of the periphery of the brew roller 4 and cool during and after contact with the hot slab 3;
• a second radial drilled pipe 23 which collects water having circulated in the annular space 60 to bring it into a second blind axial hole 24, symmetrical with the blind hole 21, but provided in the right end extension 40b of the inductor of left, as already mentioned, in engagement via a sealed male-female interlock, with the left end extension 50 a of the right inductor 50 in the intermediate bearing 10;
• a third blind hole drilled 25 formed axially in this left end extension 50a and on which is stitched a third radial daughter drilled pipe 26, similar to the preceding daughter lines, and which opens into the annular space 61 formed between the ferrule 12 of the brewing roller right 5 and its concentric inner inductor 50 to be able to ensure a circulation of water in the vicinity of the periphery stirrer roll 5 and cool during and after contact with the hot slab 3;
• a fourth radial drilled duct 27 opening into a fourth blind drilled axial hole 28 in the right end extension 50b of the stirring roll 5, a second axial passage 29, equivalent to the left axial passage 20, formed in the axis of the right end bearing 15 for connecting an outlet water box 31 with a water discharge line 30.

Note that, in the embodiment considered, it is a face of the wall of the water box, inlet 18 and outlet 31, which constitutes the connection terminal board 16 and 17 respectively, the son link 41a, 41b; 51a, 51b inductors are of course insulated to join them by passing through the water boxes, as is the case here.

For slabs 3 of very large width (for example 2400 mm), the divided baffle roll 1 according to the embodiment which has just been described makes it possible to avoid deformations, in particular an arrow, which would inevitably occur in the case of slabs 3. The absence of the central bearing 10. This allows these deformations to be canceled by providing each constituent brewing roll of the assembly with a relatively small length, comparable to or even lower than that of conventional brewing rollers used on continuous slab casting machines. usual widths (up to 2m and more commonly 1600mm).

• le fait que les connexions électriques d'un inducteur donné se trouvent toutes du même côté du demi rouleau qui incorpore cet inducteur;
• le fait qu'il faut prévoir des moyens de communication entre les circuits de refroidissement de chaque demi rouleau brasseur, par exemple en mettant bout à bout et de façon étanche les deux fusées d'extrémité en regard à l'intérieur du palier central intermédiaire pour former une conduite unique étanche.

The design of the divided brewing roll 1 in its embodiment in two brewing half-rolls 4 and 5 which has just been described is not substantially modified compared to the usual design, apart from:

• the fact that the electrical connections of a given inductor are all on the same side of the half-roll which incorporates this inductor;
• the fact that it is necessary to provide means of communication between the cooling circuits of each half-roll stirrer, for example by putting end-to-end and in a sealed manner the two opposite end flares inside the intermediate central bearing for form a single sealed pipe.

This solution of providing a cooling circuit common to the two half-rollers brewers 4, 5 avoids having to place water inlet and / or outlet lines in the central bearing 10, in the same way that it does not. It is not necessary to install electrical connection terminals, as already mentioned above.

Such a set of mechanically coupled "left-right" polyphase inductors is not very visually distinguishable from a single inductor. Simply, the connection wires of the windings of one to the phases of the power supply will all be directed preferably to an electrical connection panel present at one end of the roller and the connecting wires of the second inductor all directed towards each other. connection panel mounted at the other end. Here, the connecting wires 45a, 45b of the left inductor 45 are directed to the nearest panel 16 mounted on the left rolling bearing 9, and the connecting wires 55a, 55b of the right inductor 55 are directed to the nearest panel 17 mounted on the right rolling bearing 15.

Intermediate-stage split brewing rollers according to the invention can be integrated without particular difficulties to a segment of the structure of the casting machine which also conventionally carries other usual rollers for supporting and guiding the slab. It should be noted that, even in the case of very wide slabs, the latter they can continue to be made in one piece, because their rigidity is greater than that of brewers of equivalent length because they do not have to integrate inductors.

By way of nonlimiting example, for the casting of extra-wide slabs, namely of 2400 mm wide, it is possible to provide brewing rollers divided into two half-rolls, such as 4 and 5, which have a ferrule length of 1150 mm each, with an intermediate rolling bearing approximately 200 mm wide. The diameter of the stirrer rollers 4, 5 can be him, of the order of 230 mm.

Alternatively, it can be expected that for at least some of the brew rollers divided into two half rolls and intermediate bearing equipping a continuous slab casting machine, the lengths of the two rings are unequal. Indeed, the absence of contact between the central bearing and the slab that the portion of the slab passing opposite this bearing is not cooled. Also, providing divided brewing rollers having contiguous stirring rollers unequal length by arranging their intermediate bearing shifted between two successive divided brewing rollers will ensure that it is not always the same portion of the width of the slab which be concerned by this lack of cooling. This will improve the homogeneity of the cooling of the slab if necessary.

We will now give, with reference to Figures 4, 5, and 6 , some examples illustrating the new possibilities offered to controlled electromagnetic stirring in the secondary cooling zone of a continuous slab casting machine by the divided stirring rollers according to the invention when they are used in several, in a coordinated manner.

In this case, in the three examples now considered, they will be used here in pairs 70a and 70b, placed at the same level on the metallurgical height, opposite one another, on both sides of the large faces of the casting slab.

For simplicity, it will be assumed that they are divided brewing rolls of the single ferrule type, and therefore without intermediate rolling bearing, each incorporating two monolithic inductors, 71 and 72 in the roller 70b and 73 and 74 in the paired roller 70a. . The two inductors facing each other on separate rollers are connected in parallel to one and the same polyphase power supply. In this case, via their respective connection boxes not shown, the inductors 71 and 73 are connected to the power supply 78, and the inductors 72 and 74 are connected to the power supply 79. The latter will preferably be identical to the 78 power supply, but nevertheless distinct in order to easily ensure the various desired settings as to the direction of sliding magnetic fields, as will be seen.

The slab 3 is first formed in a continuous casting mold 75 by means of a submerged nozzle 76 centered on the casting axis A and supplying the molten metal to the mold by side outlet openings. The slab leaves the mold to reach, below, the zone of the secondary cooling while progressing towards the bottom of the machine of casting at a controlled speed so as to maintain at a controlled level the height position of the liquid meniscus 77 within the mold. It is in this zone of the secondary cooling of the casting machine that the holding and guiding rollers are located, including the two divided brewing rollers 70a and 70b of the invention.

If the operator wishes to perform a brewing configuration ensuring the establishment of a vertical circulation of the liquid metal in the middle of the liquid well, it will be sufficient to connect the two inductors in each divided brewing roller so that they produce magnetic fields sliding in opposite directions in the same roller and sliding in the same direction in the two rollers facing each other on either side of the large faces of the slab (or facing each other above the other on the same side of the slab, according to a configuration not shown here)

More specifically, as shown in figure 4a if it wishes to obtain a circulation rising in the center, the operator will give the sliding fields opposite directions convergent, namely sliding on a given inductor 71 (and 73) going towards its homologous inductor 72 (and 74 respectively) of the same roll 70b (and 70a).

Conversely, as shown in figure 5a if it wishes to effect a flow of the descending metal in the center of the slab, it will give the sliding magnetic fields divergent opposite directions, namely sliding on a given inductor 71 (and 73) away from its counterpart 72 (and 74 respectively) of the same roller 70b (and 70a).

In addition, it can move from one configuration to another, even during the same casting, simply by reversing two phases by a rocker provided in each of the power supplies 78 and 79.

In the case of thick slabs in particular, the operator could also want, durably or temporarily, to impose a rotating stirring in a plane perpendicular to the casting axis A. It will then be enough for him to achieve his objective of modifying the electrical connections so as to that, as shown in figure 6a , the two magnetic fields slide in the same direction on the two inductors of the same roll and in the opposite direction between the two rollers.

It goes without saying that the invention can not be limited to the derealization examples described, but that it extends to multiple variants or equivalents to the extent that its definition given by the following claims is respected. For example, it will be understood that is meant by the term "rocket" used to qualify the support elements mounted at the ends of the or two ferrules constituting a divided baffle roll, covers any transmission member capable of providing a connection rigid seal between ferrules and rolling bearings that carry them in free axial rotation

Claims (4)

1. A split stirring roll (1) for a machine for the continuous casting of large cross section flat products (3) such as a slab, comprising:

   - an element in axial rotation designed to come into rolling contact with the large surface of the cast slab (3), said element consisting of at least one cylindrical tubular body (6) held at its ends by two spindles (7, 14), of generally frustoconical shape, the small bases (7b, 14b) of which rest on two end rolling bearings (9, 15) attached to the rigid structures (2) of the frame of the casting machine;

   - an electromagnetic stirring equipment consisting of two linear inductors aligned end-to-end and filling up the internal free space of said tubular body (6), coaxially with the latter and at a short distance in order to arrange an annular space (60) between them;

   - a cooling circuit, including said annular space (60), by circulation of a cooling liquid in order to secure the heat levels of the said tubular body (6) in contact with the slab (3) and of said electromagnetic stirring equipment;

   - and electric connection terminals in order to ensure the electric connection of said electromagnetic stirring equipment with an external electricity supply,

   characterized in that said electromagnetic stirring equipment designed to come into rolling contact with the large surface of the cast slab (3) on which it is resting, consists of two distinct aligned cylindrical tubular bodies (6, 12),
   in that it comprises a third intermediate rolling bearing (10) between the said two other end rolling bearings (9, 15) and delimiting with the latter two half stirring rolls (4, 5) situated on either side of the said intermediate bearing (10) and each formed by one of the said two tubular bodies (6, 12),
   and in that said two linear inductors are of polyphase type (40, 50), electrically independent and each able to generate a travelling magnetic field sliding, independently one with the other.
2. A split stirring roll according to claim 1, characterized in that said electromagnetic stirring equipment comprises a magnetic core which is common to the two inductors that built it.
3. A split stirring roll according to claim 1, characterized in that each of the two inductors forming said electromagnetic stirring equipment has its own magnetic core distinct from that of the other inductor.
4. A continuous caster of metal slabs according to claim 3, characterized in that the said two split stirring rolls (70a, 70b) are placed facing one another, either on either side of the large faces of the cast slab, or one above the other on one and the same large face, and in that the two polyphase linear inductors (71, 72; 73, 74) which each incorporates are connected to electricity supplies (78, 79) so as to generate travelling magnetic fields which slide in opposite directions on the two inductors (71, 72) of one and the same split stirring roll (70b) and in the same direction on the inductors (71, 73) facing one another in distinct split stirring rolls (70a, 70b).

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