EP0286960A1 - Device for electromagnetically stirring liquid metal in a continuous-casting line - Google Patents

Abstract

The inductor comprises two portions each having its own casing (3, 4) and capable of pivoting about a hinge (7), thereby enabling the inductor to be opened and removed rear-wardly on a supporting carriage (8), as shown. The carriage is advanced when the inductor is to be closed around metal being cast (A) from a continuous casting mold (1).

Description

The present invention relates to obtaining a long metallurgical product by continuous casting. It relates more particularly to an electromagnetic equipment usable for stirring the metal which remains liquid within the product during its progression along the casting line. It is known that during this progression, the cast product cools and solidifies little by little from its surface and that a stirring of the metal remaining liquid is conventionally carried out because the setting in motion of this metal improves the quality final metallurgical of the cast product. If this setting in motion is caused by an electromagnetic induction, it is called "electromagnetic stirring". Such stirring is used industrially at one or more levels of the continuous casting line: at the level of the mold (called level M by specialists), below the mold in the so-called secondary cooling zone (level S), and at the bottom of the solidification well (level F).

It is also known that stirring can be obtained by means of a mobile magnetic field, either rotating or sliding, which penetrates the cast product.

We also know that these magnetic fields are produced by static, polyphase inductors, placed as close as possible to the cast product. The rotating fields are produced by so-called "rotary" inductors. Sliding fields are produced by so-called "linear" inductors.

When it is desired to brew in a plane perpendicular to the pouring axis, rotary stirring is well suited for round, square or slightly rectangular products, that is to say close in cross-section to the square shape, which is the the case of billets and blooms. For such applications, the rotary inductor is that which makes it possible to achieve the best penetration of the magnetic induction in the heart of the cast product and thus to act effectively on the whole mass of the liquid to be stirred.

For its part, linear mixing is well suited for flat products, such as slabs.

Known rotary inductors are always constructed so as to create a magnetic induction passing through the cast product perpendicular to the casting axis, the rotation of the induction around this axis being obtained by supplying the inductor with polyphase currents (generally two-phase in the case of a square and three-phase inductor in the case of a round inductor). In order to ensure uniform rotation of the magnetic field, the inductor completely surrounds the cast product. More precisely, no rotating field inductor has been produced or proposed publicly which does not completely surround the cast product, and it appeared impossible to economically use a rotating field as soon as the configuration of the casting machine continues. , at the level where one intended to carry out the mixing, did not allow the inductor to completely surround the poured product.

A linear inductor was then used which was placed on the most accessible face, or on the only accessible face of the casting line. That is to say that the least efficiency of such an inductor was accepted in the cases where rotary stirring is most effective.

To benefit from the efficiency of rotary stirring despite the problem posed for this by the space requirement around the casting line, a first solution may be to use several partial inductors, mechanically separated but electrically and magnetically coupled and to arrange them symmetrically with respect to the cast product, so that they produce a rotating field like a single rotary inductor of known type. However, such a solution does not always make it possible to resolve all the difficulties encountered for the implantation of a rotating field inductor on a preexisting continuous casting line.

This may be the case when the path of the metal, after it leaves vertically under the mold, gradually curves towards a horizontal direction. This curvature of the casting line forms a lower surface on the side of its concavity and an upper surface on the side of its convexity. If you then want to do a brewing rotating just below the mold in a place where the skin of solidified metal is still thin on the surface of the cast product, and where it is therefore essential to guide the cast product over almost its entire perimeter and over a certain height by support rollers very close to each other, and if in addition the inductor cannot be placed inside the rollers due to the relatively large stirring power that must be applied, it is necessary to have the inductor all around the rollers. But this can only be easily achieved by introducing the inductor or the two half-inductors from the lower side of the line, this because the upper side is occupied by beams which constitute a support structure for the assembly of the casting line. Such a mode of introduction of the inductor generally obliges to withdraw the first guide segment, that is to say the structure which comprises and carries these rollers, to put in place or remove the inductor or the two half-inductors, and it imposes significant constraints in terms of assembly and maintenance operations.

Other cases also arise for which the installation of two half-inductors, or a rotary inductor of the conventional type, is made difficult and sometimes impossible by the configuration of the casting line, if one has only rotating field inductors of known types.

An object of the present invention is to make possible and easy the installation, operation, maintenance and replacement of an inductor device in most cases where the configuration of the continuous casting lines considered seemed to oppose it at the level proposed brewing.

To this end, the subject of the present invention is a device for electromagnetic stirring of liquid metal for a continuous casting line, this device being intended to stir, in the vicinity of an ingot mold, the internal liquid mass of a poured metallic product which leaves and descends continuously from this ingot mold along a casting axis, this mass being surrounded by an outer skin, initially thin, of solidified metal, this cast product being surrounded by a guide segment carrying support rollers,
this device comprising, to carry out the stirring, an inductor at least partially surrounding at least this cast product and suitable for causing a magnetic field to penetrate therein substantially perpendicular to this axis and rotating around it,
this inductor being heavy and comprising at least coils to create this magnetic field, a rigid carcass for holding these coils and cooling circuits,
this device also comprising an electrical distribution box for supplying these coils from an external source,
- and a water distribution box to supply these cooling circuits,
this device being characterized by the fact that said inductor consists of two separable inductor parts disposed substantially on either side of a separation plane passing through said casting axis, each of these parts comprising coils, a carcass, and its own cooling circuit,
this device further comprising spacing means allowing the carcasses of the two inductor parts to move apart on either side of said separation plane according to inductor opening and closing movements,
- And an inductor carrier carriage carrying these two inductor parts and these spacing means and capable of moving between a front service position which places this inductor around said cast product and a rear withdrawal position which clears the space around of this product.

In addition, depending on the circumstances, the following preferred arrangements may be adopted:
- Said spacing means comprise a hinge guiding a rotation of the two said carcasses around an axis of rotation which is substantially parallel to said casting axis and which is located next to the inductor, at the rear thereof ,
- And support means carried by said carriage to support each of the two carcasses during a limited rotation around of this axis of rotation so as to allow sometimes to open said inductor on its front side to allow said movements of said carriage carrying this inductor, sometimes to close it at least partially around said cast product when this carriage is in its said position service to stir the liquid metal in this product.
- Said carriage has the shape of a coated U opening forward to allow to engage the two branches of this U on either side of said cast product, each of said carcasses being provided at its lower part d 'A rolling means which, during said opening and closing movements, rolls on a raceway formed on an upper face of one of these branches, to constitute said support means.
- Said electrical distribution and water distribution boxes are arranged at the rear of said inductor.
- In the case where the axis of a continuous casting line is first substantially vertical and then gradually curves towards a horizontal casting direction passing through intermediate directions, which defines a lower surface side in the concavity of this axis towards this horizontal pouring direction, and an opposite upper surface side, and where a line support structure is arranged on the upper surface side of this line and therefore hinders access thereto on this side, said axis of rotation s 'extends in a said intermediate direction close to the vertical, the direction of movement of said carriage is horizontal to facilitate movement and said front side of the inductor and the carriage look towards said upper surface side.
- In the case where the stirring must be carried out at a level of a continuous casting line where the support rollers of the cast product are very close to each other, said inductor in the service position not only surrounds said cast product, but also said guide segment, and the support rollers and their bearings located in the magnetic field are made of non-magnetic austenitic steel, as well as, optionally, the entire segment.
- Each of said carcasses is guided and carried by said hinge and said carriage by means of a support.
- Said water distribution box is carried by said carriage and connected to the cooling circuits of said inductor parts by flexible pipes and to an external supply by an inlet pipe and a return pipe also flexible.
- Said electrical distribution box is carried by said carriage and supplies each of the two said inductive parts by means of flexible wires and two terminal boxes fixed to each of said inductive parts.
- Said inductor is a bipolar polyphase inductor formed by two half-inductors respectively constituting the two said inductor parts and each contained in a said metal carcass, these two half-inductors being mechanically separable and electrically and magnetically coupled in order to be equivalent in service to a single inductor.
- The device further comprises mechanical means for opening, closing and locking in the service position of said supports and said inductive parts.

The device also generally comprises an electrical and hydraulic control panel ensuring the maneuvers and the supply of water and electric current.

The device according to the invention thus comprises two halves of a mechanical assembly articulated around a hinge and provided with operating and feeding means. It can be used with advantage in a very large number of practical cases. It can consist of two mechanically separable half-inductors electrically and magnetically coupled, either completely or almost completely surrounding, after locking, the casting line continues at the level of mixing considered, or arranged on two opposite faces of the line. But it can just as easily be made up of two inductors distinct from the electrical and magnetic points of view, either partially surrounding the continuous casting line, or placed on two of its opposite faces.

The invention is particularly advantageous when it is desired use a rotating field and the configuration of the continuous casting line precludes the installation of a rotating field inductor of known type. In this case, the two half-inductors locked in the service position are practically equivalent to a rotary inductor of known type completely surrounding the continuous casting line at the level considered.

Thanks to the invention, the handling of the inductor parts, their maintenance and their replacement are particularly easy.

• Les figures 1A, 1B et 1C représentent un dispositif selon l'invention en perspective cavalière schématique et simplifiée à trois stades successifs de sa mise en oeuvre.
• La figure 2 représente une vue en plan de l'ensemble du porte-­inducteur, du chariot et des deux demi-inducteurs de ce dispositif en position ouverte dite de retrait.
• La figure 3 représente une vue en plan du même ensemble en position fermée, dite de service.
• La figure 4 est un schéma électrique de la boîte de distribution électrique et des deux boîtes à bornes supportées par le chariot.
• La figure 5 représente une vue en coupe des deux demi-inducteurs en service présentant la configuration des lignes de flux magnétique à un instant donné du cycle électromagnétique.

In order to clearly understand the invention, there will be described below, by way of nonlimiting example, an inductor holder according to the invention, mounted on a U-shaped carriage, in the case of two half three-phase bipolar inductors, of generally cylindrical shape with circular base, which are intended to be placed at level S, just below the ingot mold for continuous casting of a billet, in an area where the supporting rollers of the cast metal product are very close to each other and are arranged on the four sides of the product, their assembly constituting a "guide segment".

• FIGS. 1A, 1B and 1C represent a device according to the invention in schematic and simplified perspective perspective at three successive stages of its implementation.
• 2 shows a plan view of the assembly of the inductor, the carriage and the two half-inductors of this device in the open position called withdrawal.
• FIG. 3 represents a plan view of the same assembly in the closed position, called the service position.
• Figure 4 is an electrical diagram of the electrical distribution box and the two terminal boxes supported by the carriage.
• FIG. 5 represents a sectional view of the two half-inductors in service presenting the configuration of the magnetic flux lines at a given instant of the electromagnetic cycle.

Figures 1A, 1B and 1C provide a good understanding of the principle of the invention.

The curved axis of a casting line is represented at A. This axis simultaneously represents the path of the metal product cast which here is a bloom of steel. This bloom is represented only by this axis. It is formed in an ingot mold 1 of continuous casting from which it flows and which is completed downwards by four series of very close rollers, on each face of the bloom; their roughly square section envelope constitutes the "segment" 2. It is at level S of this segment that the electromagnetic stirring of the liquid part of the product is to be carried out.

The carcasses 3 and 4 containing the two half-inductors as well as their respective supports 5 and 6 are articulated around the rod 7b of a hinge 7 and rest on a carriage 8, movable in horizontal-tal translation, d-shaped 'U.

The laying, around segment 2 at level S, of the two half-inductors is carried out by the mechanical device of the invention in the following manner, passing through the three stages shown in FIGS. 1A, 1B, 1C.

In 1A, all of the carcasses 3 and 4 of the two half-inductors, their supports 5 and 6 and the hinge 7, in the closed position is suspended from a lifting machine 9, which comes to deposit them in 1B on the carriage 8, which is notched like a U in the direction of the segment 2. The two halves of the device are then half-opened by mechanical means not shown in these figures and visible in FIGS. 2 and 3, at the same time as the l cooling water inlet, water return, and electrical cables, by means of hoses not shown.

Then, the carriage 8 is pushed by mechanical means towards the segment 2 until it occupies the position shown in FIG. 1C (or in phantom in FIG. 1B); the two halves of the articulated device are then closed, and a locking device is operated opposite the hinge 7.

The inductor consisting of the two half-inductors is then in the operating position at level S.

Subsequently, its removal is carried out by a series of reverse maneuvers from those of the installation.

Some details of the inductor holder appear in Figures 2 and 3.

The carriage 8, rectangular, has a large U-shaped notch 10 of two rolling tracks 27 and 28. It supports:
. the two carcasses 3 and 4 of the two half-inductors, by means of their respective supports 5 and 6 which are articulated around the rod 7b of the hinge 7. This rod is fixed on the carriage. The two carcasses are supported by means of two rollers 29 and 30 rolling on the tracks 27 and 28 and each receiving a yoke not shown, fixed to the base of each of the two carcasses.
. a hydraulic distribution box for cooling the half-inductors: a hose 11, connected upstream to the general water network, supplies cooling water to the hydraulic box 12, which distributes it over the two half-inductors through the two lines 13 and 14; the water return is effected by the two pipes 15 and 16, which converge in a second compartment of the hydraulic box 12, and the water is then evacuated by a hose not shown, similar to the hose 11. The valve water intake, not shown, is controlled from a control console located near the carriage.
. an electrical distribution box 17 supplied from an appropriate power equipment, in three-phase current, by four flexible cables including three phase cables such as 18 and a neutral cable such as 18b. In the present example, each half-inductor comprises three coils, one per phase, requiring six incoming wires, such as 19, or twelve in all, which start from the box 17.
. two terminal boxes 20 and 21, which respectively supply the half-inductors contained in the carcasses 3 and 4; the entire electrical diagram of the electrical distribution box and the two terminal boxes is given in Figure 4.
. the mechanical means 22 and 23 allowing the opening and closing of the two movable parts around the hinge 7. A gusset welded to each carcass, provided with a rod 31 and 31b and a yoke 32 and 32b ensures all the flexibility desired when operating the screw-nut system 33 and 33b by means of the crank 34 and 34b.
The above is an example of manual opening and closing control. It is also possible to perform these functions either hydraulically or electrically, the control being able to be located either on the trolley or at the control console.

In FIG. 3, in the closed position, which is the stirring position, a locking system 24 gives the assembly of the two mobile parts the necessary rigidity and ensures the closure of the magnetic flux despite the very narrow intervals 25 and 26, visible in Figure 5, which remain between the two half-inductors.

In this position, the half-inductors completely surround the continuous casting line, that is to say the cast product 27 and the rollers as 28 grouped in segment 2, and produced as well as their bearings in non-magnetic austenitic stainless steel .

Each half-inductor here comprises three coils regularly spaced from each other. Each of them is in phase with the coil of the other half-inductor which is diametrically opposite to it. Let B1 and B1b be the coils of phase 1, B2 and B2b the coils of phase 2, B3 and B3b the coils of phase 3 (Figure 5).

FIG. 4 is an electrical diagram of the assembly inside the distribution box 17 and the two terminal boxes 20 and 21.

The flexible supply cables are marked Ph. 1, Ph.2, Ph.3, and N, respectively for phases 1, 2, 3 and for the neutral, and are connected to terminals 18 and 18b of the carriage 8.

The terminal U1 of the terminal box 21 is supplied by phase 1, and it is connected to the coil B1, the other end of which is connected to the terminal U11 of the box 21.

Via the distribution box 17, the terminal U11 is connected to the terminal U22 of the other terminal box 20. The terminal U22 is connected to the coil B1b of the other half-inductor, diametrically opposite to B1 . The other end of the coil B1b is connected to the terminal X of the box 20. Thus, the two coils B1 and B1b are in phase and in series.

Similarly, phase 2 successively traverses terminal V1 of the terminal box 21, the coil B2 of the half-inductor 4, the terminal V11 of the box 21, the distribution box 17, the terminal B22 of the box 20, the coil B2b of the other half-inductor 3, and the terminal Y of the box 20. Thus B2 and B2b are indeed in phase and in series.

Finally, phase 3 successively traverses the terminal W1 of the box 20, the coil B3b of the half-inductor 3, the terminal W11 of the terminal box 20, the distribution box 17, the terminal W22 of the box 21, the coil B3 of the half-inductor 4 and the terminal Z of the terminal box 21. Thus, the two coils B3 and B3b are in phase and in series.

In the distribution box 17, the three terminals X, Y, Z are connected to each other and to terminal 18b of the carriage 8, itself connected to the cable N.

Thus, the mechanical device according to the invention, with its electrical distribution box and its two terminal boxes supported by the carriage, is such that the separation into two half-inductors practically does not harm the electromagnetic efficiency of the assembly thus formed.

FIG. 5 is a diagram of the configuration of the magnetic flux at a determined instant of the electromagnetic cycle. The lines of this flow are shown in thin lines. It turns with the evolution of the power supply cycle. The intervals 25 and 26 existing between the two magnetic cores are very narrow and only slightly reduce the efficiency of the magnetic flux.

• 1er cas : Machine de coulée continue telle que l'implantation et la maintenance d'un brasseur à l'endroit choisi, nécessite le démontage d'une partie importante de la machine.
• 2ème cas : Machine de coulée continue dans laquelle le mannequin qui sert d'amorce à la ligne de métal coulé est enfilé entre les rouleaux et introduit à la base de la lingotière au moyen d'un bras mécanique qui se déplace dans un plan vertical.
  Au niveau S et au niveau F, à cause du déplacement du bras, il est impossible de placer un inducteur de type classique entourant le produit coulé. Le dispositif selon l'invention permet d'escamoter l'inducteur lors de cette opération et constitue alors une bonne solution.
• 3ème cas : Machine de coulée continue capable de couler des formats de tailles très différentes pour lesquels, pour des raisons métallurgiques et technologiques, il est nécessaire d'utiliser par exemple deux types de brasseurs S ou F : un type adapté au brassage des gros formats, l'autre type -de diamètre intérieur plus faible - adapté au brassage des petits formats. Des coulées successives avec brassage des petits, puis des grands formats, peuvent s'effectuer sans intervention sur la machine - sans démontage de l'inducteur adapté aux petits formats lors de la coulée des gros formats -lorsque le dispositif selon l'invention est utilisé pour l'inducteur adapté aux petits formats -(ce dernier pouvant être aisément escamoté de la ligne).
• 4ème cas : Machine de coulée continue dans laquelle la taille du mannequin est supérieure au format maximale coulé. Dans ce cas avec une solution classique, le diamètre intérieur de l'inducteur doit être dimensionné en fonction de la taille de ce mannequin. Le dispositif selon l'invention permet de dimensionner le diamètre intérieur en fonction seulement de la taille du produit coulé, ce qui conduit à un dimensionnement plus faible et donc à une puissance installée plus faible, à performances de brassage égales.

The mechanical device according to the present invention applies to all cases where a rotary inductor in one piece cannot be installed at the desired level on a continuous casting line. It is also applicable to a pair of linear inductors whose installation would present difficulties for particular reasons.

• 1st case: Continuous casting machine such as the establishment and maintenance of a brewer at the chosen location, requires the disassembly of a large part of the machine.
• 2nd case: Continuous casting machine in which the mannequin which serves as a primer for the line of cast metal is threaded between the rollers and introduced at the base of the mold using a mechanical arm which moves in a vertical plane.
  At level S and level F, because of the movement of the arm, it is impossible to place a conventional type inductor surrounding the cast product. The device according to the invention allows the inductor to be retracted during this operation and is therefore a good solution.
• 3rd case: Continuous casting machine capable of casting formats of very different sizes for which, for metallurgical and technological reasons, it is necessary to use for example two types of brewers S or F: a type suitable for brewing large formats , the other type - of smaller internal diameter - suitable for brewing small formats. Successive flows with mixing of small, then large formats, can be carried out without intervention on the machine - without disassembly of the inductor suitable for small formats during the casting of large formats - when the device according to the invention is used for the inductor suitable for small formats - (the latter can be easily retracted from the line).
• 4th case: Continuous casting machine in which the size of the dummy is greater than the maximum cast format. In this case with a conventional solution, the inside diameter of the inductor must be sized according to the size of this mannequin. The device according to the invention allows the internal diameter to be dimensioned as a function only of the size of the cast product, which leads to a smaller dimensioning and therefore to a lower installed power, with equal stirring performance.

It is understood that one can, without departing from the scope of the invention, imagine variants and improvements of detail, as well as envisage the use of equivalent means.

Claims (10)

1 / Device for electromagnetic stirring of liquid metal for continuous casting line, this device being intended to stir, in the vicinity of an ingot mold (1), the internal liquid mass of a cast metal product which leaves and descends continuously from this ingot mold along a casting axis (A), this mass being surrounded by an initially thin outer skin of solidified metal, this cast product being surrounded by a guide segment (2) carrying support rollers,
this device comprising, to carry out the stirring, an inductor at least partially surrounding at least this cast product and suitable for causing a magnetic field to penetrate therein substantially perpendicular to this axis and rotating around it,
this inductor being heavy and comprising at least coils to create this magnetic field, a rigid carcass for holding these coils and cooling circuits,
this device also comprising an electrical distribution box for supplying these coils from an external source,
- and a water distribution box to supply these cooling circuits,
- This device being characterized by the fact that said inductor consists of two separable inductor parts arranged substantially on either side of a separation plane (25, 26) passing through said casting axis (A), each of these parts comprising its own coils (B1, B2, B3, B1b, B2b, B3b), a carcass (4, 3) and a cooling circuit (14, 16, 13, 15),
- This device further comprising spacing means (7, 27, 28, 29, 30) allowing the carcasses (4, 3) of the two inductive parts to move apart on either side of said separation plane according to movements inductor opening and closing,
- And an inductor carrier carriage (8) carrying these two inductor parts and these spacing means and capable of moving between a front service position which places this inductor around said cast product and a rear withdrawal position which releases l space around this product. 2 / Device according to claim 1, characterized in that said spacing means comprise a hinge (7) guiding a rotation of the two said carcasses (4, 3) about an axis of rotation (7B) which is substantially parallel said casting axis (A) and which is located next to the inductor, at the rear thereof,
- And support means (27, 28, 29, 30) carried by said carriage (8) to support each of the two carcasses during a limited rotation around this axis of rotation so as to allow opening said inductor on its front side to allow said movements of said carriage carrying this inductor, sometimes to close it at least partially around said cast product when this carriage is in its said service position to stir the liquid metal in this product. 3 / Device according to claim 1, characterized in that said carriage (8) has the shape of a lying U opening forwardly to allow to engage the two branches of this U on either side of said cast product (A), each of said carcases (3, 4) being provided at its lower part with a rolling means (29, 30) which, during said opening and closing movements, rolls on a path of bearing (27, 28) formed on an upper face of one of these branches, to constitute said support means. 4 / Device according to claim 2, characterized in that said electrical distribution boxes (17, 20, 21) and water distribution (18) are arranged at the rear of said inductor. 5 / Device according to claim 2, applicable to a continuous casting line whose axis (A) is first substantially vertical and then bends gradually towards a horizontal casting direction through intermediate directions, which defines a lower surface side in the concavity of this axis towards this horizontal pouring direction, and an opposite upper surface side, a line support structure being arranged on the upper surface side of this line and therefore hampering access thereto on this side;
- This device being characterized in that said axis of rotation (7b) extends in a said near intermediate direction from the vertical, the direction of movement of said carriage (8) being horizontal to facilitate movement,
- And said front side of the inductor and the carriage (8) looking towards said upper side. 6 / Device according to any one of claims 1 to 5, applying to a level of a continuous casting line where there are rollers for supporting the cast product which are very close to each other, characterized in that said inductor in the service position surrounds not only this cast product (A), but also said guide segment (2), and in that the support rollers and their bearings located in the magnetic field are made of non-magnetic austenitic steel. 7 / Device according to claim 2, characterized in that each of said carcasses (3, 4) is guided and carried by said hinge (7) and said carriage (8) via a support (5, 6) . 8 / Device according to claim 4, characterized in that said water distribution box (12) is carried by said carriage (8) and connected to the cooling circuits of said inductive parts (3, 5, 4, 6) by flexible pipes (13, 14, 15, 16) and to an external supply by an inlet pipe (11) and a return pipe also flexible. 9 / Device according to claim 4, characterized in that said electrical distribution box (17) is carried by said carriage and supplies each of the two said inductive parts (3, 5, 4, 6) by means of flexible wires (19) and two terminal boxes (20, 21) fixed to each of said inductor parts. 10 / Device according to claim 1, characterized in that said inductor is a polyphase bipolar inductor consisting of two half-inductors (3, B1b, B2b, B3b, 4, B1, B2, B3) respectively constituting the two said inductive parts and each contained in a said metal carcass (3, 4), these two half-inductors being mechanically separable and electrically and magnetically coupled so as to be equivalent in service to a single inductor.

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