EP0391822B1 - Method and apparatus for manufacturing thin metal products by continuous casting - Google Patents
Method and apparatus for manufacturing thin metal products by continuous casting Download PDFInfo
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- EP0391822B1 EP0391822B1 EP90470007A EP90470007A EP0391822B1 EP 0391822 B1 EP0391822 B1 EP 0391822B1 EP 90470007 A EP90470007 A EP 90470007A EP 90470007 A EP90470007 A EP 90470007A EP 0391822 B1 EP0391822 B1 EP 0391822B1
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- product
- magnetic field
- rolls
- value
- separation force
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/06—Continuous casting of metals, i.e. casting in indefinite lengths into moulds with travelling walls, e.g. with rolls, plates, belts, caterpillars
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1213—Accessories for subsequent treating or working cast stock in situ for heating or insulating strands
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
Definitions
- the invention relates to obtaining thin metallic products directly by continuous casting. It relates more particularly to obtaining thin steel slabs, that is to say flat products whose final thickness rarely exceeds 100-120 mm, but is most often around 20-50 mm.
- Continuous casting installations for steel slabs having these small thicknesses are distinguished from continuous casting installations for slabs of standard thickness (of the order of 150-200 mm), in particular by the presence, downstream of the ingot mold in the direction of extraction of the product, from at least one pair of rollers, called pinch rollers. These have the role of bringing, without actual rolling, the product to its final thickness after it leaves the ingot mold, by only bringing the large faces of the cast product together.
- the ingot mold the design of which derives from that of conventional continuous casting ingot molds, does not in fact make it possible to directly obtain the desired small thicknesses.
- the spacing of the pinch rollers is fixed, in principle, throughout the casting and equal to the thickness desired for the product. They exert their grip on the product so as to bring about the early closure of the liquid well. On leaving the rolls, the product is therefore normally fully solidified throughout its section. In any case, it no longer has a completely liquid heart.
- a problem to be solved in the operation of such a machine is the adjustment of the depth of the liquid well (also called "metallurgical height").
- pinch rollers are designed to shape a product whose core is still liquid. If the liquid well closes upstream of the pinch rollers, these must therefore act on a product which is entirely solid or pasty state. To bring the product to the desired thickness, they will have to undergo a severe spacing effort on the part of the product, which in fact amounts to real rolling on a solid product. Such an effort, if it is too great, or if it is repeated too frequently and for too long, can cause serious damage to the rollers themselves and to their holding members.
- a machine capable of withstanding such large spacing forces would be hardly compatible in size with the rest of the casting installation, because of the great rigidity of the frame which would be necessary. In any event, its cost would be much higher than that of a normal installation.
- the object of the invention is to propose a method for rapid adjustment of the depth of the liquid well, making it possible to reduce the force undergone by the pinch rollers to its nominal value as soon as an abnormal increase in this force is observed.
- This variable magnetic field can be mobile and therefore exert a stirring action on the liquid core of the cast product, stirring which, as is known, promotes the evacuation of heat, or on the contrary be stationary and exert an inductive heating action on the cast product.
- the invention also relates to a continuous casting device for implementing this process, characterized in that it comprises means for measuring the spacing force exerted by the product poured on the pinch rollers, at least one inductor generating a variable magnetic field in the product poured upstream of the pinch rollers or between them, and means d slaving of said magnetic field to the value of the spreading force exerted by the product on the pinch rollers.
- the inductor (s) can be located between the ingot mold and the pinch rollers, or housed in the pinch rollers, as described for example in Luxembourg patent n ° 67,753 filed on 07.06.1973 and the content of which is incorporated by reference herein description.
- These inductors can impart stirring movements to the liquid core of the cast product, or exert a heating action on the cast product.
- an increase in the stirring action of the liquid core therefore tends to accelerate the solidification of the product and to raise the closing point of the liquid well. Conversely, a decrease in the stirring action tends to delay the solidification of the product and bring down the closing point of the liquid well.
- the intensity of the stirring is modulated as a function of the measurement of the force exerted by the product on the pinch rollers, the spacing of which, in normal operation, is kept constant and equal to the thickness desired for the product.
- the pinch rollers are designed to undergo a force, the value of which, which is measured by sensors continuously or at close time intervals, corresponds to the closing of the liquid well. If F becomes greater than its normal value, it is the indication that the pinch rollers undergo an effort on the part of a product whose core is no longer in the liquid state. Such a deviation from normal operation of the machine may be due to factors such as a voluntary reduction or not in the casting speed, a drop in the temperature of the liquid metal feeding the ingot mold, etc.
- the start and the end of the casting during which the temperature of the liquid metal and the speed of movement of the product can vary in significant proportions, also constitute critical periods. Indeed, it is then difficult to adjust the operating parameters of the machine so as to permanently locate the closing point of the liquid well at the desirable level.
- the possibility to influence the speed of solidification of the metal by means of the intensity of stirring of the liquid core provides the operator with an additional means of action for controlling the operation of the machine.
- the operator gradually decreases the intensity of the electromagnetic stirring so as to reduce the movements of the metal to slow down its solidification.
- the force exerted on the rollers is measured. If it remains greater than F1, a further decrease in the intensity of the mixing is carried out. If it is between Fo and F1, the new intensity of stirring is maintained until, possibly, a return to normal of the pouring conditions makes this stirring intensity insufficient and moves the closing point of the liquid well below princely rolls. Such a displacement must result in an effort less than Fo, and it is then necessary to increase the intensity of stirring to bring the effort into the interval [Fo, F1].
- a threshold value F2 greater than F1 beyond which it is considered that the force tending to spread the pinch rollers must imperatively not be supported for more than a few moments.
- the crossing of this threshold F2 must then lead not only to a significant and abrupt reduction in the intensity of stirring, but also to a separation of the rollers in stages.
- the force supported by the rollers is measured. If it remains greater than F2, the spacing of the rollers is increased. When it becomes less than F2, the rollers are then brought together. Then, if the force becomes greater than F2, the rollers are again moved aside.
- warning value F3 less than F1 such that, when increasing, the spreading force reaches F3, the modification of the action of the magnetic field.
- F4 a warning value greater than Fo such that, when decreasing, the spreading force reaches F4, the magnetic field is modified. This further limits the risk of defects in the product, which would be due to too late closing of the liquid well.
- the organs which control the intensity of the stirring and the spacing of the pinch rollers are controlled by the operator or the data processing unit which manages the operation of the casting machine, according to the information provided by the necessary measuring instruments: measurements of the force on the rollers, the distance between the rollers, the electrical parameters of the electromagnetic stirrers, the casting speed, etc.
- the electromagnetic stirrers with a sliding field can belong to the various known types of stirrers, imparting vertical translational movements to the metal or perpendicular to the direction of extraction, according to the large faces of the product or rotational movements.
- they are of the type known as "brewing rollers", described for example in patent FR 2 187 468 in the name of the applicant. They are then included in rollers which also serve to support the product (without compressing it) between the lower part of the mold and the pinch rollers.
- Plan brewers arranged opposite the large sides of the product in this same area of the machine can also be used.
- the single appended figure shows schematically an example of installation for continuous casting of thin slabs according to the invention, seen in section and in profile.
- the poured product 1 leaves the ingot mold 2, supplied with liquid metal by the nozzle 3, in the partially solidified state: the core 4 is in the liquid state, and it is enclosed by a peripheral layer 5 in the pasty state or fully solidified, the thickness of which increases as the product progresses through the machine, solidifying.
- the installation includes a pair of pinch rollers 6, 6 ′ in free rotation or controlled in the direction indicated by the arrows, placed at a certain distance from the mold, outside of its immediate vicinity.
- rollers reduce the thickness of the product to the desired value by bringing together the layers of metal which have started to solidify on the large faces of the mold, so as to close the liquid well. They are provided with means 7.7 ′ for adjusting their spacing, and for maintaining it at a determined value.
- the installation also comprises means of electromagnetic stirring of the liquid core 4. They can be constituted, as shown in the figure, by a pair of polyphase planar stirrers 8, 8 ′ arranged opposite the large faces of the product, between the bottom of the ingot mold and the pinch rollers and generating a sliding magnetic field. Sensors measure the rolling forces F and F ′ exerted by the product respectively on the pinch rollers 6 and 6 ′, and transmit the results of these measurements to an information processing unit 9.
- This unit controls, according to the information transmitted by the sensors, the operating parameters of the brewers which determine the intensity of the movements inside the liquid core, and this permanently. On the other hand, this unit also controls the spacing of the pinch rollers in cases where the rolling force exerted on one of them by the product exceeds the threshold F2 previously defined.
- brewers located between the bottom of the mold and the pinch rollers
- these Brewers in an ingot mold may be insufficient to ensure alone a sufficiently sudden variation in the speed of solidification of the liquid core.
- Another variant consists in housing the inductors in the pinch rollers themselves, made tubular for this purpose. They are then particularly well suited to an acceleration of solidification in the case where the liquid well closes below the pinch rollers. They can also stir the liquid metal only in the latter case, or be permanently active like the devices described above. They can be used alone or in combination with other agitation devices for the liquid heart.
- variable but stationary field inductors the role of which is to provide a permanent or intermittent flow of heat to the liquid heart.
- This heat flow can be modulated so as to keep the liquid well closed at the pinch rollers. It is increased when the liquid well closes upstream of the nip rollers, and decreased when the liquid well closes below the nip rollers.
- Such a device is particularly advantageous to implant inside the pinch rollers, since it can then act in the same area where its effect must be felt as a priority.
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- Mechanical Engineering (AREA)
- Continuous Casting (AREA)
- Treatment Of Steel In Its Molten State (AREA)
- Led Devices (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
Abstract
Description
L'invention porte sur l'obtention de produits métalliques minces directement par coulée continue. Elle concerne plus particulièrement l'obtention de brames minces en acier, c'est à dire de produits plats dont l'épaisseur finale excède rarement 100-120 mm, mais se situe le plus souvent autour de 20-50 mm.The invention relates to obtaining thin metallic products directly by continuous casting. It relates more particularly to obtaining thin steel slabs, that is to say flat products whose final thickness rarely exceeds 100-120 mm, but is most often around 20-50 mm.
Les installations de coulée continue de brames en acier ayant ces faibles épaisseurs se distinguent des installations de coulée continue de brames d'épaisseur standard (de l'ordre de 150-200 mm), notamment par la présence, en aval de la lingotière dans le sens d'extraction du produit, d'au moins une paire de rouleaux, dits rouleaux pinceurs. Ceux-ci ont pour rôle d'amener, sans laminage proprement dit, le produit à son épaisseur finale après sa sortie de la lingotière, en réalisant seulement le rapprochement des grandes faces du produit coulé. La lingotière, dont la conception dérive de celle des lingotières de coulée continue classique, ne permet pas en effet d'obtenir directement les faibles épaisseurs souhaitées. L'écartement des rouleaux pinceurs est fixe, en principe, pendant toute la coulée et égal à l'épaisseur désirée pour le produit. Ils exercent leur emprise sur le produit de manière à provoquer la fermeture anticipée du puits liquide. A sa sortie des rouleaux, le produit est donc normalement entièrement solidifié dans toute sa section. En tout cas il ne présente plus de coeur à l'état complétement liquide.Continuous casting installations for steel slabs having these small thicknesses are distinguished from continuous casting installations for slabs of standard thickness (of the order of 150-200 mm), in particular by the presence, downstream of the ingot mold in the direction of extraction of the product, from at least one pair of rollers, called pinch rollers. These have the role of bringing, without actual rolling, the product to its final thickness after it leaves the ingot mold, by only bringing the large faces of the cast product together. The ingot mold, the design of which derives from that of conventional continuous casting ingot molds, does not in fact make it possible to directly obtain the desired small thicknesses. The spacing of the pinch rollers is fixed, in principle, throughout the casting and equal to the thickness desired for the product. They exert their grip on the product so as to bring about the early closure of the liquid well. On leaving the rolls, the product is therefore normally fully solidified throughout its section. In any case, it no longer has a completely liquid heart.
Pour réaliser une réduction d'épaisseur maximale, on a avantage à placer les rouleaux pinceurs immédiatement à la sortie de la lingotière. Toutefois cet emplacement n'est pas sans inconvénients. En particulier, il risque de conduire à un retrait prématuré du produit coulé de la paroi refroidie de la lingotière dans la partie finale de celle-ci, ce qui peut provoquer une percée. On peut donc concevoir des installations dans lesquelles les rouleaux pinceurs sont suffisamment éloignés de la sortie de la lingotière, d'une distance de l'ordre de 1 m par exemple.To achieve a maximum thickness reduction, it is advantageous to place the pinch rollers immediately at the outlet of the mold. However, this location is not without drawbacks. In particular, it risks leading to premature withdrawal of the product poured from the cooled wall of the mold in the final part thereof, which can cause a breakthrough. It is therefore possible to design installations in which the pinch rollers are sufficiently distant from the outlet of the ingot mold, by a distance of the order of 1 m for example.
Un problème à résoudre dans l'exploitation d'une telle machine est le réglage de la profondeur du puits liquide (encore appelé "hauteur métallurgique"). Comme on l'a vu, les rouleaux pinceurs sont conçus pour mettre en forme un produit dont le coeur est encore liquide. Si le puits liquide se ferme en amont des rouleaux pinceurs, ceux-ci doivent donc agir sur un produit qui se trouve entièrement à l'état solide ou pâteux. Pour amener le produit à l'épaisseur désirée, ils devront subir un effort d'écartement sévère de la part du produit, ce qui équivaut en fait à un véritable laminage sur produit solide. Un tel effort, s'il est trop important, ou s'il se répète trop fréquemment et trop longtemps , peut entraîner de graves détériorations des rouleaux eux-mêmes et de leurs organes de maintien. D'autre part, une machine capable de supporter des efforts d'écartement aussi importants serait difficilement compatible en taille avec le reste de l'installation de coulée, du fait de la grande rigidité du bâti qui serait nécessaire. En tout état de cause, son coût serait très supérieur à celui d'une installation normale.A problem to be solved in the operation of such a machine is the adjustment of the depth of the liquid well (also called "metallurgical height"). As we have seen, pinch rollers are designed to shape a product whose core is still liquid. If the liquid well closes upstream of the pinch rollers, these must therefore act on a product which is entirely solid or pasty state. To bring the product to the desired thickness, they will have to undergo a severe spacing effort on the part of the product, which in fact amounts to real rolling on a solid product. Such an effort, if it is too great, or if it is repeated too frequently and for too long, can cause serious damage to the rollers themselves and to their holding members. On the other hand, a machine capable of withstanding such large spacing forces would be hardly compatible in size with the rest of the casting installation, because of the great rigidity of the frame which would be necessary. In any event, its cost would be much higher than that of a normal installation.
Le but de l'invention est de proposer une méthode de réglage rapide de la profondeur du puits liquide, permettant de ramener l'effort subi par les rouleaux pinceurs à sa valeur nominale dès qu'une augmentation anormale de cet effort est constatée.The object of the invention is to propose a method for rapid adjustment of the depth of the liquid well, making it possible to reduce the force undergone by the pinch rollers to its nominal value as soon as an abnormal increase in this force is observed.
A cet effet, l'invention a pour objet un procédé de coulée continue de produits métalliques minces, notamment en acier, dans une installation comprenant une lingotière suivie, dans le sens d'extraction du produit coulé, par des rouleaux pinceurs, destinés à provoquer, par réduction de l'épaisseur dudit produit en cours de coulée, la fermeture du puits de solidification, caractérisé en ce que :
- on mesure la force d'écartement exercée en permanence sur les rouleaux pinceurs par le produit ;
- et, dans une zone située en amont des rouleaux pinceurs, ou entre ceux-ci, on applique au coeur du produit encore liquide un champ magnétique variable, tout en asservissant l'action dudit champ magnétique à la valeur de la force d'écartement mesurée, de manière que celle-ci ne dépasse pas durablement une valeur limite supérieure donnée à l'avance représentative de l'effort tolérable momentanément sans dommages par les rouleaux pinceurs.
- the spreading force permanently exerted on the pinch rollers by the product is measured;
- and, in a zone located upstream of the pinch rollers, or between them, a variable magnetic field is applied to the core of the still liquid product, while controlling the action of said magnetic field to the value of the spacing force measured , so that it does not durably exceed an upper limit value given in advance representative of the force tolerable momentarily without damage by the pinch rollers.
Ce champ magnétique variable peut être mobile et exercer donc une action de brassage sur le coeur liquide du produit coulé, brassage qui, comme on le sait, favorise l'évacuation de la chaleur, ou au contraire être stationnaire et exercer une action de chauffage inductif sur le produit coulé.This variable magnetic field can be mobile and therefore exert a stirring action on the liquid core of the cast product, stirring which, as is known, promotes the evacuation of heat, or on the contrary be stationary and exert an inductive heating action on the cast product.
L'invention a également pour objet un dispositif de coulée continue pour la mise en oeuvre de ce procédé, caractérisé en ce qu'il comporte des moyens de mesure de l'effort d'écartement exercé par le produit coulé sur les rouleaux pinceurs, un inducteur au moins générant un champ magnétique variable dans le produit coulé en amont des rouleaux pinceurs ou entre ceux-ci, et des moyens d'asservissement dudit champ magnétique à la valeur de l'effort d'écartement exercé par le produit sur les rouleaux pinceurs.The invention also relates to a continuous casting device for implementing this process, characterized in that it comprises means for measuring the spacing force exerted by the product poured on the pinch rollers, at least one inductor generating a variable magnetic field in the product poured upstream of the pinch rollers or between them, and means d slaving of said magnetic field to the value of the spreading force exerted by the product on the pinch rollers.
Le ou les inducteurs peuvent être situés entre la lingotière et les rouleaux pinceurs, ou logés dans les rouleaux pinceurs, comme décrit par exemple dans le brevet luxembourgeois n° 67 753 déposé le 07.06.1973 et dont le contenu est incorporé par référence dans la présente description.The inductor (s) can be located between the ingot mold and the pinch rollers, or housed in the pinch rollers, as described for example in Luxembourg patent n ° 67,753 filed on 07.06.1973 and the content of which is incorporated by reference herein description.
Ces inducteurs peuvent imprimer des mouvements de brassage au coeur liquide du produit coulé, ou exercer une action de réchauffage sur le produit coulé.These inductors can impart stirring movements to the liquid core of the cast product, or exert a heating action on the cast product.
Comme on l'aura compris, c'est par l'intermédiaire de l'action de brassage exercée sur le coeur liquide pour faciliter l'évacuation de la surchauffe ou au contraire par l'action de réchauffage exercée sur le produit que l'on règle la profondeur du puits liquide.As will be understood, it is through the stirring action exerted on the liquid core to facilitate the evacuation of the overheating or on the contrary by the reheating action exerted on the product that adjusts the depth of the liquid well.
Le brassage du coeur liquide du produit en cours de coulée est aujourd'hui très largement répandu en coulée continue de produits en acier de formats conventionnels : blooms, billettes et brames d'épaisseur de 200 mm environ. Ses buts habituels sont l'obtention de structures de solidification favorables aux propriétés d'emploi du produit final, telles qu'un forte proportion de section solidifiée en mode équiaxe, et une diminution des ségrégations. Mais le brassage joue aussi un rôle dans l'évacuation des calories du métal : celle-ci est d'autant plus rapide que la mise en mouvement du métal liquide est plus intense.The mixing of the liquid core of the product during casting is today very widespread in continuous casting of steel products of conventional formats: blooms, billets and slabs with a thickness of approximately 200 mm. Its usual aims are to obtain solidification structures favorable to the properties of use of the final product, such as a high proportion of solidified section in equiaxial mode, and a reduction in segregation. However, stirring also plays a role in the removal of calories from the metal: this is all the more rapid as the setting in motion of the liquid metal is more intense.
Toutes choses étant égales par ailleurs, une augmentation de l'action de brassage du coeur liquide tend donc à accélérer la solidification du produit et à faire remonter le point de fermeture du puits liquide. Inversement, une diminution de l'action de brassage tend à retarder la solidification du produit et à faire descendre le point de fermeture du puits liquide.All other things being equal, an increase in the stirring action of the liquid core therefore tends to accelerate the solidification of the product and to raise the closing point of the liquid well. Conversely, a decrease in the stirring action tends to delay the solidification of the product and bring down the closing point of the liquid well.
En coulée continue de produits de forte section, cet effet du brassage sur le refroidissement du produit n'a qu'une importance relativement secondaire, dans la mesure où le refroidissement est principalement assuré, en dessous de la lingotière, au moyen d'un fluide refroidissant projeté sur la surface du produit. D'autre part, on ne cherche pas à régler avec une grande précision le point de fermeture du puits liquide, qui se situe généralement à plusieurs mètres sous la lingotière. En revanche, dans la coulée de brames minces, la plus faible épaisseur du coeur liquide rend celui-ci très sensible à tous les phénomènes qui peuvent accélerer sa solidification, et notamment aux mouvements de convection forcée tels que ceux induits par un champ magnétique mobile. En établissant de tels mouvements en permanence au sein du coeur liquide et en modulant leur intensité, on se donne donc une possibilité de réglage de la profondeur du puits de solidification sans intervenir sur les paramètres de fonctionnement de la machine. On a vu que, dans le cas de la coulée continue de brames minces avec rouleaux pinceurs éloignés de la lingotière, un tel réglage était d'une très grande importance. Cette possibilité peut s'ajouter ou se substituer à d'autres moyens de refroidissement du produit agissant à partir de sa surface, telle que la projection d'un fluide refroidissant. Elle présente l'avantage d'agir directement sur le coeur liquide et de procurer un temps de réaction bref.In continuous casting of products of large cross-section, this effect of stirring on the cooling of the product is only of relatively secondary importance, since the cooling is mainly ensured, below the mold, by means of a cooling fluid sprayed onto the surface of the product. On the other hand, no attempt is made to adjust with great precision the point of closure of the liquid well, which is generally located several meters below the ingot mold. On the other hand, in the casting of thin slabs, the smaller thickness of the liquid core makes it very sensitive to all the phenomena which can accelerate its solidification, and in particular to forced convection movements such as those induced by a mobile magnetic field. By establishing such movements permanently within the liquid core and by modulating their intensity, there is therefore a possibility of adjusting the depth of the solidification well without intervening in the operating parameters of the machine. We have seen that, in the case of the continuous casting of thin slabs with pinch rollers distant from the mold, such an adjustment was of very great importance. This possibility can be added to or substituted for other means of cooling the product acting from its surface, such as the projection of a cooling fluid. It has the advantage of acting directly on the liquid core and of providing a short reaction time.
L'intensité du brassage est modulée en fonction de la mesure de l'effort exercé par le produit sur les rouleaux pinceurs, dont l'écartement est, en marche normale, maintenu constant et égal à l'épaisseur désirée pour le produit. Les rouleaux pinceurs sont conçus pour subir une force, dont la valeur F, que l'on mesure au moyen de capteurs de manière continue ou à des intervalles de temps rapprochés, correspond à la fermeture du puits liquide. Si F devient supérieure à sa valeur normale, c'est l'indice que les rouleaux pinceurs subissent un effort de la part d'un produit dont le coeur ne se trouve déjà plus à l'état liquide. Un tel écart par rapport au fonctionnement normal de la machine peut être dû à des facteurs tels qu'une diminution volontaire ou non de la vitesse de coulée, une baisse de la température du métal liquide alimentant la lingotière, etc... Le début et la fin de la coulée, pendant lesquelles la température du métal liquide et la vitesse de défilement du produit peuvent varier dans des proportions importantes, constituent également des périodes critiques. En effet, il est alors difficile d'ajuster les paramètres de fonctionnement de la machine de manière à situer en permanence le point de fermeture du puits liquide au niveau souhaitable. La possibilité d'influer sur la vitesse de solidification du métal par l'intermédiaire de l'intensité du brassage du coeur liquide procure à l'opérateur un moyen d'action supplémentaire pour maîtriser le fonctionnement de la machine.The intensity of the stirring is modulated as a function of the measurement of the force exerted by the product on the pinch rollers, the spacing of which, in normal operation, is kept constant and equal to the thickness desired for the product. The pinch rollers are designed to undergo a force, the value of which, which is measured by sensors continuously or at close time intervals, corresponds to the closing of the liquid well. If F becomes greater than its normal value, it is the indication that the pinch rollers undergo an effort on the part of a product whose core is no longer in the liquid state. Such a deviation from normal operation of the machine may be due to factors such as a voluntary reduction or not in the casting speed, a drop in the temperature of the liquid metal feeding the ingot mold, etc. The start and the end of the casting, during which the temperature of the liquid metal and the speed of movement of the product can vary in significant proportions, also constitute critical periods. Indeed, it is then difficult to adjust the operating parameters of the machine so as to permanently locate the closing point of the liquid well at the desirable level. The possibility to influence the speed of solidification of the metal by means of the intensity of stirring of the liquid core provides the operator with an additional means of action for controlling the operation of the machine.
Un exemple de mise en oeuvre du procédé va à présent être décrit. Au moyen de modélisations mathématiques et d'essais sur la machine, on détermine pour des conditions de coulée données (format du produit, vitesse de coulée, température du métal liquide alimentant la lingotière, etc...) quels paramètres de fonctionnement du dispositif de brassage du coeur liquide permettent en principe à la fermeture du puits liquide d'intervenir au niveau le plus favorable, c'est-à-dire au niveau des rouleaux pinceurs. Par ailleurs, on se fixe pour F deux valeurs seuils Fo et F1. Fo est une valeur en dessous de laquelle l'effort est jugé anormalement faible et traduit un risque de non-fermeture du puits liquide. F1 est une valeur au delà de laquelle on considère que l'effort subi par les rouleaux est trop important et ne doit pas être soutenu en permanence. Si cette valeur F1 est atteinte, cela signifie que le puits de solidification se ferme trop tôt. En conséquence, l'opérateur diminue par paliers l'intensité du brassage électromagnétique de manière à réduire les mouvements du métal pour ralentir sa solidification. Après chaque diminution incrémentale, l'effort exercé sur les rouleaux est mesuré. Si il demeure supérieur à F1, une nouvelle diminution de l'intensité du brassage est effectué. Si il est compris entre Fo et F1, la nouvelle intensité du brassage est maintenue jusqu'à ce que, éventuellement, un retour à la normale des conditions de coulée rende cette intensité de brassage insuffisante et déplace le point de fermeture du puits liquide en dessous des rouleaux princeurs. Un tel déplacement doit se traduire par un effort inférieur à Fo, et il est alors nécessaire d'augmenter l'intensité de brassage pour ramener l'effort dans l'intervalle [Fo, F1].An example of implementation of the method will now be described. By means of mathematical modeling and tests on the machine, it is determined for given casting conditions (product format, casting speed, temperature of the liquid metal feeding the ingot mold, etc.) which operating parameters of the mixing of the liquid core in principle allows the closing of the liquid well to intervene at the most favorable level, that is to say at the level of the pinch rollers. Furthermore, we set for F two threshold values Fo and F1. Fo is a value below which the force is considered abnormally low and indicates a risk of non-closing of the liquid well. F1 is a value beyond which it is considered that the force undergone by the rollers is too great and must not be constantly supported. If this value F1 is reached, this means that the solidification well closes too early. Consequently, the operator gradually decreases the intensity of the electromagnetic stirring so as to reduce the movements of the metal to slow down its solidification. After each incremental decrease, the force exerted on the rollers is measured. If it remains greater than F1, a further decrease in the intensity of the mixing is carried out. If it is between Fo and F1, the new intensity of stirring is maintained until, possibly, a return to normal of the pouring conditions makes this stirring intensity insufficient and moves the closing point of the liquid well below princely rolls. Such a displacement must result in an effort less than Fo, and it is then necessary to increase the intensity of stirring to bring the effort into the interval [Fo, F1].
Par ailleurs, on peut se fixer une valeur seuil F2 supérieure à F1, au delà de laquelle on considère que l'effort tendant à écarter les rouleaux pinceurs ne doit impérativement pas être supporté plus de quelques instants. Le franchissement de ce seuil F2 doit alors entraîner non seulement une diminution importante et brutale de l'intensité du brassage, mais encore un écartement des rouleaux par paliers. Après chaque palier, la force supportée par les rouleaux est mesurée. Si elle demeure supérieure à F2, l'écartement des rouleaux est augmenté. Lorsqu'elle devient inférieure à F2, les rouleaux sont alors rapprochés. Ensuite, si la force redevient supérieure à F2, les rouleaux sont à nouveau écartés. Si, au contraire, après un rapprochement des rouleaux, la force demeure inférieure à F2, le rapprochement est poursuivi, et ainsi de suite jusqu'à ce que les rouleaux soient revenus à leur écartement nominal, avec une force inférieure à F2. A partir de là, pour ramener la force à une valeur comprise entre Fo et F1, on ne joue plus que sur l'intensité du brassage.Furthermore, it is possible to set a threshold value F2 greater than F1, beyond which it is considered that the force tending to spread the pinch rollers must imperatively not be supported for more than a few moments. The crossing of this threshold F2 must then lead not only to a significant and abrupt reduction in the intensity of stirring, but also to a separation of the rollers in stages. After each level, the force supported by the rollers is measured. If it remains greater than F2, the spacing of the rollers is increased. When it becomes less than F2, the rollers are then brought together. Then, if the force becomes greater than F2, the rollers are again moved aside. If, on the contrary, after bringing the rollers closer together, the force remains below F2, the approximation is continued, and so on until the rollers have returned to their nominal spacing, with a force lower than F2. From there, to reduce the force to a value between Fo and F1, we only play on the intensity of the mixing.
Pour tenir compte de l'inertie de l'action du champ magnétique, on peut également se fixer une valeur d'avertissement F3 inférieure à F1 telle que, lorsque en augmentant, l'effort d'écartement atteint F3, on opère la modification de l'action du champ magnétique. On peut ainsi anticiper un franchissement du seuil F1 et diminuer les risques de détérioration de la machine. Symétriquement, on peut fixer une valeur d'avertissement F4 supérieure à Fo telle que, lorsque en diminuant, l'effort d'écartement atteint F4, on opère la modification du champ magnétique. On limite ainsi encore un peu plus les risques de défauts dans le produit, qui seraient dus à une fermeture trop tardive du puits liquide.To take account of the inertia of the magnetic field action, it is also possible to set a warning value F3 less than F1 such that, when increasing, the spreading force reaches F3, the modification of the action of the magnetic field. We can thus anticipate crossing the threshold F1 and reduce the risk of damage to the machine. Symmetrically, one can set a warning value F4 greater than Fo such that, when decreasing, the spreading force reaches F4, the magnetic field is modified. This further limits the risk of defects in the product, which would be due to too late closing of the liquid well.
Les organes qui contrôlent l'intensité du brassage et l'écartement des rouleaux pinceurs sont commandés par l'opérateur ou l'unité de traitement de l'information qui gère le fonctionnement de la machine de coulée, d'après les informations fournies par les instruments de mesure nécessaires : mesures de l'effort sur les rouleaux de l'écartement des rouleaux, des paramètres électriques des brasseurs électromagnétiques, de la vitesse de coulée, etc...The organs which control the intensity of the stirring and the spacing of the pinch rollers are controlled by the operator or the data processing unit which manages the operation of the casting machine, according to the information provided by the necessary measuring instruments: measurements of the force on the rollers, the distance between the rollers, the electrical parameters of the electromagnetic stirrers, the casting speed, etc.
Les brasseurs électromagnétiques à champ glissant utilisables peuvent appartenir aux différents types de brasseurs connus, imprimant au métal des mouvements de translation verticaux ou perpendiculaires à la direction d'extraction, selon les grandes faces du produit ou des mouvements de rotation. Avantageusement, mais non exclusivement, ils sont du type dit "rouleaux brasseurs", décrits par exemple dans le brevet FR 2187468 au nom de la demanderesse. Ils sont alors inclus dans des rouleaux qui servent, par ailleurs, à soutenir le produit (sans le comprimer) entre la partie inférieure de la lingotière et les rouleaux pinceurs. Des brasseurs plans, disposés en regard des grandes faces du produit dans cette même zone de la machine peuvent également être utilisés.The electromagnetic stirrers with a sliding field that can be used can belong to the various known types of stirrers, imparting vertical translational movements to the metal or perpendicular to the direction of extraction, according to the large faces of the product or rotational movements. Advantageously, but not exclusively, they are of the type known as "brewing rollers", described for example in
La figure unique annexée schématise un exemple d'installation de coulée continue de brames minces selon l'invention, vue en coupe et de profil. Le produit coulé 1 sort de la lingotière 2, alimentée en métal liquide par la busette 3, à l'état partiellement solidifié : le coeur 4 est à l'état liquide, et il est enserré par une couche périphérique 5 à l'état pâteux ou entièrement solidifié, dont l'épaisseur croît au fur et à mesure que le produit progresse dans la machine en se solidifiant. L'installation comporte une paire de rouleaux pinceurs 6, 6′ en rotation libre ou asservie dans le sens indiqué par les flèches, placés à une certaine distance de la lingotière, hors de son voisinage immédiat. Ces rouleaux réduisent l'épaisseur du produit jusqu'à la valeur désirée en rapprochant les couches de métal qui ont commencé à se solidifier sur les grandes faces de la lingotière, de manière à fermer le puits liquide. Ils sont munis de moyens 7,7′ permettant de régler leur écartement, et de maintenir celui-ci à une valeur déterminée. L'installation comporte également des moyens de brassage électromagnétique du coeur liquide 4. Ils peuvent être constitués, comme représenté sur la figure, par une paire de brasseurs plans polyphasés 8, 8′ disposés en regard des grandes faces du produit, entre le bas de la lingotière et les rouleaux pinceurs et générant un champ magnétique glissant. Des capteurs mesurent les efforts de laminage F et F′ exercés par le produit respectivement sur les rouleaux pinceurs 6 et 6′, et transmettent les résultats de ces mesures à une unité de traitement de l'information 9. Cette unité commande, en fonction des informations transmises par les capteurs, les paramètres de fonctionnement des brasseurs qui déterminent l'intensité des mouvements à l'intérieur du coeur liquide, et ce de façon permanente. D'autre part, cette unité commande également l'écartement des rouleaux pinceurs dans les cas où la force de laminage exercée sur l'un d'eux par le produit dépasse le seuil F2 précédemment défini.The single appended figure shows schematically an example of installation for continuous casting of thin slabs according to the invention, seen in section and in profile. The poured product 1 leaves the
En plus ou à la place des brasseurs situés entre le bas de la lingotière et les rouleaux pinceurs, il est également possible d'utiliser des brasseurs inclus dans la lingotière. Toutefois, comme ils doivent agir sur un coeur liquide d'un volume relativement important et comme ils sont situés assez loin du fond du puits liquide, ces brasseurs en lingotière risquent d'être insuffisants pour assurer à eux seuls une variation suffisamment brutale de la vitesse de solidification du coeur liquide.In addition to or instead of the brewers located between the bottom of the mold and the pinch rollers, it is also possible to use brewers included in the mold. However, since they must act on a liquid core of a relatively large volume and since they are located far enough from the bottom of the liquid well, these Brewers in an ingot mold may be insufficient to ensure alone a sufficiently sudden variation in the speed of solidification of the liquid core.
Une autre varaiante consiste à loger les inducteurs dans les rouleaux pinceurs eux-mêmes, rendus tubulaires à cette fin. Ils sont alors particulièrement bien adaptés à une accélération de la solidification dans le cas où le puits liquide se referme en dessous des rouleaux pinceurs. Ils peuvent d'ailleurs ne brasser la métal liquide que dans ce dernier cas, ou être actifs en permanence comme les dispositifs précédemment décrits. Ils peuvent être employés seuls ou en combinaison avec d'autres dispositifs d'agitation du coeur liquide.Another variant consists in housing the inductors in the pinch rollers themselves, made tubular for this purpose. They are then particularly well suited to an acceleration of solidification in the case where the liquid well closes below the pinch rollers. They can also stir the liquid metal only in the latter case, or be permanently active like the devices described above. They can be used alone or in combination with other agitation devices for the liquid heart.
Enfin, il est possible de remplacer une partie ou la totalité des inducteurs à champ mobile assurant le brassage du coeur liquide par des inducteurs à champ variable mais stationnaire, dont le rôle est d'apporter en permanence ou de façon intermittente un flux de chaleur au coeur liquide. Ce flux de chaleur peut être modulé de façon à maintenir la fermeture du puits liquide au niveau des rouleaux pinceurs. Il est augmenté lorsque le puits liquide se referme en amont des rouleaux pinceurs, et diminué lorsque le puits liquide se referme en dessous de rouleaux pinceurs. Un tel dispositif est particulièrement avantageux à implanter à l'intérieur des rouleaux pinceurs, puisqu'il peut alors agir dans la zone même où son effet doit être prioritairement ressenti.Finally, it is possible to replace some or all of the moving field inductors ensuring the mixing of the liquid core by variable but stationary field inductors, the role of which is to provide a permanent or intermittent flow of heat to the liquid heart. This heat flow can be modulated so as to keep the liquid well closed at the pinch rollers. It is increased when the liquid well closes upstream of the nip rollers, and decreased when the liquid well closes below the nip rollers. Such a device is particularly advantageous to implant inside the pinch rollers, since it can then act in the same area where its effect must be felt as a priority.
Claims (10)
- Process for the continuous casting of thin metal products, particularly steel products, in an installation comprising an ingot mould (2) followed, in the direction of withdrawal of the cast product, by squeezing rolls (6,6′) intended to cause, by a reduction of the thickness of the said product, the closing of the solidification pool, characterized in that:- the separation force exerted on the squeezing rolls by the product is measured;- and, in a zone located upstream of the squeezing rolls or between the latter, a variable magnetic field is applied to the still molten core of the product, matching the action of the said magnetic field to the value of the separation force measured so that the latter does not exceed, over a long period, an upper limit value given in advance and representing the force that the squeezing rolls can tolerate temporarily without damage.
- Process according to Claim 1, characterized in that the magnetic field is a stationary variable magnetic field, having an inductive heating effect on the product.
- Process according to Claim 1, characterized in that the magnetic field is a variable magnetic field which is mobile in translation, having a stirring effect on the molten core of the product.
- Process according to Claims 1 to 3, characterized in that the action of the said magnetic field is matched to the value of the rolling force measured so that the latter is maintained between two values which are fixed in advance: an upper limit value F1, representing the separation force which is not to be exceeded over a long period in order not to damage the rolls, and a lower limit value Fo, representing the presence downstream of the rolls of a core of the product which is still molten.
- Process according to Claim 4, characterized in that, if the separation force exceeds a fixed value F2 which is greater than or equal to the said limit value F1, the separation of the rolls is increased by increments so as to bring the separation force back to a value which is less than F1, and the separation of the rolls is then brought back, in stages, to its nominal value, by ensuring that the separation force does not exceed the value F2.
- Process according to Claim 4, characterized in that, in order to take into account the inertia of the action of the magnetic field, when the separation force, when increasing, reaches a fixed warning value F3 which is less than F1, the action of the magnetic field is modified.
- Process according to Claim 4, characterized in that in order to take into account the inertia of the action of the magnetic field, when the separation force, when decreasing, reaches a fixed warning value F4 which is greater than Fo, the action of the magnetic field is modified.
- Device for the continuous casting of thin metal products, particularly steel products, of the type comprising an ingot mould (2) followed, in the direction of withdrawal of the cast product, by squeezing rolls intended to cause, by reduction of the thickness of the product, the closing of the solidification pool, characterized in that it also comprises:- means for measuring the separation force exerted by the cast product on the squeezing rolls (6, 6′),- inductors, (8,8′) housed in at least one of the squeezing rolls or upstream of the latter and which can generate a variable magnetic field in the part of the cast product which is still molten, located upstream of the squeezing rolls (6,6′) or between these,- and means (9) for matching the said inductors to the separation force exerted by the product on the squeezing rolls in order to prevent this force exceeding over a long period an upper limit value given in advance and representing the force that the squeezing rolls can tolerate temporarily without damage.
- Device according to Claim 8, characterized in that the inductor is a multiphase sliding-field inductor.
- Device according to Claim 8, characterized in that the inductor is a single-phase induction coil.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8904862 | 1989-04-06 | ||
FR8904862A FR2645462B1 (en) | 1989-04-06 | 1989-04-06 | PROCESS AND DEVICE FOR OBTAINING THIN METAL PRODUCTS BY CONTINUOUS CASTING |
Publications (2)
Publication Number | Publication Date |
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EP0391822A1 EP0391822A1 (en) | 1990-10-10 |
EP0391822B1 true EP0391822B1 (en) | 1992-09-02 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP90470007A Expired - Lifetime EP0391822B1 (en) | 1989-04-06 | 1990-03-16 | Method and apparatus for manufacturing thin metal products by continuous casting |
Country Status (16)
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US (1) | US5027884A (en) |
EP (1) | EP0391822B1 (en) |
JP (1) | JPH02295659A (en) |
KR (1) | KR900015838A (en) |
AT (1) | ATE80072T1 (en) |
CA (1) | CA2013853A1 (en) |
CS (1) | CS163790A2 (en) |
DD (1) | DD293284A5 (en) |
DE (1) | DE69000282T2 (en) |
DK (1) | DK0391822T3 (en) |
ES (1) | ES2035737T3 (en) |
FR (1) | FR2645462B1 (en) |
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HU (1) | HU208267B (en) |
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US5518064A (en) * | 1993-10-07 | 1996-05-21 | Norandal, Usa | Thin gauge roll casting method |
CN108856662B (en) * | 2018-06-21 | 2020-12-01 | 中国科学院宁波材料技术与工程研究所 | Method for preparing Fe-based nanocrystalline alloy strip |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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DE1583608A1 (en) * | 1967-09-09 | 1970-08-20 | Demag Ag | Continuous casting device for metals, especially steel |
US3882923A (en) * | 1972-06-08 | 1975-05-13 | Siderurgie Fse Inst Rech | Apparatus for magnetic stirring of continuous castings |
FR2352611A1 (en) * | 1976-05-28 | 1977-12-23 | Siderurgie Fse Inst Rech | Detection of liq. zone in continuous casting - by creating magnetic field and comparing with reference value |
JPS59159934A (en) * | 1983-03-02 | 1984-09-10 | Kawasaki Steel Corp | Continuous casting method of blank material for producing directional silicon steel plate |
JPS60148651A (en) * | 1984-01-13 | 1985-08-05 | Kawasaki Steel Corp | Continuous casting machine |
JPS60238001A (en) * | 1984-05-09 | 1985-11-26 | Ishikawajima Harima Heavy Ind Co Ltd | Continuous production of thin sheet |
JPS61132247A (en) * | 1984-11-30 | 1986-06-19 | Kawasaki Steel Corp | Continuous casting method |
JPS62263854A (en) * | 1986-05-12 | 1987-11-16 | Kawasaki Steel Corp | Prevention method for molten steel spout-out from end part of continuous casting slab |
-
1989
- 1989-04-06 FR FR8904862A patent/FR2645462B1/en not_active Expired - Fee Related
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1990
- 1990-03-16 ES ES199090470007T patent/ES2035737T3/en not_active Expired - Lifetime
- 1990-03-16 EP EP90470007A patent/EP0391822B1/en not_active Expired - Lifetime
- 1990-03-16 DK DK90470007.7T patent/DK0391822T3/en active
- 1990-03-16 DE DE9090470007T patent/DE69000282T2/en not_active Expired - Fee Related
- 1990-03-16 AT AT90470007T patent/ATE80072T1/en not_active IP Right Cessation
- 1990-04-02 HU HU902045A patent/HU208267B/en not_active IP Right Cessation
- 1990-04-03 US US07/503,864 patent/US5027884A/en not_active Expired - Fee Related
- 1990-04-03 CS CS901637A patent/CS163790A2/en unknown
- 1990-04-04 CA CA002013853A patent/CA2013853A1/en not_active Abandoned
- 1990-04-04 RU SU904743487A patent/RU1795927C/en active
- 1990-04-06 JP JP2091968A patent/JPH02295659A/en active Pending
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- 1990-04-06 PL PL28467890A patent/PL284678A1/en unknown
- 1990-04-06 KR KR1019900004728A patent/KR900015838A/en not_active Application Discontinuation
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1992
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ATE80072T1 (en) | 1992-09-15 |
EP0391822A1 (en) | 1990-10-10 |
US5027884A (en) | 1991-07-02 |
JPH02295659A (en) | 1990-12-06 |
DD293284A5 (en) | 1991-08-29 |
FR2645462B1 (en) | 1991-05-31 |
PL284678A1 (en) | 1991-08-26 |
DK0391822T3 (en) | 1992-12-21 |
ES2035737T3 (en) | 1993-04-16 |
CS163790A2 (en) | 1991-10-15 |
HU902045D0 (en) | 1990-08-28 |
RU1795927C (en) | 1993-02-15 |
DE69000282D1 (en) | 1992-10-08 |
DE69000282T2 (en) | 1993-02-11 |
HU208267B (en) | 1993-09-28 |
FR2645462A1 (en) | 1990-10-12 |
HUT57100A (en) | 1991-11-28 |
GR3006443T3 (en) | 1993-06-21 |
KR900015838A (en) | 1990-11-10 |
CA2013853A1 (en) | 1990-10-06 |
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