EP0382702B1 - Method of manufacturing a thin steel slab by continuous casting - Google Patents

Method of manufacturing a thin steel slab by continuous casting Download PDF

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Publication number
EP0382702B1
EP0382702B1 EP90870018A EP90870018A EP0382702B1 EP 0382702 B1 EP0382702 B1 EP 0382702B1 EP 90870018 A EP90870018 A EP 90870018A EP 90870018 A EP90870018 A EP 90870018A EP 0382702 B1 EP0382702 B1 EP 0382702B1
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EP
European Patent Office
Prior art keywords
slab
less
cooling
thin
process according
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EP90870018A
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German (de)
French (fr)
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EP0382702A2 (en
EP0382702A3 (en
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Stéphan Wilmotte
Paul Naveau
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Centre de Recherches Metallurgiques CRM ASBL
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Centre de Recherches Metallurgiques CRM ASBL
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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
    • B22D11/124—Accessories for subsequent treating or working cast stock in situ for cooling

Definitions

  • the present invention relates to a method for manufacturing a thin steel slab by continuous casting according to the preamble of claim 1.
  • a thin slab is a rectangular product having the usual width of a continuous casting slab, but whose thickness is less than 100 mm and more precisely is between 60 mm and 20 mm.
  • the continuously cast slabs have a significantly greater thickness, which is generally of the order of 200 mm. They are intended for the manufacture of flat products, such as strips or sheets of various thicknesses.
  • the classic way of this production consists in reducing the thickness of the slab to the desired final value, by a series of rolling operations ranging from roughing to finishing. These multiple rolling operations require prior reheating, powerful and bulky installations, and are ultimately very expensive.
  • a thin slab constitutes an intermediate product the production of which requires the execution of several of the abovementioned operations, namely at least the roughing operations.
  • the casting speed of current continuous casting machines is limited to around 3 m / min. It will be recalled that the casting speed is in fact the speed with which the slab is extracted from the casting mold. On the one hand, it is necessary to ensure the formation of a solidified skin of sufficient thickness at the outlet of the mold and on the other hand to guarantee the complete solidification of the slab before cutting and preferably before the straightening point.
  • the casting speed could be increased while ensuring the formation of the required solidified skin, by appropriately increasing the length of the mold.
  • this increases the friction forces on the slab and increases the risk of breakthrough by tearing the solidified skin.
  • An increase in the casting speed also leads to an increase in the metallurgical length, that is to say the length of the liquid well. To keep this metallurgical length within the desired limits, it is therefore necessary to ensure complete solidification of the slab in a shorter time. In this respect, an increase in the length of watered has little effect; on the other hand, an increase in the flow rate of the nozzles in the secondary cooling zone intensifies the cooling and reheating cycles to which the skin of the slab is subjected alternately and increases the risk of cracking of the solidified skin.
  • secondary cooling should be applied for a time and / or with an intensity allowing the formation of a solidified skin having a sufficient thickness.
  • the object of the present invention is to propose a method for manufacturing a thin steel slab by continuous casting, which allows on the one hand to substantially increase the casting speed while avoiding the aforementioned drawbacks and on the other hand to eliminate several of the costly rolling operations mentioned above.
  • the method of the invention also makes it possible to manufacture a thin slab capable of directly feeding a hot rolling train of steel strips.
  • a method of manufacturing a thin steel slab by continuous casting in which the steel is poured into a mold where it undergoes primary cooling, and at least the outlet section of which has a smaller width or equal to 60 mm, extracts from the mold a slab having a thickness less than 60 mm and having a solidified skin, then submits the slab to a secondary cooling during which an uninterrupted layer of pressurized coolant is formed on at least part of the surface of the slab and ensures the flow of coolant over the surface of the slab in the direction of progression -ci, is characterized in that the thin slab is cooled, during secondary cooling, to a surface temperature below 800 ° C and preferably below 600 ° C.
  • this layer of coolant allows the application on the outer face of the solidified skin, of a pressure at least partially compensating for the ferrostatic pressure existing on the inner face and of this fact achieves support for this skin.
  • the pressure applied by the liquid layer on the product can be adjusted between 0.2 bar and 2 bar.
  • the casting speed is greater than 3 m / min, and preferably between 6 m / min and 20 m / min.
  • said uninterrupted layer of coolant is kept under pressure for a period such that the solidified thickness is at least equal to 5 mm, and preferably greater than 7 mm for a slab of 20 mm thick. and 10 mm for a slab 40 mm thick.
  • cooling according to the invention therefore makes it possible to increase the casting speed, without risk of breakthrough, while retaining the same metallurgical length.
  • the surface temperature of the slab is substantially between 750 ° C and 900 ° C. This temperature level is much lower than that which is encountered with traditional cooling by sprinklers, where the temperature is usually of the order of 1150 ° C. to 1250 ° C.
  • An additional feature is to laminate the thin slab into a hot strip, either while the core is still in a pasty state, or immediately after the slab is fully solidified, said rolling preferably being carried out continuously.
  • FIG 1 illustrates the principle of the method of the invention by means of an implementation device, shown very schematically.
  • This ingot mold 1 is conventionally made of copper and cooled with water. It can also be in the form of 2 wheels or 2 strips, cooled with water between which the steel flows.
  • the steel undergoes primary cooling (zone A) which causes a thin surface film to solidify, then it leaves the mold 1 in the form of a thin slab 2, 40 mm thick, with a thin solid film with a thickness of at least 3 mm.
  • the slab 2 then enters the secondary cooling zone B where it is subjected to intense and continuous cooling by means of an uninterrupted layer 3 of pressurized coolant liquid.
  • This layer 3 is here formed by means of a device 4 known per se, which is not part of the present invention and which it is not necessary to describe in detail. However, it should be noted that this device does not touch the slab at any point and that it does not therefore cause any friction force.
  • the secondary cooling zone B is symbolized here by a single device 4; it goes without saying that this zone B could, as necessary, comprise several separate devices 4, possibly separated by support rollers.
  • the slab 2 At the exit from the secondary cooling zone B, the slab 2 has a thicker solidified skin and the cooling by the pressurized liquid ceases. The slab then moves in the air while continuing its solidification (zone C).
  • the slab 2 can then be transmitted, preferably directly, to a hot rolling stand symbolized by the cylinders 5.
  • Figure 2 illustrates the evolution of the surface temperature of the slab (T s - left vertical axis) and the thickness of the solidified skin (e - right vertical axis) as a function of the distance from the meniscus (L - horizontal axis).
  • Curves (b) and (d) show that the metallurgical length is the same in both cases.
  • Figure 2 shows that conventional secondary cooling has little effect on the temperature reached at the outlet of the ingot mold (curve a); surface temperature at the point of solidification total is of the order of 1200 ° C. This very high value, as well as the low speed value, are unfavorable elements for direct rolling.
  • cooling according to the invention causes a rapid reduction in this surface temperature, followed by heating in zone C to a temperature of around 850 ° C (curve c), which, combined with a high casting speed is a favorable element for direct rolling of the slab.
  • the method of the invention therefore makes it possible to manufacture thin steel slabs by continuous casting at a speed significantly higher than the usual speed, and to supply these slabs under temperature and structural conditions favorable to direct rolling.
  • the slabs thus produced are less prone to segregation.
  • their manufacture by the process of the invention makes it possible to avoid numerous rolling operations, in particular roughing, as well as the reheating which precedes them.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Metal Rolling (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

The steel is cast in a mould (1), at least the exit section of which has a width which is less than or equal to 60 mm, and a slab (2) having a thickness of less than 60 mm and possessing a solidified skin is removed from this mould. The slab undergoes a secondary cooling, during which an uninterrupted layer of pressurised cooling liquid (3) is formed on at least one part of the surface of the slab, and the cooling liquid is caused to flow over the surface of the slab in the direction of progression of the latter. The casting speed is greater than 3 m/min and is preferably between 6 m/min and 20 m/min. The slab is cooled, during the secondary cooling, to a surface temperature which is less than 800 DEG C and preferably less than 600 DEG C. The thin slab may be directly hot-rolled. <IMAGE>

Description

La présente invention concerne un procédé de fabrication d'une brame mince en acier par coulée continue selon le préambule de la revendication 1.The present invention relates to a method for manufacturing a thin steel slab by continuous casting according to the preamble of claim 1.

Au sens de la présente invention, une brame mince est un produit parallélépipédique ayant la largeur usuelle d'une brame de coulée continue, mais dont l'épaisseur est inférieure à 100 mm et plus précisément est comprise entre 60 mm et 20 mm.Within the meaning of the present invention, a thin slab is a rectangular product having the usual width of a continuous casting slab, but whose thickness is less than 100 mm and more precisely is between 60 mm and 20 mm.

Actuellement, les brames coulées en continu ont une épaisseur nettement supérieure, qui est généralement de l'ordre de 200 mm. Elles sont destinées à la fabrication de produits plats, tels que des bandes ou des tôles d'épaisseurs diverses. La voie classique de cette fabrication consiste à réduire l'épaisseur de la brame jusqu'à la valeur finale désirée, par une série d'opérations de laminage allant du dégrossissage à la finition. Ces multiples opérations de laminage exigent un réchauffage préalable, des installations puissantes et encombrantes, et sont en définitive très coûteuses.Currently, the continuously cast slabs have a significantly greater thickness, which is generally of the order of 200 mm. They are intended for the manufacture of flat products, such as strips or sheets of various thicknesses. The classic way of this production consists in reducing the thickness of the slab to the desired final value, by a series of rolling operations ranging from roughing to finishing. These multiple rolling operations require prior reheating, powerful and bulky installations, and are ultimately very expensive.

Dans cette voie classique, une brame mince constitue un produit intermédiaire dont l'obtention nécessite l'exécution de plusieurs des opérations précitées, à savoir au moins les opérations de dégrossissage.In this conventional way, a thin slab constitutes an intermediate product the production of which requires the execution of several of the abovementioned operations, namely at least the roughing operations.

Par ailleurs, la vitesse de coulée des machines de coulée continue actuelles est limitée à environ 3 m/min. On rappelle que la vitesse de coulée est en fait la vitesse avec laquelle la brame est extraite du moule de coulée. Il faut en effet d'une part assurer la formation d'une peau solidifiée d'une épaisseur suffisante à la sortie du moule et d'autre part garantir la solidification complète de la brame avant la découpe et de préférence avant le point de redressement.Furthermore, the casting speed of current continuous casting machines is limited to around 3 m / min. It will be recalled that the casting speed is in fact the speed with which the slab is extracted from the casting mold. On the one hand, it is necessary to ensure the formation of a solidified skin of sufficient thickness at the outlet of the mold and on the other hand to guarantee the complete solidification of the slab before cutting and preferably before the straightening point.

Dans le cas particulier de la coulée continue des brames minces, diverses technologies ont récemment vu le jour qui permettent d'atteindre des vitesses de coulée plus élevées que dans le cas des brames classiques; ainsi une technologie, décrite dans 'Iron and Steel Engineer', May 1987, p. 51, permet, notamment grâce à un moule spécial, d'obtenir une vitesse de coulée de 5 à 6 m/min pour une brame de 50 mm d'épaisseur.In the particular case of continuous casting of thin slabs, various technologies have recently emerged which make it possible to achieve higher casting speeds than in the case of conventional slabs; thus a technology, described in 'Iron and Steel Engineer', May 1987, p. 51, allows, in particular thanks to a special mold, to obtain a casting speed of 5 to 6 m / min for a slab of 50 mm thick.

En principe, on pourrait augmenter la vitesse de coulée tout en assurant la formation de la peau solidifiée requise, en augmentant de façon appropriée la longueur du moule. Toutefois, on augmente ainsi les efforts de frottement sur la brame et on multiple les risques de percée par déchirure de la peau solidifiée.In principle, the casting speed could be increased while ensuring the formation of the required solidified skin, by appropriately increasing the length of the mold. However, this increases the friction forces on the slab and increases the risk of breakthrough by tearing the solidified skin.

Une augmentation de la vitesse de coulée entraîne également un accroissement de la longueur métallurgique, c'est-à-dire de la longueur du puits liquide. Pour maintenir cette longueur métallurgique dans les limites désirées, il faut donc assurer la solidification complète de la brame en un temps plus court. A cet égard, une augmentation de la longueur arrosée n'a que peu d'effet; d'autre part, un accroissement du débit des gicleurs dans la zone de refroidissement secondaire intensifie les cycles de refroidissement et de réchauffage auxquels la peau de la brame est soumise en alternance et aggrave le risque de fissuration de la peau solidifiée.An increase in the casting speed also leads to an increase in the metallurgical length, that is to say the length of the liquid well. To keep this metallurgical length within the desired limits, it is therefore necessary to ensure complete solidification of the slab in a shorter time. In this respect, an increase in the length of watered has little effect; on the other hand, an increase in the flow rate of the nozzles in the secondary cooling zone intensifies the cooling and reheating cycles to which the skin of the slab is subjected alternately and increases the risk of cracking of the solidified skin.

Pour supprimer le risque de percée, il convient d'appliquer le refroidissement secondaire pendant un temps et/ou avec une intensité permettant la formation d'une peau solidifiée ayant une épaisseur suffisante.To eliminate the risk of breakthrough, secondary cooling should be applied for a time and / or with an intensity allowing the formation of a solidified skin having a sufficient thickness.

Parmi les solutions qui ont été proposées pour résoudre le problème figure le procédé décrit dans la demande de brevet européen 87870033.5 (publication n° 0 241 445) où, pour assurer le refroidissement intense d'une brame d'acier coulée en continu, on forme, entre la brame et la paroi du moule, une couche continue d'eau de refroidissement sous pression.Among the solutions which have been proposed to solve the problem is the process described in European patent application 87870033.5 (publication no. 0 241 445) where, to ensure the intense cooling of a steel slab continuously cast, one forms , between the slab and the mold wall, a continuous layer of pressurized cooling water.

La présente invention a pour objet de proposer un procédé de fabrication d'une brame mince en acier par coulée continue, qui permet d'une part d'augmenter sensiblement la vitesse de coulée tout en évitant les inconvénients précités et d'autre part de supprimer plusieurs des coûteuses opérations de laminage mentionnées plus haut. Le procédé de l'invention permet également de fabriquer une brame mince pouvant alimenter directement un train de laminage à chaud de bandes d'acier.The object of the present invention is to propose a method for manufacturing a thin steel slab by continuous casting, which allows on the one hand to substantially increase the casting speed while avoiding the aforementioned drawbacks and on the other hand to eliminate several of the costly rolling operations mentioned above. The method of the invention also makes it possible to manufacture a thin slab capable of directly feeding a hot rolling train of steel strips.

Conformément a la présente invention, un procédé de fabrication d'une brame mince en acier par coulée continue, dans lequel on coule l'acier dans un moule où il subit un refroidissement primaire, et dont au moins la section de sortie présente une largeur inférieure ou égale à 60 mm, extrait du moule une brame ayant une épaisseur inférieure à 60 mm et présentant une peau solidifiée, soumet ensuite la brame à un refroidissement secondaire au cours duquel on forme une couche ininterrompue de liquide de refroidissement sous pression sur au moins une partie de la surface de la brame et assure l'écoulement du liquide de refroidissement sur la surface de la brame dans le sens de la progression de celle-ci, est caractérisé en ce que l'on refroidit la brame mince, pendant le refroidissement secondaire, jusqu'à une température de surface inférieure à 800°C et de préférence inférieure à 600°C.According to the present invention, a method of manufacturing a thin steel slab by continuous casting, in which the steel is poured into a mold where it undergoes primary cooling, and at least the outlet section of which has a smaller width or equal to 60 mm, extracts from the mold a slab having a thickness less than 60 mm and having a solidified skin, then submits the slab to a secondary cooling during which an uninterrupted layer of pressurized coolant is formed on at least part of the surface of the slab and ensures the flow of coolant over the surface of the slab in the direction of progression -ci, is characterized in that the thin slab is cooled, during secondary cooling, to a surface temperature below 800 ° C and preferably below 600 ° C.

De façon connue par la demande de brevet européen n° 87870033.5, cette couche de liquide de refroidissement permet l'application sur la face extérieure de la peau solidifiée, d'une pression compensant au moins partiellement la pression ferrostatique existant sur la face intérieure et de ce fait réalise un soutien de cette peau. Par réglage des conditions d'injection, on peut ajuster la pression appliquée par la couche de liquide sur le produit entre 0,2 bar et 2 bar.As is known from European patent application No. 87870033.5, this layer of coolant allows the application on the outer face of the solidified skin, of a pressure at least partially compensating for the ferrostatic pressure existing on the inner face and of this fact achieves support for this skin. By adjusting the injection conditions, the pressure applied by the liquid layer on the product can be adjusted between 0.2 bar and 2 bar.

Selon l'invention, la vitesse de coulée est supérieure à 3 m/min, et de préférence comprise entre 6 m/min et 20 m/min.According to the invention, the casting speed is greater than 3 m / min, and preferably between 6 m / min and 20 m / min.

Ces valeurs de la vitesse de coulée permettent de former à la sortie du moule une peau solidifiée d'une épaisseur suffisante pour supporter l'application de la couche de liquide, sans risque de percée. Cette épaisseur est, pour fixer les idées, égale au moins à 3 mm.These values of the casting speed make it possible to form, at the outlet of the mold, a solidified skin of sufficient thickness to support the application of the layer of liquid, without risk of breakthrough. This thickness is, to fix ideas, equal to at least 3 mm.

Toujours selon l'invention, on maintient ladite couche ininterrompue de liquide de refroidissement sous pression pendant une durée telle que l'épaisseur solidifiée soit au moins égale à 5 mm, et de préférence supérieure à 7 mm pour une brame de 20 mm d'épaisseur et à 10 mm pour une brame de 40 mm d'épaisseur.Still according to the invention, said uninterrupted layer of coolant is kept under pressure for a period such that the solidified thickness is at least equal to 5 mm, and preferably greater than 7 mm for a slab of 20 mm thick. and 10 mm for a slab 40 mm thick.

Il est en effet apparu qu'un refroidissement secondaire intense et continu de la brame mince dans ces conditions permettait, pour une même vitesse de coulée, de réduire la longueur métallurgique. Inversément, un refroidissement conforme à l'invention permet donc d'augmenter la vitesse de coulée, sans risque de percée, tout en conservant une même longueur métallurgique. En outre, on a constaté qu'à la fin de la longueur métallurgique, c'est-à-dire lorsque la brame est entièrement solidifiée, la température de surface de la brame est comprise sensiblement entre 750°C et 900°C. Ce niveau de température est nettement inférieur à celui que l'on rencontre avec un refroidissement traditionnel par gicleurs, où la température est habituellement de l'ordre de 1150°C à 1250°C.It has indeed appeared that intense secondary cooling and continuous thin slab under these conditions allowed, for the same casting speed, to reduce the metallurgical length. Conversely, cooling according to the invention therefore makes it possible to increase the casting speed, without risk of breakthrough, while retaining the same metallurgical length. In addition, it has been found that at the end of the metallurgical length, that is to say when the slab is fully solidified, the surface temperature of the slab is substantially between 750 ° C and 900 ° C. This temperature level is much lower than that which is encountered with traditional cooling by sprinklers, where the temperature is usually of the order of 1150 ° C. to 1250 ° C.

Une caractéristique supplémentaire consiste à laminer la brame mince en une bande à chaud, soit alors que le coeur est encore à l'état pâteux, soit immédiatement après que la brame soit entièrement solidifiée, ledit laminage étant de préférence effectué en continu.An additional feature is to laminate the thin slab into a hot strip, either while the core is still in a pasty state, or immediately after the slab is fully solidified, said rolling preferably being carried out continuously.

On va maintenant décrire un exemple de mise en oeuvre du procédé de l'invention, en faisant référence aux dessins annexés, dans lesquels la

Figure 1
illustre le principe du procédé au moyen d'un dispositif de mise en oeuvre; et la
Figure 2
montre l'évolution de l'épaisseur solidifiée et de la température de surface de la brame mince, refroidie d'une part suivant une méthode classique et d'autre part suivant le procédé de l'invention.
We will now describe an example of implementation of the method of the invention, with reference to the accompanying drawings, in which the
Figure 1
illustrates the principle of the method by means of an implementation device; and the
Figure 2
shows the evolution of the solidified thickness and the surface temperature of the thin slab, cooled on the one hand according to a conventional method and on the other hand according to the method of the invention.

La Figure 1 illustre le principe du procédé de l'invention au moyen d'un dispositif de mise en oeuvre, représenté de manière très schématique.Figure 1 illustrates the principle of the method of the invention by means of an implementation device, shown very schematically.

Un acier est coulé dans une lingotière 1 de coulée continue de brames. Cette lingotière 1 est classiquement en cuivre et refroidie à l'eau. Elle peut également se présenter sous la forme de 2 roues ou de 2 bandes, refroidies à l'eau entre lesquelles s'écoule l'acier. La lingotière présente à sa sortie une largeur l = 40 mm. L'acier subit dans la lingotière 1 un refroidissement primaire (zone A) qui provoque la solidification d'une mince pellicule superficielle, puis il quitte la lingotière 1 sous la forme d'une brame mince 2, de 40 mm d'épaisseur, avec une fine pellicule solide d'une épaisseur au moins égale à 3 mm. La brame 2 pénètre alors dans la zone de refroidissement secondaire B où elle est soumise à un refroidissement intense et continu au moyen d'une couche ininterrompue 3 de liquide de refroidlssement sous pression. Cette couche 3 est ici formée au moyen d'un dispositif 4 connu en soi, qui ne fait pas partie de la présente invention et qu'il n'est pas nécessaire de décrire en détail. On précise toutefois que ce dispositif ne touche la brame en aucun point et qu'il ne suscite dès lors aucun effort de frottement.Steel is poured into a mold 1 for continuous slab casting. This ingot mold 1 is conventionally made of copper and cooled with water. It can also be in the form of 2 wheels or 2 strips, cooled with water between which the steel flows. The mold has a width l = 40 mm at its outlet. In the mold 1, the steel undergoes primary cooling (zone A) which causes a thin surface film to solidify, then it leaves the mold 1 in the form of a thin slab 2, 40 mm thick, with a thin solid film with a thickness of at least 3 mm. The slab 2 then enters the secondary cooling zone B where it is subjected to intense and continuous cooling by means of an uninterrupted layer 3 of pressurized coolant liquid. This layer 3 is here formed by means of a device 4 known per se, which is not part of the present invention and which it is not necessary to describe in detail. However, it should be noted that this device does not touch the slab at any point and that it does not therefore cause any friction force.

La zone de refroidissement secondaire B est symbolisée ici par un seul dispositif 4; il va de soi que cette zone B pourrait, selon les besoins, comporter plusieurs dispositifs 4 distincts, éventuellement séparés par des rouleaux de support.The secondary cooling zone B is symbolized here by a single device 4; it goes without saying that this zone B could, as necessary, comprise several separate devices 4, possibly separated by support rollers.

A la sortie de la zone de refroidissement secondaire B, la brame 2 présente une peau solidifiée plus épaisse et le refroidissement par le liquide sous pression cesse. La brame se déplace ensuite dans l'air tout en poursuivant sa solidification (zone C).At the exit from the secondary cooling zone B, the slab 2 has a thicker solidified skin and the cooling by the pressurized liquid ceases. The slab then moves in the air while continuing its solidification (zone C).

La brame 2 peut alors être transmise, de préférence directement, à une cage de laminage à chaud symbolisée par les cylindres 5.The slab 2 can then be transmitted, preferably directly, to a hot rolling stand symbolized by the cylinders 5.

On peut également laisser le liquide de refroidissement de la zone B s'écouler librement sur la brame dans la zone C, et même jusqu'aux cylindres de laminoir 5. Ce ruissellement ne modifie pas sensiblement la fin de la solidification de la brame 2. En revanche, le liquide peut utilement contribuer à réduire la charge thermique des cylindres de laminoir 5, car cette charge thermique est relativement élevée en raison de la faible vitesse de rotation des cylindres 5.You can also let the coolant from zone B flow freely over the slab in zone C, and even to rolling mill rolls 5. This runoff does not appreciably modify the end of the solidification of the slab 2. On the other hand, the liquid can usefully contribute to reducing the thermal load of the rolling mill rolls 5, since this thermal load is relatively high due to the low speed of rotation of the cylinders 5.

La Figure 2 illustre l'évolution de la température de surface de la brame (Ts - axe vertical gauche) et de l'épaisseur de la peau solidifiée (e - axe vertical droit) en fonction de la distance à partir du ménisque (L - axe horizontal).Figure 2 illustrates the evolution of the surface temperature of the slab (T s - left vertical axis) and the thickness of the solidified skin (e - right vertical axis) as a function of the distance from the meniscus (L - horizontal axis).

La figure compare les deux cas suivants :

  • 1) Coulée continue d'une brame de 40 mm d'épaisseur dans une lingotière 1 longue de 1 m (zone A), refroidissement secondaire classique par gicleurs et rouleaux de support sur une longueur de 3,4 m (zone B) puis refroidissement dans l'air jusqu'à solidification complète (zone C); la vitesse de coulée était de 6 m/min. Les courbes correspondantes sont les courbes a, b en trait plein.
  • 2) Coulée continue d'une brame de 40 mm d'épaisseur dans une lingotière 1 longue de 1 m (zone A), refroidissement secondaire intense et continu sur une longueur de 3,4 m immédiatement à la sortie de la lingotière 1 (zone B), puis refroidissement dans l'air jusqu'à solidification sensiblement complète (zone C); la vitesse de coulée était de 12 m/min. Les courbes correspondantes sont les courbes c, d en trait interrompu.
The figure compares the following two cases:
  • 1) Continuous casting of a slab 40 mm thick in an ingot mold 1 1 m long (zone A), conventional secondary cooling by sprinklers and support rollers over a length of 3.4 m (zone B) then cooling in the air until complete solidification (zone C); the casting speed was 6 m / min. The corresponding curves are curves a, b in solid lines.
  • 2) Continuous casting of a slab 40 mm thick in an ingot mold 1 1 m long (zone A), intense and continuous secondary cooling over a length of 3.4 m immediately at the exit of ingot mold 1 (zone B), then cooling in air until substantially complete solidification (zone C); the casting speed was 12 m / min. The corresponding curves are curves c, d in broken lines.

Les courbes (b) et (d) montrent que la longueur métallurgique est la même dans les deux cas.Curves (b) and (d) show that the metallurgical length is the same in both cases.

Par ailleurs, en ce qui concerne la température de surface de la brame, la Figure 2 montre que le refroidissement secondaire classique a peu d'effet sur la température atteinte à la sortie de la lingotière (courbe a); la température de surface au point de solidification totale est de l'ordre de 1200°C. Cette valeur très élevée, de même que la faible valeur de la vitesse, sont des éléments défavorables pour un laminage direct. Par contre, un refroidissement suivant l'invention provoque une diminution rapide de cette température de surface, suivie d'un réchauffement dans la zone C jusqu'à une température d'environ 850°C (courbe c), ce qui, combiné à une vitesse de coulée élevée, est un élément favorable pour un laminage direct de la brame.Furthermore, with regard to the surface temperature of the slab, Figure 2 shows that conventional secondary cooling has little effect on the temperature reached at the outlet of the ingot mold (curve a); surface temperature at the point of solidification total is of the order of 1200 ° C. This very high value, as well as the low speed value, are unfavorable elements for direct rolling. On the other hand, cooling according to the invention causes a rapid reduction in this surface temperature, followed by heating in zone C to a temperature of around 850 ° C (curve c), which, combined with a high casting speed is a favorable element for direct rolling of the slab.

Le procédé de l'invention permet donc de fabriquer des brames minces en acier par coulée continue à une vitesse nettement supérieure à la vitesse habituelle, et de fournir ces brames dans des conditions de température et de structure favorables au laminage direct. Les brames ainsi fabriquées sont moins sujettes à la ségrégation. En outre, leur fabrication par le procédé de l'invention permet d'éviter de nombreuses opérations de laminage, notamment de dégrossissage, ainsi que le réchauffage qui les précède.The method of the invention therefore makes it possible to manufacture thin steel slabs by continuous casting at a speed significantly higher than the usual speed, and to supply these slabs under temperature and structural conditions favorable to direct rolling. The slabs thus produced are less prone to segregation. In addition, their manufacture by the process of the invention makes it possible to avoid numerous rolling operations, in particular roughing, as well as the reheating which precedes them.

Claims (7)

  1. Process for manufacturing a thin steel slab by continuous casting, in which the steel is cast into a mould in which it is subjected to primary cooling and at least the exit cross-section of which mould has a width of less than or equal to 60 mm, a slab having a thickness of less than 60 mm and having a solidified shell is extracted from the mould, next the slab is subjected to secondary cooling during which an uninterrupted film of pressurized cooling liquid is formed on at least part of the surface of the slab, and the cooling liquid flows away on the surface of the slab in the direction of progression of the latter, characterized in that the slab is cooled to a surface temperature of less than 800°C during the secondary cooling.
  2. Process according to Claim 1, characterized in that the slab is cooled to a surface temperature of less than 600°C during the secondary cooling.
  3. Process according to either of Claims 1 and 2, characterized in that the casting rate is greater than 3 m/min.
  4. Process according to Claim 3, characterized in that the casting rate is between 6 m/min and 20 m/min.
  5. Process according to any one of Claims 1 to 4, characterized in that the said uninterrupted film of pressurized cooling liquid is maintained for a time such that the thickness of the solidified shell is at least equal to 5 mm.
  6. Process for using a thin slab manufactured in accordance with any one of Claims 1 to 5, characterized in that the said thin slab is hot rolled directly into a strip.
  7. Process according to Claim 6, characterized in that the said rolling is carried out continuously.
EP90870018A 1989-02-10 1990-02-05 Method of manufacturing a thin steel slab by continuous casting Revoked EP0382702B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
BE8900138A BE1002826A6 (en) 1989-02-10 1989-02-10 PROCESS FOR PRODUCING A THIN STEEL SLAB BY CONTINUOUS CASTING.
BE8900138 1989-02-10

Publications (3)

Publication Number Publication Date
EP0382702A2 EP0382702A2 (en) 1990-08-16
EP0382702A3 EP0382702A3 (en) 1991-06-12
EP0382702B1 true EP0382702B1 (en) 1997-04-09

Family

ID=3884009

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90870018A Revoked EP0382702B1 (en) 1989-02-10 1990-02-05 Method of manufacturing a thin steel slab by continuous casting

Country Status (4)

Country Link
EP (1) EP0382702B1 (en)
AT (1) ATE151321T1 (en)
BE (1) BE1002826A6 (en)
DE (1) DE69030396D1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110421002A (en) * 2019-07-08 2019-11-08 江苏煌明能源科技有限公司 Bar Wire Product is without heating furnace continuous casting direct-rolling process

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3616844A (en) * 1970-02-24 1971-11-02 Benteler Geb Paderwerk Apparatus for continuous casting of metal ingots
FR2153152A1 (en) * 1971-09-21 1973-05-04 Creusot Loire Continuous casting curved cooling guide - improves casting quality by supporting it on pressurised fluid and rollers
US3918467A (en) * 1972-01-21 1975-11-11 Siderurgie Fse Inst Rech Apparatus for the cooling of a continuously cast product
CH616354A5 (en) * 1976-09-23 1980-03-31 Hitachi Ltd Continuous casting apparatus
EP0241445B1 (en) * 1986-03-18 1989-10-11 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Method and apparatus for cooling a continuously cast metal product

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110421002A (en) * 2019-07-08 2019-11-08 江苏煌明能源科技有限公司 Bar Wire Product is without heating furnace continuous casting direct-rolling process

Also Published As

Publication number Publication date
ATE151321T1 (en) 1997-04-15
EP0382702A2 (en) 1990-08-16
DE69030396D1 (en) 1997-05-15
EP0382702A3 (en) 1991-06-12
BE1002826A6 (en) 1991-06-25

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