EP0709151B1 - Casting surface for a continuous metal casting mould with movable walls - Google Patents

Casting surface for a continuous metal casting mould with movable walls Download PDF

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Publication number
EP0709151B1
EP0709151B1 EP95402231A EP95402231A EP0709151B1 EP 0709151 B1 EP0709151 B1 EP 0709151B1 EP 95402231 A EP95402231 A EP 95402231A EP 95402231 A EP95402231 A EP 95402231A EP 0709151 B1 EP0709151 B1 EP 0709151B1
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EP
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Prior art keywords
dimples
casting
dimple
perimeter
circular
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EP95402231A
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German (de)
French (fr)
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EP0709151A1 (en
Inventor
Hugues Legrand
Christian Marchionni
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Thyssen Stahl AG
USINOR SA
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Thyssen Stahl AG
USINOR SA
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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
    • B22D11/04—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds
    • B22D11/05—Continuous casting of metals, i.e. casting in indefinite lengths into open-ended moulds into moulds having adjustable walls
    • 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
    • B22D11/0637—Accessories therefor
    • B22D11/0648—Casting surfaces
    • B22D11/0651—Casting wheels

Definitions

  • the invention relates to the continuous casting of metals. More specifically, it concerns installations for the continuous casting of metals such as steel by solidification liquid metal on a movable wall or between two movable walls. These movable walls may, in particular, be constituted by the lateral surfaces of one or two cylinders with horizontal axis energized internally.
  • the pouring space containing the liquid steel is defined by the lateral surfaces of the cylinders, on which the solidification of the strip is initiated, and by plates of refractory side closures applied against the ends of the cylinders.
  • micro-cracks which have just been mentioned have their origin in the gradients thermal which are established in the skin of the product during its solidification against the cooled wall of the cylinder, and which generate stresses there.
  • a certain roughness is commonly printed on the surface of the cylinders. Of air (or inert gas blown and confined above the casting space) is trapped in the recessed parts of the surface before it comes into contact with liquid metal. It forms a gaseous "mattress" between the metal and the cylinder, and this mattress tends to decrease the cooling rate of the skin, so the gradients thermal.
  • the roughness also makes it possible to distribute the stresses and the deformations thermal on a scale such that they do not cause faults.
  • the protrusions would solidify while their presence on the strip is undesirable. If the dimples have suitable dimensions, the metal which penetrates there does not solidify there at once. The protrusions then constitute reserves of material which have a more plastic behavior than the neighboring portions of the skin solidified on the smooth parts of the cylinder. When cooling the skin which is accompanied by a contraction of the metal, these protrusions behave like expansion joints: They contract faster than their surroundings while absorbing the internal tensions in the skin resulting from its contraction, and which, without it, could lead to cracking of the surface of the strip. This contraction accentuated also makes that on the solidified and cooled strip, one no longer observes or practically more protuberances. So that these dimples can fully play their role, it is also necessary that the distances which separate them are maintained between lower and upper limits specified in this document, which depend on the diameter dimples.
  • Document EP409645 proposes to use as inerting gas space for pouring of the installation a gas partially soluble in the steel, to avoid the appearance of serrations on the surface of the strip, which would be due to an exaggerated expansion of the gas during the initiation of solidification, if it was completely insoluble. Conversely, a fully soluble gas may no longer play its role of mattress between the cylinder and band. It is proposed to use for this purpose, as soluble gas, nitrogen, hydrogen, carbon dioxide or ammonia, this soluble gas being mixed with argon or helium. The soluble gas content recommended in this mixture is 30 to 90%.
  • the object of the invention is to provide the dimples with a configuration which allows them to play their role in preventing micro-cracks with even greater efficiency increased compared to the practice of the Prior Art.
  • the invention relates to a casting surface of an ingot mold of continuous casting of moving wall metals, of the type having dimples in shape general circular or elliptical, characterized in that said dimples have lobes around their edges.
  • Said casting surface may, in particular, be constituted by the lateral surface of a cylinder or two cylinders cooled in rotation.
  • the invention consists in giving the dimples a form no longer circular or oval, but a lobed shape.
  • lobed form is meant that, at from a general shape at least approximately circular or elliptical, the around the dimples has portions where its radius of curvature is significantly smaller, in absolute value, than the mean radius of curvature of the dimple.
  • This perimeter can thus be constituted by an alternation of portions with low radius of curvature whose concavity is successively turned inwards and then towards the outside of the dimple.
  • lobed dimples according to the invention provide an increase in the length of the borders, therefore of this effect of cooling, for a surface of the dimples which remains identical to the Prior Art. In these conditions, the overall speed of cooling of the strip is not modified, since this depends, all other things being equal, on the percentage of the surface of the cylinders which is occupied by the dimple openings.
  • the circular dimple 1 according to the prior art shown in top view in FIG. 1 (we have neglected the deformations due to the curvature of the surface of the cylinder, whose radius, which is of the order of 250 to 750 mm, is very large compared to the dimensions of the dimples, which are of the order of mm or less) has a radius R, an area S (equal to ⁇ R 2 ) and a perimeter P (equal to 2 ⁇ R).
  • R radius
  • S equal to ⁇ R 2
  • P equal to 2 ⁇ R
  • This lobed dimple 2 is inscribed in a circle of radius R ', this radius R' being calculated so that the lobed dimple 2 has a surface S 'equal to the surface S of the preceding circular dimple 1.
  • the periphery of this lobed dimple 2 is in the form of an alternation of semicircles 3, 4, 5, 6, the concavities of which are turned towards the inside of the dimple, and of quarter circles 7, 8, 9, 10 whose concavities are turned towards the outside of the dimple.
  • the radius of curvature "a" of semicircles 3-6 and the radius of curvature "a"'of quarter circles 7-10 are both equal to R' / 3.
  • the ratio P '/ S' is equal to 2.95 / R ', that is, expressed as a function of the radius R of the circular surface dimple equivalent, at 2.43 / R, while P / S for this circular dimple would only be equal to 2 / R. So we have, with a lobed dimple, a perimeter significantly greater than that a circular dimple of equivalent surface, which increases the anti-micro-cracking effect sought during the solidification of the strip.
  • dimples can be formed on the copper ferrule, which constitutes usually the outer surface of the cylinders, for example by rolling a wheel bearing a relief engraving reproducing their shape.
  • This engraving repels the shell material on the desired depth (which is of the order of 5 to 100 ⁇ m as usually), and therefore causes the appearance of reliefs on the edges of the dimples. It is then necessary to rectify the surface of the shell in order to eliminate these reliefs.
  • dimples that has been described and represented is not limiting, and other types of lobed dimples, having different shaped lobes and / or in number are possible. Instead of being written exactly in a circle, dimples may only be approximately, or also be included in a ellipse. Optimally, it is recommended that the lobed dimples have a perimeter P ' between 1.1 and 1.5 times the perimeter P of circular dimples which would have a identical unit area. If P 'is less than 1.1 times P, the gain obtained is too low and not detectable.
  • the invention is not only applicable to cylinders intended to equip a steel casting machine between two cylinders, but also on any casting surface of a ingot mold with movable wall (s), such as the surface of a cylinder of a casting machine very thin strips on a rotating cylinder, or that of a strip on a pouring of metal between two moving bands

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Continuous Casting (AREA)
  • Coating With Molten Metal (AREA)

Abstract

The ingot mould, e.g. for molten steel, consists of two cooled rollers (2) set with a gap between them forming the moulding surface. Each of the rollers has a series of circular or elliptical recesses (7-10) formed by surface lobes (3-6). The lobed surface has a perimeter which is 1.1-1.5 times greater than an equivalent roller with a cylindrical surface.

Description

L'invention concerne la coulée continue des métaux. Plus précisément, elle concerne les installations de coulée continue des métaux tels que l'acier par solidification du métal liquide sur une paroi mobile ou entre deux parois mobiles. Ces parois mobiles peuvent, en particulier, être constituées par les surfaces latérales d'un ou deux cylindres à axe horizontal énergiquement refroidis intérieurement.The invention relates to the continuous casting of metals. More specifically, it concerns installations for the continuous casting of metals such as steel by solidification liquid metal on a movable wall or between two movable walls. These movable walls may, in particular, be constituted by the lateral surfaces of one or two cylinders with horizontal axis energized internally.

Ces dernières années ont vu s'accomplir des progrès sensibles dans le développement des procédés de coulée de minces bandes d'acier directement à partir de métal liquide. Le procédé qui semble, à l'heure actuelle, être le plus susceptible de déboucher rapidement sur une application industrielle est la coulée entre deux cylindres refroidis intérieurement tournant autour de leurs axes horizontaux dans des sens opposés, et disposés en regard l'un de l'autre, leur entrefer ayant une largeur sensiblement égale à l'épaisseur que l'on désire conférer à la bande coulée (par exemple de quelques mm). L'espace de coulée renfermant l'acier liquide est défini par les surfaces latérales des cylindres, sur lesquelles s'initie la solidification de la bande, et par des plaques de fermeture latérales en réfractaire appliquées contre les extrémités des cylindres.The last few years have seen significant progress in development of processes for casting thin steel strips directly from liquid metal. The process that seems to be the most likely at the moment quickly leading to an industrial application is the casting between two cylinders internally cooled rotating around their horizontal axes in directions opposite, and arranged opposite one another, their air gap having a width substantially equal to the thickness that you want to give to the cast strip (for example a few mm). The pouring space containing the liquid steel is defined by the lateral surfaces of the cylinders, on which the solidification of the strip is initiated, and by plates of refractory side closures applied against the ends of the cylinders.

L'obtention immédiate d'une bonne qualité de surface de la bande est un élément essentiel de la réussite de l'opération de coulée. En effet, l'intérêt majeur de la coulée de bandes minces directement à partir de métal liquide est la possibilité qu'elle donne de supprimer ou de réduire considérablement l'ampleur de l'opération de laminage à chaud du demi-produit épais habituellement coulé. Lorsque l'acier est coulé en formats épais, il est possible de supprimer les défauts de surface par meulage. Or cette opération n'est pas possible sur les bandes minces. Dans les procédés de coulée de bandes minces, il est donc nécessaire d'obtenir une surface sans défauts dès la coulée.Obtaining a good surface quality immediately is an element essential to the success of the casting operation. Indeed, the major interest of the casting of thin strips directly from liquid metal is the possibility that it gives of eliminate or significantly reduce the scale of the hot rolling operation thick semi-finished product usually cast. When steel is cast in thick formats, it surface defects can be removed by grinding. However, this operation is not possible on thin strips. In thin strip casting processes, it is therefore necessary to obtain a surface without defects from the casting.

Les micro-fissures dont il vient d'être question ont pour origine les gradients thermiques qui s'établissent dans la peau du produit au cours de sa solidification contre la paroi refroidie du cylindre, et qui y génèrent des contraintes. Pour réduire ces contraintes, on imprime couramment une certaine rugosité à la surface des cylindres. De l'air (ou un gaz d'inertage insufflé et confiné au-dessus de l'espace de coulée) est emprisonné dans les parties en creux de la surface avant que celle-ci n'entre en contact avec le métal liquide. Il forme un "matelas" gazeux entre le métal et le cylindre, et ce matelas tend à diminuer la vitesse de refroidissement de la peau, donc les gradients thermiques. La rugosité permet aussi de répartir les contraintes et les déformations thermiques à une échelle telle qu'elles ne provoquent pas de défauts.The micro-cracks which have just been mentioned have their origin in the gradients thermal which are established in the skin of the product during its solidification against the cooled wall of the cylinder, and which generate stresses there. To reduce these constraints, a certain roughness is commonly printed on the surface of the cylinders. Of air (or inert gas blown and confined above the casting space) is trapped in the recessed parts of the surface before it comes into contact with liquid metal. It forms a gaseous "mattress" between the metal and the cylinder, and this mattress tends to decrease the cooling rate of the skin, so the gradients thermal. The roughness also makes it possible to distribute the stresses and the deformations thermal on a scale such that they do not cause faults.

Dans le document EP0309247, il est proposé de réaliser cette rugosité sous forme de "fossettes", c'est-à-dire de gravures en creux isolées les unes des autres, d'ouverture circulaire ou ovale d'un diamètre de l'ordre de 0,1 à 1,2mm et d'une profondeur de 5 à 100 µm. Lorsque la surface du cylindre arrive au contact du métal liquide, celui-ci pénètre dans les fossettes, dont les dimensions sont choisies pour que, sous l'effet des forces de tension superficielle, du métal liquide puisse y pénétrer et former des protubérances, sans toutefois les remplir totalement. Il faut, en particulier, éviter que le métal liquide ne vienne au contact du fond de fossettes qui seraient trop larges et/ou trop peu profondes, car il s'y refroidirait à une vitesse normale. On n'obtiendrait plus l'effet d'atténuation des gradients thermiques recherché, et de plus, les protubérances se solidifieraient alors que leur présence sur la bande est indésirable. Si les fossettes ont des dimensions convenables, le métal qui y pénètre ne s'y solidifie pas immédiatement. Les protubérances constituent alors des réserves de matière qui présentent un comportement plus plastique que les portions avoisinantes de la peau solidifiées sur les parties lisses du cylindre. Lors du refroidissement de la peau qui s'accompagne d'une contraction du métal, ces protubérances se comportent comme des joints de dilatation: Elles se contractent plus vite que leurs environnements tout en absorbant les tensions internes à la peau résultant de sa contraction, et qui, sans cela, pourraient conduire à une fissuration de la surface de la bande. Cette contraction accentuée fait également que sur la bande solidifiée et refroidie, on n'observe plus ou pratiquement plus de protubérances. Pour que ces fossettes puissent pleinement jouer leur rôle, il faut également que les distances qui les séparent soient maintenues entre des limites inférieure et supérieure précisées dans ce document, qui dépendent du diamètre des fossettes.In document EP0309247, it is proposed to produce this roughness under form of "dimples", that is to say hollow engravings isolated from each other, circular or oval opening with a diameter of the order of 0.1 to 1.2mm and a depth from 5 to 100 µm. When the cylinder surface comes into contact with metal liquid, it enters the dimples, the dimensions of which are chosen so that, under the effect of surface tension forces, liquid metal can penetrate it and form protuberances, without however completely filling them. In particular, avoid the liquid metal coming into contact with the bottom of dimples which are too wide and / or too shallow, as it would cool there at normal speed. We would no longer obtain the desired thermal gradient attenuation effect, and moreover, the protrusions would solidify while their presence on the strip is undesirable. If the dimples have suitable dimensions, the metal which penetrates there does not solidify there at once. The protrusions then constitute reserves of material which have a more plastic behavior than the neighboring portions of the skin solidified on the smooth parts of the cylinder. When cooling the skin which is accompanied by a contraction of the metal, these protrusions behave like expansion joints: They contract faster than their surroundings while absorbing the internal tensions in the skin resulting from its contraction, and which, without it, could lead to cracking of the surface of the strip. This contraction accentuated also makes that on the solidified and cooled strip, one no longer observes or practically more protuberances. So that these dimples can fully play their role, it is also necessary that the distances which separate them are maintained between lower and upper limits specified in this document, which depend on the diameter dimples.

Le document EP409645 propose d'utiliser comme gaz d'inertage de l'espace de coulée de l'installation un gaz partiellement soluble dans l'acier, pour éviter l'apparition de dentelures sur la surface de la bande, qui seraient dues à une dilatation exagérée du gaz lors de l'initiation de la solidification, si celui-ci était totalement insoluble. Inversement, un gaz entièrement soluble risquerait de ne plus jouer son rôle de matelas entre le cylindre et la bande. Il est proposé d'utiliser à cet effet, comme gaz soluble, de l'azote, de l'hydrogène, du bioxyde de carbone ou de l'ammoniac, ce gaz soluble étant mélangé à de l'argon ou de l'hélium. La teneur en gaz soluble conseillée dans ce mélange est de 30 à 90 %.Document EP409645 proposes to use as inerting gas space for pouring of the installation a gas partially soluble in the steel, to avoid the appearance of serrations on the surface of the strip, which would be due to an exaggerated expansion of the gas during the initiation of solidification, if it was completely insoluble. Conversely, a fully soluble gas may no longer play its role of mattress between the cylinder and band. It is proposed to use for this purpose, as soluble gas, nitrogen, hydrogen, carbon dioxide or ammonia, this soluble gas being mixed with argon or helium. The soluble gas content recommended in this mixture is 30 to 90%.

Le but de l'invention est de procurer aux fossettes une configuration qui leur permette de jouer leur rôle de prévention des micro-fissures avec une efficacité encore accrue par rapport à la pratique de l'Art Antérieur.The object of the invention is to provide the dimples with a configuration which allows them to play their role in preventing micro-cracks with even greater efficiency increased compared to the practice of the Prior Art.

A cet effet, l'invention a pour objet une surface de coulée d'une lingotière de coulée continue des métaux à paroi mobile, du type comportant des fossettes de forme générale circulaire ou elliptique, caractérisée en ce que lesdites fossettes présentent des lobes sur leur pourtour. Ladite surface de coulée peut, notamment, être constituée par la surface latérale d'un cylindre ou de deux cylindres refroidis en rotation.To this end, the invention relates to a casting surface of an ingot mold of continuous casting of moving wall metals, of the type having dimples in shape general circular or elliptical, characterized in that said dimples have lobes around their edges. Said casting surface may, in particular, be constituted by the lateral surface of a cylinder or two cylinders cooled in rotation.

Comme on l'aura compris, l'invention consiste à donner aux fossettes une forme non plus circulaire ou ovale, mais une forme lobée. Par forme lobée, on entend que, à partir d'une forme générale au moins approximativement circulaire ou elliptique, le pourtour des fossettes comporte des portions où son rayon de courbure est significativement plus faible, en valeur absolue, que le rayon de courbure moyen de la fossette. Ce pourtour peut ainsi être constitué par une alternance de portions à faible rayon de courbure dont la concavité est successivement tournée vers l'intérieur puis vers l'extérieur de la fossette.As will be understood, the invention consists in giving the dimples a form no longer circular or oval, but a lobed shape. By lobed form is meant that, at from a general shape at least approximately circular or elliptical, the around the dimples has portions where its radius of curvature is significantly smaller, in absolute value, than the mean radius of curvature of the dimple. This perimeter can thus be constituted by an alternation of portions with low radius of curvature whose concavity is successively turned inwards and then towards the outside of the dimple.

L'invention sera mieux comprise à la lecture de la description qui suit, faisant référence aux figures annexées :

  • la figure 1 qui montre une fossette selon l'Art Antérieur ;
  • la figure 2 qui montre un exemple de fossette selon l'invention destinée à se substituer à la précédente.
The invention will be better understood on reading the following description, referring to the appended figures:
  • Figure 1 which shows a dimple according to Prior Art;
  • Figure 2 which shows an example of a dimple according to the invention intended to replace the previous one.

L'un des paramètres essentiels dans l'action des fossettes sur la solidification de la peau est le refroidissement intense du métal qui se produit sur leur bordure. Par rapport aux fossettes à ouverture circulaire ou ovale, les fossettes lobées selon l'invention procurent un accroissement de la longueur des bordures, donc de cet effet de refroidissement, pour une surface des fossettes qui reste identique à l'Art Antérieur. Dans ces conditions, la vitesse globale de refroidissement de la bande n'est pas modifiée, puisque celle-ci dépend , toutes choses étant égales par ailleurs, du pourcentage de la surface des cylindres qui est occupé par les ouvertures des fossettes. L'accroissement de la vitesse de refroidissement de la bande induit par la configuration des fossettes selon l'invention ne se fait sentir qu'au niveau microscopique, d'autant plus qu'à surface égale des fossettes, la distance minimale qui sépare les bords de deux fossettes voisines est plus faible dans le cas des fossettes lobées que dans le cas des fossettes circulaires. D'autre part, pour un périmètre de fossette donné, le volume de gaz emprisonné à l'intérieur de la fossette est plus faible dans le cas d'une fossette lobée que dans le cas d'une fossette circulaire. On amoindrit donc les problèmes liés à la dilatation du gaz dont il a été question plus haut.One of the essential parameters in the action of dimples on the solidification of the skin is the intense cooling of the metal that occurs on their border. Through compared to dimples with circular or oval opening, lobed dimples according to the invention provide an increase in the length of the borders, therefore of this effect of cooling, for a surface of the dimples which remains identical to the Prior Art. In these conditions, the overall speed of cooling of the strip is not modified, since this depends, all other things being equal, on the percentage of the surface of the cylinders which is occupied by the dimple openings. The increase in the speed of cooling of the strip induced by the configuration of the dimples according to the invention is felt only at the microscopic level, all the more so when the surface is equal dimples, the minimum distance between the edges of two neighboring dimples is more weak in the case of lobed dimples than in the case of circular dimples. Else share, for a given dimple perimeter, the volume of gas trapped inside the dimple is lower in the case of a lobed dimple than in the case of a dimple circular. We therefore lessen the problems associated with the expansion of the gas in which it was question above.

La fossette circulaire 1 selon l'Art Antérieur représentée en vue de dessus sur la figure 1 (on a négligé les déformations dues à la courbure de la surface du cylindre, dont le rayon, qui est de l'ordre de 250 à 750 mm, est très grand par rapport aux dimensions des fossettes, qui sont de l'ordre du mm ou moins) a un rayon R, une surface S (égale à π R2) et un périmètre P (égal à 2πR). De la même façon, on a représenté à la même échelle sur la figure 2 un exemple (bien entendu non limitatif) de fossette lobée 2 selon l'invention. Cette fossette lobée 2 est inscrite dans un cercle de rayon R', ce rayon R' étant calculé pour que la fossette lobée 2 ait une surface S' égale à la surface S de la fossette circulaire 1 précédente. Le pourtour de cette fossette lobée 2 se présente sous la forme d'une alternance de demi-cercles 3, 4, 5, 6, dont les concavités sont tournées vers l'intérieur de la fossette, et de quarts de cercle 7, 8, 9, 10 dont les concavités sont tournées vers l'extérieur de la fossette. Le rayon de courbure "a" des demi-cercles 3-6 et le rayon de courbure "a"' des quarts de cercle 7-10 sont tous deux égaux à R'/3. Les centres de courbure des demi-cercles 3-6 sont situés sur les milieux des côtés d'un carré centré sur le cercle de rayon R', et les centres de courbure des quarts de cercle 7-10 sont situés sur les coins de ce même carré. Un calcul simple montre que la surface S' de cette fossette lobée 2 selon l'invention est égale à R'2(π+16)/9, et que son périmètre P' est égal à 2πR'. Pour que S'=S, il faut donc que R'=3R√π/(π+16), soit R'=1,22R.The circular dimple 1 according to the prior art shown in top view in FIG. 1 (we have neglected the deformations due to the curvature of the surface of the cylinder, whose radius, which is of the order of 250 to 750 mm, is very large compared to the dimensions of the dimples, which are of the order of mm or less) has a radius R, an area S (equal to π R 2 ) and a perimeter P (equal to 2πR). In the same way, there is shown on the same scale in Figure 2 an example (of course not limiting) of lobed dimple 2 according to the invention. This lobed dimple 2 is inscribed in a circle of radius R ', this radius R' being calculated so that the lobed dimple 2 has a surface S 'equal to the surface S of the preceding circular dimple 1. The periphery of this lobed dimple 2 is in the form of an alternation of semicircles 3, 4, 5, 6, the concavities of which are turned towards the inside of the dimple, and of quarter circles 7, 8, 9, 10 whose concavities are turned towards the outside of the dimple. The radius of curvature "a" of semicircles 3-6 and the radius of curvature "a"'of quarter circles 7-10 are both equal to R' / 3. The centers of curvature of semicircles 3-6 are located on the midpoints of the sides of a square centered on the circle of radius R ', and the centers of curvature of quarter circles 7-10 are located on the corners of this same square. A simple calculation shows that the area S 'of this lobed dimple 2 according to the invention is equal to R' 2 (π + 16) / 9, and that its perimeter P 'is equal to 2πR'. So that S '= S, it is thus necessary that R' = 3R√π / (π + 16), that is R '= 1,22R.

Dans ces conditions, pour ce type de fossettes lobées, le rapport P'/S' est égal à 2,95/R', soit, exprimé en fonction du rayon R de la fossette circulaire de surface équivalente, à 2,43/R, alors que P/S pour cette fossette circulaire serait seulement égal à 2/R. On a donc bien, avec une fossette lobée, un périmètre sensiblement supérieur à celui d'une fossette circulaire de surface équivalente, ce qui permet d'accroítre l'effet anti-micro-fissures recherché lors de la solidification de la bande. De même, dans le cas où on désire conserver un périmètre constant pour le pourtour des fossettes, mais diminuer leur surface pour limiter le volume de gaz emprisonné, on impose alors P'=P, soit 2πR'=2πR, d'où R'=R et S'/S=(π+16)/9π=0,68. A périmètre égal, cette configuration de fossettes permet donc de diminuer d'environ un tiers la surface des fossettes, donc le volume de gaz emprisonné, par rapport à des fossettes circulaires.Under these conditions, for this type of lobed dimples, the ratio P '/ S' is equal to 2.95 / R ', that is, expressed as a function of the radius R of the circular surface dimple equivalent, at 2.43 / R, while P / S for this circular dimple would only be equal to 2 / R. So we have, with a lobed dimple, a perimeter significantly greater than that a circular dimple of equivalent surface, which increases the anti-micro-cracking effect sought during the solidification of the strip. Likewise, in the case where want to keep a constant perimeter around the dimples, but reduce their surface to limit the volume of trapped gas, we then impose P '= P, or 2πR' = 2πR, hence R '= R and S' / S = (π + 16) / 9π = 0.68. At equal perimeter, this configuration of dimples therefore allows the area of dimples to be reduced by about a third, so the volume of trapped gas, relative to circular dimples.

A surface de fossettes égale, les fossettes selon l'invention permettent de diminuer la distance séparant deux fossetttes, puisque, comme on l'a vu, R'=1,22R. Cet amoindrissement est favorable dans le cas où on désire couler des aciers tels que les aciers inoxydables austénitiques du type AISI 304. Il est connu, par le document EP309247, d'imposer à cet effet des distances entre fossettes très faibles (moins de 0,35 mm) pour obtenir une structure de solidification favorable. L'utilisation de fossettes selon l'invention procure un degré de liberté supplémentaire pour l'obtention de ce résultat.With an equal dimple surface, the dimples according to the invention make it possible to decrease the distance separating two dimples, since, as we have seen, R '= 1.22R. This reduction is favorable in the case where it is desired to cast steels such as AISI 304 type austenitic stainless steels. It is known from the document EP309247, to impose very small distances between dimples for this purpose (less than 0.35 mm) to obtain a favorable solidification structure. The use of dimples according to the invention provides an additional degree of freedom for obtaining this result.

Ces fossettes peuvent être formées sur la virole en cuivre, qui constitue habituellement la surface externe des cylindres, par exemple en y faisant rouler une molette portant une gravure en relief reproduisant leur forme. Cette gravure repousse la matière de la virole sur la profondeur désirée (qui est de l'ordre de 5 à 100 µm comme habituellement), et provoque donc l'apparition de reliefs sur les bords des fossettes. Il est ensuite nécessaire de rectifier la surface de la virole afin d'éliminer ces reliefs.These dimples can be formed on the copper ferrule, which constitutes usually the outer surface of the cylinders, for example by rolling a wheel bearing a relief engraving reproducing their shape. This engraving repels the shell material on the desired depth (which is of the order of 5 to 100 μm as usually), and therefore causes the appearance of reliefs on the edges of the dimples. It is then necessary to rectify the surface of the shell in order to eliminate these reliefs.

Bien entendu, l'exemple de fossettes qu'on a décrit et représenté n'est pas limitatif, et d'autres types de fossettes lobées, comportant des lobes différents en forme et/ou en nombre sont envisageables. Au lieu d'être inscrites exactement dans un cercle, les fossettes peuvent ne l'être qu'approximativement, ou aussi être inscrites dans une ellipse. Optimalement, il est conseillé que les fossettes lobées aient un périmètre P' compris entre 1,1 et 1,5 fois le périmètre P des fossettes circulaires qui auraient une surface unitaire identique. Si P' est inférieur à 1,1 fois P, le gain obtenu est trop faible et non décelable. Si P' est supérieur à 1,5 fois P, cela signifie que le contour des fossettes présente des circonvolutions nombreuses et profondes, ce qui implique que les bords d'une fossette qui se font face sont à une très faible distance les uns des autres. Dans ce cas il y a un risque que le métal ne puisse pénétrer dans la fossette, qui ne peut alors plus jouer son rôle. Il est enfin important que ces fossettes ne présentent pas d'angles vifs qui créeraient des conditions de solidification anormales à leur niveau, qui pourraient générer des défauts dans la bande.Of course, the example of dimples that has been described and represented is not limiting, and other types of lobed dimples, having different shaped lobes and / or in number are possible. Instead of being written exactly in a circle, dimples may only be approximately, or also be included in a ellipse. Optimally, it is recommended that the lobed dimples have a perimeter P ' between 1.1 and 1.5 times the perimeter P of circular dimples which would have a identical unit area. If P 'is less than 1.1 times P, the gain obtained is too low and not detectable. If P 'is greater than 1.5 times P, this means that the contour of the dimples has many deep convolutions, which means that the edges of a dimple that face each other are a very short distance from each other. In this in this case there is a risk that the metal cannot enter the dimple, which can then no longer to play one's role. Finally, it is important that these dimples do not have sharp angles which would create abnormal solidification conditions at their level, which could generate defects in the web.

L'invention n'est pas seulement applicable aux cylindres destinés à équiper une machine de coulée d'acier entre deux cylindres, mais aussi à toute surface de coulée d'une lingotière à paroi(s) mobile(s), telle que la surface d'un cylindre d'une machine de coulée de bandes très minces sur un cylindre en rotation, ou celle d'une bande d'une machine de coulée de métal entre deux bandes en défilementThe invention is not only applicable to cylinders intended to equip a steel casting machine between two cylinders, but also on any casting surface of a ingot mold with movable wall (s), such as the surface of a cylinder of a casting machine very thin strips on a rotating cylinder, or that of a strip on a pouring of metal between two moving bands

Claims (5)

  1. Casting surface of a moving-wall mould for the continuous casting of metals, of the type including dimples of circular or elliptical general shape, characterized in that the perimeter of the said dimples has portions in which its radius curvature is smaller, in absolute value, than the mean radius of curvature of the dimple.
  2. Casting surface according to Claim 1, characterized in that the said perimeter consists of an alternation of portions having a small radius of curvature, the concavity of which faces successively the inside and then the outside of the dimple.
  3. Casting surface according to Claim 1 or 2, characterized in that the said dimples have a perimeter length lying between 1.1 and 1.5 times the perimeter length that a circular dimple of equivalent surface area would have.
  4. Casting surface according to one of Claims 1 to 3, characterized in that it consists of the lateral surface of a cooled rotating roll.
  5. Casting surface according to one of Claims 1 to 3, characterized in that it consists of the lateral surface of two cooled rolls rotating in opposite directions and defining a casting space between them.
EP95402231A 1994-10-31 1995-10-06 Casting surface for a continuous metal casting mould with movable walls Expired - Lifetime EP0709151B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9413028 1994-10-31
FR9413028A FR2726209B1 (en) 1994-10-31 1994-10-31 CASTING SURFACE OF A CONTINUOUS CASTING LINGOTIERE OF MOBILE WALL METALS

Publications (2)

Publication Number Publication Date
EP0709151A1 EP0709151A1 (en) 1996-05-01
EP0709151B1 true EP0709151B1 (en) 1999-09-08

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EP95402231A Expired - Lifetime EP0709151B1 (en) 1994-10-31 1995-10-06 Casting surface for a continuous metal casting mould with movable walls

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EP (1) EP0709151B1 (en)
JP (1) JPH08206791A (en)
KR (1) KR960013520A (en)
AT (1) ATE184226T1 (en)
AU (1) AU689632B2 (en)
DE (1) DE69511984T2 (en)
DK (1) DK0709151T3 (en)
ES (1) ES2137467T3 (en)
FR (1) FR2726209B1 (en)
GR (1) GR3032048T3 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1295859B1 (en) * 1997-11-12 1999-05-28 Acciai Speciali Terni Spa COOLING ROLLER FOR CONTINUOUS CASTING MACHINES
WO2001085369A1 (en) 2000-05-12 2001-11-15 Nippon Steel Corporation Cooling drum for continuously casting thin cast piece and fabricating method and device therefor and thin cast piece and continuous casting method therefor
AU2008100847A4 (en) 2007-10-12 2008-10-09 Bluescope Steel Limited Method of forming textured casting rolls with diamond engraving

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2037232T3 (en) * 1987-09-24 1993-06-16 Nippon Steel Corporation REFRIGERATION DRUM FOR CONTINUOUS CAST MACHINES TO MANUFACTURE THIN METALLIC STRAP.
US5103895A (en) 1989-07-20 1992-04-14 Nippon Steel Corporation Method and apparatus of continuously casting a metal sheet
CA2047688C (en) * 1990-01-12 1996-11-19 Isao Suichi Thin continuous cast plate and process for manufacturing the same
JPH082484B2 (en) * 1990-10-19 1996-01-17 新日本製鐵株式会社 Austenitic stainless steel strip-shaped slab with excellent surface quality, thin plate manufacturing method, and strip-shaped slab
AU646547B2 (en) * 1991-01-11 1994-02-24 Nippon Steel Corporation Cooling drum for casting thin cast piece; device for and method of forming dimples on peripheral surface of said drum

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GR3032048T3 (en) 2000-03-31
FR2726209B1 (en) 1996-11-29
DK0709151T3 (en) 2000-04-03
EP0709151A1 (en) 1996-05-01
AU3316495A (en) 1996-05-09
JPH08206791A (en) 1996-08-13
KR960013520A (en) 1996-05-22
AU689632B2 (en) 1998-04-02
FR2726209A1 (en) 1996-05-03
DE69511984T2 (en) 2000-05-18
ATE184226T1 (en) 1999-09-15
ES2137467T3 (en) 1999-12-16
DE69511984D1 (en) 1999-10-14

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