EP0588743A1 - Installation for continuous casting of thin metallic products between rolls - Google Patents

Abstract

The installation includes two cooled rolls (1, 2) driven in rotation and two lateral walls (3) pressed against the front ends (6, 7) of the rolls and delimiting with the latter a casting space for the liquid metal, and, at least locally in zones (10, 11) in which the lateral walls face the front ends of the rolls, a layer (21) of a self-lubricating solid material. <IMAGE>

Description

The present invention relates to a device for continuous casting of metals comprising two cylinders with parallel axes, driven in opposite directions and separated by a predetermined distance, and two fixed walls for closing the casting space defined between the two. cylinders.

Such devices are already known and used in particular for obtaining thin metallic products, such as sheets or strips, in particular made of steel.

One of the problems encountered in the use of this type of device is to seal the liquid metal between the cylinders and the fixed side walls, taking into account the fact that the cylinders expand in their axial direction during casting.

In an attempt to solve this problem, it has already been proposed, in document FR 2647376, to provide each side wall with rollers or balls brought into contact with the sides of the cylinders by elastic support means acting on the rear of the side walls. and so as to define an operating clearance between the edges of the cylinders and the active surface, on the side of the casting space, of the side walls. Such an arrangement is however complex. In addition, the raceway of the rollers or balls cannot be located just at the periphery of the cylinders. As the expansion of the cylinders may be different between the periphery and the area of the raceway, it follows that said operating clearance may vary during casting.

It has also been proposed to flatten the side walls of refractory material directly against the sides of the cylinders by springs, but this arrangement requires providing a lubricant in liquid or solid form at the interface, continuously during casting. . This lubricant is liable to pollute the liquid metal, by entering the casting space. Furthermore, the clearance between the side wall and the cylinders being practically eliminated, this arrangement promotes undesirable heat exchanges between them, and the wear of the refractory cannot be completely eliminated despite the lubrication.

Also known, from document FR 2666256, are side walls comprising, facing the edges of the cylinders, frustoconical disc portions, called "mops" by analogy of shape, made of a material having specially adapted thermal and mechanical characteristics, different refractory material located between these mops and in contact with the liquid metal. These mops are either permanently pressed against the sides of the cylinders, or kept at a distance from them with a slight cold clearance before casting and at the start of casting, but liable to come into contact during the expansion of the cylinders in progress. of casting. In both cases, an injection of lubricant at the interface is necessary.

The object of the present invention is to solve the problems mentioned above, to eliminate the supply of lubricant, whether by injection of a liquid lubricant or by depositing a solid or pasty lubricant, and to facilitate installation. of the device and / or the replacement of the side walls.

With these objectives in view, the invention relates to a continuous casting device between cylinders of thin metallic products, in particular steel, comprising two cooled cylinders driven in rotation and two side walls pressed against the front ends of the cylinders and delimiting with those here a liquid metal pouring space, characterized in that it comprises, at least locally in areas where the side walls face the front ends of the cylinders, a layer of a self-lubricating solid material.

The expression "self-lubricating solid material" generally designates any solid material with a low coefficient of friction, which cannot be consumed under normal conditions of use.

Thanks to the invention, the injection of liquid lubricant is eliminated. In addition, the thickness of said layer defines a fixed clearance between the edges of the cylindrical surfaces of the cylinders and the side walls, even when said cylinders expand axially at the periphery.

Preferably, this material is a self-lubricating plastic material, such as polytetrafluoroethylene (PTFE) known under the name teflon, or alternatively perfluorinated polyethylene propylene (FEP) or diallylisophthalate, or other similar self-lubricating plastic materials.

The use of a layer of self-lubricating solid material at the cylinder-side wall interface makes it possible to greatly reduce friction without adding lubricant. As there is practically no wear, therefore consumption of this layer, its thickness remains constant during the implementation of the device, during casting.

According to a variant of the invention, said layer consists of a localized coating of the side wall.

According to another variant, said layer is formed by a part, projecting relative to the surface of the side wall, of a plate fixed in a groove of said side wall.

• ladite couche est continue sur un secteur annulaire s'étendant du haut en bas de ladite zone ;
• le secteur annulaire a un rayon extérieur sensiblement égal à celui des cylindres ;
• le secteur annulaire a un rayon extérieur inférieur à celui des cylindres ;
• le secteur annulaire a un rayon extérieur inférieur de 5 à 10 mm à celui des cylindres ;
• le revêtement est réalisé par un procédé de dépôt en couche mince tel que dépôt chimique, dépôt en phase vapeur, ou par plasma.

According to additional features:

• said layer is continuous over an annular sector extending from top to bottom of said zone;
• the annular sector has an outer radius substantially equal to that of the cylinders;
• the annular sector has an outer radius smaller than that of the cylinders;
• the annular sector has an outside radius of 5 to 10 mm less than that of the cylinders;
• the coating is produced by a thin layer deposition process such as chemical deposition, vapor deposition, or by plasma.

According to yet another variant, said layer is discontinuous and formed by a plurality of studs spaced apart from each other.

In this variant, preferably, each stud is formed by the end of a sliding bar in a bore in the side wall, perpendicular to the surface of the latter, and adjustable in position.

• le matériau autolubrifiant est un matériau composite, notamment à base de matière plastique autolubrifiante ou comportant une telle matière (par exemple : PTFE + MoS₂ + fibre de verre, PTFE + fibres métalliques orientées, PTFE dans une matière métallique frittée, polyimide aromatique + graphite, etc...)
• l'épaisseur de la couche est comprise entre 0,01 et 0,1 mm.

According to other characteristics:

• the self-lubricating material is a composite material, in particular based on self-lubricating plastic material or comprising such a material (for example: PTFE + MoS₂ + fiberglass, PTFE + oriented metallic fibers, PTFE in a sintered metallic material, aromatic polyimide + graphite, etc ...)
• the thickness of the layer is between 0.01 and 0.1 mm.

Finally, said layer can also be fixed to the front walls of the cylinders.

Other characteristics and advantages will appear in the description which will be given of various embodiments of the invention, in a continuous casting device between cylinders of thin steel products.

• la figure 1 est une vue schématique partielle d'un dispositif de coulée entre cylindres ;
• la figure 2, est une vue en coupe selon la ligne II-II de la figure 1 ;
• la figure 3 est une demi-vue de la paroi latérale dans une première variante de l'invention ;
• la figure 4 est une vue similaire à celle de la figure 2, dans le cas d'une paroi latérale pourvue de portions de disques en forme de serpettes ;
• les figures 5, 6 et 7 sont des demi-vues de face de la paroi latérale pourvue de serpettes ;
• les figures 8, 9 et 10 sont des vues de la serpette, selon trois variantes, en coupe selon respectivement les lignes VIII-VIII de la figure 5, IX-IX de la figure 6 et X-X de la figure 7.

Reference is made to the appended drawings in which:

• Figure 1 is a partial schematic view of a casting device between cylinders;
• Figure 2 is a sectional view along line II-II of Figure 1;
• Figure 3 is a half view of the side wall in a first variant of the invention;
• Figure 4 is a view similar to that of Figure 2, in the case of a side wall provided with disc portions in the form of mops;
• Figures 5, 6 and 7 are half front views of the side wall provided with mops;
• FIGS. 8, 9 and 10 are views of the mop, according to three variants, in section along lines VIII-VIII of FIG. 5 respectively, IX-IX of FIG. 6 and XX of FIG. 7.

Figure 1 shows the two cylinders 1, 2 of a casting device between cylinders, and a side wall 3 for closing the casting space 4. During the casting, for example of a steel, the latter is poured according to arrow F into the casting space 4, solidifies on contact with the cooled walls of cylinders 1 and 2, and is extracted downwards during the rotation of the cylinders, according to arrows F1, to form a thin strip 5.

The side wall 3 is pushed towards the front ends 6, 7 of the cylinders, for example by elastic means, such as springs 8, or any other pressure means.

In the variant shown in FIG. 2, the wall 3 essentially consists of a plate of refractory material comprising a flat surface 9, at least in the zones 10, 11 where the side wall faces the cylinders.

In these zones 10, 11, the wall 3 comprises a coating 21 of a self-lubricating solid material. This coating forms a continuous layer from top to bottom of the side wall 3 (fig. 3) on an annular sector 22 whose outside radius Re is slightly smaller than that of the cylinders and has a thickness of 0.01 to 0.1 mm.

Under the effect of the springs 8, the coating 21 is pressed against the front end surface 6, 7 of the cylinders, determining between the latter and the surface 9 of the side wall a clearance j1 of value equal to the thickness of the coating. The center of curvature of the annular sector 22 coinciding with the axis of the cylinder, there also remains between the outer edge 23 of the coating and the cylindrical wall of the cylinder a radial clearance j2, which avoids direct contact between the coating and the cast metal, the latter can not infiltrate the weak play j1. The clearance j2 is preferably 5 to 10 mm; but it can be reduced compared to these values, if not canceled, in the case where the nature of the coating 21 does not prohibitively prohibit any contact with the molten cast metal.

The coating 21 is preferably made of Teflon, or other self-lubricating plastic. The self-lubricating qualities of this material result of the transfer of a thin oriented film of this material onto the opposing surface in movement in contact with said material, which ensures very good sliding as soon as this transfer is achieved and virtually eliminates any subsequent consumption of said material.

A particular advantage of self-lubricating plastics is that it is possible to deposit them in a thin layer directly on the surface of the side wall facing the cylinder.

This coating can be produced by any known type of deposition process suitable for the material concerned, for example by chemical deposition, chemical or physical vapor deposition, etc.

In Figure 4, there is shown a variant of the invention applied to a casting device having side walls 3 provided with disc portions such as those described in document FR 2666256 already cited in the introductory part.

In this variant, the side wall 3 comprises a housing 31 provided with a recess in which is placed a plate 32 of refractory material, the flush surface 33 of which has a shape corresponding to the vertical cross section of the casting space 4 defined between the two cylinders 1 and 2. This plate 32 is bordered on each side by portions of metal frustoconical discs 34, 35, also called "mops" fixed to the housing 31 by screws 36 shown only by their axes in FIG. 4.

These mops 34, 35 have an outer radius Re1 substantially equal to that of the cylinders, so that the edges 37 formed by their edges of larger radius face the edges 38 formed by the edges of the cylindrical walls of the cylinders.

In the variant shown in FIGS. 5 and 8, the layer 21 of self-lubricating solid material is formed by a part of a plate 38 of this material, projecting from the surface 39 of the mop 34. This plate 38 is held by anchoring in a groove 40 in dovetail machined in the mop. To avoid sliding of the plate 38 in the groove 39, the latter is closed downwards, to form a stop 41.

In the variant shown in Figures 6 and 9, the layer 21 of self-lubricating solid material covers the entire surface 39 of the mop. In this case, said layer preferably consists of a coating deposited according to one of the methods already mentioned in the description of the first variant.

In the variant shown in FIGS. 7 and 10, the layer of self-lubricating solid material is discontinuous and consists of a plurality of studs 51 distributed over the height of the mop 34. These studs can be circular, as shown in FIG. 7 and of diameter slightly less than the width of the mop. Preferably, each stud 51 is formed by the end of a bar 52 made of self-lubricating material, which can slide in a bore 53 machined in the pruning rod perpendicularly to the surface 39 thereof. Each bar comprises means, not shown, for adjusting in axial position, in the direction of the arrows 54, so as to be able to adjust the overhang of these bars relative to the surface 39. This makes it possible to compensate for any wear of the studs, and also possibly to independently adjust the overhang of each stud.

The invention is not limited to the examples which have just been described. We can for example combine in the same realization of the characteristics described above in the context of several variants. The layer of self-lubricating solid material may also be fixed or deposited on the front walls of the cylinders, near their periphery, in the form of a continuous or discontinuous strip.

Claims (12)

1) device for continuous casting between cylinders of thin metallic products, in particular steel, comprising two cooled cylinders (1, 2) driven in rotation and two lateral walls (3) pressed against the front ends (6, 7) of the cylinders and delimiting with these a pouring space (4) of the liquid metal, characterized in that it comprises, at least locally in zones (10, 11) where the side walls face the front ends of the cylinders, a layer (21 ) a solid, self-lubricating material. 2) Device according to claim 1, characterized in that said layer is constituted by a localized coating of the side wall. 3) Device according to claim 1, characterized in that said layer is formed by a part, projecting relative to the surface (39) of the side wall, of a plate (38) fixed in a groove (40) of said side wall. 4) Device according to claim 1, characterized in that said layer is continuous on an annular sector (22) extending from top to bottom of said zone. 5) Device according to claim 4, characterized in that the annular sector has a radius (Re) equal to or slightly less than that of the cylinders. 6) Device according to claim 2, characterized in that the coating is produced by a thin film deposition process such as chemical deposition, vapor deposition, or plasma deposition. 7) Device according to claim 1, characterized in that said layer is discontinuous and constituted by a plurality of studs (51) spaced therebetween. 8) Device according to claim 7, characterized in that each stud (51) is formed by the end of a bar (52) sliding in a bore (53) of the side wall, perpendicular to the surface (39) of this, and adjustable in position. 9) Device according to claim 1, characterized in that the solid material layer comprises a self-lubricating plastic. 10) Device according to claim 1, characterized in that said layer is formed by a composite self-lubricating material. 11) Device according to claim 1, characterized in that the thickness of the layer is between 0.01 and 0.1 mm. 12) Device according to claim 1, characterized in that said layer is fixed or deposited on the front walls (6,7) of the cylinders.

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