EP0360635A1 - Side wall for a continuous casting plant between movable walls, installations with walls, method suitable for contiuous casting thin metallic products - Google Patents

Abstract

Side wall for a continuous casting device between movable walls of metallic products, in particular of thin products, device comprising two cooled movable walls which are opposite and driven simultaneously in the same direction (3, 4) and two of the said side walls (6) delimiting the casting space, characterised in that the side wall comprises in the vicinity of the movable walls (1, 2), two inserts (7, 8) of a material having good thermal conductibility, which adjoin the edge (11) of the movable walls, present a face (73, 83) directed towards the casting space, extend so as to be in the proximity of the neck (5) between the movable walls, and delimit between them a zone consisting of a covering of thermally insulating material (9), the surface (91) of which is plane or concave. The invention applies particularly to continuous casting between cylinders of thin steel products. <IMAGE>

Description

The present invention relates to an installation for continuous casting of thin metallic products and in particular steel, between movable walls, in particular between cylinders, and more particularly the side walls commonly designated by the term "small faces", delimiting the casting space. near the side edges of said movable walls.

A problem common to different types of continuous casting installation between movable walls is to seal the lateral ends of the casting space located between the movable walls.

Another problem is to avoid catching the cast metal on the side walls, this catching being able to cause breakthroughs on the edges of the cast product.

Yet another problem is to avoid the formation of a solidified corner in contact with these walls above the neck, that is to say of the narrowest passage level between the movable walls.

To solve these problems, it has already been proposed to use thermally insulating side walls, in order to limit solidification initiating their contact, and thus to avoid the formation of said corner. A device of this type is described in particular in French patent application No. 87 05234 in the name of the owner of this application.

It is also known, in particular from documents US 303 8219 and EP 212 423, to arrange the side walls in relief, that is to say whose surfaces deviate symmetrically from one another towards the neck. This arrangement allows in particular the lateral expansion of the product as it approaches the neck, this expansion being caused by the corner rolling effect too early solidified or in the course of solidification.

These provisions do not, however, prevent infiltration of liquid metal between side walls and movable walls, solidification is poorly controlled at this level. Indeed, if the side wall is sufficiently insulating to avoid solidification of the cast metal on contact, liquid metal can infiltrate at the junction between side wall and movable wall. In addition, the materials used to make these very insulating side walls generally have little mechanical resistance. They are, therefore, quickly worn by the friction of the metal and the ends of cylinders, which further promotes infiltration.

If, conversely, the side walls are less insulating, the cast metal solidifies on contact, but this solidification being difficult to control, problems of jamming, catching or irregularity of the edges of the product may remain, even in the case of side walls in draft.

The present invention aims to remedy the aforementioned drawbacks and to promote cooling over the entire width of the cast product and in particular on the edges of its long sides, without however creating a premature solidification in contact with side walls.

With these objectives in view, the object of the present invention is a side wall for a device for continuously casting thin metallic products between movable walls, comprising two cooled movable walls facing each other and driven simultaneously in the same direction and delimiting with two said fixed side walls a casting space.

According to the invention, the side wall is characterized in that it comprises a closure plate held against the edges of the movable walls, and two inserts made of material of good thermal conductivity which penetrate into the casting space between the walls movable, adjoin the edge of said movable walls, have a face directed towards the pouring space, extend up to the proximity of the neck between said movable walls, and delimiting between them an area consisting of a coating of material thermally insulating with a flat or concave surface.

Thanks to the device according to the invention, the metal skin solidified in contact with the cooled movable walls extends on the face of the inserts directed towards the casting space. The continuous skin obtained covers the joint between the movable wall and the inserts, thereby preventing liquid metal infiltration therein. In addition, no skin is formed in contact with the inter-insert area of the side walls, since the latter is very insulating.

According to a particular arrangement of the invention, the surface of the side wall opposite the casting space, formed by the faces of the inserts directed towards the casting space and the surface of the insulating coating, is generally in clearance. In this arrangement, the relief of the side walls allows lateral expansion of the edges of the cast product. Simultaneously, the edges of the skin which form in contact with the inserts are progressively pressed by the ferrostatic pressure against the movable walls.

According to another complementary arrangement, said faces of the inserts facing the casting space are also inclined relative to a vertical plane perpendicular to the movable walls, this inclination gradually reducing from the upper end to the lower end of the inserts , or their faces opposite the casting space are substantially perpendicular to the movable walls.

In this case the progressive plating effect of the edges of the solidified skins is further accentuated, these solidified skins widening and thickening gradually so as to form, near the level of the neck, two skins of substantially constant thickness over the entire product width.

This particular arrangement makes it possible in particular to minimize the forces exerted on the walls of the cylinders, perpendicular thereto.

Indeed, if from the level of the liquid metal, the solidification of the edges of the skin forms tabs perpendicular to the wall of the cylinders, these tabs tend to thicken as they approach the neck and the ferrostatic pressure may be insufficient for the evenly press against the cooled walls of the cylinders, which leads to solidification irregularities, and also a greater force near the neck where the tongues meet and tend to be "rolled".

In addition, if these tabs do not press well on the cooled walls, the seal is no longer ensured between cylinder and side wall, and liquid metal may seep between the tongue and the adjacent side wall. The risk is practically eliminated thanks to the particular provision indicated above.

The invention also relates to an installation for continuous casting of thin metallic products between movable walls, in particular between cylinders, this installation being characterized in that it comprises lateral walls according to one of the above arrangements.

The subject of the invention is also a process for the continuous casting of thin metallic products, in particular of thin steel strips, according to which the above installation is used, the casting space is supplied with liquid metal while maintaining its level. below the upper end of the inserts and of the insulating coating, the movable walls are driven simultaneously and in the same direction, whereby the liquid metal solidifies on contact with said cooled movable walls by forming solidified skins whose edges extend over the surfaces of the inserts directed towards the casting space, these skins widening and thickening as the movable walls move until they meet near the level of the neck between said movable walls, and we extract continuously down the solidified thin metal product.

The invention will be better understood and other characteristics and advantages will appear on reading the description which will be given of a preferred embodiment of the invention, in the case of casting between cylinders.

• - la figure 1 est une représentation schématique partielle d'une installation de coulée continue entre cylindres, montrant la disposition d'une paroi latérale conforme à l'invention ;
• - la figure 2 est une vue en coupe selon le plan II-II de la figure 1 ;
• - les figures 3 à 6 sont des schémas montrant l'évolution de la solidification du produit aux différents niveaux indiqués sur la figure 2 ;
• - la figure 7 est une vue en plan d'une paroi latérale particulièrement adaptée à un dispositif de coulée selon l'in­vention ;
• - la figure 8 est une vue en coupe verticale de cette paroi, selon la ligne VIII-VIII de la figure 7 ;
• - la figure 9 est une vue en coupe de cette paroi au niveau de la ligne IX-IX ;
• - la figure 10 est une autre vue en coupe horizontale, selon X - X de la figure 7.

Reference will be made to the appended drawings in which:

• - Figure 1 is a partial schematic representation of a continuous casting installation between cylinders, showing the arrangement of a side wall according to the invention;
• - Figure 2 is a sectional view along the plane II-II of Figure 1;
• - Figures 3 to 6 are diagrams showing the evolution of solidification of the product at the different levels indicated in Figure 2;
• - Figure 7 is a plan view of a side wall particularly suitable for a casting device according to the invention;
• - Figure 8 is a vertical sectional view of this wall, along the line VIII-VIII of Figure 7;
• - Figure 9 is a sectional view of this wall at the line IX-IX;
• FIG. 10 is another view in horizontal section, along X - X of FIG. 7.

The schematic drawings of FIGS. 1 to 6 are given purely for educational purposes and it will be understood that the relative dimensions of the various elements have not been voluntarily observed, this in order to facilitate understanding of the subject of the invention and goals.

In Figure 1 is shown one end of a continuous casting installation between cylinders, comprising two cylinders 1 and 2, the second of which has been symbolized only by the trace 21 of the end of its wall.

The two cylinders, with parallel axes and located in the same horizontal plane P, are rotated in opposite directions according to arrows 3 and 4, and spaced at the neck 5, corresponding to the level of the plane P passing through the axes of the cylinders, a distance corresponding to the thickness of the cast product.

The liquid metal is supplied, according to one of the well-known methods, in the casting space delimited, on the one hand, by the part of the walls of the cylinders situated above the neck and, on the other hand , by the side walls located at the edges of the cylinders and in leaktight contact with said edges. It is clear that the side walls being fixed and the walls of the cylinders movable, a minimum functional clearance must be respected between them to avoid intense friction and the wear which would result therefrom. As a result, the seal cannot be absolute and infiltration of liquid metal may occur. Reducing the risk of infiltration is in particular one of the aims of the present invention.

Indeed, if the side wall is made up as indicated at the beginning of this specification, of a sufficiently insulating material so that the liquid metal does not solidify on contact, the metal skin solidified on contact with the cooled walls of the cylinders s he stops just at the joint between side wall and cylinder, and the risk of infiltration at this level is great.

The idea which presided over the present invention is precisely to achieve sealing against liquid metal by promoting the extension of the solidified skin on the part of the side wall directly adjacent to the cylinders, while facilitating the shaping of the edges of these skins, and avoiding solidification of the metal in contact with the side walls. It is therefore the solidified skin which covers the joint between cylinder and side wall, which constitutes a tight wall preventing infiltration.

In Figure 1 is shown a side wall, or "small face" 6, consisting of a vertical flat plate 61 held with a functional clearance against the ends of the cylinders 1 and 2, that is to say against the edges of the cylindrical surfaces thereof. This plate 61 carries two inserts 7, 8 made of a material with good thermal conductivity. Each insert is a thin strip, preferably close to half the thickness of the cast product, curved according to the curvature of the cylinders, and protrudes from the plate 61 towards the inside of the casting space so as to match the edge 11 of the cylindrical wall. The lower ends 71, 81 of the inserts of the same side wall meet at a level preferably situated slightly above the neck 5. The width of the inserts protruding from the plate 6, decreases regularly from their upper ends 72, 82, up to their lower ends 71, 81. The face 73, 83 of the inserts, facing the casting space, is, at any level, inclined relative to the generator of the cylinder situated at this level, this inclination gradually increasing from the upper ends of the inserts to their lower ends where it is around 90 °. In other words, the face 73, 83 of each insert is a left surface, a horizontal generator of which forms with the corresponding generator of the adjacent cylinder, an obtuse angle, for example of approximately 135 °, at the upper end 72, 82, this angle gradually decreasing downwards until it is substantially equal to 90 ° at the lower end.

The zone located between the inserts of the same small face consists of a plate or a coating of insulating refractory material 9, the surface 91 of which faces the casting space, is preferably flat and inclined with respect to the vertical to form the draft described above and clearly visible in Figure 2, so as to form a continuous surface with the faces 73, 83 of the inserts, without roughness at their junction lines. Advantageously, the refractory material 9 is hardened on the surface to avoid too rapid wear by the cast metal.

It will of course be understood that during casting, the level of liquid metal must be kept below the upper limit of the inserts and of the refractory material.

The lower ends of the inserts can form, as indicated in FIG. 2, a sudden detachment 62 with respect to the plate 61, similar to that shown in the document EP 212 423 already cited, which allows, at the level of the neck, the free lateral expansion of the edges of the cast product. However, as will be described in more detail by Following this memo, ensure continuity between the surfaces of the inserts 73, 83 and of the refractory material 91, and the wall portion 63 immediately underlying it.

The faces 73, 83 of the inserts can also be plane in the same plane as the surface 91 of the insulating refractory material 9, which simplifies the production of said inserts. The continuity of the solidified skin at the joint between cylinders and inserts is also ensured. However, this arrangement is less favorable for the formation and the desired development of said skin, in accordance with the description which will be given in relation to FIGS. 3 to 6.

These figures are horizontal sections of the casting installation, during casting, at the different levels identified in FIG. 2.

FIG. 3 schematically represents a section at level III near the level N of the liquid metal. In contact with the cooled walls of cylinders 1 and 2, the molten metal 10 solidifies and forms, on each cylinder, a solidified skin of small thickness 101, 102. This skin is extended by a tongue 103, 104, solidified in contact with the inserts 7, 8 which are thermally conductive and cooled due to their proximity to the cooled walls of the cylinders and of contact with the metallic mass of the plate 61. On the other hand, the cast metal does not tend to solidify on contact with the insulating refractory material 9. Note that the solidified skin seals from the level above at the point 105, 106 between cylinders and inserts.

Figure 4 is a section at intermediate level IV when the skin 101, 102 arrives at this level due to its entrainment by the walls of the rotating cylinders. Simultaneously, the tongues 103, 104 accompany this movement by sliding on the faces 73, 83 of the inserts.

The cooling of the cast metal continues and the thickness of the skin 101 ′, 102 ′ and of the tongue 103 ′, 104 ′ increases. The width of the face 73, 83 of each insert is reduced due to the increase in its inclination relative to the wall of the cylinder. Simultaneously, the contact width of the solidified skin with the cylinder increases due to the relief of the side wall, and the tongue is applied progressively against the wall of the cylinder under the effect of ferrostatic pressure. Due to the relief of the surface 91 of the refractory 9, the casting space widens.

At level V of the lower end of the inserts (Figure 5), the thickness of the skin 101˝, 102˝ has further increased. The two tabs formed on each insert are applied to the walls of the cylinders and simultaneously meet at 108.

At the neck (level VI, FIG. 6), the two skins are in total contact and form the product 109 of desired section, the lateral expansion of the edges caused by the rolling effect is authorized by the final increase in width of the casting space, until it comes into contact with the wall portions 63.

As will have already been understood, the device according to the invention:
- ensures the tightness of the casting space,
- allows lateral expansion of the product,
- controls the formation and development of solidified skin and especially its edges (tabs), while avoiding the formation of solid skin on the side walls.

Figures 7 to 10 show a preferred embodiment of a small face according to the invention.

In this embodiment, the plate 61 is made up of several elements assembled by screwing, so as to allow the inserts 7, 8 to be maintained. It comprises a flat support plate 64 on which are fixed, by screws 111 and held in position by centering pins 112, two bearing plates 65, 66 whose flat surface is designed to be placed opposite the ends of the cylinders, and shaped so as to have a curved edge 67, 68, of the same radius as the cylinders and precisely following on from these.

The metal inserts 7, 8 are applied against the curved edges 67, 68, and in contact with the support plate 64. They are held in position by pins 74 fixed in the support plates 65, 66 which penetrate into oblong holes 75 made in the inserts, so as to prevent the displacement thereof in the direction parallel to the axis of the cylinders, while allowing a slight displacement parallel to the edges of the support plates to allow the longitudinal expansion of said inserts.

The thickness of the inserts is constant (for example 2 mm). Their width varies from their upper ends, where they project from the plane of the surface of the support plates by a few millimeters (5 to 10 mm, for example), to their lower ends where the projection is much smaller (1 to 2 mm for example). These values are given for information only and depend in particular on the general dimensions of the installation. These values correspond to a draft of the inserts, and also of the refractory lining of the order of 1 to 3 °. The faces 73, 83 of the inserts 7, 8 are shaped as indicated above, so as to have a regular variation in their inclination relative to the wall of the cylinders. The inserts therefore have at their upper ends, a bevel section with an angle close to 45 °, this angle increasing downwards until forming, at the lower end, a quadrangular section.

An intermediate metal plate 69, two sides of which are shaped according to the curvature of the inserts, is inserted between them to keep them pressed against the curved edges 67, 68 of the support plates 65, 66. The intermediate plate 69 is fixed by screw 113 on the support plate 64.

The intermediate plate 69 has a thickness less than that of the support plates 65, 66, so as to allow the establishment against this plate 69, and between the inserts, of an insulating refractory material 9 whose face 91 opposite the casting space is flush with the faces 73 and 83 of the inserts. This insulating material can be a prefabricated and glued plate on the intermediate plate 69, or it may be a material deposited in place, for example by projection.

The lower ends of the inserts of the intermediate plate 69, and of the insulating refractory lining 9, are located at the same level, slightly above the neck. At this level, the lower ends of the inserts are slightly spaced in order to maintain a certain width at the "tip" of the insulating refractory material, to avoid embrittlement of this tip.

Below this level (corresponding to level V in FIG. 2), the side wall is extended by a guide shoe 120, fixed by screws 114 on the support plate 64. The rear part 121 of the guide shoe is inserted in corresponding recesses 122, 123, produced in plates of support thickness 65, 66. The front part 124 of the guide shoe is machined so as to have edges 125, 126 of curvature corresponding to that of the edges 67, 68 of the support plates 65, 66. The face of this guide shoe, facing the cast product, has above the neck, a clearance area 127 in the extension of the face 91 of the refractory lining 9, and in below the neck (level of plane P), a vertical flat area 128 situated in the same plane as the surface of the support plates 65, 66.

The guide shoe 120 is made of a material having good wear resistance characteristics, for example cast iron.

The particular configuration of the guide shoe 120 which has just been described, in particular with regard to the undercut area 127, has the advantage, compared with the recess 62 shown in FIG. 2, of ensuring the continuity of the side wall at contact of the cast product, and thus avoid excessively rapid wear or tearing of the lower ends of the inserts and of the refractory lining.

Of course, the invention is not limited to the embodiment described above by way of example. Modifications technological developments may be made to the various constituent elements of the side wall and to their method of assembly.

For example, the inserts may be made of a material which is not exclusively metallic, such as compounds of the boron nitride type, BN with SiALON or Si₃N₄, or AlN; or SiC.

Provision may also be made for the face 91 of the refractory lining, instead of being planar, to be concave.

We can also provide that the inserts penetrate further forward between the cylinders, so that the guide shoe also enters between them and is therefore prominent relative to the bearing plates.

It will also be possible to promote the formation of the tabs of the solidified skin by a localized cooling device, near the inserts, the support plates and / or the support plate, and also of the pad or even by direct cooling of the inserts.

Claims (8)

1) Side wall for a continuous casting device between movable walls of metallic products, in particular thin products, device comprising two cooled movable walls facing each other, driven simultaneously in the same direction (3,4) and delimiting with two said lateral walls fixed (6) a pouring space, characterized in that it comprises a closure plate held against the edges of the movable walls (1,2), and two inserts (7,8) made of material of good thermal conductivity, which penetrate into the pouring space between the movable walls, adjoin the edge (11) of said movable walls, have a face (73,83) directed towards the pouring space, extend as far as the neck (5) between the movable walls, and delimit between them an area consisting of a coating of thermally insulating material (9) whose surface (91) is flat or concave. 2) side wall according to claim 1, characterized in that the surface (91,73,83) of the side wall facing the casting space, formed by the faces (73,83) of the inserts directed towards the casting space and the surface (91) of the insulating coating, is generally undercut. 3) side wall according to one of claims 1 and 2, characterized in that said faces (73, 83) of the inserts facing the casting space, are also inclined relative to a vertical plane perpendicular to the movable walls, this inclination gradually reducing from the upper ends (72,82) to the lower ends (71,81) of the inserts, where said faces (73,83) are substantially perpendicular to the movable walls. 4) side wall according to claim 2 characterized in that the draft is about 1 to 3 °. 5) side wall according to claim 3, characterized in that the inclination of the faces (73,83) of the inserts facing the casting space, at their upper end, is about 135 ° relative to the generatrîce of the adjacent movable wall. 6) side wall according to one of claims 1 to 5, characterized in that it comprises below the inserts and refractory lining, and adjacent to their lower ends, a shoe (120) whose surface opposite the casting space has above the neck 5, a zone (127) in relief in the extension of the surfaces (91,73 , 83) of the inserts and of the refractory lining, and, below the neck 5, a vertical plane area 128. 7) Installation for continuous casting of thin metallic products between movable walls, in particular between cylinders, characterized in that it comprises side walls according to one of claims 1 to 6. 8) Process for continuous casting of thin metallic products, characterized in that the installation according to claim 7 is used, the casting space is supplied with liquid metal while maintaining its level below the upper end of the inserts and of the insulating coating, the movable walls are driven simultaneously and in the same direction, whereby the liquid metal solidifies on contact with said cooled movable walls, forming solidified skins whose edges extend over the surfaces of the inserts directed towards the pouring space , these skins widening and thickening as the movable walls move until they meet near the level of the neck between said movable walls, and the solidified thin metallic product is continuously extracted downwards.

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