EP1144142B1 - Side wall for installation for continuous casting of metal strips - Google Patents

Abstract

A side wall closing the casting space of an installation for continuous casting of thin metal strips between unwinding cooled walls, including a support plate, on the rear face of which thrust members exert their action, and an active face arranged against the front face of the support plate. Lateral portions are designed to be worn by contact with the edges of the cooled walls over a maximum depth "e" and a length "1". The support plate and the active part are urged in contact with each other in a way enabling them to be disengaged non-destructively. The support plate front face has in its central part a recess whereof the depth is greater than "e" and the outer edges of the front face have a general shape which matches that of the outer edges of the active part and have a length less than "1".

Description

The invention relates to the continuous casting of metals. It concerns more particularly installations for the continuous casting of thin metallic strips of the type called "casting between cylinders".

Directly pouring thin metal strips a few mm thick from liquid metal (steel, stainless steel and other ferrous alloys, copper, for example example) can take place on a so-called "casting between cylinders" installation, supplied with liquid metal from a distributor, using a pouring nozzle. The machine has an ingot mold whose casting space is delimited on its long sides by a pair of internally cooled cylinders with parallel horizontal axes rotating around of these axes in opposite directions, and on its short sides by closing plates in refractory material, called "side faces", which are applied by thrust against the flat ends of the cylinders. The solidification of the liquid metal is product against cooled cylindrical surfaces of cylinders, by skin formation solidified that is joined at the neck (the area where the gap between the surfaces cylinders is minimal) to form the strip, which is continuously extracted from the space of casting. On certain installations (which generally flow products of a thickness slightly stronger), the cylinders can be replaced by bands cooled by scroll, which is given a curved shape at the entrance to the casting space. These installations also have side faces similar to those of casting between cylinders, and means for applying these lateral faces against the edges tapes. They are usually designated by the term "inter-band casting".

Conventionally, each side face is constituted as follows. It includes firstly a support plate, preferably made of a material with strong insulating properties, such as silica. Most often, it is fixed on its rear face (the one facing outside the pouring space) to a metal plate on which the organs act thrust. But if the support plate has mechanical strength and rigidity sufficient, it can be expected that the thrust members exert their action directly on the support plate. On the front face of this support plate, there is the active part of the lateral face, i.e. the material or materials which are intended to come into contact with cylinders and liquid metal. Very often the external areas of this active part, which must come into contact with the cylinders or be in the vicinity of the neck, are made in a first material for which the qualities of resistance to abrasion and to corrosion by liquid metal. such as SiAlON® or silicon carbide, and the zone central part of this active part, which must be in contact with the liquid metal, is produced in a second material for which insulating properties are preferred, such as foam silica. The element or elements making up the external zones are often designated by the term "Insert", and the element or elements forming the remainder of the lateral face by the term "heart". The side faces, before the start of casting, undergo a preheating which aims to avoid solidification of metal on their active part when filling the space of poured by liquid metal.

The lateral faces have a fundamental importance in the success of a casting metal strips between cylinders, in particular steel strips. A bad tightness of their contacts with the edges of the cylinders can lead to exfiltration of liquid metal outside the casting space, which compromises the regularity of the operation of the installation, therefore the quality of the tape. In extreme cases, these exfiltration can lead to stopping the flow. Similarly, a rupture during casting of one of its elements, or a decohesion of the multiple elements making up the face active, lead to stop the casting without delay. Special attention must therefore be made to the choice of materials making up the lateral faces, some of which (in the materials making up the insert) are very expensive. Likewise, the assembly of the lateral face, and in particular the realization of its active part, is an operation complex that must be performed by highly qualified and careful personnel, and this assembly (as well as the drying of the refractories and the bonding materials used which follows) is time consuming. The side panels can only be used for one single casting, after which they are disassembled, and at least their active part is brought to scum. For these reasons, the side faces constitute one of the main elements of the cost of operation of an installation for casting thin strips between cylinders (or, in general, between two walls which are cooled in movement), and any technical progress which would reduce spending on time and related matters, without altering their performance and reliability is highly desirable.

The object of the invention is to propose a design of the lateral faces of a installation of casting thin metal strips between two walls cooled in scrolling whose cost of manufacture and use is significantly lowered compared to with side faces of classic design.

To this end, the invention relates to a lateral face for closing the space of casting of a continuous casting installation of thin metal strips between two walls cooled in movement, in particular of "casting between cylinders" or of "casting between bands ", of the type comprising a support plate, on the rear face of which thrust members exert their action in order to apply said lateral face to the slices of said walls cooled, optionally by means of a plate metallic integral with the rear face of the support plate, and an active face disposed against the front face of the support plate, the lateral portions of which are intended to wear out in contact with said sections of said walls cooled to a maximum depth "e" and a width "1", the support plate and the active part being brought into contact with one another in a way allowing their non-destructive separation, characterized in that the front face of the support plate has in its central part a recess whose the depth is greater than "e", and in that the outer edges of said front face have a general shape which matches that of the outer edges of the active part and have a width less than "1".

As will be understood, the invention consists in designing the lateral face of so as to authorize a use of its active part for no longer just one, but two flows, by simply turning this active part between the two flows. To this end, we must in particular give a particular shape to the front face of the support plate. This results in considerable savings on the preparation time of the lateral face prior to the second casting in the series.

• la figure 1 qui montre vue de face (figure 1a) et vue de dessus en section selon Ib-Ib une face latérale de coulée de bandes minces selon l'art antérieur dans son état initial (figure 1b), et vue de dessus en section selon Ib-Ib après son utilisation (figure 1c);
• la figure 2 qui montre vue de dessus en section selon Ib-Ib un premier exemple de face latérale de coulée de bandes minces selon l'invention dans son état initial, avant sa première utilisation (figure 2a) et avant sa deuxième utilisation (figure 2b) ;
• la figure 3 qui montre vue de dessus en section selon Ib-Ib un deuxième exemple de face latérale de coulée de bandes minces selon l'invention dans son état initial, avant sa première utilisation ;
• la figure 4 qui montre vue de dessus en section selon Ib-Ib un troisième exemple de face latérale de coulée de bandes minces selon l'invention dans son état initial, avant sa première utilisation ;
• la figure 5 qui montre vue de dessus en section selon Ib-Ib un quatrième exemple de face latérale de coulée de bandes minces selon l'invention dans son état initial, avant sa première utilisation.

The invention will be better understood on reading the description which follows, given with reference to the following appended figures:

• Figure 1 which shows front view (Figure 1a) and top view in section according to Ib-Ib a side face of casting thin strips according to the prior art in its initial state (Figure 1b), and top view in section according to Ib-Ib after its use (Figure 1c);
• Figure 2 which shows a top view in section according to Ib-Ib a first example of a lateral face for casting thin strips according to the invention in its initial state, before its first use (Figure 2a) and before its second use (Figure 2b );
• Figure 3 which shows a top view in section according to Ib-Ib a second example of a lateral face for casting thin strips according to the invention in its initial state, before its first use;
• Figure 4 which shows a top view in section according to Ib-Ib a third example of a lateral face for casting thin strips according to the invention in its initial state, before its first use;
• Figure 5 which shows a top view in section according to Ib-Ib a fourth example of a lateral face for casting thin strips according to the invention in its initial state, before its first use.

For reasons of clarity of the presentation of the basic principles of the invention, the various elements of the lateral faces have not been shown to scale in the figures. Usually, the casting rolls have a diameter of the order of 500 to 1500 mm, and the collar has a width of a few mm, corresponding to the thickness of the strips that one desires flow.

• une plaque support 2 en matériau réfractaire aux propriétés isolantes élevées, solidaire sur sa face arrière 3 d'une platine métallique 4 refroidie, sur laquelle des organes de poussée (non représentés) exercent leur action dans la direction indiquée par les flèches 5, de manière à appliquer la face latérale 1 contre les tranches des cylindres de coulée ; les contours 6, 6' desdits cylindres sont dessinés en pointillés, et le niveau du col 7 est indiqué par une ligne x-x en trait interrompu ;
• une partie active disposée sur la face avant 8 plane de la plaque support 2, et qui est composée de deux éléments, à savoir un coeur 9 en un matériau réfractaire dont on privilégie les propriétés isolantes (tel que la mousse de silice), et un insert 10 en un matériau réfractaire dont on privilégie les propriétés de résistance à l'usure par frottement et à la corrosion par le métal liquide (tel que le SiAlON®, le carbure de silicium) ; dans l'exemple représenté, l'insert 10 est constitué par une pièce unique, mais il peut aussi être constitué par la juxtaposition de plusieurs pièces ; le coeur 9 et l'insert 10 sont solidarisés l'un à l'autre, par exemple par collage, et l'ensemble de la partie active qu'ils constituent est enserré dans une ceinture 11, de préférence métallique, qui renforce sa cohésion.

The example of lateral face 1 according to the prior art, shown diagrammatically in FIG. 1, comprises the following elements:

• a support plate 2 of refractory material with high insulating properties, secured on its rear face 3 to a cooled metal plate 4, on which thrust members (not shown) exert their action in the direction indicated by the arrows 5, so applying the side face 1 against the edges of the casting rolls; the contours 6, 6 'of said cylinders are drawn in dotted lines, and the level of the neck 7 is indicated by a line xx in broken lines;
• an active part arranged on the flat front face 8 of the support plate 2, and which is composed of two elements, namely a core 9 made of a refractory material whose insulating properties are preferred (such as silica foam), and a insert 10 made of a refractory material, the properties of which are resistant to wear by friction and to corrosion by liquid metal (such as SiAlON®, silicon carbide); in the example shown, the insert 10 is formed by a single piece, but it can also be formed by the juxtaposition of several pieces; the core 9 and the insert 10 are secured to one another, for example by gluing, and the whole of the active part which they constitute is enclosed in a belt 11, preferably metallic, which strengthens its cohesion .

The support plate 2 and the active core 9-insert 10 part are maintained one against the other, preferably by means used to separate them after casting without destroying them or, at least, without damaging the support plate 2, so that this the latter can be reused after said casting. Bolting, or a solid cradle of the support plate 2 or integrated into it and into which the active part is inserted, are examples of such means.

After having been used for a single casting, the side face 1 is located in the state shown in Figure le. The portions of insert 10 which rubbed against the cylinders have been eroded to a depth "e" which can be of the order of several mm, even a few cm (typically about 10 mm), depending on the duration of the pouring, the nature of the material of insert 10 and the amount of friction to which it has been subjected. The heart 9 was dug under the effect of corrosion by liquid metal, and also under the effect of friction with the moving liquid metal inside the casting space 12. On the other hand, the active part is often covered, at least in places, with a layer of solidified metal 13 which is deposited there at the end of casting. For these reasons, the active part of the side face 1 is no longer reusable during a subsequent casting, unless one performs machining of the entire active part in order to restore its surface condition initial, which would be long and costly.

The first example of a lateral face according to the invention 14, represented in the figure 2, when viewed from the front, has the same appearance as the lateral face according to the prior art 1 shown in front view in Figure la. This will also be the case for the other examples of lateral face according to the invention which will be described later, except for the fourth example shown in Figure 5). We will therefore not present a specific front view for the examples of lateral face according to the invention. In Figure 2, the common elements with the side face 1 according to the prior art are designated by the same references. We find there conventionally a support plate 15 of insulating refractory material, the rear face 3 is secured to a metal plate 4 on which the thrust members act. However, the front face 16 of the support plate 15 is not flat: it has in its central part, over its entire height, a recess 17 whose shape and function will explained below.

The active part of this lateral face 14 also has a configuration special. It has a central plate 18 made of a low-insulating refractory coefficient of expansion (based on silica, for example), having on both sides recesses 19, 20. In each of these recesses 19, 20, a formed assembly is housed a core 21, 21 'and an insert 22, 22', whose constitutions and dimensions (at the possible exception of the thickness) are identical to those of the core 10 and the insert 9 of the lateral face 1 according to the prior art previously described. The two heart-insert sets 21-22, 21'-22 'are secured to the central plate 18 by means of an adhesive allowing relative displacements of the glued parts sufficient to absorb the expansions differentials due to the different natures of the materials involved. An example of such glue consists of the product marketed under the name "REFRACOL N ° 4 ", which is a refractory jointing cement based on corundum, comprising a binder based on sodium silicate. This binder makes the glue glassy at high temperature, so as to allow the relative movements of the glued parts while working in shear.

The support plate 15 and the active part of the lateral face 14 must, this time, must be held against each other by means authorizing their non-destructive decoupling, such as those already cited as an example for the lateral face 1 of the prior art (bolting, cradle).

After having been prepared and assembled, the lateral face 14 according to the invention is mounted on the casting machine, in the position shown in Figure 2a, and used the usual way for a first pour. At the end of this first pour, the face before the active part is found in the state previously described (and represented on the Figure 1c) of the front face of the active part of the side face 1 of the prior art. The cylinders have worn the outer edges of the insert 22 to a thickness "e" and a width "1", the core 21 has been hollowed out by chemical and mechanical erosion due to the liquid metal, and solidified metal 13 covers at least in places the front face of the active part. A once the first casting is completed, the active part of the lateral face 14 is separated from the support plate 15, then turned over and replaced on the support plate 15. From this the core 21 and the insert 22, which constituted the front face of the active part during the first pour may constitute the rear face during a second pour. Conversely, the core 21 'and the insert 22', which constituted the rear face of the active part during the first casting constitute the front face during this second casting. This simple disassembly, turning and reassembly operation, which can be carried out very quickly, was therefore enough to find a ready-to-use side face, while the preparation of a new lateral face 1 of the type according to the prior art would have been much longer. It will be noted, in particular, that an operation for drying the refractories and the bonding material is not necessary for the preparation of the second casting, since all the elements of the lateral face 14 have already undergone this drying prior to the first pour.

In order for the side face 14 reassembly operation to be possible, the recess 17 of the support plate 15 must meet the following conditions. Its depth must be sufficient for the parts of the insert 22 and of the core 21 which are in relief of a thickness equal to "e" (or possibly greater than "e" in areas where solidified metal 13 is present) relative to the worn outer edges of the insert 22 can be housed there after the reversal of the active face. In other words, the depth of the recess 17 must be greater than the sum of "e" and the maximum thickness of the layers of solidified metal 13. It is therefore necessary to estimate at least roughly the maximum values that could take these parameters during the first casting, and manufacture the support plate 15 in result. We can, possibly, in this calculation, take into account only "e", and decide that if there is solidified metal 13 on the active part, it will be removed by means mechanical. This may however increase the preparation time of the side face before the second pour. As for the outer edges 23, 23 'of the support plate 15, they must have a general shape which matches that of the outer edges of the insert 22, and a width less than the width “1” of the worn parts of the insert 22, so that it can be there insert. Machining of said worn parts of the insert 22 prior to reassembly of the side face is generally not necessary, the action of the cylinders during the first casting being sufficient for this purpose. It can be noted that in the lateral face 1 of the art anterior, it is the entirety of the front face 8 of the support plate 2 which transmits to the part activates the forces exerted by the thrust members, while in the lateral face 14 according to the invention, these forces are transmitted only by the outer edges 23, 23 'of the plate support 15. But this situation is in no way embarrassing, since said external edges 23, 23 'are precisely located opposite the areas of the active part which must rub against the cylinders, so where the good transmission of forces from the thrust members is particularly necessary to guarantee the tightness of the casting space 12. From this point in view, the new configuration 15 of the support plate is therefore even more effective than the old configuration 2.

The second example of a lateral face according to the invention 24, represented in the figure 3 in its initial state before the start of the first pour, differs from the example preceding only by the configuration of the central plate 25 of its active part. In this second example, said central plate 25 is a simple flat plate whose outline matches that of the 22-core 21 insert assembly. The cohesion of the entire active part of the lateral face 24 is provided by a preferably metallic belt 26 similar to the belt 11 of the lateral face 1 of the prior art described above, while the configuration of the side face 14 of the previous example amounted to integrating such a belt to the central plate 18 itself. The presence of a belt 26 independent of the central plate 25 is advantageous in that it facilitates the cohesion of the central plate 25 even in the event of rupture thereof.

The third example of a lateral face according to the invention 27, represented in the figure 4 in its initial state before the start of the first pour, differs from the example previous in that the central plate 25 of the active part is deleted. It is the same core 21 and the same insert 22 which are used during the two castings, successively on their two faces. Again, a preferably metallic belt 26 ensures their cohesion.

The fourth example of a lateral face according to the invention 28, shown in the Figure 5 in its initial state before the start of the first pour, differs from the example previous in that the active part is formed of only one element 29, the functions combine those of the core 21 and the insert 22 of the previous example. Like this element 29 must seal the casting space 12 by its contact with the cylinders, it must be made of a material for which the resistance properties to wear and corrosion by metal must be favored. But he must also have, optimally, insulating properties as good as possible and good resistance thermal shock and cracking, to have acceptable behavior in its central part. Materials such as boron nitride-SiAlON® can be used for this effect. The presence of a belt 26 surrounding the active part of the lateral face 28 is not not essential, since this active part is in one piece and in principle its cohesion is assured. However, such a belt 26 is still recommended, because it can minimize the consequences of possible cracking of element 29 during its use.

In the same way, it is possible in all the previous examples from the front lateral according to the invention, to replace the insert assemblies 22, 22'-core 21, 21 ' arranged on each face of the central plate 18, 25 by single elements similar to element 29. A reduction in the preparation time of the lateral face is thus obtained, but in return, the cost of the materials is increased since the materials capable of correctly performing both the insert function and the heart function are more more expensive than the materials more conventionally used for one or the other of these functions.

The invention can be applied not only to casting installations between cylinders, but also to all types of thin strip casting installations metallic using lateral faces according to the aforementioned prior art which are applies against slices of walls that are being cooled while traveling, such as installations between bands.

Claims (5)

1. Side wall for closing off the casting space of a caster for continuously casting thin metal strip between two moving cooled walls, especially a "twin-roll caster" or a "twin-belt caster", of the type comprising a support plate (15), on the rear face (3) of which plate thrust members exert their action, for the purpose of applying the said side wall against the end faces of the said cooled walls, optionally via a metal baseplate (4) fastened to the rear face (3) of the support plate (15), and an active face placed against the front face of the support plate (15), the lateral portions of which are intended to be worn away on contact with the said end faces of the said cooled walls to a maximum depth "e" and over a width "1", the support plate (15) and the active part being brought into contact with each other in a manner allowing them to be separated non-destructively, characterized in that the front face of the support plate has, in its central part, a recess (17), the depth of which is greater than "e", and in that the external edges (23, 23') of the said front face have a general shape which matches that of the external edges of the active part and have a width of less than "1".
2. Side wall according to Claim 1, characterized in that it includes a band (26) surrounding the said active part.
3. Side wall according to Claims 1 and 2, characterized in that the said active part comprises at least one core (21) and one insert (22).
4. Side wall according to Claim 3, characterized in that its active part comprises a central plate (18) having, on each of its two faces, a core (21, 21') and an insert (22, 22').
5. Side wall according to Claim 4, characterized in that the said band is structurally incorporated into the said central plate (18).

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