MXPA98007320A - Side side for the obturation of the cold space of a continuous bond installation of metal bands between cylinders and installation of colada asi equip - Google Patents

Abstract

The invention has an object, a lateral face (11) for sealing the casting space (6) of a continuous casting installation of metal strips of the type consisting of two cylinders (5, 5i) of internally cooled opposing rotations, horizontal axes, whose cylindrical lateral surfaces define a casting space (6), whose width in the neck (7) determines the thickness of the band, said lateral face (11) having an active part (3) intended to rub against the edges (4) of the cylinders (5, 5i) in the course of the casting and to face said casting space (6), characterized in that the dimensions of said active part (3) are such that its edge (12). ) lower is destined to be located at a distance (d) equal to, at least, 1 mm above the neck (7) when the side face (11) is mounted in the casting installation. The invention also has as an object a continuous casting installation of metal strips of the type consisting of two cylinders (5, 5i) of internally cooled opposing rotations, of horizontal axes, whose cylindrical lateral surfaces define a casting space (6), whose width in the neck (7) determines the thickness of the band, and two lateral faces of sealing of its casting space, characterized in that said side faces are of the type preceding

Description

SIDE FACE FOR OBTURATION OF THE DB COLADA SPACE AN INSTALLATION OF CONTINUOUS BOND OF METALLIC BANDS BETWEEN CYLINDERS B INSTALLATION OF COLADA ASI EQUIPADA FIELD DB THE INVENTION The invention relates to the continuous casting of thin metal strips, made directly from liquid metal. More precisely, it refers to the lateral sealing of the casting space of the facilities called "casting between cylinders", applied especially to the casting of steel or ferrous alloy strips.

BACKGROUND DB THE INVENTION In this type of installations, whose application to the continuous casting of steel bands of a few millimeters in thickness is in course of industrialization, the thickness of the casting is delimited, on the one hand, by cylindrical lateral surfaces cooled internally of two horizontal cylinders next , which rotate in opposite directions around their axes, REF ,: 028357. against which the liquid metal begins its solidification, and on the other, by plates of refractory material applied by elastic means against the flat ends of the cylinders (called "ridges"). These plates laterally block the casting space, so as to prevent the leakage of liquid metal outside the installation. Its lower edge is located below the "neck", that is, the area where the surfaces of the cylinders are closest to each other, and whose width corresponds substantially to the thickness desired for the band. The side sealing plates must, of necessity, be strongly pre-heated before casting, so that the liquid metal will not be solidified against them during the filling of the ingot mold (whose bottom is blocked, during the operation, by a piece called "manikin", which is extracted from the casting space when the cylinders rotate and drag, with it the beginning of the band) and in the first moments of casting. But even if a similar concern is taken, the lateral faces constitute a thermally sensitive point of the machine, because they inevitably create in their vicinity an area where the extraction of heat from the liquid metal is abnormally high. In particular, this is the case in the vicinity of the cylinders which, as they are internally cooled by water circulation, have a tendency to cool the side faces in the vicinity of the areas in which the contact takes place. From this, it may turn out that the solidification of the steel on the sides of the cylinders takes place noticeably more rapidly than in the portions of the cylinders closest to their central areas, and that can be a source of problems. In fact, normally the "scabs" of metal that solidify on each of the cylinders, and whose thickness at a given point grows progressively as the cylinder rotates, must meet, to form the band, either exactly at the level of the neck, either very slightly below that level. If this joint of scabs occurs noticeably much lower than the neck, the band runs the risk of not being sufficiently at the exit of the cylinders and can crack. There is also the danger of presenting internal porosities. On the other hand, if the joint of the crusts is made upstream of the neck, the thickness of the solidified band at the level of the neck is greater than the nominal width of the neck, due in particular to the influence of the too cold lateral faces. It is then necessary to separate the cylinders from one another to avoid having to make a rolling effort on the band, when they are not designed for it. This separation of the cylinders is a source of defects for the band, which are linked to the changes they imply in the thickness and the solidification mode of the product. Another consequence of the abnormal conditions of the solidification of the band in the vicinity of the lateral faces is the strong pressure exerted by the metal, in the process of solidification, in the lower part of the lateral faces. Often, this pressure is sufficient to push back the side face in at least a part of its height, which can locally ruin the tightness of the contact between cylinders and side faces. Liquid metal can then escape out of the laundry space.

DESCRIPTION DB THE INVENTION The purpose of the invention is to propose a configuration of casting installation, which makes it possible to create conditions for solidification of the strip in the vicinity of the lateral faces that are not susceptible to disturbing the regularity of the casting process. Said configuration should, likewise, limit the phenomenon of recoil of the lateral faces. The subject of the invention is a lateral face for sealing the casting space of a continuous casting installation of metal strips of the type comprising two cylinders of internally cooled opposing rotations, with horizontal axes, whose cylindrical lateral surfaces define a casting space, -whose width in the neck determines the thickness of the band7, said side face having an active part destined to rub against the edges of the rolls during the casting and to face said casting space, characterized in that the dimensions of the said active part is such that its lower edge is intended to be located at a distance equal to, at least, 1 mm above the neck, when the side face is mounted in the casting installation. The invention also has as an object a continuous casting installation of metal strips of the type comprising two cylinders of internally cooled opposing rotations, with horizontal axes, whose cylindrical lateral surfaces define a casting space whose width in the neck determines the thickness of the casting. the band, and two lateral sealing faces of its casting space, characterized in that said side faces are of the type described above. According to the invention, the active part of the lateral face, that is to say, its part that is in contact with either the edges of the cylinders, or with the liquid metal enclosed in the space of the casting, will have been understood according to the invention. It is interrupted not below the neck as usual, but above it. A free space is left on both sides of the neck where the metal is not in contact with any refractory material and therefore does not exert any pressure on the lateral faces. Thus, the material present in front of that free space can not cause a retraction of the lateral faces, even if its solidified fraction was abnormally high. On the other hand, this free space offers the possibility for the solidified or solidifying metal to extend towards the outside of the casting space, which limits the stresses that the cylinders' sides have to bear. The inventors have realized that the cooling conditions of the steel inside the ingot mold, with the usual casting parameters, were such that from a level, which can be placed a few centimeters above the neck, the solidification of the metal in the edges of the casting space, although still incomplete, is already sufficiently advanced so that no significant leakage of liquid metal to the outside of the machine, even if the metal was no longer retained by the side faces. From this, the inventors deduced that the suppression of the lower part of the side faces of the prior art was possible. This suppression makes the casting machine more tolerant with slight deviations in the process of solidification of the band. In effect, with the invention, a thickness of the solidified crusts on the edges of the cylinders, somewhat more important than that provided in the last millimeters or centimeters, which precede the neck, no longer causes the lateral faces to retreat to the neck, no longer loss of tightness in the upper levels of the associated laundry space. On the other hand, excessively solidified band parts have the possibility of extending laterally if the cylinders exert a compression force on them, which makes the need to separate the cylinders to minimize the stresses considerably less likely. The invention thus seeks a greater stability of the casting conditions, which is aimed at a better overall quality of the band and a higher reliability of the casting installation. The invention will be better understood by reading the following description in relation to the following appended figures: Figure 1 schematic, front view (figure 1) and profile (figure lb) in section according to Ib-Ib, a side side of casting continuous between cylinders according to the prior art; and figure 2 schematizes, front view (figure 2a) and profile (figure 2b) in section according to Ilb-IIb, a side face of continuous casting between cylinders according to the invention. The side face 1 according to the prior art, shown schematically in Figure 1, comprises a support plate 2, in which the active part 3 of the side face 1 is engaged, that is to say, its portion intended, during casting, to to be in contact with the edges 4 of the cylinders 5 and 5 '(of which only the contours in figure Ia have been represented with dotted lines), with the liquid steel that will contain the space 6 for casting the machine and, below the level of the neck 7 where the cylinders 5, 5 'are closer to each other, with the band solidified. Means (not shown) known per se ensure the application of the side face 1 against the edges 4 of the cylinders 5, 5 '. Said means allow, thanks to springs or jacks, temporary recesses of the lateral face 1, in case of infiltration of metal between its active part 3 and the edge 4 of a cylinder 5, 5 'or of excessive exertion exerted by the band, in the process of solidification, on its lower part. Reference can be made in particular to EP-A-0 698 433 for the description of an (non-limiting) example of such means. The active part 3 is divided, in the example shown, into two portions. The portion 8 in double circular arc which, when the side face 1 is mounted on the machine, constitutes the area of contact with the edges 4 of the cylinders 5, 5 ', the immediate vicinity of this contact area and the area that surrounds the neck 7, is constructed of a first refractory material. Its essential quality is a high hardness to resist as best as possible the friction of the edges 4 of the cylinders 5, 5 'and (around the neck 7) of the band in the process of solidification or already solidified. It is, for example, SiAlON or boron nitride. It can be constituted by a single piece or by varying joined pieces and mutually solidary. Its lower edge 9 is located below the level of the neck 7, so that it makes a total lateral sealing of the casting space 6. The remaining portion 10 of the active part 3 is of a refractory material representing a high insulating power, such as silica or alumina. The active part 3 of the lateral face 1 is cantilevered, with respect to the support plate 2, in a thickness equal to at least its maximum tolerable wear during the course of the casting, for example, 10 mm. In the course of the casting, the portions of the active part 3, which are in contact with the edges 4 of the cylinders 5, 5 ', basically work with friction, with the consequence that, little by little, the other portions of the the active part 3, which is only used at a more moderate speed since they are in contact only with the steel, liquid or in the course of solidification, penetrate slightly into the interior of the casting space 6. As a variant, the entire active part 3 of the side face 1 can be constituted by a single piece. In figure 2, which represents a side face 11 according to the invention mounted on the casting installation, the common elements with those of figure 1 are designated with the same references. According to the invention, for the reasons that have been said, the lower edge 12 of the active part 3 of the side face 11, which ensures contact with the cylinders 5,5'and seals the lower part of the casting space 6, and it is not located below the neck 7, but at a distance "d" above it. This distance "d" can be very small, up to 1 mm, if the growth of the solidified crusts on the edges of the cylinders 5, 5 'is usually regulated with great precision, and if the proportion of solid matter, present in the metal, which is not fully solidified yet in this region of the casting space 6, is capable of passing very rapidly from 0 to 100%. These parameters depend notably on the kind of the laundry. The steel classes that contain more carbon and different alloying elements, such as stainless steels, have solidification intervals (the difference between liquid and solid temperatures) larger than those of ordinary steel grades or ferro-nickel alloys, and this makes the mastery of their conditions more delicate. of solidification. Said large solidification interval implies, above all, that a significant proportion of solid matter in the vicinity of the lateral face 11 begins to be observed at relatively high levels of the casting space 6. For these steels, with a large solidification interval, it is therefore necessary to provide a greater distance "d" than for the classes with a narrow solidification interval, which solidify rapidly once the temperature of the liquid phase has been reached. In practice, a distance "d" between 10 and 40 mm is suitable for the most common classes of stainless steels, cast in the form of strips of thickness 3 mm with cylinders of diameter of 1500 mm and casting speeds of the order of Im / mm. The optimal choice of the distance "d" also depends on the ferrastatic pressure, which prevails in the lower part of the casting space, therefore, the geometry of the casting installation and the nominal level of the liquid steel surface present in the the laundry space. Good results have been obtained with a distance "d" of 1 to 7 mm in a machine equipped with cylinders of 600 mm in diameter, during the casting of low alloy carbon steels and ferrosilicon alloys. Preferably, in order to reduce the mechanical stresses which are exerted on it and which could involve its rapid and uncontrolled degradation, the lower edge 12 of the active part 3 of the side face 11, facing the pouring space 6, it has no sharp angle, but rounded 13 and whose radius of curvature can be, for example, of the order of 10 to 20 mm. The same function can be ensured by a beveling of the lower edge 12, according to an inclined plane of, for example, 45 °.

It is also possible to provide for the possibility of cooling the strip plate by spraying a fluid (water, nitrogen, liquid argon ...) between the lower edge of the active part 3 of the side face 11 and the neck 7. This cooling it can be carried out permanently, in order to ensure that the edge of the band is always sufficiently solidified to prevent it from tearing, allowing liquid metal to escape. It can also be carried out only when the initiation of said ripping of the edge is observed, or when the sequence of the cast parameters makes suspicion of risks of the tear. As a means of supplying cooling fluid on the strip plate, for example, one or more conduits 14 can be used which pass through the support plate 2 and open into the space 15 between the support plate 2, the edges 4 of the cylinders 5, 5 'and the neck 7. But other means of fluid supply, which would eventually be independent of the side face 11, such as one or two sprayers, which would be arranged below the side 11 and oriented side towards the griddle of the band.

An indicator of the effectiveness of the invention is the number of lateral side reversals observed during casting. It has thus been found that said number could be divided by three in the whole of the cast, in comparison with the use of lateral faces, which descend to the neck. The improvement is even more sensitive when considering the first minutes of the casting, during which the operation of the casting machine is not yet perfectly stabilized. These findings have been made during the casting of austenitic stainless steel type SUS 304, cast in bands of 3 mm thickness, with a distance "d" equal to 25 mm and a cylinder diameter of 1500 mm. The adaptation of said side faces to an existing casting installation may, if necessary, require the provision of some modifications to the phantom, so that all the casting space 6 is sealed laterally during its filling before the start of casting. . It is clear that the application of the invention is not limited to the precise configuration of the side face, which is just presented as an example, but is applicable to any other configuration that allows an interruption of the active part below the neck. It is well understood that the invention is applicable not only to casting between steel strip cylinders and other ferrous alloys, but to any other metal capable of being cast by this method.

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Claims (6)

1. - Side face (11) for sealing the casting space of a continuous casting installation of metal strips of the type comprising two internally cooled opposing rotating cylinders, with horizontal axes, whose cylindrical lateral surfaces define a casting space whose width in the neck determines the thickness of the band, said side face having an active part intended to rub against the edges of the rolls during the casting and to face said casting space, characterized in that the dimensions of said active part they are such that their lower edge is intended to be located at a distance (d) equal to at least 1 mm above the neck when the side face is mounted in the casting installation.

2. - Lateral side according to claim 1, characterized in that said lower edge has a rounded face facing the casting space.

3. - Side face according to claim 1 or 2, characterized in that said lower edge has a bevel in front of the casting space.

4. Side face according to one of claims 1 to 3, characterized in that said active part is mounted on a support plate, and in that said support plate comprises at least one conduit, which passes through and opens into the space between the support plate, the edges of the cylinders and the neck, said conduit being able to be connected to means for injecting a cooling fluid.

5. - Installation of continuous casting of metal bands of the type comprising two cylinders of internally cooled opposing turns, with horizontal axes, whose cylindrical lateral surfaces define a casting space, whose width in the neck determines the thickness of the band, and two faces side walls of its casting space, characterized in that said side faces are of the type according to one of claims 1 to 4.

6. - Installation according to claim 5, characterized in that it comprises means for projecting a cooling fluid on the strip plate above the neck. SUMMARY OF THE INVENTION The invention has an object a lateral face (11) for the sealing of the space (6) casting a continuous casting installation of metal strips of the type consisting of two cylinders (5, 5 ') of antagonistic turns cooled internally, of horizontal axes, whose cylindrical lateral surfaces define a casting space (6), whose width in the neck (7) determines the thickness of the band, said side face (11) having an active part (3) intended to rub against the edges (4) of the cylinders (5, 5 ') in the course of the casting and to face the aforementioned casting space (6), characterized in that the dimensions of said active part (3) are such that its edge (12). ) lower is intended to be located at a distance (d) equal to, at least, 1 mm above the neck (7) when the side face (11) is mounted on the casting installation. The invention also has as an object a continuous casting installation of metal strips of the type consisting of two cylinders (5, 5 ') of internally cooled opposing rotations, of horizontal axes, whose cylindrical lateral surfaces define a casting space (6), whose width in the neck (7) determines the thickness of the band, and of two lateral faces of sealing of its casting space, characterized in that said side faces are of the preceding type.