EP0950451A1 - Casting pipe for introducing molten metal in a continuous casting mould - Google Patents

Abstract

A nozzle (1) for the introduction of liquid metal into a continuous casting mold, of the type comprising a first tubular part (2) of which one end is connected to a vessel enclosing the liquid metal and the other end emerges into a second hollow part (4) of elongated shape of which at least one portion of the inner space (3) is oriented essentially perpendicular to the tubular part (2). The hollow part (4) incorporates a hole (5, 6) at each of its ends, as well as one or several outlet holes (7 - 17) cut in its bottom (18) and/or lateral walls, a perforated regulator (23 - 34) being arranged in the inner space (3) in such a manner that the liquid metal must pass through the perforations before traversing through the outlet holes (7 - 17). The perforated regulator (19, 38, 39, 41, 43) incorporates, on at least a portion of the width of its upper face, a raised part (20, 37, 42, 44) comprising a top situated on the longitudinal horizontal axis of the hollow part (4), the perforations (23 - 34) being distributed on either side of this top.

Description

The invention relates to the continuous casting of metals. It concerns more precisely the nozzles made of refractory material through which the liquid metal is introduced to be cast, such as steel, in the ingot mold of a continuous casting installation, in particular of a casting between cylinders.

These nozzles are connected by their upper end to the container serving as tank of liquid metal, called a distributor, and their lower end plunges into the bath of liquid metal present in the mold where the solidification of the cast product. The primary role of these nozzles is to protect from atmospheric oxidation the jet of liquid metal on its path between the container and the ingot mold. They allow also, thanks to appropriate configurations of their lower end, to orient favorably the flow of liquid metal in the ingot mold so that solidification of the product is carried out under the best possible conditions.

Directly pouring thin metal strips a few mm thick from liquid metal (steel or copper, for example) can take place on an installation called "casting between cylinders". It includes an ingot mold whose casting space is delimited on its long sides by a pair of internally cooled cylinders with axes horizontal parallel and rotating around these axes in opposite directions, and on its short sides by closing plates (called side faces) of refractory material applied against the ends of the cylinders. The cylinders can also be replaced by cooled endless belts.

When pouring between cylinders, two-part nozzles are often used (see, for example, document EP-A-0771600). The first part is composed of a tube cylindrical, the upper end of which is connected to an opening in the bottom of the distributor which constitutes the reserve of liquid steel supplying the ingot mold. This orifice is can be closed at will by the operator, partially or completely, thanks to a stopper or a drawer system ensuring the regulation of the metal flow. From the section of this hole depends on the maximum metal flow that can flow inside the nozzle. The second part, fixed to the lower end of the preceding tube, for example by screwing, or being integrated construction, is intended to be immersed in the liquid metal bath present in the mold. It is composed of a hollow element inside which opens the lower orifice of the preceding cylindrical tube. The interior space of this hollow element has a general shape more or less elongated according to the dimensions of the casting space of the machine on which the nozzle is to be mounted. It is oriented substantially perpendicular to the tube. When the nozzle is in service, the hollow element is placed parallel to the cylinders, and the liquid metal flows into the mold through gills formed on the sides of the hollow element, generally at each of its ends. In the latter case, the metal flows leaving the nozzle are thus oriented preferably in the direction of the lateral faces, in order to bring hot metal onto their surfaces, thereby preventing unwanted metal solidifications from occurring there (so-called "parasitic solidifications") which would seriously disturb the functioning of the machine. The openings can have a horizontal or oblique downward orientation. Various orifices of lesser importance than these gills can also be provided on the side walls and / or the bottom of the nozzle, in order to directly supply hot metal the regions of the mold located on the sides of the nozzle and / or under it. So we aim, in particular, to improve the thermal homogeneity of the metal present in the mold.

One of the main difficulties encountered in the use of these nozzles is that, in general, the liquid metal does not completely fill their internal space, and the flow of metal is often irregular and swirling. It is in particular the case when the orifice of the distributor does not have its maximum opening. That leads to a strong instability of the metal currents leaving the gills, and the flows at the inside of the mold becomes distant from their optimal configuration as the nozzle is theoretically supposed to impose. We then observe the appearance of irregularities in the solidification of the product, which can seriously affect its final quality, especially in the when thin strips are poured.

This problem is remedied by inserting into the internal space of the nozzle obstacles which impose pressure drops on the metal by blocking its natural flow. At an equal liquid metal flow rate, the speed of the flow is limited and thus the filling the interior space of the nozzle. In this way, the erratic variations of metal flows out of the nozzle are attenuated. In the case of nozzles in two previously cited parts, these obstacles can be inserted in the first part cylindrical or in its extension (see document EP-A-0 765 702). They can also include a "strip", that is to say a parallelepipedic element elongated in porous or perforated refractory placed inside the second part of the nozzle (the hollow element), and that the liquid metal must pass through before reaching all or part of the various orifices opening into the casting space of the ingot mold (see document JP-A-1-317658).

If the nozzle has on the one hand a perforated strip and on the other hand orifices formed in the bottom and / or the side walls of its second elongated part (in addition to vents directed towards the short sides of the casting space), it is important that these various orifices are supplied with liquid metal uniformly over the entire length of said second part. Only on this condition can we guarantee satisfactory homogeneity of the metal flows inside the casting space. However, tests on hydraulic models show that this condition is not generally not satisfied when using a very elongated nozzle, particularly suitable for a use on a casting installation of very wide thin strips (of the order of 1 m and more), and equipped with a perforated parallelepiped strip. We observe that certain perforations in the nozzle are crossed by a stream of metal at a high flow rate, and others by an insufficient flow of metal. This affects good nutrition in hot metal from the entire casting space, and can lead to irregularities in the solidified thickness of the product on the cylinders, which is an essential parameter for the quality of the final tape.

The object of the invention is to propose a nozzle configuration of the type which just described, which provides a metal supply to the most homogeneous possible over its entire length.

To this end, the invention relates to a nozzle for the introduction of a metal liquid in a continuous metal casting ingot mold, of the type comprising a first tubular part, one end of which is intended to be connected to a container containing said liquid metal, and the other end of which opens into a second part hollow of elongated shape with at least a portion of the interior space oriented substantially perpendicular to said first tubular part, said hollow part having a hole at each of its ends, as well as one or more outlet openings formed in its bottom and / or its side walls, a strip provided with perforations being disposed in the interior space of said hollow part so that the liquid metal must pass through said perforations before passing through said outlet orifices, characterized in that said strip comprises over at least a portion of the width of its upper face a part in relief comprising a vertex situated on the horizontal axis longitudinal of said hollow part, said perforations being distributed on both sides of said summit.

As will be understood, the invention consists in providing on the upper face of the strip a part in relief over at least a portion of its width. This part in relief must have a substantially triangular or rounded cross section, so that to “burst” the metal jet which strikes it and to distribute said metal so symmetrical on the cross section of the nozzle, preventing it from rebounding vertically by disturbing the regularity of the flows. We thus obtain a filling more homogeneous and more constant over time than with a simple form strip parallelepiped providing a simple horizontal plane surface with a jet of liquid metal which the crash.

• la figure 1a qui montre, vue de face et en coupe longitudinale, un exemple de busette selon l'invention, 1a figure 1b qui montre, vue de côté en coupe transversale selon Ib-Ib, la réglette de la figure 1a, 1a figure lc qui montre de la même façon une variante de la réglette de la figure 1a ;
• la figure 2 qui montre vue de côté en coupe transversale un deuxième exemple de réglette, pouvant se substituer à celle de la figure 1a ;
• la figure 3 qui montre vue de côté en coupe transversale un troisième exemple de réglette pouvant se substituer à celle de la figure 1a ;
• la figure 4 qui montre vue de côté en coupe transversale un quatrième exemple de réglette pouvant se substituer à celle de la figure 1a ;
• la figure 5 qui montre vue de côté en coupe transversale un cinquième exemple de réglette pouvant se substituer à celle de la figure 1a.

The invention will be better understood from the following description, given with reference to the following appended figures:

• Figure 1a which shows, front view and in longitudinal section, an example of nozzle according to the invention, 1a Figure 1b which shows, side view in cross section according to Ib-Ib, the slide of Figure 1a, 1a Figure lc which similarly shows a variant of the strip of Figure 1a;
• Figure 2 which shows a side view in cross section of a second example of a strip, which can replace that of Figure 1a;
• Figure 3 which shows side view in cross section a third example of a strip which can replace that of Figure 1a;
• Figure 4 which shows side view in cross section a fourth example of a strip which can replace that of Figure 1a;
• Figure 5 which shows side view in cross section a fifth example of a strip which can replace that of Figure 1a.

• deux ouïes 5, 6 de section rectangulaire dans l'exemple représenté, ménagées chacune à une extrémité de l'élément creux 4, destinées à être orientées vers les petits côtés de l'espace de coulée, et par lesquelles transitera l'essentiel du flot de métal liquide traversant la busette 1 ; dans l'exemple de la figure 1a, ces ouïes 5, 6 sont orientées horizontalement, mais elles peuvent également être orientées de manière oblique ; elles peuvent aussi avoir une section de forme différente (par exemple circulaire), de manière classique ;
• une série d'orifices de sortie 7-17 cylindriques de petit diamètre orientés verticalement, ménagés dans le plan médian du fond 18 de l'élément creux 4, et destinés à alimenter directement en métal chaud les zones de l'espace de coulée situées sous la busette; en variante, on peut, comme il est connu dans le document EP-A-0 771 600, prévoir non pas une mais deux séries de tels orifices, disposées chacune de part et d'autre du plan médian du fond 18 de l'élément creux 4.

The nozzle 1 according to the invention shown in FIG. 1a is, thanks to its narrow and elongated shape, particularly suitable for use on an installation for casting thin strips between two internally cooled cylinders and rotated, according to a process now well known. As in the prior art described above, it comprises a first part composed of a cylindrical tube 2, the upper end of which, not shown, is intended to be connected to the outlet orifice of a distributor. This cylindrical tube 2 opens into the interior space 3 of the second part of the nozzle 1, composed of a hollow element 4 of elongated shape, sufficiently narrow to allow its insertion into the casting space of the installation. According to the prior art, this hollow element 4 has various orifices through which the liquid metal can exit from the nozzle 1, namely:

• two vents 5, 6 of rectangular section in the example shown, each formed at one end of the hollow element 4, intended to be oriented towards the short sides of the casting space, and through which most of the flow will pass liquid metal passing through the nozzle 1; in the example of FIG. 1a, these openings 5, 6 are oriented horizontally, but they can also be oriented obliquely; they can also have a section of different shape (for example circular), in a conventional manner;
• a series of vertically oriented small diameter cylindrical outlet ports 7-17, arranged in the median plane of the bottom 18 of the hollow element 4, and intended to directly supply hot metal to the areas of the pouring space located under the nozzle; as a variant, it is possible, as is known in document EP-A-0 771 600, to provide not one but two series of such orifices, each arranged on either side of the median plane of the bottom 18 of the element hollow 4.

Another variant would be to add to the outlet ports 7-17 (or to their substitute) orifices made in the large side walls of the hollow element 4, and oriented towards the long sides of the casting space (in other words towards the cylinders in the case of a casting installation between cylinders). These holes 7-17 can also not be strictly cylindrical, but have a section for example elliptical. They can also (in particular according to one of the variants of EP-A-0 771 600) be obliquely oriented. Finally, they can be replaced by one or more slots each extending over part or all of the length of the bottom 18 of the element hollow 4, and which it would be important for them to be supplied in a homogeneous manner over their entire length.

The nozzle 1 also has, arranged in its interior space 3, a perforated strip 19 resting on shoulders 36 formed on the walls of the gills 5, 6. Its function is, as is known, to create pressure drops in the liquid metal, so as to better fill the interior space 3, and thereby regularize the liquid metal flows out of the nozzle 1. According to the invention, this strip 19 has a different from the classic parallelepiped shape, in that it has a raised part 20 whose apex is intended to be located on the longitudinal horizontal axis of hollow part 4 of the nozzle 1. In the example shown in FIGS. 1a and 1b, this raised part 20 relates only to the central portion of the width of the upper face 21 of the strip 19, and has a triangular cross section whose dimensions do not not vary over the length of the strip 19. The remaining parts of this upper face 21 are flat, and it is on these flat parts, flush with the raised part 20, that are formed the perforations 22, 22 ', 23-34 which the liquid metal must pass through before reach the lower part 35 of the interior space 3 of the nozzle 1, then flow out of the nozzle 1 through the lower part of the openings 5, 6 and the orifices 7-17. In the configuration shown, part of the metal can flow out of the nozzle 1 through the upper part of the gills 5, 6, therefore without having passed through the perforations 23-34 of the strip 19. But according to the invention, the metal which flows out of the nozzle 1 through the orifices outlet 7-17 must have previously crossed the perforations 23-34 of the strip 19.

Alternatively, as shown in Figure lc, the cross section of the part in relief 20 of the strip 19 may have the shape of a triangle whose point has been leveled, and thus present a flat part 36 at its top.

It goes without saying that the representation of the nozzle 1 is only schematic, and that only the elements and details necessary for understanding the invention appear therein. In particular, in order not to overload figure la, we have not shown the way in which the different parts of the nozzle 1 are assembled together, this way is not not distinguishing from what is usual for this kind of nozzle. For example, the tube cylindrical 2 and the hollow element 4 can be fixed to each other by screwing.

Similarly, the external shape of the hollow element 4 of the nozzle 1 is only a non-limiting example and can be modified.

FIG. 2 represents a variant of a strip according to the invention, in which the raised part 37, of triangular cross section, covers the entire width of the strip 38. The top of the raised part 37 can also be leveled, in a manner comparable to what we observe on the variant of figure 1c. Figure 3 shows a variant of the configuration of Figure 2: the strip 39 has a raised portion 40 of cross section triangular, and whose thickness decreases between its middle and its ends. This variable thickness configuration of the raised part 40 can also be adapted to the case of Figure 1, where the raised portion 20 covers only the central portion of the width of the strip 19. By this variant, we seek, if necessary, to prevent the orifices located at the in the vicinity of the ends of the nozzle 1 are not supplied in a deficit by compared to the orifices located near its central part, therefore directly below the casting jet, in particularly in the case where a very long nozzle is used (of the order of 700 mm for example).

FIG. 4 shows an example of a strip 41, the raised part 42 of which also has a triangular section, but a rounded section. Again, the raised portion 42 can cover the entire upper face of the strip 40 (as shown), or only a portion of this upper face, and its thickness may be identical over the entire length of the strip 40, or decrease between its central part and its ends.

Finally, FIG. 5 shows an example of a strip 43, in which the part in relief 44 covers only a central portion of the upper surface of the strip 43, and has a rectangular cross section at its base and triangular at its top. On the other hand, said upper surface has bevelled edges 45, 46.

The examples of strips which have been described and shown are not limiting, and other configurations can be imagined, for example by combination of essential characteristics of the preceding examples. On the other hand, the position of the strip can be modified according to the internal geometry of the nozzle. Instead of being placed inside the louvers as shown, it can be placed entirely above or below gills, the main thing being that liquid metal must pass through it before flow out of the nozzle through the outlet openings in the bottom of the element hollow. The nozzle may also have other obstacles, in addition to the strip.

It is also conceivable that all the perforations of the strip cannot do not have the same diameter, and / or are placed at irregular distances the one share compared to others, if we observe that this contributes to further improving the distribution of the liquid metal leaving the bottom of the nozzle. Likewise, the perforations may not be strictly vertical but oblique.

By way of example, the following test results can be given. They were produced on a hydraulic model where the configurations of a nozzle 1 have been reproduced, the hollow element 4 of which has a length of 700 mm and an internal width of 54 mm, and is provided with a strip having the same length. and width. In the reference configuration, the strip has a strictly parallelepiped shape and a thickness of 20 mm. It has two rows of cylindrical perforations 12 mm in diameter, the axes of which are placed at a distance of 15 mm from the edges of the strip. These perforations have their axes 24 mm apart, and the axes of the perforations closest to the ends of the strip are located 35 mm from said ends. In the configuration according to the invention, the strip is of the type 19 shown in FIGS. 1a and 1b, with a central part in relief of triangular cross section 20, the apex of which overhangs the upper face of the strip 19 by 20 mm. The perforations are arranged in the same way as for the reference strip. The bottom of the hollow element 4 comprises in both cases a central row of 26 orifices comparable to the orifices 7-17 in FIG. The proportion of water passing through the nozzle 1 which exited therefrom through each of the openings 5, 6 and through each of the orifices at the bottom of the hollow element 4 was measured on the model. The results of the measurements are given in table 1 The orifices have been numbered from one end to the other of the nozzle 1, the holes N ° 13 and 14 being located on either side of the vertical axis of the nozzle 1. Distribution of the flow of liquid leaving the nozzle between the vents and the orifices Reference strip Invention strip Port number % of total outgoing flow by Port number % of total outgoing flow by left hearing 25.5 left hearing 21.2 1 2.2 1 2.3 2 2.1 2 2.3 3 2.1 3 2.3 4 2.0 4 2.2 5 2.1 5 2.3 6 2.1 6 2.3 7 1.2 7 2.2 8 2.0 8 2.2 9 1.9 9 2.1 10 1.7 10 2.0 11 0.9 11 1.8 12 1.6 12 1.7 13 2.6 13 3.0 14 2.6 14 3.0 15 1.6 15 1.7 16 0.9 16 1.8 17 1.7 17 2.0 18 1.9 18 2.1 19 2.0 19 2.2 20 1.2 20 2.2 21 2.1 21 2.3 22 2.1 22 2.3 23 2.0 23 2.2 24 2.1 24 2.3 25 2.1 25 2.3 26 2.2 26 2.3 right hearing 25.5 right hearing 21.2 Total 100.0 Total 100.0

In the reference configuration, the holes in the bottom of the nozzle are very unevenly supplied: a proportion of the liquid flow passes through them which varies from 0.9 to 2.6% (0.9 to 2.2% if the two central orifices are not taken into account numbered 13 and 14 which it is normal for them to be supplied in a privileged manner since they are located directly above the casting jet). We see that even two neighboring orifices can be supplied with very different flow rates. In the strip configuration according to the invention, the dispersion of the flow rates is much less: they vary from 1.7 to 3.0% (1.7 2.3% if the central holes are not taken into account).

As has been said, the nozzle according to the invention finds a preferred application in installations for the continuous casting of thin strips of steel between cylinders. But it can also be used on continuous product casting installations metallurgical of other formats and / or other metals, for which great regularity metal feed to the pouring space is helpful.

Claims (7)

Nozzle (1) for the introduction of a liquid metal into a casting mold metal continuous, of the type comprising a first tubular part (2), one of which end is intended to be connected to a container containing said liquid metal, and of which the other end opens into a second hollow part (4) of elongated shape, at least a portion of the interior space (3) is oriented substantially perpendicular to said first tubular part (2), said hollow part (4) comprising a hole (5, 6) at each of its ends, as well as one or more outlet orifices (7-17) formed in its bottom (18) and / or its side walls, a strip provided with perforations (22, 22 ', 23-34) being arranged in the interior space (3) of said hollow part (4) so that the liquid metal must pass through said perforations (22, 22 ', 23-34) before pass through said outlet orifices (7-17), characterized in that said strip (19, 38, 39, 41, 43) has at least a portion of the width of its upper face a portion in relief (20, 37, 42, 44) comprising a vertex situated on the longitudinal horizontal axis of said hollow part (4), said perforations (22, 22 ', 23-34) being distributed on one side and on the other side of said summit. Nozzle according to claim 1, characterized in that said raised part (20, 37) is of triangular cross section. Nozzle according to claim 2, characterized in that said raised part (20, 37) of triangular section with its leveled point. Nozzle according to claim 2 or 3, characterized in that the section transverse of the upper face (21) of said strip (19) is triangular in its part central (20) and planar in its lateral parts, and in that said perforations (22, 22 ', 23-34) are provided in said lateral parts. Nozzle according to claim 1, characterized in that said raised part (42) of said strip (41) has a cross section of rounded shape. Nozzle according to one of claims 1 to 5, characterized in that the face upper of said strip (43) has bevelled edges (45, 46). Nozzle according to one of claims 1 to 6, characterized in that said part in relief (40) of the strip (39) has a variable thickness, which decreases between the center and the ends of the strip (39).

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