EP0911096B1 - Pouring nozzle for metal continuous casting machine, especially for twin roll caster - Google Patents

Abstract

A nozzle for a continuous casting installation, notably casting between rolls, incorporates at its lower end two ears (18, 18') cut in its lateral wall opposite each other at the ends of a tubular portion (17) of its inner space. The ears (18, 18') include some vertical extensions (20, 20', 20) in their two upper angles (19, 19').

Description

The invention relates to the continuous casting of metals. Specifically, it concerns the nozzles made of refractory material which bring the liquid metal into the space of casting continuous casting machines, especially those that are suitable for casting thin strips a few mm thick, especially steel.

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 contained in the mold, where the solidification of the product must begin sank. The primary role of these nozzles is to protect the jet of liquid metal on its path between the container and the mold. They also allow, thanks to appropriate configurations of their lower end, to orient favorably liquid metal flows into the mold so that the product solidifies takes place in the best possible conditions.

The casting of thin metal strips a few mm thick directly at from liquid metal (steel or copper, for example) can take place on a so-called installation of "casting between cylinders". It includes an ingot mold whose casting space is defined on its long sides by a pair of internally cooled cylinders with horizontal axes 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 ends of cylinders. Cylinders can also be replaced by bands endlessly cooled.

When pouring between cylinders, two-part nozzles are often used (see, for example, document EP-A-0 771 600). The first part consists 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 built-in 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 made at each end of the hollow element. The metal flows coming out of the nozzle are thus preferably oriented in the direction of the lateral faces, so to bring hot metal to their surfaces, and thus avoid the occurrence of unwanted solidifications of metal (called "parasitic solidifications") which would disturb seriously the operation of the machine. The gills can have an orientation horizontal or downward oblique. Various holes of less importance than these gills can also be provided on the side walls and / or the bottom of the nozzle, so to directly supply hot metal to the regions of the mold located on the sides of the nozzle and / or under it. The aim is thus, in particular, to improve the thermal uniformity of the metal present in the mold.

A simple preferential orientation of the hot metal flows towards the faces lateral, however, is often insufficient to permanently guarantee an absence of parasitic solidifications, in particular in the vicinity of the contact zones between the cylinders and the side faces. This results in degradations of the lateral faces which compromise the sealing of the casting space. Metal can then seep between the side faces and the cylinders and solidify there, which further aggravates the deterioration of the lateral faces, or even escape in a liquid state from the machine, with all the risks that this entails for installation and staff. In all cases, the quality of the edges of the strip is adversely affected. In addition, when the solid metal resulting from these solidifications parasites is entrained in the bottom of the casting space, it must pass between the cylinders in creating a thickness of metal which is added to the normal thickness of the product. It follows that the cylinders must momentarily absorb an additional force which forces them to temporarily move away from each other to avoid deterioration. We can also attend a retraction of the lateral face, with the risk of losing the seal of the casting space associated with it.

The object of the invention is to provide a nozzle which, when used on a continuous casting installation between cylinders, allows better than existing nozzles of prevent the formation of parasitic solidifications on the lateral faces.

The subject of the invention is a nozzle for installation for the continuous casting of metals, in particular of casting between cylinders, of the type comprising at its lower end two openings made on its side wall opposite one another at the ends of a tubular portion of its interior space, characterized in that said vents comprise vertical extensions in their two upper angles.

According to a preferred embodiment, said gills are shaped so as to give the liquid metal emerging from said vertical extensions an orientation substantially horizontal or ascending, and at least part of the remainder of the liquid metal a downward orientation.

As will be understood, the invention consists in modifying the configuration of the gills conventional nozzles, providing them with vertical extensions in their two angles higher. The function of these vertical extensions is to provide greater speed of exit to the metal leaving the lateral parts of the gills, which is thus more likely directly reach areas of the casting space where it is desirable for the metal to be as hot as possible to avoid the appearance of parasitic solidifications on the faces side. This is, in particular, the case for the upper parts of the casting space of the casting machines between cylinders close to the contact zones between the cylinders and the side faces. The preferred configuration previously described, where the metal leaving the central part of the gills is oriented essentially towards the bottom of the casting space, also allows hot metal to be brought directly into the lower areas of casting space. In this way we seek to avoid the presence of parasitic solidifications on the side faces that would form just above the neck (the level where the surfaces of the cylinders are closest to each other).

• la figure 1 qui représente très schématiquement une installation de coulée continue entre cylindres vue de côté, montrant les zones où des solidifications parasites sont les plus susceptibles de se produire contre les faces latérales;
• la figure 2, qui montre vue de face en coupe selon IIb-IIb (figure 2a) et de profil (figure 2b) un premier exemple de busette selon l'invention;
• la figure 3, qui montre vue de face en coupe selon IIIb-IIIb (figure 3a) et de profil (figure 3b) un deuxième exemple de busette selon l'invention;
• la figure 4, qui montre vue de face en coupe selon IVb-IVb (figure 4a) et de profil (figure 4b) un troisième exemple de busette selon l'invention.

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

• FIG. 1 which very schematically represents a continuous casting installation between cylinders seen from the side, showing the zones where parasitic solidifications are most likely to occur against the lateral faces;
• Figure 2, which shows a sectional front view along IIb-IIb (Figure 2a) and in profile (Figure 2b) a first example of a nozzle according to the invention;
• Figure 3, which shows a front view in section along IIIb-IIIb (Figure 3a) and in profile (Figure 3b) a second example of a nozzle according to the invention;
• Figure 4, which shows a sectional front view along IVb-IVb (Figure 4a) and in profile (Figure 4b) a third example of a nozzle according to the invention.

Installation of continuous casting of thin metal strips between cylinders shown very schematically in Figure 1 comprises in known manner a pair of internally cooled cylinders 1, 1 'with horizontal axes. Their external surfaces 2, 2 ' ensure the solidification of the liquid metal that the nozzle 3, connected to a distributor not shown, brings into the casting space 4 thanks to its gills 5. The casting space 4 is defined by said external surfaces 2, 2 'of the cylinders 1, 1' where they face each other. It is laterally closed by refractory side faces, including, to make the space visible casting 4, only one of them 6 is shown. They are applied against lateral ends 7, 7 'of the cylinders 1, 1'. The minimum width "e" of the casting space 4 corresponds substantially to the desired thickness for the cast strip, and is encountered at level of the neck 8, that is to say where the external surfaces 2, 2 'of the cylinders 1, 1' are the most close to each other. In the case of steel casting, it is optimally at the neck 8 that the solidified metal skins formed on the cylinders must meet 1, 1 ′ inside the casting space 4. A too early end of solidification would oblige the cylinders 1, 1 'to exert a rolling force on the product, while they do not have the mechanical resistance necessary for this purpose. Conversely, an end of solidification located substantially below the neck 8 would cause the appearance of defects on the product, due in particular to its lack of rigidity at the outlet of the casting installation.

During casting, the risk of parasitic solidifications can be expected of metal on the side faces 6 are the largest in the area 9 located just above of the neck 8. Indeed, the neck 8 is, as we said, the level at which the solidification of the strip, and this zone 9 is therefore that where the temperature of the liquid metal in contact with the faces side 6 must reach its minimum value. The experience of the inventors shows that this zone 9 around the neck 8 is effectively sensitive to parasitic solidifications, but that two other places are also of great importance from this point of view. These are zones 10, 11 located in the upper part of the pouring space, below the nominal level 12 reached by the surface of the liquid metal, and bordering the contact arcs between the cylinders 1, 1 'and each of the side faces 6. The explanation is probably only in these areas 10, 11, the contact between the lateral face 6 and a portion of the cylinder 1, 1 'which has just carried out a long journey in the open air, therefore outside the thermal influence of liquid metal, creates abnormally cold zones on said lateral face 6. Consequently, provided that the liquid metal which reaches these areas has itself cooled after carrying out a relatively long stay in casting space 4 due to the distance sometimes important between these zones 10, 11 and the vents 5 of the nozzle 3, there is a risk of initiation of a parasitic solidification. Between these zones 10, 11 and the previously mentioned zone 9, located above the neck 8, the risks of parasitic solidifications are reduced. On the one hand the cylinders 1, 1 'are there in a more favorable thermal state, and on the other hand the hot metal leaving the vents 5 of the nozzle 3 reaches more directly in these regions of the pouring space 4, without having, in the meantime, been excessively cooled.

FIG. 2 shows a first type 13 of nozzle made of refractory material according to the invention. The geometry of this nozzle 13 is mainly calculated to avoid parasitic solidifications in the upper zones 10, 11 of the lateral faces 6 previously described. In known manner, this nozzle 13 is formed of two parts. The first part is a tube 14 whose upper end not shown is intended to be connected to the distributor containing the liquid steel to be poured. The second part is a head hollow 15 fixed to the tube 14, for example by screwing. Alternatively, both parties can be brought together in one piece. The lower end of the hollow head 15 can, as shown, be slightly tapered to better fit the general shape of the space 4. Its interior space has a cylindrical portion 16 extending the space inside the tube 14. This cylindrical portion 16 opens into a tubular portion 17 which is substantially perpendicular to it, and whose cross section, in the example shown, has a generally rectangular shape. Each end of this tubular portion 17 has a hole 18, 18 'intended, once the nozzle 13 mounted to be oriented towards one of the side faces 6 closing the casting space 4 of the casting machine.

According to the invention, the vents 18, 18 'have in their upper corners 19, 19' vertical extensions 20, 20 ', 20 "whose width represents only a relatively small fraction of the total width of the hearing 18, 18 '. For example, for a total width hearing 18, 18 'of 60 mm and a height of 35 mm, we can provide that each vertical extension 20, 20 ', 20 "has a width of 10 mm and a height of 10 mm about. They constitute the outlet openings of recesses 21, 21 'which themselves extend the tubular portion 17 of the interior space of the hollow head 15 on at least the portion terminal of its length, or even over its whole as shown in FIG. 2a. The function of these vertical extensions 20, 20 ', 20 "and of these recesses 21, 21' will now be explained.

Modeling of flows inside geometry nozzles identical or comparable to that of the nozzle 13 have shown that the flow of liquid metal leaving the nozzle preferentially flowed according to the perimeter of the hearing corresponding, and that the speed of the liquid metal circulating in the tubular portion 17 of the interior space of the hollow head 15 was therefore maximum in the vicinity of its walls vertical 22, 22 '. The metal which circulates in the vicinity of said vertical walls 22, 22 'leaves thus vents 18, 18 'with a higher energy than the metal which circulates in the vicinity of the center of the tubular portion 17. For this reason, it penetrates deeper into the casting space 4, and arrives faster, warmer and in greater proportion on the faces 6. According to the invention, the presence of the vertical extensions 20, 20 ', 20 "located in the upper corners 19, 19 'of the openings 18, 18' and of the recesses 21, 21 'which there drive allows to take advantage of this phenomenon to reduce the risk of formation of parasitic solidifications on the upper zones 10, 11 of the lateral faces 6. roughly its usual flow and flow mode with the main flow of liquid metal coming out of the central part of the openings 18, 18 'since the shape and the surface of the openings 18, 18' are only slightly modified. But simultaneously, we orient the flow of metal with energy elevated out of the lateral parts of the vents 18, 18 'at higher altitudes than with a nozzle without these extensions 20, 20 ', 20 ", in other words in the direction of the zones 10, 11. The average temperature of the molten metal which reaches the in the vicinity of said zones 10, 11, which makes the formation of parasitic solidifications. Such an effect could not be obtained by a simple increase in the height of the gills 18, 18 'over their entire width, as this would increase too much substantially their surface. This would result in an overall decrease in the exit speed of the metal at constant flow: we would probably not obtain the desired effect in zones 10, 11 of the side faces 6, and furthermore the conditions of arrival of the hot metal would be degraded the rest of the side faces 6, with the risk of seeing parasitic solidifications appear to new places. Similarly, locate the vents 18, 18 'higher in the casting space 4 without modifying their shape and their dimensions (by changing the geometry of the nozzle 13 or by decreasing the depth of its immersion in the casting space 4) would likely to deteriorate the circulation of liquid metal in the lower part of the space casting 4, and thus generate other parasitic solidifications.

In the example shown in Figure 2, the recesses 21, 21 'and the vertical extensions 20, 20 ', 20 "of the vents 18, 18' are directed horizontally and parallel to the general orientation of the tubular portion 17 of the interior space of the head 15. But, of course, we can also plan to give the two extensions vertical 20, 20 ', 20 "of the same opening 18, 18' and their corresponding recesses 21, 21 ' significantly divergent and / or ascending directions, with the aim, if necessary, of direct the metal flows more frankly towards the upper zones 10, 11 of the lateral faces 6 which are the most sensitive to parasitic solidifications.

In the example which has just been described, the openings 18, 18 ′ have a general shape rectangular, but other shapes can be envisaged, in particular for their edges lower: triangular with point down, rounded ... The essential, from the point of view of the invention resides in the presence of the vertical extensions 20, 20 ', 20 "in the corners upper gills 18,18 '.

As has been said, the geometry of the nozzle 13 which has just been described aims at first place to solve the problem of parasitic solidifications which can occur in zones 10, 11 of the side faces 6 located in the upper part of the casting space 4, in the vicinity of the cylinders 1, 1 '. Its use supposes that one does not notice usually annoying parasitic solidifications in the zones 9 of the lateral faces 6 located just above the neck 8. This may be the case, in particular, if the nozzle 13 is submerged relatively deep into the casting space 4, or if the casting space 4 has a reduced depth because the cylinders 1, 1 ′ have a small diameter: in these conditions, the hot metal leaving the nozzle 13 has no difficulty reaching said zones 9. For cases where solidification problems also arise parasites in these zones 9, it is proposed to use a nozzle 23 as shown in the figure 3.

The general design of this nozzle 23 is the same as that of the nozzle 13 of FIG. 2, and the identical elements of these two nozzles 13, 23 are designated by the same references in FIGS. 2 and 3. The essential modification resides in the fact that the tubular portion 17 of the interior space of the head 15 present, at least in its parts terminals 24, 24 'close to the vents 18, 18', an inclination of an angle α relative to the horizontal. This inclination makes it possible to orient the jets of liquid metal coming from the part central hearing 18, 18 'towards the lower part of the casting space 4, with for the purpose of ensuring the supply of hot metal in the vicinity of the lower zone 9 of the side face 6 which corresponds to it. The value of the angle α (which can reach if necessary several tens of degrees) must be determined according to the shapes and dimensions respective of the pouring space 4 and the nozzle 23, as well as the depth nominal immersion of the nozzle 23. Simultaneously, the vents 18, 18 'are, as in the nozzle 13 of Figure 2 and according to the invention, provided in their angles upper 19, 19 'of vertical extensions 20, 20', 20 "which constitute the orifices of outlet of recesses 21, 21 'opening into the tubular portion 17 of the interior space of the head 15. The presence of the vertical extensions 20, 20 ', 20 "makes it possible to obtain streams of liquid metal exiting at high speed from the lateral parts of the nozzle 23 for go to irrigate the casting space 4 near the upper zones 10, 11 of the faces lateral 6, where the risks of parasitic solidifications are greatest. In the example shown in Figure 3, the recesses 21, 21 'and the vertical extensions 20, 20', 20 " vents 18, 18 'are directed horizontally and parallel to the general orientation of the tubular portion 17 of the interior space of the head 15. But, of course, as we said about the nozzle 13 of figure 2, one can also plan to give to the two vertical extensions of the same hearing and their corresponding recesses of the divergent and / or ascending directions in order, if necessary, to direct the metal flows more frankly towards the upper zones 10, 11 of the lateral faces 6 sensitive to parasitic solidifications.

• une portion 26, 26' de forme générale rectangulaire s'étendant sur toute la largeur de l'ouïe 18, 18', munie dans ses angles supérieurs 19, 19' de prolongements verticaux 20, 20', 20" qui constituent les orifices de sortie d'évidements 21, 21' sensiblement horizontaux comme représenté (ils peuvent aussi être ascendants, et éventuellement divergents) débouchant dans la portion tubulaire 17 de l'espace intérieur de la tête 15;
• une portion 27, 27' située sous la précédente et constituant la partie inférieure de l'orifice de sortie de la partie terminale 24, 24' de l'espace intérieur 17 de la tête 15; cette portion 27, 27' a une largeur plus faible que la précédente (par exemple de moitié), et est centrée sur l'axe de symétrie vertical de l'ouïe 18, 18'.

The nozzle 25 shown in FIG. 4 is, in a way, a compromise between the nozzles 13, 23 in FIGS. 2 and 3. In fact, its vents 18, 18 ′ each comprise both:

• a portion 26, 26 'of generally rectangular shape extending over the entire width of the hole 18, 18', provided in its upper corners 19, 19 'with vertical extensions 20, 20', 20 "which constitute the orifices of outlet of recesses 21, 21 ′ substantially horizontal as shown (they can also be ascending, and possibly divergent) opening into the tubular portion 17 of the interior space of the head 15;
• a portion 27, 27 'located under the previous one and constituting the lower part of the outlet orifice of the terminal part 24, 24' of the interior space 17 of the head 15; this portion 27, 27 'has a narrower width than the previous one (for example by half), and is centered on the vertical axis of symmetry of the hearing 18, 18'.

As in the nozzle 23 of FIG. 3, said end portion 24, 24 'of the space inside 17 of head 15 is inclined downward by an angle α with respect to the horizontal. But this inclination only concerns the central parts of the interior space 17, those which lead to the lower portions 27, 27 'of the openings 18, 18'.

Compared to the nozzle 23 of Figure 3, we seek here not to orient directly towards the lower zone 9 of the side faces 6 than a smaller fraction of the liquid metal, which may, however, for certain configurations of casting installations, be sufficient to avoid parasitic solidifications.

It goes without saying that the nozzles 13, 23, 25 which have been described and shown are not as examples of implementation of the invention. One can imagine adapting the invention to nozzles having other remarkable characteristics known in themselves. Through example, provision may be made to fill the cylindrical interior spaces with the tube 14 and / or the hollow head 15, or of the tubular portion 17 of the interior space of the head 15 by one or more obstacles which stabilize the flows. The aim would in particular be to improve the filling the louvers 18, 18 'with liquid metal: this would allow us to benefit more assuredly advantages of the invention. Such obstacles are, for example, described in the document EP-A-0 765 702. This last document describes nozzles whose hollow head has a very elongated shape, which can also benefit from the invention. The invention is also fully adaptable to nozzles whose side walls and / or the bottom of the hollow head 15 would be fitted with perforations allowing direct supply of hot metal to the areas of the pouring space 4 located along the nozzle or below it, such as the perforations described in document EP-A-0 771 600.

It also goes without saying that the nozzles according to the invention can be installed on other continuous casting plants than thin strip casting plants between two cylinders, if their use gives liquid metal flows advantageous configurations.

Claims (6)

1. Nozzle for metal continuous casting installation, particularly for roll casting of the type, comprising a first tubular part (14) destined for the connection to the tundish of the continuous casting installation, and a second part comprising an inner space, having a tubular portion (17) substantially perpendicular aligned with said first part (14), and comprising at each of its outer ends two outlets (18, 18'), characterised in that said outlets (18, 18') comprise vertical extensions (20, 20', 20") solely in their upper angles (19, 19').
2. Nozzle according to claim 1, characterised in that said vertical extensions (20, 20', 20") are aligned horizontally and in parallel to the general orientation of said tubular portion (17).
3. Nozzle according to claim 1, characterised in that said vertical extensions (20, 20', 20") are aligned in an ascending way.
4. Nozzle according to claim 1 or 3, characterised in that said vertical extensions (20, 20', 20") of each outlet (18, 18') are aligned according to two divergent directions.
5. Nozzle (23, 25) according to one of the claims 1 to 4, characterised in that, outside of said vertical extensions (20, 20', 20"), said outlets (18, 18') are aligned, for at least one portion of their section, according a declining direction.
6. Nozzle according to one of the claims 1 to 5, characterised in that its inner space is equipped with one obstacle or with obstacles, intended for calming down the outflow of the casted liquid metal.

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