REFRACTORY ASSEMBLY

Abstract: The invention concerns a refractory assembly for a device for regulating a pouring flow rate. Downstream from a pouring channel (7), it is comprised of at least two refractory plates (1, 2) perpendicular to one axis of the channel (Z-Z) and equipped with the respective orifices (10, 20). The device includes, upstream from the plates, means for injecting a fluid (F) capable of cooperating mechanically with the pouring (C). According to the invention, this injection is effected upstream from the plates and in an angular sector of the channel (7) less than 360 DEG , in the direction of displacement (X-X) of the sliding plate (1) toward its stop position.

Description: REFRACTORY ASSEMBLY. Description The invention concerns a device for regulating the flow rate of a pouring, notably of an installation for pouring a molten metal, such as steel or cast iron. It concerns more particularly the injection of an inert fluid such as argon, in a refractory assembly used in a regulating device of this type. This fluid is designed to cooperate mechanically with the molten metal. Devices for regulating the flow rate have a pouring channel, downstream from which two refractory plates, each with an orifice, are usually interposed. These plates are essentially perpendicular to the axis of the channel and one of the plates can slide relative to the other, toward one side of the channel. In the pouring position, the aperture of the sliding plate coincides essentially with the axis of the pouring and the respective apertures of the plates mutually communicate. On the other hand, in the pouring stop position the aperture of the sliding plate is offset at a distance from the other plate and the two plates thus close off their mutual aperture. In the known regulating devices, a means of injection is generally distributed over the entire periphery of the channel for injecting the said fluid all around the axis of the channel. The radial injection of the fluid thus permits a uniform and axisyrnmetric injection. However, it can be provided that the sliding plate is slightly offset relative to the other plate, in an intermediate position between the said pouring and stop positions to furnish a moderate or low pouring flow rate. The molten metal then encounters an obstacle formed by the edge of the aperture of the sliding plate with regard to the axis of the channel. An erosion of this orifice generally results. Moreover, solid deposits can form on the edge of the aperture, above the sliding plate, in a zone of recirculation of the molten metal. The present invention is intended to improve this situation. It then concerns a refractory assembly used in a regulating device of the said type and having, downstream form the pouring channel, at least two refractory plates essentially perpendicular to the axis of the channel and equipped with the respective orifices. One of the plates is designed to slide relative to the other plate toward one side of the channel, from a pouring position in which the respective orifices essentially communicate to a pouring stop position in which the plates essentially close off their mutual orifice. The refractory assembly also has injection means essentially upstream form the plates for a fluid capable of cooperating mechanically with the molten metal to avoid deposits in the said recirculation zone. According to a general characteristic of the invention, the refractory assembly has an internal nozzle with an essentially cylindrical, hollow form upstream from the plates. The internal wall of this nozzle delimits the said pouring channel. The injection means are designed to inject the fluid in directions essentially radial to the nozzle, in an angular sector less than 360° and opposite the side of the channel with regard to the sliding plate when it is in the closure position. The molten metal is thus perturbed locally by the injected fluid and mechanically (even thermally) isolated, from the wall in the recirculation zone. The said angular sector is preferably less than or equal to about 270°, so as to concentrate the fluid flux more intensely in the zone of molten metal recirculation. For some applications, the angular sector is preferably close to 120°. According to an advantageous optional characteristic of the invention, the internal nozzle has in an essentially transversal section a recess that communicates with the interior of the pouring channel and forms a crown of angular sector less than 360°. The fluid is then injected through this recess. This recess preferably accommodates an insert effected in a porous refractory material, in which the fluid is injected toward the inside of the pouring channel. Other advantages and characteristics of the invention will appear from reading the following detailed description and an examination of the attached drawings: - figure 1 is a partial schematic view, in longitudinal section, of a refractory assembly for a regulating device according to the invention; - figure 2 is a view in longitudinal section of an internal nozzle of the device, according to a preferred implementation mode of the invention; - figure 3 is a cross-sectional view of the nozzle shown in figure 2. The attached drawings and the following detailed description essentially contain elements of a certain nature. They could not only serve to better understand the present invention, but also contribute to its definition, if necessary. Reference is first made to Figure 1 , which schematically shows a refractory assembly for a regulating device for a molten metal pour (arrows C), notably in a steel-making or metallurgical installation. The refractory assembly in the example described has three refractory plates, one of which, designated as 1, can slide between the other two, 2 and 3. The three plates 1, 2 and 3 are essentially superposed and perpendicular to the pouring axis Z-Z, vertical in the example described. Upstream from the plates, it has an internal refractory nozzle 4, designed to be seated at least partially in a pouring hole that has a bottom wall of a continuous casting distributor (not shown) in the example described. The internal nozzle 4 constitutes an element of the pouring channel that connects the pouring distributor to an ingot mold of the installation. The internal nozzle 4 is of an essentially cylindrical, hollow general form, its internal wall 43 (figure 2) delimiting a pouring channel 7. More particularly, the nozzle 4 is of an essentially truncated conical form. The pouring channel 7 communicates with an aperture 20 of the upstream refractory plate 2. In the example described, the upstream plate 2 and the downstream plate 3 are fixed with regard to the internal nozzle 4, while the intermediate plate 1 can slide from a pouring position toward a pouring stop position (toward the right of Figure 1 , as shown), thus, displacement of the aperture 10 of the sliding intermediate plate 1, essentially along the horizontal X-X axis, allows regulating the pouring flow rate. Indeed, in the pouring position the aperture 10 communicates with the orifice 20 of the upstream plate 2 on the one hand and with the aperture 30 of the downstream plate 3 on the other. In the pouring stop position, the orifice 10 is offset toward the right of figure 1 and a portion of refractory plate 11 in the vicinity of the orifice 10 (shown to the left of the orifice 10 in Figure 1) sensibly closes off the orifice 20 of the upstream plate 2 on the one hand and the orifice 30 of the downstream plate 3 on the other. Thus, when the orifice 10 of the sliding intermediate plate 1 is offset relative to the pouring channel 7 along the axis X-X, the flow rate of pouring decreases, up to the point that the pouring is interrupted when the sliding plate 1 is in an extreme position corresponding to the said pouring stop position, on the other hand, when the axis of the orifice 10 is substantially merged with the pouring axis, the flow rate of pouring is maximal. In an intermediate position of the plate 1 , the molten metal encounters a first obstacle corresponding to the upper wall of the part 11 of the sliding plate 1, in the vicinity of orifice 10. The respective apertures 20 and 10 of plates 2 and 1, sensibly offset relative to each other, form an essentially curved-in pouring trajectory C. The metal stagnates in the zone 6 called the "dead zone of recirculation". In a metallurgical installation of molten steel, for example, solid deposits of alumina and solidified steel can form in this zone 6, capable of perturbing the displacement of the sliding plate 1, even obstructing the orifice 20 of the upstream plate 2. The general idea is to inject a fluid capable of cooperating mechanically with the molten metal so as to create a local turbulence and/ or a sleeve protecting the walls of the nozzle in order to counteract the formation of a deposit. This fluid is chosen so as not to react chemically with the molten metal. In practice, an inert gas such as argon is injected. In the known regulating devices, this injection is generally made all around the pouring axis Z-Z. A circular aperture is provided that extends over 360° of the pouring channel for injecting the gas radialy. However, this axisymmetric injection in no way resolves the problem posed by the recirculation in zone 6 and the resulting deposit. One of the goals of the present invention is to furnish a localized injection of the fluid capable of cooperating mechanically with the molten metal in order to limit, even eliminate the recirculation of molten metal in the said zone 6. According to a preferred embodiment of the present invention, the internal nozzle 4 has a recess 40 in its internal wall 43, which extends over an angular sector less than 360°, in a plane essentially perpendicular to the axis of the nozzle Z-Z. An insert 5 made of a porous refractory material is located in this recess; the inert gas is injected in it (arrows F) . The flux of injected gas creates a turbulence localized in the zone 6 of potential deposition, and protects the wall by the formation of a thermally insulating, gaseous sheet. Preferably, the angular sector on which the recess 40 of the internal nozzle 4 extends is close to 120° in the example described (Figure 3). In particular, the recess 40 presents, in a cross section of the nozzle (Figure 3), a form of crown or collar of angular cross section A less than 270° and close to 120° in the example. As shown in Figure 2, the internal nozzle 4 has a circular slot 41 for supplying the fluid from the external connector 46 up to the injection zone 5. The slot 41 is prolonged locally by an orifice 42 that communicates with the recess 40 and through which the gas is injected (arrow F). the gas F is introduced into the pores of the insert 5 by being directed essentially in a transversal plane and in an angular sector close to 120°, toward the center of the channel 7. Thus, a localized injection of the fluid advantageously makes it possible to limit, even prevent the formation of a deposit in the zone 6, in particular, when the pouring trajectory is essentially curved inward, the sliding plate 1 being in an intermediate position (Figure 1), defining a pouring flow rate less than the maximum flow. Of course, the present invention is not limited to the implementation form described previously by means of example. It also extends to other variants. Another implementation form consist of seating a metal pipe in the body of the nozzle, connecting the external connector 46 directly to the slot 41. It should be understood that the injection of fluid can also be effected through a plurality of orifices arranged in a plane essentially perpendicular to the axis of the nozzle 4 and distributed over an angular sector less than 360°, e.g., close to 120°. In a variant, the nozzle 4 can have a slot in a plane essentially perpendicular to its axis Z-Z, and which extends over an angular sector less than 360°, according to a general characteristic of the invention. The injection of fluid is effected in both cases with regard to a zone of the channel capable of containing a zone of molten metal recirculation. This recirculation forms principally on the side of the channel opposite the side 45 (Figure 1) toward which the plate 1 slides from its pouring position toward its stop position. It is to be noted that in the USP 4,632,283, a refractory assembly is disclosed having injection means in the upstream plate 2 for injecting the fluid through a portion of the plate 2 distant relative to the sliding plate 1 in its stop position (to the left of the orifice 20, as shown in figure 1) in order to orient the injected flux essentially in the direction of displacement of the sliding plate 1. However, the upstream plate 2, having such injection means, requires a boss (also named spigot) on its upper surface, around its orifice 20. This boss, which has a slot, a plurality of orifices or even a porous insert for injecting the fluid, extends toward the internal nozzle, with a significant height along the axis of pouring Z-Z to effect an effective injection of the fluid. It is also necessary to provide a homologous recess in a lower part of the nozzle for accommodating this boss. The applicant found that, surprisingly, the molten metal undergoes a loss of heat in circulating from the internal nozzle to the upstream plate 2. This loss of heat is greater, the higher the boss. Thus, an excessively high boss causes the formation of solid deposits on the intermediate plate 1, which is exactly the contrary of the effect sought in USP 4,632,283. An injection of fluid from the nozzle, according to the invention, permits limiting this heat loss. It is also possible to equip the refractory assembly according to the invention with an intermediate sliding plate 1 having a porous refractory insert and secondary injection means (arrows F^ in the direction of sliding of the plate 1 from its stop position to its pouring position (from the right to the left in Figure 1) in order to eliminate a possible deposition associated with the recirculation of metal above the upper face of a part 31 of the downstream plate 3 in the proximity of its orifice 30 (to the right of the orifice 30, as shown in Figure 1). This secondary injection extends preferably over an angular sector less than 360°. In addition, a porous insert or any other means of injection of the fluid can also be located in the downstream plate 3, on the side opposite the closure of the sliding plate 1 in order to protect the zone under the sliding plate, to the left of its pouring aperture from a possible recirculation. In the example described, the refractory assembly has three superposed refractory plates, one of the plates, the intermediate one, sliding between the other two. In a variant, only two refractory plates 1 and 2 can be provided downstream from the nozzle 4. The lower plate 1 is then designed to slide relative to the plate 2 toward a side 45 of the channel. The sliding plate 1 is generally located below the fixed plate 2, while the principal injection of fluid is always done from the side of the channel opposite the side 45, toward which the sliding plate 1 is displaced from its pouring position to its stop position. In another variant of the refractory assembly according to the invention, the internal nozzle 4 and the upstream plate 2 are made of a single monoblock refractory piece. The internal nozzle 4 is a refractory piece that is generally part of the upper zone of the refractory assembly designed to connect a continuous casting distributor to an ingot mold of the pouring installation. In a variant, this nozzle can be part of a refractory assembly connecting a pouring ladle to the distributor, or an electric furnace to a pouring ladle.

Claims: Claims. 1. Refractory assembly for a device for regulating the flow rate of a pouring, notably of a metallurgical or steel-making installation of the type having at least two refractory plates (1, 2) essentially perpendicular to an axis of the channel (Z-Z) and equipped with the respective apertures (10, 20) downstream from a pouring channel (7), one of the plates (1) being designed to slide relative to the other plate (2) toward one side (45) of the channel, from a pouring position in which the respective orifices (10, 20) essentially communicate to a pouring stop position in which the plates (11, 21) essentially close off their mutual orifice (10, 20), the device also having injection means, for a fluid (F) capable of cooperating mechanically with the molten metal (C) , characterized in that the injection means are located in a part of the pouring channel (7) located upstream from the plates (1, 2) and in that said injection means are designed to inject the fluid (F) in an angular sector of the channel (7) less than 360° and opposite the side (45) of the channel relative to the sliding plate (1) in the stop position, so as to orient the fluid (F) essentially in the direction of displacement (X-X) of the sliding plate ( 1) from its pouring position to its stop position. 2. Assembly according to claim 1, characterized in that it has an internal nozzle (4), essentially hollow and cylindrical in form and of a refractory material upstream from the plates, while the injection means are designed to inject the fluid (F) in directions essentially radial to the said nozzle in an angular sector less than 360°. 3. Assembly according to claim 2, characterized in that the internal nozzle has a recess (40) in an essentially transverse section, communicating with the internal pouring channel (7) and forming a crown of angular sector (A) less than 360°, while the injection means are designed to inject the fluid in the recess (40). 4. Assembly according to claim 3, characterized in that the said recess (40) is designed to accommodate an insert (5) of porous refractory material. 5. Assembly according to one of claims 1 to 4, characterized in that the internal nozzle has an essentially transverse slot (41) extending over a peripheral part of the nozzle, while the injection means are designed to inject the fluid (F) in at least part of the slot (41). 6. Assembly according to one of the claims 1 to 5, characterized in that the internal nozzle has at least one orifice (42) extending in an essentially radial direction of the tube and essentially parallel to the direction of displacement of the sliding plate, while the injection means are designed to inject the fluid (F) in the orifice (41). 7. Assembly according to claim 6, characterized in that the said orifice (42) is designed to accommodate a metal pipe capable of feeding the fluid (F). 8. Assembly according to any one of the claims 1 to 7, characterized in that the said angular sector (A) is less than or equal to ca. 270°. 9. Assembly according to claim 8, characterized in that the angular sector (A) is close to 120°. 10. Assembly according to any one of the claims 1 to 9, characterized in that at least one of the plates (10, 20, 30) is composed at least partially of a porous refractory material, and that at least a portion of the fluid (F, F^ is also injected in the porous portion of the plate. 11. Assembly according to any one of the claims 1 to 10, characterized in that the internal nozzle (4) and the plate (2) directly downstream from the nozzle are comprised of a single monoblock refractory piece. 12. Assembly according to any one of the claims 1 to 10, characterized in that the fluid (F) is comprised of argon.

Inventors: BOISDEQUIN VINCENT, BOISDEQUIN, VINCENT
Applicants: BOISDEQUIN VINCENT, VESUVIUS CRUCIBLE CO, BOISDEQUIN, VINCENT, VESUVIUS CRUCIBLE COMPANY
Application year: 1999
Main classification: B22D41
IPC codes: B22D11, B22D41