MXPA99003603A - Plant for transferring liquid metal, method of operation, and refractories - Google Patents

Abstract

The invention relates to a plant for transferring liquid metal, in particular steel, between an upstream container (2) and a downstream container (10), comprising:an upstream container (2);a tapping spout (28);a downstream container (10), a flow regulator (26) for regulating the flow of liquid metal through the tapping spout (28);a set of refractory assemblies (8, 12, 30, 32, 64, 66, 74) which are placed between the upstream container and the downstream container, delimiting the tapping spout (28) via which the liquid metal flows from the upstream container (2) into the downstream container (10), each refractory assembly of the tapping spout (28) having at least one mating surface (22) forming a joint with a corresponding surface of an adjacent refractory assembly;a shroud channel (18;40) placed around the tapping spout (28) near at least one mating surface (22) between refractory assemblies (8, 12, 30, 32, 64, 66, 74), this shroud channel having an inlet (44) capable of allowing the introduction of materials;in which plant means (32, 34;36) are provided for introducing a sealing agent into the shroud channel (40;18).

Description

INSTALLATION FOR THE TRANSFER OF A LIQUID METAL.

PROCEDURE FOR ITS IMPLEMENTATION, AND REFRACTORY MATERIALS.

TECHNICAL FIELD The present invention relates to installations for the transfer of a liquid metal from a container located upstream to a container located downstream, comprising: a container located upstream; a container located downstream; a pouring channel; a device for regulating runoff, to regulate the flow of liquid metal through the pouring channel; a set of refractory assemblies disposed between the container located upstream and the container located downstream, which delimits the pouring channel through which the liquid metal drains from the container located upstream to the container located downstream, each comprising the refractory assemblies of the casting channel, at least one connecting surface forming a joint or a junction with a corresponding surface of an adjacent refractory assembly; a protection channel, arranged around the pouring channel at the level of at least one connecting surface between refractory assemblies. The term "refractory assembly" refers to a monolithic part constituted by one or more grades or types of refractory material, and which optionally comprises other constituents, for example a metallic coating. The term "run-off regulating device" refers to any type of device used in this technical field, such as a pour plug, a slide, or even a simple throttle.

PREVIOUS ART In such an installation, the presence of a flow-regulating device in the pouring channel implies, when the liquid metal is drained, a drop in pressure. If the pouring channel is not perfectly watertight, it is possible that the air is sucked into it, as a consequence of this depression. In general, this is also the case, in particular at the level of the splicing surfaces between the different refractory assemblies that form the pouring channel, whose sealing is difficult to achieve and maintain. Therefore, air is sucked into the pouring channel, which leads to a degradation of the quality of the metal. In order to solve this problem, the resource consisting of creating, by means of a protection channel, an over-pressure of a neutral gas around the pouring channel, at the level of each of the critical splicing surfaces is known. By the term "neutral gas" is meant in this case a gas that does not adversely affect the quality of the cast metal. Among the gases usually used are rare gases such as argon, but also other gases such as nitrogen or carbon dioxide. According to a known embodiment, a groove is formed in at least some of the joining surfaces between two adjacent refractory assemblies. Said groove is fed in neutral gas under pressure, and thus forms an annular protection channel disposed around the pouring channel. An embodiment of this type is disclosed in for example U.S. Patent 4,555,050 and EP 0,448,641. In the particular case in which some successive refractory assemblies are movable with respect to each other, the use of a protection channel is also known. French Patent Application FR 2227 073 discloses a slide with two plates, each of which comprises an orifice for the passage of the liquid metal; the sliding of one of the plates with respect to the other, allows to regulate the flow rate of the liquid metal. These two plates each comprise, along their common joining plane, a "U" -shaped groove, placed parallel to but opposite to the other, in such a way that the branches of one of the the "U" ride on the branches of the other "U", which materialize an annular and closed protection channel, whatever the relative position of both plates. According to another known embodiment, a closed chamber surrounding the outer part of the splicing surfaces is practiced, and the chamber is supplied with neutral gas under overpressure. An embodiment of this type has been disclosed in for example U.S. Patent No. 4,949,885. All these known dispositions allow to replace the aspiration of air by a neutral gas suction, which suppresses the chemical problem linked with the contact of the liquid metal with the air.

CRITIQUE OF PREVIOUS ART However, these known solutions have several disadvantages. The introduction of gas into the pouring channel is not suppressed.

Moreover, it is increased, because the slot or camera is in over-pressure. This is a drawback, in particular in the case of a metal transfer between a distributor and a continuous casting mold. The gas introduced into the pouring channel flows into the mold and causes there disturbances such as turbulence, a displacement of the coating powder, and entrapment of said powder in the liquid metal. In addition, the gas entrained in the mold can dissolve in the liquid metal and subsequently create defects in the solidified metal. On the other hand, in order to reduce the speed of the liquid metal upon its arrival in the mold, and thus reduce the turbulence in said mold, numerous jetting tubes are used which have an outlet section larger than their entry section. In such a case, the rate of runoff of the liquid metal progressively decreases. The presence of a significant amount of gas in the tube can prevent the correct functioning of this type of tube; the runoff can detach from the walls of the tube, and the liquid metal then falls in the form of a jet in the mold. The quality of a joint surface between two refractory assemblies can vary in an uncertain manner in the course of using the casting channel. Defects may arise; in particular, in the case of movable refractory assemblies with respect to each other, the wear of the splicing surface can cause significant leaks. Among the installations that include mobile refractory assemblies, we have the regulating slides and the devices to change the protective jet tubes. One possibility to limit the entry of gas into the pouring channel is to regulate the flow of neutral gas introduced into the protection channel. In this case, if the leakage defect becomes significant, it may be the case that the flow of neutral gas is no longer sufficient for only the neutral gas to enter the pouring channel. In this case, the pressure in the protection channel becomes negative, and it is possible for the ambient air to be sucked into the pouring channel. However, if the tightness is good, a fixed flow of neutral gas is nevertheless introduced into the protection channel, the pressure in the protection channel increases, and the neutral gas enters the pouring channel without this being really necessary .

Another possibility is to regulate the pressure of the neutral gas when it is injected into the protection channel. In this case, if the leakage defect becomes significant, the flow rate of the neutral gas admitted into the pouring channel is important, which results in the aforementioned defects. In practice, when the leakage flow is important, there is no alternative but to use these two modes of reduction as an alternative, accepting a certain amount of air sucked in instead of a large excess of neutral gas. This makes the administration of regulation a complex matter and necessarily includes a compromise or transaction between two types of disadvantages. The neutral gas used is usually argon. The use of argon implies a high cost, given that the protection channel must be permanently fed and that leaks can be important. This is particularly the case in which the protection channel is constituted by an outer chamber, whose sealing is difficult to achieve, and which requires a large flow of gas to maintain an overpressure in it. This drawback is particularly important in continuous casting applications between the casting ladle and the distributor. A sliding door including means for introducing a lubricating fluid between two parts is known from French Patent FR 2 529 493. further, French Patent Application FR 2 560 085 discloses wear parts, made of refractory material, which make it possible to introduce, in the very core of the refractory material, an impregnation substance that impales the pores of the refractory material. This technique allows to avoid the infiltration of liquid metal in the pores of the refractory material. However, although they may somewhat improve the air tightness of a joint between the refractory assemblies, neither of the two documents mentioned above describe ways to prevent air from entering the casting channel.

OBJECT OF THE INVENTION The object of the present invention is precisely an installation for the transfer of the liquid metal, which does not have the aforementioned drawbacks. It also has as its object a method for improving the sealing of the joining surfaces between the refractory assemblies, during the use of the casting channel.

DESCRIPTION The invention relates to an installation for the transfer of liquid metal, in particular steel. An installation of this type generally comprises a pouring channel through which the metal drains from the upstream container towards the downstream container; the channel is delimited by a set of refractory assemblies arranged between both containers. Each of the refractory assemblies of the casting channel comprises at least one surface forming a joint surface with a corresponding surface of an adjacent refractory assembly. There is a regulating device of the runoff, to regulate the flow of the liquid metal through the pouring channel; and there is a protection channel disposed around the pouring channel at the level of at least one joint surface between refractory assemblies. Said protection channel comprises an entrance suitable to allow the entry of materials. The invention is characterized in that the installation comprises means for introducing a clogging agent into the protection channel and means for injecting a neutral gas into the protection channel. In a preferred variant of the invention, the means for introducing a clogging agent comprise a cartridge mounted on a duct linked to the outlet of the protection channel. It is advantageous if said means allow predetermined clogging agent doses to be introduced into the protection channel. It is preferable that the protection channel comprises an outlet capable of allowing the escape of an excess of clogging agent and / or of a fluid, for example the neutral gas. It is advantageous that the protection channel comprises an entrance in one of its extremities and an exit in its other extremity. Said channel is preferably linear and continuous. The output allows an excess of clogging agent to be evacuated to the outside of the installation. In an embodiment of the invention, it is proceeded to splice, at the outlet of the protection channel, suitable means to maintain a pressure at the outlet of the protection channel, while allowing an excess of clogging agent to escape at the same time. Said means can be a calibrated load loss. This calibrated load loss is open to the outdoors. The function fulfilled by this calibrated load loss will be explained in the following. The invention also relates to a method for the operation or use of an installation for the transfer of a liquid metal and an inert gas, such as those described above, characterized in that a clogging agent is introduced into the protection channel. The clogging agent can be a pulverized product, and in particular a powder. It is advantageous that said powder comprises grains of different sizes. The powder can be chosen from graphite or other refractory materials that do not adversely affect the quality of the metal. The powder may also be a fusible product such as an enamel, the viscosity of which in the liquid state is sufficient to at least partially seal the leakage from the protective channel. The clogging agent can also be chosen between paints and resins. In this case, this agent covers the walls of the protection channel in a sealed manner.

The clogging agent can also be a non-volatile product, chosen from the salts and metals, liquid at the temperature of the protection channel. It is advantageous if said non-volatile product is introduced in the form of a melting wire as it penetrates into the protective channel., 40. Preferably an aluminum wire is used. Finally, the clogging agent can be produced by reacting two bodies, inactive at room temperature, and which react with each other at the temperature of the protection channel. The introduction of this clogging agent can be carried out continuously or intermittently. The neutral gas can be used to transport this clogging agent into the protection channel. A first method in which neutral gas is injected into the protection channel, is the one comprising the following steps: - the neutral gas pressure is regulated at the entrance of the protection channel, at a predetermined value; - the corresponding flow of neutral gas injected into the protection channel is measured; - the clogging agent is introduced into the protection channel, when the value of said flow exceeds a predetermined value. A second method in which neutral gas is injected into the protection channel, is the one comprising the following steps: regulating the flow rate of the neutral gas injected into the protection channel, at a predetermined value; - the neutral gas pressure is measured at the entrance of this channel; - the clogging agent is introduced into the protection channel, when the value of said pressure falls below a predetermined value. A third method in which neutral gas is injected into the protection channel, applicable when the protection channel comprises an output, comprises the following steps: - the flow rate of neutral gas injected into the protection channel is regulated, at a predetermined value; - the pressure of the neutral gas is measured at its entrance in the protection channel; - the flow rate of the neutral gas is determined, at its outlet in the open air; - the predetermined value of the flow of the neutral gas in the protection channel is adjusted, so that the flow of the neutral gas at its outlet in the open air is always positive; - the flow rate of the neutral gas drawn into the casting channel is determined by the difference between the flow rate of the neutral gas injected into the protection channel and the flow rate of the neutral gas at its outlet in the open air; a clogging agent is introduced into the protection channel when said neutral gas flow sucked into the pouring channel exceeds an admitted limit. It is advantageous that the determination of the flow rate of the neutral gas at its outlet from the protection channel is carried out by measuring the pressure difference resulting from the flow of neutral gas in a calibrated load loss connected to the outlet of the protection channel. As the loss of load in the protection channel is weak, the pressure measured at the entrance of the protection channel is practically equal to this pressure difference. This method is therefore applied in the case where the installation for the liquid metal transfer comprises, at the outlet of the protection channel, suitable means for maintaining a pressure, such as a calibrated load loss. It is stated that part of what is described and illustrated in this application constitutes an object claimed in the application Minutes n ° DESCRIPTION OF THE FIGURES Other features of the invention will emerge, based on the reading of the following description, with reference to the attached figures. In the figures: Figure 1 is an assembly view, in vertical section, of an installation for the transfer of liquid metal, according to the prior art; Figure 2 is a detail view, in vertical section, of an installation for the transfer of liquid metal, according to the invention, comprising means for the introduction of a clogging agent; Figure 3 is a detail view, in vertical section, of an installation of this type according to the invention, in which the means for introducing a clogging agent comprises a cavity made in the breast or in the mass , properly speaking, of a refractory assembly; Figure 4 is a detailed view, in vertical section, of an installation for the transfer of liquid metal according to the invention, in which the linear protection channel is constituted by a slot comprising an inlet and an outlet, practiced in a refractory assembly; Figure 5 is a view similar to that of Figure 4, in which the protection channel is constituted by a camera; Figure 6 is a schematic representation of an installation according to the invention, and of its auxiliary circuits, comprising means for the injection of neutral gas and for the introduction of a clogging agent; Figure 7 is a top view, of a detail of an installation according to the invention; shows a refractory assembly in which a linear protection channel is constituted by a slot comprising an inlet and an outlet; Figures 8 and 9 are top and front views of two plates of a slide of an installation for the transfer of the liquid metal, according to the invention, the slide being in a completely open position; Figures 10 and 11 are top and front views of these same two plates, the slide being in a completely closed position.

DETAILED DESCRIPTION OF A FORM OF REALIZATION Figure 1 shows an installation for the transfer of liquid metal according to the prior art. It comprises a container located upstream, 2. In the example shown, the container located upstream, 2, is a distributor comprising a steel bottom wall, 4, covered with a layer of refractory material, 6. It is provided a pouring hole in the bottom of the distributor. Said pouring orifice is delimited by an internal pouring nozzle 8, mounted in the thickness of the refractory material and passing through the bottom wall, 4, of steel. The installation also comprises a container located downstream, 10. In the example shown, the downstream container, 10, is constituted by a continuous casting mold. The inner nozzle 8 ends in its lower part by means of a plate 12. Under the inner nozzle 8 there is a jet protector tube, 32, which in its upper part ends in a plate 16 that adapts to the plate 12 of the nozzle interior 8. In a manner known per se, the plates 12 and 16 are applied one against the other by means known per se, in order to achieve the greatest possible sealing between them. There is a protection channel, closed, 18, constituted by an annular groove, 20, made in the connecting surface 22 between the plate 12 and the plate 16. There is a channel, 24, for the supply or arrival of a neutral gas, linked to said annular groove 20. By means of the reference number 26, flow regulating means of the metal have been designated, in this case, a pouring plug. The inner nozzle 8 and the jet protection tube, 32, delimit a pouring channel, 28, through which the metal drains from the upstream container, 2, to the container located downstream, 10. In the example represented embodiment, the installation comprises only two refractory assemblies (the interior nozzle 8 and the jet protector tube, 32), but could comprise a greater number of them, as for example in the case of an installation equipped with a slide comprising three plates. Each of the refractory assemblies, 8, 32, which delimit the casting channel 28, comprises at least one surface forming a connecting surface 22 with a corresponding surface of an adjacent refractory assembly. Figure 2 is a detail view of a part of an installation for the transfer of the liquid metal, according to the invention. Said figure shows a collecting nozzle 30 inserted in the jet protection tube, 32, which thus form a pouring channel, 28. The junction between both refractory assemblies comprises a junction surface 22. There is a protection channel closed, 18, constituted by an annular groove 20 made in the connecting surface 22 of the jet protection tube, 32, with the collecting nozzle 30. There is a line 24 for the supply or arrival of the neutral gas, linked to said annular groove. 20. There is a cartridge 33 containing a clogging agent, and a dosing device 34, which allows the clogging agent to be introduced into the neutral gas supply duct, 24. This dosing apparatus, 34, can be a rotary distributor, which it comprises a cylinder, each of whose rotations introduces a predetermined amount of clogging agent into the neutral gas supply pipeline, 26. The dosing device 34 can be commanded manually. Its operation can also be automated. The introduction can be continuous or intermittent. In this variant, the clogging agent is transported by the neutral gas stream which plays the role of carrier fluid in this case. The clogging agent thus penetrates into the protective channel 18, and is entrained by the neutral gas in the refractory interstices 30 and 32. Therefore, it clogs or clogs said interstices. There are therefore two advantages: on the one hand, the flow rate of gas admitted into the pouring channel 28 and which disturbs the pouring of the liquid metal is diminished; and on the other hand, gas consumption is reduced, which reduces costs. In the example shown in Figure 2, the clogging agent is a powder carried by a carrier gas or vehicle. It is advantageous if said powder is made up of grains of different sizes. In this way, the coarser grains obstruct the most important leaks, and the finest grains complete the filling of the smallest leaks and the interstices between the coarse grains. Flattened grains, i.e. flakes, are preferably used. The flakes have the following advantages: they are more easily transported by the circulation of the carrier gas; they are deformed so as to adapt to the shape of the interstices that have to be obstructed. The powder may be constituted by graphite or by another refractory material which does not adversely affect the quality of the metal. The invention also relates to other forms of clogging agent and to other ways of introducing it. The mode of introduction may include the use of a neutral gas as a carrier fluid or vehicle. The clogging agent can also be introduced into the protection channel 18 without the aid of a carrier fluid. The clogging agent can be a liquid. In particular, it can be a product such as a fat or an oil that can be introduced in liquid or viscous form. These products are obtained by cracking solid products that ensure the sealing of leaks, and volatile products that are evacuated. In this variant, it is advantageous to provide, in the protection channel 18, at least one outlet opening so that the volatile products can escape towards the outside of the installation and not towards the pouring channel 28.

The clogging agent can also be a solid product such as a metallic wire. A clogging agent of this type is solid at room temperature, but melts at the temperature prevailing inside the protection channel. Figure 3 shows a variant of an installation for the transfer of the liquid metal, according to the invention. In this variant, there is a cartridge 36 containing a clogging agent, arranged in a cavity of the plate 38. The cartridge 36 may comprise a fusible casing which melts or melts upon the commissioning of the plate 38 in a device such as a slide or a tube changer. The supply pipe 24, of the neutral gas, is connected to the upper part of the cartridge 36, such that, when the fusible jacket melts, the clogging agent is drawn into the protection channel 18. A refractory material of this type, can be used very simply in an existing installation, without it being necessary to modify it. It is sufficient to mount a refractory plate such as 38, comprising an integrated cartridge, 36, instead of a conventional plate. A single dose of clogging agent is introduced into the plane of the splicing surface, 22, between plates 38 and 16, to seal the leaks between them. Both in the embodiment of FIG. 2 and in that of FIG. 3, the protection channel 18 is a closed annular channel comprising a neutral gas supply. The introduction of a clogging agent into this protection channel, 18, makes it possible to improve the sealing and therefore the protection of the liquid metal conferred by the protection channel 18. However, these two embodiments do not make it possible to ensure that the agent of clogging is distributed evenly throughout the length of the protection channel. Figure 4 represents an installation for the transfer of the liquid metal according to an embodiment of the invention. In this case, the protection channel 40 is constituted by a non-annular but linear groove, 42, and comprises an inlet 44 at one of its ends linked to the pipe 24 for the neutral gas supply, and an outlet 46 at its other end. tip. This open arrangement of the protection channel 40 makes it possible to ensure that the circulation of the neutral gas carries the clogging agent throughout the protection channel. The circulation velocity of the neutral gas is sufficient everywhere in the protection channel 40, and prevents plugging of the protective channel 40 by the clogging agent. in particular in the sensitive parts of this channel, such as the elbows, the zones of section changes, and the ascending zones. Thanks to the outlet 46 it is avoided that a neutral gas overpressure is created in the protection channel 40. It is possible to adapt, at the outlet of the protection channel 40, a device that allows a slight overpressure to be maintained in this channel. , this while allowing the escape of a possible excess of clogging agent. Such a device, for example, can be a simple loss of load.

In the example of figure 4, the protection channel has a helical shape. This embodiment is particularly adapted to conical splicing surfaces. In the example shown, the slot 42, the inlet 44 and the outlet 44, have been made in a single refractory assembly 32, but these three elements could be installed in the other refractory assembly 30, in whole or in part, without leaving the the scope of the invention. Figure 5 is a detailed view of a part of an installation for the transfer of liquid metal according to the invention, similar to those shown in figures 2 and 4. Unlike the protection channels 40, 18, shown in FIGS. 2, 4, the protection channel shown in FIG. 5 is a chamber 48 made by a housing 50 surrounding the periphery of the connection surface between the collecting nozzle 30 and the jet protection tube32. According to the invention, it is possible to introduce a clogging agent into the protection channel 48. A seal, 52, ensures the tightness of the chamber 48. Said chamber can be supplied with a neutral gas under pressure, by means of the channeling 24, similarly to what has been described above. In this way, it is not air which is drawn into the pouring channel, 28, but the neutral gas contained in the chamber 48. The chamber 48 can be annular and closed, and comprise only one input 44. In a variant, it can In this case, it is advantageous for the chamber to have a linear and continuous arrangement, the inlet 44 being at one of its ends, and the outlet 46 being at its other end. The following describes in detail, with reference to Figure 6, the different procedures for the use of an installation according to the invention and its accessories, in the case of using a neutral gas to transport the filling agent. The supply in neutral gas is constituted by a source, which can be for example a cylinder, a pressure reducer 54, a flowmeter 56 and a regulator 58 that allows regulating the flow or pressure. In a first method, the pressure, P, of the neutral gas at the entrance of the protection channel is regulated to a predetermined value, and the corresponding flow of neutral gas injected into the protection channel is measured. The manometer 60 indicates this pressure. The flow meter 56 indicates this flow rate. When this flow exceeds a predetermined value, which is indicative that an excessive flow of neutral gas is being admitted into the pouring channel 28, a quantity of clogging agent is introduced. The pressure value P r, can be of the order of 0.2 bar. This method is preferably applied in the installations in which the protection channel 40, 16 is closed, or when this channel is open, but comprises, at its outlet 46, a loss of load 61. In a second procedure, it is regulated the neutral gas flow to the inlet 44 of the protection channel 40, 18, at a predetermined value, and the corresponding pressure of neutral gas injected into said channel is measured. When this pressure falls below a predetermined value, which is indicative that an excessive flow rate is being admitted in the pouring channel 28, a quantity of clogging agent is introduced. The predetermined value of the neutral gas flow rate is chosen in such a way that it is greater than the maximum possible flow rate of neutral gas admitted in the casting channel 28, and that therefore there is always an excess of neutral gas. This method is preferably applied in those installations in which the protection channel 40, 18 is open and when said channel comprises, at its outlet 46, a loss of load 61. The opening 46 in fact allows evacuation towards the outside of the installation, the excess of neutral gas and clogging agent. Said opening also makes it possible to maintain the pressure in the protective channel 40, at a low value. Thus, while remaining certain that only neutral gas can be sucked into the pouring channel 28, the amount of neutral gas sucked into the pouring channel is reduced to a minimum compatible with the state of the splicing surface, 22, because the pressure in the protection channel is reduced. This procedure offers the advantage of requiring a very simple administration, with optimum efficiency. The introduction of the clogging agent can also be continuous, since the excess of clogging agent is automatically drawn out through the outlet 46 together with the excess of neutral gas. There is no risk of clogging the gas pipeline, 24, nor the protection channel, 40, due to the accumulation of the clogging product. Another advantage of the method is that, since the circuit does not have any dead zone, the neutral gas circulates along the length of the protection channel 40 with a speed sufficient to ensure the transport of the clogging agent in any place where it can be necessary. A third procedure, is a refinement of the preceding process, and allows the introduction of a clogging agent to be commanded when the flow rate of neutral gas sucked into the casting channel 28 exceeds an allowable limit. In view of this procedure, a second flow meter is added to the outlet 46 of the protection channel, in order to measure the excess of neutral gas escaping through said outlet. In this way, it is possible to know the flow rate of neutral gas actually sucked in the pouring channel 28, by difference with the flow rate Qin of neutral gas injected into the protection channel 40. It is advantageous that the flowmeter is realized by a loss of calibrated charge, 61, and by means of a pressure gauge 60. The flow rate Qout, which passes through the calibrated head loss 61, generates a slight pressure P, n in the protection channel 40, read on the gauge 60. The relationship between pressure measured on the gauge 60, P, p, and the neutral gas flow rate, Qout, escaping at exit 62, is determined by known empirical relationships, such as: Qout = KM (Pin) where "K" is a constant of staggering the load loss calibrated. As the loss of load of the protective channel 40 is weak, the pressure Pi, measured by the pressure gauge 60 at the inlet of the protective channel 40, is substantially equal to the pressure that would be measured at the outlet 46 of this channel. The arrangement of the manometer 60 at the entrance 44 of the protection channel makes it possible to avoid the difficulties of splicing it with the outlet.

These difficulties include environmental difficulties in the vicinity of the pouring channel 28, and soiling of the manometer by an excess of clogging agent. When the load loss is calibrated in the form of a tube of 3 to 4 mm in diameter and 1 to 4 m in length, a small overpressure is generated (from 0.1 to 0.3 bar), which is not very harmful to the leakage flow. This embodiment offers the advantage of being able to remotely measure the excess flow that escapes at the outlet of the protection channel 40. Another advantage of this method is that this form of flow meter is extremely simple and robust and can be installed directly in the exit of the refractory material, despite the difficulties inherent to the difficult environment. Therefore, it is not necessary to install a complementary channel to install the flow meter in a protected place accessible to the operator. This third method therefore makes it possible to evaluate at all times the leakage flow of neutral gas sucked into the casting channel 28, and to act, whether manually or automatically, on the introduction of the clogging agent, when this flow exceeds a tolerated limit. The continuous introduction of the clogging agent is preferred when the quality of the splicing surface can be altered at any time. In particular, this is the case of the splice surfaces between plates, 64, 66, of a slide for the regulation of a pouring jet, which are frequently in motion and therefore represent the risk of creating at all times new leaks This is also the case of the splicing surfaces between a collecting nozzle 30 of a ladle slide and a jet protective tube, 32. The movements of the slide, and the vibrations of the tube, 32, induced by the run-off of the liquid metal , can at any time create a deterioration of the quality of the splicing surface, 22. One of the applications of the invention, described below, will preferably be used in the case of splicing surfaces that are predominantly static during casting. , but that can be altered periodically. This is in particular the case of tube exchangers such as those described in US Patent 4,569,528. In a tube changer of this type, the tube has in its upper part a plate that is forcefully applied against a fixed plate of the container located upstream. When the tube has worn out, it is replaced by a new tube, usually by sliding a new tube against the fixed top plate.

The splicing surface, 22, is generally strongly altered by the operation of the tube change, whereas it is only rarely altered during the life of the tube, the splicing surface 22 being then static. For an application of this type, a preferred variant of the method according to the invention is that which consists in commanding the introduction of the filling agent only when the condition of the quality of the splicing surface, 22, so requires. When the leakage rate rises beyond a predetermined acceptable value, that is, when the pressure read on the pressure gauge 60 falls below a predetermined threshold, the introduction of the clogging agent starts. As soon as the flow rate of the leaks has been reduced to a predetermined value, that is to say, as soon as the pressure of the pressure gauge 60 has risen again above a threshold, the introduction of the clogging agent is interrupted. This method can be easily automated by means of the attachment of a double-threshold pressure detector, 63. An improvement applicable to each of the above-mentioned methods according to the invention is that which envisages an additional power supply pipeline. neutral gas, constituted by a valve, 68, possibly commanded, a flow regulator, 70, and a flowmeter, 72. The valve 68 is opened simultaneously with the start of the introduction of clogging agent, in order to provide an additional flow of neutral gas during the introduction. This improvement offers the advantage of being able to regulate the main flow of neutral gas provided by the regulator 58, at a relatively low level, for example of 10 N l / min, which is sufficient during the normal operation of casting when the splicing surface , 22, has a correct sealing, and of having a sufficiently large flow rate when the connecting surface, 22, has deteriorated, for example after a tube change, in order to preserve an excess of neutral gas, to guarantee an efficient transport of the liquid. clogging agent and ensuring the evacuation of the excess thereof, via the outlet 46. Figure 7 is a top view, of a refractory assembly 74 according to the invention. The inlet 44 and the outlet 46 of the protection channel, 40, constituted by a linear slot 42, emerge at the periphery of the refractory assembly through holes drilled in the mass of the refractory material. This refractory assembly 74 could for example be a lower face of an inner nozzle, an upper face of a jet protective tube, a plate of a tube changer, or more generally, any section of a pouring channel 28. Figures 8, 9, 10 and 11, show an example of embodiment of a device according to the invention constituted by an upper plate 64 traversed by an orifice forming a pouring channel, 28, a lower plate 66 that also comprises an orifice , suitable for sliding horizontally with respect to one another, which allows the regulation of the flow rate of the liquid metal by variation of the opening of the casting channel 28. Both plates comprise, each of them, a slot in the form of "U", 76. In contrast to the known grooves of the prior art, for example in French Patent Application FR 7414636, both superimposed "U" are covered in only one of their branches, in a portion of their long element 78 which is variable as a function of the relative position of both plates 64 and 66. Branches 80 and 82 do not overlap each other, and are linked, at their respective extremities, to outlet 46 and to the channeling input 24. Therefore, in this installation there is a continuous linear protection channel 40, comprising an entrance in one of its ends and an exit in the other, surrounding the pouring channel, 28. Therefore, this The arrangement allows adopting the procedure for the regulation of the injection of neutral gas according to the invention, adapting a calibrated load loss either within the lower plate 66, or spliced to the outside thereof. The separation between the branches of the "U" of the upper plate 64, differs from the separation between the branches of the "U" of the lower plate 66. At least one of these "U" is therefore dissymmetric with respect to to the orifice forming the casting channel 28. This embodiment is particularly suitable for the system known as the "sliding type casting nozzle". It illustrates that the invention can be applied to a wide variety of facilities for the transfer of a liquid metal.

Claims (24)

1. NOVELTY OF THE INVENTION CLAIMS 1. - An installation for the transfer of a liquid metal, especially steel, between a container located upstream and a container located downstream, of the type comprising: a container, located upstream; a pouring channel; a container, located downstream; a flow regulating device, for regulating the flow of the liquid metal through the pouring channel; a set of refractory assemblies, disposed between the container located upstream and the container located downstream, which delimits the pouring channel through which the liquid metal drains from the container located upstream towards the container located downstream, each one comprising of the refractory assemblies of the casting channel, at least one joint surface forming a joint or a joint with a corresponding surface of an adjacent refractory assembly; a protection channel, arranged around the pouring channel at the level of at least one connecting surface between refractory assemblies, said protection channel comprising an entrance apt to allow the introduction of materials; characterized in that it comprises means for introducing a clogging agent into the protection channel; means for injecting an inert gas into the protection channel.
2. 2. An installation for the transfer of a liquid metal, according to claim 1, characterized in that the means for introducing a clogging agent, comprise a cartridge mounted in a channel linked to the entrance of the protection channel.
3. 3. An installation for the transfer of a liquid metal, according to any one of the preceding claims, characterized in that the means for introducing a clogging agent comprise means that allow predetermined doses of clogging agent to be introduced into the protection channel.
4. 4. An installation for the transfer of a liquid metal, according to any one of the preceding claims, characterized in that the protection channel comprises an outlet able to allow the escape of materials.
5. 5. An installation for the transfer of a liquid metal, according to claim 4, characterized in that the entrance of the protection channel is at one of the ends of said channel, and the outlet is at the other end.
6. 6. An installation for the transfer of a liquid metal, according to any one of claims 4 and 5, characterized in that the protection channel is linear and continuous.
7. 7. An installation for the transfer of a liquid metal, according to any one of claims 4 to 6, characterized in that there are suitable means to maintain a pressure at the outlet of the protection channel, which while still allowing the escape of an excess of clogging agent, they are spliced with the exit of the protection channel.
8. 8. An installation for the transfer of a liquid metal, according to claim 7, characterized in that the means able to maintain a pressure at the exit of the protection channel that allow an excess of clogging agent to escape, are a loss of calibrated load that ends in an outdoor outlet.
9. 9. A method for the operation or use of a facility for the transfer of a liquid metal, as described in any of the preceding claims, characterized in that a filling agent and an inert gas are introduced into the protective channel .
10. 10. A process according to claim 9, characterized in that the clogging agent is a pulverized product.
11. 11. A method according to claim 10, characterized in that the pulverized product is a powder.
12. 12. A method according to claim 11, characterized in that the powder comprises grains of different sizes.
13. 13. A method according to any one of claims 11 and 12, characterized in that the powder is chosen between the graphite and other refractory material that does not adversely affect the quality of the metal.
14. 14. A process according to any one of claims 11 and 12, characterized in that the powder is a fusible product such as an enamel, whose viscosity in liquid state is sufficient to seal, at least partially, the leaks of the channel protection.
15. 15. A process according to any of claims 9 and 10, characterized in that the clogging agent is chosen between paints and resins, and covers the walls of the protection channel with a tight layer.
16. 16. A process according to claim 9, characterized in that the clogging agent is a non-volatile product, chosen among the salts and metals, liquid at the temperature of the protection channel, 17.- A process according to the claim 16, characterized in that the non-volatile product is introduced in the form of a wire that melts as it enters the protection channel. 18. A process according to any one of claims 9 to 17, characterized in that the clogging agent is produced by reacting at least two bodies, inactive at room temperature, and reacting with each other at the channel temperature. of protection (18; 40). 19. A method according to any one of claims 9 to 18, characterized in that the introduction of the clogging agent is carried out continuously. 20. A process according to any one of claims 9 to 18, characterized in that the introduction of the clogging agent is effected intermittently. 21. - A method according to any one of claims 9 to 20, characterized in that a neutral gas is used to transport the clogging agent in the protection channel. 22. A method according to claim 21, characterized in that: the pressure of the neutral gas is regulated at the entrance of the protection channel, at a predetermined value; the corresponding flow of neutral gas injected into the protection channel is measured; the clogging agent is introduced into the protection channel when the value of said flow exceeds a predetermined value. 23. A method according to claim 21, characterized in that: the flow rate of the neutral gas injected into the protection channel is regulated at a predetermined value; the pressure of the neutral gas is measured at the entrance of this channel; the clogging agent is introduced into the protection channel when the value of said pressure falls below a predetermined value. 24. A method according to claim 21, which can be used in an installation according to claim 7 or 8, characterized in that: the flow rate of neutral gas injected in the protection channel is regulated at a preset value; the flow rate of the neutral gas is determined, at its outlet in the open air; the predetermined value of the flow of the neutral gas in the protection channel is adjusted, so that the flow of the neutral gas at its outlet in the open air is always positive; the flow rate of neutral gas sucked into the casting channel is determined by the difference between the flow rate of the neutral gas injected into the protection channel and the flow rate of the neutral gas at its outlet into the open air; a clogging agent is introduced into the protection channel when said neutral gas flow sucked into the pouring channel exceeds an admitted limit.