EP0748266A1

EP0748266A1 - Device for controlling a flow of liquid steel from a ladle to a continuous casting distributor

Info

Publication number: EP0748266A1
Application number: EP95911356A
Authority: EP
Inventors: François RICHARD
Original assignee: Vesuvius France SA
Current assignee: Vesuvius France SA
Priority date: 1994-03-04
Filing date: 1995-02-27
Publication date: 1996-12-18
Also published as: AU1895795A; MX9603846A; RU2150349C1; FR2716819B1; CN1071608C; JPH10507131A; CN1146737A; WO1995023663A1; BR9506975A; FR2716819A1; PL179542B1; SK111496A3; CZ252696A3; AU691888B2; US5772908A; PL316134A1; CA2184742A1

Abstract

A device for controlling a flow of liquid steel from a ladle (1) to a continuous casting distributor (8). The device includes a frame connected to the ladle (1) and comprising a guide assembly; a plate (3) movable on the guide assembly for sealing the casting opening (2); an assembly for compressing said plate (3); and a jet nozzle tube (4) extending from the casting opening (2). The plate for sealing the casting opening (2) is a sealing plate (3) designed only to seal the casting opening (2); the jet nozzle tube (4) and a plate (34) together form a rigid assembly moving along the guide assembly to a position opposite the casting opening where it replaces the sealing plate (3) which is thus driven from this position; and a compression assembly holds the plate (34) of the plate/jet nozzle tube assembly (4, 34) in sealing contact with a fixed upper plate (30).

Description

DEVICE FOR CONTROLLING THE FLOW OF LIQUID STEEL BETWEEN A POCKET AND A CONTINUOUS CASTING DISTRIBUTOR

The present invention relates to a device for controlling the flow of liquid steel between a ladle and a continuous casting distributor able to contain a bath of molten steel, said ladle being able to contain and transport a quantity of molten steel between a remote site and a continuous casting floor, said ladle being provided with a pouring orifice which makes it possible to transfer the liquid steel into the distributor, this pouring orifice being surrounded by a fixed upper plate, a device comprising a frame linked to the pocket and comprising guide means; a plate capable of moving on the guide means and of closing the pouring orifice; the device further including means for pressurizing this plate; means for protecting the jet of liquid steel during its passage from the pocket to the distributor, these means comprising in particular a jet protection tube intended to be placed in the extension of the pouring orifice and which has a lower end intended to be immersed in the bath of liquid steel contained in the distributor.

It also relates to a method for controlling the flow of liquid steel between a ladle and a continuous casting distributor able to contain a bath of molten steel, said ladle being able to contain and transport a quantity of molten steel between a site. remote and a continuous casting floor, said ladle being provided with a pouring orifice which makes it possible to transfer the liquid steel into the distributor, this pouring orifice being surrounded by a fixed upper plate.

According to the prior art, the pocket is generally equipped with a slide valve capable of generally receiving two refractory plates each pierced with an orifice. One of these plates (the upper plate) is fixed. It is connected to an internal nozzle placed in the pouring orifice of the bag. The other plate (the lower plate) is movable relative to the fixed plate. When the orifice of the fixed plate and that of the movable plate are offset, the pouring orifice is completely closed. When the orifices of the refractory plates overlap more or less, the flow of steel is throttled, which makes it possible to regulate its flow. An example of such a device is described in European patent EP 202,213.

At the start of a casting sequence the pocket is empty. We equip it with a drawer that we close. The steel bag is then filled and, after various processing operations, it is transported to the continuous casting floor. A common practice is to place the full pocket on a turnstile which rotates half a turn to bring the pocket above the dispatcher.

Furthermore, the current imperatives of steel quality increasingly require the steel jet to be protected against any contact with air between the pocket and the distributor to prevent its oxidation. A commonly used method consists in extending the pouring orifice of the ladle by a revised jet protection tube made of a refractory material. The end of this tube plunges into the steel bath contained in the distributor so as to ensure a sealed channel between the pocket and the distributor. This jet protection tube is generally mounted on a nozzle, called a collecting nozzle, integral with the movable plate of the pocket shutter valve.

The jet protection tube must generally be put in place at the very place of pouring, that is to say when the bag is placed above the continuous casting distributor. Indeed, it is rarely possible to equip the bag with the jet protection tube before it is brought to the casting site because existing workshops generally do not have sufficient clearance under the bag to accommodate such a tube on the equipment. where the bag must reside or be transported before casting, for example the oven, the treatment in bags, the transfer carts.

There are therefore three functions to be performed for the transfer of the liquid steel from the ladle to the distributor: the complete sealing of the pouring orifice during transport of the ladle and also, for safety reasons, in the event of 'incident or accident occurring during casting operations; - the regulation of the flow of liquid steel which in particular makes it possible to maintain the level of liquid steel in the distributor at a desired height; protection of the jet of liquid steel against oxidation by air. According to current practice, the first two functions are fulfilled by the pocket drawer, and the third by the jet protection tube.

When the bag is empty, the drawer is closed and the jet protection tube is removed. The drive means of the drawer (cylinders) are disconnected. The pocket is taken to a workshop where the wear of the refractories of the drawer is checked. These refractories are changed if their wear has been observed.

A conventional continuous casting installation as just described has a number of drawbacks.

The seal between the collecting spout of the pocket drawer and the jet protection tube is made on site, on the casting floor, in unfavorable conditions. It therefore does not ensure a good seal.

This joint has no mechanical strength. It is therefore necessary to provide a means for keeping the jet protection tube applied against the collecting nozzle. This is generally achieved by means of a manipulator which comprises a collar which supports the head of the jet protection tube and which applies it to the collecting nozzle. However, as the collecting nozzle is mobile at the same time as the plate on which it is fixed, the inertia of the manipulator which is added to that of the tube and to the hydrodynamic resistance of the liquid steel in which the lower end plunges jet protection tube, creates mechanical stresses on the junction between the collecting nozzle and the jet protection tube. These stresses aggravate the problems of tightness and resistance of the seal over time.

The refractory plates of the drawer wear out relatively quickly because they constantly rub against each other for the duration of the casting in the presence of steel. They must therefore be changed frequently. The duration which is necessary for this change is variable according to the difficulty of the operations to be carried out. This consequently results in irregularities in the cycle of rotation of the bag. These irregularities disturb the organization of the continuous casting sequences. For example, if we find that the change of the refractory plates of the drawer will take too long, we can decide to use a reserve pocket. The operation of the installation requires the availability of reserve pockets.

The present invention specifically relates to a device for controlling the flow of liquid steel for a ladle which overcomes these drawbacks.

These objects are achieved by the fact that: the plate capable of closing the pouring orifice is a closing plate intended solely for closing the pouring orifice; the jet protection tube is formed into a solid and rigid assembly with a plate; this assembly being able to be received and to move on the guide means to come opposite the pouring orifice to replace the closing plate which is pushed; pressurizing means being provided to keep the plate of the plate / jet protection tube assembly applied with sealing against the fixed upper plate.

Thanks to these characteristics, the jet protection plate and tube are produced in a solid assembly. This assembly can be produced in a single piece. It can also consist of an assembly of several parts forming a rigid assembly. We therefore remove a connection between a tube and a collecting nozzle. Furthermore, it is not necessary to support the jet protection tube by means of a manipulator since the latter forms one with the plate a monobloc assembly which is retained in the guide means linked to the pocket.

The installation of the jet protection plate / tube assembly is therefore carried out in a single operation.

Verification of refractories is simplified because the bottom plate is disassembled and visible after each pour.

Preferably, the device further comprises a manipulator independent of the pocket and located in a position linked to the continuous casting floor, this manipulator comprising at least two actuation means, for example jacks, a first actuation means making it possible to bring and / or remove the plate / tube assembly to the entry of the guide means, and a second actuating means which makes it possible to introduce the closure plate and / or the plate of the plate / jet protection tube assembly into the guide means of the frame and to push the plate of the plate / tube assembly opposite the pouring orifice so that it pushes the closure plate or vice versa.

More preferably, the second actuating means consists of a fork formed by two fingers, a first finger which allows the plate / tube assembly and the closure plate to be pushed, and a second finger which makes it possible to exert an action. reciprocal to bring the closure plate and the plate / tube assembly opposite the fixed plate.

Preferably said first finger is able to support the plate / tube assembly.

In a preferred embodiment, the manipulator comprises a guide and the frame a counter guide in which the guide of the manipulator engages to adjust the position of the manipulator relative to the frame. The guide and the counter guide also make it possible to make internal to the device the forces exerted by the actuating means and the reaction forces which they cause. These forces cancel each other out respectively.

In order to facilitate their handling, the closure plate and / or the jet protection tube plate assembly can be placed in a support which comprises said pressurizing means.

More preferably still, the means for regulating the flow of liquid steel from the continuous casting ladle to the distributor consist of means for constricting the passage section offered to the liquid steel at the lower end of the tube. jet protection intended to be immersed in the bath of liquid steel contained in the distributor. According to the devices of the prior art, the throttling of the flow of liquid steel, that is to say the area of the pouring channel where the passage section is reduced to regulate the flow, is located upstream of the tube. spray protection. As a result, under the effect of a physical phenomenon known as the venturi, the interior of the jet protection tube is in depression relative to the atmosphere. It follows that the slightest leak in the channel downstream of the constriction results in an air intake which leads to the degradation of the quality of the steel.

Thanks to the present characteristic of the invention, the pouring channel is in overpressure with respect to the atmosphere and the phenomenon of venturi is eliminated. This removes radically the previously observed phenomena of air suction and this even in the case where the flow channel is not airtight. As a result, the quality of steel is significantly improved. In addition, the plate of the plate / tube assembly is in a fixed position. It does not wear out.

The verification of the refractories can be reduced to a simple operation of language, that is to say of cleaning the taphole using an oxygen lance. This operation can be automated, which removes a tedious task of checking refractories. As a result of this simplification of the verification of the refractories the duration of the cycle is reduced and above all the cycle is made more regular, which simplifies the problems of organization of the continuous casting.

According to one embodiment, the means for constricting the passage section offered to the liquid steel comprise a refractory brick secured to the distributor, located opposite an orifice of the jet protection tube, regulating the flow liquid steel being obtained by varying the position of the pocket relative to that of the distributor and / or by varying the position of the distributor relative to that of the pocket.

According to one embodiment, the jet protection tube is extended by a sleeve coaxial with the tube and sliding with hard friction on this tube so as to provide security if the distance between the continuous ladle and the distributor was accidentally reduced. According to one embodiment, the means for constricting the passage section offered to the liquid steel consist at least of a refractory brick which is movable opposite at least one outlet orifice for the liquid steel provided at the bottom of the spray protection tube.

According to one embodiment, several orifices are provided in the lower part of the jet protection tube, these orifices being regularly spaced from each other, and the means for constricting the passage section offered to the liquid steel are actuated symmetrically to do not create a lateral reaction force on the end of the tube.

According to one embodiment the jet protection tube has at least one lateral orifice at its lower part and in that the regulation of the flow of the liquid steel is obtained by a sleeve coaxial with the jet protection tube, movable in translation along the jet protection tube and / or mobile in rotation around this tube.

According to one embodiment, the cuff comprises at least one orifice making it possible to regulate the flow of the liquid steel, the lower edge of this orifice being located higher than the lower edge of the orifice.

According to one embodiment, the closure plate comprises a solid zone called the closure zone and an access orifice situated outside the closure zone, the access orifice possibly being provided with a collecting nozzle, to allow access to the pouring hole of the continuous pouring ladle without having to remove the jet protection tube.

According to one embodiment, the access opening of the closure plate is located between the plate of the plate / jet protection tube assembly and the closure zone of the closure plate when said closure plate and said plate are engaged. in the guide means, this position of the access opening being intended to reduce the distance necessary to pass from the position in which the access opening is opposite the tap hole to the position in which the tube jet protection is next to this hole of casting.

According to one embodiment, said first finger is able to support the plate / tube assembly.

The process for controlling the flow of liquid steel between a ladle and a continuous casting distributor is characterized in that:

introducing a closure plate capable of closing the pouring orifice in guide means linked to the pocket; - This closure plate is pushed opposite the fixed upper plate while applying it sealingly against this fixed upper plate; the ladle is filled with liquid steel; the ladle is brought to the continuous casting floor; a jet protection plate / tube assembly independent of the pocket is introduced into the guide means on the continuous casting floor; the plate / jet protection tube assembly is pushed, which drives out the closure plate, while applying it sealingly against the fixed upper plate.

After the steps defined above, for example when the bag is empty or in the event of an incident, the closure plate is again pushed opposite the fixed upper plate while applying it tightly against this fixed upper plate, which closes the pouring opening and simultaneously releases the plate / jet protection tube assembly. According to the invention, the jet protection tube plate assembly is put into place in the guide means of the frame by means of a manipulator independent of the pocket and situated in a position linked to the casting site, the plate is moved. closing and / or the jet protection tube plate assembly by means of actuation linked to this manipulator.

According to the invention, the function of regulating the flow of the liquid steel is ensured independently of the function of closing the pouring orifice by means of the closure plate linked to the pocket.

The flow of the liquid steel is regulated by more or less closing an orifice situated at the end of the jet protection tube immersed in the bath of liquid steel contained in the distributor.

The opening located at the end of the jet protection tube is more or less closed by varying the position of the bag relative to that of the distributor and / or by varying the position of the distributor relative to the position of the poached.

Other characteristics and advantages of the present invention will appear on reading the following description of embodiments given by way of illustration with reference to the appended figures. In these figures: FIG. 1 is a simplified overall view of a device for controlling the flow of liquid steel according to the invention; Figures 2 to 4 illustrate the different steps of the method for controlling the flow of liquid steel according to the present invention; Figure 5 is a more detailed sectional view, on an enlarged scale, of the steel flow control device shown in Figures 1 to 4; - Figure 5a is a cross-sectional view of the device of Figure 5; Figure 6 is a top view of the device shown in Figure 5, the manipulator being spaced from the frame; Figure 7 is a view identical to Figure 6, the manipulator being attached to the frame; - Figure 8 is a view identical to Figures 6 and 7, the closure plate and the plate / jet protection tube assembly having been moved; Figures 9 to 14 are alternative embodiments of the means for regulating the flow of steel.

FIG. 1 shows an overall view of the device for controlling the flow of liquid steel between a pocket 1 and a distributor 8. The pocket 1 comprises a metal casing covered with a refractory coating 1b. She is able to contain a quantity of liquid steel 5. An internal nozzle 7 passes through the refractory lining 1b. The nozzle 7 defines a tap hole 2 which allows the passage of the liquid steel. The taphole is surrounded by a fixed refractory plate 30, the underside of which defines a flat sliding surface. The internal nozzle 7 and the fixed plate 30 can be made in one piece, that is to say pressed in a single operation.

They can also be produced separately and then assembled in the same sheet metal.

In accordance with the invention, the steel flow control device comprises a plate / jet protection tube assembly 4, 34 intended to ensure the protection of the liquid steel in particular against the oxygen of the air during its transfer from the pocket 1 towards the distributor 8. The jet protection tube 4 is located in the extension of the pouring orifice 2. It has a lower end 4a intended to be immersed in a bath of liquid steel 6 contained in the distributor 8.

The plate 34 can slide on the fixed plate 30. It is introduced into guide means (not shown in Figure 1) which will be described later. It can also be applied against the fixed plate 30 so as to form a sealed connection between these two plates by means of pressurization (not shown in FIG. 1) which will also be described later.

The jet protection tube 4 and the plate 34 can be produced in a monobloc assembly (pressed in a single operation) or consist of two assembled parts. However, in all cases, they constitute a rigid and non-deformable assembly. The connection between the tube 4 and the plate 34 is capable of transmitting a significant mechanical force. This is the reason why, according to the present invention, it is not necessary to support the jet protection tube by means of a manipulator. In fact, the connection of the tube to the plate has sufficient mechanical strength for the forces communicated to the plate 34 to be transmitted directly to the jet protection tube 4.

FIG. 1 also shows the closing plate 3. This plate has a solid area called the closing area 32a. The closing area 32a, when it is placed opposite the pouring orifice 2, enables the pocket 1 to be sealed off. The closure plate 3 is used in particular when the pocket transports steel from one site to another.

The closure plate 3 also includes an access hole 36, extended by a nozzle in the embodiment shown in FIG. 1. The function of this access hole 36 will be described with reference to FIGS. 2 to 4.

It will be noted that the closure plate 3 is not part of the means for protecting the jet of liquid steel against air. This constitutes a difference with the previously known devices using a drawer with two and more rarely three plates. In fact, in these devices, the plates of the drawer are located on the path of the steel. They are said to "see" steel. These plates rub against each other during the regulation of the casting. Consequently, they wear out. On the contrary, according to the present invention, the closure plate 3 is placed in position opposite the pouring orifice 2 when the bag is closed and then moved away from this position when the plate assembly is put in place. / spray protection tube. It is therefore not subject to permanent wear.

FIGS. 2 to 4 show the successive stages of the method for controlling the flow of liquid steel of the invention for a device such as that which has been represented in FIG. 1. The pocket is first closed by the introduction of the closure plate 3 into guide means linked to the bag on a site remote from the continuous casting floor, for example a converter or an electric oven. The ladle is filled with steel and then it is transported to the continuous casting floor. It is placed above a distributor 8, as shown in FIG. 2. The jet protection plate / tube assembly 4, 34 is brought horizontally due to the insufficient space which exists between the pocket and the distributor. . Then the tube is gradually straightened to bring the plate 34 into the guide means linked to the pocket 1, while the lower end 4a of the tube 4 is immersed in the liquid metal bath 6 of the distributor 8. The plate is then pushed 34 opposite the pouring orifice 2, which drives the closure plate 3 (position shown in Figure 3). If the opening operation has taken place properly, the casting continues from the position shown in Figure 3. If on the contrary, as happens from time to time, the steel has frozen in the orifice pouring 2, it is necessary to return to the position shown in FIG. 4. In this position the access hole 36 makes it possible to introduce an oxygen lance into the pouring orifice 2 in order to unblock it. When the liquid steel begins to flow, the lance is withdrawn and the plate 34 is again pushed into the position shown in FIG. 3 without depositing the jet protection tube. Preferably, the access orifice 36 is disposed on the side of the movable plate 3 which is in contact with the plate 34. In other words the access orifice is disposed between the solid obturation area 32a of the plate 3 and the plate 34. In this way the path between the access orifice 36 and the tube 4 is as short as possible. This arrangement makes it possible to prevent the liquid metal from freezing in the pouring orifice at the time of opening. The time required to move from one position to another is very short, on the order of one to two seconds. It is in fact known that the obstruction of the pouring orifice occurs mainly at the start of casting, while the pouring channel is still cold. The currently known devices require a delay of ten seconds between the time when one passes from the unblocking orifice to the establishment of the pouring tube. This too long delay causes the metal to freeze in the pouring orifice. In order to avoid this phenomenon, it is necessary, in the previously known devices, to let a large quantity of steel flow in a free jet so as to ensure heating of the pouring orifice 2. The liquid metal which is poured during this period is in contact with air and pollutes the metal contained in the distributor, which leads to derating of a significant part of the cast steel. The position of the access orifice 36, in the immediate vicinity of the pouring orifice 2, makes it possible to avoid this method by reducing the time for passing from one position to the other to approximately one to two seconds. This time is short enough to prevent the metal from freezing in the runner. As a result, it is not necessary to proceed as was done previously, by heating the pouring channel by the passage for one to two minutes of the steel jet. In this way the liquid metal contained in the distributor 8 is not polluted and it is not necessary to decommission it. The contact seal 35 between the movable plate 3 and the plate

34 of the jet protection tube is advantageously provided so as to have no gaps in order to ensure a complete seal between the two plates for change from one to the other.

FIG. 5 shows a more detailed view, on an enlarged scale, of the device for controlling the flow of liquid steel represented in FIGS. 1 to 4. The frame 15 is fixed under a base plate 17 integral with the pocket of casting 1. The frame 15 comprises guide means, constituted for example by a slide or rails, which make it possible to receive both the closure plate 3 and the plate 4 of the plate / jet protection tube assembly. The closure plate 3 is housed in a support 27 which includes pressurizing means (not shown in FIG. 5) which make it possible to apply it in sealed manner against the fixed plate 30. Similarly, the plate 34 is mounted in a support 29 which includes pressurizing means (not shown in FIG. 5) which make it possible to apply the upper face of the plate 34 against the lower face of the fixed plate 30 with the creation of a tight seal between these two plates. FIG. 5 also shows the cross section of the fingers 40 of a manipulator which will be described in more detail with reference to FIGS. 6 to 8.

One of these fingers 40 (on the right in FIG. 5) is pierced with an orifice to receive an axis 42 secured to the support 29 of the plate / jet protection tube assembly. The axis 42 thus makes it possible to fix the plate / jet protection tube assembly on the finger of this manipulator. The axis 42 also makes it possible to remove the support 29 from the frame.

FIG. 5a shows a cross-sectional view of the device. The frame 15 comprises rails 15a on which slides the support 29 of the tube and of the plate 34. The springs 50 push on pads 51 which are applied to the rails 15a. The action of the springs 50 pushes the plate 34 upwards against the fixed plate 30. The entry of the guide rails 15a is inclined so that the springs 50 are relaxed when the support 29 is presented at the entry of these rails . The springs are compressed progressively as the plate / tube assembly is pushed towards the fixed plate 30. The pressurization of the plate 34 is thus carried out gradually. The pressure reached is sufficient to ensure sealing when the plate 34 (or the plate 3) comes opposite the pouring orifice 2. FIG. 6 shows a top view of the device of the invention. The manipulator designated as a whole by the general reference 44 comprises a jack body 46 which slides on the jack rod 48, the two ends of which are fixed to the manipulator 44. The jack constitutes the second actuation means. The cylinder body 46 supports the two fingers 40 which have been described above. These fingers act as forks to push the plates 3 and 34 in one direction or the other. The support 29, shown in plan in FIG. 6 is articulated around the axis 42 of masters so that the tube can be presented in a horizontal position when it is inserted between the pocket and the distributor, as described above. . The support 29 includes springs 50 which constitute the means for pressurizing the plate 34.

In FIG. 6, the manipulator 44 is shown in the position away from the pocket 1. It can be brought closer to this pocket thanks to the first actuation means (not shown), for example jacks. The guide 52 secured to the manipulator 44 cooperates with a counter guide 54 secured to the frame 15. These two guides make it possible to automatically adjust the position of the manipulator relative to the pocket. When the manipulator advances the guide 52 fits into the counter guide 54, which ensures the centering of the manipulator.

In Figure 7 there is shown the manipulator 44 in position adjoining the frame 15. In this position the counter guide 54 is fully fitted in the guide 52 of the manipulator and the support 29 is placed next to the support 27 of the closure plate 3. This support 27 comprises, like the support 29 of the springs 50 constituting means for pressurizing the closure plate 3. The guide 52 and the counter guide 54 make it possible to cancel the reaction forces of the jack 46 of such so that no effort is transmitted to pocket 1.

The jack is then actuated to push the support 29 against the support 27 and move them simultaneously, which results in the position shown in FIG. 8. In this figure the jet protection tube is opposite the pouring orifice 2 while the cover plate has been driven out of this position. However, it continues to be held by the guide rails of the frame. From this position it is possible to easily return to the position shown in Figure 7 by actuating the cylinder 46 in the opposite direction. It is also possible to switch to the position shown in FIG. 4 in which the access hole of the closure plate 3 is located opposite the pouring orifice 2 in order to clean this orifice by means of a lance. oxygen.

The device which has just been described makes it possible to regulate the flow of liquid steel by sliding the plate on the guide means using the manipulator. However, with this solution, the constriction of the passage section is located at the upper part of the jet protection tube, which gives rise, as has been recalled, to a phenomenon of venturi.

This is why, according to an alternative embodiment, the flow rate of the liquid steel is regulated at the lower end of the jet protection tube.

In Figures 1 and 9 a refractory brick 10 is arranged on the bottom of the distributor.

The tube 4 has an orifice of sufficient section to allow the passage of the maximum flow required for the liquid metal.

To regulate the flow of liquid metal from the bag 1 to the distributor 8, it suffices to vary the passage section offered to the fluid at the lower end of the pouring tube 4. This can be obtained by a wide variety of means appropriate. In particular, in the device shown in Figure 1, you can lower the breast pocket to bring the lower end of the tube 4 closer to the refractory brick 10. The same result could be obtained by leaving the pocket fixed and bringing the distributor closer of the latter. One can also imagine varying the position of the two containers simultaneously.

This device has, in addition to its great simplicity, the important advantage of avoiding the phenomenon known as the venturi which leads to the suction of air into the pouring tube. In fact, as can be seen, the smallest passage section offered to the fluid is located between the lower end of the tube 4 and the refractory brick 10. The jet protection tube is kept under overpressure with respect to the atmosphere during all casting, regardless of the degree of rolling of the jet. A possible leak in the tube or at the junction of the tube with the bag cannot therefore cause any air suction, which guarantees the quality of the metal produced.

The fact that the safety closing function is ensured by the closing plate

3 independently of the regulating function is advantageous since a certain clearance can be permanently left between the lower end 4a of the pouring tube

4 and the refractory brick 10. In this way, the risk of destroying the tube 4 by accidental contact against the refractory brick 10 is reduced.

The flow is adjusted by regulating the distance between the ladle and the distributor 8. It will be noted that at the start of casting the distance between the ladle and the distributor is generally greater than the limit value allowing regulation. Therefore the flow is maximum for a certain period. This does not, however, present any drawback since it is necessary at this time to fill the distributor as quickly as possible.

The operator then has several minutes to reduce the distance between the pocket and the distributor until the rolling value is reached.

Although the distance between the bag and the distributor cannot be regulated quickly, that is to say with a short reaction time, given the large mass of each of the two containers, the regulation obtained by the method and the device of the invention is nevertheless sufficient in particular because the distributor has a large free surface so that the level of the liquid metal which it contains varies slowly.

In the variant embodiment illustrated in FIG. 9, the tube 4 is equipped at its lower end with a ferrule 14 mounted tightly at the lower end of the tube. In the accidental event that the distance between the pocket 1 and the distributor 8 is reduced too strongly, the ferrule 14 will slide forcibly on the tube. This avoids the rupture of the tube 4 which would not fail to occur if its lower end were to strike the refractory brick 10. The ferrule 14 thus plays the role of a safety member.

In the alternative embodiment illustrated in FIG. 10, the obstruction more or less significant of the lower opening of the tube 4 is not achieved by adjusting the distance between the pocket 1 and the distributor 8, but by moving a refractory brick 16 relative to the orifice of the pouring tube 4 by independent external means (not shown in Figure 10). This embodiment has the advantage of avoiding having to move heavy loads such as the pocket or the dispatcher. It also makes it possible to have an independent set of containers that can be replaced quickly during casting. It is indeed always possible to replace the brick 16 by letting the maximum flow flow in the tube 4 where, if this maximum flow cannot be temporarily authorized, to close the pouring orifice 2, by means of the device independent of complete closure 3 as explained previously during all or part of the time for changing the refractory brick 16.

According to the alternative embodiment illustrated in FIG. 11, at least one refractory brick 20 is placed opposite the lateral orifice 18. The exemplary embodiment represented in FIG. 4 comprises two symmetrical orifices 18 and two refractory bricks 20. The or the bricks 20 can be brought closer or distant from the orifices 18 to limit the passage section offered to the fluid. The bricks 20 are actuated by an independent external mechanism not shown in the figure.

In the particular case where the tube 4 has only one orifice such as 18 or more orifices located on the same side of the tube, the brick or bricks 20 can be kept fixed and the distance between the orifice (s) 18 and the or bricks 20 can be regulated by a lateral movement of the pocket 1.

The particular embodiment shown in FIG. 11 in which the orifices are arranged symmetrically with respect to the longitudinal axis of the jet protection tube, the effect of the lateral reaction forces produced by the ejection of the liquid metal compensate each other . Thus, the jet protection tube is not subjected to a significant bending moment. The movement of the brick or bricks 20 relative to the orifice or orifices 18 can be rotary, linear or any other composition of movement insofar as it makes it possible to reduce the passage section offered to the fluid and therefore to control the flow of liquid metal. In the alternative embodiment illustrated in FIG. 12, the tube 4 comprises at least one lateral outlet orifice 18. A cuff 22 concentric with the tube 4 is placed around the latter and can slide longitudinally under the action of displacement means not shown. on the face. The cuff 22 more or less closes the outlet orifices 18 of the tube 4. In an identical manner to what has been described with reference to FIG. 4, it is preferable for the outlet orifices 18 to be distributed symmetrically over the periphery of the tube 4 in order to compensate for the reaction forces exerted at the lower end of the tube.

It will be noted that the flow control cuff 22 does not have the role of completely closing the orifices 18 since the closure is also ensured by separate means, an operating clearance can be provided between the cuff 22 and the tube 4. This tolerance greatly facilitates production and secures operation by eliminating the risks of blocking the cuff on the tube.

In the alternative embodiment shown in FIG. 3, the protective tube 4 comprises, at its lower end, one or more lateral orifices 18, as in the case of the embodiments of FIGS. 4 and 5. A refractory sleeve 24 is mounted at the lower end of the jet protection tube 4. The cuff 24 has one or more orifices 19. It is movable in rotation relative to the tube 4 so that its or its orifice (s) 19 can be moved relative to the orifice or to the orifices 18 of the jet protection tube 4. The passage sections of these orifices thus overlap more or less completely, which makes it possible to provide the desired regulation. An identical result can also be obtained by translating the cuff 24 along the tube 4.

For this embodiment as for the previous embodiments, it is possible to provide a clearance between the cuff 4 and the jet protection tube 4, which also facilitates the production of this variant.

There is shown in Figure 13 a detail of an advantageous variant of the cuff 24. In fact, as explained above, the shell is not precisely adjusted to the outside diameter of the tube 4, and there is play between these two parts. Consequently, when the orifice 18 (Fig. 13) is closed from the top, the liquid metal tends to pass between the cuff 24 and the outside diameter of the tube 4 and to spurt out from the surface of the liquid metal bath. To avoid this phenomenon, the opening (s) 18 is closed from the bottom. To this end, the cuff 24 has orifices 19, for example in a number equal to that of the orifices 18. The obturation is effected by the lower edge of the recesses, by raising the shell upwards. Thus, most of the jet is directed upwards (arrows 23). This jet is absorbed by the liquid metal bath. Another part of the flow passes in the clearance which exists between the tube 4 and the cuff 24 (arrows 21) which is without disadvantage because this flow is directed towards the bottom of the distributor. The closure can also be ensured by a rotary movement of the cuff 24, the orifice (s) of this cuff being slightly offset upwards relative to the orifices 18 of the tube.

Claims

1. Device for controlling the flow of liquid steel between a ladle (1) and a continuous casting distributor (8) capable of containing a bath of molten steel, said ladle being capable of containing and transporting a quantity of steel liquid between a remote site and a continuous casting floor, said ladle being provided with a pouring orifice (2) which makes it possible to transfer the liquid steel into the distributor (8), this pouring orifice (2) being surrounded by a fixed upper plate (30), device comprising a frame (15) linked to the pocket (1) and comprising guide means; a plate (3) capable of moving on the guide means and of closing the pouring orifice (2); the device further including means for pressurizing this plate (3); means for protecting the jet of liquid steel during its passage from the pocket (1) to the distributor (8), these means comprising in particular a jet protection tube (4) intended to be placed in the extension of the pouring orifice (2) and which has a lower end (4a) intended to be immersed in the bath of liquid steel contained in the distributor (8), characterized in that: the plate capable of closing the pouring orifice ( 2) is a closure plate (3) intended only for closing the pouring orifice (2); the jet protection tube (4) is formed into a rigid assembly with a plate (34); this assembly can be received and move on the guide means to come opposite the pouring orifice to replace the closure plate (3) which is pushed out of this position; pressurizing means being provided to keep the plate (34) of the plate / jet protection tube assembly (4,34) applied with sealing against the fixed upper plate (30).

2. Device according to claim 1, characterized in that it further comprises a manipulator (44) independent of the pocket (1) and located in a position linked to the continuous casting floor, this manipulator comprising at least two means of actuation, for example jacks, a first actuation means for bringing and / or removing the plate / tube assembly at the entrance of the guide means, and a second actuation means which makes it possible to introduce the closure plate and / or the plate from the plate assembly / jet protection tube in the guide means of the frame and pushing the plate of the plate / tube assembly opposite the pouring orifice so that it pushes the closure plate or vice versa.

3. Device according to claim 2, characterized in that the second actuating means consists of a fork formed by two fingers, a first finger (40), which makes it possible to push the plate / tube assembly and the plate closure, and a second finger (40) which makes it possible to exert a reciprocal action to bring the closure plate and the plate / tube assembly opposite the fixed plate.

4. Device according to claim 3, characterized in that said first finger (40) is capable of supporting the plate / tube assembly.

5. Device according to any one of claims 2 to 4, characterized in that the manipulator (44) comprises a guide (52) and the frame (15), a counter guide in which the guide of the manipulator engages to adjust the position of the manipulator relative to the frame (15).

6. Device according to any one of claims 1 to 5, characterized in that the closure plate (3) and / or the plate / jet protection tube assembly (4, 34) are arranged in a support (27 , 29) which comprises said pressurizing means.

7. Device according to any one of claims 1 to 6 characterized in that it comprises means (10, 16, 20, 22, 24) for achieving a constriction of the passage section offered to the liquid steel at l 'lower end (4a) of the jet protection tube (4) intended to be immersed in the bath of liquid steel (6) contained in the distributor (8).

8. Device according to claim 7 characterized in that the means for constricting the passage section offered to the liquid steel comprise a refractory brick (10) integral with the distributor (8), located opposite '' an orifice of the jet protection tube (4), the regulation of the flow of the liquid steel being obtained by varying the position of the pocket (1) relative to that of the distributor (8) and / or by varying the position of the distributor (8) relative to that of the pocket (1).

9. Device according to claim 7 characterized in that the jet protection tube (4) is extended by a cuff (14) coaxial with the tube (4) and sliding with hard friction on this tube so as to provide security if the distance between the continuous casting ladle (1) and the distributor (8) was accidentally reduced.

10. Device according to claim 7 characterized in that the means for making a constriction of the passage section offered to the liquid steel consist at least of a refractory brick (16) movable opposite at least one outlet orifice for the liquid steel provided at the lower part (4a) of the jet protection tube (4).

11. Device according to claim 7 characterized in that several orifices (18) are provided in the lower part (4a) of the jet protection tube (4), these orifices (18) being regularly spaced from each other, and in that the means for constricting the passage section offered to the liquid steel are actuated symmetrically so as not to create lateral reaction force on the end (4a) of the tube (4).

12. Device according to claim 7 characterized in that the jet protection tube (4) has at least one lateral orifice (18) at its lower part and in that the regulation of the flow of the liquid steel is obtained by a cuff

(24) coaxial with the jet protection tube (4), mobile in translation along the jet protection tube (4) and / or mobile in rotation around this tube (4).

13. Device according to claim 12 characterized in that the cuff (18) comprises at least one orifice (19) making it possible to regulate the flow of the liquid steel, the lower edge of this orifice (19) being located higher than the lower edge of the orifice (18).

14. Device according to any one of claims 1 to 13 characterized in that the closure plate (3) has a solid area (32a) called the closure area and an access orifice (36) located outside the area closing, the access orifice (36) possibly being provided with a collecting nozzle, to allow access to the pouring orifice (2) of the continuous casting ladle (1) without having to deposit the tube jet protection (4).

15. Device according to claim 14 characterized in that the access orifice (36) of the closure plate (3) is located between the plate (34) of the plate / jet protection tube assembly (4, 34) and the closing area (32a) of the closing plate (3) when said closing plate (3) and said plate (34) are engaged in the guide means, this position of the access opening ( 36) being intended to reduce the distance necessary to pass from the position in which the access orifice (36) is opposite the tap hole (2) to the position in which the jet protection tube (4) is next to this tap hole

(2).

16. Method for controlling the flow of liquid steel between a ladle (1) and a continuous casting distributor (8) capable of containing a bath of molten steel, said ladle being capable of containing and transporting a quantity of steel liquid between a remote site and a continuous casting floor, said ladle being provided with a pouring orifice (2) which makes it possible to transfer the liquid steel into the distributor (8), this pouring orifice being surrounded by an upper plate fixed (30), characterized in that: - a closing plate (3) is introduced which is able to close the pouring orifice

(2) in guide means linked to the pocket (1); this closing plate (3) is pushed opposite the upper plate fixed (30) while applying it sealingly against this fixed upper plate (30); filling the ladle (1) with liquid steel; the ladle is brought to the continuous casting floor; - A jet protection plate / tube assembly (4, 34) independent of the pocket is introduced into the guide means on the continuous casting floor or in its vicinity; the plate / jet protection tube assembly (4, 34) is pushed, which drives out the closure plate (3) while applying it sealingly against the fixed upper plate (30).

17. A method of controlling the flow of liquid steel, characterized in that, after the steps defined in claim 16, for example when the pocket (1) is empty or in the event of an incident, the plate is pushed again closing (3) opposite the fixed upper plate (30) and it is applied with sealing against this fixed upper plate (30), which closes the pouring orifice (2) and simultaneously releases the plate / assembly jet protection tube (4, 34).

18. Method according to claim 16 or 17 characterized in that the jet protection tube plate assembly (4, 34) is put into place in the guide means of the frame by means of an independent manipulator (44) of the pocket (1) and located in a position linked to the pouring floor, and in that the closure plate (3) and / or the jet protection tube plate assembly (4, 34) is moved by actuation means linked to this manipulator.

19. Method according to any one of claims 16 or 17 characterized in that one ensures the function of regulating the flow of the liquid steel independently of the function of closing the pouring orifice (2) at by means of the closure plate (3) linked to the pocket (1).

20 Method according to claim 19 characterized in that one regulates the flow liquid steel by closing more or less an orifice located at the end (4a) of the jet protection tube (4) immersed in the bath of liquid steel (6) contained in the distributor (8).

21. The method of claim 20 characterized in that one more or less closes the orifice located at the end (4a) of the jet protection tube (4) by varying the position of the pocket (1) by relative to that of the distributor (8) and / or by varying the position of the distributor (8) relative to the position of the pocket

(1).