EP0305426B1 - Installation for pouring liquid metal, and process for its implementation - Google Patents

Abstract

Installation for pouring liquid metal, comprising a metallurgical receptacle (1), designed to contain liquid metal (2), provided with a pouring hole (6) and under said hole (6) a principal closing and opening device (8) for same (6). Also an auxiliary device (12) for preheating, sealing and unsealing said pouring hole (6), disposed thereabove (6) and comprising an elongated element (13) designed for partial immersion in the liquid metal (2) and made of a refractory and/or insulating material (34) which sinters on contact with the liquid metal; also means (14, 15, 17, 18, 21) for holding the elongated element (13) over the pouring hole (6), so sealing it before and during the first stage of the pouring of the liquid metal (2) into the receptacle (1) and for lifting said element (13) from the pouring hole (6), said element consisting of at least one longitudinal pipe (23) issuing aft right angles with, or/in the vicinity of the pouring hole (6) and connected with at least one pressurized gas source (30), enabling the preheating and/or unsealing of the hole (6). Application particularly in preheating and/or unsealing of the pouring hole (6) of a metallurgical receptacle (1).

Description

The present invention relates to a liquid metal casting installation comprising a metallurgical container intended to contain liquid metal, provided with a pouring orifice and comprising under this orifice a main device for closing and opening said orifice according to the preambule of the claim 1.

The invention also relates to the method for implementing this installation.

It is known that any metallurgical container such as a ladle or a continuous pouring distributor, mainly with slab or bloom, comprises a device for closing the pouring orifice to allow it to be closed, before and during the start of the pouring of the liquid metal into this container, then the release of this orifice to allow the pouring of the liquid metal into a second metallurgical container, for example in a continuous casting mold.

Such a device must also allow partial or total sealing of this orifice if it is necessary to limit the flow rate or interrupt the pouring of the liquid metal.

The most well-known sealing devices are the stopper rods fitted with a conventional refractory lining requiring heating before the metal is poured to avoid any risk of solidification of the metal in contact with its surface. These cattails are heavier and difficult to handle.

The closure devices currently used are drawer nozzles. These give full satisfaction with regard to the sealing function before and during casting and at the end of it. On the other hand, it may happen that, despite the care taken to prepare the pouring container before a pouring, a plug of various debris, slag and / or solidified metal is formed in the pouring opening preventing the pouring of the metal. liquid or severely limiting it.

Such an incident can seriously disrupt the operation of the molten metal casting workshop, by delaying the pouring of the metal for the time necessary to unblock the blocked pouring orifice, or by extending the duration of the pouring as for example in in the case of a continuous casting installation of liquid metal with several lines, if the casting manager decides to give up using the obstructed line and to use only the other available lines.

If all the lines are obstructed, it can happen that the metal must be poured into emergency ingot molds allowing its solidification into ingots which will then be remelted.

Incidents of unclogging are therefore always generating additional costs by loss of productivity.

The solution generally consists in trying to burn with oxygen the incandescent magma forming the plug which obstructs the pouring orifice. For this, a metal tube is introduced into this orifice through the lower part of the metallurgical vessel, into which a jet of oxygen is supplied. A flame is formed on contact with the magma, the heat of which melts the latter. This operation is always very delicate. In fact, it often happens that by melting the magma, the pouring orifice and / or the drawer device are damaged. In addition, this operation is dangerous for the personnel who perform it.

Such a method of unblocking is made even more delicate when a pouring tube is used under the metallurgical receptacle intended to prevent the liquid metal from contacting the air and the risk of oxidation, while limiting projections. An attempt has been made to design pouring tubes provided substantially in their axis with a metal pipe through which oxygen is supplied if the liquid metal does not flow through the pouring opening when the drawer device is opened. . But unclogging the underside of the metallurgical vessel has never been entirely satisfactory.

Another solution is also proposed in US-A-4 667 858 to avoid blockage of the pouring orifice of a metallurgical container equipped with a closure device of the nozzle nozzle type. This solution consists in putting sand in the pouring opening above the drawer. However, when the drawer is opened, the sand flows and pollutes the metal of the lower container.

It is also known in the way of developing steels to use cattails of metallurgical vessels consisting of a hollow metal central tube covered with a refractory protection. These cattails are intended to inject into the liquid steel baths purifying gases, whether or not added with powders, in order to purify the steel bath, in order to cool it, to purge it, and to reduce its flow through the orifice exit. These gases and powders are also intended to cool these cattails. They are not designed to achieve the objectives of the present invention and have a method of use opposite to the present invention.

The object of the present invention is to remedy the aforementioned drawbacks by creating a liquid metal pouring installation of the aforementioned simple and efficient type, allowing the preheating, the sealing and the unblocking of a pouring orifice of the metallurgical container, which allows in particular, for a low cost, the rapid and effective removal of a plug obstructing the pouring orifice.

According to the invention, the installation is characterized in that it also comprises an auxiliary device for preheating, closing and unblocking the pouring orifice, placed above said orifice, and comprising an elongated element intended to be partially immersed in the liquid metal and made of a refractory and / or refractory insulating material which can be sintered on contact liquid metal, means for holding the elongated element on the pouring orifice so as to close it before and during the start of the pouring of liquid metal into the container and for lifting this element above the orifice casting, this element comprising at least one longitudinal duct opening at right angles and / or in the vicinity of the pouring orifice and which is connected to at least one source of pressurized gas allowing the preheating and / or unclogging of said orifice.

This device, which is only used as an auxiliary for preheating and / or closing the pouring orifice at the start of casting, can be simple and therefore light and economical. This device by its mere presence on the pouring orifice before the arrival of the liquid metal, also considerably limits the risk of debris of any kind falling into the pouring orifice to obstruct it. In addition, this device, which is placed on the pouring orifice and is lifted slightly above it, allows, in the event of the presence of a possible plug, to send directly to this plug at very short distance, therefore with great precision, an oxidizing gas, such as for example oxygen or any other gas enriched with oxygen, oxidizing and / or reducing, to melt this plug. The fact that the elongated element is preferably made of a material capable of sintering on contact with the liquid metal allows the latter to maintain its mechanical cohesion throughout the duration of its stay in this liquid metal.

According to an advantageous embodiment of the invention, the refractory insulating material, sinterable in contact with the liquid metal, is composed of refractory inorganic particles, such as silica and / or alumina and / or magnesia, and optionally organic and / or refractory fibers, agglomerated using an organic and / or inorganic binder, capable of sintering on contact with the liquid metal.

Since this material has a density and a thermal conductivity significantly lower than that of conventional refractories, this material does not require any preheating and does not risk causing solidification of the liquid metal on contact.

In addition, this material remains slightly malleable after sintering, which is favorable for good sealing of the pouring orifice.

Finally, this material is very economical and easy to use.

According to a preferred embodiment of the invention, the duct is constituted at least by a metal tube disposed longitudinally inside the elongated element and emerging at the end of this element located above the orifice of pouring, the end of this tube opposite the pouring opening being connected at least by a tube to a source of oxygen and / or similar oxidizing gas and / or reducing gas under pressure, bubbling gas, a powder feed mechanism, grains, metallic wire.

The presence of a metal tube arranged longitudinally inside the elongated element allows a very simple construction of this element to which the tube serves as a frame. As indicated above, the jet of oxygen or enriched gas emerging at the end of the tube and of the elongated element situated above the pouring orifice forms a flame in contact with the liquid metal and attacks at very low distance and therefore with great precision the magma obstructing the pouring orifice without damaging the walls of this orifice or the elements of the slide or rotary shutter. It is also possible to ignite the gas leaving the elongated element using a torch in order to preheat the outlet or using any other ignition device, such as, for example, by a system. of electrodes.

The material of which the elongate element is preferably made being both refractory and insulating, the thickness of this material around the metal tube can be reduced and this elongate element can thus be very light compared to a traditional stopper rod.

• a) on met en place sur l'orifice de coulée l'élément allongé du dispositif auxiliaire ou principal de préchauffage, d'obturation et de débouchage,
• b) on commence à remplir le récipient de métal liquide,
• c) lorsque le métal liquide atteint dans le récipient le niveau voulu, on ouvre le dispositif principal d'obturation, puis
• d) on soulève légèrement l'élément allongé du dispositif auxiliaire au-dessus de l'orifice de coulée,
• e) si le métal liquide ne s'écoule pas normalement par l'orifice de coulée, on commande l'arrivée du gaz oxydant dans le conduit de l'élément pour éliminer par fusion le bouchon formé dans l'orifice de coulée,
• f) dès que le métal s'écoule normalement par l'orifice de coulée, on relève complètement l'élément allongé.

According to another aspect of the invention, the method for implementing an installation according to the invention comprises the following steps:

• a) the elongate element of the auxiliary or main preheating, sealing and uncorking device is placed on the pouring orifice,
• b) one begins to fill the container with liquid metal,
• c) when the liquid metal reaches the desired level in the container, the main closure device is opened, then
• d) the elongate element of the auxiliary device is slightly raised above the pouring orifice,
• e) if the liquid metal does not flow normally through the pouring orifice, the arrival of the oxidizing gas is controlled in the conduit of the element to remove by fusion the plug formed in the pouring orifice,
• f) as soon as the metal flows normally through the pouring orifice, the elongated element is completely raised.

Other features and advantages of the invention will appear in the description below.

• la figure 1 est une vue en coupe transversale d'une installation conforme à un mode de réalisation de l'invention;
• la figure 2 est une vue en coupe analogue à la figure 1, l'élément allongé de l'installation selon l'invention étant soulevé au-dessus de l'orifice de coulée, et étant différent de celui représenté à la figure 1;
• la figure 3 est une vue en coupe axiale longitudinale de l'élément allongé d'une installation conforme à l'invention.

In the appended drawings given by way of nonlimiting examples:

• Figure 1 is a cross-sectional view of an installation according to an embodiment of the invention;
• Figure 2 is a sectional view similar to Figure 1, the elongated element of the installation according to the invention being lifted above the pouring orifice, and being different from that shown in Figure 1;
• Figure 3 is an axial sectional view longitudinal of the elongated element of an installation according to the invention.

In the embodiment of the installation shown in FIG. 1, we see at 1 a metallurgical container constituted by a distributor 1 of a continuous casting installation. This distributor 1 containing liquid metal 2 such as molten steel comprises an outer steel casing 3, internally lined with a permanent refractory coating 4 which is itself preferably protected by a refractory insulating coating 5.

The casting distributor 1 comprises a pouring orifice 6 formed in a pouring nozzle 7 usually made of refractory material. Under the pouring orifice 6 of the distributor 1 is installed a main shutter device 8 with a drawer 9. In the example shown, the main shutter device with drawer 8 may include a tube 10 allowing the blowing of argon in the nozzle 7 which in this case is made of porous refractory material. Under the drawer closure device 8 is mounted a pouring tube 11.

The pouring orifice 6 of the distributor 1 is equipped with an auxiliary preheating and / or obturation and uncorking device 12, which mainly comprises an elongated element 13 disposed substantially vertically on the pouring orifice 6 so that the '' seal.

Element 13 is axially traversed by a tube 23 which serves as a frame.

The elongate element 13 can be lifted above the pouring orifice 6 by any known manual or remote-controlled system.

In the example shown, this control device comprises a lever 14 articulated at 16 on a stand 17 carried by the casing 3 of the distributor 1. The lever 14 is articulated on the one hand to a collar 15 which encloses the upper part of the tube 23 above the element 13 and on the other hand to a link 18 guided by a sheath 20. The link 18 is controlled in translation by an operating lever 21 articulated at 22 on the casing 3.

According to a particularly simple embodiment of the elongated element 13 shown in Figure 3; this element has inside its metal tube 23, generally of ordinary steel, for example a standardized tube with nominal diameter 1˝ (25.4 mm). The tube 23 is externally threaded at its lower end and screwed into a threaded sleeve 24. The end of the sleeve 24 opposite the tube 23 is for example welded to a washer 25 provided in its center with a circular orifice 26 in which is welded along the axis of the tube 23 a tubular element 27 of diameter smaller than that of the tube 23. At 35, there is shown a layer of insulating material covering the surface of the bath of liquid steel.

In the example shown in FIG. 3, the elongated element 13 is composed of several annular parts 13a, 13b, 13c fitted one on the other around the metal tube 23. These parts 13a, 13b, 13c can be joined to each other for example by means of a refractory adhesive. It is possible to interpose between the annular parts 13c one or more parts 13e of a larger diameter, in particular in the region of the slag and / or of the layer of insulating material 35 covering the surface of the bath of liquid steel (FIG. 1).

Furthermore, the part 13a adjacent to the pouring orifice 6 has a spherical surface 13d determined to be able to be applied in a sealed manner on the frustoconical edge 31a of the seat brick 31 and on the edge of the nozzle 7 housed in that -this.

The end 28 of the tube 23 opposite the pouring orifice 6 is connected to a source of oxygen 30 under pressure by means of a flexible tube 29.

The elongate element 13 can be produced in several ways. For example, the tube 23 and the sleeve 24 are assembled, to which the washer 25 and the tube section 27 have been previously fixed, to which a porous plug allowing the gases to pass is added, and the insulating coating is produced in a single operation. refractory to the press or by accelerated filtration under pressure or by suction using a suitable material 34 described below. The material 34 constituting the different parts 13a, 13b, 13c of the element 13 is a refractory and / or refractory thermal insulating material composed of particles refractory inorganics, such as silica and / or alumina, and / or magnesia, ... and optionally organic and / or refractory fibers, the whole being agglomerated using organic binders and / or inorganic, liable to sinter on contact with liquid metal 2.

The composition of the refractory thermal insulating material and the particle size of its constituents are adjusted so that sintering occurs, in the case of steel metallurgy, between 800 ° C and 1500 ° C. However, the addition of a mineral binder frees the composition from the sintering constraints. The specific mass of this material can vary between 0.5 and 2.9 kg / dm³ depending on the composition and the particle size of its constituents.

To facilitate the production of the elongated element 13 in a single operation, the outer walls of the tube 23, the sleeve 24, the washer 25 and the tube section 27 can be coated beforehand with an adhesive facilitating the adhesion of the material 34 to metal.

Another way of making the element 23 consists in separately preparing the end part 13a having substantially the shape of a hemisphere extended by a cylinder, then screwing the tube 23 into the sleeve 24 and then threading onto the tube 23 the various prefabricated tubular parts 13b, 13c.

The lower part 13a intended to close the pouring orifice 6, which supports the pressure hydrostatic of the liquid metal and rests on the periphery of the pouring orifice 6 has the maximum thickness of refractory and / or refractory insulating material 34. It has for example an outside diameter of 132 mm and a total height of 100 mm which includes the height of the frustoconical recess allowing the nesting, for example 15 mm, and the height of the threaded sleeve 24, or for example 52 mm, the upper part of the sleeve flush with the level of the refractory and / or refractory insulating material .

The upper tubular parts 13b, 13c which support less effort, can have a thinner thickness of material 34 and have, for example, an outside diameter of around 75 mm for an inside diameter of the order of 35 to 40 mm, and a height 150 mm unit.

Parts 13a, 13b, 13c can be produced, for example, by press or by accelerated filtration under pressure or by suction. They can be refractory and / or insulating refractory. They may have a larger diameter in the slag area than the elements 13b and 13c.

We will now describe with reference to Figures 1, 2 and 3 the method for implementing the installation according to the invention in the case shown where the container is a continuous casting distributor.

When the distributor 1 comprising an auxiliary device 12 and a main device 8 is ready for a new casting, the new elongated element 13 is fixed to the arm 14. The element 13 rests by its own weight on the bottom of the distributor 1 and care is taken to center the lower spherical part 13a on the pouring orifice 6. The element 13 being in place, the device is placed at drawer 8 in closed position. The mere presence of the element 13 on the pouring orifice 6 will therefore prevent the introduction of undesirable foreign matter into this orifice.

We begin to fill the distributor 1 with liquid metal. On contact with the latter, or due to the radiation of the liquid metal, the refractory insulating material 34 surrounding the element 13 begins to sinter. This sintering continues inside the material, as the temperature inside the parts 13a, 13b, 13c increases.

Thanks to this sintering, the cohesion of the material is maintained, despite the decomposition of the binder. In addition, it has been found that the liquid metal does not wet the surface of the material of the element 13, so that the behavior of this element is not likely to be disturbed by undesirable metal adhesions. The material of the element 13 being insulating, there is no metal solification against its surface. In addition, the material 34 of the element 13 remains slightly malleable even after sintering, which further improves the sealing conditions of the pouring orifice 6.

Preferably when the liquid metal in the distributor 1 reaches the required level, the surface of the bath of liquid steel is covered with an insulating material. then the main shutter valve device 8 is opened, then, using the levers 21 and 14, the element 13 is slightly raised above the pouring orifice 6, as shown in FIG. 2. If the metal flows normally, element 13 can be lifted to its upper release position and kept there by any blocking device (not shown).

If the metal does not flow at all, it does not flow normally in the pouring orifice 6, the element 13 is lowered again on this orifice 6 and oxygen is blown through the tube 23 and the tube section 26 which forms a nozzle. Upon contact with the liquid metal, a flame 32 is immediately formed which will melt and disappear any magma 33 of metal and foreign matter obstructing the pouring orifice 6.

As soon as the metal flows normally, the element 13 is raised to its upper release position and held there. Then one can, when a blowing of argon is planned, open the arrival of argon by the pipe 10 in the nozzle 7 to drive out of the vicinity of the orifice 6 possible impurities.

When the pouring is almost finished, it is possible to close the pouring orifice 6 by means of the elongated element before ordering the closing of the drawer nozzle 8. If the drawer nozzle is closed directly, risk the accumulation above the drawer 9 in the orifice 6 of a puddle of steel and / or slag and powder insulator which risks solidifying in the orifice 6 and making it more difficult to replace the drawer nozzle 8 and that of the nozzle 7. On the contrary, by proceeding as indicated above, the drawer nozzle 8 is closed. that the orifice 6 is completely cleared. It is thus possible to interrupt the casting before the passage of slag in the nozzle without risking complicating the restoration of the installation before a new casting.

At the end of casting, the arrival of oxygen or enriched gas, and / or oxidant and / or reducing agent is disconnected from the tube 23, the element 13 is dismantled and replaced by a new element.

The invention is not limited to steel metallurgy and can be used for all liquid metals, in particular aluminum, copper and their alloys, provided that the composition and the particle size of the materials constituting the material the element 13 whose parts 13a or 13b or 13c or 13e are refractory insulators are adapted to allow sintering of this material in contact with the liquid metal.

This refractory insulating material can at will be acidic, basic or neutral depending on the composition chosen according to the intended use. The total charge of the refractory component (s) of this material can reach 99.5%, the percentage of fibers being able to reach 20%. Preferably, the refractory insulating parts not subjected to sintering contain an inorganic binder.

The installation according to the invention can be adapted for example to a ladle and / or to each pouring orifice of a distributor, the length of the element 13 being adapted to the conditions of use. The drawer nozzle can be replaced by a barrel nozzle.

Furthermore, the tube 23, the sleeve 24, the washer 25, the section of the tube 27 can be replaced by equivalent elements assembled by any known means.

It goes without saying that one can take advantage of the device 12 to introduce into the steel bath through the tube 23 all gases and useful treatment materials (bubbling gas, powders, grains, metallic wires, etc.).

Claims (9)

1. Installation for casting liquid metal, comprising a metallurgical receptacle (1) adapted to contain liquid metal (2), provided with a casting orifice (6) and comprising below this orifice (6) a principal device (8) for closing and opening said orifice (6), characterized in that it also comprises an auxiliary device (12) for preheating, closing and unplugging the casting orifice (6), disposed above said orifice (6), and comprising an elongated element (13), adapted to be partially immersed in the liquid metal (2) and made of a refractory and/or insulating refractory material (34) which is sinterable when in contact with the liquid metal (2), means (14, 15, 17, 18, 21) to maintain the elongated element (13) on the casting orifice (6) so as to close it before and during the beginning of casting of the liquid metal (2) into the receptacle (1) and to raise this element (13) above the casting orifice (6), this element (13) comprising at least one longitudinal conduit (23) opening opposite or in proximity to the casting orifice (6) and which is connected to at least one source of gas (30) under pressure permitting the preheating and/or the unplugging of the orifice (6).

2. Installation according to claim 1, characterized in that the insulating refractory material (34) sinterable in contact with the liquid metal (2) comprises inorganic refractory particles such as silica and/or alumina and/or magnesia, and if desired organic and/or refractory fibers, held together by an organic and/or inorganic binder, adapted to sinter in contact with the liquid metal.

3. Installation according to one of claim 1 or 2, characterized in that the conduit or conduits provided in the elongated element (13) are constituted by one or more metallic tubes (23) disposed longitudinally within the elongated element (13) and opening at the end of this element located above and/or in proximity to the casting orifice (6), the extremity or extremities (28) of this or these tubes (23) opposite the casting orifice (6) being connected by one or more conduits (29) to a source of oxygen and/or similar oxidizing gas and/or reducing gas under pressure (30), bubbling gas, to a mechanism for supplying powders, particles, metallic wire.

4. Installation according to claim 3, characterized in that the elongated element (13) is comprised by several members (13a, 13b, 13c, 13e) interfitting within each other about the metallic tube (23).

5. Installation according to claim 4, characterized in that the member (13a) of the elongated element (13) adjacent the casting orifice (6) comprises a metallic sleeve (24) which is axially connected by screwing to the end of the metallic tube (23).

6. Installation according to one of claims 3 to 5, characterized in that the end of the elongated element (13) adjacent the casting orifice (6) comprises a metallic tubular element (27) of a diameter less than that of the metallic tube (23) and connected axially to this latter.

7. Installation according to one of claims 1 to 6, characterized in that the end (13a) of the elongated element (13) adjacent the casting orifice (6) has a substantially spherical surface.

8. A process for using an installation according to one of claims 1 to 7, characterized in that it comprises the following steps:

a) the elongated element (13) of the auxiliary device (12) for closing and unplugging is put in place on the casting orifice (6),

b) the filling of the receptacle (1) with liquid metal (2) is begun,

c) when the liquid metal (2) achieves in the receptacle (1) the desired level, the principal closure device (8) is opened, then

d) the elongated element (13) of the auxiliary device (12) is raised slightly above the casting orifice (6),

e) if the liquid metal (2) does not flow normally through the casting orifice (6), oxidizing and/or reducing gas (30) is fed through the conduit (23) of the element (13) to eliminate by melting the plug (33) formed in the casting orifice (6),

f) as soon as the metal flows normally through the casting orifice (6) the elongated element (13) is raised completely.

9. Process according to claim 8, characterized in that after step a) and before step b), the outlet region (6) of the metallurgical receptacle (1) is preheated.

Images