EP0066492B1 - Process for the manufacturing of a casting tube - Google Patents

Abstract

The casting tube is constituted by a mixture of refractory particles and fibers embedded in a binder which is not capable of withstanding the temperature attained when liquid metal flows within the tube. The refractory particles are sinterable in a tube zone which is directly exposed to the heat of the liquid metal. At least in a zone which is not directly exposed to the heat of the liquid metal, the casting tube also contains a refractory binder which is capable of withstanding the heat in this zone.

Description

The present invention relates to a method for manufacturing a pouring tube intended to be placed under the pouring orifice of a metallurgical vessel, (such as a ladle) and to be immersed in the bath of molten metal which is poured into a second metallurgical container (such as a flow distributor placed under the aforementioned ladle).

In its French patent no. 2 333 599, the Applicant described a pouring tube made of thermally insulating material and of low density constituted by a mixture of refractory particles such as silica, alumina or magnesia and mineral fibers such as glass wool or rock wool or organic fibers, coated in an organic binder (for example phenolic resin) or inorganic (refractory cement or silicate).

To manufacture such a tube, the latter is formed around a perforated sleeve, from a pasty and aqueous mixture comprising the aforementioned constituents and the excess water contained in this mixture is sucked out from inside the perforated sleeve. cited above. The tube reinforced externally by a metal frame is then carried in an oven to evaporate the residual water and harden the binder.

When in use, the tube is engaged in a substantially leaktight manner around the pouring nozzle of the upper container (ladle).

Such a tube has excellent thermal insulation power and therefore prevents the cooling of the liquid metal which is poured from the ladle into the tundish.

In addition, such tubes resist the temperature of the liquid metal (steel or liquid iron) which is poured inside this tube. This resistance is explained by the sintering of the inorganic particles which this tube contains and which makes it possible to ensure the cohesion of the latter after decomposition or disintegration of the binder. Without this sintering, the tube would fall to dust after decomposition of the organic binder or disintegration of the inorganic binder.

The Applicant has noted, however, that this sintering does not take place at the end of the tube which is adjacent to the pouring orifice of the upper metallurgical vessel. In fact, at this end, the internal face of the tube is protected by the pouring nozzle which thus prevents this end of the tube from being brought to a temperature sufficient to allow sintering. Consequently, this end of the tube crumbles quickly under the effect of mechanical shock and the abrasion which it undergoes during successive engagements and clearances of the tube relative to the pouring nozzle.

Likewise, the lower part of the pouring tube which plunges into the molten metal bath contained in the lower container, tends to wear out quickly by melting and / or chemical attack by the products which cover the surface of the molten metal. cited above.

To remedy this drawback, the Applicant has proposed to protect the upper and lower ends of the pouring tubes with rings of refractory material. These thus considerably extend the life of the pouring tubes.

However, the attachment of these rings to the tubes presents some difficulty. In addition, these rings weigh down the tubes, which makes their handling less easy.

The object of the present invention is to remedy this drawback by creating a pouring tube which is simple to manufacture and has excellent mechanical and thermal resistance, although being free of refractory rings at its ends.

The process targeted by the invention for manufacturing a pouring tube comprises the steps consisting in forming the tube around a perforated sleeve from a pasty and aqueous mixture of refractory particles, fibers and an organic binder and / or inorganic, to suction the excess water from the mixture inside the perforated sleeve, then to carry the tube in an oven to evaporate the residual water and harden the mixture.

According to the invention, this process is characterized in that after or during the water suction step, the end of the tube intended to be placed near the pouring orifice of the first is made to penetrate metallurgical container and / or in the end of the tube intended to immerse in the molten metal poured into the second container, an aqueous solution of a binder having, after hardening, refractory properties superior to those of the basic organic and / or inorganic binder which is contained in the entire tube.

During the aspiration step, a proportion of water equal to about 30 to 40% by weight of the mixture is extracted from the pasty and aqueous mixture. Therefore, matter has the property of being able to re-absorb water. This is what allows the aqueous binder solution to penetrate inside the material at the ends of the tube.

After passing through the oven, the water from this binder as well as the residual water contained in the whole of the tube is evaporated and this hardened binder as well as the basic organic and / or inorganic binder which is contained in the whole. of the tube.

Because the binder introduced into the ends of the tube has, after hardening, refractory properties greater than that of the base binder, the thermal and mechanical resistance of the end of the tube adjacent to the pouring orifice which is not subjected to is improved. sintering indicated above, as well as that of the end of the tube which plunges into the liquid metal which is poured the lower container.

This extends the life of the tubes in a manner comparable to the case where these tubes have refractory rings at their ends, avoiding however the drawbacks resulting from the use of such rings.

According to an advantageous version of the invention, the aqueous binder solution having refractory properties is made to penetrate into the upper end of the tube, so that this binder permeates an area of this end over a height at least equal to the following height which the tube is intended to be engaged around the pouring nozzle of the first container.

This area is therefore made refractory, which allows it to be very resistant despite the absence of sintering in this area.

According to another advantageous version of the invention, the aqueous binder solution having refractory properties is made to penetrate into the lower end of the tube so that this binder permeates an area of this end over a height at least equal to the following depth which the tube is intended to be immersed in the liquid metal contained in the second container.

Thus, this part of the tube is not likely to be damaged in contact with the liquid metal and aggressive products which cover the surface of the latter. As a binder having the desired refractory properties, it is possible to use a phosphatic compound, boric acid, ethyl silicate and alkali silicates.

The best results are however obtained using aluminum monophosphate.

This binder can be penetrated into either end of the tube, by gravity, by dipping or by pressure injection.

• . la figure 1 est une vue schématique en élévation et en coupe longitudinale partielle d'une installation de fabrication d'un tube de coulée;
• . la figure 2 est une vue en coupe longitudinale d'un tube de coulée vertical muni d'un récipient permettant la pénétration par gravité d'un liant réfractaire dans l'extrémité supérieure du tube;
• . la figure 3 est une vue en coupe longitudinale d'un tube horizontal muni d'un récipient permettant la pénétration par gravité d'un liant réfractaire à l'une des extrémités du tube;
• . la figure 4 est une vue en coupe partielle à échelle agrandie d'un tube obtenu conformément à l'invention, engagé autour d'une busette de coulée, d'une matière étanche ou non;
• . la figure 5 est une vue en coupe partielle d'un tube dont l'extrémité inférieure trempe dans une solution de liant réfractaire;
• . la figure 6 est une vue en coupe partielle et à plus grande échelle, de l'extrémité inférieure d'un tube de coulée, conforme à l'invention;
• . la figure 7 est une vue en coupe longitudinale partielle de l'extrémité supérieure d'un tube de coulée, illustrant un autre mode d'introduction d'un liant réfractaire dans cette extrémité du tube;
• . la figure 8 est une vue en coupe longitudinale partielle de l'extrémité supérieure d'un tube de coulée, illustrant des moyens pour injecter sous pression un liant réfractaire dans cette extrémité du tube.

Other features and advantages of the invention will appear in the description below. In the appended drawings, given by way of nonlimiting example:

• . Figure 1 is a schematic elevational view in partial longitudinal section of an installation for manufacturing a pouring tube;
• . Figure 2 is a longitudinal sectional view of a vertical pouring tube provided with a container allowing the penetration by gravity of a refractory binder into the upper end of the tube;
• . Figure 3 is a longitudinal sectional view of a horizontal tube provided with a container allowing the penetration by gravity of a refractory binder at one end of the tube;
• . Figure 4 is a partial sectional view on an enlarged scale of a tube obtained according to the invention, engaged around a pouring nozzle, of a waterproof material or not;
• . Figure 5 is a partial sectional view of a tube, the lower end of which dips in a solution of refractory binder;
• . Figure 6 is a partial sectional view on a larger scale, of the lower end of a pouring tube, according to the invention;
• . Figure 7 is a partial longitudinal sectional view of the upper end of a pouring tube, illustrating another mode of introduction of a refractory binder in this end of the tube;
• . Figure 8 is a partial longitudinal sectional view of the upper end of a pouring tube, illustrating means for injecting under pressure a refractory binder into this end of the tube.

In the embodiment of FIG. 1, the installation for manufacturing a pouring tube comprises a frustoconical sleeve 1 perforated laterally and mounted in rotation about a horizontal axis XX 'and comprised between two rollers 2, 3 also frustoconical mounted in rotation around two axes YY 'and Z-Z'- parallel to the axis X-X'.

In the space between the perforated sleeve 1 and the rollers 2, 3, a frustoconical cost tube 4 is formed, from a pasty and aqueous mixture of refractory particles (silica, alumina, magnesia, etc.) and mineral or organic fibers, coated in an organic or inorganic binder.

• particules inorganiques réfractaires
• (silice et/ou alumine et/ou magnésie
• et/ou dolomie): 70 à 90% en poids;
• composés organiques en grains ou en
• fibres synthétiques et/ou naturels
• (par exemple fibres de cellulose): 0 à 20% en poids;
• fibres minérales (par exemple fibres
• de verre, de roche, de scories
• ou d'amiante): 0 à 20% en poids;
• liant organique: par exemple de la
• colle ou une résine phénol
• formaldéhyde: 2 à 10% en poids;
• fondants (par exemple oxyde
• de métaux alcalins ou
• alcalino-terreux): 0 à 10% en poids.

The composition of this mixture in the dry state is for example the following:

• refractory inorganic particles
• (silica and / or alumina and / or magnesia
• and / or dolomite): 70 to 90% by weight;
• organic compounds in grain or in
• synthetic and / or natural fibers
• (for example cellulose fibers): 0 to 20% by weight;
• mineral fibers (e.g. fibers
• glass, rock, slag
• or asbestos): 0 to 20% by weight;
• organic binder: for example
• glue or phenol resin
• formaldehyde: 2 to 10% by weight;
• fluxes (e.g. oxide
• of alkali metals or
• alkaline earth): 0 to 10% by weight.

This mixture is added before use of about 40 to 50% of water to obtain an easily formable slurry or paste between the rollers 2, 3 and the perforated sleeve 1. During the rotation of the latter, one sucks inside from the perforated sleeve 1 through the central pipe 5, the excess water contained in the pasty material of the tube 45. About 30 to 40% of water is thus extracted from this material.

After this operation, the frustoconical tube 4, partially dry, is externally surrounded by a rigid frame constituted for example by a sheet metal sleeve 6, as indicated in FIG. 2. Preferably, the angle of the frustoconical surface of the metal sleeve 6 is 0.1 to 10 ° greater than the angle of the frustoconical surface of the tube 4. This considerably facilitates the engagement of the tube 4 in the sleeve 6, while eliminating any risk of cracks.

According to the invention, after or during the aforementioned suction step and before carrying the tube 4 protected externally by the metal sheet 6, in the oven, the end 4a of the tube 4 which is intended is made to penetrate. to be placed under the pouring orifice of a metallurgical container, an aqueous solution 7 of a binder having, after hardening, refractory properties superior to those of the basic organic or inorganic binder which is contained in the assembly of the tube 4.

In the example of the embodiment according to FIG. 2, the refractory binder solution 7 is made to penetrate by gravity into the upper end 4a of the tube 4 arranged vertically, by means of a container 8 in the form of a crown, open towards the top in which the pierced bottom 8a is applied to the upper edge of the end of the tube 4.

The refractory binder 7 in aqueous solution can be a phosphoric compound, boric acid, ethyl silicate, a silica sol or alkaline silicates.

The best results have been obtained using aluminum monophosphate.

When the tube 4 is made from acidic refractory particles, such as silica, a solution containing 20 to 50% is preferably used (preferably this 40%) by weight of pure aluminum monophosphate, therefore acid.

When the tube is made from basic refractory particles, such as magnesia, an aqueous solution preferably comprising 20 to 50% by weight of aluminum monophosphate, neutralized by an alkaline oxide, is used.

In the case of the embodiment according to FIG. 2, the aqueous solution of refractory binder 7 penetrates by gravity into the end 4a of the tube 4. This penetration is possible because the material of the tube 4 has lost 30 to 40% of its weight of water during the aspiration step, so that this material is thus able to re-absorb an almost equivalent amount of water.

The speed of penetration of the refractory binder solution 7 into the end of the tube depends on its viscosity which is itself a function of the concentration of the solution.

In the case of a solution containing less than about 20% of aluminum monophosphate, the penetration of the solution is rapid. However, when the end 4a of the tube is saturated with water (after having absorbed 30 to 40% of water) the concentration of monophosphate is insufficient with regard to the refractory properties sought.

Furthermore, when the solution 7 contains more than approximately 50% of aluminum monophosphate, this solution is too viscous, so that it penetrates too slowly and to an insufficient depth from the end 4a of the tube.

The best results are obtained using a 40% by weight solution of pure or neutralized aluminum monophosphate. Under these conditions, the solution 7 penetrates into the end 4a of the tube over a depth p (see FIG. 4) at least equal to the height h according to which the end 4a of the tube 4 is intended to be engaged on the pouring nozzle. 9 of the first container.

There is thus obtained in the hatched area, shown in Figure 4 of the end 4a of the tube 4, an average concentration of aluminum monophosphate of between 5 and 10% by weight approximately. After steaming of the tube 4, the water contained in the latter is eliminated by evaporation and the basic binder contained in the whole of the tube as well as the binder introduced by the solution 7 harden.

When using the tube 4 manufactured in accordance with the invention, the refractory particles of the tube located in the area where they are exposed directly to the heat given off by the jet of metal passing through the tube, sintering, which makes it possible to maintain the mechanical cohesion of the tube beyond the decomposition or disintegration temperature of the base binder.

On the other hand, this sintering does not take place in the hatched zone of FIG. 4 which is protected from heat by the pouring nozzle 9. However, the cohesion of this zone is ensured thanks to the binder which is introduced therein by means of solution 7. This binder by hardening gives this zone refractory properties clearly superior to those of the material located under the latter. Thus, this zone exhibits remarkable thermal and mechanical behavior. As a result, the seal between the nozzle 9 and the end 4a of the tube 4 remains excellent, even after numerous successive clearances and engagements of the tube with respect to the nozzle 9. The life of the tube 4 is therefore considerably prolonged. .

The refractory binder solution 7 can also be introduced by gravity into the end 4a of a tube 4, arranged horizontally, as shown in FIG. 3. In this figure, the container 10 in the shape of a crown has a perforated side wall 1 Oa which is applied against the edge of the end 4a of the tube. This container 10 is supplied with solution 7 by a vertical funnel 11.

It is also advantageous to be able to improve the thermal and mechanical behavior of the lower end 4b of the pouring tube 4, which is intended to immerse in the liquid metal which is poured into the lower container. This result can be obtained as before, by penetrating into this end 4b of the tube 4 a solution of refractory binder 7, after the suction step of the process for manufacturing this tube.

In the example in FIG. 5, this solution 7 is penetrated by dipping the end 4b of the tube 4 in a container containing this solution 7.

The gravity penetration methods illustrated in FIGS. 2 and 3 can, of course, also be applied for the impregnation of the lower end 4b of the tube 4. Of course, the tramping method illustrated in FIG. 5 may also be suitable. for impregnating the upper end 4a.

Whatever the method used, it is necessary for the refractory binder solution 7 to penetrate into the end 4b of the tube, over a height h _i (see hatched part of FIG. 6), at least equal to the depth at which this end 4b of the tube is intended to immerse in the liquid metal which is contained in the lower container.

This impregnation of refractory binder gives this end 4b of the tube 4, sufficient mechanical and thermal properties to allow it to resist contact with liquid metal and aggressive products which cover the surface of this metal.

Of course, the invention is not limited to the examples which have just been described, and numerous modifications can be made to these.

Thus, the refractory binder solution 7 can also be made to penetrate into the end 4a of the tube 4, by means of a frustoconical container 12 fitted into the tube 4 and comprising a perforated side wall 13 which allows the solution 7 to pass through. .

Furthermore, the solution 7 can also be injected under pressure into the end 4a or 4b of the tube 4. Thus, in the case of the tube of Figure 8, the outer sheet 14of the latter comprises in the vicinity of the upper end 4a an annular bead 15 making it possible to form around the thermally insulating wall of the tube an annular space communicating with a lateral tube 16, through which the solution of refractory binder 7 can be injected under pressure, during the aspiration step. Pressure injection makes it possible to use binder solutions which are more viscous than the previous ones, and therefore more concentrated, which makes it possible to improve the refractory power of the ends 4a and 4b of the tube 4. Subsequently, the the aforementioned bead and a portion of the injection tube may serve as a neutral gas injector when using the tube in a steelworks.

In an alternative embodiment of the tube according to the invention, the refractory binder is distributed throughout the tube. In this case, it is possible to add the refractory binder at the start directly into the initial mixture. This solution is perfectly suited for use as a refractory binder, ethyl silicate, silica soils and boric acid.

Thus, ethyl silicate can be added to the initial mixture in alcoholic solution containing 28 to 40% by weight of Si0 ₂ .

The silica soils can be used in aqueous dispersion at 30 to 40% by weight of Si0 ₂ .

In these two cases, the binder is added to the mixture to obtain a final concentration of Si0 ₂ in the tube of between 0.1 to 10%.

Experience shows that when the tube is heated, the silica migrates to the surface, which is advantageous for obtaining refractory properties.

In the case of the use of boric acid as a binder, the preferred concentration of the latter in the tube is preferably between 0.1 and 13% by weight.

Claims (8)

1. Method for fabricating a casting tube (4) which is intended to be placed beneath the casting outlet of a metallurgical vessel and to be immersed in the molten metal bath which is poured into a second vessel placed beneath the first vessel, this method comprising the steps which consist in forming the tube (4) around a perforated sleeve (1) by means of an aqueous mixture of refractory particles in paste form, of fibers and of an organic and/or inorganic binder, in sucking the excess water of the mixture into the interior of the perforated sleeve (1 then in heating the tube (4) within an oven in order to evaporate the residual water and to allow the mixture to harden, characterized in that, after or during the water-suction step, there is introduced into the end (4a) of the tube (4) which is intended to be placed near the casting outlet of the first metallurgical vessel and/or into the end (4b) of the tube which is intended to di^p into the molten metal as it is being poured into the second vessel, an aqueous solution (7) of a binder endowed after hardening with higher refractory properties than those of the basis organic and/or inorganic binder wich is contained within the tube (4) as a whole.

2. Method in accordance with claim 1, the casting tube being intended to be engaged around the casting nozzle (9) which forms an extension of the casting.outlet of the first vessel, characterized in that the aqueous solution of binder (7) having refractory properties is introduced into the end portion (4a) of the tube (4) so as to ensure that this binder impregnates a zone of this latter over a height (p) at least equal to the height (h) at which the tube (4) is intended to be engaged around the casting nozzle (9) of the first vessel.

3. Method in accordance with claim 1, characterized in that the said aqueous binder solution (7) having refractory properties is introduced into the lower end (4b) of the tube (4) in such a manner as to ensure that this binder impregnates a zone of this latter over a height (h,) at least equal to the depth to which the tube (4) is intended to be immersed in the metal contained in the second vessel.

4. Method in accordance with either of claims 1 or 3, characterized in that the binder is introduced into the interior of the tube (4) in the form of an aqueous solution containing approximately 20 to 50% by weight of phosphate compound.

5. Method in accordance with any one of claims 1 to 4, characterized in that the aqueous binder solution (7) is introduced into one end and/or the other end (4a, 4b) of the tube (4) under the action of gravity by means of a container (8, 10) applied against the end of the tube (4) and containaing the said solution (7).

6. Method in accordance with any one of claims 1 to 4, characterized in that the aqueous binder solution (7) is introduced into one end and/or the other end (4a, 4b) of the tube (4) by dipping in a vessel containing the said solution (7).

7. Method in accordance with any one of claims 1 to 4, characterized in that the aqueous binder solution (7) is introduced into one end and/or the other end (4a, 4b) of the tube (4) by injection of the said solution (7) under pressure and/or a partial vacuum by means of a nozzle (16) connected to the wall of the tube (4) in leak-tight manner after or during the suction step.

8. Method in accordance with any one of claims 1 to 7, in which a frusto-conical tube is formed and this latter is engaged within a frusto-conical metallic sleeve, characterized in that the angle of the frusto-conical surface of the metallic sleeve exceeds by 0.1 to 10° the angle of the frusto-conical surface of the tube.

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