EP0065514A1

EP0065514A1 - Thermally insulating casting tube for metallurgic container.

Info

Publication number: EP0065514A1
Application number: EP80902236A
Authority: EP
Inventors: Jean-Charles Daussan; Gerard Daussan; Andre Daussan
Original assignee: Daussan SAS
Current assignee: Daussan SAS
Priority date: 1980-11-26
Filing date: 1980-11-26
Publication date: 1982-12-01
Also published as: US4660808A; CA1183325A; ZA817593B; ES8301131A1; AU544222B2; MX157119A; ATE13829T1; DE3070789D1; WO1982001836A1; AU7717281A; DE65514T1; ES507420A0; EP0065514B1

Abstract

A heat insulating casting tube is disposed between the outlet orifice of a first metallurgical vessel and a second metallurgical vessel. One end of the casting tube has a removable and substantially leaktight engagement about a casting nozzle or an adapter forming an extension of the nozzle of the first vessel. The casting tube is formed of a material sinterable under the action of the heat of the liquid metal as it flows in the tube. A ring of refractory material is disposed on the tube end engaged on and surrounding the lateral surface of the casting nozzle or adapter. The internal surface of this ring is shaped as the lateral surface of the casting nozzle or adapter and has a substantially leaktight engagement with that lateral surface. The height of the ring is such that its bottom edge is located above the zone in which the liquid metal which is poured into the tube would be liable to come into contact with the internal surface of the tube.

Description

"Hermetically sealed t pipe for metallurgical container"

The present invention relates to a thermally insulating pouring tube intended to be placed between the pouring orifice of a first metallurgical container such as a ladle and a second metallurgical container such as a tundish.

Known pouring tubes are produced in different categories of materials.

In one of these categories, the tube material is highly refractory such as silica, magnesia, zirconia, and isostatic pressed carbon.

These materials have the advantage of having remarkable mechanical and heat resistance, so that the tubes produced in such materials have a very long service life.

The disadvantages of these materials are however numerous.

Firstly, due to their poor thermal insulating power and / or to avoid their bursting, these tubes require long and costly preheating before casting the liquid metal, to limit the risks of solidification of this metal in contact with their wall, this solidification can cause a complete sealing of these tubes. Secondarily, these tubes are heavy, therefore difficult to handle and are very expensive.

To remedy the aforementioned drawbacks, the applicant has described in its French patent No. 2 333 a pouring tube made of thermal insulating material consisting of refractory inorganic particles (silica, alumina, magnesia) possibly added with mineral or organic fibers, these particles and fibers being coated in an organic or inorganic binder.

Because of its remarkable insulating properties of this material, such tubes require no preheating. In addition, these tubes are light and therefore easy to handle and inexpensive.

During the casting of the liquid steel, the organic constituents of the material of these tubes decompose but the cohesion of the tube is maintained as a result of the sintering of the inorganic particles, under the effect of the heat given off when the liquid metal passes through it. inside the tube. The decomposition of organic constituents and the sintering of inorganic particles give the material a porous structure with a high power of thermal insulation.

However, at the upper end of these tubes by which they are engaged in the nozzle of the ladle, the aforementioned sintering does not take place because the material of the tube is at this location, not in direct contact with the liquid metal spray.

Therefore, at this end, the material tends to crumble quickly, so that at the end of casting, the seal is no longer formed between the pouring tube and the pouring nozzle on which its end is engaged.

This leakage then risks allowing the introduction of air inside the tube, by suction effect, which is likely to form inclusions of oxides within the metal. As a result, such pouring tubes generally become unusable after a single casting operation. The finding of this drawback is the basis of the present invention.

The object of this invention is therefore to remedy this drawback, by creating a pouring tube having all the advantages of the tubes described in the patent. French n ° 2333 599 while having a considerably extended lifespan.

The pouring tube covered by the invention is intended to be placed between the orifice of a first metallurgical container and a second metallurgical container, one end of this pouring tube being intended to be engaged in a removable and substantially watertight on the pouring nozzle or an adapter extending the nozzle of the first container, this pouring tube being made of a material constituted by inorganic particles, erentually added with fibers, coated in a binder, these inorganic particles being sinterable under the effect of heat of the liquid metal passing through this tube.

According to the invention, this pouring tube is characterized in that its end intended to be engaged on the pouring nozzle comprises a ring of refractory material, the internal surface of this ring being intended to come into direct contact with the nozzle of couiee or with the adapter extending the nozzle. This refractory ring thus mechanically reinforces the part of the pouring tube which does not undergo the sintering effect indicated in the introduction to this description.

Thanks to this refractory ring, the seal between the tube and the pouring nozzle remains excellent after several successive casting operations.

In addition, this refractory ring does not reduce the insulating properties of the pouring tube and does not entail any risk of solidification of the liquid metal, since this ring does not come into direct contact with this metal.

According to an advantageous version of the invention, the height of the above-mentioned refractory ring is at least equal to the distance over which the end d tube is intended to be engaged on the pouring nozzle of the first metallurgical container.

The seal between the pouring tube and the nozzle are thus maintained in excellent conditions. According to a preferred version of the invention, the pouring tube is produced by molding and the ring of refractory material is fixed to the material of the wall. of the tube, during this molding.

The fixing of the refractory ring to the tube can thus be carried out without any additional difficulty.

Since the end of the pouring tube opposite the pouring nozzle is generally intended to immerse in the molten metal which is poured into the second metallurgical vessel, it is advantageous that this end of the pouring tube also includes a refractory ring.

Thus, this end of the pouring tube is not liable to wear out by melting on contact with the liquid metal, and therefore, the life of this tube is further extended.

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

In the accompanying drawings, given by way of nonlimiting examples: - Figure 1 is a view in partial longitudinal section, of the bottom of a ladle and a tundish placed under the latter, a conformal pour tube the invention being disposed under the outlet nozzle of the ladle, - Figure 2 is a partial longitudinal sectional view, on a large scale, showing the upper end of the pouring tube, engaged on the pouring nozzle, as well as the jet of liquid metal passing in this tube,

FIGS. 3 to 7 are views in partial long tudinal section, showing various variants of the invention,

FIG. 8 is a view in longitudinal section of the lower end of an advantageous version of the pouring tube according to the invention, immersed in the liquid metal contained in the pouring distributor,

- Figure 9 is a longitudinal sectional view of a pouring tube engaged on an adapter for another nozzle with drawer and Figure 10 is a / Variant in longitudinal section.

In the embodiment according to FIG. 1, the bottom of the ladle 1 includes a pouring nozzle 3 made of a highly refractory material such as silica, refractory brick magnesia or zirconia. This pouring nozzle 3 is disposed above a pouring distributor 4. Around this nozzle 3 is engaged in a removable manner, the upper end 5a of a pouring tube 5, slightly truncated, the lower end of which is intended to be immersed in the liquid metal which is introduced into the tundish 4.

The means for removable attachment of the coulter tube 5 to the nozzle 3 are not shown. These means can be of the kind described in French patents No. 2,333,599 and No. 77 35,874 of 11/29/1977. The pouring tube 5 comprises an outer protective sleeve 6 made of metal sheet, for example of steel, which surrounds an inner wall 7 made of a thermally insulating and light material. This material consists of inorganic particles (silica, alumina, magnesia), added with inorganic fibers, coated in an organic binder such as a synthetic resin or an inorganic binder. The composition of this material is such that the inorganic particles sinter under the effect of the heat given off by the molten metal which is poured into the tube, which makes it possible to maintain the cohesion and the insulating properties of this material, despite the decomposition of the organic components thereof. According to the invention, the end 5a of the tube 5 engaged on the pouring nozzle 3 comprises a ring 8 of refractory material, the internal surface 8a of this ring being in direct contact with the casting nozzle e 3. The refractory material of the ring 8 is of the same nature as that of the nozzle 3. It can be, for example, silica, magnesia, refractory brick, isostatically pressed carbon or chamotte. These materials all have the advantage of having excellent mechanical and thermal resistance. In addition, they have a very high dimensional stability, so that it is possible to obtain a very precise adjustment of the ring 8 on the nozzle 3.

In the embodiment according to FIGS. 1 and 2, the height of the refractory ring / is greater than the distance over which the end 5a of the tube 5 is engaged on the pouring nozzle 3.

In addition, the thickness of the wall of the refractory ring 8 is substantially equal to the thickness of the wall 7 of the tube 5, so that the inner Sa and outer surfaces of the ring 8 are located substantially in the extension inner 7a and outer surfaces of the wall 7 of the tube 5.

The thermally insulating wall 7 is obtained by molding in a mold, the outer wall of which is formed by the sheet 6. This molding makes it possible to obtain direct adhesion of the material of the wall 7 to the sheet 6. In addition, the direct connection between the material of the wall 7 and the refractory ring 3 can also be obeyed during this molding. However, other means of fi xati on the ring 8 can be provided for than the sheet 6 and / or to the insulating wall 7, such as screws, cement or glue. In the variant embodiment of the figure, the contact surface between the refractory ring 9 and the insulating material constituting the wall 7 of the pouring tube comprises an annular recess 10. The ring

9 is thus fitted onto the wall 7, which improves the mechanical connection between this wall 7 and the ring

9 obtained during molding. In addition, this annular step 10 makes it possible to maintain a certain thermal insulation in the part 7b of the wall 7.

In the version shown in the figure of the wall 4, the thickness / of the ring 11 is less than that of the wall 7 of the. tube, the inner surface 11a of this ring 11 being disposed substantially in the extension of the internal surface 7a of the wall 7. This ring 11 is thus entirely embedded in an annular recess 7c formed at the end of the tube. This arrangement is favorable as regards the solidity of the fixing of the ring 11 to the wall 7 and the thermal insulation in line with the ring 11 in the part 7d.

In the embodiment of FIG. 5, the refractory ring 12 has an internal diameter smaller than the internal diameter of the tube and the external surface 12a of this ring is arranged in the extension of the internal surface 7a of the tube. The fixing of this ring 12 in the tube is ensured by the interlocking which results from the taper of the outer surface

7a 12a of the ring 12 and of the inner surface / of the tube.

This fixing can possibly be reinforced by gluing or other suitable mechanical means.

In the variant of Figure 6, the ring re fraction 13 has an outside diameter greater than the inside diameter of the tube and this ring is partly embedded in an annular shoulder 13a formed in the wall 7. In the embodiment of FIG. 7, the refractory ring 14 presents at the upper part of its inner surface an annular widening 14a, receiving the free end of the nozzle 3. This arrangement improves the seal between the upper part of the tube and the nozzle 3. In addition, the shoulder 14b constitutes a stop which ensures perfect axial positioning of the tube with respect to the nozzle, avoiding any risk of relative jamming between the nozzle and the ring 14. The above-mentioned embodiments have the following technical advantages in common:

Firstly, given the mechanical properties of the refractory material constituting the rings 3, 9, 11, 12, 13 and 14, it is possible to obtain a very precise adjustment between the inner surface of these rings and the outer surface of the nozzle 3.

On the other hand, given the high abrasion resistance of these rings, a perfect seal between them and the nozzle 3 is maintained even after several successive placement of the tubes on the nozzle.

During casting, the rings according to the invention undergo no chemical transformation. generally In addition, since these rings are made of a refractory material of the same nature as that of the nozzle 3, these rings undergo thermal expansion comparable to that of the nozzle 3. so that no play is formed between these rings and the nozzle. The junction thus remains perfectly sealed and any possible introduction of air inside the tube is avoided. and any risk of oxidation of the liquid metal.

During casting, the diameter of the liquid metal jet 15 (see FIG. 2) which flows from the nozzle 3 is braked due to the gradual narrowing of the inside diameter of the tube 5, which results in a widening of the jet 15 to its upper part 15a. The contact between the jet of liquid metal 15 and the wall of the tube 5 causes sintering of the material constituting this wall. This sintering maintains the mechanical cohesion of this material during casting. This sintering does not however take place in the zone 16b of the wall 7 close to the nozzle 3, because the latter is not in direct contact with the metal jet 15, as can be seen in FIG. 2. This zone 16b thus tends to crumble due to the decomposition of the binder under the effect of heat. Thus, in the absence of the refractory ring 3, at the end of casting, the zone 16b of the wall 7 of the tube 5 would be completely decomposed and this would necessarily result in a significant annular clearance between the upper part of the wall 7 of the tube and the nozzle 3. This play would thus allow the introduction of air inside the tube and consequently, the oxidation of the liquid metal, so that this tube would no longer be usable for a new casting. In the case of the invention, the decomposition of the zone 16b of the wall 7 of the tube 5 does not cause any drawback, since the ring 8 ensures at the end of casting, as at the beginning of it, a perfect seal between the nozzle 3 and the tube 5. In addition, at the end of casting, the part of the wall 7 located below the zone 16b remains perfectly coherent and retains a high power of thermal insulation due to the porous structure obtained by sintering .

Thus, the tube according to the invention remains useful. readable for several successive flows.

When the end of the tube 5 is intended to immerse in the liquid metal, which is poured into the tundish 4, the outer sheet 6 melts in contact with the liquid metal and the same applies to the material of the wall 7 of the tube. This can also prevent the reuse of the pouring tube 5.

To remedy this problem, it is advantageous to provide the free end of the tube 5 with another ring 16 made of refractory material resistant to contact with liquid metal 17, as shown in FIG. 8.

The height of this ring 16 corresponds at least to the depth of immersion of the end of the pouring tube in the metal 17 contained in the tundish distributor.

In the embodiment shown, the thickness of the wall of this ring 16 is substantially equal to the thickness of the wall 7 of the tube, plus that of the sheet 6. This sheet 6 completely covers the wall 7 of the tube and stops at the level of the ring 16 to avoid direct contact with the liquid metal 17.

The ring 16 can be fixed to the wall 7 of the tube 5 during the molding of this wall, as in the case of the upper rings shown in FIGS. 1 to 7. The fixing of this ring 16 to the wall 7 is improved when the contact surface of this attachment has an annular recess 16a as shown in FIG. 8.

Thanks to the refractory ring 16, the end of the tube 5 does not risk being damaged in contact with the liquid metal 17, and therefore, this tube can be reused for several successive castings.

Of course, the invention is not limited to the examples which have just been described and it is possible to bring numerous modifications to these without departing from the scope of the invention.

Thus the invention can also be applied to the case where an adapter 18 is interposed between a short nozzle 19, and the pouring tube 5, as indicated in FIG. 9. This nozzle 19 is part of the drawer 20 of a system of 'opening and closing called "drawer nozzle" of the orifice of a ladle. In this case, the adapter 18 made of refractory material has at its upper part an annular cavity 21 which receives the end of the nozzle 19. The frustoconical lower end 18a of the adapter 18 is nested in the interior surface 11a of a refractory ring 11.

In this embodiment, the refractory ring 11 plays the same role with respect to the adapter 13 as with respect to the pouring nozzle 3 in the case of the preceding embodiments.

This adapter 18 is necessary in all cases where the pouring nozzle is too short. This adapter 18 sometimes also acts as a box for collecting the gases intended to be blown into the liquid steel.

In addition, the shape and method of attachment of the upper refractory ring can be modified to suit all possible shapes of nozzles, provided that the inner surface of the ring is in direct contact with the outer surface of the nozzle.

Likewise, the shape and the method of fixing the lower year 16 can be modified, provided that the liquid metal contained in the tundish does not come into direct contact with the insulating wall 7 and with the external sheet 6.

For ease of assembly and to prevent the lower ring from deteriorating during transport, it can be incorporated into the sheet 6. The molten steel coming from in contact with the sheet 6 melts the latter over the entire immersion depth in the steel bath. Therefore, it is advantageous to incorporate this ring high enough in the outer sheet 6 so that the lower part of this non-molten sheet can hold the ring in place. Of course, the pouring tube according to the invention can be used for other metallurgical vessels than the ladles and the tundish. On the other hand, it is advantageous that the outer sheet

6 of the pouring tube 5 comprises an annular bead 22 projecting outwards (see FIG. 2) defining an empty annular space 23 between the sheet and the thermally insulating inner wall 7. This bead 22 serves to hold, by means of a support 24, the tube 5 in abutment against the external surface of the nozzle 3.

In the embodiment shown in FIG. 2, the empty annular space 23 communicates with a horizontal tube 25 connected to a source of non-oxidizing or inert gas such as argon. This bead 22. is preferably arranged opposite the non-sinterable zone 16b adjacent to the annea 8 of the wall 7, which remains porous. Thus, the gas introduced into the annular space 19 diffuses through the wall 7, in a regular manner, all around the latter and penetrates the interior of the tube 7, providing the liquid metal with additional protection against the oxidation.

In the embodiment of FIG. 10, the external sheet 6 has at its upper part a second annular bead, constituted by a winding 26 from the edge of the sheet towards the inside. This winding 26 is supported on the adjacent end of the insulating wall 7. This winding 26 defines an annular duct communicating with an intake manifold 28 of inert gas such as argon. Winding 26 presents a series of openings 27 directed radially towards the axis of the tube 5.

The advantage of this arrangement is as follows: since the ring 8 is made of hard refractory material, this material is liable to flake when it is brought too suddenly into contact with the refractory and hard material of the same kind as the nozzle 3 or the extension 19. The scales thus formed can generate air inlets inside the pouring tube 5, by suction (Venturi effect). The winding 26 provided with openings 27 makes it possible to produce jets of argon or other inert gas all around the nozzle 3, thus avoiding any penetration of air inside the tube 5.

Claims

1. Thermally insulating pouring tube (5) intended to be placed between the pouring orifice of a first metallurgical container (1) and a second metallurgical container (4), one of the ends (5a) of the tube being intended to be removably and substantially sealed on the pouring nozzle (3) or on an adapter (18) extending the nozzle (19) of the first container (1), this pouring tube being made of a material by inorganic particles possibly added with fibers, coated in a binder, these inorganic particles being sinterable under the effect of the heat of the liquid metal passing through this tube, characterized in that the end (5a) of the tube intended to be engaged on the pouring nozzle (3) comprises a ring (8, 9, 11, 12 13, 14) made of refractory material, the internal surface of this ring being intended to. come into direct contact with the casting nozzle (3) or with the adapter (18) extending the nozzle (19).

2. pouring tube according to claim 1, characterized in that the height of the ring (8, 9, 11,

12, 13, 14) in refractory material is at least equal to the distance over which said end (5a) of the tube (5) is intended to be engaged on said pouring nozzle.

3. pouring tube - according to any one of claims 1 or 2, the tube being produced by molding, characterized in that the ring (8, 9, 11, 12, 13, 14) of refractory material is fixed to the material of the wall (7) of the tube (5), during the molding of the latter.

4. pouring tube according to any one of claims 1 to 3, characterized in that the thickness of the wall of the refractory ring (8, 9, 11) is substantially equal to the thickness of the wall ( 7), the inner and outer surfaces of the ring being located substantially in the extension of the inner and outer surfaces of the wall (7) of the tube.

5. pouring tube according to claim 4, characterized in that the contact surface between the refractory ring (9) and the wall (7) of the tube comprise at least one annular recess (10).

6. pouring tube according to any one of claims 1 to 3, characterized in that the thickness of the refractory ring (11) is less than that of the wall (7) of the tube, the inner surface (11a ) of this ring being disposed substantially in the extension of the inner surface (7a) of the tube.

7. pouring tube according to any one of claims 1 to 3, characterized in that the internal diameter of the refractory ring (12, 13) is less than the internal diameter of the tube.

8. pouring tube according to claim 7, characterized in that the outer surface (12a) of the ring (12) is arranged in the extension of the inner surface (7a) of the tube.

9. pouring tube according to claim 7, characterized in that the outside diameter of the refractory ring (13) is greater than the inside diameter of the tube and in that this ring is partly embedded in an annular shoulder (13a) formed in the wall (7) of the tube.

10. pouring tube according to any one of claims 1 to 9, characterized in that the refractory ring (14) has at the upper part of its inner surface an annular widening (14a) intended to receive the free end of the pouring nozzle (3).

111. Pouring tube conforming to any one of claims 1 to 10, the end of this tube opposite the nozzle (3) of the first container (1) being intended to immerse in the liquid metal (17) which is poured into the second container (4), characterized in that that said end of the tube also includes a refractory ring (16).

12. pouring tube according to claim 11, characterized in that the height of the ring (16) is at least equal to the depth of immersion of the tube (5) in the liquid metal (17) contained in the second pouring container (4).

13. pouring tube according to any one of claims 11 or 12, characterized in that the thickness of the ring (16) is substantially equal to the thickness of the wall (7) of the tube (5).

14. pouring tube according to any one of claims 1 to 13, and comprising an outer metal protective sheet, characterized in that this sheet has an annular bead (18) projecting outward and defining a space empty annular (19) between this sheet and the inner wall (7) of the tube, this space communicating with a tube (21) connected to a source of non-oxidizing or inert gas.

15. pouring tube according to claim 14, characterized in that said annular bead (18) is adjacent to the refractory ring (8).

16. pouring tube according to any one of claims 14 or 1 5, characterized in that the outer sheet (6) has at its upper part a bead ring formed by a winding (26) of the edge of the sheet this winding being in abutment on the adjacent end of the wall (7) of the tube and defining in its interior an annular joint communicating with an inert gas intake manifold, this winding (26) having a series of openings ( 27) directed radially towards the axis of the tube.