EP0102292B1 - Tubes for pouring molten metal - Google Patents

Abstract

A tube for continuous casting of molten metal is composed of a thin sheet-metal cladding and of an internal lining of heat-insulating material which is sinterable at the casting temperatures involved. The upper end of the casting tube is attached in air-tight manner to the discharge outlet of a first vessel for containing molten metal. The lower end of the casting tube dips into the molten metal of a second vessel located downstream with respect to the first vessel. In conjunction with the sheet-metal cladding, the casting tube comprises a tubular reinforcement member embedded within the lining material. The reinforcement member extends to the full depth of that portion of the casting tube which is in contact with the molten metal.

Description

The present invention relates to pouring tubes for the conduct of liquid metal in a transfer operation thereof.

All pouring tubes made of insulating material, in particular those described in French patents Nos. 2,333,599 and 2,433,995, have experienced certain drawbacks and limitations which the present invention proposes to remedy.

In particular, it has been observed that the embodiments described in FIG. 5, 6 and 7 of French Patent No. 2,333,599 exhibit, at the start of casting, a lack of air tightness of the tube. Indeed, during the passage of steel through the tube, the interior thereof is subjected to a succession of pressures and depressions. When the inside of the tube is under vacuum, these previous embodiments allow air to pass through to the steel, through the pores of the insulating material and the holes in the perforated reinforcement, which can adversely affect the purity of the material. steel at the start of casting.

The embodiments described in Figs. 1, 3 and 4 for example of patent N ° 2 333 599 do not have this characteristic because of the continuous external metallic envelope of the pouring tube, on the other hand when the end of this tube plunges into the liquid steel, the outer sheet which comes into contact with it is brought to a temperature such that it melts or loses all mechanical strength. During the passage of the steel in the tube, the overpressure existing in this tube often causes a rupture of the entire submerged portion thereof whose insulating material is not sufficiently resistant. The debris thus produced can create slag in the steel; moreover, the steel jet can thus be brought into contact with air.

To remedy this situation, it has also been proposed to mount a sleeve outside the submersible end of the pouring tube (Fig. 1 of French patent No. 2,433,995, this reinforcement sleeve being directly subject on the outer sheet of the tube. This is to prevent the liquid steel from destroying the outer metallic envelope of the submersible part of the tube. If this protection often proves effective, it nevertheless has the disadvantage of increasing the outside diameter of the end of the tube, the weight, the price, and constitute a constraint for the user of the tube when, for certain reasons, the sleeve must be put in place at the places of use of the tube.

To remedy this drawback, those skilled in the art are led, logically, to increase the resistance of the insulating material by increasing its thickness. This obviously has the drawback of increasing the weight and the price of the tube and of decreasing its handling. The logic would also like that one increases the thickness of the sheet or its resistance to fusion, but one would run up against the same disadvantages.

The present invention aims to eliminate the drawbacks listed above.

According to the invention, the pouring tube composed of a thin external metallic casing and an internal coating of sinterable insulating material at the temperatures in play, its upper end being fixed in a substantially sealed manner to the outlet orifice of a liquid metal container, the lower end of the pouring tube immersed in the liquid metal of a second container located downstream from the first, is characterized in that it comprises, in combination with the external metal envelope, a reinforcement of tubular reinforcement embedded in the coating material, this reinforcement extending in height over the part of the tube in contact with the liquid metal, substantially from the lower edge of the sintered tube immersed in the bath of liquid steel up to a region above the level of this liquid.

Experience shows this unexpected result that this reinforcement is capable of preventing the submerged part of the tube from breaking in contact with the ambient liquid metal, when the external envelope has disappeared or lost its resistance.

Preferably, the reinforcing reinforcement consists of a metal sleeve associated with anchoring means, such as a perforated sheet or a mesh.

The reinforcing reinforcement may also consist of a layer of a mechanically resistant material distinct from the coating material, such as woven fibers - or not, or a tubular layer of mineral and / or organic grains joined together by a binding, organizing - or not.

For its part, the inner coating of the tube can be an acid or basic sinterable material.

The pouring tube thus arranged can receive various applications. Thus, it can be mounted under the outlet orifice of a container for molten metal such as a ladle or a transfer container and be part in particular of a drawer system which can be moved transversely relative to the axis of the tube.

The tube can also constitute a removable nozzle engaged at the top of a pouring tube proper and connecting the latter, in leaktight manner, to the orifice of the casting container located upstream.

Other characteristics of the invention will also result from the description below.

• La figure 1 est une vue en coupe axiale d'un système de coulée comportant trois tubes de coulée ou busettes conformes à l'invention.
• La figure 2 est une vue à plus grande échelle de la partie comprise entre les lignes X-X₁ et X₂-X₃ d'un élément de la figure 1.
• La figure 3 est une vue en coupe axiale à plus grande échelle d'un élément de la figure 1.

In the appended drawings, given by way of nonlimiting examples:

• Figure 1 is an axial sectional view of a casting system comprising three pouring tubes or nozzles according to the invention.
• Figure 2 is an enlarged view of the part between lines XX ₁ and X ₂ -X ₃ of an element of Figure 1.
• FIG. 3 is a view in axial section on a larger scale of an element of FIG. 1.

In FIG. 1 which represents a complete continuous casting system, we see at 10 the base of the ladle, lined with its refractory lining 12, at 22 the sinterable insulating refractory and at 23 the seat brick of the fixed nozzle 21.

The orifice of the nozzle 21 can be concealed by a sliding shutter, the moving plate of which is seen at 30 and the fixed plate at 35, both pierced with an orifice for the passage of the metal. The shutter is in the closed position in FIG. 1.

Under this shutter is placed the pouring tube 3, which can slide transversely to its axis at the same time as the plate 30 and a removable connection nozzle 19 mounted in leaktight manner thanks to a refractory cement joint between the plate 30 which allows its mounting and the upper part of the tube 3 where it is engaged. The nozzle 19 is supported, in the example shown, on an inner hoop 17, metallic and / or refractory formed at the top of the pouring tube 3.

All of these moving parts are guided in transverse sliding relative to the axis of the tube 3 by a support 8 movable in translation (see the arrows), itself guided by fixed ears 8a. All of these parts constitute a drawer system.

The tube 3 is located between the ladle 10 and the tundish 13, commonly called "tundish". This in turn carries a pouring tube 4 - or nozzle - which can also belong to a drawer system and which is located between the distributor 13 and the continuous casting mold 15.

In the example considered, the invention is applied both to the pouring tubes 3 and 4 and to the connection nozzle 19.

The tubes 3 and 4 are thus constituted respectively by a thin outer metal casing 1 and 2 whose thickness is of the order of a millimeter. In the case of the pouring tube 3, the thin metal casing 1 has an annular boss 7 which comes to bear on the sliding support 8.

The metal envelopes 1 and 2 are lined inside a coating of sinterable insulating material 3a and 4a, acid or basic, the density of which can vary from 0.7 to 2.

• - Si0₂ ................... 80 à 95%
• - CaO................... 0 à 2%) à l'état de fibres
• - Al₂0₃ ................. 0 à 2%) inorganiques
• - liant tel que:
• . phénol-formol,
• . urée-formol ou
• . résine synthétique.. 0,5 à 3%
• - fibres organiques... 0 à 3%
• - eau résiduelle......... traces,
  la perte au feu du matériau étant avantageusement
  inférieure à 6%.

An acid formula can contain:

• - Si0 ₂ ................... 80 to 95%
• - CaO ................... 0 to 2%) in the form of fibers
• - Al ₂ 0 ₃ ................. 0 to 2%) inorganic
• - binder such as:
• . phenol-formaldehyde,
• . urea-formalin or
• . synthetic resin .. 0.5 to 3%
• - organic fibers ... 0 to 3%
• - residual water ......... traces,
  the loss on ignition of the material being advantageously
  less than 6%.

• . MgO....................... 60 à 90%
• . CaO........................ 0 à 3%
• . Si0₂........................ 0 à 20%
• Fe₂0₃ ...................... 0 à 4%
• . Liant (comme précédemment)... 0,5 à 3%
• . Fibres organiques........... 0 à 3%
• . Eau résiduelle,
  la perte au feu étant avantageusement inférieur à 6%.

A basic formula which may be suitable for coating 3 is as follows:

• . MgO ....................... 60 to 90%
• . CaO ........................ 0 to 3%
• . Si0 ₂ ........................ 0 to 20%
• Fe ₂ 0 ₃ ...................... 0 to 4%
• . Binder (as before) ... 0.5 to 3%
• . Organic fibers ........... 0 to 3%
• . Residual water,
  the loss on ignition being advantageously less than 6%.

According to the invention, there is incorporated, within the coatings 3a and 4a of the tubes 3 and 4, a reinforcing reinforcement 5 and 6 respectively which is combined in its action with the external metallic envelope 1 or 2 of the tube considered.

The frame 5 or 6 can preferably be made using a steel sheet about 2 mm thick provided with anchoring means; it may, in particular, include perforations with a diameter of 10 mm, themselves spaced 5 mm apart. It can also be a wire mesh.

The reinforcement 5 or 6 can also be produced by means of a layer of fibers constituting a nonwoven and / or of a tubular layer of mineral and / or organic grains joined together by an organic or mineral binder. The reinforcement considered can also be made by means of a fabric of fibers, for example mineral fibers. In all cases, the reinforcement must be mechanically resistant with respect to the material of the coating of the tube within which it is incorporated.

The thickness of the armature is advantageously between 0.3 and 15 mm depending on the thickness of the coating 3a or 4a of the pouring tube.

For the two tubes 3 and 4, the height of the reinforcements 5 and 6 is such that it reaches - or preferably exceeds - the upper level of the cast metal coming into contact with the outside of the tube.

According to the advantageous embodiment described, the removable interior nozzle 19 of the pouring tube 3 is also produced in accordance with the present invention and comprises (FIG. 3) an internal reinforcement frame 31 similar to the frames 5 and 6 and which extends over the entire height of this nozzle. The nozzle 19 is thus composed of a solid and / or perforated metal envelope 20 lined internally with sinterable refractory insulating material 19a similar to the coatings 3a and 4a and in which the frame 31 is embedded.

In FIG. 1, the distributor 13 is shown with liquid metal 14 filling it up to level NN1. The continuous casting ingot mold 15 is shown with its metal ingot 16 being solidified.

The mode of action of the means provided for the invention, as shown by experience, is the following (see FIG. 2).

Reference will be made to the case of the tube 3, that of the nozzle 4 being identical and the operating conditions being fairly similar for the nozzle 19.

In the part of the tube 3 immersed in the steel bath, the tubular region 26 of the coating 3a located behind the thin outer metal casing 1 can only sinter when the corresponding part of this metal casing 1 has melted approximately along the line 1 b located near level N-N1.

The face 25 corresponding to the lower edge of the sintered tube freely because it plunges unhindered into the bath of liquid steel 14.

The inner face 24 of the pouring tube, which is substantially in contact with the metal jet, progressively sintered during the sequential casting (s) until the sintering reaches the sintered part 26. This progressive sintering of the mass of the coating 3a is only possible thanks to the internal frame 5 which while strengthening the plunging part of the tube allows it to undergo this transformation without risk of rupture.

Figure 1 shows the pouring tubes 3 and 4 just before the lower part of their metal casing 1 and 2 has melted.

When the part of the metal casing has melted along line 1b, the sintering process does not generally reach a sufficient degree of progress at this time so that the plunging end of the tube, assumed to be homogeneous, can withstand the effect of internal pressure and turbulence of liquid steel, which occur at this location.

Precisely, during this period of time, the reinforcing reinforcements, such as 5, 6 or 31, embedded in the sinterable material, provide the necessary relay to allow the completion without breaking of the sintering process. The cutting of the plunging end of the tube which normally occurred along line 1b is then eliminated, which avoids any contact of the metal with the ambient air.

Of course, the reinforcement provided by the invention, while remaining coaxial with the pouring tube, must be adapted to the shape of the latter.

Claims (9)

1. Casting tube (3,4,19) composed of a thin external metal jacket (1, 2, 20) and of an internal lining (3a, 4a, 19a) of heat-insulating material which is sinterable at the temperatures involved, its upper end being attached in an air-tight manner to the discharge outlet of a vessel for containing molten metal (10, 13), the lower end of the casting tube (3,4,19) being immersed in the molten metal of a second vessel (13, 15) located downstream with respect to the first, characterized in that it comprises, in conjunction with the external metal jacket (1, 2, 20), a tubular reinforcement member (5, 6, 31) which is embedded within the lining material; this reinforcement member extends upwards along that portion of the tube which is in contact with the molten metal, substantially from the bottom edge of the sintered tube which dips in the molten steel bath to a region located above the level (NNI) of this molten steel.

2. Casting tube in accordance with claim 1, characterized in that the reinforcement member (5, 6, 31) is constituted by a metallic sleeve associated with anchoring means such as a perforated sheet-metal element or a wire-mesh element.

3. Casting tube in accordance with claim 1, characterized in that the reinforcement member is constituted by a layer of material which has high mechanical strength and is different from the lining material, such as woven or nonwoven fibres, or a tubular layer of mineral and/or organic particles bonded together by means of a binder which may or may not be an organic binder.

4. Casting tube in accordance with one of claims 1, 2 or 3, characterized in that the sinterable heat-insulating material of the internal lining (3a, 4a, 19a) is acid, has a density within the range of 0.7 to 2 and corresponds to the following composition:

-Si0₂..............80 to 95 %

- CaO............... 0 to 2 %) in the state of

- Al₂0₃............. 0 to 2 %) inorganic fibres

- binder such as:

. phenol-formol,

. urea-formol,

. synthetic resin... 0.5 to 3 %

- organic fibres.... 0 to 3 %

- residual water,
wastage of the material by burning being advantageously less than 6 %.

5. Casting tube in accordance with one of claims 1, 2 or 3, characterized in that the sinterable heat-insulating material of the internal lining (3a, 4a, 19a) has a density within the range of 0.7 to 2, is basic and corresponds to the following composition:

- MgO......................... 60 to 90 %

-CaO.......................... 0 to 3 %

- Si0₂.......................... 0 to 20 %

- Fe0₃......................... 0 to 4 %

- Binder (as above).......... 0.5 to 3 %

- Organic fibres................ 0 to 3 %

- Residual water,
wastage of material by burning being advantageously less than 6 %

6. Casting tube in accordance with one of claims 1 to 5, characterized in that it is mounted beneath the discharge outlet of a vessel for containing molten metal such as a casting ladle or a transfer vessel.

7. Casting tube in accordance with claim 6, characterized in that it forms part of a slide-valve system which is capable of transverse displacement with respect to the axis of the tube.

8. Casting tube in accordance with claim 6, characterized in that it constitutes a removable connecting nozzle (19) which is engaged in the top end of a casting tube proper and connects this latter in airtight manner to the discharge outlet of the casting vessel located upstream.

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