EP0825910B1 - Device and process for changing a continuous casting tube of a distributor in a steel-works - Google Patents

Abstract

PCT No. PCT/FR96/00572 Sec. 371 Date Feb. 24, 1998 Sec. 102(e) Date Feb. 24, 1998 PCT Filed Apr. 15, 1996 PCT Pub. No. WO96/34713 PCT Pub. Date Nov. 7, 1996A tube changing device is comprised of a chassis (16) mounted of the distributor (2), refractory pieces (10, 18, 22) that delimit a casting gutter, these refractory pieces being comprised of at least one fixed place (18) and a tube having a plate (24) in its upper part, means for generating pressure for applying the plate (24) of the tube (22) against the fixed plate (18), a position for introducing a new tube (22a), a casting position and a position for evacuating the worn tube (22b), guidance means (18, 48) that permit the new tube (22a) to pass from the introduction position to the casting position and the worn tube (22) to pass from the casting position to the evacuation position, actuation means (34, 36) for moving the new tube from the introduction position to the casting position and the worn tube from the casting position to the evacuation position. The introduction position, casting position and evacuation position are arranged around a convex cylindrical surface (18) that constitutes the periphery of the fixed plate.

Description

The present invention relates to a device for changing a pouring tube continues according to the preamble of claim 1, which is based on EP-A-442515.

It generally applies to slab casting and more particularly to casting of thin slabs.

In a continuous steel plant, the steel is poured from a ladle into a distributor, and distributor in one or more molds. To protect the steel from contact with air between the distributor and the mold, the steel is isolated from the atmosphere at by means of a submerged refractory tube fixed to the bottom of the distributor and whose end lower plunges into the mold.

This tube wears out and clogs quickly, especially in its lower part. This limits the duration of the pour. To extend this period, devices have been designed which make it possible to replace a used tube with a new one. For economic reasons, it is preferable to change the tube without interrupting the pouring, that is to say without raising the distributor.
In these devices, called tube change devices, the tube is provided with a plate at its upper part, this plate can be attached or formed in one piece with the tube. This plate can slide, while maintaining a sealed junction, on the underside of a fixed distributor plate. In what follows the whole of the tube and the plate associated with it are simply called the tube. A new tube is introduced into the mold, next to the used tube. Means are used to push the new tube into the casting position while the used tube is pushed back to the other side of the mold.

To allow a tube change without raising the distributor, the lower end new tube must be immersed in the mold steel before the used tube is pushed to its evacuation position. In the same way the used tube remains submerged in the steel when it is in the evacuation position.

An example of such a device is known from document EP 0 192 019.

These known devices have several drawbacks.

It is necessary that the mold has a sufficient width for three tubes can be placed side by side: the position of the new tube, the position of the tube which is sinking, and the position that the used tube will take after exchange. In many cases the mold does not have a sufficient width and other processes more unfavorable should be used.

To change the tube, we generally use a cylinder that pushes the new tube at its plate, which presses on the plate of the used tube. It is essential that this effort is transmitted through the plates of the new tube and used tubing. In other words it is essential that these plates come into contact with each other before the lower ends of the tubes touch each other. Otherwise, the forces exerted at the end of the tubes would cause their jamming in the tubes of the tube change and their rupture. So that the device is working properly so it is necessary that the plates have a length greater than the bulk of the end of the tubes in the direction of the great mold size. This requirement is easy to meet in the case of a slab thick. Indeed, the tube then has a compact section approximately circular and the plate can easily have a length greater than the diameter outside of the tube. On the other hand, in the case of a thin slab casting, the mold is very narrow. In order to maintain a large passage section, the end of the tube must be very elongated in the direction of the large dimension of the mold. Consequently the plates provided at the upper end of the tube must themselves be very elongated. As a result, in addition to an additional cost, an increase in their bulk and increased difficulty in maneuvering the tube in the reduced volume between the bottom of the distributor and the mold.

In order to overcome this drawback, it has been imagined to introduce an intermediate plate between the plates of the tubes. Such an arrangement is described for example in the patent WO95 / 03906. This intermediate plate effectively reduces the dimension plates but it requires additional handling, gives birth to a risk of forgetting the intermediate plate and poses alignment problems.

Finally, when the tube is put in place, its end must be introduced into the mold, then plunged into steel. Likewise, when removing the used tube the lower end of the tube must be extracted from the steel, then from the mold.

In existing art, these handling operations are generally carried out manually by a operator who carries and directs the tube by means of a clamp possibly associated with supports intended to facilitate operations. In the case of thick slabs, these manual handling is relatively easy because there are several centimeters clearance between the tube and the edges of the mold and because the steel skin solidified on the walls of the mold is thick and robust and does not fear possible impact with the tube, due to manual handling. In the case of thin slabs the problem of handling becomes critical because the clearance between the tube and the mold walls is reduced a few millimeters and the skin solidified in this type of thin slab is weak thick and brittle. Contact of the tube with this skin would induce a significant risk of break the skin, which would cause a mold breakthrough and stop the casting. The manipulations must therefore be extremely precise if one does not want to strike the tube.

Manual handling of the tube is therefore unrealistic and it would be necessary to use a or several very precise manipulators both for the introduction and for the withdrawal of the tube. Such a manipulator would not only be very expensive but also difficult to place in the working one which is reduced and must remain accessible to operators. The The present invention specifically relates to a tube changing device which overcomes these disadvantages.

According to the main characteristic of the invention, the insertion position, the pouring position and the discharge position are arranged around a convex cylindrical surface having a horizontal axis perpendicular to the large dimension of the mold, this cylindrical surface constituting , the periphery of the fixed plate.
The tube plate has a concave cylindrical shape which adapts to the convex cylindrical surface of the fixed plate so as to maintain a tight seal between these surfaces when the new tube passes from the insertion position to the casting position and the passage of the used tube from the casting position to the discharge position by a rotational movement around the axis of the cylindrical surface.
The fixed plate is advantageously placed as low as possible below the mold so that the overall circle described by the tubes during their rotation is minimum. Thanks to this characteristic, the device can be used even when the width of the mold is less than three times the length of the end of a tube. Indeed, since the introduction of the new tube and the evacuation of the used tube is effected by a rotational movement, it suffices that the circle described by the end of the tube does not strike the edge of the mold. Even in a narrow mold, you can change the tube without having to lift the distributor. Optionally when the width of the mold is reduced it is possible to slightly raise the distributor so that the circle of dimensions of the tube escapes the edges of the mold while keeping the tube submerged in the casting position.

The tube plate can without any inconvenience be significantly smaller than the end of the tube. Indeed, the radius of the cylindrical surface is much less than the radius of the circle described by the end of the tube. It is therefore sufficient that the ratio of the length of the plate at the length of the end of the tube is in the same ratio as the radius from the cylindrical surface to the radius of the circle traversed by the end of the tube.

Last but not least, the new tube is entirely out of steel, and even usually out of the mold, when in its insertion position and the tube used is entirely out of steel, and even generally out of the mold when is in its evacuation position.

Thanks to this preferred characteristic, when introducing a new tube, and the evacuation of a used tube, the tube is guided by the device change of tube itself. This guidance is a rotation guidance given by the cylindrical surface of the fixed plate on which the concave surface of the plate slides of the tube. The device also provides lateral guidance of the tube in the mold. These two guides are very easily precise. This eliminates the handling problem very important and it eliminates the need to use an expensive manipulator and difficult to implement.

The invention also relates to a method for changing the distributor tube of continuous casting of steelworks to replace a used tube with a new one, in which a new tube is placed in a tube changing device, then pushed into the pouring position, while simultaneously the used tube is pushed from the pouring position to a discharge position.

The method is characterized in that the new tube is put into place in the tube change in a position outside the mold, bring the new tube in its casting position by rotation around a horizontal axis perpendicular to the large dimension of the mold, which has the effect of making a rotation of the used tube around this same axis, bringing the used tube into a evacuation position outside the mold in place, the center of rotation being located as low as possible.

• on met en place le tube neuf dans le dispositif de changement de tube ;
• on amène le tube usagé à sa position de coulée par une rotation ce qui a pour effet de faire effectuer une rotation au tube usagé autour de ce même axe ;
• on extrait le tube usagé du dispositif de changement de tube ;
• on baisse le répartiteur jusqu'à sa position normale de coulée.

In difficult circumstances, when the width of the mold is particularly reduced, the distributor is raised enough so that the circle which will be described by the end of the new tube during its rotation avoids the edge of the mold, without the tube which is in sinking ceases to be immersed in the liquid steel of the mold;

• the new tube is placed in the tube changing device;
• the used tube is brought to its pouring position by a rotation which has the effect of causing the used tube to rotate around this same axis;
• the used tube is removed from the tube changing device;
• the distributor is lowered to its normal casting position.

This process makes it possible to change the tube if the mold has reduced width without having to stop casting.

According to a preferred variant of the process of the invention, the new tube is placed in the tube changing device in a substantially horizontal position, brings the new tube to its casting position by a rotation of approximately 90 ° around a horizontal axis, which has the effect of causing the user tube to rotate substantially 90 ° around this same axis, the used tube is extracted from the device tube change in a substantially horizontal position.

Preferably the actuating means comprise a rotor mounted rotating around from the horizontal axis of the cylindrical surface, this rotor comprising a pushing finger the new tube under the pressurizing means.

Preferably the finger moves back and forth to take a tube new

Preferably, the device comprises first retaining means which make it possible to keep the new tube in its insertion position and second retaining means which keep the used tube in its evacuation position.

Preferably the guide means and the retaining means are designed so to allow the introduction of the new tube and the evacuation of the used tube in a direction perpendicular to the large dimension of the mold.

Preferably in that the means for pressurizing the plate transmit radial forces on the back of the plate.

Preferably in that the edges of the plates are made so as to ensure a contiguous contact so as to leave no gap between two successive plates during the passage of the seal opposite the pouring orifice.

Preferably in that the cylindrical plate comprises locking means in rotation relative to the chassis.

Other characteristics and advantages of the present invention will become apparent from reading of the description which follows of an exemplary embodiment given by way of illustration in reference to the appended figures.

• la figure 1 est une vue en coupe longitudinale d'un dispositif de changement de tube conforme à la présente invention ;
• la figure 2 est une vue schématique en coupe longitudinale qui illustre la position du dispositif pendant un changement de tube ;
• la figure 3 est une vue transversale en coupe selon la ligne 3-3 de la figure 1.

In these figures:

• Figure 1 is a longitudinal sectional view of a tube changing device according to the present invention;
• Figure 2 is a schematic view in longitudinal section which illustrates the position of the device during a tube change;
• Figure 3 is a cross-sectional view along line 3-3 of Figure 1.

The distributor designated by the general reference 2 has been shown only partially. It includes a steel bottom wall 4 covered with a layer of refractory 6. It contains liquid steel 8. The bottom of the distributor 2 is crossed by an internal nozzle 10 and which allows the passage of the liquid steel 8. The steel flow passing through the internal nozzle 10 can be controlled by a stopper rod 12 or optionally by a drawer device interposed between the bottom of the distributor and the tube change (device not shown).

A fixing plate or base plate 14 is fixed under the bottom plate 4 of the distributor. The chassis 16 of the tube changing device according to the invention is fixed under the base plate 14. A fixed plate 18 is mounted in the chassis 16. This fixed plate is presented as a cylinder of refractory material comprising at its upper part a socket 19 and which allows to receive the lower end of the internal nozzle 10. The fixed plate is crossed by an orifice 20 which extends the channel of the internal nozzle 10. The center of the fixed plate 18 has been designated by the letter O. A tube designated by the general reference 22 is mounted at the bottom of the fixed plate 18. The tube 22 has, at its upper part, a plate 24 of form concave which is applied tightly to the fixed plate 18. Means for placing in pressure 36 are provided for applying the plate 24 of the tube 22 against the fixed plate 18.

The length of the lower end of the tube has been designated by the reference 26.

Below the tube changing device is the casting mold 28 which has a large dimension designated by the reference 30 and generally called width and a small dimension 31. The mold contains the liquid steel 8, still in the liquid state, and solidified only in contact with the walls of the mold which are cooled with water, to form a skin 32.

In FIG. 1, a second tube, designated by the reference 22a, has been placed on the cylindrical surface 18. The tube 22a is a new tube intended to replace the tube 22. To this end the invention provides actuation means for passing the new tube 22a from its insertion position shown in Figure 1 to the casting position which is that of the tube 22 and to simultaneously pass the tube 22 from the position of pouring in the discharge position 22b. In the embodiment shown actuating means consist of a cross bar 34 applied against the upper edge of the plate 24a of the new tube. The bar 34 is linked to the rotor 48 likely to rotate on the same axis as the fixed plate. Means of actuation also include a jack 37 mounted under the base plate 14 and which allows to activate the bar 34.

FIG. 2 shows the new tube 22a and the used tube 22 being changed. It can be seen that the lower end of the new tube 22a which was entirely outside the liquid steel 8 of the mold, and even entirely outside the mold 28 in its insertion position shown in FIG. 1, is not immersed in the steel only when the tube is placed in the casting position. In the insertion position 22a and in the discharge position 22b, the tube is applied without being pressed against the cylindrical surface 18. The pressurization takes place gradually when it passes from the insertion position 22a to the pouring position. . Also the pressure is gradually released when the tube passes from the casting position to the discharge position 22b. The plate 24a of the new tube enters under rocker arms 36 having one end actuated by an elastic means such as for example springs and another end, visible in FIG. 2, adapted to the back of the plate 24, 24a of the tube. The end of the rocker arm 36 exerts a radial action on the plates 24, 24a, 24b of the tubes, in other words an action directed preferentially towards the center O of the fixed plate 18. It can thus be seen that the device for changing the tube of the invention, like a device of the prior art, provides three positions, namely a position for introducing a new tube, a casting position and a position for discharging a used tube. However, unlike the prior art, when the tubes are arranged in this respective position they are not parallel to each other but arranged radially on the fixed plate 18. As can be seen in FIG. 2, the used tube 22 is already partially out of the mold when the new tube 22a enters it. For the operation of the device to be possible it is sufficient that the avoidance circle 38 described by the point of the tubes 22, 22a, 22b furthest from the center O of the fixed plate 18 does not meet the angle 40 of the mold. casting 28. In the case where the circle 38 would strike the angles 40 it would still be possible to slightly raise the distributor from a distance 42 (see FIG. 1) such that the tube 22 remains still immersed in the liquid steel 8 of the mold . By raising the distributor, the center O of the fixed plate 18 is raised, and consequently the position of the avoidance circle 38. A view is shown in FIG. 3
in cross section of the tube changing device of the invention. The cylindrical plate 18 is taken between two plates of insulating refractory material 44 which can be an integral part of the plate 18. The plates 44 possibly have a metal casing on their outer face, or even on both. A screw 46 or any other blocking means keeps the two plates 44 and the cylindrical plate 18 against the frame 16 in application. A rotor 48 is mounted to rotate on cylindrical bearings 50 of the frame 16. The rotor 48 consists of two flanges 52 interconnected by the crossbar 34 forming the pushing finger which actuates the new tube when it is put in place. In the configuration illustrated by the example each flange 52 is provided with a rod 54 which passes through a bean-shaped light 56 pierced in the frame 16. The two fingers 54 are connected to a drive fork 58 which is itself integral of the rod of the jack 37. The jack 36 is double acting. It makes it possible to pull and push the fork 58 and therefore to make a back and forth movement in rotation with the finger 34. During this movement the two axes 54 describe an arc of a circle of approximately 90 ° around the axis XX of the cylindrical part 18. This is the reason why the jack 37 is articulated with respect to the base plate about an axis 60 so as to allow its angular movement. It will be noted that the orifice 20 which passes through the cylindrical plate 18 can be cylindrical, as in the embodiment shown, but it can also have a section which widens. In this case the runner at the entrance to the tube 22 has a corresponding flared shape in order to maintain the continuity of the section of the runner.

On the other hand, means are provided for immobilizing the cylindrical plate in rotation. 18 relative to the frame 16. Indeed, it is subjected to rotational forces relatively large exerted by the friction forces of the plates 24 of the tubes during their rotation.

FIG. 3 makes it possible to observe an exemplary embodiment of the means of setting in pressure plates 24, tubes such as 22. These means include rocker arms 36 articulated in their central part on ball screws 62 mounted in the frame 16. At their outer end the rocker arms 36 are pushed by springs 64. A their inner end, which may possibly have a concave shape which fits on the outer face of the plates 24, the rocker arms 36 exert an action radial directed towards the axis X-X of the cylindrical plate 18. There is provided at least one pair of rocker arms, and preferably several pairs in order to guarantee a force of application distributed along the plates 24.

The puddles 52 of the rotor 48 advantageously have a diameter greater than that of the fixed plate 18 to serve as lateral guide to the tube. One of the flanges 52 of the rotor 48 has two notches, namely a notch respectively of introduction of the new tube and a notch of evacuation of the used tube. These notches are intended to allow the introduction of the new tube and the extraction of the tube used by the face of the mold, that is to say in other words to allow to introduce it in the insertion position and to extract it from the evacuation position by moving it in a direction perpendicular to the large dimension 30 of the mold (see Figure 1). (parallel to the cylinder axis).

Retaining means are provided in order to keep the new tube 22a in its position of introduction. These means consist of a curved sheet 66 disposed on one side of the frame. On the other side of the frame there is only provided a lug placed in the position bottom of the tube to allow its introduction. Identical restraints are provided in the discharge area in order to keep the used tube in the position extraction.

The operation of this device is as follows. When you want to make a tube change, the tube which is in the casting position being worn or clogged, we begins by introducing a new tube 22a in the insertion position, shown on the left in FIG. 1. At this moment the actuating finger 34 is located at the part top of the fixed plate 18, near the internal nozzle 10. The introduction of the new tube 22a can be made, as in the embodiment described, depending on the face front of the mold, allowing easy handling of the tube. But we can also consider, in an alternative embodiment, to introduce the new tube in another direction for example radial with respect to the fixed plate. It is then necessary to provide means of retainers adapted to this new direction. The new tube 22a being in place in the retaining means, the actuator 37 is actuated which exerts a tensile force on the fork 58, 54 from right to left, according to Figure 1 so as to drive the rotor 48 rotating counterclockwise. Note that the fork 58 distributes the force of the jack on the two axes 54 so that the forces are symmetrical. The actuating finger 34 pushes the plate 24a of the new tube 22a. This plate 24a is advantageously made contiguous with the plate of the used tube 22 so that there is no gap between them allowing the passage of steel liquid. It is possible to close the runner beforehand using the distaff 12. It is also possible, given the absence of a gap between the plates, to change the tube without closing the pouring channel.

When the used tube 22 arrives in the discharge position 22b, the new tube 22a has replaced and the metal casting can continue normally. We have everything time required to remove the used tube 22b which is kept in the means of restraints that have been described previously. The cylinder 37 is then actuated in the other sense so as to return the finger 34 to its initial position. The cycle can then start again for a new tube change.

Claims (11)

1. Tube changing device for a continuous-casting tundish in a steel plant, comprised of a chassis (16) mounted on the tundish (2); refractory pieces (10, 18, 22) that delimit a flow channel for the passage of steel from the tundish (2) to a continuous casting mould (28) having a large dimension and a small dimension (31), these refractory pieces being comprised of at least one bed plate (18) and a tube (22), a position for introducing a new tube (22a), a casting position and an evacuation position for a worn tube (22b), these positions being arranged around an horizontal axis (X-X) perpendicular to the large dimension of the mould; actuating means (34,36) for moving the new tube from the introduction position to the casting position and the worn tube from the casting position to the evacuation position, characterised in that the fixed plate (18) has a cylindrical convex surface having an axis (X-X), and in that the tube (22) has a plate (24) at its top part, said plate (24) having a cylindrical concave shape that is adapted to the cylindrical convex surface of the fixed plate (18); pressurising means (36, 64) for sealingly applying the plate (24) of tube (22) against the fixed plate (18), so that the plates slide under pressure while keeping a tight junction between these surfaces when a new tube is moved from the introduction position to the casting position, and when a worn tube is moved from the casting position to the evacuation position.
2. Device according to claim 1, characterised in that the actuating means are comprised of a rotor (48), rotatably mounted around the horizontal axis (X-X) of the convex cylindrical surface (18), this rotor including a finger (34) that pushes the new tube (22a) under the pressurising means (36).
3. Device according to claim 2, characterised in that the finger (34) effects a back-and-forth movement for taking up a new tube (22a).
4. Device according to any of claims 1 to 3, characterised in that it has first holding means (66) that permit maintaining the new tube (22a) in its introduction position and second holding means (66) that permit maintaining the worn tube (22b) in its evacuation position.
5. Device according to claim 4, characterised in that the guidance means and the holding means (66) are designed to permit the introduction of the new tube (22a) and the evacuation of the worn tube (22b) along a direction perpendicular to the large dimension (30) of the mould.
6. Device according to any of claims 1 to 5 characterised in that the pressurising means for applying pressure to the plate (24) transmit radial forces to the back of the plate.
7. Device according to any of claims 1 to 6 characterised in that the plates edges are designed to assure nesting contact so as not to leave any space between two successive plates during passage of the joint opposite the casting orifice.
8. Device according to any of claims 1 to 7, characterised in that the cylindrical plate (18) has rotational blocking means (46) for blocking it relative to the chassis (16).
9. Process for changing a tube of a continuous-casting tundish in a steel plant for replacement of a worn tube with a new tube, where a new tube is placed in a tube changing device in an introduction position where the tube does not contact the steel in the mould (28), then pushed into a casting position by a rotation around an horizontal axis (X-X) perpendicular to the large dimension of the mould, while the worn tube is simultaneously rotated around same axis and moved to an evacuation position where it does not contact the steel in the mould (28), and from which it is taken out of the tube changer device, characterised in that the new tube moves from its introduction position to its casting position by sliding under pressure of its plate (24) on the fixed plate (18) and in that the worn tube moves from the casting position to its evacuation position by sliding under pressure of its plate (24) on the fixed plate (18) so that the plates slide under pressure while keeping a tight junction between these surfaces when a new tube is moved from the introduction position to the casting position, and when a worn tube is moved from the casting position to the evacuation position.
10. Process according to claim 9, characterised in that the tundish (2) is raised sufficiently so that a circle (38) that will be described by the end of the new tube (22a) and by the end of the worn tube (22b) avoids the edge (40) of the mould, but without the tube in the process of casting (22) ceasing to be immersed in the molten steel (8) of the mould (28).
11. Plate-tube assembly for a tube changer device, comprising a plate (24) integral with a tube (22), said plate (24) being adapted to slide under pressure on a fixed plate (18) of said tube changer device and to receive pressurising means which sealingly apply it on the fixed plate (18), said integral plate (24) having a concave cylindrical shape.

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