EP0759335B1 - Supporting device for the side walls of a continuous roll caster installation for the production of metallic strips - Google Patents

Abstract

The support, designed for the lateral face of a continuous casting unit with two cooled cylinders (1) having horizontal axes, consists of a carriage (5) which can be moved parallel to the axes of the cylinders and has a thrust member (6) and a panel (4) joined to the lateral face of a cylinder through a thrust plate (8) and thrust elements (9, 9', 9", 9'"). The panel has at least one long bolt (11, 11') which passes through the thrust plate and has its free end equipped with a stop (13, 13') which can be applied against the rear face of the thrust plate. The long bolts can be three in number, distributed over an area corresponding to the shape of the lateral face, and the thrust elements (9, 9', 9", 9'") can be in the for of springs or power cylinders.

Description

The invention relates to the continuous casting of metals. More specifically, it concerns the devices for lateral containment of liquid metal in the ingot molds of thin strip continuous casting machines, the casting space of which is limited by the side surfaces close to two cylinders with horizontal axes, energetically internally cooled and rotated in opposite directions.

On this type of continuous casting machine, called "casting between cylinders", of which industrial application to the casting of steel strips about 2 to 10 mm thick is currently in progress, the lateral confinement of the liquid metal in the space of casting defined by the cylinders is ensured by plates which are applied against flat ends of the cylinders, called "edges", by an appropriate device. These plates are usually referred to as "side faces" or "small faces ". Their central part intended to be in contact with liquid metal is made of material refractory, as well, in general, as their periphery which rubs against the cylinders in gradually wearing out. They must be in contact as tight as possible with cylinders, because liquid metal infiltration in their area of contact would have disastrous effects on the quality of the edges of the strip. These would take a serrated form, and would be excessively fragile. They would risk then separate from the rest of the strip and stay glued to the cylinders. If this collage persisted for a full revolution of the cylinders and if the shreds of the edges penetrated so in the casting space this could cause serious deterioration of the cylinder surfaces. At worst, these metal infiltrations could reach outside the machine, which would require the immediate stopping of the casting.

• les déformations des cylindres et des faces latérales, dues aux sollicitations mécaniques et thermiques qu'ils subissent, en particulier au tout début de la coulée lors de leur mise en régime thermique;
• l'usure progressive des faces latérales ou des cylindres, qui n'est pas toujours uniforme sur l'ensemble de leurs zones de contact;
• l'usure instantanée des faces latérales provoquée par le passage d'une infiltration de métal solidifié.

Such leaks can have multiple causes, including:

• the deformations of the cylinders and of the lateral faces, due to the mechanical and thermal stresses which they undergo, in particular at the very beginning of the casting when they are brought into thermal regime;
• progressive wear of the lateral faces or of the cylinders, which is not always uniform over all of their contact zones;
• the instantaneous wear of the lateral faces caused by the passage of an infiltration of solidified metal.

It has already been proposed to solve these sealing problems by causing controlled wear of the side faces by controlled friction of these against the cylinders. The contact surfaces of the lateral faces are thus constantly regenerated, by adapting them as best as possible to any changes in the shape of the parts of the cylinders on which they are based. Mention may be made, in this regard, of document EP-A-546206. He teaches first of all to strongly press the lateral faces against the cylinders in rotation before the start of the casting, in order to make them marry the exact initial configuration of the edges of the cylinders. Then we release this a little pressure, then start the casting by temporarily putting a strong pressure on the side faces, so as to deliberately create wear which conforms the faces lateral to the edges of the cylinders. During casting, we continue to apply the faces side against the cylinders, compensating for their wear by a displacement at a predetermined moderate speed. This causes controlled wear ensuring the permanent renewal of the contact surfaces between the lateral faces and the cylinders.

French patent application FR9408319 which is not published in time and which corresponds to EP-A-0698433, a document under Article 54 (3) EPC. makes an improvement to this procedure and those who derive from it by providing means to slightly deform the lateral faces by modulating the pressure applied to their different areas. Thus, we take into account temporary or permanent inequalities in the forces exerted on the different parts of the lateral faces by the cylinders. Such inequalities can occur, for example, in the case of parasitic solidification of metal seeped between the side face and a cylinder, or when the two edges of the cylinders against which the side face is applied are not perfectly coplanar and orthogonal to the axes of the cylinders.

However, these procedures have the disadvantage of imposing on each face lateral wear by friction which is certainly measurable by means of the forward speed of the side face, but which is not easily controllable. She can be unnecessarily important in the event that the casting takes place without incident particular.

The object of the invention is to provide the operator with the means of imposing on the lateral face a controlled wear which would not be higher than what would be strictly necessary for the smooth running of the casting.

To this end, the invention relates to a device for supporting a lateral face of a continuous casting installation between cylinders of thin metal products of the type with two cooled cylinders with horizontal axes, two side faces applied against the edges of the rolls, said support device comprising a carriage movable on command in a direction parallel to the axes of the cylinders, a pushing device carried by said carriage, and a plate integral with the face lateral, connected to said pushing device via a pushing plate and thrust members bearing on said thrust plate and said plate, (see: EP-A-0698433). Said plate comprises at least one tie rod passing through the plate thrust and the free end of which is fitted with a stop which can be applied against the rear face of said push plate.

As will be understood, according to the invention the plate supporting the small face is equipped with one or more tie rods passing through the thrust plate, and the free ends can abut against the rear face of the thrust plate. Thus, the thrust members, which normally tend to move the plate away from the push plate to apply the side face against the cylinders causing its wear, see their action limited when this wear has become sufficiently pronounced so that this abutment is achieved. There is then only one minimal friction between the side face and the cylinders, and wear on the side face almost canceled.

• la figure 1 qui montre schématiquement vus de profil un dispositif selon l'invention et l'un des cylindres de coulée contre lesquels l'une des faces latérales de la machine de coulée entre cylindres est appliquée, les tirants étant en position telle qu'ils autorisent l'éloignement progressif de la platine par rapport à la plaque de poussée;
• la figure 2 qui montre le même dispositif alors que les tirants sont en butée contre la face arrière de la plaque de poussée.

The invention will be better understood on reading the description which follows, given with reference to the following figures:

• Figure 1 which schematically shows in profile a device according to the invention and one of the casting rolls against which one of the side faces of the casting machine between rolls is applied, the tie rods being in position such that allow the progressive displacement of the plate relative to the thrust plate;
• Figure 2 which shows the same device while the tie rods are in abutment against the rear face of the thrust plate.

Figure 1 shows a side part of a casting machine between two close cylinders with horizontal axes rotated and internally cooled, of which only one of the cylinders 1 is visible. The other side of the machine is equipped in the same way. The casting space defined by the two cylinders is closed laterally by a side face 2 of refractory material whose front face is applied against the edges 3 of the cylinders 1. The lateral face 2 is fixed by its face rear on a plate 4 which is made of a material such as a metallic material. This plate 4 is preferably cooled to prevent it from being affected by deformations of purely thermal origin.

Displacement and bearing force on the cylinders 1 of the side face 2 are controlled by an assembly which acts on the plate 4 and which will be described in more detail detail. In known manner, it comprises a carriage 5 movable to control according to a direction parallel to the cylinder axes 1. On this carriage 5 is mounted a device for thrust 6 such as a jack (or group of jacks) controlled by pressure or position, comprising a rod 7 which can be moved when ordered, always in the same direction parallel to the axes of the cylinders 1. As in the French patent application FR9408319 already mentioned, the rod 7 attacks a thrust plate 8, which itself carries a set of thrust members 9, 9 ', 9' ', 9' '', such as springs or jacks piloted, exerting their force on the rear face 10 of the plate 4. These members are distributed over an area whose shape preferably corresponds to that of the lateral face 2. Their usual function is to strongly apply the side face 2 against the edges of the cylinders 1, via the plate 4. But they allow a slight receding of at least the portion of the lateral face 2 which is situated in their extension, when a parasitic solidification is interposed between it and one of the cylinders 1, without as much as the contact conditions between the rest of the side face 2 and the cylinders 1 are strongly affected. We will refer to the text of the French request above for more details.

According to the invention, in the example shown in Figures 1 and 2, a plurality tie rods 11, 11 ′ are fixed to the rear face of the plate 4 and oriented substantially perpendicular to it. These tie rods 11, 11 ′ pass through the thrust plate 8 thanks to passages 12, 12 'which are provided for this purpose, and their free end is equipped a stop 13, 13 'of dimensions greater than those of the passages 12, 12'. The lengths of tie rods 11, 11 'are chosen so that the stops 13, 13' can come to bear against the rear face 14 of the thrust plate 8 before the members 9, 9 ', 9' ', 9' '' thrust have reached their maximum possible extension. The material tie rods must have good strength and stability properties dimensional to the temperatures encountered in this area of the machine. We recommend using, for example, stainless steel with a low coefficient of dilation.

FIG. 1 represents the installation in its initial state, at the start of the casting, with a side face 2 having a thickness (e). Given the initial position of the pushing device 6, the springs which, in the example shown, constitute the thrust members 9, 9 ', 9' ', 9' '', are in a state of compression corresponding to a distance (d) between the plate 4 and the thrust plate 8. On the other hand, the stops 13, 13 ' tie rods 11, 11 'are, in this initial state, at a distance (d') from the rear face 14 of the push plate 8.

FIG. 2 represents the same installation at a later instant in the casting. In the meantime, the position of the pushing device 6 has not changed, but the face lateral 2 underwent progressive wear, due to its friction against the edges of cylinders 1. This wear gradually increased the distance between the thrust plate 8 and the plate 4 under the action of the springs 9, 9 ', 9' ', 9' '' and the loosening of their state of compression. This distance, or at least its variations, can be estimated for example using displacement sensors integrated into the organs 9, 9 ', 9' ', 9' '' thrust. When this wear has been such that the lateral face has taken a thickness equal to (e-d '), the distance between the push plate 8 and the plate 4 has taken a value equal to (d + d '), and the stops 13, 13' of the tie rods 11, 11 'have come to be resting on the rear face 14 of the push plate 8. This had the effect to interrupt the advancement of the plate 4 towards the cylinders 1. At this time, running normal installation, side face 2 is no longer applied against the edges of cylinders 1 with a very low force guaranteeing minimal friction between them, just enough to seal the pouring space. This minimal friction keeps very little wear on the side face 2, and therefore increases its lifetime.

We can therefore propose a casting procedure which would be the next. Prior to casting, the installation is placed in the configuration previously described and shown in Figure 1. Then we start casting, and by following the progressive wear of the side face 2, we end up in the configuration previously described and shown in Figure 2, where the stops 13, 13 ' tie rods 11, 11 'are in abutment against the rear face 14 of the thrust plate 8. The when this state is reached can be detected, for example, by sensors displacement integrated in the thrust members 9, 9 ', 9' ', 9' ''. If solidified metal comes fit between the side face 2 and one of the cylinders 1, the side face 2-plate assembly 4 can retreat at least locally, this decline being all the more localized as this together has a certain flexibility and that the pushing members 9, 9 ', 9' ', 9' '' are more numerous. At this time, the stop 13, 13 'of one or more tie rods 11, 11' is no longer in contact with the push plate 8, and the push member (s) 9, 9 '', 9 '', 9 '' 'closest to the infiltration area resume their function firm application of the side face 2 against the cylinders 1. This lasts until the disappearance of the infiltration if its presence is only temporary, or, if the infiltration persists for a long time, until the local wear of the side face 2 causes the resumption of contact between the abutment (s) 13, 13 'and the thrust plate 8.

In order to periodically regenerate the surface of the side face 2 which is at contact of the cylinders 1 and thus avoid that too pronounced local wear does deteriorate the sealing conditions at its level, it is planned to carry out periodically setting the rod 7 of the pushing device 6 into motion direction of the cylinders 1. The thrust plate 8 is thus brought closer to the cylinders 1, this which has the effect of moving the stops 13, 13 'from all the tie rods 11, 11' relative to the push plate 8 and restore firm application of side face 2 against the cylinders 1 by the thrust members 9, 9 ', 9' ', 9' ''. This firm application lasts until the wear on the side face 2 is sufficiently pronounced for the contact between the stops 13, 13 ′ and the thrust plate 8 is again achieved, and that we thus find the desired minimum friction conditions. We can choose to perform this operation on a regular basis, imposing an average speed of displacement of the order of 1 to 10 mm / h at the thrust plate 8. This speed of displacement corresponds to the speed of wear which one wishes to impose on the face lateral 2 in the absence of infiltration of solidified metal. This speed is notably lower than those usually imposed by conventional devices of application of the lateral faces against the cylinders, which amount to a few tens of mm / h. We can also choose to superimpose this displacement systematic periodic of the rod 7 of the episodic displacements more important to moments determined by the operator or the automaton which manages the operation of the installation. This may be the case when, for example, there have been setbacks in relatively large amplitudes over part or all of the lateral face 2, which would be the indication of the presence of infiltrations of solidified metal between the side face 2 and the cylinders 1 likely to cause exceptional wear of the side face 2. In these cases, it is desirable to obtain rapid regeneration of the surface of the 2-cylinder side face contact 1, which allows displacement of the rod 7 specially made for this purpose.

In principle, the presence of a single tie rod, placed for example in the region central of the plate 4 supporting the lateral face, is sufficient to obtain the effect research. However, it is preferable to provide a plurality of tie rods 13, 13 '(for example three) distributed on the plate 4 over a zone of shape corresponding to that of the side face 2. In this way, in particular when the side face 2-plate assembly 4 presents a certain flexibility or possibilities of travel in the three dimensions, it is possible to better take into account the local setbacks of the face lateral 2, as well as the misalignment of the edges of the cylinders 1 one on the other. So that, during the deflections of the plate 4 which would not be strictly parallel to the axis of the cylinders 1, the displacements of the tie rods 11, 11 'are not embarrassed, there must be a sufficiently large clearance between them and the walls of the passages 12, 12 'provided for them in the push plate 8.

The invention is, moreover, perfectly compatible with the use of faces side 2 which, as it is known, would give an oscillating movement in the plane of the flat faces of the cylinders 1, 1 '.

The device according to the invention can be supplemented by one or more sensors position providing a value representative, at least at a given time, of the distance between the side face 2 and the cylinders 1. They make it possible to ensure that during the phases where wear of the side face 2 is sought, there is good contact between it and the cylindersl. On the other hand, during normal operation of the installation, may wish this contact not to be fully realized, and endeavor to maintain permanent play of 0.1 to 0.2 mm, small enough to prevent metal leakage liquid but making it possible to eliminate wear on the side face 2 by friction. Alone Corrosion by liquid metal would then remain as a cause of wear. It is advantageous to integrate these sensors (for example of the capacitive type) with the stops 13, 13 ′ tie rods 11, 11 'for measuring their distance from the thrust plate 8. Thus, when the thrust members 9, 9 ', 9' '' ', 9' '' have an adjustable extension when ordered (if by example they are piloted jacks), we can, after the stops 13, 13 'have come in contact with the push plate 8, roll back the side face 2 while decreasing the extension of the thrust members 9, 9 ', 9' ', 9' '' by a distance corresponding to this clearance.

Claims (8)

1. Device for supporting a side wall (2) of an installation for the twin-roll continuous casting of thin metal products of the type including two cooled rolls (1) with horizontal axes, two side walls (2) applied against the sides (3) of the rolls (1), the said support device including a carriage (5) which can be displaced on command in a direction parallel to the axes of the rolls (1), a thrust device (6) carried by the said carriage (5) and a panel (4), integral with the side wall (2), connected to the said thrust device (6) by means of a thrust plate (8) and thrust members (9, 9', 9'', 9''') bearing on the said thrust plate (8) and the said panel (4), characterized in that the said panel (4) includes at least one tie (11, 11') passing through the thrust plate (8) and the free end of which is equipped with a stop (13, 13') which can be applied against the rear face (14) of the said thrust plate (8).
2. Device according to Claim 1, characterized in that the said plate (4) includes three ties (13, 13').
3. Device according to Claim 1 or 2, characterized in that the said ties (13, 13') are distributed over a zone with a shape corresponding to that of the side wall (2).
4. Device according to one of Claims 1 to 3, characterized in that the said thrust members (9, 9', 9'', 9''') are springs.
5. Device according to one of Claims 1 to 3, characterized in that the said thrust members (9, 9', 9'', 9''') are controlled rams.
6. Device according to one of Claims 1 to 5, characterized in that it includes one or more position sensors supplying a representative value, at least at a given instant, of the distance between the side wall (2) and the rolls (1).
7. Device according to Claim 6, characterized in that the said position sensor or sensors are adapted to the measurement of the distances between the stops (13, 13') of the ties (11, 11') and the thrust plate (8).
8. Device according to Claim 6 or 7, characterized in that the said position sensor or sensors is/are of the capacitive type.

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