EP0561724B1 - Apparatus for twin roll casting of metallic products - Google Patents

Abstract

The apparatus includes two counter-rotating rolls with parallel axes arranged opposite one another, with a certain spacing, and two fixed side walls bearing on the axial ends of the rolls, delimiting a casting space. Each of the side walls includes two bearing plates (25) in the form of portions of a ring or of a disk which are each in frictional contact with a plane front face of one of the two rolls. Each of the bering plates (25) incudes a plurality of successive annular sectors (27a, 27b, 27c, 27d) in the circumferential direction which can be deformed elastically with respect to one another so as to be capable of being displaced, in the axial direction with respect to the rolls, during casting. The annular sectors may be delimited by radial cups (32a, 32b, 32c) which are machined through the entire thickness of a metal strip. <IMAGE>

Description

The invention relates to a device for the continuous casting of a metal product between cylinders, having flexible side walls.

There are known devices for continuously casting a metal product and in particular a thin metal strip comprising two counter-rotating cylinders with horizontal and parallel axes disposed opposite one another with a spacing corresponding to the thickness of the product to be cast.

The liquid metal is poured into a pouring space defined by the portions of the surfaces of the cylinders situated above a plane passing through the parallel axes of these cylinders and by fixed end side walls called small faces bearing on the axial ends of the cylinders.

The small faces must be applied against the axial ends of the cylinders, so as to obtain an effective seal to prevent any leakage of molten metal.

It is also necessary to avoid or limit the solidification of the metal in contact with the side walls.

For this purpose, it has been proposed to produce these walls in a thermally insulating material, so as to prevent significant cooling of the molten metal in contact with the side walls.

However, it has proven to be very difficult to obtain both good thermal insulation characteristics and sufficient mechanical strength of the walls.

In particular, the wear resistance of the insulating walls is generally insufficient to ensure a long casting time without changing the walls.

It has therefore been proposed, for example in French patent application 90-11000, to use side walls comprising a part made of thermally insulating refractory material inserted between the cylinders and placed between two metal plates in the form of disc portions or portions of ring in contact each rubbing with a flat front face of the cylinder.

The metal plates have an external edge of frustoconical shape, the edge delimiting the large base of the frustoconical surface is placed in contact with the corresponding cylinder, so as to be superimposed on the edge of the cylinder. The pieces of insulating refractory material from the side walls are interposed between the frustoconical edges of the two metal plates.

During casting, the rolls expand under the effect of the heat of the liquid metal, in particular in the direction of their axes and along their edges coming into contact with the metal plates of the side walls.

The expansion of the cylinders in the axial direction occurs in an area of the cylinders coming into contact with the molten metal during casting and solidification, the temperature of which varies according to the circumferential direction of the cylinder. The deformation of the cylinders in the axial direction is therefore essentially variable depending on the circumference of the cylinder and concerns only part of the circumference of the cylinder.

In addition, because the cylinders are rotating about their axes, the deformation of the cylinders in the axial direction has a cyclical character.

In the case of the side walls known from the prior art comprising metal plates or blades in contact with the axial ends of the cylinders, it is not possible to ensure perfect contact between the metal blades and the cylinders, due to the variable and cyclic deformation of these cylinders in the axial direction.

The object of the invention is therefore to propose a device for the continuous casting of a metallic product comprising two counter-rotating cylinders with parallel axes arranged opposite each other with a certain distance and two fixed side walls bearing on the axial ends of the cylinders delimiting a casting space between the cylinders and each comprising two annular plates which are in rubbing contact each with a flat front surface of one of the two cylinders at one of the ends of the cylinder and at least one interleaved complementary wall between the two plates and between the cylinders, this device making it possible to obtain good contact between the annular plates and the cylinders during casting, despite the variable and cyclic deformation of the cylinders in the axial direction.

For this purpose, each of the plates of each of the side walls has a plurality of successive annular sectors in the circumferential direction elastically deformable with respect to each other, so as to be able to move in the axial direction relative to the cylinders, during casting. .

In order to clearly understand the invention, a description will now be given, by way of nonlimiting example, with reference to the attached figures, of a device for continuously casting a thin metal strip, according to the invention.

Figure 1 is a front elevational view of a side wall of a casting device according to the invention.

Figure 2 is a partial sectional view along 2-2 of Figure 1 of the casting device according to the invention.

Figure 3 is a sectional view along 3-3 of Figure 1.

FIG. 4 is a partial plan view of a first face of an annular plate of a side wall of the casting device shown in FIGS. 1, 2 and 3.

FIG. 5 is a partial plan view of the second face of the annular plate shown in FIG. 4.

Figure 6 is a sectional view along 6-6 of Figure 4.

FIG. 7 is a sectional view along 7-7 of FIG. 4.

Figures 8, 9 and 10 relate to an alternative embodiment of the casting device according to the invention.

Figure 8 is a sectional view through a plane passing through the axis of the cylinders of a side wall and the end portion of the cylinders in contact with this side wall.

Figure 9 is a sectional view similar to the view of Figure 8 showing the position of a metal support plate of a side wall as shown in Figure 8, when this wall is not in contact with the cylinders of the casting device.

FIG. 10 is a plan view of a metal support plate for the wall shown in FIG. 8.

Figure 11 is a schematic perspective view showing in a greatly exaggerated manner, the deformation during casting of a cylinder of a continuous casting machine between cylinders.

Figure 12 is a schematic sectional view showing the bearing position of a plate of a side wall as shown in Figure 8, on the edge of a cylinder deformed by expansion in the axial direction.

FIG. 1 shows the front face directed towards the cylinders of a casting device between cylinders, of a side wall generally designated by the reference 1.

As can be seen in FIGS. 2 and 3, the casting device comprises two counter-rotating cylinders with parallel axes 2, 3 arranged opposite and with a certain spacing between their lateral surfaces, so as to delimit a casting space which is closed, at each of the front ends of the cylinders, by a side wall such as 1.

The casting space between the cylinders has a minimum width corresponding to the thickness of the product to be cast, in the plane containing the axes of rotation of the cylinders 2 and 3.

The side wall 1 comprises two metal support plates 4, 5 in the form of annular sectors having an angular amplitude of the order of 60 ° and which are brought into contact along their external annular edge with the edge of the cylinders 2, 3.

As can be seen in particular in FIG. 3, the outer edge of the support plates 4, 5 is chamfered and has a frustoconical shape. The half-angle at the top of the truncated cone has a value close to 60 °. The support plates 4, 5 are kept in rubbing contact with the edge of the cylinders 2, 3 in rotation, so that the edge of the frustoconical edge corresponding to the large base is superimposed with the edge of the corresponding cylinder 2, 3.

Between the frustoconical edges of the support plates 4, 5 is interposed a piece of refractory material 6 which is preferably at the start of casting, protruding in the axial direction, inside the casting space 8 delimited by the side surfaces of the cylinders 2 and 3 and by the side walls 1 also called small faces.

During a casting operation, liquid metal is poured into the space 8 and comes into contact with the cylinders 2 and 3 which are rotated.

The cylinders 2 and 3, the outer wall of which is cooled, make it possible to cool and solidify the liquid metal, so that it gradually forms, two skins solidified in contact with the cylinders 2, 3 in rotation, the skins solidified joining at level of the narrowest part or neck of the casting space 8 situated in the vicinity of the axial plane of the cylinders 2 and 3.

In addition to the metal support plates 4, 5 and the piece of refractory material 6 interposed between these support plates, the side wall 1 comprises a set of support and holding elements which is connected to the frame of the casting installation to ensure the support of the side wall against the front ends of the cylinders.

The support and holding assembly which has the form of a housing comprises two plate holders 10, 11 in the form of annular sectors on which the support plates 4, 5 are fixed by screws and a support plate 12 resting on the plate holders 10, 11 on the face of these plate holders opposite the support plates 4, 5.

The support plate 12 is itself fixed by welding to a holding assembly 13 which can be attached and fixed by screws 14 to a fixed part 15 of the casting installation.

As can be seen in FIG. 3, clamping devices such as 16 fixed on the support plate 12 make it possible to exert a force in the axial direction of the cylinders 2 and 3, on the piece of refractory material 6, by the through a coil spring 17.

The helical spring 17 exerts the axial force on the part 6, by means of a ring 18, a metal part 19 and a protective plate of refractory material 20 having a hardness greater than the material of the part 6.

The piece of refractory material 6 intended to come into contact with the liquid metal inside the casting space 8 comes to bear, by two edges of frustoconical shape, on the frustoconical edges facing the plates d 'support 4 and 5 and on the flat rear face of the plates 4 and 5 opposite the face of these plates 4 and 5 bearing on the cylinders 2 and 3.

The plate holders 10 and 11 have, along their entire length, a transverse groove 21 (or 22) located in the vicinity of the corresponding support plate 4 or 5 and extending over a substantial part of the width of the plate holder 10 or 11. The grooves 21 and 22 which separate the plate holders 10 and 11 into two parts of unequal importance make it possible to obtain a certain elasticity of the mounting, due to the possibilities of bending of the plate holder at the level of the area of junction between the two parts located on either side of the groove.

In addition, the grooves 21 and 22 make it possible to limit the heat transfers via the plate holders.

We will now refer to FIGS. 4 to 7 to describe the bearing plates of the side walls of the casting device shown in FIGS. 1, 2 and 3.

In Figures 4 and 5, there is shown a portion 25 of a support plate such as 5 which is constituted by a metal blade in the form of an annular sector comprising a first face which is shown in Figure 4 and which is intended coming into contact with the edge of the cylinder 3 and a second opposite face which is shown in FIG. 5 and which is intended to come into contact with the corresponding support plate holder 11 and with the piece of refractory material 6.

Each of the support plates 4 and 5 may consist of several elements 25 as shown in Figures 4 and 5, arranged one after the other and fixed on the corresponding plate holder.

As can be seen in FIGS. 6 and 7, the annular element 25 constituting a part of the support plate 5 comprises a heel 26 constituting its internal part and a blade 27 of thinner thickness than the heel 26 and constituting its external part.

The heel 26 is crossed by openings 28 constituting housings for fixing screws 30 of the support plate 5 on the corresponding plate holder 11, as shown in FIG. 2.

The screw holes 28 comprise a frustoconical entry part opening onto the face 25a of the element 25 directed towards the cylinder 3 and intended to receive the head of the screw 30.

The heel 26 of the element 25 is also crossed by a lubrication orifice 29 opening onto the face 25b of the element 25 which is fitted against the plate holder 11, at the level of the heel 26 and against the complementary piece of refractory material .

At its opposite end, the lubrication orifice 29 opens onto the face 25a of the element 25, inside a slot 31 machined in the direction radial of the blade 27 extending the heel 26 outwards.

During the operation of the casting installation, a liquid lubricant is introduced into the lubrication orifice 29, via a lubricant distribution cavity machined in the plate holder 11.

The lubricant reaches via the orifice 29, in the opening 31 which is on the face 25a of the blade 27 located opposite or in contact with the surface of the cylinder 3. This provides lubrication rubbing surfaces of the blade 27 of the element 25 of the support plate and of the cylinder 3.

According to the invention, the external part of the annular element 25 constituting the blade 27 is separated into successive sectors 27a, 27b, 27c, 27d by cutouts 32a, 32b, 32c in radial direction relative to the element 25 and following the entire thickness of the blade 27.

Cutouts 33, 33a, 33b, 33c of circumferential direction passing through the blade 27 over its entire thickness and arranged one with respect to the other with a certain spacing each intersect a radial cutout 32a, 32b or 32c.

The cutouts 32a, 32b, 32c, 33a, 33b, 33c allow the successive sectors 27a, 27b, 27c, 27d of the element 25 of the support plate 5, to deform independently of each other, in in particular by bending, in a direction perpendicular to the faces 25a and 25b of the element 25, that is to say in an axial direction relative to the cylinders 2 and 3.

In addition, the sectors 27a, 27b, 27c and 27d of the metal strip 27 are perfectly elastic and are capable of returning to their initial position, after displacement in the axial direction, for example due to the expansion of the cylinder 3.

As can be seen in FIGS. 6 and 7, the blades 27 made up of successive annular sectors 27a, 27b, 27c, 27d have a certain inclination in the axial direction, towards the cylinder 3, so that the outer end of the blade 27 constitutes the part of this blade coming into contact with the cylinder 3, and that the internal part of the blade 27 secured to the heel 26 has a certain clearance J relative to the front surface of the cylinder 3, when it is brought into contact side wall and cylinders.

Preferably, the radial cuts such as 32a, 32b, 32c and the circumferential cuts such as 33a, 33b, 33c are made by electro-erosion and have a width of the order of 0.4 mm.

The outward bending of the blade 27 is such that the deflection of the blade 27 corresponding to the clearance J of the heel 26 of the support plate relative to the cylinder 3 is between 0.5 and 1 mm.

It should be noted that in FIGS. 6 and 7, the element 25 of the support plate has been shown in its initial position, before the start of the casting installation and before a compression force is applied. on the support plate to bring it into contact with cylinder 3.

By the effect of the compression of the side wall and of the support plate against the cylinder 3, the face 25a of the support plate is pressed against the external annular edge of the cylinder 3.

During the operation of the installation, the annular sectors 27a, 27b, 27c, 27d of the element 25 of the support plate are liable to deform in the axial direction of the cylinders, with respect to each other , in particular by bending, owing to the fact that these sectors are separated by the radial cutouts 32a, 32b and 32c and that the length of the connection zones between these sectors annular and the heel of the support plate is reduced by the presence of the circumferential cuts 33a, 33b and 33c. The successive annular sectors 27a, 27b, 27c, 27d therefore have good flexibility which allows them to adapt to the deformation profile of the cylinder under the effect of expansion and to the cyclic nature of this deformation, during the rotation of the cylinders. .

The choice of an alloy with low thermal expansion and high mechanical characteristic for producing the support plates of the side walls makes it possible to obtain deformation and elastic return characteristics of the sectors of the support plates making it possible to ensure contact perfect between the edge of the bearing plates and the corresponding cylinders, despite the deformation in the axial direction of the cylinders during casting.

These results are obtained in particular due to the use of support plates comprising an external part produced in the form of a thin and flexible blade separated by cuts in successive annular sectors in the circumferential direction and also having a camber from their outer ends towards the cylinder.

The refractory material constituting the part 6 closing the casting space on its lateral sides is preferably a fibrous refractory having good thermal insulation characteristics and a relatively low hardness. This material may in particular have a hardness significantly lower than the hardness of the protective plate 20 coming into contact with its external face. Such a fibrous material can consist, for example, of alumina fibers impregnated with zirconia gel. Such a product is marketed under the name of Procélit.

In Figure 8, there is shown a side wall and the end portions of the cylinders of an installation continuous casting between cylinders according to the invention and according to an alternative embodiment.

The side wall generally designated by the reference 40 comprises a support 41 in the form of a box having two curved side walls 42 and 43 constituting the support plate holders similar to the elements 10 and 11 shown in FIGS. 2 and 3 .

Two metal support plates 44 and 45 in the form of annular sectors as shown in FIG. 10 are fixed respectively to the plate holders 42 and 43, by screws 46.

As can be seen in FIGS. 8 and 10, the support plates such as the plate 45 have successive sectors such as 45a, 45b, 45c, 45d, 45e and 45f which are separated by cutouts in radial direction passing through the blade metal in the form of an annular sector constituting the plate 45, along its entire thickness.

Each of the sectors such as 45a comprises from the outside towards the inside of the plate 46, a shoe 47 and a flexible blade 48 secured to a heel 49 by means of which the plate 45 is fixed to the plate holder by through a screw 46.

As can be seen in FIGS. 8 and 9, the pads 47 have a profiled shape in the radial direction, limited by two faces inclined relative to each other 47a and 47b making an acute angle.

The external face 47a of the shoe 47 is intended to come to bear against the external edge of the corresponding cylinder 50 of the casting installation.

The external face of the pads of the support plate 44 likewise comes into contact with the external edge of the second cylinder 51 of the casting installation, in the service position of the side wall 40.

The pads 47 of profiled shape are separated from each other by the radial cuts 52 of small width which can be produced by electro-erosion.

The elastic blades 48 whose thickness is substantially less than the thickness of the pads 47 are separated from each other by radial slots 53 having a width in the circumferential direction of a few millimeters.

The parts 49 of the sectors of the plate 45 constituting the fixing heels of the support plate are integral with each other to form a single fixing heel in the form of an annular sector.

As can be seen in FIG. 9 in which a part of the side wall 40 is shown, when this wall is not in abutment against the cylinders 50 and 51, the sectors of the support plates such as the plate 45 are slightly arched outwards, so that the end of the pads 47 projects outwards and has an arrow F , due to the cambering preload of the sectors of the support plate 45.

When the side wall is brought into contact with the cylinders 50 and 51 and applied with a certain force in the axial direction against the front ends of these cylinders, the external face 47a of the pads 47 of the support plates such that 45 is pressed against against the outer edge of the corresponding cylinder.

The outer edge of the cylinders 50 and 51 coming into contact with the pads such as 47 of the support plates is coated with an anti-wear layer, respectively 54 and 55.

The wear layers 54 and 55 produced in an annular zone on the edge of the cylinder can be produced by coating or by treatment of the surface of the cylinder.

This wear layer can be constituted for example by a nitride such as boron nitride or by a carbide such as chromium carbide.

The internal faces such as 47b of the elastic deformable sectors constituting the support plates are inclined and constitute, for the assembly of a support plate, a substantially frustoconical surface.

Between the frustoconical surfaces of the two support plates located opposite the side wall 40 is interposed a piece 56 of refractory material disposed inside the housing 41 and comprising two external surfaces of frustoconical shape.

The piece of refractory material 56 closes the casting space 58 formed between the cylinders 50 and 51.

The refractory piece 56 which is made of a relatively soft material such as a fibrous refractory material has good thermal insulation characteristics and makes it possible to avoid heat transmission between the liquid metal and the housing 41 of the side wall 40. more, the relatively soft part 56 is susceptible to wear by the metal being solidified or solidified, so that a cavity is formed in the part 56 inside which the metal can partially solidify and constitute a lateral slide for the part being cast and solidifying in the casting space 58 and driven by the cylinders 50 and 51 in rotation.

In addition, the part 56 makes it possible to transmit the axial steering force exerted on the housing 41 of the wall 40 to the support plates 44 and 45, so as to apply them to the ends of the cylinders 50 and 51.

Parts 59 and 59 ′ made of a second refractory material are disposed against the internal face of the blades 48 of the support plates 44 and 45.

The parts 59 and 59 ′ have a surface opposite the flexible blades 48 of substantially frustoconical shape extending the surface 47b of the pads 47.

The part 56 made of a first refractory material is not applied directly to the surface 47b of the pads 47 and to the frustoconical surface of the parts 59 and 59 ′ in a second refractory material.

A relatively thin layer 60 of a third refractory material is interposed between the part 56 and the frustoconical surfaces of the pads 47 and the parts 59 and 59 '.

The second refractory material constituting the parts 59 and 59 ′ is a highly insulating material which is intended to protect the flexible blades 48, so that these blades do not lose their elasticity under the effect of the heat coming from the liquid metal filling the pouring space 58.

Indeed, as will be explained with reference to Figure 12, when the cylinders 50 and 51 are deformed in the axial direction, the pads 47 of the bearing plates 44 and 45 come into contact with the edge of the cylinder only in a annular zone of very small width.

As a result, the pads 47 are little cooled in contact with the cylinders 50 and 51 and that the heat of the liquid metal transmitted to the end portion of the pads 47 reaches the blades 48 by conduction. In order to preserve the elasticity of the blades 48, it is therefore necessary to limit the supply of heat to these blades to the heat transmitted by conduction by the pads 47.

The third refractory material constituting the layers 60 must have very good elasticity characteristics in order to be able to adapt to the movements of the pads 47 of the blades 48 and of the insulating parts 59 and 59 ', during the expansion of the cylinders in the axial direction.

Preferably, the first refractory material constituting the part 56 is a fibrous material such as the material sold under the name Procélit.

The second highly insulating material constituting the parts 59 and 59 ′ is preferably a refractory foam such as silica foam.

The metallic material constituting the support plates 44 and 45 is preferably a steel having a low coefficient of expansion and high mechanical characteristics such as a Maraging steel.

We can for example use the steel sold under the name Marphy 2.17 containing less than 0.02% carbon, 17 to 19% nickel, 7.5 to 8.5% cobalt, 4.6 5.2% molybdenum, 0.3-0.5% titanium and 0.005-015% aluminum, the proportions being by weight and the balance of the composition, with the exception of unavoidable impurities, being consisting of iron.

In FIGS. 11 and 12, one sees a front end part of a cylinder 61 of a continuous casting installation between cylinders and, in a highly exaggerated manner, the deformation 62, in the axial direction of the cylinder 61, caused by expansion under the effect of the heat of the liquid metal poured in contact with the cylinder 61.

As can be seen in FIG. 11, the deformation 62 relates to an external annular zone of the cylinder 61 and has an increasing amplitude from the interior of the cylinder towards the exterior and from the upper part of the casting space to the lower part of this pouring space corresponding to the neck at which a partially solidified product is extracted.

In addition, due to the rotation of the cylinder, as shown schematically by the arrow 63, the deformation 62 relates to a constantly variable area of the cylinder 61 and has a cyclical character.

As can be seen in FIG. 12, the pads 47 of the support plates come into contact with the external end part of the deformed zone 62, the contact of this external part or possibly of the entire surface 47a of the pad 47 being ensured due to the elasticity of the blades 48.

A perfectly tight contact is therefore constantly maintained between the support plate and the cylinder whatever the axial deformation of this cylinder.

In addition, the forces making it possible to apply the side wall against the cylinders are distributed over a larger surface, the flexibility of the blades 48 making it possible to adapt the position of the pads 47.

The casting device according to the invention therefore has the advantage of having side walls which can adapt perfectly to the deformations of the cylinder in the axial direction during casting.

The invention is not limited to the embodiments which have been described.

Thus the support plates can be constituted by crown or disc portions comprising successive deformable sectors in the circumferential direction produced in any manner, either by cutting a monobloc plate or by using elements reported.

The support plates can be made of steel or carbon fibers.

The refractory materials constituting the internal part of the side wall in contact with the support plates and the anti-wear materials for coating the cylinders may be different from those which have been described.

The invention applies to any installation for casting a metal product between two cylinders.

Claims (12)

1. Device for the continuous casting of a metal product, comprising two counter-rotating rolls (2, 3; 50, 51, 61) with parallel axes arranged facing each other with a certain gap and two fixed side walls (1, 40) which bear on the axial ends of the rolls, delimiting a casting space (8, 58) between the rolls, and each of which side walls comprises two bearing plates (4, 5; 44, 45) of circular or annular shape which are each in rubbing contact with a plane front face of one of the two rolls (2, 3; 50, 51, 61) at one of the ends of the rolls and at least one additional wall (6, 56) inserted between the two plates (4, 5; 44, 45) and between the rolls (2, 3; 50, 51), characterized in that each of the bearing plates (4, 5; 44, 45) of each of the side walls comprises a plurality of successive annular sectors (27a, 27b, 27c, 27d, 45a, 45b, ..., 45f) in the circumferential direction, these sectors being elastically deformable with respect to one another so as to be able to move in the axial direction, with respect to the rolls (2, 3; 50, 51, 61) during casting.
2. Device according to Claim 1, characterized in that each of the bearing plates (4, 5; 44, 45) consists of at least one metal blade of annular shape having cuts (32a, 32b, 32c; 52, 53) along a radial direction, over its entire thickness and over part of its width in the radial direction, delimiting the elastically deformable sectors (27a, 27b, 27c, 27d; 45a, ..., 45f).
3. Device according to Claim 2, characterized in that the blade (25, 45) has, in its radially cut zone, a thickness less than its thickness in the uncut zone constituting a heel piece (26, 49) for fixing the blade (25, 45) to a support.
4. Device according to either of Claims 2 and 3, characterized in that the cut part of the metal blade (25, 45) is prestressed, so as to exhibit a curvature towards the outside of the blade (25, 45) in the direction of the contact surface of the corresponding roll (3, 51).
5. Device according to any one of Claims 2 to 4, characterized in that the blades (25, 45) constituting the bearing plates further comprise cuts (33a, 33b, 33c) in the circumferential direction over their entire thickness, these intersecting the cuts (32a, 32b, 32c) in the radial direction.
6. Device according to any one of Claims 1 to 5, characterized in that the bearing plates (4, 5; 44, 45) are each fixed to a plate holder (10, 11; 42, 43) of curved shape and have transverse lubrication orifices (29) communicating with a lubricant supply cavity inside the corresponding plate holder and emerging in a slot (31) on the face (25a) of the bearing plate coming into contact with the side of the roll (3).
7. Device according to Claim 6, characterized in that the bearing-plate holders (10, 11) have, over their entire length, a groove (21, 22) over a substantial part of their thickness in a plane parallel to the faces of the bearing plates (4, 5).
8. Device according to Claim 2, characterized in that the successive deformable sectors (45a, ..., 45f) of the metal blades constituting the bearing plates (44, 45) comprise, successively in the radial direction, from the outside towards the inside of the bearing plate, a bearing shoe (47) and a flexible blade (48) whose thickness is less than the thickness of the shoe (47).
9. Device according to Claim 8, characterized in that the shoes (47) have two faces (47a, 47b) inclined with respect to each other and making an acute angle, one of the faces (47a) being intended to come into contact with the side of the corresponding roll (50, 51) and the other face (47b) with the additional wall (56) of the side wall (40).
10. Device according to Claim 9, characterized in that the additional wall (56) consists of a piece made of a first refractory material, in that at least one piece (58, 59) made of a second refractory material is arranged so as to be in contact with the flexible blades (48) of each of the bearing plates and in that a layer (60) made of a third refractory material is inserted between the additional wall (56) and, on the one hand, the shoes (47) and, on the other hand, the piece (58, 59) made of a second refractory material, the first refractory material being a fibrous thermally insulating material, the second refractory material being a very insulating material and the third refractory material being an elastic material.
11. Device according to Claim 10, characterized in that the first refractory material consists of alumina fibres impregnated with zirconia and in that the second material consists of silica foam.
12. Device according to Claim 10, characterized in that the inner face of the deformable sectors of the bearing plates (4, 5) which is opposite that face of the sectors coming into contact with the corresponding rolls (2, 3) is in contact with part of the side wall (1) and consists of an insulating refractory material.

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