EP0428464B1 - Cylinder for single-roll or twin-roll continuous caster - Google Patents

Description

The present invention relates to the continuous casting of thin metallic products such as sheets or strips, in particular steel, on one or between two cylinders, and more particularly the constitution of these cylinders.

For casting installations of this type, it is known to use cylinders whose external peripheral surface, on which the cast metal is caused to solidify, is cooled by the circulation of a cooling fluid inside the cylinder. Commonly these cylinders have a central part or "core" surrounded by a ferrule made of thermally conductive material, such as copper. The circulation of the cooling fluid takes place in channels made either at the interface between the core and the shell, or in the shell itself.

A known problem in the use of these cylinders results from the deformation of the shell due to its heating by contact with the molten metal. As the metal constituting the shell heats up, it tends to expand radially and axially. Radial expansion tends to increase the diameter of the cylinder, which, in the case of casting between cylinders, leads to a reduction in the spacing between the cylinders and therefore to a reduction in the thickness of the cast product. In addition, this radial expansion is not necessarily uniform over the entire width of the cylinder, it can result in variations in thickness depending on the width of the product.

The axial expansion tends to increase the width of the shell, in the axial direction of the cylinder. However, this axial expansion occurs essentially at the level of the external surface of the shell, whereas, due to the internal cooling, there is practically no expansion at the level of the cooling channels. It follows a differential expansion which leads to a bulging of the external surface of the shell, the diameter of the latter being greater in its axially middle part at the diameter towards the ends, that is to say at the edges of the shell. This convexity of the cylinders is prohibitive because it leads to the production of a cast product of smaller thickness in its middle zone than on its edges, which is inadmissible for the subsequent rolling of this product.

To compensate for this hot convexity, it has already been proposed to give the outer surface of the shell a concave cold shape. It is thus possible to obtain a product whose surfaces are flat, or even preferably very slightly curved, which is desirable for subsequent rolling.

However, such an arrangement may be insufficient, especially in the case of large width cylinders. In this case, it would indeed be necessary to have a large concavity of the external surface of the shell when cold, which, at the start of the casting, would lead to too great spacing of the cylinders in the axially median zone.

In an attempt to solve this problem, it has already been proposed, in document EP 98968, to rigidly hold the ferrule on the core only in the axially median zone, and to leave the edges of the ferrule free, not linked to the core of the cylinder. , and kept radially away from it, so as not to prevent the expansion of the latter in the axial direction, expansion which would inevitably cause a bulge if the edges of the shell were rigidly linked to the core which does not expand not.

This arrangement therefore makes it possible to limit the increase in the diameter of the shell in its axially median zone by blocking its radial expansion. However, it does not eliminate the possibility of bulging deformation due to differential axial expansion between the external surface of the shell and the area of the cooling ducts, since the edges of the shell can, following this differential expansion, approach the core. .

In addition, such an arrangement cannot be suitable in the case of casting between cylinders where the forces exerted radially on the shell by the cast product (rolling forces) are very significant near the closing walls of the casting space. , and therefore precisely on the edges of the shell. Indeed, because the shell is not supported on its edges by the core, said efforts can significantly deform the edges of the shell, accentuating its bulging.

The object of the present invention is to propose a cylinder for the casting of thin metallic products making it possible to obtain a cast product of satisfactory dimensional characteristics for a subsequent rolling of this product. More specifically, it aims to solve the various problems mentioned above.

With these objectives in view, the invention relates to a cylinder for a device for continuously casting thin products on one or between two cylinders, comprising a core and a ferrule in which are made conduits for the circulation of a fluid. cooling.

According to the invention, this cylinder is characterized in that the ferrule is rigidly linked to the core in its axially median part and over substantially its entire circumference, by an assembly preventing any radial and axial displacement, in this median part, of the ferrule by in relation to the core, and in that the ferrule is in contact with the core over its entire width, and it is held thereon by its edges by radial holding means allowing axial displacement but preventing radial displacement of said edges of the shell relative to the heart.

According to a preferred arrangement, the assembly linking the shell to the core in its axially middle part is an assembly in dovetail or in the form of a "T" slide.

According to a particular arrangement of the invention, the ferrule is also maintained in axially intermediate zones between its axially middle part and its edges by holding means allowing axial movement but preventing radial movement of said intermediate zones of the shell relative to the heart.

Thanks to the invention, the ferrule is thus held firmly on the heart, at least in its axially middle part and on its edges; any radial displacement of the latter following expansion is therefore prevented, but displacements in the axial direction of the lateral zones of the shell are authorized, which avoids the bulging of the wall which would be due to a buckling caused by a clamping of the edges of the ferrule preventing its axial expansion.

According to another particular arrangement, said edge holding means consist of flanges comprising a circular groove of rectangular section into which penetrates in the axial direction, a corresponding rib of the edges of the shell, with axial play and without radial play.

According to yet another arrangement, more particularly advantageous, the core comprises a circumferential groove of dovetail section, in which is clamped a rib, of corresponding dovetail section, of the internal wall of the ferrule, the heart being for this purpose composed of a central part or hub whose periphery forms one side of said dovetail groove, and an annular flange fitted to the hub and whose periphery forms the other side of said groove, the hub and the annular flange being assembled by clamping means acting axially to ensure the clamping of the rib of the ferrule in the groove of the core.

According to a complementary arrangement, said annular flange also carries a circular groove of rectangular section into which the corresponding rib of one of the edges of the shell penetrates to ensure its maintenance, a flange likewise ensuring the maintenance of the other edge of the ferrule.

This arrangement has the particular advantage, as will be understood more easily below, of allowing the use of ferrules of different width, keeping the same hub, and only changing the ferrule, the flange and the annular flange mentioned. above.

Other characteristics and advantages will appear in the description which will be given by way of example of a cylinder according to the invention, for a continuous casting installation between cylinders of thin steel products such as strips of a few millimeters d thickness and several tens of centimeters in width.

• la figure 1 est une demi-vue en coupe axiale d'un cylindre conforme à l'invention ;
• la figure 2 est une demi-vue en coupe axiale d'un cylindre adapté pour couler des produits de plus grande largeur ;
• la figure 3 est une vue partielle simplifiée en coupe axiale d'une variante de l'invention ;
• la figure 4 représente une autre variante encore selon laquelle l'assemblage virole-coeur est réalisé par des rainures étagées à l'inverse des exemples précédents.

Reference is made to the accompanying drawings in which:

• Figure 1 is a half view in axial section of a cylinder according to the invention;
• Figure 2 is a half view in axial section of a cylinder adapted to pour products of greater width;
• Figure 3 is a simplified partial view in axial section of a variant of the invention;
• FIG. 4 represents yet another variant according to which the shell-core assembly is produced by stepped grooves, unlike the previous examples.

The cylinder shown in section in FIG. 1 comprises a hub 1 rigidly connected, for example by shrinking, on a shaft 2 for driving in rotation. The ends of the shaft 2 are provided for journalling in bearings of the casting installation, and one of these ends is connected to rotation drive means, not shown.

The hub 1 carries on one side an annular flange 3 and on the other a flange 4, these three coaxial parts and assembled by tie rods 5, represented in the figures only by their axis, form the heart 6 of the cylinder.

A ferrule 7, made of thermally conductive material such as copper, surrounds the core of the cylinder while being adjusted both on the hub 1, on the flange 3 and on the flange 4.

Inside and in its axially median zone, the shell has a circumferential rib 9 of dovetail section. This rib 9 is engaged in a groove 10 of corresponding section, one side 10 ′ (the right side in the drawing of Figure 1) is machined in the hub 1, and whose other side 10 '' is formed by a projection 3 ′ of the annular flange 3. In other words, it is the assembly formed after assembly of the hub 1 and the annular flange 3, and forming the core 6 of the cylinder, which determines the groove 10.

It will be readily understood that this arrangement consisting in forming the groove 10 by the assembly of the two parts forming the core, is necessary to allow the fitting of the ferrule. The fact that the section of the rib 9 of the ferrule and of the corresponding groove is in dovetail has the advantage of pressing the ferrule very effectively on the heart by simply clamping the different parts of the heart together. . In addition, the conical bearing surfaces formed by the oblique surfaces of the circular groove at the dovetail ensure an energetic tightening of the ferrule on the core, which allows the transmission of a high torque without risk of slipping between ferrule and hub. This clamping effect is further accentuated during the heating of the shell because of the camber of the shell which tends to occur and which further increases the contact pressure on the conical surfaces of the assembly.

The ferrule is also held by its edges by means of circular grooves 13,14 of rectangular section produced respectively in the annular flange 3 and the flange 4, and in which engage without radial clearance of the ribs 11, 12 extending the ferrule in the axial direction. An axial clearance "j" when cold is provided respectively between said grooves 13, 14 and the ribs 11, 12 so as to allow the axial displacement of the ribs in the ribs, which can occur by axial expansion of the ferrule during its heating . Furthermore, the retention of the edges of the shell by this system of grooves and ribs avoids possible detachment of the edges of the shell of the core of the cylinder, detachment which could be caused by the radial expansion of said edges.

To ensure the most homogeneous cooling possible of the shell, the cooling water is made to circulate according to the arrows in FIG. 1, in the opposite direction in adjacent conduits 8. For this purpose the cylinder has water inlet pipes 20, connected to a rotary joint not shown. These pipes 20 open into a circular distribution channel 21. The water arriving in this channel is directed on the one hand towards an end 7 ′ of the shell by holes 22 made in the flange 4, and holes 23 made in the ferrule and opening into half of the total number of cooling conduits 8, supplying alternately one in two of these conduits. On the other hand, the water from the distribution channel 21 is directed towards the other end 7 '' of the shell by axial conduits 24 drilled in the hub and holes 25 and 26 produced respectively in the annular flange 3 and the ferrule, similarly to the holes 22 and 23, the holes 26 in the shell supplying the other half of the cooling conduits.

Evacuation of the cooling water is ensured in an equivalent manner by holes 23 ′, 22 ′ and 26 ′, 25 ′, conduits 24 ′, a collecting channel 21 ′, and outlet conduits 20 ′.

To ensure a homogeneous distribution of the water flows, the various pipes and bores are regularly distributed radially and circular grooves such as 27, 28 into which the various bores open, such as 25, can be produced at the level of the different contact surfaces. of the various constituent parts of the core.

These said grooves also make it possible to avoid precise circumferential positioning when assembling the different constituent parts of the cylinder and in particular of the shell on the core.

For the same purpose of ensuring a homogeneous distribution of the water flows in the various cooling conduits, provision is preferably made for means making it possible to adjust the pressure drop in the direct water circulation circuit (from the right to the left according to the figure, in the conduits 8) comprising the holes 22,23, 23 ′, 22 ′. In fact, this circuit is shorter than the circuit leading the water to circulate in the cooling conduits in the opposite direction (from left to right) and therefore the pressure drops are less significant there. Said means therefore make it possible to equalize the pressure drop in the two said circuits. They may consist, for example, of reducing the minimum passage section in the shortest circuit, either by making the holes 22,22 ′ to a smaller diameter than the holes 25, 25 ′, or by interposing in said circuit parts provided calibrated orifices or any other equivalent means.

Of course, it is also possible to maintain the two edges of the ferrule by flanges such as 4, the annular flange then having the function of supporting the ferrule and its tightening by the dovetail assembly, the flange located on the side of this flange serving only to maintain the edge of the corresponding ferrule. In other words the annular flange 3 is in this case replaced by two parts including a flange identical to that (4) located on the other side of the shell, the assembly of the various constituent parts of the heart being carried out as indicated previously by tie rods 5.

One can also, of course, use, on both sides, flanges such as the flange 3 in other words the ferrule is then in direct contact with the hub 1, only in its middle part, by the surface constituting the bottom of the groove 10 , and in contact with the flanges 3 on each side.

Preferably, the width of the dovetail groove is at least about half the width of the ferrule. It has in fact been observed that the width of the groove conditions the deformation of the external surface of the shell during casting. For example, for a ferrule 865 mm wide, the external surface of which is, cold, cylindrical with a straight generator, the maximum variation, when hot, of the external diameter of the ferrule over its width, is 0.12 to 0 , 25 mm if the width of the groove is approximately 300 mm, 0.11 to 0.17 mm, if this width is approximately 350 mm, and 0.05 to 0.14 mm if this width is about 430 mm, half the width of the shell.

In the latter case, the generator of the ferrule has a slight bulge in the middle and in the axially intermediate zones between the sides of the dovetail rib and the edges of the ferrule, that is to say at the places where it is not kept on the heart. These hot deformations can of course be compensated by additional machining carried out cold so as to obtain a rectilinear generator, or a very slightly concave one, in the regime established during casting. These deformations are clearly less than that of the order of a millimeter which can be observed in the ferrule-heart connection systems according to the prior art.

To further limit this deformation, the assembly can be carried out in accordance with the simplified representation of FIG. 3. In this case the ferrule 7 is held on the core 6 in its axially middle part and on its edges, as in the previous example . In addition, it is also held in axially intermediate zones between the middle part and the edges by grooves 30.

In addition, it is also held in axially intermediate zones between the middle part and the edges by grooves 30 and corresponding ribs 31, similar to the grooves and ribs for holding the edges, preventing the radial displacement, and therefore the camber, of the shell in line with these grooves and ribs, but allowing relative axial displacement, an axial clearance, when cold, being provided for this purpose between grooves and ribs.

Another advantage of the configuration of assembly of the different parts of the cylinder previously described in relation to Figure 1, will emerge in view of Figure 2 which shows a cylinder having a ferrule of greater width. This cylinder is constituted in a similar manner to that previously described and in particular the hub 1 is identical, as is the dovetail assembly.

Only the width of the ferrule 7 is different, as well as the annular flange 3 '' and the flange 4 ′ which are adapted to the new width of the ferrule.

It will easily be understood that the casting of products of different widths therefore requires only the replacement of these three parts (ferrule, flange and flange), the hub 1 remaining the same regardless of the width of the ferrule.

FIG. 4 schematically represents another variant of the invention. In this case the dovetail assembly is reversed, that is to say that it is the core which comprises in its axially median part a rib 39 which is clamped in a corresponding groove 40 of the ferrule. Similarly, the retention of the ferrule on its edges, and possibly in intermediate zones, is ensured by groove-rib systems 41, preventing the radial deformation of the ferrule 7 ′ while allowing its axial displacement, relative to the core 6 ′ of the cylinder. To allow the ferrule to be put in place, it can be made up of two parts which are symmetrical with respect to the axially median plane and assembled by tie rods 42. The core itself can be made up of two separate parts at said median plane, means being provided to separate these two parts from one another and thus ensure the blocking of the dovetail assembly.

Whatever the variant, the outer surface of the ferrule can be cold machined according to a profile taking into account the hot deformations which may remain, so as to form, in the established casting regime, a perfectly cylindrical or slightly concave surface in order to obtain a cast product whose surfaces are flat or have the slight curvature desirable for subsequent rolling.

Claims (10)

1. Roll for a device for continuous casting of thin metal products onto one roll or between two rolls, including a core (6) and a shell (7) in which conduits (8) are made for the circulation of a coolant, characterized in that the shell (7) is rigidly linked to the core (6) in its axially central part and substantially over its entire circumference by an assembly (9,10) preventing any axial or radial displacement, in this central part, of the shell with respect to the core, and in that the shell is in contact with the core over its entire width and is held in place by its edges (7',7'') against the core by radial holding means (11,12,13,14) allowing axial displacement but preventing radial displacement of the said edges of the shell with respect to the core.
2. Roll according to Claim 1, characterized in that the shell is also held in place in axially intermediate zones between its axially central part and its edges are held in place by radial holding means (30,31) allowing axial displacement but preventing radial displacement of the said intermediate zones of the shell with respect to the core.
3. Roll according to Claim 1, characterized in that the said means for holding the edges in place are formed by flanges (4) which include a circular groove (14) of rectangular cross-section in which a corresponding rib (12) of the edges of the shell penetrates, in the axial direction, with an axial clearance (j) and without radial clearance.
4. Roll according to Claim 1, characterized in that the assembly linking the shell to the core in its central part is a dovetail or "T"-groove assembly.
5. Roll according to Claim 4, characterized in that the core (6) comprises a circumferential groove (10) of dovetail section, in which a rib (9), of corresponding dovetail section, of the inner wall of the shell is clamped, the core being for this purpose composed of a central part or hub (1), the periphery of which forms one side (10') of the said dovetail groove, and of an annular clamp (3) fitted onto the hub and the periphery of which forms the other side (10'') of the said groove, the hub (1) and the annular clamp (3) being assembled by clamping means (5) acting axially in order to clamp the rib of the shell in the groove of the core.
6. Roll according to Claim 5, characterized in that the said annular clamp (3) also has a circular groove (13) of rectangular section in which the corresponding rib (11) of one (7'') of the edges of the shell penetrates in order to hold it in place, a flange (4) likewise holding the other edge (7') of the shell in place.
7. Roll according to one of Claims 4 to 6, characterized in that the width of the dovetail groove (10) is at least approximately half the width of the shell.
8. Roll according to Claim 4, characterized in that the dovetailed assembly of the shell onto the core is formed by a rib (39) of the core (6') clamped in a groove (40), of corresponding section, of the shell (7').
9. Roll according to one of Claims 1 to 8, characterized in that the shell (7) includes cooling conduits (8) parallel to the axis of the roll, the ends of these conduits, located towards the same edge of the shell, being alternately connected to a coolant inlet (20) and a coolant outlet (20') so as to circulate the said coolant in opposite directions in two adjacent conduits.
10. Roll according to one of Claims 1 to 9, characterized in that the outer surface of the shell is concave when cold.

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