AU721453B2 - Roll for a metal rolling or continuous casting installation - Google Patents

Description

Roll for a metal rolling or continuous casting installation This invention concerns a roll for a metal rolling or continuous casting installation. More precisely, it concerns a new roll structure usable both for the backup and working rolls of hot or cold rolling mills and for the rolls used in continuous casting installations between rolls producing flat metallic products, the rolled or cast products being ferrous or non-ferrous.

Rolls used in such installations including a shell coaxially enclosing a core or hub which is possibly installed on a shaft are already known. Depending on uses, these rolls are rotated by a drive system or simply installed so as to rotate in bearings. The mechanical and thermal characteristics of the materials used for the shell and the core respectively are selected to suit the stresses to which these items are submitted. The core is conventionally made from steel and mainly has mechanical strength characteristics adapted to support the loads generated by the worked product and possibly the rotational drive torque. The shell must support, on the one hand, the mechanical stresses due to the pressure of the rolled or cast product and, on the other hand, especially for hot rolling working rolls or casting rolls, the thermal stresses. It is often cooled either by outside spraying or, especially for casting rolls, by circulating a cooling fluid in channels made within the thickness of the shell.

It is known that, under the effect of the various stresses, the rolls, and more especially their shells, deform. In rolling installations, it is well known to compensate the deformations, which are mainly bending deformations of the complete roll, by adjusting the camber and the balance of the roll stands.

In continuous casting installations between rolls, where the deformations of the shell are mainly of a thermal origin, it is already known to connect the shell to the hub only locally, for example in an axially median part of the roll, to allow a certain freedom of deformation of the shell in relation to the hub and thus limit the stresses in the shell. Also, it is known to adapt the cooling to compensate, or at least to control in part, the deformations of the shell to obtain a required profile for the outside surface of the shell and thus the required profile for the cast product.

The aim of this invention is to provide a roll enabling better control of the outside profile of the shell, that is to say the form of its generatrix, by acting directly on the shell to compensate the deformations of the roll and the possible resulting geometrical defects in the product, in order to obtain the required profile for the said product. The aim of the invention is also to limit the effect of local or temporary overpressures which may be caused, for casting between rolls, by variations in the solidification condition of the cast strip or other spurious phenomena which may cause, as it is known to do under such circumstances, a variation in the spacing of the bearings supporting the rolls to limit these overpressures.

With these targets in mind, the subject of the invention is a roll for a rolling mill or a continuous casting installation between two such rolls, including a hub and an outside shell coaxial with the hub, characterised in that it includes, between the hub and the outside shell, a deformable shell including a number of annular cells axially juxtaposed and supplied with a liquid under pressure, each cell being delimited by an inner cylindrical wall in contact with the hub and an outer cylindrical wall in contact with the outside shell, 22 Z connected by two lateral deformable walls presenting, in a section through a radial plane, convex faces disposed facing each other.

As it will be better understood later, the pressure which is exerted in each cell on the convex faces of the lateral walls tends to straighten them and, by the resulting knuckle joint effect (that is to say the buttressing effect of the lateral walls between the inner and outer cylindrical walls), generates at level of the concerned cell a force separating the said cylindrical walls from each other. On account of the rigidity of the hub, the inner cylindrical wall is not liable to significantly self deform and. the said separating force leads to high radial loads on the outer cylindrical wall, which lead to an increase in its radius, and therefore to the deformation of the outside shell. As it will be easily understood, these loads increase as the convexity of the lateral walls decreases, whilst remaining of course above a practical minimum required to avoid the inversion of the convexity of the walls, that is to say cambered, under the effect of the internal pressure of the cell.

It is to be noted that the radial deformation of the outer walls of the cells necessarily leads to a circumferential lengthening of these walls. This lengthening and the deformation of the lateral walls of the cells is possible, remaining within the elastic limits of the component materials, as their amplitudes remain low, the dimensional variations sought to correct the profile of the roll in compliance with the aim of the invention being around one micron to a tenth of a millimetre on roll radius which conventionally is around several decimetres.

A person skilled in the art will easily understand that the inner pressure of the cell naturally tends to directly increase the spacing between the cylindrical walls due to the load generated by the pressure on the said cylindrical walls. However, the radial load on the outer cylindrical wall and on the outside shell, due to the above mentioned knuckle joint effect, is added, and in a predominant manner, when the convexity of the lateral walls is sufficiently low and the width of the cell (in roll axial direction) is limited in relation to its thickness (in radial direction). Moreover, these two aspects are on a part due to the fact that for a given cell thickness or height, its width can be reduced as the convexity decreases. Also, the more the width of the cell is low, the more the number of juxtaposed cells for a given axial distance is high, and therefore the more the cylindrical wall separating force exerted globally over the said axial distance could be high, as the force due to the said knuckle joint force generated by each cell is multiplied by the number of cells, whereas the global force resulting from the pressure exerted directly on the cylindrical walls depends mainly on the axial length of the cylindrical wall area submitted to this pressure and not to the number of juxtaposed cells over this length.

Moreover, it will be easily understood that, further the increase of the global force, the use of many juxtaposed cells enables, as it will be seen better later, to more efficiently control the local deformations of the roll by independently adjusting the pressure in each cell or in each group of juxtaposed cells.

For this purpose, according to a specific arrangement of the invention, the set of cells can be divided into several groups of juxtaposed cells, the cells of a given group being connected and supplied with same pressure, the supply pressures of two separate groups being independently adjustable.

The cells could be distributed over complete axial length of the outside shell or, alternatively, over only a part of this length, for example, only at the two ends K. or, conversely, only in its median part, in order, more especially, to be able to act on the deformation of the outside shell in the corresponding areas, the outside shell then being possibly attached directly to the hub, in a known manner, in the axial area or areas without cells.

The deformable shell could consist of separated cells each with its specific inner and outer cylindrical walls, the cells being then juxtaposed by stacking in axial direction between the outside shell and the hub.

Alternatively, the inner and outer cylindrical walls could respectively consist of one and the same part for a set of juxtaposed cells to which the lateral walls of each cell are attached.

Other advantages and features will appear in the description which will be given of a roll in compliance with the invention for a continuous casting installation between two rolls and several examples of application of the invention to rolling mill rolls.

Refer to the appended drawings where: figure 1 represents a sectional view along a radial plane of a roll in compliance with the invention for a continuous casting installation between rolls; figures 2 and 3 schematically represent two possible applications of a roll in compliance with the invention in roll stands; figures 4 and 5 represent two variants of realisation where the cells are used only over a part of the axial length of the shell; figure 6 shows yet another mode of realisation in which the deformable shell is formed of a number of axially juxtaposed and independent cells.

The roll shown on figure 1 is especially intended for a continuous casting installation between two rolls the principle of which is well known. Here it is simply recalled that such an installation includes two rolls where the walls are forcefully cooled by circulating a cooling liquid inside. In the casting installation, the axes of these rolls are parallel, located in a horizontal plane, and rotated in opposite directions. Documents EP- A-0499562 and EP-A-0428464 can especially be referred to further information on the arrangement of these rolls and the known means of cooling their walls.

The roll of figure 1 includes a shaft 1, a hub 2, an outside shell 3 and an intermediary deformable shell 4, located between the hub 1 and the outside shell 3 and coaxially to these.

The outside shell 3, made of copper or alloy with good heat conductivity properties, includes a number of cooling channels 31, extending in an axial direction and drilled within the thickness of the shell. Distribution channels 21 are made in the hub 2, to bring a cooling liquid into the cooling channels 31, this liquid being supplied and evacuated by the supply channels 22 and the return channels 23 drilled in the end revolving joints 24, 25. The design of these various channels together forming a general cooling circuit may be modified without leaving the scope of the invention. Document EP-A- 0428464, describing other possible designs of the cooling circuit, can especially be referred to.

The intermediary shell 4 includes an inner cylindrical wall 41 in contact with the hub 2 and an outer cylindrical wall 42 in contact with the outside shell 3.

The inner cylindrical wall 41 is held in axial position against a shoulder 26 of the hub by means of a nut 27.

The inner cylindrical walls 41 and the outer cylindrical walls 42 define between them a number of annular cells 43 delimited by the lateral walls 44, 44' Each cell 43 has a hollow ring shape with for axis the rotational axis A of the roll. Each cell 43 is delimited: towards the axis of the roll, by a portion of the inner cylindrical wall 41, towards the outside, by a portion of the outer cylindrical wall 42, and laterally by the lateral walls 44, 44'.

In a section through a radial plane, as can be seen on figure 1, the two lateral walls 44, 44' of any cell 43 are curved with their convex faces opposite each other.

Each lateral wall 44, 44' is attached, for example by welds 45, to the inner cylindrical wall 41 and to the outer cylindrical wall 42 respectively. The lateral walls 44, 44' are thin, for example around several millimetres, so that they will elastically deform under the effect of an internal pressure applied in each cell.

The axial positioning of the outside shell 3 in relation to the deformable shell 4 is defined, for example, by rings 32 placed in a circumferential groove made in the outer cylindrical wall 42 and which are pushed, when the roll is installed, by means of rods 33, into a corresponding groove made in the bore of the outer shell 3. It can be easily understood that, in such a case, the outside shell 3 is first placed on the deformable shell 4, then the rings 32 are pushed by the rods 33, via the inside of the deformable shell, to ensure axial keying of the two shells one on the other and only then is the assembly of the two shells installed on the hub 2.

The cells 43 are supplied with fluid under pressure by the supply lines 51, 52, 53 each connected to a source (not shown) of liquid under pressure adjustable in an independent manner. In the example shown, the line 51 directly supplies the first cell, on the left of figure 1, and the next three cells, by the connecting lines 51', which connect two adjacent cells by passing through their respective lateral walls. The line 52 passes through the first four cells, emerges into the fifth one and supplies in series the next seven cells via the connecting line 521 In a similar manner, the line 53 supplies the last four cells, on the right of figure 1. The pressure in each group of cells connected together by the intermediary lines can thus be specifically adjusted. The various cell supply lines are preferably formed of metallic pipes made of rigid tubes, welded or brazed to the lateral walls 44, 44' at the crossing of these walls, to ensure sealing. They are however sufficiently deformable to take the deformations of the lateral walls 44, 44' when the cells are pressurised, these deformations remaining low.

It can again be noted that the link between the cooling channels 31 of the outside shell 3 and the distribution channels 21 of the hub is ensured by the spaces 48 located between two adjacent cells of the two groups of cells located towards the axial ends of the rolls.

The respective diameters of the hub 2, of the outside shell 3 and of the deformable shell 4 are defined so as to obtain a fit without clearances, or even a slight interference fit, when the cells are not pressurised. In order to facilitate installation, the compartments between the cells can then be pressurised, by means of other lines not shown but easily made by a man skilled in the art, so as to slightly reduce the thickness of the deformable shell and thus create a slight radial clearance between the deformable shell and the outside shell and/or between the deformable shell and the hub.

During operation, the pressure in each group of cells is adjusted to the required value to create a more or less important swelling of the cells, that is to say a separation of the two lateral walls of a given cell leading to a radial deformation of the outside shell. The cell supply pressures could, for example, be adjusted by servovalves installed on the supply lines 51, 52, 53 and controlled by cast strip flatness measurement means (such as, for example, a flatness roller or a profile gauge) or by sensors measuring the deformations of the outside shell to obtain the required profile for the outside surface of the rolls and therefore the required profile for the strip.

The drawing on figure 2 shows a first application for a roll according to the invention such as a rolling mill roll 100 in a so-called two-high mill stand. One or both rolls can be made according to the invention. It is to be noted that in the example shown on this figure, a first group of cells is formed by the cells 430 located at the two axial ends which are all supplied by a first distribution line 510, and a second group is formed by the cells 431 located in the axially median part of the roll and supplied by a second line 520. This example shows a design variant of the supply of the cells which is achieved here by radial channels 511, 521, drilled in the hub and passing through the inner cylindrical wall 410 of the deformable shell 400. Each cell is thus supplied by a radial channel 511, 521, all radial channels supplying the cells of a given cell group being connected to the same supply line drilled in the hub 200 along an axial direction. A similar design could of course be adapted to the case of the previously described casting roll.

Figure 3 shows another application of the roll according to the invention as backup roll 110 in a rolling mill four-high stand.

Figure 4 shows another design of a roll in compliance with the invention where the hub 210 includes a median shoulder 211 with a diameter more or less equal to the inside diameter of the outside shell 310. The outside shell 310 can be solidly attached to the said shoulder 211, the cells 430 then being placed only at the axial ends on each side of the shoulder.

Inverse of the previous example, figure 5 shows a design where the hub 220 includes a shoulder 221 located at one axial end of the roll onto which an edge of the shell bears directly. The axially opposite edge of the shell bears on a bush 222 fitted onto the hub. The deformable shell is located in the axially median part of the roll, between the shoulder 221 and the bush 222. A nut 223 ensures the axial attachment of the bush 222.

In the variant shown on figure 6, the deformable shell 404 consists of the juxtaposition, in the axial direction, of several independent cells 414, that is to say in this case, the inner and outer cylindrical walls are not common to several cells as in the examples described previously. Here, each cell 414 has its own outer cylindrical wall 415 and its own inner cylindrical wall 416 which form an independent element, generally of toric form, with the lateral walls. The deformable shell then consists during installation by the stacking of several of these toric elements over a portion or the complete axial length of the outside shell. This variant enables easier maintenance of the assembly.

The invention is not limited to the designs and applications described above only as an example. In particular, the various design variants of the cells and their pressure supply means could be combined together within a given roll.

Claims (8)

1. 2. Roll in accordance with claim 1, characterised in that the set of cells (43) is divided into several groups of juxtaposed cells, the cells of a given group being connected together and supplied with same pressure, the supply pressures of the two separate groups being independently adjustable.
2. 3. Roll in accordance with claim 1, characterised in that the cells (43) are distributed over the complete axial length of the outside shell (3)
3. 4. Roll in accordance with claim 1, characterised in that the cells (43) are distributed over only a portion of the axial length of the outside shell (3) Roll in accordance with claim 1, characterised in that the deformable shell consists of separated cells (414) each with its specific inner cylindrical walls (416) and its outer cylindrical walls (415), these cells being juxtaposed by stacking in the axial direction between the outside shell and the hub.
4. 6. Roll in accordance with claim i, characterised N in that the inner cylindrical walls (41) and the outer -1 -cylindrical walls (42) respectively consist of one and the same part for a set of juxtaposed cells on which the lateral walls (44, 44') of each cell are attached.
5. 7. Roll in accordance with claim i, characterised in that the cells (430, 431) are supplied under pressure by radial channels (511, 521) made in the hub and passing through the inner cylindrical wall (410) of the deformable shell (400)
6. 8. Roll in accordance with claim 1, characterised in that two adjacent cells (43) of a given group of cells are connected by deformable lines 52') passing through the lateral walls (44, 44') of the said cells.
7. 9. Roll in accordance with claim i, characterised in that the outside shell includes internal cooling channels these cooling channels being supplied by passages (48) located between two adjacent cells (43) Continuous casting installation between rolls characterised in that it includes two rolls according to any of the claims 1 to 9.
8. 11. Roll stand characterised in that it includes at least one roll according to any of the claims 1 to 7.