EP1560667B1 - Method for increasing the range of production of a metal product rolling installation and installation therefor - Google Patents

Abstract

The invention is aimed at enlarging the production range of an installation for the cold rolling of metal strip, incorporating at least two rolling cages (L1, L2) operating in tandem. At least one of the cages (L1) is equipped with a transformation means allowing the configuration of the cage to be changed, whilst conserving the same means for the application of the rolling effort, in a manner to arrange at least two configurations each corresponding to a production range. The configuration of the transformable cage is chosen as a function of the characteristics of the product to be rolled, the production range being thus enlarged. An Independent claim is also included for a rolling mill installation for putting this method of enlarging the production range into service.

Description

The subject of the invention is a method for extending the production range of a cold rolling plant for metal products in strip form and also covers the installations provided with means for implementing the process in order to widen their range of products. production, (see for example JP-A-05 228504 ).

The cold rolling is normally carried out in several successive passes, in two opposite directions on a reversible train, or on several mill stands operating in tandem.

It is known that, in a rolling mill, the product is driven between two working rolls whose spacing is less than the gross thickness of the product upstream. There is a flow of the metal which is frictionally driven in the chock between the rolls, to an outlet section whose thickness corresponds substantially to the spacing between the working rolls. During this operation, the structure of the metal changes and its hardness increases.

During rolling, the working rolls tend to deviate from one another and the air gap between the generatrices opposite must be maintained by application, between the cylinders, a clamping force often called force or rolling force. The rolling force to be exerted to obtain a certain degree of reduction in thickness depends, in particular, on the diameter of the working rolls which determines the length of the reduction zone as well as the mechanical and metallurgical characteristics, such as its elastic limit, its composition, for example, low-carbon low-carbon steel, stainless steel, alloy steel, etc.

In general, a cold tandem rolling mill comprises a succession of cages arranged one after the other in the path of the strip, to ensure a gradual reduction in the thickness thereof.

Each roll stand comprises, in a conventional manner, two support columns spaced apart and connected by sleepers, between which is mounted a set of superposed rolls having parallel axes and placed substantially in the same clamping plane substantially perpendicular to the direction of movement of the product.

We can make rolling mills of different types. In general, in a rolling mill, the rolling product passes between two working rolls which define the rolling plane; these cylinders are generally of relatively small diameter compared with the forces to which they are subjected; they are supported, respectively, on at least two support cylinders between which is applied the rolling force.

It is known that the rolling stands used in the metallurgical industry can have several types of configurations depending on the nature of the product to be treated.

The most common rolling mills, especially for large productions, are of the "quarto" type comprising two working cylinders each associated with a larger diameter support cylinder, or of the "sexto" type, in which intermediate cylinders are interposed. between each working cylinder and the corresponding support cylinder.

This arrangement allows the use of small diameter cylinders that can be associated with side support rollers, in a configuration called "Z.HIGH".

Other configurations, including a greater or smaller number of cylinders can also be used in industry, but for smaller productions.

The cylinders are supported on each other along substantially parallel bearing lines, and directed along a generatrix whose profile, normally straight, depends on the forces applied and the strength of the cylinders. Generally the clamping force is applied by screws or jacks interposed between the cage and the ends of the shaft of a support cylinder, the other support cylinder bearing by these ends directly on the cage, or by via a wedging device or height adjustment to compensate for variations in diameters of all the cylinders which wear out gradually. The cylinders must therefore be able to move relative to the cage and, for this purpose, are carried by rotary support called chocks, which are slidably mounted vertically inside windows formed in the two columns of the cage, and each provided with two guiding faces of the chock, parallel to the clamping plane.

As the support rolls have a large diameter, the corresponding guide faces are generally formed directly on the two uprights of the corresponding column of the cage. On the other hand, the working rolls having a smaller diameter, their chocks are smaller and the corresponding guide faces, which are narrower, are arranged, generally, on two massive pieces fixed on the two posts flanking the window and extending projecting inwardly therefrom.

The clamping forces are normally applied between the two ends of the two support cylinders. Since the rolled product, of variable width does not completely cover the length of the working rolls, each roll can bend under the action of the forces applied and the result is a variation in the thickness of the passage space of the roll. band between the working cylinders, which generates defects in profile and flatness.

To try to correct these profile defects across the rolled product, it was first proposed to compensate the deformation of the rolls due to the rolling force, by a bulge of their surface obtained by machining according to a particular profile.

However, the lack of thickness on the profile across the rolled product is complex because it is the result of all the deformations of all cylinders, which are of different diameters, and the deformation of all the constituent parts of the rolling mill cage under the stress.

That is why, in recent years, more sophisticated systems have been developed for modulating the correction made.

In a first known system, controlled bending forces are applied to both ends of the shaft of each working roll, in order to achieve cambering effects to continuously correct the distribution of stresses.

For this purpose, hydraulic cylinders are usually used placed on either side of each chock and bearing in one direction on the fixed cage and in the other on projecting lateral parts forming support lugs of the chock. Usually, these bending cylinders are housed with their hydraulic circuits inside the two projecting pieces used to guide the work chocks. These parts thus form support blocks of the cylinders which are often called hydraulic blocks.

It is thus possible to perform a so-called negative bending, by tightening the chocks of the two working cylinders, to compensate for an excess thickness of the edges of the product or a so-called positive bending, by spacing the same chocks of the two work rolls to compensate for an excess thickness of the central part of the product.

It has also been proposed, in so-called "sexto" rolling mills, to interpose an intermediate cylinder between each working roll and the associated support roll, which makes it possible to control an axial displacement, in opposite directions, of the two intermediate rolls in order to apply the rolling force, not on the whole table of cylinders, but only on the width of the product. This reduces the deformations of the cylinders and gives a product of better flatness.

Furthermore, the use of intermediate rolls makes it possible to use working rolls of smaller diameter and thus to reduce the rolling force required for the same reduction in thickness.

It is also possible to perform an axial displacement, in opposite directions, of the working rolls in the quarto mills, and / or the intermediate rolls in the sexto mills, in order to better control the distribution of the stresses over the width of the product.

In addition, in quarto mode as in sexto mode, special provisions chocks can combine the bending system and the cylinder displacement system.

In another system known as "CVC", the working rolls of a "quarto" rolling mill, and / or the intermediate rolls, are given in a "sexto" mill, complementary curvilinear profiles making it possible, by axial displacement of cylinders, of create a variable curvature between the upper cylinder and the lower cylinder.

More recently, it has also been proposed to modulate the rolling force along the generatrix of contact with the working roll or the intermediate roll, by transmitting the rolling force by means of a cylinder comprising a rotating envelope around a fixed shaft and supported on it by means of a series of cylinders to vary the distribution of stresses along the generatrix support.

All these devices, as well as other improvements, developed for several years, have made it possible in the cold rolling technique, in particular in tandem mills, to constantly improve the quality of the final product. However, these devices are expensive and are therefore profitable only from a certain volume of production. In addition, this profitability must be maintained for several years to justify the amount of investment.

However, because the rolling occurs by flow of the metal between the two working rolls, it is necessary to adapt to the mechanical, metallurgical and dimensional characteristics of the product, the diameter of the working rolls, the torque applied to those and, in a general manner, all the means making it possible to exert the rolling force.

In addition, it should be noted that, in a tandem rolling mill, the rolling determines, by hardening, a gradual increase in the hardness of the product and, consequently, in the rolling force to be applied for the same reduction in thickness, thickness and thickness. one cage to the next.

Therefore, the application means of the clamping force may saturate in power if the hardness of the starting material is too high.

So far, it seemed necessary, especially for large productions to use equipment adapted to a certain range of products whose characteristics remain in a fairly limited field. In practice, installations of very large capacity, for example exceeding 1 million tons per year, have been carried out only for two families of steel, on the one hand steel for body panels and on the other hand , steels for packaging.

However, the needs of users are constantly evolving in the direction of a diversification of qualities required and a change, sometimes brutal, quantities to provide. Thus, in the automotive industry, we are moving towards the use of steels with very specific shades to obtain high performance.

For example, for the body sheet, we have seen appearing successively the shades called, in the trade, CQ, DQ, DDQ, EDDQ whose elastic limit extends from 180 MPa to 250 MPa as well as very hard steels having a high elastic limit (HSLA) up to 600 MPa. In contrast, very low carbon soft steels (IF) with an elastic limit of about 160 MPa are also required.

In addition, it is sought to reduce, as much as possible, the weight of the products manufactured without decreasing the strength and therefore, for the same performance, sheets with thinner and smaller thicknesses that require reduction rates are required. high, while maintaining the same requirements of regularity of thickness, flatness and surface quality.

On the other hand, even the rolling process must be able to adapt to the quality of the treated steels.

Thus, recently, we have developed steels called "TRIP" (TRansition Induced Plasticity) which are developed so that the final recrystallization is only in the stamping phase, while it occurred previously in the accelerated cooling phase at the exit of the hot train or during cold rolling. In addition, while for common or soft steels the breaking limit is only slightly greater than the yield strength (Re ≈ 0.8 Rm), TRIP steels have a breaking limit of up to twice the value of the elastic limit. The work hardening curve from which the pattern of the rolling passes is determined is therefore completely different. Moreover, such steels are generally characterized by the value of their limit of rupture and not, as previously, by that of their elastic limit.

The iron and steel industry is therefore subject to contradictory requirements. On the one hand, rolling mills must be equipped with expensive devices, specially adapted to the characteristics of the products to be rolled to obtain the desired qualities and, secondly, the quantities requested by customers are often insufficient to make such equipment profitable.

The object of the invention is to solve all these problems by means of a method making it possible to widen the production range of a rolling mill by having the possibility of treating thereon, steels having dimensional characteristics, mechanical and metallurgical, while maintaining sufficient productivity for all metal grades and benefiting, however, from all means necessary to optimally guarantee the qualities of thickness, flatness and surface quality desired for the rolled product.

The invention thus provides a production tool easily adaptable to changing needs, both in the quality of the rolled product in the quantities to provide.

The invention encompasses a method for expanding the production range of a cold rolled metal strip mill according to claim 1.

In particular, the configuration of the transformable cage can be chosen according to the hardness of the material constituting the product to be rolled. The production range can thus include products whose rupture limit after hot working can range from less than 160 MPa to at least 1000 MPa.

Particularly advantageously, the rolling stands are each associated with means for controlling at least one of the quality factors such as the thickness regularity, the flatness and / or the surface condition, changes the configuration of at least one of the rolling stands according to the dimensional, mechanical and metallurgical characteristics of the product, so as to maintain the same quality over the overall production range of the plant.

In a first embodiment, to adapt to the specific characteristics of a product to be rolled, is passed at least one transformable cage of a quarto configuration comprising two working rolls supported on two support cylinders, a configuration sexto comprising two working cylinders supported by intermediate cylinders on the same support cylinders, and vice versa.

In a second embodiment, in order to adapt to the specific characteristics of the product to be rolled, at least one transformable cage of a sexto configuration is passed comprising two working rolls respectively bearing, by a pair of first intermediate rolls, on a pair of support cylinders, an "octo" type configuration comprising two working cylinders respectively bearing, by a pair of second intermediate cylinders, on the same first intermediate cylinders and the same support cylinders, and vice versa.

To further broaden the production range, it is possible to equip at least one transformable cage removable means of lateral support of the work rolls, to allow, in an additional configuration, the use of very small work rolls diameter.

By thus choosing the configuration of at least one stand of the rolling mill, the invention makes it possible to achieve a thickness reduction of at least 70% in one pass for the entire extended production range.

Preferably, at least the configuration of the first roll stand is changed to give it a sexto configuration for rolling strips having, at the mill inlet, a rupture limit equal to or greater than 600 MPa and a quarto configuration for rolling strips with a lower breaking limit.

However, it may also be advantageous to change the configuration of the last cage to control the surface quality of the product at the exit of the rolling mill.

On the other hand, for certain categories of steel, it may be more advantageous to change the configuration of at least one of the intermediate cages, in particular to give it an eight-cylinder configuration, with working cylinders of very small diameter .

The invention also covers a rolling plant according to claim 15.

• La figure 1 est une vue schématique partielle, en élévation, d'une installation selon l'invention comprenant quatre cages de laminage en configuration quarto.
• La figure 2 est une vue schématique, en élévation de l'installation selon l'invention, après transformation de la première et de la dernière cage.
• La figure 3 représente schématiquement, en élévation, une cage de laminage selon l'invention en configuration quarto.
• La figure 4 est une vue à échelle agrandie de la partie centrale de la cage de la figure 3, après transformation en configuration sexto.
• La figure 5 représente, en élévation, un autre mode de réalisation d'une cage transformable, en configuration sexto.
• La figure 6 représente, en élévation, la partie centrale de la cage de la figure 5, après transformation en configuration octo avec appuis latéraux.
• La figure 7 montre la cage octo de la figure 6, en position de démontage des cassettes.
• La figure 8 montre la cage octo de la figure 6, en position de démontage des appuis latéraux.
• La figure 9 est une vue partielle en élévation, montrant une variante du dispositif d'appui latéral.
• La figure 10 est une vue de dessus, avec arraché partiel, de l'extrémité d'une cassette pour la configuration octo de la figure 8.
• La figure 11, est une vue en coupe selon la ligne I, I de la figure 9.

The invention also covers other advantageous features which will appear in the following description of certain particular embodiments, given by way of example and shown in the accompanying drawings.

• The figure 1 is a partial schematic view, in elevation, of an installation according to the invention comprising four rolling stands in a quarto configuration.
• The figure 2 is a schematic view, in elevation of the installation according to the invention, after transformation of the first and the last cage.
• The figure 3 schematically represents, in elevation, a rolling stand according to the invention in quarto configuration.
• The figure 4 is an enlarged view of the central part of the cage of the figure 3 , after transformation into sexto configuration.
• The figure 5 represents, in elevation, another embodiment of a transformable cage, sexto configuration.
• The figure 6 represents, in elevation, the central part of the cage of the figure 5 , after transformation into octo configuration with lateral supports.
• The figure 7 shows the octo cage of the figure 6 , in disassembly position of the cassettes.
• The figure 8 shows the octo cage of the figure 6 , in the disassembly position of the lateral supports.
• The figure 9 is a partial view in elevation, showing a variant of the lateral support device.
• The figure 10 is a top view, partially broken away, of the end of a cassette for the octo configuration of the figure 8 .
• The figure 11 , is a sectional view along the line I, I of the figure 9 .

The figure 1 schematically shows a tandem rolling mill with four cages operating continuously, that is to say without tape engagement, the mill being fed by coils welded end to end. Schematically, such an installation comprises, in a running direction of the strip, an inlet section E, a rolling section L and an output section S.

The rolling section L comprises, in the example shown, four cages operating in tandem, that is to say simultaneously carrying out a reduction in thickness on the product and controlled so as to maintain between them traction level, generally high, consistent with the strength of the product and allowing, as we know, to achieve a greater thickness reduction in each cage.

The inlet section E comprises devices, not shown, for putting the band in traction, placed just in front of the first cage and a guiding device G. The outlet section S generally comprises a fractional shear C to form coils and, for example, two winders B, B 'each having a device for guiding and deflecting D, D'.

It does not seem necessary to describe in more detail such a continuous rolling mill whose characteristics and advantages have been indicated, for example, in an article entitled "Coupled tandem pickling from Sainte Agathe to Sollac Florange" published in La Revue de la Metallurgie, March 1998 .

In particular, such an installation may include a greater or lesser number of cages operating in tandem and, depending on the nature and destination of the product, various processing sections of the metal strip disposed or not in a continuous line.

Generally, it is known that, in a tandem rolling installation, the thickness of the product is gradually reduced in the successive cages of the installation and that the reduction rate that can be performed in each cage depends on the mechanical characteristics. and dimensional of the product and, obviously, the means available to apply the rolling force.

Usually, therefore, for each product to be rolled, a rolling pattern is established which determines the amount of reduction in thickness to be made in each cage, taking into account that the crushing of the product determines, by hardening, an increase in its hardness and, consequently, the rolling force to be applied, in the following cages, for a certain reduction in thickness.

It is known that the thickness reduction rate that can be achieved depends on a certain number of rolling parameters.

An essential parameter is obviously the diameter of the working rolls on which the flow conditions of the metal in the rolling right-of-way depend.

Indeed, since the metal is frictionally driven along the circular faces of the rolls which limit the roll grip, a large diameter relative to the reduction in thickness to be made makes it possible to reduce the angle of friction and thus favors the training of the band.

Therefore, it seems normal, for cold rolling, to use working cylinders of fairly large diameter, of the order of 500 mm, for example.

Moreover, a large diameter has other advantages, for example to allow a relatively large wear range and to make more efficient the necessary cooling of the cylinders which is performed by the periphery.

Of course, the smaller diameters make it possible, with equal reduction, to reduce the rolling force required, but the wear range is reduced and the service life of the rolls is shorter, which leads to an increase in the cost of production. In addition, the contact arc being smaller, the stability of the cage is more difficult to maintain, especially in the case of tandem mills which, as we know, allow to exercise strong traction upstream and downstream of each roll stand.

But other factors are also involved in the rolling process such as the lubrication of the rolls and, in a tandem mill, the tensile forces applied to the strip, upstream (T _e ) and downstream (T _s ) respectively. air gap.

dans laquelle µ est le coefficient de frottement, F l'effort de laminage, T_e et T_s les efforts de traction à la sortie et à l'entrée de la cage de laminoir et D le diamètre des cylindres de travail.It has thus been established that the maximum possible thickness reduction during a rolling pass can be given by the formula: $${\mathrm{\Delta }}_{\mathrm{e}}\mathrm{\le }\mathrm{2}\left(\mathrm{\mu }\mathrm{+}\frac{{\mathrm{T}}_{\mathrm{e}}\mathrm{-}{\mathrm{T}}_{\mathrm{s}}}{\mathrm{2}\mathrm{<figure-callout\; id="2"\; label="F\; D"\; filenames="imgf0002.png"\; state="\{\{state\}\}">F\; </figure-callout>}}\right)\mathrm{D}{}^2\mathrm{}$$

wherein μ is the friction coefficient, F the rolling force, T _e and T _s the tensile forces at the exit and at the entrance of the roll stand and D the diameter of the work rolls.

For the establishment of a rolling pattern corresponding to the grade and the format of a rolling product, it is therefore necessary, taking into account the means available, to determine these various parameters, so as to achieve, in the best possible possible conditions, a rolling of the product to the thickness required for a normal speed of scrolling corresponding to the production capacity of the installation.

In this respect, an essential quality required of a rolling mill is to provide a product having a thickness and surface qualities as constant as possible. For this, it is necessary to constantly adjust the factors involved in the thickness reduction process, in order to maintain, throughout the production, the stability of the reduction of thickness and the qualities of flatness and surface condition required.

The formula indicated above shows that the choice of a large diameter is favorable to maintaining the stability of the reduction rate. However, a large diameter increases the length of the rolling right-of-way and, consequently, the rolling force to be applied.

Moreover, during rolling, to ensure the stability of the thickness reduction, one can act on the rolling force and the tensile forces applied to the product.

Indeed, in a tandem mill, the high traction obtained between two successive cages can increase the possible reduction in thickness. However, the formula indicated above shows that a relatively large rolling force, resulting from a large diameter, decreases the influence of the tractions. The stability of the rate of reduction is ensured by that of the coefficient of friction which depends on the quality of lubrication and the roughness of the cylinders.

In addition, the tensile forces that can be applied to the strip, respectively at the inlet and the outlet of the installation, depend on the devices placed respectively upstream and downstream thereof and are less than the forces generated. by a cage of the tandem mill on those who frame it.

To increase the possibilities of adjustment of the rolling force, it may be preferable to reduce the diameter of the working rolls in the first and the last cage, but it must also be taken into account that a relatively large diameter is favorable to drive the product and transfer the roughness to the last cage when necessary.

Indeed, for a good number of products of high quality, the surface aspect is important and the downstream treatments of the band (galvanizing, painting, etc.) impose a precise and constant roughness of the surface and this roughness is given by that of the working rolls of the last cage of the tandem mill. Now, it is known that the impression of the roughness of the rolls on the strip is all the easier as the diameter is high. It is therefore another factor of choice for a large diameter of the working rolls, even in the last cage.

It therefore appears that the possibilities of action on the various rolling parameters, some of which affect each other, are rather small and that is why, until now, high capacity tandem rolling installations were usable only for a fairly limited production range.

For example, for the production of body panels, we generally start with a hot strip having a thickness of at least 3 mm and we must obtain, at the output of the installation, a fairly thin thickness , of the order of 0.7 to 0.8 mm.

For the usual qualities of body panels, such a thickness reduction rate of up to 80% can be obtained in an installation of the type shown in FIG. figure 1 comprising 4 or 5 quarto cages with working cylinders whose diameter can, without disadvantage, being located in a range substantially from 530 mm to 620 mm, the actual range of use being of the order of 58 mm to 80 mm, which is economical vis-à-vis the service life of the cylinders .

Normally, the hardness range of the products that can be laminated while maintaining the desired surface quality and the stability of the thickness reduction is limited. In practice, the rupture limit can be, for example up to 600 MPa. Above this breaking point, there is saturation of the mechanical drive means of the cylinders whose power is limited and one can not exert the rolling force necessary to obtain the desired reduction in thickness. As a result, a tandem rolling plant is normally only usable for a relatively limited range of products for which the characteristics of the different organs have been determined and, until now, it seemed necessary to have specialized installations for the rolling of other grades of steel, in particular those with a rupture limit greater than 600 MPa, such as TRIP steels.

The invention solves this problem simply, quickly and economically, by simply changing the configuration of at least one of the mill stands, so as to modify the diameter of the work rolls and, thus, the range of products that can be processed in the rolling mill.

Thus, by equipping at least one of the cages means for easily changing the configuration, it will be possible, thanks to the method according to the invention, to greatly expand the production range of a tandem mill.

By way of example, the conventional type installation presented schematically on the figure 1 , comprising four roll stands operating in tandem and each equipped in quarto configuration, is adapted, as we have seen, to the production with a large capacity, of standard quality sheets, for example for the automotive industry.

Depending on its design and installed capacity, such an installation can produce around 600,000 tons / year at 2.5 Mt / year, the production capacity being even greater than the range of steel grades. to manufacture is more reduced.

Each cage L1, L2, L3, L4 is of the quarto type shown schematically on the figure 1 and therefore comprises, inside a cage having two spaced apart columns 10, a pair of working cylinders 2, 2 'resting on support cylinders 3, 3' and limiting a passing air gap of the product M which passes , in a rolling plane P substantially horizontal, in a direction orthogonal to the axes of the two working rolls, the axes of the various cylinders being placed substantially in a vertical clamping plane P ₁ .

As usual, each cylinder is rotatably mounted about its axis, on anti-friction bearings housed in sliding mounted chocks, parallel to the clamping plane P ₁ , in windows of each column 10 of the cage.

As shown in figure 3 , the working rolls 2, 2 ', which have a diameter smaller than the support rollers 3, 3', are carried by two chocks 20, 20 'slidably mounted along vertical guide faces 12a, 12b formed at the ends two pieces 13a, 13b projecting inside the window 11 while the guide faces of the chocks 30, 30 'of the support rolls 3, 3' are arranged along the vertical sides 11a, 11 b of each window 11 of the cage.

In the lower part of each column 10 of the cage, is disposed a hydraulic clamping device 15 which, in the embodiment of the figure 3 , is equipped with a piston for applying the rolling force and to control the thickness regulation by bearing on the chock 30 'of the lower bearing cylinder 3'. In the upper part of each column 10, there is also a screw clamping device 16 which makes it possible to keep the stack of rolls tight by compensating for variations in height due to wear of the rolls. This device 16 may comprise, for example, a screw driven by a geared motor and bearing on the corresponding chock 30 of the upper support cylinder 3.

Of course, other devices, for example hydraulic, can be used for clamping and setting the rolls.

It should be noted that, as will be seen below, the windows 11 and the means 15, 16 for clamping and setting the cylinders are dimensioned to allow adjustment over a large amplitude of the spacing between the support cylinders 3, 3 '.

In known manner, each roll stand is also equipped with devices for controlling the flatness of the product by bending (or bending) the work rolls.

As usual, these bending devices are constituted, for each chock, of two sets of jacks 5, 5 'supported on each side of the window 11, on the two uprights of each column 10, the latter being provided, furthermore , guiding faces between which the two chocks 20, 20 'are slidably mounted parallel to the vertical clamping plane P ₁ in which are substantially placed the axes of the cylinders.

As indicated above, these lateral guide faces 12a, 12b are formed at the ends of two projecting parts 13a, 13b integral with the two uprights of each column 10 and on which bear, generally, the bending cylinders 4, 4 '.

It is known, on the other hand, that the bending cylinders must act on the ends of the working cylinders or intermediate cylinders in sexto configuration, or in a positive direction of separation from the rolling plane, to compensate for excessive thinning of the edges rolled product, in a negative direction towards the rolling plane. It is therefore possible to use either double-acting cylinders fixed on the chock or on an intermediate piece, or two pairs of jacks acting in opposite directions on bearing portions of each chock, on each side thereof.

Moreover, even in a quarto configuration, it is advantageous to also benefit from the possibility of axial displacement of the rolls with their chocks. Several provisions have been proposed for this purpose, but it is advantageous for the bending cylinders to move with the chocks on which they rest, so that the forces applied remain centered with respect to the centering bearings mounted in the chock.

Finally, to achieve a configuration change allowing, according to the invention, to go for example from a quarto configuration to a sexto configuration, it is particularly advantageous to keep the same bending means that remain fixed on the columns.

The arrangements according to the invention make it possible to solve these various problems.

The Figures 3 and 4 show a first embodiment according to the invention of a transformable cage, in quarto or sexto configuration. As usual, the cambering means of the cylinders are mounted, with their hydraulic supply circuits, in massive parts 4a, 4b called "hydraulic blocks" and fixed on the two uprights of each column 10 of the cage, in the central portion of it.

Each hydraulic block 4a, 4b carries, at the level of the rolling plane P, a piece 13a, 13b which projects inwards towards the inside of the window and carries, at its inner end, a vertical guide face 12a, 12b chocks 20, 20 'of the work rollers 2, 2' which are provided with bearing parts 21 called "ears", which project outwardly on either side of the vertical clamping plane P1.

In the embodiment of the figure 3 the bearing portions 21, 21 'of the two upper and lower chocks 20', respectively, are offset with respect to the axis of the corresponding working roll, on the opposite side to the rolling plane P, so as to pass, respectively, above and below the protruding parts 13a, 13b, to cooperate with sets of bending cylinders, respectively upper 5 and lower 5 '.

In the embodiment of the figure 3 each assembly 5 comprises at least one pair of opposed cylinders 51, 52 placed on either side of the lug 21 and bearing against it, respectively in the positive direction of separation of the rolling plane and in the negative sense of approximation.

Of course, the arrangement is symmetrical with respect to the rolling plane P and the clamping plane P ', each hydraulic block 4a, 4b carrying two sets of cylinders, respectively upper 5 and lower 5'.

Furthermore, to allow the axial displacement of the working rolls without off-centering of the forces applied, the bending cylinders, respectively positive 51a and negative 52a, placed on the same side of the clamping plane P ₁ , are housed in a support piece 40a slidably mounted, parallel to the axes of the cylinders, on the corresponding hydraulic block 4a fixed in the central part of the column 10 and it is the same on the other side of the clamping plane P ₁ .

Thus, each working roll, for example the upper roll 2, is associated with two support pieces 40a, 40b mounted sliding axially on the two hydraulic blocks 4a, 4b and on which bear, respectively, the positive bending cylinders 51a. , 51b and the negative bending cylinders 52a, 52b. In known manner, the two support pieces 40a, 40b are associated with means, not shown, such as hydraulic cylinders, resting on the cage to control the axial displacement of the assembly formed by the working cylinder 2 and its two chocks 20 with the associated support pieces 40a, 40b carrying the sets of bending cylinders 5a, 5b.

Of course, it is the same, on the other side of the rolling plane P, for the lower work roll 2 'and its chocks 20' each associated with two support pieces 40'a, 40'b mounted sliding axially on the hydraulic blocks 4a, 4b.

We see that in the quarto configuration of the figure 3 , the protruding parts 13a, 13b serve only to guide the chocks 20, 20 'of the two cylinders, between their opposite ends 12a, 12b.

However, each projecting piece 13 also carries two sets of cylinders, respectively upper 50 and lower 50 'provided for the bending of the working rolls in the sexto configuration shown in FIG. figure 4 .

In this configuration, in fact, the cage comprises the same support cylinders 3, 3 'but these have been separated so as to replace each working cylinder 2 of the quarto configuration by a set of two superimposed cylinders, respectively a new one. working cylinder 22 of smaller diameter and an intermediate cylinder 32.

As indicated above, the windows 11 and the clamping means 15, 16 are sized to give a sufficient adjustment amplitude to the support cylinders 3, 3 '.

As shown in figure 4 , each chock 23 of a working cylinder 22 of small diameter has the same width as a chock 20 of a working cylinder 2 in a quarto configuration and is thus guided vertically between the ends 12a, 12b of the two projecting parts 13a , 13b. In addition, each chock 23 is provided, substantially at the axis of the cylinder 22, with lateral projecting parts forming lugs which engage in notches formed in the guide faces 12a, 12b of the two protruding parts 13a. 13b so as to cooperate with the bending jack assemblies 50 housed in each projecting piece 13a, 13b and each having a pair of opposing cylinders, respectively 55 of positive bending and 56 of negative bending.

Moreover, in this sexto arrangement, the chocks 33, 33 'of the intermediate cylinders 32, 32' are mounted to slide vertically, on guide faces 41, 41 'parallel to the clamping plane and arranged on the facing faces of the parts of FIG. sliding support 40, 40 'each carrying the two sets of bending cylinders, respectively positive 51, 51' and negative 52, 52 'previously described in the quarto configuration of the figure 3 .

Thus, the same sets of cylinders 5, 5 'provided, in the quarto configuration, for the bending of the working rolls 2, 2' and mounted on the same sliding support pieces 40, 40 'serve, in the sexto configuration, for the cambering of the intermediate rollers 32, 32 ', with the same possibility of axial displacement.

According to the invention, the change of configuration can therefore be done by preserving, not only all the means 15, 16, 3, 3 'of application of the rolling force but also the means for adjusting the transmission conditions of this such as the bending means 5, 5 'or axial displacement 40, 40'.

For this, however, it is necessary that the support lugs 34 of the chocks 33 of the upper intermediate cylinder 32, in the sexto configuration are placed substantially at the same level as the ears 21 support of the chocks 20 of the upper working roll 2 of large diameter, in the quarto configuration and it is the same on the other side of the rolling plane for the lower work rolls 2 'and intermediate 22'.

It is advantageous, for this purpose, to use the particular arrangement of the chocks, represented on the Figures 3 and 4 in which the lugs 21 of the chocks 20 of the working roll 2 are offset away from the rolling plane P with respect to the axis of the roll 2 while, for the intermediate roll 32, the lugs 34 of the chock 33 are shifted to the rolling plane P with respect to the axis of the cylinder, the arrangement being symmetrical with respect to the rolling plane, for the lower rolls.

Other arrangements are possible, however, as will be seen later.

Thus, in the two configurations, the same sliding support pieces 40, 40 'can be preserved with the same sets of bending cylinders 5, 5' and simultaneously, on the one hand, a positive or negative cambering of the corresponding cylinders and on the other hand, an axial displacement, in opposite directions, of the two working rolls 2, 2 'in the quarto configuration, or of the two intermediate rolls 32, 32' in the sexto configuration.

Since the same support cylinders 3, 3 'are maintained, the height adjustment possibilities of said cylinders must be adapted to the size of the work rolls of the intermediate rolls, which is greater in the sexting configuration than in the quarto configuration. It suffices, however, that the piston of the clamping cylinder 15 and the set screws 16 of the upper support cylinder 3 have a sufficient stroke, and that the window 11 is dimensioned accordingly.

With these provisions, it is possible to transform a cage from a quarto mode to a sexto mode and vice versa, keeping the same support cylinders 3, 3 ', the same means of application of the clamping force 15, 16 and the same hydraulic blocks 4a, 4b with the bending cylinders and the means for controlling the axial displacement of the cylinders.

Because the support pieces 40, 40 'are the same in both configurations and are slidably mounted parallel to the axes of the rolls, it is possible to change the configuration of the rolling mill by means of a known type of roll replacement device. to remove, by displacement parallel to their axes, a set of work rolls, to replace them with other cylinders. Indeed, in the provision of the figure 4 each small-diameter working cylinder 22 associated with an intermediate cylinder 32, together with their chocks, forms a cassette-mounted assembly that can be moved axially to be removed from or inserted into the cage, said assembly being carried by the support pieces 40a, 40b which slide axially. Thus, it is possible to remove in bulk either the two working rolls 2, 2 'in the quarto mode, or the two sets, respectively upper and lower of work rolls 22, 22' and intermediate rolls 32, 32 ' , in the sexto mode.

For this purpose, it is possible to use a device for replacing cylinders of known type which may be, for example, of the so-called "push-through" type described in the patent. EP-0618018 or of the type comprising a trolley called "side-shifter" as described in the patent US 4435970 . Such devices may be used in a rolling mill according to the invention to switch from "sexto" mode to "quarto" mode and vice versa. In fact, it suffices to install in advance, in a reserve compartment provided for the new cylinders, large diameter working rolls equipped with their specific chocks, to extract the intermediate cylinders and the working cylinders. used in the "sexto" mode and to introduce the big cylinders alone, the cage thus being transformed into "quarto" mode. The clamping and clamping devices 16 will make it possible to bring the support rolls 3, 3 'into contact with the working rolls 2, 2' whose overall dimensions are smaller than the stacking of two small diameter working rolls. 22 'increased by the two intermediate cylinders 32, 32'.

The inverse maneuver with the aid of the cylinder change device makes it possible to switch, in the other direction of the "quarto" mode, to the "sexto" mode.

Thus, while retaining the same means of applying the rolling force, thickness regulation and flatness correction, it is possible to switch quickly from a "quarto" mode with large working cylinders to a mode "Sexto" with smaller cylinders, for example, to adapt to a change in hardness of the product to be rolled.

The figure 2 shows, by way of example, the installation represented on the figure 1 after transformation of the first (L1) and the last (L4) cages in sexto configuration, the intermediate cages L2, L3 remaining in quarto configuration.

A plant thus transformed makes it possible to treat steels in a wider range of hardness and, in particular, the new grades sought for body panels, which have a high yield strength and thus have a high hardness right from the first stand.

According to the invention, this first cage L1 is therefore of the transformable type represented on the Figures 3 and 4 allowing to quickly go from the quarto configuration planned for the usual steels to a sexto configuration, which makes it possible to ensure from the first pass, a significant reduction and, thus, to achieve thickness reductions of up to 70% on the entire tandem mill for this type of steel.

In this sexto configuration, to respect the possibilities of adjusting the height of the clamping means 16 and wedging 15, the diameter of the working rolls can be chosen in a range that can range from 360 mm to 485 mm depending on the wear range selected. and the width of the mill.

In this respect, it should be noted that for small diameters of working rolls the horizontal deflection of the roll can become significant and be detrimental to the flatness of the band and the stability of the roll stand. This deviation is all the more important that the bearing points of the working cylinder are remote, that is to say that the rolling mill is wide. By way of example, a wear range of 360 mm to 405 mm may be used for a 66 "rolling mill and a range of 425 mm and 485 mm for a mill with a width of 80".

In the same way, according to the embodiment of the figure 2 it has been observed that it would be interesting to use also working rolls of smaller diameter on the last cage L4 because, at the exit of the tandem mill 1, the metal of the strip is at its maximum hardness. It is therefore preferable that the last cage L4 is also transformable in order to configure it in sexto mode for the manufacture of steels with a very high elastic limit and particularly those of the "TRIP" type.

Furthermore, it is particularly advantageous, in order to maintain the quality of the product over this extended range of characteristics, that the rolling mill is equipped with the same means for regulating thickness and for correcting flatness defects such as cambering and displacement devices. axial axis of the cylinders, as described above with reference to the Figures 3 and 4 .

Thus, the changes to be made to the transformable cage to allow the configuration change are relatively limited and their cost is largely offset by the benefits provided.

Indeed, it is already sufficient to change the configuration of the first stand of the rolling mill to expand the range of production and thus respond without delay to a change in the load plan.

For example from the installation represented on the figure 1 , which is adapted to the usual metal qualities, with working rolls of the order of 530 to 620 mm, it is possible to transform the first cage L1 to give it a configuration "sexto" with work rolls having a diameter chosen in a range of 360 mm to 485 mm, which allows, without further modification of the installation, to treat, for example, high-strength steels in the first cage L1 which carries out most of the reduction of thickness.

On the other hand, the two intermediate cages L2 and L3, which usually achieve a smaller thickness reduction, can remain in "quarto" mode with large cylinders.

However, since the hardness of the product increases from one cage to the next, it may be necessary to also give the last cage L4 a configuration "sexto" with small cylinders to obtain the desired overall reduction of thickness.

It should be noted that this transformation of the rolling stands is done by means of a rapid cylinder change device which, in any case, is necessary for the replacement of the used cylinders.

The arrangements according to the invention therefore make it possible to adapt, with a great deal of flexibility, to a change in the mechanical and dimensional characteristics of the products to be rolled, and thus to considerably broaden the production range of the installation.

Since the means for applying the rolling force and the means for adjusting the transmission conditions thereof are retained, the same installation can be adapted very quickly to a change in the characteristics of the product while maintaining the same performance. of final quality on the product, in particular regularity of thickness, flatness and surface quality.

Generally, it will suffice, as we have just seen, to change the configuration of the first cage and possibly the last stand of the rolling mill to expand the usual production range of a tandem mill, especially to hard steels.

However, the evolution of the technique leads customers to ask steelmakers steels with characteristics increasingly varied.

For example, it may be necessary to produce very hard steels having a large variation of elastic limit during hardening.

In this case, the hardness of the steel increases from one cage to the next and, for very hard steels, it can be difficult to achieve the desired total reduction in thickness because there is a limit on intermediate cages.

It is then advantageous, in a more advanced embodiment of the invention, to equip at least one intermediate cage with configuration change means making it possible, in particular, to use rolls of very small diameter, for example between 140 and 160 mm.

Such a working roll diameter requires lateral supports, as in the configuration known as "Z-HIGH".

We can therefore consider, in a transformable cage of the type described above and shown on the Figures 3 and 4 , replace each work roll 2, 2 'of relatively large diameter, in a quarto configuration, with a "Z-HIGH" type insert comprising a small diameter cylinder, an intermediate cylinder and lateral support rollers.

In such an arrangement, the frame of the insert may be provided with lateral support parts placed substantially at the same level as the bearing lugs of the chocks of the working cylinders 2, 2 'so as to adapt to the same devices. which in "Z-HIGH" configuration act on the intermediate cylinders.

However, one can not have, in this case, an axial displacement system configuration "Z-HIGH". In addition, with small work rolls, it is necessary to motorize the intermediate cylinders which, in a sexto configuration turn in opposite directions of the work rolls. It is therefore necessary that the rotary drive motors, their power supply and their regulation are capable of operating in both directions of rotation at full speed and at full power, in order to drive either the working cylinders in the quarto configuration or the intermediate cylinders in sexto configuration.

Moreover, it happens quite often that the user prefers that the installation has a basic configuration sexto for all applications, each cage can be equipped with working cylinders having a wide range of diameters.

To solve these problems, in another embodiment the rolling mill therefore comprises at least one transformable cage of the type shown in FIGS. Figures 5 to 12 , which can have large diameter working cylinders in a sexto configuration ( figure 5 ) and cylinders of very small diameter with lateral supports, in an eight-cylinder configuration ( figure 6 ).

The figure 5 shows, in elevation, the central part of such a transformable cage, sexto configuration. As in the case of figure 4 , the cage thus comprises six cylinders superimposed on both sides of the rolling plane P, respectively two work rolls 22, 22 ', two intermediate rolls 32, 32' and two support rollers 3, 3 '.

With regard to the bending device and the chocks of the rolls, the Figures 5 to 7 show a variant in which each chock is provided on each side of the clamping plane, two support portions spaced apart from each other on either side of the horizontal plane passing through the axis of the cylinder and passing respectively above and below a projecting piece integral with the column of the cage and in which are housed the bending cylinders.

Thus, each chock 23 of a work roll 22 is provided on each side of the clamping plane P ₁ with two bearing parts 24, 25 passing respectively above and below a piece 42 fixed on the hydraulic block 4 and extending inwardly projecting from the window to a vertical side 43 of lateral guiding of the chock 23. Each projecting piece 42 carries at least one pair of cylinders not shown acting in sense opposed, respectively on an upper support portion 24 of the chock 23 for the positive camber of the cylinder 22 and on a lower portion 25 for the negative bending.

Therefore, while in the provision of Figures 3 and 4 , the two working chocks 20, 20 'were guided, on each side, by the same projecting piece 13a, 13b centered on the rolling plane P, in the variant of Figures 5 and 6 , the working chocks 23, 23 'are guided laterally by two separate pieces 42, 42' arranged on either side of the rolling plane P. However, as in the previous provision, the chocks 33, 33 'of the intermediate cylinders 32, 32 'are slidably mounted between vertical guide faces 41, 41' formed at the ends of two support pieces 40, 40 'which, as before, are slidably mounted on the hydraulic blocks 4a, 4b parallel to the axes of the cylinders.

However, the positive and negative bending cylinders of the working chocks 23, 23 'are mounted on the second projecting pieces 42, 42' and not on the sliding parts 40, 40 'as in the case of Figures 3 and 4 .

The provision of the figure 5 allows the replacement of a relatively large working cylinder 22 by a set 6 mounted in cassette comprising a working cylinder of small diameter 61 associated with an intermediate cylinder 62. The sum of the diameters of the two cylinders 61, 62 being of the same order as the diameter of the working cylinder 22 of the sexto arrangement represented on the figure 5 , so that the intermediate cylinders 32, 32 'remain substantially at the same level.

On the other hand, as shown in figure 7 , the two cylinders 61, 62 of each cassette 6 are rotatably mounted, at their ends, on two frames 7 having a shape similar to that of the chocks 23 of the working cylinders 22 of the sexto configuration and therefore comprising parts of 71, 72 spaced vertically the same distance as the support portions 24, 25 of a work chock 23 and thus passing, respectively, above and below the projecting parts 42a, 42b whose ends 43 form vertical guide faces of the frame 7 in the form of a chock.

Thus, it is possible to change the configuration of the rolling mill by replacing each working cylinder 22 of the sexto configuration with a cassette 6 to move into an eight-cylinder configuration called "octo" using the same support rollers 3, 3 'and the same first intermediate cylinders 32, 32 'and having, on each side of the rolling plane P, a small-diameter working roll 61, 61' associated with a second intermediate roll 62, 62 '.

Since the frame 7 of each cassette 6 of an octo configuration has the same profile as the chocks 23 of the working cylinder 22 of the sexto configuration, it is possible to use a system for rapid replacement by displacement parallel to the axes of the cylinders. chocks 23 or chassis 7 supported, by means of rollers 26, 73, on rails 46 formed on the projecting parts 42a, 42b.

As shown in figure 5 , above the rolling plane, the rollers 26 are mounted on the upper bearing portions 24 of the upper chock 22 or 71 of the frame 7 of the octo insert. Below the rolling plane P, rollers 26 ', 73' are fixed on the lower bearing portions 24 'of the chocks 22' or 71 'of the frames 7'.

The projecting parts 42, 42 'carry sets of bending cylinders which remain in place during the configuration change and act, in the positive or negative direction, either on the working cylinders 22, 22' in the sexto configuration, or on the second intermediate cylinders 62, 62 ', in the octo configuration.

The Figures 10 and 11 show in detail the mounting of the frame of an octo insert comprising a working cylinder 61 of small diameter and a second intermediate cylinder 62.

Each second intermediate cylinder 62 is provided at each end with a journal carried by a bearing 74 whose outer cage is fixed on the chassis 7, which thus acts as a chock for the cylinder 62.

On the other hand, the associated working cylinder 61 is simply rotatably mounted at each end on an axial abutment bearing 75 but this latter is mounted, with a possibility of transverse play, in a retaining member 76 fixed on the internal face of the frame 7 and comprising a spring device 77 which permanently applies the working cylinder 61 to the intermediate cylinder 62, so as to take into account a variation, by wear, of the diameters of the rolls, as shown in FIG. figure 11 .

As can be seen, the arrangements which have just been described make it possible to retain, in the two sexto and octo configurations, the same bending means housed in the protruding parts 42, 42 'and the same first intermediate cylinders 32 which can be adjust the axial position, in both configurations, by means of the support pieces 40, 40 '.

Moreover, in the octo configuration, the first intermediate cylinders rotate in the same direction as the small diameter working rolls. It is therefore not necessary to use motors with two directions of rotation, the driving torque being able to be applied, by means of extensions, or on the working rolls of fairly large diameter in the sexto configuration, or on the first intermediate cylinders, in the octo configuration.

The arrangements according to the invention therefore make it possible to switch quickly from a sexto configuration equipped with work rolls having a diameter in a high range, for example 495 mm to 515 mm, to an eight-cylinder configuration having small diameter working rolls, for example in the range 140mm / 160mm associated with intermediate rollers 62 in the range 330mm / 355mm.

However, working rolls of such small diameter may bend during rolling and therefore should preferably be associated with side support rollers in an X arrangement, shown by way of example on the figure 6 .

Each working roll of small diameter, respectively upper 61 and lower 61 ', is thus maintained laterally by two sets of rollers 8a, 8b each mounted on a support frame 81 which can slide in a direction inclined relative to the rolling plane. P, on guides 82 fixed on the corresponding amount of the column of the cage, the sliding of the support 81 being controlled by a jack 83.

Preferably, each set of rollers 8 can be easily disassembled with its support frame 81, so as to clear the central space of the cage in the sexto configuration shown in FIG. figure 5 , the four slides 82 and the cylinders 83 remaining alone fixed on the columns 10 of the cage.

Therefore, to go from sexto configuration to the figure 5 at the octo configuration of the figure 6 it is sufficient to replace on the slideways 82 the frame 80 supporting the support rollers 8 and to fix them on the rods of the cylinders 83, as shown in FIG. figure 6 .

The dismantling of the four sets of rollers 8 can be carried out as shown on the Figures 7 and 8 .

When it is desired to change from the octo configuration to the sexto configuration, the sets of rollers 8 are moved back inside the slideways 82 in order to clear the entire central space of the rolling mill, as indicated on FIG. figure 7 . It is then possible to remove the inserts 6 with their support frame 7 from the cage and replace them with the two large diameter working rollers 22, 22 'carried by their chocks 23, 23' which roll on the rails 46, 46. ', so as to restore the sexto configuration represented on the figure 5 .

One or more side support assemblies 8, 8 'can be easily removed from the cage for maintenance or replacement. For this purpose, after removal of the working cylinders or inserts, is brought into the central space of the cage a dismounting bridge 85 resting, by rollers, on the upper rails 46 and carrying two orthogonal walls forming a cross 86 which limits four quadrants in which can be introduced the four sets of rollers 8 pushed by the cylinders 83. The frame 81 of support rollers are then disconnected from the cylinders and the bridge 85 can be removed from the cage, by axial displacement, taking away the four sets of rollers 8, 8 '.

As indicated above, it is particularly advantageous to equip the intermediate cages of a tandem rolling mill with such an arrangement making it possible to switch rapidly from a sexto configuration to an eight-cylinder configuration with small diameter working rolls, in the cases where the rolling mill's production range has to be extended to very hard steels having a large variation of elastic limit during hardening. The passage in small cylinder octo configuration makes it possible, in fact, to avoid the power saturation that is usually encountered in tandem rolling for steels of this type.

Of course, the invention is not limited to the details of the embodiments that have just been described, variants that can be imagined without departing from the scope of protection of the invention, as defined in the appended claims. .

In particular, it is only by way of example that there is shown, in the figures, two types of chocks, the invention being applicable to other types and other ways of bending which can remain in place, in all configurations, as the support portions of the chocks of work rolls or intermediate rolls are placed substantially at the same level.

On the other hand, if it is preferable, in the case of axial displacement of the rollers, to move the bending means at the same time, these could also be housed in fixed parts of the hydraulic blocks, the pressures in the various cylinders being then set according to the position of the median plane of the chock with respect to the amounts of the cage.

Similarly, the device for axial displacement of the rollers could be used in combination with working rolls having a curvilinear profile of the 'CVC' type to achieve a variation of the crown, or it could be used, in known manner, with work rolls having part of their machined table to carry out a control of the thinning of the banks of the rolled strips.

It would also be possible, without departing from the scope of the invention, to use a support cylinder with a deformable envelope, of the type described, for example, in the document EP-A-0248738 to increase the flatness control capabilities of the transformable cage, in particular thus equipping the last cage L4 of the tandem mill.

Moreover, when cylinders of very small diameter associated with lateral support means are used, as in the case of Figures 5 and 6 it may be preferable to separate from the rolling plane the sliding control cylinders of the lateral support means. For this, one could advantageously use the arrangement shown on the figure 9 in which each jack 83 for controlling the sliding of a set of rollers 8 is articulated on the column 10 around an axis spaced apart from the rolling plane and controls the rotation of an angled lever 87 connected to the frame 81 for supporting the rollers support 8 by a connecting rod 88 articulated at its ends.

On the other hand, the tandem mill to which the invention applies may be of any known type and may include a greater or lesser number of cages.

Moreover, the invention has been described in its application to the production of sheets for the automotive industry but can be applied to any other type of product for which it is advantageous to expand the production range of an installation , for example aluminum.

The reference signs inserted after the technical features mentioned in the claims, are intended only to facilitate the understanding of the latter and in no way limit the scope.

Claims (29)

1. Method for increasing the production range of an installation for cold rolling of strip-shaped metal products, said installation comprising at least two rolling stands (L1, L2) operating in tandem for progressively reducing the thickness of the product (M), each stand consisting of two housings (10) between which at least four stacked rolls, two back-up rolls (3, 3') and two work rolls (2, 2') respectively, are slidably mounted, in a direction parallel to a clamping plane (P1), each roll being mounted in a rotatable manner around its axis on two chocks, and means (15, 16) of applying a rolling force between said rolls with adjustment of their respective gaps allowing, for a given stand configuration, a certain rate of thickness reduction to be achieved, taking into account the dimensional, mechanical and metallurgical properties of the product (M), with said properties corresponding to a given production range, characterised in that at least one of the rolling stands is a convertible stand (4) of the type comprising means of quickly replacing a first pair of work rolls (2, 2') by two cassette-type assemblies (6, 6'), each comprising a pair of work rolls of smaller diameter (22, 22')(61, 61'), each associated with an intermediate roll (32, 32')(62, 62'), in that said convertible stand (4) is equipped with roll bending means (5, 5') mounted on support parts (40, 40') (42, 42') integral with the housings (10) of the stand (1) and projecting towards the clamping plane (P1), and in that, on each side of the rolling plane (P), said roll bending means (5, 5') and their support pieces are the same in the two configurations and remain in place in the housings (10) of the stand (1) so as to work respectively either in conjunction with back-up lugs (21, 24, 25) of the chocks of the work rolls (2, 22) in the first configuration or with back-up lugs (34, 71, 72) of the chocks (33, 71) of the intermediate rolls (32, 62) in the second configuration, said back-up lugs (21, 24, 25) (34, 71, 72) of the chocks (20, 33, 63) being arranged, in each of the configurations, substantially at the same level relative to the rolling plane (P), on each side of the latter, said convertible stand thus allowing, by retaining the same means (15, 16) of applying the rolling force and the same roll bending means (5, 5'), at least two configurations each suited to one production range to be provided, and, for rolling a product (M), selecting the configuration of the convertible stand as a function of the properties of said product (M) such that said product properties are included in the production range corresponding to the selected configuration.
2. Method according to claim 1, characterised in that the configuration of the convertible stand is selected as a function of the hardness of the material constituting the product to be rolled.
3. Method according to claim 2, characterised in that the change in configuration of the convertible stand enables an overall production range to be covered including products with a breaking limit after hot rolling ranging from less than 160 MPa to at least 1000 MPa.
4. Method according to one of the preceding claims for increasing the production range of a rolling installation, said installation comprising at least two rolling stands (L1, L2), each associated with means of controlling at least one of the quality factors such as thickness regularity, flatness and surface roughness, characterised in that the configuration of at least one of the rolling stands (L1) is changed as a function of the dimensional, mechanical and metallurgical properties of the product (M) so as to maintain the same quality across the overall production range of the installation.
5. Method according to one of the preceding claims, characterised in that in order to adapt to the specific properties of a product (M) to be rolled, at least one convertible stand (L1) is converted from a four-high configuration comprising two work rolls (2, 2') supported on two back-up rolls (3, 3') to a six-high configuration comprising two work rolls (22, 22') supported, via two intermediate rolls (32, 32'), on the same back-up rolls (3, 3'), and vice versa.
6. Method according to one of claims 1 to 4, characterised in that in order to adapt to the specific properties of the product (M) to be rolled, at least one convertible stand (L1) is converted from a six-high configuration comprising two work rolls (22, 22') supported respectively, via a pair of first intermediate rolls (32, 32'), on a pair of back-up rolls (3, 3'), to an eight-high configuration comprising two work rolls (61, 61') supported respectively, via a pair of second intermediate rolls (62, 62'), on the same first intermediate rolls (32, 32') and the same back-up rolls (3, 3'), and vice versa.
7. Method according to one of claims 5 and 6, characterised in that at least one convertible stand (L1) is equipped with removable lateral back-up means (8, 8') of the work rolls so as to allow the use, in an additional configuration, of work rolls (61, 61') of very small diameter that may be associated with lateral back-up means (8, 8').
8. Method according to one of the preceding claims, characterised in that the configuration of at least the first stand (L1) of the tandem rolling mill is changed in the strip travel direction.
9. Method according to claim 8, characterised in that the first stand (L1) of the tandem mill is converted to a four-high configuration for rolling strip having a breaking limit less than or equal to 600 MPa.
10. Method according to one of the preceding claims, characterised in that at least the first stand (L1) of the tandem rolling mill is converted to a six-high configuration for rolling strip having a breaking limit equal to or greater than 600 MPa at the entry to the mill.
11. Method according to one of the preceding claims, characterised in that the configuration of the first (L1) and last (L4) stand of the rolling mill is changed.
12. Method according to one of the preceding claims, characterised in that the configuration of at least one intermediate stand (L2, L3) of the tandem mill is changed.
13. Method according to one of claims 1 to 7, characterised in that the configuration of at least one intermediate stand (L2, L3) of the tandem mill is changed while retaining the configuration of the first (L1) and last (L4) stand of the rolling mill.
14. Method according to one of the preceding claims, characterised in that the configuration of at least one of the stands (L1) of the tandem rolling mill is selected as a function of the mechanical and metallurgical properties of the product in order to achieve a reduction in thickness of at least 70% in one pass over the overall production range.
15. Rolling installation for implementing the method according to one of the preceding claims, said installation comprising means of controlling the travel of the product (M) along a rolling plane (P), successively in at least two rolling stands (L1, L2) operating in tandem, each stand consisting of two housings (10) between which at least four stacked rolls, two back-up rolls (3, 3') and two work rolls (2, 2') respectively, are slidably mounted, in a direction parallel to a clamping plane, and means (15, 16) of applying a rolling force between said rolls with adjustment of their respective gaps, characterised in that at least one convertible stand (4) is equipped with means of quickly replacing a first pair of work rolls (2, 2') by two cassette-type assemblies (6, 6'), each consisting of a work roll (61, 61') of smaller diameter, associated with an intermediate roll (62, 62'), said convertible stand being thus provided with two possible configurations, a first configuration having at least four rolls adapted to a first production range, and a second configuration having at least six rolls adapted to a second production range, respectively, in that said convertible stand further comprises roll bending means (5,5') mounted on support parts (40, 40') (42, 42') integral with the housings (10) of the stand (1) and projecting towards the clamping plane (P1), and in that, on each side of the rolling plane (P), said roll bending means (5, 5') and their support parts are the same in the two configurations and remain in place in the housings (10) of the stand (1) so as to work either in conjunction with back-up lugs (21, 24, 25) of the chocks of work rolls (2, 22) in the first configuration or with back-up lugs (34, 71, 72) of the chocks of the intermediate rolls (32, 62) in the second configuration, respectively, said back-up lugs (21, 24, 25) (34, 71, 72) of the chocks (20, 33, 71) being arranged, in each of the configurations, substantially at the same level relative to the rolling plane (P), on each side of the latter.
16. Installation according to claim 15, characterised in that the back-up lugs (21, 21') of the chocks (20, 20') of the work rolls (2, 2') in a first configuration are offset with respect to the roll axis, on the side opposite the rolling plane P, and in that the back-up lugs (34, 34') of the chocks (33, 33') of the intermediate rolls (32, 32') in a second configuration are offset towards the rolling plane (P) with respect to the roll axis, such that said lugs (21, 21') of the work rolls (2, 2') and (34, 34') of the intermediate rolls (32, 32') are arranged substantially at the same level and work in conjunction with the same bending means (5, 5').
17. Installation according to claim 16, characterised in that the chocks (20, 20')(23, 23') of the work rolls (2, 2') and (22, 22') of the first and of the second configuration respectively, are slidably mounted between guiding faces (12a, 12b) provided at the ends of protruding parts (13a, 13b) integral with the housings (10) of the stand and supporting bending means (50, 50') that work only in conjunction with the work rolls (22, 22') of the second configuration.
18. Installation according to claim 17, characterised in that the chocks (33, 33') of the intermediate rolls (32, 32') of the second configuration are slidably mounted, in a direction parallel to the clamping plane P₁, between guiding faces (41) provided at the ends of support parts (40, 40') on which roll bending means (5, 5') of said intermediate rolls (32, 32') and of the work rolls (2, 2') of the first configuration are supported.
19. Installation according to one of claims 15 to 18, characterised in that the support parts (40, 40') bearing the bending means (5, 5') of the work rolls (2, 2') of the first configuration and of the intermediate rolls (32, 32') of the second configuration, are slidably mounted, in a direction parallel to the roll axes and in opposite directions, above and beneath the rolling plane (P) respectively, in order to adjust the roll nip to the product width in each of the configurations.
20. Installation according to one of claims 15 to 19, characterised in that the configuration change means allow the convertible stand (4) to be converted from a four-high configuration having two work rolls (2, 2') and two support rolls (3, 3') to a six-high configuration having two work rolls (22, 22'), two intermediate rolls (32, 32') and the same support rolls (3, 3').
21. Installation according to claim 20, characterised in that the convertible stand (4) is equipped, in a first four-high configuration, with two back-up rolls (3, 3') and two work rolls (2, 2') of quite large diameter and, in a second six-high configuration, with the same support rolls (3, 3'), two work rolls of smaller diameter (22, 22') and two intermediate rolls (32, 32').
22. Installation according to claim 15, characterised in that the chocks of the work rolls (22, 22') in a first configuration and of the intermediate rolls (62, 62') in a second configuration are slidably mounted between guiding faces (43, 43') provided at the ends of protruding support parts (42, 42') on which bending means (5, 5') are supported, and in that the chocks (23, 23') of the work rolls (22, 22') of the first configuration and the chocks (7, 7') of the intermediate rolls (62, 62') of the second configuration are each equipped with two pairs of offset back-up lugs (24, 25, 24', 25')(71, 72, 71', 72') projecting respectively above and below the support parts (42, 42') and supporting the same roll bending means (5, 5') mounted on the same support parts (42, 42') so as to act in a positive clearance direction or in a negative approach direction of the roll ends.
23. Installation according to claim 22, characterised in that the configuration change means allow the convertible stand (4) to be converted from a six-high configuration comprising two work rolls (22, 22') supported respectively, via a pair of first intermediate rolls (32, 32'), on a pair of support rolls (3, 3') to an eight-high type configuration comprising two work rolls (61, 61') supported respectively, via a pair of second intermediate rolls (62, 62'), on the same first intermediate rolls (32, 32') and the same support rolls (3, 3').
24. Installation according to claim 22, characterised in that the convertible stand (4) is equipped, in a six-high configuration, with a pair of back-up rolls (3, 3'), a pair of first intermediate rolls (32, 32') and a pair of work rolls (22, 22') and, in an eight-high configuration, with the same back-up rolls (3, 3') and the same first intermediate rolls (32, 32'), between which two cassette-type assemblies (6, 6') are intercalated, each consisting of a small-diameter work roll (61, 61') associated with a second intermediate roll (62, 62').
25. Installation according to claim 24, characterised in that the chocks (33, 33') of the first intermediate rolls (32, 32') are slidably mounted between guiding faces (41) provided at the ends of two support parts (40, 40') which are slidably mounted parallel to the roll axes.
26. Installation according to one of claims 24 and 25, characterised in that each cassette-type assembly (6, 6') of the eight-high configuration comprises a second intermediate roll (62, 62') having two necks, each supported by a holding frame (7, 7') in the form of a chock supporting a bearing (74) and a small-diameter work roll (61, 61') having two centring necks, each supported by an axial thrust bearing (75) accommodated in a box (76) connected to the frame (7, 7') holding said second intermediate roll (62, 62') by spring-type means (77) for pressing the work roll (61, 61') on said second intermediate roll (62, 62').
27. Installation according to one of claims 23 to 26, characterised in that the convertible stand (4) is equipped with lateral back-up means (8, 8') mounted on housings (10) of the stand (1) and displaceable between two positions, a distant position for the six-high configuration and an engaged position for lateral back-up of each small diameter work roll (61, 61'), in the eight-high configuration.
28. Installation according to claim 27, characterised in that in an X arrangement, each small-diameter work roll (61, 61') is held laterally by two sets of rollers (8a, 8b), each mounted on a support frame (81) which can slide along in a direction that is inclined relative to the rolling plane (P), on guide bars (82) fixed on the housings (10) of the stand (4).
29. Installation according to claim 28, characterised in that in order to change from the eight-high configuration to the six-high configuration, the sets of rollers (8) are moved backwards in the guide bars (82) so as to free up the central space of the stand (4) in order to allow the withdrawal of the assemblies (6, 6') and their replacement by two large-diameter work rolls (22, 22').

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