WO2011018126A1

WO2011018126A1 - Method and device for automatically adjusting the position of working rolls in rolling equipment

Info

Publication number: WO2011018126A1
Application number: PCT/EP2009/064601
Authority: WO
Inventors: Vincent Cronier
Original assignee: Siemens Vai Metals Technologies Sas
Priority date: 2009-08-12
Filing date: 2009-11-04
Publication date: 2011-02-17
Also published as: EP2464470B1; EP2464470A1

Abstract

The present invention relates to a method and device for adjusting an offset (O) of a pair of working rolls (2, 2') relative to a pair of support rolls (3, 3') in rolling equipment, said offset (O) being defined in that a plane (P') containing the axes of rotation of said working rolls (2, 2') is offset relative to a plane (P) which is perpendicular to the traveling plane of a strip (1) to be rolled and through which the axes of said support rolls (3, 3') of said working rolls (2, 2') pass, characterized in that the device includes: a module (8) for identifying rolling parameters; a module (9) for determining, from said rolling parameters, at least one first offset value (O) enabling a reduction in the stresses parallel to a traveling plane of a strip (1) on the working rolls (2, 2'); an offset controller (10) for maintaining said offset at said first offset value throughout the duration of a rolling program, unless at least one other offset value has been predetermined.

Description

Method and device for automatically adjusting the position of the working rolls of a rolling mill.

The present invention relates to a method and a positioning device, i.e. automatic position adjustment, a pair of working rolls of a rolling plant, according to the preambles of claims 1 and 10.

In particular, the invention relates to the rolling of metal strips, especially special steels such as stainless steels, with the aid of a rolling installation generally comprising at least one rolling stand, comprising at least two superposed working rolls. vertically, each having their longitudinal axis of rotation parallel to the plane of travel of the metal strip and placed in the same clamping plane substantially perpendicular to the running direction of the strip. During rolling, the working rolls are generally pressed against each other by a pair of support rolls having their longitudinal axis in said same clamping plane, and between which a pressure - or a force - is applied. rolling. Such a rolling plant consisting of four vertically superimposed cylinders, two small diameter working rolls associated with two larger diameter supporting rolls, is called a "quarto". If two other intermediate cylinders are interposed respectively between the working roll and the support roll, the rolling installation is then formed of six vertically superimposed rolls, ie a pair of working rolls, framed by a first pair of rolls. intermediate supports, themselves framed by a second pair of final support cylinders. Such cylinder arrangement is usually referred to as "sexto" or "6-" High. "Finally, a sexto type mill may have lateral supports, for example each side of each of the work rolls is in contact with a lateral support roll which is itself supported laterally, in particular by two rows of rollers. The sexto rolling mills having said lateral supports are generally referred to as laterally supported sexto-type rolling mills.In all cases, the rollers bear against each other along bearing lines. substantially parallel and directed along a generatrix whose profile, normally rectilinear, depends on the forces applied and the strength of the cylinders.

Laterally supported sexto-type rolling stands are known to those skilled in the art and are in particular subject to US Pat. Nos. 4,270,377 and 4,531,394. The justification for this particular arrangement of the various cylinders and rollers lies in the adaptation of the diameter of the working rolls to the resistance to plastic flow of the metal to be rolled. Indeed, the large diameter working rolls, such as those equipping the quarto cage, have a large arcuate contact surface of the working roll with the belt, and therefore require a greater rolling force than with working cylinders of smaller diameter that would have a smaller contact area with the band. For steels having a moderate resistance to plastic flow, it is preferred quarto rolling mills whose large working rolls facilitate the stability of the rolling operation and which wear out less quickly. But for some steels such as stainless steels or other high tensile steels, the choice of small diameter work rolls is necessary in order to maintain reasonable rolling forces. For this reason, sexto-type rolling mills with working cylinders of small diameters are used. For a the same force exerted on the strip normally at its running plane, the greater the hardness of the metal to be rolled, the greater the diameter of the working rolls must be reduced in order to reduce the contact area between said working roll and the strip, and thus increase the rolling pressure. Unfortunately, working rolls of very small diameter pose bending problems during rolling. Indeed, the diameter of these working rolls is such that it is impossible to drive them directly, as is usual for cylinders of larger diameter, for example using extensions transmitting at one of their ends the rolling torque from a motorcycle gearbox unit. The transmission of the torque is then ensured, in the case of these working cylinders of small diameters, by friction on the intermediate support cylinders which are themselves driven by a motorcycle gear unit. This friction transmission generates between the working cylinder and the intermediate support cylinder a tangential force proportional to the transmitted torque. In the case of rolls of very small diameter, this tangential force causes a longitudinal bending of the working roll leading to defects in the flatness of the rolled strip.

In order to avoid this harmful flexion, and as described in US Pat. Nos. 4,270,377 and 4,531,394, each working roll is supported, at least on the input side of the strip in the grip of the work rolls, by means of lateral supports. This is generally a pair of lateral support cylinders, themselves each supported by two rows of rollers, the lateral support cylinder and its rollers being fixed on supports whose position is adjustable in order to adapt to different diameters of new or worn work rolls. In other variants, such as that described by US Pat. No. 6,003,355, said rollers are replaced by pushers. oil film sisters, which act as support for the lateral support cylinders.

As previously described, the torque transmitted by friction by the support cylinder to the working roll generates on the latter a horizontal force, or in other words a tangential force, proportional to said torque. Another means of counterbalancing this horizontal force, apart from the use of lateral supports, has been described in particular in US Patents 4,631,948 and US 6,003,355. These patents propose a horizontal shift of the longitudinal axis of the working roll relative to the vertical plane perpendicular to the plane of travel of the strip passing through the axis of the support roll which drives it by friction, in order to generate another effort horizontal proportional to the rolling force. In other words, the pair of working rolls is displaced so that the plane perpendicular to the band formed by the axes of rotation of said work rolls is offset relative to the plane perpendicular to the band formed by the axes of rotation of the support rolls. . In other words, the working rolls are each displaced in a substantially horizontal plane containing their axis of rotation while keeping a constant air gap, ie a constant thickness of the strip to be rolled, and the support rolls must adapt their po- vertical position with horizontal displacement of the working rolls. This offset is intended to oppose the two horizontal forces applied to the working roll, ie the horizontal force due to the frictional transmission of the rotational torque of the support roll and the horizontal force resulting from said shifting of the work rolls, in order to reduce or cancel their result. Such a device characterized by an offset, also called offset, between the longitudinal axis of rotation of the working roll and a plane passing through the longitudinal axes of rotation of the support rollers ensuring their friction drive has been proposed, either directly in order to oppose the horizontal forces, or in addition to a lateral support device to prevent the lateral bending of a working cylinder of small diameter. The compensation of the horizontal forces is in particular obtained by a shift of the working rolls on the output side of the strip of the right-of-way of said work rolls.

In general, rolling mills operate according to a defined rolling schedule for each rolling product. By rolling program, reference is made in particular to the reduction in thickness referred to in each of the successive rolling passes (reversible rolling mills) and / or in each of the successive rolling stands (tandem and reversible mills with several stands). Each rolling program is specific to a rolling product, in particular by defining a set of rolling parameters adapted to said rolled product and capable of configuring the operations of the rolling mill. Before each new product to be rolled, it is thus necessary to introduce into the control automation system of the rolling mill, a rolling program adapted to the product to be rolled.

Reversible rolling cages in which the strip is laminated alternately in one direction and then in the other may have no rolling parameters related to said offset (the plane passing through the axis of the working rolls coincides with the plane passing through the axis of the intermediate support rolls) or may have a different rolling parameter at each pass and reversing the direction of the offset in the rolling direction. The spacing of the lateral support cylinders of a working cylinder may be slightly greater than the spacing required to clamp said working cylinder so that, under the conditions of rolling temperatures, there may be a slight clearance leaving more of freedom to the work roll, in particular to bind during changes of direction of rotation for which it is advantageous that the transmission of friction movement has to overcome, initially, only the inertia of the working cylinder, then in a second time, after contact and gradually , the inertia of the lateral support cylinders. During rolling, in one direction or the other, the working roll comes into contact with the lateral support cylinder arranged in opposition to the tangential force. Slack adjusters acting in parallel with the direction of movement of the backing rollers may also bring the work roll into contact with the two side bearing rolls with preload enabling expansion to develop. In the case of tandem mills, that is rolling mills having a plurality of rolling stands in which the web travels in a single direction, a fixed offset value is generally used for rolled products whose characteristics are similar. The position of the lateral supports is, in turn, adjusted by the operator at each change of cylinder to take into account the actual diameter of the working rolls, either directly by means of a control of jacks able to adjust said offset, or indirectly by means of a program for managing a sequence of cylinder changes.

Nevertheless, dynamic offset variation solutions have been proposed, as for example in US Pat. No. 5,406,817, which describes a control system ensuring both the adjustment of the offset and a cambering of the work rolls from position measurements, therefore of deformation, of said working rolls. This system uses narrow rollers with strong bending pressures on the ends of the work rolls and to be located beyond the widest rolled product right-of-way so that inevitable marks of contact between the rollers and the rollers do not affect the quality of the rolled strip. Such an arrangement implies on the one hand an expensive expansion of the entire rolling stand. And secondly, the system is redundant to the extent that the offset allied with the intrinsic rigidity of the lateral support means is able to ensure control of horizontal or tangential forces without using a bending system. This last aspect has been taken into consideration in the US Pat. No. 4,631,948 which recommends the use of an offset capable of compensating without bending the bending of the work rolls, said offset being adjusted by means of lateral supports on said working rolls. pressure difference cylinders piloted in real time between the input and output sides of the strip according to a fixed value of tangential forces. Similarly, US Pat. No. 6,003,355 describes a dynamic system for controlling tangential efforts by varying the offset in order to optimize the operation of lateral supports operating not by rollers, but by pads and oil film. This control of the efforts seems justified here by the need to avoid any rupture of the oil film which would lead to a direct contact of the pads with the lateral supports and the deterioration of the cylinders.

In each of the two patents US Pat. No. 6,003,355 and US Pat. No. 4,631,948, the offset is adjusted in a continuous manner, in real time, as a function of continuous measurements of the forces exerted during rolling on the lateral bearing cylinders. This continuous adaptation based on continuous measurements of the tangential forces also causes a continuous variation in the horizontal position of the axes of rotation of the two work rolls. This variation of the horizontal position of the work rolls must be constantly compensated by the vertical adjustment of the position of the rolls of Intermediate and final support to maintain the thickness of the rolled strip unchanged regardless of the adjusted value of the offset. Unfortunately, such a compensation greatly complicates the action of the automatic system for controlling the thickness of the rolled strip generally fitted to rolling mills. On the other hand, the variation of the positions of the work rolls, intermediate and final support is not performed instantly or completely simultaneously. Consequently, an inevitable transient phase of adaptation of their respective position takes place, during which the air gap of the working rolls is liable to vary (opening or forcing), resulting in a degradation of the regularity of the thickness of the the rolled strip. Thus, a constant adaptation of the offset generally leads to a constant variation in the thickness of the product to be rolled, which can be intolerable for quality products. This is why the constant adjustment of the offset is not used in practice. In fact, the thickness tolerances of the rolled products have become so rigorous that the automatic thickness control systems must compensate for the smallest variations in the rolling process, such as, for example, eccentricity-type geometrical defects. circularity rolling cylinders which, however, are only a few micrometers. It is therefore undesirable, if they do not have a rigorously indispensable character as in US Pat. No. 6,003,355 where the maintenance of the oil film between the cylinder and the pads is absolutely necessary for the process, to introduce into the rolling process additional variations in the position of the axes of the working rolls, or in other words, variations in the geometry of the air gap, which are difficult to manage. Thus, the continuous adaptation of the offset in order to balance the tangential forces, ie the stresses parallel to the running plane of the resulting band on the work rolls, is not compatible. with the current systems of automatic control of the tape thickness and has many disadvantages, in particular due to the complexity of its management.

An object of the present invention is to provide a simple method and a device for automatically adjusting the offset of working rolls of a rolling mill, compatible with an automatic control system of the thickness of the strip to be rolled. , compact, economically advantageous.

For this purpose, a device and a method are provided by the contents of claims 1 and 10. A set of sub-claims also has advantages of

The invention.

From a method of adjusting an offset of a pair of work rolls with respect to a pair of support rolls in a rolling mill, said shift being defined in that a first plane containing the axes of rotation of said work rolls is offset with respect to a second plane, in particular perpendicular to a running plane of a strip to be rolled, said second plane passing through the axes of rotation of said support rolls of said work rolls, the method according to the invention is characterized by an automatic realization of the following steps: an identification, in particular at the beginning of a rolling program, of rolling parameters, in particular an identification in the rolling program or in a database, in particular incorporated at the rolling installation, at least one rolling parameter relating to an adjustment set point of the rolling installation and at least one para relative rolling mill a configuration of the rolling mill, the adjustment set point being, for example, a rotational speed of the support rolls, a rolling force, or band pulls, and the configuration of the installation being for example the diameter of the working rolls or the geometrical characteristics of the installation of rolling;

a determination, in particular by a calculation, from said rolling parameters, of at least a first offset value, in particular determined at the beginning of said rolling program and making it possible to reduce or cancel parallel forces to a scrolling plane the resulting tape on the work rolls; a first shift, at the beginning of the rolling program, of said work rolls according to said first predetermined offset value, said offset being for example implemented by an offset control device;

maintaining said first offset until the end of said rolling program, unless at least one other offset value has been determined, in particular at the beginning or during said rolling program.

From a device for adjusting an offset of a pair of work rolls with respect to a pair of support rolls in a rolling mill, said shift being defined in that a first plane containing the axes of rotation of said work rolls is offset with respect to a second plane, in particular perpendicular to a running plane of a strip to be rolled, said second plane passing through the axes of rotation of the support cylinders of said work rolls, the device according to the invention is characterized in that it comprises:

a module for identifying rolling parameters, in particular able to identify in a rolling program or in a database said parameters of rolling, in particular at the beginning of said rolling program, said rolling parameter being able for example to be an adjustment setpoint of the rolling installation or a rolling parameter relating to the configuration of the rolling installation;

a module for determining, in particular by calculation, from said rolling parameters, at least a first offset value, in particular determined at the beginning of said rolling program, and making it possible to reduce or cancel parallel forces to a running plane of the resulting strip on the work rolls;

an offset controller adapted to maintain said offset at said first offset value for the duration of the rolling program, unless at least one other offset value has been determined, particularly at the beginning or in progress of said rolling program.

Thus, the present invention makes it possible, on the one hand, to adjust automatically, at the beginning of a rolling program, the first offset of said pair of work rolls from said automatic identification of the rolling parameters, and on the other hand, maintaining said first offset for the duration of the rolling program, as long as no other offset value has been determined. If another offset value has been determined, either at the beginning of said rolling program or during said program, the first offset will then be maintained throughout the rolling program, except for a transitional period during which the offset will be temporarily held constant at said other offset value. Thus, the method according to the invention is characterized in particular by a temporary automatic modification of the offset to the value of said other offset value during said rolling program, especially in case of variation of at least one rolling parameter. , said identification module being able to identify said rolling parameter, and the determination module being able to determine its variation, and if necessary, as will be described later, to determine said other temporarily valid adjustment value. during the rolling program.

Indeed, the method according to the invention is in particular characterized by an identification of nominal rolling parameters and special rolling parameters, so that said nominal rolling parameters are able to be distinguished from the special rolling parameters during the rolling. identification of said rolling parameters by the identification module. The first ones, ie the nominal rolling parameters, are rolling parameters valid for the whole of a rolling program, or in other words, for the whole of one or more products to be rolled. Except for certain parts of said rolling stock or certain configurations of the rolling mill, which indeed require adaptation of the nominal rolling parameters to special values and giving rise to said special rolling parameters.

The nominal rolling parameters are capable of allowing the determination of said first offset value, whereas the special rolling parameters are capable of enabling the determination of at least one other offset value, for example a second and a third value of shift, which will only intervene temporarily. Thus, the determination module is, on the one hand, able to determine the said first offset value from the rolling parameters. nominal, said first offset value serving as a setpoint for the controller to control and maintain said offset at said first offset value. But also, on the other hand, the determination module is able to determine said other offset value from the special rolling parameters. The offset maintained at said first offset value is referred to as the first offset or the nominal offset. The other offsets, ie offsets whose value has been determined from special rolling parameters, are simply referred to as special offsets. For the sake of clarity, said first offset value will be called the nominal offset value, while any offset value different from this nominal offset value will be referred to as the special offset value.

In particular, the identification module is able to identify at the beginning of the rolling program the nominal rolling parameters necessary for the determination by the determination module, and in particular by calculation, of the horizontal nominal offset of said first plane containing the axes of rotation. rotation of the working rolls relative to said second vertical plane, defined by the axes of rotation of the support rolls, as well as the special rolling parameters, related for example to a management of the rolling of a strip in continuous spinning by the rolling program and / or corresponding to the identified variation of at least one nominal rolling parameter during a rolling program, such as for example a position of a splicing weld of two successive bands (possibly identified by a welding detector ), or a position and a length of band characterized by a thickness of band (possibly identified by ja thickness), or metallurgical characteristics (possibly identified for example by traceability data of the strip obtained on an upstream process of its transformation) different from the thickness or features of the rest of the scrolling tape. In addition, and advantageously, the identification module is also able to identify during said rolling program, said special rolling parameters.

Thus, the identification module is able to identify on the one hand nominal rolling parameters, and on the other hand special rolling parameters. These different rolling parameters can come from, among other things, a part of a database linked to the rolling mill, a rolling program, or to be entered by an operator in said rolling program or said base. data, but also on the other hand, said rolling parameters can be identified by the identification module from signals coming from devices for analyzing characteristics of the strip or the processing installation. Said analysis devices are for example and non-exhaustively, tape thickness gauges, welding detectors, force sensors on the working rolls, or displacement or position measuring sensors of said cylinders. working, traction force sensors, etc. These different devices are able to send, in particular in real time, a signal to the identification module which processes these signals in order to determine at least one rolling parameter which is relative thereto. At the beginning of a rolling program, a set of nominal and special rolling parameters can be determined. Then during rolling, the nominal parameters are memorized by the determination module as set nominal values for the setting of the nominal shift of the working rolls, while the special rolling parameters on the one hand allow the determination module determining, at the beginning of a rolling program, transient special offsets, in particular, occurring according to a temporal datum or according to a datum related to a length of web on the other hand, to determine, during rolling, said special offsets following the real-time identification of rolling parameters which would have varied, for example, and whose value would no longer be equal to the value of the parameter. nominal rolling mill identified at the beginning of the rolling program, or, would exceed a threshold value fixed by the determination module, and predefined, for example either by automatic calculation by the determination module, or by an operator entering directly into the module of determining said threshold value.

According to an advantageous characteristic of the method according to the invention, on the basis of these nominal and special rolling parameters, the module for determining the displacement value is able to determine respectively said nominal offset value of the working rolls and the at least one of the said special shift values of the working rolls, in particular at the beginning of the rolling program, provided that the special parameters are identified and / or revealed in the rolling program of the rolling mill or in the rolling mill. data. Indeed, at the beginning of the rolling program, only the rolling program and the database are able to provide special rolling parameters, since said analysis devices can not transmit any special rolling parameters relating to the strip. or at the rolling plant, since at the beginning of the rolling program, said strip is not yet running in the rolling mill. In particular, the determination module is able to determine, in particular in real time, whether rolling parameters identified in real time lead to a special offset. In other words, the determination module is able to process in real time said special rolling parameters from the identification module, whereas said parameters The nominal rolling meters are set at the beginning of the rolling program for the entire duration of the rolling program, and therefore no longer change during the said rolling program period, but instead serve as a reference for special rolling parameters. In particular, the determination module is able to compare values of special rolling parameters with nominal rolling parameter values or corresponding threshold values in order to decide whether a special offset must or must not be determined, and then transmitted to the control module. If a special offset has been determined by the determination module at the beginning of the rolling program, said special offset occurs temporarily during the duration of said rolling program. If a special offset is determined during the rolling program, which means that special rolling parameter values have, for example, exceeded one or more threshold values or are no longer equal to the value of the nominal rolling parameter that corresponds to them. have caused the determination of a special offset during a rolling operation, then said special offset takes effect immediately, from the moment of its determination, and ends as soon as for example, said special rolling parameters having caused said offset special values return to values allowed by the determination module, ie values not exceeding said threshold values, or, for example, values equal to the nominal values of the rolling parameters.

For example, a nominal rolling parameter could be a defined web thickness at the beginning of the rolling program, a special rolling parameter would then be a real time measurement of said web thickness during the rolling program, a threshold value for this special rolling parameter would be a tolerance value with respect to the strip thickness. If this tolerance value is exceeded during rolling, a new offset value, ie a special offset, is automatically determined by the determination module, then transmitted to the control module so that the control module sets the shift between the work rolls according to said offset value special. After a defined period of time, or after said measurement of the real-time thickness returns below said threshold value, the determination module is able to transmit to the control module the nominal offset value which will be maintained until at the end of the rolling program, unless there is a determination of a new special offset value.

These special parameters are therefore, exceptionally, taken into account in order to set, during the rolling program, a temporary or transient offset, ie a special offset value different from the value of the nominal offset of said first plane defined by the axes of rotation. working cylinders relative to the plane perpendicular to the band defined by the axes of rotation of the support cylinders, for example during the passage of a weld in the air gap of the working rolls. Once the weld has passed through the air gap of the working cylinders, the shifting of the work rolls returns to its nominal value, as determined by the determination module for the rest of the band, thus ending the period transient shift. Such a temporary offset, the value of which equals the said special offset value, can also simply be entered, in particular by an operator, either in the rolling program or in the databank related to the transformation installation in order to be taken into account during rolling by the determination module, either directly in the determination module by defining, for example, a transitory period depending in particular on a running speed of the strip and during which a specific offset predefined by said operator is controlled by the controller. In this case, it will not be an automatic determination by calculating the offset value made by the determination module from the identification of the rolling parameters, but from a manual determination by the controller. operator of said value, said operator having for example himself estimated some rolling parameters and entered said value in the rolling program or in the determination module. Also, and particularly advantageously, said database used for identifying the rolling parameters by the identification module is for example able to contain all the rolling programs to be performed by a rolling mill, so that said offset is set automatically, product after product, and not only for a single type of product to be rolled.

In order to implement this transient shift, the control device according to the invention is able to temporarily change the offset of said work rolls in case of determination of at least one other shift value, ie a special shift value. , by the determination module at the beginning or during the rolling program. When modifying said nominal offset, the offset of the working rolls is temporarily maintained at a special offset value, either determined by calculation from the special rolling parameters by said determination module, or determined in a free manner. of calculations by the determination module from one or more of said special rolling parameters, in particular determined from an offset value predefined by an operator and entered for example in the determination module or in the database . In the latter case, the identification module is able to identify said offset value predefined by said operator as a rolling parameter. special linked to a predefined offset value, so that the determination module is able to recognize in said special rolling parameter related to the predefined offset value said special offset defined by the operator, and thus said determination module is suitable determining without calculation the special offset value from the special rolling parameter related to the predefined offset value, then simply transmitting said special offset value to the controller.

The control device then comprises in particular hydraulic or electromechanical adjustment actuators for adjusting the position of the lateral support cylinders and their support rollers in order to position the working cylinders according to the offset controlled by the control device. . In particular, the control device further comprises a device for measuring the position of the work rolls capable of performing at least one measurement, particularly in real time, of the position of the work rolls. This position measuring device is in particular able to supply at least one signal relating to said position measurement to the identification module and used during the management of the offset by the identification module, the determination module and the control module. control device. The measurement of the position of the working rolls is in particular a direct or indirect measurement of the position of said rolls, based on a measurement technique with or without contact. This is for example the use of non-contact sensors of the horizontal displacement of the cylinders, or displacement or position sensors coupled to actuators for adjusting the position of the working rolls. Measuring the position of the working rolls makes it possible firstly to check, for example during rolling, that the position of the work rolls is in agreement with the offset values determined by the determination module, for example For example, threshold values, or predefined values, but also, on the other hand and in particular, to help the precise positioning of said working rolls by the control device which is able to process in particular information concerning the position of the work rolls. transmitted by the device for measuring the position of the work rolls.

Also, the method according to the invention is characterized by at least one measurement, in particular in real time, of said forces parallel to the running plane resulting on the working rolls. To this end, the control device comprises at least one force measuring device able to measure, by contact or free contact and in particular in real time, the parallel forces to the running plane of the resulting strip on at least one working cylinders. In addition, said force measuring device is in particular capable of supplying at least one signal relating to the measurement of forces to said identification module in order to determine at least one rolling parameter related to said measurement of forces.

Unlike US Pat. Nos. 6,003,355 and 4,631,948, the method and the device according to the invention are not essentially based on continuous measurements of the tangential forces in order to adjust the position of the work rolls. Indeed, according to US Pat. Nos. 6,003,355 and 4,631,948, the continuous measure of tangential forces makes it possible to position said working rolls in order to at least reduce said resultant tangential forces on the work rolls. On the other hand, according to the device and the method according to the invention, said measurement of the tangential forces, or in other words, parallel forces to the resultant running plane on the working rolls, serves only to control the value of said forces. Indeed, the positioning of said cylinders is based on the identification automatic cation of rolling parameters, such as, for example, the rolling speed, the value of the tensile force of the strip upstream and downstream of the rolling stand, the torques of forces transmitted to the working rolls, or the characteristics material and geometrical of the strip and cylinders involved in the rolling operation. From these parameters, the determination module determines a nominal offset value of the work rolls, and this nominal value is kept constant throughout the rolling program, unless a special offset value has been or is determined. , then temporarily maintained, for example, when the force measuring device, or the position measuring device, respectively indicate tangential forces or a position which exceed predetermined threshold values in the determination module. These predetermined threshold values in the determination module are limit values for the tolerance of the forces or the position which are determined by the determination module according to the rolling parameters, or entered manually by an operator, either directly in the determination module. , and thus recorded in predetermined manner in said offset determining module, either in the rolling program or the database. If these threshold values are reached, the cylinder offset is in particular temporarily modified according to a predetermined value in order to avoid any damage to the rolling installation.

Thus, the method according to the invention is particularly advantageously characterized by the identification, by the identification module, of at least one rolling parameter from at least one signal coming, in general, from at least one measurement made by at least one of said analysis devices. In particular, the method according to the invention is characterized by the identification of at least one parameter rolling from said force measurement and at least one other rolling parameter from said position measurement. In particular, the identification module is in particular able to transform at least one signal received from at least one analysis device into at least one rolling parameter linked to said received signal and to identify it as a rolling parameter. nominal or special. In addition, the method is also characterized by a temporary automatic modification of said offset as soon as at least one of said special rolling parameters exceeds a predefined threshold value, in particular, as soon as said measurement of said forces parallel to the rolling plane resulting on the cylinders of work or the position of said cylinders exceed a threshold value. For this purpose, the control device is able to temporarily change the offset of said working rolls if a predetermined threshold value is exceeded, by at least one of said special rolling parameters, in particular when at least one rolling parameter is linked. said parallel forces to the resultant scroll plane on the work rolls, or to the position of said work rolls, exceeds said threshold value. This automatic modification has in particular a role of controlling the rolling operations related to securing the rolling installation.

Finally, the identification module, the determination module and the control device of a rolling stand can in particular advantageously be included in the control automation system of a rolling mill, so that it is possible to in particular, to exchange information with the determination, identification and control modules of other rolling stands of the same rolling installation and included in the same control automation system, in order to transmit for example to cages located downstream adjustment information offsets having a special offset value, the ultimate goal being to prevent said downstream cages and provide for example transient offsets settings for said downstream cages.

Examples of embodiment and application are provided with the aid of the following figures: FIG. 1 embodiment according to the invention of a device for adjusting an offset of a pair of working rolls of a sexto rolling mill supported laterally. Figure 2 Distribution of forces in a rolling mill whose work rolls are driven by friction.

FIG. 1 shows an exemplary embodiment of a device for adjusting an offset or offset O of the first plane P 'in which the axes of rotation of a pair of working rolls 2, 2' are located with respect to the second plane P perpendicular to the strip and in which are the axes of rotation of a first pair of support rollers 3, 3 'of a sexto mill supported laterally. The band 1 passes between the two working cylinders 2, 2 'supported vertically, and in particular driven by friction, by said first pair of intermediate support rollers 3, 3', themselves supported vertically by a second pair of cylinders. end support linders not shown and bearing on said first pair of support cylinders 3, 3 'intermediate. The working cylinders 2, 2 'are also each supported laterally by lateral support rolls, 4a and 4' respectively supporting the working rolls 2 and 2 'on the input side of the band, and 4b and 4'b supporting both respectively the work rolls 2 and 2 'on the output side. The lateral support cylinders of a work roll are in particular arranged symmetrically on either side of the work roll. Each of the lateral support cylinders is itself supported laterally by two rows of support rollers 5, each row being composed of a plurality of rollers arranged side by side along a common axis on a support 62 common to two rows, said support 62 being able to move relative to a fixed support 61 integral with the structure of the rolling mill.

For this, an actuator 63 ensures a displacement of the support 62 and therefore of the rollers 5 and each of the lateral support rolls 4a, 4 'a, 4b, 4'b with parallel longitudinal axes. The displacement of the support 62 thus makes it possible to move the working rolls in order to adjust the offset O according to a determined offset value, for example by calculation, by a determination module 9 and transmitted by the latter to a control device 10 The offset O corresponds more precisely to the distance between the first plane P 'substantially perpendicular to the running direction of the strip 1 and in which are the axes of rotation of the working rolls 2, 2' and the second plane P perpendicular to a running direction of the strip 1 in which are the axes of rotation of the support cylinders 3, 3 '. This offset O is determined by the determination module 9 from rolling parameters identified at the beginning of a rolling program or during said program by an identification module 8 in a database or in said linked rolling program. to an automation system 7 of the rolling mill or by devices for analyzing the characteristics of the strip or rolling mill, such as a position measuring device 64 able to directly or indirectly measure the position of the rolling mill. at least one of the working cylinders. Said analysis devices transmit in particular to the identification module 8 of the signals from which said identification module 8 is able to identify at least one rolling parameter. The automation system 7 in particular manages the rolling operations according to a rolling program adapted to each product to be rolled, and in particular comprises at least said database relating to the characteristics of the strip and the rolling mill. . The identification device 8 makes it possible in particular to transmit to the determination module 9 the rolling parameters identified in particular from the data coming from the database of the automation system 7 or within the rolling program, necessary for the Determination of the offset O. Advantageously, the identification module 8 makes it possible to manually enter laminating parameters, for example to correct errors that would come from the database or the rolling program, or from inserting rolling parameters that would be missing for the determination of said offset by the determination module 9.

In particular, the identification module 8 is able to differentiate the nominal rolling parameters, ie valid for nominal strip and rolling mill characteristics, special rolling parameters, temporarily or transiently validated for special configurations of the strip or rolling mill. Examples of special parameters are in particular the position in the continuous band of a weld as well as the characteristics relating to the size of this weld, or the position according to the length of the strip of a band length interval for which a The metallurgical characteristic of the web changes, or a speed of travel increased for a short time, or a variation in thickness or variations of the webs upstream and downstream of the working rolls. Once everything or part of these identified rolling parameters, either at the beginning of a rolling program or during said program, they are communicated, in particular by the identification module 8 to the determination module 9. Therefore, the determination module 9 will be able to determine different offsets. If certain parameters are missing, the determination module 9 is in particular able to warn the identification module 8 and to send it information concerning the missing rolling parameters. Advantageously, the identification module alerts a control station or issues an alert signal as soon as it receives said information concerning said missing rolling parameters. From the nominal rolling parameters, the determination module 9 is able to determine said nominal rated offset, and from the special rolling parameters, at least one of said offsets described as special. The nominal rolling parameters are used to define a nominal offset or offset valid for the rolling of the entire belt, with the exception of temporary variations of the offset, in particular when special offset or offset values have been determined by the module. 9, at the beginning of the rolling program and transmitted, in particular according to a time scale or a length of the running tape, to the offset control device 10, either during rolling, and transmitted immediately. In fact, the different offset values, whether nominal or special, are transmitted to the shift control device 10 which controls the positioning of the work rolls 2, 2 ', in particular by means of said actuators 63, according to said offset values transmitted by the determination module 9. Advantageously, the working rolls 2, 2 'are positioned at the beginning of a rolling program based on a nominal offset determined by the determination module 9. Advantageously, the offset control device 10 is able to manage the shift of the rolls, in particular the transition from a nominal offset to a special offset and vice versa. Maintaining said offset at a special offset value is in particular according to a time scale or as a function of a length of strip scrolled, or, depending on at least one signal, treated as a parameter of rolling by the identification module 8, and transmitted either by at least one detector capable of determining at least one characteristic of the strip before entering the air gap, said characteristic being decisive for the rolling operations, such as, for example, the presence of a weld, either by a device able to control characteristics of the rolling stand during rolling operations, such as for example the position of the work rolls, or measured voltages on the strip upstream or downstream of the rolls working. In addition, and advantageously, the control device 10 comprises at least one measuring device 64 able to directly or indirectly measure the position of at least one of the working rolls, in particular by coupling with the actuator 63. other types of position measuring devices, such as displacement sensors with contact or free contact can be used to measure, directly or indirectly, the position and movements of each of the working rolls 2, 2 '. In addition, the control device 10 comprises in particular at least one force measuring device (not shown in the figure), making it possible to measure, in particular in real time, the forces, in particular parallel to the plane of scrolling. of the band, resulting in at least one of the working cylinders. Advantageously, since the identification module 8 is able to process signals from said analysis devices, it is in particular also able to process the signals relating to the measurements of said forces delivered by the force measuring devices and to transmit to the determination module 9 rolling parameters relating to said signals in order to adapt the value offset so that the value of the measurement of said forces remains below a threshold value predefined by an operator or by calculation via the determination module 9. If necessary, if the value of the measurement of said forces exceeds said threshold value, the determination module 9 is particularly capable of transmitting information relating to the measurement of said forces to the control automation system of the rolling installation. The force measuring device advantageously makes it possible to detect any accidental overloads of the rolling mill.

Thus, the position measuring and force measuring devices 64 make it possible to ensure that the resulting forces on the working rolls or the position of the work rolls do not exceed pre-recorded or predefined threshold values in the module. These pre-recorded or predefined values can come from a calculation based on rolling parameters, from the automation system 7, or can be entered and recorded manually in the determination module 9 by a user or a user. operator. If these threshold values are reached, the cylinder offset is in particular immediately modified for a predefined or calculated temporary duration, in particular according to a new special offset value, in order to avoid any damage to the rolling installation.

The distribution of forces in a rolling mill whose working rolls are driven by friction is shown in FIG. 2 with the same numbering as in Figure 1. Nevertheless, in FIG. 2 only the upper support and work rolls 2 and the band 1 are shown. The distribution of forces for the lower support cylinders 3 'and work 2' is obtained by symmetry via the tape running plane, ie the median horizontal plane of the strip 1. As shown in FIG. 1, the band 1 passes between the two working cylinders 2, 2 ', each of them being rotated by a motorized support cylinder 3, 3'. Said support cylinder 3 transmits to the working roll 2 a tangential force FT depending on the transmitted torque T and the radius of said support roll 3. In order to compensate for the effect of this tangential force FT on the working roll, and as a function of imposed on the upstream band TM and on the downstream side of the strip in the working rolls, the axis of rotation of the working rolls is shifted in the direction of the running direction of the strip by a value of offset or offset 0 sufficient for a clamping force F generates a horizontal force FL dependent 0 and radii RI and RW cylinders respectively supportive and working. The horizontal force FL generated by the offset is ideally equal, in first approximation, to the horizontal component of the forces FT + (TM - TV) / 2.

In summary, the method and the device according to the invention have several advantages over the existing methods and devices in that: they guarantee a set of constant values of the offset during the rolling of a strip, said set comprising a valid constant value of offset valid for most of the band and at least one special value of offset, which is also kept constant but intervenes temporarily during a phase transient rolling during which the offset is adapted to a special characteristic of the strip or the rolling mill, as for example in the case of the passage of a weld in the rolling mill;

they use pre-existing data relating to the characteristics of the strip and found for example in the database linked to the rolling installation, or in the rolling program;

they provide a simple management of the offset, free of a continuous adaptation of the offset as a function of tangential force measurements resulting on the work rolls;

they ensure a compatibility of the automatic adjustment of said offset with a device for controlling the thickness of the strip by avoiding irrelevant offset variations and optimizing a maintenance of the offset at a constant nominal value in first approximation while allowing as a second approximation temporary special values held constant;

- they ensure the automatic adjustment of the offset at least with each change of intermediate working or support rolls, at each change of rolling program, and at the achievement of predefined threshold values for rolling parameters, for measuring position of the work rolls and for measuring the resultant forces on the work rolls.

Claims

claims

1. A method of adjusting an offset (0) of a pair of work rolls (2, 2 ') with respect to a pair of support rollers (3, 3') in a rolling mill, said offset (0) being defined in that a first plane (P ') containing the axes of rotation of said work rolls (2, 2') is shifted with respect to a second plane (P) passing through the axes of said rolls of supporting (3, 3 ') said working rolls (2, 2'), characterized by an automatic realization of the following steps:

an identification of rolling parameters;

a determination, from said rolling parameters, of at least a first offset value (0) for reducing parallel forces to a running plane of a resultant strip (1) on the work rolls (2, 2 ');

a first offset (0) of said work rolls (2, 2 ') according to said first offset value (0) previously determined;

maintaining said first offset (0) until the end of a rolling program, unless at least one other offset value has been determined.

2. Method according to claim 1, characterized by a temporary automatic change of offset (0) to the value of said other offset value during said rolling program.

3. Method according to one of claims 1 or 2, characterized by the identification of at least one rolling parameter in said rolling program or in a database.

4. Method according to one of claims 1 to 3, characterized by the identification of at least one rolling parameter from at least one signal originating from at least one measurement carried out by at least one device for analyzing the characteristics. of the strip or rolling mill.

5. Method according to one of claims 1 to 4, characterized by at least one position measurement of the work rolls (2, 2 ') and the identification of at least one rolling parameter related to said position measurement.

6. Method according to one of claims 1 to 5, characterized by at least one measurement of said stresses parallel to the resultant scroll plane on the working rolls (2, 2 ') and the identification of at least one rolling parameter related to said measure of effort.

7. Method according to one of claims 1 to 6, characterized by an identification of nominal rolling parameters and special rolling parameters.

8. Method according to claim 7, characterized in that the nominal rolling parameters are capable of allowing the determination of said first offset value and the special rolling parameters of said other offset value.

9. Method according to one of claims 7 to 8, characterized by a temporary automatic modification of said offset (O) as soon as at least one of said special rolling parameters exceeds a threshold value.

A device for adjusting an offset (O) of a pair of work rolls (2, 2 ') with respect to a pair of support rollers (3, 3 ') in a rolling mill, said offset (0) being defined in that a first plane (P') containing the axes of rotation of said work rolls (2, 2 ') is shifted with respect to a second plane (P) passing through the axes of said support cylinders (3, 3 ') of said work rolls (2, 2'), characterized in that it comprises:

an identification module (8) of rolling parameters;

a determination module (9), from said rolling parameters, of at least a first offset value (0) making it possible to reduce stresses parallel to a running plane of a resulting strip (1) on the cylinders; working (2, 2 ');

an offset controller (10) adapted to maintain said offset at said first offset value throughout the duration of a rolling program, unless at least one other offset value has been determined.

11. Device according to claim 10, characterized in that the identification module is adapted to transform at least one signal received from at least one device for analyzing the characteristics of the strip or the rolling mill in at least a rolling parameter related to said received signal.

12. Device according to one of claims 10 or 11, characterized in that the control device (10) comprises actuators (63) for adjusting hydraulic or electromechanical.

13. Device according to one of claims 10 to 12, characterized in that the control device (10) comprises a measuring device (64) for the position of the working rolls (2, 2 ').

14. Device according to one of claims 10 to 13, characterized in that the control device (10) comprises at least one force measuring device capable of measuring the forces parallel to the running plane of the strip (1). resultant on at least one of the work rolls (2, 2 ').

15. Device according to one of claims 13 to 14, characterized in that the force measuring devices and positions are capable of each providing at least one signal to the identification module.

16. Device according to one of claims 10 to 15, characterized in that the identification module (8) is able to identify nominal rolling parameters, as well as special rolling parameters.

17. Device according to claim 16, characterized in that the determination module (9) is able to determine said first offset value (O) from said nominal rolling parameters and said other offset value from the rolling parameters. special.

18. Device according to one of claims 10 to 17, characterized in that said control device (10) is able to temporarily change the offset (O) of said working rolls (2, 2 ') in case of determination of said other offset value.

19. Device according to claim 16 to 18, characterized in that said control device (10) is able to temporarily modify the offset (O) of said cylinders of working if a threshold value is exceeded by at least one of said special rolling parameters.

Device according to one of claims 10 to 19, characterized in that the identification module (8), the calculation module (9) and the control device (10) are included in a control automation system ( 7) of the rolling mill.