FR2537021A1 - Six-high rolling mill stand - Google Patents

Abstract

A rolling mill stand has two work rolls, two intermediate rolls and two back-up rolls. The intermediate rolls are axially displaceable to suit strip of different width. A control unit receives signals from sensors for profile deviations across the strip width and/or tension variations and controls the screwdown forces for the bending cylinders in the housings of the work rolls and intermediate rolls. Curvature deviations in the strip centre are compensated by bending the intermediate rolls, and in the edge zones by bending the work rolls. This permits the prior setting of optimum values and a constant adjustment of them during the rolling operation.

Description

 The present invention relates to a rolling stand which comprises on the one hand two working rolls, two intermediate rolls and two support rolls (sexto cage), in which also at least the support rolls and the intermediate rolls provided between them and the working cylinders are as a whole superimposed in a common vertical plane, the intermediate cylinders being arranged with the possibility of axial displacement, in which on the other hand blocks integral with the columns are provided with vertical guide faces for the chocks of the working cylinders and intermediate cylinders and have displacement means for balancing and bending the cylinders, while on each block are vertically guided a lower guide piece and an upper guide piece provided with guide faces for the chocks of the intermediate cylinders and that the displacement means constituting the bending devices for the cyl other means are provided which can be moved horizontally parallel to the axes of the cylinders with respect to the chocks and / or the guide pieces, and in which, in addition, the means of movement provided for in the said blocks are also assigned to the chocks of the two working cylinders as bending devices which attack guide parts which on the one hand are retained in the blocks by means of vertical guides and on the other hand have horizontal guides for chocks.

 A multi-cylinder cage in which intermediate cylinders can move longitudinally to avoid excessive rolling of the product in the region of its edges is already described in patent invention DE 955 131. However, it has been found that despite the relatively complicated structure of this cage it was not possible to influence with all the desirable precision on the profile of the right-of-way.

 In the patent of invention US 4 194 382 are described cages with five and six cylinders in which the axially displaceable intermediate cylinders are provided with bending devices. It is recommended there to decrease the table lengths, of the working cylinders in the direction of support cylinders, and it is indicated therein that in addition the work cylinders and the support cylinders can other equipped with bending devices, with the reserve however that the work cylinders are too rigidly embedded for the effect obtained is sensitive, and that because of the rigidity of the support cylinders the action of bending devices thereon remains weak.

 The patent applications DE -A- 2 334 492-and 3 115 461 represent sexto cages with axially displaceable intermediate cylinders and working cylinders which can be preloaded in bending unilaterally, in connection with a control device of any necessary and which, on the basis of prescribed or measured values for example by means of sensors, determines the optimal bending of the intermediate rolls and the working rolls and establishes or regulates these bends, the flatness of the laminate and the distribution of the tensions which can, by measuring devices according to the invention patent DE -C- 1 573 407, to be one monitored, the other adjusted on the basis of their results. It has however been revealed that when one wants to act on the profile of the right-of-way it is certainly possible to take account of general trends but that one cannot, with such provisions, make a relatively fine correction or apply locally.

 In patent application DE -A- 3 107 693, a sexto cage is described, the intermediate cylinders of which can be prestressed in bending and moved axially. This cage is in particular able to laminate strips of very variable widths and, with moderate bending forces, this cage ensures for all strip widths to be rolled effective conditions to a large extent constant in connection with extremely Hertz pressures weak at the support lines of working cylinders and intermediate cylinders. It allows an optimal choice of diameters both with regard to the working cylinders and the intermediate cylinders and finally also makes it possible to replace all these cylinders without problem. Another advantage is the low wear of the working cylinders, since these are only not corrected around the edges of the table of the intermediate cylinders, and it is favorable that the lever arm of the bending forces which attack the movable intermediate cylinders remains constant for all the widths of strip to be laminated.

 In the patent for invention DE 3 122 128, an additional bending of the working rolls provides an effective widening of the bending correction range in conjunction with an optimization of the linear pressure at the points where there is contact between the working rolls. working and the intermediate cylinders and further between these and the supporting cylinders.

 The problem to which the invention provides a solution was, in the case of a sexto cage according to the patent of invention 3,122,128, to explain the relationships between the bending of the working rolls and that of the supporting rolls in the case of displaceable support cylinders, so that perfect, defined and optimal control is made possible, and in addition to designing a control device which, both on the basis of prescribed values and of captured values, makes it possible to ensure a presetting on optimal values before the setting of iron and, during rolling, to carry out corrections on the basis of observed and introduced and / or captured values.

 The solution according to the invention consists in providing a control device which, on the basis of values entered manually and / or values read from data carriers and / or memories and / or values supplied by sensors upstream of the cage, on the one hand, prescribes the movements of the intermediate cylinders best suited to obtaining a predetermined grip profile as well as the value and the direction of the adjustment forces to be exerted by the bending devices of the working cylinders and intermediates, on the other hand, on the basis of deviations from the grip profile and / or deviations in the tension of the strip observed over the width thereof during rolling, the optimal corrections to obtain a profile of prescribed grip, this essentially compensating by modification of the bending of the intermediate cylinders the curved defects of the strip observed in the middle of it and by modification of the bending of the working cylinders the def others bulging on the banks.

 Bar the selective and mutually balanced implementation of the flexions of the working cylinders and the intermediate cylinders, it is thus possible to remedy with precision bulging defects occurring at different points in the length of the profile of the right-of-way.

It has proved useful that when compensating for a defect in the convexity of the strip, the control device additionally activates the bending of the working rolls very slightly in the opposite direction to the bending of the intermediate rolls and that during the compensation of 'a curved defect at the edges this device also activates the bending of the intermediate cylinders in the opposite direction to the bending of the working cylinders. Automatic compensation for differences in tension in the width of the strip can further be obtained by having a strain gauge downstream of the rolling stand which communicates to the control device the tensions of the strip measured at different points of the width of the latter. device then compensating for the differences in tension by influencing the bending of the working and intermediate cylinders and, optionally, the axial displacement of the intermediate cylinders. It is however also possible to implement "upward" regulations, possibly additional for example by determining the profile of the strip by measuring its thickness upstream of the cage, the value measured in different parts of the width of the strip then being applied as a disturbing quantity to the control device.

 For the measurement of the tensions in the strip, the use of a dynamometric tensile roller known per se has given good results.

your characteristics of the invention will appear in detail in the description of an example of execution made below with reference to the appended drawing; on the latter
FIG. 1 is a view in vertical section of a rolling mill stand,
FIGS. 2a, 2b and 2c are enlarged views of different bulges of a laminated strip,
FIGS. 3, 4 and 5 illustrate the effects of the flexions of the working rolls and of the intermediate rolls on the convexity of laminated strip,
FIG. 6 is a graph showing different variations in the profile of the right-of-way,
FIG. 7 shows diagrammatically an apparatus for measuring the tensions in the strip, arranged downstream of a sexto cage, and
- Figure 8 shows a control device with the inputs and outputs assigned to it.

 In fig. 1 is shown in section a sext cage in the columns 1 of which are guided two working cylinders 2 and 3, two intermediate cylinders 4 and 5 as well as two support cylinders 6 and 7. While the support cylinders 6 and 7 are , by means of their chocks 8 and 9, guided directly by wear plates of the opening 10 of the columns 1, it is provided for the working cylinders 2 and 3 as well as for the intermediate cylinders 4 and 5, in the openings 10 in the columns 1, blocks 12 integral with these columns.

The chocks 13 of the upper working cylinder 2 are connected to guide parts 17 by embedding in the vertical direction but with the possibility of a horizontal displacement to allow the replacement of the cylinder or cylinders. These guide pieces 17 are guided with the possibility of vertical movement in the blocks 12. Similarly, the chocks 14 of the lower working cylinder 3 are connected to guide pieces 18 which, too, can move vertically in the blocks 12 integral with the columns 1. The chocks 15 of the upper intermediate cylinder 4 are assigned guide pieces 19, here too these chocks are connected to the guide pieces 19 by embedding in the vertical direction but with the possibility of displacement in the horizontal direction. 16 of the lower intermediate cylinder 5 are likewise assigned guide parts 20 and horizontal guides 21.

The latter, between the chocks 15 and 16 for the intermediate cylinders 4 and 5 and the corresponding guide parts 19 and 20, are designed so that not only do they allow the replacement of the intermediate cylinders 4 and 5 at the same time as that of the working cylinders 2 and 3, but also also provide an axial displacement of the intermediate cylinders 4 and 5 relative to the working cylinders 2 and 3 and support 6 and 7. This axial displacement of the intermediate cylinders is used to adapt the cage rolling mill with different widths of strip to be laminated, since this prevents the strips from being more heavily laminated in the region of their longitudinal edges as well as the high stress of the sections of the working rolls 2 and. 3 which act on the edges of the laminate.

 For a rolling stand to be used for rolling strips in a wide width range, it has been found that it is essential to operate, at all strip widths capable of being rolled, under constant effective conditions. with a Hertz pressure as low as possible between the working cylinders 2 and 3 and the intermediate cylinders 4 and 5, and being able to choose an optimal diameter for all these cylinders taking into account the problem of rolling and the control of the peripheral forces. The rolling mill stand shown therefore has special provisions in the region of the chocks of the intermediate cylinders 4 and 5. In the chocks 15 and 16 of the upper 4 and lower 5 intermediate cylinders are assigned, in the region of the blocks 12 integral with the columns, means displacement 22 in the form of hydraulic cylinders 22 installed in the blocks 12 of the corresponding guide parts 19 and 20. We see in fig. 1 that these parts 19 and 20 each consist of a part. 23 on the column side and a portion 24 assigned to the chock 15 of the intermediate cylinder 4 and to the chock 16 of the intermediate cylinder 5. In the column side 23 are installed the displacement means 22 forming the bending devices for the intermediate cylinders 4 and 5; these means 22 attack by their piston rods 25 the parts 24 ′ on the chock side. The operational connection between these piston rods 25 and the chock side parts 24 of each guide piece 19 or 20 is carried out so that it is in measure, by means of chocks 15 and 16, to exert on the intermediate cylinders 4 and 5 bending forces at least in the direction of the support cylinders 6 and 7. However, it is particularly advantageous that the connection between the rods piston 25 of the displacement means 22 and the chock side 24 of the guide piece 19 is designed so that the bending forces can be exerted both in the direction of the corresponding support cylinder 6 or 7 as in the opposite direction. The displacement means 22 are thus double-acting and their piston rods 25 are connected in tension and in compression to the chock side part 24 of the guide pieces 19 and 20. The two parts 23, 24 of the guide piece 1 9 are assembled to each other with the possibility of moving exclusively vertically with respect to one another; they cannot describe relative horizontal displacements.

 your guide pieces 17 and 18 for chocks 13 and 14 of the two working rolls 2 and 3 have basically the same structure as the guide pieces 19 and 20 of the two intermediate cylinders.

Each of the guide pieces 17 and 18 is made up of a column part 53 and a part 54 assigned to the chock 13 or 14. From the column side part 53 the displacement means 55 which form the bending devices for working cylinders 2 and 3 are also incorporated in the form of jacks whose piston rods 56 attack the chocks side 54, so that with their help can be exerted by chocks 17 or 18 both positive bending forces that negatives on the working rolls 2 and 3. These two parts 53 and 54 of the guide piece 17 or 18 can move exclusively vertically with respect to one another; they cannot describe relative horizontal displacements.

 your games on column 5? guide parts 17 and 18 are supported by means of counterpushes against the blocks 12 and / or one against the other, so that the chocks side parts 54 of these parts and consequently also the chocks 13 and 14 for the working cylinders 2 and 3 can be moved by the displacement means 55 forming the bending device, whatever the support position of the parts on the column side 53, in order to bend the working cylinders. your counter supports are provided as jacks 57 (fig. 1) which connect the column side parts 53 of the guide parts 17 and 18 to each other in such a way that they make basic adjustment possible of the grip between the working cylinders 2 and 3 while allowing a common vertical relative movement of the guide parts 17 and 18 relative to the blocks 12 to a limited extent.

 But independently of such a vertical displacement of the set of working cylinders between the blocks 12, these two cylinders 2 and 3 can, by the displacement means 55, be bent in the positive or negative direction independently of each other .

 In the rolling stand shown in fig. 1 are incorporated in each of the guide pieces 19 and 20 for the chocks 15 and 16 of the intermediate cylinders 4 and 5 two displacement means 22 which are located one at a distance from the other in the direction of the axes of the cylinders and form together the bending devices for the intermediate rolls. The possibility of axial displacement of the intermediate rolls required for rolling is ensured by the fact that the chocks 15 and 16 of these rolls are engaged in the vertical direction, by means of the horizontal guides 21, with the c8té chock portion 24 of each guide piece 19 or 20. Your means of movement located in pairs one behind the other must be kept constant, in any possible axial position of the intermediate cylinders 4 and 5, their bending lever arm. To this end, they are designed and controlled so that the inflection forces which they exert can be modified as a function of the position of instantaneous axial movement of the two chocks 15 and 16 relative to the guide piece 19 or 20. In one of the extreme axial displacement positions of the chocks 15 and 16 of the intermediate cylinders, it is the displacement means 22 disposed on the same side which acts on these chocks with that situated on the opposite column 1 in the same direction, while when the axial displacement returns, these flexion means weaken, the others, that is to say those which complete the pairs, which come into action in increasing fashion, so that the bending forces exerted by a pair of means of displacement in bending vary with the axial displacement of an intermediate cylinder, whereby lever arms always equal in that the bending forces acting on a support cylinder are displaced with him.

 the effective bending stresses of the working and intermediate cylinders are based on the observation that the bending of the working cylinders and that of the intermediate cylinders does not differ only in terms of their rigidity and as regards their embedding, but because that, considered mathematically, an intermediate cylinder bending causes substantially quadratic-parabolic deformations, while a united working cylinder bending must generally be described by members of a high order. 2a is then indicated a total convex, assumed by way of example, of a laminated strip, representing the elevation of the strip profile above a plane connecting the upper sides of the edge of the strip. A total bulge of this kind can be reduced to a bulge as shown in FIG. 2b, which not only is symmetrical with respect to the median perpendicular but also has its crest on the latter and can be described mathematically by substantially quadratic members. In fig. 2c is drawn the part of the total convex of FIG. 2a which exceeds that according to fig. 2b.This remaining part, shown in fig. 2c, the total convex of FIG. 2a, is called the curved edge, can be described mathematically by members of high order and has several maxima - generally two - that can be expected to be found in the vicinity of the strip edge.

On the basis of this observation, it is to be expected that a domed strip such as that shown for example in FIG. 2b can other obtained by pre-bending the intermediate cylinders, and that a curved like that shown in FIG. 2c can be by bending the intermediate cylinders, so that the total crown shown in FIG. 2a. Should be attainable by simultaneous bending, in defined ratios, of the working rolls and intermediate rolls. It has now been found that the prescribed strip bombs are - retaining the other parameters determined essentially by the bending forces on the working rolls. However, it has also been found that the bending forces on the working rolls still exert an influence, which is why we have shown in FIG. 3 characteristic curves 26 to 30 substantially straight for different values
discreet of striped doming. line 26 shows the ratio between the deflection of the support cylinder and the deflection of the working cylinder which corresponds to a negative convexity with a relative value of 0.2; line 27 corresponds to a bulge of -0.1; line 28 indicates the curved 0, that is to say an upper strip surface which, as regards its quadratic members, is absolutely planar, while lines 29 and 30 relate to curved strip of + 0.1 and +0.2.

your lines of the same bulge therefore require a bending of the intermediate cylinders accompanied by a bending in the opposite direction of the working cylinders.

 A similar graph for edge bending is shown in fig. 4. Lines 31 to 35 here correspond to edge flexions from -0.04 to + 0.04, line 33 corresponding to edge flexion 0 and lines 34 and 35 indicating positive edge flexions. We see here that different bank flexions, that is to say the passage from one line to the next, is obtained by modifications of the flexion of the working rolls, by observing that a slight modification of the opposite direction of the flexion intermediate cylinders is helpful.

 your possibilities which arise from this are explained with reference to fig. 5 and 6. In these figures the families of characteristic curves 26 to 30 and 31 to 35 are plotted on the same graph 9 so that for any modifications both of the bending of the strip and of the edge bending the necessary bends of the intermediate cylinders and working can be read. If, for example, the desired total bending is reached by modifying the bending of the strip alone, it is advantageous for the rolling bends to be modified by displacement of the bending forces in the direction of the double arrow 41, and when the bending of the prescribed strip is reached a displacement of the forces in the direction of the double arrow 42 can other effected for the correction of the edge bending alone.

 These guidelines can be easily put into practice, as shown in fig. 6-. Thus, preferably before the setting of iron, one proceeds to the adjustment of the cage as regards the axial displacement of the intermediate cylinders, ia bending of the working and intermediate cylinders, so that for example one can obtain a right-of-way having the ideal shape of a rectangle 44; this form is only mentioned here by way of example, because in practice it is customary to desire a slight domed position. This preliminary adjustment is represented by point 51, but if it turns out that for example instead of the shape of section 44 of the laminate a shape of section 45 was obtained at work point 51, this may be corrected by an increase. of the domed strip. In the case of a defective convex according to 45, it is necessary to modify the flexions of the intermediate and working cylinders in the direction of the arrow 41 pointing upwards, so that the convex is displaced towards the positive side and that the profile 45 approximates the profile 44. Conversely, in the case of a too negative convex it is necessary to modify the bending forces of the cylinders in the direction of the part of the arrow 41 pointing downwards. In the case of extreme corrections, negative values of the bending of the cylinders become necessary, as shown in Fig. 6. If at working point 51 an undesirable strip section such as that designated by the reference 47 is obtained, it is necessary move the working point in the direction of the upper half-arrow 42 by increasing the bending of the intermediate rolls and reducing the bending of the working rolls to the negative range. Likewise, in the case of a negative convexity of the strip along the section designated by the reference 48, the working point 51 can be moved along the lower part of the arrow 41 by reducing the bending of the intermediate cylinders and by increasing slightly that of the working cylinders. Finally, we can carry out all kinds of combined movements, according to which both the width of the strip and that of the edge are modified, for example in opposite directions, by carrying out corrections by displacement of the working point. along other lines, for example along one of the arrows 43.

 Good results have been obtained when these corrections are carried out automatically, as is generally known for obtaining a cold-rolled strip free from stresses. For this purpose, the cage of FIG. 1, of which only the cylinders 2 to 7 have been shown diagrammatically in FIG. 7, an apparatus for measuring the strapping tensions; when the latter passes over this device 61, it indicates the voltages detected in different parts of the width of the strip 60.

 A control device 62 using these data is shown in fig.8. It can be programmed manually via an input keyboard 63 and it is also possible, via a data carrier reader 64, to transmit the program to a memory or other device. of laminas and possibly precalculated values. you have the control command 62 is thus already able9 on the basis of the prescribed values, to determine a favorable working point and to act on the servo-valves 65 and C6 for adjusting the displacement of the cylinders. on other servo-valves 67 to 72 which represent the positioning members to be actuated by this control device and which make it possible to carry out the adjustments of the bends on the right and left side of the intermediate cylinders as well as the corresponding bends of the working cylinders. It is further provided that the resulting values for the bending of the intermediate cylinders are each decomposed into two partial values totaling the full value, the ratio between the two partial values being in a ratio prescribed by the axial displacement of the intermediate cylinders to keep the effective lever arm constant for bending these cylinders.

 It is advantageous that the adjustment operations are protected as it is known per se in regulation and positioning technique, by providing that sensors (not shown in the drawing) determine the actual values and return them to the control device in order to be compared to the set values. Other values exerting an influence on the rolling and characterizing the working point are, by sensors of which only the sensor 73 has been represented here, determined and sent in the control device so that the corresponding parameters, for example the force can be entered. The control device 61 is also connected to the control device which, in this example, consists of a dynamometric traction roller. The pulls, or tensions in the strip, determined in the different parts of the width of the strip 60, are transmitted to the control device 62, so that the latter is able to balance the differences by notably modifying the bending of the working cylinders and intermediate cylinders, possibly also using axial displacement of the intermediate cylinders.

 The control device 62 can itself be built on various principles. First of all, it is possible to store values, in particular to determine the working point in advance so that, for the strip width to be laminated considered, the reduction per pass, the diameter of the rolls, the quality of the material to be laminated and other parameters concerned, it is possible to selectively call up stored values. However, it is also possible, in order to determine such values, to provide programmed computers. It is also possible to selectively enter manually into the keyboard 63, for example the width of the strip, to call it from a memory reproducing the program. of the day's lamination, to resume it from data carriers such as punched or magnetic cards or the like, inserted into the reader of such carriers.

Finally, it is possible to individually determine the width of the laminate, for example by sensors upstream of the cage and to transmit it to the control device, which is then able to prescribe for each practical case the optimal working point as regards relates to the axial displacement of the intermediate cylinders, the flexions of the intermediate and working cylinders and their mutual relationship, and, by visual observation and stored by means of the keyboard 63, better still by measurement by means of the traction dynamometer 61, profile faults can be determined and immediately corrected by modifying the deflections of both the working and intermediate cylinders, precise and thorough compensation for these faults being made possible on the basis of the recognized relationships between the various parameters and introduced into the device 62.

Claims (4)

1. Roll stand with two rolls on the one hand  working, two intermediate cylinders and two cylin  support dres (sexto cage), in which at least the  support cylinders and intermediate cylinders  provided between these and the working cylinders are,  as a whole, superimposed in a vertical plane  common, the intermediate cylinders can be moved  axially created, in which, on the other hand, blocks are  column covers are provided with guide faces  vertical for the chocks of the working rolls and  intermediate cylinders and include means for  displacement to balance and flex the cylin  dres, while on each block are guided vertica  There is also a lower guide piece and a  upper guide with guide faces for  the chocks of the intermediate cylinders and that the  displacement means constituting the devices for  flex the intermediate cylinders are provided  horizontally movable parallel to the  axes of the cylinders with respect to chocks and / or  guide pieces, and in which finally are affec  also to the chocks of the two tra cylinders  range of means of travel provided for in the said  blocks as bending devices that attack  guide parts which are retained in the blocks  through vertical guides and present  horizontal guides for chocks,  r e m a r q u a b 1 e e n c e q u 'elle  comprises a control device (62) which, on the  base of manually entered values and / or values  read on data carriers and / or memories and / or  values provided by sensors assigned to the cage,  on the one hand, the displacements of the inter cylinders are prescribed  medial in ~ the axial direction best suited to obtaining  tion of a predetermined right-of-way profile as well as the  value and direction of the efforts to be exerted by the des  bending positive of working and inter cylinders  mediaries, on the other hand performs, on the basis of deviations  of the grip profile and / or deviations in the voltage of the  strip observed on the width of it during  lamination, optimal corrections to obtain a  prescribed grip profile, this by compensating essential  by modifying the bending of the cylinders in  the curved defects noted in the middle  of the strip and by modification of the bending of the cy  working files the bulging faults detected at  edges of the strip. 2. rolling stand according to claim 1, remarkable  in that when compensating for a defect in a bulging  of the strap the control device (62) actuates  bending the working rolls very slightly in  opposite direction of bending of intermediate cylinders  while when compensating for a bulging defect  at the banks this device activates the bending of the cylin  dres intermediaries in opposite direction of the bending of  working cylinders.  axial cementing of the intermediate cylinders.  lindres intermediate and possibly on the move  health on bending of working rolls and cy  control compensating for voltage differences in action  points the width of the latter the device  (62) the strapping tensions (60) measured differently  constraint (61) which communicates to the control device  quable in that after it is arranged a gauge of  3. Roll stand according to claim 1 or 2, remarks 4. rolling stand according to claim 3, remarkable  in that the strain gauge (61) is made up  by a dynamometric traction roller.