FR2664510A1 - PROCESS FOR REVERSIBLE ROLLING. - Google Patents

Abstract

The subject of the invention is a method for rolling a flat product (5) by successive passes in a reversible rolling mill, alternately in one direction and then in the other. According to the invention, the product (5) having a roughly uniform gross thickness (e0), the cylinders (2, 2 ') are given, for the first starting pass P1, a spacing (e1) less than (e0) determining a angle of attack (A1) sufficiently small to avoid refusal of engagement and during this first pass P1, the spacing of the cylinders (2, 2 ') is reduced to a value (e2) such that the total reduction in thickness (e0 - e2) remains compatible with the maximum power and force of the rolling mill, then, for the second pass P2, the working rolls (2, 2 ') are given a spacing (e3) such that the angle of attack (A2) is small enough to avoid refusal of engagement and, during this second pass P2, the spacing between the cylinders is reduced to a value e4 compatible with the power and the maximum force of the rolling mill, and so on. The invention applies especially to the rolling of metal sheets.

Description

The subject of the invention is a process for rolling a flat product in a

  reversible mill The invention applies in particular to the hot rolling of aluminum but can also be used for other non-ferrous metals and even, under certain conditions, for metals

ferrous such as steel.

  It is known that hot rolling can be carried out

  advantageously reversibly in a rolling mill comprising

  a single cage associated with means for controlling the passage of the rolling product alternately in a direction

  then in the other In a general way, the rolling mill com-

  takes, in a quarto assembly, two working cylinders

  associated with two support cylinders, intermediate cylinders

  can also be interposed between the cylinders

  and work cylinders in a sexto assembly.

  The assembly is placed between the two uprights of a rigid cage, each cylinder being carried by two chocks mounted sliding in windows arranged on the two uprights.

of the cage.

  The means for controlling the passage of the product between the working cylinders, alternately in one direction and then in the other, may consist of, for example, two roller tables placed on either side of the cage. steel, the sheet should be heated in an oven

placed next to the cage.

  Such reversible mills can be used, for example, as routers in a belt train or

  good in aluminum or steel sheet metal work.

  The rolling is done from a raw part

  such as a bloom or slab having a large thickness.

  This may, for example, be 600 mm in the case of

  aluminum and 250 mm in the case of steel.

  The rolling is therefore carried out in successive passes in one direction then in the other by performing, at each pass, a reduction in thickness which may be, for example, from 40 to 50 mm. For this purpose, the chocks of the rolls are mounted sliding in the windows of the cage and is applied between the two support cylinders a clamping force, for example by means of two cylinders mounted on the cage and bearing, respectively, on the two chocks of a cylinder

of support, the other being blocked.

  Generally, in a rolling process, the product has, at the entrance of the cage, a thickness greater than the spacing of the working rolls which therefore tend to crush it by producing a certain reduction in thickness The metal is thus applied to a circular sector of each cylinder between two horizontal planes corresponding to the outer face of the product respectively at the inlet and the outlet of the rolling mill. The pinching of the product between the two rolls determines its advance, one at least cylinders being rotated. It is possible to define, at the input of the rolling mill, an angle of attack A corresponding to the dihedral limited by the external face of the product and the plane tangent to the cylinder at the level where the latter comes into contact with the product. The value of the angle of attack is therefore a function of the diameter of the

  cylinder and thickness reduction produced, ie

  tell the difference between the thickness of the product before entering the mill and the width of the existing gap

  between the two working cylinders.

  During rolling, thanks to the friction between the work rolls and the product on the surface of the two cylindrical sectors, the drive is carried out without difficulty insofar as the reduction in thickness is compatible with the torque and the effort that we pet't

  on the other hand, at the time of

  product, friction is exerted solely on

  the two lateral edges that come in contact respectively-

  with the two cylinders and it is conceivable that the engagement can not occur if the angle of attack A is too important. In view of the fact that the diameter of the working rolls must remain rather small and that, moreover, it tends to decrease because of the wear of the rolls, it is therefore necessary to limit the reduction in thickness produced by

  each pass to avoid a "refusal of commitment" General-

  The reduction in thickness thus limited for geometrical reasons is less than that which could theoretically have been achieved taking into account the rolling power available and results in an increase in the

  number of passes required and therefore a decrease

  productivity of the rolling mill.

  The subject of the invention is a novel method of

  rolling to overcome this disadvantage.

  According to the invention, the product having a gross thickness e O substantially uniform, is given to the working cylinder, for the first start pass P1, a spacing e 1 <eo determining an angle of attack A, sufficiently small to avoid a refusal of commitment 2 _ 'it decreases, during this first pass P 1, the spacing of the rolls to a

  value e 2 such that the total reduction of thickness (eo e 2) -

  remains compatible with the maximum power and force of the rolling mill, then, for the second pass P 2, the work rolls are given a gap e 3 such that the difference (e 2 e 3) determines a

  angle of attack A small enough to avoid a refusal

  in the course of this second pass P 2 -o the spacing of the cylinders

  up to a value e 4 such that the total reduction of

  the 4 remains compatible with the power and the maximum force

  malesdu mill and so on, the spacing of the working rolls being set at the beginning of each pass Pn, to a value e 2 n-1 as tell that the decrease of gauge (e 2, -2 e 2, l) determines an angle of attack An, sufficiently small to avoid a refusal of commitment, then decreased, during this pass Pn, to a

  value e 2 N such that the total reduction of thickness e 2 N -

  e 2 (nl 1) remains compatible with the maximum power and

males of the rolling mill.

  The thickness reduction is thus continued in two steps for each pass, as long as the thickness at the end of a pass risks determining a refusal of engagement for a reduction in the spacing of the working cylinders to the next pass. Compatible with the rolling power and

  the rolling is then finished in the normal way.

  The adjustment at each pass of the spacing of the cylinders can be done manually However, this adjustment can advantageously be performed by means of an automatic regulation system of the clamping force associated with a mathematical model programmed so as to

  calculate, at each pass, the reduction in thickness

  kill in two stages, depending on the available torque,

  given the mechanical and dimensional characteristics

  the rolling mill and the product and the nature of the rolled metal.

  The invention will be better understood by the description

  following of a particular embodiment given as a

  for example, with reference to the accompanying drawings.

  Figure 1 shows schematically, in elevation, a quarto mill; Figure 2 shows the rolling process during the first pass, in two successive diagrams 2a, 2b; Figure 3 shows the rolling process during

  of the second pass, in two successive patterns 3 a, 3 b.

  FIG. 1 diagrammatically shows a conventional quarto mill comprising a cage 1 consisting of two spaced apart amounts 11 provided with windows 13

  and between which are placed four cylinders, respectively

  two work rolls 2 and 2 'and two support rollers 3 and 3' each cylinder is carried at its ends by bearings mounted in chocks, respectively 21, 21 ', 31, 31' which slide along faces vertical guides 12 arranged along the windows 13 As is well known, the chocks 21, 21 'of the working rolls 2, 2' are guided along the lateral faces of two hydraulic blocks 14, 14 'fixed on the faces 12, 12 'of each

  window 13 and in which are housed cylinders allow-

  both to exert on the chocks 21, 21 'efforts of

  bending the work rolls 2, 2 '.

  The cage is provided on the other hand with cylinders clamping means, for example hydraulic cylinders 4, which bear on one side on each chock 31 of the support cylinder 3 and the other on the cage, the chocks 31 'of

  the other support cylinder 3 'resting on fixed stops.

  The cylinders 4 thus exert in the vertical plane P passing

  the axes of the cylinders, a tightening force which determines

  mine approximation of the two working cylinders 2, 2 '.

  The rolling technique, which has been used since

  the beginnings of the iron and steel industry, has been continually perfected

  However, this technique is adapted to the different working conditions, in particular the nature of the metal and the dimensions of the product to be rolled, in particular the thickness that one wishes to obtain. just described is found in most

  rolling mills which may differ in the number and size

  rolls and the various ancillary devices.

  In particular, to precisely adjust the thick-

  the laminate and its flatness by avoiding defects resulting from the deformation of the rolls and the distribution of stresses, various provisions have been developed, such as the bending of the rolls, already

  mentioned, or the setting of the profile of the support cylinders.

  As has been indicated, the invention is especially applicable to a hot mill of the reversible type, which means that the product 5 passes between the working rolls 2, 2 'alternately in one direction and then in the other, that is to say, with reference to FIG. 1, from left to right then from right to left and so on, the reduction in thickness being carried out gradually in successive passes For this purpose, the cage 1 can placed between two conventional type roller tables and therefore

  not shown on the drawing.

  Figure 2 schematically illustrates the process of

  rolling during the first pass Pl called start.

  In Figure 2a, on the left of Figure 2, there is shown the end 50 of the product 5 which comes into contact with the work rolls 2, 2 'The product 5 has a gross thickness eo and the gap, limited by the generatrices 20, 20 'of the cylinders 2, 2' lying in the clamping plane, has a width e 1. The angle of attack A 1 is also represented, which corresponds to the dihedral between each lateral face 51 of the product 5 and the tangential plane T at the point of contact of the edge 52 with the cylinder 2 It can be seen that the value of the angle of attack A is a function of the ratio between the diameter (d) of the cylinder and the arrow (a) which is equal to

  half of the thickness reduction (eo el).

  According to the invention, instead of seeking to obtain the greatest reduction in thickness possible with the risk of

  determine a refusal of commitment because of an angle of attack

  that A 1 too important, we give to the spacing (el) of the cylin-

  2, 2 'a value which, taking into account the gross thickness (eo) and the diameters (d) of the cylinders, guarantees a good engagement of the product 5 The end 50 of the product 5 is therefore reduced to the thickness ( el) by the passage between the cylinders

2, 2 '.

  * we then actiles suriles cylinders 4 to further reduce the spacing of the cylinders

  up to a value (e 2) which is set so that the reduction

  total thickness (eo ez) presents the maximum possible value given the torque that can be applied to the cylinders and which depends on the available power and force. The first rolling pass P1 is thus continued until passage of the downstream end 54 of the product 5 which therefore comprises a first portion 50 of thickness (el) and a second part

53 thick (e 2).

  The first start pass P1 which, as indicated by an arrow in FIG. 2, was carried out from left to right, is then completed, the product 5 being on the right.

cylinders 2 and 2 '.

  The second rolling pass P 2 is then carried out according to the process indicated in FIG. 3, that is to say

right to left.

  The part of the product 5 which now comes into contact with the rollers 2, 2 'is then its end 54 of width (e 2). As before, the spacing (e 3) of the rolls 2, 2' is adjusted so that the angle of attack A 2 is sufficiently reduced to avoid a refusal of commitment The product then begins to pass between the cylinders 2 and 2 ', the rolled portion 55 having a thickness (e 3) As we have

  shown schematically in Figure 3b, in the course of -

  this second rolling pass, we increase the effort of Y '

  tightening the cylinders to determine their approximation -

  up to a gap (e 4) which is set so that the total thickness reduction (el e 4) remains compatible with the maximum power and rolling force The rolled product at the end of this second pass P 2 comprises therefore a part 55 of thickness (e 3)

  and a portion 56 of thickness (e 4).

  The thickness reduction is thus continued in two steps at each pass P, a first engagement step

  for which the spacing (ea 1) is such that the angle of attack

  that Ai is sufficiently small to avoid a refusal to

  and a second stage in which the

  decylinder in a manner compatible with the maximum power and strength of the mill to further reduce the thickness of the mill.

  produces up to a value (e 2 n).

  At each p 7 asse, the total reduction in thickness (e 2 (, I) e 2 n) is greater than that which had to be respected before to avoid a refusal of commitment. that the ratio between the diameter d of the cylinders which remains substantially fixed and the thickness e of the product which decreases with each pass is such that, by immediately realizing the reduction of maximum thickness compatible with the rolling power, it is not risky a refusal of commitment The rolling process can then continue until the thickness is obtained

  desired, the total number of passes being substantially decreased.

  The adjustment of the clamping force which makes it possible to obtain, at each pass, the optimal reduction of thickness, can be carried out manually by an experienced operator who is familiar with his equipment, but the current means make it possible to carry out this adjustment automatically in conditions to use a minimum number of passes and, therefore, to achieve the maximum possible productivity. Indeed, we have been developing for some time

  automatic regulation systems and models of pre-

  tightening of the clamping force according to the dimensions of the product and the nature of the metal which make it possible to perform at each pass the maximum thickness reduction compatible

with the possibilities of the rolling mill.

  FIG. 1 shows, by way of example, a system of this type which uses a regulation system 6 making it possible to adjust the hydraulic feed rate of the jack to its

  entry 41 in accordance with the indications given by a

  measuring rod 61 which is associated with the chock 31 of the support cylinder 3 and makes it possible to measure the position of the axis of the cylinder and consequently the spacing of the working rolls taking into account the deformations of the cage.

  regulation system 6 receives a signal emitted by the

  tif measurement 61 and representative of the position of the chock 31 and the assembly thus constitutes a digital loop of position control of the clamping function of a distance

  cylinders displayed on input 62 of the control system.

tion 6.

  For the implementation of the invention, a mathematical model 63 is established which calculates the maximum possible reduction in thickness as a function of the clamping force and the driving torque compatible with the possibilities of the rolling mill, taking into account account of all the mechanical and dimensional characteristics of the rolling mill and the product and, in particular, of the nature of the rolled metal The model 63 is thus programmed so as to display on the inlet 62 of the regulator 6 first of all the first instruction of clamping position to ensure a good banding commitment given the diameter of the cylinders and then, during the pass, the optimal thickness setpoint calculated by the

model 63.

  Of course, the invention is not limited to the details of the embodiment which has just been described as a simple example and which could give rise to variants. In particular, the system has been described in the context of a quarto rolling mill but it is appplicable the same

  duet or sexto or any other type of tape.

  black. Similarly, other control systems could be devised to determine the minimum number of passes of

  rolling compatible with the power of the rolling mill.

1 'v

Claims (1)

1. A method of rolling a flat product (5) in a reversible la-minoir comprising at least two working cylinders (2, 2 ') with parallel axes superimposed along a clamping plane P inside a cage (1), means for controlling the passage of the product between the rolls (2, 2 '), in one direction and then in the other, and so on alternately, in successive passes and means (4) of adjustment the clamping position of the rolls for rolling the product (5), characterized in that the product (5) having a substantially uniform gross thickness (%) is fed to the rolls (2, 2 '), for the first start pass P1, a spacing (e 1) of less than (e 0) determining an angle of attack (A 1) sufficiently small to avoid a refusal of engagement and decreasing, during this first pass P ,, the spacing of the rolls (2, 2 ') to a value (such that the total reduction in thickness (e O es) remains compatible with the maximum power and force of the rolling mill, then, for the second pass e ,, the work rolls (2, 2 ') are given a gap (e 3) such that the difference (e ) determines a reduced angle of attack (A) to avoid a refusal of engagement and decreases, during this second pass P, the spacing of the cylinders to a value e 4 such that the total thickness reduction (e 4 e) remains compatible with the maximum power and the force of the rolling mill, and so on, the spacing of the working rolls (2, 2 ') at the beginning of each pass Ph being set to a value (e, -t) such that the gap decrease (in 2 e, _ X) determines an angle of attack (An) sufficiently small to avoid a commitment refusal, and then decreased, during this period. pass P so as to decrease the thickness of the rolled product (5) to a value (ez) such that the total thickness reduction (e.sub.i, l) e ) remains compatible with the characteristics of the rolling mill. 2. The rolling method as claimed in claim 1, characterized in that the reduction in thickness is continued in two steps for each pass until the thickness (ezn) reached at the end of the pass P no longer runs the risk of determining a refusal of commitment for a reduction in the deviation of the working rolls to the next pass Pn + compatible with the maximum power and force of the rolling mill and that the rolling is then completed in a normal way. 3 rolling method according to one of the claims   1 and 2, characterized in that the spacing of the rolls (2, 2 ') is adjusted at each pass by means of a system (6, 61) for automatic regulation of the clamping force associated with a   mathematical model (63) programmed to calculate, at each   that passes, the reduction of thickness to be carried out in two stages, according to the possible effort and power of rolling   and taking into account the mechanical and dimensional characteristics-   the rolling mill and the product and the nature of the rolled metal.