EP1781429B1 - Method for straightening a metal strip and straightening machine - Google Patents

Abstract

The invention relates to a method for straightening a metal strip (1) which is guided in the direction of transportation (R) through a straightening machine (2) and is straightened. In the straightening device (2), the metal strip (1) is impinged upon by a straightening force (F) which is applied by a plurality of straightening rollers (3) in the direction (N) which is perpendicular to the surface of the metal strip (1). According to the invention, prior to the metal strip (1) entering into the straightening machine (2), the thickness (d) of the metal strip (1) is determined and the position (a) of the straightening rollers (3) in the direction (N) which is perpendicular to the surface of the metal strip (1) is taken into account according to the determined thickness (d).

Description

The invention relates to a method for straightening a metal strip which is conveyed in a conveying direction by a straightening machine, wherein in the straightening machine, the metal strip is applied by a number straightening rollers in the direction normal to the surface of the metal strip with a straightening force, wherein before Entry of the metal strip in the straightening machine, the thickness of the metal strip is determined and the employment of straightening rolls in the direction normal to the surface of the metal strip in dependence of the determined thickness, wherein on the outlet side of the straightening machine, a measurement takes place, with the buckling tendency and a deviation of the directed metal strip is determined from the ideal line in the direction normal to the surface of the metal strip, and wherein the employment of the leveling rolls in the direction normal to the surface of the metal strip depending on the bulge and the deviation is such that the metal strip after Richtvorg ang is as level as possible.

In plants for the production and treatment of steel strips, these are usually supplied to the plant for further processing or treatment in coils, then taken up in an inlet part and unrolled and threaded in this way for treatment in the system. The unwinding reels convey the metal strip into the system. For this purpose, the curved strip beginnings must be directed to allow threading of the tape in the inlet part of the system and to possibly make a trouble-free removal of the scrap pieces at the beginning of the tape possible.

The quality of the band treatment and that of the band as such depends on how well it succeeds in planning the first rolled up band, ie. H. to bring flat state. For this purpose straightening machines are known which bring the initially uneven incoming band by applying the belt with a number of straightening rollers in a plane band condition.

It is therefore necessary to ensure by means of a suitable procedure during straightening that the highest possible degree of flatness is present after the straightening process. In the straightening machine designed as a roll straightening machine, usually three to seven rolls or rolls are used. To adapt to the strip thickness, the upper leveling rolls are adjustable or adjustable normal to the surface of the metal strip. For this purpose, electric actuators or mechanical Spindelhubsysteme, occasionally also eccentric used.

A method of the type mentioned is from the DE 21 17 489 A1 known. There, a metal strip is fed to a straightening machine, where it is directed so that it leaves as possible just the machine again. In the conveying direction in front of the machine, the thickness of the sheet is measured. Behind the machine, a displacement measuring device is provided, with which the deflection of the metal strip in the direction normal to the belt surface can be measured. This results in a measure of the flatness of the band.

A similar solution is in the JP 62 214825 A described.

The EP 1 275 446 A2 discloses a method for eliminating transverse curvatures of a metal strip in a strip processing line with a strip handling device to be traversed by the metal strip. In this case, the transverse curvature is detected in a band process line area and eliminated by means of a correction roller that can be set in its immersion depth. The elimination of the transverse curvature occurs in a belt process line region immediately before the belt treatment device.

From the DE 102 30 449 A1 For example, a method for determining a position control amount of a straightening roller for correcting flatness deviations of a metal strip in a straightening machine is known. The method described provides that actual coefficients of a shape function suitable for displaying the strip shape are first determined from recorded values of the flatness deviations of the strip. Then, target coefficients are determined from these actual coefficients. Finally, the target coefficients are converted into position control variables for the straightening roller.

The DE 38 40 016 A1 discloses a method for straightening metal straps, wherein the straightening forces are measured at least on one of the straightening rollers of a roller straightening machine and the straightening roller positions are adjusted as a function of the measured values. It is envisaged here that each straightening force acting perpendicular to the axes of rotation of the straightening rollers or the roller bearings or to the frame of the straightening machine is measured individually and that the straightening rollers are adjusted automatically in the region of the occurring varying pressure forces as a function of these measured values.

The DE 33 08 616 C2 is based on a method for straightening metal strips, in which the metal strip between top and bottom staggered straightening rolls promoted and is bent alternately with decreasing degree of deformation alternately, wherein the straightening rollers according to the sheet metal cross section and the Blechselnfestigkeit in the sense of a given degree of deformation against each other are adjustable. In particular, provision is made for the straightening force on the straightening rolls to be measured during straightening, for the respective sheet strength to be determined from the straightening force and for the sheet metal cross-section, and for adjusting the straightening rolls to be continuously corrected in accordance with the respective sheet strength.

Other special constructive solutions of straightening machines for metal bands or procedure for their operation go from the EP 0 765 196 B1 , of the EP 0 182 062 B1 , of the WO 02/076649 A1 , of the DE 34 14 486 C2 , of the DE 42 16 686 A1 , of the EP 0 035 009 B1 and the JP 111 92 510 out.

A previously unthought problem is that although the material properties of the metal strip to be straightened are taken into account, however, due to thickness variations of the strip, sometimes no satisfactory straightening result is achieved. Straightening is problematic, especially in the case of non-rolled-out strip ends, since the beginning of the strip or the strip end has a large fluctuation in the strip thickness. In some cases, there are wedge-shaped or even step-shaped thickness profiles over the longitudinal axis of the metal strip, so that a reproducible leveling process can only be achieved with great difficulty.

The invention is therefore based on the object to provide a method of the type mentioned, in which it is possible in a simple manner to overcome the above disadvantage, d. H. ensure a high-quality directional result even in the case of large variations in the thickness of the metal strip along its longitudinal axis.

The solution of this problem by the invention is characterized in that the determination of the bulge tendency and the deviation is effected by a force measurement.

So that the thickness measurement can be carried out in a simple manner, it is advantageously carried out at a sufficient distance in front of the leveling rolls. Therefore, a development provides that the employment of the straightening rollers is time-controlled taking into account the distance of the measurement of the thickness before the straightening rollers and the conveying speed of the metal strip in the conveying direction. About the distance of the measurement before the rollers and the conveying speed so a dead time is determined, which is taken into account in the regulation of the employment of the rollers.

In order to ensure a high final quality of the strip in terms of its degree of flatness, it is provided that on the outlet side of the leveler a measurement takes place, with the buckling tendency and the deviation of the directed metal strip from the ideal line, d. H. the ideal center plane, is determined in the direction normal to the surface of the metal strip, and that the employment of straightening rolls in the direction normal to the surface of the metal strip in dependence of the bulge tendency and the deviation takes place so that the metal strip is as flat as possible after the straightening process.

In the case of determining the buckling tendency by a force measurement, the force measurement is advantageously carried out by a straightening roller arranged on the outlet side. An alternative solution provides that the force is measured by one or more to the straightening rollers separate touch rollers.

A further improvement of the method according to the invention can be achieved by measuring the size of the straightening force applied by the straightening rolls during the straightening process in the straightening machine and the adjustment of straightening rolls in the direction normal to the surface of the metal strip - also - depending on the measured straightening force , It is thus possible to achieve a comparison of the material-dependent desired-actual force.

The conveying direction can be reversed if necessary. This may be useful if the straightened band behind the leveler does not meet the desired flatness requirements. For this purpose, the adjustment values between the inlet side of the straightening machine and the outlet side of the straightening machine are mirrored so that in the reverse conveying direction the adjustment values correspond to the conveying direction. In this way, the beginning of the tape can be directed a second time in the reverse direction so that it comes to rest with an optimized directional result on the inlet side of the leveler. Optionally, then a third time can be directed again in the forward direction or the beginning of the tape can be continued by the open machine.

Positionally controlled adjusting elements are preferably provided which are suitable for setting the leveling rolls in the direction normal to the surface of the metal strip. It is provided with particular advantage that the position-controlled adjusting elements are designed as hydraulic piston-cylinder systems.

Finally, means for measuring the bowing tendency and the deviation of the directional metal strip from the ideal line in the direction normal to the surface of the metal strip may be provided, which are arranged on or in the conveying direction behind the outlet of the metal strip from the leveler. These means can be formed by one or two (above, below) to the straightening rollers separate touch rollers.

The invention makes it possible to achieve a very good directional result, even with strongly varying thickness of the metal strip to be straightened, which improves the overall quality of the produced metal strip or makes the production of the strip easier and more reliable.

Fig. 1a und Fig. 1b

schematisch die Seitenansicht eines Endbereichs eines Metallbandes;

Fig. 2

schematisch eine Richtmaschine zum Richten eines Metallbandes;

Fig. 3

eine zu Fig. 2 ähnliche Ansicht mit Darstellung der wichtigsten Regelgrößen;

Fig. 4

einen Teil des Regelkreises zur Durchführung des Richtprozesses; und

Fig. 5

eine detailliertere Darstellung des Regelkreises zur Durchführung des Richtprozesses.

In the drawing, an embodiment of the invention is shown.
Show it:

Fig. 1a and Fig. 1b

schematically shows the side view of an end portion of a metal strip;

Fig. 2

schematically a straightening machine for straightening a metal strip;

Fig. 3

one too Fig. 2 similar view showing the most important controlled variables;

Fig. 4

a part of the control loop for carrying out the straightening process; and

Fig. 5

a more detailed representation of the control loop for performing the straightening process.

In the FIGS. 1 a and 1b are side views of a metal strip 1 to be subjected to a straightening process. Shown is the area of the beginning of a tape nichtausalzten band. It is typical that the thickness d of the metal strip 1 over the longitudinal axis of the strip, which corresponds to the conveying direction R, is not constant. In Fig. 1a it is the case to see that the metal band 1 is wedge-shaped. Fig. 1 b shows the case of a stepwise thickness of the band 1.

The straightening of such a metal strip is extremely difficult and efficient possible only with the straightening machine 2, as in Fig. 2 is shown.

The metal strip 1 is conveyed in the directional machine 2 in the conveying direction R at a constant speed v. The straightening machine 2 is designed as a roller straightening machine and has a number of straightening rollers 3. The four lower and three upper straightening rollers 3 are each arranged on a carrier 15 and 16. Both carriers can be moved relative to each other in the direction N normal to the surface of the metal strip 1. The lower carrier 16 is arranged stationary, while the upper carrier 15 can be moved in the direction N over a position-controlled adjusting element 8 in the form of a hydraulic piston-cylinder system. The adjusting movement of the straightening rollers 3 is designated by a. When hiring the straightening rollers 3, the force designated F acts between the rollers, causing a deformation of the metal strip 1, so that after leaving the leveler 2, the metal strip 1 has a high degree of planeness.

The aim here is that the metal strip 1 behind the outlet 4 of the straightening machine 2 takes the form shown by solid lines (ideal line). However, in general and without further measures, it is to be expected that the metal strip 1 has a bulging tendency which is expressed in a deviation x from the ideal line - either upwards or downwards - as indicated by the dashed lines.

To prevent this, the procedure is as follows: In the conveying direction R upstream of the inlet 7 of the straightening machine 2, a means 6 for measuring the thickness d of the metal strip is arranged in the form of a suitable sensor known per se. The distance - measured in the conveying direction R - between the sensor 6 and the center of the straightening rollers is denoted by b.

The sensor 6 measures the thickness d of the metal strip 1 and forwards the measured value to a control device 9. The employment a of the upper to the lower straightening rollers 3 by the adjusting element 8 takes place as a function of the measured thickness d. In this case, the dead time is taken into account, which passes until the metal strip 1 has moved from the place of measurement to the location of the straightening rollers 3. The dead time is easily determinable with knowledge of the distance b and the conveying speed v.

In order to find the correct amount for employment a, a corresponding algorithm is stored in the control 9 for this purpose, or it is closed on the basis of stored waveforms on the correct and appropriate value of the yield strength and thus the employment a, which is set via the control element 8 becomes.

At the outlet 4 of the leveler a sensing roller 5 is arranged, which detects the deviation x of the metal strip 1 of the ideal position. The measured deviation value is likewise passed to the controller 9, which corrects the position a by means of its internally stored algorithms or curve profiles. Instead of a separate feeler roller 5, this measurement can be done with the last in the conveying direction R straightening roller 3 '.

In Fig. 3 is the rough control concept for the regulated delivery a of the straightening rollers 3 to see. The control device 9 receives the measured thickness d of the metal strip 1 from the sensor 6 as an input parameter. In addition, it is also fed the straightening force F, which is determined by a force or pressure cell 10. As a further input variable receives the control device 9 at the outlet. 4 the straightening machine 2 measured deviation x of the metal strip 1 from the ideal line, measured in the direction N normal to the surface of the metal strip 1. It is further indicated that the control device 9 has available tape data D which are stored in a database 17.

In the control device 9, an algorithm or a table is deposited which, depending on the thickness d, the deviation x, the straightening force F and the belt data D, the delivery required for an optimal work result a, which is represented by the functional relationship a = f ( d, x, F, D) is indicated.

Some control technical details are in this Fig. 4 can be seen: The force or pressure cell 10 detects the force acting in the hydraulic actuators 8 pressure p, which can be converted via a converter 14 in the straightening force. Band data D are stored in the database 17, ie, for example, information about optimum deformation values for defined materials that make up the metal band 1. An optimal reference value for the straightening force can be compared from the database 17 with the measured value, which takes place at the subtractor 18. In a slow, z. B. superimposed force controller 11, the difference signal is processed and then fed via a limiter 12 to another subtractor 19. The power controller 11 may be designed to achieve various operating conditions and switched off, z. B. by a force regulator 11 associated switches. There also runs an optimal value for the desired employment a from the database 17 and the measured value for the employment a. The difference signal is fed to the controller 13, which outputs a control value for the position a to the control elements 8.

Further details on the control scheme go out Fig. 5 out. In the database 17 here both sets of curves as well as tables are deposited, which indicate, inter alia, the optimal for the straightening yield point St of the material to be processed of the metal strip 1. In the left-hand area of the database 17 are families of curves which define the present yield strength St for given strip thicknesses d. Here, the hot strip yield strength of starting material be considered for the cold rolling process and the cold strip yield strength. (Possible starting and end points of the family of curves) The actual value of the thickness d of the metal strip 1 is provided by the sensor 6. With knowledge of the conveying speed v and the distance b (see FIG. Fig. 2 ), the time can be determined until the metal strip 1 has passed from the location of the thickness measurement to the location of the straightening rollers 3. This is in Fig. 5 indicated by the deadtime element T _T as a function of the speed v.

With the actual thickness value, the optimum yield point is determined in the area of the database 17 shown on the left and transmitted to the area of the database 17 shown on the right. Based on stored data or stored algorithms, the required position a and straightening force F relative to the width B of the metal strip 1 (transverse to the conveying direction R) can be determined as a function of the thickness d.

The multiplication of this value with the actual width B in the multiplier 20 supplies the desired straightening force F _Soll . This value is fed to a controller 21, behind which the actual straightening force F _{Ist is} subtracted at a subtraction point. This is determined by the force or pressure cell 10 and the converter 14. The difference value is fed to the controller 22, which passes its signal via the limiter 12 to a subtraction point 23.

The target value for the employment a comes from the database 17 and passes through a controller 24 equally to the subtraction point 23. There also enters the measured value for the current employment a. The difference of the signal is fed to the (main) controller 13, which ejects the control value for the position a and sends it to the control elements 8.

Shown is the case of only one actuator 8, although preferably on both sides of the carrier 15 and 16 each have an actuator 8 is present. The circuit construction doubles in this case.

In the exemplary embodiment, therefore, a continuous strip thickness measurement takes place, the result of which is passed via the explained control system to position-controlled hydraulic cylinders. The actual strip thicknesses are detected by the thickness measuring sensor 6 and the necessary adjustment values are provided by the position-controlled hydraulic cylinders. The closed loop ensures a continuous adjustment of straightening rollers, eliminating the influence of strip thickness.

In order to eliminate the influences of the strength of the metal strip 1, a result-oriented control method is used insofar as also the outlet-side deviation from the ideal position is detected. From the measurement of the deviation or the pressurization of the force or pressure cell 10, a conclusion can be made, as the readjustment must be made to again set an optimal straightening result. Thus, a largely arc-free outlet of the metal strip 1 is achieved from the leveler 2. Furthermore, the contact pressure is detected in the hydraulic cylinders. This pressure allows conclusions to be drawn about the material properties, especially if the strip thickness is known. These data can also be evaluated for position control and integrated into the control loop.

The adjustment values and their courses are collected in the database 17 and can thus be used to preset the straightening machine 2 when straightening another metal strip 1 or when starting a new installation as start values.

Instead of the aforementioned sensors (for the thickness d, the deviation x and the straightening force F), any other sensors can be used, for. B. optical encoder.

LIST OF REFERENCE NUMBERS

1

metal band

2

straightener

3

straightening roll

3 '

straightening roll

4

outlet side

5

follower roll

6

Means for measuring the thickness

7

inlet side

8th

position-controlled actuating element

9

control device

10

Force / load cell

11

slow force regulator

12

limiter

13

Controller (P-controller)

14

Converter

15

carrier

16

carrier

17

Database

18

subtractor

19

subtractor

20

multiplier

21

regulator

22

regulator

23

subtraction

24

regulator

R

conveying direction

N

Direction normal to the surface of the metal band

F

straightening force

d

Thickness of the metal strip

a

Employment of straightening rollers

b

Distance of the thickness measurement before the leveling rolls

v

conveyor speed

x

Deviation of the directed metal strip

D

Tape data (database)

p

print

St

Stretch limit

B

Width of the metal band

Claims (6)

1. Method of straightening a metal strip (1), which is conveyed in a conveying direction (R) through a straightening machine (2) and in that case straightened, wherein in the straightening machine (2) the metal strip (1) is acted on with a straightening force (F) by a number of straightening rolls (3) in a direction (N) normal to the surface of the metal strip (1), wherein prior to entry of the metal strip (1) into the straightening machine (2) the thickness (d) of the metal strip (1) is ascertained and the adjustment (a) of the straightening rolls (3) in the direction (N) normal to the surface of the metal strip (1) is carried out in dependence on the ascertained thickness (d), wherein at the outlet side (4) of the straightening machine (2) a measurement is carried out by which the tendency to arching and a deviation (x) of the straightened metal strip (1) from the ideal line in the direction (N) normal to the surface of the metal strip (1) are ascertained and wherein the adjustment (a) of the straightening rolls (3) in the direction (N) normal to the surface of the metal strip (1) is so carried out in dependence on the tendency to arching and the deviation (x) that the metal strip (1) is as flat as possible after the straightening process, characterised in that the determination of the tendency to arching and the deviation (x) is carried out by a force measurement.
2. Method according to claim 1, characterised in that the adjustment of the straightening rolls (3) is carried out regulated in time with consideration of the spacing (b) of the measurement of the thickness (d) in front of the straightening rolls (3) and the conveying speed (v) of the metal strip (1) in conveying direction (R).
3. Method according to claim 1, characterised in that the force measurement is carried out by a straightening roll (3') arranged at the outlet side.
4. Method according to claim 1, characterised in that the force measurement is carried out by at least one scanning roller (5) separate from the straightening rolls (3).
5. Method according to any one of claims 1 to 4, characterised in that during the straightening process in the straightening machine (2) the magnitude of the straightening force (F) exerted by the straightening rolls (3) is measured and the adjustment (a) of the straightening rolls (3) in the direction (N) normal to the surface of the metal strip (1) is carried out in dependence on the measured straightening force (F).
6. Method according to any one of claims 1 to 5, characterised in that the adjustment target values between inlet side and outlet side are so mirrored in the case of reversed direction of conveying that the adjustment target values are optimally set independently of the current conveying direction.

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