EP1819456B2 - Method and mill train for improving the slipping out of a metal rolled strip whose rolled strip end runs out at a rolling speed - Google Patents

Abstract

A method for improving the running-out of a metal rolled strip (1), the rolled trailing strip end (1a) of which exits out of a respectively last roll stand (2) of a multistand rolling mill (3) at a rolling speed, wherein during rolling between two consecutive roll stands (F1, F2, F3 . . . Fn) the strip tension (a) is adjusted to stabilize the strip position, provides that shortly before the rolled trailing strip end (1a) exits the developing rolling force differences are measured separately for each roll stand (F1, F2, F3 . . . Fn), that from this the pivot value (16) and the pivot direction are derived for forming a corrective value for the adjustment of the rolls (10, 11) and that the adjustment is corrected.

Description

The invention relates to a method and a rolling line for improving the Ausfädelns a metal strip whose rolling strip end expires at rolling speed from a respectively last yielding mill of a multi-stand rolling mill, wherein during rolling between two successive stands for stabilizing the strip tension is adjusted ,

During hot rolling of steel, the rolling speed is adjusted so that a required final rolling temperature of the metal strip, in particular steel strip, is achieved. These Endwalztemperaturen must be complied with in order to achieve the desired metallurgical properties. A reduction in the rolling speed is undesirable even at the end of the tape. Threading out the metal strip at rolling speed, however, is problematic, especially at high rolling speeds and thin end thicknesses.

During rolling, the strip tension set between the rolling stands is a decisive factor for stabilizing the strip run. When unthreading the rolled strip end from a framework, the strip tension is reduced shortly before or at the latest with the unthreading from the rolling stand. The rolled strip end is then drawn without tension into the next mill stand. In this phase, the tape is unstable and minor disturbances or deviations can lead to "bleeding" of the rolled strip end in the nip. In such a case, the metal strip runs out of the center of the frame, generating differential rolling forces and skewing the roll gap, which in turn accelerates bleeding. Causes for this process can be a non-parallel roll gap, temperature differences across the bandwidth, a thickness wedge over the belt width or belt hardness differences.

It is known ( EP 0 875 303 B1 ), to provide a differential rolling force between the drive and operating side of the rolling stands corrective control of the roll column with compensation of the bending and Balancierkräfte by a corrective value-controlled control of the roll nips. In this case, the control, before further processing of the flat products, is supplied with an additional correction manipulated variable formed from horizontal forces measured at all individual rollers. The solution represents a so-called cross-module, over which the strain values on the two sides of the stand are converted. The expansion values can be compensated for by corresponding position setpoints for the two position setpoints for the two positioning systems on the drive side and the operator side of the rolling stands.
However, if the rolled strip ends are too large, this control will not be able to stabilize the metal strip.

Previous attempts to minimize by the intervention of the taxpayers in the rolling process, the swinging of the rolled strip end or even to avoid or replace by an automatic control the helmsman, did not lead to a satisfactory result. When engaging in the starting position during the removal of the strip tension, the running of the rolled strip end can not be avoided and it comes to Verwalzungen and corresponding problems in the next rolling stands. In the worst case, the rolled strip end tears off and damage to the working and back-up rolls occurs. In the case of metal strip mills, which have to have very low surface defects (thin steel strip), a single mouldering process may mean that the rolling process has to be interrupted and the work rolls must be replaced in one or more stands.

Method for improving the threading of a metal strip whose rolling strip end expires at rolling speed from a respectively last-yielding rolling stand of a multi-stand rolling mill, are from the article " The Upgrade of the Rouge Steel Hot Strip Mill ", Paul Smith et al., AISE Steel Technology Magazine, June 2003 , and the JP 10-005840 A known.

The invention has for its object to consider the unthreading of the rolled strip end at each momentarily resulting last rolling stand of a rolling train as an independent process step and to evaluate the setting of rolling forces on both sides of the rolling stand in a timely manner.

The stated object is achieved by a method according to claim 1 and a rolling train according to claim 2. The method provides that, shortly before composing the rolled strip end from a stand, the differential rolling forces generated between the drive side and the operator side are measured separately for each rolling mill, from which the swivel value and pivoting direction of the differential rolling force are derived to form a correction value for the setting of the rolls and the employment is corrected. The advantage is that the initial situation is improved before the threading out and a bleeding of the rolled strip end is largely avoided. The direction and the value of the differential rolling force are determined for this phase and thus a "swivel value" is calculated for the metal strip. These steps are carried out separately for each mill, so that the properties of the metal strip at this point and its geometric values, the thickness and the hardness, the flatness and the surface are each included in the measurement.

Furthermore, according to the invention, the results of the respective measuring step are utilized adaptively from metal roll strip to metal roll strip and the results of the respective measuring step are adaptively utilized from metal roll strip to metal roll strip. The advantage is the processing of experience gained.

One application is that the measurement result for the helmsman in the control center is displayed and the helmsman performs the correction manually during the rolling process.

The application according to the invention is achieved by forming an average value of the differential rolling force between the drive side and the operator side after the rolling strip end has been taken out for a selected strip length and utilized in the following metal strip.

A rolling mill for hot rolling a metal strip, In particular, a thin steel strip is provided with a plurality of rolling mill stands having their work rolls and backup rolls respectively driven on the drive side for maintaining a strip train for stabilizing the strip run and a high rolling speed, and measuring devices for measuring the rolling force on the drive side and the operator side, respectively are provided.

The stated object is achieved according to the invention in that the rolling forces on the drive side and on the operator side by force gauges shortly before leaving the rolled strip end are determined as Differenzwalzkraft, wherein an evaluation unit for the differential rolling force of the metal strip end and a computer unit for the calculation of a so-called swivel value for the adjustment of the rolls during the passage of the metal strip end are provided. The advantages here are also those that have already been shown for the process.

In an embodiment of the rolling stands, it is proposed that the force measuring devices for the differential rolling force of the metal strip end consist of load cells, which are each arranged below the lower support roller.

The inventive design of the measuring devices is designed to the effect that is connected to the computer unit a branch for the forwarding of the swivel value either to an automatic for consideration in the current or next metal strip and / or a display of a swivel recommendation for the helmsman.

It is also advantageous that the automatic and / or the display is connected to a swivel setpoint comparator and / or a swing-Istwertvergleicher and that both are connected to a position control of the hydraulic adjustment on the drive side or to a position control of the hydraulic adjustment on the operator side ,

A further embodiment is that the position controls, including a position control for the absolute position setpoint, are each connected to a cylinder force control for the drive side and the operator side.

In the drawing, embodiments of the method and for the formation of the control or regulation are shown, which are described in more detail below.

Fig. 1A

einen stabilen Bandlauf beim Wälzen mit Bandzug,

Fig. 1 B

einen instabilen Bandlauf beim Ausfädeln des Bandendes, das "verläuft", bei nicht paralleler und symmetrischer Anstellung der Walzen,

Fig. 2

ein Blockschaltbild für die Steuerung bzw. Regelung des Verfahrens und

Fig. 3

die Berechnung des "Schwenkwertes" aufgrund der in den aufeinanderfolgenden Walzgerüsten einer Band-Walzstraße auftretenden Walzkräfte.

Show it:

Fig. 1A

a stable band during rolling with strip tension,

Fig. 1 B

an unstable band during the unthreading of the band end, which "runs", in non-parallel and symmetrical adjustment of the rollers,

Fig. 2

a block diagram for the control or regulation of the method and

Fig. 3

the calculation of the "swivel value" due to the rolling forces occurring in the successive rolling stands of a strip rolling mill.

In Fig. 1A is a stable strip during rolling of a metal strip 1 is shown, wherein the rolled strip end 1a enters the respective last roll stand 2 a hot strip rolling mill 3. The rolling forces are in each case symmetrical to the middle of the framework 2a (FIG. Fig. 2 ) acting effectively. In the frame F2, the adjustment of the rollers 10,11 is not parallel, but on the drive side 4 further open than on the operator side 5. This setting leads by the clamping of the metal strip 1 in the adjacent stands F1 and F3 to an asymmetrical band voltage distribution over the bandwidth whereby the strip is stabilized and prevents the metal strip 1 from running laterally. In this state, the tape take-in speeds for the stand F2 on the drive side 4 and the operator side 5 are the same.

In Fig. 1B is shown an unstable tape during the unthreading of the rolled strip end 1 a, wherein after the threading out of the rolled strip end 1 a from the frame F1 of the stabilizing strip tension is missing and there is different tape feed speeds between the drive side 4 and the operator side 5 of the frame F2. The metal strip 1 is drawn in this case at a higher speed on the drive side 4, so that the rolled strip end 1a rotates and extends to the drive side 4 out. Such a process is dangerous and can lead to the described damage.

When leaving the rolled strip end 1 a from the framework center 2a (see. Fig. 2 ), the generated rolling forces on the drive side 4 and on the operator side 5 are compared or separately measured for each rolling stand F1, F2, F3, Fn ... and then evaluated. The direction and the value of the differential rolling force are calculated from these measured values.

The results of the respective measuring step are automatically used within the ongoing rolling process from roll stand (F1) to rolling stand (F2..F3..Fn) or adaptively from metal strip 1 to a new metal strip 1.

A recovery application is designed such that the measurement result for the helmsman in the control center is displayed on a monitor and the helmsman makes the correction manually during the rolling process.

Another utilization possibility is that after the threading out of the rolled strip end 1a for a selected strip length, an average value of the differential rolling force between the drive sides 4 and the operator sides 5 is formed and utilized for the respectively following metal strip 1.

In Fig. 2 is a roll stand 2 from the hot strip rolling mill 3 ( Fig. 1 ), the work rolls 10 and back-up rolls 11 each on the drive side 4, wherein the belt tension is set to stabilize the belt run and for a high rolling speed. In addition, measuring devices for measuring the rolling force on the driving side 4 and the operator side 5 described below are provided.

While leaving the rolled strip end 1a from the rolling stand 2, the rolling forces in the next rolling stand 2 on the drive side 4 and on the operator side 5 by means of force gauges 12 and 13 (eg., Load cells 17 and 18) measured and determines the differential rolling force; Thereafter, the differential rolling force is determined in an evaluation unit 14 as occurring in an individual case actual differential rolling force of the respective metal strip end 1 a. In a connected computer unit 15, a correction value is calculated, which is referred to in the jargon as "tilt value" 16 for the employment of the working and support rollers 10, 11. The "swivel" 16 thus indicates a correction of the employment of the rollers 10, 11 in a rolling stand 2. As force measuring 12, 13 for the differential rolling force of the metal strip end 1a come in addition to load cells 17, 18 and other to be arranged in the roll stand Dehn- or compressive stress Measuring instruments into consideration.

Furthermore, (cf. Fig.2 ) to the computer unit 15, a branch 19 for the forwarding of the swivel 16 either connected to an automatic 20 for consideration when running or next metal roller 1 and / or a display 21 a swivel recommendation for the helmsman. Accordingly, the helmsman's automatic slew setpoint 23 is routed to a branch 24 in which the values are passed to a hydraulic control / drive side position control (rollers) 25 and to a hydraulic control position control 26 on the operator side 5. The swing setpoints 22 and 23 are added to the absolute position setpoint 27 and subtracted.

The position controls 25, 26 of the hydraulic actuators on the drive side 4 and on the operator side 5 operate with these position setpoints and are connected to a cylinder force control 29 and 30 for the drive side 4 and the operator side 5, respectively.

In Fig. 3 For example, evaluations of the differential force at the rolled strip end 1a are shown. After the threading 31 out of the frame F _i-1 , a mean value 32 of the differential force is formed for a specific time or strip length. For the remaining time or length of tape until unthreading 33 from the stand Fi, a relative deviation 34 is then integrated with this mean value. The size of the value thus calculated determines the size of the pan value 16 and the sign the direction of "pan".

LIST OF REFERENCE NUMBERS

1

Metal rolled strip

1a

Rolled strip end

1 b

thin steel band

2

rolling mill

2a

stand center

F1, F2, F3, ... Fn

in the rolling line successive rolling stands

3

Hot strip rolling mill

4

driving side

5

operator side

6

rolling direction

7

Force of the piston-cylinder unit on the drive side

8th

Force of the piston-cylinder unit on the operator side

9

Load page

10

Stripper

11

supporting roll

12

Force gauge on the drive side

13

Force gauge on the operator side

14

Evaluation unit

15

computer unit

16

"Pivot value"

17

Load cell

18

Load cell

19

Branch for data forwarding

20

automatic

21

Display for a swivel recommendation

22

automatic slew setpoint

23

Pivot setpoint of the helmsman

24

branch

25

Position control of hydraulic adjustment / drive side

26

Position control of hydraulic adjustment / operator side

27

absolute position setpoint

28

29

Cylinder force control

30

Cylinder force control

31

Discharging from a scaffold

32

Average

33

Discharging from a scaffold F _i

34

relative deviation from the mean

Claims (3)

1. Method for improving slipping-out of a rolled metal strip (1), the rolled strip end (1a) of which runs at rolling speed out of a roll stand (2), which is last each time, of a multi-stand rolling train (3), wherein, during the rolling, the strip tension (σ_F1,F2,F3) is set between two successive roll stands (F1/F2; F2/F3 ... Fn) for stabilisation of the strip course, wherein shortly before departure of the rolled strip end (1a) from a stand (2) the differential rolling forces produced between the drive side (4) and the operator side (5) are separately measured for each roll stand (F1, F2, F3 ... Fn) by means of force measuring devices (12, 13), wherein the force measuring devices (12, 13) for the differential rolling force of the rolled strip end (1a) are respectively arranged below the lower backing roll (11), a slew value (16) and slew direction of the differential rolling force are derived therefrom for formation of a correction value for adjustment of the rolls (10, 11) and the adjustment is corrected, and wherein the slew value (16) is determined in a computer unit (15) and by way of a branch (19) a slew recommendation for a controller is passed on to an automatic system (20) and/or a display (21) and an automatic slew target value (23) or a slew target value (22) of the controller is supplied to position regulation means (25) of the hydraulic adjustment on the drive side (4) and position regulation means (26) of the hydraulic adjustment on the operator side (5) and wherein the slew target values (22, 23) are added to or subtracted from an absolute position target value (27) and the position regulation means (25, 26) operate with these position target values and are each connected with cylinder-force regulation means (29) for the drive side and cylinder-force regulation means (30) for the operator side (5), wherein the results of the respective measuring step are adaptively evaluated from rolled metal strip (1) to rolled metal strip (1) and wherein after slipping-out of rolled strip end (1a) a mean value of the differential rolling force between the drive side (4) and the operator side (5) is formed for a selected strip length and is evaluated in the following rolled metal strip.
2. Rolling train for hot-rolling of a rolled metal strip (1), particularly a thin steel strip (1b), with a plurality of roll stands (2), which operate on a rolling line and the work rolls (10) and backing rolls (11) of which are driven on the drive side (4) for maintenance of a strip tension for stabilisation of the strip course and for a high rolling speed and respective measuring devices for measuring the rolling force on the drive side (4) and on the operator side (5) are provided, wherein the rolled strip end (1a), during rolling of the metal strip (1), runs at rolling speed out of a roll stand (2), which is last each time, of the multi-stand rolling train (3) and the rolling forces on the drive side (4) and on the operator side (5) are determinable as differential rolling force by means of force measuring devices (12; 13) for the differential rolling force of the rolled strip end (1a), which are respectively arranged below the lower backing roll (11), shortly before departure of the metal strip end (1a), wherein an evaluating unit (14) for the differential rolling force of the metal strip end (1a) and a computer unit (15) for computation of a so-called slew value (16) for adjustment of the rolls (10, 11) during transit of the rolled strip end (1a) are provided, wherein a branch (19) for passing on the slew value (16) to an automatic system (20) for consideration in the next rolled metal strip (1) and/or a display (21) for a slew recommendation for the controller is connected with the computer unit (15), and wherein the automatic system (20) and/or the display (21) is or are connected with a slew target value comparator (22, 23) and both are connected with position regulation means (25) of the hydraulic adjustment on the drive side (4) and with a position regulating means (26) of the hydraulic adjustment on the operator side (5) and wherein the position regulation means (25, 26) with inclusion of a position regulation for the absolute position target value (27), to or from which the slew target values (22, 23) are added or subtracted, operate with these position target values and are each connected with cylinder force regulation means (29, 30) for the drive side (4) and the operator side (5), and wherein the results of the respective measuring step are adaptively evaluated from rolled metal strip (1) to rolled metal strip (1) and wherein after the slipping-out of the rolled strip end (1a) a mean value of the differential rolling force between the drive side (4) and the operator side (5) is formed for a selected strip length and is evaluated in the following rolled metal strip (1).
3. Rolling train according to claim 2, characterised in that the force measuring devices (12, 13) for the differential rolling force of the metal strip end (1a) consist of force measuring cells (17, 18).

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