Method for operating a rolling train

Abstract

The invention relates to a method for operating a rolling train, and to a corresponding rolling train. The rolling train has a plurality of roll stands n, where n = 1 to N, which are arranged one behind the other in a rolling direction R and each have two rotationally driven working rolls for rolling a metal strip. Furthermore, a strip tension control circuit 120 is provided for controlling the actual strip tension of the metal strip 20 to a predefined target strip tension in a tension section 110 between two roll stands arranged one behind the other. In order to reduce thickness deviations in the metal strip to be rolled, said deviations being caused by acceleration and / or deceleration phases during said strip tension control, the invention proposes that a manipulated variable is applied not only to a roll stand delimiting the tension section 110 on the outlet side or inlet side, but also to the rotary drives for other roll stands or rolls upstream or downstream. Thus, according to the invention, at least one rotary drive upstream and downstream of the tension section is integrated into the active strip tension control.

Description

[0001] Method for operating a rolling mill

[0002] The invention relates to a method for operating a rolling mill with a plurality of rolling stands arranged one behind the other in a rolling direction, each with two work rolls driven by a rotary drive for rolling a metal strip. Furthermore, the invention relates to said rolling mill.

[0003] In the prior art, such rolling mills and methods for their operation are generally known; see Figure 2. In particular, it is known in multi-stand rolling mills 100 to regulate the actual strip tension M45 of the metal strip to be rolled in a drawing section 110 between two rolling stands n and n+1 arranged one behind the other within the rolling mill to a predetermined target strip tension. This is typically achieved by applying a control variable S5 in the form of a suitable correction value for the rotational speed of at least one of the work rolls of the nth or n+Tth rolling stand to the rotary drive Dn for the work roll. Accordingly, in the prior art, strip tension control is achieved using a strip tension control loop 120, in which the rotary drive D5 for at least one work roll serves as the actuator and the correction value S5 applied to the rotary drive for the rotational speed of the work roll serves as the control variable.

[0004] In other words, according to the prior art, the correction value for the rotational speed of the work rolls is added to the rotational speed of the work roll of the exit-side rolling stand n+1 of the drawing section or to the rotational speed of the work roll of the entry-side rolling stand n of the drawing section in order to set the desired target strip tension within the strip tension control system. All subsequent rolling stands in the case of control towards the exit and all upstream rolling stands in the case of control towards the entry are controlled in accordance with the mass flow. During the daily operation of a rolling mill, acceleration and deceleration phases occur regularly. These result in mass flow disturbances in the case of the aforementioned strip tension control, which in turn leads to disturbances in the thickness of the metal strip being rolled.This means a reduced quality of the ultimately resulting finished rolled metal strip and a reduction in the maximum productivity of the rolling mill due to rejects in the rolled metal strip, as well as a reduced possibility for the optimized selection of the best strategic exit thickness.

[0005] The invention is based on the objective of further developing a known method for operating a rolling mill and a corresponding known rolling mill in such a way that the said thickness deviations in the metal strip to be rolled are reduced due to acceleration and / or deceleration phases within the framework of the said strip tension control.

[0006] This problem is solved by the method according to claim 1. This method is characterized in that at least one modified second control variable in the form of at least one modified second correction value for the rotational speed of a work roll of at least one other than the nth or n+1 rolling stand and / or for the rotational speed of at least one rotary-driven roll in the rolling mill is derived from the first control variable.is calculated and that, if the first control variable is switched to the rotary drive for the work rolls of the n + 1'th rolling stand: the second control variable is switched to the rotary drive for the work roll of the other rolling stand upstream of the train and / or the second control variable is switched to a rotary drive for the roll upstream of the train; or that, if the first control variable is switched to the rotary drive for the work rolls of the n'th rolling stand: the second control variable is switched to a rotary drive for the work roll of the other rolling stand downstream of the train and / or the second control variable is switched to a rotary drive for the roll downstream of the train.

[0007] The term "first control variable" is not limited to a single control variable. In particular, there can be two first control variables. The term "first" refers to a first side, i.e., the entry or exit side of the track, or the area upstream or downstream of the track. Similarly, the term "second control variable" is not limited to a single control variable. There can be multiple second control variables. The term "second" refers to the side of the track opposite the first side. That is, if the first control variable refers to the exit side of the track, or the area downstream of the track, then the second control variable refers to the entry side of the track, or the area upstream of the track, and vice versa.

[0008] In simplified terms, the invention provides that the strip tension control for applying control variables is also applied to rotary drives other than those for the work rolls of the nth or n+1th rolling stand that defines the drawing section. Suitable options include the rotary drives of work rolls from other rolling stands in the mill or the rotary drives of rollers in the mill, each located outside the drawing section. The rotary drives for the work rolls of the other rolling stands or for the rollers in the mill are thus integrated into the strip tension control within the drawing section according to the present invention. Therefore, according to the invention, at least one rotary drive before and after the drawing section is integrated into the active strip tension control.

[0009] This operating mode of the rolling mill according to the invention offers the advantage that, if the strip tension control is applied, in particular by applying the first control variable to the rotary drive for the work rolls of the n+1th rolling stand on the outward side of the drawing section, the mass flow is stabilized upstream of the drawing section and resulting deviations in the thickness of the metal strip are advantageously significantly reduced. Conversely, if the first control variable is applied to the rotary drive for the work rolls of the nth rolling stand on the inward side of the drawing section, disturbances in the mass flow and resulting deviations in the thickness of the metal strip to be rolled downstream of the drawing section can be significantly reduced.

[0010] In this way, the quality of the rolled strip is significantly improved and tighter strip thickness tolerances can be maintained, although acceleration and deceleration phases still occur within the strip tension control. The amount of scrap material produced is reduced.

[0011] Another advantage is that the method according to the invention is also suitable for retrofitting existing rolling mills.

[0012] The problem of the invention is further solved by a rolling mill according to claim 8. The advantages of this solution correspond to the advantages previously mentioned in relation to the claimed method.

[0013] Advantageous embodiments of the inventive method and the inventive rolling mill are the subject of the dependent claims.

[0014] General:

[0015] A rolling stand in a rolling mill typically has two work rolls that together create a roll gap for rolling and thickness reduction of the metal strip to be rolled. During the rolling process, the two work rolls are engaged with the metal strip; in this case, it is necessary that the typically synchronized rotational speeds of the two work rolls are adjusted by the correction value according to the invention. In the case of a rolled gap, the metal strip is typically only engaged with the lower work roll; in this case, it is generally sufficient if only the rotational speed of the lower work roll is adjusted by the correction value according to the invention. The same applies to a rotary-driven roll, which typically also only contacts the metal strip on one side, without creating a driver roll gap with an opposing roll.However, this case is not excluded within the scope of the present invention, since the roller can also be part of a pair of driver rollers; in this case, the same applies as for the two work rollers of a rolling stand. Within the scope of the present invention, a single roller can engage with either the top or the bottom of the metal strip.

[0016] Advantageously, for the calculation of the second control variables according to the invention, which, as mentioned, represent a correction value for the rotational speed of rollers or work rolls, tracked variables are used, which in the case of a continuously operating rolling mill also ensure a mass flow-correct change of the setting in the respective rolling stands or in the respective rotary-driven rolls during product changes.

[0017] The description includes two figures, whereby

[0018] Figure 1 shows the rolling mill according to the invention and the method according to the invention for its operation; and

[0019] Figure 2 shows a rolling mill with a strip tension control system according to the state of the art.

[0020] The invention is described in detail below with reference to Figure 1 in the form of exemplary embodiments. In both figures, identical technical elements are designated with the same reference numerals.

[0021] Figure 1 shows a rolling mill 100 with a plurality of rolling stands n arranged one behind the other in a rolling direction R, with n=1 to n=N. Each of the rolling stands is symbolized in Figure 1 by two opposing work rolls, each of which opens a roll gap for rolling the metal strip 20. Each pair of work rolls is typically associated with a rotary drive Dn for rotating the work rolls. In this respect, the reference numeral Dn also represents the work rolls of the nth rolling stand.

[0022] Furthermore, the rolling mill 100 has a strip tension control loop 120 for controlling the actual strip tension of the metal strip 20, represented by the measuring signal M45, in a tension section 110 between the nth and n+1th rolling stands to a predetermined target strip tension. The rolling stands n and n+1 limit the tension section 110 on the entry and exit sides with respect to the rolling direction R. In Figure 1, the tension section 110 is shown by way of example between the n=4th and n=5th rolling stands, i.e., between the penultimate and last rolling stands in the rolling mill; however, this is not mandatory. In principle, the tension section can be configured between any two successive rolling stands.

[0023] The control is achieved by applying a first manipulated variable S5 in the form of a suitable correction value for the rotational speed of at least one of the work rolls of the n+Tten rolling stand to its rotary drive Dn+1 for the work roll as an actuator of the strip tension control loop 120. Alternatively or additionally, the first manipulated variable S4 can also be applied in the form of a suitable correction value for the rotational speed of at least one of the work rolls of the n'tten rolling stand to its rotary drive Dn as an alternative actuator for the strip tension control loop 120. The first manipulated variable S4, S5 is calculated and output by a strip tension controller Z45 based on a control deviation in the form of a difference between the actual strip tension M45 and the target strip tension. The strip tension controller Z45 is a central component of the strip tension control loop 120.

[0024] In addition, the rolling mill 100 or the strip tension control loop 120 has a calculation and control device 130 according to the invention for calculating at least one modified second control variable S34, S3, S23, S2, S12, S1, S5 in the form of at least one modified second correction value for the rotational speed of at least one work roll of at least one other than the nth or n+1th rolling stand and / or for the rotational speed of at least one roll R1, R12, R23, R34 in the rolling mill 100 based on the first control variable S4, S5. The calculation and control device 130 is further configured to apply the second control variables to the rotary drives Dn of the other work rolls and / or the rolls.

[0025] Figure 1 illustrates, in particular, a first case in which the first control variable S5 is applied to the rotary drive Dn=5 for the work rolls of the n=5th rolling stand, which are located downstream of the rolling section 110 in the rolling direction or which limit it at the exit end. In this case, the at least one second control variable S1, S2, S3 is applied to the rotary drive D1, D2, D3 for the work roll of one of the other rolling stands n=1, n=2 and / or n=3 upstream of the rolling section 110. Alternatively or additionally, at least one other second control variable SO, S12, S23, S34 can be applied to a rotary drive (not shown in Figure 1) for at least one of the rolls R1, R12, R23, R34 upstream of the rolling section.In this way, the core idea of ​​the invention is realized, namely, within the framework of the strip tension control, not only to apply a control variable S5 at the output side of the traction section 110 to the rotary drive D5 for the work rollers located there, but also to apply at least a second control variable S34, S3, S23, S2, S12, S1 , SO to rotary-driven rollers and / or work rollers upstream of the traction section 110.

[0026] Not shown in Figure 1, but analogously a second case also applies, whereby the activation of the first control variable S4 on the rotary drive of the work rolls of the entry-side rolling stand n=4 of the drawing section 110 is possibly combined with the activation of at least one second control variable on rotary-driven rollers and / or work rolls downstream of the drawing section 110.

[0027] Optionally, a combination of the first and second cases is also conceivable within the framework of strip tension control. In both individual cases and in the case of the combination, the mass flow on both sides of the tension path is advantageously stabilized, and deviations in the thickness of the metal strip resulting from the actual strip tension control are thereby significantly reduced.

[0028] The calculation of at least one second manipulated variable SO, S1, S12, S2, S23, S3, S34 is carried out according to Figure 1 in calculation modules BO*, B1*, B12*, B2*, B23*, B3* and B34* respectively, which are each assigned to the rotary-driven work rolls or rotary-driven rollers of the rolling mill 100. All these calculation modules receive the first manipulated variable S5 as an input and calculate at least one of the second manipulated variables from it as follows:

[0029] S34 = S5 * [(h45 / h34) * V3 * 1 / (SL5 + 1)

[0030] S3 = S34 * 1 / (SL3 + 1)]

[0031] S23 = S3 * (h34 / h23) * (SL3 + 1)

[0032] S2 = S23 * 1 / (SL2 + 1)

[0033] S12 = S2 * (h23 / h12) * (SL2 + 1)

[0034] S1 = S12 * 1 / (SL1 + 1)

[0035] SO = S1 * (h12 / h1) * (SL1 + 1)

[0036] As can be seen from the formulas, the value for the manipulated variable S5 initially enters the calculation of the manipulated variable S34 as the main multiplier. This, in turn, enters the calculation of the manipulated variable S3 as the main multiplier, and so on. Therefore, the calculation of the second manipulated variables for the rollers or work rolls located further away from the track 110 is successively or iteratively based on the calculated correction values ​​for the rotational speed(s) (second manipulated variables) for rotary-driven rollers or work rolls located between the more distant rollers or work rolls and the track 110. In particular, the value for the first manipulated variable S5 on the output side of the track 110 is thus incorporated into each of the calculations for the second manipulated variables upstream of the track 110.In other words, each of these second control variables, as shown in Figure 1, is calculated by weighting the correction value S5 for the rotational speed of at least one work roll of the n+1th (here, for example, the n=5th) rolling stand with a roll weighting factor. This roll weighting factor is enclosed in square brackets in the formula for calculating the second control variable S34. Similarly, a roll weighting factor for the first control variable, or the corresponding correction factor, can also be calculated for each of the other second control variables S34, S3, S23, S2, S12, S1, and S0.

[0037] As can be seen from the formulas, the calculation of the respective roll weighting factors also incorporates a lead SL5, SL3, SL2, SL1 of the metal strip 20. For the second control variables S23, S12, SO for the rotary drives of the rolls R23, R12 and R0, the lead of the metal strip at the work rolls of the rolling stands D3, D2, D1 downstream of the respective roll in the rolling direction R is included. For the second control variables S3, S2 and S1 for the rotary drives Dn with n=1, 2 and n=3 of the work rolls of the rolling stands n=1, n=2 and n=3, the lead of the metal strip 20 at these work rolls is included.

[0038] The at least one roller R1, R12, R23, R34 can be a drive roller – with respect to the rolling direction R – upstream of the rolling stand n or downstream of the rolling stand n+1, in particular in an intermediate stand section between two rolling stands arranged one behind the other within the rolling mill. However, the intermediate stand section of the draw section 110 is excluded.

[0039] Rolling mill 100 can be a finishing mill in which the rolling stands arranged in series are designed for hot rolling the metal strip. Alternatively, rolling mill 100 can be a cold rolling mill in which the rolling stands are designed for cold rolling the metal strip. According to one embodiment of the invention, a correction for load redistribution HL34 is advantageously included in the formula for the second control variable S34, so that instead of S34 = S5 * (h45 / h34) * V3 * 1 / (SL5 + 1), the following applies:

[0040] S34 = S5 * (h45 / (h34 - HL34)) * V3 * 1 / (SL5 + 1 )

[0041] Reference symbol list

[0042] 20 metal band

[0043] 100 rolling mill

[0044] 110 train route

[0045] 120 belt tension control loop

[0046] 130 Calculation and control unit

[0047] BO* Calculation Module

[0048] B1* Calculation module

[0049] B12* Calculation Module

[0050] B2* Calculation Module

[0051] B23* Calculation module

[0052] B3* Calculation module

[0053] B34* Calculation module

[0054] M45 determined actual strip tension (measurement signal) n rolling stand

[0055] Dn Rotary drive for the work roll(s) of the nth rolling stand or these

[0056] Working roller(s)

[0057] R1 Roll h1 Strip thickness at the entry of the rolling stand n = 1 h12 Strip thickness between the rolling stands n = 1 and n = 2 h23 Strip thickness between the rolling stands n = 2 and n = 3 h34 Strip thickness between the rolling stands n = 3 and n = 4 h45 Strip thickness between the rolling stands n = 4 and n = 5 h5 Strip thickness at the exit of the rolling stand n = 5

[0058] R rolling direction

[0059] R1 role

[0060] R12 roll

[0061] R23 roll

[0062] R34 Roller S4 first control variable

[0063] S5 first control variable

[0064] SO second control variable

[0065] S1 second control variable S2 second control variable

[0066] S3 second control variable

[0067] S34 second control variable

[0068] S23 second control variable

[0069] S12 second control variable SL1 lead of rolling mill n = 1

[0070] SL2 Leading rolling mill n = 2

[0071] SL3 Leading Rolling Stand n = 3

[0072] SL4 Leading rolling mill n = 4

[0073] SL5 Leading rolling mill n = 5 Z45 Strip tension regulator

Claims

Patent claims:

1. Method for operating a rolling mill (100) with a plurality of rolling stands n with n=1 to N arranged one behind the other in a rolling direction (R) with each of two work rolls driven by a rotary drive (Dn) for rolling a metal strip (20), comprising the following process steps: - Determining and controlling the actual strip tension of the metal strip (20) in a drawing section (110) between the nth and the n+1th rolling stand of the rolling mill (100) to a predetermined target strip tension by applying a first control variable (S4, S5) in the form of a suitable correction value for the rotational speed of at least one of the work rolls of the nth or the n+1th rolling stand to the rotary drive (Dn) for the work roll as an actuator; characterized in that at least one modified second control variable (S34, S23, S12, S1, S1, S2, S3) in the form of at least one modified second correction value for the rotational speed of a work roll of at least one other than the nth or n+1th rolling stand and / or for the rotational speed of at least one rotary-driven roll (R1, R12, R23, R34) in the rolling mill (100) is derived from the first control variable (S4, S5);and that when the first control variable (S5) is switched on to the rotary drive (Dn) for the work rolls of the n+Tten rolling stand:; - that at least one second control variable (S1 , S2, S3) is switched to the rotary drive (Dn) for the work roll of at least one of the other rolling stands (n=1 , n=2, n=3) upstream of the train path (110) and / or that at least one second control variable (SO, S12, S23, S34) is switched to a rotary drive for the roll (R1 , R12, R23, R34) upstream of the train path (110), or that, if the first control variable (S4) is switched to the rotary drive (Dn) for the work rolls of the nth rolling stand: - at least one second control variable on a rotary drive (Dn with n > n+2) for the work roll of at least one of the other rolling stands (n > n+2) downstream of the train track (110) and / or at least one second actuating variable is switched to a rotary drive for at least one of the rollers downstream of the train track (110).

2. Method according to claim 1, characterized in that the at least one roll (R1 , R12, R23, R34) is a driver roll in the rolling direction (R) upstream of the rolling stand n or downstream of the rolling stand n+1, in particular in an intermediate stand area between two rolling stands arranged one behind the other within the rolling mill (100).

3. Method according to claim 2, characterized in that the at least one modified second control variable (S34, S23, S12, SO) in the form of a modified correction value for the rotational speed of at least one of the rolls (R34, R23, R12, R1) upstream of the drawing section (110) is calculated by weighting the correction value (S5) for the rotational speed of the at least one work roll of the n+Tten rolling stand with a roll weighting factor.

4. Method according to claim 3, characterized in that the lead (SL5, SL3, SL2) of the metal strip (20) at one of the respective rolls (R34, R24, R12, R1) in the rolling direction (R) is included in the calculation of the roll weighting factor.

5. Method according to claim 2, characterized in that the at least one modified second control variable (S3, S2, S1) is in the form of a modified correction value for the rotational speed of at least one of the working rollers of one of the upstream of the train path. (110) arranged other rolling stands (n=3, n=2, n=1) is calculated by weighting the modified control variable (S34, S23, S12) for the roll immediately downstream of the other rolling stand in the rolling direction (R) with a work roll weighting factor.

6. Method according to claim 5, characterized in that the lead (SL3, SL2, SL1) of the metal strip (20) at the respective rolling stand (n=3, n=2, n=1) is included in the calculation of the work roll weighting factor.

7. Method according to one of the preceding claims, characterized in that the n'th rolling stand is the penultimate rolling stand n=N-1 seen in the rolling direction (R) and the n+Tth rolling stand is the last rolling stand n=N in the rolling mill (100).

8. Rolling mill (100) with a plurality of rolling stands n with n=1 to N arranged one behind the other in a rolling direction (R), each rolling stand having two work rolls driven by a rotary drive (Dn) for rolling a metal strip (20); a strip tension control loop (120) for controlling the actual strip tension of the metal strip (20) in a tension section (110) between the nth and the n+Tth rolling stand of the rolling mill (100) to a predetermined target strip tension by applying a first control variable (S4, S5) in the form of a suitable correction value for the rotational speed of at least one of the work rolls of the nth or n+Tth rolling stand to the rotary drive (Dn) for the work roll as an actuator of the strip tension control loop (120); characterized by a calculation and control device (130) for carrying out the Procedure according to one of the preceding claims.

9. Rolling mill (100) according to claim 8, characterized in that the calculation and control device (130) is configured to calculate the at least one modified second control variable (S3, S23, S2, S12, S1, S1, S2) in the form of at least one modified second correction value for the rotational speed of at least one work roll of at least one other than the nth or n+1th rolling stand and / or of at least one roller (R1, R12, R23, R34) in the rolling mill (100) on the basis of the first control variable (S4, S5); and that the calculation and control device (130) is further configured to apply the second control variables to the rotary drives of the other work rolls and / or rollers.

10. Rolling mill (100) according to claim 8 or 9, characterized in that the calculation and control device (130) for at least one of the rotary-driven work rolls of the other rolling stands and / or the rollers has an associated calculation module (BO*, B1*, B12*, B2*, B23*, B3*, B34*) which receives as input the first control variable (S5) and which calculates at least one modified second control variable (SO, S1 , S12, S2, S23, S3, S34) and outputs to the rotary drive for the respective associated work roll or roller (R1 , R12, R23, R34).

11. Rolling mill (100) according to one of claims 8 to 10, characterized in that the rolling mill (100) is a finishing rolling mill with the rolling stands for hot rolling the metal strip or a cold rolling mill with the rolling stands for cold rolling the metal strip.

Images