DE10037867A1 - Flexible rolling process, for metal strip, involves work roll bending line control during or immediately after each roll gap adjustment to obtain flat strip - Google Patents

Abstract

Flexible metal strip rolling, involving work roll bending line control during or immediately after each roll gap adjustment to obtain flat strip, is new. A flexible rolling process for metal strip comprises adjusting the roll gap during rolling to achieve different strip thicknesses along the strip length, the bending lines of the work rolls being controlled in dependence on the adjusted roll gap during or immediately after each roll gap adjustment in order to achieve strip flatness.

Description

The invention relates to a method for flexible rolling of a metal strip, wherein the metal strip during the rolling process by one between two work rolls zen formed nip and the nip ge during the rolling process Aiming is to tape different lengths along the length of the metal band to achieve thick.

Flexible rolling as a process for the production of flat metal strips with over their length defines different strip thicknesses is already known in practice. The flexible rolling is characterized in that during the rolling process Roll gap is moved specifically. Here are different lengths of tape cuts with different strip thicknesses rolled over different stones conditions can be connected. The goal of flexible rolling is Rolled products with load and weight-optimized cross-sectional shapes put. The process is usually designed as strip rolling from coil to coil. The strip tension applied over the reel supports the rolling process and significantly improves the straightness of the finished strip profile in the longitudinal direction, i.e. in Rolling direction.

When rolling as part of the conventional strip rolling process, there are tion of the rolling stock located in the entry zone to the roll gap is considerable Forces required which lead to elastic deflection of the rollers. The deflection of the rollers mounted at both ends results in a bending line, which is usually parabolic and corresponds to the central axis of the roller. Since the deflection is a deviation from the uniform gap dimension or from corrective measures are required.

One measure, the deviation from the ideal gap - caused by the through bending of the rolls - correcting them consists of crowning the roll bales. Here ter is understood to be the barrel-shaped or bulbous design of the roll bales. With this type of correction it is possible to use only the work rolls, only the backup roll zen or both the work rolls and the backup rolls to bombie ren. The crowning is the deflection caused by the rolling forces and the egg balance of the rollers is caused so that the gap between the Rolling runs smoothly again, d. H. is constant over the length of the rollers. In  As a rule, however, the correction of the bending line is not complete and applies because the Roll shape or the crowning is not changeable, only for a certain one Operating case.

Another possibility for correction consists in that one roll bale each Horizontal rotation around the center of its line of contact with the kor responding roller is placed obliquely to its axis. Through this slant The gap at the ends of the roll bale changes while it is in the middle remains unchanged. The inclination of the rollers allows the variability an approximate compensation of the deflection for almost all operations falls, but is the aforementioned parabolic in terms of achievable accuracy grinding the roller bales equate.

It is also possible to apply forces to the trunnion of the whale zen to generate a bending moment, which ent the bending moments during rolling counteracts. This pretensioning of the rollers, like the inclined position, also allows approximate compensation for almost all operating cases. The disadvantage is, however significantly increased bearing load. With regard to the achievable compensation preloading comparable to parabolic grinding.

Finally, there is another possibility to correct the work roll cooling, which is a thermal crowning.

It goes without saying that the aforementioned correction options for education an ideal roll gap in rolling mills both individually and in Kombina tion can be used together.

In contrast to the conventional strip rolling process, it is with flexible rolling particularly problematic that during the rolling process due to the frequent Changes in thickness of the metal strip constantly large load fluctuations on the roller occur, which on the one hand bring about the desired change in strip thickness, on the other hand, a significant change, especially for wider metal strips the roll load across the width. This will make the bend line of the work rolls, thus the geometrical formation of the roll gap and thus  flatness is affected unless there is a correction to achieve uniformity Gap occurs. With flexible rolling, the nip is corresponding to the move the required belt profile without correction, this creates for this load change a characteristic unplanned band profile across the width. Because of this unplanned There is a risk of edge waves or band tears because the related heights Shape change and corresponding change in length shape not constant across the width. Because of this, there are different thicknesses across the Width and different lengths resulting from these tape errors.

Flatness is an essential requirement for a metal band. It is important to for further processing the same ratios from the middle of the belt to the edge of the belt to be able to guarantee. If the tapes are not flat, this can have undesirable effects come when reeling. This manifests itself in friction stress peaks at the cones tact areas in the coiled reel either in the middle of the strip or at the strip channel te depending on the belt profile. Depending on the Umschlin angle and the occurring friction conditions to stick the leaded coil, especially if there is a glow following the rolling treatment is carried out.

In the conventional strip rolling process for the production of flat metal strips Over its length of constant thickness, both the strip thickness and the Flatness constantly set, monitored via complex control loops and at open occurring deviations are regulated via corresponding actuators. A regulatory device for regulating the roll deflection in the con conventional strip rolling process is known for example from DE 22 64 333 C3.

The problem is that there is a certain response time in the known control and requires a certain period of time for the regulation to respond and the Effect of a disturbance variable change through the effect of the regulation within the Measuring accuracy is corrected. This problem of the response of the scheme and The required control time plays a significant role, especially in flexible rolling Role, because sometimes very short tape sections with different thicknesses high rolling speeds must be rolled, and the flatness  ultimately should be guaranteed over the entire length of the flexibly rolled strip. This is extremely difficult, especially for wider metal strips.

The object of the present invention is to provide a method for flexible rolling a To provide metal strip in which a good flatness can be achieved can, even with relatively wide bands.

The previously derived and described task is the one in a method gangs described type essentially solved according to the invention that wah After each adjustment of the roll gap or immediately afterwards the bending lines of the ar finishing rolls depending on the set roll gap to achieve flatness of the metal strip can be controlled. It is essential in the invention that Influencing the bending lines of the work rolls when setting the roll gap - each if necessary initially - not via a regulation, but via a controller, in other words, a process in which one size - in this case the bending lines of the ar beitswalzen - of a different size - in this case the roll gap - in a pre given, fixed connection is influenced.

In the invention, the compensation of the bending line change is due to the load changes in a roll gap change by knowledge of the bending line dependency on the respective roll gaps. If, for example, the roll gap is adjusted from S ₁ to S ₂ for a specific rolling stock, this adjustment of the rolling gap leads to a change in the deflection of the work rolls. This bending lens change is known and forms the basis of the controlled compensation. The knowledge of the change in the bending line can follow from the given geometry, but can in particular be obtained empirically, namely in that corresponding measurement variables are fed back during the rolling process.

As a result, the bending line is directly dependent on the respective roll gap ten by application, d. H. Increase or decrease certain back bends Forces adjusted to a uniform gap dimension over the length of the roll gap hold. Through this controlling intervention on the rolling process when setting the Rolling gap can be targeted on the metal strip, before one  possible subsequent regulation becomes effective at all, ultimately to a to provide its entire width of flat metal tape.

It is particularly advantageous if the flatness following the control and especially immediately after setting the roll gap via at least one Control loop is regulated. The invention therefore provides that initially, d. H. at the on set the roll gap, only a control is carried out. External disturbances with off The changing nip cannot be taken into account here. However, if the control intervention is completed, the regulation responds to the in Eliminate the remaining flatness and thus a flat metal band aim.

During flexible rolling it changes due to the given thickness of the metal strip required several times to adjust the roll gap. thats why according to the invention further provided that shortly before or during the renewed Adjusting the roll gap, the flatness control is interrupted and the bie Lines of the work rolls are controlled again depending on the new roll gap become. So there is a constant change between control and regulation depending on the predetermined change in thickness of the metal strip over its Length.

For control purposes, depending on the different roll gaps certain back bending forces on the work rolls and / or the backup rolls brings to a work roll bend or a backup and work roll bend to achieve. Corresponding to this, to correct an unplannedness of the Metal strip adapted to the respective load case back bending forces on the Ar beitswalzen and / or backup rolls applied to a work rollsbie to achieve and / or support and work roll bending. The aforementioned Control or regulation can preferably be carried out with the work and / or Implement backup roll bending because here - the travel speed of the roll gap accordingly - quick changes can be realized, which is precisely the case with fle xiblen rolls with sometimes very short strip sections is important. Would be conceivable but also other ways of influencing flatness, e.g. B. by Ver push of intermediate rolls in the six-high mill stand, by hydraulically supported  Rolling or by cross-rolling. However, the goal is in any case, a plan, to produce flexibly rolled strip and at the same time the ability to reel it To improve or optimize metal strips.

So that the control responds as quickly as possible after the control, which, as has already been stated, especially with flexible rolling from erhebli cher importance, it is recommended that the measurement of flatness optically pre is taken. The optical measurement of the flatness can be done directly behind the ar Realize rollers in a simple way. The flatness of the metal strip preferably over the entire width of the metal strip behind the roll gap for each Length increment measured.

It is particularly preferred in connection with the optical measurement that Measurement of the flatness of lasers distributed over the entire width of the metal strip thickness measuring stations are provided and that the laser thickness measurement via Triangu lation takes place. The laser thickness measurement over the entire width of the metal strip enables an easy optimization of the bending line of the working whale online Zen. The laser thickness measurement via triangulation enables the small measurement stain and the high measuring frequencies of 1 kHz and more even with short bandab cut about 50 mm in length to determine the cross profile.

It is understood that it is fundamentally possible to use measuring means other than optical ones to determine an unevenness remaining in the band after the control use. For example, a stressometer roll can be used.

For the rest, it is advantageous not only to regulate the flatness of the metal strip, but also the strip thickness of the metal strip in the longitudinal direction. This can be seen in Re Gelkreis be integrated to bend the work rolls.

In the following, the invention is based on an exemplary embodiment only illustrative drawing explained again. It shows

Fig. 1 is a schematic representation of a portion of a rolling stand without genbiegung Ge,

Fig. 2 is a view of the roll stand from Fig. 1 with counter-bending and

Fig. 3 shows a control loop.

In Figs. 1 and 2, a part of a rolling stand 1 is the one shown without reverse bending (Fig. 1) and on the other hand with counter bending (Fig. 2). In particular, ge shows a cylindrical work roll 2 with roll balls 3 and journals 4 , 5 , which are mounted in bearings 6 , 7 . Above the work roll 2 there is a support roll 8 with a cylindrical support roll barrel 9 and bearing journals 10 , 11 which are mounted in bearings 12 , 13 . The work roll 2 shown and the support roll 8 are the upper rolls of the roll stand 1 . Not Darge represents the two lower corresponding rollers, namely a lower Ar beitswalze and a lower backup roller. The roll gap S is located between the two work rolls.

It goes without saying that the invention can be used both in a four-high mill stand and in a two- high mill stand and that instead of cylindrical rollers 2 and support rollers 8 , cambered rollers can in principle also be used.

In Fig. 1, an application is shown during the rolling of a metal strip, not shown, where a rolling force F _W is applied to the work roll 2. The rolling force F _W causes an elastic deflection of the work roll 2 , so that the bending line B of the work roll 2 results. The rolling force F _W leads not only to a deflection of the work roll 2 , but also to a deflection of the backup roll 8 , which is not shown in detail, however.

In FIG. 2, the state of the rolls 2, 8 shown with counter-bending. In contrast to the state shown in FIG. 1, the roll gap S has a constant, uniform gap dimension, that is to say an at least substantially constant constant distance between the two facing surfaces of the work rolls. In the state shown in Fig. 2, the work roll 2 is not bent. The rolling force F _W act on the backing roll 8 applied counter bending forces F _B ent.

In the embodiment shown, the bending line B, which corresponds to the central axis of the work roll 2 , runs parallel to the outside of the work roll 2 . This is not the case with a cambered roll barrel 3 . In this case, the work roll is bent at a roll gap which is constant over the length of the work roll, in contrast to the illustration according to FIG. 2, although the line or surface of the work roll which limits the roll gap runs horizontally.

The inventive method for flexible rolling of a metal strip now runs so that the roll gap S is specifically moved during the rolling process in order to achieve a predetermined change in thickness of the metal strip over its length. It is essential here first that during the setting of the roll gap S or immediately thereafter the bending lines B of the work rolls 2 are controlled in dependence on a set roll gap in order to achieve a flatness of the metal strip. This is possible by knowing the bending line dependency of the different roll gaps. This compensates for the deviation from the ideal gap caused by the different roll gaps.

Following the control intervention described above when setting the roll gap S, the flatness is regulated via the control circuit shown in FIG. 3. As a result, a flatness remaining in the strip after the controlling intervention is corrected. If the roll gap S is adjusted again later, the regulation is interrupted and controlled again in the manner explained above.

For control purposes, depending on the various nips, predetermined bending forces F _{B are} applied to the support rollers 8 in order to achieve a work and support roller bending. With the same goal, rebending forces F _{B are} applied to the work rolls 2 to compensate for the flatness.

For control purposes, a measured value acquisition is first carried out using appropriate measuring means. Both the longitudinal and the transverse profile are measured. Then there is the longitudinal profile or cross profile detection, the control deviation between the actual and target value of the respective control variable being determined. The respective correction values are then fed to a control loop. In the longitudinal profile detection, the change Δh in the thickness of the metal strip is corrected to the predetermined target value in accordance with the predetermined target value. A corresponding change ΔS of the roll gap is required for this. Finally, the change in roll gap S in turn depends on the back bending forces F _B to be applied to the respective work rolls 2 .

Claims (10)

1. A method for flexible rolling of a metal strip, wherein the metal strip is guided during the rolling process through a roll gap formed between two work rolls and the roll gap is specifically moved during the rolling process in order to achieve different strip thicknesses over the length of the metal strip, as characterized by that during each adjustment of the roll gap or immediately afterwards, the bending lines of the work rolls are controlled as a function of the set roll gap in order to achieve a flatness of the metal strip. 2. The method according to claim 1, characterized in that the flatness in the connection to the control and especially immediately after the setting of the roll gap is regulated via at least one control loop. 3. The method according to claim 2, characterized in that just before or during the adjustment of the flatness is interrupted when the roll gap is readjusted and the bending lines of the work rolls as a function of the renewed roll gap can be controlled again for the new rolling case to achieve flatness. 4. The method according to any one of claims 1 to 3, characterized in that for Control depending on the different nips predetermined Rebending forces are applied to the work and / or back-up rolls to a To achieve work roll bending or a support and work roll bending. 5. The method according to any one of claims 2 to 4, characterized in that for Correcting an unevenness of the metal strip depending on the load suitable rebending forces are applied to the work and / or back-up rolls, around a work roll deflection and / or support and work roll deflection achieve. 6. The method according to any one of claims 2 to 5, characterized in that the Non-contact flatness measurement, e.g. B. optically.   7. The method according to any one of claims 2 to 6, characterized in that the Flatness of the metal strip over the entire width of the metal strip behind the Roll gap is measured for each length increment. 8. The method according to claim 6 or 7, characterized in that for measuring the Flatness laser thickness measuring stations distributed over the entire width of the metal strip are provided and that the laser thickness measurement is carried out via triangulation. 9. The method according to any one of claims 2 to 5, characterized in that the Touching flatness measurement, e.g. B. is done via a stressometer role. 10. The method according to any one of claims 1 to 9, characterized in that the Strip thickness of the metal strip is regulated in the longitudinal direction.