EP0121148B1 - Method of making hot rolled strip with a high quality section and flatness - Google Patents

Description

The invention relates to a method and a rolled strip tandem mill for the production of rolled strip, in which this is passed through the hot strip tandem mill and is thereby subjected to a condition control during the rolling process, which is a strip profile control and in at least the last roll stand one of a flatness measurement of the from the last stand the hot strip tandem mill emerging from the rolled strip outgoing strip profile and flatness control.

In the production of rolled strip, which is subjected to a hot rolling process and a cold rolling process one after the other, a condition control takes place for each pass in both the hot strip tandem mill that performs the hot rolling process and the cold strip tandem mill that carries out the cold rolling process. Such a state control includes various control processes such as, for example, the speed control, the thickness control, the strip tension control, the strip profile control and the strip flatness control, which can influence one another to a greater or lesser extent and thus also have corresponding repercussions on the condition of the rolled strip.

The mutual effects of the strip profile control and the strip flatness control have proven to be particularly problematic for the condition of the rolled strip in the course of the rolling process in a cold strip tandem mill. It has been shown that a perfectly flat cold-rolled strip can only be rolled out if the strip profile present when it enters the cold-rolled tandem mill remains as unaffected as possible. Conversely, it has been shown that if an influence is exerted on an uneven strip profile in the cold strip tandem mill, only an unplanned cold strip can be rolled out. Even an attempt to correct the strip profile by only a hundredth of the strip thickness can lead to waves and / or bumps appearing on the rolled strip which reach a height of up to twenty-two mm at a distance of about one meter in the longitudinal direction of the strip.

This disadvantage can be avoided if the cold strip tandem mill is supplied with a rolled strip which, in addition to a strip profile that is almost uniform over the entire width, already has a minimum degree of strip flatness.

From DE-A-2 354 649 it is known to roll thickness-regulating in all stands of the hot strip tandem mill and to influence the emerging profile of the rolled strip for the last influencing stages at the end of the rolling process by bending the rolls forming the respective roll gap without changing the thickness. This bending of the rolls is varied in accordance with the measurement results of a sensor arranged behind the last stand of the hot strip tandem mill, which controls the flatness of the rolled strip that has already emerged from the hot strip tandem mill. This rolling process did not lead to the expected satisfactory results.

Experiments with profile corrections in the first rolling stands of hot strip mills have shown that the profile change is destroyed by the rolling passes in the subsequent rolling stands. However, the flatness of the finished strip did not change. Changes in the shape of the roll gap in the last rolling stands led to a simultaneous change in profile and flatness. From these experiments, it was learned that the profile can only be changed permanently in the last rolling stands, but experience has shown that it can only be done in small increments from roll pass to roll pass and that the last roll pass can preferably be used to adjust the strip flatness.

With long products, i.e. strips and long sheets, profile correction is based on a material flow along and across the rolling direction. The ability of the material to flow transversely to the rolling direction depends on the geometric rolling conditions, such as thickness, decrease, width and roll diameter, as well as other parameters such as material strength, strip temperature, coefficient of friction between the roll and the rolling stock, and the strip tension.

Flatness correction, on the other hand, is based on different lengthening of the strip with a small, practically negligible material flow across the rolling direction.

The invention has for its object to design the generic method so that a rolling strip is provided for the cold rolling process, which has a uniform strip profile and a minimum degree of strip flatness over the entire width.

This object is achieved by determining and determining the critical thickness of the rolled strip below which no substantial reshaping of the rolled strip in the direction of the width can be achieved, rolling this rolled strip, the thickness of which is significantly greater than the determined critical thickness in succession in a first and second Rolling stage in which the rolled strip is passed through at least one roll gap forming this, reducing the thickness of the rolled strip in the first rolling stage to essentially the critical thickness determined, checking the reaction of the thickness of the rolled strip in this rolling stage by measuring the thickness behind the first Rolling step and setting at least the last roll gap in this first rolling step based on the result of the measurement of the thickness, measurement of the flatness of the rolled strip in the second rolling step at least at one point in the course of this rolling step and reduction of the thickness of the rolled strip in this second rolling step f is a thickness below the critical thickness based on the measurement of the flatness of the rolled strip.

With this solution, namely in two, a first and a second rolling stage, in which, based on the determination of the critical thickness of the respective rolled strip in the first stage, the reduction of the rolled strip is carried out with the means of the thickness control technology while spreading the rolled strip cross-section to the critical thickness and In the subsequent second rolling stage, further reduction can only be achieved with the means of flatness control in correspondingly small steps while elongating the strip. According to the task, a rolled strip is produced that has a uniform strip profile over the entire width and a minimum degree of strip flatness.

The proposed method is based on the knowledge that a profile influence on the rolled strip can be achieved while avoiding flatness errors, as long as the flow resistance of the material across the rolling direction is still so low that a minimum amount of strip width is set in the roll gap in addition to the strip elongation. It was found that with today's design of the hot strip tandem mill, which is customary with regard to the work roll diameter, the limit for influencing the profile of the rolled strip while avoiding flatness errors is a roll strip thickness of approximately 12 mm. This limit value of the thickness, i.e. the critical thickness, can be determined experimentally for each hot strip tandem mill depending on the rolling material, temperature, roll diameter and decrease or pass distribution.

According to a further method feature of the invention, the height of the last roll gap in the first rolling stage can be set in accordance with the comparison of the result of a measurement of the thickness of the rolled strip behind the first rolling stage with a predetermined standard experience value, the result of the measurement of the flatness of the rolled strip can be compared with a given standard experience value. Furthermore, according to the invention, the size of the reduction in the thickness of the rolled strip in the first rolling stage can be determined and regulated on the basis of measurements of the thickness of the rolled strip within the second rolling stage.

A rolled strip tandem mill for producing rolled strip in which it is subjected to a state control during the rolling process, which includes a strip profile control and, in the last rolling stand, a strip profile and flatness control based on a flatness measurement of the rolled strip emerging from this stand, with which the methods explained above are carried out can consist of a group of roll stands with a roll gap height equal to or greater than the critical thickness to which profile measuring devices and profile controllers are assigned, which are connected to strip profile actuators on the roll stands, while the last roll stand of this group and all other roll stands of the hot strip tandem mill flatness measuring devices and have flatness controllers which are connected to strip flatness actuators, the last rolling stand of the first group optionally being influenced either by profile measuring devices and profile controllers or by flatness measuring devices and flatness controllers is cash. According to the invention, the profile measuring devices or the flatness measuring devices can be arranged downstream of the roll gap to be controlled of the roll stands of the first group or of the subsequent roll stands.

Further forms of training of the claimed hot strip tandem mill are laid down in subclaims.

When this method is carried out with the appropriately designed hot strip tandem mills, the flatness control acts in a manner known per se only on the last rolling stand of the hot strip tandem mill. For profile control, the profile measuring device at the outlet of the street first detects the deviation of the strip profile generated by it. The required adjustment of the roll gap of the last stand, that is to say the nth stand, is automatically determined with the aid of pre-calculated characteristic curves for the actuating behavior of the roll set. Then, assuming a constant elongation of the strip across the strip, the required adjustment of the roll gap shape in the previous stands is determined step by step. In accordance with the required roll gap shape changes, the roll gap shape actuators of the first size or sizes are now automatically adjusted to the pre-calculated dimension. Delayed by the advancement time of the strip from the adjusted stand to the next, not yet adjusted, this next stand is then also adjusted, this procedure is continued until the last of the roll nips has also been adjusted in the calculated amount.

When the section of material of the rolled strip that has been tracked since the start of the individual adjustment measures has reached the profile measuring device and its profile has been measured, a new correction cycle can be initiated if necessary. The flatness control acting independently of this solely on the last roll stand remains constantly in effect and also has a shorter cycle time due to the shorter transport times between the place of adjustment (roll stand n) and the place of measurement, and thus has more favorable control dynamics.

The control dynamics of the profile control is due to the previously mentioned transport times of the rolled strip from the point of adjustment (first Scaffolding of the road) to the place of measurement (behind the last scaffolding). The control dynamics are sufficient to compensate for slowly occurring profile changes (roller wear, thermal crowning) sufficiently quickly. Relatively quick and short-term profile changes, e.g. B. due to short-term changes in the rolling force, cannot be corrected due to the transport routes by a corresponding backward regulation (up to 20% short-term increase in rolling force when rolling over rail points (skidmarks)), cause additional bending of the roller sets and thus distort the profile of the strip and its flatness.

If the described cyclical profile measurement happens accidentally at a rail station, this results in setting commands that are correct for the rail station but incorrect for the rolled strip that is influenced with a time delay. The successful use of a feed-back flatness control therefore requires a feedforward control that compensates for the influence of changes in rolling force.

For this purpose, the change in the shape of the roll gap as a result of a change in the rolling force is calculated for each roll stand, depending on the strip and roll dimensions. The change in manipulated variable required to compensate for this change can be represented in equations or sets of curves and automatically taken into account.

The rolling force of each roll stand is thus detected with the force measuring devices which are present anyway, and changes in the force are compensated for directly in accordance with previously determined curves by interventions in the profile actuators (for example work roll bending force).

The gap shape setting values, which are improved in the course of the rolling by the interventions of the closed flatness and profile control loops, are used to gradually improve the pre-setting values stored with the data of the pass schedule and the material data.

In the event of changes to the pass schedule, previously saved setting values are used which, if necessary, can be improved with the aid of the families of curves already mentioned, based on a current pass schedule precalculation (based on current pre-strip strength information from the pass stitches). This means that the best possible profile and flatness setting is available for the beginning of the strip, which requires only minor corrections by closed control loops.

Experience has shown that the increase in the strip profile in the middle of the strip is in the range from 0.5% to approx. 1.5% of the final thickness. Depending on the intended use of the hot strip, the control objective is to minimize the elevation of the strip center or to a predetermined value of z. B. 1.0% of the nominal thickness reproducible. The setting range for the setting of the roll gap shape should therefore ideally be 0.75% of the nominal thickness and should still have sufficient reserves to compensate for changes in rolling force and other disturbance variables.

With a finished strip thickness of z. B. 3 mm, this corresponds to a required profile adjustment range of 22.5 _f lm for the last scaffold. Modern work roll back-bending systems have a setting range of more than 100 µm - ± 50 _f lm at medium to full strip width, so that there are still relatively large reserves to compensate for disturbance variables.

vergrößerter Stellbereich erforderlich. Hierbei empfiehlt es sich, zusätzlich andere Walzspalt-Einstellmechanismen zu verwenden, um das Biegesystem stets innerhalb seiner Stellgrenzen zu halten. Als zusätzliches Stellglied kommt z. B. eine gezielte Änderung der thermischen Walzenbombierung oder die axiale Verschiebung von speziell geschliffenen Arbeitswalzen in Frage. Diese relativ träge wirkenden Stellmechanismen werden so angesteuert, daß das sehr schnell wirkende Arbeitswalzen-Rückbiegesystem möglichst in der Mitte seines Stellbereiches arbeitet.For the stands in front there is a ratio of the thicknesses of the rolling strip that is running out

increased adjustment range required. It is advisable to use other roll gap adjustment mechanisms in order to keep the bending system always within its setting limits. As an additional actuator comes z. B. a targeted change in the thermal roller crowning or the axial displacement of specially ground work rolls in question. These relatively sluggish-acting adjustment mechanisms are controlled so that the very fast-acting work roll back-bending system works as far as possible in the middle of its adjustment range.

In numerous cases, e.g. B. in aluminum hot strip mills, it may be sufficient to work alone with the adjustment range of the work roll back bending system. Due to the relatively good roll gap lubrication and the large deformation even in the last roll passes, the profile and flatness control can be limited to the last two to three passes. When rolling steel without roll lubrication, at least the last two to five passes for profile and flatness control are required (the low number applies to large final thicknesses h> 5 mm and the higher number applies to small final thicknesses).

unter Berücksichtigung der erforderlichen Reserven für das Ausregeln von Störgrößen, wird auch ein modernes stark ausgelegtes Arbeitswalzen-Rückbiegesystem diesen Anforderungen nicht allein genügen. Die Unterstützung durch eine gezielte thermische Bombierung (Stellbereich ca. 40 µm ) kann jedoch in vielen Fällen schon ausreichend sein, um aufwendigere Stellmittel einzusparen.As already mentioned in the explanation of the type of process mentioned in the first place, for the hot rolling of steel strip with a critical thickness of approximately 12 mm, such a large material flow across the rolling direction is still possible that an effective profile correction can be carried out. Actuators for adjusting the profile and flatness are therefore required at least from the rolling stand, the outlet thickness of which is below the critical thickness. The required adjustment range for this first control framework is approx.

taking into account the necessary reserves for the correction of disturbance variables Even a modern, strong work roll back-bending system does not alone meet these requirements. The support by a targeted thermal crowning (adjustment range approx. 40 µm) can, however, in many cases be sufficient to save more complex adjustment means.

In both types of process, however, the belt profile actuators can be used to roll bend, roll adjustment, roll limitation, roll swiveling, zone cooling of the roll bales, as well as axial work roll, intermediate roll (e.g. with six-high stands) and backup roll displacement in the corresponding roll stands of the hot strip tandem mill can be influenced individually and / or simultaneously.

• Fig. 1 in schematisch vereinfachter Darstellung eine fünfgerüstige Warmbandtandemstraße, die wahlweise für die Auswalzung von Warmband eingesetzt werden kann, das entweder eine Enddicke von mehr als 3 mm oder aber eine Enddicke von weniger als 3 mm aufweist für die Durchführung der ersten Verfahrensart,
• Fig. 2 die Warmbandtandemstraße nach Fig. 1 im Betriebszustand für die Auswalzung dicker Warmbänder,
• Fig. 3 die Warmbandtandemstraße nach Fig. 1 in ihrer Betriebsstellung für die Auswalzung dünner Warmbänder,
• Fig.4 ebenfalls in schematisch vereinfachter Darstellung eine 7-gerüstige Warmbandtandemstraße für die Durchführung der zweiten Verfahrensart und
• Fig. 5 bis 7 Diagrammdarstellungen der Zustandsregelungen bei der Durchführung der zweiten Verfahrensart.

The invention is explained in more detail with reference to the exemplary embodiments shown in the drawing, and it shows:

• 1 shows a schematically simplified illustration of a five-stand hot strip tandem mill, which can be used optionally for the rolling out of hot strip, which either has a final thickness of more than 3 mm or a final thickness of less than 3 mm for carrying out the first type of process,
• 2 shows the hot strip tandem mill according to FIG. 1 in the operating state for the rolling out of thick hot strips,
• 3 shows the hot strip tandem mill according to FIG. 1 in its operating position for the rolling out of thin hot strips,
• Figure 4 also in a schematic simplified representation of a 7-stand hot strip tandem mill for the implementation of the second type of process and
• 5 to 7 show diagrams of the state controls when carrying out the second type of process.

The hot strip tandem mill according to FIGS. 1 to 3 comprises, in addition to the five roll stands 1 to 5, a take-up reel 6 for the hot strip 7 provided on the outlet side. A profile measuring device 8, 9 and 10 is provided behind each of the roll stands 1, 2 and 3, and that Roll stand 3 is designed so that the rolled strip running out of its roll gap can have a maximum thickness of approximately 12 mm.

Behind the roll stand 3 of the roll stand groups 1 to 3 of the hot strip tandem mill formed from the roll stands 1, 2 and 3 there is also a flatness measuring device 10 '. Only one flatness measuring device 11 and 12 is provided behind each further roll stand 4 and 5 of the hot strip tandem mill.

Each of the profile measuring devices 8, 9 and 10 works together with a profile controller 13, 14 and 15, while the flatness measuring devices 10 ', 11 and 12 are each assigned a flatness controller 15', 16 and 17.

The strip profile can be scanned on each of the rolled strips 7 emerging from the rolled rolls 1, 2 and 3 via the profile measuring devices 8, 9 and 10, the resulting measurement values being supplied as actual values to the profile regulators 13, 14 and 15 and with the target values stored therein can be compared, which correspond to the optimal strip profile in the area of the respective roll stand 1, 2 and 3. The difference values resulting from the respective comparison are given as manipulated values on belt profile actuators of stands 1, 2 and 3. The belt profile actuators can act on the roll bending, the roll adjustment, the roll limitation, the roll swiveling, the zone cooling of the roll bales as well as the axial work roll, intermediate roll (e.g. with six-high stands) and back-up roll displacement, advantageously in this way, that the available control options for the belt profile can be used either individually or with several or all at the same time. A so-called CVC roll stand (DE-PS-3 038 865) can also be used as a means of influencing the strip profile. The belt profile actuators can also cause the CVC rollers to move axially. It is important that the rolled strip 7 emerging from the roll stand 3 has an optimal strip profile, even if it slightly exceeds the "critical thickness" of approximately 12 mm. In addition, the rolling strip 7 emerging from the roll stand 3 must have a minimum of strip flatness, at least when it slightly exceeds the "critical thickness" of 12 mm when it emerges from the roll gap. In order to achieve this, the possibility - already indicated - is provided of also assigning a strip flatness control 10 ', 15' to the last roll stand 3 which can still be operated with strip profiles 10, 15 and which corresponds to the strip flatness controls 11, 16, 12, 17 of the roll stands 4 and 5 corresponds. The arrangement is such that, depending on the decrease or stitch distribution provided in the hot strip tandem line according to the respective pass schedule, the roll stand 3 either with strip profile control 10.15 according to FIG. 2 or with strip flatness control 10 ', 15' according to FIG 3 can be operated.

The mill stands 4 and 5 of the hot strip tandem mill are operated exclusively with flatness control 11, 16 and 12, 17, respectively, so that the hot strip 7 that runs out of the hot strip tandem mill and is taken up by the take-up reel 6 has a finished thickness that is both over 3 mm (FIG. 2) and can also be less than 3 mm (Fig. 3), in addition to an optimal band profile also has a considerable flatness quality.

In Figure 1 of the drawing, the overall structure of the five-stand hot strip tandem mill is shown, wherein it can be seen that the third roll stand 3 has both a profile control 10, 15, and is equipped with a flatness control 10 ', 15'.

The rolling stand 3 can thus be driven either with profile control 10, 15 or with flatness control 10 ', 15'.

A comparison of FIGS. 2 and 3 makes it clear that the boundary from influencing the profile to influencing the flatness of the hot strip either between the third roll stand 3 and the fourth roll stand 4 (FIG. 2) or between the second roll stand 2 and the third roll stand (FIG. 3 ) may lie. Therefore, according to FIG. 1, the third roll stand 3 is assigned on the one hand the profile controller 15 and on the other hand the flatness controller 15 ', the profile controller 15 on the profile measuring device 10 and the flatness controller 15' on the flatness measuring device 10 'between the third roll stand 3 and the fourth roll stand 4 can address.

It can be seen from FIG. 2 that a hot strip with an initial thickness of 38 mm is to be rolled down to a final thickness of more than 8 mm in the hot strip tandem mill. The hot strip 7 behind the first roll stand 1 still has a thickness of 24.7 mm and behind the roll stand 2 its thickness is still 16.5 mm. Behind the roll stand 3, the hot strip 7 with 12.3 mm has already reached the "critical thickness" of about 12 mm, while behind the fourth roll stand 4 a thickness of 9.8 mm and behind the fifth roll stand 5 a thickness of 8.14 mm is present.

In the rolling process according to FIG. 2, not only do the two roll stands 1 and 2 work with profile control 8.13 and 9.14, but also the roll stand 3 is operated there with profile control 10, 15, so that only the roll stands 4 and 5 work with flatness control.

Of course, the profile control 10, 15 for the roll stand 3 can optionally work by reaching through to the roll stands 1 and 2, with such a reach-through control the own profile control 8.13 or 9.14 of the roll stands 1 and 2 could be omitted. The profile measuring device 10 for the roll stand 3 can also be arranged behind the stand 4 or 5, for example. This also applies if a flatness correction is carried out in stands 4 and 5.

It can be seen from FIG. 3 that a - thinner - hot strip 7 with an initial thickness of 30 mm should be rolled down to a - also thinner - final thickness of 2.5 mm. In this case, the hot strip behind the first roll stand 1 has a thickness of 15.3 mm, while behind the second roll stand 2 it already falls below the —critical thickness “of approximately 12 mm, namely 8.3 mm thick. The hot strip 7 runs out of the third roll stand 3 with a thickness of 5.0 mm, while it has the thickness of 3.4 mm behind the fourth roll stand 4 and the final thickness of 2.5 mm behind the fifth roll stand 5.

In the rolling according to FIG. 3, only the two roll stands 1 and 2 work with profile control 8.13 and 9.14, while the roll stand 3 is already set up for operation with flatness control 10 ', 15' and also the roll stands 4 and 5 with flatness control 11, 16 and 17 work.

During the subsequent rolling out of the hot strip in a cold strip tandem mill, this can be run essentially without strip profile control, but with strip flatness control, in order to obtain a finished rolled strip with high strip profile and strip flatness quality with a thickness of, for example, 0.3 mm.

It is not absolutely necessary to carry out the strip profile control in all stands of the hot strip tandem mill that roll in the area above the "critical thickness". It is sufficient to equip only one scaffold with the profile control or to have the profile control only effective in one scaffold. It is only essential that the profile control takes place above the "critical thickness".

Finally, it should also be mentioned that according to the method according to the invention for producing rolled strip with high strip profile and flatness, it is possible to use work rolls with bale diameters, as are common today for the design of hot strip tandem lines and also cold strip tandem lines.

The end section of a hot strip tandem mill shown in FIG. 4, which here comprises, for example, seven stands, consists of stands 62 with the order numbers F1-F7. All scaffolding 62 are equipped with devices and adjusting means for adjustment, thickness control, balancing and bending which are not part of the invention. Each stand 62 has two support rollers 60 and two work rollers 61 in a known manner. The adjusting devices for balancing and bending the work rolls 61 are accommodated in blocks 63 which are fixed to the stand, as seen in the rolling direction, in front of and behind the work rolls 61, arranged in the roll stand 62, while the thickness control is effected via the adjusting device 64.

Each stand 62 of the series F1-F7 has control and regulating devices 21, 22, 23, 24, 25, 26 and 27 for issuing the control commands for balancing and bending the work rolls 61, and control and regulating devices 31, 32, 33, 34 , 35, 36 and 37 for issuing the control commands for shifting the work rolls 61 in the axial direction and control and regulating devices 41, 42, 43, 44, 45, 46 and 47 for issuing the control commands for setting and regulating the thickness of the roll set 60, 61 assigned.

A computer 40, which calculates and monitors the control values for the entire road, is arranged in a known manner above and above the control and regulating devices for employment and thickness control 41-47 via a common control rail.

The control and regulating devices 51, 52, 53, 54, 55, 56 and 57, which are assigned to the respective rolling stands of the series F1-F7 as independent devices, influence for the profile control, the control devices already mentioned for balancing and bending as well as the adjustment and thickness control, ie the control and regulating device 51, the control and regulating devices 21 and 41, etc. The control and regulation is carried out according to a model specification (target value) of the profile , which is given to the computers 51-57 by the computer 50 via a common setpoint rail.

Behind the last stand F7 of the road, in addition to checking the thickness of the strip by means of a thickness measuring device 48, which is directly connected to the control and regulating devices for employment and thickness 41-47, the rolled profile of the strip with the profile measuring device 58 and its flatness checked with a flatness measuring device 38. The profile measuring device 58 forwards the determined measurement result to the profile computer 50, which compares the actually rolled profile with the specified profile model and, if necessary, forwards corresponding correction instructions for conversion into control commands for the roll stands to the independent control and regulating devices 51-57. The measurement result determined by the flatness measuring device 38 is fed to the flatness computer 30, which, if necessary, passes on corresponding correction commands to the control and regulating device 57 for the rolled profile assigned to the last stand F7, which are converted into control commands in the control and regulating devices 27 and 47 for Balancing and bending as well as adjustment and thickness control in this (last scaffold) is caused. The computers 40, 50 and 30 are in turn connected to a process computer 70 which, in a known manner, can handle the large number of data which is being passed through and determined, such as thickness, width, weight, temperature, strength and profile, and the decreases, speeds and forces which occur during rolling, and furthermore compares the roll diameter and flattening as actual values with empirical target values and, if necessary, forwards corresponding correction instructions to the computers 40, 50 and 30.

It can also with this roller mill where the rolled strip has reached the range of the critical thickness mentioned (KD), here z. B. behind the third frame F3, a profile measuring device 59 can be arranged, which is connected either alone or in addition to the already mentioned profile measuring device 58 behind the last frame F7 to the profile computer 50. If only the profile measuring device 59 is arranged behind the third stand F3, then there is a shortening and thus a more dynamic behavior of the control loop, as well as the possibility of making minor possible corrections in the stands F4-F7 following the stand F3. If, in such an arrangement, the profile of the rolled strip is additionally measured again, as described, by a profile measuring device arranged behind the last stand F7 of the street, then a comparison of the two measuring results of the profile measuring device 59 and the profile measuring device 58 also enables conclusions to be drawn about the state of the Pull the roll stands yourself, since a comparison of the actual profiles determined by the two profile measuring devices with the specified model profile can have the result that the model profile can no longer be reached from a control point of view and the causes for this can lie in the road itself (roller wear, irregular wear, etc. ).

As can be seen from the pass schedule according to FIG. 5, when a finished strip of 2 mm strip thickness (hatched) or a finished strip of 4 mm (not hatched) is rolled out, the critical thickness (KD) is already undershot behind the stand F2 or F3.

Fig. 6 shows that when such finished strips are rolled out, the cross-flow of the material (spreading) in the first two stands F1 and F2 is very large, then already decreases in stand F3, and that only in stand F4, especially in stands F5 to F7 minor corrections that do not significantly influence the profile are still possible.

7 shows the manipulated amounts required for profile correction in the individual stands, as can be calculated from the formula already explained.

Overall, it can be seen that the critical thickness (KD) for stand F3 (unfavorable) is undershot, the adjustment range of the bend for both stands F5 - F7 is sufficient and the adjustment range of the work roll bending system in unfavorable cases for stand F4 is not sufficient. Here the bending system is supported by another actuator, e.g. B. Axial displacement of CVC rolls.

To support the bending system (returning the bending force to the center of the adjustment range if possible), the cheapest (or the cheapest combination among the known adjustment means) must be selected taking into account the required adjustment range.

In practice, the adjustment of the roll gap in the stand can be slightly corrected in order to take advantage of the material flow that is still present at right angles to the rolling direction, even with small strip thicknesses.

Claims (8)

1. Method for the production of rolled strip, in which this is conducted through a tandem hot-strip roll train and in that case during the rolling operation subjected to a state regulation which comprises a strip profile regulation and - in at least the last roll stand - a strip profile regulation and a planarity regulation originating from a planarity measurement of the rolled strip issuing from the last stand of the tandem hot-strip roll train, characterised by the following steps:

a) determining and filing the critical thickness of the rolled strip to be rolled, below which thickness no further substantial deformation of the rolled strip in direction of the width is attainable,

b) rolling of this rolled strip, the thickness of which is substantially greater than the determined critical thickness, successively in a first and a second rolling stage, in each of which the rolled strip is conducted through at least one roll gap forming this,

c) reducing the thickness of the rolled strip in the first rolling stage to substantially the determined critical thickness,

d) checking the reduction in the thickness of the rolled strip in this rolling stage by measurement of the thickness behind the first rolling stage and adjusting at least the last roll gap in this first rolling stage by reason of the result of the measurement of the thickness,

e) measuring the planarity of the rolled strip in the second rolling stage at at least one place in the course of this rolling stage and

f) reducing the thickness of the rolled strip in this second rolling stage to a thickness lying below the critical thickness by reason of the measurement of the planarity of the rolled strip.

2. Method according to claim 1, characterised thereby, that the height of the last roll gap in the first rolling stage is set in accordance with the comparison of the result of a measurement of the thickness of the rolled strip behind the first rolling stage with a given empirical standard value.

3. Method according to claim 1, characterised thereby, that the result of the measurement of the planarity of the rolled strip is compared with a given empirical standard value.

4. Method according to claim 1, characterised thereby, that the magnitude of the reduction in the thickness of the rolled strip in the first rolling stage is determined and regulated by reason of measurements of the thickness of the rolled strip within the second rolling stage.

5. Tandem hot-strip roll train for the production of rolled strip, in which this is during the rolling operation subjected to a state regulation which comprises a strip profile regulation and - in the last roll stand - a strip profile regulation and a planarity regulation originating from a planarity measurement of the rolled strip issuing from the last stand of the tandem hot-strip roll train, characterised thereby, that in a group (1 to 3) of roll stands (1, 2 and 3) with a roll gap height equal to or greater than the critical thickness (KD), below which thickness no further substantial deformation of the rolled strip in direction of the width is attainable, profile-measuring devices (8, 9,10) and profile regulators (13,14,15) are allocated, which stand in connection with strip profile setting members at the roll stands (1, 2 and 3), whilst the last roll stand (3) of this group (1, 2 and 3) and all remaining roll stands (4 and 5) display planarity-measuring devices (10', 11, 12) and planarity regulators (15', 16, 17), which are connected with strip planarity setting members, and that the last roll stand (3) of the group (1 to 3) is in that case influenceable selectably either by profile-measuring devices (10) and profile regulators (15) or by planarity-measuring devices (10') and planarity regulatory (15').

6. Tandem hot-strip roll train according to claim 5, characterised thereby, that either the profile-measuring devices (8, 9, 10) or the planarity-measuring devices (10', 11, 12) are arranged downstream of the roll gap, which is to be regulated, of the roll stands (1, 2 and 3 or 3, 4 and 5).

7. Tandem hot-strip roll train for the production of rolled strip, in which this is during the rolling operation subjected to a state regulation which comprises a strip profileregulation and - in the last roll stand - a strip profile regulation and a planarity regulation originating from a planarity measurement of the rolled strip issuing from the last stand of the tandem hot-strip roll train, characterised thereby, the tandem hot-strip roll train displays n roll stands (F1 to F7) and a planarity-measuring device (38) and a profile-measuring device (58) downstream thereof are arranged downstream of the nth roll stand (F7), of which the planarity-measuring device (38) is connected with a planarity computer (30), the output signals of which influence devices (27, 37, 47) for the setting-on and bending of the rolls of the n^th roll stand (F7) the profile-measuring device (58) is connected with a profile computer (50), the output signals of which influence devices (27, 37, 47) for the setting-on and bending of this roll stand (F7) and the preceding (n-1 )^th to (_n-3)th or (n-4)th roll stands (F6 - F4 or F3) and planarity computer (30) as well as profile computer (50) are connected with a process computer (70), which displays comparison devices and fixed value stores and issues correction instructions.

8. Tandem hot-strip roll train according to one or more of the claims 5 to 7, characterised thereby, that the strip profile setting members, the bending of the rolls, the setting-on of the rolls, the offset of the rolls, the pivotation of the rolls, the zonal cooling of the roll barrels as well as the axial displacement of the working rolls, the intermediate rolls and of the backing rolls in the first roll stands are influenceable individually and/or simultaneously.

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