EP2563533B1 - Reduction of the strip tension of rolling stock between two rolling units to a minimum - Google Patents

Description

Technical area

The invention relates to a method and a device for minimizing the strip tension of a rolling stock, wherein the rolling stock is transported by means of a roller table between two roller units in engagement with the rolling stock.

• Transportieren des Walzguts mittels eines Rollgangs zwischen zwei in Eingriff mit dem Walzgut befindlichen Walzeinheiten, wobei in einer Senke, die in einem Streckenabschnitt des Rollgangs zwischen den beiden Walzeinheiten angeordnet ist, eine Walzgutschlinge ausgebildet wird;
• Erfassen eines Messwerts einer Schlingentiefe der Walzgutschlinge mittels einer Messeinrichtung; und
• Regeln der Hauptantriebe der Walzeinheiten mittels einer Regeleinrichtung unter Berücksichtigung des Messwerts der Schlingentiefe, sodass der Bandzug minimiert wird.

Specifically, the invention relates to a method for minimizing the strip tension of a rolling stock, comprising the following steps:

• Transporting of the rolling stock by means of a roller table between two rolling units in engagement with the rolling stock, wherein in a sink, which is arranged in a stretch section of the roller table between the two rolling units, a Walzgutschlinge is formed;
• Detecting a measured value of a loop depth of the rolling stock loop by means of a measuring device; and
• Controlling the main drives of the rolling units by means of a control device taking into account the measured value of the loop depth, so that the strip tension is minimized.

• einen Rollgang, der das Walzgut zwischen zwei in Eingriff mit dem Walzgut befindlichen Walzeinheiten transportiert;
• eine Regeleinrichtung, die die Walzeinheiten so regelt, dass sich in einer Senke, welche in einem Streckenabschnitt des Rollgangs vorgesehen ist, eine Walzgutschlinge ausbildet, deren Schlingentiefe im Wesentlichen der freien Durchbiegung des Walzgutes in diesem Streckenabschnitt entspricht; und
• eine Messeinrichtung zur Erfassung einer Walzgutschlinge, wobei der Messwert der Messeinrichtung der Regeleinrichtung (10) zuleitbar und bei der Regelung der Hauptantriebe der Walzeinheit oder der Treiber verwendbar ist.

Furthermore, the invention relates to a device for minimizing the strip tension of a rolling stock, comprising:

• a roller table, which transports the rolling stock between two rolling units engaged with the rolling stock;
• a control device that controls the rolling units so that in a depression, which is provided in a stretch section of the roller table, a Walzgutschlinge forms whose loop depth substantially corresponds to the free deflection of the rolling stock in this stretch; and
• a measuring device for detecting a rolling stock loop, wherein the measured value of the measuring device of the control device (10) feedable and usable in the control of the main drives of the rolling unit or the driver.

State of the art

In the production of a hot strip, rolling is usually carried out in rolling mills with a plurality of separate rolling units and rolling operations. The rolling stock may e.g. come from a separate continuous casting device. Each rolling process can take place in individual reversing stands, or take place in several rolling units, which can each be composed of several rolling stands. Usually, the rolls of these stands are driven by drives whose speed is set by a higher-level control device.

The rolling stock may also be a hot strip, which is produced in a continuous casting process in a cast-rolling composite plant from an upstream, in particular inline continuously arranged continuous casting machine.

In such rolling plants, the problem arises that it is difficult to accurately differentiate between the drive power required for the deformation of the rolling stock and the driving power required for applying a strip tension and for conveying the hot strip. Therefore, a rolling stand can not be operated as a belt tension controlled drive element. It must be decoupled the mass flow between successive Walzstaffeln.

In known systems for the production of strip steel (conventional hot strip mills), this decoupling between two rolling scales can be realized so that the supplied material is divided into slabs and the distances between the individual rolling scales (Vorgerüste and finishing mill) are chosen so that never both Rollstaffeln at the same time are engaged on the same preamble. However, this results in a large length of the system, which causes high investment costs and thermal losses. Alternatively, the split into pieces pre-strip can also be wound up in specially designed facilities and handled again, but this is also associated with a corresponding effort.

It is known that for the coupling of two successive rolling units engaged in a minimum Zugregelung can be done either by a direct tension control or by a loop control. In both cases a minimum belt tension is always required to control. However, this at least necessary strip tension, which is necessary for regulation and / or available from tension measurement quantities, can exceed the yield point of the hot rolled material to be processed. Even a partially or completely free hanging material loop forms an additional Bandzugkomponente by its own weight. If the sum of the strip tension components locally exceeds the yield point of the rolling stock to be processed, the quality and yield reduction of the end product produced are unavoidable. In particular, constrictions over the width of the rolling stock and resulting reworking on the end product lead to a significant loss of the ratio of material used and discharged material.

• Transportieren des Walzguts mittels eines Rollgangs zwischen zwei in Eingriff mit dem Walzgut befindlichen Walzeinheiten, wobei in einer Senke, die in einem Streckenabschnitt des Rollgangs zwischen den beiden Walzeinheiten angeordnet ist, eine freihängende Walzgutschlinge ausgebildet wird;
• Erfassen eines Messwerts einer Schlingentiefe der Walzgutschlinge mittels einer Messeinrichtung; und
• Regeln der Hauptantriebe der Walzeinheiten mittels einer Regeleinrichtung unter Berücksichtigung des Messwerts der Schlingentiefe, sodass der Bandzug minimiert wird.

From the JP 6234613 A already a generic device and a method for minimizing the strip tension of a rod-shaped long product is known with the following steps:

• Transporting the rolling stock by means of a roller table between two rolling units in engagement with the rolling stock, wherein in a sink, which is arranged in a stretch section of the roller table between the two rolling units, a free-hanging Walzgutschlinge is formed;
• Detecting a measured value of a loop depth of the rolling stock loop by means of a measuring device; and
• Controlling the main drives of the rolling units by means of a control device taking into account the measured value of the loop depth, so that the strip tension is minimized.

Due to the free-hanging rolling stock loop, however, a not insignificant strip tension is introduced into the rolling stock, which is particularly useful in hot long products, as e.g. arise in the continuous production of strip steel in a cast-rolling composite plant, which can lead to constrictions and / or cracks in the belt. As the strip tension can be further reduced or how the loop depth, in particular dynamically for different operating conditions, can be adjusted, does not emerge from the Scriptures.

To avoid the disadvantages of the above-mentioned prior art, but also for continuous strip production plants in a semi-endless or endless multi-stage hot rolling process in which Vorgerüststraße and finishing line are connected by a long pre-strip, is a satisfactory solution of decoupling two consecutive rolling stages not yet known.

Illustrations of the invention

The invention is based on the object to provide a method and an apparatus with which a minimization to complete avoidance of the strip tension of a rolling stock between two successive rolling units is possible in a simple manner.

This object is achieved for a method having the features of patent claim 1 and for a device having the features of patent claim 10.

The invention is based on the finding that a minimization or cancellation of the tensile forces acting on the rolling stock can advantageously be achieved by providing a depression in the conveying path between two successive rolling units controlled by a regulating device along a section of track. In this depression, a rolling stock loop is formed whose loop depth is kept by the control device to a value which corresponds to the free deflection of the rolling stock in this section. The deflection depends essentially on the material, the cross-sectional shape and the temperature of the rolling stock. According to the invention, it has been recognized that it is necessary, in particular, to calculate the nominal value of the loop depth as a function of the material (eg the chemical composition), the cross-sectional shape (eg the actually occurring thickness and width of the rolling stock) and the temperature in real time and the control as a reference variable to underlie. Furthermore, it is necessary, the rolling stock loop at least outside a central portion associated with the apex of Walzgutschlinge is to be supported, so that the effective longitudinal extent of the rolling stock loop and thus the tensile stresses in the rolling stock can be reduced to a value of almost zero.

In a particularly preferred embodiment of the method, the product formed from the length of the rolling stock loop, the loop depth and the thickness of the pre-strip is maintained at a value between 2 * 10 ⁵ mm ³ and 6 * 10 ⁷ mm ³ .

A preferred embodiment of the method may be such that the transport device is formed by a roller table, which simultaneously forms a support for the rolling stock loop. In this support, the rolling stock loop is supported at least at one point of a support line, which is predetermined by the curvature line of the free deflection of the rolling stock in the track section to be bridged. The individual support elements are below the main transport line (pass line) of the rolling stock. They are preferably arranged on a support line which runs parallel or equidistant to the elastic line of the free deflection, that is, it is just as strongly curved or bent. This has the consequence that the rolling stock enters this reduction due to its own weight and it comes to a virtually draft-free "embedding" in this sink. This ensures that applied in a rolling mill, even with a continuous mode of production on the rolled strip no unacceptably high tensile stress. During production, the width tolerance and the cross-sectional tolerance can be better met. It no longer comes to unwanted constrictions or even a crack of the rolling stock. In an exemplary application in a cast-rolling composite plant, the casting process is less exposed to strong negative influences from the rolling process.

In a particularly preferred embodiment of the method, the main drives of the rolling units and optionally also the drivers are controlled such that the vertex of the rolling stock loop is kept at a distance of 10 mm to 50 mm by a roller assigned to the vertex of the roller table. Very particularly preferred is a distance between 15 mm and 30 mm.

A very particularly favorable variant of the method can be such that in the roller table each axis of a roller is arranged at an equal distance from the support line. The rolling stock loop is thus virtually draft-free in this "roller bed".

It may be favorable if individual rollers of the roller table by means of a lifting and lowering device or an entire roller table segment by means of a drive device is height adjustable. This facilitates the threading of the tape head. If the individual roles of a roller table by separate drives in its vertical position are displaced, the support line can be adapted very well to bending mechanical properties of the rolling stock. The strip tension is nearly zero both in the sink and in the immediate vicinity of upstream and downstream. It hardly comes to disturbing Zug- and mass flow fluctuations from the rolling mill in the casting plant. Depending on the material properties, it may be advantageous if the rolled material loop is pressed downwards at the inlet and / or at the outlet to the sink by means of a pressure roller.

It is advantageous if the control device specifies a shape of the "roller table loop" in which only a very short freely hanging loop section is formed. This ensures that it hardly comes to a disturbing weight of the sagging loop. In the rolling mill then the strip tension upstream, downstream and in the "roller table loop" is almost zero.

In order to detect the loop depth of the rolling stock loop, various measuring devices can be used, for example contactless or contacting measuring devices known per se. The measured value of the loop depth is fed to the control device. In the control device, a model and control algorithm is implemented. By taking into account the loop depth, the control device can determine appropriate corrections for the rolling speed as a function of the rolling process and predefine the feeding and / or discharging rolling units. Fluctuations in the mass flow at the entrance or at the exit of the roller table can be detected promptly, preferably in real time, by a change in the loop depth, and thus can be compensated directly.

The object stated at the outset is also achieved by a generic device in which, according to the invention, the roller table forms a support for the rolled material loop in at least one off-center section of the track section, the support line of the roller table corresponding to the free deflection in this section of the chain line.

An advantageous embodiment can be constructed so that the transport device is a roller table, which forms a support of the rolling stock loop in the sink. The sink is formed by an arrangement of rollers of the roller table, wherein seen in the transport direction in the stile section rollers with an increasingly smaller diameter and then rollers are arranged with an increasingly larger diameter.

Another advantageous embodiment of the invention may be constructed so that the sink of the transport means is defined by two adjoining sections of the transport means, e.g. two pivotable roller table segments, is formed. The construction may be such that the roller table sections are each pivotable about a pivot axis which is located at an end remote from the impact point of the segments. In this way, a recess in the horizontal transport plane of the conveyor can also be produced, in which a loop-like design of the rolling stock is possible. The support is preferably again on the support line and relieves the loop of its own weight.

In practical application, it has proved to be advantageous if by means of the control device, the vertex of the rolling stock loop is held by an opposing roller in the lowered roller portion at a distance of less than 50 mm.

Brief description of the drawings

Figur 1

ein Ausführungsbeispiel der Erfindung, mit einer frei hängenden Walzgutschlinge;

Figur 2

ein Ausführungsbeispiel der Erfindung, wobei die Walzgutschlinge in einem Rollenbett eingebettet liegt;

Figur 3

die Anordnung gemäß Figur 2, wobei nur die zulaufende Walzeinheit mit dem Walzgut in Eingriff ist;

Figur 4

die Anordnung gemäß Figur 2, wobei nur die ablaufende Walzeinheit mit dem Walzgut in Eingriff ist;

Figur 5

die Anordnung gemäß Figur 2, wobei sowohl die zulaufende als auch die ablaufende Walzeinheit jeweils mit einem Walzgut in Eingriff ist;

Figur 6

ein weiteres Ausführungsbeispiel der Erfindung, bei dem die Senke durch Rollen gebildet wird, deren Durchmesser in Transportrichtung gesehen zunächst ab und dann wieder zunimmt;

Figur 7

eine weitere Ausführungsform mit einem vertikal absenkbaren Rollensegment;

Figur 8

eine weitere Ausführungsform mit zwei schwenkbaren Rollgangsegmenten;

Figur 9

ein Ausführungsbeispiel der Erfindung, bei der die Tiefe der Schlinge in der Senke mittels einer Abstandsmesseinrichtung erfasst wird;

Figur 10

ein Ausführungsbeispiel der Erfindung, bei der die Tiefe der Schlinge in der Senke mittels einer Kameraeinrichtung erfasst wird;

Figur 11

ein Ausführungsbeispiel der Erfindung, bei der die Tiefe der Schlinge in der Senke mittels einer berührenden Messeinrichtung in Verbindung mit einer Drehwinkelmessung und/oder Positionsmessung erfasst wird;

Figur 12

ein Blockschaltbild, welches die Einbindung der Regeleinrichtung in eine übergeordnete Produktionsplanung darstellt;

Figur 13

ein Ausführungsbeispiel in welchem die Walzgutschlinge von Rollen eines Rollgangs gestützt wird, welche jeweils mittels einer zugeordneten Antriebsvorrichtung höhenverstellbar sind.

To further explain the invention, reference is made in the following part of the description to the drawings in which further advantageous embodiments, details and further developments of the invention can be found.
It shows:

FIG. 1

an embodiment of the invention, with a free-hanging Walzgutschlinge;

FIG. 2

an embodiment of the invention, wherein the rolling stock loop is embedded in a roller bed;

FIG. 3

the arrangement according to FIG. 2 wherein only the incoming rolling unit is engaged with the rolling stock;

FIG. 4

the arrangement according to FIG. 2 wherein only the running roller unit is engaged with the rolling stock;

FIG. 5

the arrangement according to FIG. 2 wherein both the incoming and outgoing rolling units are each engaged with a rolling stock;

FIG. 6

a further embodiment of the invention, in which the sink is formed by rollers whose diameter seen in the transport direction initially decreases and then increases again;

FIG. 7

a further embodiment with a vertically lowerable roller segment;

FIG. 8

a further embodiment with two pivotable roller table segments;

FIG. 9

an embodiment of the invention, wherein the depth of the loop is detected in the sink by means of a distance measuring device;

FIG. 10

an embodiment of the invention, wherein the depth of the loop is detected in the sink by means of a camera device;

FIG. 11

An embodiment of the invention, in which the depth of the loop is detected in the sink by means of a contacting measuring device in conjunction with a rotation angle measurement and / or position measurement;

FIG. 12

a block diagram illustrating the integration of the control device in a higher-level production planning;

FIG. 13

an embodiment in which the rolling stock loop is supported by rollers of a roller table, which are each height adjustable by means of an associated drive device.

Embodiment of the invention

The principle underlying the invention will initially be described in the FIG. 1 illustrated sketch explained. In FIG. 1 is a feeding roller unit 2 and a discharge roller unit 25 to see, each with a rolling stock 1 are engaged. The control of the rolling units 2, 25 is carried out by a control device 10. Between the two roller units 2.25, a transport or conveyor 5 is shown, which is designed as a roller table. This roller table 5 has a track section 27, in which a lowerable roller table segment 30 is drawn. When introducing the rolling stock 1, this roller table segment 30 is flush with the transport or conveying plane. During rolling, in which both the roller unit 2 and the roller unit 25 with the Walzgut 1 is engaged, for the purpose of decoupling of the rolling units 2, 25, the roller table segment 30 is lowered down, so that in the sink 26 a rolling stock loop 6 is formed. As explained in more detail below, according to the invention, the loop depth 18 of this rolled material loop 6 is controlled so that it corresponds to the free deflection in the section 27. Under free deflection is to be understood as the deflection of a both sides freely cut portion of the rolling stock 1, which rests each end without friction.

The FIG. 2 also shows a transport sink between two located in engagement with the rolling stock 1 rolling units 2, 25. In contrast to FIG. 1 Here, the depression 26 is designed so that the rolling stock loop 6 is supported by the rollers. The support line again corresponds to the free deflection. This deflection in the section 27 is essentially dependent on the thickness, the temperature and the material of the rolled strip 1. In the embodiments discussed here, the thickness of the rolled strip 1 is approximately between 8 mm and 20 mm.

FIG. 3 and FIG. 4 each show an uncoupled discrete operation of the rolling units 2, 25, wherein in FIG. 3 the rolled strip 1 enters the transport sink 26 and in FIG. 4 leave them again.

FIG. 5 shows the uncoupled simultaneous operation of the rolling units 2, 25, wherein a leaking rolled strip is engaged with the rolling unit 25, an incoming rolled strip with the feeding roller unit 2 is engaged.

FIG. 6 shows another possible embodiment of the invention. The transport depression 26 is formed by a section 27 is formed by rollers whose diameter initially decreases in the transport direction, then increases again. This creates a depression in the conveying plane. The rolling stock loop settles in this recess and is supported from below. The support is on a support line, which is defined by the line connecting the points of contact of the rollers in this section. According to the support line is designed in accordance with the bending stiffness of the rolled strip.

The FIG. 7 shows another possible embodiment of the device according to the invention. Here is a roller table segment 30 can be lowered by means of an adjusting device 29, not shown here with respect to the conveying plane. The lowering can be done so far that a free hanging loop arises, or - as in FIG. 7 drawn -, only to the extent that the apex 24 of the rolling stock 6 experiences a support.

In the FIG. 8 a further embodiment of the device according to the invention is outlined. The recess in the transport plane is formed here by sections 31 of the roller table, which are each pivotable about the axes 32 by means of the adjusting device 29 downwards.

The measuring device 7 for measuring the loop depth 18 can, for example, by means of a distance measurement ( FIG. 9 ), a camera system ( FIG. 10 ) or else by means of a roll touching the rolled strip from above in conjunction with a rotation angle measurement or position measurement ( FIG. 11 ). Advantageously, the contacting roller can be formed simultaneously in the form of a depression roller, which in addition to the measurement of the loop depth 18 at the same time contributes to the fact that the loop down in the depression is pressed. It goes without saying that the measurement methods shown here can also be arranged below the rolled strip 1 or on the side.

In the FIG. 12 a block diagram is shown, in which the integration of the control device 10 is shown in a higher-level production planning with background memories shown symbolically. Large distances between two successive, to be decoupled roller units, as well as any interim rolling mill processing devices, such as belt division devices, belt stretchers and / or Banderhitzungsvorrichtung, could make the installation of appropriate sets of propulsion necessary. This is in FIG. 12 drawn. The illustrated drive roller sets are designed such that the inlet-side drive roller sets align the rolling stock in the direction of the feeding roller unit, the outlet-side drive roller sets align the rolling stock in the direction of discharging roller units. In FIG. 12 a typical arrangement is sketched with a band heater, in which determines the portion of the rolling stock with the lowest tensile and / or bending stiffness, in the case of hot strip, the hottest part, the optimal location and design of Tränsportsenke.

The FIG. 13 shows an embodiment of the device according to the invention, in which the vertical arrangement of the rollers of the transport device is selected so that the points of contact between rolling stock and roller respectively lie on the support line, which corresponds to the line of curvature, also called chain line, the free deflection of the rolling stock in the section 27 , In FIG. 13 show two rolling scales, a relay roughing 2 and a scale finishing mills 25, the rolling speed of the control device 10th is given. The rolling stock 1 is a hot strip. The arrow 22 indicates the direction of the mass flow. When the rolled stock 1 leaves the last stand of the roughing stand 2 at a high temperature, usually more than 1100 ° C., it is particularly susceptible to tensile stress. Too high a strip tension can lead to unwanted constrictions in pre-strips in a hot strip, whereby the width tolerance can no longer be met. In extreme cases, this pre-strip can also be torn or even separated during the manufacturing process. As already explained, the speed control of the two rolling units or rolling stages 2, 25 must therefore be decoupled from one another, since it is not possible to operate a rolling stand at the same time as band-tensioned elements. "Speedmaster" is the casting machine (in FIG. 13 not shown in detail), which lies upstream of the roller unit 2.

The decoupling of the mass flow is achieved by the sink 26 according to the invention, which, in contrast to a loop in a strip accumulator, has a much smaller depth. In this depression 26, a so-called "roller table loop" is formed, that is, the hot strip is guided as long as possible supporting. Only in a short section 11 in the middle can occur in the regulation of the mass flow to form a gravitational loop. According to the invention, it has been recognized that virtually no strip tension acts on the rolling stock 1 through such a "roller table loop".

In FIG. 13 For example, on the exit plane 19 of the last rolling stand of the roughing stand 2, a rolling table 4 conveys the rolled strip 1 to a first driver 3. After the driver 3, the rolling stock 1 enters the inventively designed Roller table 5. This roller table 5 is not flat, but lowered with respect to the exit plane 19 of the roughing stands 2 down into a depression 26. The lowering of the rolling stock 1 may be simply caused by gravity, but may also be enforced by a depressing roller, especially in thick rolling. After lowering the hot strip 1 in the roller table 5 is again high. The rolling stock loop 6 has a continuous curvature. The rolling stock 1 emerging from the depression 26 at the end of the roller table 5 passes in the further course to a second driver 8 which lies approximately on the entry plane 20 of a second roller table 12. Subsequently, the rolling stock 1 enters the finishing train 25 a.

When entering the finishing train 25, the hot strip 1 may still have a temperature of up to 1250 ° C. As already mentioned, this high temperature makes the hot strip 1 sensitive to tensile stress. The control device 10 ensures a decoupling of the speeds, so that in the roller table 5 almost band reference zero prevails.

The speed of the rollers of the drivers 3, 8 is precisely controlled by the control device 10 so that the stationary mass flow is kept constant, but temporary fluctuations are absorbed by the loop-shaped formation of the hot strip 1. The hot strip 1 is either on all rollers 9 of the roller table 5 touching, or is slightly lifted in a central region 11 of the sink 26 of the supporting roles by there is formed by speed control of the rolling mill main drives or the driver roller drives a gravitational loop.

Like from the FIG. 1 it can be seen, the axes of the rollers 9, each lying on a line parallel to the support line 23, are arranged symmetrically with respect to a perpendicular 15. This results in respect to the perpendicular 15 substantially symmetrical Walzgutschlinge 6. The support line 23 corresponds to the chain line of the free deflection.

The shape of the rolling stock loop 6 is detected in the example shown by means of a contactless measuring device 7. This is an optical detector here, but as stated above, it can also be designed differently. In this case, the detector 7 measures the loop depth 18 or the distance between the apex 24 of the rolled strip loop 6 and a roller 21 located opposite the apex 24. The measured value of the detector 7 is fed to the control device 10 via connecting lines 16. The control device 10 is also connected via connecting lines 16 to the rolling stands of the rolling scale 2 and the rolling stands of the finishing scale 25, and to the drivers 3, 8. It controls this drive unit so that the sheet of rolling stock loop 6 either completely flies on the rollers 9 of the roller table 5, or is slightly lifted off the underlying rollers 9 in the apex area. Particularly favorable is a distance of less than 30 mm. When the environment around the apex 24 of the loop 6 is lifted off the supporting rollers 9, a gravimetric loop part 11 is formed in the region 11 which is kept as short as possible by the control device 10. In other words, due to the sensitive regulation, the rolling stock loop 6 has almost touching contact with the rollers 9 over the entire conveying path. The regulating device 10 ensures that sections 13 and 14 are much larger in comparison to the middle section 11, thereby ensuring the desired Minimization of the strip tension between the rolling stands 21, 22 or between the drivers 3, 8.

As a result of the invention acts on the pre-strip 1 virtually only a very small membrane voltage. Thanks to the invention, in the continuous production of steel strip, an undesirable change in shape of the rolled strip 1, such as constrictions or even cracks, can be reliably prevented.

The vertical position of the rollers 9 in the roller table 5 can be fixed, or by an in FIG. 1 sketchily indicated, the respective rollers 9 associated drive device 32, separately (eg., A drive device per roller) can be adjusted.

If the weight of the pre-strip for gravity lowering in the roller table 5 is not sufficient (which may be the case with thick belts or slabs), can by a pressure acting from top to bottom pinch roller (in FIG. 1 not shown) the rolling stock are pressed into the recess of the roller loop pit.

Of particular advantage is the subject invention in fully continuous or endlessly operated plants (casting-rolling systems with endless belt production), as in this type of plant so far no possibility of satisfactory deceleration is known.

LIST OF REFERENCE NUMBERS

1

Rolling stock, hot strip

2

feeding roller unit, roughing

3

driver

4

Roller table at the exit of the roughing 2

5

Transport equipment, roller table

6

Rolled sling, roller table sling

7

measuring device

8th

driver

9

Rollers of the roller table 5

10

control device

11

middle range, gravitational loop

12

Rolling table at the entrance of the production scale 25

13

inlet section

14

exit section

15

vertical

16

electrical connection lines

17

distance

18

sling depth

19

outlet level

20

inlet plane

21

Roll, opposite to 24

22

Arrow (mass flow direction, transport direction)

23

support line

24

vertex

25

outlet side roller unit, finishing stands

26

Sink in roller table 5

27

Track section, length of the rolling stock loop

28

Rolling-measuring device

29

Actuator, lifting and lowering device

30

Roller segment

31

Roller segment

32

driving device

Claims (15)

1. Method for reducing the strip tension of rolling stock (1) to a minimum, comprising the following method steps:

   - transporting the rolling stock (1), by means of a roller table (5), between two rolling units (2, 25) which are in engagement with the rolling stock, wherein a rolling stock loop (6) is formed in a depression (26) arranged in a section (27) of the roller table (5) between the two rolling units (2, 25), and the rolling stock loop (6) is supported by the roller table (5) at least in one off-center portion (13, 14) of the section (27), wherein the supporting line (23) of the roller table (5) in this portion corresponds to the catenary curve of the free span;

   - detecting a measured value of a loop depth (18) of the rolling stock loop (6) by means of a measuring device (7) ;

   - calculating a desired value of the loop depth (18), in particular depending on the material, thickness and temperature of the rolling stock (1), such that the desired value corresponds substantially to the free span;

   - controlling the main drives and/or the gap adjustment of the rolling units (2, 25) by means of a control device (10) taking the desired value and the measured value of the loop depth (18) into consideration, such that the loop depth (18) corresponds as far as possible to the desired value.
2. Method according to Claim 1, characterized in that the product formed from the length (27) of the rolling stock loop (6), the loop depth (18) and the thickness of the roughed strip is selected to be between 2*10⁵ mm³ and 6*10⁷ mm³.
3. Method according to Claim 1 or 2, characterized in that the distance between an imaginary horizontal pass line and the vertex of the rolling stock loop (6) is between 10 mm and 100 mm, preferably between 15 mm and 60 mm.
4. Method according to Claim 1, characterized in that the main drives of the rolling units (2, 25) and/or drivers (3, 8), which may be present, are controlled in such a way that the vertex (24) of the rolling stock loop (6) is held at a distance of between 10 mm and 50 mm, preferably between 15 mm and 30 mm, from a roller of the roller table (5) which is assigned to the vertex (24).
5. Method according to Claim 4, characterized in that each axis of each roller (9) in the section (27) is arranged at an equidistant distance from the supporting line (23) in the roller table (5).
6. Method according to either of Claims 4 and 5, characterized in that the vertical arrangement of a roller (9) with respect to an entry plane (19) and/or with respect to an exit plane (20) is set by means of a drive apparatus (32).
7. Method according to one of Claims 4 to 6, characterized in that the form of the rolling stock loop (6) is predefined in such a way that a gravitation loop is formed in a region (11).
8. Method according to Claim 1, characterized in that the width of the rolling stock (1) before and/or within or after the section (27) is detected metrologically by means of a rolling stock measuring device and the measured value is forwarded to the control device (10).
9. Method according to Claim 8, characterized in that the control device (10) determines a control variable for controlling the rolling units (2, 25) from the fed measured value of the width of the rolling stock (1) and a desired roll gap.
10. Apparatus for reducing the strip tension of rolling stock (1) to a minimum, comprising:

    - a roller table (5), which transports the rolling stock (1) between two rolling units (2, 25) which are in engagement with the rolling stock (1);

    - a control device (10), which controls the rolling units (2, 25) in such a way that a rolling stock loop (6) is formed in a depression (26) provided in a section (27) of the roller table (5), the loop depth (18) of which rolling stock loop corresponds substantially to the free span of the rolling stock (1) in this section (27) ;

    - a measuring device (7) for detecting a rolling stock loop (6), wherein the measured value of the measuring device (7) can be forwarded to the control device (10) and can be used for controlling the main drives of the rolling unit (2, 25) or the drivers (3, 8), characterized
    in that the roller table (5) forms a support for the rolling stock loop (6) in at least one off-center portion (13, 14) of the section (27), wherein the supporting line (23) of the roller table (5) in this portion corresponds to the catenary curve of the free span.
11. Apparatus according to Claim 10, characterized in that the depression (26) is formed by an arrangement of rollers (9) of the roller table (5), wherein, as seen in the transporting direction, rollers (9) having a progressively decreasing diameter and then rollers (9) having a progressively increasing diameter are arranged in the section (27).
12. Apparatus according to Claim 10, characterized in that the depression (26) is formed by a section (27) in which a roller table segment (30) can be lowered vertically by means of a controlled drive unit (29).
13. Apparatus according to Claim 10, characterized in that the depression (26) is formed by a section (27) in which at least one roller table segment (31) can be pivoted about an associated pivot axis (32) by means of a controlled drive unit (29).
14. Apparatus according to Claim 10, characterized in that the rolling stock loop (6) has a vertex (24) and the rollers (9) are arranged symmetrically with respect to a vertical (15) which passes through the vertex (24).
15. Apparatus according to one of Claims 10 to 14, characterized in that a rolling stock measuring device (28) is provided for metrologically detecting a width of the rolling stock (1) before and/or within or after the section (27) and the measured value can be forwarded to the control device (10).

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