Method for Rolling Rolling Stock Having a Transitional Region

Abstract

The invention relates to a method for rolling a product in a rolling train comprising at least two roll stands having a roll gap, the product to be rolled comprising a transition region. If a critical transition region crosses the rolling train, the roll gaps of the roll stands are successively opened and closed according to the position of the transition region moving at speed through the rolling train, in the direction of the direction of travel of the conveyor. The opening of the roll gaps occurs parallel to the position of the critical transition region when the product is displaced. A transition region is critical when the structure requires the roll gaps to be opened. The inventive opening of the roll gaps, when the device is moving, enables the controlled transition of a product to be rolled with extreme variations in dimensions and/or hardness, for a shorter length.

Description

FIELD OF INVENTION

The invention relates to a method for rolling rolling stock in a mill train that has at least two roll stands each having one roll gap, with the rolling stock requiring to be rolled having at least one transitional region. The invention relates further to a computing device for appropriately regulating a mill train.

BACKGROUND OF THE INVENTION

Particularly in the case of a continuously operated mill train the rolling stock has a plurality of partial areas that can differ in terms of their dimensions and/or material properties (also temperatures). Two successive partial areas of the rolling stock are joined by means of a transitional region. The plurality of partial areas of rolling stock are a result of, for example, supplying metal coils singly and welding them together prior to rolling. The partial areas of the rolling stock correspond in this case to individual coils. The rolling stock is as a rule separated again into single coils after being rolled.

DE 101 59 608 A1 describes a rolling method for a strip having one seam weld in a mill train having a plurality of roll stands and at least one draw tension measuring element. According to DE 101 59 608 A1, setting variables for the rolling speed and for screwing down the roll stands are determined as a function of the position of the seam weld within the mill train.

Known methods for rolling rolling stock having a transitional region operate reliably only when the physical characteristics of said transitional region are such that the change in the at least one dimension and/or at least one material property between the partial area of the rolling stock in front of the transitional region and the partial area behind the transitional region is relatively slight. When, according to known methods, partial areas having extremely different properties and/or dimensions are rolled in direct succession, that will as a rule be associated with substantial disruptions to the process variables. In extreme cases said disruptions can cause the rolling stock to split.

SUMMARY OF INVENTION

The object of the invention is to avoid the disadvantages known from the prior art and provide a method with the aid of which rolling stock having at least one transitional region can be reliably rolled, even in the possible presence of in part substantial differences in terms of the dimensions and/or properties of the rolling stock between partial areas of the rolling stock joined by means of a transitional region.

Said object is achieved by means of a method of the type described in the introduction, with the roll gap of at least one roll stand being opened, when the transitional region's physical characteristics so require, as a function of the position of the transitional region of the rolling stock moving at a speed through the mill train. Said object is further achieved by means of a corresponding computing device for regulating the mill train.

The invention enables rolling stock to be rolled reliably even when successive partial areas thereof differ substantially in terms of, for instance, strip thickness, strip hardness, and/or alloying. According to the invention it is no longer imperative for rolling stock to be assembled in a lengthy planning process from partial areas, which is to say single coils or, as the case may be, single strips, in such a way that the differences between successive strips are relatively only slight. Thus, for example, it is possible according to the invention when production schedules are tight to assemble rolling stock from coils or, as the case may be, strips without taking the individual coils' or, as the case may be, strips' properties or, as the case may be, dimensions into account, and to reliably roll the rolling stock continuously. That will result in a substantial increase in the operating plant's flexibility and reliability.

The roll gap of at least one roll stand will be opened only in the case of a critical transitional region, which is to say when the physical characteristics of the transitional region so require. Critical transitional regions are transitional regions that join partial areas of rolling stock having properties or, as the case may be, dimensions differing in such a way that their transit through a roll stand having a closed roll gap would entail substantial disruptions to the process variables. If a transitional region is critical, its physical characteristics will require a roll gap to be opened. That applies also to the following developments of the invention. Stopping of the operating plant before a critical transitional region enters it is inventively avoided, resulting in an increase in throughput rate.

It is expedient for a roll stand's roll gap to be opened no later than when the critical transitional region of the rolling stock has reached said roll stand.

In each case no more than one of the roll gaps of the mill train's roll stands is advantageously open at any instant within the method's application. According to said development of the invention and that described in the preceding, as much of the rolling stock as possible will be rolled in accordance with the required product properties and the portion of spoilage thus significantly reduced.

It is furthermore expedient for said roll stand's roll gap to be closed when the critical transitional region has traversed said roll stand.

The front tension in the rolling stock in front of and behind a roll stand is advantageously equalized before the roll gap of said roll stand is opened so as to minimize the adverse impact on the rolling process taking place on the roll stands involved, which is to say particularly on said roll stand and those surrounding it.

The rotating speed of at least one of the rolls, in particular the work rolls, of the roll stand is advantageously matched to the speed of the rolling stock when the roll gap is closed. Controlled closing of the roll gap in this manner using speed synchronizing will largely prevent undesired roll-surface damage.

The speed of the rolling stock is therein advantageously measured. The accuracy of synchronizing will be enhanced thereby.

The speed of the rolling stock is advantageously determined with the aid of at least one model. A particularly efficient method of speed determining will be provided thereby.

The reduction in a roll stand is advantageously regulated in a time-optimized manner with regard to the position of the transitional region in the mill train. The reduction in a roll stand is diminished when the transitional region is approached, with compensatory adjusting of the change in peripheral precession to the speed of the roll stand's rolls.

Before a transitional region's transit, the roll gap is advantageously eased through controlled opening of the screw-down device. The relational speeds of the mill train's other drives are preferably additionally adjusted accordingly. Disrupting of the process variables will in this way be prevented.

The front tension in the rolling stock in front of a roll stand is advantageously regulated by way of the other roll drives' rotating speed as long as the reduction in said roll stand has been reduced around the critical transitional region.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details will emerge from the following description of exemplary embodiments in conjunction with the drawings, in which:

FIG. 1 shows a mill train having computing equipment,

FIGS. 2 and 3 show examples of rolling stock having a seam weld,

FIG. 4 shows examples of rolling stock having a wedge,

FIG. 5 shows rolling stock having a transitional region between two roll stands,

FIG. 6 is a schematic of the curve of the front tension with roll gaps closed,

FIG. 7 shows-an example of front-tension regulating in the rolling stock.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a mill train 10 for rolling rolling stock 1 that moves through the mill train 10 at a speed v. The mill train 10 has at least two roll stands 2 which rolling stock 1 traverses. Rolling stock 1 traverses the mill train 10 in the direction of strip travel x. Rolling stock 1, preferably a metal strip, is continuously rolled in the mill train 10. The mill train 10 is preferably a cold-rolling mill train for steel having as a rule more than three roll stands 2. Located downstream of the roll stands 2 is a coiling device 3 on which the rolled rolling stock 1 is coiled.

The mill train 10, in particular the stands 2 of the mill train 10, is/are coupled to a computing device 4. Located in the mill train 10 are generators, not shown further in the drawing, which convey, for example, measuring signals to the computing device 4. The computing device 4 conveys preferably control signals to actuators in the mill train 10.

The computing device 4 preferably has a model 12 that models processes in the mill train 10 with the aid of data relating to, for example, rolling stock 1.

The directions indicated in FIG. 1, namely the direction of strip travel x, the direction of strip thickness y, and the direction of strip width z, principally relate only to the position of the rolling stock 1 and the position of the roll stands 2, not, though, to the arrangement of the computing device 4 in relation to the mill train 10. The roll stands 2 each have a roll gap 11, only intimated in FIG. 1. A roll stand 2 has at least two work rolls of which at least one is arranged in the direction of strip thickness y above the rolling stock 1 and at least one in the direction of strip thickness y below the rolling stock 1. The roll gap 11 is located between said work rolls. Back-up rolls, likewise not shown further in the drawing, are as a rule provided in addition to the work rolls.

In particular in the case of cold rolling, rolling stock 1, for example sheet metal, is increasingly produced in continuous mill trains 10, with the coils that are as a rule supplied singly being welded together in the run-in of the production plant, of which the mill train 10 is also a constituent part. The mill train 10 rolls the rolling stock 1, consisting of a plurality of coils welded together, continuously, which is to say without stopping. In the production plant's run-out the rolling stock is separated again into single coils. That is done by, for example, shearing or cutting. Particularly when production schedules are tight, rolling stock 1 is rolled in a continuous mill train 10 without taking account of the properties of the individual coils forming the rolling stock 1. The individual coils differ in terms of, for example, thickness and/or width in the direction of strip thickness y or, as the case may be, the direction of strip width z and/or with respect to their alloying and/or hardness.

FIG. 2 shows a section of rolling stock 1 having two partial areas 1a, 1b that correspond to two different coils and differ in thickness. The two partial areas 1a, 1b of the rolling stock 1 are joined by a transitional region 9, with the transitional region 9 having a seam weld 5.

FIG. 3 shows a section of rolling stock 1 having two partial areas 1a, 1b each corresponding to different coils. The two partial areas 1a, 1b are joined by a transitional region 9, with the transitional region 9 having a seam weld 5. The seam weld 5 is only intimated in both FIG. 3 and FIG. 2. The partial areas 1a, 1b or, as the case may be, coils shown in FIG. 3 differ in width.

FIG. 4 shows a section of rolling stock 1, with two partial areas 1a, 1b being in this case joined by a transitional region 9 between the two partial areas 1a, 1b corresponding preferably to two coils. The transitional region 9 is in FIG. 4 shown by way of example only as being almost wedge-shaped. The transitional region 9 has in many cases a thickness curve differing from that shown. Thus the thickness of the rolling stock 1 in the transitional region 9 can initially also increase then decrease. What was said previously applies analogously to the width of the rolling stock 1.

Properties such as strip thickness, strip width, strip hardness, and/or alloying change at the transitional region 9. If the rolling stock is assembled with no account taken of the properties of the coils or, as the case may be, subsequent partial areas, then properties of the rolling stock 1 can change abruptly particularly at the seam welds 5.

FIG. 5 shows by way of example a transitional region 9 embodied as a wedge 6 between two roll stands 2′ and 2″, with the roll stand 2′ being arranged in front of the roll stand 2″. The roll stand 2′ has a top work roll 7′ and a bottom work roll 8′. The roll stand 2″ likewise has a top work roll 7″ and a bottom work roll 8″. Located between the top work roll 7′ or, as the case may be, 7″ and the bottom work roll 8′ or, as the case may be, 8″ of a roll stand 2′ or, as the case may be, 2″ is the roll gap 11′ or, as the case may be, 11″.

The partial areas 1a, 1b of the rolling stock 1 have on the one hand a difference in strip thickness already present prior to run-in into the first roll stand 2. On the other hand, the strip thickness of the rolling stock 1 also changes during traversing of the roll stand 2′, 2″ with a closed roll gap 11′, 11″. Thus before entering the roll stand 2′ the partial area 1b of the rolling stock 1 has a strip thickness h1 that is greater than its strip thickness h2 on exiting the roll stand 2′. Likewise, the strip thickness h3 before entering the roll stand 2″ is greater than the strip thickness h4 on exiting the roll stand 2″. The difference between the strip thicknesses h1 and h2 or, as the case may be, h3 and h4 is due to the reduction in the roll stands 2′, 2″.

The reduction occurring in a roll stand 2, 2′, 2″ is due to the rolling force exerted by the work rolls 7′, 7″, 8′, 8″ on the rolling stock 1. The roll gap 11, 11′, 11′″ is said to be closed when both the at least one top and the at least one bottom work roll 7′, 7″ or, as the case may be, 8′, 8″ of a roll stand 2,2′, 2″ are in contact with the rolling stock 1 or, as the case may be, exert a rolling force on the rolling stock 1. The roll gap 11, 11′, 11″ of a roll stand 2, 2′, 2″ is open when in a roll stand 2, 2′, 2″ the rolling stock 1 is not in contact with the at least one work roll 7′, 7″ or 8′, 8″, in particular the at least one top work roll 7′, 7″, at least on one side of the rolling stock 1 in the direction of strip thickness y, in particular on the top side of the rolling stock 1.

As already described in the foregoing, the rolling stock 1 sometimes has one or more transitional regions 9 due to whose physical characteristics a traversing by a transitional region 9 of said type of a roll stand 2 having a closed roll gap 11 would lead to substantial disruptions in the process variables. The transitional region 9 will exhibit said type of critical physical characteristics when the partial areas 1a, 1b, joined by the transitional region 9, of rolling stock 1 differ substantially in at least one of their properties and/or at least one dimension. A considerable risk associated with a transitional region 9 that is critical in this way is that the rolling stock 1 will split when traversing a closed roll gap 11. The roll gap 11 of a roll stand 2 is therefore opened as a function of the position of said type of transitional region 9. If a transitional region 9 of a rolling stock 1 is moving at a speed v through the mill train 10, then the roll gap 11 of a roll stand 2 will be opened if the physical characteristics of said transitional region 9 so require.

During continuous rolling operations a critical transitional region 9 traverses the roll stands 2 of the mill train 10 successively. The computing device 4 therein drives the mill train 10 in such a way that the roll gaps 11 of the roll stands 2 will be opened stand by stand and in parallel with the critical transitional region's position as the rolling stock 1 moves. A roll gap 11″ of a roll stand 2′″ will therein be opened no later than when the critical transitional region 9 reaches said roll stand 2″. The roll gap 11 of a roll stand 2 will preferably not be opened until shortly before a critical transitional region 9 runs into said roll stand 2, and it will be closed when the critical transitional region 9 has traversed the roll stand 2. Preferably at most one roll gap 11 of the roll stands 2 is open or, as the case may be, in particular fully open at a specific instant while the rolling stock 1 is being moved through the mill train. As a consequence of the roll gaps 11 of individual roll stands 2 being opened only as briefly as possible, the portion of spoilage will be very small and an extremely large portion of the rolling stock 1 can be rolled in a controlled manner. Alongside the saving in time, this is a major advantage compared to what are termed “open-gap” processes according to which a mill train 10 is stopped before a critical transitional region 9 is run in, all the roll gaps 11, 11′, 11″ are then opened, the critical transitional region 9 is driven through the entire mill train 10 with the roll gaps 11, 11′, 11″ open, and further according to which all the roll gaps 11, 11′, 11′″ are thereafter closed again and the rolling process is then resumed.

FIG. 6 is a schematic of the curve of the front tension T over the direction of strip travel x in a mill train 10. Located at the positions x₁, x₂, x₃, x₄ are stands 2 of the mill train. A coiling device 3 is arranged at the position x₅. During regular rolling operations the front tension T in the rolling stock 1 reduces behind the first roll stand 2 at the position x₁ at each roll stand 2 up to the coiling device 3. To prevent the rolling stock 1 from impacting or, as the case may be, splitting when a roll gap 11 is opened, the front tension T in the rolling stock 1 in front of and behind the roll stand 2 is equalized before the roll gap 11 of a roll stand 2 is opened. This means that if the roll gap 11 of a roll stand 2 is being opened, the front tension T in the environs of said roll stand 2 will ideally be constant shortly before the roll gap 11 is opened, while it is being opened, and briefly thereafter.

It is furthermore advantageous for the reduction in a roll stand 2 to be diminished in a time-optimized manner with compensatory adjusting of the change in peripheral precession to the roll speed. The roll gap 11 is preferably eased through controlled opening of the screw-down device in the roll stand 2 depending on the transition to a position-regulated or rolling-force-regulated operating mode, with the relational speed of the drives of the other roll stands 2 of the mill train 10 then being adjusted accordingly. Disrupting of the process variables is in this way prevented. The relational speed is the speed in a roll stand 2 relative to the other roll stands 2 of the mill train 10.

Should it not be possible to reliably roll a transitional region 9 through controlled opening of the screw-down device with the roll gap 11 closed, then—as described previously—the roll gap 11 will be opened. If a roll gap 11 has been opened owing to a critical transitional region 9, it will be closed in a controlled manner when the critical transitional region 9 has passed through until contact is made with the strip. The roll speed is therein synchronized with the measured and/or modeled speed v of the rolling stock 1.

FIG. 7 shows two roll stands 2′ and 2″, with the roll stand 2″ being located downstream of the roll stand 2′. Both roll stands 2′ and 2″ have a roll-stand screw-down device 2a′ or, as the case may be, 2a″ and a roll-stand drive 2b′ or, as the case may be, 2b″. A front-tension regulator 13 is provided. Measurement variables and/or values, determined with the aid of models, for the front tension T in the rolling stock 1 between the two roll stands 2′ and 2″ are advantageously conveyed to the front-tension regulator 13. Described below is an advantageous variant of inventive front-tension regulating in the rolling stock 1 in front of the roll stand 2″. During standard rolling operations the front tension T is regulated via the backward slip of the roll stand 2″ by means of the roll-stand screw-down device 2a″ of the roll stand 2″. So long as the reduction in the roll stand 2″ is being diminished around the critical transitional region 9, the front-tension regulator 13 will adjust the front tension T by means of the rotating speed of the roll-stand drive 2b′ of the roll stand 2′.

The idea underlying the invention can be summarized substantially as follows:

The invention relates to a method for rolling rolling stock 1 in a mill train 10 having at least two roll stands 2, with each roll stand 2 having a roll gap 11 and with the rolling stock 1 requiring to be rolled having at least one transitional region 9. When a critical transitional region 9 traverses the mill train 10, the roll gaps 11 of the at least two roll stands 2 will be closed and opened successively in the direction of strip travel x as a function of the position of the transitional region 9 moving at a speed v through the mill train 10. The roll gaps 11 are opened in parallel with the position of the critical transitional region 9 with the rolling stock 1 being moved. A transitional region 9 is critical if its physical characteristics require roll gaps 11 to be opened. The changes in at least one of the dimensions or, as the case may be, properties such as the hardness or alloying of the rolling stock 1 around the transitional region 9 could, with the roll gap 11 closed, lead to substantial disruptions in the process variables or, as the case may be, cause the rolling stock 1 to split. Inventive stand-by-stand opening of the roll gaps 11 with the plant running will also enable controlled transiting by a rolling stock 1 exhibiting extreme changes in dimension and/or hardness with an ensuing deviation length that is slight.

Equalizing of the tensile force will prevent slipping of the rolls, in particular of the work rolls 7′, 7″, 8′, 8″ of the roll stands 2. Nor will any equalizing operations then be performed on the front tension T in the adjacent stands when the roll gap 11 is opened in a roll stand 2. The speed v of the rolling stock 1 is measured and/or determined with the aid of at least one model 12 implemented in the computing device 4. Placing the work rolls 7′, 7″, 8′, 8″ onto the rolling stock 1 with a synchronized roll speed will prevent damage to the rolls. Time-optimized opening and closing of the roll gap 11 will minimize the length of deviation.

The position of the transitional region 9 in the mill train 10 is tracked from a synchronizing point 8, sited preferably at the entrance of mill train 10, by means of differential speed monitoring.

Claims

1.-13. (canceled)

14. A method for rolling a material in a mill train, comprising: providing a rolling stock material having a transitional region; providing a plurality of roll stands each having a roll gap; and opening the roll gap of at least one of the roll stands as required by a physical characteristic of the transitional region as a function of a position of the transitional region of the rolling stock moving at a speed through the mill train and wherein a tension in the rolling stock in front of and behind the one of the roll stands is equalized before opening the roll gap.

15. The method as claimed in claim 14, wherein the roll gap is opened before the transitional region has reached the roll stand.

16. The method as claimed in claim 15, wherein only one of the roll gaps in the mill train is opened at a time.

17. The method as claimed in 16, wherein the roll gap is-closed when the transitional region has traversed the roll stand.

18. The method as claimed in claim 17, wherein a rotating speed of a roll of one of the roll stands is matched to a linear speed of the rolling stock when the roll gap is closed.

19. The method as claimed in claim 18, further comprising measuring the linear speed of the rolling stock.

20. The method as claimed in claim 18, wherein the linear speed of the rolling stock is determined by a model.

21. The method as claimed in claim 18, wherein a reduction in a roll gap is regulated with regard to the position of the transitional region relative to the mill train.

22. The method as claimed in claim 21, wherein the roll gap is increased by opening a screw-down device before the transit of the transitional region.

23. The method as claimed in claim 22, further comprising adjusting relational speeds of drives of the other roll stands of the mill train.

24. The method as claimed in claim 23, wherein the tension of the rolling stock in front of the roll stand is regulated based on a rotating speed of drives of the remaining roll stands if the reduction in the roll stand has been reduced around a critical transitional region.

25. A computing device, comprising: a random access memory module; a non-volatile data storage device operatively connected to the memory module; and an executable program stored in the storage device that controls a mill train, by: providing a plurality of roll stands each having a roll gap, and opening the roll gap of at least one of the roll stands when a physical characteristic of a transitional region of a roll stock material requires as a function of the position of the transitional region of the rolling stock moving at a speed through the mill train, wherein a tension in the rolling stock in front of and behind the roll stand is equalized before opening the roll gap.

26. The computing device as claimed in claim 25, further comprising opening the roll gap before the transitional region reaches the roll stand.

27. The computing device as claimed in claim 26, wherein only one of the roll gaps in the mill train is opened at a time.

28. The computing device as claimed in claim 27, further comprising closing the roll gap when the transitional region has traversed the roll stand.

29. The computing device as claimed in claim 28, wherein a rotating speed of a roll of one of the roll stands is matched to a linear speed of the rolling stock when the roll gap is closed.

30. A method for rolling a rolling stock material having at least one transitional region in a mill train, comprising: providing a plurality of roll stands each having a roll gap; opening the roll gap of one of the roll stands based on a physical characteristic of the transitional region, a position of the transitional region relative to the mill train and a linear speed of the rolling stock through the mill train, wherein a tension of the rolling stock in front of and behind one of the roll stand is equalized before opening the roll gap; matching a rolling speed of a roll of at least one of the roll stands to the linear speed of the rolling stock through the mill train; and closing the roll gap once the transitional region has traversed the roll stand.

31. The method as claimed in claim 30, wherein a reduction in a roll gap is regulated with regard to the position of the transitional region relative to the mill train.

32. The method as claimed in claim 31, wherein the tension of the rolling stock in front of the roll stand is regulated based on a rotating speed of drives of the remaining roll stands if the reduction in the roll stand has been reduced around a critical transitional region.