EP2718035A1 - Method, computer program and rolling mill train for rolling a metal strip - Google Patents

Abstract

The invention relates to a method, a computer program and a rolling mill train for cold rolling a metal strip (200). In order to achieve a shortening of undesired off-gauge lengths, the method according to the invention provides that the head (210) of the metal strip (200) already undergoes a thickness reduction at the first active rolling stand (n) in the rolling mill train, and then is transported on to the next rolling stand, in order to undergo a further thickness reduction there. The method according to the invention also provides for further reducing the initial pass thickness at the n-th rolling stand in accordance with the tensile stress that has built up in the meantime between the n+1-th and the n-th rolling stand.

Description

 Process, Computerprog ramm and rolling mill for rolling a metal strip

The invention relates to a method, a computer program and a rolling train for rolling a metal strip. The rolling train comprises N in the rolling direction successively arranged active rolling stands.

In the prior art, such methods, computer programs and rolling stands are basically known. Thus, international publication WO 2009/049964 A1 discloses a rolling train with at least two rolling stands, wherein the metal strip undergoes a reduction in thickness when passing through the rolling stands because the rolling gaps of the rolling stands are each set to a predetermined piercing thickness. The strip tension in particular between two stands is monitored and, if necessary, suitably adjusted by means of suitable setting means. Before entering the rolling stock in the nip this is set in the vertical direction substantially to the inlet side Walzgutkopfdicke. After entering the rolling stock in the nip this is closed to a predetermined value and substantially simultaneously with the closing, the peripheral speed of the work rolls is changed depending on the size of the roll gap, in particular increased.

Without documentary proof, the method shown there, which is state of the art, will be explained in more detail below with reference to FIG. The starting point is a four-stand tandem rolling mill 10, which has a pay-out reel 8 and a take-up reel 12 downstream. The method shown in Figure 3 for cold rolling a metal strip 200 provides that initially all scaffolds of the tandem mill 10 are driven up, so that first the metal strip is passed with the tape head 210 without thickness reduction through the roll nips of the rolling stands to the take-up reel 12 to be wound there; see Figures 3a and b). With the winding creates a tensile stress in the metal strip between the take-up reel 12 and the unwinding reel 8; see Figure 3c).

After the tension is built up, the work rolls of the rolling stands are all first placed on the metal strip 200, see Figure 3d), before rolling on the first stand begins, in which its work rolls are fed to a nip having a predetermined piercing thickness; see FIG. 3e). The thickness jump in the metal strip caused in this way by the first roll stand then passes sequentially through all following rolling stands of the tandem mill 10. In this case, a successive start of the rolling takes place on the individual stands, as soon as said thickness jump passes through the respective stand; see Figures 3f and 3g). The last rolling mill of the tandem mill is preferably set to the desired target thickness for the metal strip.

There are two main reasons for carrying out this process: Firstly, the force and labor requirements for rolling without train is significantly higher than with train and on the other hand, the band is very quickly uneven, especially in the thin thicknesses of cold rolling, if the roll gap profile for incoming profile of the metal strip fits and so the rolling over the bandwidth undergoes different elongations. As a rule, metal tape with unevenness can not be wound or rolled on by a follower, ie it can be further reduced in thickness.

A disadvantage of this method is that on the tape head a considerable length of the metal strip does not have the desired thickness and therefore as Maßmaßlänge must be scrapped again. A similar situation arises at the end of the tape. Here, the return train is missing as soon as the belt leaves the unwinding reel 8 or abuts the last windings of the federal government. In conventional driving, the rolling nips of the individual rolling stands are also opened here; Here, too, dimension lengths result.

Based on this prior art, the invention has the object of developing a method, a computer program and a rolling mill for cold rolling a metal strip to the effect that the unwanted Maßmaß be significantly shortened.

This object is achieved by the method claimed in claim 1. This method is characterized in that the piercing thickness of the nth rolling stand of the rolling mill is set to a second predetermined piercing thickness smaller than the first piercing thickness of the nth in accordance with the tensile stress between the nth and the n + 1 'th rolling stand active rolling mill, is further reduced.

The term "active rolling mills" refers to those rolling mills of the rolling mill which contribute to a reduction in the thickness of the metal strip by setting their nip height accordingly. [0003] Roll mills with an open nip are not included in the active rolling mills in the sense of the invention, but they can easily be used between two active mills within In this case, however, the rolling mills with open nip remain irrelevant to the method according to the invention. The order of steps of the method according to the invention is not necessarily strictly adhered to. Thus, the steps a and b as well as the steps d and e can each be interchanged in their order. That is, it does not matter for the inventive method, whether the setting of the roll nip to a predetermined piercing thickness before the metal strip is transported to the respective rolling stand or after the metal strip or the tape head of the metal strip has already arrived on the input side of the rolling stand. In any case, the setting of the roll gap should be completed, however, if the respective relevant point of the metal strip from which a reduction in thickness is to take place, has come into the nip.

The parameter n designates the rolling mills of the rolling train arranged one behind the other in the rolling direction.

The parameter k denotes the number of changes made, in particular reductions, the piercing thickness per roll stand per rolling process.

The parameter x designates the rolling stands upstream of the rolling stand n.

The piercing thicknesses are parameterized in the present description in each case with the two parameters k and n. The piercing thicknesses are typically functions of the time; ie the changes in piercing thicknesses are time-dependent. Structure of the tensile stress in the present invention means an increase in the tensile stress.

The advantage of the method according to the invention is that a built-up and recognized modified tensile stress in the metal strip between the nth and n + 1'th roll stand is used to further reduce the piercing thickness on the n'ten active rolling stand. The method according to the invention makes it possible in this way, already with the cold rolling of the metal strip, i. begin with the thickness reduction of the metal strip before the tape head reaches the take-up reel and is wound by this to build up tensile stress. In other words, the structure of the tensile stress is advanced by the inventive method spatially and temporally from the take-up reel on the first active rolling stands. In this way, a very significant reduction of unwanted Maßmaßlängen is achieved.

A further reduction of the dimension lengths is achieved by repeating steps d) to h) for n = n + 1 to n = N-1, respectively. In other words, the method according to claim 1 is particularly advantageously applied not only to two adjacent active rolling stands n and n + 1 of the rolling train, but preferably to all rolling mills or roll stand pairings of the rolling train. Finally, in the case of such a "horizontal" expansion of the method according to the invention in the rolling direction, almost all rolling mills n with n <n <N-1 would be set sequentially not only to a first, but also at least to a second, further reduced predetermined piercing thickness. as mentioned, lead to a further reduction of unwanted Maßmaßlängen. An even further reduction of the Maßmaßlänge can be advantageously achieved in that after the construction of the tension between the n'ten and the η + 1 'th mill stand not only the nip roll n'ten roll stand, but also the nip of at least one of further upstream rolling stands x with 1 <x <n-1 is further reduced to a predetermined piercing thickness. This is technically possible because the change in tension between two rolling stands also has an effect on the tension of the metal strip between upstream rolling stands. In this way it can be achieved that the piercing thicknesses of individual rolling stands not only twice k = 2, but even more frequently k> 2 can be successively refined ever finer, in view of the ultimate target thickness. In other words, with the described method according to the invention, it is possible to successively further reduce the piercing thickness already in the first rolling stands of the rolling train in the course of an iteration process, ie to advance a strong reduction in thickness to early stands of the rolling train. In this way, the Maßmaßlängen be further reduced.

An even further reduction of the Maßmaßlängen is achieved when the take-up reel is used to build a tension between the take-up reel and N'ten roll stand of the rolling mill and the resulting tensile stress is in turn used for a further reduction of the piercing thickness at N'ten roll stand , The second predetermined piercing thickness of the N'ten rolling stand is smaller than the first piercing thickness D _{k = 1 N of} the N'ten rolling stand and smaller than the current piercing thickness D _{k N-1 of} the N-1 'th rolling stand.

The respective settings or changes in the piercing thicknesses of the individual rolling mills just described are precalculated in each case in a control device of the rolling train. The calculation and Determining in each case so that in each rolling stand, taking into account the expected tensile stresses and the material properties of the stock metal strip and taking into account the technological limitations, the inlet thickness and the target thickness, the maximum possible thickness reduction for the metal strip is set. This leads to a further optimization of the method according to the invention and thus to a further reduction of the unwanted dimension lengths.

All piercing thicknesses k with 1 <k <K of all rolling mills of the rolling train are preferably matched to one another such that the K'ten predetermined piercing thickness D _K, N of the N'th rolling stand is the desired target thickness for the metal strip.

The method according to the invention preferably already starts at the head of the respective metal strip, likewise in order to reduce the dimension lengths. In contrast to the prior art, the beginning of the tape in the method according to the invention does not first pass through the open nips of all scaffolds, but already when passing through the tape head through the rolling stands of the rolling mill, piercing of the metal strip is already on the belt head.

The reduction of the piercing thicknesses in the individual rolling stands is preferably not discontinuous in the sense of a jump function, but continuous, e.g. ramped over time.

Reducing the piercing thicknesses at the η + 1 'th rolling stand advantageously begins only when that of one of the preceding Rolled mills generated, for example, wedge-shaped thickness-reduced portion of the metal strip reaches the η + 1 'te roll stand.

The above object is further achieved by a computer program product whose program code is designed to control the rolling mills of the rolling train and to transport the metal strip according to the claimed method.

Finally, the above object is further achieved by a rolling train with a control device for carrying out the method according to one of claims 1 to 9.

The advantages of the computer program product as well as the rolling mill correspond to the advantages mentioned above with respect to the claimed method.

FIG. 4 shows the boundary conditions of a stitch plan calculation for adjusting the nip of the work rolls in a rolling mill, as known from the prior art. Accordingly, the stitch plan calculation takes into account technological boundary conditions, such as the features of the metal strip on the inlet and outlet side, the inlet thickness, the desired target thickness and technological limitations. In addition, the calculation of the maximum possible piercing thickness takes place with additional consideration of the material of the metal strip to be rolled, the friction between the work rolls and the metal strip and taking into account further framework data. From all the above data, the rolling model then calculates the required parameters for setting the work rolls, ie the rolling force, the rolling moment, the roll bending, the displacement, the Outlet thickness and gain factors of the technical regulation and in particular also the said maximum possible piercing thickness.

The description is a total of four figures attached, wherein

Figure 1 a) - f) the inventive method without take-up reel;

Figure 2 a) - d) the inventive method with take-up reel;

Figure 3 a) - h) a cold rolling process according to the prior art; and

the boundary conditions for the passplan calculation according to the prior art,

demonstrate.

The invention will be described in more detail below with reference to Figures 1 and 2. In FIGS. 1 and 2, the same technical elements are designated by the same reference numerals. Two pairs of superimposed circles or rollers denote in Figures 1 and 2 respectively always a pair of work rolls with a clamped nip. According to FIG. 1, the method according to the invention provides in a first method step a) for the nip roll nip to be set to a predetermined first piercing thickness _n before the metal strip 200 with the strip head 210 passes the nip roll nip; see Figure 1 a). The metal strip 200 is then brought with its tape head 210 further to the n'te mill stand, where it, including its tape head 210 is reduced to the first piercing thickness D _{1 n} in its thickness; see Figure 1 b). The metal strip 200 is then further transported according to FIG. 1 c) from the nth roll stand to the η + 1 'th roll stand, where it is set by the first piercing thickness D _{1 in + 1} with Di _{, n +} i <D _{1 n} Working rolls of the η + 1 'th rolling mill to learn a further reduction in thickness. It then builds a tensile stress in the metal strip between the η + 1 'and the n'ten roll stand. This tensile stress is measured by means of a tension measuring device 50, for example a tension measuring roller. The method according to the invention then further provides that then the piercing thickness at the n'th roll stand is further reduced to a second predetermined piercing thickness D _{2, n} . The second piercing thickness of the nth rolling stand is less than its first piercing thickness.

This reduction of the piercing thickness at the nth roll stand preferably takes place in a ramp over time, resulting in a wedge-shaped decrease in the thickness of the metal strip 200. The structure of a tensile stress between the η + 1 'th and the η + 2'ten roll stand can be used to perform a second reduction in thickness to a second predetermined piercing thickness D _{2, n +} i even in the η + 1' th rolling mill. This thickness reduction is also preferably ramped as a function of time. Ideally, the second predetermined piercing thickness D _{2, n} + i already corresponds to the desired target thickness for the metal strip, see FIG. 1 f). Depending on the total thickness reduction required, it may be necessary for the rolling train to have more than two active rolling stands 300. In this case, the described method according to the invention is preferably to be extended to all rolling mills of the rolling train, ie quasi in the horizontal direction. In this case, ie in the case of more than two rolling mills in the rolling train, it is also advantageous that, after the tensile stress has been established between the nth and the η + 1'th rolling mills, the rolling gap of at least one of the further upstream rolling mills is adjusted to one each predetermined Abstechdicke is further reduced.

Figure 2 shows how, finally, also the built-up tension between the take-up reel 400 and the last stand of the rolling train, i. The N'ten rolling stand, can be used to achieve a further reduction in thickness, preferably towards the desired target thickness at the N'ten rolling stand. For this purpose, initially leaves the tape head 210, the last N'te rolling stand 300 in the direction of take-up reel 400 to be coiled there; see Figures 2a) and b). The coiling results in the formation of a tensile stress in the metal strip between the take-up reel 400 and the N'ten stand 300, which is detected by the tension measuring device 50; see Figure 2c). This recognized increase in draft between the take-up reel 400 and the nth roll stand can then be used to further reduce the piercing thickness at the stand, preferably to the desired target thickness. The last setting of the roll gap on the first roll stand takes place when the reduction of the piercing thickness of the metal strip realized thereby is sufficient to roll the desired target thickness at the exit of the N'th roll stand of the rolling train.

Advantageously, the method according to the invention also applies to a reversing cold rolling mill. After the first pass through the reversing road then reaches the metal strip then on the frame N is not yet the desired target thickness. The process is then repeated for at least one return and re-runs through the road until the desired target thickness is reached.

Claims

claims 1 . Method for rolling a metal strip (200) in a rolling train with 1 <n <N and N> 2 in the rolling direction one after the other arranged active rolling stands, comprising the following steps: a) setting the roll gap of the n'th roll stand (300) to a predetermined first piercing thickness D _kn with k = 1;  b) transporting the metal strip with the tape head (210) ahead to the n'ten roll stand (300); c) piercing the metal strip to the first piercing thickness D _{k = 1, n} in the n'ten roll stand; d) setting the nip of the n + 1 'th rolling stand (300) to a predetermined first piercing thickness D _{k = 1 n + 1} , which is smaller than the first Pitch thickness D _k = _{1 n of} the n'th active rolling stand;  e) transporting the metal strip to the n + 1'th roll stand; f) piercing the metal strip to the first piercing thickness D _{k = 1 n + 1 of} the n + 1 'th rolling stand; and  g) building up a tensile stress in the metal strip between the nth and n + 1'th rolling stands;  marked by h) reducing the piercing thickness of the n'th roll stand in accordance with the tensile stress between the n'ten and n + 1 'th rolling stand to a second predetermined piercing thickness D _{2, n} , which is smaller than the first Piercing thickness D _{k = 1 n of} the n'th active rolling stand. 2. The method according to claim 1, marked by: repeating steps d) to h) for n = n + 1 to n = N-1, respectively. 3. The method according to claim 1 or 2,  characterized,  that after building up the tension between the n'th and n + 1 'th Roll stand and the nip of at least one of the further upstream rolling stands x with 1 <x <n-1 is further reduced to a respective predetermined piercing thickness. 4. The method according to claim 2 or 3,  marked by:  Further transport of the metal strip after passing through the N'ten Roll stand with the first piercing thickness D _k = i, N TO one  Coiler;  Winding the strip beginning of the metal strip on the reel device (400); and  Build up a tensile stress in the metal strip between the  Coiler and the N'ten roll stand; and  Reduce the piercing thickness of the N'th roll stand according to the tension between the N'th roll stand and the coiler (400) to a second predetermined piercing thickness D ₂ , N which is smaller than the first piercing thickness D _{k = 1 N of} the N'th rolling stand and smaller than the current piercing thickness D _{k N-1 of} the N-1 'th rolling stand. 5. Method according to one of the preceding claims,  characterized in that the adjusted piercing thicknesses or roll gap heights for the individual rolling stands (300) are calculated in advance so that they take into account the expected Tensile stresses and the material properties of the metal strip respectively allow the maximum possible thickness reduction for the metal strip. 6. The method according to claim 3 and / or 4, characterized in that the piercing thicknesses and the distribution of the piercing thicknesses of all the active rolling stands (300) of the rolling mill for rolling the metal strip are precalculated so that the first predetermined piercing thickness D _{k N of} the N'th rolling mill is the desired target thickness for the metal band. 7. The method according to any one of the preceding claims,  characterized,  that during the passage of the metal strip through the rolling stands of the rolling train, the piercing of the metal strip preferably also includes the piercing of the strip head. 8. The method according to any one of the preceding claims, characterized  marked that  Reducing the piercing thicknesses of the rolling stands is ramped over time. 9. The method according to claim 8,  characterized in that  the reduction of the piercing thickness in the case of the η + 1'th roll stand only begins when the region of the metal strip produced by one of the preceding rolling stands, for example in a wedge-shaped thickness, reaches the n + 1'th roll stand. 10. Computer program product with a program code for running on a microprocessor in the controller of a rolling mill with a A plurality of rolling stands, characterized in that the Progrannncode is adapted to control the rolling stands and for transporting the metal strip according to the method of any one of claims 1-9. Rolling mill with  1 <n <N and N> 2 in the rolling direction successively arranged active rolling stands (300); a tension measuring device (50) for measuring the tension between two active stands arranged one behind the other; and a control device for individually setting the rolling gaps of the rolling stands to a respective predetermined piercing thickness, characterized in that in that the control device and the rolling train are designed to carry out the method according to one of Claims 1 to 9.