WO2008068172A1 - Roll gap measurement for a cluster rolling mill - Google Patents

Abstract

The invention relates to a method for direct roll gap measurement on a cluster rolling mill (1), wherein a height (h<SUB>1</SUB>) of a roll gap (300) is determined in accordance with a thickness (W<SUB>PT</SUB>, W<SUB>PB</SUB>) of a roll assembly (100, 200) of the cluster rolling mill (1), wherein the thickness (W<SUB>PT</SUB>, W<SUB>PB</SUB>) of the roll assembly is set with respect to at least one fixed point (F<SUB>PT</SUB>, F<SUB>PB</SUB>) in relation to a distance of the fixed point (F<SUB>PT</SUB>, F<SUB>PB</SUB>) away from a plane (O, U) of a metal strip (2) to be rolled, wherein this relation is a measure of the height (h<SUB>1</SUB>) of the roll gap (300). Furthermore, the invention relates to a cluster rolling mill, in particular a reducing roll stand, for a cold-rolling mill, in which a position measuring sensor for measuring a height (h<SUB>1</SUB>) of a roll gap (300) of the cluster rolling mill (1) is provided on an upper mill part (10) and/or a lower mill part (20).

Description

description

Roll gap measurement for a multi-roll mill

The invention relates to a method for a direct nip measurement in a cluster mill stand or a multi-roll mill stand. Furthermore, the invention relates to a Vielwalzengerüst, in particular a Reduziergerüst, for a cold rolling mill.

Cold rolling is a forming of a metal strip, in particular a wide-flat metal strip, below its recrystallization temperature. For cold rolling of thin, hard materials such. As stainless steels, silicon steels, nickel alloys and other metals, such as. As copper and copper alloys, work rolls are required in a rolling mill with a small diameter. As a result, a smaller force is required for the same thickness reduction of the metal strip, which improves the quality of the metal strip. Furthermore, the reduction in the work roll size also involves a reduction in operating costs. Although smaller work rolls wear faster, they are easier to handle, cheaper to replace and, above all, faster to rework, with lower tolerances.

An essential objective of cold rolling mills is to achieve the highest possible strip quality. One of the most important criteria for strip quality is the achievable thickness tolerance. In order to achieve the tightest possible Dentenzoleranzbands, it is therefore necessary to keep a nip in the mill stand constant. This task is performed by a belt thickness control with its subordinate control loops of an adjustment control, which regulates a position of the two work rolls to each other.

During the cold rolling process, a wide variety of defect effects affect the thickness control. Besides the mistakes of the input material (thickness and hardness oscillations), change in the friction in the nip (lubrication), change of the flow sheath (strip tension), there are also disturbances on the nip by increasing the roll diameter due to heating, by an elasticity of the rolling stand, as well as roll gap changes a roll eccentricity.

This applies in particular to a last rolling stand in the direction of production or for a last pass in a reversing stand. Such a rolling stand is in particular a so-called multi-roll stand, in which a multiplicity of rolls (eight or more, in particular 12, 18 or 20 rolls) of different sizes are arranged symmetrically in two wedges (roll packs). Here are the two work rolls the tips of the wedges there, which are each directed perpendicular to the metal strip. Such multi-roll stands are capable of achieving high strip thickness reduction values and / or maintaining very accurate strip tolerances. For this reason, they are also often used as Reduziergerüste. Especially for the cold rolling of stainless steels, 20-roll stands with roll packages of 10 rolls each have prevailed. These are very well suited to meet the demand for high degrees of deformation, tight tolerances and good surface quality.

In twin-stand rolling mills, in the prior art for controlling a nip height depending on a measured value of a nip measurement, the nip sensors are arranged between the roll necks of the duo mill stand. The problem with such an arrangement is in particular their susceptibility to damage if in the rolling stand an unforeseen event such. B. a crack of the metal strip takes place. In such a case, not only does the duo mill stand need to be opened to remove the tape remnants, but it may also be necessary to replace the position sensors for the nip measurement and to adjust a closed loop control loop. This is time consuming and increases production costs significantly. Furthermore, with such an arrangement only rolling mills can be equipped whose working roller diameter does not fall below a certain level, since the transducers require a predetermined height. If a diameter difference between a roll bale and a roll neck of the work rolls is smaller than this minimum height, the roll gap transducers can no longer be accommodated.

In the case of multi-roll stands, a so-called indirect roll gap measurement is state of the art, in which displacement encoders are mounted on hydraulic setting cylinders of the rolling stand on the drive and operating side in order to determine the position of the pistons relative to the setting cylinder. The position measurement values are related to the rolling gap of the rolling stand after a calibration process. The position measured value is compared with a required setpoint value and the deviation as a control deviation is applied to a controller which, in addition to the additive correction signals from different compensation circuits, generates an actuating signal for the hydraulic adjustment of the rolls of the rolling mill stand.

The indirect roll gap control, which consists essentially of the position control and compensation circuits, such. B. for consideration of Walzenexzentrizität exists, has the disadvantage that no direct detection of the roll gap is given. It can thus be certain factors influencing the multi-roll stand, z. As a rolling force-dependent framework stretch, only calculate and switch on a set plan pre-taxing a set-up. Ie. a measurement of the piston position is only an indirect measure of the nip, which is also state of the art for quarto and sexto rolling mills.

In order to be able to precisely regulate the individual disturbance variables in a rolling mill or a roll stand, it is necessary to detect a position of the rolls as accurately as possible relative to one another. It is therefore an object of the invention to provide an improved method for a nip measurement in a multi-roll mill, as well as an improved multi-roll mill to deliver. In particular, it is an object of the invention to realize a direct nip measurement in a multi-roll stand and to specify a corresponding multi-roll stand, as well as to specify a corresponding measuring method for this in order to be able to prevent damage to the roll gap transducers in the event of a tape break.

The object of the invention is achieved by a direct measurement of a distance position between a framework upper and a framework lower part, wherein the distance is a measure of a height of a roll gap of a cluster roll stand. According to the invention, a position measuring transducer is mounted directly between the upper and lower part of the framework, whereby a method for direct nip measurement in the multi-roll stand can be realized. In the direct nip measurement method of the present invention, the height of the nip is determined in accordance with a thickness of a roll stack of the cluster mill, with the pack thickness being set in relation to a fixed point on a respective skeleton part of the cluster mill, with a difference to a strip plane removal a metal strip to be rolled is a measure of the height of the roll gap.

According to the invention, the position measuring device for the roll gap measurement is not located on an adjusting device for the two frame parts. Ie. in a distance measurement of the two frame parts to each other, fall off those disturbances, which in a measurement of a piston position, such as. As a compressibility of an oil column and a rolling force-dependent structure elongation occur.

The advantages of direct roll gap control for a multi-roll stand are realized by applying the measuring principle of the direct roll gap measurement to a multi-roll stand in accordance with the invention. As a result, it is possible to dispense with an inlet-side thickness measuring device for emergency operation of the multi-roll stand. According to the invention, a faster target measurement takes place, since a roll gap is directly produced here. proportional setpoint value can be specified. This results in narrowest thickness tolerances and dimensional tolerances of the different rolling materials, which in particular leads to better fine tolerances in the so-called "fillet piece" of the metal strip, resulting in good flatness and a high surface quality. Roll stand, makes it possible to make the work rolls very small in diameter, so that a minimum end thickness tolerance is possible even with wide tapes by a high deformation at low stitch counts.Furthermore, this smaller roll grinding machines are applicable, which can reduce the overall investment and maintenance costs results in a compact design of the mill stand, an economical use of carbide rollers, a quick and easy roll change, and a high discharge rate with reduced edge cracks.

According to the invention, the position transducer determines a distance between the framework top and the framework bottom. In this case, a position or a distance of a fixed point on the upper frame part is preferably determined with respect to a fixed point on the lower frame part. These fixed points can z. B. in an inlet region and / or an outlet region of the cluster roll stand on the scaffold upper or framework lower part may be provided. Furthermore, as fixed points, contact points of a respective roll package are available on the upper or lower frame part. In particular, suitable for this purpose is a respective vertex of a respective cavity of a framework part.

Preferably, for this purpose, such fixed points to the relevant cavities, which serve for a determination / definition of a respective roll packet thickness, wherein the roll pack thicknesses together with the distance of the two fixed points to each other, form a measure of the roll gap of the cluster roll stand. A respective other end for the determination / definition of the respective roll packet thickness is preferably a rolling point of the corresponding roll stack of the cluster roll stand, ie a point from which the roll gap or the height of the roll gap is defined. Ie. The measured distance between the two fixed points (that is to say, for example, the distance between the two contact points of the respective roll package at the respective cavity) minus the respective roll package thickness results in a height of the roll gap or a measure of this in a preferred embodiment of the invention.

The respective rolling point of the respective roll package is z. B. defined by the fact that at the respective rolling point of the outer circumference of the respective work roll has a Tangentialge speed, which corresponds to the speed of the metal strip in the production direction behind the cluster mill stand.

According to the invention, however, it is also possible to locate the fixed point (s) at an arbitrary position, wherein, for the determination of the roll gap, a respective distance of the relevant fixed point to a starting point of a definition point for the roll packet thickness is taken into account.

According to the invention, it is possible to determine the height of the roll gap exclusively from scaffold-dependent costs and the respective roll packet thickness. In a preferred embodiment of the invention, the height of the roll gap is at a distance of two least spaced apart from each other

Points of a respective cavity, a respective height of the two cavities and a respective roll packet thickness determined. Furthermore, in a preferred embodiment of the invention, it is possible to determine the roll gap from a distance between the two vertices of the two cavities and the respective roll packet thickness. In a further preferred embodiment of the invention, the height of the roll gap is determined from a distance of a framework top to a scaffold underside, and the respective distances of each respective adjacent, respective vertices of the respective cavities, and a respective roll packet thickness. According to the invention, the respective distances are preferably determined only in a vertical direction, ie horizontal portions of these dimensions are not taken into account.

Further preferred embodiments of the invention will become apparent from the remaining dependent claims.

The invention will be explained in more detail below with reference to embodiments with reference to the accompanying drawings. In the drawing show:

1 is a schematic diagram of the prior art for explaining a direct roll gap measurement in a duo-rolling mill; 2 is a schematic diagram of a roll gap measurement according to the invention in a 20-roll rolling stand; 3 shows a side view of a 12-roll rolling stand for

Explanation of the direct roll gap measurement according to the invention; 4 shows a side view of a scaffold upper part of the 12-

Roller rolling stand from FIG. 3 for explaining a definition of a roll packet thickness; and FIG. 5 positions according to the invention for position encoders for measuring a distance between the scaffold and a frame bottom part.

The following statements relate to a direct roll gap measurement according to the invention for a 12-roll or 20-roll roll stand. However, the invention should not be limited to such rolling mills, but relate to multi-roll stands with roll packages, wherein a roll package has at least 3 rolls in a 1-2 arrangement. D. h., The invention is particularly applicable to rolling stands with two roll packages, wherein a single roll package 3, 4, ..., n, n + 1 rolls, thus inventively a multi-roll mill with a total of 6, 8,. .., 2n, 2n + 2 rollers. 1 shows the prior art of a direct nip measurement, as it is currently used exclusively in Duo and Quarto rolling stands. Here, a roll gap 300 of a duo stand is directly determined, which is defined by a position of an upper work roll 110 to a lower work roll 210. A height hi of the roll gap 300 corresponds to the smallest distance between the two work rolls 110, 210. D. h. the height hi of the nip 300 corresponds to a distance of an upper roll point 112 to a lower rolling point 212. Here, a rolling point 112, 212 is that fixed, outer point on a respective work roll 110, 210, at which a peripheral speed of the respective work roll 110, 210 a Belt speed of a metal strip 2 in a production direction P behind the rolling stand corresponds, and the relevant work roll 110, 210, the metal strip 2 just touched. Similarly, for a multi-roll stand 1 according to the invention (see FIGS. 2-5), a height hi of the roll gap 300 is the smallest distance between two roll packages 100, 200 or the smallest distance between two work rolls 110, 210 of the respective roll packages 100, 200 of the cluster roll stand 1 Are defined.

The nip 300 is measured directly between the work rolls 110, 210 on a drive and on an operating side of the duo stand. For this purpose, there are special roll gap transducers 400, which scan measuring tracks on the roll necks 114, 214 of the work rolls 110, 210 in order to determine the roll gap 300. This results in accordance with FIG 1, the following geometric condition:

S = h _x + X _τ + X _B.

Here, the through or the roll gap transducer 400 measured distance S between the two roll pins 114, 214 of the two working rollers 110, 210 by hi (height of the roll gap), X _τ (smallest distance of the upper roller point 112 to the rolling pin 114) and X _B ( smallest distance of the lower rolling point 212 to the roll neck 214). The following is supposed to the index T (= top) concern the framework upper part 10 and the index B (= bottom) the framework lower part 10.

X _τ and X _B can be substituted by the respective geometric conditions at the respective work roll 110, 210. Ie. :

d "d, d. d,

X _τ = and X _Ώ =

Here, d _{wτ is} the outer diameter of upper work _roll 110, d _{zτ is} the diameter of roll neck 114 of upper work roll 110, d _{WB is} the outer diameter of lower work roll 210 and d is _{ZB is} the diameter of roll neck 214 of lower work roll 210.

This results in the height hi of the roll gap 300 as a function of the geometric conditions on the work rolls 110, 210 and the measured distance S to:

] _η - C _ I ^{WT ZT} II ^{WB ZB}

¹ I

The geometrical dimensions d _w , d _WB , d _z , d _{ZB of} the work _rolls 110, 210 are constant in the first approximation, as long as the work _rolls 110, 210 are installed in the duo rolling mill, that is roller-dependent. It follows that hi is proportional to S. Ie. S is a direct measure of the height hi of the roll gap 300. This so determined Walzspaltistwert hi is compared with a roll gap setpoint and the deviation is applied as a control deviation to a controller that generates a Stelligsig- signal for a hydraulic adjustment of the two work rolls 110, 210.

By directly detecting the height hi of the roll gap 300 in the direct roll gap control, expansions of the duo roll stand have no influence on a thickness hi of the outgoing roll gap. the metal bands 2 (viewing without plastic re-stretching of the metal strip 2).

The method according to the invention for direct roll gap measurement will now be explained in more detail with reference to FIG. 2 on the basis of a multi-roll stand 1, which in the present exemplary embodiment is designed as a 20-roll rolling stand 1. The invention should furthermore preferably relate to a multi-roll stand 1, in which a framework upper part 10 can be moved relative to a framework lower part 20. This is illustrated in FIG 2 on the left of the scaffold shell 10 with the double arrow, d. H. the frame upper part 10 is movable relative to the frame lower part 20. In addition, the invention should relate in particular to a cluster mill 1, which is adjustable by means of four columns. Ie. the upper housing part 10 is movable relative to the lower housing part 20 along four columns arranged in the corner regions of the multi-drum stand 1.

According to the invention, a direct measurement of a position of the upper housing part 10 relative to the lower housing part 20 is now applied, such a distance being a measure of the height hi of the rolling gap 300. In particular, 20-roll rolling mills (see FIG. 2) have prevailed among the multi-roll stands for rolling cold metal strip 2. Due to the roll configuration realized there, it is possible to use work rolls 110, 210 with a very small diameter.

The multi-roll stand 1 according to the invention has the upper frame part 10 which can be moved relative to the lower frame part 20, whereby the multi-roll stand 1 preferably has a rolling mill stand from

Split-house type is. Each of the frame parts 10, 20 has a cavity 150, 250, in each of which a roll pack 100, 200 is mounted. The respective roller package 100, 200 has a single work roll 110, 210, two inner intermediate rolls 120, 220, three outer intermediate rolls 130, 230 and four support bearing rolls 140, 240. In this case, the respective inner intermediate rolls 120, 220 are preferably axially displaceable and the respective outer intermediate rolls 130, 230 are motor-driven. exaggerated. As already mentioned above, the cluster mill 1 does not have, as shown in FIG 2, a 1-2-3-4 arrangement, but can also - such. As shown in Figures 3-5 - be constructed as a 12-roll rolling stand a 1-2-3 arrangement or in another arrangement. Moreover, it is possible to form the cluster mill 1 not with support bearing rollers 140, 240 but with support bearings 140, 240. This is shown in dashed lines on the framework lower part 20 of FIG3.

According to the invention, a current distance S of the upper frame part 10 to the lower frame part 20 is determined during operation of the multi-roll stand 1 and brought into a relation to a respective roll package height W _P and a respective height G of the cavity 150, 250, so that a proportional measure of the height hi of the nip 300 gives.

In this case, the distance S of the upper frame part 10 with respect to the lower frame part 20 is detected by means of at least one position encoder 400 for the roll gap measurement. According to the invention, the distance S is determined with respect to two fixed points FP _T , FP _B on the cluster roll stand 1. In this case, a fixed point FP _{T is provided} on the upper frame part 10 and the other fixed point FP _B on the lower frame part 20. Where these are located on the multi-roll stand 1, in principle does not matter. The position encoder 400 determines a horizontal distance S between these two fixed points FP _T , FP _B , which results according to the invention a measure hi for the nip 300. This can be done in different ways.

In a first exemplary embodiment of the invention, the distance S of the upper frame part 10 to the lower frame part 20 is determined such that a distance S between a lower side of the upper frame part 10 with respect to an upper side of the lower frame part 20 is measured. In this case, the respective fixed point FP can lie in an inlet region 30 or an outlet region 40 of the metal strip 2 in the multi-roll stand 1. In the present example, the fixed point FP _{T of} the upper frame is Part 10 at a free end of the cavity 150, and analogously, the fixed point FP _{B of} the frame base 20 is also located at a free end of the cavity 250th D. h. the respective fixed point FP _T , FP _B is in each case a common point of the respective cavity 150, 250 with a lower (10) and an upper side (20) of the respective frame part 10, 20. This distance S of the two fixed points FP _T , FP _B is now measured and set in relation to the framework dimensions X _τ , X _B. This results in the following geometric relationship:

S = h _x + X _τ + X _B.

Ie. the distance S of the two fixed points FP _T , FP _B corresponds to a sum of a distance X _{τ of} the fixed point FP _T to the upper side O of the rolled metal strip 2 and the height hi of the rolled metal strip 2 (corresponds to the height hi of the roll gap 300) and Distance X _{B of} the underside U of the rolled metal strip 2 to the fixed point FP _B. X _τ and X _B can now again be expressed via framework-dependent constants. In this case (see also FIG. 3 for a better understanding):

X, = VL - G. and X _π = VL - G _Έ

Which, in a first approximation, leads to:

I _-1 = S - (w _{pτ -G 1} ) - (W _PB - G _B ).

Ie. the height hi of the nip 300 depends on the measured distance S between the upper frame part 10 and the lower frame part 20, a height W _{PT of} the upper roll stack 100, a height W _{PB of} the lower roll stack 200, a height G _{τ of} the cavity 150 of FIG Scaffold shell 10 and a height G _{B of} the cavity 250 of the frame base 20. Here again the heights G of the respective cavity 150, 250 are scaffold-dependent and thus constant. The respective height W _{P of} the roll package

100, 200 is also constant as long as the rolls or roll packages 100, 150 are installed. This in turn results in a proportional behavior of the distance S of the In this case, the corresponding reference surfaces adjacent to the scaffolding upper part 10 and the lower frame part 20 arranged reference surfaces, the top O and the bottom U of the rolled metal strip. 2

It is also possible to consider only one half up or down with respect to a center line M of the rolled metal strip 2. This results in the following geometric dependency:

S ^h i +

2 2

This results in the height hi of the roll gap 300 to:

h _± = S - 2W _PT + 2G _T.

This can be carried out analogously for a lower half of the metal strip 2, ie for X _B. Such a determination of the height hi of the roll gap 300, which is based on symmetry considerations, is particularly suitable for embodiments of multi-roll stands 1 according to the invention in which no very high demands are placed on the accuracy of the roll gap control of the roll stand 1. However, if very high demands are placed on the accuracy of the roll gap control, which is the case in particular with reduction roll stands, the first approach is more appropriate.

Moreover, it is advantageous - now with particular reference to the 12-roller mill of FIG 3 - to lay the fixed points FP _T , FP _B , ZB on a boundary point of the respective cavity 150, 250; and in particular to a respective point of the cavity 150, 250, of which a respective height W _PT , W _PB of the respective roll package 100, 200 defines to the respective rolling point 112, 212, wherein the minimum (linear) distance between the rolling points 112, 212 corresponds to the height hi of the nip 300 (definition). In particular, a respective vertex FP _T *, FP _B * of the cavity 150, 250 is suitable for this purpose. Thus, a position encoder 400 measures a distance S 'of the two vertexes FP _T *, FP _B *. This results in the height hi of the roll gap 300 to:

_pτ W - h, = S ^'- W _PB.

It is advantageous in the measurement of S ', that is a corresponding provision of the position encoder 400 between the two vertices FP _T * and FP _B *, that this depends only on the measurement of S' and the respective height W _{P of} the roll stack 100, 200 ,

In addition, it is possible with the position encoder 400 z. B. to determine the distance S '' between the top of the scaffold shell 10 and the underside of the frame base 20. There are now several ways to express the height hi of the roll gap 300 via S ''.

A turn leads over the distance of the two vertices FP _T *, FP _B *, whereby a respective distance Y _τ , Y _{B of} the corresponding side of the frame part 10, 20 to the respective vertex FP _T *, FP _B * is determined. It follows:

¹ Ci ₁ = S ^" - Y ₁ - Y _B - W _pτ - W _PB .

Furthermore, it is possible to include a thickness measurement of the metal strip 2 according to the invention. Is z. B. X _τ - (Distance bottom U of the outlet side metal strip 2 to the bottom of the scaffold shell 10) known (see FIG 3), the result is the height hi of the roll gap 300 to:

¹ Ci ₁ = X _τ , + G _τ - W _pτ .

A reference surface for this determination is the underside U of the metal strip 2, whereby it is possible to measure the height hi of the nip 300 without knowing about a height W _PB of the roll lower roll packages 200 to determine. An analogous procedure results for the top O of the metal strip 2:

h_ = ^X _B. + G _B - W _PB .

Furthermore, such a procedure is possible with respect to a center line M of the metal strip 2 with knowledge of an inlet-side strip thickness ho. So it follows, for. B. using X _{T "} (distance top side of the inlet-side metal strip 2 to the bottom of the scaffold shell 10):

1I ₁ = h ₀ + 2X _T "+ 2G _T - 2W _PT .

In addition, in FIG. 3, alternative fixed points FP are shown. It should be noted here either that a roll pack thickness Wp is defined with respect to this fixed point FP, or a corresponding offset ΔX of the fixed point FP is taken into account at a point on the corresponding roll pack 100, 200, from which a respective roll pack thickness W _{P is} defined is. The latter is z. B. on the right in FIG 3, in which an offset Δ X _{τ of} a fixed point FP _{T is defined} with respect to a support point 145 of the upper support bearing roller 140 at a boundary surface 152 of the cavity 150. This is also shown in the lower part of FIG. 3 (ΔX _B ).

Furthermore, it is possible according to the invention to carry out a plurality of such measurements in parallel and to determine a corresponding mean value for the strip thickness hi or the height hi of the gap 300.

According to the invention, it is not necessary, as shown in FIG 3, a height W _{P of} a roll stack 100, 200 between a support point 145, 245 of the corresponding roll stack 100, 200 at the apex FP _T *, FP _B * of the respective cavity 150, 250 for respective rolling point 112, 212 to define. This is shown in FIG. So it is z. B. possible, a roll pack thickness W _PT from the fixed point FP _T (attachment point of Right supporting bearing roller 140 on the boundary surface 152 of the cavity 105) horizontally with respect to the rolling point 112 and a top O rolled metal strip 2 to define. Such a height of the roll package W _PT is less than that shown in FIG. If the fixed point FP _{T is} not located on the boundary surface 152 of the cavity 150, then again a corresponding offset Δ X _τ must be taken into account, which is illustrated on the right and left in FIG. Furthermore, it is possible to determine the roll pack thickness W _PT with respect to a journal of a roll 110, 120, 130, 140 of the roll stack 100 or a bale of the relevant roll. The former is shown on the left in FIG. Analog, of course, a lower roller package 200 are considered.

FIG. 5 shows, according to the invention, preferred positions or measuring positions of the position encoder 400 or a plurality of position encoders 400 for the roll gap measurement according to the invention. Here, a horizontal distance between the two frame parts 10, 20 is determined in each case.

According to the invention, the position encoder 400 is provided on the upper frame part 10 and / or the lower frame part 20 and not on a setting cylinder or setting piston for positioning the upper frame part 10 with respect to the lower frame part 20. According to the invention, the position encoder 400 determines a position of a fixed point FP on a frame part 10, 20 with respect to a fixed point FP of the other frame part 20, 10.

According to the invention, the position encoder 400 may be provided at arbitrary points of the cluster roll stand 1. There are, however, preferred positions. These are located in particular in the inlet region 30 and outlet region 40 of the cluster roll stand 1. For this comes z. B. an underside of the framework upper part 10 or an upper side of the frame lower part 20 in question. Further, it is possible to arrange the position encoder 400 on the outside of the cluster mill stand 1, whereby z. B. a distance of an upper side of the cluster roll stand 1 (upper side te of the scaffold upper part 10) with respect to the underside of the multi-roll stand 1 (underside of the lower frame part 20) is determined. Furthermore, it is possible to place the position encoder 400 in or in the vicinity of the respective vertex FP _T *, FP _B * of the relevant cavity 150, 250. In particular, a point 145 on or in the multi-roll stand 1, from which a respective height W _PT , W _{PB of} the respective roll stack 100, 200 is defined.

According to the invention, the measurement principle of the direct roll gap measurement is realized by measuring a gap S proportional to the roll gap 300 between a top and bottom roll or their chocks. In this way, a direct roll gap control for a cluster roll stand 1 can be achieved. Furthermore, a direct roll gap control for a cluster roll stand 1 can be realized, which is realized by measuring a roll gap-proportional spacing on or within the multi-roll stand 1.

Claims

claims 1. A method for a direct nip measurement in a multi-roll stand (1), wherein a height (hi) of a roll gap (300) in dependence on a thickness (W _PT , W _PB ) of a roll stack (100, 200) of the cluster roll stand (1) determined becomes, whereby, with respect to at least one fixed point (FP, FP _T , FP _T *, FP _B , FP _B *) the roll packet thickness (W _PT , W _PB ) in a relation to a distance of the fixed point (FP, FP _T , FP _T *, FP _B , FP _B *) is set by a strip plane (O, U, M) of a metal strip (2) to be rolled, this relation being a measure of the height (hi) of the roll gap (300). 2. The method according to claim 1, wherein the roll packet thickness (Wp _T , W _PB ) from a rolling point (112, 212) defining an end of the nip (300) on a respective work roll (110, 210). 3. The method according to claim 2, wherein the roll packet thickness (W _PT , W _PB ) is defined by a connecting distance from the rolling point (112, 212) to an arbitrary point, preferably a fixed point, in the roll stack (100, 200). 4. The method according to any one of claims 1 to 3, wherein the Roll packet thickness (W _PT , W _PB ) through the connection path from the rolling point (112, 212) to a support point (145, 245) of the roll stack (100, 200) at a cavity (150, 250) of the cluster roll stand (1) is defined. 5. The method according to any one of claims 1 to 4, wherein the roll packet thickness (W _PT , W _PB ) through the connection path from the rolling point (112, 212) to a vertex (FP _T *, FP _B *, 145, 245) of a boundary surface ( 152, 252) of the cavity (150, 250) of the cluster mill (1) is defined. 6. The method according to any one of claims 1 to 5, wherein the fixed point (FP, FP _T , FP _B ) may be provided at an arbitrary position, and in the consideration of the roll packet thickness (W _PT , W _PB ) an offset (.DELTA.X) added which corresponds to a distance (ΔX) between a support point (145, 245) of the roll stack (100, 200) at the cluster mill stand (1) and the fixed point (FP, FP _T , FP _B ). 7. The method according to any one of claims 1 to 6, wherein the fixed point (FP) on the boundary surface (152, 252) of the cavity (150, 250) of the Vielwalzengerüsts (1), and the fixed point (FP *) preferably the vertex ( FP *) of the boundary surface (152, 252) of the cavity (150, 250). 8. The method according to any one of claims 1 to 7, wherein the height (hi) of the roll gap (300) of framework-dependent constants (G _τ , G _B , S, S ', S'', Y _T , Y _B , ΔX _T , ΔX _B ) and the roll package thickness (W _PT , W _PB ) is determined. 9. The method according to any one of claims 1 to 8, wherein the height (hi) of the roll gap (300) from the distance (S) of the scaffold upper part (10) to the framework lower part (20), the respective height (G _τ , G _B ) of Cavity (150, 250) and the respective roll package thickness (W _PT , W _PB ) is determined. 10. The method according to claim 9, wherein from the distance (S) of the scaffold upper part (10) to the framework lower part (20), the height (G _τ ) of the cavity (150) and the height (G _B ) of the cavity (250) a sum from which the roll pack thickness (W _PT ) of the upper roll stack (100) and the roll pack thickness (W _PB ) of the lower roll pack (200) is subtracted, resulting in a measure of the height (hi) of the roll gap (300). 11. The method according to any one of claims 1 to 8, wherein the height (hi) of the roll gap (300) from the distance (S ') of the Vertex (FP _T *) of the scaffold upper part (10) to the vertex (FP _B *) of the frame base (20) and the respective roll packet thickness (W _PT , W _PB ) is determined. 12. The method according to claim 11, wherein the distance (S ') of the vertex (FP _T *) of the scaffolding upper part (10) to the vertex (FP _B *) of the frame base (20), the roll packet thickness (W _PT ) of the upper roll stack (100) and the roll pack thickness (W _PB ) of the lower roll pack (200) is subtracted, resulting in a measure of the height (hi) of the roll gap (300). 13. The method according to any one of claims 1 to 8, wherein the height (hi) of the roll gap (300) from the distance (S '') of the top of the cluster roll stand (1) to the bottom of the multi-roll stand (1), a distance ( Y _τ ) of an upper side of the upper frame part (10) to the upper vertex (FP _T *), a distance (Y _B ) of an underside of the lower frame part (20) to the lower vertex (FP _B *) and the respective Walzenpaketdi- WICK (W _PT , W _PB ) is determined. 14. The method according to claim 13, wherein the distance (S '') of the top of the cluster roll stand (1) to the bottom of the cluster roll stand (1), the distance (Y _τ ) of the top of the scaffold upper part (10) to the top vertex (FP _T *) and the distance (Y _B ) of the underside of the lower frame part (20) to the lower vertex (FP _B *), and the roll pack thickness (W _PT ) of the upper roll stack (100) and the roll pack thickness (W _PB ) of the lower roll pack (200 ), which gives a measure of the height (hi) of the roll gap (300). 15. The method according to any one of claims 1 to 14, wherein in the determination of the distances (G _τ , G _B , S, S ', S'', Y _τ , Y _B , AX _T , ΔX _B ) and the roll pack thicknesses (W _PT , W _PB ) these are only considered on a one-dimensional basis and preferably on the basis of their respective amounts. 16. The method according to any one of claims 1 to 15, wherein the distance (S, S ', S'') between the scaffold upper part (10) and the lower frame part (20) by a position encoder (400) is detected. 17. Multi-roll stand, in particular Reduziergerüst, for a cold rolling mill, - In which a position encoder (400) for measuring a height (hi) of a roll gap (300) of the Vielwalzenge- scaffold (1) on a scaffold upper part (10) and / or a scaffold base (20) is provided. 18. A cluster mill according to claim 17, wherein the position encoder (400) is not provided on a setting cylinder for a positioning of the scaffolding upper part (10) relative to the lower frame part (20) of the cluster mill (1). 19. A cluster mill according to claim 17 or 18, wherein the position encoder (400) has a position of a fixed point (FP, FP _T , FP _T *, FP _B , FP _B *) relative to the upper frame part (10) and / or the lower frame part (20). certainly. 20. A cluster mill according to one of claims 17 to 19, wherein the position encoder (400) the position of a fixed point (FP _T , FP _T *, FP _B , FP _B *) on the upper frame part (10) or on the lower frame part (20) relative to the lower frame part (20) or the framework upper part (10). 21. A cluster mill according to one of claims 17 to 20, wherein the position encoder (400) between the scaffolding upper part (10) and the framework lower part (20) is arranged. 22 cluster mill according to one of claims 17 to 21, wherein the position encoder (400) in an inlet region (30) and / or an outlet region (40) to be rolled metal strip (2) in the cluster roll stand (1) is provided. 23. A cluster mill according to one of claims 17 to 21, wherein the position encoder (400) determines a position of a contact point (145, 245) of a roll stack (100, 200) on a cavity (150, 250) of the cluster roll stand (1). 24. cluster mill according to claim 23, wherein the support point (145, 245) of the roll stack (100, 200) a vertex (FP _T *, FP _B *) of a boundary surface (152, 252) of the cavity (150, 250) of the cluster mill stand ( 1). 25. A cluster mill according to one of claims 17 to 24, wherein for determining the height of the roll gap (300) of the cluster roll stand (1), a control or regulation unit of the cluster roll stand (1) carries out a method according to one of claims 1 to 15.