EP1694447B1 - Optimised shift strategy as a function of strip width - Google Patents

Abstract

The invention relates to a method for the optimization of shift strategies, as a function of the strip width, for best possible usage of the advantages of CVC/CVC<SUP>Plus </SUP>technology in operation of strip-edge oriented shifts in 4-/6-roller stands, comprising a pair of working rollers and a pair of support rollers for a 4-roller stand and, in addition, a pair of intermediate rollers for a 6-roller stand, whereby at least the working rollers and the intermediate rollers cooperate with devices for axial shifting, characterized in that selection of the shift position (VP), for the shifting working/intermediate rollers, is made as a function of strip width. The working/intermediate rollers are then positioned in various positions (P), relative to the strip edge and, within differing strip width ranges (B), the shift position (VP) of each roller is given by an incremental linear progressive function.

Description

The invention relates to a method of optimizing shifting strategies as a function of belt width for the best use of the advantages of CVC / CVC ^plus technology in belt edge shift operation in 4/6 roll stands comprising a pair of work rolls and back up rolls plus a pair of intermediate rolls at 6-roll stands, wherein at least the work rolls and the intermediate rolls cooperate with devices for axial displacement, and wherein each work / intermediate roll has a bale extended by the CVC Verschiebehub on one side regrind in the bale edge. A generic method and a generic device are eg off DE-A 100 37 004 known.

In the past, the quality requirements of cold rolled strip in terms of thickness tolerances, achievable final thicknesses, band profile, flatness, surfaces, etc. have been steadily increasing. The variety of products on the market for cold-rolled sheets also leads to an ever more diverse range of products in terms of material properties and geometric dimensions. As a result of this development, the desire for more flexible plant concepts and operating modes in cold tandem mills - optimally adapted to the final product to be rolled - is becoming increasingly important.

The achievement of a desired final thickness as well as the realization of certain acceptance distributions (tailoring design), especially for higher-strength grades, is significantly influenced by the working roll diameter. With decreasing work roll diameter, the required rolling force is reduced by a more favorable flattening behavior. The reduction in diameter are limited both by the transmission of the torques forth and in terms of roll deflection. If the journal cross sections are not sufficient for transmitting the drive torques, then the work rolls can move over Frictionally engaged by the adjacent roller to be driven. In the case of a 4-roll stand, however, heavy drive elements (motor, comb gear, spindles) for the realization of a backup roller drive are required, which make the system more expensive. Here it makes sense to carry out individual scaffolding (usually the front) as 6-roll stands with intermediate roller drive.

In addition to the vertical deflection, the horizontal deflection of the work rolls and intermediate rolls also plays an important role in the flatness of the strip. Due to the horizontal displacement of the work / intermediate rollers from the center plane of the framework, a support of the set of rollers, which leads to a substantial reduction of the horizontal deflection takes place.

In addition, the 6-roll mill has an additional, fast actuator in the intermediate roll bend. In combination with the work roll bending, the 6-roll mill thus has two independent in effect on the nip actuators. In the first frame, a rapid adaptation of the roll gap to the incoming strip profile is thus ensured in order to avoid flatness defects. In the last framework both actuators can be effectively used in the flatness control.

• CVC/CVC^plus - Technologie
• Technologie des bandkantenorientierten Verschiebens

For classic scaffolding types 4-High and 6-High, there are essentially two further scaffolding conceptions in addition to basic concepts with bending systems and fixed roll crowns acting as a roll gap, which additionally influence the roll gap by moving work rolls or intermediate rolls based on different active principles.

• CVC / CVC ^plus technology
• Band edge-oriented shifting technology

These are separate scaffolding concepts, as different roll geometries are required.

In the classic CVC technology as used in the EP 0 049 798 B1 is described, the bales of the displaceable rollers are always longer by the axial displacement stroke than the fixed, unshifted rollers. This ensures that the sliding roller can not be pushed with its bale edge under the fixed roll barrel. Thus, surface damage / marks are avoided. The work rolls are generally supported over their entire length on the intermediate or backup rolls. Thereby, the rolling force exerted by the back-up rolls is transmitted to the entire length of the work rolls. This has the consequence that the laterally projecting beyond the rolling stock and thus not involved in the rolling process ends of the work rolls are bent by the force exerted on them rolling force in the direction of the rolling stock. From this detrimental deflection of the work rolls results in a bending of the middle roller sections. It causes too little rolling out of the central band area and a strong rolling out of the band edges. These effects are particularly effective when changing rolling conditions during operation and when rolling strips of different widths.

In contrast, in the technology of band edge-oriented shifting, as in the DE 22 06 912 C3 is disclosed using rolls of equal bale length throughout the set of rolls. The displaceable rollers are designed geometrically on one side in the bale edge region and provided with a regrind to reduce locally occurring load peaks. The operating principle is based on the band edge-oriented Nachschieben the bale edge, either before, on or even behind the band edge. In particular with 6-roll stands, the displacement of the intermediate roll under the support roll leads to a specific influence on the effectiveness of the positive work roll bending. A disadvantage, however, affects in this process, the axial displacement of the rollers on the load distribution in the respective contact joints out. As the bandwidth decreases, the maximum load peak of the contact force distribution increases dramatically.

In the patent DE 36 24 241 C2 (Method for operating a rolling mill for producing a rolled strip), both methods are combined. The aim is to equalize the adverse deflection of the work rolls under rolling force over the entire bandwidth spectrum and to increase the effectiveness of the roll bending systems while shortening the displacement paths, without the continuous rolling operation must be interrupted. This goal is achieved by the band edge-oriented shifting of intermediate or work rolls with an applied CVC grinding. The bale edges of the CVC rollers are positioned in the area of the strip edge. As in the case of strip edge oriented technology, the set of rolls consists of rolls of equal bale lengths.

The technologies discussed are each separate framework concepts, since different roll geometries are required. There is a desire to realize these technologies / driving styles by a scaffolding concept with geometrically equal set of rollers. The basic procedure for the realization of a strip edge oriented shift strategy excluding the intermediate rolls and exclusively in a 6-roll mill using a geometrically equal set of rolls was in the DE 100 37 004 A1 described in detail.

The object of the invention is that of the DE 100 37 004 A1 To extend known band edge-oriented shift strategy on the work rolls so that a scaffolding concept with geometrically equal set of rollers is realized.

The stated object is achieved by the characterizing features of claim 1 by specifying the displacement position of the displaceable working / intermediate roller as a function of the bandwidth at which the working / intermediate roller is positioned in different positions relative to the strip edge, wherein within different bandwidth ranges while the shift position of the respective roller is predetermined by piecewise linear approach function.

Depending on the material properties, the free parameters of the attachment function are chosen so variably predefinable that the predetermined positions are set relative to the strip edge. The strip edge-oriented shifting of the work / intermediate rolls is carried out so that they are shifted relative to the neutral displacement position (s _ZW = 0 or s _AW = 0) in the middle of the framework symmetrically by the same amount in the direction of its axis against each other.

As a basis for the scaffolding concept, the roller configuration made of the CVC / CVC ^plus technology is used for a 6-roll or 4-roll stand. The displaceable intermediate or work roll has a bale which is longer by the CVC displacement stroke and which is symmetrical in the center of the frame for the neutral displacement position s _ZW = 0 or s _AW = 0.

The work / intermediate roll with longer and symmetrical bale is used during the strip edge-oriented shifting either with a cylindrical, crowned or superimposed CVC / CVC ^plus -schliff. By suitable execution of a one-sided regrind in combination with the superimposed roll grinding and the bandwidth-dependent optimization of the axial displacement position, the deformation behavior of the set of rolls and the effectiveness of the positive work roll bending (6-roll stand) can be specifically influenced. The roll gap can thus be optimally adjusted.

The cylindrical bale of the working / intermediate roller can additionally be overlaid with a curved contour (eg CVC / CVC ^plus grinding).

Due to the superimposed, curved contour of the work / intermediate roller, the required displacement stroke can be reduced since the start of the regrind of the work / intermediate roller is positioned clearly in front of the strip edge. On the one hand, the load distribution is reduced as a result of the longer contact length. On the other hand, the maximum of the load distribution due to CVC / CVC ^plus grinding shifts increasingly towards the middle of the framework with decreasing bandwidth.

During axial displacement of the work / intermediate roller, the beginning of the regrind is positioned outside, on or within the band edge, ie already within the bandwidth. The positioning depends on the belt width and the material properties, whereby the elastic behavior of the roller set as well as the effectiveness of the positive work roll bending (6-roll stand) can be adjusted.

By optimizing the shift position of the work / intermediate rollers targeted bale areas are hidden within the set of rollers from the power flow. Resulting, negatively affecting deformations are reduced, since the principle of the "ideal framework" is approximated. However, the occurring load distributions increase in the respective contact joints due to the reduced contact lengths.

The opposite displacement of the CVC / CVC ^plus rollers also results in the possibility of a targeted influencing of the band profile in the sense of a preset actuator. If the curved contour is selected in such a way that it generates no or minimum crown in the maximum negative displacement position and a maximum crown in the maximum positive displacement position, then the bandwidth-dependent framework deformation can be partially compensated. The remaining part is compensated for by the decreasing bandwidth increasing effect of positive work roll bending.

Further advantages, details and features of the invention will become apparent from the following explanations of some schematically illustrated in drawing figures embodiments. For clarity, the same rolls are provided with the same reference numerals.

Fig. 1

den einseitigen Rückschliff im Bereich der Ballenkante einer Arbeits-/Zwischenwalze,

Fig. 2

Gerüstkonzeption für bandkantenorientiertes Verschieben mit überlagertem CVC/CVC^plus -Schliff der Zwischenwalzen,

Fig. 3

Gerüstkonzeption für bandkantenorientiertes Verschieben mit überlagertem CVC/CVC^plus -Schliff der Arbeitswalzen,

Fig. 4a-4c

Positionierung des Zwischenwalzenrückschliffs,

Fig. 5a-5c

Positionierung des Arbeitswalzenrückschliffs,

Fig. 6

Vorgabe der Verschiebeposition in Abhängigkeit der Bandbreite.

Show it:

Fig. 1

one-sided regrind in the area of the bale edge of a work / intermediate roll,

Fig. 2

Framework concept for strip edge-oriented shifting with superimposed CVC / CVC ^plus grinding of the intermediate rolls,

Fig. 3

Scaffolding concept for band edge-oriented shifting with superimposed CVC / CVC ^plus grinding of the work rolls,

Fig. 4a-4c

Positioning the intermediate roll regression,

Fig. 5a-5c

Positioning of the work roll regrind,

Fig. 6

Specification of the shift position depending on the bandwidth.

In FIG. 1 schematically the appearance and the geometric arrangement of a one-sided regression d in the bale edge of a working / intermediate roller 10, 11 is shown. In the DE 100 37 004 A1 is a one-sided regression, as used here, already described in detail and shown in a drawing figure.

The length 1 of the unilateral regrind d in the region of a ball edge of the working / intermediate roller 10, 11, is divided into two juxtaposed areas a and b. In the first inner region a, starting at the point d ₀ , the regression y (x) follows the circle equation (I - x) ² + y ² = R ² with R for the roll radius. With the coordinates x and y drawn in, a regression y (x) of the range a then results from:

Range a: = (R ² - (R - d) ² ) ^1/2 ⇒ y (x) = R - (R ² - (I - x) ² ) ^1/2

If a minimally required diameter reduction 2d predetermined as a function of the outer boundary conditions (rolling force and resulting roll deformation) is reached, then the regrind y (x) extends linearly up to the bale edge, resulting in the region b.

Range b: = I - a ⇒ y (x) = d = const.

The transition between region a and b can be performed with or without a continuously differentiable transition. Furthermore, this transition of the regression can also be made with a sequential withdrawal of the resulting from the flattening measure d according to a previously determined table. The regression y (x) is then, for example in the transition region shallower than a radius and at the end much steeper. For reasons of grinding technology, the transition to the cylindrical part via a correspondingly larger heel in the transition between a and b is carried out (about 2d).

The diameter reduction 2d by the regrind y (x) is predetermined such that in a 6-roll stand the work roll 10 can bend freely around the regrind y (x) of the intermediate roll 11 without having to fear contact in the region b. In the 4-roll stand, the regrind y (x) is only used to locally reduce the load peaks that occur.

Normally, the one-sided regrind is on the upper working / intermediate roller 10, 11 on the operating side BS and on the lower working / intermediate roller 10, 11 on the drive side AS, as in the FIGS. 2 and 3 is cited. On the principle of action, however, nothing changes when reversing the reverse on the upper working / intermediate roller 10, 11 on the drive side AS and at the lower working / intermediate roller 10, 11 on the operating side BS attaches.

In FIG. 2 the roll set of a 6-roll stand is shown, consisting of the work rolls 10, the intermediate rolls 11 with extended bales and the support rollers 12. The rolled strip 14 is arranged symmetrically in the middle of the frame. The illustrated displacement of the intermediate roller 11 by the amount s _ZW = "+" indicates that it has been shifted in the direction of the drive side AS. (Positive displacement means that the upper work / intermediate roll 10, 11 is displaced in the direction of the drive side AS and the lower work / intermediate roll 10, 11 in the direction of the operating side BS.)

In FIG. 3 is the set of rolls of a 4-roll stand shown, consisting of the work rolls 10 with extended bales and the support rollers 12. Again, a positive shift was performed and that of the work rolls 10 by the amount s _AW = "+".

In the Figures 4a-4c and 5a-5c is the axial displacement of the working / intermediate roller 10, 11 by a displacement m again shown in detail. In the illustrated displacement positions of FIGS. 4a and 5a was the beginning d _{0 of} the regression y (x) outside the band edge (m = +), in FIGS. 4b and 5b on the band edge (m = 0) and in FIGS. 4c and 5c within the band edge (m = -), ie already positioned within the bandwidth.

Depending on the bandwidth, the shift position is predetermined in different bandwidth regions by piecewise linear attachment functions, which are based on different positions of the beginning d _{0 of} the regression relative to the band edge. The sliding work / intermediate roll is not, as is conventional, with a fixed dimension m as in the FIGS. 4 and 5 shown, positioned in front of the strip edge, but depending on the bandwidth in different positions P (α, β, χ, see Table 1) relative to the band edge. Within different bandwidth ranges B (a, b, c, d, e, see Table 1), the displacement position VP (w, x, y, z, see Table 1) of the respective roller is predetermined by piecewise linear approach function. The free parameters of the attachment function are chosen such that the positions P given in Table 1 are set relative to the band edge. This also results in the displacement position VP of the roller. Depending on the material properties, the parameters can be variably specified.

In FIG. 6 is shown in the form of a diagram an example of the specification of the bandwidth-dependent displacement position of the intermediate roll in a 6-roll stand. Plotted on the ordinate, the predetermined displacement position VP in mm and on the abscissa of the bandwidth area B. Parallel to the abscissa in the upper part of the diagram, the maximum displacement position VP _max . and in the lower part the minimum displacement position VP _min . drawn in dashed form.

• Bei einem Rückschliffbeginn d₀ an der Zwischenwalze im Abstand P = α in mm außerhalb der Bandkante B = a in mm ergibt sich eine Verschiebeposition VP von w in mm.
• Bei einem Rückschliffbeginn d₀ an der Zwischenwalze im Abstand P = β in mm außerhalb der Bandkante b < B < d in mm ergibt sich eine Verschiebeposition VP zwischen x bis z in mm.
• Bei einem Rückschliffbeginn d₀ an der Zwischenwalze im Abstand P = χ in mm innerhalb der Bandkante B = e in mm ergibt sich eine Verschiebeposition VP von z in mm.

From this diagram, for different positions P, the obtained displacement positions VP are to be fetched with the aid of Table 1 as follows:

• In a regrind beginning d ₀ at the intermediate roller at a distance P = α in mm outside the belt edge B = a in mm results in a displacement position VP of w in mm.
• In a regrind beginning d ₀ at the intermediate roller at a distance P = β in mm outside the belt edge b <B <d in mm results in a displacement position VP between x to z in mm.
• In a regrind beginning d ₀ at the intermediate roller at a distance P = χ in mm within the belt edge B = e in mm results in a displacement position VP of z in mm.

An essential advantage of the scaffolding concept described is that with only one geometrically identical set of rollers, the CVC / CVC ^plus technology and the technology of band-edge-oriented shifting can be realized in the manner set forth above. There are no longer different types of rollers necessary. Differences exist only in applied roll grinding or a regrind upwards given specifications. In addition, the possibility of combining the two technologies together and optimizing the deformation behavior of the rolling mill and the load distribution in the contact joints using different shift strategies is (ESS technology = E nhanced S hifting S trategies).

LIST OF REFERENCE NUMBERS

10

Stripper

11

intermediate roll

12

supporting roll

14

rolled strip

a

first, inner section length of d

b

second, outer section length of d

d

Regrind (corresponds to a diameter reduction of 2d)

d ₀

Beginning of d

l

Length of d

m

displacement stroke

s _AW

Shift amount of a work roll

s _ZW

Displacement amount of an intermediate roller

x, y

Cartesian coordinates

AS

driving side

B

bandwidth

BS

operating side

P

Position of 10, 11 relative to the band edge

R

roll radius

R ₀

Starting roll radius

VP

shift position

Claims (6)

1. Method for optimising shifting strategies as a function of strip width for the best possible utilisation of the advantages of CVC/CVC^plus technology in the operation of strip edge-oriented shifting in four-high and six-high rolling stands, each comprising a pair of work rolls (10) and a pair of backup rolls (12) and, additionally in the case of six-high rolling stands, a pair of intermediate rolls (11), wherein at least the work rolls (10) and in the case of six-high rolling stands, the intermediate rolls (11) co-operate with devices for axial shifting, and wherein each of these intermediate rolls (11) has a barrel, which is lengthened by the amount of the CVC shifting stroke, with a one-sided setback y(x) in the area of the barrel edge, characterised in that each work roll (10) also has a barrel, which is lengthened by the amount of the CVC shifting stroke, with a one-sided setback y(x) in the area of the barrel edge, and in the same manner as the intermediate roll (11) the work roll (10) is positioned in different positions (P) relative to the strip edge (14) according to predetermination of the shift position (VP) of the shiftable work roll / intermediate roll (10, 11) as a function of the strip width, and within different strip width regions (B) the shift position (VP) of the respective roll is predetermined by a piecewise-linear step function.
2. Method according to claim 1, characterised in that depending on the material properties the free parameters of the step function are so variably presettable that the predetermined positions (P) relative to the strip edge (14) are established.
3. Method according to claim 1, characterised in that the strip edge-oriented shifting of the work rolls / intermediate rolls (10, 11) is carried out in such a way that the rolls are each symmetrically shifted relative to the neutral shift position (s_ZW = 0 or s_AW = 0) in the stand centre by the same amount axially towards each other.
4. Rolling mill comprising four-high or six-high rolling stands in a CVC design each with a pair of work rolls (10) and a pair of backup rolls (12) in the case of a four-high rolling stand and, additionally, in the case of a six-high rolling stand, a pair of intermediate rolls (11), wherein at least the work rolls (10) and the intermediate rolls (11) co-operate with devices for axial shifting, for carrying out the method according to one or more of claims 1 to 3, characterised in that the rolling stands have a geometrically identical roll set, wherein each of the shiftable work rolls / intermediate rolls (10, 11) of the rolling stands has a symmetrical barrel which is longer by the amount of the axial CVC shifting stroke and is provided with a curved roll contour with superimposed (CVC/CVC^plus cross-section) and with a one-sided setback (d).
5. Rolling mill according to claim 5, characterised in that the length (l) of the one-sided setback y(x) of the work rolls / intermediate rolls (10, 11) is divided into two adjacent regions (a) and (b), wherein the first region (a), beginning with the radius (R₀), obeys the equation of the circle (I - x)² + y² = R², and the region (b) runs linearly, from which the following setback y(x) or the following diameter reduction 2 • y(x) is obtained for these regions due to the dimension resulting from the roll flattening:

   Region a: = (R² - (R - d)²)^½ ⇒ y(x) = R - (R² - (1 - x)²)^½

   Region b: = 1 - a ⇒ y(x) = d = constant.
6. Rolling mill according to claims 4 and 5, characterised in that the transition of the setback y(x) between the regions (a) and (b) is carried out with a sequential setback of the dimension (d), which results from the roll flattening, according to a determined table.

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