EP1699573B1 - Combined operating modes and frame types in tandem cold rolling mills - Google Patents

Abstract

A cold rolling mill has groups of paired working rollers (10) with supporting rollers (12), followed by six pairs of roller frames with intermediate rollers (11). The working rollers and intermediate rollers have limited axial sliding freedom. The cold rolling mill combines CVC/CVC(plus technology, Per Cross Technology, and the use of strip edge-orientated axial slip of the working and intermediate rollers. The CVC/CVC(plus technology employs CVC roller contours, in which each working roller or intermediate roller has an extension that embraces the side shift zone. The Per Cross technology facilitates azimuth swivel movement of the working and intermediate rollers parallel to the plane through which the strip advances. The strip edge-orientated axial slip of the working and intermediate rollers facilitates equal and opposite shift of these rollers relative to a neutral position.

Description

The invention relates to a method for the combined operation of individual rolling stands within a cold tandem mill, comprising a pair of work rolls and back-up rolls in 4-roll stands and additionally a pair of intermediate rolls in 6-roll stands, wherein at least the work rolls and the intermediate rolls cooperate with devices for axial displacement.

• SHIGEMATSU K ET AL: "ADVANCED TECHNOLOGIES OF THE NEW VOLD STRIP MILL AT KASHIMA STEEL WORKS" CAHIERS D'INFORMATIONS TECHNIQUES DE LA REVUE DE METALLURGIE, REVUE DE METALLURGIE. PARIS, FR, Bd. 92, Nr. 6, 1. Juni 1995 (1995-06-01), Seiten 795-803, XP000527745 ISSN: 0035-1563

bekannt.A method and a device according to the preambles of claims 1 and 5 is eg from document:

• SHIGEMATSU K ET AL: "ADVANCED TECHNOLOGIES OF THE NEW VOLD STRIP MILL AT KASHIMA STEEL WORKS" CAHIERS D'INFORMATIONS TECHNIQUES DE LA REVUE DE METALLURGIE, REVUE EN METALLURGIE. PARIS, FR, Vol. 92, No. 6, 1 June 1995 (1995-06-01), pages 795-803, XP000527745 ISSN: 0035-1563

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 classical plant concept of a cold tandem mill consists in the juxtaposition of several 4-roll stands. The number of scaffolds needed will be largely determined by the total quantity and the final thickness to be achieved. In addition to the basic concepts with bending systems and fixed roll crowns as actuators influencing the roll gap, there are essentially three further framework designs which additionally influence the roll gap, either by displacement or by pivoting of the work rolls based on different active principles.

• Technologie des bandkantenorientierten Verschiebens
• CVC/CVC^plus - Technologie
• PC - Technologie (Per Cross - Schwenken der Arbeitswalzen)

These are:

• Band edge-oriented shifting technology
• CVC / CVC ^plus technology
• PC technology ( P er C ross - Swiveling the work rolls)

As a result of different technological criteria, it may make sense to deviate from the classical plant concept (consisting exclusively of 4-roll stands) and to construct individual stands as 6-roll stands.

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, the work rolls can be driven by frictional engagement by the adjacent roll. 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.

An additional influence on the rolling operation with respect to the flatness and the roll gap is in a pivoting of the work rolls, wherein, as in the JP 57 190 704 A is described for 4-roll stands, the work / intermediate rolls are pivoted about a common pivot point in the roll axis center parallel to the strip plane against each other by the same amount at the same time.

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

Another criterion for the quality of the final product is the surface finish of the expiring belt. Textured (roughened) and chrome-plated rollers allow the surface of the belt to be pre-set in a targeted manner. In order to avoid marks on the end product by shifting wear edges or shades on the belt surface by the occurrence of relative speed differences across the width of the outgoing belt, it makes sense to run the last stand of a cold tandem mill as a 6-roll mill. The work rolls are cylindrical or slightly crowned. They are not moved in the rolling process.

The active principles described above are separate scaffolding concepts, since 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. 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.

For reasons of cost-effectiveness, efforts are being made to carry out all the scaffolding as equally as possible in order to reduce the costs for maintenance and replacement parts. In the past, cold tandem mills have therefore been designed in the classical layout or throughout the technologies described.

The object of the invention is to realize these technologies / modes of operation by means of a scaffold design with a geometrically identical set of rolls, which is not limited to a 6-roll stand and not only to the intermediate rolls.

• Verwendung der CVC/CVC^plus - Technologie mit CVC-Walzkonturen höherer Ordnung, wobei jede Arbeits- / Zwischenwalze einen um den Verschiebehub verlängerten Ballen besitzt;
• Verwendung der Per Cross (PC) - Technologie, wobei jede Arbeits- / Zwischenwalze parallel zur Bandebene verschwenkt werden kann;
• Verwendung des bandkantenorientierten Verschiebens der Arbeits- / Zwischenwalzen, wobei jede Arbeits- / Zwischenwalze einen um den Verschiebehub verlängerten Ballen mit einem zylindrischen oder balligen Schliff besitzt und diese relativ zur neutralen Verschiebeposition in Gerüstmitte symmetrisch um jeweils den gleichen Betrag in Richtung ihrer Rotationsachse gegeneinander verschoben werden.

The stated object is achieved by the feature combinations specified in claims 1 and 5, respectively.

• Using the CVC / CVC ^plus technology with higher order CVC rolling contours, each work / intermediate roll having a bale extended by the displacement stroke;
• Using the P he C ross (PC) - technology, wherein each working / intermediate roll can be pivoted parallel to the strip plane;
• Use of the band edge-oriented displacement of the work / intermediate rolls, each work / intermediate roll has a bale extended by the Verschiebehub with a cylindrical or spherical grinding and these are symmetrical relative to the neutral displacement position in the middle of the scaffold shifted by the same amount in the direction of its axis of rotation against each other ,

An installation for carrying out the method is characterized by the features of claim 5

As a basis for the scaffolding concept, the CVC / CVC ^plus technology roll configuration is used for a 6-roll or 4-roll stand. The slidable intermediate or work roll has a bale which is longer around the CVC displacement stroke and which is symmetrical in the center of the frame for the neutral displacement position.

The working / intermediate roller with longer and symmetrical bale is used during the band edge-oriented shifting either with a cylindrical or crowned ground. By suitable design of a regrind in the area of the bale edge 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 selectively influenced and the roll gap can be optimally adjusted ,

Furthermore, by optimizing the displacement position of the work / intermediate rollers targeted bale areas within the set of rollers from the power flow hidden. 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 framework designs described are modified according to the invention such that the roll gap is influenced either by the displacement or the pivoting of the work / intermediate roll. A 6-roll stand is absolutely necessary in any case, if an additional, affecting the edge drop of the tape actuator is to be implemented in the framework. This requires two independent displacement systems for profile and flatness. The system layout is determined by these criteria. Depending on the demands placed on the rolling process, the range of system configurations ranges from the classic cold tandem mills, consisting of 4-roll stands, to combined plants consisting of 4- / 6-roll stands up to the cold tandem mill. which consists exclusively of 6-roll stands. The basic procedure for realizing a strip edge-oriented shift strategy excluding the intermediate rolls and exclusively in a 6-roll mill using a geometrically identical set of rolls is in the DE 100 37 004 A1 described in detail.

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

die Geometrie der Zwischenwalze ohne Walzenschliff in einem 6- Walzengerüst,

Fig. 2

die Geometrie der Arbeitswalze ohne Walzenschliff in einem 4- Walzengerüst,

Fig. 3

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

Fig. 4

Gerüstkonzeption mit verlängertem Zwischenwalzenballen,

Fig. 5

Gerüstkonzeption mit verlängertem Arbeitswalzenballen,

Fig. 6a-6c

Positionierung des Zwischenwalzenrückschliffs,

Fig. 7a-7c

Positionierung des Arbeitswalzenrückschliffs.

Show it:

Fig. 1

the geometry of the intermediate roll without roll grinding in a 6-roll stand,

Fig. 2

the geometry of the work roll without roll grinding in a 4-roll mill,

Fig. 3

the unilateral regrind in the area of the bale edge of a work / intermediate roll,

Fig. 4

Scaffolding concept with extended intermediate roll bale,

Fig. 5

Scaffolding concept with extended work roll bale,

Fig. 6a-6c

Positioning the intermediate roll regression,

Fig. 7a-7c

Positioning of the work roll regrind.

In the Figures 1 and 2 the geometry of the intermediate / working roll 11, 10 is shown without roll grinding. In Fig. 1 The displaceable intermediate roller 11 provided with an extended bale is located between the work roll 10 and the support roller 12 in the neutral displacement position s _ZW - = 0 symmetrically in the center of the frame YY. In Fig. 2 the work roll 10 has an extended bale. You too is in neutral displacement position s _AW = 0 symmetrical in the middle of the framework YY.

In the FIG. 3 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 I of the unilateral regrind d in the region of a ball edge of the work / intermediate roller 10, 11 is divided into two adjoining areas a and b. In the first inner region a, starting at the point d ₀ , the regression d follows the circle equation (I - x) ² + y ² = R ² with R for the roll radius. For the area a then an amount d (x) of the regression d of: $$\mathrm{Area\; a}\mathrm{:}\mathrm{=}{\left({\mathrm{R}}^{\mathrm{2}}\mathrm{-}{\left(\mathrm{R}\mathrm{-}\mathrm{d}\right)}^{\mathrm{2}}\right)}^{\mathrm{1}\mathrm{/}\mathrm{2}}\mathrm{\Rightarrow }\mathrm{d}\mathrm{=}\mathrm{d}\left(\mathrm{x}\right)\mathrm{=}\mathrm{R}\mathrm{-}{\left({\mathrm{R}}^{\mathrm{2}}\mathrm{-}{\left(\mathrm{l}\mathrm{-}\mathrm{x}\right)}^{\mathrm{2}}\right)}^{\mathrm{1}\mathrm{/}\mathrm{2}}$$

If a minimally required diameter reduction 2d predetermined as a function of the outer boundary conditions (rolling force and resulting roll deformation) is achieved, then the regrind d extends linearly up to the bale edge, resulting in the region b. $$\mathrm{Area\; b}\mathrm{:}\mathrm{=}\mathrm{l}\mathrm{=}\mathrm{a}\mathrm{\Rightarrow }\mathrm{d}\mathrm{=}\mathrm{d}\left(\mathrm{x}\right)\mathrm{=}\mathrm{const}\mathrm{,}$$

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 regrind d is then, for example, in the transition area flatter than a radius and at the end much steeper. For technical reasons, the transition is to the cylindrical part via a correspondingly larger heel in the transition between a and b perform (about 2d).

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

Normally, the one-sided regrind d is at the upper working / intermediate roller 10, 11 on the operating side BS and at the lower working / intermediate roller 10, 11 on the drive side AS, as in FIGS. 4 and 5 is shown. On principle, however, nothing changes, if one attaches the regrind d inversely to 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.

In the FIGS. 6a to 6c the axial displacement of the intermediate roller 11 is shown by a displacement m. In Fig. 6a becomes the beginning d _{0 of} the regression d outside (m = +), in Fig. 6b on (m = 0) and in Fig. 6c within (m = -) of the band edge, ie already positioned 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.

In the FIGS. 7a to 7c Finally, in the same way as in the intermediate roll 11 in the FIGS. 6a to 6c performed strip edge-oriented displacements of the work roll 10 is shown.

In different bandwidth ranges, the shift position is given by piecewise linear attachment functions, which are based on different positions of the beginning d _{0 of} the regression d relative to the band edge.

An essential advantage of the framework design described is that CVC / CVC ^plus technology and the technology of band edge-oriented shifting can be realized with only one geometrically identical set of rollers. There are no longer different types of rollers necessary. Differences exist only in applied roll grinding or a regrind upwards given specifications. There is the possibility of combining these two technologies in addition to a pivoting of the work / intermediate rollers in the belt level.

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

setback

d ₀

Beginning of d

d (x)

of x dependent amount 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

BS

operating side

R

roll radius

ro

Starting roll radius

X X

axis of rotation

Y-Y

stand center

Claims (8)

1. Method for operation of the roll stand of a tandem cold rolling train, comprising a respective pair of working rolls (10) and backing rolls (12) in four-roll stands and additionally a pair of intermediate rolls (11) in six-roll stands, wherein at least the working rolls (10) and the intermediate rolls (11) co-operate with devices for axial displacement, characterised by the combined use of the following technologies within the multi-stand tandem cold rolling train:

   - use of the CVC/CVC^plus technology with CVC roll contours of higher order, wherein each working/intermediate roll (10, 11) has a circumferential surface extended by the displacement stroke;

   - use of the Per Cross (PC) technology, wherein each working/intermediate roll (10, 11) can be pivoted relative to the strip plane; and

   - use of displacement, which is oriented to strip edge, of the working/intermediate rolls (10, 11), wherein each working/intermediate roll (10, 11) has a circumferential surface, which is prolonged by the displacement stroke, with a cylindrical or spherical form and these are displaced relative to one another symmetrically by in each instance the same amount in the direction of the axis (X-X) of rotation thereof relative to the neutral displacement position (s_ZS = 0 or s_AW = 0) at the stand centre (Y-Y).
2. Method according to claim 1, characterised in that for use of the displacement oriented to strip edge the working/intermediate rolls (10, 11) are provided with a reducing grind (d) at one end, wherein on displacement of each working/intermediate roll (10, 11) the start (d₀) of the reducing grind (d) is positioned outside or on or within the strip edge, i.e. within the strip width of the strip (14).
3. Method according to claim 1 or 2, characterised in that the displacement position of the working/intermediate roll (10, 11) in different strip width ranges is predetermined by section-by-section linear step functions, on which different positions of the start (d₀) of the reducing grind (d) relative to the strip edge (14) are based.
4. Method according to claim 1, 2 or 3, characterised in that a best possible utilisation of the technology combination within the multi-stand tandem cold rolling train is effected by optimised displacement strategies as a function of the strip width.
5. Tandem cold rolling train comprising four/six-roll stands with a respective pair of working rolls (10) and backing rolls (12) in four-roll stands and additionally a respective pair of intermediate rolls (11) in six-roll stands, wherein at least the working rolls (10) and the intermediate rolls (11) co-operate with devices for axial displacement, characterised in that the working/intermediate rolls (10, 11) of the roll stands each have a symmetrical circumferential surface, which is extended by the axial displacement stroke, with a cylindrical or spherical form, which for the neutral displacement position (S_ZW = 0 or S_AW = 0) is located symmetrically at the stand centre (Y-Y); and that the roll stands are appropriately selected to enable a combination of the different technologies:

   - the displacement, which is oriented to strip edge, of the working/intermediate rolls (10,11),

   - the CVC technology and

   - the pivotation of the working rolls (10), the PC technology (Per Cross), within the multi-stand tandem cold rolling train.
6. Tandem cold rolling train according to claim 5, characterised in that the circumferential surface of the working/intermediate rolls (10, 11) is provided at one end with a reducing grind (d), the length (I) of which is separated into two mutually adjoining regions (a) and (b), wherein the first region (1), beginning with the radius (R₀), follows the trigonometric function $${\left(\mathrm{l}\mathrm{-}\mathrm{x}\right)}^{\mathrm{2}}\mathrm{+}{\mathrm{y}}^{\mathrm{2}}\mathrm{=}{\mathrm{R}}^{\mathrm{2}}$$

   

   and the region (b) extends linearly, wherefrom the following reducing grind (d) or following diametral reduction (2d) results for these regions $$\mathrm{region}\left(\mathrm{a}\right)\mathrm{:}\mathrm{=}{\left({\mathrm{R}}^{\mathrm{2}}\mathrm{-}{\left(\mathrm{R}\mathrm{-}\mathrm{d}\right)}^{\mathrm{2}}\right)}^{½}\mathrm{\Rightarrow }\mathrm{d}\mathrm{=}\mathrm{d}\left(\mathrm{x}\right)\mathrm{=}\mathrm{R}\mathrm{-}{\left({\mathrm{R}}^{\mathrm{2}}\mathrm{-}{\left(\mathrm{l}\mathrm{-}\mathrm{x}\right)}^{\mathrm{2}}\right)}^{½}$$

   

   $$\mathrm{region}\left(\mathrm{b}\right)\mathrm{:}\mathrm{=}\mathrm{l}\mathrm{=}\mathrm{a}\mathrm{\Rightarrow }\mathrm{d}\mathrm{=}\mathrm{d}\left(\mathrm{x}\right)\mathrm{=}\mathrm{const}\mathrm{.}$$

   
7. Tandem cold rolling train according to claim 5 or 6, characterised in that the transition of the reducing grind (d) between the regions (a) and (b) is carried out with a sequential feedback of the dimension (d), which results from the roll flattening, according to a determined table.
8. Tandem cold rolling train according to any one of claims 5 to 7, characterised in that the tandem cold rolling train is constructed with an appropriate concept to realise the CVC/CVC^plus technology, as well as the technology of displacement oriented to the strip edge as well as optionally the PC technology, with only one geometrically identical roll set.

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