EP1789210B1 - Convex roll used for influencing the profile and flatness of a milled strip - Google Patents

Abstract

Rolling stand for producing rolled strip, which includes work rolls, which are supported on backup rolls or intermediate rolls and backup rolls. The work rolls and/or the backup rolls and/or the intermediate rolls can be axially shifted relative to one another. The barrel length (L) of each intermediate roll in a six-high rolling stand or of each work roll in a four-high rolling stand has a cylindrical roll barrel section (Z) and a convexly curved roll barrel section (R(x)), such that the transition point from the cylindrical to the curved roll barrel section, calculated from the cylindrical end of the roll barrel, is in the range of L/2≰x<L. The curved contour, which extends towards opposite ends of the two rolls over a portion of the barrel, is described by a polynomial R(x)=ao+ . . . anxn, where n≧5.

Description

The invention relates to a rolling stand for producing a rolled strip, comprising work rolls, which optionally supported on backup rolls or intermediate rolls and backup rolls, wherein the work rolls and / or the backup rolls and / or the intermediate rolls are axially displaceable against each other.

A generic rolling mill is eg off DE 691 15 746 T known.

Rolling mills are known with displaceable pairs of rolls, each roll at least one of these pairs of rollers is provided with a curved towards a ball end towards extending curved contour, which extend to the two rollers each to opposite sides over part of the Walzgutbreite, wherein the curved contour runs over the entire length of the bale of both rollers and has a shape in which the two bale contours complement each other in a certain relative axial position complementary.

So will in the DE-C-36 24 241 a rolling mill described in which the work rolls each have a to a roll end tapered and the other end of the bale expanding, curved contour and are arranged in the axial direction adjustable in the manner that in each case the tapered end of a work roll or intermediate roll between a rolling stock and the end of the associated support roller, preferably aligned and held on each edge of the rolling stock.

Furthermore, from the EP 0 249 801 B1 a rolling mill for the production of rolled strip is known in which the rollers are provided with a substantially over the entire length of the bale extending curved contour. The contours of all rollers are designed in the initial state or unloaded state, the axial course of the sum of the effective roll bale diameters in each relatively changed axial position of the rolls relative to each other assumes a course deviating from a constant course and follows a mathematical function symmetrical to the roll center.

Usually, the curved contour of the rollers runs mathematically according to a third-order polynomial. On the basis of the shift amounts used in practice and the actual bending values on the rollers, there is generally a positive and negative setting range for the CVC rollers (CVC = Continuously Variable Crown). Conventional CVC grinding is useful if negative CRA values are required (CRA = equivalent crown for the normal crowning of a roll).

In the past, negative experiences have been made in practical operation with respect to roller wear with the x ³ grinding of the CVC rolls on stands of the six-high design. The large diameter difference of the intermediate rolls caused increased wear and rough surfaces on the back-up rolls, with the damage pattern on the back-up rolls corresponding to the shape of the CVC cut after a longer run-time. For quarto scaffolds, the cut-off amplitude was initially also significantly greater than required for the rolled programs, so that the unfavorable wear pattern on the back-up rolls also set in here.

Since, based on the shift amounts and actual bending values used in practice, the negative setting range of the CVC cut was not always necessary in the past, and taking into account the negative bend, only positive CVC effects are required, it is the object of the invention to provide a shape To specify the roll grinding in a purely positive range, with which also the above-mentioned disadvantages of the x ³ grinding the CVC rollers are avoided.

This object is achieved with the characterizing features of claim 1, characterized in that the roll barrel length L of each intermediate roll in a six-high stand or each work roll in a four-high rolling mill from a cylindrical roll barrel section Z and a convexly curved roll barrel section R (x) composed , wherein the transition point A from the cylindrical to the curved roll barrel portion in the range L / 2 <= x <L is selectable (x is calculated from the cylindrical end of the bale), and the curved contour, which is located on the two rolls each to opposite sides over a Part of the Walzgutbreite extends towards the bale end, by a mathematical polynomial R (x) = a ₀ + ... a _n x ⁿ with n> = 5 is described.

The use of such convex roller with partial convex contour of the roll bale, which is ultimately a subset of CVC ^plus , results in a uniform distribution of the contact stresses between the superposed rolls. This is problematic, for example, especially for rolls with an S-shaped joint (CVC), since this can lead to local tension peaks in the ball area, which cause an increased roll wear and can only be prevented by appropriate compensation grinding of the overlying rolls.

According to the invention, the rolls provided with a convexly curved roll barrel section are formed with a roll diameter that is so large that the bending forces have a substantially parabolic (x ² ) effect on the roll gap profile.

Rolls with conventional x ³ -CVC cuts also provide a predominantly parabolic effect, so that there is hardly any actuator that can compensate for planarity errors of higher order. This is especially true for the so-called Z-high scaffolds, which are equipped due to the small work roll diameter for design reasons without work roll bending. By the inventive use of intermediate rolls or work rolls with a higher order finish x ⁵ + x ⁶ + x ⁷ ... this disadvantage can be prevented.

By the feature according to the invention that the transition point A from the cylindrical to the curved roll barrel portion in the range L / 2 <= x <L can be variably selected, different objectives of the profile adjustment can be achieved. If the transition point A is, for example, at x = L / 2, predominantly parabolic (x ² ) flatness errors are combated, for a transition point A of x => L / 2 more and more higher order errors (x ⁴ and higher) can be compensated.

So that the inventively designed rolls can develop their full effect, the remaining rolls of the roll stand are formed with a continuous cylindrical roll barrel except the convex rolls.

Further advantages and details of the invention are explained in more detail below with reference to exemplary embodiments illustrated in schematic drawing figures.

Fig. 1

die Walzen eines Sexto-Gerüstes mit erfindungsgemäß ausgebildeten Zwischenwalzen,

Fig. 2

die Walzen eines Quarto-Gerüstes mit erfindungsgemäß ausgebildeten Arbeitswalzen,

Fig. 3

einstellbare Walzspaltprofile für ein Sexto-Walzgerüst,

Fig. 4

Stellfelder auf der Basis des Sexto-Walzgerüstes der Fig. 3,

Fig. 5

ein Walzspaltprofil für das Sexto-Walzgerüst der Fig. 3 mit erfindungsgemäß ausgebildeten Arbeitswalzen,

Fig. 6

ein Walzspaltprofil für das Sexto-Walzgerüst der Fig. 3 mit klassischen CVC-Arbeitswalzen,

Fig. 7

die Pressungsverteilung zwischen der Zwischenwalze und der Stütz-walze für das Walzspaltprofil der Fig. 5,

Fig. 8

die Pressungsverteilung zwischen der Zwischenwalze und der Stütz-walze für das Walzspaltprofil der Fig. 6.

Show it:

Fig. 1

the rolls of a six-high stand with inventively formed intermediate rolls,

Fig. 2

the rolls of a four-high stand with work rolls designed according to the invention,

Fig. 3

adjustable nip profiles for a six-high rolling stand,

Fig. 4

Stellfelder on the basis of the Sexto rolling stand of Fig. 3 .

Fig. 5

a nip profile for the six-high stand of Fig. 3 with work rolls designed according to the invention,

Fig. 6

a nip profile for the six-high stand of Fig. 3 with classic CVC work rolls,

Fig. 7

the pressure distribution between the intermediate roll and the support roll for the nip profile of Fig. 5 .

Fig. 8

the pressure distribution between the intermediate roll and the support roll for the nip profile of Fig. 6 ,

In FIG. 1 a sexto-framework for the production of a rolled strip 1 with work rolls 10, 11, intermediate rolls 20, 21 and back-up rolls 30, 31 is shown. The work rolls 10, 11 and the support rollers 30, 31 are cylindrical over their entire length of bale and not axially displaceable in the illustrated embodiment, while the intermediate rollers 20, 21 according to the invention arranged axially displaceable in the direction of arrow 22 and with a partially convexly curved roll barrel section R (x) are formed. The transition point A between the curved roll barrel section R (x) and the remaining cylindrical roll barrel section Z is located in the intermediate rolls 20, 21 shown exactly in the middle of the roll barrel length L, ie at x = L / 2 (x is calculated from the cylindrical end of the bale ), whereby the intermediate rollers 20, 21 are mainly suitable for controlling parabolic (x ² ) flatness errors.

In the FIG. 2 the alternative application of the invention to inventively designed work rolls 15, 16 in a four-high stand for producing a rolled strip 1 with work rolls 15, 16 and back-up rolls 30, 31 is shown. While the cylindrical support rollers 30, 31 are arranged axially non-displaceable here, too, the work rolls 15, 16 designed as convex rolls can be axially displaced in the direction of the arrow 12. Compared to the training of the work rolls 10, 11 of the Sexto scaffold of FIG. 1 is clearly seen that the formation of the work rolls 15, 16 in the form of convex rolls leads to much thicker rolls.

In the FIG. 3 are in a coordinate system, the possible adjustable nip profiles for a six-high rolling mill with small work rolls for two different intermediate rolls with convexly curved roll barrel section and a classic CVC intermediate roll for the entire displacement range but constant intermediate roll bending value. The diagram contains in vertical division the square influence of the nip, indicated by the symbols 25 for positive and 25 'for negative changes. The non-quadratic changes are indicated in horizontal division by the symbols 26 for positive and 26 'for negative changes. To illustrate the achievable effect of the horizontal scale is compared to the vertical reproduced much larger.

As can be seen from the coordinate system, in the case of an intermediate roller 20 with a transition point from the cylindrical to the curved roll barrel section of A = L / 2, a predominantly quadratic profile influencing can be seen during its displacement between the maximum displacement position 29 and the minimum displacement position 29 '. In the case of an intermediate roller 20 'with a transition point of A> L / 2, a profile influencing in the range of x ^{4 is} clearly visible with its corresponding displacement between the two possible displacement positions 29 and 29'. The profile effect shown for comparison for a classic CVC intermediate roll 20 "also again shows a predominantly quadratic effect in its displacement within the possible limits 29 and 29 '.

In the FIG. 4 are in one of the FIG. 3 the corresponding nip roll profiles for the intermediate roll 20 according to the invention and for the classic CVC intermediate roll 20 ", which results if, in addition to the intermediate roll displacement, the intermediate roll deflection is variable FIG. 3 The positioning field 23 for the intermediate roll 20 according to the invention and the steep field 24 for the CVC intermediate roll 20 "are clear. The positioning field 24 of the CVC intermediate roll 20" makes clear that a residual error x ⁴ always occurs at the zero point of the coordinate system (rectangular profile).

In the FIG. 5 is an example achievable nip profile 3 for the six-high stand of Fig. 3 illustrated with inventively formed intermediate rolls when the optimum value for the intermediate roll bending and for the intermediate roll displacement is set. The course of the roll gap profile 3 is shown over the entire roll barrel length L and the position of the strip width 2. This illustration clearly shows that the roll gap profile 3 deviates from a linear horizontal course only in the area of the strip edges 5.

Like from the FIG. 6 can be seen remains at a on the basis of the same Sexto rolling stand of the Fig. 3 when using classically trained CVC intermediate rolls deviating from a linear horizontal course x ⁴ residual error in the roll gap profile, as this is already in the Fig. 4 shows.

To the good results of the convex rolls with the horizontal course of the nip profile 3 of the Fig. 5 also results in the wear-prone pressure distribution 4 between the intermediate roll and the support roller, shown in the FIG. 7 ,

From the comparison to CVC rollers, with the nip profile 3 of the Fig. 6 a pressure distribution 4 between the intermediate roll and the backup roll corresponding to FIG. 8 It becomes clear that, when convex rolls are used, a more uniform or even stress profile is obtained, and the roller life for the convex rolls is thus correspondingly increased.

reference numeral

1

rolled strip

2

Rolling bandwidth

3

Roll gap profile

4

pressure distribution

5

strip edges

10, 11

cylindrical stripper

12

Shifting direction of the work roll

15, 16

Work roll according to the invention

20, 20 ', 21

intermediate roll

20 "

CVC intermediate roller

22

Displacement direction of the intermediate roller

23, 24

Stellfeld

25, 25 '

square proportion

26, 26 '

not square share

27

Between roll shifting

28

Intermediate roll bending

29

maximum displacement position

29 '

minimum displacement position

30.31

supporting roll

A

Transition point between curved and cylindrical roll barrel section

L

Roll barrel length

R (x)

convex roll barrel section

x

Running direction for determining the position of the transition point A from the cylindrical roller bale end

Z

cylindrical roll barrel section

Claims (5)

1. Roll stand for producing a rolled strip (1), comprising working rolls (10, 11, 15, 16), which are supported optionally at backing rolls (30, 31) or intermediate rolls (20, 21) and backing rolls (30, 31), wherein the working rolls (10, 11, 15, 16) and/or the backing rolls (30, 31) and/or the intermediate rolls (20, 21) are axially displaceable relative to one another, wherein the circumferential surface length L of each working roll (15, 16) in a four-high roll stand is composed of a cylindrical roll circumferential surface section Z and a convexly curved roll circumferential surface R(x), characterised in that the circumferential surface length L of each intermediate roll (20, 21) in a six-high roll stand is composed of a cylindrical roll circumferential surface section Z and a convexly curved roll circumferential surface segment R(x), wherein the transition point A from the cylindrical to the curved roll circumferential surface segment, calculated from the cylindrical roll circumferential surface end, is selectable in the region L/2 < = x < L in the curved contour, which extends at the two rolls (15, 16, 20, 21) respectively towards opposite sides over a part of the rolling stock width in direction towards the circumferential surface end, is described by a mathematical polynomial R(x) = a₀ + ... a_nxⁿ, wherein n > = 5.
2. Roll stand according to claim 1, characterised in that the rolls (15, 16, 20, 21) provided with a convexly curved roll circumferential surface section R(x) and termed convex rolls are formed with a roll diameter of such a size that the bending forces act substantially parabolically (x²) on the rolling gap profile (3).
3. Roll stand according to claims 1, 2 or 3, characterised in that for regulation and prevention of predominantly parabolic (x²) planarity errors the transition point A is fixed at a value of x = L/2.
4. Roll stand according to claims 1, 2 or 3, characterised in that for regulation and prevention of predominantly errors of higher order, x⁴ and higher, the transition point A is fixed at a value of x = > L/2.
5. Roll stand according to one or more of claims 1 to 4, characterised in that apart from the rolls (15, 16, 20, 21) provided with a convexly curved roll circumferential surface section R(x) the remaining rolls of the roll stand are formed with a continuous cylindrical roll circumferential surface Z.

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