DE10045259A1 - Control method for rolling a strip in a roll stand - Google Patents

Abstract

Regulating process comprises tilting one of the working and/or supporting rolls in a mill stand by an angle relative to a counter roll to compensate for an asymmetric roll gap and to improve the strip flow. Preferred Features: The upper and lower rolls can be pushed apart to promote the process.

Description

The invention relates to a control method for rolling a strip in one Roll stand comprising at least a pair of work rolls, backup rolls as well occasionally also intermediate rolls.

During the rolling process, the work rolls are subject to both thermi as well as a high mechanical load. As a result of this results there is a thermal radial expansion of the rollers, and it additionally arises wear of the work rolls. Due to different conditions of Stress on the top and bottom of the belt can be the amount of a thermal Radial expansion and wear on the top and bottom roller below be different.

When using sliding work rolls, this can lead to asymmetrical Lead conditions in the roll stand. It can z. Legs upper work roll have a much higher thermal crown than the bottom roller. In addition, the wear of individual work rolls can have significant differences. In the case of hiring a ver equally large change in the axial sliding position arises different gap between the rollers of a pair of rollers on the right and left side. Under load, this results in an asymmetrical, i.e. H. wedge-shaped roll gap.  

To reduce such asymmetry, it is in the prior art knows to cool the upper and lower work roll differently, with un Different amounts of coolant, e.g. B. water is driven. if the Roll gap lubrication is active, the measure can also be used be that different oil quantities are set on the top and bottom roller the. This can cause major differences from the thermal crown or in the ver wear behavior are at least partially relativized.

Document DE 196 18 712 A1 describes a control method for a roller train prepared for rolling a strip consisting of a pair of work rolls, a pair Back-up rollers and a pair of intermediate rollers. The existing one Regulations for rolling force, bending force and roll displacement are set to be values specified in a roll stand model with a roll bending model were determined online. To determine the target values for rolling force and bending force and roll displacement are shown online in the roll bending model at the support point relations between the rolling force, the bending back force and the roll ver shift on the one hand and a corresponding roll gap profile on the other determined on the part.

The document also shows that such control procedures are wide are common. There are also differential equations for calculating the through Bends and force curves in the rollers as well as solutions of this differential equations known in principle.

Starting from the aforementioned prior art, the object of the invention an improvement, while avoiding an asymmetrical roll gap Achieve the tape run, improve the tape shape and equal conditions settings on top and bottom rollers.  

The solution for the FaN is that no one is alike due to external constraints Have conditions set on the top and bottom rollers, an automatic one Swiveling the set of rollers suggested to have this negative effect compensate.

The procedure according to the invention is such that for the compensation of a be drive-related asymmetrical roll gap and to improve the belt run one of the rolls of a roll set of work and / or backup rolls around one Angular amount is pivoted relative to the counter roller.

An embodiment of the method provides that the compensation is unequal Rolling conditions in the nip between the upper and lower rolls of a work roll zsatzes a calculable amount of a pivot angle α on one of the rollers, preferably on the top roller.

A further embodiment provides that a swiveling amount of a roll set zes, for example, is made on a scaffold, the work or Intermediate rolls are axially shifted.

Another embodiment of the method provides that a swivel amount a set of rollers, for example on a stand, the Work or intermediate rolls are not shifted.

A control method according to the invention according to the previous Merk painting is characterized by the steps specified in claim 6 and for converting the determined wedge shape of the roll gap for the corresponding effective areas linear to the distance of the positions or the camp distance and totaling the amount, relationship specified in the claim.  

A complementary measure to minimize asymmetry is that To shift the top and bottom rollers differently so that U is not equal (≠) U 'is. This can be for several strips of a rolling program or just for out selected bands are made.

When shifting the work rolls cyclically, different ver sliding levels and steps for top and bottom roller can be set to the To positively influence the shape (slope) of wear and thermal crowns. Preferably, the roller with z. B. postponed major wear, d. H. you set a larger displacement amplitude.

When presetting for the respective band, the differential shift amount is between the two rollers in a predetermined permissible search range len that the asymmetry is minimized primarily in the band edge area.

The procedure for this optimization is u. a. according to the in the documentary ment EP 0 618 020 B1 and EP 0 850 704 A1 described method. The Op Timing of the contour and the flatness close to the edge are however asymmet transfer effects, d. H. both sides of the band are considered.

The control algorithm also takes into account the different elastic behavior with different shift amounts on the top and bottom roller, so that these additional influences, e.g. B. by different levels of bending force the right and left side or panning can be compensated.

It is planned to combine the two measures above, wherein the pivoting of the roller set on the body area of the belt and setting different shift positions more on the belt edge  Act. Preferred meadow, the shift position is optimized first and in the second Step of the swing amount set.

Further details, features and advantages of the invention result from the The following explanation of some shown schematically in the drawings Embodiments.

Show it:

Fig. 1 shows a state for an unloaded scaffold with unshifted work rolls and backup rolls superimposed,

Fig. 2 shows a state of FIG. 1, however, rollers with axially shifted work,

Fig. 3 shows a single-ended nip with a drawn straight from the same in the field of bandwidth shifted Ar beitswalzen,

Fig. 4 is an asymmetry zen in the contact area between the working and Stützwal,

Fig. 5 set shifting positions on upper and lower roll in from dependence on the number rolled strips,

Fig. 6 work roll shift positions and roll gap differences with different shift strategies.

Here mean:
B: bandwidth
L _Cont contact length between work and backup rolls
L _A : bearing distance / distance of the support rollers
S: Tilt / swivel amount
U: Work roll shift of the top roll
U 'work roll displacement of the lower roll (in the opposite direction)
n: number of tapes
α: swivel angle

The contours of the work rolls 1 , 1 'in FIG. 1 show an approximately symmetrical thermal expansion in a state for an unloaded stand with work rolls 1 , 1 ' not shifted. The upper work roll 1 , however, has a significantly more pronounced thermal crown than the lower work roll 1 '.

When using displaceable work rolls 1 , 1 ', this can lead to asymmetrical conditions in the roll stand. These conditions shown in FIG. 2. Dar is provided also an unloaded rolling stand, the upper work roll 1, for example, has a significantly higher thermal Crown than the Un terwalze 1 '. Work roll wear is also different. If there is a relatively large change in sliding position from band to band (for example U = 60 mm), this results in a gap of different sizes between the rollers 1 , 1 'or 1 , 2 and 1 ', 2 'on the right and left Side one. This creates an asymmetrical wedge-shaped roll gap under load.

The aim of the measures according to the invention is the conditions of such Reduce or eliminate asymmetry. Do these with the known means such as different cooling or nip lubrication reduce, according to the invention an automatic pivoting of the Roll set proposed to the undesirable effect of asymmetry  compensate.

Here, according to the procedure shown in the example of FIG. 2, the larger gap between the work rolls 1 , 1 'and work and back-up rolls 2 , 2 ' is moved to the left by the amount "S", or it is around the center of the stand panned right and left by the amount S / 2. The determined or calculated swivel amounts "S" can change in accordance with a change in the thermal crown's over the length of the strip, which must be taken into account from case to case.

If the shapes of the upper 1 and lower work roll 1 'are present, the roll gap in the range of the strip width can be calculated for the shifted work roll state, as shown in FIG. 3. In this case, by means of the determination of a regression line through the roll gap difference, the inclined days or wedge shape of the roll gap results. The compensation angle α _WS (alpha) which can then be determined gives the required portion of the swivel amount "S _WS " in the roll gap for the range of the strip width B. This amount can be extrapolated by simply converting the distance between the positions.

Because the asymmetries also act between the work and back-up rolls 1 , 1 '/ 2 , 2 ', the wedge is evaluated the same for the contact area between the work and back-up rolls, as shown in FIG. 4. The sum of the two effects (in the roll gap and between the support and work rolls) leads to the swivel amount "S".

In order to influence the shape of the work roll wear and the thermal crown, the work rolls are cyclically shifted, as is known from the literature. With different wear or thermal crowns on the top and bottom, it can be positive to set different shift amounts (U, U ') for each strip in a rolling program, as shown in FIG. 5. When different displacement amplitudes and steps are set, the effect of work roll wear in the belt edge area is primarily influenced effectively.

The effect of different displacement positions in the roll gap with much higher wear such. B. the bottom roller makes the extreme example of FIG. 6 clear. This shows the work rolls in the shifted state and below the associated roll gap differences. Effects with a conventional shifting strategy (left) and with an unevenly optimized shifting position on the top and bottom rollers (right) are shown. As a result of the optimization process for the respective band, the asymmetries in the region of the band (band edge) are minimized, which is shown in FIG. 6 at the bottom right.

The invention optimally achieves the object stated at the outset.

Claims (16)

1. Control method for rolling a strip in a roll stand, comprising at least a pair of work rolls ( 1 , 1 '), back-up rolls ( 2 , 2 ') and occasionally also intermediate rolls ( 3 , 3 '), characterized in that to compensate for an operationally asymmetrical Roll gap and to improve the Bandlau fes one of the rolls of a set of rolls of work ( 1 , 1 ') and / or back-up rolls ( 2 , 2 ') is pivoted by an angular amount (α) relative to the counter roll. 2. Control method according to claim 1, characterized in that to support the effect of the method, the upper ( 1 ) and lower work roll ( 1 ') are shifted to different degrees. 3. Control method according to claim 1 or 2, characterized in that to compensate for unequal rolling conditions in the roll gap between the upper ( 1 ) and lower roll ( 1 ') of a work roll set ( 1 , 1 ') a calculable amount of the pivot angle (α) at one of the Rolling, preferably on the top roller ( 1 '), is set. 4. Control method according to one or more of claims 1 to 3, characterized in that a pivoting amount (S) of a roller set ( 1 , 1 ') or ( 2 , 2 ') is carried out on a stand, the working ( 1 , 1 ') or intermediate rollers ( 3 , 3 ') are axially shifted against each other by an amount U or U '. 5. Control method according to claim 1 or 2, characterized in that a swivel amount (S) of a roller set ( 1 , 1 ') or ( 2 , 2 ') is made on a stand, the working ( 1 , 1 ') or intermediate rollers ( 3 , 3 ') are not pushed ver. 6. Control method according to one or more of claims 1 to 5, characterized in that the swivel amount (S) is determined with the following work steps:

• - Measurement of the thermal crown and the state of wear on the pair of work rolls ( 1 , 1 ') for various rolling programs,
• - adaptation of the wear coefficients and evaluation of the heat flows,
• - separate calculation of the thermal crown and the work roll wear for the upper ( 1 ) and lower work roll ( 1 ') under online conditions, taking into account boundary conditions such as strip width (B), rolling time, pause time, shift positions, cooling effect on the work rolls,
• - If the shapes of the two work rolls ( 1 , 1 ') are present, calculate the roll gap for the shifted state of the work rolls ( 1 , 1 ) as well as the inclined position and / or wedge shape of the roll gap in the range of the strip width,
• - Evaluation of the wedge shape of the roll gap and its inclined position in the contact area (K) between work and backup rolls,
• - Conversion of the determined wedge shapes for the corresponding effective ranges line ar to the distance between the positions or the bearing distance (L _A ) and totaling the amount according to the following relationship:
  S = K _WS .S _WS .L _A / B + K _AS .S _AS .L _A / L _cont

Where:
B: bandwidth
K _WS : weighting factor of the amount in the roll gap
K _AS : Weighting factor of the effect between work and backup roll
L _A : bearing distance or distance of the positions
L _Cont : length of contact between work roll and backup roll
S: swivel amount
S _WS : Oblique position in the roll gap
S _AS : share of inclined position between work roll and backup roll. 7. Control method according to claim 6, characterized in that the shape of the work rolls ( 1 , 1 ') is not calculated, but measured online and the swivel amount (S) and / or the roll displacement position is determined according to the explained scheme. 8. Control method according to one or more of claims 1 to 7, characterized characterized in that instead of pivoting the roller set, the analog Effect by using different work roll bending forces of the left and right side is realized. 9. Control method according to one or more of claims 1 to 8, characterized characterized that the online determined amount of swivel or the difference force set before tapping the tape and ver if necessary over the tape length will change. 10. Control method according to claim 1 or 2, characterized in that for several belts of a rolling program the upper and lower work roll positive influence of the form of wear cyclically differently shifted be. 11. Control method according to claim 10, characterized in that preferred wise for the roller with greater wear or larger thermal crown a larger displacement amplitude is set. 12. Control method according to claim 11, characterized in that the difference limit between the two rollers for individual strips in a given A permissible search range is set so that the asymmetry is predominant is minimized in the band edge area.   13. Control method according to one or more of claims 1 to 12, characterized characterized that different elastic behavior of the rollers of a Roll set with unequal shift amounts above and below taken into account become. 14. Control method according to claim 13, characterized in that as a result uneven shift amounts due to this effect above and below or to the right and different bending forces are set on the left or the swivel amount (α) is corrected. 15. Control method according to one or more of claims 1 to 14, characterized characterized in that the two measures of claims 1 and 2 miteinan which are combined in such a way that the pivoting of the roller set on the Body area of the band and setting different displacement positions are more aligned with the belt edge. 16. Control method according to claim 15, characterized in that in the first Step optimized the sliding position and in the second step the swivel amount is set.