EP1269131A2

EP1269131A2 - Prevention of self-starting rattling oscillation in rolling mills

Info

Publication number: EP1269131A2
Application number: EP00941881A
Authority: EP
Inventors: Oskar Bschorr; Hans-Joachim Raida
Original assignee: Dofasco Inc
Current assignee: ArcelorMittal Dofasco Inc
Priority date: 1999-04-23
Filing date: 2000-04-20
Publication date: 2003-01-02
Anticipated expiration: 2020-04-20
Also published as: WO2000065319A3; AU779828B2; ATE257586T1; US20020072457A1; DE50004997D1; JP2002542944A; BR0009988A; WO2000065319A2; US6773383B2; EP1269131B1; DE19918555C1; CA2371111A1; AU5671100A

Abstract

A vibration damping roll is provided for rolling contact with a vibrating structure. The vibration damping roll incorporates a wave guide consisting of radially alternating rigid and flexible material having at least two rigid elements disposed adjacent to flexible material and may be provided in the form of a layered structure, a spiral structure, or a plurality of discrete rigid elements disposed in a matrix of flexible material.

Description

Avoidance of self-excited chatter vibrations in rolling mills

The object of the invention is to exclude the rat marks that occur, for example, when cold-rolling sheet steel. In unfavorable operating conditions, peπodic vibrations occur beyond the basic vibrations and grow exponentially. As a result, the rolling stock suffers from quality degradation, leads to rejects and also damage to the Rolling mill Even in the case of weak rat stabilization, so-called thickness and shape waves occur. The same chattering phenomena occur in addition to steel in the other rolling stock, also when rolling paper, as well as when rolling strip and wire

In order to avoid a build-up of vibrations as the cause of rattling, there are brakes attached to the support roller or work roller. It is assumed that roller friction also dampens the roller vibrations. That this idea does not apply in the general case proves the heavy and dangerous brake squeal, as is well known This is a so-called self-excited vibration caused by braking, the vibration energy of which ultimately provides the braking process.Self-excitation is caused here by a degressive coefficient of friction, i.e. if the friction force F decreases with increasing friction speed v, i.e. dF / dv <0 becomes negative - that one Such braking is not satisfactory, is also shown by the fact that most rolling mills are equipped with automatic vibration monitoring. When a certain vibration level is exceeded, a rolling parameter is changed, - usually the rolling speed is reduced - to au s coming to the critical operating area Even such a secondary procedure cannot satisfy, since it does not eliminate the primary causes For this reason, and because of the great economic importance, a European research program was started to find the causes and above all remedies against the feared chatter phenomenon Find

The object of the invention is. switch off the self-excitation of vibrations in rolling mills a priori

This task is solved by installing resistance transducers in the rolling mill. The installation location is determined by the position of the vibration mode that tends to feed back resonance vibrations. Technical designs of resistance transducers are the vibration absorbers, e.g. described in VDI directive 2737, sheet 1 (1980) and the resonance eliminators Vibration absorbers have a spectrally adjustable resistance curve. Resistance transmitters that are effective in several degrees of translation and rotation are advantageous. Vibration absorbers in a layered construction are suitable. As is known per se from DP 24 12672 and DP 3113268, resonance absorbers, on the other hand, only work at their resonance frequency and are to be used where Chatter frequency is precisely known and constant In addition to this state of the art, it is advantageous to design the resistance transducers in the form of a roller and co-rotating. This allows the resistance of the resistance transducer to be coupled as close and as hard as possible to the Rolling center in which the rolling energy is converted into deformation work in order to stabilize unstable conditions with rolling forces and moments with a degressive force curve. Active resistance transmitters are still in the development stage, according to the known rules of antisound technology - the subject of the invention is explained in more detail using various examples Fig 1 rolling process designations

Fig 2 Modal replacement system

Fig. 3 to 5 resistance rollers for vibration stabilization

Fig. 6 and 7 co-rotating resistance body for vibration stabilization

Fig. 8 and 9 Fixed resistance transducers

Fig. 10 to 12 Resistanzkorper acting on the rolling stock

The following designations are agreed in the description (X = number of the figure) X0 = rolling mill, rolling stand, XI, X2 = rolling, X3 = rolling stock, X4 = resistance roller, body, sensor X5 = sensor for controlling an active resistance sensor, X6 = Coupling link

1 shows a typical rolling mill 10 in which the rolling stock 13 is rolled by the wall thickness h (eml) by the amount h onto the wall thickness h (ausl) by two work rolls 11 (and 11 ^' ), which are held by two support rolls 12, h = h (eml) - h (ausl) The vertical forces and deflections occurring on the work roll are Fj and in the horizontal direction F ₂ and \ ₂ and the moments and angles of rotation are T and φ ₅ The forces and deflections (speed of deflection) on the incoming material are F ₄ and \ ₄ (x) and on the outgoing material F- * and xt (x * - In the general case, the moments and angles of rotation T ₆ , φ ₆ and T ₇ , φ ₇ also occur on the rolling stock in the immediate vicinity of the rolling location. According to the known theory of modal analysis, the rolling system 10 can be reduced to the individual modes n in terms of vibration technology , consisting of the modal mass M _n , the modal damping D _n and the modal spring C _n According to FIG. 2, each mode n forms a closed, single-path oscillator. The same equivalent circuit diagram also applies to rotary modes with the angles of rotation φ, which is decisive for the stability of the mode oscillation is the amount and the sign of the differential excitation factor E _n = dF _n / dx ' _n (x * _n - dx _n / dt = speed, \ "= acceleration) If the sign is positive, E acts like a resist nz and steams, with a negative sign it is a vibration exciter. When natural vaporization predominates, ie D -r E> 0 it is a stable vibration system with an exponentially decreasing oscillation x When a negative excitation factor E ie beι D predominates - ^* - E <0, on the other hand, the vibration grows exponentially.This self-excitation causes a rattling effect in the uncoupled single-mode oscillators - with the coupling of two modes n and m with the excitation gands E ^ = dF _m / dx * _n , self-excited chatter vibrations can also occur For this purpose, the initial calibration is given in FIG

After the task and the solution, only the vibration-dynamic forces F and deflections x are of interest (the torques and angles of rotation are then included) .The constant values such as the rolling force F (hn) and the nominal rolling speed v ₀ are in the preparation of the modal equivalent circuit diagrams according to Fig. 2 transformed away Also here the interference forces caused by inhomogeneities and their positively excited vibrations should be disregarded. The relevant problem here is the self-excited vibration, i.e. the question of whether the individual vibration modes are stable and how large the resistance R of the resistors to be used must be so that the total value D + E + R> 0, that is positive

Fig. 3 shows a rolling stand 30 consisting of work rolls 31 (and 31 '), support roll 32 and the rolling stock 33 To self-excited vibrations in vertical xi. - To prevent direction, a resistance roller 34 is coupled to the support roller 32 and rotates due to the pressure with which its axis of rotation is parallel to the other axes and lies in the central plane. The resistance roller 34 consists of a plastic with a high internal Damping, for example made of polyurethane and has a spectral resistance in the xi direction, at the critical chatter frequency this is R. FIG. 2 is used as a vibration-equivalent circuit diagram, especially the case n = 1, since work and support roller 31 and 32 are hard-coupled via their contact they vibrate in phase in the relevant lower frequency range, so that the mass sum of both shafts 31 and 32 can practically be used as the mode mass Mi. The decisive spring constant = dFi dxi is determined by the taper of the rolling stock. A rolling force F (h) is necessary to prevent warping h = h (eml) - h (ausl) can be achieved with the rolling parameters v = v ₀ (v = rolling speed) and h = ho, then C * = 2dF (h) / ie here the roller diameter is above and below of the rolled stock 33, therefore also the factor 2. In order of magnitude the spring constant can also be estimated according to Ci = 2F (h) / h, this value corresponds to the average spring stiffness he deformation of the rolling stock by h by a force F (h) can only be described as elastic suspension because the rolling stock is constantly replenished at speed v (this description does not apply to a standing roll with v - = 0) under steaming D, the natural internal friction losses are summarized, this can be determined from a reverberation measurement on the stationary roll stand 30. The critical size for the vibration stability is the excitation value τ = Ei = dF) / dx * ι, in particular there is a negative value - with a degressive rolling force curve - the danger of an increase in vibration The decisive vibration equation for mode n = 1 is

M, x "ι + (D, + R, -r Ei) X *, + C, x, = F (h ₀ )

The integration provides an i-vibration with the angular frequency κ> ιo and the exponential factor exp (-ηcüiot) (the static deformation due to the constant rolling load F (ho) is omitted here)

Xi = x ₁₀ exp (-ηωiot) sin (ωiot) with αuo and η = (Di + Ri + Ei) / ωιo Mi

The sign of the loss factor η determines the stability of the vibration. If the value is positive, the vibration amplitude decreases due to damping. If the sign is negative, there is a (theoretically exponential) increase in a resonance vibration with the frequency α> ιo and a peπodically changing rolling force Fj. This causes chatter marks with periodic thickness fluctuations in the rolling stock (thickness waves) By switching on the resistance R = Ri coming from the resistance roller 34, self-excitation can be prevented

> 0 damping vibration stability <0 self-excitation chatter

Adapted to the special installation conditions and to the position of the vibration modes n which tend to self-excitation, FIGS. 4 to 9 show different embodiments for damping with a resistance R. In FIG. 4, a rolling stand 40 again consists of work and support rolls 41 and 42 and the Rolling stock 43 The resistance is applied here, comparable to FIG. 3, by two resistance rollers 44 acting on the work roller 41. This attachment again allows the vertical \ _x direction to be steamed, to the same extent the horizontal x ₂ direction and also the torsional vibration φ ₃ Im in the latter case, the resistance roller 44 is also designed for torsional vibrations and has the rotational resistance R _^ In the case of an antisymmetric torsional vibration - when the two work rollers 41 and 41 'oscillate in the opposite direction - the moment of inertia settles Θ ₃ from the sum of work and support rollers 41 and 42 together The term C-, = dTs / dcp acts as the torsion spring for the specified operating condition, characterized by the index () o by the rolling speed v ₀ , rolling force F (h), taper ho and working moment T-, ₀ If, as in the example in FIG. 3, the natural self-damping D _> and the connected resistance R ₃ compensate the excitation term E ₅ = dTs / dφ * _D , a stable oscillation system is present. Without the installation of the resistance roller 44, on the other hand, there is a vibration simplification and there is undulating chatter marks (shape waves) in the assumed antisymmetric vibration mode

The multi-dimensional resistance effect according to FIG. 4 can also switch off the self-excitation of two coupled modes n and m (the classic example of a mutual excitation of two modes is the fluttering of aircraft wings). The vibration equation for such a mode coupling is

M _n x ^* " _n -ι- (D _n - R _π ) x ^* _n i- C„ x _n = (dF _ra / dx _n ) x _n M _m x " _m + (D _m -r R _m ) x * _m - C _m x _m = (dFJ dx _m ) x _m

The left side of the equation describes the single-resonance resonance oscillator of the n and m modes. The excitation elements E _mn = dF _m / dX _n on the right side are decisive for the vibration coupling and stability. In the general case, chatter marks with combined thickness and shape waves are to be expected for self-excitation

In FIG. 5, the resistance roller 54 acting on a roller 51 does not consist of a homogeneous plastic, but of an annular layering of steel and plastic.For the relevant lower frequency range, this layering can be described as a quasi-homogeneous waveguide and again characterized by a resistance R thanks to the higher one Mass, the greater design freedom, resonance allows higher resistance densities to be achieved, so that a continuous cylindrical roller is not necessary and individual roller disks are sufficient. In order to ensure good vibration-dynamic coupling of the resistance rollers 54 to the roller 51, the contact must have a high Hertzian spring constant. This is achieved if the outer jacket of the resistance roller 54 is also made of steel - If, however, the resistance roller 54 is designed as a resonator, it may be expedient to dimension the spring constants of the Hertzian contacts, the Hertzian spring rate nte and the roller mass result in a resonator with the required resonance frequency It is advantageous with this solution that the Hertzian spring constant and thus the resonance frequency can be readjusted by the contact pressure

In FIG. 6, the resistance sensor 64 is fitted inside the support roller 62. In FIG. 7, there is a resistance sensor 74 on the edge of the work roller 71, consisting of concentric steel / plastic layers

The exemplary embodiments in FIGS. 8 and 9 show fixed resistance bodies 84 and 94 which act on the rollers 81 and 91. In FIG. 8, the resistance body 84 is coupled by means of a slide bearing shell 86 and can suppress vibrations perpendicular to the bearing. In the example in FIG. 9, the resistance becomes R actively generated For this purpose, a sensor 95 senses the oscillation speed x * of the roller 91 and in the resistance transducer 94 - here - a force F proportional x * is electrodynamically transmitted to the roller 91. This takes place according to the principle of the linear motor or by eddy current braking for the Control is available from anti-noise technology (AVC = active vibration control) known solutions The proportional factor of F and x ^* represents the resistance, as is known R = F / x *

Fanned mode oscillations can also occur in the rolling stock itself. A negative excitation factor E ₃ = (-ffydx's (designation according to FIG. 1) is able to excite a longitudinal resonance in the rolling stock or a factor E ₅ = dT ₅ / dφ ^* 5 to excite a bending line resonance Effect of mode fanning If v and c are the rolling speed and the traveling speed of the rolling stock, then the fusing factor is μ = (v / c) ^" This can be understood as" negative damping ", ie as a vibration generator (see Critical Vibration Concentrations in Complex Structures Journal for Noise Abatement 45, March 1998 Springer-Verl) In order to exclude these vibration characteristics, a resistance roller 104 with a resistance R acts on the rolling stock 103 in FIG. 10. The principle of action is identical to the resistance rollers described in FIG. 3. In addition, here is an adaptation of the resistance R to the impedance of the rolling stock to effect an impedance jump As is known as a reflector, in the case of resistance equality, on the other hand, a maximum of vibration energy is withdrawn from the vibration system. In FIG. 11, in comparison to FIG. 9, an active resistance transmitter 114 controlled by the signal x * of the fast sensor 115 is used to generate a resistance R. Finally, the embodiment according to FIG for damping transverse bending vibrations in the rolling stock 123 For this purpose, a perforated plate 12 is brought into the vicinity of the rolling stock 123, so that the air friction in the perforations acts as a steamer with a resistance R that can be set in terms of construction

Claims

Protection claims. Stabilization of rolling mills against self-excited chatter vibrations and against disturbing thickness and / or shape waves in the rolling stock, characterized in that resistors X4 are force and / or momentarily coupled to the rolling mill, so that their point and / or torque resistance in the range of the critical chatter frequency is vibrationally dynamic acts directly on the rolling point with the plastic deformation of the rolling stock and the chatter caused by degressive rolling forces (moments) cancels the stabilization of rolling systems according to claim 1, characterized in that the resistance transducers X4 consist of a steaming plastic or a concentric or disc-shaped Layering made of steel and plastic, like the known vibration absorbers in a layered construction, are also effective in several degrees of freedom of vibration, including torsional vibrations and are designed to be roll-shaped and co-rotating Claim 1, characterized in that the mass of a co-rotating resistance sensor X4 together with the Hertzian spring constant of the contact line form a mechanical resonator, the resonance frequency of which is controlled by the contact pressure. Stabilization of rolling mills according to Claims 1 to 3, characterized in that to avoid thickness waves Roll-shaped resistors 34 co-rotating in the rolling stock are coupled to the support roll 32 or, in the absence thereof, directly to the work roll 31 and the axes of the rolls 31, 32 and 34 are arranged in parallel and in one plane. Stabilization of rolling plants according to claims 1 to 3, thereby characterized in that, in order to avoid shape and / or thickness waves in the rolling stock, one or more roller-shaped, rotating resistors 44 are coupled to the work roll 41. Stabilization of rolling systems according to claims 1 to 3, characterized in that (instead of a full one over the entire width de r work roll 51) to the work roll 51 several separate, disc-shaped and co-rotating resistors 54 are coupled. Stabilization of rolling systems according to claims 1 to 3, characterized in that a passive or active resistor 64 is attached to the inside of a support roller 62 or work roll stabilization Rolling mills according to claims 1 to 3, characterized in that resistors 74 are coupled to the ends of a work roll 71 and / or support roll 72. Stabilization of rolling mills according to claims 1 to 3, characterized in that a resistance sender 84 is attached to the slide bearing 86 a work roll 81 is coupled stabilization of rolling systems according to claims 1 and 2, characterized in that an active resistance transducer 94 is coupled to a work roll 91 em according to the known regulation of the anti-noise and anti-vibration technology via a vibration sensor 95 controlled stabilization of the roll Plants according to claims 1, 2, 3 and 10, characterized in that in order to avoid self-excited vibrations, co-rotating resistors 104, active resistors 114 or a perforated shield surface 124 are coupled directly to the rolling stock 103, 113 and 123