EP0005450A2 - Arrangement for treating the pass line height variations in a continuous rolling mill - Google Patents

Abstract

Arrangement for treating the pass line height variations in a continuous rolling mill having a plurality of stands between which loop lifters are arranged whose lifter arm fixes an angle alpha between pass line parallel and arm axis, and for correcting strip feed and/or tension within the rolled strip in the event of a variation of the pass line height D, comprising the following elements: a) an adder circuit (34), by means of which the diameters of the back-up and work rolls (5,6;7,8) and further addable quantities influencing the pass line height D can be added to give an electrical analog value UD corresponding to the pass line height, b) two function generators (42, 43) which are downstream of the adder circuit and process an electrical quantity U alpha and UD proportional to the angle alpha , taking as a basis the functional relationships: U1 = f1 (U alpha , UD) and UM/Z = f2 (U alpha , UD) to give a signal in each case, the signals generated by the function generator being input, with conventional matching, to control circuits for controlling the roll speed and the drive of the loop lifter arm (in the equations: U1 = analog electrical quantity with respect to the strip feed; UM/Z = analog electrical quantity with respect to the strip tension factor). The arrangement thus makes it possible to keep the tension Z automatically constant when the pass line height D changes. <IMAGE>

Description

The invention relates to an arrangement for the operational detection of the change in the rolling line height in a rolling mill with a plurality of stands, between which loop lifters are arranged, the lifting arm spanning an angle α between the rolling line and the arm axis, and for correcting the strip supply and / or tension within the rolled strip when it occurs a change in the rolling line height.

Broadband rolling mills known per se are divided into a roughing and an intermediate line, which can be designed as reversing or semi-continuous lines, and into a continuous broadband finishing line. The hot strip is given its final dimensions and shape in the latter. Influencing factors are roll gap, roll peripheral speed, roll shape, rolling force and tension between the roll stands.

The train Z has a decisive influence and must therefore be kept constant even if the material flow is temporarily disrupted. This is achieved by allowing a so-called loop between the individual scaffolds, the length L of which is regulated. For this purpose, loop lifters are installed, which are attached to the underside of the with rollers that are attached to a loop lifter arm In order to keep the tape tension and tape supply constant, control devices have become known which influence the torque of the loop arm and the speed control of the main drive. The belt tension is generated by the loop lifter and its position is used as a parameter for loop control. As is known per se (cf. A. HEINDEL, control devices for main drives and loop lifter drives of broadband finishing lines, Siemens-Z. 40 (1960), p. 795 ff), the torque of the loop lifter and thus the belt tension are produced with such known devices . The angular position of the loop lifter is specified by a setpoint and the torque is applied by an adjustable drive.

In the rolling mills according to the prior art, the problem arises that the setpoint generator can specify a sling lifter angle and thus a certain strip supply, but this strip supply is only assigned to a specific rolling line height. If the roll diameter changes, it can no longer be assumed that the rolling line height passed through between the individual stands is the same. In order to compensate for this error, shims are, as is known, placed under the roller chocks when changing the roller. If these mechanical corrections are not made, considerable tensile fluctuations could occur in the material, which could lead to large dimensional changes in the material.

• a) einen Additionsschaltkreis, mit dem die Durchmesser der Stütz- und Arbeitswalzen sowie weitere, addierbare, die Walzlinienhöhe beeinflussende Größen zu einem der Walzlinienhöhe entsprechenden elektrischen Analogwert U_D addierbar sind,
• b) zwei dem Additionsschaltkreis nachgeschaltete Funktionsgeneratoren, die eine dem Winkel a proportionale elektrische Größe U_a und U_D unter Zugrundelegung der funktionalen Beziehungen:
  
  bzw.
  
  zu einem Signal verarbeiten, wobei das von den Funktionsgeneratoren erzeugte Signal unter üblicher Anpassung Regelkreisen zur Steuerung der Walzendrehzahl und des Antriebes des Schlingenheberarmes eingegeben wird (dabei ist: U₁ = analoge elektrische Größe zum Bandvorrat;
  U_M/Z = analoge elektrische Größe zum Bandzugfaktor).

It is therefore the task to compensate for the change in the rolling line height with the aid of an arrangement which practically makes mechanical corrections of the rolling line height, for example by means of washers, superfluous, which carries out the corrections electronically and which are the same when the rolling line changes what cause a quick comparison the right sizes allows for a supply of trains and tapes. This object is achieved according to the invention by an arrangement which has the following parts:

• a) an addition circuit with which the diameters of the support and work rolls as well as further, addable variables influencing the rolling line height can be added to an electrical analog value U _D corresponding to the rolling line height,
• b) two function generators connected downstream of the addition circuit, which have an electrical variable U _a and U _D proportional to the angle a on the basis of the functional relationships:
  
  or.
  
  Process into a signal, the signal generated by the function generators being entered with customary adjustment loops to control the roller speed and the drive of the loop arm (where: U ₁ = analog electrical quantity to the supply of strip;
  U _{M / Z} = analog electrical quantity to the tension factor).

The principle of the arrangement according to the invention is explained with reference to the drawing.

• Figur 1 zeigt in schematischer Ansicht drei Walzgerüste einer Fertigstraße mit den dazwischengeschalteten Schlingenhebern;
• Figur 2 zeigt ein Diagramm, bei dem der Bandvorrat 1 über dem Winkel o aufgetragen ist;
• Figur 3 zeigt ein Diagramm, bei dem der Bandzug Z (dargestellt als Bandzugfaktor M/Z; M = Drehmoment des Schlingenhebers) über dem Winkel a aufgetragen ist;
• Figur 4 ein Blockschaltbild der Schlingen- und Schlin_- genheberregelung;
• Figur 5 ein detailliertes Blockschaltbild des in Figur 4 dargestellten, strich-punktiert eingefaßten Teilkreises;
• Figur 6 eine Skizze, die die geometrischen Beziehungen zwischen zwei Walzgerüsten verdeutlicht.

The figures in the drawing show:

• Figure 1 shows a schematic view of three rolling stands of a finishing train with the loop lifters interposed;
• FIG. 2 shows a diagram in which the tape supply 1 is plotted over the angle o;
• FIG. 3 shows a diagram in which the band tension Z (shown as band tension factor M / Z; M = torque of the loop lifter) is plotted against the angle a;
• Figure 4 is a block diagram of the loop and Schlin _- genheberregelung;
• FIG. 5 shows a detailed block diagram of the partial circle shown in dash-dotted lines in FIG. 4;
• Figure 6 is a sketch that illustrates the geometric relationships between two roll stands.

In Figure 1, a sequence of three rolling stands 1, 2, 3 within a seven-stand continuous finishing train of a hot strip mill is shown schematically. The smaller inner work rolls 5, 6 and the larger outer support rolls 7, 8 of each roll stand are mirror images of the rolling line 4. In a departure from the (imaginary) rolling line 4, a strip 9 to be rolled is raised with the aid of loop lifters 10, 11 to form so-called loops 12. As described at the beginning, the slings are required to create a defined and constant band tension between the individual stands. Furthermore, an entry table 13 is provided on the entry side of each stand, which guides the strip to be rolled exactly in front of the gap between the work rolls 5, 6.

The loop lifter 10 or 11 consists in principle of a torque drive 14 with a pivot point 14 'and a loop lifter arm 15 with roller 16 which presses below the band in the apex of the sling and thus raises the band. An angle a is measured between the axis of the loop lifter arm 15 and a parallel to the rolling line. The angle a is the directly measurable quantity from which the actual values of strip tension and strip supply are determined.

An angle a ₀ corresponds to a strip supply 1 of the strip located between two stands compared to the direct connection between two roll nips at an average rolling line height D. If a pair of rollers 5, 6 or 7, 8 with a different diameter is replaced by the existing one, the changed diameters result in a changed rolling line height with respect to the pivot point 14 'of the loop lifting arm 15. Thus, at constant angle a, the strip supply and strip tension would no longer be the same; the actual strip stock would be larger and the actual strip tension would be less if the rolling line was down and smaller or larger if the rolling line were shifted upwards compared to a defined mean rolling line height.

The roller diameters are subject to considerable changes due to wear and subsequent processing. The distance D between the center of rotation of the sling lifter and the rolling line is thus changed abruptly by changing the roll. Without going into this, the angle a would have been kept constant by the automatically acting electronic control unit, but the strip tension could change considerably, which would lead to malfunctions and defective products.

• 1. Stützwalzendurchmesser C s
• 2. Arbeitswalzendurchmesser C_a
• 3. Höhe des Drehpunktes des Schlingenhebers H
• 4. Höhe evtl. vorhandener mechanischer Unterlegstücke K.

By definition, the rolling line height D depends on the following sizes:

• 1. Back-up roll diameter C s
• 2. Work roll diameter C _a
• 3. Height of the center of rotation of the loop lifter H
• 4. Height of any mechanical washers K.

bei einer mittleren Walzlinienhöhe dar. Wesentliche Änderungen des Bandvorrates ergeben sich dann, wenn der definierte Abstand D_m sich ändert. Aufgetragen ist die funktionale Abhängigkeit für zwei Extremwerte:

• D_min (Walzen sehr dünn)
• D_max (Walzen sehr dick).

In order to be able to show the relationships, reference is made to FIGS. 2 and 3. In FIG. 2, the tape supply 1 is plotted as a function of certain positions of the looping arm, expressed by the setting angle a, for a specific case of the stand spacing and further defined geometric values. The curve labeled D represents the dependency

with a medium rolling line height. Significant changes in the strip stock occur when the defined distance D _m changes. The functional dependency is plotted for two extreme values:

• D _min (rollers very thin)
• D _max (rollers very thick).

The following example is also shown in FIG. 2: In order to maintain a strip supply of 1 = 30 mm at an average rolling line height D _m , the angle a of the loop lifter must be set to 32 ° and regulated. If the pairs of rolls are changed, the result is, for example, a rolling line height D. If the original angular position of a = 32 ° were maintained, this would result in a band reserve of 42 mm, ie the loop would be too large. In order to achieve the correct tape supply of 30 mm, a changed angle a of 27 ° must be set. The values of the tape supply can be determined from a function 1 = f ₃ (a, D).

mit h = R sin a - DThe function f ₃ is:

with h = R sin a - D

The geometric variables used here can be derived from FIG. 6.

FIG. 3 shows the dependence of the belt tension factor M / Z (torque M of the loop lifter for a specific tension Z) from the angle a to explain the next conceptual step. Since the tension Z is to be kept constant, the tape tension factor and thus the torque must be corrected accordingly when D changes.

In the example, an angle of 32 ° was originally assigned to a D. If - as explained with reference to FIG. 2 - the angle a is corrected to 27 °, the strip tension factor of 0.119 would result for a D _min to be taken into account. To maintain the constant tension, the torque would have to be increased by 0.119: 0.113.

In addition, dash-dotted curves are given in FIGS. 2 and 3, which each indicate the maximum deviations of the strip length or the strip tension factor:

These curves show that the differences between the extreme values can be approximately linearized in the range of the angle change from 10 to 40.

FIG. 4 shows a block diagram for realizing the invention. The components of the control loop are shown in simplified form to clarify the principle. The loop lifter arm 15 is driven by the loop lifter motor 14, which is a constantly excited DC shunt motor. The armature supply of the motor 14 takes place via a power converter 19. Each loop motor 14 has its own speed control with subordinate current control. The actual speed value is recorded by the EMF of the motor in the computer 18 (EMF formation). The EMF is formed from the armature current and armature voltage. Depending on the desired direction of movement, the speed controller 20 designed as an EMF controller receives a specific setpoint in addition to the EMF.

To generate a defined torque and thus strip tension, the controller 20 receives an addition value from the addition amplifier 21 as a limiting variable, which is composed of the signals for dead weight, strip weight and strip tension. According to the deviations from the target value, the manipulated variable, i.e. H. the armature current for the motor 14 is changed via the current regulator 29. The individual torque components for dead weight, strip weight and strip tension are formed in the adaptation controllers 23, 24, 25 intended for this purpose and added to a setpoint value which acts as a limitation on the controller 20. The output of the EMF controller 20 is thus the setpoint for the current controller 29.

Furthermore, for the timely consideration of the setpoint specifications such. B. tape stock, tape dimensions, etc., a control of the loop and loop lifter control required. The necessary inputs for the control are automatically specified in the input part 40 by the beginning and end of the strip or manually and via the control 41 the individual compo nenten supplied, as can be seen from Figure 4.

During operation, the setting angle a is continuously measured by a sensor 22. As already described, the band weight and the dead weight of the loop lifter are taken into account as torque components, which are calculated from a, via the function generators 23, 24. The setting angle a is also used as a measurement variable for loop control. According to the invention, the respective rolling line height D is also taken into account in the control. The rolling line height is determined by adding the roll diameters and possibly further variables influencing the rolling line height in the circuit 33, and is represented as a corresponding analog value U _D. It is the responsibility of two downstream function generators 42, 43 to determine the electrical analog value U _{M / Z} and U1 for the strip tension factor M / Z and the strip supply 1 as a function of the setting angle a and the fixed predetermined rolling line height D.

In the control loop 27 (“loop regulator”), the calculated value, dependent on a and D, for the tape supply ^U _l ^{= f} ₂ ( ^U _a , U _D ) is compared with the set value for the tape supply. The roller motor 129 is controlled by means of the control module 28 (“speed control”) and thus the strip supply 1 is set.

FIG. 5 shows the part of the block diagram located in the dash-dotted box in FIG. 4. The circuits 30, 31, 32 allow the manual setting of the values determined by physical measurement for the support roll diameter, work roll diameter and total thickness of the washers and deliver corresponding analog voltage values at their outputs. The voltage values are added in an adding amplifier 33. In another adder 34 are provided as further correction ^g Rössen the difference in height of the run-in table and the rolling line heights of the adjacent scaffolding considered. The entire correction can also be switched off via the switch 35. A voltage value U _D , which corresponds to the currently measured rolling line height D, is accordingly present at the inputs 36 and 37 of the function generators 42 and 43. Voltage values corresponding to the currently measured angle a are entered at the further inputs 38, 39.

The construction of the function generators 42, 43 will not be explained in detail, since their construction is familiar to a person skilled in the art if the underlying functions are known. The generators are based on the following functions:

The geometric details can be seen in FIG. 6. The circuits shown in FIGS. 4 and 5 are based on the task of ensuring that the strip supply and the strip tension Z are at a predetermined desired value to keep. The setpoints are of each _W alz- beginning in the regulator circuits 20, fixed 27th

Volume 1:

ist und daß beispielsweise D = D_M und der festgelegte Bandvorrat 1 = 30 mm ist, so stellt sich ein Winkel _{a =} 32° ein. Sollwert und tatsächlich ermittelter Bandvorrat stimmen überein.If one assumes that

and that, for example, D = D _M and the specified tape supply 1 = 30 mm, an angle _{a =} 32 ° is established. The target value and the actual tape supply match.

If D changes, for example D = D _min , then with unchanged a = 32 ° there is a changed l ₁ = 42 mm. However, since l ₁ deviates from the target value, the speed for motor 29 is changed so that the deviation from 1 is taken into account. If this is the case, a is set to 27 ° (see FIG. 2).

At the same time, the belt tension factor M / Z changes. While D = D _{m is} the factor at a = 32 ⁰ 0.113, ie a constant tension is generated at a moment of M = Z 0.113, we now have (M / Z) = f ₄ ( _a , _D ) with a = 27 °; D = D _min (M / Z) = 0.119 (see Figure 3).

Since the deviation of the tension from the nominal value should be 0, the belt tension must be adjusted by the control circuit 20, 29 so that the deviation becomes 0.

The arrangement according to the invention thus enables the change in the rolling line to be detected by using function generators which take into account both the current value for a and a set D.

Claims (1)

Arrangement for the operational recording of the change in the rolling line height in a rolling mill with several stands, between which loop lifters are arranged, the lifting arm of which spans an angle a between the rolling line parallel and the arm axis, and for the correction of strip supply and / or tension within the rolling strip if a change occurs the rolling line height D, characterized by a) an addition circuit (34) with which the diameters of the support and work rolls (5, 6; 7, 8) and further addable variables influencing the rolling line height can be added to an electrical analog value U _D corresponding to the rolling line height, b) two function generators (42, 43) connected downstream of the addition circuit, which have an electrical variable U and U _D proportional to the angle a, on the basis of the functional relationships:

or.

Process into one signal each, with the signals generated by the function generators being input with the usual adaptation of control loops for controlling the rolling speed and the drive of the loop arm. (Where: U _{1 =} analog electrical quantity to the tape supply; U _{M / Z} = analog electrical quantity to the tension factor).

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