DE2263674A1 - METHOD OF MANUFACTURING STRIP-SHAPED ROLLED MATERIAL USING A COMPUTER - Google Patents

Description

WESTINGHOUSE Erlangen, December 22nd, 1972

Werner-von-Siemens-Strasse

My reference: VPA 72/8328 Hk / Tue

Process for the production of "strip-shaped rolling stock under Using a calculator

Priority is given to U.S. patent application serial no. 215 of 6.1.72 used.

The invention "relates to a process for the production of" tape-shaped Rolled stock in a rolling mill containing at least two roll stands using a computer and application a thickness control dependent on the rolling force, including a device for measuring the deviation of the Thickness of the rolling stock leaving the rolling mill from the target thickness.

The empty roll gap and the speed at each stand a tandem mill or a reversing mill is used for each pass to achieve a gradual decrease up to adjusted to the desired thickness of the rolling stock by the operator. Under the normally justified assumption, the loaded roll gap corresponds to the fact that there is little or no elastic recovery of the rolling stock on a roll stand the thickness of the one running out of this roll stand Rolling stock.

As provided by the rolling mill or by a computer based on a model equation for calculating the adjustment

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specified initial conditions for setting the roll gap can be wrong and there at any point in time Certain rolling parameters act on the loaded roll gap, must to precisely maintain the desired thickness of the one Roll stand running out rolling stock, the roll stand can be equipped with an automatic thickness control device. To The current state of the rolling mill technology, in particular the steel rolling technology, is used for the frame of a reversing rolling mill and in tandem mills for predetermined rolling stands one Applied thickness control device.

The most widespread use is the one under the name "Gauge" known methods for regulating the thickness as a function of the rolling force in metal rolling mills and in particular found in hot rolling mills (DTPS 977 352, 631 500). Experience has shown that this thickness control is special is effective.

The method for regulating the thickness via the rolling force uses Hook's law to regulate the employment position of a roll stand a. This means that the loaded roll gap during rolling corresponds to the unloaded roll gap or corresponds to the Anatellpoaition plus the roll stand elongation which is exerted on the rolls by the rolling stock Separation force is caused. To apply this principle to the thickness control, the separation force of a rolling force sensor detected on the respective roll stand provided and the adjustment position is controlled in such a way that it compensates for changes in the rolling force from a reference value and the loaded roll gap at an essentially constant one Value holds. The basic relationship for thickness control via the rolling force is given by the following well-known formula:

(1) h = S ₀ + F / M

Here, h = loaded roll gap (thickness of the expiring Walagut)

S = unloaded roll gap (adjustment position)

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Έ = separation force

M = rolling mill spring constant or stand elongation constant

In its typical design, the thickness control device is an analog working arrangement with analog comparison and Amplifier circuit. Control the signals which are fed to the arrangement and which are proportional to the rolling force and the setting position the employment according to the following equation:

(2) AS = - AF / to

Therein, AF is measured deviation from an initial rolling force AS controlled change of the roll gap setting from an initial setting

After setting the empty nip and the speed for the respective stand and for one or more steps have been determined by the rolling mill, the Rolling process initiated. The positions are controlled so that the thickness of the running out of the roll stand Rolled stock is regulated. By satisfying the condition given in equation (2) and that given in equation (1) The load roll gap h is kept practically constant according to equation (1).

At the point in time at which the rolling stock enters the respective roll stand, the adjustment position caused thereby becomes and the separating force that occurs is measured and from this it is determined how large the thickness of the to be maintained the rolling stock running out of the stand. During the rolling process, the separation force and the adjustment position monitored, every undesired change in the separating force detected and by a corresponding change in the contact position compensated. The thickness h 'of the rolling stock determined when the rolling stock enters the roll stand corresponds to the adjustment position S at the run-in including that at the run-in

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determined and divided by the spring constant M. The thickness h of the outgoing strip is at every point in time during the rolling process in accordance with the relationship according to equation (1) and corresponds to the setting position S for the unloaded roll gap plus the rolling force F divided by the spring constant M. The thickness error Ah results from subtraction ^{the thickness h 1} determined at the inlet from the initial thickness h. These relationships are shown in the following equations (3), (4) and (5).

(3) h = S _e +

(4) h = S _{0 +}

(5) h - h ¹ = Ah = S _n - S _p + (F - FJA;

An important prerequisite for the rolling process, which is inaccurate Compliance causes a constant thickness error is the setting of the roll gap by the rolling mill. from the setting of the adjustment position and the speed on an individual roll stand, it depends on whether the actual outlet thickness of the beginning of the strip corresponds to or deviates from the desired outlet thickness. If the thickness control device is the The rolling force measured in the stand is used as a reference value, the rolling stand is controlled as a function of the rolling force in such a way that that the associated actual thickness is continuously achieved until the adjustments to achieve the correct, constant thickness can be adjusted from the outside.

The starting position is set with each new roller electromechanical measurements are calibrated and, if necessary, further calibrations are carried out on different successive ones Points in time made during the life of a roller. In any case, the initial calibration is an operational one Subject to change and any change requires a readjustment of employment to correct the operation of the

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Thickness control device. There will be deviations from the calibration caused by changes in the heating of the roll stand, the speed (thickness of the oil film in the bearings), the Roll wear, through different settings of the adjusting spindles to control the shape of the rolling stock and possibly due to changes in other rolling mill parameters.

If the initial calibration migrates, changes occur in the setting position that causes the face rollers. aside from that the relation between the setting position and the size of the empty roll gap changes. As a result, the actual roll gap deviates, i.e. the initial thickness of the rolled material from the expected value calculated from the empty roll gap. The deviation is that Thickness error that can be corrected by adjusting or recalibrating the adjustment. If the elongation constant changes, then the actual roll gap also deviates from the one calculated on the basis of the originally assumed expansion constant Value. This deviation can be corrected in the same way by adjusting the position.

To correct such a continuous thickness error, normally a known thickness monitoring device is used, which adjusts the adjustment via the thickness control device triggers. The thickness monitor includes an X-ray or other ray type Thickness measuring device at one or more predetermined points of the rolling process, usually at least one Point is arranged behind the rolling mill, so that the actual thickness achieved in the roll stand or stands after a transport time has elapsed is measured between this point and the roll stand. The monitoring device compares the actual thickness with the desired thickness of the outgoing rolling stock and delivers a analog feedback signal that shows how the thickness control device works of a reversing mill or one or more specified stands of a tandem mill are influenced in such a way that that the desired, steady starting thickness is achieved. on

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In this way, the conventional monitoring system ensures a correction of constant ones delayed by the transport time Thickness defects caused or caused by a rolling parameter or a combination of rolling parameters can be.

In rolling mills controlled by the rolling mill, the monitoring device possibly partially from the correction of a constant thickness error by recalibrating the adjustment be relieved between stitches if there is a constant thickness error over the length of the workpiece and from workpiece to workpiece would persist. In this way, a reduction in the length of the non-dimensional workpiece can be compared to the length achieved on the basis of the transport time associated with the monitoring device. In the same In this way, the corrective intervention of the monitoring system, which is triggered by thickness errors when the rolling stock enters, can be avoided is made by changes to the adjustment provided by the rolling mill or by a computer system from workpiece to workpiece be reduced.

It is already known, according to a program-controlled digital computer to be used for the automatic control of the strip thickness in a hot rolling mill (Iron and Steel Engineer, December 1967, Pages 75 to 86).

The invention is based on the object, using a computer from different, assumed and during the Rolling determined parameters to automatically determine a control sequence that the desired, constant Tape thickness results.

According to the invention, this object is achieved in that during the rolling of a first workpiece accordingly a predetermined relationship between the thickness deviation and the rolling speeds in the first and second stands

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a correction variable is determined which is used to control the Roll gap of the first stand is used for the passage of a second workpiece of the same type. At a whale plant with more than two stands, the correction variable ar; several selected scaffolding according to a weighting factor distributed in such a way that the proportion of the correction variable with increasing distance from last roll stand of the rolling mill decreases. The correction variable is derived from the ratio of the rolling speed at the last Stand to the rolling speed at the respective stand multiplied by the ratio of the thickness deviation and the Evaluation factor that determines the desired proportion of the correction variable for the respective framework.

To regulate the thickness, at least one condition is determined that causes a thickness error, and the setting position is on one or on each of several pre-determined roll stands of the rolling mill controlled. Furthermore, the total amount of an adjustment movement (change of position) is determined, which for Correction of the error condition with an assumed expansion constant and with assumed plasticity values of the rolling stock is required. The Waisk force is determined in the device for regulating the thickness as a function of the rolling force.

A correction value is calculated in relation to the thickness error or to that measured behind the last stand Thickness deviation. This correction value is evaluated on selected stands before the last roll stand. The calculated correction value is used during the rolling of a first rolled strip to adjust the roll gap to the selected roll stands are finally determined before other rolled strips that are the same as this first rolled strip are produced. The roll gap setting on a selected number of stands in front of the last stand is corrected, while the last stand is controlled by a rolling force thickness control device. This correction is based on the principle of Constant volume taking into account the rolling speed

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in the last roll stand and the rolling speed in the to corrective roll stand of the measured thickness deviation and a predetermined weight factor determined.

A digital computer is used to determine the error-dependent correction of the pitch movement as well as to perform other control functions for the rolling mill.

The computer works according to a program that contains a program for the automatic control of the thickness via the rolling force (AGC) contains. The latter takes place at predetermined time intervals to calculate the adjustment movement, which is necessary for correction of a thickness defect is required on every roll stand equipped with a thickness control, including the Correction that can be traced back to a rolling force error determined on this stand. The pitch movement for Correction of a rolling force error is made on the basis of calculations based on selected values of the plasticity of the workpiece and the framework strain constant are used as a basis, which are stored in a data memory in the computer system or have been determined by the computer in another way.

For a more detailed explanation of the invention, reference is made to the drawings referenced. Show it

Pig. 1 is a schematic representation of a hot strip tandem mill and a digital computer system for automatic thickness control.

2 and 3 each a diagram of a framework expansion curve and a decrease curve for a roll stand,

4 curves of a stand deflection and a deformation of the rolling stock to derive the pitch movement to correct a thickness error,

5 shows a graphic representation of typical plasticity values,

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Pig. 6A, 6B, 6C show a flow chart of a program for

automatic thickness control,

Pig. 7A and 7B show a flow chart of a subroutine for

an X-ray thickness measuring device,

Pig. 8 is a flow chart of a subroutine for feedforward control;

Pig. 9 is a flow chart of a feedback subroutine; Fig. 10 is a flowchart of an adaptive subroutine; and Fig. 11 is a flowchart of an initial subroutine.

In Fig. 1 is a tandem hot strip finishing mill with a shown by a process computer 13 improved thickness control. The invention is, however, to various types of Rolling mills, for example reverse hot rolling mills, can be used in which a thickness control is used via the rolling force is.

The rolling mill contains a number of rolling stands, one of which however, only the roll stands S1 and S6 are shown. That Rolled stock 15 enters the rolling mill in the form of an ingot and is used during the transport by the successive Roll stands extended. After passing through the rolling mill, it is wound onto a reel 17 as a strip. The incoming one Known grade steel ingot is typically about 2.5 cm thick and about 0.5 cm wide up to 2 m. The outgoing tape is usually about the same width, while the thickness of the production order depends.

During the rolling process, the successive roll stands work at gradually higher speeds, so that the same volume in the unit of time through the individual frameworks

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runs. Each stand produces a predetermined decrease so that the incoming ingot becomes a strip through the total decrease is reduced from the desired thickness.

Each stand is equipped in the usual way with a pair of backup rolls 19 and 21 and a pair of work rolls 23 and 25, through which the rolling stock 15 passes. To drive the drive rollers, each roll stand has a large one in terms of speed controllable direct current motor 27 assigned.

As already stated, the sum of the empty roll gap and the stand elongation is determined in accordance with the Hook's law is essentially the thickness of each one single stand running out rolling stock. A pair of adjusting motors are required to change the roll gap on each roll stand 21 for the drive of Anste "> oil spindles 31 provided, which are attached to the attack opposite ends of the backup rolls and thereby exert pressure on the work rolls. Usually are the two adjusting screws 31 on each roll stand in the same position, but they can be used to guide the strip be set to different positions during threading, for example to achieve flatness or another form of tape or possibly for other purposes.

A sensor in the usual design provides one of the contact positions corresponding electrical quantity on each roll stand. To achieve an exact match between the contact position and the unloaded gap between the associated work rolls, the pitch guide 33 can contain Device for determining the setting position in the manner already described at predetermined time intervals be calibrated.

The rolling force is detected at each of the selected rolling stands by a rolling force sensor 35, which has an analog electrical

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Sch.es signal generated. At least & n each with an automatic thickness control equipped mill is a Ί & 1ζ ~ pressure gauge 35 provided often;! Jedoc3i also ί ■ rolling stands without thickness control with Druckaießgeräten.

The number of those equipped with an automatic thickness control In the course of the mill planning process, rolling stands are designed in accordance with the standard values relating to the performance Fixed costs. In increasing mai there is the tendency assign a thickness control device to all stands of a hot rolling mill. In the present lall it is assumed that each stand is equipped with a device for regulating the thickness as a function of the rolling force.

In the usual way, side guides 37 with motor drives are arranged at predetermined points along the rolling mill. The side guides 37 are during the adjustment of the rolling mill based on the width of the to be rolled Good 15 pressed and "limit the sides of the Walzgutweges for guiding the belt.

The process computer 13 automatically controls the operation of the tandem rolling mill 11 and, if necessary, an associated one Production process, for example the operation of a rough rolling mill. The process computer preferably contains 13 a programmed digital process computer 39 associated with the various sensors and various control devices of the rolling mill to achieve control of a number of different, operational steps connected is. Advantageously, the computer control system 13 the usual analog, manually and / or automatically operated control devices for the auxiliary Operation for performing specified operations included.

Based on these considerations, the computer system includes

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a computer system for the direct operation of a finishing mill with a thickness control device dependent on the rolling force.

The process computer is connected to known input systems, which usually have a switching device for querying contacts or other signals representing the current status of various operations, a device for interrogation and Adaptation of analog process signals as well as controlled by the miller and other information input devices 41, for example a chart recorder, and other input devices. The information input device 41 is shown in FIG. 1 only represented by one block, although various input devices are normally connected to the computer 39 are. Various types of information, such as the one desired, are entered into the computer Final thickness and temperature of the strip, input thickness, width and temperature, quality of the steel to be rolled, plasticity values, Hardware-dependent programs, control programs, etc.

The input switching devices and the analog input devices connect the computer 39 to the rolling process via the measured variables. The computer system includes one Computer for automatic thickness control, hereinafter referred to as AGC computer (Automatic Gauge Control Computer) is. Various signals derived from the rolling process are fed to the input part of this computer, namely:

(1) a rolling force signal from the pressure gauge 35 located on each roll stand,

(2) signals corresponding to the setting position from the sensors 33 arranged on the roll stands,

(3) signals generated by tacho generators 49 and proportional to the speed of the adjusting motors,

(4) signals generated by tachogenerators 43, proportional to the rolling speeds, which are used to calculate the Compensation, acceleration and distance

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Between the measuring device and the rolling mill dependent delay time be used,

(5) e% n thickness deviation signal from a thickness measuring device 4-7 working with X-rays at the output of the rolling mill for the programmed control via the thickness regulation,

(6) a signal provided by a temperature sensor or pyrometer 45 and proportional to the inlet temperature (the inlet temperature the beginning of the forest is saved),

(7) Signals proportional to the width of the rolling stock from potentiometers connected to the side guides for the Calculation of the framework strain constant, etc.

When the rolling stock enters the roll gap of a stand measured rolling force is saved and used as a setpoint for the Thickness control is used when the AGC computer intervenes on the respective stand in direct operation.

Typically, the digital computer 39 is an output switching device connected · During the operation of this output switching device, various control devices are in Depending on the calculated or specified by the control program Tax measures taken.

The control devices are controlled directly by the exit switchgear or actuated by analog signals transmitted via βΛηβη digital-to-analog converter from the output switching device are derived. The most important, from the output switching device The measures triggered are those that bring about the employment Commands ^ which the control devices 55 for commissioning the AnstellmotPren 29 are supplied, and the signals that a Means 53 for controlling the speed and the Tensile stress to achieve a change in the drive speed are supplied so that the fa ^ z force exerted on the rolling stock is compensated for the change in thickness by an adjustment movement will.

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Furthermore, display and printing devices are connected to the outputs of the computer 51 connected, such as digit displays, punch tape punches and telex devices, so that the The rolling miller is informed about the rolling process and made aware of an incident or alarm that affects one Requires intervention. The printing devices are used to record the rolling data in accordance with the instructions of the Computer program used.

The AGC calculator uses Hook's law to determine of the total amount of a change in employment made to each A stand equipped with a thickness control is required at the time of the calculation of a rolling force and thickness error correction is, i.e. to correct to the desired value of the roll gap and the thickness of the respective stand outgoing rolling stock.

The calculation determines the total change in the empty roll gap, which is necessary to eliminate a new value of the elongation constant or the rolling force and the thickness error State is required. The calculated correction value for the change in the contact position is stored in a contact program of the AGC computer to determine the adjustment time evaluated by the adjustment motor until the end of the adjustment correcting Movement needed.

During the rolling process, the computer-dependent thickness control device operates the rolling stands in such a way that a strip with the desired thickness and the exact shape, i.e. a flat ribbon with a slight curvature.

The thickness control, which is dependent on the computer, is carried out by a on the rolling force dependent control circuit on each of the rolling stands and achieved by the control device containing the thickness measuring device and acting on the adjustment.

_BATH ORIGINAL

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The signal generated by the thickness measuring device 47 corresponds to the difference between the measured and the desired thickness of the strip leaving the rolling mill. In some! Cases it may be desirable to use one of the absolute thickness of the tape corresponding signal as the basis for the readjustment of employment.

For the thickness control, the programmed AGC computer processes the signals that the position encoder assigned to the position, the pressure gauges and the thickness gage arranged on each roll stand supply. In addition, the computer 39 is each a signal proportional to the speed of the adjusting motor is supplied and thereby the programmed adjustment of the adjustment ensured. To trigger the control actions, the computer uses a thickness control program, which is part of the overall program The thickness control program includes programs for controlling the components of the computer and programs to trigger the control processes.

The one in Pig. 2 curves shown serve to explain the Application of Hook's law to a roll stand and to Explanation of the basis on which the process computer and in particular the computer-dependent thickness control device a Control speed, accuracy and stability improvement and other operational benefits.

A curve representing the stand elongation determines the distance between the work rolls of a rolling stand as Puncture of the separation force and the setting position. The slope of the curve is the known framework strain constant M, the changes is subject to, as already described. If an exact calibration of the adjustment is known and the adjustment screws so are set so that the work rolls just touch each other, then the zero position of the adjustment is accurate without load Are defined. The associated scaffold elongation curve is 61

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draws. Theoretically it is assumed for an exact calibration that that the setting position at which the rollers just touch each other is assigned the value zero. Indeed However, due to the non-linearity of the lower part of the stand elongation curve, the rollers touch each other slightly at one negative value for the contact position. A calibration of the employment in the sense of the theoretical condition as exact however, it is convenient and pertinent to the rolling process.

If the adjusting screws are moved in the positive sense, the empty roll gap increases, as shown in the graphic Representation to the right shifted strain curve 67 is indicated, wherein the intersection of the theoretical curve shape with the abscissa the new empty roll gap S-. indicates. By changing the position in the negative sense, in in the same way the expansion curve shifted to the left.

In each adjustment position and with precise calibration of the adjustment, the thickness of the rolling stock exiting the roll stand corresponds to the empty roll gap S ₁ plus the stand expansion caused by the rolling stock. If the calibration of the adjustment is not accurate, i.e. if the numerical value assigned to the theoretical roll contact of the setting position deviates from zero, for example due to the wear of the roll curvature, the thickness of the rolling stock running out of the stand is equal to the empty roll gap plus stand expansion plus / or minus deviation from the calibration position.

The amount of stand elongation depends on the characteristic decrease curve of the rolling stock. A decrease curve 65 shown in FIG. 2 for a strip with a predetermined width represents the amount of the rolling force which is required _{to reduce the entry thickness of the rolling stock to the size H 1n.} The slope of the curve 65 indicates the plasticity P of the rolling stock. In this case

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the curve 65 is shown as being linear, although it is normally slightly non-linear. The desired rolling stock thickness H-. is the condition JC achieved in this case, since the amount of the _{rolling force required to reduce the rolling stock from the thickness H 11} T to the thickness H ~ is equal to the amount of the separating force required to stretch the rolls to the load nip IL · is, ie the intersection of the elongation curve 67 at the initial _{slope S 1} with the decrease curve 65 is at the desired thickness value.

If, as in Pig. 2, the thickness of the rolling stock exiting from the roll stand is increased by the amount GE of a thickness error to HL - during a stitch and thus the intersection point PC results, then because of the decrease in the plasticity of the rolling stock and because of the greater, through the Acceptance curve 69 shown inlet thickness Hy ₁₁ J the roll gap can be reduced to a smaller value, which ensures compliance with the exact thickness corresponding to the intersection point FC. The point of intersection FC of the expansion curve with the new decrease curve 69 lies at the desired thickness H ^, as indicated by the expansion curve 63. In other words, the correction of the pitch causes the empty roll gap to be reduced by the amount AS “™ to a new value which, with the new stand expansion, adds up to the desired thickness EL ·.

After a change in the adjustment from an initial position S ^ ₀ to another position S _Q (FIG. 3), for the rolling force error FE and the associated thickness error GE, not only the change in the rolling force from an initial value F _R , but also the change in the adjustment can be considered from the initial position S-. The amount of correction of the adjustment position required to achieve the desired thickness Ώ ~ is denoted by Δ Sd «. The new pitch position S ^ is then

(6) s _{i =} s _o -

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Where S is the pitch position with the roll gap unloaded,

Δ5 _ϋΏ the required correction quantity for the on-position.

According to the invention, the correction _{variable AS RF} for the thickness control is calculated according to the following programmed algorithm:

(7) AS _Rp = (K / P + I) -GE

Where GE = thickness error,

K = 1 / M = scaffold elongation constant (cm / t) P = plasticity of the rolling stock (cm / t)

Equation (7) is derived with reference to Fig. 3 as follows:

(8) GE = FE * K

(9) Af = GE / P = expected from the correction of the employment

Whale force change.

(10) As _RF = AF κ f Af P = AF - (k + p)

(11) AS _RF = GE / P (K + P) = GE (K / P + 1)

To calculate in advance the amount of the change in employment that is required to correct a thickness error, the thickness error GE is calculated as follows:

(12) GE = (F _x - F _R ) -K ₊ (S _o - S _1o )

When calculating thickness errors, equation (12) determines the difference between the actual value Fy and the nominal value F _{R of} the rolling force in relation to the stand elongation constant, and from this difference the amount of a rolling force change is subtracted that was required by a pitch movement to correct a previous rolling force error. For the point PC in FIG. 2, S _Q = S _{1 Q} in equation (12).

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As a rule, however, S has a different value than S ₁ , as shown in FIG. 3.

A corrective movement of the adjustment by the specified amount causes a further change in the rolling force and the rolling force error FE becomes zero when the control device has calculated the precalculated Behavior - shows and if no new rolling force error occurs during the correction period. If that If the control system does not behave as calculated in advance, FE does not become zero and a new rolling force error PE occurs to the extent that that the adjustment movement carried out by the pre-calculated amount increases the thickness of the rolling stock at the exit of the Cannot correct the framework.

The reference value S ₁ of the pitch, which is used as the basis for determining the thickness error GE in equation (12), results in:

<"> ^S 1o new - ^S 1o - ³ M ^{+ 3} EPP

There is: S ^ = readjustment controlled by the thickness measuring device

of employment,

S.
HPP - anticipated change of employment by

Forward control to compensate for a rolling force error.

The reference value S., _Λ can be calculated according to equation (13),

1 O

if the variables S ^ and S _R pp change, in order to prevent the thickness control device from responding to the changes in the rolling force which can only be traced back to a change in the position, such as a change in position for recalibration by an external control system, for the correction made in direct operation during the run-in of the rolling stock in the roll stand, for the advance compensation of a change in the rolling stock speed, or a rolling force error or for other correction of a

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Thickness error. If a thickness measuring device is not used, the corresponding quantity S «in equation (13) is omitted.

In general, the magnitude of the expansion constant K of each frame is known relatively precisely. You will first determined by the known text of the work roll adjustment and is determined before each pass, taking into account the width of the rolled material and the diameter of the backup rolls are recalculated. Each strain curve 61 determined in this way is used for the computer-dependent thickness control is saved.

The way in which the strain constant K is stored is different. In the present case, the inclination of the linear part of the strain curve is saved as a single value. The non-linear part of the strain curve is made up of three assumed straight lines with different slopes whose slope is saved as three separate values that correspond to the rolling force range. As the later, The rolling data output from the data collection of the computer initially represent unknown relationships that are dependent on the computer The operational calculations can determine changes in the elongation constant as a function of rolling parameters the strain constant is programmed in accordance with these relationships under dynamic operating conditions will.

The operating value of the rolling stock plasticity P at each roll stand is also determined relatively precisely. In the present case are a series of plasticity values stored in the computer to determine the different values of plasticity that on the different roll stands with the different quality and thickness classes of the rolled stock under different operating conditions and occur at different times during rolling. The saved plasticity values are based on a unit width of the rolled material. To the

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To determine the appropriate value in each case, the stored values PW are divided by the width of the material to be rolled.

The thickness control in a hot rolling mill, in which one programmed Evaluation of the rolling force signals applied by a digital computer comprises a combination of a number of process flows. Information about the rolling force, the setting position and the stand elongation are used to determine the Strip thickness used during machining in each roll stand. To determine the absolute strip thickness, the of the thickness of the strip exiting the last roll stand determined by the measuring device is evaluated.

A multi-stand and a Conti rolling mill require a thickness control device to maintain a uniform thickness. A single strip is used in all roll stands at the same time rolled. As a result, the thickness control device must be able to detect the thickness defects in each roll stand so quickly as possible and these thickness errors - if necessary - to correct in several roll stands. Pure this There are two possible measuring systems for purposes: an X-ray thickness measuring device and a thickness measuring device Detection of the rolling force.

X-ray thickness gauges can be placed behind each roll stand. You work exactly, are. However, it is expensive, difficult to maintain and errors can only be detected when the rolled strip covers the distance between has passed through the work rolls and the gauge. On the other hand, there is a device for detecting a thickness defect Significantly less expensive due to the rolling force and can easily be installed in all roll stands. It represents thickness errors when the tape is still between the rollers, allowing a faster determination of the required Correction of the pitch position of each roll stand. However, it is disadvantageous that the rolling force measurement is only one

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Relative determination of the tape thickness allows, since it only determines how high the deviation of the tape thickness from the thickness of the beginning of the strip entering the roll stand.

A practical combination of the two systems for detecting a thickness defect is the use of a whale force signal for fast calculation of the desired error correction and the use of an X-ray thickness measuring device behind the last roll stand to determine the absolute thickness of the strip leaving the last stand. The values for the quick correction are derived from the rolling force signal in connection with the determined value of the contact position and the specified elasticity value of the roll stand is calculated. The value of the thickness error supplied by the measuring device becomes Calculation of corrections to be carried out simultaneously on the individual roll stands is used, so that the absolute value of the Thickness of the strip leaving the roll stand can be brought to the desired value. The output of each of these two SystBme causes a change in the pitch position of each roll stand.

2 shows the linear approximation curve 67 of the stand elongation and the decrease curve 65 for the rolling process in a rolling stand. The empty roll gap S ₁ is equal to the strip thickness that would be achieved without the roll separation force that occurs. If the rolling force increases while the roll gap is kept constant, the initial strip thickness also increases because the roll stand expands. The rolling stock deformation characteristic is shown by the line. When the rolling force is increased, the rolling stock is plastically deformed and the initial thickness decreases.

The initial thickness of the rolling stock is determined by the point JC, in which the rolling force exerted by the rolling stand is the Deformation of the rolling stock required force keeps the balance. Changes in the thickness of the incoming rolling stock and / or

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Changes in the hardness of the rolling stock result in a change in the rolling force and the initial thickness of the rolling stock. To correct these changes in thickness, the control device must change the position.

The main advantage of regulating the strip thickness via the rolling force Facility is the ability to detect strip thickness changes as they occur during rolling Roll gap arise. Changes in the rolling stock hardness are usually caused by changes in temperature.

Fig. 5 shows the operation of a device for detection of thickness errors, the elongation curve 67 and the plasticity curve 65 the initial condition and the elongation curve and the plasticity curve 69 a pole state during the Represent rolling. Compared to the initial conditions, the employment is in the sense of a reduction in the roll gap changed and the roll separation force has increased because, for example, a harder, cold point on the rolled strip Roll stand passes through.

The required correction of the thickness error by changing the pitch depends not only on the strip thickness error, but also on the respective values of the stand elongation constant and the plasticity of the rolled stock. In Pig. 3 shows how the thickness error GE is eliminated by correcting the pitch As "-". The correction AS _R -, of the pitch is about twice the size of the thickness error GE, because the correction process causes an increase in the rolling force due to the greater decrease. Relatively soft rolling stock requires a correction Δ St, ™ of the adjustment of approximately the size of the thickness error, while hard rolling stock requires a larger correction compared to the thickness error. The necessary change in the position of AS _RJ to correct a thickness error is described with reference to Pig. determined according to the following relationship:

. (14) ASgp = X + GE

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X is the amount of the roll gap change and thus the

Change in the strip thickness due to the roll stand elongation,
GE the thickness error.

The roll stand elongation X can be derived from the relationship

(15) X = K- ΔΡ
can be determined

AF the change in the rolling force shown in FIG. 3, when the thickness error GE is corrected.

The illustration in FIG. 4 also shows

(16) GE = P

According to equation (9), AF = GE / P. In conjunction with equation (15) results

(17) X = KGE / P

and from equation (14) and equation (17)

(18) AS _Rp = K GE / P + GE = GE (K / P + 1)

The correction AS _{Rf of} the adjustment is in FIG. 3 in the ratio of the thickness error GE to the desired initial thickness IL. and the respective actual thickness H _x .

5 shows a graphic representation of stored, typical plasticity values PW for a seven-stand, Hot strip tandem mill. The six curves cover an area of inlet thickness from approximately 2.5 to 3.1 cm in one area the initial thickness of about 0.1 to 0.6 cm. These values can be entered into the memory of the computer by the rolling mill or set up by the adaptive program.

The main program shown in Fig. 6 as a flow chart for the thickness control and the associated flow chart in Fig.

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relate to the program connected to the measuring device the same operation, with both programs through the Sampling of the analog input signals can be initiated. The program for the thickness control maintains a constant initial thickness based on the initial parameters set by the rolling mill of the rolling stock upright, while the program connected to the measuring device controls the thickness by monitoring the Final thickness and, if necessary, supported by adaptive corrections.

The thickness control program makes corrections while a strip is being rolled Deviations from the initial thickness on each roll stand by adjusting the roll gap accordingly. A deviation the initial thickness on a roll stand from the initial thickness is expressed as the change in the rolling force on that roll stand from detected this initial value. From the error of the initial thickness, which is queried and determined every two tenths of a second, a correction value for the roll gap is determined and äie Correction carried out by adjusting the pitch position of the respective scaffolding.

The main program for the thickness control includes a sub-program, for making corrections based on the thickness of the rolling stock entering a rolling stand specified conditions traces a determined thickness error back to the previous stand for setting the roll gap. This subroutine is shown as a flow chart in FIG. Such a feedback correction is usually executed when the adjustment position for a roll stand has reached an upper or lower limit value and a further adjustment movement is required in a sense that exceeds the limit value, and so can the preceding roll stand support the functioning of the affected framework.

6A, 6B and 6C is the flow chart of a preferred embodiment of a program for thickness control for a hot strip

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tandem mill shown. In program step 10 determined whether the automatic thickness control system (AGC program) has been selected by the rolling mill and is "ready for operation". Shortly after the beginning of the rolling stock has entered the rolling stands of the rolling mill, the program begins to run and The initial rolling force, the initial speed and the initial pitch are measured at each roll stand and stored in memory saved on the computer. In program step 12 it is determined whether the respective query is not a query of the thickness measuring device is} for a typical rolling mill, for example, seven roll stands and an additional thickness measuring device are required be queried, which is arranged behind the last roll stand. Program step 12 relates to the Sequence of analog signal inputs; if it is a question of an input signal coming from the measuring device the program continues to the subroutine for the meter at step 14. If it is not If it is a sequence of the thickness control program with respect to one of the roll stands, the program goes to step 16 over, in which it is determined whether the rolling force has been selected by the rolling mill for this roll stand. The program step 18 is used to determine whether the automatic query has been activated for this roll stand. The condition of the Steps 16 and 18 must be fulfilled, otherwise the program goes to step 20, which is one of the initial values The display sets, and goes to step 22, which shows a lamp indicating the display "thickness control on" for this mill stand switches off on the control panel. The operator controls the sequence of the thickness control program by means of a selector switch for the rolling force a. In program step 24 it is determined whether the adjustment position for the roll stand has been set is. If this is the case, the program checks in step 26 whether there is rolling stock in the stand, and in step 28 whether this is the first query after the entry of the rolled strip. Each of these conditions must be met in order for the program to continue be fulfilled on this roll stand. At the first

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ask, the infeed of the rolling stock will be in this Time at the roll stand with measured values of the rolling force, the rolling stock speed and the pitch position stored in program step 30, since these values will be required later for control purposes.

In program step 32, the run-in rolling force is applied to the respective Scaffolding with the list of given values of the elongation constant entered in the memory in relation to each other to the well-known, non-linear course of the framework strain curve for determining the value K of the strain constant and used these for the following calculations for the operation of the scaffolding. As is known, the upper part is the Linear expansion curve. With program step 34- the determined value K of the expansion constant on the bandwidth converted. In step 36, the range of the initial thickness for the framework is determined, so that with step 38 im Self-learning mode, the average plasticity PW is set for this thickness range. At the program step 40, the plasticity constant P is calculated from the average value PW by dividing it by the known width of the tape. In program step 42, a hardness correction value based on the known degree of hardness of the strip to be rolled is used determined by the rolling mill. With the program step 44, the plasticity P for the roll stand is shown of the hardness value corrected.

In program step 46, the adjustment position is read off. It should also be mentioned that the program from step 29 via the End switch provided in the program 29 "Not start of tape" goes to step 46 if the query in step 28 is not the first when the strip enters the stand. If at In step 48 the rolling force measuring device is operating, the thickness error is calculated in step (Pig. 6B) according to equation (13). At step 52, the required correction is A

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calculated according to equation (20). In step 54 it is checked whether the correction value for the adjustment is greater than the minimum value of an insensitivity range specified by the rolling mill is. If the value is in the insensitivity range, eo if it is suppressed in step 56, if the value is outside of the insensitivity range, then in step 58 the average error becomes calculated. If in step 60 the correction value for the employment is not within the predetermined maximum limits, the program proceeds to step 62, where the Correction value is limited to the maximum value, and in step 64 a subroutine is initiated, whereby the excess Part of the correction value for the thickness error from the rolling stand to the following stands of the rolling mill for forward control will. In step 66 it is checked whether a correction value for forward control is to be expected from a preceding stand, for example due to a furnace slide caused cold spot (skid mark). Possibly it is determined in step 58 whether the skid mark begins to run into the scaffolding. If there is a skid brand or a similar condition approaches the roll stand, the movement of the adjusting device is to begin. If in step 66 none If a forward correction is to be expected, the correction that may be required for the roller frame is carried out and the program goes to step 70 to check whether there is a skid mark in the frame. Isn't a skid brand in the roll gap and neither is it Expecting the skid mark, the program goes to step 72 to calculate the required new contact position for this Roll stand over. Whether there is a skid mark in the roll gap of the roll stand and, if so, whether the adjustment screws are already moving is determined in step 74. If this is the first check, the adjustment screws will move in the desired direction at full speed at step 76 to correct for the skid mark caused thickness error triggered. In step 78 it is checked whether the end of the skid mark has reached the roll stand

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has enough, and if necessary the pitch correction value "at Program step 80 made ineffective. The counter assigned to the employment is corresponding to the known number of The counting pulses required for the skid mark to pass through the scaffolding are set and, in step 82, the counter is if it is not at zero, it is counted down during each request as it relates to the operation of the roll stand correction of the skid mark is required.

If at step 70 there is no skid mark in the roll gap of the roll stand, so the program goes to step 72, in which a correction of the pitch for the roll stand is calculated with it the thickness error on this roll stand is eliminated. At the step. 82 it is checked whether the new position is outside the specified Limits lies. If necessary, the adjustment movement exceeding the limit value is switched to on in step 84 previous stand returned after in step 85 the value exceeding the limits is provided with a sign. If, as in step 81, the new pitch position is within the specified limits, a check is made in step 86 to determine whether the pressure measuring device on the preceding roll stand is not working. In step 88 it is checked whether the rolling stand's own pressure measuring device is in operation. Then the setpoint for the Employment is calculated and in step 90 it is determined whether the end of the rolling stock has already run out of the previous roll stand is. In step 92 the transport time is checked and in step 94 it is determined whether full compensation is required is, and if necessary in step 96 the compensation value specified in the pitch regulation. Otherwise partial compensation is carried out at the step. The program then goes to Step 100 above, in which the new position of the adjusting screws for the scaffold is calculated. In step 102 the percentage Change of the initial position calculated and in step 104 it is checked whether the calculated position is within the specified limit values for the scaffolding. At step 106

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If necessary, the adjustment movement for the scaffolding kept within the intended limits. If in step 108 the previous position of the stand was zero, then in step 110, a lamp indicating the operation of the thickness control device to the rolling mill is switched on. Was the employment position not zero, the direction of the pitch movement is determined in steps 112 and 114, the control loop contains opposite commands via program steps 116 and 118. At step 120, the controller receives of the roll stand command to move the adjusting screws in the desired direction, and at step 122 the new value is the The setting position of the scaffolding is entered in the memory for the following processes. If at step 124 the tape is still is in the previous stand, the program ends, if not a subroutine for the preparation of the next strip and an iieuadjustment of the pitch position in relation to the end of the tape at step 126 can be performed.

That in connection with your step 14 of the flowchart for the thickness control program (Pig. 6A) mentioned with the thickness measuring device The associated subroutine (monitoring program) is shown as a flowchart in FIGS. 7A and 7B to explain the program sequence shown. In step 170 it is checked whether the rolling mill has selected the program. At step 172 determines whether the intended time delay for the next correction has expired and a test is made at step 174, whether one of possibly two measuring devices arranged behind the last roll stand has been selected. At the step it is determined whether the measuring device is in operation. If the result of one of the tests 170, 172, 174 or 176 is negative then the program is ended. At step 178 the desired final thickness of the tape is read from memory. At the Step 180 becomes the percentage deviation between the desired final thickness and the actual thickness measured by the measuring device certainly. At step 180, the percentage deviation

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between the desired final thickness and that of the measuring device measured actual thickness "is determined. In step 182 it is checked whether whether the deviation exceeds a limit value, if applicable raised an advertisement, raised an error message at step 184, and exited the program.

If the deviation is not too great, it is checked during the sciiritt, whether this is the first query while the rolling stock is running, and if so, a display is set in step 188. This ends the program. If it was not the first indication while the rolling stock is running, it is determined in step 190 that whether this is the last query at the beginning of the tape. At step 192, the last query at the beginning of the rolling stock is identified Display triggered. At step 194, the program goes through a predetermined subroutine which will be described later and then via a strip beginning program to step 196, in which the setting position of the respective roll stand for the next, same strip material is set. In step 198, the actual runout thickness is determined. At step 200 checked whether the rolling mill for normal operation on the initial conditions otherwise, in step 201, the determined thickness becomes the nominal thickness. At the step 202 it is checked whether the percentage deviation is greater than a predetermined value, for example 10 # greater. In step 204 (fig. 7B) the values specified in the computer are compared with the value provided by the rolling mill » so that the desired or nominal thickness of the tape is achieved again. At step 206, the percentage deviation from the desired nominal thickness determined again.

At step 208, the line speed in the last roll stand becomes determined, and the constant volume relationship taking into account the thickness error of the working method for selected Roll stands, for example for three Walssge.rüate, based on. In step 210 the last roll stand is selected and then the correction is made to the one selected Roll stands made. In step 212 it is checked whether the adjustment screws of the selected scaffold are set are, and at step 214 it is checked whether the from the meter

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dependent control device from the rolling mill for this stand has been selected. In step 216, the meter-dependent correction value for the selected roll stands and determines the proportional distribution. This process is carried out for all selected roll stands. If the Tests carried out in steps 212 and 214 show an incorrect result, then the one relevant for the stand number is used Number counted in step 218 and checked in step 220 whether the number of this roll stand is zero. At step 222 the correction value is limited. If it is determined in step 224 that the thickness control device dependent on the rolling force is switched off, then a correction value dependent on the measuring device is made in step 226 for this stand issued. This ensures that the correction, which is dependent on the measuring device, is only activated when the rolling force is switched off Dependent thickness control device can be made on the respective roll stand. With step 228 the number of corrections determined. In step 230 it is checked whether a sufficient number of roll stands have been corrected is. In step 232 it is checked whether the particular roll stand under consideration is the first roll stand, and in step 234 the last roll stand is selected. At step 236, the time required for the Strip has run from the respective roll stand to the next roll stand before the next correction to the selected one Roll stands must be made. This is a puncture of the speed and the associated distance.

Referring to step 64 of the Pig. In the flow chart shown in FIG. 6B, the subroutine in Pig. 8th shown as a flow chart. At step 250, if it is the last stand, there can be no forward correction thickness error must be taken into account and the subroutine is ended. Otherwise, if in step 252 a first, a signal indicating a skid mark occurs, a counter is set at step 254, and an indication is triggered at step 256.

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i) the direction of the adjustment movement, for example due to the ground a skid mark, is determined at step 258, for example to determine whether there is a soft spot in the band, and at step 260 the required transport time in relation to the belt speed at the respective Roll stand calculated. If the first signal from a skid mark does not occur at step 262, then the stand is of the payer at any time during the program sequence elevated. In step 264 the last correction value is used as the new correction value and the subroutine is ended. The transport time calculated in step 260 is stored in step 266 and the rolling stand is selected in step 260, which supplies the signals for the forward control.

The reverse control subroutine mentioned at step 84 in Fig. 6B is shown in Fig. 9 as an explanatory flowchart the mode of operation shown. If step 270 is the first roll stand, it is a return an error correction on a previous roll stand is not possible, so that the program ends. Otherwise the previous roll stand N - 1 is selected in step 272, if the roll stand under consideration is denoted by N. At step 274, they are triggered, if any Read the display signals and check why the feedback subroutine was initiated. At step 276 it is determined whether the rolling force from the pressure gauge on the roll stand N-1 was in error, and if necessary, at step 278, the required amount of feedback correction for the roll stand N - 1 calculated. If the rolling force signal was present on stand H-1, then a test is made in step 280 to see if the adjusting screws of this framework have been set precisely, and if necessary, in step 278 the correction value for the Repatriation calculated. The return program may be necessary if the adjustment position on stand N exceeds the limit values and if the pressure measuring device on the roll stand N-1 has delivered incorrect values. Steps 276 and 280 relate refer to the occurrence of either of these two cases. At step 282 the roll stand N is set and the subroutine

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runs back to the thickness control program shown in FIG. 6C.

That at step 194 in Pig. The adaptive subroutine mentioned in Figure 7A is in Pig. IO as a flow chart to explain how it works shown. The adaptive program is used to calculate the mean value of the plasticity of each such value used for the quality class of the rolling stock and for each roll stand. At step 300, the rolling stock speed becomes on the last roll stand and the initial thickness is determined. The starting thickness is determined by the X-ray machine Measuring device measured. The speed at the last roll stand becomes the fulfillment of the relationships for the constant volume needed. Purely the determination of the rolling stock speed in the individual roll stands becomes a digital one Measuring circuit used. The mean value of the plasticity and the deviation from this value are calculated for each roll stand, beginning with the interrogation of the first roll stand at «step 302. In step 304 it is checked whether this The scaffolding is set correctly. Palis no, goes the adaptive program into the edge start program. The rolling speed becomes using at step 306 the principle of constant volume determines the initial thickness. If the stand is the first stand at step 308, the program goes to step 310 because the principle the constant volume for determining the entry thickness on the first roll stand cannot be used and the program therefore cannot calculate the plasticity value for the first framework. At step 308, if the scaffold is not the first Stand, the program reads in step 310 the nominal diameter of the rolling stock and also the manually entered width and at step 312 the plastic constant PW is calculated.

If necessary, the position of the side guides can also be used as an indicator for the width of the rolling stock. At the step 314 it is checked that the calculated plasticity value N is actually positive. If the value is not positive, you can

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Program into the tape end program. At step 316 the thickness range is determined for storage. At step 318 the average plasticity value for this Thickness range determined. In step 320 the standard deviation is calculated and in step 322 it is calculated according to the thickness range of the rolled strip is saved. In step 324 it is determined whether the respective roll stand is the last stand is, and - if not - the program goes back to the step for further implementation of the process on each roll stand If, however, the stand is the last roll stand in step 324, the program continues to the "beginning of strip" subroutine. The tape beginning subroutine mentioned at step 196 in Fig. 7A is in Pig. 11 to explain how it works shown.

The strip speed at the last roll stand is detected in step 400. The initial weight factors are at step used and characterized by each of the roll stands, where the proportional factor for the beginning of the strip is equal to 1 and the proportional factor for the mill stand is set equal to 3 so that the desired relationship 3/3 »2/3 and 1/3 for the three selected Roll stands are maintained, for example going back from roll stand 6 to stand 4 and then to stand 2. At step 404 the mill stand number is counted and at step 406 it is determined whether the caliper is to provide a Thickness error and has been selected to guide the rolling process on this roll stand. If necessary, at step 408 determines the necessary correction for this roll stand. Otherwise, in step 410, a lower scaffold Number dialed until it is zero at step 412. This mode of operation provides the relationship of the desired Correction of 3/3, 2/3 and 1/3 of the thickness deviation for the respective roll stands. If the share factor on the roll stand Is zero, the subroutine is finished. After step 408 has elapsed, the roll stand number is counted off in step 414, and in step 416 the proportion factor is reduced, and in step 418 it is checked whether the proportion factor is zero.

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If this condition is not met, the program goes back to step 406. If the proportion factor is zero, then in step 408 the correction for this roll stand is made according to the determined the following relationship:

(19) Corrections. - V / V.

where the proportion factor for the roll stand with the highest number equals 1, and for the: roll stand with the; lowest number is 3 and where V ™ is the speed at the last roll stand and V ^ _{n is} the speed at the respective roll stand.

They are automatic, depending on the rolling force · Thickness control device is dependent on analog scanning which is scanned at periodic intervals of 2/10 seconds of the rolling force error on a roll stand or the thickness deviation determined by the measuring device.

To correct thickness errors on the respective framework,

the following conditions must be met:

1. The "Automatic thickness control" switch must be used accordingly

be set (step 10 in Pig. 6A),

2. The measuring device measuring the rolling force must be selected (step 16 in Pig. 6A),

3 · the roll stand must be included in the automatic operation (step 18 in Pig. 6A),

4. The roll gap must be set (step 24 in Pig. 6A).

If one of these four conditions is not met. iat, works the thickness control program without making a correction.

If a strip has just entered the roll gap of a roll stand (program step 26) and at this point in time the

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The first query is carried out (step 28), the initial values for the adjustment position and the rolling force are stored (Step 30) and the values for the stand elongation constant and the rolling stock plasticity are selected.

Every time the rolling force of a roll stand is reduced by the analog Scanning device is queried, the new value is compared with the initial value and any deviation is immediate based on a thickness error at the output of the stand (step 50) f from which the correction value for the Roll gap is determined (step 52). If the correction value for the roll gap lies within a predetermined insensitivity range, it is not taken into account in step 56. Otherwise it is checked whether it has a maximum value exceeds. If the limit value is exceeded, not only the roll gap on the stand (N) itself, but also the of the next roll stand (H + 1) corrected. This type of correction is known as feedforward control. If a large change in the roll gap is required at the roll stand H, this can be done the time for the required movement of the adjusting device be so long that a filing of the tape without thickness correction runs through the roll stand. To compensate for the thickness error on this part, the roll gap change required for correction on the next stand (N + 1) is already T seconds carried out after detection of the fault in the stand H. The time T is slightly smaller than the transport time between the two scaffolding. About T seconds after the defect has left the roll stand N, the correction executed by the following roll stand N + 1. If, however, the If the size of the correction value is within the specified limits, no feedforward control is carried out.

The new pitch position is calculated in step 72. Before the pitch is corrected, the absolute position is checked (step 82) to determine whether it is at a predetermined upper or lower limit. When the correction

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would exceed this limit, a feedback correction quantity becomes set for the roll gap of the stand N (step 34).

The following conditions must be met before a return can be carried out from roll stand N:

1. The roll stand N is not the first roll stand (step 270),

2. the roll pressure measuring device for roll stand N-1 is not in operation or the pitch position of stand N is up out of bounds (steps 86 and 82),

3. the pressure measuring device on roll stand N is in operation (step 88),

4. a feedback signal from roll stand N is not yet available.

When these conditions are met, the feedback subroutine occurs in action (step 84 or flow chart of FIG. 9).

The subroutine carries out three tests on roll stand N - 1:

1. A roll stand N-1 actually exists (step 270).

2. The contact position on the roll stand N-1 is not at the same Limit as the roll stand N (step 274), i.e. if the pitch position on roll stand N is at its upper one Limit is the setting position of the roll stand N-1 is not at its upper limit.

3. The roll gap on roll stand N - 1 is calibrated (step 280)

If these three conditions are met, a thickness correction is carried out on the basis of a feedback signal at the roll stand N-1. Due to a specified time delay, no further feedback correction can be carried out on roll stand N - 1. until the point on the strip that has been corrected due to the return reaches the roll stand N. The time delay corresponds to Transport time between roll stands N - 1 and N.

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After all the corrections have been made to a roll stand, the resulting direction of movement of the adjusting screws determined (steps 112 and 114), and a signal identifying this direction to the speed controller of the adjusting motors given (step 116 or 118). If anöV-xlseuben are moved downwards, the controller assigned to the adjusting screws is opened. With an upward movement of the The associated regulator is closed by adjusting screws. Each regulator control calls for a corresponding correction of the belt speed on a neighboring scaffolding so that the level of control is kept constant. Every time the employment is changed, a correction of the belt speed is made to anticipate a change in the control level ·

The task of the monitoring program connected to the measuring device consists of determining the thickness of the final product in absolute units. The one from the rolling force dependent thickness control device works on the basis of changes the adjustment position and thus changes in the thickness of the rolling stock and less depending on the absolute Employment position. For this reason there is a discrepancy between the desired and the actual thickness. The thickness gauge provides a setpoint for this comparison.

The information provided by the measuring device is based on two things Way used. When the thickness control dependent on the rolling force does not work on the last roll stand or makes the adjustment tests impossible for other reasons, the setting position on the last roll stand is set by the measuring device. If, on the other hand, the job on the last roll stand is positioned by the thickness control device, then the settings are made on the last three roll stands corrected from the measuring device to achieve the desired initial thickness.

In addition, the monitoring program at step

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The plasticity averages are updated and corrections at the beginning at step 196 of the tape. The tape end subroutine calculates the readjustment for the respective roll stand based on the deviation supplied by the measuring device and takes this into account Adjustment variable in the initial setting for the next same strip that follows the strip that has just been rolled. This With regard to the strips following a first strip, the method enables an incorrect correction by the rolling mill the initial setting made.

When the end of a strip leaves a mill stand, the thickness control program must move the mill stand for the next strip prepare for the initial conditions by adjusting the adjusting device. When the next tape is the same thickness as the previous one should have and during the rolling of the previous strip the initial setting immediately one thickness deviation detected by the measuring device, this error must occur when setting the adjusting screws for the next strip must be taken into account. This is achieved by calculating a correction value for each of the selected roll stands, where the correction value is used as an additional value for the setpoint of the initial setting. The first thickness query by the thickness measuring device is not evaluated because the measurement on the normally bent starting section of the Band can be made. The second time the gauge detects the thickness of a new tape, the correction values calculated for the beginning of the tape and stored for the next tape. In most applications, the adjusting device no correction value supplied to the last roll stand. Only the roll stands and their measuring devices are corrected the number of selected roll stands is limited to three, for example.

The task of the beginning of the tape subroutine is that the computer system supports the rolling mill with the initial setting of each roll stand of a rolling mill. The programmed one

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Computer for the automatic thickness control works in such a way that the rolling miller sets the target value for the desired contact position on each roll stand by means of an adjusting knob and the computer selects the roll gap of the corresponding Adjusts the rolling mill to this setpoint. Then the workpiece is rolled and the beginning of the workpiece becomes any Assume a thickness that is dependent on this nominal value of the adjustment. One problem with this is that the miller is not sure specifies the correct adjustment setpoints at the first attempt, so that the strip is too thick or too thin for each roll stand rolls out and the miller has to change his position. With the previously used thickness control devices, the rolling mill could make the necessary changes to each roll stand by eye and by gradually approaching them achieve the adjustment positions for the product to be rolled, which is a reasonably accurate thickness for the beginning of a subsequent tape delivered.

The programmed, computer controlled automatic thickness control device according to the invention can for starters of a first strip or bar does not do much, because the computer does not have enough at this point in time has operationally obtained information, but the computer can take over the job of the rolling miller, step by step Approaches to the correct setting positions a better and more accurate thickness at the beginning of the subsequent, similar To achieve bars.

When the beginning of the first strip has passed through all the rolling stands and the thickness measuring device located behind the last stand reached, the thickness gauge measures the thickness deviation after a short delay. This deviation indicates to what extent the initial adjustments made by the miller were satisfactory. Then a Correction value based on these initial settings is calculated, the same as the thickness determined by the measuring device

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deviation at the beginning of the tape multiplied by the constant volume relationship on the framework to be corrected is multiplied by a distribution constant. The correction value is the Adjustment devices for the roll stands supplied so that the adjustment position for the following strip is equal to the adjustment position for the previous band plus or minus the correction, depending on whether the correction value is in relation to the desired Tape thickness is positive or negative. The full correction value is assigned to the selected stand with the highest in the ranking Number, while the stand with the middle number is a fraction, e.g. two thirds, of the full correction value and the last stand with the lowest number also receives a fraction, "... e.g. one third, of the full correction value. Of course, more than three stands, for example five stands, can be corrected accordingly.

This program for automatic thickness control can be used with a smaller computer without model equations to determine the Initial adjustment for the scaffolding are carried out. The miller can use his own experience and knowledge for the Apply the initial setting of each »rolling stand and then the cone system described here takes over the operation quick correction of these manual initial settings.

The Banüaniang subroutine described uses the principle of constant volume to determine the correction values that are required for the settings made by hand are required and works with the smaller computer. The beginning of the tape correction is only used on selected roll stands on the basis of the deviation determined by the measuring device at the beginning of the workpiece executed. The thickness measuring device is arranged behind the last roll stand and the output signal corresponding to the deviation is equal to the difference between the nominal thickness of the rolling stock leaving the last roll stand and the measured thickness Actual thickness. An average value of the measured deviation is used for correction over the entire length of the tape and is used for

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- 43 - ^VPA 72

the next, similar tape - also based on the total length - is used.

The strip speed is measured digitally at each roll stand and the speed determined for the correction at the beginning of the strip in the selected stands to calculate the thickness error on stand N according to the principle of constant volume is used and the adjustment of the stand is corrected for the next strip, taking into account the calculated value. The last operational adjustment values are used for selected rolling stands for rolling the next similar one Strip determined taking into account the thickness error measured on the last roll stand and this thickness error is distributed over the previously selected roll stands. The operationally determined thickness error becomes a return used according to the principle of constant volume to correct the rolling process at the beginning of the next strip. The measured one Thickness error is applied to the selected roll stands in the ratio of the constant volume and the proportional factors returned. The initial setting for the next band is determined by the rolling mill and corrected using the method described here for correcting thickness errors. This feedback correction is made every; two tenths of a second for the entire length of the tape and corrects the position provided by the rolling mill.

4 claims
characters

- 44 309829/0797

Claims (4)

- 44 - VrA 72/8323 Claims (l ^ Process for the production of strip-shaped rolling stock in a rolling mill containing at least two roll stands using a computer and using one thickness control dependent on the rolling force, including a device for measuring the deviation of the thickness of the rolling stock leaving the rolling mill of the nominal thickness, characterized in that during rolling of a first workpiece according to a predetermined relationship between the thickness deviation and the rolling speeds a correction variable is determined in the first and second framework, which is used to control the Roll gap of the first stand is used for the passage of a second, similar workpiece. 2. The method according to claim 1 for a rolling mill with more than two stands, characterized in that the correction variable is distributed over several selected stands according to an evaluation factor such that the proportion of the correction variable increases with increasing distance from the last stand of the rolling mill decreases. 3. The method according to claim 2, characterized in that the correction variable from the ratio of the rolling speed on the last roll stand to the rolling speed on the respective stand multiplied by the ratio of the thickness deviation to the evaluation factor which determines the desired proportion of the correction variable for the respective stand, is determined. 4. The method according to claim 3 »characterized in that that part of the allotted to a scaffold Portion of the correction variable or the correction variable itself, which is brought about together with one of the thickness control device Change of the roll gap a predetermined - 45 - 309829/0797 - 45 - VPA 72 / 8-528 Exceeds the limit value, is distributed to one or more preceding or following G-frames. 309829/0797 Blank page