US3892112A - Rolling mill gauge control - Google Patents

Abstract

A rolling mill gauge control system and method are disclosed for controlling the delivery thickness or gauge of a strip workpiece leaving one or more roll stands of a tandem rolling mill. The initial roll opening setting and the initial speed setting for each roll stand are typically provided by an operator or a schedule calculation computer system prior to the passage of the work strip through the roll stand. Assuming these initial speed settings are correct, the known mass flow operational condition of the work strip in relation to the last stand target delivery gauge is used to establish the initial desired mass flow delivery gauge from each controlled roll stand of the rolling mill in relation to the desired delivery gauge from the last roll stand. Then as the work strip passes through each successive roll stand, and before the work strip reaches the X-ray gauge measurement device following the last roll stand, the roll force determined actual delivery gauge from each roll stand is compared with the initial desired mass flow delivery gauge to determine a work strip gauge error leaving the latter roll stand, which gauge error is utilized for determining a desired correction in the roll opening setting for that roll stand before the work strip reaches the X-ray gauge device.

Description

United States Patent Smith, Jr. July 1, 1975 ROLLING MILL GAUGE CONTROL [57] ABSTRACT [75] Inventor: Andrew W. Smith, Jr., Pittsburgh, A rolling mill gauge control system and method are Pa. disclosed for controlling the delivery thickness or auge of a stri workpiece leavin one or more roll [73] Asslgnee: .lestmghwse Electr'c Etands of a tandem rolling mill. The initial roll opening Pmsburgh setting and the initial speed setting for each roll stand [22] Filed: Mar. 27, 1974 are typically provided by an operator or a schedule calculation com uter s stem rior to the assa e of [2]] App! 455l59 the work strip tlFrough i he roll stand. Assur ning hese initial speed settings are correct, the known mass flow [52] US. Cl. 72/11 operational condition of the work strip in relation to [51] Int. Cl. B21b 37/08 the last stand target delivery gauge is used to establish [58] Field of Search 72/6-12, 16, the initial desired mass flow delivery gauge from each 72/19, 20, 21 controlled roll stand of the rolling mill in relation to the desired delivery gauge from the last roll stand.

[56] References Cited Then as the work strip passes through each successive UNITED STATES PATENTS roll stand, and before the work strip reaches the X-ray 2 726 541 12/1958 Sims 73/885 gauge measurement fnowmg h last 3'232O84 H1966 Sims M 72/16 stand, the roll force determined actual delivery gauge 3:332:263 7,1967 Beadle at 72/7 from each roll stand is compared with the initial de- 3,56l,237 2/1971 Eggers et a1. 72/7 sired mass flow delivery gauge to determine a work 3,592,031 7/1971 Sutton et a1. 72/8 strip gauge error leaving the latter roll stand, which 3,600,920 8/1971 Smith, Jr 72/8 gauge error is utilized for determining a desired cor- Primary ExaminerMilton S. Mehr Attorney, Agent, or Firm-R. G. Brodahl ROLL OPENING CONTROL n ROLL 4 POSITION DETECTOR,

rection in the roll opening setting for that roll stand before the work strip reaches the X-ray gauge device.

10 Claims, 8 Drawing Figures ROLL OPENING CONTROL X-RAY .GAUGE GAUGE CONTROL SHEET ROLL OPENING CONTROL 2 Q D m F fl N r N I\ F s F M L M S 2 3 W. M H K e P r F m F N K lm n Z Cv I US ROU T P l r K GAUGE CONTROL KF(N) 2 u mm H R W W0 l LIT I C K m H S R H %D m MF(N) w QmOu 440m SHEET Mm m SHEET 3 CONTROLLED ROLL LAST ROLL OPERATOR sTANDIl) STAND(LS) 'fgxggi figfl H(LS) FsILsI MWEE T GEISGE DETERMINATION FPM(I) H(LS)-XFPM(LS)*FS(LS) FPM(I)X- Fsm H I Fm ROLL FORCE I COS(I) GAuGE HRFII) GAUGE ERROR M30) DETERMINATION 7 DETERMINATION PM K T) HRF(I)=MSD(I)+COS(I)+K(I)F(I) GEm-Hm ROLL OPENIN M30) DETERMINATION KU) Km GE) P(I) ,DELsI1I=-GE(1)*[ I] GDREEII) SDREF(I)=MSD(I)+DELS(I) I FIG.6

n nnnn n (I mm mm 3,892,112 SHEET 4.

FIGURE 3 E TABLISHING DESIRED DELIVERY GAGEaHI I III-0R EACH STAND P IOR T8 ENTE ING FIRST STAND USING REFERENCE INITIAL STAND SPEED. FPM( I I! ND DESIRED DELIVERY GAGEJHILSI SET STAND CBUNTER IFI HI I I HILSHFP ILSI'F ILSII (FP H I NFSI I I I LAST STAND CHECK IF I I IEQO L5) G5 TB 100 GB TB 32 END FIGURE 4 c CALCULATE GAGE ERRBR GEN) AND SCREWDBWN REFERENCE soREFm TB CBNTRBL GAGE SET srmo CBUNTER hrs DETERMINE GAGE ERROR -I I I I 1*'(I (2+I'1F( I I I 1 "EXP I K3+MFI I I I I HRF I I HSD( I I +C6S( I H-KF' 1 1 EII IBHRH I I-H( I I DETERMINE ROLL. BPENING CBRRECTIBN DEL I I ='GE( I I r (K( I I/P( I I )+1 I LIMIT AND BUPU RBLL D ENI PBSITIBN REFERENCE SDREFI I I MSDI I I+DEL$I I I L ST STAND CHECK IFII -E LSI E T6 100 I I *1 66 TB 32 END Hes ROLLING MILL GAUGE CONTROL BACKGROUND OF THE INVENTION The present invention relates to tandem metal workpiece reduction rolling mills and more particularly to such rolling mills including roll force sensing load cells operative with selected roll stands for controlling the delivery gauge of the work strip leaving those roll stands.

In the operation of a metal rolling mill, the unloaded roll opening and the speed of each roll stand are initially set up, before the work strip enters that roll stand, either by an operator or by a schedule calculation control computer to produce a work strip reduction resulting in a desired on-gauge finished work product leaving that roll stand. It is usually assumed that the loaded roll opening'of a roll stand equals the stand delivery gauge, since there is little or no elastic workpiece recovery.

Because the provided roll stand set up conditions may be in error and since certain mill parameters affect the stand loaded roll opening during the actual rolling operation, a stand gauge control system is employed to control the stand delivery gauge.

The well known roll force gauge control system has been used to provide desired gauge control operation (the workpiece thickness is also sometimes spelled gage) for one or more stands of tandem rolling mills, using Hookes law for controlling the roll opening position at a given roll stand. The loaded roll opening and hence the work strip delivery gauge from that given roll stand, under normal workpiece rolling conditions, equals the unloaded roll opening position plus the mill stand spring stretch caused by the roll separating force applied to the work rolls by the workpiece. The roll separating force is measured by a load cell or other suitable force detecting device operative with the roll stand. The roll opening position is then controlled to balance roll force changes from a reference or initial lock on value and thereby to hold the loaded roll opening at a substantially constant value. The following formula relationship can be used to establish the delivery gauge of the work strip leaving a controlled roll stand where h is the loaded roll opening and the delivery gauge of the work strip, S is the unloaded roll opening position, and K is the roll stand mill spring constant multiplied by F, the measured roll separating force. The asterisk is the well known Fortran programming symbol for multiplication.

A typical prior art roll force gauge control system for a roll stand is an analog feedback system operative to make a comparison of the determined work strip delivery gauge with a desired reference gauge leaving the roll stand, and responsive to measured stand roll force and measured roll opening position to control the roll opening position in accordance with the following error condition AS K AF where AS is the error in roll opening position to be corrected in relation to a reference roll opening position and AF is the measured change in roll force from a desired force reference and K is the roll stand mill spring constant.

Once the unloaded roll opening position and stand speed initial setups have been determined and made by either a mill operator or a schedule calculation computer system for a particular work strip passage through the roll stands to effect a desired gauge reduction, the actual rolling operation can be started and the controlled roll openings are then regulated to provide the desired work strip delivery gauge from each controlled roll stand of the rolling mill.

It is known in the prior art, as shown by U.S. Pat. No. 3,600,920 by the same inventor, to recalibrate the roll opening control for a given roll stand, after the work strip has passed through all of the roll stands of a tandem rolling mill, in relation to the last roll stand actual delivery gauge as measured by an X-ray gauge positioned after the last roll stand. The speed relationship of a given roll stand as compared to the last roll stand is utilized to determine the mass flow actual delivery gauge leaving that given roll stand. The difference between the roll force acutal delivery gauge of that given roll stand and the latter mass flow actual delivery gauge is utilized for recalibration of the roll opening control apparatus, such as a screwdown or hydraulic position control mechanism, for that given roll stand.

The well known gauge meter or roll force gauge control system has been widely used to produce stand gauge control in metal rolling mills, and particularly in tandem hot steel strip rolling mills and reversing plate mills where experience has demostrated that roll force control is particularly effective. Earlier publications and patents such as an article entitled Installation and Operating Experience with Computer and Programmed Mill Controls by M. D. McMahon and M. A. Davis in the 1963 Iron and Steel Engineer Yearbook at pages 726 and 733, an article entitled Automatic Gauge Control for Modern I-Iot Strip Mills by J. W. Wallace in the December 1967 Iron and Steel Engineer at pages to 86, an article entitled Control Computer Teaches Itself To Roll Metals by A. W. Smith in the Westinghouse Engineer for July 1970 at pages 108 to 113, U.S. Pat. No. 3,561,237 issued Jan. 9, 1971 to Eggers et al. and U.S. Pat. No. 2,726,541, issued Dec. 13, 1955 to R. B. Sims describe the theory upon which operation of the roll force and related gauge control systems is based. Attention is also called to U.S. Pat. No. 3,568,637 issued Mar. 9, 1971, U.S. Pat. Nos. 3,574,279 and 3,574,280 issued Apr. 13, 1971 to A. W. Smith, which relate to roll force automatic gauge control systems.

SUMMARY OF THE INVENTION In accordance with the principles of the present invention, a control system and method for controlling the delivery gauge or thickness of workstrip product leaving one or more roll standsof a tandem rolling mill includes the determination of the mass flow target delivery gauge of the work strip for each controlled roll stand in relation to the last stand target delivery gauge before the workstrip has arrived at the X-ray gauge following the last roll stand, and then comparing the roll force determined actual delivery gauge for the same roll stand with this mass flow target delivery gauge to establish a gauge error for correction by an adjustment of the roll opening position setting for that roll stand.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of a roll force gauge control arranged for operation with a tandem rolling mill in accordance with the present invention;

FIG. 2 shows a curve to illustrate the mill spring characteristic for a typical roll stand in relation to the determination of the stretch of a controlled roll stand;

FIG. 3 shows a flow chart to illustrate the determination of mass flow target delivery gauge for each roll stand before a given work strip passes through the rolling mill;

FIG. 4 shows a flow chart to illustrate the determination of the gauge error and roll opening position reference for each controlled roll stand;

FIG. 5 is a functional illustration of the control of workstrip delivery gauge from a roll stand in accordance with the present invention;

FIG. 6 illustrates the situation where the tail end of a previous work strip and the head end of a subsequent work strip are passing through the rolling mill at the same time;

FIG. 7 shows a program listing prepared in relation to the flow chart of FIG. 3; and

FIG. 8 shows a program listing prepared in relatio to the flow cart of FIG. 4.

GENERAL DESCRIPTION OF THE GAUGE CONTROL SYSTEM AND ITS OPERATION There is shown in FIG. 1 a controlled four high rolling mill stand S(N) operative with a gauge control 12 in accordance with the principles of the present invention. Generally, the invention is applicable to control the operation of one or more tandem rolling mill stands for which roll force gauge control is employed. The tandem rolling mill shown in FIG; 1 includes a last stand S(LS).

A workpiece 2 enters the roll stand S(N) at the entry end and it is reduced in thickness and transported through the succeeding roll stands to the delivery end of the rolling mill. The entry workpiece would be of known steel grade and it typically would have a known gauge or thickness. The delivered workpiece would have a desired target gauge or thickness H(LS) based upon the production order for which it is intended.

In the reduction rolling process, the succeeding roll stands operate at successively higher speeds to maintain proper workpiece mass flow. Each stand produces a predetermined reduction or draft such that the total mill draft reduces the entry workpiece to strip with the desired gauge or thickness.

Each stand is conventionally provided with a pair of back-up rolls 4 and 6 and a pair of work rolls 8 and 10 between which the workpiece 2 is passed. A large DC drive motor 11 is controllably energized at each stand to drive the corresponding work rolls at a controlled speed.

In relation to roll stand S(N), the sum of the unloaded work roll opening MSD(N) and the mill stretch K(N) AF(N) substantially defines the roll force determined workpiece gauge I-IRF(N) delivered from the controlled roll stand S(N) in accordance with Hookes law. A well known calibration offset COS(N) can be included to provide desired calibration of the roll opening control apparatus operative with the roll stand S(N), which roll opening control apparatus could be a pair of screwdown motors or a hydraulic positioning apparatus, to position the back-up rolls and thereby apply pressure to the work rolls. A conventional roll opening position detector 14 provides an electrical signal representation MSD(N) of the unloaded roll opening position. Roll force detection is provided at the roll stand S(N) by a conventional load cell 16 which generates an electrical analog signal F(N) proportional to the roll separating force between the work rolls. A speed sensing transducer 18, such as a pulse transducer, generatesa stand speed signal FPM(N).

The gauge control 12 provides automatic gauge or thickness for the operation of the mill stand S(N). The gauge control 12 can include a programmed general purpose process control digital computer system, which is interfaced with the various mill operational sensors and the various mill control devices to provide control over the operation of the mill stand S(N). According to user preference, the gauge control 12 can also include well known and conventional manual and- ,/or automatic analog controls for back-up operation in performing other preselected mill functions.

On the basis of these considerations, a suitable digital computer system for the on-line roll force gauge control system 12 would be a Prodac 2000 (P2000) sold by Westinghouse Electric Corporation. A descriptive book entitled Prodac 2000 Computer Systems Reference Manual has been published in 1970 by Westinghouse Electric Corporation and made available for the purpose of describing in greater detail this computer system and its operation.

The digital computer system is associated with well known predetermined input systems, typically including a conventional contact closure input system which scans contact or other signals representing the sensed status of various process operating conditions, a conventional analog input system which scans and converts process analog signals, and operator controlled and other information input devices and systems such as paper tape, teletypewriter and dial input systems. Various kinds of information can be entered into the computer system through the input devices including, for example, desired strip delivery gauge H(LS) and temperature, strip entry gauge and width and temperature (by entry detectors if desired), grade of steel being rolled, plasticity P tables, hardware oriented programs and control programs for the programming system, and so forth. The contact closure input systems and the analog input systems interface the computer system with the process through the medium of measured or detected variables, which include the following:

1. A roll force signal F(N) from the load cell 16 at the roll stand S(N) proportional to stand roll separating force for use in roll force gauge control.

2. Roll opening position signal MSD(N) generated by the respective position detector 14 for use in roll force gauge control.

3. A roll stand speed signal FPM(N) from a pulse generator 18 operative with the drive motor 11 of the controlled roll stand S(N).

4. A roll stand speed signal FPM(LS) from a pulse generator 17 operative with the drive motor 19 of the last roll stand S(LS).

It is noted at this point in the description, that the measured stand roll force and the measured stand roll opening position in relation to the workpiece head end are stored and used as references for roll force gauge control system functioning, if it is desired to operate in the well known lock-on mode of roll force gauge control operation.

To effect determined output control actions, controlled devices are operated directly by means of output system contact closures or by means of analog signals derived from output system contact closure through a digital to analog converter. The principal control action outputs from the gauge control 12 includes a positioning command signal SDREF(N) applied to the roll opening control 15 for the controlled roll stand 8(1) and other controlled roll stands, and a speed control signal applied to the drive motor 11 of roll stand S(N) and the other roll stands in accordance with respective desired speed setting for mass flow operational conditions.

Display and printout systems such as numeral display, tape punch, and teletypewriter systems also can be associated with the outputs of the digital computer gauge control system in order to keep the mill operator generally informed about the mill operation and in order to signal the operator regarding an event or alarm condition which may require some action on his part.

Generally, the gauge control 12 uses Hookes law to determine the total amount of screwdown movement required at the roll force controlled stand S(N) at the calculating point in time for roll force and gauge error correction, i.e. forloaded roll opening and stand delivery gauge correction to the desired value. The calculation defines the total change in the unloaded roll opening position setting required to correct for determined gauge error causing conditions.

As well known to persons skilled in this art, the desired roll opening correction DELS(N) in relation to controlled roll stand S(N) is calculated to enable roll force gauge control operation in accordance with the following programmed relationship algorithm:

where:

GE(N) gauge error of controlled roll stand S(N) K(N) stand S(N) mill spring constant (in/l0 lb.)

P(N) workpiece plasticity (in/ lb.) in relation to stand S(N).

Generally the operative value of each stand spring constant K is relatively accurately known. It is first determined by the well known work roll screwdown test, and it can be recalculated if desired prior to each workpiece pass on the basis of the workpiece width and the backup roll diameter. Each resultant spring curve is stored for on-line gauge control use.

The operative value of the workpiece plasticity P at each roll stand is also relatively accurately determined. If desired, P tables can be stored in the storage memory of the digital computer system associated with the gauge control 12 to identify the various values of P which apply to the controlled roll stand S(N) for various grade class and gauge class workpieces under various operating conditions and at various operating times during the rolling of the workpiece strip 2.

A main advantage of using the roll force gauge control system is the ability to detect error changes in strip gauge the instant they take place as the product is being rolled in the roll stand. A change in strip delivery gauge or thickness can be caused by a change in entry thickness, or a change in hardness as usually caused by a change in temperature. This change in delivery gauge can be immediately detected by feedback information monitoring of the roll separating force on the roll stand.

There is shown in FIG. 2 a curve to illustrate the typical mill spring characteristic for a roll stand, such as controlled roll stand S(N). The curve is a plot of measured roll force MF(N) for a typical roll stand (N) against the resulting stretch KF(N) of the roll stand, or the product of K(N) the stand spring constant and P(N) the stand roll force. The curve shown in FIG. 2 can be mathematically represented by the relationship.

where K K and K are constants established by data collecting and curve fitting techniques well known and practiced for several years by persons skilled in this art. The curve is established by closing together the stand work rolls, through operation of the roll opening control of the roll stand, until some minimum roll force is sensed by the stand load cell, and then progressively closing the work rolls by predetermined incremental settings and reading the corresponding roll force for each such setting. Then, knowing the mill spring characteristic curve for a given roll stand of the rolling mill, the values of constants K K and K for that roll stand are determined by well known curve fitting techniques. It should be noted in relation to above equation (4) that the double asterisk represents the well known Fortran programming symbol for an exponential and the single asterisk indicates multiplication.

There is shown in FIG. 3 the flow chart of a program utilized to determine the mass flow target delivery gauge for each controlled roll stand, such as roll stand S(I), where I is a roll stand index, before the work strip has passed through the rolling mill and become operative with the X-ray gauge positioned after the last roll stand S(LS). At step 20 a stand counter is initially set to one. At step 22 the mass flow target delivery gauge is determined for a given roll stand (I) successively indexed by the stand counter, firstly such as roll stand one and then secondly roll stand two and so forth. At step 24 a check is made to see if that given roll stand (I) is the last stand, and if it is not the program goes to step 26 where the stand index I is incremented by one to the next succeeding roll stand, and steps 22 and 24 are repeated until the check at step 24 indicates that index stand I is now the last roll stand S(LS), when the program operation ends.

There is shown in FIG. 4 the flow chart of a program utilized to determine the gauge error and roll opening position reference for each controlled rollstand of the rolling mill in accordance withthe present invention, after the work strip has entered the first roll stand and before the work strip reaches the X-ray gauge positioned after the last roll stand S(LS). At step 30 the stand index counter is set to one. At step 32, the mill stretch KF(I) for the indexed roll stand (I) is determined in accordance with above equation (4). Then the roll force determined actual delivery gauge I-IRF(I) leaving the roll stand (I) is determined in accordance with the well known relationship:

HRF(I) MSD(I) COS(I) KF(I) where MSD(I) is the unloaded roll opening position "error GE( I) for' roll stand (I) is determined by the relationship: e I

GE(I) HRF(I) H(l) where H(I) is the mass flow target delivery gauge for indexed rollstand (1) determined at step 22 of the program flow chart shown in FIG. 3 and HRF (I) is the roll force actual delivery gauge leaving roll stand (I). At step 34 the roll opening correction DELS(I) for roll stand (I )is determined in accordance with the relationship of above equation (3), where roll stand (N) is how the index roll stand (I). At step 36 the roll opening position reference for indexed roll stand (I) is established by the'relationship:

a e SDREF(I).= MSD(I) DELS(I) where M SD(I )is the present unloaded roll opening position setting for roll and stand (I) and DELS(I) is the desired roll opening correction for roll stand (I), which roll opening position reference SDREF (I can be limit checked and output to the roll opening control apparams for index roll stand (I). At step 38 a check is made to see if roll stand (I) is the last stand of the rolling mill, and if not at step 40 the index (I) is incremented by one and the pro'gramstep 32, 34 and 36 are repeated for succeeding roll stands of the rolling mill until the index roll stand (I) is the last roll stand (LS), when the program operation ends. The'pro gram illustrated by FIG. 3 is intended'to be signal for stability and related control system practical operation reasons.

run just before each work strip enters the first roll stand of the rolling mill, as can be monitored by well known work strip position sensing tranducer'devices. The program illustrated by FIG. 4 is intended to be run periodicfally, such as five times per second, for all controlled 7 up speed reference FPM(LS) for the last roll stand (LS )and theinitial target delivery gauge H(LS) leaving the last roll stand (LS). The forward slip characteristic FS (I) for the controlled roll stand (I) and the forward slip character istics FS(LS) for the last roll stand (LS) arie predetermined and supplied byv the operator. At

step '52 the'roll force determined actual delivery gauge,

I-IRF(I) leaving controlled roll stand (I) is established after the work strip is passing through the roll stand (I). At step 54 the gauge error GE(I) in the work strip leaving roll stand (I) is determined. At step 56 the roll opening correction DELS(I) and the associated roll opening position reference SDREF(I) are determined,

with the position reference signal being output to the controlled roll stand (I), after limiting this reference The process control programs are organized in away to accommodate the normal mill condition where the head end of one succeeding workpiece is entering the early stands while the 'tail end of the previous workpiece is still being rolled in the later stands. This conditionis shown in FIG. 6 where workpiece A is being rolled in stands S4 and S5 when the new workpiece B is in stands S1 and S2. It is necessary that the initial stand speeds, roll openings and desired delivery gauge be established by the operator or by the schedule calculation computer prior to the entry of the new workpiece into stand S1 so that the mill setups may be changed to the new value as soon as the tail end of the previous workpiece leaves a particular stand. Just prior to the entry of the new workpiece into a first stand, the initial speed FPM(I) and desired target gauge or thickness H(LS) are used to determine the desired gauge from each stand as shown in FIG. 3 so that the desired gauge H(I) is available for the gauge error determination as shown in 4.

' This gauge error and screwdown reference calculation is initiated as soon as a workpiece enters a stand and repeated periodically (such as five times per second) until the workpiece leaves the stand.

, For instance, under the conditions shown in FIG. 6, the gauge error and screwdown reference calculations shown in FIG. 4 are being performed for workpiece A with a first stand FS value of 4 and a last stand LS value of 5. The same calculations are used to control the gauge of workpiece B in stands S1 and S1 by using a first stand FS value of 1 and at last stand LS value of 2. Each setof calculations used the desired stand delivery gauge H(I) value that was established by the procedure shown in FIG. 3 for that particular workpiece prior to its entry into the mill.

In FIGS. 7 and 8 there are included two instruction program listings that have been prepared to determine the roll force automatic gauge control operation of a tandem rolling mill in accordance with the here disclosed control system and method. The instruction program listings are written in Fortran language suitable for use with the PRODAC P2000 digital computer system, which is sold by Westinghouse Electric Corporation for real time process control computer applications. Many of these digital computer systems have already been supplied to'customers, including computer instruction books and descriptive documentation to explain to persons skilled in this art the operation of the hardware logic and the executive software of this digital computer system..The instruction program listings are included to provide an illustration of one suitable embodiment of the present control system and method that has acutally been prepared. The instruction program listings have not been debugged through the course of extensive practical operation for the real time control'of a rolling mill. It is well known by persons skilled in this art that most real time process control ap- 1. A method of controlling the delivery gauge of a work strip passing through at least one roll stand of a tandem rolling mill in accordance with a desired delivery gauge leaving the last rolling stand of said rolling mill, with said one roll stand having a pair of work rolls and a roll force measurement device, said method including the steps of establishing a target delivery gauge for said work strip leaving said one roll stand in relation to said desired delivery gauge, the speed setting of said one roll stand and the speed setting of the last roll stand, establishing the actual delivery gauge of said work strip leaving said one roll stand in relation to the measured roll force of said one roll stand,

comparing said target delivery gauge with said actual delivery gauge to determine a work strip gauge error leaving said one roll stand, and

establishing the roll opening between said pair of work rolls of said one roll stand in relation to said gauge error.

2. The method of claim 1, with said target delivery gauge being established in accordance with the mass flow relationship including the speed setting of the last roll stand of said rolling mill before said work strip passes through said last roll stand.

3. The method of claim 1, with said target delivery gauge being established before said work strip passes through the last roll stand of said rolling mill.

4. The method of claim 1, with said target delivery gauge being established in relation to the operation of the last roll stand and before the work strip passes through the last roll stand of the rolling mill.

5. The method of claim 1, with said target delivery gauge being established before said work strip passes through the last roll stand of said rolling mill and with said actual delivery gauge being established after said work strip passes through said one roll stand.

' 6. In an apparatus for controlling the delivery gauge of a work strip passing through at least one roll stand of a tandem rolling mill having a plurality of roll stands and in accordance with the desired delivery gauge leaving the last roll stand of said rolling mill, with said one roll stand having a pair of work rolls and a roll force measurement device, the combination of means for determining a desired delivery gauge of said one roll stand in relation to said desired delivery gauge, the speed setting of said one roll stand and the speed setting of said last roll stand,

means for determining the actual delivery gauge of said one roll stand in relation to a predetermined operation of said one roll stand, means for determining a gauge error in the work strip leaving said one roll stand in relation to said desired delivery gauge of said one roll stand and said actual delivery gauge of said one roll stand and,

means for controlling the roll opening setting of said pair of work rolls of said one roll stand in relation to said gauge error.

7. The apparatus of claim 6, with said means for determining a desired delivery gauge of said one roll stand being operative before said work strip passes through the last roll stand of said rolling mill.

8. The apparatus of claim 6, with said means for determining the actual delivery gauge of said one roll stand being operative after said work strip passes through said one roll stand.

9. The apparatus of claim 6, with said desired delivery gauge of said one roll stand being determined in relation to the speed setting of said one roll stand before said work strip passes through said rolling mill.

10. The apparatus of claim 6, with said desired delivery gauge of said one roll stand being determined before said work strip passes through said rolling mill and with said actual delivery gauge of said one roll stand being determined after said work strip passes through said one roll stand.

Claims (10)

1. A method of controlling the delivery gauge of a work strip passing through at least one roll stand of a tandem rolling mill in accordance with a desired delivery gauge leaving the last rolling stand of said rolling mill, with said one roll stand having a pair of work rolls and a roll force measurement device, said method including the steps of establishing a target delivery gauge for said work strip leaving said one roll stand in relation to said desired delivery gauge, the speed setting of said one roll stand and the speed setting of the last roll stand, establishing the actual delivery gauge of said work strip leaving said one roll stand in relation to the measured roll force of said one roll stand, comparing said target delivery gauge with said actual delivery gauge to determine a work strip gauge error leaving said one roll stand, and establishing the roll opening between said pair of work rolls of said one roll stand in relation to said gauge error.

2. The method of claim 1, with said target delivery gauge being established in accordance with the mass flow relationship including the speed setting of the last roll stand of said rolling mill before said work strip passes through said last roll stand.

3. The method of claim 1, with said target delivery gauge being established before said work strip passes through the last roll stand of said rolling mill. mill.

4. The method of claim 1, with said target delivery gauge being established in relation to the operation of the last roll stand and before the work strip passes through the last roll stand of the rolling mill.

5. The method of claim 1, with said target delivery gauge being established before said work strip passes through the last roll stand of said rolling mill and with said actual delivery gauge being established after said work strip passes through said one roll stand.

6. In an apparatus for controlling the delivery gauge of a work strip passing through at least one roll stand of a tandem rolling mill having a plurality of roll stands and in accordance with the desired delivery gauge leaving the last roll stand of said rolling mill, with said one roll stand having a pair of work rolls and a roll force measurement device, the combination of means for determining a desired delivery gauge of said one roll stand in relation to said desired delivery gauge, the speed setting of said one roll stand and the speed setting of said last Roll stand, means for determining the actual delivery gauge of said one roll stand in relation to a predetermined operation of said one roll stand, means for determining a gauge error in the work strip leaving said one roll stand in relation to said desired delivery gauge of said one roll stand and said actual delivery gauge of said one roll stand and, means for controlling the roll opening setting of said pair of work rolls of said one roll stand in relation to said gauge error.

7. The apparatus of claim 6, with said means for determining a desired delivery gauge of said one roll stand being operative before said work strip passes through the last roll stand of said rolling mill.

8. The apparatus of claim 6, with said means for determining the actual delivery gauge of said one roll stand being operative after said work strip passes through said one roll stand.

9. The apparatus of claim 6, with said desired delivery gauge of said one roll stand being determined in relation to the speed setting of said one roll stand before said work strip passes through said rolling mill.

10. The apparatus of claim 6, with said desired delivery gauge of said one roll stand being determined before said work strip passes through said rolling mill and with said actual delivery gauge of said one roll stand being determined after said work strip passes through said one roll stand.

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