US3782151A - Automatic gauge control system for tandem rolling mill - Google Patents

Automatic gauge control system for tandem rolling mill Download PDF

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Publication number
US3782151A
US3782151A US00230298A US3782151DA US3782151A US 3782151 A US3782151 A US 3782151A US 00230298 A US00230298 A US 00230298A US 3782151D A US3782151D A US 3782151DA US 3782151 A US3782151 A US 3782151A
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United States
Prior art keywords
tension
gauge
last
stands
signal
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US00230298A
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English (en)
Inventor
R Peterson
J Cook
H Bolkey
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AEG Westinghouse Industrial Automation Corp
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Westinghouse Electric Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/48—Tension control; Compression control
    • B21B37/52—Tension control; Compression control by drive motor control

Definitions

  • the range control means [56] Reierences a is automatically tutrned ONlwhg n tthe $3tgft ⁇ :1tu?e of a guage error correc ion signa m ica es a e ension UNITED STATES PATENTS between the last two stands is outside its permissible 3,531.96l lO/l970 Dunn 72/8 range w the tension between the last two stands is $32583 $11322 ZZZ essihw in limits 1 w.
  • the present invention is particularly adapted for use in an automatic gauge control system for a multistand rolling mill wherein final output gauge is controlled by controlling tension in the strip material being rolled between the last two stands. Normally, the tension is varied by varying the speed of the last stand relative to the next to the last stand.
  • the strip material after passing through the last stand, progresses to a thickness measuring device which develops an electrical signal proportional to actual gauge.
  • This signal when compared with a desired gauge signal as determined by the operator of the mill, develops a gauge deviation signal when the actual and desired gauges are not the same.
  • This deviation signal is applied through an automatic gauge control system and a tension regulator to the speed regulator for the last stand. Both minimum and maximum limits are set on tension. Without such limits, strip breakage or difficulty in tracking the strip material through the mill may occur.
  • the tension between the last stands is within the upper and lower limits of the system, it operates satisfactorily.
  • the allowable tension range provided for between the last two stands is not sufficient to adequately control thickness. That is, the system performs well when not saturated; but it frequently saturates on either minimum or maximum tension. For that matter, on certain products, it may go from saturation in one direction to saturation in the other direction during the rolling of one coil.
  • a tandem mill automatic gauge control system wherein gauge is controlled by varying tension between the last two stands in the mill, means for raising or lowering the master reference speed signals to both of the last stands by the same percentage simultaneously when a tension error signal, determined by a gauge deviation signal and normally controlling the speed of the last stand, falls outside predetermined maximum and minimum limits.
  • a tension error signal determined by a gauge deviation signal and normally controlling the speed of the last stand
  • the deadband range control means of the invention which simultaneously increases the speed of the fourth and fifth stands is actuated periodically, and after each actuation sufficient time is permitted to elapse until the strip material at the bite of the fourth stand progresses to a thickness measuring device. If it is then found that the gauge has been corrected such that the gauge deviation signal falls within permissible limits, no further corrective action is taken via tension variation between the third and fourth stands.
  • FIG. 1 is a schematic block diagram of the automatic gauge control system of the invention
  • FIG. 2 is a detailed block and schematic circuit diagram of the range control circuitry of the invention.
  • FIG. 3 is a graph illustrating a typical ON and OFF cycle of operation of the gauge error sampling circuitry of FIG. 2.
  • a five-stand tandem rolling mill including five stands S1, S2, S3, S4 and S5.
  • Strip material to be rolled passes between the rolls of the successive stands 81-85 and is progressively reduced in gauge while the speed of the strip material increases at the output of each stand.
  • the rolls for each of the stands are provided with drive motors, only motors M3, M4 and M5 being shown in FIG. 1.
  • Motors M3-M5 are controlled by speed regulators SR3, SR4 and SR5, respectively, which receive a master speed reference signal on lead 12 from master pilot controller 13.
  • each of the stands S1 through S5 is provided with a screwdown mechanism and screwdown control, only the screwdown SD4 for stand S4 being shown in FIG. 1.
  • the screwdown SD4 can be controlled by stand S4 tension controller 15 which receives a tension signal from tensiometer 17 in contact with the strip 10 between stands S3 and S4. If the tension between stands S3 and S4 should rise above or fall below predetermined maximum and minimum values, corrective action is taken through the screwdown SD4 to either increase or decrease the roll bite opening of stand 84 until the tension between stands S3 and S4 is again within permissible limits.
  • the gauge of the strip material issuing from the last stand S5 is measured by an X-ray gauge 14 or the like which produces a signal on lead 16 proportional to actual gauge.
  • the signal from X-ray gauge 14 is compared at summing point 18 with a gauge reference signal on lead 20 determined by the operator of the mill, or possibly by a computer.
  • the gauge reference signal is proportional to desired output gauge. If the desired or reference output gauge signal on lead 20 is not equal to the actual gauge signal on lead 16, a gauge deviation signal is developed which is applied to an automatic gauge control circuit 22, the details of which will be explained hereinafter.
  • the function of the automatic gauge control circuit 22 is to vary the gain of the gauge control loop as a function of transport time between the bite of the rolls of the last stand S5 and the thickness gauge 14. At low mill speeds, the gain of the loop is maintained low by circuit 22 and varied as a function of the crosssectional area of the strip between the last two stands. At high mill speeds, on the other hand, the gain of the loop is increased and varied as a function of both crosssectional area and the speed of the last stand.
  • the output signal from the atuomatic gauge control circuit 22 is summed at summing point 24 with a tension reference signal on lead 26 and with an actual tension signal on lead 28 derived from a tensiometer 30 in engagement with the strip material between the last stands S4 and S5.
  • the signal from the gauge control circuit 22 and the tension reference signal 26 are summed and compared in subtractive relationship at point 24 with the actual tension signal from tensiometer 30.
  • the resulting signal is then applied as an error signal to a tension regulator 32.
  • the details of the tension regulator 32 may be had by reference to copending application Ser. No. 230,300 filed concurrently herewith. However, for purposes of the present application, it will be sufficient to state that the function of the tension regulator is to compensate for the transfer function relating interstand tension between the last two stands to the operating speeds of the last two stands. Specifically, it has been found that the transfer function is dependent upon the cross-section area of the strip between the last two stands, as well as the speed of the next to the last stand. Consequently, the tension regulator 32 compensates for this variation in transfer function as the cross-sectional area of the strip varies, as well as the speed of the next to the last stand varies. The output of the tension regulator 32, comprising a modified gauge deviation signal, is then summed at summing point 34 with the master speed signal on lead 12 and applied to the speed regulator SR5 for stand S5.
  • range control circuitry identified by the reference numeral 36 in FIG. 1, is provided for maintaining the tension between stands 54 and S5 fixed when the tension limits approach the maximum or minimum permissible values.
  • the range control circuit 36 changes the output signal on lead 38 proportional to percent tension error. This is added to the master speed signal on lead 12 for stands M4 and M5, whereby the speeds of these stands are increased simultaneously and in an amount equal to the percent error.
  • the tension between stands S3 and S4 is varied to effect a gauge correction, notwithstanding the fact that the tension between stands S4 and S5 remains constant.
  • the screwdown SD4 will be adjusted to vary the roll gap between the rolls of the stand S4 to bring the tension between stands S3 and S4 back to the desired value.
  • Maximum and minimum tension reference signals are applied to the automatic gauge control circuit 22 and to the range control circuit 36.
  • Range control circuit 36 is activated to maintain tension between stands S4 and S5 constant when the automatic gauge control circuit 22 reaches approximately 60 percent of its full output in either direction.
  • the gauge deviation signal from summing point 18 is applied to error compensation amplifier 44 which produces a linear output signal variable above and below the zero axis, depending upon the polarity of the deviation signal, and is limited at values above and below the zero axis.
  • the output signal from amplifier 44 comprising a signal on lead 46 proportional to deviation from desired gauge, is then multiplied in multiplier 48 with a signal proportional to the cross-sectional area of the strip A, between the last stands S4 and S5.
  • multiplier 48 is then multiplied in multiplier 48 with a signal proportional to the cross-sectional area of the strip A, between the last stands S4 and S5.
  • the signal from multiplier 48 is then applied to a second multiplier 50 where it is multiplied with a signal V proportional to stand S5 speed.
  • This signal may be derived, for example, by means of a tachometer generator or the like coupled to the rolls of the fifth stand.
  • the signal at the output of the multiplier 48 is applied through potentiometer 52 to a summing point 54.
  • the signal at the output of multiplier 50 is applied through potentiometer 56 to the same summing point 54.
  • Summing point 54 is connected to the input of an operational correction amplifier 58 having a feedback path including a variable limiter 60.
  • the reason for multiplying the gauge deviation signal by cross-sectional area A, and fifth stand speed V is to vary the gain of the tension loop as a function of transport time between the bite of the rolls in the last stand and the thickness gauge 14 as is more fully explained in aforesaid copending application Ser. No. 230,299, filed concurrently herewith.
  • the movable taps of potentiometers 62 and 64 are also connected to operational amplifiers 68 and 70 in the deadband range control circuit 36.
  • Amplifiers 68 and 70 act as inverters, their outputs being connected through potentiometers 72 and 74, respectively, to the inputs of two deadband operational amplifiers 76 an 78.
  • Summed with the outputs of amplifiers 68 and 70 and applied to the inputs of deadband amplifiers 76 and 78 is the gauge deviation signal on lead 66.
  • the arrangement is such that when the deviation signal is of one polarity, and assuming that it exceeds 60 percent of the limit establshed by potentio-meter 72 or 74, an output will appear from amplifier 76 and will pass through diode 80.
  • an output from amplifier 78 after passing through diode 82, will trigger or energize a relay ZCR through amplifier 86. in either case, regardless of whether a lCR or 2CR is energized, contacts 1CR-1 or 2CR-2 will be closed to trigger an ON-OFF oscillator 88.
  • the output of amplifier 76 or that from amplifier 78, (depending upon the polarity of the gauge deviation signal ⁇ will be applied to the input of a summing operational amplifier 90, having an adjustable limiter 92 in one of its feedback paths.
  • the output of the amplifier 90 is adapted to be applied through normally open contacts 3CR-1 to the input of a range integrating operational amplifier 94 having a capacitor 96 in one of its feedback paths. Contacts of 3CR-1, in turn, are controlled by relay 3CR of the ON- OFF oscillator 88.
  • the output of amplifier 76 or 78 comprising a fixed voltage is applied to the input of the integrating operational amplifier 94 which integrates it and applies it through potentiometer 98 to the input of a multiplier 100 where it is multiplied by the master speed reference signal on lead 12.
  • Multiplication of the-master speed reference signal in multiplier 100 by the gauge error correction signal from amplifier 94 gives at the output of the multiplier a signal proportional to a percentage of the master speed signal, which percentage is proportional to the gauge correction deviation error from circuit 94.
  • This signal is then applied through a potentiometer 102 to summing point 104 where it is summed with the original master speed reference signal on lead 12.
  • the output of multiplier 100 will be zero and the signal applied to the voltage dividers 110 and 112 will be, in essence, the master speed reference signal on lead 12.
  • the voltage across dividers 110 and 112 will be increased in an amount proportional to the gauge error correction signal. Since the signal is applied to both voltage dividers 110 and 112, the speeds of stands S4 and S5 will be increased or decreased simultaneously in the same amount, thereby maintaining the tension between stands S4 and S5 constant. The tension between stands S3 and S4, however, will be varied to effect a gauge correction.
  • the ON-OFF oscillator 88 once relay lCR or 2CR is energized indicating that the gauge deviation signal has reached 60 percent of its maximum value in either the positive or negative direction, the ON-OFF oscillator will be triggered to initially energize relay 3CR, whereupon contacts of 3CR-ll close and the gauge error correction signal is applied to the input of integrating amplifier 94 where it is stored. At the end of the timed ON interval, relay 3CR is de-energized for an OFF time which is approximately equivalent to the time required for the strip to move from stand S4 to the X-ray gauge 14. At the expiration of this OFF delay, the range control is again allowed to cycle if the automatic gauge control amplifier 58 is still out of range.
  • the cycling sequence is shown in FIG. 3.
  • the ON- OF F oscillator includes an integrator and the relay 3CR is triggered or energized in response to a negative voltage.
  • the cycle starts at time t,. Contacts 1CR-l or 2CR-2 close. Between times t, and t while the integrator within the oscillator 88 is building up voltage, contacts 3CR-l are closed and the constant voltage output of circuit is applied to integrator 94. At time t zero voltage is reached at the output of the oscillator and the relay 3CR is de-energized, opening contacts 3CR-l. Relay 3CR remains de-energized until time 1 is reached, whereupon the cycle repeats, assuming that contacts llCR-l or 2CR-2 are closed.
  • the OFF time between times and 1 is, as mentioned above, equal to the time required for the strip material to move from stand S4 to the X-ray gauge 14. If, at time t the thickness detected by X-ray gauge 14 produces a gauge deviation signal which is within plus or minus 60 percent of the minimum or maximum tension reference signals in automatic gauge control circuit 22, either relay lCR or 2CR will become de-energized again, thereby deactivating the ON-OFF oscillator 88. If, however, the gauge deviation signal is still outside plus or minus 60 percent of the maximum or minimum tension reference signal, the oscillator 88 is again cycled until the gauge is again within permissible limits and both the relays lCR and 2CR are de-energized. This, then, permits tension control to transfer back to the stand S5 until the gauge deviation signal again falls outside of the permissible band.
  • tension between stands S4 and S5 is maintained constant, tension between stands S3 and S4 is controlled by tension control 15 working on the screwdown for stand S4.
  • a system for controlling the gauge of strip material issuing from a tandem rolling mill wherein an actual output gauge signal is compared with a desired gauge signal to derive a gauge deviation signal used to vary the speed of the last stand in the mill relative to the next to the last stand, and wherein said gauge deviation signal is effective to vary last stand speed only when it falls within predetermined maximum and minimum values; the combination of:
  • deadband range'control circuit means to which said gauge deviation signal is applied and which will produce a gauge error correction signal at output terminal means thereof only when said gauge deviation signal falls outside a range of values encompassed within said maximum and minimum values
  • the improvement which comprises measuring the gauge of strip material at the output of said tandem mill and comparing it with desired gauge to develop a gauge deviation signal for controlling the speed of the last stand, electrically sensing when the tension between the last two stands is outside a permissible range of tension values by comparison of said gauge deviation signal with tension reference signal means, and when the tension is outside said range of tension values periodically and simultaneously adjusting the speeds of the last two stands to maintain the tension between the last two stands essentially constant while varying tension between the next to the last stand and its preceding stand to effect a gauge correction until comparison of said gauge deviation signal with said reference signal means indicates that tension is again within said range of tension values.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Metal Rolling (AREA)
US00230298A 1972-02-29 1972-02-29 Automatic gauge control system for tandem rolling mill Expired - Lifetime US3782151A (en)

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US23029872A 1972-02-29 1972-02-29

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US (1) US3782151A (cs)
JP (1) JPS5226225B2 (cs)
BE (1) BE796054A (cs)
CA (1) CA968869A (cs)
ZA (1) ZA73827B (cs)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3863478A (en) * 1972-09-06 1975-02-04 Nippon Steel Corp System for controlling rolling mills
US3996776A (en) * 1974-03-05 1976-12-14 Gec-Elliott Automation Limited Strip thickness control
US4016735A (en) * 1975-09-23 1977-04-12 Westinghouse Electric Corporation Range control for an automatic gauge control system of a rolling mill
US4187707A (en) * 1977-09-26 1980-02-12 Secim Thickness control method and apparatus for a rolling mill
US4286447A (en) * 1979-03-12 1981-09-01 Westinghouse Electric Corp. Method and apparatus for automatic gauge control system for tandem rolling mills
US4998427A (en) * 1989-11-29 1991-03-12 Aeg Westinghouse Industrial Automation Corporation Method for rolling on-gauge head and tail ends of a workpiece
US5012660A (en) * 1989-11-29 1991-05-07 Aeg Westinghouse Industrial Automation Corporation Control system and method for compensating for speed effect in a tandem cold mill

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972269A (en) * 1957-04-08 1961-02-21 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3049036A (en) * 1957-04-08 1962-08-14 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3508425A (en) * 1968-03-07 1970-04-28 Gen Electric Tension limit modification control
US3531961A (en) * 1968-03-13 1970-10-06 Westinghouse Electric Corp Method and system for controlling strip thickness in a tandem reduction mill

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972269A (en) * 1957-04-08 1961-02-21 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3049036A (en) * 1957-04-08 1962-08-14 Westinghouse Electric Corp Automatic strip thickness control apparatus
US3508425A (en) * 1968-03-07 1970-04-28 Gen Electric Tension limit modification control
US3531961A (en) * 1968-03-13 1970-10-06 Westinghouse Electric Corp Method and system for controlling strip thickness in a tandem reduction mill

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3863478A (en) * 1972-09-06 1975-02-04 Nippon Steel Corp System for controlling rolling mills
US3996776A (en) * 1974-03-05 1976-12-14 Gec-Elliott Automation Limited Strip thickness control
US4016735A (en) * 1975-09-23 1977-04-12 Westinghouse Electric Corporation Range control for an automatic gauge control system of a rolling mill
US4187707A (en) * 1977-09-26 1980-02-12 Secim Thickness control method and apparatus for a rolling mill
US4286447A (en) * 1979-03-12 1981-09-01 Westinghouse Electric Corp. Method and apparatus for automatic gauge control system for tandem rolling mills
US4998427A (en) * 1989-11-29 1991-03-12 Aeg Westinghouse Industrial Automation Corporation Method for rolling on-gauge head and tail ends of a workpiece
US5012660A (en) * 1989-11-29 1991-05-07 Aeg Westinghouse Industrial Automation Corporation Control system and method for compensating for speed effect in a tandem cold mill

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Publication number Publication date
BE796054A (fr) 1973-08-28
CA968869A (en) 1975-06-03
ZA73827B (en) 1973-11-28
JPS5226225B2 (cs) 1977-07-13
JPS48100360A (cs) 1973-12-18

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Owner name: AEG WESTINGHOUSE INDUSTRIAL AUTOMATION CORPORATION

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Effective date: 19900313