US3848443A - Automatic control method and apparatus for a rolling mill - Google Patents

Automatic control method and apparatus for a rolling mill Download PDF

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Publication number
US3848443A
US3848443A US00365668A US36566873A US3848443A US 3848443 A US3848443 A US 3848443A US 00365668 A US00365668 A US 00365668A US 36566873 A US36566873 A US 36566873A US 3848443 A US3848443 A US 3848443A
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Prior art keywords
roll
speed
tension
stands
stand
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R Peterson
J Cook
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AEG Westinghouse Industrial Automation Corp
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Westinghouse Electric Corp
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Priority to US00365668A priority Critical patent/US3848443A/en
Priority to BE144952A priority patent/BE815781A/xx
Priority to JP6104374A priority patent/JPS548463B2/ja
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Publication of US3848443A publication Critical patent/US3848443A/en
Assigned to AEG WESTINGHOUSE INDUSTRIAL AUTOMATION CORPORATION reassignment AEG WESTINGHOUSE INDUSTRIAL AUTOMATION CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WESTINGHOUSE ELECTRIC CORPORATION
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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 metal strip is automatically maintained on-gauge by suitable adjustments of the workroll settings, of the speed thereof and, particularly in a cold mill, this is often done in response to interstand tension variations, in addition to variations in other parameters sensed at different locations along the workpiece pass line. While such adjustments and corrections can be made more accurately at run speed, thereby to assure at the output the desired product delivery gauge, manual or automatic control has not received sufficient attention in the past to adequately provide the same quality of control at lower speeds of operation, particularly during start up of the mill operation.
  • the strip of material is threaded successively through all the stands, and a certain number of wraps are taken on the windup reel before the rolling mill is accelerated to run speed.
  • Industrial practice sometimes allows for an intermediate speed, somewhat above thread speed before proceeding to desired final run speed. If the run speed of a rolling mill is in the order of 5000 feet per minute, thread speed is typically in the order of 5 percent of run speed, eg 250 feet per minute. At such low speeds,
  • Another object of the present invention is to automatically and concurrently control the speeds of the respective work stands in a multistand rolling mill and the roll gaps of the workstands before acceleration of the mill in order to provide more on-gauge material being rolled.
  • A-further object of the present invention is to provide an improved cold mill operation in which relatively soft material is effectively kept under correct tension during thread speed operation and better maintained ongauge, manually or automatically.
  • a method and apparatus are provided for controlling the delivery gauge of work strip material issuing from a tandem rolling mill, by providing a substantially constant mass flow condition in relation to adjacent roll stands through desired tension operation, sensing a deviation from said desired tension, translating said tension deviation into a speed change at a selected one of said stands thereby to cancel said tension deviation and maintain said desired tension, and changing the stand roll gap of the subsequent one of said stands to reduce said change in roll speed of said selected stand to zero.
  • the above referenced copending application discloses a fast control loop for correcting changes in interstand tension by controlling a selected stand speed through operation of a tension control loop including an adaptive tension regulator having a transfer function interposed to compensate for strip cross section area and for the adjacent stands relative speeds.
  • This adaptive tension regulator also includes a control loop effective at thread speed operation of the rolling mill, but no provision is made for tension control by roll gap adjustment at thread speed.
  • FIG. I is a schematic diagram of the work rolls of two adjacent stands in a rolling mill illustrating metal flow under the rolls at each stand;
  • FIG. 2 is a representation of the stress-strain curve typical of a metal under stress
  • FIG. 3 is a schematic diagram of a two-stand tandem rolling mill accordding to the invention.
  • FIG. 4 comprises waveforms illustrating the operation of the embodiment of the invention shown in FIG.
  • FIG. 5 is a schematic diagram of a multistand cold mill embodying the invention in the preferred form.
  • FIG. 6 illustrates in greater detail part of the circuit shown in FIG. 5.
  • a strip of material entering a stand S, with a thickness H is reduced under the rolls to a thickness H,.
  • the thickness is further reduced from H, to H
  • the law of constant volume of the plastically deformed metal is expressed by the relation H,V, H V
  • Metal cohesion in the workstrip is expressed by a tension developed between roll stands.
  • PSI PSI l.15 PSI in which PSI- is the tension (per square inch) under the rolls along the axis of flow (see FIG. 1), PSI,.- is the transversal force component due to the action of the work rolls exerted in the spacing between work rolls, and PSI is the resultant representing yield tensile stress. The latter thus is a constant. From equation (I) it appears that, should the roll gap be narrowed by screwdown, PSI will increase and therefore PSI, must decrease to keep the sum constant. The converse is true if the roll gap is increased. In other words decreasing the roll opening of stand 8, will decrease the tension between roll stands S, and 8, while increasing the roll opening of stand 8, will increase the interstand tension. assuming the roll opening H, of stand S, remains the same.
  • each of the roll stands Prior to threading, manually, or automatically, each of the roll stands has been given proper speed and roll opening settings. Then the mill is run at thread speed. If the gauge of the strip is not well controlled during this first phase of the mill operation an appreciable length of the workstrip will be wasted and this can be very costly on the overall production.
  • the present invention provides a solution to overcome this difficulty, and thus affords full advantage of interstand tension control which in a cold mill is best indicated.
  • the invention combines with a tension loop which has a slow response for the reasons just given, a fast response loop responsive to interstand tension changes for adjusting the speed of one of the adjacent roll stands, the operations of the two loops being coordinated as will now be explained with particularity by reference to FIGS. 3 and 4.
  • work strip 10 is passed through a two-stand tandem rolling mill.
  • the work rolls of stand S, and the work rolls of stand 8 have been initially set by their respective screwdown controllers 8D,, SD, and by the respective speed controllers SR,, SR to predetermined roll openings H H and roll speeds V V respectively.
  • the screwdowncontrollers SD,, SD actually control the screw positioning motors M which move the screwdown mechanisms.
  • a signal indicative of the screw position is fed back by a tachometer T for each stand.
  • the speed controllers SR,, SR determine the speed of drive motors M, and M respectively.
  • Each speed controller, SR,, SR has a setpoint provided by a master reference adjusting the rolling mill automatically for a desired constant mass flow and a predetermined delivery gauge. All this is conventional.
  • a tensiometer 30 senses a tension T, existing in the work strip between the two stands 8,, S The output signal of tensiometer 30 is applied over lead 11 to a ten sion regulator 130, but not directly.
  • the tension signal from lead 11 is compared at 14 with a tension reference and the error signal so derived is applied over lead 15 to a tension controller 13, which is part of the tension regulator 130.
  • a signal is derived representing an error in tension, ERROR which over lead 200 is applied as input to a speed error correction controller 13'.
  • ERROR error in tension
  • the latter circuit is also part operation of the rolling mill has increased beyond a transition level, e.g. at 10% of the normal speed ofop- Y eration.
  • Such disabling of the tension regulator 130 may be manual, or automatic, for instance in response to the count of tachometer 40.
  • the control signal derived at the output of the speederror correction controller 13' is-used as input, over" lead 12, for the screwdown controller SD 'of stand S,
  • FIG. 4 shows with curves A to D respectively, cumulative effects of speed correction and roll opening adjustment which in I given instant t tensiometer 30 senses a tension which;
  • the invention is not limited to control of two roll stands only. Preferably it is applicable to a multistand rolling mill.
  • the roll opening of the first stand of the mill is generally known because an X-ray gauge is commonly used at such stand. Knowing the roll opening H of the first stand, the invention offers a method of adjusting the roll opening H of the second stand as has been explained hereabove. H being correctly adjusted, by the same technique the roll opening of stand 8;, is in turn adjusted. All the stands are by this method successively brought to the right screwdown position. It is clear that this method of adjusting screwdown during thread speed operation can be conducted manually by an operator instead of using automatic control. The stand screwdown settings are changed until the correct speed is achieved on all stands. Thus, while the correct speed can be easily known and fixed, the settings of the stand screws cannot be easily calculated as explained hereabove. This difficulty is readily overcome when the method and apparatus according to the present invention are used.
  • FIG. shows a cold mill including four stands S S S and 5,.
  • a work strip of material is threaded through the work rolls onto a winding reel 43 after being passed and pulled through the rolls of each of the work stands.
  • Motors M M M M drive the rolls of the respective stands at a speed determined by speed regulators 51, 52, 53, 54, respectively, the latter responding to a master speed reference signal derived over lead 29 and respective summing points 1, 2 and 3, from a master mill speed controller, not shown.
  • the gauge issuing from stand 1 is measured by an X-ray gauge, or the like, producing a signal on lead 95 which is proportional to actual gauge error of the work strip delivered by stand 8,.
  • the gauge issuing from stand 4 is measured by an X-ray gauge 6, producing a signal on lead 96 which is proportional to the delivery gauge error of the work strip wound on the reel 43.
  • an X-ray gauge 6 measuring a signal on lead 96 which is proportional to the delivery gauge error of the work strip wound on the reel 43.
  • tension regulators 41, 42 and 44 provide an actual tension signal applied to respective tension regulators 41, 42 and 44 over leads 55, 56 and 57, respectively.
  • Each tension regulator is operative to respond to a tension error signal obtained by comparison of an interstand tension signal received from respective leads 55, 56, 57,with a tension reference signal received from the lead lines 18.
  • Tension regulator 41 has its output 65 connected through a summing point 5, to speed regulator 51 of stand S Similarly, the output 66 of tension regulator 42 is connected through a summing point 6 to speed regulator 52 of stand 8 For reasons explained later no tension regulator is associated with the speed regulator 53 of stand S
  • Tension regulator 44 has its output 67 connected through a summing point 7 to speed regulator 54 of stand 5,.
  • Each of these tension regulators is simi-v lar to the tension regulator 130 of FIG. 3. Therefore each includes a tension controller such as tension controller 13 of FIG. 3 and a speed error correction controller such as shown by 13 on FIG. 3.
  • Conventional automatic gauge control circuits 55 and 56 are provided at the entry and at the delivery end of the rolling mill which are responsive to X-ray gauges G and G respectively, as generally known.
  • Each work stand has a screwdown system. Screwdown controllers 81, 82, 83,84 control the positions of screws 101, 102, 103,
  • Screwdown controller 81 of stand S receives a control signal from the entry automatic gauge control circuit 56.
  • the output of tension regulator 41 of stand S is applied to the screwdown controller 82 of stand S but not directly.
  • the output of circuit 82 is applied to screwdown error correction controller 92 and the output of circuit 92 is applied to a circuit 72 having a transfer function which is a certain function of the velocity of the metal strip 10 between stands S and S
  • the output from circuit 72 is in turn corrected by a circuit 62 having a transfer function representing the cross-section area of the work strip of material 10 between stand 8, and S
  • the output of circuit 62 is applied to screwdown controller 82.
  • the output 66 of tension controller 42 of stand S is applied over lead 116 to screwdown 83 of stand 8:, in a loop comprising a screwdown error correction controller 93, circuit 73 introducing a transfer function of the velocity of the workstrip between stands S and S and an area compensating circuit 63, velocity and area being taken from the strip between stands S and S
  • the output 67 from tension regulator 44 is applied over lead 117 to screwdown controller 84 of the last stand S in a loop including screwdown error correction controller 94, a correcting circuit as function of velocity between stands 8:, and S4 74 and an area compensating circuit 64, velocity and area being taken from the strip between stands S3 and S4.
  • Circuits 92, 93 and 94 of the screwdown error correction controllers are shown in more detail on FIG. 6.
  • Various limiters are provided in order to disable those circuits when the speed of the mill is above a given minimum speed of operation since they should be operable only at thread speed or somewhat above thread speed.
  • These disabled circuits are tension regulators 41, 42 and 44 respectively disabled by signals on leads 75, 76 and 77, and screwdown error correction controllers 92, 93 and 94 respectively disabled by signals appearing on leads 85, 86 and 87.
  • Those circuits as explained herebelow, cease to be effective when the mill is accelerated to full speed of operation.
  • the disabling signals thus, may be generated in response to the tachometers 400, 500 or 700.
  • the speed of stand S is modified by speed regulator 51 in order to correct the tension detected by tensiometer 111, and in the same fashion subsequent stand S has its speed modified so as to correct the tension sensed by tensiometer 112.
  • the speed regulator 54 following the sensing device 113 which is adjusted in speed to correct the intertension.
  • the speed regulator 54 must be adapted to change roll speed in the opposite direction as compared to front stands S, or S Considering now roll gap changes, it appears from FIG. 5 that the outputs of the tension regulators 41, 42 and 44 are all applied over leads 115, 116 and 117, respectively, to the screwdown system of the next subsequent stand.
  • the tension regulator 41 will respond to a difference between the signal on lead 55 and the tension reference signal 18. As a result at point 5 a voltage will appear indicating a tension error condition. If the tension error corresponds to an excess of tension relative to the tension reference, speed regulator 51 will increase the speed of the rolls at stand S thus above the initial speed setting. Since such roll speed response is fast, the roll speed is readily adjusted, and tension between stands S and S returns to normal. As explained above, in response to such tension error the screwdown controller 82 will narrow the gap between the rolls of stand S which in effect will reduce tension between stands 8, and S and cause the speed regulator 51 in turn to reduce the speed of stand 8,. While the response of the roll gap loop is relatively slow, the speed of stand S will progressively return to the initial setting set by the master speed reference while the tension between stands will be maintained substantially at the level indicated by the tension reference.
  • the screwdown system of stands 5 S or 8 includes a screw error correction controller 92, 93 or 94 and two transfer functions 72, 62 or 73, 63, or 74, 64 which will be now considered with particularity.
  • FIG. 6 representing in detail the circuit of block 92, 93 or 94.
  • FIG. 6 typically shows the circuitry of screw error correction controller 92 of FIG. 4. The same circuit is used for the other two controllers 93 and 94 of FIG. 5.
  • the error signal derived over lead 115 from the output of tension regulator 44 (FIG. 5) is applied, through contacts CR1 ofa relay CR, to a potentiometer 200. Between contacts CR1 and potentiometer 200 a derivation path to ground is provided from junction 210 through contacts CR2 of the same relay CR.
  • FIG. 6 shows that relay CR is energized by a source V-through contacts SC of a limiter circuit 214 controlled by a signal over lead 85. When the mill is to be started the control signal on lead 85 causes the limiter circuit 214 to close contacts SC and energize relay CR.
  • circuits 72, 62, 73, 63 and 74, 64 are in terposed in the loop of the corresponding screwdown system.
  • circuits 72 and 62 for the purpose of explanation, these have been interposed at the output of the screwdown error correction controller 92 in order to compensate for the velocity of the strip of material before stand S and for the cross-section area of the work strip, also before it reaches the stand operated on by controller 92.
  • Compensation by circuit 72 may be proportional to velocity, but not necessarily. Any function of velocity may be selected as the transfer characteristic of circuit 72. All the necessary teachings can be found in the earlier mentioned copending application.
  • the method of claim 1 including the steps of: providing initial settings for the speeds and the roll openings of at least said pair of stands for said desired mass flow condition when the rolling mill operation is thread speed operation and threading the work strip material through said roll stands with said tension deviation sensing and speed adjustment steps being conducted during said thread speed operation of the rolling mill.
  • a method of correcting the roll opening of the work rolls of a correction roll stand of a multi-stand cold mill running at thread speed comprising the steps of: detecting an error in the tension of the material being rolled ahead of said correction roll stand, with said tension error being representative of an error in roll opening between the work rolls of said correction roll stand; changing the roll speed ofa selected roll stand adjacent the location of said detection tension error, changing the roll opening of said correction roll stand in response to said tension error; changing the roll speed of said selected roll stand in relation to said correction roll stand roll opening change for achieving the desired roll opening of said correction roll stand.
  • a method of rolling a strip of soft metal in a cold mill having a plurality of roll stands initially adjusted in speed and roll opening for maintaining a desired relatively constant mass flow passage of said metal with desired tension condition between a selected pair of adjaquent roll stand of said pair of roll stands in response to said tension error condition and concurrently changing in a second direction opposite to said first direction the speed of said one roll stand in relation to said roll opening control.
  • apparatus for controlling the passage of a strip of material through a plurality of tandem roll stands with each said roll stands being adjustable in roll speed and roll opening to maintain a relatively constant mass flow condition for the material passing through said plurality of roll stands with a desired tension condition between said stands, the. combination of: means for sensing a tension error between a selected two adjacent roll stands; means for converting said tension error into a speed correction signal; faster response means for controlling the speed of one of said two adjacent roll stands in response to said speed error correction signal; and slower response means for controlling the roll opening of the subsequent one of said two adjacent roll stands in response to said speed error correction signal.
  • each pair of said roll stands is provided with such said means for sensing a tension error relative to adjacent roll stands, means for converting said tension error, faster response means and slower response means, and including means responsive to the speed of at least one of said work stands exceeding a predetermined transition speed level for disabling at least one of said faster response means and said slower response means to prevent operation thereof, said transition speed level corresponding to acceleration of the rolling mill to normal run speed.
  • the apparatus of claim 9 including means for providing a signal corresponding to the area of the work'strip of material for modifying the operation of said slower response means.
  • the apparatus of claim 9 including means for providing a signal corresponding to the velocity of said work strip material for modifying the operation of said SlOWGI' response means.

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  • Mechanical Engineering (AREA)
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US00365668A 1973-05-31 1973-05-31 Automatic control method and apparatus for a rolling mill Expired - Lifetime US3848443A (en)

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US00365668A US3848443A (en) 1973-05-31 1973-05-31 Automatic control method and apparatus for a rolling mill
BE144952A BE815781A (fr) 1973-05-31 1974-05-31 Appareil et methode de commande automatique pour laminoir
JP6104374A JPS548463B2 (enExample) 1973-05-31 1974-05-31

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3977223A (en) * 1974-04-02 1976-08-31 John Lysaght (Australia) Limited Hot strip mill tension control
DE2823071A1 (de) * 1977-05-28 1978-11-30 Nippon Steel Corp Verfahren zum walzen von metallwerkstuecken und walzwerk zur durchfuehrung dieses verfahrens
US4307591A (en) * 1980-03-31 1981-12-29 Westinghouse Electric Corp. Rolling mill looper control system
FR2537284A1 (fr) * 1982-12-07 1984-06-08 Voest Alpine Ag Procede pour determiner la difference du nombre de tours d'au moins deux arbres, disposition de circuits pour la mise en oeuvre de ce procede et procede pour commander la traction de la bande dans une installation de pliage et de planage par etirage
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
US5103662A (en) * 1990-05-01 1992-04-14 Allegheny Ludlum Corporation Tandem rolling mill tension control with speed ratio error discrimination
US5799526A (en) * 1995-06-08 1998-09-01 Clecim Process and plant for cold rolling with compensation for ovalization of the rolling rolls
US20080058980A1 (en) * 2006-08-30 2008-03-06 Takeaki Nakano Strip threading method and strip threading device
US20190366403A1 (en) * 2017-01-16 2019-12-05 Sms Group Gmbh Method for tension control

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55158818A (en) * 1979-05-29 1980-12-10 Nippon Kokan Kk <Nkk> Controlling method for sheet thickness in rolling mill
CH697624B1 (de) * 2005-02-23 2008-12-31 Main Man Inspiration Ag Walzeinrichtung für ein Inline-Walzen eines durch Bandgiessen, insbesondere Zweirollen-Bandgiessen hergestelltes Stahlband.

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3170344A (en) * 1961-09-19 1965-02-23 Gen Electric Method and apparatus for controlling the thickness of rolled strip material
US3196646A (en) * 1961-10-30 1965-07-27 Armco Steel Corp Method and apparatus for maintaining substantially constant strip gauge in a tandem mill
US3212310A (en) * 1962-05-31 1965-10-19 Armco Steel Corp Automatic gauge and tension control system
US3440846A (en) * 1967-06-06 1969-04-29 United States Steel Corp Apparatus for maintaining the gauge of steel strip
US3507134A (en) * 1968-02-20 1970-04-21 Westinghouse Electric Corp Interstand tension control for tandem cold rolling mills
US3768286A (en) * 1972-02-29 1973-10-30 Westinghouse Electric Corp Interstand tension regulator for a multistand rolling mill

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3170344A (en) * 1961-09-19 1965-02-23 Gen Electric Method and apparatus for controlling the thickness of rolled strip material
US3196646A (en) * 1961-10-30 1965-07-27 Armco Steel Corp Method and apparatus for maintaining substantially constant strip gauge in a tandem mill
US3212310A (en) * 1962-05-31 1965-10-19 Armco Steel Corp Automatic gauge and tension control system
US3440846A (en) * 1967-06-06 1969-04-29 United States Steel Corp Apparatus for maintaining the gauge of steel strip
US3507134A (en) * 1968-02-20 1970-04-21 Westinghouse Electric Corp Interstand tension control for tandem cold rolling mills
US3768286A (en) * 1972-02-29 1973-10-30 Westinghouse Electric Corp Interstand tension regulator for a multistand rolling mill

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3977223A (en) * 1974-04-02 1976-08-31 John Lysaght (Australia) Limited Hot strip mill tension control
DE2823071A1 (de) * 1977-05-28 1978-11-30 Nippon Steel Corp Verfahren zum walzen von metallwerkstuecken und walzwerk zur durchfuehrung dieses verfahrens
US4307591A (en) * 1980-03-31 1981-12-29 Westinghouse Electric Corp. Rolling mill looper control system
FR2537284A1 (fr) * 1982-12-07 1984-06-08 Voest Alpine Ag Procede pour determiner la difference du nombre de tours d'au moins deux arbres, disposition de circuits pour la mise en oeuvre de ce procede et procede pour commander la traction de la bande dans une installation de pliage et de planage par etirage
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
EP0430047A3 (en) * 1989-11-29 1992-08-26 Aeg Westinghouse Industrial Automation Corporation A method for rolling on-gauge head and tail ends of a workpiece
US5103662A (en) * 1990-05-01 1992-04-14 Allegheny Ludlum Corporation Tandem rolling mill tension control with speed ratio error discrimination
US5799526A (en) * 1995-06-08 1998-09-01 Clecim Process and plant for cold rolling with compensation for ovalization of the rolling rolls
US20080058980A1 (en) * 2006-08-30 2008-03-06 Takeaki Nakano Strip threading method and strip threading device
US20190366403A1 (en) * 2017-01-16 2019-12-05 Sms Group Gmbh Method for tension control
US11426778B2 (en) * 2017-01-16 2022-08-30 Sms Group Gmbh Method for tension control

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Publication number Publication date
JPS548463B2 (enExample) 1979-04-16
BE815781A (fr) 1974-12-02
JPS5020968A (enExample) 1975-03-05

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