US3375688A - Method and apparatus for rolling metal strip and sheet - Google Patents

Method and apparatus for rolling metal strip and sheet Download PDF

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US3375688A
US3375688A US457104A US45710465A US3375688A US 3375688 A US3375688 A US 3375688A US 457104 A US457104 A US 457104A US 45710465 A US45710465 A US 45710465A US 3375688 A US3375688 A US 3375688A
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roll
deflection
rolls
mill
output
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US457104A
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Louis H Taylor
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Youngstown Res and Dev Co
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Youngstown Res and Dev Co
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D23/00—Mine roof supports for step- by- step movement, e.g. in combination with provisions for shifting of conveyors, mining machines, or guides therefor
    • E21D23/04—Structural features of the supporting construction, e.g. linking members between adjacent frames or sets of props; Means for counteracting lateral sliding on inclined floor
    • E21D23/0472—Supports specially adapted for people walking or transporting material
    • 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
    • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
    • 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
    • B21B37/46—Roll speed or drive motor control

Definitions

  • ABSTRACT OF THE DISCLOSURE A method and apparatus for rolling metal sheet in a rolling mill a small diameter work roll and at least one upper and one lower backing roll for the work roll which are driven by separate motors in which deflection of the small work roll is controlled by effecting changes in apportionment of the torque applied by the motors to the driven backing rolls. Means are provided to sense the amount and direction of the deflection of the small Work roll which produces a signal related to the amount and direction of the deflection. An error signal is produced related to the difference between the sensed position and the desired position and transmitted to the motors to effect changes in apportionment of the applied torque and thereby control deflection of the work roll and the shape of the issuing strip.
  • This invention relates to a method and apparatus for rolling metal strip and sheet, and more particularly to a method and apparatus for maintaining deflection of a small diameter work roll of a roll stand substantially at a given position in the roll pass of the stand.
  • the deflection to which my invention relates is in a direction with and opposite to travel of metal through the mill, and the small work roll is one of a plurality of rolls of a stand, all of whose longitudinal axes are in substantially the same vertical plane.
  • this small diameter work roll is on a -high stand, a 3-high stand, a 4-high stand, or a 6-high stand where it is the smallest diameter roll of the stand.
  • On the S-high stand it has an upper and lower intermediate roll each of larger diameter and an upper and a lower backing roll each of greater diameter than the intermediate rolls and each backing roll in frictional engagement with its intermediate roll.
  • This work roll is in frictional engagement with the one intermediate roll and forms with the other intermediate roll a roll pass through which the metal travels and in which it is reduced in thickness.
  • the roll On the 3-high mill, the roll is the smallest roll and is disposed between two backing rolls, each of which is driven by an electric motor.
  • this small diameter work roll forms with a larger diameter work roll the roll pass.
  • the diameter of the larger work roll is substantially about one and onehalf to four times the diameter of the small work roll.
  • the two work rolls are interposed between upper and lower intermediate rolls which, in turn, are interposed between upper and lower backing rolls.
  • the upper intermediate roll is in frictional engagement with one of the work rolls and the lower intermediate roll is in frictional engagement with the other work roll while the upper backing and upper intermeditae rolls are in frictional engagement as are the lower intermediate and lower backing rolls.
  • the given position of the small work roll in the roll pass can be one at which the longitudinal axis of the small work roll is in vertical alignment with the longitudinal axes of the other rolls of the mill or it can be one at which the small work roll is bowed or deflected in a direction with or opposite to travel of metal through the mill. In this latter case, the longitudinal axis of the small work roll is not in vertical alignment with the longitudinal axes of the other rolls of the mill. Selection of the given position is dependent upon production of a desired shape in the rolled metal which in most cases is flat, and takes into consideration crown in the rolls due to the shape of the roll bodies and/ or to heat generated by reduction of the metal.
  • the given position may be changed intentionally to obtain a desired shape in the metal or to maintain shape. This change in the given position may be required because of variations in conditions in the roll pass such as heat build-up in the roll body or bodies or because of variations in the metal itself, such as hard spots or off-gauge.
  • Driving force or torque for the small work results from frictional engagement with at least one backing roll or intermediate roll and from application of forward tension to the metal by a winding reel or another stand on the exit side thereof.
  • FIGURE 1 which shows diagrammatically a S-high mill, that mill comprises a top backing roll 1 and a bottom backing roll 2 with a top intermediate roll 3 and a lower intermediate roll 4 disposed therebetween.
  • the top intermediate roll is in frictional engagement with the top backing roll
  • the lower intermediate roll is in frictional engagement with the bottom backing roll with the backing rolls being driven by electric motors, not shown.
  • the intermediate rolls can be driven instead of the backing rolls.
  • a small diameter work roll 5 in frictional engagement with the lower intermediate roll 4 and forming a roll pass with the top intermediate roll 3. Extending through the roll pass is metal strip 6.
  • a combination of two resulting forces rotates the work roll 5.
  • the first resulting force acts on the top side of the roll and comprises a portion of strip delivery tension T and tangential force F generated by the top backing roll 1 acting upon the top intermediate roll 3 and extending transversely through the strip thickness to the top part of the work roll 5.
  • the sum of these two forces tends to move the roll 5 towards the delivery side of the mill as shown by arrow 7.
  • the second resulting force acts on the lower side of the work roll 5 and comprises a tangential force F produced by rotation of the lower backing roll 2 in frictional engagement with the intermediate roll 4.
  • the second factor which causes the deflection results from a combination of forces generated by operation of a screwdown mechanism and of tolerances in the roll bearings and chocks.
  • the screwdown mechanism When the screwdown mechanism lowers the top backing roll and the top intermediate roll to establish a given roll pass to effect a particular reduction, the screwdown mechanism exerts a force On the rolls.
  • This force in combination with the tolerances between the roll necks, the bearings and/ or the chocks and tolerances in the mill housing, may cause the work roll to deflect in the direction with or opposite to travel of strip through the mill. Such deflection occurs because of the small amount of space between the bearings and the roll neck and between the chocks and the mill housings, thus enabling the roll necks and/or shocks to shift or move a small amount when subjected to the screwdown force.
  • Control over deflection of the small work roll to obtain a desired shape or flatness in the strip encounters further complications from a heat build-up in the rolls, especially during sustained rolling periods.
  • This heat build-up cannot be completely dissipated by flood coolant and generally effects an expansion or swelling commonly called crown in a center portion of the small roll and/or in any other roll. Presence of the crown causes over-rolling of the center portion of the strip, thereby requiring compensation in the position of the small roll in the roll pass to minimize if not eliminate its effect upon the shape of the strip.
  • regulation of deflection of the single small roll presents many problems which place severe requirements upon a control system therefor.
  • My invention permits full utilization of the advantages of the small diameter work roll by maintenance of de flection of the roll at a given position in the roll pass and by ability to effect an extremely fast correction for deviations in deflection from the given position. Specifically, it comprises maintaining the deflection of a small diameter work roll substantially at a given position in the roll pass and/or controlling the amount of deflection of this work roll in the roll pass on a rolling mill which has at least one upper backing and at least one lower backing roll for the work roll. This deflection of the small work roll is in the direction substantially with and substantially opposite to travel of the metal through the mill. Each of the backing rolls has a diameter greater than the diameter of the small work roll and the rolls are disposed substantially vertically of one another.
  • the work roll and one of the upper and lower backing rolls form a roll pass through which metal is reduced in thickness and another backing roll is in frictional engagement with the work roll.
  • At least one electric motor is operatively connected to an upper backing roll and at least one electric motor is operatively connected to a lower backing roll. Maintenance and/or control of the deflection results from increasing and decreasing the amount of the deflection by effecting changes in apportionment of applied torque by the motors between the driven rolls through sensing amount and direction of deflection of the work roll from the given position.
  • a signal related to the amount of deflection and related to the direction thereof is generated and then from the signal an error signal related to the difference between the sensed position of the work roll and the given position of the work roll and related to the direction of deflection is produced. Thereafter, the error signal is utilized in regulation of output torque of the electric motors for effecting the changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position.
  • the sensing of deflection of the small work roll includes sensing the rate of change of deflection and the signal is related to the rate of change of deflection. Further, the error signal is related to the rate of change of difference between the sensed position and the given position of the small work roll.
  • a current related to the magnitude of the error signal and related to the direction of the error signal is produced from this error signal and then applied to the electric motors for effecting the changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position or to control the amount of deflection of the small work roll.
  • the current which is produced from the error signal is applied preferably to the armatures of the electric motors to effect the changes in apportionment of applied torque, but it can alternatively be applied to the fields of the electric motors to effect the changes in apportionment.
  • One such current which I have employed comprises a first part which is substantially continuous, is related in magnitude to the amount of the deflection and related to the direction of the deflection.
  • This current also has a second part which is pulses of short duration related in magnitude to the amount of the deflection and related to the direction of deflection.
  • the first part is a major portion of the current and requires a longer time interval to effect a change in apportionment of applied torque than the second part.
  • My invention also includes a method of rolling the strip in which a mill operator observes the shape of the strip as it issues from the mill and then, based upon his observation, he controls the amount of deflection of the small work roll to produce a desired shape.
  • a mill operator observes the shape of the strip as it issues from the mill and then, based upon his observation, he controls the amount of deflection of the small work roll to produce a desired shape.
  • increases and/or decreases the amount of deflection of the small work roll through making changes in apportionment of the torque applied by the motors to the driven upper and lower rolls.
  • Such changes in apportionment of the torque comprise increas ing or decreasing the amount of output torque of the motor or motors which rotate one driven roll relative to the amount of output torque of the motor or motors which turn the other driven roll through operation of controls for the motors.
  • My invention in apparatus for maintaining deflection of the small diameter work roll substantially at a given position in the roll pass comprises a means for sensing amount and direction of the deflection with this sensing means disposed opposite a face of the roll so that deflection is toward and away therefrom.
  • a signal generating means which produces from the deflection a signal related to the amount of deflection and related to direction of the deflection.
  • an error signal generating means which produces from the signal an error signal related to the difference between a sensed position of the small work roll and the given position of this small work roll, and is related to the direction of the deflection.
  • An error signal transmitting means is joined to the error signal generating means and connected to one of the electric motors which are drivingly connected to rolls of the mill and of means coupled to the electric motors for regulating output torque of these motors to effect changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position.
  • the signal generating means is such that the signal is also related to rate of change of deflection of the small work roll and the error signal generating means is such that the error signal is also related to rate of change of deflection of this small work roll.
  • the error signal generating means is connected to a current producing means and utilizes the error signal to generate a current related to the magnitude of the error signal and related to its direction. This current is then transmitted to the electric motors for regulating their operation to control output torque and thereby effect the changes in apportionment of applied torque to the driven rolls.
  • This current is applied, preferably, to the armatures of the electric motors, but can also be applied to the fields of these electric motors.
  • the means coupled to the electric motors for regulating their output torque includes a controllable variable load producing device which regulates output torque of the electric motors, in connected to the error signal generating means, and is responsive to the error signal for effecting the changes in apportionment of applied torque.
  • a controllable variable load producing device include electrically operated friction brakes which are disposed in engagement with the output shaft of the electric motors and which include an eddy current absorption dynamometer with a DC.
  • excitation winding regulated by the error signal or a current produced therefrom in push-pull manner with no resultant mill speed change or with a non-overlapping individualload control; gener ators which are coupled to the motors, whose output is dissipated as heat through load resistors: and whose field is regulated the same as the above dynamometer; generators which are coupled to the electric motors from which power is recovered, and whose fields are controlled the same as the above dynamometer; and hydraulic load devices which work upon the output shafts of the electric motors. All of these devices are responsive to the error signal for effecting the changes in apportionment of the applied torque.
  • the small work rolls to which my invention is especially directed may have diameters ranging from about A" to about 8.
  • FIGURE 1 shows diagrammatically a 5-high mill
  • FIGURE 2 is a schematic view of one device for detecting deflection of the single small roll of a S-high mill
  • FIGURE 3 is a schematic view of a second sensing device
  • FIGURE 4 is a schematic view of a third sensing device
  • FIGURE 5 is a schematic view of a fourth sensing devlce
  • FIGURE 6 is a schematic view of a fifth sensing device
  • FIGURE 7 is a schematic view of a sixth sensing device
  • FIGURE 8 is a schematic diagram showing my invention applied to a Z-stand, S-high tandem mill
  • FIGURE 9 is a block-diagram of apparatus for generating the error signal which is used to maintain deflection of the roll at a given position;
  • FIGURE 10 is a schematic wiring diagram of one embodiment of a slow acting regulating system and a fast acting regulating system which receives the error signal and generates therefrom a reversible push-pull continuous current and reversible push-pull pulses of current for producing the regulated buck-boost output armature current;
  • FIGURE 11 is a schematic wiring diagram showing a first modification of the embodiment of FIGURE 10;
  • FIGURE 12 is a schematic wiring diagram of a second modification of the embodiment of 'FIGURE 10;
  • FIGURE 13 is a schematic wiring diagram of a second fast regulating system for the embodiment of FIGURE 10;
  • FIGURE 14 is a schematic wiring diagram of a third fast regulating system for the embodiment of FIGURE 10:
  • FIGURE 15 is a schematic wiring diagram of a third modification of the embodiment of FIGURE 10;
  • FIG. 16 is a schematic wiring diagram of a fourth modification of the embodiment of FIGURE 10.
  • FIGURE 17 is a schematic wiring diagram of a system which receives the error signal and generates therefrom a current which is delivered to the armatures of the electric motors which are drivingly connected to rolls of the mill for effecting changes in apportionment of applied torque to the driven rolls;
  • FIGURE 18 is a block diagram similar to that of FIG- URE 9, but adapted to the system of FIGURE 17;
  • FIGURE 19 is a schematic wiring diagram of a system which receives the error signal and generates therefrom a current which is delivered to the fields of the electric motors which are drivingly connected to rolls of the mill;
  • FIGURE 20 is a schematic diagram of a G-high mill equipped with my invention.
  • FIGURE 21 is a schematic diagram of a drive for a rolling mill with changes in apportionment of applied torque to the driven rolls of the mill effected through electrically operated friction brakes connected to driven spindles which are joined to the driven rolls.
  • the S-high mill of FIGURE 1 mounts apparatus 9 for detecting deflection of the single small diameter 'WOIk roll in a roll pass formed by the upper intermediate roll 3 and the small diameter roll itself.
  • the lower backing roll 2 is driven by two motors 10 and 11 connected in tandem with motor 10 being shown in FIGURE 2, and the top backing roll is driven by two motors 12 and 13 connected in tandem.
  • the upper intermediate roll 3 is in frictional engagement with the upper backing roll 1 and the lower intermediate roll 4 is in frictional engagement with the lower backing roll 2.
  • the roll drive connected to the backing rolls it may alternatively be joined to the intermediate rolls, one of which also functions as a backing roll for the work roll 5.
  • a signal gen-' erator 14 Connected to the sensing apparatus 9 is a signal gen-' erator 14 which produces from deflection of the roll 5 a signal related in magnitude and related to direction of the deflection.
  • This signal travels to a push-pull output amplifier 15 (FIGURE 9) where a first portion continues to a push-pull driver amplifier 16 whose output is delivered to a slow acting regulating system 17 (FIGURE 10) and a second portion advances to a bias and trigger generator combination 19 whose output is transmitted to a fast action regulating system 19.
  • the slow regulating system produces a reversible push-pull substantially continuous current and the fast regulating system generates reversible push-pull pulses of current of short duration.
  • a buck-boost generator 20 whose output is applied to the armatures of the motors for driving the backing rolls 1 and 2.
  • 1 By boosting the armature current of one roll drive motor combination and bucking the armature current of the other roll drive motor combination, 1 effect a change in apportionment of torque applied to the driven rolls 1 and 2 to maintain the roll 5 at or return it to a given position in the roll pass.
  • nozzles 21 and 21a connected to conduits 22 and 22a leading from a source of fluid under pressure such as air or liquid straddle both sides of the roll 5, are substantially opposite the face 24 of the roll 5, and are substantially in alignment with the center line of the roll and substantially midway between the ends of the face 24 thereof so that deflection of the roll 5 in the direction with or opposite to strip travel through the roll pass is toward one nozzle and simultaneously away from the other nozzle.
  • Safety bars 25 and 25a mount and position the nozzles opposite the roll face.
  • nozzles are located close to the roll face across gaps 26 and 26a between the ends of the nozzles and the roll face so that deflection of the roll '5 produces a change in pressure of the fluid under pressure in the conduits.
  • the length of the gaps between the nozzle and the roll face is from about 0.005 to about 0.050" when the roll and its intermediate and backing rolls are in axial alignment as shown in FIGURE 1.
  • impingement of two jets of air or fluid against the roll face produces back pressure in the conduits 22 and 22a with this back pressure being less when the roll is deflected away from one nozzle to lengthen the gap and greater when the deflection is toward the nozzle to shorten the gap.
  • impingement of the two jets against the roll face produces equal amounts of back pressure in the conduits 22 and 22a.
  • the back pressure affects the pressure of air or fluid forming the jet and as the gap shortens, the back pressure increases and as the gap lengthens, it decreases.
  • the conduits are connected to a signal generator 14 comprising a transducer 27 and a linear variable differential transformer (LVDT) 28 whose output is transmitted to an amplifier 29.
  • LVDT linear variable differential transformer
  • FIGURES 3 and 4 show two other types of roll deflection sensing devices which utilize electromagnetic induction to induce eddy currents in the surface of the roll 5 where high frequencies such as 50 kilocycles and higher are used, or to effect changes in the inductive reactance in one or two electromagnetic inductors which changes correspond to shortening and lengthening of gaps between the inductors and the roll face.
  • I locate two electromagnetic inductors 45 and 46, one on each side of the small roll 5 and connect each inductor into a bridge circuit 46a in which each inductor forms one arm of the reactance bridge.
  • the other two arms of the bridge are resistors 45a and 45b of selected values.
  • the two corners of the bridge formed by the junctions of the two resistors and the two inductors are connected to a high frequency source 47a of alternating current as provided by the driver oscillator 75.
  • the other two corners of the bridge formed by the junctions of resistor 45a and inductor 45 and of resistor 45b and inductor 46 are the outputs of the reactance bridge and are connected to the amplifier 29.
  • the reactance bridge circuit has a null balance RC network comprising a variable capacitor 450 and a variable resistor 45d connected in parallel and across one input corner 45e and one output corner 45].
  • each inductor changes in reactance as a result of roll deflection are nonlinear.
  • the two in combination when disposed in the reactance bridge circuitry, will produce a substantially linear output as a function of roll deflection.
  • Each inductor is spaced apart from the roll 5 to provide small gaps 48 and 49 between the roll face and the leading face of each inductor, and each inductor generates magnetic lines of flux which travel from the inductor across the gaps to the roll face. It has been found that a gap between the roll face and the leading face of the inductor of about 0.005 to about 0.025" effects satisfactory detection of roll deflection.
  • the single inductor 51a of FIGURE 4 operates similarly to those of FIGURE 3 except that its output is nonlinear and it requires additional compensation circuitry for the non-linearity output.
  • a reactance bridge circuit 51b similar to circuit 46a, would have a variable inductance for one arm and a proper valued resistor associated with the variable inductance as another arm.
  • the other half of the bridge comprises the inductor 51a and the resistor 45]).
  • FIGURES 5 and 6 show two additional devices for detection of roll deflection which use changes in reluctance of the magnetic circuit which bridges one or two small gaps to detect the deflection.
  • two transformers 54 and 55 are located on each side of the single small diameter roll 5 and the primary winding of each transformer is connected to a source of A.C. power 47, as provided by an oscillator such as oscillator 75 of FIGURE 9.
  • Transformer 54 has a primary winding 56 and a secondary winding 57 and transformer 55 has a primary winding 58 and a secondary winding 59.
  • Each transformer is spaced apart from the work roll 5 to form the small gaps 60 and 61 between the roll face and each transformer and each primary winding directs magnetic flux linkages to the roll 5 across the gaps and to its secondary winding. It has been found that a gap between the roll face and the transformer of about 0.005" to about 0.025" effects satisfactory detection of roll deflection.
  • the two primary windings are connected series aiding and the two secondary windings are connected in series bucking.
  • an amplifier 50 Connected to the two secondary windings 57 and 59 is an amplifier 50 so that output voltage of the two secondary coils travels thereto for production of a signal.
  • the two output voltages in the secondary circuit are opposite in phase and the net output of the two transformers is the difference between the two output voltages.
  • This net output voltage is related in amount to the magnitude of the deflection and is directional in accordance with the direction of deflect-ion.
  • An amplifier 50 generates from this net output voltage a signal which is related to the amount of deflection and which has characteristics of direction of deflection.
  • FIGURE 6 shows a single transformer 62 positioned on one side of the single small diameter work roll 5 for detection of roll deflection.
  • its voltage output to the amplifier 50 when there is no deflection of the roll and the roll is in the given position in the roll pass is matched with a standard voltage in the amplifier.
  • there is roll deflection towards or away from the transformer there is a resulting increase or decrease in the voltage output of the transformer, thereby causing the amplifier to generate a signal of the same character as the signal produced when using two transformers.
  • FIGURE 7 shows another device for detection of roll bar 72 on the other side of the roll 5 is a second bar 73 parallel thereto and having on its side opposite the other face of the roll 5 a cushion 74 made from a material which does not mark or mar the surface of the roll 5 should it contact same in deflection.
  • This other bar assists to maintain the roll 5 within a given range of deflection so that should there be excessive deflection, the small roll will not break or fracture.
  • the roll deflection sensing devices disclosed herein have ability to detect very small amounts of roll reflection suhh as 0.0001 from which a signal is produced for maintenance of the roll substantially at a given position in the roll pass. Additionally, these devices are such that use of a flood coolant on the mill does not affect their operation or reduce their ability to detect small amount of deflection.
  • the linear variable differential transformer '28 has connected thereto an. oscillator 75 which supplies AC. power of high frequency therefor.
  • the signal output of this linear variable differential transformer advances to an. amplifier 29 where it is amplified and forwarded to a phase detector 76.
  • This detector rectifies the A.C. roll position signal to provide a DC. voltage related to the displacement of the roll from its given position in the roll pass with a polarity indicating the direction of the displacement.
  • a roll position selector 77a produces an adjustable reference DC. voltage so that a position at which the roll is maintained can be selected by a mill operator.
  • This reference DC. voltage along with the output of the phase detector 76 is fed to a difference amplifier 78. which provides an output voltage or error signal related to the difference between the actual roll position and the desired position chosen on the selector 77a.
  • output voltage signal from the amplifier 78 is related in magnitude to the amount of deflection and is related to deflection which comprises a tube 63 for delivering a fluid such as oil against the face of the roll 5 from a source of oil entering the tube through a flexible pipe 64.
  • nozzle 65 of the tube is opposite the face of the roll 51 and separated therefrom by a film of oil.
  • the pressure of the oil issuing from the nozzle 65 in combination with the pressure of a spring 69a, to be described hereinafter, may be such that the nozzle backs away from the roll 0.0001" to about 0.001. Accordingly, the nozzle rides this film of oil and avoids a metal-to-metal contact with the roll to eliminate marking the roll face.
  • the rear end 66 of the tube 63 engages an upper portion 67 of a pivoted arm 68 maintained in its neutral position corresponding to zero deflection of the roll from its given position in the roll pass by a spring actuated plunger 69 in contact with an upper portion of the arm.
  • the lower end 70 of the arm 68 engages one end of a rod 71 which carries a magnetic core (not shown) corresponding to core 39.
  • This core is disposed in a linear variable differential transformer 28a identical to the transformer 28. Consequently, defiection of the roll toward and away fro-m the nozzle 65 operates the linear variable transformer 28a in the same manner as transformer 28 to detect deflection of the roll.
  • a bar 72 extending substantially parallel to the longitudinal axis of the roll 5 carries. the tube 63. Opposite the the direction of deflection.
  • the push-pull output amplifier 15 receives the output DC. voltage signal from the difference amplifier 78 and provides sufficient power to drive two separate push-pull circuits which deliver portions of the output voltage signal of the amplifier 78 to the fast acting regulation system 19 (FIGURE 10) and the slow acting regulation system 17.
  • a first portion of the output of this push-pull amplifier '15 is transmitted to one separate.
  • push-pull circuit 79' comprising arate generator 80 and. an attenuator 81 connected in parallel with a frequency compensation network 82 and a second attenuator 83.
  • This first portion like the output voltage signal of the amplifier 78, has a magnitude related to the amount of deflection and is related to the direction of deflection.
  • the rate generator 80 is a differentiating circuit that gives an output signal related to the velocity of the deflection.
  • the frequency compensation network 82 controls the higher frequency phase of the circuit and amplitude response of feedback circuits to be described hereinafter.
  • the attenuators 8'1 and 83 control the gain of a feedback loop and the amount of dam'pening.
  • This parallel circuitry advances to an adder 84 which combines the roll position error signal of the compensation network 82 and the rate signal of the rate generator 80 in the proper phases to produce an output error signal.
  • This sign-a1 is fed to the slow regulation system 17 through the push-pull driver amplifier 16, which is in circuit with two control fields 85 and 86 of a rotating amplifier 87 (FIGURE 10), such as Amplidyne, Rototrol, Regulex regulators.
  • a second portion of the output of the -push-pull amplifier is transmitted to a second separate push-pull circuit 88 identical to that circuit 79 comprising the rate generator 80, frequency compensation network 82, the two attenuators 81 and 83 and the adder 84. From the circuit 88, the resulting output error signal is transmitted to the bias and trigger generator 18 connected to thyra- 11 trons which are a part of the fast acting regulating system 19.
  • the reference voltage produced by the roll position selector 77 is carefully regulated so that it does not fluctuate with line voltage, load or temperature changes.
  • This reference voltage is derived from a calibrated roll position setting potentiometer located on the mill and convenient for the operator to select a given position. This reference voltage is then used to preselect the performance level required of the regulated quantity which is a current difference corresponding to torque differentials in the mill motor armatures.
  • the given position referred to in this application includes a small band of movement such as plus-minus 0.0005, and on wide mills, may be plus minus 0.005.
  • a small band of movement such as plus-minus 0.0005, and on wide mills, may be plus minus 0.005.
  • the upper and lower driven mill rolls have separate motors to permit effecting a change in apportionment of the torque applied by the motors to the driven rolls, and preferably effecting the change in apportionment of the torque between the two roll drives without affecting the total amount of torque imparted to the rolls themselves. It is further preferable that the change in apportionment be made without affecting the main generators current output.
  • the foregoing roll drive in combination with my dual regulating system, achieves correction for roll deflection in intervals such as 4 to 17 or 20 milliseconds.
  • a main generator 89 driven by an AC. motor 90, is connected to the mill motors 10, L1, 12 and 13 with mill motors 12 and '13 driving the top backing roll 1 and connected in parallel, and mill motors and 11 driving the lower back-ing roll 2 and connected in parallel.
  • Mill motor 10 is in series electrically with mill motor 12, as is mill motor 11 in series electrically with mill motor 13, and motors 11 and 12 are connected to one side of the generator 89 and motors 10 and 13 are connected to the other side of this generator.
  • the buckboost generator 20 Connected across natural neutral points 91 and 92 on line 93 in the mill motors power circuits is the buckboost generator 20 driven by its AC. motor 94.
  • the buck-boost generator has a main field 95 connected to the Amplidyne regulator 87 of the slow acting regulation system 17, and a fast field 96 is in circuit with the fast acting regulating system 19.
  • the fast field is a relatively few-turn coil of heavy wire for current input from two back-to-back connected bridge rectifiers 97 and 98 so that the output from the bridges is transformed to field flux which adds to or subtracts from the flux of the main field 95.
  • the main field 95 is a relatively high impedance winding having more turns per coil of small size wire.
  • the buck-boost generator experiences rapid changes in field flux
  • its field frame is preferably a laminated construction of good grade electrical sheet for fast response and low hysteresis and eddy current losses.
  • the armature current of the generator 20 flows in either direction in line 93, as indicated by arrows 100 and 101 (FIGURE 10) and increases the armature current in the upper roll drive motors in direction 100, while simultaneously decreasing armature current in the lower roll drive motors. This effects a change in the apportionment of torque delivered by the two roll drives and thereby moves the small work roll towards the given position or maintains same thereat.
  • the Amplidyne regulator 87 is driven by the AC. motor 94a and has the two matched high impedance control fields 85 and 86 connected to the driver amplifier 16. One fields connection is reversed as to the other so that when each receives an equal amount of DC. output voltage from the amplifier 16, the resultant magnetic field fiux is zero for one cancels the other.
  • the driver amplifier 16 (FIGURE 9) includes circuits which affect its time-rate output such as gain, rate feedback, bias and adjustable time constants, and additionally, has two output push-pull circuits which receive the push-pull signal from the adder 84.
  • the driver amplifier 16 When the push-pull signal is received by the driver amplifier 16, one output voltage is raised an amount equal to that that the other output voltage is lowered.
  • Which output circuit has its voltage raised is dependent upon the direction of deflection of the roll 5, and the amount of raise and of reductiofii is dependent upon the amount of deflection of the ro Application of this DC.
  • the output voltage from the driver amplifier causes one control field 85 or 86 to drive to a higher excitation level, while the other control field is driven to a lower excitation level to effect a net ampere turn current in one direction or the other to induce a voltage in the armature of the Amplidyne.
  • Arrows 103 and 104 indicate the direction of voltage induced in the armature 105 of the Amplidyne 87 by control fields 85 and 86. Accordingly, the armature 105 of the Amplidyne delivers a variable and directional excitation current to the main field 95 of the buck-boost generator 20 which current must have reversible polarity to effect maintenance of the roll 5 in the given position.
  • a negative feedback for the armature 105 of the Amplidyne comprises a differential field 106 connected across the armature 105 and a network of back-to-back connected zener diodes 107 and 108. This negative feedback improves transient performance and stability of the Am-

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Description

April 2, 1968 u. H. TAYLOR 3,375,588.
METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET Filed May 19, 1965 14 Sheets-5heet l INVENTOR. Louis H. Taylor BY W LL 6W,
H/S ATTORNEYS April 1968 L. H. TAYLOR 3,375,688
METHOD AND APPARATUS FOR ROLLING METAL STRIP AI ID SHEET Filed May 19, 1965 14 Sheets-Sheet 2 0 0 u I ----0 -0 AMPLIFIER AMPLIFIER Fig.5 I Fig.6
INVENTOR. I Louis H. Taylor BY 6%,
H/S ATTORNEYS April 2, 1968 L. H. TAYLOR 3,375,583
METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET Filed May 19, 1965 14 Sheets--Sheet 5 TRANSDUCER LV DT INVENTOR. Louis H. Taylor BY WM, 6
QMQ'WM HIS A TTORNE Y5 L. H. TAYLOR April 2, 1968 METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET 14 Sheets--Sheet 5 Filed May 19, 1965 iq. IO
/N l E N T 05. Louis H. Taylor HIS ATTORNEYS H. TA YLOR 3,375,688
METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET A ril 2, 1968 14 Sheets-$heet 6 Filed May 19, '1965 April 1968 H. TAYLOR 3,375,688
METHOD AND APPARATUS FOR ROI JLING METAL STRIP AND SHEET Filed May 19, 1965 14 Sheets-Sheet 7 I38 I39 I40 I32 5:; I37 A 93 A {Isl I05 I07 87 A L l 4 l? Fig.1.? W M W INVENTOR.
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METHOD AND APPARATUS FOR ROLLING METAL STRIP AN D SHEET 7 Filed May 19, 1965 14 Sheets-$heet 8 INVENTOR. Louis H. Taylor Fig.1.? Byw {Us I JM+ HIS A TTOfi/VEYS p 968 L.VH.TAYLOR 3,375,688
METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET Filed May 19, 1965 14 heets-Sheet a Louis H. Taylor JAGM. I? 7" W116 H/S A TTORNEYS L. H. TAYLOR April 2, 1968 METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET Filed May 19, 1965 14 Sheets-$heet 10 Taylor INVENTOR. Louis H. BY I KM MM- HIS. ATTORNE rs April 2, 1968 HfTAYLOR 3,375,688
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LOU/5 H. 721M! 0 BY PM W April 2, 1968 L. H. TAYLOR METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET l4 Sheets-Sheet 14.
Filed May 19, 1965 UPPER ROL L OlQ/I/E' REACT/0N Tf/QUSTJ/DE IN VEN TOR LOU/5 h. 7I4YLOJQ BY LL aw. {M M HA5 ATTOR/VEVS United States Patent 3,375,688 METHOD AND APPARATUS FOR ROLLING METAL STRIP AND SHEET Louis H. Taylor, Youngstown, Ohio, assignor to The Youngstown Research and Development Company, Youngstown, Ohio, a corporation of Ohio Continuation-impart of application Ser. No. 239,199, Nov. 21, 1962. This application May 19, 1965, Ser. No. 457,104
27 Claims. (Cl. 7221) ABSTRACT OF THE DISCLOSURE A method and apparatus for rolling metal sheet in a rolling mill a small diameter work roll and at least one upper and one lower backing roll for the work roll which are driven by separate motors in which deflection of the small work roll is controlled by effecting changes in apportionment of the torque applied by the motors to the driven backing rolls. Means are provided to sense the amount and direction of the deflection of the small Work roll which produces a signal related to the amount and direction of the deflection. An error signal is produced related to the difference between the sensed position and the desired position and transmitted to the motors to effect changes in apportionment of the applied torque and thereby control deflection of the work roll and the shape of the issuing strip.
This application is a continuation-in-part of my application Ser. No. 361,418, filed Apr. 21, 1964, now Patent No. 3,275,918, which is a continuation-in-part of my application Ser. No. 239,199, filed Nov. 21, 1962, now abandoned, which is a continuation-in-part of my application Ser. No. 734,321, filed May 9, 1958, now Patent No. 3,077,800.
This invention relates to a method and apparatus for rolling metal strip and sheet, and more particularly to a method and apparatus for maintaining deflection of a small diameter work roll of a roll stand substantially at a given position in the roll pass of the stand. The deflection to which my invention relates is in a direction with and opposite to travel of metal through the mill, and the small work roll is one of a plurality of rolls of a stand, all of whose longitudinal axes are in substantially the same vertical plane.
Generally, this small diameter work roll is on a -high stand, a 3-high stand, a 4-high stand, or a 6-high stand where it is the smallest diameter roll of the stand. On the S-high stand, it has an upper and lower intermediate roll each of larger diameter and an upper and a lower backing roll each of greater diameter than the intermediate rolls and each backing roll in frictional engagement with its intermediate roll. This work roll is in frictional engagement with the one intermediate roll and forms with the other intermediate roll a roll pass through which the metal travels and in which it is reduced in thickness.
On the 3-high mill, the roll is the smallest roll and is disposed between two backing rolls, each of which is driven by an electric motor.
On the 6-high mill, this small diameter work roll forms with a larger diameter work roll the roll pass. The diameter of the larger work roll is substantially about one and onehalf to four times the diameter of the small work roll. The two work rolls are interposed between upper and lower intermediate rolls which, in turn, are interposed between upper and lower backing rolls. The upper intermediate roll is in frictional engagement with one of the work rolls and the lower intermediate roll is in frictional engagement with the other work roll while the upper backing and upper intermeditae rolls are in frictional engagement as are the lower intermediate and lower backing rolls.
The given position of the small work roll in the roll pass can be one at which the longitudinal axis of the small work roll is in vertical alignment with the longitudinal axes of the other rolls of the mill or it can be one at which the small work roll is bowed or deflected in a direction with or opposite to travel of metal through the mill. In this latter case, the longitudinal axis of the small work roll is not in vertical alignment with the longitudinal axes of the other rolls of the mill. Selection of the given position is dependent upon production of a desired shape in the rolled metal which in most cases is flat, and takes into consideration crown in the rolls due to the shape of the roll bodies and/ or to heat generated by reduction of the metal. During the course of rolling, the given position may be changed intentionally to obtain a desired shape in the metal or to maintain shape. This change in the given position may be required because of variations in conditions in the roll pass such as heat build-up in the roll body or bodies or because of variations in the metal itself, such as hard spots or off-gauge.
Driving force or torque for the small work results from frictional engagement with at least one backing roll or intermediate roll and from application of forward tension to the metal by a winding reel or another stand on the exit side thereof.
In recent years, there has developed an increasing demand for wide metal strip and sheet, particularly in the very thin gauges such as 0.001 to 0.008" with a special emphasis upon flatness. Although it is recognized that small diameter work rolls readily bite into the metal being rolled, reduce screw pressures and make reductions in gauge of the metal which cannot be made with larger diameter rolls, efforts to use such small diameter rolls, especially those which are too small to be driven through their necks (those with diameters 1" to 4") have been unsuccessful. This has resulted from inability to control the deflection of these rolls in the plane of metal travel through the mill as a consequence of which it has been highly difficult to obtain a specified degree of flatness in the strip or sheet. The uncontrolled deflection or bowing of the small diameter work roll causes over-rolled edges or ripples and/or over-rolled center portions or buckles in the strip. When this occurs in the thin gauges, it is costly and troublesome, if not impossible, to remove the buckles and riflles and off-gauge strip is produced, thereby rendering it unsatisfactory for specifications and orders.
Two factors can cause this deflection, the first being an unbalance of force acting upon the small work roll and the second being a combination of forces generated by the screwdown mechanism of the stand acting upon the top backing roll and of the tolerances in the bearings and chocks for the backing rolls, intermediate: rolls and the work roll. Considering first the deflection caused by the unbalance of forces acting upon the rolls, and referring to FIGURE 1 which shows diagrammatically a S-high mill, that mill comprises a top backing roll 1 and a bottom backing roll 2 with a top intermediate roll 3 and a lower intermediate roll 4 disposed therebetween. The top intermediate roll is in frictional engagement with the top backing roll, and the lower intermediate roll is in frictional engagement with the bottom backing roll with the backing rolls being driven by electric motors, not shown. However, the intermediate rolls can be driven instead of the backing rolls. Disposed between the two intermediate rolls is a small diameter work roll 5 in frictional engagement with the lower intermediate roll 4 and forming a roll pass with the top intermediate roll 3. Extending through the roll pass is metal strip 6.
A combination of two resulting forces rotates the work roll 5. The first resulting force acts on the top side of the roll and comprises a portion of strip delivery tension T and tangential force F generated by the top backing roll 1 acting upon the top intermediate roll 3 and extending transversely through the strip thickness to the top part of the work roll 5. The sum of these two forces tends to move the roll 5 towards the delivery side of the mill as shown by arrow 7.
The second resulting force acts on the lower side of the work roll 5 and comprises a tangential force F produced by rotation of the lower backing roll 2 in frictional engagement with the intermediate roll 4. The other component of this second resulting force is the entry tension T which, together with the tangential force F acts to move the work roll 5 towards the entry side of the mill as shown by arrow 8. Consequently, for equilibrium conditions corresponding to a servo lateral deflection and zero bearing loads on the rolls, the following condition exists: (T +F )=(T +F The second factor which causes the deflection results from a combination of forces generated by operation of a screwdown mechanism and of tolerances in the roll bearings and chocks. When the screwdown mechanism lowers the top backing roll and the top intermediate roll to establish a given roll pass to effect a particular reduction, the screwdown mechanism exerts a force On the rolls. This force, in combination with the tolerances between the roll necks, the bearings and/ or the chocks and tolerances in the mill housing, may cause the work roll to deflect in the direction with or opposite to travel of strip through the mill. Such deflection occurs because of the small amount of space between the bearings and the roll neck and between the chocks and the mill housings, thus enabling the roll necks and/or shocks to shift or move a small amount when subjected to the screwdown force.
Control over deflection of the small work roll to obtain a desired shape or flatness in the strip encounters further complications from a heat build-up in the rolls, especially during sustained rolling periods. This heat build-up cannot be completely dissipated by flood coolant and generally effects an expansion or swelling commonly called crown in a center portion of the small roll and/or in any other roll. Presence of the crown causes over-rolling of the center portion of the strip, thereby requiring compensation in the position of the small roll in the roll pass to minimize if not eliminate its effect upon the shape of the strip. Thus, regulation of deflection of the single small roll presents many problems which place severe requirements upon a control system therefor.
Full realization of advantages from use of the single small diameter work roll has been hampered by inability to very quickly effect a correction or compensation for deflection to maintain or return the roll at or to a given position in the roll pass. Since the metal is traveling through the mill at speeds from about 500 f.p.m. to about 6,000 f.p.m., a substantial amount of defectively-shaped strip can result where even a 24 second period is c0nsumed in returning the work roll to its given position. Production of defectively-shaped strip is unwanted for it must either be cut out of the coil or the coil diverted to another order, thereby materially increasing costs of manufacture.
My invention permits full utilization of the advantages of the small diameter work roll by maintenance of de flection of the roll at a given position in the roll pass and by ability to effect an extremely fast correction for deviations in deflection from the given position. Specifically, it comprises maintaining the deflection of a small diameter work roll substantially at a given position in the roll pass and/or controlling the amount of deflection of this work roll in the roll pass on a rolling mill which has at least one upper backing and at least one lower backing roll for the work roll. This deflection of the small work roll is in the direction substantially with and substantially opposite to travel of the metal through the mill. Each of the backing rolls has a diameter greater than the diameter of the small work roll and the rolls are disposed substantially vertically of one another. The work roll and one of the upper and lower backing rolls form a roll pass through which metal is reduced in thickness and another backing roll is in frictional engagement with the work roll. At least one electric motor is operatively connected to an upper backing roll and at least one electric motor is operatively connected to a lower backing roll. Maintenance and/or control of the deflection results from increasing and decreasing the amount of the deflection by effecting changes in apportionment of applied torque by the motors between the driven rolls through sensing amount and direction of deflection of the work roll from the given position. From this sensing, a signal related to the amount of deflection and related to the direction thereof is generated and then from the signal an error signal related to the difference between the sensed position of the work roll and the given position of the work roll and related to the direction of deflection is produced. Thereafter, the error signal is utilized in regulation of output torque of the electric motors for effecting the changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position. Preferably, the sensing of deflection of the small work roll includes sensing the rate of change of deflection and the signal is related to the rate of change of deflection. Further, the error signal is related to the rate of change of difference between the sensed position and the given position of the small work roll.
In one embodiment of my invention, a current related to the magnitude of the error signal and related to the direction of the error signal is produced from this error signal and then applied to the electric motors for effecting the changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position or to control the amount of deflection of the small work roll. The current which is produced from the error signal is applied preferably to the armatures of the electric motors to effect the changes in apportionment of applied torque, but it can alternatively be applied to the fields of the electric motors to effect the changes in apportionment. One such current which I have employed comprises a first part which is substantially continuous, is related in magnitude to the amount of the deflection and related to the direction of the deflection. This current also has a second part which is pulses of short duration related in magnitude to the amount of the deflection and related to the direction of deflection. The first part is a major portion of the current and requires a longer time interval to effect a change in apportionment of applied torque than the second part.
I prefer to effect these changes in apportionment of applied torque without substantially affecting the amount of total torque delivered to the driven rolls. Such is accomplished by increasing amount of applied torque to one of the driven rolls by increasing output torque of the motor or motors connected thereto, while simultaneously decreasing the amount of applied torque delivered to the other driven roll by decreasing output torque of its motor or motors. In this way, the small work roll is brought back from its deflected position towards the given position. In practice of my method, I can so carry out the sensing of deflection and utilization of the error signal that deflection of the small work roll is maintained within a range of substantially $00005" of the given position. A range of deflection of :0.005" and more can be used for some rollings. This range of deflection in which the small work roll is maintained is in part dependent upon the flatness of the strip, the width of the mill and the diameter of the small roll.
My invention also includes a method of rolling the strip in which a mill operator observes the shape of the strip as it issues from the mill and then, based upon his observation, he controls the amount of deflection of the small work roll to produce a desired shape. In controlling the amount of deflection he increases and/or decreases the amount of deflection of the small work roll through making changes in apportionment of the torque applied by the motors to the driven upper and lower rolls. Such changes in apportionment of the torque comprise increas ing or decreasing the amount of output torque of the motor or motors which rotate one driven roll relative to the amount of output torque of the motor or motors which turn the other driven roll through operation of controls for the motors.
While entry and delivery tension upon the metal strip have an affect upon deflection of the small work roll, I effect maintenance of deflection of this small work roll at the given position in the roll pass through control over the torque applied to the driven rolls of the mill and not through regulation of amounts of tension in the strip. From the standpoint of mill operation, it is preferable to independently regulate amounts of tension in the strip and not attempt to control deflection of the small work roll by changing amounts of tension applied to the metal strip. This is particularly true in rolling the very thin strip, some of which has low yield strengths, wherein it is important to closely maintain amounts of tension within allowable unit stress and thereby avoid strip breakage.
My invention in apparatus for maintaining deflection of the small diameter work roll substantially at a given position in the roll pass comprises a means for sensing amount and direction of the deflection with this sensing means disposed opposite a face of the roll so that deflection is toward and away therefrom. Connected to the sensing means is a signal generating means which produces from the deflection a signal related to the amount of deflection and related to direction of the deflection. Connected to the signal generating means is an error signal generating means which produces from the signal an error signal related to the difference between a sensed position of the small work roll and the given position of this small work roll, and is related to the direction of the deflection. An error signal transmitting means is joined to the error signal generating means and connected to one of the electric motors which are drivingly connected to rolls of the mill and of means coupled to the electric motors for regulating output torque of these motors to effect changes in apportionment of applied torque to the driven rolls to maintain the small work roll substantially at the given position.
Preferably, the signal generating means is such that the signal is also related to rate of change of deflection of the small work roll and the error signal generating means is such that the error signal is also related to rate of change of deflection of this small work roll.
In one embodiment of the apparatus, the error signal generating means is connected to a current producing means and utilizes the error signal to generate a current related to the magnitude of the error signal and related to its direction. This current is then transmitted to the electric motors for regulating their operation to control output torque and thereby effect the changes in apportionment of applied torque to the driven rolls. This current is applied, preferably, to the armatures of the electric motors, but can also be applied to the fields of these electric motors.
The means coupled to the electric motors for regulating their output torque includes a controllable variable load producing device which regulates output torque of the electric motors, in connected to the error signal generating means, and is responsive to the error signal for effecting the changes in apportionment of applied torque. Examples of the controllable variable load producing device include electrically operated friction brakes which are disposed in engagement with the output shaft of the electric motors and which include an eddy current absorption dynamometer with a DC. excitation winding regulated by the error signal or a current produced therefrom in push-pull manner with no resultant mill speed change or with a non-overlapping individualload control; gener ators which are coupled to the motors, whose output is dissipated as heat through load resistors: and whose field is regulated the same as the above dynamometer; generators which are coupled to the electric motors from which power is recovered, and whose fields are controlled the same as the above dynamometer; and hydraulic load devices which work upon the output shafts of the electric motors. All of these devices are responsive to the error signal for effecting the changes in apportionment of the applied torque.
The small work rolls to which my invention is especially directed may have diameters ranging from about A" to about 8.
In the accompanying drawings, I have shown preferred embodiments of my invention, in which:
FIGURE 1 shows diagrammatically a 5-high mill;
FIGURE 2 is a schematic view of one device for detecting deflection of the single small roll of a S-high mill;
FIGURE 3 is a schematic view of a second sensing device;
FIGURE 4 is a schematic view of a third sensing device;
FIGURE 5 is a schematic view of a fourth sensing devlce;
FIGURE 6 is a schematic view of a fifth sensing device;
FIGURE 7 is a schematic view of a sixth sensing device;
FIGURE 8 is a schematic diagram showing my invention applied to a Z-stand, S-high tandem mill;
FIGURE 9 is a block-diagram of apparatus for generating the error signal which is used to maintain deflection of the roll at a given position;
FIGURE 10 is a schematic wiring diagram of one embodiment of a slow acting regulating system and a fast acting regulating system which receives the error signal and generates therefrom a reversible push-pull continuous current and reversible push-pull pulses of current for producing the regulated buck-boost output armature current;
FIGURE 11 is a schematic wiring diagram showing a first modification of the embodiment of FIGURE 10;
FIGURE 12 is a schematic wiring diagram of a second modification of the embodiment of 'FIGURE 10;
FIGURE 13 is a schematic wiring diagram of a second fast regulating system for the embodiment of FIGURE 10;
FIGURE 14 is a schematic wiring diagram of a third fast regulating system for the embodiment of FIGURE 10:
FIGURE 15 is a schematic wiring diagram of a third modification of the embodiment of FIGURE 10;
'FIGtURE 16 is a schematic wiring diagram of a fourth modification of the embodiment of FIGURE 10;
FIGURE 17 is a schematic wiring diagram of a system which receives the error signal and generates therefrom a current which is delivered to the armatures of the electric motors which are drivingly connected to rolls of the mill for effecting changes in apportionment of applied torque to the driven rolls;
FIGURE 18 is a block diagram similar to that of FIG- URE 9, but adapted to the system of FIGURE 17;
FIGURE 19 is a schematic wiring diagram of a system which receives the error signal and generates therefrom a current which is delivered to the fields of the electric motors which are drivingly connected to rolls of the mill;
FIGURE 20 is a schematic diagram of a G-high mill equipped with my invention; and
FIGURE 21 is a schematic diagram of a drive for a rolling mill with changes in apportionment of applied torque to the driven rolls of the mill effected through electrically operated friction brakes connected to driven spindles which are joined to the driven rolls.
Referring to FIGURES 2, 9 and 10, the S-high mill of FIGURE 1 mounts apparatus 9 for detecting deflection of the single small diameter 'WOIk roll in a roll pass formed by the upper intermediate roll 3 and the small diameter roll itself. As shown, the lower backing roll 2 is driven by two motors 10 and 11 connected in tandem with motor 10 being shown in FIGURE 2, and the top backing roll is driven by two motors 12 and 13 connected in tandem. The upper intermediate roll 3 is in frictional engagement with the upper backing roll 1 and the lower intermediate roll 4 is in frictional engagement with the lower backing roll 2. Although I have shown the roll drive connected to the backing rolls, it may alternatively be joined to the intermediate rolls, one of which also functions as a backing roll for the work roll 5.
Connected to the sensing apparatus 9 is a signal gen-' erator 14 which produces from deflection of the roll 5 a signal related in magnitude and related to direction of the deflection. This signal travels to a push-pull output amplifier 15 (FIGURE 9) where a first portion continues to a push-pull driver amplifier 16 whose output is delivered to a slow acting regulating system 17 (FIGURE 10) and a second portion advances to a bias and trigger generator combination 19 whose output is transmitted to a fast action regulating system 19. The slow regulating system produces a reversible push-pull substantially continuous current and the fast regulating system generates reversible push-pull pulses of current of short duration. These two currents are fed to a buck-boost generator 20 whose output is applied to the armatures of the motors for driving the backing rolls 1 and 2. By boosting the armature current of one roll drive motor combination and bucking the armature current of the other roll drive motor combination, 1 effect a change in apportionment of torque applied to the driven rolls 1 and 2 to maintain the roll 5 at or return it to a given position in the roll pass.
Considering the sensing apparatus of FIGURE 2, nozzles 21 and 21a connected to conduits 22 and 22a leading from a source of fluid under pressure such as air or liquid straddle both sides of the roll 5, are substantially opposite the face 24 of the roll 5, and are substantially in alignment with the center line of the roll and substantially midway between the ends of the face 24 thereof so that deflection of the roll 5 in the direction with or opposite to strip travel through the roll pass is toward one nozzle and simultaneously away from the other nozzle. Safety bars 25 and 25a mount and position the nozzles opposite the roll face.
These nozzles are located close to the roll face across gaps 26 and 26a between the ends of the nozzles and the roll face so that deflection of the roll '5 produces a change in pressure of the fluid under pressure in the conduits. Preferably, the length of the gaps between the nozzle and the roll face is from about 0.005 to about 0.050" when the roll and its intermediate and backing rolls are in axial alignment as shown in FIGURE 1.
Within the range of deflection of the roll 5, impingement of two jets of air or fluid against the roll face produces back pressure in the conduits 22 and 22a with this back pressure being less when the roll is deflected away from one nozzle to lengthen the gap and greater when the deflection is toward the nozzle to shorten the gap. When the rolls 5, 1, 2, 3 and 4 are in axial alignment, impingement of the two jets against the roll face produces equal amounts of back pressure in the conduits 22 and 22a. The back pressure affects the pressure of air or fluid forming the jet and as the gap shortens, the back pressure increases and as the gap lengthens, it decreases. Accordingly, as the work roll 5 deflects toward the nozzle 26, back pressure in the conduit 22 increases, thereby reducing the strength of the jet from the nozzle 26 and increasing pressure in the conduit 22. Simultaneously, the roll 5 deflects away from the nozzle 26a and decreases back pressure in conduit 22a accompanied by an increase in pressure of the jet from the nozzle 26:: and a decrease in pressure in the conduit 22a. This change in strengths of the jets and the changes in pressures in the conduits are used for detection of roll deflection and the magnitude of the changes are related to the amount of deflection and the direction of change dependent upon an increase or decrease in pressure.
To convert changes in fluid pressure in the conduits into a signal for controlling operation of the mill, the conduits are connected to a signal generator 14 comprising a transducer 27 and a linear variable differential transformer (LVDT) 28 whose output is transmitted to an amplifier 29. The operation of this transducer 27 and the linear variable differential transformer is described in my Patent No. 3,077,800.
FIGURES 3 and 4 show two other types of roll deflection sensing devices which utilize electromagnetic induction to induce eddy currents in the surface of the roll 5 where high frequencies such as 50 kilocycles and higher are used, or to effect changes in the inductive reactance in one or two electromagnetic inductors which changes correspond to shortening and lengthening of gaps between the inductors and the roll face. As shown in FIGURE 3, I locate two electromagnetic inductors 45 and 46, one on each side of the small roll 5 and connect each inductor into a bridge circuit 46a in which each inductor forms one arm of the reactance bridge. The other two arms of the bridge are resistors 45a and 45b of selected values. The two corners of the bridge formed by the junctions of the two resistors and the two inductors are connected to a high frequency source 47a of alternating current as provided by the driver oscillator 75. The other two corners of the bridge formed by the junctions of resistor 45a and inductor 45 and of resistor 45b and inductor 46 are the outputs of the reactance bridge and are connected to the amplifier 29. The reactance bridge circuit has a null balance RC network comprising a variable capacitor 450 and a variable resistor 45d connected in parallel and across one input corner 45e and one output corner 45].
As to each inductor, changes in reactance as a result of roll deflection are nonlinear. However, the two in combination, when disposed in the reactance bridge circuitry, will produce a substantially linear output as a function of roll deflection.
Each inductor is spaced apart from the roll 5 to provide small gaps 48 and 49 between the roll face and the leading face of each inductor, and each inductor generates magnetic lines of flux which travel from the inductor across the gaps to the roll face. It has been found that a gap between the roll face and the leading face of the inductor of about 0.005 to about 0.025" effects satisfactory detection of roll deflection.
For practical purposes, it is better to move the roll against one inductor and null-balance the bridge. The output voltage of the bridge will then be a function of the roll displacement away from that coil and will rise to a maximum value when the roll is against the opposite coil. At a midway gap point, the output voltage will then be substantially one-half of its maximum value which is conducive to good detection and regulating techniques as it can now be matched against an equal reference voltage. Any deviation from this reference is detected by a difference amplifier 78 (FIGURE 9) which can now be further fed into the proper functional circuitry of a regulating system to restore balance.
The single inductor 51a of FIGURE 4 operates similarly to those of FIGURE 3 except that its output is nonlinear and it requires additional compensation circuitry for the non-linearity output. In this regard, a reactance bridge circuit 51b, similar to circuit 46a, would have a variable inductance for one arm and a proper valued resistor associated with the variable inductance as another arm. The other half of the bridge comprises the inductor 51a and the resistor 45]).
The roll deflection sensing devices of FIGURES 3 and 4 are described more fully in my Patent No. 3,077,800.
FIGURES 5 and 6 show two additional devices for detection of roll deflection which use changes in reluctance of the magnetic circuit which bridges one or two small gaps to detect the deflection. As shown in FIGURE 5, two transformers 54 and 55 are located on each side of the single small diameter roll 5 and the primary winding of each transformer is connected to a source of A.C. power 47, as provided by an oscillator such as oscillator 75 of FIGURE 9. Transformer 54 has a primary winding 56 and a secondary winding 57 and transformer 55 has a primary winding 58 and a secondary winding 59. Each transformer is spaced apart from the work roll 5 to form the small gaps 60 and 61 between the roll face and each transformer and each primary winding directs magnetic flux linkages to the roll 5 across the gaps and to its secondary winding. It has been found that a gap between the roll face and the transformer of about 0.005" to about 0.025" effects satisfactory detection of roll deflection. The two primary windings are connected series aiding and the two secondary windings are connected in series bucking.
Connected to the two secondary windings 57 and 59 is an amplifier 50 so that output voltage of the two secondary coils travels thereto for production of a signal.
Because the two secondary windings are connected series bucking, the two output voltages in the secondary circuit are opposite in phase and the net output of the two transformers is the difference between the two output voltages.
This net output voltage is related in amount to the magnitude of the deflection and is directional in accordance with the direction of deflect-ion. An amplifier 50 generates from this net output voltage a signal which is related to the amount of deflection and which has characteristics of direction of deflection.
FIGURE 6 shows a single transformer 62 positioned on one side of the single small diameter work roll 5 for detection of roll deflection. In using the single transformer, its voltage output to the amplifier 50 when there is no deflection of the roll and the roll is in the given position in the roll pass is matched with a standard voltage in the amplifier. When there is roll deflection towards or away from the transformer, there is a resulting increase or decrease in the voltage output of the transformer, thereby causing the amplifier to generate a signal of the same character as the signal produced when using two transformers.
FIGURE 7 shows another device for detection of roll bar 72 on the other side of the roll 5 is a second bar 73 parallel thereto and having on its side opposite the other face of the roll 5 a cushion 74 made from a material which does not mark or mar the surface of the roll 5 should it contact same in deflection. This other bar assists to maintain the roll 5 within a given range of deflection so that should there be excessive deflection, the small roll will not break or fracture.
The roll deflection sensing devices disclosed herein have ability to detect very small amounts of roll reflection suhh as 0.0001 from which a signal is produced for maintenance of the roll substantially at a given position in the roll pass. Additionally, these devices are such that use of a flood coolant on the mill does not affect their operation or reduce their ability to detect small amount of deflection.
Referring to FIGURE 9, the linear variable differential transformer '28 has connected thereto an. oscillator 75 which supplies AC. power of high frequency therefor. The signal output of this linear variable differential transformer advances to an. amplifier 29 where it is amplified and forwarded to a phase detector 76. This detector rectifies the A.C. roll position signal to provide a DC. voltage related to the displacement of the roll from its given position in the roll pass with a polarity indicating the direction of the displacement.
A roll position selector 77a produces an adjustable reference DC. voltage so that a position at which the roll is maintained can be selected by a mill operator. This reference DC. voltage along with the output of the phase detector 76 is fed to a difference amplifier 78. which provides an output voltage or error signal related to the difference between the actual roll position and the desired position chosen on the selector 77a. The
output voltage signal from the amplifier 78 is related in magnitude to the amount of deflection and is related to deflection which comprises a tube 63 for delivering a fluid such as oil against the face of the roll 5 from a source of oil entering the tube through a flexible pipe 64. A
nozzle 65 of the tube is opposite the face of the roll 51 and separated therefrom by a film of oil. The pressure of the oil issuing from the nozzle 65 in combination with the pressure of a spring 69a, to be described hereinafter, may be such that the nozzle backs away from the roll 0.0001" to about 0.001. Accordingly, the nozzle rides this film of oil and avoids a metal-to-metal contact with the roll to eliminate marking the roll face. The rear end 66 of the tube 63 engages an upper portion 67 of a pivoted arm 68 maintained in its neutral position corresponding to zero deflection of the roll from its given position in the roll pass by a spring actuated plunger 69 in contact with an upper portion of the arm. The lower end 70 of the arm 68 engages one end of a rod 71 which carries a magnetic core (not shown) corresponding to core 39. This core is disposed in a linear variable differential transformer 28a identical to the transformer 28. Consequently, defiection of the roll toward and away fro-m the nozzle 65 operates the linear variable transformer 28a in the same manner as transformer 28 to detect deflection of the roll.-
A bar 72 extending substantially parallel to the longitudinal axis of the roll 5 carries. the tube 63. Opposite the the direction of deflection.
The push-pull output amplifier 15 receives the output DC. voltage signal from the difference amplifier 78 and provides sufficient power to drive two separate push-pull circuits which deliver portions of the output voltage signal of the amplifier 78 to the fast acting regulation system 19 (FIGURE 10) and the slow acting regulation system 17. A first portion of the output of this push-pull amplifier '15 is transmitted to one separate. push-pull circuit 79' comprising arate generator 80 and. an attenuator 81 connected in parallel with a frequency compensation network 82 and a second attenuator 83. This first portion, like the output voltage signal of the amplifier 78, has a magnitude related to the amount of deflection and is related to the direction of deflection. The rate generator 80 is a differentiating circuit that gives an output signal related to the velocity of the deflection.
The frequency compensation network 82 controls the higher frequency phase of the circuit and amplitude response of feedback circuits to be described hereinafter.
V The attenuators 8'1 and 83 control the gain of a feedback loop and the amount of dam'pening.
The output of this parallel circuitry advances to an adder 84 which combines the roll position error signal of the compensation network 82 and the rate signal of the rate generator 80 in the proper phases to produce an output error signal. This sign-a1 is fed to the slow regulation system 17 through the push-pull driver amplifier 16, which is in circuit with two control fields 85 and 86 of a rotating amplifier 87 (FIGURE 10), such as Amplidyne, Rototrol, Regulex regulators.
A second portion of the output of the -push-pull amplifier is transmitted to a second separate push-pull circuit 88 identical to that circuit 79 comprising the rate generator 80, frequency compensation network 82, the two attenuators 81 and 83 and the adder 84. From the circuit 88, the resulting output error signal is transmitted to the bias and trigger generator 18 connected to thyra- 11 trons which are a part of the fast acting regulating system 19.
The reference voltage produced by the roll position selector 77 is carefully regulated so that it does not fluctuate with line voltage, load or temperature changes. This reference voltage is derived from a calibrated roll position setting potentiometer located on the mill and convenient for the operator to select a given position. This reference voltage is then used to preselect the performance level required of the regulated quantity which is a current difference corresponding to torque differentials in the mill motor armatures.
Maintenance of the small roll in the given position requires that overall performance of the regulating system consisting of the fast and slow systems prevent overor undershooting which can bring about oscillations of various frequencies in the roll. In this regard, various time constants of various elements of the mill, both electrical and mechanical, which add up to an overall time constant, must be taken into consideration and each individual time constant reckoned with in designing the regulating system to prevent oscillation.
It has been found that time constants in the various components of the electrical system can be varied within reason by changes in L/R ratios of each circuit. In this connection, the L/R ratio can be shortened by increasing R through addition of external resistors which, of course, effect power losses and require an increase in size or capacity of components in the circuits.
The given position referred to in this application includes a small band of movement such as plus-minus 0.0005, and on wide mills, may be plus minus 0.005. Within this small band of movement, I achieve regulation of deflection of the roll so that the deflection does not exceed on either side of a given line substantially parallel to the longitudinal axis of the rolls, the ranges set forth.
Inorder to achieve very fast and careful regulation of deflection of the roll, it is mandatory that the upper and lower driven mill rolls have separate motors to permit effecting a change in apportionment of the torque applied by the motors to the driven rolls, and preferably effecting the change in apportionment of the torque between the two roll drives without affecting the total amount of torque imparted to the rolls themselves. It is further preferable that the change in apportionment be made without affecting the main generators current output. The foregoing roll drive, in combination with my dual regulating system, achieves correction for roll deflection in intervals such as 4 to 17 or 20 milliseconds.
Referring to FIGURE 10, a main generator 89, driven by an AC. motor 90, is connected to the mill motors 10, L1, 12 and 13 with mill motors 12 and '13 driving the top backing roll 1 and connected in parallel, and mill motors and 11 driving the lower back-ing roll 2 and connected in parallel. Mill motor 10 is in series electrically with mill motor 12, as is mill motor 11 in series electrically with mill motor 13, and motors 11 and 12 are connected to one side of the generator 89 and motors 10 and 13 are connected to the other side of this generator.
Connected across natural neutral points 91 and 92 on line 93 in the mill motors power circuits is the buckboost generator 20 driven by its AC. motor 94.
The buck-boost generator has a main field 95 connected to the Amplidyne regulator 87 of the slow acting regulation system 17, and a fast field 96 is in circuit with the fast acting regulating system 19. The fast field is a relatively few-turn coil of heavy wire for current input from two back-to-back connected bridge rectifiers 97 and 98 so that the output from the bridges is transformed to field flux which adds to or subtracts from the flux of the main field 95. On the other hand, the main field 95 is a relatively high impedance winding having more turns per coil of small size wire.
Since the buck-boost generator experiences rapid changes in field flux, its field frame is preferably a laminated construction of good grade electrical sheet for fast response and low hysteresis and eddy current losses.
Through addition to or subtraction from the field flux of the main field and the fast field 96 of the buckboost generator 20 by operation of the fast and slow systems 17 and 19, I produce a steep rise or fall in induced voltage of the armature 99 of the generator 20 and provide a corresponding steep rise or fall buck-boost output armature current. Accordingly, the armature current of the generator 20 flows in either direction in line 93, as indicated by arrows 100 and 101 (FIGURE 10) and increases the armature current in the upper roll drive motors in direction 100, while simultaneously decreasing armature current in the lower roll drive motors. This effects a change in the apportionment of torque delivered by the two roll drives and thereby moves the small work roll towards the given position or maintains same thereat. Of course, flow of the armature current of the booster in the direction of arrows 101 has the opposite effect as to increasing armature current in the bottom roll drive and decreasing it in the top roll drive. Thus, the total amount of torque imparted to the driven rolls remain substantially the same but the amount of torque delivered to one driven roll relative to the other driven roll is affected whereby correction for deflection and maintenance of the roll substantially at the given position is achieved.
' Forcing the fields 95 and 96 of the buck-boost generator 20 with higher than normal field supply voltage from the slow acting regulation system 17 and the fast acting regulation system 19 produces a fast response from the generator 20. Additionally, an external resistor 102 in series with the generator armature 99 reduces the time constant of the regulated power circuit, including the mill motors 10, 11, 12 and 13 by reducing the L/R ratio. However, use of this resistor is not essential.
Considering the slow acting regulation system 17, the Amplidyne regulator 87 is driven by the AC. motor 94a and has the two matched high impedance control fields 85 and 86 connected to the driver amplifier 16. One fields connection is reversed as to the other so that when each receives an equal amount of DC. output voltage from the amplifier 16, the resultant magnetic field fiux is zero for one cancels the other.
The driver amplifier 16 (FIGURE 9) includes circuits which affect its time-rate output such as gain, rate feedback, bias and adjustable time constants, and additionally, has two output push-pull circuits which receive the push-pull signal from the adder 84. When the push-pull signal is received by the driver amplifier 16, one output voltage is raised an amount equal to that that the other output voltage is lowered. Which output circuit has its voltage raised is dependent upon the direction of deflection of the roll 5, and the amount of raise and of reductiofii is dependent upon the amount of deflection of the ro Application of this DC. output voltage from the driver amplifier causes one control field 85 or 86 to drive to a higher excitation level, while the other control field is driven to a lower excitation level to effect a net ampere turn current in one direction or the other to induce a voltage in the armature of the Amplidyne. Arrows 103 and 104 indicate the direction of voltage induced in the armature 105 of the Amplidyne 87 by control fields 85 and 86. Accordingly, the armature 105 of the Amplidyne delivers a variable and directional excitation current to the main field 95 of the buck-boost generator 20 which current must have reversible polarity to effect maintenance of the roll 5 in the given position.
A negative feedback for the armature 105 of the Amplidyne comprises a differential field 106 connected across the armature 105 and a network of back-to-back connected zener diodes 107 and 108. This negative feedback improves transient performance and stability of the Am-
US457104A 1962-11-21 1965-05-19 Method and apparatus for rolling metal strip and sheet Expired - Lifetime US3375688A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868839A (en) * 1972-12-29 1975-03-04 Aerospatiale Shaping machine with servo-assisted forming tool
US4059794A (en) * 1974-07-15 1977-11-22 British Steel Corporation Method and apparatus for monitoring pass alignment in rolling mills
US4116028A (en) * 1976-11-02 1978-09-26 Sumitomo Metal Industries, Ltd. Rolling mill

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US2601792A (en) * 1946-07-27 1952-07-01 Frank P Dahlstrom Apparatus for rolling strip material
US2651954A (en) * 1949-09-27 1953-09-15 Frank P Dahlstrom Method of and means for rolling strip material
US3018676A (en) * 1956-12-31 1962-01-30 Natalis H Polakowski Apparatus for rolling strip metal
US3077800A (en) * 1958-05-09 1963-02-19 Youngstown Res And Dev Company Apparatus and method for detecting and compensating for roll deflection on a rollingmill
US3124020A (en) * 1964-03-10 Methods of and apparatus for controlling rolling mills

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3124020A (en) * 1964-03-10 Methods of and apparatus for controlling rolling mills
US2601792A (en) * 1946-07-27 1952-07-01 Frank P Dahlstrom Apparatus for rolling strip material
US2651954A (en) * 1949-09-27 1953-09-15 Frank P Dahlstrom Method of and means for rolling strip material
US3018676A (en) * 1956-12-31 1962-01-30 Natalis H Polakowski Apparatus for rolling strip metal
US3077800A (en) * 1958-05-09 1963-02-19 Youngstown Res And Dev Company Apparatus and method for detecting and compensating for roll deflection on a rollingmill

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3868839A (en) * 1972-12-29 1975-03-04 Aerospatiale Shaping machine with servo-assisted forming tool
US4059794A (en) * 1974-07-15 1977-11-22 British Steel Corporation Method and apparatus for monitoring pass alignment in rolling mills
US4116028A (en) * 1976-11-02 1978-09-26 Sumitomo Metal Industries, Ltd. Rolling mill

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