US3545239A

US3545239A - Method and apparatus for controlling flatness of rolled strip

Info

Publication number: US3545239A
Application number: US764560A
Authority: US
Inventors: George E Kennedy
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1968-10-02
Filing date: 1968-10-02
Publication date: 1970-12-08
Anticipated expiration: 1987-12-08

Description

Dec. 8,1970 6.15. KENNEDY f 3,

METHOD AND APPARATUS FOR c on'r ao mme FLATNESS oFRoLLnD sum? FiledOci. 2,1968 2Shee ts-Sheet1 mm UL 1c PUMP flrbmuuc pan TROL$ 8 VIBRATION V CONTROLLER INVENTOR. 65006; E. KENNEDY A 'f forney Trans 'T' 2 mp 1 mr ducer 25 6 3 3 0 28 Dec. 8,1970 a. E. KE DY 3,545,239 METHOD AND APPARATUS FOR cox'rnopnnx e OFROLLEDSTRI'P Filed 0630.2, 1968 BSheets-Sheet 2 can fro! IN VE/V TOR.

}' I GEOI KG EEKENNED Attorney] United States Patent 3,545,239 METHOD AND APPARATUS FOR CONTROLLING FLATNESS OF ROLLED STRIP George E. Kennedy, Churchill Borough, Pa., assignor to United States Steel Corporation, a corporation of Delaware Filed Oct. 2, 1968, Ser. No. 764,560 Int. Cl. B21b 37/00 US. Cl. 72-10 7 Claims ABSTRACT OF THE DISCLOSURE Apparatus for automatically controlling hydraulically actuated adjustable roll contour mechanism in strip rolling mills including a vibration transducer mounted on the rolling mill and operable by vibrations due to undulations in the rolled strip, means for rectifying the signal, and null seeking means for receiving the vibration signal as input and driving the hydraulicactuator to vary the adjustable roll contour mechanism toward a minimum vibration State. A method of controlling the flatness in rolling steel products in an adjustable roll contour rolling mill includ ing the steps of obtaining a signal proportional to vibrations due to undulations in the product, and adjusting the contour of the roll to reduce the signal so as to obtain minimum undulation in the product.

This invention relates to a method and apparatus for producing flat products in a mill having a pair of adjustable contour work rolls, and particularly to the production of hot or cold rolled steel strip.

In order to produce flat strip, the roll pass must be so shaped that undulations do not occur in the strip. This is most often done by crowning at least one of the rolls so as to obtain the proper work roll contour. Improper crown results in undulations of various types in the strip. In general, excessive crown produces center buckling and insufficient crown produces edge wrinkles. The crown required to produce a flat product, i.e., one without wrinkles or buckles, varies with the amount of reduction, amount of tension, rolling speed, and thermal expansion of the rolls which may vary during the rolling operation. Thus, it is often necessary to vary the contour of the work rolls during the rolilng of any one coil of strip. For this reason, various adjustable roll contour mechanisms have been provided on both hot and cold rolling mills. Fox

Pat. No. 3,024,679 dated Mar. 13, 1962, discloses one type of rolling mill with which my invention may be used. The present practice is for the operator to manually change the contour when he visually recognizes undulations in the rolled product. This practice has two disadvantages. First, the corrections are not always made, either because the operator has not noticed the undulations or because the rolled product has been unobserved when the undulations are present. Secondly, there is an inherent time lag between the observations of the undulations and making the change in roll contour. I have found that undulations in the strip produce vibrations in the rolling mill, such as in the mill housing, in the exit idler housing and bearing, and subsequent roll stands and that these undulation vibrations can be isolated from extraneous vibrations and detected to provide a signal indicating that undulations are present.

It is therefore an object of my invention to provide apparatus for detecting undulations in an elongated flat product being rolled.

Another object is to provide apparatus for automatically changing the contour of work rolls to reduce or eliminate undulations in an elongated flat product being rolled.

3,545,239 Patented Dec. 8, 1970 A further object is to provide a method of controlling the flatness in an elongated flat product being reduced by passing through adjustable contour work rolls which method is more accurate and reliable than former methods.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIG. 1 is a schematic view of a conventional rolling mill with which my invention may be used;

FIG. 2 is a schematic transverse view of the roll stand of FIG. 1 with my control system also being schematically shown;

FIG. 3 is a schematic view of the control circuit of my invention; and

FIG. 3A is a view showing the relay coils and their contacts as positioned in the circuit of FIG. 3.

Referring more particularly to FIGS. 1 and 2 of the drawings, reference numeral 1 indicates a rolling mill housing which supports

chocks

2, 2L, 3 and 3L. An upper back-up roll 4 is journaled in chocks 2, lower back-up roll 4L in chocks 2L, upper work roll 5 in chocks 3, and lower work roll 5L in chocks 3L. Screw downs 6 determine the roll gap as the strip S passes between the work rolls. Hydraulic actuators 7 between

chocks

2 and 3 and between

chocks

2L and 3L are connected to hydraulic pressure controls 8 which are supplied with fluid by hydraulic pump 9 so as to adjust the contour of the work rolls. The controls 8 include a valve 8V which is operated by a reversible motor 8M (FIG. 3). The parts so far described are conventional as shown by the above mentioned Fox patent. Strip S from a coil mounted on an uncoiler 10 passes over an idler roll 11 supported in bearings 11B which are mounted in a housing 11H. The strip then passes through the

work rolls

5, 5L, over an exit idler roll 12 which is supported in bearings 12B mounted in housing 12H, and then to coiler 13. This equipment is conventional and more than one roll stand may be provided also in a conventional manner.

According to my invention I attach a vibration pickup element 14 to any member of the mill which is subject to vibration due to the strip being rolled. This may be the chock 3L as shown in FIG. 2, an exit idler roll hearing or housing, or any subsequent element in the line, such as the next roll stand. The element 14 is preferably a vibration pick-up and analyzer, Model 314, manufactured by the International Research and Development Corporation, Worthington, Ohio, which generates an electrical signal proportional to the frequency and amplitude of the vibrationsand supplies the signal to a vibration controller 16 described in detail below. The vibration controller 16 is also electrically connected to hydraulic pressure controls 8, being a conventional type pressure regulator controlled either by a direct motor 8M, drive as shown in the preferred embodiment or through I a motor driven recorder with a retransmitting slidewire which regulates the voltage on a solenoid valve.

The function of the controller 16 is to seek the direction of a null of the induced vibration and to generate a signal to be sent to the hydraulic pressure controls 8. This signal to controls 8 initiates actuation of cylinder 7 adjusting the roll contour on such a manner as to minimize the induced vibration in the strip S and the mill. The vibration control 16 performs a continuing function to terminate the correction signal when the induced vibration reaches a minimum.

The vibration controller 16, as shown in FIG. 3, includes an energizing circuit 17 having an amplifier 18 connected to a full wave rectifier 20. Connected to the output terminals of rectifier 20 through a bistable amplifier 22 is relay coil 24 of a relay having normally closed contact 24C and normally open contact 24C1. In parallel with amplifier 22 is a transformer 26. Connected across transformer secondary 265 is a bistable amplifier 28 in series with a blocking diode 30. Amplifier 28 energizes relay coil 32 having normally closed contacts 32C and 32C1 and normally open contact 32C2.

Also, a part of the controller 16 is null measuring circuit 34 powered by D-C voltage source L1-L2. A reset switch 36 is connected to power source Ll-LZ in parallel with normally open relay contact 38C and in series with switch 40, normally open relay contact 42C (operated by relay coil 42) and relay coil 38 (having normally open contacts 38C and 38C1). Relay coil 42 is connected across power source L1-L2 in series with normally closed

relay contacts

44C and 46C (operated by coils 44 and 46, respectively). Connected across power source L1-L2 in series with normally open contact 38C1 are several parallel circuits: normally closed contact 48C (operated by coil 48) in series with time delay relay coil 50 (having a normally closed contact 50C); contact 24C in series with time delay relay coil 54 (having normally closed contact 54C); contact 32C in parallel with normally closed contact 58C and in series with time delay relay coil 60 (having normally open contact 60C and normally closed contact 60C1); contact 32C1 in parallel with normally closed contact 64C and in series with time delay relay coil 66 (having normally open contact 66C and normally closed contact 66C1). Connected across power socure L1-L2 in series with contacts 3801 and 50C are several parallel circuits: contact 24C1 in series with two parallel branches, the first including contacts 64C1 and 60C1 and coil 58 (having normally closed contacts 58C and 58C1 and normally open contacts 58C2 and 58C3) and the second including contacts 54C, 58C1, 66C and relay coil 64 (having normally closed contacts 64C and MCI and normally open contacts 64C2 and 64C3); contact 32C2, which is in series with energizing coil 46 (having normally closed contacts 46C and normally open contacts 46C1) and contacts C1 and 60C1 which are connected in paralel, and also in series with relay coil 44 (having normally closed contact 44C and normally open contact MCI) and contacts MCI and 66C1 which are connected in parallel; contact 64C2 in series with hydraulic puressure controls terminal SR and contact 5852; and contact 58C3 in series with hydraulic pressure controls terminal 8R1 and contact 64C3. Reversible motor SM is connected between terminals SR and 8R1.

Providing mill load information to null measurement circuit 34 are load cell 72 connected to back-up roll 4, amplifier 74 and relay coil 48 having a normally closed contact 48C.

In basic operation, the automatic change of contour of the work rolls and SL is accomplished by varying the hydraulic pressure to the actuating cylinder 7, which through back-up

rolls

4 and 4L controls the work rolls 5 and SL. The change in hydraulic pressure is accomplished through the hydraulic pressure controls 8 which are driven by the null-measuring circuit 34. The circuit 34 supplies an operating voltage to the hydraulic controls 8 through contacts 58C2 and 58C3 to cause motor 8M to move valve 8V toward a closed position so as to lower the hydraulic pressure, or through contacts 64C2 and 64C3 to cause motor 8M to open valve 8V so as to raise the hydraulic pressure to the actuating cylinder 7. It is to be noted at this point that in the control system both sets of

contacts

58C and 64C cannot be closed at the same time. In order that any existing pressure may be maintained thus maintaining the existing contour of the rolls, the circuit 34 provides a zero-voltage function wherein there is no supply voltage to the hydraulic controls 8 and therefore they are unresponsive to change the system hydraulic pressure.

The vibration control system is energized by means of the reset switch 36 and may be deenergized at any time by means of the off switch 40. When strip S enters the work rolls, the load cell 72, operating through amplifier 74, energizes relay coil 48 to open contact 48C so as to deenergize relay coil 50,, which after a time delay closes contact 50C to energize the null-measuring system 34 for the hydraulic pressure controls 8. The time delay of relay 50 in included in the system so that mill conditions may stabilize before activating the roll-bending control system. When vibrations occur because of undulations in the strip, a vibration signal is produced by vibration pickup 14 and the signal is amplified and rectified to D-C through the full-wave rectifier 20. Thus, vibration provides a signal to turn on bi-stable amplifier 22 and energize relay coil 24. Energization of coil 24 closes contact 24C1 so as to energize relay coil 58 which will close its contacts 58C2 and 58C3 to lower the hydraulic pressure. The circuits are designed so that initial action of the controls 8 will lower the hydraulic pressure to the cylinder 7; that is, relay 58 will be energized before relay 64. This is accomplished by means of relay 54. When relay 24 is energized, indicating the need for regulator action, relay 54 is deenergized, but contact 54C will not close until the time delay has elapsed, thus preventing energization of relay 64.

Bi-stable amplifier 28 senses any increase in vibration through the transformer 26 and diode 30. Diode 30 prevents the sensing of a decrease in vibration. If relay 58 is energized and an increase in vibration has caused relay 32 to be energized, relay 60 will be deenergized and after a time delay will deenergize relay 58 and at the same time energize and seal in relay 46 through contact 46C1. Closing of contact 58C1 will energize relay 64 to increase rollbending pressure. If vibration continues to increase after this reversal of the pressure-regulator action, relay 66, after a time delay, will be deenergized and contact 66C will open and contact 66C1 will close. Closing of contact 66C1 will energize relay 44, and open contact 44C which will deenergize relay 42 which, after a time delay will open contact 42C and denergize the control system 34. The control system must be reactivated through the reset switch 36.

In normal operation, vibration will result initially in lowering of pressure by means of relay 58 as described above. If this lowering of pressure causes an increase in vibration, the control system will be switched to raise the pressure by means of relay 64 as described above. Pressure will then be adjusted until vibration is at a minimum and relay 24 is deenergized. As the vibration is decreased by raising the pressure, relay 32 which will not sense a decrease in vibration, will be deenergized, thus deenergizing relay 46 and preventing lock-out of the control system through relay 42 in case the vibration again starts to increase because of overshoot resulting from the increase in pressure. If the vibration decreases and then starts to increase while the pressure is being raised through relay 64, relay 66 will be deenergized and, after a time delay, the opening of contact 66C will deenergize relay 64 which in turn will energize relay 58 to lower the pressure.

When action of the pressure regulator decreases vibration to a minimum, relay 24 will be deenergized and the control 8 will maintain a fixed pressure until vibration again increases. This increase in vibration will cause relay 58 to be energized first and if the vibration continues to increase, action of the system will be corrected as described above. Initial lowering of pressure has been selected because rolling forces will normally increase from head to tail of the strip being rolled, thus requiring less roll-bending force to produce good shape.

It will be noted that the vibrations generated by the non-flat product in turn generates sound waves. Thus, a sonic detection device could be substituted for the vibration pick-up element providing satisfactory results with appropriate modification of the system.

While several embodiments of my invention have been shown and described, it will be apparent that other adoptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. Apparatus for detecting undulations in a flat product being rolled in a rolling mill comprising vibration detecting means operable by vibrations in said rolling mill due to undulations in said product, and means connected to said detecting means for producing a signal proportional to said vibrations.

2. Apparatus according to claim 1 in which said rolling mill includes a pair of adjustable contour work rolls through which the product passes, and means for changing the contour of said rolls; said apparatus incluuding means connected to said signal producing means for opcrating said contour changing means to change the contour of said rolls.

3. Apparatus according to claim 2 in which the vibration detecting means is a vibration transducer mounted adjacent an operable member of the mill which produces a signal proportional to the vibrations.

4. Apparatus according to claim 3 in which the means connected to said signal producing means for operating said contour changing means includes means for a null method of measurement of said signal connected to the signal producing means and said control means for actuating the means for changing the contour of said rolls, whereby the null method of measurement will vary the contour of the rolls seeking to minimize the undulation in the product.

5. Apparatus according to claim 4 in which the means for changing the adjustable crown on a roll is a roll bending mechanism.

6. Apparatus according to claim 4 in which the means for changing the adjustable crown on a roll is a roll expanding mechanism.

7. The method of controlling the flatness in a product reduced by passing through a pair of adjustable contour work rolls; which method comprises the steps of obtaining a signal proportional to vibrations due to undulations in said product, and adjusting the contour of said work rolls to reduce the magnitude of said signal.

References Cited UNITED STATES PATENTS 3,024,679 3/ 1962 Fox 72245 3,455,149 7/1969 Foster et al. 73-71.4 3,460,365 8/ 1969' Howard 72-21 3,470,739 10/ 1969 Takafuji et al. 73-159 MILTON S. 'MEHR, Primary Examiner