US2851911A

US2851911A - Rolling mills

Info

Publication number: US2851911A
Application number: US483910A
Authority: US
Inventors: Hessenberg Wilfred C Frederick
Original assignee: British Iron and Steel Research Association BISRA
Current assignee: British Iron and Steel Research Association BISRA
Priority date: 1954-01-26
Filing date: 1955-01-25
Publication date: 1958-09-16
Anticipated expiration: 1975-09-16
Also published as: USRE25075E; FR1142917A; DE1118866B; GB780486A; BE535052A

Description

p 1958 w. c. F. HESSENBERG 2,851,911

ROLLING MILLS Filed Jan. 25. 1955 United States Patent F ROLLING MILLS illttilired Cecil 'Frede'rick liessenbergnsBi-omleyn England,

.assignonto-The lBritish-rlronrfia Steel :Research EAssocia- L tion, London,-E ngland ApplicationJanuaryflS, 1955', SerialNo. 483,910

;,Glaims: priori y, application. Great Britain ,-January;26, 1954 .This :invention relates .to rolling.mills,,particularly,,tor steel. Rolling mills may be :so. arranged. that the, rolled material .is ,passing ;throngh. a number .of.,.individual. roll standstat thesame time. ,The continuous ..st rip,.,mill-.in .which the strip: passes ,simultaneously through several astandssarranged in tandem is a..well,known example. One of the objects of continuous rolling isnto aproduce long lengths of .materialhaving a desired-:cross-section .which varies.v as .little :as .possible, ,from zone, end ;to ,the other. -,.In a. .tandem strip, .mill, changes;in...thickness,may occur as the. resultof disturbances in.one..or,-more-.of .the. roll ;s,tands... and Lit ;.is .desirable; that .these..should .be. corrected ,before Ithe materiahissues 1mm hegdast stand. A Obiechof .thisinvention is .to ,provide, a, method fona'chievingithis.

Itaisua. characteristic. of- .continuous mills ,that, .pnless .j the [material ,is;,allowed to. .aecurnulatebetween ,thestands or is subjected to increasingandfinally destructiyedensile stresses,..the rate;. in volume, unitsper...second..at, which .materiaL leaves. one standmust. equal .therate .at .which .it. enters v.the next. It .is...a1so.we1l, known t hat',in..the rolling. of metals;theirdensityis.notrappreciablysafiected by the. deformation .they, receive. ,.-I't is. therefore, possi- ,ble .to, ;state.j.that inna continuous.,;mill twherethe material ne,ither, accumulates .nor. is subjectedto in reasing tension .between ..the ,stands,,;the, volume, ,ofimaterial :passing: any point v ina giventimeis ithehsamemfor, all .points.,throughout'the system. In the special case of a wide striprrnill where the width of the strip is not afiected by rolling, the thickness ofsthe strip multipliedbyatthenspeed ofthe strip will yieldathesameeproduct at,,. any point. product is the output of'the mill.

The present invention employs the above -features-- to provide apparatus -or a measuring the issuing thickness c of strip from a -rolling mill and for controlling-"the; mill tormaintaina strip-thickness at a----'de"sired value. fThus, aaccording tothe-present invention?in a methodof measur- Ling the thickness-ofl str-ipleaving a=rolling milh the-outgoing thicknessisderived from measurement of the speed sand thickness of thestrip prior -to-=- passage ';out-of :the crnill rand of-ithespeed-of the stripdeaW-ing the-= mill. "--For a multi-stand mill ,i, the ,sp.eed-;.and;;thickness is measured .between any two adjacent stands. so that the,,output can "be' derived; the-outputis--'then' compounded with the speed of the strip leaving the mill to give an indication of the issuing strip thickness.

The invention includes apparatus for maintaining at the desired value the thickness of wide strip leaving a multi-stand rolling mill comprising means for producing signals in accordance with the speed (v and the thickness (h of the strip between two adjacent .stands of the mill, means for producing a signal in accordance with the speed of the strip (v leaving the mill, means for compounding the said signals to produce a resultant signal, representing the issuing thickness, in accordance with Patented Sept. 16, 1958 and means controlled by the resultant signal for maintaining the issuing thickness at the desiredvalue.

The invention will be more readily understood by. way of example from the following description of a continuous multi-stand steel rollingmill, reference being made to the accompanying drawing which is a schematic representation of the mill.

;In the drawing, the rolls of the stands of the mill are indicated at 12a, 12b, 12c etc., it being understood that. :the mill may have as many stands as may be desirable. Between any two adjacent stands, there are located a micrometer 13 which gives an electrical signal on the output lines 14 in accordance with the thickness of the strip 15 between those stands, and a device for giving an electric signal proportional to the. linear. speed Jofia'the, 'stripas; itpasses between the-stands. This. device consists, of a discjl6' mounted on the rotor-ofa tachometric generator17, the arrangement being such that theplane 'of'the disc 16 is aligned with the direction of motion a-ofthe;strip15 and ,thedisc rotatesatthe ,same peripheral This speed as the strip. The micrometer13 and thedevice .16, 17 are shown between the last twostands of the mill, but it will be understood that they maybe located between any two-other stands.

7 A second device for measuring the speed of the strip .is located. at the issuing @side of ,the. :last roller stand 12a. This device is similar to the device 16, 17 andcomprises a disc .18 in. frictional contact-with the strip and carried onthe motor of a tachometric generator, 19.

1 .The;millzis provided--with .the customary, reeling rdrum .ztlforqthe strip, the reeler motor 211anda drivingmotor .22 andscrew-down motor 23 foreach'ofthe rollerstands; .-the driving motor 22 drives the rolls,-whereas the screw- *-down. motor,23 causes adjustment-in.the-initialsetting of the work rolls 12 in relation to one another.

The output. of generator 1 9.; appearing at ,lines .24 ,is applied across an arcuate potentiometer 25. The signal appearing betweenthe slider 26 ofthe potentiometer and tone endof the potentiometer is applied inseriesopposi- .tiontolhe output from generator,17 to. the input of..a high gain amplifier 27, the output from which is .connected to a light motor 28. The rotor shaftof motor .28 carries the slider 26 of potentiometer 25 and also .the.slider- 29 of a second arcuate potentiometer 30. The ;electric 1signal appearing on the output lines 14-of micronl ter, 13 is applied across potentiometer. 30,and, the signalappearing on the slider 29,and;one end ,:of'the potentiometer is proportional to the outgoing thickness .of..the..s trip and an indication of that thickness can :be

givenby connecting the twopoints to a imeter 31.

Alternatively, a signal may be derived proportional to thei.de,viation of the issuingthickness ,froma, given value ,by connecting slider 29 and one. side of .the po- .tentiometer 30 ,in series opposition, to. a. source. ofvolt- ,age indicated in the vdrawing as a battery-32, connected acrossthe. potentiometer 33. .The sliderarm29 .is con- ,anected. to..,the.,s lider 34 of potentiometer .33 and the difierence voltage 1 appears .onslines 35.

In order to provide an automatic control system for maintaining the issuing thickness of the strip substantially at a given value determined by the setting of the potentiometer 33, the signal appearing on lines 35 may be applied to the reeler motor 21, as shown, or alternatively to any of the screw-down motors 23 of the roll stands or to any of the drive motors 22, as indicated in chain line.

The operation of the system is as follows. If the speed and thickness of the strip between stands 12a and 12b are v I1 and the speed and thickness of the strip, as it leaves the mill, are v and k then the voltage applied across potentiometer 25 is V proportional to v and the voltage appearing between slider arm 26 and one end of the potentiometer is kV where k is determined by the position of the slider on the potentiometer. The voltage applied the input of amplifier 27 is therefore proportional to (V kV where V is proportional to v as the gain of the amplifier 27 is large the angular position of the rotor shaft of motor 28 will be since at balance the input to the amplifier will be very nearly zero. Thus, as the voltage applied across potentiometer 30 is proportional to h the signal appearing at the slider 29 and one end of the potentiometer 30 is proportional to and because the output for wide strip is constant along the whole length of the strip and therefore h v =h v this signal is proportional to 12 the issuing thickness of the strip and the meter 31 will indicate that thickness.

When used, the potentiometer 33 applies a constant voltage h in opposition to the voltage from potentiometer 30 and the signal appearing at output lines 35 is therefore h h, the deviation of the thickness from a given value.

When this voltage is applied to control any of

motors

21, 22 or 23, the rolling mill will operate to maintain the output signal on lines 35 zero or, in other words, the issuing thickness of the strip at the desired value h, determined by the position of the slider 34.

As will be appreciated, the system illustrated in the accompanying drawing enables the thickness or gauge of the strip leaving the mill to be measured indirectly with the attendant advantage that the strip thickness is measured as it leaves the last roll stand and not at some distance from that stand. This advantage is of particular value when the system is used for automatic control of the mill as it enables irregularities in the thickness to be compensated immediately instead of after a time lag.

In another embodiment, the micrometer and the two speedometers are employed as before, but in this case percentage variations are measured. The signals from the micrometer and speedometer located between the stands are compounded to give a resultant signal equal to the output (v xh From this resultant signal is obtained a signal proportional to the percentage variation of the output from a given value, the given value corresponding to a desired thickness. Similarly, the signal from the speedometer measuring the speed of the issuing strip is modified to give a signal proportional to the percentage variation in the issuing strip thickness from the given value, again corresponding to the desired thickness. The two percentage signals are applied in series opposition to give a difference signal proportional to the percentage variation of the issuing thickness of the strip from the desired value. This signal can be applied to the reeling motor or to the screw-down or driving motors of the stands to compensate automatically for variations in the thickness and to maintain that variation zero.

As a result of the adjustments in accordance with the percentage variation signal, there will occur changes in the tensions in the strip between the stands, which will bring the Whole system into a new equilibrium. Changes in the thickness arising anywhere in the mill will be ofiset by the efiects of these changes in tension on the strip thickness in such a way that there will be no resultant change in the thickness of the strip as it leaves the final stand.

What is claimed, is:

1. In a rolling mill having a motor operated final stand and at least one motor operated preliminary stand, manually adjustable means for controlling the thickness of the strip issuing from said final stand, first variable signal generating means responsive to the velocity of a partially finished strip supplied to said final stand, second variable signal generating means responsive to the thickness of said strip supplied to said final stand, third variable signal generating means responsive to the velocity of the strip issuing from said final stand, and a signal correlating means responsive to the setting of said manually adjustable means and all of said signal generating means, said correlating means varying the speed of operation of said final stand motor so as to maintain the product of the thickness and velocity of said issuing strip constant to the product of the thickness and velocity of said supplied strip.

2. A rolling mill as set forth in claim 1, wherein said signal correlating means comprises a motor having a rotor, the position of said rotor being adjustable in response to changes in the difference between the signals produced by said first and third signal generating means, and a potentiometer having a slider coupled to said rotor, said second signal generating means comprising a source of voltage across said potentiometer, the difierence in the signals generated by said first and third signal generating means being detectable across said slider and one terminal of said potentiometer.

3. A rolling mill as set forth in claim 2, further comprising a second potentiometer, said first signal generating means being connected across said second potentiometer, said second potentiometer having a slider connected to said rotor and a high gain amplifier connected across one terminal and said slider of said second potentiometer, the voltage drop across one terminal and said slider of said second potentiometer being applied to the input of said high gain amplifier for controlling said final stand motor.

References Cited in the file of this patent UNITED STATES PATENTS 1,977,619 Boyer Oct. 23, 1934 2,051,018 Umansky Aug. 11, 1936 2,137,611 Hetler Nov. 22, 1938 2,264,095 Mohler Nov. 25, 1941 2,275,509 Dahlstrom Mar. 10, 1942 2,281,083 Stoltz Apr. 28, 1942 2,297,812 Stoltz Oct. 6, 1942 2,303,596 Zeitlin Dec. 1, 1942 2,332,272 Shayne Oct. 19, 1943 FOREIGN PATENTS 533.162 Great Britain Feb. 7. 1941