GB1567786A

GB1567786A - Rolling metal sheet or strip

Info

Publication number: GB1567786A
Application number: GB5410176A
Authority: GB
Original assignee: WALZMASCHINENFABRIK AUGUST SCHMITZ GmbH
Current assignee: WALZMASCHINENFABRIK AUGUST SCHMITZ GmbH
Priority date: 1975-12-29
Filing date: 1976-12-24
Publication date: 1980-05-21
Also published as: FR2336988B1; DE2559016A1; IT1065538B; FR2336988A1; SE7614410L; DE2559016B2; DE2559016C3

Description

(54) ROLLING METAL SHEET OR STRIP (71) We, WALZMASCHINENFABRIE: AUGUST SCHMITZ G.m.b.H., a Joint Stock Company organised under the laws of Germany (Fed. Rep.) of Wahlerstrasse 2--6, 4oQ0 Dusseldorf 30, Germany (Fed. Rep.), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the rolling of metal sheet or strip and, more particularly, to a rolling mill for rolling metal sheet or strip and to a method of rolling metal sheet or strip in a rolling mill.

It is known for a rolling mill to comprise a first, relatively small diameter work roll, also known as a Taylor roll, cooperating with a second, relatively large diameter work roll to define a roll pass through which the metal sheet or strip travels as it is reduced in thickness. The two work rolls are in frictional engagement with respective backing rolls in a multi-roll stand. The Taylor roll is driven indirectly by a first drive motor driving the associated backing roll. In a sixroll stand the second work roll will also be driven indirectly through its associated backing roll by a second drive motor. In this case, each backing roll is associated with a respective, larger diameter support roll.

Alternatively, in a five-roll stand, the second drive motor is connected directly to the second drive motor is connected directly to the second work roll and in this case the backing roll for the Taylar roll, on the one hand, and the second work roll, on the other hand, are frictionally engaged by respective, large diameter support rolls.

In operation of such a rolling mill, the Taylor roll is deflected laterally out of a vertical plane containing the axes of rotation of the other rolls of the stand. By adjusting the extent of such deflection, the work roll camber is effectively varied as in previously proposed camber control devices in which the work rolls are adapted for variable deflection in the plane containing the axes of the rolls.

It has been previously proposed in U.K.

Patent Specification No. 1,022,963 to control the lateral deflection of the Taylor roll by control means including measuring means for ascertaining the magnitude and direction of the deflection of the Taylor roll and comparison means for comparing the measured value with a reference value so as to generate a correction signal whereby the supply currents of the two individually supplied drive motors for the driven rolls are varied in a controlled manner.

In practice, such torque control means comprising a measuring device and closed control circuit has shown two serious drawbacks: 1. When the rolling mill is started up, the drive motors are in a "control low", in which the currents may increase to the level of the current limitation. This condition lasts until a minimum rolling speed is achieved, which generally corresponds to the threading speed at which the beginning of the strip enters the reel. Controlled operation of the rolling mill is only possible from this speed.

Since the control circuit cannot become effective before this operating condition, lengths of strip occur at the beginning and end of the strip, which have not been processed with the optimum roll camber and thus do not correspond to the requimements as regards tolerance.

2. The measuring member located directly beside the thin working roll is subjected directly to the rough rolling mill operation and may be damaged by leakages connected with the penetration of rolling oil or rolling emulsion, and by tearing of the strip material.

With regard to the control accuracy required, the measuring device cannot be located outside the danger zone. However, a breakdown of the measuring device results in a stoppage of the rolling mill and a long period of shutdown.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantages.

According to a first aspect of the present invention there is provided a rolling mill for rolling metal sheet or strip, comprising a first, relatively small diameter, work roll and a second, relatively large diameter, work roll together defining a roll pass and frictionally engaged by respective backing rolls in a multi-roll stand, a first drive motor for driving the backing roll engaging the first work roll, a second drive motor for driving the second work roll or its backing roll, and control means for controlling the lateral deflection of the first work roll out of a vertical plane containing the axes of rotation of the other rolls of the stand, said control means comprising: adjustable means for presetting a value a alllax wherein a is the desired lateral deflection of the first work roll, and amax is the maximum permissible deflection of the first work roll, and circuitry adapted to generate signals Ml, M2 determining the apportionment between said motors of the total torque delivered to the driven rolls in accordance with the formulae:: DAY DO M1=Mw.--AM; M2=Mw.-+AM (1) Dr DA where the second drive motor is arranged to drive the backing roll of the second work roll, or DM M1=Mw.--AM; M2=Mw+AM (2) DT where the second drive motor is arranged to drive the second work roll directly, and, in either case, a #M=-.(Mw- ---- MT) (3) 2DT amax wherein:: AM corresponds to the torque change which is positive in the case of one of the drive motors and negative in the case of the other drive motor, DM is the diameter of the or each driven backing roll, Dr is the diameter of the first work roll, DA is the diameter of the second work roll, MT is the maximum permissible torque at the first work roll having regard to its deflection, and Mw is a torque value applied to each driven roll and calculated -from the current inputs of the drive motors.

According to a second aspect of the present invention there is provided a method of rolling metal sheet or strip in a rolling mill comprising a first, relatively small diameter, work roll and a second, relatively large diameter, work roll together defining a roll pass and frictionally engaged by respective backing rolls in a multi-roll stand, a first drive motor for driving the backing roll engaging the first work roll, and a second drive motor for driving the second work roll or its backing roll, said method comprising controlling the lateral deflection of the first work roll out of a vertical plane containing the axes of rotation of the other rolls of the stand by presetting a value a amax wherein a is the desired lateral deflection of the first work roll, and may is the maximum permissible deflection of the first work roll, and generating signals M1, M2 determining the apportionment between said motors of the total torque delivered to the driven rolls in accordance with the formulae: D, DM M1=Mw.--#M; M2=M"..-+AM (1) Dr where the second drive motor is arranged to drive the backing roll of the second work roll, or DM M1=Mw.--#M; M2=Mw+AM (2) Dr where the second drive motor is arranged to drive the second work roll directly, and, in either case, D%T a AM=-.(M- Mr) (3) 2DT amax wherein: : AM corresponds to the torque change which is positive in the case of one of the drive motors and negative in the case of the other drive motor, DM is the diameter of the or each driven backing roll, Dr is the diameter of the first work roll, DA is the diameter of the second work roll, MT is the maximum permissible torque at the first work roll having regard to its deflection, and Mw is a torque value applied to each driven roll and calculated from the current inputs of the drive motors.

The invention will now be further des cribed by way of example only with reference to the drawings, in which: Fig. 1 is a diagram of a six-high roll stand with control circuit, Fig. la shows a five-high roll stand, on which the control device according to Fig 1 can be used and Fig. 2 is a diagrammatic simulation of a control circuit.

The six-high roll stand illustrated -in Fig.

I has two- backing rolls 1, 2, two work rolls 3, 4 and two driven intermediate rolls 5, 6.

TheKworking roll 3 is a thin, so-called Taylor whose lateral deflection a is predetermined and can also be maintained by the torque control device. The lateral deflection a may also be set at zero, whereby the roll camber is minimal.

The five-high roll stand according to Fig.

la differs in that the lower intermediate roll 6 of the sixghigh roll stand is missing. In this case, the thicker work roll 7 is driven.

Apart from the backing rolls 1 and 2, whose diameter is immaterial for the mathematical equations, in Figs. 1 and la, the diameters of the rolls are given as DM for the driven intermediate roll or rolls 5, 6, DA for the thicker work roll 4, 7 and Dr for the thin working roll.

From the circuit diagram designed for the six-high roll stand with equal diameters DBl of the intermediate rolls, the two computers 10 and 11 are firstly considered, in which the necessary individual torques Ml and M2 for the motors 11 and 21 of the intermediate rolls 5 and 6, produced by a shift in the torque, can be calculated as current values from the differential torque AM introduced, according to the formulae: DM DM M1=Mw.--AM; M2=Mw.-+AM (1) Dr DA which currents are converted into the supply currents J, and J in a subsequent power amplifier 12.

Apart from the diameters of the work and intermediate rolls, the torques Mw applied to the two wcrk rolls 3, 4 are fed into the computers 10 and 11, which torques are the same despite the different diameter. The value-Mw thus represents an operational characteristic of the roll stand and is determined by the formula given in the computer 13: DT.DAhMB.

Mw= DT.DM + DA.DM The value MeZ contained in this formula fur the total torque of both drive motors 11 and 21 is prepared by the computer 14, to which the momentary supply currents J1 and J2 are introduced and in which the sum Jges is formed, which corresponds to the total torque M,,s.

The mathematical equations are based on the fact that the total torque Mge,s. is constant. However, since at the time of starting up the roll stand, the supply currents J1 and J2- and thus their sum increase, this constancy is to be understood such that due to the introduction of the differential torque AM into the - computers 10 and 11, the momentary sum of the torque remains constant, i.e. the shift of the torque takes place in opposite directions by the same amount in the case of each drive motor 11 and 21.

Due to this, the starting condition for correct retention of the lateral deflection a of the thin working roll 3 is determined. If the roll stand has reached it predetermined roll ing speed, the total torque effectively re- mains constant.

Presetting of the desired lateral deflection a of the thin working roll 3 takes place in an adjusting device 15 and more accurately a by the quotient , where a,ia is the amax mum admissible deflection of the thin working roll 3, for reasons of stability. Thus, percentages of the hundred percent maximum admissible deflection are regulated with the adjusting device 15, since at the time of rolling, visual observation of the rolled stock or measuring devices are used which indicate the flatness of the rolled strip. Since the adjusting device 15 does not allow an adjustment of more than one hundred percent, the thin working roll 3 cannot be deflected to breaking point.

The preset percentage valve is supplied to a computer 16, in which the differential torque AM is calculated according to the formula: Dnr a AM=-.(Mw MT) (3) 2Dr amnx Apart from the roll diameters and the torque Mm of the working rolls ascertained in the appliance 13, this computer receives a value Mr, which is the maximum admissible torque at the thin working roll, in view of the deflection of the thin working roll 3 and thus can be calculated as a fixed value for any diameter.

From the computer 16, the differential torque AM is supplied to the two computers 10 and 11 connected in parallel, in whichas aforementioned, the shift in torque of opposed - direction takes place and signals are produced at the output side, which correspond to the individual torques M, and M2 necessary for the desired bending deflection of the thin working rolL For a five-high roll stand according to Fig. la, the circuit diagram according to Fig. 1 is suitable provided that Dw is made to equal DA.As regards the computers 10 and 11, the following formulae now apply: DM Mi=Mw.--AM, M2=M1N + AM (2) Dr The embodiment according to Fig. 1 was primarily shown to promote an understanding of the torque shift without measurement of the deflection of the Taylor roll 3 and based solely on mathematical equations.

Since only simple types of calculation are required of the computers, another possibility of the construction of the electrical circuit exists, namely that of simulating a straight-line chart according to Fig. 2 by means of a permanently wired circuit.

The straight-line chart 20 illustrated in Fig. 2 is a model representing the operation of such a permanently wired circuit, in which, for a predetermined MT of 300 kpm, for example (Mr=maximum admissible torque on the thin working roll) sets of curves on the basis of the formulae (1) or (2) with (3) are introduced, which-in the illustration-are represented as straight lines.

Recorded on the left along a linear vertical a scale 21 are the percentage value of amax from 0 to 100%, whereof the desired value is set at the adjusting device 15. The straightline chart also contains a vertical scale 22 with a linear division of 0 to 2800 kpm for the possible total torques Mz as well as vertical scales 23 and 24 from 0 to 1500 kpm respectively for the individual torque M and ME produced during the torque shift.

From the arrows pointing inwards or outwards and shown as extensions of the scales, it will be understood with reference to Fig.

1 that the circuitry simulated by the straightline chart 20 has an input from the computer 14 for determining the total torque Mges and furthermore is the functional equivalent of the computers 10, 11 and 16, likewise the computer 13 for introducing the torque at the working rolls representing the operating condition. At the output side, the circuitry simulated by the straight-line chart 20 supplies the individual torques M1 and M2 or signals proportional to the latter, which are supplied to the power amplifier 12. In this respect, Fig. 2 is part of the control circuit shown in Fig. 1. The relationship of the scales 21, 22, 23 and 24 as well as their distances apart result from the mathematical equations and in this respect are simulated in a permanently wired circuit, as known to a control expert.

Fig. 2 includes a line 26 which starts from the mark 100% of the scale 21 and whose inclination is determined by the existing total torque of 900 kpm on the scale 22. This line 26 is one of many sets of curves which is controlled by the adjusting device 15 and the- total torque Mge supplied by the computer 14. As can be seen, the line 26 intersects the scales 23 and 24 at the marks 600 kpm for Ml and 300 kpm for M2, whereby the trimmed or shifted individual torques for the drive motors 1 and 2 are fixed.

It will be understood that each percentage value set on the scale 21 and each total torque of the scale 22 corresponds to a straight-line, which produces the division of torque at the intersection with the scales 23 and 24. Since all the scales begin at zero, one limit value of the straight-line chart simulating circuit includes the starting condition of the roll stand. The other limit value is represented by the broken line 27, which corresponds to the curve for a maximum total torque of 2,700 kpm, and 100% bending deflection of the thin working roll and which produces a torque distribution of 1200 and 1500 kpm.

WHAT WE CLAIM IS:- 1. A rolling mill for rolling metal sheet or strip, comprising a first, relatively small diameter, work roll and a second, relatively large diameter, work roll together defining a roll pass and frictionally engaged by respective backing rolls in a multi-roll stand, a first drive motor for driving the backing roll engaging the first work roll, a second drive motor for driving the second work roll or its backing roll, and control means for controlling the lateral deflection of the first work roll out of a vertical plane containing the axes of rotation of the other rolls of the stand, said control means comprising: adjustable means for presetting a value a ama wherein a is the desired lateral deflection of the first work roll, and anlax is the maximum permissible deflection of the first work roll, and circuitry adapted to generate signals Ml, M2 determining the apportionment between said motors of the total torque delivered to the driven rolls in accordance with the formulae: D3l DM M,=M,.----M: M2=Mw.-+M (1) DT DA where the second drive motor is arranged to drive the backing- roll of the second work roll, or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. For a five-high roll stand according to Fig. la, the circuit diagram according to Fig. 1 is suitable provided that Dw is made to equal DA. As regards the computers 10 and 11, the following formulae now apply: DM Mi=Mw.--AM, M2=M1N + AM (2) Dr The embodiment according to Fig. 1 was primarily shown to promote an understanding of the torque shift without measurement of the deflection of the Taylor roll 3 and based solely on mathematical equations. Since only simple types of calculation are required of the computers, another possibility of the construction of the electrical circuit exists, namely that of simulating a straight-line chart according to Fig. 2 by means of a permanently wired circuit. The straight-line chart 20 illustrated in Fig. 2 is a model representing the operation of such a permanently wired circuit, in which, for a predetermined MT of 300 kpm, for example (Mr=maximum admissible torque on the thin working roll) sets of curves on the basis of the formulae (1) or (2) with (3) are introduced, which-in the illustration-are represented as straight lines. Recorded on the left along a linear vertical a scale 21 are the percentage value of amax from 0 to 100%, whereof the desired value is set at the adjusting device 15. The straightline chart also contains a vertical scale 22 with a linear division of 0 to 2800 kpm for the possible total torques Mz as well as vertical scales 23 and 24 from 0 to 1500 kpm respectively for the individual torque M and ME produced during the torque shift. From the arrows pointing inwards or outwards and shown as extensions of the scales, it will be understood with reference to Fig.

It will be understood that each percentage value set on the scale 21 and each total torque of the scale 22 corresponds to a straight-line, which produces the division of torque at the intersection with the scales 23 and 24. Since all the scales begin at zero, one limit value of the straight-line chart simulating circuit includes the starting condition of the roll stand. The other limit value is represented by the broken line 27, which corresponds to the curve for a maximum total torque of 2,700 kpm, and 100% bending deflection of the thin working roll and which produces a torque distribution of

1200 and 1500 kpm.

DM M1=Mw.--AM; M2=Mw+AM (2) DT where the second drive motor is arranged to drive the second work roll directly, and, in either case, a AM =.(MW MT) (3) 2DT amax wherein: AM corresponds to the torque change which is positive in the case of one of the drive motors and negative in the case of the other drive motor, DM is the diameter of the or each driven backing roll, DT is the diameter of the first work roll, DA is the diameter of the second work roll, MT is the maximum permissible torque at the first work roll having regard to its deflection, and MW is a torque value applied to each driven roll and calculated from the current inputs of the drive motors.

2. A method of rolling metal sheet or strip in a rolling mill comprising a first, relatively small diameter, work roll and a second, relatively large diameter, work roll together defining a roll pass and frictionally engaged by respective backing rolls in a multi-roll stand, a first drive motor for driving the backing roll engaging the first work roll, and a second drive motor for driving the second work roll or its backing roll, said method comprising controlling the lateral deflection of the first work roll out of a vertical plane containing the axes of rotation of the other rolls of the stand by presetting a value a almas wherein a is the desired lateral deflection of the first work roll, and amax is the maximum permissible deflection of the first work roll, and generating signals M1, M2 determining the apportionment between said motors of the total torque delivered to the driven rolls in accordance with the formulae: DM DM M1 = Mw.----#M; M2 =Mw. --+ #M (1) Dr DA where the second drive motor is arranged to drive the backing roll of the second work roll, or DM M1 = Mw. ---- #M; M2 = Mw+#M (2) DT where the second drive motor is arranged to drive the second work roll directly, and, in either case, Dmr a AM=-.(Mw- MT) (3) 2Dr asleax wherein: : AM corresponds to the torque change which is positive in the case of one of the drive motors and negative in the case of the other drive motor, DAr is the diameter of the or each driven backing roll, DT is the diameter of the first work roll, DA is the diameter of the second work roll, MT is the maximum permissible torque at the first work roll having regard to its deflection, and Mw is a torque value applied to each driven roll and calculated from the current inputs of the drive motors.

3. A rolling mill for rolling metal sheet or strip, substantially as herein described with reference to and as illustrated in the accompanying drawings.

4. A method of rolling metal sheet or strip in a rolling mill, substantially as herein described with reference to the accompanying drawings.