US3312092A - Control arrangement for level rolling metal plates and sheets in reversible rolling mills - Google Patents

Description

April 4,

Filed Oct.

J. NEUMANN AND SHEETS IN REVERSIBLE ROLLING MILLS 2 Sheets-Sheet 1 K. CONTROL ARRANGEMENT FOR LEVEL ROLLING METAL PLATES April 4, 1967 K. J. NEUMANN 3,312,092 ATEs CONTROL ARRANGEMENT FOR LEVEL ROLLING METAL PL AND SHEETS IN REVERSIBLE ROLLING MILLS l 2 Sheets-Sheet 2 Filed Oct. 25, 1963 United States Patent Olce 3,312,092 Patented Apr. 4, 1967 3,312,092 CONTROL ARRANGEMENT FR LEVEL RULLING METAL PLATES AND SHEETS EN REVERSIBLE ROLLING MiLLS Karl Josef Neumann, St. Ingbert, Saar, Germany, assignor to Verwaltungsgesellschaft Moeller und Neumann Ottone Handelsgesellschaft Filed Oct. 25, 1963, Ser. No. 318,984 Claims priority, application Great Britain, Oct. 25, 1962, 40,399/62 13 Claims. (Cl. 72-13) The invention relates to a control -arrangement for level rolling metal plates and sheets, and more particularly to a control arrangement in which the rolling action produces a correct overall flow of the rolled material to provide a level surface and an even thickness of the plates and sheets.

A correct ow control in rolling metal sheets is particularly important in the final passes so as to prevent that the rollers exert varying pressures either in the center or along the edges because of the roller deflection due to the rolling pressure. In a correct ow controlled rolling operation the sheet ows, i.e. is stretched or pressed uniformly over its entire width.

It is in the nature of the product, namely the at metal sheet, that during rolling between dat rolle-rs the sheet has a tendency not to come out straight with respect to the mill. The sheets are thus rolled by conducting them centrally of the groove caused by the deflection of the work rollers. The metal sheet has thus a greater thickness at the center than at the edges. For this reason it is necessary to apply smalle-r rolling pressures during the nal passes in order that the roller deliection becomes smaller and to have a metal sheet which comes out of the last pass with surfaces which are as much as possible parallel to each other. Even in the linal pass some deflection of the smooth rollers will occur so that even in the case of hot rolled metal sheets there is always a greater thickness in the center than along the edges, even if it is only a few hund-reds of a millimeter.

In the last series of passes it is therefore necessary to consider, -aside from adjusting the amount of reduction to be rolled, also the need for a lower pressure in order to carry out the `final pass with a predetermined rolling pressure at which the roller deflection, considering a certain camber in the grinding of the rollers, would produce only a very small guide groove. For this reason it has been the practice for the operator to set the reduction during the final series of passes with decreasing values according toa previously determined pass schedule, but largely according to his own judgment in the expectation that with this reduction the rolling pressure would also drop. But this is not always the result, considering for example the case where between two passes an extended pause may occur during which the rolled material cools down. Consequently the material would have a higher specific deformation resistance so that in spite of a decreased reduction relative to the previous pass, the rolling pressure predetermines the roller deflection and the formation of the groove is the same or larger than in the previous pass. Only experience and good judgment ot the operator can produce a good result with the operating methods practiced hitherto.

A particular difficulty resides in the fact that the rolling pressure should not drop linearly in a uniform manner, but that it should drop relatively more during the rst passes of the last series of passes, and less during the nal pass because t-he rolling action takes place only in that case with a correct ow control and without the formation of folds. It is practically impossible for the operator to correctly observe the curve according to which the rolling pressure should drop merely by actuating the adjusting device, thus by reducing the passes.

Accordingly it is an object of the invention to make the liow controlled rolling independent of the experience or judgment of the operator by means of -a novel electronic control arrangement.

Control arrangements are already known in which during the rolling operation the rolling pressure, the thickness of the reciprocating metal sheet and the Width of the sheet are measured and -are used as basis for the pass reduction in the subsequent passes, wherein the values are derived during the rolling operation from sample sheets and merely serve for the subsequent controlled rolling of the sheets having the same dimensions and of the same quality steel. The meaning of the term pass reduction `as herein employed signifies the amount by which the thickness of the rolled sheet is reduced with each pass, as indicated in FIGURE 1 at Ah. But it is known that in mills for rolling coarse stock varying end thicknesses are often rolled from one sheet to the next. It is therefore another object of the invention to derive from the measurement values of an existing guide pass the pass reduction for the subsequent pass of the same sheet according to a predetermined rolling pressure schedule.

The contr-ol arrangement of the invention includes also the continuously increasing deformation resistance of the sheet during cooling so that in the calculated pass reduction also the cooling during operation stoppage between two passes is taken into consideration.

Instead of introducing the decreasing rolling pressure according to a predetermined rolling pressure schedule, the control arrangement of this invention proposes to determine the rolling pressure by introducing the width of the sheet according to a predetermined schedule of the roller dellections which decrease toward the last pass, wherein the pass reductions are pre-calculated for the passes which follow the guide pass, and whereby a check is made to see if the sum of the pass reductions corresponds to the diterence between the crosssectional sheet thickness so measured in the guide pass and the desired nal thickness sn of the sheet.

In case of a deviation the pre-calculation is to be repeated with `a dilerent characteristic of roller deflection or a di'erent number of passes in the last series of passes until the difference so-sn correspond-s to the sum oi the pass reductions.

The invention comprises also a method of operating the novel control arrangement according to which the precalculation of the last series of passes is repeated with each pass of this series while decreasing the set number of passes. j

The invention is described hereafter by way of examples, but without limitation thereto, in conjunction with the accompanying drawings showing the control arrangeient in the form of block diagrams and in which:

FIG. l shows a rolling process and illustrates clearly the significance of the symbols employed in the formulas given in this description;

FlG. 2 shows a block diagram of a control arrangement for determining the pass reduction of the passes following a guide pass based on a predetermined rolling pressure; and

FlG. 3 shows a block diagram of the same control arrangement for calculating a pass series after the introduction of the characteristics of the desired course of the roller deflection.

The mathematical basis for the control arrangement of the invention is the so-called Eckelund formula In this formula Pw is the rolling pressure. The value d is the so-c-alled pressed length which may be seen lrom FIG. 1 land depends on the roller diameter d and he reduction Ah according to the formula given here. lhe sheet width b is also variable, even when the rolling )poration is started with the slabs having the same dimenions, because during the first passes not only longitudii-ally pressing passes are carried out, but after turning the lab by 90 transversely pressing passes are also made, o that the width isA not always the same lat the beginning )f the final pass series. The value Kw is the specific deormation resistance of the work material and depends )n the thickness s of the work material, the rolling speed v tnd the work material temperature t. It is equal to the um of the existing specific deformation 'resistances KS :inuence of the outlet thickness s of the work material),

(v (influence of the work material speed v) and Kt (in- Y luence of the rolled material temperature t). The course f the values of the existing specific deformation resist- Luces as functions of s, v and t is obtained from known yalues. The values increase with the increase of the 'olling speed and with the reduction of the outlet thickless s and temperature t. We have thus:

From FIGURE l we obtain for a subsequent reverse )ass additionally so-sl-:Alz

The control diagram illustrated in FIGURE 2 is deigned for the purpose of determiningj `at the beginning if the nal pass series in which a decreasing rolling pres- `ure speed w is applied, the values Pw, Ab and b by measirements and to derive therefrom the specific deformaion resistance KW of the particular sheet. Conversely he reduction A111 :of the sheet for the subsequent pass is :alculated from the probable Kw-value for the subsequent )ass yand from the predetermined rolling pressure over he pressed length Id. The Width of the rolled material b 'emains the same because in this instance no widening )asses are carried out.

The operation of the control arrangement illustrated s as follows:

The frame 1 of the reversible mill is `provided with the iressure gauge box 2 for measuring the rolling pressure W. Thickness measuring devices 3 and 4 are mounted )n both sides of the frame and in each case only the neasuring device which lies behind the frame in the rollng direction will feed its value into line 17. This is obained by `alternately connectible contacts 5 and 6 in ines 7 and 8. In the case illustrated, in which the sheet s rolled from left to right, contact 6 is closed and conact 5 is opened, so that only the measured value of the hickness gauge 4 is relayed as absolute value. In `a :omparison device 9 the difference Aho between the measlrement values of the thickness gauge devices 3 and 4 is )btained, which is introduced over line 9a and closed :ontact 9b into a calculator 12. A width gauge 10 which s illustrated only schematically and which operates ap- Jropriately by a photoelectric scanning of the sheet edges, nay be l`disposed `on either side of the frame, and furnish :ontinuously measurement values, as the sheet width does 1ot change for several passes upon starting the control for :arrying out the last pass series. After a speed increase )f the rollers the rolling speed v is taken from the num- )er of revolutions of the rollers and is calculated and ndicated in device 11.

The effect of the control is the following: The derived 'eduction Abo from comparison device 9 enters calculator l2 into which the roller diameter d is also fed from the adjusting device 13. In calculator 12 the pressed length do is calculated according to the formula indicated above 1nd fed to calculator 14. The sheet width b from meas- 1ring device 10 and the existing rolling pressure PW(J from y)fessure gauge box 2 are also fed to this calculator. The

specific deformation resistance KW of the just worked sheet is calculated from these values according to the formula indicated and is fed to a device 15. A function element 16 is associated with calculator 15 and the outlet strength sc from the thickness measuring device is introduced into this element over line 17. It furnishes the existing deformation resistance Ks depending on the sheet outlet thickness s0 according to the function Ks), which is introduced into the device according to known values. In the device 15 Ks is deducted from KW so that at rest the two existing values Kv-l-Kt are obtained. This sum is 'conducted further into the device 13 in which the existing deformation resistance KV based on the rolling speed is deducted. Kv is furnished by the function device 19` into which the rolling speed Vo passes over line 20 and into which the dependence value Kv=f(v) is fed.

From device 18 the rest value Kt goes into the function element 21 into which the dependence Kt=f(t) is fed so that the work material temperature t is eliminated at the outlet and may be read on the indicator 22. In this respect the calculator system is employed also to determine the actual temperature of the work material.

From this point on all the calculations are directed to determining through the kW-value which is correct and changed for the subsequent pass and through a smaller rolling pressure a new redu-ction Ahl. The kw-value changes due to cooling of the metal sheet which depends on the time t between the two passes and the sheet thickness s.

After a measurement value for temperature t is available the same instruments may be employed for the reverse calculation in a second calculating operation only when the flow of the first calculating operation in the direction described so far is interrupted. While the sheet is still being worked this is obtained by actuating a solenoid 23 for the contacts 5, 6, 9b, 24 and 32 in such a manner that the lines 8 for the value s, 9b for Aho, 25 for the value PW 4and 32 for the value V are interrupted without closing line 7 of gauge 3. But some values must be retained or stored for the reverse calculation such as the sheet width b in device 26, temperature t in device 27 and the initial thickness s in device 28. The measured temperature to of the guide sheet is fed into calculator 29 which in reference to the time and the measured sO-value feeds a continuously decreasing temperature value t1 into the calculator 21, The time factor is introduced by a timing device 30 into the calculator 29 while the value s0 is introduced through device 28. The value so remains constant until the beginning of the following pass, thus until a new measurement value which must come from the gauge 3.

The continuously decreasing temperature value furnishes in device 21 a new higher Kt-value which is fed into device 18 For the following pass a greater rolling speed V1 is employed which is set at the adjusting device 21 and fed into the function device 19. This device furnishes a new and increased Kv-value which is processed in device 18 and forms at the outlet a new value Kv-l-Kt fed to the calculator 15. Since in the first calculating pass a new sheet thickness s is not yet available, rather the original Ks-value is present, a Kw1-value is fed from calculator 15 into device 14 which value is corrected only in view of the decreasing temperature and the increased rolling speed.

With the new value Kw1 a new ldl value is calculated in device 14 from the available sheet width b from device 26 and from the pre-selected decreased rolling pressure PW from the adjusting device 33. The device 12 derives now from the introduced value ldl a new reduction Abl. However, this value cannot be correct yet because the existing deformation resistance KS has not been changed yet. In order to obtain a provisional new outlet thickness s1 for the following ipass A111 is fed to a calculator 34 into which through a line 35 also the outlet thickness so retained by device 2S is introduced by the running pass. The difference so-Ahl is formed in device 34 which provides the new approximate sheet thickness s1 which is indicated in device 34a. The value s1 is fed into line 17 and furnishes now `over the function device 16 a new value Ks which is introduced into device 15 and after being added to the constantly received values Kv-l-Kt, of which K, changes constantly under the influence of the running time factor, is added thereto and provides an improved value Kw1. After repeating the calculating processes in devices 14 and 12 an improved value A111 is obtained and over device 34 lan improved value s1, which in turn causes a new calculating operation through device 16, To the extent that the calculating operations are constantly repeated in circuits 17, 16, 15, 14, 12 and 34 a correct reduction Ahl is derived in a constantly approaching manner for the subsequent pass. From the differential device 34 the reduction Ahl is fed to device 36 for the following pass. This value Ahl which changes mainly due to the influence of the constantly running time factor determines in device 36 the number of the revolutions for the adjusting motor 37 which is `operated through switch 38. The value A111 may change under the inuence of the running time factor until starting the rolling of the work material in the reverse pass, but thereafter is blocked in a manner not shown in detail. The actual reduction A111 is equal to the adjusting value of the upper roller when Working always with the same rolling pressures since the reduction in the previous guide pass is determined with the frame under load so that the roller gap is eliminated. Due to the decreasing rolling pressure which takes place during this process a correction factor may be determined in the adjusting device 36 in a known manner not shown in detail. This correction factor is comparatively the same as the decreasing roller gap and corrects the `reduction A111 determined for the following pass to a smaller adjustment than Ah1 Accordingly the difference between two rolling pressures PWD-Pm from device 33 and the spring constant of the frame would :have to be introduced into the adjusting device 36.

In the case where the functions introd-uced into devices 16, 19, 21 and 29 are correct the rolling pressure which was pre-selected at 33 must be shown -at the indicator instrument 39. If this is not the case the reason for this can be, aside from the exactness in collecting the measurement values, only in that roller wear has occurred or that the roughness of the rollers is changing. As only small deviations are expected in this respect it is possible to adjust during the rolling operation the value for the roller diameter set at 13 also while the work material passes between the rollers in lorder to obtain the pre-selected rolling -pressure at 39. As the diameter of the rollers and their surface conditions changed only slowly such corrections will be necessary only from time to time. On the basis of test values one could also consider a change of the value in device 13 from pass to pass in very small magnitudes automatically.

During the second pass and after carrying out any necessary corrections at device 13 the solenoid 23 is so actuated that switches 5, 9b, 24 and 32 are closed while switch 6 `remains open. In this manner the running pass is again a guide pass for a Subsequent third pass.

The operation described so far forms the basis for further automation especially in View of the fact that the relationship between the pre-selected, decreasing rolling pressures and the consequently decreasing roller deflection depend up to an extended parallel condition of the roller jacket lines in the rolling gap on the sheet width. In this respect it should ybe understood that with the same rolling pressure the rollers will exhibit la greater deflection the smaller the sheet width. In the case of a narrow sheet width the rolling pressure acts more as a point load and in the case of a Igreater sheet width more as a stretch or area load. The goal should therefore be that after the first guide pass the last desired rolling pressure is determined in reference to the sheet width b which varies from sheet to sheet, under which pressure the Iroller deflection forms the smallest possible groove, thus rolling a finished sheet with optimum tolerance throughout its width.

In reference to FIGURE 3 a control diagram is shown which is necessary as a supplement to the diagram of FIGURE 2 when after a guide pass it is desired to change to a determination of the reductions going backwards from the last pass. The guide pass is still necessary in order to retain the values of the sheet width, the temperature and the rolling speed, because the temperature and the rolling speed must be determined for the last pass according to the novel process.

The control arrangement of FIGURE 3 corresponds 4to the devices of FIGURE 2 with regard to the calculating devices 12, 14, 15, 1.6, 18, 19 and 21. The starting point for the calculations are the values of the roller deliection Y which beginning at the last pass with the index n have the smallest value and which are set in the example illustrated up to the fourth last pass by the index '71*3" at the devices 40-43. Depending on Whether the guide pass goes to the right or to the left the number n of the passes following the guide pass is also set in the device 44 so that the work material is rolled in the final pass to the exact point without requiring an empty pass. In setting the number of passes n in device 44 it is determined also how many of the devices 40-43 are to furnish the values.

At the beginning the minimum roller deflection Yn is fed from the device 40 into a function device 45 in which the rolling pressure is calculated as function of the sheet width b, the roller diameter d and the roller deflection Y. The sheet width b is furnished by device 26 of the arrangement of FIGURE 2. The rolling pressure calculated for the last ypass is fed into calculator 14 into which the sheet width b is also introduced. The pressed length ld which is initially set at random is fed from the adjusting device 60 into device 14.

In the device 14 a Kw-value is derived which is fed into a differential device 47 where it is compared with a KW- value derived from devices 15, 16, 18, 19 and 21 in the manner described above in order to determine the value for the nal pass n. The end temperature tn is set in device 48 with a free selection and is fed into device 21 in order to determine the existing deformation resistance Kt. Also the rolling speed must be set according to the number of passes bymeans of devices 49, 50, 51 and 52. During the rst calculating process the value Vn `is taken from device 49 and the pertaining Kv-value is calculated in device 19. From the previously set desired value of the sheet thickness sn which comes into device 46 through line S3 the Ks-value is calculated in device 16 and fed to device 15.

In the case where the comparison of the Kw-values in device 47 produces a difference which deviates from zero an impulse is fed to the adjusting device 60 and changes the pre-selected value Id taken there at random in a direction corresponding to the sign of the deviation until through device 14 a Kw-value is fed into the comparison device which is equal to the value in the device 15. At the same time the value ld is fed into device 12 in which the reduction Abn of the last pass is calculated which is fed into the device 62.

As soon as in device 47 the difference which is equal to zero is set, a pulse is fed through line 55 to the adjusting device 41 for the ruler deflection Yn 1 of the next -to the last pass in order to feed :now this value for the following calculation to device 45. While this takes place the value Yn from device 40 is cancelled. The pulse in line 55 which initiates the determination of the values for the next to the last pass is also fed to the adjusting devices 49-52 in order to cancel the value from 49 and to feed the value from 50` together with Vn 1 into device 19. Furthermore adjusting devices 56, 57 and 58 are provided in front of device 21 in which the temperature differences are pre-set from pass to pass and in which during the second calculating process the temperature tn l is taken from device 56. In order to consider the sheet thickness during the determination of Ks in the function device 16 the sum which represents the next to the last sheet thickness .tn l is determined from the desired thickness sn in device 46 and the already determined reduction Ahn in device 61. This value is fed to the device 16 during the second calculating process.

After determining the KW-value a zero difference cannot exist now in calculator 47 because the new rolling pressure calculated which pertains to the next to the last pass is still coupled in device 14 with the previous ld-value. The difference which is obtained again from device 47 is conducted again over line 59 to device 60 in which the pressed length ld is adjusted until the value fed into device 14 leads to a KW-value which corresponds to the KW-value from devices 15, 18 and 21. With the adjustment of the value ld in device 60 the device 14 furnishes to device 12 the ld-value which approaches a border value and from which now the reduction Ahn 1 of the next to the last pass is calculated and conducted to device 64.

As soon as any values are obtained in devices 64 or 63 the previously adjusted fixed values for the imaginary second to the last pass is taken off in a conventional manner not described in detail by a feed back coupling from devices 42, 57 and 51 with the index 1t-2. A new reduction Ahn 2 is finally obtained at 66 and in device 65 a new sheet thickness s 3. In a corresponding manner the reduction Ah 3 is obtained after a fourth calculating process in device 68 and in device 67 the sheet thickness so' is derived before the fourth last pass.

In the case of an assumed pass number 11:4 the value so would have to be equal to the outlet thickness so of the running guide pass when the course of the Y-values which determine the rolling pressure has been correctly set over the four imaginary passes. In order to control this so is compared in device 69 with the s,J value available from line 35. The difference is fed to a function device 70v into which various functions of y depending on the number of passes are fed, as the four lines in FIGURE 3 indicate. yn, which is the permissible deection of the rollers in the last pass, must be constant as starting point. Depending on whether the difference so-so is positive or negative a function different from the original function is set in the function device 70 by means of a signal from device 69. In the case where the original function was set along line 71 and the difference .rd-so is positive the calculated reductions are too large i.e. another function of y must be set which represents smaller deflection values for example the function along line 72. With these y-values the precalculation is repeated and in certain cases repeated several times until with a difference sO-so' is zero the correct function of y is set. The resulting values for the rolling pressures Pv in device 45 represent then the correctly decreasing rolling pressu-re for the adjusting device 33 shown in FIGURE 2.

Into the function device 70 only functions of y between two border values may be introduced as each course of y or PW must satisfy the requirement for a correct fiow adjusted rolling operation, In the case where a large difference so-so exists it is possible that from 69 no atter or no steeper course of y may be set over n, n-l, 11-2, n-3 at device 70. In that case the number of passes must be changed.

For this purpose a connection 74 is provided from the function device 70 to the adjusting device 44 for the pass number n. Over this line the difference .ro-s is conducted to 44 in case it is too large in order to be able to adjust at 70 another one of the introduced functions of y. If for example at 70 the border value function according to line 73 is set and tvo-s0 is still positive it is possible to reduce the sum of the reductions Ah only by a reduction of the number of passes in order to obtain a smaller sa. This is obtained through device 44 yby means of a signal from device 70 when this device can no longer process a pulse which it has received.

In device 44 the pass number is adjusted appropriately by an even number, at least by 2, so as to avoid an empty pass. In the assumed case the values at 42 and 43 and correspondingly at 57, 58 and at 51, 52 would be cancelled. As the temperature of the guide pass is available from device 27 in FIGURE 2 and since now only a temperature drop over two succeeding passes needs to -be considered the values at 48 and 56 should be corrected simultaneously.

A new calculation with only two remaining passes will produce at 69 a negative difference so-so' as at 70 the function according to line 73 is still set, and this difference causes at 70 a larger value yn 1 in that a function of y with a steeper characteristic is set until the difference is equal to zero. The rolling pressures PW derived at 35 are conducted into the adjusting device 33 shown in FIGURE 2.

The device 70 changes thus within permissible limits ultimately the rolling pressure course within a predetermined number of passes without deviating from the principle of a correct flow adjusted rolling. Only when the values conducted to device 70 are out of range for this device they are conducted into device 44 in order to change the pass number.

The values derived from the pre-calculation according to FIGURE 3 may be used in various ways for further rolling operations. First of all it is possible to store from devices 62, 64, 66 and 68 the reductions in device 36 of FIGURE 2 and to employ them before each reversing step of the rolling operation. But as indicated above the values PW for the rolling pressure may be supplied from device 45 and fed according to need to the adjusting device 33 of FIGURE 2. In this case the rolling mill is controlled, as stated at the start, over the rolling pressure course now determined with greater exactness, from device 33 wherein each pass may be again the guide pass for the following pass in order to control the temperature continuously and so as to consider work stoppages.

It should also be pointed out that in the control arrangement according to predetermined rolling deflections according to FIGURE 3 the sheet end thickness sn is the basis for determining the existing deformation resistance Ks at 16 for the final pass because the determining initial thickness sn 1 is still not available.

From the resulting value sn sn 1 which provides too large a reduction Ahn an sn 1 value is calculated at 61 from which an improved KS is obtained at 16 and over the zero-comparison at 47 etc., a Ahn value which is again improved is obtained which, in a continuing approximation finally provides the correct initial thickness sn 1 for the final pass. Only when the values at 62 or 61 have adjusted the predetermined values with the index n-l may be employed for the second calculating process.

The same applies to the prior passes because first the initial sheet thickness must be available with as much exactness as possible before a correct Ks-value is available as basis for the calculation.

What is claimed is:

1. In a reversible rolling mill having at least one pair of opposed rollers for reducing the thickness of a metal sheet having a specific deformation resistance which varies as a function of its temperature during a series of passes including at least a pair of passes therethrough, and means for varying the spacing of said rollers, the improvement comprising: first means for generating a rst signal indicative of the reduction in thickness taking place as said sheet is passing through said -rollers during the first of said pair of passes; second means for generating a second signal indicative of the width of said sheet; third means for generating a third signal indicative of the pressure being exerted by said rollers on said sheet during said first of said pair of passes; fourth means for generating from said first, said second, and said third signals, a fourth signal indicative of said specific deformation resistance of said sheet; fifth means for conducting said first, said second, and said third signals to said fourth means; sixth means for selectively preventing said fifth means from conducting said first and said third signals to said fourth means; said fourth means including means, operable when said sixth means is preventing conduction of said first and said third signals to said fourth means for generating a fth signal indicative of the continuously changing specific deformation resistance of said sheet; said fourth means further including means for generating from said fth signal, a sixth signal indicative of a reduced roll spacing corresponding to a desired change in thickness of said plate during said second pass of said at least one pair of passes which will produce a predetermined desired pressure on said sheet in the second pass of said at least one pair of passes; sixth means responsive to said sixth signal for causing said means for varying the spacing of said rollers to move said rollers to said reduced spacing subsequent to said first pass and prior to said second pass.

2. The improvement as defined in claim 1 wherein said first means further includes means for generating a seventh signal indicative of the thickness of said sheet resulting from said first pass; and wherein said fourth means further includes means for deriving an eighth signal indicative of the outlet thickness of said sheet which will result from said reduced spacing during second pass, and means responsive to said seventh signal for modifying said sixth signal to cause said sixth signal to more accurately indicate the reduced roll spacing corresponding to a desired change in thickness of said plate durin-g said second pass of said at least one pair of passes which will produce a predetermined desired pressure on said sheet in the second pass of said at least one pair of passes.

3. The improvement as defined in claim 1 wherein said means for generating said sixth signal generates a signal which produces a reduced roll pressure during said second pass of said at least one pair of passes.

4. The improvement as defined in claim 1 wherein said fourth means further includes means for generating, from the known permissible deflection of said rollers during the last pass of said series of passes, signals indicative of the desired rolling pressures for each pass of said series of passes.

5. The improvement as defined in claim 4 wherein said fourth means further includes means responsive to said signals indicative of the desired rolling pressures for said series of passes for pre-calculating the required change in roller spacing for each pass of said series of passes.

6. The improvement as defined in claim 5 wherein said means for pre-calculating the lrequired change in roller spacing for each pass 0f said series of passes includes means for causing said pre-calculation to be repeated with each pass of the series of passes while decreasing the number of passes in said series of passes.

7. The method of controlling screw settings in a reversible hot rolling mill for the flow adjusted level rolling of plates and sheets comprising during a first operating the steps of measuring during a guide pass the rolling force, the inlet and outlet thickness, the speed and the width of the work material, computing the parameters measured to develop under the terms of a Vrolling formula a rst signal responsive to the partial specific deformation resistance KW of the guide work material, developing a second signal resonsive to the partial specific deformation resistance KS in function of the actual thickness of the work material, developing a third signal responsive to the partial specific deformation resistance Kv in function of the actual speed Iof the work material, subtracting said second and third signal from said first signal to establish a fourth signal responsive to the remaining partial specie deformation resistance K1 being dependent on the actual work material temperature, eliminating from said fourth signal a fifth signal to responsive to the actual temperature of the work material, and comprising during a second operation the steps of switching off all measured values, storing the fifth signal to and the outlet thickness value su, developing a fictive temperature t1 as sixth signal in function of `the outlet thickness value so and the time lapse given by chronometer, developing a fictive value responsive to the partial specific deformation resistance K1 as seventh signal, adding said second and third signal to said seventh signal to produce a fictive value responsive to the specific deformation resistance Kw1, pre-setting a rolling force value for the following pass less than the value measured during the guide pass, and computing said fictive, pre-set and stored parameters to establish under the terms of said rolling formula and output signal A111 responsive to the pass reduction for the lfollowing pass, each following pass serving as guide pass for the next pass.

8. The method according to claim 7, in which during the second operation a new pre-set speed value v1 is introduced to adapt said third signal to the conditions of the following pass.

9. The method according to claim 7, in which during the the second operation a -fictive outlet thickness value S1 of the material to be rolled in the following pass is developed from said outlet thickness value So of the guide pass and the determined pass reduction value Al11 for steady correction of said first signal, resulting in a corrected pass reduction value A111, this operation being terminated by switching in all measured values with the beginning o-f the following pass.

10. The method according to claim 7, in which the rolling force to be pre-set during the second operation steps is scheduled for pass-bypass decreasing rolling force.

11. The method of controlling screw settings in a reversible hot rolling mill for the ow adjusted level rolling of plates and sheets comprising during `a first operation the steps of measuring during a guide pass the rolling force, the inlet Iand outlet thickness, the speed and the width of the Work material, computing the parameters measured to develop under the tenms of a rolling formula a first signal responsive to the specific deformation resistance Kw of the guide work material, eliminating a second signal responsive to the partial specific deformation resistance K1 dependent on the actual work material temperature, and comprising during a second operation the steps of switching off all measured values, steadily correcting said second signal K1 in function of the time 4lapse given bya chronometer, reestablishing a fictive value Kw1 of said first signal, pre-setting a rolling force Value for the following pass, and computing said fictive preset values with stored measured values to establish under the terms of said rolling formula an output A111 responsive to the pass reduction for the 4following pass, each following pass serving as guide pass for the next pass.

12. The method according to claim :11, wherein during the second operation steps a rolling force schedule is established in advance for a pre-set number of passes of a last pass series, comprising the steps of pre-setting for each pass a roll deiiection value yn, yn 1, yn 2, yn3, from which values the last yn corresponds to the permissible and necessary roll deflection during the final pass and the foregoing values are chosen in accordance with the desired flow adjusted level of rolling operation, computing each deflection value to establish a corresponding rolling force schedule in function of said defiection values, the measured width of the work material and the diameter of the rolls, simulating the rolling operation backwards from `the final pass and the desired final thickness sn of the work material by adding the sum of pass reduction values computed for each fictive pass under the terms `of a rolling formula and said rolling force schedule to said desired final thickness value sn, comparing this sum so with the measured outlet thickness value so of the guide pass, repeating said simulating operation in the case a difference is obtained in said comparison.

13. The method according to claim 12, in that for each pass of the simulated rolling operation a speed value and a temperature value is preset and a ctive pass reduction v-alue Ahn, Ahn 1, Ahn1, Ahn 2, Ahn 3 is computed to establish a rst signal responsive to the specific deformation KW of the work material in function of the preset speed and temperature values and the thickness values developed from the pass reduction values for each fictive pass, said specific deformation values KW being compared with the corresponding values eliminated from the computing operation under the terms of a rolling formula, the

output of said comparison is made and held zero by varying a parameter ld proportional to the computed pass reduction values.

References Cited by the Examiner UNITED STATES PATENTS 2,281,083 4/1942 StOltZ 72-13 2,767,604 10/1956 Whalen 72-13 2,985,043 5/1961 Roberts 72--13 3,111,946 11/1963 KOSS et al. 72-13 CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Assistant Examiner.

Claims (1)

1. IN A REVERSIBLE ROLLING MILL HAVING AT LEAST ONE PAIR OF OPPOSED ROLLERS FOR REDUCING THE THICKNESS OF A METAL SHEET HAVING A SPECIFIC DEFORMATION RESISTANCE WHICH VARIES AS A FUNCTION OF ITS TEMPERATURE DURING A SERIES OF PASSES INCLUDING AT LEAST A PAIR OF PASSES THERETHROUGH, AND MEANS FOR VARYING THE SPACING OF SAID ROLLERS, THE IMPROVEMENT COMPRISING: FIRST MEANS FOR GENERATING A FIRST SIGNAL INDICATIVE OF THE REDUCTION IN THICKNESS TAKING PLACE AS SAID SHEET IS PASSING THROUGH SAID ROLLERS DURING THE FIRST OF SAID PAIR OF PASSES; SECOND MEANS FOR GENERATING A SECOND SIGNAL INDICATIVE OF THE WIDTH OF SAID SHEET; THIRD MEANS FOR GENERATING A THIRD SIGNAL INDICATIVE OF THE PRESSURE BEING EXERTED BY SAID ROLLERS ON SAID SHEET DURING SAID FIRST OF SAID PAIR OF PASSES; FOURTH MEANS FOR GENERATING FROM SAID FIRST, SAID SECOND, AND SAID THIRD SIGNALS, A FOURTH SIGNAL INDICATIVE OF SAID SPECIFIC DEFORMATION RESISTANCE OF SAID SHEET; FIFTH MEANS FOR CONDUCTING SAID FIRST, SAID SECOND, AND SAID THIRD SIGNALS TO SAID FOURTH MEANS; SIXTH MEANS FOR SELECTIVELY PREVENTING SAID FIFTH MEANS FROM CONDUCTING SAID FIRST AND SAID THIRD SIGNALS TO SAID FOURTH MEANS; SAID FOURTH MEANS INCLUDING MEANS, OPERABLE WHEN SAID SIXTH MEANS IS PREVENTING CONDUCTION OF SAID FIRST AND SAID THIRD SIGNALS TO SAID FOURTH MEANS FOR GENERATING A FIFTH SIGNAL INDICATIVE OF THE CONTINUOUSLY CHANGING SPECIFIC DEFORMATION RESISTANCE OF SAID SHEET; SAID FOURTH MEANS FURTHER INCLUDING MEANS FOR GENERATING FROM SAID FIFTH SIGNAL, A SIXTH SIGNAL INDICATIVE OF A REDUCED ROLL SPACING CORRESPONDING TO A DESIRED CHANGE IN THICKNESS OF SAID PLATE DURING SAID SECOND PASS OF SAID AT LEAST ONE PAIR OF PASSES WHICH WILL PRODUCE A PREDETERMINED DESIRED PRESSURE ON SAID SHEET IN THE SECOND PASS OF SAID AT LEAST ONE PAIR OF PASSES; SIXTH MEANS RESPONSIVE TO SAID SIXTH SIGNAL FOR CAUSING SAID MEANS FOR VARYING THE SPACING OF SAID ROLLERS TO MOVE SAID ROLLERS TO SAID REDUCED SPACING SUBSEQUENT TO SAID FIRST PASS AND PRIOR TO SAID SECOND PASS.

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