DE2440235A1 - METHOD AND DEVICE FOR ROLLING STRIP MATERIAL - Google Patents

Description

6 Frankfurt a. MI
Paikslxaße 13

7995

GEC-ELLIOTT AUTOMATION LIMITED, Borehamwood, Herfordshire WD6 1RX, England, GREYHAM FRANK BRYANT, Norwood Green, England country PETER DAVID SPOONER, Pinner, Middlesex, England

Method and apparatus for rolling strip material

The invention relates to a method and a device for Rolling of strip material, it relates particularly but not exclusively to a method for rolling metal strips, such as steel strip, and it also relates to the strip material made by this process.

It is known that when rolling steel strips, especially wide, thin strips, precautions must be taken, to prevent a so-called bad profile. The term "profile" refers to the transverse cross-section of the Tape, i.e. on the transverse thickness profile and on transverse fluctuations in the longitudinal tension / tension stress of the tape. Large differences in tension across the cross-section of the belt can lead to buckling of the belt, i.e., to a "manifest bad shape". If the tape is subjected to sufficient longitudinal tension, in this way bulging can be avoided, but the risk of bulging is not necessarily eliminated; the ribbon

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in this case has a "latently poor profile", for example it can bulge if it is cut into smaller ribbons.

When the strip is introduced into a rolling mill, in particular into a multi-stand tandem rolling mill for thickness reduction in successive Rolling steps, the shape of the nose, i.e. the first meter of the strip, can cause major problems during insertion raise, since no tensile forces can attack to make an "obvious bad profile ". In some cases it is possible that a bad profile of the nose is on the nose Entry into a scaffolding (or, if used, into an automatic Insertion device). The operator then has to stop the rolling mill, cut off the bad nose and try the insertion again. The consequence of this is undesirable waste and a reduction in the Usage time of the rolling mill.

The object of the invention is to provide a method for rolling strip material in which these difficulties in insertion of the material can be avoided or reduced, and to specify an apparatus for carrying out this method.

This object is achieved according to the invention by a method for rolling strip material in a rolling mill with at least an adjustable roll stand through the following process steps solved:

(a) At least an approximate calculation of the rolling force and the required thickness that the nose of the strip material will take should theoretically take in the individual stands, based on measurements of the material to be rolled Mill settings and data, and a calculation of the theoretical crown of the rolls each Scaffolding;

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(b) at least an approximate determination of the ideal rolling force for each individual stand, which together with the crowning of the rollers of this stand of the nose one for introduction in the following roll stand suitable shape or a shape lying within specified deviation limits gives; -

(c) a comparison of the calculated rolling force of each individual stand with the determined ideal rolling force of this Stand, and, provided that the calculated rolling force deviates from the determined ideal rolling force so far that the The nose profile is not suitable for further insertion or is outside the specified limit values, a change the rolling mill settings for generating a rolling force and / or a roll crown for each individual stand, because of the nose an insertable profile or a Profile received within the specified limits;

(d) passing the strip material through the rolling mill, and, while the individual interframe tensile forces come into effect one after the other, the change and adaptation of the Rolling mill settings to the settings suitable for a given rolling plan (if these values are not are already set); and .

(e) rolling the strip material essentially according to the rolling schedule.

To achieve the object, a rolling mill with at least one controllable roll stand is also provided, which is marked is through

(a) Devices for continuous measurement of the rolling mill settings and data relating to the material to be rolled, Means for calculating the approximate rolling force to

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indicate the required thickness, theoretically at the nose of the strip material on each individual roll stand should be available, and devices for calculating the crowning of the rolls of the individual stands;

(b) Means for at least approximate determination of the ideal rolling force for each individual stand, which together with the calculated roll crowning of this stand of the nose for introduction into the following roll stand give a suitable profile or a profile that lies within predetermined limit values;

(c) means for comparing the calculated rolling force and the determined ideal rolling force of the individual rolling stands, and, if the calculated rolling force deviates from the determined ideal rolling force so far that the nose a profile that is not suitable for further introduction or a profile that is outside the specified limit value possesses, means for changing the rolling mill settings to a rolling force and / or a roll crown in every single stand to generate the nose an insertable profile or a profile within predetermined Limit values there;

(d) Devices for guiding the strip material through the rolling mill and for changing and adapting the rolling mill settings to those corresponding to a predetermined rolling schedule, suitable settings (if the settings do not already have these values), while the Inter-framework tension forces come into play one after the other; and

(e) means for rolling the strip material accordingly the rolling plan or scheme.

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The interstand tension also includes the tension between the last stand and the roll.

The rolling mill settings, which can be changed in process step (c) include e.g. the roller spacing and, alternatively or additionally, in the case in which the possibility of change the roll crown is given (e.g. in the case of bushings that allow roll deflection) the roll crown is also given.

The calculation of the roll crown in step (a) is preferably based on the knowledge of the roll crown of the roll stand in question, which e.g. ground in during the manufacture of the roll is and also comes about through roller wear during operation, it is also based on knowledge the thermal dissipation in the rollers during their operation and the idle times, which in a mathematical model of the dynamic, thermal crowning of the rolls are processed and deliver the thermal crowning present in each case.

These calculations can be carried out, for example, in a computer, preferably in a suitably programmed digital computer.

The invention also includes the strip material made by the method indicated. In a preferred embodiment, this rolled strip material consists, for example, of steel or aluminum.

In the following embodiments with reference to FIGS. 1 and the drawing described for example. The Management of a steel belt within a multi-stand Tandem cold rolling mill is referred to by way of example.

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That. resulting after a pass through a roll stand The profile of the nose of a steel strip depends on how exactly the rolling force that occurs when rolling the nose of that rolling force which deforms the work rolls (by bending and flattening) just so much that the total crowning (ground and thermal) of the roller is compensated. If the compensation is correct, the roll shape adapts exactly to this transversal thickness profile of the incoming strip, resulting in a perfect starting profile. On the other hand, is that If the compensation is not accurate, then the roll shape will not adapt to the incoming transversal during the rolling out of the nose Thickness profile, there are then different degrees of a "bad profile". There are two ways to compensate given, either the total curvature of the rolls by additional devices for changing the roll crowning, e.g. corresponding bushings, must be changed, or the rolling force present during the rolling out of the nose must be changed will. For stands without bushes to change the roll crown only the latter option comes into question.

The description further relates, for example, to a 4-stand tandem rolling mill which has bushings for changing the roll crowning in the first and last stand.

To obtain a "good profile" of the nose are as follows Process steps required:

(a) The rolling force theoretically acting on the nose, ie on the first few meters of the strip, is calculated according to known models and provides the rolling force F _T as a function of the interstand thickness during the strip passage, the interstand tensions, the stretching tension of the strip and the nip friction.

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Such a model gives the following relationship for the Stand i:

i i * i "i

F _T ^X = Wf (hy ¹ , T, K, ^ u ¹ ),

where Fm = total rolling force

W = width of the strip to be rolled

= Thickness of the tape when it is inserted

T = interstand tension

i
K sr clamping tension of the strip ya ^x S = friction in the roll gap of the stand i

f indicates that F _{m is} a function of the above variables.

The roll crown is calculated as follows:

The ground crown is known from the dimensions of the rolls for each stand. The thermal crown, which must be added to the base crowning is then calculated as follows:

First, when precalculating the sizes for a band, a coefficient Ci of thermal crown per unit speed is calculated for each stand. The equation for this calculation is based on the amount of losses in each nip entering the rolls. This causes differential thermal expansion and changes in the crown of the rolls.

The coefficient for the thermal crowning of the stand i is calculated on the assumption that the rollers are in a steady running condition, i.e. that the belt is already is rolled at the unit speed for an infinitely long time. "-...-,

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The formula for Ci is as follows: Ce

₊ h ¥

where Ce = coefficient of thermal expansion of the work rolls

Hrc = coefficient of heat transfer from the roller to the coolant

Tc = calculated roll torque

W = bandwidth

h J = thickness at the exit from the framework i

R ¹ = work roll radius of the stand i

O * = tensile stress on exit from stand i f ¹ = forward slip of stand i,

and where Ec is given as:

Ec = K ¹ "" Η In (1-r ¹ " ¹ ) + -K Ln (1-r * * *) +

r ^J

with K ss yield stress at exit from framework i r = decrease in thickness at exit from framework i, i.e. the decrease in thickness between the entry into the rolling mill and the exit from the stand

Second, approximate values of thermal crowning C ¹ (t) are calculated every 15 seconds using the following procedure:

1. A single measurement of the stand speed £ t). will made for all scaffolding.

2. Crowning for the steady state at time t is calculated as

CS ₀ ¹ (t) = O) ₁ C ¹ ; i = 1,2,3,4

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Here, C ^{1 means} the crowning per unit of speed for the steady state, as calculated above, and CO ₀ ⁰¹ (t) represents the thermal crowning that would be achieved if the rollers were to run at speed 63 for an infinitely long time. would run.

3. The actual thermal crown C ^ (t) at time t is therefore given by the equation:

k . All values of the variables ci> and C ^ o are constantly updated by entering new values every 15 seconds.

C ² Oo (t) is calculated from the current and previous values of the crowning of the swung-in state, ie C °> o (t), and from previous values of the actual thermal crowning, ie C ₀₀ Ot-At), where ^ t represents the sampling interval of 15 seconds. I ·,., Ip Ig are constants.

b). After the calculated roll crown is obtained, the ideal rolling force can be calculated in the following manner will:

The zero profile rolling force per unit of strip width is given by:

b = + It

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C ₀₆ represents the contactor value of the work roll crowning, fi, i = 1,2, .... are constants, GC is the base crowning of the stand i; Wf is the width of the roll surface; h ° represents the dimension when entering the rolling mill. The ideal rolling force is therefore given by F * = S ¹ W (W = width of the strip).

c). The deviation F _L from the ideal profile is ^{1 1} (1 + f ₁₂ W + J ₁₃ Ii _1-1 ) i = 1 to 4.

fi are constants.

The inequality (F * - F _T *) ^ F _n , ¹ <(F * + F *)

O Lt """" L "~~ O Lm

is tested for scaffolding 1 to 4 one after the other. No changes are made until this Limit has been exceeded. If this limit is exceeded, there will be a small change FIi in the rolling force of each Scaffolding made so that the force returns within the required limits. This minimal change brings the rolling force as close as possible to that value which gives the desired dimensions, it therefore causes a minimal change in dimensions.

If this limit value is exceeded in any framework, the following definitions are used

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the standard deviation for the compensation of a bad profile during the introduction is defined by the following equations:

Δ h ¹ - -1

The following lower and upper limit values exist for the values 4 h ^1:

Ah ¹ = f _i6 if Ah ¹ < f _i6

= f ₁₇ if ^ h ¹ > f ₁₇ h / = Vl f ₁₅ i 4 ^ 1-1. ^

= O (for the first stand, i.e. the dimension when entering the rolling mill)

Δhi = change only to the profile in the framework i H

h ¹ = dimension at the exit from the framework i

i ⁼ ^ ^nderun S ^the Rolling force with the exit dimension of the Scaffolding i

4 " ^f i7 constants

FIi is defined mathematically above and represents the Obtaining an acceptable profile required Change in rolling force. Mi = rolling mill module ·

hi-1 dimension when entering the framework i = total change in dimension of the framework i-1

™ total insertion change in dimension of the framework i,

i consisting of two parts, (i) the change h

only of the profile, and

(ii) composed of the effect of Er _T ~

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The settings for the stands of the rolling mill can then be loaded

recalculate.

then on the rolling forces F, + F ₁ ¹ and the dimensions h * +

The first and the last stand have, for example, bushings for roll bending, the required bushing forces Ji (for stand i) are given by the equations
KO ₉ H-Pr _n ¹ CKO, + KO _2. ) + KOc- GC ¹

_8th ^

given, where KO-toKO ^ _{0 represent} constants that are given by the mill dimensions.

These changes are made to the various scaffolding, and the mill is then ready to receive the strip material.

d). Changing the settings (i.e. the spindle positions for rollers, roller speeds, bushing forces) Return to the appropriate settings of a given rolling schedule effect are carried out by the at each Changes made to the stand can be undone while the strip material runs into the next stand. on in this way the amount of non-dimensionally stable material produced is reduced to a minimum.

The change in the settings is preferably carried out without disturbing the interframe tensions, for example by using non-interactive dimensional accuracy control methods, which are described in the "Journal of The Iron and Steel Institute ¹¹ , Volume 209, Part 11, November 1971, p. 869 are described to 875.

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Fig. 1 shows an embodiment formed with the aid of a digital computer 22 (cf. FIG. 2) in which block 100 represents the predetermined rolling schedule (i.e., interstand sizes and stresses). This rolling plan can be read, for example, in a preferred embodiment from a punched tape, or can be read by a computer program be calculated. This plan is fed into a computer, block 101, for calculating the infeed rolling force entered, in which the rolling force theoretically acting on the nose according to process step a) of the described Method is calculated.

The nominal rolling plan of the block 100 is also sent to the computer 102 for calculating the thermal crown supplied, which calculates the thermal crowning according to the described method step a), this Size processed by the zero profile rolling force computer 103 in the manner described in method step b) will.

The output signals of the blocks 101 and 103 are in the comparator 104 in accordance with the process step c) compared with one another as described, the output signal of block 104 is used to calculate the socket force settings and the changes to the dimensions required for the introduction according to method step c). The initial program is then used to make these settings in the rolling mill during the introduction to undertake the strip material, and to reverse it again in accordance with the manner described in process step d) close.

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2 shows a rolling mill with 4 stands 1 to 4, with strip-shaped rolling material, spindle position controllers 5 to 8, speed controllers 9 to 12 and bushing force regulators 13 and 14. The digital computer 22, see FIG. 1, calculates the bushing forces J ₁ , J ^ and the introductory dimensional corrections h ™ ¹ , which are fed to the controllers via the amplifiers 15 to 21 and the summing amplifiers 23 and 24.

As an alternative, the rolling mill is equipped with automatic tension control devices in which the adjusting spindles the individual scaffolding are also used; these facilities can then be used to Undo import changes while the strip is moving through the mill.

If the rolling mill has no bushings for roll bending, then it is difficult to achieve both a correct thickness and an exact profile for the nose of the strip material. When using bushings for roll bending by adjusting the roll gap and the bushing forces, this is essential easier to get both a correct thickness and an accurate, correct profile.

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Claims (3)

Claims Method for rolling strip material in a rolling mill with at least one controllable roll stand, characterized by the following process steps: (a) an at least approximate calculation of the rolling force and the required thickness that the nose of the strip material should theoretically have in the individual stands based on measurements of the rolling mill settings and data relating to the material to be rolled, and a calculation of the theoretical crowning of the rolls of each Scaffolding, (b) at least an approximate determination of the ideal rolling force for each individual stand, which together with the Crowning of the rolls of this stand of the nose is suitable for introduction into the subsequent roll stand Shape or a shape lying within specified deviation limits, (c) a comparison of the calculated rolling force of each individual stand with the determined ideal rolling force of this stand, and, provided that the calculated rolling force deviates from the determined ideal rolling force so far that the The nose profile is not suitable for further insertion or is outside the specified limit values, a Change of the rolling mill settings to generate a rolling force and / or a roll crown for each individual stand, due to which the nose is an insertable Receives a profile or a profile within the specified limit values, (d) the introduction of the strip material through the mill and, during the individual interstand tensile forces successively come to the effect that 509809/0913 Changing and adapting the rolling mill settings to the settings suitable for a given rolling plan (if these values are not already set), and (e) rolling the strip material essentially according to the rolling schedule. 2. Rolling mill for performing the method according to claim 1, characterized by (a) Means for continuously measuring the rolling mill settings relating to the material to be rolled and data, means for calculating the approximate rolling force and for specifying the required thickness, the theoretically should be present at the nose of the strip material in each individual roll stand, and facilities for calculating the crowning of the rolls of the individual stands, (b) Means for at least approximate determination of the ideal rolling force for each individual stand which together with the calculated roll crowning of this structure of the nose an introduction to the following Give the rolling stand a suitable profile or a profile that is within specified limit values, (c) Means for comparing the calculated rolling force with the determined ideal rolling force of each Rolling stands, and devices for changing the rolling mill settings, which, provided the calculated rolling force deviates so far from the specific ideal rolling force that the nose is unsuitable for further insertion Has a profile or a profile lying outside predetermined limit values, a rolling force and / or a roll crown in each individual stand that the 509809/0913 Nose gives an insertable profile or a profile within specified limits, (d) Means for guiding the strip material through the mill and for changing and adjusting the mill settings to the appropriate settings corresponding to a given rolling plan (provided that the Settings do not already have these values), while the inter-framework tension forces take effect one after the other come and (e) Means for rolling the strip material according to the rolling schedule. 3. strip material, characterized, that it is rolled according to the method according to claim 1. ReRb / Pi. 509809/0 913