EP0008037B1 - Device for tension control in a continuous rolling mill - Google Patents

Abstract

1. Device for regulating the tension transmitted in the goods to be rolled in a rolling mill which contains m stages, comprising a speed regulator at each stage and comprising a regulating device (e.g. 1.24) which is superimposed upon the speed regulator in at least m-1 stages and which serves to adjust the rolling speeds of the stages which follow one another in the direction of rolling, and with a calculating circuit (e.g. 1.14) which is in each case assigned to the regulating devices and which serves to calculate the actual value of the regulating quantity (e.g. Mz1 ) from the relevant drive moment, acceleration moment and deformation moment, characterized in that in order to stabilise the speed characteristics of the rolling mill, each of the stages (1 to m) is assigned a regulating device (1.24 to m.24) of this kind and these regulating devices are superimposed by a common correcting regulator (27) which is supplied with the output signal (DELTA n*) of one of the regulating devices by way of input quantity, and from whose output signal (Fk * or sigmak *), from the theoretical value of the tension force (FA * or SigmaA *) on the drive side of the particular associated and of the possibly preceding stage and from other rolling parameters the theoretical value (Mz*) for the regulating devices is formed in each case in a calculating means (1.28 to m.28).

Description

The invention relates to a device for controlling the tensile force transmitted in the rolling stock in a rolling mill containing m stands, with a speed controller on each stand and with a control device superimposed on the speed controller on at least m-1 stands for adjusting the roll speeds of the stands in succession in the rolling direction and each a computing circuit assigned to the control devices for calculating the actual value of the controlled variable from the respective drive, acceleration and deformation torque. DE-A-2541 071 describes a device of this type which is intended to make it possible to set the speed ratios required for a defined tensile stress in the rolling stock in a short time and in a simple manner. The tensile stress in front of and behind each stand, to which a tension differential control device is assigned, is determined from the drive torque, the acceleration torque and the deformation torque in the roll gap. One of the stands takes on the function of a guide stand, which essentially determines the rolling speed in the street. However, it cannot be ruled out that tensile stresses deviating from the nominal value occur in front of and behind the guide scaffold, which result from the sum of the torque errors of the other scaffolds. This disadvantage becomes all the more serious the larger the number of scaffolding on a street.

The invention is therefore based on the object of providing a device of the type mentioned at the beginning with which a rolling mill can be operated with an even distribution of the tensile stresses or moments regardless of the number of stands.

According to the invention, this object is achieved in that such a control device is assigned to each of the stands to stabilize the speed behavior of the rolling mill and a common correction controller is superimposed on these control devices, to which the output signal of one of the control devices is fed as an input variable and from its output signal from the setpoint the tensile force on the drive side of the respectively associated and possibly preceding stand and from further rolling parameters, the setpoint for the control devices is formed in one computing element in each case.

This avoids that the sum of the torque errors leads to a constant change in the speed and thus the rolling speed.

The invention is explained below using an exemplary embodiment shown in the drawing.

In Fig. 1, the work rolls 5 of a roll stand including an associated DC drive motor 6 and a speed controller 7 with a downstream actuator 8 are shown schematically. A tachometer generator 9 coupled to the motor supplies an output signal which is proportional to the speed and which is compared with a setpoint n ^* . To achieve the correct speed relationships between the drives of several stands on a rolling mill, an additional speed setpoint dn ^{* is} fed to the comparison point. Furthermore, a current transformer 10, which supplies _a voltage proportional to the armature current i _a , and a sensor 11 are provided, the output voltage Φ of which is proportional to the flux in the field winding 13. F _E denotes the tensile force acting in the rolling stock 12 in the rolling direction on the entry side of the stand and F _A denotes the tensile force on the exit side.

A control device 24 shown in FIG. 2 has the task of comparing the train-related actual torque value with the associated setpoint value and forming the additional speed setpoint value Δn * from the deviation. The actual value of the train-related torque is determined by means of a computing circuit 14.

The drive torque Ma = Φ · i _a is composed of the acceleration torque Mb and the rolling torque Mw, which in turn is the sum of the deformation moments Mh and Hv of the horizontal and vertical rollers, and the torque Mz caused by the tensile stress.

So it is:

The acceleration torque Mb can be derived from the speed n and the deformation moments Mh and Mv result from the rolling forces Fh and Fv measured by means of rolling force transducers by multiplication by a factor Kh or Kv corresponding to the lever arm of the rolling forces. The factor Kh can be determined for universal stands based on the roll gap geometry and is specified by hand. The lever arm factor Kh is calculated in a balancing circuit for duo scaffolds. The factor Kv, on the other hand, depends on various non-detectable influencing variables and is therefore determined with the aid of the adjustment circuit and then stored. The arithmetic circuit 14 accordingly receives the measured values i _a , Φ, n and Fh as well as the variables Fv and Kh, if necessary corresponding stress, which is formed by means of a differentiating element 17, and the stresses proportional to the deformation moments, which result from the rolling force signals Fh and Fv by means of a multiplier 19 hzw. of a multiplier 20 are formed, are subtractively applied to the summing element. To determine the factor Kh or Kv, the differential voltage at the output of the summing element 16, which is proportional to the moment Mz, is fed to a comparison point 21. If the scaffolding is a duo, switches 18 and 22 assume the position shown in dashed lines.

After painting in the first scaffold of the road, an integrator 23 connected downstream of the comparison point changes the lever arm factor until the product Fh-Kh and the product Φ · i _a minus the acceleration torque Mb are of the same magnitude. The lever arm factor Kh calculated in this way is saved for the rest of the stitch in the second stand before the tapping.

For a universal scaffold, the switches 18 and 22 assume the position shown for determining the lever arm factor Kv.

When calculating Kv, inaccuracies in the manually entered factor Kh are largely compensated for. For all subsequent stands of the rolling mill, the automatic adjustment of the lever arm factor Kh for duo or Kv for universal stands with subsequent storage takes place in the same way, but with additional consideration of the train F _E on the entry side. The associated, the comparison point 21 in Fig. 2 supplied entrance side z _J gbeding- th moment M _e corresponds steady state the exit-side component of the tension set value corresponding to the preceding control unit, and thus the preceding frame is specified, multiplied by the rolling radius of the scaffold, for that the lever arm factor is being calculated. In any case, the calculation runs so quickly that it ends before the rolling stock enters the next stand.

The difference between the output signal Mz of the summing element 16 and a torque setpoint Mz ^* is fed to the control device 24. The torque setpoint is determined by means of a computing element 28 from the specific train a ^* specified by the helmsman, the roll cross sections A, the roll diameter dw and a correction variable. The speed correction value A n ^* supplied by the control device 24 is during the tapping phase of each stand of the speed control of the following or all subsequent drives - in the example shown as Δ n ₂ 'of the speed control on stand 2 - and after the tapping in the following stand via a reversing amplifier 25 the speed control of the own drive - in the example as Δ n * _{1 of} the speed control on stand 1 - supplied. A switch 26 is provided for switching, which must briefly assume the intermediate position shown so that the output signal of the control device is reset to zero. The actuation signal for switch 26 is conveniently E; derived from the change in the output voltage of the rolling force transducers at the time of tapping.

In Fig. 3, a continuous roll train is shown schematically, which includes, for example, four stands. The stands including the drive and the speed controller are shown schematically by the rollers 1 to 4. A computing circuit 14 and a regulating device 24 are assigned to each scaffold, which are designated in this figure with 1.14 to 4.14 and with 1.24 to 4.24, respectively, according to their assignment to the respective scaffold. The speed correction value .DELTA.n * _{4 of} the control device 4.24 of the last stand forms the input variable for a correction controller 27 superimposed on all control devices 24 in the exemplary embodiment shown. The setpoint Mz ^* of the torque dependent on the train is in each case in a computing element 1.28 to 4.28 from the output variable of the correction controller, which, for example, in FIG. 3 represents the correction target value σ _K * of the specific tensile stress related to the unit area, and from the magnitudes valid for the respective scaffold; namely the target value σ _E *, σ _A * of the specific tensile stress on the entry - or exit side, the entry and exit side cross section A of the rolling stock and the diameter dw cei rolls calculated.

und für das zweite Gerüst

In analoger Weise sind die entsprechenden Größen für das dritte und gegebenenfalls jedes weitere Gerüst einzusetzen. Am letzten Gerüst m ist der Wert für MA"* Null.In Fig. 3 the specific tensile stresses o, the entry and exit moments M _E , M _A and the correction moments M _kA , M _{kE are} entered, which occur between or on the individual stands. While the entry and exit moments on each stand are opposite to each other, the correction moments act in the same direction. The setpoint Mz ^* for the train-dependent torque on the respective scaffold is the difference between the setpoint M _E ^{* of} the entry torque and the sum of the setpoint M _A * of the exit _torque , the corrected setpoint M _kA * of the exit _torque and the corrected setpoint M _kE ^* the entry torque. The first scaffolding applies

and for the second scaffold

In an analogous manner, the corresponding sizes for the third and, if necessary, each further scaffold are to be used. At the last stand m the value for MA "* is zero.

In the exemplary embodiment described so far, the correction controller 27 intervenes on the target values of the specific train (N / mm ² ), which takes into account the probability that the train error components are larger where the larger cross sections are rolled. Instead, an embodiment can also be selected in which the controller 27 influences the target values of the tensile forces. The output variable of the controller is then a corrected longitudinal tensile force setpoint F _k ^*.

The following then applies differently:

This execution of the correction intervention brings advantages with constant absolute error distribution in the street.

In both cases, the setpoint value influences the rolling torques of all stands until the desired speed control of the road is reached, i.e. here, for example, the speed of the drive on the last stand is kept constant at the value that was obtained at the time the last control device was released . This state means that the output voltage of the last control device m.24 is regulated to zero. Since the correction controller 27 intervenes only via the control devices 24, these cannot run to the stop. The already existing speed correction variable Δ n * _m at the output of the control device for the last stand serves as the difference between the speed setpoint and the actual speed value for the correction controller.

Further details of the mode of operation can be seen in FIGS. 4 to 6. During the tapping phase in stand 1, ie during the time from the tapping of the beginning of the rolling stock in stand 1 to the tapping in stand 2 (FIG. 4), the moment Mz ₁ = 0 dependent on the train, because M _E1 = M _A1 = 0. During the piercing phase, the lever arm factor K of the rolling force for stand 1 is determined, as explained in connection with FIG. 2.

The determination of the lever arm factor is ended as soon as the output voltage M _{z1 of} the arithmetic circuit 1.14 has become zero. The lever arm factor is saved for the rest of the stitch.

With the tapping in the frame 2 (FIG. 5), the control device 1.24 becomes effective, at whose actual value input the output voltage M _{z1 of} the arithmetic circuit 1.14 is present and whose setpoint input receives an initially constant setpoint Mz ^* . The output voltage Δ n * of the control device 1.24 is fed via a proportional element 1.29 with storage behavior to the speed controller of the drive on the second stand as an additional speed setpoint Δ n ^* ₂ '. If the rule adjustment of the control device 1.24 is reached, the relationship applies

Consequently, Mz ^* i = - M _A1 for scaffold 1, because the input moment M _{El in} front of scaffold 1 is always zero.

The additional speed setpoint .DELTA.n * ₂ 'is expediently not only fed to the speed controller of the following stand (shown in dashed lines), but also to the speed controllers of the other subordinate stands to accelerate the setting of the final speed relations.

During the piercing phase in the scaffold 2, the associated lever arm factor is determined and stored in the same way as described in connection with FIG. 5. The actual torque value M _Z2 = M _EZ then arises at the output of the computing circuit 2.14, since M _{A2 is} still equal to zero.

When the rolling stock 12 is tapped in the stand 3, the proportional member 1.29 is switched to “save”, the output signal of the control device 1.24 is briefly set to zero and the output of the proportional member is then switched to the speed controller on the stand 1 via the reversing amplifier 25 as Δ n * (Self-adjustment for scaffold 1). The additional speed setpoint .DELTA.n * ₂ 'is further specified to the speed controller on stand 2 from memory 1.29. This additional speed setpoint remains superimposed when the control device 2.24 is switched to self-adjustment and the additional speed setpoint Δ n * _{2 is} specified by tapping the rolling stock in stand 4. The additional setpoint .DELTA.n * _{2 of} the control device 2.24, which acted on the speed controller of the tower 3 until the tapping in the tower 4, is also further specified for the tower 3 as a stored value .DELTA.n * ₃ ', while the output of 2.24 after zeroing is switched to the speed controller of stand 2 with the opposite sign as Δ n * ₂ .

This procedure guarantees a smooth transition to self-adjustment.

As already indicated in the explanation of the switchover of the control device 2.24 to self-adjustment, the processes described in connection with the stand 2 are repeated on all further stands. The sequence on the scaffold 4 or the last scaffold m differs from these processes only in that this scaffold is switched to self-adjustment immediately after the calculation of the associated lever arm factor has been completed and in the exemplary embodiment shown the additional speed setpoint Δ n * ₄ or Δ n * _m , as already explained in connection with FIG. 3, is supplied to the correction controller 27 common to all stands.

As can be seen from the description, the penultimate, mill-guiding stand is first operated at a fixed speed. With the release of the last control device 4.24, the scaffolding-free operation begins. It therefore becomes the overriding correction at the same time controller 27 released, which, as already explained, now takes over the speed control of the road with the participation of all scaffolding instead of a control scaffold.

Claims (3)

1. Device for regulating the tension transmitted in the goods to be rolled in a rolling mill which contains m stages, comprising a speed regulator at each stage and comprising a regulating device (e. g. 1.24) which is superimposed upon the speed regulator in at least m-1 stages and which serves to adjust the rolling speeds of the stages which follow one another in the direction of rolling, and with a calculating circuit (e. g. 1.14) which is in each case assigned to the regulating devices and which serves to calculate the actual value of the regulating quantity (e. g. Mz_i) from the relevant drive moment, acceleration moment and deformation moment, characterised in that in order to stabilise the speed characteristics of the rolling mill, each of the stages (1 to m) is assigned a regulating device (1.24 to m.24) of this kind and these regulating devices are superimposed by a common correcting regulator (27) which is supplied with the output signal (Δ n*) of one of the regulating devices by way of input quantity, and from whose output signal (F_k ^* or _Ok ^*), from the theoretical value of the tension force (F_A ^* or _OA ^*) on the drive side of the particular associated and of the possibly preceding stage and from other rolling parameters the theoretical value (Mz^*) for the regulating devices is formed in each case in a calculating means (1.28 to m.28).

2. Device as claimed in claim 1, characterised in that the calculating means (1.28 to m.28) are supplied not only with the output quantity (F_k ^*) of the selected regulating device (e. g. 4.24) and the theoretical value (F_A ^*) of the tension force, but also with the associated roll diameter (dw) by way of additional rolling parameter.

3. Device as claimed in claim 1, characterised in that the calculating means (1.28 to m.28) are supplied not only with the output quantity (_Ok ^*) of the selected regulating device (e. g. 4.28) and the theoretical value (σ_A*) of the specific tension stress, but also with the rolled goods cross-sections (A_A, A_E) preceding and following the relevant stage together with the associated roll diameter (dw) by way of additional rolling parameter.

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