EP0439663A1 - Method of controlling a continuous multistand rolling mill - Google Patents

Abstract

The invention relates to a control device for a continuous multistand rolling mill, in particular a light section mill, which has a computer with a memory for rolling program-specific variables, e.g. rotational speed set point values, armature currents and exit cross-sections and for the calculation of derived variables, e.g. the rolling stock tensions between the stands, minimum tension control being performed by controlling the rotational speeds of the individual stands (1m;1n) of the mill via additional rotational-speed set point values, these values being formed in accordance with a predetermined computing rule taking into account stored empirical values (KE) and the additional rotational-speed set point values being formed in accordance with the following computing rule: <IMAGE>

Description

The invention relates to a control device for a continuous, multi-stand rolling mill, in particular a steel mill, which has a computer with a memory for rolling program-specific sizes, e.g. Speed setpoints, armature currents and outlet cross sections as well as for the calculation of derived quantities, e.g. the rolling tensile stresses between the stands.

From DE-28 00 197 A1, as a related art, a method and an arrangement for regulating the rolling tension between the rolling stands of a tandem rolling mill are known, in which the tension in the rolling stock is calculated on the basis of the detected rolling force and the detected rolling moment and via tension Control compensation signals, which compensate for the deviation in tension, are regulated to a constant value. For control purposes, the reference lever arm for an i-th roll stand is calculated and stored in a memory and used to regulate the longitudinal tension of the rolling stock between the i-th and (i + 1) th roll stand, with the reference lever arm and more than one of the physical quantities of the rolling process including the thickness of the rolling stock at the entrance and exit of the i-th roll stand, the roll gap of the i-th roll stand and the rolling force on the i-th roll stand. The tensile stress is calculated on the basis of the calculated lever arm and the recorded values of the rolling force and the rolling moment.

Such a regulation is too complex for certain applications, particularly when rolling profiles or bars. This applies in particular to the modernization of existing, relatively slow-working rolling mills.

It is an object of the invention to provide a control device for the rolling tension in a design that acts as a minimum tension control, which is considerably less expensive than the known minimum tension control devices and is particularly suitable for bar and section steel mills. In particular, it should advantageously be avoided that the rolling train goes beyond the usual photocells and current and voltage measuring devices with complex sensors that measure forces, e.g. for the rolling force or the rolling force lever arm.

The object is achieved in a surprisingly simple manner in that, for minimum tension control, the speeds of the individual stands of the rolling mill are controlled via additional speed setpoints, these being formed according to a predetermined calculation rule, taking into account stored empirical values. All that is required is a relatively simple computer with a memory, which stores the essential electrical values of a rolling mill that result during operation and evaluates them for use, the evaluation leading to a minimal train control behavior.

In an embodiment of the invention it is provided that the empirical values are determined by an auxiliary program, stored and used with continuous correction to control the rolling process. As a result of the continuous correction, ie learning behavior, the control device according to the invention acts like a control method with a closed control loop and thus achieves simple, automatic, train-optimal adjustment of a rolling train. Only the response time of the control is longer than with direct control with sensors, but this can often be accepted, especially in the case of bar and section steel mills, since slight deviations from the optimal minimum pull do not have as disruptive effects as in sheet metal rolling mills.

gebildet werden, wobei K_E aus den gespeicherten Erfahrungswerten ermittelt wird. Der Erfahrungswert K_E wird dabei in Form einer prozentualen Drehzahländerung je N/mm² und ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

in Form eines spezifischen Zuges in ebenfalls N/mm² eingegeben und im Rechner in Stromgrößen umgeformt. So ergibt sich eine Zugregelung, insbesondere eine Minimalzugregelung, die unter Berücksichtigung der im Stab herrschenden Zugspannungen arbeitet. Durch die prozentuale Drehzahländerung, ihre Größe bewegt sich im Bruchteilsbereich eines Prozents, wird eine genaue Regelung erreicht, die insbesondere den Anforderungen von Stab- und Profilstahlstraßen Rechnung trägt, aber auch bei Blechwalzstraßen zur Anwendung kommen kann. Wie sich gezeigt hat, führt der sich einstellende längere Regelzyklus unter Normalbedingungen nicht zu Toleranzüberschreitungen.In a further embodiment of the invention it is provided that the additional speed setpoints according to the calculation rule

are formed, whereby K _{E is determined} from the stored empirical values. The empirical value K _E is in the form of a percentage change in speed per N / mm² and ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

entered in the form of a specific train in N / mm² and converted into current values in the computer. This results in a tension control, in particular a minimum tension control, which works taking into account the tension in the rod. The percentage change in speed, the size of which is in the fraction of a percent, results in precise control, which takes into account the requirements of bar and section steel mills in particular, but can also be used for sheet metal rolling mills. As has been shown, the longer control cycle that arises does not lead to tolerance violations under normal conditions.

To carry out the invention, it is provided that the armature current J _{A is} filtered, in particular subjected to filtering in a Butterworth filter or similar filter. This results in a very advantageous smoothing of the armature current and one simply obtains a representative current mean value for the further calculations.

% über den Erfahrungswert K_E bezeichnet J_A1 den Ankerstrom vor dem Anstich im Folgegerüst, d.h. ohne Beeinflussung durch das Folgegerüst, J_A2 den Ankerstrom nach dem Anstich im Folgegerüst, d.h. mit Einfluß des Folgegerüstes und ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

den Zugstromsollwert, der separat, in der Regel vorab, ermittelt wird. Dies geschieht aus gespeicherten Walzdaten und den festen Walzstraßenparametern, wie Getriebeübersetzung, Feldschwächverhältnis etc.In the above-mentioned simple calculation rule used according to the invention for forming the additional speed setpoints n $\genfrac{}{}{0ex}{}{\text{*}}{\text{Z}}$

% above the empirical value K _E denotes J _A1 the armature current before the tapping in the secondary scaffold, ie without being influenced by the secondary scaffold, J _A2 the armature current after the tapping in the secondary scaffold, ie with the influence of the secondary scaffold and ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

the train current setpoint, which is determined separately, usually in advance. This is done from stored rolling data and the fixed rolling mill parameters, such as gear ratio, field weakening ratio, etc.

FIG 1

die schematische Darstellung einer Walzstraße mit der Steuerung eines Gerüstes bei größeren Walzgutgeschwindigkeiten,

FIG 2

die schematische Darstellung einer Walzstraße mit der Steuerung eines Gerüstes bei kleineren Walzgutgeschwindigkeiten und

FIG 3

die Prinzipdarstellung der erfindungsgemäßen Steuereinrichtung.

Further advantages and details emerge from the following description of exemplary embodiments, using the drawing and in conjunction with the subclaims. The drawing shows:

FIG. 1

the schematic representation of a rolling mill with the control of a stand at higher rolling stock speeds,

FIG 2

the schematic representation of a rolling mill with the control of a stand at lower rolling stock speeds and

FIG 3

the schematic diagram of the control device according to the invention.

% ermittelt und über den Signalweg 13 dem Gerüst 1_m+1 aufgegeben. Die Durchlaufzeit des Walzgutes zwischen den Gerüsten 1_m und 1_m+1 ist in eine Beruhigungszeit t_A1 zum Ausregeln des Anstichstoßes im Gerüst 1_m und eine Sicherheitszeit t_S1 aufgeteilt, wobei nach der Beruhigungszeit t_A1 die Sollwertänderung für das folgende Gerüst 1_m+1 ermittelt wird. Die Regelrichtung wird durch die strichlierte Linie 14 angegeben, kann aber auch entsprechend der strichlierten Linie 14', also entgegengesetzt, verlaufen.In FIG 1, the individual roll stands are denoted by 1 and an index. The symbolically represented rolling stock passes through one after the other in the direction of the arrow. The minimum tension control by the control device 2 is shown in this example between the roll stands 1 _m and 1 _{m + 1} . The armature current J _A1 and J _{A2 is} measured on the roll stand 1 _m and is applied to the control device 2 via the signal path 12. In the control device 2, the additional speed setpoint n $\genfrac{}{}{0ex}{}{\text{*}}{\text{Z}}$

% determined and given to the scaffold 1 _{m + 1} via signal path 13. The throughput time of the rolling stock between the stands 1 _m and 1 _{m + 1} is divided into a calming time t _A1 for regulating the tapping in the stand 1 _m and a safety time t _S1 , with the setpoint change for the following stand 1 _{m +} after the calming time t _{A1 1 is} determined. The control direction is indicated by the dashed line 14, but can also run according to the dashed line 14 ', that is, in the opposite direction.

The adjustment of the individual stands takes place at high rolling stock speeds, for example with rolling stock head times from stand to stand under one to two seconds, in such a way that the additional speed setpoint is not changed until the next rolling pass. The control cycle therefore extends from rod to rod.

In FIG. 2, in which the rolling stands are denoted by 1 _n , the arrangement and mode of operation of the control device 2 is in principle corresponding to FIG. 1, but here the next following stand 1 _{n + 1 is} already influenced during the same pass through the rolling stock. Made possible by the lower rolling stock speed, the tapping of the stand 1 _{n is} first corrected in a calming time t _A1 , the current value is stored in the control device 2 _n-1 and an adjustment is carried out. The resulting renewed load current is corrected in the calming time t _B1 and the current J _{A1 is} stored for the calculations of the minimum draft control 2 _n . A safety time t _{S1 is also} provided here, which avoids a time overlap.

In FIG. 3, 2 also designates the control device according to the invention, in the computer part 2 'of which a rolling stock replica is contained as a model. Furthermore, the control device 2 has a setpoint setting part 2 ″ in which the speed setpoint n * is formed, the signal of which is designated by 11. 2 '' 'denotes the parameter input unit of the control device 2, to which signals from a keyboard or a monitor are applied via the signal path 8. The replica of the rolling stock is entered via various photo cells etc. via signal path 9, the respective position of the rolling stock. Thus, the computer 2 can enter the armature currents, which are preferably input via the six-pole Butterworth filter 10, divided into the closed state and the tensile state, into the memories 3 and 4 in relation to the position.

, ein Erfahrungswert, der drehzahl- und walzprogrammabhängig ist, aus der Parametereingabe 2''' aufgegeben wird. In der Einheit 5 wird aus diesen Daten der Zugstromfehler ΔJ_A ermittelt und zusammen mit dem Erfahrungswert K_E dem Multiplikator 6 aufgegeben, in dem der Zugstromsollwert n* gebildet wird. Die Übergabeeinheit, die dafür sorgt, daß das Signal geschwindigkeitsabhängig in einer Walzgutlücke oder beim laufenden Stab entsprechend FIG 2 als Verstellbefehl über den Sollwertsteller 2'' als Sollwert n* gebildet wird, ist mit 7 bezeichnet. Die Einheiten 3,4,5, 6 und 7 bilden zusammen den Rechenteil der Steuereinrichtung für die fortlaufende Ermittlung und zeitgerechte Abgabe des Drehzahlsollwertes n*.From the memories 3 and 4, the signals of the armature currents for the draft-free and the tensile state reach the difference-forming device 5, which also contains the tensile current setpoint ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

, an empirical value, which is dependent on the speed and rolling program, is entered from parameter input 2 '''. In unit 5, the traction current error ΔJ _{A is} determined from this data and, together with the empirical value K _E , is fed to the multiplier 6, in which the traction current setpoint n * is formed. The transfer unit, which ensures that the signal is formed as a function of the speed in a rolling gap or when the rod is running as shown in FIG. 2 as an adjustment command via the setpoint adjuster 2 ″ as setpoint n *, is designated by 7. The units 3, 4, 5, 6 and 7 together form the computing part of the control device for the continuous determination and timely delivery of the speed setpoint n *.

wobei ΔJA den Zugstromsollwert (A), AZ* die spezifische Zugkraft im Walzgut (N/mm²), A_A den Austrittsquerschnitt (mm²), d_W den Walzendurchmesser (mm), n* den aktuellen Drehzahlsollwert (Upm), J_AN den Ankernennstrom des Motors (A), i die Getriebeübersetzung und P_N die Motornennleistung (KW) bedeutet.Specific trains are converted into armature currents according to the equation

where ΔJA the tensile current setpoint (A), AZ * the specific tensile force in the rolling stock (N / mm²), A _A the outlet cross section (mm²), d _W the roll diameter (mm), n * the current speed setpoint (rpm), J _AN the nominal armature current of the engine (A), i means the gear ratio and P _N the nominal engine power (KW).

Claims (9)

Control device for a continuous, multi-stand rolling mill, in particular a steel mill, which has a computer with a memory for sizes specific to the rolling program, for example speed setpoints, armature currents and outlet cross sections, and for calculating derived sizes, for example the tensile stresses between the stands,
characterized,
that the speeds of the individual stands (1n) of the rolling mill are controlled via additional speed setpoints for minimum tension control, these being formed according to a predetermined calculation rule, taking into account stored empirical values (K _E ). Control device according to claim 1,
characterized,
that the empirical values are determined by a disturbance variable evaluation program, stored and used to control the rolling process. Control device according to claim 1 or 2,
characterized,
that the additional speed setpoints according to the calculation rule

are formed, whereby K _{E is determined} from the stored empirical values. Control device according to claim 1, 2 or 3,
characterized,
that the empirical value K _E in the form of a percentage change in speed per N / mm² and ΔJ $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

is formed in the form of a specific train in N / mm². Control device according to claim 1, 2, 3 or 4,
characterized,
that the armature current J $\genfrac{}{}{0ex}{}{\text{*}}{\text{A}}$

filtered, in particular filtering with Butterworth filters or similar filters. Control device according to claim 1, 2, 3, 4 or 5,
characterized,
that the empirical value K _{E is} determined again after control movements which exceed limit values. Control device according to claim 1, 2, 3, 4, 5 or 6,
characterized,
that the required train setpoint for the control is determined on the basis of the train actual value tolerances for several unregulated runs. Control device according to one or more of the preceding claims,
characterized,
that it has memory (3, 4) for the armature currents in the closed and tensioned state, a difference-forming unit (5) for the stored armature currents and a multiplier (6) for the output value of the difference-forming unit (5) with the empirical value (K _E ). Control device according to one or more of the preceding claims,
characterized,
that it has a computer with a rolling path replica, a parameter input and a setpoint adjuster.

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