DD296863A5 - METHOD AND ARRANGEMENT FOR SPEED CORRECTION IN THE CONTINUOUS COLD ROLLING OF PIPES - Google Patents

Abstract

The invention relates to the continuous cold rolling of pipes via an internal tool. It is used to set the rolling speeds on to be expected by dimensional tolerances of the tube billets changed rolling conditions. The task is solved by measuring a size that is proportional to the dimensional tolerances of the tube blanks, eg. As speed and / or armature current and derivative of signals, when exceeded by based on dimensional tolerances of the tube billets changed straight line of the permissible tensile coefficient is exceeded. For this purpose, a correction speed series is retrieved from a precalculated and stored correction rotational speed series and brought to the setting. {Tube rolling, continuous; Cold; Mandrel; Rolling mill; Control; Speeds; Adaptation; Dimensional tolerances; tube blanks}

Description

Field of application of the invention

The invention relates to the technical field of continuous rolling, in particular the continuous rolling of pipes in the cold state via an internal tool. It serves to set the speed to anticipated rolling conditions.

Characteristic of the known state of the art

In continuous rolling mills, it is known that the speed series are calculated as a function of the intended individual take-offs in the rolling mills and, in general, under consideration of a tensile coefficient together with the calibration calculation. During the rolling process, however, there are again and again undefined discontinuities.

Thus, in the continuous cold rolling of pipes over a mandrel bar as an internal tool, dimensional tolerances of the tube billets result in a change in the height of the draft in the first rolling stand realizing the wall.

Under certain circumstances, the beginning of the wall removal is shifted to an adjacent scaffolding. As a result, the speed of the affected and subsequent scaffolds no longer conforms to the law of volume constancy.

It comes to rolling with too high or too low train. It may even come to the pressure build-up between the affected scaffolding. The result is reduced tool life, poor deployment and even lost production.

In order to eliminate these negative phenomena, DD-PS (Application No. WP B21 b / 274562-6) proposes to make a measurement of the wall thickness and the diameter of the tube billets prior to rolling, to determine the actual decreases in the first stands of the rolling mill and adjust the rotational speeds of the rollers accordingly, the calibration of the maximum allowable plus tolerance of the tube blanks emanates. The disadvantage here is that a high cost for the required measurement technique is necessary and provide the known measuring methods not sufficiently reliable results.

Other proposals for compliance with a minimum train (DD-PS 144011, DD-PS 238741) use measured variables of the rolling process in a row arranged scaffolding and derive from correction commands for the rotational speeds of these and adjacent scaffolding. These proposals can not be achieved in the continuous cold rolling of pipes over a mandrel bar

because this correction takes effect too late. The affected and the follower framework, which already require a speed correction in the continuous cold rolling of pipes over a mandrel bar, according to these proposals provide only the output signals for deriving the correction commands.

Object of the invention

The aim of the invention is to carry out the continuous cold rolling of pipes via an inner tool, the detection and correction of tolerances of the pipe blank to be expected discontinuities of the rolling process with low technical and economic effort and thus to avoid reduced tool life, deteriorated spreading and production losses.

Explanation of the essence of the invention

The invention is based on the object, indeterminate discontinuities caused by dimensional tolerances of the tube blanks to quickly detect during the rolling process, evaluate and lower by a speed correction while rolling the same Walzgutstückes under harmless for the rolling limits.

According to the invention the object is achieved in that a realizing during rolling in the first, wall decrease scaffolding the dimensional tolerances of the tube billets proportional size, such. As the speed and / or armature current of the motor, detected in this scaffold and compared with values of this size at normal, the process of the speed and calibration calculation corresponding load.

In case of deviation beyond predetermined limits from the normal value correction commands are derived to adapt the rolling speeds to the really expected rolling conditions. For this purpose, a corresponding speed series is retrieved from a group of precalculated and stored correction speeds and brought to setting. The acquisition of the measured values, their evaluation, the derivation of correction commands as well as the execution of the correction take place in the period up to the tapping of the tube billets in the following framework.

For performing the setpoint comparison, derivation of the correction commands and execution of the correction devices known per se are arranged in the following manner and interconnected in circuit.

The measurement result of the rotational speed and / or the armature current are fed to a microcomputer together with a time signal of a time-constant frequency generator

The microcomputer interacts with a speed setpoint specification. The speed setpoint input is also connected to a matching stage, which is further connected to the microcomputer and a sequence adjustment of the drives is ^f . The setpoint speed series is set via the speed setpoint specification, the adaptation stage and the sequence adjustment of the drives.

During the piercing of the tube blank beginning between the rollers of the first, wall decrease realizing scaffold, the measurement of the speed and / or the armature current and the supply of measured values to the microcomputer. This compares the values with the normal load values stored in the speed reference preset, d. H. Pipe dies without tolerances. If predetermined limits are exceeded, the microcomputer sends a signal to the desired speed value specification for releasing a correction speed series from a precalculated and stored in her correction speed series and line to the Anpaßstufe, which simultaneously receives a signal from the microcomputer to determine the necessary speed changes of the affected drives. These values are forwarded to the sequence adjustment of the drives and thus the speed of the affected rollers changed The time signals from the puncture in the first, wall detaching scaffolding to the piercing in the scaffold are counted by the microcomputer and the determined time with einheoretischen time for the passage of the tube beginning through the gap between scaffolds compared. If the deviation is too great, the microcomputer issues a command to the speed command value preset to a post-correction in the manner described above by releasing a new correction speed series.

embodiment The invention will be explained in more detail in the following example. The accompanying drawing shows the block diagram of

used measuring and control devices.

For cold rolling, tube blanks with a nominal wall thickness of 2.6 mm are used. According to TGL 9012, the wall may be maximum

Be 2,925mm. By operational organizational definition, the range of 2.6 to 2.9mm is allowed.

The calibration is based on a nominal wall thickness of 2.8 mm and straight lines of λ = 1.05 in the first two Wall removal realizing stitches. For this purpose, the speed calculation takes place under consideration of a tensile coefficient of 2%. If a tube blank with a wall thickness of 2.85 mm is used, the degree of stretching becomes the first wall decrease

realizing scaffolding greater than 1.05, the tensile coefficient is consumed and there is already a slight pressure build-up in

Longitudinal direction in the pipe between these stands. Corresponding to higher decrease arise in the drive motor of the first

On this signal, a precalculated and stored speed series is retrieved and set. The new speed series is based on the framework in question in these 2% higher and recorded all the following scaffolding. By comparing the actual speed of the pipe start with a theoretical speed, a check is made as to whether the set speed series is sufficient. If not, it will be corrected again.

With a small wall thickness of the tube blank, a correspondingly lower speed series is set. If there is no wall removal in the first scaffold intended for wall removal, the following scaffolding will be included in this correction mechanism.

For permissible degrees of yield of 1.1 to 1.12, for each first, wall-detaching framework, 4 to 6 correction rotational speed series are sufficient which deviate from one another by the tensile coefficient in the framework concerned and are calculated in a known manner for the subsequent structures.

The speeds 1 and the armature current 2 are constantly detected by existing in the rolling mill gauges.

The measuring signals of the rotational speed 1 are fed directly to the armature current 2 via an A / D converter 3 to a microcomputer 4. At the same time, the microcomputer 4 receives time signals from a time constant frequency generator 9 via the A / D converter 3.

The microcomputer compares the size of the measuring signals of the armature current 2 and the speed drop when tapping the tube blank with a size that was obtained when puncturing tube blanks without dimensional tolerances, d. H. with the theoretical normal state, which is stored in a speed setpoint default 5.

If the differences of the measurement signals exceed the value that indicates an overshoot of the train, then the microcomputer 4 retrieves from the correction speed series stored in the speed setpoint input 5 a suitable correction speed series which is fed directly to a matching stage 6. In response to a signal from the microcomputer 4, the determination of the necessary change in speed in order to adapt to the new drive motors 8 takes place in the adaptation stage.

In order to check the set speed series, the clock signals generated by the time-constant frequency generator 9 are counted in the microcomputer 4 and the actual pipe speed is determined from the puncture in the scaffolding concerned to the piercing in the follower. By comparison with the theoretical tube speed resulting from the peripheral speed of the rollers, the microcomputer 4 determines remaining differences. If these differences exceed the tensile coefficient, the microcomputer 4 triggers a post-correction in the manner described above by setting a new speed series.

To avoid false circuits, the microcomputer 4 is only then command to retrieve a correction speed series when both the armature current and the Drehzahlabf all points to large dimensional tolerances of the tube blank.

With this solution, a correction of the speeds is still during the rolling process of the tube blank, point out in the first measurement signals to large dimensional tolerances secured.

Claims (5)

1. A method for speed correction in the continuous cold rolling of tubes via a mandrel running along as an inner tool for adjusting the speed to be expected by dimensional tolerances of the tube billets changed rolling conditions using continuously during the rolling process measured values, characterized by detecting the dimensional tolerances of the tube billet proportional measured values during the puncture of this billet in the framework in which wall removal takes place for the first time, comparison of the size of these measured values with corresponding sizes obtained during rolling of tube billets without dimensional tolerances, and derivation of correction commands for setting a correction speed series which is recalled from a precalculated and stored correction speed series , in all rolling stands affected by dimensional tolerances, until the roughing of the billet in the following stand and by measuring the actual pipe speed between these two scaffolds, comparison with the theoretical pipe speed and post-correction of the speeds. 2. The method according to claim 1, characterized by detecting the speed drop during the tapping and / or power consumption immediately after the puncture of the tube blank in the framework in the first time Wandabnahme takes place, as a measure of the height of the dimensional tolerances of the tube blank and as an output signal for the determination the correction commands. 3. The method according to claim 1, characterized by a crowd of the first wall decrease realizing rolling mill starting precalculated and stored correction speed series, which differentiate in this framework by a maximum of the permissible Zugkoeffizienten of each other. 4. The method according to claim 1, characterized by counting of clock cycles from puncture of the tube billet in the first, wall removal realizing scaffolding to the piercing in the scaffold to determine the actual pipe speed between these stands. 5. Arrangement for speed correction in the continuous cold rolling of tubes on a follower mandrel rod for adjusting the speeds of the rolls to be expected by dimensional tolerances of the tube billets changed rolling conditions using an existing speed and / or armature current measurement, characterized by a circuit connection of the speed (1 ) and / or the armature current measurement (2) and a clock timing and counting (9) via an AD converter (3) with a microcomputer (4), by connecting a speed setpoint (5) with the microcomputer (4) and a matching stage ( 6), wherein the adaptation stage (6) each has a further connection to the microcomputer (4) and to a sequence adjustment (7) of the drives.