DE3511219A1 - Method and arrangement for automatic process monitoring and diagnosis in continuous rolling mills - Google Patents

Abstract

To monitor the rolling process and assess the quality of the product, a multiplicity of measured variables are recorded and evaluated during the process of manufacture. The evaluation of characteristic process variables, in particular, is intended to supply information on the progress of production and the quality of the product. For this purpose, the invention proposes that the beginning and end of various process states of a production process be determined by means of a device (32) for following the displacement of the material (19) undergoing working and that the characteristic process variables be recorded and averaged within a local area between the beginning and end of process states selected process-specifically and be assigned to the corresponding process states. A set of process-variable averages arising during a production process can be compared with a set of predeterminable desired values. The desired values are provided with predeterminable tolerance ranges, the exceeding or undershooting of which is recorded by the process-variable averages corresponding to the desired values. The limit-value overshoots or undershoots are evaluated for diagnostic purposes by being compared with known sets of overshoots or undershoots. <IMAGE>

Description

description

The invention relates to a method for automatic process monitoring and diagnosis in continuous rolling mills, which are characteristic of the rolling process Process variables are recorded and evaluated.

The invention also relates to an arrangement for performing the Procedure.

The rolling process in continuous rolling mills is monitored by a helmsman, who may also intervene in the rolling process. For monitoring are available to the helmsman in addition to the measured values and characteristics of the input material and of the product (in the case of continuous tube rolling mills these are, for example: hollow block weight, Hollow block length, mandrel bar diameter, hollow block outside diameter, hollow block temperature; Contour tube diameter, contour tube length; Material characteristics) Process variable measured values for Available from which the helmsman can draw conclusions about disruptions in the production process (e.g. roll breakage, wrong roll speed setting, wrong material dimensions and for continuous tube rolling mills: wrong mandrel bar diameter, rough mandrel bar surface and poor mandrel lubrication) and can affect the product quality. Such Process variable measured values are, for example, the armature currents of the roller drive DC machines, the roll speeds and the rolling stock temperature values.

At present, the large number of characteristic data and measurands are manageable to keep short-term fluctuations in the process variable measured values, in particular the roller drive currents, e.g. eliminated by averaging over the entire measurement process.

However, this averaging makes the measurement data less meaningful drastically reduced, since process-related measured value fluctuations cancel each other out in the mean value can and are therefore not recognizable and evaluable. Furthermore, different, successive process states, which also change in the course of the measured values over time have not been taken into account by separate recording, i.e. disturbances that are only present during a process state, cannot or cannot be unambiguously be recognized.

The process states mentioned are in the time domain, in which do not change the process conditions. For example, join Continuous rolling mills in which the rolling stock is rolled from several rolling stands at the same time a transition into a new process state.

The object of the invention is to provide a method for automatic process monitoring and diagnosis in continuous rolling mills to indicate that the evaluation of a large number of characteristic Measured variables (e.g. currents, torques, temperatures, speeds), which differ in their temporal The course can change depending on process settings or process disturbances. The method should draw early conclusions about the current process status (process diagnosis), allow the manufacturing process and product quality. Deviations in the production process and system malfunctions, in particular also causes of quality-impairing Faults in the area of the continuous rolling mill should be reliably and quickly detectable and can be analyzed so that the process can be intervened immediately if necessary can to compensate for unwanted deviations and dangerous situations, inferior quality and avoid scrap. Furthermore, an arrangement for carrying out the method can be specified.

The object is achieved according to the invention by the features of the characterizing Part of claim 1 solved. By tracking every process state assign a time range of its effectiveness. Process states (local areas, which can be converted into time ranges at known rolling speeds) selected, where experience has shown that this is typical for the quality of the production process Behavior of characteristic process variables can be observed. Within the The time ranges assigned to the process-specific process states become the characteristic ones Process variables recorded and averaged. It is possible either only during the Presence of one process state or during several successive ones Process states to perform the averaging of the process variable. The ones won in this way Measured mean values (process variable mean values) are assigned to the respective process status and can be saved.

The drive torques are preferably used as characteristic process variables the roll stands and / or temperature values of the block being processed or billets measured this when passing between the roll stands and / or immediately behind the last roll stand.

According to an advantageous embodiment of the invention, a Set of process variable mean values occurring during a production process compared with a set of predefinable setpoints. The setpoint sets can through Experience can be gained by working with manufacturing processes with different process boundary conditions and satisfactory end product the measured process variable mean values are saved will.

The setpoint specification is preferably automatically per se in the production process adapted to changing process conditions. The setpoint specification has been adapted Consideration of the rolling speed, e.g.

the rolling speed on the first roll stand, and the rolling stock temperature possible at the entry into the first roll stand. The setpoints are preferably with afflicted with predeterminable tolerance ranges. If the measured values are not within the Tolerance ranges, exceeding or falling below are registered and included an assignment to the corresponding measured mean values and a serial number of the product (e.g. pipe) for comparison with customer complaints, random samples, etc. saved.

The exceeding or falling below the limit values can be advantageous Way to be evaluated for process diagnostic purposes. Are for example as process variables the armature currents of the roll stands are measured, on the one hand the drive current limit value deviations, which were formed for a roll stand for different process states with one another are compared and on the other hand the drive current limit value deviations of a Roll stand compared with those of the neighboring stands in the same process conditions will. The combination of exceeding or falling below the limit values are respectively compared with stored combinations for which the cause (process disturbance, Incorrect setting, defective rolling material) is known. Is the determined limit value combination correct? corresponds to one of the stored ones, so conclusions can be drawn with great accuracy be drawn to the cause and assigned to the product.

The invention provides for carrying out the method according to the invention an arrangement in which a position tracking device is provided, the current position of the material being processed (e.g. block or stick) during the production process. This is done for example by measuring the time of entry of the material into the first roll stand and by measuring the angular velocity of the first and, if necessary, further ones Rollers. The position tracking device is specifiable at the beginning and end Local intervals from switching signals and controls at least one averager, so that when a selected process state (location interval) is present, a Averages the process variable measured value.

The arrangement according to the invention is preferably implemented by a programmable Setpoint memory supplemented by different sets of process variable setpoints are storable. As already mentioned, such sentences are different for Process boundary conditions (rolled material, inlet cross-section, outlet cross-section, etc.) given. The setpoint sets are in an evaluation unit with the during a The set of process variable mean values during the manufacturing process is compared and it a combination of overshoots and undershoots of the setpoint is formed.

It is advantageous to have a process diagnostic device in the evaluation unit downstream. Combinations of setpoint over- and underflows are stored, for which various, known causes of interference underlie. These combinations are determined with those of the evaluation unit Combinations compared, which means that faults can be located immediately after a production process possible The error analysis result can be displayed optically or acoustically and logged will.

The inventive method and the corresponding arrangement for Implementation of the method can easily be adapted to given rolling processes.

The measuring range limits (start and duration of the measuring intervals) can be shifted. The tolerance ranges and the reference values (setpoints) can be freely specified and can be changed at any time. They can be continuously adapted to process conditions (Adaptation). It is a targeted recording of process variables for all particularly meaningful ones Local intervals (time intervals) by means of any number and local (Temporal) arrangement of areas with respect to the measurement curve of a process variable is possible. It is an automatic evaluation of the measured variables and a process diagnosis of the evaluation results possible. The evaluation and diagnosis process provides a manageable number meaningful data that allow a quick assessment of the process situation, so that system malfunctions and their causes can be identified at an early stage.

Based on the drawing, in which an embodiment of the invention is shown, the invention and further advantageous embodiments and Further developments and further advantages are explained and described in more detail.

1 shows a structural diagram of the arrangement according to the invention and FIG. 2 shows the roll drive current curve of six drives of a continuous rolling mill.

In Fig. 1 a continuous rolling mill with six roll stands 11, 12, 13, 14, 15, 16, with an incoming hollow block 17 which receives a mandrel bar 18 in its interior, and an outgoing tube, the so-called contour tube 19, with a mandrel bar 20 outlined. The rolling direction is indicated by an arrow 21.

For the acquisition of measurement data of the incoming into the first roll stand 11 Hollow block 17 is a diameter measuring device 22, a length measuring device 23 and a temperature measuring device 24 is provided, its diameter sensor 25, length sensor 26 and temperature sensor 27 are directed towards the incoming hollow block 17. The hollow block outside diameter, Hollow block length, hollow block inlet temperature but also the hollow block weight and the mandrel bar diameter, which is not included in the present exemplary embodiment and the material properties of the rolling stock determine the process conditions, which affect the rolling process. Such sizes should be used before each rolling are checked for compliance with their tolerance limits.

In addition to the parameters that determine the process conditions, at the inlet by a photocell or an IR sensor 28 and a downstream circuit 29 the times of the piercing and the run-out (from the first roll stand 11) of the Hollow block 17 detected.

Furthermore, the angular velocity is determined by a speed measuring device 30,31 of the rolls of the first roll stand 11 measured. From the measurement of the angular velocity and the time of entry into the first roll stand 11 is in the position tracking device 32 a path tracing of the hollow block is carried out. Even if this is the better one Was not shown for the sake of clarity, can be measured by measuring the angular velocities the rolls of other roll stands 12,13,14,15,16 and by evaluating the measurement results by means of the position tracking device 32 the Meaningfulness and accuracy of the Improve tracking.

The position tracking device 32 indicates at each point in time where the hollow block 17 is located, i.e.

from which roll stand 11,12,13,14,15,16 he at the respective point in time is captured. With the position tracking device 32, the respective Determine process status. The process state is understood here to mean a rolling state, in which all rolling parameters are the same. For example, the point of the hollow block runs into a (further) roll stand or the hollow block end from a roll stand, so there is a change between two process states.

In the case of a continuous rolling mill, in which the rolling stock is produced by several at the same time Roll stands can usually be rolled in three areas: - Filling of the rolling mill (successive piercings in the rolling mill stands). The number the rolling-related process states is equal to the number of roll stands.

- Filled rolling mill (all rolling stands are engaged). The process state is equal to the last process state after filling.

- Emptying the rolling mill (successive outlets from the Roll stands). The number of roll-related process states is equal to the number of roll stands minus 1.

The status area "full rolling mill" does not exist if the length of the rolled stock is not sufficient for this. Then you can be in a middle state range Piercing and outlets alternate. The different process states, in particular Changes between process states can, for example, occur in the drive current of the roll stands be recognized. This will be discussed later.

In addition to the detection of the process conditions, according to the method shown in Fig. 1 shown structure diagram, characteristic process variables are continuously recorded: a) Roller drive currents.

The roller drive machines are often DC machines 33, whose armature current is mostly proportional to the torque output. By Armature current values determined by ammeter 34 are stored in detection devices 35 prepared for further processing. (If you use synchronous machines instead of DC machines a, then instead of the armature current measured values, arithmetic variables occur that are measured from Operating parameters are determined and the drive torques or the associated work, which flows into the rolling stock, characterized).

b) outlet temperature.

The temperature of the contour tube surface immediately after the last one The roll stand depends on the previous rolling process. It is measured by a temperature meter 36 continuously detected with temperature sensor 37.

c) contour tube diameter.

The outer diameter of the contour tube at the outlet of the last roll stand is also dependent on the previous rolling process and is measured by a diameter measuring device 38 continuously detected with diameter sensor 39.

d) length of the tube.

The length of the contour tube at the end of the rolling train is measured by a length measuring device 40 determined with length sensor 41.

The roller drive currents, the outlet temperature and the continuous tube diameter are subject to constant fluctuations during rolling. For example, the currents can be superimposed by strong interference frequencies especially caused by defective speedometer machines but also by the gearbox. These fluctuations in the measurement signals make it difficult to assess the measurement results.

In Fig. 2, the drive currents are lii to 1l6 for the roll stands 11 to 16 of a rolling train shown over time t. Despite the fluctuations are The different process states can be taken from the time ranges from the current curves can be assigned.

The measured current value Iii for the first roll stand 11 increases during the piercing suddenly and then drops to an approximately constant value. When tapping In the second roll stand 12 (sudden increase from 112) the current 111 drops a lower value, since the second roll stand 12 is now also pulling work for transport and in this case (contour tube) has taken over the deformation of the rolling stock. At the In the third roll stand 13, the stream 111 drops again.

There are also characteristic current changes for certain Process states when disruptions occur in the production process. To by evaluation The drive current measured values are used to infer the causes of malfunctions due to the current changes (and also the measured values of the outlet temperature and the contour pipe diameter) one Averaging 42 is supplied (see FIG. 1).

For each characteristic process variable, areas (local areas of the rolling stock, which can be converted into time ranges if the rolling speed is known are defined) within which the measured value is averaged. The definition selected areas is made on the basis of experience and is carried out through Input 43 of corresponding data into the position tracking device 32. The position tracking device 32 controls switching elements 44 which are located in the averaging device 42. Each A switching element 44 can be assigned to the measuring branch (currents, temperature, diameter) be. The switching elements 44 activate the individual mean value formers assigned to the measuring branches during the selected areas.

In Fig. 2, selected areas are each shown as a bar. As a result, the current readings will be 112, 115 and 116 within three, respectively Time ranges (time windows) averaged. The time ranges go through the link with the rolling speed back to the definition of local areas. The first Time window A1 of stream 111 essentially covers the first two process states up to the piercing through the third roll stand 11. The oscillation behavior of the current 111 was excluded, however. The second time window A2 of the stream 111 is present in a medium-sized production area, the process status of which is characterized is that all rollers are engaged. The third time window A3 of the current In extends to an area shortly before the point in time at which the rolling stock runs out from the first roll stand 11. The time ranges Bi, Ei and A (í = 1,2,3) for the streams 112, 115 and 116.

The averaging unit 42 outputs pairs of values in which each area A1, Bj, E, F assigns an average current value. Corresponding pairs of values can also consist of the course of the outlet temperature or the contour of the pipe diameter. The value pairs that occur during a production process form one sentence of process variable mean values, the individual values of which in an evaluation unit 45 with Setpoints of a setpoint set are compared.

A setpoint memory 46 contains setpoint sets of range mean values stored for different process conditions. When certain process conditions are specified by the helmsman and / or by the diameter measuring device 22, the length measuring device 23, the temperature measuring device 24 or the speed measuring device 31 becomes the associated setpoint set selected and output to a limit value setter 47. In the limit value setter 47 are the individual setpoints of the setpoint set upper and / or lower setpoint limit values assigned. The limit value ranges can be specified by the helmsman.

Such a setpoint set with limit values is shown in the Evaluation unit 45 with the set determined under the corresponding process conditions of process variable mean values evaluated by adding each process variable mean value with is compared to the associated setpoint. Exceeding and falling below the target value tolerance ranges are registered and a set of data is formed which is now only contains the information whether in the individual measuring ranges Ai, Bi, one over or The target value tolerances have been exceeded. This information set is fed to a process diagnosis unit 48.

In the process diagnostic unit 48 there are sets of setpoint deviations which correspond to the known causes of malfunctions in the rolling process. A comparison the determined setpoint deviations with the stored setpoint deviations enables a diagnosis of the rolling process after the production sequence of a rolled product.

The diagnosis result is provided by an output unit 50 by written, optical or acoustic means are issued and announced to the helmsman.

This can then take the necessary measure 51 to control the other Initiate rolling processes. It can also save the measurement data of the evaluated process as a Classify in an exemplary manner and store as reference values in the setpoint memory.

Since usually setpoints are not available for all possible process conditions are stored in the target value memory 46, the target values can be corrected Variables that characterize the process conditions take place.

For this purpose the output values of the diameter measuring device 22, the length measuring device 23, the temperature measuring device 24 and the speed measuring device 31 is supplied to the setpoint storage unit 46. Another possibility for correction is by influencing the process mean values accordingly in the evaluation unit 45 given.

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Claims (15)

Claims 1. A method for automatic process monitoring and diagnosis in continuous rolling mills, which are characteristic of the rolling process Process variables are recorded and evaluated, characterized in that start and End of different process states of a production sequence by means of a path tracking (32) of the material being processed (19) can be determined, and that the characteristic process variables within a local area between the start and end process-specifically selected process states are detected and averaged and the corresponding process states are assigned. 2. The method according to claim 1, characterized in that a during a set of process variable mean values with a Set of specifiable setpoints is compared and evaluated. 3. The method according to claim 2, characterized in that the setpoints are subject to predefinable tolerance ranges and that exceeding or falling below the tolerance ranges through the process variable mean values corresponding to the setpoints be registered. 4. The method according to claim 3, characterized in that the limit value over- or undershoots are evaluated for diagnostic purposes. 5. The method according to claim 4, characterized in that the limit value over- and undershoots with a predeterminable combination of limit value deviations known cause of failure can be compared. 6. The method according to any one of claims 1 to 5, characterized in, that the drive current measured values (111 to 1t6) of the Roll stand drives (33) are used. 7. The method according to any one of claims 1 to 6, characterized in, that, as characteristic process variables, the measured temperature values in the processing material located between the roll stands and / or immediately behind the last roll stand are used. 8. The method according to any one of claims 2 to 7, characterized in that that an adaptation of the setpoint specifications by taking process conditions into account he follows. 9. The method according to any one of claims 2 to 8, characterized in that that an adaptation of the setpoint specifications by taking into account the rolling speed he follows. 10. The method according to any one of claims 2 to 9, characterized in that that an adaptation of the setpoint specifications by taking into account the rolling stock temperature takes place at the entry into the first roll stand. 11. The method according to any one of claims 2 to 10, characterized in that that an adaptation of the setpoint specifications by taking into account the rolling speed of the first roll stand takes place. 12. Arrangement for automatic process monitoring and diagnosis at Continuous rolling mills with transducers and evaluation units for acquisition and evaluation of for the rolling pro- show characteristic process variables for carrying out the process according to one of claims 1 to 11, characterized in that a position tracking device (32) for the ongoing determination of the respective positions of the one being processed Material (19) is provided that the position tracking device (32) at least a switching element (44) downstream, and that the switching element (44) in predeterminable Position intervals at least one averaging device (42) activated during the measured value of a characteristic process variable by running through the position interval determined. 13. Arrangement according to claim 12, characterized in that a programmable Setpoint memory (46) is provided in which sets of process variable setpoints can be stored and that the setpoint memory (46) and the averaging unit (42) have an evaluation unit (45) is connected downstream, in which a setpoint set with the during a production process accruing set of process variable mean values is comparable and with regard to Deviations can be evaluated. 14. The arrangement according to claim 13, characterized in that one Process diagnostic device (48) is connected downstream of the evaluation unit (45), and that in the process diagnostic device (48) typical setpoint deviations with known The cause of the fault can be saved. 15. The arrangement according to claim 14, characterized in that the process diagnostic device (48) an output unit (50) for the optical and / or acoustic transmission of information is subordinate.