Title of Invention

"PROCESS AND SYSTEM FOR PICKLING A METAL STRIP"

Abstract

Process and system for pickling a metal strip (2), in particular a rolled strip, by means of a pickling plant (1); through which the metal strip (2) passes and in which the metal strip (2) is pickled using a pickling liquid, the pickling result being a function of pickling parameters (Tz,TA,v,Cs,CFe, B, p). The pickling result is measured and at least one pickling parameter (TZ,TA ,v C S, C Fe, B, P) is automatically varied, as a function of the measurement of the pickling result, so as to improve the pickling result.

Full Text

Description The invention relates to a process and system equipment for pickling a metal strip, in particular a rolled strip, by means of a pickling plant, through which the metal strip passes and in which the metal strip is pickled using a pickling liquid, the pickling - result being a function of pickling parameters. In order to clean metal strips, in particular in order to remove scale layers on rolled strips, these are pickled in a pickling plant using a picklinq liquid, generally acid. The amount removed by the pickling is a function of pickling parameters. These are, for example: temperature of the pickling liquid, speed at which the metal strip passes through the pickling plant, the acid content in the pickling liquid, the metal content in the pickling liquid, in particular the iron content in the pickling liquid, strip parameters,1 such as material and geometric dimensions, and the turbulent pressure of the pickling liquid. These pickling parameters have to be set in such a way that as far as possible the desired amount of material is removed from the metal strip. Deviations from the desired optimum value are associated with high costs. If too much material is removed, that is to say if it is not only the scale layer that is removed from a rolled strip but also metal from the surface of the rolled strip, then the metal or iron content. in the pickling liquid increased to a disproportionate extent. Since the purification of the pickling liquid is complicated and expensive, too high a removal rate is undesirable. In addition, in the event of too high a removal rate, damage to the metal strip may occur. On the other hand, if too much material, in particular too much scale, remains on the metal strip, then this has to pass - 2 - through the pickling plant again. This additional operation is complicated and expensive. Setting the pickling parameters to achieve the best possible pickling result is carried out, as is known, by an operator of the pickling plant. However, this leads to fluctuations in the pickling result. The pickling result is to be understood, for example, as the amount of material removed or the amount of scale that has remained on the metal strip. The object of the invention is to specify a process and equipment for pickling a metal strip by means of which the pickling result is improved. Furthermore, it is desirable to reduce the costs for the pickling of a metal strip. According to the invention, the object is achieved by a process according to Claim 1 and equipment according to Claim 10. In this case, in a pickling process of the type described above, the pickling result is measured and at least one pickling parameter is automatically varied, as a function of the measurement of the pickling result, so as to improve the pickling result. The automatic variation allows the setting of the corresponding pickling parameter by an operator to be dispensed with. In this way, a more constant and better pickling result is achieved. A saving is also made in corresponding operating personnel. The pickling parameters to be set are considered to be, in particular, the temperature of the pickling liquid in the pickling plant, which is determined, for example, from the temperature of the pickling liquid in the feed into the pickling plant and the temperature of the pickling liquid in the discharge from the pickling plant, and the speed of the metal strip, the acid parameters of the pickling liquid, the iron concentration in the pickling liquid, the turbulent pressure of the pickling liquid in the 'pickling plant and the properties of the metal strip, such as its material and its geometric dimensions. In this case, the temperature of the pickling liquid is - 3 - the pickling parameter that is particularly suitable for automatic setting. Since the temperature of the pickling liquid in the pickling plant is difficult to measure and difficult to control, use is advantageously made of the feed temperature of the pickling liquid into the pickling plant, the discharge temperature of the pickling liquid from the pickling plant or both temperatures instead of the temperature of the pickling liquid in the pickling plant. The pickling result is advantageously measured by measuring defects and/or unpickled points on the metal strip. The defects and/or unpickled points are advantageously classified and counted. The classification of the defects and/or unpickled points is in this case advantageously carried out in relation to their size and/or their shape. The defects and/or unpickled points classified and counted in this way are advantageously assessed. The assessment is carried out by means of a fuzzy assessor, by means of a neural network or by means of a neural fuzzy assessor. However, the measured values can also be assessed directly, that is to say unclassified, by a fuzzy assessor, a neural network or a neural fuzzy assessor, but indirect assessment, that is to say the assessment of the classified and counted defects and/or unpickled points, is more advantageous. The result of the assessment by means of a fuzzy assessor, by means of a neural network or by means of a neural fuzzy assessor are set points for at least one pickling parameter. Further advantages emerge from the following description of exemplary embodiments. In detail: FIG 1 shows a strip plant operated in accordance with the invention FIG 2 shows an arrangement for training an assessor. In FIG 1, reference symbol 1 designates a pickling plant, through which a metal strip 2 passes in - 4 - the direction of the arrow designated by reference symbol 3. The metal strip 2 is pickled in the pickling plant 1, using a pickling liquid. The pickling liquid is fed to the pickling plant 1 from a pickling liquid tank 13 via feed lines 18, 19 and a heat exchanger 10. For the purpose of pickling, the pickling liquid is sprayed against the metal strip 2 from nozzles 6, 7. The pickling agent running away is intercepted and fed to the pickling liquid tank 13 via a line 20,. The heat exchanger 10 is used for heating the pickling liquid. For this purpose, steam from a steam generator 12 is fed to the heat exchanger via a steam line 16. The amount of steam can be set via a valve 11. The steam condenses in the heat exchanger 10. The water thus produced is fed to the steam generator 12 via a condensate line 17. The pickling result, that is to say the amount of material removed, or the amount of undesired material, such as scale, for example, that has remained on the metal strip 2, is a function of pickling parameters. These pickling parameters may be, for example, the temperature of the pickling liquid in the pickling plant 1, the speed v of the metal strip 1, the acid parameters cs of the pickling liquid, the iron concentration cFe in the pickling liquid, the turbulent pressure p of the pickling liquid in the pickling plant 1 and the properties B of the metal strip, such as its material and its geometric dimensions. In the present exemplary embodiment, the temperature of the pickling liquid is the only pickling parameter influenced. This is a particularly advantageous configuration, but the pickling result is improved further if further pickling parameters are set in a similar fashion. The temperature Tz of the pickling liquid in the feed and the temperature TA of the pickling liquid in the discharge are measured using temperature 'measuring instruments 9 and 8. The pickling result is measured by means of an optical measuring instrument 4. The signal from the - 5 - measuring instrument 4 is fed to a classifier 5, in which defects on the metal strip or unpickled points of a material to be pickled away, such as scale, for example, are classified and counted. The defects or points of unremoved material may be classified, for example, in accordance with the defect categories "hole", "dark spot", "light spot", "long dark stripes", "long bright stripes", "short dark stripes" and "short light stripes", in accordance with the following table: The frequencies of the individual defect categories are fed to an assessor 15. This ascertains a set point Tz for the temperature of the pickling liquid - 6 - in the feed from the frequencies of the defect categories, from the temperature TA of the pickling liquid in the discharge, the temperature Tz of the pickling liquid in the feed, the speed v of the metal strip 2, the acid parameters cs of the pickling liquid, the iron concentration cFe in the pickling liquid, the turbulent pressure p of the pickling liquid and the properties B of the metal strip 2. The assessor 15 is advantageously designed as a fuzzy assessor, as a neural network or as a neural fuzzy assessor. In this case, the neural fuzzy assessor considered is advantageously a neural fuzzy system according to the article "Neuro-Fuzzy", H.-P. PreuB, V. Tresp, VDI-Berichte 113, ISBN 3-18-091113-1, 1994, pages 89 to 122. The set points Tz for the temperature of the pickling liquid in the feed are fed to a controller 14, which sets the valve 11 as a function of the temperature Tz of the pickling liquid in the feed and the set point Tz* of the temperature of the pickling liquid in the feed. FIG 2 shows equipment similar to that in FIG 1. However, a set point Tz *B is predefined for the controller 14 by an operator 21. The set point Tz * of the temperature of the pickling liquid in the feed, which is ascertained by the assessor 15, does not go into the controller 14. The equipment according to FIG 2 has a learning algorithm 23, by means of which the assessor 15 ascertains a set point for the temperature in the feed as a function of the set point T2 * of the temperature of the pickling liquid in the feed, which is ascertained by the assessor 15, of the set point Tz *B of the temperature of the pickling liquid in the feed, which is ascertained by the operator 21, and as a function of further pickling parameters: temperature Tz of the pickling liquid in the feed, temperature TA of the pickling liquid in the discharge, the speed v of the metal strip 2, the acid parameters cs of the pickling liquid, the iron concentration cFe in - 7 - the pickling liquid, the turbulent pressure p of the pickling liquid in the pickling plant and the properties B of the metal strip 2. We Claim: 1. A process for pickling a metal strip (2), in particular a roller strip, comprising the steps of : passing the rolled strip through a pickling plant whereby the rolled strip is pickled by a pickling liquid; measuring a pickling result, the pickling result being a function of pickling parameters ( Tz, Ta, V, Cs, CFC, B, p) and measured by measuring defects comprising unpickled points on the metal strip; and automatically changing at least one of the pickling parameters to improve the pickling results, characterized in that the at least one of the pickling parameters is automatically changed using one of: i) a fuzzy evaluator, ii) a neural network, and iii) a neural fuzzy evaluator, the at least one of the pickling parameters being automatically changed as a function of defects on the metal strip to improve the pickling result, the defects comprising unpickled points of a material to be pickled off the metal strip. 2. The process as claimed in claim 1, wherein the at least one of the pickling parameters comprises a temperature of the pickling liquid in a pickling liquid feed ( Tz ) a temperature of the pickling liquid in a pickling liquid discharge( TA), a speed of the metal strip ( V), acid parameters of the pickling liquid ( Cs), iron concentration in the pickling liquid ( CFE), and a turbulent pressure of the pickling liquid. 3. The process as claimed in claim 1, wherein the at least one of the pickling parameters changed is a temperature of the pickling liquid (TA- Tz). 4. The process as claimed in claim 1, wherein the defects on the metal are classified and counted. 5. The process as claimed in claim 1, wherein the defects on the metal strip are classified and counted in relation to size and shape of each defect. 6. The process as claimed in claim 1, comprising: setting by an operator of the pickling plant the pickling parameters; comparing the pickling parameters set by the operator to pickling parameters determined by the one of the neural network and the neural fuzzy evaluator; and training the one of the neural network and the neural fuzzy evaluator to reduce a deviation between the pickling parameters set by the operator and the pickling parameters determined by the one of the neural network and the neural fuzzy evaluator. 7. The process as claimed in claim 1, wherein the at least one of the pickling parameters is automatically changed using one of: i) a fuzzy evaluator, ii) a neura network, and iii) a neural fuzzy evaluator, and at least one of pickling parameters being automatically changed as a function of a classification of defects on the metal strip to improve the pickling result, the defects comprising unpickled points of a material to be pickled off the metal strip. 8. A system for pickling a metal strip(2) , in particular a rolled strip, by carrying out the process as claimed in claims 1 to 8, comprising a plurality of instruments (4,5); and plant (1) through which the metal strip (2) passes at a determined speed (V) in a designated direction (3), said pickling plant (1) configured to have a pickling liquid storage tank (13) feeding said plant (1) pickling liquid via feed lines (18, 19) and via a heat exchanger (10), the pickling liquid being sprayed against the metal strip (2) by means of a plurality of nozzles (6,7), the un-consumed pickling liquid being fed back to said storage tank (13) via a feed line (20), said heat exchanger (10) heating the pickling liquid on receiving steam via a steam line (16) and a valve (11) from a steam generator (12) having a condensate line (17) through which water from said heat exchanger (10) being fed to said steam generator (12), at least two measuring instruments (8,9) are disposed at the feed and the discharge points to measure temperatures ( Tz, TA) of the pickling liquid, characterized in that an optical measuring instrument (4) is provided in said designated direction (3) away from said pickling plant (1) for measuring defects on the pickled metal strip comprising unpickled points; and in that means (5) for classifying and counting said defects based on signals received from the optical measuring instrument (4) is adjacently provided. 9. A system as claimed in claim 9 comprising an assessor evaluator(15) selected from the group consisting of a fuzzy evaluator, a neural network, and a neural fuzzy evaluator. Process and system for pickling a metal strip (2), in particular a rolled strip, by means of a pickling plant (1); through which the metal strip (2) passes and in which the metal strip (2) is pickled using a pickling liquid, the pickling result being a function of pickling parameters (Tz,TA,v,Cs,CFe, B, p). The pickling result is measured and at least one pickling parameter (TZ,TA ,v C S, C Fe, B, P) is automatically varied, as a function of the measurement of the pickling result, so as to improve the pickling result.

Documents:

01645-cal-1998 abstract.pdf

01645-cal-1998 claims.pdf

01645-cal-1998 correspondence.pdf

01645-cal-1998 description(complete).pdf

01645-cal-1998 drawings.pdf

01645-cal-1998 form-1.pdf

01645-cal-1998 form-2.pdf

01645-cal-1998 form-3.pdf

01645-cal-1998 form-5.pdf

01645-cal-1998 g.p.a.pdf

01645-cal-1998 letters patent.pdf

01645-cal-1998 priority document others.pdf

01645-cal-1998 priority document.pdf

1645-CAL-1998-CORRESPONDENCE 1.1.pdf

1645-CAL-1998-CORRESPONDENCE 1.2.pdf

1645-CAL-1998-PA.pdf