Method and device for pickling rolled metal, in particular steel strips

Abstract

In a method and device for pickling a rolled metal, in particular, steel strip, the metal strip (1) is fed to a regulated pickling process. In order to carry out the pickling process not only on the basis of conventional pickling parameters but rather taking into consideration additional parameters from outside of the pickling vat, it is proposed to regulate the pickling process, in addition to the pickling medium parameters, by parameters of the coil (2) and/or metal strip determined and/or measured before the metal strip (1) enters the pickling section (3).

Description

[0001] The present invention relates to a method and device for pickling of a metal, in particular, steel strip fed to a regulated pickling process.

[0002] DE 197 43 022 A1 discloses a method of pickling a metal strip based on a measurement in the displacement direction after the pickling plant and in which according to defect categories, which are determined by a measuring unit, pickling parameters such as, e.g., temperature of the pickling liquid, displacement speed of the metal strip, acid content in the pickling liquid, metal content, in particular, iron content, strip parameters such as, e.g., material and geometrical dimension, are adjusted. In this respect, the defects can only be subsequently determined as well as a conclusion made as to favorable pickling. The control system deals only with the pickling plant itself.

[0003] According to another known method (EP-0 482 785 A1), turbulent streams, which are generated in a pickling container with nozzles, are used. Thereby, an optimal pickling result with a minimal consumption of a pickling medium can be achieved. This result should be achieved by controlling the turbulence of the stream in the pickling medium dependent on the displacement speed of the to-be-pickled strip. A far-reaching effect is not to be expected.

[0004] A further method of pickling a rolled strip in a pickling plant is disclosed in EP-0 602 437 B1. The method is based on a particular operating mode according to which several pickling vats adjoin each other one after the other. In the pickling vats, an acid-containing pickling medium is sprayed by spraying nozzles arranged on a vat partially sidewise of, above and below the strip displacement plane, with the nozzles being variably controlled and with the pickling medium being introduced in an arbitrary preselected amount. At that, the acid concentration, and/or medium temperature, and/or the outlet speed of the pickling medium from nozzles are preselected.

[0005] An object of the invention is to carry out the pickling process not only on the basis of conventional pickling parameters but rather taking into consideration additional parameters outside of the pickling vat.

[0006] According to the invention, this object is achieved by regulating the pickling process, in addition to the pickling medium parameters, by parameters of a coil and/or metal strip determined and/or measured before the metal strip enters the pickling section. The advantage consists in that the pickling parameters are so adjusted in advance that under- or over-pickling is prevented, in that the acid concentration and the acid supply are correctly adjusted, whereby the pickling medium is economically used, and in that the correct temperature can be calculated in advance, together with other adjustable pickling parameters. At that, the scale, which is removed after casting, shaping, and annealing, and other coatings are already taken into consideration. The invention also takes into consideration the preliminary breaking of the scale (by a stretching-bending-straightening leveller), whereby fissures and pores are formed in the scale layer, which increases the surface on which the acid acts. In cases when the scale is removed by an abrasive or hydromechanical treatment, the scale quantity, which is dissolved in the pickling process, is reduced. Thereby, the preliminary descaling permits to reduce pickling time. In case, the temperature of the metal strip increases before the strip enters in the pickling section, the contact time of the strip surface with the pickling medium increases at an optimal pickling temperatures.

[0007] The heating path of the metal strip is shortened and the pickling time falls. The pickling time also falls when the scale is removed by laser-optical means before the strip enters the pickling section, and the quantity of the to-be-dissolved scale is reduced.

[0008] The method includes preadjustment of the pickling process in accordance with measured values of a coil effected on a basis of a set-up computation model, and regulating the process on a basis of a regulating computation model that takes into consideration at least measured values for the scale, strip temperature, pickling medium temperature, and/or acid concentration. The quantity of the scale, e.g., needs not to be assessed, as was the case previously. An integration of the additional scale calculation model takes place. A target variable of such optimization can be: minimum energy use, variable coil output, acceleration reaction dependent on the surface contamination, minimizing the consumption of the pickling medium and losses of the pickling medium, minimizing overpickling, and minimizing underpickling. With regulated descaling units, measurement units for determining scaling can determine thickness of the scale layer, shape, distribution and color. To this end, precise calculation models are used.

[0009] According to an embodiment of the invention, the servo components of the pickling section are regulated or readjusted based on a measured value for the scale deposit before the pickling section. This makes possible regulation of the pickling section with a least possible transit time.

[0010] Advantageously, additional measured values for scale deposits or coating are determined in a region in a displacement direction in front of the pickling section, and are used for readjustment of the servo components of the pickling section and/or dependent on measured and/or calculated values.

[0011] Other parameters outside of the pickling section are taken into consideration by controlling the pickling times based on strip entrance data of the coil and on the system adjustment.

[0012] In accordance with another method step, the measured values for the coating or the scale are used for regulation of a pretreatment unit arranged upstream of the pickling section.

[0013] It is advantageous that the pretreatment unit and the servo components of the pickling section are readjusted in accordance with the measured and calculated values.

[0014] In device for pickling a metal, in particular, steel strip fed in a displacement direction from a coil of a pickling plant, for which a regulation by a plurality of parameters is contemplated, the object of the invention is achieved by communicating measured values from coil measured value or data transducers via a set-up computation model and a regulating computation model to adjustment units of a pickling section. Thereby, the pickling section can be operated with precise regulation which results in the above-discussed advantages.

[0015] In one embodiment of the device, it is provided that measured value from coil measured value transducers are input into the regulating computation model. The set-up computation model uses general entrance data for the metal strip. The scale deposits can be calculated by using a trial computation model for effecting preliminary adjustment of the slow and rapid servo components of the pickling section or readjustment in accordance with comparison.

[0016] In another case, the measured values of a measured value transducer for coating or scale are used for readjustment of the servo components of the pickling section.

[0017] According to other features, a pretreatment unit, the measured values of which are input into the regulating computation model, is arranged upstream of the pickling section. Upon recognition of the exigency and by suitable evaluation of the coil data and the instant system set-up, the pretreatment unit can influence the pickling time. As a pretreatment unit, a heating unit, a mechanical, abrasive, hydromechanical, laser-optical, or oscillating descaler can be used.

[0018] Further improvement is achieved by providing an induction heating unit between the pretreatment unit and the pickling section. The inductive preheating of the metal strip takes place before the pickling section and is used for rapid regulation of the metal strip temperature and for adjustment of the metal strip pickling temperature.

[0019] The embodiments of the invention are schematically shown in the drawings and will be explained in detail below.

[0020] The drawings show:

[0021] FIG. 1 a block-diagram of a basic design of a coil and pickling plant with regulation,

[0022] FIG. 2 a first variant of the same block-diagram with a measured value transducer,

[0023] FIG. 3 a second variant of the block-diagram with a pretreatment unit,

[0024] FIG. 4 a third variant of the block-diagram with a measured value transducer and a pretreatment unit, and

[0025] FIG. 5 a fourth variant of the block-diagram with a measured value transducer, a pretreatment unit, and induction heating.

[0026] According tot he basic design shown in FIG. 1, a metal strip is fed from a coil 2 into a pickling section 3. At that, coil data 4 from a data transducer 4a and a data transducer 4b are introduced into a set-up computation model 6 and/or into a regulation computation model 8 and are processed in accordance with the program. In the set-up computation model 6 further measured values 7 can be taken into consideration. Thereby, the pickling process is regulated, in addition to the pickling medium parameters, before the metal strip 1 is fed into the pickling section 3, by parameters of the coil 2 and/or the metal strip 1 which were determined, in the system 5, with servo components and/or measured.

[0027] In accordance with a first variant according to FIG. 2, in addition to the presetting of the pickling medium parameters, additionally acquires measured values, which characterized the coating or scale and which are determined by a measured value transducer M in a scale registration unit 10, are processed in the regulating computation model 8. The pickling process is regulated, respectively (FIGS. 1-5), on the basis of the set-up computation model 6 with preset measured values of the coil 2 and on the basis of the regulating computation model 8 which takes into account at least the measured values for the scale, bath temperature, the temperature of the pickling medium and/or acid concentration. The additional measured values for scale deposits before the pickling section 3 are used for regulating or readjusting the servo elements in the system 5.

[0028] In accordance with a second variant represented in FIG. 3 and a suitable evaluation of the coil information 4, a pretreatment unit H, which influences the pickling time, is used. In addition, the slow and rapid servo components of the pickling section 3 are readjusted in accordance with measured and/or calculated values output by the regulating computation model 8, in particular, taking into consideration the changed pickling times.

[0029] According to a third variant, represented in FIG. 4, additional measured value of the scale deposits and coatings is determined by the measured value transducer M of the scale registration unit 10 located in front of the pickling section 3 in the displacement direction 9, and is used for readjusting of the servo components of the pickling section 3 and/or in accordance with measured and calculated values. Besides, the pickling times are regulated on the basis of the strip inlet information of the coiler 2 and the system set-up. The acquired measured values with respect to coating and scale are used for regulating a pretreatment unit H located upstream of the pickling section 3.

[0030] On the basis of the fourth variant according to FIG. 5, in addition to the scale registration unit 10 and the pretreatment unit H, an induction heating unit W is provided between the pickling section 3 and the pretreatment unit H. The pickling time is defined as a contact time of a to-be-cleaned surface with the pickling medium necessary for a reliable removal of the contamination from the strip 1. The pretreatment unit H can include a preheating unit in form of the induction heating unit W.

[0031] The pretreatment unit H basically includes a mechanical, abrasive, hydromechanical, laser-optical, or oscillating descaler. The induction preheating of the metal strip by the induction heating unit W is effected before the pickling section and serves for a rapid regulation of the metal strip and pickling medium temperatures. 1 List of Reference Numerals 1. Metal Strip 2. Coil 3. Pickling Section 4. Coil-data 4a. Data Transducer 4b. Data Transducer 5. System With Servo Components 6. Set-up Computation Model 7. Measured Values 8. Regulating Computation Model 9. Displacement Direction 10. Scale Registration Unit M Measured Value Transducer H Pretreatment Unit W Induction Heating Unit

Claims

1. A method of pickling a rolled metal, in particular, steel strip fed to a regulated pickling process,

characterized in that

the pickling process is regulated, in addition to pickling medium parameters, by parameters of the coil and/or the metal strip determined and/or measured before the metal strip is fed into the pickling section.

2. A method according to claim 1,

characterized in that

the pickling process is preadjusted, on a basis of a set-up computation model, with measured values of the coil and is regulated on a basis of a regulating computaiton model that takes into consideration at least measured values for scale, bath temperature, pickling medium temperature, and/or acid concentration.

3. A method according to claim 1 or 2,

characterized in that

servo parameters of pickling are regulated or readjusted based on measured values for scale deposits before the pickling section.

4. A method according to one of claims 1 through 3,

characterized in that

additional measured values for scale deposits or coating are determined in a region in a displacement direction before the pickling section and are used for readjustment of the servo components of the pickling section and/or in accordance with measured and calculated values.

5. A method according to one of claims 1 through 4,

characterized in that

pickling times are regulated based on strip entrance data of the coil and the system adjustment.

6. A method according to one of claims 1 through 5,

characterized in that

the measured values for the coating or the scale are used for regulating a pretreatment unit located upstream of the pickling section.

7. A method according to claim 6,

characterized in that

the pretreatment unit and the servo components of the pickling section are readjusted in accordance with the measured or regulated values.

8. A device for pickling a metal, in particular, steel strip fed in a displacement direction from a coil of a pickling plant, for which a regulation by a plurality of parameters is contemplated,

characterized in that

measured values from coil measure value or data transducers (4a; 4b) are communicated via a set-up computation model (6) and a regulating computation model (8) to adjustment units of a pickling section.

9. A device according to claim 8,

characterized in that

measured values from the coil measured value transducers (4a; 4b) are input into the regulating computation model (8).

10. A device according to one of claims 8 or 9,

characterized in that

measured values of a measured value transducer (M) related to coating or scale are used for readjustment of servo components of the pickling section (3).

11. A device according to one of claims 8 and 9,

characterized in that

a pretreatment unit (H), measured values of which are input into the regulating computation model, is located upstream of the pickling section.

12. A device according to one of claims 7 through 11,

characterized in that

an induction heating unit (W), for the strip (1) is provided between the pretreatment unit (H) and the pickling section (3).