Cleaning plant for cleaning wound metal strips supplied with a surface oxide layer and method for cleaning metal strips.

Abstract

A cleaning plant for metal products. A cleaning plant for hot-rolled metal strips provided with a surface oxide layer, the plant comprising unwinding means (1) for unwinding at least one coil of rolled strip and pickling means (3) for pickling said rolled strip; wherein measuring means (11) are provided for measuring the thickness of the surface oxide layer, arranged between said unwinding means and said pickling means; and wherein gaseous hydrogen detection means (12) are provided for detecting the presence of gaseous hydrogen in the gases produced by said pickling means. A corresponding cleaning method is also claimed.

Description

1 / 31 Cleaning plant for cleaning wound metal strips supplied with a surface oxide layer and method for cleaning metal strips. Field of invention

[0001] The present invention relates to a cleaning plant for oxidized metal products, in particular hot-rolled strips, and a method for cleaning them. Knowledge technique

[0002] Conventional strip cleaning lines aim to remove the surface oxide layer that is created on hot-rolled metal products. In fact, during the hot rolling process, sheets, whether formed by the continuous forming machine or introduced into the line from an external station via a reheating furnace known as hot loading, are rolled and reduced in thickness to define a first strip with a thickness generally between 0.8 and 12 mm.

[0003] Because hot rolling is performed at high temperatures, and after winding the strip is rolled at a temperature between 200°C and 750°C depending on the chemical composition and use of the final product, various sections of the metal product surface are exposed to oxidizing agents such as air and water. In fact, it is not possible to treat the metal strip in an inert atmosphere, and this causes oxidation of the product's surface layers, which, in addition to determining a loss of finished material weight, is also a problem to be addressed. Petition 870260046305, dated 05 / 15 / 2026, page 14 / 97 2 / 31 resolved in a subsequent finishing process since the oxide formed can damage the surface quality of the product during cold winding and / or during painting. This oxide layer generally consists of ferrous oxide in the part closest to the metal, that is, in the innermost part, and magnetite and hematite on the outside.

[0004] Additionally, the finishing process is generally not carried out immediately downstream of the hot rolling process. The hot-rolled strip is commonly wound onto coils of the desired diameter or weight (dependent on the thickness of the strip coming off the winding line) and allowed to cool to ambient temperature in storage areas arranged close to the hot rolling line. This, therefore, can cause further oxidation of the strip surfaces.

[0005] Sometimes, hot rolling and pickling occur in different locations so that strip coils can be transported under conditions that are very aggressive from the point of view of corrosive attack, for example, in the presence of salt air if they are transported by ship.

[0006] However, if this oxide layer, generally known as scale or flakes, remained intact and adhered firmly to the metal strip, it would exert a protective action on the latter. However, due both to the action of atmospheric agents during transport and storage, and to the inevitable rupture of the scale itself, it is difficult to keep the oxide layer intact. Petition 870260046305, dated 05 / 15 / 2026, p. 15 / 97 3 / 31

[0007] Additionally, moisture penetrates the cracks and reacts with the earthy oxide layer closest to the metal surface, for example, steel, forming ferrous and ferric hydroxides which, due to the increase in volume, cause further detachment of the oxide layer, thus allowing attack on another part of the metal.

[0008] The hot-rolled strip must be finished on the finishing line at a later stage, according to production requirements.

[0009] The said strip may remain in a storage facility for several days before being finished, so that it has had time to cool and reach ambient temperature, determining the production of oxide layers that can reach 5 to 20 µm per side of the strip, for example. The oxide thickness is directly proportional to the nominal thickness of the strip, but also to the temperature of the strip during its winding.

[00010] Therefore, it is necessary to clean the oxide coating from the material before performing cold rolling treatments on the product and subsequent coating (e.g., galvanizing or tin plating, painting, etc.). This is especially important since this oxide layer, or scale, can damage the surface quality of the finished product and make rolling difficult.

[00011] In the current technique, the strip is cleaned by means of special descaling and pickling line designs, which commonly precede cold rolling. Typically, an unwinding line is provided for the previously hot-rolled strip, followed by a device for Petition 870260046305, dated 05 / 15 / 2026, page 16 / 97 4 / 31 break the scale so that it can be more easily removed through subsequent treatments. The scale is cleaned of the product through consecutive steps, which include introducing the product into acid tanks (chemical pickling). The product can then be brushed and rinsed.

[00012] The current economic and environmental situation requires manufacturers to increasingly apply adapted methods or technologies to optimize process controls while minimizing energy consumption, product consumption, such as pickling acids, and intended waste processing, such as material yield and material quality yield.

[00013] However, currently, it is not possible to precisely identify a priori the optimal process parameters to remove the exact amount of oxide with the minimum amount of acid.

[00014] In a disadvantageous way, instead, it is very likely that more acid than necessary will be used, removing even a good portion of the product, that is, a portion of the base metal of the strip, to ensure successful cleaning, but at the cost of production efficiency. In fact, pickling process operators generally prefer to produce slightly over-pickled strips to avoid quality rejection if under-pickled oxide residues not removed by the previous chemical attack are still present at the outlet of the pickling media. Petition 870260046305, dated 05 / 15 / 2026, page 17 / 97 5 / 31

[00015] An excessively stripped strip has the following disadvantages, among others: - a reduced production capacity of the plant; - a greater drop in yield due to the effect of chemical attack; - Different surface quality (roughness) of the same strip, which can negatively influence subsequent strip winding and coating processes; - the increased use of consumable products.

[00016] Conversely, in the case of an under-cleaned strip, it is possible that the acid used or the residence time in the treatment tanks is insufficient. Therefore, the strip is not optimally cleaned and must be discarded / downgraded or reprocessed.

[00017] Additionally, the evolution of steel grades required to meet ever-increasing performance requirements, such as increased tensile and elastic strength and percentage elongation at break, has complicated the chemical treatments to be performed on these steel categories.

[00018] For example, the gradual but strong push to shift from hydrocarbon-based energy mobility to electric mobility is increasing the production of non-oriented grain plates, which are characterized by a high presence of silicon in the alloy, and, disadvantageously, silicon oxides are particularly difficult to remove in pickling tanks. Petition 870260046305, dated 05 / 15 / 2026, page 18 / 97 6 / 31

[00019] This greatly influences the chemical pickling process, which in the future will need to be flexible and allow for a rapid change in reaction kinetics for the various and different products to be treated.

[00020] The need to provide an innovative cleaning plant for metal strips capable of overcoming the aforementioned disadvantages is, therefore, still felt. Summary of the invention

[00021] It is an objective of the present invention to provide a cleaning plant for metal strips that allows the detection of a plurality of useful data for operators to optimally adjust, preferably automatically, the operating parameters of chemical pickling, making it highly accurate, cost-effective and environmentally sustainable.

[00022] It is a further objective of the invention to provide a plant for detecting and processing said plurality of data in real time to automatically and instantly adjust the pickling operating parameters, thereby achieving precise control of the chemical pickling process and thus further improving the pickling conditions compared with prior art solutions.

[00023] Automatic adjustment of pickling parameters is achieved, for example, by means of software to simulate the oxide layer along the strip and control the pickling kinetics. Petition 870260046305, dated 05 / 15 / 2026, page 19 / 97 7 / 31

[00024] The invention solution is quite flexible and allows for rapid variation of the reaction kinetics even with different products being processed.

[00025] The present invention thus achieves at least one of the objectives mentioned above by a cleaning plant for cleaning rolled metal strips provided with an oxide surface layer, said plant comprising - unwinding means for unwinding at least one coil of laminated strip; - chemical pickling methods for pickling said rolled strip; - measuring means for measuring the thickness of the surface oxide layer, arranged between said unwinding means and said chemical pickling means; wherein said measuring means comprise at least one laser source cooperating with a fiber optic spectrometer, defining a LIBS (Laser Induced Breakdown Spectroscopy) system adapted to analyze oxide composition beyond thickness; wherein means of detecting gaseous hydrogen are provided to detect the presence of gaseous hydrogen in the gases produced by said chemical pickling means; and wherein a processing unit is provided, adapted for processing data at least from said measuring means and said gaseous hydrogen detection means, and adapted for adjusting parameters of Petition 870260046305, dated 05 / 15 / 2026, page 20 / 97 8 / 31 operation of said chemical pickling methods, defining the optimal conditions of the pickling process.

[00026] An additional aspect of the invention relates to a method for cleaning metal strips to be carried out by the aforementioned plant, which comprises the following steps: a) unwind at least one coil of laminated strip using the unwinding means; b) measure the thickness of the surface oxide layer of the rolled strip using the measuring instruments; c) to perform the said pickling of the said laminated strip by means of chemical pickling methods; wherein, in step b), the measurement of the surface oxide layer thickness is performed, along with an analysis of the oxide composition, by at least one laser source associated with a fiber optic spectrometer, defining a LIBS (Laser-Induced Breakdown Spectroscopy) system; wherein said fiber optic spectrometer measures the presence of oxygen while the laser from said laser source penetrates the surface oxide layer positioned on the strip until the unoxidized base material is reached, and the thickness of the surface oxide layer is equal to the depth excavated in said oxide layer by means of the laser source when said spectrometer detects the absence of oxygen; wherein, in step c), the detection of hydrogen gas in the gases produced by said chemical pickling methods is provided by means of hydrogen gas detection methods; Petition 870260046305, dated 05 / 15 / 2026, page 21 / 97 9 / 31 and in which data processing is provided from both said measuring means and said gaseous hydrogen detection means and, appropriately, the adjustment of the operating parameters of said chemical pickling means, by means of the processing unit.

[00027] Advantageously, the plant and method of the invention allow: maximize the production capacity of chemical pickling media; To improve material yield by minimizing acid attack on the oxide-free surface of the strip; To improve product quality by eliminating stretches in under-pickled or over-pickled strips; - Optimize energy and acid consumption.

[00028] Knowledge, through measurement, of the oxide layer thickness and the O2 / Fe ratio, and the detection of hydrogen gas in the gases emitted from the acid pickling tanks allow for greater flexibility and optimal estimation of the pickling parameter adjustment. The optimization of process control, determined by the combined processing of data detected by means of at least one LIBS system and the means of detecting hydrogen gas in the gases, advantageously allows for the minimization of energy consumption, product consumption (such as pickling acid), and intended processing residue as material yield and material quality yield. Petition 870260046305, dated 05 / 15 / 2026, page 22 / 97 10 / 31

[00029] The thickness of the oxide layer is measured by a technology known as LIBS (Laser-Induced Breakthrough Spectroscopy) which uses a pulsed laser to achieve the removal and vaporization of the oxide layer. The phase change of the oxide from the solid to the gaseous state generates a plasma state and, by reading the radiation emitted by the de-excitation of the excited species using a spectrometer, it is possible to identify the various elements present in the oxidized layer. It is confirmed that the base material has been reached when the spectrum of the oxidized layer no longer contains oxygen, and the thickness of the oxidized layer can be defined by knowing the number of pulses emitted by the laser up to that point.

[00030] Knowledge of the chemical reactions that occur in pickling tanks, where, for example, hydrochloric acid (used in particular for pickling low / medium carbon steel strip) is primarily used, provides interesting insights for evaluating chemical attack combinations on the non-oxidized base material. The reactions that occur are as follows: 1) FeO + 2HCl → FeCl2 + H2O 2) Fe2O3 + 6HCl → 2FeCl3 + 3H2O 3) Fe3O4+ 8HCl FeCl2+2FeCl3+4H2O 4) Fe + 2HCl → FeCl2 + H2(gas)

[00031] Reactions 1) to 3) represent the effect of the presence of various types of oxide in the reaction, while reaction 4) shows that when an acid reacts with iron, without the presence of oxide, the result of the reaction comprises the development of hydrogen in gaseous form. From Petition 870260046305, dated 05 / 15 / 2026, page 23 / 97 Based on this observation, it was decided to measure the amount of hydrogen present in the gases, in order to use this value as a parameter to evaluate the extent of the pickling process, and advantageously in combination with the data on the oxide layer detected by means of the LIBS system.

[00032] In a first variant of the invention, detection of any residual oxides on the strip is provided by means of first optical detection means arranged at the inlet of the last chemical pickling tank. This allows the operational pickling parameters of the last pickling tank to be altered, further minimizing the quality of the residue. In fact, the presence of clearly visible oxide residues on the strip surface allows the level of under-pickling to be assessed and prompt intervention to be made, by virtue of the aforementioned software, to optimize the pickling conditions, in the pickling parameters of the last pickling tank, such as the travel speed and thus the strip feed speed, and / or the turbulence level of the acid solution present in the last tank.

[00033] In a second variant of the invention, detection is provided, by means of second optical detection means arranged downstream of the stripping means, of the surface properties of the strip, such as surface roughness and / or reflectivity and / or gray level and / or emissivity. These properties are an indicator of the level of over-stripping of the material. In fact, acid etching on an oxide-free surface changes not only its roughness but also its texture. Petition 870260046305, dated 05 / 15 / 2026, p. 24 / 97 12 / 31 crystalline through the effect of different attack on the edge of the crystalline grains. This feedback allows, through pickling optimization software, that the pickling operating parameters be modified upstream of the pickling line, further minimizing quality residue.

[00034] In a third variant of the invention, detection of any residual oxides in the strip is provided by means of third-party optical detection means arranged downstream of the pickling means. This feedback also allows, through pickling optimization software, that the pickling operating parameters be modified upstream of the pickling line, again minimizing quality residue.

[00035] In a fourth variant of the invention, a mass balance is provided, using acid and iron concentration analyzers, in the spent acid solution and in the regenerated acid solution, which are continuously moved to and from the pickling media, respectively, thus allowing further refinement of pickling control.

[00036] The functionalities of some or all of the variants of the invention can be combined in an advantageous manner.

[00037] In general, in the case of excessive pickling, the pickling operating parameters can be modified as follows: - Increase the process speed if plant conditions allow (increase in production capacity); Petition 870260046305, dated 05 / 15 / 2026, page 25 / 97 13 / 31 Reduce bath turbulence to decrease reaction kinetics (reducing energy consumption); Reduce the bath temperature to decrease the reaction kinetics (reduce energy consumption); to reduce the acid concentration (decrease in acid consumption).

[00038] In the case of under-pickling, instead, the pickling operating parameters can be modified as follows: slow down the process (decrease in production capacity); Increase the turbulence of the bath to increase the reaction kinetics; Increase the bath temperature to increase the reaction kinetics; - increase the acid concentration. Brief description of the figures

[00039] Additional features and advantages of the invention will become more apparent in light of the detailed description of a preferred, but not exclusive, embodiment of a metal strip cleaning plant illustrated by means of a non-limiting example, with the aid of the accompanying drawings in which:

[00040] Figure 1 shows a diagrammatic view of an embodiment of a power plant according to the invention.

[00041] Figure 2 shows a flowchart that refers to an example of a cleaning method according to the invention. Petition 870260046305, dated 05 / 15 / 2026, page 26 / 97 14 / 31

[00042] Figure 3 shows a diagrammatic view of a part of the system of the invention. Detailed description of exemplary embodiments of the invention.

[00043] The figures show some examples of embodiments of a cleaning plant for oxidized metal strips. In particular, the dotted components in Figure 1 may be optional, considered individually or together.

[00044] The power plant according to the present invention, in all its embodiments, comprises, in sequence: - unwinding means 1 for unwinding at least one coil of laminated strip having an oxide surface layer; - measuring means 11 for measuring the thickness of the surface oxide layer; - Chemical pickling methods 3 for pickling the rolled strip.

[00045] In a first variant, the unwinding means 1 comprise a single laminated strip unwinding line, preferably a single unwinding reel.

[00046] In a second variant of the unwinding means 1, a double unwinding line is provided for rolled strips followed by a cutting and welding machine to provide continuity for the unwound strip to be pickled.

[00047] In particular, at least two unwinding reels and a machine may be supplied. Petition 870260046305, dated 05 / 15 / 2026, page 27 / 97 15 / 31 Welding, preferably a laser welding machine, capable of producing joints between the strips unwound by the unwinding reel, thus defining a continuous strip, i.e., allowing a continuous supply of metal strip downstream of the unwinding means. A tensioning device may optionally be provided to adjust the strip tension.

[00048] Possible storage systems (not shown) are provided upstream and / or downstream of the chemical pickling media 3.

[00049] Preferably, between the unwinding means 1 and the pickling means 5, at least one scale-breaking device 3 may advantageously be provided, said scale-breaking device using, for example, mechanical systems to break the oxide layer, to make the latter more removable by means of subsequent chemical pickling means.

[00050] The measuring means 11 for measuring the oxide layer thickness comprise, in particular, at least one laser source cooperating with a fiber optic spectrometer, defining a LIBS (Laser-Induced Breakdown Spectroscopy) system also adapted to analyze the oxide composition and / or the concentration of the oxide constituent elements. The term oxide composition refers to the chemical nature of the individual oxide or oxide mixtures. The term concentration of oxide constituent elements refers to the concentration of individual ionic species constituting the individual oxide. Petition 870260046305, dated 05 / 15 / 2026, page 28 / 97 16 / 31

[00051] Advantageously, said fiber optic spectrometer is configured to measure the presence of oxygen as the laser from the laser source penetrates the oxide layer present on the surface of the laminated strip in the direction of the non-oxidized base material.

[00052] The system uses a laser source for point ablation of the oxide layer. The laser source provides the energy necessary to bring the species, which belong to the oxide layer removed by ablation along its thickness, into the plasma state. The de-excitation of the ions that constitute the plasma allows, through the use of the spectrometer, both the identification of the species present and their concentration. The thickness of the oxide layer is advantageously detected by the disappearance of the oxygen signal.

[00053] Therefore, the fiber optic spectrometer can measure the presence of oxygen during point ablation of the oxide layer. When the spectrometer detects, after a time t of erosion, thus during ablation, the absence of oxygen, the measurement of the depth of the eroded material layer at time t will correspond with the thickness of the surface oxide layer.

[00054] In other words, software calculates the erosion depth, which will be equal to the thickness of the surface oxide layer at the disappearance of the oxygen peak, given the erosion time t and the erosion rate.

[00055] By virtue of spectrometric measurement, it is possible to know both the thickness of the oxide layer Petition 870260046305, dated 05 / 15 / 2026, page 29 / 97 17 / 31 regarding its composition (e.g., O2 / Fe ratio). Based on this data, it becomes possible to optimally define the pickling operating parameters using optimization software to optimize the pickling process kinetics. An additional advantage of using LIBS technology is its minimal invasiveness; it is a non-destructive technology because the only damage caused is the ablation of the material, creating a cavity with dimensions that depend on the laser's focal point.

[00056] In an advantageous variant, two or more measuring means 11, 11' are provided, arranged above and below the feed line of the rolled strip, to calculate the thickness of the oxide layer on both the upper and lower faces of the strip and the difference between the edge and the center of the strip.

[00057] In particular, at least one measuring means 11 is provided arranged above the feed line of the rolled strip 8 and at least one measuring means 11' is provided arranged below the feed line of the rolled strip 8.

[00058] When two or more measuring means 11 and two or more measuring means 11' are provided, at least four or more laser sources associated with a respective fiber optic spectrometer are provided, defining four or more LIBS systems.

[00059] The measuring means 11 and thus the LIBS system or LIBS systems can be arranged in a Petition 870260046305, dated 05 / 15 / 2026, page 30 / 97 18 / 31 fixed or mobile manner with respect to the laminated strip feed line 8.

[00060] The thickness of the oxide layer can be measured in several ways.

[00061] For example, it is possible to perform the measurement statistically by temporarily interrupting the inflow of the strip into the cleaning plant (for example, during strip welding) and restarting once the data is obtained.

[00062] Alternatively, the measurement can be carried out continuously, for example, by arranging the measuring means 11 in transports adapted to be moved along with the metal strip.

[00063] Advantageously, in all embodiments of the invention's plant, gaseous hydrogen detection means 12 are provided to detect the presence of gaseous hydrogen in the gases produced by said chemical pickling means 3.

[00064] Such gaseous hydrogen detection means 12 both comprise and consist of a detection instrument adapted for performing thermal conductivity measurements. For example, such gaseous hydrogen detection means 12 comprise one, two or more thermal conductivity detectors.

[00065] In particular, a detection instrument may be used comprising (Figure 3): - two ducts 30, 31, in which the flow of gases produced by a pickling tank 15 is divided and advanced; Petition 870260046305, dated 05 / 15 / 2026, page 31 / 97 19 / 31 a combustion chamber 32, such as a catalytic furnace, arranged along said two conduits, such as conduit 30, for ignition of combustion in such a way that hydrogen, if present, is burned in the gas flow of the related conduit 30; thermal conductivity detectors 33, 34 to detect a possible difference in thermal conductivity between the flows of two conduits, downstream of the combustion chamber 32.

[00066] If a difference in thermal conductivity is detected between the flows of the two conduits, this may confirm the presence of hydrogen gas in the gases and thus excessive stripping of the strip surface.

[00067] In the combustion chamber, since the temperature of the gases is generally below 80°C, a spark can be ignited to burn gaseous hydrogen, which is the only component reactive to the spark.

[00068] The measurement of hydrogen gas present in the gases produced by chemical pickling methods is thus obtained by comparing the two thermal conductivity signals emitted by the conductivity detectors (in the sample gas and in the hydrogen-free reference gas), thereby achieving high measurement accuracy.

[00069] Preferably, the chemical pickling means 3 comprise two or more chemical pickling tanks, containing an acidic solution, arranged in sequence. The hydrogen gas detection means 12 may be positioned to detect the presence of hydrogen gas in the gases produced by at least the Petition 870260046305, dated 05 / 15 / 2026, page 32 / 97 20 / 31 last chemical pickling tank 15, preferably in the gases produced only by the last tank 15 among said two or more chemical pickling tanks.

[00070] In a variant of the invention, the first optical detection means 13 are provided, arranged at the inlet of said last chemical pickling tank 15, to detect any residual oxide on the strip surface. Such first detection means 13 comprise, for example, at least one system for video analysis of the strip, which may include one or more cameras with a possible corresponding lighting system that allows, if any oxide residues are visible on the strip surface, to modify by virtue of the aforementioned software the pickling operating parameters of the last pickling tank 15, further minimizing quality rejection due to under-pickling in a surprisingly optimal manner. In particular, one or more cameras are provided to analyze three different areas of the strip surface, such as the operator edge, the motor edge and the center.

[00071] This video analysis system allows, for example, comparing the color or brightness of the strip with color scales that indicate different degrees of product cleanliness, previously loaded into the memory of a processing unit 10. Through the use of digital cameras with high pixel density, for example, it is possible to define the ratio of the defective area to the stripped area for each square meter of strip, the minimum and maximum sizes of the defective areas and their position on the strip. Petition 870260046305, dated 05 / 15 / 2026, page 33 / 97 21 / 31 (top surface / bottom surface, center / edge, head / tail or coil body, i.e., the part of the strip between the head and the tail).

[00072] Optionally, secondary optical detection means 14, arranged downstream of the chemical stripping means 3, may be provided to detect properties such as surface roughness and / or reflectivity and / or gray level and / or emissivity of at least one surface of the strip. Such secondary optical detection means 14 comprise, for example, an optical sensor adapted to detect any residual surface effect, signs of over-stripping of the surface. This feedback also allows modification of the upstream stripping operating parameters, thus minimizing quality deviation.

[00073] For example, such a sensor is a pyrometer that measures the emissivity of the stripped surface, which represents the ability of a surface to absorb heat and then transmit that energy through its emission in the infrared range.

[00074] The action of the acid on the metal strip surface modifies the surface roughness and consequently also the emissivity, which becomes an index to define possible effects of under-pickling or over-pickling of the strip surface.

[00075] Third optical detection means 9, also arranged downstream of the chemical stripping means 3, may also be provided to detect any residual oxide on the surface of the strip. This feedback also Petition 870260046305, dated 05 / 15 / 2026, p. 34 / 97 22 / 31 allows for the modification of upstream stripping operating parameters, thus minimizing quality deviation due to possible under-stripping. The third optical detection means 9 may comprise a video analysis system similar to that of the first optical detection means 13.

[00076] The order in which the second optical detection means 14 and the third optical detection means 9 are arranged downstream of the chemical pickling means 3 is irrelevant.

[00077] Preferably, rinsing media for rinsing the pickled strip are arranged between the chemical pickling media 3 and the second and / or third optical detection media 14, 9.

[00078] In all embodiments of the invention's plant, the following can be provided: - Regeneration means 17 to regenerate an exhausted acid solution that comes from chemical pickling means 3 and obtain a regenerated acid solution; - at least one tube 18 to transport the exhausted acid solution from the chemical pickling media 3 to the regeneration media 17; a first flow meter 4, preferably arranged along the tube 18, to measure the flow rate of said exhausted acid solution directed to the regeneration media 17; - a first analyzer 6, preferably arranged along tube 18, to analyze the concentration of acid and iron in the exhausted acid solution; Petition 870260046305, dated 05 / 15 / 2026, p. 35 / 97 23 / 31 - at least one tube 19 to transport the regenerated acid solution from the regeneration media 17 to the chemical pickling media 3; a second flow meter 5, preferably arranged along tube 19, to measure the flow rate of the regenerated acid solution directed to the chemical pickling media 3; - a second analyzer 7, preferably arranged along tube 19, to analyze the concentration of acid and residual iron in the regenerated acid solution.

[00079] Regeneration methods 17 comprise, for example, a chemical reactor in which iron in the form of an oxide is separated, by a pyrohydrolysis reaction, from the exhausted acid solution, which is then concentrated and returned for pickling. In the reactor, the exhausted acid solution (with a high iron content) is heated in an oxidizing atmosphere which causes the solution to vaporize and, while on the one hand the free acid is recovered, on the other hand the iron is removed as an oxide.

[00080] This configuration allows obtaining a mass balance of the chemical reaction necessary to completely remove the oxide layer, using acid and iron concentration analyzers in the exhausted acid solution and the regenerated acid solution, which are continuously moved to and from the chemical pickling media 3, respectively. In fact, these analyzers allow for further refinement of pickling control since they allow calculating the amount of scale already removed through knowledge, by means of statistical models. Petition 870260046305, dated 05 / 15 / 2026, page 36 / 97 24 / 31 well known based on various treatments, of the amount of initial oxide to be removed from the unwound strip of the coil.

[00081] Advantageously, a processing unit 10 is provided, configured to process measurement data from at least the measurement means 11, possibly also from the measurement means 11', and from the gaseous hydrogen detection means 12, and to adjust operating parameters of the chemical pickling means 3 in an appropriate manner.

[00082] Preferably, processing unit 10 can also be configured to process strip cleanliness level data from at least one of the following: the first means of optical detection 13, to possibly adjust the pickling operating parameters of the last pickling tank; and - the second optical detection means 14 and / or the third detection means 9, to possibly further adjust the operating parameters of the chemical pickling means 3.

[00083] When the regeneration media 17 are supplied, the processing unit 10 can also process data from the first flow meter 4, the first analyzer 6, the second flow meter 5, and the second analyzer 7, to adjust the operating parameters of the chemical pickling media 3 appropriately.

[00084] Regarding the method of cleaning the metal strip of the invention, which can be carried out by the plant Petition 870260046305, dated 05 / 15 / 2026, page 37 / 97 25 / 31 mentioned earlier, the said method comprises the following steps: a) unwind at least one coil of laminated strip using unwinding means 1; b) measure the thickness of the surface oxide layer of the rolled strip using measuring means 11, 11'; c) to strip the laminated strip using chemical stripping methods 3.

[00085] In step b), the thickness of the surface oxide layer is measured, along with an analysis of the oxide composition, by means of at least one laser source associated with a respective optical fiber spectrometer, which defines a Laser Induced Breakdown Spectroscopy (LIBS) system.

[00086] Advantageously, during step c), gaseous hydrogen detection is provided in the gases produced by the chemical pickling means 3 by means of said gaseous hydrogen detection means 12, preferably in the gases produced by the last pickling tank 15, i.e., the one distal to the unwinding means 1.

[00087] The combined processing of data from the measuring means 11 and the hydrogen gas detection means 12 and the consequent adjustment of the operating parameters of the chemical pickling means 3, by means of the processing unit 10, surprisingly allows optimizing the pickling process. Petition 870260046305, dated 05 / 15 / 2026, p. 38 / 97 26 / 31

[00088] Figure 2 shows an example of a flowchart of part of a cleaning method according to the invention.

[00089] Advantageously, processing unit 10 uses software, preferably installed in said processing unit 10, which includes a pickling adjustment template, or more simply a pickling template, 20 configured to adjust one or more of the following pickling parameters, such as: process speed, that is, the strip feed speed at which the strip travels through the pickling tanks; concentrations of acid, for example, hydrochloric acid, in the acidic solution of pickling tanks; temperature of the acid solution in the pickling tanks; - turbulence level of the acidic solution.

[00090] The pickling model 20 then generates a process configuration and applies this configuration to the strip that is entering the pickling tanks.

[00091] The pickling model 20 interacts with an oxide layer simulation model 21, or more simply the oxide layer model or scale model 21, preferably included in said processing unit 10.

[00092] The oxide layer simulation model 21 produces simulation data of the surface oxide layer along the strip, in particular, along the entire length of the strip. Petition 870260046305, dated 05 / 15 / 2026, page 39 / 97 27 / 31

[00093] The pickling adjustment model 20 adjusts pickling parameters comprising the strip feed rate in the chemical pickling media 3 and / or the turbulence level of the acid solution present in said chemical pickling media 3, preferably said pickling parameters further comprising the acid concentration in the acid solution and / or the temperature of said acid solution.

[00094] The simulation data is sent to the pickling adjustment model 20.

[00095] In order to produce the simulation data, the oxide layer simulation model 21 acquires both first input data 22, relating to the strip as wound on the coil, and second input data 23 consisting of the data detected by the measuring means 11, 11' during the operation of the plant.

[00096] The first input data 22 comprise at least the strip thickness, strip width, metal grade, strip winding temperature; while the second input data 23 comprise the surface oxide layer thickness and oxide composition and preferably also the concentration of the oxide constituent elements.

[00097] Simulation data for the surface oxide layer along the strip are obtained by comparing the first input data 22 and the second input data 23 with a database containing data relating to a set of strips of different thicknesses, Petition 870260046305, dated 05 / 15 / 2026, p. 40 / 97 28 / 31 width, metal material and wound at different winding temperatures.

[00098] In more detail, a 21-scale model acquires initial 22-data input, such as the initial data of the strip as wound onto the coil, which comprise - strip thickness; - strip width; - steel grade; - strip winding temperature; - possible production data.

[00099] A scale model 21 also acquires, during the operation of the invention's plant, the second input data 23 consisting of the data detected by the measuring means 11, 11', namely, the thickness of the surface oxide layer, the oxide composition and the concentration of oxide constituent elements and, in particular, the presence of oxygen. [000100] Using both the first input data 22 and the second input data 23, the scaling model 21, for example, by means of a comparison with a database preferably containing archived oxide measurements that refer to a set of strips of different thickness, width, material and wound at different winding temperatures, generates a simulation of the amount of oxide present along the length of the strip. [000101] Preferably, the oxide surface layer simulation data comprise at least one of the following data sets: - thickness in micrometers; Petition 870260046305, dated 05 / 15 / 2026, page 41 / 97 29 / 31 - weight in grams / m2 of oxide to be removed; - Estimate of the average oxide composition; - strip stripping coefficient. [000102] As is known, a stripping coefficient is defined as a coefficient Kd, the value of which is less than or equal to 1 but greater than 0.5. This value is used as a multiplication coefficient to define the strip feed rate or the stripping speed. The maximum speed will occur for Kd = 1. For strips with difficult stripping, Kd = 0.5. [000103] This information is sent to the pickling model 20 to define the pickling parameters, such as those listed above, preferably customized for the head, center, and tail of the strip to be processed. The pickling model 20 then generates the process configuration. [000104] At least one control cycle is provided to enhance the control of the pickling process. For each control cycle, one or more values ​​provided by the pickling model 20 are compared with the respective value measured or analyzed by corresponding instrumentation installed throughout the plant. If the difference between the measured value and the value provided by the pickling model 20 does not exceed a threshold value (Error: NO), the model estimate is considered adequate and no feedback is generated. Conversely, if the difference between the measured value and the value provided by the pickling model 20 exceeds the threshold value (Error: YES), feedback is generated requiring the pickling model 20 to generate a Petition 870260046305, dated 05 / 15 / 2026, page 42 / 97 30 / 31 value shift to improve process control. [000105] In the flowchart in Figure 2, which refers to an example variant of the invention's power plant in which, in addition to a measuring means 11, are provided - the regeneration media 17 associated with the first flow meter 4, first analyzer 6, second flow meter 5 and second analyzer 7, - the means of detecting gaseous hydrogen 12, - the first means of optical detection 13, - the second optical detection means 14, - the third optical detection means 9, the following control cycles are cascaded one over the other: a first control cycle to possibly adjust the mass balance of the chemical pickling reaction, which uses the values ​​of the flow rate of exhausted acid solution, the concentration of acid and iron in the exhausted acid solution, the flow rate of regenerated acid solution, and the concentration of residual acid and iron in the regenerated acid solution, detected by the first flow meter 4, the first analyzer 6, the second flow meter 5, and the second analyzer 7, respectively; a second control cycle to possibly reduce / eliminate excessive pickling, indicated by the presence of possible hydrogen gas in the gases from at least the last pickling tank, said presence being detected by hydrogen gas detection means 12; Petition 870260046305, dated 05 / 15 / 2026, page 43 / 97 31 / 31 - a third control cycle to possibly reduce / eliminate under-pickling, indicated by the presence of residual oxide on the surface of the strip entering the last pickling tank, said presence being detected by the first optical detection means 13; a fourth control cycle to possibly reduce / eliminate under-pickling, indicated by the presence of residual oxide on the strip surface at the outlet of the last pickling tank, said presence being detected by the third optical detection means 9; a fifth control cycle to possibly reduce / eliminate excessive stripping, using the surface roughness and / or reflectivity and / or gray level and / or emissivity values ​​of at least one strip surface, detected by the second optical detection means 14. [000106] The second control cycle mentioned above provides that, if the difference between the hydrogen gas value in the gases, detected by the hydrogen gas detection means 12, and the hydrogen gas value in the gases provided by the stripping adjustment model 20 exceeds a predetermined limit value, feedback is produced, which prompts the stripping adjustment model 20 to adjust at least one stripping parameter so that said difference does not exceed said limit value. The first, third, fourth and fifth control cycles, individually or all together, may be optional. Petition 870260046305, dated 05 / 15 / 2026, page 44 / 97

Claims

1 / 9 CLAIMS 1. Cleaning plant for cleaning rolled metal strips provided with a surface oxide layer, the plant characterized in that it comprises - unwinding means (1) for unwinding at least one coil of rolled strip; - chemical pickling means (3) for pickling said rolled strip; - measuring means (11) for measuring the thickness of the surface oxide layer, arranged between said unwinding means (1) and said chemical pickling means (3); wherein said measuring means (11) comprise at least one laser source cooperating with an optical fiber spectrometer, defining a Laser Induced Breakdown Spectroscopy (LIBS) system also adapted to analyze the oxide composition; wherein gaseous hydrogen detection means (12) are provided for detecting the presence of gaseous hydrogen in the gases produced by said chemical pickling means (3);wherein a processing unit (10) is provided, configured to process data at least from said measuring means (11) and said gaseous hydrogen detection means (12), and configured to adjust operating parameters of said chemical pickling means (3) in an appropriate manner, wherein said processing unit (10) comprises: Petition 870260046305, dated 05 / 15 / 2026, page 45 / 97 2 / 9 - an oxide layer simulation model (21), adapted to produce surface oxide layer simulation data along the strip, acquiring first input data (22) relating to the strip as wound on the reel, and second input data (23) consisting of data detected by the measuring means (11) during plant operation;- a pickling adjustment model (20), adapted to adjust pickling parameters comprising the feed rate of the strip in the chemical pickling media (3) and / or the turbulence level of the acid solution present in said chemical pickling media (3), said pickling parameters further comprising the acid concentration in the acid solution and / or the temperature of said acid solution; wherein simulation data are sent to the pickling adjustment model (20);and wherein at least one control cycle is provided, adapted so that when the difference between a hydrogen gas value in the gases, detected by the hydrogen gas detection means (12), and a hydrogen gas value in the gases provided by the stripping adjustment model (20) exceeds a limit value, feedback is produced requesting that the stripping adjustment model (20) adjust at least one stripping parameter so that said difference does not exceed said limit value.

2. Cleaning plant, according to claim 1, characterized in that said chemical pickling means comprise two or more chemical pickling tanks Petition 870260046305, dated 05 / 15 / 2026, page 46 / 97 3 / 9, and in which said gaseous hydrogen detection means (12) are positioned to detect the presence of gaseous hydrogen in the gases produced by at least the last chemical pickling tank (15).

3. Cleaning plant, according to claim 1 or 2, characterized in that said gaseous hydrogen detection means (12) both comprise and consist of detection instruments adapted to perform thermal conductivity measurements.

4. Cleaning plant, according to claim 2, characterized in that first optical detection means (13) are provided to detect any residual oxide on the surface of the strip, said first optical detection means (13) being arranged at the entrance of said last chemical pickling tank (15).

5. Cleaning plant, according to claim 4, characterized in that additional optical detection means (9, 14) are provided to detect the cleanliness level of the strip, arranged downstream of said chemical stripping means (3).

6. Cleaning plant, according to claim 5, characterized in that said additional optical detection means comprise second optical detection means (14) for detecting the surface roughness and / or reflectivity and / or gray level and / or emissivity of at least one surface of the strip.

7. Cleaning plant, according to claim 6, characterized in that said additional optical detection means further comprise third Petition 870260046305, dated 05 / 15 / 2026, page 47 / 97 4 / 9 optical detection means (9) for detecting any residual oxide on the surface of the strip.

8. Cleaning plant, according to any one of claims 1 to 7, characterized in that it is provided with: - regeneration means (17) for regenerating an exhausted acid solution from the chemical pickling means (3) and obtaining a regenerated acid solution; - a first flow meter (4) for measuring the flow rate of said exhausted acid solution directed to the regeneration means (17); a first analyzer (6) for analyzing the acid and iron concentration in said exhausted acid solution; - a second flow meter (5) for measuring the flow rate of said regenerated acid solution directed to the chemical pickling means (3); a second analyzer (7) for analyzing the residual acid and iron concentration in said regenerated acid solution;wherein said processing unit (10) is also adapted to process data at least from said first flow meter (4), said first analyzer (6), said second flow meter (5), and said second analyzer (7), and to adjust the operating parameters of said chemical pickling media (3) in an appropriate manner.

9. Cleaning plant, according to claim 4, characterized in that said processing unit (10) is also adapted to process data from said first optical detection means (13), and to adjust the operating parameters of said chemical pickling means (3) in an appropriate manner.

10. Cleaning plant, according to claim 6, characterized in that said processing unit (10) is also adapted to process data from said first optical detection means (13) and said second optical detection means (14), and to adjust the operating parameters of said chemical pickling means (3) in an appropriate manner.

11. Cleaning plant, according to claim 7, characterized in that said processing unit (10) is also adapted to process data from said first optical detection means (13), said second optical detection means (14) and said third optical detection means (9), and to adjust the operating parameters of said chemical pickling means (3) in an appropriate manner.

12. Cleaning plant, according to any one of claims 9 to 11, characterized in that it provides - regeneration means (17) for regenerating an exhausted acid solution from the chemical pickling means (3) and obtaining a regenerated acid solution; - a first flow meter (4) for measuring the flow rate of said exhausted acid solution directed to the regeneration means (17); Petition 870260046305, dated 05 / 15 / 2026, p.49 / 97 6 / 9 a first analyzer (6) for analyzing the acid and iron concentration in said exhausted acid solution; - a second flow meter (5) for measuring the flow rate of said regenerated acid solution directed to the chemical pickling media (3); a second analyzer (7) for analyzing the residual acid and iron concentration in said regenerated acid solution; wherein said processing unit (10) is also adapted to process data at least from said first flow meter (4), said first analyzer (6), said second flow meter (5) and said second analyzer (7), and to adjust the operating parameters of said chemical pickling media (3) in an appropriate manner.

13. Method for cleaning metal strips, to be carried out by a plant as defined in any one of claims 1 to 12, characterized in that it comprises the following steps: a) unwinding at least one coil of rolled strip using unwinding means (1); b) measuring the thickness of the surface oxide layer of the rolled strip using measuring means (11); c) performing said pickling of said rolled strip using chemical pickling means (3); wherein, in step b), the measurement of the thickness of the surface oxide layer is carried out together with an analysis of the oxide composition, using at least one laser source associated with a fiber optic spectrometer, defining a Laser Induced Breakdown Spectroscopy (LIBS) system;wherein said optical fiber spectrometer measures the presence of oxygen while the laser of said laser source penetrates the surface oxide layer present in the laminated strip in the direction of a non-oxidized base material, and the thickness of the surface oxide layer is equal to the depth excavated in the laminated strip by the laser source when said spectrometer detects the absence of oxygen; wherein, in step c), detection of hydrogen gas in the gases produced by said chemical pickling means (3) is provided by means of hydrogen gas detection means (12); wherein data processing of both said measuring means (11) and said hydrogen gas detection means (12) and adjustment of the operating parameters of said chemical pickling means (3) in an appropriate manner is provided by means of the processing unit (10);wherein said processing unit (10) comprises: - an oxide layer simulation model (21), adapted to produce surface oxide layer simulation data along the strip, acquiring first input data (22) relating to the strip as wound on the coil, and second input data (23) consisting of data detected by the measuring means (11) during plant operation; Petition 870260046305, dated 05 / 15 / 2026, page 51 / 97 8 / 9 - a pickling adjustment model (20), adapted to adjust pickling parameters comprising the feed rate of the strip into the chemical pickling media (3) and / or the turbulence level of the acid solution present in said chemical pickling media (3), said pickling parameters further comprising the acid concentration in the acid solution and / or the temperature of said acid solution; where the simulation data are sent to the stripping adjustment model (20);and wherein at least one control cycle is provided, adapted so that when the difference between a hydrogen gas value in the gases, detected by the hydrogen gas detection means (12), and a hydrogen gas value in the gases provided by the stripping adjustment model (20) exceeds a limit value, feedback is produced requesting that the stripping adjustment model (20) adjust at least one stripping parameter so that said difference does not exceed said limit value.

14. Cleaning method according to claim 13, characterized in that the first input data (22) comprise at least strip thickness, strip width, metal material grade, strip winding temperature; and in that the second input data (23) comprise surface oxide layer thickness and oxide composition.

15. Cleaning method, according to claim 14, characterized in that the simulation data of the surface oxide layer along the strip are obtained Petition 870260046305, dated 05 / 15 / 2026, page 52 / 97 9 / 9 by comparing said first input data (22) and said second input data (23) with a database containing data relating to a set of strips of different thickness, width, metal material and wound at different winding temperatures.

16. Cleaning method according to claim 13, characterized in that said pickling parameters further include the acid concentration in the acid solution or the temperature of said acid solution.

17. Cleaning method according to claim 15, characterized in that said simulation data comprises at least one of the following data: - thickness in micrometers; - weight in grams / m2 of oxide to be removed; - estimate of the average oxide composition; - strip stripping coefficient. Petition 870260046305, dated 05 / 15 / 2026, p. 53 / 97

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