Metal product cleaning equipment

Abstract

The invention relates to metal product cleaning equipment. An apparatus for cleaning a rolled metal strip provided with a surface oxide layer, the apparatus comprising an unwinding device for unwinding at least one rolled strip roll, and a pickling device for pickling the rolled strip; wherein a measuring device arranged between the unwinding device and the pickling device is provided for measuring the thickness of the surface oxide layer. A related cleaning method is also claimed.

Description

[0001] This application is a divisional application of an application filed on May 24, 2018, with application number 201880034216.6 and invention name “Metal Product Cleaning Equipment”. Field of the Invention

[0002] The invention relates to a cleaning device for oxidized metal products. Background Art

[0003] Lines for cleaning conventional type strips aim to eliminate the surface oxide layer formed on hot rolled metal products. In fact, during the hot rolling process, the slab formed by the continuous caster is rolled and reduced in thickness to define a first strip having a thickness generally between 0.8 mm and 12 mm.

[0004] Since hot rolling is carried out at high temperatures, usually between 200°C and 800°C, the surface of the metal product is exposed to oxidizing agents, such as air and water, in different parts. In fact, it is not always possible to process the metal strip in an inert atmosphere, and this leads to oxidation of the surface layer of the product, which, in addition to determining the weight loss of the material, is also a problem that must be solved in the subsequent finishing process. This oxide layer generally includes ferrous oxide in the part closest to the metal (ie towards the inside), and when moving away from there the oxide layer generally includes magnetite and hematite.

[0005] Furthermore, finishing processes are not usually carried out immediately downstream of the hot rolling process. Hot rolled strip is usually coiled into coils of the required weight or diameter (the data depends on the strip thickness output from the rolling line) and cooled at room temperature in a warehouse arranged close to the hot rolling line. As a result, this leads to further oxidation of the strip surface.

[0006] Furthermore, hot rolling and pickling sometimes take place at different locations, so that the coils can be transported even under conditions that are extremely aggressive from a corrosion point of view, such as in the presence of brackish air.

[0007] However, if this oxide layer (commonly referred to as scale) remains intact and firmly adheres to the metal strip, it protects the metal strip. However, it is difficult to keep the oxide layer intact due to the effects of atmospheric media during transportation and storage, as well as the inevitable cracking of the scale itself.

[0008] Furthermore, moisture penetrates into the slits and reacts with the ferrous oxide layer closest to the metal surface (e.g. steel) to form ferrous and ferric hydroxides, which, due to the increase in volume, causes further separation of the oxide layer, allowing another part of the metal to be corroded.

[0009] Subsequently, according to production requirements, the hot rolled strip should be finished in a finishing line.

[0010] This strip can even remain in the warehouse for a few days before final finishing, whereby it has all the time to cool down and reach room temperature, determining the oxide layer, which can reach 5-20 μm on each side of the strip, for example. The thickness of the oxide is proportional to the nominal thickness of the strip, but also to the temperature of the strip during coiling.

[0011] Therefore, before the product is subjected to cold rolling and subsequent coating treatment (such as galvanizing or tinning), the material needs to be cleaned from the oxide coating. This is particularly important because this oxide layer or scale, in addition to making rolling difficult, can also damage the surface quality of the finished product.

[0012] Background technology for cleaning the strip is carried out by a special arrangement of descaling and pickling lines, which usually precede the cold rolling. Usually, a line for unwinding the hot-rolled strip is provided, followed by devices suitable for breaking up the scale so that it can be removed more easily by the following treatments. The cleaning of the product from the scale is carried out by successive steps which introduce the product into an acid bath (pickling). The product is then rinsed.

[0013] Among the problems involved in this type of cleaning, there is of course the considerable consumption and subsequent disposal of the acid. In addition, it is necessary to consider the dangers that chemical pickling poses to the operator from the point of view of the management of corrosive liquids and any accidents.

[0014] Disadvantageously, in the prior art, the amount of scale present on the article prior to pickling was not known a priori.

[0015] Therefore, operators currently make assumptions about initial scale removal based on their experience.

[0016] As mentioned above, acid attack results in a weight loss of the article that has passed through the acid cleaning system.

[0017] However, although it is possible to determine the amount of product loss, it is not possible to optimize the cleaning parameters because this control is performed ex post facto after making an approximate assumption about the amount of initial scale to be removed.

[0018] At present, it is not possible to determine in advance the treatment parameters to remove the exact amount of oxide with the minimum amount of acid required. Disadvantageously, it is very likely that a larger amount of acid is used, thus also removing a portion of the "good" product, i.e. a portion of the base metal of the strip, to ensure a good result of cleaning.

[0019] Conversely, in a worse case scenario, the acid used (or the time spent in the pickling tank) may not be enough, so the article is not optimally cleaned and must be discarded or processed again.

[0020] In summary, there are two types of defects that can occur in pickling tanks: - Insufficiently pickled materials have residual oxide stains on the surface. Usually the most stubborn oxides are not removed by the pickling process, which may lead to product degradation; - Over-pickling of material, in which the acid solution also attacks the base metal of the strip, thus producing a significant reduction in thickness and a strong change in surface roughness. Even this defect can lead to a degradation of the product.

[0021] Therefore, it is necessary to provide an innovative device for cleaning metal strips which can overcome the above-mentioned disadvantages. SUMMARY OF THE INVENTION

[0022] An object of the present invention is to provide an apparatus for cleaning metal strip which allows detecting data which are useful to the operator to optimally adjust the operating parameters of the pickling, making the pickling more precise, cost-effective, ecologically sustainable and safe.

[0023] A further object of the invention is to provide a device which allows detecting and processing data to automatically adjust the operating parameters of the pickling, further improving the pickling conditions with respect to the solutions of the prior art.

[0024] The invention therefore meets at least one of the above objects by a cleaning device for cleaning a metal strip having a surface oxide layer, the cleaning device comprising, according to claim 1: - an unwinding device for unwinding at least one rolled strip coil; - a pickling device for pickling the rolled strip; - a measuring device for measuring the thickness of the surface oxide layer, the measuring device being arranged between the unwinding device and the pickling device; Characterized in that the measuring device comprises at least one laser source cooperating with a fiber optic spectrometer, thereby defining a LIBS system (Laser Induced Breakdown Spectrometer), which is also suitable for analyzing the composition of oxides and the concentration of oxide components.

[0025] Advantageously, the fibre optic spectrometer is adapted to measure the presence of oxygen when laser light from the laser source penetrates the rolled strip towards the non-oxidised substrate.

[0026] Another advantage can be represented by the fact that a software installed in the LIBS system is provided, which is suitable for calculating the thickness of the surface oxide layer, i.e., for calculating the depth of the material layer etched by the laser source at the etching time t at which the spectrometer starts to detect the absence of oxygen, the rate of etching by the laser being known. Preferably, said depth is calculated along a direction perpendicular to the plane defined by the advancing strip.

[0027] A further aspect of the invention relates to a method for cleaning a metal strip which can be performed by the aforementioned apparatus, the method comprising the following steps according to claim 14: - unwinding at least one rolled strip coil by means of an unwinding device; - measuring the thickness of the surface oxide layer of the strip by means of a measuring device; - pickling the rolled strip by a pickling device; wherein, in step b), in addition to measuring the thickness of the surface oxide layer, an analysis of the composition of the oxide and the concentration of the components of the oxide is carried out by means of at least one laser source associated with a fiber spectrometer, defining a LIBS system (Laser Induced Breakdown Spectroscopy); and wherein the fiber optic spectrometer measures the presence of oxygen when laser light from the laser source penetrates the rolled strip toward the unoxidized base metal, and the thickness of the surface oxide layer is equal to the depth dug into the rolled strip by the laser source when the spectrometer would detect the absence of oxygen.

[0028] Therefore, during the precise ablation of the oxide layer by the laser source, the fiber optic spectrometer measures the presence of oxygen. Therefore, during the ablation process, when the spectrometer detects the absence of oxygen after the etching time t, the measured value of the depth of the etched material layer at time t will correspond to the thickness of the surface oxide layer.

[0029] In other words, as the oxygen peak disappears, once the corrosion time t and the corrosion rate are known, the software calculates the corrosion depth, which will be equal to the thickness of the surface oxide layer. In addition, the LIBS system also provides information related to the composition of the oxide (e.g., O / Fe ratio), allowing further optimization of the pickling conditions.

[0030] Advantageously, the solution of the invention allows measuring the thickness of the surface oxide layer and possibly also the O / Fe ratio in only 15s÷20s.

[0031] Advantageously, a precise measurement of the thickness of the oxide layer present on the rolled strip, provided upstream of the pickling device, allows the operator to appropriately adjust the operating parameters of the pickling device. In fact, by precisely detecting the thickness of the oxide layer or scale formed on the article to be cleaned and its characteristics, preferably but not necessarily just before pickling, it is easier to safely estimate the operating parameters of the cleaning device and the amount of cleaning agent.

[0032] In a variant of the invention, the oxide layer thickness measurement data may be processed by a processing unit programmed to automatically adjust the operating parameters of the pickling device.

[0033] In all variants, optical detection means can be provided for detecting data relating to the strip cleaning level, the optical detection means being arranged downstream of the pickling device.

[0034] In a variant with a processing unit, the processing unit can be configured to also process the strip cleaning level data and, possibly, further adjust the operating parameters of the pickling. In fact, by means of feedback received from an optical detection device downstream of the pickling device, it is possible to control the cleaning quality obtained and further optimize the parameters until the desired cleaning target is reached. Unlike what happens in the background art, where the cleaning process is determined by experience and is usually calibrated to perform a cleaning greater than required to ensure adequate results, by knowing the oxide start data, i.e. the known pickling kinetics, the optimal treatment conditions can be set in advance. By analyzing the pickling output results, it is possible to understand whether the operating parameters of the pickling are optimal, sufficient or insufficient.

[0035] By means of the solution of the invention, it is thus possible to optimize the management parameters of the pickling with respect to the actual article to be pickled, thereby reducing the size of the machine, reducing or even eliminating the cleaning systems using acid and saving the base material of the metal article at the end of the cleaning.

[0036] In addition to reducing pollutants and energy costs in the system, risks to operator health are further reduced.

[0037] The dependent claims describe preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further characteristics and advantages of the invention will become more apparent from the detailed description of a preferred but not exclusive embodiment of an apparatus for cleaning a metal strip disclosed by way of non-limiting manner, said embodiment being shown by way of explanation and not by way of limitation, with the help of the accompanying drawings, in which: Figure 1 shows a diagrammatic view of a first embodiment of a device according to the invention; Figure 2shows a diagrammatic view of a second embodiment of the device according to the invention; Figure 3 A diagrammatic view of a third embodiment of the device according to the invention is shown.

[0039] Elements drawn with dashed lines are optional. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0040] Referring to the drawings, some exemplary embodiments of apparatus for cleaning oxidized metal strip are shown.

[0041] The device according to the invention, in all its embodiments, comprises in sequence: - an unwinding device 1 for unwinding at least one rolled strip coil having a surface oxide layer; - measuring devices 4, 4' for measuring the thickness of the surface oxide layer; - A pickling device 5 for pickling the rolled strip.

[0042] In a first variant, the unwinding device 1 comprises a single unwinding line of the rolled strip, preferably a single unwinding reel.

[0043] In a second variant of the unwinding device 1 , the rolled strip is provided with a double unwinding line followed by a cutter and a welder in order to provide continuity to the strip to be pickled.

[0044] In particular, at least two unwinding reels and a welder, preferably a laser welder, can be provided, capable of producing a joint between the strip unwound from the unwinding reels, thereby defining a continuous strip, i.e. allowing continuity of the feed of the metal strip downstream of the unwinding device. Optionally, a tensioning device for adjusting the tension of the strip can be provided.

[0045] Preferably, at least one scale breaking device 3 can be advantageously provided between the unwinding device 1 and the pickling device 5 , which uses, for example, a mechanical system for breaking the oxide layer so that it can be removed more easily by the subsequent pickling device.

[0046] In the first embodiment ( Figure 2 ), a measuring device 4' for measuring the thickness of the oxide layer is arranged between the unwinding device 1 and the scale crushing device 3, so as to detect the thickness of the input scale and thus calibrate the scale crushing device 3 and the subsequent pickling device 5. Preferably, a weight sensor 2 can be advantageously provided to weigh the amount of scale separated from the strip by the action of the scale crushing device 3. Based on the data detected by the measuring device 4' and the weight of the scale detected by the weight sensor 2, the operator can better estimate the pickling operation parameters.

[0047] In the second embodiment ( Figure 1 ), a measuring device 4 for measuring the thickness of the oxide layer is arranged between the scale breaking device 3 and the pickling device 5. In this case, the thickness of the oxide layer input to the pickling device 5 is detected, so that only the pickling device is calibrated on the basis of the data detected by the measuring device 4. The scale breaking device 3 will therefore be set according to the experience of the operator, comparing its operating parameters with the thickness of the hot rolled strip supplied to the cleaning device.

[0048] In the third embodiment ( Figure 3 ), a first measuring device 4' arranged between the unwinding device and the scale crushing device 3, and a second measuring device 4 arranged between the scale crushing device 3 and the pickling device 5 are provided instead. Therefore, by accurately knowing the data input to the scale crushing device 3 and the data input to the pickling device 5, an optimal calibration of the two units can be obtained. Also in this third embodiment, a weight sensor 2 can be provided to weigh the amount of scale separated from the strip by the action of the scale crushing device 3. Based on the data detected by the measuring device 4' and the measuring device 4 and the weight of the scale detected by the weight sensor 2, the operator can better estimate the pickling operation parameters.

[0049] Advantageously, the measuring device 4 , 4 ′ for measuring the thickness of the oxide layer comprises at least one laser source associated with a fiber optic spectrometer, defining a LIBS system (Laser Induced Breakdown Spectroscopy).

[0050] The LIBS system, as a system known per se, is not described in detail here.

[0051] The spectrometer uses a laser source to perform precise ablation of the oxide layer. The laser source provides the energy required to introduce species belonging to the oxide layer (removed by ablation along the thickness of the oxide layer) into the plasma state. By using the spectrometer, deexcitation of the ions constituting the plasma allows identification of the species present and their concentration. The disappearance of the oxygen signal makes it possible to easily deduce the thickness of the oxide layer.

[0052] In fact, spectroscopy measures the presence of various elements, starting from the outer surface of the article, penetrating towards the unoxidized base material. When the presence of oxygen is no longer detected, this means that the bottom of the oxide layer has been reached, and therefore, the depth of excavation corresponds to the measurement of the oxide thickness. Through spectroscopic measurements, it is therefore possible to know the thickness of the oxide layer and the composition of the oxide layer as well as the concentrations of the components of the oxide. Therefore, from these data it becomes possible to define the pickling operating parameters in an optimal way. Another advantage of using the LIBS technique is its minimal invasiveness, the technique being a micro-destructive technique, since the only damage produced is the ablation of the material, producing holes, the size of which depends on the laser focus point.

[0053] In an advantageous variant, two or more measuring devices 4, 4' are provided, which are arranged above and below the rolled strip feed line, in order to calculate the thickness of the oxide layer on the upper and lower sides of the strip, and the difference between the edge and the center of the strip.

[0054] In particular, in each region of the plant in which the above-mentioned measuring devices are provided, at least one measuring device arranged above the rolling strip feed line and at least one measuring device arranged below the rolling strip feed line are provided.

[0055] When two or more measuring devices 4' arranged between the unwinding device and the scale breaking device 3 and / or two or more measuring devices 4 arranged between the scale breaking device 3 and the pickling device 5 are provided, at least four or more laser sources are provided, and the four or more laser sources are respectively associated with the fiber optic spectrometers, defining four or more LIBS systems.

[0056] These LIBS systems can be arranged in a fixed or movable manner relative to the rolling strip feed line.

[0057] Measuring the thickness of the oxide layer can be done in different ways.

[0058] For example, measurements can be taken in a static manner, temporarily interrupting the material flow to the cleaning equipment (such as during strip welding) and restarting it once the data is acquired.

[0059] Alternatively, the measurement may be performed continuously, for example by placing the measuring device on a carriage adapted to move with the metal strip.

[0060] In all the above-described embodiments, an optical detection device 6 for detecting the strip cleaning level may be provided downstream of the pickling device 5 in order to provide the operator with information on the effectiveness of previously set pickling operation parameters.

[0061] Preferably, a cleaning device for cleaning the pickled strip is arranged between the pickling device 5 and the optical inspection device 6 .

[0062] A processing unit 7 may also be provided which is configured to process the measurement data originating from the measuring device 4 and / or 4 ′ and to adjust operating parameters of the pickling device 5 and / or the scale breaking device 3 .

[0063] Advantageously, the processing unit 7 may also be configured to process the strip cleaning level data originating from the optical inspection device 6 and possibly further adjust operating parameters of the pickling device 5 .

[0064] The data originating from the measuring devices 4 , 4 ′, including values ​​for the thickness of the oxide layer, the composition of the oxide layer and the concentration of the oxide components, are stored and processed in the processing unit 7 , which will then determine, in particular, the operating parameters of the pickling device 5 and / or the scale breaking device 3 , and then receive feedback on the pickling results via the optical detection device 6 .

[0065] For example, such optical inspection means 6 comprise at least one system for video analysis of the strip downstream of pickling, which will allow, for example, the colour or brightness of the strip to be compared with chromatic scales indicating different degrees of cleaning of the article, which scales are preloaded in the memory of the processing unit 7. For example, using a high pixel density digital camera, it is possible to define the relationship between defective areas and pickled areas per square metre of strip, the minimum and maximum size of defective areas and the location of defective areas on the strip (upper surface / lower surface, centre / edge, head / tail or coil body, i.e. the portion of the strip between the head and the tail).

[0066] As regards the pickling devices, they may comprise at least one chemical pickling tank; or a dry pickling system; or a dry pickling system followed by at least one chemical pickling tank; or a first dry pickling system followed by a second dry pickling system.

[0067] In the case of pickling only by means of one or more pickling tanks, the flow rate of the prescribed corrosive liquid (usually acid) is preferably adjusted by the operator on the basis of data provided by the measuring device 4 or preferably directly by the processing unit 7 .

[0068] In a preferred process variant, the previously hot rolled and oxidized strip, coming from the unwinding unit or unwinding reel and possibly treated by the scale breaking device 3, is subjected to a measurement of the scale thickness upstream of the pickling tank, preferably by LIBS. The operator or the processing unit 7 receives data related to the thickness detected on both sides and edges of the strip and sets the process conditions related to complete pickling of the oxide layer that is more difficult to remove. This ensures a correct cleaning of the strip.

[0069] Furthermore, the operator and / or the processing unit can also know the thickness of the strip loaded on the unwinding unit, which corresponds to the coiled thickness of the strip at the end of the hot rolling line. In fact, by knowing the amount of oxide to be removed, it is possible to pre-set the mass balance of the chemical reaction to be carried out so as to completely eliminate the oxide layer. Therefore, the data detected by the measuring device 4, 4' and the thickness of the strip when coiled after hot rolling are important not only for allowing the operator or the processing unit to establish the amount of pickling acid suitable for this strip thickness and the relative thickness and type of oxide / scale, but also possibly for the travel speed of the strip in the pickling tank. In fact, for extremely oxidized products, it is better to provide a lower travel speed (allowing a longer contact time between the acid and the product); vice versa, for slightly oxidized products, it is better to provide a higher travel speed.

[0070] As the acid attacks the oxides, causing the scale to separate from the article, the acid, once exhausted, combines with the oxides in the form of salts and is collected by a collecting device at the bottom of the pickling tank.

[0071] By means of a system for measuring the concentrations of iron, Fe, and acid placed at the inlet line of the new or regenerated liquid pickling solution and at the outlet line of the discharged solution, it is possible to calculate the amount of scale removed by performing precise process control.

[0072] The strip thus continues to be rinsed and leaves the pickling zone.

[0073] Once out, the strip is inspected by an optical inspection device 6 which verifies the actual result of the previous pickling. In case of detection of insufficient cleaning, the operator or the processing unit 7 can increase the amount of cleaning liquid (usually acid) or reduce the strip travel speed; vice versa, if excessive cleaning, the travel speed can be increased or the amount of cleaning liquid can be reduced.

[0074] In the case where pickling is carried out only by dry pickling equipment, one or more laser cleaning devices are provided, which are suitable for emitting concentrated laser pulse beams, such as the laser pulse beams disclosed in US5736709, which are preferably adjusted by the operator based on the data provided by the measuring device 4, or preferably directly by the processing unit 7.

[0075] The use of this technology as a pickling system allows the use of acids to be eliminated, which allows, on the one hand, a considerable simplification of the equipment and, on the other hand, a management that is easier and more respectful of the environment.

[0076] In a preferred treatment variant, the previously hot rolled and oxidized strip, coming from the unwinding unit or unwinding reel and possibly treated by the scale breaking device 3, is subjected to a measurement of the scale thickness upstream of the dry pickling apparatus, preferably by LIBS. An operator or processing unit 7 receives data relating to the thickness detected on both sides and edges of the strip and sets the operating parameters of the dry pickling apparatus, such as, for example, the energy of the laser pulses on different zones of the strip, to ensure correct cleaning of the strip.

[0077] For very precise cleaning, in the case of a plurality of laser cleaning devices, further measuring devices, preferably laser sources associated with respective fiber optic spectrometers, may be provided, each further measuring device being interposed between a laser cleaning device and the next cleaning device. Thus, the strip is descaled by a single laser cleaning device operating with parameters set by a processing unit or an operator based on measurement data of the oxide layer detected directly upstream of the single cleaning device.

[0078] Once the dry pickling operation is completed, the strip is inspected by an optical inspection device 6 which verifies the quality of the cleaning.

[0079] The high-power laser pulse directed at the oxide layer is held for a moment, causing the surface to deform rapidly due to the high temperature, resulting in the separation of the oxide scale that has been weakened in the previous step. In addition, given the different crystal microstructures of the two components, the oxide of the surface-most layer will tend to sublime, while the inner oxide layer will experience instantaneous heating and deform in a different way relative to the metal below. This thermal shock is similar to a sound wave passing through the material, which causes the oxide scale to separate from the strip substrate.

[0080] Suction devices may be provided, possibly assisted by brushing devices, to collect the removed oxide so that it can be weighed and compared with initial data relating to the height of the oxide layer thickness and with the expected removal.

[0081] Furthermore, such dry pickling equipment has the advantage that by collecting pure oxides instead of contamination from other materials, this allows their recovery in other applications, for example, to a furnace or to be sold on the market as scrap supplement.

[0082] An advantage of using an oxide layer thickness measuring device in combination with a laser dry pickling apparatus is that the laser energy can be adjusted on different parts of the strip, for example on the edges, so as to work with higher efficiency in areas where greater oxidation is detected without reducing the travel speed of the strip.

[0083] In the case of mixed pickling, a dry pickling apparatus is provided, followed by at least one chemical pickling tank, one or more laser cleaning devices are provided, followed by at least one chemical pickling tank, the one or more laser cleaning devices being suitable for emitting a concentrated laser pulse beam, such as, for example, those disclosed in US5736709.

[0084] The operator and / or processing unit 7 receives data related to the oxide thickness detected on the sides and edges of the strip and sets operating parameters of the dry pickling apparatus, such as, for example, the energy of the laser pulses on different areas of the strip, and operating parameters of the chemical pickling, such as the amount of cleaning liquid (usually acid) and / or the strip travel speed.

[0085] Advantageously, laser dry pickling removes most of the oxide layer and completes the operation by a slight corrosive attack with acid, acting on the roughness of the article to obtain an optimal surface, which will be particularly suitable for electroplating and / or painting processes.

[0086] In fact, while most of the oxide layer is eliminated by laser treatment, any surface peaks remain intact; through the corrosive action of the acid pickling, the surface is made uniform and its morphology is regulated.

[0087] Since the amount of corrosive liquid is limited in this case, its management is simpler and easier to handle, and also more ecologically sustainable.

[0088] Finally, in the case of mixed pickling, one or more laser cleaning devices are provided by a first dry pickling apparatus, followed by a second dry pickling apparatus, followed by at least one mechanical pickling apparatus, the one or more laser cleaning devices being suitable for emitting a concentrated laser pulse beam, such as the laser pulse beam disclosed in US5736709, the mechanical pickling apparatus preferably being provided with rotating abrasive brushes located at the upper and lower surfaces of the strip.

[0089] The operator or processing unit 7 receives data related to the oxide thickness detected on both sides and edges of the strip and sets operating parameters of the first dry pickling device, such as, for example, the energy of the laser pulses on different areas of the strip, and operating parameters of the second dry pickling device, such as, for example, the contact pressure of the brushes, the relative speed of the brushes with respect to the strip, the torque of the brush motor.

[0090] Advantageously, laser dry pickling is used to remove most of the oxide layer and to complete the operation by gently removing the surface material layer with a rotating brush, which can change the surface appearance of the product and control its surface roughness.

[0091] The method for cleaning a metal strip of the present invention can be implemented by the aforementioned device, and the method comprises the following steps: a) unwinding at least one rolled strip coil by means of an unwinding device 1; b) measuring the thickness of the surface oxide layer of the rolled strip by means of measuring devices 4, 4'; c) pickling the rolled strip by a pickling device 5; Therein, in step b), the measurement of the thickness of the surface oxide layer is performed, while analyzing the composition of the oxide and the concentration of the components of the oxide, by means of at least one laser source, the at least one laser source being associated with a fiber spectrometer, thereby defining a LIBS system (Laser Induced Breakdown Spectroscopy).

[0092] In an embodiment of the device there are provided: - at least one scale breaking device 3, which is between the unwinding device 1 and the pickling device 5; a first measuring device 4 ′, which is arranged between the unwinding device 1 and the at least one scale breaking device 3; - a second measuring device 4, which is arranged between the at least one scale breaking device 3 and the pickling device 5; - an optical detection device 6, which is arranged downstream of the pickling device 5 and is used to detect the cleaning level of the strip; - and a processing unit 7 for processing the measurement data originating from said first measuring device 4 ′ and said second measuring device 4 , and the strip cleaning level data originating from said optical detection device 6 ; After step a), the method provides: - measuring the thickness of the surface oxide layer of the rolled strip by means of a first measuring device 4 ′; - processing the measurement data originating from said first measuring device 4 ′ by means of a processing unit 7 and adjusting the operating parameters of said at least one scale breaking device 3; - Descaling the rolled strip by means of the at least one scale breaking device 3; - measuring the thickness of the surface oxide layer of the rolled strip by means of a second measuring device 4; - Processing the measurement data from the second measuring device 4 by means of a processing unit 7 and adjusting the operating parameters of the pickling device 5; - pickling the rolled strip by means of a pickling device 5; - Detecting the cleaning level of the rolled strip by means of an optical detection device 6; - Processing the strip cleaning level data originating from said optical detection device 6 by means of a processing unit 7 and possibly further adjusting said operating parameters.

[0093] This application also relates to the following contents.

[0094] 1) A cleaning device for cleaning a rolled metal strip having a surface oxide layer, the device comprising: an unwinding device for unwinding at least one rolled strip coil; A pickling device for pickling the rolled strip; a measuring device for measuring the thickness of the surface oxide layer, the measuring device being arranged between the unwinding device and the pickling device; Therein, the measuring device consists of at least one laser source, which cooperates with a fiber spectrometer, thereby defining a LIBS system (Laser Induced Breakdown Spectroscopy), which is also suitable for analyzing the composition of oxides and the concentration of oxide components.

[0095] 2) The cleaning equipment according to 1), wherein at least one oxide scale breaking device is arranged between the unwinding device and the pickling device.

[0096] 3) The cleaning device according to 2), wherein the measuring device is arranged between the at least one oxide scale breaking device and the pickling device, or between the unwinding device and the at least one oxide scale breaking device.

[0097] 4) The cleaning device according to 2), wherein a first measuring device and a second measuring device are provided, wherein the first measuring device is arranged between the unwinding device and the at least one oxide scale crushing device, and the second measuring device is arranged between the at least one oxide scale crushing device and the pickling device.

[0098] 5) Cleaning equipment according to any one of 2) to 4), wherein a weight sensor is provided to weigh the amount of oxide scale separated from the strip by the at least one oxide scale crushing device, and preferably a suction device is provided, which may be assisted by a sweeping device to collect the separated oxide so that the separated oxide can be weighed.

[0099] 6) Cleaning device according to any of the preceding claims, wherein in each area of ​​the device where the measuring devices are provided, at least one measuring device is arranged above the rolled strip feed line and at least one further measuring device is arranged below the rolled strip feed line.

[0100] 7) A cleaning device according to any of the preceding claims, wherein a processing unit is provided for processing the measurement data originating from the measuring device and for adjusting the operating parameters of the pickling device.

[0101] 8) The cleaning apparatus according to any of the preceding claims, wherein an optical detection device is provided, which is arranged downstream of the pickling device for detecting the strip cleaning level.

[0102] 9) Cleaning apparatus according to 8), wherein the processing unit is configured to process the strip cleaning level data originating from the optical detection device and possibly further adjust the operating parameters.

[0103] 10) A cleaning apparatus according to any of the preceding claims, wherein the pickling device comprises at least one chemical pickling tank; or a dry pickling system; or a dry pickling system followed by at least one chemical pickling tank; or a first dry pickling system followed by a second dry pickling system.

[0104] 11) The cleaning device according to 10), wherein the dry pickling system is a laser pickling device and / or a mechanical pickling device, preferably a rotating abrasive brush.

[0105] 12) Cleaning apparatus according to any of the preceding claims, wherein the fiber optic spectrometer is adapted to measure the presence of oxygen when laser light from the laser source penetrates the rolled strip towards a non-oxidized substrate.

[0106] 13) A cleaning device according to 12), wherein software installed in the LIBS system is provided, the software being suitable for calculating the thickness of the surface oxide layer, the thickness of the surface oxide layer being defined by the depth of the material layer etched by the laser source when the fiber optic spectrometer starts to detect the corrosion time t when there is no oxygen, and the etching rate by the laser is known.

[0107] 14) A method for cleaning a metal strip, the method being executable by a device according to any one of the preceding claims, the method comprising the following steps: a) unwinding at least one rolled strip coil by means of the unwinding device; b) measuring the thickness of the surface oxide layer of the rolled strip by the measuring device; c) pickling the rolled strip by the pickling device; wherein in step b), the measurement of the thickness of the surface oxide layer and the analysis of the composition of the oxide and the concentration of the components of the oxide are performed simultaneously by at least one laser source associated with a fiber spectrometer, defining a LIBS system (Laser Induced Breakdown Spectroscopy); And wherein the fiber optic spectrometer measures the presence of oxygen when laser light from the laser source penetrates the rolled strip toward an unoxidized substrate, and the thickness of the surface oxide layer is equal to the depth dug into the rolled strip by the laser source when the spectrometer would detect the absence of oxygen.

[0108] 15) The method according to 14), wherein when the following items are provided, - at least one scale breaking device between said unwinding device and said pickling device; - a first measuring device, which is arranged between the unwinding device and the at least one scale breaking device; - a second measuring device, which is arranged between the at least one scale breaking device and the pickling device; - an optical detection device, arranged downstream of the pickling device, for detecting the strip cleaning level; - and a processing unit for processing the measurement data originating from the first measuring device and the second measuring device, and the strip cleaning level data originating from the optical detection device; After step a), the method provides: - measuring the thickness of the surface oxide layer of the rolled strip by means of the first measuring device; - processing the measurement data originating from the first measuring device by means of the processing unit and adjusting the operating parameters of the at least one scale breaking device; - descaling the rolled strip by means of the at least one scale breaking device; - measuring the thickness of the surface oxide layer of the rolled strip by means of the second measuring device; - processing the measurement data originating from the second measuring device by means of the processing unit and adjusting the operating parameters of the pickling device; - pickling the rolled strip by means of the pickling device; - detecting the cleaning level of the rolled strip by means of the optical detection device; - processing the strip cleaning level data originating from the optical detection device by the processing unit and possibly further adjusting the operating parameters.

[0109] 16) The method according to 14) or 15), wherein the thickness of the surface oxide layer is measured within 15s÷20s.

Claims

1. A cleaning device for cleaning a rolled metal strip having a surface oxide layer, the device comprising: An unwinding device (1) for unwinding at least one rolled strip coil; A pickling device (5) for pickling the rolled strip; A measuring device (4, 4') for measuring the thickness of a surface oxide layer, wherein the measuring device (4, 4') is arranged between the unwinding device (1) and the pickling device (5); wherein the measuring device (4, 4') consists of at least one laser source, which cooperates with a fiber optic spectrometer, thereby defining a LIBS system (Laser Induced Breakdown Spectrometer), which is also suitable for analyzing the composition of oxides and the concentration of oxide components; and The device also includes a system for measuring the concentration of iron and acid placed at the inlet line of the new or regenerated liquid pickling solution and at the outlet line of the discharged solution in order to calculate the amount of scale removed.

2. The cleaning device according to claim 1, wherein at least one scale breaking device (3) is arranged between the unwinding device (1) and the pickling device (5).

3. The cleaning device according to claim 2, wherein the measuring device (4', 4) is arranged between the at least one scale breaking device (3) and the pickling device (5), or between the unwinding device (1) and the at least one scale breaking device (3).

4. The cleaning device according to claim 2, wherein a first measuring device (4') and a second measuring device (4) are provided, wherein the first measuring device (4') is arranged between the unwinding device (1) and the at least one oxide scale breaking device (3), and the second measuring device (4) is arranged between the at least one oxide scale breaking device (3) and the pickling device (5).

5. Cleaning device according to any one of claims 2 to 4, wherein a weight sensor (2) is provided to weigh the amount of scale separated from the strip by the at least one scale breaking device (3), and preferably a suction device is provided, which may be assisted by a sweeping device to collect the separated oxide in order to weigh the separated oxide.

6. A cleaning device according to any one of the preceding claims, wherein In each area of ​​the plant in which the measuring devices (4', 4) are provided, at least one measuring device (4', 4) is arranged above the rolling strip feed line and at least one further measuring device (4', 4) is arranged below the rolling strip feed line.

7. Cleaning device according to any of the preceding claims, wherein a processing unit (7) is provided for processing the measurement data originating from the measuring device (4) and for adjusting the operating parameters of the pickling device (5).

8. Cleaning apparatus according to any of the preceding claims, wherein an optical detection device (6) is provided, which is arranged downstream of the pickling device (5) for detecting the strip cleaning level.

9. Cleaning apparatus according to claim 8, wherein the processing unit (7) is configured to process the strip cleaning level data originating from the optical detection device (6) and possibly further adjust the operating parameters.

10. Cleaning equipment according to any of the preceding claims, wherein the pickling device (5) comprises at least one chemical pickling tank; or a dry pickling system; or a dry pickling system followed by at least one chemical pickling tank; or a first dry pickling system followed by a second dry pickling system.

11. Cleaning equipment according to claim 10, wherein the dry pickling system is a laser pickling device and / or a mechanical pickling device, preferably a rotating abrasive brush.

12. Cleaning apparatus according to any one of the preceding claims, wherein the fiber optic spectrometer is adapted to measure the presence of oxygen when laser light from the laser source penetrates the rolled strip towards an unoxidized substrate.

13. A cleaning device according to claim 12, wherein software installed in the LIBS system is provided, the software being suitable for calculating the thickness of the surface oxide layer, the thickness of the surface oxide layer being defined by the depth of the material layer etched by the laser source when the fiber optic spectrometer starts to detect the corrosion time t when there is no oxygen, the corrosion rate by the laser being known.

14. A method for cleaning a metal strip, the method being executable by means of an apparatus according to any one of the preceding claims, the method comprising the steps of: a) unwinding at least one rolled strip coil by means of the unwinding device (1); b) measuring the thickness of the surface oxide layer of the rolled strip by means of the measuring device (4, 4'); c) pickling the rolled strip by the pickling device (5); wherein in step b), the measurement of the thickness of the surface oxide layer and the analysis of the composition of the oxide and the concentration of the components of the oxide are performed simultaneously by at least one laser source associated with a fiber spectrometer, defining a LIBS system (Laser Induced Breakdown Spectroscopy); And wherein the fiber optic spectrometer measures the presence of oxygen when laser light from the laser source penetrates the rolled strip toward an unoxidized substrate, and the thickness of the surface oxide layer is equal to the depth dug into the rolled strip by the laser source when the spectrometer would detect the absence of oxygen.

15. The method according to claim 14, wherein: When the following items are provided, at least one oxide scale breaking device (3) between the unwinding device (1) and the pickling device (5); a first measuring device (4') arranged between the unwinding device (1) and the at least one scale breaking device (3); a second measuring device (4) arranged between the at least one scale breaking device (3) and the pickling device (5); an optical detection device (6), which is arranged downstream of the pickling device (5) and is used to detect the strip cleaning level; and a processing unit (7) for processing the measurement data originating from the first measuring device (4') and the second measuring device (4), and the strip cleaning level data originating from the optical detection device (6); After step a), the method provides: Measuring the thickness of the surface oxide layer of the rolled strip by means of the first measuring device (4'); Processing the measurement data from the first measuring device (4') by means of the processing unit (7) and adjusting the operating parameters of the at least one scale breaking device (3); Descaling the rolled strip by means of the at least one scale crushing device (3); Measuring the thickness of the surface oxide layer of the rolled strip by the second measuring device (4); Processing the measurement data from the second measuring device (4) by the processing unit (7) and adjusting the operating parameters of the pickling device (5); Pickling the rolled strip by means of the pickling device (5); Detecting the cleaning level of the rolled strip by means of the optical detection device (6); The strip cleaning level data originating from the optical detection device (6) are processed by the processing unit (7) and the operating parameters may be further adjusted.

16. The method according to claim 14 or 15, wherein the thickness of the surface oxide layer is measured within 15s÷20s.

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