Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/55—Specular reflectivity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
  • G01N21/474—Details of optical heads therefor, e.g. using optical fibres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
  • G01N21/8901—Optical details; Scanning details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/20—Metals
  • G01N33/208—Coatings, e.g. platings
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N2021/4704—Angular selective
  • G01N2021/4709—Backscatter
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N2021/4735—Solid samples, e.g. paper, glass
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
  • G01N21/474—Details of optical heads therefor, e.g. using optical fibres
  • G01N2021/4742—Details of optical heads therefor, e.g. using optical fibres comprising optical fibres
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/06—Illumination; Optics
  • G01N2201/061—Sources
  • G01N2201/06113—Coherent sources; lasers
  • G01N2201/0612—Laser diodes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/08—Optical fibres; light guides

Definitions

• the present invention relates to the determination of the characteristics of a surface coating of metallurgical products, in particular online, during the movement of said product during manufacture. It is more particularly the determination of galvanized coating characteristics on steel bands, especially the type known commercially as the GALVALLIA ® sheets.
• these sheets are galvanized strips which undergo a so-called alloying heat treatment, aimed at providing these strips with improved surface characteristics, for example allowing better adhesion of the paints or offering better stampability.
• This alloying treatment is a heat treatment carried out on the galvanized strip in an alloying tower where the galvanized strip passes continuously. The heat treatment aims to ensure diffusion of the iron from the sublayer to the surface, to achieve the objectives mentioned above.
• the alloying rate is around 10% in proportion of iron compared to zinc.
• the desired level of alliance that is to say the relative importance of this diffusion, varies considerably from one user of said bands to another, and it is therefore important to be able to ensure during manufacture a continuous monitoring of the level of alloying.
• the adjustment parameters of the installation which performs the alloy heat treatment namely essentially the temperature and the duration of the treatment.
• n ' be sensitive only to physico-chemical variations of the surface.
• physico-chemical variations of the extreme surface are in fact an image of the migration of the iron atoms from the coating to the extreme surface, which corresponds to the level of alloying of the product.
• defects may appear on the strips, such as for example dusting or peeling of the coating, due to an excessive level of alloying.
• the present invention aims in particular to solve these problems and to provide online control of the level of surface alloying in order to be able to guarantee a homogeneous and reproducible product, and to ensure the piloting of the alloying tower. It aims in particular to limit the defects occurring on these strips, such as dusting or peeling of the coating, and to ensure a homogeneous and reproducible product, in particular by avoiding or at least reducing the zones transient under or over-alliation, i.e. areas where the level of alloy is uncertain due to voluntary changes in process parameters, and whose control cannot be performed quickly enough. More generally, the invention aims to allow online determination of surface characteristics of a strip coating, which may vary depending on the physico-chemical characteristics of said coating.
• the invention firstly relates to a method for measuring the characteristics of a surface coating of metallurgical products, in particular on-line during the movement of said product during manufacture, characterized in that, in order to expose an area of the surface of said product to incident radiation directed orthogonally to said surface and then to measure, also in a direction orthogonal to the surface, the energy of the radiation reflected by the exposed area, said light is illuminated exposure area by means of an optical fiber of 1 illumination connected to a source of emission of the incident radiation under a predetermined wavelength, and the reflected radiation is measured by means of a measuring optical fiber connected to a sensor, the free ends of the two optical fibers being stripped and kept in close proximity to one another and parallel to each other.
• the invention therefore exploits the fact that changes in surface properties due to changes in the physico-chemical characteristics of the coating result in variations in the reflection properties of said surface. Furthermore, the configuration, according to which both the illumination and the observation of the reflected radiation are carried out orthogonally to the surface, makes it possible to remain sensitive only to the physicochemical variations of the surface by freeing itself from morphological variations. In fact, the results expected from the measurement by the implementation of the invention will only be achieved if this orthogonality is respected and if the two optical fibers concerned, forward fiber and return fiber of the radiation, are very close to one of the other in their terminal portion facing the surface of the product. This is carried out in accordance with the invention from commercial optical fibers, the free end of which is stripped beforehand, that is to say that they are freed from their usual bulky otic focusing accessories in order to keep only the fiber. itself in a stripped state.
• the free ends of the two optical fibers can therefore be kept in the immediate vicinity of the surface, typically for example at a distance of approximately 10 to 50 mm from the latter, and parallel to one another.
• This arrangement makes it possible to avoid the use of any other optical focusing system, while allowing, thanks to the small section of the optical fibers used (of the order of 0.1 mm generally), and thanks to the authorized close approximation of the fibers between they (maximum center distance also of the order of 0.1 mm), the measurement almost exactly in the illuminated area, and with an orientation normal to the surface both for the illumination and for the measurement, as will be seen better later.
• the information drawn in real time from this measurement can then be used as a control parameter to control the alliation tower, and also be used in quality control to guarantee customers the alloying properties of an entire reel delivered.
• the radiation used is in the near infrared range, more particularly in the vicinity of 830 nm of wavelength.
• This field of radiation has indeed been revealed, following the tests carried out by the inventors, an optimum for the sensitivity of the measurement, taking also into account the sources of radiation currently available, such as for example a laser diode working at this wave length.
• the reflected radiation is also measured in one or more directions oblique to the surface, for example from 0 to 30 ° relative to the normal to the surface, which makes it possible to evaluate the energy scattered. by said surface and to draw additional information therefrom on the level of alloying or on other characteristics of the surface, such as for example micro-geometric characteristics, which can also be possibly correlated with the measurement of direct reflection. to give additional information on the general characteristics of the coating.
• the measurement of the radiation reflected in one or more directions not orthogonal to the surface allows in itself to obtain an assessment of the level of alloying because, independently of morphological characteristics such as micro roughness or the like, it has been found a link between the scattering according to certain angles of reflection and the level of alloy, the higher the level of alloy, the more the reflected radiation is diffuse.
• the comparison between the intensity of the radiation reflected in a direction inclined relative to the surface, and that of the reflected radiation perpendicular to this surface alone makes it possible to assess the importance of the alliance, as we will see later.
• the invention also relates to a device for implementing the method defined above, characterized in that it comprises a measuring head having a front surface intended to be placed facing the surface of the product to be inspected, and comprising an optical fiber for illumination and an optical fiber for measurement, these two optical fibers each having, at the front face of the head, a stripped free end so that the corresponding terminal portions of said fibers are arranged parallel and brought together one on the other as much as possible, the other end of the optical fiber for illumination being moreover connected to a source of light radiation and the other end of the optical fiber for measurement being connected to a sensor, the device comprising in in addition to means for processing the signal supplied by said sensor to determine the intensity of the radiation transmitted to it by the measuring optical fiber (3).
• the device comprises a distance sensor for permanently monitoring or measuring the distance between the ends of the optical fibers and the surface of the product
• the measuring head comprises at least one additional optical fiber connected to a specific sensor, and the end portion of which is oriented obliquely relative to the end portion of the optical fiber for illumination.
• the orientation of the different fibers will also be determined so that their directions are concurrent on the same surface area illuminated by the illuminating fiber.
• the radiation source is a laser diode, whose emission wavelength ⁇ is approximately 830 nm.
• FIG. 2 is a schematic view of the device
• FIG. 3 is a sectional view of the measuring head - Figure 4 is a graph illustrating the results of a series of measurements on GALVALLIA ® sheet coils having different levels of alloying.
• a strip of moving steel has been shown, a zone 11 of its surface 1 of which is lit by infrared radiation 23 coming from the end 21 of an optical fiber for lighting 2, held perpendicular to the surface of the strip.
• a second optical fiber 3 parallel to the illumination fiber 2 and in direct proximity thereof, has its end 31 located at the same level as that of the first fiber, and captures the reflected radiation 33, supplied by the optical fiber of illumination and reflected by the strip.
• the surface area 12 seen by the optical fiber of measure 3 is not exactly the illuminated zone 11, but, thanks to the fact that this distance is very small and due to the natural formation of a diffusion cone 23 coming from the end of the fibers, there is an overlap 13 relatively large areas respectively illuminated and observed, allowing to assimilate the radiation captured by the measuring fiber 3 to all of the radiation from the illumination fiber 2 and reflected perpendicular to the surface 1.
• FIG. 2 illustrates an exemplary embodiment of the device, in the form of a box 5 containing on the one hand a measuring head 51 and two non-contact distance sensors 52, of a type known per se, arranged on the same wall 53 of the box, which will be placed in use at a distance of the order of a few tens of millimeters from the surface of the controlled strip.
• the measuring head 51 shown in section in FIG. 3, comprises a body 54 of cylindrical shape which essentially comprises a front wall 55 in which are pierced several orifices 61 to 64, intended to receive the ends of the various optical fibers of the system.
• the first of these orifices 61 is perpendicular to the external surface of the front wall 55, and of a shape suitable for simultaneously receiving the optical light fiber 2 and the measurement fiber 3.
• the other three orifices 62, 63, 64 are oriented according to increasing angles with respect to the direction of the first orifice, namely for example 10, 20 and 30 °, and their directions are concurrent, and they each receive the end of a complementary optical fiber, respectively 41,42,43 .
• all of the fibers 2, 3, 41, 42, 43 are grouped together in the same beam 56 which leaves the housing 5.
• the optical light for illumination 2 is connected to a source of infrared radiation, such as that a laser diode 24, and the other fibers 3, 41, 42, 43 are respectively connected to sensors 34, 44, of type known per se, for measuring the intensity of the reflected radiation, the signals from the sensors being processed by a processing unit 57.
• the graph in FIG. 4 illustrates the results of measurements carried out using the device which has just been described on a moving strip.
• the measurements were carried out during the running of 10 reels of bands, marked bl to bl0, having different rates of alliance.
• the first two coils b1 and b2 have an alloying rate of approximately 10%, and a dusting, measured under standardized test conditions, of 3 to 4 grams / m 2 (mass of powder separated from the strip in the test conditions)
• the coils b3 to b6 have an alloying rate of 12% and a dusting of 5 to 6 g / m 2 .
• the coils b7 to b9 have an alloying rate of 11% and a dusting of 4 g / m 2.
• the coil blO has a alloying rate of 13% and a dusting of 7 g / m 2 .
• the two plots which are represented therein respectively correspond to the measurements of the intensity reflected as a function of time, that is to say as a function of the length of strip of sheet metal traveling in the alloying furnace.
• the line Tl located at the top of the graph represents the intensity of the radiation picked up by the measuring optical fiber 3
• the line T2 located the most down represents the intensity of the radiation picked up by the optical fiber 43 which passes in orifice 64 inclined at 30 °.
• the invention is not limited neither in the production of the device OR of the measuring head, nor in the implementation of the method, in the example described above.
• the infrared laser diode may be replaced by other sources of radiation, of adequate wavelength as a function of the surface to be checked.
• We can also similarly control products other than GALVALLIA ® , and also analyze the signals from the various sensors connected to the optical fibers having different inclinations, to draw other information, in particular on morphological characteristics of the surface. .

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• Food Science & Technology (AREA)
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• Spectroscopy & Molecular Physics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 2002
  • 2002-08-01 FR FR0209845A patent/FR2843197B1/fr not_active Expired - Fee Related
• 2003
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  • 2003-07-29 JP JP2004525482A patent/JP2005534915A/ja active Pending
  • 2003-07-29 WO PCT/FR2003/002388 patent/WO2004013619A2/fr active Application Filing
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