EMAT system for detecting surface and internal discontinuities in conductive structures at high temperatures

Description

Domaine technique

[0001] This invention relates generally to ultrasonic non-destructive testing (UNDT) technology. It specifically relates to an electromagnetic acoustic transducer (EMAT) for UNDT applications, its implementations and its industrial applications.

[0002] The technical field of the invention specifically concerns EMAT transducers: a. Which are non-vibrating type transducers, which do not vibrate mechanically, but induce and / or receive ultrasonic mechanical vibrations by electromagnetic means; b. For investigating or analyzing materials by means of transmitting means and / or receiving means adapted to induce ultrasonic waves in a conductive test body or to receive ultrasonic waves from this body for testing purposes, this by electromagnetic means; and, for viewing the interior of objects by transmitting and / or receiving such an emitted ultrasonic wave through the object; and, c. As such, which belong to the international patent class Int. CI. G01N 29 / 24 and / or to the United States patent class US CI. 73 / 643.

[0003] The technical field of the invention is limited to EMAT transducers which are furthermore: a. Equipped with significant electromagnetic coupling means, located between the active electromagnetic parts of the transducer and the test body, for increasing the coupling of a high-frequency magnetic field between the active electromagnetic parts of the transducer and the surface of the conductive test body traversed by eddy currents; and, b. Of the specific type whose electromagnetic coupling means consist of a laminated magnetic core, made of a matrix of laminated thin sheets internally incorporating either a ferromagnetic or ferrimagnetic material; and, c. Of the specific type whose electromagnetic coupling means are equipped with active cooling means, for dissipating the thermal energy generated by induced current loops on the periphery of the laminated thin sheets of their electromagnetic coupling means.

[0004] The invention is preferably implemented in Laser-EMAT type equipment and / or EMAT-EMAT equipment, which combines both: an ultrasound generator consisting of a high-power pulsed laser or an EMAT generating ultrasound, and an ultrasound EMAT receiver.

[0005] The preferred use of the invention is the objective 3D physical scanning and the ultrasonic non-destructive testing UNDT, at high throughput of the surface and internal discontinuities, in a production line of large structures, and / or thick structures, and / or components manufactured from a conductive material, such as steel slabs during their casting, in an industrial environment at high temperature above 1000°C.

[0006] The invention can be used to automatically optimize the adjustment of the parameters of dynamic reduction (DNS) and / or dynamic secondary cooling (DSC) of a continuous casting of steel slabs in a steel mill, at a temperature above 1000°C. Technique antérieure

[0007] EMAT technologies are used for non-destructive testing of structures made of conductive material, under harsh conditions. Non-destructive testing (NDT) technologies are commonly used in industrial environments, for structural monitoring or inspection of structures and components of various shapes and sizes without damaging them. However, operating conditions and temperature, type of implementation, size and structural complexity of the components tested for inspection, limit the number and types of available NDT techniques that can be used effectively and their applications.The raw data provided by prior art NDT systems are not suitable for sophisticated and deep detection of defects and their 3D location, in large components processed under severe and / or extremely hot operating conditions above 1000°C, such as those encountered during continuous casting of steel slabs in steel mills.

[0008] Ultrasonic Non-Destructive Testing (UNDT) is a family of NDT based on the propagation of ultrasonic waves in the object or material under test. In conventional UNDT testing, an ultrasonic probe connected to a diagnostic machine is passed over the object under inspection. Conventional UNDT methods use beams of short-wavelength, high-frequency mechanical waves, transmitted from an ultrasonic generating probe through the material under test, and detected by the same probe or another ultrasonic receiving probe, to identify structural defects in the component. The main probes for performing UNDT tests are piezoelectric transducers, laser transducers, and electromagnetic acoustic transducers (EMATs). Conventional piezoelectric UNDT tests offer many advantages: safety, flexibility, and cost.However, piezoelectric tests have some limitations, namely: the need to use a couplant; and the need for a good surface finish. They require mechanical contact between the test pieces and the probes. When testing hot parts, the difficulty of finding a suitable couplant for piezoelectric UNDT tests increases with temperature. In general, piezoelectric UNDT tests cannot be operated above 100°C.

[0009] The main aspect of the prior art of the invention concerns electromagnetic acoustic transducers (EMATs). Among the UNDT technologies, the EMAT method is based on a magnetic coupling mechanism. Sound waves are generated within the material, not by contact with the material surface of the test pieces. EMATs offer strong advantages over conventional piezoelectric transducers. An EMAT can generate and receive different wave modes in conductive and ferromagnetic materials, without physical contact or liquid coupling with the test pieces. Such contactless and coupling-free features increase the reliability of the test. Because the physical properties of the transmission path do not change. In addition, the required tolerance specifications for the position and propulsion of the test pieces in front of the EMAT probes are flexible.This makes conventional EMATs well suited for industrial applications involving medium inspection temperature (up to 600°C), and poor surface conditions of moving test parts.

[0010] There are two main components in an EMAT. One is a magnet, and the other is an HF electric coil. The magnet can be a permanent magnet or an electromagnet, which produces a static or quasi-static magnetic field. The electric coil (or electrical circuit) carries an HF current. It emits or is induced by a high-frequency magnetic field. The EMAT phenomenon is reversible. Therefore, the same EMAT probe can be used either as an ultrasonic transmitter in an inspected material, or as an ultrasonic receiver of an ultrasonic signal emitted by an inspected material, or in a combination of both operating modes. The prior art uses EMATs in a wide range of applications, including thickness measurement of metal products, pipeline flaw detection, rail flaw detection, flaw detection in steel products, etc.

[0011] It is known from the prior art to attach a wear plate to an EMAT, to protect the magnet and the electric coil circuit from wear due to the movement of the EMAT in front of the inspected material. The wear plate is usually arranged between the inspected material and the active components of the EMAT, including the magnet and the electric coil circuit. Common wear plates have the disadvantage of introducing higher reluctance paths between the magnetically active part of the EMAT and the inspected material.

[0012] The main challenge of common EMAT technology is that EMAT probes suffer from low magnetic transduction efficiency for both the static magnetic field generated by the magnet(s) and the emitted or received RF magnetic field. It is known from the prior art that introducing a magnetic core, made of a high permittivity material, such as ferromagnetic or ferrimagnetic, between a magnetic transmitter and a magnetic receiver can increase the induced magnetic field strength by hundreds or thousands of times. The magnetic core itself creates a magnetic field that adds to the emitted field. The magnetic field amplification effect depends on the magnetic permittivity of the magnetic core material. It is also known that the interposition of a magnetic core can have negative side effects in the case of a variable RF magnetic field, related to eddy currents generated in the magnetic core.These cause significant energy losses, which depend on the frequency of the HF magnetic field. When the magnetic core is made of a single continuous piece, the variable HF magnetic field causes large eddy currents, according to closed loops of electric current running through the entire section of the magnetic core, deployed perpendicular to the emitted variable HF magnetic field. The eddy currents circulating through the magnetic core cause, due to the resistance of its material, significant power losses by Joule effect. This is the reason why the prior art frequently uses a matrix laminated magnetic core, consisting of a stack of active thin sheets, made of a magnetically active material, of the ferromagnetic or ferrimagnetic type, separated by insulating passive thin sheets. The insulating passive thin sheets serve as eddy current barriers.So that eddy currents can only flow in narrow loops, perpendicular to the emitted field, in the thickness of each magnetically active thin sheet. Since the current in an eddy loop is substantially proportional to the area of ​​its loop, a prior art matrix laminated magnetic core aims to minimize the area of ​​any eddy current loops, which are by nature perpendicular to the emitted HF magnetic field.

[0013] In order to overcome magnetic reluctance, it is known from the prior art document US patent 7,546,770 B2 to include in an EMAT a matrix laminated magnetic core, constituted in the form of a sandwich matrix comprising a multitude of thin ferromagnetic laminated sheets arranged in layers. Insulating thin sheets are interposed between ferromagnetic thin sheets, to constitute the sandwich matrix of the matrix laminated magnetic core. The EMAT is specifically and exclusively described in a configuration according to which the HF electric coil is configured to induce eddy currents on the surface of the inspected material, and not to receive them. It should therefore be noted that this prior art relates to and describes a probe configured as an EMAT transmitter only, and not as a receiver. The laminated magnetic core is arranged between the magnet and the inspected material.It is not placed directly in front of the HF electric coil. The entire outer surface of the laminated magnetic core is covered with a continuous conductive layer, made of an electrically conductive material. It is known that an electric coil having the shape of a turn, and supplied with an electric current, produces a bundle of magnetic field lines, consisting of a multitude of magnetic field loops substantially parallel to the axis of the circular turn, and passing through the interior of the turn. The absolute intensity of each magnetic field loop is variable. It depends on its point of passage and its distance from the center of the turn. It is also known that an HF alternating magnetic field loop produces eddy currents on a material placed near its center, the direction of which is substantially perpendicular to the HF magnetic field loop.Consequently, and although this is not described in this prior art, it is understood that when this EMAT operates in HF emission mode, its spiral electric coil generates in the direction of the magnetic core a multitude of HF alternating magnetic field loops, of variable absolute intensities, passing through the center of the spiral. The axis of the described electric coil is substantially parallel to the stacking plane of the thin sheets. The HF alternating magnetic field loops are therefore substantially parallel to the stacking plane of the thin sheets of laminated magnetic core. This therefore induces a multitude of induced current loops, distributed only on the surface of the continuous conductive layer which completely envelops the laminated magnetic core. These induced current loops are topologically distributed on the surface of the conductive layer in an inhomogeneous, unorganized, continuous and non-discrete manner.They have an absolute intensity that varies inhomogeneously depending on their position on the continuous conductive layer. They are oriented approximately perpendicular to the stacking plane of the thin sheets. The induced current loops on the surface of the conductive layer are therefore approximately perpendicular to the ferromagnetic laminated thin sheets. Therefore, no ferromagnetic laminated thin sheet is surrounded at its periphery by an induced current loop. The induced current loops on the surface of the conductive layer are mainly parallel to the surface of the inspected object.

[0014] The laminated magnetic core of this prior art provides mechanical protection of the magnet and the high-frequency RF electric coil. It also provides improved transmission of the static magnetic flux from the magnet to the inspected material. This laminated magnetic core provides a global, but weak fuzzy and topologically inhomogeneous, high-frequency coupling of the RF magnetic field between the RF electric coil and the eddy currents at the surface of the inspected material facing the probe and the RF electric coil. The coupling of this RF magnetic field is done globally and inhomogeneously, by the outer continuous conductive layer, and not selectively and / or locally by each of the inner ferromagnetic laminated thin sheets.

[0015] According to this prior art, the HF electric coil is arranged on the magnet, at a large distance from the laminated magnetic core and the inspected material. In such an arrangement of the magnet, additional losses are generated during the transmission of the HF electromagnetic energy between the HF electric coil and the inspected material. This arrangement of the laminated magnetic core of an EMAT minimizes the flux leakage of the static magnetic field generated by the magnet. But it degrades the quality of the coupling of the HF magnetic field between the eddy currents on the surface of the inspected material facing the probe and the HF electric coil of the EMAT. This HF magnetic coupling is of inhomogeneous intensity between, on the one hand, the different local active fractions of the material facing each of the edges of each ferromagnetic laminated thin sheet and, on the other hand, the HF electric coil.

[0016] According to this prior art, the laminated magnetic core is thermodynamically passive. It does not include any active cooling means that can actively extract part of the heat energy generated by the surface-induced current loops from the perimeter of the ferromagnetic laminated thin sheets of the magnetic core. This EMAT, which is not actively thermally protected, cannot operate reliably at temperatures above 600°C for a long time.

[0017] In a traditional EMAT, such protection of active parts is provided by an electromagnetically passive protective plate made of an insulating material, fixed on the working side of the transducer, distancing its active parts from the inspected material. The thickness of this protective plate is the result of a compromise between mechanical strength, the required operating temperature, and the transduction efficiency of the EMAT.

[0018] The prior art also provides EMATs equipped with hollow, non-laminated passive magnetic cores. These magnetic cores are equipped with cooling means or not, for high-temperature operation. But these prior art EMATs do not combine a laminated magmatic core and cooling means internal to such a laminated core, and they do not optimize and homogenize the HF magnetic coupling and / or do not effectively minimize the flux leakage of the HF magnetic field between the HF electric coil and the inspected material.

[0019] The reception of ultrasonic signals by an EMAT operating in receive mode works in the same way as an EMAT operating in transmit mode. The receiving direction of the EMAT operating in receive mode can be changed easily and purely electronically. This directivity makes it possible to achieve a high signal-to-noise ratio of an EMAT operating in receive mode.

[0020] There has been very limited exploitation of prior art EMATs, for inspection in harsh industrial environment and / or high temperature conditions above 1000°C, to perform continuous, moving line scanning of large areas of moving plate-like structures from a single location, in a manner analogous to that used at low temperatures in pipe and rail inspection.

[0021] A second aspect of the prior art concerns Laser-EMAT UNDT technology, which improves the overall sensitivity of UNDT systems using an EMAT, and their adaptability to average temperatures up to 600°C. The UNDT phenomenon requires an ultrasonic generator and an ultrasonic receiver.

[0022] A common Laser-EMAT system combines both an ultrasonic generator made of a high-power pulsed laser, and an EMAT operating in receiving mode as an ultrasonic receiver. The prior art describes such combined UNDT devices for the detection of surface and subsurface discontinuities in a structure. They are based on the joint exploitation of i) an ultrasonic transmitter made of a pulsed laser directing a laser beam towards the structure at an emission point, and generating ultrasonic surface waves and shear waves in the structure, when the radiation of the pulsed laser beam is absorbed by the structure; and ii) an ultrasonic receiver made of an EMAT acting in receiving mode detecting the ultrasonic surface waves and / or shear waves at a detection point.When a high-energy laser beam is fired at the surface of the material of a component under test, such as a steel slab, the local pulse causes rapid heating, leading to the explosion of a plasma on the component surface. Such an explosion generates ultrasonic waves throughout the component material. The laser generates two distinct types of waves in the material. One is propagated on or near the component surface. This is the most prominent detectable signal, propagating transversely across the component surface. The other is propagated deep at a wide angle throughout most of the component material. When the component material is conductive, the EMAT ultrasonic receiver of the Laser-EMAT system is used to detect the ultrasonic signal generated in the material under test, by the combined effects of its HF electric coil and magnet.Vibrations on the surface and inside the material, initiated by the ultrasonic signal produced by the Laser, and influenced by echoes from material discontinuities and their locations, induce an HF electric current in the detection circuit of the EMAT ultrasonic receiver, via eddy currents generated in the inspected material. Surface and internal discontinuities of the component located between the laser impact and the EMAT ultrasonic receiver can thus be detected and located by signal processing of the current in the HF electric coil, by identifying changes and disturbances in the received ultrasonic signal caused by discontinuities in the inspected material.

[0023] These combined UNDT devices show better efficiency in detecting discontinuities than single EMAT devices, based on EMATs used in both transmitter and receiver mode. Because pulsed lasers are more efficient, directional and powerful as an ultrasonic sound transmitter than conventional EMAT transmitters. The main disadvantage of common Laser-EMAT systems is that they retain the limitations and disadvantages of the common EMAT receiver they use as a receiver, as discussed above. The laser beam can operate at high temperature above 600°C. But prior art EMATs cannot.

[0024] A third prior art aspect of the invention relates to the optimized automatic adjustment of the parameters of the dynamic soft reduction (DSR) of a continuous casting of steel parts at a temperature of about 1200°C, such as steel slabs and / or billets being cast, in the production of a steel mill. The steel slabs are usually further processed into finished steel products, which include sheets, plates, coils of strip metal, pipes, and tubes.

[0025] During solidification of the steel casting, between the solid and liquid phases of the metal, there is a region within the slab that is neither completely solid nor liquid. The fraction (percentage) of solid in this "soft" region depends on the thermal properties and composition of the steel. The volume of steel transformed from liquid to solid shrinks due to the change in density associated with the lowering of the casting temperature. This shrinkage during solidification leads to voids in the inter-dendritic structure. At the crater of the final solidification region, a central segregation zone occurs. Internal segregation defects, and porosity in the center of the slab structure, during the continuous steel casting process of the slabs have an extremely negative effect on the properties of the finished steel products subsequently produced from the slab.This central segregation degrades the quality of steel products, especially thick steel plates. It results in inconsistent mechanical properties and potential failure of final steel products.

[0026] There have been many prior art attempts to seek to reduce or detoxify the central segregation of steel slabs from these defects incurred during continuous casting. A general practice to overcome this problem is to reduce the casting speed. Obviously, this affects the overall flow rate of the casting. Another prior art practice is to apply Soft Reduction (SR) during the last stage of solidification, and / or Dynamic Secondary Cooling (DSC). The basic idea of ​​any kind of Soft Reduction (SR) is to suppress the formation of central macro-segregation and porosity, by compensating for solidification shrinkage and interrupting the suction flow of residual steel.The SR operation must be carried out at an appropriate reduction intensity, and vertically to the appropriate soft zone of the final solidification stage, using pinch rolls or other similar specialized equipment. SR can only be carried out where the center of the slab is not yet stiff. The optimal point is the end of the solidification zone. The reduction intervals must be located between the two-phase solid-liquid zone and the solidification end of the casting slab; this is to improve the density and homogeneity of the center of the slab. The problem is that the exact position of this optimal point of completion of solidification is variable and unknown, since it is located at the center of the steel slab and therefore invisible according to the technical means of the prior art.

[0027] In the "light reduction at the end of solidification" (LSR) method, a plurality of reduction rolls are arranged at several reduction intervals near the roughly estimated solidification completion position of the slab and the reduction area of ​​the slab during continuous casting. LSR is a method for gradually reducing the generation of voids in the center of the slab and the flow of molten soft steel. Static soft reduction (SSR), provided by adjusting the fixed pinch roll spacing, has been employed by the prior art to improve the internal quality of steel slabs in continuous casting. However, the location of pinch rolls at fixed reduction intervals is only optimized and is applicable for a specific set of casting parameters. This means that the casting operation must be kept as stable as possible.The fixed SSR reduction zone imposes a restriction on the overall casting operation. Operational events make it difficult to maintain a stable state of casting parameters for long periods. Casting parameters such as casting speed and superheating can change during the casting process. Therefore, the solidification range shifts during the process. The operational efficiency of the SSR method is low.

[0028] To achieve greater operational flexibility while maintaining good internal quality, prior art has proposed a dynamic soft reduction (DSR) system, which takes into account transient casting conditions, evolving solidification processes, and the behavior of the inspected material. DSR, whether combined with dynamic secondary cooling (DSC) or not, has proven to be a more effective means than SSR for minimizing segregation and porosity in cast steel slabs. DSR parameters must be carefully defined to effectively eliminate center segregation and improve the internal quality of the cast slab. It is important to apply soft reduction at the right location and with accurate pinch roll spacing and clearance during the solidification phase. If DSR occurs too early, the reduction simply distorts the outer faces of the slab and does not effectively penetrate the center.Applied too late, the slab is already fully solid, and the deformation resistance is too high, resulting in excessive loads on the equipment rolls. The main parameters influencing the reduction, which determine the effectiveness of the dynamic soft reduction DSR position, are the slab format, casting speed, steel analysis (thermal properties), superheating and cooling rate. To achieve effective dynamic soft reduction DSR, it is necessary to dynamically control the spacing of the pinch rolls, and preferably their position, according to the actual varying geometric state of the internal solidification process, taking into account the current and historical conditions of the casting.

[0029] The time-accurate provision of: i) a dynamic 3D mapping (3DM) of the slab being cast, and / or ii) the 3D location of the central segregation zone of the steel slabs and / or the position of segregation defects; provided by a dynamic 3D mapping system (3DMS) of the cast, are the basic requirements for the implementation of effective dynamic soft reduction DSR and / or dynamic secondary cooling DSC.

[0030] Prior art DSR / DSC systems generally include the following means: a. a 3D dynamic mapping system (3DMS) of the steel casting; b. a computerized DSR optimization system (DSRM), generating dynamic DSR optimization parameters (PCSD) based on the dynamic 3D mapping (3DM) provided by the 3DMS system and on the casting parameters; c. a digital DSR activator (ASR), dynamically adjusting the DSR action parameters (PASD), according to the PCSD generated by the DSRM; d. optionally, a DSC optimization system (DSCM), generating dynamic DSC optimization parameters (PCSC) based on the dynamic 3D mapping (3DM) provided by the 3DMS system and the casting parameters; e. optionally, a digital DSC activator (ASC), dynamically adjusting the DSC action parameters (PASC) of the DSC water flow, according to the PCSC generated by the DSCM.

[0031] The three important parameters of DSR reduction, such as the position and geometry of the reduction zone, the dynamics and reduction ratio, the value of roller spacing in the reduction section, should be comprehensively considered in the algorithm of the DSRM optimization computer model.

[0032] Prior art 3DMS dynamic 3D mapping systems for steel casting operate solely by simulation. They perform: a. a numerical simulated prediction based on theoretical algorithms; and based on a mathematical model of heat transfer and solidification in the cast slab; and, b. not by a physical detection of an actual observed 3D dynamic mapping (3DM) of the interior of the steel cast slab, the location of the central soft zone, and the position of discontinuities in the middle of the cast slab.

[0033] A recent variant of a prior art 3DMS dynamic 3D steel casting mapping system is based in particular on an algorithmic interpretation of data from a 2D thermal monitoring system of the exterior of the cast slab.

[0034] None of the prior art steel casting 3D dynamic mapping systems (3DMS) offer an accurate and reliable observed definition of the 3D mapping of discontinuities in the reduction / solidification zone of the slab being cast, and / or the location of the slab's soft middle zone and / or segregation defects. The parameters of soft reduction DSR, such as the position and geometry of the reduction zone, the dynamics and rate of reduction, the value of the roll spacing in the reduction section, are adjusted by the prior art based on theoretically model-predicted, but unobserved, and often misleading, information of the central soft zone and the state of discontinuities within the cast slab. Thus, DSR and / or DSC parameters are often adjusted inappropriately and inefficiently in a continuous steel casting machine.They fail to effectively adjust, through adequately adjusted gentle dynamic reduction and / or secondary dynamic cooling, the excessive segregation and porosity of the center of cast slabs during the solidification process. Problème technique

[0035] It is clear from the above analysis of the prior art that another approach is necessary to solve, among others, the following technical problems of Ultrasonic Non-Destructive Testing (UNDT): a. To offer in a single EMAT probe a combined solution to the following three technical problems: i. to increase the transmission of the HF magnetic field energy, to maximize the HF magnetic coupling and / or to minimize the HF magnetic field flux leakage, between the electric coil and the eddy currents generated on the surface of the inspected material; and, ii. to provide a surface topological homogeneity of the efficiency of this high-frequency electromagnetic coupling, between the electric coil and the eddy currents on the surface of the inspected material facing the probe; and, iii. to have a capability of operation at high temperatures of the inspected material above 1000°C. b. To offer in a single UNDT device a combined solution to the following two technical problems: i. to optimize the resolution of the detection of surface and deep subsurface discontinuities in a thick metallic structure; and, ii.have the capability to operate at elevated temperatures of the inspected material in excess of 1000°C. c. Offer a 3D scanner of conductive structures, providing a combined solution to the following two technical problems: i. provide continuous line-based 3D scanning of large, thick conductive moving structures, such as metallurgical slabs, from a single location, generating a high-resolution observed 3D map of that structure, including providing the location of surface and deep subsurface discontinuities; and, ii. have the capability to operate in a harsh industrial environment, at elevated temperatures of the inspected material in excess of 1000°C. d.To enable an optimized automatic adjustment of the DSR (PASD) action parameters of dynamic soft reduction (DSR) and / or the DSC (PASC) action parameters of dynamic secondary cooling (DSC) of a continuous casting of steel slabs in a steel mill, based on the observed state of the interior of the cast slab; by solving in a single device the combination of the following four technical problems: i. to provide continuously an observed 3D dynamic mapping (3DM) of the interior of the cast slab; ii. to define continuously in an observed 3D manner the location of the central soft zone of the slab melt and / or segregation defects, based on a 3D physical observation, and not simply provided by a numerical simulation prediction by a theoretical algorithm based on a mathematical model; iii. to detect precisely, the observed position of the reduction point of the cast slabs, based on a 3D physical observation; iv.to improve the accuracy and reliability of automatic adjustment of dynamic soft reduction (DNS) and / or dynamic secondary cooling (DSC) parameters of continuous slab casting at temperatures above 1000°C; in order to reduce segregation defects and porosity in the central molten soft zone of the steel slab structure during the continuous casting process in a steel mill. Solution technique

[0036] Briefly, in accordance with one aspect of the invention, an Electromagnetic Acoustic Transducer (EMAT) for detecting surface and internal discontinuities in an electrically conductive inspected material is provided; this in order to offer a technical solution to the above technical problem (a). In a manner counterintuitive to the person skilled in the art, and unlike the conventional configuration of prior art EMATs implementing a laminated magnetic core, the technical solution of the invention consists in particular in that: a. It is not intended to reduce the area of ​​the eddy current loops inside the active HF plates of the laminated magnetic core. On the contrary, the invention seeks to increase the area and the effect of the induced current loops in the active HF (ferromagnetic) plates; but this in a topologically organized configuration and orientation in an appropriate manner, to take advantage of it to improve the efficiency and homogeneity of the coupling, as well as the performance of the EMAT. b.The EMAT is not configured so that in transmission mode: i) the HF alternating magnetic field loops induced by the HF electric coil in the magnetic core are substantially parallel to the stacking plane of the thin sheets of laminated magnetic core; and ii) a multitude of induced current loops are distributed only on the surface of a continuous conductive layer which completely envelops the laminated magnetic core, and iii) the induced current loops are topologically distributed over the entire surface of the conductive layer in an inhomogeneous, non-organized, continuous and non-discrete manner, and iv) these induced current loops are oriented substantially perpendicular to the stacking plane of the thin sheets.But on the contrary, according to the invention, the EMAT is configured so that in emission mode: i) the HF alternating magnetic field loops induced by the HF electric coil in the magnetic core are substantially perpendicular to the stacking plane of the thin sheets of laminated magnetic core; and ii) the induced current loops are positioned only on the periphery of the HF active plates, and are oriented in a plane parallel to the plane of the HF active plates which they encircle on their peripheries, and are therefore perpendicular to the surface of the inspected object; and iii) the induced current loops are topologically distributed in a discrete and distant manner, but homogeneously each on the periphery of the HF active plates; and iv) these induced current loops are thus oriented substantially parallel to the stacking plane of the thin sheets. c.The EMAT is not configured so that the HF active plates are made of a solid sheet. But on the contrary, according to the invention, the HF active plates are pierced in their centers, by a via hole, around which rotates, perpendicular to its axis, a current loop induced on the periphery of each HF active plate. d. The EMAT is not configured with an HF electric coil with a turn circuit, distant from the laminated magnetic core, and separated from the magnetic core by a magnet, emitting in emission mode a variable HF magnetic field flux of inhomogeneous absolute intensity on a continuous conductive layer surrounding all the HF active plates of the magnetic core. But on the contrary, according to the invention, the EMAT is configured with an HF electric coil with a meander circuit, composed of a succession of parallel portions of electrical conductors. The magnetic core is not covered with a continuous conductive layer.Each portion of electrical conductor carries an electric current of similar absolute intensity but in the opposite direction to the neighboring portion of electrical conductor. The portions of electrical conductor are alternately superimposed directly opposite and on the upper edge of each active HF plate of the laminated magnetic core. In transmission mode, the HF electric coil thus emits a variable HF magnetic field flux of equivalent intensity in each active HF plate, and which is substantially perpendicular to them. e. According to the invention, in transmission mode, the neighboring active HF plates are surrounded by induced current loops rotating in opposite directions.In this way, in the successive portions of the frontal zones of the surface of the material facing each of the active HF plates of the laminated magnetic core, a variable HF magnetic field flux is induced, with opposite directions for each active HF plate, but with almost equal absolute intensity in each frontal zone facing a neighboring active HF plate. In this way, on the surface of the inspected material, facing the laminated magnetic core, an eddy current matrix formed of parallel vectors, with approximately equal intensities, but with opposite directions. This elaborate topological configuration leads to a greater resolution of the EMAT. Résumé de l'invention

[0037] The EMAT includes: a. At least one Magnet or electromagnet, configured to generate a Static or quasi-static Magnetic Field in the Inspected Material; b. At least one high-frequency RF Electric Coil (or electrical circuit), the latter being either configured as an RF Electromagnetic Transmitter of an RF Emitted Electromagnetic Field if the EMAT is used in Transmit Mode, and / or, or configured as an RF Electromagnetic Receiver of an RF Electromagnetic Field if the EMAT is used in Receive Mode; c. At least one Perforated Matrix Laminated Magnetic Core, configured to concentrate and direct an RF Emitted Electromagnetic Field; of the type comprising a Matrix (sandwich) consisting of a multitude of laminated Thin Sheets, stacked periodically along the Matrix Axis.

[0038] The sandwich matrix comprises a First Multitude of HF Active Platelets. They are insulated from each other. They internally incorporate a Magnetic Material with high magnetic permeability. Each HF Active Platelet externally incorporates an electrically conductive material; and / or is externally covered with an electrically conductive layer on its Peripheral Edges. A Grooved Cylindrical Opening passes through each Thin Sheet of the Matrix, and opens onto each of the two lateral Matrix Faces. A multitude of Magnetic Via Holes, of similar dimensions and section, and with a closed lateral perimeter, are perforated through and substantially in the center of each of the multiple HF Active Platelets of the Matrix. They are aligned to form by their alignment the Grooved Cylindrical Opening. A multitude of Induced Current Loops are generated in the HF Active Platelets.

[0039] The peculiarity of this EMAT lies in the combination of the following technical means. Each Magnetic Via Hole, made in each hollow HF Active Pad, is located between the First Edge Face facing the Inspected Surface, and the Second Edge Face facing the Electric Coil. Each Magnetic Via Hole of the Grooved Cylindrical Opening is internally free of any hard material; and is free of any electrical conductor passing through it. When the EMAT is in operation, the Induced Current Loops are induced inside the Active Pad Skin on the Peripheral Edges of HF Active Pads, and are substantially parallel, and separated from each other. They encircle the Magnetic Via Holes of their HF Active Pad, and rotate around.

[0040] In an alternative embodiment of the invention, a Laser-EMAT Probe (LEMAT), for inspecting an Inspected Material, by receiving an ultrasonic signal emitted from this Inspected Material, is presented; in order to provide a technical solution to the above technical problem (b).

[0041] This LEMAT includes: a. An EMAT according to the invention, as set forth above, configured in Receive Mode, to receive an ultrasonic signal from the Inspected Material; and b. A Laser Source configured to fire a high energy Laser Beam at a Firing Point on the surface of the Inspected Material.

[0042] The Laser Source generates ultrasonic waves producing Primary Ultrasonic Waves, propagating on the surface and / or inside and in depth of the Inspected Material. This generates Secondary Ultrasonic Waves resulting from the echoes of the interactions with the discontinuities located on and / or inside the Inspected Material and depending on their locations, propagating on the surface and / or inside the Inspected Material. This generates Material Eddy Currents on the Inspected Material, induced by the Secondary Ultrasonic Waves, under the influence of the Static Magnetic Field generated by the EMAT Magnet. This in turn induces an HF Emitted Electromagnetic Field, emitted by the Material Eddy Currents in the Inspected Material, which is representative of the surface topography and internal Discontinuities of the Inspected Material.

[0043] In another embodiment of the invention, a Multi Laser-EMAT (MLEMAT) 3D Scanner is presented for the detection of Discontinuities on and inside a moving cylindrical Conductive Structure; in order to provide a technical solution to the above technical problem (c).

[0044] The MLMAT includes: a. A Conductive Structure to be 3D scanned; b. A Chassis Frame configured to surround the Conductive Structure; c. A multitude of Laser-EMAT Probe (LEMAT) probes according to the invention, as indicated above, fixed on the Chassis Frame, positioned and configured such that each of the First Active Edge Faces of each of their Perforated Matrix Laminated Magnetic Cores faces the Conductive Structure; and, d. Displacement Means configured to linearly displace the cylindrical Conductive Structure relative to the Chassis Frame.

[0045] The peculiarity of this MLEMAT lies in the fact that the Loop of Openings, made of the virtual line connecting the centers of each successive Grooved Cylindrical Opening of each Perforated Matrix Laminated Magnetic Core of each of the adjacent EMATs of the MLEMAT, encircles the Conductive Structure.

[0046] In another embodiment of the invention, an adaptation of the 3D Multi Laser-EMAT Scanner (MLEMAT) according to the invention, as indicated above, is presented for the automatic adjustment of the Dynamic Soft Reduction (DSR) of a continuous casting of steel slabs, at a casting temperature above 1000 ° C; and offers a technical solution to the above technical problem (d).

[0047] The steel slab is continuously pushed through a Dynamic Soft Reduction System (DSRD), to suppress the formation of macro-segregation and porosities in the Central Soft Zone inside the Steel Slab, dynamically compensating for solidification shrinkage and interrupting the suction flow of residual molten metal in the Steel Slab. The Electrical Coils of each EMAT of each Laser-EMAT of the MLEMAT are connected to a 3D Dynamic Casting Mapping System (3DMS). This 3DMS includes Analog and Digital Processing Means (MDAN) configured to combine and process the Secondary Ultrasonic Electrical Currents emitted in the Electrical Coils of each Laser-EMAT of the MLEMAT, which are induced in each Electrical Coil of this Laser-EMAT by the Eddy Currents of the Material in the Frontal Zone of the Inspected Material of the Steel Slab.These Material Eddy Currents result from the interactions of echoes generated by the Laser Sources with the Discontinuities on and inside the Inspected Material in the Frontal Zone of the First Edge Face of this Laser-EMAT. The MDANs combine the Secondary Ultrasonic Electric Currents from each EMAT and generate a 3D Dynamic Mapping (3DM) of the cast Steel Slab, in the Slab Structure Section of the Frame Plane, based on the combination and numerical analysis of these multiple Secondary Ultrasonic Electric Currents in each Laser-EMAT of the MLEMAT. A DSR Optimization System (DSRM) of the cast DSR, is connected to the 3DMS. It receives the 3DM of the Steel Slab and numerically generates a set of Dynamic DSR Optimization Parameters (DSDP). A Digital DSR Activator (DSA) is connected to the DSRM. It dynamically adjusts the DSR Action Parameters (PASD), based on the PCSDs generated by the DSRM.

[0048] The particularity of this MLEMAT lies in the following combination of technical means. The Cooling Means of each of its EMATs according to the invention generate a Heat Flux of a cooling Heat Fluid. It is pushed inside each Magnetic Via Hole and each Spacer Via Hole of the Grooved Cylindrical Opening of each Perforated Matrix Laminated Magnetic Core of each adjacent EMAT of the MLEMAT; this at a Cooling Temperature (TF) significantly lower (by at least 50°C) than the Curie Temperature (TC) of the Magnetic Material of the hollowed-out HF Active Wafers. Thus the Dynamic Soft Reduction (DSR) and / or the Dynamic Secondary Cooling (DSC) are automatically set dynamically, at a casting temperature above 1000°C. Brève description des dessins

[0049] These and other features, aspects, and advantages of the present invention will be better understood when the following detailed description is read in conjunction with the accompanying drawings, in which like characters represent like parts throughout the drawings, in which: There figure 1 [Fig. 1 ] is a schematic perspective representation of an EMAT transducer of the invention. The figure 2 [Fig. 2 ] is a schematic cross-sectional representation of an EMAT transducer of the invention. The figure 3 [Fig. 3 ] is a schematic perspective showing the mode of operation of one of the HF Active Platelets in the Perforated Matrix Laminated Magnetic Core of an EMAT transducer of the invention, used in Transmission Mode. The figure 4 [Fig. 4 ] is a schematic perspective showing the mode of operation of one of the HF Active Platelets in the Perforated Matrix Laminated Magnetic Core of an EMAT transducer of the invention, used in Reception Mode. The figure 5 [Fig. 5 ] is a schematic perspective showing the Perforated Matrix Laminated Magnetic Core of an EMAT transducer of the invention, consisting of the stacking of its HF Active Platelets and its Passive Platelets. The figure 6 [Fig. 6 ] is a partial schematic perspective view of the electromagnetic operation of the HF Active Platelets of the Perforated Matrix Laminated Magnetic Core of an EMAT transducer of the invention, used in Transmission Mode. The figure 7 [Fig. 7 ] is a schematic perspective of an alternative embodiment of some of the Thin Sheets of the Perforated Matrix Laminated Magnetic Core of an EMAT transducer of the invention, for dynamically lifting its Perforated Matrix Laminated Magnetic Core out of the Inspected Material. The figure 8 [Fig. 8 ] is a schematic sectional view of a Laser-EMAT (LEMAT) probe according to the invention. The figure 9 [Fig. 9 ] is a schematic side view of a Multi Laser-EMAT (MLEMAT) 3D scanner according to the invention. The figure 10 [Fig. 10 ] is a schematic perspective in section of a 3D Multi Laser-EMAT Scanner (MLEMAT) according to the invention, for the automatic adjustment of the Dynamic Soft Reduction (DSR) and / or the Dynamic Secondary Cooling (DSC) of a continuous casting of molten Steel Slabs, carried out at the level of its EMAT probes. The figure 11 [Fig. 11 ] is a schematic perspective in section of a 3D Multi Laser-EMAT Scanner (MLEMAT) according to the invention, for the automatic adjustment of the Dynamic Soft Reduction (DSR) and / or the Dynamic Secondary Cooling (DSC) of a continuous casting of molten Steel Slabs, carried out at the level of its Laser sources. figure 12 [Fig. 12 ] is a functional diagram of a Multi Laser-EMAT 3D Scanner (MLEMAT) according to the invention, for the automatic adjustment of the Dynamic Soft Reduction (DSR) and / or the Dynamic Secondary Cooling (DSC) of a continuous casting of molten Steel Slabs. Description des modes de réalisation

[0050] The embodiments described below are generally directed to an improved EMAT system (1), which can be used for Non-Destructive Testing (NDT) of a Conductive Structure (90) at a temperature above 1000°C.

[0051] Referring to figure [ Fig. 1 ], and to the figure [ Fig.3 ] we see an Electromagnetic Acoustic Transducer (EMAT) (1) for the detection of surface and internal Discontinuities (2) in an electrically conductive Inspected Material (3). Two Magnets (4) are configured to generate a Static Magnetic Field (SMF) or quasi-static in the Inspected Material (3). It is understood that each Magnet (4) could be replaced by an electromagnet. An HF Electric Coil (6) (or electric circuit) is placed directly above a Perforated Matrix Laminated Magnetic Core (22). Its Winding Plane (7) (or circuit plane) is parallel to the local Inspected Surface (8) of the Inspected Material (3) facing the EMAT (1). The two Magnets (4) are positioned on either side of the Perforated Matrix Laminated Magnetic Core (22).

[0052] Referring to figure [ Fig.3 ], we find that the EMAT (1) can be used in Emission Mode (EM). The HF Electric Coil (6) is configured as an HF Electromagnetic Transmitter (9) of an HF Emitted Electromagnetic Field (HFEMF). It is connected to the output of at least one Alternating Current Source (11), driving into the HF Electric Coil (6) an HF Alternating Current (AC) at ultrasonic frequency. This induces an HF Emitted Electromagnetic Field (HFEMF) in the direction of the Inspected Material (3). The HF Emitted Electromagnetic Field (HFEMF) produces Material Eddy Currents (14) on the surface of the Inspected Material (3). This generates Lorentz Forces (15) at ultrasonic frequency in the Inspected Material (3), by the interaction of the Material Eddy Currents (14) with the Static Magnetic Field (SMF). This can also generate Magnetostriction if the Inspected Material (3) is ferrimagnetic.The perturbation of the Lorentz Forces (15) generates Primary Ultrasonic Waves (17) directly in the Inspected Material (3).

[0053] Referring to figure [ Fig.4 ], it is understood that the EMAT (1) can also be used in Reception Mode (RM). The HF Electric Coil (6) is then configured as an HF Electromagnetic Receiver (18). It is traversed by a Secondary Ultrasonic Electric Current (19) at ultrasonic frequency. This HF current consists of Secondary Ultrasonic Electric Signals (88) generated by an HF Emitted Electromagnetic Field (HFEMF) induced by Eddy Currents of the Material (14). These Eddy Currents of the Material (14) are produced on the Inspected Surface (8) of the Inspected Material (3) by Secondary Ultrasonic Waves (21), under the influence of an external ultrasonic source, in interaction with the Static Magnetic Field (SMF). These Eddy Currents of the Material (14) are representative of the surface and internal Discontinuities (2) of the Inspected Material (3).

[0054] Referring again to figure [ Fig. 1 ] and to the figure [ Fig. 2 ], we see that a Perforated Matrix Laminated Magnetic Core (22) is positioned between the Inspected Surface (8) of the Inspected Material (3) and the HF Electric Coil (6), which directly faces it. The Perforated Matrix Laminated Magnetic Core (22) is configured to concentrate and direct the Emitted HF Electromagnetic Field (HFEMF) in the direction and / or from the Inspected Material (3), depending on whether the mode of use of the EMAT (1) is in transmission or reception. It is of the type comprising a sandwich Matrix (23) consisting of a multitude of laminated Thin Sheets (24). They are stacked periodically along the Matrix Axis (25), between the two main Matrix Faces (26) of the Matrix (23), parallel to its Stacking Plane (27).The Perforated Matrix Laminated Magnetic Core (22) has multiple adjacent grooved lateral Edge Faces (35) extending substantially perpendicular to the Stacking Plane (27) and parallel to the Matrix Axis (25).

[0055] Referring to figure [ Fig. 2 ], we see that one of the Edge Faces (35), the First Edge Face (36) of the Die (23), faces the Inspected Surface (8) of the Inspected Material (3). The other, the Second Edge Face (37) of the Die (23) is located substantially opposite the First Edge Face (36), and faces the HF Electric Coil (6).

[0056] Referring to figure [ Fig. 1 ] and to the figure [ Fig. 5 ], we see that each laminated Thin Sheet (24) of the Matrix (23) has a spatial geometry and lateral dimensions similar to those of the neighboring Thin Sheets (24) in the Matrix (23). It presents two main lateral Sheet Surfaces (32), parallel to the Stacking Plane (27).

[0057] Referring again to figure [ Fig. 1 ] and to the figure [ Fig. 5 ], we see that the successive adjacent Peripheral Edges (33) combined of each Thin Sheet (24) form a grooved Border Surface (34) of the Die (23), surrounding the Die Axis (25). The Core Axis (38) of the Die (23), substantially joins the centers of the First Border Face (36) and the Second Border Face (37). It is positioned substantially perpendicular to the Die Axis (25).

[0058] Referring to figure [ Fig. 5 ] and to the figure [ Fig. 6 ], we see that the sandwiched Matrix (23) comprises a First Multitude (28) of HF Active Platelets (29) (four are shown in the figures), or groups of such platelets. Each HF Active Platelet (29) is isolated from the others. It internally incorporates a Magnetic Material (in particular ferromagnetic or ferrimagnetic) with high magnetic permeability. The Magnetic Material has a certain Curie Temperature (CT). It externally incorporates an electrically conductive material. It can alternatively be externally covered with an electrically conductive layer on its Peripheral Edges (33). A Grooved Cylindrical Opening (39) passes through each Thin Sheet (24) of the Matrix (23), along an Opening Axis (40) of the Matrix (23), substantially parallel to the Matrix Axis (25) and perpendicular to the Core Axis (38). It opens onto each of the two Matrix Faces (26).A multitude of Magnetic Via Holes (41), of similar cross-sectional dimensions and with a closed perimeter, are punched through and substantially in the center of each of the multiple HF Active Plates (29) thus hollowed out of the Matrix (23), along an axis substantially parallel to the Inspected Surface (8). They are aligned along an axis parallel to the Inspected Surface (8) to form by their alignment the Grooved Cylindrical Opening (39). They have a Longitudinal Via Hole Envelope (42), along the Opening Axis (40) of the sandwiched Matrix (23), the lateral perimeter of which is closed. Referring to FIG. [. Fig. 3 ] and to the figure [ Fig. 4 ] we see that when the EMAT (1) is in operation, a multitude of closed Induced Current Loops (43) are induced by the HF Emitted Electromagnetic Field (HFEMF). This is either emitted by the HF Alternating Current (AC) at ultrasonic frequency in the HF Electric Coil (6) when the EMAT is in emission mode as shown in figure [ Fig. 3 ], and / or emitted by the Eddy Current of the Material (14) at ultrasonic frequency in the inspected Material (3) when the EMAT is in reception mode as shown in figure [ Fig. 4 ]. The Induced Current Loops (43) are located inside the Active Pad Skin (48) of the periphery of each HF Active Pad (29) of the Perforated Matrix Laminated Magnetic Core (22). As it appears [ Fig. 6 ] they are arranged according to a Loop Map (LM), defining the topology, distribution, and relative positions of all the Induced Current Loops (43).

[0059] With reference to figure [ Fig. 2 ] the following features of the EMAT (1) are noted. Each Magnetic Via Hole (41) in each HF Active Pad (29) is located between the First Edge Face (36) facing the Inspected Surface (8), and the Second Edge Face (37) facing the HF Electric Coil (6). Each Magnetic Via Hole (41) of the Grooved Cylindrical Opening (39) is internally free of any hard material. In particular, it is free of any electrical conductor passing through it. With reference to figure [ Fig. 6 ] we see that the Loop Map (LM) is topologically discrete and consists of a multitude of Induced Current Loops (43) in each HF Active Pad (29), (or groups of such Active Pads) distant from each other. With reference to figure [ Fig. 3 ] it is seen that the Induced Current Loops (43) (or group of such Loops) are induced inside the Active Pad Skin (48) on the Peripheral Edges (33) of the HF Active Pads (29). They are each arranged in a loop plane parallel to the Stacking Plane (27), and substantially perpendicular to the surface of the Inspected Material (3). They are substantially parallel, and separated from each other, between their respective HF Active Pads (29). They encircle the Magnetic Via Holes (41) of their HF Active Pad (29) and rotate around. With reference to FIG. [ Fig. 6 ] we see that each Core Spacer Slice (49) of the Perforated Matrix Laminated Magnetic Core (22) and its surface, located between two adjacent HF Active Plates (29) (or group), is free from any Induced Current Loops (43), and more generally free from any induced electric current.

[0060] Referring to figure [ Fig. 3 ], it is seen that the Emitted RF Electromagnetic Field (HFEMF), and the Perforated Matrix Laminated Magnetic Core (22) are configured in such a way that, when the EMAT (1) is in operation, the RF Core Magnetic Field (HFIMF) has a significant component of RF Core Transverse Magnetic Field (MFTHF), which is perpendicular to the Stacking Plane (27), perpendicular to each RF Active Wafer (29), and substantially parallel to the surface of the Inspected Material (3). The RF Magnetic Flux (MFHF) inside the Perforated Matrix Laminated Magnetic Core (22) has a significant component perpendicular to the Core Axis (38) and parallel to the surface of the Inspected Material (3). And therefore it is not perpendicular to the Inspected Surface (8) of the Inspected Material (3). The closed Induced Current Loops (43) are generated by the HF Core Transverse Magnetic Field (HFTMF) on the Peripheral Edge (33) of each HF Active Pad (29).

[0061] Referring to figure [ Fig. 5 ] and to the figure [ Fig. 6 ], It is understandable that a dual combined and interactive physical effect occurs inside the Perforated Matrix Laminated Magnetic Core (22). On the one hand, each of the multiple parallel and topologically discrete Induced Current Loops (43) distant from each hollowed-out HF Active Plate (29) separately generates a high-frequency magnetic field. This separately and locally increases the discrete and selective high-frequency magnetic coupling between - a narrow Local Active Fraction (44) of the Inspected Surface (8) facing its First Edge Face (36), - and the HF Electric Coil (6). The parallel Induced Current Loops (43) of the HF Active Plates (29) participate by mutualization in the overall reduction of the high-frequency magnetic reluctance of the EMAT (1).On the other hand, the Internal Perimeter (45) of each Magnetic Via Hole (41) in each HF Active Pad (29) of the Matrix (23) creates a Thermally Conductive and Convective Surface (46) in the center of its HF Active Pad (29). This produces an internal Thermal Cooling effect to dissipate a fraction of the local electrical and heat energy generated by the Induced Current Loop (43) specific to each HF Active Pad (29). This contributes by mutualization to the improvement of the efficiency of the EMAT (1).

[0062] Referring to figure [ Fig. 5 ], we see the Perforated Matrix Laminated Magnetic Core (22), with its HF Active Platelets (29) separated by Passive Platelets (53). Each HF Active Platelet (29) hollowed out of the Matrix (23) (or group of such Active Platelets) is separated from its neighbors, at the adjacent Core Spacer Slices (49), by at least one sheet of a Second Multitude (54) of Passive Platelets (53) made of an electrically insulating material. Each Passive Platelet (53) is perforated by a Via Spacer Hole (57). Each Passive Pad (53) is positioned and configured such that the Magnetic Via Holes (41) in the First Multitude (28) of HF Active Pads (29) of the Array (23), as well as the Spacer Via Holes (57) of the Second Multitude (54) of Passive Pads (53) of the Array (23), are aligned parallel to the Array Axis (25). They form by their alignment and combination the Grooved Cylindrical Opening (39).

[0063] This configuration of the Electromagnetic Acoustic Transducer (EMAT) (1) has the following characteristics. Each Via Spacer Hole (57) in each Passive Wafer (53) is located between the First Edge Face (36) facing the Inspected Material (3), and the Second Edge Face (37) facing the RF Electric Coil (6). Each Via Spacer Hole (57) of the Grooved Cylindrical Opening (39), is internally free of any hard material. In particular it is free of any electrical conductor passing through it. It is understandable that the internal periphery of each Via Spacer Hole (57) in each Passive Wafer (53) of the Matrix (23) creates a free internal Thermally Conductive and Convective Surface (46) in the center of the Passive Wafer (53).This produces an internal Thermal Cooling effect in this Hole Via Spacer (57) to dissipate a fraction of the electrical and heat energy generated by the Induced Current Loops (43) of the neighboring HF Active Pads (29). This contributes by mutualization to the improvement of the efficiency of the EMAT (1).

[0064] As shown in figure [ Fig. 5 ], it is recommended by the invention that for each Passive Plate (53), the Peripheral Edges (33) of their peripheries are free of any conductive material covering their surfaces. So that the grooved Edge Surface (34) of the Perforated Matrix Laminated Magnetic Core (22), is not continuously covered and / or made up of an electrically conductive layer, but on the contrary it is made up of an alternation edge to edge of on the one hand conductive rings around the HF Active Plates (29) and on the other hand insulating rings around the Passive Plates (53).

[0065] According to a preferred embodiment of the invention, which appears in figure [ Fig. 5 ], the Perforated Matrix Laminated Magnetic Core (22) of the EMAT (1) comprises Cooling Means (58). They generate a Heat Flow (59) of a Heat Fluid (60) at a Cooling Temperature (TF). This Heat Flow (59) is forced to pass through the Grooved Cylindrical Opening (39) of the Matrix (23). This configuration of the EMAT (1) has the following characteristics. The cooling Heat Flow (59) is configured to pass successively through one of the Magnetic Via Holes (41) of the First Multitude (28) and, alternatively, at least one of the Spacer Via Holes (57) of the Second Multitude (54). It licks the entire Hole Wall Surfaces (62) of each successive Magnetic Via Hole (41) and / or each Spacer Via Hole (57) of the Matrix (23).It is understandable that this increases the internal thermal cooling effect in each HF Active Plate (29) of the Matrix (23); each of which is subject to an Induced Current Loop (43) and heat dissipation. It is recommended by the invention that the Cooling Temperature (TF) of the Heat Flux (59) be set significantly lower (by at least 50 ° C) than the specific Curie Temperature (TC) of the Magnetic Material of each hollowed HF Active Plate (29).

[0066] Referring to the [ Fig. 7 ], we see an advantageous variant embodiment of the EMAT (1) of the invention. At least one (and preferably a multitude of) Thin Sheet(s) (24) of the Perforated Matrix Laminated Magnetic Core (22) is - either pierced by a Cushion Hole (63), - or, provided with a Cushion Notch (64). These openings pass through the Annular Wall (65) formed between their Via Holes (41, 57), and the portion of their First Edge Face (36) facing the Inspected Material (3), this in a direction parallel to the Stacking Plane (27). This creates a Cushion Recess (66) between the Via Holes (41, 57) of the Thin Sheet (24) and the First Edge Face (36) facing the Inspected Material (3). The Cooling Means (58) are configured to extract a Cushion Fluid Flow (67) from the Heat Flow (59) passing through the Via Holes (41, 57). They flow under pressure this extracted Cushion Fluid Flow (67) through the Cushion Recess (66).This creates a lifting Air Cushion (70) between the Perforated Matrix Laminated Magnetic Core (22) and the Inspected Material (3), at the Cushion Recess (66) facing the Inspected Material (3). This lifts the Perforated Matrix Laminated Magnetic Core (22) above the Inspected Material (3) by a Cushion Gap (68). This arrangement is reliable. It ensures automatic mechanical adjustment of the Cushion Gap (68). It is understood that this arrangement considerably reduces the heat energy transferred by conduction between the Inspected Material (3) and Perforated Matrix Laminated Magnetic Core (22), as well as to the active parts. This arrangement eliminates friction. It significantly increases the operating time and availability of the EMAT (1), by limiting wear between maintenance phases.

[0067] Referring to figure [ Fig. 5 ], an alternative embodiment of the EMAT (1) of the invention is shown. The two outer lateral Edge Faces (35) of the two outer Thin Sheets located on the Matrix Faces (26) are either made of, or covered (as illustrated) by, a Conductive Cover Layer (69) of an electrically conductive material. This configuration of the EMAT (1) has the following characteristics. A Via Hole of similar transverse dimensions to those of the Magnetic Via Holes (41) is punched through each of the two Conductive Cover Layers (69). The multiple Thin Sheets (24) and the two Conductive Cover Layers (69) of the Matrix (23) are positioned relative to each other, so that their multiple via holes are aligned to form by continuity the Grooved Cylindrical Opening (39).

[0068] According to a preferred variant of the invention, which is described in figure [ Fig. (5 )], the perimeter of each Magnetic Via Hole (41) provided in each HF Active Pad (29) is rectangular. The center of each Magnetic Via Hole (41) is substantially located and centered at the center of gravity of its HF Active Pad (29). And, the perimeter of each Magnetic Via Hole (41) is positioned at a substantially constant Ring Distance (Rd) from the perimeter of the Peripheral Edges (33) of its HF Active Pad (29). It is understandable that in this configuration, each HF Active Pad (29) is topologically configured as a rectangular Active Ring (71), thermodynamically cooled from the heating of the Induced Current Loop (43) generated around it.

[0069] Referring to figure [ Fig. 1 ] and to the figure [ Fig. 2 , we see a recommended variant embodiment of the EMAT (1) of the invention. The Second Edge Face (37) of the Perforated Matrix Laminated Magnetic Core (22) directly faces the HF Electric Coil (6). No Magnet (4) or other element is positioned between - on one side the Second Edge Face (37) of the Matrix (23) and - on the other side the HF Electric Coil (6).

[0070] Referring to figure [ Fig. 6 ], another preferred embodiment of the EMAT (1) of the invention is shown. The HF Electric Coil (6) and the First Multitude (28) of HF Active Pads (29) in the Matrix (23) are configured such that: the orientation, pitch, size and shape of each of the Circuit Face Edges (72) of each HF Active Pad (29), located in the Second Edge Face (37) of the Matrix (23), and facing the HF Electric Coil (6); are consistent and correlated with the geometric parameters, including the orientation, pitch, size and shape, of the Conductor Fractions (75) of the HF Electric Coil (6) successively facing each of these Circuit Face Edges (72).

[0071] A preferred arrangement of the above configuration appears with reference to Figure [ Fig. 3 ]. It is seen that the HF Electric Coil (6) has at least a portion of Linear Conductor (73). This is positioned close to and directly above a Circuit Face Edge (72). It is tangent, along a parallel axis, to this neighboring portion of the perimeter of an HF Active Pad (29) located in the Second Edge Face (37) of the Matrix (23) facing the HF Electric Coil (6). It is seen that a feature of this arrangement of the invention is that the portion of Linear Conductor (73) and the Perforated Matrix Laminated Magnetic Core (22) are configured such that, when the EMAT (1) is in operation, an Induced Current Loop (43) is induced in the Active Pad Skin (48) around the perimeter of the HF Active Pad (29). It surrounds its Magnetic Via Hole (41).So that this achieves a local selective HF magnetic coupling between - on the one hand an HF Alternating Current (AC) driven in the Linear Conductor (73) extending on and along the perimeter of the HF Active Pad (29), and, - on the other hand the Eddy Currents of the Material (14) generated in the narrow Local Active Fraction (44) of the Inspected Surface (8) facing the HF Active Pad (29).

[0072] It is known that the HF Emitted Electromagnetic Field (HFEMF) created by a Linear Conductor (73) carrying a current is ortho radial. Consequently, the HF Magnetic Flux Lines (MFHF) are essentially circles surrounding the Linear Conductor (73).

[0073] If the EMAT (1) is in Emission Mode (EM), as described in the figure Fig.3 , then the HF Alternating Current (AC) flowing through the Linear Conductor fraction (73) produces a looped ortho-radial magnetic flux, generating a Conductor HF Magnetic Flux Loop (76), creating a HF Core Transverse Magnetic Field (HFCMF), which is substantially perpendicular to the facing HF Active Pad (29). This causes an Induced Current Loop (43) on the surface of the Active Ring (71) of the HF Active Pad (29). This Induced Current Loop (43) emits a multitude of HF magnetic flux loops that produce topologically ordered Material Eddy Currents (14) all oriented along an axis substantially parallel to the plane of the facing HF Active Pad (29) in close proximity directly above.

[0074] It is also known that a circular coil supplied with a current produces a bundle of magnetic field lines, in the form of a multitude of magnetic flux loops parallel to the axis of the circular coil, and passing through its center.

[0075] With reference to figure [ Fig. 4 ], it is understood that when the EMAT (1) is used in Receiving Mode (RM), then the component of the Material Eddy Currents (14) parallel to the Stacking Plane (27) generated at the surface of the material, under the influence of an external ultrasonic source, induce a Material RF Magnetic Flux Loop (77), creating a RF Core Transverse Magnetic Field (HFTMF) substantially perpendicular to the Active Ring (71) of the RF Active Pad (29) facing these Material Eddy Currents (14). This creates an Induced Current Loop (43) inside its Active Pad Skin (48). The Induced Current Loop (43) longitudinally surrounding this HF Active Plate (29) then emits a multitude of HF magnetic flux loops which encircle the fraction of Linear Conductor (73) which is tangent to it along an axis parallel to a part of the perimeter of this HF Active Plate (29).This inductively generates a Secondary Ultrasonic Electrical Signal (88) which creates an HF Alternating Current (AC) in the Linear Conductor fraction (73).

[0076] According to a preferred embodiment of the invention which appears in figure [ Fig. 3 ] and to the figure [ Fig. 6 ], the HF Electric Coil (6) is a Meander Circuit (74). It has a multitude of (at least two) fractions of Linear Conductor (73) (four are shown in the figure [ Fig. 6 ]). They are parallel and adjacent to each other. The multitude of these Linear Conductor fractions (73) of the Meander Circuit (74) are positioned successively in proximity to, and directly above, a Circuit Face Edge (72) of one of the HF Active Plates (29), located in the Second Edge Face (37) of the Matrix (23) facing the HF Electric Coil (6). They are configured so that the HF Alternating Current (AC) successively flowing through each of the parallel and adjacent Linear Conductor fractions (73) of the Meander Circuit (74) is oriented in alternating opposite directions. It is observed that an HF Magnetic Flux Loop of Conductor (76) substantially perpendicularly surrounds each Linear Conductor fraction (73) of the Meander Circuit (74), and penetrates substantially perpendicularly into the interior of the HF Active Plate (29) facing it. It is also noted that this provision has the following characteristics.The Linear Conductor fractions (73) of the Meander Circuit (74) and the Perforated Matrix Laminated Magnetic Core (22) are configured such that when the EMAT (1) is in Emission Mode (EM), two neighboring HF Active Plates (29), surmounted by two neighboring Linear Conductor fractions (73), are traversed in their Active Plate Skin (48) by two neighboring Induced Current Loops (43). They are each composed of an HF alternating electric current rotating in an opposite Direction of Rotation (78), around the Opening Axis (40) passing through their Magnetic Via Holes (41), one being clockwise, while the other is counterclockwise.

[0077] Referring to figure [ Fig. 1 ], it is seen that the Opening Depth (Od) of the Grooved Cylindrical Opening (39) of the Perforated Matrix Laminated Magnetic Core (22), along its Opening Axis (40), is substantially equal and consistent with a First Transverse Dimension (FTd) of the HF Electric Coil (6) of the EMAT (1). In addition, the grooved Second Edge Face (37) of its Perforated Matrix Laminated Magnetic Core (22), facing the HF Electric Coil (6), has a transverse dimension, in a direction perpendicular to the Opening Axis (40) of the Matrix (23), which is substantially equal and consistent with a Second Transverse Dimension (STd) of the HF Electric Coil (6) of the EMAT (1).

[0078] According to a preferred configuration of implementation of the invention, which appears in figure [ Fig. 5 ], the Geometric Dimensions of Sheet (79) of the Thin Sheets (24) perforated from its Matrix (23) and the combined geometric dimensions of its Perforated Matrix Laminated Magnetic Core (22) are selected to be decorrelated from the wavelengths of the main harmonics of the HF Emitted Electromagnetic Field (HFEMF). This understandably prevents mechanical resonance of its Perforated Matrix Laminated Magnetic Core (22) at the ultrasonic operating frequency of the EMAT (1).

[0079] According to another preferred configuration of implementation of the invention, the Geometric Sheet Dimensions (79) of the Thin Sheets (24) perforated with its Perforated Matrix Laminated Magnetic Core (22) are chosen in such a way that, at the ultrasonic operating frequency of the EMAT (1), they are either much smaller than the wavelengths of the ultrasonic waves generated in these Thin Sheets (24), or, substantially equal to an odd number of quarters of the wavelengths of the ultrasonic waves generated in these Thin Sheets (24).

[0080] According to another preferred configuration of the invention, described in figure [ Fig. 2 ], the grooved First Edge Face (36) of the Perforated Matrix Laminated Magnetic Core (22), facing the Inspected Material (3) and parallel to the Grooved Cylindrical Opening (39) is either covered or covered with an Insulating Layer (81) (as shown), made of an electrically insulating material. One of the faces of the Insulating Layer (81) is arranged opposite the Grooved Cylindrical Opening (39), and covers the edge belonging to the First Edge Face (36), of the perimeter of each of the HF Active Platelets (29).

[0081] The EMAT (1) of the invention, and its variants set forth above, provide a technical solution to the technical problem (a) above. This EMAT (1) increases the transmission of the energy of the HF Emitted Electromagnetic Field (HFEMF). It maximizes the HF magnetic coupling and minimizes the flux leakage of the HF Emitted Electromagnetic Field (HFEMF), between the HF Electric Coil (6) and the Eddy Currents of the Material (14) generated on the surface of the Inspected Material (3). It ensures a surface topological homogeneity of the efficiency of this high-frequency electromagnetic coupling between the HF Electric Coil (6) and the inspected Eddy Currents of the Material (14) facing the transducer. It operates at high temperatures of the Inspected Material (3) above 1000°C.

[0082] Referring to figure [ Fig. 8 ], a Laser-EMAT Probe (LEMAT) (82) is shown, for inspecting an Inspected Material (3), by receiving an ultrasonic signal from this Inspected Material (3). The LEMAT comprises the combination of: i) an Electromagnetic Acoustic Transducer (EMAT) (1) according to the invention as described above, and ii) a Laser Source (84). The EMAT (1) is configured in Reception Mode (RM), to receive a Secondary Ultrasonic Electrical Signal (88) from the Inspected Material (3). the HF Electrical Coil (6) is configured as an HF Electromagnetic Receiver (18). As shown in FIG. [ Fig. 4 ], this Secondary Ultrasonic Electrical Signal (88) is electrically induced by an HF Emitted Electromagnetic Field (HFEMF) emitted by the Inspected Material (3), generated by Eddy Currents of the Material (14) produced in the Inspected Material (3) by Secondary Ultrasonic Waves (21). These Eddy Currents of the Material (14) are representative of the surface and / or internal Discontinuities (2) of the Inspected Material (3). As shown in figure [ Fig. 8 ], the Perforated Matrix Laminated Magnetic Core (22) is located between the RF Electric Coil (6) of the EMAT (1) and the local surface of the Inspected Material (3). It directly faces the RF Electric Coil (6). It maintains a Protective Gap (83) between the Inspected Material (3) and the RF Electric Coil (6). It reduces the magnetic reluctance of the EMAT (1). It is actively thermodynamically protected from the high temperatures and harsh surface conditions of the Inspected Material (3). The Laser Source (84) is configured to fire a high-energy Laser Beam (85) at a Firing Point (86) on the surface of the Inspected Material (3). The Laser Beam (85) generates Primary Ultrasonic Waves (17) propagating on the surface and / or inside the Inspected Material (3).This causes the generation of Secondary Ultrasonic Waves (21) resulting from the echoes of the interactions of the Primary Ultrasonic Waves (17) with the discontinuities (2) on and / or inside the Inspected Material (3). These Secondary Ultrasonic Waves (21) propagate on the surface and / or inside the Inspected Material (3). They cause the generation of Eddy Currents of the Material (14) on the surface of the Inspected Material (3) induced by the mechanical vibrations of the Secondary Ultrasonic Waves (21) under the influence of the Static Magnetic Field (SMF) generated by the Magnet (4) of the EMAT (1). This causes the induction of an HF Emitted Electromagnetic Field (HFEMF) emitted by the Eddy Currents of the Material (14) present on the surface of the Inspected Material (3), representative of the geometry and position of the Discontinuities (2) of the surface and internal to the Inspected Material (3).The processing of this HF Emitted Electromagnetic Field (HFEMF) through the EMAT (1) generates the Secondary Ultrasonic Electrical Signal (88) in the HF Electrical Coil (6).

[0083] Referring to figure [ Fig. 4 ], or the EMAT (1) is configured in Reception Mode, it is observed that the Laser-EMAT Probe (LEMAT) (82) has the following technical characteristics. A multitude of remote Induced Current Loops (43) are induced, by the HF Emitted Electromagnetic Field (HFEMF) emitted by the Eddy Currents (14) in the Inspected Material (3) under the influence of the Laser Source (84), inside the Active Wafer Skin (48) on the Peripheral Edges (33) of each HF Active Wafer (29) of the Perforated Matrix Laminated Magnetic Core (22). As shown in figure [ Fig. 6 ], these induced Current Loops (43) of each HF Active Pad (29) (or group) are distant from each other. These Eddy Current Loops (43), surround and rotate around the Active Ring (71) magnetically, surrounding the Magnetic Via Holes (41) of the HF Active Pad (29). They are located between the First Edge Face (36) facing the Inspected Material (3) and the Second Edge Face (37) facing the HF Electric Coil (6). They are positioned substantially perpendicular to these two Edge Faces (36, 37).

[0084] It is understandable that in such a LEMAT (82), a double combined and interactive physical effect occurs inside the Perforated Matrix Laminated Magnetic Core (22). On the one hand, as it appears [ Fig. 4 ], each of the multiple discrete and parallel Induced Current Loops (43) of each hollowed-out HF Active Plate (29) (or group), separately generates a high-frequency magnetic field. It separately and locally increases the high-frequency magnetic coupling between - a Local Active Fraction (44) of the Inspected Surface (8) facing the First Edge Face (36), - and the HF Electric Coil (6). This homogenizes the high-frequency coupling, and participates by mutualization in the overall reduction of the high-frequency magnetic reluctance of the EMAT (1). On the other hand, as appears [ Fig. 5 ], the Internal Perimeter (45) of each Magnetic Via Hole (41) in each HF Active Pad (29) of the Matrix (23), creates a free internal Thermally Conductive and Convective Surface (46) in the center of its HF Active Pad (29). This produces an internal Thermal Cooling effect to dissipate a fraction of the electrical and heat energy generated by the Armature Current Loop (43) of its specific HF Active Pad (29). And this contributes by mutualization to the improvement of the efficiency of the EMAT (1).

[0085] The LEMAT (82) of the invention provides a technical solution to the technical problem (b) above. It optimizes the resolution of the detection of surface, subsurface and deep subsurface Discontinuities (2) in a thick metal structure. It operates at high temperatures of the Inspected Material (3) above 1000°C.

[0086] Referring to figure [ Fig. 9 ], we see a 3D Multi Laser-EMAT Scanner (MLEMAT) (89), for the detection of surface and / or internal Discontinuities (2) inside a movable cylindrical Conductive Structure (90). The MLEMAT (89) comprises: a) a Conductive Structure (90) to be scanned in 3D; b) a Chassis Frame (93); c) a Multitude of Probes (96) made of at least two Laser-EMAT Probes (LEMAT) (82) according to the invention, and d) Displacement Means (97). The Conductive Structure (90) to be scanned in 3D is made of an electrically conductive Inspected Material (3). It has a cylindrical structure generated along a Structure Axis (91), and a substantially constant Structure Section (92). The Chassis Frame (93) is configured to surround the Conductive Structure (90) at a Frame Distance (Fd). Its Frame Plane (95) is substantially perpendicular to the Structure Axis (91) of the Conductive Structure (90).The Displacement Means (97) are configured to linearly displace the cylindrical Conductive Structure (90) relative to the Chassis Frame (93), along a Displacement Direction (Md), substantially combined with the Structure Axis (91).

[0087] This Multi Laser-EMAT (MLEMAT) 3D Scanner (89) has the following characteristics which appear when referring to the figure [ Fig. 10 ]. The Opening Loop (99), constituted by the virtual line joining the centers of each successive Grooved Cylindrical Opening (39) of the Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the Laser-EMAT Probes (LEMAT) (82) of the MLEMAT (89), encircles the Conductive Structure (90).

[0088] It is also seen that the Multitude of Probes (96) made of Laser-EMATs (82) are fixed on the Chassis Frame (93), positioned and configured in a position such that the juxtaposition of the multitude of neighboring First Edge Faces (36) of the Perforated Matrix Laminated Magnetic Cores (22) of each of the adjacent Laser-EMAT (LEMAT) Probes (82), facing the Inspected Material (3), are substantially contiguous to each other, constitutes a substantially continuous grooved Inspection Ring (100). This grooved Inspection Ring (100) surrounds and covers the perimeter of the Conductive Structure (90), in a Structure Section (92) of the Conductive Structure (90) neighboring the Frame Plane (95).

[0089] In a preferred embodiment of the Multi Laser-EMAT (MLEMAT) 3D Scanner (89), which appears with reference to FIG. [ Fig. 11 ], the Laser Source (84) of each LEMAT (82) consists of an Optical Fiber (101), fixed on the Chassis Frame (95), having a Firing End (102) facing the Conductive Structure (90). Each Optical Fiber (101) is connected to a Laser Generator (103). This configuration of the Multi Laser-EMAT 3D Scanner (MLEMAT) (89) has the following characteristic. The Laser Firing Loop (104), constituted by the virtual line joining the Firing Ends (102) of each adjacent Laser-EMAT Probe (LEMAT) (82) of the MLEMAT (89), encircles the Conductive Structure (90) and is substantially parallel to the Opening Loop (99).

[0090] In a preferred implementation variant of the 3D Multi Laser-EMAT (MLEMAT) scanner (89) of the invention, it is operated for the detection of surface and / or internal Discontinuities (2) of a Metallurgical Slab (105). The Conductive Structure (90) is then a cylindrical Metallurgical Slab (105) movable relative to the MLEMAT (89). The Opening Loop (99), constituted by the virtual line joining the centers of each successive Grooved Cylindrical Opening (39) of the Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the Laser-EMAT (LEMAT) Probes (82) of the MLEMAT (89), encircles the movable cylindrical Metallurgical Slab (105).

[0091] In another preferred implementation of the 3D Multi Laser-EMAT Scanner (MLEMAT) (89) of the invention, it is used for the detection of surface and / or internal Discontinuities (2) of a movable cylindrical Steel Slab (105); continuously cast in a steel mill at a Casting Temperature (TS) above 1000 ° C. The HF Active Platelets (29) hollowed out of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89) are made of a Magnetic Material, for example of the ferromagnetic or ferrimagnetic type, having a Curie Temperature (TC) lower than the Casting Temperature (TS). This 3D Multi Laser-EMAT Scanner (MLEMAT) (89) has the following characteristic. As shown in FIG. [ Fig. 10 ], each Grooved Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each EMAT (1) of each adjacent LEMAT (82) of the MLEMAT (89), is connected to Cooling Means (58) generating a Heat Flux (59) of a cooling Heat Fluid (60). The Heat Fluid (60) is pushed under pressure inside each hole via (41, 57) of the Grooved Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89), at a Cooling Temperature (TF) significantly lower (by at least 50°c) than the Curie Temperature (TC) of the Magnetic Material of the hollowed-out HF Active Platelets (29).

[0092] The MLEMAT (89) of the invention, and its variants set forth above, provide a technical solution to the technical problem (c) above. This MLEMAT performs continuous 3D scanning by line of large and thick moving Conductive Structures (90), such as metallurgical slabs (105), from a single location, generating a high-resolution observed 3D map of this structure, including providing the location of deep surface and subsurface Discontinuities (2). It operates at high temperatures of the Inspected Material (3) above 1000°C.

[0093] Referring to figure [ Fig. 12 ], the Multi Laser-EMAT 3D Scanner (MLEMAT) (89) according to the invention is shown as indicated above, configured for the automatic adjustment of the dynamic parameters of the Soft Dynamic Reduction (DSR) of a Steel Slab (105) continuously cast in a steel mill at a Casting Temperature (TS) above 1000 ° C. The Steel Slab (105) is continuously pushed through a Soft Dynamic Reduction Device (DSRD), to suppress the formation of a macro-segregation zone and porosity zones inside the Steel Slab (105); this by dynamically compensating for the solidification shrinkage of the steel and interrupting the suction flow of the residual molten metal in the Central Soft Zone (106) of the Steel Slab (105).

[0094] This MLMAT (89) is coupled to a Soft Dynamic Reduction Device (DSRD) which comprises: i) a 3D Dynamic Mapping System (3DMS), generating a Dynamic 3D Map (3DM) of the casting of the Steel Slab (105); ii) a computerized DSR Optimization System (DSRM), generating Dynamic DSR Optimization Parameters (PCSD), based on the Dynamic 3D Map (3DM) and on the casting parameters; and iii) a Digital DSR Activator (ASR), dynamically adjusting the DSR Action Parameters (PASD) of the Soft Dynamic Reduction Device (DSRD), according to the PCSD generated by the DSRM.

[0095] This 3D Multi Laser-EMAT Scanner (MLEMAT) (89) has the following characteristics. The HF Electric Coils (6a, 6b, 6) of each EMAT (1a, 1b, 1) of each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89) are each connected to the 3D Dynamic Mapping System (3DMS). They transmit to it a Secondary Ultrasonic Electrical Signal (88a, 88b, 88) induced in each HF Electric Coil (6a, 6b, 6) by the Eddy Currents of the Material (14) on the Frontal Zone (110) of the Inspected Material (3) of the Steel Slab (105) locally facing each EMAT (1a, 1b, 1). The DSR Optimization System (DSRM) is equipped with Analog and Digital Processing Means (MDAN). The MDANs are configured to receive the multitude of Secondary Ultrasonic Electrical Signals (88a, 88b, 88) included in the Secondary Ultrasonic Electrical Currents (19a, 19b, 19) flowing through each HF Electrical Coil (6) in each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89).The MDANs are also configured to identify changes and disturbances in each Secondary Ultrasonic Electrical Signal (88a, 88b, 88) of each Laser-EMAT (82a, 82b, 82), caused by Discontinuities (2) in the Local Active Fraction (44a, 44b, 44) of the Inspected Material (3) facing each Laser-EMAT (82a, 82b, 82), and numerically deduce the Frontal Defect Topology (DTa, DTb, DT) in this Local Active Fraction (44a, 44b, 44).The MDANs are also configured to digitally combine the Frontal Defect Topologies (DTa, DTb, DT), and digitally generate a three-dimensional Dynamic 3D Map (3DM) physically observed by the MLEMAT of the interior of the Steel Slab casting (105), in the Frontal Zone (110) facing the Inspection Ring (100) in the Structure Section (92) of the Frame Plane (95), based on the combination and digital analysis of the combined signals of the multiple Secondary Ultrasonic Electrical Signals (88a, 88b, 88).

[0096] As shown in figure [ Fig. 10 ], the Cooling Means (58) generate a Heat Flux (59) of a Heat Fluid (60), pushed under pressure inside each hole via (41, 57) of the Grooved Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89); this at a Cooling Temperature (TF) significantly lower (by at least 50°C) than the Curie Temperature (TC) of the Magnetic Material of the hollowed-out HF Active Platelets (29).

[0097] It is understood that thanks to this MLEMAT (89), the DSR Action Parameters (PASD) of the Soft Dynamic Reduction Device (DSRD) can be dynamically adjusted in an optimal manner, based on a 3D Dynamic Mapping (3DM) of the casting of the Steel Slab (105) physically observed by the MLEMAT (89), this at a Casting Temperature (TS) greater than 1000 ° C.

[0098] Referring to figure [ Fig. 12 ], we see a variant of the Multi Laser-EMAT 3D Scanner (MLEMAT) (89) for the automatic adjustment of the dynamic parameters of the Dynamic Soft Reduction (DSR) which also allows the adjustment of the Dynamic Secondary Cooling (DSC) of a Steel Slab (105) continuously cast in a steel mill at a Casting Temperature (TS) above 1000 ° C.The MLMAT (89) is coupled to a Dynamic Secondary Cooling Device (DSCD) which further comprises a computerized DSC Optimization System (DSCM), generating Dynamic Secondary Cooling (DSC) DSC Optimization Parameters (PCSC) based on the physically observed Dynamic 3D Mapping (3DM) of the casting of the Steel Slab (105), in the Structural Section (92) of the Frame Plane (95), by combining and numerically analyzing the combined signals of the multiple Secondary Ultrasonic Electrical Signals (88a, 88b, 88) in each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89), and on the casting parameters. It also includes a Digital DSC Activator (ASC), dynamically adjusting the DSC Action Parameters (PASC) of the Dynamic Secondary Cooling (DSC) water flow, according to the PCSC generated by the DSCM, based on the 3D Dynamic Mapping (3DM) physically observed by the MLEMAT (89).

[0099] The MLEMAT (89) for automatic adjustment of DSR and / or DSC of the invention provides a technical solution to the technical problem (d) above. It provides automatic adjustment of the DSR Action Parameters (PASD) of dynamic soft reduction (DSR) and / or DSC Action Parameters (PASC) of dynamic secondary cooling (DSC), of a continuous casting of Steel Slabs (105) in a steel mill, based on the observed state of the interior of the cast Steel Slab (105). It continuously provides a Dynamic 3D Map (3DM) observed of the interior of the cast Steel Slab (105). It continuously defines in a 3D observed manner the location of the Central Soft Zone (106) in fusion of a Steel Slab (105) and its segregation defects, based on a 3D physical observation, and not simply provided by a numerical simulation prediction by a theoretical algorithm based on a mathematical model.It accurately detects the observed position of the reduction point of a cast Steel Slab (105) based on 3D physical observation. It improves the accuracy and reliability of automatic parameter adjustment of Dynamic Soft Reduction (DNS) and Dynamic Secondary Cooling (DSC) of a continuous casting of Steel Slabs (105) at temperatures above 1000°C. It can reduce segregation defects and porosity in the molten Central Soft Zone (106) area of ​​the structure of Steel Slabs (105) during the continuous casting process in a steel mill. Avantages apportés

[0100] The MLEMAT (89) for DSR and DSC of the invention offers valuable industrial advantages in the automated non-destructive testing of hot-cast steel slabs in the steel industry: a. It can operate at a Steel Slab casting temperature that can exceed 1200°C. b. It can perform continuous 3D mapping of cast Steel Slabs at a speed of up to 1 meter per second. c. It allows direct transit between steel casting and steel rolling, without the need to cool the Steel Slabs down to 100°C max to perform their NDT with common instruments. d. It saves the gas commonly used to reheat the Steel Slabs to 1200°C after NDT and before steel rolling. e. It provides continuously observed 3D mapping of cast Steel Slabs, to automatically and dynamically adjust the parameters of the continuous casting equipment. f. It continuously identifies, with high definition and reliability, all types of discontinuities (internal and surface) in the cast Steel Slabs, as well as their coordinates. g.It improves the standardization, quality control, and accuracy of quality grading of produced Steel Slabs, and increases the added value of continuous casting. h. It provides automatic, real-time fine-tuning of dynamic parameters for DSR and / or DSC of a continuous casting of Steel Slabs. i. It provides early detection of discontinuities in Steel Slabs, and automatically allows their possible referral to previous production processes based on their quality, resulting in considerable savings in time, energy, materials, and labor. j. It increases the performance and productivity of a steel casting machine by 7% or more. k. It can be installed without significant structural changes in the existing casting equipment of a steel mill, as it is compact. Application industrielle

[0101] The invention has industrial applications in the metallurgical industry, and in particular in the steel industry, for quality testing and automatic adjustment of the DSR and / or DSC of hot steel slabs at more than 1000°C in continuous casting lines of steel mills, and for quality control of semi-finished products of the steel industry. The invention also has industrial applications in the railway industry, for high-speed control of railway rails, and control of wheel sets. The invention also has industrial applications in the oil and gas industry, chemistry and nuclear industry, for on-line testing of pipes and pipelines, drilling devices and equipment in hazardous and / or high-temperature environments.

[0102] Although only certain features of the invention have been illustrated and described herein, numerous modifications and changes will occur to those skilled in the art within the scope of the appended claims.

Claims

1. An Electromagnetic Acoustic Transducer (EMAT) (1) for the detection of surface and internal Discontinuities (2) in an electrically conductive Inspected Material (3), comprising: a. At least one Magnet (4) or an electromagnet, configured to generate a Static Magnetic Field (SMF) or quasi-static field in the Inspected Material (3); b. At least one HF Electrical Coil (6), this being of the type i. either configured as an HF Electromagnetic Transmitter (9) of an Emitted HF Electromagnetic Field (HFEMF), if the EMAT (1) is used in Transmission Mode (EM), and then connected to the output of at least one Alternating Current Source (11), causing an HF Alternating Current (AC) at ultrasonic frequency to flow in the HF Electrical Coil (6), • inducing the Emitted HF Electromagnetic Field (HFEMF) in the direction of the Inspected Material (3), • producing Eddy Currents (14) on the surface of the Inspected Material (3), • generating ultrasonic frequency Lorentz Forces (15) in the Inspected Material (3) through interaction of the Eddy Currents (14) with the Static Magnetic Field (SMF) and / or a Magnetostriction, • the perturbation of which generates Primary Ultrasonic Waves (17) directly in the Inspected Material (3); ii. and / or configured as an HF Electromagnetic Receiver (18), if the EMAT (1) is used in Reception Mode (RM), and then traversed by a Secondary Ultrasonic Electric Signal (88) at ultrasonic frequency, • generated by an Emitted HF Electromagnetic Field (HFEMF), • induced by Eddy Currents (14) produced on the Inspected Surface (8) of the Inspected Material (3) by Secondary Ultrasonic Waves (21), under the influence of an ultrasonic source, interacting with the Static Magnetic Field (SMF), and representative of surface and internal Discontinuities (2) of the Inspected Material (3); c. At least one Perforated Matrix Laminated Magnetic Core (22), configured to concentrate and direct the Emitted HF Electromagnetic Field (HFEMF) in the direction or from the Inspected Material (3); of the type comprising a sandwich Matrix (23), i. composed of a multitude of Thin Laminated Sheets (24) stacked periodically along the Matrix Axis (25), these Thin Sheets (24) being positioned between the two main Matrix Faces (26) of the Matrix (23), parallel to its Stacking Plane (27), ii. having multiple adjacent lateral Border Faces (35), extending substantially perpendicular to the Stacking Plane (27) and perpendicular to the Matrix Axis (25); • one of them, the First Border Face (36) of the Matrix (23), facing the Inspected Surface (8) of the Inspected Material (3), • and the other, the Second Border Face (37) of the Matrix (23) being located substantially opposite to the First Border Face (36), and facing the HF Electrical Coil (6); iii. each Thin Laminated Sheet (24) of the Matrix (23) • having a spatial geometry and lateral dimensions similar to those of the neighbouring Thin Sheets (24) in the Matrix (23); and, • having two main lateral Sheet Surfaces (32), parallel to the Stacking Plane (27); iv. whose successive adjacent Peripheral Edges (33) combined of each Thin Sheet (24) constitute a grooved Border Surface (34) of the sandwich Matrix (23), surrounding the Matrix Axis (25), and, v. defining a Core Axis (38) of the Matrix (23), substantially joining the centers of the First Border Face (36) and the Second Border Face (37); positioned substantially perpendicular to the Matrix Axis (25); vi. This sandwich Matrix (23) comprising at least a First Multitude (28) of Active HF Plates (29) (or groups of such plates), each of them • being isolated from each other, • externally incorporating an electrically conductive material; and / or being externally covered with an electrically conductive layer on its Peripheral Edges (33), and, • internally incorporating a ferromagnetic or ferrimagnetic Magnetic Material, and a Curie Temperature (TC); This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in combination by the fact that: d. It includes a Grooved Cylindrical Opening (39), i. passing through each Thin Sheet (24) of the Matrix (23), along an Opening Axis (40) of the Matrix (23), substantially parallel to the Matrix Axis (25) and perpendicular to the Core Axis (38), and, ii. leading to each of the two lateral Matrix Faces (26); e. It includes a multitude of Magnetic Via Holes (41), i. of similar cross-sectional dimensions, ii. drilled through and substantially in the center of each of the multiple Active HF Plates (29) thus hollowed out of the Matrix (23), along an axis substantially parallel to the Inspected Surface (8), iii. having a Via Hole Longitudinal Envelope (42), along the Opening Axis (40) of the Matrix (23), whose closed lateral perimeter, and, iv. aligned to form the Grooved Cylindrical Opening (39) by their alignment; and, f. It includes a multitude of closed Induced Current Loops (43) which, when the EMAT (1) is in operation, are i. induced by the Emitted HF Electromagnetic Field (HFEMF), which is either emitted by the ultrasonic frequency HF Alternating Current (AC) in the HF Electrical Coil (6), and / or emitted by the ultrasonic frequency Eddy Currents (14) in the Inspected Material (3), ii. located inside the Active Plate Skin (48) of the periphery of each Active HF Plate (29) of the Perforated Matrix Laminated Magnetic Core (22), iii. arranged according to a Loop Mapping (LM), defining the topology and relative positions of all the Induced Current Loops (43); g. Each Magnetic Via Hole (41) in each Active HF Plate (29) is located between - the First Border Face (36) facing the Inspected Surface (8), and, the Second Border Face (37) facing the HF Electrical Coil (6); h. Each Magnetic Via Hole (41) of the Grooved Cylindrical Opening (39) is internally free of any hard material, and in particular free of any electrical conductor passing through it; i. The Loop Mapping (LM) is topologically discrete and consists of a multitude of discretely distributed Induced Current Loops (43) of Active HF Plates (29) (or groups of such Active Plates) distant from each other; j. The distant Induced Current Loops (43) (or groups of such Loops), i. are induced inside the Active Plate Skin (48) on the Peripheral Edges (33) of the Active HF Plates (29), ii. are each arranged according to a loop plane parallel to the Stacking Plane (27), and substantially perpendicular to the surface of the Inspected Material (3); iii. are substantially parallel, and separated from each other, between their respective Active HF Plates (29), iv. encircle the Magnetic Via Holes (41) of their respective Active HF Plates (29) and rotate around; and, k. Each Core Spacing Slice (49) of the Perforated Matrix Laminated Magnetic Core (22) and its surface, located between two adjacent Active HF Plates (29) (or group), is free of Induced Current Loops (43); So that a combined and interactive double physical effect occurs inside the Perforated Matrix Laminated Magnetic Core (22): I. Each of the multiple parallel and topologically discrete Induced Current Loops (43) of each hollowed Active HF Plate (29), i. separately and locally generates a high-frequency magnetic field, ii. separately and locally increases the discrete and selective high-frequency magnetic coupling between - a narrow Local Active Fraction (44) of the Inspected Surface (8) facing the Active HF Plate (29), - and the HF Electrical Coil (6), and, iii. participates through mutualization in the overall reduction of the high-frequency magnetic reluctance of the EMAT (1); m. The Internal Perimeter (45) of each Magnetic Via Hole (41) in each Active HF Plate (29) of the Matrix (23), i. creates a free internal Thermo-Conductive and Convective Surface (46) in the center of its specific Active HF Plate (29), ii. produces an internal Thermal Cooling effect to dissipate a fraction of the local electric and calorific energy generated by the Induced Current Loop (43) of its specific Active HF Plate (29), and, iii. participates through mutualization in the improvement of the efficiency of the EMAT (1).

2. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, in which: a. Each hollowed Active HF Plate (29) of the Matrix (23) (or group of such Active Plates) is separated from its neighbors at the level of the adjacent Core Spacing Slices (49) by at least one sheet of a Second Multitude (54) of Passive Plates (53) made of an electrically insulating material; b. Each Passive Plate (53) is perforated by a Spacer Via Hole (57); and, c. Each Passive Plate (53) is positioned and configured such that: i. the Magnetic Via Holes (41) in the First Multitude (28) of Active HF Plates (29) of the Matrix (23), as well as the Spacer Via Holes (57) of the Second Multitude (54) of Passive Plates (53) of the Matrix (23), ii. are aligned parallel to the Matrix Axis (25), to form by their alignment and combination the Grooved Cylindrical Opening (39); This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in combination in that: d. Each Spacer Via Hole (57) in each Passive Plate (53) is located between: i. the First Border Face (36) facing the Inspected Material (3), and, ii. the Second Border Face (37) facing the HF Electrical Coil (6); and, e. Each Spacer Via Hole (57) of its Grooved Cylindrical Opening (39): i. is internally free of any hard material, ii. and in particular is free of any electrical conductor passing through it; So that the internal perimeter of each Spacer Via Hole (57) in each Passive Plate (53) of the Matrix (23) creates: f. a free internal Thermo-Conductive and Convective Surface (46) in the center of the Passive Plate (53), g. which produces an internal Thermal Cooling effect in this Spacer Via Hole (57) to dissipate a fraction of the electrical and calorific energy generated by the Induced Current Loops (43) of the neighboring Active HF Plates (29), and participates through mutualization in the improvement of the efficiency of the EMAT (1).

3. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 2, characterized in that, for at least one Passive Plate (53) and preferably for all: a. The Peripheral Edges (33) of their perimeters are free of any conductive material covering their surfaces; b. So that the Grooved Border Surface (34) of the Perforated Matrix Laminated Magnetic Core (22) is not continuously covered and / or composed of an electrically conductive layer, but on the contrary is composed of an alternating edge-to-edge arrangement of, on one hand, conductive rings around the Active HF Plates (29) and, on the other hand, insulating rings around the Passive Plates (53).

4. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, of the type also comprising: a. Cooling Means (58) i. generating a Heat Flow (59) of a Cooling Fluid (60) at a Cooling Temperature (TF), ii. configured so that the Heat Flow (59) is forced to pass through the Grooved Cylindrical Opening (39) of the Matrix (23); This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in combination in that: b. The Heat Flow (59) is configured: i. to successively pass through at least one Magnetic Via Hole (41) of the First Multitude (28) and, alternatively, at least one Spacer Via Hole (57) of the Second Multitude (54), ii. to sweep the entire Surface of the Wall of the Hole (62) of each successive Magnetic Via Hole (41) and / or each Spacer Via Hole (57) of the Matrix (23), iii. to increase the internal thermal cooling effect in each Active HF Plate (29) of the Matrix (23); each being subjected to an Induced Current Loop (43) and heat dissipation; and, c. The Cooling Temperature (TF) of the Heat Flow (59) is more than 50° C lower than the Curie Temperature (TC) specific to the Magnetic Material of each hollowed Active HF Plate (29).

5. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 4, characterized in that, in combination: a. At least one (and preferably a multitude of) Thin Sheets (24) of the Perforated Matrix Laminated Magnetic Core (22): i. is either perforated by a Cushion Hole (63), or, provided with a Cushion Notch (64), passing through the Annular Wall (65) between their Via Holes (41, 57), and the portion of their First Border Face (36) facing the Inspected Material (3), in a direction parallel to the Stacking Plane (27), ii. to create a Cushion Recess (66) between the Via Holes (41, 57) of the Thin Sheet (24) and the First Border Face (36) facing the Inspected Material (3); and, b. The Cooling Means (58) are configured to: i. extract a Cushion Fluid Flow (67) from the Heat Flow (59) passing through the Via Holes (41, 57), ii. flow this extracted Cushion Fluid Flow (67) under pressure through the Cushion Recess (66), iii. create a Lifting Air Cushion (70) between the Perforated Matrix Laminated Magnetic Core (22) and the Inspected Material (3), at the level of the Cushion Recess (66) facing the Inspected Material (3), and, iv. thus lift the Perforated Matrix Laminated Magnetic Core (22) from the Inspected Material (3) by a Cushion Spacing (68).

6. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that, in combination: a. The two external Sheet Surfaces (32) of the two outermost Thin Sheets located on the Matrix Faces (26) are either composed of, or covered by a Conductive Covering Layer (69), of an electrically conductive material; b. This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in combination in that: c. A via hole of similar transverse dimensions to those of the Magnetic Via Holes (41) is perforated through each of the two Conductive Covering Layers (69); d. The multiple Thin Sheets (24) and the two Conductive Covering Layers (69) of the Matrix (23) are positioned relative to each other so that their multiple via holes are aligned to form by continuity the Grooved Cylindrical Opening (39).

7. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that: a. The perimeter of each Magnetic Via Hole (41) in each Active HF Plate (29) is rectangular.

8. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 7, characterized in that, in combination: a. The center of each Magnetic Via Hole (41) is substantially located at the center of gravity of its Active HF Plate (29); and, b. The perimeter of each hole of each Magnetic Via Hole (41) is arranged substantially at a constant Ring Distance (Rd) from the perimeter of its Active HF Plate (29); c. So that each Active HF Plate (29) is topologically configured as a rectangular Active Ring (71), thermodynamically cooled from the heating of the Induced Current Loop (43) generated around it.

9. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in combination in that: a. the Second Border Face (37) of the Perforated Matrix Laminated Magnetic Core (22) directly faces the HF Electrical Coil (6), and, b. no Magnet is positioned between - on one side the Second Border Face (37) of the Matrix (23) and - on the other side the HF Electrical Coil (6).

10. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in combination in that: a. the orientation, pitch, size, and shape of each Circuit-Facing Edge (72) of each Active HF Plate (29), located in the Second Border Face (37) of the Matrix (23), and facing the HF Electrical Coil (6); b. are consistent and correlated with the geometric parameters, including orientation, pitch, size, and shape, of the Conductor Fractions (75) of the HF Electrical Coil (6) successively facing each of these Circuit-Facing Edges (72).

11. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 10, wherein: a. The HF Electrical Coil (6) has at least one part of Linear Conductor (73); and, b. This part of Linear Conductor (73) is positioned near and directly above an Edge Circuit Surface (72), and is tangent along an axis parallel to this neighboring part of the perimeter of an HF Active Wafer (29) located in the Second Edge Surface (37) of the Matrix (23) facing the HF Electrical Coil (6); This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in combination in that the fraction of Linear Conductor (73) and the Perforated Matrix Laminated Magnetic Core (22) are configured such that, when the EMAT (1) is in operation, an Induced Current Loop (43) c. is induced in the Skin of the Active Wafer (48) around the perimeter of the HF Active Wafer (29), d. surrounds its Magnetic Via Hole (41), e. so that it achieves a selective local HF magnetic coupling between: i. an HF Alternating Current (AC) driven in the Linear Conductor (73) extending over and along the perimeter of the HF Active Wafer (29), and, ii. the Eddy Currents of the Material (14) generated in the narrow Local Active Fraction (44) of the Inspected Surface (8) facing the HF Active Wafer (29).

12. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 11, wherein: a. The HF Electrical Coil (6) is of the type with multiple (at least two) fractions of Linear Conductor (73); parallel and adjacent to each other, like a Meander Circuit (74), b. These multiple parallel fractions of Linear Conductor (73) are i. positioned successively near and directly above an Edge Circuit Surface (72) of an HF Active Wafer (29), located in the Second Edge Surface (37) of the Matrix (23) facing the HF Electrical Coil (6), and, ii. iconfigured so that the alternating current (AC) flowing successively through parallel and adjacent fractions of Linear Conductor (73) is oriented in alternating opposite directions; c. At least one HF Magnetic Flux Loop of Conductor (76) substantially perpendicularly surrounds each fraction of Linear Conductor (73), and penetrates substantially perpendicularly inside the HF Active Wafer (29) facing it; This Electromagnetic Acoustic Transducer (EMAT) (1) being characterized in that the fractions of Linear Conductor (73) of the HF Electrical Coil (6) and the Perforated Matrix Laminated Magnetic Core (22) are configured such that when the EMAT (1) is in Transmission Mode (EM): d. Two neighbouring HF Active Wafers (29), surmounted by two neighboring fractions of Linear Conductor (73), e. Are traversed in their Skin of Active Wafer (48) by two neighboring Induced Current Loops (43), each composed of an HF alternating electric current rotating in an opposite Rotation Direction (78), around the Opening Axis (40) passing through their Magnetic Via Holes (41), one being clockwise, while the other is counterclockwise.

13. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that, in combination: a. the Opening Depth (Od) of the Slotted Cylindrical Opening (39) of its Perforated Matrix Laminated Magnetic Core (22), along its Opening Axis (40), b. is substantially equal and consistent with a First Transverse Dimension (FTd) of at least one HF Electrical Coil (6) of the EMAT (1).

14. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that, in combination: a. the slotted Second Edge Surface (37) of its Perforated Matrix Laminated Magnetic Core (22), facing an HF Electrical Coil (6), b. has a transverse dimension, in a direction perpendicular to the Opening Axis (40) of the Matrix (23), that is substantially equal and consistent with a Second Transverse Dimension (STd) of at least one HF Electrical Coil (6) of the EMAT (1).

15. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that, in combination, the geometric dimensions of the perforated Thin Sheets (24) of its Perforated Matrix Laminated Magnetic Core (22) and / or the combined geometric dimensions of its Perforated Matrix Laminated Magnetic Core (22) are selected to: a. Be decorrelated from the wavelengths of the main harmonics of the HF Electromagnetic Field (HFEMF) emitted, and, b. Prevent mechanical resonance of its Perforated Matrix Laminated Magnetic Core (22) at the ultrasonic operating frequency of the EMAT (1).

16. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, characterized in that, in combination, the geometric dimensions of the perforated Thin Sheets (24) of its Perforated Matrix Laminated Magnetic Core (22) are, at the ultrasonic operating frequency of the EMAT (1): a. Either less than the wavelengths of the ultrasonic waves generated in these Thin Sheets (24), b. Or, substantially equal to an odd number of quarters of the wavelengths of the ultrasonic waves generated in these Thin Sheets (24).

17. An Electromagnetic Acoustic Transducer (EMAT) (1) according to claim 1, of the type where the grooved First Edge Surface (36) of the Perforated Matrix Laminated Magnetic Core (22), facing the Inspected Material (3) and parallel to the Slotted Cylindrical Opening (39) is covered with an Insulating Layer (81), made of an electrically insulating material; this EMAT (1) being characterized in combination in that furthermore one of the faces of the Insulating Layer (81) a. Is disposed on the side of the Slotted Cylindrical Opening (39), and, b. overs, on the edge belonging to the First Edge Surface (36), the perimeter of each perforated HF Active Wafer (29).

18. A Laser-EMAT Probe (LEMAT) (82), for inspecting a conductive Inspected Material (3), by receiving an ultrasonic signal from this Inspected Material (3), comprising the combination of: a. An Electromagnetic Acoustic Transducer (EMAT) (1) according to any one of claims 1 to 17, i. configured in Reception Mode (RM), to receive an ultrasonic signal from the Inspected Material (3), ii. whose HF Electric Coil (6) is configured as an HF Electromagnetic Receiver (18), • induced by an Emitted HF Electromagnetic Field (HFEMF) emitted by the Inspected Material (3), • generated by Eddy Currents From The Material (14), produced in the Inspected Material (3) by Secondary Ultrasonic Waves (21), representative of surface and / or internal Discontinuities (2) of the Inspected Material (3), and, iii. whose Perforated Matrix Laminated Magnetic Core (22) • is located between the HF Electric Coil (6) of the EMAT (1) and the local surface of the Inspected Material (3), and, • directly faces the HF Electric Coil (6); b. A Laser Source (84) configured to: i. fire a high-energy Laser Beam (85) at a Shooting Point (86) on the surface of the Inspected Material (3), ii. generate ultrasonic waves producing Primary Ultrasonic Waves (17) propagating on the surface and / or inside the Inspected Material (3), and, iii. cause the generation of Secondary Ultrasonic Waves (21) resulting from interactions of Primary Ultrasonic Waves (17) with Discontinuities (2) on and / or inside the Inspected Material (3), propagating on the surface and / or inside the Inspected Material (3), iv. cause the generation of Eddy Currents From The Material (14) on the surface of the Inspected Material (3), induced by the mechanical vibrations of Secondary Ultrasonic Waves (21) under the influence of the Static Magnetic Field (SMF) generated by the Magnet (4) of the EMAT (1), and, v. cause the induction of an Emitted HF Electromagnetic Field (HFEMF) emitted by the Eddy Currents From The Material (14) present on the surface of the Inspected Material (3), representative of the geometry and position of the surface and internal Discontinuities (2) of the Inspected Material (3); This Laser-EMAT Probe (LEMAT) (82) being characterized in that: c. A multitude of parallel and spaced Induced Current Loops (43), i. are induced by the Emitted HF Electromagnetic Field (HFEMF) emitted by the Eddy Currents From The Material (14) at ultrasonic frequency of the Inspected Material (3) under the influence of the Laser Source (84), ii. inside the Active Lamella Skin (48) on the Peripheral Edges (33) of each HF Active Lamella (29) of the Perforated Matrix Laminated Magnetic Core (22); d. These Induced Current Loops (43) of each HF Active Lamella (29) i. are spaced apart from each other, ii. are each arranged in a loop plane parallel to the Stacking Plane (27), and substantially perpendicular to the surface of the Inspected Material (3); iii. surround and rotate around the Magnetic Via Holes (41) of their HF Active Lamella (29); iv. are located between the First Edge Face (36) facing the Inspected Material (3) and the Second Edge Face (37) facing the HF Electric Coil (6), and, v. are positioned substantially perpendicularly to the two Edge Faces (36, 37); So that a combined and interactive double physical effect occurs inside the Perforated Matrix Laminated Magnetic Core (22): e. Each of the multiple parallel and topologically discrete Induced Current Loops (43) of each HF Active Lamella (29), i. separately generates a high-frequency magnetic field, ii. separately, locally, and discretely increases the high-frequency magnetic coupling between - a narrow Local Active Fraction (44) of the Inspected Surface (8) facing its HF Active Lamella (29), - and the HF Electric Coil (6), and, iii. homogenizes the high-frequency coupling, and participates by mutualization in the overall reduction of high-frequency magnetic reluctance, and in the increase of the resolution of the EMAT (1); f. The Inner Perimeter (45) of each Magnetic Via Hole (41) in each HF Active Lamella (29) of the Matrix (23), i. creates a free internal Thermo-Conductive and Convective Surface (46) at the center of its HF Active Lamella (29), and, ii. produces an internal Thermal Cooling effect to dissipate a fraction of the local electrical and thermal energy generated by the Induced Current Loop (43) of its specific HF Active Lamella (29), and, iii. participates by mutualization in the improvement of the efficiency of the EMAT (1).

19. A Multi Laser-EMAT 3D Scanner (MLEMAT) (89), for detecting surface and / or internal Discontinuities (2) inside a moving cylindrical Conductive Structure (90), comprising the combination of: a. A Conductive Structure (90) to be 3D scanned, i. made of an electrically conductive Inspected Material (3), ii. having a cylindrical structure generated along a Structure Axis (91), iii. having a substantially constant Structure Section (92); b. A Frame Chassis (93), i. configured to surround the Conductive Structure (90) at a Frame Distance (Fd), ii. whose Frame Plane (95) is substantially perpendicular to the Structure Axis (91) of the Conductive Structure (90); c. A Multitude of Probes (96) made of at least two Laser-EMAT Probes (LEMAT) (82) according to claim 18, each of the Laser-EMAT Probes (82) being i. fixed on the Frame Chassis (93), and, ii. positioned and configured such that each of the First Edge Faces (36) of their Perforated Matrix Laminated Magnetic Core (22) faces the Conductive Structure (90); d. Movement Means (97) configured to move linearly i. the cylindrical Conductive Structure (90) relative to the Frame Chassis (93), ii. in a Moving Direction (Md), substantially coinciding with the Structure Axis (91); This Multi Laser-EMAT 3D Scanner (MLEMAT) (89) being characterized in that: e. the Loop of Openings (99), i. constituted by the virtual line joining the centers of each successive Slotted Cylindrical Opening (39) of the Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the Laser-EMAT Probes (LEMAT) (82) of the MLEMAT (89), ii. encircles the Conductive Structure (90).

20. A Multi Laser-EMAT 3D Scanner (MLEMAT) (89) according to claim 19, characterized in combination in that its Multitude of Probes (96) made of Laser-EMAT (82) are fixed on the Frame Chassis (93) positioned and configured in a position such that: a. The juxtaposition of the multitude of adjacent First Edge Faces (36) of the Perforated Matrix Laminated Magnetic Cores (22) of its adjacent Laser-EMAT Probes (LEMAT) (82), facing the Inspected Material (3), are substantially contiguous with each other; and, b. It forms a substantially continuous slotted Inspection Ring (100), surrounding and covering the perimeter of the Conductive Structure (90), in a Structure Section (92) of the Conductive Structure (90) adjacent to the Frame Plane (95).

21. A Multi Laser-EMAT 3D Scanner (MLEMAT) (89) according to claim 19, of the type in which a. The Laser Source (84) of each LEMAT (82) consists of an Optical Fiber (101), fixed on the Frame Chassis (95), having a Shooting End (102) facing the Conductive Structure (90); and, b. Each Optical Fiber (101) is connected to a Laser Generator (103); This Multi Laser-EMAT 3D Scanner (MLEMAT) (89) being characterized in that the Laser Shooting Loop (104), c. constituted by the virtual line joining the Shooting Ends (102) of each adjacent Laser-EMAT Probe (LEMAT) (82) of the MLEMAT (89), d. encircles the Conductive Structure (90) and is substantially parallel to the Loop of Openings (99).

22. A Multi Laser-EMAT 3D Scanner (MLEMAT) (89) according to claim 19, for detecting surface and / or internal Discontinuities (2) of a Metallurgical Slab (105), in which: a. The Conductive Structure (90) is a mobile cylindrical Metallurgical Slab (105) relative to the MLEMAT (89); This Multi Laser-EMAT 3D Scanner (MLEMAT) (89) being characterized in that: b. The Loop of Openings (99), constituted by the virtual line joining the centers of each successive Slotted Cylindrical Opening (39) of the Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the Laser-EMAT Probes (LEMAT) (82) of the MLEMAT (89), encircles the mobile cylindrical Metallurgical Slab (105).

23. A Multi-Laser EMAT 3D Scanner (MLEMAT) (89) according to claim 22, for detecting surface and / or internal discontinuities (2) in a Steel Slab (105), of the type where: a. The Conductive Structure (90) is a cylindrical Steel Slab (105) in motion, continuously cast in a steel mill at a Casting Temperature (TS) above 1000°C, and, b. The hollow HF Active Plates (29) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89) are made of a magnetic, ferromagnetic, or ferrimagnetic material, having a Curie Temperature (TC) lower than the Casting Temperature (TS); This Multi-Laser EMAT 3D Scanner (MLEMAT) (89) being characterized in combination in that each Slotted Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89) is connected to Cooling Means (58) generating a Heat Flux (59) of a cooling Heat Fluid (60), c. pushed under pressure inside each hole via (41, 57) of the Slotted Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1) of the MLEMAT (89); d. at a Cooling Temperature (TF) more than 50°C lower than the Curie Temperature (TC) of the magnetic material of the hollow HF Active Plates (29).

24. A Multi-Laser EMAT 3D Scanner (MLEMAT) (89) according to claim 23, for the automatic adjustment of the dynamic parameters of Soft Dynamic Reduction (DSR) of a continuously cast Steel Slab (105) in a steel mill at a Casting Temperature (TS) above 1000°C, of the type where: a. The Steel Slab (105) is continuously pushed through a Soft Dynamic Reduction Device (DSRD), to suppress the formation of a macro-segregation zone and porosity zones inside the Steel Slab (105), by dynamically compensating for the steel solidification shrinkage and by interrupting the flow of suction of the residual molten metal in the Central Soft Zone (106); b. The MLMAT (89) is coupled to this Soft Dynamic Reduction Device (DSRD) which comprises: i. A Dynamic 3D Mapping System (3DMS), generating a Dynamic 3D Mapping (3DM) of the casting of the Steel Slab (105), ii. A computerized DSR Optimization System (DSRM), generating Dynamic DSR Optimization Parameters (PCSD), based on the Dynamic 3D Mapping (3DM) and the casting parameters, and, c. A Digital DSR Actuator (ASR), dynamically adjusting the Action Parameters of DSR (PASD) of the Soft Dynamic Reduction Device (DSRD), based on the PCSD generated by the DSRM; This Multi-Laser EMAT 3D Scanner (MLEMAT) (89) being characterized in combination in that: d. The HF Electric Coils (6a, 6b, 6) of each EMAT (1a, 1b, 1) of each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89) are each connected to the Dynamic 3D Mapping System (3DMS), and transmit a signal of their Secondary Ultrasonic Electric Signal (88a, 88b, 88) induced in each HF Electric Coil (6a, 6b, 6) by the Eddy Currents of the Material (14) on the Front Zone (110) of the Inspected Material (3) of the Steel Slab (105) facing locally to each EMAT (1a, 1b, 1); e. The DSR Optimization System (DSRM) is equipped with Analog and Digital Processing Means (MDAN) configured to: i. Receive the multitude of Secondary Ultrasonic Electric Signals (88a, 88b, 88) included in the Secondary Ultrasonic Electric Currents (19a, 19b, 19) flowing through each HF Electric Coil (6a, 6b, 6) in each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89), and, ii. Identify changes and disturbances in each Secondary Ultrasonic Electric Signal (88a, 88b, 88) of each Laser-EMAT (82a, 82b, 82), caused by the Discontinuities (2) in the Local Active Fraction (44a, 44b, 44) of the Inspected Material (3) facing each Laser-EMAT (82a, 82b, 82), and deduce and generate digitally the Frontal Topology of Defects (DTa, DTb, DT) in this Local Active Fraction (44a, 44b, 44), and, iii. Digitally combine the Frontal Topology of Defects (DTa, DTb, DT), and digitally generate a three-dimensional Dynamic 3D Mapping (3DM) physically observed by the MLEMAT (89) from inside the casting of the Steel Slab (105), in the Front Zone (110) facing the Inspection Ring (100) in the Structure Section (92) of the Frame Plane (95), based on the combination and digital analysis of combined signals from the multiple Secondary Ultrasonic Electric Signals (88a, 88b, 88); and, f. The Cooling Means (58) generate a Heat Flow (59) of a cooling Heat Fluid (60), i. pushed under pressure inside each hole via (41, 57) of the Slotted Cylindrical Opening (39) of each Perforated Matrix Laminated Magnetic Core (22) of each adjacent EMAT (1a, 1b, 1) of the MLEMAT (89); ii. at a Cooling Temperature (TF) significantly lower (by at least 50°C) than the Curie Temperature (TC) of the magnetic material of the hollow HF Active Plates (29); g. So that the Action Parameters of DSR (PASD) of the Soft Dynamic Reduction Device (DSRD) can be dynamically and automatically adjusted optimally, based on a Dynamic 3D Mapping (3DM) of the casting of the Steel Slab (105) physically observed by the MLEMAT (89), at a Casting Temperature (TS) above 1000°C.

25. A Multi-Laser EMAT 3D Scanner (MLEMAT) (89) according to claim 24, for the automatic adjustment of the dynamic parameters of Soft Dynamic Reduction (DSR) and for the Secondary Dynamic Cooling (DSC) of a continuously cast Steel Slab (105) in a steel mill at a Casting Temperature (TS) above 1000°C, characterized in that the MLMAT (89) is coupled to a Secondary Dynamic Cooling Device (DSCD) which further comprises: a. A computerized DSC Optimization System (DSCM), generating Dynamic DSC Optimization Parameters (PCSC) for the Secondary Dynamic Cooling (DSC) based i. on the Dynamic 3D Mapping (3DM) physically observed of the casting of the Steel Slab (105), in the Structure Section (92) of the Frame Plane (95), by combination and digital analysis of combined signals from the multiple Secondary Ultrasonic Electric Signals (88a, 88b, 88) in each Laser-EMAT (82a, 82b, 82) of the MLEMAT (89), ii. and on the casting parameters; b. A Digital DSC Actuator (ASC), dynamically adjusting the Action Parameters of DSC (PASC) of the water flow of the Secondary Dynamic Cooling (DSC), based on the PCSC generated by the DSC Optimization System (DSCM) based on the Dynamic 3D Mapping (3DM) physically observed by the MLEMAT (89)