Measuring assembly and method for determining the concentration of different elements in a metal strand produced by a continuous casting method

Abstract

The invention relates to a measuring assembly (1) and to a method for determining the concentration of different elements in a metal strand (2) produced by a continuous casting method. The measuring assembly (1) comprises a heat protection housing (3), a measuring head (4) provided in the heat protection housing (3), and a measuring lance (5) which is mechanically connected to the measuring head (4) and extends through a housing opening (34) of the heat protection housing (3) in the direction of a metal strand (2) to be analyzed. The measuring assembly (1) is characterized by additionally having a cooling air feed (6) which is connected to the heat protection housing (3) and serves to feed cooling air (7) into the heat protection housing (3), the measuring lance (5) being provided at a distance from the heat protection housing (3) in the region of the housing opening (34) such that between the measuring lance (5) and the heat protection housing (3) a cooling air outlet (35) is formed through which cooling air (7) introduced into the heat protection housing (3) by the cooling air feed (6) can exit during the operation of the measuring assembly (1) and flow along the exterior of the measuring lance (5).

Description

[0001] SPT1 12W0 1

[0002] Measuring setup and method for determining the concentration of different elements in a metal strand produced by a continuous casting process

[0003] Description

[0004] The present invention relates to a measuring arrangement according to the preamble of claim 1 and to a method for determining the concentration of different elements in a metal strand produced by a continuous casting process according to claim 10.

[0005] Continuous casting is a casting process for producing metal strands, which can consist of different metal alloys. The molten metal is poured into a bottomless, cooled mold, creating a skin of solidified metal on the outside of the liquid metal. This skin gradually spreads into the interior of the metal strand. Initially, the core of the metal strand is still molten and easily malleable. The continuous metal strand is drawn vertically downwards from the mold and deflected in a circular arc into a horizontal position while being actively cooled. The solidified continuous strand is then cut into semi-finished products of the desired length and usually passively cooled. This means the semi-finished product is left to stand until it reaches a suitable transport temperature.

[0006] Such continuous casting or continuous casting processes are generally carried out continuously. If metal strands with different compositions are to be produced, the mold is filled successively with the corresponding alloys. The resulting continuous metal strand then has a transition zone in which the initially used metal alloy transitions into the subsequently used metal alloy. However, such transition zones of the metal strand usually cannot be used for their original purpose. Therefore, in the processes known from the prior art, a rather generously dimensioned safety zone, sometimes more than 8 m long, is removed from the metal strand. This transition zone can then be remelted or sold as lower-quality material.

[0007] Considering economic viability and energy / resource efficiency, it is desirable to keep the transition zone, and thus the material loss, as small as possible. Currently, there is no measurement method that can directly determine the length of the transition zone during the continuous casting process. Therefore, for quality reasons, the transition zone is regularly estimated to be significantly larger than actually necessary.

[0008] Prior art has shown that analytical methods using laser-induced plasma spectroscopy of molten metals or in highly heated baths are known.

[0009] European patent application EP 4 336 173 A1 discloses a method for regulating or controlling a melting furnace for melting metal in order to produce a metal melt. It further discloses an analysis of the composition of the produced metal melt using laser-induced plasma spectroscopy.

[0010] European patent EP 2 376900 B1 discloses a measuring device with a measuring head for laser-induced plasma spectroscopy for the chemical analysis of compounds of a highly heated bath in a dusty environment.

[0011] The present invention is based on the objective of providing a measuring arrangement and a measuring method for determining the concentration of different elements in a metal strand produced by a continuous casting process, which can be used, for example, for a more precise determination of a transition zone between different metal alloys in the produced metal strand.

[0012] This problem is solved by a measuring arrangement with the features of claim 1.

[0013] Such a measuring setup is used to determine the concentration of different elements in a metal strand produced by a continuous casting process. The measuring setup is applied to the still-hot metal strand. Typically, the temperature of such a metal strand shortly after exiting a mold ranges from approximately 700 °C to approximately 1600 °C. Although the ambient temperature decreases with increasing distance from the metal strand, the measuring setup cannot be positioned arbitrarily far away from the strand to still obtain accurate measurements. Therefore, special thermal protection measures are necessary for the measuring setup.

[0014] The measuring arrangement therefore comprises a thermally insulated housing and a measuring head located within the housing. Furthermore, the measuring head is mechanically connected to a measuring lance (SPT1 12W0 3). This measuring lance extends through an opening in the thermally insulated housing from the measuring head, through the housing, and towards the metal strand to be analyzed. Since continuous casting processes – as explained above – are carried out continuously, the metal strand to be analyzed moves in a feed direction. This means that there is relative movement between the measuring head and the measuring lance connected to it on the one hand, and the metal strand to be analyzed on the other.

[0015] According to one aspect of the present invention, the measuring arrangement further comprises a cooling air supply. This cooling air supply is connected to the thermal protection housing and serves to supply cooling air into the thermal protection housing. The measuring lance does not touch the thermal protection housing in the area of ​​the housing opening. Rather, the measuring lance is arranged at a distance from the thermal protection housing. Thus, a cooling air outlet is formed between the measuring lance and the thermal protection housing in the area of ​​the housing opening. Through this cooling air outlet, cooling air, which is introduced into the thermal protection housing via the cooling air supply, can exit the thermal protection housing again during operation of the measuring arrangement. In addition, the cooling air outlet is designed such that the cooling air exiting the thermal protection housing through the cooling air outlet can flow along an outer surface of the measuring lance.

[0016] By providing such a cooling air supply and outlet, the interior of the thermal protection housing, in which the measuring head is located, can be cooled particularly efficiently. This allows the sensitive optical and electronic components located in the measuring head to be protected very effectively from the high temperatures caused by the thermal radiation of the metal strand being analyzed. Thus, the sophisticated cooling system (featuring the cooling air supply and outlet) enables the use of the measuring arrangement on a moving metal strand being analyzed, which cools down slowly during its movement but still maintains a very high temperature of several hundred degrees Celsius or even over 1000 °C.With previously available measuring arrangements, it was not possible to determine the concentration of different elements in a freshly cast metal strand. Therefore, as explained above, it was necessary to remove a transition zone between different metal alloys from the metal strand, applying a very large safety margin. In contrast, the measuring arrangement described and claimed here enables the determination of the concentration of different elements in SPT1 12W0 4 a freshly cast metal strand during the manufacturing process, i.e., in real time or as an inline method.

[0017] The measuring lance serves to direct optical measurement radiation exiting the measuring head onto the metal strand to be analyzed. Furthermore, the measuring lance provides a distance between the metal strand being analyzed and the measuring head, and prevents dust and other contaminants from reaching the measuring head. It also serves to purge the beam path and the measurement area with process gas. In one embodiment, the measuring lance incorporates a ceramic mesh, which is optionally applied to a matrix.

[0018] According to one embodiment, the measuring arrangement is not only designed to cool the measuring lance on its exterior during operation. Rather, in this embodiment, the measuring arrangement has a second cooling device by means of which air or an inert gas, such as nitrogen, is passed through an interior area of ​​the measuring lance. In this embodiment, the measuring lance is thus cooled not only from the outside but also from the inside during operation. This results in particularly efficient cooling of the measuring lance and, consequently, of the entire measuring arrangement. The objective of the present invention—to use a particularly sensitive optical system, such as that contained in the measuring head, under extreme high-temperature conditions in the vicinity of a freshly cast metal strand to be analyzed—is achieved in a particularly advantageous manner in this embodiment.

[0019] According to one embodiment, the cooling air supply has a fan with which cooling air can be directed through the cooling air supply into the heat protection housing.

[0020] In one embodiment, the number of contact points between the thermal protection housing and the measuring head is kept to a minimum to minimize heat conduction from the housing to the measuring head. In other words, only as many mechanical contact points are implemented between the thermal protection housing and the measuring head as are necessary for the secure mounting of the measuring head within the housing. The contact points are designed to have the smallest possible surface area.

[0021] In one embodiment, the measuring arrangement includes a control unit that is operationally coupled to the measuring head. The control unit serves to control the measuring head. The SPT1 12W0 5

[0022] The control unit can also include other elements of the measuring arrangement, such as a spectrometer for evaluating measurement or test radiation detected by the measuring arrangement, which allows conclusions to be drawn about the elemental composition of the metal strand. For this purpose, a collecting optic can be provided in the measuring head, for example, which collects radiation emitted or reflected from the metal strand and couples it into an optical fiber. The optical fiber then guides this radiation from the measuring head to the control unit connected to the measuring head, where the radiation is evaluated in a spectrometer. If the measuring head and the control unit are spatially separated, particularly sensitive components of the measuring arrangement can be housed in the control unit.Furthermore, the control unit requires less heat shielding than the measuring head, as it can be positioned at a greater distance from the metal strand being analyzed. Typically, an operational connection between the measuring head and the control unit includes at least electrical conductors. Such a connection can also include optical conductors, for example, as explained above, a fiber optic cable.

[0023] In one embodiment, the measuring arrangement includes a camera that is operationally coupled to the measuring head. This coupling can be direct or indirect. For example, the camera can be coupled to a control unit, which in turn is operationally coupled to the measuring head. The camera can then forward recorded signals to the control unit, which evaluates them and converts them into control signals for the measuring head. The camera serves to determine an actual measurement position and / or an intended measurement position of an optical measurement beam exiting the measuring head. Alternatively or additionally, the camera serves to determine an actual pre-ablation position and / or an intended pre-ablation position of an optical pre-ablation beam exiting the measuring head. Typically, a first radiation source, such as a first laser, is arranged in the measuring head to generate the measurement beam.To generate the pre-ablation radiation, a second radiation source, such as a second laser, is typically arranged in the measuring head. Alternatively, it is also possible that the measurement radiation and / or the pre-ablation radiation are not generated by radiation sources located in the measuring head, but by radiation sources located, for example, in the control unit. The radiation generated there can then be guided to the measuring head via optical fibers, from where it is directed through the measuring lance onto the metal strand to be analyzed. SPT1 12W0 6.

[0024] Pre-ablation radiation is used for the preliminary cleaning (pre-ablation) of the surface to be analyzed. Pre-ablation radiation removes impurities from the surface of the metal strand under investigation.

[0025] In one embodiment, the measuring radiation is laser radiation generated by a laser with a power output in the range of 10 W to 60 W, particularly 20 W to 50 W, and particularly 30 W to 40 W. In another embodiment, the pre-ablation radiation is radiation generated by a second laser with a power output in the range of 100 W to 400 W, particularly 150 W to 375 W, particularly 200 W to 350 W, particularly 250 W to 330 W, particularly 275 W to 325 W, and particularly around 300 W. A particularly suitable wavelength for the measuring radiation and / or the pre-ablation radiation is in the range of 1000 nm to 1100 nm, particularly 1040 nm to 1080 nm, particularly 1060 nm to 1070 nm, and particularly around 1064 nm.

[0026] In one embodiment, the measuring head features an (automatic) focusing system. This focusing system allows for adjusting the focus point of the optical measurement radiation exiting the measuring head and / or the focus point of the optical pre-ablation radiation exiting the measuring head. For this purpose, the focusing system can move the measuring head relative to the thermal protection housing. This movement preferably occurs along a Z-axis that is perpendicular to the metal strand being analyzed and extends upwards from the metal strand towards the measuring head or the thermal protection housing. By changing the height of the measuring head within the thermal protection housing, the measuring head, along with the measuring lance rigidly connected to it, can be moved closer to or further away from the metal strand being analyzed.In one variant of this design, the focusing system is also capable of moving the measuring beam and / or the pre-ablation beam laterally, in particular along a Y-axis that runs perpendicular to the Z-axis and also perpendicular to a feed direction of the metal strand to be measured running along an X-axis. This can be achieved via an optical deflection system such as one or more mirrors. The focusing system then makes it possible, in particular, to adjust the focal plane to the plane of the surface of the metal strand to be analyzed by moving the measuring head along the Z-axis and, furthermore, to selectively irradiate a desired position on the surface of the metal strand by laterally shifting the measuring beam or the pre-ablation beam. Alternatively, the measuring and / or pre-ablation positioning can be performed purely mechanically by manual or motorized linear axes. SPT1 12W0 7.

[0027] In one embodiment, the control unit serves to adjust the focus point of the optical measurement radiation exiting the measuring head and / or the focus point of the optical pre-ablation radiation exiting the measuring head using the focusing system. The actual measurement position and / or the intended measurement position of the optical measurement radiation exiting the measuring head, as detected by the camera, is used as the input for this adjustment. Alternatively or additionally, the actual pre-ablation position and / or the intended pre-ablation position of the optical pre-ablation radiation exiting the measuring head can be used as the input. Thus, in this embodiment, it is possible to achieve an adjustment, such as a correction of the subsequent pre-ablation or measurement locations, by optically monitoring the actual conditions during pre-ablation or measurement.This design enables automatic control of the measurement position and / or the pre-ablation position based on a previously defined measurement position and / or pre-ablation position. For example, this design makes it particularly easy to move or position the optical measurement radiation, especially laser measurement radiation, and / or the optical pre-ablation radiation, especially laser pre-ablation radiation, on the surface of the metal strand to be measured in such a way that the measurement track runs exactly within the pre-ablation track. This ensures that measurements are only taken at those points on the surface of the metal strand that have been previously cleaned by pre-ablation. This allows for a more accurate and unadulterated determination of the concentration of different elements in the metal strand. For example, the measurement position of the optical measurement radiation can be kept constant.The camera then monitors whether the pre-ablation performed immediately before the measurement actually takes place at the intended measurement position. If this is not the case, the focus of the pre-ablation radiation is adjusted so that the pre-ablation occurs precisely at the points on the surface of the metal strand where the subsequent measurement by the optical radiation is to take place.

[0028] In one embodiment, the measuring head is a measuring head of a spectrometer, in particular a device for performing laser-induced plasma spectroscopy (LIBS), laser-induced fluorescence spectroscopy, Raman spectroscopy, or surface reflection infrared absorption spectroscopy. Laser-induced plasma spectroscopy is a particularly suitable method for determining the concentration of different elements in the metal strand being analyzed. Therefore, in one variant, the measuring head is a measuring head of a device for laser-induced plasma spectroscopy, i.e., a LIBS spectrometer. SPT1 12W0 8

[0029] In one embodiment, the measuring arrangement includes a heat shield. This heat shield is positioned between a distal opening of the measuring lance and a component located in the measuring head, particularly an optical or electronic component. The distal opening of the measuring lance faces directly toward the metal strand being measured. During operation of the measuring arrangement, the measuring radiation and, if applicable, the pre-ablation radiation exit the measuring arrangement through the distal opening of the measuring lance to strike the surface of the metal strand being analyzed. The heat shield provides particularly effective protection for sensitive components, especially sensitive optical or electronic components, within the measuring head. The heat shield can, for example, be a rotatable disc that has at least one opening transparent to optical radiation.Typically, such a rotating disc is equipped with several corresponding openings. These openings can be closed—for example, by rotating the disc or by placing a cover over the opening. This effectively prevents heat radiation from the metal strand being analyzed from entering the measuring head. This extends the service life of the sensitive optical and electronic components within the measuring head. During operation, this heat shield is typically closed whenever a measurement is not in progress. It is only opened when a measurement is required. In this way, the overall exposure to heat radiation affecting the optical and electronic components of the measuring head is significantly reduced.

[0030] A particularly suitable position for the heat shield is located in the area between a distal end of the measuring head (i.e., an end oriented towards the measuring lance) and a proximal end of the measuring lance (i.e., an end oriented towards the measuring head). In other words, the heat shield is positioned between the measuring head and the measuring lance in one configuration. However, it could equally well be located at any point in the measuring lance (typically in a proximal section of the measuring lance) or in the measuring head itself (typically in a distal region of the measuring head) to provide a comparable level of protection for the electronic and optical components within the measuring head.

[0031] In one embodiment, the measuring arrangement features a removable insert. This insert has at least one replaceable optical window, which serves to protect components, particularly optical or electronic components, of the measuring head that are located proximal (i.e., away from the metal strand being analyzed) to the optical window. This optical window prevents negative influences from the thermal radiation emitted by the metal strand being analyzed from reaching the interior of the measuring head. Instead, the optical window itself is exposed to the thermal radiation and may be affected in its optical transmittance. Therefore, the optical window can also be referred to as a sacrificial window.Because the optical window is located within the removable insert, it can be easily replaced should its optical transmittance fall below a predefined threshold. The optical and electronic components located proximal to the optical window are thus protected by it and do not need to be replaced themselves, even after extended use in measuring hot metal strands. Since the optical window is easily replaceable within the removable insert, such a replacement is significantly simpler than replacing other optical or electronic components within the measuring head, which might otherwise be difficult to access.

[0032] Another aspect of the present invention relates to a method for determining the concentration of different elements in a metal strand produced by a continuous casting process. This method is carried out using a measuring arrangement as described above. The method comprises the steps described below.

[0033] First, the thermal protection housing, the measuring head, and the measuring lance of the measuring arrangement are positioned above a metal strand moving in the feed direction. This metal strand has a high temperature of several hundred degrees Celsius up to more than 1000 degrees Celsius and emits a correspondingly strong thermal radiation.

[0034] To prevent the measuring head from overheating, cooling air is drawn into the thermal protection housing through the cooling air inlet. The cooling air then passes through the thermal protection housing and exits through the cooling air outlet. The cooling air then flows along the outside of the measuring lance, cooling it from the outside.

[0035] In a further process step, optical measuring radiation from the measuring head is directed through the measuring lance onto the metal strand. This optical measuring radiation can be generated directly in the measuring head, for example by a laser. SPT1 12W0 10

[0036] In a further process step, test radiation is detected by the measuring arrangement. This test radiation is generated in the metal strand by the measurement radiation (for example, in the case of laser-induced plasma spectroscopy) or is reflected by the metal strand as part of the measurement radiation (for example, in the case of surface reflection infrared absorption spectroscopy).

[0037] The concentrations of different elements in the metal strand are then determined by analyzing the test radiation using the measuring setup. The determined concentration can be an absolute concentration (expressed, for example, in an SI unit) or a relative concentration (expressed, for example, in relation to other elements in the metal strand). A spectrum exhibiting a characteristic profile for a specific element concentration (e.g., through specific bands, peaks, or lines, or through intensity values ​​or surface integrals of specific bands, peaks, or lines) is also considered a "concentration" in this sense. The term "concentration" is therefore not limited to numerical values ​​immediately understandable to a human user, but also includes concentration-specific measurements or data from which the concentration of an element can be determined through computer-aided or machine-based evaluation.

[0038] In this way, the composition of the metal strand – at least with regard to some elements – can be determined with high accuracy. Consequently, it is possible to determine whether the metal strand just produced consists of a transition material that resulted from the mixing of a previously used alloy with a subsequently used alloy and is therefore unsuitable for further use of the metal strand. If so, the corresponding section of the metal strand consisting of such a transition material (or transition alloy) is either discarded, remelted, or sold as a lower-quality metal strand.By precisely determining the composition of the metal strand, the corresponding transition zone between different metal alloys can be determined with high accuracy. This means that only a very small section of the metal strand needs to be treated separately as a transition alloy strand. The removal of a generously sized safety zone of several meters of the metal strand is therefore no longer necessary, as the transition zone is no longer determined "on suspicion" but is precisely defined by measurement. Thus, for example, a transition zone of only 1 m in length can be discarded, whereas safety zones with a SPT1 12W0 11.

[0039] Lengths of up to 8 meters can be discarded. The costs previously incurred by discarding the generously sized safety zone can thus be reduced to, for example, one-eighth. In other cases, the cost reduction may be greater or lesser depending on the degree to which the respective alloys mix in the mold used to produce the metal strand. Even then, however, the transition zone can be precisely and selectively removed from the metal strand, ensuring that no excess, high-quality metal is unnecessarily removed and discarded, resulting in significant cost savings.

[0040] In one embodiment, optical pre-ablation radiation from the measuring head is additionally directed through the measuring lance onto the metal strand. This pre-ablation radiation cleans the surface of the metal strand, thus improving the quality of subsequent measurements taken at the pre-cleaned areas. The determination of the elemental composition of the metal strand can therefore be performed more accurately. Consequently, a transition zone between different metal alloys within the metal strand can be determined with even greater precision.

[0041] In one embodiment, the measuring arrangement comprises a control unit and a camera operationally coupled to the measuring head. The control unit serves to control the measuring head. The camera is typically also operationally coupled to the control unit, so that operational coupling between the camera and the measuring head occurs indirectly via the control unit. In this embodiment, the control unit adjusts the focus location of the optical measurement radiation exiting the measuring head and / or the focus location of the optical pre-ablation radiation exiting the measuring head. This adjustment is based on an actual measurement position determined by the camera and / or the intended measurement position of the optical measurement radiation exiting the measuring head.Alternatively or additionally, the adjustment is made depending on an actual pre-ablation position determined by the camera and / or intended pre-ablation position of the optical pre-ablation radiation exiting the measuring head.

[0042] In one embodiment, the concentrations of a plurality (at least 2, in particular exactly 2, 3, 4, 5, 6, 7, 8, 9 or 10) of elements in the metal strand are determined as a function of their relative position in the strand. This enables a spatially resolved determination of the composition of the metal strand with respect to the analyzed elements. This allows for the identification of a transition zone between different metal alloys within the metal strand in a particularly simple manner. SPT1 12W0 12

[0043] In one embodiment, the obtained element concentrations are analyzed using a classification algorithm to classify the respective position in the metal strand as a transition region or a non-transition region. Suitable classification algorithms include multivariate data analysis algorithms such as principal component analysis (PCA) or partial least squares regression (PLS). Other suitable classification algorithms are neural networks, particularly backpropagating networks, and artificial intelligence (AI) methods trained on appropriate training data. Suitable input parameters include the obtained raw spectra, results of a previously performed data analysis such as PCA or PLS analysis, or absolute concentration values.Each of these input variables is to be understood as a “concentration”, since it is indicative of the concentration of an element in the metal strand and thus provides information about the elemental composition of the metal strand (at least with regard to the elements analyzed).

[0044] In one embodiment, the first derivative of each specific concentration (C) is calculated as a function of its relative position (s) in the metal strand (dC / ds). The magnitudes of these calculated first derivatives are then summed. A change in the composition of the metal strand is detected when the sum of the magnitudes of the calculated first derivatives exceeds a predefined threshold. By considering the concentrations of different elements (and not just a single element), changes in the composition of the metal strand can be detected particularly quickly and reliably. This is because the concentration of a particular element may not change between different metal alloys used. In contrast, the concentration of other metals may change between these different metal alloys.By determining the concentration of more than one element, changes in the metal alloys used, and thus in the composition of the produced metal strand, can be detected particularly quickly, reliably and easily.

[0045] In one embodiment, a material transition region is defined in the metal strand by assigning a starting point of the material transition region to the relative position of the metal strand at which the sum of the magnitudes of the calculated first derivatives exceeds the first limit. Similarly, an endpoint of the material transition region is assigned to the relative position of the metal strand at which the sum of the magnitudes of the calculated first derivatives falls below a second limit. The material transition region then represents precisely the region of the metal strand that begins with an increasing change in the concentrations of the elements analyzed and ends when the changes in the concentrations of the analyzed elements again diminish. The metal strand sections located before and after the material transition region can be assigned to a first metal alloy or a second metal alloy, respectively.The material transition zone can be assigned to a second metal alloy and considered the desired metal strand products of the respective metal alloys. The material transition zone, however, can be removed from the metal strand, as it does not have a material composition corresponding to either the desired first or second metal alloy.

[0046] All variants and configurations of the measuring arrangement can be combined with each other in any way and can be applied to the method individually or in any combination. Likewise, all variants and configurations of the method can be combined with each other in any way and can be applied to the measuring arrangement individually or in any combination.

[0047] Further details of aspects of the present invention are explained below with reference to exemplary embodiments and figures. These show:

[0048] Figure 1 shows a schematic representation of an exemplary embodiment of a LIBS-

[0049] Measurement setup;

[0050] Figure 2A shows an enlarged view of the thermal protection housing of the LIBS-

[0051] Measuring setup of Figure 1;

[0052] Figure 2B is an enlarged detail view of the area marked “B” in Figure 2A;

[0053] Figure 3A shows a detailed view of the heat protection housing and the measuring head of the LIBS measuring arrangement of Figure 1;

[0054] Figure 3B shows the thermal protection housing and measuring head of the LIBS measuring arrangement of Figure 1 during operation;

[0055] Figure 3C shows a schematic representation of the cooling air flow through the heat protection housing of the LIBS measuring arrangement of Figure 1;

[0056] Figure 4A shows an embodiment of a window cassette in a first operating state; SPT1 12W0 14

[0057] Figure 4B shows a detail view of the window cassette of Figure 4A;

[0058] Figure 4C shows the window cassette of Figure 4A in a second operating state;

[0059] Figure 5A shows three diagrams for the spatially resolved determination of the concentrations of different elements; and

[0060] Figure 5B is a diagram of the spatially resolved magnitudes of the first derivatives of the measured values ​​of Figure 5A.

[0061] Figure 1 shows a schematic representation of an embodiment of a LIBS measuring arrangement 1. This LIBS measuring arrangement 1 is arranged above a metal strand 2 to be analyzed, which moves in a feed direction V. The feed direction V runs along an X-axis. The metal strand 2 has a high temperature of several hundred °C to over 1000 °C and radiates corresponding heat 20 upwards towards the LIBS measuring arrangement 1.

[0062] The LIBS measuring arrangement 1 comprises a thermal protection housing 3 in which a measuring head (not shown in Figure 1) is arranged. A measuring lance 5 projects downwards from the thermal protection housing 3, extending to just above the metal strand 2. The measuring lance 5 serves to protect the measuring head arranged in the thermal protection housing 3 from heat 20 and to direct a measuring radiation 41 emitted by this measuring head onto the metal strand 2.

[0063] At its upper end, the thermal insulation housing 3 has a cooling air inlet 6. Cooling air 7 is introduced into the thermal insulation housing 3 via this cooling air inlet 6 by means of a fan 60. The cooling air 7 has a temperature of less than 30 °C and is circulated by the fan 60 at a volume flow rate of approximately 10 m³ / h. 3 / min is directed into the thermal protection housing 3.

[0064] The LIBS measuring arrangement 1 further comprises a control unit 8, which is located further away from the metal strand 2 to be analyzed than the thermal protection housing 3. The control unit 8 is operationally connected to the thermal protection housing 3 and the measuring head arranged therein via a connecting line 80. The connecting line 80 comprises a bundle of different conductors. SPT1 12W0 15

[0065] Furthermore, the LIBS measuring arrangement 1 includes a first camera 9, which is also operationally connected to the measuring head located in the thermal protection housing 3. This connection is typically implemented via the control unit 8, so that the control unit 8 receives an input signal from the first camera 9 and can, for example, use it to adjust the position of the measuring beam 41 or a focus point of the measuring beam 41.

[0066] The first camera 9 is shown in Figure 1 outside the thermal protection housing 3 in a separate thermal protection housing for visualization purposes only. In reality, the first camera 9 is located inside the thermal protection housing 3.

[0067] Furthermore, a second camera 10 is provided, with which a previously measured measurement path on the surface of the metal strand 2 can be observed.

[0068] To ensure that the measuring arrangement 1 is securely positioned above the metal strand 2, it is mounted on a steel frame 11. To effectively block the heat 20 rising from the metal strand 2, a microporous insulating material 111, which provides good thermal insulation, is attached below a surface 110 of the steel frame 11. This allows the overall temperature on the surface 110 of the steel frame 11 to be kept at a lower level, making it possible to also provide a platform 112 there for maintenance purposes of the LIBS measuring arrangement 1.

[0069] Figure 2A shows an enlarged view of the thermal insulation housing 3 from Figure 1. In this and all subsequent figures, similar elements are always identified by the same reference numerals.

[0070] The thermal insulation housing 3 has a door 30 through which an interior of the thermal insulation housing 3, in which a measuring head (not shown in Figure 2A) is arranged, is accessible. A base plate 31 is attached to one top side of the thermal insulation housing 3, with which the thermal insulation housing 3 can be suspended from a suitable structure. For transport and as an aid to installation, several eye bolts 32 are attached to one top side of the base plate 31. In addition, a connecting nozzle 33 is formed on the top side of the base plate 31, to which the cooling air supply (see Figure 1 for more details) can be connected.

[0071] On one side of the thermal protection housing 3, the connecting line 80 to the control unit is shown in cross-section. The measuring lance 5 protrudes from the underside of the thermal protection housing 3. It extends to just before the surface of the metal strand (not shown in Figure 2A), which is to be analyzed with the LIBS measuring arrangement 1 described herein. A focal point 410 of the measuring radiation 41 emerging from the measuring lance 5 lies approximately 50 mm below a distal opening 51 of the measuring lance 5.

[0072] The area shown in Figure 2A with a box labeled "B" is enlarged in Figure 2B. It can be seen that not only a single optical beam emerges from the distal opening 51 of the measuring lance 5, but rather a measuring beam from a measuring radiation 41 of a LIBS excitation laser and a pre-ablation beam from a pre-ablation radiation 42 of a pre-ablation laser. The measuring beam and the pre-ablation beam strike the surface of a metal strand (not shown in Figure 2B) at a first focus point 410 and a second focus point 420, respectively. This strand is moved in the feed direction V below the measuring lance 5.

[0073] Figure 3A shows the thermal protection housing 3, already depicted in Figures 1 and 2A, in a view without doors, thus revealing the interior of the thermal protection housing 3. As described above, a measuring head 4 is arranged inside the thermal protection housing 3 and is mounted so as to be vertically displaceable relative to the housing 3 along a Z-axis. This allows the relative distance between the distal opening 51 and a metal strand to be analyzed underneath to be adjusted. Consequently, the focal point 410 of the measurement radiation 41 and the focal point 420 of the pre-ablation radiation 42 can also be adjusted. Thus, a suspension that allows vertical displacement of the measuring head 4 relative to the thermal protection housing 3 along the Z-axis is part of a focusing system 43.

[0074] The first camera 9 is located in a lower area of ​​the thermal protection housing 3, which can monitor the measurement location at the focus point 410 well from its position there.

[0075] A removable cassette 12, which acts as a removable insert, is arranged between the measuring head 4 and the measuring lance 5. The removable cassette 12 contains an optical window that protects the measuring head 4 from heat radiation entering through the measuring lance 5. This removable cassette 12 will be explained in more detail in Figures 4A to 4C.

[0076] As can be seen from Figure 3A, the removable cassette 12 is arranged distal to the measuring head 4 and proximal to the measuring lance 5; it is therefore located between the measuring head 4 and the measuring lance 5. SPT1 12W0 17

[0077] Figure 3B shows another view of the thermal protection housing 3 and the measuring head 4. The focusing system 43 is again shown, which enables vertical movement of the measuring head 4 relative to the thermal protection housing 3 along the Z-axis. Apart from the focusing system 43, the measuring head 4 has no contact points with the thermal protection housing 3 in order to reduce heat transfer from the thermal protection housing 3 to the measuring head 4.

[0078] The measuring head 4 contains a LIBS excitation laser 411 and a pre-ablation laser 421. The LIBS excitation laser 411 emits the measurement radiation 41 from the measuring head 4. The measurement radiation 41 is guided through an interior of the measuring lance 5 onto the metal strand 2 to be analyzed. The pre-ablation laser 421 generates the pre-ablation radiation 42, which also exits the measuring head 4 and is guided through the interior of the measuring lance 5. The pre-ablation radiation 42 pre-cleans those areas of the surface of the metal strand 2 that are subsequently irradiated with the measurement radiation 41 to perform the LIBS analysis. Due to the movement of the metal strand 2 in the feed direction V, a measurement beam generated by the measurement radiation 41 is spatially positioned in front of a pre-ablation beam generated by the pre-ablation radiation 42.The measuring radiation 41 is emitted shortly after the pre-ablation radiation 42, so that the measuring radiation 41 strikes the same area of ​​the surface of the metal strand 2 that was previously cleaned by the pre-ablation radiation 42. The distance D between a lower edge of the heat shield housing 3 and the surface of the metal strand 2 is a maximum of 1200 mm.

[0079] Figure 3C schematically shows the flow of cooling air 7 through the thermal protection housing 3. The cooling air 7 is directed into the interior of the thermal protection housing 3 through the connecting nozzle 33. There, it flows along the Z-axis past an outer surface of the measuring head 4. As it does so, the cooling air 7 is continuously heated. An opening 34 is formed on the underside of the thermal protection housing 3, through which the measuring lance 5 extends into the interior of the thermal protection housing 3. However, the measuring lance 5 does not touch the thermal protection housing 3. Instead, a cooling air outlet 35 is provided between the thermal protection housing 3 and the measuring lance 5 in the area of ​​the housing opening 34, through which the cooling air 7 flows from the interior of the thermal protection housing 3. The cooling air 7 is guided along an outer surface of the measuring lance 5 and then spreads away from the measuring lance 5 into the surrounding area.This cooling air routing through the interior of the thermal protection housing 3 along the measuring head 4 and along the outside of the measuring lance 5 ensures effective SPT1 12W0 18.

[0080] Cooling of the measuring head 4 and the sensitive optical and electronic components arranged therein.

[0081] Figure 4A shows a detailed view of the removable cassette 12, which is located below the measuring head 4 inside the thermal protection housing 3. This removable cassette 12 can be pulled out from its position below the measuring head 4 in the direction of the arrow. A handle 121 of the removable cassette 12 is particularly easily accessible from the outside, as the thermal protection housing 3 also has a door at this point (not shown in Figure 4A).

[0082] Figure 4B shows that the removable cassette 12 has several optical windows 122 through which light and heat radiation must pass to reach the measuring head 4. These optical windows 122 wear out over time. However, they protect sensitive optical and electronic components located proximal to the removable cassette 12 within the measuring head 4. The optical windows 122 are themselves arranged in a removable carrier 123, which can be replaced if necessary. Once a new carrier 123 has been inserted into the removable cassette 12, the removable cassette 12 can be pushed back into its original position, as shown in Figure 4C. To do this, the removable cassette 12 is inserted in the direction of the arrow into a corresponding receptacle below the measuring head 4.

[0083] Figure 5A shows three concentration diagrams. The top diagram plots the nickel concentration 15 along the length of an analyzed metal strand. It shows that the nickel concentration 15 initially remains at approximately 0.7%, then increases to about 1.1% over a length of approximately 100 dm.

[0084] Such a transition is less evident in the middle diagram, which shows the manganese concentration 16. Here, there is only a slight increase in concentration from 1.3% to 1.4%, as can be seen from the corresponding mean value lines. However, the measured values ​​scatter relatively widely around these mean value lines.

[0085] The bottom diagram shows the chromium concentration (17) along the length of the analyzed metal strand. It can be seen that the concentration drops from 2.1% to approximately 1.7% over a length of about 100 dm. SPT1 12W0 19

[0086] Analyzing only the manganese concentration 16 would not reliably detect a material change that occurred at a length of 100 dm in the metal strand. However, including the nickel concentration 15 and / or the chromium concentration 17 makes such a material change more readily apparent.

[0087] The evaluation of the determined concentration values ​​is shown in more detail in Figure 5B. Figure 5B shows the magnitude of derivative 150 of the nickel concentration 15, the magnitude of derivative 160 of the manganese concentration 16, and the magnitude of derivative 170 of the chromium concentration 17. Figure 5B also shows the sum 180 of the magnitudes of the three derivatives 150, 160, and 170. Changes in the material composition are particularly evident from this sum 180. The material change was carried out at a length of 100 dm of the analyzed metal strand. The sum 180 of the concentrations already exceeds a first limit value at a length of approximately 87.5 dm. The sum 180 of the concentrations then continues to increase before subsequently decreasing again. At a length of approximately 112.5 dm, the sum 180 of the concentrations falls below a second limit value. Therefore, the range from 87.5 dm to 112.5 dm is defined as material transition range 21.In this material transition zone 21, the metal strand exhibits an undesirable mixed composition. This material transition zone 21 can therefore be discarded or melted down. In contrast, the metal strand up to a length of 87.5 dm can be used as a metal strand of the first metal alloy used, and the metal strand from a length of 112.5 dm can be used as a metal strand of the second metal alloy used. The material transition zone 21 to be discarded or otherwise used is significantly smaller than in the case of metal strands produced by a prior art process. Thus, the measuring arrangement and the measuring method described here enable a particularly economical production of metal strands in a continuous casting process.

[0088] Reference symbol list

[0089] 1 Measuring setup

[0090] 2 metal strands

[0091] 20 Heat

[0092] 21 Material transition zone

[0093] 3 thermal insulation housings

[0094] 30 Door of the thermal insulation housing

[0095] 31 Base plate of the thermal insulation housing

[0096] 32 Eyebolt SPT112W0

[0097] 33 connecting pieces

[0098] 34 Housing opening

[0099] 35 Cooling air outlet

[0100] 4 measuring head

[0101] 41 Measurement radiation

[0102] 410 Focus point of the measurement radiation

[0103] 411 LIBS excitation laser

[0104] 42 Pre-ablation radiation

[0105] 420 Focus location of the pre-ablation radiation

[0106] 421 Pre-ablation lasers

[0107] 43 Focusing system

[0108] 5 measuring lance

[0109] 51 Distal opening of the measuring lance

[0110] 6 Cooling air supply

[0111] 60 fan

[0112] 7 Cooling air

[0113] 8 Control unit

[0114] 80 connecting cable

[0115] 9 First Camera

[0116] 10 Second Camera

[0117] 11 steel frame

[0118] 110 Surface area of ​​the steel frame

[0119] 111 Insulation material

[0120] 112 Platform

[0121] 12 Removable cassette

[0122] 121 Handle of the removable cassette

[0123] 122 Optical window

[0124] 123 Removable carrier

[0125] 15 Nickel concentration

[0126] 150 First derivation of nickel concentration

[0127] 16 Manganese concentration

[0128] 160 First derivation of manganese concentration

[0129] 17 Chromium concentration

[0130] 170 First derivation of chromium concentration

[0131] 180 Sum of the first derivatives

[0132] D distance

[0133] V Feed direction SPT112W0 21

[0134] Z Z-axis

Claims

SPT1 12W0 22 Patent claims 1. Measuring arrangement (1 ) for determining the concentration of different elements in a metal strand (2) produced by a continuous casting process, comprising • a thermal insulation housing (3), • a measuring head (4) arranged in the thermal protection housing (3), and • a measuring lance (5) mechanically connected to the measuring head (4) and extending through a housing opening (34) of the thermal protection housing (3) in the direction of a metal strand (2) to be analyzed, characterized in that the measuring arrangement (1 ) further comprises a cooling air supply (6) which is connected to the thermal protection housing (3) and serves to supply cooling air (7) into the thermal protection housing (3), wherein the measuring lance (5) is arranged at a distance from the thermal protection housing (3) in the area of ​​the housing opening (34), so that a cooling air outlet (35) is formed between the measuring lance (5) and the thermal protection housing (3), through which, during operation of the measuring arrangement (1 ), cooling air (7), which is introduced into the thermal protection housing (3) through the cooling air supply (6), can exit and flow along an outside of the measuring lance (5).

2. Measuring arrangement (1 ) according to claim 1 , characterized in that the measuring arrangement (1 ) has a control unit (8) operatively coupled to the measuring head (4) for controlling the measuring head (4).

3. Measuring arrangement (1 ) according to claim 1 or claim 2, characterized in that the measuring arrangement (1 ) has a camera (9) operationally coupled to the measuring head (4) which is provided and configured to i) determine an actual measuring position and / or an intended measuring position of an optical measuring radiation (41 ) emerging from the measuring head (4) and / or ii) determine an actual pre-ablation position and / or an intended pre-ablation position of an optical pre-ablation radiation (42) emerging from the measuring head (4). SPT1 12W0 23 4. Measuring arrangement (1 ) according to one of the preceding claims, characterized in that the measuring head (4) has a focusing system (43) with which a focus location (410) of an optical measuring radiation (41 ) emerging from the measuring head (4) and / or a focus location (420) of an optical pre-ablation radiation (42) emerging from the measuring head (4) can be adapted.

5. Measuring arrangement (1) according to claims 1 to 4, characterized in that the control unit (8) is provided and configured to adjust the focus point (410) of the optical measuring radiation (41) emerging from the measuring head (4) by means of the focusing system (43) depending on i) the actual measuring position and / or intended measuring position of the optical measuring radiation (41) emerging from the measuring head (4) determined by the camera (9) and / or ii) the actual pre-ablation position and / or intended pre-ablation position of the optical pre-ablation radiation (42) emerging from the measuring head (4).

6. Measuring arrangement (1 ) according to claim 4 or 5, characterized in that the focusing system (43) is provided and configured to effect a vertical movement of the measuring head (4) relative to the heat protection housing (3) and optionally to effect a lateral movement of the focus point (410) of the optical measuring radiation (41 ) exiting the measuring head (4) and / or the focus point (420) of the optical pre-ablation radiation (42) exiting the measuring head (4) transverse to a feed direction (V) of a metal strand (2).

7. Measuring arrangement (1 ) according to one of the preceding claims, characterized in that the measuring head (4) is a measuring head of a device for laser-induced plasma spectroscopy.

8. Measuring arrangement (1 ) according to one of the preceding claims, characterized in that the measuring arrangement (1 ) has a heat shield which is arranged between a distal opening (51 ) of the measuring lance (5) and a component located in the measuring head (4).

9. Measuring arrangement (1) according to one of the preceding claims, characterized in that the measuring arrangement (1) has a removable insert (12) which has at least one replaceable optical window (122) which SPT1 12W0 24 serves to protect components of the measuring head (4) that are located proximal to the optical window (122).

10. Method for determining the concentration of different elements in a metal strand (2) produced by a continuous casting process using a measuring arrangement (1) according to one of the preceding claims, the method comprising the following steps: a) positioning the heat shield housing (3), the measuring head (4), and the measuring lance (5) above a metal strand (2) moving in the feed direction (V), b) guiding cooling air (7) through the cooling air supply (6) into the heat shield housing (3), through the heat shield housing (3), and through the cooling air outlet (35) so that the cooling air (7) flows along the outside of the measuring lance (5), c) guiding optical measuring radiation (41) from the measuring head (4) through the measuring lance (5) onto the metal strand (2), d) detecting test radiation generated in the metal strand (2) by the measuring radiation (41) or reflected by the metal strand (2) as part of the measuring radiation (41). is achieved by the measuring arrangement (1 )and e) Determination of the concentration of different elements in the metal strand (2) by analyzing the test radiation using the measuring arrangement (1 )., 1 1. Method according to claim 10, characterized in that additionally optical pre-ablation radiation (42) from the measuring head (4) is directed through the measuring lance (5) onto the metal strand (2).

12. Method according to claim 10 or 11, characterized in that the measuring arrangement (1) comprises a control unit (8) operationally coupled to the measuring head (4) for controlling the measuring head (4) and a camera (9) operationally coupled to the measuring head (4), wherein the control unit (8) is determined by i) an actual measuring position and / or intended measuring position of the optical measuring radiation (41) emerging from the measuring head (4) as determined by the camera (9) and / or ii) an actual pre-ablation position and / or intended pre-ablation position of the optical radiation emerging from the measuring head (4) as determined by the camera (9). SPT1 12W0 25 pre-ablation radiation (42) adapts a focus location (410) of the optical measurement radiation (41) emerging from the measuring head (4) and / or a focus location (420) of the optical pre-ablation radiation (42) emerging from the measuring head (4) by means of a focusing system (43).

13. Method according to one of claims 10 to 12, characterized in that the concentration (15, 16, 17) of a plurality of elements in the metal strand (2) is determined as a function of the relative position in the metal strand (2).

14. Method according to claim 13, characterized in that the first derivative (150, 160, 170) of each specific concentration (15, 16, 17) is calculated via the relative position in the metal strand (2) and that a sum (180) of the magnitudes of the calculated first derivatives (150, 160, 170) is formed, wherein a change in the composition of the metal strand (2) is detected when the sum (180) of the magnitudes of the calculated first derivatives (150, 160, 170) exceeds a first limit value.

15. Method according to claim 14, characterized in that a material transition region (21 ) is defined in the metal strand (2) by assigning a starting point of the material transition region (21 ) to the relative position in the metal strand (2) at which the sum (180) of the magnitudes of the calculated first derivatives (150, 160, 170) exceeds the first limit, and by assigning an end point of the material transition region (21 ) to the relative position in the metal strand (2) at which the sum (180) of the magnitudes of the calculated first derivatives (150, 160, 170) falls below a second limit.

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