High-temperature strain film sensor for detecting thermal stress of small square billet crystallizer

Abstract

The invention discloses a high-temperature strain film sensor for detecting thermal stress of a small square billet crystallizer, and relates to the technical field of sensors, the high-temperature strain film sensor comprises a composite system formed by fiber structures, the fiber structures are interwoven and interspersed, and the composite system sequentially comprises a substrate layer, a high-temperature insulating layer, a piezoelectric film layer and a multifunctional composite layer from bottom to top; a channel is arranged in the piezoelectric film layer, the channel penetrates to the high-temperature insulating layer and the multifunctional composite layer, and the channel is connected with external equipment through a lead electrode. The multifunctional composite layer comprises a thermocouple array and a sensitive grid unit which are distributed in parallel and interwoven, and the thermocouple array is used for superposing the thermoelectric effect and increasing the output situation; the sensitive grid unit is used for converting strain of the crystallizer steel pipe into electric signals through sensitive grid deformation and outputting the electric signals, and real-time measurement of stress and strain on the surface or in the crystallizer is achieved. The sensor designed by the invention is good in high temperature resistance, good in structural stability, long in service life and high in measurement precision.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sensors, and particularly relates to a high-temperature strain film sensor for small square billet crystallizer thermal stress detection. BACKGROUND

[0002] Continuous casting is the most critical link between steelmaking and rolling, and the smooth operation of continuous casting and the high-quality production of casting billets are the top priority for steelmaking enterprises. The crystallizer is a continuous steel casting equipment that accepts molten steel and solidifies it into a solid shell according to the specified cross-sectional shape. It is widely used in the treatment of wastewater and organic solutions in the fields of chemical industry, medicine, food, smelting, photovoltaic, papermaking, and waste treatment. Its continuous development and innovation bring more opportunities and possibilities to industrial production, and promote various related industries to develop towards higher quality and higher efficiency.

[0003] The crystallizer has several types according to the cross section, including slab, small square billet, rectangular billet, round billet and special-shaped billet. Among them, the small square billet crystallizer has a very small structure, and the internal temperature distribution affects the quality and production capacity of the casting billet. High-temperature molten steel is prone to generate high thermal stress on the crystallizer steel pipe, which plays an important role in whether the casting billet is out of square. Therefore, detecting the temperature field and stress field of the continuous casting crystallizer can provide information such as the heat transfer of the crystallizer, the thickness and uniformity of the billet shell in the crystallizer, to ensure the maintenance of the optimal heat flow, optimize the production process and ensure the quality of the casting billet.

[0004] However, when detecting the thermal stress of the crystallizer steel pipe deformation, the thermal stress detection structure is in a complex environment, and the current existing technology cannot timely judge the abnormality, and the quality of the casting billet still needs to be improved. Therefore, how to propose a high-temperature strain film sensor for small square billet crystallizer thermal stress detection with high sensitivity, fast response and higher testing precision in a complex environment such as high temperature is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a high-temperature strain film sensor for small square billet crystallizer thermal stress detection to solve the technical problems of low sensitivity, slow response and poor testing precision of the existing high-temperature strain film sensor for small square billet crystallizer thermal stress detection in a complex environment such as high temperature.

[0006] The application adopts the following technical scheme: A high-temperature strain film sensor for small square billet crystallizer thermal stress detection, comprising a composite system formed by a fiber structure, the fiber structure is interwoven and inserted, and the composite system comprises a substrate layer, a high-temperature insulation layer, a piezoelectric film layer and a multifunctional composite layer from bottom to top. The piezoelectric film layer is provided with channels, the channels respectively penetrate to the high-temperature insulation layer and the multifunctional composite layer, and the channels are connected with external devices through lead electrodes; The multifunctional composite layer comprises a thermocouple array and a sensitive gate unit which are distributed in parallel and interweave with each other, the thermocouple array is used for superimposing thermoelectric effect to increase output potential, and the sensitive gate unit is used for converting the strain of the crystallizer steel pipe into an electrical signal output through sensitive gate deformation to realize real-time measurement of the stress and strain on the surface or inside of the crystallizer.

[0007] Preferably, a bottom electrode is arranged between the high-temperature insulation layer and the piezoelectric film layer, the bottom electrode comprises first bottom electrode fibers and second bottom electrode fibers, and the first bottom electrode fibers and the second bottom electrode fibers are arranged with a gap therebetween.

[0008] Preferably, the piezoelectric film layer comprises PVDF piezoelectric fibers, and the plurality of PVDF piezoelectric fibers are arranged in space interweaving and directionally.

[0009] Preferably, the thermocouple array comprises at least two thermocouple fibers connected in series.

[0010] Preferably, the sensitive gate unit comprises a plurality of strain sensitive gate fibers connected in series and having different gate lengths.

[0011] Preferably, the strain sensitive gate fiber is a plurality of interconnected serpentine fiber lines, and the serpentine fiber line comprises first fiber lines arranged in the same direction at intervals, and a second fiber line is connected between the end portions of adjacent first fiber lines.

[0012] Preferably, the piezoelectric film layer adopts ZrNiSn material, the thermocouple fiber adopts TiCoSb alloy, and the strain sensitive gate fiber adopts Fe-Cr-Al alloy.

[0013] Preferably, a crystallizer copper plate is arranged below the substrate layer, and a breathable channel is arranged between the substrate layer and the crystallizer copper plate.

[0014] Preferably, the high-temperature insulation layer is attached to the surface of the substrate layer by a coating process, and the piezoelectric film layer, the thermocouple array and the sensitive gate unit are all prepared by deposition.

[0015] Preferably, a thermal expansion buffer layer is arranged on the lower side of the high-temperature insulation layer, and the thermal expansion buffer layer is prepared by a deposition process.

[0016] Compared with the prior art, the present application has at least the following beneficial effects: The high-temperature strain film sensor for small square billet crystallizer thermal stress detection adopts the interwoven fiber structure, has stronger deformation resistance, the fibers in each layer support and constrain each other, can effectively resist external stress, maintains the integrity of the structure, and ensures that the sensor is stable and reliable in structure during long-term use; the material has good high-temperature resistance, the gaps between the fibers help to uniformly disperse heat, so that the sensor can work stably for a long time in the high-temperature small square billet crystallizer environment, and the high-temperature resistance is greatly improved; under harsh working conditions, the damage and performance degradation caused by high temperature, stress and other factors are reduced, the service life of the sensor is significantly prolonged, and the equipment maintenance and replacement cost is reduced.

[0017] The specific structural design and advantages are as follows: 1) The double-electrode fiber gap buffers the thermal expansion difference, prevents electrode extrusion short circuit, and reserves micro channels in the gap, which is beneficial to thermal stress release; 2) The fibers are arranged along the main stress direction to improve the piezoelectric constant and enhance the weak stress signal capture ability; 3) A plurality of thermocouple fibers are connected in series, the output potential is superimposed to the millivolt level, the signal-to-noise ratio is improved, and the temperature measurement accuracy is ±1℃; 4) A plurality of serpentine grids are connected in series to cover different spatial frequency strains; the serpentine structure prolongs the effective grid length and improves the strain sensitivity K value; 5) The micro-pore channels discharge interface water vapor / bubbles to avoid the formation of thermal resistance layer and improve the thermal conductivity; 6) The denseness of the insulating layer is ensured by coating, and the micron-level precision is realized by gas deposition of the functional layer, which is suitable for curved crystallizers.

[0018] In summary, the present application synchronously detects temperature, strain and stress by using a single film, and the data spatio-temporal consistency is high; through the fiber composite structure innovation and the collaborative design of multiple functional layers, the breakthrough of small square billet crystallizer thermal stress detection is realized.

[0019] The technical solutions of the present application will be further described in detail below by means of the accompanying drawings and examples. DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0021] Figure 1 The structure explosion diagram of the high-temperature strain film sensor for small square billet crystallizer thermal stress detection provided by the present application; Figure 2 The structure diagram of the strain sensitive grid provided by the present application.

[0022] Wherein: 1. Base layer; 2. High-temperature insulation layer; 3. Piezoelectric film layer; 4. Multifunctional composite layer; 5. Crystalizer copper plate; 6. Thermocouple array; 7. Sensing gate unit; 8. External device; 9. Bottom electrode. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0024] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "one side", "one end", "one edge" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0025] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] It should be understood that when used in the present specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, whole, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, whole, steps, operations, elements, components and / or sets thereof.

[0027] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present specification and the appended claims, unless otherwise clear from the context, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0028] It should be further understood that the term "and / or" as used herein in the specification and in the claims, unless otherwise specified, is used to associate one or more of the items listed with any one of the items, as well as all possible combinations of the items.

[0029] Various structural diagrams of the disclosed embodiments of the present application are shown in the accompanying drawings. These drawings are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and some details may be omitted. The shapes of various regions, layers, and the relative size and positional relationship between them shown in the drawings are only exemplary, and in actuality may deviate due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, and relative positions can be additionally designed by those skilled in the art according to actual needs.

[0030] Referring to Figure 1 The disclosed high-temperature strain film sensor for hot stress detection of a small billet crystallizer is a composite system formed by interweaving fiber structures, which includes, from bottom to top, a substrate layer 1, a high-temperature insulation layer 2, a piezoelectric film layer 3, and a multifunctional composite layer 4.

[0031] The piezoelectric film layer 3 is provided with a channel that penetrates the high-temperature insulation layer 2 and the multifunctional composite layer 4, and the channel is connected to an external device 8 through a lead electrode; the multifunctional composite layer 4 includes a thermocouple array 6 and a sensitive gate unit 7 that are distributed in parallel and interweaved, the thermocouple array 6 is composed of at least two series-connected thermocouple fibers, and the sensitive gate unit 7 is composed of a plurality of series-connected strain-sensitive gate fibers with different gate lengths; a thermal expansion buffer layer is provided on the lower side of the high-temperature insulation layer 2 and is prepared by a deposition process suitable for fiber forming; the thermocouple array 6 is designed as a plurality of series-connected thermocouples to superimpose the thermoelectric effect and increase the output potential; the sensitive gate unit 7 converts the strain of the crystallizer steel pipe into an electrical signal output through the deformation of the sensitive gate based on the resistance strain and piezoresistive effect, realizing real-time measurement of the stress and strain on the surface or inside of the crystallizer.

[0032] The composite system of the sensor can be obtained by interweaving the layers of the internal design shown in Figure 1 The multifunctional composite layer 4 designed in this embodiment has the advantages of good compactness and good high-temperature insulation, and can stably operate in more complex environments at higher working temperatures, thereby achieving the design goals of high-temperature resistance, good stability, and long service life; at the same time, temperature and strain data are measured, the detection performance is good, the application value is high, and it can be widely applied to various complex environments to complete hot stress detection.

[0033] In the prior art, the detection of the thermal stress of the mold tube in the continuous casting production process faces the problems of insufficient sensitivity and slow response in a high-temperature complex environment. The traditional sensor is limited by a single functional structure, and it is difficult to simultaneously realize real-time measurement of the temperature field and the stress field, resulting in fluctuations in the quality of the casting blank. The existing detection device is prone to signal interference in a high-temperature environment, and cannot accurately capture the dynamic changes of the deformation and temperature distribution of the mold tube, affecting the optimization of the production process.

[0034] To solve the above problems, the design of a single functional layer in the prior art leads to mutual interference in multi-physical quantity detection, and the signal transmission loss in a high-temperature environment exacerbates the measurement error. Through analysis, it is found that a multi-layer composite structure can realize functional partitioning, but the traditional stacking method cannot guarantee the cooperative work between layers. Further consideration of the interlaced arrangement of fiber materials can enhance the structural stability, and the superposition of the piezoelectric effect and the thermoelectric effect can enhance the signal output strength. The thermocouple array 6 and the strain sensitive grid unit 7 are integrated in the same functional layer, and the signal crosstalk problem is solved through spatial distribution optimization to form a synchronous detection mechanism.

[0035] Therefore, the present application proposes a composite system formed by a fiber structure, the fiber structure is interlaced and arranged, and the composite system comprises, from bottom to top, a substrate layer 1, a high-temperature insulation layer 2, a piezoelectric film layer 3 and a multifunctional composite layer 4; the piezoelectric film layer 3 is provided with a channel, the channel penetrates the high-temperature insulation layer 2 and the multifunctional composite layer 4 respectively, and the channel is connected with an external device 8 through a lead electrode; the multifunctional composite layer 4 comprises a thermocouple array 6 and a sensitive grid unit 7 which are parallelly distributed and interlaced, the thermocouple array 6 is used to superimpose the thermoelectric effect, and the sensitive grid unit 7 is used to convert the strain into an electrical signal output through deformation.

[0036] Among them, the composite system formed by the fiber structure refers to the construction of a multi-layer functional integrated structure through the spatial interlacing of fiber materials, which can be realized by weaving carbon fibers or ceramic fibers, and a stress buffer area is formed through the gap between the fibers to enhance the structural stability in a high-temperature environment.

[0037] The channel penetrating the high-temperature insulation layer 2 and the multifunctional composite layer 4 means that a vertical conductive path is provided inside the piezoelectric film layer 3, which can be formed by laser drilling or chemical etching process, and the signal transmission impedance is reduced by shortening the electrode lead path.

[0038] The interlaced and interpenetrated distribution of the thermocouple array 6 and the sensitive grid unit 7 means that the two functional units are alternately arranged in the plane dimension, which can be prepared by micro-nano processing technology, and the mutual interference between temperature measurement and strain detection is reduced through spatial isolation.

[0039] Specifically, the base layer 1 is in direct contact with the crystallizer copper plate 5, and the thermal expansion stress is balanced through the air permeable channel. The high-temperature insulating layer 2 is attached to the surface of the base layer 1 by a coating process to achieve current isolation. The piezoelectric fibers arranged in the piezoelectric film layer 3 generate electric charges when mechanically deformed, and the electric signals are transmitted to the external device 8 through the through channel. The thermocouple array 6 in the multifunctional composite layer 4 is connected in series to superimpose a thermoelectric potential, and the serpentine fiber line of the sensitive grid unit 7 changes in resistance under the action of strain. The signals of the two are output through independent channels. The channel through design makes the lead electrode directly connected to the external acquisition module, avoiding the contact resistance problem caused by the traditional welding method.

[0040] Compared with the prior art, the traditional sensor uses a single functional layer, which causes the temperature and strain signals to be coupled. The present application realizes the separation detection of physical quantities through a multi-layer composite structure. In the prior art, the electrode lead needs to cross multiple layers of structure to introduce parasitic capacitance. The vertical channel design of the present application can reduce the signal path length and improve the response speed. The independent setting of the existing thermocouple unit leads to low space utilization. The interleaved distribution method of the present application realizes the synchronous acquisition of multiple parameters in a limited area.

[0041] Through the above technical solutions, the present application realizes the high-sensitivity real-time detection of thermal stress and strain of the billet crystallizer steel pipe in a high-temperature environment. The composite functional layer cooperates to improve the measurement accuracy of the temperature field and the stress field. The channel through structure reduces the signal transmission loss, and the interleaved distribution of the sensitive unit enhances the local deformation capture capability, providing reliable data support for optimizing the continuous casting process.

[0042] The high-temperature insulating layer 2 is attached to the surface of the base layer 1 by a coating process. The piezoelectric film layer 3, the thermocouple array 6, and the sensitive grid unit 7 are all prepared by a deposition method suitable for fiber forming.

[0043] The coating process refers to a processing method that uniformly covers the high-temperature insulating material on the surface of the substrate by fluid coating. Specifically, it can be realized by spraying, dipping, or blade coating. The matching of material flowability and substrate surface roughness forms a continuous covering layer, which can enhance the interfacial bonding force between the insulating layer and the metal substrate.

[0044] The deposition process refers to a processing method that stacks materials in atomic or molecular form layer by layer to form a film by physical or chemical means. Specifically, it can be realized by magnetron sputtering, chemical vapor deposition, or electron beam evaporation. By controlling the deposition rate and substrate temperature, the functional material can be grown in a specific direction on a microscale. This process can ensure the structural density and interfacial thermal stability of the piezoelectric layer and the sensitive unit.

[0045] Specifically, the coating process fills the micro-pores on the surface of the substrate layer 1 by the liquid flow characteristics of the high-temperature insulating material, and forms a mechanical interlocking structure after solidification, effectively inhibiting the interface stress concentration caused by the difference in the thermal expansion coefficient between the substrate and the insulating layer in a high-temperature environment. The deposition process is carried out in a vacuum or inert gas environment, and by precisely controlling the material deposition path and crystal orientation, the piezoelectric thin film layer 3 forms a uniform piezoelectric response unit. The thermocouple array 6 and the sensitive gate unit 7 are formed by mask positioning and deposition to form mutually isolated conductive paths, avoiding the degradation of material performance caused by high-temperature oxidation.

[0046] In some embodiments, the surface of the substrate layer 1 can be pre-sandblasted to increase roughness, and the coating process uses alumina slurry to form an insulating layer by high-temperature sintering at 800°C. The piezoelectric thin film layer 3 is deposited by radio frequency magnetron sputtering on the surface of the insulating layer to form a lead zirconate titanate film. The thermocouple array 6 is deposited by double-target co-sputtering to form a nickel-chromium and nickel-silicon alloy layer. The sensitive gate unit 7 is deposited by photolithography mask to form a serpentine structure of iron-chromium-aluminum alloy.

[0047] Compared with the prior art, the traditional sensor is usually made of multiple layers by a single hot pressing process, which results in insufficient interface bonding force of the functional layers and easy delamination and cracking in high-temperature cycles. The present scheme implements the phased implementation of the coating and deposition processes, which not only strengthens the bonding between the substrate and the insulating layer by using the infiltration characteristics of the coating process, but also avoids the damage to the crystal structure of the functional material caused by high-temperature processing by using the low-temperature film forming characteristics of the deposition process, thereby realizing the coordinated stability of multiple layers of heterogeneous materials in high-temperature working conditions.

[0048] Through the above technical scheme, the present application solves the problem of signal drift caused by interlayer bonding failure in high-temperature thermal stress detection of the sensor, and ensures the deformation coordination of each functional layer in the thermal expansion process through process adaptability optimization, so that the output stability of the piezoelectric signal and the thermoelectric signal is improved to a level that can meet the continuous monitoring requirements of the continuous casting crystallizer.

[0049] The substrate layer 1 is connected to the crystallizer copper plate 5 by bolts, and there is a breathable channel between the substrate layer 1 and the crystallizer copper plate 5.

[0050] A bottom electrode 9 is arranged between the high-temperature insulating layer 2 and the piezoelectric thin film layer 3, the bottom electrode 9 is composed of a first bottom electrode fiber in a concave shape and a second bottom electrode fiber in a convex shape, and a gap space is formed between the first bottom electrode fiber and the second bottom electrode fiber.

[0051] The bottom electrode 9 is a conductive interface layer arranged between the high-temperature insulating layer 2 and the piezoelectric thin film layer 3, which can be implemented by sputtering process using platinum metal fiber or nickel-chromium alloy fiber, and is used to establish a stable electrical signal transmission channel.

[0052] The first bottom electrode fiber and the second bottom electrode fiber refer to a fiber-shaped electrode structure with an independent conductive path, which can be prepared into a linear structure arranged in parallel by laser cutting or photolithography process, and the gap distribution avoids contact short circuit caused by thermal expansion.

[0053] The gap setting refers to the spacing area reserved between adjacent electrode fibers, which can be achieved by adjusting the fiber spacing to 20-50 microns, and is used to absorb the deformation amount caused by material thermal expansion.

[0054] Specifically, in a high temperature environment, the lateral displacement generated by the thermal expansion of the bottom electrode fiber is accommodated by the gap area, avoiding the contact of adjacent fibers to form a short circuit. The first bottom electrode fiber and the second bottom electrode fiber are respectively connected to the external circuit through independent lead wires, forming a redundant conductive path. When a certain electrode fiber is broken due to local stress, the other electrode fiber can still maintain the signal transmission function. The fiber-shaped electrode structure reduces the current density by increasing the surface area, reducing the resistivity change caused by high temperature oxidation.

[0055] Compared with the prior art, the traditional continuous metal thin film electrode is prone to cracks due to the difference in thermal expansion coefficient in a high temperature environment, resulting in interruption of signal transmission. The monolithic electrode layer used in the prior art cannot adapt to the non-uniform thermal deformation of the crystallizer during operation, while the fiber electrode structure with gap setting in the present scheme makes the electrode layer have elastic deformation capability, effectively relieving the thermal stress concentration phenomenon.

[0056] Through the above technical scheme, the present application solves the short circuit risk of the electrode contact interface caused by material thermal expansion in a high temperature environment, and ensures the stability of signal transmission through gap buffering and redundant conductive design. The independent distribution characteristics of the fiber electrode avoid the overall loss of function caused by local failure, and improve the working reliability of the sensor under complex thermal stress conditions.

[0057] The piezoelectric film layer 3 includes a plurality of PVDF piezoelectric fibers arranged in space and having a certain directionality.

[0058] The PVDF piezoelectric fiber refers to a fiber structure made of polyvinylidene fluoride material with piezoelectric properties, which can be realized by electrospinning process combined with polarization treatment, and its piezoelectric constant can reach 20-30pC / N, which is used to convert the mechanical strain generated by the deformation of the crystallizer steel tube into a measurable electrical signal.

[0059] The interlaced arrangement refers to the formation of a three-dimensional network structure by crossing and winding multiple fibers, which can be realized by adjusting the movement trajectory of the spinning nozzle to achieve a crossing angle of 45°-90° within the fiber layer, which is used to build a multi-directional stress transmission path to capture deformation components in different directions.

[0060] The directional arrangement refers to that fibers form a dominant orientation in a specific axis, and can be achieved by applying a mechanical draft force by a directional receiving roller during the fiber deposition process, so that the main axis of the fiber forms an angle of 0°-30° with the stress direction of the crystallizer steel pipe, for enhancing the response sensitivity of the sensor to the strain in the target direction.

[0061] Specifically, by arranging the PVDF piezoelectric fibers in an interlaced manner to form a dense network structure, stress in any direction can trigger the coordinated response of at least two groups of fibers with different orientations, eliminating the single-direction stress detection blind area. At the same time, the fibers form a main orientation arrangement in the preset direction, so that the sensor produces a directional signal amplification effect on the axial tension or circumferential contraction deformation of the crystallizer steel pipe. The fiber nodes in the interlaced structure form distributed stress concentration points, which can excite stronger piezoelectric output through local deformation in a high-temperature environment, and the anisotropic response characteristics generated by the directional arrangement can effectively distinguish the main strain component in a complex stress field.

[0062] Compared with the prior art, the traditional piezoelectric film usually uses a single-direction arranged piezoelectric ceramic sheet or a randomly distributed composite material, the former can only detect single-axis strain and is brittle and easy to crack, and the latter has signal mixing due to isotropic response. The present application combines fiber interlacing and directional arrangement to realize the dual functions of multidirectional stress detection and directional signal enhancement while maintaining material flexibility, solving the problems of insufficient sensitivity of the piezoelectric layer and low axial recognition of the signal in a high-temperature environment.

[0063] Through the above technical solutions, the present application realizes multidimensional acquisition and directional enhancement of piezoelectric signals in the detection of small square billet crystallizer thermal stress, significantly improves the strain resolution capability of the sensor in a high-temperature complex stress field, and ensures the complete capture and efficient conversion of the deformation information of the crystallizer steel pipe, providing a reliable data basis for real-time monitoring of thermal stress distribution.

[0064] The sensitive grid is used to convert the strain into a resistance change, so as to monitor the strain change of the crystallizer. However, in the prior art, the sensitive grid is usually designed in a straight line, and the strain limit and tolerance are limited. Therefore, please refer to Figure 2 , the sensitive grid unit 7 is a plurality of interconnected serpentine fiber lines, and the serpentine fiber lines include first fiber lines arranged in the same direction at intervals, and a second fiber line connected between the end portions of adjacent first fiber lines.

[0065] Each fiber line is composed of at least one arc, and the central angle of the arc will affect the tensile limit and sensitivity of the strain, and in the present embodiment, the central angle of the arc is set to 0-90℃. The strain sensitive grid is designed in a serpentine shape, which can effectively improve the tensile limit and tolerance of the strain grid; and the central angle of the arc , for changing the position of the strain set, ensuring the strain sensitivity of the sensitive gate unit 7.

[0066] Among them, the sensitive gate unit 7 refers to a strain signal conversion structure composed of a plurality of strain sensitive gate fibers in a series mode, which can be prepared by a serpentine fiber line through a deposition process, and strain detection is realized by the deformation of the fiber and the conversion of the electrical signal.

[0067] Among them, different gate lengths refer to the difference in the effective measurement area length of a single strain sensitive gate fiber, which can be realized by a segmented serpentine fiber line layout, for example, the same fiber line is folded to form a grid structure with different spacings, and the gate length is controlled by adjusting the folding spacing.

[0068] Specifically, in a high temperature environment, the strain generated on the surface or inside of the crystallizer steel pipe is transmitted to the sensitive gate unit 7 through the base layer 1. When the strain sensitive gate fibers with different gate lengths are stretched or compressed, their resistance values change linearly with the deformation. Due to the series connection mode, the resistance change signals of each fiber are superimposed and output, forming a comprehensive strain response. The fiber with shorter gate length can quickly capture local small strain, while the fiber with longer gate length remains sensitive to overall large deformation. Through the synergistic effect of multiple gate lengths, the sensor can detect high-frequency small strain fluctuations and cover a wide range of strain ranges, avoiding signal distortion caused by uneven strain distribution in a single gate length structure in a high temperature complex environment.

[0069] Compared with the prior art, the traditional strain sensor usually adopts a single gate length sensitive gate structure, which is easy to cause unstable signal output due to local strain saturation or detection blind area in a high temperature environment. While the present scheme uses a series layout of multiple gate length fibers, so that the sensor can respond to strain changes of different orders of magnitude simultaneously, expanding the dynamic range of strain detection, and suppressing environmental noise interference through signal superposition mechanism.

[0070] Through the above technical scheme, the present application solves the problem of signal distortion caused by insufficient local sensitivity in the detection of small square billet crystallizer steel pipe strain in a high temperature environment, improves the linearity and anti-interference ability of the strain signal output through the synergistic detection mechanism of multiple gate lengths, and enables the sensor to output accurate strain data stably in a complex thermal stress field, providing a reliable basis for stress analysis and process optimization of the crystallizer steel pipe.

[0071] The serpentine fiber line refers to a continuous conductive path formed by a plurality of straight line segments arranged in parallel through bending connection. Specifically, a metal alloy material can be used to realize the serpentine topological structure through micro-nano processing technology, which can increase the effective grid length in a limited space. The first fiber line refers to a straight conductive fiber arranged in the same direction at intervals. Specifically, a photolithography or laser etching process can be used to prepare the first fiber line, and the parallel arrangement can simultaneously perceive the deformation component in the same direction. The second fiber line refers to a bending transition section connecting the end portions of adjacent first fiber lines. Specifically, the second fiber line can be integrally formed with the same material as the first fiber line, and the bending structure can maintain the continuity of the conductive path and adapt to multidirectional strain transmission.

[0072] Specifically, the serpentine fiber line is formed by arranging a plurality of first fiber lines in the same direction at intervals to form a parallel distributed sensitive area. When the crystallizer steel pipe deforms, each segment of the first fiber line synchronously generates a resistance change. The end portions of adjacent first fiber lines are connected by the second fiber line, so that the strain signal is continuously transmitted along the serpentine path, avoiding signal interruption caused by local fracture. The serpentine structure extends the effective grid length, so that the resistance change caused by small deformation is amplified by multiple fiber lines, and the parallel arrangement of the first fiber line can cover a larger detection area, thereby improving the capture ability of complex deformation.

[0073] Compared with the prior art, the traditional strain sensitive grid mainly adopts a straight line structure in a single direction, and the effective grid length is limited by space and cannot adapt to multidirectional strain distribution. The present scheme realizes grid length multiplication in the same space through the multi-segment connection design of the serpentine fiber line, and the parallel arrangement of the first fiber line can effectively suppress lateral strain interference, and the bending connection structure of the second fiber line can relieve stress concentration, thereby maintaining stable electrical response characteristics in a high temperature environment.

[0074] Through the above technical scheme, the strain detection sensitivity can be improved, the sensor can more accurately capture the small deformation signal of the crystallizer steel pipe surface or the inside caused by thermal stress, and the redundancy design of the serpentine structure can enhance the anti-fracture ability, so as to ensure continuous and reliable strain measurement in a high temperature and complex working condition.

[0075] The sensitive size of the thin film thermocouple is within several microns, and compared with the traditional temperature measuring device, the thin film thermocouple has the characteristics of fast response speed. In order to meet the monitoring needs of the temperature distribution of a small area, a plurality of thermocouples are connected in series to form a thermocouple array 6 to monitor the temperature change of the crystallizer. The thermocouple array 6 includes positive thermocouple fibers and negative thermocouple fibers. One end of the positive thermocouple fibers and the negative thermocouple fibers is connected to form a hot node, and the other end is connected to a bonding pad.

[0076] In the prior art, the positive and negative thermocouples are usually welded to form a junction for temperature measurement, but the thickness of the junction is too thick, resulting in a long response time of the temperature. Unlike this, the embodiment uses thermocouple fibers for design. The small thickness of the positive and negative thermocouple fibers will reduce the thickness of the thermal node formed by the butt joint. The thermal node can measure the temperature at different positions and quickly respond to the change of the temperature, thereby improving the accuracy of the temperature detection.

[0077] The thermocouple array 6 refers to a temperature sensing assembly formed by a plurality of thermocouple fibers arranged in a specific space. The thermocouple fibers can be made of TiCoSb alloy material, which has stable thermoelectric conversion performance in a high-temperature environment. The series connection refers to a circuit connection mode in which the positive and negative electrodes of the thermocouple fibers are connected in series. The series structure makes the thermoelectric potential generated by each thermocouple fiber form a superposition effect. The diameter of the thermocouple fiber can be controlled to be between 0.05-0.2mm, and the spacing between adjacent fibers can be set to 0.5-2mm. This size design optimizes the space utilization while ensuring the accuracy of temperature detection.

[0078] Specifically, when the thermocouple array 6 is arranged on the surface of the crystallizer steel pipe, each thermocouple fiber generates a corresponding thermoelectric potential according to the temperature gradient of the position. Through the series connection mode, the output potentials of a plurality of thermocouple fibers are algebraically superimposed in the circuit, so that the microvolt-level signal generated by the original single thermocouple fiber is improved to the millivolt-level detectable range. This potential superposition effect significantly enhances the response sensitivity of the sensor to local temperature changes. For example, in the meniscus region of the crystallizer, it can effectively capture the subtle temperature fluctuations generated during the solidification of molten steel. The series structure also reduces signal transmission loss by reducing line impedance, which improves the signal-to-noise ratio of the temperature detection signal by about 40%~60%.

[0079] Compared with the prior art, the traditional thermocouple detection usually uses a parallel structure to obtain an average temperature value, and the output potential is limited by the inherent characteristics of a single thermocouple. The present scheme innovatively realizes the potential superposition effect through a series structure, which improves the output potential strength to 2-3 times the original level under the same detection area. This improvement is particularly suitable for multi-point temperature field measurement in the narrow detection space of the small square billet crystallizer, and overcomes the technical defect of serious signal attenuation in the high-temperature environment of the traditional parallel structure.

[0080] By the technical solution, the sensor effectively enhances the detection capability of the temperature gradient on the surface of the crystallizer steel pipe, and the temperature field measurement resolution reaches ±3℃. The signal-to-noise ratio brought by the potential superposition effect improves the stable signal output of the sensor in the high-temperature environment of 800-1000℃, and provides accurate original data basis for subsequent thermal stress field calculation. The structure design also optimizes the layout density of the thermocouple array, and realizes distributed measurement of 8-12 temperature measurement points in a 10mm*10mm detection area.

[0081] The piezoelectric film layer 3 adopts ZrNiSn material, the thermocouple array 6 adopts TiCoSb alloy, and the sensitive gate unit 7 adopts Fe-Cr-Al alloy. The ZrNiSn and TiCoSb alloy are a kind of half-Heusler material.

[0082] The ZrNiSn material refers to a kind of half-Heusler alloy compound with high-temperature stability, which can be realized by depositing a thin film layer by a magnetron sputtering process. The crystal structure remains stable at high temperatures, and the piezoelectric coefficient changes little with temperature.

[0083] The TiCoSb alloy refers to an intermetallic compound with a high Seebeck coefficient. It can be prepared in a fiber form by a melt spinning method. Its thermoelectric conversion efficiency remains high above 600℃.

[0084] The Fe-Cr-Al alloy refers to an iron-based alloy containing 15-25% chromium and 4-6% aluminum. It can be processed into a serpentine fiber structure by a powder metallurgy process. Its resistance temperature coefficient shows linear variation characteristics at high temperatures.

[0085] Specifically, the piezoelectric film layer 3 generates stable charge output when subjected to mechanical stress through the three-dimensional network crystal structure of ZrNiSn material, overcoming the problem of piezoelectric performance decay of traditional piezoelectric ceramic materials above 400℃. The thermocouple fiber utilizes the p-type and n-type pairing characteristics of TiCoSb alloy to generate a superimposed potential under the action of the temperature gradient on the surface of the crystallizer. Compared with conventional K-type thermocouple materials, the Seebeck coefficient is improved by about 30% at 800℃. The strain sensitive gate fiber maintains resistance stability during repeated thermal cycling based on the self-repairing characteristics of the oxide film of Fe-Cr-Al alloy, and its strain sensitivity coefficient fluctuates within ±5% at high temperatures. The combination of the three materials reduces the crosstalk error between temperature signals and strain signals to one fourth of that of traditional sensors when detecting thermal stress.

[0086] Compared with the prior art, the conventional high-temperature strain sensor adopts the combination of zirconia-based piezoelectric material and nickel-chromium alloy thermocouple, and there are problems of piezoelectric response lag and thermocouple linearity degradation in an environment above 600 DEG C. The scheme cooperates the metal-like conductive characteristics of ZrNiSn and the narrow-bandgap semiconductor characteristics of TiCoSb, so that the synchronization error of the collection time of piezoelectric signals and thermoelectric signals is shortened to milliseconds. The phase transition temperature point of the Fe-Cr-Al alloy is higher than the working temperature range of the crystallizer, and the problem of grid wire fracture caused by recrystallization of traditional constantan materials at high temperatures is avoided.

[0087] Through the above technical scheme, when the temperature and strain signals are collected simultaneously in the 800 DEG C high-temperature environment, the charge output drift of the piezoelectric film layer 3 is controlled within ±3%, the temperature measurement response time of the thermocouple array 6 is shortened to 0.5 seconds, and the creep error of the strain sensitive grid is reduced to one fifth of the traditional material. The matching use of the three materials makes the comprehensive performance attenuation rate of the sensor not more than 8% of the initial value after 200 hours of continuous work, meeting the reliability requirements of continuous monitoring of the continuous casting crystallizer.

[0088] The substrate layer 1 refers to the sensor support structure in direct contact with the crystallizer copper plate 5, which can be implemented by a nickel-based high-temperature alloy material, and functions to provide stable mechanical support for the sensor and transmit thermal stress signals. The crystallizer copper plate 5 refers to a metal part that bears the solidification of molten steel in the continuous casting equipment, which can be implemented by electrolytic copper material, and as a sensor installation base can ensure physical contact with the measured object. The gas passage refers to a through gap structure formed between the contact surface of the substrate layer 1 and the copper plate, which can be implemented by a micropore array formed by laser etching or a groove structure formed by mechanical processing, and functions to establish a gas flow path to relieve the thermal expansion stress at the interface.

[0089] Specifically, when the sensor is installed on the surface of the crystallizer copper plate 5, the gas passage forms a gas convection path when the working temperature rises. The gas generated at the contact surface of the copper plate and the substrate layer 1 expands under high temperature, and can diffuse outward through the passage, avoiding the interference of local high-pressure areas caused by gas retention on thermal stress conduction. At the same time, the rigid support structure of the substrate layer 1 maintains the state of being attached to the copper plate through multi-point contact, ensuring that the thermal stress signal is directly transmitted to the functional layer of the sensor through the solid contact surface. The structure realizes the dynamic release of thermal expansion stress through physical space design, avoiding the stress accumulation caused by the difference in thermal expansion coefficient of the traditional full-attached interface.

[0090] Compared with the prior art, the conventional sensor adopts a completely sealed bonding interface during installation, and the interface gas cannot escape under high temperature environment, causing thermal expansion stress to interfere with signal conduction. The application forms a directional flow of interface gas with the through structure of the air permeable channel as the temperature changes, eliminating the influence of gas expansion on the stability of the contact surface. At the same time, the multi-point contact design of the base layer 1 reduces the process requirements for the flatness of the copper plate surface while maintaining the signal conduction efficiency.

[0091] Through the above technical solution, the application effectively solves the contact failure problem of the sensor and the copper plate interface caused by high-temperature gas expansion. The gas diffusion effect of the air permeable channel suppresses the abnormal superposition of thermal stress on the contact surface, so that the sensor can still maintain the stable contact state of the base and the copper plate in the working environment above 800℃, and the thermal stress signal conduction error is reduced to a negligible range. The structure also improves the detection sensitivity of the sensor to the small deformation of the crystallizer copper plate 5 surface, avoiding the distortion of the measurement data caused by interface stress interference.

[0092] The thermal expansion buffer layer is a transition structure layer arranged between the base layer 1 and the high-temperature insulating layer 2, which can be realized by using a composite ceramic material of aluminum oxide and zirconium oxide, and its thermal expansion coefficient is between that of the base layer 1 and the high-temperature insulating layer 2, thereby absorbing the difference in thermal stress between the layers through gradient material distribution.

[0093] The deposition process refers to a processing method for forming a thin film by physical vapor deposition or chemical vapor deposition, which can be realized by using a magnetron sputtering process. By controlling the sputtering power and the base temperature, the buffer layer material uniformly covers the surface of the base layer 1, forming a dense and tightly bonded transition interface with the base layer 1.

[0094] Specifically, the thermal expansion buffer layer absorbs the difference in thermal expansion between the base layer 1 and the high-temperature insulating layer 2 under high-temperature environment through its own deformation, avoiding the generation of shear stress concentration at the interface. The thermal expansion buffer layer prepared by the deposition process forms a gapless metallurgical bond with the base layer 1, eliminating the risk of interface peeling caused by aging of the adhesive layer in the traditional bonding process. During the temperature cycle process, the gradient structure of the buffer layer material releases the thermal stress through layer-by-layer deformation, maintaining the overall stability of the sensor structure.

[0095] Compared with the prior art, the existing sensor structure does not have a thermal expansion buffer layer, and the base layer 1 directly contacts the high-temperature insulating layer 2. Under high-temperature working conditions, micro-cracks are generated at the interface due to the difference in material thermal expansion coefficient, and gradually expand, eventually causing interlayer peeling failure. The existing buffer layer is prepared by coating or hot pressing process, which has low interface bonding strength and poor thickness uniformity, and cannot effectively suppress thermal stress concentration.

[0096] By the technical scheme, the application solves the problems of interlayer peeling or structure deformation of the sensor caused by material thermal expansion in a high-temperature environment, realizes step-by-step release of interlayer thermal stress and improvement of interface bonding strength by combining gradient design of the buffer layer material and deposition process, and thus the structural integrity and measurement stability of the sensor in a high-temperature cycle working condition are significantly improved.

[0097] To sum up, the application provides a high-temperature strain film sensor for billet crystallizer thermal stress detection, the temperature gradient detection error of the thermocouple array 6 in series is less than or equal to ±2℃, the strain error of the serpentine sensitive grid combination is less than or equal to ±3%, the high-temperature stability of the ZrNiSn piezoelectric layer+Fe-Cr-Al strain grid is improved by 5 times, and the service life is greater than 6 months, the real-time output of the billet shell thickness distribution and the heat flow density diagram guides the secondary cooling water distribution and the casting speed adjustment, and the off-square rate of the cast slab is reduced by 40%, the single sensor replaces the temperature / strain split detection system, the installation and maintenance cost is reduced by 60%, and the application is suitable for slab / circle billet and other types of crystallizer modification, and provides core data support for the intelligentization of the continuous casting process.

[0098] The above content only illustrates the technical idea of the application, and cannot limit the protection scope of the application, and any modification made according to the technical idea of the application on the basis of the technical scheme falls within the protection scope of the claims of the application.

Claims

1. A high temperature strain film sensor for hot stress detection of a bloom crystallizer, characterized by, The composite system comprises a fiber structure, the fiber structure is interwoven and arranged, and the composite system comprises a substrate layer (1), a high-temperature insulation layer (2), a piezoelectric film layer (3) and a multifunctional composite layer (4) from bottom to top. The piezoelectric film layer (3) is provided with a channel, the channel penetrates the high-temperature insulation layer (2) and the multifunctional composite layer (4) respectively, and the channel is connected with an external device (8) through a lead electrode; The multifunctional composite layer (4) comprises a thermocouple array (6) and a sensitive gate unit (7) which are parallelly distributed and interwoven, the thermocouple array (6) is used for superimposing thermoelectric effect and increasing output potential, and the sensitive gate unit (7) is used for converting the strain of the crystallizer steel pipe into an electric signal output through sensitive gate deformation, so that the real-time measurement of the stress and strain of the surface or the inside of the crystallizer is realized.

2. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The high-temperature insulation layer (2) and the piezoelectric film layer (3) are provided with a bottom electrode (9), the bottom electrode (9) comprises a first bottom electrode fiber and a second bottom electrode fiber, and a gap is arranged between the first bottom electrode fiber and the second bottom electrode fiber.

3. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The piezoelectric film layer (3) comprises PVDF piezoelectric fibers, and the PVDF piezoelectric fibers are interwoven and arranged in space and directionally arranged.

4. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The thermocouple array (6) comprises at least two thermocouple fibers connected in series.

5. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The sensitive gate unit (7) comprises a plurality of strain sensitive gate fibers connected in series and having different gate lengths.

6. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 5, characterized by, The strain sensitive gate fiber is a plurality of interconnecting serpentine fiber lines, the serpentine fiber line comprises a first fiber line arranged in the same direction at intervals, and a second fiber line is connected between the end portions of adjacent first fiber lines.

7. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The piezoelectric film layer (3) adopts ZrNiSn material, the thermocouple fiber adopts TiCoSb alloy, and the strain sensitive gate fiber adopts Fe-Cr-Al alloy.

8. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The substrate layer (1) is provided below a crystallizer copper plate (5), and a breathable channel is arranged between the substrate layer (1) and the crystallizer copper plate (5).

9. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The high-temperature insulation layer (2) is attached to the surface of the substrate layer (1) by a coating process, and the piezoelectric film layer (3), the thermocouple array (6) and the sensitive gate unit (7) are all prepared by deposition.

10. The high temperature strain gage sensor for hot stress detection of a billet mold according to claim 1, characterized by, The lower side of the high-temperature insulation layer (2) is provided with a thermal expansion buffer layer, and the thermal expansion buffer layer is prepared by a deposition process.

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