Method for manufacturing high-temperature strain gage grid wire

Abstract

The application discloses a preparation method of a high-temperature strain gage grid wire, and the preparation method comprises the following steps: vacuum electric arc smelting of super-high-temperature strain alloy material, rolling into a foil with uniform curvature, heat treatment of the foil to obtain a uniform fine-grained structure, preparation of the foil after the heat treatment into a grid wire by using a femtosecond laser direct writing technology, in-situ real-time monitoring and defect self-correction of the grid wire, functionalization of the grid wire, integrated packaging of the grid wire, and the like. The preparation method of the high-temperature strain gage grid wire uses a femtosecond laser to replace traditional mechanical means such as drawing and wire winding to prepare the grid wire, the grid wire is uniform in size, high in precision and good in material performance, so that the measurement precision of the grid wire can be ensured and the grid wire has long-term reliability in a high-temperature environment, and the preparation process of the grid wire can be integrated on a laser platform, so that the preparation process is simple and efficient, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of high-temperature strain gauge grid wire preparation technology, and more specifically, to a method for preparing high-temperature strain gauge grid wire. Background Technology

[0002] High-temperature strain gauge wires are an important component of strain gauges. Strain gauges are widely used in various mechanical tests. When an external force is applied to a strain gauge, the high-temperature strain gauge wires can sensitively capture minute deformations and convert them into electrical signals. This makes the strain gauge more accurate and reliable when measuring minute strains, and it can accurately measure even in high-temperature environments.

[0003] In related technologies, the fabrication of high-temperature strain gauge grid wires mainly employs a combination of metal wire drawing and mechanical winding processes. Regarding processing precision, traditional wire drawing processes are limited by die wear and the inhomogeneity of material plastic deformation, making precise control of the grid wire linewidth difficult. Furthermore, defects such as wire breakage, surface cracks, and uneven microstructure are prone to occur. Mechanical positioning errors and metal wire tension fluctuations in the winding process further reduce the consistency of the grid wire geometry, resulting in significant dispersion in the strain gauge's resistance values. Secondly, in terms of material properties, dislocation multiplication and lattice distortion generated during cold drawing introduce a large amount of residual stress into the metal wire. These internal stresses undergo stress relaxation at high temperatures, causing zero-point drift and unstable temperature coefficients in the strain gauge, limiting the grid wire's service life, reliability, and measurement accuracy. Moreover, traditional manufacturing processes require multiple process conversions, resulting in high production costs. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the defects and shortcomings of the existing technology by proposing a method for preparing high-temperature strain gauge wires. The method uses femtosecond lasers to replace traditional mechanical means such as drawing and winding to prepare the wires. The wires are uniform in size, have high precision, and good material properties, which can ensure the measurement accuracy of the wires and make them reliable in high-temperature environments for a long time. Moreover, the preparation process of the wires can be integrated into a laser platform, making the preparation process simple, efficient, and reducing production costs.

[0005] The method for preparing high-temperature strain gauge grid wires according to embodiments of the present invention includes: vacuum arc melting of ultra-high temperature strain alloy material and rolling it into a foil with uniform curvature; heat-treating the foil to obtain a uniform fine-grained structure; preparing the heat-treated foil into grid wires using femtosecond laser direct writing technology; performing in-situ real-time monitoring and defect self-correction on the grid wires; and performing functionalization post-processing and integrated packaging on the grid wires.

[0006] The method for preparing high-temperature strain gauge wires in this invention utilizes femtosecond lasers instead of traditional mechanical methods such as drawing and winding to prepare the wires. The wires are uniform in size, have high precision, and good material properties, thus ensuring the measurement accuracy of the wires while maintaining long-term reliability in high-temperature environments. Furthermore, the wire preparation process can be integrated into a laser platform, making the preparation process simple, efficient, and reducing production costs.

[0007] In some embodiments, the process of vacuum arc melting of ultra-high temperature strain alloy materials and rolling them into foils with uniform curvature includes: melting ultra-high temperature strain alloy materials such as Fe-Cr-Al alloy, Ni-Cr, Pt-W, and high-entropy alloys and rolling them into uniform foils with a thickness of 15–30 μm.

[0008] In some embodiments, the heat treatment of the foil to obtain a uniform fine-grained structure includes: subjecting the foil to a double-cycle heat treatment of 1070°C solution treatment and 850°C aging treatment to obtain a uniform fine-grained structure with an average grain size of 3–5 μm and a dislocation density of <1×10¹³ m⁻², providing a low-defect substrate for subsequent "cold working".

[0009] In some embodiments, the process of fabricating the heat-treated foil into grid wires using femtosecond laser direct writing technology includes:

[0010] A femtosecond laser with an 800nm, 180fs, and 1kHz to 1MHz adjustable repetition frequency was used, and the laser was focused to a 0.6μm spot using an apochromatic objective lens with NA=0.8.

[0011] In some embodiments, the method for preparing the high-temperature strain gauge grid wire further includes:

[0012] The three-level path of "coarse scan - fine scan - compensation scan" is executed by using a galvanometer and a six-axis ultra-precision displacement platform coupled control.

[0013] The adaptive power algorithm is invoked synchronously to correct the energy attenuation caused by plasma shielding in real time.

[0014] In some embodiments, the in-situ real-time monitoring and defect self-correction of the grid wire includes:

[0015] Coaxial confocal microscopy combined with a deep learning defect recognition network is used to perform frame-level analysis of ablation groove width, edge burrs, and repetitive pulse overlap rate.

[0016] In some embodiments, the method for preparing the high-temperature strain gauge grid wire further includes: automatically comparing the system with the CAD design values ​​and dynamically adjusting the scanning speed or pulse energy when the error is >0.2μm.

[0017] In some embodiments, the functionalization post-processing and integrated packaging of the gate wire includes:

[0018] After laser writing is completed, Ar is performed at the same workstation. + Spray micropolishing;

[0019] An insulating / anti-oxidation film is then formed by low-temperature atomic layer deposition.

[0020] In some embodiments, the method for preparing the high-temperature strain gauge grid wire further includes:

[0021] A window is opened in the lead pad area using laser selective removal technology;

[0022] Resistance welding is used to weld the leads to the pad area.

[0023] In some embodiments, the method for preparing the high-temperature strain gauge grid wire further includes:

[0024] A high-temperature vapor phase coating of SiO2–Y2O3 is applied to the entire surface to form a protective layer that can operate continuously in an oxidizing atmosphere at 1200℃. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a method for preparing high-temperature strain gauge grid wires according to an embodiment of the present invention. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] like Figure 1 As shown, the method for preparing the high-temperature strain gauge grid wire in this embodiment of the invention includes: vacuum arc melting of ultra-high temperature strain alloy material and rolling it into a foil with uniform curvature; then heat-treating the foil to obtain a uniform fine-grained structure; then using femtosecond laser direct writing technology to prepare the heat-treated foil into a grid wire; then performing in-situ real-time monitoring and defect self-correction on the grid wire; and finally performing functionalization post-processing and integrated packaging on the grid wire.

[0028] It should be noted that the traditional high-temperature strain gauge grid wire preparation process usually requires a multi-station process of drawing, annealing, winding, welding leads, and Teflon tape encapsulation. However, mechanical processing methods such as drawing and winding are limited by mold wear and the unevenness of material plastic deformation, making it difficult to achieve precise control of the grid wire linewidth, and are prone to defects such as wire breakage, surface cracks, and uneven structure.

[0029] This application introduces femtosecond laser cutting technology to replace traditional mechanical preparation methods, which improves cutting accuracy while avoiding damage to the material properties of the foil. Furthermore, this application can complete the entire preparation process on the same laser platform, making the preparation process simpler and more efficient compared to the multi-station process of traditional technology.

[0030] The method for preparing high-temperature strain gauge wires in this invention utilizes femtosecond lasers instead of traditional mechanical methods such as drawing and winding to prepare the wires. The wires are uniform in size, have high precision, and good material properties, thus ensuring the measurement accuracy of the wires while maintaining long-term reliability in high-temperature environments. Furthermore, the wire preparation process can be integrated into a laser platform, making the preparation process simple, efficient, and reducing production costs.

[0031] Furthermore, the process of vacuum arc melting of ultra-high temperature strain alloy materials and then rolling them into foils with uniform curvature includes:

[0032] The material is made by melting and rolling Fe-Cr-Al alloy or Ni-Cr, Pt-W, high-entropy alloy and other ultra-high temperature strain alloy materials into uniform foil with a thickness of 15-30 μm.

[0033] Furthermore, the heat treatment of the foil to obtain a uniform fine-grained structure includes: performing a double-cycle heat treatment of the foil at 1070℃ solution treatment and 850℃ aging treatment to obtain a uniform fine-grained structure with an average grain size of 3–5 μm and a dislocation density of <1×10¹³ m⁻², providing a low-defect substrate for subsequent "cold working". It is understandable that the double-cycle heat treatment can avoid the large amount of work hardening accumulated inside the filament during traditional continuous drawing, providing a stable metallic phase for femtosecond laser micro / nano removal.

[0034] Furthermore, the process of fabricating grid wires from heat-treated foil using femtosecond laser direct writing technology includes:

[0035] A femtosecond laser with an 800nm, 180fs, and 1kHz to 1MHz adjustable repetition frequency was used, and the laser was focused to a 0.6μm spot using an apochromatic objective lens with NA=0.8.

[0036] Furthermore, by utilizing the coupled control of a galvanometer and a six-axis ultra-precision displacement platform, a three-stage path of "coarse scan - fine scan - compensation scan" is executed; simultaneously, an adaptive power algorithm is invoked to correct the energy attenuation caused by plasma shielding in real time.

[0037] Specifically, it can "write" grid wire patterns with a grid width of 5–50 μm and a grid pitch of 10–100 μm on a two-dimensional plane in one go, with an actual heat-affected zone of <10 nm, which can achieve true "cold processing" and completely eliminate the bending stress and annealing and tempering steps generated by traditional winding.

[0038] Furthermore, in-situ real-time monitoring and defect self-correction of the grid wires include:

[0039] Coaxial confocal microscopy combined with a deep learning defect recognition network is used to perform frame-level analysis of ablation groove width, edge burrs, and repetitive pulse overlap rate.

[0040] The system then automatically compares the data with the CAD design values ​​and dynamically adjusts the scanning speed or pulse energy when the error exceeds 0.2μm. This closed-loop system ensures dimensional accuracy during the manufacturing stage, eliminating the need for post-processing screening and significantly improving yield.

[0041] Furthermore, the functionalization and integrated packaging of the grid wires include:

[0042] After laser writing is completed, Ar is performed at the same workstation. + Spray micropolishing is performed to remove the sub-nanometer resolidification layer, followed by the formation of an insulating / anti-oxidation film via low-temperature atomic layer deposition (ALD). Specifically, an 80nm Al2O3 insulating / anti-oxidation film is deposited using 250°C low-temperature atomic layer deposition (ALD).

[0043] Furthermore, a window is opened in the lead pad area using laser selective removal technology, and then the lead is welded to the pad area using resistance welding. Finally, a SiO2–Y2O3 high-temperature vapor phase coating is applied to the entire structure, forming a protective layer that can operate continuously in an oxidizing atmosphere at 1200℃. Therefore, the functionalized post-processing and integrated packaging of this application can achieve full-process integration of "processing – insulation – lead – packaging" on the same platform. Compared with the traditional multi-station process that requires separate drawing, annealing, wire winding, lead welding, and Teflon tape encapsulation, the complexity is reduced by more than 50%.

[0044] Furthermore, after the grid wires are prepared, reliability evaluation and calibration are required. Specifically, 6 to 12 sensitive grids are randomly selected from a batch of production, and their resistance is measured at room temperature. The average value and dispersion of the resistance are statistically analyzed. Then, resistance drift test is performed in a high-temperature furnace at room temperature to 1200℃ for 10 thermal cycles. Finally, fatigue life test is performed on the high-temperature fatigue test specimen at room temperature to 1200℃ with a loading amplitude of 500με.

[0045] The aforementioned reliability evaluation and calibration can verify the long-term stability of femtosecond laser gratings under extreme service conditions, providing quantitative data support for engineering applications in fields such as aero-engines and nuclear power primary loops.

[0046] In summary, this invention, through the organic combination of metal foil as a substrate, femtosecond laser as a processing method, precision motion control platform, and subsequent surface treatment, breaks through several bottlenecks in the prior art, significantly improving the structural accuracy, material properties, and adaptability of the high-temperature strain gauge grating wire, and fully leveraging the unique advantages of the synergistic integration of new materials and advanced manufacturing processes.

[0047] Specifically, the high-temperature strain gauge grid wire prepared in this application has the following advantages over traditional grid wires:

[0048] 1. Measurement accuracy: The linewidth tolerance of the femtosecond laser direct-write grating is controlled within ±0.2μm, and with coaxial closed-loop correction, the resistance dispersion is ≤1%; the linewidth tolerance of the traditional winding process is generally ±5μm, and the resistance dispersion is ≤2%.

[0049] 2. High Temperature Limit: After continuous service testing at 1200℃ for 100 hours, the sensitivity coefficient retention rate of this invention is >80%, while traditional grid wires show a coefficient decay of >30% at 900℃. This invention can cover monitoring scenarios of 1000–1150℃, such as aero-engine combustion chambers and first-stage stator blades of heavy-duty gas turbines, thus broadening the application boundaries of the product.

[0050] 3. Fatigue life: Due to the double protection of "no bending stress + fine grain structure", the resistance change of the grid wire after 106 stress cycles is ≤0.3%, and the life is about 3 times longer than that of traditional grid wire.

[0051] Secondly, the preparation cost and delivery cycle of this application are both reduced, specifically as follows:

[0052] 1. Process integration: This application completes the seven-step process of "drawing - insulation - lead wire - packaging" on the same laser platform. The production line equipment is reduced from the traditional four major sections to a flexible unit, and the overall cost of site, fixtures and labor is reduced by 40%.

[0053] 2. Improved Yield Rate: Real-time defect self-correction increases the first-pass yield to over 98%, while traditional processes often suffer from yield rates hovering around 85% due to issues such as wire breakage during drawing and winding deviation. Every 10 percentage point increase in yield rate reduces unit manufacturing costs by approximately 6%, significantly enhancing price competitiveness.

[0054] 3. Shorter delivery time: Laser direct writing only requires loading CAD data to change models without changing the wire mold or fixture. The single model changeover time is reduced from the original 4-6 hours to <30 minutes, which can meet the needs of fast and customized delivery.

[0055] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0059] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high-temperature strain gauge grid wires, characterized in that, include: The ultra-high temperature strain alloy material is vacuum arc melted and then rolled into a foil with uniform curvature. The foil is subjected to heat treatment to obtain a uniform fine-grained structure, which includes: subjecting the foil to a double-cycle heat treatment at 1070℃ solution temperature and 850℃ aging temperature to obtain an average grain size of 3–5µm and a dislocation density of <1×10⁻⁶. 13 m -2 The uniform, fine-grained structure provides a low-defect substrate for subsequent "cold working"; The process of fabricating a grid wire from the heat-treated foil using femtosecond laser direct writing technology includes: A femtosecond laser with an 800nm, 180fs, and 1kHz~1MHz adjustable repetition rate was used, and the laser was focused to a 0.6µm spot using an apochromatic objective lens with NA=0.

8. The grid wires are subjected to in-situ real-time monitoring and defect self-correction. The grid wires are functionalized and then integrated into a single package. The three-stage path of "coarse scan - fine scan - compensation scan" is executed by using a galvanometer and a six-axis ultra-precision displacement platform coupled control. The adaptive power algorithm is invoked synchronously to correct the energy attenuation caused by plasma shielding in real time.

2. The method for preparing high-temperature strain gauge grid wire according to claim 1, characterized in that, The process of vacuum arc melting of ultra-high temperature strain alloy material and rolling it into a foil with uniform curvature includes: The Fe-Cr-Al alloy or Ni-Cr, Pt-W, and high-entropy alloys are melted and rolled into uniform foils with a thickness of 15–30 µm.

3. The method for preparing high-temperature strain gauge grid wire according to claim 1, characterized in that, The in-situ real-time monitoring and defect self-correction of the grid wire includes: Coaxial confocal microscopy combined with a deep learning defect recognition network is used to perform frame-level analysis of ablation groove width, edge burrs, and repetitive pulse overlap rate.

4. The method for preparing high-temperature strain gauge grid wire according to claim 3, characterized in that, Also includes: The system automatically compares the values ​​with the CAD design and dynamically adjusts the scanning speed or pulse energy when the error is greater than 0.2µm.

5. The method for preparing high-temperature strain gauge grid wire according to claim 4, characterized in that, The functionalization post-processing and integrated packaging of the grid wires include: After laser writing is completed, Ar is performed at the same workstation. + Spray micropolishing; An insulating / anti-oxidation film is then formed by low-temperature atomic layer deposition.

6. The method for preparing high-temperature strain gauge grid wire according to claim 5, characterized in that, Also includes: A window is opened in the lead pad area using laser selective removal technology; Resistance welding is used to weld the leads to the pad area.

7. The method for preparing high-temperature strain gauge grid wire according to claim 6, characterized in that, Also includes: A high-temperature vapor phase coating of SiO2–Y2O3 is applied to the entire surface to form a protective layer that can operate continuously in an oxidizing atmosphere at 1200℃.

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