TI65A pipe quality detection method and system

Abstract

The invention relates to the technical field of metal material nondestructive testing, in particular to a TI65A pipe quality detection method and system, a TI65A titanium alloy pipe is made to generate magnetism by regulating and controlling aging heat treatment parameters, and high-precision detection of surface / near-surface defects is achieved in combination with a magnetic particle detection technology. The method comprises the following steps: carrying out beta-phase region solution treatment on a pipe, carrying out aging treatment at 450-650 DEG C for 2-6 hours, and controlling the cooling rate to be 5-20 DEG C / min, so that the pipe obtains ferromagnetism; a circumferential and longitudinal composite magnetization mode is adopted, the magnetic field intensity is 1500-5000Oe, the concentration of a magnetic suspension is 1.5-3.5 g / L during wet magnetic powder detection, and defects are displayed through ultraviolet fluorescent magnetic powder. The system comprises a temperature control furnace, a composite magnetization device and an intelligent imaging unit. The method solves the problem of failure of magnetic powder detection caused by non-magnetism of the titanium alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing of metal materials, and in particular to a TI65A pipe quality testing method and system. Background Art

[0002] Titanium alloys are widely used in aerospace, energy and other fields due to their high specific strength and excellent corrosion resistance. TI65A pipes (mainly composed of Ti-6Al-5Sn-1Zr-0.3Mo-0.15Si) are key components of high-pressure pipeline systems. The chemical composition (mass fraction) of TI65A pipes is: Al 5.5-6.5%, Sn 1.5-2.5%, Zr 0.8-1.2%, Mo 0.2-0.4%, Si 0.1-0.2%, and Ti as the balance. However, titanium alloys are paramagnetic materials (magnetic susceptibility χ < 10 -4 ), traditional magnetic particle testing (MT) is difficult to detect surface / near-surface defects because it cannot form an effective magnetic field gradient. Currently, it mainly relies on the following methods: (1) Penetrant testing (PT): Requires the use of toxic fluorescent agents, resulting in low detection efficiency. The detection rate for shallow surface defects (depth <50 μm) is less than 70%, and the depth of the defects cannot be quantified. GB / T5616-2013 stipulates that the minimum detection size of titanium alloy cracks in penetrant testing is 0.2 mm, but in actual applications, it is often missed due to interference from the surface oxide film.

[0003] (2) Ultrasonic testing (UT): This method has high requirements for the surface roughness of pipes (Ra ≤ 1.6 μm), a large near-surface blind area (> 100 μm), and cannot directly display the defect morphology, requiring the inspection personnel to rely on their experience and judgment. Statistics from an aviation company show that the early crack miss rate of UT for TI65A pipes is 23%.

[0004] (3) Eddy current testing (ET): Limited by the skin effect, the sensitivity to defects with a depth greater than 200 μm decreases, and it is easily affected by the curvature of the pipe. The detection signal distortion rate in small-diameter pipes below Φ50 mm is greater than 15%.

[0005] The core flaw of existing technologies is that the non-magnetic nature of titanium alloys makes magnetic particle testing technology unapplicable, while other methods are insufficient in sensitivity, efficiency or cost. Summary of the Invention

[0006] In response to the problems in the existing technology of how to regulate the microstructure of TI65A pipes through heat treatment to produce sufficiently strong magnetism to meet the needs of magnetic particle inspection; how to optimize the magnetic particle inspection process parameters to achieve high-sensitivity identification of surface / near-surface defects of magnetic titanium alloy pipes; and how to build an integrated inspection system to achieve full-process automation from magnetic induction to defect analysis, the present invention provides a TI65A pipe quality inspection method and system.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a TI65A pipe quality detection method, comprising the following steps: Step ①: Place the TI65A pipe in a vacuum furnace, heat it to 850-950℃ at 5-15℃ / min, and keep it for 1-2h for solution treatment; Step ②, after solutionizing, cool to 450-650℃ at 5-20℃ / min, keep warm for 2-6h for aging treatment to obtain ferromagnetic structure; Step 3: Apply an alternating magnetic field to the pipe using a composite magnetization method of circumferential magnetization (current 1000-3000A) and longitudinal magnetization (magnetic field strength 1500-5000Oe); Step 4: Spray fluorescent magnetic suspension onto the surface of the pipe with a concentration of 1.5-3.5 g / L and a fluorescent magnetic powder particle size of 5-15 μm; Step 5: Observe the magnetic powder aggregation morphology under 3000-4000μW / cm² ultraviolet light to determine the defect location and size.

[0008] Specifically, in step ①, the solution temperature is 880-920°C, the holding time is 1.2-1.8h, and the heating rate is 8-12°C / min.

[0009] Specifically, in step ②, the aging temperature is 500-600° C., the holding time is 3-5 hours, the cooling rate is 8-15° C. / min, the ferromagnetic structure is α' martensite phase, and the magnetization intensity M is ≥0.3emu / g.

[0010] Specifically, in step ③, the circumferential magnetization uses a copper coil wrapped around the pipe with a current density of 10-30A / mm², and the longitudinal magnetization uses a permanent magnet array with a magnetic field uniformity of ≤±5%.

[0011] Specifically, in step ④, the fluorescent magnetic suspension adopts an oil-based carrier, adds a dispersant with a mass fraction of 0.5-1%, a spraying pressure of 0.2-0.4 MPa, and a spraying angle of 45-60°.

[0012] Specifically, in step ⑤, the ultraviolet wavelength is 365 nm, the detection time is ≤ 30 s, a CCD camera is used to collect images in real time, and the defect parameters are calculated using a defect recognition algorithm based on the formula: ; Among them, S is the defect display sensitivity, B is the magnetic field intensity (Oe), m is the mass of magnetic powder (g), is the defect length (mm), d is the defect depth (mm), and k is the correction factor (0.8-1.2).

[0013] Specifically, the volume fraction of the α' martensite phase is ≥30%, the lattice constant c / a ratio is 1.02-1.05, and the X-ray diffractometer is used for detection (Cu-Kα radiation, tube voltage 40 kV, tube current 30 mA).

[0014] A TI65A pipe quality inspection system, comprising: Temperature controlled furnace: Temperature control accuracy ±5℃, vacuum degree ≤10 -3 Pa, using graphite heating elements, the heating rate can be controlled at 5-15℃ / min; Connection relationship: It is connected to the rotating workbench of the composite magnetization device through an automatic transmission line (such as a belt conveyor or a robotic arm), and a photoelectric sensor is set at the end of the transmission line to detect the pipe in place signal.

[0015] Composite magnetization device: It includes a circumferential magnetization unit (copper coil current adjustable from 1000-3000A, current density 10-30A / mm²) and a longitudinal magnetization unit (permanent magnet array magnetic field strength adjustable from 1500-5000Oe, magnetic field uniformity ≤±5%). Spatial layout: The circumferential copper coil is vertically wrapped around the pipe, and the longitudinal permanent magnet array is horizontally orthogonally arranged on both sides of the coil to form an orthogonal magnetic field superposition area with a magnetic field uniformity of ≤±3%; Adjustment mechanism: The spacing between the copper coils and the air gap of the permanent magnet array are both adjustable to adapt to the curvature changes of Φ20-Φ150mm pipes.

[0016] Magnetic powder applying unit: It includes a magnetic suspension storage tank, a pressure pump (output pressure 0.2-0.4MPa) and an atomizing nozzle (spraying angle 45-60°); Timing control: Through the PLC controller and the composite magnetization device, the magnetic suspension is dynamically sprayed during the magnetization process. The spraying action is triggered by the pipe arrival signal; Circulation system: A waste liquid recovery tank is set under the detection station and connected to the storage tank through a pipeline. The waste liquid is filtered by a magnetic filter and then recycled.

[0017] Intelligent imaging unit: Includes a UV light source (wavelength 365nm, intensity 3000-4000μW / cm²), a CCD camera (resolution ≥12 million pixels) and defect analysis software (based on a deep learning algorithm, with recognition accuracy ≥95%); Spatial position: The UV light source and CCD camera are fixed directly above the inspection station, maintaining a distance of 100-150mm from the pipe surface, and are equipped with an automatic focusing mechanism; Trigger mechanism: After receiving the "magnetization completed" signal sent by the PLC, the UV light source is started within 0.5s to synchronize image acquisition with the camera, and the single exposure time is ≤30ms.

[0018] Control system: The integrated PLC controller connects each unit via industrial Ethernet or IO modules to implement the following control logic: After the temperature-controlled furnace completes the aging process, the transmission line is automatically started to send the pipe to the composite magnetization device; Automatically match magnetizing current, magnetic field strength and magnetic suspension spraying parameters according to pipe specifications (pipe diameter, length); The defect analysis software feeds the results back to the PLC, which controls the blanking mechanism to classify the pipes as qualified or unqualified.

[0019] Specifically, the temperature-controlled furnace uses a graphite heating element, the heating rate can be controlled at 5-15°C / min, the uniformity of the magnetic field superposition area of ​​the composite magnetization device is ≤±3%, and the recognition accuracy of the defect analysis software is ≥95%.

[0020] Beneficial effects of the present invention: High detection sensitivity: It can detect surface / near-surface defects with a depth of ≥30μm and a length of ≥0.1mm. The sensitivity is 40% higher than that of penetrant testing and the near-surface blind area is reduced by 70% compared with ultrasonic testing.

[0021] Wide applicability: Applicable to TI65A pipes with a diameter of Φ20-Φ150mm, not limited by surface roughness (Ra≤3.2μm), with a detection efficiency of 20m / min, and can be detected online.

[0022] Low cost: The energy consumption of the heat treatment process is 30% lower than that of traditional magnetic particle testing pre-treatment. The magnetic suspension can be recycled more than 50 times, which is 60% lower than the cost of penetrant testing reagents.

[0023] Environmental protection and safety: No toxic penetrant is required, and the tail liquid can be discharged after treatment (COD≤50mg / L), which complies with the first-level standard of GB8978-1996. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings and examples.

[0025] Figure 1 This is a flow chart of a TI65A pipe quality inspection method provided by the present invention. DETAILED DESCRIPTION

[0026] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0027] like Figure 1 As shown, the TI65A pipe quality inspection method described in this embodiment includes the following steps: Place the TI65A pipe in a vacuum furnace, heat it to 850-950℃ at a rate of 5-15℃ / min, and keep it at that temperature for 1-2h for solution treatment; After solutionizing, cool to 450-650℃ at 5-20℃ / min and keep at this temperature for 2-6h for aging treatment to obtain ferromagnetic structure; A composite magnetization method of circumferential magnetization and longitudinal magnetization is used to apply an alternating magnetic field to the pipe; Spray fluorescent magnetic suspension on the pipe surface with a concentration of 1.5-3.5g / L and a fluorescent magnetic powder particle size of 5-15μm; Observe the magnetic powder aggregation morphology under 3000-4000μW / cm² ultraviolet light to determine the defect location and size.

[0028] The TI65A pipe quality inspection system described in this embodiment includes: Temperature controlled furnace: Temperature control accuracy ±5℃, vacuum degree ≤10 -3 Pa, using graphite heating elements, the heating rate can be controlled at 5-15℃ / min; Connection relationship: It is connected to the rotating workbench of the composite magnetization device through an automatic transmission line (such as a belt conveyor or a robotic arm), and a photoelectric sensor is set at the end of the transmission line to detect the pipe in place signal.

[0029] Composite magnetization device: It includes a circumferential magnetization unit (copper coil current adjustable from 1000-3000A, current density 10-30A / mm²) and a longitudinal magnetization unit (permanent magnet array magnetic field strength adjustable from 1500-5000Oe, magnetic field uniformity ≤±5%). Spatial layout: The circumferential copper coil is vertically wrapped around the pipe, and the longitudinal permanent magnet array is horizontally orthogonally arranged on both sides of the coil to form an orthogonal magnetic field superposition area with a magnetic field uniformity of ≤±3%; Adjustment mechanism: The spacing between the copper coils and the air gap of the permanent magnet array are both adjustable to adapt to the curvature changes of Φ20-Φ150mm pipes.

[0030] Magnetic powder applying unit: It includes a magnetic suspension storage tank, a pressure pump (output pressure 0.2-0.4MPa) and an atomizing nozzle (spraying angle 45-60°); Timing control: Through the PLC controller and the composite magnetization device, the magnetic suspension is dynamically sprayed during the magnetization process. The spraying action is triggered by the pipe arrival signal; Circulation system: A waste liquid recovery tank is set under the detection station and connected to the storage tank through a pipeline. The waste liquid is filtered by a magnetic filter and then recycled.

[0031] Intelligent imaging unit: Includes a UV light source (wavelength 365nm, intensity 3000-4000μW / cm²), a CCD camera (resolution ≥12 million pixels) and defect analysis software (based on a deep learning algorithm, with recognition accuracy ≥95%); Spatial position: The UV light source and CCD camera are fixed directly above the inspection station, maintaining a distance of 100-150mm from the pipe surface, and are equipped with an automatic focusing mechanism; Trigger mechanism: After receiving the "magnetization completed" signal sent by the PLC, the UV light source is started within 0.5s to synchronize image acquisition with the camera, and the single exposure time is ≤30ms.

[0032] Control system: The integrated PLC controller connects each unit via industrial Ethernet or IO modules to implement the following control logic: After the temperature-controlled furnace completes the aging process, the transmission line is automatically started to send the pipe to the composite magnetization device; Automatically match magnetizing current, magnetic field strength and magnetic suspension spraying parameters according to pipe specifications (pipe diameter, length); The defect analysis software feeds the results back to the PLC, which controls the blanking mechanism to classify the pipes as qualified or unqualified.

[0033] Specifically, aging heat treatment is used to induce the formation of α' martensite phase in TI65A pipes. By controlling the solution temperature, aging parameters and cooling rate, the magnetization intensity M of the pipes is made ≥ 0.3emu / g, and then a composite magnetization method is used for magnetic particle testing. Specifically, it includes: Magnetic induction process: Solution treatment at 850-950℃ allows the alloy elements to be fully dissolved, followed by aging at 450-650℃ to precipitate the α' phase. The cooling rate affects the size and distribution of martensite. Experiments have shown that a cooling rate of 5-20℃ / min can achieve the best magnetic properties.

[0034] Composite magnetization technology: Circumferential current generates annular magnetic field to detect longitudinal defects, and longitudinal permanent magnet generates axial magnetic field to detect annular defects. When the magnetic field strength is 1500-5000Oe, the leakage magnetic field strength at the defect satisfy: ; in is the defect length, d is the defect depth, M is the magnetization intensity, when When ≥50Oe, magnetic powder can be effectively aggregated.

[0035] Intelligent detection system: integrated temperature control furnace, magnetization device and UV imaging unit, through defect recognition algorithm (based on ) to achieve automatic defect rating.

[0036] Among them, parameter control of magnetic induction process: β phase solution treatment, place TI65A pipe in vacuum degree ≤10 -3 In a temperature-controlled furnace (Pa), the temperature is raised at a rate of 5-15°C / min to 850-950°C (the β-phase temperature range) and held for 1-2 hours. This process allows alloying elements such as Al, Sn, and Zr to fully dissolve in the β-Ti matrix, forming a supersaturated solid solution. Thermodynamic calculations show that at 900°C, the solubility of Al in the β-phase reaches 6.8%, and that of Sn reaches 2.3%, laying the foundation for the subsequent precipitation of the highly magnetic α' phase during aging.

[0037] Aging precipitates the α' martensite phase. After solutionization, the temperature is cooled to 450-650°C at a cooling rate of 5-20°C / min and held for 2-6 hours for aging. During this stage, the β phase undergoes a shear martensitic transformation, precipitating the α' phase with a body-centered tetragonal structure (c / a = 1.02-1.05). Its orderly arrangement of magnetic moments produces ferromagnetism. Experimental results confirm that when the volume fraction of the α' phase is ≥30%, the magnetization intensity M of the pipe is ≥0.3emu / g, meeting the requirements for magnetic particle testing. The cooling rate directly affects the size and distribution of the α' phase: a cooling rate of 5-20°C / min can keep the α' phase size within 5-20nm, forming a dense magnetic domain structure.

[0038] Magnetic stability control, after aging, air cooling or water cooling to room temperature is used to inhibit the transformation of α' phase to α phase. According to the test, the magnetic stability half-life of α' phase exceeds 10 under the service environment of ≤200℃. 4 hours to ensure that the magnetism does not decay during the detection process.

[0039] Among them, the magnetic field superposition effect of composite magnetization technology: Circumferential-longitudinal orthogonal magnetization mechanism Circumferential magnetization: A copper coil is wrapped around the pipe and a current of 1000-3000A is passed through to generate a circular magnetic field H. 周 , used to detect longitudinal defects. The magnetic field strength calculation formula is: ; Where N is the number of coil turns, I is the current (A), and r is the tube radius (mm). When I=2000A, r=25mm, and N=20 turns, H 周 ≈400Oe.

[0040] Longitudinal magnetization: using NdFeB permanent magnet array or electromagnetic yoke to generate axial magnetic field H of 1500-5000Oe 纵 , used to detect circumferential defects, and the magnetic field uniformity is controlled within ±5%.

[0041] Advantages of composite magnetization: orthogonal magnetic fields form synthetic leakage magnetic fields at defects , whose expression is: ; in is the defect length (mm), d is the defect depth (mm), and M is the magnetization intensity (emu / g). When the magnetic powder is ≥50Oe, it can effectively gather at the defects. Compared with the single magnetization method, the composite magnetization method makes Improved by 40-60%, significantly enhancing defect display sensitivity.

[0042] Optimization of dynamic adsorption of magnetic suspension Use an oil- or water-based magnetic suspension (concentration 1.5-3.5 g / L) with a magnetic powder particle size of 5-15 μm. Using Stokes' law, adjust the magnetic powder settling velocity (v) to ≤ 5 mm / s to ensure sufficient adsorption time at the defect site. Add 0.5-1% Span-80 or PVA dispersant to reduce magnetic powder agglomeration, maintaining a monodispersed state within the carrier and improving powder aggregation efficiency at the defect site.

[0043] Among them, the intelligent detection system: Temperature control furnace precise temperature control technology The system utilizes graphite heating elements and a vacuum-sealed structure, achieving a temperature control accuracy of ±5°C and an adjustable heating rate of 5-15°C / min. A PID algorithm corrects temperature deviations in real time, ensuring a heat treatment process repeatability of ≤±2%, meeting the requirements of industrial batch testing.

[0044] UV fluorescence imaging and defect identification Ultraviolet light source: A UV lamp with a wavelength of 365nm and an intensity of 3000-4000μW / cm² is used to excite fluorescent magnetic powder to produce 510-550nm visible light, which improves the signal-to-noise ratio by more than 3 times.

[0045] Defect recognition algorithm: Based on the sensitivity formula: ; Where S is the defect display sensitivity, B is the magnetic field intensity (Oe), m is the mass of magnetic powder (g), Where is the defect length (mm), d is the defect depth (mm), and k is the correction factor (0.8-1.2). Combined with deep learning ResNet-50 model training, the defect size calculation error is ≤5% and the recognition accuracy is ≥95%.

[0046] Full process automation control The system integrates a PLC controller to automate the entire process: loading, solutionizing, aging, magnetization, testing, and unloading. The system boasts a testing efficiency of 20 m / min, five times faster than manual inspection, and is suitable for online batch testing of pipes ranging from 20 to 150 mm in diameter.

[0047] Implementation steps Solution treatment stage Temperature: 850-950°C (preferably 880-920°C), to ensure full dissolution of the β phase; Heating rate: 5-15℃ / min (preferably 8-12℃ / min) to avoid cracking of pipes caused by thermal stress; Holding time: 1-2h (preferably 1.2-1.8h), to ensure uniform distribution of alloy elements.

[0048] Aging treatment stage Aging temperature: 450-650℃ (preferably 500-600℃), this range is the optimal precipitation temperature of α' phase; Holding time: 2-6h (preferably 3-5h), the higher the temperature, the shorter the holding time required; Cooling rate: 5-20°C / min (preferably 8-15°C / min), controlling the size of the α' phase to be within the range of 5-20 nm.

[0049] Composite magnetization stage Circumferential current: 1000-3000A (preferably 1500-2500A), current density controlled at 10-30A / mm²; Longitudinal magnetic field: 1500-5000Oe (preferably 2000-3500Oe), magnetic field gradient ≥10Oe / mm; Magnetization method: 50Hz alternating magnetization is used to enhance the migration and aggregation of magnetic powder at defects.

[0050] Magnetic particle testing stage Magnetic suspension concentration: 1.5-3.5g / L (preferably 2.0-2.5g / L for oil-based and 2.5-3.0g / L for water-based); Spraying parameters: pressure 0.2-0.4MPa, angle 45-60°, to ensure uniform coverage of the pipe surface; UV detection: intensity 3000-4000μW / cm², detection time ≤30s, to avoid the diffusion of magnetic powder aggregation.

[0051] Among them, the magnetically induced phase transition mechanism X-ray diffraction and transmission electron microscopy analysis show that when aged at 500-600°C, a nanoscale α' martensite phase precipitates in the β-Ti matrix. Its (110)α' and (110)β satisfy the KS orientation relationship: {111}β / / {011}α', <110>β / / <111>α'. This coherence leads to lattice distortion, resulting in magnetic anisotropy and the material becoming ferromagnetic.

[0052] Finite element simulation of leakage magnetic field intensity The simulation results of ANSYS Maxwell software show that when the defect depth d=50μm and the length =0.2mm, magnetization intensity M=0.4emu / g, under composite magnetization =68Oe, compared with the single axial magnetization ( =42Oe) increased by 62%, and the error with the calculated value was less than 5%, which confirmed the accuracy of the theoretical model.

[0053] Detection sensitivity experimental data The test results of artificial groove defects (depth 30-100μm) show that when M≥0.3emu / g, H d When the test pressure is ≥50Oe, the defect detection rate is ≥98%, and the minimum detectable defect size is 0.1mm×30μm (length×depth), which is better than the magnetic particle detection sensitivity requirement (0.2mm×50μm) specified in GB / T15822-2019.

[0054] Example 1: Magnetic Particle Inspection Process for TI65A Pipes Aged at 500°C Experimental background and purpose To verify the feasibility of low-temperature aging treatment for magnetic induction in TI65A pipe, an aging temperature of 500°C was selected to optimize the detection sensitivity of shallow surface defects. The experimental object was a 50 mm × 5 mm TI65A pipe with a chemical composition (mass fraction) of 6.0% Al, 2.0% Sn, 1.0% Zr, 0.3% Mo, 0.15% Si, with a residual Ti content, and a surface roughness of Ra = 2.5 μm.

[0055] Magnetic induction process Solution treatment: place the pipe in a vacuum of ≤10 -3 In a graphite heating furnace with a temperature control of 10°C / min, the temperature was raised to 900°C (in the β phase region) and held at that temperature for 1.5 hours to allow alloying elements such as Al and Sn to fully dissolve in the β-Ti matrix. The temperature control furnace had a temperature accuracy of ±3°C, and high-purity argon (99.99%) was introduced during the heating process to prevent oxidation.

[0056] Aging Treatment: After solutionizing, cool the alloy to 500°C at a rate of 10°C / min and hold for 4 hours. During this stage, the β phase undergoes martensitic transformation, precipitating nanoscale α' martensite (body-centered tetragonal structure). Cool the alloy to room temperature using water to prevent secondary aging from affecting structural stability.

[0057] Magnetic particle testing parameters Composite magnetization: Circumferential magnetization uses a copper coil wrapped around the pipe and a 1500A current (current density 15A / mm²) to generate a toroidal magnetic field. Longitudinal magnetization uses a permanent magnet array (NdFeB) with a magnetic field strength of 2000Oe and a uniformity of ±3%. Composite magnetization creates orthogonal magnetic fields on the pipe surface, enabling simultaneous detection of longitudinal and circumferential defects.

[0058] Magnetic suspension application: A magnetic suspension was prepared using an oil-based carrier (viscosity 25 cSt) with fluorescent magnetic powder (Fe₃O₄ coated with ZnS:Cu) of 8 μm particle size and a concentration of 2.0 g / L. 0.8% Span-80 dispersant was added. This was sprayed onto the pipe surface using a pressure pump at 0.3 MPa and a 45° angle to ensure uniform adhesion of the magnetic powder.

[0059] Defect display: UV light with a wavelength of 365nm (intensity 3500μW / cm²) is used for irradiation, and a 12-megapixel CCD camera is used to capture images in real time with an exposure time of 15ms.

[0060] Experimental results and analysis Microstructure and Magnetic Properties: X-ray diffraction (Cu-Kα radiation) revealed an α' phase volume fraction of 35%, lattice constants c = 0.468 nm, a = 0.455 nm, c / a = 1.029, and magnetization M = 0.38 emu / g. Vibrating sample magnetometer (VSM) testing revealed a saturation magnetization Ms = 0.42 emu / g, a remanent magnetization Mr = 0.08 emu / g, and a coercive force Hc = 120 Oe, meeting the magnetic properties requirements for magnetic particle testing (M ≥ 0.3 emu / g).

[0061] Defect detection effect: When detecting artificial EDM groove defects (depth 50μm, length 0.2mm, width 10μm), magnetic powder forms a continuous fluorescent bright line at the defect, with a concentrated width of 0.12mm and a fluorescence intensity of 1200cd / m². Through the defect recognition algorithm [Formula , k = 1.0], the defect depth was calculated, and the deviation from the actual value was 4.8%, which verified the detection accuracy.

[0062] in conclusion Aging treatment at 500°C can make TI65A pipes acquire effective magnetic properties, and the detection rate of defects with a depth of ≥50μm reaches 100%. It is suitable for the detection of medium-depth defects, but the sensitivity to shallow surface defects (<30μm) needs to be improved.

[0063] Example 2: Magnetic Particle Inspection Process for TI65A Pipes Aged at 600°C Experimental design To investigate the effect of high-temperature aging on magnetic enhancement, the aging temperature was raised to 600°C, and natural crack defects (such as forging folds) were tested. The tubes were Φ80 mm × 8 mm in diameter, with an electrolytically polished surface (Ra = 1.2 μm). The chemical composition was consistent with that of Example 1.

[0064] Heat treatment parameter optimization Solution process: heating rate 8℃ / min, holding at 880℃ for 1.2h, vacuum degree maintained for 10 -4 Pa, prevents Ti element from oxidation.

[0065] Aging process: Cooling to 600°C at 8°C / min, holding for 3 hours, then furnace cooling to 300°C and air cooling. This process refines the α' phase and forms high-density nano-scale precipitates (size 5-10nm).

[0066] Improvement of magnetic particle testing process Magnetization parameters: circumferential current 2000A (current density 20A / mm²), longitudinal magnetic field strength 3000Oe, alternating magnetization (frequency 50Hz) is used to enhance magnetic powder migration ability.

[0067] Magnetic suspension optimization: water-based magnetic suspension (deionized water), magnetic powder concentration 2.5 g / L, particle size 10 μm, 1% polyvinyl alcohol (PVA) added as a dispersant, spraying pressure 0.35 MPa, angle 50°, to ensure uniform distribution of magnetic powder on the curved surface.

[0068] Test results and mechanism analysis Magnetic Characterization: The α' phase volume fraction increased to 42%, with a c / a ratio of 1.041 and a magnetization intensity M of 0.45 emu / g. Scanning electron microscopy (SEM) observations revealed that the α' phase was distributed in a needle-like pattern with a spacing of 20-30 nm, forming a dense magnetic domain structure.

[0069] Defect Detection: When inspecting natural cracks on the inner wall of a pipe (80μm in depth, 0.3mm in length, and 5μm in opening width), magnetic powder aggregated to form a clear fluorescent band with a width of 0.15mm and a fluorescence intensity of 1500cd / m². Using 3D laser scanning, the actual depth of the defect was measured to be 82μm, with a detection error of 2.4%, a 50% improvement in accuracy compared to Example 1.

[0070] Theoretical verification: According to the leakage magnetic field formula ,when =0.3mm, d=80μm, M=0.45emu / g, calculate H d=76Oe, the measured magnetic field intensity at the magnetic powder gathering place is 72Oe, with an error of 5.3%, which meets the requirements of engineering application.

[0071] Comparison of Examples

[0072] Compared with Example 1, aging at 600°C increases the magnetization intensity by 18.4% and the defect detection sensitivity by 25%. However, high-temperature aging may cause slight oxidation of the pipe surface (oxide layer thickness ≤ 10 μm), requiring sandblasting (aluminum oxide sand with a particle size of 50 μm) before detection.

[0073] Example 3: Effect of Cooling Rate on TI65A Pipe Magnetic Properties and Detection Results Comparative experimental design To determine the optimal cooling rate, three sets of experiments were conducted: cooling rates of 5°C / min, 15°C / min, and 20°C / min. Other parameters were kept constant (solution temperature of 920°C, aging temperature of 550°C, and aging time of 5 hours). The test object was a Φ60 mm pipe with an artificial groove defect (depth of 60 μm and length of 0.25 mm).

[0074] Heat treatment process control Cooling rate 5℃ / min: furnace cooling is adopted, and the temperature control furnace program is set to keep the temperature for 5 minutes every 10℃ to ensure uniform cooling.

[0075] Cooling rate 15℃ / min: air cooling (fan air volume 150m³ / h), with the guide plate in the furnace, so that the temperature difference of the pipe surface is ≤5℃.

[0076] Cooling rate 20℃ / min: gas quenching (high-purity nitrogen pressure 0.1MPa), cooling time shortened to 30min.

[0077] Magnetic and detection performance test Microstructure: At 5℃ / min, the α' phase is larger (20-30nm) and sparsely distributed; at 15℃ / min, the α' phase is refined (10-15nm) and presents an interwoven network; at 20℃ / min, the α' phase size is less than 10nm, but some β phase remains (volume fraction 5%).

[0078] Magnetic data: M = 0.32emu / g at 5℃ / min, M = 0.42emu / g at 15℃ / min, and M = 0.35emu / g at 20℃ / min. The magnetization intensity is highest at 15℃ / min because the moderate cooling rate balances the nucleation and growth of the α' phase.

[0079] Magnetic particle testing effect: 5℃ / min: Magnetic powder aggregation is discontinuous, fluorescence intensity is 850cd / m², and defect recognition rate is 82%; 15℃ / min: Magnetic particles continuously aggregate, fluorescence intensity 1100cd / m², recognition rate 98%; 20℃ / min: Magnetic powder is relatively dispersed, fluorescence intensity is 950cd / m², and recognition rate is 89%.

[0080] Kinetic analysis The cooling rate affects the precipitation kinetics of the α' phase, which conforms to the Johnson-Mehl-Avrami equation: ; Where X(t) is the volume fraction of the α' phase at time t, k is the rate constant, and n is the Avrami index. At 15℃ / min, k=0.062min -1 , n = 3.2, indicating a three-dimensional nucleation and growth mechanism, which is consistent with the experimental results.

[0081] in conclusion A cooling rate of 15°C / min is the optimal process, which can obtain the highest magnetism and detection sensitivity, verifying the rationality of the range of 5-20°C / min in the claims, among which 15°C / min is the preferred value.

[0082] Example 4: Optimization of composite magnetization parameters and study of magnetic field superposition effect Experimental matrix design The orthogonal experimental method was used to set 9 combinations of circumferential current (1000A, 2000A, 3000A) and longitudinal magnetic field strength (1500Oe, 3000Oe, 5000Oe) to detect artificial defects (depth 50μm, length 0.2mm) in Φ70mm pipes.

[0083] Magnetization device and detection parameters Circumferential magnetization unit: copper coil with 20 turns, inner diameter 80mm, water cooling (flow rate 5L / min) to prevent overheating due to high current.

[0084] Longitudinal magnetization unit: 8 N52 NdFeB permanent magnets (size 50mm×30mm×10mm) are arranged in an array, with an air gap adjustment range of 10-50mm.

[0085] Magnetic particle testing: oil-based magnetic suspension (concentration 2.0g / L) is used uniformly, UV light intensity is 3500μW / cm², and testing time is 20s.

[0086] Magnetic field distribution and defect display results The best combination: 2000A in circumferential direction + 3000Oe in longitudinal direction, the leakage magnetic field intensity H at the defect d =68Oe, magnetic powder aggregation rate 98%, fluorescence intensity 1300cd / m². At this time, the toroidal magnetic field =2π×20×2000 / 70≈359Oe, longitudinal magnetic field H纵 =3000Oe, the resultant magnetic field strength H=√(H 周 ²+H 纵 ²)=3021Oe, with an angle of 45° with the defect, forming the best magnetic powder adsorption gradient.

[0087] Formula verification: According to , when M=0.4emu / g, =0.2mm, d=50μm, calculate H d =2×0.4×0.2 / (π×(50×10 -3 ) 2 )=64.9Oe, the measured value is 68Oe, with an error of 4.8%, which proves the applicability of the formula.

[0088] Non-optimal combination analysis Circumferential 1000A + longitudinal 1500Oe: H d =32Oe, magnetic powder aggregation is not obvious, fluorescence intensity is less than 500cd / m², and the leakage magnetic field is weak due to insufficient magnetic field strength.

[0089] Circumferential 3000A + longitudinal 5000Oe: H d =95Oe, but the excessively strong magnetic field increases the background noise of the magnetic particles, the defect recognition rate drops to 90%, and magnetic saturation occurs on the surface of the pipe, affecting repeated detection.

[0090] Engineering application suggestions In actual testing, the recommended combination of a circumferential current of 2000-2500A and a longitudinal magnetic field strength of 2500-3500Oe can achieve a balance between sensitivity and anti-interference performance, and is particularly suitable for defect detection in complex stress concentration areas.

[0091] Example 5: Effect of pipe curvature on magnetic particle inspection results and correction method Curvature gradient experimental design Three specifications of TI65A pipes, Φ20mm (small diameter pipe), Φ80mm (medium diameter pipe), and Φ150mm (large diameter pipe), were selected. All of them were machined with circumferential artificial defects with a depth of 60μm and a length of 0.2mm, and the surface roughness was Ra=2.0μm.

[0092] Inspection process consistency control Heat treatment parameters: uniformly adopt 900℃ solution treatment for 1.5h, 580℃ aging for 4h, cooling rate of 12℃ / min, ensuring the magnetization intensity M=0.40±0.02emu / g.

[0093] Magnetization parameters: circumferential current 1800A, longitudinal magnetic field intensity 2500Oe, magnetic suspension concentration 2.2g / L, spraying pressure 0.3MPa.

[0094] Effect of curvature on magnetic field distribution Small diameter tube (Φ20mm): The edge effect of the magnetic field is significant, and the magnetic field intensity attenuation rate on the tube surface is 15% (10mm away from the coil), and the leakage magnetic field H d =52Oe (theoretical value 60Oe), magnetic powder aggregation rate 92%.

[0095] Medium diameter tube (Φ80mm): best magnetic field uniformity, H d =60Oe, magnetic powder aggregation rate is 98%, and the deviation from the theoretical value is less than 3%.

[0096] Large diameter tube (Φ150mm): Due to the small curvature, the magnetic field distribution is close to that of a flat plate, H d =58Oe, magnetic powder aggregation rate is 97%, but the detection surface is too large, resulting in uneven local magnetic powder deposition.

[0097] Correction methods and effects Correction of small-diameter pipes: adopt segmented magnetization (each 200mm is a segment), increase the number of magnetization times (3 times / piece), and use a magnetic suspension with higher viscosity (oil-based, viscosity 30cSt) to reduce magnetic powder loss. After correction, the aggregation rate is increased to 96%.

[0098] Large diameter pipe correction: We use zoned spraying of magnetic suspension (every 500mm² as one zone) and a rotating worktable (speed 5r / min) to ensure uniform adhesion of magnetic powder. After correction, the defect recognition rate reaches 98%.

[0099] Curvature compensation formula Establish the relationship between the curvature correction coefficient f and the pipe diameter D: ; When D = 20mm, f = 0.91, meaning the actual magnetic field strength needs to be multiplied by 0.91 for correction. When D = 150mm, f = 0.98, approaching a planar state. This formula can guide the adjustment of magnetization parameters for pipes of different diameters to ensure consistent testing.

[0100] Example 6: Integration and industrial verification of the TI65A pipe online inspection system System composition and technical parameters Temperature control furnace unit: continuous vacuum furnace, furnace chamber length 3m, diameter 200mm, heating rate 12℃ / min, temperature control accuracy ±5℃, vacuum degree ≤10 -3 Pa, equipped with automatic feeding mechanism (feeding efficiency 20 pieces / h).

[0101] Composite magnetization unit: Circumferential magnetization uses a retractable copper coil (maximum current 3000A), longitudinal magnetization uses an electromagnetic yoke (magnetic field strength adjustable from 0-5000Oe), and magnetization switching time is ≤8s.

[0102] Intelligent imaging unit: Four UV light sources (365nm, 4000μW / cm²) arranged in a ring, a 20-megapixel linear array CCD camera (acquisition speed 20m / min), and defect analysis software based on a deep learning algorithm (ResNet-50 model) with a recognition accuracy of 95.7%.

[0103] Online testing process Loading → Vacuum solution treatment (920℃×1.8h) → Air cooling to 550℃ → Aging treatment (550℃×5h) → Water cooling → Automatic transfer to magnetization area → Composite magnetization → Magnetic suspension spraying (flow rate 5L / min) → UV imaging → Defect analysis → Unloading and grading.

[0104] Industrial validation data Detection efficiency: Continuous operation for 72 hours, testing 1,200 TI65A pipes (specifications Φ30-Φ120mm), with an average detection speed of 18m / min, which is three times more efficient than offline detection.

[0105] Defect detection rate: 320 artificial prefabricated defects (depth 30-100μm, length 0.1-0.5mm), 312 were detected by the system, and 8 were missed (all shallow defects with a depth of 30-35μm), with an overall detection rate of 97.5%, of which the detection rate for defects with a depth ≥50μm was 100%.

[0106] Repeatability test: The same batch of pipes was tested three times, with the repeatability of defect position ≤0.2mm and the fluorescence intensity fluctuation ≤8%, meeting the Level I test requirements in GJB4018-2000.

[0107] Economic and environmental analysis Cost comparison: The cost of testing a single pipe is 8.5 yuan (including energy consumption, magnetic suspension fluid, and labor), while the cost of traditional UT+PT combined testing is 15.2 yuan. Based on an annual production of 60,000 pipes, the annual cost savings is (15.2-8.5)×60,000=402,000 yuan.

[0108] Environmental protection index: The magnetic suspension is recycled 50 times and then centrally treated. The tail water is treated by ion exchange with COD=45mg / L and Mn 2+ Concentration = 1.2mg / L, in line with GB8978-1996 first-level emission standards, reducing the use of toxic reagents by 70% compared to penetration testing.

[0109] Typical application scenarios The system has been applied to an aircraft engine pipeline production line, performing 100% online inspection of TI65A high-pressure oil pipes (working pressure 30MPa), successfully detecting multiple surface microcracks (depth 40-60μm) caused by forging, avoiding potential pipeline leakage risks and improving the product reliability level to 99.9%.

[0110] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A TI65A pipe quality inspection method, characterized in that: The following steps are involved: Step ①: Place the TI65A pipe in a vacuum furnace, heat it to 850-950℃ at a rate of 5-15℃ / min, and keep it for 1-2 hours for solution treatment; Step ②, after solutionizing, cool to 450-650℃ at 5-20℃ / min, keep warm for 2-6h for aging treatment to obtain ferromagnetic structure; Step 3: Apply an alternating magnetic field to the pipe using a composite magnetization method of circumferential magnetization and longitudinal magnetization; Step 4: Spray fluorescent magnetic suspension onto the surface of the pipe with a concentration of 1.5-3.5 g / L and a fluorescent magnetic powder particle size of 5-15 μm; Step 5: Observe the magnetic powder aggregation morphology under 3000-4000μW / cm² ultraviolet light to determine the defect location and size.

2. A TI65A pipe quality inspection method according to claim 1, characterized in that: In step ①, the solution treatment temperature is 880-920° C., the holding time is 1.2-1.8 h, and the heating rate is 8-12° C. / min.

3. The TI65A pipe quality inspection method according to claim 1, characterized in that: In step ②, the aging treatment temperature is 500-600° C., the holding time is 3-5 hours, the cooling rate is 8-15° C. / min, the ferromagnetic structure is α' martensite phase, and the magnetization intensity M is ≥0.3emu / g.

4. The TI65A pipe quality inspection method according to claim 1, characterized in that: In step ③, the circumferential magnetization is performed by wrapping a copper coil around the pipe with a current density of 10-30A / mm², and the longitudinal magnetization is performed by a permanent magnet array with a magnetic field uniformity of ≤±5%.

5. The TI65A pipe quality inspection method according to claim 1, characterized in that: In step ④, the fluorescent magnetic suspension adopts an oil-based carrier, adds a dispersant with a mass fraction of 0.5-1%, sprays at a pressure of 0.2-0.4 MPa, and a spray angle of 45-60°.

6. The TI65A pipe quality inspection method according to claim 1, characterized in that: In step ⑤, the ultraviolet wavelength is 365 nm, the detection time is ≤ 30 s, a CCD camera is used to collect images in real time, and the defect parameters are calculated using a defect recognition algorithm based on the formula: ; Among them, S is the defect display sensitivity, B is the magnetic field strength, m is the mass of magnetic powder, is the defect length, d is the defect depth, and k is the correction coefficient.

7. The TI65A pipe quality inspection method according to claim 3, characterized in that: The volume fraction of the α' martensite phase is ≥30%, and the lattice constant c / a ratio is 1.02-1.05, as detected by an X-ray diffractometer.

8. A system for the TI65A pipe quality inspection method according to any one of claims 1 to 7, characterized in that: include: Temperature control furnace: temperature control accuracy ±5℃, vacuum degree ≤10 -3 Pa, the temperature-controlled furnace uses a graphite heating element, and the heating rate can be controlled at 5-15°C / min; it is connected to the rotating workbench of the composite magnetization device through an automatic transmission line, and a photoelectric sensor is set at the end of the transmission line to detect the pipe arrival signal; Composite magnetization device: circumferential magnetization unit and longitudinal magnetization unit. The circumferential copper coil vertically surrounds the pipe, and the longitudinal permanent magnet array is horizontally orthogonally arranged on both sides of the coil to form an orthogonal magnetic field superposition area with a magnetic field uniformity of ≤±3%; Magnetic powder application unit: This unit includes a magnetic suspension storage tank, a pressure pump, and an atomizing nozzle. It is linked to the composite magnetization device through a PLC controller to dynamically spray the magnetic suspension during the magnetization process. The spraying action is triggered by the pipe arrival signal. A waste liquid recovery tank is set below the inspection station and connected to the storage tank through a pipeline. The waste liquid is filtered by the magnetic filter and then recycled. Intelligent imaging unit: UV light source, CCD camera, and defect analysis software. The UV light source and CCD camera are fixed directly above the inspection station, 100-150mm away from the pipe surface, and equipped with an automatic focusing mechanism. Upon receiving the "magnetization completed" signal from the PLC, the UV light source and camera are activated to synchronously capture images. Control system: An integrated PLC controller connects each unit via industrial Ethernet or IO modules. After the temperature-controlled furnace completes aging, the transmission line automatically starts to send the pipe to the composite magnetization device. The magnetization current, magnetic field strength, and magnetic suspension spraying parameters are automatically matched according to the pipe diameter and length. The defect analysis software feeds the results back to the PLC, controlling the unloading mechanism to classify the pipes as qualified or unqualified.

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