Method for ultrasonic testing of a round bar

Abstract

The application discloses a kind of round bar piece ultrasonic testing methods, it is for the round bar piece of diameter not more than 12mm, comprising: selecting contrast sample;Radial in contrast sample is opened as artificial reflector along the direction of hole;Control probe so that incident sound wave is produced pure transverse wave by axial oblique incidence of contrast sample;Adjust the incidence angle and sensitivity gain of probe, so that the wave height of secondary reflected sound wave of artificial reflector is not lower than set threshold, to determine detection sensitivity and the optimum incidence angle of probe;Control ultrasonic wave is obliquely incident along the axis of contrast sample and the bar piece to be examined, control relative helical linear motion between probe and corresponding bar piece, and obtain corresponding ultrasonic reflection signal;According to the ultrasonic reflection signal of contrast sample and the bar piece to be examined obtained is compared to obtain the organization state of the bar piece to be examined.The application can realize the measurement and evaluation of the grain organization state inside round bar piece under the premise of not destroying material structure.

Description

Technical Field

[0001] The present invention relates to the field of metal detection, and in particular to an ultrasonic detection method for round rods. Background Art

[0002] Superalloys, with their high hot strength and thermal stability, are essential materials in aerospace engine manufacturing. A new turbofan engine's superalloy content accounts for over 50% of its weight. Superalloys offer excellent high and low-temperature strength, long-term stability, excellent corrosion resistance and thermal deformation resistance, as well as good processing ductility and satisfactory weldability. They are widely used in high-temperature, load-bearing components such as turbine disks, compressor disks, and fasteners in aviation, aerospace, and ground-based gas and flue gas turbine engines.

[0003] In practical applications, high-temperature alloys used in fasteners have long had important problems such as poor organizational uniformity and unstable performance. The main problem is the large grain size difference (more than 3 levels), especially the core banded crystals, such as small-sized bars of high-quality GH2132 high-temperature alloy and high-quality GH4169 high-temperature alloy.

[0004] Although the product structure and performance have been greatly improved through continuous improvement of production technology, it is still inevitable that there will be some local uneven structure and banded grains. The currently known detection method is mainly metallographic method. Due to the large number of small-sized rods, the metallographic analysis work is bound to be heavy and the cycle is long. In addition, metallographic analysis uses a physical destruction method and cannot evaluate the grain size of the actual rod as a whole.

[0005] How to analyze and evaluate the overall microstructure and grain size of high-temperature alloy fastener rods using existing non-destructive testing techniques is a problem that needs to be solved by those skilled in the art.

[0006] The loss of acoustic energy and changes in propagation velocity caused by the interaction of ultrasound with a material's microstructure are two key parameters used to characterize material structure and properties using ultrasound, and they also form the theoretical basis for nondestructive evaluation of material microstructures. Ultrasonic velocity and ultrasonic attenuation are the most common methods. The main causes of ultrasonic propagation attenuation are diffusion attenuation, scattering attenuation, and absorption attenuation. Scattering attenuation is related to the size of the grains or other small particles in the material. For a given grain size, attenuation increases with increasing detection frequency.

[0007] Within a given time range, the backscattered part of the signal formed by the interference of signals caused by each single scatterer in the incident ultrasonic field appears as a noise signal on the fluorescent screen.

[0008] The existing product has a large difference in grain size (5 to 10 levels) inside the material, among which the banded grains distributed in the central area are the most serious. The grain size of the organization in this area is mainly 5 to 6 levels, and the grain size is about 0.044mm to 0.062mm.

[0009] When the grain size of the material is about 1 / 10 of the wavelength, scattering will occur. The larger the grain size, the more severe the scattering phenomenon. Under this grain size condition, 10MHz longitudinal wave probes usually do not show scattering phenomenon or the scattering phenomenon is not obvious.

[0010] Longitudinal wave testing is commonly used to examine the internal grain structure of materials. Small-scale materials are typically inspected using the longitudinal wave water immersion method, which observes the irregular, random reflection signals between the interface echo and the primary bottom wave (or between the primary and secondary bottom waves). Longitudinal waves, a wave type in which the particle vibration direction is parallel to the wave propagation direction, have strong penetrating power. Their scanning path is perpendicular to the banded crystal-rich region, resulting in a short path. The cumulative signal generated by the interference of individual scatterers is weak. Furthermore, the maximum frequency of commonly used ultrasonic probes in China is 10 MHz (wavelength: 0.59 mm), which essentially does not generate scattered signals. While there are a few domestic manufacturers of high-frequency ultrasonic probes (above 15 MHz, wavelength 0.4 mm to 0.24 mm), the supporting equipment is expensive and the results are less than ideal. Summary of the Invention

[0011] Purpose of the invention: In view of the above-mentioned shortcomings, the present invention proposes an ultrasonic detection method for round rods. Without destroying the integrity of the material, the existing ultrasonic water immersion automatic detection equipment is used to adopt ultrasonic shear waves to measure and evaluate the overall internal grain structure state of the high-temperature alloy rod.

[0012] Technical solution:

[0013] An ultrasonic testing method for round rods, which is for round rods with a diameter not greater than 12 mm, comprises:

[0014] Select rods with the same material and specifications as the rods to be tested, and with the same heat treatment process, surface condition and acoustic performance as the rods to be tested, and with uniform internal structure and grain size not less than the set grade as comparison samples;

[0015] A transverse hole with a set diameter and a set depth is opened radially inward in the comparison sample as an artificial reflector;

[0016] The probe is controlled so that the incident sound wave is incident obliquely along the axial direction of the comparison sample to generate a pure shear wave; the incident angle and sensitivity gain of the probe are adjusted so that the wave height of the secondary reflected sound wave of the artificial reflector on the comparison sample is not lower than a set threshold, thereby determining the detection sensitivity and the optimal incident angle of the probe;

[0017] According to the aforementioned detection sensitivity and the probe's optimal incident angle, the probe is controlled to transmit ultrasonic waves obliquely along the axial direction of the comparison sample and the rod to be tested, the relative spiral linear motion between the probe and the corresponding rod is controlled, and the corresponding ultrasonic reflection signal is obtained;

[0018] The tissue state of the inspected rod is obtained by comparing the obtained comparison sample with the ultrasonic reflection signal of the inspected rod.

[0019] The tissue state of the inspected rod is obtained by comparing the ultrasonic reflection signals of the obtained comparison sample and the inspected rod:

[0020] If the amplitude of the reflected signal of the tested rod is not greater than that of the comparison sample, it is judged to be qualified;

[0021] If the amplitude of the reflected signal of the inspected rod is greater than that of the comparison sample, and the difference between the two is not less than 5%, it is determined to be a suspicious signal, and the suspicious part of the inspected rod is obtained.

[0022] The suspicious rods are processed in any of the following ways:

[0023] 1) Retesting the tested rod according to claim 1, if the amplitude of the reflection signal of the tested rod is not greater than the amplitude of the reflection signal of the comparison sample, the rod is judged to be qualified; if the amplitude of the de-reflected signal of the tested rod is greater than the amplitude of the reflection signal of the comparison sample, the rod is judged to be unqualified;

[0024] 2) Use metallographic analysis and test comparison on the suspicious parts of the inspected rod to confirm whether the suspicious parts of the inspected rod are qualified;

[0025] 3) Under the premise of meeting the minimum delivery length requirement, cut off the suspicious part of the inspected rod.

[0026] The probe frequency is 10 MHz, the bandwidth is -6 dB < 70%, the probe chip size is Φ6 mm, the probe focal length is 25-30 mm, and the set threshold is 80%.

[0027] The inspected rod is a round rod made of GH4169 steel and having a diameter of 12 mm, 8.1 mm, 5.5 mm or 9.5 mm.

[0028] The rod to be tested is a round rod made of YZGH2132 with a diameter of 9.5 mm.

[0029] The water immersion point focusing probe of a certain channel of the multi-channel pulse reflection ultrasonic flaw detector is used to perform ultrasonic testing on the inspected rod, and the probes of other channels are used to perform flaw detection on the inspected rod simultaneously.

[0030] The diameter of the artificial reflector is 0.8 mm, and the hole depth is 1 / 2D, where D is the diameter of the comparison sample.

[0031] The set level of the grain size is not less than level 6.

[0032] The refraction angle of the ultrasonic shear wave ranges from 45° to 60°.

[0033] Beneficial effects: The present invention uses ultrasonic shear waves to measure and evaluate the overall internal grain structure of high-temperature alloy rods without destroying the material structure of the rods. The method is simple, fast, and efficient, the detection results are highly reliable, and there is no need to purchase special detection instruments and equipment. At the same time, combined with metallographic analysis, the overall internal structure of the inspected material can be detected and determined, providing an effective basis for product quality assurance, and is also of great significance for product quality supervision and guidance and improvement of production technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of ultrasonic incident of the present invention; wherein 1 is the probe, 2 is the rod to be tested, and 21 is the band-shaped crystal area.

[0035] Figure 2 Schematic diagram of the ultrasonic axial shear wave incident once on the comparative sample of the present invention; wherein 3 is the comparative sample, and 31 is the artificial reflector; Figure 2 (a) Schematic diagram of single incident ultrasonic axial shear wave; Figure 2 (b) is the ultrasonic reflection signal diagram of the first reflected wave of the axial shear wave.

[0036] Figure 3 Schematic diagram of the ultrasonic axial shear wave incident once on the comparison sample of the present invention; wherein, Figure 3 (a) Schematic diagram of secondary incidence of ultrasonic axial shear wave; Figure 3 (b) is the ultrasonic reflection signal diagram of the secondary reflection wave of the axial shear wave.

[0037] Figure 4 This is an example diagram of a round bar with a steel grade of GH4169 and a diameter of 12 mm; Figure 4 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 12 mm in diameter; Figure 4 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 12 mm; Figure 4 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 12 mm.

[0038] Figure 5 This is an example diagram of a round bar with a steel grade of GH4169 and a diameter of 8.1 mm; Figure 5(a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 8.1 mm in diameter; Figure 5 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 8.1 mm; Figure 5 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 8.1 mm.

[0039] Figure 6 This is an example diagram of a round bar with a steel grade of GH4169 and a diameter of 5.5 mm; Figure 6 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 5.5 mm in diameter; Figure 6 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 5.5 mm; Figure 6 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 5.5 mm.

[0040] Figure 7 This is an example diagram of a round bar with a steel grade of GH4169 and a diameter of 9.5 mm; Figure 7 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 9.5 mm in diameter; Figure 7 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 9.5 mm; Figure 7 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 9.5 mm.

[0041] Figure 8 This is an example diagram of a round bar with a steel grade of YZGH2132 and a diameter of 7 mm; Figure 8 (a) is the ultrasonic reflection signal diagram of a round rod made of YZGH2132 steel and 7 mm in diameter; Figure 8 (b) is a cross-sectional view of the normal microstructure of a round bar with a diameter of 7 mm and a steel grade of YZGH2132; Figure 8 (c) is a cross-sectional view of the abnormal microstructure of a round rod with a steel grade of YZGH2132 and a diameter of 7 mm. DETAILED DESCRIPTION

[0042] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0043] The ultrasonic detection method of a round rod of the present invention comprises the following steps:

[0044] (1) A rod with the same material and specifications as the rod to be tested, and with the same heat treatment process, surface condition and acoustic performance as the rod to be tested, and with uniform internal structure and grain size of not less than 6, is selected as a comparison sample; the length of the comparison sample meets the minimum requirements of the dynamic test of the equipment, and a horizontal hole with a diameter of 0.8 mm is opened radially inward on it as an artificial reflector 31, and the hole depth is 1 / 2D, where D is the diameter of the comparison sample, such as Figure 2 As shown;

[0045] In the present invention, the rod to be inspected is a small-sized high-temperature alloy round rod with a diameter not greater than 12 mm.

[0046] (2) Debug the comparison sample;

[0047] First, make the incident direction of the sound wave of the selected immersion point focusing probe perpendicular to the axis of the rod, and then deflect the incident angle along the axial direction of the comparison sample to generate a pure shear wave with a refraction angle β in the range of 45° to 60° inside the comparison sample, such as Figure 2 As shown, based on this premise, by adjusting the ultrasonic instrument and probe angle to adjust the probe's incident angle and sensitivity gain, the height of the secondary reflected sound wave of the artificial reflector on the comparison sample is made not less than 80%, thereby determining the detection sensitivity and the optimal incident angle of the probe;

[0048] In the present invention, the probe frequency is 10 MHz and the probe chip size is Φ6 mm;

[0049] When a probe with a higher bandwidth is used for detection, due to the presence of the low-frequency part, the penetration of the sound wave is stronger, the scattering effect caused is lower, and the slight change in the grain size of the inspected material is not easy to be detected. Therefore, the bandwidth of the present invention adopts -6dB<70%;

[0050] For a probe with a certain wafer diameter, the smaller the focal length, the smaller the focal zone length, the smaller the focal diameter, the higher the focal zone energy concentration, and the higher the signal-to-noise ratio, which is not conducive to detecting changes in the internal grain structure of the material. While ensuring detection sensitivity, the advantage of using a probe with a larger focal length is that a larger focal length increases the focal zone length and the focal diameter, thereby expanding the detection range, being more sensitive to changes in the internal grain structure of the detected material, and improving detection efficiency. Therefore, the probe focal length of the present invention is 25-30mm.

[0051] This invention utilizes ultrasonic shear wave testing. For profiles, this method primarily targets the detection of longitudinal surface and near-surface defects on the inner and outer walls of pipes and rods. To ensure the ultrasonic wave is a single, pure shear wave within the material, the beam scanning range is typically limited to one-fifth of the material's diameter, due to the shape of the material being tested. Shear waves propagate vibration energy under shear forces, with the vibration direction perpendicular to the propagation direction. Therefore, the shear wave propagation process carries more information about the material's microstructure.

[0052] In order to effectively detect the core banded crystal area of ​​the round rod and achieve full coverage of the shear wave scanning inside the material, a straight probe is used to obliquely project along the axial direction of the round rod, such as Figure 1 As shown in the figure, the straight probe can obtain the required shear wave by adjusting the incident angle. The sound velocity of the shear wave is about half of the sound velocity of the longitudinal wave, and its wavelength is 0.32mm. When the grain size of the material is about 1 / 10 of the wavelength, the material will have scattering phenomenon. The grain size of the problematic material is basically larger than 0.04mm, which meets the conditions for causing scattering effect.

[0053] Compared to circumferential surface and near-surface shear wave detection methods, this method can excite pure shear waves at a wider angle and ensure full coverage of the material's interior. Using shear waves for internal scanning at a wider angle, it can extend the detection distance in the material's center (where banded crystals are concentrated) and enhance the interference signal intensity caused by individual scatterers in the banded crystal region, resulting in higher sensitivity and easier observation and evaluation.

[0054] (3) according to the probe detection incident angle obtained in step (2), the probe is obliquely incident along the axis of the comparison sample and the rod to be tested, the relative spiral linear motion between the probe and the corresponding rod is controlled, and the corresponding ultrasonic reflection signal is obtained through the probe;

[0055] The relative spiral linear motion between the probe and the corresponding rod can be that the probe rotates around the circumference of the corresponding rod while the rod moves forward in a straight line; or the probe remains stationary while the corresponding rod moves forward in a spiral direction;

[0056] (4) Comparing the ultrasonic reflection signals of the comparison sample and the inspected rod obtained in step (3) to obtain the tissue state of the inspected rod, specifically:

[0057] If the reflection signal amplitude of the tested rod (i.e. background noise) is not greater than the reflection signal amplitude of the comparison sample, it is judged to be qualified;

[0058] If the de-reflected signal amplitude of the inspected rod is greater than the reflected signal amplitude of the comparison sample, it is determined to be a suspicious signal and the suspicious part of the inspected rod is obtained; wherein, the suspicious signal refers to the reflected signal segment corresponding to the inspected rod whose reflected signal amplitude is greater than the reflected signal amplitude of the comparison sample and the difference between the two is not less than 5%;

[0059] (5) The rods that are determined to be suspicious in step (4) are processed in any of the following ways:

[0060] 1) Return to step (2) to re-adjust the comparison sample and repeat steps (3) to (4). If the amplitude of the reflection signal of the tested rod is not greater than the amplitude of the reflection signal of the comparison sample, it is judged to be qualified;

[0061] If the reflected signal amplitude of the inspected rod is greater than that of the comparison sample, it is judged as unqualified;

[0062] 2) Use metallographic analysis and test comparison on the suspicious parts of the inspected rod to confirm whether the suspicious parts of the inspected rod are qualified;

[0063] 3) Under the premise of meeting the minimum delivery length requirement, cut off the suspicious part of the inspected rod.

[0064] Figures 4 to 8 They are respectively specific embodiments of the present invention;

[0065] in, Figure 4 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 12 mm in diameter; Figure 4 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 12 mm; Figure 4 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 12 mm.

[0066] Figure 5 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 8.1 mm in diameter; Figure 5 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 8.1 mm; Figure 5 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 8.1 mm.

[0067] Figure 6 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 5.5 mm in diameter; Figure 6 (b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 5.5 mm; Figure 6 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 5.5 mm.

[0068] Figure 7 (a) is the ultrasonic reflection signal diagram of a round rod made of GH4169 steel and 9.5 mm in diameter; Figure 7(b) is a cross-sectional view of the normal microstructure of a round bar with a steel grade of GH4169 and a diameter of 9.5 mm; Figure 7 (c) is a cross-sectional view of the abnormal microstructure of a round bar with a steel grade of GH4169 and a diameter of 9.5 mm.

[0069] Figure 8 (a) is the ultrasonic reflection signal diagram of a round rod made of YZGH2132 steel and 7 mm in diameter; Figure 8 (b) is a cross-sectional view of the normal microstructure of a round bar with a diameter of 7 mm and a steel grade of YZGH2132; Figure 8 (c) is a cross-sectional view of the abnormal microstructure of a round rod with a steel grade of YZGH2132 and a diameter of 7 mm.

[0070] According to the above embodiments and the results of metallographic analysis and comparison, the feasibility of the axial ultrasonic shear wave detection of the present invention for detecting and evaluating the internal structure state of small-sized rods is proved.

[0071] In addition, the present invention adopts a multi-channel pulse reflection ultrasonic flaw detector, and the probes of one or two channels can be selected to perform ultrasonic detection of the rod tissue state of the present invention, while the probes of other channels can perform rod flaw detection simultaneously, thereby not only realizing the detection of the rod tissue state, but also performing the rod flaw detection task.

[0072] This method, based on the principle of ultrasonic backscattering, uses a simple, rapid, and efficient technique without damaging the material structure. The technique provides highly reliable test results and eliminates the need for specialized testing equipment. Combined with metallographic analysis, it can detect and determine the overall internal structure of the material being tested, providing an effective basis for product quality assurance. Furthermore, this method is of great significance for product quality supervision and the guidance and improvement of production technology.

[0073] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations (such as quantity, shape, position, etc.) can be made to the technical solution of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. An ultrasonic testing method for round rods with a diameter not exceeding 12 mm, characterized in that: include: Select rods with the same material and specifications as the rods to be tested, and with the same heat treatment process, surface condition and acoustic performance as the rods to be tested, and with uniform internal structure and grain size not less than the set grade as comparison samples; A transverse hole with a set diameter and a set depth is opened radially inward in the comparison sample as an artificial reflector; The probe is controlled so that the incident sound wave is incident obliquely along the axial direction of the comparison sample to generate a pure shear wave; the incident angle and sensitivity gain of the probe are adjusted so that the wave height of the secondary reflected sound wave of the artificial reflector on the comparison sample is not lower than a set threshold, thereby determining the detection sensitivity and the optimal incident angle of the probe; According to the aforementioned detection sensitivity and the probe's optimal incident angle, the probe is controlled to transmit ultrasonic waves obliquely along the axial direction of the comparison sample and the rod to be tested, the relative spiral linear motion between the probe and the corresponding rod is controlled, and the corresponding ultrasonic reflection signal is obtained; The tissue state of the inspected rod is obtained by comparing the ultrasonic reflection signals of the obtained comparison sample and the inspected rod; The tissue state of the inspected rod is obtained by comparing the ultrasonic reflection signals of the obtained comparison sample and the inspected rod: If the amplitude of the reflected signal of the tested rod is not greater than that of the comparison sample, it is judged to be qualified; If the amplitude of the reflected signal of the inspected rod is greater than that of the comparison sample, and the difference between the two is not less than 5%, it is determined to be a suspicious signal, and the suspicious part of the inspected rod is obtained; The diameter of the artificial reflector is 0.8 mm, and the hole depth is 1 / 2D, where D is the diameter of the comparison sample.

2. The ultrasonic detection method for round rods according to claim 1, characterized in that: The suspicious rods are processed in any of the following ways: 1) Retest the inspected rod according to claim 1. If the amplitude of the reflection signal of the inspected rod is not greater than the amplitude of the reflection signal of the comparison sample, the inspected rod is judged to be qualified; if the amplitude of the de-reflected signal of the inspected rod is greater than the amplitude of the reflection signal of the comparison sample, the inspected rod is judged to be unqualified; 2) Use metallographic analysis and test comparison on the suspicious parts of the inspected rod to confirm whether the suspicious parts of the inspected rod are qualified; 3) Under the premise of meeting the minimum delivery length requirement, cut off the suspicious part of the inspected rod.

3. The ultrasonic detection method for round rods according to claim 1, characterized in that: The probe frequency is 10 MHz, the bandwidth is -6 dB < 70%, the probe chip size is Φ6 mm, the probe focal length is 25-30 mm, and the set threshold is 80%.

4. The ultrasonic detection method for round rods according to claim 3, characterized in that: The inspected rod is a round rod made of GH4169 steel and having a diameter of 12 mm, 8.1 mm, 5.5 mm or 9.5 mm.

5. The ultrasonic detection method for round rods according to claim 3, characterized in that: The rod to be tested is a round rod made of YZGH2132 with a diameter of 9.5 mm.

6. The ultrasonic detection method for round rods according to claim 3, characterized in that: The water immersion point focusing probe of a certain channel of the multi-channel pulse reflection ultrasonic flaw detector is used to perform ultrasonic testing on the inspected rod, and the probes of other channels are used to perform flaw detection on the inspected rod simultaneously.

7. The ultrasonic detection method for round rods according to claim 1, characterized in that: The set level of the grain size is not less than level 6.

8. The ultrasonic detection method for round rods according to claim 1, characterized in that: The refraction angle of the ultrasonic shear wave ranges from 45° to 60°.

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