Detection method and detection device for steam turbine fixing pin

Abstract

The invention provides a detection method and device for a steam turbine fixing pin, and the method comprises the steps: controlling an ultrasonic detector to rotate and scan around the axis of a to-be-detected fixing pin in response to a detection starting instruction, so as to transmit ultrasonic waves to the to-be-detected fixing pin, and enabling the fixing pin to be arranged at the joint of a blade root and a turbine wheel disc, the blade is fixed on a turbine wheel disc through a blade root; reflected waves of the to-be-detected fixing pin are obtained from an ultrasonic detector, the reflected waves comprise at least one of bottom waves, late waves and defect reflected waves, a new late wave is formed every time the ultrasonic waves are reflected on the side wall of the to-be-detected fixing pin, and all the late waves appear after the first bottom wave and are reflected by the defect reflected waves; the defect reflected wave is a signal reflected by the ultrasonic wave when the ultrasonic wave encounters a defect in the fixing pin; and determining a detection result of the to-be-detected fixing pin according to the sound wave type in the reflected wave. According to the invention, the accuracy of defect detection of the to-be-detected fixing pin is improved.

Description

Technical Field

[0001] The present application relates to the field of ultrasonic detection technology, and in particular to a detection method and a detection device for a steam turbine fixing pin. Background Art

[0002] As a key connecting component, the root fixing pin of the turbine blade is subjected to alternating loads for a long time. It is easy to crack due to fatigue from long-term operation, leading to fracture accidents. In the existing technology, domestic and foreign standards such as GB / T 11345-2013 (weld inspection), NB / T 47013.3-2023 (forging inspection) and ASME Volume V, etc., do not cover the ultrasonic inspection method of slender rod fixing pins in service. The technical supervision specifications currently do not have specific content for the supervision of blade root fixing pins, nor do they have relevant inspection and detection standards for fixing pin fatigue cracks. It is a blind spot and dead angle for supervision and inspection in the industry.

[0003] In recent years, some thermal power generation companies have successively encountered the problem of broken blade root fixing pins of the last stage blades of low-pressure rotor turbines. The broken blade root fixing pins affect the firmness of the connection of the turbine blades, reduce the service life, and even cause unplanned shutdown accidents of the unit due to blade falling off. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a detection method and a detection device for a steam turbine fixing pin to overcome at least one of the above-mentioned defects.

[0005] In a first aspect, an embodiment of the present application provides a method for detecting a turbine fixing pin, the method comprising: in response to a start detection instruction, controlling an ultrasonic detector to rotate and scan around the axis of the fixing pin to be tested so as to send an ultrasonic wave to the fixing pin to be tested, wherein the fixing pin to be tested is arranged at the junction of a blade root and a turbine disk, so as to fix the blade on the turbine disk through the blade root; obtaining a reflected wave of the fixing pin to be tested from the ultrasonic detector, the reflected wave comprising at least one of a bottom wave, a late wave and a defect reflected wave, wherein each additional reflection of the ultrasonic wave on the side wall of the fixing pin to be tested forms a new late wave, and all late waves appear after the first bottom wave, and the defect reflected wave is a signal reflected back by the ultrasonic wave when encountering a defect inside the fixing pin; determining the detection result of the fixing pin to be tested according to the type of sound wave in the reflected wave.

[0006] In an optional embodiment of the present application, in response to a start detection instruction, the ultrasonic detector is controlled to rotate and scan around the axis of the fixed pin to be tested to send ultrasonic waves to the fixed pin to be tested, including: calibrating the sound beam incident angle and gain parameters of the detector probe, and coating the ultrasonic coupling agent on the end face of the fixed pin to be tested; driving the detector probe to move circumferentially along the outer surface of the fixed pin to be tested, and controlling the detector probe to rotate around the axis of the fixed pin to be tested at a preset speed to perform ultrasonic scanning detection.

[0007] In an optional embodiment of the present application, the method further includes: generating a reflection waveform graph based on the acquired reflected wave reflected by the fixed pin to be tested for display, wherein the horizontal axis of the reflection waveform graph is the distance of the ultrasonic wave from the emission point to the reflection point and then back to the emission point, and the vertical axis of the reflection waveform graph is the amplitude of the reflected wave, and the reflection waveform graph is used to characterize the propagation and reflection of the ultrasonic wave in the fixed pin to be tested; and identifying each type of sound wave in the reflected wave reflected by the fixed pin to be tested according to the waveform in the reflection waveform graph.

[0008] In an optional embodiment of the present application, the detection result of the fixed pin to be tested is determined in the following manner: if a bottom wave and equally spaced late waves are detected in the reflection waveform diagram, the detection result of the fixed pin to be tested is determined to be a first detection result, and the first detection result is used to characterize that there is no defect inside the fixed pin to be tested; if a bottom wave, a late wave, and a defect reflection wave located before the bottom wave are detected in the reflection waveform diagram, the detection result of the fixed pin to be tested is determined to be a second detection result, and the second detection result is used to characterize that there is a defect inside the fixed pin to be tested and it is not completely broken; if the bottom wave disappears in the reflection waveform diagram, and there are late waves and defect reflection waves, the detection result of the fixed pin to be tested is determined to be a third detection result, and the third detection result is used to characterize that the fixed pin to be tested is completely broken.

[0009] In an optional embodiment of the present application, the defect position in the fixed pin to be tested is determined in the following manner: according to the longitudinal wave path difference between adjacent late waves, the defect reflection wave, the bottom wave and the late wave in the reflected wave reflected by the fixed pin to be tested are distinguished, the bottom wave is the reflection signal of the ultrasonic wave directly reaching the bottom of the fixed pin to be tested, the late wave is the signal of the ultrasonic wave delayed after being reflected by the side wall of the fixed pin to be tested, and the longitudinal wave path difference is fixed; according to the comparison of the amplitude of the defect reflection wave with the preset DAC curve, it is judged whether the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve, and the threshold is the limit value for judging whether the amplitude of the defect reflection wave exceeds the normal range in ultrasonic detection; if the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve, it is determined that the defect equivalent value exceeds the standard and marked as a defect; if the amplitude of the defect reflection wave does not exceed the threshold of the preset DAC curve, it is determined that the defect equivalent value does not exceed the standard; according to the path of the first defect reflection wave that arrives and the propagation speed of the ultrasonic wave in the fixed pin to be tested, the defect position in the fixed pin to be tested is determined.

[0010] In an optional embodiment of the present application, the preset DAC curve is determined in the following manner: a fixed pin test block is manufactured, and a plurality of straight-cut grooves are machined on the fixed pin test block along the axial direction as an artificial reflector, the fixed pin test block is the same size as the fixed pin actually used, and the groove positions are arranged according to the force structure of the fixed pin; the time base range is adjusted so that the sound path corresponding to the full length of the fixed pin test block covers the screen time base line, and an ultrasonic detector is used to perform ultrasonic detection on the fixed pin test block; the amplitude of the reflected wave of each straight-cut groove is detected in turn, the maximum amplitude value under different sound paths is recorded, and a preset DAC curve is generated by fitting, and the preset DAC curve is used to characterize the corresponding relationship between the equivalent size of the fixed pin test block and the change of the reflected wave amplitude with distance, so as to provide a benchmark for defect quantification.

[0011] In an optional embodiment of the present application, the longitudinal wave path difference between the late waves is calculated by the following formula:

[0012]

[0013] Wherein, △x is the longitudinal wave path difference between adjacent late waves, d is the diameter of the fixed pin to be measured, and a s is the refraction angle between the incident normal and the ultrasonic sound beam at the first reflection position, c L is the longitudinal wave speed, c s is the shear wave speed.

[0014] In a second aspect, an embodiment of the present application further provides a detection device for a turbine fixing pin, the device comprising: an ultrasonic transmitting module, for responding to a start detection instruction, controlling an ultrasonic detector to rotate and scan around the axis of the fixing pin to be tested, so as to transmit an ultrasonic wave to the fixing pin to be tested, wherein the fixing pin to be tested is arranged at the junction of the blade root and the turbine disk, so as to fix the blade on the turbine disk through the blade root; a reflected wave acquisition module, for acquiring a reflected wave reflected by the fixing pin to be tested from the ultrasonic detector, the reflected wave comprising at least one of a bottom wave, a late wave and a defect reflected wave, each additional reflection of the ultrasonic wave on the side wall of the fixing pin to be tested forms a new late wave, all late waves appear after the first bottom wave, and the defect reflected wave is a signal reflected back by the ultrasonic wave when encountering a defect inside the fixing pin; a detection result determination module, for determining the detection result of the fixing pin to be tested according to the type of sound wave in the reflected wave.

[0015] In a third aspect, an embodiment of the present application further provides an electronic device, comprising: a processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor and the memory communicate via the bus, and when the machine-readable instructions are executed by the processor, the steps of the method described above are performed.

[0016] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are executed.

[0017] The detection method and detection device for turbine fixing pins provided in the embodiment of the present application respond to the start detection instruction, control the ultrasonic detector to rotate and scan around the axis of the fixing pin to be tested to send ultrasonic waves to the fixing pin to be tested, and the fixing pin to be tested is set at the junction of the blade root and the turbine disk, so as to fix the blade on the turbine disk through the blade root; obtain the reflected wave of the fixing pin to be tested from the ultrasonic detector, and the reflected wave includes at least one of a bottom wave, a late wave and a defect reflected wave. Each additional reflection of the ultrasonic wave on the side wall of the fixing pin to be tested forms a new late wave, and all late waves appear after the first bottom wave. The defect reflected wave is a signal reflected back by the ultrasonic wave when encountering a defect inside the fixing pin; according to the type of sound wave in the reflected wave, the detection result of the fixing pin to be tested is determined. Through this application, the accuracy of the detection of the fixing pin to be tested is improved to ensure the safe operation of the turbine.

[0018] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 One of the flow charts of the method for detecting a steam turbine fixing pin provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the structure of the fixed pin to be tested provided in the embodiment of the present application during testing;

[0022] Figure 3 The second flowchart of the method for detecting a steam turbine fixing pin provided in an embodiment of the present application;

[0023] Figure 4 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a first test result;

[0024] Figure 5 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of a first detection result;

[0025] Figure 6 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a second test result;

[0026] Figure 7 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of a second test result;

[0027] Figure 8 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a third test result;

[0028] Fig. 9 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of a third test result;

[0029] Fig.10 A flow chart for determining the defect position in the fixed pin to be tested provided in an embodiment of the present application;

[0030] Fig.11 A schematic diagram of the structure of a fixed pin test block provided in an embodiment of the present application;

[0031] Fig.12 A schematic diagram of the structure of a detection device for a steam turbine fixing pin provided in an embodiment of the present application;

[0032] Fig.13A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application usually described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, each other embodiment obtained by those skilled in the art without making creative work belongs to the scope of protection of the present application.

[0034] First, the application scenarios to which the present application is applicable are introduced. The present application can be applied in the field of ultrasonic detection technology.

[0035] The research found that the shortcomings of the existing technology for detecting cracks in the root fixing pin of steam turbine blades are summarized as follows:

[0036] 1) Lack of specific supervision and inspection standards: The current technical supervision specifications do not include specific supervision content for blade root fixing pins; nor are there relevant inspection and testing standards for fatigue cracks in fixing pins, making this area a blind spot and dead angle for supervision and inspection;

[0037] 2) Existing standards are not applicable: Although the national standards, the Energy Bureau standards and the power standards stipulate the ultrasonic flaw detection method, these standards are mainly applicable to welds, steel bars, raw material parts, etc., and do not cover the ultrasonic detection technical requirements for the blade root fixing pins in the service state;

[0038] 3) Unclear evaluation criteria: The evaluation criteria for the blade root fixing pin defect reflection signal are not explained in the existing technical literature, resulting in a lack of unified standards for the evaluation of the test results.

[0039] In summary, the background technology has obvious deficiencies in ultrasonic detection of blade root fixing pins, and new detection methods and technical standards are needed to fill this gap.

[0040] Based on this, an embodiment of the present application provides a detection method and device for a turbine fixing pin, which rotates and scans the fixing pin to be tested through an ultrasonic detector, analyzes the bottom wave, late wave and defect reflection wave in the reflected wave, accurately determines the state of the fixing pin, and ensures the safe operation of the turbine.

[0041] The purpose of the present invention is to fill the gap in the existing field of turbine blade root fixing pin detection, ensure the service safety of the turbine unit, and avoid the impact of the blade root fixing pin breaking on the connection firmness of the turbine blade and reducing the service life, and even cause unplanned shutdown accidents of the unit caused by blade falling off and breaking.

[0042] See also Figure 1 , Figure 1 This is one of the flow charts of the method for detecting a steam turbine fixing pin provided in the embodiment of the present application. Figure 1 As shown in, the detection method for a steam turbine fixing pin provided in an embodiment of the present application includes:

[0043] S101 . In response to a start detection instruction, control an ultrasonic detector to rotate and scan around an axis of a fixed pin to be detected, so as to send ultrasonic waves to the fixed pin to be detected.

[0044] The fixing pin to be tested is arranged at the joint between the blade root and the turbine wheel disc, and is used to fix the blade on the turbine wheel disc through the blade root.

[0045] Among them, in response to the start detection instruction, the ultrasonic detector is controlled to perform uniform rotation scanning around the axis of the fixed pin to be tested. During this process, the ultrasonic detector sends high-frequency ultrasonic signals to the fixed pin to be tested to penetrate and detect its internal structure. The fixed pin, as a key connecting component, is located at the junction of the blade root and the turbine disk, and plays an important role in firmly fixing the blade on the turbine disk.

[0046] The specific operations are as follows:

[0047] Calibrate the acoustic beam incident angle and gain parameters of the detector probe, and apply ultrasonic coupling agent on the end surface of the fixing pin;

[0048] First, in order to ensure the accuracy and reliability of ultrasonic testing, the detector probe is accurately calibrated, which includes calibrating the incident angle of the probe's sound beam to ensure that the ultrasonic wave can be incident on the fixed pin to be tested at the correct angle, so as to obtain a clear reflected wave signal. At the same time, the gain parameter needs to be calibrated to adjust the intensity of the ultrasonic signal so that it can produce a sufficient signal-to-noise ratio at the receiving end, which is convenient for subsequent signal processing and analysis.

[0049] After calibration, evenly apply a layer of ultrasonic coupling agent on the end face of the fixed pin. During testing, the probe should be slowly rotated and moved in a circular direction. The main function of the ultrasonic coupling agent is to fill the tiny gap between the probe and the end face of the fixed pin to reduce the energy loss of the ultrasonic wave during propagation and eliminate the air's obstruction to the ultrasonic wave. In this way, the ultrasonic wave can penetrate the fixed pin more smoothly and be reflected and scattered inside it.

[0050] The detector probe is driven to move circumferentially along the outer surface of the fixed pin to be tested, and the detector probe is controlled to rotate around the axis of the fixed pin to be tested at a preset speed to perform ultrasonic scanning detection.

[0051] See also Figure 2 , Figure 2 A schematic diagram of the structure of the fixed pin to be tested provided in the embodiment of the present application during testing; Figure 2 As shown, it includes a detector probe 1 and a fixed pin 2 to be tested.

[0052] Figure 2 The middle interface 3 is the surface where the detector probe 1 contacts the fixed pin 2 to be tested. Next, the detector probe 1 is driven to move circumferentially along the outer surface of the fixed pin to be tested. The purpose of this step is to ensure that the detector probe 1 can scan all parts of the fixed pin, so as to fully detect whether there are defects inside it. In order to achieve this goal, the control probe is rotated around the axis of the fixed pin to be tested at a preset speed. During the rotation process, the probe will continuously emit ultrasonic signals and receive signals reflected from the inside of the fixed pin.

[0053] When a defect is found, inspection and verification should be carried out from the other end of the fixing pin to determine the defect amplitude and position, and the value on the side with the higher defect reflection equivalent value should be recorded and evaluated. When the bottom wave decreases, inspection, verification and analysis should be carried out from both ends of the fixing pin.

[0054] S102, obtaining the reflected wave of the fixed pin to be tested from the ultrasonic detector.

[0055] The reflected wave includes at least one of a bottom wave, a late wave and a defect reflected wave. Each time the ultrasonic wave is reflected once on the side wall of the fixed pin to be tested, a new late wave is formed. All late waves appear after the first bottom wave. The defect reflected wave is a signal reflected back by the ultrasonic wave when it encounters a defect inside the fixed pin.

[0056] Here, after sending the ultrasonic signal, the ultrasonic detector immediately enters the receiving mode to capture the sound wave signal reflected from the inside of the fixed pin to be tested. These reflected wave signals include various types, such as bottom wave (that is, the signal reflected from the bottom surface after the ultrasonic wave directly penetrates the fixed pin), late wave (the signal formed after the ultrasonic wave is reflected multiple times on the side wall of the fixed pin, each reflection will form a new late wave, and all late waves appear immediately after the first bottom wave) and defect reflection wave (the signal reflected when the ultrasonic wave encounters defects such as cracks and pores inside the fixed pin).

[0057] The root fixing pin of the steam turbine blade is mainly a slender rod structure. During the detection process, serious side wall interference will occur, and the late wave H1 will affect the detection result. The late wave comes from the side wall reflection and always appears after the first bottom wave B1, so it is called a late wave. A late wave will appear after each reflection, so there are often multiple late waves.

[0058] Specifically, see Figure 3 , Figure 3 The second flow chart of the method for detecting a steam turbine fixing pin provided in the embodiment of the present application includes:

[0059] S201 , generating a reflection waveform diagram according to the acquired reflection wave reflected by the fixed pin to be tested for display.

[0060] The horizontal axis of the reflection waveform diagram is the distance of the ultrasonic wave from the emission point to the reflection point and then back to the emission point, and the vertical axis of the reflection waveform diagram is the amplitude of the reflected wave. The reflection waveform diagram is used to characterize the propagation and reflection of the ultrasonic wave in the fixed pin to be tested;

[0061] In this step, the ultrasonic detector collects and processes the ultrasonic signals reflected from the fixed pin to be tested. After conversion and processing, these signals are used to generate an intuitive reflection waveform graph. The reflection waveform graph is an important visual tool that helps the inspector clearly see the propagation and reflection of the ultrasonic wave in the fixed pin to be tested.

[0062] Specifically, the horizontal axis of the reflection waveform usually represents the distance from the emission point to the reflection point and then back to the emission point, which is the so-called sound path. This distance is obtained by calculating the propagation speed and propagation time of the ultrasonic wave in the medium. The vertical axis of the reflection waveform represents the amplitude of the reflected wave, which reflects the energy intensity of the ultrasonic wave reflected when it encounters different medium interfaces or defects.

[0063] Through the reflection waveform diagram, the inspector can visually observe the propagation path of the ultrasonic wave in the fixed pin to be tested, the location of the reflection point, the intensity of the reflected wave, etc. This information is crucial for the subsequent judgment of whether there are defects inside the fixed pin, the type and location of the defects, etc.

[0064] S202 , identifying each type of sound wave in the reflected wave reflected by the fixed pin to be tested according to the waveform in the reflected waveform diagram.

[0065] After obtaining the reflection waveform, the next step is to identify the type of each sound wave based on the characteristics in the waveform. In ultrasonic testing, common types of sound waves include bottom waves, late waves, and defect reflection waves.

[0066] The bottom wave is the signal reflected from the bottom surface after the ultrasonic wave directly penetrates the fixed pin to be tested. It usually appears as a relatively stable waveform in the reflection waveform diagram. Its position and amplitude are related to parameters such as the thickness and material of the fixed pin.

[0067] The late wave is a signal formed by multiple reflections of the ultrasonic wave on the side wall or other non-bottom surface of the fixed pin to be tested. Due to the long reflection paths, the late wave usually appears after the bottom wave, and its waveform may be more complex, containing multiple sub-waves.

[0068] The defect reflection wave is the signal reflected by the ultrasonic wave when it encounters the defect inside the fixing pin. The characteristics of the defect reflection wave, such as waveform, position and amplitude, depend on factors such as the type, size and position of the defect. Therefore, by carefully observing and analyzing the defect reflection wave characteristics in the reflection waveform diagram, the inspector can accurately determine whether there is a defect inside the fixing pin and the specific location and type of the defect.

[0069] S103: Determine the detection result of the fixing pin to be tested according to the type of the sound wave in the reflected wave.

[0070] In this step, the collected reflected wave signals are analyzed, and the internal structural state of the fixed pin to be tested is comprehensively judged based on characteristic parameters such as the type, intensity, and time delay of the sound waves. If obvious defective reflected waves are detected, or the number and intensity of late waves are abnormal, it is determined that the fixed pin has internal defects or structural damage and needs further processing or replacement. On the contrary, if the reflected wave signal is normal, it indicates that the fixed pin is in good condition and can continue to be used. This step is crucial to ensure the safe and stable operation of the steam turbine.

[0071] Specifically, the detection result of the fixed pin to be tested is determined by the following method:

[0072] If the reflected waveform diagram contains a bottom wave and delayed waves arranged at equal intervals, it is determined that the detection result of the fixed pin to be tested is the first detection result, and the first detection result is used to indicate that there is no defect inside the fixed pin to be tested;

[0073] See also Figure 4 , Figure 5 , Figure 4 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a first test result; Figure 5 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of the first detection result. Figure 4 , Figure 5 As shown, when the fixed pin to be tested is intact, a bottom wave and its accompanying late wave will appear on the display screen, and the arc in the figure is the DAC curve.

[0074] DAC curve, full name Distance-Amplitude Curve, is a curve that describes the echo height of a certain regular reflector as it changes with distance. In ultrasonic testing, due to factors such as signal attenuation and beam diffusion, the echo amplitudes generated by defects of the same size at different depths (i.e., different distances) are different. Therefore, in order to accurately assess the size of the defect, it is necessary to draw a DAC curve as a reference.

[0075] Here, if the bottom wave can be clearly observed in the reflection waveform, accompanied by equally spaced late waves, this indicates that the ultrasonic wave encountered no obvious obstruction or reflection anomaly when propagating inside the fixed pin to be tested. The existence of the bottom wave proves that the ultrasonic wave can penetrate the fixed pin and successfully reflect back from the bottom surface, while the equally spaced late waves further confirm the uniformity and integrity of the internal structure of the fixed pin. Therefore, the first test result is determined, that is, there is no defect inside the fixed pin to be tested.

[0076] If a bottom wave, a late wave, and a defective reflected wave located before the bottom wave are detected in the reflection waveform diagram, it is determined that the detection result of the fixed pin to be tested is the second detection result, and the second detection result is used to indicate that there is a defect inside the fixed pin to be tested and it is not completely broken;

[0077] See also Figure 6 , Figure 7 , Figure 6 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a second test result; Figure 7 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of the second test result. Figure 6 , Figure 7 As shown, when the fixing pin to be tested is not completely broken, the display screen will simultaneously show the defect reflection wave, the delayed wave accompanied by the defect reflection wave, the bottom wave and the delayed wave accompanied by the bottom wave.

[0078] Among them, when there are not only bottom waves and late waves in the reflection waveform diagram, but also defect reflection waves located before the bottom waves, this indicates that the ultrasonic wave encountered some kind of defect inside the fixing pin during propagation. The defect reflection wave appears earlier than the bottom wave, which means that the defect is located in the upper part of the fixing pin or near the probe. However, since the bottom wave still exists, it means that the fixing pin is not completely broken, but only partially damaged or defective. Therefore, it is determined as the second test result, that is, there is a defect inside the fixing pin to be tested and it is not completely broken.

[0079] If it is detected that the bottom wave disappears in the reflection waveform diagram, and there are late waves and defect reflection waves, it is determined that the detection result of the fixed pin to be tested is the third detection result, and the third detection result is used to indicate that the fixed pin to be tested is completely broken.

[0080] See also Figure 8, Fig. 9 , Figure 8 The fixed pin to be tested provided in the embodiment of the present application is a structural schematic diagram of a third test result; Fig. 9 The fixed pin to be tested provided in the embodiment of the present application is a waveform diagram of the third test result. Figure 8 , Fig. 9 As shown in the figure, when the fixing pin to be tested is completely broken, the bottom wave of the display disappears, and the defect reflection wave and the delayed wave accompanying the defect reflection wave are displayed at the broken position.

[0081] If the bottom wave in the reflection waveform graph disappears completely, accompanied by the appearance of delayed waves and defect reflection waves, this indicates that the ultrasonic wave encountered serious obstacles during propagation and could not penetrate the fixing pin to reach the bottom surface for reflection. The disappearance of the bottom wave means that the fixing pin has been broken somewhere or there is serious structural damage, which makes it impossible for the ultrasonic wave to continue to propagate. Therefore, it is determined as the third test result, that is, the fixing pin to be tested has been completely broken.

[0082] In an optional embodiment, when one of the following problems exists, it is evaluated as unqualified: 1) defects evaluated as cracks; 2) defects in which the amplitude reaches the scrap line excluding echo signals such as dirt and structural reflections; 3) defects in which the defect wave reaches zone I and the bottom wave appears reduced; 4) the bottom wave reduction amount reaches more than 6dB.

[0083] When testing the fixed pin to be tested, if a defective reflection wave appears before the bottom wave and its equivalent exceeds the threshold of the DAC curve, it can be scrapped; when the defective reflection wave is in zone I, it needs to be recorded and tracked for regular re-inspection. When the defective reflection wave is below zone I, no record is made; when a defective reflection wave appears and no bottom wave appears, it can be judged that the fixed pin is completely broken and needs to be replaced.

[0084] Zone I is a specific area in ultrasonic testing, which is usually used for preliminary classification and recording of defects. In the application of DAC curve, Zone I usually refers to the area below the DAC curve but above a certain set threshold. This threshold is usually set according to the inspection standards and requirements.

[0085] When the reflected wave of the detected defect falls within zone I, it means that although the defect has not reached the scrap standard, it still needs attention. Therefore, it is necessary to record and handle these defects, and keep track of them for regular re-inspection. In this way, potential defects can be discovered and handled in a timely manner to ensure the safety and reliability of the fixing pin.

[0086] For further information, see Fig.10 , Fig.10 A flowchart for determining the defect position in the fixed pin to be tested provided in an embodiment of the present application; Fig.10 As shown, the defect position in the fixed pin to be tested is determined by:

[0087] S301, distinguishing defect reflection waves, bottom waves and late waves in the reflection waves reflected by the fixed pin to be tested according to the longitudinal wave acoustic path difference between adjacent late waves, wherein the bottom wave is a reflection signal of the ultrasonic wave directly reaching the bottom of the fixed pin to be tested, and the late wave is a signal of the ultrasonic wave arriving late after being reflected by the side wall of the fixed pin to be tested, and the longitudinal wave acoustic path difference is fixed;

[0088] In this step, the basic principles and characteristics of ultrasonic detection are used to distinguish different types of reflected waves based on the longitudinal wave path difference between adjacent late waves.

[0089] Bottom wave: The bottom wave is the signal reflected from the bottom surface after the ultrasonic wave directly penetrates the fixed pin to be tested. In the reflection waveform diagram, the bottom wave usually appears as a stable waveform, and its position is related to the thickness of the fixed pin and the propagation speed of the ultrasonic wave.

[0090] Late waves: Late waves are signals formed after multiple reflections of the ultrasonic wave on the side walls or other non-bottom locations of the fixed pin to be tested. Due to the long reflection paths, the late waves usually appear after the bottom waves, and their waveforms may be more complex. The longitudinal wave path difference between adjacent late waves is fixed, which depends on the geometry of the fixed pin and the propagation path of the ultrasonic wave.

[0091] Defect reflection wave: Defect reflection wave is the signal reflected by the ultrasonic wave when it encounters the defect inside the fixing pin. The waveform, position and amplitude of the defect reflection wave depend on factors such as the type, size and position of the defect.

[0092] By comparing the longitudinal wave path difference between adjacent late waves, the bottom wave, late wave and defect reflection wave can be distinguished, laying the foundation for defect judgment and location determination in subsequent steps.

[0093] S302, judging whether the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve according to the comparison between the amplitude of the defect reflection wave and the preset DAC curve, where the threshold is the limit value for judging whether the amplitude of the defect reflection wave exceeds the normal range in ultrasonic detection;

[0094] In this step, the amplitude of the defect reflection wave is compared with the preset DAC (Distance-AmplitudeCorrection) curve. The DAC curve is drawn based on the test results of a series of known defects and is used to determine whether the amplitude of the defect reflection wave exceeds the normal range during ultrasonic testing.

[0095] The preset DAC curve is usually preset based on the material, thickness of the fixed pin to be tested, the performance of the ultrasonic testing equipment, etc. It reflects the amplitude relationship between the normal reflection wave (such as the bottom wave and the late wave) and the defect reflection wave at different distances.

[0096] The threshold is the limit value on the DAC curve used to determine whether the amplitude of the defect reflection wave exceeds the standard. When the amplitude of the defect reflection wave exceeds the corresponding threshold on the DAC curve, it is considered that the equivalent value of the defect exceeds the standard and needs to be marked as a defect.

[0097] S303, if the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve, it is determined that the defect equivalent value exceeds the standard and marked as a defect;

[0098] If the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve, then the equivalent value of the defect is judged to be excessive and needs to be marked as a defect. This step is the key link in determining whether a defect exists in ultrasonic testing.

[0099] S304, if the amplitude of the defect reflection wave does not exceed the threshold of the preset DAC curve, it is determined that the defect equivalent value does not exceed the standard;

[0100] If the amplitude of the defect reflection wave does not exceed the threshold of the preset DAC curve, then it is judged that the reflection intensity of the defect is within the normal range, that is, the equivalent value of the defect does not exceed the standard, which may be a minor defect or a flaw that has little impact on the structural integrity.

[0101] In this case, it is usually not necessary to mark or process the defect in particular, but the specific inspection standards and requirements may determine whether these minor or non-significant defects need to be recorded or reported. In some cases, even if the amplitude of the defect reflection wave does not exceed the standard, if the defect is located in a critical structural part or may pose a potential threat to the long-term operation safety of the equipment, further analysis and decision-making may be required based on the specific application scenario and risk assessment results.

[0102] S305 , determining the defect position in the fixed pin to be tested according to the wave path of the first defect reflection wave that arrives and the propagation speed of the ultrasonic wave in the fixed pin to be tested.

[0103] When an abnormal reflection signal (defect reflection wave) is found, the first reflection wave and the late wave will also appear at the defect. The path difference between the abnormal reflection signal late wave H1 and the bottom wave B1 can be confirmed, and the position and equivalent value of the defect can be determined by the first arriving reflection wave. In addition to determining the defect depth position by the first arriving reflection wave, the fixing pin can also be inspected on the other side to verify the depth position of the defect.

[0104] After the existence of the defect is determined, the location of the defect is determined based on the wave path of the first defect reflection wave that arrives and the propagation speed of the ultrasonic wave in the fixed pin to be tested.

[0105] Here, the wave path refers to the total distance that the ultrasonic wave travels from the emission point to the reflection point and then back to the emission point. In the reflection waveform diagram, the wave path of the defect reflection wave can be calculated by measuring the relationship between its arrival time and the ultrasonic propagation speed.

[0106] The propagation speed of ultrasonic waves in the fixed pin to be tested depends on factors such as the material and temperature of the fixed pin. Usually, the propagation speed is calibrated before ultrasonic testing to ensure the accuracy of the measurement results.

[0107] By calculating the path of the first reflected wave of the defect and combining it with the propagation speed of the ultrasonic wave, the specific position of the defect in the fixed pin to be tested can be determined.

[0108] Specifically, the preset DAC curve can be determined in the following manner:

[0109] A fixed pin test block is manufactured, and a plurality of straight grooves are machined on the fixed pin test block along the axial direction as an artificial reflector. The fixed pin test block has the same size as the actual fixed pin, and the groove positions are arranged according to the force structure of the fixed pin;

[0110] See also Fig.11 , Fig.11 This is a schematic diagram of the structure of the fixed pin test block provided in the embodiment of the present application; Fig.11 Here, in order to avoid mutual interference between the grooves, each fixed pin test block is engraved with a straight groove. For example, the groove depth h1 is 1 mm.

[0111] The distance amplitude curve is produced by using the grooves at different positions on the fixed pin test block. When producing, the first wave reflection wave of the groove defect is selected as the benchmark to eliminate the interference of the late wave. The distance amplitude curve is the detection benchmark sensitivity. The detection sensitivity is generally not lower than the benchmark sensitivity. Too low detection sensitivity will affect the ability to detect defects. Therefore, in order to ensure that defects are not missed during the actual detection process, the detection sensitivity must be improved to ensure that the evaluation line at the maximum detection sound range is not lower than 20% of the display screen scale, which is conducive to improving the ability to detect fixed pin defects.

[0112] Here, first of all, it is necessary to select the same material as the actual fixing pin to make the test block. This can ensure the consistency of the ultrasonic propagation characteristics of the test block and the actual fixing pin.

[0113] The dimensions of the fixed pin test block should be exactly the same as the fixed pins actually used, including key dimensions such as length and diameter. This helps to ensure that the propagation path of the ultrasonic wave during the test is consistent with the actual use; multiple straight grooves are machined along the axial direction on the fixed pin test block as artificial reflectors. The size and depth of these straight grooves should be set according to the predetermined defect equivalent to simulate different types of defects. The groove position should be arranged according to the force structure of the fixed pin to ensure that the reflection characteristics of the fixed pin under different force states can be fully reflected.

[0114] Adjust the time base range so that the sound path corresponding to the full length of the fixed pin test block covers the screen time base line, and use an ultrasonic detector to perform ultrasonic testing on the fixed pin test block;

[0115] In an optional embodiment, the time base range of the ultrasonic detector is adjusted to an appropriate value so that the sound path corresponding to the full length of the fixed pin test block can completely cover the screen time base. This helps to ensure that the reflected waves of each straight cut groove can be accurately captured during the detection process; the fixed pin test block is ultrasonically tested using an ultrasonic detector. During the detection process, it should be ensured that the ultrasonic beam can accurately irradiate each straight cut groove, and the amplitude of the reflected wave of each straight cut groove is recorded.

[0116] Here, a high-frequency longitudinal wave straight probe or a small-angle longitudinal wave oblique probe is used to adjust the scanning speed of the instrument. The scanning speed should be adjusted according to the length of the fixed pin, and the maximum detection range should be at least 80% of the full scale of the time baseline. The distance-amplitude curve (DAC curve) is made by using three different sound path depth h1 grooves on the fixed pin comparison test block as reflectors, and this is used as the reference sensitivity.

[0117] Preferably, when using the straight probe longitudinal wave method for detection, on the premise of meeting the requirements of on-site detection, a probe with a larger chip size is given priority; when using the small-angle longitudinal wave method for detection, on the premise of meeting the requirements of on-site detection, a probe with a chip size of 8mm×8mm is given priority.

[0118] On the screen of the ultrasonic detector, there is a horizontal "time axis", called the time base line. This line is used to show the time or distance that the ultrasonic wave propagates in the material. The baseline full scale refers to the maximum display range of this time axis, that is, the complete length from the leftmost end (starting point) to the rightmost end (end point), which is equivalent to the "full scale display" of the instrument screen.

[0119] It corresponds to the maximum detection distance of ultrasonic wave propagation in the material. For example, if the full scale of the baseline represents the distance of 200 mm for ultrasonic wave propagation in steel, if the length of the fixed pin is 160 mm, after adjusting the scanning speed, the detection range of 160 mm should be 80% of the baseline (that is, 160 mm corresponds to 80% of the full scale of the baseline). In this way, the signal distribution on the screen is clearer, avoiding the signal being "crowded together" and difficult to distinguish.

[0120] The amplitude of the reflected wave of each straight cut groove is detected in turn, the maximum amplitude value under different sound path is recorded, and the preset DAC curve is generated by fitting. The preset DAC curve is used to characterize the corresponding relationship between the equivalent size of the fixed pin test block and the change of the reflected wave amplitude with distance, providing a benchmark for defect quantification.

[0121] The collected data is used to fit and generate a preset DAC curve through mathematical methods (such as the least square method, etc.). The curve should be able to accurately characterize the corresponding relationship between the equivalent size of the fixed pin test block and the change of the reflected wave amplitude with distance.

[0122] After the DAC curve is generated, it needs to be verified and optimized. The accuracy of the curve can be verified by comparing the amplitude of the defect reflection wave in the actual detection with the corresponding value on the DAC curve. If a large deviation is found, the curve can be adjusted and optimized to improve the accuracy of the detection.

[0123] The preset DAC curve can provide a benchmark for quantitative defect detection, helping inspectors accurately determine the equivalent size and location of defects. At the same time, the DAC curve can also be used to evaluate the performance and stability of the inspection equipment, as well as to optimize the inspection parameters and conditions.

[0124] Preferably, the longitudinal acoustic path difference Δx (single path) between the late waves is specific, and the longitudinal wave is incident obliquely on the steel / air interface. L = about 70°, α S =33°, the deformed transverse wave is very strong, from which △x can be calculated. Here, α L It is the angle between the ultrasonic beam at the first reflection position and the incident normal.

[0125] Specifically, the longitudinal wave path difference between the late waves is calculated by the following formula:

[0126]

[0127] Wherein, △x is the longitudinal wave path difference between adjacent late waves, d is the diameter of the fixed pin to be measured, and a s is the refraction angle between the incident normal and the ultrasonic sound beam at the first reflection position, c L is the longitudinal wave speed, c s is the shear wave speed.

[0128] Here, the incident normal refers to the straight line passing through the incident point and perpendicular to the reflection surface (or refraction surface) in the reflection or refraction phenomenon of light. It is a reference line used to determine the angle of incidence, angle of reflection or angle of refraction; a transverse wave is a wave in which the vibration direction of the medium particle is perpendicular to the propagation direction.

[0129] The present application is based on portable A-type pulse manual ultrasonic testing, and utilizes the reflection wave principle of high-frequency longitudinal wave straight probe and small-angle longitudinal wave oblique probe to determine the distance amplitude curve (DAC curve). Since most fixing pins are slender rod types, when ultrasonic testing is used, the reflected waves are extremely complex due to the side wall effect, and it is difficult to distinguish the specific location of the defect in the workpiece. Therefore, it is proposed to use the first reflected wave to achieve the quantification and positioning of the defect. Through this application, qualified testing technicians can accurately determine the crack defect of the blade root fixing pin, thereby avoiding missed judgment and misjudgment.

[0130] This application uses a digital ultrasonic testing instrument, 1-10MHz high-frequency longitudinal wave straight probe and small-angle longitudinal wave oblique probe, to debug the distance amplitude curve on the designed fixed pin test block, and adjust the instrument detection sensitivity, and implement on-site detection on the end face of the fixed pin. When an abnormal reflection signal is found during on-site detection, the depth of the defect and the equivalent amplitude of the defect are determined by the arrival time of the first wave, thereby eliminating the influence of other "late waves". Based on this, the crack defect of the fixed pin to be tested in the turbine can be accurately determined, which solves the current technical problem of difficult determination of defects in the fixed pin detection of the turbine, and fills the gap in the industry.

[0131] The detection method and detection device for turbine fixing pins provided in the embodiments of the present application respond to the start detection instruction, control the ultrasonic detector to rotate and scan around the axis of the fixing pin to be tested, so as to send ultrasonic waves to the fixing pin to be tested; obtain the reflected wave of the fixing pin to be tested from the ultrasonic detector, the reflected wave includes at least one of a bottom wave, a late wave and a defect reflected wave, each additional reflection of the ultrasonic wave on the side wall of the fixing pin to be tested forms a new late wave, all late waves appear after the first bottom wave, and the defect reflected wave is a signal reflected back by the ultrasonic wave when encountering a defect inside the fixing pin; determine the detection result of the fixing pin to be tested according to the type of sound wave in the reflected wave, and through the present application, the accuracy of the detection of the fixing pin to be tested is improved to ensure the safe operation of the turbine.

[0132] Based on the same inventive concept, the embodiment of the present application also provides a detection device for a turbine fixing pin corresponding to the detection method for a turbine fixing pin. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the above-mentioned detection method for a turbine fixing pin in the embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0133] See also Fig.12 , Fig.12 This is a schematic diagram of the structure of the detection device for the steam turbine fixing pin provided in the embodiment of the present application. Fig.12 As shown in , the detection device 120 for the steam turbine fixing pin includes:

[0134] The ultrasonic transmitting module 121 is used to control the ultrasonic detector to rotate and scan around the axis of the fixed pin to be tested in response to the start detection instruction, so as to transmit ultrasonic waves to the fixed pin to be tested, wherein the fixed pin to be tested is arranged at the junction of the blade root and the turbine disk, and is used to fix the blade on the turbine disk through the blade root;

[0135] A reflected wave acquisition module 122 is used to acquire reflected waves reflected by the fixed pin to be tested from the ultrasonic detector, wherein the reflected waves include at least one of bottom waves, late waves and defect reflected waves. Each time the ultrasonic wave is reflected once on the side wall of the fixed pin to be tested, a new late wave is formed. All late waves appear after the first bottom wave. The defect reflected wave is a signal reflected back by the ultrasonic wave when it encounters a defect inside the fixed pin.

[0136] The detection result determination module 123 is used to determine the detection result of the fixing pin to be tested according to the type of the sound wave in the reflected wave.

[0137] See also Fig.13 , Fig.13 This is a schematic diagram of the structure of the electronic device provided in the embodiment of the present application. Fig.13 As shown in , the electronic device 500 includes a processor 510 , a memory 520 and a bus 530 .

[0138] The memory 520 stores machine-readable instructions executable by the processor 510. When the electronic device 500 is running, the processor 510 communicates with the memory 520 via the bus 530. When the machine-readable instructions are executed by the processor 510, the above-mentioned Figure 1 The specific implementation of the steps of the method for detecting the steam turbine fixing pin in the method embodiment shown can be found in the method embodiment, and will not be repeated here.

[0139] The present application also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the computer program can execute the above-mentioned Figure 1 The specific implementation of the steps of the method for detecting the steam turbine fixing pin in the method embodiment shown can be found in the method embodiment, and will not be repeated here.

[0140] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0141] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of devices or units can be electrical, mechanical or other forms.

[0142] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0143] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0144] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application can essentially be embodied in the form of a software product, or in other words, the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0145] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-mentioned embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-mentioned embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for detecting a fixing pin of a steam turbine, characterized in that: include: In response to a start detection instruction, the ultrasonic detector is controlled to rotate and scan around the axis of the fixed pin to be tested, so as to send ultrasonic waves to the fixed pin to be tested, wherein the fixed pin to be tested is arranged at the junction of the blade root and the turbine wheel disc, and is used to fix the blade on the turbine wheel disc through the blade root; Acquire the reflected wave of the fixed pin to be tested from the ultrasonic detector, wherein the reflected wave includes at least one of a bottom wave, a late wave and a defect reflected wave. Each time the ultrasonic wave is reflected once on the side wall of the fixed pin to be tested, a new late wave is formed. All late waves appear after the first bottom wave. The defect reflected wave is a signal reflected back by the ultrasonic wave when it encounters a defect inside the fixed pin; The detection result of the fixing pin to be tested is determined according to the type of the sound wave in the reflected wave.

2. The method according to claim 1, characterized in that In response to the start detection instruction, the ultrasonic detector is controlled to rotate and scan around the axis of the fixed pin to be detected to send ultrasonic waves to the fixed pin to be detected, including: Calibrate the acoustic beam incident angle and gain parameters of the detector probe, and apply ultrasonic coupling agent on the end surface of the fixed pin to be tested; The detector probe is driven to move circumferentially along the outer surface of the fixed pin to be tested, and the detector probe is controlled to rotate around the axis of the fixed pin to be tested at a preset speed to perform ultrasonic scanning detection.

3. The method according to claim 1, characterized in that The method further comprises: Generate a reflection waveform diagram according to the acquired reflected wave reflected by the fixed pin to be tested for display, wherein the horizontal coordinate of the reflection waveform diagram is the distance of the ultrasonic wave from the emission point to the reflection point and then back to the emission point, and the vertical coordinate of the reflection waveform diagram is the amplitude of the reflected wave, and the reflection waveform diagram is used to characterize the propagation and reflection of the ultrasonic wave in the fixed pin to be tested; According to the waveform in the reflection waveform diagram, each type of sound wave in the reflected wave reflected by the fixed pin to be tested is identified.

4. The method according to claim 3, characterized in that The detection result of the fixed pin to be tested is determined by: If a bottom wave and delayed waves arranged at equal intervals are detected in the reflection waveform diagram, it is determined that the detection result of the fixed pin to be tested is a first detection result, and the first detection result is used to indicate that there is no defect inside the fixed pin to be tested; If a bottom wave, a late wave, and a defective reflected wave located before the bottom wave are detected in the reflection waveform diagram, it is determined that the detection result of the fixed pin to be tested is a second detection result, and the second detection result is used to indicate that there is a defect inside the fixed pin to be tested and it is not completely broken; If it is detected that the bottom wave disappears in the reflection waveform diagram, and there are late waves and defective reflection waves, it is determined that the detection result of the fixed pin to be tested is the third detection result, and the third detection result is used to indicate that the fixed pin to be tested is completely broken.

5. The method according to claim 4, characterized in that The defect position in the fixed pin to be tested is determined by: According to the longitudinal wave acoustic path difference between adjacent late waves, the defect reflection wave, bottom wave and late wave in the reflected wave reflected by the fixed pin to be tested are distinguished, wherein the bottom wave is the reflection signal of the ultrasonic wave directly reaching the bottom of the fixed pin to be tested, and the late wave is the signal of the ultrasonic wave delayed after being reflected by the side wall of the fixed pin to be tested, and the longitudinal wave acoustic path difference is fixed; According to the comparison between the amplitude of the defect reflection wave and the preset DAC curve, it is judged whether the amplitude of the defect reflection wave exceeds the threshold value of the preset DAC curve, and the threshold value is the limit value for judging whether the amplitude of the defect reflection wave exceeds the normal range in ultrasonic detection; If the amplitude of the defect reflection wave exceeds the threshold of the preset DAC curve, it is determined that the defect equivalent value exceeds the standard and marked as a defect; If the amplitude of the defect reflection wave does not exceed the threshold of the preset DAC curve, it is determined that the defect equivalent value does not exceed the standard; The defect position in the fixed pin to be tested is determined according to the wave path of the first defect reflection wave that arrives and the propagation speed of the ultrasonic wave in the fixed pin to be tested.

6. The method according to claim 5, characterized in that The preset DAC curve is determined by: A fixed pin test block is manufactured, and a plurality of straight grooves are machined on the fixed pin test block along the axial direction as an artificial reflector. The fixed pin test block has the same size as the fixed pin actually used, and the groove positions are arranged according to the force structure of the fixed pin; The time base range is adjusted so that the sound path corresponding to the full length of the fixed pin test block covers the screen time base line, and an ultrasonic detector is used to perform ultrasonic testing on the fixed pin test block; The amplitude of the reflected wave of each straight cut groove is detected in turn, the maximum amplitude value under different sound path is recorded, and a preset DAC curve is generated by fitting. The preset DAC curve is used to characterize the corresponding relationship between the equivalent size of the fixed pin test block and the change of the reflected wave amplitude with distance, providing a benchmark for defect quantification.

7. The method according to claim 5, characterized in that The longitudinal path difference between the late waves is calculated by the following formula: Wherein, △x is the longitudinal wave path difference between adjacent late waves, d is the diameter of the fixed pin to be measured, and a s is the refraction angle between the incident normal and the ultrasonic sound beam at the first reflection position, c L is the longitudinal wave speed, c s is the shear wave speed.

8. A detection device for a steam turbine fixing pin, characterized in that: include: An ultrasonic transmitting module, for responding to a start detection instruction, controlling an ultrasonic detector to rotate and scan around an axis of a fixed pin to be tested, so as to transmit ultrasonic waves to the fixed pin to be tested, wherein the fixed pin to be tested is arranged at a junction between a blade root and a turbine wheel disc, and is used to fix the blade on the turbine wheel disc through the blade root; A reflected wave acquisition module, used for acquiring reflected waves reflected by the fixed pin to be tested from the ultrasonic detector, wherein the reflected waves include at least one of bottom waves, late waves and defect reflected waves. Each time the ultrasonic wave is reflected once on the side wall of the fixed pin to be tested, a new late wave is formed. All late waves appear after the first bottom wave. The defect reflected wave is a signal reflected back by the ultrasonic wave when it encounters a defect inside the fixed pin. The detection result determination module is used to determine the detection result of the fixing pin to be tested according to the type of sound wave in the reflected wave.

9. An electronic device, characterized in that: include: A processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor and the memory communicate via the bus, and the processor executes the machine-readable instructions to perform the steps of any method as claimed in claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are executed.

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