CN103336055A - The Method of Detecting the Weld Seam Quality of the Main Circuit Pipeline of Nuclear Power Plant Using Phased Array Ultrasonic - Google Patents

Abstract

A method for detecting the weld quality of a main pipeline of a nuclear power station by adopting phased array ultrasonic belongs to the technical field of ultrasonic nondestructive detection and evaluation. The method adopts a set of phased array ultrasonic testing system which comprises a Dynaray Lite ultrasonic phased array detector, a computer integrated with an UltraVision3.2R9 phased array operating system, a scanner and a calibration test block. And selecting a proper area array probe and matching with focusing law parameters, ultrasonic parameters and mechanical parameters to carry out layered detection on the welding line and the surrounding area of the main pipeline with the thickness of 66-99 mm. Layered penetration in the existing means for detecting the main pipeline can only detect the opening defect on the surface of the welding seam; the ray detection can not carry out quantification on the depth of the defect and is insensitive to area type defects such as cracks, incomplete fusion and the like; the conventional ultrasonic detection technology has the defects of low detection efficiency, high cost, weak imaging capability and the like. The method overcomes the defects, has good quantitative precision and high efficiency in field detection, and has great economic and social benefits.

Description

The Method of Detecting the Weld Seam Quality of the Main Circuit Pipeline of Nuclear Power Plant Using Phased Array Ultrasonic

technical field

The invention relates to a method for detecting the weld seam quality of a main loop pipeline of a nuclear power plant by using phased array ultrasound, which belongs to the technical field of ultrasonic nondestructive testing and evaluation.

Background technique

Centrifugal Casting Austenitic Stainless Steel (CCASS) with a wall thickness of 66-99 mm is one of the main materials used in the primary circuit coolant pipes of pressurized water reactor nuclear power plants. The pipes are generally connected by welding, and the welding quality is good. Damage is directly related to the safety and reliability of nuclear power plant operation. In the inspection specification and outline (IWA-2232APP.I) of nuclear power plants and nuclear power plants, mandatory requirements for non-destructive testing are put forward for the processing quality of the main circuit pipeline welds and the conditions during service. The research and development of accurate and reliable non-destructive testing technology for main loop pipeline welds is an urgent engineering demand for the safe operation of nuclear power plants.

Current testing standards and technical conditions require layered penetrant testing and radiographic testing for such welds with conventional ultrasonic testing as an auxiliary means. However, layered penetration can only detect opening defects on the surface of the weld, and the detection procedure is cumbersome, slow, and long. Radiographic detection is harmful to the human body, and it is not sensitive to area-type defects such as cracks and incomplete fusion, which are very harmful. Missed detection is prone to occur, which brings great hidden dangers to the safe operation of nuclear power facilities; the accessibility of conventional ultrasonic detection is poor, and the accuracy of detection results is easily affected by coupling conditions and the level of technical personnel, making it difficult to perform fast and accurate detection.

Contents of the invention

The purpose of the present invention is to provide a method for detecting the quality of the welding seam of the main loop pipeline of a nuclear power plant by using phased array ultrasonic. Compared with the conventional ultrasonic detection method, this method effectively improves the accessibility by adjusting the phase delay of each element in the probe to transmit/receive to deflect and focus the sound beam. At the same time, the detection resolution, signal-to-noise ratio and sensitivity can be greatly improved by optimizing the control of the focus position, focal area size and sound beam direction. The ultrasonic phased array uses electronic methods to control the scanning of the sound beam, and completes the fast scanning without moving or less moving the probe, which not only improves the detection speed, but also ensures the stability and consistency of the coupling conditions. The rich scanning mode also helps to correctly identify the defect signal.

The technical solution adopted by the present invention to solve the technical problem is: a method for detecting the quality of the weld seam of the main circuit pipeline of a nuclear power plant using phased array ultrasonic, which is characterized in that: it adopts a Dynaray Lite ultrasonic phased array detector, UltraVision3.2R9 A phased array operating system, a low-frequency double-crystal longitudinal-wave surface array probe, a scanner and a calibration test block constitute a device for detecting the weld area of a centrifugally cast austenitic stainless steel main pipe with a thickness of 66-99 mm. It uses the following measurement steps:

(1) Understand the material grade, weld type, welding process, size and scope of the tested part; carry out surface treatment on the tested part: for the contact surface, remove welding spatter and splashes that hinder the free movement of the probe or weaken the propagation of ultrasonic vibration. For any rough things, ensure that the surface roughness Ra does not exceed 6.3 μm, so that the probe can move freely on the complete contact surface; for the weld surface, remove the irregular shape that makes the defect signal blurred or cannot be found; Make a clear weld mark, weld position mark line and weld position reference point on the surface of the workpiece; select the appropriate coupling agent according to the material to be tested;

(2) Establish a sample model in the UltraVision3.2R9 phased array operating system, and measure the sound velocity and attenuation of the longitudinal wave in the inspected area;

(3) According to the test results of longitudinal wave sound velocity and attenuation in the inspected area, edit the material properties in the model and select an appropriate inspection angle;

(4) Layer the detection area in the thickness direction for the weld seam of the tested part and the area adjacent to the base metal of at least 10mm, use a 1.5MHz area array probe to detect and scan the area 0-20mm below the surface; 1.0MHz area array probe to detect and scan 20-60mm area below the surface; 0.5MHz area array probe detects and scans the range from 60mm below the surface to the bottom surface;

(5) Connect the 1.5MHz area array probe and the Dynaray Lite ultrasonic phased array detector to assemble the phased array detection system; select the artificial horizontal through hole in the area 0-20mm below the surface on the standard block, and determine the phase control according to the depth of the defect. The focal law, ultrasonic settings and mechanical settings of the array system, add dynamic volume corrected sector scan pictures, B scan pictures, C scan pictures and D scan pictures in the detection interface of the UltraVision3.2R9 phased array operating system; in UltraVision3.2R9 The analysis interface of the phased array operating system adds static volume corrected sector scans, B scans, C scans and D scans; performs wedge delay and longitudinal wave sound velocity calibration for the phased array detection system;

(6) Calibrate the stepping speed of the scanner, assemble the 1.5MHz area array probe and the scanner; set the scanning trajectory, resolution and scanning stepping speed; start the scanner to scan the tested part, Record the scanning results; analyze the scanning results, read the defect information in the 0-20mm area below the scanned surface in the obtained static sector scan, A-scan and B-scan, determine the type of defect and record the size of the defect; Area-type defects encountered in the inspection process, combined with multi-view using -6dB method to measure the defect length;

(7) When using 1.0MHz and 0.5MHz area array probes to detect and scan the areas 20-60mm below the surface and 60mm to the bottom, respectively, select the artificial horizontal through holes in the area 20-60mm below the surface on the standard block and the area 60mm to the bottom. Calibrate the phased array system through the artificial horizontal through hole, and the remaining steps are the same as steps (5) and (6).

The beneficial effect of the present invention is: to overcome layered penetration can only detect the surface opening defect of the weld, the detection procedure is cumbersome, the speed is slow, and the cycle is long; the ray detection is harmful to the human body, and it is very harmful to cracks, unfused areas, etc. Type defects are not sensitive, and it is easy to miss detection, which brings great hidden dangers to the safe operation of nuclear power facilities; the accessibility of conventional ultrasonic detection is poor, and the accuracy of detection results is easily affected by coupling conditions and the level of technical personnel, so it is difficult to conduct rapid Accurate detection and other shortcomings. The invention can quickly and accurately detect the quality and service state of the main loop pipeline of the nuclear power plant, the equipment used has strong adjustability, high measurement accuracy, stable and reliable on-site detection results, and is of great significance to the smooth construction and safe operation of the nuclear power plant.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Figure 1 is a schematic diagram of the hardware structure connection of the device used in the method for detecting the processing quality and service status of the main circuit pipeline weld seam of a nuclear power plant by using phased array ultrasound.

Figure 2 is a sector scan diagram corresponding to the 30mm and 50mm depth holes on the weld seam of the phased array detection circumferential test block.

Fig. 3 is a fan scan diagram of the position with the strongest echo amplitude corresponding to a crack on the weld seam of the circumferential test block detected by the phased array.

Figure 4 is a B-scan corresponding to two adjacent cracks on the weld of the circumferential test block detected by the phased array.

Figure 5 is a sector scan diagram corresponding to the 35mm and 60mm depth holes on the weld seam of the phased array detection axial test block.

Fig. 6 is a sector scan diagram of the position with the strongest echo amplitude corresponding to a crack in the axial test block detected by the phased array.

Fig. 7 is a B-scan corresponding to a crack in the axial test block detected by the phased array.

Detailed ways

The phased array ultrasonic detection method for the weld quality of the main circuit pipeline of nuclear power plant consists of Dynaray Lite ultrasonic phased array detector, UltraVision3.2R9 phased array operating system, low frequency dual crystal longitudinal wave area array probe and scanner shown in Figure 1. and calibration test block. It can detect centrifugally cast austenitic stainless steel nuclear power plant main circuit pipes with a wall thickness of 66-99mm. The detection process is as follows:

(1) For the centrifugally cast austenitic stainless steel phased array test axial test block with a thickness of 92mm, it is known that the welding method is narrow gap automatic welding, and 100% inspection must be carried out on the weld seam and the range of 10mm adjacent to the base metal. Surface treatment of the tested part: For the contact surface, remove welding spatter and any rough things that hinder the free movement of the probe or weaken the propagation of ultrasonic vibrations, and ensure that the surface roughness Ra does not exceed 6.3 μm, so that the probe is completely on the contact surface It can move freely on the surface; for the surface of the weld, remove the irregular shape that makes the defect signal obscure or cannot be found. Make a clear weld mark, weld position mark line and weld position reference point on the surface of the tested part. The couplant is a special couplant for austenitic stainless steel.

(2) According to the size information of the pipe section, the weld seam model of the pipe section is established in the sample design module of the UltraVision3.2R9 phased array operating system, and a 0.5MHz area array probe is selected to assemble an ultrasonic phased array inspection system. Set parameters in the UltraVision3.2R9 phased array operating system. ①Setting of focusing law: Dynaray Lite is selected for the hardware of the testing instrument; 0.5MHz area array TRL probe is selected for the probe, the number of active axis chips is 10, the chip spacing is 6.5mm, the chip size is 6.4mm, the number of driven axis chips is 5, and the chip spacing is 7mm , wafer size 6.9mm; wedge wedge angle setting 20.5°, roof angle 0°, first wafer height 16mm, longitudinal wave sound velocity 2330m/s, transverse wave sound velocity 1157m/s, wedge length 90mm, width 51mm, height 60mm. The sound beam angle is fan-swept from -30° to 30°; the sound beam focusing method is projection focusing, and the focus position is 8mm away from the reference point; the chip interface is double Hypertronics, and the number of chip excitations is full chip. ②Ultrasonic settings: the gain value is set to 45dB; the time base is set to 0.43mm to 58.31mm; the digitization frequency is set to 100MHz; the pulse repetition frequency is 125Hz; the excitation voltage is 100V; the pulse width is 500ns. ③Mechanical setting: select internal clock for type; set resolution to 1mm; set range to 200mm. Use the upper and lower surfaces of the standard block to calibrate the wedge delay and longitudinal wave sound velocity. In the detection interface of UltraVision3.2R9 phased array operating system, dynamic volume-corrected sector scan and online A-scan are added, and the measured sound velocity of longitudinal wave in the area around the weld is 5793m/s, and the attenuation is 0.08dB/mm.

(3) In the sample design module of the UltraVision3.2R9 phased array operating system, set the sound velocity of the longitudinal wave of the material to 5793m/s.

(4) Layer the detection area in the thickness direction for the weld seam of the tested part and the area adjacent to the base metal of at least 10mm, use a 1.5MHz area array probe to detect and scan the area 0-20mm below the surface; 1.0MHz area array probe to detect and scan 20-60mm area below the surface; 0.5MHz area array probe detects and scans the area 60mm-92mm below the surface.

(5) Select a 1.5MHz area array probe to assemble an ultrasonic phased array detection system. Modify some parameters in the UltraVision3.2R9 phased array operating system. ①Setting of focusing law: 1.5MHz area array TRL probe is selected as the probe, the number of chips on the driving axis is 8, the chip spacing is 3.5mm, the chip size is 3.4mm, the number of driven axis chips is 4, the chip spacing is 4mm, and the chip size is 3.9mm; The wedge angle of the block is set to 19°, the roof angle is 0°, the height of the first chip is 8.5mm, the sound velocity of the longitudinal wave is 2330m/s, the sound velocity of the transverse wave is 1157m/s, the length of the wedge is 44mm, the width is 22.23mm, and the height is 25mm; the sound beam angle is selected from Sector scan from 11° to 70°; the sound beam focusing method is projection focusing, and the focus position is 8mm away from the reference point; ②Ultrasonic settings: the gain value is set to 45dB; the time base is set to 0.43mm to 50.3mm; the pulse width is 300ns. Add dynamic volume corrected sector scan, B scan, C scan and D scan to the detection interface of UltraVision3.2R9 phased array operating system; add static volume correction to the analysis interface of UltraVision3.2R9 phased array operating system The passed sector scan, B scan, C scan and D scan; select the 10mm deep hole on the standard block to perform wedge delay and longitudinal wave sound velocity calibration.

(6) Calibrate the stepping speed of the scanner, assemble the 1.5MHz area array probe and the scanner. Set the scanner to move in a straight line at a constant speed of 1mm/s, and the scanning range is 200mm. Start the scanner to scan and record the scan results. Analyzing the scanning results, it is observed in the obtained static sector scan image, A-scan signal and B-scan image that there are two air holes and four cracks in the region of 0-20mm below the scanning surface, and the air holes are imaged in the middle of the fan-scan image Position, move the probe left and right to maximize the amplitude of the A-scan signal corresponding to the stomata, and read the depth of the stomata; for cracks, make it always image at 30° on the sector-scan map, and use UltraVision3.2R9 phase control in the obtained B-scan map The -6dB area size measurement tool on the array operating system is used to quantify the crack length.

(7) Select a 1.0MHz area array probe to assemble an ultrasonic phased array detection system. Modify some parameters in the UltraVision3.2R9 phased array operating system. ①Setting of focusing law: the probe selects 1.0MHz area array TRL probe, the number of active axis chips is 12, the chip spacing is 5mm, and the chip size is 4.5mm, the number of driven axis chips is 5, the chip spacing is 6mm, and the chip size is 5.5mm; The wedge angle is set to 19.5°, the roof angle is 0°, the height of the first crystal is 12mm, the sound velocity of the longitudinal wave is 2330m/s, the sound velocity of the transverse wave is 1157m/s, the length of the wedge is 77mm, the width is 51mm, the height is 35.7mm, and the sound beam angle is selected from 11° to 70° fan sweep. ②Ultrasonic settings: the gain value is set to 45dB; the time base is set to 0.43mm to 80.31mm; the pulse width is 500ns. Add dynamic volume corrected sector scan, B scan, C scan and D scan to the detection interface of UltraVision3.2R9 phased array operating system; add static volume correction to the analysis interface of UltraVision3.2R9 phased array operating system Passed sector scans, B-scans, C-scans and D-scans. Choose a 50mm deep hole on the standard block to calibrate the wedge delay and longitudinal wave sound velocity.

(8) Calibrate the stepping speed of the scanner, assemble the 1.0MHz area array probe and the scanner. Set the scanner to move in a straight line at a constant speed of 1mm/s, and the scanning range is 200mm. Start the scanner to scan and record the scan results. Analyzing the scanning results, it was observed in the obtained static sector scan image, A-scan signal and B-scan image that there were four air holes in the area 20-60mm below the scanning surface, one of which was a 30mm deep hole and a 50mm deep hole as shown in Figure 2 , so that the stomata appear in the middle of the sector scan image, move the probe left and right to maximize the amplitude of the A-scan signal corresponding to the stomata, and read the stomata depth.

(9) Select a 0.5MHz area array probe to assemble an ultrasonic phased array detection system. Modify some parameters in the UltraVision3.2R9 phased array operating system. ①Setting of focusing law: 0.5MHz area array TRL probe is selected for the probe, the number of chips on the driving axis is 10, the chip spacing is 6.5mm, the chip size is 6.4mm, the number of driven axis chips is 5, the chip spacing is 7mm, and the chip size is 6.9mm; The wedge angle of the block is set to 20.5°, the roof angle is 0°, the height of the first wafer is 16mm, the sound velocity of the longitudinal wave is 2330m/s, the sound velocity of the transverse wave is 1157m/s, the length of the wedge is 90mm, the width is 51mm, and the height is 60mm. The sound beam angle selects sector sweep from 11° to 70°. ②Ultrasonic settings: the gain value is set to 45dB; the time base is set to 0.43mm to 100mm; the pulse width is 1000ns. Add dynamic volume corrected sector scan, B scan, C scan and D scan to the detection interface of UltraVision3.2R9 phased array operating system; add static volume correction to the analysis interface of UltraVision3.2R9 phased array operating system Passed sector scans, B-scans, C-scans and D-scans. Choose the 80mm deep hole on the standard block for wedge delay and longitudinal wave sound velocity calibration.

(10) Calibrate the stepping speed of the scanner, assemble the 0.5MHz area array probe and the scanner. Set the scanner to move in a straight line at a constant speed of 1mm/s, and the scanning range is 200mm. Start the scanner to scan and record the scan results. Analyzing the scanning results, four air holes and six cracks were observed in the area from 60mm below the scanning surface to the bottom surface in the obtained static sector scan image, A-scan signal and B-scan image. For pores, make it image in the middle of the sector scan map, move the probe left and right, make the A-scan signal amplitude corresponding to the pores maximum, and read the depth of the pores; for cracks, make it always image at the 30° position on the sector scan map as shown in Figure 3 As shown, in the obtained B-scan image, the -6dB area size measurement tool on the UltraVision3.2R9 phased array operating system is used to quantify the crack length, as shown in Figure 4.

Table 1 and Table 2 show the results and errors of the above-mentioned phased array circumferential test block using phased array ultrasonic testing.

Table 1 Detection results and error analysis of air holes on the circumferential test block by phased array detection

Note: The actual diameter of the pores is 3mm.

Table 2 Phased array detection results and error analysis of cracks on the circumferential test block

Note: The cracks with a depth of 83mm are axial, and the others are circumferentially arranged.

(11) According to the above method, the 92mm thick phased array test axial test block is tested. The sector scan diagrams corresponding to the 35mm and 60mm deep holes on the weld seam of the phased array test axial test block are shown in Figure 5. Figure 6 shows the fan-scan diagram of the position with the strongest echo amplitude corresponding to a crack in the axial test block detected by the array control, and Figure 7 shows the B-scan diagram corresponding to the crack at this place. The defect measurement results and errors are shown in Table 3 and Table 4.

Table 3 Detection results and error analysis of air holes on the axial test block by phased array detection

Note: The actual diameter of the pores is 3mm.

Table 4 Phased array detection results and error analysis of cracks on the axial test block weld

Note: The second crack with a depth of 83mm is axial, and the others are arranged circumferentially.

ASME Boiler and Pressure Vessel Code Volume XI Nuclear Power Plant Equipment In-Service Inspection Rules stipulates the requirements for ultrasonic inspection and verification of coarse-grained austenitic pipe welds. If the quantitative performance verification results meet the following criteria, the inspection procedures, equipment and personnel Quantitatively accepted.

(a) Compared with the actual length of the defect, the root mean square error of the defect length measured by ultrasonic is less than or equal to 0.75in. (19mm), and the crack length of the base metal at 75% of the base metal wall thickness is measured.

(b) Compared with the actual depth of the defect, the root mean square error of the ultrasonic measurement of the defect depth shall not exceed 0.125in. (3.2mm).

Requirements for arrangement of flaws in quantitative samples when ultrasonically measuring length.

(a) At least 10 defects.

(b) At least 1/3 of the total number of defects, rounded up, the depth shall be 5%-30% of the nominal wall thickness of the pipe. At least 1/3 of the total number of defects, rounded up, and its depth should be greater than 30% of the nominal wall thickness of the pipe. At least one and at most 10% of the total number of defects, rounded up, shall be axial.

This method quantifies the length when detecting cracks. The total number of cracks on the circumferential test block detected by phased array is 10, of which 4 cracks are cracks with a depth of 5-30% of the wall thickness, and the depth is greater than 30% of the nominal wall thickness of the pipeline. There are 6 cracks, one of which is an axial crack; the total number of cracks on the axial test block detected by phased array is 10, of which 5 are cracks with a depth of 5-30% of the wall thickness, and the depth is greater than 30% of the pipeline There are 5 cracks in the nominal wall thickness, one of which is an axial crack. The defect layout of the two test blocks meets the requirements, and the length quantification is checked and accepted according to the standard (a). The root mean square difference of the crack length quantification on the circumferential test block and axial test block detected by phased array is 5.03mm and 6.01mm respectively. All are less than 19mm, meeting the standard requirements.

Requirements for arrangement of flaws in quantitative samples when ultrasonically measuring length.

(a) At least 10 defects.

(b) Defects in depth quantified specimen sets shall be described as follows

The remaining defects shall fall into any of the above categories.

This method quantifies the depth when detecting pores. The total number of pores on the circumferential test block detected by phased array is 10, among which there are 3 pores whose depth is 5-30% of the wall thickness, and the depth is 31-60% of the wall thickness. There are 3 air holes, and 4 air holes with a depth of 61-100% of the wall thickness; the total number of air holes on the phased array test axial test block is 18, of which there are 5 air holes with a depth of 5-30% of the wall thickness , there are 7 pores with a depth of 31-60% of the wall thickness, and 6 pores with a depth of 61-100% of the wall thickness. The defect layout of the two test blocks meets the requirements, and the depth quantification is checked and accepted according to the standard (b). The root mean square difference of the pore depth quantification on the circumferential test block and the axial test block detected by phased array is 1.29mm and 1.31mm, respectively. Both are less than 3.2mm, meeting the standard requirements.

The analysis shows that the defect layout and detection results on the phased array detection circumferential test block and the phased array detection axial test block meet the ASME boiler and pressure vessel code, which proves that the inspection regulations and equipment are qualified in quantitative aspects, and in engineering application has an extremely important meaning.

Claims (1)

1. A method for using phased array ultrasonic detection of the weld processing quality of the main loop pipeline of a nuclear power plant, characterized in that: it adopts Dynaray Lite ultrasonic phased array detector, UltraVision3.2R9 phased array operating system, low frequency double crystal longitudinal wave The detection system for detecting the weld seam of the centrifugally cast austenitic stainless steel main pipe with a thickness of 66-99mm composed of an area array probe, a scanner and a calibration test block; the measurement steps it adopts are as follows: (1) Understand the material grade, weld type, welding process, size and scope of the tested part; carry out surface treatment on the tested part: for the contact surface, remove welding spatter and splashes that hinder the free movement of the probe or weaken the propagation of ultrasonic vibration. For any rough things, ensure that the surface roughness Ra does not exceed 6.3 μm, so that the probe can move freely on the complete contact surface; for the weld surface, remove the irregular shape that makes the defect signal blurred or cannot be found; Make a clear weld mark, weld position mark line and weld position reference point on the surface of the workpiece; select the appropriate coupling agent according to the material to be tested; (2) Establish a sample model in the UltraVision3.2R9 phased array operating system, and measure the sound velocity and attenuation of the longitudinal wave in the inspected area; (3) According to the test results of longitudinal wave sound velocity and attenuation in the inspected area, edit the material properties in the model and select an appropriate inspection angle; (4) Layer the detection area in the thickness direction for the weld seam of the tested part and the area adjacent to the base metal of at least 10mm, use a 1.5MHz area array probe to detect and scan the area 0-20mm below the surface; 1.0MHz area array probe to detect and scan 20-60mm area below the surface; 0.5MHz area array probe detects and scans the range from 60mm below the surface to the bottom surface; (5) Connect the 1.5MHz area array probe and the Dynaray Lite ultrasonic phased array detector to assemble the phased array detection system; select the artificial horizontal through hole in the area 0-20mm below the surface on the standard block, and determine the phase control according to the depth of the defect. The focal law, ultrasonic settings and mechanical settings of the array system, add dynamic volume corrected sector scan pictures, B scan pictures, C scan pictures and D scan pictures in the detection interface of the UltraVision3.2R9 phased array operating system; in UltraVision3.2R9 The analysis interface of the phased array operating system adds static volume corrected sector scans, B scans, C scans and D scans; performs wedge delay and longitudinal wave sound velocity calibration for the phased array detection system; (6) Calibrate the stepping speed of the scanner, assemble the 1.5MHz area array probe and the scanner; set the scanning trajectory, resolution and scanning stepping speed; start the scanner to scan the tested part, Record the scanning results; analyze the scanning results, read the defect information in the 0-20mm area below the scanned surface in the obtained static sector scan, A-scan and B-scan, determine the type of defect and record the size of the defect; Area-type defects encountered in the inspection process, combined with multi-view using -6dB method to measure the defect length; (7) When using 1.0MHz and 0.5MHz area array probes to detect and scan the areas 20-60mm below the surface and 60mm to the bottom, respectively, select the artificial horizontal through holes in the area 20-60mm below the surface on the standard block and the area 60mm to the bottom. Calibrate the phased array system through the artificial horizontal through hole, and the remaining steps are the same as steps (5) and (6).

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