Ultrasonic detection method for nuclear grade alloy steel pipeline welding joint

Abstract

The invention discloses an ultrasonic detection method for a nuclear-grade alloy steel pipeline welded joint, which adopts a set of ultrasonic detection system comprising an ultrasonic phased array detector, a test block, an ultrasonic probe, an ultrasonic wedge block and a scanning device, and utilizes a phased array ultrasonic detection technology to detect the welded joint of the nuclear-grade alloy steel pipeline in an automatic or manual scanning mode. Scanning according to a set focusing criterion and a specified sensitivity level to obtain an echo signal, and performing acceptance evaluation according to a given acceptance criterion. According to the advanced ultrasonic detection method disclosed by the invention, aiming at a nuclear-grade alloy steel pipeline full penetration welding butt joint with the thickness of not less than 25mm, the nondestructive detection effect can be not lower than the radiographic inspection requirement of the welding joint, and the volume type defect with the minimum size of 0.7 mm can be effectively detected, so that the technology has no radiation risk, can be used for cross construction, and can be widely applied to the field of nuclear-grade alloy steel pipeline full penetration welding butt joints with the thickness of not less than 25mm. The construction period can be shortened on the premise that the quality is guaranteed, and great economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic nondestructive testing, and in particular relates to an ultrasonic testing method for nuclear-grade alloy steel pipeline welding joints. Background Art

[0002] Nuclear power plants are constructed with multiple types of work at the same time. Radiographic detection requires a special time window for radiographic detection, and there are also radiation safety risks, which have a certain impact on the overall construction period and safety of nuclear power plants. Ultrasonic detection does not have radiation safety risks. Ultrasonic technology is more sensitive than radiographic detection for dangerous area defects such as cracks and lack of fusion (see ASME VARTICLE 1TABLE A-110). The pressure pipelines in a certain military nuclear project have strict requirements on welding process and post-weld heat treatment process. No radiographic inspection plugs are set, and only double-wall single-shadow penetration can be used. Since the thickness of some pipelines exceeds 50mm, the penetration thickness of double-wall single-shadow exceeds the maximum penetration thickness of Ir192 source, and radiographic detection cannot be effectively implemented.

[0003] The non-nuclear industry has successfully applied phased array technology as an effective volumetric detection method in actual projects, and formed the standards DL / T 1718-2017 Technical Specification for Phased Array Ultrasonic Testing of Welded Joints in Thermal Power Plants and NB / T47018.15-2021 Nondestructive Testing of Pressure Equipment Part 15 Phased Array Ultrasonic Testing.

[0004] Chapter 6 of NB / T 47018.15-2021 specifies the phased array ultrasonic testing method and quality classification for pressure pipeline welds with a thickness of 3.5 to 150 mm for fine-grained isotropic and low-acoustic-attenuation metals. However, the allowable defect indication length for weld quality acceptance in this standard and DL / T1718 is 10 mm or even more than 50 mm, while the current radiographic acceptance criteria for nuclear-grade pipeline welds require the detection of a single circular display with a size of 0.7 mm. Therefore, the existing phased array ultrasonic testing standards cannot meet the needs of military nuclear engineering projects.

[0005] The US nuclear power code case ASME CC N659-1 clearly defines the conditions for ultrasound to replace X-ray, but it is not yet included in RG1.84. The French nuclear power standard RCC-M 2017 TABLES7710.1 has clearly stated that nuclear grade 1 ferritic steel butt joints can use RCC-M MC 2900 advanced ultrasonic technology as a replacement for X-ray detection, but there is a lack of specific inspection processes and acceptance criteria, and it cannot directly guide the implementation of the inspection. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an ultrasonic detection method for nuclear grade alloy steel pipeline welding joints in view of the above-mentioned deficiencies in the prior art, the detection capability of which is not lower than the acceptance requirements of Section 11 of the energy industry standard NB / T20328.3 of the People's Republic of China.

[0007] The technical solution adopted to solve the technical problem of the present invention is to provide an ultrasonic detection method for nuclear grade alloy steel pipeline welding joints. The ultrasonic detection method adopts a detection system for detection. The detection system includes: an ultrasonic phased array detector, a calibration test block, a comparison test block, a simulation test block, an ultrasonic probe, an ultrasonic wedge, and a scanning device. The scanning device includes an automatic scanner and an encoder. The calibration test block is used for calibration of the ultrasonic phased array detector. The ultrasonic detection method includes the following steps:

[0008] (1) Establish the joint size model of the alloy steel pipe welding joint under inspection in the inspection system;

[0009] (2) Determine the preset inspection area, which includes the weld area and the heat affected zone;

[0010] (3) Determine the ultrasonic probe for testing, the number of wafers for testing, the curvature of the ultrasonic wedge, and the gap between the ultrasonic wedge and the surface to be tested;

[0011] (4) Select standard test blocks to calibrate the test system and determine the test blocks, including standard test blocks and comparison test blocks;

[0012] (5) The detection sensitivity is set and verified using a comparison test block;

[0013] (6) Determine the detection focusing mode, the focusing rule corresponding to the detection focusing mode, and the scanning method;

[0014] (7) Set the depth compensation TCG curve, set the baseline sensitivity, and scan sensitivity;

[0015] (8) Setting the scanning area according to the requirements of steps (1) to (7), selecting the ultrasonic probe, connecting the ultrasonic probe and the ultrasonic phased array detector, and setting the focusing law, mechanical settings, sensitivity settings, and ultrasonic wedge settings according to the thickness of the alloy steel pipe welded joint workpiece to be inspected;

[0016] (9) Assembling an ultrasonic probe, an ultrasonic probe track, and an automatic scanner so that the detection area of ​​the ultrasonic probe covers the detection area preset in step (2), scanning the inspected part, recording the scanning results, and reading defect information in the inspected area;

[0017] (10) Based on the scanning results, the defect information is analyzed and the quality of the alloy steel pipeline welding joints is assessed according to the preset criteria.

[0018] Preferably, the step (1) is specifically to establish a joint size model of the inspected part in the detection system according to the material grade, specification, joint type, groove size, and welding process of the inspected alloy steel pipe welding joint.

[0019] Preferably, when establishing the joint size model of the inspected alloy steel pipe weld joint in step (1), the weld joint is ground flat, and weld marks, welding position marks, and welding position reference points are made, and a nuclear-grade coupling agent is selected according to the inspected material.

[0020] Preferably, in step (2), the width of the heat-affected zone is 13 mm, and mechanical line scanning is adopted, and the scanning type is sector scanning.

[0021] Preferably, the ultrasonic probe used in step (3) is a 5 MHz ultrasonic probe, the number of chips is not less than 16, the curvature of the ultrasonic wedge matches the shape of the test piece, and the maximum gap between the ultrasonic wedge and the surface of the test piece does not exceed 0.5 mm.

[0022] Preferably, the detection sensitivity in step (4) uses a Φ2 transverse through hole as a standard reflector.

[0023] Preferably, the standard test block in step (4) is any one of a CSK-IA type carbon steel test block, an A type sound beam deflection evaluation test block, and a B type sound beam deflection evaluation test block.

[0024] Preferably, the material of the comparison test block in step (5) is selected from P91 or P36 material which is the same as the product weld, and is prepared using the same welding process as the product welding. The comparison test block model or specification uses PRB series general test blocks or GS series ship-type test blocks.

[0025] Preferably, the focus mode detected in step (6) is depth focus.

[0026] Preferably, in step (6), the focusing law is set separately for the primary wave and the secondary wave, and the scanning mode and the focusing law setting are shown in the following table:

[0027]

[0028]

[0029] Preferably, in step (7), a depth compensation TCG curve is set, with Φ2 sensitivity set as the reference sensitivity and Φ2-30dB as the scanning sensitivity.

[0030] Preferably, the following step (i) is further included between step (9) and step (10):

[0031] Analyze the defect information, and when the defect in the defect information is characterized as a volume defect, measure the defect size.

[0032] Preferably, the step (i) analyzes the defect information and quantifies the defect. When the defect in the defect information is characterized as a volume defect, the defect size is specifically measured as follows:

[0033] When the defect display amplitude is greater than or equal to φ2-24dB and less than or equal to φ2-18dB, record its indicated length as 1mm; when the defect display amplitude is greater than or equal to φ2-18dB and less than or equal to φ2-12dB, use the absolute sensitivity method φ2-18dB to measure the length, and the amplitude of the absolute sensitivity method is φ2-18dB; when the defect display amplitude is greater than or equal to φ2-12dB and less than or equal to φ2-4dB, and the defect reflection wave has only one high point, use the -6dB method to measure its indicated length; when the peak value of the defect reflection wave fluctuates and there are multiple high points, the endpoint -6dB method should be used to measure its indicated length.

[0034] Preferably, the preset criteria in step (10) is that if any one of the following conditions is met, the defects of the alloy steel pipeline weld joint are determined to be unacceptable:

[0035] a) Any one or more of the following planar defects, including cracks, lack of fusion and lack of penetration, shall be regarded as unqualified;

[0036] b) For non-planar defects:

[0037] Amplitude>φ2-4dB, defect is unqualified;

[0038] φ2-18dB≤Amplitude≤φ2-4dB, L≥t / 3, the defect is unqualified;

[0039] L<t / 3, if the cumulative length of defects is greater than t within the length of 12t, and the minimum distance between adjacent defects exceeds 6L, the defects are unqualified; where L is the maximum indication length and t is the nominal thickness;

[0040] c) For φ2-30dB≤amplitude≤φ2-4dB, if the distance between any two defects is less than 20mm, the defect is unqualified.

[0041] Preferably, the welded joint of the alloy steel pipe under inspection is a butt welded joint of a thick-walled alloy steel pipe.

[0042] Preferably, the thickness of the welded joint of the alloy steel pipe under inspection is not less than 25 mm.

[0043] The beneficial effects of the ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in the present invention are as follows: the advanced ultrasonic detection method can replace the radiographic inspection of thick-walled alloy steel welded joints in nuclear engineering, solving the situation where nuclear engineering construction and non-destructive testing (radiation) cannot be cross-constructed, avoiding radiation safety risks, and at the same time, for the sensitivity to dangerous areal defects such as cracks and lack of fusion in thick-walled alloy steel, the advanced ultrasonic technology can obtain better results than radiographic detection. In addition, the minimum size volume defects that need to be detected according to the radiographic standards can be detected, which can solve the contradiction between the nuclear power construction progress and the high confidence of welding quality.

[0044] The ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in the present invention is aimed at full-penetration butt joints of nuclear-grade alloy steel pipelines with a thickness of not less than 25 mm. Its non-destructive detection effect can achieve no less than the requirements of radiographic inspection of welded joints, and can effectively detect volume defects with a minimum size of 0.7 mm. This technology has no radiation risk, can be cross-constructed, and can shorten the construction period while ensuring quality. It has great economic and social benefits and is feasible for engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a diagram of an ultrasonic detection system for alloy steel pipeline welded joints in Example 2 of the present invention;

[0046] Figure 2 It is a schematic diagram of the sound field coverage of the ultrasonic detection of the alloy steel pipeline welding joint in Example 2 of the present invention;

[0047] Figure 3 It is the image analysis interface of the ultrasonic detection method for nuclear grade alloy steel pipeline welded joints in Example 2 of the present invention. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0049] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0050] Example 1

[0051] This embodiment provides an ultrasonic detection method for a nuclear-grade alloy steel pipeline weld joint. The ultrasonic detection method uses a detection system for detection. The detection system includes: an ultrasonic phased array detector, a calibration test block, a comparison test block, a simulation test block, an ultrasonic probe, and a scanning device. The scanning device includes an automatic scanner and an encoder. The calibration test block is used for calibrating the ultrasonic phased array detector. The ultrasonic detection method includes the following steps:

[0052] (1) Establish the joint size model of the alloy steel pipe welding joint under inspection in the inspection system;

[0053] (2) Determine the preset inspection area, which includes the weld area and the heat affected zone;

[0054] (3) Determine the ultrasonic probe for testing, the number of wafers for testing, the curvature of the ultrasonic wedge, and the gap between the ultrasonic wedge and the surface to be tested;

[0055] (4) Selecting standard test blocks to calibrate the detection system, determining the detection calibration sensitivity, and selecting standard test blocks; the calibration test blocks include standard test blocks and comparison test blocks, and selecting standard test blocks and comparison test blocks for detection;

[0056] (5) The detection sensitivity is set and verified using a comparison test block;

[0057] (6) Determine the detection focusing mode, the focusing rule corresponding to the detection focusing mode, and the scanning method;

[0058] (7) Set the depth compensation TCG curve, set the baseline sensitivity, and scan sensitivity;

[0059] (8) Setting the scanning area according to the requirements of steps (1) to (7), selecting the ultrasonic probe, connecting the ultrasonic probe and the ultrasonic phased array detector, and setting the focusing law, mechanical settings, sensitivity settings, and ultrasonic wedge settings according to the thickness of the alloy steel pipe welded joint workpiece to be inspected;

[0060] (9) Assembling an ultrasonic probe, an ultrasonic probe track, and an automatic scanner so that the detection area of ​​the ultrasonic probe covers the detection area preset in step (2), scanning the inspected part, recording the scanning results, and reading defect information in the inspected area;

[0061] (10) Based on the scanning results, the defect information is analyzed and the quality of the alloy steel pipeline welding joints is assessed according to the preset criteria.

[0062] The beneficial effects of the ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in this embodiment are as follows: this advanced ultrasonic detection method can replace the X-ray inspection of thick-walled alloy steel welded joints in nuclear engineering, solving the situation where nuclear engineering construction and non-destructive testing (X-ray) cannot be cross-constructed, avoiding radiation safety risks, and at the same time, for the sensitivity to dangerous areal defects such as cracks and lack of fusion in thick-walled alloy steel, this advanced ultrasonic technology can obtain better results than X-ray detection. In addition, the minimum size volume defects that need to be detected according to X-ray standards can be detected, which can solve the contradiction between the progress of nuclear power construction and the high confidence of welding quality.

[0063] The ultrasonic detection method and detection system for nuclear-grade alloy steel pipeline welded joints in this embodiment can achieve a non-destructive detection effect not lower than the radiographic inspection requirements for welded joints for full penetration butt joints of nuclear-grade alloy steel pipelines with a thickness of not less than 25 mm, and can effectively detect volume defects with a minimum size of 0.7 mm. This technology has no radiation risk, can be cross-constructed, and can shorten the construction period while ensuring quality. It has great economic and social benefits and is engineering feasible.

[0064] Example 2

[0065] like Figure 1 As shown, this embodiment provides an ultrasonic detection method for a nuclear-grade alloy steel pipeline welded joint. The ultrasonic detection method uses a detection system for detection. The detection system includes: an ultrasonic phased array detector, a calibration test block, a comparison test block, a simulation test block, an ultrasonic probe, an ultrasonic wedge, and a scanning device. The scanning device includes an automatic scanner and an encoder. The scanner is used for scanning, and the encoder is used for encoding. The scanner is connected to the encoder. The ultrasonic probe is used to connect to the ultrasonic phased array detector. The calibration test block and the ultrasonic wedge are matched with the ultrasonic phased array detector. The ultrasonic probe and the ultrasonic wedge are a probe combination. The calibration test block is used for calibrating the ultrasonic phased array detector. The ultrasonic detection method includes the following steps:

[0066] (1) Establish the joint size model of the alloy steel pipe welding joint under inspection in the inspection system;

[0067] (2) Determine the preset inspection area, which includes the weld area and the heat affected zone;

[0068] (3) Determine the ultrasonic probe for testing, the number of wafers for testing, the curvature of the ultrasonic wedge, and the gap between the ultrasonic wedge and the surface to be tested;

[0069] (4) Select standard test blocks to calibrate the test system and determine the test blocks, including standard test blocks and comparison test blocks;

[0070] (5) The detection sensitivity is set and verified using a comparison test block;

[0071] (6) Determine the detection focusing mode, the focusing rule corresponding to the detection focusing mode, and the scanning method;

[0072] (7) Set the depth compensation TCG curve, set the baseline sensitivity, and scan sensitivity;

[0073] (8) Setting the scanning area according to the requirements of steps (1) to (7), selecting the ultrasonic probe, connecting the ultrasonic probe and the ultrasonic phased array detector, and setting the focusing law, mechanical settings, sensitivity settings, and ultrasonic wedge settings according to the thickness of the alloy steel pipe welded joint workpiece to be inspected;

[0074] (9) Assembling an ultrasonic probe, an ultrasonic probe track, and an automatic scanner so that the detection area of ​​the ultrasonic probe covers the preset detection area in step (2), performing semi-automatic or automatic scanning on the inspected part, recording the scanning results, displaying the scanning data in the form of A-scan signals and images, and displaying the images in the form of B-scan, C-scan, and S-scan. Analyzing the scanning results, reading defect information in the inspected area in the fan scan image; reading defect information in the inspected area in the fan scan image, A-scan, and C-scan images;

[0075] (10) Based on the scanning results, the defect information is analyzed and the quality of the alloy steel pipeline welding joints is assessed according to the preset criteria.

[0076] The TCG curve is used to set the detection process sensitivity.

[0077] Specifically, the ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in this embodiment is an advanced ultrasonic detection method for nuclear-grade thick-walled alloy steel pipeline welded joints. The method in this embodiment uses phased array ultrasonic inspection technology to scan automatically or manually according to a set focus criterion and a specified sensitivity level to obtain echo signals, and perform acceptance evaluation according to given acceptance criteria.

[0078] Preferably, the step (1) is specifically to establish a joint size model of the inspected part in the detection system according to the material grade, specification, joint type, groove size, and welding process of the inspected alloy steel pipe welding joint.

[0079] Preferably, when establishing the joint size model of the inspected alloy steel pipe weld joint in step (1), the weld joint is ground flat, and weld marks, welding position marks, and welding position reference points are made, and a nuclear-grade coupling agent is selected according to the inspected material.

[0080] Preferably, in step (2), the width of the heat-affected zone is 13 mm, and mechanical line scanning is adopted, and the scanning type is sector scanning.

[0081] Preferably, the ultrasonic probe used in step (3) is a 5 MHz ultrasonic probe, the number of chips is not less than 16, the curvature of the ultrasonic wedge matches the shape of the test piece, and the maximum gap between the ultrasonic wedge and the surface of the test piece does not exceed 0.5 mm.

[0082] Preferably, the detection sensitivity in step (4) uses a Φ2 transverse through hole as a standard reflector.

[0083] Preferably, the standard test block in step (4) is any one of the CSK-IA type carbon steel test block, the A type sound beam deflection evaluation test block, and the B type sound beam deflection evaluation test block in the energy industry standard NB / T47013 of the People's Republic of China.

[0084] Preferably, the material of the comparison test block in step (5) is selected from P91 or P36 material which is the same as the product weld, and is prepared by the same welding process as the product welding. The model or specification of the comparison test block adopts the PRB series general test block in the energy industry standard NB / T 47013 of the People's Republic of China or the GS series ship-type test block in NB / T 47013.3.

[0085] Preferably, the focus mode detected in step (6) is depth focus.

[0086] Preferably, in step (6), the focusing law is set separately for the primary wave and the secondary wave, and the scanning mode and the focusing law setting are shown in the following table:

[0087]

[0088]

[0089] Preferably, in step (7), a depth compensation TCG curve is set, with Φ2 sensitivity set as the reference sensitivity and Φ2-30dB as the scanning sensitivity.

[0090] Preferably, the following step (i) is further included between step (9) and step (10):

[0091] Analyze the defect information, and when the defect in the defect information is characterized as a volume defect, measure the defect size.

[0092] Preferably, the step (i) analyzes the defect information and quantifies the defect. When the defect in the defect information is characterized as a volume defect, the defect size is specifically measured as follows:

[0093] When the defect display amplitude is greater than or equal to φ2-24dB and less than or equal to φ2-18dB, record its indicated length as 1mm; when the defect display amplitude is greater than or equal to φ2-18dB and less than or equal to φ2-12dB, use the absolute sensitivity method φ2-18dB to measure the length, and the amplitude of the absolute sensitivity method is φ2-18dB; when the defect display amplitude is greater than or equal to φ2-12dB and less than or equal to φ2-4dB, and the defect reflection wave has only one high point, use the -6dB method to measure its indicated length; when the peak value of the defect reflection wave fluctuates and there are multiple high points, the endpoint -6dB method should be used to measure its indicated length.

[0094] Preferably, the preset criteria in step (10) is that if any one of the following conditions is met, the defects of the alloy steel pipeline weld joint are determined to be unacceptable:

[0095] a) Any one or more of the following planar defects, including cracks, lack of fusion and lack of penetration, shall be regarded as unqualified;

[0096] b) For non-planar defects:

[0097] Amplitude>φ2-4dB, defect is unqualified;

[0098] φ2-18dB≤Amplitude≤φ2-4dB, L≥t / 3, the defect is unqualified;

[0099] L<t / 3, if the cumulative length of defects is greater than t within the length of 12t, and the minimum distance between adjacent defects exceeds 6L, the defects are unqualified; where L is the maximum indication length and t is the nominal thickness;

[0100] c) For φ2-30dB≤amplitude≤φ2-4dB, if the distance between any two defects is less than 20mm, the defect is unqualified.

[0101] Preferably, the welded joint of the alloy steel pipe under inspection is a butt welded joint of a thick-walled alloy steel pipe.

[0102] Preferably, the thickness of the welded joint of the alloy steel pipe under inspection is not less than 25 mm.

[0103] like Figure 2 As shown in FIG. 1 , the acoustic field coverage diagram of the ultrasonic detection of the alloy steel pipeline welding joint in this embodiment is shown. Figure 3 As shown, the image analysis interface of the ultrasonic detection method for nuclear grade alloy steel pipeline welded joints in this embodiment.

[0104] The beneficial effects of the ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in this embodiment are as follows: this advanced ultrasonic detection method can replace the X-ray inspection of thick-walled alloy steel welded joints in nuclear engineering, solving the situation where nuclear engineering construction and non-destructive testing (X-ray) cannot be cross-constructed, avoiding radiation safety risks, and at the same time, for the sensitivity to dangerous areal defects such as cracks and lack of fusion in thick-walled alloy steel, this advanced ultrasonic technology can obtain better results than X-ray detection. In addition, the minimum size volume defects that need to be detected according to X-ray standards can be detected, which can solve the contradiction between the progress of nuclear power construction and the high confidence of welding quality.

[0105] The ultrasonic detection method for nuclear-grade alloy steel pipeline welded joints in this embodiment is aimed at full-penetration butt joints of nuclear-grade alloy steel pipelines with a thickness of not less than 25 mm. Its non-destructive testing effect can achieve no less than the requirements of radiographic inspection of welded joints, and can effectively detect volume defects with a minimum size of 0.7 mm. This technology has no radiation risk, can be cross-constructed, and can shorten the construction period while ensuring quality. It has great economic and social benefits and is feasible for engineering.

[0106] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An ultrasonic detection method for nuclear grade alloy steel pipeline welded joints, characterized in that: The ultrasonic detection method uses a detection system for detection. The detection system includes: an ultrasonic phased array detector, a calibration test block, a comparison test block, a simulation test block, an ultrasonic probe, an ultrasonic wedge, and a scanning device. The scanning device includes an automatic scanner and an encoder. The calibration test block is used for calibration of the ultrasonic phased array detector. The ultrasonic detection method includes the following steps: (1) Establish the joint size model of the alloy steel pipe welding joint under inspection in the inspection system; (2) Determine the preset inspection area, which includes the weld area and the heat affected zone; (3) Determine the ultrasonic probe for testing, the number of wafers for testing, the curvature of the ultrasonic wedge, and the gap between the ultrasonic wedge and the surface to be tested; (4) Select standard test blocks to calibrate the detection system; (5) The detection sensitivity is set and verified using a comparison test block; (6) Determine the detection focusing mode, the focusing rule corresponding to the detection focusing mode, and the scanning method; (7) Set the depth compensation TCG curve, set the baseline sensitivity, and scan sensitivity; (8) Setting the scanning area according to the requirements of steps (1) to (7), selecting the ultrasonic probe, connecting the ultrasonic probe and the ultrasonic phased array detector, and setting the focusing law, mechanical settings, sensitivity settings, and ultrasonic wedge settings according to the thickness of the alloy steel pipe welded joint workpiece to be inspected; (9) Assembling an ultrasonic probe, an ultrasonic probe track, and an automatic scanner so that the detection area of ​​the ultrasonic probe covers the detection area preset in step (2), scanning the inspected part, recording the scanning results, and reading defect information in the inspected area; (10) Based on the scanning results, the defect information is analyzed and the quality of the alloy steel pipeline welding joints is assessed according to the preset criteria.

2. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1 is characterized in that: The step (1) specifically involves establishing a joint size model of the inspected part in the detection system according to the material grade, specification, joint type, groove size, and welding process of the inspected alloy steel pipeline welding joint.

3. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: When establishing the joint size model of the alloy steel pipeline welded joint of the inspected piece in step (1), the welded joint is ground flat, and weld marks, welding position marks, and welding position reference points are made, and a nuclear-grade coupling agent is selected according to the material of the inspected piece.

4. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In the step (2), the width of the heat-affected zone is 13 mm, and mechanical line scanning is adopted, and the scanning type is sector scanning.

5. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: The ultrasonic probe used in step (3) is a 5 MHz ultrasonic probe, the number of chips is not less than 16, the curvature of the ultrasonic wedge is consistent with the shape of the test piece, and the maximum gap between the ultrasonic wedge and the surface of the test piece does not exceed 0.5 mm.

6. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: The detection sensitivity in step (4) uses a Φ2 transverse through hole as a standard reflector.

7. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In the step (4), the standard test block is any one of a CSK-IA type carbon steel test block, an A type sound beam deflection evaluation test block, and a B type sound beam deflection evaluation test block.

8. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In the step (5), the material of the comparison test block is selected to be P91 or P36 material which is the same as the product weld, and is prepared by the same welding process as the product welding. The model or specification of the comparison test block is PRB series general test block or GS series ship-type test block.

9. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In the step (6), the focus mode is detected as deep focus.

10. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In step (6), the focusing law is set separately for the primary wave and the secondary wave. The scanning mode and the focusing law setting are shown in the following table:

11. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: In the step (7), a depth compensation TCG curve is set, with Φ2 sensitivity set as the reference sensitivity and Φ2-30dB as the scanning sensitivity.

12. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: The following step (i) is also included between step (9) and step (10): Analyze the defect information, and when the defect in the defect information is characterized as a volume defect, measure the defect size.

13. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: The step (i) analyzes the defect information and quantifies the defect. When the defect in the defect information is characterized as a volume defect, the defect size is measured as follows: When the defect display amplitude is greater than or equal to φ2-24dB and less than or equal to φ2-18dB, record its indicated length as 1mm; when the defect display amplitude is greater than or equal to φ2-18dB and less than or equal to φ2-12dB, use the absolute sensitivity method φ2-18dB for length measurement, and the amplitude of the absolute sensitivity method is φ2-18dB; When the defect display amplitude is greater than or equal to φ2-12dB and less than or equal to φ2-4dB, and the defect reflection wave has only one high point, the -6dB method is used to measure its indicated length; When the peak value of the defect reflection wave fluctuates and has multiple high points, its indicated length should be measured using the endpoint -6dB method.

14. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 1, characterized in that: If the preset criteria in step (10) meet any one of the following conditions, the defects of the alloy steel pipeline weld joint are determined to be unacceptable: a) Any one or more of the following planar defects, including cracks, lack of fusion and lack of penetration, shall be regarded as unqualified; b) For non-planar defects: Amplitude>φ2-4dB, defect is unqualified; φ2-18dB≤Amplitude≤φ2-4dB, L≥t / 3, the defect is unqualified; L<t / 3, if the cumulative length of defects is greater than t within the length of 12t, and the minimum distance between adjacent defects exceeds 6L, the defects are unqualified; where L is the maximum indication length and t is the nominal thickness; c) For φ2-30dB≤amplitude≤φ2-4dB, if the distance between any two defects is less than 20mm, the defect is unqualified.

15. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to any one of claims 1 to 14, characterized in that: The welded joint of the alloy steel pipe under inspection is a butt welded joint of a thick-walled alloy steel pipe.

16. The ultrasonic detection method for nuclear grade alloy steel pipeline welded joints according to claim 15, characterized in that: The thickness of the welded joint of the alloy steel pipe under inspection shall not be less than 25mm.

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