Full coverage nondestructive testing method for steel lining welds in underground chambers of compressed air energy storage power stations

Abstract

The present invention discloses a method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations, including: using a low-frequency magnetic detection method to detect defects in steel lining welds and determine the depth of defects, and using a universal calibration test block in a calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method. If the detectable thickness range covers the thickness of the steel lining to be detected, the weld detection work is completed. If it cannot be covered, proceed to the next step; pre-treat the surface of the steel lining weld to be detected and the surface of the adjacent parent material to expose the metallic luster; review the thickness of the steel lining; and use a shear wave ultrasonic detection method to detect the steel lining weld area that is not detected by the low-frequency magnetic detection method. The method of the present invention solves the problem of structural integrity detection of steel lining welds in underground chambers of compressed air energy storage power stations, and at the same time has the characteristics of intuitive detection results and high detection sensitivity, and can achieve high-sensitivity full coverage detection of welds.

Description

Technical Field

[0001] The invention belongs to the technical field of compressed air energy storage, and relates to a full coverage nondestructive testing method for steel lining welds in underground chambers of compressed air energy storage power stations. Background Art

[0002] With the continuous advancement of the construction of my country's new power system, the energy storage industry has ushered in rapid development. Among them, compressed air energy storage is suitable for large-scale energy storage and is widely used in energy storage on the grid side, power supply side and user side. It can play the role of peak load regulation, frequency regulation, capacity backup, reactive power compensation, black start, etc. At present, the construction of compressed air energy storage power stations is mainly concentrated in areas with rich salt cavern resources, such as Jintan, Jiangsu, Yingcheng, Hubei, Feicheng, Shandong, etc. The use of existing salt cavern resources can greatly reduce construction costs and improve project economy. However, this also limits the development of compressed air energy storage and cannot meet the energy storage development needs of other regions. In order to solve this problem, artificial underground gas storage (underground chamber) has gradually become the mainstream choice for large-scale compressed air energy storage power stations.

[0003] The steel flexible sealing layer (steel lining) is an important part of the underground chamber. It is located inside the underground chamber, containing compressed air. The outside is the concrete secondary lining, primary support, surrounding rock, etc., which plays an important role in cavity sealing and structural stress conduction. Therefore, the structural integrity and long-term operation reliability of the steel lining are crucial. The steel lining of the underground chamber of the compressed air energy storage power station is usually welded on-site by a large number of thin-walled curved steel plates. Generally, high-strength carbon steel or low-alloy steel with good fatigue resistance is selected. Depending on the capacity of the gas storage reservoir, the weld can reach several thousand meters or even tens of thousands of meters. Due to the structural limitations of the underground chamber, the steel lining can only be welded from one side and formed from both sides from the inside, and there are multiple welding positions such as flat welding, vertical welding, and overhead welding. This brings certain difficulties to on-site welding and welding quality control, and also brings new challenges to steel lining detection. In addition, the energy storage system has high requirements for the cleanliness of the compressed air in the gas storage reservoir and the steel lining, otherwise it may have an adverse effect on equipment such as the expander during the expansion and energy release stage. Therefore, the steel lining detection cannot bring additional difficult-to-handle impurities to cause secondary pollution.

[0004] At present, researchers have not yet proposed a special system detection method for the steel lining welds of the underground chamber of the compressed air energy storage power station. Because its structure is similar to the flat plate butt structure weld, it is easy to think of directly borrowing the flat plate butt weld detection method for detection, generally using surface magnetic powder or penetration detection, internal ultrasonic detection methods. However, although traditional surface detection technologies such as magnetic powder and penetration can make surface defects intuitively visible, they are limited to detecting open defects on the surface or buried defects about 1mm near the surface. Moreover, the contrast enhancer, magnetic suspension, penetrant, cleaning agent and other reagents used in the detection will cause secondary pollution and are not suitable for direct application in the detection of steel linings. At the same time, the existing ultrasonic testing standard (NB / T47013.3-2015) stipulates that ultrasonic testing is only applicable to plate testing with a thickness of more than 6mm, while the steel lining of the underground chamber of the compressed air energy storage power station currently in use has reached 4mm, and the existing standards are no longer applicable. In addition, conventional ultrasonic testing mostly uses oil coupling agents, which will also cause secondary pollution problems. In summary, the conventional method will have a blind spot in the detection of thin-walled steel plate welds below 6 mm (the standard is not applicable), and will cause secondary pollution on the other hand. Therefore, it is urgent to study new detection methods. Summary of the invention

[0005] The purpose of the present invention is to provide a method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations, which solves the problem of structural integrity testing of steel lining welds in underground chambers of compressed air energy storage power stations. At the same time, it has the characteristics of intuitive testing results and high detection sensitivity, and can achieve high-sensitivity full coverage detection of welds.

[0006] The technical solution adopted by the present invention is a method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations, which is specifically implemented in the following steps:

[0007] Step 1: Use the low-frequency magnetic detection method to detect defects on the steel lining weld and determine the defect depth. At the same time, use the universal calibration test block in the calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method. If the detectable thickness range covers the thickness of the steel lining to be detected, the weld detection work is completed. If it cannot be covered, proceed to step 2;

[0008] Step 2: pre-treat the surface of the steel lining weld to be inspected and the adjacent parent material surface to expose the metallic luster;

[0009] Step 3: Review the thickness of the steel lining;

[0010] Step 4: Use the shear wave ultrasonic detection method to detect the steel lining weld area that was not detected by the low-frequency magnetic detection method in step 1.

[0011] The present invention is also characterized in that:

[0012] Step 1 is implemented according to the following steps:

[0013] Step 1.1, using the universal calibration test block in the calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method;

[0014] Step 1.2: Use a low-frequency magnetic flaw detector to detect defects, specifically:

[0015] The defect display film is pasted on the inner surface of the steel lining to be inspected, the magnetic yoke is placed across the two sides of the weld, and the inspection is carried out in a cross-shaped manner. During the movement, the coverage of the two inspections before and after is kept overlapping by at least 10% to ensure that no inspection is missed. Electromagnetic is applied and the changes on the display film are continuously observed;

[0016] Step 1.3, when magnetic traces appear on the defect display film, change at least two magnetic field application angles, select the angle where the defect is more obvious, take photos on site and save them, and mark the position of the magnetic traces;

[0017] Step 1.4, using the depth comparison test block in the calibration comparison test block to quantify the defect depth;

[0018] Step 1.5: Rating the inspection results of the steel lining weld.

[0019] The specific structure of the calibration comparison test block is:

[0020] The calibration comparison test blocks include a set of universal calibration test blocks and a depth comparison test block. The universal calibration test block consists of 15 test pieces with a thickness interval of 1 mm, among which the thickness of the thinnest test piece is 1 mm and the thickness of the thickest test piece is 15 mm. The surface of the test piece is provided with three circular grooves of different depths and three right cross grooves of different depths. The depths of the circular grooves are 7μm, 15μm and 30μm respectively, and the lengths of the two straight lines of the right cross grooves are 6mm. The groove depths are 7μm, 15μm and 30μm respectively; the depth comparison test block is an oblique wedge-shaped test block with a length of 150mm and a thickness of 15mm. Its top is a plane and its bottom is an inclined surface. The edge of the top plane is engraved with a 150mm scale, and the bottom inclined surface is evenly provided with three linear grooves of different depths, and the groove depths are 7μm, 15μm and 30μm respectively.

[0021] In step 1.1, the specific steps for determining the thickness range that can be detected by the low-frequency magnetic detection method using a universal calibration test block are as follows:

[0022] Select a test piece from the universal calibration test block. The thickness of the test piece is the same as that of the thin-walled steel part to be tested, or the thickness is closest to and larger than that of the thin-walled steel part. Then stick the defect display film on the non-grooved surface of the test piece. Adjust the pulse frequency of the yoke-type low-frequency magnetic flaw detector to 50Hz, place the yoke on the non-grooved surface, and start the flaw detector. Adjust the pulse frequency value. If it can be adjusted to the display film on the calibration test piece to show magnetic marks, it means that the detectable thickness range of the low-frequency magnetic detection covers the thickness of the steel lining to be tested. If there is no magnetic mark, use other calibration test pieces that are thinner than the steel lining to be tested and test them in descending order of thickness until magnetic marks appear. The maximum thickness D of the test piece that can show magnetic marks is the maximum detection depth of the low-frequency magnetic detection.

[0023] In step 1.4, the specific steps for using the depth comparison test block to quantify the defect depth are:

[0024] After the position of the defect magnetic mark is determined, slowly increase the pulse frequency of the low-frequency magnetic flaw detector until the defect magnetic mark disappears, and lock the equipment parameters at this time; stick the defect display film to the non-grooved surface of the depth comparison test block; place the yoke on the non-grooved surface and restart the detection instrument; observe the displayed length of the surface magnetic mark, compare the scale to read the corresponding defect depth, and determine the depth of the detected defect.

[0025] Step 4 is implemented according to the following steps:

[0026] Step 4.1, using the CSK-IA test block, through the ultrasonic detector's built-in adjustment program, the first step is to find the highest reflected wave of the Φ50mm and Φ100mm arcs at the same time, measure the front length of the probe, and then input it into the instrument; the second step is to find the highest wave of the Φ50mm step hole with a depth of 30mm, and input it into the instrument to determine the actual K value of the probe;

[0027] Step 4.2, using the ultrasonic contrast test block to draw the DAC curve and make reference points or reference lines;

[0028] Step 4.3, apply water as coupling agent to the polished areas on both sides of the weld to be inspected, select the DAC curve produced by the first channel, and adjust the coupling compensation to 4dB. Adjust the reflection amplitude of the 2mm deep side through hole to more than 80% of the full screen, place the ultrasonic probe in the area for zigzag scanning, and the scanning speed should not exceed 150mm / s. During the scanning process, always pay attention to the waveform changes on the oscilloscope screen, and focus on observing the one or three reflection echoes within the TD range of the weld root. After the single-side scanning is completed, repeat the scanning on the opposite side to ensure full coverage of the weld.

[0029] Step 4.4, when the detected reflected echo exceeds the DAC curve, the position information of the defect is verified from multiple angles on at least both sides of the weld. If the defect is located inside the weld joint, the -6dB method is used to measure the length, and the information on the side with the longer length is used as the record information. The depth, length, position, and amplitude of the defect are recorded, and the position is marked on the joint surface; if the detected defect is within the root position of the weld, the second channel reference point or reference line is called to compare the waveform and reflection equivalent to determine the nature and size of the defect;

[0030] Step 4.5: Inspect, rate and evaluate the quality of the steel lining welds.

[0031] In step 4.2, the specific structure of the ultrasonic comparison test block is:

[0032] The ultrasonic contrast test block consists of three parts, namely the transverse through hole area in the middle and the first step groove area and the second step groove area at both ends; six transverse through holes are distributed in sequence from top to bottom in the transverse through hole area, the horizontal spacing between each transverse through hole is ≥15mm, the vertical spacing is 3mm, and the distance between the top transverse through hole and the upper surface of the test block is 3mm, and the distance between the bottom transverse through hole and the lower surface of the test block is 2mm; the first step groove area includes six steps, the height of each step differs by 3mm, and the height of the step at the end is 3mm; the second step groove area includes seven steps, the height of each step differs by 3mm, and the height of the step at the end is 2mm; a groove with a width of 0.1mm and a depth of 1mm is provided in the center of the step along the width direction of the test block.

[0033] Step 4.2 is as follows:

[0034] Through the built-in adjustment program of the ultrasonic detector, select the first channel, and according to the thickness of the steel lining, select all the transverse through holes in the transverse through holes whose depth is greater than the thickness of the steel lining and closest to the thickness of the steel lining to make a DAC curve, and use the DAC curve as a comparison curve; select the second channel, select the groove depth with the same thickness as the steel lining to be inspected or the two groove depths closest to the groove depth as the benchmark, and make reference points or reference lines.

[0035] In step 4.4, the specific rating criteria are:

[0036] 1) When the defect is characterized as crack, lack of fusion, or lack of penetration, it is judged as unqualified;

[0037] 2) When the defect reflection equivalent exceeds the DAC curve, it is an excessive defect and is judged as unqualified;

[0038] When the defect reflection equivalent does not exceed the DAC curve, there are two cases: a. When the length of a single defect is ≥ the plate thickness, it is judged as unqualified; b. When the length of a single defect is less than the plate thickness, it is judged as a record defect and is qualified.

[0039] The beneficial effects of the present invention are:

[0040] The method of the present invention is aimed at the characteristics and requirements of the steel lining of the underground chamber of the compressed air energy storage power station, such as thin steel plate wall thickness, invisible outer wall, long weld length, and pollution-free detection, and fully considers factors such as non-destructive detection efficiency, sensitivity and economy. The steel lining weld is detected by a low-frequency magnetic detection method. During the detection process, a self-made calibration comparison test block is used for calibration and defect depth determination, which can achieve a full coverage detection of thin-walled (generally less than 8mm) steel linings, and the detection procedure is simple and the detection results are intuitive; for thicker thin-walled steel linings (greater than 8mm), on the basis of low-frequency magnetic detection, shear wave ultrasonic detection is used as an auxiliary means to achieve full coverage detection of welds. The method of the present invention makes full use of the characteristics and advantages of the above two detection methods, with strong process pertinence, high sensitivity, good detection effect, and can well ensure the quality of steel lining welding, and the detection is pollution-free throughout the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the method of the present invention;

[0042] Figure 2 It is a schematic diagram of the structure of a single universal calibration test piece in the calibration comparison test block used in the method of the present invention;

[0043] Figure 3 is a top view of a depth comparison test block in the calibration comparison test block used in the method of the present invention;

[0044] Figure 4 is a side view of a depth comparison test block in the calibration comparison test block used in the method of the present invention;

[0045] Figure 5 It is a schematic diagram of the structure of the grooves carved on the inclined surface of the depth comparison test block in the calibration comparison test block used in the method of the present invention;

[0046] Figure 6 It is a schematic diagram of the structure of the ultrasonic contrast test block used in the method of the present invention;

[0047] Figure 7 It is a top view of the ultrasonic contrast test block used in the method of the present invention.

[0048] In the figure, 1. circular groove, 2. regular cross groove, 3. linear groove, 4. transverse through hole area, 5. first step groove area, 6. second step groove area, 7. step, 8. groove, 9. transverse through hole. DETAILED DESCRIPTION

[0049] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Embodiment 1:

[0051] The present invention provides a method for nondestructive testing of the weld seams of the steel lining of the underground chamber of the compressed air energy storage power station. Figure 1 As shown, the specific implementation steps are as follows:

[0052] Step 1: Use low-frequency magnetic detection method to detect defects in steel lining welds and determine the defect depth.

[0053] The principle of low-frequency magnetic detection is: the low-frequency magnetic flaw detector uses the principle of DC pulse current phase modulation and frequency conversion to magnetize the yoke. Because it is driven by DC pulse current, the instantaneous startup impact magnetization current is large, and the magnetic flux generated is more than ten times that of the traditional industrial frequency (50Hz) AC magnetic field flaw detector. Different magnetization frequencies are used to generate different pulse widths to maximize the detection sensitivity while minimizing the energy consumption of the equipment.

[0054] The flaw detection is carried out by a low-frequency magnetic flaw detector. The specific process parameter requirements are as follows:

[0055] (1) Magnetization method: yoke method, magnetic pole spacing range: 75-200mm;

[0056] (2) Magnetizing current type and parameters: DC pulse current, pulse frequency range: 0<f≤50Hz;

[0057] (3) Lifting force: ≥177N;

[0058] (4) Test block type: self-made calibration comparison test block for low-frequency magnetic testing;

[0059] (5) Magnetic trace display medium: defect display film;

[0060] (6) Magnetization time: 1-3s.

[0061] Among them, the structure of the self-made low-frequency magnetic detection calibration comparison test block is as follows: Figure 2-Figure 5 As shown, it includes a set of universal calibration test blocks and a depth comparison test block. The universal calibration test block consists of 15 test pieces of different thicknesses. The test piece thickness ranges from 1 to 15 mm, and the thickness interval is 1 mm. Figure 2 As shown, each test piece is processed with three circular grooves 1 and three cross-shaped grooves 2, wherein the depths of the three circular grooves 1 are 7μm, 15μm and 30μm respectively; the lengths of the two straight lines of the three cross-shaped grooves 2 are both 6mm, and the groove depths are 7μm, 15μm and 30μm respectively. In addition, the diameters of the three circular grooves 1 can be 10mm, 25mm and 40mm respectively, and as shown in FIG. Figure 2As shown, a circular groove with a small diameter can be placed inside a groove with a large diameter, and the test piece can be a square test piece with a side length of 60 mm. Under this diameter and side length dimension and the arrangement of the circular grooves, the diagonal of the test piece is slightly larger than the yoke spacing, which just meets the use requirements and is the minimum size solution.

[0062] like Figure 3-Figure 5 As shown, the depth comparison test block is an oblique wedge-shaped test block, with a flat top and an inclined bottom. The test block is 150 mm long, 15 mm thick, and ≥ 100 mm wide. The edge of the top plane of the test block is engraved with a 150 mm scale, and the bottom inclined surface is evenly provided with three linear grooves 3 with depths of 7 μm, 15 μm, and 30 μm, respectively. The side of the test block is provided with a groove depth mark.

[0063] The material of the calibration comparison test block is the same as that of the steel lining to be tested or is 45# steel, and its main chemical composition conforms to GB699 "High-quality carbon structural steel grades and general technical conditions". After normalizing, the grain size should reach above level 7, and there should be no defects greater than 1μm groove defect magnetic marks in all directions inside and on the surface. The surface roughness of the test block is: Ra≤0.4um on each surface; end face parallelism≤5um; no obvious scratches, bumps, rust and other defects on the outer surface.

[0064] The specific detection steps are as follows:

[0065] Step 1.1: Use the universal calibration block in the calibration comparison block to calibrate and adjust the detection capability of the low-frequency magnetic detector:

[0066] Select a calibration test piece with the same thickness as the thin-walled steel lining to be tested or slightly thicker than the thin-walled steel lining (if the steel lining thickness is 4.5mm, select a 5mm thick test piece), and stick the defect display film on the non-grooved surface of the test piece; adjust the pulse frequency of the yoke-type low-frequency magnetic flaw detector to 50Hz, place the yoke on the non-grooved surface, and start the flaw detector; adjust the pulse frequency value. If it can be adjusted to the display film on the calibration test piece to show magnetic marks, it means that the steel lining weld can be tested only by low-frequency magnetic detection, and the entire detection work is completed after step 1 is completed; if there is no magnetic mark display, use other calibration test pieces thinner than the steel lining to be tested in descending order of thickness until magnetic marks appear, and record the maximum thickness D of the test piece that can show magnetic marks, that is, the maximum detection depth of low-frequency magnetic detection is determined. After step 1 is completed, continue with steps 2 to 4. Lock the equipment parameters when magnetic marks are displayed as detection parameters.

[0067] Step 1.2: On-site testing implementation:

[0068] The defect display film is pasted on the inner surface of the steel lining to be inspected, the magnetic yoke is placed across the two sides of the weld, and the inspection is carried out in a cross-shaped manner. During the movement, the coverage of the two inspections before and after is kept overlapping by at least 10% to ensure that no inspection is missed. Electromagnetic is applied and the changes on the display film are continuously observed;

[0069] Step 1.3, Defect Record:

[0070] When magnetic traces appear on the defect display film, change at least two magnetic field application angles, select the angle where the defect is more obvious, take photos and save them on site, and mark the position of the magnetic traces. When the inspection is completed, cut the display film in the area and save it;

[0071] Step 1.4: Quantify the defect depth using the depth comparison test block in the calibration comparison test block:

[0072] After the position of the defect magnetic mark is determined, slowly increase the pulse frequency of the low-frequency magnetic flaw detector until the defect magnetic mark disappears, and lock the equipment parameters at this time; stick the defect display film to the non-grooved surface of the depth comparison test block; place the yoke on the non-grooved surface and restart the detection instrument; observe the displayed length of the surface magnetic mark, and read the corresponding defect depth against the scale (10:1 ratio, such as a defect length of 50mm, the corresponding depth is 5mm), that is, determine the depth of the detected defect.

[0073] Step 1.5, Inspection rating and quality assessment:

[0074] According to the steel lining inspection standard (reference NB / T47013.4-2015), the inspection results of the welded joints are graded, where the linear magnetic trace length ≤1.5mm is rated as Grade I, the circular defect magnetic trace diameter ≤2.0mm, and the number in the evaluation frame (assessment frame size is 35mm×100mm) is rated as Grade I, and those exceeding Grade I are rated as Grade II; compare with the steel lining quality standards, contracts and other regulations to determine whether the weld is qualified.

[0075] Embodiment 2:

[0076] On the basis of Example 1, implement:

[0077] If in step 1.1, the steel lining thickness test piece can show magnetic traces, then the entire detection work is completed at this time; if the steel lining thickness test piece has no magnetic traces, determine the maximum detection depth D of the low-frequency magnetic detection and proceed to step 2.

[0078] Step 2: Pretreatment of weld and adjacent base material surface:

[0079] Use angle grinders and other equipment to mechanically grind the steel lining until its metallic luster is exposed. The grinding range is 2KT of the weld surface and the parent material on both sides, where K represents the probe K value in S4 ultrasonic testing, and T represents the thickness of the steel lining. The single-side grinding width is not less than 50mm;

[0080] Step 3: Check the thickness of steel lining:

[0081] Use an ultrasonic thickness gauge or other instrument to measure the thickness of the parent material adjacent to the weld, and the thickness should not be less than the theoretical minimum design wall thickness of the steel lining;

[0082] Step 4: Use shear wave ultrasonic testing method to detect the steel lining weld.

[0083] For steel linings with slightly greater thickness that cannot be fully covered by low-frequency magnetic testing, the maximum depth D that can be detected by low-frequency magnetic testing has been determined in step 1. For the remaining parts that cannot be detected, shear wave ultrasonic testing suitable for thicker steel lining weld detection is used to achieve full coverage detection of the weld.

[0084] Principle: Ultrasonic flaw detection is a non-destructive testing method that uses the energy change of the ultrasonic propagation waveform reflection situation of the difference in acoustic properties of the material and its defects to inspect the internal defects of the material. The pulse reflection method uses transverse waves in oblique flaw detection. On the oscilloscope screen of the ultrasonic instrument, the horizontal axis represents the propagation time of the sound wave, and the vertical axis represents the amplitude of the echo signal. For the same uniform medium, the propagation time of the pulse wave is proportional to the sound path. Therefore, the presence of the defect can be judged by the appearance of the defect echo signal; the distance of the defect from the detection surface can be determined by the position of the echo signal to achieve defect location; the equivalent size of the defect can be judged by the echo amplitude.

[0085] Equipment process parameters:

[0086] (1) Detection method: pulse reflection ultrasound detection (A-ultrasound);

[0087] (2) Probe parameters: K2-K5, frequency range: 3≤f≤5MHz;

[0088] (4) Coupling method: water

[0089] (5) Test block type: CSK-IA, homemade ultrasonic contrast test block;

[0090] (6) Scanning method: zigzag scanning.

[0091] Among them, the structure of the homemade ultrasonic contrast test block is as follows Figure 6 , Figure 7As shown, it is a block structure with a length of ≥310mm, a thickness of ≥40mm, and a height of 20mm. The two ends of the length direction are stepped structures. The whole is composed of three parts, namely the transverse through hole area 4 located in the middle and the first step groove area 5 and the second step groove area 6 located at the two ends. Among them, the first step groove area 5 includes six steps 7, the height of each step is 3mm different in sequence, and the height of the step at the end is 3mm; the width of each groove platform (i.e., step) is ≥15mm, and the center of each groove platform is processed with a groove 8 with a width of 0.1mm and a depth of 1mm along the width direction of the test block, which is used to simulate the vertical crack at the root of the weld. When the test block is in use, the probe is incident obliquely from the lower surface of the test block to the groove to form an echo, and the root of the groove (i.e. the surface of the groove platform) is taken as the groove depth value. The simulated depth of the groove area on this side (from the end to the middle) is 3mm, 6mm, 9mm, 12mm, 15mm, and 18mm respectively.

[0092] The second step groove area 6 includes seven steps 7, the height of each step differs by 3mm, and the height of the step at the end is 2mm; the width of each groove platform (i.e., step) is ≥15mm, and the center of each groove platform is processed with a groove 8 with a width of 0.1mm and a depth of 1mm along the width direction of the test block, which is used to simulate the vertical crack at the root of the weld. When the test block is in use, the probe is obliquely incident from the upper surface of the test block to the groove to form an echo, and the root of the groove (i.e., the surface of the groove platform) is used as the groove depth value. The simulated depth of the groove area on this side (from the end to the middle) is: 2mm, 5mm, 8mm, 11mm, 14mm, 17mm, 20mm (located on the lower surface of the test block).

[0093] The middle transverse through hole area 4 is distributed six from top to bottom For the transverse through holes 9, the horizontal interval between each hole is ≥15mm, and the distance between the topmost hole and the edge of the first stepped groove area 5 is ≥25mm; the vertical interval is 3mm, and the topmost hole is 3mm away from the upper surface of the test block; therefore, the depths of the transverse through holes from top to bottom are 3mm, 6mm, 9mm, 12mm, 15mm, and 18mm, and correspondingly, the depths of the transverse through holes from bottom to top are 2mm, 5mm, 8mm, 11mm, 14mm, and 17mm, respectively.

[0094] The overall height of the ultrasonic comparison test block is 20mm, which can cover the current thickness range of the steel lining of the compressed air energy storage underground chamber; the test block thickness is ≥40mm, which meets the requirements of the transverse through hole size required for the ultrasonic inspection test block and can well avoid the influence of the side wall echo. The material of the ultrasonic comparison test block is the same as the material of the steel lining to be tested or is 45# steel, and its main chemical composition conforms to GB699 "High-quality Carbon Structural Steel Grades and General Technical Conditions". After normalizing treatment, the grain size reaches above level 7, and the internal direction is not greater than Defect signal of ultrasonic reflection signal of flat bottom hole. The surface roughness of the test block is: Ra≤0.4um on each surface; parallelism of end face ≤5um; no obvious scratches, bumps, rust and other defects on the outer surface; the depth of each step groove is marked on the side of the test block.

[0095] The specific detection steps are:

[0096] Step 4.1, determination of the probe front and K value:

[0097] Using the CSK-IA test block and the built-in adjustment program of the ultrasonic detector, the first step is to find the highest reflected waves of the Φ50mm and Φ100mm arcs at the same time, measure the front length of the probe, and then input it into the instrument; the second step is to find the highest wave of the Φ50mm step hole with a depth of 30mm, and input it into the instrument to determine the actual K value of the probe;

[0098] Step 4.2: Use the ultrasonic contrast test block to draw a distance amplitude curve (DAC curve):

[0099] Through the built-in adjustment program of the ultrasonic detector, select the first channel, and according to the thickness of the steel lining, select all the transverse through holes in the transverse through hole with a depth slightly larger than the thickness of the steel lining to make a DAC curve (for example, if the thickness of the steel lining is 6mm, select transverse through holes with depths of 2mm, 3mm, 5mm, 6mm, and 8mm as transverse through holes for making curves), complete the production of the distance amplitude curve, and use it as a comparison curve. Select the second channel, select the groove depth of the same thickness as the steel lining to be inspected or the two groove depths closest to the groove depth as the reference (for example, if the thickness of the steel lining is 6mm, select a groove with a depth of 6mm; if the thickness of the steel lining is 7mm, select a groove depth of 6mm and 8mm), and make reference points or reference lines.

[0100] Step 4.3: On-site testing implementation:

[0101] Apply water as coupling agent to the polished areas on both sides of the weld to be inspected, select the DAC curve made in the first channel, input coupling compensation 4dB, adjust the reflected amplitude of the 2mm deep through hole to more than 80% of the full screen, place the ultrasonic probe in the area for zigzag scanning, and the scanning speed should not exceed 150mm / s. During the scanning process, always pay attention to the waveform changes on the oscilloscope screen, and focus on observing the one or three reflected echoes within the TD range of the weld root. After the single-side scanning is completed, repeat the scanning on the opposite side to ensure full coverage of the weld.

[0102] Step 4.4, Defect Record:

[0103] When the detected reflected echo exceeds the DAC curve, the defect location and other information shall be verified from multiple angles on at least both sides of the weld. If the defect is located inside the weld joint, the -6dB method shall be used to measure the length, and the information on the longer side shall be used as the record information. The depth, length, position, amplitude, etc. of the defect shall be recorded, and the position shall be marked on the joint surface. If the detected defect is at the root of the weld, the second channel reference point or reference line shall be called to compare the waveform and reflection equivalent to determine the nature and size of the defect.

[0104] Step 4.5, Inspection rating and quality assessment:

[0105] According to the steel lining inspection standard (reference NB / T47013.3-2015), the inspection results of the welded joints are rated:

[0106] 1) When the defect is characterized as crack, lack of fusion, or lack of penetration, it is judged as unqualified;

[0107] 2) When the defect reflection equivalent exceeds the DAC curve, it is an excessive defect and is judged as unqualified;

[0108] When the defect reflection equivalent does not exceed the DAC curve, there are two cases: a. When the length of a single defect is ≥ the plate thickness, it is judged as unqualified; b. When the length of a single defect is less than the plate thickness, it is judged as a record defect, judged as qualified, and the defect information is recorded, and monitoring will be strengthened in the future.

[0109] Embodiment 3:

[0110] The full coverage nondestructive testing method for the steel lining weld of the underground chamber of the compressed air energy storage power station is implemented in the following steps:

[0111] Step 1: Use the low-frequency magnetic detection method to detect defects on the steel lining weld and determine the defect depth. At the same time, use the universal calibration test block in the calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method. If the detectable thickness range covers the thickness of the steel lining to be detected, the weld detection work is completed. If it cannot be covered, proceed to step 2;

[0112] Step 2: pre-treat the surface of the steel lining weld to be inspected and the adjacent parent material surface to expose the metallic luster;

[0113] Step 3: Review the thickness of the steel lining;

[0114] Step 4: Use the shear wave ultrasonic detection method to detect the steel lining weld area that was not detected by the low-frequency magnetic detection method in step 1.

Claims

1. A method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations, characterized in that: Follow the steps below to implement it: Step 1: Use the low-frequency magnetic detection method to detect defects on the steel lining weld and determine the defect depth. At the same time, use the universal calibration test block in the calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method. If the detectable thickness range covers the thickness of the steel lining to be detected, the weld detection work is completed. If it cannot be covered, proceed to step 2; Step 2: pre-treat the surface of the steel lining weld to be inspected and the adjacent parent material surface to expose the metallic luster; Step 3: Review the thickness of the steel lining; Step 4: Use a shear wave ultrasonic detection method to detect the steel lining weld area that is not detected by the low-frequency magnetic detection method in step 1; Step 1 is implemented as follows: Step 1.1, using the universal calibration test block in the calibration comparison test block to determine the thickness range that can be detected by the low-frequency magnetic detection method; Step 1.2: Use a low-frequency magnetic flaw detector to detect defects, specifically: The defect display film is pasted on the inner surface of the steel lining to be inspected, the magnetic yoke is placed across both sides of the weld, and the inspection is carried out in a cross-shaped manner. During the movement, the coverage of the two inspections before and after is kept overlapping by at least 10% to ensure that no inspection is missed. Electromagnetic is applied and the changes on the display film are continuously observed; Step 1.3, when magnetic traces appear on the defect display film, change at least two magnetic field application angles, select the angle where the defect is more obvious, take photos on site and save them, and mark the position of the magnetic traces; Step 1.4, using the depth comparison test block in the calibration comparison test block to quantify the defect depth; Step 1.5: Rating the inspection results of the steel lining weld.

2. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 1 is characterized in that: The specific structure of the calibration comparison test block is: The calibration comparison test block comprises a group of universal calibration test blocks and a depth comparison test block. The universal calibration test block is composed of 15 test pieces with a thickness interval of 1 mm, wherein the thickness of the thinnest test piece is 1 mm and the thickness of the thickest test piece is 15 mm. The surface of the test piece is provided with three circular grooves (1) of different depths and three right cross grooves (2) of different depths. The depths of the circular grooves (1) are 7 μm, 15 μm and 30 μm respectively. The lengths of two straight lines of the right cross grooves (2) are both 6 mm. The groove depths are 7 μm, 15 μm and 30 μm respectively. The depth comparison test block is an oblique wedge-shaped test block with a length of 150 mm and a thickness of 15 mm. The top of the test block is a plane and the bottom is an inclined surface. The edge of the top plane is engraved with a 150 mm scale. The bottom inclined surface is evenly provided with three linear grooves (3) of different depths. The groove depths are 7 μm, 15 μm and 30 μm respectively.

3. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 2 is characterized in that: In step 1.1, the specific steps for determining the thickness range that can be detected by the low-frequency magnetic detection method using a universal calibration test block are as follows: Select a test piece from the universal calibration test block, the thickness of which is the same as that of the thin-walled steel piece to be tested, or the thickness is closest to that of the thin-walled steel piece and larger than that of the thin-walled steel piece, and then paste the defect display film on the non-grooved surface of the test piece; adjust the pulse frequency of the yoke-type low-frequency magnetic flaw detector to 50Hz, place the yoke on the non-grooved surface, and start the flaw detector; adjust the pulse frequency value, if it can be adjusted to the display film on the calibration test piece to show magnetic marks, it means that the detectable thickness range of the low-frequency magnetic detection covers the thickness of the steel lining to be tested; If there is no magnetic mark displayed, use other calibration test pieces that are thinner than the steel lining to be tested and test them in descending order of thickness until magnetic marks appear. The maximum thickness D of the test piece that can display magnetic marks is the maximum detection depth of low-frequency magnetic detection.

4. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 2 is characterized in that: In step 1.4, the specific steps for using the depth comparison test block to quantify the defect depth are: After the position of the defect magnetic mark is determined, slowly increase the pulse frequency of the low-frequency magnetic flaw detector until the defect magnetic mark disappears, and lock the equipment parameters at this time; stick the defect display film to the non-grooved surface of the depth comparison test block; place the yoke on the non-grooved surface and restart the detection instrument; observe the displayed length of the surface magnetic mark, compare the scale to read the corresponding defect depth, and determine the depth of the detected defect.

5. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 1 is characterized in that: Step 4 is implemented according to the following steps: Step 4.1, using the CSK-IA test block, through the ultrasonic detector's built-in adjustment program, the first step is to find the highest reflected wave of the Φ50mm and Φ100mm arcs at the same time, measure the front length of the probe, and then input it into the instrument; the second step is to find the highest wave of the Φ50mm step hole with a depth of 30mm, and input it into the instrument to determine the actual K value of the probe; Step 4.2, using the ultrasonic contrast test block to draw the DAC curve and make reference points or reference lines; Step 4.3, apply water as coupling agent to the polished areas on both sides of the weld to be inspected, select the DAC curve produced by the first channel, set the coupling compensation to 4dB, adjust the reflected amplitude of the 2mm deep side through hole to more than 80% of the full screen, place the ultrasonic probe in the area for zigzag scanning, and the scanning speed should not exceed 150mm / s. During the scanning process, always pay attention to the waveform changes on the oscilloscope screen, and focus on observing the one or three reflected echoes within the TD range of the weld root. After the single-side scanning is completed, repeat the scanning on the opposite side to ensure full coverage of the weld; Step 4.4, when the detected reflected echo exceeds the DAC curve, the position information of the defect is verified from multiple angles on at least both sides of the weld. If the defect is located inside the weld joint, the -6dB method is used to measure the length, and the information on the side with the longer length is used as the record information. The depth, length, position, and amplitude of the defect are recorded, and the position is marked on the joint surface; if the detected defect is within the root position of the weld, the second channel reference point or reference line is called to compare the waveform and reflection equivalent to determine the nature and size of the defect; Step 4.5: Inspect, rate and evaluate the quality of the steel lining welds.

6. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 5 is characterized in that: In step 4.2, the specific structure of the ultrasonic contrast test block is: The ultrasonic contrast test block is composed of three parts, namely a transverse through hole area (4) located in the middle, and a first step groove area (5) and a second step groove area (6) located at both ends. Six transverse through holes (9) are distributed in sequence from top to bottom in the transverse through hole area (4), the horizontal spacing between each transverse through hole (9) is ≥15 mm, the vertical spacing is 3 mm, and the distance between the top transverse through hole (9) and the upper surface of the test block is 3 mm, and the distance between the bottom transverse through hole (9) and the lower surface of the test block is 2 mm. The first step groove area (5) includes six steps (7), the height of each step (7) differs by 3 mm, and the height of the step (7) at the end is 3 mm. The second step groove area (6) includes seven steps (7), the height of each step (7) differs by 3 mm, and the height of the step (7) at the end is 2 mm. The center of the step (7) is provided with a groove with a width of 0.1 mm and a depth of 1 mm along the width direction of the test block.

7. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 6 is characterized in that: Step 4.2 is as follows: Through the built-in adjustment program of the ultrasonic detector, select the first channel, and according to the thickness of the steel lining, select all the transverse through holes in the transverse through holes whose depth is greater than the thickness of the steel lining and closest to the thickness of the steel lining to make a DAC curve, and use the DAC curve as a comparison curve; select the second channel, select the groove depth with the same thickness as the steel lining to be inspected or the two groove depths closest to the groove depth as the benchmark, and make reference points or reference lines.

8. The method for full coverage nondestructive testing of steel lining welds in underground chambers of compressed air energy storage power stations according to claim 5 is characterized in that: In step 4.4, the specific rating criteria are: 1) When the defect is characterized as crack, lack of fusion, or lack of penetration, it is judged as unqualified; 2) When the defect reflection equivalent exceeds the DAC curve, it is an excessive defect and is judged as unqualified; When the defect reflection equivalent does not exceed the DAC curve, there are two cases: a. When the length of a single defect is ≥ the plate thickness, it is judged as unqualified; b. When the length of a single defect is less than the plate thickness, it is judged as a record defect and is qualified.

Images