Defect inspection method, defect inspection device, and defect inspection program

Abstract

To appropriately inspect a defect inside a weld having a two-layer structure of a carbon steel layer and stainless steel weld metal, for a weld joint for clad steels joined by the weld.SOLUTION: A defect inspection method is to inspect a defect inside a weld in which carbon steel weld metal and stainless steel weld metal are laminated, for a weld joint for joining clad steels by the weld, and the defect inspection method includes: a transversal wave oblique angle step of performing flaw detection on at least the carbon steel weld metal of the weld and a first portion including a boundary between the weld and the clad steels, by using a transversal wave oblique angle flaw detection method; a vertical wave oblique angle step of performing flaw detection on at least the stainless steel weld metal of the weld and a second portion including the boundary between the stainless steel weld metal and the clad steels, by using a vertical wave oblique angle flaw detection method; and a determination step of determining success or failure on the basis of results of flow detection performed in the transversal wave oblique angle step and vertical wave oblique angle step.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a defect inspection method, a defect inspection apparatus, a defect inspection program, and a test piece.

Background Art

[0002] There is known a defect inspection method for inspecting defects inside a welded joint that joins structures together by a welded portion (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As such a welded joint, for example, a configuration in which clad steels are welded together by a welded portion having a two-layer structure of a carbon steel weld metal and a stainless steel weld metal has been proposed. There is a need for a technique for appropriately inspecting defects inside such a two-layer structure welded portion.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide a defect inspection method, a defect inspection apparatus, a defect inspection program, and a test piece capable of appropriately inspecting defects inside a welded joint of clad steel joined by a welded portion having a two-layer structure of a carbon steel weld metal and a stainless steel weld metal..

Means for Solving the Problems

[0006] The defect inspection method relating to this disclosure is a defect inspection method for inspecting defects inside a welded joint in which clad steels are joined by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, and includes a transverse angle inspection step in which a first portion of the weld, including at least the carbon steel weld metal and the boundary between the weld and the clad steel, is inspected by transverse angle inspection; a longitudinal angle inspection step in which a second portion of the weld, including at least the stainless steel weld metal and the boundary between the stainless steel weld metal and the clad steel, is inspected by longitudinal angle inspection; and a determination step in which a pass or fail is determined based on the inspection results in the transverse angle inspection step and the longitudinal angle inspection step.

[0007] The defect inspection apparatus according to this disclosure comprises an acquisition unit that acquires a first inspection result obtained by inspecting a first portion of a welded joint, which joins clad steels together by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, including at least the carbon steel weld metal of the weld and the boundary between the weld and the clad steel, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion of the weld, which includes at least the stainless steel weld metal of the weld and the boundary between the stainless steel weld metal and the clad steel, using longitudinal wave oblique angle testing, and a display unit that displays the first inspection result and the second inspection result.

[0008] The defect inspection program relating to this disclosure causes a computer to perform an acquisition step of obtaining a first inspection result obtained by inspecting a first portion of a welded joint, which joins clad steel plates by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, including at least the carbon steel weld metal of the weld and the boundary between the weld and the clad steel, using transverse wave oblique angle inspection, and a second inspection result obtained by inspecting a second portion of the weld, which includes at least the stainless steel weld metal of the weld and the boundary between the stainless steel weld metal and the clad steel, using longitudinal wave oblique angle inspection.

[0009] The test specimen according to this disclosure is a test specimen for calibrating a defect inspection device used in longitudinal wave testing, and comprises a pair of test steel plates formed of clad steel or carbon steel, and a test weld formed of stainless steel weld metal, which is welded to the pair of test steel plates and has a test hole of a predetermined diameter. [Effects of the Invention]

[0010] According to this disclosure, a defect inspection method, defect inspection apparatus, defect inspection program, and test specimen are provided that can appropriately inspect defects inside a welded joint of clad steel, which is joined by a two-layer weld consisting of carbon steel weld metal and stainless steel weld metal. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an example of a welded joint that is subject to inspection by the defect inspection method according to this embodiment. [Figure 2A] Figure 2A is a schematic diagram showing an example of a defect inspection apparatus according to this embodiment. [Figure 2B] Figure 2B shows an example of the relationship between beam path length and echo height. [Figure 3] Figure 3 is a flowchart showing an example of a defect inspection method according to this embodiment. [Figure 4] Figure 4 is a schematic diagram illustrating an example of flaw detection operation in the transverse wave angle process. [Figure 5] Figure 5 is a schematic diagram illustrating an example of flaw detection operation in the longitudinal wave oblique angle process. [Figure 6A] Figure 6A is a schematic diagram (cross-sectional view) showing an example of a test specimen according to this embodiment. [Figure 6B] Figure 6B is a schematic diagram (top view) showing an example of a test specimen according to this embodiment. [Figure 7] Figure 7 is a schematic diagram illustrating an example of the calibration of a defect inspection device. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components in the following embodiments include those that are easily substituted or substantially identical to those that are easily substituted by those skilled in the art.

[0013] The defect inspection method according to this embodiment inspects defects inside the weld of a welded joint in which two base materials are joined together by a weld. Figure 1 is a diagram showing an example of a welded joint that is subject to inspection by the defect inspection method according to this embodiment. The welded joint 100 shown in Figure 1 is used as part of a structure such as a chimney. As shown in Figure 1, the welded joint 100 has a pair of clad steel plates 10 and a welded joint 20.

[0014] A pair of clad steel plates 10 are, for example, made of clad steel, and are formed into plates of the same or substantially the same thickness. The clad steel plates 10 are arranged at a predetermined interval. Each clad steel plate 10 has a clad steel base material (carbon steel) 11 and a clad steel cladding material (stainless steel) 12.

[0015] The welded joint 20 has a structure in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated together. The carbon steel weld metal 21 joins the clad steel base material (carbon steel) 11 of the clad steel plate 10 together. The stainless steel weld metal 22 joins the clad steel cladding material (stainless steel) 12 of the clad steel plate 10 together. The stainless steel weld metal 22 may be provided spanning over a portion of the clad steel base material (carbon steel) 11 of the clad steel plate 10.

[0016] Figure 2A is a schematic diagram showing an example of a defect inspection device 50 according to this embodiment. In the defect inspection method according to this embodiment, the defect inspection device 50 shown in Figure 2A can be used. The defect inspection device 50 has a probe 51, a control unit 52, and a display unit 53. The probe 51 emits, for example, ultrasonic waves and receives ultrasonic waves reflected from the object to be inspected. The probe 51 converts the received ultrasonic waves into an electrical signal and transmits it to the control unit 52 as a defect inspection result.

[0017] The control unit 52 comprehensively controls the operation of the defect inspection device 50. The control unit 52 includes a processing device such as a CPU (Central Processing Unit) and a storage device such as a RAM (Random Access Memory) or a ROM (Read Only Memory).

[0018] The control unit 52 includes an acquisition unit 54, a display control unit 55, and a storage unit 57. The acquisition unit 54 acquires the flaw detection result transmitted from the probe 51. The display control unit 55 causes the display unit 53 to display the acquired flaw detection result as an image. Based on the flaw detection result displayed on the display unit 53, the operator determines pass or fail. Note that the control unit 52 may be configured to include a determination unit 56 that determines pass or fail based on the acquired flaw detection result.

[0019] In addition, for the determination of pass or fail, when a defect exceeding a predetermined echo height is detected, the defect length (the total of the defect evaluation length or the defect evaluation lengths) is measured, and if the defect length exceeds a predetermined value, it is determined as failed. FIG. 2B is a diagram showing an example of the relationship between the beam path and the echo height. In FIG. 2B, the case of flaw detection at three points in the thickness direction of the welded part 20 is shown. Further, Table 1 below is a table showing the relationship between the plate thickness of the welded joint 100 and the boundary value of the defect evaluation length. Also, Table 2 below is a table showing the relationship between the echo height region and the defect evaluation length. Note that Table 1 and Table 2 are created based on the descriptions in the Ultrasonic Flaw Detection Standard for Steel Structure Welding Parts and Its Explanation (Japan Society of Civil Engineering). Also, Table 3 is created based on the descriptions in the Ultrasonic Flaw Detection Standard SSBS401 - 2004 for Stainless Steel Building Structure Welding Parts (Japan Institute of Steel Construction).

Table 1

Table 2

Table 3

[0020] As shown in Figure 2B, Table 1 and Table 2, for example, if the defect evaluation length is 15 mm or more and the total defect evaluation length is 20 mm or more for a clad steel plate 10 with a plate thickness of 9 mm in the region with the highest echo height (V), or if the defect evaluation length is 31.5 mm or more (3t / 4) and the total is 42 mm or more (t) for a clad steel plate 10 with a plate thickness of 42 mm, measured at "(2) second point", the product will be deemed unacceptable.

[0021] Furthermore, as shown in Figure 2B, Table 1 and Table 2, for example, if a clad steel plate 10 with a thickness of 9 mm is measured in a region with a low echo height (II) and the defect evaluation length is 30 mm or more and the sum of defect evaluation lengths is 40 mm or more, or if a clad steel plate 10 with a thickness of 42 mm (t) is measured with a defect evaluation length of 63 mm or more (3t / 2) and the sum of 84 mm or more (2t) at "(2) second point", it will be considered unacceptable.

[0022] Furthermore, if a defect is detected in which the echo height exceeds a predetermined value (for example, if the echo height is region (V), etc.), the product may be rejected without measuring the length of the defect.

[0023] Furthermore, if the control unit 52 has a determination unit 56, the determination unit 56 can determine whether the inspection result is acceptable or unacceptable based on the contents described in Tables 1 and 2 above. In this case, the contents described in Tables 1 and 2 are stored in the storage unit 57 in advance. The determination unit 56 determines, for example, whether the acquired echo height exceeds a predetermined value. If the determination unit 56 determines that the echo height exceeds a predetermined value, it measures the defect length (defect evaluation length or the sum of defect evaluation lengths) based on the contents of Table 2. The determination unit 56 can automatically determine whether the result is acceptable or unacceptable based on Table 1, using the measured defect evaluation length or the sum of defect evaluation lengths and the plate thickness measured in advance. The determination unit 56 may be configured to perform all of the following: determining whether the echo height exceeds a predetermined value, measuring the defect length, and determining whether the result is acceptable or unacceptable, or it may be configured to perform only some of these tasks.

[0024] The memory unit 57 stores various types of information. The memory unit 57 has storage such as a hard disk drive or a solid-state drive. Alternatively, an external storage medium such as a removable disk may be used as the memory unit 57. The memory unit 57 stores programs, data, etc., necessary for the acquisition unit 54, display control unit 55, and determination unit 56 to perform their respective functions. The memory unit 57 may also store training data, learning models, etc., for the determination unit 56 to perform its determinations.

[0025] The memory unit 57 stores, for example, a defect inspection program. The defect inspection program causes a computer, such as the control unit 52, to execute an acquisition step to acquire a first inspection result obtained by inspecting a first portion 31 of a welded joint 100, which joins clad steel plates 10 together by a welded joint 20 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, including the carbon steel weld metal 21 of the welded joint 20 and the boundary R1 between the welded joint 20 and the clad steel plate 10, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion 32 of the welded joint 20, which includes the stainless steel weld metal 22 of the welded joint 20 and the boundary R2 between the stainless steel weld metal 22 and the clad steel plate 10, using longitudinal wave oblique angle testing, and a determination step to determine whether the joint passes or fails based on the acquired first and second inspection results.

[0026] Figure 3 is a flowchart showing an example of a defect inspection method according to this embodiment. As shown in Figure 3, the defect inspection method according to this embodiment includes a transverse wave angle adjustment step S10, a longitudinal wave angle adjustment step S20, and a determination step S30.

[0027] In the shear wave angle inspection process S10, the first portion 31, which includes at least the carbon steel weld metal 21 of the weld 20 and the boundary R1 between the weld 20 and the clad steel plate 10, is inspected using the shear wave angle inspection method. Figure 4 is a schematic diagram showing an example of the inspection operation in the shear wave angle inspection process S10. Figure 4 also shows a top view (viewed from the clad steel composite 12 side). As shown in Figure 4, in the shear wave angle inspection process S10, the probe 51 is selected to have a refraction angle α of 45 to 70 degrees depending on the plate thickness, and ultrasonic waves are irradiated onto the first portion 31 from both sides of one and the other surface of the clad steel plate 10 while moving it within the range of X (distance parallel to the weld line) and Y. For example, if a clad steel plate 10 has a thickness of 18 mm and a contactor with a refraction angle of 70 degrees is selected, the beam path length 1S = 2t / cos(70°) = approximately 105 mm, and Y can be moved within a range of Y = 2t × tan(70°) = approximately 99 mm starting from the weld line. The probe 51 receives ultrasonic waves reflected by the first part 31, converts the received ultrasonic waves into an electrical signal, and transmits it to the control unit 52 as the first flaw detection result.

[0028] When inspecting the first part 31 using longitudinal wave oblique angle testing, ultrasonic waves easily penetrate the carbon steel weld metal 21 of the first part 31, which may lead to an overestimation of defects. In contrast, by inspecting the first part 31 using transverse wave oblique angle testing, as in this embodiment, the overestimation of defects can be suppressed.

[0029] The longitudinal wave angle inspection process S20 inspects the second portion 32, which includes at least the stainless steel weld metal 22 of the weld 20 and the boundary R2 between the stainless steel weld metal 22 and the clad steel plate 10, using the longitudinal wave angle inspection method. Figure 5 is a schematic diagram showing an example of the inspection operation in the longitudinal wave angle inspection process S20. Figure 5 also shows a top view (viewed from the clad steel composite 12 side). As shown in Figure 5, ultrasonic waves are irradiated onto the second portion 32 from both sides of one and the other surface of the clad steel plate 10 while moving the probe 51. The probe 51 receives the ultrasonic waves reflected by the second portion 32, converts the received ultrasonic waves into an electrical signal, and transmits it to the control unit 52 as the second inspection result.

[0030] In the longitudinal wave angle process S20, for example, the flaw detection range using the probe 51 can be set as follows. The probe 51 is selected to have a refraction angle β of 45 to 70 degrees depending on the plate thickness, and ultrasonic waves are irradiated onto the first part 31 from both sides of one and the other surface of the clad steel plate 10 while moving it within the range of X (distance parallel to the weld line) and Y. For example, if the thickness of the clad steel plate 10 is 18 mm and a probe with a refraction angle of 45 degrees is selected, the beam path length is 0.5S = t / cos(45°) = approximately 25 mm, and the range of Y = t × tan(45°) = approximately 18 mm starting from the weld line can be set.

[0031] If the thickness of the clad steel plate 10 is t, the depth of the flaw detection range is the range that is t / 2 in depth from the surface of the clad steel composite material (stainless steel) 12, and the upper limit range can be set to 10 mm. Furthermore, if the thickness of the clad steel composite material (stainless steel) 12 exceeds 2 mm, the above flaw detection range and upper limit range can each be increased by 2 mm. By setting the range in this way, the range of the second part 32 can be set so that ultrasonic waves are irradiated over the entire area of ​​the stainless steel weld metal 22 in the longitudinal wave angle process S20 without measuring the depth of the stainless steel weld metal 22 of the welded part 20.

[0032] When attempting to inspect the second part 32 using transverse wave oblique angle testing, the ultrasonic waves are attenuated by the stainless steel weld metal 22 of the second part 32, making it difficult to adequately inspect the inside of the stainless steel weld metal 22. In contrast, by inspecting the second part 32 using longitudinal wave oblique angle testing, as in this embodiment, ultrasonic waves can be transmitted into the inside of the stainless steel weld metal 22, allowing for thorough inspection of the interior.

[0033] In addition, in the longitudinal wave angle process S20, prior to the above-mentioned flaw detection operation, the defect inspection device may be calibrated using a test piece 200 corresponding to the welded joint 100. Figures 6A and 6B schematically show an example of a test piece 200 according to this embodiment. Figure 6A shows a cross-sectional view, and Figure 6B shows a top view (viewed from the clad steel composite 112 side). The test piece 200 shown in Figures 6A and 6B is a test piece for calibrating the defect inspection device 50 used in the longitudinal wave flaw detection method. The test piece 200 comprises a test steel plate 110 and a test weld 120.

[0034] The test steel plate 110 is made of clad steel or carbon steel. The test steel plate 110 may be made of the same material as the clad steel base material (carbon steel) of the welded joint 100 described above. In the examples shown in Figures 6A and 6B, the test steel plate 110 has a clad steel base material (carbon steel) 111 and a clad steel cladding material (stainless steel) 112, similar to the clad steel plate 10. The clad steel cladding material (stainless steel) 112 is made of stainless steel, for example. The dimensions of the test steel plate 110, such as its thickness, and the spacing between pairs of test steel plates 110 can be the same as the dimensions of the clad steel plate 10 of the welded joint 100 described above and the spacing between pairs of clad steel plates 10.

[0035] The test weld 120 is formed by welding a pair of test steel plates 110 together. The test weld 120 is formed entirely of stainless steel weld metal, for example. Test holes 121 of a predetermined diameter are formed in the test steel plates 110 and the test weld 120. The diameter of the test holes 121 (predetermined diameter) can be set to approximately 3 to 4 mm. As shown in Figures 6A and 6B, the test steel plates 110 and the test weld 120 are provided with two test holes 121, 5 mm apart from the flaw detection surface, for adjusting the sensitivity of the echo height.

[0036] Furthermore, in the test steel plate 110 and the test weld 120, if the thickness of the clad steel plate 10 is t, one test hole 121 is provided at a position t / 2 for measuring the refraction angle of the flaw detection. The depth DP of the hole can be set using the following formula, which is determined by the wavelength of the ultrasonic waves to be irradiated, the beam path, and the width of the probe, in order to ensure a stable echo height. DP = 2 × λ ​​× S / D

[0037] For example, in the case of a test steel plate 110 with a thickness of 18 mm, λ: Wavelength (sound speed / frequency) Sound speed 3230m / sec Frequency 2MHz S: Maximum beam path length used (see Figure 7) 105 mm If D: the width of the transducer (probe 51) (see Figure 7) is 14 mm, DP = 2 × 3230000 / 2000000 × 10⁵ / 14 = 24.255 (mm) Therefore, it is possible to set a depth hole of 24.255 mm or more.

[0038] Calibration of the defect inspection device 50 involves calibrating the probe 51 of the defect inspection device 50 so that it can properly detect the test holes 121 by inspecting the test weld 120 of the test piece 200 using longitudinal wave oblique angle flaw detection.

[0039] Figure 7 is a schematic diagram showing an example of the calibration of the defect inspection device 50. Figure 7 also shows a top view (viewed from the clad steel composite 12 side). As shown in Figure 7, in the calibration of the defect inspection device 50, ultrasonic waves are irradiated onto the test weld 120 while moving the probe 51 on the test steel plate 110, similar to the flaw detection in the longitudinal wave angle process S20. The probe 51 transmits the flaw detection results to the control unit 52, and the display control unit 55 in the control unit 52 displays the flaw detection results as an image on the display unit 53.

[0040] The operator, for example, looks at the image displayed on the display unit 53 and, while determining whether the position, dimensions, range, etc., of the test hole 121 are being detected appropriately, selects a transducer 51 with an appropriate frequency and refraction angle, and adjusts the sensitivity of the ultrasonic waves received by the transducer 51.

[0041] In this embodiment, the entire test weld 120 of the test piece 200 is made of stainless steel. In this case, calibration can be performed on a portion that contains a sufficient amount of stainless steel, which can suppress underestimation of defects when inspecting with longitudinal wave angle beam testing, and allows for a safer evaluation compared to the case where two types of weld metals of clad steel are used.

[0042] The determination step S30 determines whether the weld is pass or fail based on the flaw detection results from the transverse wave angle process S10 and the longitudinal wave angle process S20. In the determination step S30, the acquisition unit 54 acquires the first flaw detection result and the second flaw detection result transmitted from the probe 51. The display control unit 55 displays the acquired first flaw detection result and the second flaw detection result on the display unit 53. The first flaw detection result and the second flaw detection result are displayed on the display unit 53 as echo heights corresponding to the internal conditions of the weld 20, for example (see Figures 4 and 5).

[0043] The operator looks at the first and second flaw detection results displayed on the display unit 53, and for example, identifies a portion where the echo height exceeds a predetermined value as a defective portion, and determines the defect length (defect evaluation length or the sum of defect evaluation lengths) of that defective portion. The operator makes a pass / fail judgment based on the determined defect length and the echo height of that defective portion. At least one of the defect determination, defect length calculation, and pass / fail judgment may be performed by the determination unit 56 of the control unit 52.

[0044] The first part 31 inspected by the transverse angle beam inspection method and the second part 32 inspected by the longitudinal angle beam inspection method may partially overlap. Hereinafter, this overlapping part will be referred to as the overlapping part 33 (see Figure 1). In the judgment process S30, if the inspection result of either the transverse angle beam inspection method or the longitudinal angle beam inspection method is determined to be unacceptable for the overlapping part 33, then both inspection results of the transverse angle beam inspection method and the longitudinal angle beam inspection method are determined to be unacceptable. In this case, the defects can be reliably corrected by correcting the defects in both inspection results. In this way, by making both inspection results unacceptable when the inspection result of either the transverse angle beam inspection method or the longitudinal angle beam inspection method is determined to be unacceptable for the overlapping part 33, it is possible to avoid situations where, for example, even if a defect caused by one inspection result is corrected, a correction from the other inspection result remains.

[0045] As described above, the defect inspection method according to the first aspect of this disclosure is a defect inspection method for inspecting defects inside a welded joint 100 in which two clad steel plates 10 of clad steel are joined by a welded joint 20 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, and includes a transverse wave angled step S10 in which a first portion 31 including at least the carbon steel weld metal 21 of the welded joint 20 and the boundary R1 between the welded joint 20 and the clad steel plate 10 is inspected by transverse wave angled inspection; a longitudinal wave angled step S20 in which a second portion 32 including at least the stainless steel weld metal 22 of the welded joint 20 and the boundary R2 between the stainless steel weld metal 22 and the clad steel plate 10 is inspected by longitudinal wave angled inspection; and a determination step S30 in which a pass or fail is determined based on the inspection results in the transverse wave angled step S10 and the longitudinal wave angled step S20.

[0046] With this configuration, in inspecting defects in a two-layer welded joint 20 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, the first part 31 including the carbon steel weld metal 21 is inspected by transverse wave oblique angle testing, and the second part 32 including the stainless steel weld metal 22 is inspected by longitudinal wave oblique angle testing, making it possible to properly inspect defects inside the two-layer welded joint 20. In other words, when attempting to inspect the first part 31 by longitudinal wave oblique angle testing, ultrasonic waves easily penetrate the carbon steel weld metal 21 of the first part 31, which may lead to an overestimation of defects. In contrast, inspecting the first part 31 by transverse wave oblique angle testing can suppress the overestimation of defects. Furthermore, when attempting to inspect the second part 32 by transverse wave oblique angle testing, ultrasonic waves are attenuated by the stainless steel weld metal 22 of the second part 32, making it difficult to adequately inspect the inside of the stainless steel weld metal 22. In contrast, by inspecting the second part 32 using longitudinal wave oblique angle testing, ultrasonic waves can be transmitted into the interior of the stainless steel weld metal 22, allowing for thorough inspection of the interior.

[0047] The defect inspection method according to the second aspect of this disclosure determines that the inspection result is unsatisfactory in the determination step S30 of the defect inspection method according to the first aspect of this disclosure if the echo height is higher than a predetermined value and the defect length is longer than a predetermined value. With respect to the overlapping portion 33 of the first portion 31 and the second portion 32 that is inspected in overlapping manner by both transverse-wave angle-angle inspection and longitudinal-wave angle-angle inspection, if the inspection result of one of the transverse-wave angle-angle inspection and longitudinal-wave angle-angle inspection is determined to be unsatisfactory, then both inspection results of the transverse-wave angle-angle inspection and longitudinal-wave angle-angle inspection are determined to be unsatisfactory. In this case, the defect can be reliably corrected by correcting the defect in both inspection results. In this way, by making both inspection results unsatisfactory when one of the inspection results of the transverse-wave angle-angle inspection and longitudinal-wave angle-angle inspection is determined to be unsatisfactory for the overlapping portion 33, it is possible to avoid situations where, for example, even if a defect in one inspection result is corrected, a correction from the other inspection result remains.

[0048] The defect inspection method according to the third aspect of this disclosure involves calibrating the defect inspection device 50 using a test piece corresponding to the welded joint 100 in the longitudinal wave angle inspection process S20 of the defect inspection method according to the first or second aspect of this disclosure. The test piece 200 is configured such that two test steel plates 110 made of clad steel or carbon steel are joined by a test weld 120 made of stainless steel weld metal, and a test hole 121 of a predetermined diameter is formed in the test weld 120. The calibration involves calibrating the defect inspection device 50 to detect the test hole 121 by inspecting the test weld 120 of the test piece 200 using the longitudinal wave angle inspection method. Therefore, the detection accuracy of the longitudinal wave angle inspection method can be improved.

[0049] A defect inspection apparatus 50 according to a fourth aspect of this disclosure comprises an acquisition unit 54 that acquires a first inspection result obtained by inspecting a first portion 31, which includes at least the carbon steel weld metal 21 of the weld 20 and the boundary between the weld 20 and the clad steel plate 10, of a welded joint 100 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion 32, which includes at least the stainless steel weld metal 22 of the weld 20 and the boundary between the stainless steel weld metal 22 and the clad steel plate 10, using longitudinal wave oblique angle testing, of a welded joint 100 in which clad steel plates 10 are joined by a weld 20 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, of a first portion 31, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion 32, which includes at least the stainless steel weld metal 22 of the weld 20 and the boundary between the stainless steel weld metal 22 and the clad steel plate 10, using longitudinal wave oblique angle testing, and a determination unit 56 that determines whether to accept or reject based on the acquired first inspection result and second inspection result.

[0050] With this configuration, the judgment unit 56 can automatically determine whether the product passes or fails based on the first and second inspection results, thereby reducing the burden on the operator.

[0051] A defect inspection program according to a fifth aspect of this disclosure causes a computer to perform an acquisition step of acquiring a first inspection result obtained by inspecting a first portion 31 of a welded joint 100, which joins clad steel plates 10 together by a weld 20 in which carbon steel weld metal 21 and stainless steel weld metal 22 are laminated, including at least the carbon steel weld metal 21 of the weld 20 and the boundary between the weld 20 and the clad steel plate 10, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion 32 of a welded joint 100, which includes at least the stainless steel weld metal 22 of the weld 20 and the boundary between the stainless steel weld metal 22 and the clad steel plate 10, using longitudinal wave oblique angle testing, and a determination step of determining whether to accept or reject based on the acquired first inspection result and second inspection result.

[0052] With this configuration, the judgment unit 56 can automatically determine whether the product passes or fails based on the first and second inspection results, thereby reducing the burden on the operator.

[0053] A test piece 200 according to a sixth aspect of the present disclosure is a test piece 200 for calibrating a defect inspection device 50 used in longitudinal wave testing, comprising a pair of test steel plates 110 formed of clad steel or carbon steel, and a test weld 120 formed of stainless steel weld metal, which is formed by welding the pair of test steel plates 110 and has a test hole 121 of a predetermined diameter.

[0054] This configuration makes it possible to provide a test piece 200 that can improve the detection accuracy of the longitudinal wave angle flaw detection method.

[0055] The technical scope of the present invention is not limited to the embodiments described above, and modifications can be made as appropriate without departing from the spirit of the invention. For example, the transverse wave angle angle process S10 and the longitudinal wave angle angle process S20 may be performed in either order. Furthermore, the determination process S30 may be performed in real time while displaying the flaw detection results obtained in the transverse wave angle angle process S10 and the longitudinal wave angle angle process S20 on the display unit 53.

[0056] Furthermore, for example, the clad steel plate 10 described above may be replaced with a clad steel pipe used for circumferential joints with a plate thickness of 9 mm or more and a diameter of 500 mm or more, or for steel pipe length joints with a bend diameter of 750 mm or more. [Explanation of symbols]

[0057] 10 Clad steel plate 11. Clad steel base material (carbon steel) 12. Clad steel composite material (stainless steel) 20 Welded parts 21 Carbon steel weld metal 22 Stainless steel weld metal 31 Part 1 32 Part 2 33 Overlapping part 50 Defect Inspection Device 51 Probe 52 Control Unit 53 Display section 54 Acquisition Department 55 Display Control Unit 56 Judgment section 57 Memory section 100 Welded Joints 110 Test steel plate 111 Test clad steel base material (carbon steel) 112 Test Clad Steel Lamination (Stainless Steel) 120 Test weld 121 Test holes 200 test specimens R1,R2 boundary S10 Shear wave oblique process S20 Longitudinal wave oblique process S30 Judgment process

Claims

1. A defect inspection method for inspecting defects inside a welded joint in which clad steels are joined together by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, A transverse wave angle inspection step is performed to inspect a first portion, including at least the carbon steel weld metal of the weld and the boundary between the weld and the clad steel, using transverse wave angle inspection. A longitudinal wave oblique angle inspection step is performed to inspect at least the stainless steel weld metal of the weld and the second portion including the boundary between the stainless steel weld metal and the clad steel using longitudinal wave oblique angle inspection, A determination step in which a pass or fail is determined based on the inspection results in the transverse wave angle process and the longitudinal wave angle process. Includes, In the determination step, if the echo height is higher than a predetermined value and the defect length is longer than a predetermined value in the flaw detection result, it is determined to be unsatisfactory. If, for an overlapping portion of the first and second parts that is inspected using both the transverse wave angled flaw detection method and the longitudinal wave angled flaw detection method, the flaw detection result of both the transverse wave angled flaw detection method and the longitudinal wave angled flaw detection method is determined to be unsatisfactory, it is determined to be unsatisfactory. Defect inspection methods.

2. In the longitudinal wave angle process, the defect inspection device is calibrated using a test piece corresponding to the welded joint. The aforementioned test specimen is constructed by joining a pair of test steel plates, each made of clad steel or carbon steel, with a test weld made of stainless steel weld metal, and a test hole of a predetermined diameter is formed in the test weld. The calibration involves calibrating the defect inspection device to detect the test hole by inspecting the test weld on the test piece using the longitudinal wave oblique angle flaw detection method. The defect inspection method according to claim 1.

3. An acquisition unit that acquires, in a welded joint in which clad steels are joined together by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, a first inspection result obtained by inspecting a first portion including at least the carbon steel weld metal of the weld and the boundary between the weld and the clad steel using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion including at least the stainless steel weld metal of the weld and the boundary between the stainless steel weld metal and the clad steel using longitudinal wave oblique angle testing, A display unit that displays the first flaw detection result and the second flaw detection result, A determination unit that determines whether to accept or reject based on the acquired first and second flaw detection results, Equipped with, The determination unit determines that the product is unacceptable if the echo height is higher than a predetermined value and the defect length is longer than a predetermined value in the first and second inspection results. If, for an overlapping portion of the first and second parts that is inspected using both the transverse angle beam inspection method and the longitudinal angle beam inspection method, one of the inspection results from the first and second inspection results is determined to be unacceptable, the determination unit determines that both the first and second inspection results are unacceptable. Defect inspection device.

4. An acquisition step to obtain a first inspection result obtained by inspecting a first portion of a welded joint, which joins clad steel plates by a weld in which carbon steel weld metal and stainless steel weld metal are laminated, including at least the carbon steel weld metal of the weld and the boundary between the weld and the clad steel, using transverse wave oblique angle testing, and a second inspection result obtained by inspecting a second portion of the weld, which includes at least the stainless steel weld metal of the weld and the boundary between the stainless steel weld metal and the clad steel, using longitudinal wave oblique angle testing. A determination step in which a pass or fail result is determined based on the acquired first and second flaw detection results. Have the computer run it, In the determination step, if the echo height is higher than a predetermined value and the defect length is longer than a predetermined value in the first and second inspection results, it is determined to be unsatisfactory. If, for an overlapping portion of the first and second parts that is inspected using both the transverse angle beam inspection method and the longitudinal angle beam inspection method, one of the inspection results from the first and second inspection results is determined to be unsatisfactory, then both the first and second inspection results are determined to be unsatisfactory. Defect inspection program.

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