JP5574731B2 - Ultrasonic flaw detection test method - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection test method that performs nondestructive inspection using ultrasonic waves, and more particularly to an ultrasonic flaw detection test method for flaw detection of a heat-affected zone at a welded portion.

  In the inspection of pipe welds in thermal power plants and the like, an ultrasonic flaw detection test is performed as a nondestructive inspection, and defects in the heat affected zone formed around the boundary portion of the welded part are detected by the test. As such an ultrasonic flaw detection test method, for example, a TOFD (Time of Flight Diffraction) method using a diffracted wave is known. Specifically, a transmitting probe is arranged on one side in the width direction of the welded portion, and a receiving probe is arranged on the other side in the width direction. Then, an ultrasonic wave is transmitted from the transmitting probe to the inside of the subject toward the weld, and the ultrasonic wave diffracted by the defect is received by the receiving probe to detect the defect. (For example, refer to Patent Document 1).

  As another method, a tandem method using a reflected wave is known. Specifically, a transmitting probe and a receiving probe are arranged on one side in the width direction of the welded portion. Then, an ultrasonic wave is transmitted from the transmitting probe to the inside of the subject at a predetermined angle toward the surface facing the flaw detection surface, and the reflection reflected at the boundary between the surface and the welded portion is detected. The defect is detected by receiving with a toucher (for example, refer to Patent Document 2).

Japanese Patent No. 4148959 Japanese Patent No. 3739368

However, in the TOFD method as in Patent Document 1, if there is a defect such as a blow hole in the welded portion between the transmitting probe and the receiving probe, the defect in the welded portion Even the diffracted light is received by the receiving probe, and only the defect of the heat-affected zone cannot be accurately identified. Moreover, since the TOFD method cannot detect defects near the flaw detection surface, it is necessary to combine another method such as the oblique flaw detection method near the flaw detection surface in order to inspect the entire thickness direction of the welded portion. It was necessary to carry out the test twice or more only on the heat-affected zone on one side. Furthermore, since it is necessary to arrange probes on both sides in the width direction of the welded part, there is a problem that it cannot be applied when a flat flaw detection surface is not formed on one side in the welded part width direction.
On the other hand, in the tandem method as in Patent Document 2, an ultrasonic flaw detection test can be performed as long as a flat flaw detection surface is formed on one side in the width direction of the weld location. It will not detect any defects. However, even if ultrasonic waves are transmitted from the transmitting probe at a predetermined angle, depending on the size of the bevel angle at the boundary of the welded portion, the reflected light is reflected on the surface opposite to the flaw detection surface and on the flaw detection surface. The position when returning will be different. Therefore, in the tandem method, the relative position between the transmitting probe and the receiving probe is set according to the bevel angle of the boundary, and the mutual positional relationship is accurately maintained during the inspection. It was necessary to keep.

  The present invention has been made in view of the above-described circumstances, and is an ultrasonic flaw detection test capable of detecting defects in a heat affected zone formed around a boundary portion in a welding location easily and accurately with a minimum apparatus configuration. A method is provided.

In order to solve the above problems, the present invention proposes the following means.
The present invention is an ultrasonic flaw detection test method for detecting defects in a heat-affected zone formed around a boundary portion of a welded part in a specimen welded with a predetermined bevel angle, and includes a plurality of vibrators said been probes arranged on one side of definitive welding point to inspection surface of the object, the refraction angle of the ultrasonic wave the is incident into the subject from the inspection surface while transmitted from the probe, the In accordance with the size of the bevel angle at the boundary of the welded portion, the probe is adjusted so that it is received by at least a part of the plurality of transducers from the flaw detection surface to the inside of the subject. And the ultrasonic wave is incident as a refracted wave in a transverse wave mode, is reflected by a surface facing the flaw detection surface, is converted into a longitudinal wave mode, and the boundary on the one side of the welding location is the longitudinal wave mode. The refraction angle so that the light is reflected substantially vertically A first ultrasonic transmission / reception step of setting and transmitting / receiving ultrasonic waves with the probe; and entering the ultrasonic wave from the flaw detection surface into the subject, and a boundary on the opposite side to the one side of the welding location And the step of setting the refraction angle so as to be reflected substantially vertically by the portion, and inspecting the boundary portion on the opposite side where ultrasonic waves are transmitted and received by the probe .

  According to this method, the refraction angle of the ultrasonic wave transmitted from the probe and made incident on the inside of the subject from the flaw detection surface is determined according to the size of the bevel angle of the boundary portion of the welding location. By adjusting so as to be received by at least a part of the plurality of transducers of the probe, it is possible to detect a defect in the heat affected zone only from one side in the width direction of the welded portion of the subject. In addition, according to the bevel angle of the boundary, the refraction angle of the ultrasonic wave transmitted from the probe and incident from the flaw detection surface to the inside of the subject is adjusted, and one probe having a plurality of transducers is used. By enabling transmission / reception, it is possible to easily and accurately perform a test for detecting defects in the heat-affected zone without having to adjust the positional relationship between the probes using a plurality of probes.

Furthermore , in the first ultrasonic transmission / reception process, the refraction angle is set so that the reflection is performed substantially perpendicularly at the boundary, so that the ultrasonic wave transmitted from the probe is almost the same again after being reflected at the boundary. It is received by the probe along a route, and transmission / reception can be performed with a probe having a minimum size.

Furthermore , by making the ultrasonic wave transmitted from the probe incident from the flaw detection surface in a transverse wave mode with a small refraction angle, the incident refracted wave is a longitudinal wave mode with a large reflection angle on the surface facing the flaw detection surface. Will be reflected. For this reason, ultrasonic waves can be reflected vertically and received by the probe without separating the probe in the width direction from the welding location even at a boundary portion having a large bevel angle.

In the ultrasonic flaw detection test method described above, the reflected wave reflected by the surface facing the flaw detection surface and the boundary portion on one side in the same mode as the refracted wave incident from the flaw detection surface into the subject. A second ultrasonic transmission / reception step for transmitting / receiving with the probe, and when the bevel angle of the boundary changes in the thickness direction of the subject, the bevel angle is relatively The first ultrasonic transmission / reception step is performed for a large range in the thickness direction, and the second ultrasonic transmission / reception step is performed for the range in the thickness direction where the bevel angle is relatively small. It is characterized by implementation.

  According to this method, by combining the first ultrasonic transmission / reception process and the second ultrasonic transmission / reception process by the size of the bevel angle, without changing the position in the width direction of the welding location with the same probe, The presence or absence of defects in the heat affected zone can be detected over the entire thickness direction of the subject.

  According to the ultrasonic flaw detection test method of the present invention, it is possible to easily and accurately detect defects in the heat affected zone formed around the boundary portion in the welded portion.

It is a schematic diagram showing an example of an ultrasonic inspection system used in an ultrasonic inspection test of an embodiment of the present invention. It is sectional drawing for demonstrating the behavior of the ultrasonic wave transmitted with the ultrasonic flaw detection test method of embodiment of this invention. It is sectional drawing explaining the tandem scanning implementation process in the ultrasonic testing method of embodiment of this invention. It is sectional drawing explaining the linear scan implementation process in the ultrasonic flaw detection test method of embodiment of this invention. It is sectional drawing explaining the tandem scan implementation process in the ultrasonic flaw detection test method of an Example. It is sectional drawing explaining the linear scan implementation process in the ultrasonic flaw detection test method of an Example. It is sectional drawing explaining the case where the back surface reflection is carried out in the same mode, and it is made to reflect perpendicularly to a boundary part in the ultrasonic testing method of an Example. It is sectional drawing explaining the case where the whole boundary part has a big bevel angle | corner in the ultrasonic testing method of embodiment of this invention. It is sectional drawing explaining the case where the whole boundary part has a small bevel angle | corner in the ultrasonic testing method of embodiment of this invention. It is sectional drawing explaining the case where the boundary part on the opposite side to the side by which the probe is arrange | positioned is tested in the ultrasonic testing method of embodiment of this invention.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an example of an ultrasonic flaw detection system used for the ultrasonic flaw detection test of the present embodiment. As shown in FIGS. 1 and 2, the ultrasonic flaw detection system 100 includes two probes 110 (110A and 110B), control of ultrasonic waves transmitted from the two probes 110, and received ultrasonic waves. And a signal processing device 120 for analyzing sound waves. The signal processing device 120 includes input means 121 such as buttons and knobs for inputting information, and output means 122 such as a display for outputting information.

  In addition, the probe 110 includes a transmission / reception surface 111a in which a plurality of transducers 113 are arranged, and a probe main body 111 that constitutes a phased array capable of transmitting and receiving ultrasonic waves, and the probe main body 111 is inclined. And a wedge 112 mounted on the flaw detection surface 201. The plurality of transducers 113 constituting the probe body 111 are composed of piezoelectric elements, and each oscillates independently and oscillates an ultrasonic wave based on an electric signal input from the signal processing device 120. It is possible to receive. Therefore, the probe body 111 can transmit ultrasonic waves at a desired angle from all or a part of the plurality of transducers 113 under the control of the signal processing device 120, and It is possible to receive ultrasonic waves input from all or part of the transducer 113 and output the ultrasonic signals to the signal processing device 120 as electrical signals.

  The wedge 112 includes a contact surface 112a that is attached in close contact with the flaw detection surface 201, and an attachment surface 112b that is attached in close contact with the transmission / reception surface 111a that transmits and receives ultrasonic waves in the probe body 111. For this reason, the ultrasonic wave transmitted in the longitudinal wave mode from the transmission / reception surface 111a of the probe main body 111 in the direction intersecting the transmission / reception surface 111a propagates inside the wedge 112 in a direction inclined with respect to the flaw detection surface 201. Then, the light is refracted at the refraction angle corresponding to the material of the wedge 112 and the subject 200 on the flaw detection surface 201 and is incident on the inside of the subject 200 from the flaw detection surface 201.

Here, with respect to the axis L perpendicular to the flaw detection surface 201, the incident angle of the ultrasonic wave S1 incident on the flaw detection surface 201 from the probe main body 111 is θ ₀ , and is refracted by the flaw detection surface 201 to enter the subject 200. When the refraction angle of the propagating refracted wave S ₁ is θ ₁ , the sound speed at the wedge 112 is V ₀ , and the sound speed at the subject 200 is V ₁ , the following relational expression is established.

Here, the ultrasonic wave S _{1 that} is oscillated from each transducer 113 of the probe 110 and propagates through the wedge 112 is a longitudinal wave mode, and the velocity of sound in the longitudinal wave mode is input to V ₀ . From <Equation 1 <, the incident angle is the refraction angle θ _{1 that} is the control center angle of the phased array in the desired mode (eg, 5900 m / S for steel when V ₁ is longitudinal wave, 3200 m / S for transverse wave) θ ₀ can be determined.

Further, the refracted wave S ₁ propagating through the subject 200 at the refraction angle θ ₁ is reflected by the boundary portion of the welded part and the back surface 202 opposite to the flaw detection surface 201. In the following description, the flaw detection surface 201 and the back surface 202 are assumed to be parallel, and the incident angle on the back surface 202 is assumed to be equal to the refraction angle θ ₁ on the flaw detection surface 201 for ease of explanation. , when the back surface 202 is not parallel to the Sagukizumen 201 may be replaced with the theta ₁ below at an angle relative to an axis perpendicular to the rear surface 202. When the incident light is incident on the back surface 202 in the transverse wave mode, when the incident angle θ ₁ is larger than the second critical angle θ _c2 determined by the material of the subject 200, the reflection angle θ ₂ is the same as the incident angle θ1. so that the reflected by the reflection wave S ₂ only mode transverse wave having the same mode size. When the incident angle θ ₁ is equal to or _smaller than the second critical angle θ _c2 , the light is reflected in the transverse wave mode, and the reflected wave S ₃ in the longitudinal wave mode is reflected at the reflection angle θ ₃ satisfying <Equation 2>. It will be reflected. Here, since the sound velocity V _1L in the longitudinal wave mode is larger than the sound velocity V _1S in the transverse wave mode, the reflection angle becomes larger than the incident angle by a ratio corresponding to the sound velocity ratio V _1L / V _1S .

The same applies to the case where the light beam is incident on the back surface 202 in the longitudinal wave mode. The angle corresponding to the second critical angle θ _c2 is defined as a critical angle. And in the longitudinal wave mode, which is the same mode, and also in the transverse wave mode with a reflection angle satisfying <Equation 2>, and when it is equal to or _larger than the second critical angle [theta] _c2 , <Equation 2>. Reflection is performed only in the transverse wave mode at a reflection angle satisfying the above.

In this embodiment, the refracted wave S ₁ transmitted from the probe main body 111 and propagating from the flaw detection surface 201 to the inside of the subject 200 is welded based on the relational expressions of <Equation 1> and <Equation 2>. The refraction angle θ ₁ is obtained so that the reflected wave reflected by the boundary portion of the probe can be received by the same probe 110, and the probe main body is set so that the incident angle θ ₀ becomes the refraction angle θ _1. Ultrasound is transmitted from the vibrator 113. The ultrasonic flaw detection test method of the present embodiment is for detecting defects in the heat affected zone formed around the boundary at the welded portion of the subject 200 to be inspected. it is characterized by changing the refractive angle theta ₁ depending on.

  Next, a method for detecting defects in the heat affected zone around the boundary of the welded portion 203 of the subject 200 will be specifically described. As shown in FIG. 1, the subject 200 is configured by butt welding two plate-like members 200A and 200B made of the same material. Here, each of the plate-like members 200A and 200B has a groove shape having two different bevel angles φ1 and φ2 in the thickness direction, and a bevel angle φ1, which is an angle with respect to the surface (the flaw detection surface 201), φ2 is set at a smaller angle at the first boundary portion 204 on the front surface side than at the second boundary portion 205 on the rear surface 202 side. And the defect of the heat affected zone 206 formed in the circumference | surroundings of the 1st boundary part 204 and the 2nd boundary part 205 is implemented with respect to such a test object 200 as follows.

First, as shown in FIG. 1, as a probe placement step, two probes 110 are placed on both sides of the welded portion 203 in the width direction. Next, as shown in FIG. 3, as a tandem scan execution step (second ultrasonic transmission / reception step), a defect in the heat affected zone 206 around the first boundary portion 204 is detected. In FIG. 3, the probe 110 composed of the probe main body 111 and the wedge 112 shown in FIGS. 1 and 2 is shown in a simplified manner, and only the range of the contact surface 112a in the wedge 112 is displayed. doing. The same applies to FIGS. 4 to 10 below. That is, as shown in FIG. 3, in each probe 110, ultrasonic waves are transmitted from a plurality of transducers 113 corresponding to the range A separated from the welding location 203, and propagated through the subject 200 to be transmitted to the back surface 202. From the flaw detection surface 201 so as to be reflected by the first boundary portion 204 and received by the plurality of transducers 113 corresponding to the range B close to the welding spot 203 of the same probe 110 again. setting the angle of refraction refracted waves S ₁ propagating inside the object 200.

Next, as a linear scan execution process (first ultrasonic transmission / reception process), a defect of the heat affected zone 206 around the second boundary 205 is detected. That is, as shown in FIG. 4, in each probe 110, ultrasonic waves are transmitted from all or a part of the transducers 113 of the probe 110 and propagated in a transverse wave mode inside the subject 200, and the back surface. The refraction angle is set so that the light is reflected in the longitudinal wave mode at 202 and is reflected vertically at the second boundary portion 205.
That is, the reflection angle θ ₃ on the back surface 202 is obtained from the bevel angle φ _{2 of} the second boundary portion 205. Next, from the reflection angle θ ₃ and <Equation 2>, the incident angle θ ₁ on the back surface 202, that is, the refraction angle θ ₁ can be obtained. For this reason, the ultrasonic wave is transmitted by the transducer 113 corresponding to the range C so that the refraction angle θ ₁ is obtained, so that the reflected wave from the second boundary portion 205 can be received in the same range C.

Hereinafter, examples of the present embodiment will be described.
As shown in FIGS. 5 to 7, two plate-like members 200A and 200B having a thickness of 50 mm are used as the first boundary portion 204 from the surface to a depth of 30 mm, and the bevel angle φ ₁ is set to 5 degrees. , until the rest of the back surface 202 to set the bevel angle phi ₂ to 20 degrees as a second boundary 205, as an example the case of inspecting a heat affected zone 206 of the subject 200 constructed by welding the two.

Then, as shown in FIG. 5, when the tandem scan execution step is performed on the first boundary portion 204 with the refraction angle θ ₁ being 35 degrees, the first boundary 204 is used as the transmission transducer 113 due to geometric conditions. An axis perpendicular to the flaw detection surface 201 is reflected from the first boundary portion 204 with the welded portion 203 side of the transmission vibrator 113 as a reception vibrator 113 from the upper end of the section 204 to 65.8 mm. An ultrasonic wave incident at 45 degrees with respect to L can be received.

In the linear scan execution step, the bevel angle φ _{2 of} the second boundary portion 205 is 20 degrees, so the reflection angle θ ₂ on the back surface 202 is set to 70 degrees. For this reason, when a mode conversion wave is used, the refraction angle (incident angle) θ ₁ is calculated backward from <Equation 2> to be 30 degrees. Then, as shown in FIG. 6, 83.2 mm from the upper end of the first boundary portion 204 is required due to geometric conditions. That is, by using the probe 110 having a size capable of performing transmission or reception within a range of 83.2 mm from the upper end of the first boundary 204 on the flaw detection surface 201, the probe 200 can be used with the single probe 110. On the other hand, the tandem scan execution step and the linear scan execution step can be performed without moving in the width direction of the welded portion 203.

On the other hand, when the reflected wave is reflected by the back surface 202 in the transverse wave mode and enters the second boundary portion 205 perpendicularly and the reflected wave is measured, as shown in FIG. The same measurement can be performed by transmitting or receiving by the probe 110 in a range of 192.8 mm. However, in order to perform the tandem scan execution process at the same position, the size of the probe 110 is 192. It will be as large as .8mm.
As described above, by using the mode conversion, the size of the probe 110 can be increased while the tandem scan execution process can be performed at the same position as compared with the case where only the ultrasonic wave of the single mode is used. From 192.8 mm to 83.2 mm, the size can be reduced to less than 1/2.

In the above description, the welding location 203 having the first boundary portion 204 and the second boundary portion 205 set to _two different bevel angles φ ₁ and φ ₂ is inspected. However, the present invention is not limited to this, and the present invention may be applied to a welding spot 203 having a single bevel angle φ.
In this case, when the bevel angle φ is large, a linear scan execution step is performed over the entire boundary as shown in FIG. Further, when the bevel angle φ is small, the tandem scan execution process is performed over the entire boundary portion as shown in FIG. 9, so that the probe 110 with the minimum size can be used over the entire boundary portion. It is possible to detect a defect at a time without shifting the position of the probe 110.

Further, in the above, the probes 110 are arranged on both sides in the width direction of the welded part 203, the heat affected zone 206 around the boundary portion on one side is inspected with one probe 110A, and the other probe 110B is inspected. In this case, the heat affected zone 206 around the boundary portion on the other side is inspected. However, one probe 110 is arranged only on one side of the welded portion 203, and the heat affected zone 206 on both sides is arranged by the probe 110. It is good also as what inspects.
That is, first, with respect to the heat affected zone 206 on one side where the probe 110 is arranged, the first boundary portion 204 and the second boundary portion 205 are similar to the measurement method described with reference to FIGS. A refraction angle is set according to the bevel angles φ ₁ and φ ₂ , and a tandem scan execution process and a linear scan execution process are performed.

Next, as shown in FIG. 10, each of the first boundary portion 204 and the second boundary portion 205 opposite to the side on which the probe 110 is disposed is vertical according to the bevel angles φ1 and φ2. The refraction angle θ1 is set so as to reflect the light. As a result, the reflected waves reflected by the first boundary portion 204 and the second boundary portion 205 are received by each transducer 113 through the same path as the incident wave, and a defect can be detected.
For this reason, in a welded joint portion between a straight pipe 200C having a constant pipe diameter in the axial direction and a tapered pipe 200D having a pipe diameter changing in the axial direction as shown in FIG. It is possible to detect a defect in the heat affected zone 206 on both sides without being affected by the shape of 200D.

As described above, according to the ultrasonic flaw detection test method of this embodiment, the refraction angle θ _{1 of the} ultrasonic wave transmitted from the probe 110 and incident from the flaw detection surface 201 to the inside of the subject 200 is set to the welding location 203. Is adjusted so that at least a part of the plurality of transducers 113 of the probe 110 receives the signal according to the bevel angles φ ₁ and φ ₂ of the boundary portion of the probe 110. For this reason, the defect in the heat affected zone 206 can be detected only from one side in the width direction of the welded portion 203 of the subject 200. In the present embodiment, the refraction angle θ _{1 of the} ultrasonic wave transmitted from the probe 110 and incident from the flaw detection surface 201 into the subject 200 is adjusted according to the bevel angles φ ₁ and φ ₂ at the boundary. Thus, transmission / reception can be performed by one probe 110 having a plurality of transducers 113. For this reason, the test which detects the defect in the heat affected zone 206 can be implemented easily and correctly, without having to adjust a mutual positional relationship using the several probe 110. FIG.

  Here, when an ultrasonic flaw detection test is performed on the same subject 200 by the TOFD method, the probe 110 is arranged on both sides, the inspection is performed on the boundary portion on one side, and then the boundary portion on the other side is performed. Perform an inspection. Further, in the vicinity of the surface, it is necessary to separately inspect both sides by the oblique flaw detection method, and it is necessary to perform a total of four tests. However, in the ultrasonic flaw detection test of the present embodiment, since transmission / reception is performed with the same probe, the ultrasonic flaw detection test can be simultaneously performed with the probes on both sides, that is, with a maximum of one test. Defects can be detected in the heat affected zone on both sides of the weld location. Further, in the ultrasonic flaw detection test method of the present embodiment, the defect is detected using the reflected wave, and since the diffracted wave is not used unlike the TOFD method, the defect detected in the heat affected zone, the welding It is possible to separate the defects in the location temporally, and the two can be easily identified.

  Further, in the linear scan execution step (first ultrasonic transmission / reception step), the refraction angle is set so as to reflect substantially perpendicularly at the boundary portion, so that the ultrasonic wave transmitted from the probe 110 is reflected at the boundary portion. After being reflected on the probe 110, the probe 110 receives the signal again through substantially the same path, and transmission / reception can be performed with the probe 110 having the minimum size.

Further, by making the ultrasonic wave transmitted from the probe 110 incident from the flaw detection surface 201 in a transverse wave mode with a small refraction angle, the incident refracted wave S ₁ is a surface facing the flaw detection surface 201 and has a large reflection angle. Will be reflected in the longitudinal wave mode. For this reason, ultrasonic waves can be reflected vertically and received by the probe 110 without separating the probe 110 from the welding location 203 in the width direction even at a boundary portion having a large bevel angle.

  In particular, by combining the linear scan execution process (first ultrasonic transmission / reception process) and the (tandem scan execution process) second ultrasonic transmission / reception process depending on the size of the bevel angle φ, the welding location of the same probe 110 can be reduced. The presence or absence of a defect in the heat affected zone 206 can be detected over the entire thickness direction of the subject 200 without changing the position in the width direction 203.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

110, 110A, 110B Probe 113 Vibrator 200 Subject 201 Flaw detection surface 202 Back surface (surface opposite to flaw detection surface)
203 welding location 204 first boundary 205 second boundary 206 heat-affected zone S ₁ refracted wave θ ₁ refraction angle φ, φ ₁ , φ ₂ bevel angle

Claims (2)

An ultrasonic flaw detection test method for detecting defects in a heat-affected zone formed around a boundary portion of a welded part in a specimen welded with a predetermined bevel angle,
Place a plurality of probes composed of a vibrator on one side of the subject of the probe definitive scratch surface welding point, ultrasonic wave is incident to the inside of the subject from the inspection surface while transmitted from the probe Is adjusted so as to be received by at least a part of the plurality of transducers of the probe according to the bevel angle of the boundary portion of the welded portion ,
An ultrasonic wave is incident from the flaw detection surface into the subject as a refracted wave in a transverse wave mode, reflected by a surface facing the flaw detection surface and converted into a longitudinal wave mode, and in the longitudinal wave mode. A first ultrasonic transmission / reception step of setting the refraction angle so as to reflect substantially perpendicularly at the boundary portion on the one side of the welding location, and transmitting / receiving ultrasonic waves with the probe;
The refraction angle is set so that an ultrasonic wave is incident from the flaw detection surface to the inside of the subject and reflected substantially perpendicularly at a boundary portion on the opposite side to the one side of the welded portion, and the probe is used to And a step of inspecting a boundary portion on the opposite side where sound waves are transmitted and received. The ultrasonic flaw detection test method according to claim 1 ,
The probe is adapted to receive the reflected wave reflected from the boundary portion on one side and the surface facing the flaw detection surface in the same mode as the refracted wave entering the subject from the flaw detection surface. A second ultrasonic transmission / reception step for transmitting and receiving,
When the bevel angle of the boundary portion changes in the thickness direction of the subject, the first ultrasonic transmission / reception step is performed for the range in the thickness direction where the bevel angle is relatively large, The ultrasonic testing method according to claim 2, wherein the second ultrasonic transmission / reception step is performed for a range in the thickness direction in which the bevel angle is relatively small.

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