JP2001141705A - Ultrasonic flaw detecting method of piping welded joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure a minute crack 3 generated on the inner surface of a pipe 2. SOLUTION: A focusing ultrasonic probe 11 is arranged in a base position having a required distance from a welded joint on the outer surface of a pipe 2 along the pipe axial direction 16, and the ultrasonic probe 11 is scanned over the whole circumference while shifting the position by a minute pitch of 1-5 deg. in the circumferential direction 33. Three kinds of reflected waves 5 of the reflected wave 5 obtained by making an ultrasonic wave 4 incident on the welded joint 12 from the pipe axial direction 16, the reflected wave 5 obtained by making the ultrasonic wave 4 incident on the welded joint 12 with an inclination of 5-15 deg. from the pipe axial direction 16, and the reflected wave 5 obtained by making the ultrasonic wave 4 incident on the welded joint 12 with an inclination of -5 deg. to -15 deg. from the pipe axial direction 16 are measured, and the maximum value of the three reflected waves 5 from the same reaching position is adapted to estimate the shape of a crack 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to vibration fatigue cracks and stresses generated from an inner surface near a weld joint due to unevenness of the inner surface, tensile residual stress, and metallurgical deterioration, such as a welded joint of a pipe. The present invention relates to an ultrasonic flaw detection method for a welded pipe joint, in which corrosion cracking is estimated from the outside, and a manufacturer can obtain information for determining whether or not the product can be shipped and a user for determining whether or not replacement is necessary.

[0002]

2. Description of the Related Art When the depth of a crack in a pipe reaches 1/10 or more of the pipe thickness, the crack grows rapidly in a shorter time than the time spent so far, and may penetrate the pipe. It has been known. Therefore, the depth is 1/1 of the pipe thickness
It is desired that a relatively shallow crack of about 0 or less can be detected.

With respect to cracks on the inner surface of a pipe, an ultrasonic flaw detection method for detecting a reflected wave (echo) from the crack by applying an ultrasonic wave is currently in use. Specifically, FIG.
As shown in (a), the ultrasonic probe 1 is connected to a crack 3 of the pipe 2.
20 ゜ to 30 可能
The ultrasonic wave 4 is incident at the spread of ゜ (divergence angle), the change in sound pressure of the reflected wave 5 reflected by the crack 3 is changed to an electric signal as shown in FIG. 15B, and the peak value is measured. .
Then, referring to the relationship between the depth of the crack 3 and the peak value of the electric signal, which has been confirmed in advance, the crack 3 at the position is determined.
Estimate the depth of Thereafter, the above measurement is performed many times at different positions to obtain the depth and spread of the crack 3. In FIG. 15, reference numeral 6 denotes a welded joint.

[0004]

However, in such conventional ultrasonic flaw detection means, the divergence angle of the ultrasonic wave 4 is 2.
A standard ultrasonic probe 1 of 0 ° to 30 ° is used, but a shallow crack 3 equivalent to 1/10 of the tube thickness, or 0 to 30 °.
Since the sound pressure obtained from a shallow crack 3 of 5 mm or less is low,
It was difficult to distinguish between signal and noise.

For this reason, as shown in FIG. 16A, a strong reflected sound pressure can be obtained from the crack 3 by using a focused ultrasonic probe 7 having a narrow divergence angle of 5 ° to 10 °. However, since the visual field was narrow, the actual crack 3 having a so-called position fluctuation, which approached or moved away from the welding line at a distance equivalent to the pipe thickness, was sometimes overlooked. Further, since the angle of divergence is narrow, there is a problem that it is difficult to obtain a stable reflected sound pressure from an actual crack 3 having a large number of uneven surfaces and presenting a zigzag shape, and has not been widely used.

Accordingly, an object of the present invention is to provide an ultrasonic flaw detection method for a pipe welded joint capable of solving the above-mentioned problems and accurately measuring minute cracks generated on the inner surface of the pipe. .

[0007]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a position of a welded joint extending in a circumferential direction of a pipe is set in a circumferential direction along the welded joint. In the ultrasonic flaw detection method for pipe welded joints, in which ultrasonic waves are incident from the outer surface of the pipe while moving and the reflected waves from the cracks are detected and the cracks are measured, the position where the cracks are estimated near the welded joint and the ultrasonic Determine the distance to the base point where the ultrasonic probe should be placed with respect to the weld joint based on the incident angle, and move the focused ultrasonic probe with a narrow ultrasonic divergence angle from the weld joint on the outer surface of the pipe in the axial direction of the pipe. It is arranged at a base position having a distance, and the focused ultrasonic probe is scanned over the entire circumference while moving the position by a small pitch of 1 ° to 5 ° in the circumferential direction, and the tube axis is aligned with the welding joint. Reflected waves obtained by injecting ultrasonic waves from A reflected wave obtained by injecting ultrasonic waves at an angle of 5 ° to 15 ° from the pipe axis direction with respect to the hand, and an ultrasonic wave at an angle of -5 ° to -15 ° from the pipe axis direction with respect to the weld joint The three types of reflected waves, which are the reflected waves obtained by the incidence, are measured,
The feature is that the shape of the crack is estimated by using the maximum value of the types of reflected waves.

[0008] According to the first aspect of the present invention, a focused ultrasonic probe is used.
Since a high reflected sound pressure can be obtained from the crack, it is possible to reliably discriminate the signal from the noise and detect a minute crack.

The focused ultrasonic probe is moved in the circumferential direction by 1 to 5 mm.
By scanning over the entire circumference while moving the position by a small pitch of ゜, it is possible to measure the entire circumference without omission.

A reflected wave of ultrasonic waves incident from the tube axis direction,
The maximum value among the three types of reflected waves, that is, the reflected wave incident at an angle of 5 ° to 15 ° from the tube axis direction and the reflected wave incident at an angle of -5 ° to -15 ° from the tube axis direction, is used. By doing so, a stable reflected sound pressure can be obtained from a real crack having a zigzag shape.

As described above, it is possible to reliably and accurately measure minute cracks generated on the inner surface of the pipe.

According to the second aspect of the invention, ultrasonic waves are incident on the welded joint extending in the pipe axis direction of the pipe from the outer surface side of the pipe while moving the position in the pipe axis direction along the welded joint. In the ultrasonic flaw detection method for pipe welded joints that detects reflected waves from cracks and measures cracks, an ultrasonic probe is applied to the welded joint based on the position where cracks are estimated near the welded joint and the angle of incidence of ultrasonic waves. Determine the distance to the base point to be placed, the ultrasonic divergence angle of the narrow focussing type ultrasonic probe is located at the base position having the above distance in the circumferential direction from the welded joint on the outer surface of the pipe, the focusing type supersonic Scanning the ultrasonic probe over the entire length of the weld joint while moving the position at a required pitch in the pipe axis direction,
A reflected wave obtained by injecting ultrasonic waves into the weld joint from the circumferential direction, and a reflected wave obtained by injecting ultrasonic waves at 5 ° to 15 ° from the circumferential direction into the weld joint -5 ° to -1 from the circumferential direction with respect to the welded joint
The reflected wave obtained by injecting the ultrasonic wave at an angle of 5 ° is measured, and the reflected wave is measured, and the maximum value of the three reflected waves from the same arrival position is used to crack the reflected wave. It is characterized by estimating the shape of.

According to the second aspect of the present invention, a focused ultrasonic probe is used.
Since a high reflected sound pressure can be obtained from the crack, it is possible to reliably discriminate the signal from the noise and detect a minute crack.

By scanning the focused ultrasonic probe over the entire length of the welded joint while moving the position thereof at a required pitch in the tube axis direction, the entire length of the welded joint can be measured without leakage.

A reflected wave of ultrasonic waves incident from the circumferential direction;
The maximum value among three types of reflected waves, that is, a reflected wave incident at an angle of 5 ° to 15 ° from the circumferential direction and a reflected wave incident at an angle of -5 ° to -15 ° from the circumferential direction, is adopted. By doing so, a stable reflected sound pressure can be obtained from a real crack having a zigzag shape.

As described above, it is possible to reliably and accurately measure minute cracks generated on the inner surface of the pipe.

According to the third aspect of the present invention, the position closer to the welded joint by a distance of 0.1 to 0.3 times the pipe thickness with respect to the base point position, and the position of the pipe thickness of 0.1 to 0.3 times the base point position. 1 to
The operation according to claim 1 or 2 is performed by setting the position apart from the welded joint by a distance of 0.3 times as a new base point position, and further, if necessary, further reducing the pipe thickness by 0.1 mm relative to the first base point position. A new base position is a position that is closer to the welded joint by a distance of 4 to 0.6 times, and a position that is separated from the welded joint by a distance of 0.4 to 0.6 times the pipe thickness with respect to the initial base position. The method according to claim 1 or 2 is performed, and the shape of the crack is estimated by employing the maximum value of the three or five types of reflected waves obtained from the same position.

According to the third aspect of the present invention, the position of the base point is changed in the tube axis direction.
Alternatively, by performing the operation of claim 2, it becomes possible to perform measurement in a range corresponding to the tube thickness. Therefore, it is possible to measure an actual crack having a so-called position fluctuation approaching or moving away from the welding line without leakage.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 to 5 show an embodiment of the present invention. Note that the same or equivalent parts as those in the conventional example are denoted by the same reference numerals and description thereof will be omitted.

The ultrasonic flaw detector for a pipe welded joint used in this embodiment includes a focused ultrasonic probe 11 having a narrow divergence angle of the ultrasonic wave 4 and a focused ultrasonic probe (not shown). A driving unit for moving the probe 11 along the welding joint 12, a moving unit control unit for controlling the driving unit, and a rotation for tilting the focused ultrasonic probe 11 with respect to the welding joint 12. A driving unit, a driving unit control unit for controlling the rotation driving unit, and a sound pressure signal peak value A / D for obtaining the maximum value of the reflected wave 5
Conversion unit, sound pressure signal of reflected wave 5 and focused ultrasonic probe 1
A recording unit for recording the inclination angle 13 of the first unit, a plotting unit for plotting the sound pressure signal of the reflected wave 5 and the inclination angle 13 of the focused ultrasonic probe 11, and various setting panels. .

The welding joint 12 extending in the circumferential direction 33 of the pipe 2 is moved along the welding joint 12 in the circumferential direction 33.
When the ultrasonic wave 4 is incident from the outer surface side of the pipe 2 while detecting the reflected wave 5 from the crack 3 and the crack 3 is measured, as shown in FIG. Base position 1 where ultrasonic probe 1 should be placed with respect to welded joint 12 based on the position where crack 3 in the vicinity is estimated and the incident angle of ultrasonic wave 4
A distance 15 to 4 is determined.

Next, a focused ultrasonic probe 11 having a narrow divergence angle of the ultrasonic wave 4 is arranged at a base position 14 having the above-mentioned distance 15 from the welded joint 12 on the outer surface of the pipe 2 in the pipe axis direction 16. The focused ultrasonic probe 11 is scanned over the entire circumference while moving the position in the circumferential direction 33 by a small pitch of 1 ° to 5 ° in small increments.

Then, as shown in FIG. 1B, the ultrasonic wave 4 is incident on the welded joint 12 from the pipe axis direction 16 (perpendicular to the welding joint 12), and a reflected wave 5 is obtained. Further, as shown in FIG.
The ultrasonic wave 4 is incident at an angle of 6 to 5 ° to 15 °, and a reflected wave 5 is obtained. Further, as shown in FIG. 1D, the ultrasonic wave 4 is incident on the welded joint 12 at an angle of −5 ° to −15 ° from the pipe axis direction 16, and a reflected wave 5 is obtained. As described above, the three types of reflected waves 5 from almost the same arrival position are measured.

In this case, the operation of injecting the ultrasonic wave 4 from the tube axis direction 16 at one place and the operation of 5 to 15 ° from the tube axis direction 16 are performed.
操作 Incline the ultrasonic wave 4 and inject it into the tube axis direction 16
After performing all the operations of making the ultrasonic wave 4 incident at an angle of −5 ° to −15 °, the focused ultrasonic probe 11 may be caused to scan in the circumferential direction 33.

Alternatively, the focusing type ultrasonic probe 11 is scanned in the circumferential direction 33 while performing the operation of inputting the ultrasonic wave 4 from the tube axis direction 16, and then tilted by 5 ° to 15 ° from the tube axis direction 16. The focusing type ultrasonic probe 11 is caused to scan in the circumferential direction 33 while performing an operation of making the ultrasonic waves 4 incident thereon, and finally, the ultrasonic waves 4 are inclined by −5 ° to −15 ° from the tube axis direction 16. The focusing ultrasonic probe 11 may be caused to scan in the circumferential direction 33 while performing the incident operation.

The position of the focusing ultrasonic probe 11 when the focusing ultrasonic probe 11 is inclined is determined by the arrival of the ultrasonic wave 4 due to the inclination of the focusing ultrasonic probe 11. Correct the position.

However, the inclination angle 1 of the focusing ultrasonic probe 11
3 is small, or when the angle of incidence of the focused ultrasonic probe 11 is 45 ° or less, the arrival position of the ultrasonic wave 4 due to the inclination of the focused ultrasonic probe 11 and the focused ultrasonic probe Since the deviation from the position of the child 11 is small, the operation of correcting the position may be omitted. When a relatively deep crack 3 is used as a control, the allowable range of the measurement error of the length of the crack 3 is large.
The operation of correcting the position can be omitted.

Finally, as shown in FIG. 1 (e), the relationship between the crack 3 and the position is determined by using the maximum value of the three types of reflected waves 5 from the substantially same arrival position. By plotting, the shape of the crack 3 is estimated.

Further, in addition to the above, a position 17 close to the weld joint 12 by a distance of 0.1 to 0.3 times the pipe thickness with respect to the base position 14 and a pipe thickness 0 with respect to the base position 14. The above operation is performed by setting the position 18 away from the weld joint 12 by a distance of .1 to 0.3 times as a new base point position.

Further, if necessary, a position 19 closer to the welded joint 12 by a distance of 0.4 to 0.6 times the pipe thickness with respect to the initial base position 14, and a pipe thickness with respect to the initial base position 14. The above operation is performed with the position 20 distant from the welded joint 12 by a distance of 0.4 to 0.6 times as a new base point position.

Then, the maximum value of the three or five types of reflected waves 5 obtained from the same position is adopted to
Is estimated.

Next, the operation of this embodiment will be described.

As shown in FIGS. 1 and 2, in the ultrasonic flaw detector of the pipe welding joint 12, the focused ultrasonic probe 11 enters the ultrasonic wave 4 having a narrow divergence angle into the pipe 2, and A reflected wave 5 from a crack 3 generated in the vicinity is received. The focused ultrasonic probe 11 has a substantially constant beam spread, and has a directivity of about ± 10 ° as shown in FIG. The moving unit control unit sends a control signal to the moving drive unit to move the focused ultrasonic probe 11 along the welding joint 12 at a required pitch. The drive control unit sends a control signal to the rotary drive to tilt the focused ultrasonic probe 11.

Then, the sound pressure signal peak value A / D converter determines the maximum value of the reflected waves 5 at the same position. Further, the recording unit records the sound pressure signal of the reflected wave 5 and the inclination angle 13 of the focusing ultrasonic probe 11, and the plotting unit plots the same.

As described above, by using the focused ultrasonic probe 11, a high reflected sound pressure can be obtained from the crack 3, so that the minute crack 3 can be detected by reliably discriminating the signal and the noise. Will be able to

By scanning the converging type ultrasonic probe 11 over the entire circumference while moving the position in the circumferential direction 33 by a small pitch of 1 ° to 5 °, the entire circumference can be measured without leakage. Becomes

The reflected wave 5 that the ultrasonic wave 4 is incident from the tube axis direction 16, the reflected wave 5 that is incident at an angle of 5 to 15 degrees from the tube axis direction 16, and −5 to -15 from the tube axis direction 16安定 By adopting the maximum value of the three types of reflected waves 5 with the reflected wave 5 incident at an angle, stable reflection from the actual crack 3 having a zigzag shape with many uneven surfaces Sound pressure can be obtained.

That is, as shown in FIG. 1, the actual crack 3 is an aggregate of small planes 21 to 23 having a diameter of 1 mm to 5 mm. However, since most of them have an inclination within 20 °, the ultrasonic wave 4 is moved ± 5 ° from the tube axis direction 16.
Most cracks 3 can be measured by making the light incident at an angle of ゜ to ± 15 °. In addition, as shown in FIG. 4, if the ultrasonic wave 4 is merely incident without being inclined, a sufficient reflected sound pressure cannot be obtained from the crack 3 having an inclination of 10 ° or more.

As described above, the minute cracks 3 generated on the inner surface of the pipe 2 can be reliably and accurately measured.

The base position 14 is set to ± 0.1 to ± 0.1 of the tube thickness.
By performing the above operation while changing the pipe axis direction 16 to ± 0.3 times or further ± 0.4 to ± 0.6 times the pipe thickness, measurement can be performed for a range equivalent to the pipe thickness. It becomes possible. Therefore, as shown in FIG. 5, the so-called position fluctuation that approaches or moves away from the welding line (weld joint 12) depending on the variation in the axial direction of the welding weak point portion (i.e.,
D) It is possible to measure a certain actual crack 3 without omission. In addition, a welding weak point part is insufficient penetration of a groove, protrusion of a welding toe part, and 400 to 600 degreeC during welding.
Deteriorated portion caused by being kept in the temperature range for a long time.

As another embodiment of the present invention, the outer surface of the pipe 2 is moved while moving in the pipe axis direction 16 along the weld joint 12 with respect to the weld joint 12 extending in the pipe axis direction 16 of the pipe 2. The present invention can be applied to the case where the ultrasonic wave 4 is incident from the side and the reflected wave 5 from the crack 3 is detected to measure the crack 3.

In this case, the crack 3 near the welded joint 12
Is determined based on the estimated position and the incident angle of the ultrasonic wave 4 to the base position 14 where the ultrasonic probe 1 is to be placed with respect to the weld joint 12, and the diverging angle of the ultrasonic wave 4 is narrow. The ultrasonic probe 11 is arranged at a base position 14 having the distance 15 in the circumferential direction 33 from the welded joint 12 on the outer surface of the pipe 2,
The focusing type ultrasonic probe 11 is scanned over the entire length of the weld joint 12 while moving the position in the tube axis direction 16 at a fine pitch, for example, 1 mm to 2 mm, and is superposed from the circumferential direction 33 with respect to the weld joint 12. The reflected wave 5 obtained by injecting the sound wave 4, the reflected wave 5 obtained by injecting the ultrasonic wave 4 at an angle of 5 ° to 15 ° from the circumferential direction 33 with respect to the welding joint 12, and welding The reflected wave 5 obtained by injecting the ultrasonic wave 4 at −5 ° to −15 ° from the circumferential direction 33 with respect to the joint 12 is measured, and three kinds of reflected waves 5 are measured.
The shape of the crack 3 is estimated by plotting the relationship between the crack 3 and the position by using the maximum value of the three types of reflected waves 5 from the substantially same arrival position.

As described above, even when the present invention is applied to the welded joint 12 extending in the pipe axis direction 16 of the pipe 2, a high reflected sound pressure can be obtained from the crack 3 by using the focused ultrasonic probe 11. Therefore, it is possible to detect the minute crack 3 by reliably discriminating the signal and the noise.

By scanning the focused ultrasonic probe 11 over the entire length of the welded joint 12 while moving the position thereof by a small pitch in the tube axis direction 16, the entire length of the welded joint 12 can be measured without leakage. Becomes

The reflected wave 5 that the ultrasonic wave 4 is incident from the circumferential direction 33, the reflected wave 5 that is incident at an angle of 5 ° to 15 ° from the circumferential direction 33, and the reflected wave 5 that is -5 ° to -15 from the circumferential direction 33よ う By adopting the maximum value of the three types of reflected waves 5 including the reflected wave 5 incident with an inclination, a stable reflected sound pressure can be obtained from the actual crack 3 having a zigzag shape. become.

As described above, the minute cracks 3 generated on the inner surface of the pipe 2 can be reliably and accurately measured.

[0048]

Embodiments of the present invention will be described below. (Example 1) The inner surface of a pipe 2 having a nominal diameter of 20 mm and a pressure resistance of 160 kg has depths of 0.5 mm and 1.0 m, respectively.
m, 1.5mm, 2.0mm, 2.5mm, 3.0m
m, a slit-shaped artificial defect having a width of 0.5 mm is provided, and the incident angle with respect to the outer surface of the pipe 2 is 70 °, and the focal diameter is 2 m.
m, the focused ultrasonic probe 11 having a focal length of 2 mm to 8 mm expressed in the depth direction is pressed to move on the circumference of the pipe 2 every 1 °, and the ultrasonic wave 4 is aimed at the slit. By transmitting and receiving, the peak value of the sound pressure signal of the reflected wave 5 was recorded.

As a result, as shown in FIG. 6, the noise was several percent, and it was confirmed that the slit having a depth of 0.5 mm could be clearly recognized.

On the other hand, as a comparative example, when the standard ultrasonic probe 1 having a wide divergence angle is used, as shown in FIG.
Noise at a height of 20% was observed on the CRT screen of the dB display, and it was confirmed that the slit having a depth of 0.5 mm was hidden by the noise and could not be detected. (Example 2) A welded joint 12 was made of a stainless steel pipe and a socket having a nominal diameter of 20 mm and a pressure resistance of 160 kg, and was subjected to a 42% concentration of a boiling magnesium chloride aqueous solution.
Dipped for 5 hours. The focused ultrasonic probe 11 used in the first embodiment is used for the pipe 2 and the focused ultrasonic probe 1 is used.
The scanning was performed under the conditions that the tilt angle 13 of 1 was ± 10 ° and the moving distance (angle) in the circumferential direction 33 was 10 °.

As a result, as shown in FIG.
A relatively high reflected wave 5 was obtained at the position of {100}. The maximum depth of crack 3 was 2.0 mm (100% position corresponds to 2 mm), and the length of stress corrosion crack 3 was 75 ° in angle display. This almost coincided with the depth of the crack 3 obtained by cutting the pipe 2 and observing it with a microscope, as shown in FIG.
On the other hand, when the focusing type ultrasonic probe 11 is used without being inclined, as shown in FIG. 10, a sufficient reflected sound pressure cannot be obtained, and furthermore, a crack 3 is generated at a position of 60 ° or 80 °. Was not detected. (Example 3) A welded joint 12 was made of a stainless steel pipe and a socket having a nominal diameter of 20 mm and a pressure resistance of 160 kg, and was subjected to a boiling magnesium chloride aqueous solution having a concentration of 42%.
Dipped for 0 hours. The focused ultrasonic probe 11 used in the first embodiment is used for the pipe 2 and the focused ultrasonic probe 1 is used.
The scanning was performed under the condition that the inclination angle 13 of one was ± 10 ° and the moving distance (angle) in the circumferential direction 33 was 1 °.

As a result, as shown in FIG.
A reflected wave 5 that is twice the noise at a position between 70 ° and 360 °
I got From the calibration diagram, the maximum depth of crack 3 is 0.6mm
(100% position corresponds to 2 mm). This was relatively close to the depth 0.25 mm of the crack 3 obtained by cutting the pipe 2 and observing it with a microscope, as shown in FIG.

On the other hand, as a comparative example, when the measurement was performed without tilting the focused ultrasonic probe 11, as shown in FIG. When a standard ultrasonic probe 1 having a wide width is used, FIG.
As shown in FIG. 4, it was buried in noise.

[0054]

As described above, according to the first aspect of the present invention, by using a focused ultrasonic probe,
Since a high reflected sound pressure can be obtained from the crack, it is possible to reliably discriminate the signal from the noise and detect a minute crack.

The focused ultrasonic probe is moved in the circumferential direction by 1 to 5 mm.
By scanning over the entire circumference while moving the position by a small pitch of ゜, it is possible to measure the entire circumference without omission.

A reflected wave of ultrasonic wave incident from the tube axis direction;
The maximum value among the three types of reflected waves, that is, the reflected wave incident at an angle of 5 ° to 15 ° from the tube axis direction and the reflected wave incident at an angle of -5 ° to -15 ° from the tube axis direction, is used. By doing so, a stable reflected sound pressure can be obtained from a real crack having a zigzag shape.

As described above, it is possible to reliably and accurately measure minute cracks generated on the inner surface of the pipe.

According to the second aspect of the present invention, by using the focused ultrasonic probe, a high reflected sound pressure can be obtained from cracks, so that signals and noise can be reliably discriminated to detect minute cracks. Will be able to

By scanning the focused ultrasonic probe over the entire length of the welded joint while moving the position thereof at a required pitch in the tube axis direction, the entire length of the welded joint can be measured without leakage.

A reflected wave of ultrasonic waves incident from the circumferential direction;
The maximum value among three types of reflected waves, that is, a reflected wave incident at an angle of 5 ° to 15 ° from the circumferential direction and a reflected wave incident at an angle of -5 ° to -15 ° from the circumferential direction, is adopted. By doing so, a stable reflected sound pressure can be obtained from a real crack having a zigzag shape.

As described above, it is possible to reliably and accurately measure minute cracks generated on the inner surface of the pipe.

According to the third aspect of the present invention, it is possible to perform measurement in a range equivalent to the pipe thickness by changing the base point position in the pipe axis direction and performing the operation of the first or second aspect. Becomes Therefore, it is possible to exert a practically useful effect that an actual crack having a so-called position fluctuation which approaches or moves away from the welding line can be measured without leakage.

[Brief description of the drawings]

FIGS. 1A to 1E are views showing a flaw detection method using a focused ultrasonic probe according to an embodiment of the present invention.

FIG. 2A is a partially enlarged side sectional view showing a state in which a crack of a pipe welded joint is measured by using the focused ultrasonic probe according to the embodiment of the present invention, and FIG. 3A is a graph showing waveforms of an ultrasonic wave and a reflected wave in FIG.

FIG. 3 is a graph showing the directivity of a focused ultrasonic probe.

FIGS. 4 (a) and (b) are views similar to FIG. 1 in a case where a focused ultrasonic probe is not tilted as a comparative example.

FIG. 5 is a perspective view showing fluctuation of a position of a crack near a weld joint.

FIG. 6 is a graph showing reflected waves from a slit-shaped artificial defect according to the first embodiment.

FIG. 7 is a graph showing reflected waves from a slit-shaped artificial defect according to a comparative example of Example 1.

FIG. 8 is a graph showing reflected waves from a typical stress corrosion cracking according to Example 2.

FIG. 9 is a graph showing a typical shape of stress corrosion cracking observed by a microscope.

FIG. 10 is a graph showing reflected waves from typical stress corrosion cracking according to a comparative example of Example 2.

FIG. 11 is a graph showing reflected waves from minute stress corrosion cracking according to Example 3.

FIG. 12 is a graph showing the shape of micro stress corrosion cracking observed with a microscope.

FIG. 13 is a graph showing reflected waves from minute stress corrosion cracking when the focused ultrasonic probe according to the comparative example of Example 3 is not tilted.

FIG. 14 is a graph showing reflected waves from minute stress corrosion cracking when a standard ultrasonic probe according to a comparative example of Example 3 is used.

FIG. 15A is a partially enlarged side sectional view of a conventional example showing a state in which a crack of a pipe welded joint is measured using a standard ultrasonic probe, and FIG. 15B is a sectional view of FIG. It is a graph which shows the waveform of an ultrasonic wave and a reflected wave.

FIG. 16 (a) is a partially enlarged side sectional view of a conventional example showing a state in which a crack of a pipe welded joint is measured using a focusing type ultrasonic probe, and (b) is (a). It is a graph which shows the waveform of an ultrasonic wave and a reflected wave.

[Explanation of symbols]

 2 Piping 3 Crack 4 Ultrasonic wave 5 Reflected wave 11 Focused ultrasonic probe 12 Weld joint 13 Inclination angle 14 Base point position 15 Distance 16 Tube axis direction 17 Position 18 Position 19 Position 20 Position 33 Circumferential direction

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Muneaki Shibayama 2109-8 Yashimanishimachi, Takamatsu City, Kagawa Prefecture Inside Shikoku Research Institute (72) Inventor Masazumi Iwata 2109-8 Yashimanishimachi Takamatsu City, Kagawa Prefecture Shikoku Corporation 2G047 AA07 AB01 AB07 BA03 BB02 BC07 BC10 BC11 DB17 EA10 EA11 GB24 GF31 GG09 GG24

Claims (3)

[Claims] 1. A welding joint extending in a circumferential direction of a pipe,
An ultrasonic flaw detection method for pipe welded joints, in which ultrasonic waves are incident from the outer surface of the pipe while moving in the circumferential direction along the welded joint to detect reflected waves from the crack and measure the crack, the vicinity of the welded joint The distance to the base point where the ultrasonic probe should be placed with respect to the weld joint is determined based on the position where the crack is estimated and the incident angle of the ultrasonic wave, and a focused ultrasonic probe with a narrow ultrasonic divergence angle is used. It is arranged at a base position having the above distance in the pipe axis direction from the welded joint on the outer surface of the pipe, and the converging type ultrasonic probe is circumferentially moved by a small pitch of 1 ° to 5 ° in the circumferential direction while moving around the entire circumference. And a reflected wave obtained by injecting ultrasonic waves into the welded joint from the pipe axis direction, and by injecting ultrasonic waves into the welded joint at an angle of 5 ° to 15 ° from the pipe axis direction. The obtained reflected wave and -5 ° from the pipe axis direction with respect to the welded joint ~ -1
Measure the three types of reflected waves obtained by injecting ultrasonic waves at an angle of 5 °, and use the maximum value of the three types of reflected waves from the same arrival position to crack An ultrasonic flaw detection method for a pipe welded joint, comprising estimating a shape of a pipe. 2. A welding joint extending in a pipe axis direction of a pipe,
An ultrasonic flaw detection method for pipe welded joints in which ultrasonic waves are incident from the outer surface of the pipe while moving in the pipe axis direction along the welded joint to detect a reflected wave from the crack and measure the crack, the vicinity of the welded joint The distance to the base point where the ultrasonic probe should be placed with respect to the weld joint is determined based on the position where the crack is estimated and the incident angle of the ultrasonic wave, and a focused ultrasonic probe with a narrow ultrasonic divergence angle is used. It is arranged at a base position having the above distance in the circumferential direction from the welded joint on the outer surface of the pipe, and scans the focused ultrasonic probe over the entire length of the welded joint while moving the position at a required pitch in the pipe axis direction. And a reflected wave obtained by injecting ultrasonic waves into the weld joint from the circumferential direction, and a reflected wave obtained by injecting ultrasonic waves into the weld joint at an angle of 5 ° to 15 ° from the circumferential direction. -5 ゜ from the circumferential direction to the reflected wave and the weld joint ~ -1
Measure the three types of reflected waves obtained by injecting ultrasonic waves at an angle of 5 °, and use the maximum value of the three types of reflected waves from the same arrival position to crack An ultrasonic flaw detection method for a pipe welded joint, comprising estimating a shape of a pipe. 3. A pipe thickness of 0.1 to 0.3 with respect to the base point position.
Claim 1 or Claim 2, wherein a position closer to the welded joint by a distance twice and a position away from the welded joint by a distance of 0.1 to 0.3 times the pipe thickness with respect to the base position are new base positions. Perform the operation of Item 2 and, if necessary, add 0.4 mm of the tube thickness to the initial base position.
The position closer to the welded joint by a distance of ~ 0.6 times and the position separated from the welded joint by a distance of 0.4 to 0.6 times the pipe thickness with respect to the initial base position are defined as new base positions. The method according to claim 1 or 2, wherein the shape of the crack is estimated by using the maximum value of the three or five types of reflected waves obtained from the same position. Or the ultrasonic flaw detection method of the pipe welding joint according to claim 2.