JPH09318605A - Method for testing welded part by ultrasonic surface sh wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic testing method capable of individually detecting the defective portions of a welded part caused by incomplete penetration or uneven penetration from the surface of a side opposite the route part of the welded part. SOLUTION: In a method for testing the defective portion of the back side of the welded part of a tested body 8 from the outside by ultrasonic waves, a probe 10 for producing an ultrasonic pulse composed of a horizontal wave vibrated in parallel with the surface 9 of the tested body 8 and perpendicular to an advancing direction is stuck to the outer surface 9 of the tested body 8, a surface SH wave is made incident in the surface 9 from the probe 10 by a shallow angle, the surface SH wave is brought to the defective portion of the back side of the tested body 8, a reflection wave from the defective portion is detected by the probe 10 or a different receiving probe and thus the detective portion is detected.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ultrasonic surface SH of an ultrasonic wave.
The present invention relates to a method of inspecting a welded portion from outside after welding steam / water pipes and the like of a boiler or the like of a power plant by waves and the like.

[0002]

2. Description of the Related Art When welding a small-diameter pipe to a pipe for nuclear power, thermal power generation, etc., as shown in FIG. 1, a base end of a nozzle base 3 is welded to a mother pipe 2 of a steam / water pipe 1 to form a nozzle base 3 The target small-diameter pipe 4 is welded to the tip of the. Welded portion 16 between mother pipe 2 and nozzle base 3
Is pre-grooved into the shape shown in FIG. 1 and welded to this portion. At that time, as shown in FIG. 2, a groove 6 due to poor penetration may remain in the root portion 5 inside the welded portion 16, or
As shown in FIG. 5, extra metal 7 is generated due to sagging of molten metal. It is necessary to accurately detect the type and size of the defect in the welded portion 16.

As a non-destructive inspection method, an ultrasonic flaw detection method is widely used. For vibrations in which an ultrasonic wave propagates in a solid, a longitudinal wave in which particles constituting the solid move in the traveling direction of the ultrasonic wave, There is a transverse wave that oscillates in a direction perpendicular to the traveling direction of sound, and the transverse wave includes an SV wave that oscillates perpendicularly to the solid surface and an SH wave that oscillates parallel to the solid surface. SH waves traveling along the surface are called surface SH waves. The surface SH wave is a shear wave traveling with a spread of about 15 ° from the flaw detection surface.

Conventionally, as a nondestructive inspection method for defects in welded portions of joints, the magazine "Nondestructive Inspection", Vol. 44, No. 12 (1995), No. 946-6, issued by the Japan Nondestructive Inspection Association.
As described on page 50, a beveled flaw detection method using an ultrasonic SV wave and a flaw detection method using an ultrasonic surface SH wave are known.

[0005]

In the conventional ultrasonic oblique angle flaw detection method, it was not possible to distinguish between the above penetration failure and sagging. In addition, the conventional method for inspecting a welded portion using an ultrasonic surface SH wave is only known to detect flaws from the surface of the root portion where a welding defect exists, and it is said that inspection cannot be performed from the surface opposite to the root portion. Was there. Therefore, the conventional method for inspecting a welded portion using an ultrasonic surface SH wave cannot inspect from the root portion of the inner surface like the welded portion shown in FIG.
It has been considered that this is not applicable when the inspection must be performed from the surface opposite to the root portion 5. This is because when the surface SH wave of the ultrasonic wave enters the test body from the ultrasonic wave,
Since ultrasonic waves propagate along the surface of the incident specimen and detect reflected ultrasonic waves, it is possible to detect only defects on the incident side surface and not on the back side. Has been.

Therefore, an object of the present invention is to provide an ultrasonic flaw detection method capable of distinguishing and detecting defects in a welded part due to poor penetration and sagging from the surface of the welded part opposite to the root part. To do.

A further object of the present invention is to provide a method of detecting a defect of poor penetration in a welded portion, by which the depth of the defect can be estimated from the surface on the opposite side of the defect.

[0008]

In order to achieve the above object,
As a result of intensive studies by the present inventors, a surface SH that propagates a transverse ultrasonic pulse oscillating in a direction parallel to the surface of the test body from the probe along the tube surface at a shallow angle with respect to the tube surface.
When incident as a wave, the surface SH wave enters the test body with a radiation characteristic as shown in FIG. 4 and advances with a spread of about 15 °. Therefore, if the positional relationship between the probe and the weld is properly selected, the test We have found that welding defects on the back side of the body can also be detected by surface SH waves, and have completed the present invention.

That is, according to the present invention, in an inspection method for inspecting a defect on the back side of a welded portion of a test body from the outside by ultrasonic waves, an ultrasonic pulse composed of transverse waves vibrating parallel to the surface of the test body and perpendicular to the traveling direction is used. The generated probe is brought into close contact with the outer surface of the test body, and the surface SH wave is incident from the probe at a shallow angle with respect to the surface, and the surface SH wave reaches the defect on the back side of the test body. In summary, a method of inspecting a welded portion by an ultrasonic surface SH wave is characterized in that a reflected wave from the defect is detected by the probe or a separate receiving probe to detect the defect. .

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the method for inspecting a welded portion by ultrasonic waves according to the present invention will be specifically described with reference to the drawings.
FIG. 5 shows a test body 8 having a groove 6 due to poor penetration by the inspection method of the welded portion by the ultrasonic surface SH wave of the present invention (FIG. 5).
It is explanatory drawing of the method of detecting the defect of the test body 8 (FIG. 5b) which has the surplus 7 by a) or sag. A probe 10 for transmitting and receiving ultrasonic waves is brought into close contact with the surface 9 of the test body 8 on the side opposite to the welding defect groove 6.

As the vibrator of the probe 10 used in the present invention, a transverse wave piezoelectric element obtained by Y-cutting a crystal, and other piezoelectric elements made of various ceramics are used. The piezoelectric element 11 of the probe 10 is sandwiched between a wedge 12 made of synthetic resin such as polymethylmethacrylate resin and a backing material 13 made of synthetic resin as shown in FIG. 1
0. The angle with respect to the bottom surface of the piezoelectric element 11, that is, the incident angle λ of the ultrasonic wave on the test body 8 is substantially equal to the angle called the critical angle at which the refraction angle of the ultrasonic wave incident on the test body 8 such as a steel material is just 90 degrees. The angle is necessary to improve the transmission / reception efficiency.

A thin acoustic coupling agent made of a viscous liquid is thinly applied to the bottom surface of the probe 10 and brought into close contact with the surface 9 of the test body 8, and ultrasonic waves are transmitted through the thin layer of the acoustic coupling agent as efficiently as possible. Make it communicate. An ultrasonic pulse of a transverse wave that is oscillated from the probe 10 in parallel with the surface 9 of the test body 8 is incident on the surface 9 at a shallow angle close to the critical angle at which the surface SH wave is generated. 8 is refracted on the surface to become a pulse of the surface SH wave, and propagates as a transverse wave traveling in the test body 8 with a spread of about 15 ° from the surface 9 as shown in FIG. A part of the transverse wave that spreads in the test body 8 within a range of about 15 ° is reflected by the groove 6 and traces the incident path in the opposite direction, and the probe 10
Is reached and detected. It is preferable to use the same probe as the probe 10 that has emitted ultrasonic waves for reception as the above-mentioned reception probe, but a separate reception probe may be used.

The time from pulse emission to echo detection and the echo intensity are displayed on a display device such as an oscilloscope or recorded and read. While the ultrasonic pulse is emitted from the probe 10 at a constant interval to detect its echo, the probe 10 is scanned along the surface 9 of the test body 8 and, from the position and size of the observed echo, Find the location of the defect.

[0014]

【Example】

Example 1 A width of 100 mm and a length of 150 mm shown in FIG.
A groove 6 having a width of 6 mm and a depth of 2 mm is provided in the width direction on one surface of a test body 8 made of a steel plate having a thickness of 16 mm, and a probe 10 is brought into close contact with a surface 9 opposite to the groove 6. The probe 10 is placed at a position where the horizontal distance W = 50 mm from the groove 6 to the probe 10,
A transverse ultrasonic pulse vibrating more parallel to the surface 9 is emitted to enter as a surface SH wave, the echo of the SH wave is detected by the same probe 10, and from the pulse incidence to echo detection on the horizontal axis. By displaying the time and the intensity of the echo on the vertical axis, the flaw detection figure of FIG. 7 is obtained. In FIG. 7, A is a reflected wave from the groove 6, and T is a reflected wave from the end face 14 of the test body 8.

The position of the probe 10 is gradually moved in a direction perpendicular to the direction of the groove 6 to detect an echo as in FIG. 7, and the height of the echo A from the groove 6 is plotted on the vertical axis. Probe 1
If the distance from the reference point of 0 is plotted along the abscissa as the dotted line, FIG. 8 is obtained.

Although two peaks are recognized in FIG. 8, the interval d between these two peaks changes depending on the depth h of the groove 6. That is, if the incident angle of the surface SH wave is θ, then h = d cos θ (1) holds. This is the surface SH incident from the probe 10.
The wave is reflected by the vertical wall surface 15 of the groove 6 on the probe 10 side, and this is observed as an echo. However, the reflection does not occur uniformly on the entire surface of the vertical wall 15, but the vertical direction of the groove 6 on the probe 10 side. Since the reflections from the projecting and entering corners at the lower and upper ends of the wall surface are strong, the echo intensity increases when the distance W between the probe 10 and the groove 6 and the incident angle θ have a constant relationship. Is.

Therefore, the depth h of the groove 6 can be obtained from FIG. For example, in FIG. 8, d = 3 mm, θ = 71 °
Therefore, h≈1 mm is required.

[Embodiment 2] Next, a width of 100 m shown in FIG. 5b.
On a single side of a test body 8 having a length of m, a length of 150 mm, and a thickness of 16 mm, a linear ridge 6 having a width of 6 mm and a height of 4.5 mm is provided, and a probe is provided on a surface 9 opposite to the ridge 7. Stick 10 together. The probe 10 is closely attached to a position where the horizontal distance W = 50 mm from the extra scale 7 to the probe 10, and the probe 1 is attached in the same manner as in the first embodiment.
9 is obtained by emitting an ultrasonic pulse of a transverse wave from 0, detecting the echo of the SH wave, displaying the time from pulse incidence to echo detection on the abscissa, and the intensity of the echo on the ordinate. In FIG. 9, B is a reflected wave from the extra scale 7, and T is a reflected wave from the end surface 14 of the test body 8. FIG. 9 shows a flaw detection pattern detected with the same sensitivity as in FIG. 7. However, since the reflected wave from the extra scale 7 in FIG. 9 is extremely small, the detection sensitivity is increased and displayed as shown in FIG. Groove 6 due to poor penetration in FIG.
There is a sensitivity difference of 30 dB between the echoes from No. 1 and the echo from the sag 7 of FIG. 9, and the surplus 7 due to sagging is not detected by the detection sensitivity of the groove 6 with a penetration failure of 1 mm. In this way, the echoes from the groove 6 and the echoes from the extra layer 7 have greatly different intensities, so that they can be clearly distinguished.

[0019]

According to the method for inspecting a welded portion by the ultrasonic surface SH wave of the present invention, the probe cannot be brought close to the inside of the welded portion like the welded portion of a small diameter pipe to a steam / water pipe or the like. Even if the surface SH wave of the ultrasonic wave is incident from the outside of the small-diameter pipe, it is possible to detect the defect of the welded part on the back side, and clearly distinguish the groove due to poor penetration and the excess due to sagging. It is also possible to obtain the depth of the groove due to defective penetration.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a welded portion in which a nozzle is welded to a pipe of a nuclear power or thermal power plant boiler or the like.

FIG. 2 is a cross-sectional view of a welded portion having a poor penetration.

FIG. 3 is a cross-sectional view of a welded portion where sagging occurs.

FIG. 4 is a radiation characteristic diagram of surface SH waves.

FIG. 5 is an explanatory diagram of a method for inspecting a welded portion by an ultrasonic surface SH wave of the present invention.

FIG. 6 is a cross-sectional view showing propagation as an ultrasonic surface SH wave emitted from a probe.

FIG. 7 is a flaw detection figure of a welded portion having a poor penetration by the inspection method of the welded portion by the ultrasonic surface SH wave of the present invention.

FIG. 8 is a graph in which the peak height of the flaw detection figure of FIG. 6 is dotted with respect to the position of the probe.

FIG. 9 is a flaw detection figure of a welded portion caused by sag by a method for inspecting a welded portion using an ultrasonic surface SH wave of the present invention.

FIG. 10 is a flaw detection figure shown with increased sensitivity in FIG.

[Explanation of symbols]

 1 Steam / water pipe 2 Mother pipe 3 Pipe base 4 Small diameter pipe 5 Root part 6 Groove 7 Overfill 8 Test body 9 Surface 10 Probe 11 Piezoelectric element 12 Wedge 13 Backing material 14 End face 15 Vertical wall surface 16 Welding part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yuichiro Yoshikawa, 2-10-20 Ebie, Fukushima-ku, Osaka City, Japan Stock Company (72) Noriyuki Okajima 2--10-20, Ebie, Fukushima-ku, Osaka Stock Company Inside the Japanese arm

Claims (4)

[Claims] 1. A test method for ultrasonically inspecting a defect on the back side of a welded portion of a test body from the outside, which generates an ultrasonic pulse composed of a transverse wave oscillating parallel to the surface of the test body and perpendicular to the traveling direction. Adhere the tentacle to the outer surface of the test piece,
A surface SH wave is incident from the probe at a shallow angle with respect to the surface to cause the surface SH wave to reach a defect on the back side of the test body, and a reflected wave from the defect is received by the probe or a separate reception. A method for inspecting a welded portion by an ultrasonic surface SH wave, which is characterized by detecting a defect with a probe for ultrasonic waves. 2. The method for inspecting a welded portion by an ultrasonic surface SH wave according to claim 1, wherein the defect is a groove-shaped defect due to defective penetration in the groove. 3. The peak height of the reflected wave from the groove-like defect is measured while moving the probe along the surface of the test body, and the peak height is measured with respect to the moving position of the probe. The method for inspecting a welded portion by ultrasonic surface SH waves according to claim 2, wherein the depth of the groove-like defect is obtained from the interval between two peaks generated when dot-stitching. 4. The method for inspecting a welded portion by an ultrasonic surface SH wave according to claim 1, wherein the defect is a defect due to sagging of a groove portion.