JP3723512B2 - Ultrasonic flaw detector and automatic flaw detector using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic flaw detector, and more particularly to an ultrasonic flaw detector suitable for automatically flaw-detecting circumferential welds such as gas pipes using SH waves.
[0002]
[Prior art]
In recent years, research and development of ultrasonic flaw detection using SH waves (Shear Horizontal Wave) has progressed, and future development as an ultrasonic flaw detection method because of its advantageous characteristics that it is less susceptible to external influences or mode conversion does not occur. Is expected.
[0003]
However, flaw detection using an ultrasonic SH wave probe requires the use of a high-viscosity special contact medium, and the echo height (crest value) due to the change in the contact medium thickness between the probe and the material to be inspected. ) Changes, there is a problem that a predetermined time is required to stabilize it. Therefore, the fact is that it is hardly applied to automatic flaw detection.
[0004]
Here, Japanese Patent Laid-Open No. 2001-99818 discloses an ultrasonic flaw detector using the SH wave.
[0005]
However, the ultrasonic flaw detector disclosed in the above publication stores the film thickness stable holding time of the contact medium in advance, and the stop time of the ultrasonic probe at the data collection position is longer than the film thickness stable holding time. The measurement is started on the condition that it has become, and it takes several minutes or more as the probe pressing holding time until the echo height is stabilized. In other words, the problem peculiar to the SH wave that the echo height has to be stabilized has not been solved at all, and the inspection material can be inspected intermittently by scanning it.
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve such problems of the prior art, and does not require a probe pressing holding time until the echo height is stabilized, and continuously scans the material to be inspected for flaw detection. It is an object of the present invention to provide an obtained ultrasonic flaw detector.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a probe that has a contact surface that protrudes downward so that only a range through which an ultrasonic transmission / reception wave passes is in contact with an object to be inspected, and that transmits and receives an SH wave. An ultrasonic flaw detector comprising a probe holder for storing and holding the probe, wherein the probe holder is in a position to be inspected across the contact surface of the probe. The probe is inserted between a contact portion protruding downward to contact the material, an upper end portion of the probe holder, and a surface facing the contact surface of the probe. A second elastic member that is interposed between a first elastic member that urges the inspection material vertically downward, a horizontal side surface of the probe holder, and both horizontal side surfaces of the probe. comprising of an elastic member, the first elastic member, the probe or heavy 5kg vertically downwards against the inspected material 1 there is provided an ultrasonic flaw detection apparatus characterized by biasing in kg weight or less.
[0008]
According to such an invention, a probe having a contact surface protruding downward is applied so that only a range through which ultrasonic transmission / reception waves pass is in contact with the material to be inspected. Here, the “range in which the ultrasonic transmission / reception wave passes” is a range equivalent to the range in which the ultrasonic transmission / reception wave is assumed to pass, or the reflected echo at the periphery of the probe contact surface is at the time of flaw detection. In order to prevent the noise from becoming a noise factor, this means a slightly wide range including the assumed range. By applying a probe with a small contact area in this way, it is possible to significantly shorten the time until the echo height is stabilized.
[0009]
The probe holder of the ultrasonic flaw detector according to the present invention includes a contact portion protruding downward so as to contact the material to be inspected at a position facing the probe contact surface, and a probe. A first elastic member that is interposed between the upper end of the child holder and the surface facing the contact surface of the probe and urges the probe vertically downward against the material to be inspected; To do. Therefore, the positional relationship between the probe and the probe holder is not fixed and can be changed elastically via the first elastic member. Here, if the probe holder is pressed against the material to be inspected so that the contact portion of the probe holder is in contact with the material to be inspected, the contact surface of the probe sandwiched between the contact portions is Since the first elastic member urges the inspection material vertically downward, the probe contacts the surface of the inspection material in the range sandwiched between the contact portions. Stable inspection can be performed while maintaining a parallel state between the surface and the surface of the material to be inspected.
[0010]
The probe holder of the ultrasonic flaw detector according to the present invention further includes a second elastic member interposed between the horizontal side surface of the probe holder and the horizontal side surfaces of the probe. Therefore, when the probe is scanned with the probe in contact with the surface of the inspection material (that is, when the probe is moved relatively in the horizontal direction with respect to the inspection material), the second Since the position of the probe is stabilized by the urging force of the elastic member, the parallel state between the contact surface of the probe and the surface of the material to be inspected generated by the first elastic member is more reliably maintained. Is possible.
[0011]
Furthermore, since the first elastic member is configured to urge the probe vertically below the material to be inspected at 5 kg weight or more and 10 kg weight or less, the echo height increases instantaneously. While it is possible to significantly reduce the time to stabilize, the reaction force to the scanning device for scanning the probe holder and the material to be inspected is not too great, and there is no need to increase these strengths excessively. Therefore, it is possible to provide a practically suitable ultrasonic flaw detector.
[0012]
As described above, according to the present invention, a probe holder that can apply a probe with a small contact area and stabilize the parallel state between the contact surface of the probe and the surface of the material to be inspected. As a result, it is possible to provide an ultrasonic flaw detection apparatus that can perform flaw detection by continuously scanning the material to be inspected without requiring the probe pressing and holding time until the echo height is stabilized.
[0013]
Note that the positional relationship in the vertical direction, which means “downward” and “upper end”, has been described based on the case where the material to be inspected is positioned below the ultrasonic flaw detector according to the present invention.
[0015]
The present invention is an automatic flaw detection apparatus for automatically flawing a circumferential welded portion of a steel pipe, and surrounds the steel pipe at a position separated from the ultrasonic flaw detector by a predetermined distance from the circumferential welded portion of the steel pipe. An annular guide rail arranged in such a manner as to hold the ultrasonic flaw detector in order to rotate the ultrasonic flaw detector in the circumferential direction of the steel pipe while being in contact with the outer surface of the steel pipe, and The present invention also provides an automatic flaw detection apparatus comprising a rotating member that rotates by driving a motor along a guide rail.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of an ultrasonic flaw detector according to an embodiment of the present invention, in which (a) is a longitudinal sectional view, (b) is an AA sectional view of (a), ( c) shows a BB cross-sectional view of (a).
[0017]
As shown in FIG. 1, the ultrasonic flaw detector 1 according to the present embodiment includes a probe 11 that transmits and receives SH waves, and a probe holder 12 that houses and holds the probe 11.
[0018]
Here, the probe 11 has a contact surface 111 that protrudes downward so that only the range through which ultrasonic transmission / reception waves pass is in contact with the material to be inspected. More specifically, as shown in FIG. 2, in order to prevent reflected echoes at the periphery of the contact surface 111 from becoming a noise factor at the time of flaw detection, the range S is assumed to be greater than the range S in which an ultrasonic wave is assumed to pass. The contact surface 111 has a slightly wide range.
[0019]
FIG. 3 shows a probe 11 according to the present embodiment and a conventional probe 11 ′ having a large contact area (all lower surfaces of the probe are contact surfaces 111 ′) as shown in FIG. (A) is a result of comparing changes in echo heights after contact with a predetermined material to be inspected, and (a) shows the results when each probe is pressed against the material to be inspected with a weight of 5 kg, (b). Shows the results when each probe is pressed against the material to be inspected with a weight of 7.5 kg. In the example shown in FIG. 3, the probe 11 according to this embodiment the area of the contact surface 111 is 56 mm ² SH Namisagu probe "5Z5 × 5A90-SH" ( "5" frequency (5 MHz), "Z "Is the vibrator material (zircon / lead titanate-based porcelain)," 5x5 "is the vibrator dimensions (5mm x 5mm)," A "is the model (diagonal angle)," 90 "is the refraction angle (90 °) , “SH” means an SH wave probe), and the conventional probe 11 ′ is an SH wave probe “5Z5 × 5A90-SH” with an area of the contact surface 111 ′ of 128 mm ^2. Are comparing.
[0020]
As shown in FIG. 3, it can be seen that the probe 11 according to the present embodiment having a small contact area has an echo height that instantaneously reaches a predetermined level as compared with the conventional probe 11 ′. This is considered to be because the contact area between the probe and the material to be inspected tends to be instantaneous on a uniform thin film because the contact area is about 1/2 to 1/3 of the conventional one. Further, as shown in FIG. 3, as the load pressing the probe 11 is increased, the echo height is instantaneously increased and the time until stabilization is significantly shortened. However, if the pressing load of the probe 11 is excessively increased, the reaction force to the probe holder 12 that stores and holds the probe 11 and the scanning device for scanning the material to be inspected also increases. Therefore, the pressing load of the probe 11 is considered to be about 5 to 10 kg.
[0021]
Next, the probe holder 12 shown in FIG. 1 described above is free as a contact portion that protrudes downward at a position facing the contact surface 111 of the probe 11 so as to contact the material to be inspected. It is inserted between the bearing 121, the upper end 122 of the probe holder 12, and the surface 112 facing the contact surface 111 of the probe 11, and the probe 11 is perpendicular to the inspection object downward. And a spring member 123 as a first elastic member for urging the spring.
[0022]
Therefore, the positional relationship between the probe 11 and the probe holder 12 is not fixed and can be elastically changed via the spring member 123. Here, if the probe holder 12 is pressed against the material to be inspected so that the free bearing 121 of the probe holder 12 contacts the material to be inspected, the probe 11 sandwiched between the free bearings 121 is Since the contact surface 111 is urged vertically downward with respect to the material to be inspected by the spring member 123, the probe follows the uneven state of the surface of the material to be inspected in the range sandwiched between the free bearings 121. Thus, it is possible to perform a stable inspection while maintaining the contact surface 111 of 11 and the surface of the material to be inspected in a parallel state.
[0023]
In the ultrasonic flaw detector 1 according to this embodiment, the support member 13 is attached to the outer surface 124 of the probe holder 12 in a state where the probe holder 12 can rotate about the axis X. . By applying a pressing force to the upper end surface 131 of the support member 13, the pressing force is transmitted to the probe holder 12 via the axis X, and further, the spring member 123 is transmitted from the upper end portion 122 of the probe holder 12. Will be transmitted to the probe 11 via.
[0024]
In the ultrasonic flaw detector 1 according to this embodiment, the probe holder 12 is inserted between the inner side surface 125 of the probe holder 12 and the side surface 113 of the probe 11. Rubber members 126 as elastic members (in this embodiment, four rubber members in total with respect to one side surface 113 of the probe 11 are provided). Accordingly, the rubber member 126 is also used when scanning the inspection material with the probe 11 in contact with the surface of the inspection material (that is, moving the probe 11 relatively in the horizontal direction with respect to the inspection material). Since the position of the probe 11 is stabilized by the biasing force, the parallel state between the contact surface 111 of the probe 11 generated by the spring member 123 and the surface of the material to be inspected can be more reliably maintained. Is possible. In the present embodiment, a configuration including a total of eight rubber members 126 has been described. However, the present invention is not limited to this, and can be configured from various materials as long as they are elastic members such as spring members. In addition, the number and arrangement location thereof can be appropriately selected according to the pressing force applied to the probe 11 and the properties of the surface of the material to be inspected.
[0025]
As described above, according to the ultrasonic flaw detector 1 according to the present embodiment, the probe 11 having a small contact area is applied, and the contact surface 111 of the probe 11 and the surface of the inspection object are parallel. The probe holder 12 that can stabilize the state does not require the probe pressing and holding time until the echo height is stabilized, and can inspect the material to be inspected continuously by scanning. It is.
[0026]
Hereinafter, the features of the present invention will be further clarified by showing examples.
[0027]
(Example 1)
For an inspection material having an electric discharge machining slit formed on the surface of a flat plate material having a thickness of 6 mm, the ultrasonic flaw detector 1 shown in FIG. Flawed. In addition, “Sonicoat SH-B” manufactured by Nichiai Acetylene Co., Ltd. was used as the contact medium.
[0028]
FIG. 4 shows the result of automatic flaw detection under the above conditions. The vertical axis in FIG. 4 indicates the height of the reflected echo from the slit (relative value with 100% when stationary), and the horizontal axis indicates the scanning speed. As shown in FIG. 4, although the height of the reflected echo is lower than that at rest, it falls within a drop of about 4.5 dB and is stable with almost no fluctuation in the height of the reflected echo in the scanning speed range of 1 to 10 mm / s. It was found that automatic flaw detection was possible.
[0029]
(Example 2)
As shown in FIG. 5, the ultrasonic flaw detector 1 shown in FIG. 1 is attached to the rotating member 2 at a predetermined distance from the welded part P1 of the steel pipe P as the material to be inspected, and the guide rail surrounds the steel pipe P. Automatic flaw detection was performed by rotating the rotating member 2 by a motor drive (manually possible) along the line 3 (scanning speed 5 mm / s). The steel pipe P as the material to be inspected has an outer diameter of 200 mm and a wall thickness of 5.8 mm. Further, on the inner surface of the weld P1, the width is 0.1 mm, the length is 6 mm, and the depths are 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0, respectively, at substantially regular intervals along the circumferential direction. A total of six electric discharge machining slits of .8 mm and 1.0 mm were formed. In addition, as a contact medium, “Sonicoat SHN-B25” manufactured by Nichiai Acetylene Co., Ltd. was applied to the entire circumference of the range in which the probe 11 of the flaw detector 1 is in contact.
[0030]
FIG. 6 shows the result of automatic flaw detection under the above conditions (the waveform of the reflected echo observed with an oscilloscope). The vertical axis in FIG. 6 represents the height of the reflected echo from each slit (relative value with the height of the reflected echo from the slit having a depth of 0.3 mm as 100%), and the horizontal axis represents the predetermined position of the steel pipe P. The positions in the circumferential direction with reference to are shown. As shown in FIG. 6, it was found that all the electric discharge machining slits can be detected with a very good detection ability (S / N ratio). In FIG. 6, since the height of the reflection echo of the 0.3 mm slit having the smallest depth is displayed as 100%, the reflection echo from the slit having a depth of 0.4 mm or more is electrically saturated. In reality, a linear echo height was obtained according to the slit depth, and it was found that the inspection accuracy was sufficient for identifying the defect depth. Note that the automatic flaw detector (ultrasonic flaw detector 1, rotating member 2, and guide rail 3) described in the present embodiment replaces the guide rail 3 even when the outer diameter of the steel pipe P as the material to be inspected changes. It can be used only by itself and is extremely convenient.
[0031]
【The invention's effect】
As described above, according to the ultrasonic flaw detector according to the present invention, a probe having a small contact area is applied and the parallel state between the contact surface of the probe and the surface of the inspection object is stabilized. With the configuration of the probe holder that can be used, it is possible to perform flaw detection by continuously scanning the material to be inspected without requiring the probe pressing and holding time until the echo height is stabilized. In addition, an SH wave probe that transmits and receives SH waves is applied as a probe, and an extremely excellent effect that automatic flaw detection using the SH wave probe can be put into practical use is achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an ultrasonic flaw detector according to an embodiment of the present invention.
FIG. 2 is a rear view of the probe shown in FIG.
FIG. 3 shows a comparison result of changes in echo heights after a probe according to the present invention and a conventional probe are brought into contact with a predetermined material to be inspected.
FIG. 4 shows the results of Example 1 of the present invention.
FIG. 5 is a perspective view showing a schematic configuration of an automatic flaw detector used in Embodiment 2 of the present invention.
FIG. 6 shows the results of Example 2 of the present invention.
FIG. 7 is a rear view of a conventional probe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ultrasonic flaw detector 11 ... Probe 12 ... Probe holder 111 ... Contact surface 121 ... Contact part (free bearing)
123... First elastic member (spring member)
126 ... second elastic member (rubber member)

Claims (2)

A probe having a contact surface protruding downward so that only a range through which ultrasonic transmission / reception waves pass is in contact with the material to be inspected, and transmitting and receiving SH waves;
An ultrasonic flaw detector comprising a probe holder for storing and holding the probe,
The probe holder is
A contact portion protruding downward so as to contact the object to be inspected at a position facing the contact surface of the probe;
First inserted between an upper end portion of the probe holder and a surface facing the contact surface of the probe, and urges the probe vertically downward with respect to the material to be inspected. An elastic member of
A second elastic member interposed between a horizontal side surface of the probe holder and both horizontal side surfaces of the probe ;
The ultrasonic flaw detection apparatus according to claim 1, wherein the first elastic member urges the probe vertically with respect to a material to be inspected at a weight of 5 kg or more and 10 kg or less . An automatic flaw detector that automatically flaws a circumferential weld of a steel pipe,
The ultrasonic flaw detector according to claim 1 ,
An annular guide rail disposed so as to surround the steel pipe at a predetermined distance from the circumferential weld of the steel pipe;
Rotation that holds the ultrasonic flaw detector while rotating the ultrasonic flaw detector in the circumferential direction of the steel pipe while being in contact with the outer surface of the steel pipe and that is rotated by a motor along the guide rail An automatic flaw detection device comprising: a member.

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