JP2552178B2 - Ultrasonic flaw detection method for steel pipe welds - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic flaw detection method for a welded portion of a steel pipe and an apparatus therefor.

[Conventional technology]

FIG. 2 shows an example of the structure of a commonly used ultrasonic phased array device, and its structure and operation are disclosed in, for example, Japanese Patent Application Laid-Open No. 57-147053.

In FIG. 2, first, the array type probe 1 composed of N-channel narrow strip-shaped transducers 1 ₁ , 1 ₂ , ..., 1 _N has the transducers 1 ₁ , 1 ₂ ,. , 1 _N associated with N-channel ultrasonic transmitters 2 ₁ , 2 ₂ , ..., 2 _N , and N-channel ultrasonic receivers 3 ₁ , 3 ₂ , ... , 3 _N
Is connected to an ultrasonic receiver group 3 including

In addition, each of the ultrasonic transmitters 2 ₁ and 2 is included in the ultrasonic transmitter group 2.
An external trigger signal for generating an ultrasonic transmission pulse from ₂ , ..., 2 _N can be input from the transmission controller 4, and the transmission controller 4 is an ultrasonic transmitter used to transmit an ultrasonic wave. And the delay time set value of the external trigger signal given to each of them are programmed in advance by the computer 5. Thus, the ultrasonic waves can be emitted from the programmed transducers in a predetermined repetition period according to the delay time set according to the ultrasonic wave transmission direction and the ultrasonic wave focusing distance.

On the other hand, in the reception operation, first, ultrasonic waves are received by the array type probe 1 and the ultrasonic wave receiver group 3. This received signal becomes _N reception signals in the ultrasonic receivers 3 ₁ , 3 ₂ , ..., 3 _N , and after each reception signal is amplified, it is received in the A / D converter 7 by the reception controller. The signal from 6 is digitized while shifting the digital conversion start time and input to the adder 8. In the adder 8, the channels to be added are selected by the signal from the reception controller 6, the signals of the selected channels are added, the result is displayed on the display device 9, and the reception operation is completed. Here, in the reception controller 6, the delay time setting value that determines the start of digital conversion in the A / D converter 7 and the channel selected in the adder 8 are stored in the computer 5
Is programmed in advance by. The delay time is calculated by the computer 5 according to the ultrasonic wave reception direction and the focusing distance.

That is, the ultrasonic phased array device can deflect the ultrasonic beam in any direction by setting the delay time, and can focus the ultrasonic beam at any position. Further, the ultrasonic beam can be scanned without scanning the probe (without mechanically moving the probe). Such a scanning method is generally referred to as an electronic scanning method. In this electronic scanning method, as shown in FIG. A linear scanning method in which scanning is performed on a straight line such as a broken line, ..., A dashed line, and FIG.
As shown in the figure, the ultrasonic beam is changed by sequentially changing the ultrasonic wave transmission / reception direction.
..., there is a sector scanning method in which scanning is performed in a fan shape such as a one-dot chain line.

A method using the linear scanning method or the sector scanning method will be described below, but the state of propagation of the ultrasonic beam is actually as shown by the solid line, dotted line, and chain line in FIGS. 3 (a) and 3 (b). It should be expressed with a width, but it will be difficult to understand if a large number of beams overlap and overlap, so all the figures that will appear in the future will be represented by the solid, dotted, and dashed lines in Figures 4 (a) and (b). It is represented by a line that represents the locus of the center of.

When an ultrasonic phased array device is applied to flaw detection of a steel pipe, it is general to perform flaw detection by a linear scanning method, and an example thereof is disclosed in JP-A-61-18860.
The refraction angle θr and therefore the incident angles θi are all the same,
It is considered to change the deflection angle α. Deflection angle alpha may be varied by the delay time setting of the ultrasound transmission pulses applied to the transducer groups, and the theta _i the same alpha _{i (i} =
1, 2, ... are geometric conditions of the steel pipe and the probe (that is, the center position of the array type probe 1 in the XY coordinate system with the center O of the steel pipe as the origin and the inclination of the ultrasonic transmitting / receiving surface thereof, This can be obtained from the number of transducers in the transducer group and their intervals, the outer diameter R of the steel pipe 11, and this α _i can be set arbitrarily in the phased array, so that the refraction angles θr are all the same. is there.

However, in the case of an actual steel pipe, the cross-section of the steel pipe, that is, the shape of the surface that contains the propagation path of the ultrasonic beam is not necessarily a perfect circle, and when automatic flaw detection is performed on the actual flaw detection line, vibration or spatter of the steel pipe during transportation, etc. It is difficult to keep the inclination of the ultrasonic transmitting / receiving surface relative to the steel pipe surface constant due to the deposits on the steel pipe surface. Therefore, it is conceivable that the inclination of the probe deviates from the setting and the ultrasonic beam does not correctly aim at the target region of the welded portion of the steel pipe. That is, the incident angle θ _i is deviated, and the refraction angle θ _r is deviated, but as can be seen from Snell's law, when ultrasonic waves are incident on steel from water, a slight deviation of θ _i causes a large deviation of θ _r. As a result, the ultrasonic beam may largely deviate from the target flaw detection area. Therefore, the inventors of the present invention have proposed a method for making it possible to detect flaws in a target region of a steel pipe weld correctly even if the steel pipe has a non-circular cross section and the inclination of the probe is not as set. It is disclosed in Japanese Patent Publication No. An embodiment in the Japanese Patent Application No. 61-237722 is shown in FIGS. 6 (a) to 6 (c) and FIG. FIG. 6A shows a state in which the upper portion of the welded portion 12 of the steel pipe 11 is flaw-detected by one skip using the array type probe 1 coupled with the water of the couplant by the coupling device 10. Further, FIG. 6 (b) is an enlarged view of the portion where the ultrasonic beam is incident on the steel pipe in FIG. 6 (a).

Based on setting conditions such as the outer diameter / wall thickness of the steel pipe 11, the position / tilt of the probe 1, the desired incident angle, etc., the ultrasonic beam 2 is transmitted by a sector scan as shown in FIG.
Send 1, ..., 29. Sector scanning at this time enables transmission and reception of a large number of ultrasonic beams over a wide range around a desired incident angle set so as to reach a target flaw detection area. When the ultrasonic beams 21, ..., 29 are incident on the steel pipe 11, they are refracted according to Snell's law and the ultrasonic beams 31 ,.
However, the refraction angle varies depending on the shape of the steel pipe, the inclination of the probe, and the like. The ultrasonic beams 31, ..., 39 propagate through the steel pipe 11 and the welded portion 12, and if there is a defect in the propagation path, they are reflected and returned there.

The receiving operation is performed by the method as described above with reference to FIG.
All ultrasonic beams transmitted by sector scanning are received, and flaw detection data is obtained.

However, if the flaw detection is performed only by such sector scanning, it is unclear whether the ultrasonic beam propagates as set because the refraction angle changes depending on the shape of the steel pipe, the inclination of the probe, and the like as described above. So, the receiving probe for monitor
13 is arranged in the vicinity of the welded part 12, and the ultrasonic beam 31, ..., 39 is received by the ultrasonic receiver 14 while timing is controlled by the signal from the transmission controller 4, and the array type probe 1 and monitor The peak detector 15 performs peak detection on the signal in the gate set by the beam path calculated from the geometrical arrangement of the receiving probe 13 for use, and inputs the data to the computer 5. The computer 5 uses the transmission controller 4
, The data of the peak detector 15 is input corresponding to the ultrasonic beams 31 ,. In the computer 5, as shown in FIG. 6 (c), the size of the data of the peak detector is judged, the maximum value is calculated (5-1), and the ultrasonic beam corresponding to the maximum value is received by the monitor reception probe 13
Beam received by (hereinafter referred to as pilot beam)
(5-2). Further, the computer 5 inputs data such as the positions of the array type probe 1 and the monitor receiving probe 13, the scanning pitch of the sector scan, the outer diameter and the wall thickness of the steel pipe (5-3), and geometrically by these data. Based on the pilot beam, the number of ultrasonic beams (referred to as an offset beam) to the number of ultrasonic beams (referred to as the number of effective beams) that reach the upper portion of the target steel pipe welded portion 12 are calculated ( 5-4), the flaw detection data by the ultrasonic beam matching the calculation result is replaced with the flaw detection data by the already input ultrasonic beams 31 ,.
-6) is selected (5-5), and defect inspection is performed using this.

In the case of FIG. 6A, the ultrasonic beam 37 is a pilot beam, the offset beam is 34, the ultrasonic beams selected as flaw detection data are 34, 35, 36, and the effective beam number is 3.

However, it is difficult to place the monitor probe inside the steel pipe when the lower part of the welded part of the steel pipe is to be inspected by 0.5 skip (direct ultrasonic beam is applied to the defect without reflecting on the inner and outer surfaces of the steel pipe). Since it is long, the monitor probe is supported by, for example, a long rod. Therefore, when the monitor probe is arranged outside the steel pipe, the method as shown in FIG. 7 disclosed in Japanese Patent Application No. 61-237722 is considered. To be

In this method, the monitor reception probe 13 is attached to the weld 12
It is placed on the opposite side of the array type probe 1 by sandwiching it, and the direction of the ultrasonic beam is monitored by it. Based on the result, the ultrasonic beam reaching the lower part of the target steel pipe weld is judged and the beam is detected. The defect inspection is performed by using the flaw detection data obtained by.

[Problems to be Solved by the Invention]

In the case of Fig. 6 (a), which is a flaw detection on the upper part of the steel pipe welded part, or for flaw detection on the lower part of the steel pipe welded part, it is skipped 1.5 times.
In the case like the figure, there is no problem because the ultrasonic wave before reaching the weld 12 is monitored by the monitor reception probe 13.
In the case of Fig. 7 in which the lower part of the welded part of the steel pipe is flaw-detected by 0.5 skip, the ultrasonic wave after passing through the welded part 12 will be received by the monitor receiving probe 13, and especially the welded part like the UO steel pipe. It may happen that you can't accurately monitor what's rising. In the case of FIG. 7,
The ultrasonic beam of 47 is maximized by the monitor receiving probe 13, and the inspection may be performed by using the flaw detection result by the ultrasonic beams of 44 to 46. For example, as shown in FIG.
The ultrasonic beam of is reflected as shown by the arrow and received by the monitor receiving probe 13 more strongly than the ultrasonic beam of 47, so the inspection result by the ultrasonic beam of 42 to 44 was inspected and the target welded part It may happen that the lower part cannot be flaw-detected correctly.

Therefore, in the present invention, even if the lower portion of the welded portion of the steel pipe is flaw-detected with 0.5 skips, the target area can be properly flaw-detected.

[Means for solving the problem]

The present invention will be described with reference to FIG. 1. In the method of obliquely flaw-detecting a lower portion of a steel pipe welded portion using an ultrasonic phased array device, a large number of ultrasonic beams are applied to the entire flaw detection range by the phased array device. The ultrasonic beam and ultrasonic waves around the ultrasonic beam set so as to reach each of the flaw detection ranges (a, b, ...) Obtained by dividing the entire flaw detection range into a plurality of flaw detection ranges. The beam is gated based on the set propagation path of the ultrasonic beam to obtain the peak echo height, the maximum echo height of the peak echo heights is calculated, and the maximum echo height is set to the above. The ultrasonic beam (62, 63 ...) That is selected is the flaw detection result of the flaw detection range (a, b, ...).

[Action]

In the present invention, an ultrasonic beam (62 for a, 63 for b, 63, for b, ...
...) and the ultrasonic beam around it (61 for 62)
63 and 63, 62 and 64, ...) are gated based on the set propagation path of the ultrasonic beams 62, 63 ,. Echo height (Each peak echo height of 61-63, 62-64, ...)
The maximum echo height of the above is calculated, and the maximum echo height is set as the flaw detection result of the flaw detection range a, b, ... Even if there is a change in the propagation direction of the ultrasonic beam due to the non-circularity of the flaw detection cross section of the steel pipe and the change in the inclination of the probe when flaw detection is performed at the bottom of the weld with 0.5 skip, the target flaw detection area can be reliably inspected.

For example, the propagation direction of the ultrasonic beam is shifted, 62 is 61,
63 is at 62, ... 61 or vice versa
If 62 is the position of 62, 63 is the position of 63, ..., If the echo of 62 is the flaw detection range a, the echo of 63 is the flaw detection range b ,. However, if the maximum of the echoes of 61 to 63, 62 to 64, ... Is the flaw detection result of the flaw detection range a, b, ...
Ultrasonic beam 63 or 61 to 62, 64 or 62 to 63,
.. Instead, the flaw detection areas a, b, ... are to be flaw-detected (61 to 63, 62 to 64, ... The gate is a, b, ... It is determined based on the propagation paths of 62, 63, ...), and the flaw detection result is correct.

〔Example〕

Hereinafter, specific examples will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of the present invention performed using the ultrasonic phased array device shown in FIG. 2 described above, and an array type coupled with water as a contact medium by a coupling device 10. Welded part of steel pipe 11 using probe 1
The lower part of 12 is shown to be inspected.

Based on setting conditions such as the outer diameter / wall thickness of the steel pipe 11, the position / tilt of the probe 1, the desired incident angle, etc., an ultrasonic beam is transmitted by sector scanning according to a command from the computer 5. Sector scanning at this time enables transmission and reception of a large number of ultrasonic beams over a wide range around a desired incident angle set so as to reach a target flaw detection area. When the ultrasonic beam is incident on the steel pipe 11 as in FIG. 6 (b), it is refracted based on Snell's law to become an ultrasonic beam 61, ..., 69, whose refraction angle is the shape of the steel pipe or the probe. Fluctuates due to the inclination of. The ultrasonic beams 61, ..., 69 propagate through the steel pipe 11 and the welded portion 12, and if there is a defect in the propagation path, they are reversed and returned.

In the present invention, the entire flaw detection area under the welded portion is divided into a plurality of flaw detection areas. Each of the divided flaw detection areas is divided into the first flaw detection area.
In the figure, a, b, ... g, and beams 62, 63, ...
.. is an ultrasonic beam for flaw detection in the flaw detection areas a, b, ...

The receiving operation is performed by the method as described above with reference to FIG.
All ultrasonic beams transmitted by sector scanning are received, and flaw detection data is obtained.

Just by performing flaw detection by such sector scanning,
As mentioned above, the refraction angle changes depending on the shape of the steel pipe and the inclination of the probe, so it is unknown whether the ultrasonic beam propagates as set, but in the case of flaw detection with 0.5 skip, the ultrasonic beam is reflected inside the steel pipe. Since it directly hits the defect without causing the change, the change due to the shape of the steel pipe, the inclination of the probe, or the like is not increased, and it is considered that the influence due to the change is small. In other words, compared with the flaw detection such as 1.0, 1.5, 2.0 skip reflected on the inner and outer surfaces of the steel pipe, the ultrasonic beam of 0.5 skip may slightly deviate from the target flaw detection range, but it is considered that it does not largely deviate. .

This is shown in Fig. 10, and (a) 0.5
A comparison between skip and (b) 1.0 skip is shown. In 1.0 skip of FIG. 10 (b), the ultrasonic beam 73 as set is set.
On the other hand, when the array type probe 1 is tilted by +0.5, the ultrasonic beam 74 is largely separated, but it is 0. in FIG. 10 (a).
It can be seen that in the 5 skip, the ultrasonic beam 72 is not so far apart when the array type probe 1 is tilted by + 0.5 ° with respect to the set ultrasonic beam 71.

Therefore, the total flaw detection range by the ultrasonic beams 61, 63, ..., 69 is divided into several ranges, a gate is provided for each flaw detection range, and the ultrasound beam set so as to reach each flaw detection range and its surroundings. It is assumed that the computer 5 calculates the maximum echo height in each gate from among the ultrasonic beams, and inspects each flaw detection range based on the echo height.
That is, in the 0.5-skip flaw detection, the ultrasonic beam may be slightly out of the target flaw detection range, which is always covered by monitoring the maximum echo.

In Fig. 1, the flaw detection data by 61, 62, 63 ultrasonic beams are all gated based on the set propagation path of 62 ultrasonic beams to find the peak echo height, and the 3
The maximum echo height of the two is calculated, and the result is used as the flaw detection result in the area where 62 beams are flaw-detected. Similarly 62,63,64
As an example, a method of obtaining a flaw detection result in a range in which 63 beams are flaw-detected by the beam of No. 6 and finally a flaw detection result in a range in which 68 beams are flaw-detected by 67, 68, and 69 beams can be considered as an example.

Further, by using an array type probe having a larger number of transducers, linear scanning with the same refraction angles is performed, sector scanning is performed at each linear scanning point, and flaw detection is performed with the maximum echo in each sector scanning. But it's okay.

To add further explanation here, providing a gate for each of the above-mentioned flaw detection ranges means that for each flaw detection range a, b, ..., in the propagation path of the ultrasonic beam 62, 63 ,. It is to provide a gate based on. That is, regarding the flaw detection range a, the reception signal is passed for a predetermined time before and after the time required for the ultrasonic beam 62 to reciprocate in its propagation path (before and after the time when the beam is transmitted and the reflected wave returns). A means (this is called a "gate") that does not pass the received signal outside the period is provided. This also applies to the flaw detection ranges b, c, .... Further, the ultrasonic beam set so as to reach each flaw detection range is an ultrasonic beam 62, 63, ... which is designed to reach the flaw detection range a, b, ...・ We say.

Regarding the flaw detection range a, if the received signal is extracted by applying a gate to the ultrasonic beams 61, 62, 63 based on the propagation path of the ultrasonic beam 62, if the deflection is as planned, the ultrasonic beam
61 to 63 are as shown in FIG.
The propagation path of 3 is longer or shorter than that of 62, and its echo is blocked by the gate in whole or in part (the gate and the beam are wide), whereas the echo of the ultrasonic beam 62 is gated. Pass through and become maximum. The deflection is not as planned and the ultrasonic beam 61 is further shifted to the left, 62
At 61 and 63 at 62, the ultrasonic beam 6,
The echo of 62 is partially or wholly blocked by the gate, and the echo of the ultrasonic beam 62 passes through the gate and becomes maximum. On the contrary, if the ultrasonic beams 61 and 62 are displaced to the positions of 62 and 63, the echoes of the ultrasonic beams 62 and 63 become weak because some or all of them are blocked by the gate, and the echo of the ultrasonic beam 61 becomes Pass the gate and maximize. Therefore, regarding the flaw detection range a, if the echoes of the ultrasonic beam 62 and the ultrasonic beams 61 and 63 around the ultrasonic beam 62 are taken out through the gate of the flaw detection range a and the maximum echo is adopted, even if the deflection is as planned. It is possible to obtain the correct flaw detection result without using. Flaw detection range
The same applies to b, c, ....

 Next, an example of the flaw detection result is shown.

A sample obtained by applying a notch-shaped artificial defect to the weld portion of a UO steel pipe having an outer diameter of 76 cm (30 inches) and a wall thickness of 17.5 mm was subjected to repeated flaw detection by the method according to the present invention and the conventional method for comparison.

Array type probe, frequency 4MHz, element pitch
0.8mm, using 24 driving channels,
The probe is tilted so that the beam in the middle of the sector scan has a deflection angle of O ° and a refraction angle of 53 ° (case), and from this state, the probe is tilted 0.5 ° to 1 ° left and right (case). Was set and measured. An example of these measurement results (flaw detection waveforms) is shown in FIG. (A) is based on the method of the present invention, and (b) is based on the ordinary method. The vertical axis of the figure represents the height of the defect echo, and the horizontal axis represents time. The graphs having three in each of (a) and (b) correspond to the above cases to. It can be seen that the method according to the present invention of (a) gives the same measurement result in any case, and the reproducibility is much better than that of the usual method of (b).

〔The invention's effect〕

As described above, according to the present invention, when detecting a steel pipe welded portion by 0.5 skip, even if there is a change in the propagation direction of the ultrasonic beam due to the non-circularity of the steel pipe inspection cross section and the change in the inclination of the probe, the target The flaw detection area can be reliably inspected, and the reliability and reproducibility of the inspection are greatly improved.

Further, since the monitor reception probe is not necessary, the probe does not erroneously detect the pilot beam and cause the flaw detection result to be erroneous.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of an ultrasonic phased array device, FIGS. 3 and 4 are linear scanning and sector scanning explanatory diagrams, and FIG. 5 is a linear scanning. 6 (a) to (c) and FIGS. 7 to 9 show an embodiment of the prior application, and FIG. 10 shows the degree of fluctuation in 0.5 skip and 1.0 skip. And FIG. 11 is a diagram showing an example of a result in the example of the present invention. 1: Array type probe, 2: Ultrasonic transmitter group, 3: Ultrasonic receiver group, 4: Transmission controller, 5: Computer, 6: Reception controller,
7: A / D converter, 8: Adder, 9: Display device, 10: Coupling device, 11: Steel pipe, 12: Steel pipe weld, 13: Monitor receiving probe, 14: Ultrasonic receiver, 15: Peak detector, 21,22, ...
… 29: Ultrasonic beam, 31,32, …… 39: Ultrasonic beam, 41,4
2, ... 49: Ultrasonic beam, 51,52, ... 59: Ultrasonic beam,
61,62, …… 69: ultrasonic beam, 71,72,73,74: ultrasonic beam.

Front page continuation (72) Inventor Yoichi Fujikake 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Co., Ltd. Kimitsu Works Ltd. (72) Inventor Kiyomi Horikoshi 1 Kimitsu, Chizu Pref. Nippon Steel Co., Ltd. Kimitsu Works (72) Inventor Kiyohide Tamaki 1 Toshiba Town, Fuchu City, Tokyo Inside Toshiba Fuchu Factory, Ltd. (72) Inventor Yoshio Udagawa 728 Hishoe, Higashi Osaka City, Osaka Japan Claut Kramer Forster Stock Company Osaka Office (56) References JP-A-60-14166 (JP, A)

Claims (1)

(57) [Claims] 1. A method for oblique-angle flaw detection of a lower portion of a steel pipe weld using an ultrasonic phased array device, wherein a large number of ultrasonic beams are transmitted to and received from the entire flaw detection range by the phased array device. For the ultrasonic beam set to reach each of the flaw detection ranges obtained by dividing into a plurality of flaw detection ranges and the ultrasonic beams around it, apply a gate based on the propagation path of the set ultrasound beam Obtain the peak echo height, calculate the maximum echo height of the peak echo height,
An ultrasonic flaw detection method for a welded portion of a steel pipe, wherein the maximum echo height is set as a flaw detection result in a range in which the ultrasonic beam is set for flaw detection.