JPH0267957A - Ultrasonic flaw detecting method for welded part of steel pipe - Google Patents

Abstract

PURPOSE:To perform correct flaw detection of a target region when the flow detection of a part beneath a welded part is performed at a 0.5 skip by setting a position where ultrasonic wave beams are transmitted and received and a gate which receives the ultrasonic wave beams from the position of the welded part of a steel pipe. CONSTITUTION:Ultrasonic wave beams 61-69 are transmitted in a sector scanning pattern by a command from a CPU 5 based on the flowing conditions: the outer diameter and the thickness of a steel pipe 11; the position and the inclination of a probe 1; and the setting of a desired incident angle. The beams 61-69 are propagated in the steel pipe 11 and a welded part 12. When there is a defect in the path, the beam is reflected at the defect and returned. The entire flaw detecting range of the beams 61-69 is divided into several ranges. A gate is provided in every flaw detecting range. The maximum echo height in each gate is computed in the CPU 5 among the ultrasonic wave beams which are set so as to reach each flaw detecting region and the ultrasonic wave beams in the vicinity of the region. When the beam exceeds the predetermined threshold value, it is judged that there is a defect in the part beneath the welded part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic flaw detection method and apparatus for a welded portion of a steel pipe.

[Conventional technology]

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

In FIG. 2, first, an N-channel narrow rectangular vibrator 11+ 1! The array type probe 1 composed of +...r IN includes each vibrator 11, 1□,
...... N-channel ultrasonic transmitter group 2 including N-channel ultrasonic transmitters 2++2z+..., 2N attached to l, l, respectively, and N-channel ultrasonic receiver 3□3g+
...+3N is coupled to the ultrasonic receiver group 3.

In addition, each ultrasonic transmitter 2++ is included in the ultrasonic transmitter group 2.
It is possible to input an external trigger signal from the transmission controller 4 to generate an ultrasonic transmission pulse from 2g+...+2N. The channels of the device and the delay time settings of the external trigger signals applied to each of them are programmed in advance by the computer 5. As a result, ultrasonic waves can be emitted from each of the programmed transducers at a predetermined repetition period according to the delay time set according to the ultrasonic transmission direction and the ultrasonic focusing distance.

On the other hand, in the receiving operation, first, the array type probe 1 and the ultrasonic receiver group 3 receive ultrasonic waves. This received signal is sent to the ultrasonic receivers 33, 3□, . . .

3N becomes N received signals, and each received signal is further amplified and then digitized in the A/D converter 7 while shifting the digital conversion start time according to the signal from the reception controller 6, and then sent to the adder 8. is input.

The adder 8 selects the channels to be added based on the signal from the reception controller 6, adds the signals of the selected channels, displays the result on the display device 9, and completes the reception operation. Here, a delay time setting value for determining the start of digital conversion in the A/D converter 7 and a channel to be selected in the adder 8 are programmed in advance in the reception controller 6 by the computer 5. Further, this delay time is calculated by the computer 5 according to the receiving direction and focusing distance of the ultrasonic waves.

In other words, 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.

Also, without scanning the probe (without moving it mechanically)
Ultrasonic beam scanning is possible. This type of scanning method is generally called the electronic scanning method, and this electronic scanning method includes the method shown in Figure 3 (
As shown in a), while sequentially switching multiple transducer blocks for ultrasonic transmission and reception, the ultrasonic beam is changed to solid lines, broken lines, etc.
..., - Linear scanning method that scans on a straight line as shown by the dotted chain line, and ultrasound beam transmission method that sequentially changes the direction of ultrasound transmission and reception using multiple transducer blocks as shown in Figure 3 (b). There is a sector scanning method in which a sector scan is performed using solid lines, broken lines, . . . , -dotted and dashed lines.

Below, methods using the linear scanning method and sector scanning method will be explained, but the propagation of the ultrasonic beam is actually as shown in the solid two-dot line and -dot-dashed line in Figures 3 (a) and (b). However, it becomes difficult to understand when a large number of beams come out and overlap, so all the figures that will be compared from now on will be the solid one-dot line in Figures 4 (a) and (b).

-It shall be expressed by a line representing the locus of the center of the beam, such as a dotted chain line.

When using an ultrasonic phased array device to detect flaws in steel pipes, it is common to use a linear scanning method.
An example is disclosed in JP-A-61-18860, in which it is considered to change the deflection angle α so that the refraction angle θr and therefore the incident angle θi are all the same. Deflection angle α
can be changed by setting the delay time of the ultrasonic transmission pulse given to the transducer group, and αi to keep θl the same
(i-1+2,...) is the geometrical condition of the steel pipe and probe (i.e., for example,
- It can be determined from the center position of the array type probe 1 in the Y coordinate system, the inclination of its ultrasonic transmitting and receiving surface, the number of transducers in the transducer group and their spacing, and the outer diameter R of the steel pipe 11. Since α1 can be set arbitrarily, all refraction angles θ are the same.

However, in the case of actual steel pipes, the shape of the cross section of the steel pipe, that is, the surface that includes the propagation path of the ultrasonic beam, is not necessarily a perfect circle. Due to deposits on the steel pipe surface, it is difficult to maintain a constant inclination of the ultrasonic transmitting and receiving surface with respect to 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 area of the steel pipe weld. In other words, the angle of incidence θ is distorted, which in turn causes the angle of refraction θ to be distorted, but as we know from Snell's law, when an ultrasonic wave is incident on steel from water, a slight deviation in θ will greatly increase θ. This could cause the ultrasonic beam to miss the target flaw detection area.Therefore, the inventors discovered that even if the cross section of the steel pipe is non-circular, the inclination of the probe may not be as set. However, Japanese Patent Application No. 61-237722 discloses a method for correctly detecting flaws in the target area of a steel pipe weld. Shown in Figures (a) to (C) and Figure 7.
Figure (a) shows a steel pipe 1 using an array type probe l coupled with couplant water by a coupling device 10.
The upper part of the welded part 12 of No. 1 is detected with one skip. Further, FIG. 6(b) is an enlarged view of the portion in FIG. 6(a) where the ultrasonic beam is incident on the steel pipe.

Based on the setting conditions such as the outer diameter and wall thickness of the steel pipe 11, the position and inclination of the probe 1, and the desired angle of incidence, the ultrasonic beam 2 is scanned in sectors as shown in FIG. 6(b) according to instructions from the computer 5.
1. ......, 29 is sent. Sector scanning at this time allows a large number of ultrasonic beams to be transmitted and received over a wide range around a desired angle of incidence set to reach the target flaw detection area.

Ultrasonic beam 21. When the beam 29 enters the steel pipe 11, it is refracted based on Snell's law and becomes an ultrasonic beam 31. ..., 39, but the refraction angle varies depending on the shape of the steel pipe, the inclination of the probe, etc. The ultrasonic beam 31. ..., 39 is the steel pipe 11 and the welded part 12
If there is a defect in the propagation path, it will be reflected back.

The reception operation is performed in the same manner as described above in FIG. 2, and all the ultrasonic beams transmitted by sector scanning are received to obtain flaw detection data.

However, if flaw detection is only performed by such sector scanning, it is unclear whether the ultrasonic beam is propagating as set because the refraction angle varies depending on the shape of the steel pipe, the inclination of the probe, etc. as described above. Therefore, monitor reception probe 1
3 is placed near the welding part 12, and the ultrasonic beams 31, 39 are received by the ultrasonic receiver 14 while being timed by the signal from the transmission controller 4, and the array The peak detector 15 performs peak detection on the signal within the gate set by the beam path calculated from the geometric arrangement of the shaped probe 1 and the monitoring receiving probe 13, and inputs the data to the computer 5.The combiator 5 Since the transmission controller 4 is controlled, the data of the peak detector 15 is the ultrasonic beam 31.
It is input corresponding to No. 39.

The computer 5 determines the magnitude of the data of the peak detector as shown in FIG. 6(C), and calculates the maximum value.
-1), the ultrasonic beam corresponding to the maximum value is the beam received by the monitor receiving probe 13 (hereinafter referred to as the pilot beam) (5-2), and the computer 5 further uses the array probe 1 and the monitor receiving probe 1
Manually input the data such as the position of step 3, the scanning pitch of the sector scan, the outer diameter and wall thickness of the steel pipe 5-3), and use these data to geometrically calculate the number of ultrasonic beams (offset beams) with respect to the pilot beam. Calculate how many ultrasonic beams (referred to as the effective number of beams) reach the upper part of the target steel pipe welded part 12 from the number of ultrasonic beams (referred to as 5-4)
), the flaw detection data using the ultrasonic beam that matches this calculation result is transferred to the ultrasonic beam 31. ...
... Select from the flaw detection data (5-6) according to 39 (5-5), and perform defect inspection using this.

In the case of FIG. 6(a), the ultrasonic beam 37 is the pilot beam, the offset beam is 34, and the ultrasonic beams selected as flaw detection data are 34, 35.36, making the number of effective beams 3.

However, when detecting the lower part of a steel pipe weld with a 0.5 skip (directly applying the ultrasonic beam to the defect without reflecting it on the inner and outer surfaces of the steel pipe), it is difficult to place the monitor probe inside the steel pipe ( Since the steel pipe is long, the monitor probe must be supported by a long rod, for example). Therefore, if the monitor probe is to be placed outside the steel pipe, a method as shown in Fig. 7 disclosed in Japanese Patent Application No. 61-237722 is used. is possible.

In this method, the monitoring receiving probe 13 is
It monitors the direction of the ultrasonic beam, determines the ultrasonic beam that will reach the lower part of the target steel pipe weld based on the results, and Defect inspection is performed using beam-based flaw detection data.

[Problem to be solved by the invention]

In the case of Fig. 6 (a), which is the flaw detection of the upper part of a steel pipe weld, or the flaw detection of the lower part of a steel pipe weld, 1.5 skips are used.
In the case shown in the figure, there is no problem because the ultrasonic waves before reaching the weld 12 are monitored by the monitoring receiving probe 13, but in the case shown in Fig. 7, where the lower part of the steel pipe weld is detected with 0.5 skips, Since the ultrasonic waves that have passed through the welded portion 12 are received by the monitoring receiving probe 13, it may not be possible to accurately monitor the welded portion, especially for UO steel pipes where the welded portion is raised. In the case of Fig. 7, the ultrasonic beam of 47 is the maximum in the monitoring receiving probe 13, and inspection can be performed using the flaw detection results of ultrasonic beams of 44 to 46. For example, as shown in Fig. 9, the welded part The ultrasonic beam 45 was reflected at the bottom as shown by the arrow, and was received more strongly by the monitoring receiving probe 13 than the ultrasonic beam 47, so the inspection was performed using the flaw detection results from ultrasonic beams 42 to 44, and the target was not detected. It is also possible that the lower part of the weld cannot be detected correctly.

Therefore, in the present invention, even when testing the lower part of a steel pipe weld with 0.5 skips, it is possible to accurately test the target area.

[Means to solve the problem]

The present invention is a method for angle inspection of the lower part of a steel pipe weld using an ultrasonic phased array device, in which a large number of ultrasonic beams are transmitted and received by sector scanning, and the position at which the ultrasonic beam is transmitted and received and the position of the steel pipe weld are disclosed. Set a gate to receive the reflected ultrasonic beam from the gate, select the reflected ultrasonic beam with the maximum echo height within the gate, and detect a defect at the bottom of the steel pipe weld when the reflected ultrasonic beam is above a predetermined threshold level. It is characterized by determining that there is.

[Effect]

According to the present invention, when detecting the lower part of a steel pipe weld in 0.5 skips, even if there is a variation in the propagation direction of the ultrasonic beam due to the non-circularity of the test cross section of the steel pipe and the change in the inclination of the probe, the target The flaw detection area can be reliably inspected.

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

FIG. 1 is a schematic diagram showing an embodiment of the present invention carried out using the ultrasonic phased array device shown in FIG. It shows how the lower part of the welded part 12 of the steel pipe 11 is detected using the probe l.

Based on setting conditions such as the outer diameter and wall thickness of the steel pipe 11, the position and inclination of the probe l, and the desired angle of incidence, an ultrasonic beam is transmitted in sector scanning according to a command from the computer 50. Sector scanning at this time allows a large number of ultrasonic beams to be transmitted and received over a wide range around a desired angle of incidence set to reach the target flaw detection area. The ultrasonic beam is shown in Fig. 6 (
Similarly to b), when the ultrasonic beam is incident on the steel pipe 11, it is refracted based on Snell's law and becomes an ultrasonic beam 61. ..., 69, but the refraction angle varies depending on the shape of the steel pipe, the inclination of the probe, etc. The ultrasonic beam 61. ..., 69 propagates inside the steel pipe 11 and the welded part 12, and if there is a defect in the propagation path, it is reflected there and returns.

The reception operation is performed in the same manner as described above in FIG. 2, and all the ultrasonic beams transmitted by sector scanning are received to obtain flaw detection data.

If flaw detection is only performed by sector scanning, it is unclear whether the ultrasonic beam is propagating as set because the refraction angle varies depending on the shape of the steel pipe and the inclination of the probe, as mentioned above. In the case of flaw detection at The impact is thought to be small. In other words, 1, 0. Compared to flaw detection with 1.5, 2.0 skips, etc., the ultrasonic beam with 0.5 skips may deviate slightly from the target flaw detection range, but it is thought that it will not deviate significantly.

This is illustrated in Figure 10, where (a) 0.
A comparison between 5 skip and (b) 1.0 skip is shown.

With a skip of 1.0 in Figure 10), the ultrasonic beam 74 when the array probe l is tilted +0°5 will be far apart from the ultrasonic beam 73 as set, but as shown in Figure 1θ (a). In the 0,5 skip, the array type probe 1 is also +〇,
It can be seen that when tilted by 5 degrees, the ultrasonic beam 72 does not move far apart.

Therefore, the ultrasonic beams 61, 63 .・・・・・・、6
The total flaw detection range according to 9 is divided into several ranges, a gate is provided for each flaw detection range, and the computer 5 selects each of the ultrasonic beams set to reach each flaw detection range and the surrounding ultrasonic beams. The maximum echo height within the gate will be calculated, and each flaw detection range will be inspected based on that echo height. That is, in flaw detection with 0.5 skips, the ultrasonic beam may deviate slightly from the target flaw detection range, but this is compensated for by always monitoring the maximum echo.

In Figure 1, the flaw detection data from ultrasonic beams 61, 62, and 63 are all gated based on the set propagation path of the 62 ultrasonic beams to obtain the peak echo height, and the peak echo height is determined by the three maximum echo heights. Calculate the result as 62
This is the flaw detection result for the range detected by the beam. Similarly 62
．． As an example, use a beam of 63.64 to obtain the flaw detection results for the range detected by beam 63, and finally use a beam of 67°68.69 to obtain the flaw detection results for the range detected by beam 68. Conceivable.

Another method is to use an array type probe with a larger number of transducers to perform linear scanning with all the refraction angles the same, perform sector scanning at each linear scanning point, and detect defects using the maximum echo in each sector scanning. But that's fine.

〔Example〕

U with outer diameter 76 cm (30 inches) and wall thickness 17.5 rIm
Samples of O-steel pipes with notch-shaped artificial defects in the welded portions were subjected to repeated flaw detection using the method of the present invention and the conventional method, and were compared.

The array type probe used had a frequency of 4 MHz, an element pitch of 0.8 mm, and a drive channel number of 24 channels, and the probe was rotated so that the beam in the middle of sector scanning had a deflection angle of 0 and a refraction angle of 53°. In addition, the probe was further changed artificially by 0.5 to 1°.

An example of the result of the flaw detection waveform is shown in FIG.

(a) is obtained by the method of the present invention, and (b) is obtained by the conventional method. It can be seen that the method according to the present invention has much better reproducibility than the conventional method.

〔Effect of the invention〕

As described above, according to the present invention, when a steel pipe weld is tested with 0.5 skips, even if there is a variation in the propagation direction of the ultrasonic beam due to the non-circularity of the steel pipe test cross section and the change in the probe inclination, , the target flaw detection area can be reliably inspected, greatly improving the reliability and reproducibility of inspection.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the implementation state of the present invention, Fig. 2 is an explanatory diagram of an ultrasonic phased array device, Figs. 3 and 4 are explanatory diagrams of linear scanning and sector scanning, and Fig. 5 is linear scanning. Fig. 6 (a) to (C) and Fig. 7 to 9 are diagrams showing an example of the method for flaw detection of steel pipes, Fig. 10 is a 0.5 skip and a 1.0 skip. FIG. 11 is a diagram showing an example of the results in an example of the present invention. 1 Near array 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 welded part, 13: Receiving probe for monitoring, 14: Ultrasonic receiver, 15; Peak detector, 21.22. ...29: Ultrasonic beam, 3
1,32. ...39: Ultrasonic beam, 41.4
2.・・・・・・49: ti sound wave heem, 51.5
2. ...59: Ultrasonic beam, 61.62.
...69: Ultrasonic beam, 71.72,73
．． 74: Ultrasonic beam.

Claims (1)

[Claims] 1. In a method of angle inspection of the lower part of a steel pipe weld using an ultrasonic phased array device, a large number of ultrasonic beams are transmitted and received by sector scanning, and the reflection from the position where the ultrasonic beam is transmitted and received and the position of the steel pipe weld is detected. Set a gate to receive the ultrasonic beam, select the reflected ultrasonic beam with the maximum echo height within the gate, and determine that there is a defect in the lower part of the steel pipe weld when the reflected ultrasonic beam is above a predetermined threshold level. An ultrasonic flaw detection method for steel pipe welds, which is characterized by determining that.