JPS62192655A - Ultrasonic flaw detecting method - Google Patents

Abstract

PURPOSE:To detect similar defects with the same detection sensitivity even if they are at different positions by varying the degree of convergence of an ultrasonic wave beams according to the length of a beam path and making sound pressure constant when the ultrasonic wave reaches a target weld zone. CONSTITUTION:An ultrasonic wave phased array converges an ultrasonic wave beam freely, so an ultrasonic wave beam 2 received by a block of vibrators 41-47 shown in a figure (b) is not converged because of its short beam path. Further, an ultrasonic beam 3 transmitted by a block of vibrators 514-520 in figure (a) is converged greatly because of its long path. Namely, when a linear scan is made, the way of convergence is varied according to respective beam paths to make the sound pressure constant when an ultrasonic wave beams reaches the target weld zone. Therefore, similar defects can be detected with the same detection sensitivity regardless of the positions of the defects.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oblique ultrasonic flaw detection method used, for example, in welded parts of steel pipes.

[Conventional technology]

Generally, in the angle ultrasonic flaw detection method for welded steel pipes, an ultrasonic beam is passed from a probe into the steel pipe through a couplant such as water or oil, and the ultrasonic beam is present inside the welded part. The presence or absence of a defect can be determined by the echo reflected from the defect. In this case, it is necessary to pass the ultrasonic beam so that the entire weld in the steel pipe wall thickness direction can be the target area for flaw detection, to ensure that the flaw detection sensitivity is constant regardless of the positional relationship between the defect and the probe, and to attenuate due to the flaw detection distance. It is important that the

Ultrasonic phased array devices that are currently in general use include narrow rectangular transducers 51, 52, . ......Using an array type probe 6 in which 5N transducers are lined up, the ultrasonic beam is scanned by electronically switching transmission and reception of ultrasonic waves from each transducer using a phase control device flN (for example, multi-real Materials Evaluati
on) July 1980 issue, pp. 34-37). Therefore,
Ultrasonic beams can be deflected in any direction and focused at any position. Furthermore, the ultrasound beam can be scanned without scanning the probe (without mechanically moving it). This type of scanning method is generally referred to as the electronic scanning method, and this electronic scanning method includes a linear scanning method in which an ultrasound beam is scanned in a straight line over the object to be inspected while sequentially switching multiple groups of transducers for transmitting and receiving ultrasound waves. and a sector scanning method in which an ultrasonic beam is scanned in a fan shape inside an object to be inspected while sequentially changing the timing of ultrasonic transmission and reception by a plurality of transducer groups.

FIG. 4 is a diagram showing oblique flaw detection of a welded part of a certain cross section of a steel pipe using the linear scanning method, and is an example showing how the upper half of the welded part of the steel pipe is detected in one skip. First, as shown in FIG. 4 (al), the ultrasonic beam 9 transmitted from a block consisting of a set of camera elements 5I to 57 enters the steel pipe 1 via the couplant, and after being reflected on the inner surface of the steel pipe. The weld seam 8 is reached and the ultrasonic beam 9 inside the weld
A block including a set of the same transducers 51 to 57 receives reflected echoes from defects existing in the range where the oscillators propagate. Next, as shown in FIG. 4B, flaw detection is performed using an ultrasonic beam 10 transmitted from a block in which the transducers 52 to 56 are set by shifting one transducer. Furthermore, similar flaw detection is performed while shifting the transducers one by one, and finally, flaw detection is performed using the ultrasonic beam 11 transmitted from a block consisting of one set of transducers 514 to 520, as shown in the same figure (C1). As shown in FIG. 5, the transducers 51 to 520 are divided into blocks and linear scanning is performed to detect flaws in the flaw detection range 17 in the upper half of the weld.

Further, as shown in FIG. 6, the flaw detection range 18 of the lower half of the weld is comprised of transducers 41, 42 . . . . are arranged in array type probes 7 in a skip of, for example, 0.5, and the entire cross section of the welded portion including the upper half is detected.

[Problem that the invention seeks to solve]

When inspecting the entire cross section of a weld as shown in Figures 5 and 6, the beam path of the ultrasonic beam transmitted from a block consisting of seven transducers (from the time the ultrasonic beam is transmitted until the time it is received) is As shown in FIG. The ultrasonic beams 20) received by the blocks differ greatly. On the other hand, since the ultrasonic beam is diffused when it enters the steel pipe or propagates inside the steel pipe, the sound pressure of the ultrasonic beam 19 and the ultrasonic beam 20 will be different when they reach the target weld. The same type/dimensions/
Detection sensitivity also differs for shape defects. That is, even if a defect can be detected by the ultrasonic beam 20, it may not be possible to detect it by the ultrasonic beam 19.

[Failure to solve the problem]

A feature of the present invention is that the degree of convergence of the ultrasonic beam is changed depending on the length of the beam path, so that the sound pressure when the ultrasonic beam reaches the target weld is kept constant.

In the ultrasonic phased array, the ultrasonic beam can be focused freely, so as shown in FIG. 1(b), the transducers 41 to 4
As for the ultrasonic beam 2 received by a block consisting of 7, the beam path is short, so it is not focused, and as shown in Fig. 1 (
As shown in a), the ultrasonic beam 1 transmitted from a block including a set of transducers 514 to 52'O has a long beam path and is therefore largely focused. That is, when performing linear scanning, by changing the focusing method according to each beam path length, it is possible to keep the sound pressure constant when the ultrasonic beam reaches the target welding part. Therefore, regardless of the location of the defect, similar defects can be detected with the same detection sensitivity.

Here, the effective beam width of the ultrasonic wave varies depending on the focusing method, but this is due to changing the number of transducers switched when sequentially scanning the ultrasonic beam. If it is long, reduce it (if you keep doing it, it won't be a problem.

FIG. 2 shows a schematic diagram of a system according to the invention.

The arithmetic/control unit 13 determines the focus size of the ultrasonic beam transmitted from each transducer block that performs linear scanning,
The phase control device 14 and pulser/receiver 15 transmit and receive ultrasonic waves while controlling the timing of transmitting and receiving ultrasonic waves from each transducer, and after processing the received signals in the arithmetic/control device 13, the flaw detection results are displayed on the display device 16. indicate.

Although the present invention has been described above using the example of angle-angle flaw detection of steel pipe welds, the method of the present invention can be applied to all angle-angle flaw detection using array type probes.

〔Example〕

FIG. 8 shows a schematic diagram of an experimental system in which angle flaw detection of a steel pipe was performed using an array type probe based on the present invention. 29 is a steel pipe to be tested, with an outer diameter of 245 mm and a wall thickness of 11 mm. 30 is a through drill hole with an outer diameter of 3.2 mm. 31 is an array type probe with a frequency of 5 MHz.
It is composed of two small oscillators, and the oscillator spacing is 1.5 cranes. 32 is a water tank for flaw detection, and 33 is a jig and a driving motor for fixing the array type probe and driving it up and down. 34 is a steel pipe rotation jig, 35 is a rotation jig 34
This is the motor that drives the. 36 is an array type probe 31
37 is a rail for sliding the array probe 31 in the X direction.

38 is a motor for moving the array type probe 31-' in the IY direction, and 39 is a rail for sliding the array type probe 31 in the Y direction. 40 is a control device for controlling the motors 33, 36, 38 for moving the array type probe 31 in the X direction, Y direction, and Z direction and the steel pipe rotation motor 35; 41 is a control device for controlling the array type probe 3;
This is an indicator that displays the position of the steel pipe in the X direction, Y direction, and Z direction and the rotation angle of the steel pipe.

FIG. 11 is an example of the results of flaw detection of a through-drill hole in a steel pipe performed using the system shown in FIG. 8.

Using the eight center transducers of the array type probe 31, the steel pipe 29 was rotated by the steel pipe rotation motor 35, and the beam path was changed to detect flaws of 0.5. 1.
0. 1,5. The height of the reflected echo from the through drill hole 30 at 2.0 skip is shown.

FIG. 11 (1) shows the results when flaw detection is performed without focusing. For example, in the case of 0.5 skip, the ultrasonic beam becomes 1.0 as shown in 42 in FIG. In the skip, it is diffused as shown at 44 in FIG. 10(a). 1.
5 and 2.0 skips are even more diffused. Therefore,
It can be seen that as the number of skips (corresponding to the distance between the play-type probe 31 and the through drill hole 30) increases, the reflected echo height decreases, and the detection sensitivity decreases with distance. FIG. 11(2) shows the results when the ultrasonic beam is focused according to the beam path according to the present invention. For example, in the case of 0.5 skip,
3, in 1.0 skip, Figure 10 (45 of bl)
It is focused to the extent that it does not spread like 1.5.2
．． The same applies to 0 skip. Therefore, it can be seen that the reflected echo height is almost constant regardless of the number of skips, and the detection sensitivity decreases with distance is small.

〔Effect of the invention〕

As described above, according to the present invention, similar defects can be detected with the same detection sensitivity, regardless of the difference in beam path length caused by the difference in the location of the defect. Furthermore, when drawing a defect tomographic image using measurement data, there is also the advantage that no correction is required based on the beam path.

In addition, in the explanation of FIG. 1, FIG. 4, FIG. 5, FIG. 6, and FIG.
1 [! However, there are no restrictions on the number of transducers constituting the array type probe or their size. 1st
In the explanation of FIGS. 4 and 7, in linear scanning,
Although the number of transducer blocks that emit sequentially scanned ultrasonic beams is seven, this may be any number, and the number of transducers that are switched when sequentially scanning ultrasonic beams is also
There is no need to limit it to one at a time.

In Figures 1, 5, 6, and 7, the entire cross section of the weld seam is tested using two play-type probes, but there are restrictions on the number of array-type probes and the number of transducers used for linear scanning. Not done.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the focusing control method of an ultrasonic beam according to the present invention, Fig. 2 is a detailed explanatory diagram of the present invention, Fig. 3 is an explanatory diagram of an ultrasonic phased array device, and Fig. 4 is a linear scanning Fig. 5 and Fig. 6 are explanatory diagrams showing the flaw detection range covered by linear scanning, Fig. 7 is a diagram explaining the difference in beam path due to the difference in the transducer block that transmits the ultrasonic beam, Fig. 8 is a schematic diagram of an experimental system for conducting oblique flaw detection of steel pipes using an array type probe based on the present invention, and Figs. 9 and 10 are oblique flaw detection experiments of steel pipes using an array type probe based on the present invention. FIG. 11 is a graph showing an example of the flaw detection results of a through-drill hole in a steel pipe according to the present invention. 1.29: Steel pipe, 2, 3, 9, 10, 11° 19.2
0, 42.43, 44.45: Ultrasonic beam, 41,
42. ......, 51, 52. ......: Vibrator, 6, 7.31 near array probe, 8: Welding seam, 13: Arithmetic/control device, 14: Phase control device, 15: Pulser/receiver-116: Display device,
17.18: Flaw detection range, 30: Penetrating drill hole,
32: Water tank, 33 Near array probe holding/vertical drive motor, 34: Steel pipe holding/rotation jig, 35: Rotation jig drive motor, 36 Near array probe X-axis drive motor, 37: x-axis slide Rail, 38 near array type probe Y-axis drive motor, 39: Y-axis slide rail, 40: Each drive motor control device, 4t: x, y
, Z position/T rotation angle indicator. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Figure 1 Figure 2 (b) Figure 3 Figure 8 (d) (b) Figure 9 Figure 10 H (Phantom Figure 11

Claims (1)

[Claims] In ultrasonic flaw detection using an ultrasonic phased array device, the ultrasonic transmission and reception timing of each transducer making up the phased array device is controlled so that the ultrasonic beam is focused according to the beam path. An ultrasonic flaw detection method characterized by keeping the pressure constant.