JPS63261156A - Ultrasonic flaw detecting method and probe - Google Patents

Abstract

PURPOSE:To make the echo of an ultrasonic wave projected by a longitudinal wave probe large and to improve flaw detection performance for an austenite steel weld zone by sending the longitudinal wave from an oblique longitudinal wave probe and receiving a mode-conversion transverse wave echo generated on the opening-side surface of a defect. CONSTITUTION:The longitudinal wave 7 is projected on the plane defect 3 open on one surface of the austenite steel weld zone 2 from the oblique longitudinal wave probe 6 mounted on the opposite surface and the mode-conversion transverse wave echo 8 generated on the opening-side surface is received to detect the plane defect. Further, the slanting surfaces of a couple of wedges 18a and 18b which have a sound insulator between them are formed on vibrator fitting surfaces 19a and 19b which slant outward at a proper angle in a plane crossing an ultrasonic wave beam, and a transmitting vibrator 20 and a receiving vibrator 21 which have partial spherical surfaces of different curvature are mounted on those fitting surfaces 19a and 19b; and the transmitting vibrator 20 projects the longitudinal wave on the plane defect at the austenite steel weld zone 2 and the receiving vibrator 21 receives its mode-conversion transverse echo.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic flaw detection method and a probe suitable for flaw detection of austenitic stainless steel containers such as atomic couplants, and welded parts of piping.

[Conventional technology]

Traditionally, austenitic stainless steel containers.

As shown in the vertical cross-sectional view of FIG. 7, ultrasonic beams for welded parts of piping, etc., are used to detect crack defects 3 included in austenitic steel welded parts 2 of austenitic steel base metal 1. , an ultrasonic longitudinal wave 7 that is also transmitted to the austenite structure is projected onto the welding part 2 at an angle of refraction θ from an oblique longitudinal wave probe 6 placed on the surface 5 of the base material, to detect the damage from the crack defect 3. The defect size is measured by receiving echoes.

However, when the ultrasonic longitudinal wave 7 is incident on the weld corner 4' as shown in the figure for a crevice surface defect B opened in the bottom surface 4 of the base material, K, as shown in FIG. The drawback is that the ultrasonic echo is extremely low at most refraction angles, making accurate detection difficult.

[Problem that the invention seeks to solve]

The present invention was proposed in view of the above circumstances, and
An object of the present invention is to provide an ultrasonic flaw detection method and a probe that can thicken the echoes of ultrasonic waves projected from a longitudinal wave probe and improve the flaw detection performance for austenitic steel welds.

[Failure to solve the problem]

To avoid this, the present invention projects a longitudinal wave from an oblique longitudinal wave probe placed on the opposite surface onto a planar defect with an opening on one side of the austenitic steel weld, and generates a mode on the opening side surface. When the converted transverse wave echo is received and the above-mentioned planar defect is detected, a pair of inclined surfaces with a sound insulating material sandwiched between them are tilted outward at an appropriate angle to each other in a plane perpendicular to the ultrasonic beam. A transducer (G transducer) and a receiver/shock transducer are respectively placed on the transducer mounting surface, and are partially spherical with different curvatures on both of the transducer mounting surfaces. The present invention is characterized in that a longitudinal wave is projected onto a planar defect and the mode-converted transverse wave echo thereof is received by the receiving transducer.

[For production]

With the above-described configuration, it is possible to obtain an ultrasonic flaw detection method and probe that can thicken the echo of the ultrasonic waves projected from the longitudinal wave probe and improve the flaw detection performance for austenitic steel welds.

C Embodiment 7] The fourth embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the ultrasonic flaw detection method of the present invention, and FIG. 2 is a waveform diagram of transverse waves in FIG. 1. , Fig. 3 and Fig. 4 are explanatory diagrams showing the applicable defect range of the method of the present invention, Fig. 5 is a longitudinal cross-sectional view showing the ultrasonic beam and focusing method in the method of the present invention, and Fig. 6 is a diagram illustrating the method of focusing. FIG.

First of all, referring to the bottom of Fig. 1, a crack defect 3 is included inside the austenitic steel welded part 2 of the austenitic steel base metal 1, and this crack defect 6 has a crack surface shape that opens on the bottom surface 4 of the base metal. Assume defects. An ultrasonic longitudinal wave 7 with a refraction angle θ1 incident from the oblique longitudinal wave probe 6 placed on the base material surface 5 hits the crack defect 3 and is reflected, and then hits the bottom surface 4 and forms a mode-converted transverse wave 8 there. is generated and reflected. This transverse wave 8 is received by the longitudinal wave probe 6 at an angle θ2, produces a large echo, and is displayed on the CRT 10 of the flaw detector 9.

On the CRT 10 of the flaw detector 9, as shown in FIG. Because of the long path, the two can be separated and easily identified.

In this way, in the method of the present invention, the incidence of the longitudinal wave 7 on a part of the corner with low echo is avoided, the longitudinal wave 7 is applied to the upper part of the corner, and the mode conversion transverse wave 8 with high echo generated at the bottom surface 4 is received. By doing so, it is possible to accurately detect echoes reflected from crack defects and cavities.

In addition, the position where the longitudinal wave 7 hits the crack defect 6 in order to generate this mode conversion transverse wave) 3 is calculated as shown in Figures 6 and 4.
Since it is a value of 2 that changes depending on the A+i angle θ1 in the figure, it is inappropriate for shallow crack defects of 20% or less of the base material thickness.

Furthermore, in order to make the method of the present invention work effectively, as shown in FIG. 5, if the ultrasonic beam is narrowed down, a better result on an 8/N basis can be expected. In this case, if the probe has only one vibrator, focusing will be difficult because the beam path at the defect surface will be different. Therefore, by using a split type probe 16 in which the transducer is divided into transmitting and receiving transducers, and shifting the focal length of the transmitting transducer and receiving transducer at the defective field to be different, the ultrasonic waves can be focused on the defective field. becomes easier.

FIG. 6 shows the details of the split type probe 16, which consists of a pair of plastic "M18a, 1" with a sound insulating material 17 interposed therebetween.
03. facing evening in a plane perpendicular to the beam of 8 b. θ4
(θ6-・θ4) Slanted transducer tray/['' surface 19 a
, 19 bfK, partially spherical transmitting oscillators 20. each having a curvature. A receiving vibrator 21 is attached.

The factors that determine the focusing range of this split type probe 16 are the curvature and diameter of the transducer 20.21, and the transducer mounting surfaces 19a, 1.
9b progression θ3. By appropriately selecting θ4, it is possible to effectively focus the ultrasonic beam on the six cracked defect surfaces.

〔Effect of the invention〕

In short, according to the present invention, a longitudinal wave is projected from an oblique longitudinal wave probe placed on the opposite surface to a planar defect 1 having an opening on one side of an austenitic steel weld, and generated on the opening side surface. Detecting the above-mentioned planar defects by receiving mode-converted transverse wave echoes, and making the inclined surfaces of a pair of curtains with a sound insulating material sandwiched between them tilt outward at an appropriate angle to each other in a plane perpendicular to the ultrasonic beam. A transmitting vibrator and a receiving vibrator are formed on the vibrator mounting surface, and the transmitting vibrator and the receiving vibrator are respectively mounted and the austenitic steel is welded from the transmitting vibrator. In addition to projecting a longitudinal wave onto a planar defect in the area and receiving its mode-converted transverse wave echo with the receiving transducer, the echo of the ultrasonic wave projected from the longitudinal wave probe is increased;
The present invention is extremely useful industrially because it provides an ultrasonic flaw detection method and probe that can improve flaw detection performance for austenitic steel welds.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing an embodiment of the ultrasonic flaw detection method of the present invention, Fig. 2 is a waveform diagram of the transverse wave shown in Fig. 1, and Fig. 3 and Fig. 4 are explanations showing the applicable defect range of the method of the present invention. 5 is a vertical cross-sectional view showing the ultrasonic beam focusing method in the method of the present invention,
FIG. 6 is a perspective view showing the entire probe in FIG. 5. FIG. 7 is a longitudinal cross-sectional view showing a conventional ultrasonic flaw detection method, and FIG. 8 is a chart showing the echo height of the same. DESCRIPTION OF SYMBOLS 1... Orstenitic steel base material, 2... Austenitic steel bath contact part, 3... Cracking defect, 4... Base metal bottom surface,
5... Base material surface, 6... Longitudinal wave probe, 7... Ultrasonic longitudinal wave, 8... Mode conversion transverse wave, 9... Flaw detector, 10
...CR, T, 11... Transverse wave echo, 12... Longitudinal wave echo, 16... Split type probe, 17... Sound insulation layer,
18a, 18b...Plastic wedge, 19a, 19
b... Vibrator mounting surface, 20... Transmitting vibrator, 21.
...Receiving transducer. Agent: Masafumi Tsukamoto, Patent Attorney ν) cpz! -1 shi (Miya+-1 Gorori? I crab-[Ding

Claims (2)

[Claims] (1) A longitudinal wave is projected onto a planar defect with an opening on one side of the austenitic steel weld from an oblique longitudinal wave probe placed on the opposite surface, and the mode conversion shear wave echo generated on the opening side surface is detected. An ultrasonic flaw detection method characterized by detecting the above-mentioned planar defects by receiving signals. (2) The inclined surfaces of a pair of wedges with a sound insulating material sandwiched between them are formed on the transducer mounting surfaces and are inclined outward at an appropriate angle to each other in a plane perpendicular to the ultrasonic beam, and both of the transducer mounting surfaces A transmitting transducer and a receiving transducer each exhibiting partial spherical shapes with different curvatures are mounted on the transmitting transducer.Longitudinal waves are projected from the transmitting transducer onto a planar defect in the austenitic steel weld, and the mode-converted transverse wave echo is transmitted to the receiving transducer. An ultrasonic probe characterized by receiving signals at