JPS6089748A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To perform flaw detection at the dead zone part of corner part of a material to be detected by making a creeping wave incident from the surface of the material to be detected, and receiving its reflected wave. CONSTITUTION:A flaw detector 6 is equipped with a longitudinal critical angle ultrasonic wave (creeping wave) probe 5 and the creeping wave 8 is emitted to the material 1 to be detected. In this case, the wave 8 is emitted from the surface of the material 1 to a corner part 7. The creeping wave incident to the material 1 to be detected propagates the material 1 toward the corner part 7 along its section-directional surface to perform the flaw detection. Consequently, the flaw detection of the corner part which is improssible by a conventional method is attained. The creeping wave oscillaters as a compressional wave parallel to the traveling direction, so the influence of a water drop, etc., on a propagation path is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic flaw detection device for detecting internal defects in a test material having a cross-sectional shape having any corner portion other than a square billet steel material.

[Prior art]

Ultrasonic flaw detection for surface or internal defects in steel materials has conventionally been carried out using the vertical method, in which ultrasonic waves are applied directly below the surface of the material to be inspected, the oblique method, in which ultrasonic waves are applied obliquely from the surface using refraction, and the surface wave is used. The surface wave method, which detects flaws only in the surface layer, is used individually or in combination.

However, in these conventional ultrasonic flaw detection methods, if the cross-sectional shape of the material to be tested has corners, a so-called dead zone, which is impossible to detect, occurs due to restrictions on the location of the probe on the outer surface of the material to be tested. However, no matter how the various methods are combined, there are still parts that cannot be detected. For example, if we take a square billet steel material as an example of a material to be inspected, as shown in FIG. 1 (al), the globe 2a [
Therefore, in the vertical method in which the ultrasonic waves 3a are emitted directly downward, a dead zone occurs on the surface of the entire circumference of the square billet cross section, under the epidermis, and at the four corners, as shown by the shaded area 4a in the same figure (bl). In addition, as shown in Fig. 82 (al), in the bevel method in which the ultrasonic wave 6b is applied obliquely from the surface with the probe 2b, the four corners and the central part are A dead zone occurs, and in the surface wave method in which surface flaw detection is performed by emitting a surface wave 3c from the probe 2c as shown in Fig. 6 (al), the area shown by the shaded area 4c is excluded as shown in Fig. 6 (cl). Although it is possible to detect surface defects around the entire circumference, if there are water droplets, etc. on the path of the ultrasonic wave 3c, it will cause significant attenuation and false echoes, leading to false detection, and avoiding the disadvantage that stable flaw detection is difficult. I can't do it.

[Summary of the invention]

The present invention has been made to eliminate these drawbacks of the conventional method, and is capable of detecting dead zones at the four corners, including the surfaces that still remain even with the combination of the vertical method and the oblique method. The present invention aims to provide an ultrasonic flaw detection device that is not adversely affected by the presence of water temperature, etc., and can even be used in combination with the vertical method or the oblique method.

In other words, the feature of the ultrasonic flaw detection device of the present invention is that longitudinal critical angle ultrasonic waves (creeping waves) are incident on the surface of a test material having a cross-sectional shape with corners in the cross-sectional direction. It is equipped with a creeping wave flaw detection system that detects defects in the corners of the test material from the reflected waves.

Longitudinal wave critical angle ultrasonic wave (creeping wave) used for flaw detection in the present invention r, I', i Incident angle θ as shown in Figure 4
The maximum energy is obtained near the refraction angle of 90 degrees of the longitudinal wave incident on the boundary surface, and the incident angle is at the sound speed C1 of the incident material and the sound speed C2 of the refracting material. is given by the following equation.

θ=s in-” (Cs/Cz) ”’ (1)
Now - as an example, if the incident material is a normal organic gas (cl = 2
720 mlB) steel material (Cz=59
00 m/s) The creeping wave emission condition, that is, the incident angle θ, is approximately 27.4 degrees from the above equation (1). At this time, a refracted transverse wave with a refraction angle of about 36 degrees also propagates in the steel with very little energy, but most of the energy of the propagating wave is occupied by the creeping wave.

A creeping wave is a critical angle wave with a longitudinal wave oblique angle.17 The main energy propagates near the subcutaneous area, including the surface of the specimen, and at the subsurface propagation depth, that of the surface wave is practically one wavelength. On the other hand, it can range from several layers to more than a dozen mouths. In addition, in the case of a surface wave, the material particles in the propagation path vibrate in an elliptical rotation motion on the material surface, whereas in the case of a creeping wave, they vibrate along the particle surface as a compressional wave parallel to the direction in which the ultrasonic wave travels. For this reason, in surface waves, the energy is significantly attenuated by water films and water droplets that exist on the ultrasonic propagation path, and at the same time generates false echoes, whereas in creeping waves, the energy is largely attenuated by these effects. It is possible to detect flaws deep under the skin in stable conditions.This method has an extremely advantageous feature over the surface wave method in that it does not require treatment to remove water from the surface of the material being tested prior to flaw detection. This can be said to be a point.Since it is possible to detect defects in areas that cannot be detected by either the vertical method or the oblique method,
When used in combination with each of these methods, it becomes possible to detect complete damage in the cross section of the test material.

[Embodiments of the invention]

FIG. 5 (al is a block diagram showing the configuration of the main parts of the device according to the embodiment of the present invention, and the creeping wave probe 5
and a flaw detector main body 6. The flaw detector main body 6 includes a probe 5
Since there is no normal type and ah including the driving of the , the signal processing of the received echoes, and the display/recording unit, the description thereof will be omitted. The creapin wave probe 5 moves from the surface of the material 1 to the corner 7.
Ultrasonic waves (creeping waves) 8 at a critical angle with respect to longitudinal waves are emitted diagonally toward the object, and the echoes thereof are received. The probe 5 is preferably placed on the flat surface of the test material 1 at a distance of 0.5 to 1. It is arranged through a water gap 9 of approximately Ow thickness. Eight ultrasonic creeping waves emitted from the probe 5 propagate along the surface of the specimen 1 in the cross-sectional direction (direction perpendicular to the longitudinal direction) toward the corner 7 in the interior including the surface. At the corner portion 7, a general steel material (for example, a square billet) is processed to have a curved surface (R) with a normal radius of curvature, so that the component reflected in the direction of the probe at the corner portion is extremely small. Normally, so-called corner reflection echoes do not occur.

51) is an explanatory diagram showing an example of the probe arrangement and the flaw detection area according to the present invention in a cross section of a square billet in order to contrast with Fig. 1 (bl) and Fig. 2 (bl), excluding the shaded area 1o. 1
1 is the area that can be detected by the creeping wave flaw detection system of the present invention. This region 11 is shown in Fig. 1 (bl) and Fig. 2 (b).
It includes the insensible distortion portion remaining by any of l.

As shown in this FIG. It is possible to detect defects in corners. 3. Figure 6 shows the probe arrangement and test hole (defect) position for flaw detection of a square billet according to the present invention, and shows the flaw detection by the probe at each arrangement position. The resulting echo waveform is shown in Figure 7 (al (b) (
Shown in c). An echo waveform as shown in FIG. 7 (al) is obtained by the probe 5a placed at position A in FIG. Eco a, b + e
is appearing. d in FIG. 7 fal is displayed as a defective echo of the test hole d in FIG. 6 detected by the refracted transverse wave ultrasound simultaneously transmitted from the creeping wave probe 5a. Further, an echo waveform as shown in FIG. 7 (bl) is obtained by the probe 5b placed at position B, and a defective echo e appears at a position on the time axis corresponding to the test hole e. Place @C
The probe 5c placed at the corner is aimed at a corner where there is no test hole, and the resulting echo waveform shows that it is a sound area as shown in FIG. 7(c).

〔Effect of the invention〕

As described above, according to the present invention, effective ultrasonic flaw detection can be performed on dead areas at corners that could not be detected by the conventional vertical method, oblique angle method, or surface wave method. There is no need for pre-treatment such as water removal treatment on the surface of the test material as in the case of . In addition, by making the probe follow the surface, it is virtually unaffected by changes in the cross-sectional shape of the material to be tested (creating waves can be prevented, making stable flaw detection possible, and compared to conventional vertical flaw detection). It is possible to inspect the entire cross section of a specimen with a rectangular cross section by using it in combination with the flaw detection method and the oblique angle method.If the echo signals of each flaw detection method are processed separately, it is also possible to distinguish between surface defects and internal defects.

[Brief explanation of the drawing]

Figure 1 (al (bl) is an explanatory diagram showing the vertical method of ultrasonic flaw detection and a schematic diagram showing the dead zone of the flaw detection cross section,
Figure (al) (b) is an explanatory diagram showing the oblique angle method ultrasonic flaw detection method and a schematic diagram showing the dead zone of the flaw detection cross section, and Fig. 3 (
al (b) is an explanatory diagram showing the ultrasonic flaw detection method of the surface wave method and a schematic diagram showing the dead zone of the flaw detection cross section by it, FIG. FIG. 5 (al is a block diagram showing the configuration of the main part of the apparatus according to the embodiment of the present invention, FIG. 5 (bl is an explanatory diagram showing an example of the arrangement of the probe according to the present invention and the flaw detection area for the cross section of a square billet, Fig. 6 is an explanatory diagram showing the probe arrangement and the position of the test hole (defect) for flaw detection of a square billet according to the present invention, and Fig. 7 (al (bl) (c) shows the previous flaw detection results with each probe. It is an echo waveform diagram shown. 1... Test material, 5.5m, 5b, 5c... Creeping wave probe, 6... Flaw detector main body, 7... Corner part, 8... ...Ultrasonic Creeping Wave, 9...
water gap. Agent Patent Attorney Sanro Kimura

Claims (1)

[Claims] A creeping wave flaw detection system that applies longitudinal critical angle ultrasonic waves from the surface of a specimen having a cross-sectional shape with corners in the cross-sectional direction and detects defects in the corners of the specimen from the reflected waves. An ultrasonic flaw detection device characterized by being equipped with.