JPS5952983B2 - Ultrasonic angle flaw detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic angle flaw detector, and particularly to an ultrasonic angle flaw detector that can simultaneously detect defects on the inner and outer surfaces of a thick-walled steel pipe.

Generally, ultrasonic angle flaw detection equipment is used for nondestructive inspection of steel pipes that require high quality because they can detect defects on the inner and outer surfaces and within the wall thickness of steel pipes with high sensitivity.

However, in such angle-angle flaw detection of steel pipes, as the wall thickness of the pipe increases, the ultrasonic beam does not hit the inner surface of the pipe, making it impossible to detect inner surface defects. The outer diameter of the tube is D,
If the tube thickness is , then the relationship between /D and the refraction angle θO for outer surface defect detection and the refraction angle θi for inner surface defect detection of the ultrasonic beam is slnθi−slneo t/D■...・・・・・・・・・・・・(1)2
There is a relationship of sin θi.

As shown in Figure 1, when the ultrasonic beam becomes tangent to the inner surface of the tube, θi2900, so /D=(
1-sinθo)/2 (2).

/D obtained by equation (2) is theoretically the flaw detectable limit Jt/D at the refraction angle θo for detecting the tube outer surface. Figure 2 shows the relationship between the refraction angle θo and the flaw detection limit /D.The area A below the curve a in the figure is the area where internal defects can be detected, and when the refraction angle θO The ultrasonic beam is applied to the steel pipe 1 whose thickness is 1 in Fig. 1.
It propagates as shown by 0. Also, the area above curve a is the area where internal defects cannot be detected, and the pipe thickness shown by the chain line is 2
An ultrasonic beam propagates as indicated by reference numeral 10' through the steel pipe 1'. That is, even if the refraction angle θO for detecting defects on the outer surface is constant, the angle of incidence of the ultrasonic beam on the outer surface side as shown in FIGS. However, the angle of incidence on the inner surface changes with /D, and as /D increases, the value becomes larger than the refraction angle θO. □If the beam does not hit, it becomes difficult to detect internal defects. Conventionally, the refraction angle in ultrasonic angle flaw detection is generally 35° to 70° for the following reasons.

(b) The round-trip passage rate of the ultrasonic beam is the third highest between water and steel.
As shown in the figure, it shows a high value at a transverse wave refraction angle of 35° to 70°. In addition, when the shear wave refraction angle is less than 33°, the longitudinal wave T and the shear wave T
s coexist and the round-trip passage rate is low. (B)
As shown in FIG. 4, the reflectance at a right angle to the ultrasonic beam is 100% at a transverse wave refraction angle of 35° to 55°.

In this way, in normal ultrasonic angle flaw detection of steel pipes, the transverse wave refraction angle is set to approximately 35° or more, so the maximum t/D that allows flaw detection to the inner and outer surfaces of the steel pipe is approximately 0.2, and the t/D is 0
．． It is difficult to apply ultrasonic angle angle flaw detection to detect defects on the inner surface of a pipe with two or more thick walled steel pipes.

In addition, conventional methods have the disadvantage of low throughput because flaws are detected on the inner and outer surfaces of steel pipes separately. The present invention
The object of the present invention is to provide an ultrasonic angle angle flaw detection device capable of performing angle angle flaw detection on the inner surface of thick-walled steel pipes, which was previously impossible, and capable of simultaneously detecting flaws on the inner and outer surfaces.

The ultrasonic angle flaw detection device according to the present invention includes a probe that emits an ultrasonic beam with a refraction angle of 35° to 55° for flaw detection on the outer surface of steel pipes, and a probe that emits an ultrasonic beam with a refraction angle of 35° to 55° for flaw detection on the inner surface of steel pipes. It is characterized in that a probe that emits an ultrasonic beam at a refraction angle is placed on the outer surface of the steel pipe.

゛]ZDt7. The relationship between the angle of refraction θ and the inner surface incidence angle θi is shown in FIG. 5.

As is clear from this figure, for example, t/D is 30 to 1.
5 (%), when the refraction angle θ is 15° to 30°, the inner surface incident angle θi is approximately 45°, and the reflectance from the corner is 100%. In the same figure, conversely, the inner surface incidence angle θi
It can be seen that the refraction angle θ at which the reflectance is 100% when the angle is 15° to 30° is 15° to 30°. Therefore, in the present invention, regarding the ultrasonic beam for flaw detection on the inner surface of steel pipes,
It is preferable to arrange a probe on the outer surface of the steel pipe so that its refraction angle is 15° to 30°. Embodiments of the present invention will be described below with reference to the drawings.

6 and 7 are a cross-sectional view and a longitudinal cross-sectional view, respectively, of an ultrasonic angle flaw detection apparatus according to an embodiment of the present invention.

A probe holder 2 is placed with a slight gap S around the outer periphery of a steel pipe 1 to be inspected that moves in the axial direction. This probe holder 2 has four probes 6a, 6b, 6c, 6d.
is installed. Of these, the probes 6a and 6C exist on the same plane perpendicular to the axis of the holder 2, and the probes 6b and 6C exist on the same plane perpendicular to the axis of the holder 2.
d exists on another same plane parallel to the above-mentioned plane and slightly shifted in the axial direction. In other words, probes 6a and 6C
The probes 6b and 6d are offset from each other in the axial direction. This deviation L (FIG. 7) is preferably about 715 mm, for example. This can prevent interference of ultrasound beams. The probes 6a and 6b are for detecting defects on the outer surface of the steel pipe 1, and the probes 6C and 6d are for detecting defects on the inner surface.

The outer surface defect detection probes 6a and 6b transmit ultrasonic beams 7A and 7b whose refraction angle θO on the outer surface of the steel pipe is 3.
The ultrasonic beams are mounted at an angle of 5° to 55°, and are arranged so that the ultrasonic beams travel in opposite directions to prevent deterioration in detection ability due to directionality of defects. That is, if the ultrasonic beam 7a of the probe 6a travels counterclockwise as shown in the figure, the respective nozzles 3a, 3b are arranged so that the ultrasonic beam 7b of the probe 6b travels clockwise.
The position and direction of Each probe is housed in a probe fixture 4, and the fixture 4 is connected to the holder 2 with bolts 8.
Fixed. Reference numeral 5 indicates a holding nut for the fixture 4.
By setting the refraction angle θO for external surface defect detection to 35° to 55°, as mentioned above, the incident angle of the ultrasonic beam to the external surface defect is equal to the refraction angle, so the round-trip passage rate of the ultrasonic beam is high ( (see FIG. 3), and the reflectance at right angles is 100% (see FIG. 4).

This makes it possible to detect external defects with high sensitivity. Similarly to the probes 6a and 6b, the inner surface defect detection probes 6C and 6d are arranged so that the traveling directions of their ultrasonic beams 7C and 7d are opposite to each other.

At that position, the refraction angle θi for inner surface flaw detection is 15° to 33°.
It is determined that ゜. Within this range, depending on the ratio t/D of tube thickness to tube outer diameter, the angle of incidence of the ultrasonic beam on the inner surface defect can be between 35° and 55°, thus reducing the reflectance from the corner. can be set to 100%. As a result, defects on the inner surface of thick-walled steel pipes can be detected with high sensitivity. Further, by using such an ultrasonic angle flaw detector having two types of probes, it is possible to simultaneously detect flaws on the inner and outer surfaces of a steel pipe.

That is, first, using a test pipe with artificial defects processed on the inner and outer surfaces, the gate, sensitivity, etc. are adjusted so that the inner surface artificial defects are detected by the inner surface flaw detection channel, and the outer surface artificial defects are detected by the outer surface flaw detection channel. Detects flaws on the inside and outside at the same time.
This reduces the number of equipment, simplifies processes, and reduces the number of handling operations, resulting in a significant improvement in overall processing capacity. It should be noted that the present invention enables flaw detection of not only thick-walled steel pipes but also steel pipes that are subject to conventional angle angle flaw detection by replacing the probe holder and changing the refraction angle of the ultrasonic beam. Not even.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the propagation state of an ultrasonic beam in oblique angle flaw detection of steel pipes, Figure 2 is a diagram showing the detection limit ratio t/D of pipe thickness and pipe outer diameter with respect to the angle of refraction, and Figure 3 Figure 4 shows the relationship between the refraction angle of the ultrasonic beam and the round trip pass rate, Figure 4 shows the reflectance of the ultrasonic beam at right angles, and Figure 5
The figure shows the relationship between the refraction angle and the inner surface incidence angle using t/D as a parameter, and FIG. 6 is a cross-sectional view of the ultrasonic angle flaw detection apparatus according to the embodiment of the present invention, and FIG. 7 is a longitudinal sectional view of FIG. 6, taken along the line I-VI. 1... Steel pipe to be inspected, 2... Probe holder 3a, 3b... Nozzle, 4...
Probe fixture, 6a, 6b, 6c, 6d... Probe, 7a, 7b, 7C, 7d... Ultrasonic beam.

Claims (1)

[Scope of Claims] 1. A probe that emits an ultrasonic beam with a refraction angle of 35° to 55° for flaw detection on the outer surface of steel pipes, and an ultrasonic wave beam with a refraction angle such that the reflectance is 100% for flaw detection on the inner surface of steel pipes. An ultrasonic angle flaw detection device characterized by having a beam-emitting probe arranged on the outer surface of a steel pipe. 2. A probe that emits an ultrasonic beam with a refraction angle of 35° to 55° for flaw detection on the outer surface of steel pipes, and a probe that emits an ultrasonic beam with a refraction angle of 15° for flaw detection on the inner surface of steel pipes.
2 probes each emitting an ultrasonic beam of ~30°.
The ultrasonic angle flaw detection device according to claim 1, wherein the ultrasonic angle flaw detection device is individually arranged on the outer surface of a steel pipe. 3 Two probes with ultrasonic beams propagating in opposite directions with refraction angles of 35° to 55° for the outer surface flaw detection of steel pipes, and two probes with refraction angles of 15° to 30° and opposite directions for the inner surface flaw detection of the steel pipes. The ultrasonic bevel according to claim 1 or 2, characterized in that two probes having ultrasonic beams propagating in the same direction are arranged on the outer surface of the steel pipe so as to be shifted in the axial direction of the steel pipe. Flaw detection equipment.