JPS618657A - Ultrasonic flaw detecting method of steel sheet edge part - Google Patents

Abstract

PURPOSE:To reduce the region where flaw detection of a steel sheet edge part is not performed, by deflecting incident angles of left and right vibrators in divided type vertical probe, and transmitting ultrasonic beam to the edge part side. CONSTITUTION:A sound dividing surface 5 of the probe 2 is placed parallel to the steel sheet edge 8 and as near as possible to the steel sheet edge 8, and the probe 2 is scanned in a direction 9. Ultrasonic incident angles of a transmitting vibrator 3 and a detecting vibrator 3a are regulated to different angles respectively, and the beam propagating positions are deflected to the edge part 8 side. By reducing a nonsensible band 11 of the part 8, the region where flaw detection is not performed in the part 8 is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an improvement in a method of ultrasonic flaw detection using a split vertical probe for the purpose of detecting internal defects in steel plates such as thick hot-rolled steel strips. In particular, the present invention relates to a flaw detection method for reducing the undetectable area at the edge of a steel plate.

[Prior art]

Steel plate edges are often processed or welded in subsequent processes after rolling, and as these may cause welding defects due to residual defects, strict non-destructive testing is required. This is the part where there is.

On the other hand, because the edge of a steel plate is uneven in shape due to sagging caused by shearing, there is an area that cannot be detected at the edge when performing ultrasonic flaw detection. Conventionally, it has been extremely difficult to reduce the dead zone at the edge. This was a major issue in sonic flaw detection, but there was no effective method.

The principle of the conventional flaw detection method for steel plates using a split-type vertical probe (for example, as shown on page 61 of "Ultrasonic Flaw Detection Test A" published by the Japan Nondestructive Inspection Association (1976, April 1)) is shown in Figure 1. show.

In FIG. 1, a split vertical probe 2 has two transducers 3. and 3a, wedge 4. The ultrasonic beam, which is composed of a plug 6 and an acoustic splitting surface 5 and is transmitted from the transmitting transducer 3, has an angle of incidence of several degrees, is refracted at the surface of the steel plate to be inspected, and is irradiated onto the steel plate, further detecting defects, etc. The temporarily sealed echo 7a due to the transmission beam follows a path in the opposite direction, symmetrical to the transmitted beam. and is received by the receiving transducer 3a.

The specifications of the probe, such as the size of the transducer and the angle of incidence, are determined by the type and size of the defect to be detected and the range of applicable plate thickness. A probe 2 of the same size, ie, a probe 2 that is symmetrical in left and right directions, is used, and the probe 2 is arranged at the edge of the steel plate as shown in FIG. 2a (top view) and FIG. 2b (side view).

2a and 2b, the probe scanning direction 9 (arrow) is parallel to the steel plate edge and the acoustic splitting plane 5 of the probe 2 is perpendicular to the steel plate edge. It was placed in

As a result, the flaw detection performance of the conventional method first suffers from a decrease in sensitivity due to the slope θt10 caused by shearing of the edge of the steel plate. An example of this decrease in sensitivity is shown in Figure 3.
is 0.2° to 1.0°, depending on the dimensions of the vibrator.
This occurs significantly at small tilt angles.

Second, the dead zone 11 at the edge of FIG. 2b is 5z8x8ND, that is, 5
M) This is an example using split type vertical probe 2 with 2 lf transducer dimensions @ 8mm x 8mm+, but the distance from the flawed edge is 7m.
It is known that sufficient detection performance cannot be obtained unless the distance is at least m.

[Purpose of the invention]

An object of the present invention is to provide a new ultrasonic flaw detection method for steel plate edges that overcomes the above-mentioned problems, that is, to reduce the undetectable area of steel plate edges.

[Structure and operation of the invention]

The gist of the present invention is to provide an ultrasonic flaw detection method for the edge of a steel plate using a split vertical probe, in which the acoustic splitting surface of the split vertical probe is arranged parallel to the edge of the steel plate. The method involves deflecting the incident angle of the ultrasonic beam of the transmitting and receiving transducer that is divided across the two sides, and shifting the beam propagation position toward the edge of the steel plate for flaw detection.

The details of the method of the present invention will be explained below according to examples.

FIG. 5 shows a diagram of the principle of the method of the present invention. The orientation of the probe 2 is as shown in FIG. The probe scanning direction 9 is taken.

Further, as shown in FIG. 5b, the ultrasonic incident angles of the transmitting transducer 3 and the receiving transducer 3a are set to different angles, respectively, so that the beam propagation position is biased toward the edge portion side 8. That is, for example, as shown in Fig. 5b, the incident angle of the receiving pendulum located on the edge side 8 is set to 0°, and the angle of incidence on the transmitting side is set to about 8° instead of about 4° in the past. .

By adopting such a method, the present invention achieves the fifth b.
The decrease in sensitivity to the inclination θh12 of the edge portion 8 shown in the figure is as follows: As shown in the example shown in FIG. 6, the angle at which the echo height decreases to 172 is 2. o.

And it has been greatly improved, and the edge part is also insensible? As shown in FIG. 7, 1F11° can be sufficiently detected even with a diameter of 4 mm.

The probe shown in FIGS. 6 and 7 above is 5z8X8N.
Probe D, 5 MHz, transducer size 8 m
It is a segmented vertical probe measuring 8 mm by 8 mm, with an incident angle of 8° for the transmitting transducer 3 and 0° for the receiving transducer 3a.

In addition to the above-mentioned probe structure used to carry out the method of the present invention, there is also a method in which a plurality of transmitting and receiving transducers are combined with an acoustic dividing plane in between.

Examples are shown in Figures 8a and 8b.

Figure 8a shows the transmitting oscillators as 31+, 32+3a and three parts I.
FIJ (incidence angle and dimensions are the same), the sound field distribution of the transmitted beam is different within the steel plate, and it is particularly effective as a means for making the sound field uniform in the thickness direction.

In addition, Fig. 8b shows the transmitting oscillator divided into three parts at 34°35.
+36 incident angle θ1. θ2. By changing θ3 and dimensions, this also aims to further homogenize the sound field in the thickness direction.

Furthermore, as shown in FIG. 9, by using a bowl-shaped focal type vibrator as the receiving vibrator, it is possible to improve the detection performance so that minute defects can be detected. Up to now, an example has been described in which the receiving transducer 3a is arranged on the edge side and the transmitting transducer 3 is arranged inside the edge, but it is also possible to implement the arrangement in reverse.

〔Effect of the invention〕

As explained above, the present invention biases the incident angles of the left and right transducers of the split vertical probe so that the propagation path of the ultrasonic beam is on the edge side, thereby determining the thickness of the steel plate, which should be detected. Transducer dimensions, taking into account defects.

By determining and applying the probe specifications such as the incident angle, it is possible to significantly reduce the dead zone at the edge of the steel plate, and the resulting effects are very large.

[Brief explanation of drawings]

Figure 1 is a cross-sectional structural diagram of a conventional split layer probe. Figures 2a and 2b are diagrams of the principle of the conventional method;
Figure a is a plan view, and Figure 2b is a side view. Fig. 3 is a graph showing an example of the slope characteristic of the edge part of the conventional method.
FIG. 4 is a graph showing an example of the edge defect detection ability of the conventional method, and FIGS. 5a and 5b are failures. FIG. 5A is a plan view and FIG. 5B is a side view. FIG. 6 is a graph showing an example of the edge slope characteristic of the method of the present invention, and FIG. 7 is a graph showing an example of the edge defect detection ability of the method of the present invention. Figures 8a, 8b, and 9 are cross-sectional views of other probe structures for use in practicing the present invention. 1: Test material 2: Split vertical probe 3.31
~36: Transmitting transducer 3a, 3a1: Receiving transducer 4: Wedge 5: Acoustic dividing surface 6: Plug 7: Transmitting ultrasonic beam 7a: Reflected echo 8: Steel plate edge 9:
Probe scanning direction 10: Tilt angle θt 11: Edge dead zone 12: Tilt angle θh 4th ■ ≧ 6th BND Figure 58

Claims (1)

[Claims] In an ultrasonic flaw detection method for the edge of a steel plate using a split-type vertical probe, the acoustic splitting surface of the split-type vertical probe is arranged parallel to the edge of the steel plate, and the splitting is performed across the acoustic splitting surface. An ultrasonic flaw detection method for an edge of a steel plate, characterized in that the incident angle of an ultrasonic beam of a transducer for transmitting and receiving is biased, and the beam propagation position is shifted toward the edge of the steel plate for flaw detection.