JP6123537B2 - Ultrasonic flaw detection method - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection method, and more particularly to an ultrasonic flaw detection method capable of reliably discriminating surface defects of steel materials and internal defects immediately below the surface.

  As this kind of ultrasonic flaw detection method, the one shown in Patent Document 1 is known. This is when a bevel probe is provided for a round member, and when the ultrasonic reflected wave from the probe has one peak, a surface defect (surface defect) is assumed and there are two or more peaks. Are defined as epidermal defects (internal defects directly under the surface).

JP 58-135960 A

  However, in the above conventional method, there is a case where the two peaks cannot always be clearly separated, so that there is a problem in that there is no certainty in discriminating the surface defect of the steel material and the internal defect directly under the surface.

  Therefore, the present invention solves such problems, and an object of the present invention is to provide an ultrasonic flaw detection method capable of reliably discriminating between surface defects of steel materials and internal defects directly under the surface.

  In order to achieve the above object, according to the first aspect of the present invention, an ultrasonic transverse wave beam (B) is incident on the cross section of the steel material (M) at a refraction angle (θ) within a predetermined angular range, and the transverse wave beam (B) Obtaining an intensity distribution with the horizontal axis representing the scan position in the circumferential direction of the steel (M) and the vertical axis representing the time variation of the reflected wave intensity of the ultrasonic wave at each scan position, and the reflected wave intensity in the intensity distribution The surface defect (M1) generated in the steel material (M) and the internal defect (M2) immediately below the surface are discriminated based on the size of the area of a certain area or more.

  In the first invention, the area of the reflected wave intensity distribution in the reflected wave intensity distribution obtained from the surface defect and the internal defect has a significantly smaller area due to the surface defect than the area due to the internal defect. . As a result, even if the intensity peak of the ultrasonic reflected wave cannot be clearly separated, the surface defect and the internal defect can be reliably determined.

  In the second invention, expansion processing and contraction processing are performed on the intensity distribution.

  In the second aspect of the present invention, even when regions having a reflected wave intensity of a certain level or more are separated, the area comparison of the regions can be performed satisfactorily.

  The reference numerals in the parentheses indicate the correspondence with specific means described in the embodiments described later.

  As described above, according to the ultrasonic flaw detection method of the present invention, it is possible to reliably discriminate between surface defects of steel materials and internal defects directly under the surface.

It is sectional drawing of the round bar steel materials explaining the use condition of this invention method. It is an expanded sectional view of a surface ridge part. It is a graph which shows the time change of the reflected wave intensity in the surface ridge part. It is an expanded sectional view of an internal defect part. It is a graph which shows the time change of the reflected wave intensity in an internal defect part. It is a distribution map of the reflected wave intensity in the surface ridge part. It is a graph which shows the time change of the reflected wave intensity along the XX line of FIG. It is a distribution map of the reflected wave intensity in an internal defect part. It is a graph which shows the time change of the reflected wave intensity along the YY line of FIG.

  The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention. Hereinafter, implementation of the method of the present invention will be described.

  FIG. 1 shows a cross section of a round steel bar M, in which a R0.2 semicircular groove M1 is formed as a surface flaw, and a φ0.4 circular horizontal hole M2 is formed as an internal defect immediately below the surface. Has been. The array probe 1 is provided at a predetermined distance from the outer peripheral surface of the round bar steel M. In the array probe 1, the ultrasonic oscillation surface 11 facing the outer peripheral surface of the round bar steel M is an arc surface substantially concentric with the outer peripheral surface of the round bar steel M. The round bar steel M and the array probe 1 are installed in water.

  The necessary number of ultrasonic transducers (not shown) of the array probe 1 are driven to enter the round bar steel M so that the transverse wave refraction angle θ is 40 to 45 ° within the round bar steel M. An ultrasonic beam B that converges near the opposite surface is oscillated. By sequentially driving the necessary number of ultrasonic transducers, the ultrasonic beam B output from the array probe 1 is scanned in a predetermined range W in the circumferential direction of the round bar steel M. The entire circumference of the round bar steel M is scanned with the ultrasonic beam B as described above by rotating the round bar steel M appropriately or by providing a plurality of the same type of array probes 1 adjacent to the whole circumference of the round bar steel M. can do.

  As shown in FIG. 2, the oscillated ultrasonic beam B has a direct reflection R1 on the surface M1 and a reflection R2 on the surface of the round bar steel M, as shown in FIG. The intensity of the reflected wave received increases only at a relatively short time t1, as shown in FIG. On the other hand, in the portion of the internal defect M2 immediately below the surface, as shown in FIG. 4, the direct reflection R3 at the defect M2 and the reflection R4 at the surface of the round bar steel M are the reflection R4 and the reflection at the surface. Since it takes longer than the reflection R3, the intensity of the reflected wave received by the array probe 1 becomes larger for a relatively long time t2, as shown in FIG.

  When the ultrasonic beam B is scanned in the circumferential direction of the round bar steel M as described above with respect to the surface defect M1 and the internal defect M2, the distance from the array probe 1 to the surface defect M1 and the internal defect M2 is as follows. It differs depending on the scanning position of the ultrasonic beam B. For this reason, when the scanning position of the ultrasonic beam B in the circumferential direction is taken on the horizontal axis and the time is taken on the vertical axis, the distribution map of the intensity change of the reflected wave is drawn as shown in FIGS. A high luminance region (white portion in each figure) in which the reflection intensity is high due to the presence of M1 and the internal defect M2 appears in an inclined line shape. The high brightness area is relatively narrow in the case of the surface defect M1 (FIG. 6) and relatively wide in the case of the internal defect M2 (FIG. 8). FIG. 7 (1) and FIG. 9 (1) showing the change in reflected wave intensity at a certain ultrasonic beam scan position (X position in FIG. 6, Y position in FIG. 8) in each distribution chart are respectively shown. 3 and will naturally correspond to FIG.

  Therefore, the following processing is performed on the above distribution map to calculate the area of a high luminance region (region where the reflected wave intensity is a certain level or more) in the distribution map obtained by processing. Hereinafter, FIGS. 7 (2) to (5) correspond to changes in reflected wave intensity at the X position in FIGS. 6 (2) to (5), and FIGS. 9 (2) to (5) are similar to FIG. This corresponds to the reflected wave intensity change at the Y position in (2) to (5).

  (2) in FIG. 6 and FIG. 8 is obtained by cutting the intensity value (luminance value) of the reflected wave in (1) with a certain threshold. (3) in both figures is obtained by performing expansion processing on the intensity value obtained in the processing of (2) to fill in the breaks in the intensity distribution. (4) in both figures is a result of applying the contraction process to the intensity value obtained in the process of (3) and returning the excessive spread by the expansion process. (5) in both figures is obtained by further cutting the intensity value obtained by the process (4) with a certain threshold value.

  When the area of the high-intensity region (white portion in each figure) is calculated from the intensity distributions of FIGS. 6 (5) and 8 (5) obtained by the above processing, the reflected wave intensity distribution (FIG. 6) due to the surface defect M1. The area of the high intensity region in (5)) is less than or equal to half the area of the high intensity region in the reflected wave intensity distribution (FIG. 8 (5)) due to the internal defect M2 directly below the surface. Accordingly, it is possible to reliably determine whether the surface defect M1 or the internal defect M2 from the size of the area of the high intensity region in the reflected wave intensity distribution. In addition, in the said embodiment, although the round bar steel material was made into object, it is not restricted to a round bar.

DESCRIPTION OF SYMBOLS 1 ... Array probe, B ... Shear wave beam, M ... Round bar steel material, M1 ... Surface defect, M2 ... Internal defect.

Claims (2)

An ultrasonic transverse wave beam is incident on the cross-section of the steel material at a refraction angle within a predetermined angle range, and the time of the reflected wave intensity of the ultrasonic wave at each scan position with the horizontal axis representing the scan position of the transverse wave beam in the circumferential direction of the steel material. Obtaining an intensity distribution with the change on the vertical axis, and distinguishing surface defects generated in steel materials and internal defects directly under the surface from the size of the area of the reflected wave intensity in the intensity distribution above a certain level Ultrasonic flaw detection method. The ultrasonic flaw detection method according to claim 1, wherein expansion processing and contraction processing are performed on the intensity distribution.