Method for detecting ultrasonic flaw

Abstract

To provide a method for ultrasonic flaw detection that can ensure a sufficient inspection range at an end portion of an object to be inspected and reliably detect flaws.SOLUTION: An array-type ultrasonic probe 1 that emits ultrasonic waves B perpendicularly from an oscillation surface 1a is arranged such that the oscillation surface 1a of the probe is inclined at a predetermined angle α with respect to an ultrasonic incident surface 2a of an object 2 to be inspected, whereby the emitted ultrasonic waves B is refracted at the ultrasonic incident surface 2a toward an end portion 21 of the object 2 to be inspected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic flaw detection method, and more particularly to an ultrasonic flaw detection method that can reliably detect flaws occurring at the edge of an object to be detected. [Background technology]

[0002] The edges of the object to be inspected are often not at right angles due to chamfering or sagging during cutting, and even if an ultrasonic probe for perpendicular inspection is moved along the surface of the workpiece, it is difficult to make ultrasonic waves enter the object at the edges, making inspection difficult.

[0003] Therefore, Patent Document 1 discloses a flaw detection method in which an ultrasonic probe is positioned along the surface of a steel plate via a water film, and ultrasonic waves are incident from the oscillation surface of the probe at an oblique angle to the surface of the steel plate, the ultrasonic waves are reflected by the underside of the steel plate, and the ultrasonic waves are directed toward the edge of the steel plate, and the reflected waves from defects in the edge of the steel plate are received to detect the defects.

[0004] Explaining this in more detail with reference to Figure 4, an array-type ultrasonic probe 1 having multiple vibrators is positioned in the water above and away from the top surface 2a of the round steel bar 2, and the lower surface 1a of the probe 1, which is the oscillation surface, is positioned parallel to the top surface 2a of the round steel bar 2. In this state, a certain number of vibrators of the probe 1 are excited with a predetermined time difference, and an ultrasonic beam B is incident obliquely from the oscillation surface 1a of the probe 1 onto the top surface 2a of the round steel bar 2, where it is refracted and directed inside the round steel bar 2 toward its end 21 (angle beam flaw detection).

[0005] By sequentially switching the excitation of the above-mentioned fixed number of vibrators and moving the ultrasonic beam B in the longitudinal direction parallel to the top surface 2a of the round bar steel while maintaining its angle, the position of the ultrasonic beam B incident on the end 21 of the round bar steel 2 changes left and right accordingly, and is reflected by the flaws d1, d2, d3 present in the end 21, and then returns to the vibrators of the probe 1, where the flaws d1 to d3 are detected. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2005-201800 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned conventional method, the composite wavefront of ultrasonic waves output from multiple transducers excited with a predetermined time difference generates a beam B of sufficient intensity that is incident on the top surface 2a of the round steel bar at a predetermined angle of incidence, and at the same time, ultrasonic waves B1 are generated by the composite wavefront that is emitted perpendicularly from the oscillation surface 1a of the probe 1 positioned parallel to the top surface 2a of the round steel bar and perpendicularly incident on the top surface 2a of the round steel bar, and this ultrasonic wave B1 is reflected upward by the bottom surface 2b of the round steel bar 2 and input again to the transducer of the probe 1. For this reason, there was a problem in that the flaw signals due to the reflected waves from the bottom surface 2b of the round steel bar were superimposed on the flaw signals due to the reflected waves from the flaws d1 to d3 present at the end 21 of the round steel bar 2, thereby narrowing the detection range.

[0008] Therefore, the present invention is intended to solve such problems, and aims to provide an ultrasonic flaw detection method that can ensure a sufficient flaw detection range at the edge of the object to be detected and perform reliable flaw detection. [Means for solving the problem]

[0009] In the first invention, an array-type ultrasonic probe (1) emits ultrasonic waves (B) perpendicularly from an oscillation surface (1a), and the oscillation surface (1a) is arranged so as to be inclined at a predetermined angle (α) with respect to an ultrasonic incident surface (2a) of an object to be inspected (2), so that the emitted ultrasonic waves (B) are refracted by the ultrasonic incident surface (2a) toward an end (21) of the object to be inspected (2).

[0010] In the first invention, the oscillation surface of the array ultrasonic probe is arranged at a predetermined angle with respect to the ultrasonic incident surface of the object to be detected, and the oscillated ultrasonic waves are refracted at the ultrasonic incident surface toward the edge of the object to be detected, thereby making it possible to effectively detect flaws occurring within the edge. In this case, ultrasonic waves are emitted perpendicularly from the inclined oscillation surface, so the problem of the narrowing of the detection range due to overlapping noise signals caused by reflected waves from surfaces opposite the ultrasonic incident surface can be avoided, and a sufficient detection range can be secured at the edge of the object to be detected, allowing for reliable flaw detection.

[0011] In the second invention, the object to be detected (2) is a rod body having both end portions (21, 22), and a pair of ultrasonic probes (1A, 1B) are provided to emit ultrasonic waves (B) that are refracted in the directions of the both end portions (21, 22), respectively.

[0012] According to the second invention, flaw detection can be performed while ensuring a sufficient flaw detection range over the entire length of the object to be detected, including both end portions.

[0013] The symbols in parentheses above indicate, for reference, the correspondence with specific means described in the embodiments to be described later. [Effects of the Invention]

[0014] As described above, according to the ultrasonic flaw detection method of the present invention, a sufficient flaw detection range can be secured at the edge of the object to be detected, thereby enabling reliable flaw detection. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view showing ultrasonic flaw detection in one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional flaw detection diagram according to an embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view showing ultrasonic flaw detection in another embodiment of the present invention. [Figure 4] FIG. 1 is a cross-sectional view showing conventional ultrasonic flaw detection. [Figure 5] FIG. 1 is a cross-sectional view of a conventional ultrasonic flaw detection. DETAILED DESCRIPTION OF THE INVENTION

[0016] The embodiments described below are merely examples, 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.

[0017] An example of ultrasonic flaw detection using the method of the present invention is shown in Figure 1. In Figure 1, a round steel bar 2, which is the object to be detected, is immersed in water and has three concave artificial flaws d1, d2, and d3 formed on the bottom surface 2b of its end 21. Meanwhile, an array-type ultrasonic probe 1 with a rectangular cross section is placed in the water above and away from the round steel bar 2, at an angle to the horizontal top surface 2a of the round steel bar 2.

[0018] The flat lower surface of the ultrasonic probe 1, i.e., the oscillation surface 1a on which multiple oscillators are arranged adjacently, is inclined upward toward the end 21 of the round steel bar 2. The ultrasonic probe 1 simultaneously excites a certain number of oscillators, and outputs an ultrasonic beam B perpendicular to the oscillation surface 1a toward the top surface 2a, which is the ultrasonic incidence surface (hereinafter simply referred to as the incidence surface) of the round steel bar 2.

[0019] When the inclination angle of the ultrasonic probe 1 (i.e., the oscillation surface 1a) is set to α, the angle of incidence of the ultrasonic beam B at the top surface (incident surface) 2a of the round steel bar 2 also becomes α. Therefore, with the sound speed in water being C1 and the sound speed of the longitudinal wave in the round steel bar 2 being C2, the refraction angle θ of the ultrasonic beam B into the round steel bar 2 is determined by the following equation (1) based on Snell's law: sinα / C1=sinθ / C2 …(1)

[0020] According to the above formula (1), when the round steel bar 2 is made of, for example, SUS303 33D, if the refraction angle θ of the ultrasonic beam B into the round steel bar 2 is desired to be 45 degrees as shown in Figure 1, the inclination angle α is 10.22 degrees. Note that the refraction angle θ does not necessarily have to be 45 degrees.

[0021] According to the above-described flaw detection method, the oscillation surface 1a of the ultrasonic probe 1 is tilted toward the end 21 of the round steel bar 2, and the flaw detection beam B is output perpendicularly from the oscillation surface 1a toward the incident surface 2a of the round steel bar 2. This prevents the generation of relatively strong ultrasonic waves B1 (see FIG. 4) directed toward the round steel bar 2b by a composite wavefront that is perpendicular to the incident surface 2a (top surface of the round steel bar) 2a, as occurs in the conventional case where the oscillation surface 1a of the ultrasonic probe 1 is parallel to the incident surface 2a of the round steel bar 2. This also prevents the problem of the flaw detection range being narrowed by the reflected wave from the bottom surface 2b of the round steel bar. In addition, since it is sufficient to simultaneously excite a certain number of transducers without any time lag, the excitation circuit is simplified and the intensity of the ultrasonic beam can be increased.

[0022] FIG. 2 shows a cross-sectional view of a round bar end 21 using the flaw detection method of this embodiment. This image was obtained by simultaneously exciting a certain number of transducers on the oscillation surface (bottom surface) 1a of the probe 1, which is inclined at a predetermined angle α relative to the incident surface 2a of the round bar 2. An ultrasonic beam B perpendicular to the oscillation surface is incident on the incident surface (top surface) 2a of the round bar 2 at an angle α and refracted at an angle θ toward the end 21 of the round bar 2. In this state, the excitation of the transducers of the probe 1 is sequentially switched, moving the transducer in a direction parallel to the top surface 2a of the round bar 2. The horizontal axis of FIG. 2 represents the flaw detection depth, the vertical axis represents the distance in the direction of the transducer alignment, and the gray level corresponds to the signal intensity. As shown, only flaw signals Sd1-Sd3 due to ultrasonic waves reflected from three artificial flaws d1-d3 appear within the flaw detection window W, ensuring sufficient flaw detection range.

[0023] In contrast, in the conventional flaw detection method in which the oscillation surface 1a of the probe 1 is parallel to and faces the incident surface 2a of the round steel bar 2, as shown in Figure 5, a noise signal SN due to the reflected wave from the bottom surface 2b of the round steel bar facing the incident surface 2a is generated widely within the flaw detection window W, thereby narrowing the flaw detection range.

[0024] (Other embodiments) As shown in Figure 3, a pair of ultrasonic probes 1A and 1B are provided, each with an oscillation surface 1a inclined upward toward both end portions 21 and 22, and these probes 1A and 1B are moved together or separately in the longitudinal direction of the round steel bar 2 as shown in Figures 3(1) and 3(2), while simultaneously rotating the round steel bar 2. This allows flaw detection to be performed while ensuring a sufficient detection range over the entire length of the round steel bar 2, including both end portions 21 and 223.

[0025] In the above embodiments, the object to be detected is a round steel bar, but the object is not limited to this and may be a square steel bar, a steel plate, etc. Also, the object is not necessarily limited to steel material. [Explanation of symbols]

[0026] 1,1A,1B...array type ultrasonic probe, 1a...oscillation surface, 2...round steel bar (object to be tested), 2a...ultrasonic incidence surface, 21,22...end, B...ultrasonic.

Claims

1. An ultrasonic flaw detection method in which an array type ultrasonic probe that emits ultrasonic waves from an oscillation surface perpendicular to the oscillation surface is positioned so that the oscillation surface is inclined at a predetermined angle with respect to the ultrasonic incident surface of the object to be detected, and the emitted ultrasonic waves are refracted at the ultrasonic incident surface toward the end of the object to be detected.

2. 2. The ultrasonic flaw detection method according to claim 1, wherein the object to be detected is a rod having both ends, and a pair of ultrasonic probes are provided for emitting ultrasonic waves that are refracted in the directions of the both ends, respectively.

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