JP6446888B2 - Ultrasonic flaw detection method for round bars - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection method for a round bar material, and more particularly, to an ultrasonic flaw detection method that can satisfactorily identify and detect a surface flaw of a round bar material and a surface flaw near the surface.

  Manufacture because the round bar material can be made good by simply removing it by cutting etc., if the surface defect generated on the outer peripheral surface of the round bar material and the surface layer defect generated inside the round bar material can be clearly identified. Yield is improved. Therefore, in Patent Document 1, a circle-shaped array-type ultrasonic probe is used to adjust the swing angle of an ultrasonic beam, and ultrasonic waves are incident on the inside of a round bar to detect flaws on the surface layer. At the same time, it has been proposed that surface flaw detection be performed by generating surface waves on the surface of a round bar.

JP 59-126952 A

  However, in the above conventional flaw detection method, since surface waves are used for detecting surface flaws, there is a problem that the accuracy of wrinkle detection is influenced by the surface roughness of the round bar material. There was also a problem that wrinkles could not be detected at the supporting part.

  Therefore, the present invention solves such a problem, and can be accurately detected by distinguishing surface wrinkles and surface wrinkles without being affected by the surface roughness of the round bar material or the presence or absence of support portions. An object of the present invention is to provide an ultrasonic flaw detection method for a material.

In order to achieve the above object, according to the first aspect of the present invention, a pair of rectangular wave pulse voltages (2a, 2b) close to each other are applied to the piezoelectric vibrator (12) of the ultrasonic receiver / oscillator (1) and Ultrasonic waves output from the piezoelectric vibrator (12) of the sound wave receiving oscillator (1) are incident on the inside of the round bar (4) at a predetermined refraction angle (θ) to detect wrinkles of reflected waves. When there is no phase inversion in the waveform (3cd), it is determined that the round bar (4) has a surface flaw (41), and when there is a phase inversion in the reflected wave wrinkle detection waveform (3cd) It is determined that the round bar (4) has a surface ridge (42).

  In the first invention, it is possible to reliably distinguish and detect surface wrinkles and surface wrinkles generated in a round bar material by the presence or absence of phase inversion in the wrinkle detection waveform of the ultrasonic reflected wave.

In the second aspect of the invention, the ultrasonic receiver / oscillator (1) is pivoted relative to the round bar (4) while maintaining a constant interval.

In the third invention, the predetermined refraction angle is set to 30 ° to 70 ° .

  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 for a round bar material of the present invention, it is possible to accurately detect a surface flaw and a surface flaw without being affected by the surface roughness or the presence or absence of a support portion.

It is sectional drawing of an ultrasonic receiving oscillator. It is a figure which shows the input-output waveform of the piezoelectric vibrator of an ultrasonic receiving oscillator. It is a figure which shows the waveform of the output ultrasonic wave of an ultrasonic receiving oscillator. It is sectional drawing which shows the ultrasonic path | route in a round bar. It is sectional drawing which shows the ultrasonic path | route in a round bar. It is a figure which shows the waveform of the reflected wave from a surface flaw. It is a figure which shows the waveform of the reflected wave from a surface layer ridge.

  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.

  FIG. 1 shows an example of an ultrasonic receiving oscillator that outputs a broadband ultrasonic wave having a short pulse duration used in the method of the present invention. In FIG. 1, an ultrasonic receiver / oscillator 1 has a cylindrical housing 11 with one end open, and a plate-like piezoelectric vibrator 12 is disposed so as to close the opening. A metal front plate 13 is joined to the front surface of the piezoelectric vibrator 12. A damper layer 14 made of a resin material having excellent ultrasonic attenuation characteristics is provided in the housing 11 behind the piezoelectric vibrator 12, and a power supply line reaching the piezoelectric vibrator 12 in the center hole 141 of the damper layer 14. 15 is inserted.

  A pair of adjacent rectangular pulse voltage 2a, 2b as shown in FIG. Each of the pair of pulse voltages 2a and 2b lasts for ½ wavelength of a high frequency of 7 MHz, for example, and separates the distance between them by ½ wavelength. In this way, as shown in FIG. 2 (2), the first application of the pulse voltage 2a generates a 7 MHz ultrasonic wave 3a that gradually attenuates (indicated by the chain line in the figure), and the subsequent application of the pulse voltage 2b As shown in 2 (3), an ultrasonic wave 3 b of 7 MHz that is delayed by one wavelength and similarly attenuated (indicated by a chain line in the figure) is generated.

  As a result, the piezoelectric vibrator 12 outputs an ultrasonic wave 3c obtained by combining the ultrasonic waves 3a and 3b as shown in FIG. In the synthesized output ultrasonic wave 3c, a mountain wave is superimposed, and the 1.5th wave becomes stronger (the amplitude becomes larger) than others, and the wave number becomes sufficiently small.

  An example of the actual waveform of the output ultrasonic wave 3c is shown in FIG. As is clear from FIG. 3, a negative waveform having a relatively large amplitude (intensity) exists between a pair of front and rear positive waveforms having a relatively small amplitude (intensity), and the difference between the positive and negative intensities is large. It is a wide band with a sufficiently small wave number in which 3.5 waves exist in .5 μs.

The ultrasonic wave 3c output from the piezoelectric vibrator 12 of the ultrasonic receiving oscillator 1 is made incident from the outer peripheral surface of the round bar 4 to the inside at a predetermined refraction angle θ as shown in FIGS. Here, θ is often in the range of 30 ° to 70 °. In this state, when the ultrasonic receiving oscillator 1 is relatively swiveled concentrically while maintaining a constant interval with respect to the round bar 4, a surface ridge 41 that opens to the outer peripheral surface of the round bar 4 is formed as shown in FIG. 4. If it has occurred, a part of the ultrasonic wave 3c that reaches the surface ridge 41 is reflected by the surface ridge 41 toward the surface of the round bar. At this time, since the acoustic impedance of air is very small (about 5 digits) compared to the acoustic impedance of the metal material constituting the round bar, it is incident on the boundary between the metal material and air. The phase of the sound wave is reversed by reflection on the surface ridge 41. Then, the phase is further reversed upon reflection on the surface of the round bar 4 under the same conditions, and the reflected wave 3cr1 is eventually the same as the phase of the incident ultrasonic wave 3c, as if the phase is not reversed. The waveform returns to the ultrasonic receiver 1 with a waveform like that.

  On the other hand, as shown in FIG. 5, when the surface layer ridge 42 is generated immediately below the surface of the round bar 4, a part of the incident ultrasonic wave 3 c is directly reflected on the surface of the surface layer ridge 42. Since the light is incident on the boundary between the metal and the air, the reflected wave 3cr2 is reversed in phase and returned to the ultrasonic receiving oscillator 1. Since the time until these reflected waves 3cr1 and 3cr2 return to the ultrasonic oscillator 1 is about the same, by setting a reflected wave detection window in this time range and capturing the wrinkle detection waveform, Whether the surface bar 41 or the surface layer 42 is generated on the round bar 4 can be reliably determined by the presence or absence of the phase inversion.

  Here, a round groove of R 0.3 mm is formed as a surface ridge on a white bar round steel bar of Φ38 mm, and a horizontal hole of φ0.6 mm is formed as a surface ridge at a position 1 mm immediately below the surface layer, and a refraction angle (θ) 44 FIGS. 6 and 7 show examples of reflected waves obtained by causing the output ultrasonic wave 3c shown in FIG. The wrinkle detection waveform 3cd in the reflected wave shown in FIG. 6 is a super output waveform in which a negative waveform having a relatively large amplitude (intensity) exists between a pair of front and rear positive waveforms having a relatively small amplitude (intensity). Since it has the same phase as the sound wave 3c and there is no phase inversion, it can be determined that the round bar steel has surface defects.

  On the other hand, the wrinkle detection waveform 3cd in the reflected wave shown in FIG. 7 has a positive waveform with a relatively large amplitude (intensity) between a pair of negative waveforms with a relatively small amplitude (intensity). Since the output ultrasonic wave 3c has a phase opposite to that of the output ultrasonic wave 3c and has a phase inversion, it can be determined that the round bar steel has surface flaws.

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic wave receiving oscillator, 3c ... Ultrasonic wave, 3cd ... Wedge detection waveform, 4 ... Round bar material, 41 ... Surface wrinkles, 42 ... Surface wrinkles.

Claims (3)

A pair of rectangular pulse voltages close to each other are applied to the piezoelectric vibrator of the ultrasonic receiver / oscillator, and the ultrasonic wave output from the piezoelectric vibrator of the ultrasonic receiver / oscillator is transmitted from the outer peripheral surface of the round bar to a predetermined value. When the refraction angle is incident on the inside and the reflected wave wrinkle detection waveform has no phase reversal, it is determined that the round bar has surface wrinkles, and the reflected wave wrinkle detection waveform has phase reversal The method for ultrasonic flaw detection of a round bar material is characterized in that it is determined that the round bar material has a surface flaw. The ultrasonic inspection method for a round bar material according to claim 1, wherein the ultrasonic wave receiving oscillator is relatively swiveled and moved concentrically with respect to the round bar material at a constant interval. The method for ultrasonic inspection of a round bar material according to claim 1 or 2, wherein the predetermined refraction angle is 30 ° to 70 °.

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