JPH02151761A - Automatic surface wave flaw detection - Google Patents

Abstract

PURPOSE:To enable highly reliable flaw detection by a method wherein automatic flaw detection is performed with surface waves detected by making ultrasonic waves slantly enter an outer peripheral surface of a specimen. CONSTITUTION:A generating and receiving circuit 18 outputs low frequency driving signals according to an instruction from an arithmetic control circuit 20, emits ultrasonic waves having the same frequency as driving signals from a slanted angle probe 12, and transmits surface waves along a facial layer of a specimen 10. The probe 12 detects an echo of the surface wave or the surface wave that has come around the outer periphery of the specimen 10 and supplies a detection signal indicating the echo or the surface wave that has come around to the circuit 18. The circuit 18 removes noise from the detection signal as well as amplifies the detection signal and supplies it to the circuit 20 via an A/D-converter 22. The circuit 20 processes an input signal and verifies that the surface wave is actually transmitted to a flaw-detection region as the specimen moves lengthwise while it automatically identifies existence of a defect on the surface or under the surface, and the results are output to a display/recorder 24 and a marker 26.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic surface wave flaw detection method for automatically detecting defects on the outer peripheral surface or under the skin of a member to be inspected using surface waves.

BACKGROUND ART It is known that defects existing on the surface or under the skin of a member to be measured can be detected by using surface waves that propagate along the surface layer of the member to be measured.

However, when automatically performing flaw detection using surface waves, it is necessary to confirm whether or not the ultrasonic waves are actually propagating through the flaw detection site of the member to be inspected during or before and after flaw detection.

However, when performing flaw detection using surface waves, it is not possible to obtain a bottom echo that can be used as an ultrasonic transmission confirmation signal as in the case of vertical flaw detection. Alternatively, it has been difficult to automatically detect defects under the epidermis with high reliability.

Means for Solving the Problems The inventor of the present invention has conducted various studies against the background of the above-mentioned circumstances, and has found that it is possible to use a surface wave that circulates around the outer peripheral surface of a member to be inspected as the ultrasonic transmission confirmation signal. I found that. The present invention has been made based on this knowledge.

That is, the gist of the present invention is to provide surface wave automatic flaw detection that automatically detects defects on the outer peripheral surface or under the skin of a member to be inspected by using surface waves that propagate in the circumferential direction on the surface layer of the member to be inspected. A method comprising: (a) an ultrasonic wave incidence step in which a surface wave is propagated in the circumferential direction along the surface layer of the inspected member by obliquely injecting an ultrasonic wave onto the outer circumferential surface of the inspected member; ]) a detection step of detecting a surface wave that has made at least one turn around the outer peripheral surface of the inspected member; and (C) when a surface wave that has made at least one turn around the outer circumferential surface of the inspected member is detected in the detection step; The method includes an automatic flaw detection process that performs automatic flaw detection using surface waves.

Operation and Effects of the Invention By doing this, the surface waves propagated by obliquely injecting the ultrasonic waves onto the outer circumferential surface of the inspected member in the ultrasonic wave injection process at least rotate the outer circumferential surface of the inspected member. If this is detected in the detection process, automatic flaw detection using surface waves is carried out in the automatic flaw detection process, making highly reliable automatic ultrasonic flaw detection possible.

EXAMPLE Hereinafter, an application example of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an automatic flaw detection device that uses surface waves to automatically detect defects on the surface or under the skin of a billet 10, which is a longitudinal steel material with a substantially regular square cross section, while it is traveling. In the figure, four sides 10a, 10b, 10 of a billet 10 are shown.
An oblique flaw detector 12 is disposed in close proximity to one side surface 10a of 10c and 10d and fixed in position by a bracket (not shown). This angle flaw detector 12 is an ultrasonic vibrator 1 that emits ultrasonic waves, such as a piezoelectric ceramic.
4, and a holder 16 that is made of a material that efficiently transmits ultrasonic waves, such as a hard resin, and that holds the ultrasonic transducer 14 in an inclined position, between the holder 16 and the side surface 10a. It is disposed close to the side surface 10a in a case (not shown) for filling the water with water. The angle flaw detector 12 propagates the surface waves along the surface layers of the four side surfaces 10a, 10b, 10c, and lod by emitting ultrasonic waves toward the side surface 10a at an angle that efficiently generates surface waves. .

The transmitter/receiver circuit 18 outputs a drive signal of a relatively low frequency, for example, 0.5 to IMHz, in accordance with a command from the arithmetic control circuit 20, and causes the angle flaw detector 12 to emit an ultrasonic wave of the same frequency as the drive signal. Billet l as shown by the dashed line
A surface wave is propagated along the surface layer of O. Angle flaw detector 12
detects the echo of the surface wave or the surface wave that has gone around the outer peripheral surface of the billet 10, and supplies a detection signal representing the echo or the surface wave that has gone around the outer circumferential surface of the billet 10 to the transmitter/receiver circuit 18. The transmitter/receiver circuit 18 removes noise from the detection signal, amplifies the detection signal, and connects the A/D converter 22.
The signal is supplied to the arithmetic control circuit 20 via.

The arithmetic control circuit 20 is composed of, for example, a microcomputer, and processes the input signal according to a pre-stored program, and as the billet 10 moves in the longitudinal direction, the surface wave is actually applied to the flaw detection head. In addition to confirming that the defect is being propagated, the presence or absence of a surface or subepidermal defect is automatically determined, and the determination result is output to the display/recorder 24 and marker 26.

FIG. 2 shows an example of the operation of the arithmetic control circuit 20. First, in step S1, it is determined whether or not the starting end of the billet 10, which is continuously run in the longitudinal direction by a roller conveyor (not shown), has been reached. This determination is made based on a signal from a detector (not shown). When it is determined that the starting end of billet 1-10 has arrived, in step S2, it is determined whether the surface waves are actually propagating through the surface layer of the flaw detection portion of billet 10, that is, the side surfaces 10a, 10b, 10c, and 10d. An ultrasonic pulse is emitted from the oblique flaw detector 12 to confirm the ultrasonic transmission 61! in step S3. It is determined whether the recognition signal is detected. The ultrasonic transmission confirmation signal is a surface wave that has gone around the outer peripheral surface of the billet 1-10 and is detected by the oblique flaw detector 12. FIG. 3 shows the waveform detected by the oblique flaw detector 12, where A is an ultrasonic oscillation pulse and K is a rounded surface wave used as an ultrasonic transmission confirmation signal. Further, T in FIG. 3 indicates the effective flaw detection range in this device, which is half of the entire circumference of the billet 10, that is, half of the side surface 10a, half of the side surface 10b,
and corresponds to half of the side surface 10c. Note that the surface waves that have gone around the outer circumferential surface of billet 10 are relatively attenuated, so in order to remove noise, billet I
It is detected through a temporal gate that opens only in a predetermined time period based on the sound speed in O, and is amplified at a predetermined amplification factor.

If it is determined in step S3 that the ultrasonic transmission confirmation signal is not detected, the conveyor is stopped in step S4, and the abnormality of the surface wave automatic flaw detection device is displayed and recorded on the display/recorder 24,
An abnormality alarm is output. However, if it is determined in step S3 that the ultrasonic transmission confirmation signal has been detected, it is determined in step S5 whether or not it is the end of the billet 10. If it is determined that it is the end of the billet 10, this flow is terminated, but if it is determined that it is not the end of the billet 10, in step S6, an ultrasonic pulse for surface wave flaw detection is Angle flaw detector 1
2 is emitted at a predetermined cycle, and the echoes and magnitudes of the ultrasonic pulses are detected.

Then, in step S7, it is determined whether there is a defect on the surface of the billet 10 or under the epidermis based on the echo of the ultrasonic pulse and its size. If it is determined that there is no defect, steps 85 and subsequent steps are repeated, so that the surface defects of the billet 10 are continuously detected. However, if it is determined that there is a defect, step S8 is performed. After the marker 26 is activated to mark the defective portion of the billet 10 and the defect is displayed and recorded on the display/recorder 24, step 35
The following will be executed:

As described above, according to the above-mentioned automatic surface wave flaw detection apparatus, in step S2, an ultrasonic pulse is emitted to confirm whether or not the surface wave is actually propagating through the flaw detection area of billet 1-10. In step S3, it is determined whether or not a surface wave that rotates around the outer peripheral surface of the billet 10, that is, an ultrasonic transmission confirmation signal K is detected.
If the ultrasonic transmission confirmation signal K is detected in Step 3, automatic flaw detection using surface waves is carried out in steps S6 and S7, so that highly reliable automatic surface wave flaw detection is possible.

Further, as described above, if the ultrasonic transmission confirmation signal K is not detected in step S3, the surface wave automatic flaw detection is stopped and an abnormality alarm is output. Lack of water between flaw detector 12 and billet 1-10 (poor coupling), transmitter/receiver circuit 18
It is possible to take appropriate measures for defects such as defects prior to surface wave automatic flaw detection.

One application example of the present invention has been described above based on the drawings, but
The invention has utility in other aspects as well.

For example, in the application example described above, ultrasonic waves are emitted and received by the common oblique flaw detector 12, but the emitting transducer and the receiving transducer may be separately installed.

In addition, in the above application example, the surface waves that went around the outer peripheral surface of the billet 1o were detected as the ultrasonic transmission confirmation signal, but the surface waves that went around twice or more were detected as the ultrasound transmission confirmation signal. It is also good.

Further, although the billet 10 described above had a square cross section,
It may have a rectangular or circular cross-sectional shape.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of an example of a device to which the present invention is applied. FIG. 2 is a flowchart illustrating the operation of the apparatus of FIG. FIG. 3 is a diagram showing waveforms obtained with the apparatus of FIG. 1. lO: billet (part to be inspected)

Claims (1)

[Scope of Claims] An automatic surface wave flaw detection method that automatically detects defects on the outer peripheral surface or under the skin of a member to be inspected by using surface waves propagating in the circumferential direction of the surface layer of the member to be inspected, comprising: an ultrasonic wave incidence step in which a surface wave is propagated in the circumferential direction along the surface layer of the inspected member by obliquely injecting the ultrasonic wave onto the outer circumferential surface of the inspected member; a detection step of detecting a surface wave that has made one full turn; and an automatic flaw detection step of performing automatic flaw detection using the surface wave if a surface wave that has made at least one full turn of the outer peripheral surface of the inspected member is detected in the detection step; A surface wave automatic flaw detection method comprising: .