JPH0396858A - Ultrasonic flaw detecting device - Google Patents

Abstract

PURPOSE:To accurately remove a reflected echo from the end parts of a material to be inspected by constituting a surface echo detection system and a defect echo detection system independently and detecting the existence of the surface echo based on the timing of the echo received from the ends of the material. CONSTITUTION:This device is equipped with a defect echo detecting means 5 which detects a defect echo reflected by a defect of the material (steel pipe) 2 to be inspected from the echo, a surface echo detecting means 62 which detects a surface echo reflected by the surface of the steel pipe 2 from the echo, a surface echo decision means 63 which decides whether or not the echo is surface echo based on the timing of the echo detected by the surface echo detecting means 62, and a defect detection control means 6 which signifies the detection result of the defect echo detecting means 5 only when the surface echo decision means 63 decides that there is the surface echo. Consequently, a water reflection echo and a reflection echo from the end parts of the steel pipe 2 can accurately be removed and an area of flaw nondetection of the end part can be made as small as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic flaw detection device for flaw detection of various materials such as pipes.

[Prior art]

Automatic flaw detection using ultrasonic waves uses equipment that performs water immersion flaw detection. For example, an automatic flaw detection device for water immersion testing of pipes has a probe installed on the inner peripheral wall of a drum-shaped rotating body that has a through hole in the axial direction, and the rotating body is moved while filling the inside with water. Rotating probe type flaw detection equipment is generally used, which detects flaws around the entire circumference of the pipe using a probe that rotates and penetrates the pipe to be inspected at the center of rotation, and rotates together with the rotating body. There is.

When testing tube flaws using such a flaw detection device, the tip of the tube.
When the trailing edge is detected, an echo similar to the defect echo reflected by the defect appears. Such edge detection echoes were sometimes erroneously determined to be defective echoes. Therefore, in order to prevent erroneous determination of echoes, a tube passage detector is installed on the upstream side of the tube conveyance path to detect the passage of the tube, and a speed detector is installed in the conveyance rod path to detect the tube conveyance speed. There is a device installed. This involves detecting passage of the tube by the tube passage detector, and predicting the time required from the detection until the tip and rear ends of the tube reach the probe position from the detection results of the speed detector, Based on this predicted result, end detection echoes are removed by setting the tip and rear end of the tube as undetected areas.

However, as mentioned above, in the system that sets the undetected area, there is a problem that the undetected area is wider than necessary due to the detection error of each detector and the setting error of the undetected area. .

To solve this problem, Japanese Patent Application Laid-Open No. 50129
There is a flaw detection method as disclosed in Publication No. 091.

This is done by installing a circuit that generates a gate that distinguishes between surface echoes detected on the surface of the material to be inspected and defective echoes. Only defective echoes are valid. In this flaw detection method, defect echoes and edge detection echoes cannot be distinguished from each other by the presence of surface echoes.
1I There is no need to set up a flaw detection castle.

[Problems to be Solved by the Invention] However, in the flaw detection device B-1 equipped with the gate as described above, defect work: No and edge detection echoes are distinguished based on the presence or absence of surface echoes. I-3. For example, in the angle angle flaw detection method, the intensity of surface echoes is smaller than the defect echoes in polished materials with good surface quality. However, there was a problem that it could not be applied to flaw detection using surface echo.

In addition, when applying the above-mentioned flaw detection method using a cage to a rotating probe type flaw detection device, water rotates in the rotating body in the same way as the probe, but the material to be inspected is placed at the center of this rotation. In a state where no water is present, a cavity is created near the center of rotation due to centrifugal force without the water present, and a reflected echo (water !l; 1 echo) is generated from the interface between this cavity and the water. appear. The water reflected echo reflected from the interface between the cavity and the water may be mistakenly judged as a surface echo during flaw detection of the material to be inspected. There is a risk that an echo and an edge detection echo that appears during edge flaw detection of a material to be inspected may be mistakenly determined to be a defect detection echo.

The present invention has been made in view of the above circumstances, and the surface echo detection system and the defective echo detection system are configured as independent circuits, and the presence or absence of surface echoes can be determined by quickly receiving the echoes. The surface echo discrimination accuracy is good by performing the process based on the speed, and the water reflection echo and the reflection from the edge of the material to be inspected are accurately removed, and the undetected area at the edge is as much as possible. The purpose is to provide a small ultrasonic flaw detection device.

[Means to solve the problem]

The ultrasonic flaw detection device according to the present invention detects defects by injecting ultrasonic waves into a material to be inspected and receiving reflected echoes. A defect echo detection means for detecting a defect echo, a surface echo detection means for detecting a surface echo reflected from the echo on the surface of the inspected material, and an early or late reception timing of the echo detected by the surface echo detection means. surface echo discriminating means for discriminating whether the echo is a surface echo or not; and a defect for validating the detection result of the defect echo detecting means only when it is determined by the surface echo discriminating means that there is a surface echo. The present invention is characterized by comprising a detection control means.

[Effect]

In the present invention, since the defect echo and the surface echo are detected by separate detection means, it is possible to detect a weak surface echo, and only the defect echo when there is a surface echo is effective. , the detection of echoes reflected at the edges of the inspected material is suppressed, and the presence or absence of surface echoes is determined by the early/late reception timing of the surface echoes. It is possible to prevent erroneous identification of reflected echoes other than surface echoes due to changes in flaw detection conditions.

〔principle〕

As mentioned above, in a rotary probe type flaw detection device, if there is no steel pipe to be inspected within the flaw detection range of the probe, a cavity is generated near the axis of the rotating body, and the ultrasonic waves traveling through the water are It is reflected at the interface between this cavity and water, and a water reflected echo similar to a surface echo appears.

FIG. 3 is a timing chart showing the relationship between appearance times of surface echoes and water-reflected echoes. The size of the cavity constantly changes due to the rotation of the water in the rotating body 10, and as the distance from the probe to the cavity changes, the propagation time of the ultrasound changes. As shown in Figure 1, the water reflection echo W does not appear at a fixed position in the Tying Chart-12 like the surface echo S. When distinguishing between a surface echo S and a water-reflected echo W using this method, the elapsed time from the rise of the gate word for detecting the surface echo S to the rise of the surface echo S must be determined in advance. Setting time t
s, and determine that it is a surface echo S when the variation state amount of the time t from the rise of the G1 signal to the rise of the detected echo signal with respect to the set time ts is less than a predetermined amount. do.

In the present invention, defect echoes and surface echoes are detected using separate gates, and as mentioned above, if there is a surface echo, there is a steel pipe within the flaw detection range of the probe, so it is detected in this case. Detection is performed using only the detected defect echoes as valid.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on drawings showing embodiments thereof. FIG. 1 is a block diagram of an apparatus for performing oblique flaw detection, which is an ultrasonic flaw detection apparatus according to the present invention.

In the figure, 1 is a probe, and the probe 1 has a rotating body 10 mounted on the inner circumferential side of a drum-shaped rotating body 10 having a through hole in the axial direction.
It is arranged at a predetermined angle with respect to the center of zero.

The interior of the rotating body IO is always filled with water by a predetermined means, and during ultrasonic flaw detection, the water is rotated around this center by the rotation of the axis of the rotating body 10. The @tube 2, which is the material to be inspected, is transferred so as to pass through the axis of the rotating body 10 in the axial direction, and the probe 1 rotates together with the rotating body 10.
The entire circumference and length is inspected using the water immersion ultrasonic flaw detection method.

The probe 1 is excited at predetermined intervals by an oscillator 3, and causes ultrasonic waves to be incident on the steel pipe 2. In this way steel pipe 2
The ultrasonic waves incident on the outer surface of the steel pipe 2. It is reflected by a reflection source such as the cavity or a defect, and detected by the probe I as an echo.

The echo of this detection result is given to the lth amplifier 4 and the second amplifier 61 provided in the defect detection control section 6 that controls the output of the flaw detection result.

The echo input to the first amplifier 4 is amplified by a predetermined amount and is applied to the l-th gate circuit 5. FIG. 2 is a timing chart showing the operation of the gate circuit. As described above, the transmitted wave T transmitted from the probe first appears in the echo detected when flaw detection is performed. Next, a surface echo S and a defect echo F appear. In the first gate circuit 5, a first gate CZ is set in a time domain after a predetermined time has elapsed from the surface echo S in order to detect the defect echo F, and if there is an echo within this range, this echo is detected as the first gate. The signal passes through the gate circuit 5 and is applied to the control switch 67 of the defect detection control section 6 .

Note that the position of the first gate G + is adjusted by experimentally detecting artificial defects formed on the inner and outer surfaces of the steel pipe 2 in advance.

The defect detection control unit 6 includes a 21st VL width converter 61, a second gate circuit 62 that generates a second gate for detecting the surface echo S, and a surface echo determination unit 63 that determines the presence or absence of the surface echo S. , the echo given to the second amplifier 6l is amplified by a predetermined amount and given to the second gate circuit 62 and the time/voltage converter 631 of the surface echo discrimination section 63.

In the second gate circuit, the time region in which the surface echo S appears is determined based on the distance between the probe 1 and the steel pipe 2 obtained in advance as shown in FIG. 2, and the second gate G2 is set in this time region. . If there is an echo within this second gate G2, a high-level hell signal is given to the discriminator 634 of the surface echo discriminator 63.

The surface echo discrimination section 63 includes a time/voltage converter 631,
Takagi pass filter 632, comparator 633, discriminator 634
The connections are configured in this order.

The time/voltage converter 631 to which the echo is applied from the second amplifier 61 converts the time t from the rise of the second gate signal to the rise of the echo as shown in FIG. A pass filter 632 is provided. The Takagi pass filter 632 supplies only a certain portion of the high frequency of the voltage signal above a certain frequency to the comparator 633 in order to detect the fluctuation state of the voltage signal. The comparator 633 has a set value representing the permissible fluctuation amount of the voltage signal inputted in advance, and compares a certain amount of high frequency given from the Takagi pass filter 632 with the set value. If the high frequency power given from the Takagi pass filter is less than the set value, a high frequency signal is given to the discriminator 634.

Extracting the high frequency component of the voltage signal in this way is as follows:
This is to study the fluctuation state of echo reception timing within the second gate. When the steel pipe 2 exists within the flaw detection range of the probe 1, the reception timing of the echoes is approximately constant, and even if the reception timing fluctuates, it is a gradual fluctuation. However, if the steel pipe 2 does not exist within the flaw detection range, a cavity will be created as described above.
Since the size of the cavity changes rapidly, the timing for receiving the echo changes much more than in the case where the steel pipe 2 is present. For this reason, by extracting a certain high frequency part of the voltage signal and examining the fluctuation state of reception queuing from the magnitude of the certain high frequency part, it can be determined whether the detected echo is a surface echo or not.

The discriminator 634 determines that a surface echo exists when the high-level signal is simultaneously applied from the second gate circuit 62 and the comparator 633, and the high-level signal is applied to the control switch 67.

When the control switch 67 receives a high-level signal from the discriminator 634, it is turned on and outputs the flaw detection result of the defect echo output from the first gate circuit 5 to the outside.

As explained above, surface echoes and defect echoes are detected separately, and when these echoes are obtained simultaneously, the defect echo is considered valid. However, in detecting surface echoes, water reflection echoes from cavities and surface echoes are Since this determination is made based on whether the echo reception timing is early or late, erroneous determination of surface echoes can be prevented. Further, if no surface echo is obtained, the detected defect echo is not output, so the edge detection echo that appears when the edge of the inspection target is detected is not output as a flaw detection result.

In this embodiment, the case where the oblique flaw detection method is used has been described, but the present invention is not limited to this, and the present invention can also be applied to the vertical flaw detection method.

〔effect〕

As described in detail above, the ultrasonic flaw detection device according to the present invention has a surface echo detection system and a defect echo detection system each having an independent circuit structure, and also determines whether or not there is a surface echo by changing the reception timing of the echo early or late. Since it is carried out based on The present invention has excellent effects, such as making it possible to accurately remove J echoes and reducing the undetected area at the end.

[Brief explanation of drawings]

Fig. 1 is a process diagram of an ultrasonic flaw detection device according to the present invention that performs oblique flaw detection, Fig. 2 is a timing chart 1 showing the operating state of the gate circuit, and Fig. 3 is a surface echo and boundary detection. It is a timing chart showing the relationship between echo and application time. 2... Steel pipe 5... First gate circuit 6... Defect detection control section 62... Second gate circuit 63...
Surface echo discrimination unit

Claims (1)

[Scope of Claims] 1. In an ultrasonic flaw detection device that detects defects by injecting ultrasonic waves into a material to be inspected and receiving echoes thereof, defects reflected from defects in the material to be inspected from the echoes. A defect echo detection means for detecting an echo; a surface echo detection means for detecting a surface echo reflected from the surface of the inspected material from the echo; and early or late reception timing of the echo detected by the surface echo detection means. surface echo discriminating means for discriminating whether the echo is a surface echo or not; and a defect for validating the detection result of the defect echo detecting means only when it is determined by the surface echo discriminating means that there is a surface echo. 1. An ultrasonic flaw detection device comprising: detection control means.