JPH0346373Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application The present invention relates to a water immersion ultrasonic flaw detection device for steel pipes, etc. using a focus type probe, and specifically proposes an ultrasonic flaw detection device that is capable of noise discrimination. be.

Conventional technology and its problems In general, defects in steel pipes are detected using the water immersion angle angle flaw detection method, as shown in Figure 3, while the flat probe 1 is fixed and the steel pipe 2 is rotated around its axis. Flaws are detected using a device that sends it in the axial direction.

Transmission pulses output from the transmission circuit 3 are sent to the flat probe 1. The flat probe 1 that receives the transmitted pulse emits an ultrasonic wave toward the surface of the steel pipe 2, enters the steel pipe 2 using water 4 as a medium, and is propagated while being reflected from the outer and inner surfaces. If a defect exists, it is detected by the flat probe 1 as a reflected wave from the defect.

The signal detected by the flat probe 1 is amplified by a preamplifier 5 and an amplifier 6. If we take the signal at this stage as a time lapse, the fourth
The waveform will be as shown in the figure. Here, T is a transmitted pulse emitted from the flat probe 1, S is a surface echo reflected from the surface of the steel pipe 2, F is a defect echo reflected from a defect, and N is noise.

Next, the signal sent from the amplifier 6 corresponding to this waveform is sent to a gate unit 7. In the gate unit 7, the time position where the defect exists, that is, the gate position, is adjusted by a comparison test piece prepared with an artificial defect in advance, and only the signal at the gate position is extracted from the signal sent from the amplifier 6. The waveform shown in FIG. 6 is obtained from which the transmitted pulse T and surface echo S are removed. Note that N in the figure indicates noise generated at the gate position. A signal corresponding to this waveform is further sent to an amplitude determination circuit 8.

Here, it is determined whether the signal sent to the amplitude determination circuit 8 is above or below a level to be detected as a defect. If the level is higher than the level to be detected as a defect, a signal is sent to the marker drive circuit 14 of the next circuit, which delays driving by the required amount, sends a signal to the next marking device 15, and then sends a signal to the next marking device 15.
The marker liquid is sprayed onto the defective part of the steel pipe to be inspected. The flat type probe 1 is a probe not equipped with a focusing lens as shown in Fig. 5A, and the width of the emitted ultrasonic beam A tends to be slightly wider than the width of the flat type probe 1. become. Figure B shows the sound pressure distribution of the flat type probe 1.
As shown in the figure, the distribution is approximately equal in the middle part in the width direction and becomes smaller on both sides. Therefore, the steel pipe 2 shown in FIG.
When rotated in the direction, defect echoes F11 to F11 corresponding to positions x11 to x18 of defect B in B of the same figure
F18 is obtained. In the example in the figure, the number of defect echoes obtained while defect B passes through the width of beam A is
Figures F ₁₁ to F ₁₈ show that this number is determined by the surface movement speed of the steel pipe 2 and the number of pulses transmitted from the transmitting circuit 3 per unit time (hereinafter referred to as repetition frequency) when the beam width is constant. ) varies depending on
The slower the surface movement speed and the higher the repetition frequency, the greater the number.

It should be noted that the defect echoes F in FIGS. 4 and 6 mentioned above are expressed as one defect echo F by grouping the defect echoes F ₁₁ to F ₁₈ in FIG. 5B.

As can be seen _{from FIG} . All detected defect echoes F ₁₁ ~
If there are multiple _F18s in a row that are at or above the level that can be detected as a defect, it is determined to be a defect. Therefore, even if there is no defect, if noise enters the gate position, since this noise is usually a single signal, it will not be determined as a defect, and erroneous determination due to noise can be prevented.

However, in the case of pipes that require strict quality, such as steel pipes for nuclear power, the above-mentioned flat probe cannot perform flaw detection with a high S/N ratio, and when detecting small pipes, the beam of the probe If the width is wide, the incidence efficiency of ultrasonic waves into the tube is low and satisfactory flaw detection cannot be performed, so a line focus type probe equipped with a focusing lens 9a having a concave curved surface in one direction as shown in Fig. 7A is used. 9 (hereinafter referred to as a focus type probe) is used.

In this focus type probe 9, the emitted ultrasonic beam A is focused on the surface of the steel pipe 2 by a focusing lens 9a, and the sound pressure distribution is as shown in FIG.
The distribution has a peak value in the center and becomes extremely small on both sides. Therefore, when the defect B of the steel pipe 2 is detected using the focus type probe 9 in the same manner as in the case of the flat type probe 1, the position of the defect B is X ₁
Defect echoes F ₁ to F ₃ corresponding to ~X ₃ are obtained.
Note that, as in the case of the flat probe 1, the number of defective echoes obtained depends on the surface movement speed of the steel pipe 2 and the repetition frequency, assuming the beam width is constant, but usually it is approximately 1 per pulse. A surface movement speed of about 0.5 mm to 1.0 mm is used, and in this case, the number of defective echoes is 2 to 3. When the number of defect echoes is 3, small defect echoes F ₁ and F ₃ are obtained before and after the large defect echo F ₂ , as shown in FIG. 7B, and when the number of defect echoes is 2, F ₂ A defect echo that is smaller and larger than F ₁ and F ₃ can be obtained. In this case, since the beam width of the ultrasound is narrow, there are the largest defect echo F ₂ and smaller defect echoes before and after it.
F ₁ and F ₃ occur. For this reason, it is not possible to obtain an appropriate judgment signal even if you check whether there are multiple consecutive defects that exceed the level to be detected as a defect.
The amplitude determination circuit 8 has no choice but to make a determination using only the signal of the maximum reflected echo _F2 . Therefore, if the level to be detected as a defect is level AR in FIG. 8, then _F2 is detected as a defect. When making such a determination, if noise N enters the gate position even though there is no defect, the noise cannot be discriminated and it is detected as a defect, and even normal pipes are often detected as defective.

Purpose of the invention The present invention has been made in view of the above circumstances, and its purpose is to provide an ultrasonic flaw detection device that is capable of noise discrimination even when using a focus type probe.

Structure of the invention This invention uses a focus type probe to inject ultrasonic waves onto the surface of a material to be inspected using water as a catalyst, detects reflected waves from the material to be inspected, and detects defects by signal processing of the reflected waves. In water immersion ultrasonic flaw detection equipment that sets a gate and detects defect echoes within the gate, a focus-type probe that injects ultrasonic waves onto the surface of the test material and detects reflected waves from the test material. an amplification/gate section that amplifies the reflected wave detected by the probe and further extracts only the signal within the gate at the time position where the defect exists; A Hi level comparator that outputs a signal when the level is higher than the set value set assuming that a level comparator; a counter circuit that counts the frequency of the signal from the Lo level comparator and outputs a signal when the frequency is equal to or greater than a preset value; a signal from the Hi level comparator;
This water immersion ultrasonic flaw detection device is characterized by comprising an AND logic circuit that outputs a signal only when a signal from the counter circuit is received.

Embodiments The present invention will be described in detail below based on drawings showing embodiments thereof.

Figure 1 shows the device of the present invention, and Figure 2 is a block diagram.
The figure shows the waveform of the detection signal obtained by the apparatus of FIG. 1 after passing through the gate unit.

In FIG. 1, 9 is a focus type probe. A transmission pulse output from the transmission circuit 3 is sent to a focus type probe 9. The focus type probe 9 that receives the transmission pulse emits ultrasonic waves with a narrow beam width toward the surface of the steel pipe 2, and the emitted ultrasonic waves are transmitted to the water 4.
is input into the steel pipe 2 as a medium, and if a defect exists, it is detected by the focus type probe 9 as a reflected wave from the defect.

The signal detected by the focus type probe 9 is amplified by a preamplifier 5 and an amplifier 6, which are part of the amplification/gate section, and sent to the gate unit 7, which is also a part of the amplification/gate section. .

The gate unit 7 has the following circuits, a Hi level comparator 10 and a Lo level comparator 11.
Only the signal at the time position where the defect exists is sent.

Note that the time position where the defect exists, that is, the gate position, is adjusted using a comparison test piece in which an artificial defect has been processed in advance.

The signal sent from the gate unit 7 is Hi
It is sent to the level comparator 10 and the Lo level comparator 11 at the same time. The Hi level comparator 10 determines the level of the signal to be detected as a defect.
It is set in advance. This setting value is set based on the signal level from the artificial defect of the comparison test piece processed with the artificial defect. The Hi level comparator 10 sends a pulse signal to the AND logic circuit 13 only when the signal sent from the gate unit 7 is larger than the set value.

On the other hand, the Lo level comparator 11
It is set to a value lower than level comparator 10,
When the signal from the gate unit 7 is above a set value, a pulse signal is sent to the counter circuit 12. Said Lo
The pulse signal output from the level comparator 11 enters a counter circuit 12, which counts the frequency of the pulse signal, and sends a pulse signal to the AND logic circuit 13 when the frequency is greater than a preset value.

The signal level set value in the Lo level comparator 11 and the pulse signal frequency set value in the counter circuit 12 are determined as follows.

That is, when using the focus type probe 9, the repetition frequency and the surface of the steel pipe 2 are adjusted so that the number of defect echoes obtained while the defect passes through the width of the beam is 2 to 3 as described above. The moving speed is set. Therefore, when the number of defective echoes obtained while passing through the width of the defective beam is 2, the set value in the counter circuit 12 is set to 2, and the set value in the Lo level comparator 11 at this time is:
The level is set so that the smaller of the two signals can be detected. Also, the number of defective echoes is 3.
In this case, the setting value in the counter circuit 12 is set to 3.
The setting value of the Lo level comparator 11 is set to a level at which the smallest signal among the three can be detected.

Note that the counter circuit 12 counts the frequency of the pulse signal when the pulse signal from the Lo level comparator 11 is continuous, but when the pulse signal is interrupted for a preset time or more, it resets the counter and starts a new one. Configured to start counting.

The pulse signals of the Hi level comparator 10 and the counter circuit 12 are sent to an AND logic circuit 13.

AND logic circuit 13 is Hi level comparator 1
0 and a signal when receiving the pulse signal of the counter circuit 12 is output, and when any signal is missing, no signal is output.

The above operation will be explained with a concrete example.

First, more specifically than the rotation speed of the steel pipe 2, the surface movement speed of the steel pipe 2 is set based on the repetition frequency transmitted from the transmission circuit 3 and the beam width of the focus type probe 9. With this setting, for example, while the defect B shown in FIG. 7A passes through the width of the beam A of the focus type probe 9, signals F ₁ to F ₃ shown in FIG. 7B can be obtained. Next, as shown in Figure 2,
The setting value of the Hi level comparator 10 is set to Hi level, which is the level at which defects are detected, and Lo
The setting value of the level comparator 11 is set to a Lo level at which the lowest one among F ₁ to _{F 3} can be detected. Note that the set value of the counter circuit 12 at this time is 3.

When flaw detection is started in this state, if there is a defect in the steel pipe 2 that is higher than the level to be detected, F ₁ , F ₂ ,
The defective echo of _F3 is transmitted from gate unit 7 to Hi level comparator 10 and Lo level comparator 1.
1 at the same time.

The Hi-level comparator 10 determines that _F2 , which is a defective echo that is higher than the set value of the Hi-level comparator, is defective, and sends a pulse signal to the AND logic circuit 13. In the Lo level comparator 11,
The defective echo is higher than the set value of Lo level.
F ₁ , F ₂ , and F ₃ are detected and three consecutive pulse signals are sent to the counter circuit 12 . Counter circuit 12
counts the frequency of pulse signals sent from the Lo level comparator 11, and sends a pulse signal to the AND logic circuit 13 when the set value reaches 3.
In the AND logic circuit 13, after receiving the pulse signal from the Hi-level comparator 10, a pulse signal is input from the counter circuit 12 after a time period corresponding to one pulse determined by the repetition frequency has elapsed, so at this time, the marker drive circuit Send a signal to 14.

During flaw detection, even though there are no defects, a single noise occurs at the gate position as shown in Figure 2.
In the Hi level comparator 10, as a defect,
A pulse signal is sent to the AND logic circuit 13, but since the low level comparator 11 detects only one signal, only one pulse signal is sent to the counter circuit 12, and the set number of 3 is not reached. Therefore, no pulse signal is sent to the AND logic circuit 13.

As described above, the device of the present invention distinguishes between noise and defect signals and detects only the defect signals, thereby making it possible to prevent false detection.

Note that noise may also continuously generate a much larger number of pulses than a normal defect. Such noise can be detected by providing an upper limit setting value to the counter of the counter circuit 12, and the pulse signal can be prevented from being sent from the counter circuit 12 to the AND logic circuit 13.

The above explanation is for the case of oblique flaw detection, but it can also be applied to the case of vertical flaw detection using a focus type probe.

Further, although the above description is about flaw detection of steel pipes using a focus type probe, it can also be used for flaw detection of other types of flaws such as steel materials, wire rods, bar steel, etc. using other focus type probes.

Alternatively, the output from the AND logic circuit 13 may be sent to a display circuit, a circuit for separating materials from lines, or the like.

Effects of the Invention As detailed above, the inventive device takes advantage of the fact that low-level defect echoes occur before and after the peak defect echo when flaws are detected using a focus type probe. This method counts defect echoes at a low level to distinguish between noise and defect signals, and excludes noise.This has the excellent effect of preventing false detection and enabling highly accurate flaw detection. have

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the device of the present invention;
The figure shows the waveform of the signal from the gate unit of the detection signal obtained with the device shown in FIG. Waveforms entering the gate unit, Figure 5A is a conceptual diagram of the ultrasonic beam of a flat type probe, Figure 5B is a sound pressure distribution diagram of a flat type probe, and Figure 6 is a conceptual diagram of the ultrasonic beam of a flat type probe. The waveform of the detection signal from the gate unit of the detection signal detected using the flat type probe shown in the figure, and the conceptual diagram of the ultrasonic beam of the focus type probe equipped with a concave curved transducer, are shown in Figure 7A. The figure shown in Figure 7B is a sound pressure distribution diagram of the focus type probe, and Figure 8 is the signal from the gate unit of the detected signal detected using the focus type probe of Figure 7. waveform. 1...Flat type probe, 2...Steel pipe, 3...
Transmission circuit, 4...Water, 5...Preamplifier, 6...
Amplifier, 7... Gate unit, 8... Amplitude judgment circuit, 9... Focus type probe, 10... Hi
Level comparator, 11...Lo level comparator, 12...Counter circuit, 13...AND
Logic circuit, 14...Marker drive circuit, 15
...Marking device.

Claims (1)

[Claim for Utility Model Registration] Using a focus type probe, injecting ultrasonic waves into the surface of a test material using water as a medium, detecting reflected waves from the test material, and signal processing of the reflected waves. In water immersion ultrasonic flaw detection equipment, which sets a defect detection gate and detects defect echoes within this gate, the focus type ultrasonic flaw detector injects ultrasonic waves into the surface of the material to be tested and detects the reflected waves from the material to be tested. a probe; an amplification/gate unit that amplifies the reflected wave detected by the probe and extracts only a signal within the gate at a time position where a defect exists; and a signal level from the amplification/gate unit. a Hi level comparator that outputs a signal when the signal level from the amplification/gate section is greater than or equal to a preset value, and a Lo level comparator that is preset to a lower value than the Hi level comparator and outputs a signal when the signal level from the amplification/gate section is greater than or equal to the preset value. a counter circuit that counts the frequency of the signal from the Lo level comparator and outputs a signal when the frequency is greater than or equal to a preset value; and a signal from the Hi level comparator.
A water immersion ultrasonic flaw detection device comprising an AND logic circuit that outputs a signal only when the signals from the counter circuits are both input.