JP2928463B2 - Ultrasonic flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to an ultrasonic flaw detector
More particularly, the present invention relates to an ultrasonic flaw detector which inspects flaws based on attenuation of ultrasonic waves perpendicularly incident on the surface of a material to be inspected such as a steel material or a composite material.

[0002]

2. Description of the Related Art Conventionally, ultrasonic inspection of metal materials has been performed by:
The oblique flaw detection method and the vertical flaw detection method are used. In particular, only the oblique flaw detection method is often used for the inspection of the flaw of a steel pipe. However, the oblique flaw detection method detects cracks on the inner and outer surfaces of the steel pipe, but does not detect flaws inside the steel pipe (parts other than the vicinity of the inner and outer surfaces) because the ability to detect flaws is insufficient. For this purpose, a vertical flaw detection method is used.

In this vertical flaw detection method, as shown in a schematic diagram in FIG. 5, an inspection material (for example, steel pipe) 4 from a probe 3 connected to an ultrasonic flaw detection apparatus 1 via a coaxial cable 2.
The ultrasonic flaw detector 1 detects the reflected echo from the material 4 to be inspected by the ultrasonic flaw detector 1 based on the reflected echo signal obtained by receiving the probe 3 from the material 4 to be inspected. The surface 4
The position and size of the flaw 5 existing inside from a to the inner surface 4b are detected.

FIG. 6 is a block diagram showing an example of a conventional ultrasonic flaw detector used as the above-described ultrasonic flaw detector 1. As shown in FIG. 5, the ultrasonic flaw detector 10 is connected to the probe 3 via the coaxial cable 2 as in FIG. A medium (usually water) for transmitting an ultrasonic wave and a mechanism for maintaining a relative positional relationship between the probe and the material to be inspected are required between the probe 3 and the material to be inspected 4. However, the description is omitted.

[0005] The ultrasonic flaw detector 10 includes a synchronization signal oscillating unit 1.
1, a transmission unit 12, a reception unit 13, a sweep wave generation unit 14, a display unit 15, a gate unit 16, a peak hold unit 17, an alarm unit 18, and a recording output unit 19. The synchronization signal oscillating unit 11 oscillates a synchronization signal for activating the operation of each unit of the pulse type ultrasonic flaw detector 10.

The transmitting section 12 receives the synchronizing signal a shown in FIG. 7A oscillated and output from the synchronizing signal oscillating section 11,
A pulse having a large amplitude and a short time width is generated, and the pulse is output to the probe 3 via the coaxial cable 2 to excite the pulse. As a result, the probe 3 emits an ultrasonic wave and vertically enters the inspection target material 4.

[0007] The receiving section 13 receives and amplifies the ultrasonic echo received by the probe 3 from the test object 4 into an electric signal. The components of the receiving unit 13 detect an amplifier that amplifies the echo signal, an attenuator that sets the sensitivity of the ultrasonic flaw detector 10, and an AC waveform envelope that is an output of the attenuator, and outputs a DC detection signal. Although they are detectors, their illustration is omitted.

[0008] The sweep wave generator 14 is provided with a synchronizing signal oscillator 11.
Receiving the synchronizing signal a output from the controller, a sweep signal necessary for displaying the output signal of the receiving unit 13 on the display unit 15 described below is generated. The display unit 15 is a device that displays an output signal of the receiving unit 13, and is, for example, a cathode ray tube (CR)
T), a vertical deflection circuit for amplifying the output of the receiving unit 13 to an amplitude and a DC potential required for CRT display, a sweep wave generating unit 14
, A horizontal deflection circuit for amplifying the output sweep wave to an amplitude and a DC potential required for CRT display, a luminance and focus adjustment circuit, and the like.

The gate section 16 generates an echo necessary for flaw detection from the echo signals received by the probe 3 and amplified and output by the receiving section 13 based on the synchronization signal a in FIG.
The signal is selected and output based on the gate signal shown in FIG.
The gate section 16 includes a circuit capable of setting a starting point and a width of a range in which an echo is to be gated, with the echo from the surface of the test object 4 among the echo signals as a reference time point. FIG. 7B shows the output signal of the gate section 16 as a flaw echo. This flaw echo is not always received, and is rarely received and output.

The peak hold section 17 is a circuit for holding a signal having a voltage value proportional to the maximum amplitude value of the flaw echo output from the gate section 16 at the gate until the next cycle of echo reception. Therefore, this peak hold unit 17
From the maximum amplitude value of the output flaw echo of the gate unit 16 is
When the voltage is A1 as shown in FIG. 7B, a voltage having a value of A2 proportional to the voltage is output as shown in FIG.

The alarm section 18 generates and outputs an alarm signal when the amplitude of the flaw echo output from the gate section 16 exceeds a predetermined alarm level. This alarm level can be adjusted according to the inspection purpose. If necessary, the setting can be changed so that an alarm signal is output when the amplitude of the flaw echo output from the gate section 16 becomes smaller than a preset alarm level.

The recording output unit 19 includes a peak hold unit 17
Is converted into a recording signal suitable for use of a recording device such as a recorder to be used, and is output.

[0013]

However, in the above-mentioned conventional ultrasonic flaw detector, there is a problem that an uninspected area is generated just below the outer surface of the inspected material 4 and on the bottom side. This will be described in more detail. The transmission unit 12 receives the synchronization signal a from the synchronization signal oscillation unit 11 shown in FIG.
(Same as the synchronization signal a in FIG. 7A) is received as an input signal, and a large-amplitude pulse shown in FIG. 8B is generated to excite the probe 3.

Thus, the probe 3 emits an ultrasonic wave, vertically enters the inspection object 4, receives an ultrasonic echo reflected from the inspection object 4, and converts it into an electric signal. The echo signal is input to the receiving unit 13. As a result, the receiving unit 13 outputs an echo signal shown in FIG.

Here, in FIG. 8C, T is a pulse obtained by amplifying the output pulse of the transmission unit 12, and is a transmission wave having a relatively wide time width. S is a reflected wave at the boundary between the ultrasonic wave propagation medium (usually water) and the outer surface of the test object 4, and is called an outer surface echo or S wave. F is an echo received when there is a flaw in the ultrasonic wave propagation path in the test object 4 and is a flaw echo. Further, B is a reflected wave from the inner surface of the test object 4 and is called an inner surface echo or a B wave.

Therefore, the gate section 16 of the conventional ultrasonic flaw detector 10 sets the starting point of the gate after a certain time from the rise of the synchronization signal a, and sets the starting point of the output echo signal of the receiving section 13 shown in FIG. As shown in FIG. 3D, a gate signal is generated so as to output the flaw echo F of FIG.

When the inspection material 4 is a steel pipe and the entire surface (in the circumferential direction and the axial direction) is to be flaw-detected, one of the probe 3 and the inspection material (steel pipe) 4 is rotated. In addition, it is necessary to fix the other, and transport the inspection target material 4 in the axial direction. For this reason, at this time, the diametrical and eccentric vibrations of the material to be inspected 4 occur to some extent due to the change in the outer diameter and the deformation of the material to be inspected.
The probe 3 and the outer surface 4a of the test object 4 indicated by LW in FIG.
And the incident angle fluctuate to vary the magnitude of the S-wave. Also, the magnitude of the S-wave varies depending on the unevenness of the material surface.

In the setting of the gate of the gate section 16 described above,
The setting is made as shown in FIG. 8D so that the S wave does not enter the gate even when the size and width of the S wave are maximized. Therefore, when the distance LW becomes shorter and the S wave approaches the T wave, the time between the rising point of the S wave and the rising point of the gate signal becomes wider, and the flaw echo F received during that time may be gated. Can not. That is, the flaw detection range immediately below the outer surface increases. The area where the flaw cannot be detected immediately below the outer surface is the probe 3
The lower the frequency, the larger. Naturally, it is difficult in principle to detect the flaw echo F that is located immediately below the outer surface and included in the S wave.

In the case where the material 4 to be inspected has a seamless (seamless) steel pipe, the center of the outer surface circle and the center of the inner surface circle are slightly inconsistent (uneven thickness). With the rotation, the thickness indicated by t in FIG. 5 changes. Therefore, conventionally, even when the thickness t is minimum, the gate width is set so that the inner surface echo B does not enter the gate of the gate section 16.

Therefore, as the thickness t increases, the time from the end point of the gate to the rising point of the inner surface echo B increases. That is, in this case, it is not possible to detect a flaw near the inner surface (bottom surface) of the material 4 to be inspected, which is represented by a flaw echo generated within the time from the gate end point to the rising point of the inner surface echo B.

Conventionally, in order to adjust the gate, a test material processed with an artificial flaw is required, and it is necessary to insert the test material into an inspection device including the ultrasonic flaw detector 10. This is a major problem in automation of the apparatus.

On the other hand, as a method of judging the flaw of the conventional vertical flaw detection method, there is a method of judging a decrease in the echo B on the inner surface. This method is a method of judging the size of a flaw, since the amplitude of the inner surface echo B decreases when a flaw is present during the propagation of the ultrasonic wave. However, according to this conventional method, it is difficult to automatically determine the flaw because the amplitude of the inner surface echo B changes even due to the eccentricity of the material in the automatic inspection.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an ultrasonic wave capable of substantially eliminating an uninspected area and automatically detecting a flaw of a material to be inspected without using a test material having an artificial flaw. An object of the present invention is to provide a flaw detection device.

[0024]

According to the present invention, in order to achieve the above object, the present invention operates at intervals of a predetermined cycle, and causes a probe to transmit ultrasonic waves to a material to be inspected at each cycle. Thereby, based on the reflected echo signal received through the probe, the ultrasonic wave reflected from the material to be inspected, in the pulse type ultrasonic flaw detector for inspecting the flaw in the material to be inspected, from among the received reflected echo signals A gate section for gate-outputting the inner surface echo, a peak hold section for holding and outputting a signal having a voltage value proportional to the peak level of the output signal of the gate section for each preset cycle, and a peak hold section. A first filter for separating and filtering a low frequency component of an amplitude variation caused by rotation of the inspection object or the probe from the output signal, a signal delay unit for delaying an output signal of the peak hold unit, A configuration having a variable gain amplifying section for amplifying an output signal of the signal delay section based on a gain controlled by an output signal of the filter, and a second filter for removing low frequency components from the output signal of the variable gain amplifying section; It was done.

Further, the present invention provides an arithmetic operation unit for performing an operation of a predetermined procedure on the output signal of the peak hold unit and the output signal of the first filter, the operation of the signal delay unit and the variable gain amplifier unit. A configuration provided instead may be used.

Further, the gate section of the present invention gates the inner surface echo in the input reflected echo signal based on the gate signal starting at a predetermined time after the reference to the outer surface echo in the input reflected echo signal. It is what it was.

Further, in the present invention, the probe is configured so that ultrasonic waves are incident perpendicularly to the outer surface of the material to be inspected and the inspection is performed while rotating one of the probe and the material to be inspected. .

[0028]

[0029]

According to the ultrasonic flaw detector of the present invention, a specific echo is gate-output from the reflected echo signals received by the gate unit, and this gate output signal is supplied to the variable gain amplifier unit through the peak hold unit and the signal delay unit. At the same time, the gain of the variable gain amplifier is controlled based on the low frequency component of the amplitude fluctuation caused by the rotation of the test object or the probe separated and filtered by the first filter from the output signal of the gate unit. Then, a signal from which the amplitude fluctuation caused by the rotation of the material to be inspected or the probe is substantially removed from the variable gain amplifier is output.

In the present invention, the output signal of the variable gain amplifier is output through a second filter that selects only high frequency components that change rapidly due to the presence of a defect. The flaw can be inspected stably, automatically, and accurately based on the specific echo gated out by the unit.

In the case where an arithmetic unit for performing an operation according to a predetermined procedure is used for the output signal of the peak hold unit and the output signal of the first filter, the output signal of the variable gain amplifying unit is used. An equivalent signal can be output from the calculation unit.

Further, since the gate section is configured to gate the inner surface echo in the input reflected echo signal based on the gate signal having a gate starting point after a predetermined time with reference to the outer surface echo in the input reflected echo signal, Even if the distance between the material to be inspected and the probe fluctuates due to the rotation of the material to be inspected or the probe, the inner surface echo is always gated and the flaw is inspected based on the amplitude of the inner surface echo. be able to.

[0033]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of a first embodiment of the present invention. 6, the same components as those of FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted.

The ultrasonic flaw detector 20 according to the present embodiment includes a synchronizing signal oscillating unit 11, a transmitting unit 12, a receiving unit 13, a sweep wave generating unit 14, a display unit 15, a gate unit 21, and a peak hold unit 1.
7, a low-pass filter 22, a signal delay unit 23, a variable gain amplifier 24, a high-pass filter 25, an alarm unit 26, and a recording output unit 27.

That is, the ultrasonic flaw detector 20 of this embodiment
In this embodiment, the gate section 21 is changed to a configuration in which the gate starting point and the gate width are set so as to gate the echo from the inner surface of the material 4 to be inspected. Filter 22, signal delay unit 23,
The variable gain amplifier 24 and the high-pass filter 25 are provided, and the output signal of the high-pass filter 25 is supplied to the alarm unit 26 and the recording output unit 27.

Thus, in the present embodiment, the change in the magnitude of the inner surface echo for each material 4 to be inspected is detected by the low-pass filter 22 using the inner surface echo attenuation method, and the sensitivity is changed by the variable gain amplifier 24. Is corrected, and the high-pass filter 25 is used to detect, using the high-pass filter 25, a decrease signal of the inner surface echo caused by the flaw included in the fluctuation of the inner surface echo height caused by the scanning of the inspection target material 4. The flaws can be automatically detected even when the fluctuates, and without using a test piece in which an artificial flaw is processed.

Next, the operation of this embodiment will be described.
As described above, the synchronization signal a (FIG. 7) output from the synchronization signal oscillating unit 11 and having a constant transmission cycle shown in FIG.
(A), in synchronism with FIG. 8 (A)), a large-amplitude pulse as shown in FIG. 2 (B) is output from the transmission unit 12 to the probe 3 via the coaxial cable 2. . Thereby, as described above, the reflected wave of the ultrasonic wave vertically incident from the probe 3 into the test object 4 is received by the probe 3, and further,
The reflected echo signal as shown in FIG. 2C is input to the gate unit 21 via the receiving unit 13 after being converted into a reflected echo signal of an electric signal.

The gate section 21 has a gate starting point at a fixed time after the rise of the outer surface echo S, which is the first reflected echo in the input reflected echo signal, and the inner surface echo B
2D, a gate signal as shown in FIG. 2D having such a width as to be able to gate the inner surface echo B even if fluctuates, is used to gate the reflected echo signal. Such a gate portion 21
2 from the gate section 21 by the so-called S echo synchronization of FIG.
As shown in (E), a signal b obtained by gating the inner surface echo B in the reflected echo signal is output.

The gate output signal b is supplied to the peak hold section 17 and is peak-held. Therefore, the output signal of the peak hold unit 17 is an analog signal having an amplitude proportional to the amplitude of the inner surface echo B of the inspection material 4, and the amplitude varies in each transmission cycle of the ultrasonic flaw detector 20.

The frequency component of the amplitude variation of the output signal of the peak hold unit 17 is the frequency component f _C of the amplitude variation due to the rotation of the material 4 to be inspected and the ultrasonic wave propagating in the material 4 to be inspected. 4 is divided into frequency components f _{F of} amplitude fluctuations generated by being masked by the flaws in the reference numeral 4. Of these frequency components f _C and f _F , f _C is the same as the frequency of rotation (in this case, the probe 3 is fixed) at the time of flaw detection of the test object 4. Since the rotation frequency of the test object 4 is 1 Hz or less, f _C is 1 Hz or less.

In the vertical inspection of the material 4 to be inspected, particularly a steel pipe, the transmission repetition frequency of the ultrasonic inspection device is usually 1 unit.
It is set to about kHz. The duration of the amplitude fluctuation that occurs when the ultrasonic waves propagating in the inspection material 4 is masked by the flaws in the inspection material 4 is about several periods of transmission (except for the presence of a large flaw, but No problem). Therefore, the amplitude fluctuation frequency components f _F caused propagating ultrasonic waves to be inspected material 4 is masked flaw of the test material 4 is good as 100Hz larger. Since there is such a difference between the two amplitude fluctuation frequency components f _C and f _F , as described later,
It is easy to remove one by the low-pass filter 22 or the high-pass filter 25.

FIG. 3 shows an example of a change in the output signal of the peak hold unit 17 due to the rotation of the material 4 to be inspected. When this waveform is viewed in detail (when the time axis is enlarged), the amplitude fluctuates every transmission cycle of the ultrasonic flaw detector 20. F1 and F2 in FIG. 3 indicate that the propagation of the ultrasonic wave is masked by the flaws inside the test object 4 and the echo on the inner surface is reduced. The larger the flaw, the greater the decrease in the amplitude of the output signal of the peak hold unit 17.

In FIG. 3, F1 and F2 are flaws having substantially the same size. However, in the circuit having the structure of FIG. 6, F1 and F2 cannot be evaluated as the same flaw, and the amplitude is zero. F2 falling closer to the potential is evaluated as a large flaw. In the present invention, F1 and F2 are evaluated as the same flaw to make vertical flaw detection more effective.

The output signal of the peak hold unit 17 is branched into two, one of which is obtained by removing the frequency component f _F in the low-pass filter 22 (filtering the frequency component f _C ) and controlling the gain of the variable gain amplifier 24. (The input voltage value is Vc). The other of the output signals of the peak hold unit 17 is supplied to the signal delay unit 23, where the delay is adjusted by a time equal to the delay time of the low-pass filter 22. Such an analog signal delay circuit capable of adjusting the delay time can be easily realized by, for example, a bucket brigade integrated circuit.

The output signal of the signal delay unit 23 is input to another input terminal of the variable gain amplifier 24 (this input voltage value is denoted by Vi). The variable gain amplifier 24 amplifies the input voltage Vi based on the gain controlled by the input voltage Vc, and outputs an output voltage Vo having a value represented by the following equation.

[0046]

Vo = k · Vi / Vc (1) where k is a constant determined by the circuit configuration.
A circuit having such a function can be easily manufactured using a commercially available integrated circuit.

As can be seen from the equation (1), the circuit composed of the low-pass filter 22, the signal delay unit 23 and the variable gain amplifying unit 24 allows the amplitude of the frequency component f _C of the amplitude variation accompanying the rotation of the material 4 to be inspected. Gain control (AG
By performing C), the output signal of the peak hold unit 17 is taken out of the variable gain amplifying unit 24 with the amplitude fluctuation component accompanying the rotation of the test material 4 almost removed.
It is supplied to the high-pass filter 25.

The high-pass filter 25 sufficiently attenuates and removes the frequency component f _C of the amplitude fluctuation caused by the rotation of the material 4 to be inspected in the input signal, and the ultrasonic wave propagating in the material to be inspected 4 filtering the frequency component containing the amplitude fluctuation frequency components f _F resulting masked to scratch the wood 4.

The output signal of the high-pass filter 25 is supplied to an alarm section 26 and a recording output section 27, respectively. The alarm unit 26 includes a predetermined alarm level and a high-pass filter 25.
The level of the output signal is compared with the output signal, and when the level becomes lower than the alarm level, an alarm signal is generated and output. This alarm level can be adjusted according to the inspection purpose.

The recording output section 27 converts the output signal of the high-pass filter 25 into a recording signal suitable for use of a recording device such as a recorder to be used, and outputs the recording signal.

The output signal of the high-pass filter 25 is a signal exactly corresponding to the amplitude of the inner surface echo B in the material 4 to be inspected, and its amplitude changes depending on whether a flaw exists or not. Therefore, a flaw can be detected based on the amplitude. Assuming that the reception level of the inner surface echo B when there is no flaw is B _S and the reception level of the inner surface echo B when there is a flaw is B _F , the ratio k _B (= B _F / B _S ) is obtained. Be evaluated.

As described above, according to the present embodiment, since the inner surface echo B is gate-output by the S echo synchronization in the gate unit 21, the inspection material 4 is rotated with the rotation of the inspection material 4. The diametrical vibration causes the gate portion 21
The internal surface echo B can be output stably even if the time between the transmission wave T and the external surface echo S in the reflected echo signal shown in FIG. It is possible to remove the non-detectable area immediately below the outer surface and the non-detectable area near the inner surface.

FIG. 4 shows a configuration diagram of a second embodiment of the ultrasonic flaw detector according to the present invention. In the figure, the same components as those of FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. An ultrasonic flaw detector 30 shown in FIG. 4 includes a digital peak hold unit 31 and a digital low-pass filter 3 on the output side of the gate unit 21.
2. An arithmetic unit 33, a digital high-pass filter 34, an alarm unit 35, and a recording output unit 36 are provided, and are constituted by digital circuits.

The digital peak hold section 31 holds a digital signal having a value proportional to the maximum amplitude value of the echo gated by the gate section 21 until the next cycle of echo reception. The calculation unit 33 calculates the expression (1) for the output signal of the digital low-pass filter 32 and the output signal of the digital peak hold unit 31. After receiving the gate signal from the gate unit 21, the calculation unit 33 delays by a time equal to the delay time of the digital low-pass filter unit 32 and starts a predetermined calculation.

The digital signal output from the arithmetic section 33 is supplied to a digital high-pass filter 34, which sufficiently attenuates and removes the frequency component f _C of the amplitude fluctuation caused by the rotation of the material 4 to be inspected. ultrasonic waves propagating through the inner frequency components including the amplitude fluctuation frequency components f _F resulting masked to flaw of the test material 4 is filtered by digital processing.

The alarm section 35 and the recording output section 36 respectively receive the digital signal output from the digital high-pass filter 34 and perform the same operations as the alarm section 26 and the recording output section 27 by digital processing. And output a recording signal.

[0057]

As described above, according to the present invention, the output signal of the variable gain amplifying unit or the calculating unit is used to remove the low frequency component of the amplitude fluctuation caused by the rotation of the material to be inspected or the probe. By outputting through a filter, based on the specific echo gated by the gate unit,
Since the flaw can be inspected automatically and accurately, the flaw can be accurately inspected without using a test piece in which an artificial flaw is processed.

Further, according to the present invention, the gate portion gates the inner surface echo in the input reflected echo signal based on the gate signal having a gate starting at a predetermined time after the outer surface echo in the input reflected echo signal as a reference. Therefore, even if the distance between the inspection material and the probe due to the rotation of the inspection material or the probe fluctuates, the gate of the internal surface echo is always output based on the amplitude of the internal surface echo. Since the flaw is inspected, it is possible to prevent the flaw-detecting range immediately below the outer surface and the flaw-detecting range near the inner surface from being generated even if amplitude fluctuations occur due to rotation of the material to be inspected or the probe.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the device of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG. 1;

FIG. 3 is a diagram showing an output signal waveform of a peak hold unit accompanying rotation of a material to be inspected.

FIG. 4 is a configuration diagram of a second embodiment of the device of the present invention.

FIG. 5 is a schematic diagram for explaining a vertical flaw detection method.

FIG. 6 is a configuration diagram of an example of a conventional device.

FIG. 7 is a timing chart for explaining the operation of the conventional device.

FIG. 8 is a timing chart for explaining a problem of the conventional device.

[Explanation of symbols]

 1, 10, 20, 30 ... Ultrasonic flaw detector 2 ... Coaxial cable 3 ... Probe 4 ... Material to be inspected 11 ... Synchronous signal oscillator 12 ... Transmitter 13 ... Receiver 14 ... Sweep wave generator 15 ... Display 17 ... Peak hold unit 21 ... Gate unit 22 ... Low pass filter 23 ... Signal delay unit 24 ... Gain variable amplifying unit 25 ... High pass filter 31 ... Digital peak hold unit 32 ... Digital low pass filter 33 ... Operation unit 34 ... Digital high pass filter

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shigetoshi Hyodo 1 Nishinocho, Higashimukojima, Amagasaki City, Hyogo Sumitomo Metal Industries Co., Ltd. Steel Pipe Works (56) References JP-A-60-224060 (JP, A) 60-78345 (JP, A) JP-A-56-69554 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 29/00-29/28

Claims (4)

(57) [Claims] 1. A probe operates at intervals of a preset cycle to cause an ultrasonic wave to be incident on a material to be inspected from a probe at each of the above-described periods, whereby ultrasonic waves reflected from the material to be inspected are reflected by the probe. A pulse-type ultrasonic flaw detector for inspecting a flaw in the material to be inspected based on a reflected echo signal received through a gate unit, a gate unit for outputting an inner surface echo from the received reflected echo signal, A peak hold unit for holding and outputting a signal having a voltage value proportional to the peak level of the output signal of the unit at each of the preset periods; and outputting the inspection target material or the search signal from the output signal of the peak hold unit. A first filter that separates and filters a low frequency component of an amplitude variation caused by rotation of the stylus; a signal delay unit that delays an output signal of the peak hold unit; and an output signal of the first filter. Wherein a gain variable amplifier for amplifying an output signal of the signal delay unit on the basis of a gain controlled, that a second filter for passing only high frequency components from the output signal of said gain variable amplifier by Ultrasonic flaw detector. 2. The apparatus is operated at intervals of a preset cycle to cause an ultrasonic wave to be incident on a material to be inspected from a probe for each of the above-described periods, whereby ultrasonic waves reflected from the material to be inspected are reflected by the probe. A pulse-type ultrasonic flaw detector for inspecting a flaw in the material to be inspected based on a reflected echo signal received through a gate unit, a gate unit for outputting an inner surface echo from the received reflected echo signal, A peak hold unit for holding and outputting a signal having a voltage value proportional to the peak level of the output signal of the unit at each of the preset periods; and outputting the inspection target material or the search signal from the output signal of the peak hold unit. A first filter for separating and filtering a low-frequency component of amplitude fluctuation due to rotation of the stylus; an output signal of the peak hold unit and an output signal of the first filter are predetermined. A calculation section that performs calculation procedure that is, the ultrasonic flaw detection apparatus characterized by a second filter for passing only high frequency components from the output signal of the arithmetic unit. 3. The gate section gates an inner surface echo in the input reflected echo signal based on a gate signal having a gate starting point after a predetermined time based on the outer surface echo in the input reflected echo signal. Claim 1 characterized by the following:
Or the ultrasonic flaw detector according to 2. 4. The probe is characterized in that an ultrasonic wave is perpendicularly incident on an outer surface of the inspection object and an inspection is performed while rotating one of the probe and the inspection object. The ultrasonic flaw detector according to any one of claims 1 to 3.