JPS6213626B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides flaw detection for ultrasonic flaw detection using the reflection method for steel materials, etc., outside the range of the flaw detection gate provided in the thickness direction of the test material, that is, on the front and back sides of the test material. The present invention relates to an ultrasonic flaw detector capable of detecting a defect of a certain size or larger in the dead zone on the back side of the dead zone.

Ultrasonic flaw detection is widely used to detect defects in steel plates, laminations, etc., but most of them are based on vertical flaw detection. The disadvantage of this vertical flaw detection method is that the transmitted pulse is extremely large compared to the received signal from the material being tested, which results in a large dead zone in the direction of the thickness of the material to be tested, making it impossible to detect flaws with a thickness of approximately 10 mm or less. That's true. In order to eliminate this drawback, several excellent methods such as the partial water immersion method and the two-piece probe method have been used, and now the two-piece probe method is used for most flaw detection of thin steel plates. The tentacle method is being implemented.

With the advent of this two-piece probe method, the dead zone in the thickness direction has become somewhat smaller, and flaw detectors have also been improved, making it possible to detect flaws in steel plates with a thickness of about 4 to 6 mm.

However, even now that such improvements have been made, there still remains a flaw detection dead zone of about 1.5 to 2 mm for both the front and back layers. Of this dead zone, the dead zone on the surface side is designed to prevent the reflected signal from the surface of the tested material from being confused with the reflected signal from defects near the surface, taking into account the variation in the gap between the probe and the tested material. This is caused by setting the starting point of the flaw detection gate slightly inward from the surface.
In addition, the dead zone on the back side is set at the end point of the flaw detection gate in order to prevent the reflected signal from the back side from being confused with the reflected signal from defects near the back side, and to take into account changes in the thickness of the test material. This is caused by setting it slightly inward from the back surface.

On the other hand, in order to respond to changes in manufacturing conditions for steel materials, such as changes in defect occurrence patterns due to continuous casting, etc., and expansion of uses for steel materials, detection of defects present in the front and back layers has become extremely important.

Regarding defects on the surface layer, even if it is within the dead zone on the surface side, the reflected signal from a large defect can be detected by normal flaw detection, as the multiple reflection signals remain inside the flaw detection gate and are extracted. Large defects in the dead zone on the surface side can also be detected by the method using a gate. However, defects within the dead zone on the back side cannot be detected by conventional flaw detection methods using normal flaw detection gates.

In view of the above circumstances, the present invention is capable of detecting a defect of a certain size or more in the flaw detection dead zone on the back side of the material to be inspected. In ultrasonic flaw detection equipment that detects flaws by converting pulses into ultrasonic waves using a probe and inputting them into the test material, and then receiving the flaw detection signals, the gate opening timing signal is determined based on the thickness information of the test material that is input separately. A setting controller that outputs the a gate circuit that extracts a first reflected signal and a second reflected signal from the defect, respectively;
A device that calculates a thickness signal from the interval between the first reflected signal and the second reflected signal from the gate circuit, and a device that compares the thickness signal from the device and the test material thickness comparison signal from the setting controller. and a thickness determination section that outputs a defect signal when the thickness signal is outside the range of the test material thickness comparison signal.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the apparatus shown in FIG.

In the figure, 1 is a setting control unit that controls the components described later in relation to each other and instructs a comparison signal of the thickness of the material to be inspected for determining a large defect in the backside dead zone, and 2 is an ultrasonic wave generator. A main synchronization output section generates a main synchronization output Xm at a period Tm that is longer than the time interval at which the flaw detection signal can attenuate, and 3 is a transmitting section that generates a transmission pulse Et in synchronization with the signal from the main synchronization output section 2. 4 is the gate starting point signal X _g1S , _{X g2s} , X _g3s from the setting control unit 1, and three gate signals _{X g1 , X g2 ,} This is a gate section generator that outputs _g3 , and here gate starting point signal X _g1
S ,X _g2s ,X _g3s gate width signal X _g1l ,X _g2l ,X _g3l
is created by inputting thickness information t to the setting control section 1 from the outside. The gate output X _g1 is for setting a normal flaw detection gate, and this flaw detection gate is set between the surface layer and the back layer of the material 6 to be inspected by conventionally known means. Gate signals X _g2 and X _g3 are used to set gates that are specially provided in the present invention in order to detect relatively large defects in the dead zone on the back side of the test material 6, in addition to the normal flaw detection gates. The gate signal X _g2 is set to have a width twice as wide as the dead zone on the back side, centered _on the thickness of the material 6 to be inspected, and the gate _signal It is set to the same width as .

Next, 5 is a probe connected to the transmitter 3, and the figure shows, as an example, a state in which a two-part probe is placed on a specimen 6 for flaw detection. In the present invention, the probe 5 is not necessarily limited to a two-piece probe.

The transmitted pulse output _Et is converted into an ultrasonic wave by the probe 5, propagates through the test material 6, is reflected by the defect F and the back surface B, and is converted into an electric signal by the probe 5 again. and is received as flaw detection signal _E1 . This flaw detection signal E ₁ is amplified to a predetermined size by the reception amplifier 7 and sent to the analog gate 8, where the signal E _g1 of each section specified by the gate section generator 4 is sent to the analog gate 8. , E _g2 , E _g3 are extracted. That is, the gate section generating section 4 and the analog gate 8 constitute a gate circuit A.

Here, the signal E _g1 is a reflected signal extracted from a defect existing within a normal flaw detection area, and this defect signal E _g1 is sent to a defect display section 12, which will be described later. The signal E _g2 is the first reflected signal from the back surface of the material to be inspected 6 when there is no defect in the back side dead zone or if there is a defect but the magnitude of the reflected signal from the defect is smaller than the reflected signal from the back surface. and
If there is a defect in the backside dead zone that has a reflection signal larger than the backside reflection signal, this is the first reflection signal from that defect. The signal E _g3 is a second reflected signal obtained following the first reflected signal E _g2 . A flip-flop circuit 9 generates _a rectangular wave E2 that is set by the first reflected signal _Eg2 and reset by the second reflected signal _Eg3 . The width of this rectangular wave E ₂ corresponds to the thickness of the test material 6 if there is no large defect as described above in the dead zone on the back side of the test material 6 . On the other hand, if there is a large defect as described above in the back side dead zone, that is, a large defect whose ratio to the defect reflection signal exceeds 1, the width of the rectangular wave E ₂ is 6 Corresponds to the distance from the surface to the defect, and is a square wave when the aforementioned large defect does not exist.
This value is smaller than the width of _E2 , that is, the width corresponding to the thickness of the material 6 to be inspected. Further, in order to make the operation of the flip-flop circuit 9 more stable, a reset signal E is inputted from the setting control section 1 in synchronization with the main synchronizing signal _Xn , and the flip-flop circuit 9 is reset by this signal.

Reference numeral 10 denotes a counter that counts the clock O ₅ for converting the thickness of the material to be inspected, which is generated at minute regular intervals in the setting control unit 1, and outputs the width of the rectangular wave E ₂ . However, when there is no large defect in the back dead zone, it corresponds to the thickness of the specimen 6, and when there is a large defect in the back dead zone, it corresponds to the distance from the surface of the specimen 6 to the defect. Reference numeral 11 denotes a thickness determining section, which will be described later. Generally, in steel materials, etc., there is a certain range of variation in plate thickness with respect to the nominal thickness. Also, depending on the location of the defect, the first reflected signal E _g2 is located within the gate X _g2 (gate width X _g2l ) and is extracted, but the second reflected signal E _g3 is extracted from the gate X _g3 (gate width width x _g2l ) and may not be extracted.
The output E ₃ is a very large value. Therefore, the setting control unit 1 sets a certain range before and after the nominal thickness of the test material 6, specifically from {(nominal thickness) - (constant value)} to {(nominal thickness) + (constant value)} is generated, and the thickness determination section 11 compares the output signal E ₃ from the counter 10 with the thickness comparison signal E _l , and outputs the output _{signal E 3 .} If it is out of the range of the thickness comparison signal E _l , it is determined that there is a defect, and a defect signal E ₄ is output.
And this defect signal E ₄ and the analog gate 8
A defect signal E _g1 is displayed on the defect display section 12.

Since the present invention is as described above, defects in the normal flaw detection area and large defects in the front dead zone are detected by the analog gate 8 as the defect signal E g1 by the normal flaw detection procedure, and large defects in the back dead zone are detected by the analog gate 8 as the defect signal E _g1 . A defect is detected as a defect signal _E4 by the thickness determining section 11 according to the procedure according to the present invention. Therefore, conventionally, defects within the dead zone on the back surface of the test material 6 could not be detected at all, but with the apparatus of the present invention, defects larger than a certain size can be detected even within the dead zone on the back surface. can. Further, in the present invention, since defect detection is performed as described above, even if the test material 6 vibrates and an error occurs in the tracing of the probe 5, the defect can be detected without being affected by the error.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the apparatus shown in FIG. 1: Setting control section, 2: Main synchronization generation section, 3: Transmission section, 4: Gate section generation section, 5: Probe, 6: Material to be inspected, 7: Receiving amplifier, 8: Analog gate section, 9: Flip-flop circuit, 10: counter, 11: thickness determination section, 12: defect display section,
A: Gate circuit, a: Main synchronization signal, b: Transmission pulse, c: Reception signal, d~f: Gate signal, g~
i: Output signal from the analog gate section, j: Output signal from the flip-flop circuit.

Claims (1)

[Claims] 1 In an ultrasonic flaw detection device that converts the transmitted pulses from the pulse transmitter into ultrasonic waves using a probe and inputs them into the test material, and then receives the flaw detection signals for flaw detection, the test material plate is input separately. A setting controller outputs a gate opening timing signal based on the thickness information, and a signal from the setting controller extracts reflection signals from defects within the flaw detection area slightly inside the front and back surfaces of the test material. A gate circuit extracts a first reflected signal and a second reflected signal from a defect near the front or back surface of the inspection material, and the thickness is calculated from the interval between the first reflected signal and the second reflected signal from the gate circuit. A device for obtaining a signal compares the thickness signal from the device with the test material thickness comparison signal from the setting controller, and when the thickness signal is outside the range of the test material thickness comparison signal, detects a defect signal. An ultrasonic flaw detection device characterized by comprising a thickness determination section that outputs an output.