JP2003014706A - Method and apparatus for inspection of welding of tank steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus wherein a weld part and its thermal influence part can be inspected from the upper part of a coating on the surface of a tank steel plate. SOLUTION: The method and the apparatus are constituted in such a way that longitudinal cracks 18a, 18b in the direction of a weld bead 18 and a transversal crack 18c in a direction crossing the weld bead 18 are flaw-detected by a creeping wave method using three ultrasonic probes 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tank steel plate welding inspection method and apparatus for inspecting a welded part of a tank steel plate having a coating on the surface or a scratch on the surface of a heat-affected zone thereof.

[0002]

2. Description of the Related Art Conventionally, in outdoor tanks, inspecting for scratches on the surface of a welded part of a tank steel plate and its heat-affected zone has been conducted in accordance with the Fire Service Law. As a conventional inspection method, after peeling off the coating film etc. coated on the surface of the tank steel plate by sandblasting etc., the inspection by the penetrant flaw detection method or the magnetic particle flaw detection method is carried out, and the permeation instruction pattern formed on the damaged portion Alternatively, the scratches generated on the surface of the welded portion of the tank steel plate and its heat-affected zone were inspected by visually observing the magnetic powder pattern.

On the other hand, a flaw detector for traveling on the surface of a large steel structure has been proposed by Japanese Patent Laid-Open No. 10-288610 (hereinafter referred to as "known example"). With this device, it is possible to repaint with a grinder that removes paint and rust etc. near the welded part before flaw detection work, flaw detection of the welded part with an ultrasonic probe, and paint sprayed from a paint spray nozzle. I'm trying to do it.

[0004]

However, in the above-mentioned conventional example, in the inspection by the penetration flaw detection method or the magnetic particle flaw detection method, the removal of the coating film is an essential condition in view of its principle and performance. In addition, the inspector visually observes the permeation instruction pattern or magnetic powder pattern formed at the site where the scratch has occurred,
Since it relies on visual inspection by humans, there is a risk that omission or overlooking of scratches may occur due to environmental conditions or implementation conditions (illuminance, power supply, workmanship, eye fatigue).

Further, in the inspection by the penetrant flaw detection method or the magnetic particle flaw detection method, the flaw detection work is carried out manually by the inspector, and in addition to scratches such as cracks, puncture scratches and shallow undercuts are detected. Inspection experience and skill required for discrimination were required, and in addition, inspection and repair work required labor and time.

Prior to the inspection, the coating film or the like coated on the surface of the tank steel plate must be peeled off by sandblasting or the like. However, there is a problem in that it takes time and labor to cover and restore the coating film and the like and the cost other than the inspection increases.

Also, in the above-mentioned known example, since the paint and rust on the surface of the steel sheet are peeled off by the grinder, the peeling work takes time, and the cleaning work of the peeling powder takes time and labor.

[0008] On the other hand, due to the amendment of the Fire Service Act of "Fire Danger No. 93" in August 2000, a method of inspecting the welded part of the tank steel plate from the coating on the surface of the tank steel plate was approved, but it was technical. At present, there is no proposal of an inspection method or an inspection apparatus that can expect sufficient inspection performance due to difficulty.

The present invention is to solve the above-mentioned problems.
The purpose of the invention is to provide a method and a device for inspecting a welded part and its heat-affected zone from the coating on the surface of a tank steel plate. We do not provide a device that can improve the uniformity of inspection quality and the detection accuracy more than before by eliminating the uncertainties of inspection quality that depend on the physical skill and flaw detection conditions and performing stable and accurate flaw detection. It is what

[0010]

A welding inspection method for a tank steel sheet according to the present invention for achieving the above-mentioned object is to prevent scratches occurring on a surface of a welded portion of a tank steel sheet having a coating on the surface or a surface of a heat-affected zone thereof. A welding inspection method for a tank steel sheet to be inspected, wherein a vertical crack in a direction of a welding bead and a lateral crack in a direction intersecting the direction of the welding bead are flaw-detected by a creeping wave method using a plurality of ultrasonic probes. It is characterized by doing.

Here, as a method for detecting flaws in a state where the surface of the tank steel plate is covered, a bevel method, a surface wave method, and a creeping wave method can be considered.

In the bevel angle method, although it can be detected by the single reflection method, it is affected by corrosion on the back surface of the bottom plate, and this has a great effect on the detection performance, so that it is generated at the welded portion of the tank steel plate or the surface of its heat affected zone. It is difficult to inspect the wound stably and accurately.

On the other hand, there are surface waves (Rayleigh waves), surface SH waves, and creeping waves as ultrasonic waves that propagate near the surface of the steel sheet.

The surface wave (Rayleigh wave) has its energy concentrated at about one wavelength below the surface and propagates along the surface even when the shape of the surface changes, and propagates inside the steel sheet. Absent. Therefore, the effect of the unevenness of the steel plate surface is significant, the attenuation is remarkable when the surface is rough like a weld bead, and especially the bead width is wide like a tank weld, and the weld surplus is not subjected to a smooth finish. However, it becomes difficult to detect scratches.

In the surface SH wave, a horizontally polarized transverse wave is generated by a vibrator and propagated in a 90 degree direction through a wedge, and the surface SH wave probe is Since the transverse wave propagates through the wedge and the transverse wave passes through the steel sheet as it is, it is necessary to use a special viscous contact solute between the wedge and the steel sheet to stabilize the echo. However, there is a problem in that the probe has poor scannability.

Further, in each of the above surface wave methods, the sensitivity is easily affected by the attenuation of the coating, and since the relationship between the size of the scratch and the echo height is not quantitative, the size of the scratch can be immediately known from the detected echo waveform. Is difficult.

The creeping wave is a longitudinal wave surface wave generated near the criticality of the longitudinal wave, and when the incident angle is the critical angle of the longitudinal wave,
A wave that propagates with a longitudinal wave component in the direction of the refraction angle of 90 degrees and travels straight below the surface of the steel sheet. Even if the surface shape of the steel sheet is changed, the steel sheet travels substantially straight, and the influence of surface irregularities is small.

Since a general surface wave propagates only on the surface of the steel sheet, a creeping wave is distributed and propagates inside the steel sheet. Therefore, the creeping wave has a higher refraction angle than the conventional shear wave oblique flaw detection. It is possible to detect flaws in a large area and detect flaws near the surface of the steel sheet. It is also effective for flaw detection on thin steel plates.

Further, in the creeping wave method, the effect of attenuation of sensitivity due to the coating is small, and the relationship between the size of the scratch and the echo height is quantitative, so that the size of the scratch can be immediately known from the detected echo waveform. Is easy.

From the above reason, as an ultrasonic flaw detection method in the welding inspection of the tank steel sheet of the present invention, a scratch generated on the surface of the welded portion of the tank steel sheet or the surface of the heat-affected zone thereof in a state where the tank steel sheet surface is coated. When inspecting, it is best to apply the creeping wave method.

Particularly, by setting the frequency of the ultrasonic probe to about 2 MHz or less, it is possible to reduce the influence of the attenuation of the sensitivity due to the coating.

According to the welding inspection method for a tank steel plate according to the present invention, a plurality of ultrasonic probes for flaw detection by the creeping wave method are used to coat the welding bead on the surface of the tank steel plate. The vertical crack in the direction and the lateral crack in the direction intersecting with the direction of the weld bead can be detected at once and accurately.

A tank steel plate welding inspection apparatus according to the present invention is a tank steel plate welding inspection apparatus for inspecting a welded portion of a tank steel sheet having a coating on its surface or a scratch on the surface of a heat-affected zone thereof. A traveling carriage that travels on a tank steel plate having a coating on the surface, and is provided in the traveling carriage,
At least three ultrasonic probes that detect vertical cracks in the direction of the welding bead and lateral cracks in the direction intersecting with the direction of the welding bead by the creeping wave method, and the ultrasonic waves provided in the traveling carriage. It has a position detection means for detecting the position information of the site detected by the probe, and a calculation / flaw detection display means for displaying / outputting the output of the ultrasonic probe via the ultrasonic flaw detector. And

According to the above-mentioned structure, the ultrasonic probe provided on the traveling carriage traveling on the tank steel plate having the coating on the surface along the weld bead causes longitudinal cracks in the direction of the weld bead and the weld bead. Lateral cracks in the direction intersecting with the direction are detected at any time by the creeping wave method according to the traveling operation of the traveling carriage, and the traveling carriage is provided with the position information of the portion detected by each ultrasonic probe. The position detection means detects at any time according to the traveling operation of the traveling vehicle, and the output of the ultrasonic probe is associated with the flaw detection information and the position information via the ultrasonic flaw detector, and displayed / output by the calculation / flaw detection display means. By doing so, it is possible to automatically and accurately inspect the scratches generated on the surface of the welded portion of the tank steel plate or its heat-affected zone.

Further, the traveling carriage travels forward and / or backward on the rail, the ultrasonic probe is supported by a probe unit, and the probe unit is cantilevered by the traveling carriage. Is a probe welding bead distance adjusting mechanism capable of varying the distance between the ultrasonic probe and the welding bead, and a plurality of ultrasonic probes each independently arranging a probe unit height capable of varying the height. In the case of having the height adjusting mechanism, the traveling carriage travels on the rail, so that the straight traveling performance is secured and the inspection accuracy can be improved. Also, by using a cantilever type as a method of holding the ultrasonic probe by the traveling carriage, it is possible to reduce the size of the device in the width direction compared to the device configuration that straddles the welding bead, and avoid obstacles near the welding bead. Since it can be inspected, it is also advantageous for inspecting the vicinity of the corner of the tank.

A probe welding bead distance adjusting mechanism and a probe unit height adjusting mechanism allow smooth running while keeping the distance between the welding bead and the ultrasonic probe constant, and particularly along one rail. It is preferable to drive the traveling carriage by traveling.

Typical weld shapes of a welded portion of a tank steel plate having a coating on the surface include butt welding and lap welding. The height of the ultrasonic probe on both sides can be adjusted with the weld bead as the boundary in order to detect the generated flaw.

By providing the traveling carriage with the bidirectional traveling functions such as the forward traveling function and the backward traveling function, repeated inspection of the same welded portion can be easily performed, and further, the traveling carriage can be moved from the rail at the end of the tank. There is no need to detach and change the traveling direction, or detach the traveling carriage from the rail and carry it to the inspection start point side to reposition it, instead of the power cable and signal cable routed between the measurement unit and the display unit. It can be handled smoothly.

In the case where a pair of transmitter and receiver are arranged on both sides of the weld bead as a boundary, as an ultrasonic probe for detecting a vertical crack in the direction of the weld bead by the creeping wave method. In addition, it is possible to avoid the effect of echo due to the shape of the weld bead by separately performing flaw detection from the sides of the weld bead to the center of the weld bead as the flaw detection range of the ultrasonic probe. The presence or absence of vertical cracks in the direction of can be accurately detected.

Further, when the transmitter and the receiver of the ultrasonic probe for detecting a vertical crack are arranged in line symmetry with the welding bead interposed therebetween, the welding bead is used as a boundary on both sides thereof. In the pair of transmitters and receivers arranged, there is no possibility that the receiver receives the creeping wave emitted from the transmitter of the other pair and erroneously detects it. Therefore, when a vertical crack in the direction of the weld bead is flaw-detected by the creeping wave method, the interference effect of the creeping wave can be prevented.

Further, as an ultrasonic probe for detecting lateral cracks in a direction intersecting with the direction of the weld bead by the creeping wave method, a transmitter is arranged on one side of the weld bead as a boundary, and the other side is arranged. When the receivers are arranged symmetrically, the ultrasonic waves transmitted from the transmitter are reflected by the transverse cracks in the direction intersecting the direction of the welding bead and are returned by the receivers symmetrically arranged across the welding bead. However, the presence or absence of scratches can be accurately detected.

The calculation / flaw detection display means records the output signal obtained from the position detection means and the output signal obtained from the ultrasonic flaw detector, and monitors the response time of the input ultrasonic wave. It is preferable that the input signal is determined to be a cracking signal when the output value at 1 exceeds a preset detection threshold.

Further, it is preferable that the ultrasonic signal exceeding the detection threshold value is color-coded into threshold values in accordance with the position information obtained by the position detecting means and displayed as crack information on a two-dimensional plane.

Further, the calculation / flaw detection display means binarizes and image-processes the ultrasonic signal represented on the two-dimensional plane based on the position information with the detection threshold as a reference, and from the result, the flaw in the traveling direction is detected. It is preferable to calculate the length.

Further, the calculation / flaw detection display means displays the crack detection position on the drawing of the tank steel plate based on the position information obtained by the position detection means based on the ultrasonic signal exceeding the detection threshold. However, it is preferable to configure so as to output to the output medium.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a welding inspection method for a tank steel plate and an apparatus therefor according to the present invention will be specifically described with reference to the drawings. 1 is a plan view showing the structure of a tank steel plate welding inspection apparatus according to the present invention, FIG. 2 is a side view showing the structure of a tank steel plate welding inspection device according to the present invention, and FIG. 3 is a tank steel plate according to the present invention. It is a front view which shows the structure of a welding inspection apparatus.

FIG. 4 is a block diagram showing the structure of each part of the tank steel plate welding inspection apparatus according to the present invention, FIG. 5 is a block diagram showing the structure of a control system for performing data processing, and FIG. 6 is a three-channel ultrasonic probe. 7A and 7B are plan views showing the arrangement of the tentacles, FIGS. 7A and 7B are views showing the state of flaw detection of vertical cracks and lateral cracks in the butt welding portion, and FIGS. 8A and 8B are lap welding. It is a figure which shows the mode of the flaw detection of the vertical crack in a part, and a horizontal crack.

9 to 12, each drawing (a) is a view showing a flaw detection echo waveform when various kinds of flaws generated on the surface of the welded portion or its heat-affected zone is detected, and each figure (b) is a sound portion. A diagram showing an echo waveform formed by a weld bead shape, etc.
13 is a flow chart for processing flaw detection data, FIG. 14 is a flow chart for detecting flaws, FIG. 15 is a diagram showing a state in which flaws of an actual tank steel plate are inspected and displayed, and FIG. It is a figure which shows the structure of the threshold value which determines a flaw detection, FIG.16 (a) is a vertical crack detection result,
16 (b) is a diagram showing the results of lateral crack detection, and FIG. 17 is an example in which the echo height of the obtained flaw detection echo waveform is expressed in shades.

Welding inspection apparatus 1 for tank steel plate according to the present invention
Is configured so that a scratch generated on the surface of the welded portion of the tank steel plate whose surface is coated with the coating 24 or the like or its heat-affected zone can be inspected by a self-propelled method.

1 to 4, the welding inspection apparatus 1 is
Traveling carriage 2 traveling on a tank steel plate having a coating on the surface
And a welding bead of a tank steel plate mounted on the traveling carriage 2.
At least three ultrasonic probes 3 for detecting vertical cracks in the direction of 18 and transverse cracks in the direction intersecting with the direction of the weld bead 18 by the creeping wave method, and the traveling carriage 2 as well.
And a rotary encoder 4 serving as position detecting means for detecting position information in the tank of a portion detected by the ultrasonic probe 3.

The traveling carriage 2 is a traveling rail 5 laid along a weld bead 18 on a tank steel plate having a coating on the surface.
It is configured to be capable of traveling forward or backward, and is driven and rotated by a DC (direct current) motor 6 to which electric power is supplied from a DC (direct current) power source 8, and large and small travel guide wheels 9. , 10 and the balance wheel 11 rotate along one traveling rail 5.

The rotational drive of the DC motor 6 is controlled by the speed controller 19, and thereby the traveling of the traveling carriage 2 is stopped, traveling is stopped and speed is controlled, and forward and backward are controlled.

A rotary encoder 4 is attached to the rotating part of the traveling guide wheel 10 so that each flaw detection position of the ultrasonic probe 3 in the tank can be detected by the position information detected by the rotary encoder 4. It has become.

Further, the traveling carriage 2 is provided with a water supply unit 31, and the water contained in the water tank 32 is pumped up by the pump 12 and the solenoid valve 33 is controlled to control the tank steel plate having a coating on the surface. And water is supplied between the ultrasonic probe 3 and the ultrasonic probe 3 so that the ultrasonic probe 3 prevents the ultrasonic sensitivity from being attenuated.

As shown in FIGS. 1 to 3, the ultrasonic probe 3
Is supported by a child carriage 16 which also serves as a probe unit, and the child carriage 16 is provided with a traveling carriage 2 via a gimbal mechanism 17.
The probe unit clamp lever 13 provided on the main body of the traveling carriage 2 is operated so as to be supported by a cantilever, and the surface of the traveling carriage 2 is covered with the water supplied by the water supply unit 31. It is possible to lower the welded portion of the tank steel plate or its heat-affected zone to a position where flaw detection is performed and set it, or raise it to retract it.

In the figure, reference numeral 14 is a probe unit height adjusting mechanism for independently adjusting the placement heights of the plurality of ultrasonic probes 3 respectively. The probe unit height adjusting mechanism 14 and the gimbal mechanism 17 are provided. By appropriately adjusting the height of the ultrasonic probe 3 by using, both of the flaw detection of the butt welding portion of the tank steel plate as shown in FIG. 7 and the flaw detection of the lap welding portion of the tank steel plate as shown in FIG. 8 are performed. It is ready to respond. Reference numeral 15 denotes a probe welding bead distance adjusting mechanism that finely adjusts the distance between the ultrasonic probe 3 and the welding bead 18.

Generally, the tank bottom steel plate does not have a completely flat surface, but has "waviness" due to lap welding of the upper plate and the lower plate. Further, locally, the welding points at the joints of the tank bottom steel plate are locally formed. Etc. have unevenness.

In order to allow the four child carriages 16 equipped with the ultrasonic probes 3 to completely follow and follow such waviness and local unevenness of the tank bottom steel plate, the child carriages 16 are moved. Is attached to the traveling carriage 2 via a gimbal mechanism 17.

The child carriage 16 on which the ultrasonic probe 3 is mounted is
Since the ultrasonic probe 3 is attached to the traveling carriage 2 via the gimbal mechanism 17, the probe surface of the ultrasonic probe 3 always moves completely to follow the undulations and local irregularities of the steel plate at the bottom of the tank. I guarantee that.

The sub-carriage 16 has a structure in which the sub-carriage wheels are attached to the sub-carriage frame, and the ultrasonic probe 3 has a constant gap between the sub-carriage frame and the tank bottom steel plate at the center of the sub-carriage frame. Installed as required.

Water is transmitted to each child carriage 16 via a water supply branch (not shown) provided in the traveling carriage 2 in order to efficiently transmit ultrasonic waves between the ultrasonic probe 3 and the tank bottom steel plate. Is supplied to each child carriage 16 through a pipe (not shown), and the water supplied to each child carriage 16 is supplied to the ultrasonic probe 3 and the tank bottom from a water supply hole (not shown) provided in the child carriage 16. It is supplied so that it always exists in the gap with the steel plate.

Further, the rotary encoder 4 for detecting the flaw detection position of the ultrasonic probe 3 by measuring the traveling distance of the traveling carriage 2 rotates in synchronization with the movement of the traveling guide wheels 10 of the traveling carriage 2. Is attached to.

First of the ultrasonic probe 3 in the present embodiment
As shown in FIG. 6, the channel (hereinafter referred to as "1CH") and the second channel (hereinafter referred to as "2CH") detect vertical cracks 18a and 18b in the direction of the weld bead 18 by the creeping wave method. As the ultrasonic probe 3, a pair of transmitter T and receiver R is arranged on both sides of the weld bead 18 as a boundary.

In 1CH and 2CH of the ultrasonic probe 3, a two-transducer type probe having a pair of a transmitter T and a receiver R is used as a reflection type probe.

That is, it is arranged on the right side of the welding bead 18 in FIG.
Pair of transmitters T₁And receiver R₁And the first channel
A pair of transmissions that are configured and located to the left of the weld bead 18.
Child T ₂And receiver R₂And make up the second channel,
The ultrasonic probe 3 of the first and second channels of
The vertical cracks 18a, 18b in the direction of the card 18 are made to be the creeping wave method.
More flaw detection.

In this embodiment, as shown in FIG.
The transmitter T ₁ and the receiver R ₁ of the channel, and the transmitter T ₂ and the receiver R _{2 of} the second channel are arranged line-symmetrically with the welding bead 18 interposed therebetween. That is, the transmitter T ₁ of the first channel
And the transmitter T ₂ of the second channel are aligned in the horizontal direction, and the receiver R ₁ of the first channel and the receiver R ₂ of the second channel are aligned in the horizontal direction.

Thus, with a simple structure, the creeping wave generated from the transmitter T ₁ of the first channel is erroneously detected by the second channel.
To prevent erroneous detection of the creeping wave received by the receiver R _{2 of the} channel or, conversely, erroneously received by the receiver R ₁ of the first channel by the creeping wave generated from the transmitter T ₂ of the second channel. Can be done.

Although not shown, the transmitter T ₁ and receiver R ₁ of the first channel, and the transmitter T ₂ and receiver R _{2 of} the second channel are arranged point-symmetrically with the welding bead 18 in between. In the case, that is, the transmitter T ₁ of the first channel and the receiver R ₂ of the second channel are forward in the traveling direction, and the transmitter T ₂ of the _second channel and the receiver R ₁ of the first channel are backward in the traveling direction. In order to prevent erroneous detection, the welding bead 18 of the transmitter T ₁ and the receiver R ₁ of the first channel, and the transmitter T ₂ and the receiver R _{2 of} the second channel 18 is arranged in order to prevent erroneous detection. It is necessary to separate the separation distance in the direction along with a predetermined distance. In this case, the structure is complicated and the signal processing is also complicated.

The third channel of the ultrasonic probe 3 (hereinafter referred to as "3CH") for flaw detection of the lateral crack 18c in the direction intersecting the direction of the weld bead 18 by the creeping wave method.
With the weld bead 18 as a boundary, the transmitter T and the receiver R arranged on both sides of the weld bead 18 form a pair.

That is, the transmitter T ₃ and the receiver R ₃ arranged on the right side of the welding bead 18 of FIG. 6 constitute a third channel, and the welding bead 18 is formed by the ultrasonic probe 3 of the third channel. The lateral crack 18c in the direction intersecting with the direction is detected by the creeping wave method.

The position of the ultrasonic probe 3 of 3CH is adjusted so that the transmitter T ₃ and the receiver R ₃ are symmetrical with respect to the welding bead 18. Transmitter T ₃ and lateral crack 18c
The angle θ between the straight line connecting to and the straight line connecting the lateral crack 18c and the receiver R ₃ may be less than 180 degrees, but a particularly preferable angle θ is in the range of 75 degrees or more and 85 degrees or less. . Each drawing is an example when the angle θ is set to 80 degrees.

With the arrangement of the ultrasonic probe 3 described above, it is possible to inspect the surface of the welded portion of the tank steel plate or the surface of the heat-affected zone of the tank steel plate by measuring from above the coating of the tank bottom steel plate.

FIG. 7 (a) shows vertical cracks 18a and 18b of the weld bead 18 at the portion where the tank steel plates are butt-welded together.
The state of flaw detection by the ultrasonic probe 3 of the second channel is shown.

FIG. 7B shows a state in which the lateral crack 18c of the welding bead 18 at the portion where the tank steel plates are butt-welded is detected by the ultrasonic probe 3 of the third channel.

FIG. 8A shows a state in which the vertical cracks 18a and 18b of the weld bead 18 at the portion where the tank steel plates are lap-welded are flaw-detected by the ultrasonic probes 3 of the first and second channels, respectively.

FIG. 8 (b) shows a state in which the lateral crack 18c of the welding bead 18 at the portion where the tank steel plates are lap-welded is detected by the ultrasonic probe 3 of the third channel.

The ultrasonic flaw detection data and the position data are expanded I / O from the traveling carriage 2 equipped with the ultrasonic probe 3 and the rotary encoder 4 of the measuring unit 21 via the cable connector 20.
The data is sent via the F section 27 to the calculation / flaw detection display section 28 serving as a calculation / flaw detection display means.

The calculation / flaw detection display unit 28 displays the echo waveform from the output of the ultrasonic probe 3 and the output of the rotary encoder 4 as shown in FIGS. A computer 23 such as a notebook personal computer (hereinafter referred to as “notebook PC”) that displays a screen as shown in FIGS.
have.

In FIG. 4, the computer 23 provided in the calculation / flaw detection display unit 28 includes a CPU (central processing unit),
It has a storage device such as a RAM (random access memory) and processes signals from the high-speed A / D board 25 and the digital I / O board 26 and saves them in the storage device.

The computer 23 is provided with an alarm 34 serving as a notification means, and when the flaw detection echo waveform measured by the ultrasonic probe 3 also serving as the detection means does not reach the check level threshold value a shown in FIG. Informs by the alarm 34 that the measurement is impossible, and when the detection level threshold b is exceeded, the alarm 34 informs that the flaw is detected.

That is, the calculation / flaw detection display unit 28 records the output signal obtained from the rotary encoder 4 and the output signal obtained from the ultrasonic flaw detector 29, and outputs the response time of the input ultrasonic wave in the inspection range. When the value exceeds the detection level threshold b which is a preset detection threshold, the input signal is determined to be a cracking signal.

The expansion I / F section 27 is a box for setting the counter board 30, the high speed A / D board 25 and the digital I / O board 26, and the high speed A / D board 25 and the digital I / O board 26. And counter board 30 are all IS
Notebook PC without ISA bus because it is for A bus
The extended I / F unit 27 is required when used in. To connect the expansion I / F unit 27 to a notebook PC,
Use C PC card slot. In addition, extended I / F
USB (Universal Serial Bus) with high-speed A / D, I / O, and counter as microcomputer board without using section 27
There is also a way to connect.

The counter board 30 is a board for counting the length measurement pulses from the rotary encoder 4, and counts on the board side without imposing a load on the CPU of the notebook PC. The count value can be acquired from the notebook PC side at any timing.

The high-speed A / D board 25 is a board for converting the analog waveform output (voltage of 0V to 5V) of the ultrasonic flaw detector 29 into an 8-bit digital value at a high speed, and a reception waveform of about 2 MHz of 20 MHz. Convert at speed (about 10 conversions per wavelength).

The digital I / O board 26 is an ultrasonic flaw detector.
It is used for communication between 29 and a computer 23 such as a notebook PC, and commands and data are communicated as 8-bit signals as 0 or 1 signals depending on the level of the voltage (0V or 5V). .

The ultrasonic flaw detector 29 has a function of transmitting a pulse signal to the ultrasonic probe 3 and a function of receiving a reflection echo thereof, and outputs the reflection echo as an analog waveform. The gain of the received echo is set from the computer 23 such as a notebook PC via the digital I / O board 26.

FIG. 5 is a block diagram showing the structure of a control system for performing data processing. The flaw detection data is processed according to the flow chart shown in FIG. 13, and the flaw detection processing is performed according to the flow chart shown in FIG.

That is, by using the drawing created by the tank steel plate drawing software, the measurement points in the tank can be displayed in the drawing as shown in FIG. The ultrasonic signal that exceeds the detection level threshold value b is color-coded into threshold values in accordance with the position information obtained by the rotary encoder 4, and is shown as crack information in FIG.
It is displayed on a two-dimensional plane as shown in.

The flaw detection waveform is A / D (analog / digital)
Convert and save the waveform as a digital value. Ultrasonic signals that exceed the clipping level threshold c shown in FIG. 16 are represented on a two-dimensional plane, binarized as image processing, and then connected component processing is performed.
The length and position of the flaw are automatically calculated and displayed for the component that exceeds the detection level threshold b.

In the monitoring range area shown in FIGS. 16 (a) and 16 (b), the ultrasonic signal is classified by the above-mentioned threshold value and displayed in arbitrary colors. On the other hand, as for the waveform acquisition range other than the monitoring range, as shown in FIG.
It is preferable that gray scale display of 256 gradations according to the echo height of the ultrasonic signal shown in (b) is possible.

In FIG. 15, the file No. 8 shows the inspection data of the weld bead 18 between the bottom plate No. 24 and the bottom plate No. 28 indicated by “α”, and the display column 35 is an example in which the scratch length is displayed. .

Then, the calculation / flaw detection display unit 28 displays the crack detection position on the drawing of the tank steel plate based on the position of the scratch extracted as described above, as shown in FIG. Output to the output medium.

An analog waveform signal obtained from the RF output of the ultrasonic flaw detector 29 is A / D converted by the high-speed A / D board 25 and taken into the computer 23. The fetching cycle is synchronized with the SYNC signal of the ultrasonic flaw detector 29. The length measurement count of the encoder obtained from the counter board 30 at the time of loading is processed, and the moving distance of the traveling carriage 2 is acquired. An analog waveform obtained from the RF output of the ultrasonic flaw detector 29 is stored in the memory of the computer 23 every time the moving distance advances by 1 mm. The waveform data stored in the memory of the computer 23 when the flaw detection is completed is stored in the hard disk of the computer 23.

The water supply section 31 has a water tank 32, a pump 12 and a solenoid valve 33. The opening / closing of the solenoid valve 33 and the start / stop of the pump 12 are performed based on an instruction from the computer of a measurement start / end switch signal provided in the traveling vehicle 2 which is transmitted to a computer (not shown) of the measurement unit 21. .

The ultrasonic probe 3 mounted on the child carriage 16 is
Since it is attached to the traveling carriage 2 under a fixed positional relationship, if it is possible to know the positional relationship between one position in the traveling carriage 2 and the tank bottom steel plate, ultrasonic waves in the child carriage 16 can be detected. It is possible to know which position on the tank bottom steel plate the flawed position of the probe 3 corresponds to.

Therefore, by mounting the rotary encoder 4 for measuring the traveling distance on the traveling carriage 2 and grasping the traveling distance from the specific position of the steel plate at the bottom of the tank, the flaw detection position of the ultrasonic probe 3 during traveling can be determined. The position corresponding to the tank bottom steel plate can be specified in real time, and the flaw detection echo waveform at the specified position can be detected.

Therefore, by combining the flaw detection echo waveform of the ultrasonic probe 3 and the detection value of the rotary encoder 4, the appearance of flaws on the surface of the welded portion at a specific position in the steel plate at the bottom of the tank or the surface of the heat affected zone thereof. Can be inspected.

Further, when the relationship between the position and the flaw detection echo waveform is displayed on the screen, it is possible to grasp the state of flaws occurring on the surface of the welded portion or its heat affected zone over the entire tank bottom steel plate.

In the actual welding inspection, the measurer lays the traveling rail 5 along the predetermined route on the weld bead 18 on the steel plate at the bottom of the tank, and causes the traveling carriage 2 to travel by itself. Take a measurement.

The traveling speed of the traveling carriage 2 is determined in consideration of the processing speed of the measurement data, and is usually 10 mm / sec to 200 mm.
Measurement is performed at a traveling speed of mm / sec. In the present embodiment, the traveling carriage 2 is a self-propelled type that travels along the traveling rail 5, but instead of the traveling rail 5, a traveling guidance sensor is arranged to travel along the welding bead 18. It may be of a self-propelled type, or may be of a push type in which the grip 22 is gripped for traveling.

As an example of the present embodiment, the ultrasonic probe 3 has vertical cracks 18a, 18 having a width of 3.0 mm and a length of 6.0 mm.
The rotary encoder 4 has a length measuring accuracy of 0.1.
%, Which can measure forward and backward distance is used.

For the echo waveform data detected by the ultrasonic probe 3, the count of the rotary encoder 4 provided on the traveling carriage 2 is acquired, for example, every 1 mm, and at the same time as the flaw detection, the echo waveform data is determined according to the acquisition position. Display of 256 shades of black and white by echo height (C scope display)
By doing so, the vertical cracks 18a, 18b and the lateral cracks 18c are evaluated. Further, the echo waveform data obtained every 1 mm is saved in a file together with the position detection information of the rotary encoder 4.

As illustrated in FIG. 17, a place where the echo height is large is displayed in black and a place where the echo height is small is displayed in white. Therefore, the two-dimensional distribution of the vertical cracks 18a, 18b and the lateral cracks 18c is shown. The situation can be grasped, it is easy to distinguish from noise such as shape echo by the welding bead 18, and vertical cracks 18a, 18b and lateral cracks 18c can be accurately judged.

The pulse repetition frequency of the ultrasonic probe 3 is 1 kHz, and the echo waveform data acquired every 1 mm has a sufficient effect of detecting the flaw length to be measured.

Next, the case where the welding inspection apparatus 1 according to the present invention is applied to the welding inspection of a cylindrical tank will be described. The details of the measurement include initial condition setting, measurement condition setting, measurement method,
It is divided into measurement result displays.

First, as the initial condition setting, the tank inner diameter,
The number of annular plates and the size of the bottom steel plate basic plate are input to the computer 23 of the calculation / flaw detection display unit 28. Computer 23
Draws an annular plate and divides the entire bottom steel plate vertically or horizontally based on the input data, and creates a bottom steel plate plate division diagram while further dividing each of the divided regions. The divided areas are automatically numbered.

Next, as the measurement condition setting, the number of the plate having the weld bead 18 to be measured is selected from the plan view of the bottom steel plate, and the traveling rail 5 is laid along the weld bead 18. The origin, the measurement start point and the measurement direction at the time of measurement of the weld bead 18 formed on the plate of the selected number are determined and input.

Next, as a measuring method, the reference point of the traveling carriage 2 is made to coincide with the measurement starting position, the measurement start switch is turned on, and the traveling carriage 2 is allowed to travel in the measuring direction at a speed of 10 mm / sec to 200 mm / sec. . The traveling carriage 2 travels on the traveling rail 5 along the welding beads 18.

When the traveling carriage 2 reaches the end point of the welding bead 18 to be measured, the measurement end switch is turned on.

From the bottom steel plate plan view, the number of the plate on which the weld bead 18 to be measured next is selected, and the laying position of the traveling rail 5 is changed as necessary to perform the measurement. In the split drawing, when the welding inspection of all the welding beads 18 is completed, the welding inspection of the entire tank bottom plate is completed.

As shown in FIGS. 9 to 12, the echo waveform detected by each ultrasonic probe 3 is displayed on the display of the computer 23 such as a notebook PC, and the tank steel plate is displayed as shown in FIGS. 15 and 16. The crack detection position is displayed in accordance with the drawing, and the echo height of the flaw detection echo waveform obtained is expressed in shades as shown in FIG. 17 and displayed on the display of the notebook PC 23. If necessary, the screen display contents can be output by a monochrome or color printer.

FIG. 9 (a) shows a flaw echo waveform obtained by flaw detection of the vertical crack 18a formed at the left end portion of the weld bead 18 in the lap welding portion with the 2CH ultrasonic probe 3, and FIG. 9 (b) shows The figure shows a flaw detection echo waveform of a sound portion in the case where there is no vertical crack 18a, and the two are compared.

In the flaw detection echo waveform of FIG. 9A, the peak waveform A that appears first is the flaw detection echo waveform of the vertical crack 18a. Further, as shown in FIG. 9B, an echo waveform is formed as noise due to the shape of the welding bead 18 even in a sound portion.

FIG. 10 (a) shows a flaw echo waveform obtained by flaw detection of the vertical crack 18b formed at the right end portion of the weld bead 18 in the lap welding portion with the ultrasonic probe 3 of 1CH, and FIG. 10 (b).
Shows a flaw detection echo waveform of a sound portion in the case where there is no vertical crack 18b and compares the two.

In the flaw detection echo waveform of FIG. 10 (a), the peak waveform B that appears first is the flaw detection echo waveform of the vertical crack 18b. Further, as shown in FIG. 10B, an echo waveform is formed as noise due to the shape of the welding bead 18 even in a sound portion.

FIG. 11 (a) shows a flaw detection echo waveform obtained by flaw detection of the vertical crack 18a formed in the center of the weld bead 18 in the lap weld portion by the 2CH ultrasonic probe 3, and FIG. 11 (b).
Shows a flaw detection echo waveform of a sound part in the case where there is no vertical crack 18a and compares the two.

In the flaw detection echo waveform of FIG. 11A, the peak waveform C that appears first is the flaw detection echo waveform of the vertical crack 18a. Further, as shown in FIG. 11B, an echo waveform is formed as noise due to the shape of the welding bead 18 even in a sound portion.

In the flaw detection echo waveform of the sound part shown in FIG. 11B, a peak waveform N as noise having a relatively large peak value is shown, but FIG. 9A, FIG. 10A,
In FIG. 11 (a), the peak waveforms A, B, C of the echo obtained by flaw detection of the vertical crack 18a are followed by the peak waveform N as noise due to the shape of the welding bead 18, etc., so that the discrimination is easy.

Further, since the peak waveform N as noise having such a relatively large peak value appears, a pair of transmitter T and receiver R is provided on both sides of the welding bead 18 as a boundary in this embodiment. The 1CH and 2CH ultrasonic probes 3 are arranged to detect flaws on each of the left and right sides of the welding bead 18.

FIG. 12 (a) shows a flaw detection echo waveform obtained by flaw detection of the lateral crack 18c formed on the weld bead 18 at the lap weld with the 3CH ultrasonic probe 3, and FIG. 12 (b) shows the lateral crack 18c. The waveforms of flaw detection echoes of a sound part in the case of no existence are shown and the two are compared.

In the flaw detection echo waveform of FIG. 12 (a), the peak waveform D that appears first is the flaw detection echo waveform of the lateral crack 18c. Further, as shown in FIG. 12B, an echo waveform is formed as noise due to the shape of the welding bead 18 even in a sound portion.

FIG. 17 shows the vertical crack 18a shown in FIG.
Vertical crack 18a shown in 11 (a) is formed continuously, and 2CH
Of the ultrasonic probe 3 and the echo heights of these flaw detection echo waveforms are determined by the rotary encoder 4.
It is an example of a schematic diagram in the case of expressing in black and white gradation of 256 gradations together with the position information obtained by. In the figure, E is a grayscale display corresponding to the vertical crack 18a formed at the left end of the weld bead 18, and F is a grayscale display corresponding to the vertical crack 18a formed at the center of the weld bead 18. The other part is a gray scale display corresponding to the healthy part.

In the above-mentioned embodiment, an example in which it is applied to the bottom plate steel plate of the tank is shown. However, as shown in the above-mentioned conventional example, the side plate of the tank is attracted by magnetic force or the like so as to run by itself. The trolley 2 is configured to travel in the vertical direction and similarly run along the weld bead 18 of the side plate steel sheet to inspect the surface of the welded portion of the side plate steel sheet or the scratch on the surface of the heat affected zone. It may be configured as follows.

Although the above embodiments have been described using specific numerical values, the present invention is not limited to these numerical values.

[0115]

EFFECTS OF THE INVENTION Since the present invention has the above-described structure and operation, it is possible to provide a method and apparatus capable of performing a welding inspection from the coating on the surface of a tank steel plate.

That is, according to the welding inspection method for a tank steel sheet according to the present invention, welding is performed with the surface of the tank steel sheet covered by using a plurality of ultrasonic probes for flaw detection by the creeping wave method. A vertical crack in the direction of the bead and a lateral crack in a direction intersecting the direction of the weld bead can be detected at once and accurately.

Further, according to the welding inspection apparatus for a tank steel plate according to the present invention, the welding bead is welded by each ultrasonic probe provided on the traveling carriage traveling on the tank steel plate having the coating on the surface along the welding bead. The vertical cracks in the direction of and the transverse cracks in the direction intersecting with the direction of the weld bead are detected at any time by the creeping wave method according to the traveling operation of the traveling carriage, and the portion detected by each ultrasonic probe is detected. The position detection means provided on the traveling vehicle detects the position information of the traveling vehicle at any time according to the traveling operation of the traveling vehicle, and the output of the ultrasonic probe is associated with the flaw detection information and the position information through the ultrasonic flaw detector. ,
By displaying / outputting by the calculation / flaw detection display means, it is possible to automatically and accurately inspect the scratches generated on the surface of the welded portion of the tank steel plate or the heat affected zone thereof.

When the traveling carriage travels on the rail and the ultrasonic probe is supported by the traveling carriage in a cantilever manner, the traveling carriage travels on the rail to ensure the straight-ahead performance. The accuracy can be improved. Also, by supporting the ultrasonic probe in a cantilevered manner with respect to the traveling carriage, it is possible to reduce the size of the device in the width direction compared to the device configuration that straddles the welding bead, and for inspection of narrow parts at the corners of the tank. Is also advantageous.

When an ultrasonic probe for detecting a vertical crack in the direction of the weld bead by the creeping wave method is used, a pair of transmitter and receiver are arranged on both sides of the weld bead as boundaries. Is able to avoid the influence of the echo due to the shape of the welding bead by separately performing flaw detection from each side of the welding bead to the center of the welding bead as the flaw detection range of the ultrasonic probe. The presence or absence of vertical cracks in the direction can be accurately detected.

Further, when the transmitter and the receiver are arranged line-symmetrically with the welding bead in between, a pair of the transmitter and the receiver arranged on both sides of the welding bead as a boundary are different from each other. There is no risk that the receiver receives the creeping wave emitted from the transmitter and erroneously detects it.

Further, as an ultrasonic probe for flaw detection of transverse cracks in the direction intersecting with the direction of the welding bead by the creeping wave method, a transmitter is arranged on one side of the welding bead as a boundary, and a reception is made on the other side. If the children are placed symmetrically,
The ultrasonic waves transmitted from the transmitter are reflected by the transverse cracks in the direction intersecting the direction of the welding bead and returned by the receivers symmetrically placed across the welding bead to accurately detect the presence or absence of scratches. Can be done.

[Brief description of drawings]

FIG. 1 is a plan view showing the configuration of a tank steel plate welding inspection apparatus according to the present invention.

FIG. 2 is a side view showing the configuration of the tank steel plate welding inspection apparatus according to the present invention.

FIG. 3 is a front view showing the configuration of a tank steel plate welding inspection apparatus according to the present invention.

FIG. 4 is a block diagram showing the configuration of each part of the tank steel plate welding inspection apparatus according to the present invention.

FIG. 5 is a block diagram showing a configuration of a control system that performs data processing.

FIG. 6 is an explanatory plan view showing an arrangement configuration of a three-channel ultrasonic probe.

7 (a) and 7 (b) are diagrams showing the state of flaw detection of vertical cracks and lateral cracks in a butt weld.

8 (a) and 8 (b) are vertical cracks in the lap weld,
It is a figure which shows the mode of the flaw detection of a lateral crack.

FIG. 9A is a diagram showing a flaw detection echo waveform when various flaws generated on a surface of a welded portion or a heat-affected zone thereof are flaw-detected;
(B) is a figure which shows the echo waveform formed by a weld bead shape etc. in a sound part.

FIG. 10A is a diagram showing a flaw detection echo waveform when various flaws generated on a surface of a welded portion or a heat-affected zone thereof are flaw-detected;
(B) is a figure which shows the echo waveform formed by a weld bead shape etc. in a sound part.

FIG. 11A is a diagram showing a flaw detection echo waveform when various flaws generated on a surface of a welded portion or a heat-affected portion thereof are flaw-detected;
(B) is a figure which shows the echo waveform formed by a weld bead shape etc. in a sound part.

FIG. 12A is a diagram showing a flaw detection echo waveform when various flaws generated on a surface of a welded portion or a heat affected zone thereof are flaw-detected;
(B) is a figure which shows the echo waveform formed by a weld bead shape etc. in a sound part.

FIG. 13 is a flowchart of processing flaw detection data.

FIG. 14 is a flowchart of a flaw detection process.

FIG. 15 is a diagram showing a state in which a scratch on an actual tank steel plate is inspected and displayed.

FIG. 16 is a diagram showing a configuration of a threshold value for determining unmeasurable or flaw detection based on a flaw detection echo waveform, FIG. 16A is a diagram showing a vertical crack detection result, and FIG. 16B is a diagram showing a lateral crack detection result.

FIG. 17 is a diagram showing an example in which the echo height of the obtained flaw detection echo waveform is expressed by shading.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Welding inspection apparatus 2 ... Traveling vehicle 3 ... Ultrasonic probe 4 ... Rotary encoder 5 ... Traveling rail 6 ... DC motor 7 ... Drive wheel 8 ... DC power supply 9, 10 ... Travel guide wheel 11 ... Balance wheel 12 ... Pump 13 ... Probe unit clamp lever 14 ... Probe unit height adjustment mechanism 15 ... Probe welding bead distance adjustment mechanism 16 ... Child carriage 17 ... Gimbal mechanism 18 ... Weld beads 18a, 18b ... Vertical crack 18c ... Side crack 19 ... Speed controller 20 ... Cable connector 21 ... Measuring section 22 ... Grip 23 ... Computer 24 ... Painting 25 ... High-speed A / D board 26 ... Digital I / O board 27 ... Expansion I / F section 28 ... Computation / flaw detection display section 29 ... Ultrasonic flaw detection Container 30 ... Counter board 31 ... Water supply unit 32 ... Water tank 33 ... Solenoid valve 34 ... Alarm 35 ... Display columns A, B, C, D, N ... Peak waveforms T, T ₁ , T ₂ , T ₃ ... Transmitter R, R ₁ , R ₂ , R ₃ ... Receiver a Check level threshold b Detection level threshold c Cut level threshold

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiro Nojiri             4-8 Konan, Minato-ku, Tokyo Asahi Engineering             Nearing Co., Ltd. (72) Inventor Tatsuya Fukunaga             4-8 Konan, Minato-ku, Tokyo Asahi Engineering             Nearing Co., Ltd. (72) Inventor Hiroyuki Haga             4-8 Konan, Minato-ku, Tokyo Asahi Engineering             Nearing Co., Ltd. (72) Inventor Fuminori Kiyota             4-10-13 Ibori, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture             No. New Japan Non-Destructive Inspection Co., Ltd. (72) Inventor Ryota Kajiki             4-10-13 Ibori, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture             No. New Japan Non-Destructive Inspection Co., Ltd. (72) Inventor Motonori Yasunaga             4-10-13 Ibori, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture             No. New Japan Non-Destructive Inspection Co., Ltd. (72) Inventor Yuji Nishimura             4-10-13 Ibori, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture             No. New Japan Non-Destructive Inspection Co., Ltd. F term (reference) 2G047 AA07 AB07 AC12 BA03 BC02                       BC03 CB01 DB03 EA10

Claims (10)

[Claims] 1. A welding inspection method for a tank steel sheet for inspecting a welded portion of a tank steel sheet having a coating on the surface or a scratch occurring on the surface of a heat-affected zone of the tank steel sheet. Welding inspection method for tank steel plates, characterized by detecting lateral cracks in a direction intersecting with the direction of by a creeping wave method using a plurality of ultrasonic probes. 2. A welding inspection apparatus for a tank steel sheet, which inspects a welded portion of a tank steel sheet having a surface coating, or a scratch occurring on the surface of a heat-affected zone thereof, which travels on a tank steel sheet having a coating surface. A traveling carriage, and at least three or more ultrasonic probes provided on the traveling carriage to detect vertical cracks in the direction of the welding bead and lateral cracks in a direction intersecting with the direction of the welding bead by the creeping wave method. A position detection means provided on the traveling carriage for detecting position information of a portion detected by the ultrasonic probe; and an output of the ultrasonic probe displayed via an ultrasonic flaw detector.
A welding / inspection device for a tank steel plate, comprising: a calculation / flaw detection display unit for outputting. 3. The traveling carriage travels forward and / or backward on a rail, the ultrasonic probe is supported by a probe unit, and the probe unit is cantilevered by the traveling carriage. Is a probe welding bead distance adjusting mechanism capable of varying the distance between the ultrasonic probe and the welding bead, and a plurality of ultrasonic probes each independently arranging a probe unit height capable of varying the height. The tank steel plate welding inspection device according to claim 2, further comprising a height adjusting mechanism. 4. An ultrasonic probe for flaw detection of vertical cracks in the direction of the weld bead by a creeping wave method has a pair of transmitter and receiver arranged on both sides of the weld bead as boundaries. The welding inspection device for a tank steel plate according to claim 2 or 3, characterized in that. 5. The tank steel plate welding inspection apparatus according to claim 4, wherein the transmitter and the receiver are arranged in line symmetry with the welding bead interposed therebetween. 6. An ultrasonic probe for flaw detection of lateral cracks in a direction intersecting with the direction of the welding bead by creeping wave method, wherein a transmitter is arranged on one side of the welding bead as a boundary and the other side is arranged. The welding inspection device for a tank steel plate according to any one of claims 2 to 5, wherein the receivers are arranged symmetrically. 7. The calculation / flaw detection display means records an output signal obtained from the position detection means and an output signal obtained from the ultrasonic flaw detector, and monitors a response time of an input ultrasonic wave. The welding inspection apparatus for a tank steel plate according to any one of claims 2 to 6, wherein the input signal is determined to be a cracking signal when the output value in 1 exceeds a preset detection threshold value. 8. The ultrasonic signal exceeding the detection threshold value is color-coded into threshold values in accordance with the position information obtained by the position detecting means, and displayed on a two-dimensional plane as crack information. The welding inspection device for a tank steel plate according to any one of claims 2 to 6. 9. The calculation / flaw detection display means binarizes and image-processes an ultrasonic signal represented on a two-dimensional plane based on the position information with the detection threshold as a reference, and from the result, a flaw in a traveling direction is obtained. 9. The length is calculated.
Welding inspection device for tank steel sheet. 10. The calculation / flaw detection display means displays the crack detection position in accordance with the position information obtained by the position detection means on the basis of the ultrasonic signal exceeding the detection threshold value on the drawing of the tank steel plate. Then, the welding inspection device for a tank steel plate according to claim 7, wherein the welding inspection device outputs the output to an output medium.