JP2010175259A - Ultrasonic flaw detector and ultrasonic flaw detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detector capable of precisely discriminating between the shape echo caused by a back wavy shape and the flaw echo caused by a flaw, and an ultrasonic flaw detecting method. <P>SOLUTION: The ultrasonic flaw detector is equipped with a waveform memory means 13 for storing the waveform of a reflected echo at each scanning position, a peak detecting means 15 for detecting a peak from the waveform of the reflected echo at each scanning position stored in the waveform memory means 13, a peak grouping means 19 for comparing the respective peaks at adjacent scanning positions detected by the peak detecting means 15 with each other to group the peaks of the same reflection source, an echo discriminating means 21 for discriminating between the flaw echo and the shape echo with respect to the respective grouped peaks, a cell image forming means 23 for forming a cell image so as not to display the peak of the same group as the peak, which is judged to be the shape echo by the echo discriminating means 21, as a flaw and a display means 25 for displaying the formed cell image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic flaw detection apparatus and method for inspecting a defect in a welded part of an inspection object using ultrasonic waves.

  As shown in FIG. 8, the ultrasonic oblique angle flaw detection method makes an ultrasonic wave incident from the probe 5 to the welded portion 3 of the inspection object 1 with a predetermined refraction angle, and from the defect 31 (flaw) or the back wave 33. This is a method for evaluating the position and size of the defect 31 and the back wave 33 by measuring the beam path length and echo height of the reflected echo.

The positions of the defect 31 and the back wave 33 are calculated from the beam path distance from the incident point of the probe 5 to the peak of the defect echo reflected by the defect 31 and the shape echo reflected by the back wave 33, and the refraction angle.
When the probe 5 is moved in a direction perpendicular to the welded portion 3 (Y direction), the positions of defect echoes and shape echoes are calculated on the scanning line corresponding to the position of the probe 5 and A cross-sectional image of the weld cross section is obtained. A plane image (C scope) and a cross-sectional image (B scope) of the defect 31 and the back wave 33 in the welded portion 3 are obtained by performing flaw detection continuously in the parallel direction (X direction) with respect to the welded portion 3. .
And a defect is specified from the defect displayed on an image, and a back wave, and the quality of the welding part 3 is determined. Therefore, it is important to distinguish whether the reflected echo is a defect echo due to a defect or a shape echo due to a back wave.

As an example of a method of imaging a defect in the welded portion 3 obtained by ultrasonic flaw detection and distinguishing it from a back wave, for example, Patent Document 1 discloses the following ultrasonic flaw detection apparatus.
“Ultrasonic wave detection means for detecting an echo reflected from the ultrasonic wave that is reflected by a discontinuous portion of the inspection object, by entering ultrasonic waves into the inspection object;
Scanning means for moving the ultrasonic detection means at at least two pitches along the defect inspection range of the inspection object;
Projecting the discontinuous portion at a position corresponding to the reflected echo on the same surface, and creating a range in which the discontinuous portion is continuous on the same surface as a cell; and
Defect existence area setting means for setting a defect existence area that is determined that there is a possibility that a defect of the inspection object exists from the distribution of the cells created by the cell creation means;
Defect echo identifying means for determining whether or not the reflected echo corresponding to the discontinuous portion in the defect existing area is a defect echo of the inspection object;
Display means for displaying the output of the defect presence area setting means and the defect echo identification means;
An ultrasonic flaw detection apparatus comprising: a correction means for correcting outputs of the defect presence area setting means and the defect echo identification means. (See Patent Document 1)

JP-A-10-82766

It is often seen that defects occur near the back wave in the weld. And since the ultrasonic beam propagates in the inspection object with a certain spread, if there is a defect close to the back wave, the peak of the back wave echo appears close to the peak of the defect echo. Is seen. In such a case, it is important to distinguish whether the peak source is a defect or a back wave.
In this regard, in Patent Document 1, a cell image is created based on a waveform obtained by ultrasonic flaw detection, and whether the shape echo or the defect echo is determined based on the created cell image is determined by a defect echo identification unit. Like to do. Then, for those determined to be defective echoes, the cell image is colored, and finally the engineer determines whether or not the defect is based on the original waveform of the echo corresponding to the colored cell image.

  However, when the positions of the back wave echo and the defect echo are close to each other as described above, it is extremely difficult to make a determination by a computer such as a defect echo identification means on the basis of the created cell image. For this reason, there is a possibility of erroneous detection. In consideration of this point, the determination by the defect echo identification means is given in a more severe direction. That is, in the determination by the defect echo identification means, it is determined in the direction of the defect echo, and it is determined that the defect is larger than the actual one, or the shape echo is determined as the defect echo. For this reason, there is a problem that the number of cell images that require final confirmation by an engineer increases and the efficiency of inspection deteriorates.

  Further, in the technique of the above-mentioned Patent Document 1, after all acquisition of reflected echoes by the ultrasonic probe is completed, a cell image is created and a determination process is performed based on the cell image. It is not possible to display defects in real time.

The present invention has been made to solve such a problem, and an ultrasonic flaw detector capable of accurately distinguishing between a shape echo caused by a shape like a back wave and a defect echo caused by a defect. And to obtain a method.
It is another object of the present invention to provide an ultrasonic flaw detection apparatus and method capable of displaying cell images in real time.

In the above-mentioned Patent Document 1, a waveform of a reflected echo is recorded, a cell image is formed without distinguishing whether the waveform is a shape echo or a defect echo, and whether it is a shape echo or a defect based on the created cell image. It was to judge whether it was an echo.
Inventing such a conventional idea, the inventor considered that shape echoes or defect echoes were preliminarily determined based on recorded waveforms, and a cell image was created based on the determination results. . Then, in order to determine whether it is a shape echo or a defect echo based on the waveform, we considered grouping the peaks that appear in each waveform, and determining whether each grouped peak is a shape echo or a defect echo.
The present invention is based on such an idea, and specifically has the following configuration.

(1) An ultrasonic flaw detection apparatus according to the present invention scans a probe at a predetermined pitch along a defect inspection range of an inspection object, and detects ultrasonic waves incident on the inspection object by the probe. In an ultrasonic flaw detector that detects the presence or absence of a defect based on a reflected echo, a waveform storage means for storing the waveform of the reflected echo at each scanning position, and a waveform of the reflected echo at each scanning position stored in the waveform storage means Peak detection means for detecting peaks, peak grouping means for comparing the peaks at adjacent scanning positions detected by the peak detection means to group those of the same reflection source, and for each grouped peak Echo identification means for identifying whether it is a defect echo or a shape echo, and the same group as the peak determined to be a shape echo by the echo identification means A cel creation means for creating a cel so as not to display the over click as a defect, it is characterized in that a display means for displaying the cell image that was created.

(2) Also, in the above-described (1), the peak grouping means determines that the beam path lengths are equal for each peak detected at the adjacent scanning position in consideration of the change in the scanning position. The same reflection source is grouped into the same group.

(3) In the above (1) or (2), the echo identification means uses a waveform at a specific scanning position preset as a shape echo is detected as a reference waveform, and the reference waveform Based on the above, whether each peak is a shape echo or a defect echo is identified.

(4) Also, in the case described in (3) above, when flaw detection is performed on the welded part of the inspection object, the scanning position where the center of the ultrasonic beam passes through the point where the center position of the weld bead and the plate thickness intersect is specified. The peak generated at a position farther than the plate thickness for each peak of the reference waveform is regarded as a shape echo, and the peak occurring before the shape echo is regarded as a defect echo. To do.

(5) The ultrasonic flaw detection method according to the present invention includes a Y-direction moving step of moving the probe at a predetermined pitch in a direction (Y direction) orthogonal to the welded portion of the object to be inspected, and a termination position in the Y direction. An X-direction moving step that moves at a predetermined pitch in the direction along the weld (X direction) when moved,
At each position moved at a predetermined pitch in the Y direction, a flaw detection operation by the probe is performed, a waveform storing step for storing a reflected echo waveform, a peak detecting step for detecting a peak from the stored waveform, and an adjacent A peak grouping process that compares the peaks of each waveform at the scanning position to group the same reflection source, and echo identification that identifies whether each of the grouped peaks is a defect echo or a shape echo A cell image creation step for creating a cell image so as not to display as a defect a peak in the same group as the peak determined to be a shape echo by the echo identification step, and a display step for displaying the created cell image It is characterized by comprising.

(6) In the above described (5), the waveform storing step and the peak grouping step are performed for each scanning at each scanning position, and every time the scanning in the Y direction at a certain X position is completed, An echo identification process, a cell image creation process, and a display process are performed, and the same operation is repeated at each X position.

  In the present invention, whether a defect echo or a shape echo is identified based on the waveform of a reflected echo at each scanning position, and a defect corresponding to a peak determined to be a defect echo is displayed as a cell image. As a result, identification is accurate and erroneous determination can be prevented.

It is a block diagram which shows the structure of the ultrasonic flaw detector which concerns on one embodiment of this invention. It is explanatory drawing of the movement path | route of the probe which concerns on one embodiment of this invention. It is explanatory drawing of the peak detection range which concerns on one embodiment of this invention. It is explanatory drawing of the peak detection method which concerns on one embodiment of this invention. It is explanatory drawing of the peak detection method which concerns on one embodiment of this invention. It is explanatory drawing of the peak grouping which concerns on one embodiment of this invention. It is explanatory drawing of the processing method in the case of performing an ultrasonic flaw by the ultrasonic flaw detector which concerns on one embodiment of this invention. It is explanatory drawing of a general ultrasonic flaw detection method.

[Embodiment 1]
In the present embodiment, an oblique flaw inspection for examining a defect in the welded portion 3 using an ultrasonic wave traveling obliquely with respect to the surface of the inspection object 1 such as a pipe will be described as an example.
FIG. 1 is a block diagram showing a configuration of an ultrasonic flaw detector according to an embodiment of the present invention. The ultrasonic flaw detector according to the present embodiment includes a probe 5, scanning means 7, control means 9, AD conversion means 11, waveform storage means 13, peak detection means 15, and peak grouping means. 19, an echo identification unit 21, a cell image creation unit 23, and a display unit 25. Hereinafter, each configuration will be described in detail.

<Probe>
The probe 5 receives a reflected echo that is reflected by a reflection source such as a discontinuous portion in the inspection object 1 and enters the inspection object 1 and returns.
The scanning means 7 holds the probe 5 and can move at a predetermined pitch (for example, 1 mm) in the orthogonal direction (Y direction) and the parallel direction (X direction) to the welded portion 3 as shown in FIG. It is like that.
The movement of the scanning means 7 is controlled by the control means 9 and, as shown in FIG. 2, (X0, Y1), (X0, Y2),... (X0, Yn) starting from (X0, Y0). ), And (X0, Yn) is followed by (X1, Yn), (X1, Yn-1), (X1, Yn-2) (X1, Yn). Y0) is advanced at a predetermined pitch, and the same operation is repeated until the position (Xn, Y0) is reached.
Each time the probe 5 moves by a predetermined pitch in the Y direction, an ultrasonic wave enters the device under test 1 and receives reflected waves.

<AD conversion means>
The AD conversion means 11 performs AD conversion on the waveform data of the reflected echo received by the probe 5 and converts it into digital waveform data. This digital waveform data is stored in the waveform storage means 13.

<Peak detection means>
The peak detection unit 15 detects each peak of each waveform based on the waveform data stored in the waveform storage unit 13. Various settings can be made as to what kind of waveform is recognized as a peak. For example, when the waveform is higher than a predetermined height and only within the weld bead, and the valley of the waveform is 6 dB or more, a separate echo is used. To do.
The waveform data received by the probe 5 includes data on reflected echoes reflected away from the welded portion 3, but the peak detection means 15 is subject to detection by welding. It is set within a predetermined range including the part 3. FIG. 3 is a diagram showing a predetermined range in the welded portion 3 of the groove, and the range surrounded by the oblique lines in FIG. 3 is a portion including the groove and a part of the base material. The predetermined range for peak detection can be set by the position of the probe 5 and the beam path. Conversely, whether the obtained data is within the predetermined range depends on the position of the probe 5 and the beam path. Can be determined.

The peak of each waveform detected by the peak detection means 15 is stored in the waveform storage means 13.
4 and 5 are explanatory diagrams for explaining a method of detecting the peak of each waveform by the peak detecting means 15.
Figure 4 is at a certain position X-axis direction in which the probe 5 _{(X p),} a position shifted 1 pitch in the Y-axis direction _{(X p, Y q),} (X p, Y q + 1), (X p, A state is shown in which ultrasonic waves are incident at three adjacent scanning positions of Y _{q + 2} ). And the black circle shown to the welding part 3 has shown the defects a and b. Moreover, the curved black line shown in the welding part 3 has shown the surface of the back wave, and a reflective echo generate | occur | produces in this position. FIG. 5 shows the peak detection means 15 based on the reflected echo waveforms at the positions (X _p , Y _q ), (X _p , Y _{q + 1} ), (X _p , Y _{q + 2} ) shown in FIG. It is the figure which showed the detected peak typically, the vertical axis | shaft shows echo height and the horizontal axis shows the beam path length. Further, (a) (b) ( c) Fig. In FIG. 5, respectively, of FIG _{4 (X p, Y q)} , (X p, Y q + 1), (X p, Y q + 2) to the reflection echo at the position It corresponds.

At the position of (X _p , Y _q ), since the defect a exists in the path of the beam center, the reflected echo due to the defect a appears at a high peak a as shown in FIG. In FIG. 5A, peaks b and c appear when the expanded ultrasonic wave is reflected by the defect b and the back wave c. In addition, reflecting on the surface of the back wave means that the beam path exceeds the plate thickness, so that it appears at a position farther than the plate thickness position of the beam path, as shown in FIG. Become.
At the position of (X _p , Y _{q + 1} ), since the defect b exists in the beam center path, as shown in FIG. 5B, the reflected echo due to the defect b appears at a high peak. Further, reflected echoes due to the defect a and the back wave c appear as peaks a ′ and c ′, respectively.
In FIG. 5B, “′” is attached to the symbols “b” and “c” to indicate that the peak that appears is due to the defect b and the back wave c.
At the position of (X _p , Y _{q + 2} ), there is no defect in the path of the beam center, but the ultrasonic wave spread by the defect b existing in the vicinity of the beam center is reflected, and a peak b ″ appears. Further, since there is a back wave in the path of the beam center incident at this position, it appears as a peak c ″ in FIG.

<Peak grouping means>
The peak grouping unit 19 performs processing for grouping the peaks detected by the peak detecting unit 15 that are regarded as the same reflection source. The grouping process may be performed every time the flaw detection operation at each flaw detection position is completed, or may be performed when a predetermined pitch movement is completed in the Y direction at a position where the X axis is located. In the following description, a case will be described in which the flaw detection operation at each flaw detection position is performed each time it is completed.

The peak grouping means 19 groups the peaks detected at the adjacent scanning positions, which are determined to have the same beam path when considering the change in scanning position, into the same group as those of the same reflection source. This will be specifically described below.
FIG. 6 is an explanatory diagram for explaining the grouping method of the peak grouping means 19, and explains the grouping method when the peak shown in FIG. 5 is detected.

If the three peaks a, b, and c shown in FIG. 5 are detected at the scanning position (X _p , Y _q ), each peak is divided into three groups, and the group names are A, B, and C, respectively. . FIG. 6A shows a table in which each peak is grouped.
Next, it is determined which of the groups A, B, and C the peaks a ′, b ′, and c ′ detected at the scanning position (X _p , Y _{q + 1} ) belong to, and the determined group is assigned a group. Divide. The determination of which group the peaks a ′, b ′, and c ′ belong to will be described, for example, for the peak a ′. If it is determined that the beam path of the peak a ′ is equal to the beam path of the peak a, the same reflection source Into the same group, that is, group A. Whether or not the peak a ′ is equal to the beam path of the peak a is determined based on the scanning position (X _p , Y _{q + 1} ) where the peak a ′ is detected and the scanning position (X _p , Y _q ) where the peak a is detected. If the beam path length is calculated in consideration of this shift, the beam path of peak a ′ is different from the beam path of peak a by a predetermined distance. When within the error range, it is determined that the beam path lengths are equal.
FIG. 6B shows a table in which peaks a ′, b ′, and c ′ are determined to be in groups A, B, and C, respectively.

Similarly, the peaks b ″ and c ″ detected at the scanning position (X _p , Y _{q + 2} ) are also grouped. FIG. 6C shows a table in which the peaks b ″ and c ″ are determined to be in groups B and C, respectively.
When a peak that does not belong to the group A, B, or C is detected at a certain scanning position, it may be grouped as a new group, for example, group D.
Since peak data at each scanning position is immediately grouped by the peak grouping means 19, it is possible to display cell images in real time.

<Echo identification means>
The echo identification means 21 identifies whether each grouped peak is a shape echo or a defect echo.
The identification method uses the waveform detected at the scanning position where the center of the ultrasonic beam passes the point where the center of the weld bead intersects the plate thickness as the reference waveform, and each peak is shaped based on the peak of this reference waveform. Identify whether it is an echo or a defect echo. Specifically, of the peaks of the reference waveform, a peak occurring at a position farther than the plate thickness is regarded as a shape echo, and a peak occurring before the peak of the shape echo is regarded as a defect echo.

For example, in the example shown in FIG. 4, the scanning position (X _p , Y _{q + 2} ) corresponds to the scanning position where the center of the ultrasonic beam passes through the point where the center position of the weld bead and the plate thickness intersect with each other. ) To identify whether each peak is a shape echo or a defect echo. As is clear from FIG. 5C, since the peak c ″ is a peak generated at a position far from the plate thickness, the peak c ″ is regarded as a shape echo and the group to which the peak c ″ belongs. The peaks grouped in C are shape echoes.

<Cell picture creation means>
The cell image creation means 23 creates a cell image for the peak identified as a defect echo by the echo identification means 21. The cell image is created by dividing the predetermined range for detecting the peak data shown in FIG. 3 into, for example, cubic cells each having a length of 1 mm, and detecting each of the cells by the peak detecting means 15. By matching the measured peaks. Of course, the peak detected by the peak detecting means 15 includes both defect echoes and shape echoes. However, the cell image creating means 23 only selects the peaks identified by the echo identifying means 21 as being defective echoes. Make it visible. That is, since the peak position and echo height identified as a defect echo by the echo identification means 21 are known, image data is created by associating this with the cell. In other words, such processing means that the peaks identified as shape echoes are not visually colored, that is, the peaks identified as shape echoes are not displayed as defect echoes. is there.
The created image data is stored in the waveform storage means 13.

<Display means>
The display unit 25 displays the cell image on a screen such as a display based on the image data generated by the cell image generation unit 23.

Next, an ultrasonic flaw detection method using the ultrasonic flaw detector according to the present embodiment configured as described above will be described.
FIG. 7 is a flowchart for explaining the flow of data processing in the ultrasonic flaw detection method.
As described above, as shown in FIG. 2, the probe 5 starts from (X0, Y0) and is sequentially (X0, Y1), (X0, Y2),... (X0, Yn). And flaw detection operation is performed at each position.

When the ultrasonic flaw detection is started, the probe 5 is arranged by the control means 9 at the start position (X0, Y0). When the probe 5 is placed at the start position, a flaw detection operation is performed, and the reflected echo is stored in the waveform storage means 13 (S1). When the reflection echo data is stored in the waveform storage means 13, the peak detection means 15 detects the peak of the reflection echo waveform (S3).
When detecting the peak, as described above, the peak is higher than a predetermined echo height and only in the weld bead, and when the valley is 6 dB or more, it is detected as a peak of another echo.
When a peak is detected, the peak grouping means 19 performs a peak grouping process (S5). In the peak grouping process, as described above, adjacent peaks of each peak recorded in the waveform storage means 13 are compared to determine whether they are of the same reflection source, and those of the same reflection source are grouped. Group as.
When the above operation ends, the control means 9 determines whether or not the probe 5 has reached the end position in the Y direction (S7). The end position in the Y direction is the Yn position when the moving direction of the probe 5 is in the positive direction of the Y axis, and conversely when the moving direction of the probe 5 is in the negative direction. , Y0. If the probe 5 has not reached the end position, the control means 9 controls the scanning means 7 to move the probe 5 in the Y-axis direction by one pitch (S9). Specifically, the probe 5 is moved to (X0, Y1), and the same operation as described above is performed (S1 to S9).

  If it is determined in S7 that the probe 5 has reached the end position in the Y-axis direction, the echo identification means 21 determines whether the peak of each group is a shape echo or a defect echo. Identify (S11). As described above, as an example of the identification method, the center of the ultrasonic beam passes through the point where the center position of the weld bead and the plate thickness intersect, and the peak generated at a position farther than the plate thickness is regarded as a shape echo. The peak generated before the shape echo is regarded as a defect echo. However, other methods may be used.

  When it is identified whether each peak is a shape echo or a defect echo, the cell image creation means 23 creates colored visible image data in the corresponding cell for the peak identified as a defect echo. (S13). The created cell data is stored in the waveform storage means 13.

  When the image data is created, the cell image is displayed on the screen of the monitor or the like by the display means 25 (S15). As described above, in the present embodiment, the cell image is displayed in real time every time a row of flaw detection in the Y axis is completed.

  When the cell image is displayed, the control means 9 determines whether or not the flaw detector can be further moved in the X-axis direction (S17). If the flaw detector can be moved, it moves one pitch in the X-axis direction (S19). ) At the position of the X-axis, it moves by one pitch in the Y-axis direction and performs the same operation as described above (S1 to S19).

The above operation is repeated, and if it is determined in S17 that the flaw detector cannot be further moved in the X-axis direction, the process is terminated.
At this time, the cell image display at the flaw detection position (Xn, Y0) is completed, and the display means 25 displays a predetermined range of defects shown in FIG.
Finally, the defect is evaluated based on the image displayed by the engineer, the waveform on which the image is based, and the pass / fail of the object 1 is determined.

As described above, according to the present embodiment, whether the shape echo or the defect echo is identified by the waveform of the reflected echo, the identification is accurate and erroneous determination can be prevented.
In addition, since the cell image is displayed simultaneously with the scanning of the probe 5, the defect can be evaluated in real time.

In addition, in said embodiment, although the back wave of the welding part was demonstrated, it can carry out similarly about the case of a surface wave. However, in the case of a surface wave, the reference scanning position for echo identification is a position where the center of the ultrasonic beam is reflected once at the plate thickness position and passes through the center of the surface wave bead.
In the above description, the case where a peak that is a shape echo is detected at the reference position has been described. However, when the shape echo peak is not detected at the reference position, the shape echo that should be detected originally is detected. May be obtained by calculation, and a peak corresponding to the shape echo obtained by the calculation may be regarded as a shape echo.
In the above description, as adjacent scanning positions to be compared when grouped, those adjacent in the Y-axis direction have been described, but scanning positions adjacent in the X-axis direction may be compared.

DESCRIPTION OF SYMBOLS 1 Test object 3 Welding part 5 Probe 7 Scanning means 9 Control means 11 AD conversion means 13 Waveform storage means 15 Peak detection means 19 Peak grouping means 21 Echo identification means 23 Cell image creation means 25 Display means

Claims (6)

Ultrasound that scans the probe at a predetermined pitch along the defect inspection range of the inspection object and detects the presence or absence of a defect based on the reflected echo of the ultrasonic wave incident on the inspection object by the probe In flaw detection equipment,
Waveform storage means for storing the waveform of the reflected echo at each scanning position, peak detection means for detecting a peak from the waveform of the reflected echo at each scanning position stored in the waveform storage means, and detection by the peak detection means Peak grouping means for comparing the peaks at adjacent scanning positions and grouping those of the same reflection source, and echo identification means for identifying whether each of the grouped peaks is a defect echo or a shape echo A cell image creating means for creating a cell image so as not to display a peak of the same group as the peak determined to be a shape echo by the echo identifying means, and a display means for displaying the created cell image. An ultrasonic flaw detector provided with the apparatus. The peak grouping means groups the peaks detected at the adjacent scanning positions that are determined to have the same ultrasonic beam path considering the change in scanning position into the same group as those of the same reflection source. The ultrasonic flaw detector according to claim 1. The echo identification unit identifies whether each peak is a shape echo or a defect echo based on the reference waveform based on a waveform at a specific scanning position set in advance as a shape echo is detected. The ultrasonic flaw detector according to claim 1 or 2. When flaw detection is performed on the welded part of the object to be inspected, the scanning position where the center of the ultrasonic beam passes through the point where the center position of the weld bead intersects the plate thickness is defined as the specific scanning position, and each peak of the reference waveform is more 4. The ultrasonic flaw detector according to claim 3, wherein a peak occurring at a far position is regarded as a shape echo, and a peak occurring before the shape echo is regarded as a defect echo. A Y-direction moving step in which the probe is moved at a predetermined pitch in a direction (Y direction) orthogonal to the welded portion of the object to be inspected, and a direction along the welded portion (X direction when moved to the end position in the Y direction) And an X-direction moving step that moves at a predetermined pitch,
At each position moved at a predetermined pitch in the Y direction, a flaw detection operation by the probe is performed, a waveform storing step for storing a reflected echo waveform, a peak detecting step for detecting a peak from the stored waveform, and an adjacent A peak grouping process that compares the peaks of each waveform at the scanning position to group the same reflection source, and echo identification that identifies whether each of the grouped peaks is a defect echo or a shape echo A cell image creation step for creating a cell image so as not to display as a defect a peak in the same group as the peak determined to be a shape echo by the echo identification step, and a display step for displaying the created cell image And an ultrasonic flaw detection method. A waveform storage process and a peak grouping process are performed for each scan at each scanning position, and an echo identification process, a cell image creation process, and a display process are performed each time all scanning in the Y direction at a certain X position is completed. The ultrasonic flaw detection method according to claim 5, wherein the same operation is repeated at each X position.

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