JP5505806B2 - Discrimination method of reflection echo - Google Patents

Description

  The present invention relates to a method for discriminating reflected echoes from artificial flaws in ultrasonic flaw detection. In particular, the reflection echoes from the outer surface artificial flaw and the inner surface artificial flaw provided in the tube so that the positions in the tube axis direction are the same with each other are the reflection echoes from the outer surface artificial flaw or the reflection echoes from the inner surface artificial flaw. The present invention relates to a method for discriminating reflected echoes from artificial flaws in ultrasonic flaw detection that discriminates whether or not an object is ultrasonic.

Conventionally, an ultrasonic flaw detection method has been used as a method for examining the presence or absence of a flaw on the outer surface or inner surface of a pipe such as a steel pipe. At the end of the tube, because the ultrasonic propagation distance to the end face is short, the reflected echo from the end face enters the gate set to detect the reflected echo from the flaw. Occurs. In the case of a steel pipe, the undetected area varies depending on the thickness of the steel pipe, but the distance from the end face is in the range of 0 to 300 mm. Further, in an undetected region and an end region adjacent to the undetected region (hereinafter, an end region adjacent to the undetected region is referred to as an end adjacent region), the tube support mechanism generally determines the end of the tube. Since it cannot be supported, the positional relationship between the tube and the ultrasonic probe varies, and the sensitivity of the reflected echo from the flaw tends to decrease.
In order to examine the range of the undetected region, a test flaw detection tube is used. The tube must be provided with an outer surface artificial flaw and an inner surface artificial flaw at the same position in the tube axis direction corresponding to the undetected region and the end adjacent region.

Explanation of reflection echo from external flaw (hereinafter referred to as external flaw reflection echo) and reflection echo from internal flaw (hereinafter referred to as internal flaw reflection echo) when external artificial flaw and internal artificial flaw are provided at the same position in the tube axis direction To do.
The propagation distance of the ultrasonic wave from the ultrasonic probe to the outer surface artificial flaw is longer than that to the inner surface artificial flaw.
When the tube is thick, the difference in propagation distance becomes large, so that a flaw detection gate for detecting an outer surface flaw (hereinafter referred to as an outer flaw detection gate) and a flaw detection for detecting an inner surface flaw. It is easy to set the gates (hereinafter referred to as internal flaw detection gates) so as not to overlap. If the outer surface flaw detection gate and the inner surface flaw detection gate do not overlap, the outer surface flaw reflection echo and the inner surface flaw reflection echo can be easily distinguished.
However, when the tube is thin, the difference between the ultrasonic propagation distance from the ultrasonic probe to the external artificial flaw and the ultrasonic propagation distance from the ultrasonic probe to the internal artificial flaw is small. It is difficult to set the outer surface flaw detection gate and the inner surface flaw detection gate so as not to overlap each other. If the outer surface flaw detection gate and the inner surface flaw detection gate overlap, both the outer surface flaw reflection echo and the inner surface flaw reflection echo easily enter both the outer surface flaw detection gate and the inner surface flaw detection gate. It becomes difficult to discriminate between the flaw reflection echo and the inner flaw reflection echo.

With reference to FIG. 1, a description will be given of reflection echoes when ultrasonic flaw detection is performed on an outer surface artificial flaw and an inner surface artificial flaw when the tube is thick. FIG. 1A is a schematic diagram showing a cross section of a tube and a state of an ultrasonic probe when ultrasonic flaw detection is performed. The outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided at the same position in the tube axis direction. FIG. 1B is a reflection echo chart (A scope) obtained by the ultrasonic flaw detection shown in FIG. In FIG. 1B, the outer surface flaw reflection echo and the inner surface flaw reflection echo detected separately are represented by matching the positions of the respective surface echoes.
As the tube 101 rotates in the arrow A direction, the ultrasonic probe 102 performs ultrasonic flaw detection while relatively moving in the tube circumferential direction.
The outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 do not overlap, and the reflected echo E1 from the outer surface artificial flaw F1 enters the outer surface flaw detection gate G1, and the reflected echo E2 from the inner surface flaw detection gate G2 becomes the inner surface flaw detection gate G2. to go into. For this reason, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 can be distinguished.

Next, the reflection echo when the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are ultrasonically detected when the tube is thin will be described with reference to FIG.
FIG. 2A is a schematic view showing a state in which ultrasonic flaw detection is performed on a pipe provided with an outer surface artificial flaw and an inner surface artificial flaw.
An outer surface artificial flaw F1 and an inner surface artificial flaw F2 are individually provided at different positions in the tube axis direction in the central portion of the tube 101, and an outer surface artificial flaw F1 and an inner surface artificial flaw F2 are provided in a region adjacent to the end. . As the tube 101 rotates in the arrow A direction, the ultrasonic probe 102 performs ultrasonic flaw detection while relatively moving in the tube circumferential direction. The ultrasonic probe 102 is moved to each axial position where the outer surface artificial defect F1 or the inner surface artificial defect F2 is provided, and ultrasonically detects each artificial defect.
2 (b) and 2 (c) show that the ultrasonic probe 102 performs ultrasonic flaw detection at each position where the outer surface artificial flaw F1 or the inner surface artificial flaw F2 is provided in the central portion of the tube in FIG. 2 (a). FIG. 2D is a schematic diagram showing a cross section of the tube 101 and the state of the ultrasonic probe 102 when the outer surface is formed, and FIG. 2D is a position at the position where the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided in the end adjacent region. FIG. 2 is a schematic diagram showing a cross section of a tube 101 and a state of the ultrasonic probe 102 when the ultrasonic probe 102 performs ultrasonic flaw detection. FIGS. 2E, 2F, and 2G are charts (A scope) of reflected echoes obtained by ultrasonic flaw detection in FIGS. 2B, 2C, and 2D, respectively. In FIG. 2G, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 which are separately detected are represented by matching the positions of the respective surface echoes.

As shown in FIG. 2 (e), in ultrasonic flaw detection at a position where only the outer surface artificial flaw F1 is provided, the outer surface flaw detection gate G1 is set, and the outer surface flaw reflection echo E1 entering the outer surface flaw detection gate G1. Can be recognized.
Similarly, as shown in FIG. 2 (f), in the ultrasonic flaw detection at a position where only the inner surface artificial flaw F2 is provided, the inner surface flaw detection gate G2 is set, and the inner surface flaw detection gate G2 is reflected. The echo E2 can be recognized.
However, although the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided in the end adjacent region, since the thickness of the tube is thin, the ultrasonic probe 102 to the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided. Therefore, the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 cannot be set so as not to overlap each other (see FIG. 2G).
Therefore, both the reflected echoes E1 and E2 that have been detected are likely to enter both the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2, so that each reflected echo is reflected from the outer surface artificial flaw F1. It becomes difficult to discriminate whether it is the echo E1 or the reflected echo E2 from the inner surface artificial flaw F2.

Thus, when the thickness of the tube is thin, it is difficult to discriminate the reflected echoes from the outer surface artificial flaw F1 and the inner surface artificial flaw F2 provided at the same position in the tube axis direction. This is particularly difficult when the thickness of the steel pipe is 10 mm or less.
Further, in order to discriminate between the outer surface artificial flaw F1 provided at the same position in the tube axis direction and the reflection echo from the inner surface artificial flaw F2 in the end adjacent region, the outer surface artificial flaw F1 is provided at the same position in the tube axis direction. However, there is a problem that it is expensive and time-consuming because two tubes must be prepared and ultrasonic flaw detection must be performed for each of the tubes. There is.

  Also, as a method for discriminating the types of defects in the ultrasonic flaw detection method, for example, the methods described in Patent Documents 1 and 2 are known. When the positions in the axial direction are the same, it is not possible to distinguish between the outer surface flaw reflection echo and the inner surface flaw reflection echo.

JP 58-53756 A Japanese Unexamined Patent Publication No. Sho 63-314463

  The present invention has been made to solve such a problem of the prior art, and each reflection from the outer surface artificial flaw and the inner surface artificial flaw provided in the tube so that the positions in the tube axis direction are the same. It is an object of the present invention to provide a method for discriminating reflected echoes from artificial flaws in ultrasonic flaw detection, wherein the echoes are discriminated whether they are external surface flaw reflection echoes or internal surface flaw reflection echoes.

  In order to solve the above-mentioned problems, the present inventor has devised a position in the tube circumferential direction in which an outer surface artificial flaw and an inner surface artificial flaw are provided and a method for analyzing the detected reflected echo, so that the detected reflected echo is not an outer surface flaw. It was found that it was possible to discriminate whether it was a reflection echo or an internal flaw reflection echo.

  The present invention has been completed based on the knowledge of the present inventors. That is, in order to solve the above-described problem, the present invention provides a pipe tube in which the positions in the tube axis direction are the same, the positions in the tube circumferential direction are separated from each other, and are not opposite to each other across the tube axis. A first step of providing an outer surface artificial flaw on the outer surface and an inner surface artificial flaw on the inner surface of the tube, and performing ultrasonic testing of the tube while relatively moving the ultrasonic probe in the circumferential direction of the tube, A second step of alternately detecting a reflected echo and a reflected echo from the inner surface artificial flaw, and detecting the reflected echo from either the outer surface artificial flaw or the inner surface artificial flaw and then detecting the outer surface artificial flaw And a first time until a reflected echo from the other of the inner surface artificial flaws is next detected, and a reflected echo from either one of the reflected echoes from the other is detected next. Detected And the relationship between the first time and the second time is compared with the relationship between the position of the outer surface artificial flaw in the pipe circumferential direction and the position of the inner surface flaw in the pipe circumferential direction. And a third step of discriminating whether each of the detected reflected echoes is a reflected echo from the outer surface artificial flaw or a reflected echo from the inner surface artificial flaw. Provided is a method of discriminating reflected echoes from artificial flaws.

In the present invention, the positions of the outer surface artificial flaw and the inner surface artificial flaw in the pipe circumferential direction are spaced apart from each other, because the detected outer surface flaw reflected echo and the inner flaw reflected echo peak positions (detection time points) do not match. Refers to the position of flaws and internal artificial flaws.
In addition, the position of the outer surface artificial flaw and the inner surface artificial flaw in the pipe circumferential direction is the opposite position between the tube axis and the time from the detection of the peak of the outer flaw reflection echo to the detection time of the peak of the inner flaw reflection echo. The positions of the outer surface artificial flaw and the inner surface artificial flaw where the time from the detection time point of the inner surface flaw reflection echo to the detection time point of the outer surface flaw reflection echo peak is the same.
Further, the second time is defined as “the time from when the reflected echo from one of the other is detected until the next time the reflected echo from the one is detected”. In the state where the reflected echo from the inner surface and the reflected echo from the inner surface artificial flaw are alternately and repeatedly detected, “after detecting the reflected echo from either one” and then repeatedly, “the reflection from either one” Time until “echo” is detected.

According to the present invention, for example, in the first step of the present invention, the length measured in the moving direction of the ultrasonic probe is from the outer surface artificial flaw to the inner surface artificial flaw than the inner surface artificial flaw to the outer surface artificial flaw. The outer surface artificial flaw and the inner surface artificial flaw are provided so as to be longer in the direction. Then, in the ultrasonic flaw detection in the second step, the time from when the outer surface flaw reflection echo is detected until the inner surface flaw reflection echo is detected, the outer surface flaw reflection echo is detected after the inner surface flaw reflection echo is detected. It will be longer than the time until. Therefore, in the third step, after detecting the reflection echo from either the outer surface artificial flaw or the inner surface artificial flaw, the reflection echo from either the outer surface artificial flaw or the inner surface artificial flaw is then detected. The first time is defined as the first time, and the second time is the time from when the reflected echo from one of the other is detected until the next reflected echo from the other is detected. If the relationship between the second time and the relationship between the distance from the inner surface artificial flaw to the outer surface artificial flaw and the distance from the outer surface artificial flaw to the inner surface artificial flaw is compared, each detected reflected echo is reflected from the outer surface artificial flaw. It is possible to easily discriminate whether it is an echo or a reflection echo from an internal artificial flaw. In the above example, if the first time is longer than the second time, the reflected echo from any one of the above is a reflected echo from the outer surface artificial flaw, and the reflected echo from any one of the other is from the inner surface artificial flaw. This is a reflected echo. On the contrary, if the first time is shorter than the second time, it is a reflection echo from the inner and outer surface artificial flaws from either one of the reflection echoes, and the reflection echo from either one of the reflection echoes from the outer surface artificial flaws It is.
In this way, the reflected echoes from the outer surface artificial flaw and the inner surface artificial flaw provided on the tube so that the positions in the tube axis direction are the same as each other are reflection echoes from the outer surface artificial flaw or from the inner surface artificial flaw. It is possible to discriminate whether it is a reflected echo.

According to the present invention, even if the outer surface artificial flaw and the inner surface artificial flaw are provided on the pipe so that the positions in the tube axis direction are the same, the reflection echoes from the outer surface artificial flaw and the inner surface artificial flaw are not generated on the outer surface flaw. It is possible to easily discriminate whether it is a reflection echo or an internal flaw reflection echo. The position in the tube axis direction where the outer surface artificial flaw and the inner surface artificial flaw are provided may be at the center or at the end as long as it is outside the undetected region.
In particular, because the tube thickness is thin, the outer surface flaw detection gate and the inner surface flaw detection gate overlap, and whether the reflected echo is the outer surface flaw reflection echo or the inner surface flaw reflection echo by the outer surface flaw detection gate and the inner surface flaw detection gate? Even if it is not possible to discriminate between them, it is possible to discriminate whether the reflected echo is an outer surface flaw reflected echo or an inner surface flaw reflected echo.
By distinguishing whether the detected reflected echo is an outer surface flaw reflected echo or an inner surface flaw reflected echo, it is possible to accurately recognize the range of the undetected region in the ultrasonic flaw detection of the tube.

FIG. 1A is a schematic diagram showing a cross section of a tube and a state of an ultrasonic probe when performing ultrasonic flaw detection according to a conventional method for discriminating reflected echoes, and FIG. It is the chart (A scope) of the reflective echo obtained by the ultrasonic flaw detection shown to Fig.1 (a). FIG. 2A is a schematic view showing a state in which ultrasonic flaw detection is performed on a pipe provided with an outer surface artificial flaw and an inner surface artificial flaw in the discrimination method. FIGS. 2B and 2C show the case where the ultrasonic probe performs ultrasonic flaw detection at each position where the outer surface artificial flaw or the inner surface artificial flaw is provided in the central portion of the pipe in FIG. It is a schematic diagram which shows the cross section of this tube, and the state of an ultrasonic probe. FIG. 2D shows the cross section of the tube and the state of the ultrasonic probe when the ultrasonic probe is performing ultrasonic flaw detection at the position where the outer surface artificial flaw and the inner surface artificial flaw are provided in the end adjacent region. It is a schematic diagram which shows. FIG. 2E is a reflection echo chart (A scope) obtained by the ultrasonic flaw detection of FIG. FIG. 2F is a reflection echo chart (A scope) obtained by the ultrasonic flaw detection of FIG. FIG. 2G is a reflection echo chart (A scope) obtained by the ultrasonic flaw detection of FIG. FIG. 3 is a schematic view showing a state in which the ultrasonic flaw detector performing ultrasonic flaw detection according to the present embodiment is performing ultrasonic flaw detection on a steel pipe. FIG. 4 is a diagram showing a cross section of the steel pipe and the state of the ultrasonic probe when the ultrasonic flaw detection is performed. FIG. 5 is a chart (A scope) of reflected echoes obtained by the ultrasonic flaw detection shown in FIG. FIG. 6 is a diagram showing, in time series, reflection echoes that enter the outer surface flaw detection gate or the inner surface flaw detection gate in the ultrasonic flaw detection. FIG. 7 is a diagram illustrating a cross section of a steel pipe and a state of an ultrasonic probe in the example. FIG. 8 is a chart (A scope) of reflected echoes obtained by ultrasonic flaw detection in the example. FIGS. 9A to 9D are diagrams showing the reflected echoes entering the outer surface flaw detection gate and the inner surface flaw detection gate in time series in the embodiment, from the chart showing the reflected echo to the outer surface flaw reflection echo and the inner surface flaw reflection echo. It is a figure which shows the process in which it discriminates. FIG. 10 is a chart of actual reflected echoes discriminated in the embodiment.

Hereinafter, a method for discriminating reflected echoes from artificial flaws in ultrasonic flaw detection according to an embodiment of the present invention will be described with reference to the accompanying drawings as appropriate.
FIG. 3 is a schematic diagram showing a state in which an ultrasonic flaw detector performing ultrasonic flaw detection is performing ultrasonic flaw detection on a steel pipe.
The ultrasonic flaw detector 2 that performs ultrasonic flaw detection on the steel pipe 1 includes an ultrasonic probe 21 that transmits and receives ultrasonic waves, and an arithmetic control unit 22 that controls the operation of the ultrasonic probe 21.
The steel pipe 1 is placed on a rotation drive unit (not shown) that rotates the steel pipe 1 in the circumferential direction, and the ultrasonic probe 21 relatively moves in the pipe circumferential direction as the steel pipe 1 rotates.
Water is supplied between the steel pipe 1 and the ultrasonic probe 21 by a water supply device (not shown) so that the ultrasonic wave propagates between the steel pipe 1 and the ultrasonic probe 21. Yes.

In order to discriminate reflected echoes from artificial flaws, first, the positions in the tube axis direction should be the same, the positions in the tube circumferential direction should be separated from each other, and not the opposite positions across the tube axis. The steel pipe 1 is provided with one elongated notch extending in the axial direction as the outer surface artificial flaw F1 and the inner surface of the steel pipe 1 is provided with one elongated notch extending in the axial direction as the inner surface artificial flaw F2. ). FIG. 4 is a diagram showing a cross section of the steel pipe 1 and the state of the ultrasonic probe 21 when performing ultrasonic flaw detection. Inclination flaw detection is performed so that ultrasonic waves are incident obliquely with respect to the normal direction of the surface of the steel pipe 1 so that ultrasonic waves propagate in the circumferential direction of the steel pipe 1 to detect the outer surface artificial flaw F1 and the inner surface artificial flaw F2. Yes. In addition, in the case where an elongated notch extending in the circumferential direction of the pipe is provided, a slant in which the ultrasonic wave is incident obliquely with respect to the normal direction of the surface of the steel pipe 1 so that the ultrasonic wave propagates in the pipe axis direction of the steel pipe 1. A corner flaw may be performed.
In the present embodiment, the oblique flaw detection is performed, but the outer surface artificial flaw F1 and the inner surface artificial flaw F2 may be detected by performing the vertical flaw detection.
The length of the notch is preferably 12 mm or more and 50.8 mm or less, the width is 1 mm or less, and the depth with respect to the thickness of the steel pipe from the required quality of the steel pipe. 5% ± 12.5%.
Here, the positions of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 in the pipe circumferential direction are spaced apart from each other when the ultrasonic flaw detection is performed, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 detected. The positions of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 that do not coincide with each other.
Further, the positions of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 in the tube circumferential direction are opposite to the positions opposite to each other across the tube axis. From the detection time point of the outer surface flaw reflection echo E1 to the peak detection time of the inner surface flaw reflection echo E2. And the position of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 where the time from the detection time of the peak of the inner surface flaw reflection echo E2 to the detection time of the peak of the outer surface flaw reflection echo E1 is the same.

  As shown in FIG. 4, the angle measured in the direction in which the ultrasonic probe 21 relatively moves from the straight line connecting the tube axis and the outer artificial flaw F1 to the straight line connecting the tube axis and the inner artificial flaw F2 is α. The angle measured in the direction of relative movement of the ultrasonic probe 21 from the straight line connecting the tube axis and the inner artificial flaw F2 to the straight line connecting the tube axis and the outer artificial flaw F1 is β. Here, α + β = 360 °. In order to facilitate discrimination of reflected echoes, it is preferable that either α or β is 45 ° or more and 135 ° or less.

Next, the steel pipe 1 is rotated in the direction of the arrow A by the rotation drive unit, and ultrasonic testing of the steel pipe 1 is performed while the ultrasonic probe 21 is relatively moved in the pipe circumferential direction.
Ultrasonic waves are transmitted from the ultrasonic probe 21, and the ultrasonic waves are alternately irradiated to the outer surface artificial flaw F 1 and the inner surface artificial flaw F 2 by the rotation of the steel pipe 1, and the reflected echo E 1 and the inner surface artificial flaw from the outer surface artificial flaw F 1. The reflected echo E2 from the flaw F2 is alternately detected by the ultrasonic probe 21 (second step).
FIG. 5 is a reflection echo chart (A scope) obtained by ultrasonic flaw detection. In FIG. 5, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 which are detected separately are represented by matching the positions of the respective surface echoes. In this embodiment, since the thickness of the steel pipe 1 is thin, the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 are set to overlap each other.
Since each of the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 is contained in the outer surface flaw detection gate G1 or the inner surface flaw detection gate G2, it is recognized as a reflection echo from the outer surface flaw detection flaw F1 or the inner surface flaw detection flaw F2. .
However, since each of the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 is included in both the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2, it is a reflection echo from the outer surface artificial flaw F1 or the inner surface flaw. It cannot be discriminated whether it is a reflected echo from F2.

As described above, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 are alternately detected according to the rotation of the steel pipe 1.
FIG. 6 is a diagram showing the reflected echoes entering the outer surface flaw detection gate G1 or the inner surface flaw detection gate G2 in time series.
The reflection echo P1 that is one of the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 and the reflection echo P2 that is the other one of the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 are alternately performed. It has been detected.

Next, the first time T1 from when the peak of the reflected echo P1 is detected until the peak of the reflected echo P2 is next detected, and the peak of the reflected echo P1 after the peak of the reflected echo P2 is detected next. The second time T2 until calculation is calculated, and the relationship between the first time T1 and the second time T2 is compared with the relationship between the position of the outer surface artificial flaw F1 in the pipe circumferential direction and the position of the inner surface artificial flaw F2 in the pipe circumferential direction. Thus, it is discriminated whether each of the detected reflection echoes P1 and P2 is the outer surface flaw reflection echo E1 or the inner surface flaw reflection echo E2 (third step).
The comparison of the third step is performed as follows, for example.
The magnitude relationship between the angle α and the angle β and the magnitude relationship between the first time T1 and the second time T2 are determined. The magnitude relationship may be determined, for example, based on whether the difference between the two comparing the magnitudes is positive or negative, or whether the ratio between the two is greater than 1 or less than 1.
In the case of α <β, if T1 <T2, the reflected echo P1 is the outer surface flaw reflected echo E1, the reflected echo P2 is the inner surface flaw reflected echo E2, and if T1> T2, the reflected echo P1 is reflected from the inner surface flaw. It is the echo E2, and the reflected echo P2 is the outer surface flaw reflected echo E1.
Contrary to the above, when α> β, if T1 <T2, the reflected echo P1 is the inner surface reflected echo E2, the reflected echo P2 is the outer surface damaged reflected echo E1, and if T1> T2, the reflected echo is reflected. P1 is the outer surface flaw reflection echo E1, and the reflection echo P2 is the inner surface flaw reflection echo E2.

Thus, even if the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided on the tube 1 so that the positions in the tube axis direction are the same, the reflected echoes from the outer surface artificial flaw F1 and the inner surface artificial flaw F2 respectively. Can be easily discriminated whether it is an outer surface flaw reflection echo E1 or an inner surface flaw reflection echo E2. The position in the tube axis direction where the outer surface artificial flaw F1 and the inner surface artificial flaw F2 are provided may be the center portion or the end portion as long as it is outside the undetected region.
In particular, since the thickness of the steel pipe 1 is thin, the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 overlap, and the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 determine whether the reflected echo is the outer surface flaw detection echo E1 or the inner surface. Even if it is not possible to discriminate whether it is the flaw reflection echo E2, it is possible to discriminate whether the reflection echo is the outer surface flaw reflection echo E1 or the inner surface flaw reflection echo E2. This is particularly effective when the thickness of the steel pipe is 10 mm or less.
Since it is possible to discriminate whether the detected reflected echo is the outer surface flaw reflected echo E1 or the inner surface flaw reflected echo E2, ultrasonic waves are individually applied to each of the outer surface flaw reflected echo E1 and the inner surface flaw reflected echo E2. Since the sensitivity of the flaw detection apparatus 2 can be adjusted, the detection accuracy of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 is improved.
Then, by using the ultrasonic flaw detector 2 for which sensitivity adjustment has been performed for ultrasonic flaw detection of the steel pipe 1, it can be expected that the detection accuracy of natural flaws in areas other than the non-flaw detection area is improved.

The comparison in the third step may be performed as follows.
The time required for the ultrasonic probe 21 to move relative to the half circumference around the steel pipe 1 is defined as time TH.
When α <β, if there is a peak of the reflected echo P2 within the time TH after the peak of the reflected echo P1 is detected, that is, if T2>TH> T1, the reflected echo P1 is the outer surface flaw reflected echo E1. Thus, the reflected echo P2 is an inner surface flaw reflected echo E2. If there is a peak of the reflected echo P2 within the time TH before the time point when the peak of the reflected echo P1 is detected, that is, if T1>TH> T2, the reflected echo P1 is the internal flaw reflected echo E2 and the reflected echo P2 is This is the outer surface flaw reflection echo E1.
On the contrary, when α> β, if there is a peak of the reflected echo P2 within the time TH after the peak of the reflected echo P1 is detected, that is, if T2>TH> T1, the reflected echo P1 is The internal surface reflection echo E2 and the reflection echo P2 are the external surface reflection echo E1. If there is a peak of the reflected echo P2 within the time TH before the time point when the peak of the reflected echo P1 is detected, that is, if T1>TH> T2, the reflected echo P1 is an external flaw reflected echo E1 and the reflected echo P2 is It is an inner surface flaw reflection echo E2.
Even if the comparison in the third step is performed in this way, the same effect as the above-described comparison method can be obtained.

  In the above description, the positions of the outer surface artificial flaw F1 and the inner surface artificial flaw F2 in the tube circumferential direction are represented by the angle in the tube axis, but are not represented by the angle in the tube axis. You may represent with the distance from the outer surface artificial defect F1 to the inner surface artificial defect F2 in the moving direction, and the distance from the inner surface artificial defect F2 to the outer surface artificial defect F1.

(Example)
The steel pipe 1 was provided with one notch as the outer surface artificial flaw F1 and one notch as the inner surface artificial flaw F2 at the same position in the tube axis direction. The steel pipe had an outer diameter of 73.0 mm and a wall thickness of 5.5 mm. The notch had a length of 25.4 mm, a width of 1 mm, and a depth of 0.30 mm.
FIG. 7 is a view showing a cross section of the steel pipe 1 and a state of the ultrasonic probe 21. The angle measured in the direction in which the ultrasonic probe 21 moves from the straight line connecting the tube axis and the outer surface artificial flaw F1 to the straight line connecting the tube axis and the inner surface artificial flaw F2 is 90 °.
Then, ultrasonic flaw detection was performed by the ultrasonic probe 21 while the steel pipe 1 was rotated in the direction of arrow A by the rotation drive unit. At this time, the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 were set so as to detect the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2, but the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 overlapped. . FIG. 8 is a reflection echo chart (A scope) obtained by ultrasonic flaw detection. In FIG. 8, the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 that are separately detected are represented by matching the positions of the respective surface echoes.

FIG. 9 shows a process of discriminating the reflected echo into the outer surface flaw reflected echo E1 and the inner surface flaw reflected echo E2 from the chart in which the reflected echoes entering the outer surface flaw detection gate G1 and the inner surface flaw detection gate G2 are shown in time series. FIG.
When performing ultrasonic flaw detection, an artificial flaw judgment reference value for determining that a detected reflected echo is a reflected echo from an artificial flaw is determined in advance, and the maximum echo height among the detected reflected echoes is determined. If the length exceeds the artificial flaw determination reference value, the reflection echo is analyzed by assuming that a reflection echo from the artificial flaw has been detected (see FIG. 9A).
Subsequently, the noise judgment reference value for judging the noise is set by multiplying the maximum echo height in the reflected echo by a predetermined ratio, and the reflected echo whose echo height is lower than the noise judgment reference value is It removes as noise (refer FIG.9 (b)).
Subsequently, a reflection echo having the maximum peak echo height is selected, and the time within which TH is required for the ultrasonic probe 21 to move around the circumference of the steel pipe 1 from the point in time when the peak of the reflection echo is detected. If there is a reflected echo detected next, the reflected echo having the maximum peak echo height is the external flaw reflected echo E1, and the peak echo height is detected within the time TH from the reflected echo having the maximum peak echo height. The reflected echo is the inner surface flaw reflected echo E2.
If there is a previously detected reflected echo before the time TH when the reflected echo with the maximum peak echo height is detected, the reflected echo with the maximum peak echo height is reflected from the internal surface. The reflected echo detected between the reflected echo having the maximum peak echo height and the time TH before the time TH is the inner surface defect and the outer surface defect reflection echo E1. In this way, one set of the outer surface flaw reflection echo E1 and the inner surface flaw reflection echo E2 can be distinguished (see FIG. 9C).
Next, for the reflected echoes after removing the discriminated set of outer surface flaw reflected echo E1 and inner surface flaw reflected echo E2, a set of outer surface flaw reflected echo E1 and inner surface flaw reflected echo are sequentially processed in the same manner as described above. Discrimination of E2 can be repeated to discriminate all detected reflected echoes (see FIG. 9D).

FIG. 10 is a chart of actual reflected echoes discriminated in this way. The reflected echo is discriminated into an outer surface flaw reflected echo E1 and an inner surface flaw reflected echo E2.
Then, the sensitivity of the ultrasonic flaw detector can be adjusted using the discriminated outer surface flaw reflection echo E1 and inner surface flaw reflection echo E2.

  In addition, this invention is not restricted to the structure of the said embodiment, A various deformation | transformation is possible in the range which does not change the meaning of invention.

DESCRIPTION OF SYMBOLS 1 ... Steel pipe 21 ... Ultrasonic probe E1 ... Outer surface flaw reflection echo E2 ... Inner surface flaw reflection echo F1 ... Outer surface artificial flaw F2 ... Inner surface artificial flaw T1 ... First Time T2 ... Second time

Claims (1)

The outer surface of the pipe is provided with artificial flaws on the outer surface of the pipe so that the positions in the pipe axis direction are the same, the positions in the pipe circumferential direction are separated from each other, and the positions opposite to each other across the pipe axis are not provided. A first step of providing scratches;
A second step of performing ultrasonic flaw detection on the pipe while relatively moving the ultrasonic probe in the pipe circumferential direction, and alternately detecting reflected echoes from the outer surface artificial flaw and reflected echoes from the inner surface artificial flaw; ,
From the detection of a reflection echo from one of the outer surface artificial flaw and the inner surface artificial flaw until the next detection of a reflection echo from either the outer surface artificial flaw or the inner surface artificial flaw Calculating a first time and a second time from the detection of the reflected echo from one of the other to the next detection of the reflected echo from either one of the first time and the second time; By comparing the relationship with the relationship between the position of the outer surface artificial flaw in the pipe circumferential direction and the position of the inner surface artificial flaw in the pipe circumferential direction, each of the detected reflected echoes is a reflected echo from the outer surface artificial flaw. And a third step of discriminating whether the echo is a reflection echo from the internal artificial flaw, or a method for discriminating a reflection echo from the artificial flaw in ultrasonic flaw detection.

Images