JP2007187631A - Method and apparatus for detecting position of boundary surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect weak reflected signals from a boundary surface using a simple constitution, to detect the position of the boundary surface of first and second layers, having different properties in a test target. <P>SOLUTION: A pair of oblique angle probes 2a and 2b, capable of transmitting and receiving an ultrasonic wave, are electrically connected, in parallel to each other and placed in opposed relation to the surface 101 of the test target 100. Ultrasonic waves are respectively transmitted from a pair of the oblique angle probes 2a and 2b, and the respective reflected signal, from the boundary surface 104 and the base 105 of the test object, are respectively received by a pair of the oblique angle probes 2a and 2b to detect the position of the boundary surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a boundary surface position detection method and a boundary surface position detection device for detecting a position of a boundary surface generated between the first layer and the second layer of a test body composed of a first layer and a second layer having different properties.

  Conventionally, a method for detecting the position of an interface formed between the first layer and the second layer of a specimen composed of a first layer and a second layer having different properties, for example, high Cr, high As a method for measuring the thickness of the carburized layer generated on the inner surface of the cracking furnace tube made of Ni, the methods described in the following documents are known.

  In the method using the ultrasonic flaw detection test (UT) described in Non-Patent Documents 1 and 2, a method using a transverse wave using a bevel probe or a method combining a longitudinal wave and a transverse wave (on a reflecting surface). However, since the reflected signal from the carburizing boundary is small, it is necessary to amplify the sensitivity. However, since various waves appear as interference echoes due to sensitivity amplification, it is very difficult to distinguish signals from the carburized layer boundary.

  Further, in the method of changing the distance between the probes so that the amplitude of the signal of interest described in Patent Document 1 and Non-Patent Documents 1 and 2 is maximized, the approach limit of the probe is limited. When the tube thickness is reduced or when the boundary of the carburized layer is close to the flaw detection surface, the optimum distance between the probes cannot be obtained.

  Furthermore, in the method using the mode-converted wave described in Non-Patent Document 2, a signal from the carburized layer boundary may overlap with other signals and cannot be identified.

  In addition, in the method using the vertical probe described in Non-Patent Document 3, an experiment example in which the backscattered wave data is added is also reported, but measurement is possible with noise from the vertical probe up to 4 mm from the surface. It is impossible. Most of the tubes to be measured in the cracking furnace tube have a thickness of about 7 mm, and it is difficult to measure 50% or more of carburization by this measuring method.

  Further, as a non-destructive measurement method, a method of determining the degree of deterioration based on a magnetic amount by a ferrite indicator, a method of measuring a carburized layer thickness by an eddy current flaw detection method (ET), or the like is known. However, when the contents of Cr and Ni are different, the outer surface side is also magnetized, and this magnetism has a bad influence on the thickness measurement of the carburized layer on the inner surface side, and the reliability has been significantly reduced.

  Therefore, as described above, in the current ethylene plant, there is no method that can reliably measure the carburization depth by nondestructive inspection. Therefore, a measurement method in a nondestructive test that can be replaced with a new pipe when the carburization depth is 70 to 80% of the wall thickness is desired.

In other words, the biggest problem when measuring the carburizing depth with ultrasonic waves is that the scattered wave (reflected wave) from the carburized layer is weak, so it is necessary to set the flaw detection sensitivity to a very high level. It was difficult to distinguish carburized signal and noise.
JP 2000-321041 A Non-destructive inspection vol. 47, No. 7 (1998) P480-P486 “Detection of carburized layer generated on the inner surface of the cracking furnace of ethylene equipment” Issued by Sangyo Publishing Co., Ltd., welding technology October 2005 issue P88-P91 "Ultrasonic inspection for carburizing of furnace tube" Issued by Nippon Kogyo Publishing, February 2002 issue P33-P35 “Detection of carburized layer using ultrasonic technology”

  In view of such a conventional situation, the present invention reliably detects a reflected signal from a weak boundary surface with a simple configuration, and determines the position of the boundary surface between the first layer and the second layer having different properties in the specimen. An object of the present invention is to provide a boundary surface position detection method and a boundary surface position detection device that can be detected.

  In order to achieve the above object, a feature of the boundary surface position detection method according to the present invention is a boundary surface position detection method for detecting the position of the boundary surface between the first layer and the second layer having different properties in the specimen. A pair of oblique probes capable of transmitting and receiving ultrasonic waves are electrically connected in parallel, and the pair of oblique probes are placed relative to the surface of the specimen, and the pair of oblique probes are mounted. Detecting the position of the boundary surface by transmitting ultrasonic waves from the angle probe and receiving the reflected signals reflected from the boundary surface and the bottom surface of the specimen by the pair of oblique angle probes, respectively. It is in.

  It is desirable that the pair of oblique angle probes can adjust the angle at which ultrasonic waves are transmitted and received so that a reflected signal from the boundary surface to be received is increased.

  A plurality of pairs of the pair of oblique angle probes may be provided, and at least the pair of oblique angle probes in each group may be electrically connected in parallel.

  The pair of oblique angle probes may be scanned along the surface of the specimen, and the received reflected signals may be added to generate a measurement waveform, and image processing may be performed on the measurement waveform. In such a case, it is desirable to perform the image processing by subtracting the measurement waveform unique to each oblique angle probe from the measurement waveform of the specimen.

  In addition, the image processing may be performed by obtaining in advance a reference waveform that is a measurement waveform in a test body including only the first layer or the second layer, and subtracting the reference waveform from the measurement waveform.

  Further, it is desirable that the test body is a metallic material, the first layer and the second layer are a sound layer and a material change layer, respectively, and the probe is placed on the sound layer side.

In order to achieve the above object, the boundary surface position detection device according to the present invention is characterized in that in the boundary surface position detection device used in any of the above boundary surface position detection methods,
A pair of oblique probes capable of transmitting and receiving ultrasonic waves are electrically connected in parallel, and the pair of oblique probes are placed relative to the surface of the test body, and the pair of oblique probes To detect the position of the boundary surface by transmitting ultrasonic waves from the probe and receiving the reflected signals reflected from the boundary surface and the bottom surface of the test body by the pair of oblique angle probes, respectively. is there.

  An object of the present invention is to detect a reflected signal from a weak boundary surface with a simple configuration, and to detect the position of the boundary surface between the first layer and the second layer having different properties in the specimen. An object of the present invention is to provide a boundary surface position detection method and a boundary surface position detection device.

  Other objects, configurations, and effects of the present invention will become apparent from the following embodiments of the present invention.

Next, the first embodiment of the present invention will be described in detail with reference to the accompanying drawings as appropriate.
In the present embodiment, the test body 100 will be described taking an example of an in-furnace pipe used in a petrochemical plant or the like. This in-furnace pipe 100 is made of a high Cr, high Ni alloy, and when used for a long period of time, as shown in FIGS. Go. Therefore, as shown in FIG. 4 (d), a carbon saturated layer 103a in which carbides are more densely formed in the vicinity of the inner surface 105 of the test body is formed by the progress of carburization. Further, as shown in FIG. A carbon layer 103b in which carburization is proceeding is also formed on the outer surface 101 side. As shown in FIG. 4B, the difference in structure between the carbon layer 103b and the healthy layer 102 in which carburization has not progressed is slight.

  The inventors measured the reflected signal of ultrasonic waves using samples with different degrees of carburization. According to the measurement result, as shown in FIG. 5, only the reflected signal B from the inner surface of the sample was received in the sample in which carburization did not occur, but in addition to the reflected signal B from the inner surface of the sample in the sample in which carburization occurred. A reflection signal I from the boundary surface of the carbon saturated layer was received. It was found that by receiving these signals, it is possible to know the presence or absence of the carbon saturation layer and the approximate thickness of the carbon saturation layer. However, since the difference in structure between the carbon layer 103b and the healthy layer 102 is slight, the reflected signal is weak.

  Thus, it has been found that the position of the carburized boundary surface can be measured by receiving a large amount of a weak reflected signal as will be described later. Here, a layer in which carburization has not progressed will be described as a sound layer 102, a carbon saturated layer 103a and a carbon layer 103b as a carburized layer 103, a sound layer 102 as a first layer, and a carburized layer 103 as a second layer.

  As shown in FIG. 1B, in the boundary surface detection device 1, a pair of oblique angle probes 2 a and 2 b are placed relative to the sound layer 102 side surface 101 of the test body 100. Each of the oblique angle probes 2a and 2b can transmit and receive ultrasonic waves and is electrically connected in parallel.

  As shown in FIG. 2, the ultrasonic waves transmitted from the respective oblique angle probes 2a and 2b are incident on the test body 100, and the ultrasonic waves Na and Nb that directly propagate between the oblique angle probes 2a and 2b are generated. Arise. The ultrasonic wave incident on the test body 100 is reflected by the boundary surface 104 between the sound layer 102 and the carburized layer 103 and the test body inner surface 105, and the reflected signals are received by the pair of oblique probes 2a and 2b, respectively. .

  The reflected signals of the boundary surface 104 and the test body inner surface 105 received by the oblique angle probe 2a are transmitted from the reflected ultrasonic wave signal Ia transmitted by the probe itself and the opposite oblique angle probe 2b. Two types of reflected ultrasonic wave signals Ib are included. Since the pair of oblique angle probes 2a and 2b are electrically connected in parallel, the reflected signal can be enhanced about four times by adding all the received reflected signals.

  Further, ultrasonic signals Na and Nb directly propagating between the oblique angle probes 2a and 2b are received by the opposing oblique angle probes. The signals Na and Nb become noise signals with respect to the reflected signal. The pair of oblique angle probes 2a and 2b are electrically connected in parallel. However, since there is only one type of noise signal N received by each of the oblique angle probes 2a and 2b, they are added. However, this noise signal N is only emphasized about twice.

  When the transmission probe 111 and the reception probe 112 shown in FIG. 1 (a) are paired, since only one type of signal is received, a weak reflected signal is buried in noise. End up. On the other hand, in the case of the pair of oblique angle probes 2a and 2b capable of transmission / reception shown in FIG. 4B, the reflected signal I of the received signals is quadrupled, whereas the noise signal Since N is doubled, the influence of the noise signal N can be relatively reduced, and the reflected signal I can be detected clearly. Therefore, it is possible to accurately measure the position of the boundary surface 104 by using a pair of oblique probe 2a, 2b that can be transmitted and received electrically connected in parallel.

  Further, since the pair of oblique angle probes 2a and 2b can more strongly receive the reflected signal from the boundary surface 104, the transmission / reception angle of the ultrasonic wave can be adjusted. When the boundary surface 104 of the carburized layer 103 is close to the specimen surface 101, a pair of oblique probes 2a and 2b with a reduced ultrasonic transmission / reception angle θ can be used. Further, when the thickness of the test body 100 is large, in order to clearly obtain each reflected signal from the boundary surface of the test body bottom surface 105 and the carbon saturated layer 103a, a pair of oblique waves with a larger ultrasonic transmission / reception angle θ is obtained. Angular probes 2a and 2b can also be used. Furthermore, by using two pairs of oblique angle probes having different ultrasonic transmission / reception angles θ in combination, the position of the boundary surface 104, the boundary surface between the carbon saturated layer 103a and the carbon layer 103b, and the test A signal indicating the position of the body bottom surface 105 can be displayed simultaneously.

  The pair of oblique angle probes 2a and 2b are configured to be able to scan along the surface 101 of the test object, add the received reflection signals, generate a measurement waveform, and perform image processing. The scanning is performed by moving the specimen 101 on the surface 101 side surface 101 in the axial direction or the circumferential direction of the specimen 100 while maintaining the distance between the pair of oblique probes 2a and 2b. Then, the received signals are added for each time, a measurement waveform is generated, and the signal intensity is displayed as a B-scan image expressed in shades of color as shown in FIGS. In the case of an A-scan image, it is difficult to recognize a weak reflected signal from the boundary surface 104, but by using a B-scan image, a reflected signal having a high noise level is also recognized from the continuity of the signal. It becomes possible to do.

  Here, since the reflected signal from the boundary surface 104 is a weak signal, the reflected signal may not be clearly detected as in the B-scan image of the measurement waveform Q3 of the specimen 100 shown in FIG. This is because noise signals specific to the oblique angle probes 2a and 2b are included. The oblique angle probe generates ultrasonic waves from the vibrator and causes the ultrasonic waves to enter the test body 100 via a wedge. However, an ultrasonic wave that does not enter the test body 100 and reflects the surface 101 of the test body is also generated, and this reflected wave becomes noise inherent to the oblique probe 2a, 2b generated in the wedge. In order to reduce this noise, a sound absorbing material that absorbs reflected waves is provided in the oblique angle probe. However, since the reflected signal from the boundary surface 104 is a weak signal, it is necessary to perform a test with high sensitivity, and noise that cannot be absorbed by the sound absorbing material hinders measurement. Therefore, image processing is performed so that the reflected signal can be clearly recognized by removing the noise in the wedge of the oblique angle probes 2a and 2b itself.

  Here, image processing will be described with reference to FIGS. In each figure, the vertical axis of the B-scan image represents the specimen depth, the horizontal axis represents the scanning distance, the vertical axis of the A-scan image represents the scanning time, and the horizontal axis represents the signal intensity.

  In FIG. 6, reference sign Q <b> 1 indicates wedge noise, Q <b> 2 indicates a healthy test body including only a healthy layer, and Q <b> 3 indicates a B-scan image of each measurement waveform of the test body having a carburized layer. The measurement waveform Q1 of the noise in the wedge is obtained by transmitting ultrasonic waves within a predetermined time without bringing the oblique angle probes 2a and 2b into contact with the test body 100. 6 to 10, reference numeral P1 is an example of the waveform of the noise in the wedge, reference numeral P2 is an example of the waveform of the reference waveform, reference numeral P3 is an example of the waveform of the test body 100, and reference numerals P4 and P5 are examples of measured waveforms after image processing. It is each A-scan image shown.

  The measurement waveform Q1 of the in-wedge noise shown in FIGS. 6 and 7 is included in the measurement waveform Q3 obtained from the test body 100. Therefore, by subtracting this noise measurement waveform Q1 from the measurement waveform Q3 of the test body 100, as shown in FIG. 8, the measurement waveform Q1 of the noise in the wedge is removed, and the measurement waveform Q4 can clearly recognize the reflected signal. A B-scan image can be obtained. From the waveform examples shown in P3 and P4, it can be seen that the reflected signal is clearly obtained.

Next, a method for measuring the thickness of the carburized layer using the boundary surface detection device will be described.
First, a pair of oblique angle probes to be used are electrically connected in parallel, the noise in the wedge is measured at a predetermined time, and a measurement waveform Q1 is generated and recorded. Next, the pair of oblique angle probes 2 a and 2 b are placed relative to the sound layer 102 side surface 101. The pair of oblique angle probes 2a and 2b are scanned on the specimen surface 101 by a predetermined distance along the axial direction of the specimen 100 while maintaining the distance between the pair of oblique angle probes 2a and 2b. . The received signals are added for each time to generate a measurement waveform Q3 shown in FIG.

  Image processing is performed by subtracting the measurement waveform Q1 of the in-wedge noise recorded and measured in advance from the measurement waveform Q3. As shown in FIG. 8, the image-processed measurement waveform Q4 is displayed as a B-scan image in which the signal intensity is expressed by color shading. From this image, the reflection signal from the boundary surface 104 and the reflection signal from the test body inner surface 105 can be clearly obtained, and the thickness and carburization rate of the carburized layer are measured from the reflection signal.

  In this embodiment, the pair of oblique probes 2a and 2b are scanned along the axial direction of the test body 100. However, the scanning is similarly performed in the circumferential direction of the test body 100, and the thickness of the carburized layer and The carburization rate can be measured.

  Next, a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the member similar to the said embodiment.

  In this embodiment, the waveform used for image processing is different. In the above embodiment, the measurement waveform Q1 of the noise in the wedge of the oblique angle probe is used, but in this embodiment, the measurement waveform Q2 of the reference specimen consisting only of the healthy part is used as the reference waveform, and the measurement waveform of the specimen 100 is used. From the reference waveform Q2.

  A test body consisting only of a healthy layer is used as a reference test body, and a pair of oblique probes are scanned along the surface of the reference test body with respect to this reference test body in the same manner as in the above embodiment, and the measurement waveform shown in FIG. Q2 is generated and used as a reference waveform to perform image processing by subtracting the reference waveform Q2 from the measured waveform Q3 of the specimen. As shown in FIG. 10, the image-processed measurement waveform Q5 is displayed as a B-scan image in which the signal intensity is represented by color shading. From the waveform examples shown in P3 and P5, it can be seen that the reflected signal is clearly obtained.

  The reference waveform Q2 includes the measurement waveform Q1 of the noise in the wedge of the oblique angle probe, and further includes the signal of the sound layer. Therefore, by using the reference waveform Q2, more noise can be removed, an image from which the reflected signal can be clearly recognized can be obtained, and the thickness and carburization rate of the carburized layer can be measured from the reflected signal. Can do. Note that an image capable of clearly recognizing the reflected signal can also be obtained by dividing the measurement waveform Q3 of the test specimen by the reference waveform Q2.

Finally, reference is made to the possibilities of yet another embodiment of the invention.
In each of the above embodiments, the angle at which ultrasonic waves are transmitted and received can be adjusted so that the received reflected signal from the boundary surface can be increased. However, it is only necessary that the reflected signal from the boundary surface can be transmitted and received. In addition, in the pair of oblique probes, the angle transmitted and received may be adjusted. For example, in the case where the carburized layer has advanced to the surface of the test body, in the pair of oblique probes, Different transmission / reception angles may be set.

  Further, in each of the above embodiments, scanning was performed using a pair of oblique angle probes. However, it is not limited to a pair, and a plurality of pairs of oblique angle probes may be provided. When a plurality of bevel probes are provided, a pair of bevel probes may be electrically connected in parallel, or all bevel probes may be electrically connected in parallel. In such a case, the reflected signal can be detected more clearly by relatively reducing noise.

  In each of the above embodiments, the detection of the boundary surface of the carburized layer of the in-furnace piping has been described. However, the shape, material, etc. of the specimen are not particularly limited. Moreover, although the second layer is a carburized layer, the present invention is not limited to the carburized layer, and can be used for detecting a boundary surface between a material change layer such as nitriding, quenching layer, carbonization and the sound layer. In each of the above embodiments, the pair of oblique probes are placed on the surface of the test body on the sound layer side, but may be placed on the surface of the test body on the carburized layer side.

  The present invention can be used as a method for detecting and measuring a carburized layer in a furnace pipe used in a petrochemical plant or the like. However, the present invention is not limited to this, and detection can be easily and effectively applied to the specimen by amplifying a minute reflected signal from the interface between the first layer and the second layer having different properties. Further, the present invention can be applied to defect detection of a specimen having a coarse crystal grain and a lot of noise such as a cast product or an austenitic stainless steel weld. Furthermore, the present invention can be applied to the case where the deterioration state such as the material change of the test body is detected.

FIG. 2 is an arrangement diagram of an oblique probe, where (a) shows an arrangement of a conventional oblique probe, and (b) shows an arrangement of an oblique probe according to the present invention. It is a figure which shows the propagation path of an ultrasonic wave. It is sectional drawing of a test body. It is a figure which shows the microscope picture of the cross section of a test body, (a) is a test body outer surface vicinity, (b) is the boundary surface vicinity of a healthy layer and a carburized layer, (c) is a carbon layer, (d) is a test body. The vicinity of the surface is shown. It is a graph which shows the presence or absence and the grade of carburizing, (a) is a B-scan image of each sample, (b) is an A-scan image of the sample in which 50% carburizing has progressed. It is a graph which shows a measurement waveform. It is a graph which shows an image processing range. It is a graph which shows the measurement waveform after image processing. FIG. 7 is a view corresponding to FIG. 6 in another embodiment. FIG. 8 is a diagram corresponding to FIG. 7 in another embodiment.

Explanation of symbols

1: boundary surface detection device, 2a, 2b: oblique probe, 100: specimen, 101: surface, 102: first layer (sound layer), 103: second layer (carburized layer, material change layer), 103a: carbon saturation layer, 103b: carbon layer, 104: boundary surface, 105: inner surface (bottom surface), 111: transmission probe, 112: reception probe, I, Ia, Ib: boundary surface reflected wave, B: Internal (bottom) reflected wave, N: Surface wave (noise), P1: Wedge waveform example, P2: Healthy specimen waveform example, P3: Carburized specimen waveform example, P4, P5: Measurement waveform example, Q1: Inside wedge Image, Q2: Healthy specimen image, Q3: Carburized specimen image, Q4, Q5: Measurement waveform image, θ: Transmission / reception angle

Claims (8)

A boundary surface position detection method for detecting a position of a boundary surface between a first layer and a second layer having different properties in a test body,
A pair of oblique probes capable of transmitting and receiving ultrasonic waves are electrically connected in parallel, and the pair of oblique probes are placed relative to the surface of the test body, and the pair of oblique probes Detecting the position of the boundary surface by transmitting ultrasonic waves from the probe and receiving each reflection signal reflected from the boundary surface and the bottom surface of the test body by the pair of oblique angle probes. A characteristic boundary surface position detection method. 2. The boundary surface position according to claim 1, wherein the pair of oblique angle probes can adjust an angle at which ultrasonic waves are transmitted and received so that a reflected signal from the boundary surface to be received is increased. Detection method. The boundary surface according to claim 1 or 2, wherein a plurality of pairs of the pair of oblique probes are provided, and at least a pair of the oblique probes in each pair are electrically connected in parallel. Position detection method. The pair of oblique probes are scanned along the surface of the specimen, the received reflected signals are added to generate a measurement waveform, and image processing is performed on the measurement waveform. The boundary surface position detection method according to claim 1. 5. The boundary surface position detection method according to claim 4, wherein the image processing is performed by subtracting a measurement waveform unique to each oblique angle probe from a measurement waveform of a specimen. A reference waveform, which is a measurement waveform in a test body composed of only the first layer or the second layer, is obtained in advance, and the image processing is performed by subtracting the reference waveform from the measurement waveform. Item 5. The boundary surface position detection method according to Item 4. The test body is a metallic material, the first layer and the second layer are a sound layer and a material change layer, respectively, and the probe is placed on the sound layer side. The boundary surface position detection method according to any one of the above. It is a boundary surface position detection apparatus used for the boundary surface position detection method in any one of Claims 1-7,
A pair of oblique probes capable of transmitting and receiving ultrasonic waves are electrically connected in parallel, and the pair of oblique probes are placed relative to the surface of the test body, and the pair of oblique probes Detecting the position of the boundary surface by transmitting ultrasonic waves from the probe and receiving each reflection signal reflected from the boundary surface and the bottom surface of the test body by the pair of oblique angle probes. A characteristic boundary surface position detection device.