JPH11211700A - Ultrasonic flaw detection method and ultrasonic flaw detection apparatus used therefor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an ultrasonic inspection method capable of inspecting a defect of an object by correcting the influence of the surface roughness of the object, and an ultrasonic inspection apparatus used for the method. SOLUTION: An ultrasonic flaw detector 12 measures an echo of a transmitted wave 7 projected from a transmission probe 3, transmitted through a tube to be inspected (subject) 1, and received by a reception probe 4. At the same time, the reflected wave 17 is projected perpendicularly from the reflection probe (third probe) 11 onto the tube 1 to be inspected, reflected on the surface of the tube 1 to be inspected, and received by the reflection probe 11. Measure the echo.
Before judging the actual creep damage of the inspected tube 1, the transmitted echo and the reflected echo of the test specimen having the same material and shape as the inspected tube 1 having the simulated defect processed are measured using the ultrasonic flaw detector 12. Then, an approximation line (regression line) is obtained for each simulated defect to create a criterion for creep damage. Then, the transmitted echo and the reflected echo of the actual inspection tube 1 are measured using the ultrasonic flaw detector 12, and the creep damage is determined based on the above-described determination criteria.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method for projecting ultrasonic waves to a subject and detecting the flaws by receiving ultrasonic waves transmitted through the subject, and an ultrasonic flaw detection apparatus used therefor. It is about.

[0002]

2. Description of the Related Art Conventionally, naphtha, butane,
The heating tube of the LPG cracking furnace or the heating tube of the reforming furnace at the hydrogen or ammonia plant is HK40 (0.40% C-25%
A plurality of high carbon heat resistant centrifugally cast tubes (hereinafter, referred to as “centrifugally cast tubes”) made of Cr-20% Ni-based material or the like are assembled by welding.

[0003] In this heating tube, gas and liquid are supplied to the inside of the tube filled with the catalyst, and the inside of the tube is brought into a high temperature and high pressure state by being heated from the outside of the tube by a burner of a furnace. Then, the substance inside the heating tube reacts and changes under high temperature and high pressure.

[0004] For this reason, in the above-mentioned heating tube, the creep fisher due to the hoop stress tends to spread radially from the inner surface to the outer surface of the tube as the use time elapses. In addition, a defect may occur in the circumferential direction of the inner surface of the pipe due to a temperature difference between the inside and the outside of the pipe (high temperature outside the pipe, low temperature inside the pipe). Therefore, it is indispensable for operation stability to grasp the secular change of the heating tube and estimate the remaining life.

However, if the outer surface of the heating tube has a rough casting surface, it is difficult to apply a normal ultrasonic inspection method to the heating tube of the centrifugally cast tube because it is difficult to obtain a predetermined ultrasonic wave. there were. Therefore, in order to know the aging of the heating tube, a destructive inspection was performed exclusively.

Therefore, in order to solve this problem, the transmitting probe and the receiving probe are combined and scanned along the outer peripheral surface of the inspected tube by the water immersion method, and the inside of the thickness of the inspected tube is reduced. Ultrasonic waves are incident on the tube to be inspected by the oblique angle method from the transmitting probe so that the ultrasonic waves penetrate into a straight line connecting two points on the outer periphery of the tube to be inspected, and the ultrasonic waves are transmitted by the receiving probe. JP-A-54-128789 discloses a method of detecting a defect in the thickness of a tube to be inspected by receiving a transmitted echo of the same.

[0007]

However, a centrifugal casting tube used as a heating tube is formed by putting a solution of a steel alloy in a sand mold and sticking the solution to the outside by centrifugal force. for that reason,
Before use, the centrifugally cast tube has a rough casting surface in the form of sand of a sand mold. Then, by using the heating tube in a furnace at a high temperature, the layer having a rough casting surface is oxidized and reduced in thickness and becomes smooth. For this reason, as the centrifugally cast tube is used in a furnace as a heating tube, a phenomenon occurs in which the incident loss of ultrasonic waves on the tube surface decreases, and the attenuation of ultrasonic waves decreases.

Therefore, in the above-described conventional method of measuring only the attenuation (transmission amount) of ultrasonic waves and judging the presence or absence of creep damage from the secular change of the ultrasonic attenuation amount, the surface roughness of the centrifugally cast pipe is reduced. Since the amount of attenuation of the ultrasonic wave fluctuates greatly due to the change over time, accurate judgment was impossible.
In other words, although the purpose is to detect the attenuation of ultrasonic waves due to creep cracking, the tube surface becomes smoother due to use, and the amount of ultrasonic waves incident increases, so the amount of ultrasonic attenuation decreases gradually. Go. And finally, it was not possible to judge the presence or absence of internal creep damage until creep cracking occurred and the amount of ultrasonic attenuation increased.

Here, the relationship between the surface roughness of the centrifugally cast pipe and the amount of attenuation of the transmitted wave will be specifically described with reference to FIGS. 3, 4 and 6, which are explanatory diagrams of the present invention.

Ultrasonic flaw detector 2 shown in FIGS. 3 and 4
The present invention relates to the present invention, and details thereof will be described later, but the basic structure is the same as the conventional one. The ultrasonic flaw detector 2 arranges the transmitting probe 3 and the receiving probe 4 on the same circumference on the outer circumference of the tube 1 to be inspected at a predetermined directional angle and a predetermined interval. The receiving probe 4 can receive a transmitted echo of an ultrasonic wave 7 transmitted through the thickness of the tube 1. Needless to say, water 6 is filled in a portion corresponding to an ultrasonic path between the transmission probe 3 and the reception probe 4 and the inspection tube 1 because of the water immersion method.

An ultrasonic wave 7 indicated by an arrow in FIG.
The tube 1 is refracted at the incident point A according to the law of reflection and refraction because of the water immersion method and the oblique angle method.
And the maximum depth 2 within the thickness of the tube 1 to be inspected.
Transmit at tangential direction at T / 3 (T: wall thickness of tube) and exit point B
Is refracted and emitted out of the thickness of the test tube 1 and received by the receiving probe 4. At this time, a defect (radial fisher) is present on the path of the ultrasonic wave 7 within the thickness of the tube 1 to be inspected.
Is present, the ultrasonic wave is scattered by the defect, detected as an attenuated transmission echo by the receiving probe 4, and the existence of the defect can be detected.

FIG. 6 shows the results of measurement of the transmitted wave sensitivity value (corresponding to the amount of attenuation) and the center line surface roughness of the test piece processed with the simulated defect using the ultrasonic flaw detector 2. It is a graph. The test pieces were 0, 0.1, 0.2,
The roughness of the outer surface of the tube was changed by grinding with a lathe to 0.3 mm. Further, a test piece in which a simulated defect of a T / 2 or T / 3 slit (crack) was processed in the thickness direction and an unprocessed test piece were used.

Here, it is assumed that the transmitted wave sensitivity value is 85 dB as a result of a certain measurement. In the conventional method, creep damage was judged only from this result. However, even for the same 85 dB transmitted wave sensitivity value, the evaluation is completely different between the case where the center line surface roughness is large and the case where the center line surface roughness is small. That is, when the center line surface roughness is 80 μm, T / 3
When the approximate line (reference line) La1 of the simulated defect of the slit is lower than La1, but the center line surface roughness is 10 μm, T /
It also exceeds the approximate line (reference line) La2 of the two-slit simulated defect.

When the approximate line La1 of the T / 3 slit is compared with the case where the center line surface roughness is 20 μm and the case where the center line surface roughness is 80 μm, there is a difference of about 6 dB in the attenuation value of the transmitted wave. There is about a two-fold difference in sensitivity. That is, even when a defect having the same size is detected, the amount of transmitted echo received is twice as large depending on the level of the surface roughness.

Since the reference line (approximate line) of the simulated defect having the same size rises to the right, the tube surface becomes smoother by use, and the amount of incident ultrasonic waves increases, thereby attenuating the transmitted wave. It can be seen that the amount (transmitted wave sensitivity value) gradually decreases.

From the above, the conventional method does not consider the roughness of the tube surface, so that the error is very large and the defect cannot be accurately detected. In addition, even with the same tube in the same furnace, the rate of oxidation thinning varies depending on the temperature distribution, and the condition of the tube surface varies from inspection site to inspection site. It is important to correct.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ultrasonic flaw detection method capable of inspecting a defect of an object by correcting the influence of the roughness of the surface of the object. And an ultrasonic flaw detector used for the same.

[0018]

According to a first aspect of the present invention, there is provided an ultrasonic flaw detection method, wherein the ultrasonic probe is projected from a transmitting probe by an ultrasonic water penetration method and received by a receiving probe. A defect in the subject is determined from the transmitted echo of the subject and the roughness of the subject surface.

With the above arrangement, the transmitted echo is measured using the transmitting probe and the receiving probe, the roughness of the surface of the object is measured, and the transmitted echo is measured by scattering on the surface of the object. The amount of attenuation is corrected by the measured value of the roughness of the surface of the object to determine a defect in the object.

Specifically, a simulated defect is machined into a test piece having the same material and shape as the specimen, the transmission echo and the surface roughness of the test piece are measured, and an approximate line is obtained for each simulated defect. Develop creep damage criteria. Then, when actually inspecting the test object, the transmitted echo and the surface roughness are measured, and the creep damage is determined based on the criterion described above.

As described above, by measuring the transmitted echo of the inspection site and measuring the surface roughness, the flaw detection can be performed by correcting the influence of the surface roughness of the subject. Therefore, the secular change of the heating tube can be accurately grasped, and the remaining life can be estimated with high accuracy. Therefore, unnecessary replacement of the heating tube can be prevented, and the operation can be performed safely and economically.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration of the first aspect, the roughness of the surface of the subject is a center line surface roughness or a maximum roughness. It is characterized by being a measured value.

With the above arrangement, in addition to the operation of the first aspect, the transmission echo is measured using the transmission probe and the reception probe, and the center line surface roughness is measured using the roughness measuring device. Alternatively, the maximum roughness is measured as the surface roughness of the object, and the defect in the object is determined based on the transmitted echo and the center line surface roughness or the maximum roughness.

Specifically, a simulated defect is machined into a test piece having the same material and shape as the specimen, and the transmission echo and the center line surface roughness or the maximum roughness of the test piece are measured. An approximation line is obtained and a criterion for creep damage is created. Then, when performing actual flaw detection of the subject, the transmitted echo and the center line surface roughness or the maximum roughness are measured,
Creep damage is determined based on the above criteria.

As described above, the influence of the roughness of the surface of the subject is corrected by measuring the transmitted echo of the inspection site and measuring the center line surface roughness or the maximum roughness using the roughness measuring device. Flaw detection can be performed. The roughness measuring device required for this correction is a general measuring device,
The increase in the amount of work is also minor.

According to a third aspect of the present invention, in order to solve the above-mentioned problems, in addition to the configuration of the first aspect, the roughness of the surface of the object is set such that the ultrasonic wave is perpendicular to the object. , And is a measured value of a reflected echo obtained by receiving the reflected echo reflected.

According to the above configuration, in addition to the operation of the first aspect, the transmission echo is measured using the transmission probe and the reception probe, and the ultrasonic wave is projected perpendicularly to the subject. The reflected echo is measured using a third probe that receives the reflected wave (hereinafter, referred to as a “reflected probe”), and the defect in the subject is determined based on the transmitted echo and the reflected echo. .

More specifically, a simulated defect is machined into a test piece having the same material and shape as the object, transmission echoes and reflection echoes of the test piece are measured, and an approximate line is obtained for each simulated defect. Create criteria for creep damage. Then, when actually performing the flaw detection of the subject, the transmitted echo and the reflected echo are measured, and the creep damage is determined based on the above criterion.

As described above, by measuring the transmitted echo of the inspection site and the reflected echo, the flaw detection can be performed by correcting the influence of the roughness of the surface of the subject. In addition, the reflection echo required for this correction can be measured by a simple device equipped with a reflection probe that projects ultrasonic waves perpendicularly to the subject and receives reflected waves, thereby increasing the amount of work. Is also minor. Further, it is possible to provide the above-described reflection probe in a conventional ultrasonic flaw detection device having a transmission probe and a reception probe, and simultaneously measure a transmitted echo and a reflected echo, so that more efficient flaw detection is possible. Work can be done.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problems, in addition to any one of the first to third aspects, the specimen is a high-carbon heat-resistant centrifugal casting tube. It is characterized by.

According to the above configuration, in addition to the operation according to any one of the first to third aspects, a high-carbon heat-resistant material projected from the transmitting probe by the ultrasonic water penetration method and received by the receiving probe is used. A defect in the high carbon heat resistant centrifugally cast tube is determined from the transmission echo of the centrifugal cast tube and the surface roughness of the high carbon heat resistant centrifugal cast tube.

The ultrasonic flaw detection method according to any one of claims 1 to 3 is applicable to an object having a variable surface roughness. The secular change is large, and the effect of the correction is remarkable.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, a transmitting probe for projecting an ultrasonic wave to a subject and a transmitted echo transmitted through the subject are received. An ultrasonic flaw detector comprising a receiving probe, comprising: a third probe that projects ultrasonic waves perpendicularly to the subject and receives a reflected echo reflected from the subject. And

With the above configuration, the ultrasonic flaw detector measures the transmitted echo using the transmitting probe and the receiving probe, and detects the transmitted echo using the reflection probe (third probe). The reflected ultrasonic echo is measured by projecting an ultrasonic wave perpendicular to the sample.

As described above, by measuring the transmitted echo of the inspection site and the reflected echo, the flaw detection can be performed by correcting the influence of the roughness of the surface of the subject. Further, the ultrasonic flaw detector only needs to provide a reflection probe in a conventional ultrasonic flaw detector having a transmission probe and a reception probe. Since the transmitted echo and the reflected echo can be measured simultaneously, the flaw detection operation can be performed more efficiently.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] One embodiment of the present invention will be described below with reference to FIGS. In the following, the subject will be described as a high carbon heat resistant centrifugally cast tube (hereinafter, referred to as a "centrifugal cast tube").

As shown in FIGS. 3 and 4, the ultrasonic flaw detector 2 used in the ultrasonic flaw detection method according to this embodiment
The transmission probe 3 and the reception probe 4 are attached to a jig 5.

The transmitting probe 3 and the receiving probe 4 described above.
Is attached to the jig 5 so that when the ultrasonic inspection device 2 is mounted on the inspection tube 1, the ultrasonic inspection device 2 is arranged at a predetermined directional angle and interval on the same circumference of the inspection tube 1. I have.
The receiving probe 4 can receive a transmitted echo of the ultrasonic wave 7 transmitted from the transmitting probe 3 and transmitted through the thickness of the inspection tube 1. In the present embodiment,
V382 (frequency 3.5 MHz, transducer diameter 0.5 ″, focal point 3 ″ LF) as the transmitting probe 3,
As the receiving probe 4, V382 (frequency 3.5 MHz, transducer diameter 0.5 ″, focal point FLAT) manufactured by Panametrics was used.

The jig 5 is made of, for example, MMA (methyl methacrylate). And the transmitting probe 3
An opening 5a is formed in a portion corresponding to an ultrasonic path between the receiving probe 4 and the tube 1 to be inspected. Opening 5a
Since the ultrasonic inspection device 2 is mounted by being pressed against the tube 1 to be inspected, it is formed in a shape suitable for the outer peripheral shape of the tube 1 to be inspected.

Since the water immersion method is used, the jig 5 is filled with water 6 so that the jig 5 corresponds to the ultrasonic path between the transmission probe 3 and the reception probe 4 and the tube 1 to be inspected. Water 6 is retained in the part. Then, when the jig 5 is pressed against the pipe 1 to be inspected, the water 6 filled therein is prevented from leaking.
A seal 5b made of, for example, plate rubber or the like, which has elasticity, is provided at a contact portion that comes into contact with the tube 1 to be inspected. Further, the ultrasonic flaw detector 2 is provided with a water injection means and a water discharge means (not shown) for injecting and discharging the water 6 into the jig 5. Therefore, the measurement of the transmission echo by the ultrasonic flaw detector 2 includes mounting, water injection, measurement, and drainage in one.
This is done in cycles. This prevents the surrounding material such as the heat insulating material in the furnace from getting wet.

An ultrasonic wave 7 indicated by an arrow in the figure is projected from a transmitting probe 3 to which pulsed power is supplied by a flaw detector 21 (FIG. 5), which will be described later, and is transmitted to a tube 1 to be inspected via water 6. Since the light is incident at an incident angle i and is based on the water immersion method and the oblique angle method, the light is refracted at a refraction angle θ at the incident point A on the outer peripheral surface of the tube 1 to be inspected according to the law of reflection and refraction. The light passes through the thickness in the tangential direction at the maximum depth d, is refracted at the refraction angle i with respect to the incident angle θ at the emission point B on the outer peripheral surface of the test tube 1, and is emitted out of the thickness of the test tube 1; Probe 4 received through water 6
Is received by At this time, if a defect (radial fisher) exists on the path of the ultrasonic wave 7 in the thickness of the inspection target tube 1, the ultrasonic wave is scattered by the defect and the attenuated transmission echo is transmitted to the receiving probe 4. And the presence of a defect can be detected.

Further, the incident angle i of the ultrasonic wave 7 is adjusted within a range where the bottom surface reflection does not occur by the inner peripheral surface of the tube 1 to be inspected, and at the same time, the transmitting probe 3 and the receiving probe 4 are used to catch the transmitted echo. By adjusting the distance between the two, the depth f of the ultrasonic inspection within the thickness of the inspected tube 1 can be appropriately adjusted.

As shown in FIG. 5, the transmitting probe 3 and the receiving probe 4 are connected to a flaw detector 21 for supplying pulsed power, and the flaw detector 21 is connected to a recorder 22. I have. Here, in the present embodiment, USL-38 manufactured by Kraut Kramer and US
L-48 was used. As the water injection means, for example, a water injection hole (not shown) is formed in the jig 5 and connected to the water injection tank 23 so that the inside of the jig 5 can be filled with water 6. Similarly, a drain hole (not shown) is formed in the jig 5 and is connected to a drain tank 24 so that the water 6 filled in the jig 5 can be drained.

The ultrasonic flaw detection method according to the present embodiment will be described below.

First, as a preparation for conducting a flaw detection of the inspected tube 1 in the actual furnace, a criterion for judging creep damage is obtained. A simulated defect is machined into a test piece having the same material and thickness as the tube 1 to be inspected, and the transmitted wave sensitivity value (corresponding to the amount of attenuation) is changed using the ultrasonic flaw detector 2. Let me measure. At the same time, the center line surface roughness of the incident point A of the ultrasonic wave is measured by a roughness measuring instrument. Then, an approximate line between the transmitted wave sensitivity value and the center line surface roughness is obtained from the obtained measurement result for each simulated defect. In this embodiment, SURTEST SV- manufactured by Mitutoyo Co., Ltd. is used as a roughness measuring instrument.
9700 / 3D was used.

For example, as shown in FIG.
Using a ultrasonic flaw detector 2, the transmitted wave sensitivity value and the center line surface roughness of a test piece processed with a simulated defect of a slit (crack) of / 2 and T / 3 and an unprocessed test piece were determined. Measurement was performed, and approximate lines La2, La1, La0 were obtained for each of the simulated defects. The test pieces were 0, 0.1, 0.2, 0.3.
The roughness of the tube surface was changed by grinding with a lathe. Further, the regression coefficient of the approximate line to be obtained is not limited to the first-order one, but can be appropriately selected according to the correlation between the center line surface roughness and the transmitted wave sensitivity value.

Next, when flaw detection is performed on the tube 1 to be inspected in the actual furnace, the transmitted wave sensitivity value of the inspection site is measured using the ultrasonic flaw detector 2 and the center of the ultrasonic wave incident point A is measured. Measure the line surface roughness. Then, by comparing with the approximate lines La2, La1, La0 determined as reference lines for determination, it is possible to determine the defect of the tube 1 to be inspected.

That is, as shown in FIG. 8, on the coordinate plane of the center line surface roughness and the transmitted wave sensitivity value, the position where the measured value of the test tube 1 of the actual furnace is plotted with respect to the reference line is plotted. The state of the defect can be determined depending on whether it is performed.

Here, the meaning of the reference line will be described. For example, if the measurement value of a certain inspection site is plotted on the approximation line La2, it is evaluated that the inspection site has the same attenuation as the simulated defect of the T / 2 slit. this is,
This does not mean that there is creep damage of the same size as the T / 2 slit at the inspection site. In other words, what is actually detected is not the attenuation of one crack, but the attenuation of an aggregate of a very small number of defects that have occurred innumerably, which is the attenuation of the simulated defect of the T / 2 slit. It means that they are comparable. He then assesses the level of Fisher's evolving defect cluster. Naturally, the defect is detected before a defect having the same size as the simulated defect occurs.

As described above, according to the ultrasonic flaw detection method of the first embodiment, the transmitted wave sensitivity value is first applied to the test piece processed with the simulated defect by using the ultrasonic flaw detection apparatus 2. Is measured, the center line surface roughness of the ultrasonic wave incident point is measured, an approximate line is obtained for each simulated defect, and a reference line for determining creep damage is obtained. When actually inspecting a tube to be inspected, the ultrasonic wave inspection device 2 is used to measure the transmitted wave sensitivity value of the inspection site and to measure the center line surface roughness of the ultrasonic wave incident point. By comparing with the obtained reference line, the creep damage of the inspected tube 1 can be determined.

The first embodiment does not limit the scope of the present invention, and various changes can be made within the scope of the present invention. For example, a maximum roughness may be used instead of the center line surface roughness. The center line surface roughness is the average value of the roughness, and the maximum roughness is the maximum value of the difference between the peak and the valley, but is almost the same as an index of the surface roughness, and there is no difference using either of them. .

As described above, the surface roughness of the subject is
Although it can be measured separately from the transmitted wave sensitivity value by the roughness measuring instrument, it is more efficient to measure it simultaneously with the transmitted wave sensitivity value. Therefore, simultaneously with the measurement of the transmitted wave sensitivity value, an ultrasonic wave is projected perpendicularly to the subject, the reflected wave is received, the sensitivity value of the reflected wave is measured, and the measured value is used to determine creep damage. The method will be described below.

Embodiment 2 Another embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 10 to 13. In the following, similarly to the first embodiment, the subject will be described as a high-carbon heat-resistant centrifugally cast tube. For convenience of description, the same members as those in the configuration shown in Embodiment 1 are denoted by the same reference numerals,
The description is omitted.

As shown in FIGS. 1 and 2, the ultrasonic flaw detector 12 according to the present embodiment includes a jig 15 in addition to the transmission probe 3 and the reception probe 4 as well as the reflection probe 11. Is configured.

The reflection probe 11 is an ultrasonic flaw detector 1
When the probe 2 is mounted on the tube 1 to be inspected, the transmitter 2 and the receiving probe 4 on the outer periphery of the tube 1 to be inspected are arranged on the same circumference and at the center position and perpendicular to the tube 1 to be inspected. It is attached to the jig 15 so as to be performed. And the reflection probe 11
The ultrasonic wave 17 projected from the tube 1 is reflected on the outer peripheral surface of the test tube 1, and the reflected wave can be received by the reflection probe 11. In this embodiment, the reflection probe 11
As Harisonic's I302087 (frequency 2.2
5 MHz, a transducer diameter of 0.5 ″, and a focus of 1.5 ″ PF) were used.

The jig 15 is, like the jig 5 of the first embodiment, an ultrasonic probe between the transmission probe 3, the reception probe 4, and the reflection probe 11 and the tube 1 to be inspected. An opening 5a is formed in a portion corresponding to the path. In order to prevent the water 6 filled in the jig 15 from leaking, a seal 5b made of, for example, plate rubber or the like having elasticity is provided at an abutting portion that abuts on the tube 1 to be inspected.

The ultrasonic wave 7 indicated by the arrow in the figure is the transmission probe 3.
The light is transmitted by the receiving probe 4 in the tangential direction at the maximum depth d within the thickness of the tube 1 to be inspected. At this time, if a defect (radial fisher) exists on the path of the ultrasonic wave 7 in the thickness of the inspection target tube 1, the ultrasonic wave is scattered by the defect and the attenuated transmission echo is transmitted to the receiving probe 4. And the presence of a defect can be detected.

An ultrasonic wave 17 indicated by an arrow in the drawing is projected perpendicularly to the outer peripheral surface of the tube 1 to be inspected by the reflection probe 11, and the reflected wave reflected by the outer peripheral surface of the tube 1 to be inspected is reflected. The wave is received by the reflection probe 11. At this time, as the outer peripheral surface of the inspected tube 1 is rougher, the ultrasonic wave is scattered by the outer peripheral surface and is detected by the reflection probe 11 as an attenuated reflected echo, and the surface of the inspected tube 1 is roughened. The degree of roughness can be measured.

As shown in FIG. 5, the transmitting probe 3 and the receiving probe 4 are connected to a flaw detector 21, and the flaw detector 21 is further connected to a recorder 22. Similarly, the reflection probe 11 is also connected to the flaw detector 21. Further, for example, a water injection hole (not shown) is drilled in the jig 5 and connected to the water injection tank 23 so that the inside of the jig 5 can be filled with water 6. Similarly, a drain hole (not shown) is formed in the jig 5 and is connected to a drain tank 24 so that the water 6 filled in the jig 5 can be drained.

The ultrasonic flaw detection method according to the present embodiment
Instead of the center line surface roughness by the roughness measuring device of the first embodiment, the amount of attenuation of the reflected wave (vertical surface wave sensitivity value) is used as the surface roughness of the tube 1 to be inspected. Therefore, the correlation between the center line surface roughness and the vertical surface wave sensitivity value will be briefly described.

The center line surface roughness and the vertical surface wave sensitivity value of the test tube 1 were measured, and the results are as shown in Table 1. And
As shown in FIG. 10, when a regression line between the center line surface roughness and the vertical surface wave sensitivity value is obtained from the obtained measured values, it is clear that there is a good correlation. Particularly, when the center line surface roughness is 40 μm or less (the vertical surface wave sensitivity value is 28 dB or less), a very high correlation is obtained. And
As shown in FIG. 13, since the creep damage occurs when the vertical surface wave sensitivity value is 25 dB or less, the vertical surface wave sensitivity value is used as an index of the tube surface roughness instead of the center line surface roughness. Can be.

[0062]

[Table 1]

Similarly, as shown in Table 1 and FIG.
When the maximum roughness and the vertical surface wave sensitivity value of the test tube 1 are measured, and a regression line between the maximum roughness and the vertical surface wave sensitivity value is obtained from the measured values, it is clear that there is a good correlation. . Particularly, when the center line surface roughness is 250 μm or less (the vertical surface wave sensitivity value is 27 dB or less), a very high correlation is obtained. Then, as shown in FIG. 13, since the creep damage occurs when the vertical surface wave sensitivity value is 25 dB or less, the vertical surface wave sensitivity value is used as an index of the tube surface roughness instead of the maximum roughness. Can be. The correlation between the center line surface roughness and the vertical surface wave sensitivity value of the maximum roughness is substantially the same.

The ultrasonic flaw detection method according to the present embodiment will be described below.

First, as a preparation for conducting the flaw detection of the inspected tube 1 in the actual furnace, a criterion for judging creep damage is obtained. A simulated defect is machined into a test piece having the same material and thickness as the tube 1 to be inspected, and the transmitted wave sensitivity value (corresponding to the amount of attenuation) is changed using the ultrasonic flaw detector 12 to change the surface roughness of the tube. Let me measure. At the same time, the reflection probe 11 also measures the vertical surface wave sensitivity value (corresponding to the amount of attenuation of the reflected wave). Then, an approximation line between the vertical surface wave sensitivity value and the transmitted wave sensitivity value is obtained for each of the simulated defects from the obtained measurement results.

For example, as shown in FIG. 12, the above ultrasonic test was performed on a test piece in which a simulated defect of a T / 2, T / 3 slit (crack) was processed in the thickness direction and an unprocessed test piece. The transmitted wave sensitivity value and the vertical surface wave sensitivity value are measured using the flaw detector 12, and the approximate lines Lv2, Lv1, and Lv are respectively determined for each simulated defect.
v0 was obtained. The test pieces were 0, 0.1, 0.2,
The roughness of the tube surface was changed by shaving with a lathe to 0.3 mm. The regression coefficient to be obtained is not limited to the first-order one, but can be appropriately selected according to the correlation between the vertical surface wave sensitivity value and the transmitted wave sensitivity value.

Next, when flaw detection is performed on the tube 1 to be inspected in the actual furnace, the transmitted wave sensitivity value of the inspection site is measured using the ultrasonic flaw detector 12 and the vertical surface wave sensitivity value is measured. . Then, the approximate line Lv determined as a criterion is
2, the defect of the inspected tube 1 can be determined by comparing with Lv1 and Lv0.

That is, as shown in FIG. 13, on the coordinate plane of the vertical surface sensitivity value and the transmitted wave sensitivity value, the position where the measured value of the test tube 1 of the actual furnace is plotted relative to the reference line is plotted. The state of the defect can be determined depending on whether it is performed.

As described above, according to the ultrasonic flaw detection method and the ultrasonic flaw detection apparatus used in the second embodiment, first, the test piece on which the simulated defect has been processed is applied to the ultrasonic flaw detection apparatus. 12 is used to measure the transmitted wave sensitivity value, and the reflection probe 1 installed vertically to the tube surface
The vertical surface wave sensitivity value is measured by 1 and an approximate line is obtained for each simulated defect, and a reference line for judging creep damage is prepared. When actually inspecting the tube 1 to be inspected, the transmitted-wave sensitivity value of the inspection site is measured using the ultrasonic inspection device 12, and the reflection probe installed perpendicular to the tube surface is used. The creep damage of the test tube 1 can be determined by measuring the vertical surface wave sensitivity value by 11 and comparing it with the determined reference line. It is efficient if the measurement of the transmitted wave sensitivity value and the measurement of the vertical surface wave sensitivity value are performed simultaneously.

The second embodiment does not limit the scope of the present invention, and various changes can be made within the scope of the present invention. For example, in the ultrasonic flaw detector 12, since there is almost no difference in the roughness of the tube surface on the circumference where the height level from the hearth is the same, the center position where the reflection probe 11 can be easily attached. It is provided in. However, attenuation of the ultrasonic wave when measuring the transmitted wave sensitivity value occurs at the position of incidence on the tube and the position of emission from the tube. Then, the attenuation at the incident position is larger than the attenuation at the emission position. Therefore, it is desirable to measure the roughness of the tube surface at the incident position, and the reflection probe 11 may be provided as such.

As described above in Embodiments 1 and 2, the transmitted echo of the subject projected from the transmitting probe by the ultrasonic water penetration method and received by the receiving probe, and the roughness of the surface of the subject are measured. By determining the defect in the subject from the above, it is possible to consider the amount of attenuation of the ultrasonic wave caused by scattering on the surface of the subject, so that the influence of the roughness of the subject surface is corrected and the Defects can be accurately determined.

Therefore, the secular change of the heating tube can be accurately grasped, and the remaining life can be estimated with high accuracy.
Useless replacement of the heating tube can be prevented, and operation can be performed safely and economically.

The ultrasonic flaw detection method and the ultrasonic flaw detection apparatus used therefor according to the present invention can be used as long as they have different surface roughness, even if they have different materials, thicknesses and shapes. By preparing each line, it can be applied to the determination of a defect.

[0074]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of a case in which flaw detection is performed on a KHR24C centrifugally cast tube (outer diameter 110 mm, wall thickness 12 mm) manufactured by Kubota Corporation. The KHR24C centrifugally cast tube has a center line surface roughness of about 200 μm when not in use.

[Embodiment 1] One embodiment of the present invention will be described below with reference to FIGS.

The transmitting probe 3 and the receiving probe 4 have an attachment angle φ of 43 so that the maximum depth d is 2T / 3.
° (Fig. 3).

The recorder 22 (FIG. 5) records the sensitivity value when the echo height of the received ultrasonic wave is corrected to 80% on the CRT screen. According to this recording method, the coarser the surface of the tube, the smaller the amount of ultrasonic waves received, so that the same echo height is corrected by setting a higher sensitivity value. Further, as the creep damage progresses, the amount of ultrasonic wave received decreases, so that the set sensitivity value increases.

When the reference line is created, the SURTEST S manufactured by Mitutoyo Co., Ltd.
V-9700 · 3D, handy type TAYLOR-HOBSO's surtronic3 for on-site measurement
It was used.

Table 2 shows that an ultrasonic flaw detector 2 transmits a test piece obtained by processing a simulated defect of a T / 2 or T / 3 slit (crack) in the thickness direction and an unprocessed test piece. This is a result of measuring the sensitivity value and measuring the center line surface roughness and the maximum roughness with a roughness measuring instrument.

[0080]

[Table 2]

FIG. 6 shows the measurement results of the center line surface roughness and the transmitted wave sensitivity value shown in Table 2 by the approximate line L for each simulated defect.
a2, La1 and La0 are obtained and graphed together with the measurement results. Similarly, FIG. 7 is a graph in which the approximate lines Ly2, Ly1, and Ly0 are obtained for each of the simulated defects, and the measurement results of the maximum roughness and the transmission wave sensitivity value in Table 2 are graphed together with the measurement results. Note that, as the approximation line of the present example, a regression coefficient of the first order had the highest correlation, so a regression line was adopted.

Here, both the center line surface roughness (FIG. 6) and the maximum roughness (FIG. 7) show a very high correlation (80-90%) with the transmitted wave sensitivity value, It can be seen that the line is sufficiently reliable as a criterion for creep damage.

Table 3 shows the results of measuring the center line surface roughness and the maximum roughness, and the transmitted wave sensitivity value of the damaged tube extracted from the actual furnace. In addition, the presence or absence of a fisher confirmed by cross-sectional macro / micro structure observation is made to correspond.

[0084]

[Table 3]

FIG. 8 shows the measurement results of the center line surface roughness and the transmitted wave sensitivity value in Table 3 by using the approximate lines La2, La1,
This is graphed together with La0 (FIG. 6). Similarly, FIG. 9 is a graph of the measurement results of the maximum roughness and the transmitted wave sensitivity value in Table 3 together with the approximate lines Ly2, Ly1, and Ly0 (FIG. 7), which are the reference lines.

In FIG. 8, oxidation thinning of the tube surface is progressing by use, and the center line surface roughness is distributed around 10 μm. Similarly, in FIG. 9, the maximum roughness is from 60 μm to 12 μm.
It is distributed between 0 μm.

In FIGS. 8 and 9, T / 3
Fisher is detected at a portion where the transmitted wave sensitivity value is higher than the approximate lines La1 and Ly1 of the slit. As for the accuracy, Fisher is confirmed in 50% (8/15) or more of the portions where the transmitted wave sensitivity value is higher than the approximate lines La2 and Ly2 of the T / 2 slit.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 12 and 13.

Table 4 shows that the ultrasonic flaw detector 12 uses the transmission test of the ultrasonic flaw detector 12 for a test piece in which a simulated defect of a T / 2 or T / 3 slit (crack) has been processed in the thickness direction and an unprocessed test piece. The transmitted wave sensitivity value is measured by the probe 3 and the receiving probe 4,
It is the result of measuring the vertical surface wave sensitivity value with the reflection probe 11.

[0090]

[Table 4]

FIG. 12 is a graph of the measurement results of the vertical surface wave sensitivity value and the transmission wave sensitivity value in Table 4 for which approximate lines Lv2, Lv1, and Lv0 are obtained for each of the simulated defects, and graphs together with the measurement results. . Note that, as the approximation line of the present example, a regression coefficient of the first order had the highest correlation, so a regression line was adopted.

Here, the vertical surface wave sensitivity value shows a high correlation (60-80%) with the transmitted wave sensitivity value, and it can be seen that each approximate line is reliable as a criterion for creep damage.

Table 3 also shows the measurement results of the vertical surface acoustic wave sensitivity value of the damaged tube extracted from the actual furnace.

FIG. 13 shows the measurement results of the vertical surface wave sensitivity value and the transmitted wave sensitivity value in Table 3 as approximate lines Lv2 and Lv, which are reference lines.
This is a graph together with v1 and Lv0 (FIG. 12).
In FIG. 13, oxidation thinning of the tube surface is progressing by use, and the vertical surface wave sensitivity value is distributed between 20 and 23 dB. In addition, a fisher is detected at a portion showing a transmitted wave sensitivity value higher than the approximate line Lv1 of the T / 3 slit. Then, in a portion showing a transmitted wave sensitivity value higher than the approximate line Lv2 of the T / 2 slit, Fisher is confirmed at 80% (7/9) or more.

Therefore, the heating tube can be replaced based on the reference line obtained by measuring the simulated defect.
For example, for one heating tube, the roughness of the surface of the tube at a predetermined inspection site and the transmitted wave sensitivity value are measured, and even at one location, T / 3 is applied.
When the reference line (approximate line La1, Ly1, Lv1) of the slit is exceeded, the heating tube is replaced.

As described above, according to the ultrasonic inspection method and the ultrasonic inspection apparatus used in the present invention, damage can be inspected by correcting the influence of the surface roughness of the object. Then, it was confirmed that the result of the ultrasonic flaw detection and the situation of the actual damage by the observation of the cross-sectional micro / macro structure have a good correspondence.

[0097]

As described above, the ultrasonic flaw detection method according to the first aspect of the present invention provides a transmitted echo of a subject projected from a transmission probe and received by a reception probe by the ultrasonic water penetration method. When,
The defect in the object is determined from the roughness of the object surface.

Therefore, by measuring the transmitted echo of the inspection site and measuring the surface roughness, it is possible to correct the influence of the surface roughness of the test object and perform the flaw detection. Therefore, it is possible to accurately grasp the aging of the heating tube and accurately estimate the remaining life, thereby preventing wasteful replacement of the heating tube and operating safely and economically. It works.

According to the ultrasonic flaw detection method of the second aspect of the present invention, as described above, in addition to the configuration of the first aspect, the roughness of the surface of the subject is a measured value of the center line surface roughness or the maximum roughness. The configuration is as follows.

Therefore, in addition to the effect of the configuration of claim 1, by measuring the transmitted echo of the inspection site and measuring the center line surface roughness or the maximum roughness using a roughness measuring instrument, There is an effect that flaw detection can be performed by correcting the influence of the roughness of the sample surface. The roughness measuring device required for this correction is a general measuring device,
The increase in the amount of work is also minor.

According to the ultrasonic flaw detection method of the third aspect of the present invention, as described above, in addition to the configuration of the first aspect, the roughness of the surface of the object is such that the ultrasonic wave is projected perpendicularly to the object. And the measured value of the reflected echo obtained by receiving the reflected echo.

Therefore, in addition to the effect of the first aspect, flaw detection is performed by measuring the transmitted echo of the inspection site and measuring the reflected echo, thereby correcting the influence of the roughness of the surface of the subject. It has the effect of being able to do so. In addition, the reflection echo required for this correction can be measured by a simple device equipped with a reflection probe that projects ultrasonic waves perpendicularly to the subject and receives reflected waves, thereby increasing the amount of work. Is also minor. Further, it is possible to provide the above-described reflection probe in a conventional ultrasonic flaw detection device having a transmission probe and a reception probe, and simultaneously measure a transmitted echo and a reflected echo, so that more efficient flaw detection is possible. This has the effect that work can be performed.

The ultrasonic flaw detection method according to the fourth aspect of the present invention is, as described above, in addition to any one of the first to third aspects, wherein the subject is a high-carbon heat-resistant centrifugally cast tube. .

Therefore, in addition to the effect of any one of the first to third aspects, the high-carbon heat resistant centrifugally cast tube has a large change over time in the roughness of the outer surface, and the effect of correction is remarkable.

As described above, the ultrasonic flaw detector according to the fifth aspect of the present invention provides a transmitting probe for projecting an ultrasonic wave to a subject and a receiving probe for receiving a transmitted echo transmitted through the subject. An ultrasonic flaw detector comprising a probe, comprising a third probe for projecting ultrasonic waves perpendicularly to the subject and receiving reflected echoes.

Therefore, by measuring the transmitted echo of the inspection site and the reflected echo, it is possible to correct the influence of the roughness of the surface of the subject and perform the flaw detection. In addition, the ultrasonic flaw detector only needs to provide a reflection probe (third probe) in a conventional ultrasonic flaw detector having a transmission probe and a reception probe. Then, since the transmitted echo and the reflected echo can be measured simultaneously, there is an effect that the flaw detection operation can be performed more efficiently.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a configuration of an ultrasonic flaw detector according to one embodiment of the present invention.

FIG. 2 is an explanatory view schematically showing a configuration of the ultrasonic flaw detector shown in FIG.

FIG. 3 is an explanatory view schematically showing a configuration of an ultrasonic flaw detector according to another embodiment of the present invention.

FIG. 4 is an explanatory view schematically showing the configuration of the ultrasonic flaw detector shown in FIG. 3;

FIG. 5 is an explanatory diagram showing an outline of a usage state of the ultrasonic flaw detector shown in FIG. 3;

FIG. 6 is a graph showing a measurement result of a center line surface roughness and a transmitted wave sensitivity value of a centrifugal casting tube in which a simulated defect has been processed, and an approximate line thereof.

FIG. 7 is a graph showing a measurement result of a maximum roughness and a transmitted wave sensitivity value of a centrifugally cast pipe in which a simulated defect has been processed, and an approximate line thereof.

FIG. 8 is a graph showing an approximation line between the center line surface roughness and the transmitted wave sensitivity value of a centrifugally cast tube in which a simulated defect has been processed, and the measurement results of the center line surface roughness and the transmitted wave sensitivity value of a damaged tube in an actual furnace. It is.

FIG. 9 is a graph showing an approximation line between the maximum roughness and the transmitted wave sensitivity value of the centrifugally cast pipe in which the simulated defect has been processed, and the measurement results of the maximum roughness and the transmitted wave sensitivity value of the damaged tube in the actual furnace.

FIG. 10 is a graph showing measurement results of a center line surface roughness and a vertical surface wave sensitivity value of a centrifugally cast tube, and an approximate line thereof.

FIG. 11 is a graph showing a measurement result of a maximum roughness and a vertical surface wave sensitivity value of a centrifugally cast tube, and an approximate line thereof.

FIG. 12 is a graph showing a measurement result of a vertical surface wave sensitivity value and a transmission wave sensitivity value of a centrifugal casting tube in which a simulated defect has been processed, and an approximate line thereof.

FIG. 13 shows an approximation line between a vertical surface wave sensitivity value and a transmission wave sensitivity value of a centrifugally cast pipe in which a simulated defect has been processed, and a measurement result of a vertical surface wave sensitivity value and a transmission wave sensitivity value of a damaged tube in an actual furnace. It is a graph shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection tube (test object, high carbon heat resistant centrifugal casting tube) 2 Ultrasonic flaw detector 3 Transmission probe 4 Receiving probe 11 Reflection probe (third probe)

Claims (5)

[Claims] 1. A transmitted echo of a subject projected from a transmitting probe by an ultrasonic water penetration method and received by a receiving probe,
An ultrasonic flaw detection method, wherein a defect in the object is determined from the roughness of the surface of the object. 2. The ultrasonic inspection method according to claim 1, wherein the surface roughness of the subject is a measured value of a center line surface roughness or a maximum roughness. 3. The surface roughness of the subject is a measured value of a reflected echo obtained by projecting an ultrasonic wave perpendicularly to the subject and receiving a reflected echo reflected from the subject. The ultrasonic flaw detection method according to claim 1, wherein 4. The ultrasonic flaw detection method according to claim 1, wherein the subject is a high-carbon heat resistant centrifugal casting tube. 5. A transmitting probe for projecting an ultrasonic wave to a subject,
An ultrasonic flaw detector comprising a reception probe for receiving a transmitted echo transmitted through the subject, the ultrasonic flaw detector projecting an ultrasonic wave perpendicularly to the subject, and receiving a reflected echo reflected from the subject. An ultrasonic flaw detector comprising a third probe that performs the following.