JP2001133444A - Ultrasonic flaw detection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method an device for detecting the flaw of the internal defect of the diffusion surface of a metal material with high sensitivity. SOLUTION: By using a double-probe-type flaw detector with transmission and reception probes, ultrasonic waves are directly applied to a junction surface to be diffused at 45 degrees, and a reflection wave being reflected once on the surface of a material whose flaw is to be detected is captured while changing the distance between the two probes. The transmission and reception probes where an interval is variable are mounted to a pedestal with a bottom surface of the same curvature as that of a pipe diameter, and a support roller, a permanent magnet, an encoder, and signal wiring made of a shape storage alloy are mounted, thus providing the ultrasonic flaw detector for inspecting steel pipe for easily detecting the flaw without causing the rear surface of a thin steel pipe to fall off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive inspection method for a metal material, and more particularly to an ultrasonic inspection method and apparatus useful for detecting a defect on a diffusion bonding surface.

[0002]

2. Description of the Related Art Conventionally, when joining metal materials such as iron and steel, a groove having a predetermined angle is provided in a base material as shown in FIG.
A fusion welding method of performing build-up welding during this groove has been widely performed. As a means for detecting a welding defect in a weld overlay, a P / S probe (Pulse Signal Probe) type ultrasonic flaw detector in which an ultrasonic transmitting element and a receiving element are integrated is generally used, and FIG. As shown in (1), the ultrasonic wave was irradiated so as to be perpendicular to the welding surface, and the ultrasonic wave reflected along the same path was captured to detect a welding defect.
In this case, it takes a lot of man-hours to make a groove, and the outer shape of the weld is deformed or the structure changes due to heat.Therefore, in order to ensure the reliability of the weld, there are difficulties with highly skilled skills and economic burden. is there.

In recent years, as a means for solving the above-mentioned problem, a thin sheet of a metal which is easily diffused is sandwiched between joining surfaces, and high-temperature heating and pressure are applied so that plastic deformation hardly occurs near the joining surfaces. Attention has been paid to a diffusion bonding method in which atoms are bonded by diffusion. The diffusion bonding method has the advantage that it does not require special skills and is also highly efficient, and does not cause deformation of the outer shape of the bonding surface, and has the advantage that a bonding surface having a uniform structure without any structural change can be obtained. 62-9
7784). In order to perform ultrasonic flaw detection of the joint surface formed perpendicular to the material surface, as shown in FIG. 2, a two-probe method in which an ultrasonic transmitting element and a receiving element are separated and housed in two probes Can be performed. In the two-probe method, an ultrasonic transmitting element and a receiving element are separately provided, and the ultrasonic wave is reflected on a material surface and irradiated at a predetermined angle to a bonding surface, and the ultrasonic wave reflected on the bonding surface is again reflected. In this method, the light is reflected on the material surface, guided to the receiving element, and captured. However, the diffusion bonding method does not make a groove, so the bonding surface is formed perpendicular to the material surface, so that ultrasonic waves cannot be irradiated perpendicularly to the bonding surface, and the ultrasonic transmitting and receiving elements P united
It is impossible to use an ultrasonic flaw detector of the / S probe type. The conventional P
As a method of using an ultrasonic flaw detector of the / S probe type, there has been proposed a method in which a joining surface is cut at an angle as shown in FIG.
71). However, this method is not practical because cutting the material is difficult.

[0004]

However, in the conventional two-probe method, the propagation path of the ultrasonic wave on the surface of the material becomes long and the reflection is used many times, so that the ultrasonic wave is greatly attenuated. Since the noise is picked up, there is a problem that the detection sensitivity of a minute defect is lowered and is not practical. SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for greatly improving defect detection capability in an ultrasonic flaw detection method for a diffusion bonded surface subjected to simple material processing. Another object of the present invention is to provide an ultrasonic flaw detector which is particularly useful for detecting a bonding defect at a diffusion bonding portion of a steel pipe.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, in a two-probe method in which a transmitting element and a receiving element are separated, ultrasonic waves are applied to a diffusion bonding surface. Directly irradiate at a predetermined angle to the object, reflect the reflected ultrasonic wave once in the material, receive it, and perform flaw detection by appropriately changing the distance between the transmitting element and the flaw detection surface and the distance between the transmitting element and the receiving element. Has developed a method for finding internal defects that exist along the flaw detection surface perpendicular to the material surface. Further, as an apparatus used in this method, there is provided an ultrasonic flaw detector having a transmitting element and a receiving element separated on one pedestal, and the transmitting element is directed from a sample surface to a flaw detection surface perpendicular to an internal sample surface. The receiving element is configured to emit ultrasonic waves at a predetermined angle, the receiving element is configured to capture ultrasonic waves reflected from the sample surface, and the transmitting element and the receiving element are perpendicular to the sample surface on the sample surface. We have developed an ultrasonic flaw detector which can be moved arbitrarily in the direction perpendicular to the section to be measured and the distance between the transmitting element and the receiving element can be changed arbitrarily.

Further, in the ultrasonic flaw detector according to the present invention, a roller is mounted on the base of the flaw detector so that it can move around the pipe, and a magnet is mounted as an auxiliary device for efficiently performing ultrasonic flaw detection of the pipe. When performing flaw detection on steel pipes, the ultrasonic flaw detector was always attached to the steel pipe material to be measured to prevent the steel pipe from falling, and an encoder was attached so that the moving distance around the pipe material could be grasped. In addition, the signal line of the probe and the signal line of the encoder are made of a shape memory alloy to store the same curvature as the diameter of the pipe, thereby facilitating flaw detection around the pipe. Hereinafter, the present invention will be described in detail with reference to the drawings.

[0007]

FIG. 4 is a diagram for explaining the principle of ultrasonic flaw detection according to the method of the present invention. In FIG. 4, it is assumed that the plate-shaped flaw-detected material 50 having a thickness T is diffusion-bonded so as to have a bonding surface JJ perpendicular to the surface 50a at a point R. From one surface 50a of the material to be inspected 50 to the joining surface JJ
Consider the case of detecting a defect that occurs in a workpiece. In the state shown in FIG. 4, captures the defect F in that moves the ultrasound firing point P of outgoing probe 3 from the intersection R between the joint surface J-J on the surface 50a by a distance Y _1, received feeler The ultrasonic wave reflected by the child 4 is point P
It is assumed that a reflected echo appears at a point S that is separated by a distance L from. In this case, the emitted ultrasonic wave is
-Directly hits the flaw detection surface at an angle of θ degrees with respect to -J, is reflected at point F, and furthermore is point Q on the other surface 50b of the flaw detection material 50
And once reaches the reception probe 4. In the present invention, in order to minimize attenuation due to reflection, it is important to apply ultrasonic waves transmitted inside the material directly to the flaw detection surface.

In FIG. 4, T: plate thickness d: depth from the surface of the material to be inspected to the defect L: distance between the transmitting probe and the receiving probe θ: ultrasonic incident angle Y ₁ : bonding surface and transmitting the distance between the probe Y _2: joint surface and the distance between the reflection point of the test object material inner surface Y _3: the distance between the receiving probe surface and the reflection point of the test object material inner surface Y _4: Receive the bonding surface feeler Assuming the distance from the child plane, Y ₁ = d × tan θ Y ₂ = (T−d) × tan θ Y ₃ = T × tan θ Y ₄ = Y ₂ + Y ₃ . From the relation of the above equation, between the distance L between the transmitting probe and the receiving probe and the depth d from the surface of the material to be inspected to the defect, L = Y ₄ −Y ₁ = Y ₂ + Y ₃ −Y ₁ = (T−d) × tan θ + T × tan θ−d × tan θ = 2 × (T−d) × tan θ (1) Further, during the outbound probe and the distance L between the receiving probe and the distance Y ₁ between the joint surface and outgoing probe is, L = 2 × (T · tanθ-Y 1) ···· .. (2) holds. The transmitting probe 3 is moved from the joining surface JJ to Y
The reflected echo when moved by ₁ can be detected at a position where the distance between the transmitting probe 3 and the receiving probe 4 is L, and the relationship between L and Y ₁ is expressed by the above equation (2). It becomes the relationship.

The transmitting probe 3 is sequentially moved from the point R on the joint surface.
The thickness of the material 50 to be detected along the joining surface JJ
Internal defects existing in the vertical direction
You. FIG. 5 illustrates this state. FIG. 5 shows the depth d.
₁ Defect F at the position₁ With depth d_Two Inside position
Defect F_Two There is a case where there is. Transmitting probe 3 and receiving
The distance L from the probe 4 is determined by the internal defect F₁ If you want to detect
L₁ And the internal defect F _Two L to detect_Two In
You. Distance Y between the joint surface and the transmitting probe₁(= T and every
Frog) and the distance L between the transmitting probe and the receiving probe.
The relationship shown by the equation (2) is established between them. FIG.
As shown in FIG.₁ Surface J when detecting
The distance between −J and the transmitting probe 31 is t₁ And inside
Defect F_Two Interface JJ and outgoing probe 3 when detecting
The distance between the two is t_Two It is. Therefore, the transmitting probe and the receiving
If you move the Shin probe sequentially, how much from the surface
Can detect if there is a defect in the depth. Also,
FIG. 5 shows that the position where the internal defect exists is deeper from the surface.
The distance L between the transmitting probe 3 and the receiving probe 4 should be short.
I understand. According to this method, almost all areas of the joint surface are detected.
The distance between the transmitting probe and the receiving probe is L
Depends on the size of the transmitting and receiving transducers.
It is determined that it cannot be reduced to zero,
There is a limit to the depth that can be detected, and the deepest part cannot be detected.
There is a part.

[0010] As shown in Figs. 4 and 5, when the ultrasonic wave is reflected once on the material surface, the reflected echo clearly appears.
The ability to detect minute defects is also excellent. Therefore, it is important to capture the reflected wave of the single reflection as much as possible. In the case where the flaw detection position becomes deep and the distance between the probes cannot be ensured, it is inevitable to capture echoes reflected three times, which are reflected one more time. Sensitivity falls, but use is possible.

FIG. 7 shows the results of an experiment for confirming the detection accuracy by the method of the present invention. The target sample is 10 m deep from the side at a position of 4 mm depth of a 6 mm thick steel plate as shown in FIG.
m, a hole with a diameter of 0.5 mm to 3.0 mm is drilled, ultrasonic waves are irradiated at an angle of 45 degrees, the reflected wave reflected once on the back of the plate is captured, and the echo height is compared. is there. As shown in FIG. 7, according to the present invention, it is possible to clearly detect even a defect having a diameter of 0.5 mm, and it can be seen that the present invention is extremely effective for defect inspection of a diffusion bonding surface. FIG. 8 schematically shows the state of the echo when the reflected echo in the above experiment is displayed on the display. In the figure, T is a pulse echo, W is a shape echo and a reflection echo from the end face of the flaw detection material, and both have no relation to the detection of a defect. F is an echo due to an internal defect. FIG. 8A shows a case where there is no defect, and the noise level is other than the pulse echo.
On the other hand, FIG. 8B shows a case where there is a defect, and the defect echo F clearly appears. In the present invention, the ultrasonic wave is directly radiated to the flaw detection surface, and the number of reflections on the material surface is minimized, so that the length of the ultrasonic wave propagation path can be minimized, so that attenuation is small and noise is reduced. There is an advantage that a clear echo can be observed with less chance of picking up and a minute internal defect can be detected.

In another embodiment of the present invention, an ultrasonic wave incident on a material to be inspected at a predetermined angle is applied to the surface of the material to be inspected by one ultrasonic wave.
A method of directly reflecting the ultrasonic wave reflected by the flaw detection surface after being reflected twice and hitting the flaw detection surface will be described. That is, in FIG. 4, the positions of the transmitting probe 3 and the receiving probe 4 are switched, and the propagation path of the ultrasonic wave is reversed. Although the ultrasonic wave hitting the flaw detection surface is slightly weakened, there is no practical problem because the lengths of all the propagation paths are the same. In this case shown above (2) of the relationship it can be applied as it is if read as the distance between the receiver probe and the bonding surface of Y _1.

[0013]

(Embodiment 1) Next, an apparatus used in the method of the present invention will be described. 9 to 11 show an embodiment of the apparatus used in the method of the present invention. FIG. 9 is a plan view, FIG. 10 is a front view, and FIG. 11 is a side view. This embodiment is an example of an apparatus for flaw detection of a member formed by diffusion bonding of flat plates. The joining surface is formed at right angles to the flat plate surface. As shown in FIG. 9, both ends of the two pedestals 1 are fixed by frames 102a and 102b to form a framework.
Further, between the two opposing pedestals 1, a transmitting probe 3 and a receiving probe 4 incorporating a transmitting element 5 and a receiving element 6, respectively, are fitted. As shown in FIG. 11, an arm 10 is attached to a side surface of the transmitting probe 3 and the receiving probe 4, and the arm 10 is fitted in a groove 11 provided in the pedestal 1. XX along pedestal 1 between pedestals 1
It can slide and move smoothly in the direction.
One of the pedestals 1 is provided with a reference line 7 for adjusting the position of the flaw detection surface and a scale 22 for calculating the moving distance of the probe, and a marker 8 indicating the ultrasonic emission position of the probe.
By using (9) and (9), the moving distance of the probe can be determined. The bottom of the apparatus is finished to a smooth surface such that the bottom surface of the pedestal 1 and the bottom surfaces of the transmission probe 3 and the reception probe 4 are flush with each other. As shown in FIGS. It is configured to be in close contact with the surface of the material 50.

In performing the flaw detection, first, the material 50 to be flaw-detected is inspected.
The reference line 7 of the present apparatus is aligned with the flaw detection surface JJ of
Arranged so that the central axis XX is perpendicular to the inspection surface J
I do. Next, the marker 8 of the transmitting probe 3 is set to the reference line 7.
After the alignment, the transmitting probe 3 is gradually separated from the flaw detection surface JJ.
And simultaneously move the receiving probe 4 according to the equation (2).
Therefore, L = 2 × (T · tan θ−Y₁ To keep the relationship
Move and inspect. At this time, the incident angle θ of the ultrasonic wave is set to 45.
In terms of degrees, equation (2) is L = 2 × (T−Y ₁ ) And
You. With this device, you can move this device freely on a flat surface
The diffusion bonding surface of the plate-like material.
Partial defects can be detected with high accuracy. Platy place
In general, the surface shape is simple, so one device can be used widely
can do.

Next, as another example of the apparatus of the present invention, an apparatus for detecting flaws inside a pipe will be described.
The principle of measurement is the same as that of the above-mentioned flat plate. However, in the case of a tube, the bottom surface of the pedestal and the bottom surface of the probe need to be adjusted to the curvature of the outer diameter surface of the tube material, and the surface of the tube material and the bottom surface of the present apparatus need to be in close contact. For this reason, it is necessary to prepare a device for flaw detection of an internal defect in a tube material in which the bottom surface of the base and the bottom surface of the probe are changed for each outer diameter of the tube material. Basically, in this way, it is possible to detect flaws inside the pipe material.However, in the present invention, in order to facilitate flaw detection of the steel pipe, a supporting roller and a magnet are further attached to the pedestal so that the steel pipe can be detected. In this way, the suction force is always applied to allow the device to move in the circumferential direction while keeping the device in close contact with the steel pipe. In addition, an encoder is attached so that the moving distance in the circumferential direction can be measured, so that the position of the internal defect in the circumferential direction can be known. Furthermore, the use of a shape memory alloy for the signal line of the probe and the lead wire of the encoder makes it easy to detect flaws on the back surface of the tube. This will be described in detail with reference to the drawings.

(Embodiment 2) FIGS. 12 and 13 show a magnetic flaw detector for steel pipes according to the present invention. FIG. 12 is a plan view, FIG.
Is a side view. In FIG. 12, a transmitting probe 3 and a receiving probe 4 are mounted in the center of a pedestal 1, and the pedestal 1 further includes a support roller 12 and an encoder roller 2.
0 and ancillary equipment. The slide mechanisms of the probes in the vicinity of the transmitting probe 3 and the receiving probe 4 are basically the same as those of the device for a flat plate, and a detailed description thereof will be omitted.

In the flaw detector for pipes, it is necessary that the probe surface coincides with the curvature of the outer diameter of the pipe. In this apparatus, as shown in FIG. 13, the transmitting probe 3 and the receiving probe are used. The bottom surface of the tube 4 is formed integrally with the bottom surface of the base 1 so as to have the same curvature as the outer diameter surface of the tube. The pedestal 1 has a driving roller 12 for rotating the entire apparatus along the circumferential direction of the tube.
Are attached. The movement of the pedestal along the circumferential direction of the steel pipe to be inspected may be performed manually or by using a driving device.

Further, a magnet 13 is embedded in the pedestal 1 and functions to always attract the apparatus to the steel pipe when performing flaw detection on the steel pipe. For this reason, when the steel pipe stands vertically or is positioned horizontally, flaw detection on the back surface can be easily performed. The magnet 13 may be a permanent magnet or an electromagnet. In the case of an electromagnet, it can be released from adsorption by turning off the current at the time of desorption. An encoder roller 20 is attached to the pedestal 1 so that the amount of movement of the probe can be grasped when the apparatus moves in the circumferential direction. 21 is an encoder. This makes it possible to know the location of the internal defect along the circumferential direction of the tube.

In the flaw detector of the present invention, a shape memory alloy is used for the signal line of the probe and the signal line 14 of the encoder. As the shape memory alloy, a Ti49-Ni51 (at%) based alloy was used. This shape memory alloy was subjected to shape memory heat treatment to memorize a curvature that was slightly larger than the outer diameter of the tube material. The operating temperature of the shape memory alloy was set at 32 to 38 [deg.] C. so that the alloy had a predetermined shape when touched by hand. By using a shape memory alloy for the signal line in this way, the signal line, which has an arbitrary shape when the device is mounted, becomes a shape along the outer diameter of the steel pipe by being touched by hand after the mounting is completed. Can be measured smoothly without being entangled on the back of the tube.

It is also possible to guide the electric signals obtained from these signal lines to a microcomputer system, and image the flaw detection results as a plan view or a cross-sectional view and display them on a display or print them. Further, it is also possible to automate the flaw detection scanning or to attach a plurality of devices to one tube material to simultaneously perform flaw detection of a long tube material.

By using the present apparatus, even when a thin steel pipe having an outer diameter of about 30 mm, such as a boiler tube, stands at a narrow interval of about 10 mm, the entire length of the steel pipe extends in the outer circumferential direction. It becomes possible to detect internal defects.

[0022]

According to the method of the present invention, the length of the propagation path of the ultrasonic wave can be minimized, so that there is little attenuation and noise of the reflected wave, and a clear echo can be obtained. Even minute internal defects can be detected with high sensitivity.
Further, according to the flaw detector for steel pipes according to the present invention, it is easy to test a narrow space where thin steel pipes are densely packed, so that, for example, a fire tube of a boiler can be efficiently tested. With the recent improvement of ultrasonic element technology, transmitting elements and receiving elements are becoming smaller and more sophisticated,
By utilizing these technologies, it is possible to detect flaws in thin tubes. Therefore, the application range of the present invention is further expanded, and greatly contributes to labor saving and efficiency improvement.

[Brief description of the drawings]

FIG. 1 is a view showing an inspection method in a conventional fusion bonding.

FIG. 2 is a diagram in which a conventional inspection method is applied to a diffusion bonding surface.

FIG. 3 is a diagram illustrating an improved inspection method of a diffusion bonding surface.

FIG. 4 is a diagram illustrating an inspection method according to the present invention.

FIG. 5 is a diagram illustrating an example of an inspection method according to the present invention.

FIG. 6 is a diagram showing an outline of a measurement accuracy confirmation test.

FIG. 7 is a diagram showing the relationship between the size of a defect and the height of a reflected echo.

FIG. 8 is a diagram showing an example of a reflected echo in the present invention.

FIG. 9 is a plan view showing an example of the device of the present invention.

FIG. 10 is a front view of the device of FIG. 9;

FIG. 11 is a side view of the device of FIG. 9;

FIG. 12 is a plan view showing another example of the device of the present invention.

FIG. 13 is a side view of the apparatus of FIG.

[Explanation of symbols]

1 ... pedestal, 2 ... P / S probe, 3, 31, 32 ...
... Transmitting probe, 4,41,42 ... Receiving probe, 5 ...
... Sending element, 6 ... Receiving element, 7 ... Reference line, 8,
9 Marker, 10 Arm, 11 Groove, 12
..Support roller, 13... Magnet, 14... Signal line, 2
0 ····· Encoder roller, 21 ····· Encoder, 22 ····· Scale, 50 ····· Flaw detection material, 51 ····
・ Steel pipe,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiko Imamoto 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Sanshi Heavy Industries Co., Ltd. (72) Inventor Masaaki Fujita 2-5-1 Marunouchi, Chiyoda-ku, Tokyo F term (reference) in Mitsuishi Heavy Industries, Ltd. 2G047 AA06 AB01 AB07 BA02 BA03 BB02 EA10 GA05 GA06 GA13 GA19 GB03 GG19

Claims (11)

[Claims] 1. A two-probe method in which a transmitting element and a receiving element are separated from each other, wherein ultrasonic waves are directly applied to a flaw detection surface inside a material at a predetermined angle, and reflected ultrasonic waves are applied to the material within the material. An ultrasonic flaw detection method, wherein the flaw detection is performed while changing the distance between the transmitting element and the flaw detection surface and the distance between the transmitting element and the receiving element as appropriate. 2. The thickness of the material to be inspected is T, the distance between the inspection surface and the transmitting element is Y ₁ , the distance between the transmitting element and the receiving element is L,
The incident angle of the ultrasonic wave is taken as θ, L = 2 × (T · tanθ-Y 1) comprising ultrasonic testing method according to claim 1, characterized in that the flaw while maintaining the relationship. 3. A two-probe method in which a transmitting element and a receiving element are separated from each other, wherein ultrasonic waves are irradiated at a predetermined angle toward the inside of the material, and the ultrasonic waves are reflected once on the inner surface of the material. Directly capture the reflected ultrasonic waves by hitting the flaw detection surface and reflecting,
An ultrasonic flaw detection method, wherein flaw detection is performed while appropriately changing the distance between the transmitting element and the flaw detection surface and the distance between the transmitting element and the receiving element. 4. The apparatus according to claim 1, wherein the surface of the material to be inspected and the surface to be inspected form an angle of 90 degrees.
The ultrasonic inspection method according to any one of the above. 5. The ultrasonic flaw detection method according to claim 1, wherein the ultrasonic wave is applied to the surface of the flaw detection material at an angle of 45 degrees. 6. An ultrasonic flaw detector having a transmitting element and a receiving element separated on one pedestal, wherein the transmitting element transmits ultrasonic waves at a predetermined angle from a sample surface to an internal sample flaw detecting surface. The receiving element is configured to emit, and the receiving element is configured to capture ultrasonic waves reflected from the sample surface, and the transmitting element and the receiving element are movable on the sample surface in a direction perpendicular to the flaw detection surface. An ultrasonic flaw detector wherein an interval between the transmitting element and the receiving element can be arbitrarily changed. 7. The ultrasonic flaw detector according to claim 6, wherein the pedestal bottom surface, the bottom surface of the transmitting element, and the bottom surface of the receiving element have the same radius of curvature as the outer diameter of the tube to be detected. Characteristic ultrasonic flaw detector for tubing. 8. The ultrasonic flaw detector for a pipe according to claim 7, further comprising a support roller provided on the pedestal so as to be movable along the circumferential direction of the surface of the pipe. apparatus. 9. The ultrasonic flaw detector for a tube according to claim 7, wherein a magnet is further provided on the pedestal so that a suction force acts on the material to be flaw-detected. Ultrasonic flaw detector for steel pipes. 10. The ultrasonic flaw detector for a pipe according to claim 7, further comprising an encoder on a pedestal so that a moving distance of the pipe in a circumferential direction can be grasped. Ultrasonic flaw detector for tubing. 11. The ultrasonic flaw detector according to claim 6, wherein at least one of the signal line of the transmitting element, the signal line of the receiving element, and the signal line of the encoder is formed of a shape memory alloy. An ultrasonic flaw detector characterized by being performed.