JPH0695087B2 - Ultrasonic inspection method for pipes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a surface-modified steel pipe in which a base material surface is coated with various coating materials such as metal and ceramics by using a double permeation method, and two or more kinds of materials. The present invention relates to an ultrasonic flaw detection method for a tubular body, which detects abnormal portions such as peeling defects and corrosion holes that occur in a coating material or a coating interface in a clad steel pipe or the like in which the above are bonded.

[Conventional technology]

This type of surface-modified steel pipe has a coating of various functional materials on the inner surface or the outer surface of the base material, which is the surface of the base material, using plasma spraying, ion plating, etc., and the film thickness is several μm. To a few hundred μm, which is extremely thin. On the other hand, a clad steel pipe is manufactured by laminating a plurality of materials by various rolling methods, and the thickness of the laminated material is about several mm even if it is very thin or thick.

Conventionally, in addition to the thin coating material itself including the cladding material as described above, the vertical ultrasonic flaw detection method has been used to inspect an abnormal portion due to a defect or the like occurring at the interface between the coating material and the base material. However, in this flaw detection method, especially in the case of the outer coating, the reflected wave from the interface defect of the base material (hereinafter referred to as a defect wave) and the reflected wave from the surface, and in the case of the inner coating, the same as the interface defect wave, It is difficult to separate the reflected wave from the bottom surface (hereinafter referred to as the bottom wave). Therefore, in this flaw detection method, the bottom wave peak method that detects the attenuation of the bottom wave due to the defect may be used in combination, but in the case of an abnormal portion such as a peeling defect occurring at the boundary surface, the defect wave and the bottom wave It is also difficult to separate and detect both waves because the behavior of the crest values of the two are contradictory, and even if there is an abnormal part, the detection result that is almost the same as the peripheral part of the inspection is obtained, so it is rather sound. It is often mistaken for.

Therefore, in recent years, an ultrasonic flaw detection method using a double transmission method has been used in order to improve the above irrational problem. As shown in Fig. 5 (a) (J. Claut Kramer / H. Claut Kramer, "Ultrasonic Testing Technology-Theory and Practice" (Japan), Japan Management Association P353, see Fig. 22.10) After the ultrasonic waves transmitted from the ultrasonic probe 1 are vertically transmitted to the plate material 2 to be inspected submerged in water, the reflection plate 3 is arranged on the back surface side of the plate material 1 to be inspected with a predetermined distance. This is a method of detecting a double transmitted wave that is obtained by being reflected and transmitted again by the plate material 2 to be inspected. FIG. 5B shows a flaw detection waveform when the flaw detection method of FIG.
Is a double transmitted wave obtained by transmitting the plate material 2 to be inspected twice.

In this flaw detection method, the ultrasonic wave transmitted from the ultrasonic probe 1 is attenuated according to the size of the defective portion, for example, if there is a defective portion on the film boundary surface. Will be attenuated. Therefore, by measuring the ultrasonic waves of the double transmitted waves, it becomes possible to detect the defective portion based on the difference from the sound portion. However, as shown in FIG. 5 (b), when the plate material 2 to be inspected is relatively thin, for example, a coating material or the like, multiple reflected waves ZE ... Are generated due to repetition of surface waves and bottom waves of the plate material to be inspected 2. , This multiple reflected wave ZE becomes an interfering wave when only the double transmitted wave RE is separated and extracted independently, and in particular, the bottom multiple wave occurs until just before RE. Therefore, the plate material 2 to be inspected is arranged with a slight inclination with respect to the probe surface as shown in FIG.
By scattering ZE as shown by the arrow in the figure, only the double transmitted wave RE is received and detected. FIG. 6D is a diagram showing a flaw detection waveform when the flaw detection method of FIG.

By the way, although this double transmission method is applied to thin steel plates, FRP, and other plate materials, a reflection plate must be placed inside the tube as far as the tube is concerned, and there are still no application examples. .

However, if the double transmission method is applied to the pipe to be inspected, it is conceivable that the arrangement configuration as shown in FIG. 6 will be obtained according to the conventional flaw detection method. In the figure, the ultrasonic wave incident point by the ultrasonic probe 1 is arranged on the pipe zenith for simplification, but in practice, the zenith is taken into consideration in consideration of prevention of generation of pseudo defect signal due to accumulation of bubbles in water. It is conceivable that the surface modified steel pipe 4a is used as the pipe body 4 to be inspected, and
An example in which the coating material 4b is applied to the inner surface of the pipe is shown.

[Problems to be Solved by the Invention]

However, when the double transmission method is applied to the flaw detection method for the tube body 4 to be inspected, securing the sensitivity of the double transmission wave 6 becomes a problem due to the attenuation of various factors. That is, if the attenuation factor is mentioned, the attenuation a in the ultrasonic beam path process from the ultrasonic probe 1 to the reflection of the reflection plate is increased. Among them, in comparison with the bottom crest value method, it is due to the increase of the round trip distance after the inner surface of the tube. There is an attenuation a '. Furthermore, there are scattering b by the curved surface when incident on the outer surface of the tube, reflection c at the boundary surface of the coating material 5, reflection d at the inner surface (bottom surface) of the tube, loss e regarding the reflectance at the reflected wave 3, and the like. In particular, since it is a tubular body, the loss in sensitivity is large due to the factors b, c, and d.

Therefore, it is necessary to increase the sensitivity (gain) of the flaw detector using the ultrasonic probe 1, but in this case, the fourth-order bottom wave B4 due to the reflection d on the inner surface of the tube is a problem as shown in FIG. Is coming. In other words, the bottom wave B4 is composed of the reflected wave due to the true bottom reflection and the multiple reflected wave that is repeatedly reflected in the coating material 4b.
The double transmitted wave T is obtained in this bottom wave B4, and the multiple reflected wave of the bottom wave B4 and the double transmitted wave T overlap. In this respect, the same relationship as ZE and RE shown in Fig. 5 (b) is obtained, which interferes with the separation / extraction of the double transmitted wave T,
This will significantly impair the defect detection accuracy. Therefore, the device shown in FIG. 5 (c) can be used in the case of a plate material, but it cannot be applied in the case of being applied to the tubular body 4.

The present invention has been made in view of the above circumstances, and is a tube that can detect double transmitted waves with relatively high sensitivity and that can enhance reliability of defect evaluation by stably separating and extracting the double transmitted waves. An object is to provide an ultrasonic flaw detection method for a body.

[Means for Solving the Problems]

In order to solve the above problems, the present invention disposes an ultrasonic probe eccentrically by a predetermined distance from a line perpendicular to the pipe axis of the pipe to be inspected, and is arranged inside the pipe to be inspected. In this configuration, the reflecting plate surface of the reflecting plate and the ultrasonic probe surface are arranged with a relative inclination of a predetermined angle.

[Action]

Therefore, according to the present invention, since the ultrasonic wave transmitted from the ultrasonic probe is obliquely transmitted through the pipe to be inspected due to the eccentricity of the probe by taking the above-mentioned means, the ultrasonic wave has a certain angle. The light enters the reflecting plate, is reflected here, again passes through the pipe to be inspected, and emerges outside the pipe to be inspected. At this time, since the ultrasonic waves transmitted from the ultrasonic probe are obliquely transmitted through the pipe to be inspected as described above, the bottom surface wave of the pipe to be inspected and the boundary surface reflected wave of the coating material are largely caused by the curved surface reflection. Make a detour. On the other hand, the transmitted wave of the ultrasonic wave that passes through the pipe to be inspected and is incident on the reflection plate is incident on the reflection plate at an angle, but the reflection plate surface of this reflection plate is perpendicular to the transmission wave from the pipe to be inspected. Therefore, if the reflector surface is tilted by a certain angle, the ultrasonic waves from the reflector will pass through the same path as the propagation path of the ultrasonic waves transmitted by the reflection at the vertical folding, Since it passes through the tube to be inspected, the strongest double transmitted wave can be obtained.

〔Example〕

As an embodiment of the present invention, an ultrasonic flaw detection method for a pipe body to be inspected in which a coating material is applied to the inner surface of a surface-modified steel pipe will be described below with reference to the drawings.

First, each component is set as shown in FIG. 1 according to the procedure described below.

(1) The ultrasonic probe 1 has a predetermined water distance w on the zenith of the tube 4 to be inspected, that is, on the axis (z axis) perpendicular to the central axis (y axis) of the tube 4 to be inspected. Have and set. The water distance w is determined by the focal length of the ultrasonic probe 1 used and the like. At this time, the reflector 3 is in a substantially horizontal position.

(2) In addition, the ultrasonic probe 1 is designed so that the peak value of the surface wave, which is a reflected wave from the outer surface of the pipe to be inspected, is maximized.
Fine adjustment is performed on the x-axis, which is perpendicular to the axes and the z-axis. The position of the ultrasonic probe 1 at this time is the x-axis original position, that is, x = 0.

(3) Next, the eccentricity is obtained by translating from the z-axis in the left or right x direction by a predetermined distance Δx. Then, if necessary, the ultrasonic probe 1 is moved in the z direction to match the water distance w described in the item (1). This operation is performed on the flaw detection waveform so as to coincide with the starting point on the time axis of the surface wave in the item (1).

(4) Further, while observing the double-transmitted wave on the flaw detection waveform, the reflector plate 3 is rotated so that the peak value thereof is maximized, whereby the reflector plate 3 is set to the optimum tilt angle θ.

FIG. 2 is a diagram simulating the propagation behavior of the ultrasonic waves transmitted from the ultrasonic probe 1. This simulation result changes depending on the eccentricity distance Δx of the probe 1, but Δ is required to obtain the practical sensitivity of double transmitted waves.
There is an optimum distance for x. As is clear from this simulation result, the bottom wave B, which interferes with the extraction of the double transmitted wave, is significantly diverted and scattered from the reception path of the ultrasonic probe 1, while the double transmitted wave T is rather high. It is refracted in the direction of the acoustic probe 1. Therefore, the bottom surface wave B is suppressed by adjusting the eccentric distance of the ultrasonic probe 1 and the rotation angle of the reflecting plate 3,
If the double transmitted wave T is made relatively large, that is, T / B can be increased.

Incidentally, FIG. 3 is a diagram showing the relationship between the peak values of the bottom waves B3 (third order), B4 (fourth order) and the double transmitted wave T with respect to the eccentric distance Δx of the ultrasonic probe 1. As is clear from the figure, when the eccentric distance Δx exceeds, for example, 3 mm, the bottom waves B3 and B4 sharply decrease, whereas the double transmitted wave T decreases gently. Especially when the eccentric distance Δx is small, the bottom wave B
The peak values of 3 and B4 are higher than the peak value of the double transmitted wave T, but when the eccentric distance Δx reaches 3 mm, the relative peak value is reversed and the bottom wave B
3, B4 drops extremely and sharply until it is erased. on the other hand,
Since the double transmitted wave T is attenuated to some extent as the eccentric distance Δx increases, the eccentric distance is selected within a certain limit from the viewpoint of obtaining the absolute sensitivity of the double transmitted wave T.

Therefore, after setting the ultrasonic probe 1 and the reflection plate 3 as described above, flaw detection is performed on the presence or absence of a defect in the tube body 4 to be inspected and the size of the defect. That is, the ultrasonic waves transmitted from the ultrasonic probe 1 enter the tube body 4 to be inspected through a direction parallel to the z-axis line, but at this time, due to the eccentricity of the ultrasonic probe 1, It passes through the pipe 4 to be inspected with a certain inclination. The ultrasonic wave transmitted through the pipe 4 to be inspected is reflected at the boundary surface of the coating material 4b to generate a reflected wave I on the boundary surface of the coating material 4b. A bottom wave B of the pipe to be inspected is generated from the bottom part. Since the boundary surface reflected wave I and the bottom surface wave B are curved surface reflections, they largely deviate from the original transmitted wave T.

On the other hand, the transmitted wave T output through the tube 4 to be inspected travels in a direction different from the traveling direction of the tube 4 to be inspected, is vertically incident on the reflection plate 3 having an inclination angle of θ, and is reflected. It Therefore, the transmitted wave T reflected by the reflecting plate 3 is again transmitted through the same path in the tube body 4 to be inspected, and then Δ from the z axis.
Since the ultrasonic wave is output from the position separated by x in the z-axis direction, the double transmitted wave can be received by the ultrasonic probe 1.

Next, when the measurement of a certain position of the pipe body 4 to be inspected is completed, the pipe body 4 to be inspected is continuously rotated by a predetermined angle to perform the same inspection, and this is performed until it is rotated once. Further, by moving the pipe 4 to be inspected in the y-axis direction by an amount corresponding to the effective ultrasonic beam of the ultrasonic probe 1, and performing the inspection while rotating the pipe 4 to be inspected as described above, Ultrasonic flaw detection is performed over the entire length of the tube body 4 to be inspected.

Therefore, according to the above embodiment, the ultrasonic probe 1
By arranging eccentricity from the axis perpendicular to the central axis of the tube 4 to be inspected by a predetermined distance, the transmitted wave that passes through the tube 4 to be inspected has a boundary portion of the coating material 4b and the tube 4 to be inspected. Since the light is reflected on the curved surface at the bottom surface, it can be largely diverted from the propagation path of the double transmitted wave and scattered, and the double transmitted wave T can be reliably separated and extracted. FIG. 4 is a diagram showing flaw detection waveforms when the ultrasonic probe 2 and the reflector 3 are optimally set. From this figure, it is found that the bottom waves B3 and B4 which interfere with the extraction of the double transmitted wave T are almost eliminated. It can be seen that all of them are completely eliminated, and the effect of eliminating bottom surface waves is significantly higher than that in FIG.

Further, in the present method, by vertically inclining the reflecting plate 3 which is in parallel with the ultrasonic probe surface by a predetermined angle, the vertical folding reflection of the transmitted wave properly functions, and the eccentric distance of the ultrasonic probe 1 is reduced. The double transmitted wave T including the setting can be received with high sensitivity.

Although the surface-modified steel pipe is used as the base material of the pipe body 4 to be inspected in the above-mentioned embodiment, it can be applied to various pipe bodies provided with the clad steel pipe and the coating material 4b. The coating material 4b can be applied not only to the inner surface of the tube but also to the outer surface of the tube. Further, in the above embodiment, the tube body 4 to be inspected is rotated and moved, but the scanning method is not limited to this. For example, ultrasonic inspection may be performed by spiral scanning by rotating the tube body 4 to be inspected and moving the ultrasonic probe 1 in the y-axis direction. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

〔The invention's effect〕

As described above, according to the present invention, the double transmitted wave can be detected with relatively high sensitivity, and the double transmitted wave can be stably separated and extracted, so that the reliability of the defect evaluation can be improved. In particular, steel pipe products are often used in harsh environments such as high temperature and high corrosion conditions for their applications, and therefore strict quality requirements are made. However, if this flaw detection method is applied, high accuracy and reliability can be obtained. It is possible to realize a high double permeation method, and it is possible to produce a steel pipe having the above-mentioned required quality.

[Brief description of drawings]

1 to 4 are shown for explaining an ultrasonic flaw detection method for a tubular body according to the present invention, and FIG. 1 is an ultrasonic probe and reflection for explaining an embodiment of the method of the present invention. FIG. 2 is a diagram showing an arrangement configuration example of plates, FIG. 2 is a diagram showing an eccentric distance of an ultrasonic probe and a reflection direction of a bottom surface wave of a pipe to be inspected, and FIG. 3 is a bottom face with respect to an eccentric distance of the ultrasonic probe. Fig. 4 is a diagram showing the relationship between the crest values of the waves and the double transmitted waves, Fig. 4 is a level waveform diagram of the bottom wave and the double transmitted waves when the ultrasonic probe and the reflector are optimally set, Fig. 5 7 to FIG. 7 are views for explaining the conventional method, and FIG. 5 (a) is a view when the plate materials to be inspected are arranged in parallel using the double transmission method, and FIG. 5 (b). ) Is a waveform diagram obtained by the inspection in FIG. 5A, FIG. 5C is a diagram when the plate material to be inspected is inclined, and FIG. 5D is in FIG. Waveform diagram obtained by 査,
FIG. 6 is a diagram showing the relationship between the ultrasonic probe and the reflector when it is virtually applied to a tube, and FIG. 7 is a diagram showing the bottom wave and the double transmitted wave when the arrangement configuration of FIG. 6 is used. It is a level waveform diagram. 1 ... Ultrasonic probe, 3 ... Reflector, 4 ... Inspected pipe, 4a ... Surface-modified steel pipe, 4b ... Coating material, T ... Double transmitted wave, I ... Boundary surface Reflected wave, B ... Bottom wave of the pipe to be inspected.

Claims (1)

[Claims] 1. An ultrasonic flaw detection method for a pipe for inspecting a defect of the pipe to be inspected by using a double transmission method, wherein the pipe is decentered by a predetermined distance from a line perpendicular to the pipe axis of the pipe to be inspected. While arranging the ultrasonic probe, the reflecting plate surface of the reflecting plate arranged inside the tube body to be inspected and the ultrasonic probe surface are arranged at a relatively predetermined inclination angle, Of the transmitted waves of the ultrasonic waves transmitted from the probe through the pipe to be inspected, at least the bottom face of the pipe to be inspected is curved to be reflected so as to be diverted from the double transmitted wave, and the pipe to be inspected An ultrasonic flaw detection method for a tubular body, characterized in that a transmitted wave from the body is reflected vertically by the reflector.