JP3868443B2 - Ultrasonic inspection method of metal material and manufacturing method of steel pipe - Google Patents

Description

  The present invention relates to an ultrasonic inspection method of a metal material using a phased array sensor (hereinafter simply referred to as “array sensor”) and a steel pipe manufacturing method including the ultrasonic inspection method in a manufacturing process. It is possible to detect and detect fine penetrating defects that could not be detected and longitudinal non-crimping in the center of the wall thickness (hereinafter referred to as “non-crimping in the flesh”) as internal and external defects. It is what.

  For example, in ultrasonic inspection of a steel pipe, as shown in FIG. 3 (a), an oblique angle in which the ultrasonic wave 2 is obliquely incident on the surface of the steel pipe 1 and the steel pipe 1 or the sensor 3 is inclined to inspect the entire cross section. A flaw detection method is generally used. In FIG. 3A, θ1 represents an incident angle, and θ2 represents a refraction angle.

  A signal waveform (generally referred to as “A scope”) obtained by this ultrasonic oblique flaw detection method is, for example, on the time axis as shown in FIG. 3B in the water immersion method using water for coupling. Thus, the surface echo S reflected on the outer surface, the inner surface defect echo F1 reflected on the defect, and the outer surface defect echo F2 appear in this order. In order to identify these surface echo S, the inner surface defect echo F1, and the outer surface defect echo F2, A signal is selectively extracted using the defect detection gates G1 and G2.

  In addition, the oblique flaw detection method for steel pipes is affected by the ratio t / D between the thickness t of the steel pipe and the outer diameter D, and as the t / D increases, the incident angle θ3 of the ultrasonic wave with respect to the inner surface defect decreases. The reflectance of the sound wave decreases. However, if the incident angle θ1 is finely adjusted, the magnitude of the signal of the inner and outer surface defects can be made closer.

  In recent years, as an ultrasonic beam control technology, an ultrasonic wave can be oscillated at an arbitrary angle by delay-controlling the oscillation timing of the transducer using an array sensor composed of a plurality of transducers, or a multi-channel array sensor. A specific array sensor is selectively used to automate mechanical changeover, or electrical scanning is applied to create an ultrasonic beam with a wide inspection area, enabling high-efficiency or high-range inspection. Or something that is going to be adopted. As an example of these, FIG. 4 shows the principle of electrically adjusting the ultrasonic wave propagation angle by the block selection method.

  If a plurality of transducers 4 are selected and their oscillation timing is delayed, it is possible to oscillate ultrasonic waves obliquely. In FIG. 4, two blocks 5 formed by four transducers 4 are selected, and the oscillation timing of the transducer 4 is controlled to be delayed for each block 5. 1, an ultrasonic wave 2 is oscillated obliquely with respect to 1 to detect, for example, an outer surface defect 6.

  Table 1 below shows a specific example of the influence of the refraction angle θ2 in the case of FIG. 4. In this case, the difference between the defect signals on the inner and outer surfaces is the smallest, and the refraction angle θ2 is 45 °. Is optimal.

  The artificial defect used for calibration when performing the flaw detection shown in Table 1 is an axial defect with a depth of 0.2 mm processed on the inner and outer surfaces in the axial direction, and the signal magnitude is almost the same as that of the inner and outer defect echoes. Obtained.

  By the way, since the artificial defect has a relatively large reflection area, the reflectance of the ultrasonic wave is large, and the defects on the inner and outer surfaces can be detected relatively easily as in the waveform example shown in FIG. Waveform example shown in FIG. 6 because the reflection area is fine and the ultrasonic reflectance is small for penetration defects such as fine unwelded (penetration defect) due to poor welding of the sewn steel pipe and fine penetration cracks in the seamless steel pipe. As such, the detection becomes difficult. In addition, F3 in FIG. 6 shows a through-hole echo.

  Further, in the case of the non-crimping in the meat, the oblique flaw detection method cannot receive the reflection echo in principle, so that the non-crimping cannot be detected.

  Therefore, as a technique for detecting minute penetrating defects, multiple reflection within the wall thickness is performed using an array sensor 7 as shown in FIG. There is an array flaw detection method (hereinafter, referred to as “multiple reflection method”) that uses the above-described detection method.

  However, in this multiple reflection method, since the through-hole echo F3 has a multiple waveform as shown in FIG. 8, the type of defect such as an internal / external surface defect or a penetrating defect cannot be identified only from time axis information. Another problem is that it is difficult to adjust the signal height of the inner and outer surface defects by adjusting the incident angle.

  In other words, in the multiple reflection method, it is possible to detect fine penetrating defects and uncrimped in the meat that were difficult to detect by the conventional method due to the cumulative effect associated with multiple reflection, but compared to the inner surface defect echo The size of the penetrating defect echo is reduced, and the outer surface defect echo has an echo directly reflected by the defect as indicated by 2ab in FIG. Becomes bigger. Therefore, when trying to detect fine penetrating defects, overdetection of inner and outer surface defects, particularly outer surface defects, becomes a problem. For example, an inner surface defect in which the inner surface defect signal is adjusted to 50% CRT, the outer surface defect signal is adjusted to 115% CRT, and the defect detection level is adjusted to 25% CRT, the defect having a depth of 0.1 mm or more is detected. In the case of external defects, the possibility of detecting most defects having a depth of 0.05 mm or more is extremely high. Therefore, it is desired to establish a technique for detecting fine penetrating defects and the like while preventing overdetection in the conventional inspection method.

As a technique related to the present invention, array sensors are arranged in the circumferential direction of the welded pipe, ultrasonic waves are transmitted so as to form plane waves from the array sensors, and among the reflected waves received from the material to be inspected, predetermined Detection of blowhole-like defects by outputting reflected waves from a number of adjacent transducer groups and sequentially shifting the transducer groups to detect flaws at different depths simultaneously. A technique for improving the above is disclosed.
JP 9-133657 A

In addition, by setting the refraction angle of the ultrasonic waves transmitted from the array sensor arranged in the circumferential direction of the pipe and performing sector scanning from the bottom surface to the surface of the welded portion, it is possible to overlook the entire region in the depth direction of the welded portion. In particular, there has been disclosed a technique for accurately detecting a particularly small blowhole-like defect.
Japanese Patent Laid-Open No. 11-183446

In addition, the ultrasonic waves transmitted from the array sensor arranged in the circumferential direction of the tube are focused at a predetermined refraction angle, and flaw detection is performed while changing the focused position in the thickness direction and circumferential direction by sector scanning. A technique is disclosed in which even if meandering is meandering, the focus position is matched with the weld line and fine defects can be detected.
JP 2000-221171 A

  In the techniques disclosed in these patent documents, for example, in Patent Document 2, an ultrasonic beam is scanned in the thickness direction to prevent the generation of a dead band, and in Patent Document 3, a fine spherical blowhole is used by using a focus beam. The defect detection performance can be improved.

  However, it is still difficult to detect the penetrating defect and, in principle, it is impossible to detect uncrimped in the meat.

  The problem to be solved by the present invention is that, in the conventional ultrasonic flaw detection method, the penetrating defect is difficult to detect because the reflection area of the ultrasonic wave is small. This is that the reflected signal cannot be detected.

The ultrasonic inspection method of the metal material of the present invention,
In order to be able to accurately detect penetration defects and uncrimped in meat,
An ultrasonic inspection method for inspecting defects existing in a material to be inspected using an oblique flaw detection method using an array sensor in which a plurality of transducers are arranged,
First, all array sensors are divided into blocks, ultrasonic waves are oscillated for each block from the transducer of the block, and reflected waves from a test material having defects on the inner and outer surfaces are received, and the dividing operation is performed for each block. After calibrating the sensitivity when
Next, the ultrasonic wave was oscillated from the transducers of all array sensors, the reflected waves from the test material were received, and the sensitivity when all the array sensors were operated was obtained during the calibration. Calibrate based on the height of the defect echo relative to the reference defect,
After these calibrations, the reflected wave A from the material to be inspected when the ultrasonic wave is oscillated for each block from the vibrators of the divided blocks, and the target when the ultrasonic wave is oscillated from the vibrators of all the array sensors. Receives the reflected wave B from the inspection material,
Thereafter, the echo height EH _A of the reflected wave A, the ratio EH _B / EH _A echo height EH _B of the reflected wave B, that the inner surface defects when EH _B / EH _A is less than 1.5 The most important feature is that the type of defect is identified by identifying the outer surface defect when it is 1.5 or more and 2.5 or less, and the penetration defect or the non-crimping in the meat when it exceeds 2.5. It is said.

In the method of the present invention, when receiving the reflected wave A from the material to be inspected, an inner surface defect or an outer surface defect is detected using a defect detection gate for identifying an inner surface defect and a defect detection gate for identifying an outer surface defect. ,
If to identify the type of defect in conjunction with the value of the EH _B / EH _A, the identification of how the inner surface defect or an outer surface defects, more readily, would allow more reliably.

  In addition, when the material to be inspected is a steel pipe, when the above-described method of the present invention is included in the steel pipe manufacturing process, not only inner and outer surface defects but also penetration defects and unbonded in the meat in the steel pipe manufacturing line Can be detected with high accuracy.

  The present invention uses a reflected wave A from a material to be inspected when ultrasonic waves are oscillated from vibrators of divided blocks, and an object to be inspected when ultrasonic waves are oscillated from vibrators of all array sensors. Since the reflected wave B from the material is used, it is possible to detect fine penetrating defects that could not be detected by the conventional method and non-crimping in meat without causing excessive detection of defects on the inner and outer surfaces. There is.

Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.
The ultrasonic inspection method for a metal tube according to the present invention sequentially performs three steps: a first step for performing calibration, a second step for performing measurement, and a third step for performing determination. explain.

[First step]
1. Selection of refraction angle by block selection method, setting of defect detection gate, setting of inspection sensitivity The refraction angle is selected by changing the refraction angle to minimize the difference in signal height obtained from the internal and external artificial defects. To do. In the case of a steel plate, this refraction angle is usually 45 °. However, in the case of a steel pipe, the inner and outer surfaces are curved, so the angle is not 45 °.

  In addition, for example, two defect detection gates are used as the defect detection gate, and the gate position is detected so that the maximum amplitude position of the artificial defect signal becomes the center of the defect detection gate. The inspection sensitivity adjusts the gain so that the inner surface defect echo height is CRT 50%.

2. Selection of refraction angle by multiple reflection method, setting of defect detection gate, setting of inspection sensitivity After selection of refraction angle by the above block selection method, setting of defect detection gate, setting of inspection sensitivity, then all array sensors The selection of the refraction angle, the setting of the defect detection gate, and the setting of the inspection sensitivity are performed when the multiple reflection method in which the ultrasonic wave is oscillated from the ultrasonic wave is carried out.

  The delay parameter is adjusted so that the refraction angle in this case becomes the refraction angle obtained by the block selection method. The defect detection gate uses one defect detection gate and adjusts the defect detection gate to a position where an artificial defect signal is generated. The inspection sensitivity adjusts the gain so that the inner surface defect echo height is CRT 50%.

  The above calibration makes it possible to compare the echo heights of the reflected waves obtained by the block selection method and the multiple reflection method.

[Second step]
1. Measurement of defects by block selection method After the above calibration, first, ultrasonic waves are oscillated from the vibrators of the divided blocks, and for example, inner and outer surface defects and penetrating defects in the inspection material such as steel pipes or unbonded in the meat echo height EH _a reflected wave a from the measuring. Table 2 below shows that when a refraction angle is 45 degrees, a signal of an artificial defect having a depth of 0.2 mm processed on the inner surface in the axial direction is adjusted to an inner surface defect echo height of 50% CRT. the outer surface defect echo height intended when measured 67.5% CRT, a through defect of 0.3 mm, the echo height EH _a was 10% CRT.

  In this block selection method, the sensor is divided into blocks, and since there is no integration effect as in the multiple reflection method described later, the reflected wave has a simple shape. It can be easily discriminated whether it is a wave or a reflected wave due to an external surface defect. However, as described above, this block selection method does not have good detection ability such as penetration defects and uncrimped in meat.

2. Measurement of defects by multiple reflection method Next, ultrasonic waves are oscillated from transducers of all array sensors, and echoes of reflected waves B from the inner and outer surface defects and penetration defects of the inspected material and unbonded in the meat Measure height EH _B. In the example shown in Table 2 above, when the refraction angle is 45 degrees, the signal of the artificial defect with a depth of 0.2 mm processed on the inner surface in the axial direction is adjusted to the inner surface defect echo height of 50% CRT. In this case, the echo height of the outer surface defect was 115% CRT, and the echo height EH _B of the penetrating defect of φ0.3 mm was 29.5% CRT larger than that in the block selection method.

That is, when this multiple reflection method is used, a difference appears in the echo height EH _B of the reflected wave B depending on the type of defect. This is schematically shown in FIG.
In the case of the penetrating defect 8, ultrasonic waves that are oscillated from the vibrators 4a to 4c and are incident on, for example, the steel pipe 1 as the material to be inspected are reflected by the penetrating defect 8 in all cases.

  That is, the ultrasonic wave oscillated from the transducer 4 a hits the vicinity of the outer surface of the penetrating defect 8 and travels back as it is reflected to the reflected wave (hereinafter referred to as “reverse wave”). 2aa ”), two reflected waves of the reflected wave 2ab that directly go out from the steel pipe 1 are detected by the sensor 3.

  In addition, the ultrasonic wave oscillated from the transducer 4b is detected by the sensor 3 as two reflected waves of the backward wave 2ba and the reflected wave 2bb that passes through the steel pipe 1 after being reflected by the penetrating defect 8 for a while. The

Further, only the backward traveling wave 2 ca of the ultrasonic wave oscillated from the transducer 4 c is detected by the sensor 3.
As a result, when the multiple reflection method is used, five reflected waves 2aa, 2ab, 2ba, 2bb and 2ca are received by the sensor 3 (see FIG. 1A).

  On the other hand, in the case of the outer surface defect 6, only the ultrasonic wave oscillated from the transducer 4 a is reflected by the outer surface defect 6. In this case, similarly to the ultrasonic wave oscillated from the transducer 4a in the case of the penetrating defect 8, the backward traveling wave 2aa and the reflected wave 2ab are detected by the sensor 3, and as a result, two reflected waves are received. (See FIG. 1B).

  In the case of the inner surface defect 9, only the ultrasonic wave oscillated from the vibrator 4 c is reflected by the inner surface defect 9. In this case, similarly to the ultrasonic wave oscillated from the transducer 4c in the case of the penetrating defect 8, only the backward wave 2ca is sensed, and as a result, one reflected wave is received by the sensor 3 ( (Refer FIG.1 (b)).

  From the above, the magnitude of the cumulative effect obtained by the multiple reflection increases in the order of penetrating defects> outer surface defects> inner surface defects. That is, when the inner surface defect is used as a reference, an effect of 295% is obtained for the penetrating defect and 170% for the outer surface defect.

  However, only the accumulation effect is increased, and in the case of a penetrating defect, the magnitude of the reflected wave received is not necessarily larger than that of the outer surface defect or the inner surface defect. In other words, because of the above-described integration effect, the sensitivity to penetrating defects is only improved compared to the block selection method. This is shown in FIG.

  In addition, although the integration effect is large, the received wave (reflected wave including the backward wave mentioned above) is slightly received depending on the reflection path, so the received reflected wave is as shown in FIG. It will be detected multiple times within a certain time span. Therefore, unlike the conventional block selection method, information on the time axis cannot be obtained appropriately, and the type of defect cannot be determined based on the position of the detected reflected wave.

[Third step]
As described above, in the multiple reflection method, overdetection of the outer surface defect 6 and the inner surface defect 9 is unavoidable when trying to detect the fine penetrating defect 8, and the defect is detected only by the magnitude of the reflected wave. It is difficult to judge the type. On the other hand, the block selection method cannot accurately detect penetrating defects.

Therefore, in the present invention, these types of defects are compensated for each other to determine the type of defect.
That is, when the echo height of the reflected wave A obtained by the block selection method is EH _A and the echo height of the reflected wave B obtained by the multiple reflection method is EH _B , so it can be expected high cumulative effect, the EH _B »EH _a. Also, since little cumulative effect in the outer surface defects 6 can be expected, the EH _B> EH _A. In contrast, since the cumulative effect in the inner surface defects 9 can not be expected, the EH _B ≒ EH _A. Therefore, the present invention uses this difference to determine the type of defect.

That is, the inner surface defect when less than the ratio EH _B / EH _A of the echo height is 1.5, 1.5 or more, and the outer surface defects when 2.5 or less, when more than 2.5 through shape They are identified as defects or uncrimped in the meat. That is, when the defect determination level of the multiple reflection method is set to 25% CRT and an echo exceeding this is detected, the type of the defect is determined using the ratio of the detected echo height of the block selection method, If it is determined, the evaluation result of the block selection method is used. If it is determined that there is a penetration defect when it is determined that there is a penetration defect, overdetection to the inner and outer surface defects is prevented together with the determination of the defect type. This criterion is used when detecting inner and outer surface defects having a depth of 0.2 mm and penetrating defects having a diameter of 0.3 mm, and the numerical values may be changed as appropriate.

  The above is the ultrasonic inspection method for a metal material of the present invention according to claim 1 or claim 2, but instead of the determination in the third step, an inner surface defect or an outer surface defect is detected by a selection block method. If a simple defect detection gate is used, it can be determined more easily and more reliably whether the detected defect is an inner surface defect or an outer surface defect. This is the ultrasonic inspection method for a metal material according to the third aspect of the present invention.

  The present invention is not limited to the above example, and it goes without saying that the embodiment may be appropriately changed within the scope of the technical idea described in each claim. For example, when the inspection method of the present invention is included in the manufacturing process of a steel pipe, not only inner and outer surface defects but also penetrating defects and unbonded parts in meat can be accurately detected in the production line.

  The present invention can be used not only for steel pipes but also for other metal pipes and for ultrasonic inspection of metal plates.

It is a figure explaining the multiple reflection method used for this invention. It is a figure explaining the relationship between the magnitude | size of the defect signal obtained by the multiple reflection method and block selection method which are used for this invention. (A) is a figure explaining the ultrasonic oblique angle flaw detection method of a steel pipe, (b) is a figure explaining the signal waveform. It is a figure explaining a block selection method. It is a figure explaining the signal waveform at the time of detecting an internal / external surface defect by the block selection method. It is a figure explaining the signal waveform at the time of detecting a penetration defect by a block selection method. It is a figure explaining a multiple reflection method. It is a figure explaining the signal waveform at the time of flaw-detecting a flaw by a multiple reflection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe 2 Ultrasonic wave 3 Sensor 4 Vibrator 5 Block 6 Outer surface defect 7 Array sensor 8 Penetrating defect 9 Inner surface defect

Claims (5)

Using a phased array sensor in which a plurality of transducers are arranged, an ultrasonic inspection method for inspecting a defect existing in a material to be inspected using an oblique flaw detection method,
First, all phased array sensors are divided into blocks, ultrasonic waves are oscillated for each block from the transducer of the block, and reflected waves from the test material having defects on the inner and outer surfaces are received, and divided for each block. After calibrating the sensitivity when operating,
Next, the ultrasonic waves are oscillated from the transducers of all the phased array sensors, the reflected waves from the test material are received, and the sensitivity when all the phased array sensors are operated is obtained during the calibration. Calibrated based on the height of the defect echo relative to the reference defect
After these calibrations, the reflected wave A from the material to be inspected when the ultrasonic wave is oscillated for each block from the vibrator of the divided block, and the ultrasonic wave oscillated from the vibrators of all the phased array sensors Receives the reflected wave B from the material to be inspected,
Thereafter, the echo height EH _A of the reflected wave A, ultrasonography of the metal material, characterized by identifying the ratio EH _B / EH type of defect by the _A echo height EH _B of the reflected wave B . The EH _B / EH _A and the inner surface defect when less than 1.5, 1.5 or more, and the outer surface defects when 2.5 or less, when more than 2.5 central portion of the through-like defects or thickness The ultrasonic inspection method for a metal material according to claim 1, wherein the ultrasonic inspection method is distinguished from a longitudinal unbonded portion existing in the metal. When receiving the reflected wave A from the material to be inspected, a defect detection gate for identifying an inner surface defect and a defect detection gate for identifying an outer surface defect are used to detect an inner surface defect or an outer surface defect,
Ultrasonography of the metal material according to claim 1 or 2, wherein the identifying TaneYoriyuki defects together with the value of the EH _B / EH _A.   The ultrasonic inspection method for a metal material according to any one of claims 1 to 3, wherein the material to be inspected is a steel pipe. The manufacturing method of the steel pipe characterized by including the ultrasonic inspection method of the metal material of Claim 4 in a manufacturing process.

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