JP5534123B1 - Defect inspection method and defect inspection apparatus - Google Patents

Abstract

The defect inspection method is a first step in which a high frequency signal is given to a plurality of coils arranged so as to partially overlap each other in the electromagnetic ultrasonic probe to generate ultrasonic vibrations on the inspection object. A second step of receiving the ultrasonic vibration B echo by each of the plurality of coils; a third step of receiving the ultrasonic vibration F echo by each of the plurality of coils; and the plurality of coils. A fourth step of correcting the signal intensity of the B echo received at each of the plurality of coils based on operating states of the plurality of coils; a ratio between the signal intensity of the F echo and the signal intensity of the B echo after correction Is calculated for each of the plurality of coils, and an internal defect of the inspection object is evaluated based on the calculation result.

Description

The present invention relates to a defect inspection method and a defect inspection apparatus.
This application claims priority on December 20, 2012 based on Japanese Patent Application No. 2012-278563 for which it applied to Japan, and uses the content here.

Conventionally, as one of the non-destructive inspection methods, electromagnetic defects have been inspected in a non-contact manner using electromagnetic ultrasonic waves for internal defects (inclusions, internal cracks, hydrogen defects, etc.) of inspection objects such as steel materials. Ultrasonic flaw detection is known. For example, Patent Documents 1 and 2 listed below disclose an electromagnetic ultrasonic probe (EMAT) used for inspecting an internal defect of an inspection object by the above-described electromagnetic ultrasonic flaw detection method.

The electromagnetic ultrasonic probe disclosed in the following Patent Document 1 includes a permanent magnet and an inductance coil adapted to form flaw detection pulses and receive reflected pulses. An electromagnetic ultrasonic probe disclosed in Patent Document 2 below includes a magnetizer for applying a bias magnetic field to a test material, and an ultrasonic wave transmitted to the test material and reflected by the test material. And a plurality of sensor coils.

In general, in the electromagnetic ultrasonic flaw detection method, internal defects are evaluated (classified) based on the height (signal intensity) of F echoes (defect echoes) in accordance with Japanese Industrial Standards (JIS G 0801). However, the F echo varies depending on the gap between the surface of the inspection object and the coil.

For example, when the gap between the surface of the inspection object and the coil changes from 0.5 mm to 0 mm, the signal intensity of the F echo increases by about 3 dB. For example, when the gap between the surface of the inspection object and the coil changes from 0.5 mm to 1.0 mm, the signal intensity of the F echo decreases by about 3 dB. Therefore, when the gap between the inspection object and the coil cannot be maintained at a predetermined value, it is difficult to accurately evaluate the internal defect based on the F echo.

Conventionally, in order to prevent the erroneous evaluation of the internal defect due to the gap dependency of the F echo as described above, the ratio between the signal intensity of the F echo and the signal intensity of the B echo (bottom echo) (F / B ratio) ) Based on the internal defect is adopted. When the gap between the surface of the object to be inspected and the coil changes, the signal intensity of the F echo and B echo changes, but by calculating the F / B ratio, the amount of change caused by the gap contained in both echoes is canceled out. The As a result, accurate evaluation of internal defects can be performed regardless of gap changes.

Japanese Patent No. 4842922 Japanese Unexamined Patent Publication No. 2005-214686

However, in the case of adopting a configuration in which a plurality of coils for transmitting and receiving electromagnetic ultrasonic waves are arranged in a conventional electromagnetic ultrasonic probe (particularly, a plurality of coils are arranged so as to partially overlap each other. When this is done, there is a possibility that an arbitrary coil receives reflected electromagnetic waves (F echo and B echo) that should be received by the adjacent coil.

As a result of research by the present inventor, the signal intensity of the adjacent F echo received by any coil (the F echo that the adjacent coil should originally receive) is negligibly small, but the adjacent B echo received by the arbitrary coil It has been found that the signal intensity of the (B echo that should be received by the adjacent coil) is so large that it cannot be ignored.

  That is, the signal intensity of the B echo (adjacent B echo) that should be received by the adjacent coil is added to the signal intensity of the B echo received by any coil. Here, if the B echo signal intensity increases in the same way for all coils, the F / B ratio also changes in the same way for all coils. There is no hindrance (it is only necessary to change the evaluation standard value to be compared with the F / B ratio).

  However, the amount of increase in the B echo signal intensity varies depending on the operating state of each coil. Specifically, for example, when two coils adjacent to both sides of an arbitrary coil are operating normally, the signal intensity of the B echo received by the arbitrary coil includes two adjacent coils on both sides. The signal intensity of the B echo that should be received by the coil is added.

In addition, for example, when one of the two coils adjacent to both sides of an arbitrary coil is not operating due to a failure or the like, the signal intensity of the B echo received by the arbitrary coil includes Of the two coils adjacent to both sides, only the signal intensity of the B echo that should be received by one of the coils is added. Further, for example, when both of two coils adjacent to both sides of an arbitrary coil are not operating, the signal intensity of the B echo received by the arbitrary coil does not increase (that is, the arbitrary coil originally receives). Only the signal strength of the power B echo is obtained).

  For example, among the coils arranged in a plurality, the coil located at the end has only one adjacent coil. The coils other than the end receive B echoes that should be received by two adjacent coils, but the coil located at the end receives only the B echo that should be received by one adjacent coil. Therefore, the amount of increase in the B echo signal intensity inevitably differs between the coil disposed at the end and the coil disposed at the end other than the end. This means that the signal intensity of the B echo received by the coil located at the end depends only on the operating state of one coil adjacent to the coil.

As described above, when the amount of increase in the B echo signal intensity differs depending on the operating state of each coil, for the sake of safety, internal defects are evaluated with reference to the coil having the lowest B echo signal intensity. A way to do it is also conceivable. However, when this method is employed, the internal defect is overestimated for other coils having a high B echo signal intensity. As a result, there is a possibility that the efficiency of the inspection process decreases due to the extra inspection being performed.
As described above, in a conventional electromagnetic ultrasonic probe, when a configuration in which a plurality of coils are arranged adjacent to each other so as to partially overlap each other, the internal defect of the inspection object is accurately determined. It was difficult to evaluate.

The present invention has been made in view of the above-described circumstances. In an electromagnetic ultrasonic probe, a configuration in which a plurality of coils are arranged so as to be adjacent to each other and partially overlap each other is employed. Even if it exists, it aims at providing the defect inspection method and defect inspection apparatus which can evaluate the internal defect of an inspection target object correctly.

The present invention employs the following means in order to solve the above problems and achieve the object. That is,
(1) In the defect inspection method according to one aspect of the present invention, a high-frequency signal is applied to a plurality of coils arranged adjacent to each other and partially overlapping in an electromagnetic ultrasonic probe, A first step of generating ultrasonic vibrations in the second step; a second step of receiving the B echoes of the ultrasonic vibrations by each of the plurality of coils; and a F echo of the ultrasonic vibrations by each of the plurality of coils. A fourth step of correcting the signal intensity of the B echo received by each of the plurality of coils based on an operating state of the plurality of coils; and a signal intensity of the F echo and after the correction And calculating a ratio of the B echo to the signal intensity of each of the plurality of coils, and evaluating an internal defect of the inspection object based on the calculation result.

(2) In the defect inspection method according to (1), in the fourth step, when only one coil adjacent to an arbitrary coil is operating, the B echo received by the arbitrary coil May be corrected with the first correction value. When two coils adjacent to the arbitrary coil are not operating, the signal intensity of the B echo received by the arbitrary coil may be corrected with the second correction value. Furthermore, when two coils adjacent to the arbitrary coil are operating, the signal intensity of the B echo received by the arbitrary coil may be corrected with a third correction value.

(3) In the defect inspection method according to (2), the first correction value may be smaller than the second correction value. Further, when two coils adjacent to the arbitrary coil are operating, the third correction value is set to zero to correct the signal intensity of the B echo received by the arbitrary coil. It is not necessary.

(4) In the defect inspection method according to (3), the B received by the arbitrary coil in a state where two coils adjacent to the arbitrary coil are operating before the first step. Based on the difference between the signal strength of the echo and the signal strength of the B echo received by the arbitrary coil while only one coil adjacent to the arbitrary coil is operating, the first correction Obtaining a value; signal strength of the B echo received by the arbitrary coil in a state where the two coils adjacent to the arbitrary coil are operating, and the two coils adjacent to the arbitrary coil And a step of obtaining the second correction value based on a difference from the signal intensity of the B echo received by the arbitrary coil in a state where is not in operation.

(5) A defect inspection apparatus according to one aspect of the present invention includes an electromagnetic ultrasonic probe including a plurality of coils arranged adjacent to each other and partially overlapping each other; an inspection is performed on each of the plurality of coils. A high-frequency signal for generating ultrasonic vibrations on the object is supplied, and an F echo of the ultrasonic vibrations received by each of the plurality of coils based on output signals of the plurality of coils, and An arithmetic unit that calculates the signal intensity of the B echo and evaluates the internal defect of the inspection object based on the calculation result. The arithmetic device corrects the signal intensity of the B echo received by each of the plurality of coils based on an operation state determination unit that determines an operation state of the plurality of coils and an operation state of the plurality of coils. A correction execution unit for calculating the ratio of the F echo signal intensity to the corrected B echo signal intensity for each of the plurality of coils, and the ratio calculation by the ratio calculation unit. A defect evaluation unit that evaluates an internal defect of the inspection object based on the result.

(6) In the defect inspection apparatus according to (5) above, when the operation state determination unit determines that only one coil adjacent to an arbitrary coil is operating, the correction execution unit The signal intensity of the B echo received by an arbitrary coil may be corrected with the first correction value. In addition, when the operation state determination unit determines that two coils adjacent to the arbitrary coil are not operating, the correction execution unit determines the signal intensity of the B echo received by the arbitrary coil. May be corrected with the second correction value. Further, when the operation state determination unit determines that two coils adjacent to the arbitrary coil are operating, the correction execution unit determines the signal intensity of the B echo received by the arbitrary coil. May be corrected with the third correction value.

(7) In the defect inspection apparatus according to (6), the first correction value may be smaller than the second correction value. Further, when the operation state determination unit determines that two coils adjacent to the arbitrary coil are operating, the correction execution unit sets the third correction value to zero, and The signal intensity of the B echo received by an arbitrary coil may not be corrected.

(8) In the defect inspection apparatus according to (7), the arithmetic unit receives the B echo signal received by the arbitrary coil in a state where two coils adjacent to the arbitrary coil are operating. The first correction value is obtained based on a difference between the intensity and the signal intensity of the B echo received by the arbitrary coil in a state where only one coil adjacent to the arbitrary coil is operating. The signal intensity of the B echo received by the arbitrary coil while the two coils adjacent to the arbitrary coil are operating, and the two coils adjacent to the arbitrary coil are not operating. A correction value acquisition unit that acquires the second correction value based on a difference from the signal intensity of the B echo received by the arbitrary coil in a state may be further provided.

(9) In the defect inspection apparatus according to (8), the arithmetic device further includes a correction value storage unit that stores the first correction value and the second correction value acquired by the correction value acquisition unit. You may have.

According to the above aspect, even in the case where a configuration in which a plurality of coils are arranged so as to partially overlap each other adjacent to each other is adopted in the electromagnetic ultrasonic probe, the internal defect of the inspection object Can be accurately evaluated.

It is a mimetic diagram showing the composition of defect inspection device 100 concerning one embodiment of the present invention. It is a schematic diagram which shows the state seen from the arrow A2 direction of FIG. It is a figure which shows the relationship between the flaw detection position of the steel plate 200, and the signal strength of F echo and B echo which were received with the coil provided in the electromagnetic ultrasonic probe 102. FIG. It is a figure which shows the relationship between the flaw detection position of the steel plate 200, and F / B ratio. It is a schematic diagram which shows the defect map of the steel plate 200. FIG. 3 is a schematic diagram illustrating a state in which ultrasonic vibration generated in the steel plate 200 by the electromagnetic ultrasonic probe 102 propagates through the steel plate 200. It is the top view which looked at the coils 1-3 provided in the electromagnetic ultrasonic probe 102 from the arrow A3 direction of FIG. Schematic showing 14 examples (levels 1 to 14) when eight coils provided in the electromagnetic ultrasonic probe 102 are shown as ch1 to ch8 and transmission of ultrasonic waves in each ch is turned on or off. FIG. FIG. 8 is a characteristic diagram showing a value (dB) obtained by actually measuring a signal intensity of a B echo of a coil ch4 that is a data collection target ch for each of levels 1 to 14 shown in FIG. It is a flowchart which shows the correction process of the signal strength of B echo.

Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[1. Configuration example of electromagnetic ultrasonic device]
First, the configuration of a defect inspection apparatus (electromagnetic ultrasonic apparatus: EMAT) 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram illustrating a configuration of the defect inspection apparatus 100. The defect inspection apparatus 100 includes an electromagnetic ultrasonic probe 102 including a plurality of (e.g., eight) coils arranged adjacent to each other and partially overlapping, an amplifier 104 (not shown in FIG. 1), a measure. A ring roll 106, a tip detection sensor 108, a calculation device 110, a display device 120, and an alarm device 130 are provided.

A steel plate 200 that is an inspection object is placed on a passing plate table and is conveyed in the direction of arrow A1 in FIG. 1 by driving a roller of the passing plate table. The electromagnetic ultrasonic probe 102 detects an internal defect 202 of the steel plate 200 by transmitting and receiving electromagnetic ultrasonic waves by the eight coils, and a plurality of electromagnetic ultrasonic probes 102 are arranged in the width direction of the steel plate 200.
As shown in FIG. 1, for example, the electromagnetic ultrasonic probes 102 are arranged in two rows in the conveying direction of the steel plate 200, and eight electromagnetic ultrasonic waves are respectively arranged in the upstream and downstream rows in the conveying direction. A probe 102 is arranged. Further, as shown in FIG. 1, the eight electromagnetic ultrasonic probes 102 in the upstream and downstream rows are arranged so that the positions in the width direction of the steel plate 200 are different from each other, and are adjacent to each other on the upstream side. The electromagnetic ultrasonic probe 102 on the downstream side is located in the middle of the electromagnetic ultrasonic probe 102 to be operated.
By arranging a plurality of electromagnetic ultrasonic probes 102 in a staggered manner in this way, internal defects 202 located between the electromagnetic ultrasonic probes 102 that cannot be detected by the upstream electromagnetic ultrasonic probe 102 are obtained. It can be reliably detected by the electromagnetic ultrasonic probe 102 on the downstream side.

  FIG. 2 is a schematic diagram showing a state seen from the direction of arrow A2 in FIG. As shown in FIG. 2, the electromagnetic ultrasonic probe 102 is disposed close to the upper part of the steel plate 200. Air is supplied from the bottom surface of the electromagnetic ultrasonic probe 102 toward the steel plate 200, and this air causes a gap between the bottom surface of the electromagnetic ultrasonic probe 102 and the steel plate 200 to be about 0.5 mm. Have been adjusted so that. The amplifier 104 is arranged on the upper part of the electromagnetic ultrasonic probe 102, and a detection signal output from the electromagnetic ultrasonic probe 102 (more precisely, each coil provided in the electromagnetic ultrasonic probe 102). Output signal).

  The electromagnetic ultrasonic probe 102 generates ultrasonic vibrations on the surface of the steel plate 200 by each coil, and the eddy current generated by the vibration of the ultrasonic waves reflected from the bottom surface of the steel plate 200 under a static magnetic field is generated by each coil. Detect. Thereby, the echo level (B echo) of the ultrasonic vibration reflected on the bottom surface is detected. When the internal defect 202 shown in FIG. 1 occurs in the steel plate 200, the ultrasonic vibration is reflected by the internal defect 202, and the ultrasonic vibration reflected by the internal defect 202 is detected by the electromagnetic ultrasonic probe 102. The When the internal defect 202 has occurred, the echo level (F echo) of the reflected ultrasonic vibration changes, so that the internal defect 202 is based on the ratio of the F echo signal intensity to the B echo signal intensity (F / B ratio). The defect 202 can be evaluated (classified).

The arithmetic device 110 has a function of supplying a high frequency current (high frequency signal) to each electromagnetic ultrasonic probe 102. That is, the arithmetic unit 110 supplies a high-frequency current for generating ultrasonic vibration in the steel plate 200 to each of the eight coils provided in each electromagnetic ultrasonic probe 102.
In addition, the arithmetic unit 110 receives each coil based on the output signal of each electromagnetic ultrasonic probe 102 (that is, the output signal of each coil provided in each electromagnetic ultrasonic probe 102). The signal intensity of the F echo and the B echo of the ultrasonic vibration is calculated, and the internal defect 202 of the steel plate 200 is evaluated based on the calculation result.

More specifically, the calculation device 110 includes a correction value acquisition unit 112, an operation state determination unit 114, a correction execution unit 116, an F / B calculation unit (ratio calculation unit) 117, and a defect evaluation unit 118. The correction value storage unit 119 is provided.

The operating state determination unit 114 determines the operating states of all eight coils for each electromagnetic ultrasonic probe 102. Specifically, the operating state determination unit 114 has a self-diagnosis function that determines that a coil that could not detect the F echo and the B echo is a failure (that is, a non-operating state).
The correction execution unit 116 corrects the signal intensity of the B echo received by each coil based on the determination result of the operation state of each coil by the operation state determination unit 114.
Although details will be described later, the correction execution unit 116 determines that the operation state determination unit 114 determines that any one of the eight coils is adjacent to any one of the eight coils. The signal intensity of the B echo received by the first coil is corrected with the first correction value.
Further, when the operating state determination unit 114 determines that the two coils adjacent to the arbitrary coil are not operating, the correction execution unit 116 determines the signal intensity of the B echo received by the arbitrary coil. Correction is performed with the second correction value.
Further, when the operation state determination unit 114 determines that the two coils adjacent to the arbitrary coil are operating, the correction execution unit 116 determines the signal intensity of the B echo received by the arbitrary coil. Correction is performed with the third correction value.
Note that each of the above corrections is performed for all the electromagnetic ultrasonic probes 102.

The F / B calculation unit 117 calculates the F / B ratio between the signal intensity of the F echo and the corrected signal intensity of the B echo for each coil. The calculation of the F / B ratio is performed for all of the electromagnetic ultrasonic probes 102. The defect evaluation unit 118 evaluates the internal defect 202 of the steel plate 200 based on the F / B ratio calculation result by the F / B calculation unit 117.

The correction value acquisition unit 112 outputs the signal intensity of the B echo received by the arbitrary coil while two coils adjacent to the arbitrary coil are operating among the eight coils, and the arbitrary coil. The first correction value is acquired based on the difference from the signal intensity of the B echo received by the arbitrary coil while only one adjacent coil is operating.
In addition, the correction value acquisition unit 112 receives the signal intensity of the B echo received by the arbitrary coil while the two coils adjacent to the arbitrary coil are in operation, and 2 adjacent to the arbitrary coil. The second correction value is acquired based on a difference from the signal intensity of the B echo received by the arbitrary coil in a state where the two coils are not operating.
The correction value storage unit 119 stores the first correction value and the second correction value acquired by the correction value acquisition unit 112.
In addition, acquisition of said 1st correction value and said 2nd correction value is carried out in advance before the actual defect inspection, one electromagnetic ultrasonic probe 102 and the sample of the steel plate 200 which is a test object. Used experimentally. Details of the method of acquiring the first correction value and the second correction value will be described later.

The display device 120 displays the evaluation result (class classification) of the internal defect 202 based on the evaluation result of the internal defect 202 by the arithmetic device 110. Further, the alarm device 130 issues an alarm when the F / B ratio of the internal defect 202 exceeds the reference value. The steel plate 200 in which the internal defect 202 exceeding the reference value is detected leaves the normal conveyance path and is subjected to further detailed inspection.

  FIG. 3A shows the relationship between the flaw detection position in the conveying direction of the steel plate 200 and the signal intensity of the F echo and B echo. FIG. 3B shows the relationship between the flaw detection position and the F / B ratio. As shown in FIG. 3A, when the internal defect 202 occurs in the steel plate 200, the signal intensity of the F echo increases according to the size of the internal defect 202, and the signal intensity of the B echo decreases.

As a result, as shown in FIG. 3B, the F / B ratio increases at the flaw detection position where the internal defect 202 has occurred compared to the flaw detection position where the internal defect 202 has not occurred. The F / B ratio increases as the internal defect 202 increases. Therefore, based on the F / B ratio, it can be detected whether or not the internal defect 202 has occurred, and the size and position of the internal defect 202 can be evaluated.

Further, when the gap between the electromagnetic ultrasonic probe 102 and the surface of the steel plate 200 changes, the signal intensity of the B echo and the F echo changes, but by calculating the F / B ratio, the B echo and F due to the change in the gap are calculated. The amount of change in echo signal intensity can be offset. Furthermore, by evaluating the internal defect 202 based on the F / B ratio, even if the F echo and the B echo contain noise, the noise can be canceled out, and the internal defect 202 is increased. The accuracy can be evaluated.

Detection signals output from the plurality of electromagnetic ultrasonic probes 102 arranged in the width direction of the steel plate 200 are transmitted to the arithmetic device 110. A position signal output from the measuring roll 106 that measures the position from the tip of the steel plate 200 is also transmitted to the arithmetic device 110.
The tip detection sensor 108 detects the tip position of the steel plate 200, and the tip position serves as a reference when the measuring roll 106 detects the position of the steel plate 200. The arithmetic unit 110 synchronizes the F / B ratio signal and the position signal, and creates a defect map indicating the position where the internal defect 202 occurs in the steel plate 200 as shown in FIG.

  The width in the steel plate width direction of one electromagnetic ultrasonic probe 102 is about 100 mm, and the distance between adjacent electromagnetic ultrasonic probes 102 cannot be made zero. Therefore, in order to eliminate the undetected area, the electromagnetic ultrasonic probes 102 are arranged in two rows in the conveying direction of the steel plate 200 as described above, and the positions in the width direction of the steel plate 200 are different from each other in the two rows. It is arranged in a so-called staggered arrangement.

  The arithmetic device 110 is configured to detect the detection signals output from the plurality of electromagnetic ultrasonic probes 102 arranged in this manner, and the position of the steel plate 200 that moves on the through plate table that conveys the steel plate 200 with acceleration / deceleration. Are recognized, an accurate defect position is recognized, and a defect map as shown in FIG. 4 is created. As a result, it is possible to instantly grasp how much size of the internal defect 202 has occurred at which position in the conveyance direction of the steel plate 200.

[2. Effect of adjacent coil on detection value]
FIG. 5 is a schematic diagram showing a state in which ultrasonic vibration generated in the steel plate 200 by the electromagnetic ultrasonic probe 102 propagates inside the steel plate 200. As described above, for each electromagnetic ultrasonic probe 102, for example, eight coils are arranged adjacent to each other and partially overlapped. FIG. 5 representatively shows only three coils 1 to 3 among the eight coils. The coils 1 to 3 are simultaneously transmitting and receiving ultrasonic waves in synchronization.

6 is a plan view of the three coils 1 to 3 as viewed from the direction of arrow A3 in FIG. In FIG. 5, for convenience of illustration, the three coils 1 to 3 are illustrated as being arranged at regular intervals without overlapping, but in reality, as illustrated in FIG. 6, the three coils 1 to 3 are illustrated. Are arranged adjacent to each other and partially overlap each other. Eight coils including three coils 1 to 3 are arranged in a line on a printed circuit board (FPC) (not shown).

As shown in FIG. 5, the electromagnetic ultrasonic probe 102 is provided with permanent magnets 102 a corresponding to the coils 1 to 3. For example, when focusing on the coil 2, when a high frequency current is supplied to the coil 2, a magnetic field M <b> 1 that fluctuates at a high frequency is generated on the surface of the steel plate 200. An induced current I ₁ is generated on the surface of the steel plate 200 in a direction that cancels the magnetic field M ₁ . The Lorentz force F is generated by a current _{I 1} flows through the conductor in a static magnetic field M2 generated by the permanent magnets 102a (steel 200). Since the Lorentz force F fluctuates in synchronization with the high-frequency current flowing through the coil 2, the surface of the steel plate 200 vibrates due to the Lorentz force F, thereby generating ultrasonic vibration.

  As shown in FIG. 5, the ultrasonic vibration generated by the coil 2 is reflected by the bottom surface of the steel plate 200. The ultrasonic echo level (B echo) of the coil 2 reflected from the bottom surface is received by the coil 2 that has generated ultrasonic vibration, and is also received by the coils 1 and 3 adjacent to the coil 2. This is due to the fact that the ultrasonic waves propagate far away and the adjacent coils partially overlap each other as shown in FIG.

  The echo level (F echo) of the ultrasonic vibration reflected by the internal defect 202 is also received by the coil 2. The coil 2 receives reflected waves (F echo and B echo) by detecting an eddy current generated by the reflected ultrasonic wave oscillating under the static magnetic field of the permanent magnet 102.

  Since the coils 1 and 3 transmit and receive ultrasonic waves in synchronization with the coil 2, the coil 2 generates both the adjacent two coils 1 and 3 in addition to the B echo of the ultrasonic vibration generated by itself. The B echo of the ultrasonic vibration that has been made is also received.

  On the other hand, for example, when the coil 1 is located at the end of eight coils, the coil adjacent to the coil 1 is only the coil 2. Therefore, the coil 1 receives the B echo of the ultrasonic vibration generated by one adjacent coil 2 in addition to the B echo of the ultrasonic vibration generated by itself. As a result, the signal intensity of the B echo received by the coil 1 is smaller than the signal intensity of the B echo received by the coil 2.

When the internal defect 202 has arisen in the steel plate 200, ultrasonic vibration is reflected in the internal defect 202, and F echo is received by each coil. Since the area where the internal defect 202 is subjected to ultrasonic vibration is smaller than the area where the bottom surface of the steel plate 200 is subjected to ultrasonic vibration, the influence of the ultrasonic wave of the adjacent coil is small for the F echo. Further, since the propagation distance of the F echo until the coil receives it is shorter than that of the B echo, the influence of the adjacent coil on the F echo is reduced. Therefore, the signal intensity of the F echo received by each of the coils 1 to 3 is approximately the same level.
As described above, the signal intensity of the adjacent F echo received by any coil (the F echo that the adjacent coil is supposed to receive) is negligibly small, but the adjacent B echo (adjacent coil) received by the arbitrary coil is small. The signal intensity of the B echo that should be received by the user is so large that it cannot be ignored.

  Therefore, when the internal defect 202 is evaluated based on the F / B ratio, the signal intensity of the B echo received by the coil 1 is smaller than the signal intensity of the B echo received by the coils 2 and 3. 1 has an excessive F / B ratio than coils 2 and 3.

  In this way, in the electromagnetic ultrasonic probe 102, since a plurality of coils are arranged adjacent to each other and partially overlap each other, any coil can be received in addition to the B echo that should be received by itself. Another coil adjacent to this also receives the B echo to be received by the main body. Moreover, since it receives the influence of the electric field which generate | occur | produced from the other coil, the ultrasonic wave generation timing of each coil cannot be shifted. Therefore, an arbitrary coil always receives the B echo that should be received by the adjacent coil.

The underestimation of the internal defect 202 cannot detect the internal defect 202 and leads to the outflow of the defective steel plate 200. Therefore, a reference size that is recognized as the internal defect 202 is set, and the F / B ratio of the coil that is detected as the lowest F / B ratio value is used as the determination threshold value.
Thereby, the F / B ratio when the reference size is detected by another coil is equal to or greater than the determination threshold value, and it is possible to reliably prevent the situation in which the internal defect 202 is not detected by the underestimation. In the example shown in FIG. 5, since the F / B ratio of the coil 2 is lower than the coil 1 F / B ratio, the F / B ratio when the coil 2 detects the reference size becomes the determination threshold value. In this case, since at least the F / B ratio of the coil 1 is larger than the F / B ratio of the coil 2, if the evaluation based on the F / B ratio of the coil 1 is performed, the internal defect 202 is overestimated. . Therefore, it is difficult to normally evaluate the internal defect 202 based on the F / B ratio of the coil 1 located at the end.

[3. Specific configuration example of the embodiment]
In this embodiment, in order to suppress the influence of the adjacent coil on the arbitrary coil, the signal intensity of the B echo received by each coil is corrected according to the operating state of each coil. FIG. 7 shows eight coils as ch1 to ch8, and 14 examples when the transmission of ultrasonic waves in each ch is turned on (ON: operating state) or turned off (OFF: non-operating state) (level 1). To 14). The coil ch4 is a data collection target coil for detecting the B echo, and is always on. FIG. 8 is a characteristic diagram showing a value (dB) obtained by actually measuring the signal intensity of the B echo of the coil ch4 that is the data collection target ch for each of the levels 1 to 14 shown in FIG.

  Level 1 in FIG. 7 shows a case where all the ultrasonic transmissions of the eight coils (ch1 to 8) are turned on. Level 2 shows a case where only the leftmost coil ch1 is turned off and the other coils are turned on. Level 3 shows a case where the coils ch1 and ch8 at both ends are turned off and the other coils are turned on. From level 4 to level 8, the coils that are further away from the coil ch4 are sequentially turned off. Level 9 shows a case where all except the coil ch4 are turned off. Furthermore, after level 9, one of the coils outside ch3 and ch5 is sequentially turned on.

  In the present embodiment, as shown in FIG. 8, when one of ch3 and 5 adjacent to ch4 is on as compared to the case where two ch3 and 5 adjacent to ch4 are on (levels 1 to 6). (Levels 7 and 8) were found to cause a 2 dB drop in the B echo signal intensity. It was also found that when both the channels adjacent to ch4 are off (levels 9 to 14), the signal intensity of the B echo is reduced by 4 dB.

In FIG. 7, the data collection target coil is ch4. However, when ch1 or ch8 is detected at both ends, ch1 or ch8 has only one adjacent coil, so one of the adjacent coils is always present. Equivalent to the case of off (non-operating state). Therefore, in the coil ch1, even if the adjacent coil ch2 is on, the signal intensity of the B echo is reduced by 2 dB.
For the coil ch1, when the adjacent coil ch2 is off, the signal intensity of the B echo is reduced by 4 dB. Similarly, for the coil ch8, even if the adjacent coil ch7 is on, the signal intensity of the B echo is reduced by 2 dB, and when the adjacent coil ch7 is off, the reduction is 4 dB. As described above, regarding the coil located at the end portion, it can be seen that the signal intensity of the B echo is lowered even if the adjacent coil is normal.

  When evaluating the internal defect 202, a difference of 4 dB in the signal intensity of the B echo corresponds to a difference between a light defect and a medium defect. When the internal defect 202 is evaluated based on a standard equivalent to JIS G 0801, this difference cannot be ignored in actual operation. Therefore, since the difference in the signal intensity of the B echo affects the evaluation level of the internal defect 202, it is necessary to reliably suppress overestimation of the signal intensity.

  From the above results, in the present embodiment, the signal intensity of the B echo received by each coil is corrected according to the operating state of each coil. As a result, the signal intensity of the B echo received by each coil is made uniform, the error of the detection level of the internal defect 202 when evaluated based on the F / B ratio is eliminated, and the evaluation of the internal defect 202 is stabilized. It is possible to make it.

  Specifically, in the example shown in FIG. 8, when only one of the coils adjacent to an arbitrary coil is in an operating state (ON), 2 dB is added to the signal intensity of the B echo received by the arbitrary coil. If two of the coils adjacent to the arbitrary coil are in a non-operating state (off), 4 dB is added to the signal intensity of the B echo received by the arbitrary coil.

  As described above, with respect to the coils ch1 and ch8 located at both ends of each electromagnetic ultrasonic probe 102, since there is only one adjacent coil, one adjacent coil is always off (non-operating state). It is equivalent to a certain case. Therefore, when the coil ch2 adjacent to the coil ch1 is on, 2 dB is added to the signal intensity of the B echo received by the coil ch1, and when the coil ch2 adjacent to the coil ch1 is off, the signal is received by the coil ch1. 4 dB is added to the signal intensity of the B echo. The same correction is performed for the signal intensity of the B echo received by the coil ch8.

For example, when the electromagnetic ultrasonic probe 102 is placed on the steel plate 200, the coil is disconnected due to an impact when the electromagnetic ultrasonic probe 102 and the steel plate 200 come into contact with each other. It is possible. Even when an arbitrary coil is turned off due to such factors, it is possible to continuously perform defect inspection by performing the above-described correction on the signal intensity of the B echo.

  It is to be noted that the disconnection of the coil can be detected by flaw-detecting the plate (sample to be inspected) in which the above-described internal defect 202 of the reference level is artificially formed. At this time, since the F echo is not received in the disconnected coil, it can be diagnosed that a disconnection has occurred in the coil that does not receive the F echo.

As described above, according to the present embodiment, the signal intensity of the B echo received by each coil becomes a normal value (uniform value), and therefore the internal defect 202 is caused by an abnormal signal intensity (non-uniform signal intensity). It is possible to reliably prevent the overestimation of.

  In the above embodiment, when one of the coils adjacent to an arbitrary coil is off, 2 dB is added to the signal intensity of the B echo received by the arbitrary coil, and the coil adjacent to the arbitrary coil is added. When the two were off, correction was performed by adding 4 dB to the signal intensity of the B echo received by the above-mentioned arbitrary coil, but these correction amounts can be appropriately set according to the apparatus. Specifically, the characteristics of FIG. 8 are acquired in advance for levels 1 to 14, and each of a case where one of the coils adjacent to an arbitrary coil is off and a case where two of the coils adjacent to the arbitrary coil are off, respectively. , The reduction amount of the signal intensity of the B echo received by an arbitrary coil is measured, and a correction amount according to the reduction amount is set.

  In the above-described embodiment, the case where eight coils are arranged in a row for each electromagnetic ultrasonic probe 102 is described as an example, but the number of coils is not limited to eight. A plurality of coils may be arranged in a plurality of rows, and a plurality of coils may be arranged in a matrix. The number of electromagnetic ultrasonic probes 102 is not limited to 2 rows × 8. Also in these cases, each coil adjacent to an arbitrary coil is turned on / off, and the correlation between the on / off state of each adjacent coil and the decrease in the signal intensity of the B echo received by the arbitrary coil Is acquired in advance, the signal intensity of the B echo received by each coil can be corrected according to the operating state of each coil.

  Moreover, in the said embodiment, when one of the coils adjacent to an arbitrary coil is non-operating on the basis of the case where two of the coils adjacent to an arbitrary coil are operating, B received by an arbitrary coil Correction was performed by adding 2 dB to the echo signal intensity and adding 4 dB to the B echo signal intensity received by the arbitrary coil when two of the coils adjacent to the arbitrary coil are not operating.

On the other hand, you may correct | amend on the basis of the case where two of the coils adjacent to arbitrary coils are not operating. In this case, when one of the coils adjacent to an arbitrary coil is not operating, 2 dB is subtracted from the signal intensity of the B echo received by the arbitrary coil, and two of the coils adjacent to the arbitrary coil are not operating. In this case, 4 dB is subtracted from the signal intensity of the B echo received by an arbitrary coil. Even in this case, the signal intensity of the B echo received by each coil included in the electromagnetic ultrasonic probe 102 can be made uniform. However, it is common for two of the adjacent coils described above to be in operation. Therefore, the correction calculation processing (calculation time, etc.) tends to be slightly increased.

  As described above, the calculation device 110 includes the correction value acquisition unit 112, the operating state determination unit 114, the correction execution unit 116, the F / B calculation unit 117, the defect evaluation unit 118, and the correction value storage unit 119. It has.

The correction value acquisition unit 112 acquires the characteristics of FIG. 8 for the levels 1 to 14 in advance, and the signal intensity of the B echo received by the arbitrary coil with one of the coils adjacent to the arbitrary coil turned off. The amount of decrease is acquired as the first correction value. Further, the correction value acquisition unit 112 acquires, as the second correction value, the amount of decrease in the signal intensity of the B echo received by the arbitrary coil when two of the coils adjacent to the arbitrary coil are off.
The correction value storage unit 119 stores the first correction value and the second correction value acquired by the correction value acquisition unit 112.
As described above, the acquisition of the first correction value and the second correction value is performed using one electromagnetic ultrasonic probe 102 and a sample of the steel plate 200 in advance prior to actual defect inspection. Done experimentally.

The operating state determination unit 114 determines the operating states of the eight coils ch1 to ch8 for each electromagnetic ultrasonic probe 102.
The correction execution unit 116 performs correction according to the operation state determination result of each coil by the operation state determination unit 114. In the above-described example, when only one of the coils adjacent to the arbitrary coil is operating, the correction execution unit 116 sets the first correction value to the signal intensity of the B echo received by the arbitrary coil. As a result, 2 dB which is a preset value is added.
Further, when two of the coils adjacent to an arbitrary coil are not operating, the correction execution unit 116 sets a value set in advance as a second correction value for the signal intensity of the B echo received by the upper arbitrary coil. Add 4 dB.
The correction execution unit 116 sets the third correction value to zero when both coils adjacent to the arbitrary coil are operating, and the B echo signal received by the arbitrary coil. Do not correct the intensity. Note that each of the above corrections is performed for all the electromagnetic ultrasonic probes 102.

The F / B calculation unit 117 calculates a ratio (F / B ratio) between the signal intensity of the F echo and the corrected signal intensity of the B echo (F / B ratio) for each of the coils. The calculation of the F / B ratio is performed for all of the electromagnetic ultrasonic probes 102. The defect evaluation unit 118 evaluates the internal defect 202 of the steel plate 200 based on the F / B ratio calculation result by the F / B calculation unit 117.

  1 can be configured by a circuit (hardware) or a central processing unit such as a CPU and a program (software) for causing it to function.

[4. B Echo Signal Strength Correction Process According to this Embodiment]
FIG. 9 is a flowchart showing a process for correcting the signal intensity of the B echo according to the present embodiment. First, in step S10, the correction value acquisition unit 112 acquires the characteristics of FIG. 8 for the levels 1 to 14 in advance prior to actual defect inspection, and one of the coils adjacent to an arbitrary coil is in an off state. The amount of decrease in the received intensity of the B echo received by the arbitrary coil is acquired as the first correction value, and the B echo received by the arbitrary coil with two of the coils adjacent to the arbitrary coil turned off. Is obtained as the second correction value.

In the next steps S12 to S14, the operation state determination unit 114 determines the operation states of the eight coils ch1 to ch8 for each electromagnetic ultrasonic probe 102. Specifically, first, in step S12, it is determined whether or not both of the two coils adjacent to an arbitrary coil are inactive. If both of the two coils are not inactive, the process proceeds to step S14. When both of the two coils are not operating, the process proceeds to step S20, and the correction execution unit 116 adds the second correction value (4 dB) to the signal intensity of the B echo received by any coil.

  In step S <b> 14, the operating state determination unit 114 determines, for each electromagnetic ultrasonic probe 102, whether only one coil adjacent to an arbitrary coil is non-operating, and only one adjacent coil is detected. If is not in operation, the process proceeds to step S18. In step S18, the correction execution unit 116 adds the first correction value (2 dB) to the signal intensity of the B echo received by the arbitrary coil.

  In step S14, when one adjacent coil is not inactive, the process proceeds to step S16. In this case, since both of the two adjacent coils are operating, in step S16, the signal intensity of the B echo received by the arbitrary coil is not corrected. In other words, when the process proceeds to step S16, the correction execution unit 116 sets the third correction value to zero and does not correct the signal intensity of the B echo received by the arbitrary coil. After steps S16, S18, and S20, the process ends.

  As described above, according to the present embodiment, it is possible to compensate for the decrease in the signal intensity of the B echo due to the influence of adjacent coils, normalize the signal intensity of the B echo received by each coil, and make it uniform. Can be realized. Thereby, the rejection determination by the overdetection of the internal defect 202 can be reduced reliably. In addition, the S / N ratio can be improved even in a terminal coil having few adjacent coils, and the failure determination due to a pseudo defect can be greatly reduced.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Defect inspection apparatus 102 Electromagnetic ultrasonic probe 104 Amplifier 106 Measuring roll 108 Tip detection sensor 110 Calculation apparatus 112 Correction value acquisition part 114 Operation state determination part 116 Correction determination part 117 F / B calculation part (ratio calculation part)
118 Defect Evaluation Unit 119 Correction Value Storage Unit 120 Display Device 130 Alarm Device 200 Steel Plate (Inspection Object)
202 Internal defect 1-3, ch1-ch8 coil

Claims (9)

A first step of generating ultrasonic vibrations on an object to be inspected by applying a high-frequency signal to a plurality of coils arranged so as to partially overlap each other in the electromagnetic ultrasonic probe;
A second step of receiving the B echo of the ultrasonic vibration by each of the plurality of coils;
A third step of receiving an F echo of the ultrasonic vibration by each of the plurality of coils;
A fourth step of correcting the signal intensity of the B echo received by each of the plurality of coils based on an operating state of the plurality of coils;
A fifth step of calculating a ratio between the signal intensity of the F echo and the corrected signal intensity of the B echo for each of the plurality of coils, and evaluating an internal defect of the inspection object based on the calculation result When;
A defect inspection method characterized by comprising: In the fourth step,
When only one coil adjacent to an arbitrary coil is operating, the signal intensity of the B echo received by the arbitrary coil is corrected with the first correction value,
When two coils adjacent to the arbitrary coil are not operating, the signal intensity of the B echo received by the arbitrary coil is corrected with a second correction value,
When two coils adjacent to the arbitrary coil are operating, the signal intensity of the B echo received by the arbitrary coil is corrected with a third correction value.
The defect inspection method according to claim 1. The first correction value is smaller than the second correction value;
When two coils adjacent to the arbitrary coil are operating, the third correction value is set to zero, and the signal intensity of the B echo received by the arbitrary coil is not corrected. The defect inspection method according to claim 2, wherein: Before the first step,
The signal intensity of the B echo received by the arbitrary coil while two coils adjacent to the arbitrary coil are operating, and the state where only one coil adjacent to the arbitrary coil is operating Obtaining the first correction value based on a difference from the signal intensity of the B echo received by the arbitrary coil in the step;
In the state where the two coils adjacent to the arbitrary coil are operating, the signal intensity of the B echo received by the arbitrary coil, and the two coils adjacent to the arbitrary coil are not operating Obtaining the second correction value based on a difference from the signal intensity of the B echo received by the arbitrary coil;
The defect inspection method according to claim 3, further comprising: An electromagnetic ultrasound probe including a plurality of coils arranged adjacent to each other and partially overlapping;
Each of the plurality of coils is supplied with a high-frequency signal for generating ultrasonic vibration in the inspection object, and received by each of the plurality of coils based on the output signal of each of the plurality of coils. An arithmetic device that calculates the signal intensity of the F echo and the B echo of the ultrasonic vibration and evaluates an internal defect of the inspection object based on the calculation result;
With
The arithmetic unit is:
An operation state determination unit for determining operation states of the plurality of coils;
A correction execution unit for correcting the signal intensity of the B echo received by each of the plurality of coils based on the operating state of the plurality of coils;
A ratio calculation unit that calculates a ratio between the signal intensity of the F echo and the signal intensity of the corrected B echo for each of the plurality of coils;
A defect evaluation unit that evaluates internal defects of the inspection object based on the calculation result of the ratio by the ratio calculation unit;
A defect inspection apparatus comprising: The correction execution unit
When the operating state determination unit determines that only one coil adjacent to an arbitrary coil is operating, the signal intensity of the B echo received by the arbitrary coil is corrected with a first correction value. And
When the operating state determination unit determines that two coils adjacent to the arbitrary coil are not operating, the signal intensity of the B echo received by the arbitrary coil is corrected with a second correction value. And
When the operating state determination unit determines that two coils adjacent to the arbitrary coil are operating, the signal intensity of the B echo received by the arbitrary coil is corrected with a third correction value. The defect inspection apparatus according to claim 5, wherein: The first correction value is smaller than the second correction value;
When the operation state determination unit determines that two coils adjacent to the arbitrary coil are operating, the correction execution unit sets the third correction value to zero, and The defect inspection apparatus according to claim 6, wherein the signal intensity of the B echo received by the coil is not corrected. The arithmetic unit is:
The signal intensity of the B echo received by the arbitrary coil while two coils adjacent to the arbitrary coil are operating, and the state where only one coil adjacent to the arbitrary coil is operating The first correction value is acquired based on the difference from the signal intensity of the B echo received by the arbitrary coil in the state where the two coils adjacent to the arbitrary coil are operating. The difference between the signal intensity of the B echo received by an arbitrary coil and the signal intensity of the B echo received by the arbitrary coil when two coils adjacent to the arbitrary coil are not operating. The defect inspection apparatus according to claim 7, further comprising a correction value acquisition unit that acquires the second correction value based on the correction value acquisition unit.   The defect inspection apparatus according to claim 8, wherein the arithmetic device further includes a correction value storage unit that stores the first correction value and the second correction value acquired by the correction value acquisition unit. .

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