CN104755920B - Defect detecting method and flaw detection apparatus - Google Patents

Abstract

The defect inspection method includes: a first step of applying a high-frequency signal to a plurality of coils arranged adjacent to each other and partially overlapping in an electromagnetic ultrasonic probe to cause an object to be inspected to vibrate ultrasonically; a second step of vibrating the ultrasonic wave The B echoes of the above-mentioned multiple coils are respectively received by the above-mentioned multiple coils; the 3rd process, the F echoes of the above-mentioned ultrasonic vibration are respectively received by the above-mentioned multiple coils; The signal strengths of the respective received B echoes; in the fifth step, the ratios of the signal strengths of the F echoes to the corrected signal strengths of the B echoes are calculated for each of the plurality of coils, and the above-mentioned Inspect the internal defects of the object.

Description

Defect inspection method and defect inspection device

this application claims priority based on Japanese Patent Application No. 2012-278563 for which it applied to Japan on December 20, 2012, and uses the content here.

technical field

The invention relates to a defect inspection method and a defect inspection device.

Background technique

Conventionally, as one of the non-destructive inspection methods, there is known an electromagnetic ultrasonic flaw detection method for non-contact inspection of internal defects (inclusions, internal cracks, hydrogen-based defects, etc.) of an object to be inspected such as iron and steel materials using electromagnetic ultrasonic waves. For example, Patent Documents 1 and 2 below disclose an electromagnetic ultrasonic probe (EMAT) used for inspecting internal defects of an object to be inspected by the above-mentioned electromagnetic ultrasonic flaw detection method.

An electromagnetic ultrasonic probe disclosed in Patent Document 1 below includes a permanent magnet and an inductance coil suitable for forming a flaw detection pulse and receiving a reflected pulse. In addition, the electromagnetic ultrasonic probe disclosed in Patent Document 2 below includes a magnetizer for applying a bias magnetic field to the subject, and a plurality of sensors for transmitting ultrasonic waves to the subject and receiving ultrasonic waves reflected by the subject. coil.

In general, in the electromagnetic ultrasonic flaw detection method, internal defects are evaluated (classified) based on the height (signal strength) of the F echo (flaw echo) according to Japanese Industrial Standards (JIS G 0801). However, the F echo fluctuates 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 strength of the F echo increases by about 3 dB. Also, for example, if the gap between the surface of the inspection object and the coil changes from 0.5 mm to 1.0 mm, the signal strength of the F echo drops 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 internal defects based on the F echo.

Conventionally, in order to prevent erroneous evaluation of internal defects caused by the above-mentioned gap dependence of F echo, a ratio (F/B ratio) based on the signal strength of F echo to the signal strength of B echo (bottom echo) was used. ) method for evaluating internal defects. If the gap between the surface of the inspection object and the coil changes, the signal strengths of the F echo and the B echo will change, but by calculating the F/B ratio, the variation due to the gap included in the two echoes is canceled out. As a result, accurate evaluation of internal defects can be performed regardless of gap changes.

Patent Document 1: Japanese Patent No. 4842922

Patent Document 2: Japanese Patent Laid-Open No. 2005-214686

However, in conventional electromagnetic ultrasonic probes, when a plurality of coils for transmitting and receiving electromagnetic ultrasonic waves are arranged (in particular, when a plurality of coils are arranged adjacent to each other and partially overlapped), any It is possible for a coil to receive the reflected waves (F echo and B echo) of the electromagnetic ultrasonic wave that should be received by its adjacent coils.

As a result of the investigation by the present inventors, the signal strength of the adjacent F echo (the F echo that the adjacent coil should have received) received by any coil is so small as to be negligible, but the signal strength of the adjacent F echo received by any coil is negligible. The signal strength of the B echo (the B echo that should be received by the adjacent coil) is so large that it cannot be ignored.

That is, the signal strength of the B echo (adjacent B echo) which should be received by the adjacent coil is added to the signal strength of the B echo received by an arbitrary coil. Here, if the signal intensity of echoes for all coils B increases equally, the F/B ratio also changes for all coils in the same way, so there is no obstacle in the evaluation of internal defects based on the F/B ratio (as long as F/B It is sufficient to change the ratio and the evaluation reference value to be compared).

However, the amount of increase in the signal strength of the B echo 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 strength of the B echo received by the above-mentioned arbitrary coil is added to the signal strength of the adjacent two sides of the coil. The signal strength of the B echo that the two coils should have received.

In addition, for example, when one of the two coils adjacent to both sides of an arbitrary coil fails to operate due to a failure or the like, in the signal strength of the B echo received by the above-mentioned arbitrary coil, Only the signal strength of the B echo that should have been received by one of the two adjacent coils on both sides of the coil is added. Furthermore, for example, when both of the two adjacent coils on both sides of an arbitrary coil are not in operation, the signal strength of the B echo received by the above-mentioned arbitrary coil does not increase (that is, only an arbitrary The signal strength of the B echo that the coil should have received).

In addition, for example, among the coils in which a plurality of coils are arranged, there is only one adjacent coil. The coils other than the ends receive the B echoes that should be received by two adjacent coils, but the coils located at the ends receive only the B echoes that should be received by one adjacent coil. Therefore, the amount of increase in the signal strength of the B echo necessarily differs between the coils arranged at the ends and the coils arranged at other than the ends. This means that the signal strength 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.

In this way, when the amount of increase in the signal strength of the B echo differs from coil to coil depending on the operating state of each coil, it may be considered to evaluate internal defects based on the coil with the lowest signal strength of the B echo for the sake of safety. Methods. However, if this method is adopted, the internal defect will be over-evaluated about the other coils whose signal strength of the B echo is high. As a result, there is a possibility that the efficiency of the inspection process may decrease due to redundant inspections.

As described above, in the conventional electromagnetic ultrasonic probe, when a plurality of coils are arranged adjacent to each other and partially overlapped, it is difficult to accurately evaluate the internal defect of the inspection object.

Contents of the invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electromagnetic ultrasonic probe that can accurately evaluate inspection results even when a plurality of coils are arranged adjacent to each other and partially overlapped. A defect inspection method and a defect inspection device for internal defects of an object.

In order to solve the above-mentioned problems and achieve the object, the present invention adopts the following means. which is,

(1) The defect inspection method according to one aspect of the present invention includes: a first step of applying a high-frequency signal to a plurality of coils arranged adjacent to each other and partially overlapping in the electromagnetic ultrasonic probe to cause the object to be inspected to generate Ultrasonic vibration; the 2nd process, the B echo of the above-mentioned ultrasonic vibration is received respectively with the above-mentioned multiple coils; the 3rd process, the F echo of the above-mentioned ultrasonic vibration is received respectively with the above-mentioned multiple coils; The signal strengths of the above-mentioned B echoes received by the coils are corrected based on the working states of the above-mentioned multiple coils; the fifth process is to calculate the signal strength of the above-mentioned F echoes and the corrected B-echo signal strengths for the above-mentioned multiple coils respectively. The ratio of the signal intensity is used to evaluate the internal defect of the inspection target object based on the calculation result.

(2) In the defect inspection method described in the above (1), in the above-mentioned fourth step, when only one coil adjacent to any coil is operating, the above-mentioned arbitrary coil may be The signal strength of the above-mentioned B echo received is corrected with the first correction value; when the two coils adjacent to the above-mentioned arbitrary coil are not working, the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil Correction with the second correction value; when two coils adjacent to the above-mentioned arbitrary coil are operating, the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil is corrected with the third correction value.

(3) In the defect inspection method described in the above (2), the first correction value may be smaller than the second correction value. In addition, when two coils adjacent to the above-mentioned arbitrary coil are operating, the above-mentioned third correction value may be set to zero, and the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil may not be corrected. .

(4) In the defect inspection method described in the above (3), before the above-mentioned first step, it is also possible to further include: based on the above-mentioned arbitrary coil in the state where the two adjacent coils are operating The difference between the signal strength of the above-mentioned B echo received by the coil and the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil when only one coil adjacent to the above-mentioned arbitrary coil is in operation, and the above-mentioned The process of the first correction value: the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil is the same as that of the two adjacent coils adjacent to the above-mentioned arbitrary coil. A step of obtaining the second correction value from the difference in signal strength of the B echo received by the arbitrary coil in a state where the coils are not in operation.

(5) A defect inspection device related to a technical solution of the present invention includes: an electromagnetic ultrasonic probe including a plurality of coils arranged adjacent to each other and partially overlapped; The object generates a high-frequency signal of ultrasonic vibration, and based on the respective output signals of the plurality of coils, calculates the signal strength of the F echo and B echo of the ultrasonic vibration received by the plurality of coils, and evaluates the The internal defect of the above-mentioned inspection object; the above-mentioned calculation device has: an operation state determination part, which determines the operation state of the above-mentioned multiple coils; a correction execution part, based on the operation state of the above-mentioned multiple coils, respectively receives the The signal strength of the B echo is corrected; the ratio calculation unit calculates the ratio of the signal strength of the F echo to the corrected signal strength of the B echo for each of the plurality of coils; the defect evaluation unit calculates the ratio based on the ratio. Evaluate the internal defects of the above-mentioned inspection object based on the calculation result of the above-mentioned ratio of the department.

(6) In the defect inspection device described in the above (5), the correction execution unit may, when the operation state determination unit determines that only one coil adjacent to any coil is operating, The signal strength of the above-mentioned B echo received by the coil is corrected with the first correction value. In addition, the correction execution unit may use the signal strength of the B echo received by the arbitrary coil as the signal strength of the B echo received by the arbitrary coil when the operating state determining unit determines that the two coils adjacent to the arbitrary coil are not in operation. 2 correction value correction. Furthermore, the correction executing unit may use the signal strength of the B echo received by the arbitrary coil as the second coil when the operating state determining unit determines that two coils adjacent to the arbitrary coil are operating. 3 correction value correction.

(7) In the defect inspection device described in the above (6), the first correction value may be smaller than the second correction value. In addition, the correction execution unit may set the third correction value to zero when the operating state determination unit determines that two coils adjacent to the arbitrary coil are operating, and may not set the third correction value to zero by the arbitrary coil. Signal strength correction of the received B-echo above.

(8) In the defect inspection device described in (7) above, the computing device may further include a correction value acquisition unit based on the above-mentioned arbitrary coil being operated while two coils adjacent to the above-mentioned arbitrary coil are operating. The difference between the signal strength of the above-mentioned B echo received by the coil and the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil when only one coil adjacent to the above-mentioned arbitrary coil is in operation is obtained. The first correction value is based on the difference between the signal strength of the above-mentioned B echo received by the above-mentioned arbitrary coil when the two coils adjacent to the above-mentioned arbitrary coil are working. The second correction value is obtained from the difference in the signal strength of the B echo received by the arbitrary coil in the state where the coil is not in operation.

(9) In the defect inspection device described in (8) above, the calculation device may further include a correction value storage unit that stores the first correction value and the second correction value acquired by the correction value acquisition unit.

The effect of the invention

According to the above-mentioned aspect, even when the electromagnetic ultrasonic probe has a structure in which a plurality of coils are arranged adjacent to each other and partially overlapped, it is possible to accurately evaluate the internal defect of the object to be inspected.

Description of drawings

FIG. 1 is a schematic diagram showing the configuration of a defect inspection device 100 according to one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state viewed from the direction of arrow A2 in FIG. 1 .

3A is a diagram showing the relationship between the flaw detection position of the steel plate 200 and the signal strengths of F echoes and B echoes received by the coil provided in the electromagnetic ultrasonic probe 102 .

FIG. 3B is a graph showing the relationship between the flaw detection position of the steel plate 200 and the F/B ratio.

FIG. 4 is a schematic diagram showing a defect map of the steel sheet 200 .

FIG. 5 is a schematic diagram showing how the ultrasonic vibration generated in the steel plate 200 by the electromagnetic ultrasonic probe 102 propagates inside the steel plate 200 .

FIG. 6 is a plan view showing the coils 1 to 3 provided in the electromagnetic ultrasonic probe 102 viewed from the direction of arrow A3 in FIG. 5 .

7 is a schematic diagram showing 14 examples (levels 1 to 14) in which the eight coils provided in the electromagnetic ultrasonic probe 102 are represented as ch1 to ch8, and the transmission of ultrasonic waves in each ch is turned on or off.

FIG. 8 is a characteristic diagram showing the values (dB) of the signal strengths (dB) of the B echo of the coil ch4 which is the data acquisition target ch, respectively, measured for the levels 1 to 14 shown in FIG. 7 .

FIG. 9 is a flowchart showing correction processing of the signal strength of the B echo.

detailed description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in this specification and drawings, the same code|symbol is attached|subjected to the component which has substantially the same functional structure, and repeated description is abbreviate|omitted.

[1. Configuration example of electromagnetic ultrasonic device]

First, the configuration of a defect inspection device (electromagnetic ultrasonic device: EMAT) 100 according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2 . FIG. 1 is a schematic diagram showing the configuration of a defect inspection device 100 . The defect inspection device 100 includes an electromagnetic ultrasonic probe 102 including a plurality of (e.g., eight) coils arranged adjacent to each other and partially overlapped, an amplifier 104 (not shown in FIG. 1 ), a measuring roller 106, and a tip detection sensor. 108 , computing device 110 , display device 120 and alarm device 130 .

The steel plate 200 to be inspected is placed on the plate passing table, and is conveyed in the direction of arrow A1 in FIG. 1 by driving the rollers of the plate passing table. The electromagnetic ultrasonic probe 102 detects the internal defect 202 of the steel plate 200 by transmitting and receiving the electromagnetic ultrasonic wave by the above-mentioned eight coils, and a plurality of them are arranged in the width direction of the steel plate 200 .

As shown in FIG. 1 , for example, two rows of electromagnetic ultrasonic probes 102 are arranged in the conveying direction of the steel plate 200 , and eight electromagnetic ultrasonic probes 102 are arranged in the upstream and downstream rows of the conveying direction. In addition, 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, and the downstream electromagnetic ultrasonic probes 102 are located on the adjacent upstream side. The middle of the electromagnetic ultrasonic probe 102 .

By arranging the plurality of electromagnetic ultrasonic probes 102 in a zigzag shape, internal defects 202 located between the electromagnetic ultrasonic probes 102 that cannot be detected by the upstream electromagnetic ultrasonic probes 102 can be reliably detected by the downstream electromagnetic ultrasonic probes 102 .

FIG. 2 is a schematic diagram showing a state viewed from the direction of arrow A2 in FIG. 1 . As shown in FIG. 2 , the electromagnetic ultrasonic probe 102 is disposed close to the upper portion of the steel plate 200 . Air is supplied from the bottom surface of the electromagnetic ultrasonic probe 102 toward the steel plate 200, and the gap between the bottom surface of the electromagnetic ultrasonic probe 102 and the steel plate 200 is adjusted to about 0.5 mm by the air. Furthermore, the amplifier 104 is arranged above the electromagnetic ultrasonic probe 102, and amplifies the detection signal output from the electromagnetic ultrasonic probe 102 (specifically, the output signal of each coil provided in the electromagnetic ultrasonic probe 102).

The electromagnetic ultrasonic probe 102 generates ultrasonic vibrations on the surface of the steel plate 200 with the coils, and detects eddy currents generated by the ultrasonic waves reflected from the bottom surface of the steel plate 200 vibrating under the static magnetic field with the coils. Thereby, the echo level (B echo) of the ultrasonic vibration reflected by the bottom surface is detected. In addition, when the internal defect 202 shown in FIG. When an internal defect 202 occurs, since the echo level (F echo) of the reflected ultrasonic vibration changes, it is based on the ratio of the signal strength of the F echo to the signal strength of the B echo (F/B ratio) , the internal defect 202 can be evaluated (classified).

The arithmetic unit 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 high-frequency currents for generating ultrasonic vibrations in the steel plate 200 to each of the eight coils provided in the electromagnetic ultrasonic probes 102 .

In addition, the arithmetic unit 110 calculates the F echo and the B echo of the ultrasonic vibrations received by each coil based on the output signals of the electromagnetic ultrasonic probes 102 (that is, the output signals of the coils provided on the electromagnetic ultrasonic probes 102 ). Based on the signal intensity of the wave, 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 , a defect evaluation unit 118 and a correction value storage unit 119 .

The operating state determination unit 114 determines the operating states of all the eight coils for each electromagnetic ultrasonic probe 102 . Specifically, this operation state determination part 114 has the self-diagnosis function which determines that the coil which cannot detect an F echo and a B echo is malfunctioned (that is, a non-operation state).

The correction execution unit 116 corrects the signal strength of the B echo received by each coil based on the determination result of the operation state of each coil obtained by the operation state determination unit 114 .

The details will be described later, but when the operation state determination unit 114 determines that only one coil adjacent to any coil is operating among the eight coils, the correction execution unit 116 transmits the B echo received by the above-mentioned arbitrary coil The signal strength of is corrected with the first correction value.

In addition, when the operation state determination unit 114 determines that the two coils adjacent to the above-mentioned arbitrary coil are not in operation, the correction execution unit 116 uses the second correction method to correct the signal strength of the B echo received by the above-mentioned arbitrary coil. value correction.

Furthermore, when the operation state determination part 114 judges that two coils adjacent to the above-mentioned arbitrary coil are operating, the correction executing part 116 uses the third correction value for the signal strength of the B echo received by the above-mentioned arbitrary coil. fix.

In addition, each of the corrections described above is performed on all the electromagnetic ultrasonic probes 102 .

The F/B calculating part 117 calculates the F/B ratio of the signal intensity|strength of F echo and the signal intensity|strength of the corrected B echo for each coil. In addition, the calculation of the F/B ratio is performed for all the electromagnetic ultrasonic probes 102 . The defect evaluation unit 118 evaluates the internal defect 202 of the steel sheet 200 based on the calculation result of the F/B ratio obtained by the F/B calculation unit 117 .

The correction value acquisition unit 112 is based on the signal strength of the B echo received by the arbitrary coil when two coils adjacent to the arbitrary coil among the eight coils are operating, The first correction value is obtained from the difference in the signal strength of the B echo received by the above-mentioned arbitrary coil in the state where one adjacent coil is in operation.

In addition, the correction value acquisition unit 112 is based on the signal strength of the B echo received by the above-mentioned arbitrary coil when the two coils adjacent to the above-mentioned arbitrary coil are operating. The second correction value is obtained from the difference in the signal strength of the B echo received by the arbitrary coil in the state where the two coils are not in operation.

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, prior to the actual defect inspection, the acquisition of the above-mentioned first correction value and second correction value is experimentally performed in advance using one electromagnetic ultrasonic probe 102 and a sample of the steel plate 200 as an inspection object. The details of how to obtain the first correction value and the second correction value will be described later.

The display device 120 displays the evaluation results (ranking) of the internal defects 202 based on the evaluation results of the internal defects 202 obtained by the arithmetic device 110 . Furthermore, the alarm device 130 issues an alarm when the F/B ratio of the internal defect 202 exceeds a reference value. The steel plate 200 in which the internal defect 202 exceeding the reference value was detected is separated from the normal conveyance path and inspected in more detail.

FIG. 3A shows the relationship between the flaw detection position in the conveyance direction of the steel plate 200 and the signal intensities of the F echo and the B echo. In addition, FIG. 3B shows the relationship between the flaw detection position and the F/B ratio. As shown in FIG. 3A , when an internal defect 202 occurs in the steel plate 200 , the signal strength of the F echo increases and the signal strength of the B echo decreases depending on the size of the internal defect 202 .

As a result, as shown in FIG. 3B , the F/B ratio increases at the flaw detection location where the internal defect 202 occurs compared to the flaw detection location where the internal defect 202 does not occur. And, the larger the internal defect 202 is, the more the F/B ratio increases. Therefore, it is possible to detect whether or not the internal defect 202 has occurred based on the F/B ratio, and further, it is possible to evaluate the size and position of the internal defect 202 .

In addition, if the gap between the electromagnetic ultrasonic probe 102 and the surface of the steel plate 200 changes, the signal strength of the B echo and the F echo changes, but by calculating the F/B ratio, the B echo and the F echo caused by the change of the gap can be calculated. The amount of change in the signal strength of the echo cancels out. Furthermore, by evaluating the internal defect 202 based on the F/B ratio, even when noise is included in the F echo and the B echo, the amount of noise can be canceled out, and the internal defect 202 can be evaluated with high precision.

Detection signals output from a plurality of electromagnetic ultrasonic probes 102 arranged in the width direction of the steel plate 200 are transmitted to the computing device 110 . In addition, the position signal output from the measurement roller 106 which measures the position of the front-end|tip of the steel plate 200 is also transmitted to the arithmetic unit 110 .

The front end detection sensor 108 detects the front end position of the steel plate 200 , and this front end position becomes a reference when the measuring roller 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 showing the occurrence positions of the internal defects 202 in the steel sheet 200 as shown in FIG. 4 .

The width of one electromagnetic ultrasonic probe 102 in the steel plate width direction 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, as described above, the electromagnetic ultrasonic probes 102 are arranged in two rows in the conveyance direction of the steel plate 200, and are arranged in a zigzag arrangement so that the positions in the width direction of the steel plate 200 are different from each other in the two rows. .

The calculation device 110 synchronizes the detection signals output from the plurality of electromagnetic ultrasonic probes 102 arranged in this way with the position of the steel plate 200 moving on the plate passing table that has acceleration and deceleration to convey the steel plate 200, to identify the correct defect position, and to make A defect map as shown in Figure 4. Thereby, it is possible to instantly grasp at which position in the conveying direction of the steel plate 200 the internal defect 202 of what magnitude has occurred.

[2. The influence of adjacent coils on the detection value]

FIG. 5 is a schematic diagram showing how the 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. In FIG. 5 , only three coils 1 to 3 are representatively shown in the eight coils. The coils 1 to 3 transmit and receive ultrasonic waves simultaneously in synchronization.

FIG. 6 is a plan view of the three coils 1 to 3 viewed from the arrow A3 direction in FIG. 5 . In FIG. 5 , for convenience of illustration, the three coils 1 to 3 are illustrated as being arranged at certain intervals without overlapping, but actually as shown in FIG. 6 , the three coils 1 to 3 are adjacent to each other and partly overlapped. way to configure. In addition, eight coils including three coils 1 to 3 are arranged in a row on a printed circuit board (FPC) not shown.

As shown in FIG. 5 , in the electromagnetic ultrasonic probe 102 , permanent magnets 102 a are provided corresponding to the coils 1 to 3 . For example, focusing on the coil 2 , by supplying a high-frequency current to the coil 2 , a magnetic field M1 fluctuating at high frequency is generated on the surface of the steel sheet 200 . Then, an induced current I ₁ is generated on the surface of the steel sheet 200 in a direction that cancels out the magnetic field M1 . Then, the Lorentz force F is generated by the current _I1 flowing into the conductor (steel plate 200) within the static magnetic field M2 formed by the permanent magnet 102a. This Lorentz force F fluctuates synchronously with the high-frequency current flowing through the coil 2 , so the surface of the steel plate 200 vibrates due to the Lorentz force F, thereby generating ultrasonic vibrations.

As shown in FIG. 5 , the ultrasonic vibration generated by the coil 2 is reflected on the bottom surface of the steel plate 200 . The echo level (B echo) of the ultrasonic wave of the coil 2 reflected by the bottom surface is received by the coil 2 generating the ultrasonic vibration, and is also received by the coils 1 and 3 adjacent to the coil 2 . This is because ultrasonic waves propagate far away due to diffusion, and adjacent coils partially overlap each other as shown in FIG. 6 .

In addition, 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 echoes and B echoes) by detecting eddy currents generated by the reflected ultrasonic waves vibrating under the static magnetic field of the permanent magnet 102 .

Since the coils 1, 3 and coil 2 transmit and receive ultrasonic waves synchronously, the coil 2, in addition to the B echo of the ultrasonic vibration generated by itself, also receives the B echo of the ultrasonic vibration generated by the two adjacent coils 1, 3. Wave.

On the other hand, for example, when the coil 1 is located at the end of eight coils, the only coil adjacent to the coil 1 is 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 strength of the B echo received by the coil 1 becomes smaller than the signal strength of the B echo received by the coil 2 .

When an internal defect 202 occurs in the steel plate 200, the ultrasonic vibration is reflected by the internal defect 202, and the F echo is received by each coil. Since the area of the internal defect 202 receiving ultrasonic vibration is smaller than the area of the bottom surface of the steel plate 200 receiving ultrasonic vibration, the F echo is less affected by the ultrasonic waves of adjacent coils. In addition, since the propagation distance of the F echo until it is received by the coil is shorter than that of the B echo, the influence of adjacent coils on the F echo is small. Therefore, the signal strengths of the F echoes received by the coils 1 to 3 are substantially at the same level.

In this way, the signal strength of the adjacent F echo received by any coil (the F echo that the adjacent coil should have received) is so small that it can be ignored, but the adjacent B echo received by any coil (the adjacent F echo The signal strength of the B echo that the coil should have received) is too large to be ignored.

Therefore, in the case of evaluating the internal defect 202 based on the F/B ratio, since the signal strength of the B echo received by the coil 1 is smaller than the signal strength of the B echo received by the coils 2 and 3, the coil 1 and the Coils 2 and 3 have an excessively large F/B ratio.

In this way, in the electromagnetic ultrasonic probe 102, since a plurality of coils are adjacent to each other and arranged in a partially overlapping manner, any coil receives the B echo that should be received by itself and other coils adjacent to it. The B echo. In addition, due to the influence of electric fields generated from other coils, it is not possible to shift the timing of generating ultrasonic waves in each coil. Therefore, any coil will definitely receive the B echo that should be received by the adjacent coil.

An underestimation of the internal defect 202 cannot detect the internal defect 202 and leads to the outflow of the defective steel plate 200 . Therefore, the reference size for recognizing the internal defect 202 is set, and the F/B ratio of the coil whose F/B ratio value is the lowest value is used as the determination threshold.

Accordingly, the F/B ratio when the reference size is detected by other coils becomes equal to or greater than the determination threshold, and it is possible to reliably prevent the internal defect 202 from being undetected due to underestimation. In the example shown in FIG. 5 , since the F/B ratio of the coil 2 is lower than the F/B ratio of the coil 1 , the F/B ratio when the coil 2 detects the standard size becomes the judgment threshold. In this case, at least the F/B ratio of the coil 1 is higher than the F/B ratio of the coil 2, so if the evaluation based on the F/B ratio of the coil 1 is performed, the internal defect 202 will be overestimated. Thus, 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 structural example of this embodiment]

In this embodiment, in order to suppress the influence of adjacent coils on any coil, the signal strength of the B echo received by each coil is corrected according to the working state of each coil. FIG. 7 represents 8 coils as ch1 to ch8, and shows 14 examples (levels 1 to 14) of turning on (ON: active state) or off (OFF: non-operating state) the transmission of ultrasonic waves of each ch. The coil ch4 is a coil to be collected for detecting B echo data, and is always on. FIG. 8 is a characteristic diagram showing the value (dB) of the signal intensity of the B echo of the coil ch4 which is the data collection object ch, which is actually measured for each of the levels 1 to 14 shown in FIG. 7 .

At level 1 in FIG. 7 , the case where all the ultrasonic transmissions of the eight coils (ch1 to 8) are turned on is shown. Level 2 indicates a case where only the coil ch1 at the left end is turned off and the other coils are turned on. Level 3 indicates a case where the coils ch1 and ch8 at both ends are turned off, and the other coils are turned on. Within level 8 after level 4, the coils that are farther from the coil ch4 are closed sequentially. In addition, at level 9, it shows that all other than the coil ch4 are turned off. Furthermore, levels 9 and later indicate that one of the outer coils of ch3 and ch5 is sequentially turned on.

In the present embodiment, as shown in FIG. 8 , compared to the case where two ch3 and 5 adjacent to ch4 are on (levels 1 to 6), one of ch3 and 5 adjacent to ch4 is on. In the cases (levels 7 and 8), a 2dB drop occurs in the signal strength of the B echo. In addition, it can be seen that when both ch adjacent to ch4 are turned off (levels 9 to 14), a 4 dB drop occurs in the signal strength of the B echo.

In addition, in Fig. 7, the coil of the data acquisition target is set to ch4, but in the case of detecting with ch1 or ch8 located at both ends, since there is only one adjacent coil of ch1 or ch8, the 1 always closed (non-working state) case is equivalent. Therefore, in the coil ch1, even if the adjacent coil ch2 is turned on, a 2 dB drop occurs in the signal strength of the B echo.

In addition, regarding the coil ch1, when the adjacent coil ch2 is turned off, a 4 dB drop occurs in the signal strength of the B echo. Similarly, regarding the coil ch8, even if the adjacent coil ch7 is turned on, a 2 dB drop occurs in the signal strength of the B echo, and a 4 dB drop occurs when the adjacent coil ch7 is turned off. As described above, regarding the coils located at the ends, it can be seen that even if the adjacent coils are normal, the signal strength of the B echo decreases.

When evaluating the internal defect 202, a difference of 4 dB in the signal strength of the B echo corresponds to the difference between a mild defect and a moderate defect. When evaluating the internal defect 202 according to the standard corresponding to JIS G 0801, this difference is a level which cannot be ignored in practice. Therefore, since the difference in the signal strength of the B echo affects the evaluation level of the internal defect 202, it is necessary to reliably suppress excessive evaluation of the signal strength.

Based on the above results, in this embodiment, the signal strength of the B echo received by each coil is corrected according to the operating state of each coil. Thereby, the signal intensity of the B echo received by each coil is equalized, and the error of the detection level of the internal defect 202 in the case of evaluation based on F/B ratio can be eliminated, and the evaluation of the internal defect 202 can be stabilized.

Specifically, in the example shown in FIG. 8 , when only one of the coils adjacent to any coil is in the active state (on), the signal of the B echo received by the above-mentioned arbitrary coil 2dB is added to the strength, and 4dB is added to the signal strength of the B echo received by the above-mentioned arbitrary coil when two of the coils adjacent to the above-mentioned arbitrary coil are in the non-operating state (off).

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

As a cause for the coil to be closed, for example, when the electromagnetic ultrasonic probe 102 is placed on the steel plate 200 , the coil may be disconnected due to an impact when the electromagnetic ultrasonic probe 102 contacts the steel plate 200 . Even when an arbitrary coil is turned off for such a reason, defect inspection can be continuously performed by performing the above-mentioned correction on the signal strength of the B echo.

In addition, a coil disconnection can be detected by performing flaw detection on a plate (sample of an inspection target object) in which the internal defect 202 of the above-mentioned reference level is artificially formed. At this time, since the F echo cannot be received by the disconnected coil, it can be diagnosed that a disconnection occurred in the coil which did not receive the F echo.

As described above, according to this embodiment, since the signal strength of the B echo received by each coil is a normal value (uniform value), it is possible to reliably suppress the passing of abnormal signal strength (non-uniform signal strength). Intensity) for excessive evaluation of internal defects 202.

In addition, in the above-mentioned embodiment, when one of the coils adjacent to any coil is turned off, 2dB is added to the signal strength of the B echo received by the above-mentioned arbitrary coil. When two adjacent coils are turned off, a correction of 4 dB is added to the signal strength of the B echo received by any of the above-mentioned coils, but these correction amounts can be appropriately set according to the device. Specifically, the characteristics of FIG. 8 are obtained in advance for levels 1 to 14, and when one of the coils adjacent to an arbitrary coil is off, and when two of the coils adjacent to an arbitrary coil are off In each case, the amount of decrease in the signal strength of the B echo received by an arbitrary coil is measured, and a correction amount matching the amount of decrease is set.

In addition, in the above-mentioned embodiment, the case where eight coils are arranged in a row in each of the electromagnetic ultrasonic probes 102 has been described as an example, but the number of coils is not limited to eight. In addition, a plurality of coils may be arranged in a plurality of rows, and a plurality of coils may also be arranged in a matrix. The number of electromagnetic ultrasonic probes 102 is not limited to 2 rows×8. Also in these cases, by turning on/off each coil adjacent to an arbitrary coil, the ON/OFF state of each adjacent coil and the decrease amount of the signal strength of the B echo received by an arbitrary coil are obtained in advance. According to the correlation of each coil, the signal strength of the B echo received by each coil can be corrected.

In addition, in the above-mentioned embodiment, based on the case where two of the coils adjacent to an arbitrary coil are in operation, when one of the coils adjacent to an arbitrary coil is inactive, the Add 2dB to the signal strength of the B echo received by the coil, and add 4dB to the signal strength of the B echo received by the arbitrary coil when two of the coils adjacent to the arbitrary coil are not in operation fix.

On the other hand, correction may be performed based on the fact that two coils adjacent to an arbitrary coil do not operate. In this case, when one of the coils adjacent to the arbitrary coil is not in operation, 2dB is subtracted from the signal strength of the B echo received by the arbitrary coil, and in the adjacent to the arbitrary coil When two of the coils are not in operation, 4 dB is subtracted from the signal strength of the B echo received by any coil. Also in this case, the signal strength of the B echoes received by the coils included in the electromagnetic ultrasonic probe 102 can be made uniform. However, it is usually the case that two of the aforementioned adjacent coils are in operation. This tends to slightly increase the correction calculation processing (calculation time, etc.).

As described above, the computing 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 117 , a defect evaluation unit 118 , and a correction value storage unit 119 .

The correction value acquiring unit 112 acquires the characteristics of FIG. 8 with respect to levels 1 to 14 in advance, and acquires the signal strength of the B echo received by an arbitrary coil when one of the coils adjacent to the arbitrary coil is in a closed state. The amount of decrease is taken as the first correction value. Moreover, the correction value acquisition part 112 acquires the fall amount of the signal intensity|strength of the B echo received by an arbitrary coil in the state where two coils adjacent to an arbitrary coil are closed, as a 2nd correction value.

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, as described above, prior to the actual defect inspection, the acquisition of the first correction value and the second correction value is experimentally performed in advance using one electromagnetic ultrasonic probe 102 and a sample of the steel plate 200 .

The operation state determination unit 114 determines the operation states of the eight coils ch1 to ch8 for each electromagnetic ultrasonic probe 102 .

The correction executing unit 116 executes correction based on the operation state determination result of each coil obtained by the operation state determination unit 114 . In the above example, when only one of the coils adjacent to any coil is in operation, the correction execution unit 116 adds the signal strength of the B echo received by the above-mentioned arbitrary coil as the first correction value. The preset value is 2dB.

In addition, when two of the coils adjacent to an arbitrary coil are not in operation, the correction execution unit 116 adds 4 dB, which is a preset value, to the signal strength of the B echo received by an arbitrary upper coil as the second value. 2 correction value.

In addition, when both the coils adjacent to an arbitrary coil operate, the correction execution part 116 sets the 3rd correction value to zero, and does not change the signal strength of the B echo received by the said arbitrary coil fix. In addition, each of the corrections described above is performed on all the electromagnetic ultrasonic probes 102 .

The F/B calculating part 117 calculates the ratio (F/B ratio) of the signal intensity|strength of the F echo and the signal intensity|strength of the corrected B echo for each coil. In addition, the calculation of the F/B ratio is performed for all the electromagnetic ultrasonic probes 102 . The defect evaluation unit 118 evaluates the internal defect 202 of the steel sheet 200 based on the calculation result of the F/B ratio obtained by the F/B calculation unit 117 .

In addition, the components of the computing device 110 shown in FIG. 1 may be constituted by a circuit (hardware), a central processing unit such as a CPU, and a program (software) for functioning.

[4. Correction processing of signal strength of B echo in this embodiment]

FIG. 9 is a flowchart showing the correction processing of the signal strength 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 in advance with respect to levels 1 to 14 before the actual defect inspection, and acquires a condition in which one of the coils adjacent to an arbitrary coil is closed. The drop amount of the reception strength of the B echo received by the arbitrary coil is used as a first correction value, and the B echo received by the arbitrary coil is obtained when two coils adjacent to the arbitrary coil are closed. The decrease amount of the wave signal strength is used as the second correction value.

In subsequent 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, and when it is not the case that both of the two coils are inactive, the process proceeds to step S14. When both of the two coils are inactive, the process proceeds to step S20, and the correction execution unit 116 adds the second correction value (4 dB) to the signal strength of the B echo received by an arbitrary coil.

In step S14, the operating state determination unit 114 determines whether only one coil adjacent to any coil is inactive for each electromagnetic ultrasonic probe 102, and when only one adjacent coil is inactive, the process proceeds to step S14. S18 forward. In step S18, the correction executing part 116 adds the 1st correction value (2dB) to the signal strength of the B echo received by the said arbitrary coil.

In step S14, when not one adjacent coil is inactive, it progresses to step S16. In this case, since both of the adjacent two coils operate, in step S16, the correction of the signal strength of the B echo received by the said arbitrary coil is not performed. In other words, when advancing to step S16, the correction execution part 116 sets the 3rd correction value to zero, and does not perform correction of the signal strength of the B echo received by the said arbitrary coil. The process ends after steps S16, S18, and S20.

As described above, according to this embodiment, it is possible to compensate for the decrease in the signal strength of the B echo due to the influence of adjacent coils, and to normalize and equalize the signal strength of the B echo received by each coil. . Thereby, it is possible to reliably reduce the failure determination due to over-detection of the internal defect 202 . In addition, the S/N ratio can be improved also in the coil at the end where there are few adjacent coils, and it is possible to greatly reduce the failure judgment due to the pseudo-defect.

As above, preferred embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to such examples. Apparently, as long as a person with ordinary knowledge in the technical field described in the present invention can conceive of various modifications or amendments within the scope of the technical ideas described in the technical claims, it should be understood that they are also of course Belong to the technical scope of the present invention.

Label description

100 defect inspection device

102 Electromagnetic ultrasonic probe

104 amplifiers

106 measuring roller

108 Front detection sensor

110 computing device

112 Correction value acquisition part

114 Work Status Judgment Department

116 Correction Judgment Department

117 F/B calculation unit (ratio calculation unit)

118 Defect Evaluation Department

119 Correction value storage unit

120 display device

130 alarm device

200 steel plate (inspection object)

202 Internal defects

1～3, ch1～ch8 Coils

Claims (9)

1. a defect detecting method, it is characterised in that have:

1st operation, to electromagnetic ultrasonic wave pop one's head in the most adjacent and by a part coincidence in the way of arrange Multiple coils of row give high-frequency signal, make inspection object produce ultrasonic activation；

2nd operation, receives with above-mentioned multiple coils respectively by the B echo of above-mentioned ultrasonic activation；

3rd operation, receives with above-mentioned multiple coils respectively by the F echo of above-mentioned ultrasonic activation；

4th operation, duty corrections based on above-mentioned multiple coils are connect respectively by above-mentioned multiple coils The signal intensity of the above-mentioned B echo received；And

5th operation, after calculating signal intensity and the correction of above-mentioned F echo respectively to above-mentioned multiple coils The ratio of signal intensity of above-mentioned B echo, evaluate above-mentioned inspection object based on this result of calculation Internal flaw.

2. defect detecting method as claimed in claim 1, it is characterised in that

In above-mentioned 4th operation,

In the case of only 1 coil adjacent with arbitrary coil works, will by above-mentioned arbitrarily Signal intensity the 1st correction value correction of above-mentioned B echo that receives of coil；

In the case of two coils adjacent with above-mentioned arbitrary coil do not work, will be by above-mentioned Signal intensity the 2nd correction value correction of the above-mentioned B echo that the coil of meaning receives；

In the case of two coils adjacent with above-mentioned arbitrary coil work, will be by above-mentioned Signal intensity the 3rd correction value correction of the above-mentioned B echo that the coil of meaning receives.

3. defect detecting method as claimed in claim 2, it is characterised in that

Above-mentioned 1st correction value is less than above-mentioned 2nd correction value；

In the case of two coils adjacent with above-mentioned arbitrary coil work, by the above-mentioned 3rd Correction value is set as zero, and the signal not revising the above-mentioned B echo received by above-mentioned arbitrary coil is strong Degree.

4. defect detecting method as claimed in claim 3, it is characterised in that

Before above-mentioned 1st operation, also have:

Based on when two coils adjacent with above-mentioned arbitrary coil work by above-mentioned The signal intensity of above-mentioned B echo that the coil of meaning receives with adjacent only with above-mentioned arbitrary coil The signal of the above-mentioned B echo that 1 coil is received by above-mentioned arbitrary coil when work is strong The difference spent, the operation obtaining above-mentioned 1st correction value；

Based on when two coils adjacent with above-mentioned arbitrary coil work by above-mentioned The signal intensity of above-mentioned B echo that the coil of meaning receives with adjacent with above-mentioned arbitrary coil two The signal intensity of the above-mentioned B echo received by above-mentioned arbitrary coil under the idle state of individual coil Difference, obtain the operation of above-mentioned 2nd correction value.

5. a flaw detection apparatus, it is characterised in that

Possess:

Electromagnetic ultrasonic wave is popped one's head in, including multiple lines that are the most adjacent and that arrange in the way of part coincidence Circle；

Arithmetic unit, is supplied respectively to for making inspection object generation ultrasound wave shake to above-mentioned multiple coils Dynamic high-frequency signal, and based on the above-mentioned respective output signal of multiple coils, calculate by above-mentioned multiple lines The F echo of the above-mentioned ultrasonic activation that circle is respectively received and the signal intensity of B echo, based on this meter Calculate the internal flaw of evaluation of result above-mentioned inspection object；

Above-mentioned arithmetic unit possesses:

Duty detection unit, it is determined that the duty of above-mentioned multiple coils；

Revise enforcement division, duties based on above-mentioned multiple coils, revise and divided by above-mentioned multiple coils The signal intensity of the above-mentioned B echo not received；

Above-mentioned multiple coils are calculated signal intensity and the correction of above-mentioned F echo by ratio calculations portion respectively After the ratio of signal intensity of above-mentioned B echo；

Flaw evaluation portion, the result of calculation of above-mentioned ratio based on above-mentioned ratio calculations portion, evaluate above-mentioned Check the internal flaw of object.

6. flaw detection apparatus as claimed in claim 5, it is characterised in that

Above-mentioned correction enforcement division,

It is judged to that only 1 coil adjacent with arbitrary coil is just in work at above-mentioned duty detection unit In the case of work, by the signal intensity of above-mentioned B echo that received by above-mentioned arbitrary coil with the 1st Correction value correction；

It is judged to two the coil not works adjacent with above-mentioned arbitrary coil at above-mentioned duty detection unit In the case of work, by the signal intensity of above-mentioned B echo that received by above-mentioned arbitrary coil with the 2nd Correction value correction；

It is being judged to two coils adjacent with above-mentioned arbitrary coil at above-mentioned duty detection unit In the case of work, by the signal intensity of above-mentioned B echo that received by above-mentioned arbitrary coil with 3 correction value corrections.

7. flaw detection apparatus as claimed in claim 6, it is characterised in that

Above-mentioned 1st correction value is less than above-mentioned 2nd correction value；

Above-mentioned correction enforcement division is judged to adjacent with above-mentioned arbitrary coil at above-mentioned duty detection unit Two coils work in the case of, above-mentioned 3rd correction value is set as zero, will be by not above-mentioned The signal intensity correction of the above-mentioned B echo that arbitrary coil receives.

8. flaw detection apparatus as claimed in claim 7, it is characterised in that

Above-mentioned arithmetic unit is also equipped with correction value obtaining section, based on adjacent with above-mentioned arbitrary coil The signal of the above-mentioned B echo received by above-mentioned arbitrary coil under the state that two coils are working Intensity with when only 1 coil adjacent with above-mentioned arbitrary coil works by above-mentioned The difference of the signal intensity of the above-mentioned B echo that the coil of meaning receives, obtains above-mentioned 1st correction value, base In when two coils adjacent with above-mentioned arbitrary coil work by above-mentioned arbitrary line The signal intensity of above-mentioned B echo that circle receives with at two coils adjacent with above-mentioned arbitrary coil The signal intensity of the above-mentioned B echo not received under in harness state by above-mentioned arbitrary coil Difference, obtains above-mentioned 2nd correction value.

9. flaw detection apparatus as claimed in claim 8, it is characterised in that

Above-mentioned arithmetic unit be also equipped with by above-mentioned correction value obtaining section obtain above-mentioned 1st correction value and on State the correction value storage part of the 2nd correction value storage.