JP6733650B2 - Ultrasonic flaw detection method, ultrasonic flaw detection equipment, steel production equipment row, and steel production method - Google Patents

Description

The present invention relates to an ultrasonic flaw detection method, an ultrasonic flaw detection device, a steel product manufacturing equipment line, a steel product manufacturing method, and a steel product quality assurance method.

The internal defect of the round bar may be a starting point of cracks when manufacturing a machine part using the round bar as a raw material, and reduces strength and life of the machine part after manufacturing. Therefore, it has been conventionally practiced to ultrasonically detect the inside of the round bar and evaluate the internal defects of the round bar. In the conventional ultrasonic testing device for a round bar, a single ultrasonic probe for vertical and oblique angles is relatively moved along the circumferential direction and the axial direction of the round bar, thereby The entire body is inspected. However, when a non-focus probe is used for the ultrasonic probe, the ultrasonic signal is diffused as the distance from the ultrasonic probe increases, so the ultrasonic signal reflected inside the round rod (hereinafter, this Signal is called a defect signal). On the other hand, when a focusing probe is used for the ultrasonic probe, the intensity of the defect signal near the focus increases, but the intensity of the defect signal decreases because the ultrasonic signal spreads away from the focus. From such a background, Patent Document 1 discloses that aperture signals are synthesized by receiving a defect signal while scanning an ultrasonic probe and setting a delay time corresponding to the reception position for a plurality of received defect signals. A method of improving the detectability and resolution of defects by using a small-diameter ultrasonic probe by performing the treatment is described.

JP, 2005-233874, A

However, in the method described in Patent Document 1, since the synthesis width in the aperture synthesis processing is constant, the S/N ratio of the defect signal becomes lower at the position away from the focus position than at the focus position. Further, conventionally, the synthetic width has been experimentally or empirically determined, but the optimum synthetic width is the shape and size of the ultrasonic probe, flaw detection conditions such as flaw pitch and flaw depth, and the shape of the inspection material. Varies according to size. Therefore, it is very burdensome to experimentally or empirically determine the combined width. Furthermore, the inventors of the present invention have made a detailed study, and have found that the above-mentioned problem is present not only in the round rod body but also in the rectangular body such as a thick plate.

The present invention has been made in view of the above-mentioned problems, and the object thereof is to perform inspection or empirical determination by an aperture synthesizing process using a theoretically determined synthetic width without depending on the determination method. An object is to provide an ultrasonic flaw detection method and an ultrasonic flaw detection device capable of executing ultrasonic flaw detection with high detectability and resolution at each depth. Another object of the present invention is to provide a steel material manufacturing equipment line and a steel material manufacturing method capable of manufacturing steel materials with a high yield. Further, another object of the present invention is to provide a method of quality assurance of a steel product capable of providing a high quality steel product.

The ultrasonic flaw detection method according to the present invention transmits an ultrasonic signal from the ultrasonic probe to the inspection material, and receives the ultrasonic signal reflected inside the inspection material as a defect signal in the ultrasonic probe. By the ultrasonic flaw detection method for inspecting the inside of the inspection material, the ultrasonic probe receives a plurality of defect signals while changing the positional relationship between the inspection material and the ultrasonic probe. In the receiving step and each positional relationship between the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position is calculated as the received sound pressure ratio, and is calculated. Based on the received sound pressure ratio, a determining step of determining a synthesis width in the aperture synthesis processing at each depth position of the inspection material, and by performing the aperture synthesis processing using a plurality of defect signals according to the determined synthesis width And an inspection step of inspecting the inside of the inspection material.

In the ultrasonic flaw detection method according to the present invention, in the above invention, the determining step calculates the change rate of the S/N ratio of the defect signal by the aperture synthesis processing from the change rate of the received sound pressure ratio, and calculates the S/N ratio of the defect signal. The method is characterized by including a step of determining a combined width in which the rate of change of the N ratio is equal to or more than a predetermined value as a combined width in the opening combining process.

In the ultrasonic flaw detection method according to the present invention, in the above invention, in the determining step, when the ultrasonic probe is a circular ultrasonic probe, the following formulas (1) and (2) are shown. The received sound pressure ratio R is calculated using the directivity angle ψ of the ultrasonic signal, and when the ultrasonic probe is a rectangular ultrasonic probe, the following formula (1) and formula It is characterized by including the step of calculating the reception sound pressure ratio R using the directivity angle ψ of the ultrasonic signal by utilizing (3). However, the parameter m in Expressions (2) and (3) is a coefficient determined by the directivity angle ψ.

In the ultrasonic flaw detection method according to the present invention, in the above invention, the inspection step uses the following formulas (4) and (5) to calculate the defect signal A obtained by the aperture synthesis process at the reception sound of N points. The method is characterized by including a step of correcting the intensity of the defect signal A by dividing the pressure ratio R _n (n=0 to N) by the aperture-synthesized received sound pressure ratio S obtained by averaging.

In the ultrasonic flaw detection method according to the present invention, in the above invention, the determining step sets an incident range of an arbitrary ultrasonic signal on an inspection material from a positional relationship between the ultrasonic probe and a depth position of an internal defect. Then, calculate the propagation path of the ultrasonic signal based on Snell's law within the set incident range of the ultrasonic signal, and calculate by coordinate calculation to determine whether the propagation path of the ultrasonic signal passes through the internal defect. By calculating the propagation path of the ultrasonic signal for each depth position of the internal defect by repeating the above, a plurality of defect signals required for aperture synthesis processing based on the calculated propagation path of the ultrasonic signal for each depth position. And a step of calculating a delay time of.

In the ultrasonic flaw detection method according to the present invention, in the above invention, the determining step sets an incident range of an arbitrary ultrasonic signal on an inspection material from a positional relationship between the ultrasonic probe and a depth position of an internal defect. However, the angle formed by the normal line of the inspection material at the incident point of the ultrasonic signal within the set incident range of the ultrasonic signal and the line segment connecting the ultrasonic probe and the incident point of the ultrasonic signal and the assumed defect The propagation path of the ultrasonic signal for each depth position of the internal defect is determined by repeating the calculation to determine whether the angle formed by the line segment connecting the position and the incident point of the ultrasonic signal satisfies Snell's law. And a step of calculating delay times of a plurality of defect signals necessary for the aperture synthesis processing based on the calculated propagation path of the ultrasonic signal for each depth position.

The ultrasonic flaw detector according to the present invention transmits an ultrasonic signal from the ultrasonic probe to the inspection material, and receives the ultrasonic signal reflected inside the inspection material as a defect signal in the ultrasonic probe. An ultrasonic flaw detector for inspecting the inside of the inspection material by receiving a plurality of defect signals in the ultrasonic probe while changing the positional relationship between the inspection material and the ultrasonic probe. In the positional relationship between the receiving means, the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position was calculated as the received sound pressure ratio, and was calculated. Based on the received sound pressure ratio, the determining means for determining the synthetic width in the aperture synthetic processing at each depth position of the inspection material, and by performing the aperture synthetic processing using a plurality of defect signals according to the determined synthetic width, And an inspection means for inspecting the inside of the inspection material.

A steel material manufacturing equipment row according to the present invention includes a manufacturing apparatus for manufacturing a steel material, and an ultrasonic flaw detection apparatus according to the present invention for inspecting the inside of the steel material manufactured by the manufacturing apparatus, To do.

A method for manufacturing a steel material according to the present invention includes a manufacturing step for manufacturing a steel material, and an ultrasonic flaw detection method according to the present invention, including a flaw detection step for flaw detection inside the steel material manufactured in the manufacturing step. And

The quality assurance method of the steel material according to the present invention is the ultrasonic flaw detection method according to the present invention, and a quality assurance step of performing a quality assurance of the steel material from the flaw detection step for flaw detection inside the steel material and the flaw detection result obtained in the flaw detection step. And a step.

According to the ultrasonic flaw detection method and the ultrasonic flaw detection device according to the present invention, the depth of each inspection material is increased by the aperture synthesis processing using the synthetic width theoretically determined without using the experimental or empirical determination method. Therefore, ultrasonic flaw detection with high detectability and resolution can be performed. Further, according to the steel product manufacturing equipment row and the steel product manufacturing method of the present invention, the steel product can be manufactured with a high yield. Furthermore, according to the quality assurance method for steel products of the present invention, high quality steel products can be provided.

FIG. 1 is a schematic diagram showing a configuration of an ultrasonic flaw detector according to a first embodiment of the present invention. FIG. 2 is a flowchart showing a flow of determining the aperture synthesis processing condition according to the first embodiment of the present invention. FIG. 3 is a schematic diagram for explaining one aspect of the propagation route calculation processing according to the first embodiment of this invention. FIG. 4 is a schematic diagram for explaining another aspect of the propagation route calculation processing according to the first embodiment of this invention. FIG. 5 is a schematic diagram for explaining the delay time calculation process according to the first embodiment of the present invention. FIG. 6 is a diagram showing an example of a change in the relationship between the defect depth and the S/N ratio of the defect signal due to the difference in the combined width. FIG. 7 is a schematic diagram for explaining the optimum combined width calculation process according to the first embodiment of the present invention. FIG. 8 is a flowchart showing the flow of the optimum combined width calculation processing according to the first embodiment of the present invention. FIG. 9 is a diagram showing an example of the relationship between the received sound pressure ratio and the rotation angle. FIG. 10 is a diagram showing the relationship between the combined width calculated based on the distribution of the received sound pressure ratio shown in FIG. 9 and the S/N ratio improvement coefficient E. FIG. 11 is a diagram showing the result of ultrasonic flaw detection without the signal processing according to the present invention. FIG. 12 is a diagram showing a result of performing ultrasonic flaw detection by performing signal processing according to the present invention. FIG. 13 is a schematic diagram showing the configuration of the ultrasonic flaw detector according to the second embodiment of the present invention. FIG. 14 is a schematic diagram for explaining one aspect of the propagation route calculation process according to the second embodiment of the present invention. FIG. 15 is a schematic diagram for explaining another aspect of the propagation route calculation processing according to the second embodiment of the present invention. FIG. 16 is a schematic diagram for explaining the delay time calculation process according to the second embodiment of the present invention. FIG. 17 is a diagram showing a result of simulating the relationship between the combined width and the S/N ratio improvement coefficient E. FIG. 18 is a schematic diagram for explaining the optimum combined width calculation process according to the second embodiment of the present invention.

Hereinafter, the configuration and operation of the ultrasonic flaw detectors according to the first and second embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
[Constitution]
First, with reference to FIG. 1, a configuration of an ultrasonic flaw detector according to a first embodiment of the present invention will be described.

FIG. 1 is a schematic diagram showing a configuration of an ultrasonic flaw detector according to a first embodiment of the present invention. As shown in FIG. 1, an ultrasonic flaw detection apparatus 1 according to a first embodiment of the present invention is a circle manufactured by rolling a cast steel slab by an ultrasonic flaw detection method using a water immersion flaw detection method. It is an apparatus for ultrasonic flaw detection of the rod RB. This ultrasonic flaw detector 1 includes a plurality of ultrasonic probes 11, a probe head 12, a mount 13, a rotation driving device 14, a pulser 15, a receiver 16, an A/D converter 17, a recording device 18, a signal processing device 19, And the display device 20 as a main component.

The ultrasonic flaw detector according to the present invention includes a receiving unit that receives a defect signal in the ultrasonic probe while changing the positional relationship between the inspection material and the ultrasonic probe. In the ultrasonic flaw detector 1 shown in FIG. 1, the receiver 16, the A/D converter 17, and the recording device 18 correspond to receiving means. Further, the ultrasonic flaw detector according to the present invention, in each positional relationship between the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position is used as the received sound pressure ratio. A determining unit that determines the combined width in the aperture combining process at each depth position of the inspection material is calculated based on the calculated received sound pressure ratio. In addition, the ultrasonic flaw detector according to the present invention includes an inspection unit that inspects the inside of the inspection material by performing an aperture synthesis process using a plurality of defect signals according to the determined synthesis width. In the ultrasonic flaw detector 1 shown in FIG. 1, the signal processor 19 corresponds to the determining means and the inspecting means.

The ultrasonic flaw detector 11 is arranged at a position separated from the round bar RB by a predetermined distance via water as a medium in the water immersion flaw detection method, and is excited by a pulse signal output from the pulsar 15 during the ultrasonic flaw detection. Then, the ultrasonic signal is transmitted to the round bar RB. Then, the ultrasonic signal (hereinafter, referred to as a defect signal) propagated and reflected inside the round bar RB is received by the receiver 16 via the ultrasonic probe 11.

The probe head 12 is provided with a plurality of ultrasonic probes 11 and moves on a pedestal 13 arranged above the round bar RB to scan the round bar RB in the axial direction. By scanning the probe head 12 while rotating the round rod RB in the circumferential direction indicated by the arrow by the rotation driving device 14 and receiving a defect signal by the receiver 16, ultrasonic detection of the entire volume of the round rod RB is performed. be able to. The rotation speed of the rotary drive device 14 and the scanning speed of the probe head 12 are set so that the total volume of the round rod RB is not insufficient for ultrasonic flaw detection.

The analog defect signal received by the receiver 16 is converted into digital data by the A/D converter 17 in synchronization with the pulse signal output from the pulser 15, and is stored in the recording device 18. As a result, the defect signal of the total volume of the round bar RB is stored in the recording device 18. The stored defect signal is subjected to signal processing by the signal processing device 19, and the signal processing result is displayed on the display device 20. The signal processing may be performed on a defect signal stored during ultrasonic flaw detection at any time, or may be performed after all defect signals are stored.

The signal processing device 19 executes determination of aperture synthesis processing conditions as one of signal processing. In determining the aperture synthesis processing condition, the signal processing device 19 calculates the reception sound pressure ratio of the defect signal from the directivity angle of the ultrasonic probe 11, and optimally synthesizes for each ultrasonic flaw detection range based on the calculated reception sound pressure ratio. Determine the width. Then, the signal processing device 19 executes aperture synthesis processing as one of the signal processing. The inside of the round bar RB is inspected by performing the opening synthesis process using a plurality of defect signals according to the determined combined width, and the inside of the round bar RB is detected by detecting the internal defect of the round bar RB. To do.

Next, the ultrasonic flaw detection method according to the present invention will be described. The ultrasonic flaw detection method according to the present invention includes three steps: (I) receiving step, (II) determining step, and (III) inspecting step. Further, each step is executed in the order of (I) receiving step, (II) determining step, (II) determining step, and (III) inspection step.

In the receiving step, the ultrasonic probe receives a plurality of defect signals while changing the positional relationship between the inspection material and the ultrasonic probe. A known method for receiving a defect signal by an ultrasonic probe can be used in the receiving step. As an example, it can be realized by the operations of the receiver 16, the A/D converter 17, and the recording device 18 described above.

In the determination step, in each positional relationship between the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position is calculated as the received sound pressure ratio, and the calculated received sound pressure is calculated. Based on the pressure ratio, the combined width in the opening combining process at each depth position of the inspection material is determined. Calculation of the combined width at each depth position of the inspection material is the most important technique in the present invention. Therefore, the method of calculating the combined width will be described later in detail.

In the determination step, the delay time used for the aperture synthesis processing is additionally calculated. In addition, it is desirable that the combined width and the delay time be calculated for each defect depth in the determination step in terms of improvement in detectability. Note that the delay time can be calculated by using a known method as aperture synthesis processing. In the present specification, an example in which the propagation path of the transmitted ultrasonic signal in the inspection body is calculated and the delay time is determined based on the calculated propagation path will be described later.

In the inspection step, the aperture synthesis processing is executed on the flaw detection signal received in the reception step according to the delay time and the synthesis width determined in the determination step, and the inside of the inspection material is inspected based on the result of the aperture synthesis processing. A known method can be used for the aperture synthesis processing performed in the inspection step. In the present specification, an example of performing a process of adding up a plurality of waveforms included in the combined width determined in the determining step by applying the delay time also determined in the determining step will be described later.

Based on the result of the obtained aperture synthesis processing, the inside of the inspection material is inspected, and the state inside the inspection material is known, so that flaw detection can be performed. Examples of the state of the inside of the inspection material that can be subjected to flaw detection include the presence/absence of a defect, the defect position, the defect size, etc., from the intensity of the reflection signal from the defect, the reception time, and the like. The method of outputting the result of the obtained aperture synthesis processing may be appropriately determined according to the purpose of use of the result, etc., but is output in the form of a waveform or an image with respect to the position (width direction, rolling direction, depth, thickness, etc.). It is desirable that it be highly visible.

By the ultrasonic flaw detection method according to the present invention, the ratio of noise to defect signal (S/N ratio) is improved, so that the detectability can be improved.

[Determination of aperture synthesis processing conditions]
With reference to FIG. 2, the operation of the signal processing device 19 when determining the aperture synthesis processing condition, that is, the synthesis width and the delay time in the determination step will be described. In addition, an example of a method of calculating the propagation path of the ultrasonic signal used in the determination of the delay time in the determination step will be described. Here, the propagation path is a propagation path of the ultrasonic signal in the inspection body. If necessary, it may be a propagation path of an ultrasonic signal in the inspection body and in the medium. Also, an example of a method of calculating a received sound pressure ratio, which is a ratio of the received sound pressure of the defective signal to the received sound pressure of the defective signal at the reference position , which is used for determining the combined width, will be described below.

FIG. 2 is a flowchart showing a flow of determining the aperture synthesis processing condition according to the first embodiment of the present invention. The determination of the aperture synthesis processing condition is performed not only before the ultrasonic flaw detection but also based on the value obtained during the ultrasonic flaw detection such as the thickness measurement of the round bar RB by the ultrasonic signal. It may be done later.

The determination of the aperture synthesis processing condition is performed by the flaw detection condition input step (S1), the propagation path calculation step (S2), the delay time calculation step (S3), the reception sound pressure ratio calculation step (S4), and the optimum synthesis width calculation step (S5). Are executed in this order. Each step will be described in detail with the inspection body as a round bar RB.

In the process of step S1, the signal processing device 19 uses the size of the round rod RB, the size and shape of the ultrasonic probe 11, the measurement pitch, the positional relationship with the round rod RB, the ultrasonic flaw detection range, and other ultrasonic waves. Acquire flaw detection conditions. The ultrasonic flaw detection conditions may be acquired not only before the ultrasonic flaw detection but also during the ultrasonic flaw detection or after the ultrasonic flaw detection. As a result, the process of step S1 is completed, and the determination of the aperture synthesis process condition proceeds to the process of step S2.

In the processing of step S2, the signal processing device 19 uses the ultrasonic flaw detection conditions acquired in the processing of step S1 to enter the assumed defect position from the ultrasonic probe 11 into the round rod RB according to Snell's law. The propagation path of the ultrasonic signal passing therethrough is calculated (propagation path calculation processing). Details of this propagation route calculation processing will be described later. As a result, the processing of step S2 is completed, and the determination of the aperture synthesis processing condition proceeds to the processing of step S3.

In the process of step S3, the signal processing device 19 calculates a delay time at each reception position of a plurality of other defect signals with respect to a reference defect signal (delay time calculation process). Details of this delay time calculation processing will be described later. As a result, the processing of step S3 is completed, and the determination of the aperture synthesis processing condition proceeds to the processing of step S4.

In the process of step S4, the signal processing device 19 calculates the reception sound pressure ratio of the defect signal in each positional relationship between the round bar RB and the ultrasonic probe 11 (reception sound pressure ratio calculation process). Details of the received sound pressure ratio calculation processing will be described later. As a result, the processing of step S4 is completed, and the determination of the aperture synthesis processing condition proceeds to the processing of step S5.

In the processing of step S5, the signal processing device 19 determines the optimum synthesis width in the aperture synthesis processing at each depth position of the round bar RB based on the received sound pressure ratio calculated in the processing of step S4. As a result, the process of step S5 is completed, and the determination of the series of aperture synthesis processing conditions is completed.

<Propagation route calculation processing>
Next, the propagation route calculation processing in step S2 will be described in detail with reference to FIGS.

In order to obtain a defect signal having a high S/N ratio by the aperture synthesizing process, it is desirable to accurately calculate the delay time of each defective signal to be synthesized. In particular, when ultrasonically flaw-detecting a steel material having a curved surface such as the round bar RB, the propagation time of the ultrasonic signal greatly changes due to the refraction phenomenon on the curved surface. Accurate calculation is desirable. Therefore, in the present embodiment, based on the coordinates of the ultrasonic probe 11 and the assumed defect position, the ultrasonic probe 11 enters the round rod RB while satisfying Snell's law and passes through the assumed defect position. The propagation path of the sound wave signal is calculated.

Hereinafter, one mode and another mode of the propagation route calculation process according to the first embodiment of the present invention will be described with reference to FIGS. 3 and 4.

FIG. 3 is a schematic diagram for explaining one aspect of the propagation route calculation processing according to the first embodiment of this invention. Hereinafter, the position of the ultrasonic probe 11 is P, the assumed defect position is P _F , the center position of the round bar RB is O, the sound velocity in water as a medium in the water immersion flaw detection method is Vw, and the round bar RB is in the middle. The speed of sound at is written as Vs. Further, as shown in FIG. 3, the assumed defect position P _F is assumed to be on the circumference having a radius of the line segment OR.

In this aspect, first, the incident point X of the ultrasonic signal is set, and the incident angle θw of the ultrasonic signal is obtained from the angle formed by the line segment PX and the line segment OX. Next, according to Snell's law, the refraction angle θs of the ultrasonic signal satisfies the following expression (6). Therefore, by substituting the incident angle θw of the ultrasonic signal into the equation (6), the refraction angle θs of the ultrasonic signal can be obtained. Further, an intersection C of a straight line passing through the incident point X of the ultrasonic signal and refracted at the refraction angle θs and a circle having a radius of the line segment OR can be obtained. Therefore, by searching the incident point X of the ultrasonic wave where the intersection C and the assumed defect position P _F match while changing the incident point X of the ultrasonic signal, the incident point X is incident and the assumed defect position P _F is determined. It is possible to calculate the propagation path of the passing ultrasonic signal.

FIG. 4 is a schematic diagram for explaining another aspect of the propagation route calculation processing according to the first embodiment of this invention. In this aspect, first, the incident point X of the ultrasonic signal is set, and the incident angle θw of the ultrasonic signal is obtained from the angle formed by the line segment PX and the line segment OX. Then, by searching the angle θ that satisfies the Snell's law given by Equation (7) the angle θ is less formed between the ultrasonic signal line OX and the line segment P _{F X} while changing the incidence point X of the incident It is possible to calculate the propagation path of the ultrasonic signal that enters the point X and passes through the assumed defect position P _F.

In the propagation path calculation process described above, only the movement of the assumed defect position P _F accompanying the rotation of the round rod RB is considered, but when the ultrasonic probe 11 is scanned in the axial direction, It is desirable to calculate the propagation path of the ultrasonic signal in consideration of the amount of axial movement of the ultrasonic probe 11. Further, the above-described propagation path calculation process is basically performed before ultrasonic flaw detection is started based on the size and flaw detection conditions of the round rod RB. When there is a possibility that the propagation path of the ultrasonic signal differs greatly from the result of the pre-calculation, it is desirable to calculate the propagation path of the ultrasonic signal in real time based on the information obtained during ultrasonic flaw detection.

<Delay time calculation process>
Next, the delay time calculation process of step S3 will be described in detail with reference to FIG.

FIG. 5 is a schematic diagram for explaining the delay time calculation process according to the first embodiment of the present invention. As shown in FIG. 5, the position of the internal defect indicated by the white circle moves with the rotation of the round rod RB, so that the intensity and the reception time of the defect signal received by the ultrasonic probe 11 change. Specifically, the first defect signal RW1 and the second defect signal RW2 shown in FIG. 5 are the ultrasonic waves from the defects at the first defect position P1 and the second defect position P2 received by the ultrasonic probe 11, respectively. It is a reflected signal of the signal. Here, when the sound velocity in water, which is a medium in the water immersion flaw detection method, is represented by Vw, and the sound velocity in the round bar RB is represented by Vs, the propagation time T1 of the first defect signal RW1 is represented by the following equation (8), The propagation time T2 of the defect signal RW2 is represented by the following formula (9), and the delay time ΔT which is the difference between the propagation time T1 and the propagation time T2 is represented by the following formula (10).

Here, random noises cancel each other out by calculating the delay time at each reception position of a plurality of other defective signals with respect to the reference defective signal and synthesizing the plurality of defective signals. The ratio is improved. When the second defect signal RW2 is used as a reference, the first defect signal RW1 is delayed by the delay time ΔT shown in Expression (10) and added. As a result, random noises cancel each other out and defect signals whose phases are aligned strengthen each other, so that the S/N ratio of the defect signals becomes higher than that before the aperture synthesis processing. Further, when the delay time is calculated for each position of the ultrasonic probe 11 and the depth position of the round rod RB and the aperture synthesis processing is performed, the depth in the round rod RB is defective. However, the defect signal can be detected with a high S/N ratio.

<Received sound pressure ratio calculation process and optimum combined width calculation process>
Next, with reference to FIGS. 6 to 9, the reception sound pressure ratio calculation process of step S4 and the optimum synthesis width calculation process of step S5 shown in FIG. 2 will be described in detail.

The intensity of the defect signal changes according to the positional relationship between the ultrasonic probe 11 and the internal defect. Specifically, in the far field, when the defect exists on the central axis of the ultrasonic probe 11, the intensity of the defect signal becomes the strongest, and the central axis of the ultrasonic probe 11 and the internal defect The intensity of the defect signal becomes smaller as the angle formed by the propagation path of the ultrasonic wave passing through becomes larger. In order to obtain a defect signal with a high S/N ratio by the aperture synthesis process, it is necessary to add a plurality of defect signals within a range in which the defect signals have sufficient intensity. Therefore, the effect of improving the S/N ratio becomes small. In addition, since the ultrasonic signal output from the ultrasonic probe 11 propagates while being diffused, the sound pressure distribution is formed so as to widen as the distance increases. At this time, if there is a defect in the sound pressure distribution, a defect signal with sufficient intensity can be obtained. That is, the synthetic width (the number of defect signals to be added) having sufficient strength changes depending on the sound pressure distribution of the ultrasonic signal and the moving position of the defect within the sound pressure distribution. Therefore, in order to obtain a defect signal with a high S/N ratio by the aperture synthesis process, it is necessary to appropriately set the synthesis width based on the position of the internal defect and the flaw detection condition. Therefore, in this embodiment, an appropriate combined width is calculated for each depth position of the internal defect based on the received sound pressure ratio of the defect signal.

FIG. 6 is a diagram showing an example of a change in the relationship between the defect depth and the S/N ratio of the defect signal due to the difference in the combined width. Specifically, in FIG. 6, four artificial defects with a diameter of φ0.2 mm, which were machined at internal depths of 5 mm, 21 mm, 42 mm, and 63 mm of a round steel bar with a diameter of φ169 mm, were flaw-detected, and a synthetic width of 2.4°. , A synthetic width of 8.4°, a synthetic width of 22.8°, and experimental results of performing the aperture synthetic processing according to the present invention. In this experiment, a circular ultrasonic probe having a diameter of 6.4 mm and a frequency of 5 MHz was used as the ultrasonic probe 11. In addition, the plots of the combined width 2.4°, the combined width 8.4°, and the combined width 22.8° show the constant combined width (2.4°) for four artificial defect signals with different internal depths. , 8.4°, 22.8°). However, the combined widths of 2.4°, 8.4°, and 22.8° are the optimum combined widths at the internal depths of 5 mm, 21 mm, and 42 mm determined by the present invention, respectively.

As shown in FIG. 6, for a defect signal with a depth of 5 mm, the S/N ratio becomes the largest when the combined width is 2.4°, and for a defect signal with a depth of 21 mm, the combined width is The maximum S/N ratio is obtained at 8.4°, and the maximum S/N ratio is obtained at a combined width of 22.8° for a defect signal having a depth of 42 mm. Therefore, the combined width that maximizes the S/N ratio differs for each defect depth, and the maximum S/N ratio can be obtained for all the defect depths by setting an appropriate combined width for each defect depth. I understand. In fact, in the present invention, an improvement in the S/N ratio of 10 dB or more could be confirmed depending on the depth position, as compared with the case where the combined width was set constant by the defect depth, demonstrating the effectiveness of the present invention.

FIG. 7 is a schematic diagram for explaining the optimum combined width calculation process according to the first embodiment of the present invention. As shown in FIG. 7, in the present embodiment, the directivity angle ψ of the ultrasonic signal is calculated from the propagation path of the ultrasonic signal calculated by the propagation path calculation processing, and the defect signal is received when the assumed defect position is rotated. The change in the sound pressure ratio is calculated, and the combined width is calculated from the distribution of the received sound pressure ratio of the defective signal. Here, the diameter of the round bar RB is R, the rotation speed of the round bar RB is V1, the propagation velocity of the ultrasonic wave in the round bar RB is Vs, the PRF of the ultrasonic probe 11 is f, and the ultrasonic probe The frequency of the probe 11 is F, the length of the ultrasonic probe 11 is D (radius in the case of a round shape, side length in the case of a rectangle), and between the ultrasonic probe 11 and the surface of the round bar RB. Is W, the sound velocity in water, which is the medium in the water immersion flaw detection method, is Vw, the assumed defect position existing on the central axis of the ultrasonic probe 11 is P _F , and the assumed defect position P _{F is} the round bar RB surface. From the assumed defect position P _F to the assumed defect position P _F ′ after rotation by an angle θ, and the propagation path is calculated for the position P of the ultrasonic probe 11 and the assumed defect position P _F ′. The angle (directivity angle) formed by the propagation path of the ultrasonic signal and the central axis of the ultrasonic probe 11 when the processing is performed is ψ.

Since the calculation of the received sound pressure is basically performed on the assumption of the far-field sound field, it is a condition that the assumed defect position P _F satisfies the following formula (11). Here, the near field limit distance x0 is represented by the following mathematical expression (12). However, when the assumed defect position P _F does not satisfy the mathematical expression (11), the combined width can be calculated by applying the sound pressure calculation of the near field.

When the ultrasonic probe 11 is round, the ratio of the received sound pressure of the defect signal from the rotation after assumed defect position P _{F 'for} receiving sound pressure of the defect signal from the assumed defect position P _F (ratio reception sound) R can be represented by the following formulas (13) to (15) using the directivity angle ψ. However, J1 shown in Expression (14) represents a Bessel function, and m shown in Expressions (14) and (15) is a coefficient determined by the directivity angle ψ.

On the other hand, when the ultrasonic probe 11 has a rectangular shape, the reception sound pressure ratio R can be represented by the equations (13) and (15) and the following equation (16) using the directivity angle ψ. When the ultrasonic probe 11 has a complicated shape other than a circular shape or a rectangular shape, the reception sound pressure ratio R may be determined using the results of experiments or physical analysis using the finite element method or the like. .. If the defect to be detected has a strong directivity, the received sound pressure ratio R may be obtained by multiplying the expression (13) by the reflection directivity function of the defect. In the present embodiment, the combined width is calculated using the received sound pressure ratio R calculated by the above procedure.

Specifically, the ultrasonic probe 11 receives a defect signal every time the assumed defect position P _F rotates by the angular pitch Δθ. The angular pitch Δθ is represented by the following mathematical expression (17).

Received sound pressure ratio after aperture synthesis in the case where aperture synthesis processing is performed in which a defect signal acquired within a range in which the assumed defect position P _F is rotated from −n ₁ Δθ to n ₂ Δθ is subjected to addition average over delay time is performed. S is represented by the following formula (18). Here, in Expression (18), R(nΔθ) represents the received sound pressure ratio at a position rotated by nΔθ from the assumed defect position P _F. The assumed defect position P _F is not limited to the central axis of the ultrasonic probe 11, and can be set according to the flaw detection conditions.

Assuming that the noise becomes 1/N ^1/2 by the arithmetic mean of the number of additions N (=n ₁ +n ₂ +1), the S/N ratio after the aperture synthesis process is improved with respect to the S/N ratio at the assumed defect position P _F. The coefficient E is expressed by the following mathematical expression (19).

Therefore, the S/N ratio of the defect signal can be maximized by setting the synthesis width N that maximizes the S/N ratio improvement coefficient E by using Expression (19) and performing the aperture synthesis process. In addition, the S/N ratio of the defect signal can be sufficiently improved by determining the number of additions N that satisfies the following mathematical expression (20) and performing the aperture synthesis processing.

When evaluating a defect signal in ultrasonic flaw detection, not only the S/N ratio but also the intensity of the defect signal is important. If the intensity of the defect signal fluctuates greatly before and after the aperture synthesis process, it is not possible to accurately evaluate the internal defect. Therefore, it is desirable to restore the intensity reduced by the aperture synthesis process to the intensity before the process. Specifically, for the output value A after aperture synthesis processing, the corrected output value B corrected by the following equation (21) using the received sound pressure ratio S after aperture synthesis shown in equation (18) is used. By outputting, the strengths of the defect signals before the aperture synthesis processing and after the aperture synthesis processing can be matched. By matching the intensities of the defect signals before the aperture synthesis process and after the aperture synthesis process, the defect diameter and the defect length can be quantitatively evaluated.

Summarizing the above processing, the optimum combined width calculation processing is as shown in the flowchart in FIG. FIG. 8 is a flowchart showing the flow of the optimum combined width calculation processing according to the first embodiment of the present invention. As shown in FIG. 8, in the optimum synthesis width calculation process of the present embodiment, first, the signal processing device 19 temporarily sets the synthesis width in the aperture synthesis process (step S51). Next, the signal processing device 19 calculates the reception sound pressure ratio (reception sound pressure ratio change rate) S after aperture combination by averaging the reception sound pressure ratios of the defect signals using the temporarily set combination width and the mathematical expression (18). Calculate (step S52). Next, the signal processing device 19 obtains the ratio of the received sound pressure ratio S after aperture synthesis and the rate of change of noise by using the mathematical expression (19) to obtain the S/N ratio improvement coefficient E(S/N) by the aperture synthesis process. The ratio change ratio is calculated (step S53). Then, the signal processing device 19 determines whether or not the S/N ratio improvement coefficient E satisfies a predetermined condition such as the condition shown in Expression (20) (step S54), and the S/N ratio improvement coefficient E is determined. When the predetermined condition is satisfied, the signal processing device 19 determines the combined width temporarily set in the process of step S51 to be the optimum combined width (step S55). On the other hand, when the S/N ratio improvement coefficient E does not satisfy the predetermined condition, the signal processing device 19 returns the optimal synthesis width calculation process to the process of step S51.

[Example]
The excellent results of the ultrasonic flaw detection method according to the present invention will be described in Examples. In this example, a round bar sample provided with an artificial defect was subjected to ultrasonic flaw detection, and an aperture synthesis treatment was performed by the ultrasonic flaw detection method according to the present invention. As the ultrasonic probe, a circular ultrasonic probe with a diameter of 6.4 mm and a frequency of 5 MHz was used, and a round rod sample with a diameter of φ169 mm and an artificial defect of φ0.2 mm was processed. Using. The ultrasonic probe and the round rod sample were acoustically coupled by the local water immersion flaw detection method, and the water distance was 50 mm and the measurement angle pitch was 0.6°. Also, the near-field limit distance of the ultrasonic probe was 34.5 mm, which was shorter than the water distance of 50 mm, and satisfied the application conditions of this method.

FIG. 9 is a diagram showing a relationship between a received sound pressure ratio of a defect signal from an artificial defect having a surface depth of 21 mm and φ0.2 mm and a rotation angle. The measured value and the calculated value of the received sound pressure ratio are almost in agreement, which shows the effectiveness of the calculation of the received sound pressure ratio in the method of the present invention. FIG. 10 is a diagram showing the relationship between the combined width calculated based on the distribution of the received sound pressure ratio shown in FIG. 9 and the S/N ratio improvement coefficient E. However, the calculated value (curve L1) in FIG. 10 is a value obtained as a result of performing aperture synthesis processing with a synthetic width symmetrical with positive and negative symmetry about the rotation angle of 0° using the calculated value of the reception sound pressure ratio shown in FIG. Is.

In the calculated curve L1 shown in FIG. 10, the S/N ratio improvement coefficient E has a maximum value of 9.2 dB with a combined width of 8.4°, so the combined width N is an S/N ratio improvement coefficient E≧6.4 dB. N that satisfies 2.4°≦N≦21.6° that satisfies the above condition is set. Further, the curve L2 of the actual measurement value is substantially in agreement with the tendency of the curve L1 of the calculated value, and the S/N ratio improvement coefficient E is the maximum at the composite width of 8.4°, and the composite width is determined by the present invention. The effectiveness of the method was demonstrated.

11(a) and 11(b) are diagrams showing the results of ultrasonic flaw detection performed on an artificial defect having a surface depth of 21 mm and φ0.2 mm without performing signal processing according to the present invention. 12(a) and 12(b) are diagrams showing the results of ultrasonic flaw detection by performing signal processing according to the present invention on an artificial defect having a surface depth of 21 mm and φ0.2 mm. In this experiment, the combined width that maximizes the S/N ratio was calculated, and the combined width was set to 8.4°. As shown in FIGS. 12A and 12B, according to the signal processing of the present invention, the S/N ratio was improved by 6 dB, and the defect of φ0.2 mm could be detected with the S/N ratio of 21 dB. ..

[Second Embodiment]
Next, with reference to FIGS. 13 to 18, the configuration and operation of the ultrasonic flaw detector according to the second embodiment of the present invention will be described.

[Constitution]
First, with reference to FIG. 13, a configuration of an ultrasonic flaw detector according to a second embodiment of the present invention will be described.

FIG. 13 is a schematic diagram showing the configuration of the ultrasonic flaw detector according to the second embodiment of the present invention. As shown in FIG. 13, in the ultrasonic flaw detector 1 according to the second embodiment of the present invention, (1) a steel plate SP manufactured by rolling a cast steel slab is an inspection material, and ( 2) In the first embodiment of the present invention shown in FIG. 1, the steel plate SP is transported by the transport line 21 so as to pass below the ultrasonic probe 11 along the longitudinal direction of the steel plate SP. This is different from the configuration of a certain ultrasonic flaw detector 1. Since the other points are the same as the configuration of the ultrasonic flaw detector 1 according to the first embodiment of the present invention shown in FIG. 1, the description thereof will be omitted below.

[Determination of aperture synthesis processing conditions]
Next, with reference to FIGS. 14 to 18, the operation of the signal processing device 19 when determining the aperture synthesis processing condition will be described. The overall flow of determining the aperture synthesis processing condition is the same as the flow of determining the aperture synthesis processing condition according to the first embodiment of the present invention shown in FIG. However, when the inspection material is changed from the round bar RB to the steel plate SP, a part of the contents of the propagation path calculation processing, the delay time calculation processing, the received sound pressure ratio calculation processing, and the optimum combined width calculation processing is part of the first embodiment. It is different from the content in. Therefore, only the differences between these processes will be described below.

<Propagation route calculation processing>
FIG. 14 is a schematic diagram for explaining one aspect of the propagation route calculation process according to the second embodiment of the present invention. Hereinafter, the positions of the ultrasonic probe 11 moving in the longitudinal direction of the steel plate SP are P and P′, the assumed defect position is P _F , and the line connecting the position P of the ultrasonic probe 11 and the assumed defect position P _F. The point of intersection between the minute and the surface of the steel plate SP is represented by O, the speed of sound in water as a medium in the water immersion flaw detection method is represented by Vw, and the speed of sound in the steel plate SP is represented by Vs.

In the present embodiment, first, the incident point X of the ultrasonic signal is set, and the incident angle θw of the ultrasonic signal is obtained from the angle formed by the line segment P′X and the line segment XY. The line segment XY indicates the normal line of the steel plate SP passing through the incident point X. Next, according to Snell's law, the refraction angle θs of the ultrasonic signal satisfies the above equation (6). Therefore, by substituting the incident angle θw of the ultrasonic signal into the equation (6), the refraction angle θs of the ultrasonic signal can be obtained. Further, it is also possible to obtain an intersection point C between a straight line that passes through the incident point X of the ultrasonic signal and is refracted at the refraction angle θs and the line segment OP. Therefore, by searching the incident point X of the ultrasonic signal where the intersection C and the assumed defect position P _F match while changing the incident point X of the ultrasonic wave, the incident point X is incident and the assumed defect position P _F is determined. It is possible to calculate the propagation path of the passing ultrasonic signal.

FIG. 15 is a schematic diagram for explaining another aspect of the propagation route calculation processing according to the second embodiment of the present invention. In the present embodiment, first, the incident point X of the ultrasonic signal is set, and the incident angle θw of the ultrasonic signal is obtained from the angle formed by the line segment P′X and the line segment XY. Then, by searching the angle θ that satisfies the Snell's law shown in formula (7) where the angle θ is above the line XY and the line segment P _{F X} while changing the incident point X of the ultrasonic signals, the incident It is possible to calculate the propagation path of the ultrasonic signal that enters the point X and passes through the assumed defect position P _F.

<Delay time calculation process>
FIG. 16 is a schematic diagram for explaining the delay time calculation process according to the second embodiment of the present invention. As shown in FIG. 16, when the positional relationship between the ultrasonic probe 11 and the internal defect located at the assumed defect position P _F changes, the intensity and the reception time of the defect signal received by the ultrasonic probe 11 become Change. Specifically, the third defect signal RW3 and the fourth defect signal RW4 are reflection signals of ultrasonic waves from the defects received when the ultrasonic probe 11 is at the position P4 and the position P5, respectively. Here, when the sound velocity in water, which is a medium in the water immersion flaw detection method, is represented by Vw, and the sound velocity in the round bar RB is represented by Vs, the propagation time T3 of the third defect signal RW3 is represented by the above-described formula (8) (T1 is T3 , And the propagation time T4 of the fourth defect signal RW4 is the above-mentioned formula (9) (T2 is replaced by T4), and the delay time ΔT1 which is the difference between the propagation time T3 and the propagation time T4 is the above-mentioned formula (10). It can be calculated using (replace ΔT with ΔT1).

Here, random noises cancel each other out by calculating the delay time at each reception position of a plurality of defective signals with respect to a reference defective signal and synthesizing the plurality of defective signals, so that the S/N ratio of the defective signals is Be improved. When the fourth defect signal RW4 is used as a reference, the third defect signal RW3 is delayed by the delay time ΔT1 and added. As a result, random noises cancel each other out and defect signals whose phases are aligned strengthen each other, so that the S/N ratio of the defect signals becomes higher than that before signal processing. Further, by calculating the delay time for each position of the ultrasonic probe 11 and the depth position of the steel plate SP and performing the aperture synthesis processing, it is possible to obtain a high S value even if there is a defect at any depth position in the steel plate SP. The defect signal can be detected by the /N ratio.

<Received sound pressure ratio calculation process and optimum combined width calculation process>
FIG. 17 is a diagram showing a result of simulating the relationship between the combined width and the S/N ratio improvement coefficient E. Specifically, FIG. 17 shows ultrasonic flaw detection of a steel plate SP having a plate thickness of 150 mm while moving a circular ultrasonic probe having a frequency of 5 MHz and a diameter of 12.6 mm at a pitch of 0.05 mm in the width direction of the steel plate SP. Then, the relationship between the synthetic width and the S/N ratio improvement coefficient E when the aperture synthetic processing is performed on the internal defect at the depths of 25, 50, 75, 100, 125 mm (depth25, 50, 75, 100, 125) is shown. The simulation results are shown. As shown in FIG. 17, the combined width that maximizes the S/N ratio improvement coefficient E is different at each depth position, and when the combined width is constant at 0.8 and 2.6 mm at all depth positions, , The S/N ratio is reduced by up to 4 dB as compared with the case where the optimum combined width is set at all depth positions. However, the combined widths of 0.8 and 2.6 mm are the optimum values of the combined width when the aperture combining process is performed at the depths of 25 and 125 mm, respectively.

FIG. 18 is a schematic diagram for explaining the optimum combined width calculation process according to the second embodiment of the present invention. In the present embodiment, the directivity angle ψ of the ultrasonic signal is calculated from the propagation path of the ultrasonic signal calculated by the propagation path calculation processing, and the defect signal when the positional relationship between the ultrasonic probe 11 and the defect changes The change in the received sound pressure ratio is calculated, and the combined width is calculated from the distribution of the received sound pressure ratio. Here, the moving speed of the ultrasonic probe 11 in the width direction is V1, the sound velocity in the steel plate SP is Vs, the PRF of the ultrasonic probe 11 is f, the frequency of the ultrasonic probe 11 is F, and the ultrasonic wave is The length of the probe 11 is D (radius in the case of a round shape, side length in the case of a rectangle), W is the distance between the ultrasonic probe 11 and the steel plate SP surface, and is a medium in the water immersion flaw detection method. The sound velocity in a certain water is Vw, the assumed defect position existing on the central axis of the ultrasonic probe 11 is P _F , the depth of the assumed defect position P _{F from} the steel plate SP surface is d, the ultrasonic probe 11 Of the position of the ultrasonic probe 11 when moved by x from the initial position P of P, and the position P′ of the ultrasonic probe 11 and the assumed defect position P _F The angle between the propagation path of the ultrasonic signal and the central axis of the ultrasonic probe 11 is ψ (directivity angle).

The calculation of the received sound pressure is basically performed on the assumption of a long-distance sound field, and therefore, it is a condition that the assumed defect position P _F satisfies the above formula (11). Here, the short-range sound field limit distance x0 is represented by the above-mentioned mathematical expression (12). However, when the assumed defect position P _F does not satisfy the above-described mathematical expression (11), the synthetic width can be calculated by applying the sound pressure calculation of the near field.

When the ultrasonic probe 11 has a round shape, the ratio of the received sound pressure of the defect signal at the position P′ to the received sound pressure of the defect signal at the position P (received sound pressure ratio) R is described above using the directivity angle ψ. It can be expressed by equations (13) to (15). On the other hand, when the ultrasonic probe 11 has a rectangular shape, the reception sound pressure ratio R can be represented by the above-described formulas (13), (15), and (16) using the directivity angle ψ.

In the present embodiment, the combined width is calculated using the received sound pressure ratio R calculated by the above procedure. Specifically, the ultrasonic probe 11 receives a defect signal every time the ultrasonic probe 11 moves by the position Δx. The movement pitch Δx is represented by the following mathematical expression (22).

After aperture synthesis in the case where aperture synthesis processing is performed in which the defect signal acquired within the range in which the position of the ultrasonic probe 11 moves from -n ₁ Δx to n ₂ Δx is subjected to delay time and averaged The received sound pressure ratio S is expressed by the following mathematical expression (23). Here, in the mathematical expression (23), R(nΔx) represents the received sound pressure ratio at the position where the ultrasonic probe 11 moves from the position P by nΔx. The position P of the ultrasonic probe 11 is not limited to the center axis of the ultrasonic probe 11, and can be set according to the flaw detection conditions.

Assuming that the noise becomes 1/N ^{1/2 due} to the addition average of the number of additions N (=n ₁ +n ₂ +1), the S after the aperture synthesis processing with respect to the S/N ratio at the position P of the ultrasonic probe 11 is calculated. The /N ratio improvement coefficient E is represented by the above-mentioned mathematical expression (19).

Therefore, the S/N ratio of the defect signal can be maximized by setting the synthesis width N that maximizes the S/N ratio improvement coefficient E by using Expression (19) and performing the aperture synthesis process. In addition, the S/N ratio of the defect signal can be sufficiently improved by determining the number of additions N that satisfies the above-described mathematical expression (20) and performing the aperture synthesis processing. Note that, similarly to the first embodiment, it is desirable to correct the intensity reduced by the aperture synthesis process to the intensity before the process.

Although the embodiments to which the invention made by the present inventors has been described have been described above, the present invention is not limited to the description and the drawings that form a part of the disclosure of the present invention according to the present embodiment. For example, the present invention may be applied as an inspection device that constitutes a steel product manufacturing equipment row, and the inside of the steel product manufactured by the manufacturing device may be inspected and detected in the ultrasonic testing device according to the present invention. Further, the present invention may be applied as an inspection step included in the method for manufacturing a steel product, and the inside of the steel product manufactured in the manufacturing step may be inspected and flaw-detected. In the flaw detection step, defects inside the steel material are detected based on the result of the opening synthesis processing in the inspection step, and results regarding presence/absence of defects, defect position, defect size, etc. are obtained.

Furthermore, the present invention may be applied to a quality assurance method for steel products, and the quality of the steel products may be guaranteed by inspecting the inside of the steel products and performing flaw detection. Specifically, according to the present invention, the inside of a steel material can be inspected in a flaw detection step, and the quality of the steel material can be guaranteed from the flaw detection result obtained in the flaw detection step. In the flaw detection step, defects inside the steel material are detected based on the result of the opening synthesis processing in the inspection step, and results regarding presence/absence of defects, defect position, defect size, etc. are obtained. In the quality assurance step that follows, it is determined whether the manufactured steel material meets the criteria specified in advance based on the results related to the presence/absence of defects, the defect position, and the defect size obtained in the flaw detection step. Guarantee. As described above, all other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the present embodiment are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic flaw detector 11 Ultrasonic probe 12 Probe head 13 Frame 14 Rotation drive device 15 Pulser 16 Receiver 17 A/D converter 18 Recording device 19 Signal processing device 20 Display device RB Round bar

Claims (9)

The inside of the inspection material is inspected by transmitting an ultrasonic signal from the ultrasonic probe to the inspection material and receiving the ultrasonic signal reflected inside the inspection material as a defect signal in the ultrasonic probe. An ultrasonic flaw detection method for
A receiving step of receiving a plurality of defect signals in the ultrasonic probe while changing the positional relationship between the inspection material and the ultrasonic probe;
In each positional relationship between the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position is calculated as the received sound pressure ratio, and the calculated received sound pressure ratio Based on the determination step of determining the combined width in the opening combination process at each depth position of the inspection material,
An inspection step of inspecting the inside of the inspection material by executing an aperture synthesis process using a plurality of defect signals according to the determined synthesis width;
An ultrasonic flaw detection method comprising: In the determining step, the rate of change of the S/N ratio of the defect signal by the aperture synthesis processing is calculated from the rate of change of the received sound pressure ratio, and a synthesis width in which the rate of change of the S/N ratio of the defect signal is equal to or more than a predetermined value is calculated. The ultrasonic flaw detection method according to claim 1, further comprising a step of determining a synthetic width in the aperture synthetic processing. In the determining step, when the ultrasonic probe is a circular ultrasonic probe, the ultrasonic wave is received using the directivity angle ψ of the ultrasonic signal by using the following formulas (1) and (2). When the sound pressure ratio R is calculated and the ultrasonic probe is a rectangular ultrasonic probe, the directivity angle ψ of the ultrasonic signal is calculated by using the following formulas (1) and (3). The ultrasonic flaw detection method according to claim 1 or 2, further comprising the step of calculating the reception sound pressure ratio R by using. However, the parameter m in Expressions (2) and (3) is a coefficient determined by the directivity angle ψ.
In the inspecting step, the defect signal A obtained by the aperture synthesis processing is arithmetically averaged with the reception sound pressure ratios R _n (n=0 to N) at N points by using the following mathematical expressions (4) and (5). The ultrasonic flaw detection method according to claim 1, further comprising a step of correcting the intensity of the defect signal A by dividing the received sound pressure ratio S after aperture synthesis.
The determining step sets the incident range of any ultrasonic signal in the inspection material from the positional relationship between the ultrasonic probe and the depth position of the internal defect, and the snell of the ultrasonic signal within the set incident range of the ultrasonic signal. The ultrasonic signal propagation path is calculated based on the law, and the calculation is repeated to determine whether the ultrasonic signal propagation path passes through the internal defect by coordinate calculation. A step of calculating a propagation path of the sound wave signal, and calculating delay times of a plurality of defect signals necessary for aperture synthesis processing based on the calculated propagation path of the ultrasonic wave signal for each depth position. The ultrasonic flaw detection method according to any one of claims 1 to 4. The determining step sets the incident range of an arbitrary ultrasonic signal in the inspection material from the positional relationship between the ultrasonic probe and the depth position of the internal defect, and the ultrasonic wave is set within the set incident range of the ultrasonic signal. The angle formed by the normal line of the inspection material at the signal incident point and the line segment connecting the ultrasonic probe and the ultrasonic signal incident point, and the line segment connecting the assumed defect position and the ultrasonic signal incident point The propagation path of the ultrasonic signal for each depth position of the internal defect is calculated by repeatedly performing the calculation to determine whether the angle formed by Snell's law is satisfied, and the ultrasonic signal for each calculated depth position is calculated. The ultrasonic flaw detection method according to any one of claims 1 to 4, further comprising a step of calculating delay times of a plurality of defect signals required for the aperture synthesis processing based on the propagation path of (1). The inside of the inspection material is inspected by transmitting an ultrasonic signal from the ultrasonic probe to the inspection material and receiving the ultrasonic signal reflected inside the inspection material as a defect signal in the ultrasonic probe. An ultrasonic flaw detector for
Receiving means for receiving a plurality of defect signals in the ultrasonic probe while changing the positional relationship between the inspection material and the ultrasonic probe,
In each positional relationship between the inspection material and the ultrasonic probe, the ratio of the received sound pressure of the defect signal to the received sound pressure of the defect signal at the reference position is calculated as the received sound pressure ratio, and the calculated received sound pressure ratio Based on the determination means for determining the combined width in the opening combination processing at each depth position of the inspection material,
Inspecting means for inspecting the inside of the inspection material by executing aperture synthesis processing using a plurality of defect signals according to the determined synthesis width,
An ultrasonic flaw detector, comprising: Manufacturing equipment for manufacturing steel,
The ultrasonic flaw detector according to claim 7, which inspects the inside of the steel material manufactured by the manufacturing apparatus,
A steel material manufacturing equipment line comprising: Manufacturing steps for manufacturing steel,
The ultrasonic flaw detection method according to any one of claims 1 to 6, comprising a flaw detection step of performing flaw detection inside the steel material manufactured in the manufacturing step,
A method of manufacturing a steel material, comprising: