JP5994852B2 - Steel quality evaluation method and quality evaluation apparatus - Google Patents

Description

  The present invention relates to a steel material quality evaluation method and a quality evaluation apparatus that detect a steel material using ultrasonic waves and evaluate the quality of the steel material based on a flaw detection result.

  In general, a sheet steel material is manufactured through a plurality of processes such as continuous casting, hot rolling, pickling, cold rolling, and galvanization. Defects that are a problem in the final product of such a sheet steel material are surface defects that are problematic in appearance and defects directly under the surface layer (in the range of about 50 μm to 10 mm in depth from the surface) that are manifested by pressing. These defects may occur in each of the aforementioned processes. For example, defects generated in the continuous casting process include alumina inclusions and powder inclusions. In addition, it is said that one of the causes of surface defects is that bubbles under the surface of the steel material appear on the surface during scale-off treatment in the hot rolling process, and the scale is clogged in the bubbles. Since these inclusions and bubbles usually exist directly under the surface layer of continuously cast steel slabs, defects such as those under the surface layer of steel slabs can be obtained as much as possible by electromagnetic stirring or braking technology in the mold of the continuous casting machine. Efforts to prevent it from occurring are being implemented.

  As one of the methods for evaluating the quality of the steel slab in order to judge whether the casting conditions of the continuous casting process are appropriate, after grinding the surface of the material to be inspected cut out from the steel slab for about several millimeters, There is a method of statistically examining the distribution state of inclusions and bubbles inside the inspection material by detecting the inspection material using an ultrasonic flaw detection method. The ultrasonic flaw detection method is an inspection method widely used for flaw detection inside a steel product. The generally known ultrasonic flaw detection method is a method for flaw detection using a vertical pulse echo method in which an ultrasonic signal is incident perpendicular to the flaw detection surface. Are acoustically coupled with oil or water, and an echo signal is received by an ultrasonic probe. However, according to this ultrasonic flaw detection method, the central part of the thickness of the material to be inspected can be sufficiently detected, but the extreme surface layer part several millimeters below the surface is a dead zone where ultrasonic signals and echo signals cannot be detected. Can't flaw to get into.

  From such a background, a method for increasing the frequency of an ultrasonic signal to, for example, about 50 MHz has been proposed as a method for flaw detection of the extreme surface layer portion (in the range of about 50 μm to 2 mm deep from the surface) of the material to be inspected. ing. Specifically, Patent Document 1 discloses the time width of a surface echo signal received by increasing the frequency of an ultrasonic signal in a method for flaw detection using a vertical pulse echo method through water. A method for detecting a multiple reflection echo signal which is shortened and is generated by a defect existing in a surface layer portion is described. According to this method, since it becomes possible to detect a defect echo signal that could not be detected in the conventional dead zone region, it is possible to detect defects in the extreme surface layer portion.

Japanese Patent Laid-Open No. 01-237449 JP 09-257762 A

  However, the ultrasonic flaw detection method described in Patent Document 1 has the following problems. Hereinafter, the problems of the ultrasonic flaw detection method described in Patent Document 1 will be described with reference to FIGS.

  11 and 12 respectively show the ultrasonic signal when the surface layer portion (in the range of several mm to 10 mm from the surface) of the inspection object having a rough surface is detected using the ultrasonic flaw detection method described in Patent Document 1. It is a figure which shows the waveform of a reflection path | route and an echo signal. As shown in FIG. 11, when the surface S of the material to be inspected is rough, the ultrasonic signal transmitted from the ultrasonic flaw detector 100 and reflected by the defect D inside the material to be inspected is reflected at the mountain portion of the surface S. The path R1 and the valley portion of the surface S propagate along the reflection path R2. For this reason, when an inspection material having a rough surface S is detected, a difference occurs in the propagation time of the ultrasonic signal due to the unevenness of the surface S. On the other hand, as shown in FIG. 12C, the echo signals received by the ultrasonic flaw detector 100 are the surface echo signal ES1 and the defect echo signal propagated through the reflection path R1 (see FIG. 11) shown in FIG. This is the sum of the echo signal including EF1 and the echo signal including the surface echo signal ES2 and the defect echo signal EF2 propagated through the reflection path R2 (see FIG. 11) shown in FIG.

  For the above reasons, a time difference occurs between the surface echo signal ES1 propagated through the reflection path R1 and the surface echo signal ES2 propagated through the reflection path R2. Specifically, if the material to be inspected is steel and a part having a 1 mm dent is detected on the surface, the sound speed of steel is about 5900 m / s and the sound speed in water is about 1490 m / s. A surface echo signal ES2 propagated through the reflection path R2 appears at a position corresponding to about 4 mm below the surface with respect to the surface echo signal ES1 propagated through the path R1. For this reason, as shown in FIGS. 12C and 12D, the time width of the surface echo signal ES included in the echo signal received by the ultrasonic flaw detector 100 becomes long, and the surface echo signal ES detects a defect. Therefore, the noise enters the flaw detection gate set for this reason, and the S / N is lowered. As a result, the surface layer defect cannot be detected with high accuracy.

  In addition, in order to solve such a problem, Patent Document 2 discloses that the surface of a steel material is ground and then the surface of the steel material is detected by using an ultrasonic flaw detection method, thereby suppressing the generation of noise due to surface irregularities. How to do is described. However, according to the technique described in Patent Document 2, it becomes impossible to detect defects in the ground surface portion.

  In many cases, the material to be inspected has not only a flat surface but also a non-flat portion having a rough surface and large irregularities compared to the average surface roughness of the flat portion. For example, in the case of a thick plate, a seamless pipe, etc., a dent may be generated by a scale being pushed into the surface in a rolling process or the like, or a dent may be present in a part that has been partially maintained. Further, a recess called an oscillation mark exists on the surface of the continuously cast steel piece. For this reason, provision of the technique which can detect the defect of the surface layer part which has an unevenness | corrugation with high precision was anticipated.

  This invention is made | formed in view of the said subject, The objective is to provide the quality evaluation method and quality evaluation apparatus of the steel material which can detect a defect of the surface layer part which has an unevenness | corrugation with high precision.

  In order to solve the above-described problems and achieve the object, a quality evaluation method for a steel material according to the present invention scans an ultrasonic signal toward a surface facing the surface of a steel material including a surface layer portion, A step of receiving an echo signal from the steel material generated by scanning, and calculating a propagation path of the echo signal from the surface using the waveform data of the echo signal, and a scanning direction of the ultrasonic signal from the calculated propagation path A step of calculating a shape profile of the surface in the step, and a detection range of an echo signal derived from a defect in the steel material is set as a flaw detection gate based on the shape profile of the surface, and the maximum value of the echo signal in the set flaw detection gate And a step of generating and outputting a defect instruction image in which is mapped.

  In the quality evaluation method for a steel material according to the present invention, in the above invention, the step of calculating the shape profile calculates an envelope waveform with respect to a waveform of an echo signal from the surface, and calculates the propagation path length from the envelope waveform. The method further includes a step of calculating a shape profile of the surface in the scanning direction on the ultrasonic signal by performing a smoothing process on the profile of the propagation path in the scanning direction of the ultrasonic signal.

  The quality evaluation method for a steel material according to the present invention is characterized in that, in the above invention, the smoothing process is a smoothing process using a moving average process.

  In the steel material quality evaluation method according to the present invention, in the above invention, the step of receiving the echo signal includes the step of receiving a line-focused ultrasonic signal through water, And a second piezoelectric vibrator that receives the echo signal, and the first piezoelectric vibrator and the second piezoelectric vibrator comprise the first piezoelectric vibration. Using flaw detection means arranged opposite to each other through an acoustic separator so that the intersection position of the ultrasonic signal transmitted by the child and the central axis of the received signal visual field is located within a predetermined depth range in the steel material It is characterized by performing.

  In the quality evaluation method for a steel material according to the present invention, in the above invention, the first and second piezoelectric vibrators may be disposed on a surface where the first piezoelectric vibrator and the second piezoelectric vibrator face each other. In the vertical and parallel directions, signals transmitted or received are arranged to be diffused and focused.

  In order to solve the above-mentioned problems and achieve the object, the steel material quality evaluation apparatus according to the present invention scans an ultrasonic signal toward a surface facing the surface of the steel material including the surface layer portion, and the ultrasonic signal A flaw detection means for receiving an echo signal from the steel material generated by scanning, and a propagation path of the echo signal from the surface using the waveform data of the echo signal, and scanning of the ultrasonic signal from the calculated propagation path A calculation means for calculating a shape profile of the surface in the direction, and a detection range of an echo signal derived from a defect in the steel material is set as a flaw detection gate based on the shape profile of the surface, and the echo signal in the set flaw detection gate is set Image generation means for generating and outputting a defect instruction image in which the maximum value is mapped.

  According to the quality evaluation method and quality evaluation apparatus for steel materials according to the present invention, it is possible to accurately detect defects in the surface layer portion having irregularities.

FIG. 1 is a block diagram showing the configuration of a steel quality evaluation apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart showing the flow of the quality evaluation process for steel material according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing an echo signal generated along with scanning of an ultrasonic signal. FIG. 4 is a diagram for explaining a method of calculating the propagation path of the B echo. FIG. 5 is a diagram for explaining a method of calculating a B scope image. FIG. 6 is a diagram for explaining a method of smoothing the B scope image. FIG. 7 is a diagram for explaining a method for generating a defect instruction image. FIG. 8 is a diagram illustrating an example of a C scope image and a B scope image. FIG. 9A is a side view showing the configuration of the ultrasonic probe. FIG. 9B is a plan view showing the configuration of the ultrasonic probe. FIG. 10 is a schematic diagram for explaining the configuration of the piezoelectric vibrator. FIG. 11 is a diagram illustrating a reflection path of an ultrasonic signal when a surface layer portion of a test object having a rough surface is detected. FIG. 12 is a diagram illustrating waveforms of an echo signal and a gate signal when a surface layer portion of a test object having a rough surface is detected.

  Hereinafter, a steel quality evaluation apparatus and a quality evaluation method according to an embodiment of the present invention will be described with reference to the drawings.

[Configuration of quality evaluation equipment]
First, with reference to FIG. 1, the structure of the quality evaluation apparatus of the steel material which is one Embodiment of this invention is demonstrated.

  FIG. 1 is a block diagram showing the configuration of a steel quality evaluation apparatus according to an embodiment of the present invention. As shown in FIG. 1, the quality evaluation apparatus for steel material according to an embodiment of the present invention includes an ultrasonic flaw detector 10, a flaw detector control unit 11, an A / D conversion unit 12, a waveform memory 13, and a black skin shape profile. A calculation unit 14, a defect instruction imaging unit 15, and a defect instruction output unit 16 are provided as main components.

  The ultrasonic flaw detector 10 transmits an ultrasonic signal toward the steel material 1 and receives a reflection signal of the ultrasonic signal from the steel material 1 as an echo signal.

  The flaw detector control unit 11 controls the drive of the ultrasonic flaw detector 10 and outputs an echo signal received by the ultrasonic flaw detector 10 to the A / D converter 12.

  The A / D converter 12 converts the waveform data of the analog echo signal output from the flaw detector control unit 11 into the waveform data of the digital echo signal, and converts the waveform data of the echo signal converted into the digital form It is stored in the waveform memory 13.

  The black skin shape profile calculation unit 14, the defect instruction imaging unit 15, and the defect instruction output unit 16 are realized by an information processing apparatus such as a microprocessor executing a computer program.

  The black skin shape profile calculation unit 14 calculates the shape profile of the black skin surface S 1 of the steel material 1 using the waveform data of the echo signal stored in the waveform memory 13.

  The defect instruction imaging unit 15 generates, as a defect instruction image, an image of a defect existing on the surface layer portion of the steel material 1 based on the shape profile of the black skin surface S1 of the steel material 1 calculated by the black skin surface profile calculation unit 14 To do.

  The defect instruction output unit 16 outputs the defect instruction image generated by the defect instruction imaging unit 15.

[Quality evaluation process]
The steel material quality evaluation apparatus having such a configuration detects defects in the surface layer portion having irregularities by executing the following quality evaluation process. Hereinafter, with reference to the flowchart shown in FIG. 2, operation | movement of the quality evaluation apparatus of the steel materials at the time of performing quality evaluation processing is demonstrated.

  FIG. 2 is a flowchart showing the flow of quality evaluation processing according to an embodiment of the present invention. In the flowchart shown in FIG. 2, an ultrasonic flaw detector 10 has a surface S <b> 2 (hereinafter referred to as a scanning plane S <b> 2) facing the black skin surface S <b> 1 of a plate-shaped steel material 1 cut out from a continuously cast steel piece. The steel material 1 is set so as to face (see FIG. 1), and starts at the timing when the quality evaluation apparatus is instructed to execute the quality evaluation process, and the quality evaluation process proceeds to step S1.

  In the process of step S <b> 1, the flaw detector control unit 11 sets the value of the program counter p that specifies the position in the length direction of the steel material 1 to 1. Thereby, the process of step S1 is completed and a quality evaluation process progresses to the process of step S2.

  In the process of step S2, the flaw detector control unit 11 reads the width direction scanning data Data (p) corresponding to the value of the program counter p. Thereby, the process of step S2 is completed and the quality evaluation process proceeds to the process of step S3.

  In the process of step S3, the flaw detector control unit 11 moves the steel material 1 and the ultrasonic flaw detector 10 to move the ultrasonic flaw detector 10 to the position in the length direction of the steel material 1 corresponding to the program counter p. Moving. The flaw detector control unit 11 moves the steel material 1 and the ultrasonic flaw detector 10 relatively along the width direction of the steel material 1 in accordance with the width direction scanning data Data (p) read out in the process of step S2. By transmitting an ultrasonic signal from the ultrasonic flaw detector 10, the ultrasonic signal is scanned toward the scanning surface S2. The flaw detector controller 11 outputs an echo signal received by the ultrasonic flaw detector 10 to the A / D converter 12. The A / D converter 12 converts the waveform data of the analog echo signal output from the flaw detector control unit 11 into the waveform data of the digital echo signal, and the waveform of the echo signal converted into the digital form Data is stored in the waveform memory 13. Thereby, the process of step S3 is completed and the quality evaluation process proceeds to the process of step S4.

  In the processing of step S4, the black skin shape profile calculation unit 14 extracts an echo signal (hereinafter referred to as B echo) from the black skin surface S1 from the waveform data of the echo signal stored in the waveform memory 13. Then, the shape profile (B scope image, bottom surface position information) of the black skin surface S1 is calculated using the extracted B echo. Here, a method for calculating the shape profile of the black skin surface S1 will be described in detail with reference to FIGS. As shown in FIG. 3, by sending an ultrasonic signal from the ultrasonic flaw detector 10, B echo EB from the black skin surface S1 of the steel material 1, echo signal from the defect D in the steel material 1 (hereinafter referred to as F echo). And EF and an echo signal ES from the scanning plane S2 is generated.

  When calculating the shape profile of the black skin surface S1, the black skin surface profile calculation unit 14 calculates the propagation path length (propagation time or depth position) of the B echo. Specifically, as shown in FIG. 4, the black skin surface profile calculation unit 14 uses the B echo gate to convert the B echo waveform data from the waveform data of the echo signal stored in the waveform memory 13. The propagation path length ΔT is calculated from the rise of the B echo waveform BL in the B echo gate. When calculating the propagation path length ΔT of the B echo, an envelope waveform (detection waveform) L1 is calculated by subjecting the absolute value of the B echo waveform BL to processing such as low-pass filter processing and moving average processing. It is desirable that the propagation time when the amplitude of the waveform L1 is equal to or greater than the threshold value Tb be the propagation path length ΔT. Then, as shown in FIGS. 5A and 5B, the black skin shape profile calculation unit 14 determines the propagation path length ΔT of the B echo EB in the scanning direction of the ultrasonic signal based on the propagation path length ΔT of the B echo. Is generated as a shape profile of the black skin surface S1 in the scanning direction of the ultrasonic signal. Thereby, the process of step S4 is completed and the quality evaluation process proceeds to the process of step S5.

  In the process of step S5, the black skin shape profile calculation unit 14 performs a smoothing process on the shape profile of the black skin surface S1 generated by the process of step S4. In the process of step S4, the shape profile of the black skin surface S1, including the F echo immediately below the black skin surface S1, is captured. For this reason, as shown in FIG. 6, the black skin shape profile calculation unit 14 performs a smoothing process on the shape profile of the black skin surface S1, thereby calculating the shape of the true black skin surface S1. The smoothing process can be performed by performing a moving average process or a low-pass filter process using a digital IIR filter, FIR filter, or the like. Thereby, the process of step S5 is completed, and the quality evaluation process proceeds to the process of step S6.

  In the process of step S6, the defect instruction imaging unit 15 sets the F echo detection range as a flaw detection gate based on the shape profile of the black skin surface S1 smoothed by the process of step S5. Specifically, as shown in FIG. 7, the defect instruction imaging unit 15 sets a predetermined amplitude range based on the shape profile of the black skin surface S1 as a flaw detection gate. Then, the defect indication imaging unit 15 generates an F echo profile (F scope image) in the scanning direction of the ultrasonic signal with reference to the black skin surface S1 using the flaw detection gate, and maximizes the amplitude of the F echo. The value (maximum echo height) and its position coordinates are calculated. By setting the flaw detection gate based on the shape profile of the black skin surface S1, the flaw detection gate can be set so as to follow the unevenness of the black skin surface S1, so that defects on the surface layer portion having the unevenness can be detected with high accuracy. it can. Thereby, the process of step S6 is completed and the quality evaluation process proceeds to the process of step S7.

  In the process of step S7, the defect instruction imaging unit 15 outputs the maximum echo height calculated by the process of step S6 and its position coordinates to a temporary storage memory (not shown). Thereby, the process of step S7 is completed, and the quality evaluation process proceeds to the process of step S8.

  In step S8, the flaw detector control unit 11 determines whether there is unprocessed width direction scanning data Data (p). If there is unprocessed width direction scanning data Data (p) as a result of the determination, the flaw detector control unit 11 advances the quality evaluation process to the process of step S9. On the other hand, when there is no unprocessed width direction scanning data Data (p), the flaw detector control unit 11 advances the quality evaluation process to the process of step S10.

  In the process of step S9, the probe control unit 11 increments the value of the program counter p by one. Thereby, the process of step S9 is completed, and the quality evaluation process returns to the process of step S2.

  In the process of step S10, the defect indication imaging unit 15 maps the maximum echo height and the position coordinates of each width direction scanning data Data (p) output to a temporary storage memory (not shown) in the length direction of the steel material 1. By doing so, a defect instruction image is generated. The defect instruction output unit 16 outputs the defect instruction image generated by the defect instruction imaging unit 15. Thereby, the process of step S10 is completed and a series of quality evaluation processes are complete | finished.

  In the process of step S10, the defect indication imaging unit 15 performs a labeling process on the position coordinates having the maximum echo height equal to or higher than a preset threshold value, and determines the number of defects, the defect diameter, the defect depth based on the labeling process result. It is also possible to calculate and output the size.

  As is clear from the above description, according to the steel material quality evaluation apparatus which is an embodiment of the present invention, the flaw detector control unit 11 is a scanning surface S2 facing the black skin surface S1 of the steel material 1 including the surface layer portion. And the echo signal from the steel material 1 generated along with the scan of the ultrasonic signal is received, and the black skin shape profile calculation unit 14 uses the waveform data of the echo signal to obtain the black skin surface. The propagation path of the echo signal from S1 is calculated, the shape profile of the black skin surface S1 in the scanning direction of the ultrasonic signal is calculated from the calculated propagation path, and the defect indication imaging unit 15 and the defect indication output unit 16 are Based on the shape profile of the black skin surface S1, a detection range of an echo signal derived from a defect in the steel material 1 is set as a flaw detection gate, and a defect indication image in which the maximum value of the echo signal in the set flaw detection gate is mapped It formed, to output. According to such a configuration, by setting the flaw detection gate based on the shape profile of the black skin surface S1, the flaw detection gate can be set to follow the unevenness of the black skin surface S1, so that the surface layer portion having the unevenness can be set. Defects can be detected with high accuracy.

[Example 1]
In this embodiment, a steel material having a width (C direction) of 300 mm, a length (L direction) of 300 mm, and a thickness of 5 mm is processed from a continuously cast steel piece, and the black skin surface is scanned with ultrasonic waves from an ultrasonic probe. The steel material was installed so that the surface was opposite, and the reflected signal from the inside of the steel material was received while mechanically scanning the ultrasonic probe. At this time, the ultrasonic probe uses a single probe with a frequency of 5 MHz, a vibrator diameter of 12.8 mm, and a focal length of 60 mm. The ultrasonic wave was transmitted and received with the flaw detection pitch being 0.5 mm pitch in both the C direction and the L direction of the steel material. Further, the mechanical scanning direction of the ultrasonic probe was the width direction (C direction), and the flaw detection was performed 400 times while shifting by 0.5 mm in the length direction. The received waveform was stored in the waveform memory for each scan, and the nth received waveform in the C direction was linked as Data (n) and stored in the waveform memory. Then, after ultrasonically flaw-detecting the entire surface of the steel material and measuring the received waveform, flaw detection was performed under the black skin.

  For the propagation path of B echo, the absolute value of the received waveform is subjected to moving average processing of 50 points (equivalent to 0.1 μsec in propagation time), the envelope waveform is calculated, and the position where the amplitude of the envelope waveform is equal to or greater than the threshold Tb Calculated by reading. Since it is preferable that the threshold value Tb for calculating the propagation path of the B echo is as small as possible, a steel material having no defect is flawed in advance and set as the maximum value of noise level of the flaw detection waveform +0.5 dB. In smoothing filter processing for the shape profile of the black skin, 10 points of moving average processing were performed and smoothing processing was performed. FIG. 8 shows a two-dimensional image (C scope image and B scope image) obtained by flaw detection of a defect (depth direction: 0.1 mm to 2.0 mm) immediately below the black skin surface according to the present example. According to this example, it was possible to detect a bubble defect of about φ0.8 mm at a depth of 0.1 mm, which was difficult with the conventional ultrasonic flaw detection method. From the above, according to the present Example, it has confirmed that the defect of the surface layer part which has an unevenness | corrugation could be detected with high precision.

[Example 2]
In Example 1, a single probe having a frequency of 5 MHz, a vibrator diameter of 12.8 mm, and a focal length of 60 mm was used as the ultrasonic probe. However, when a single probe is used as an ultrasonic probe, a dead zone occurs due to the influence of the reflected wave from the steel surface, so it is possible to detect within 3 mm from the bottom of the steel surface where the ultrasonic signal enters. Can not. Therefore, in this example, ultrasonic flaw detection was performed using an ultrasonic probe as shown in FIGS. 9A and 9B.

  9A and 9B are a side view and a plan view showing the configuration of the ultrasonic probe, respectively. As shown in FIGS. 9A and 9B, the ultrasonic probe used in this embodiment includes a piezoelectric vibrator 51 and a piezoelectric vibrator 52, and the piezoelectric vibrator 51 and the piezoelectric vibrator 52. Are arranged opposite to each other with an acoustic separator 53 interposed therebetween.

  The piezoelectric vibrators 51 and 52 have a shape capable of transmitting and receiving an ultrasonic signal in a line focus shape. Specifically, when the shape of the piezoelectric vibrators 51 and 52 is a rectangular shape, as shown in FIG. 10, the piezoelectric vibrators 51 and 52 are arranged so that the ultrasonic signal is focused on the long side LS side. The short side SS side is formed so as to be flat so that the ultrasonic signal is diffused. The piezoelectric vibrators 51 and 52 may be formed by attaching an acoustic lens to a flat piezoelectric vibrator so that an ultrasonic signal can be transmitted and received in a line focus form.

  In the present embodiment, the piezoelectric vibrator 51 transmits an ultrasonic signal UB in a line focus shape using a water immersion method as an acoustic coupling method, that is, through water. The piezoelectric vibrator 52 has a line focus-like reception signal field RS, and receives an echo signal generated with the ultrasonic signal UB transmitted by the piezoelectric vibrator 51. The piezoelectric vibrators 51 and 52 are formed such that signals transmitted or received are diffused and converged in directions perpendicular to and parallel to the surfaces of the piezoelectric vibrator 51 and the piezoelectric vibrator 52 facing each other. Has been.

  Further, the piezoelectric vibrator 51 and the piezoelectric vibrator 52 adjust the angles φ1 and φ2 of the central axis with respect to the normal line of the steel material surface S1, thereby the center of the ultrasonic signal UB transmitted by the piezoelectric vibrator 51. The intersection position P between the axis L1 and the central axis L2 of the received signal visual field RS is arranged so as to be located within a predetermined depth range Dc in the steel material. The piezoelectric vibrator 51 and the piezoelectric vibrator 52 are arranged such that the focal depth F in the steel is within a predetermined depth range Dc in the steel.

  According to the ultrasonic probe having such a configuration, the piezoelectric vibrator 51 and the piezoelectric vibrator 52 are directed in a direction different from the regular reflection direction. For this reason, the signal transmitted from the piezoelectric vibrator 51 and reflected by the surface of the steel material is not easily received by the piezoelectric vibrator 52, and the amplitude of the surface reflected wave (S echo) is reduced. Further, since the acoustic separator 53 blocks the scattered wave that is reflected on the surface of the steel material and leaks into the piezoelectric vibrator 52, the amplitude of the surface reflected wave is further reduced, and the dead zone can be reduced as much as possible. .

  Note that the two-divided probe used for the flaw detection of a thick plate has the same configuration as the ultrasonic probe used in the present embodiment. However, in the two-divided probe, the wedge is made of a resin material, and the acoustic coupling method is a water thin film method (gap method). For this reason, if the gap (distance) between the two-divided probe and the steel material fluctuates in the opening direction even a little, multiple reflection occurs between the wedge bottom surface portion and the steel material surface, and noise is generated. On the other hand, the ultrasonic probe used in the present embodiment does not use a wedge, so no noise is generated due to distance fluctuation.

  In the conventional technique, the ultrasonic signal is increased in frequency to narrow the dead zone of the S echo, and the ultrasonic signal is focused in order to receive the reflected wave from the defect with a high S / N ratio. Yes. However, when the ultrasonic signal is increased in frequency and focused, the depth range of the steel material capable of flaw detection becomes narrower. On the other hand, the ultrasonic probe used in this example is arranged so that the side where the line-focused ultrasonic signal is diffused intersects the depth direction of the steel material. A reflected wave from a defect existing in the measurement depth range Dc shown in FIG. 9A can be received. As a result, the dead zone can be narrowed and a wide depth range of the steel material can be detected without increasing the frequency of the ultrasonic signal.

  The embodiment to which the invention made by the present inventors is applied has been described above, but the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the quality evaluation method and quality evaluation apparatus of the steel material which can detect a defect of the surface part which has an unevenness | corrugation with high precision can be provided.

DESCRIPTION OF SYMBOLS 1 Steel materials 10,100 Ultrasonic flaw detector 11 Flaw detector control part 12 A / D conversion part 13 Waveform memory 14 Black skin shape profile calculation part 15 Defect instruction | indication imaging part 16 Defect instruction | indication output part 51,52 Piezoelectric vibrator 53 Sound separator D Defect S1 Black skin S2 Scanning surface

Claims (5)

A method for evaluating the quality of a steel material comprising a surface having a non-flat portion with a large surface roughness compared to the average surface roughness of the flat portion,
A step towards a surface opposite to the surface including the surface layer portion to scan the ultrasonic signal, receiving echo signals from steel produced with the scanning of the ultrasonic signals,
Calculating the propagation path of the echo signal from the surface using the waveform data of the echo signal, calculating the shape profile of the surface in the scanning direction of the ultrasonic signal from the calculated propagation path;
A defect in which the range of a predetermined distance based on the shape profile of the surface is set as a flaw detection gate that is a detection range of an echo signal derived from a defect in the steel material, and the maximum value of the echo signal in the set flaw detection gate is mapped Generating and outputting an instruction image,
The step of calculating the shape profile calculates an envelope waveform for the waveform of the echo signal from the surface, calculates the propagation path from the envelope waveform, and calculates the propagation path profile in the scanning direction of the ultrasonic signal. A method for evaluating the quality of a steel material, comprising a step of calculating a shape profile of the surface in a scanning direction of an ultrasonic signal by performing a smoothing process.   The steel material quality evaluation method according to claim 1, wherein the smoothing process is a smoothing process using a moving average process.   The step of receiving the echo signal includes a first piezoelectric transducer that transmits a line-focused ultrasonic signal through water and a line-focused received signal field, and receives the echo signal. Two piezoelectric transducers, and the first piezoelectric transducer and the second piezoelectric transducer transmit the ultrasonic signal transmitted by the first piezoelectric transducer and the central axis of the received signal field. The steel material according to claim 1 or 2, wherein flaw detection means are arranged so as to face each other via an acoustic separator so that the crossing position of the steel material is within a predetermined depth range in the steel material. Quality evaluation method.   In the first and second piezoelectric vibrators, signals transmitted or received are diffused in directions perpendicular to and parallel to the surfaces of the first piezoelectric vibrator and the second piezoelectric vibrator facing each other. The steel material quality evaluation method according to claim 3, wherein the steel material quality evaluation method is arranged so as to converge. A steel material quality evaluation apparatus comprising a surface having a non-flat portion with a large surface roughness compared to the average surface roughness of the flat portion,
Towards the opposite surface to the surface including the surface layer portion to scan the ultrasonic signals, and testing means for receiving echo signals from steel produced with the scanning of the ultrasonic signals,
A calculation means for calculating a propagation path of the echo signal from the surface using the waveform data of the echo signal, and calculating a shape profile of the surface in the scanning direction of the ultrasonic signal from the calculated propagation path;
A defect in which a predetermined distance range based on the shape profile of the surface is set as a flaw detection gate that is a detection range of an echo signal derived from a defect in the steel material, and the maximum value of the echo signal in the set flaw detection gate is mapped Image generating means for generating and outputting an instruction image,
The calculation means calculates an envelope waveform with respect to a waveform of an echo signal from the surface, calculates the propagation path from the envelope waveform, and performs a smoothing process on the propagation path profile in the scanning direction of the ultrasonic signal. A quality evaluation apparatus for steel material, characterized in that the shape profile of the surface in the scanning direction of the ultrasonic signal is calculated.