JP5558666B2 - Surface defect evaluation apparatus and method for round bar steel by water immersion ultrasonic flaw detection using an electronic scanning array probe - Google Patents

Description

  The present invention relates to an apparatus and method for on-line inspection of surface defects (surface defects) on round steel bars, and more particularly to an apparatus and method for evaluating surface defects on round steel bars by water immersion ultrasonic flaw detection using an electronic scanning array probe. It is about.

  Round steel bar made of special steel is obtained by rolling a steel piece. Usually, multi-stage rolling is performed by a rough row rolling mill, a middle row rolling mill, and a finishing row rolling mill arranged in tandem. By this rolling, the steel slab is gradually reduced in diameter and lengthened to obtain a round bar steel. Depending on the user's request, the round bar steel obtained by rolling is further subjected to heat treatment, peeling processing, etc. to obtain round bar steel (product).

  The round bar steel manufactured in this way may have surface defects. There may be a surface flaw caused by a flaw of a steel slab, or it may be a surface flaw generated in a rolling or later process, but depending on the shape and size of the surface flaw, the quality of the round bar steel is impaired. Therefore, it is necessary to inspect surface flaws according to the purpose of round bar steel and to ship only high quality round bar steel. Surface flaw inspection methods include the ultrasonic flaw detection method, leakage magnetic flux flaw detection method, eddy current flaw detection method, and magnetic particle flaw detection method.The physical properties and dimensions of the test material, automatic flaw detection, the type and size of the defect to be detected, etc. It is necessary to decide the method to be actually adopted in consideration.

  In response to quality requirements for surface defects that are becoming more sophisticated year by year, there is an increasing need for detection of crimped defects having a width of about 0.5 μm. A crimped wrinkle is not a “large defect” in terms of the wrinkle width, but rather is a defect close to a “small defect”, but is also a defect that must be taken care of in the inspection process.

  However, the crimped wrinkle is “a thing that cannot be detected” even under the condition that the surface flaw can be normally detected on-line by the leakage magnetic flux flaw detection method. There is no difference that it is a kind of surface flaw, but since it is a sufficiently narrow defect, it is difficult to detect it by leakage flux flaw detection.

  Even the eddy current flaw detection method cannot detect the crimped wrinkle. The magnetic particle flaw detection method has a high flaw detection ability, but is a sensory test and relies heavily on visual determination, so the flaw evaluation is not stable and workability is low. In addition, this is a ferromagnetic test method, and non-magnetic materials cannot be inspected.

  On the other hand, with regard to the ultrasonic flaw detection method, the ultrasonic beam can be controlled particularly in the ultrasonic flaw detection method using an electronic scanning array probe, so it is possible to examine the improvement of flaw detection ability from the viewpoint of the device configuration and method. I thought.

  As a conventional method for detecting surface defects by ultrasonic flaw detection using an array probe, there is an ultrasonic flaw detection method for detecting defects at the ends of steel plates and in the vicinity of the ends (see, for example, Patent Document 1). According to the method described in Patent Document 1, it is preferable that a plurality of array probes are arranged so that when ultrasonic waves are incident on the steel plate surface from the probe, the ultrasonic waves reflected from the bottom surface detect the end of the steel plate. Are used to detect flaws with a refraction angle of 37 to 65 ° when ultrasonic waves are incident on the steel sheet surface.

Moreover, in the conventional phased array ultrasonic flaw detector, the operation of an ultrasonic flaw detector at a nominal frequency of 1 to 20 MHz is recommended (for example, see Non-Patent Document 1).
JP 2005-201800 JP ASTM E2491-06

  However, the method described in Patent Document 1 is a direct contact method of providing a water film as far as the figure is seen, and automatic flaw detection and workability are insufficient. The problem of wear on the probe surface also occurs. An array probe having a flat shape in which elements are linearly arranged is used, and is not suitable for round bar flaw detection. Since it is a one-time reflection method, the accuracy of evaluation of surface defects decreases due to the influence of the shape and surface roughness of the bottom surface of the steel plate (first reflection point).

  In addition, in order to obtain detection of surface defects having a minimum width of 0.5 μm, it is only necessary to use a transverse wave in steel, and it is not necessary to limit the refraction angle to 37 to 65 °. Further, in the evaluation method described in Non-Patent Document 1, detection of surface defects having a minimum width of 0.5 μm is obtained, for example, flaw detection is performed on a round bar steel material (especially the thick circle side) having a diameter of 10 to 100 mm. From the standpoint of both, it is necessary to limit the flaw detection frequency.

  The present invention was made in order to solve such a conventional problem, and is a void type surface defect including a crimped defect having a width of about 0.5 μm or more in a round steel bar product (surface defect due to burning crack or transformation crack). It is to provide an on-line precision ultrasonic flaw detection method using an electronic scanning phased array probe.

The surface defect evaluation apparatus for round bar steel by immersion ultrasonic flaw detection using the electronic scanning array probe of the present invention is a probe having a substantially circumferential surface centered on the central axis of the round bar steel, facing the round bar steel. A plurality of excitation elements aligned on the probe surface, and at least one array probe unit disposed so that the probe surface and the surface of the round steel bar have a predetermined water distance; A plurality of excitation elements adjacent to each other in a predetermined range among a plurality of excitation elements are selected to form a simultaneous control element group, and the excitation elements in the simultaneous control element group are simultaneously controlled to generate an ultrasonic beam having a predetermined frequency. And a control unit that performs control to detect the surface defects in the round bar steel by causing the ultrasonic beam to enter the round bar steel at a predetermined refraction angle, and the control unit is generated by the simultaneous control element group. The ultrasonic beam generates a focal point, and that focal point The focal point is controlled so that the position of the opening of the surface defect and the position before and after the position of the opening of the surface defect with respect to the traveling direction viewed from the central axis of the ultrasonic beam, and the S / N ratio of the echo from the surface defect is maximized. reduction and control unit, and performs control for irradiating an ultrasonic beam generated by the simultaneous control element groups from both sides of the specific surface defect with respect to the circumferential direction of the round bar steel to a specific surface defect.

Further, the surface defect evaluation method of round bar steel by water immersion ultrasonic flaw detection using the electronic scanning array probe of the present invention is a substantially circumferential surface shape centering on the central axis of the round bar steel, facing the round bar steel. The plurality of excitation elements of the at least one array probe unit are arranged such that the plurality of excitation elements are aligned with each other and the probe surface and the surface of the round steel bar have a predetermined water distance. A plurality of adjacent excitation elements within a predetermined range are selected to form a simultaneous control element group, and the excitation elements in the simultaneous control element group are simultaneously controlled to generate an ultrasonic beam of a predetermined frequency. The beam is incident on the inside of the round bar steel at a predetermined refraction angle, surface defects in the round bar steel are detected, the ultrasonic beam generated by the simultaneous control elements has a focal point, and the focal position of the ultrasonic beam is Surface with respect to the direction of travel as seen from the central axis The position of the opening of Recessed move focus so that its longitudinal position to maximize the S / N ratio of the echo from the surface defects, simultaneous from both sides of the specific surface defect with respect to the circumferential direction of the round bar steel A specific surface defect is irradiated with an ultrasonic beam generated by the control element group .

  According to the surface defect evaluation apparatus and method for round bar steel by ultrasonic flaw detection using the electronic scanning array probe of the present invention, the round bar steel product includes a crimp-type scissors having a width of about 0.5 μm or more. It is possible to accurately detect surface defects (surface defects such as baking cracks and transformation cracks).

  Hereinafter, a surface defect evaluation apparatus and method for round bar steel by ultrasonic flaw detection using an electronic scanning array probe according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing the configuration of a surface defect evaluation apparatus for round bar steel by ultrasonic flaw detection using the electronic scanning array probe of the present embodiment. FIG.1 (b) is a front view of the surface defect evaluation apparatus of the round bar steel by the ultrasonic flaw using the electronic scanning type array probe of this embodiment, and Fig.1 (a) is a figure of this embodiment. It is the figure which looked at the surface defect evaluation apparatus of the round bar steel by the ultrasonic flaw using the electronic scanning type array type probe in the T section of the round bar steel.

  The surface defect evaluation device 100 for round bar steel by ultrasonic flaw detection using the electronic scanning array type probe of the present embodiment (hereinafter, also simply referred to as the surface defect evaluation device 100 for round bar steel) includes a control unit 10, It comprises two array probe units 20-1 and 20-2.

  The control unit 10 is constituted by, for example, a personal computer.

  The round steel bar A to be inspected is conveyed through a hole (not shown) of the water tank 30. The water tank 30 is filled with water 40. Then, when the entire round steel bar A in the water tank 30 is completely immersed in the water 40, the round bar steel surface defect evaluation apparatus 100 according to the present embodiment can perform ultrasonic flaw detection by a so-called water immersion method. For simplification of the drawings, the description of the water 40 is omitted in the subsequent drawings. However, in the round bar steel surface defect evaluation apparatus of the present embodiment, the array probe unit 20 and the round bar steel A described later are used. It is assumed that water 40 exists between them and ultrasonic flaw detection is performed by a water immersion method.

  Also, a minimum guide (not shown) is provided for minimizing misalignment during round bar steel material conveyance (flaw detection), and the round bar steel A is conveyed in the direction B in the figure. The operations of the array probe units 20-1 and 20-2 are controlled by the control unit 10, and the control unit 10 detects the defect signal detected by the array probe unit 20-1 and the array probe unit 20-2. A map of defect detection positions in the round steel bar A is created by combining all of the above.

  In addition, probe surfaces 20-1a and 20-2a having substantially circumferential surfaces are formed on the surfaces of the array probe unit 20-1 and the array probe unit 20-2 facing the round steel bar A. ing. As shown in FIG. 1A, when the array probe unit 20-1 and the array probe unit 20-2 are arranged above and below the round bar steel A, the array probe unit 20-1 The probe surfaces 20-1a and 20-2a, which are substantially circumferential surfaces with each other, are combined with each other to form a concentric probe surface centered on the central axis of the round steel bar A. .

  With such a configuration, when the array probe unit 20-1 and the array probe unit 20-2 are arranged above and below the round steel bar A, the array probe unit 20-1 and the array probe unit are arranged. The probe surface 20-2 can cover all directions (360 °) around the round steel bar A.

  The number of array probe units is not limited to two. As shown in FIG. 2, a concentric probe surface is formed by combining a large number of array probe units 20-1 to 20-n. May be.

  FIG. 3 is a diagram showing a detailed configuration of the array probe unit of the present embodiment. FIG. 3 is a view of the round steel bar A as seen from the T cross section. As shown in the drawing, a large number of excitation elements (hereinafter also simply referred to as elements) 25 are arranged on a probe surface 20 a having a substantially circumferential surface of the array probe unit 20. For example, the excitation element 25 is arranged in 128 elements on the probe surface 20a.

  Here, among a large number of excitation elements 25, a group of a plurality of excitation elements 25 aligned in a predetermined range that are simultaneously controlled when generating an ultrasonic beam to be described later is defined as a simultaneous control element group 21. The simultaneous control element group 21 is one in which an apparent oscillator is electronically formed by a group of a plurality of excitation elements 25 such as 16, 32, 64, for example.

  For example, when 128 excitation elements 25 are arranged on the probe surface 20a of the array probe unit 20, the 1st to 32nd excitation elements 25 from the left are simultaneously controlled. The excitation elements 25 are simultaneously controlled, and the 97th to 128th excitation elements 25 from the left are controlled as appropriate. Thus, the simultaneous control element group 21 is configured.

  In the present embodiment, the flaw detection frequency of the ultrasonic beam generated by the simultaneous control element group 21 is 4 to 20 MHz, preferably 5 to 10 MHz. This is because a crimped wrinkle having a width of 0.5 μm cannot be detected when the flaw detection frequency is less than 4 MHz. Also, in the case of flaw detection of relatively thick round bar steel materials with a diameter of 50 to 100 mm, the influence of ultrasonic attenuation in the steel material increases at flaw detection frequencies exceeding 10 MHz, and the detection performance begins to deteriorate, exceeding 20 MHz. This is because there is a detection omission.

  In the present embodiment, the dimension in the circumferential direction of the probe surface 20a of the round steel bar A of the simultaneous control element group 21 (the length of the arc-shaped thick line E in the figure) is 8 to 30 mm, preferably Is 10-15 mm.

  This is because when the apparent transducer diameter is small, that is, when the size of the simultaneous control element group 21 in the range of the round bar circumference is less than 8 mm, the focus of the ultrasonic beam becomes insufficient, and surface defects are detected. This is because the performance decreases. Further, when the apparent vibrator diameter is large, that is, when the size of the range of the simultaneous control element group 21 in the range of the circumferential direction of the round bar exceeds 30 mm, the dead zone becomes large. This is because the dead zone and the gate interfere with each other and noise increases. The vibrator dimension in the direction along the round bar rolling direction may be about 10 to 20 mm (for example, 15 mm).

  A in the figure is a round bar steel to be evaluated, and its diameter is 15 to 100 mm. C in the figure is a surface defect present in the vicinity of the surface of the round steel bar A.

  D in the figure is an ultrasonic beam generated by the simultaneous control element group 21. As shown in the figure, a part of the ultrasonic beam D is put in the round steel bar A to detect flaws.

  In the figure, s is the central axis of the ultrasonic beam D. t indicates a normal direction with respect to the surface of the round steel bar A at the incident point viewed from the central axis s of the ultrasonic beam D.

  In the figure, θa represents an incident angle with respect to the surface of the round steel bar A at the incident point viewed from the central axis s of the ultrasonic beam D. In the figure, θb represents the transverse wave refraction angle with respect to the surface of the round steel bar A at the incident point as seen from the central axis s of the ultrasonic beam D. In the present embodiment, the transverse wave refraction angle θb is 30 to 65 °, preferably 30 to 45 °.

  This is because the transverse wave in steel can be effectively utilized when the transverse wave refraction angle is 30 to 65 °. Also, the transverse wave has a shorter wavelength than the longitudinal wave, and is suitable for detecting wrinkles and minute defects having a very small wrinkle width. In particular, the refraction angle of 30 to 35 ° is generally avoided from the viewpoint of eliminating the influence of longitudinal waves, but according to the new knowledge of the present inventors, for detection of surface defects having a width of 0.5 μm, Rather, this is because it was found to be equal to or greater than when the refraction angle is 45 °.

  In the figure, l is a water distance, which indicates the distance between the surface of the probe surface 20a of the simultaneous control element group 21 and the surface of the round steel bar A. In the present embodiment, the water distance 1 is set to 15 to 50 mm, preferably 19 to 45 mm.

  This is because reverberation echoes are likely to occur when the water distance l is less than 15 mm. Although the flaw detection cannot be performed if the steel material can be transported in a substantially stationary state, automatic flaw detection at a general transport speed (about 1 to 2.5 m / sec) is significantly hindered.

  On the other hand, when the water distance l exceeds 50 mm, the attenuation of ultrasonic waves in water increases, and the surface flaw detection ability decreases. In particular, leakage of detection occurs on a surface wrinkle having a wrinkle width of 0.5 μm.

  FIG. 4 is a conceptual diagram for explaining the operating state of the simultaneous control element group 21 of the present embodiment. The simultaneous control element group 21 includes a delay circuit 23 and a large number of excitation elements 25a to 25p.

  Each excitation element 25 a to 25 p is connected to a delay circuit 23 controlled by the control unit 10. From the delay circuit 23, the excitation pulse 22 is emitted toward each of the excitation elements 25a to 25p. When receiving the excitation pulse 22, each excitation element 25 a to 25 p emits an ultrasonic wave 24. The timing at which the excitation pulse 22 is emitted can be set for each excitation element 25 by the delay circuit 23. That is, the simultaneous control element group 21 is a so-called array probe.

  In the example of FIG. 4, the excitation elements 25 a to 25 p receive the excitation pulse 22 at the same time. At the same time, an ultrasonic wave 24 is emitted. As shown in FIG. 4, the group of ultrasonic waves 24 (that is, the ultrasonic beam D) is focused at the focal point F1. In FIG. 4, an arrow U <b> 1 indicates the traveling direction of the ultrasonic beam D.

  FIG. 5 also shows the simultaneous control element group 21. In the example of FIG. 5, the leftmost excitation element 25 a receives the excitation pulse 22 latest. The excitation element 22 that is farther away from the leftmost excitation element 25a receives the excitation pulse 22 earlier. The leftmost excitation element 25a emits the ultrasonic wave 24 with the latest delay. The excitation element 20 that is farther away from the leftmost excitation element 25 emits the ultrasonic wave 24 earlier. Due to this timing shift, the ultrasonic beam D is focused at the focal point F2, as shown in FIG. In FIG. 5, an arrow U <b> 2 indicates the traveling direction of the ultrasonic beam D.

  As is clear from the comparison between FIGS. 4 and 5, the traveling direction U2 of the ultrasonic beam D is different from the traveling direction U1. In the simultaneous control element group 21, the traveling direction of the ultrasonic beam D can be arbitrarily set by controlling the transmission timing of the excitation pulse 22, and the incident angle of the ultrasonic beam D to the round steel bar A is also arbitrary. It becomes possible to set to.

  FIG. 6 shows a vertical surface defect observed in the T cross section when the surface defect evaluation apparatus for a round bar steel of this embodiment is used (protrused substantially perpendicularly to the surface tangential direction of the round bar steel. FIG. 5 is a schematic diagram of flaw detection of a flaw having a length in the rolling direction (hereinafter simply referred to as a vertical flaw).

  FIG. 6A is a diagram illustrating a case where an ultrasonic beam is incident from the right side of the vertical ridge C1 (an example in which the refraction angle θb is 32 °). FIG. 6B is a diagram illustrating a case where an ultrasonic beam is incident from the left side of the vertical ridge C1 (an example in which the refraction angle θb is 32 °). FIG. 6C is a diagram illustrating a case where an ultrasonic beam is incident at a refraction angle different from the case of FIG. 6A from the right side of the vertical ridge C1 (an example where the refraction angle θb is 42 °).

  Since the detection ability does not change between the case of FIG. 6A and the case of FIG. 6B for the same vertical ridge C1, in the case of the vertical ridge C1, at least either the left side or the right side of the vertical ridge C1 If ultrasonic waves are incident on the surface, wrinkle detection can be performed. The same applies when the incident angle is changed as shown in FIG.

  FIG. 7 shows an oblique surface defect observed in the T section when the surface defect evaluation apparatus for a round bar steel according to the present embodiment is used. FIG. 2 is a schematic diagram of flaw detection for a flaw having a length in a direction (hereinafter, simply referred to as an oblique flaw).

  FIG. 7A is a diagram illustrating a case where an ultrasonic beam is incident from the right side of the oblique eyelid C2 (an example in which the refraction angle θb is 32 °). FIG. 7B is a diagram showing a case where an ultrasonic beam is incident from the left side of the oblique eyelid C2 (an example in which the refraction angle θb is 32 °). FIG. 7C is a diagram showing a case where an ultrasonic beam is incident from the right side of the oblique eyelid C2 at a refraction angle different from that in FIG. 7A (an example where the refraction angle θb is 42 °).

  Moreover, FIG. 7 shows an example when the direction of the oblique rod C2 is inclined by 25 ° from the normal direction with respect to the surface of the round steel bar A at the rod opening.

  The detection ability for the same oblique eyelid C2 is better in the cases of FIGS. 7A and 7C than in the case of FIG. 7B. In particular, in the case of FIG. 7B, there is a case where the slanted eyelid C2 is detected and the incidence of the ultrasonic beam D as shown in FIG. 7A is indispensable.

  Actually, the steel material in which the heel direction is inclined to the left side with respect to the normal direction and the steel material inclining to the right side must be flaw-detected, but the ultrasonic beam D of FIG. By transmitting the (b) type ultrasonic beam D alternately so that the two do not interfere with each other, it is possible to prevent the detection of the oblique eyelid C2.

  According to the surface defect evaluation apparatus and method of the round bar steel of this embodiment, the detection / non-detection of oblique wrinkles depends on the direction of ultrasonic incident on the wrinkles, but in addition to the refraction angle, the ultrasonic waves are detected from both sides of the wrinkles. By making the light incident, the wrinkle detection characteristic can be made less susceptible to the direction of the wrinkle.

  In the apparatus and method for evaluating surface defects of a round steel bar according to the present embodiment, it is easier to increase the flaw detection speed if the refraction angle is fixed, but the ultrasonic wave of the third refraction angle as shown in FIG. A beam may also be incorporated for flaw detection. The refraction angle can be freely changed within a range in which the surface flaw detection accuracy can be ensured. For example, a flaw detection method in which the ultrasonic beam D is incident from the left and right of the flaw at a refraction angle of 44 ° may be used.

  FIG. 8 shows an image of the focal position of the ultrasonic beam as seen from the T cross section when the surface defect evaluation apparatus and method for round bar steel of this embodiment is used (the beam shape behind the focal point is omitted). It is a schematic diagram.

  FIG. 8A is a diagram illustrating a case where the focal point of the ultrasonic beam is controlled to Fa in the drawing with the aim of detecting the surface wrinkle opening. FIG. 8B is a diagram showing a case where the focal point of the ultrasonic beam is controlled to Fb in the rear side of the state of FIG. 8A with respect to the traveling direction viewed from the central axis of the ultrasonic beam. is there. FIG. 8C is a diagram illustrating a case where the focal point of the ultrasonic beam is controlled to Fc in the drawing on the front side of the state of FIG. 8A with respect to the traveling direction viewed from the central axis of the ultrasonic beam. .

  FIG. 9 is a schematic diagram showing an example of the positional relationship between the focal position of the ultrasonic beam and the surface wrinkles as seen from the T section when the surface defect evaluation apparatus and method for round bar steel of this embodiment are used.

  FIG. 9A is a diagram illustrating a case where the focal point of the ultrasonic beam is controlled to Fa in the drawing with the aim of detecting the surface flaw opening. By doing so, the S / N ratio of the echo from the surface defect C can be maximized. It should be noted that the focal position may be slightly shifted in the vicinity of Fa as long as the S / N ratio of the echo from the surface ridge C is not impaired.

  FIG. 9B is a diagram illustrating a case where the focal point of the ultrasonic beam is controlled to Fb in the rear side of the state of FIG. 9A with respect to the traveling direction viewed from the central axis of the ultrasonic beam. is there. FIG. 9C is a diagram showing a case where the focal point of the ultrasonic beam is controlled to Fc in the drawing in front of the state of FIG. 9A with respect to the traveling direction viewed from the central axis of the ultrasonic beam. .

  By changing the focal position of the ultrasonic beam D from Fa to Fc with respect to the traveling direction seen from the central axis s of the ultrasonic beam D, the ultrasonic beam D makes various contact with the surface defect C, and the surface defect By detecting the state of the maximum S / N ratio while the S / N ratio of the echo from C varies, the surface flaw detection accuracy is further improved.

  Thus, according to the surface defect evaluation apparatus and method of the round bar steel of this embodiment, the S / N ratio of echoes from the surface defects can be maximized because the condition is focused on the surface defects. The focus shape is, for example, a line focus.

  When the length of the surface defect in the depth direction is, for example, a millimeter order or more, the maximum S / N ratio is not always obtained by focusing at the surface defect opening. Therefore, in the surface defect evaluation apparatus and method for a round bar steel according to this embodiment, the focus position is controlled to a position intended for detection of the surface defect opening and a range before and after the position. This eliminates the need for re-flaw detection to obtain the maximum S / N ratio.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

  The round bar steel A is inspected by the round bar steel surface defect evaluation apparatus 100 according to the present embodiment under predetermined conditions. The round steel bar A may be a black skin material or a peeling material. By satisfying the condition, it is possible to detect surface defects C including crimped defects having a width of 0.5 μm or more. The same flaw detection conditions can be used for machine structural steel, bearing steel, stainless steel, tool steel, etc. (specifically, SCR420, SUJ2, SUS304, SKD6, etc.).

(Representative example 1)
The array probe unit 20 of the surface defect evaluation apparatus 100 for the round bar steel of this embodiment is provided with an element group capable of emitting an ultrasonic beam having a flaw detection frequency of 7 MHz, and flaw detection is performed on a round bar steel A having a diameter of 40 mm. The water distance l is set to be 32 mm.

  Conditions regarding electronic scanning are set on the personal computer screen of the control unit 10. That is, regarding the apparent transducer size by the simultaneous control element group 21, the range E in the circumferential direction of the probe surface 20 a on the substantially circumferential surface of the array probe unit 20 is set to 11 mm. Together with the axial size of the steel bar A, the apparent vibrator area should be 11 mm x 15 mm. In general, the apparent size in the axial direction of the vibrator by the simultaneous control element group 21 is generally a fixed value.

  The transverse wave refraction angle θb viewed from the central axis s of the ultrasonic beam D is set to + 45 ° and −45 °. If the transverse wave refraction angle θb is determined, the ultrasonic incident angle θa is automatically determined by Snell's law using the values of underwater longitudinal wave sound velocity (1480 m / sec) and in-steel transverse wave sound velocity (3230 m / sec).

  With respect to the direction of the path of the ultrasonic beam D, a gate is set before and after the first reflection point (position where the front surface opening is planned), and the focal point F is set aiming at the position of the first reflection point. Here, the gate is a measurement range in the path direction of the ultrasonic beam D, for example, a dimension range of 5% of the diameter of the round bar A below the surface (95 to 100% d with respect to the diameter d). ) To cover.

  Furthermore, regarding the evaluation conditions, an echo level that can detect the crimped ridge C having a width of 0.5 μm or more is set. Note that the echo level at which a crimped wrinkle with a width of 0.5 μm or more can be detected is preferably tested by preparing a test piece having an artificial surface wrinkle with a width of 0.5 μm or approximately the same size, but indirectly. It may be a method of confirming automatically.

  After setting surface flaw detection evaluation conditions by ultrasonic flaw detection, round steel bar A is loaded and passed through the round bar steel surface defect evaluation apparatus 100 of this embodiment at a predetermined conveying speed to perform water immersion ultrasonic flaw detection. Do.

  A map indicating the presence or absence of wrinkle detection and a wrinkle detection position is output, and pass / fail judgment is performed. In addition, the map of a wrinkle detection position takes the distance of the axial direction of a round bar steel material on a horizontal axis, for example, and an echo height on a vertical axis | shaft.

(Representative example 2)
The array probe unit 20 of the round bar steel surface defect evaluation apparatus 100 of this embodiment is provided with a simultaneous control element group capable of emitting an ultrasonic beam having a flaw detection frequency of 5 MHz. The water distance l is set to be 30 mm.

  Conditions regarding electronic scanning are set on the personal computer screen of the control unit 10. That is, regarding the apparent transducer size by the simultaneous control element group 21, the range E in the circumferential direction of the probe surface 20 a of the substantially circumferential surface of the array probe unit 20 is set to 13 mm, Together with the axial size of the steel bar A, the apparent vibrator area should be 13 mm x 15 mm.

  The transverse wave refraction angle θb viewed from the central axis s of the ultrasonic beam D is set to + 45 ° and −45 °. With respect to the direction of the path of the ultrasonic beam D, a gate is set before and after the first reflection point (position where the front surface opening is planned), and the focal point F is set aiming at the position of the first reflection point.

  Furthermore, regarding the evaluation conditions, an echo level that can detect the crimped ridge C having a width of 0.5 μm or more is set.

  After setting the flaw detection evaluation conditions for surface defects by ultrasonic flaw detection, the round steel bar A is inserted and passed through the round bar steel surface defect evaluation apparatus 100 of the embodiment at a predetermined conveying speed to perform water immersion ultrasonic flaw detection. . A map indicating the presence or absence of wrinkle detection and a wrinkle detection position is output, and pass / fail judgment is performed.

(Representative example 3)
The array probe unit 20 of the surface defect evaluation apparatus 100 of the round bar steel of this embodiment is provided with an element group capable of emitting an ultrasonic beam having a flaw detection frequency of 7 MHz, and flaw detection is performed on a round bar steel A having a diameter of 36 mm. Set the water distance l to be 34 mm.

  Conditions regarding electronic scanning are set on the personal computer screen of the control unit 10. That is, with respect to the size of the apparent transducer by the simultaneous control element group 21, the range E in the circumferential direction of the probe surface 20a on the substantially circumferential surface of the array probe unit 20 is set to 11 mm. Along with the axial size of A of 15 mm, the apparent vibrator area is set to 11 mm × 15 mm.

  The transverse wave refraction angle θb viewed from the central axis s of the ultrasonic beam D is set to + 32 ° and −32 °.

  With respect to the direction of the path of the ultrasonic beam D, a gate is set before and after the first reflection point (position where the surface ridge opening is planned), and the focal point F changes within the position of the first reflection point and the gate range before and after the first reflection point. Set as follows.

  Furthermore, regarding the evaluation conditions, an echo level that can detect the crimped ridge C having a width of 0.5 μm or more is set.

  After setting surface flaw detection evaluation conditions by ultrasonic flaw detection, round steel bar A is loaded and passed through the round bar steel surface defect evaluation apparatus 100 of this embodiment at a predetermined conveying speed to perform water immersion ultrasonic flaw detection. Do. A map indicating the presence or absence of wrinkle detection and a wrinkle detection position is output, and pass / fail judgment is performed.

  In the following, an example in which parameters related to the flaw detection frequency, the range size of the simultaneous control element group, the water distance, the transverse wave refraction angle, the ultrasonic wave incident direction on the ridge, and the focal position are changed in the same manner as the above representative example The results of water immersion ultrasonic flaw detection using the surface defect evaluation apparatus for round bar steel of this example are shown.

  In addition, the column which shows the numerical range in the following table | surface has the meaning which takes any one value within the range. Also, in the dead zone column, the case where there was no influence of the dead zone (invasion of surface echo) into the gate was indicated as ◯, and the case where there was a negative was indicated as x.

  In the column for detection accuracy of surface flaws, the target wrinkle is detected when the S / N ratio is 2.2 or more, ◎, the one detected when the S / N ratio is 1.5 or more and less than 2.2, ○, S / N When the ratio was less than 1.5 and detection / non-detection could not be clearly confirmed, x was displayed. “General surface flaw” means surface flaws with a width of 5 μm or more, and “crimp-shaped flaw” means surface flaws with a width of 0.5 μm or more and less than 5 μm. Mainly intended for void type surface flaws such as burning cracks and transformation cracks doing.

  In the column of the direction of ultrasonic wave incident on the heel, “one direction” means, for example, when flaw detection is performed by transmitting ultrasonic waves with only a refraction angle of + 32 °, “two directions” means, for example, + 45 ° and -45 ° This means that when ultrasonic waves are transmitted at a refraction angle of flaw detection.

(Influence of flaw detection frequency)
Table 1 shows the influence of the flaw detection frequency.

  From Table 1, the standard conveyance speed is measured by the ultrasonic flaw detector equipped with the array probe of the present embodiment, with a round bar steel of φ15-100mm gated in the range of 90-100% of the steel diameter. (1 ~ 2.5m / sec) When performing ultrasonic flaw detection, the range of simultaneous control elements, axial element dimensions, water distance, transverse wave refraction angle, ultrasonic incident direction to the ridge, focal position If the conditions (1) and (2) are appropriate, there is no dead band (invasion of the surface echo into the gate) at a flaw detection frequency of 3 to 25 MHz, and it can be seen that good detection accuracy can be ensured.

  In particular, it can be seen that surface flaws can be detected with higher detection accuracy by setting the flaw detection frequency of ultrasonic waves emitted from the element group to 4 to 20 MHz (preferably 5 to 10 MHz).

  Further, when the influence of the flaw detection frequency is examined in detail, in the flaw detection of a round bar steel of φ15 to φ49, good detection accuracy is obtained for general surface defects at a flaw detection frequency of 3 to 25 MHz. However, a crimped surface flaw having a flaw width of 0.5 μm cannot be detected at a flaw detection frequency of 3 MHz, and the flaw detection frequency of 4 to 25 MHz is required. In particular, the condition of 5 to 20 MHz is the best.

  Similarly, in flaw detection of φ50-100 round bar steel, general surface defects can be detected when the flaw detection frequency is 3-25 MHz, and particularly good detection accuracy is obtained when the flaw detection frequency is 3-20 MHz. However, the crimped surface flaw cannot be detected under the condition of a flaw detection frequency of 3 MHz or 25 MHz, but can be detected at a flaw detection frequency of 4 to 20 MHz. When the flaw detection frequency is 5 to 10 MHz, good detection accuracy can be obtained.

  Overall, from the viewpoint of flaw detection comparison of φ15-100 round bar steel under the same conditions, both general surface and crimped surface flaws can be detected at a flaw detection frequency of 4-20MHz, and good detection accuracy at flaw detection frequency of 5-10MHz. Will be obtained.

(Influence of range size of simultaneous control elements)
Table 2 shows the influence of the range size of the simultaneous control element group.

  Table 2 shows that a round bar steel of φ15-100mm is gated in the range of 90-100% of the steel material diameter, and the ultrasonic flaw detector equipped with the array probe of this case is used for standard conveying speed (1 (~ 2.5m / sec) under the conditions of ultrasonic flaw detection, the flaw detection frequency, axial element dimensions, water distance, transverse wave refraction angle, ultrasonic wave incident direction to the ridge, and focal position are appropriate. If there is a simultaneous control element group in the range of 7 to 35 mm and a flaw detection of a round bar steel of φ35 to 100 mm is performed, it can be seen that there is no dead zone (invasion of surface echo into the gate).

  In particular, the dimension in the circumferential direction of the probe surface 20a of the round bar steel A of the simultaneous control element group (the length of the arcuate thick line E in the figure) is 8 to 35 mm (preferably 10 to 35 mm). Thus, it can be seen that surface defects can be detected with higher detection accuracy.

  However, when flaw detection is performed on a round steel bar having a small diameter of 15 to 34 mm, if the range of the simultaneous control element group is as large as 35 mm, a dead zone occurs and surface flaws cannot be detected. Therefore, in flaw detection of φ15-34mm round bar steel, the range of simultaneous control elements should be 30mm or less, and in flaw detection of φ35-100mm round bar steel, surface flaws should be detected in the range of simultaneous control elements 35mm or less. In flaw detection of 15 to 100 mm round bar steel, if the range of the simultaneous control element group is 8 mm, the detection accuracy of the crimped surface defect is lowered, and if the range of the simultaneous control element group is 7 mm, the surface defect cannot be detected.

(Effect of water distance)
Table 3 shows the effect of water distance. In the column “occurrence of reverberation echo”, “no occurrence” is indicated by “◯”, and occurrence is indicated by “X”.

  Table 3 shows that a round steel bar with a diameter of 15 to 100 mm is gated in the range of 90 to 100% of the steel material diameter, and an ultrasonic flaw detector equipped with the array probe of the present invention is used to measure the standard conveyance speed (1 It can be seen that surface flaws can be detected with higher detection accuracy by setting the water distance l to 15 to 50 mm (preferably 19 to 45 mm) when performing ultrasonic flaw detection under the condition of ~ 2.5 m / sec.

  In addition, even if the flaw detection frequency, the range of the simultaneous control element group, the axial element size, the transverse wave refraction angle, the ultrasonic wave incident direction to the ridge, and the focal position are appropriate, if the water distance is reduced to 13 mm, It can be seen that reverberation echo (influence of ultrasonic waves reciprocating between the probe and the round steel bar surface) occurs, and surface defects cannot be detected.

  When the water distance is 15 mm or more, no reverberation echo occurs, and good surface flaw detection accuracy is obtained at a water distance of 15 to 50 mm. If the water distance is 60 mm, regardless of reverberation echo, the detection accuracy of general surface defects decreases, and crimped surface defects cannot be detected.

(Influence of transverse wave refraction angle)
Table 4 shows the influence of the transverse wave refraction angle.

  Table 4 shows that a round bar steel with a diameter of 15 to 100 mm is gated in the range of 90 to 100% of the steel diameter, and an ultrasonic flaw detector equipped with the array probe of the present invention is used to obtain a standard conveyance speed (1 (~ 2.5m / sec) under the condition of ultrasonic flaw detection, flaw detection frequency, simultaneous control element group range, axial element size, water distance, ultrasonic incident direction to fistula, focal position It can be seen that there is no dead band at a transverse wave refraction angle of 28 to 68 ° if the angle is set appropriately.

  However, it can be seen that surface wrinkles cannot be detected when the transverse wave refraction angle is 28 ° or 68 °, and surface wrinkles can be detected when the transverse wave refraction angle is 30 ° to 65 °. It can be seen that good detection accuracy can be obtained at a transverse wave refraction angle of 30 ° to 65 ° for a general surface flaw and a transverse wave refraction angle of 30 ° to 45 ° for a crimped flaw.

(Effects of changing the direction of ultrasonic incident on the ridge to 1 direction / 2 directions)
Table 5 shows the effect of setting the direction of ultrasonic wave incident on the ridge to 1 direction / 2 directions. The 1 direction is the flaw detection condition in which ultrasonic waves are irradiated from one side of the scissors when looking at the T section of the round steel bar including the surface scissors, and the 2 directions are ultrasonic waves alternately from the left and right sides of the scissors. Is a condition that is irradiated.

  Table 5 shows that a round bar steel with a diameter of 15 to 100 mm is gated in the range of 90 to 100% of the steel diameter, and an ultrasonic flaw detector equipped with the array probe of the present invention is used to obtain a standard conveyance speed (1 When performing ultrasonic flaw detection under the condition of ~ 2.5m / sec), the flaw detection frequency, the range of the simultaneous control element group, the axial element dimensions, the water distance, the transverse wave refraction angle, and the focal position are set appropriately. Thus, it can be seen that there is no dead zone regardless of whether the ultrasonic wave incident direction on the eyelid is one direction or two directions.

  However, when the incident direction of the ultrasonic waves to the ridge is one direction, the angle between the round bar steel surface and the heel when viewed from the T section of the round bar steel including the surface heel is irradiated from the obtuse angle side. Although the surface flaw detection accuracy is relatively good, if the ultrasonic wave is irradiated from the side where the angle between the round bar steel surface and the flaw is an acute angle, the surface flaw detection accuracy is deteriorated or cannot be detected. There is not. When the incident direction of ultrasonic waves on the heel is two directions, the detection of surface folds is stable because the direction of the angle between the round bar steel surface and the heel is an obtuse angle. It can be seen from Table 5. These tendencies are the same for both general surface flaws and crimped surface flaws.

(Influence of focal position)
Table 6 shows the influence of the focal position.

  Table 6 shows that a round bar steel with a diameter of 15 to 100 mm is gated in the range of 90 to 100% of the steel diameter, and an ultrasonic flaw detector equipped with the array probe of the present invention is used to obtain a standard conveyance speed (1 (~ 2.5m / sec) under the condition of ultrasonic flaw detection, flaw detection frequency, range of simultaneous control element group, axial element size, water distance, transverse wave refraction angle, ultrasonic incident direction to ridge, If the conditions are appropriate, it can be seen that there is no dead zone regardless of whether or not the focus is set.

  However, when looking at the accuracy of detecting surface defects, the focus condition is also important. That is, when the focus is not set near the first reflection point in the round bar steel, the surface flaw is detected in the vicinity of the first reflection point in the round bar steel, but the general surface flaw can be detected but the crimped surface flaw is detected. Cannot be detected. On the other hand, when the focus is set in the vicinity of the first reflection point in the round bar steel, the detection accuracy of the general surface flaw can be improved, and a satisfactory result can be obtained also for the crimped surface flaw. .

  Furthermore, with regard to the direction of the central axis of the ultrasonic beam propagating in the round bar steel, the focus is occasionally changed in the range of `` position 0.5 mm before the first reflection point to position 0.5 mm behind the first reflection point after reflection '' ( When the setting was changed (according to a predetermined rule), the detection accuracy was further improved. Thus, it can be seen that good detection accuracy can be ensured for general surface flaws even with the condition setting targeted to obtain good detection accuracy with the crimped surface flaws.

  As described above, according to the surface defect evaluation apparatus for round bar steel by ultrasonic flaw detection using the electronic scanning array probe of the present invention and the method thereof, the width 0.5 in the round bar steel product having a diameter of 15 to 100 mm, It is possible to accurately detect void-type surface defects (baking cracks and surface defects such as transformation cracks) including crimped defects of about μm or more.

It is a figure which shows the structure of the surface defect evaluation apparatus of the round bar steel by the ultrasonic flaw using the electronic scanning type array probe of this embodiment. It is a figure which shows the other structure of the surface defect evaluation apparatus of the round bar steel by the ultrasonic flaw using the electronic scanning type array probe of this embodiment. It is a figure which shows the detailed structure of the array probe unit of this embodiment. It is a conceptual diagram for demonstrating the operating state of the simultaneous control element group 21 of this embodiment. It is a conceptual diagram for demonstrating the operating state of the simultaneous control element group 21 of this embodiment. It is a schematic diagram of the flaw detection of the vertical surface flaw seen in the T cross section at the time of using the surface defect evaluation apparatus of the round bar steel of this embodiment. It is a schematic diagram of the flaw detection of the oblique surface flaw seen in the T cross section at the time of using the surface defect evaluation apparatus of the round bar steel of this embodiment. It is a schematic diagram which shows the image of the focal position of the ultrasonic beam seen in the T cross section at the time of using the surface defect evaluation apparatus of the round bar steel of this embodiment. It is a schematic diagram which shows the example of the positional relationship of the focal position of the ultrasonic beam seen from the T cross section at the time of using the surface defect evaluation apparatus of the round bar steel of this embodiment, and a surface flaw.

Explanation of symbols

100: Surface defect evaluation apparatus 10 for round bar steel by ultrasonic flaw detection using an electronic scanning array probe 10: Control unit 20: Array probe unit 21: Simultaneous control element group 23: Delay circuit 25: Excitation element 30 : Tank 40: Water

Claims (12)

A surface defect evaluation device for round bar steel by water immersion ultrasonic flaw detection using an electronic scanning array probe,
A plurality of excitation elements are aligned on a substantially circumferential probe surface facing the round bar steel and centered on a central axis of the round bar steel, and the probe surface and the surface of the round bar steel have a predetermined surface. At least one array probe unit arranged to have a water distance;
A plurality of excitation elements adjacent to each other in a predetermined range are selected from the plurality of excitation elements of the array probe unit to form a simultaneous control element group, and the excitation elements in the simultaneous control element group are controlled simultaneously. A control unit that generates an ultrasonic beam having a predetermined frequency, makes the ultrasonic beam enter the inside of the round bar steel at a predetermined refraction angle, and performs control to detect surface defects in the round bar steel;
With
The controller is
The ultrasonic beam generated by the simultaneous control element group generates a focal point, and the focal position is the position of the opening of the surface defect and the position before and after the traveling direction viewed from the central axis of the ultrasonic beam. Control to move the focal point so that the S / N ratio of echoes from the surface defects is maximized ,
The controller is
An electronic scanning array probe characterized by performing control to irradiate the specific surface defect with an ultrasonic beam generated by the group of simultaneous control elements from both sides of the specific surface defect in the circumferential direction of the round bar steel Surface defect evaluation equipment for round steel bar by water immersion ultrasonic flaw detection   2. The electronic scanning array probe according to claim 1, comprising a plurality of the array probe units, wherein the plurality of array probe units are arranged so as to surround the entire circumference of the round bar steel. 3. Surface defect evaluation equipment for round steel bar by water immersion ultrasonic flaw detection   The flaw detection frequency of the ultrasonic beam generated by the simultaneous control element group is 4 to 20 MHz, according to the water immersion ultrasonic flaw detection using the electronic scanning array probe according to claim 1 or 2. Round bar steel surface defect evaluation equipment.   4. The dimension of the range in a substantially circumferential direction around the central axis of the round bar steel on the probe surface of the simultaneous control element group is 8 to 30 mm. 5. For evaluating surface defects of round steel bar by water immersion ultrasonic flaw detection using the electronic scanning array probe described in 1.   5. The surface defect evaluation apparatus for round bar steel by water immersion ultrasonic flaw detection using the electronic scanning array probe according to claim 1, wherein the water distance is 15 to 50 mm.   The electronic scanning array according to any one of claims 1 to 5, wherein a transverse wave refraction angle at an incident point to the round bar steel as seen from a central axis of the ultrasonic beam is 30 ° to 65 °. Surface defect evaluation equipment for round steel bars by water immersion ultrasonic flaw detection using a probe. A method for evaluating surface defects of round steel bars by water immersion ultrasonic flaw detection using an electronic scanning array probe,
A plurality of excitation elements are aligned on a substantially circumferential probe surface facing the round bar steel and centered on a central axis of the round bar steel, and the probe surface and the surface of the round bar steel have a predetermined surface. A simultaneous control element group is configured by selecting a plurality of adjacent excitation elements in a predetermined range among a plurality of excitation elements of at least one array probe unit arranged to have a water distance,
Simultaneously controlling the excitation elements in the group of simultaneous control elements to generate an ultrasonic beam of a predetermined frequency;
The ultrasonic beam is incident on the inside of the round bar steel at a predetermined refraction angle to detect surface defects in the round bar steel,
The ultrasonic beam generated by the simultaneous control element group has a focal point, and the focal position is the position of the opening of the surface defect and the position before and after that with respect to the traveling direction viewed from the central axis of the ultrasonic beam. Move the focus so that the S / N ratio of echoes from the surface defects is maximized ,
An electronic scanning array probe is used , wherein the specific surface defect is irradiated with an ultrasonic beam generated by the simultaneous control element group from both sides of the specific surface defect in the circumferential direction of the round bar steel . Surface defect evaluation method for round steel bars by water immersion ultrasonic flaw detection. The electronic scanning array probe according to claim 7 , comprising a plurality of the array probe units, wherein the plurality of array probe units are arranged so as to surround the entire circumference of the round bar steel. Of surface defects of round steel bar by water immersion ultrasonic flaw detection 9. The flaw detection frequency of the ultrasonic beam generated by the simultaneous control element group is 4 to 20 MHz, according to the water immersion ultrasonic flaw detection using the electronic scanning array probe according to claim 7 or 8. Method for evaluating surface defects of round steel bars. The dimension of the range of the substantially circumferential direction centering on the center axis | shaft of the said round bar steel of the probe surface of the said simultaneous control element group is 8-30 mm, The any one of Claim 7 to 9 characterized by the above-mentioned. Method for evaluating surface defects of round steel bar by water immersion ultrasonic flaw detection using the electronic scanning array probe described in 1. The said water distance is 15-50 mm, The surface defect evaluation method of the round bar steel by the water immersion ultrasonic flaw using the electronic scanning type array probe in any one of Claim 7 to 10 characterized by the above-mentioned. The electronic scanning array according to any one of claims 7 to 11 , wherein a transverse wave refraction angle at an incident point to the round bar steel as viewed from a central axis of the ultrasonic beam is 30 ° to 65 °. Surface defect evaluation method for round bar steel by water immersion ultrasonic flaw detection using a probe.

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