JP7107439B2 - Round bar surface flaw inspection method and surface flaw inspection device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a surface flaw inspection method and a surface flaw inspection device for a round bar.

In the flaw detection inspection of long materials with a circular cross section such as round steel bars and steel pipes (hereinafter simply referred to as round bars) using the leakage magnetic flux inspection method, the round bar is conveyed in the longitudinal direction while the probe head is moved in the circumferential direction of the round bar. There is an inspection method in which the round bar is rotated along the axis, and an inspection method in which the probe head travels in the longitudinal direction of the round bar while rotating the round bar around its axis. In this case, in any inspection method, a flaw signal is received from a flaw on the surface of the round bar by the probe (probe) in the probe head of the leakage magnetic flux flaw detector, and the height of the flaw signal is the judgment reference value. The presence or absence of flaws is determined depending on whether or not the above conditions are met. Note that the criterion value is defined in advance according to the allowable flaw depth required for the product.

Of these two flaw detection methods, the inspection method in which the probe head rotates along the circumference of the round bar is more effective than the inspection method in which the probe head travels in the longitudinal direction of the round bar. can shorten the time required for Therefore, from the viewpoint of production efficiency, it is preferable to use an inspection method in which the probe head is rotated along the circumferential direction of the round bar. It is rare.

For example, in Patent Document 1, as a surface flaw inspection method for a round bar, the detection results of flaw signals in a plurality of measurement regions that are continuous in the circumferential direction, and the first judgment criterion that is the judgment reference value of the height of the flaw signal A method is disclosed for determining the presence or absence of surface defects using a value and a second criterion value. According to Patent Document 1, a defect having a narrow width and a long defect can be detected at the same position in the circumferential direction.
In addition, Patent Document 2 discloses a method for determining the presence or absence of flaws by using a plurality of measurement areas arranged in the circumferential direction and the longitudinal direction as determination areas for flaw signals detected by a method similar to Patent Document 1. . According to Patent Document 2, even when the round bar rotates or vibrates during leakage magnetic flux testing, flaws that are continuous in the longitudinal direction can be detected with high accuracy.

Patent No. 5978889 Patent No. 6451678

However, when there is a defect caused by a material such as a cast slab, the height of the defect signal is intermittently low, and continuous defects below the second criterion value in Patent Documents 1 and 2 may occur. For this reason, it was difficult to determine such continuous flaws with the surface flaw inspection methods described in Patent Documents 1 and 2. Further, if the height value of the flaw signal, which is the second determination reference value, is lowered so that flaws caused by the material such as slab can be detected, there is a possibility of overdetection.

Therefore, the present invention has been made with a focus on the above problems, and is an inspection method in which a probe head is rotated along the circumferential direction of a round bar while conveying the round bar in the longitudinal direction. It is an object of the present invention to provide a surface flaw inspection method and a surface flaw inspection device for a round bar that can accurately detect scratches.

According to one aspect of the present invention, while conveying the round bar in the longitudinal direction, or while moving the probe head of the leakage magnetic flux flaw detector in the longitudinal direction of the round bar, By rotating the flaw detection head, the round bar, or both the flaw detection head and the round bar so as to rotate along the circumferential direction of the round bar, the surface of the round bar is inspected in the longitudinal direction and the circumferential direction, respectively. A flaw detection step of detecting a flaw signal by detecting leakage magnetic flux in a plurality of divided measurement regions; and a plurality of judgment regions including at least one of the measurement regions and arranged in the circumferential direction and the longitudinal direction. a determination step of determining whether there is a flaw on the surface of the round bar based on the representative flaw signal that is the largest flaw signal of the measurement region included in the region; It includes a first determination step, a second determination step, and a third determination step for determining that the surface of the rod has the above-mentioned flaw, and in the first determination step, the height of the representative flaw signal is It is determined that the flaw is present in the determination region that is equal to or greater than the first determination reference value, and in the second determination step, the height of the representative flaw signal in the determination region is higher than the first determination reference value. One determination region or a plurality of determination regions continuous in the longitudinal direction, which is equal to or greater than a low second determination reference value, is defined as a first region, and the first region is a plurality of the determination regions continuous in the longitudinal direction. When the determination area consists of determination areas and the number of the determination areas of the first area is equal to or greater than a predetermined number, it is determined that the flaw is present in the determination area of the first area, and the third determination is performed. In the step, the height of the representative flaw signal of the determination region is equal to or greater than the second determination value, the determination region is one determination region or a plurality of determination regions continuous in the longitudinal direction, and the first region The determination region equal to the position in the circumferential direction is defined as a second region, the determination region between the first region and the second region is defined as a third region, and the third region is defined as When the representative flaw signal of the determination region is less than the second determination reference value and equal to or greater than the third determination reference value, and the number of the determination regions in the longitudinal direction of the third region is the first At least one of the cases where the number of the determination regions in the longitudinal direction of at least one of the region and the second region is equal to or less than the number of the determination regions, and the number of the first region, the second region, and the third region when the number of the determination regions is equal to or greater than a predetermined number, in the determination regions of the first region, the second region, and the third region A surface flaw inspection method for a round bar is provided for determining that there is the above flaw.

According to one aspect of the present invention, a probe head is provided, and the probe head moves the round bar while conveying the round bar in the longitudinal direction or moving the round bar in the longitudinal direction. By rotating the flaw detection head, the round bar, or both the flaw detection head and the round bar so as to rotate along the circumferential direction of the bar, the surface of the round bar is divided in the longitudinal direction and the circumferential direction, respectively. a leakage magnetic flux flaw detector that detects flaw signals by detecting leakage magnetic flux in a plurality of measurement areas; a determination unit that determines whether there is a flaw on the surface of the round bar based on the representative flaw signal that is the largest flaw signal of the measurement region included in the determination region, wherein the judgment unit includes: A first determination step, a second determination step, and a third determination step are performed to determine whether the surface of the bar has the above-mentioned flaw, and in the first determination step, the height of the representative flaw signal is It is determined that the flaw is present in the judgment region that is equal to or greater than the judgment reference value of 1, and in the second judgment step, the height of the representative flaw signal in the judgment region is lower than the first judgment reference value. One determination region or a plurality of determination regions continuous in the longitudinal direction, which is equal to or greater than a second determination reference value, is defined as a first region, and a plurality of determination regions continuous in the longitudinal direction are defined as the first region. When it is composed of regions and the number of the determination regions of the first region is a predetermined number or more, it is determined that the flaw is present in the determination region of the first region, and the third determination step is performed. Then, the determination region is one determination region or a plurality of determination regions continuous in the longitudinal direction in which the height of the representative flaw signal of the determination region is equal to or greater than the second determination value, and the first region and The determination regions having equal positions in the circumferential direction are defined as a second region, the determination region between the first region and the second region is defined as a third region, and the third region is defined as a third region. When the representative flaw signal of the determination region is less than the second determination reference value and equal to or greater than the third determination reference value, and the number of the determination regions in the longitudinal direction of the third region is the first region and at least one of the case where the number of the determination regions in the longitudinal direction of at least one of the second regions is equal to or less than the number of the determination regions, and the above-mentioned When the number of determination regions is equal to or greater than a predetermined number, the flaw is present in the determination regions of the first region, the second region, and the third region. Provided is a round bar surface flaw inspection apparatus that determines that

According to one aspect of the present invention, in an inspection method in which the probe head is rotated along the circumferential direction of the round bar while conveying the round bar in the longitudinal direction, flaws continuous in the longitudinal direction can be accurately detected. .

1 is a configuration diagram showing a round bar surface flaw inspection apparatus according to an embodiment of the present invention; FIG. It is a schematic diagram which shows a leakage magnetic flux flaw detection apparatus. It is a flow chart which shows the surface defect inspection method of the round bar concerning one embodiment of the present invention. It is a front view which shows the measurement area|region of a round bar. It is a perspective view which shows the measurement area|region of a round bar. It is a flow chart which shows flaw judging processing. It is explanatory drawing which shows the detection result of a flaw signal. It is explanatory drawing which shows the detection result of the flaw signal in a modification. It is explanatory drawing which shows the detection result of the flaw signal in a modification. It is a graph which shows the detection result of the flaw signal in the measurement area|region with a continuous flaw.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. However, it will be evident that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are schematically shown to simplify the drawings.

<Device configuration>
A round bar surface flaw inspection apparatus 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. A surface flaw inspection apparatus 1 is an apparatus for detecting surface flaws on a round bar 2, which is a steel bar with a circular cross section, using a leakage magnetic flux detection method. As shown in FIG. It includes a roll 4 , a leakage magnetic flux flaw detector 5 , a determination section 6 and a storage section 7 .

A plurality of transport rolls 3 are arranged in the longitudinal direction of the transported round bar 2 (horizontal direction with respect to the paper surface of FIG. 1) with the leakage magnetic flux flaw detector 5 interposed therebetween. The plurality of transport rolls 3 transport the round bar 2 in the longitudinal direction of the round bar 2 by being rotationally driven. In the example shown in FIG. 1, the round bar 2 is conveyed leftward with respect to the plane of FIG.
A plurality of pinch rolls 4 are provided side by side in the longitudinal direction of the conveyed round bar 2 with the leakage magnetic flux flaw detector 5 interposed therebetween. Moreover, the plurality of pinch rolls 4 are provided above the plurality of conveying rolls 3 (the upper side with respect to the paper surface of FIG. 1) so as to face the plurality of conveying rolls 3 in the vicinity of the leakage magnetic flux flaw detector 5 . A plurality of pinch rolls 4 restrain the round bar 2 being conveyed from above, thereby suppressing looseness and deflection during conveyance of the round bar 2.例文帳に追加

As shown in FIG. 2, the leakage magnetic flux flaw detector 5 has a pair of detection heads 51a and 51b provided facing each other so as to sandwich the conveyed round bar 2 on a plane perpendicular to the conveying direction of the round bar 2. have. A pair of probe heads 51a and 51b have excitation yokes 52a and 52b, excitation coils 53a and 53b, and probes 54a and 54b, respectively. The excitation yokes 52a and 52b are made of silicon steel and are formed in a substantially U-shape on the plane perpendicular to the direction in which the round bar 2 is conveyed. spaced apart by the required gap. The excitation coils 53a and 53b are coils wound around the excitation yokes 52a and 52b with a required number of turns, respectively, and are connected to an excitation power source (not shown). The probes 54a and 54b are magneto-sensitive elements such as search coils and Hall elements, and are arranged between the magnetic poles of the excitation yokes 52a and 52b, respectively. In such a leakage magnetic flux flaw detector 5, the round bar 2 is magnetized via the excitation yokes 52a and 52b by energizing and exciting the excitation coils 53a and 53b by the excitation power source. The probes 54a and 54b detect the magnetic flux leaking from the magnetized surface of the round bar 2 due to the flaws on the surface of the round bar 2. FIG. Also, the pair of probe heads 51a and 51b are configured to be rotatable in the circumferential direction of the round bar 2 being transported around the axis of the round bar 2 being conveyed. The leakage magnetic flux flaw detector 5 outputs a signal indicating the strength of the defect leakage magnetic flux and corresponding to the depth of the surface flaw detected by the probes 54a and 54b to the determination unit 6 as a flaw signal.

The determination unit 6 determines whether or not there is a flaw on the surface of the round bar 2 based on the flaw signal acquired from the leakage magnetic flux flaw detector 5 and the flaw signal stored in the storage unit 7 . The determination unit 6 also outputs the flaw signal acquired from the magnetic flux leakage flaw detector 5 to the storage unit 7 .
The storage unit 7 stores the flaw signal acquired from the determination unit 6 and outputs the stored flaw signal to the determination unit 6 . The determination unit 6 and the storage unit 7 are computers including a central processing unit (CPU), a main storage device (internal storage device), an auxiliary storage device (external storage device), and the like.

<Surface flaw inspection method>
Next, a surface flaw inspection method for the round bar 2 according to the present embodiment will be described with reference to FIGS. 3 to 7. FIG. In this embodiment, first, as shown in FIG. 3, a detection loop is started (S100). A detection loop is started when the round bar 2 is conveyed to the leakage magnetic flux flaw detector 5 and the downstream end of the round bar 2 in the conveying direction reaches the pair of probe heads 51a and 51b.

In the detection loop, first, the leakage magnetic flux flaw detector 5 detects a flaw signal in the measurement area on the same track T _i (S102).
Here, the leakage magnetic flux flaw detector 5 detects the leakage magnetic flux on the entire surface of the round bar 2 by rotating the pair of probe heads 51a and 51b with respect to the round bar 2 being conveyed. In this embodiment, the leakage magnetic flux flaw detector 5 is arranged in the circumferential direction of the round bar 2 as shown in FIG. Leakage magnetic flux is detected for each region (also referred to as “sector”) S ₁ to S ₈ . 5, the leakage magnetic flux flaw detector 5 divides the round bar 2 in the longitudinal direction of the round bar 2 at regular intervals (also referred to as “tracks”) _Ti as shown in FIG. leakage magnetic flux is detected (i=1 to n (natural number)). That is, the leakage magnetic flux flaw detector 5 rotates the pair of probe heads 51a and 51b by 180 degrees, so that eight sectors S ₁ to S ₈ corresponding to the entire outer peripheral length of the round bar 2 are detected in a region corresponding to one track in the longitudinal direction. Detect leakage magnetic flux every time. By continuously performing the rotating operation of the pair of probe heads 51a and 51b at a predetermined rotational speed and the conveying operation of the round bar 2 at a predetermined conveying speed, the entire length and circumference of the round bar 2 are Leakage magnetic flux is detected over . Incidentally, as shown in FIG. 5, the measurement area is defined by eight sectors S ₁ to S ₈ and a plurality of tracks T _i in the longitudinal direction and the circumferential direction of the round bar 2 . The leakage magnetic flux flaw detector 5 outputs flaw signals for each measurement area to the determination unit 6 .

In step S102, the determination unit 6 acquires flaw signals of eight sectors S ₁ to S ₈ that are measurement areas in one track T _i .
After step S102, the determination unit 6 determines the presence or absence of a surface flaw in a determination region R _j described later according to each measurement region based on the acquired flaw signals of the eight measurement regions by the flaw determination process described later. (S104).
Next, the processing of steps S102 and S104 is performed for all the tracks T _i , thereby ending the detection loop (S106) and the defect determination by the surface defect inspection apparatus 1 is completed.

Next, with reference to FIG. 6, the flaw determination processing in step S104 will be described in detail. In the flaw determination process, as shown in FIG. 6, first, a determination loop is started (S200).
In the determination loop, first, the determination section 6 determines whether or not the representative flaw signal of the determination region _Rj is equal to or greater than the first determination reference value (S202). Here, the determination area _{Rj is an area composed of two circumferentially adjacent measurement areas on the same track T i .} In this embodiment, eight determination regions R ₁ to R ₈ are set according to the number of sectors S. FIG. In each track T _i , the determination area R ₁ is composed of the measurement areas of sectors S ₁ and S ₂ , the determination area R ₂ is composed of the measurement areas of sectors S ₂ and S ₃ , and the determination area R ₃ is composed of the measurement areas of sector S ₃ . , _S4 , decision region _R4 consists of the measurement regions of sectors _S4 and _S5 , decision region R5 consists of the measurement regions of sectors _S5 and _S6 , decision region _{R6 consists} of sector S ₆ and _S7 , the decision area _R7 consists of the measurement areas of sectors _S7 and _S8 , and the decision area _R8 consists of the measurement areas of _{sectors S8} and S1. In other words, the determination regions _{Rj are set in a state in which adjacent determination regions in the circumferential direction of the round bar 2 overlap each other in the regions divided by the tracks T i .} In step S202, the determination unit 6 determines a representative flaw signal of the determination region _Rj to be determined from the acquired flaw signals for each measurement region, and determines whether or not the representative flaw signal is equal to or greater than a preset first judgment reference value. judge. The representative flaw signal is the value of the larger flaw signal (higher signal and higher leakage magnetic flux) of the two measurement regions included in the determination region _Rj . Also, the first criterion value is a value that is not likely to be affected by noise, and is set to a value such that the S/N ratio is 3, for example.

If the representative flaw signal in the determination region _Rj is less than the first reference value as a result of the determination in step 202, the determination unit 6 determines whether the representative flaw signal in the determination region _Rj is greater than or equal to the second determination reference value. is determined (S204). The second determination reference value is set to a value smaller than the first determination reference value, for example, set to a value such that the S/N ratio is 2.
As a result of the determination in step S204, when the representative flaw signal of the determination region _Rj is equal to or greater than the second reference value, the determination unit 6 determines whether or not the number of tracks in the _first region D1 is equal to or greater than a predetermined number. (S206). The first region D1 is a region including a judgment region _Rj in which the presence or absence of flaws is judged, and is at least _one judgment region R in which the representative flaw signal is equal to or greater than the second judgment reference value. In addition, the first region D1 is continuous in the longitudinal direction when _a plurality of determination regions R in which the representative flaw signal is equal to or greater than the second determination reference value is arranged in the longitudinal direction, and the representative flaw signal is the first. A plurality of judgment regions R _j having a judgment reference value of 2 or more. In the present embodiment, as shown in FIG. 3, the defect determination process (S104) is performed _each time a defect signal is detected in each track T _i . This is done only for the determination region _Rj in which the defect signal has already been detected.

The _first area D1 will be described with reference to FIG. FIG. 7 shows the detection results of flaw signals in the measurement area divided by sectors S ₁ to S ₈ and track T _i . In addition, in FIG. 7 and FIG. 8 similarly showing the detection result of the flaw signal, the measurement area indicated by "1" indicates the measurement area where the flaw signal is greater than or equal to the first judgment reference value, and is indicated by "2". The measurement area indicates a measurement area where the flaw signal is greater than or equal to the second judgment reference value and less than the first judgment reference value. A measurement region where the flaw signal is less than the second criterion value is shown, and a measurement region indicated by "-" is a measurement region where the flaw signal is less than the third judgment criterion value, which will be described later. Further, in the examples shown in FIGS. 7 and 8, the defect determination process (step S104) in the determination regions R ₁ to R ₈ for the tracks T ₁ to T ₁₀ is performed from the track T ₁ downstream in the transport direction. Each is done in turn.

Here, a case where flaw determination processing is performed in the determination region R ₁ (also referred to as “determination region R _1A ”) of track T ₃ in FIG. 7 will be described. In the determination loop (step S200) of the determination region _R1A , the representative flaw signal of the determination region _R1A becomes equal to or greater than the second determination reference value and less than the first determination reference value, and in step S206, the _first region D1 is specified. is done. In step S206, at the time of the flaw determination process for the determination region _R1A , there is no determination region _Rj that is continuously positioned in the determination region _R1A in the longitudinal direction and the representative flaw signal is equal to or greater than the second determination reference value. , is specified as the first region D ₁ is only the determination region R _1A (the first region D _1A in FIG. 7).

Also, a case where flaw determination processing is performed in the determination region R ₄ (also referred to as “determination region R _4B ”) of track T ₄ in FIG. 7 will be described. In the determination loop of the determination region _R4B , the representative flaw signal of the determination region _R4B becomes equal to or greater than the second determination reference value and less than the first determination reference value, and the _first region D1 is specified in step S206. In step S206, at the time of the defect determination process for the determination region _R4B , the determination region Rj, which is continuously positioned in the determination region _R4B in the _longitudinal direction and has the representative defect signal equal to or greater than the second determination reference value, is the track. It becomes the determination area R ₄ (also referred to as “determination area R _4D , R _4C ”) of T ₂ and T ₃ . Therefore, the first region D ₁ is specified as three continuous determination regions R _4B to R _4D (first region D _1B in FIG. 7).

Furthermore, a case where flaw determination processing is performed in the determination region R ₇ (also referred to as “determination region R _7E ”) of track T ₄ in FIG. 7 will be described. In the determination loop of the determination region _R7E , the representative flaw signal of the determination region _R7E becomes equal to or greater than the second determination reference value and less than the _first determination reference value, and the first region D1 is specified in step S206. In step S206, at the time of the flaw determination process for the determination region _R7E , there is no determination region _Rj that is continuously positioned in the determination region _R7E in the longitudinal direction and the representative flaw signal is equal to or greater than the second determination reference value. , the first region D ₁ is only the determination region R _7E (the first region D _1C in FIG. 7). Note that, as shown in FIG. 7, the representative flaw signal of the determination region _R7 (also referred to as "determination region _R7F ") of the track _T5 adjacent to the determination region _R7E is equal to or greater than the second determination reference value. However, when the defect processing signal for track _T4 is _issued , the defect signal for track T5 is not detected. Therefore, at the stage of the flaw determination process of the determination area _R7E , the first area D becomes one determination area of the determination area _R7E , and at the stage of the flaw determination process of the determination area _R7F , the first area D ₁ becomes two determination areas, that is, determination areas R _7E and R _7F .

The number of tracks in the _first region D1 is the number of tracks T _i included in the _first region D1, and indicates the number of determination regions _Rj included in the _first region D1 in the longitudinal direction.
The predetermined number in step S206 is a value determined corresponding to the length determined to be a continuous flaw, and is determined from the length of the flaw to be detected and the length of the track _Ti in the longitudinal direction. In this embodiment, as an example, the predetermined number is four. That is, in step S206, the determination unit 6 acquires the determination result of the flaw signal in the same sector S stored in the storage unit 7 for the determination region _Rj of the track T _i to be determined. Then, the determination unit 6 determines the _first area D1 from the determination result, and determines whether or not the number of tracks corresponding to the longitudinal length of the _first area D1 is four or more.

As a result of the determination in step S206, if the number of tracks in the _first area D1 is less than the predetermined number, the determining unit 6 selects the second area where the _first area D1 and the round bar 2 are located at the same circumferential position. It is determined whether D2 exists ₍ S208). The _second region D2 is at least one determination region R _j in which the representative flaw signal of the determination region R j is equal to or greater than the second determination reference value, and at least one determination region R _j in which the representative flaw signal is less than the second threshold The determination region _Rj is aligned with the _first region D1 in the longitudinal direction via the determination region _Rj . Further, similarly to the _first region D1, when a plurality of determination regions R _j in which the representative flaw signal is equal to or greater than the second threshold exist continuously in the longitudinal direction, all the continuous determination regions R _j becomes the _second region D2.

A region between the _first region D1 and the _second region D2 is called a _third region D3. _{The third} region D3 is a region where the positions of the round bar ₂ in the circumferential direction are equal to those of the first region D1 and the _second region D2, and the _first region D1 and the second region D2 They are adjacent to each other. That is, the first area D ₁ , the third area D ₃ and the second area D ₂ are areas that are contiguously arranged in order (D ₁ →D ₃ →D ₂ ) in the longitudinal direction. are the same.

The _second area D2 and the _third area D3 will be described with reference to FIG. For example, in FIG. 7, when the flaw determination process is performed in the determination region R ₁ (also referred to as “determination region R _1G ”) of track T ₉ , the determination region R _1G is the first region D ₁ (D _1D ). is judged. Further, in step S208, the determination regions R ₁ of the tracks T ₅ and T ₆ (also referred to as “determination regions R _1H and R _1I ”) are determined to be the second regions D ₂ (D _2D ), and the tracks T ₇ and T 7 are determined as the second regions D 2 (D 2D ). The determination region R ₁ of T ₈ (also referred to as “determination regions R _1J and R _1K ”) is determined to be the third region D ₃ (D _3D ).

As a result of the determination in step S208, if the _second area D2 exists, the determination unit 6 determines whether or not the _third area D3 satisfies the connection condition (S210). The connection condition is a condition under which the first area D1, the _second area D2, and the _third area D3 are judged as _one continuous flaw, and in the present embodiment, the _third area D3 When the representative flaw signals of all the determination regions _Rj are equal to or greater than the third determination reference value, it is determined that connection is possible.

As a result of the determination in step S210, if the _third area D3 satisfies the connection condition, the determining unit 6 determines that the number of tracks of the _first area D1, the _second area D2, and the _third area D3 is predetermined. It is determined whether or not the number is greater than or equal to the number (S212). In step S212, determination similar to that in step S206 is performed for the three areas of the _first area D1, the _second area D2, and the _third area D3. The predetermined number of tracks in step S212 is a value determined corresponding to the length determined to be a continuous flaw, and is determined from the length of the flaw to be detected and the length of the track _Ti in the longitudinal direction. In this embodiment, as an example, the predetermined number is set to 4 as in step S206. That is, in step S212, the determination unit 6 determines that the number of tracks corresponding to the length in the longitudinal direction connecting the three regions of the first region D ₁ , the second region D ₂ and the third region D ₃ is four. It is determined whether or not the above is satisfied.

As a result of the determination in step S204, if the representative flaw signal of the determination region _Rj is less than the second determination reference value, as a result of the determination in step S208, if the _second region D2 does not exist, the determination in step S210 is performed. As a result, if the _third area D3 does not satisfy the connection condition, or as a result of the judgment in step S212, the number of tracks in the _first area D1, the _second area D2, and the _third area D3 is predetermined. If it is less than the number, the determination unit 6 determines that there is no flaw on the surface of the round bar 2 in the determination region _Rj (S214). It should be noted that the determination in step S214 is the determination of the presence/absence of flaws at the timing of detection of the flaw signal in the track T including the judgment region _Rj . Therefore, even in the judgment region _Rj where it is judged that there is no flaw, it may be judged that there is a flaw depending on the result of the subsequent flaw judgment processing. Furthermore, in step S214, the determination unit 6 outputs the determination result to the storage unit 7. FIG.

On the other hand, as a result of the determination in step S202, when the defect signal in the determination region _Rj is equal to or greater than the first determination reference value, as a result of the determination in step S206, the number of tracks in the _first region D1 is equal to or greater than the predetermined number. case, or if the number of tracks in the first area D ₁ , the second area D ₂ and the third area D ₃ is equal to or greater than a predetermined number as a result of the determination in step S212, the determination unit 6 determines at least the determination area It is determined that there is a flaw on the surface of the round bar 2 at _Rj (S216). At this time, if it is determined that there is a flaw from the result of the determination in step S206, the flaw is present in the _first region D1, which is made up of a predetermined number or more of the plurality of determination regions _Rj used for the determination in step S206. It is determined that there is Further, when it is determined that there is a flaw from the result of determination in step S212, all of the plurality of determination regions R _j of the first region D ₁ , the second region D ₂ and the third region D ₃ have the flaw. It is determined that there is Furthermore, in step S216, the determination unit 6 outputs the determination result to the storage unit 7. FIG.

After steps S214 and S216, the storage unit 7 stores the determination result regarding the presence or absence of flaws in the determination region _Rj (S218). At this time, with respect to the determination region _Rj in which it is determined that there is a flaw, it may also be possible to store the result of the determination in step S202, step S206, and step S212.
Next, steps S202 to S218 are performed for all determination regions _Rj , and the determination loop ends (S220).

<Modification>
Although the invention has been described with reference to particular embodiments, it is not intended that the invention be limited by these descriptions. Various modifications of the disclosed embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description of the invention. Therefore, the claims should be construed to cover those variations or embodiments that fall within the scope and spirit of the invention.

For example, in the above-described embodiment, the leakage magnetic flux flaw detector 5 is configured to have a pair of probe heads 51a and 51b, but the present invention is not limited to such an example. The number of probe heads provided may be one or three or more.
Further, in the above embodiment, the round bar 2 is a steel bar with a circular cross section, but the present invention is not limited to such an example. The round bar 2 may be a long member having a circular cross section, and may be a steel pipe or the like.

Furthermore, in the above-described embodiment, the probe heads 51a and 51b are configured to rotate in the circumferential direction of the round bar 2 around the axial center of the round bar 2 being conveyed, but the present invention is not limited to such an example. . It suffices if the probe head is configured to relatively rotate along the circumferential direction of the round bar 2 . That is, the flaw detection head may be fixed without being rotated and the round bar 2 may be rotated around its axis by a turning roller, or both the flaw detection head and the round bar 2 may be rotated. It is also possible to change the rotation direction or the rotation speed of the flaw detection head and the round bar 2 by rotating them around the axis.
Furthermore, in the above-described embodiment, the leakage magnetic flux flaw detector 5 rotates the pair of probe heads with respect to the round bar 2 being conveyed, so that the leakage magnetic flux flaw detector 5 detects the leakage magnetic flux on the entire surface of the round bar 2 . However, the present invention is not limited to such an example. The probe head may be moved in the longitudinal direction of the round bar 2 instead of conveying the round bar 2 . That is, the round bar 2 and the probe head can be moved relative to each other in the longitudinal direction of the round bar 2 .

Furthermore, in the above embodiment, the leakage magnetic flux is detected in the measurement area divided into eight sectors S ₁ to S ₈ , but the present invention is not limited to this example. The measurement area may be divided into a plurality of areas in the circumferential direction of the round bar 2, and is appropriately set according to the size of the diameter of the round bar 2 and the detection accuracy and specifications of the leakage magnetic flux flaw detector 5. For example, the measurement area may be an area obtained by dividing the round bar 2 into 24 to 130 areas in the circumferential direction.

Furthermore, in the above-described embodiment, the determination region _Rj is composed of two measurement regions arranged in the circumferential direction, but the present invention is not limited to such an example. The determination region _Rj may be one measurement region as in Patent Document 1, or may be composed of three or more measurement regions arranged in the circumferential direction. In the case where the determination region _Rj is a plurality of measurement regions arranged in the circumferential direction, the number of measurement regions included in the determination region _Rj depends on the size of the deviation of flaws due to assumed rotation and vibration, and the size of the measurement region. determined as appropriate depending on By setting the determination region _Rj as a plurality of measurement regions arranged in the circumferential direction, even if the round bar 2 rotates or vibrates during transportation, flaws continuous in the longitudinal direction can be accurately detected. Moreover, when the determination region _Rj is one measurement region, the flaw determination process may be performed with the measurement region as the determination region _Rj every time the flaw signal of each measurement region is detected. That is, the defect determination process may be performed in parallel with the operation of detecting the defect signal of the round bar 2 . Furthermore, when the determination region _Rj is one measurement region, the representative flaw signal is the flaw signal in the measurement region. Also, when the determination region _Rj is three or more measurement regions, the representative flaw signal is the flaw signal in the measurement region where the flaw signal is the largest (highest signal) among the three or more measurement regions.

Furthermore, in the above embodiment, the process of step S216 is performed when the number of tracks in the _first area D1 is equal to or greater than the predetermined number in step S206, but the present invention is not limited to such an example. For example, if the number of tracks in the _first area D1 is equal to or greater than a predetermined number in step S206, the same processing as in step S208 may be performed. In this case, in the same process as step S208, if the _second area D2 does not exist, the process of step S216 is performed, and it is determined that there is a flaw in the _first area D1. On the other hand, in the same process as step S208, if the _second area D2 exists, the same process as step S210 is performed. Then, in the same process as step S210, if the _third area D3 satisfies the connection condition, the process of step S216 is performed in the _first area D1, the _second area D2 and the _third area D3. It is determined that there is a flaw. On the other hand, in the same process as step S210, if the _third area D3 does not satisfy the connection condition, the process of step S216 is performed, and it is determined that there is a flaw in the _first area D1.

Furthermore, in the above embodiment, after step S206 or S212, when it is determined that there is a flaw in step S216, the _first region D1 or the _first region D1, the second region D2 and the _second Area D of ₃ Although it is determined that there are flaws in the three areas of 3, the present invention is not limited to such an example. For example, in this case, when the height of the representative flaw signal is equal to or higher than the third judgment reference value in the judgment region _Rj adjacent to the region judged to have a flaw in the above embodiment at the same circumferential position. may be determined that there is a further flaw in this determination region _Rj . At this time, if the determination regions _Rj having the third determination reference value or more are continuous in the longitudinal direction, it may be determined that there is a flaw in the plurality of determination regions _Rj .

Furthermore, in the above embodiment, in step S210, it is determined that connection is possible when the representative flaw signals of all the determination regions _Rj of the _third region D3 are equal to or greater than the third determination reference value. The invention is not limited to such examples. For example, to determine whether or not the _third region D3 satisfies the connection condition, the number of determination regions _Rj (the number of tracks) in the longitudinal direction of the _third region D3 is the same as the number of the first region D1 and the _first region D1 and the third region D1. It may be determined that connection is possible when the number of determination regions (the number of tracks) in at least one of the _two regions D2 in the longitudinal direction is equal to or less than the number of determination regions. Alternatively, both the linking condition based on the number of determination regions and the linking condition in the above embodiment may be used, and it may be determined that linking is possible when either one of the linking conditions is satisfied.

Furthermore, in the above-described embodiment, the surface flaw inspection apparatus 1 is configured to determine only the presence or absence of flaws on the round bar 2, but the present invention is not limited to this example. For example, the surface flaw inspection apparatus 1 may be provided with a marking device (not shown), and may be configured to mark, as in Patent Document 1, a judgment region judged to have flaws using this marking device.

Furthermore, in the above-described embodiment, the defect determination process is performed for each track after the defect signal is detected for each track, but the present invention is not limited to this example. For example, in the detection loop of step S100, only the process of step S102 is performed, and after the flaw signal is detected over the entire circumference of the round bar 2, the flaw determination may be performed based on the detection result. . In this case, the judging section 6 judges the flaw using the first judging process, the second judging process, and the third judging process.

The first to third determination steps will be described with reference to FIGS. 8 and 9. FIG. 8 and 9 map the detection results of the flaw signal in each measurement region, as in FIG. In this modified example shown in FIG. 8, as in the above modified example, flaws are detected using the determination region _Rj as one measurement region. In the examples shown in FIGS. 8 and 9, the determination area is denoted as R _{Sk, Ti} using sector S _k (k=1 to 8) and track T _i . For example, when the measurement area of sector S ₁ and track T ₂ is set as the determination area, this determination area is indicated as R _{S1, T2} .

(First determination step)
In the first determination step, it is determined that there is a flaw in the determination regions R _{Sk, Ti} in which the height of the flaw signal is equal to or higher than the first determination reference value. For example, in the range _{of sector S 1} in the example shown in FIG. It is determined that there is a flaw in the determination area.

(Second judgment step)
In the second determination step, first, at least one determination region R _{Sk, Ti} or a plurality of determination regions R _{Sk, Ti} continuous in the longitudinal direction in which the height of the flaw signal is equal to or higher than the second determination reference value is selected as the second 1 area D ₁ . At this time, since it is determined that there is a flaw in the judgment regions R _{Sk and Ti} in which the height of the flaw signal is equal to or higher than the first judgment reference value in the first judgment step, in the second judgment step, the flaw signal The determination regions R _{Sk and Ti} whose height is equal to or greater than the second determination reference value and less than the first determination reference value may be determined as the first region D ₁ . For example, in the range _{of sectors S 3} to S ₅ in the example shown in FIG. , the determination regions R _S5,T3 to the determination regions R _S5,T6 are each the first region D ₁ .

Next, in the second determination step, when the _first region D1 consists of a predetermined number or more of determination regions continuous in the longitudinal direction, it is determined that the _first region D1 has a flaw. This determination can be performed in the same manner as the process of step S206 in the above embodiment. For example, in the _range of _{sectors S 3} to S ₅ in the example shown in FIG. It is determined that there is Further, the other _first region D1 is determined to have no flaw in the second determination step.
Further, for example, as shown in the range of sector S7 in FIG. ₈ , the _first region D1 may include the flaw signal having the first criterion value or more. In this case, the five regions from the determination regions R _{S7, T4} to R _{S7, T8} are the first region D ₁ , and the number of determination regions in the longitudinal direction is four or more. It may be determined that there is _a flaw in the region D1.

(Third determination step)
In the third determination step, _first , the determination regions R _{Sk and Ti} to be the first region D1 are determined in the same manner as in the second determination step, and the _second region D2 is determined with respect to the _first region D1. It is determined whether or not there is a determination region R _{Sk, Ti} such that The _second region D2 is similar to the above embodiment, exists at the same position in the circumferential direction as the _first region D1, and the height of the flaw signal is all the second criteria One determination region R _Sk,Ti equal to or greater than the value or a plurality of determination regions R _Sk,Ti continuous in the longitudinal direction. In addition, the height of the defect signal is less than the second criterion value in all of the judgment regions _{RSk and Ti} between the _first region D1 and the _second region D2 in the longitudinal direction. That is, for the two first regions D ₁ arranged in the longitudinal direction via the judgment regions R _{Sk and Ti} in which the height of the flaw signal is less than the second judgment reference value, one is the first region D ₁ and the other becomes the second region D ₂ . At this time, for example, the _first area D1 on the downstream side (the side with the smaller track number) in the transport direction may be defined as the _second area D2. For example, in the range of sector S ₂ in the example shown in FIG. 9, the first region D ₁ consists of the two determination regions R _{S2 , T6} to R _{S2, T7} . _{, T3} is the _second area D2.

Next, in the third determination step, it is determined whether or not the _third region D3, which is the determination region _{RSk, Ti} between the _first region D1 and the _second region D2, satisfies the connection condition. do. This determination may be performed in the same manner as in step S210 in the above embodiment, or may be performed based on the number of determination areas (number of tracks) of the _third area D3 as in the above modification. good too. For example, in the range of sector S2 in _FIG . 9, when the determination regions R _S2,T6 to R _S2,T7 are set as the _first region D1, and the determination regions R _S2,T3 are set as the _second region D2 , and the third region D ₃ become two determination regions of determination regions R _S2,T4 to R _S2,T5 . At this time, when the connection condition is the same as in the above embodiment, the heights of the flaw signals in the determination regions R _{S2, T4} to R _{S2, T5} included in the third region D ₃ are all the third determination criteria. value, it satisfies the concatenation condition. _In the range of sector S4 in FIG. 9, the determination regions R _S4,T7 to R _S4,T8 are the _first region D1, and the determination regions R _S4,T2 to R _S4,T4 are the second region D1. , the third region D ₃ becomes _two determination regions of determination regions R _S4,T5 to R _S4,T6 . At this time, when the connection condition is based on the number of determination regions of the _third region D3 as in the above modified example, the number of determination regions of the _third region D3 is the same as the number of the determination regions of the _first region D1 and Since the number is greater than or equal to the number of determination regions in at least one of the _second regions D2, the connection condition is satisfied. Further, in the range of the sector S6 in FIG. ₉ , the determination regions R _S6,T8 to R _S6,T9 are set as the _first region D1, and the determination regions R _S6,T3 to R _S6,T4 are set as the second region D1. , the third region D ₃ consists of _three determination regions R _S6,T5 to R _S6,T7 . At this time, when the connection condition is the same as in the above embodiment, the heights of the flaw signals in the determination regions R _{S4, T5} to R _{S4, T7} included in the third region D ₃ are all the third determination criteria. Since it does not exceed the value, it does not satisfy the consolidation condition.

Furthermore, in the third determination step, if the _third region D3 satisfies the connection condition in the previous processing step, the flaws are present in the _first region D1, the _second region D2 and the _third region D3. It is determined that there is On the other hand, when the _third region D3 does not satisfy the connection condition, the _first region D1, the _second region D2 and the _third region D3 are judged to have no flaws in the third judgment step. . That is, in the example shown in FIG. 9, there are five determination regions from determination regions R _S2,T3 to R _S2,T7 , and seven determination regions from determination regions R _S4,T2 to R _S4,T8 . In, it is judged that there is a flaw.

In this modification, the first to third determination steps may be performed individually or sequentially. Then, based on the results of each determination process, the presence or absence of flaws in each determination region _Rj is finally determined. After that, a final judgment is made that there is a flaw in the judgment region _Rj that has been judged to have a flaw in at least one of the judgment steps from the first judgment step to the third judgment step.
Further, in this modified example, similarly to the above-described embodiment, the presence or absence of flaws may be determined using a plurality of measurement areas adjacent in the circumferential direction on the same track T _i as the determination areas _Rj .

<Effects of Embodiment>
(1) A method for inspecting a surface flaw of a round bar 2 according to one aspect of the present invention is such that the probe heads 51a and 51b of the leakage magnetic flux flaw detector 5 are moved in the circumferential direction of the round bar 2 while conveying the round bar 2 in the longitudinal direction. A flaw detection step of detecting a flaw signal by detecting a leakage magnetic flux in a plurality of measurement areas divided in the longitudinal direction and the circumferential direction on the surface of the round bar 2, and at least one measurement area , and for a plurality of judgment regions R _j arranged in the circumferential direction and the longitudinal direction, based on the representative flaw signal that is the largest flaw signal of the measurement region included in the judgment region R _j , there is a flaw on the surface of the round bar 2 and a determination step of determining that. The determination process includes a first determination process, a second determination process, and a third determination process for determining whether the surface of the round bar 2 has a flaw. In the first determination step, it is determined that there is a flaw in the determination region _Rj in which the height of the representative flaw signal is equal to or greater than the first determination reference value (for example, step S202). In the second determination step, the height of the representative flaw signal of the determination region R _j is equal to or higher than the second determination reference value lower than the first determination reference value, one determination region R _j or continuous in the longitudinal direction A plurality of determination regions R _j is defined as a first region D ₁ , and the first region D ₁ is composed of a plurality of determination regions R _j continuous in the longitudinal direction, and the determination region R _j of the first region D ₁ is equal to or greater than a predetermined number, it is determined that there is a flaw in the determination region _Rj of the _first region D1 (eg, step S206). In the third determination step, one determination region R _j or a plurality of determination regions R _j continuous in the longitudinal direction in which the height of the representative flaw signal of the determination region R _j is equal to or higher than the second determination value, A determination region _Rj having the same position in the circumferential direction as the region D1 of ₁ is defined as a _second region D2, and a determination region _Rj between the _first region D1 and the _second region D2 is defined as a third region D2. When the representative flaw signal of the judgment region R _j of the _{third region D 3 is} less than the second judgment reference value and is equal to or more than the third judgment reference value, and the length of the third region D ₃ In at least one of the cases where the number of direction determination regions R _j is less than or equal to the number of longitudinal direction determination regions R _j in at least one of the first region D ₁ and the second region D ₂ , and When the number of determination regions R _j of the region D ₁ , the second region D ₂ and the third region D ₃ is equal to or greater than a predetermined number, the first region D ₁ , the second region D ₂ and the third region It is determined that there is a flaw in the determination region _Rj of D3 ₍ for example, steps S208 to S212).

Here, FIG. 10 shows an example of the flaw signal detection result when there is a flaw on the surface. In FIG. 10, the detection result of the flaw signal indicated by the dotted line shows the case where there are two consecutive flaws intermittently in the longitudinal direction where the height of the flaw signal is equal to or higher than the second criterion value. In FIG. 10, the detection result of the flaw signal indicated by the solid line shows the case where the flaw signal partially becomes less than the second judgment reference value and equal to or more than the third judgment reference value at the center in the longitudinal direction. The continuous flaws shown by the solid line are likely to occur when the flaws are caused by the material such as the cast slab. It was not judged that there was a flaw in the _third region D3, which is less than the judgment reference value of.

However, according to the configuration (1) above, in the third determination step, the representative flaw signal of the determination region _Rj of the _third region D3 is less than the second determination reference value and is equal to or greater than the third determination reference value. In this case, by determining that there is a flaw in the _third region D3, such a continuous flaw can be detected. In addition, in the continuous flaw shown by the solid line in FIG. 10, the length in the longitudinal direction of the _third region D3 is shorter than the overall length of the continuous flaw in the longitudinal direction. Therefore, in the third determination step, when the number of determination regions Rj of at least one of the _first region D1 and the second region D2 is equal to or less than the number of the determination regions _Rj , it is determined that the _third region D3 has a flaw. This makes it possible to detect such continuous flaws. In addition, in the case of this determination, the detection sensitivity is higher than that using the third determination reference value, but the flaw can be easily detected.

This makes it possible to accurately detect flaws that are continuous in the longitudinal direction, and to prevent outflow of unsuitable materials with long surface flaws. Furthermore, it is possible to prevent a large amount of nonconforming materials from flowing out, which not only causes monetary loss to the manufacturer, but also may damage the social credibility of the manufacturer.
Further, in the above configuration (1), when detecting continuous shallow flaws, the second determination step and the third determination step are performed. Here, when detecting continuous flaws in which the height of the flaw signal is less than the second judgment reference value and equal to or higher than the third judgment reference value, the second judgment reference value used in the second judgment step is set to the above-described implementation. Continuous flaws can be detected by lowering to the third criterion value in the form. However, in this case, since shallow and long flaws that are not problematic are detected, the detection sensitivity becomes too high, resulting in over-detection. On the other hand, according to the above configuration (1), by using the second determination step and the third determination step, it is possible to suppress over-detection.

(2) In the configuration of (1) above, the determination region _Rj is composed of a plurality of measurement regions that are continuous in the circumferential direction.
According to the above configuration (2), determination is made based on the detection results of the flaw signals in a plurality of measurement areas that are continuous in the circumferential direction, so it is possible to eliminate seams between the measurement areas in the circumferential direction. Therefore, even when the round bar 2 rotates or vibrates during transportation, or when the flaw is positioned at the boundary of the measurement area, flaws that are continuous in the longitudinal direction can be accurately detected.

(3) The apparatus 1 for inspecting surface defects of a round bar 2 according to one aspect of the present invention has probe heads 51a and 51b. A leakage magnetic flux flaw detector that detects a flaw signal by rotating the rod 2 along the circumferential direction and detecting leakage magnetic flux in a plurality of measurement areas divided in the longitudinal direction and the circumferential direction on the surface of the round rod 2. 5, and for a plurality of determination regions _Rj that include at least one measurement region and are arranged in the circumferential direction and the longitudinal direction, based on the representative flaw signal that is the largest flaw signal of the measurement regions included in the determination region _Rj , a circle and a determination unit 6 that determines whether the surface of the rod 2 has a flaw. The determination unit 6 performs a first determination process, a second determination process, and a third determination process for determining whether the surface of the round bar 2 has a flaw. In the first determination step, it is determined that there is a flaw in the determination region _Rj in which the height of the representative flaw signal is equal to or greater than the first determination reference value (for example, step S202). In the second determination step, the height of the representative flaw signal of the determination region R _j is equal to or higher than the second determination reference value lower than the first determination reference value, one determination region R _j or continuous in the longitudinal direction A plurality of determination regions R _j is defined as a first region D ₁ , and the first region D ₁ is composed of a plurality of determination regions R _j continuous in the longitudinal direction, and the determination region R _j of the first region D ₁ is equal to or greater than a predetermined number, it is determined that there is a flaw in the determination region _Rj of the _first region D1 (eg, step S206). In the third determination step, one determination region R _j or a plurality of determination regions R _j continuous in the longitudinal direction in which the height of the representative flaw signal of the determination region R _j is equal to or higher than the second determination value, A determination region _Rj having the same position in the circumferential direction as the region D1 of ₁ is defined as a _second region D2, and a determination region _Rj between the _first region D1 and the _second region D2 is defined as a third region D2. When the representative flaw signal of the judgment region R _j of the _{third region D 3 is} less than the second judgment reference value and is equal to or more than the third judgment reference value, and the length of the third region D ₃ In at least one of the cases where the number of direction determination regions R _j is less than or equal to the number of longitudinal direction determination regions R _j in at least one of the first region D ₁ and the second region D ₂ , and When the number of determination regions R _j of the region D ₁ , the second region D ₂ and the third region D ₃ is equal to or greater than a predetermined number, the first region D ₁ , the second region D ₂ and the third region It is determined that there is a flaw in the determination region _Rj of D3 ₍ for example, steps S208 to S212).
According to the configuration of (3) above, the same effect as that of (1) above can be obtained.

1 Surface flaw inspection device 2 Round bar 3 Transfer roll 4 Pinch roll 5 Leakage magnetic flux flaw detection device 51a, 51b Probing heads 52a, 52b Exciting yokes 53a, 53b Exciting coils 54a, 54b Probes 6 Judging unit 7 Storage unit

Claims (3)

While conveying the round bar in the longitudinal direction, or while moving the probe head of the magnetic flux leakage flaw detector in the longitudinal direction of the round bar, the probe head of the magnetic flux leakage flaw detector rotates along the circumferential direction of the round bar. By rotating the probe head or the round bar or both the probe head and the round bar so as to A flaw detection step of detecting a flaw signal by detecting leakage magnetic flux for
For a plurality of determination regions that include at least one measurement region and are arranged in the circumferential direction and the longitudinal direction, based on the representative flaw signal that is the largest flaw signal of the measurement region included in the determination region, the circle A determination step of determining whether there is a flaw on the surface of the rod;
with
The determination step includes a first determination step, a second determination step, and a third determination step for determining whether the surface of the round bar has the flaw,
In the first determination step, the height of the representative flaw signal determines that the flaw is present in the determination region in which the height is equal to or higher than a first determination reference value,
In the second determination step,
One determination region or a plurality of determination regions continuous in the longitudinal direction in which the height of the representative flaw signal of the determination region is equal to or higher than a second determination reference value lower than the first determination reference value as a first region,
the determination of the first region when the first region is composed of a plurality of the determination regions continuous in the longitudinal direction and the number of the determination regions of the first region is a predetermined number or more; Determining that the area has the flaw,
In the third determination step,
The height of the representative flaw signal of the determination region is the second determination reference value or more, one of the determination regions or a plurality of the determination regions continuous in the longitudinal direction, wherein the first region and the The determination regions having equal positions in the circumferential direction are defined as a second region,
The determination region between the first region and the second region is defined as a third region,
When the representative flaw signal of the determination region of the third region is less than the second determination reference value and is equal to or more than the third determination reference value , and the first region, the second region and When the number of the determination regions of the third region is a predetermined number or more, it is determined that the flaw is present in the determination regions of the first region, the second region, and the third region. A bar surface flaw inspection method. 2. The round bar surface flaw inspection method according to claim 1, wherein said determination area comprises a plurality of said measurement areas which are continuous in said circumferential direction. It has a probe head, and the probe head rotates along the circumferential direction of the round bar while conveying the round bar in the longitudinal direction or moving the probe head in the longitudinal direction of the round bar. By rotating the probe head, the round bar, or both the probe head and the round bar, a plurality of measurement areas divided in the longitudinal direction and the circumferential direction on the surface of the round bar A leakage magnetic flux flaw detector that detects a flaw signal by detecting a leakage magnetic flux;
For a plurality of determination regions that include at least one measurement region and are arranged in the circumferential direction and the longitudinal direction, based on the representative flaw signal that is the largest flaw signal of the measurement region included in the determination region, the circle a determination unit that determines whether there is a flaw on the surface of the rod;
with
The determination unit performs a first determination step, a second determination step, and a third determination step for determining that the surface of the round bar has the flaw,
In the first determination step, the height of the representative flaw signal determines that the flaw is present in the determination region in which the height is equal to or higher than a first determination reference value,
In the second determination step,
One determination region or a plurality of determination regions continuous in the longitudinal direction in which the height of the representative flaw signal of the determination region is equal to or higher than a second determination reference value lower than the first determination reference value as a first region,
the determination of the first region when the first region is composed of a plurality of the determination regions continuous in the longitudinal direction and the number of the determination regions of the first region is a predetermined number or more; Determining that the area has the flaw,
In the third determination step,
The height of the representative flaw signal of the determination region is the second determination reference value or more, one of the determination regions or a plurality of the determination regions continuous in the longitudinal direction, wherein the first region and the The determination regions having equal positions in the circumferential direction are defined as a second region,
The determination region between the first region and the second region is defined as a third region,
When the representative flaw signal of the determination region of the third region is less than the second determination reference value and is equal to or more than the third determination reference value , and the first region, the second region and When the number of the determination regions of the third region is a predetermined number or more, it is determined that the flaw is present in the determination regions of the first region, the second region, and the third region. Bar surface flaw inspection device.

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