JP5978889B2 - Inspection method and inspection device for surface defect of round bar - Google Patents

Description

  The present invention relates to an inspection method and an inspection apparatus for a surface defect of a round bar by a leakage magnetic flux inspection method.

The flaw detection inspection of a round bar as a product by the leakage magnetic flux inspection method (hereinafter also referred to as “MLFT”) is an inspection method in which the probe head is rotated along the circumferential direction of the round bar while the round bar is conveyed in the longitudinal direction. There is an inspection method in which a probe head runs in the longitudinal direction of a round bar while rotating the round bar about an axis (see, for example, Patent Document 1).
In any of the inspection methods, the probe (probe) in the probe head of the magnetic flux leakage flaw detector receives a 疵 signal from the heel on the surface of the round bar, and the height of the 疵 signal is greater than the criterion value. The presence or absence of wrinkles is determined based on whether or not. Note that the determination reference value is defined in advance by the allowable depth required for the product.

  In general, a plurality of probes are arranged to cover 100% or more of the entire round bar. Each probe has a width of 5 to 10 mm. Usually, each probe individually performs a wrinkle determination based on a comparison with a determination reference value to evaluate the presence or absence of wrinkles. Note that a marking system such as a marking device is attached to the probe head, and a portion determined as a scissors is automatically marked. The marking position determined as wrinkles is surface-treated by removing grinders in a later process.

JP 2001-41932 A

  By the way, the probe also acquires the noise affected by the surface property of the material of the round bar and the surface component change (decarburization) simultaneously with the soot signal. For this reason, it is usually necessary that the S (signal) / N (noise) ratio is 3 or more in order to enable proper bar evaluation of the round bar. That is, it is because it is difficult to clearly discriminate between noise and the soot signal in the soot determination in the region where the S / N ratio is less than 3. Therefore, setting a determination reference value with a small S / N ratio to detect shallow wrinkles leads to “overdetection” in which noise is determined as a wrinkle signal.

  Further, the flaw detection performance of the leakage magnetic flux flaw detector needs to be subjected to wrinkle determination based on “allowable wrinkle depth” allowed for the product. However, the actual shape of the cocoon varies. For example, in the case of a closed defect or a defect having a large opening, the height (level) of the wrinkle signal may be detected lower than the determination reference value with respect to the original wrinkle depth. Therefore, in such a case, there arises a problem that even a deep wrinkle is not actually detected as a wrinkle exceeding the allowable wrinkle depth. To deal with such problems, measures such as stricter setting of the determination reference value are often taken. However, as described above, the stricter criterion value often results in a region where the S / N ratio is less than 3, resulting in unnecessary surface care due to the “overdetection”. The same problem as described above that causes a significant decrease in the maintenance efficiency occurs.

  Therefore, the present invention has been made paying attention to such problems, and it is possible to detect even a shallow wrinkle that has been difficult to discriminate from noise. It is an object to provide a method and an inspection apparatus.

  The inventor of the present application investigates the occurrence of shallow wrinkles that were difficult to discriminate from noise when the hot-rolled round bar is an object to be inspected. It has been found that it is often formed in a shape extending along the same. The reason why the shallow ridges are formed by extending along the axial direction of the round bar is because the shallow ridges are caused by defects that occur in the upstream process of hot rolling, that is, the stage until casting. It has been found that this is because the film is stretched in the rolling direction, that is, the axial direction of the round bar by hot rolling.

In addition, it was found that defects occurring in the hot rolling process were sufficiently detected even by a conventional judgment reference value in which the depth of wrinkles was relatively deep and the S / N ratio was 3 or more.
From this point of view, the inventor of the present application, in the conventional leakage magnetic flux flaw detection, evaluates wrinkles from individual “judgment depths” based on comparison between the height of the wrinkle signal acquired by each probe and the judgment reference value. We paid attention to the fact that no consideration was given to the continuity of wrinkles. That is, in long workpieces such as round bars, shallow ridges are often formed along the axial direction. Therefore, in the case of shallow ridges, continuity of ridges is recognized in the longitudinal direction. On the other hand, noise does not have such continuity. Therefore, it was considered that if the correlation (continuity, etc.) of the heights of the soot signals sequentially detected by the probe is grasped, even a shallow soot can be distinguished from noise.

  Therefore, in order to determine the continuity of the flaw, the inventor of the present application gives “judgment flaw length” in addition to “judgment flaw depth” as a criterion for processing in the flaw detection control unit of the magnetic flux leakage flaw detector. Even if a wrinkle signal exceeding a certain standard is detected, it is difficult to discriminate from noise when it is set so that it will not be judged as long as the wrinkle does not reach the “judgment length”. It was found that even shallow folds can be detected.

  That is, in order to solve the above-described problem, the method for inspecting a surface defect of a round bar according to one aspect of the present invention is to rotate the probe head along the circumferential direction of the round bar while conveying the round bar in the longitudinal direction. Or a method of inspecting the surface flaw of the round bar by a leakage magnetic flux flaw detection method by causing the probe head to run in the longitudinal direction of the round bar while rotating the round bar around the axis. A first determination step and a second determination for receiving the wrinkle signal from the wrinkle on the surface of the round bar by the probe and determining the presence or absence of the wrinkle based on whether or not the height of the wrinkle signal is equal to or higher than a criterion value Including a step, wherein the first determination step determines that the height of the wrinkle signal acquired by the probe is greater than or equal to a first determination reference value, and the second determination step includes the step of The height of the plurality of eyelid signals acquired by the probe is lower than the first criterion value. Preliminary determination for determining whether or not the second determination reference value is greater than or equal to the second determination reference value is performed with respect to each of the wrinkle signals. It is characterized by determining that it is a heel when it is continuous at different positions in the longitudinal direction and at the same position in the circumferential direction.

  Further, the inspection apparatus for surface defects of a round bar according to one aspect of the present invention is such that the probe head is rotated along the circumferential direction of the round bar while the round bar is conveyed in the longitudinal direction, or the round bar is pivoted. An inspection device for inspecting the surface defect of a round bar by a leakage magnetic flux flaw detection method by causing the probe head to run in the longitudinal direction of the round bar while rotating around the surface of the round bar by a probe in the probe head A flaw detection control unit that receives a wrinkle signal from a flaw and determines whether or not wrinkle is present based on whether the height of the wrinkle signal is equal to or higher than a determination reference value, and the flaw detection control unit includes first determination means and Having a second determination means, wherein the first determination means determines that the height of the wrinkle signal acquired by the probe is greater than or equal to a first determination reference value, and the second The determination means is a second unit in which the heights of the plurality of eyelid signals acquired by the probe are lower than the first determination reference value. Preliminary determination for determining whether or not the value is equal to or greater than a predetermined reference value is performed for each wrinkle signal, and a plurality of wrinkle signals determined by the preliminary determination to be equal to or greater than the second determination reference value are in the longitudinal direction of the round bar It is characterized in that it is determined that it is continuous when it is continuous at different positions and the same position in the circumferential direction.

  According to the present invention, when the height of the wrinkle signal is equal to or higher than the second determination reference value by the preliminary determination, it is further evaluated whether or not there is continuity in the longitudinal direction of the round bar. Even for materials with extremely low / N ratio (flaw detection standard), only wrinkle signals that are continuous in the longitudinal direction of the round bar are extracted from the wrinkle signals that contain randomly generated noise and detected as wrinkles be able to.

  For this reason, according to the present invention, in addition to the conventional first determination reference value, the second determination reference value for determining continuity is also applied, so that only the first determination reference value can be found. Since it is a defect type that detects a minute defect or a defect signal height (level) that is lower than the determination reference value, it is possible to detect even a defect having a low defect signal and a shallow depth. . Therefore, when the second determination reference value is employed in combination with the first determination reference value, overdetection can be suppressed as compared with the case where the first determination reference value is tightened. Thereby, the influence of the maintenance efficiency fall in a post process can be avoided.

  Moreover, depending on the setting of the first determination reference value, overdetection due to a noise signal that is not originally a defect may occur. By reducing the criterion value (threshold value) (with a high S / N ratio setting) and adding a second criterion value to determine the total defect, the inherently harmless defect (noise) At the same time as suppressing detection, minute harmful defects that could not be detected in the past can be detected with higher accuracy. With such an effect, it is possible to contribute to the improvement of the maintenance efficiency with respect to the grinder care which is a subsequent process.

  Here, in the apparatus for inspecting a surface defect of a round bar according to an aspect of the present invention, the second determination means includes a plurality of tracks in which the round bar is sectioned in the longitudinal direction and a plurality of tracks in which the round bar is sectioned in the circumferential direction. And the position determined to be equal to or higher than the second determination reference value by the preliminary determination is specified (mapped) to a corresponding position in the area divided by the plurality of sectors and the plurality of tracks, It is preferable that the position determined by the preliminary determination is determined to be 疵 when the position is continuous in the same sector of adjacent tracks. With such a configuration, the continuity is determined from the relationship between the mapping positions at the time of the preliminary determination when determining that the bar is continuous when it is continuous at different positions in the longitudinal direction of the round bar and at the same position in the circumferential direction. Therefore, it is suitable as a configuration for performing a flaw detection inspection with a strict standard (setting with a low S / N ratio).

  As described above, according to the present invention, it is possible to detect even a shallow ridge that has been difficult to distinguish from noise.

It is a schematic block diagram of one Embodiment of the leakage magnetic flux flaw detector which concerns on 1 aspect of this invention, The figure (a) is the front view, (b) is A arrow view in (a). It is a figure explaining the mapping (area divided into the track and the sector) with respect to the work in the wrinkle determination processing. FIG. 9A is a perspective view of the work (a figure divided into sectors), and FIG. A development view (map divided by track and sector) and an image in a state where a marking flag is set on the map are shown. It is a flowchart of the wrinkle determination process performed in the flaw detection control part of FIG. It is a flowchart of the marking process in the wrinkle determination process of FIG. FIG. 6 is a graph showing the relationship between the output of the 疵 signal (including noise) and the set judgment reference values (FL, FS), and FIG. 9 shows the 疵 when the track T makes one round (sector Sn = 0 to n). Output Z is shown. It is a figure explaining the relationship between determination length and marking when the 2nd determination reference value is applied with respect to a bag. It is a figure which compares and shows the case where the 2nd criterion value is applied with respect to a continuous wrinkle (the figure (a)), and the case where it is not made (the figure (b)).

  Hereinafter, a leakage magnetic flux flaw detection apparatus (which is an embodiment of a round bar surface flaw inspection apparatus according to one aspect of the present invention) and a flaw inspection method using the leakage magnetic flux flaw detection apparatus (round according to one aspect of the present invention) (This is an embodiment of the method for inspecting the surface defect of the rod) will be described with reference to the drawings as appropriate. In the present invention, the “round bar” includes not only a solid rod-like body but also a hollow tubular body.

  As shown in FIG. 1, the leakage magnetic flux flaw detector 10 includes a plurality of pairs of turning rollers 5 that support the lower part of a round bar (hereinafter also referred to as “workpiece”) W. The workpiece W is a steel bar produced by continuous casting and hot rolled into a round bar. The plurality of pairs of turning rollers 5 are arranged so as to be spaced apart in the axial direction of the workpiece W so as to support the entire workpiece W evenly. It rotates (see the image of the rotation of the arrow indicated by the symbol R in the figure). The traveling mechanism 4 is disposed in the vicinity of the workpiece W along the longitudinal direction of the workpiece W. A plurality (two in this example) of flaw detection carts 1 are arranged on the travel line 4a of the travel mechanism 4. The flaw detection carts 1 are arranged at predetermined intervals with respect to the travel line 4a of the travel mechanism 4 and are allowed to travel linearly along the travel line 4a by driving of the travel mechanism 4 (denoted by reference numeral D in the figure). (See the image of running arrow).

Each flaw detection carriage 1 has an excitation yoke 2 that magnetizes the workpiece W and a detection coil 3. In the vicinity of the detection coil 3, a marking gun 8 is attached as shown in FIG. 5B, and paint is applied to the wrinkle detection position on the surface of the workpiece W as necessary by a marking process described later. Marking is possible by spraying.
The exciting yoke 2 is made of silicon steel formed in a substantially U shape when viewed from the front, and both magnetic poles (N pole and S pole) thereof are arranged apart from the outer peripheral surface of the workpiece W by a required gap. . A coil connected to an excitation power source (not shown) is wound around the excitation yoke 2 with a required number of turns, and the work W is magnetized via the excitation yoke 2 by energizing and exciting the coil. The detection coil 3 is disposed between both magnetic poles of the excitation yoke 2. The output terminal of the detection coil 3 is connected to the flaw detection control unit 7 in each flaw detection carriage 1, and is configured to output a flaw detection signal (疵 signal) to the flaw detection control unit 7. As a result, each flaw detection carriage 1 can travel linearly with respect to the rotating workpiece W, so that substantially the entire outer peripheral surface of the workpiece W can be detected. When flaw detection is performed by rotating the workpiece W with respect to the flaw detection carriage 1 traveling in the workpiece longitudinal direction, the flaw detection trajectory with respect to the outer peripheral surface of the workpiece W of the detection coil 3 is spiral.

Next, the wrinkle determination process executed by the flaw detection control unit 7 will be described.
The flaw detection control unit 7 stores a CPU control program and the like in advance in a predetermined area, a CPU for controlling the entire system of the leakage flux flaw detector 10 based on a predetermined control program (not shown). A storage device such as a ROM, a RAM for storing data read from the storage device such as a ROM and a calculation result required in the calculation process of the CPU, the traveling mechanism 4 and the turning roller 5 of the leakage magnetic flux inspection device 10, etc. And an I / F (interface) that mediates input / output of data necessary for traveling drive, rotational drive, and the like. These are connected to each other via a bus, which is a signal line for transferring data, so that data can be exchanged. The flaw detection control unit 7 performs rotation control of the turning roller 5 and travel control of the travel mechanism 4 along with the wrinkle determination processing. Is also executed. In addition, a predetermined operation signal serving as an execution command for wrinkle determination processing is input to the flaw detection control unit 7 by a switch operation by an operator.

  Here, when the workpiece W is rotated by the turning roller 5, the flaw detection control unit 7 manages the workpiece W as a plurality of “sectors” divided in the circumferential direction as indicated by broken lines in FIG. (Sn = 0, 1, 2, 3...), And one rotation pulse corresponds to one sector Sn. Further, when each flaw detection carriage 1 is caused to travel by the traveling mechanism 4, a plurality of “tracks” in which the workpiece W is divided in the longitudinal direction (the left and right directions in the figure) as shown by the one-dot chain line in FIG. (T = 1, 2, 3...), And one traveling pulse is associated with one track T. Then, the flaw detection control unit 7 manages the entire surface of the workpiece W as a map by the sector Sn and the track T as shown in FIG. ) Can be stored in association with the corresponding position on the map.

  When the flaw detection control program is executed by the flaw detection control unit 7, as shown in FIG. 3, the process proceeds to step S1, and the flaw detection carriage 1 is moved to the origin (track T = 1, sector Sn = 0) on the map. (Refer to FIG. 2B). In the subsequent step S2, the soot output (depth Z) from the detection coil 3 in the current sector Sn (and track T) is acquired (see FIG. 5) and compared with a preset second determination reference value FS. To do. Here, in the present embodiment, as the determination reference value (threshold value), as shown in FIG. 5, the first determination reference value FL and the second determination reference having a value lower than the first determination reference value FL. The value FS is set. The first determination reference value FL is set to 3 as an S / N ratio so as not to be affected by noise. On the other hand, the setting value of the second determination reference value FS is 1 in the S / N ratio. Note that this value corresponds to a first determination reference value FL = about 1 mm and a second determination reference value FS = about 0.3 mm in terms of dredging output (depth Z).

  That is, in step S2, the second judgment reference value FS having a low set value is compared with the acquired soot output (depth Z), and the obtained soot output (depth Z) is compared with the second judgment standard. If the value is equal to or greater than the value FS (FS event occurrence), the value is saved (stored) in a corresponding area (current sector Sn (and track T)) on the map.

  In subsequent step S3, a series of marking processes is executed (the marking process in step S3 will be described later). After the marking process, the process proceeds to step S4, the sector count is incremented (n = n + 1), and the process proceeds to step S5. In step S5, it is confirmed whether or not the counter n of the sector Sn has made a round and returned to the origin. The setting of the counter n of the sector Sn varies depending on the diameter of the round bar (for example, n = 24 to 130). If the counter n of the sector Sn has gone around (returned to the origin) (Yes), the process proceeds to step S7, the counter n is reset (n = 0), and then the process proceeds to step S8. On the other hand, if the counter n has not made a full turn (returned to the origin) (No), the process proceeds to step S6 to transmit one rotation pulse and rotate the workpiece W by one sector, and then the process is performed in step S2. Return to.

  In step S8, one pulse is transmitted to drive each flaw detection carriage 1 for one track T, and the process proceeds to step S9. In addition, each flaw detection cart 1 is interlocked. In the subsequent step S9, the track T is incremented (T = T + 1), and the process proceeds to step S10. In step S10, it is confirmed whether or not the track count T has reached a terminal value set in advance with respect to the total length of the workpiece W. That is, if the track count T has reached the terminal value (Yes), the process proceeds to step S11 to return the flaw detection carriage 1 to the origin (track T = 1), and the wrinkle determination process is terminated. On the other hand, if the track count T does not reach the terminal value (No), the process proceeds to step S12.

  In step S12, in the same sector Sn of the adjacent track T, the flaw detection signal (habit signal) determined to be greater than or equal to the second determination reference value FS (depth Y) (occurrence of Fs event) in step S2 ( It is determined whether or not there is memory. In other words, if the saving (memory) is continuous (Yes), the process proceeds to step S13, the flag for marking is set to “ON” in the corresponding area on the map, and the process returns to step S2. If (No), the process returns to step S2 as it is (without setting a flag for marking).

Next, the marking process in step S3 will be described.
When the marking process is executed, the process shown in FIG. 4 is executed, and the process proceeds to step S21 as shown in FIG. In step S21, the soot output (depth Z) in the current sector Sn (and track T) is read. In the following step S22, the soot output (depth Z) and the first determination reference value FL (depth X) are read. ). That is, if the current soot output (depth Z) is greater than or equal to the first determination reference value FL (depth X) (Yes), the process proceeds to step S23; otherwise (No), the process proceeds to step S24. Here, as described above, the S / N ratio is set to 3 for the first determination reference value FL (depth X) with respect to the soot output (depth Z). Therefore, in the wrinkle determination based on the first determination reference value FL (depth X), discrimination from noise is easy, and a large wrinkle can be reliably detected. For example, if the defect output (depth Z) is large for a short defect K1 as shown in FIG.

  In step S23, marking is executed and the process returns. Marking is performed by spraying paint from the marking gun 8 to the wrinkle detection position (current sector Sn and track T) on the surface of the workpiece W. In step S24, a comparison is made with the second determination reference value FS (depth Y), and if the current wrinkle output (depth Z) is greater than or equal to the second determination reference value FS (depth Y) (Yes) ) The process proceeds to step S25, and if not (No), it is determined that there is no soot (soot judgment OK), and the process is returned.

Here, as described above, the second determination reference value FS (depth Y) has a smaller S / N ratio than the first determination reference value FL (depth X) (for example, the S / N ratio is 1), it is difficult to discriminate from noise only by comparison with the soot output. Therefore, step S24 is set as a preliminary determination, and in step S25, it is determined whether the wrinkle output (depth Z) that is equal to or greater than the second determination reference value FS (depth Y) is continuous for the determination length L or more. To do.
As shown in FIG. 6 as an example (K2), the determination is based on the fact that the second determination reference value FS (depth Y) is detected (occurrence of FS event) as a starting point (the left end in the figure). The determination length L is measured by recognizing K2.

  In the example of this embodiment, referring to the same sector Sn of the adjacent track T (T = 1, 2, 3,...) With respect to the current sector Sn as shown in FIG. The continuity is determined based on whether or not the marking flag is continuously stored in the same sector Sn of the adjacent track T as long as the specified length L is satisfied. In the example of FIG. 7, FIG. 7A is an example in which the defects 1 to 3 are continuously stored in the same sector Sn of the adjacent track T by a specified length L, and FIG. In this example, marking flags are stored at positions shifted to adjacent sectors (Sn-1, Sn + 1) of Sn and are not continuous to the same sector Sn.

  More specifically, as indicated by the defect K2 in the map of FIG. 2B, for example, when the traveling pulse is 10 mm (the width of one track T is 10 mm) and the heel length is made to correspond in units of 10 mm. When two (or more) marking flags are consecutive in the same sector S2 of three adjacent tracks (T = 1, 2, 3) (that is, when the specified length L = the length of the ridge is 30 mm (Note: first No marking flag is set on the first track))) and it is determined that the track has continuity. If it is determined by this determination that the marking flag is continuous (Yes), the process proceeds to step S23. If not (No), it is determined that there is no defect (determination OK), and the process returns. As an example in which it is determined that there is no wrinkle, for example, as in the defect K3 shown in FIG. 2 (a), the wrinkle is formed obliquely, and the wrinkle output (depth Z) is the same as in FIG. As in K3f and K3r shown in FIG. 5, a case where a marking flag is set in each of the sectors 5 and 6 in the adjacent tracks T = 3 and 4) is assumed. In this case, since the marking flag is not continuous in the same sector of the adjacent track, it is determined that there is no defect (defect determination OK).

  Note that step S22 of the wrinkle determination process in the flaw detection control unit 7 corresponds to the “first determination step” and the “first determination unit” described in “Means for Solving the Problem”. S25 corresponds to “second determination step” and “second determination means”. “Preliminary determination” corresponds to step S24 in “second determination step” and “second determination means”.

Next, the operation of the leakage flux testing apparatus 10, the wrinkle inspection method using the leakage flux testing apparatus 10, and the effects thereof will be described.
In this leakage magnetic flux flaw detector 10, when a predetermined operation signal is input to the flaw detection control unit 7 by a switch operation by an operator, wrinkle determination processing including rotation control of the turning roller 5 and travel control of the travel mechanism 4 is executed. The flaw detection carriage 1 starts traveling and the workpiece W is rotated around the axis by the turning roller 5.

When the flaw detection carriage 1 passes over the workpiece W, the workpiece W is magnetized by the excitation yoke 2. In the magnetized workpiece W, an amount of magnetic flux corresponding to the depth and size of the surface defects leaks to the outer peripheral surface of the workpiece W. When the detection coil 3 of the flaw detection carriage 1 detects this leakage magnetic flux, a flaw output (depth Z) having a magnitude corresponding to the depth of the surface flaw (amount of leakage magnetic flux) or the like is output to the flaw detection control unit 7. (See FIG. 5).
Here, according to the leakage magnetic flux flaw detector 10, two types based on the first determination reference value FL (depth X) and the second determination reference value FS (depth Y) are obtained by the above-described wrinkle determination processing. Judgment is possible.

  For example, as shown in Table 1, if the depth Z of the ridge is as deep as 1.5 mm, for example, the same heel determination can be performed based on the first determination reference value FL (reference 1 in Table 1). Yes (step S22). On the other hand, when the depth Z of the ridge is as shallow as 0.5 mm, for example, the heel determination is performed based on the second determination reference value FS (reference 2 in Table 1) (steps S24 and S25). And when it is determined as wrinkles in the wrinkle determination based on the second determination reference value FS, the beaded marking M illustrated in FIG. 6 can be marked on the surface of the workpiece W. Note that the example in FIG. 6 is a deep flaw (defect K2) that is shallower than the first determination reference value FL (depth X) and greater than or equal to the second determination reference value FS (depth Y), and is adjacent. This is an example in which there is a wrinkle having a length of 100 mm along the same sector Sn of the track T.

  That is, when flaw detection is started from the left end of the figure, the wrinkle output (depth Z) that is equal to or greater than the second determination reference value FS (depth Y) is stored in the storage area of the flaw detection control unit 7 at the left end of the figure. Is stored in the corresponding area on the map managed at (step S2). However, at this time, there is no other data in the same sector Sn of the adjacent track. Therefore, the marking flag is not set (step S12), and marking is not performed (for example, refer to the position of T = 1 and Sn = 2 in 疵 K2 in the map of FIG. 2B).

  Next, when the flaw detection carriage 1 moves to the same sector Sn (n = 2) of the second track T2 from the left in FIG. 2B, the flaw detection signal (信号 signal) at that position is the second determination reference value FS. Since the depth is not less than (depth Y), a marking flag is set in the corresponding area on the map (steps S12 and S13). However, the marking flag is not yet in a continuous state (in other words, the determination length L = the heel length is not yet less than 30 mm). Therefore, marking is not executed (“No” in step S25).

  Next, when the flaw detection carriage 1 moves to the same sector Sn (n = 2) of the third track T3 from the left in FIG. 2B, the flaw detection signal (信号 signal) is the second determination reference value FS at that position. Since the depth is not less than (depth Y), a marking flag is set in the corresponding area on the map (steps S12 and S13). Thereby, since the marking flag is in a continuous state (determination length L = 疵 length reaches 30 mm) (“Yes” in step S25), marking is performed (see step S23, FIG. 6). Thereafter, since the marking flag continues (the condition of the determination length L is satisfied) until the flaw detection carriage 1 reaches the right end of the 100 mm long ridge (defect K2), the marking M is continuously performed. Therefore, as shown in FIG. 6, a daisy chain-like marking pattern is formed along the ridge (defect K2). In this way, flaw detection is performed on the entire circumferential surface of the workpiece W. Incidentally, the surface where the marking M is applied is subjected to surface care by removing the grinder in a later process.

  Thus, according to the above-described leakage magnetic flux flaw detector 10 and the wrinkle inspection method using the same, it is possible to perform wrinkle determination based on the same first determination reference value as in the past (step S22), and further by preliminary determination. When the height of the wrinkle signal is equal to or higher than the second determination reference value (“Yes” in step S24), it is also evaluated whether or not there is continuity in the longitudinal direction of the round bar W (step S25). ) For example, even if the material has a very low S / N ratio (flaw detection standard), only the wrinkle signal that is continuous in the longitudinal direction of the round bar W is extracted from the wrinkle signal that includes randomly generated noise. Can be detected as a sputum.

  Therefore, according to the above-described leakage magnetic flux flaw detector 10 and the wrinkle inspection method using the same, in addition to the conventional first determination reference value FL, the second determination reference value FS for determining continuity is also provided. By applying simultaneously, it was possible to detect even a defect having a low wrinkle signal because it was a minute defect or wrinkle form that could not be found only by the first determination reference value FL. Therefore, when the second determination reference value FS is used together with the first determination reference value FL, overdetection can be suppressed as compared with the case where the first determination reference value FL is tightened. Thereby, the influence of the maintenance efficiency fall in a post process can be avoided.

  Further, depending on the setting of the first determination reference value FL, overdetection due to a noise signal that is not originally a defect may occur. However, according to the above-described leakage magnetic flux inspection apparatus 10 and the flaw inspection method using the same. In response to such over-detection, the first determination reference value FL is relaxed (the S / N ratio is set to a high setting), and the second determination reference value FS is added to comprehensively determine flaws. By doing so, detection of harmless soot (noise) that is originally harmless can be suppressed, and at the same time, minute harmful defects that could not be detected conventionally can be detected with higher accuracy. And by such an effect, it can contribute to the improvement of a maintenance efficiency also regarding the grinder care which is a post process.

The inspection method and inspection device for the surface defect of the round bar according to the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the leakage magnetic flux flaw detector 10 is described as a configuration example in which the probe head 1 travels in the longitudinal direction of the round bar W while rotating the round bar W about the axis. The leakage magnetic flux flaw detector 10 may be configured to rotate the probe head 1 along the circumferential direction of the round bar W while conveying the round bar W in the longitudinal direction.

  In the magnetic flux leakage inspection apparatus 10 of the above embodiment, the second determination means sets a plurality of tracks in which the round bar M is divided in the longitudinal direction and a plurality of sectors in which the round bar W is divided in the circumferential direction. The position where the preliminary determination is performed is specified (mapped) to the corresponding position in the area divided by the plurality of sectors and the plurality of tracks, and when the preliminary determination is continued in the same sector of the adjacent track, Although described in the example of the determination configuration, the present invention is not limited to this, and the present invention is configured such that the plurality of wrinkle signals determined to be equal to or higher than the second determination reference value by the preliminary determination are different positions in the longitudinal direction of the round bar and Various configurations can be adopted as long as they are determined to be wrinkles when they are continuous at the same position in the circumferential direction. However, in the configuration of the above embodiment, when the plurality of wrinkle signals determined to be equal to or higher than the second determination reference value by the preliminary determination are continuous at different positions in the longitudinal direction of the round bar W and at the same position in the circumferential direction. On the other hand, since it is possible to determine continuity from the relationship of the mapping position at the time of the preliminary determination, it is suitable as a configuration for performing flaw detection inspection with a strict standard (setting with a low S / N ratio). It is.

  Moreover, in the example of the above-described embodiment, the example in which the marking pattern is formed along the ridge and the surface is cleaned by removing the marking position in a subsequent process is described. However, the present invention is not limited thereto, and the automatic grinder device is used. By referring to the marking flag of the map, the wrinkle map may be created electronically, and the grinder may be automatically removed based on the wrinkle map. With such a configuration, the marking gun 8 is unnecessary.

DESCRIPTION OF SYMBOLS 1 Flaw detection trolley 2 Excitation yoke 3 Detection coil 4 Mechanism part of traveling apparatus 5 Turning roller 6 Calibration apparatus 7 Flaw detection control part 8 Marking gun 10 Leakage magnetic flux flaw detection apparatus (inspection apparatus of surface defect of round bar)
W Round bar (work)

Claims (3)

Rotate the probe head along the circumferential direction of the round bar while transporting the round bar in the longitudinal direction, or run the probe head in the longitudinal direction of the round bar while rotating the round bar around the axis. A method for inspecting the surface defect of a rod by a leakage magnetic flux inspection method,
A first determination step of receiving a wrinkle signal from a wrinkle on the surface of a round bar by a probe in the probe head and determining the presence or absence of a wrinkle based on whether the height of the wrinkle signal is equal to or higher than a determination reference value. And a second determination step,
In the first determination step, when the height of the wrinkle signal acquired by the probe is equal to or higher than a first determination reference value, it is determined as wrinkle.
In the second determination step, preliminary determination is performed to determine whether or not the heights of the plurality of wrinkle signals acquired by the probe are equal to or higher than a second determination reference value lower than the first determination reference value. A plurality of wrinkle signals determined by the preliminary determination to be equal to or higher than the second determination reference value are continuously performed at different positions in the longitudinal direction of the round bar and at the same position in the circumferential direction. A method for inspecting a surface defect of a round bar, characterized in that it is determined as a defect when in contact. Rotate the probe head along the circumferential direction of the round bar while transporting the round bar in the longitudinal direction, or run the probe head in the longitudinal direction of the round bar while rotating the round bar around the axis. An inspection device for inspecting the surface flaw of a rod by a leakage magnetic flux inspection method,
A flaw detection control unit that receives a wrinkle signal from a wrinkle on the surface of a round bar by a probe in the probe head and determines the presence or absence of a wrinkle based on whether the height of the wrinkle signal is equal to or higher than a determination reference value. The flaw detection control unit has a first determination unit and a second determination unit,
The first determination means determines that the height of the wrinkle signal acquired by the probe is wrinkle when the height is equal to or greater than a first determination reference value,
The second determination means performs a preliminary determination to determine whether or not the heights of the plurality of wrinkle signals acquired by the probe are equal to or higher than a second determination reference value lower than the first determination reference value. A plurality of wrinkle signals determined by the preliminary determination to be equal to or higher than the second determination reference value are continuously performed at different positions in the longitudinal direction of the round bar and at the same position in the circumferential direction. A device for inspecting surface wrinkles of a round bar, characterized by determining that wrinkles are present.   The second determination means sets a plurality of tracks in which the round bars are divided in the longitudinal direction and a plurality of sectors in which the round bars are divided in the circumferential direction, and is set to be equal to or higher than the second determination reference value by the preliminary determination. The determined position is specified as a corresponding position in the area divided by the plurality of sectors and the plurality of tracks, and the position specified in the preliminary determination is continuous in the same sector of the adjacent track. The apparatus for inspecting a surface defect of a round bar according to claim 2, wherein:

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