JP5970784B2 - Roll surface defect detection device - Google Patents

Description

  The present invention relates to a roll surface layer defect detection device that detects surface layer defects of a rolling roll for rolling a steel sheet.

  A rolling roll used in hot rolling or cold rolling is subjected to a thermal load or friction load on the surface during rolling. Therefore, if the same rolling roll is used repeatedly, defects such as cracks and chips may occur in the surface layer. When rolling is performed with a rolling roll in which such a defect has occurred, the defect in the rolling roll is transferred to the steel sheet and causes a defect in the steel sheet. And when the defect transcribe | transferred to the steel plate passes through the subsequent rolling process, since a defect is rolled, it will become difficult to discover the defect in a subsequent process. In order to avoid such a situation, maintenance such as grinding and polishing is performed on the rolling roll periodically (every period or every certain amount of rolling) offline (such as a roll shop).

  For example, as a conventional maintenance method for rolling rolls, Patent Document 1 describes a method of flaw-detecting the surface with an optical inspection device for each maintenance. The technique described in Patent Document 1 is a method of determining the grinding depth during maintenance using an optical inspection device. Patent Document 2 describes an inspection device of an eddy current flaw detection method. The technique described in Patent Document 2 is a method of analyzing the eddy current flaw detection signal with a plurality of filters and displaying it two-dimensionally to determine the type and size of the defect.

JP 2006-208347 A JP 60-082958 A

  However, since the conventional rolling roll maintenance method does not monitor the rolling roll for defects during rolling, rolling may continue even if defects occur, resulting in a large number of defective products. There was a possibility of producing a steel plate. In order to avoid such a situation, in the conventional rolling roll maintenance method, it was necessary to maintain the rolling roll with a margin (even if there is no sign of the occurrence of defects).

  If defects in the rolling roll can be detected during rolling, the above problems can be solved, and maintenance of the rolling roll can be performed at an appropriate timing, which not only prevents the occurrence of defective products but also prolongs the life of the rolling roll. Connected. However, it is not easy to detect defects in the rolling roll during rolling. This is because there are noise sources on the surface layer of the rolling roll, making it difficult to detect defects. If the detector is placed close to the rolling roll, the influence of the noise source can be reduced. However, in view of the influence of the rolling roll vibration, etc., the detector lift-off must be reduced in order to use it during rolling. I can't.

  The present invention has been made in view of the above problems, and its purpose is to reduce the influence of noise sources existing on the surface layer of the rolling roll and to ensure a lift-off that can withstand use during rolling. It is to provide a surface defect detection apparatus.

  In order to solve the above-mentioned problems and achieve the object, a roll surface layer defect detection device according to the present invention is induced by at least one exciting coil that generates eddy current in the surface layer portion of a rolling roll by an excitation signal and the eddy current. An eddy current flaw detection sensor having at least two detection coils for detecting the generated magnetic flux, differential amplification means for differentially amplifying a difference between detection signals from the two detection coils and outputting a difference signal, and the difference signal And a synchronous detection means for detecting synchronously with the excitation signal, wherein the excitation coil and the detection coil are arranged in the direction of the rotation axis of the rolling roll.

  According to the roll surface layer defect detection device according to the present invention, it is possible to reduce the influence of a noise source existing on the surface layer of the rolling roll and to secure a lift-off that can withstand use during rolling.

FIG. 1 is a schematic diagram showing a schematic configuration of a rolling mill to which a roll surface layer defect detection device according to an embodiment of the present invention is applied. FIG. 2 is a schematic diagram illustrating an example of the internal configuration of the sensor box. FIG. 3 is an enlarged schematic view of the E-type sensor of the roll surface layer defect detection device according to the embodiment of the present invention. FIG. 4 is a block diagram showing the overall configuration of the roll surface layer defect detection device according to the embodiment of the present invention. FIG. 5 is an image and detection values showing an example of defect detection by the roll surface layer defect detection apparatus according to the embodiment of the present invention. FIG. 6 is an image and detection values showing an example of defect detection when the excitation coil core and the detection coil core of the E-type sensor are arranged in the circumferential direction of the rolling roll. FIG. 7 is a flowchart illustrating an example of an algorithm for determining the presence of a defect from detection data detected using the roll surface layer defect detection apparatus according to the embodiment of the present invention. FIG. 8 is a diagram showing the configuration and function of the comb sensor of the roll surface layer defect detection device according to a modified embodiment of the present invention. FIG. 9 is a diagram showing a configuration of a sensor box of a roll surface layer defect detection device according to a modified embodiment of the present invention.

  Hereinafter, a roll surface layer defect detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[Configuration of Embodiment]
FIG. 1 is a schematic diagram showing a schematic configuration of a rolling mill 1 to which a roll surface layer defect detection apparatus according to an embodiment of the present invention is applied. FIG. 1A is a schematic side view illustrating a schematic configuration of the rolling mill 1, and FIG. 1B is a schematic diagram from above illustrating a schematic configuration of the rolling mill 1. As shown in FIG. 1, a rolling mill 1 to which a roll surface layer defect detection apparatus according to an embodiment of the present invention is applied includes a pair of upper and lower rolling rolls 3 a and 3 b for rolling a steel plate 2, and a pair of upper and lower rolling rolls 3 a, A pair of upper and lower backup rolls 4a and 4b for backing up 3b is provided. With the configuration shown in FIG. 1, the rolling mill 1 repeats the rolling process of transporting the steel plate 2 between a pair of upper and lower rolling rolls 3 a and 3 b a plurality of times to roll the steel plate 2 into a target shape.

  As shown in FIG. 1, a rolling mill 1 to which a roll surface layer defect detection device according to an embodiment of the present invention is applied, the sensor box 5 of the roll surface layer defect detection device according to the embodiment of the present invention is connected to the upper surface side of a steel plate 2. Near the rolling roll 3a. As will be described later, the sensor box 5 of the roll surface layer defect detection device according to the embodiment of the present invention includes an eddy current flaw detection sensor, and detects defects in the rolling roll 3a. In the rolling mill 1 shown in FIG. 1, the sensor box 5 is provided only on the rolling roll 3 a on the upper surface side of the steel plate 2, but the configuration in which the sensor box 5 is also provided on the rolling roll 3 b on the lower surface side of the steel plate 2 is also possible. Is possible.

  FIG. 2 is a schematic diagram illustrating an example of an internal configuration of the sensor box 5 illustrated in FIG. 1. FIG. 2 illustrates an internal configuration of the sensor box 5 shown in FIG. 1 as viewed from above. That is, FIG. 2 shows the internal configuration of the sensor box 5 corresponding to FIG.

  As shown in FIG. 2, the sensor box 5 of the roll surface layer defect detection device according to the embodiment of the present invention includes an E-type sensor 6 as an eddy current flaw detection sensor, a linear stage 7 that drives the E-type sensor 6, and a distance. 8 in total. As shown in FIG. 2, the linear stage 7 is provided so that the E-type sensor 6 can be driven in the width direction of the rolling roll 3a (that is, the rotation axis direction). The distance meter 8 is provided so that the distance between the rolling roll 3 a and the sensor box 5 can be measured, and monitors the lift-off of the E-type sensor 6.

  FIG. 3 is an enlarged schematic view of the E-type sensor 6 of the roll surface layer defect detection apparatus according to the embodiment of the present invention shown in FIG. As shown in FIG. 3, the E-type sensor 6 has a core having an “E” shape, and an excitation coil A is wound around the center core of the E-shape, and detection coils B and B ′ are placed around the cores at both ends. Is wound. The exciting coil A has a function of inducing an eddy current in the surface layer portion of the rolling roll 3a to be inspected by an alternating magnetic field generated by energizing the exciting signal. On the other hand, the detection coils B and B 'have a function of detecting an induced voltage due to the magnetic flux generated in the surface layer portion of the rolling roll 3a by the eddy current.

  As can be seen from FIGS. 2 and 3, in the E-type sensor 6 of the roll surface layer defect detection device according to the embodiment of the present invention, the leg portions of the E-shaped core are arranged in the rotation axis direction of the rolling roll 3a. That is, the exciting coil A and the detection coils B and B 'wound around the leg portion of the E-shaped core are also arranged in the direction of the rotation axis of the rolling roll 3a.

The E-type sensor 6 is preferably configured to satisfy the following conditional expression when the leg interval is D and the lift-off is L.
D> 0.6L
As can be seen from FIGS. 2 and 3, the E-type sensor 6 of the roll surface layer defect detection device according to the embodiment of the present invention is configured such that the leg interval of the E-type sensor 6 (that is, the core of the excitation coil A and the detection coils at both ends). The distance between the B and B ′ cores) is 8 mm, the thickness of the E-type sensor 6 is 5 mm, and the lift-off is 7 mm. Therefore, the above conditional expression is satisfied.

  Next, the overall configuration of the roll surface layer defect detection device according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the overall configuration of the roll surface layer defect detection device according to the embodiment of the present invention.

  As shown in FIG. 4, the roll surface layer defect detection device 9 according to the embodiment of the present invention includes a sensor box 5, a signal processing unit 10, an encoder 11, and a calculator 12. Further, the signal processing unit 10 includes an oscillator 13, a differential amplifier 14, a phase shifter 15, and a detector 16. As described above, the sensor box 5 needs to be arranged close to the rolling roll 3a of the rolling mill 1, but the signal processing unit 10, the encoder 11, and the calculator 12 are arranged in the vicinity of the rolling mill 1. It is not necessary to be arranged, and it is also possible to adopt a configuration in which it is arranged in a control room or the like at a distance from the rolling mill 1.

  The oscillator 13 is an oscillator that oscillates an excitation signal having a frequency of 8 kHz. The excitation signal oscillated by the oscillator 13 flows into the excitation coil A of the E-type sensor 6 via the excitation signal cable, and induces an eddy current in the surface layer portion of the rolling roll 3a to be inspected.

  The differential amplifier 14 is connected to the detection coils B and B ′ of the E-type sensor 6 and amplifies a difference between detection signals detected by the detection coil B and the detection coil B ′. The differential signal as a detection signal differentially amplified by the differential amplifier 14 passes through the phase shifter 15 and the phase shifter 15 adjusts the phase. The phase shifter 15 is for improving the discriminability between a signal generated by vibration or the like and a signal related to a defect.

  The output signal of the phase shifter 15 is input to the detector 16 and is synchronously detected by the excitation signal from the oscillator 13. That is, the detector 16 performs synchronous detection by multiplying the output signal of the phase shifter 15 and the excitation signal from the oscillator 13.

  The detection signal detected by the detector 16 is input to the computer 12 via the A / D converter. The computer 12 performs appropriate digital signal processing on the detection signal to discriminate defects from the data of the detection signal.

  On the other hand, the computer 12 receives inputs from the sensor box 5 and the encoder 11. The input signal from the sensor box 5 is for obtaining information on the position of the linear stage 7 that drives the E-type sensor 6, and the input signal from the encoder 11 is for obtaining information on the rotation of the rolling roll 3a. Is for.

  In the example of the present embodiment, the encoder 11 sets the pulse frequency so that sampling can be performed at intervals of 1 mm in the circumferential direction of the surface of the rolling roll 3 a when the rolling roll 3 a having a diameter of 600 mm rotates at a rotational speed of 80 rpm. It is set. On the other hand, the linear stage 7 that drives the E-type sensor 6 in the sensor box 5 is driven to synchronize with the rotation of the rolling roll 3a, and is set to move 10 mm per rotation of the rolling roll 3a. The computer 12 restores the position information in the width direction and the circumferential direction on the surface of the rolling roll 3 a from the information on the position of the linear stage 7 and the information on the rotation of the encoder 11, and the detection signal detected by the E-type sensor 6. The position on the surface of the rolling roll 3a can be associated.

  Furthermore, the computer 12 of the roll surface layer defect detection device 9 according to the embodiment of the present invention can also acquire lift-off information measured by the distance meter 8 from the sensor box 5. The acquired lift-off information is used by the computer 12 to correct the detection signal output or to correct the defect determination threshold.

[Detection example]
Next, an example of defect detection by the roll surface layer defect detection device 9 according to the embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is an image and detection values showing an example of defect detection by the roll surface layer defect detection device 9 according to the embodiment of the present invention. FIG. 6 shows, as a comparative example, an image and detection showing an example of defect detection when the excitation coil A of the E-type sensor 6 and the detection coils B and B ′ at both ends are arranged in the circumferential direction of the rolling roll 3a. Value.

  The defect detected in FIG. 5 and FIG. 6 is the same defect, the size is 2 mm × 3 mm, and the depth is 0.3 mm. The images in FIG. 5 and FIG. 6 are extracted from the image data of one round (about 2000 mm) × width 18 mm of the rolling roll 3a as an area including this defect. The detection value graphs in FIGS. 5 and 6 are graphs of the voltage value of the detection signal of the E-type sensor 6 corresponding to the broken line portion in the image.

  As understood by comparing FIG. 5 and FIG. 6, in the example of defect detection by the roll surface layer defect detection device 9 according to the embodiment of the present invention, the presence of defects is clear and the SN ratio is high, but in the comparative example The existence of defects is also unclear and the SN ratio is low. This is because the electromagnetic noise sources resulting from the material of the rolling roll 3a have a long distribution in the direction of the rotation axis of the rolling roll 3a. Since the difference between the detection signals of the E-type sensor 6 is amplified by the differential amplifier 14, as in the roll surface layer defect detection device 9 according to the embodiment of the present invention, the detection coil B, When the cores of B ′ are arranged in the direction of the rotation axis of the rolling roll 3a, the influence of electromagnetic noise caused by the material having a long distribution in the direction of the rotation axis is offset and detected. On the other hand, since many defects of the rolling roll 3a are point-like or cracked in the circumferential direction, the detection signals related to the defects can be detected without being canceled.

(Defect determination method)
Here, an example of a defect determination method applied to the roll surface layer defect detection apparatus 9 according to the embodiment of the present invention will be described with reference to FIG. FIG. 7 is a flowchart showing an example of an algorithm for determining the presence of a defect from detection data detected using the roll surface layer defect detection device 9 according to the embodiment of the present invention.

  As shown in FIG. 7, the algorithm of this defect determination method starts by acquiring detection data of one rotation × width 500 mm of the rolling roll 3 a by the roll surface layer defect detection device 9 according to the embodiment of the present invention ( Step S1). Thereafter, it is determined whether or not there is a portion that exceeds a predetermined threshold in the detected data (step S2). In step S2, when there is no portion exceeding the predetermined threshold value from the detection data (step S2: No), the on-line defect detection is continued, and the next rolling roll 3a has a width of 500 mm. Detection data is acquired (step S1).

  On the other hand, if there is a location that exceeds a predetermined threshold in the detected data in step S2 (step S2: Yes), it is determined whether the location that exceeds the predetermined threshold is a single shot or an area ( Step S3). That is, when a location that exceeds a predetermined threshold is detected in a region having a certain area (especially when it is detected with a width in the roll rotation axis direction), it is determined that the location that exceeds the threshold is an area, and roll rotation When there is a portion that exceeds the threshold in a single scan when scanning in the direction, it is determined that the portion that exceeds the threshold is a single shot.

  In step S3, when it is determined that the area exceeding the threshold is an area (step S3: area), it is determined that a defect exists in the area (step S4), and an alarm is issued to notify the operator of the existence of the defect. Display (step S5), and the processing of the algorithm of this defect determination method is terminated.

  On the other hand, if it is determined in step S3 that the location exceeding the threshold value is a single shot (step S3: single shot), it is determined whether or not the threshold value has been exceeded at that location in the previous detection (step S6). If the threshold is exceeded at that location in the previous detection (step S6: Yes), it is also determined that a defect exists at that location (step S4), and an alarm is sent to inform the operator of the presence of the defect. Display (step S5), and the processing of the algorithm of this defect determination method is terminated.

  If the threshold is not exceeded at that location in the previous detection (step S6: No), the location exceeding the threshold is recorded without being determined as a defect in this detection (step S7). The defect detection is continued again, and detection data of the next rolling roll 3a for one turn × width 500 mm is acquired (step S1). In this second defect detection, if the threshold is exceeded at that location, it is determined again that the location is a defect (step S6: Yes).

  As mentioned above, although the example of the defect determination method applied to the roll surface layer defect detection apparatus 9 which concerns on embodiment of this invention was demonstrated, implementation of this invention is not limited to the example of the said defect determination method, but makes various changes. It is possible. For example, if threshold determination is performed using an average value per unit area at the time of threshold determination, both a single large output value and a certain amount of output value in a certain area It can be determined that the defect is once. Further, the roll surface layer defect detection device 9 according to the embodiment of the present invention has a distance meter 8 and monitors lift-off fluctuations (offset deviation due to minute vibrations, roll wear, etc.). By correcting the detection signal or threshold value based on the value, it is possible to perform defect determination with higher accuracy.

[Configuration of Modified Embodiment]
Hereinafter, the roll surface layer defect detection device 9 according to a modified embodiment of the present invention will be described with reference to FIGS. 8 and 9. The modified embodiment shown in FIGS. 8 and 9 has a configuration in which the eddy current flaw detection sensor in the above-described embodiment is a comb-shaped sensor (hereinafter referred to as a comb-shaped sensor) instead of the E-type sensor 6. . With this configuration, the roll surface layer defect detection device 9 according to the modified embodiment of the present invention is configured not to scan the eddy current flaw detection sensor in the direction of the rotation axis of the rolling roll 3a.

  Accordingly, the configuration of the roll surface layer defect detection device 9 according to the modified embodiment of the present invention has many portions that overlap with the configuration of the roll surface layer defect detection device 9 described above, so only the configuration that is different will be described below. Do.

  FIG. 8 is a diagram showing the configuration and function of the comb sensor of the roll surface layer defect detection device 9 according to a modified embodiment of the present invention. As shown in FIG. 8, the comb sensor 17 of the roll surface defect detection apparatus 9 according to the modified embodiment of the present invention has a comb-shaped core, and is wound around each leg of the comb-shaped core. The coils (coil 1, coil 2, coil 3,...) Function as an excitation coil or a detection coil.

  Since the coils of the comb sensor 17 (coil 1, coil 2, coil 3,...) Can have the same configuration, each coil can be fixed and used as an excitation coil or a detection coil. Alternatively, it can be used by switching as a detection coil.

  The table shown in FIG. 8A shows how to use the coils of the comb sensor 17 (Coil 1, Coil 2, Coil 3,...) Fixed as excitation coils or detection coils. Yes. In this usage method, as shown in the table shown in FIG. 8A, odd-numbered coils (coil 1, coil 3, coil 5,...) Are used as detection coils, and even-numbered coils (coil 2). , Coil 4, coil 6,...) Are used as exciting coils. Further, as shown in the table shown in FIG. 8A, at the switching timing R1, the coil 1 and the coil 3 are used as detection coils, the coil 2 is used as an exciting coil, and at the switching timing R2, the coil 3 is used. And the position of the coil which functions as an excitation coil and a detection coil changes at every switching timing, such as using the coil 5 as a detection coil and using the coil 4 as an excitation coil. As a result, the comb sensor 17 can scan the legs in the arrangement direction instead of driving the E sensor 6 by the linear stage 7.

  The table shown in FIG. 8B shows a method of using the coils of the comb sensor 17 (coil 1, coil 2, coil 3,...) By switching them as excitation coils or detection coils. . In this usage method, as shown in the table shown in FIG. 8B, at the switching timing R1, the coil 1 and the coil 3 are used as detection coils, the coil 2 is used as an excitation coil, and at the switching timing R2, The functions of the coils as the excitation coil and the detection coil are changed at each switching timing, such as using the coil 2 and the coil 4 as the detection coil and using the coil 3 as the excitation coil. Even in this method, the comb-shaped sensor 17 can perform scanning in the arrangement direction of the legs instead of driving the E-shaped sensor 6 by the linear stage 7.

  FIG. 9 is a diagram showing the configuration of the sensor box 5 of the roll surface layer defect detection device 9 according to a modified embodiment of the present invention. As shown in FIG. 9, the sensor box 5 of the roll surface layer defect detection device 9 according to the modified embodiment of the present invention includes a first comb sensor 17a and a second comb sensor 17b. In the roll surface layer defect detection device 9 according to the modified embodiment of the present invention, the first comb sensor 17a and the second comb sensor 17b are required because of the first comb sensor 17a and the second comb sensor 17b. This is because the dead zone is just below the leg of the core. Therefore, as shown in FIG. 9, in the roll surface layer defect detection device 9 according to the modified embodiment of the present invention, the core legs of the first comb sensor 17a and the second comb sensor 17b are alternately arranged. (A so-called zigzag arrangement) so that the dead bands of the first comb sensor 17a and the second comb sensor 17b are mutually supplemented.

  As described above, the roll surface layer defect detection device 9 according to the modified embodiment of the present invention uses at least one excitation coil A that generates an eddy current in the surface layer portion of the rolling roll 3a by the excitation signal, and the magnetic flux induced by the eddy current. An eddy current flaw detection sensor having at least two detection coils B and B ′ to detect, a differential amplifier 14 that differentially amplifies a difference between detection signals from the two detection coils B and B ′, and outputs a difference signal; And a detector 16 for synchronously detecting the signal by the excitation signal, and the excitation coil A and the detection coils B and B ′ are arranged in the direction of the rotation axis of the rolling roll 3a, and therefore exist on the surface layer of the rolling roll 3a. The influence of noise sources can be reduced, and a lift-off that can withstand use during rolling can be ensured.

DESCRIPTION OF SYMBOLS 1 Rolling machine 2 Steel plate 3a, 3b Rolling roll 4a, 4b Backup roll 5 Sensor box 6 E type sensor 7 Linear stage 8 Distance meter 9 Roll surface layer defect detector 10 Signal processing part 11 Encoder 12 Calculator 13 Oscillator 14 Differential amplifier 15 Phase 16 Detector 17 Comb sensor 17a First comb sensor 17b Second comb sensor

Claims (3)

An eddy current flaw detection sensor having at least one excitation coil for generating an eddy current in the surface layer portion of the rolling roll by an excitation signal, and at least two detection coils for detecting a magnetic flux induced by the eddy current;
Differential amplification means for differentially amplifying a difference between detection signals of the two detection coils and outputting a differential signal;
Synchronous detection means for synchronously detecting the difference signal by the excitation signal;
Defect detection means for detecting a surface layer defect of the rolling roll by comparing the magnitude of the differential signal subjected to synchronous detection and a predetermined threshold value;
A distance detecting means for detecting a distance between the rolling roll and the eddy current flaw detection sensor,
The excitation coil and the detection coil are arranged in a rotation axis direction of the rolling roll, and the defect detection unit corrects the predetermined threshold according to a distance detected by the distance detection unit. Roll surface layer defect detection device.   The eddy current flaw detection sensor is an E-type sensor in which one excitation coil is disposed between two detection coils, and a magnetic flux between the detection coil and the excitation coil is coupled by an E-shaped core. The roll surface layer defect detection apparatus according to claim 1.   The eddy current flaw detection sensor is a comb sensor in which the detection coil and the excitation coil are alternately arranged and a magnetic flux between the detection coil and the excitation coil is coupled by a comb-shaped core. The roll surface layer defect detection apparatus described.