JP5862621B2 - Defect detection method and defect detection apparatus for steel plate end face - Google Patents

Description

  The present invention relates to a defect detection method and a defect detection apparatus for a steel sheet end face that detects minute defects generated on the end face in the width direction of a moving steel sheet such as a thin steel sheet.

  In general, defects occur in thin steel plates during rolling or shearing (trimming) at the end in the width direction. It is extremely important to detect defects occurring in thin steel sheets at an early stage and take measures to reduce the risk of sheet breakage due to outflow of defects and improve yield. For this reason, many techniques for detecting defects generated in a thin steel sheet have been proposed. Specifically, a surface inspection apparatus using a CCD camera or a laser distance meter has been proposed as a technique for detecting defects generated on the surface of a thin steel plate. Further, as a technique for detecting an internal defect of a thin steel plate, an ultrasonic flaw detection technique and an eddy current flaw detection technique have been proposed (see Patent Documents 1 and 2). Further, as a technique for detecting cracks and through holes in thin steel plates, a transmission type image processing technique and a vortex type wrinkle detection device have been proposed (see Patent Documents 3 and 4).

Japanese Patent Laid-Open No. 2-82156 JP 2000-227422 A Japanese Patent Laid-Open No. 62-129746 JP 2004-28638 A

  On the other hand, the micro defect which generate | occur | produced in the end surface of a thin steel plate is detected visually. However, when the thin steel plate is moving at high speed, it is difficult to visually detect a micro defect. Moreover, when the moving speed of a thin steel plate is made slow in order to be able to detect a micro defect, the production efficiency of a thin steel plate will fall. On the other hand, in the visual inspection of the end surface of the thin steel plate, the state of the trimmer blade is also determined based on the properties of the end surface sheared by the trimmer blade in order to determine the replacement time of the trimmer blade. Specifically, as shown in FIG. 7, the end surface P of the thin steel sheet S has a flat cut surface P1 that is sharply cut and a fractured surface P2 having irregularities, and the ratio of the fractured surface P2 to the cut surface P1. Is used to determine the state of the trimmer blade. However, since it is difficult to perform a visual inspection over the entire length of the thin steel plate, it is necessary to replace the trimmer blade earlier than the replacement time, which causes an increase in repair costs.

  In order to solve such a problem, it is conceivable to determine the presence / absence of a minute defect and the state of the trimmer blade using an end face image photographed by a camera instead of visual inspection. However, the optical conditions for determining the presence or absence of microdefects are different from the optical conditions for determining the state of the trimmer blade. For this reason, when inspecting using a camera, it is necessary to change the illumination method and field of view according to the contents to be judged, and the presence or absence of microdefects and the state of the trimmer blade under certain optical conditions It cannot be judged. Moreover, when constructing different optical conditions by installing a plurality of cameras, the equipment cost increases.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its purpose is to detect a defect on a steel sheet end face and a defect detection apparatus capable of determining the presence / absence of a micro defect and the state of a trimmer blade with a single inspection apparatus. Is to provide.

  A defect detection method for a steel sheet end face according to the present invention is a defect detection method for a steel sheet end face that detects minute defects generated on a width direction end face of a moving steel sheet, and a plurality of strobe illuminations are used and the optical conditions are Based on the step of alternately irradiating the end surface in the width direction with a plurality of different illumination lights, the step of capturing an image of the end surface in the width direction irradiated with the illumination light, and the captured image of the end surface in the width direction Determining the presence or absence of the minute defect and the state of the trimmer blade used when the widthwise end of the steel plate is sheared.

  A steel plate end surface defect detection apparatus according to the present invention is a steel plate end surface defect detection device that detects micro defects generated on a moving steel plate in the width direction end surface, and illuminates the width direction end surface under different optical conditions. A plurality of strobe illuminations for irradiating light, an imaging device for capturing an image of the end surface in the width direction irradiated with the illumination light, and an image of the minute defect based on an image of the end surface in the width direction captured by the imaging device And a determination device that determines the presence and absence and the state of the trimmer blade used when the widthwise end of the steel plate is sheared.

  According to the defect detection method and the defect detection apparatus for the steel sheet end face according to the present invention, it is possible to determine the presence / absence of a micro defect and the state of the trimmer blade with a single inspection apparatus.

FIG. 1 is a block diagram showing a configuration of a defect detection system according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration of strobe illumination for determining the presence or absence of a micro defect. FIG. 3 is a schematic diagram showing a configuration of strobe illumination for determining the state of the trimmer blade. FIG. 4 is a diagram for explaining the operation of the alignment mechanism shown in FIG. FIG. 5 is a timing chart showing the shooting timing of the high-speed camera and the lighting timing of the strobe illumination. FIG. 6 is a flowchart showing a flow of defect detection processing according to an embodiment of the present invention. FIG. 7 is a schematic diagram for explaining a minute defect, a cut surface, and a fracture surface.

  Hereinafter, the configuration and operation of a defect inspection system according to an embodiment of the present invention will be described with reference to the drawings.

[Configuration of defect detection system]
First, the configuration of a defect detection system according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a defect detection system according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration of strobe illumination for determining the presence or absence of a micro defect. FIG. 3 is a schematic diagram showing a configuration of strobe illumination for determining the state of the trimmer blade. FIG. 4 is a diagram for explaining the operation of the alignment mechanism shown in FIG. FIG. 5 is a timing chart showing the shooting timing of the high-speed camera and the lighting timing of the strobe illumination.

  As shown in FIG. 1, a defect detection system 1 according to an embodiment of the present invention includes a high-speed camera 2, strobe illuminations 3a and 3b, a position detection device 4, an alignment control device 5, an alignment mechanism 6, a trigger calculation. A device 7, a lighting controller 8, a camera controller 9, and a host monitoring device 10 are provided.

  The high-speed camera 2 is configured by an imaging device capable of continuously capturing frames exceeding 30 frames per second, and is disposed facing the end surface of the thin steel plate so that the end surface of the thin steel plate can be captured from the front. The high speed camera 2 captures an image of the end face of the thin steel plate under the control of the camera controller 9, and transmits the image data of the captured end face to the camera controller 9.

  The stroboscopic illuminations 3a and 3b are configured by an illuminating device that irradiates the end face of a thin steel plate with illumination light, and are adapted to optical conditions for determining the presence or absence of minute defects and optical conditions for determining the state of the trimmer blade, respectively. Configuration and arrangement. Specifically, as shown in FIG. 2, the stroboscopic illumination 3a irradiates the end surface P with an amount of light and an angle at which the minute defect D (see FIG. 7) generated on the end surface P of the thin steel plate S can be clearly photographed. Configured and arranged to do. Moreover, as shown in FIG. 3, the strobe illumination 3b has a light quantity and an angle at which the shape of the shear plane of the thin steel sheet S by the trimmer blade (ratio between the cut surface P1 and the fracture surface P2 shown in FIG. 7) can be clearly photographed. It is configured and installed to irradiate the end face P with illumination light. Note that when the required optical conditions differ depending on the type of minute defect, the number of strobe lights 3a may be increased according to the type of minute defect.

  The position detection device 4 is a device that detects a change in the position of the end surface of the thin steel plate accompanying the movement of the thin steel plate. The position detection device 4 inputs information on the detected end surface position of the thin steel plate to the alignment control device 5.

  As shown in FIG. 4, the alignment control device 5 is based on the position of the end surface of the thin steel plate input from the position detection device 4, and the positional relationship between the end surface of the thin steel plate and the high-speed camera 2 and the strobe lights 3a and 3b. The position of the high-speed camera 2 and the strobe lights 3a and 3b is controlled by driving the alignment mechanism 6 so that is kept constant. By aligning the high-speed camera 2 and the strobe lights 3a and 3b with respect to the position movement of the end face of the thin steel sheet, fluctuations in the inspection environment can be suppressed, and the presence or absence of minute defects and the state of the trimmer blade can be determined stably. can do.

  The trigger arithmetic unit 7 is configured to stroboscopic illumination 3a, so as to continuously take an image of the end face of the thin steel plate over the entire length of the thin steel plate based on the line pulse signal indicating the moving speed of the thin steel plate and the effective field of view of the high speed camera 2. A lighting command 3b and an imaging trigger signal of the high-speed camera 2 are input to the illumination controller 8 and the camera controller 9, respectively.

  The illumination controller 8 sends the illumination lighting command (A) for instructing the lighting of the strobe lighting 3a and the lighting lighting command (B) for instructing the lighting of the strobe lighting 3b to be input at the timing when the strobe lighting 3a or the strobe light is input. Illumination 3b is turned on.

  The camera controller 9 captures an image of the end face of the thin steel plate by controlling the high speed camera 2 at the timing when the imaging trigger signal is input from the trigger calculation device 7. Further, the camera controller 9 determines the presence / absence of a minute defect and the state of the trimmer blade using the image data of the captured end face, and transmits the determination result to the upper monitoring apparatus 10 as inspection information.

  In the present embodiment, as shown in FIG. 5, the input timing of the imaging trigger signal and the input timing of the illumination lighting commands (A) and (B) are synchronized. Thereby, an image of the end face of the thin steel plate is taken at the timing when the illumination light is irradiated on the end face of the thin steel plate from the strobe illumination 3a or the strobe illumination 3b, and the state of the photographing A and the trimmer blade for determining the presence or absence of a micro defect It is possible to alternately perform the photographing B for determining the above.

  The defect detection system 1 having such a configuration includes a trimmer used when cutting the presence / absence of a microdefect and the end of a thin steel plate with a single high-speed camera 2 by executing the following defect detection process. Determine the state of the blade. The operation of the defect detection system 1 when executing the defect detection process will be described below with reference to the flowchart shown in FIG.

[Defect detection processing]
FIG. 6 is a flowchart showing a flow of defect detection processing according to an embodiment of the present invention. The flowchart shown in FIG. 6 starts at the timing when the line pulse signal is input to the trigger computing device 7, and the defect detection process proceeds to the process of step S1. The defect detection process is repeatedly executed while the line pulse signal is input to the trigger calculation device 7.

  In the process of step S1, the camera controller 9 captures an image of the end face of the thin steel sheet by controlling the high speed camera 2 at the timing when the imaging trigger signal is input from the trigger computing device 7. Thereby, the process of step S1 is completed, and the defect detection process proceeds to the process of step S2.

  In step S2, the camera controller 9 captures the image of the steel plate end face transmitted from the high-speed camera 2 based on the image capturing timing in order to determine whether there is a minute defect or the state of the trimmer blade. Determine whether it is an image. As a result of the determination, if the image is captured to determine the presence or absence of a microdefect (imaging A shown in FIG. 5), the camera controller 9 advances the defect detection process to the process of step S3. On the other hand, when the image is for determining the state of the trimmer blade (photographing B shown in FIG. 5), the camera controller 9 advances the defect detection process to the process of step S7.

  In the process of step S3, the camera controller 9 uses a known image processing technique such as a binarization process to determine whether or not there is a minute defect in the region of the steel plate end face where the image was taken. Execute. Thereby, the process of step S3 is completed, and the defect detection process proceeds to the process of step S4.

  In the process of step S4, the camera controller 9 determines whether or not there is a minute defect in the region of the end surface of the steel plate on which the image is taken based on the process result of step S3. As a result of the determination, if there is no minute defect, the camera controller 9 ends a series of defect detection processing. On the other hand, when there is a minute defect, the camera controller 9 advances the defect detection process to the process of step S5.

  In the process of step S5, the camera controller 9 determines whether or not micro defects are periodically generated (for example, every predetermined number of times) over the length direction of the thin steel sheet based on the result of the past defect detection process. Determine. As a result of the determination, if the minute defect does not occur periodically, the camera controller 9 ends the series of defect detection processing. On the other hand, if minute defects occur periodically, the camera controller 9 advances the defect detection process to step S6.

  In the process of step S <b> 6, the camera controller 9 outputs information related to the image and occurrence position of the minute defect to the upper monitoring apparatus 10 as defect information. Thereafter, the operator takes measures to eliminate the minute defects based on the output defect information. Thereby, the process of step S6 is completed and a series of defect detection processes are complete | finished.

  In the process of step S7, the camera controller 9 calculates the ratio of the area of the fracture surface P2 to the area of the cut surface P1 in the captured image, and determines the replacement period (exchange timing) of the trimmer blade based on the calculated ratio. A trimmer blade determination process is executed. Thereby, the process of step S7 is completed, and the defect detection process proceeds to the process of step S8.

  In the process of step S8, the camera controller 9 determines whether or not it is a trimmer blade replacement period based on the process result of step S7. As a result of the determination, if it is not the trimmer blade replacement cycle, the camera controller 9 ends the series of defect detection processing. On the other hand, if it is the trimmer blade replacement cycle, the camera controller 9 advances the defect detection process to the process of step S9.

  In the process of step S <b> 9, the camera controller 9 outputs replacement cycle information that prompts replacement of the trimmer blade to the upper monitoring device 10. Thereafter, the operator replaces the trimmer blade based on the output replacement period information. Thereby, the process of step S9 is completed and a series of defect detection processes are complete | finished.

  As is apparent from the above description, in the defect detection processing according to an embodiment of the present invention, illumination light having different optical conditions is alternately irradiated on the end faces in the width direction using the strobe illuminations 3a and 3b, and the illumination light is emitted. Since the image of the irradiated end surface in the width direction is taken, the presence or absence of microdefects and the state of the trimmer blade used when shearing the end portion in the width direction of the steel sheet are determined based on the image of the end face in the width direction. The presence or absence of micro defects and the state of the trimmer blade can be determined with a single inspection device. Moreover, since it is not necessary to slow down the moving speed of a thin steel plate in order to perform an inspection, the production efficiency of the thin steel plate can be improved. Further, since the state of the trimmer blade can be determined over the entire length of the thin steel plate, the repair cost can be reduced by replacing the trimmer blade at an appropriate time.

  After annealing the thin steel plate having a thickness of 2 mm after hot rolling, the end in the width direction of the thin steel plate was sheared with a trimmer blade, and the end in the width direction after shearing was inspected with the defect detection apparatus of the present invention. Of the two strobe lights of the defect detection device, one strobe light is installed at an angle that makes it easy to detect minute defects generated at the end, and the other strobe light is a shear surface shape (cut surface and shear surface) by a trimmer blade. The ratio is set at an angle that can be accurately determined. Then, an image of the end face was taken with one camera while the two strobe lights were alternately turned on, and the presence or absence of micro defects and the shape of the shear plane were determined from the obtained images.

  As a result, it was possible to determine the presence or absence of minute defects and the shape of the sheared surface without reducing the moving speed of the thin steel plate. As an efficiency improvement effect by suppressing deceleration for inspection, for example, when the moving speed of a thin steel plate is reduced from 3 m / s to 1 m / s by 90 sec / h, an efficiency improvement of 1.67% can be obtained. It was. In addition, the equipment cost can be reduced because only one camera is required where two cameras are usually required. In addition, by continuously grasping the shape of the shear plane, the trimmer blade can be replaced at a position near the use limit due to wear, so that the effect of reducing the repair cost could be obtained.

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

DESCRIPTION OF SYMBOLS 1 Defect detection system 2 High speed camera 3a, 3b Strobe illumination 4 Position detection apparatus 5 Positioning control apparatus 6 Positioning mechanism 7 Trigger arithmetic device 8 Illumination controller 9 Camera controller 10 Host monitoring apparatus

Claims (2)

A defect detection method for a steel plate end face that detects micro defects generated on the width direction end face of the moving steel plate,
Using a plurality of strobe lights, alternately irradiating the end surface in the width direction with a plurality of illumination lights having different optical conditions; and
Capturing an image of the widthwise end face irradiated with the illumination light;
Determining the presence or absence of the micro defect and the state of the trimmer blade used when shearing the width direction end of the steel sheet based on the image of the imaged end surface in the width direction;
A method for detecting a defect on an end face of a steel sheet, comprising: A defect detection device for a steel plate end face that detects micro defects generated on the width direction end face of the moving steel plate,
A plurality of strobe lights that illuminate the widthwise end face with different optical conditions; and
An imaging device that captures an image of the end surface in the width direction irradiated with the illumination light;
A determination device that determines the presence or absence of the micro defect and the state of the trimmer blade used when shearing the width direction end of the steel sheet based on the image of the width direction end surface imaged by the imaging device;
A defect detection apparatus for a steel plate end face, comprising:

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