JP2007030000A - Steel plate edge detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel plate edge detecting method which is applicable to an inspection device for detecting surface defects and internal defects of a steel plate, and capable of correctly detecting an edge of the steel plate at low cost. <P>SOLUTION: A candidate of a channel to detect an edge is extracted from the signal of each channel obtained for each detection scan, and the estimation value of the plate width is calculated from the candidate. The calculated value is compared with the measured value of the plate width, and further, the edge channel position in the previous scan is compared with the channel position in the present scan. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is applied to an inspection apparatus for detecting surface defects and internal defects of a steel plate, and relates to a steel plate edge detection method for detecting the edge of a steel plate.

  Conventionally, ultrasonic flaw detection, eddy current flaw detection, and the like have been used to detect surface defects and internal defects of steel sheets. For example, Patent Document 1 discloses an ultrasonic flaw detector. In this device, a transmitter probe and a receiver probe made of a one-dimensional array type ultrasonic line sensor are arranged opposite to each other in the plate thickness direction with a steel strip (steel plate) interposed therebetween, and an internal defect of the steel strip is detected. Is a device for detecting

  In an ultrasonic flaw detector composed of such a line sensor, an end (edge) of a steel plate to be inspected can be detected in order to accurately detect a transmitted wave propagating through the steel plate and a reflected wave from a defect. Very important. In other words, in the vicinity of the edge of the steel plate, by accurately grasping the position of the transmitter / receiver in the width direction of the ultrasonic transmitter / receiver that transmits ultrasonic waves effectively and detects defects, the edge of the steel plate This is because it is possible to detect defects up to.

Until now, in order to detect the edge of a steel plate, the method of installing the sensor for edge detection is performed (for example, refer patent document 2). Further, in the conventional inspection logic, a so-called edge dead zone is set in which data in a range determined from the edge is not used for inspection in order to prevent over-detection of harmless defects such as patterns on the edge.
JP 2001-324482 A JP-A-8-75705

  However, in the method of installing a sensor for detecting an edge as in Patent Document 2 described above, a mechanism for causing the sensor to follow the edge is necessary in the case where the plate width to be measured is large or in a facility with a large plate meandering. Therefore, there is a problem that the apparatus becomes complicated and the maintenance load increases. In addition, the conventional method of setting the dead zone at the edge has a problem that the edge dead zone is large and a defect in the dead zone cannot be detected.

  This invention is made | formed in view of the said situation, and it aims at providing the edge detection method of the steel plate which solves the said subject and can detect the edge of a steel plate cheaply and correctly.

  The invention according to claim 1 of the present invention is applied to an inspection apparatus for detecting surface defects and internal defects of a steel sheet, and in the steel sheet edge detection method for detecting the edge of a steel sheet, the signal of each channel obtained for each detection scan. A method for detecting an edge of a steel sheet, comprising: extracting channel candidates from which edges have been detected; calculating a plate width estimated value from the candidate; and comparing the calculated value with a measured sheet width value. .

  According to the present invention, the channel candidate from which the edge is detected is extracted from the signal of each channel obtained for each detection scan, the plate width estimation value is calculated from the candidate, and the calculated value and the plate width actual measurement value are calculated. The edge channel is determined by comparing and comparing the edge channel position in the previous scan with the current channel position, so it is possible to accurately determine the edge and reduce the previously set edge dead zone. It is possible to detect defects at the edge portion.

  FIG. 1 is a diagram showing a configuration example of an ultrasonic flaw detector for carrying out the present invention. In the figure, 1 is a transmission side probe, 2 is a reception side probe, 3 is a steel plate, and 4 is a frame. A transmitting probe 1 and a receiving probe 2 composed of a one-dimensional array type line sensor are opposed to each other in the thickness direction of the steel plate 3 with the traveling steel plate 3 interposed therebetween, and are supported by a U-shaped frame 4. Has been.

  First, channel candidates whose edges are detected are extracted from the signals of the respective channels obtained for each scan performed in the width direction at a certain period. For example, the ultrasonic pulse propagation time from the transmitting probe 1 to the receiving probe 2 is measured, and the propagation time of the transmitted wave that passes through the metal plate is measured by the receiving probe. Transmitted waves that pass through the previous metal plate are divided into a receiver probe that receives the ultrasonic pulses and a receiver probe that receives the ultrasonic pulses that have a direct wave propagation time that does not pass through the metal plate. It is preferable to select the signals of the receiving side probes at both ends among the receiving side probes that receive the ultrasonic pulse having the propagation time of.

  Next, the distance between the channels (receiving probe) from which these two signals are obtained is compared with the measured plate width. When the distance and the actual measured value of the plate width are within the measurement error range, the two channels are determined to be channels that have detected an edge. The actual measured value of the plate width is actually measured upstream of the target inspection device on the conveyance route of the steel plate. In this case, the measurement method and type of the width meter are not limited, but the measurement accuracy is a sensor used in the present invention. It is desirable that the accuracy is equal to or higher than. Note that the width meter may be downstream of the ultrasonic flaw detector if there is no step of narrowing the width between the ultrasonic flaw detector and the width meter. Furthermore, it is clear that a steel plate tracking function is necessary to specify the measurement position.

  Further, the edge channel position in the previous (immediately preceding) scan is compared with the current channel position, and if the deviation is equal to or smaller than a certain magnitude, it is possible to detect the edge more reliably by determining that the channel is the edge channel. As described above, it is possible to accurately determine whether or not the detected signal is a signal from an edge, the edge dead zone that has been conventionally set is not required, and a defect in the edge portion can be detected.

  FIG. 2 shows an example of a received signal obtained for each scan of the CCD camera type surface defect inspection apparatus showing an embodiment of the present invention. The CCD camera used here has a width resolution of 0.5 mm and a longitudinal resolution of 1.0 mm, with CCD elements arranged one-dimensionally (channel numbers are assigned in sequence for each CCD element). . A threshold c for edge detection is set for the obtained signal, and channel numbers A and B of the signals a and b at both ends exceeding the threshold c are extracted. For example, when A = 150 ch and B = 3800 ch, the plate width obtained by calculation is (3800-150 + 1) × 0.5 mm = 1825.5 mm.

  When the width resolution is 0.5mm, the maximum measurement error is 1.0mm and compared with the plate width measurement value. When the deviation from the plate width measurement value is within the measurement error (1.0mm) range, channels A and B Detected channel candidates. When the line speed is 300 mpm, the steel plate must meander at a speed of 2500 mm / sec to shift the edge position by one channel during one scan (longitudinal resolution: 1.0 mm). Considering the accuracy of the above, it is normal to make equipment that does not cause meandering so far, so compare the edge channel position in the previous scan with the current channel position and if there is no deviation or less than 1 channel If there is, it can be determined that the channel is an edge channel. When the error range is exceeded in the plate width comparison, it is compared with the previous edge channel. Channels that are not determined as edge channels are determined as defect candidates, and harmless defects and harmful defects are determined by defect classification based on defect determination logic. As a result, since the edge channel can be determined as only one channel at both ends, the edge dead zone can be reduced to the limit without installing an edge detection sensor.

  Since the edge can be specified by the present invention, for example, even when the signal in the vicinity of the edge cannot clearly detect the edge as shown in FIG. 2, the defect signal can be extracted. In other words, in the conventional method, when the edge detection dead zone is small, an erroneous determination of the edge detection position occurs, or when the edge detection dead zone is large, it is out of the defect detection range.

  Although the threshold value c is set for edge detection in the above embodiment, a method of selecting an edge candidate channel by differentiation in the scan direction may be used. Further, in the embodiments, the case of a CCD type surface defect inspection apparatus has been described, but the present invention is not limited to this, and may be used in an ultrasonic internal defect inspection apparatus, a vortex internal defect inspection apparatus, or the like. It is clear.

It is a figure which shows the structural example of the ultrasonic flaw detector for implementing this invention. It is a figure which shows the example of a received signal obtained for every scan of the surface defect inspection apparatus of the CCD camera system which shows one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission side probe 2 Reception side probe 3 Steel plate 4 Frame

Claims (1)

In the steel sheet edge detection method, which is applied to an inspection device that detects surface defects and internal defects of a steel sheet, and detects the edge of the steel sheet,
Extracting the channel candidate from which the edge is detected from the signal of each channel obtained for each detection scan, calculating the estimated plate width from the candidate, and comparing the calculated value with the measured actual plate width A method for detecting an edge of a steel sheet.

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