JPH04332856A - Inspecting apparatus of surface defect of strip - Google Patents

Abstract

PURPOSE:To improve the efficiency of an operation of checking up a defective part by an inspector by a construction wherein the amount of data to be displayed is changed in accordance with the speed of conveyance of a strip. CONSTITUTION:A laser light is made to scan in a sweeping manner in the width direction of a strip 1, a reflected light therefrom is sensed 3 and converted into a voltage strength signal, and either a voltage waveform determined by a voltage waveform generator 4 or a differential waveform obtained by differentiating 5 the voltage waveform is selected 6, converted 7 into a digital value and inputted to a pretrigger circuit 8. Meanwhile, the differential waveform is compared with a prescribed threshold value in a threshold value processing element 10 so as to discriminate the existence or nonexistence of a defect, and a trigger signal is outputted therefrom. On the other hand, data on the differential waveform converted 11 into a digital value are inputted to a characteristic amount computing circuit 12 and a plurality of characteristic amounts, e.g. normalized secondary averages and differential ranges, are calculated therein. They are inputted to a neural network 13 to discriminate the existence or nonexistence of the defect, and the result is inputted to a trigger signal processing circuit 14. Since the existence or nonexistence of the defect is discriminated by using two processing systems jointly in this way, the kind and degree of the defect can be discriminated with higher precision.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for efficiently detecting surface defects (flaws) in a steel strip manufactured by cold rolling.

0002

[Prior Art] It is preferable that a steel strip manufactured by cold rolling be inspected for defects over almost the entire surface to ensure its quality. This is considered one of the most important requirements. One of the flaw inspection methods is to scan the surface of a strip running on a production line in the width direction with a laser beam, convert the reflected waves into voltage intensity using a photoelectric conversion element such as a CCD element, and detect flaws from this signal data. A method for determining the presence or absence of such a substance has already been established (see Japanese Unexamined Patent Publication No. 63-62825, etc.).

However, such optical flaw detection devices are not capable of determining the extent or nature of flaws, so they are only used as preliminary inspection devices, and the final judgment is based on visual inspection. It is customary for the examiner to make a decision after conducting a separate process.

0004

[Problems to be Solved by the Invention] In recent years, there has been a tendency to increase line speed with the aim of improving productivity, but the current situation is such that the final pass/fail judgment regarding strip surface defects must be made visually. In the quality management system,
Ultimately, there is a limit to the ability to simultaneously improve inspection accuracy and inspection speed, and this is one of the factors that prevents further increases in line speed.

The present invention was devised to solve the above-mentioned disadvantages of the prior art, and its main purpose is to increase the efficiency of the inspector's work of checking defective parts and improve productivity. An object of the present invention is to provide a strip surface defect inspection device that can contribute to the improvement of the present invention.

[0006]

[Means for Solving the Problems] This purpose is to provide a laser oscillation means, a photoelectric conversion means that receives the reflected light and converts it into voltage intensity, and a display that converts the voltage intensity into image data and displays it on a screen. A strip surface defect inspection apparatus comprising: (1) strip conveyance speed; flaw detection means for determining surface defects from voltage intensity; is detected, and the amount of data to be displayed on the display means is changed in accordance with this speed. Alternatively, (2) a plurality of flaw detection means having optimal sensitivities depending on the type and degree of flaws are prepared, and the priority order of receiving signals from these plurality of flaw detection means is changed depending on the steel type and grade. do. Alternatively, (3) divide the strip into multiple areas in the width direction, and set the priority order of triggers for writing the defective part data to the storage means according to the steel type in advance, and the trigger with the highest priority is output. The configuration is such that only the data in the area that has been set is written to the storage device. This is achieved by

[0007]

[Operation] According to this device, the inspection itself can be facilitated by displaying the flawed portion on the strip flowing in the line as a still image. In particular, by adjusting the data density according to the conveyance speed of the strip and by making the size of the flaws on the display unit the same, it is easier to judge, and the signals from multiple flaw detection means can be switched depending on the steel type and grade. This makes it possible to more accurately and easily identify flaws, and if there are multiple flaws in the width direction, only the most harmful flaw is memorized and displayed. The amount of parts required for visual inspection by the examiner is reduced to the minimum, and the amount of time that can be spent on one defect inspection can be further increased.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on specific embodiments shown in the accompanying drawings.

FIG. 1 shows the overall configuration of the apparatus of the present invention. A He-Ne laser projector 2 sweeps a laser spot toward the surface of the steel strip 1 being conveyed in the direction of arrow F in a direction perpendicular to the conveying direction, that is, in the width direction of the strip 1, and the reflected light is The light is received by a light receiver 3 made of, for example, a photomultiplier. This converts the light intensity signal into a voltage intensity signal. This voltage intensity signal is processed by a voltage waveform generator 4 to obtain a voltage waveform, which is then differentiated by a differentiating circuit 5 to obtain a differential waveform. Then, either the differential waveform or the voltage waveform is selectively switched to A/A by using the switch 6.
The data is input to the D converter 7 , where it is converted into a digital value, and the data is input to the pre-trigger circuit 8 . Note that the degree of ease of identification differs between the differential waveform and the voltage waveform depending on the structure of the material, so a more suitable signal is selected according to the coil information given from the main computer 9 and sent to the pre-trigger circuit 8. is input.

On the other hand, the differential waveform obtained by differentiating the voltage waveform is input to the threshold processing section 10. Here, the presence or absence of a flaw on the strip surface is determined by comparison with a preset threshold value, and a trigger signal (flaw detection signal) corresponding to the type and degree of the flaw is output. On the other hand,
The A/D converter 11 converts the data into, for example, an 8-bit digital value, and from this data, the feature calculation circuit 12 calculates a plurality of feature quantities (for example, normalized quadratic average and normalized differential range).
). By inputting these to the neural network 13, the presence or absence of flaws on the strip surface is similarly determined and a trigger signal is output. A plurality of trigger signals, that is, flaw detection signals, output from the threshold processing unit 10 and the neural network 13 in accordance with the type and degree of flaw are input to the trigger signal processing circuit 14.

[0011] In this way, by using the threshold processing unit 10 and the neural network 13 in combination to determine the presence or absence of a flaw, the type and degree of the flaw can be discriminated with even higher accuracy and fineness.

The trigger signal processing circuit 14 includes logic for selecting the above-mentioned plurality of trigger signals according to the steel type, grade, etc., and the plurality of trigger signals output from the threshold processing section 10 and the neural network 13. The signal is discriminated according to the coil information given from the main computer 9, and only when a predetermined trigger signal is input.
A trigger signal (data storage command) is output to the pre-trigger circuit 8 at the subsequent stage. As a result, flaw data (differential waveform or voltage waveform output) to be temporarily stored in the buffer memory built into the pre-trigger circuit 8 is selected. In addition, the welded parts of the strips are connected to the phototube 1.
5 and the amount of strip feeding obtained by calculating the output of the tachometer 17 attached to the hearth roll 16 using the computer 18, are inputted to the strobe signal generator 19, thereby controlling the welding area. By generating a nearby signal and inputting it to the trigger signal processing circuit 14, flaw data in the vicinity of the weld is ignored.

The pre-trigger circuit 8 has a built-in buffer memory for sequentially recording a plurality of screens, and receives a trigger signal (data storage Data before and after the command) is also stored.

The data of the defective portion taken into the buffer memory is input to the memory control circuit 20. here,
The priority order regarding the type of flaw and its degree is set in advance according to the steel type, and only the data around the point where the trigger signal with the highest priority is output is extracted according to the coil information given from the main computer 9. Ru. This process is performed in order to cope with the fact that the types and degrees of defects in question differ depending on the customer, that is, the standards for the degree of harm are different. This data is then processed by the image display control unit 21 and displayed as a still image on the CRT display 22, and is also converted into a document by the video printer 23 if necessary.

On the other hand, in the memory control circuit 20, the display data is thinned out in accordance with the sheet passing speed, and the data density is adjusted. This allows the lengthwise size of the displayed image to be changed as appropriate. At the same time, the board is divided into multiple areas in the width direction, prioritized according to the size of the flaw, and areas with large flaws are extracted with priority. As a result, if a plurality of flaws are present in parallel in the board width direction, only the most harmful flaw is stored. Therefore, it is possible to reliably store only necessary defects without unnecessarily increasing the number of data and requiring excessive memory capacity, or without requiring excessively high processing speed.

The final flaw data obtained in this manner is recorded in an external storage device 25 such as a magnetic storage device together with coil information, position data on the strip, or operator intervention data from the keyboard 24, and verification data is stored. or as inspection report data for customers.

[0017]

As described above, according to the present invention, since the flaws considered to be particularly important in the flawed areas on the strip are automatically selected and displayed as still images, the confirmation of the flawed areas can be verified. can be performed reliably and at high speed. Therefore, it is highly effective in reducing the workload of examiners and ensuring thorough quality control.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a surface defect inspection apparatus based on the present invention.

[Explanation of symbols]

1 Strip 2 Floodlight 3 Photo receiver 4 Voltage waveform generator 5 Differential circuit 6　Switcher 7 A/D converter 8 Pre-trigger circuit 9 Main computer 10 Threshold processing unit 11 12 Feature calculation circuit 13 Neural network 14 Trigger signal processing circuit 15 Phototube 16 Hearth roll 17 Tachometer 18 Arithmetic machine 19 Strobe signal generator 20 Memory control circuit 21 Image display control section 22 CRT display 23 Video printer 24 Keyboard 25 External storage device

Claims (3)

[Claims] 1. Laser oscillation means, photoelectric conversion means for receiving the reflected light and converting it into voltage intensity, display means for converting the voltage intensity into image data and displaying it on a screen, and detecting surface defects from the voltage intensity. A strip surface defect inspection device includes a flaw detection means for determining the flaw detection means, and a storage means for storing the data of the flawed part determined by the flaw detection means, the strip surface defect inspection device detects the strip conveyance speed, and detects the flawed portion data determined by the flaw detection means. 1. A strip surface defect inspection apparatus characterized in that the amount of data to be displayed on the display means is changed by changing the amount of data to be displayed on the display means. 2. Laser oscillation means, photoelectric conversion means for receiving the reflected light and converting it into voltage intensity, display means for converting the voltage intensity into image data and displaying it on a screen, and detecting surface defects from the voltage intensity. A strip surface defect inspection device comprising: a flaw detection means for determining the flaw; and a storage means for storing data on the flawed area determined by the flaw detection means, wherein the flaw detection means detects the type and degree of the flaw. 1. A strip surface defect inspection device comprising a plurality of flaw detection means each having an optimum sensitivity according to the flaw detection means, and the priority order of receiving signals from the plurality of flaw detection means is changed according to the type and grade of steel. 3. Laser oscillation means, photoelectric conversion means for receiving the reflected light and converting it into voltage intensity, display means for converting the voltage intensity into image data and displaying it on a screen, and detecting surface defects from the voltage intensity. A strip surface defect inspection device that divides the strip into a plurality of areas in the width direction, the strip surface defect inspection device having a flaw detection means for determining the flaw detection means, and a storage means for storing the data of the flawed part determined by the flaw detection means. At the same time, a priority is set in advance according to the steel type of the trigger for writing the defective part data to the storage means, and only the data of the area output by the trigger with the highest priority is written to the storage device. 1. A strip surface defect inspection device characterized in that: