JPH0477843B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a steel plate surface inspection device used in a continuous steel plate conveyance line.

Prior Art On the exit side of the pickling line in the rolling process, flaw detection of hot rolled steel strips is required to improve the quality of the cold rolled base material.

Conventionally, optical flaw detection methods, electromagnetic flaw detection methods, etc. have been used to detect flaws in hot rolled steel strips, but optical flaw detection methods detect contamination (water, oil, etc.) on the steel surface after pickling.
There were many erroneous detections due to the flaw detection, and additional pretreatment was required to improve flaw detection accuracy.

In addition, although electromagnetic flaw detection is superior in terms of detection accuracy and ability to detect flaws on objects to be tested that move at high speed, the measurement range is narrow, so multiple expensive probes must be arranged depending on the width of the object to be tested. It was impossible.
Furthermore, the penetrating liquid method has a problem in flaw detection speed and is therefore not suitable for flaw detection on a continuous conveyance line.

For this reason, when the steel plate is conveyed at a high speed, wide, and has dirt due to pickling, such as in a continuous conveyance line, it is difficult to completely identify the surface flaws of the steel plate using conventional methods, and the final The current situation is that the operator's intuition, visual inspection, and judgment are relied upon.

Purpose of the Invention Therefore, the present invention improves the disadvantages of the conventional technology in the surface inspection of a continuous steel plate conveyance line as described above, and can sufficiently cope with the width and conveyance speed of the steel plate, and also eliminates stains caused by pickling. It is an object of the present invention to provide a steel plate surface inspection device that can accurately determine the following.

Composition of the Invention The steel plate surface inspection apparatus according to the present invention includes an optical primary flaw detection device that is disposed on the upstream side in the steel plate conveyance direction in a continuous steel plate conveyance line, and that images the surface of the steel plate transferred on the conveyance line; An electromagnetic secondary flaw detection device is placed on the downstream side of the device in the steel sheet conveyance direction, and measures the flatness of the surface of the steel sheet conveyed on the conveyance line, and an electromagnetic secondary flaw detection device is configured to image-process the captured screen input from the primary flaw detection device. A calculation that selects a portion that is highly likely to be a surface flaw in the steel plate, instructs the secondary flaw detection device to re-measure the selected portion, and determines the flawed portion of the steel plate from the flatness measurement value of the secondary flaw detection device. It is characterized by having a control section.

Embodiments The present invention will be described below with reference to illustrated embodiments. FIG. 1 shows a control block diagram of an embodiment of the steel plate surface inspection apparatus according to the present invention. It is composed of an electromagnetic secondary flaw detection device (hereinafter referred to as electromagnetic flaw detection device) B, which is a measuring device, and an arithmetic control section C.

As shown in FIG. 2, the optical flaw detection device A is installed near the bridle roll 23 where the steel sheet 1 has little flapping, as shown in FIG.

This optical flaw detection device A consists of three ITVs (CCD cameras) 2 arranged in the width direction of the steel plate 1, and each
Three strobes 3 are provided to irradiate the imaging surface of the steel plate 1 of the ITV 2 with strobe light. Among these three strobes 3, two strobes 3 are arranged on one side in the width direction of the steel plate, and the remaining one strobe 3 is arranged on the other side in the width direction of the steel plate. In this way, the light shielding plate 4 is provided to prevent mutual interference of light between the strobes that are in a facing relationship.

These ITV2 and strobe 3 are controlled by the synchronization control unit 5.
The synchronization control unit 5 controls the strobe light emission timing in accordance with the threading speed of the steel plate 1 so that the ITV fields of view do not overlap. A timing control section 6 is connected to the next stage of the synchronization control section 5, and the imaging signal from each ITV 2 is inputted from the synchronization control section 5 to the timing control section 6. A tracking signal from a pulse generator 7 that performs sheet thread tracking is input to this timing control unit 6, and the imaging and
Calculation control section C performs image processing timing control.
output to the side. Further, a synchronization signal is outputted from the timing control section 6 to the synchronization control section 5, and synchronization control between the ITV 2 and the strobe 3 is performed according to the sheet threading speed.

Here, the relationship between the ITV2 and the strobe 3 of the optical flaw detection device A will be explained in detail according to the arrangement diagram shown in Figure 3.The strobe 3 is inserted diagonally into the ITV2 imaging range AB in order to compensate for the lack of resolution of the ITV2. It is configured to emit strobe light. In addition, data regarding the irradiation angle α and irradiation distance l of the strobe 3 are shown in Figs. 4 and 5. In order to detect a 1 mm deep flaw on one surface of the steel plate, the irradiation angle of the strobe 3 is set to 20°. By making it less than 2 mm, it is possible to generate a shadow with a length of 2 mm or more. Along with the shadows generated in this way, the steel plate 1 is exposed to the strobe light from an oblique direction.
In order to bring the illuminance ratio in the surface width direction into the resolution range of the ITV 2, the irradiation distance l from the steel plate 1 to the strobe 3 is arranged to be 1000 mm or more to obtain a good image.

In this example, three ITVs 2 and three strobes are used, but if the width of steel plate 1 is narrow,
It is possible to use only one ITV 2, and similarly, it is also possible to use only one strobe 3 if the irradiation capacity is sufficiently large.

Further, an electromagnetic flaw detector B, which is a flatness measuring device, is provided downstream of the optical flaw detector A by a predetermined length on the conveyance line. This electromagnetic flaw detection device B includes two probes 9 disposed so as to be freely displaceable in the width direction of the steel plate 1;
The eddy current flaw detection section 8 has a detection end.

The two probes 9 are screwed into two ball screws 10 that each independently extend outward in the width direction from the center of the steel plate 1 in the width direction. Motors 11 are attached to the outer ends of the ball screws 10 in the width direction of the steel plate, and the ball screws 10 rotated by the motors 11 independently move the two probes 9 across the width of the steel plate 1. It is possible to move in the direction.
A flaw detection position signal from an arithmetic control section C, which will be described later, is input to the motor 11 via a servo circuit 14.
Further, a pulse generator 12 and a tacho generator 13 are attached to each of the two motors 11, and these pulse generators 12 and tacho generators 13 cause the motor 11 to indicate the amount and direction of displacement of each probe 9. The rotation speed and rotation direction are input to the servo circuit 14. In this way, the electromagnetic flaw detection device B servo-controls the two probes 9 that cover half the area in the width direction of the steel plate 1 based on the flaw detection signal from the calculation control unit C.
Perform eddy current flaw detection.

Furthermore, the steel plate surface inspection apparatus of the present invention is provided with an arithmetic control section C that controls the optical flaw detection apparatus A and the electromagnetic flaw detection apparatus B.

This arithmetic control unit C is equipped with a 3-channel primary flaw detection unit 16, which inputs the image signal from the timing control unit 6 of the optical flaw detection device A, and performs flaw determination in real time using images at a rate of about 30 times/second. and the next frame/
The image of the flaw is stored in the memory 17. This primary flaw detection unit 16 uses differential slices to differentiate the scanning line brightness of the ITV image to detect the presence or absence of a value exceeding a set value. Next, the presence/absence of flaws is determined, and if it is determined that there is a flaw, the screen information is output to the frame memory 17.

The primary flaw detection unit 16 and the frame memory 17 are 3
Each channel is configured with three channels (3ch.) to correspond to the ITV2, but if the processing capacity is large, each channel can be configured with one channel.

A secondary flaw detection section 18 is connected to the output side of the frame memory 17.
Secondary flaw detection is performed based on the part that is determined to be flawed by the flaw determination by the primary flaw detection section 16 stored in the device and the flaw detection results inputted from the eddy current flaw detection section 8 of the electromagnetic flaw detection device B. Through this secondary flaw detection, the presence or absence of flaws is checked, and the type, depth, and level of danger of the flaws are determined.
A monitor 19 and a flaw alarm 20 are connected to the output side of the secondary flaw detection unit 18, and a still image of the flaw site and a flaw are displayed on the monitor 19 as a result of secondary flaw detection by the secondary flaw detection unit 18. The type of the defect and the quantified size of the defect are displayed, and if necessary, the defect alarm 20 is activated to notify the operator of the abnormality.

Further, the secondary flaw detection unit 18 to the primary flaw detection unit 16
A primary detection setting value change signal is output as a result of secondary flaw detection. This primary detection setting value change signal is used when it is determined that an image suspected of a flaw in the primary detection is not a flaw in the flaw detection by the electromagnetic flaw detection device B (false detection in the primary detection). Secondary detection software logic automatically changes settings such as dark area cross-sectional area, dark area length, bright area/dark area discrimination level, etc. In this way, by improving the false detection rate of the primary flaw detection section 16, it is possible to support higher-speed sheet passing inspection and to perform inspection using fewer probes.

Furthermore, the arithmetic and control unit C is equipped with a microcomputer 15, and when a flaw detection signal is input from the primary flaw detection unit 16, the optical flaw detector detects a predetermined distance from the strip tracking signal of the pulse generator 7. Control is performed by the servo circuit 14 in accordance with the arrival of the flaw detection part to the electromagnetic flaw detection device B located downstream from A in the conveyance direction. In this way, the servo circuit 14 is configured to operate each motor 11 to control the probe 9 to follow the flaw detection portion of the steel plate 1.

This microcomputer 15 detects a welding point from the flaw detection signal from the eddy current flaw detection section 8 and the input signal from the primary flaw detection section 16, and outputs a welding point detection signal to the pickling process computer 21. In addition, the pickling process computer 21 outputs display signals to the timing control unit 6 indicating the width of the plate being passed, the material, the position of the welding point, etc.

Further, the cold rolling process computer 22 is inspected for defects from the pickling process computer 21;
Information such as the position is input, and when passing the plate at the flaw detection position, the cold compression speed is lowered to prevent plate breakage accidents.

Function In the above configuration, when the steel plate 1 is conveyed on the conveyance line and reaches the optical flaw detection device A, the timing control unit 6 transmits the input tracking signal from the pulse generator 7 to the synchronous control unit. Output to 5. Therefore, the synchronization control section 5
ITV2 and strobe 3 are synchronously controlled according to the sheet passing speed.

In this way, the image signal captured by the ITV 2 is sent from the synchronization control section 5 to the timing control section 6.
The imaging signal is image-processed into a still image by the timing control section 6, and then outputted to the primary flaw detection section 16, where primary flaw detection is performed.

Here, FIGS. 6a, b, c, and d are perspective views showing steel sheet surface flaws, their cross-sectional views, imaging brightness, and 2
The following detection example is shown. Each part of the surface of the steel plate in Figure 6a shall show rash flaws, linear luster, dirt from water or oil, etc., selvage flaws, and selvage marks. The cross-sectional shape of this steel plate A-A' section is shown in Figure 6b.
The scanning line brightness on the imaging screen corresponding to the A-A' section is shown in FIG. 6c. The primary flaw detection unit 16 detects the scanning line brightness of the imaging screen based on the amount exceeding the upper and lower limit values (broken lines in Figure 6c) (the black areas in Figure 6), the peak value after differentiation, the number of peaks, etc. ,
The presence or absence of flaws is determined by comparison with a value set in advance as a limit value.

In this way, a part suspected of being a flaw is detected when the setting value is exceeded, and the screen information is stored in the frame memory 17.

At the same time, the primary flaw detection section 16
A primary flaw detection signal is output to the computer 15, and the microcomputer 15 inputting this signal sends a signal to the servo circuit 14 of the electromagnetic flaw detection device B to probe the area deemed to be a flaw by the primary flaw detection unit 16. 9 and performs eddy current flaw detection.

This electromagnetic flaw detection section 8 outputs the flaw detection results to a microcomputer 15 and a secondary flaw detection section 18. The secondary flaw detection unit 18 that receives the flaw detection results from the electromagnetic flaw detection unit B stores the flaw detection results and the frame memory 1.
Judgment is made by comparing the primary flaw detection data read from 7.

An example of secondary flaw detection is shown in Fig. 6d, where the bright line and dark line are continuously closed, and in conjunction with the flaw detection results from electromagnetic flaw detection section B, it is determined that it is a "rash flaw", and the area is Calculate depth. Similarly, a dark line that ends with an edge is considered an "ear scar" and the length is checked, and a continuous dark line and bright line closed with an edge is identified as an "ear scar." Calculate area and depth. In addition, the dark area that is not closed
and , in Fig. 1a are not considered to be flaws by secondary flaw detection.

In this manner, the output of the secondary flaw detection section 18 is input to the monitor 19, which displays a still image of the flaw site, the type of flaw, and the quantified size of the flaw, thereby informing the operator of the detection of the flaw.

Further, if necessary, an alarm is issued from the flaw alarm 20, and the rolling speed is reduced during cold rolling of the flawed area to prevent breakage of the steel plate during cold rolling.

Further, the secondary flaw detection unit 18 detects the primary flaw detection unit 1.
A primary detection setting value change signal is output to 6 to correct over-detection or under-detection in the primary flaw detection section 16.

Furthermore, a micro-controller which inputs the detection signal from the primary flaw detection section 16 and the flaw detection signal from the eddy current flaw detection section 8 is provided.
Since the computer 15 can also detect welding points on steel plates, this welding point detection signal is output to the pickling process computer 21 and used for error correction in sheet tracking in the pickling process computer 21.

To explain this point in detail, when the pickling process computer 21 receives a signal indicating welding from the welder on the pickling input side, the welding point position is calculated over time based on the movement of the pickling line. Based on this calculation, when the steel plate surface inspection device considers that the welding point has arrived, a signal is sent to the microcomputer 15 through the timing control unit 6 of the steel plate surface inspection device, and then the welding point is detected by the steel plate surface inspection device itself. By obtaining the signal, the error from the previously calculated welding position is calculated. Therefore, values such as the length of the rolled steel strip are corrected based on this error, and at the same time, the threading tracking information sent to a device other than this device is reset to correct the error.

As a result, for example, when cutting and removing a welding point on the pickling side shear, the positional information of the welding point becomes much more accurate, making it possible to perform optimal deceleration and stopping, which previously required automatic deceleration and visual stopping. Things can be fully automated.

Note that while the optical flaw detection device A is not detecting flaws, the electromagnetic flaw detection device B detects flaws near the edges of the steel plate in order to detect horizontal cracks (hair cracks) near the corners.

By adopting this example device, the amount of flaws detected is reduced to 1/4 to 1/5 compared to the case of only optical method, and the overdetection amount is 1.2 when visually compared at the sample section. As a result of applying the flaw information to the rolling speed adjustment during the cold rolling process, no plate breakage occurred during cold rolling.

In this example, the device of the present invention was installed between hot rolling and cold rolling, but by installing it after cold rolling, the final inspection of the product can be performed online and false detections caused by rolling oil can be reduced. can.

Effects of the Invention The embodiments of the steel sheet surface inspection apparatus according to the present invention are as described above, and can provide the following effects.

In the steel plate surface inspection on a continuous steel plate conveyance line, it can fully correspond to the width and conveyance speed of the steel plate, and it can accurately distinguish from scratches caused by pickling, and the number of false detections can be greatly reduced, increasing the reliability of automation. It becomes possible to significantly improve the

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of an embodiment of the steel plate surface inspection device according to the present invention, Fig. 2 is a schematic diagram showing the installation position of the ITV, Fig. 3 is a schematic diagram showing the irradiation angle and irradiation distance of the strobe, and Fig. 4 is a graph showing the relationship between strobe irradiation angle and flaw shadow length, and Figure 5 shows the relationship between irradiation distance and
A graph showing the illuminance ratio of the left and right corners of the ITV field of view, Fig. 6a is a perspective view showing an example of the surface of a steel plate, Fig. 6b is a sectional view taken along the line A-A', and Fig. 6c is a waveform diagram of the imaging luminance signal. d is a pattern showing an example of secondary flaw detection. A...Optical flaw detection device, B...Electromagnetic flaw detection device, C...Calculation control unit, 1...Steel plate, 2...
ITV, 3... Strobe, 4... Light shielding plate, 5...
Synchronous control section, 6... Timing control section, 7... Pulse generator, 8... Eddy current flaw detection section, 9...
Probe, 10... Ball screw, 11... Motor, 12... Pulse generator, 13... Tacho generator, 14... Servo circuit, 15...
...Micro computer, 16...Primary flaw detection unit, 17...Frame memory, 18...Secondary flaw detection unit, 19...Monitor, 20...Flaw alarm, 21...Pickling process computer, 22
...cold rolling process computer, 23...bridle roll.

Claims (1)

[Scope of Claims] 1. In a continuous steel plate conveyance line, an optical primary flaw detection device that is disposed on the upstream side in the steel plate conveyance direction and images the surface of the steel plate transferred on the conveyance line; An electromagnetic secondary flaw detection device is placed on the downstream side and measures the flatness of the surface of the steel sheet conveyed on the conveyance line, and an image processing device input from the primary flaw detection device is used to detect flaws on the surface of the steel sheet. and a calculation control unit that selects a portion with a high probability, instructs the secondary flaw detection device to re-measure the selected portion, and determines the flawed portion of the steel plate from the flatness measurement value of the secondary flaw detection device. A steel plate surface inspection device characterized by: