JP2509115B2 - Surface slab surface defect detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to melting and fusing of steel slabs.
The present invention relates to a method for detecting surface defects of surface layer inclusions using changes in the amount of luminance light in a bus .

[0002]

2. Description of the Related Art As a method for detecting non-metallic inclusions in a steel slab, a relatively large amount such as slag, pinhole, sand shaving, etc.
Regarding the non-metallic inclusion, there is a method described in JP-A-59-154346. But this is the fusing flame
Since a simple optical filter processing and threshold value judgment processing are directly performed on the video signal which is an analog signal of the captured image, the light emission time is 0.1 to 0.5 from the unstable melting bath that changes from moment to moment. surface intervention is instantaneous phenomenon on the order of seconds
It is extremely difficult to accurately detect a spark caused by an object by distinguishing it from the contour of the melting bath and noise.

[0003]

In order to detect surface layer inclusions on a steel slab, it is necessary to accurately measure an instantaneous phenomenon, a spark, from an unstable melting bath that changes from moment to moment, regardless of its size. Oh Ru, but conventional satisfactory results in the process is obtained, et al.
I couldn't . The present invention makes this possible.

[0004]

Means for Solving the Problems The gist of the present invention is to obtain a continuous original image by photographing the melting bath with a TV camera during the melting using the melting bath of the billet surface scarfing welding as an inspection area. A steel strip characterized by detecting only sparks due to surface inclusions by performing frequency filter processing on the original image to emphasize only the emission pattern frequency peculiar to sparks due to surface inclusions and suppress fluctuations in the light quantity of the melting bath. And a method for detecting surface defects in the steel slab surface, and a melting bath of scarfing welding is used as an inspection area during the melting, and the melting bath is photographed by a TV camera to obtain a continuous original image. A frequency filter process for emphasizing only the emission pattern frequency peculiar to the spark caused and suppressing the fluctuation of the light quantity of the melting bath is performed.
It is a method of detecting surface defects of a steel slab, which comprises inputting into an image processing device including an A / D conversion device and an image memory, and grasping a light having a light amount of a certain value or more as a spark caused by surface inclusions.

[0005]

1 (a) and 1 (c) show images obtained by picking up an image of a molten bath produced during the scarfing of steel billet surface with a television camera. (A) is an image without sparks in the melting bath 1 generated by fusing, and (c) when inclusions are present.
Spark 2 appears here.

1A and 1B are sectional views of the melting bath 1 taken along the line AA 'in FIG. 1A and the line BB' in FIG. 1C, respectively. In the present invention, the light emission pattern and the light emission pattern frequency do not mean the waveform and frequency of light when light is regarded as an electromagnetic wave, and are not shown in FIG.
(B) and (d) means the distribution state and distribution frequency of the emission luminance amount on the melting bath.

Since the melting bath is usually generated by subjecting the surface of the steel slab to ablation with high-pressure oxygen gas and LPG gas, the melting bath itself fluctuates, which in turn causes a change in the amount of light. Even in one cross section of the melting bath from the start to the end of melting for one steel piece, the light quantity variation 4 as shown in FIG. 1 (e) occurs. Therefore, although a spark having a brightness equal to or higher than the light intensity variation can be detected, it is necessary to suppress the light intensity variation in order to detect a spark having a light intensity variation level.

Therefore, as a result of various experiments conducted by the present inventors, it has been found that the influence of the fluctuation in the light quantity of the molten bath can be eliminated and the minute spark can be surely detected by frequency-filtering (differentiating) the image pickup signal of the television camera. . FIG. 1 (f) is a cross section of the light amount after the frequency filtering process, and FIG.
(G). The minute spark 5 is detected.

FIG. 2 shows an example of signal processing in the present invention. The television camera 8 takes an image of the melting bath 1 generated by the fusing. The frequency filter circuit 9 emphasizes the emission frequency peculiar to the spark in the ablation video signal obtained from the television camera 8 and suppresses the fluctuation of the light quantity of the melting bath 1.

In the present invention, the frequency-filtered signal may be displayed on a CRT screen device to allow a person to visually check the occurrence of sparks to determine the surface defect of the steel slab. The image memory 12 is input to the A / D conversion device 11 of the image processing device 10 and A / D converted.
May be introduced to detect defective sparks.

The image memory 12 is provided with a mask 13 which preliminarily distinguishes a region where sparks appear from other regions where noise such as melting fluctuation appears, and which has an image processing region only at the center of the melting bath where sparks appear. Keep it. In the image memory 12, for example, a threshold value is set, and a spark having a light amount equal to or larger than the threshold value is set as a spark.

By continuously processing the ablation image signals that are sequentially obtained when the ablation is started, it is possible to accurately detect not only an unstable melting bath that fluctuates from moment to moment but also large sparks as well as minute sparks, and the distribution of surface layer inclusions. It is possible to measure the state.

[0013]

EXAMPLE FIG. 3 shows an example of an apparatus used for carrying out the present invention.
The signal processing circuit basically used is the same as that shown in FIG.

The fusing crater 7 and the TV camera 8 are the carriage 1
It is mounted on the steel plate 5 and is movable in the width direction of the steel piece 6. The traveling carriage 15 is mounted on a traveling mount 16 and is movable in the longitudinal direction of the steel slab 6. The inspection result obtained by the image processing device 10 is stored in the external storage device 14.

The traveling carriage 15 on the traveling mount 16 is composed of a steel strip 6
From one end to the other end, a flame is blown from the smelting crater 7 and the steel slab 6 is melted and run. The molten bath formed on the steel slab 6 is imaged by the television camera 8, the fluctuation of the molten bath light amount is suppressed by the frequency filter circuit 9, the spark is emphasized, and the image is sent to the image processing apparatus 10. A / in the image processing apparatus 10
After conversion by the D conversion device 11, the image data is taken into the image memory 12,
Sparks are detected by comparing with a threshold value in an area in the mask 13 which is provided in advance. The above-described operation is continuously processed for one piece of steel, spark data is stored in the external storage device 14, and sparks and noise are discriminated after completion of the fusing, so that the surface layer defect in the steel piece can be accurately detected.

Using this apparatus, an ultra-low carbon steel billet for processing (C: 0.002% content (thickness 245 mm × width 1500)
(mm × length 9000 mm), the 1/4 position in the width direction and the adjacent position were melt-cut by the smelting crater 7, and the TV camera 8 continuously photographed the molten bath for investigation. Width direction 1 /
The four adjacent points were inspected for their adjacent points in a comparative example without frequency filtering, and the results are shown in Table 1.

[0017]

[Table 1]

However, the visual detection is performed by copying the image taken by the television camera to the CRT device without passing through the image processing device.

As described above, according to the present invention, it is possible to visually check about 3
2 times, there is about 10 times the detection capability in image processing.

[0020]

As described in detail above, the present invention can detect even minute sparks, and can quickly and accurately determine the quality of a billet. Further, for example, if the detection result and the billet manufacturing conditions are compared, it becomes useful information for improving the billet manufacturing conditions, and the production of defective billets can be prevented in advance.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing a light emission pattern of a fused bath image and a result of signal processing according to the present invention.

FIG. 2 is a diagram showing an example of a signal processing circuit for implementing the present invention.

FIG. 3 is a diagram showing an example of a surface defect detection apparatus suitable for implementing the present invention.

[Explanation of symbols]

 1 Melting bath 2 Sparks 3 Luminous pattern 4 Light intensity fluctuation 5 Micro sparks 6 Steel slab 7 Scraping crater 8 TV camera 9 Frequency filter circuit 10 Image processing device 11 A / D conversion device 12 Image memory 13 Mask 14 External storage device 15 Traveling cart 16 traveling stand

Claims (2)

(57) [Claims] 1. A steel bath for scarfing a slab of steel is used as an inspection area to inspect the molten bath with a television camera to obtain a continuous original image, and sparks caused by surface inclusions in the original image. A method for detecting surface defects on a steel slab, which comprises performing a frequency filter process for emphasizing only a specific light emission pattern frequency and suppressing fluctuations in the light quantity of a melting bath, and detecting only sparks due to surface inclusions. 2. A continuous original image is obtained by photographing the melting bath of a steel piece surface scarfing by a TV camera during the melting using the melting bath as an inspection area, and sparks caused by surface inclusions with respect to the original image. A frequency filter process is performed that emphasizes only a specific light emission pattern frequency and suppresses fluctuations in the light amount of the melting bath, and the image subjected to the frequency filter process is input to an image processing device including an A / D conversion device and an image memory, and a constant value is set. A method for detecting a surface defect of a steel slab, characterized in that a spark having the above light intensity is grasped as a spark caused by surface inclusions.