JPS5920970B2 - Method for distinguishing between water remaining on a hot-worked steel billet and scratches on the surface of a hot-worked steel billet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for automatically detecting blemishes existing on the surface of a hot-rolled steel piece and distinguishing them from other water-retaining areas.

Generally, ITV and infrared TV are widely used to detect flaws present in hot-rolled steel pieces.

The blemishes that occur on steel slabs have a scale-like appearance that partially rises from the surface of the steel slab, so in hot conditions, heat transfer from the high-temperature areas inside the steel slab is poor, and the damage is lower than that of the surrounding normal parts. As the temperature decreases and heat radiation decreases, I
When observed on TV, etc., it is perceived as a localized dark area. For this reason, when observing a video signal, only the dark portions are extracted and blurring defects are detected using this. However, on the other hand, even if rolling roll cooling water or descaler water adheres to the surface of the hot-worked steel billet, the heat radiation from the billet is blocked. Like a flaw, it is perceived as a localized dark area, and therefore, in the past, there was a problem in that the area to which water was attached was also detected as a blemish flaw. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a means for distinguishing between scratches and water-attached parts during observation using an ITV or the like, thereby increasing the reliability of detecting scratches.

In the present invention, the following points are extremely important elements in the structure of the invention. In other words, the area where the blemish exists is metallographically the same as the surrounding normal area, and exhibits the same optical properties; it is simply a different shape. . Therefore, when a strong illumination light is irradiated onto the part where the flaw is present, there is no distinction between the normal part and the flawed part, and they emit the same metallic luster. Both areas are observed as bright areas. However, if the water adhesion area is observed as a dark area even under this strong illumination, it is possible to distinguish between water and blemishes by combining two observation methods: this observation method and conventional observation means. becomes. In the present invention, as an active means to consider only the water reservoir part as a dark part, rolling roll cooling water, descaler water,
Fine powder of a light-scattering substance or a light-absorbing substance is mixed in advance with all other water used in the rolling process that may adhere to the surface of the hot steel billet.

As these substances, it is necessary to select substances that will not burn on the hot steel billet, will not cause nozzle clogging, and will not have an adverse effect on the product. For example,
Use fine iron oxide powder or fine alumina powder. If the substances used may have a negative effect on the product, it is desirable to use a method to clean the surface of the steel piece after flaw detection.
Next, one embodiment of the apparatus according to the present invention and its operation will be explained with reference to the drawings.

In FIG. 1, a cooling water tank 4 and a descaler water tank 5 are used in a rolling process as shown in which a cooling water nozzle 2 is disposed at the position of a rolling roll 1 and a descaler nozzle 3 is disposed downstream of the cooling water nozzle 2. A hopper 6 for mixing fine powder is installed in each of the tanks, and fine powder 7 having the above-mentioned optical characteristics is mixed into the water stored in the tank. The hot steel billet 8 is transported on a conveyance line 9, stops when it reaches a flaw detection point, is first photographed by an ITVlO, and is further photographed again at the same portion under strong illumination from an illumination device 11. . Now, as shown in FIG. 1, suppose that the surface of the steel piece 8 being detected coexists with a blemish flaw a and a water retention part b.
When photographed under the control of the camera illumination control device 12 (Fig. 3), the image i showing the turret a and the image b' showing the water b on the monitor screen are perceived as similar dark areas (second
Figure A). This screen is temporarily recorded on the first recording device 21 by using the signal switching device 20 shown in FIG. Next, the illumination device 11 is turned on under the control of the camera illumination control device 12, and the same surface is photographed again under strong illumination. In this state, the irradiated light on the water part is scattered or absorbed due to the influence of the fine powder mixed in the water in advance, and the water b
Only image d showing
. This image is converted into a negative image (FIG. 2C) by using the signal switching device 20 shown in FIG. The recording device 22 records the information. The image of the first recording device 21 (FIG. 2A) and the image of the second recording device (FIG. 2C) are introduced into the image composition device 24, and the composite image obtained from these two images (the second Figure D) is displayed on the monitor screen of the monitor 25. In this composite image, the image showing water disappears, and only the image showing flaws is shown as a dark area. According to the method of the present invention, the video signal of the synthesized image is discriminated by the level discriminator 26 to extract only the flaws, and the flaw determination device 2
The extracted value is compared with a set value of a flaw area tolerance set in advance in step 7, and only those exceeding the set value are treated with a solvent or the like. If a flash light source such as a strobe light is used as powerful illumination, it is possible to photograph the steel piece under non-illumination while the flash light source is being charged, and to photograph the steel piece under illumination while the flash light source is emitting light.

Therefore, the lighting can be turned on and off easily and quickly, and photography can be performed continuously. In the present invention, the illumination device is selected according to the optical properties of the light-scattering substance or light-absorbing substance used, the spectral reflectance of the hot steel billet surface, the polarization property, etc. The effects of the invention can be further enhanced by using a polarizer, a polarizing device, etc.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing an embodiment of the apparatus according to the present invention. FIG. 2 is an explanatory diagram showing an example of a photographing screen according to the present invention at each stage. FIG. 3 is a block diagram showing an embodiment of the control system and signal processing system of the present invention. 1: Rolling roll, 2: Cooling water nozzle, 3: Descaler nozzle, 4, 5: Water tank,
6: Hotsupa Jme F fine powder, 8: Steel billet, 9: Conveyance line, 1
0: ITV, 11: Lighting device, a': Image of blurring,
b': Image of the water reservoir area.

Claims (1)

[Claims] 1. In the hot rolling process, an aqueous solution mixed with fine powder of a light-scattering substance or a light-absorbing substance is used as rolling roll cooling water and descaler water, and an ITV camera installed in the hot rolling line is used to monitor the above. Photographing the surface of a hot-worked steel billet that has been rolled and descaled using an aqueous solution using self-luminescence of the steel billet; Temporarily storing an image signal corresponding to the above, then photographing the same hot steel billet surface under luminous flux irradiation with the ITV camera, and creating a negative image signal by inverting the bright and dark parts of the photographed image. , combining the negative image signal with the temporarily stored image signal, and discriminating the composite signal and determining that a defect exceeding a set value is a harmful defect. How to distinguish between scratches and scratches on the surface of a steel piece.