JPH02163645A - Hot detector for billet surface flaw - Google Patents

Abstract

PURPOSE:To detect a surface flaw without fail by composing a hot detector of a movable scarfing member, which is composed of a preceding scarfing device and succeeding scarfing device, and high speed photographing member. CONSTITUTION:A succeeding scarfing device 2 and a preceding scarfing device 1, which removes unevenness caused by oscillation generated on the surface of a billet 4, are juxtaposed in series of front and back two steps on a device truck 6 which can parallelly travel and move to the billet 4 through a rail 7. A high speed photographing means 3 such as a high speed video camera, etc., for example, is arranged by a holding member such as an arm pillar 8, etc., which is provided in the truck 6, in order to photograph scarfing fire 5 in the succeeding scarfing device 2 for surface flaw detection. A photographic window 9, which is provided in a partition shape, is interposed between the scarfing device 1 and 2 and the scarfing fire 5 can be photographed in the succeeding scarfing device 2. For reproducing a photographed picture by the video camera, a video deck and a picture processor are used. Then, since the picture can be visually observed directly by monitoring the reproduced picture, an inspector can confirm various surface flaw parts. which exist on the surface or under the surface of the billet 4 for inspection, with the naked dye by monitoring a monitor screen.

Description

[Detailed description of the invention] (Industrial application field) The present invention accurately, quickly and easily detects various surface flaws existing on the surface layer of various steel slabs produced by continuous casting method or ingot forming method. Therefore, in particular, it is concerned with a method that clearly distinguishes surface irregularities such as oscillations so that error-free detection results can be obtained.

(Prior art) As a means of detecting surface flaws in steel pieces such as steel slabs obtained by continuous casting, oxygen or A combustion flame of enriched combustible gas is injected, and while the surface of the steel piece is being melted, high-speed photography is taken of the inside of the flame in the downstream direction from the end of the combustion flame colliding with the surface of the steel piece, and the high-intensity flame generated at the surface defect is detected. There is a method that detects surface flaws by capturing eddy currents, and an outline of this technology will be described below as a prior art with reference to FIGS. 2 to 4.

That is, in FIG. 2, when a steel piece C such as a steel slab is maintained at a surface temperature of about 600 to 800'C,
A solvent flame B from a solvent vessel A is generated by a gas burner using oxygen or oxygen-enriched combustible gas as a combustion gas, and a steel piece C
A surface flaw is detected by spraying a surface solvent onto the surface of the solvent and photographing this solvent flame B with a camera D. The principle of detection by this means is, as shown in FIG. flows on the surface of the steel piece 11 in a laminar flow state,
At this time, the depth of cutting to the surface is 0.2 to 5.0 mm.
When there is no flame part at all on the surface of the steel piece 11, the laminar flow state of the flame 13 is maintained constant, but there are surface flaws 12 on the surface due to crack defects as shown in the figure. At this time, a high-intensity flame vortex region 14 is generated in a part of the solvent flame 13 along with disturbance of the flame laminar flow. Therefore, as a means of capturing and photographing the solvent flame, for example, a high-speed video camera that is capable of high-speed photography and is easy to handle is used to photograph the solvent flame, and the photographed image is transferred to a video camera and an image processing device. Various defects existing on the surface or under the surface of the steel piece 11 can be confirmed by displaying the image on an intervening monitor and visually observing the image. The reason why high-speed photography is used in this case is that it improves resolution and provides a clear reconstructed image as a visible image.
For example, as the ↑ darkest condition, the lens aperture value is F-14 ~
15. The shutter speed is 2500 m/s or more, and the focal length f is approximately 1200 to 1500 m/m.

(Problems to be Solved by the Invention) The above-mentioned detection means is capable of continuously hot-detecting surface flaws existing on various steel pieces, and is superior to the conventional overflow type and optical quive. Although it has excellent advantages, there is room for reexamination on the following points. FIG. 4 shows an example of surface flaws on the steel slab 11. On the surface of the steel slab 1, there are oscillations 1 that belong to the unevenness occurring on the surface.
7, a key crack [8] and one horizontal crack belonging to defects occurring on the surface, and it is difficult to distinguish and detect the oscillator I/- John 17, the key crack 18, and the horizontal crack 19.

That is, as shown in FIG. 5, since cracking defects such as key cracks 8 and lateral cracks 19 occur during oscillations 17, a solvent flame was applied to the oscillations 17 as shown in the figure. In this case, as in the case of a surface flaw, the flow of the solvent flame 13 is disturbed by the oscillation 17, and a high-intensity flame vortex region 14 similarly occurs, which is detected as a surface flaw. Mistakes happen.

(Means for Solving the Problems) The present invention solves the problems in the prior art described above,
In order to reliably and easily detect only surface flaws, a solvent vessel that can only remove oscillations is installed before the solvent vessel for detecting surface flaws, thereby eliminating the influence of oscillations. This method enables detection of only surface flaws by applying the necessary solvent to the surface flaw detection using a solvent device for surface flaw detection.Specifically, it is possible to detect only surface flaws. A moving solvent member in two stages, front and rear, consisting of a leading solvent vessel for removing generated unevenness, and a trailing cutting machine for detecting flaws on the surface of the steel piece, which is arranged in series following the solvent vessel;
A high-speed photographing member disposed between the two solvent vessels and movable in synchronization with both the solvent vessels, and for photographing the radiant flame part of the trailing cutting machine for detecting surface flaws. It's about doing.

(Function) According to the above-mentioned technical means of the present invention, the steel plate surface is removed prior to the trailing cutting machine for surface flaws such as key cracks 18 and horizontal cracks 19 that occur on the surface of the steel piece to be inspected. For example, the surface of the oscillation 17 is removed by applying a melting solvent of about 1 mm using a preliminary solvent device to remove the unevenness that occurs on the surface of the oscillation 17, such as the wave-like unevenness found in steel pieces made by continuous casting. As a result, surface flaws such as key cracks 18 and horizontal cracks 19 that have occurred between oscillations 17 are exposed on the surface of the steel piece, and a trailing cutter for detecting surface flaws is used to
A solvent flame is radiated onto the surface of the steel piece from which only oscillation I7 has been removed, and the solvent is applied to a depth of about 0.5 mm.
This solvent flame area is photographed using a high-speed photographing member such as a high-speed video camera, and the presence or absence of a high-intensity flame vortex region due to the flame area is used to detect only surface flaws, without being affected by irregularities such as oscillation 17. Accurate detection can be obtained without mistakes, and it is possible to improve judgment accuracy and reliability.

(Example) A suitable example of the apparatus of the present invention will be described with reference to FIG. 1 and subsequent figures.

In FIG. 1, a device trolley 6, which can run parallel to the steel slab 4 through rails 7, straddles the steel slab 4 to be tested manufactured by continuous casting method or other method, and the combustion gas is oxygen or A trailing cutter 2 is used to detect surface flaws using a gas burner that uses oxygen-enriched combustible gas such as an oxidizer refining COG, and a similar gas burner is used to detect irregularities caused by oscillations 1 and the like that occur on the surface of a steel billet 4. Pre-solvent for removal! In the figure, 5 and 5 indicate the solvent flame emitted from the slit-shaped burner nozzles in both solvent vessels 1.2. A high-speed photographing unit 4; 13 using, for example, a high-speed video camera for photographing the solvent flame 5 in the trailing burner 2 is disposed by a holding member such as an arm support 8 provided on the trolley 6, The solvent flame 5 in the trailing burner 2 can be photographed through a photographing window 9 provided in the form of a partition between both solvent vessels 1 and 2. Although not shown, the reproduction of the image taken by the video camera uses a video camera and an image processing device as is known in the art, and the reproduced image can be directly viewed on a monitor, so that the inspector can view the image on the monitor screen. By observing this, various surface flaws existing on the surface or under the surface of the steel piece 4 to be inspected can be confirmed with the naked eye. According to the above-described device embodiment, by moving the device cart 6 parallel to the surface of the rope piece 4, the preceding solvent container 1.2 and the high-speed photographing member 3 in the front and rear stages are moved synchronously. Since the preceding solvent vessel 1 provided to remove irregularities such as oscillations 17 generated on the surface of the piece 4 always precedes the trailing cutting machine 2 for detecting surface flaws, the solvent is removed from the solvent vessel 1. By spraying the flame 5 onto the surface of the rope as a solvent, it is possible to remove only the oscillations 17, thereby removing surface flaws such as key cracks 18 and horizontal cracks 19 that occur during the oscillations 17. A subsequent trailing cutter 2 for detecting surface flaws injects a solvent flame 5 onto the surface of the steel piece from which only the oscillations 17 have been removed, and depending on whether or not the flame laminar flow is disturbed, key cracking is detected. 18, lateral cracks 19 can be reliably detected. At this time, it is necessary to set the amount of solvent in the advance solvent device 1 to the optimum amount for completely removing only the oscillation 17. This shows the measurement results, where the horizontal axis shows the oscillation depth (am),
The vertical axis indicates the frequency, and in the example, by setting the optimum solvent amount [6] to one cylinder, removal without the influence of oscillation is possible. On the other hand, it is preferable to reduce the amount of solvent in the trailing burner 2 for detecting surface flaws as much as possible, and surface flaws are detected using a solvent of III11 or less. The amount was set to 0°5 cylinders. In addition, the solvent speed of both solvent vessels 1 and 2 is
In order to speed up the detection and judgment time of surface flaws, the seventh
As shown by the solvent speed value 2o shown in the figure, 27m/
It was set to min. In FIG. 7, the horizontal axis shows the cutting speed value, and the vertical axis shows the solvent depth (fflIll). The above-mentioned amount of solvent is originally determined by the solvent velocity and the oxygen pressure in the solvent vessel, but in the device of the present invention, both solvent vessels 1.2 move synchronously as one, so
The amount of solvent in both solvent vessels 1 and 2 is adjusted using the oxygen pressure of each solvent vessel 1 and 2. That is, in the embodiment, the pre-solvent vessel 1 has its oxygen pressure 1. , Okg
/c4, CO pressure 0, set to 4 kg/crl, 1.1111+ for oscillation 17 removal
Since the purpose of the trailing melt cutter 2 is to detect surface flaws on the steel piece 4, and it is necessary to reduce the amount of solvent as much as possible, in the embodiment, the trailing melt cutter 2 Oxygen pressure of 0.6 kg/c+Il, Co pressure of 0, 4 kg
/cnl to perform 0.5+nm solvent.

Figure 8 shows a relationship diagram between oxygen pressure and solvent depth, in which the horizontal axis shows oxygen pressure, the vertical axis shows solvent depth, and 2
1 indicates the oxygen pressure value of the preceding solvent machine 1, and 22 indicates the oxygen pressure value of the trailing melt cutter 2.

The setting conditions for detection in the preceding solvent vessel 1 for removing irregularities and the trailing solvent machine 2 for detecting surface flaws in the apparatus of the present invention are as follows.

Surface temperature of steel piece to be tested: 700 to 800°C Solvent speed: 27 m/min Solvent device Gas advance solvent device 1; Oxygen pressure 1.0 kg/cal.

CO gas 0.4kg/cffl Trailing cutting machine 2 + oxygen pressure 0.6 kg/c + M.

CO gas 0.4 kg/c+a In the present invention, a high-speed video camera is used as a high-speed photographing member 3 for photographing the solvent flame 5 emitted from the trailing burner 2 for detecting surface flaws on the steel piece 4. is used, but
The conditions for flame photography using this camera are as follows.

Number of frames taken: 200 frames/second, shutter speed 1. /2500 seconds Lens aperture value=16 Filter used: T-44 type FIG. 9 is a characteristic diagram of the filter used, in which the horizontal axis shows wavelength (μm) and the vertical axis shows transmittance.

By visually observing the reproduced image of the solvent flame 5 in the trailing burner 2 for detection taken under the above conditions on a monitor, it was found that the key crack 18 and the horizontal crack 1 are completely unaffected by the oscillation 17.
Detection of surface flaws such as No. 9 can be easily and reliably detected.

(Effects of the Invention) According to the device of the present invention, harmful surface defects in the steel slab that have a large impact on the rolled products after the process are detected continuously and accurately in the hot state. It can exhibit superior effects compared to the prior art in various respects. That is, in the present invention, the preceding solvent machine 1 for removing irregularities such as oscillations generated on the surface of the steel piece, and the trailing solvent machine 2 for detecting surface flaws are arranged in two stages, front and rear. ,
By melting the surface of the steel billet by approximately 1m111 using the advance solvent machine 1, it is possible to easily remove irregularities such as oscillations 17 that occur on the steel billet due to the continuous casting method.
Defects such as key cracks 18 and horizontal cracks 19 that occur in the valleys of John 17 are exposed on the surface of the steel piece, and these are
Subsequently, the trailing burner 2 radiates a solvent flame 13 onto the surface of the steel piece from which the oscillations 17 have been removed to remove the solvent, and at the same time generates a high-intensity flame vortex due to the turbulence of the laminar flame flow. Depending on the presence or absence of the region 14, cracked keys 18, horizontal cracks 19, etc. can be detected without error. In the prior art, which uses a single solvent vessel, the flame laminar flow is disturbed even in the valleys of the oscillator 17.
Because the high-intensity flame vortex region 14 occurs, it is difficult to accurately distinguish between oscillations and surface flaws, and it is difficult to accurately distinguish between oscillations and surface flaws, and the correspondence between this determination and the surface flaws that actually exist on the surface of the steel piece is insufficient. Therefore, there is a great possibility that reliability will decrease in terms of determination accuracy.

As is known, in such a raw steel piece 4, a vertical crack that enters in the same direction as the later rolling direction is harmful if the length is 100M or more, but a key crack 18 that enters in a direction perpendicular to the rolling direction, a horizontal crack Cracks 19 and the like are enlarged by rolling, so ignoring even a crack of about 1 mm will have a very large effect on the product, so the above problems will jeopardize its existence in terms of practical use as an inspection equipment. . However, according to the device of the present invention, it is possible to accurately detect only the flaws that occur on the surface of the actual rope without causing the above-mentioned problems. Since the surface of the steel sheet that is hit by the solvent flame 5 emitted from the solvent flame 5 is smooth due to the solvent from the preceding solvent device 1, the image taken by the high-speed photographing member 3 also has little noise and is easy to judge. Also, when performing automatic judgment using image processing,
Judgment is made based on the brightness difference between surface flaws and areas other than the bottom, so if the surface of the steel piece to be detected is smooth, there will be no high-intensity noise due to the influence of the surface properties of the steel piece, and the image processing will be simpler. It is also effective in terms of conversion.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment of the device of the present invention, Fig. 2 is a perspective view of a conventional solvent flame photography method, Fig. 3 is an explanatory diagram showing the detection principle of the conventional technique, and Fig. 4 is a perspective view of the surface of a steel piece. Fig. 5 is an explanatory diagram of an example of unevenness and surface flaws, Fig. 5 is an explanatory diagram of an example of false detection by conventional technology, Fig. 6 is a measurement result of oscillation depth, and Fig. 7 is a graph showing the relationship between solvent speed and solvent depth. , FIG. 8 is a graph showing the relationship between oxygen pressure and solvent depth, and FIG. 9 is a characteristic chart of the filter used. DESCRIPTION OF SYMBOLS 1... Leading solvent machine for removing surface irregularities, 2... Trailing machine for detecting surface flaws, 3... High-speed photographing member, 4... Steel piece to be detected, 5... Solvent flame , 6... equipment trolley, 7.
...Rail, 10...Oscillation depth, 17...Oscillation, I8...Key crack, 19...Transverse crack, 14...High-intensity flame vortex region. Patent applicant Kobe Steel, Ltd.

Claims (1)

[Claims] (1) Two stages of front and rear movement, consisting of a leading solvent machine for removing irregularities occurring on the surface of the steel billet, and a trailing burner placed in series following the solvent machine for detecting flaws on the surface of the steel billet. a solvent member, and a high-speed photographing device that is disposed between the two solvent vessels and is movable in synchronization with the two solvent vessels, and is for photographing the radiant flame part in the trailing cutting machine for detecting surface flaws. 1. A hot detection device for detecting flaws on the surface of a steel billet, comprising: