JP2914990B2 - Method for detecting abnormal state of molten metal surface, method for preventing abnormally molten metal surface, and apparatus for preventing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention accurately and accurately describes the level of molten metal in a continuous casting mold, for example, the occurrence of spoiling, boiling, powder shortage, etc. occurring in casting. The present invention relates to a method for automatically detecting and effectively preventing the above-mentioned fluid level abnormality based on the detection result.

[Conventional technology]

A system including a continuous casting mold (hereinafter simply referred to as a mold) includes a casting mold, an injection nozzle including a lower nozzle, an upper nozzle, and an immersion nozzle disposed at the bottom of the tundish, which is disposed in the center of the casting mold, and a sliding nozzle. Nozzle (hereinafter simply referred to as SN) or molten steel flow rate control device using a stopper, etc., capture and floating of inclusions and deoxidation products present in molten steel in the mold, and the inclusions are deoxidation products Blown into the injection nozzle for the purpose of preventing blockage of the injection nozzle due to air (hereinafter simply referred to as blown gas)
, A molten steel level control device, etc. In addition, the blowing gas is discharged from the molten metal surface in the mold.
Powder is sprayed to prevent oxidation, capture deoxidized products and inclusions, and lubricate the solidified shell and the mold. The powder melts in contact with the molten steel to form a molten layer, and flows between the mold and the solidified shell to perform the various functions described above. Further, vibration is applied to the mold for smooth drawing of the slab, and the molten steel surface discharged from the injection nozzle constantly shakes the molten metal surface in the mold. In the situation described above, the molten steel discharged from the injection nozzle is
By being cooled by the mold or the like, a meniscus is formed at the upper end of the molten metal surface along the mold and solidification is started.

Thus, in the nearby system including the template, the above factors are present in a congested state, and in a stable state, they are in a delicately balanced state. In other words, the system in the vicinity of the template is very complicated and sensitive. For this reason, it is easy to react sensitively to fluctuations in operations such as fluctuations in the amount of molten steel and casting speed in the tundish, clogging of the injection nozzle, etc. Abnormalities such as one-sided spring, insufficient powder, etc., that is, an abnormal level of the molten metal referred to in the present invention are caused. These level abnormalities are the biggest troubles in continuous casting operations, breakouts (hereinafter, referred to as breakouts).
Such as BO), and directly leads to surface quality defects such as powder entrainment in the solidified shell. Therefore, keeping the system near the mold including the above-mentioned mold stable at all times not only prevents the occurrence of troubles such as BO, but also stabilizes the continuous mold while ensuring the quality of the surface and near the surface of the slab. This is the most important point in conducting operations.

Therefore, the monitoring of the state of the molten metal in the mold has been done with great care, and many detection means have been proposed. For example, Japanese Patent Application Laid-Open No. 60-49846 discloses an infrared camera that scans the surface of a molten metal above a mold, measures the temperature on the surface of the molten metal, and its temperature distribution, and measures the thickness and the thickness of the powder layer. A method for detecting the distribution is disclosed in
No. 71723 discloses a method of selecting two or more wavelengths from radiation rays radiated from a molten metal surface in a mold, measuring a temperature on the molten metal surface by a ratio of energy levels thereof, and detecting a powder shortage situation. Also, JP-A-59-229267 discloses that
There is disclosed a method of detecting a powder shortage state by sensing an optical fiber cable on a molten metal surface and measuring a current signal according to the amount of light on the molten metal surface. However, in such a conventional method, a flame or the like generated when the gas blown into the injection nozzle flows out into the mold is erroneously detected as powder shortage, or the surface of the molten metal is constantly caused by mold vibration or the like as described above. Due to rocking, powder melted parts and flames are affected by large fluctuations such as temperature conditions on the molten metal surface due to rocking and shading, and disturbance light, so that accurate powder shortage can be detected. Was difficult. In addition, scanning time is required for temperature measurement devices, infrared cameras, and optical fibers, and it takes a relatively long time to detect the powder application status over the entire surface of the mold. There is also a problem that the operation action cannot be executed at an appropriate timing or the like. Further, even when a sudden molten metal level such as the above-described one-sided springing or boiling occurs, it is only necessary to perform a process for detecting powder shortage, and it is impossible to detect such a molten metal level. there were.

Techniques have also been proposed in which a thermocouple is buried in the mold wall, or a magnetic sensor or infrared camera is set above the mold to detect only the level of the molten metal. Is to be detected and controlled to a certain level, so that it is not possible to directly detect the level of the molten metal such as one-sided spring, boiling, and insufficient powder.

As described above, all of the conventional detection methods have only a single function, and it has been difficult to stably, quickly, and accurately detect the state of the molten metal level. In addition, many equipment and devices are congested and arranged in a narrow space near the mold as described above, and in a high-heat, multi-dust environment, the condition of the molten metal surface under such bad conditions is reduced. In fact, no practical detection device that can perform detection comprehensively and with high reliability has yet emerged. For this reason, conventionally,
It is common for a dedicated and skilled worker to monitor the level of the molten metal and determine the level of the molten metal based on his / her past experience and intuition.

[Problems to be solved by the invention]

As described above, for the nearby system including the mold, the balance of the system is lost, and the fluctuation of the water level, boiling,
Conventionally, when a level error such as powder shortage occurs, a worker monitoring the level detects the level of the level error and immediately takes appropriate action based on the detection result. I was Since the action for balancing and stabilizing the system is required to be quick and accurate, in the above-described conventional method, a dedicated and skilled operator must perform the action, and the labor saving around the system is greatly reduced. It was online. Nevertheless, there are large individual differences among workers, detection delays and erroneous detections often occur, resulting in variations in slab quality and, in extreme cases, delayed operation actions.
Sometimes connected to BO.

The present invention is intended to drastically solve the above problem, and has as a first object to accurately and promptly detect the above-mentioned mold level abnormality in a mold, and to perform the mold level abnormality based on the detection result. It is a second object of the present invention to provide a method for effectively preventing the occurrence of a continuous casting operation by providing a stable method.

[Means for solving the problem]

The present invention for solving the above-mentioned problem is provided with a pair or plural pairs of image sensors for detecting the state of the molten metal level, at positions opposed to each other with the injection nozzle therebetween, above the continuous casting mold in which the injection nozzle is disposed at the center. Then, the input screen of the hot water surface condition input from time to time from each of the image sensors, and binarized by a reference threshold to distinguish between a bright part and a dark part,
The area ratio Rn of the bright portion is determined for the molten metal surface portion in each image sensor field of view, and then the change rate Dn per unit time of the bright portion area ratio Rn is determined. It is characterized in that an abnormal state of the molten metal level is detected from the correlation between Rn and / or the change rate Dn and the abnormal state of the molten metal level. Further, in the method for detecting a molten metal level condition described above, a change rate Dn in each of the molten metal parts facing each other with the injection nozzle interposed therebetween, and a preset reference value of the change rate Dn for each molten metal part. In comparison, when both the change rates Dn sandwiching the injection nozzle both exceed the reference value of the previous value, it is determined that the boiling is performed, and when the change rate Dn of only one side exceeds the reference value, it is determined that the spring is one-sided. It is characterized by detecting an abnormal condition of the molten metal surface.

In addition, the hot water surface in each image sensor field of view,
Subdivided into set areas, the bright area ratio Rnn in each divided area and the rate of change Dnn per unit time of this bright area ratio Rnn are determined, and then compared with a reference value preset for each of the divided areas. When the bright area ratio Rnn exceeds the reference value, and the change rate Dnn does not exceed the reference value, it is determined that the powder is insufficient, and the powder insufficiency and the location of the occurrence of the powder abnormality are detected. It is characterized by the following.

In addition, depending on the level of the molten metal level detected based on the above-described method, one or two of casting speed control, flow rate control of gas blown into the injection nozzle, flow rate control of molten steel injected into the mold, and powder spraying control. The above is implemented to eliminate the above-mentioned molten metal level abnormality.

[Operation and Examples]

Hereinafter, a specific configuration of the present invention will be described with reference to the drawings showing examples.

FIG. 1 is a configuration diagram showing an example of the overall configuration based on the present invention. In FIG. 1, 1 is a mold, 2
Is a cast slab, 3 is molten steel, 4 is a solidified shell formed by cooling the molten steel 3, 5 is a powder sprayed in the mold 1, and is mainly composed of an unmelted powder layer 5a and a molten powder layer 5b. Have been. 6 is an injection nozzle, 7 and 7a are controllers for controlling the flow rate of molten steel. In this embodiment, SN is used. 8 and 8a are blow gas flow rate control devices into the injection nozzle, 9 and 9a are casting speed control devices for the slab 2,
10 is a tundish.

Reference numeral 110 denotes a liquid level abnormality detecting device, and 170 denotes a liquid level abnormality preventing device. Anomaly level detector 110
Is an image sensor 11 installed above the level of the molten metal in the mold 1 at a position opposite to the injection nozzle 6 and an input diagram screen of the level of the molten metal input from the image sensor 11 from time to time as described below. An arithmetic processing unit 12 that performs an appropriate processing operation and detects an abnormal level of the liquid level such as one-sided springing, boiling, powder shortage, and the like, and that is performed to stabilize the level of the liquid level based on the abnormal state detection, which will be described later. Control device that instructs various actions and issues control commands to each device
It is composed of 13 and.

In the present embodiment, the image sensor 11 is provided in a pair at positions opposed to each other with the injection nozzle 6 interposed therebetween. However, due to the size of the slab to be cast, the entire range of the mold surface in the mold is controlled by the pair of image sensors. If it is not possible to fit within the field of view, two pairs or two or more pairs may be provided.

The device for preventing abnormal water level 170 includes a powder dispersing device 16, an articulated support arm 15 that supports the powder dispersing device 16 at the tip, a supply device 17 that supplies the powder 5 to the powder dispersing device 16, and the support arm 15. Drive device 15 to be driven
0, a powder dusting control device 14 that drives and controls the powder dusting device 16 and the driving device 150 of the support arm 15 based on a signal indicating a powder shortage occurrence and its occurrence position detection signal. The powder dispersing device 16 has a square storage tank 16a for storing a set amount of powder 5, and the storage tank 16a is configured to be openable to the bottom or rotatable as described later. The support arm 15 is configured such that a plurality of arms (in this embodiment, two of 15a and 15b) are connected via arm driving devices 150a to 150c having a built-in rotation shaft, and the rotation shaft is freely used as a rotation fulcrum. Rotate. In addition, a lifting drive device 150d and a lifting frame 150d provided at the tip thereof
_The powder spraying control device 16 raised and lowered by ₁ and supported at the tip thereof via a connection portion 15C, specifically, the storage tank
The 16a can be freely moved forward and backward and raised and lowered on the molten metal surface in the mold 1.

In the present embodiment, the support arm 15 is of the horizontal connection type, but any type may be used as long as the powder spray 16 can move freely in the mold 1. However, according to the experience of the present inventors, the above-mentioned horizontal articulated type is advantageous because the space near the mold 1 and the tundish 10 is generally very tight. Also, the support arm 15
The combination and the number of the driving devices 150 may be appropriately determined depending on the applied space so that an effective operation can be performed.

The storage tank 16a is moved to a predetermined position in the mold 1 based on a command from the powder spraying control device 14, and the bottom of the storage tank 16a is opened or the storage tank 16a is rotated, so that the powder 5 is removed. Can be sprayed. In the present embodiment, the support device 15 and the supply device 17 for the powder 5 are attached to a gantry 18 for mounting the tundish 10, but the above device is appropriately or wholly or partially, for example, , Articulated support arm 15,
In addition, the driving device 150 for driving the support arm 15 may have a structure capable of self-running.

Next, a method for detecting a molten metal level condition according to the present invention will be described.

The brightness of the molten metal surface in the mold 1 changes from a dark state in which the front surface is covered by the unmelted powder 5a to the injection nozzle 6.
The gas blown into the mold 1 emits a large amount of gas onto the surface of the molten metal in the mold 1, or a very bright state such as a boiled state covered by the molten powder 5 b that appears due to the strong fluctuation of the molten metal. Extensive. Also,
Mold vibration, blown gas discharge, powder melted layer
The brightness of the molten metal surface constantly varies depending on the appearance of 5b and the like. The present inventors have paid attention to the fluctuation state of the brightness of the molten metal surface, and studied the correlation of the fluctuation state with the abnormality of the molten metal level. First, in order to accurately detect the brightness of the molten metal surface, the image sensor 11 was set at a position facing the molten metal surface above the mold 1. Since the injection nozzle 6 is disposed at the center of the mold 1 as described above, it is extremely difficult to view the entire mold 1 with one image sensor 11, and the present invention is directed to a high-brightness molten metal surface. Cannot be detected accurately. Thus, at the opposing site across the injection nozzle 6,
In the case where the entire range of the molten metal surface in the mold cannot be included in the field of view with a pair of image sensors due to the size of a pair or a slab to be cast, two pairs, or two or more pairs are set. Incidentally, the image sensor 11 can be applied to any camera, such as a camera using a vidicon tube generally used in a video camera, but as a result of various studies, the present inventors have found that Because the brightness inside the image fluctuates over a wide range and constantly, the size of the image can be easily reduced due to the image burn-in phenomenon, the afterimage phenomenon, and the necessity of miniaturization due to the extra space above the mold. A CCD camera using a solid-state imaging device that is advantageous against phenomena and afterimages was used. In addition, this CCD
The camera was iris-adjusted to be almost saturated during boiling.

2 and 3 are images of the molten metal surface taken by the CCD camera described above, and are images showing the state of the molten metal surface in the mold on one side with the injection nozzle interposed therebetween. FIG. FIG. 3 is an S-side image. Note that the injection nozzle is always in a bright state during casting and has nothing to do with the detection of an abnormality in the molten metal level. Therefore, the camera is installed so as to be out of the field of view of the camera. In FIGS. 2 and 3, 1
a ₁ and 1a ₂ denote the wall surfaces of the mold 1 that are in contact with the cast slab 2 or the powder 5, and 5a ₁ and 5a ₂ denote the unmelted powder of the powder 5 that is being sprayed. An image 19 or 20 as shown in FIG. 2 and FIG. 3 is input to the arithmetic processing unit 12, and an image in a frame corresponding to the mold surface shown by hatching in FIG. 2 and FIG. For the image 19a or 20a, a process for detecting a surface level abnormality of an input image as described later is performed. Here, in the present invention, the region of the image 19a or 20b corresponding to the mold surface in the mold does not necessarily have to be strictly along the boundary between the mold 1a ₁ or 1a ₂ and the mold surface 19 or 20 in practical use. Absent.

The present inventors have conducted various investigations on the correlation between the image and the abnormal state of the molten metal surface as follows. First, for each pixel constituting the input image, the brightness when the unmelted powder layer 5a is covered is dark, and the brightness when the fused powder layer 5b appears is bright, that is, A reference threshold value was set between the luminance of the unmelted powder layer 5a and the luminance of the molten powder layer 5b, and the input image was subjected to a light / dark binarization process. FIGS. 4 and 5 show another example of the N-side image and the S-side image, respectively.
This shows a state in which the molten powder layer 5b appears in the unmelted powder layer 5a in the area 0a. FIGS. 6 and 7 show binarized images 19a and 20b obtained by binarizing the input image of the molten metal surface state inputted based on FIGS. 4 and 5, respectively, by the above method. Yes, the molten powder layer 5b portion is a bright portion 50b, and the other unmelted powder layer 5b is a dark portion 5b.
It is displayed as 0a.

Next, the bright part obtained by binarization as described above, that is, the area of the molten powder layer 5b (hereinafter referred to as the bright part area)
And the ratio of the area of the entire molten metal surface portion (the total area of the molten powder layer 5b portion and the unmelted powder layer 5a) in the camera visual field corresponding to 19a and 20a, that is, the bright portion relative to the molten metal surface portion in the camera visual field An area ratio (a light area ratio referred to in the present invention, hereinafter simply referred to as an area ratio Rn) was determined, and a time change of the area ratio Rn was examined. Here, the reason for using the area ratio is from various investigations, the area of 19a or 20a corresponding to the target molten metal part is not always the same area due to the change of the slab size to be cast, etc. In addition, there is also a variation in the area of each of the molten metal surface abnormal phenomena and the same molten metal surface abnormal phenomenon, and it is difficult to stably and quantitatively detect the molten metal surface abnormal phenomenon. The area ratio of the area of the bright portion in the molten metal surface to the region of 19a or 20a corresponding to the portion was calculated. However, for the area of 19a and 20a corresponding to the inside of the molten metal surface,
If the level abnormality detection process is always possible under the same conditions, the content described below is not the area ratio,
It goes without saying that it is possible to use the absolute value of the area.

FIG. 8 shows an example of the above-mentioned investigation at the time of stable casting.
The vertical axis is the area ratio Rn, and the horizontal axis is the elapsed time.

In this embodiment, a skilled worker simultaneously monitors the condition of the molten metal level, and when the powder level is insufficient among the abnormalities of the molten metal level, the powder is sprayed at the judgment of the worker by the arrow A in FIG. Thus, it can be seen that the area ratio Rn increases with the passage of time and rapidly decreases at the same time as the powder is sprayed.

In FIG. 8, the area ratio R as shown by arrows P and Q
The fine fluctuation of n is due to the vibration of the mold, and the relative rise of the molten metal surface when the mold 1 descends.
The molten powder layer 5b appears and has a maximum as indicated by P,
Conversely, when the mold 1 rises, the molten powder layer 5b is hidden,
Since the unmelted powder layer 5a occupies a large amount, it has a minimum as indicated by Q. Similarly, the discharge and disappearance of the gas blown into the injection nozzle due to the vibration of the mold 1 from the molten metal surface corresponding to the vibration of the mold also contributes to P and Q. That is, the area ratio Rn fluctuates finely due to the fluctuation of the molten metal surface caused by the vibration of the mold or the like. As a method for accurately detecting the level of the molten metal, fluctuations such as P and Q caused by the vibration of the mold become disturbances, which is not preferable in the processing for detecting an abnormality in the molten metal level.
Therefore, it is necessary to remove the influence of the disturbance. A method of calculating the time-series average of the instantaneous value of the bright area over a preset time can be considered as a method for removing the time. However, depending on the length of the time-series time, this method requires complicated processing. In addition, it is necessary to extend the time of the time series for calculating the average to a certain extent (at least longer than the vibration period of the mold) in order to properly remove the disturbance. This is disadvantageous for the purpose of detecting an abnormal condition of the molten metal surface. For this purpose, in the present embodiment, by taking the logical product of the binarized images 19b and 20b during the time corresponding to the vibration cycle of the mold 1, the bright portion in the periodic or sudden hot water surface image is obtained. Was removed. FIG. 9 shows the processing result obtained by taking the logical product of the parts corresponding to FIG. 8, but the small fluctuations as described above are scarcely observed, and the disturbance is sufficiently removed. The time change of the ratio Rn is found stably.

By the above method, disturbance was removed, and the time change of the area ratio Rn in the mold during casting was measured. FIG. 10 shows an example of the measurement result of the area ratio Rn. In FIG. 10, two graphs are written on the upper and lower sides. This is the result of the arithmetic processing by the above method based on the input image from the camera installed at the position opposite to the injection nozzle, that is, the N side and the S side. The upper graph is the processing result of the N-side image, and the lower graph is the processing result of the S-side image. In FIG. 10, arrows X, Y, and Z indicate the timing at which the molten metal surface abnormality such as powder spraying, boiling, and single springing occurs, and the subscripts indicate the N side, the S side, and the number of times from the start of measurement. In this embodiment, at the same time, a skilled worker monitors the condition of the molten metal level and, if an abnormality occurs, performs an action to stabilize the abnormal level. Arrow X is an example when powder shortage occurs, and powder was sprayed at arrow X at the judgment of the worker. Thus, it can be seen that the area ratio Rn increases with the passage of time and rapidly decreases at the same time as the powder is sprayed.
Similarly, for the arrows Y and Z, when the boiling and the single-sided spring occur, the casting speed control, the flow rate of the gas blown into the injection nozzle, the flow rate control of the molten steel injected into the mold, And any one or two or more of powder spraying were implemented, and the above-mentioned abnormalities of the molten metal level were eliminated. Here, the timing of elimination of the molten metal level is determined by the area ratio
This is the timing when Rn is rapidly decreasing. From FIG. 10, the correspondence between the abnormal phenomenon occurring in the molten metal surface and the time change of the area ratio Rn is clear. However, although the tendency as an abnormal phenomenon can be qualitatively understood, the level of the area ratio Rn at each timing is slightly different and is not stable and cannot be clearly detected. Therefore, further quantitative evaluation is required. Then, the change rate Dn per unit time of the area ratio Rn was investigated. FIG. 11 is a diagram showing the time change of the change rate Dn, with the time axis of the horizontal axis being the same timing as in FIG. However, in FIG. 11, the rate of change at the timing of elimination of the molten metal level abnormality, that is, the negative rate of change, is a decrease in the area ratio Rn due to the powder spraying, and therefore is meaningless in the sense of detecting an abnormal situation. Not shown.

First, detection of the occurrence of one-sided springing and boiling is described in
The relationship between the area ratio Rn and the rate of change Dn in FIG. 10 and FIG. 11 became clear. That is, for the area ratio Rn, rather than relatively variations stable as that level Y _N1, Ys ₁ and Y _N2, Ys _2, but it may become the same kind of level as powder insufficient area ratio Rn The rate of change Dn is 150% / min at the maximum when powder deficiency occurs, whereas it shows a large rate of change exceeding 300% / min when both phenomena occur. Then, when a single spring occurs, Zs ₁ and Zs ₂
As described above, only one side of the opposing position of the injection nozzle shows a large positive change rate at the same time on both sides of the opposing position of the injection nozzle during boiling. Therefore, by comparing the change rate Dn of the area ratio Rn at the opposing position, it has been found that it is possible to detect the occurrence of one-sided springing and boiling. Here, with respect to boiling, when it occurs, the area ratio of the corresponding area varies relatively due to the flame of the blown gas or the like. That, and if the area ratio Rn is saturated with 100% as the arrow Y _N1, Ys _1, it may not fully 100% as shown by an arrow Y _N1, Ys _2. If the area ratio Rn is less than 100%,
The phenomenon that the surface of the water is wavy by mild boiling,
This corresponds to the so-called rip ring phenomenon. Regarding the rippling phenomenon, the prevention method for eliminating it is the same as when boiling occurs.Therefore, there is no need to distinguish it from boiling, but in the case of distinction, when the occurrence is detected. Can be detected depending on whether the value of the area ratio Rn is saturated.

Next, regarding the detection of an abnormality related to powder, that is, the powder shortage, as described above, in FIGS. 10 and 11, the change rate Dn of the area ratio Rn is, for example, indicated by an arrow.
Boiling (lip ring) arrows like X _N8 and Xs ₆
The level may be similar to Y _N2 , Ys ₂ , but the area ratio
Since the rate of change Dn of Rn is clearly as small as 150% / min at most, to detect powder shortage, the area ratio Rn
And the change rate Dn. However, as described above, the area ratio R in the case of powder shortage is
The levels of both n and the change rate Dn vary relatively and are not stable. This is because the area in the surface of the molten metal that causes powder shortage is partially, not entirely, that is, from the injection nozzle side to the short side in the mold on each side of N and S, The reason is that, by changing the area where the shortage occurs in the width direction within the mold, a change in the bright portion corresponding to the area of the shortage area is indicated. Therefore, regarding the detection of the powder shortage, it is necessary to quantitatively detect the shortage position and the shortage state with respect to the molten metal surface in the mold. Therefore, the image 19a or 20a of the mold surface in the mold
Was divided into areas.

Here, the area is divided according to the form in which the powder shortage state occurs. This idea is explained below. After the powder is melted, it is consumed by flowing between the mold wall and the slab. Therefore, as a phenomenon usually occurring on the molten metal surface, there often occurs a case where powder shortage occurs along the mold wall. However, in general, the form of the powder is in the form of powder, crow, etc., and each of them has a repose angle of about 30 to 60 °, so that the sprayed powder may not stay in one place. Absent. Therefore, the powder in the central portion in the thickness direction in the mold can move in all directions in the plane of the molten metal surface due to the oscillation of the molten metal surface due to the vibration of the mold in both the unmelted state and the molten state. Here, regarding the movement form of the powder on the mold surface,
It is determined by the swing of the molten metal surface, the mass balance of the whole powder on the molten metal surface, the heat balance in the molten state of the powder, and the like. Therefore, there may be a case where a powder shortage state occurs in the central portion in the thickness direction in the mold. Specifically, as a result of investigations by observation of the surface of the molten metal, etc., there is a slight variation, but the speed of movement in the thickness direction of the powder is generally about the same to about four times the speed in the width direction. Turned out to be. There are various powder spraying methods. In any of these methods, the powder is not sprayed at points, but naturally sprayed with a certain spray area. From the above, for the hot water portion to be targeted, increasing the number of divisions indiscriminately delays the processing speed for checking the water level abnormality, slows down the detection, and delays the action, for example, It is not efficient and meaningless because the probability of operational troubles such as restrictive BO increases. Therefore, in consideration of the above-described powder movement form, it is sufficient that the division is within about 3 divisions in the thickness direction and about 1/4 to about the same as the division width in the thickness direction in the width direction.

From the above, FIG. 2 and FIG.
19a in FIG., The area corresponding to the mold molten steel surface portion corresponding to 20a, Figure 12, 19a ₁ through 19a ₅ as shown in FIG. 13,
Until 20a ₁ through 20a _5, the injection nozzle N, and each 5 divided for S side. The dimensions of the area on each side are the same, the length in the width direction of the entire area 19a, 20a on each side is 500 mm, the length in the thickness direction is 250 mm, and the length in the width direction of the divided area is 100 mm. Here, as in the previous survey,
FIGS. 14 and 15 show the measurement results of the area ratio Rnn, with the time axis of the horizontal axis being the same timing as in FIG. 10, and FIGS. 16 and 17 show the measurement results of the change rate Dnn. There are five graphs in each of FIGS. 14 to 17, which are the measurement results of the areas corresponding to FIGS. 12 and 13, that is, 19a from the top in FIGS. 14 and 16. ₁ through 19a _5, Figure 15, for the FIG. 17 shows the results of 20a ₁ through 20a ₅ from the respective. As described above, the correspondence between the phenomenon occurring in the scene and the time change of the area ratio Rnn and the change rate Dnn is clear. And by dividing the screen, about the detection of powder shortage,
It is clear that stability and quantitative detection for each area are possible. That is, first of all, when powder shortage occurs, when one-sided springing or boiling occurs,
Although the area ratio Rnn reaches a high level of 80 to 90% or more,
As described above, even when the screen is divided, when the one-sided spring and the boiling occur, the change rate Dnn is 300% / m.
In the case of powder shortage, it is as small as 150% / min at the maximum, while it shows a large change of more than in. Therefore, it is possible to distinguish between the powder shortage, the single spring, and the boiling phenomenon. Next, when powder shortage occurs,
As shown in Fig. 11, the situation where the level of the area ratio Rn and the variation rate Dn were unstable and unstable, but the screen was divided, the situation of powder shortage in each area is clearly stable That is, it has become possible to detect it. Specifically, when a powder shortage condition occurs in one area, as seen after 3, 15, 20, 25 minutes in FIG. 14 and 3, 6 minutes in FIG. For one area, the bright area ratio Rnn increases. Regarding the detection of the powder shortage state, for each area, the reference level of the area ratio Rnn and the change rate Dnn is set, and the powder does not exceed the base level of the change rate and depends on whether the reference level of the area rate is exceeded. Shortage can be detected. When the above-mentioned state occurs over a plurality of areas, as described above, as seen after the lapse of 2, 5, 15, 23 minutes in FIG. 14, and after the lapse of 2, 5, 21, 25 minutes in FIG. Similarly, the area ratio Rnn increases for each area.
Also in this case, the area ratio Rn for each area
By setting a reference level for n and a change rate Dnn, the powder shortage can be detected by determining whether or not the reference rate of the area rate does not exceed the reference level of the change rate. As the reference level must be set according to the actual operation situation, it is necessary to set the reference level for each case according to the size of the slab to be cast and the environment around the mold. There is. Similarly, the divided areas may have the same value for at least a plurality of areas, or may have different values. In the present embodiment, by setting the reference level of the area ratio to be 70% and the reference of the change rate level to be 150% / min, it was possible to detect single spring, boiling, and powder shortage. However, it is necessary to appropriately set the reference level according to conditions such as the overall brightness in the mold, that is, the size of the injection nozzle, the length of the injection nozzle from the molten metal surface, the cross-sectional size of the slab to be cast, and the like. Therefore, the present invention is not limited to this embodiment.

As described above, it is possible to stably and quantitatively detect the state and the position related to the powder shortage. Here, even in the state where the screen is divided, the detection of the boiling and the single-spring is performed with respect to the area ratio of each area.
Needless to say, it can be detected by comparing the rate of change Dnn of Rnn and the areas facing each other across the injection nozzle.
However, since the detection of one-sided springing and boiling must be performed in the shortest time, the detection is usually performed by the above-described method without dividing the screen for each area of one side of the injection nozzle. However, this does not apply to the case where there is no problem such as no detection delay even if the screen division is performed in relation to the operation status and the detection time. In this way, it has become possible to automatically and stably and quantitatively detect powder spraying, one-sided springing, boiling, and an abnormal phenomenon of molten metal level.

As for the automatic detection of the abnormal level phenomenon described above, the image information of the image sensor installed on the mold level is detected by image processing, and in addition to this, embedded in the mold wall. By incorporating the temperature information of the thermocouple, it is possible to detect an abnormal level of the metal surface for more stable operation. That is, a plurality of rows in the casting direction, and a plurality of thermocouples in the mold circumferential direction, by embedding at a certain depth from the mold surface, to measure the temperature at the embedding point, from the embedding situation heat flux at the embedding position, Then, the heat removal amount of the solidified shell of the cast slab is calculated, the heat removal state in the circumferential direction of the mold, that is, the powder inflow state is monitored, and the abnormal state in the mold is detected. For example, when the heat removal amount in the circumferential direction of the mold is abnormally varied, it is determined that the powder is not flowing sufficiently uniformly, and the powder is sprayed on a portion corresponding to the circumferential portion determined to be insufficient. By changing the taper of the mold, changing the casting speed, or the like, it is possible to eliminate the abnormality.

Next, a description will be given of a method for preventing a molten metal level in a sense of stabilizing immediately after detecting a state of a molten metal level.

First, by the method for detecting the abnormal state of the molten metal,
A method for preventing occurrence of occurrence of boiling will be described.

When a boring rig occurs, the flow rate of the molten steel relatively decreases because the volume of the blown gas occupying the flow path of the molten steel increases. Therefore, it is necessary to adjust the casting speed corresponding to the molten steel flow product at that time. At the same time, the flow rate of molten steel is adjusted in order to suppress fluctuations in the level of molten steel in the mold. Then, the flow rate of the blown gas is adjusted in accordance with the above state to eliminate boiling, and when a powder shortage state occurs, the powder is sprayed according to the shortage position. However, if the stabilization occurs in any of the prevention stages, the adjustment may be stopped at that stage. After stabilization, the operation is gradually returned to the operating state when the abnormality occurred. Next, when a single spring occurs, the flow path of the molten steel is often disturbed by deposits such as Al ₂ O ₃ precipitated in the flow path of the molten steel, so the flow rate of the molten steel is adjusted in small increments. When the SN is used for adjusting the flow rate, one-sided springing is eliminated by trying to change the state of the attached matter by operating the SN in small increments or adjusting the flow rate of the blowing gas. At that time, the casting speed may be adjusted in some cases in order to suppress the fluctuation of the molten steel level. Also, if there is a powder shortage condition,
Spray powder according to the missing position. In the present invention, for the prevention method when automatically detecting the abnormality of the molten metal level by the method of detecting the abnormal level of the molten metal level, an instruction to perform an action to stabilize the level of the molten metal level based on the detection of the abnormal state is indicated.
The control device 13 to control issues an alarm, and based on the alarm, the worker takes an appropriate action manually, or
From the control device 13, a casting speed control device 9a, a blowing gas flow control device 8a, a molten steel flow control device 7a, a powder spraying device
A control signal may be directly sent to the control unit 16 to perform control automatically. When such automatic control is performed, the casting speed, blown gas flow rate, or molten steel flow rate is reduced to a set value determined by operating conditions such as casting width and casting speed when an abnormality occurs, thereby automatically detecting an abnormality in the level of the molten metal. If it is prevented, it gradually returns to the operating condition at the time of occurrence of the abnormality, and if it is not prevented, it is further reduced to the set value determined by the operating condition at that time, and the same control is performed. . As described above, when the occurrence of one-sided springing and boiling is detected by the above-described method for detecting an abnormal level of the liquid surface, an action for stabilizing the abnormal state of the liquid level is performed.

Next, a description will be given of a preventive device when the powder shortage is detected by the above-described method for detecting an abnormal state of the molten metal level.

As described above, the powder shortage is detected by spraying the powder on the area corresponding to the divided area because the molten metal surface is divided into the areas. As described above, the conventional powder dispersing apparatus has many problems such as clogging of the pipes, and therefore, in the present invention, as shown in FIG. 18, a powder dispersing unit in which a powder supply unit and a powder dispersing unit are separated. The device. Numeral 16 is a powder dispersing device as described above, which is a square-shaped storage tank 16a for storing a set amount of powder 5 corresponding to the divided area, supports the storage tank 16a, and includes the multi-joint type support arm 15 (this embodiment). When the support arms 15a and 15b of the example are collectively referred to, they are simply referred to as the support arms 15).
It is composed of

The support arm 15 includes a plurality of support arms 15 as described above.
a, 15b are arm driving devices 150a to 150c having a built-in rotation axis.
Are connected to each other, and freely rotate about the rotation shaft as a rotation fulcrum.
And a vertically movable structure by lifting frame 150d _1, arm drive device 150a~150c and elevation drive unit 150d
, The support frame 16b supported by the distal end of the support arm 15 via the connecting portion 15c can be freely moved forward and backward and raised and lowered on the molten metal surface in the mold 1.

The powder dispersing device 16, specifically the storage tank 16a, is supplied with a set amount of powder 5 from a supply device 17 including a hopper 17d, valves 17a, 17b, and a supply nozzle 17c, and controls to give a command such as a powder shortage position. Based on a control signal from the device 13, the control device 14 is operated, and a driving mechanism of the powder spraying device 16 and a driving device of the support arm 15 described below.
By driving and controlling 150, the powder is sprayed on the area corresponding to the powder shortage position detected by the above-described method for detecting an abnormal level of the molten metal. The control device 13 detects the powder shortage in the case where the powder shortage state is detected at the same time in a plurality of areas, for example, after the lapse of 5,26 minutes in FIGS. 14 and 15 described above. By assigning priorities to the areas, it is also possible to provide a function of performing efficient powder application.

FIG. 19 is a partial structural view showing an example of a storage tank 16a for storing a set amount of powder 5 used in the present embodiment, the storage tank 16a for storing powder, a support frame 16b for supporting the storage tank 16a, Bottom lid 16c, bottom lid that opens when powder 5 is sprayed
It comprises a drive motor 21a for driving the opening and closing of 16c and a rotating shaft 21b. Here, a storage tank 16 for storing the powder 5 is provided.
Regarding the capacity of a, first, the area was set to be equal to or smaller than the divided area in consideration of the spread of powder when sprayed according to the size of the divided area. Next, storage tank 16
The height a determines the capacity of the storage tank 16a, and the powder supply speed determined from the operation speed of the powder spraying device 16 and the capacity of the cup needs to be equal to or higher than the maximum powder consumption speed in the operation. There is. Therefore,
In this embodiment, the maximum consumption rate of the powder in the operation is 2.4 kg / min, the powder supply rate per operation is 20 seconds,
Since the specific gravity of the powder is 0.8, the required capacity of the cup 16a is 1, and the size of the storage tank 16a is determined from the area of the divided area as shown in FIG.
Considering the angle of repose at the time of supply to storage tank 16a from
The width and height were each 100 mm x 100 mm x 120 mm. still,
If the size of the storage tank 16a is not sufficiently large due to equipment restrictions and the maximum powder consumption speed is significantly higher than the supply speed of the powder spraying device 16, a plurality of spraying devices 16 are used.
For example, each of the opposite areas sandwiching the injection nozzle 6 may be covered, and a total of two powder sprayers may be used. Further, the powder supply device 17 has an angle from the hopper 17d to the supply hole 17c to the storage tank 16a such that the powder falls naturally. Then, regarding the adjustment of the fixed amount of supply from the hopper 17d to the storage tank 16a, the upper valve 17
a, can be adjusted by changing the pipe diameter and length of the pipe between the lower valve 17b, when supplying, the procedure of closing the lower valve 17b, opening the upper valve 17a, closing the upper valve 17a, opening the upper valve 17b After that, the powder in the storage tank 16a waiting below the supply nozzle 17c is supplied. Also, in the operation, when using a plurality of types of powder, by providing a hopper number corresponding to the type, the upper valve 17a, or share the supply nozzle 17c and thereafter, by providing a collection line to each hopper, Response is possible. Incidentally, as to the method of spraying the powder into the mold, in the present embodiment, a spraying means using a method in which one bottom cover 16c is opened is used, but there is no problem even if it is constituted by a plurality of bottom covers. Or spraying by rotating the storage tank 16a itself in the direction of arrow R1 or R2 as shown in FIG. 21, or as shown in FIGS. 22 and 23,
Spraying by turning over the side plate 16d and rotating the storage tank 16a in the direction of arrow R1, or by rotating or sliding the bottom lid 16c in the direction of arrow R3 or R4 as shown in FIG. You may make it. As described above, the powder is sprayed to the area corresponding to the powder shortage position detected by the method for detecting an abnormal level of the molten metal, using the powder spraying device 16.

Using the above-described method for detecting an abnormal state of the molten metal surface, the method for preventing the abnormally molten metal surface, and the device for preventing insufficient powder, the operation was performed under the casting conditions of a slab section size of 250 mm × 1250 mm and a casting speed of 1.6 m / min. Stable operation was possible without any intervention by the elderly. In other words, when continuously casting different ladle, if the ladle exchange changes the weight of molten steel in the tundish, and the level of the molten metal surface such as boiling and one-sided spring occurs, the abnormal situation can be detected quickly. Stabilize and immediately detect powder shortages,
I was able to spray powder. Also, regarding the quality of the cast slab, no surface defect or the like was generated at all, and extremely good results were obtained.

〔The invention's effect〕

As described above, the provision of the present invention makes it possible to automatically detect and prevent an abnormal situation of the mold surface in a mold. Therefore, it has become possible to reduce the force around the mold, which has conventionally been a bottleneck for labor saving, and it has become possible to obtain a stable continuous casting operation with less variation by an operator and a good slab quality. .

[Brief description of the drawings]

1 is an overall structural view showing one embodiment of the present invention, FIGS. 2 and 3 are images taken by a camera installed above a mold, and FIGS. 4 and 5 are photographed images. FIGS. 6 and 7 are binarized images of the images of FIGS. 4 and 5, FIG. 8 is a graph of the time change of the area of the bright part, and FIG. 8, a graph excluding the disturbance of the graph of FIG. 8, FIG. 10 is a graph of a time change of a light area ratio in a continuous casting operation, and FIG. 11 is a graph of a time change of a light area ratio in a continuous casting operation. Graphs, FIGS. 12 and 13 are examples of screen division, FIGS. 14 and 15 are graphs of bright area ratios corresponding to the respective divided areas, corresponding to FIG. 10, FIG. And FIG. 17 shows the change rate per unit time of the bright area ratio corresponding to each divided area, corresponding to FIG. Rough, FIG. 18 is a structural view showing one embodiment of a powder spreading device of the present invention, FIG. 19 is a partial structural view showing one embodiment of a powder spreading jig of the present invention, FIG. 20 is a powder FIG. 21, FIG. 22, FIG. 23 and FIG. 24 are views showing another example of a powder spraying storage tank. 1: Mold, 2: Slab 3: Molten steel, 4: Solidified shell 5: Powder, 5a: Unmelted powder 5b: Melted powder 50a: Binarized unmelted powder part 50b: Binarized molten powder part 6: Injection nozzle 7,7a: molten steel flow control device 8,8a: blown gas flow control device 9,9a: casting speed control device 10: tundish 11: image sensor 12: arithmetic processing device, 13: control device 14: powder spray control Device 15, 15a, 15b: Articulated support arm 15c: Connection part 150, 150a, 150b, 150c: Support arm drive 150d: Support arm elevating drive 150d ₁ : Elevating frame 16: Powder spreading device, 16a: Storage tank 16b : Support frame, 16c: Bottom cover 17: Powder supply device 17a, 17b: Valve, 17c: Supply nozzle 17d: Hopper 18: Tundish mount 19, 20: Image from camera 19a, 20a: Image signal 19a of molten metal _{1 ~19a 5, 20a 1 ~20a 5} : melt-surface portion of the divided areas 19b, 20b: binarized image 21a: drive motor, 21 b: Rotating shaft 110: Surface level detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-129126 (JP, A) JP-A-63-101048 (JP, A) Actually open Sho-63-11150 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) B22D 11/16 104 B22D 11/18 B22D 11/10

Claims (4)

(57) [Claims] Claims: 1. At a position above a continuous casting mold in which an injection nozzle is arranged at a central portion, and opposed to each other across the injection nozzle,
A pair or a plurality of pairs of image sensors for detecting the state of the bath surface are installed, and the input image of the bath surface state input from time to time from each of the image sensors is binarized by a reference threshold to distinguish between a bright portion and a dark portion. At the same time, the area ratio Rn of the bright part with respect to the molten metal surface in each image sensor field of view
Then, the change rate Dn per unit time of the light area ratio Rn is obtained, and the light area ratio Rn and / or the change rate Dn set in advance, and the correlation between the change rate Dn and the abnormal state of the liquid level, A method for detecting an abnormal condition of a molten metal level in a continuous casting mold, wherein the abnormal condition is detected. 2. A comparison is made between a change rate Dn at each of the opposed metal surfaces with the injection nozzle interposed therebetween and a preset reference value of the change rate Dn for each of the metal surfaces, and the injection nozzle is sandwiched. If both of the change rates Dn exceed the reference value, boiling is performed, and if the change rate Dn of only one side exceeds the reference value, it is determined that the spring is one-sided, and an abnormal state of the molten metal level is detected. 2. The method for detecting an abnormal state of a molten metal surface according to claim 1, wherein 3. A hot water surface in each image sensor field of view is subdivided into set areas, and a bright area ratio Rnn and a change rate Dnn of the bright area ratio Rnn per unit time in each divided area are determined. Calculated, and then compared with a reference value preset for each of the divided areas.If the bright area ratio Rnn exceeds the reference and the change rate Dnn does not exceed the reference value, it is determined that the powder is insufficient. 2. The method according to claim 1, further comprising the step of detecting a powder shortage and a position of occurrence of the powder level abnormality. 4. A control of a casting speed, a flow rate of a gas blown into an injection nozzle, and a flow rate of molten steel injected into a mold in accordance with an abnormal condition of a molten metal level detected according to claim 1, 2 or 3. A method for preventing a molten metal level, wherein one or more of the control and the powder spraying control are performed to eliminate the molten metal level.