JPH04327354A - Detection of molten metal surface level in twin roll type continuous caster - Google Patents

Abstract

PURPOSE:To quickly detect the molten metal surface level in high precision in a twin roll type continuous caster. CONSTITUTION:By watching what the height variation of molten metal surface is quickly changed according to the molten metal quantity, picture of the prescribed range to aim at boundary part 8 between a weir plate 3 and the molten metal 7 in the twin roll type continuous caster, is taken by a camera and pixel data in the range of a window 10a in the picture of a video taken by the camera are binarized into the molten metal part and the weir plate part and also, by obtaining the ratio of the pixel data in the molten metal part to the pixel data in the range of this window 10a, the height of molten metal surface level can be detected from variation of this ratio.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is particularly concerned with a dual roll system that quickly and accurately determines the molten metal level by binarizing the brightness of pixel data of an image in a predetermined range at the boundary between the weir plate and the molten metal. The present invention relates to a method for detecting the level of molten metal in a continuous casting machine.

0002

[Prior Art] As is well known, a twin roll continuous casting machine (
A casting machine (hereinafter referred to as a casting machine) rotates the molten metal supplied between two parallel rolls and weir plates installed at each end of the rolls, so that the distance and length of the rolls corresponds to the distance and length of these rolls. A plate member having a thickness and a width is continuously cast.

[0003] In order to perform stable operation with such a casting machine, it is important to maintain a constant level of molten metal poured into the space formed between these rolls and the weir plate. In most casting machines, the molten metal level is always detected, and the molten metal level is controlled based on the detection results.

[0004] Below, an overview of methods for detecting the molten metal level in some conventional casting machines will be explained.
No. 1-140361 discloses a method of detecting the molten metal level by determining the amount of molten metal from the reaction force of a roll, and controlling the molten metal level based on this.

[0005] Furthermore, Japanese Patent Application Laid-open No. 140362/1983 discloses a method of detecting the meniscus width of molten metal using a camera or the like and controlling the molten metal level based on the detection result.

Furthermore, in Japanese Utility Model Application Publication No. 1-143655, there is a method in which thermocouples are embedded in a weir plate at predetermined intervals in the vertical direction, the molten metal level is detected based on the measured temperature, and the molten metal level is controlled based on this. Disclosed.

[0007]

[Problem to be Solved by the Invention] Each of the methods for detecting the molten metal level described above is useful in its own way, but each method has a problem to be solved in that the detection accuracy is not necessarily excellent for the reasons explained below. have.

For example, in the molten metal level detection method disclosed in JP-A-61-140361, the molten metal level must be controlled after the following steps: change in molten metal level → change in solidified shell thickness → detection of roll reaction force → calculation. As a result, the time lag is large and the accuracy of controlling the molten metal level inevitably deteriorates.

Furthermore, in the molten metal level detection method disclosed in Japanese Patent Laid-Open No. 140362/1983, when pouring molten metal into the above-mentioned space, the surface of the molten metal always waves on the roll surface having a small horizontal angle.

Moreover, since it is necessary to continue pouring a predetermined amount of molten metal throughout casting, the waves of the molten metal cannot be attenuated, and the meniscus width fluctuates due to the waving phenomenon of the molten metal, resulting in poor control accuracy of the molten metal level. .

Furthermore, in the molten metal level detection method disclosed in Japanese Utility Model Application Publication No. 1-143655, there is a time lag related to the heat conduction time when the temperature of the weir plate changes due to fluctuations in the molten metal level. The control accuracy of the molten metal level deteriorates.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for detecting a molten metal level in a casting machine, which makes it possible to improve the control accuracy of the molten metal level by detecting the molten metal level quickly and with high precision.

[0013]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances, and therefore, in order to solve the above-mentioned problems, the main means adopted by the molten metal level detection method in a casting machine according to the present invention is as follows. The feature is that a weir plate is placed on each of the end faces of two rolls arranged in parallel, and a space made up of these rolls and the weir plate is placed above this space. In a molten metal level detection method for a casting machine that continuously casts plates by supplying molten metal from a nozzle, an image of the boundary between the weir plate and the molten metal surface is detected with a camera, and pixel data within a predetermined area of the detected image is collected. The luminance is binarized and the molten metal level is detected by determining the ratio of either one of the binarized pixel data.

[0014]

[Operation] According to the method for detecting the level of molten metal in a casting machine according to the present invention, the space formed by the weir plates disposed on both end faces of two rolls disposed in parallel and the two rolls. An image of a predetermined area at the boundary with the supplied molten metal surface is detected by a camera, pixel data in a predetermined range of the detected image is binarized based on its brightness, and any of the binarized pixel data is The ratio of one is required.

This means that an increase in the proportion of the molten metal surface area indicates that the molten metal level has become high, and a decrease in the proportion of the molten metal surface area indicates that the molten metal level has become low. If it increases, it indicates that the molten metal level has increased, and if it increases, it indicates that the molten metal level has decreased.However, since the weir plate is vertical, the molten metal can be detected only by image processing of the boundary area, where changes due to undulation of the molten metal surface are small. Level detected.

Furthermore, since the ratio of either one of the binarized pixel data is determined, the influence of waving on the molten metal surface can be removed like a filter, and the molten metal level can be detected with high precision.

[0017]

[Example] Examples according to the present invention will be described below with reference to FIG. 1, which is a perspective view schematically showing the molten metal level detection configuration of a casting machine, FIG. 3, the reference numerals 2 and 2 shown in FIG.
are rolls arranged in parallel at a predetermined interval, and weir plates 3, 3 are arranged at both ends of these rolls 2, 2, respectively, in contact with the end surfaces, so that the casting machine main body 1
is configured.

A tundish 4 having a pouring nozzle 6 at the bottom via a gate valve 5 is disposed above the space formed by the rolls 2, 2 and the weir plates 3, 3. Molten metal 7 is poured into the space from a hot water nozzle 6.

A camera 10 is disposed on the outside of the casting machine main body 1 and faces the boundary 8 between one of the weir plates 3 and the molten metal surface of the molten metal 7. An image as shown in FIG. 2 is input to an image processing device 11, which will be described later.

The output obtained by the calculation by the image processing device 11 is input to the controller 12, and the opening degree of the gate valve 5 is adjusted by the controller 12. Note that the reference numeral 10a is a window, which indicates a predetermined area for image processing set by the image processing device 11 to obtain pixel data.

The image processing device 11 calculates the level of the boundary portion 8 between the weir plate 3 and the molten metal surface by processing the image as shown in FIG. 2 inputted from the camera 10 according to the flow shown in FIG. , that is, detects the molten metal level.

First, in step F1, Wx,y
=Vx,y, input x and y using the keyboard to set a window, and in the next step, enter a threshold value (limit value) K using the keyboard as step F2, and proceed to step F3. Note that, as the threshold value K, a value is adopted that allows the boundary portion 8 to be clearly determined in advance off-line.

In step F3, the time axis filter α is input using the keyboard, and the process proceeds to the first step, which is the next image processing stage. As the value of this time axis filter α, 0<α≦1 is adopted, and in the case of this embodiment, 1 is adopted.

This F3 step is to remove noise caused by molten metal splashes and ripples on the molten metal surface in the 4th step described later, and in practical terms, even without this time axis filter, the conventional molten metal level can be reduced. This step is not necessarily necessary since higher detection accuracy can be obtained than the detection method.

In the first step, pixel data V having analog luminance levels from black to white is obtained from the camera 10.
Input an image that is a set of i, j and proceed to the second step.

In the second step, if the pixel data Vi,j of the window 10a of the input image is equal to or larger than the threshold value K (Vi,j ≧K), then V
i,j = 1 (white), and this pixel data Vi,j
is smaller than the threshold value K (Vi,j <K), set Vi,j = 0 (black), and these pixel data Vi
, j into 1 and 0 and proceed to the third step.

In the third step, the following molten metal level signal is created based on the binarized pixel data 1 and 0 using an arithmetic expression to be described later. That is, the window 10a
The area ratio L=(ΣVx,y/x
- Find y)×100 and proceed to the fourth step.

Of course, even if we calculate the proportion of pixel data with Vi,j = 0 (black) in the pixel data in the window 10a, we cannot indirectly calculate the proportion of pixel data with Vi,j = 1 (white). can be asked for.

[0029] In the fourth step, Ln = α·Ln
-1 + (1-α)・L is calculated, and as explained in step F3, noise caused by splashes of molten metal and ripples on the molten metal surface is removed, and the process proceeds to step 5, where D/A Outputting the output level value Ln to the controller 12 via the converter is repeated.

Depending on the output level value Ln, the opening degree of the gate valve 5 shown in FIG. 1 is opened or closed, and the output level value Ln
The required amount of molten metal is poured into the casting machine main body 1 from the tandille 4 through the pouring nozzle 6 depending on the size of the molten metal.

In this way, the molten metal surface is detected as an increase or decrease in the area ratio L, but since this is a detection of a change in the boundary portion 8, which changes less than a change in the width of the molten metal surface due to waving or the like,
Even without the noise removal step of the fourth step using the time axis filter, the molten metal level can be detected with higher accuracy than in the past.

By the way, due to a change in the specifications of a cast product, it may be necessary to change its width or thickness. In such a case, it is naturally necessary to change the casting conditions and thus the molten metal level, but it is possible to respond to changes in the casting conditions simply by changing the camera angle.

[0033]Although the above description has been made by taking as an example the case of casting in the atmosphere, this method can also be adopted in the case of non-oxidation casting. In this case, a small window for the camera 10 may be provided in the sealed container in which the casting machine main body 1 is accommodated.

[0034]

Effects of the Invention As described in detail above, according to the method for detecting the level of molten metal in a casting machine according to the present invention, the weir plates disposed on each end face of two rolls disposed in parallel can ,
A camera detects an image of a predetermined area at the boundary with the surface of the molten metal supplied to the space formed by these rolls, and then the pixel data of the detected image is binarized based on its brightness. The height of the molten metal level is detected by determining the ratio of either one of the pixel data.

Therefore, unlike the first conventional example, the pixel data of the image is binarized based on its brightness, and the pixel data is Since the calculation is only required to find the ratio of either one of the data, the time lag is reduced and the control accuracy of the molten metal level can be improved.

Furthermore, unlike the second conventional example, instead of detecting the width of the molten metal surface, the camera detects the boundary between the vertical weir plate and the molten metal surface, which has a small fluctuation range due to waving of the molten metal surface. , the molten metal level can be detected with high precision.

Furthermore, instead of measuring the temperature of the weir plate which takes a long time to change as in the third conventional example, this method measures the height of the boundary between the weir plate and the molten metal surface, which changes immediately depending on the amount of molten metal. Since the detection time lag can be shortened, it is possible to improve the control accuracy of the molten metal level.

[0038] In this way, the molten metal level can be detected with high accuracy and the molten metal level can be controlled with a small time lag, so that stable operation of the casting machine can be continued, and as a result, the quality of cast products is improved. Extremely great effects can be expected on productivity improvement and quality improvement.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing a molten metal level detection configuration of a casting machine.

FIG. 2 is an explanatory diagram of an image taken by a camera.

FIG. 3 is an explanatory diagram of an image processing flow.

[Explanation of symbols]

1...Casting machine body 2...Roll 3...Weir plate 4...Tundish 5...Gate valve 6...Pouring nozzle 7...Molten metal 8...Boundary part 10...Camera 10a...window 11...Image processing device 12...Controller

Claims (1)

[Claims] Claim 1: A weir plate is provided on each end face of two rolls arranged in parallel, and a nozzle is arranged above this space in a space constituted by these rolls and the weir plate. In a method for detecting the level of molten metal in a twin-roll continuous casting machine that continuously casts plates by supplying molten metal from A method for detecting a molten metal level in a twin-roll continuous casting machine, characterized in that pixel data is binarized based on its brightness, and the molten metal level is detected by determining the ratio of either one of the binarized pixel data. .