JPH08201142A - Luminance regulating method for molten metal level measuring image receiver - Google Patents

Abstract

PURPOSE: To accurately measure molten metal immediately after casting is started by measuring a luminance adjustable light emitting element by a radiation thermometer, so setting the luminance of the element that the measured value becomes the temperature of the molten metal, and regulating the luminance of the incident light of an image receiver in a range for obtaining the clear image of the element. CONSTITUTION: A molten metal level measuring CCD type image receiver 10 receives the image of a boundary 8 between molten metal 1 and the casting mold wall surfaces of the surfaces of the drums 2, 2' of a dual-drum type continuous casting machine, and senses the height of the molten metal level based on the image of the position of the boundary 8. Prior to the start of casing the molten metal, a light emitting element in which a luminance can be regulated such as the molten metal on the way of melting in a melting furnace or the filament of an incandescent lamp is measured by a radiation thermometer, and the luminance of the element is so set that the measured value by the thermometer becomes the temperature of the metal 1. Then, the luminance of the incident light of the receiver 10 is regulated by selecting a filter to a range for obtaining the clear image of the element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting a molten metal surface measuring receiver used for detecting the molten metal surface height in, for example, twin drum type continuous casting.

[0002]

2. Description of the Related Art FIG. 1 is an explanatory view of twin drum type thin plate continuous casting. Two horizontal drums 2 and 2 ′ serving as mold wall surfaces are arranged at the same height in parallel and close to each other, and each is rotated in the directions of arrows 6 and 6 ′. Side dams 3 and 3'are provided in close contact with the drums 2 and 2'at both ends of the drums 2 and 2'in the axial direction. The molten metal 1 is continuously poured into the upper space (melt pool) formed by the drums 2 and 2'and the side dams 3 and 3 '.
The poured molten metal 1 is cooled by the drums 2 and 2 ', and solidified shells 4 and 4'are formed on the surfaces of the drums 2 and 2'. The solidified shells 4 and 4'are the minimum gaps 7 of the drums 2 and 2 '.
Are integrated into a thin plate cast piece 5 and taken out.

When the surface of the molten metal is a solid line in FIG. 1, the solidified shell 4 starts to generate at 8 and is cooled and grown by the drum 2 from 8 to 7. When the molten metal surface rises to the position 8'in the dotted line in FIG. 1 during operation, the solidified shell 4 starts to generate at 8'and is cooled and grown by the drum 2 from 8'to 7. But the time from 8'to 7 is 8 to 7
The solidified shell in the case of the dotted line 8 ′ is overgrown due to its long time compared to the time until, and the solidified shell at 7 becomes thick. In such a case, the plate thickness of the slab becomes locally thick and the plate thickness accuracy deteriorates. In an extreme case, the molten metal overflows over the side dam and a casting accident occurs.

As described above, in twin-drum type continuous casting, for example, it is important to detect and control the molten metal surface height because it has a close relationship with the quality of the slab and a casting accident. Reference numeral 10 in FIG. 1 is a molten metal surface measuring image receiver used for detecting the molten metal surface height. This image receiver receives an image of a boundary 8 between the molten metal 1 and the wall surface of the mold (the surface of the drum 2 serving as the mold). Figure 2 is an example of the image at this time, (A)
[Fig. 3] is an explanatory diagram in the case where the molten metal surface is a solid line. The image to the right of the boundary 8 between the melt and the mold wall is the image of the drum surface, which is dark because the amount of light received from the mold wall is small, and the image of the surface of the melt to the left of 8 is the amount of light received from the surface of the melt. Because there are many, it becomes a bright color.

In the measurement of the molten metal surface position, a threshold value of brightness is set, and the boundary 8 is detected by performing image processing for binarizing the image receiving screen in white above and in black below. Figure 2
(B) is an example of the image when the molten metal surface is lowered to the dotted line 8 "in FIG. 1. The molten metal surface height is 8" from the solid line in FIG.
When the boundary between the molten metal and the drum surface moves from 8 "to 8" in Fig. 1, the position of the dark-light boundary 8 in Fig. 2 (A) is 8 "in Fig. 2 (B) in the image of the receiver as well. Move to the position. Therefore, the height of the molten metal surface can be detected by measuring the position of the boundary between black and light in the image of the CCD type image receiver.

[0006] In twin-drum type continuous casting, the temperature of the molten metal when producing a slab of low carbon steel is, for example, 1580 ° C, and the temperature of the molten metal when using stainless steel is, for example, 1530 ° C.
The temperature of the molten metal in the case of a copper alloy is, for example, 1100 ° C. When manufacturing these slabs with different molten metal temperatures, the same image receiver is used to measure the molten metal surface, and when the molten metal is low-carbon steel with a high temperature, for example, a dark-colored shading filter with a low light transmittance If the molten metal is a low-temperature copper alloy, the brightness of the incident light to be input is adjusted by using, for example, a light-shielding filter of a light color having a high light quantity transmittance.

That is, when a low-color light-shielding filter made of, for example, a copper alloy is used in casting low-carbon steel, an image with halation occurs, and the position of the boundary 8 in FIG. 2 becomes unclear. Further, when a dark-colored light-shielding filter used in, for example, low carbon steel is used in casting a copper alloy, a dark image is formed, and the position of the boundary 8 in FIG. 2 cannot be detected and becomes unclear.

This brightness adjustment of the conventional image receiver is adjusted according to the kind of the molten metal so that the position of the boundary 8 becomes a clear image while observing the image after the casting of the molten metal is started. However, for example, 256 is used for image analysis of the brightness of the receiver.
There are many brightness adjustment steps, and the selection of the filter of the receiver and the adjustment of the brightness threshold value are complicated methods of selecting the optimum conditions for the molten metal from the 256 brightness adjustment steps. However, there is a problem that the surface level measurement of the molten metal becomes uncertain during this adjustment.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a method of performing the above-mentioned brightness adjustment of a molten metal surface image receiver in advance so as to be optimum for the molten metal to be cast, prior to the start of casting. It is an object to provide a method for adjusting the brightness of a receiver, which enables accurate measurement of the molten metal surface immediately after.

[0010]

Means for Solving the Problems The present invention is (1) for measuring a molten metal surface used for receiving a boundary between the molten metal and a wall surface of a mold and detecting a molten metal surface height based on an image of the position of the boundary. In the image receiver, prior to the start of casting of the molten metal, first measure the luminous body whose brightness can be adjusted with a radiation thermometer, and set the luminance of the luminous body so that the measured value with the radiation thermometer is the temperature of the molten metal, Next, there is provided a method for adjusting the brightness of an image receiver for measuring the level of molten metal, characterized in that the brightness of incident light of the image receiver is adjusted within a range in which a clear image of the luminescent material can be obtained. The method for adjusting the brightness of a molten metal surface measuring receiver according to (1) above, wherein the molten metal is for twin-drum type continuous casting, and the mold wall surface is the surface of the drum of the twin-drum type continuous casting machine.

In the present invention, a luminous body is used, but the molten metal in the melting process in the melting furnace can be used as the luminous body, and it may be a filament of an incandescent lamp different from the molten metal to be cast. . Although a radiation thermometer is used in the present invention, a commercially available radiation thermometer can be used. The temperature T of the molten metal injected in the present invention is, for example, T = t
The temperature of the molten metal can be determined in advance by using + Δt (where t: liquidus temperature of the molten metal based on the components of the molten metal, Δt: superheat temperature of the molten metal from the liquidus temperature unique to the casting apparatus).

In the present invention, the luminous body is measured by the radiation thermometer, and the brightness of the luminous body is adjusted so that the measured value by the radiation thermometer becomes T. Next, this illuminant whose brightness has been adjusted is received by an image receiver, and the brightness of the incident light of the image receiver is adjusted by selecting a filter within a range in which an image in which the illuminant and the mold wall surface can be clearly distinguished is obtained. Next, as described above, the brightness threshold adjustment is based on the specification of the receiver, for example, 2
This is performed by selecting one of the 56 brightness adjustment steps in which the light emitter and the mold wall surface can be clearly distinguished.

According to the knowledge of the inventors of the present invention, prior to the start of casting, if a binary image processing is performed by using an image receiver whose brightness of incident light is adjusted by the above method and by setting an appropriate threshold value. At the time of casting, a clear image of the positions of the boundaries 8 and 8'in FIG. 2 is obtained immediately after the start of casting, and as a result, it is possible to accurately measure the molten metal surface immediately after the start of casting.

[0014]

When a substance whose absolute temperature is T radiates a black body, the energy E radiated has a relationship of E = σT ⁴ , and the wavelength λm corresponding to the maximum energy radiation at this time is λ
It is widely known that m × T = constant relationship.

In the present invention, the luminous body and the molten metal are not black bodies but
Further, a commercially available radiation thermometer displays the brightness in a specific wavelength range as a temperature, and a receiver converts the amount of received light into an electronic signal by, for example, an image pickup device (CCD charge coupled device).

That is, in the present invention, the image at the time of adjusting the brightness of the incident light of the image receiver is an electronic signal amount obtained by converting the light measured by the radiation thermometer emitted by the light emitter by the CCD, while being obtained during casting. The image displayed is the light emitted by the molten metal at the casting temperature C
The electronic signal converted by the CD. Therefore, each electronic signal amount corresponds to a strict absolute temperature originally.

In the present invention, the purpose is not to measure the absolute values of the amount of radiated light on the molten metal and the wall surface of the mold, but to obtain a clear image of the boundary 8 in FIG. 2 by applying binarized image processing. There is. According to the findings of the present inventors, the above C
The electronic signal amount converted by the CCD during the adjustment of the CD receiver and the electronic signal amount converted by the CCD during casting are both within a range where a clear image of the boundary 8 in FIG. 2 is obtained. Corresponding with sufficient accuracy to achieve the object of the invention.

Although the present invention has been described with reference to the twin drum type continuous casting, the molten metal is measured by using the CCD type image receiver for measuring the molten metal level even in other casting methods such as vertical continuous casting of slabs and blooms. The surface height can be detected. Even in this case, if the brightness of the CCD type image receiver is adjusted by the method of the present invention, it is apparent from the above description that the same effect as the present invention can be obtained.

[0019]

Example 1 A 500 W incandescent lamp whose filament temperature can be adjusted was used as a light emitter used for simulating molten metal. IR-630 (manufactured by Minolta Camera Co., Ltd.) is used as the radiation thermometer and KV-24 is used as the CCD type image receiver.
/ 24L CCTV camera (manufactured by Hitachi, Ltd.) was used. The twin-drum type continuous casting machine has a drum having a diameter of 400 mm and a width of 350 mm.

The luminous body was caused to emit light so that the value measured by a radiation thermometer was 1100 ° C. CCD type receiver
This light-emitting body was observed and the scale of the number of light-shielding filters was adjusted so that the clearest image of the light-emitting body was obtained. The value of the brightness at this time was 180. The brightness scale of the CCD type receiver when the clearest image on the drum surface is obtained is 15
~ 20.

Using the twin-drum type continuous casting machine, a copper alloy having a molten metal temperature of 1100 ° C. (liquidus temperature: 1050 ° C.) was cast and the brightness discrimination threshold value was adjusted to 100.
When the molten metal surface was measured using a D type image receiver and converted into a black and white binary image by image processing, a clear image of the boundary between the molten metal and the mold wall surface was obtained. It should be noted that, while the threshold value for identifying the brightness of the CCD type image receiver was changed during casting, the scale was 80-120.
It was found that between the two, an image with clear boundaries was obtained.

[0022]

Example 2 The same luminous body, radiation thermometer and CC as in Example 1
A D type image receiver and a twin drum type continuous casting machine were used. The luminous body was caused to emit light so that the value measured by the radiation thermometer was 1590 ° C. The number of light-shielding filters of the CCD image receiver was adjusted so that the clearest image of the light emitter was obtained by observing the light emitter with a CCD image receiver, and the luminance value at this time was 190. The brightness value of the CCD type image receiver when the clearest image on the drum surface is obtained is 15 to 20.

Using the twin-drum type continuous casting machine, carbon steel having a molten metal temperature of 1590 ° C. (liquidus temperature: 1500 ° C.) was cast, and the above-mentioned CCD type receiver in which the brightness scale was adjusted to 190 was used. The surface of the molten metal is measured and image processing is used to display black and white 2
When converted into a binarized image, a clear image of the boundary between the melt and the mold wall was obtained. Although the scale of the brightness of the CCD type image receiver was changed during casting, the brightness identification threshold value was 90 to 130.
It was found that between the two, an image with clear boundaries was obtained.

[0024]

According to the present invention, in casting, the boundary between the molten metal and the wall surface of the mold can be clearly measured immediately after the start of casting.

[Brief description of drawings]

FIG. 1 is an explanatory view of twin-drum type continuous casting.

FIG. 2 is an explanatory diagram of an image received by a CCD type image receiver for measuring molten metal surface.

[Explanation of symbols]

1: molten metal, 2 (2 '): drum, 3 (3'): side weir, 4 (4 '): solidified shell, 5: cast slab, 6
(6 '): Drum rotation direction, 7: Minimum gap between drums 2 and 2', 8 (8 ', 8 "): Boundary between molten metal and mold wall surface.

Claims (2)

[Claims] 1. A molten metal surface measuring image receiver used for receiving an image of the boundary between the molten metal and a mold wall surface and detecting the molten metal surface height based on the image of the position of the boundary, prior to the start of casting of the molten metal. Then, first measure the luminous body whose brightness can be adjusted by a radiation thermometer, set the brightness of the luminous body so that the measured value by the radiation thermometer is the temperature of the molten metal, and then set the brightness of the incident light of the receiver. A method for adjusting the brightness of a molten metal surface measuring image receiver, which comprises adjusting to a range in which a clear image of the luminescent material can be obtained. 2. The brightness adjustment of the receiver for measuring the molten metal surface according to claim 1, wherein the molten metal is for twin-drum type continuous casting, and the mold wall surface is the surface of the drum of the twin-drum type continuous casting machine. Method.