JPH11142246A - Temperature measuring apparatus for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a temperature measuring apparatus whose measuring accuracy is increased by a method wherein image light at the output end of an image fiber is photographed so as to be converted into image data and the temperature of a molten metal is computed on the basis of the image data. SOLUTION: An observation nozzle 8 is passed through the bottom wall of a refractory container 10 for a converter, and an image fiber 1 is inserted into the observation nozzle 8. A purge-gas supply apparatus 9 presses high-pressure argon Ar into the observation nozzle 8. Thereby, a part between the light receiving end of the image fiber 1 and an opening coming into contact with molten steel 11 is occupied by the Ar, and the Ar is blown off into the molten steel 11 from the opening so as to be levitated as air bubbles. Thermal radiation light which is generated by the molten steel 11 in the interface between the Ar to be blown off to the molten steel 11 from the observation nozzle 8 and the molten steel 11 hits the light receiving end of the image fiber 1. A CCD camera 3 photographs an image at the output end of the image fiber 1 so as to output an image signal. A personal computer 6 writes image data to be given by an image processor 5 into a memoery at its inside. Then, the personal computer 6 converts a maximum luminance value into the temperature of the molten steel 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the temperature of molten metal such as molten steel in a converter, and more particularly to an apparatus for continuously measuring the temperature of molten metal.

[0002]

2. Description of the Related Art The method currently used in on-site operation The measurement probe of a thermocouple with a protection tube called a sublance is immersed intermittently in the molten metal from the upper part of the converter to determine the temperature of the molten metal. In this method, accurate temperature measurement can be performed. However, since the temperature of the molten metal cannot be continuously grasped, fine refining control cannot be performed. In addition, there is a problem that the probe is worn out, which increases the cost.

[0003] 2. Continuous temperature measurement using a nozzle Inert gas is injected into the nozzle that penetrates the heat-resistant side wall to prevent molten metal from entering the nozzle, and the radiation thermometer is directed toward the inside of the nozzle. The temperature is measured by receiving the thermal radiation emitted by
919). Although this method enabled continuous temperature measurement,
The molten gas near the tip of the nozzle may be solidified by the purge gas during measurement, and if it blocks a part of the field of view of the radiation thermometer, the radiant energy received by the radiation thermometer decreases and the apparent temperature decreases. Observed. At this time, since it cannot be determined from the output signal of the radiation thermometer whether the visual field is blocked or the temperature is actually decreasing, there is a problem in the reliability of the measured value.

[0004] 3. Continuous temperature measurement using optical fiber Insert an optical fiber that guides spot light into a nozzle that penetrates the heat-resistant side wall or bottom wall, press-in a purge gas into the nozzle to prevent molten metal from entering the nozzle, The heat radiation generated by the molten metal is guided to a radiation thermometer by an optical fiber and a spot light is measured by a radiation thermometer (for example, JP-A-62-52423, JP-A-61-621).
-91529). This method enables continuous temperature measurement, but when the center of the visual field of the optical fiber is deviated from the center of the nozzle or the optical axis is inclined with respect to the center axis of the nozzle, or during measurement, a purge gas is used near the tip of the nozzle. If the molten metal can solidify and block part of the field of view of the fiber, the apparent temperature is observed to be low because the radiant energy received by the fiber is reduced. At this time, since it cannot be determined from the output signal of the radiation thermometer whether the visual field is blocked or the temperature is actually decreasing, there is a problem in the reliability of the measured value.

[0005]

SUMMARY OF THE INVENTION It is a first object of the present invention to measure the temperature of a molten metal through a nozzle of a heat-resistant wall. The third object is to improve the reliability of continuous measurement, and the fourth object is to automatically detect an abnormality in the measurement environment.

[0006]

(1) An image fiber (1) having a light-receiving end inserted into a nozzle penetrating a heat-resistant side wall or a bottom wall (10) for accommodating a molten metal (11); A gas supply device (9) for injecting gas to prevent molten metal from entering the nozzle; an imaging device (2, 3) for capturing image light at a light emitting end of the image fiber (1); 2,3)
The digital signal, i.e., the image data
An image processing device (5) that converts the data into data; and the imaging device (2, 2) based on image data generated by the image processing device (5).
A data processing device (6) for calculating the molten metal image position (11i) and the molten metal temperature (T) on the photographing screen of 3);

[0007] In order to facilitate understanding, the reference numerals of the corresponding elements or corresponding items of the embodiment shown in the drawings and described later are added for reference in parentheses.

The image fiber (1) has a light image transmitting function, and transmits a light image viewed forward from the light receiving end to the light emitting end. An image pickup device (2, 3) captures a light image at the light exit end to generate an image signal, and an image processing device (5) converts the image signal into image data.

In an ideal state, the image signal (and the image data)
The image represented by (ta) is, as shown in FIG.
Nozzle inner surface image 8i at the center of screen 3if of imaging device (2, 3)
f, there is a light image 11 of the molten metal at the center of this image 8if.
There will be i. The light image 11i has the highest brightness, and the nozzle inner surface image 8if has the lowest brightness. This nozzle inner surface image 8i
The area outside f is the area outside the light emitting end face of the image fiber 1 and has the lowest brightness. When the center line of the visual field of the image fiber (1) is displaced or inclined with respect to the center line of the nozzle, as shown in FIG. A part of the light image in the ideal state is missing, and the ratio of the low brightness area of the edge of the opening on the molten metal side of the nozzle in the light image 11i increases, which increases the possibility of causing a measurement error. . When the molten metal solidification amount at the molten metal side opening edge of the nozzle increases, the light image 11i of the molten metal decreases as shown in FIG. 3C, and also in this case, the brightness of the molten metal side opening edge of the nozzle is low. The proportion of the area occupied in the light image 11i is high, and there is a high possibility that a measurement error will occur.

A data processor (6) calculates the molten metal position (11i) as described above. The light image 11i of the molten metal is
As shown in FIG. 3A, when it is located at a predetermined position on the screen 3if (a predetermined area in the center of the screen), the possibility of occurrence of measurement error is low, and it is expected that the measurement value with the highest reliability will be obtained. It is. As shown in FIG. 3B, when there is a large deviation from a predetermined position of the screen 3if (a predetermined area in the center of the screen), there is a high possibility that a measurement error will occur, and the reliability of the measurement value is expected to be low. It is. As shown in FIG. 3C, even if the center of the light image 11i of the molten metal is substantially at the center of the screen 3if, if the outer edge position is greatly deviated from the outer edge position of the predetermined area and small, a measurement error occurs. Probability is high and the reliability of the measured values is expected to be low. Therefore, the reliability of the measured value can be evaluated from the molten metal image position (11i) calculated by the data processing device (6).

For example, in converter refining, temperature measurement is very important for blowing control. According to the present invention, continuous temperature measurement is enabled, and at the same time, the position of the molten metal calculated by the data processing device (6) is erroneous measurement data due to the visual field constriction due to the visual field shift or solidification of the molten metal. Since it can be excluded based on (11i), it has excellent effects in both operation technology and quality control.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (2) The data processing device extracts the highest luminance value and calculates the temperature corresponding to the highest luminance value. As described above, the light image 11i of the molten metal is obtained, and the luminance of each pixel of the light image 11i corresponds to the temperature of the molten metal at the corresponding position. According to the present embodiment, since the luminance value (ie, the maximum luminance value) at the position where the relationship between the luminance and the temperature is accurate is automatically extracted, the measurement accuracy is high. Even if the visual field obstruction due to solidification of the molten metal at the nozzle tip occurs during the measurement, stable measurement can be performed while the progress is small.

(3) The data processing device calculates the area of a high-brightness area on the photographing screen to detect a narrowed visual field. Based on this detection result, the reliability of the temperature measurement can be evaluated.

(4) The data processing device calculates the center position of the high-brightness area on the photographing screen to detect a visual field shift. Based on this detection result, the reliability of the temperature measurement can be evaluated.

(5) The data processing device extracts a high-intensity peak value LPh on the photographing screen, determines a binarization threshold value based on the extracted peak value LPh, and uses the binarization threshold value to generate an image. The data is binarized, and a high luminance area is detected based on the binarized data. Extraction of a high-luminance area is simple.

(6) The data processing device calculates the area of the high-brightness area on the photographing screen and detects the shortening of the distance of the molten metal from the light receiving end of the image fiber. The length of the observation nozzle wears with the refractory inside the furnace due to repeated operation, but the distance between the fiber tip and the molten metal can be known from the size of the molten metal in the image, and the image fiber is always installed at the optimum position it can.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0018]

FIG. 1 shows the configuration of an embodiment of the present invention. The observation nozzle 8 penetrates the bottom wall of the refractory container 10 of the converter, and the image fiber 1 is inserted into the nozzle 8. FIG. 2 shows the nozzle 8 in an enlarged manner. A purge gas supply device 9 pressurizes high-pressure argon (Ar) into the nozzle 8, whereby the space between the light receiving end of the image fiber 1 and the opening in contact with the molten steel in the nozzle 8 is occupied by Ar. Ar blows out into the molten steel 11 from the opening and floats as bubbles. Therefore, the light receiving end of the image fiber 1 is irradiated with the heat radiation emitted by the molten steel at the interface between the angling blown out from the nozzle 8 to the molten steel 11 and the molten steel 11.

The temperature of the molten steel 11 is 1400-1700 ° C.
Alternatively, the thermal radiation includes infrared and visible light. The converter process is a process in which oxygen is blown into hot metal to oxidize and remove impurities, and a high-temperature molten steel is produced by the heat generated by the oxidation of the impurities.The time for blowing oxygen into the converter is 12 to 20 minutes. Very short, during which the temperature and composition of the molten steel are controlled to target values.
Need to be Therefore, it is desired to continuously and accurately detect the molten steel temperature.

The image fiber 1 is composed of 15,000 or more optical fibers (element wires) tightly coupled and bundled to a diameter of 4 mm, and the tip (light receiving end) has a focal length close to infinity at its tip (light receiving end). A condenser lens is mounted, and an image in front of the light receiving end of the image fiber 1 is projected. The projected image is transmitted to the light emitting end of the image fiber 1 as it is. That is, a light image in front of the light receiving end of the image fiber 1 appears at the light emitting end.

The CCD camera 3 captures an image of the light exit end of the image fiber 1 through the wavelength selection filter 2 and outputs an analog image signal (video signal representing luminance). The wavelength selection filter 2 transmits light in the visible region where the luminance changes greatly with temperature. The shutter speed and reading (video signal output) of the CCD camera 3 are controlled by a controller.
LA 4 controls. The operator can adjust and select a shutter speed and a video signal level (range) via the controller 4.

The video signal is supplied to the image processing device 5. The image processing device 5 converts the video signal in the main scanning x direction 64
It is converted into digital data of 0 pixels × 480 pixels in the sub-scanning y direction, that is, image data (data representing luminance), written into an internal memory, and is repeated. Holds image data of one frame (one screen). When the image processing device 5 receives a request from the personal computer 6,
The image data of one frame in the memory is transferred to the personal computer 6. The personal computer 6 writes the image data provided by the image processing device 5 into its internal memory (hereinafter referred to as image memory).

When the personal computer 6 is instructed to measure the temperature,
Until the end of the measurement is instructed, the temperature measurement process shown in FIG. 4 is executed. In this embodiment, the CCD camera 3 is
The optical image of the image fiber 1 is photographed at a repetition rate of 0 frames / sec, and the personal computer 6 performs the temperature measurement at a cycle of approximately 5 times / sec until the temperature measurement is instructed and the measurement end is instructed, as shown in FIG. The processing shown (S1 to S21) is repeated.

With reference to FIG. 4, one temperature measurement process of the personal computer 6 will be described. First, a request is made to the image processing device 5 to transfer image data, and one frame worth of image data is written into the image memory of the personal computer 6 (step S1). In the above description, the word “step” is omitted in the step expression of FIG. Only symbols are shown. When the image data for one frame is written into the image memory, the personal computer 6 sequentially reads out the image data from the image memory, performs shading correction, and stores the corrected image data in the image memory. Is updated (S2). In this shading correction, image data (data before shading correction) addressed to each pixel is used as a reference photoelectric signal in accordance with the variation in the photoelectric conversion characteristics of each of the 640 × 480 pixels of the CCD camera 3. The calibration is performed to the level of the conversion characteristic. For example, the photoelectric conversion characteristics of the CCD camera 3 are measured in advance by observing a black body furnace capable of obtaining uniform heat radiation, and data necessary for calibration is collected. (Database). Shading correction (S
In 2), the memory is accessed with the pixel coordinates and the data before correction, and the calibration data (data after correction) is read and updated and written in the image memory.

Next, the personal computer 6 performs filtering (S
Perform 3). In this embodiment, the image data addressed to each pixel is
Data is sequentially read from the image memory, and one pixel (pixel of interest) is read.
For each of the image data, the sum of the products obtained by multiplying the image data of a total of 9 images by the weighting factors a to i, that is, 3 pixels in the main scanning x direction × 3 pixels in the sub scanning direction centering on the target pixel, is used. , Coefficient a ~
A weighted average value divided by the sum of i is calculated, and the weighted average value is updated and written as filtered image data at an address addressed to a target pixel in an image memory. Note that the value of the coefficient e addressed to the target pixel is larger than the values of the other coefficients a to d and f to i.

Next, the personal computer 6 outputs data representing the highest luminance (peak value LPh) among the image data in the image memory.
And its pixel coordinates (address on the memory) are extracted (S4). Then, it is checked whether the peak value Lph is equal to or lower than the threshold value LPTh for judging a low luminance abnormality (S5).
If it is less than Th, “brightness abnormality” is displayed on the CRT display in the output device 7. In addition, the threshold value LPTh
Is a luminance value corresponding to a temperature lower than the lower limit of the normal range of the molten steel temperature during the operation of the converter, which is input (set) in the personal computer 6 in advance. Or the temperature measurement system shown in FIG. 1 is abnormal.

If the peak value Lph exceeds the threshold value LPTh, the personal computer 6 sets the binary threshold value BTh = k · L
PTh is calculated (S7). k is 0 <k <1;
The molten steel image 11i shown in FIG.
This is determined from past measurement results and input (set) to a personal computer. Next, the personal computer 6 binarizes all the image data in the image memory with the threshold value BTh and writes the binary data into the memory (binary image memory) (S8). The binary data "1" means that the image data is equal to or larger than the threshold value BTh (substantially belongs to the molten steel image area 11i), and "0" means that the image data is equal to the threshold value BT.
h (substantially outside the molten steel image area 11i).

Next, the personal computer 6 operates on the binary image memory,
“1” surrounded by “0” is changed to “0”, and “0” surrounded by “1” is changed to “1” (S9).
As a result, the binary data in the binary image memory becomes "1" in all areas substantially belonging to the molten steel image area, and becomes "0" in all areas other than the area.

Next, the personal computer 6 generates an x-direction distribution histogram of "1" on the binary image memory (an integrated value of the number of "1" distributed in the y direction at each x position). The center of gravity position Wx is calculated (S10). Then, a y-direction distribution histogram (integrated value of the number of “1” distributed in the x direction at each y position) is generated, and the center of gravity position Wy is calculated (S11). In this embodiment, the position (Wx, Wy) is regarded as the center position of the molten steel image 11i.

Next, the personal computer 6 calculates the total Sh (the number of pixels in the molten steel image area 11i) of the integrated value of the number of "1" distributed in the y direction at each x position in the x direction distribution histogram. (S12). This sum Sh is expressed in the molten steel image area 11i.
Area. Next, the area Sh of the molten steel image area 11i is
It is checked whether it is within the setting range (STS <Sh <STL) (S13, S15). STS is a threshold value for determining the narrowing of the visual field, and STL is a threshold value for determining the reduction of the distance between the light receiving end of the image fiber 1 and the molten steel. If the setting range is out of the small side, "field narrowing" is displayed on the CRT display (S14), and if the setting range is out of the large side,
"Shortening of distance" is displayed on the CRT display.

Next, the personal computer 6 checks whether the deviation of the center position (Wx, Wy) of the molten steel image 11i from the center position (Xc, Yc) of the screen of the CCD camera 3 is equal to or larger than the set value Ra (S17). ), If it is Ra or more, the “field deviation” is C
Display on the RT display.

Next, the personal computer 6 converts the peak value Lph into a molten steel temperature T (S19). In the past, a measuring probe of a thermocouple with a protection tube was immersed in molten steel from the upper part of the converter to measure the molten steel temperature T, and the peak value LPh at that time was read, and the peak value LPh versus the molten steel temperature T was measured. A control table representing the relationship is created, and the peak value LP is determined based on the control table.
A data map in which h is an address and the peak value LPh is memory data is stored in the memory of the personal computer 6. In "calculation of temperature T" (S19), the personal computer 6 reads out the temperature T data corresponding to the peak value LPh extracted in S4 from the data map and displays it on the CRT display.

Next, the personal computer 6 transmits the above-mentioned detected or calculated data LPh, BTh, (Wx, Wy), Sh, T, and judgment data (abnormal brightness, narrowed visual field, reduced distance, reduced visual field). , In the data storage memory of the personal computer 6, the charge number previously input by the operator. The data is written in the address area in the order of time together with the time data.

Then, it is checked whether or not a measurement end instruction has been input, and if there is no end instruction, the next measurement processing is started (S21-S1).

The output device 7 includes a printer and an external storage device in addition to the above-mentioned CRT display. The operator operates the personal computer 6 to edit the data, and determines the judgment data. Along with the data, the measurement data can be displayed on a CRT display in a graph format or a table format or printed out. The data before editing and the data after editing can be written in the external storage device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system configuration according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of a nozzle 8 shown in FIG.

3A and 3B are plan views showing a photographing screen of the CCD camera shown in FIG. 1, wherein FIG. 3A is an image when a setting of a measuring instrument and a measurement environment are in a reference state, and FIG. (C) shows an image when the molten steel solidifies at the opening edge of the nozzle 8 and the molten steel surface seen by the image fiber 1 becomes smaller. , Respectively.

FIG. 4 is a flowchart showing an outline of a temperature measurement process of the personal computer 6 shown in FIG.

[Explanation of symbols]

 1: Image fiber 2: Wavelength selection filter 3: CCD camera 3if: Photographing screen 4: Controller 5: Image processing device 6: Personal computer 7: Output device 8: Observation nozzle 8ii: Nozzle inner surface image 9: Purging gas supply Apparatus 10: Refractory vessel 11: Molten steel 11i: Molten steel image

Claims (5)

[Claims] An image fiber having a light-receiving end inserted into a nozzle penetrating a heat-resistant side wall or a bottom wall for containing a molten metal; a gas for injecting an inert gas into the nozzle to prevent the molten metal from entering the nozzle; A supply device; an imaging device that captures image light at the light exit end of the image fiber; an image processing device that converts an image signal generated by the imaging device into digital data, that is, image data; and the image processing device A data processing device for calculating the position of the molten metal image and the temperature of the molten metal on the photographing screen of the imaging device based on the image data generated by the temperature controller. 2. A temperature measuring device for a molten metal according to claim 1, wherein said data processing device extracts a maximum luminance value on said photographing screen and calculates a temperature corresponding thereto. 3. The molten metal temperature measuring device according to claim 1, wherein the data processing device calculates the area of a high-brightness region on the photographing screen to detect a visual field narrowing. 4. The data processing device according to claim 1, wherein a center position of a high-brightness area on the photographing screen is calculated to detect a visual field shift.
The temperature measuring device for molten metal according to the above. 5. A data processing apparatus extracts a high-intensity peak value LPh on a photographing screen, determines a binarization threshold value based on the extracted peak value LPh, and uses the binarization threshold value to determine image data. Binarizing the data, detecting a high-luminance area based on the binarized data;
The molten metal temperature measuring device according to claim 3 or 4.