JPH10272556A - Slag outflow detection method and device - Google Patents

Abstract

(57) [Abstract] [Problem] To detect slag contamination in molten steel flow with high sensitivity even if it is slight. Running cost reduction. SOLUTION: An X-ray generator 4 is installed below a sliding nozzle 2 of a ladle, X-rays which have passed through the molten metal flowing out of the ladle are detected by a detector 5, and mixed slag is detected based on X-ray transmittance. The amount is detected, and when it reaches a predetermined value, the ladle nozzle 2 is closed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting slag mixed in molten metal at the end stage of molten metal flowing out of a first container holding molten metal.

[0002]

2. Description of the Related Art For example, in a continuous casting facility for steel,
When molten steel is poured from a ladle, which is a container, to a tundish, which is a second container, a phenomenon occurs in which slag is mixed in the molten steel and flows out into the tundish in the final stage. Since the slag deteriorates the quality of the cast slab and adversely affects the life of the refractory lining with tundish, a method of detecting the slag and stopping the injection of the molten steel is adopted. The following technology has been proposed as a slag detection method or detection device.

For example, an apparatus disclosed in Japanese Patent Application Laid-Open No. 64-27768 is as follows. That is, an annular groove is provided below a tuyere brick (perforated brick) of a ladle, and a transmission coil for generating a magnetic field and a reception coil for generating an induced voltage are embedded in this groove in pairs. When a magnetic field is formed by supplying a current to the transmission coil, an eddy current is induced in the molten steel flow passing through the tuyere brick. A voltage is further induced in the receiving coil by the magnetic field formed by the eddy current induced in the molten steel flow. The voltage induced in the receiving coil differs between the case where only molten steel passes through the tuyere brick and the case where slag is mixed in the molten steel. By detecting a change in the voltage induced in the receiving coil, a slag passing through the tuyere brick is detected.

[0004]

However, Japanese Patent Application Laid-Open No.
The technique disclosed in Japanese Patent Application Laid-Open No. 4-27768 has the following problems. In other words, when an alternating current flows, the current concentrates on the surface because the impedance of the surface in the conductor is low. This phenomenon is called a skin effect, and the degree of concentration on the surface is expressed by the following equation as “penetration depth δ”. δ = K√ρ / μf where ρ: resistivity of the conductor, f: frequency, and μ: relative permeability of the conductor.

As can be seen from this equation, the higher the frequency of the alternating current, the smaller δ, the higher the frequency of the current in the transmitting coil to increase the detection sensitivity, the lower the penetration depth into the molten steel. As a result, an electric current is induced only on the surface of the molten steel flow. Therefore, there is a problem that the detection cannot be performed unless a considerable amount of slag is mixed in the molten steel flow. Further, since the coil is installed in contact with the tuyere brick, the coil may be deteriorated due to heat conduction from the brick, or the coil may be damaged at the time of replacing the tuyere brick. Therefore, there is a problem that the running cost of the coil is high.

Accordingly, an object of the present invention is to provide a slag outflow detection method and apparatus capable of detecting with high sensitivity even a small amount of slag mixed into a molten steel stream and having a low running cost. I do.

[0007]

[Means for Solving the Problems]

(1) In the present invention, an X-ray generator (4) and an X-ray detector (4) opposed to each other across a molten metal flow path (3) from the first container (1) to the second container (Tundish TD) In 5), the molten metal flow path
The X-ray transmission amount (I) of (3) is detected, and slag mixing in the molten metal (MS) in the weld metal flow path (3) is detected based on the transmission amount. In addition, in order to facilitate understanding,
Corresponding elements or corresponding items in the embodiment shown in the drawings and described below or symbols attached thereto are added for reference.

Here, a case where molten metal (MS) is molten steel injected from a ladle 1 (first container) into a tundish TD (second container) will be described as a specific example. The intensity of X-rays generated by the X-ray generator (4) is represented by Io, and the intensity of X-rays detected by the X-ray detector (5).
Assuming that the line intensity is I, I is represented by the following equation. I = Io · exp [− (μr · tr + μs · ts + μa · ta)] (1) where μr is the X-ray absorption coefficient of the refractory in the molten metal flow path (3), and μs is the molten metal flow. The X-ray absorption coefficient of a substance passing through the path (3), μa represents the X-ray absorption coefficient of the beam path.
Also, tr, ts and ta are the molten metal flow paths (3), respectively.
Are the thickness of the refractory, the inner diameter of the molten metal channel (3), and the beam path length.

Since (μr · tr + μa · ta) becomes constant, ex
If p [-(μr · tr + μa · ta)] is a constant C, then I = Io · C · exp [− (μs · ts)] (2) Now, when slag is mixed into the molten metal (MS), μs · ts = μFe · tFe + μslag · tslag = μFe · (ts−tslag) + μslag · tslag = μFe · ts + (μslag−μFe) · tslag 3)

Here, μFe and μslag are the X-ray absorption coefficients of the molten steel and the slag, respectively, and tFe and tslag are the effective thicknesses of the molten steel and the slag in the molten metal flow path (3), respectively. From the above equations (2) and (3), I = Io · C · exp [− [μFe · ts + (μslag−μFe) · tslag]] (4) Since μFe and ts are known. , Exp [− (μF
e · ts)] as C ′, equation (4) can be expressed as: I / Io = C · C ′ · exp [− (μslag−μFe) · tslag] I / Io = C ″ · exp [(μFe−μslag ) · Tslag] (5) where C ″ = C · C ′ and is a constant. If the slag component is known, μslag is also known, so the only unknown in equation (5) is tslag, and the X-ray absorption ratio I /
Since tslag is found from the measurement of Io, the slag fraction ts
lag / (ts-tslag) can be obtained.

Io is the intensity of the X-rays generated by the X-ray generator (4), and is a known amount by measuring at a known or required timing. In the present invention, since the X-ray transmission amount (I) is detected, it is possible to know tslag, that is, the mixing ratio of slag in the molten metal according to I or I / Io.
It is possible to detect slag mixed in at the time of outflow of molten metal from the container (the ladle 1) to the second container (the tundish TD) with high sensitivity.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(2) Sliding nozzle inserted in molten metal channel (3) from first container (1) to second container (Tundish TD)
(2) X that is opposed to the molten metal channel (3)
With the X-ray generator (4) and the X-ray detector (5), the molten metal flow path
(3) The X-ray transmission amount (I) is detected, and when the transmission amount (I) rises to a predetermined value, the sliding nozzle
Close (2).

Here, assuming that the predetermined value is Is, the slag fraction tslag obtained by replacing I in the above equation (5) with Is.
The sliding nozzle (2) is closed when the slag mixing ratio increases to / (ts-tslag).

FIG. 2 shows the X-ray intensity I detected by the X-ray detector 2 when pouring molten steel from the ladle 1 (first container) shown in FIG. 1 into the tundish TD. The horizontal axis is time T. Time T ₁ until the long nozzle 3 there is no slag mixed
Only the molten steel passes through the inside, and the X-ray intensity at this time is I
_Is one. X-ray intensity absorption becomes only gradually less and less complete at time T ₂ slugs time T ₁ after the slag starts mixed X-ray becomes I _2. Here, the X-ray intensity is I ₁ <
It is I _2. Therefore, if a threshold value (Is) is set between I ₁ and I ₂ , and the sliding nozzle 2 is closed by the driving device 11 when I reaches the value, the intensity exceeds the X-ray transmission intensity Is. Injection of molten steel, which is a slag mixing ratio, is cut off.

(3) The slag mixing ratio [tslag / (ts-tslag)] in the molten metal flowing out from the transmitted X-ray dose (I) detected by the X-ray detector (5) is calculated based on the outflow time. Calculate the amount of slag that has flowed into the container.

The calculated slag mixing ratio [tslag / (ts-
tslag)] is defined as Rs, Rs = tslag / (ts−tslag) (6) From (6), the effective thickness (radial width) occupied by the slag in the inner diameter ts of the molten metal flow path (3) tslag is obtained as follows: tslag = ts · Rs / (1 + Rs) (7) Since this is an instantaneous value in time series, this t
By integrating slag, the integrated value ∫tslag · dt is the amount of slag flowing into the second container.

(4) The X-ray detector (5) includes a fluorescent plate (5a) for converting X-rays into fluorescent light, and observes a transmitted image pattern of the X-rays projected thereon, and checks the molten metal flow path (5). 3) The molten metal and slag passing through are distinguished.

By observing the transmitted image pattern of the X-rays projected on the fluorescent screen (5a), the distribution of the X-ray absorptivity of the inner hole of the molten metal flow path (3) can be measured in real time. This is because the X-rays transmitted through the portion having a small absorptance make the fluorescent plate (5a) brighter, and the fluorescent plate (5a) is dark at a position where the X-rays transmitted through the portion having a large absorptance hit. In the case of injecting molten steel from the ladle 1 to the tundish TD, since μslag <μFe, if slag is mixed in the molten steel passing through the nozzle inner hole, the X-ray absorption rate decreases. That is, since a bright portion is generated in the X-ray transmission image pattern of the fluorescent plate (5a), it becomes possible to distinguish between the molten steel passing therethrough and the slag.

(5) Using a one-dimensional or two-dimensional detector as the X-ray detector (5), the X-ray transmission image is converted into an image signal, and an image pattern represented by the image signal is analyzed by image processing. Thus, the molten metal passing through the molten metal flow path (3) and the slag are determined.

According to this, the operation (4) can be performed more quantitatively. A one-dimensional detector is, for example, a position-sensitive detector, and a two-dimensional detector is, for example, an X-ray CC.
There is a D camera. The X-ray absorption rate (I or I / Io) calculated based on the X-ray transmission amount detection signal (I) of each pixel (pixel: minimum unit of electric signal conversion) of the detector is molten metal
From the value of (MS) alone, the ratio of a value lower by a certain value can be monitored by a computer, and the molten metal and slag passing through the nozzle inner hole can be discriminated based on the ratio. In particular, when a two-dimensional detector is used, the size and form of the mixed slag with respect to the nozzle inner hole can be determined.

(6) A long nozzle (2) for guiding the molten metal (MS) flowing out of the first container (1) through the sliding nozzle (2) opened and closed by the driving device (11) to the second container (Tundish TD). 3) X-ray generator (4) and X-ray detector (5) arranged opposite to each other with the interposition sandwiched between molten metal (MS) based on the detection signal of X-ray detector (5) Detection signal processing means (8) for determining the mixing ratio [I or Rs = tslag / (ts-tslag)] of the slag, and the mixing ratio (I or Rs) reaches a predetermined value (Is or Rss). When the drive device (11)
Control means (10) for closing and driving the sliding nozzle (2) through the slag outflow detecting device.

[0022]

FIG. 1 shows an apparatus configuration for implementing the present invention in one embodiment. In FIG. 1, molten steel in a ladle 1 is injected into a tundish TD (not shown) through a sliding nozzle and then through a long nozzle 3. Long nozzle 3
The X-ray generator 4 and the X-ray detector 5 are opposed to each other, and the X-ray transmitted through the long nozzle 3 is detected by the X-ray detector 5.
Is detected.

In this embodiment, the X-ray detector 5 comprises a fluorescent plate 5a for converting X-rays into visible light, and a CCD camera 5b for photographing visible light corresponding to the X-ray image on the alarm plate 5a. An image captured by the CCD camera 5b is, for example, as shown in FIG. In FIG. 3, 5F is a field of view (frame) of the CCD camera 5b, 3i is an X-ray fluoroscopic image of the flesh portion of the long nozzle 3 (gray), MSi is an X-ray fluoroscopic image of molten steel MS (black), SLi is an X-ray fluoroscopic image (white or gray) of the slag, and the background is white. In terms of black density,
The background has the lowest density, the slag image SLi has a lower density, the long nozzle image 3i has a lower density than the slag image SLi, and the molten steel image has a higher density. When the intensity I is high, the CCD camera 5b generates a high-level luminance signal (analog image signal). This video signal is provided to the CRT 7 and an X-ray transmission visual image is displayed on the CRT 7. The video signal is also applied to the amplifier 6 and amplified, and the digital signal is
The data is converted into data (image data) and written into an image memory in the image processing device 8 for each frame.

When the image processing device 8 writes the image data for one frame into the image memory, the image processing device 8 stores the image data in the image memory.
By performing x-direction difference processing (differentiation) on the image, edge pixels having a longitudinal component in the z-direction (FIG. 3) on the image are detected, and the number of edge pixels at the same x position (x-axis projection value) is counted. From the distribution of the count values in the x direction, the left first peak position X3L and the second peak position XmL on the left half of the screen 5F and the right first peak position X3R and the second peak position on the right half of the screen 5F. −
The lock position XmR is detected. First peak position X3L, X3
R corresponds to the position of the outer surface of the long nozzle 3, and the second peak positions XmL and XmR correspond to the position of the inner surface of the long nozzle 3.

Next, the image processing device 8 calculates "second peak position XmL-first peak position X3L" (a value corresponding to the thickness of the long nozzle 3) of the left half of the screen, and similarly calculates the right half of the screen. Of the first peak position X3R-the second peak position XmR is checked, and it is checked whether the calculated value is a value corresponding to the long nozzle thickness. If so, the second peak in the x-axis direction is determined. The region between the peak positions XmL / XmR and the entire region in the z-axis direction is defined as the extraction region. Next, the image processing device 8 integrates the white density value (brightness value) represented by the image data of each pixel in the extracted area over the entire extracted area, and calculates the integrated value in the transmission X in one frame. Assume dose I. Further, the image data of each pixel in the extracted area is binarized by the threshold value Wth, and "1" (white) is given to the pixels of the image data equal to or larger than the threshold value Wth, and the image data in the extracted area is The number of pixels of "1" (white) is counted, and the count value is set as slug size data Size. And transmission X
Data representing dose I (transmission amount data I), slag size data Size, and boundary data (X3L, XmL,
XmR, X3R) to the controller 10.

The above transmission amount data I corresponds to the internal area (X) of the long nozzle 3 in the image frame 5F (FIG. 3).
(between mL / XmR) is the integrated value of the X-ray transmission brightness of the entire region, and this value is the integrated value of the brightness of the molten steel region MSi + the integrated value of the slag region SLi in the region. When the value is large, the value is high, and when the value is small, the value is low, indicating the amount of slag in one frame.

The processing described above is repeated by the image processing device 8 at a fixed period (short period), and the transmission amount data I, the slag size data Size and the boundary data are repeatedly provided to the controller 10.

When a start input is given from the operation display board (operation panel) 9, the controller 10 clears the transmission amount integration register and is input in advance from the operation display board 9. The transmission amount data I and the slag size data transmitted by the image processing device 8 in a cycle (long cycle) proportional to the flow velocity.
The data Size and the boundary data are read (sampled). Each time this reading is performed, the read data is displayed on the operation display board 9 and the slag size data Size is compared with the threshold value Sth previously input from the operation display board 9. By comparison, when Size is equal to or greater than Sth, the operation display board 9 generates an alarm indicating that slag is mixed.
The transmission amount data I is compared with a threshold value Is previously input from the operation display board 9, and the sum obtained by adding the data to the transmission amount integration register is updated to the transmission amount integration register. Write. Then, the data of the transmission amount integration register (a value corresponding to the amount of slag flowing into the tundish) is compared with a threshold value TSs previously input from the operation display board 9. When the data of the transmission amount integration register reaches the threshold value TSs, the controller 10 issues an alarm on the operation display board 9 indicating the slag outflow limit.

When the transmission amount data I exceeds the threshold value Is, the controller 10 closes the nozzle to the sliding nozzle driver 11 when the automatic mode has been input from the operation display board 9 in advance. Instruct. Operation display board 9
When the operator mode is input in advance from
The controller 10 generates an alarm indicating the nozzle closing timing on the operation display board 9. This operator
At the time of the operation, the controller 10 closes the sliding nozzle plate 2 via the sliding nozzle driver 11 in response to the closing instruction by operating the operation panel of the operator.

In the embodiment described above, the controller 10 controls the X of the entire area (between XmL / XmR) of the long nozzle 3 in the image frame 5F (FIG. 3).
The integrated value of the line transmission luminance is defined as transmission amount data I, and when this value exceeds a threshold Is, a sliding nozzle plate 2 is formed.
Is closed, the controller 10 is controlled to transmit the transmission amount data I.
The slag mixing ratio Rs = tslag / (ts-tslag) (6) is calculated based on the formula (5) and when the threshold value Rss is reached, the sliding nozzle plate 2 is driven to close. It may be a thing.

[0031]

As described in detail above, according to the present invention,
Since it is possible to detect slag mixed in when the molten metal flows out from the ladle to the tundish with high sensitivity, it is possible to improve the quality of the molten metal and extend the life of the refractory lining the tundish. Therefore, the present invention is an industrially valuable invention.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an apparatus that embodies the present invention in one embodiment.

FIG. 2 is a time chart showing an X-ray transmission intensity I detected by an X-ray detector 5 shown in FIG.

FIG. 3 is a plan view showing an image represented by an image signal of the CCD camera 5b shown in FIG.

[Explanation of symbols]

1: Ladle 2: Sliding nozzle plate 3: Long nozzle 4: X-ray generator 5: X-ray detector 5a: Fluorescent plate 5b: CCD camera 6: Amplifier 7: CRT display 8: Image processing device 9: Operation display Board 10: Controller 11: Sliding nozzle driver MS: Molten steel MSi: Molten steel see-through image SLi: Slug see-through image 3i: Long nozzle see-through image

Claims (6)

[Claims] 1. An X-ray generator and an X-ray detector opposed to each other across a molten metal flow path from a first container to a second container,
A slag outflow detection method comprising: detecting an amount of X-rays transmitted through the molten metal flow path; and detecting slag mixing in the molten metal in the weld metal flow path based on the transmitted amount. 2. An X-ray generator and an X-ray detector which oppose each other across a molten metal flow path downstream of a sliding nozzle inserted in a molten metal flow path from a first container to a second container. Detecting the amount of transmitted X-rays through the molten metal flow path and closing the sliding nozzle when the amount of transmitted X-rays rises to a predetermined value. 3. The slag mixing ratio in the molten metal flowing out from the transmitted X-ray dose detected by the X-ray detector, and further calculating the slag amount flowing into the second container from the flowing time. Item 4. The slag outflow detection method according to Item 1. 4. The X-ray detector includes a fluorescent plate for converting X-rays into fluorescent light, observes a transmission image pattern of X-rays projected thereon, and detects a molten metal and a slag passing through the molten metal flow path. 2. The slag outflow detecting method according to claim 1, wherein 5. An X-ray transmission image is converted into an image signal using a one-dimensional or two-dimensional detector as the X-ray detector,
The slag outflow detecting method according to claim 3 or 4, wherein an image pattern represented by the image signal is analyzed by image processing to determine molten metal and slag passing through the molten metal flow path. 6. An X-ray generator and an X-ray detector disposed opposite to each other across a long nozzle that guides molten metal flowing out of a first container to a second container through a sliding nozzle opened and closed by a driving device. Detector; detection signal processing means for determining a mixing ratio of slag mixed into the molten metal based on a detection signal of the X-ray detector; and, when the mixing ratio reaches a predetermined value, via the driving device. Control means for closing and driving the sliding nozzle;