JPS603955A - Detection of slag outflow - Google Patents

Abstract

PURPOSE:To detect the outflow of slag with the accuracy of the same level as in the prior art and to assure various operations without trouble during continuous casting by using a reflection mirror for receiving the thermal radiation energy of the molten metal flowing down in an immersion nozzle. CONSTITUTION:A reflection mirror 9 having an elliptical shape is horizontally installed on the outside of an immersion nozzle 5 attached to a sliding nozzle 3 installed in the bottom of a ladle 1 in such a way that the one focus thereof is positioned at the axial center of the nozzle where the molten metal flows. A receiving antenna 10 of which the detecting direction is directed to the center of the mirror 9 is installed at the other focus of the mirror 9. The thermal radiation energy of the molten steel (m) and slag S flowing down in the nozzle 5 are received by such mirror 9, the antenna 10 and a radiometer 11 connected to the antenna 10. The outflow of the slag S is detected from the change in the thermal radiation energy thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to reduce the amount of molten slag floating on the surface of the molten steel when pouring the molten steel from the ladle to the tundish or from the tundish to the mold through a nozzle during seal casting in continuous casting operation. The present invention relates to a method for remotely detecting a leak.

In recent years, as a measure to reduce inclusions in slabs, the area around the molten steel pouring from the ladle to the tundish is covered with a fireproof sealant, and the inside of the fireproof seal is filled with an inert gas such as Ar gas to prevent the molten steel pouring. A long immersion nozzle is attached to the lower end of the sliding nozzle, and the lower end of the immersion nozzle is immersed in the molten steel in the tundish, so that the molten steel pouring flow from the ladle comes into contact with the atmosphere. Seal casting has been adopted to prevent air oxidation of the molten steel pouring flow. However, in such a casting method, it is difficult to visually check the flow of slag at the end of the flow of molten steel from the ladle to the tundish, which causes deterioration in slab quality.

For this reason, methods using radiation thermometers and coil impedance measurement methods have been proposed as methods for detecting slag outflow, but in recent years these methods have been based on materials that have been frequently used for immersion nozzles. It is impossible to detect the outflow of molten slag with high precision using alumina graphite, which has high electrical conductivity and is opaque. The same applies to the case where the outer peripheral surface of the nozzle is covered with an iron shell. Further, the above-mentioned circumstances are similar to those regarding seal casting of molten steel from a tundish into a mold in continuous casting equipment.

Therefore, does the applicant have the above-mentioned drawbacks? Japanese Patent Application Laid-Open No. 1987 (1983) on how to solve the problem
It was disclosed in No.-121864. That is, a method of capturing microwave band radiant energy emitted from the molten metal flowing through the nozzle from outside the nozzle, and detecting slag outflow from changes in the radiant energy caused by the difference in emissivity between molten steel and slag. It is. That is, the thermal radiation energy PC@ with a minute frequency bandwidth Δf (1/sec) and 1ζ emitted from an object having a brightness temperature T ('K) is expressed by the following equation.

P==−T啼ΔI ・・・■ However, K: Boltzmann constant (= L38X10−”J/
6K) Furthermore, the brightness temperature T (0K) of a high-temperature object is expressed as in the following equation, where the physical temperature 'frTA (0K) of the object and the emissivity are ε (1).

T=ε・TA...0 From the above, the difference in emissivity between slag and molten steel can be detected as a difference in thermal radiation energy, and such thermal radiation energy passes through refractories (especially alumina and aluminum). , lumina-silica-based refractories have good microwave transparency),
Thermal radiant energy radiated from the molten metal flowing through the nozzle can be detected from the outside through the nozzle surface, and therefore the outflow of the slag can be detected.

The above method disclosed by the present applicant is a useful invention that can detect the outflow of slag from the outside of the nozzle even when the molten steel casting flow is not exposed as in seal casting. When measuring the thermal radiation energy in the microwave band described above using a high-sensitivity receiver 1δ device (hereinafter referred to as a radiometer) using a shaped antenna, the antenna is cast on the eaves. It is better to keep it away from the flow.

On the other hand, in continuous casting operations, the ladle and tundish are frequently replaced1, and during casting, sampling work and other work is often done near the ladle and tundish.
There are problems in that the above-mentioned antennas, radiometers, and other detectors obstruct work or interfere with other devices and incidental equipment.

The present invention has been made in view of the above-mentioned points, and it is possible to keep detectors such as antennas and radiometers that impede various operations during continuous casting operations as far away from the casting flow as possible, and to provide a good heat source. It is an object of the present invention to provide a method for detecting slag outflow by measuring radiant energy.

That is, the method of the present invention suppresses the outflow of slag when the molten metal is passed from one container to another via a nozzle by absorbing microwave band thermal radiant energy emitted from the molten metal flowing through the nozzle. A method of detecting all the outflow of slag from the change in the thermal radiation energy caused by the difference in emissivity between molten steel and slag has been developed. At the same time, a receiving antenna is placed at the other focal point of this reflecting mirror, and changes in the thermal radiation energy in the microwave band can be detected remotely using the reflecting mirror and the receiving antenna. ) This is a method for detecting slag outflow, the gist of which is to measure and detect the outflow of slag.

The method of the present invention will be explained in detail below based on the accompanying drawings.

FIG. 1 is a schematic diagram showing the implementation state of the method of the present invention, in which molten slag flowing out from a ladle of continuous casting equipment is detected.

In the drawing, (1) is the ladle, (2) is the tandish, and these are the ladle (1) and the tandish (2).
For example, a sliding nozzle (3) is fitted into the bottom of the ladle (1), and the lower end of the sliding nozzle (3) is attached to the lower end of the tundish (3) via a sealing material (4). 2) A series of immersion nozzles (5) installed to be located below the surface of the molten steel in the n1 ladle (1) flow the molten steel in the n1 ladle (1) into the tundish (2) in a non-oxidized state. I'm trying to make it work. In addition, molten slag (S) is suspended on the surface of the molten steel in the ladle (1) to prevent air oxidation of the molten steel and to keep it warm.

(6) is a tundish nozzle 111g fitted into the bottom of the other end of the tundish (2), and the lower end of the tundish nozzle (6) has a mold (7) in the same manner as above. Built to be located below the surface of the molten steel inside
The immersion nozzle (8)-41 was installed, and the tanditshu (
The molten steel from 2) is poured into the mold (γ) as a seal.

Then, one of the focal points of the immersion nozzle (5) attached to the sliding gusset (3) installed at the bottom of the ladle (1) comes to the molten metal flow position on the outside of the nozzle (5). A reflecting mirror (9) having an elliptical shape is installed completely horizontally, and at the other focal point of this reflecting mirror (9) there is a totally reflecting mirror (9) in the detection direction.
), and from the reflecting mirror (9) and the receiving antenna αψ, and the radiometer 03) K connected to this receiving antenna aψ, the water flows down inside the immersion nozzle (5). Thermal radiant energy of the molten steel (E) and slag (S) is received, and the outflow of the slag (S) is detected from changes in the thermal radiant energy. The radiometer (b) is housed in a case, for example, and is kept at a constant temperature at all times so as not to change in temperature due to heat of molten steel during continuous casting operation. Also, (Foundation)
is a recorder that is connected to the radiometer (b) and records the output of the radiometer αυ.

As the reflecting mirror (9) and the receiving antenna (to), for example, those shown in FIG. 2 are used. That is,
Figure (a) shows a reflector (9) with a spheroidal shape and a receiving antenna with a horn type, while figure (b) shows a reflection mirror with a cylindrical ellipsoidal shape. Using a mirror (9), a pill box type receiving antenna (
(to) is shown.

Next, a specific example will be shown below in which the method of the present invention is carried out using the above-mentioned reflecting mirror (9) and receiving aperture (see FIG. 3).

0 Reflector (9) Shape: An ellipsoid of revolution with an aperture of 1400 mm and a vertical width of 240 m is used.Focus position 1 is 3 m (molten metal flow level) and 114 m (receiving antenna position). .

■Receiving antenna (to) Pyramid horn antenna 1 nod size: 95m x 112m ■Radiometer (b) Frequency band: 8 to 12h4 GHz Total power type Lassi radiometer Wave section gain: Approximately 50 dB The above-mentioned reflector (9), Using the receiving antenna α0) and radiometer (9),
The reflective mirror (9) was installed at a distance of m to measure the thermal radiant energy emitted from the molten steel and slag (S).

The amount of change in the received energy received by the method of the present invention is the change in energy radiated from inside the immersion nozzle (5) t (brightness temperature difference of about 500° between molten steel and slag) O about 40% (
The brightness temperature difference was 200°K), and the start of outflow of slag (S) could be detected with sufficient accuracy using a radiometer (b).

In addition, Fig. 4 shows the directivity distribution of the reflector (9) and receiving antenna of this specific example with 0 clauses, and Fig. 5 shows the change in the output of the radiometer (b) during casting. The point indicated by the arrow in the figure is the point at which the slag (S) starts flowing out.

As described above, according to the method of the present invention, in order to receive the thermal radiation energy of the molten metal flowing down the immersion nozzle using a reflecting mirror having an ellipsoidal shape, a receiving antenna or a radiometer is placed near the immersion nozzle as in the conventional method. (30-50m) Even without installing an IC, it is possible to detect slag outflow with the same accuracy as conventional methods, and it is useful for various operations during continuous casting operations.
It has the great effect of not causing any damage.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the method of the present invention in practice, and FIG. 2 is a perspective view showing a reflecting mirror and a receiving antenna used in the method of the present invention. B) Rat 2nd Example, FIG. 3 is a drawing showing a reflecting mirror and a receiving antenna used in a specific example of the method of the present invention, and FIG.
I2) is a front view, FIG. 4 is a drawing showing the directivity distribution due to a reflecting mirror and receiving antenna similar to FIG. 3, and FIG. 5 is a drawing showing changes in the output of the radiometer during casting. (1) is a ladle, (2) is a tundish, (5) is an immersion nozzle, (7) is a mold, (9] is a reflector, uO) is a receiving antenna, and 01) is a radiometer. (1 other person) Figure 2 Figure 5 Casting time (T)

Claims (1)

[Claims] (1) The outflow of slag when the molten metal flows from one container to another with all nozzles valved is captured by the thermal radiation energy in the microwave band emitted from the molten metal flowing through the nozzle. , a method for detecting slag outflow from the change in radiant energy described above due to the difference in emissivity between molten steel and slag.
Then, a radiation mirror having an ellipsoidal shape is arranged so that one focal point thereof is at the flow point of the molten metal jfVc<, and
A receiving antenna is disposed at the other focal point of the reflecting mirror, and the reflecting mirror and receiving antenna are used to remotely measure changes in the thermal radiation energy in the microwave band to detect slag outflow. Slag outflow detection method.