JPS61281811A - Downcomer for vacuum degassing device - Google Patents

Abstract

PURPOSE:To prevent the clogging in the downcomer of a vacuum degassing device which blows a gas to the molten steel in a ladle on the riser side immersed in the molten steel and returns the molten steel back to the downcomer side by forming a gaseous curtain to the inside surface of the downcomer. CONSTITUTION:An iron plate 16 in attached in the same manner as heretofore to the top end of approximately cylindrical castable refractories 15 of the downcomer 4 and an annular porous trick 21 is provided in the uppemost brick 19 of lining bricks 17-19 on the inside of the refractories 15. An annular groove 22 is formed to the outside circumferential surface of said brick 21 and a passage 23 for an inert gas is connected thereto. The downcomer 4 is attached to the bottom end of a lower vessel 8 of the vacuum degassing device and the amt. of the gas to be ejected on the downcomer 4 is made smaller than the amt. of the gas to be ejected on the riser 3 side during the reflux of the molten steel 2 to about the extent of forming the gaseous curtain along the inside wall surface of, for example, the downcomer 4. The gaseous curtain is thereby formed over the entire inside wall surface of the downcomer 4 an the sticking of slag is thoroughly eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) This invention relates to a downcomer for a vacuum degassing device.

[L animals 11 Figure 1 shows an outline of an example of a conventional vacuum degassing device. A rising pipe 3 and a descending pipe 4 are used as circulation pipes for the molten steel 2 in the ladle 1.
The molten steel is immersed in the steel, and an inert gas such as argon gas is ejected from the gas ejection part 5 on the riser pipe 3 side to raise the molten steel in the direction of the arrow 6. Accordingly, the molten steel passes through the downcomer pipe 4 and descends in the direction of the arrow 7. The degassing tank 8 is located near the hot water level 9, and above the hot water level 9, a heating device 10 is arranged substantially parallel to the hot water level 9. An alloy inlet 11 is provided near the heating device. Further, an exhaust port 12 is provided above the heating device 10.

When the molten steel steadily descends inside the downcomer pipe 4, the temperature of the molten steel is relatively low. As a result, slag easily adheres to the inner surface of the downcomer pipe 4, and there is a problem that the inside of the downcomer pipe 4 becomes clogged and becomes unnecessary after being used, for example, about 100 times.

An object of the present invention is to eliminate the drawbacks of the prior art as described above, and to make it difficult for the inside of a downcomer pipe for a vacuum degassing device to become clogged.

11 animals 1E The gist of the present invention for achieving this purpose is to immerse a rising pipe and a downcomer pipe as reflux pipes in molten steel in a ladle, and blowing gas into the rising pipe side to transfer the molten steel to the downcomer pipe side. A downcomer for a vacuum degasser is characterized in that the downcomer is provided with a gas ejection structure for forming a gas curtain on the inner surface of the downcomer.

In the vacuum degassing equipment of the ``ruta'', a gas ejection structure (for example, a porous brick 21, a general fired brick with many thin holes 25 formed in it) is used to form a gas curtain on the inner surface of the downcomer pipe 4. (or a general fired brick with many slits 27 formed inside it, or a combination thereof)
will be established.

Inert gas such as argon gas is ejected from the gas ejection structure to preferably form a gas curtain over the entire inner surface of the downcomer pipe 4 to prevent slag from adhering to the inner surface of the downcomer pipe 4.

LL Hereinafter, the present invention will be described in detail with reference to the drawings.

This invention improves the structure of the conventional downcomer pipe 4 for vacuum degassing equipment shown in FIG. It is equipped with the ejection structure shown in .

First, the embodiment shown in FIG. 2 will be described.

The monolithic refractory 15 is formed into a substantially cylindrical shape, and an iron plate 16 is attached to the upper end thereof in a conventional manner.

The inside of the monolithic refractory 15 is lined with bricks 17.18.
19 is provided, and a cylindrical molten steel passage 2° is formed inside thereof. These lining bricks 17.18.19
A ring-shaped porous brick 21 is provided in the uppermost lining brick 19. An annular groove 22 is formed on the outer peripheral surface of this porous brick 21, and a gas passage 23 for inert gas is connected thereto.

The material of the porous brick 21 is, for example, alumina, magnesia, spinel, etc.
Pore diameter 20-100 microns, air permeability 1-5 cm
3-cm/cm2-sec-cm-H20, allowing inert gas to pass through smoothly.

The annular groove 22 is formed as a pressure equalizing zone on the entire outer peripheral surface of such a porous brick 21, and a gas passage 23 is connected thereto.

Further, as the lining bricks 17, 18, and 19, ordinary fired bricks (for example, maguro bricks, etc.) are generally used.

The embodiments shown in FIGS. 3 and 4 are the same as the embodiment shown in FIG. 2 except for the gas ejection structure, so a description thereof will be omitted.

The ejection structure shown in FIG. 3 has a plurality of thin holes 25 formed in the lining brick 19. Although the shape of the holes 25 is arbitrary, it is desirable that they are arranged uniformly over the entire circumferential surface of the lining brick 19. These holes 25 are connected to a groove 26 formed in an annular shape on the outer peripheral surface of the lining brick 19, and are further connected to the gas passage 23.

The gas ejection structure shown in FIG. 4 has a slit 27 formed inside the lining brick 19, which is connected to the gas passage 23.

The slit 27 is located close to the inner wall surface of the lining brick 19, and gas is sent out little by little from there to the inner wall surface through small pores in one lining brick. For example, the lining brick 19 is made of maguro-based brick, has a pore diameter of 10 to 40μ, and has an air permeability of 0.01 to 40μ.
0.001 cm3-cm/cm2-5ec-cn
It is desirable to set it to +-H20.

l Discharge Δ11 The downcomer pipe 4 as described above is attached to the lower end of the lower tank 8 of the vacuum degasser. During melt reflux, argon gas is flowed at a flow rate of 1000 to 120011/min on the rising pipe 3 side, and argon gas is flowed at 100 to 200 Q/min on the downcomer pipe 4 side.
When the flow was performed at a flow rate of 100 min and otherwise used in the same manner as a conventional vacuum degassing device, almost no slag adhesion was observed in the downcomer pipe 4 even after 150 uses, and the effect of preventing blockage was remarkable. .

It is desirable that the amount of gas ejected on the downcomer pipe 4 side is smaller than the amount of ejected gas on the riser pipe 3 side.
The amount of gas should be enough to form a gas curtain along the inner wall surface. In particular, gas is ejected from the upper part of the downcomer pipe 4, and most of the gas is lowered downward along the inner surface of the downcomer pipe 4 by the circulating molten steel, forming a gas curtain, and a part of the ejected gas is It is most desirable to set the gas curtain so that it rises along the inner wall surface of the downcomer pipe 4 due to its buoyancy and forms a gas curtain over the entire inner wall surface of the downcomer pipe 4. By doing so, a gas curtain is formed over the entire inner surface of the downcomer pipe 4, and there is no slag adhesion. Therefore, no blockage occurs inside the downcomer pipe 4, and the downcomer pipe 4 can be used much more times than in the past.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing a conventional vacuum degassing device, and FIG. 2 is a first downcomer pipe for a vacuum degassing device according to the present invention.
3 is a cross-sectional view showing a second embodiment of the downcomer pipe for a vacuum degassing device according to the present invention; FIG. 4 is a cross-sectional view showing a third downcomer pipe for a vacuum degassing device according to the present invention. It is a sectional view showing an example. i, ladle 2, molten steel 3, rising pipe 4, descending pipe 21, porous brick 25, tfiJ hole 27...
Slit 23... Gas passage Fig. 2

Claims (5)

[Claims] (1) In a vacuum degassing device that circulates the molten steel to the downcomer side by immersing the riser pipe and the downcomer pipe as a reflux pipe in the molten steel in the ladle and blowing gas on the riser pipe side, the gas flows into the inner surface of the downcomer pipe. A downcomer pipe for a vacuum degassing device, characterized in that it is provided with a gas ejection structure for forming a curtain. (2) The downcomer pipe for a vacuum degassing device according to claim 1, wherein the gas ejection structure is composed of porous bricks. (3) The downcomer pipe for a vacuum degassing device according to claim 1, wherein the gas ejection structure is a common fired brick with many thin holes formed therein. (4) Claim 1 in which the gas ejection structure is constituted by a slit formed inside an ordinary fired brick.
A downcomer pipe for the vacuum degassing equipment described in . (5) A patent claim in which the gas ejection structure is a combination of at least two of a porous brick, a large number of thin holes provided in an ordinary fired brick, and a slit formed inside an ordinary fired brick. A downcomer pipe for a vacuum degasser according to scope 1.