JPH1150131A - Vacuum degassing vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum degassing vessel which can drastically increase the frequency of using charge of a lower vessel while restraining the deformation to less than the using limit. SOLUTION: The lower vessel in the vacuum degassing vessel is provided, at the bottom part of the lower vessel 10 in, with one pair of fitting tubes 11a, 11b to the lower ends of which a castable tube fitting flange 12 connecting the tubes is fitted. A cooling means for the fitting tubes composed of one pair of annular cooling water tubes 13 surrounding the fitting tubes to the castable tube fitting flanges, a connecting cooling water tube 14 arranged between one pair of the annular cooling water tubes, a water supplying tube communicated with one side of one pair of the annular cooling tubes and a water drainage tube 16 communicated with the other side of the annular cooling tubes, are provided to the castable tube fitting flange.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting pipe for an immersion pipe in a lower tank of a vacuum degassing tank.

[0002]

2. Description of the Related Art There is an RH degassing method in which molten steel obtained by refining molten iron in a converter is further decarburized, degassed, deoxidized and inclusions are separated. In this method, the vacuum degassing tank is evacuated to about 0.1 Torr, and the molten steel is circulated from the molten steel pot between the vacuum degassing tank and the molten steel pot by utilizing a difference from the atmospheric pressure to perform refining.

[0003] The degassing tank is composed of a lid, a body tank and a lower tank, in which the steel shell of the lower tank is formed by radiant heat radiated from the molten metal surface of the molten steel pot and circulating molten steel flow. As shown in FIG. 4, the mounting pipe attached to the bottom of the lower tank 10 is deformed outwardly into a C-shape as shown in FIG. Conventionally, in order to suppress such deformation, reinforcing ribs have been attached to the bottom surface of the lower tank in a lattice shape, or the thickness of the iron plate of the steel shell has been increased.

[0004]

However, during use, as shown by the dashed line in FIG. 4, a deformation consisting of two inwardly projecting ridges and an outwardly recessed valley formed at the center, as shown by the broken line in FIG. Occurs, and the mounting tubes 11a, 11
b is transformed into a letter "C". When this deformation increases, the immersion pipe and the molten steel pot interfere with each other, and the immersion pipe cannot enter the molten steel pot. If the charge exceeds about 1,000 charges, the deformation exceeds the use limit (50 mm). When the amount of deformation exceeds the usage limit, there is a problem that a crack is formed in the mounting portion of the reinforcing rib.

[0005] It is an object of the present invention to provide a vacuum degassing lower tank in which the above deformation can be suppressed to below the service limit and the number of charges used in the lower tank can be greatly increased.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide an immersion pipe mounting flange for connecting a pipe at the lower end of an installation pipe attached to the bottom of a lower tank of a vacuum degassing tank. A pair of annular cooling water pipes surrounding the pipe on the flange, a communication cooling water pipe provided between the pair of annular cooling water pipes, a water supply pipe communicating with one of the pair of annular cooling water pipes, and a drainage communicating with the other annular cooling water pipe. This is achieved by a lower tank of a vacuum degassing tank provided with a cooling means for an attached pipe consisting of a pipe.

[0007] The "working" flange connects the pair of mounting tubes to provide resistance to the C-shaped deformation of the tubes, and the flange blocks radiant heat from the molten steel and cools the mounting tubes. As a result, the temperature at the time of operation of these tubes and the bottom shell of the lower tank decreases, so that the deformation resistance of these members increases.

[0008]

FIG. 1 is a schematic longitudinal sectional view showing an operation state of an RH degassing facility according to the present invention. The vacuum degassing tank 1 includes a lower tank 10 made of an iron plate having a pair of mounting pipes 11a and 11b at a lower portion, a body tank 20 made of an iron plate having an exhaust pipe 7, and a lid made of an iron plate. 30. Of course, the inner surfaces of the mounting pipes 11a and 11b, the lower tank 10, the body tank 20 and the lid 30 are lined with an irregular refractory and a molded refractory brick 17. The immersion tubes 3a, 3b are connected to the mounting tubes 11a, 11b.

In the refining of molten steel, the molten steel pot 4 containing molten steel is brought under the vacuum degassing tank 1, the immersion pipes 3a and 3b are immersed in the molten steel 5, and then the exhaust pipe 7 is exhausted by an exhaust device (not shown). The gas in the vacuum degassing tank is exhausted through
The molten steel 5 is circulated between the lower tank 10 and the molten steel pot 4 by applying a Torr vacuum to the pressure difference between the atmospheric pressure and the vacuum in the tank.

[0010] The present invention relates to the structure of the lower tank described above. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a longitudinal sectional view of a lower tank according to the present invention,
FIG. 3 is a bottom view of the lower tank according to the present invention. Lower tank 1
0, the mounting pipe 11 is symmetrical with respect to the center of the bottom.
a, 11b are provided downward. Reference numeral 12 denotes an immersion tube mounting flange, which is a pair of left and right mounting tubes 11a and 11b.
It is formed by connecting the spaces. The flange 12 is provided therein with annular cooling water pipes 13 surrounding the mounting pipes 11a and 11b, respectively, and a connecting pipe 14 connecting them. Annular cooling water pipe 13 and connecting cooling water pipe 14
Can be provided by forming a groove in the flange 12 and welding a lid plate thereon, or by forming a ring-shaped cooling water pipe and a connecting cooling water pipe in a cast steel flange.

A water supply pipe 15 is connected to one annular cooling water pipe 13, and a drain pipe 16 is connected to the other annular cooling water pipe 13. Reference numeral 12a is a bolt hole for attaching the immersion tubes 3a, 3b to the attachment tubes 11a, 11b.

[0013]

[Example] Outer diameter: 80mm in a lower tank of 3050mm
And the cooling means described above was mounted and operated. As a result, the service life of the lower tank was increased to 3,000 charges, during which no cracks were found in the refractory bricks.

[0014]

As described above, the lower tank of the present invention has an integrated immersion pipe mounting flange of the mounting pipe, and further has means for cooling the mounting pipe, so that the life of the lower tub is greatly increased. Also,
The joint crack of the lining brick of the lower tank is prevented, and the life is extended.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an operation state of an RH degassing facility according to the present invention.

FIG. 2 is a longitudinal sectional view of a lower tank according to the present invention.

FIG. 3 is a bottom view of the lower tank according to the present invention.

FIG. 4 is a longitudinal sectional view showing a deformation of a mounting pipe portion of a conventional lower tank.

[Explanation of symbols]

 1 Vacuum degassing tank 3a, 3b immersion pipe 4 molten steel pot 5 molten steel 10 lower tank 11a, 11b mounting pipe 12 immersion pipe mounting flange 13 annular cooling water pipe 14 communication cooling water pipe 15 water supply pipe 16 drain pipe 17 refractory brick

Continuing on the front page (72) Inventor Hiroyuki Hiji 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Taku Ogawa 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Inside the corporation

Claims (1)

[Claims] 1. A pair of annular cooling water pipes surrounding a pipe provided at a lower end of a mounting pipe attached to the bottom of a lower tank of a vacuum degassing tank, the flange being connected to the pipe. And a cooling means for a mounting pipe comprising a communication cooling water pipe provided between the pair of annular cooling water pipes, a water supply pipe communicating with one of the pair of annular cooling water pipes, and a drain pipe communicating with the other annular cooling water pipe. A lower tank of a vacuum degassing tank, characterized in that: