JPH1017923A - Seal device for vacuum degassing lance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal device for vacuum degassing a lance which separates the outer surface of the lance and a seal tube at the time of elevating/lowering the lance and can lower the breaking frequency of the seal tube. SOLUTION: The heat resistant seal tube 3 is arranged on the inner peripheral surface of a hole 2 for inserting the lance in a vacuum vessel 1 for executing the vacuum degassing treatment of molten steel, and a pressure source 4 and a vacuum device 5 are connected with the seal tube 3. In the case of fixing the lance 6, a gap between the hole 2 for inserting the lance and the outer surface of the lance 6 is closed by pressurizing in the seal tube 3 to execute the vacuum seal. In the case of elevating/lowering the lance 6, the seal tube 3 is separated from the outer surface of the lance 6 by forcedly reducing the pressure in the seal tube 3. By this way, the breaking frequency of the seal tube at the time of elevating/lowering the lance is lowered and the service life is extended and the reduction in degassing capacity and the deterioration of the product quality can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device arranged in a lance insertion hole of a vacuum tank for vacuum degassing molten steel in a steel making process.

[0002]

2. Description of the Related Art In a steelmaking process, in a vacuum degassing apparatus for molten steel, for example, RH, DH, VOD, KIP, etc., a gas lance such as oxygen or a powder lance or a powder immersion lance is used. . As shown in FIG. 2, these lances 6 are inserted into the vacuum tank 1 from outside the vacuum tank through the lance insertion holes 2 provided in the vacuum tank 1, and the molten steel 12 in the ladle 11 is subjected to vacuum degassing. At this time, ascend and descend as necessary, and blow oxygen or powder.

Since the pressure inside the vacuum chamber 1 is reduced to a high degree of vacuum, it is important to seal the gap between the lance insertion hole 2 and the outer surface of the lance 6. That is, when the lance 6 is held and fixed in the vacuum tank, air is sufficiently prevented from entering the vacuum tank 1 from outside the vacuum tank, and when the lance 6 is moved up and down, the seal is released to allow the lance 6 to move up and down smoothly. Must be.

Conventionally, various sealing devices 10 have been put to practical use in order to improve the sealing property. In particular, a rubber seal tube 3 having heat resistance as shown in FIG. , And a sealing device provided with a pressurizing / depressurizing pipe 13 is often used. This is shown in FIG.
As shown in FIG. 4A, when the lance 6 is fixed, the inside of the seal tube 3 is pressurized to, for example, 4 to 6 atm to close the gap between the lance insertion hole 2 and the outer surface of the lance 6 and to perform vacuum sealing. As shown in (b), when the lance 6 is moved up and down, the inside of the seal tube 3 is depressurized to release the seal, and the outer surface of the lance 6 is separated from the seal tube 3 so that the lance 6 can be moved up and down. .

[0005]

However, conventionally, since the pressure reducing means of the seal tube 3 is radiated to the atmosphere, there is a problem that the pressure is not sufficiently reduced. That is,
Since one of the seal tubes 3 is at atmospheric pressure and the other is under vacuum, the seal tube 3 is pulled toward the vacuum side as shown in FIG. Therefore, the outer surface of the lance 6 and the seal tube 3 cannot be separated from each other as shown in FIG. 4B, and the seal tube 3 remains in contact with the outer surface of the lance 6 as shown in FIG. It is. In this case, when the lance 6 is moved up and down, the frequency of damage to the seal tube 3 due to small projections such as small metal sticking to the outer surface of the lance 6 increases. When the seal tube 3 is damaged, not only physical loss of the expensive seal tube 3 but also air infiltration into the vacuum chamber 1 and the degree of vacuum is deteriorated, degassing performance is deteriorated, and quality such as nitrogen pickup is reduced. May cause adverse effects.

Therefore, the present invention provides a simple lance sealing device for vacuum degassing that can sufficiently and quickly depressurize the inside of the seal tube when the lance is moved up and down, and can reliably separate the outer surface of the lance from the seal tube.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a heat-resistant seal tube is disposed on an inner peripheral surface of a lance insertion hole of a vacuum tank for sucking molten steel into the inside and blowing gas or powder with a lance to perform vacuum degassing. When a pressure source and a vacuum device are connected to the seal tube, and when the inserted lance is fixed, the inside of the seal tube is pressurized to close the gap between the lance insertion hole and the outer surface of the lance, and the lance is raised and lowered. In this case, there is provided a lance sealing device for vacuum degassing, wherein the inside of the seal tube is forcibly depressurized to separate the seal tube from the outer surface of the lance. As the vacuum device, it is preferable to use a vacuum exhaust device provided as a standard feature in the vacuum degassing device.

In the present invention, since the seal tube is connected to the vacuum device, when the lance is fixed, the inside of the seal tube is pressurized and the seal tube is brought into close contact with the outer surface of the lance, so that the lance insertion hole and the outer surface of the lance are formed. In addition to closing the gap and performing vacuum sealing, when raising and lowering the lance, forcibly depressurize the inside of the seal tube even if the seal tube is pulled to the vacuum side to reliably shrink the seal tube. Becomes possible. As a result, the outer surface of the lance and the seal tube can be separated from each other to reduce the frequency of breakage of the seal tube. As the vacuum device, any device can be used as long as it can forcibly depressurize the inside of the seal tube.For example, a venturi pump or the like may be provided exclusively for the seal tube, or in order to depressurize the vacuum tank. A vacuum exhaust device that is provided as standard equipment in the vacuum degassing apparatus may be used, and connected to this via a valve.

[0009]

FIG. 1 shows an example of a sealing device according to the present invention.

FIG. 1A shows an example in which the seal tube 3 is connected to a venturi pump 5 via an electromagnetic valve 7.
The material of the seal tube is a hollow gasket made of rubber containing reinforcing cloth or rubber alone, and has a circular, polygonal, U-shaped, or semi-elliptical cross section. As the rubber material, fluorine rubber is preferable. The thickness was 5.5 mm, the maximum cross-sectional length was 55 mm, and the heat resistance temperature was about 250 ° C. When the lance 6 is moved up and down, when the electromagnetic valve 7 is set to the illustrated position and air is blown from the pressurizing source 4, the pressure of the seal tube 3 is forcibly reduced by the action of the venturi pump 5. As a result, the seal tube 3 is separated from the outer surface of the lance 6, so that the lance 6 can be moved up and down without damaging the seal tube 3. When oxygen or powder is blown while the lance 6 is fixed, the electromagnetic valve 7 is switched, and then the gas is blown from the pressurizing source 4 at a gas pressure of 4 kg / cm ^2. 4 kg
/ Cm ² (= atmospheric pressure) within 10 seconds to close the gap between the lance insertion hole 2 and the lance 6 and perform vacuum sealing.

FIG. 1B shows an example in which a vacuum pumping device for depressurizing the vacuum chamber 1 is used without providing a dedicated vacuum device. The seal tube 3 is connected to an exhaust system of a vacuum exhaust device via a valve 8, and a pressure source for the seal tube 3 is separately provided, though not shown. In this example, lance 6
When the valve 8 is opened when raising or lowering the pressure, the inside of the seal tube 3 is forcibly reduced to 400 Torr or less, preferably to a range of 100 to 150 Torr by a vacuum exhaust device.
And within 15 seconds, preferably from atmospheric pressure to 400 Torr
The pressure is reduced to r within 5 seconds, and the seal tube 3 is separated from the outer surface of the lance 6 by about 2.5 mm, so that the lance 6 can be moved up and down without damaging the seal tube 3. When fixing the lance 6, the valve 8 is closed,
What is necessary is just to pressurize the seal tube 3 from a pressurizing source not shown. If the sealing device currently used is to be improved, the sealing device shown in FIG. 1B is advantageous in that the number of places to be improved is reduced.

[0012]

According to the sealing device for a lance for vacuum degassing of the present invention, not only can a sufficient vacuum seal be secured when the lance is fixed, but also the inside of the seal tube can be sufficiently depressurized when the lance is raised and lowered, and the outer surface of the lance and the seal tube can be sealed. Can be separated, so that the frequency of breakage of the seal tube when the lance moves up and down can be reduced. As a result, the life of the seal tube is extended, and a decrease in degassing performance and a deterioration in product quality are prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the present invention.

FIG. 2 is a diagram showing an example of vacuum degassing of molten steel.

FIG. 3 is a view showing an example of a sealing device for a lance for vacuum degassing.

FIG. 4 is a view showing vacuum sealing by a sealing device for a vacuum degassing lance and release of a seal for elevating the lance.

FIG. 5 is a view showing a problem of a conventional vacuum degassing lance sealing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum tank 2 Lance insertion hole 3 Seal tube 4 Pressurization source 5 Venturi pump 6 Lance 7 Solenoid valve 8 Valve 9 Gas cooler 10 Sealing device 11 Ladle 12 Molten steel 13 Pressurization / decompression piping

Claims (2)

[Claims] 1. A heat-resistant seal tube is disposed on an inner peripheral surface of a lance insertion hole of a vacuum tank for sucking molten steel into the inside, blowing gas or powder by a lance to perform vacuum degassing, and pressurizing the seal tube. Connecting the source and the vacuum device,
When fixing the inserted lance, pressurize the inside of the seal tube to close the gap between the lance insertion hole and the outer surface of the lance, and when raising and lowering the lance, forcibly reduce the pressure inside the seal tube and remove the seal tube from the outer surface of the lance. A lance sealing device for vacuum degassing, wherein 2. The sealing device for a lance for vacuum degassing according to claim 1, wherein the vacuum device is a vacuum exhaust device that is provided as a standard equipment in the vacuum degassing device.