JPH10183230A - Method for repairing refractory in vacuum degassing vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repairing method of a refractory in a vacuum degassing vessel which prevents damage by improving the strength of the refractory in hot-state and can prevent fall-down of a reinforced body from a reinforcing part. SOLUTION: Parts of immersion tubes 2 are dipped into molten steel 3 incorporated in a ladle 4, etc., and closed, and after evacuating the air in the vacuum degassing vessel 1 from an exhaust tube 11, the exhaust tube 11 is closed. Firstly, magnesium chloride powder or chromium chloride powder or mixed powder of these is supplied into the vacuum degassing vessel 1 and vaporized. Successively, gas of steam, oxygen or carbon dioxide or mixed gas of these is supplied in the vacuum degassing vessel 1. Instead of the magnesium chloride powder, granular material mixed with magnesia powder and aluminum powder can be supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for repairing refractories in a vacuum degassing tank.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view schematically showing an RH reflux vacuum degassing apparatus. In the figure, 1 is a vacuum degassing tank, 2
Is an immersion pipe (2a: ascending pipe, 2b: descending pipe), 3 is molten steel,
Reference numeral 4 denotes a ladle, 5 denotes an iron shell, 6 denotes scattered molten steel, 7 denotes a refractory, 8 denotes an inert gas inlet, 9 denotes an inert gas supply pipe, and 11 denotes an exhaust pipe.

As shown in FIG. 2, a dipping tube 2 (a rising tube 2a)
And the downcomer pipe 2b) is immersed in the molten steel 3 in the ladle 4 and depressurized in the vacuum degassing tank 1 to suck up the molten steel 3,
An inert gas is blown from the inert gas injection port 8, and the molten steel 3 is guided into the vacuum degassing tank 1 by utilizing the buoyancy of the gas and lowered from the downcomer pipe 2b to degas the molten steel. is there.

As described above, the refractory 7 inside the vacuum degassing tank 1 is in contact with the molten steel 3, and this contact portion is easily damaged. Generally, bricks constituting the inner wall of a container for molten metal are mainly made of magnesia for use at high temperatures. Among them, MAG type brick to which chromium oxide is added in an appropriate amount is widely used in the RH type vacuum degassing tank.

As a method for repairing bricks in an industrial furnace, a thermal spraying method has been proposed. In this method, the refractory powder is made into a semi-molten or molten state in a flame composed of oxygen and fuel gas, or by burning magnesium or silicon.
It is to adhere to the damaged part of the magcro brick. For example, Japanese Unexamined Patent Publication (Kokai) No. 62-15508 discloses a flame sprayed material applied for such a purpose.

[0006] Japanese Patent Publication No. Hei 3-9185 discloses a thermal spray repair body composed of SiO ₂ , Al ₂ O ₃ , CaO, Fe ₂ O ₃ and Na ₂ O at a specific ratio and enduring long-term use. A high siliceous thermal spray material is disclosed.
In the construction, these sprayed materials are melted by a flame, collide with a repaired portion and rapidly solidify, thereby forming a sprayed material mainly composed of a glass phase.

[0007] With regard to the vacuum degassing tank in particular, Japanese Patent Application Laid-Open No. Hei 6-158145 discloses a method for repairing a thermal spray of an RH degassing furnace. In this method, the center of the canopy of the RH degassing furnace is opened, a spraying burner / lance is inserted into the furnace, and an in-furnace observation camera is inserted from the immersion tube to confirm the damaged part of the refractory lining and repair by spraying. It is a method characterized by doing.

[0008] Japanese Patent Application Laid-Open No. Hei 8-60230 discloses that
A method for integrally repairing the refractory inside the reflux pipe and the immersion pipe of a vacuum degassing tank is disclosed. In this method, an inner refractory of an immersion pipe is cut to a predetermined size by a vertically movable swiveling drill cutter that can be raised and lowered and swiveled from below the degassing tank, and is preformed and fired along the cut inner refractory. This is a method in which a refractory sleeve for repair is inserted and fixed.

[0009]

However, the prior art has various problems. For example, a sprayed material mainly composed of a glass phase described in Japanese Patent Application Laid-Open No. 62-15508 or Japanese Patent Publication No. 3-9185 crystallizes in a cooling process and transforms into a crystal phase. Since the volume shrinks during this phase transition,
Cracks occur. For this reason, the thermal spray reinforcement becomes insufficiently bonded to the base material, and cannot be used for a long time.

[0010] Furthermore, in these techniques, when the base material is deteriorated and its strength is reduced, cracks are propagated from the base material side and the thermal sprayed reinforcing member falls off. Therefore, the life of the thermal spray reinforcing body is not determined only by the strength and spalling resistance of the thermal spray body itself. There is also a problem of such a thermal spray reinforcing body falling off, and the life is about half a year.

In the thermal spray repairing method described in Japanese Patent Application Laid-Open No. 6-158145, it is necessary to open the center of the canopy of the RH degassing furnace. Since the RH degassing furnace maintains a vacuum, it is necessary to strictly seal and the like. At the same time, it is necessary to insert a furnace observation camera from the immersion tube to check the damaged portion of the refractory lining. However, even with such a camera observation, fine cracks cannot be detected.

In addition, the repair work by this method requires a cooperative work of the work (crane work) in the upper part and the work in the lower part of the RH degassing furnace, and since both are separated, the work instruction is indirectly transmitted by a radio device or the like. Work efficiency is poor due to the means.

The method of repairing thermal spraying described in Japanese Patent Application Laid-Open No. H8-60230 is a method of integrally repairing the refractory inside the reflux pipe and the immersion pipe of the vacuum degassing tank. Repair of the refractory lining above is separately performed. There is a need to.

[0014] These operations are performed by inserting a thermal spraying device into the vacuum degassing tank or using a rotary drill cutter.
In order to insert it into the inner refractory of the immersion pipe, it is necessary to align the vacuum degassing tank and the working equipment with a crane or the like, and there is a limit in improving the working efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to enhance the strength of a refractory in a vacuum degassing tank during heating to prevent damage, and to provide a reinforcing member for reinforcement. Provided is a method for repairing a refractory of a vacuum degassing tank, which can prevent the falling off from a reinforcing portion.

[0016]

According to a first aspect of the present invention, there is provided a method for repairing refractories of a vacuum degassing tank having an immersion pipe and an exhaust pipe, wherein a part of the immersion pipe is immersed in molten steel in a ladle or the like. After the inside of the vacuum degassing tank is evacuated from the exhaust pipe, the exhaust pipe is closed.First, magnesium chloride powder or chromium chloride powder or a mixture of these powders is supplied into the vacuum degassing tank. And then steam,
A method for repairing a refractory in a vacuum degassing tank, wherein a gas containing oxygen, carbon dioxide, or a mixed gas thereof is supplied into the vacuum degassing tank.

In the present invention, in the vacuum degassing tank, the immersion pipe is immersed in the molten steel, and the molten steel rises by evacuation to heat the refractory. In this state, magnesium chloride or chromium chloride is supplied. Since these compounds are all solid at room temperature, they are supplied as powder in a vacuum degassing tank in order to promote a reaction described later. Therefore, magnesium chloride powder or chromium chloride powder or a mixture of both is supplied into a vacuum degassing tank.

Since the inside of the vacuum degassing tank is heated by molten steel, these powders are vaporized into magnesium chloride gas and chromium chloride gas, respectively. With the vaporization of the powder supplied into the vacuum degassing tank, the gas pressure in the vacuum degassing tank increases and the molten steel surface decreases. As a result, the surface of the refractory which comes into contact with the molten steel in the degassing process appears, and is covered by these vaporized magnesium gas and chromium chloride gas.

In this state, a gas containing water vapor, oxygen, carbon dioxide or a mixed gas thereof (hereinafter referred to as a reactive gas) is supplied. Examples of such a gas include H ₂ O, A gas diluted with O ₂ and CO ₂ gas or a gas which does not react with these gases is used. For example, N ₂ or Ar may be used as the diluent gas.

When O ₂ is used as the reactive gas, magnesia MgO solid can be precipitated by reaction with magnesium chloride gas. The reaction is shown below.

MgCl ₂ + 1 / 2O ₂ → MgO + Cl ₂

When H ₂ O is used as the reactive gas, magnesia MgO solid can be precipitated by reaction with magnesium chloride gas. The reaction is shown below.

MgCl ₂ + H ₂ O → MgO + 2HCl

When CO ₂ is used as the reactive gas, if a mixed gas with H ₂ is used, magnesia solid can be precipitated by the reaction with magnesium chloride.
The reaction is shown below.

MgCl ₂ + CO ₂ + H ₂ → MgO + CO + 2HCl

The reaction between water vapor H ₂ O in the reactive gas and chromium chloride can precipitate chromium oxide solids. The reaction is shown below.

2CrCl ₃ + 3H ₂ O → Cr ₂ O ₃ + 6HCl

The concentration of magnesium chloride contained in the gas containing magnesium chloride (diluent gas) is 0.1%.
vol. % Is desirable. This is 0.1
vol. If the amount is less than 10%, the reaction rate is too slow.

Reactive gases (H ₂ O, O ₂ , and C
The concentration of the reactive gas contained in the gas (diluent gas) containing O ₂ ) is 1 vol. % Is desirable. This corresponds to 1 vol. If the amount is less than 10%, the reaction rate is too slow.

As a gas containing a reactive gas, H
_{When two} or more gases are contained from among ₂ O, O ₂ and CO ₂ , pure gases may be mixed, but various combustion gases may be used. As a combustion gas, any gas obtained by burning natural gas, liquefied petroleum gas, kerosene, heavy oil, coal, coke oven gas, blast furnace gas, converter gas, or the like with air or oxygen can be used. Also,
Exhaust gas from various heating furnaces may be used as needed.

Next, the reaction on the surface and the surface layer of the brick will be described. Since the evacuation has eliminated the cracks in the bricks and the gas inside the pores, magnesium chloride and chromium chloride (containing) gas have penetrated into these pores. These react with the above-mentioned reactive gas, and precipitate magnesia and chromium oxide inside the pores, and the pores of the brick are filled as the reaction continues.

In addition, a reaction between the gas containing magnesium chloride and chromium chloride and the reactive gas continues on the surface of the porcelain brick, and the solid (magnesia, chromium oxide) continues to be deposited on the surface of the porcelain brick. In this way, a layer of the precipitate is formed on the surface of the porcelain brick. As a result, the surface of the magma brick is protected by this layer of precipitate.

As the reaction proceeds, magnesium chloride, chromium chloride and the reactive gas in the vacuum degassing tank are consumed, so that the gas pressure in the tank decreases and the molten steel surface rises. In that case, magnesium chloride, chromium chloride and the reactive gas are supplied (added) to the vacuum degassing tank sequentially or alternately.

As described above, according to the present invention, by reinforcing magnesia and chromium oxide, which are the main components of the brick (magcro brick), the reinforcing member and the brick are integrated, and the problem of falling off from the reinforcing portion is solved. You can also.

According to a second aspect of the present invention, in place of the magnesium chloride powder, a granulated material in which magnesia powder and aluminum powder are mixed is supplied, and the refractory repair of the vacuum degassing tank according to claim 1 is provided. Is the way.

The present invention utilizes the reaction between magnesium (Mg) vapor and a reactive gas. As a method of generating Mg vapor, Mg powder is easily ignited and is difficult to use, so that magnesia MgO and Al powder are reacted at a high temperature to generate Mg vapor. The reaction is shown below.

3MgO + 2Al → 3Mg + Al ₂ O ₃

In this case, the reaction temperature is 850 to 1700 ° C.
Is preferably within the range. This is because if the temperature is lower than 850 ° C., the reaction rate is too slow. On the other hand, if the temperature exceeds 1700 ° C., the generation of Mg vapor becomes intense, and it becomes difficult to control the flow rate and pressure of the gas containing the same. In the present invention, this temperature range can be easily obtained by utilizing the heat of the molten steel.

When water vapor is used as the reactive gas, magnesia MgO solid can be precipitated by reaction with magnesium vapor. The reaction is shown below.

Mg + H ₂ O → MgO + H ₂

Similarly, when CO ₂ is used as the reactive gas,
By reaction with magnesium vapor, magnesia solids can be precipitated. The reaction is shown below.

Mg + CO ₂ → MgO + CO

For a combination of Mg vapor and H ₂ O, O ₂ , and CO ₂ , a temperature of 700 ° C. or more is desirable. This is because if the temperature is lower than 700 ° C., part of the Mg vapor tends to be condensed at the stage of transfer to the reaction site, so that Mg cannot be effectively used for the intended reaction. This condition can also be easily obtained by utilizing the heat of the molten steel.

[0044]

FIG. 1 is a sectional view schematically showing one example of an embodiment of the present invention. In the figure, 1 is a vacuum degassing tank, 2 is a dip tube, 3 is molten steel, 4 is a ladle, 5 is an iron shell, 7
Denotes a refractory, and 11 denotes an exhaust pipe.

As shown in FIG. 1, the immersion tube 2 is immersed in molten steel 3 placed in a ladle 4, etc., and sealed. In this state, the inside of the vacuum degassing tank 1 is depressurized by evacuating with a vacuum pump (not shown) connected to the exhaust pipe 11.

Magnesium chloride and chromium chloride powder are supplied into the vacuum degassing tank 1 from an inlet (not shown) provided in the vacuum degassing tank. The exhaust pipe 11 is provided with a valve or the like between the exhaust pipe 11 and the vacuum pump so that the exhaust pipe 11 can be hermetically closed. After the supplied powder is vaporized and filled in the vacuum degassing tank 1, a reactive gas (H ₂ O, O ₂ , and CO ₂ ) such as water vapor is introduced.
It is desirable that the reactive gas such as steam is preheated as much as possible from the viewpoint of securing the reaction temperature. By reacting the two gases in this way, a layer of magnesia and chromium oxide is formed in the crack and on the surface of the chrome brick.

If it is desired to increase the thickness of the magnesia and chromium oxide layers on the surface of the brick, this operation can be repeated a plurality of times to achieve the object.

[0048]

According to the present invention, magnesium chloride gas and chromium chloride gas (or a gas containing them) are reacted with a reactive gas such as water vapor to form a magnesia, Since chromium oxide is deposited, it is possible to repair even minute cracks that cannot be observed.

Further, since the precipitate is the main composition of the brick, the reinforcing body and the chrome brick are integrated, and the problem of the falling off of the reinforcing body from the brick surface can be solved. Further, since the present invention utilizes the reaction of gas, there is no need to perform a positioning operation between the vacuum degassing tank and the working equipment as in a thermal spraying operation and a drill cutting operation, thereby improving the operation efficiency.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing an RH reflux vacuum degassing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum degassing tank 2 Immersion pipe 3 Molten steel 4 Ladle 5 Iron shell 6 Scattered molten steel 7 Refractory 8 Inert gas inlet 9 Inert gas supply pipe 11 Exhaust pipe

Claims (2)

[Claims] In a method for repairing a refractory in a vacuum degassing tank having a dip tube and an exhaust pipe, a part of the dip tube is immersed in molten steel placed in a ladle or the like and hermetically sealed, and the vacuum pipe is degassed from the exhaust pipe. After evacuating the vessel, the exhaust pipe is closed, and first, magnesium chloride powder or chromium chloride powder or a mixture of these powders is supplied into the vacuum degassing vessel to vaporize, and then steam, oxygen, or A method for repairing refractories in a vacuum degassing tank, wherein a gas containing carbon dioxide or a mixed gas thereof is supplied into the vacuum degassing tank. 2. The method for repairing a refractory in a vacuum degassing tank according to claim 1, wherein a granulated material in which magnesia powder and aluminum powder are mixed is supplied instead of the magnesium chloride powder.