JP2722998B2 - Heating and refining method in vacuum degassing tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating and refining a vacuum degassing tank such as an RH degassing tank or a DH degassing tank. More specifically, the present invention relates to a method for preheating a tank and heating molten steel in the tank. The present invention relates to a method for heating and refining in a vacuum degassing tank, which uses a single burner lance to raise the temperature, heat and remove deposits in the tank, and improve the refining function by spraying powder.

[0002]

2. Description of the Related Art Various techniques for dissolving and removing deposits in a vacuum degassing tank such as an RH degassing tank or a DH degassing tank have been proposed. For example, Japanese Patent Application Laid-Open No. 2-77518 discloses that RH degassing is performed when deoxidized or weakly deoxidized molten steel melted in a steelmaking furnace is degassed or decarburized by using the RH method or the DH method. The decarburization reaction of molten steel proceeds by spraying oxygen gas or oxygen-containing gas onto the surface of molten steel from a position above the molten steel surface in the DH degassing tank or the DH degassing tank by a predetermined distance, and the (CO) The CO gas generated during the degassing process near the molten steel surface is burned when the ratio of (gas + CO ₂ gas) becomes 5% or more and the CO ₂ / (CO + CO ₂ ) ratio in the exhaust gas becomes about 30% or more. In addition, there has been proposed a method of performing vacuum degassing and decarburizing treatment of molten steel by reducing the amount of drop in molten steel temperature.

[0003]

However, this technique is
This is not applicable in the killed state, that is, when CO + CO ₂ <5%. Further, the method is mainly for spraying only the oxygen-containing gas onto the molten steel surface, and is not a technique mainly for removing the deposits in the tank, so that the deposit removing effect is small.

Accordingly, the present inventors have disclosed in Japanese Patent Application No. 4-359, an apparatus for melting and removing metal or steel slag attached to a molten metal container using a burner. Molten containers consisting of a combustion-supporting gas injection hole, an injection pipe that injects a heat-generating solid substance such as iron or aluminum, or oxygen gas, and a device that switches the heat-generating solid substance or oxygen gas to the burner at any time An adhering matter removal device was proposed. However, in this removal apparatus, the deposit was removed when the tank was at a standby position (during non-degassing treatment). Further, there was no function of reducing the deposit itself, that is, the function of suppressing the deposit.

As described above, in the conventional deposit removing apparatus, three types of functions are required according to the needs of the degassing treatment and the non-treatment, that is, the tank preheating, the heating / heating of the molten steel, and the inside of the tank. It was not possible to heat and remove the kimono with just one burner. Furthermore, there is no idea that powder such as a desulfurizing agent is effectively supplied to molten steel in a vacuum degassing tank from the burner for refining, and there is nothing to predict the effect at that time.

Here, an object of the present invention is to provide a method for heating and refining in a vacuum degassing tank such as an RH degassing tank or a DH degassing tank, more specifically, preheating the tank, heating and heating the molten steel in the tank, and heating the tank. Vacuum degassing tank that uses a single burner to supply various types of powder for refining to perform refining processes such as heating and removal of internal deposits and desulfurization, reduction of inclusions in steel, and decarburization as necessary. An internal heating and refining method is provided.

[0007]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that at least an oxygen gas ejection path, a fuel gas ejection path, and a combustion supporting gas ejection path are provided from the center side. A multi-purpose burner having a triple structure is used, and at least around the combustible gas ejection path, preferably further between the oxygen gas ejection path and the fuel gas ejection path, for example, by partitioning in the fluid ejection direction, the inside of the burner gas ejection path is separated from the inside. A cooling water return channel, which is a divided annular channel, is provided, and (i)
Before the degassing process, the fuel gas and the supporting gas are injected into the tank, or (ii) at the time of the degassing process, the oxygen gas is discharged from the oxygen gas discharging passage, Simultaneously injecting gas into the molten steel, or (iii)
After the degassing process and the discharge of molten steel, simultaneously inject fuel gas from the fuel gas ejection path and combustion-supporting gas from the combustion-supporting gas ejection path, respectively, or (iv) discharge powder from the burner center hole into the hot water in a vacuum chamber. It has been found that by spraying and penetrating the surface, it is possible to perform all of preheating of the tank, heating of molten steel, dissolving and removing of deposits, and improvement of refining efficiency.

Further, the present inventors have conducted intensive studies, and have studied the flow rates of fuel gas and supporting gas when preheating the tank, the flow rates of oxygen gas, fuel gas and supporting gas when the temperature of molten steel is raised, and the flow rates of fuel gas and supporting gas. It was also found that there is a desirable range for the flow rates of the fuel gas and the supporting gas at the time of heating and removing the internal deposit. Based on these findings, the present inventors have further studied, and as a result, completed the present invention.

Here, the gist of the present invention is to provide a multi-purpose burner capable of simultaneously injecting at least two kinds of oxygen gas, fuel gas and combustion supporting gas in a vacuum degassing tank. A heating and refining method in the tank,
(i) Before the degassing process, the fuel gas and the supporting gas are injected into the vacuum degassing tank to preheat the vacuum degassing tank, or
(ii) At the time of degassing, oxygen gas and / or fuel gas and a supporting gas are injected into molten steel to heat and raise the temperature of the molten steel in the vacuum degassing tank, or (iii) degassing and molten steel After discharging, the fuel gas and the supporting gas are injected into the vacuum degassing tank to heat and melt and remove the adhered metal and slag.
v) A method of heating and refining in a vacuum degassing tank, characterized by improving refining efficiency by blowing powder under reduced pressure during degassing.

The preferred embodiments of the present invention are as follows. When performing preheating in the vacuum degassing tank, when the fuel gas is propane gas, butane gas alone or a mixture,
The supply amount of the fuel gas is 0.0025~0.010 Nm ³ / min · t, when the coke oven gas, 0.02 to 0.08 Nm ³ / min
T, and the supporting gas is preferably oxygen-enriched air having an air ratio of 1.0 to 2.0.

When raising the temperature of molten steel in a vacuum degassing tank, the flow rate when using oxygen gas is 0.05 to 0.20 Nm ³ / min · t
Or when the fuel gas is used, the flow rate of propane gas or butane gas alone or a mixture is 0.004 to
0.016 Nm ³ / min · t or coke oven gas: 0.03 to 0.
Preferably, it is 12 Nm ³ / min · t, and the supporting gas is oxygen-enriched air at 1.0 to 2.0 times the oxygen required for theoretical combustion.

When dissolving and removing adhered metal and slag in the vacuum degassing tank, when the fuel gas is propane gas or butane gas alone or as a mixture, 0.004 to 0.016 Nm ³ /
min ・ t and 0.03 to 0.12 for coke oven gas
Nm ³ / min · t, and the supporting gas has an oxygenation rate of 3
It is preferable that the oxygen-enriched air has an air ratio of 0 to 60% by volume and an air ratio of 1.0 to 2.0.

Further, at the time of degassing, powder is sprayed at a degree of vacuum of 100 Torr to 0.5 Torr from the center hole of the burner to desulfurize and remove inclusions in quicklime powder, and to promote decarburization in oxide powder. By performing the above, the refining function can be improved.

In the present invention, when the temperature is not raised during the degassing process, one or more of argon gas, carbon dioxide gas and nitrogen gas are supplied from a multipurpose burner to 0.01 or more.
It is desirable to eject (purge) 0.05 Nm ³ / min · t from the viewpoint of preventing clogging of the multipurpose burner.

[0015]

Next, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1A is a longitudinal sectional view of an example of a multipurpose burner used in the present invention, and FIG. 1B is a sectional view taken along line AA (horizontal section) in FIG. 1A.

1 (a) and 1 (b), reference numeral 1 denotes an oxygen gas ejection path, 2 denotes a fuel gas ejection path, 3 denotes a combustion supporting gas ejection path, and 4 denotes an oxygen gas ejection path 1 and a fuel gas The cooling water recirculation channel provided between the jet channel 2 and the cooling water recirculation channel 5 is a cooling water recirculation channel provided around the combustible gas jet channel. 3a shows a vent.
The oxygen gas jetting path 1 constitutes an inert gas jetting path together with the powder at the time of powder spraying, which will be described later. However, in this specification, even in such a case, the oxygen gas jetting path 1 is used for convenience. And oxygen gas ejection holes.

FIGS. 2 (a) and 2 (b) also show a longitudinal section and a transverse section, respectively, of the multipurpose burner. The cooling water recirculation channel is provided only around the fuel supporting gas ejection channel. Is provided. Such a multipurpose burner is disposed and used in a vacuum degassing tank. These multipurpose burners have an oxygen gas ejection path 1, a fuel gas ejection path 2 and a combustion supporting gas ejection path 3 as a triple structure, and simultaneously use at least two or more of oxygen gas, fuel gas, and combustion supporting gas. It is configured to be able to squirt. Therefore, preheating the tank, heating molten steel in the tank,
It is possible to perform all of the steps of raising the temperature, heating / dissolving and removing the deposits in the tank, and improving the refining function by spraying the powder.

The multipurpose burner used in the present invention may be installed at a known position in the degassing tank by a known means similar to a usual lance. As shown in FIG. 1, the multipurpose burner includes a fuel gas ejection path 2 and a oxidizing gas ejection path 3 in this order on the outer periphery of the oxygen gas ejection path 1, and the oxygen gas ejection path 1 and the fuel gas ejection path 3 Between the oxygen gas spout 1
A cooling water recirculation channel 4 is provided on the outer periphery of the combustible gas jetting channel 3 to prevent heating of the multipurpose burner. In order to sufficiently secure the cooling capacity, the cooling water recirculation water paths 4 and 5 are preferably annular water paths whose interior is divided into two by partitioning in a fluid ejection direction, for example.

In the present invention, in order to heat and raise the temperature of the molten steel, oxygen is supplied through the oxygen gas ejection passage 1 of the multipurpose burner, and oxygen gas is supplied from the oxygen gas ejection hole 1a at the tip thereof into the degassing tank. Squirt to

By making the structure of the oxygen gas ejection path 1 a known Laval lance structure or a straight lance structure, for example, an oxygen gas jet having a sound velocity or higher can be obtained, and the distance between the burner lance and the molten metal surface is about 2 m. Even in molten steel
The oxidation reaction with Al can be reliably generated, and the temperature of the molten steel can be reliably increased.

The flow rate of oxygen gas at the time of raising the temperature of molten steel is 0.05 Nm ³
/ Min · t or more and 0.20 Nm ³ / min · t or less. If it is less than 0.05 Nm ³ / min · t, there is a possibility that the temperature rise rate of the molten steel may be too small, for example, 1 ° C./min or less in a 250 ton RH degassing tank, while 0.20 Nm ³ / min · t
This is because, if it is excessive, the generation of lower oxides such as FeO and MnO may be activated to deteriorate the steel quality.

In the present invention, if a supporting gas is present during the degassing process, either the oxygen gas or the fuel gas acts as a fuel for the combustion reaction, so that at least one of them is sufficient. . Here, when the fuel gas is jetted through the fuel gas jetting path 2 and the fuel gas jetting hole 2a instead of the oxygen gas, when the fuel gas is propane gas or butane gas alone or a mixture thereof,
0.004 ~0.016 Nm ³ / min · t or so, may be about 0.03~0.12 Nm ³ / min · t is the time of the coke oven gas.

The amount of the supporting gas discharged through the supporting gas discharge passage 3 and the supporting gas discharge hole 3a is preferably about 1.0 to 2.0 times the amount of oxygen required for the theoretical combustion. Heating, dissolving and removing the adhered substance is practically 8 to 1 hour.
It is desirable to be able to process 30 tons. To achieve this, the fuel gas flow rate is 0.004 Nm ³ / mi when the fuel gas is propane gas, butane gas or a mixture thereof.
Desirably, it is not less than n · t and not more than 0.016 Nm ³ / min · t, and in the case of coke oven gas gas, it is 0.03 Nm ³ / mi.
It is desirable to set it to not less than n · t and not more than 0.12 Nm ³ / min · t. In this case, the supporting gas has an air ratio of 1.0 to 2.0.
Preferably, the oxygen-enriched air has an oxygen ratio of 30 to 60%.

Examples of the supporting gas include, for example, oxygen-enriched air having an oxygenation ratio of preferably 30 to 60% by volume. When the oxygenation rate is 30% by volume or more and 60% by volume or less, the heating temperature inside the tank is optimal for heating and dissolving and removing deposits in the tank
(Approximately 1500 ° C.).

The air ratio (excess air coefficient) at the time of heating and melting and removing metal and slag, which are deposits in the tank, is 1.0 or more.
It is desirable to set it to 0 or less. If the air ratio is less than 1.0, unburned carbon monoxide gas is contained in the exhaust gas, which is dangerous. If the air ratio is more than 2.0, the metal in the tank is excessively oxidized.

Prior to the start of the degassing process, the tank can be preheated according to the multipurpose burner used in the present invention. The preheating of the tank is performed to save energy for the purpose of suppressing the temperature drop of the molten steel by, for example, about 5 ° C. by heating for about 30 minutes. The preheating effect depends on the standby time of the molten steel, but in order to reliably achieve the above object, propane gas, butane or a mixture of butane gas is used as a fuel gas.
0.0025 Nm ³ / min · t or more and 0.010 Nm ³ / min · t or less, and if coke oven gas is used, 0.02 Nm ³ / min · t or more and 0.08 Nm ³ / min · t or less It is desirable. The air ratio is desirably 1.0 or more and 2.0 or less for the same reason as in the case of removing deposits in the tank.

Further, the efficiency of the refining can be improved by spraying powder using an inert gas as a carrier gas from a burner center hole which is an oxygen gas ejection hole. At this time, it is desirable that the degree of vacuum be higher than 100 Torr from the viewpoint of securing the powder yield and the depth of powder penetration into the molten steel in the degassing tank. However, a vacuum higher than 0.5 Torr is not preferable because it only increases the energy load for exhaust.

As a powder supply system and a specific means of powder supply, those of a technique already in practical use as a powder blowing technique may be used. This is already known to those skilled in the art and will not be described further.

Thus, in the present invention, oxygen gas,
A multipurpose burner capable of simultaneously ejecting at least two kinds of fuel gas and supporting gas is arranged in the vacuum degassing tank,
(i) Before degassing, the fuel gas and the supporting gas are injected into the vacuum degassing tank to preheat the vacuum degassing tank, or (ii) oxygen gas and / or The fuel gas and the supporting gas are injected into the molten steel to heat and raise the temperature of the molten steel in the vacuum degassing tank, or (iii) the fuel gas and the supporting gas are evacuated after degassing and discharging the molten steel. Heating and melting of adhered metal and slag by spraying into the degassing tank, or (iv) heating the inside of the vacuum degassing tank with one burner by improving the refining function by spraying powder under reduced pressure Can preheat the tank, heat molten steel in the tank, remove deposits in the tank, and improve refining efficiency.

In the present invention, when the temperature is not raised during the degassing process, in order to prevent clogging of the burner lance, argon gas or carbon dioxide gas is supplied to the oxygen gas ejection path, the fuel gas ejection path, and the combustion supporting gas ejection path. It is desirable to purge gas or nitrogen gas from 0.01 Nm ³ / min · t to 0.05 Nm ³ / min · t or less.

Table 1 is a table showing, in the heating method in the vacuum degassing tank according to the present invention, the types of gas to be jetted for the degassing treatment and the non-degassing treatment for each flow path of the multipurpose burner.

[0033]

[Table 1]

Further, the present invention will be described in detail with reference to examples, but this is an exemplification of the present invention, and the present invention is not limited thereto.

[0035]

Embodiment 1 In an RH degassing tank equipped with a multipurpose burner having the structure shown in FIG. 1, Al-killed steel for thick plates being processed
To increase the temperature by 250 tons, oxygen gas is supplied from the oxygen gas outlet 1a through the oxygen gas outlet 1 at 0.14 Nm ³ / min · t via the oxygen gas outlet 1 and propane gas and butane gas are supplied from the fuel gas outlet 2a via the fuel gas outlet 2 The mixture of 0.005 Nm ³ / min · t and the oxygen-rich gas having an oxygen content 1.5 times the oxygen required for the theoretical combustion of the fuel gas through the combustion-supporting gas outlet 3 a through the combustion-supporting gas outlet 3. The temperature of the molten steel could be raised by 30 ° C. by injecting the converted air into the molten steel for 6 minutes each.

Thereafter, after the degassing process and the discharge of the molten steel were completed, a pot was installed at the lower part of the RH degassing tank, and a mixture of propane gas and butane gas was supplied from the fuel gas outlet 2a of the multipurpose burner at 0.007 Nm ^3. / Min · t, the oxygen-enriched air is spouted from the combustible gas ejection hole 3a as an antioxidant gas under the conditions of an air ratio of 1.6 and an oxygen ratio of 50% for 25 minutes each, so that the inside of the tank of about 15 tons The attached metal and slag could be removed by heating and dissolving.

[0037]

Example 2 Further, the RH degassing tank equipped with the multipurpose burner used in Example 1 was inspected and repaired on a maintenance day, and the mixing of propane gas and butane gas was performed from 30 minutes before degassing to just before the start. 0.006Nm ³ / min ・ t
, The oxygen-enriched air having an air ratio of 1.5 is ejected from the combustion supporting gas ejection holes 3a into the respective tanks, whereby the RH is increased.
The inner wall temperature of the degassing tank could be preheated to about 1300 ℃.

[0038]

Embodiment 3 A multipurpose burner having the structure shown in FIG. 1 was installed.
In RH degassing vessel, in order to melted ultra-low硫鋼, in order to penetrate the vacuum tank molten steel surface CaO -CaF ₂ through an oxygen gas injection passage 1 (25%) powder Ar gas as a carrier, Sprayed. Vacuum degree is 2 Torr, powder supply rate is 0.6 kg / min.t
For 8 minutes. As a result, the sulfur concentration in steel was reduced to 0.
It was able to be reduced from 0018% to 0.0006%.

[0039]

Embodiment 4 A multipurpose burner having the structure shown in FIG. 1 was installed.
In the RH degassing tank, the FeO powder is passed through the oxygen gas spouting channel 1 as Ar to finish decarburization in order to melt ultra-low carbon steel.
In order to allow gas to enter the hot water inside the vacuum chamber as a carrier,
Sprayed. Vacuum degree is 1.5 Torr, powder supply rate is 0.25 kg
/min.t for 12 minutes. As a result, the carbon concentration in steel was reduced from 0.0021% to 0.0005%.

[0040]

As described above in detail, according to the present invention, the preheating of the tank, the heating / heating of the molten steel in the tank, the heating / melting removal of the deposits in the tank, and the powder supply are all performed by the same burner lance. Now you can do it. Therefore, according to the present invention, there is no need to prepare a plurality of lances,
Capital investment can be minimized (economic improvement), and the sealing performance of the vacuum degassing tank can be easily secured (operation stability improvement). In addition, RH as energy saving and other effects
-OB tuyere (nozzle installed in lower tank for blowing oxygen in RH degassing process) is not required, and the life of the refractory can be extended. In addition, the vertical lift-up burner lance reduces the amount of Ar gas used to prevent tuyere clogging, thus improving exhaust performance in actual operation and speeding up processing.

[Brief description of the drawings]

FIG. 1 (a) is a longitudinal sectional view of an example of a multipurpose burner used in the present invention, and FIG. 1 (b) is a sectional view taken along line A-A in FIG. 1 (a).
It is A section (horizontal section) figure.

2 (a) is a longitudinal sectional view of an example of a multipurpose burner used in the present invention, and FIG. 2 (b) is a sectional view taken along AA (horizontal sectional view) in FIG. 2 (a).

[Explanation of symbols]

1: oxygen gas ejection path, 2: fuel gas ejection path, 3: flammable gas ejection path, 4: cooling water recirculation water path, 5: cooling water recirculation water path, 1a: oxygen gas ejection hole, 2a: fuel gas ejection hole , 3a: Combustion gas vent

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor, Toshinori Ando, Kashima-cho, Kashima-gun, Ibaraki 3rd floor, Kashima Works Sumitomo Metal Industries Co., Ltd. (56) References JP-A-54-4811 JP-A-3-274218 (JP, A) JP-A-2-77518 (JP, A) JP-A-54-137421 (JP, A) JP-A 5-27038 (JP, U) JP-A 1-78153 (JP , U)

Claims (1)

(57) [Claims] 1. A method for heating and refining in a vacuum degassing tank, wherein a multipurpose burner capable of simultaneously injecting two or more kinds of oxygen gas, fuel gas and supporting gas is disposed in the vacuum degassing tank. ) Before the degassing treatment, the fuel gas and the supporting gas are injected into the vacuum degassing tank to preheat the inside of the vacuum degassing tank, or (ii) at the time of the degassing treatment, the oxygen gas and / or the fuel gas Injecting the supporting gas into the molten steel to heat and raise the temperature of the molten steel in the vacuum degassing tank, or (iii) after the degassing treatment and discharging the molten steel, the fuel gas and the supporting gas are discharged into the vacuum degassing tank. Heating and dissolving and removing adhered metal and slag by spraying onto the powder, or (iv) improving the efficiency of refining by blowing the powder under reduced pressure during degassing to increase the efficiency of refining. Refining method.