JPH0681023A - Method for heating and refining vacuum degassing vessel - Google Patents

Abstract

PURPOSE:To efficiently execute heating and refining by using only one set of a burner lance, by suitably injecting oxygen gas, fuel gas, combustion assist gas and powdery material into a vacuum degassing vessel from a multipurpose burner at the time of and before and after the degassing treatment. CONSTITUTION:The multipurpose burner capable of injecting two or more kinds of oxygen gas, fuel gas and combustion assist gas at the same time, is arranged in the vacuum degassing vessel to execute the heating and the refining. This multipurpose burner is constituted with a multiple pipe composed of each of injection passages 1, 2, 3 for e.g. the oxygen gas, fuel gas and combustion assist gas and is preferably provide with cooling water circulate-flowing passages 4, 5 in the inner and the outer parts. By using this burner, (1) before degassing treatment, the fuel gas and the combustion assist gas are injected to preheat the inner part of the vessel, (2) at the time of executing the degassing treatment, the oxygen gas and/or the fuel gas and the combustion assist gas are injected to heat the molten steel and raise the temp. thereof, and if necessary, the top blowing of the powdery material is executed and (3) after executing the degassing treatment and discharging the molten steel, the fuel gas and the combustion assist gas are injected to remove the stuck metal and slag after heating and melting.

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 preheating of the tank and heating of molten steel in the tank. The present invention relates to a heating / refining method in a vacuum degassing tank in which a single burner lance is used to increase 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, in Japanese Unexamined Patent Publication No. 2-77518, RH degassing is performed when undeoxidized molten steel or weakly deoxidized molten steel produced in a steelmaking furnace is degassed and 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 molten steel surface from a position above the molten steel level in the tank or the DH degassing tank, which is separated from the molten steel surface by a predetermined distance, and When the ratio of gas + CO ₂ gas is 5% or more and the CO ₂ / (CO + CO ₂ ) ratio in the exhaust gas is 30% or more, burn the CO gas generated during the degassing process near the molten steel surface. A method for vacuum degassing and decarburizing molten steel by reducing the amount of decrease in molten steel temperature has been proposed.

[0003]

However, this technique has the following problems.
Not applicable in the killed state, that is, when CO + CO ₂ <5%. Further, since the method is mainly a method of spraying only the oxygen-containing gas onto the molten steel surface and is not a technique whose main purpose is to remove the deposits in the tank, the deposit removal effect is small.

Therefore, the inventors of the present invention, as Japanese Patent Application No. 4-359, propose a fuel injection hole in a device for melting and removing metal and steel slag attached to molten metal containers by using a burner. Molten metal container including a combustion-supporting gas injection hole, an injection pipe for injecting an exothermic solid substance such as iron or aluminum or oxygen gas, and a device for switching the exothermic solid substance or oxygen gas to the burner at any time A deposit removal device was proposed. However, in this removal device, the tank removed the adhered substances at the standby position (during non-degassing process). Further, there was no function of reducing the adhered substance itself, that is, suppressing the adhered substance.

As described above, in the conventional deposit removing apparatus, there are three kinds of functions depending on the needs of degassing treatment and non-treatment, namely, tank preheating, molten steel heating / heating, and internal tank attachment. It was not possible to heat and remove the kimono with only one burner. Furthermore, there is no idea that powder such as a desulfurizing agent is effectively supplied to the molten steel in the vacuum degassing tank from the burner for refining, and there is no predictive effect at that time.

The object of the present invention is to heat and refine a vacuum degassing tank such as an RH degassing tank or a DH degassing tank, more specifically, to preheat the tank, to heat and raise the temperature of molten steel in the tank, and to heat the tank. Vacuum degassing tank that uses a single burner to perform heating and removal of internal deposits as well as desulfurization, reduction of inclusions in steel, refining treatment such as decarburization, etc. It is to provide an internal heating / refining method.

[0007]

As a result of repeated studies to solve the above-mentioned problems, the present inventors have at least an oxygen gas ejection passage, a fuel gas ejection passage, and a combustion-supporting gas ejection passage from the center side. A multi-purpose burner having a triple structure is used, and at least the periphery of the combustion-supporting gas ejection passage, preferably between the oxygen gas ejection passage and the fuel gas ejection passage, is divided into two parts by, for example, a partition in the fluid ejection direction. A cooling water return channel, which is a divided annular channel, is provided, and (i)
Before degassing, inject fuel gas and combustion-supporting gas into the tank, or (ii) during degassing, supply oxygen gas from the oxygen gas ejection passage and combustible gas from the combustion-supporting gas ejection passage. Injecting gas into molten steel simultaneously, or (iii)
After degassing and discharging molten steel, fuel gas should be injected from the fuel gas ejection passage and combustion-supporting gas should be injected simultaneously from the combustion-supporting gas ejection passage, or (iv) powder should be poured from the burner center hole into the hot water in the vacuum tank. It was found that by spraying and infiltrating the surface, it is possible to preheat the tank, raise the temperature of molten steel, dissolve and remove the deposits, and improve the refining efficiency.

Further, the inventors of the present invention have made extensive studies and have conducted a fuel gas flow rate and a combustion-supporting gas flow rate at the time of preheating the tank, an oxygen gas, a fuel gas and a combustion-supporting gas flow rate at the time of temperature rise of molten steel, and a tank. It was also found that there is a desirable range for the flow rates of the fuel gas and the combustion-supporting gas when the internal deposits are heated and removed. The present inventors have completed the present invention as a result of further studies based on these findings.

Here, the gist of the present invention is that vacuum degassing is performed by disposing a multipurpose burner capable of simultaneously ejecting at least two kinds of oxygen gas, fuel gas and combustion-supporting gas in a vacuum degassing tank. It is a method of heating and refining in the tank,
(i) Before degassing, fuel gas and supporting gas are injected into the vacuum degassing tank to preheat the vacuum degassing tank, or
(ii) During degassing, oxygen gas and / or fuel gas and supporting gas are injected into the molten steel to heat and heat the molten steel in the vacuum degassing tank, or (iii) degassing and molten steel After discharging, the fuel gas and supporting gas are injected into the vacuum degassing tank to heat and dissolve and remove the adherent metal and slag.
v) A heating / refining method in a vacuum degassing tank, which is characterized by improving the efficiency of refining by blowing powder under reduced pressure during degassing treatment.

The preferred embodiment of the present invention is as follows. When preheating in the vacuum degassing tank, when the fuel gas is a single substance or a mixture of propane gas and butane gas,
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
It is preferable that the gas is t and the combustion-supporting gas is oxygen-enriched air having an air ratio of 1.0 to 2.0.

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

When the adhered metal and slag in the vacuum degassing tank are dissolved and removed, 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 oxygen content of the combustion-supporting gas is 3
Preference is given to oxygen-enriched air 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 from the burner center hole at a vacuum degree in the range of 100 Torr to 0.5 Torr to accelerate desulfurization and inclusion removal in quicklime powder and decarburization in oxide powder. It is possible to improve the refining function by performing the above.

Further, in the present invention, at the time of no temperature rise during the degassing process, 0.01 or more of one or more of argon gas, carbon dioxide gas and nitrogen gas is supplied from the multipurpose burner.
~ 0.05 Nm ³ / min ・ t It is desirable to eject (purge) from the viewpoint of preventing clogging of the multipurpose burner.

[0015]

Next, the present invention will be described in detail together with its function and effect with reference to the accompanying drawings.

FIG. 1 (a) is a vertical sectional view of an example of a multipurpose burner used in the present invention, and FIG. 1 (b) is an AA sectional (horizontal sectional) view of FIG. 1 (a).

In FIGS. 1 (a) and 1 (b), 1 is an oxygen gas jet passage, 2 is a fuel gas jet passage, 3 is a combustion-supporting gas jet passage, and 4 is an oxygen gas jet passage 1 and fuel gas. Cooling water return water passages provided between the jetting passage 2 and 5 are cooling water return water passages provided around the combustion-supporting gas jetting passage, respectively. 3a shows a jet hole.
Note that the oxygen gas ejection passage 1 constitutes an ejection passage for the inert gas together with the powder when the powder is sprayed, which will be described later. However, in the present specification, the oxygen gas ejection passage 1 includes such a case for convenience sake. And oxygen gas ejection holes.

FIGS. 2 (a) and 2 (b) also show a vertical sectional view and a lateral sectional view, respectively, of the multipurpose burner, in which the cooling water recirculation water channel is provided only around the combustion supporting gas ejection channel. It is provided. Such a multipurpose burner is used by being installed in a vacuum degassing tank. These multipurpose burners are provided with an oxygen gas ejection passage 1, a fuel gas ejection passage 2 and a combustion-supporting gas ejection passage 3 as a triple structure, and at least two kinds of oxygen gas, fuel gas and combustion-supporting gas are simultaneously provided. It is constructed so that it can be ejected. Therefore, preheating the tank, heating molten steel in the tank,
It is possible to perform all of the temperature raising and heating / dissolving removal of the deposit in the tank, and the improvement of the refining function by spraying 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 an ordinary lance. As shown in FIG. 1, the multipurpose burner is provided with a fuel gas ejection passage 2 and a combustion-supporting gas ejection passage 3 in order on the outer periphery of the oxygen gas ejection passage 1, and the oxygen gas ejection passage 1 and the fuel gas ejection passage 3 are provided. Oxygen gas jet 1 between
A cooling water recirculation water passage 4 for preventing heating of the multi-purpose burner and a cooling water recirculation water passage 5 for preventing melting damage of the multipurpose burner are provided on the outer periphery of the combustion-supporting gas ejection passage 3. In order to ensure a sufficient cooling capacity, the cooling water return water passages 4 and 5 are preferably annular water passages whose inside is divided into two by partitioning in the fluid ejection direction, for example.

In the present invention, in order to heat and raise the temperature of molten steel, oxygen is supplied through the oxygen gas ejection passage 1 of the multipurpose burner, and the oxygen gas is ejected from the oxygen gas ejection hole 1a at the tip of the multi-purpose burner in the degassing tank. Gush out to.

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

The flow rate of oxygen gas when the temperature of molten steel is raised is 0.05 Nm ³
/ Min ・ t or more and 0.20 Nm ³ / min ・ t or less is desirable. If it is less than 0.05 Nm ³ / min ・ t, the temperature rising speed of molten steel may be too small, for example, 1 ° C / min or less in a 250 ton RH degassing tank, while it may be 0.20 Nm ³ / min ・ t.
This is because if it exceeds the above range, the production of lower oxides such as FeO and MnO becomes active, which may deteriorate the steel quality.

In the present invention, if the combustion-supporting gas is present during the degassing process, either the oxygen gas or the fuel gas acts as the fuel for the combustion reaction, so that at least one of them should be present. . Here, in the case of ejecting fuel gas instead of oxygen gas through the fuel gas ejection passage 2 and the fuel gas ejection hole 2a, when the fuel gas is a single substance or a mixture of propane gas or butane gas,
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 combustion-supporting gas ejected through the combustion-supporting gas ejection passage 3 and the combustion-supporting gas ejection hole 3a is preferably about 1.0 to 2.0 times the amount of oxygen required for theoretical combustion. The heating / dissolving removal of the attached matter is practically 8 to 8 in about 1 hour.
It is desirable to be able to process 30 tons, but the fuel gas flow rate to achieve this is 0.004 Nm ³ / mi when the fuel gas is propane gas, butane gas alone or as a mixture.
It is desirable that the value be n.t or more and 0.016 Nm ³ / min or less, and 0.03 Nm ³ / mi for coke oven gas.
It is desirable that the value be n · t or more and 0.12 Nm ³ / min · t or less. Also, in this case, the combustion-supporting gas has an air ratio of 1.0 to 2.0.
It is desirable that the oxygen-enriched air has an oxygen ratio of 30 to 60%.

As the combustion-supporting gas, for example, oxygen-enriched air having an oxygenation rate of preferably 30 to 60% by volume can be exemplified. When the oxygenation rate is 30% by volume or more and 60% by volume or less, the temperature of the inner wall surface of the tank is optimal for heating and melting and removing the deposits in the tank.
This is because (about 1500 ° C) can be achieved.

The air ratio (air excess coefficient) at the time of heating and melting and removing the metal and slag that are the deposits in the tank is 1.0 or more.2.
It is desirable to set it to 0 or less. This is because if the air ratio is less than 1.0, unburned carbon monoxide gas is contained in the exhaust gas, which is dangerous, and if it exceeds 2.0, excessive oxidation of the metal in the tank occurs.

Before starting the degassing process, the multipurpose burner used in the present invention can also preheat the tank. The preheating of the tank is performed for the purpose of energy saving 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 also depends on the length of the waiting time of the molten steel, but in order to reliably achieve the above object, when using propane gas or butane gas alone or as a mixture as the fuel gas,
0.0025 Nm ³ / min ・ t or more and 0.010 Nm ³ / min ・ t or less is desirable, and when coke oven gas is used, 0.02 Nm ³ / min ・ t or more and 0.08 Nm ³ / min ・ t or less Is desirable. The air ratio is preferably 1.0 or more and 2.0 or less for the same reason as when removing the deposits in the tank.

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

Incidentally, as a powder supply system and a specific means for powder supply, it is possible to use that of a technique already put into practical use as a powder blowing technique. This is already known to the person 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 combustion-supporting gas is arranged in the vacuum degassing tank,
(i) Before degassing, fuel gas and supporting gas are injected into the vacuum degassing tank to preheat the inside of the vacuum degassing tank, or (ii) during degassing, oxygen gas and / or Fuel gas and supporting gas are injected into molten steel to heat and heat the molten steel in the vacuum degassing tank, or (iii) After degassing and discharging molten steel, the fuel gas and supporting gas are vacuumed. Heating the vacuum degassing tank with a single burner by injecting it into the degassing tank to heat and dissolve and remove the adherent metal and slag, or (iv) improve the refining function by spraying powder under reduced pressure. By the above, it is possible to preheat the tank, heat the molten steel in the tank, remove the deposits in the tank, and improve the 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, the oxygen gas jet passage, the fuel gas jet passage and the combustion-supporting gas jet passage are provided with argon gas or carbon dioxide. It is desirable to purge gas or nitrogen gas from 0.01 Nm ³ / min · t or more to 0.05 Nm ³ / min · t or less.

In the vacuum degassing tank heating method according to the present invention, Table 1 is a table showing, for each degassing treatment and non-degassing treatment, the gas species to be ejected, 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 example of the present invention and the present invention is not limited thereto.

[0035]

Example 1 Al killed steel for thick plates being processed in an RH degassing tank equipped with a multipurpose burner having the structure shown in FIG.
To raise the temperature by 250 tons, oxygen gas is ejected from the oxygen gas ejection hole 1a through the oxygen gas ejection passage 1 to 0.14 Nm ³ / min · t, and from the fuel gas ejection passage 2 through the fuel gas ejection hole 2a to propane gas and butane gas. Of 0.005 Nm ³ / min · t of oxygen, and the oxygen content of 1.5 times as much oxygen as necessary for theoretical combustion of the fuel gas from the combustion-supporting gas ejection hole 3a through the combustion-supporting gas ejection passage 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.

After completion of the degassing process and the discharge of molten steel, a pot was installed in the lower part of the RH degassing tank, and a mixture of propane gas and butane gas was fed from the fuel gas injection hole 2a of the multipurpose burner to 0.007 Nm ³ / Min ・ t, oxygen-enriched air from the combustion-supporting gas ejection holes 3a as a combustion-supporting gas under the conditions of an air ratio of 1.6 and an oxygen ratio of 50% is jetted for 25 minutes each, and the inside of the tank of about 15 tons It was possible to heat and dissolve and remove the adherent metal and slag.

[0037]

[Example 2] Furthermore, the RH degassing tank equipped with the multipurpose burner used in Example 1 was inspected and repaired on a maintenance day, and propane gas and butane gas were mixed from 30 minutes before degassing to just before the start. Product 0.006Nm ³ / min ・ t Fuel injection hole 2a
RH by blowing oxygen-enriched air with an air ratio of 1.5 into the tank from the combustion-supporting gas ejection holes 3a.
The inner wall temperature of the degassing tank could be preheated to about 1300 ℃.

[0038]

Example 3 A multipurpose burner having the structure shown in FIG. 1 was installed.
In the RH degassing tank, in order to melt ultra-low sulfur steel, in order to inject CaO-CaF ₂ (25%) powder through the oxygen gas ejection passage 1 into the vacuum tank molten metal surface using Ar gas as a carrier, Sprayed. Vacuum degree is 2 Torr, powder feeding rate is 0.6kg / min.t
Powder for 8 minutes. As a result, the sulfur concentration in the steel was reduced to 0.
It was possible to reduce from 0018% to 0.0006%.

[0039]

Example 4 A multipurpose burner having the structure shown in FIG. 1 was installed.
In the RH degassing treatment tank, FeO powder was passed through the oxygen gas spouting path 1 as Ar for finishing decarburization in order to produce ultra-low carbon steel.
In order to use gas as a carrier to penetrate the surface of the molten metal in the vacuum tank,
Sprayed. Vacuum degree is 1.5 Torr, powder feeding rate is 0.25kg
The powder was fed for 12 minutes at /min.t. As a result, the carbon concentration in steel could be reduced from 0.0021% to 0.0005%.

[0040]

As described in detail above, according to the present invention, preheating of the tank, heating / heating of molten steel in the tank, heating / melting removal of deposits in the tank, and powder supply are all performed with the same burner lance. Now you can do it. Therefore, according to the present invention, it is not necessary to prepare a plurality of lances,
The equipment investment can be minimized (improved economy), and the vacuum degassing tank can be easily sealed (improved operational stability). Furthermore, as an energy saving and other effects, RH
-OB tuyere (nozzle installed in lower tank for blowing oxygen in RH degassing process) is not required, and life of refractory can be extended. In addition, the vertical lifting type burner lance can reduce the amount of Ar gas used to prevent tuyere clogging, which improves the exhaust performance in actual operation and speeds up the process.

[Brief description of 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 an A- line in FIG. 1 (a).
It is an A section (horizontal section) figure.

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

[Explanation of symbols]

1: Oxygen gas ejection channel, 2: Fuel gas ejection channel, 3: Burning gas ejection channel, 4: Cooling water recirculation channel, 5: Cooling water recirculation channel, 1a: Oxygen gas ejection hole, 2a: Fuel gas ejection hole , 3a: Combustible gas ejection holes

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshinori Ando No. 3 Hikari, Kashima-cho, Kashima-cho, Kashima-gun, Ibaraki Sumitomo Metal Industries, Ltd. Kashima Works

Claims (1)

[Claims] 1. A method for heating and refining in a vacuum degassing tank, which is carried out by disposing a multipurpose burner capable of simultaneously ejecting two or more kinds of oxygen gas, fuel gas and supporting gas in the vacuum degassing tank. ) Before the degassing process, the fuel gas and the combustion-supporting gas are injected into the vacuum degassing tank to preheat the inside of the vacuum degassing tank, or (ii) during the degassing process, oxygen gas and / or fuel gas Fuel-sustaining gas is injected into the molten steel to heat and raise the temperature of the molten steel in the vacuum degassing tank, or (iii) After degassing and discharging the molten steel, the fuel gas and supporting gas are placed in the vacuum degassing tank. To heat and dissolve and remove the adherent metal and slag, or (iv) during degassing, improve the efficiency of refining by blowing powder under reduced pressure to heat the inside of a vacuum degassing tank. Refining method.