JPH09272916A - Method for dissolving solidified slag in scouring vessel - Google Patents

Abstract

(57) Abstract: A method for melting solidified slag having a high melting point floating on the surface of a molten metal of a metal refining container is provided. SOLUTION: A tube having a plurality of communication holes around a central double tube is used, and a mixture of metal powder and iron oxide powder is injected from an inner tube of the double tube together with a carrier gas composed of an inert gas. , Oxygen is injected from the outer tube, fuel gas is further injected from a plurality of communication holes around the outer tube, and ignition is performed,
In the method of melting the solidified slag by the heat obtained by the thermite reaction between the metal powder and the iron oxide powder, the mixture of the metal powder and the iron oxide powder is 15 to 60 wt% of metal aluminum having a particle diameter of 0.15 mm or less, and the balance is It is made of iron oxide having a particle size of 0.4 mm or less. As a result, the solidified slag having an extremely high melting point generated in the molten steel refining process can be dissolved and removed at a high speed and at a stable speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting solidified slag having a high melting point which floats on the surface of molten metal during operation in a metal refining vessel.

[0002]

2. Description of the Related Art In the steel industry, there is a degassing method such as the RH method as a technology for removing solute components that generate a gas phase from molten steel. In this RH method, two immersion pipes are inserted into the molten steel in the ladle, and argon gas is blown into the molten steel from one of the immersion pipes while reducing the pressure, and the molten steel in the ladle is refluxed through the two immersion pipes. By doing so, the partial pressure of the gas component in the molten steel is reduced, and this gas component is removed.

In recent years, in the RH method, not only degassing but decarburization for the purpose of melting ultra-low carbon steel has become widespread. Decarburization proceeds due to the reaction between oxygen and carbon in the steel. In order to facilitate this decarburization, it is necessary to increase the oxygen concentration in the molten steel, and by blowing oxygen onto the vacuum steel bath surface at the initial stage of decarburization, which is the rate of oxygen supply, decarburization is promoted. Is common.

In the case of molten stainless steel, a part of the blown oxygen reacts with chromium, which is a component of the molten steel, to cause chromia (Cr
₂ O ₃ ) is produced. Therefore, as the decarburization progresses, the Cr ₂ O ₃ concentration in the slag on the bath surface of the molten steel in the ladle increases. Table 1 shows the slag composition and melting point on the ladle steel bath surface after RH treatment of molten stainless steel, but from the temperature of the steel bath (about 1600 ° C), it is a complete solid phase. I understand.

[0005]

[Table 1]

[0006]

However, during the RH treatment, a probe is inserted several times during the treatment to determine whether or not the target molten steel temperature and molten steel composition have been reached, and the molten steel is measured. Temperature and sampling are performed. If the slag on the ladle steel bath surface is in the liquid phase, the probe can be inserted smoothly, but if the slag is in the solid phase and is hard, it may interfere with the probe insertion, making temperature measurement or sampling impossible. is there.

In such a case, conventionally, a method of spraying a flame of a fuel gas and a method disclosed in Japanese Patent Application Laid-Open No. 02-287092 have been adopted, but both methods have a high melting point as shown in Table 1. It is not possible to create a high temperature condition that can melt the solidified slag. An object of the present invention is to provide a method for melting solidified slag having an extremely high melting point generated in a molten steel refining process at a high speed and at a stable speed.

[0008]

The present invention has been made by paying attention to a high temperature reduction reaction of a metal oxide with aluminum, a so-called thermite reaction. That is, when iron oxide as a metal oxide and aluminum powder are mixed and ignited, a violent exothermic reaction as shown in the following formula occurs. Fe ₂ O ₃ + 2Al = 2Fe + Al ₂ O ₃

The theoretical temperature of iron produced by this reaction is said to be about 3100 ° C., which is much higher than the melting point of slag shown in Table 1. Therefore, the solidified slag can be dissolved by continuously supplying the aluminum powder and the metal oxide powder.

The present invention is as follows. (1) In the method of melting solidified slag floating on the molten metal surface of a scouring vessel, a pipe having a plurality of communication holes around a central double pipe is used to remove metal from the inner pipe of the double pipe. A mixture of powder and iron oxide powder is injected with a carrier gas composed of an inert gas, oxygen is injected from the outer tube, and fuel gas is injected from a plurality of communication holes around the outer tube and ignited. A method for dissolving solidified slag in a scouring container, characterized in that the solidified slag is dissolved by heat obtained by a thermite reaction with an oxide powder. (2) The particle size of the mixture of metal powder and iron oxide powder is 0.1.
The method for dissolving solidified slag in a scouring container according to (1) above, wherein the content is 15 to 60 wt% of aluminum having a diameter of 5 mm or less and the balance is iron oxide having a particle diameter of 0.4 mm or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is to obtain the temperature of 1200 ° C. or higher required for starting the reaction of metallic aluminum and iron oxide by the combustion flame of fuel gas and oxygen. That is, the metallic aluminum powder and the iron oxide powder injected together with the carrier gas composed of the inert gas from the inner tube of the double tube arranged in the center are mixed with the oxygen injected from the outer tube of the double tube and It is heated in the process of passing through the combustion flame with the fuel gas injected from the multiple fuel gas injection holes arranged concentrically around the heavy pipe, colliding with the surface of the solidified slag, and at the same time, the exothermic reaction starts and is obtained. The solidified slag becomes molten due to the high temperature. The molten slag is removed by the jet of combustion flame and the solidified slag surface is exposed, but by continuing the injection of the metal aluminum powder and iron oxide powder and combustion of fuel gas, the molten slag is melted from the surface. However, the solidified slag is eventually reformed into a dissolved liquid phase slag.

In the present invention, in order to improve the reaction efficiency when the metal aluminum powder and the iron oxide powder collide with the surface of the solidified slag, the particle size of the metal aluminum is 0.15 mm or less, The particle size is preferably 0.4 mm or less. When the particle size of the metallic aluminum exceeds 0.15 mm, the heating when passing through the combustion flame becomes insufficient, the temperature of the metallic aluminum at the time of collision with the solidified slag is low, and the reaction efficiency decreases. On the other hand, the particle size of iron oxide is 0.4 mm
If it exceeds, the amount of rebound at the time of collision with the solidified slag increases, and the amount of iron oxide necessary for the reaction becomes insufficient, so that the reaction efficiency decreases.

In the present invention, in order to improve the dissolution rate at the time when the metal aluminum powder and the iron oxide powder collide with the surface of the solidified slag, the ratio of metal aluminum in the powder is preferably 15 to 60 wt%. Is 30 to 50
wt%. When the amount of metallic aluminum is less than 30 wt% and the balance is iron oxide, the entire amount of metallic aluminum undergoes an oxidation reaction, but an excessive amount of iron oxide adheres to the surface of the molten slag and inhibits dissolution, so that the dissolution rate decreases. In particular, 1
When it is less than 5 wt%, the decrease is remarkable. Further, when the amount of metallic aluminum exceeds 60 wt% and the balance is iron oxide, unreacted metallic aluminum adheres to the surface of the molten slag and inhibits dissolution, resulting in a reduction in removal efficiency. Also in this case, if it exceeds 60 wt%, the reduction of the removal efficiency will be serious.

The fuel gas used in the present invention is one capable of forming a combustion flame temperature of 1200 ° C. or higher necessary for initiating the reaction between the metal aluminum powder and the iron oxide powder, for example, propane-oxygen, butane-oxygen. , Acetylene-oxygen, propane-air, butane-air, acetylene-air and the like can be used.

[0015]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples. FIG. 1 shows the overall structure of the melting apparatus of the present invention. The melting device includes a burner 1 at the tip, a lance 5, a powder feeder 6, and a gas control panel 7.
A front view and a sectional view of the burner 1 are shown in FIG. In FIG. 2, the inner tube of the double tube provided in the center is a powder injection hole 2 for injecting metal aluminum powder and iron oxide powder, and the outer tube is an oxygen injection hole 3 for injecting oxygen. A plurality of fuel gas injection holes 4 are concentrically arranged around the double pipe.

The present inventors conducted a dissolution experiment of the slag mass 8 having the composition shown in Table 1. At that time, propane was used as the fuel gas, and the mixing ratio with oxygen was propane / oxygen = 15.
/ 75 Nm ³ / hr, and the supply rate of the mixed powder of metallic aluminum and iron oxide was 50 kg / hr.

The proper distance between the burner 1 and the slag mass is 3
It was 00 mm. Table 2 shows examples and comparative examples of the present invention in melting the slag mass 8 having a thickness of about 300 mm under these conditions.

[0018]

[Table 2]

In Table 2, the case where the solidified slag can be removed within the target dissolution time of 5 minutes is indicated by a circle, and the case where the solidified slag cannot be removed is indicated by a cross. In all the examples of the present invention, good removal was possible. On the other hand, in the comparative example, the case where the particle size of metallic aluminum exceeds 0.15 mm, the case where the particle size of iron oxide exceeds 0.4 mm, or the ratio of metallic aluminum in the powder is 15 to 60 wt%. Outside the range, it was impossible to dissolve and remove within the target time even if the other conditions were satisfied.

[0020]

Industrial Applicability According to the present invention, it is possible to dissolve and remove solidified slag having an extremely high melting point generated in the molten steel refining process at a high speed and at a stable rate.
The probe for temperature measurement and sampling during processing can be smoothly inserted.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an overall configuration of a melting device used in the present invention.

FIG. 2 is a front burner portion of a melting device used in the present invention, (a) is a front view and (b) is a sectional view.

[Explanation of symbols]

 1 tip burner 2 powder injection hole 3 oxygen injection hole 4 fuel gas injection hole 5 lance 6 powder feeder 7 gas control panel 8 slag mass

Claims (2)

[Claims] 1. A method for melting solidified slag floating on a molten metal surface of a scouring vessel, wherein a tube having a plurality of communicating holes around a centrally arranged double tube is used. A mixture of metal powder and iron oxide powder is injected from the inner tube together with a carrier gas composed of an inert gas, oxygen is injected from the outer tube, and fuel gas is further injected from a plurality of communication holes around the outer tube to ignite, A method for dissolving solidified slag in a scouring container, characterized in that the solidified slag is dissolved by heat obtained by a thermite reaction between a metal powder and an iron oxide powder. 2. A mixture of metal powder and iron oxide powder is 15 to 60 wt% of metallic aluminum having a particle size of 0.15 mm or less.
%, The balance consisting of iron oxides having a particle size of 0.4 mm or less, The method for dissolving solidified slag in a scouring vessel according to claim 1, characterized in that.