JPH05279723A - Method for melting low hydrogen steel - Google Patents

Abstract

PURPOSE:To easily execute refining of steel without large difference in comparison with dehydrogenation treatment time when using the ordinary vacuum degassing apparatus, at the time of executing dehydrogenation treatment to the molten steel. CONSTITUTION:In the condition of pushing slag 4 on the surface of the molten steel 1 to the wall side of a ladle 2 by blowing inert gas from the bottom part of the ladle 2 or an auxiliary immersion lance, a refractory-made immersion body 5 is dipped in the ladle 2, and on the surface of the molten steel 1 in which the slag in the immersion tube is removed and deoxidation is executed, the inert gas is blown from the upper part in the immersion body 5, and while renewing gas on the molten steel surface, the dehydrogenation is executed. Without using large-scale vacuum degassing apparatus as in the ordinary method, the solidified quantity of metal stuck in the immersion tube is small and the temp. drop is little even in the case the molten steel quantity is small and the dehydrogenation can stably be executed till low hydrogen concn. By this method, the maintenance is easy and the low hydrogen steel can surely be melted at a low cost.

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 low hydrogen steel.

[0002]

2. Description of the Related Art Hydrogen in molten steel has long been known as a harmful element that causes hair cracking during solidification, white spots after rolling, or brittle fracture or delayed fracture of steel sheets. From the viewpoint of improving or stabilizing the quality against the harsh environment, there is an increasing demand for low-hydrogen steel whose concentration has been reduced as much as possible.

On the other hand, conventionally, in the steel making stage, after the molten steel which has been refined to a required carbon concentration by oxygen blowing in a converter is received in a vessel such as a ladle, the RH method or the DH method is applied.
By using a vacuum degassing device that is connected to an exhaust device such as the method, a part of the molten steel is placed in a decompressed (vacuum) atmosphere, and the total pressure on the gas side is reduced to reduce the hydrogen content at the interface between the gas and the molten steel. Under conditions of lowering the pressure, dehydrogenate by the method shown in the following formula, in which hydrogen in molten steel is reacted to remove it as hydrogen gas, and then adjust by adding an alloy so that it becomes the target molten steel composition. The melting method is widely used.

H + H → H ₂ (gas) (1) In general, when dehydrogenating molten steel, H ₂ gas is generated by reacting hydrogen in molten steel as shown in equation (1), A method of removing this gas to the gas side is used. Here, the vacuum degassing apparatus is widely used as a method of advancing the reaction of the formula (1) in the right direction by lowering the hydrogen partial pressure on the gas side in order to proceed the dehydrogenation reaction. Is.

That is, the following "Siebert's law"
In equation (2), which is referred to as “equal hydrogen concentration” in the molten steel, the smaller the partial pressure of hydrogen on the gas side,
That is, the hydrogen concentration in the molten steel after refining can be made lower, and as shown in equation (4), the difference between the hydrogen concentration in the molten steel and the equilibrium reaching hydrogen concentration corresponding to the driving force of the dehydrogenation reaction can be calculated. Since it can be increased, the refining time required for dehydrogenation can be shortened.

[0006]

[Equation 1]

According to this method, the dehydrogenation reaction progresses to the right as shown in the equation (1) as the degree of vacuum is increased (the degree of vacuum is increased). Therefore, the molten steel is currently industrially used in the RH method and the DH method. By maintaining the surface under a vacuum as high as possible and extending the dehydrogenation treatment time in order to sufficiently carry out the reaction, it is possible to produce low hydrogen steel with a hydrogen concentration of about 1 ppm.

Further, in order to further shorten the dehydrogenation time, in order to increase the reaction interfacial area between the gas and the liquid represented by A in the above formula (4), in the vacuum degassing apparatus, the inner diameter of the vacuum chamber is set to Method for increasing the number (Japanese Patent Laid-Open No. 2-247315)
(Japanese Patent Laid-Open Publication No. 2-247325) or a method of promoting circulation of molten steel in a vacuum chamber and a ladle in order to increase the amount of molten steel brought into contact with a depressurized state (JP-A-2-247325) or increasing the amount of gas blown into molten steel. Method (JP-A-61-183407)
Issue) has been developed.

[0009]

The dehydrogenation method using the above-mentioned vacuum degassing apparatus is an effective method from the viewpoint of equilibrium because it lowers the hydrogen concentration, and it is widely used at present. As mentioned above, in order to bring a part of the molten steel into contact with a high vacuum state, a very large and expensive vacuum device is required, and since the molten steel is processed under vacuum, the refractory and the like are melted and damaged. In order to maintain the depressurized state at high temperature, detailed maintenance is required to improve the adhesion of each fitting part.

The apparatus for depressurizing the molten steel is, of course, used with sufficient preheating. However, since the apparatus as a whole is large, the larger the inner diameter of the vacuum chamber is, the more uniform the entire apparatus becomes. Difficult to preheat to a certain temperature,
At the start of the dehydrogenation treatment, the temperature drop of the molten steel becomes larger as the amount of treated molten steel decreases. Therefore, in order to stably cast molten steel that has been sufficiently dehydrogenated to reduce the hydrogen concentration in a process such as continuous casting, it is necessary to compensate for the temperature drop during dehydrogenation. Refining treatment costs increase.

Further, in order to promote the circulation of the molten steel in the vacuum chamber and the ladle, or to increase the reaction interfacial area between the gas and the molten steel in the molten steel, the molten steel is kept in contact with the molten steel under reduced pressure. As the amount of gas blown into the molten steel increases, the yield of molten steel decreases because the amount of solidified steel called solid metal that adheres to the surrounding sealed container increases when the gas leaves the molten steel surface. In addition to this, there is a problem that a great amount of labor is required to remove the adhered metal.

In view of the above circumstances, the present invention solves these problems and melts low-hydrogen steel equivalent to that manufactured by using a conventional vacuum degassing apparatus with inexpensive equipment. The purpose is to provide a manufacturing method.

[0013]

According to the present invention, (1) in a ladle in a state where an inert gas is blown from the bottom of a ladle or an auxiliary immersion lance and the molten steel surface slag is pushed to the wall side of the ladle. The slag in the dip pipe was removed by immersing the refractory dip in, while spraying an inert land gas from above the inside of the dip on the surface of the deoxidized molten steel while renewing the gas on the molten steel surface. A method for producing low-hydrogen steel, which comprises dehydrogenating.

Further, according to the present invention, (2) the molten steel area for eliminating slag in the refractory-made dipping body is 20 times the molten steel surface area in the ladle.
% Or more, the method for melting low hydrogen steel according to the item (1).

Further, the present invention is (3) characterized in that the gas flow velocity on the molten steel surface is 20 m / sec or more as the condition of the inert gas blown from above inside the refractory-made dip body. ) Or (2) the method for melting low hydrogen steel.

The present invention also provides (4) a method of spraying an inert gas from above the inside of the refractory-made dip body, wherein the temperature is 90 ° or less from a gas outlet provided on the side portion of the refractory-made dip body. The method for producing low hydrogen steel according to the above (1) to (4), characterized in that the gas is sprayed onto the surface of the molten steel at an angle. Is.

[0017]

The present inventors have investigated a method for stably reducing the hydrogen concentration in molten steel without the need for a conventional expensive and large-scale vacuum degassing apparatus, and have investigated hydrogen at the interface between molten steel and gas. Focusing on the point of reducing the partial pressure of gas, even if the surface of a part of the molten steel is not kept under reduced pressure, an inert gas such as argon is blown onto the surface of the molten steel to remove hydrogen gas generated as a result of dehydrogenation. It was found that by removing from the interface and reducing the partial pressure thereof, the dehydrogenation reaction proceeds sufficiently to a hydrogen concentration of 1 ppm or less even under atmospheric pressure, and it is possible to produce a low-hydrogen steel. Came to make.

Here, the reason for removing the slag on the molten steel surface in the ladle, which is a requirement of the present invention, is that when slag is present on the molten steel surface, the slag reacts at the interface between the gas and the molten steel. This is because it prevents the hydrogen gas from leaving the surface of the molten steel. Here, in order to carry out dehydrogenation stably, it is desirable to remove 20% or more of slag with respect to the total surface area of molten steel. The reason for this is that in an area of less than 20%, an inert gas is sprayed in the first place. This is because an effective reaction interfacial area for accelerated dehydrogenation cannot be secured and the time required for dehydrogenation becomes long even at low hydrogen concentrations.

As a method for removing slag on the surface of molten steel in the ladle by 20% or more with respect to the surface area of molten steel, for example,
Gas is blown from the bottom of the ladle or from a refractory lance soaked in molten steel, and the slag on the molten steel surface is pushed by the flow of molten steel toward the inner wall of the ladle. The method of immersing the immersion pipe and discharging the slag in the immersion pipe is simple. As another means, a method of suppressing the outflow of oxidizing slag in the converter such as slag balls and slag stoppers when receiving molten steel from the converter to the ladle, or physically removing slag from the ladle It is even more reliable if the slag in the ladle is physically removed by a method such as the scraping slug dragger method.

Next, the reason for using an inert gas as the gas sprayed on the surface of the molten steel is that when an oxidizing gas is mixed in the sprayed gas, the surface of the molten steel contains carbon, manganese, silicon, aluminum Oxidation of component elements occurs, molten oxide slag is generated at the interface, and this slag gradually accumulates, reducing the effective interfacial area for dehydrogenation.As a result, the dehydrogenation rate also decreases and the hydrogen concentration increases. 1 ppm
This is because the dehydrogenation up to the following results in obtaining a longer time.

The types of inert gas used here include:
Argon gas is generally used, but helium gas or the like is also possible, and nitrogen gas can be used if there is no problem in the material of steel, and these gases may be mixed.

The flow rate of the inert gas blown onto the surface of the molten steel from which the slag has been removed depends on the conditions of the lance for blowing the gas and the gas outlet, but the gas flow velocity on the surface of the molten steel is 2
It is effective to secure 0 m / sec or more. here,
When the gas flow velocity on the molten steel surface is 20 m / sec or less,
This is because the rate at which hydrogen gas generated by dehydrogenation is removed from the interface is slow, it is difficult to maintain the partial pressure of the hydrogen gas at the interface at a low level, and the dehydrogenation treatment time becomes long. Therefore, by ensuring a gas flow velocity of 20 m / sec or more on the surface of the molten steel, a state similar to that under reduced pressure can be ensured on the surface of the molten steel even under atmospheric pressure.
The higher this flow velocity, the greater the effect.

As a method of spraying an inert gas on the interface, a lance having a single downward hole arranged on the upper portion of the molten steel is generally used, but a lance having a plurality of holes may be used. The height of these lances on the molten steel surface is determined by the flow rate of the gas to be sprayed, the inner diameter of the lance holes, and the number of lance holes.

Further, when the inert gas is sprayed from the lance arranged above as described above, if the gas flow velocity at the molten steel interface is increased as described above, the free surface of the molten steel is violently disturbed, Since the molten steel scatters in the airtight container around it, it is conceivable that the metal may adhere to the inside of the container and reduce the yield of the molten steel. Therefore, in order to secure a larger gas flow velocity, the inner wall of the refractory dipping pipe immersed to remove the slag, just above the surface of the molten steel, provided several tuyere for gas blowing, A method of blowing an inert gas onto the surface of the molten steel at an angle of 90 degrees or less from the mouth is also more effective from the viewpoint of performing stable dehydrogenation treatment.

By such a method, in order to secure the reaction interfacial area for dehydrogenation, an inert gas is constantly flowed over the molten steel surface from which the slag has been removed, and hydrogen gas at the interface is removed, thereby increasing the dehydrogenation rate. It can be maintained.

For the above reasons, the hydrogen concentration is set to 1 pp.
When it is desired to proceed to as low as m or less and within a short time, the size of the molten steel surface area occupied by slag is made smaller in order to increase the reaction interfacial area in which dehydrogenation proceeds by blowing gas. Needless to say, strong stirring of the molten steel is effective so that hydrogen in the molten steel is always supplied to the reaction interface. In order to stir the molten steel, it is preferable to increase the amount of gas supplied from the bottom of the ladle or the refractory lance soaked in an auxiliary manner, and the gas for this purpose is the same as the gas blown from the top surface. Inert gases are preferred.

The present invention will be described in detail below with reference to FIGS.

[0028]

【Example】

Example-1 In a converter, carbon 0.15%, manganese 0.
100 ton of molten steel 1 melted to 30% was tapped in a ladle 2 in an undeoxidized state. The temperature of molten steel in the ladle after tapping is 16
It was 30 ° C.

Thereafter, while introducing Ar gas at a flow rate of 20 Nm ³ / hr from the porous plug 3 made of refractory placed at the bottom of the ladle, the slag 4 flowing out of the converter in the ladle is taken into the inner wall of the ladle. While being pushed to the portion, a cylindrical refractory dipping pipe 5 was dipped as shown in FIG. 1 to ensure that the slag 4 was not present in the dipping pipe. The diameter of the molten steel surface in the ladle 2 is 2.5 m (5 m ² ), whereas the inner diameter of the dip pipe 5 is 1.2 m (1.1 m ² ) and the slag 4 on the molten steel surface is 2 m.
2% removed. At this point, aluminum and silicon were added to the molten steel for deoxidation treatment, and the hydrogen concentration in the molten steel was measured and found to be 3.5 ppm.

Next, as shown in FIG. 2, the upper blowing lance 6 is placed at a height of 1.5 m from the surface of the molten steel 1 inside the immersion pipe 5.
Was placed, Ar gas was blown onto the molten steel surface at a flow rate of 1000 Nm ³ / hr, and dehydrogenation treatment was performed for 15 minutes. When the gas velocity on the surface of the molten steel at this time was measured, it was about 70 m / sec.
Met. During this time, 20 Ar gas was introduced from the bottom of the ladle 2.
Blowing was continued at a flow rate of Nm ³ / hr and stirring was performed. The hydrogen concentration after this dehydrogenation treatment was 0.9 ppm, and the molten steel temperature was 1600 ° C. Carbon concentration is 0.15
%, Manganese concentration is 0.30%, which is the same as the initial concentration,
The hydrogen concentration reached 1 ppm or less stably.

Example-2 In a converter, carbon 0.15%, manganese 0.
80 ton of molten steel 1 melted to 32% was tapped in a ladle 2 in a non-deoxidized state. The temperature of molten steel in the ladle after tapping is 162
It was 5 ° C.

Thereafter, while introducing Ar gas at a flow rate of 15 Nm ³ / hr from the porous plug 3 made of refractory placed at the bottom of the ladle, the slag 4 flowing out of the converter in the ladle is taken into the inner wall of the ladle. While being pushed to the portion, a cylindrical refractory dipping pipe 5 was dipped as shown in FIG. 1 to ensure that the slag 4 was not present in the dipping pipe. The diameter of the molten steel surface in the ladle 2 is 2.0 m (3.1 m ² ), whereas the inner diameter of the dipping pipe 5 is 1.0 m (0.8 m ² ) and the slag 4 on the molten steel surface is removed by 25%. Was done. At this point, aluminum and silicon were added to the molten steel for deoxidation treatment, and the hydrogen concentration in the molten steel was measured and found to be 3.7 ppm.

Next, as shown in FIG. 3, the inner wall 4 of the immersion pipe 5 is
Degassing treatment is performed by spraying Ar gas in the direction of 90 degrees from the tuyere 7 for gas blowing provided at a height of 0.3 m on the surface of molten steel 1 at a total flow rate of 1500 Nm ³ / hr to the upper portion of the molten steel. For 15 minutes. When the gas flow velocity on the surface of the molten steel at this time was measured, it was about 100 m / sec. During this period, Ar gas was continuously blown from the bottom of the ladle 2 at a flow rate of 20 Nm ³ / hr to perform stirring. The hydrogen concentration after this dehydrogenation treatment was 0.8 ppm, and the molten steel temperature was 1595 ° C.
Met. The carbon concentration is 0.15% and the manganese concentration is 0.1.
Stable hydrogen concentration of 1ppm, unchanged from the initial concentration of 31%
I have reached the following: In addition, the state of adhesion of the metal on the inner surface of the dipping tube 5 after the treatment was observed, and it was in a good state with almost no difference from the amount of adhesion when gas was sprayed from the upper lance.

Example 3 In a converter, carbon 0.14%, manganese 0.
100 ton of molten steel 1 melted to 30% was tapped in a ladle 2 in an undeoxidized state. The temperature of molten steel in the ladle after tapping is 16
It was 35 ° C.

Then, while introducing Ar gas at a flow rate of 20 Nm ³ / hr from the refractory porous plug 3 arranged at the bottom of the ladle, the slag 4 flowing out of the converter in the ladle is taken into the inner wall of the ladle. While being pushed to the portion, a cylindrical refractory dipping pipe 5 was dipped as shown in FIG. 1 to ensure that the slag 4 was not present in the dipping pipe. The diameter of the molten steel surface in the ladle 2 is 2.5 m (5 m ² ), whereas the inner diameter of the dipping pipe 5 is 0.9 m (0.6 m ² ), and the slag 4 on the molten steel surface is 1
Only 2% was removed. At this point, aluminum and silicon were added to the molten steel for deoxidation treatment, and the hydrogen concentration in the molten steel was measured and found to be 3.6 ppm.

Next, as shown in FIG. 2, the upper blowing lance 6 is placed at a height of 1.5 m from the surface of the molten steel 1 inside the immersion pipe 5.
Was placed and Ar gas was blown onto the surface of the molten steel at a flow rate of 800 Nm ³ / hr to perform dehydrogenation treatment. When the gas flow velocity on the surface of the molten steel at this time was measured, it was about 60 m / sec.
During this time, Ar gas from the bottom of the ladle 2 was 20 Nm ³ / h.
Blowing was continued at a flow rate of r and stirring was performed. When the hydrogen concentration was measured after 15 minutes of dehydrogenation and found to be 1.5 ppm, when the dehydrogenation treatment was extended for another 10 minutes, the hydrogen concentration after dehydrogenation was 0.9 ppm.
The carbon concentration after dehydrogenation treatment was 0.14% and the manganese concentration was 0.30%, which was unchanged from the initial concentration, but the molten steel temperature was 1580 ° C.

Example-4 In a converter, carbon 0.15%, manganese 0.
100 ton of molten steel 1 melted to 35% was tapped in a ladle 2 in an undeoxidized state. The temperature of molten steel in the ladle after tapping is 16
It was 32 ° C.

Thereafter, while introducing Ar gas at a flow rate of 20 Nm ³ / hr from the porous plug 3 made of refractory placed at the bottom of the ladle, the slag 4 flowing out from the converter in the ladle is taken into the inner wall of the ladle. While being pushed to the portion, a cylindrical refractory dipping pipe 5 was dipped as shown in FIG. 1 to ensure that the slag 4 was not present in the dipping pipe. The diameter of the molten steel surface in the ladle 2 is 2.5 m (5 m ² ), whereas the inner diameter of the dipping pipe 5 is 1.2 m (1.1 m ² ) and the slag 4 on the molten steel surface is 2 m.
2% removed. At this point, aluminum and silicon were added to the molten steel for deoxidation treatment, and the hydrogen concentration in the molten steel was measured and found to be 3.5 ppm.

Next, as shown in FIG. 2, the upper blowing lance 6 is placed at a height of 1.5 m from the surface of the molten steel 1 inside the immersion pipe 5.
Was placed and Ar gas was blown onto the surface of the molten steel at a flow rate of 200 Nm ³ / hr to perform dehydrogenation treatment. When the gas flow velocity on the surface of the molten steel at this time was measured, it was about 15 m / sec.
During this time, Ar gas from the bottom of the ladle 2 was 20 Nm ³ / h.
Blowing was continued at a flow rate of r and stirring was performed. The hydrogen concentration measured after 20 minutes of dehydrogenation was 1.2 ppm, so when the dehydrogenation treatment was extended for another 5 minutes,
The hydrogen concentration after the dehydrogenation treatment was 0.9 ppm. After the dehydrogenation treatment, the carbon concentration was 0.14% and the manganese concentration was 0.
The initial concentration was unchanged at 34%, but the molten steel temperature was 15
It was 82 ° C.

Comparative Example-1 In a converter, 0.18% of carbon, 0.
100 ton of molten steel 1 melted to 28% was tapped in a ladle 2 in an undeoxidized state. The temperature of molten steel in the ladle after tapping is 16
It was 30 ° C.

After that, as shown in FIG. 4, 30 mm in the ladle 2.
With the thick slag remaining, Ar gas of 20N was supplied from the refractory porous plug 3 placed in the ladle's residence.
Blowing at a flow rate of m ³ / hr ヽ At this point, aluminum and silicon were added to the molten steel for deoxidation treatment, and the hydrogen concentration in the molten steel was measured and found to be 3.9 ppm.

Next, as shown in FIG. 5, an upper blowing lance 6 is arranged at a height of 1.5 m from the surface of the molten steel 1, and Ar gas is blown at a flow rate of 1000 Nm ³ / hr to perform dehydrogenation treatment. It went for 30 minutes. When the gas flow velocity on the surface of the slag at this time was measured, it was about 60 m / sec. During this time, ladle 2
Ar gas was continuously blown in from the bottom of the reactor at a flow rate of 20 Nm ³ / hr to perform stirring. The molten steel temperature after this dehydrogenation treatment was as good as 1600 ° C, but the hydrogen concentration was 3.5 pp.
m was almost unchanged, the carbon concentration was 0.14%, and the manganese concentration was 0.25%, indicating that some of the molten steel components were also oxidized. Thus, dehydrogenation hardly proceeded without removing the slag, and the hydrogen concentration did not reach 1 ppm or less.

[0043]

According to the present invention, such degassing equipment is used in comparison with the conventional expensive and large-scale, low-hydrogen steel melting method using a vacuum degassing apparatus which requires detailed maintenance. By simply reducing the slag on the molten steel surface and spraying an inert gas without modifying or newly installing the
With a refining time of about a minute, it became possible to produce low hydrogen steel with a hydrogen concentration of 1 ppm or less. According to the present invention, the temperature drop of the molten steel is small as compared with the conventional method using the vacuum degassing apparatus, and therefore, sufficient refining treatment can be performed even under the condition that the molten steel amount is small. Further, there is little adhesion of metal and the like, and it is sufficient to remove only the metal adhered in the dip tube for the removal of the metal. Therefore, maintenance becomes very easy and the processing cost can be reduced.

Even if the hydrogen concentration is in the range of 1 ppm or more, it is needless to say that demolition can be performed on molten steel having a hydrogen concentration higher than required for quality without using a conventional vacuum degassing device. Absent.

As described above, according to the present invention, on an industrial scale, excellent effects such as easy, reliable and inexpensive production of low hydrogen steel can be obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing an example of a method of implementing the present invention.

FIG. 3 is an explanatory diagram showing an example of a method of implementing the present invention.

FIG. 4 is an explanatory diagram showing an example of a comparative example with respect to the present invention.

FIG. 4 is an explanatory diagram showing an example of a comparative example with respect to the present invention.

[Simple explanation of symbols]

1 ... Molten steel 2 ... Ladle 3 ... Porous plug 4 ... Ladle inner slurry 5 ... Immersion pipe 6 ... Top blowing lance 7 ... Tuyere provided in dipping pipe

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[Procedure amendment]

[Submission date] December 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing an example of a method of implementing the present invention.

FIG. 3 is an explanatory diagram showing an example of a method of implementing the present invention.

FIG. 4 is an explanatory diagram showing an example of a comparative example with respect to the present invention.

FIG. 5 is an explanatory diagram showing an example of a comparative example with respect to the present invention.

[Short description of reference symbols] 1 ... Molten steel 2 ... Ladle 3 ... Porous plug 4 ... Ladle inner slurry 5 ... Immersion pipe 6 ... Top blowing lance 7 ... Tuyere provided on the immersion pipe

Claims (4)

[Claims] 1. A refractory dip is immersed in a ladle in a state where an inert gas is blown from the bottom of the ladle or an auxiliary dipping lance to push the slag on the molten steel surface toward the wall of the ladle. The slag in the immersion pipe is removed, and the surface of the deoxidized molten steel is sprayed with an inert gas from above the inside of the immersion body to dehydrogenate while renewing the gas on the surface of the molten steel. Melting method. 2. The method for smelting low-hydrogen steel according to claim 1, wherein the molten steel area in which the slag is removed by the refractory-made immersion body is 20% or more of the molten steel surface area in the ladle. 3. A gas flow velocity on the surface of molten steel is set to 20 as a condition of the inert gas blown from above inside the refractory immersion body.
The method for melting low hydrogen steel according to claim 1 or 2, wherein the melting rate is set to m / sec or more. 4. A method of spraying an inert gas from above the inside of a refractory immersion body, wherein the gas is blown to the molten steel surface at an angle of 90 degrees or less from a gas outlet provided on the side of the refractory immersion body. The method for smelting low-hydrogen steel according to claim 1, 2 or 3, characterized by spraying.