JP2002249814A - Method for producing low phosphorus molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing low phosphorus molten iron with which even when using flux containing no F source such as CaF2 , dephosphorization in the molten iron can efficiently be performed. SOLUTION: In the method for producing the low phosphorus molten iron, with which the dephosphorization is performed by adding the flux as CaO source into a vessel holding the molten iron and also, supplying gaseous oxygen and/or solid oxygen source as the oxygen source, at least a part of the flux to be added in the vessel, is added into the vessel by blowing a carrier gas onto bath surface while using the carrier gas from the upper part of the bath surface in the vessel. Then, it is satisfied that a supplying speed A of the gaseous oxygen conversion in the above oxygen source supplied into the vessel to a supplying speed B of the CaO conversion in the flux blown onto the bath surface by using this carrier gas is 0.3<=A/B<=7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing low-phosphorus hot metal by a dephosphorization treatment performed as a pretreatment of hot metal.

[0002]

2. Description of the Related Art Conventionally, a steelmaking method has been developed in which dephosphorization is performed at a hot metal stage to remove P in the hot metal to some extent, and then decarburization blowing is performed in a converter. This preliminary dephosphorization treatment is performed by using equipment such as a torpedo, a hot metal pot, and a converter, and adding a CaO-based medium solvent and an oxygen source such as gaseous oxygen or a solid oxygen source (for example, iron oxide). In order to efficiently transfer P from the hot metal to the slag side during the dephosphorization treatment, control of the slag composition, slag amount, and the like is an important factor.

[0003] In particular, by adding CaF ₂ to a solvent medium, the meltability of slag is improved, the activity of Ca ions is increased by dividing the SiO ₂ network,
It has been pointed out that an effect such as an increase in the activity of O can be obtained, and CaF ₂ is widely used in actual operations to enhance the reactivity of dephosphorization. For example, Tokuho 6
In Japanese Patent No. 17496, each weight ratio of [CaF ₂ + Al ₂ O ₃ ] / CaO and Al ₂ O ₃ / CaF ₂ is defined in addition to the weight ratio of added CaO and oxygen O, CaO / O, and CaF ₂
A technique for improving the dephosphorization efficiency by addition is disclosed.

However, recently, from the viewpoint of environmental protection,
Regulation standards for the amount of F eluted in slag are being strengthened, and it is necessary to reduce the F concentration in dephosphorized slag to the utmost. Therefore, there is a strong demand for the development of a dephosphorization treatment technique that does not use an F source such as CaF _2. However, at present, slag is made to have a low basicity and operation with an extremely large amount of slag is carried out, or multiple treatments are carried out. It is the actual situation that the method of doing is performed. However, the extreme increase in the amount of dephosphorized slag, as in the former case, goes against the need to reduce the amount of slag, which is strongly demanded from the viewpoint of environmental protection. Doing so has the problem of lowering productivity and increasing the production cost of molten steel,
Therefore, they cannot be a drastic measure.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to efficiently perform hot metal dephosphorization even when a medium solvent not containing an F source such as CaF ₂ is used. An object of the present invention is to provide a method for producing low-phosphorus hot metal that can be performed.

[0006]

Means for Solving the Problems The present inventors have proposed CaF ₂
In order to find a hot metal pretreatment method that can efficiently perform dephosphorization without using an F source such as (fluorite),
Various experiments and examinations were performed using a converter type vessel. As described above, CaF ₂ plays an important role in securing the melting property of the slag, and in the experiments of the present inventors,
When CaF ₂ was not added or the amount added was small, the added medium solvent (CaO source) did not seem to be slag, and the dephosphorization reaction efficiency was lowered. However, as the experiment is repeated, the dephosphorization reaction greatly changes depending on the supply rate of oxygen and the supply rate of CaO (medium solvent). Specifically, FeO is generated in the slag by supplying oxygen. It was confirmed that there was an appropriate CaO supply rate commensurate with the production amount. Here, if the supply rate of oxygen is too small in the ratio of the supply rates of oxygen and CaO,
The amount of FeO generated in the slag is small, and CaO remains in a solid state and does not effectively act on dephosphorization. Conversely, if the supply rate of oxygen is too high, the amount of oxygen required for dephosphorization is reduced. C
Insufficient aO, and in any case, the dephosphorization rate decreases. On the other hand, if the supply rate of oxygen is too high, the amount of reactive oxygen other than oxygen required for dephosphorization increases, and this is consumed for decarburization and the like. This will result in a significant increase.

As described above, it has been found that there is an optimum oxygen / CaO supply rate ratio for efficiently dephosphorizing hot metal. Further, such optimization of the oxygen / CaO supply rate ratio has been found. It has been found that the effect of the method greatly depends on the method of supplying CaO. That is, in the hot metal dephosphorization reaction, [P] in the metal is oxidized directly or through FeO by oxygen (gas oxygen or solid oxygen source) added into the furnace to generate phosphor oxide (P ₂ O ₅ ). , while the phosphorus oxide is because it is thermodynamically unstable, which proceeds by forming a 3CaO _· P 2 _{O 5} or 4CaO _· P 2 _{O 5} in combination with CaO. Therefore, how efficiently CaO is present around the generated phosphor oxide is one of the important factors for efficiently promoting the dephosphorization reaction. Since FeO and phosphorous oxide generated by the supplied oxygen mainly exist on the metal bath surface, it is important to add a medium solvent containing CaO as a main component to the region. From this point of view, at least a part of the medium solvent to be added to the container is filled with a carrier gas from above the bath surface in the container using a carrier gas (metal bath surface), particularly preferably a metal to which oxygen is supplied. It has been found that spraying on the bath surface region (that is, the region where FeO is generated) is very effective in promoting the dephosphorization reaction.

Further, by using gaseous oxygen as a carrier gas for spraying a solvent onto the bath surface, Ca
It was found that the contact efficiency between O and FeO could be made very high, and the dephosphorization reaction could be more remarkably promoted. Further, the effect of optimizing the supply rate ratio of oxygen and CaO also differs depending on the Si concentration in the hot metal before the dephosphorization treatment, and is particularly remarkable when the Si concentration in the hot metal before the dephosphorization treatment is 0.10 mass% or less. It was found that a great effect was obtained. The present invention has been made based on the above findings, and the features are as follows.

[1] A method for producing a low-phosphorus hot metal in which a medium solvent as a CaO source is added to a vessel holding hot metal and a dephosphorization treatment is performed by supplying a gaseous oxygen and / or a solid oxygen source as an oxygen source. In the method, at least a part of the medium solvent to be added to the container is added to the container by spraying the bath surface with a carrier gas from above the bath surface in the container, and is added to the bath surface using the carrier gas. Supply rate B (kg / min / hot metal t)
on) with respect to the supply rate A (Nm ³ / min / hot metal ton) of the oxygen source supplied into the vessel in terms of gaseous oxygen, wherein the following formula (1) is satisfied. Production method. 0.3 ≦ A / B ≦ 7 (1)

[2] In the production method of the above [1], the supply rate B (kg / min / hot metal to
n) is the supply rate A (Nm ³ /
min / hot metal ton), wherein the following formula (2) is satisfied. 1.2 ≦ A / B ≦ 2.5 (2) [3] In the production method of the above [1] or [2], gas oxygen is blown onto the bath surface from above the bath surface in the vessel, and the gas oxygen A method for producing low-phosphorus molten iron, comprising spraying a medium solvent onto a bath surface region supplied with the molten iron. [4] The method according to any one of the above [1] to [3], wherein gaseous oxygen serving as at least a part of an oxygen source is used as a carrier gas for spraying a medium solvent onto a bath surface. Manufacturing method of hot metal.

[5] The method for producing low-phosphorus hot metal according to any one of [1] to [4], wherein the hot metal having a Si concentration of 0.10 mass% or less is dephosphorized. [6] The method according to any one of the above [1] to [5], wherein the medium solvent does not substantially contain the F source or CaF ₂ contained in the medium solvent is 1 kg / hot metal ton or less. Characteristic method for producing low-phosphorus hot metal. [7] The method for producing low-phosphorus hot metal according to any one of [1] to [6], wherein the hot metal temperature at the end of the dephosphorization treatment is 1360 ° C or more.

[0012]

DETAILED DESCRIPTION OF THE INVENTION In the method for producing low-phosphorus hot metal of the present invention, a medium solvent as a CaO source is added to a container holding hot metal, and a gaseous oxygen and / or solid oxygen source is supplied as an oxygen source. In preliminary dephosphorization of hot metal to be dephosphorized by spraying, at least a part of the medium solvent to be added into the container is sprayed onto the bath surface (metal bath surface) using a carrier gas from above the bath surface in the container. The supply rate B (kg / min / hot metal t) of the solvent added to the vessel and sprayed onto the bath surface using the carrier gas is converted into CaO.
on) and the supply rate A (Nm ³ / min / hot metal ton) of the oxygen source supplied into the container in terms of gaseous oxygen is as follows:
The dephosphorization treatment is performed so as to satisfy the formula (1), whereby the amount of the F source in the medium solvent can be sufficiently reduced without using a medium solvent containing an F source such as CaF _2. Even
The efficiency of the dephosphorization reaction can be dramatically increased. 0.3 ≦ A / B ≦ 7 (1)

In order to obtain a higher dephosphorization reaction efficiency, the supply rate B (kg / mi
It is preferable to perform the dephosphorization treatment so that the supply rate A (Nm ³ / min / hot metal ton) of the oxygen source in terms of gaseous oxygen satisfies the following formula (2). 1.2 ≦ A / B ≦ 2.5 (2)

As described above, in order to improve the efficiency of the dephosphorization reaction, the amount of Fe generated in the slag by the supply of oxygen is increased.
It is important to supply CaO (medium solvent) at a supply rate corresponding to the amount of O generated, and if this balance is lost, the dephosphorization rate decreases. That is, the above A / B is 0.
If it is less than 3, the supply amount of CaO is excessive with respect to the supply amount of oxygen, so that the amount of FeO generated in the slag is small,
aO remains in the slag as a solid and does not effectively act on dephosphorization, so that the dephosphorization rate decreases. On the other hand, A / B is 7
If it exceeds, the amount of CaO required for dephosphorization becomes insufficient with respect to the supply amount of oxygen, and in this case also, the dephosphorization rate decreases. At the same time, if the supply rate of oxygen is too high, the amount of inactive oxygen other than the oxygen required for dephosphorization increases, and this is consumed for decarburization, etc. This will lead to a significant increase in operating costs in the decarburization process. Further, by setting the A / B in the range of 1.2 to 2.5, the balance between the amount of FeO produced by the supply of oxygen and the amount of CaO supplied is more optimized, and a particularly high dephosphorization reaction efficiency is obtained. Can be

The effect of optimizing the supply rate ratio between oxygen and the solvent in the present invention largely depends on the method of supplying the solvent. That is, in the present invention, the medium solvent added so as to satisfy the above formula (1), preferably the above formula (2), is a medium solvent sprayed onto the metal bath surface using a carrier gas from above the bath surface in the container. Thus, for the first time, the effect of optimizing the supply rate ratio between oxygen and the solvent can be obtained. This is because, as described above, FeO and phosphor oxide (phosphor oxide generated by the reaction of oxygen with [P] in the metal) mainly generated on the surface of the metal bath are generated by the oxygen added to the furnace. This is because the dephosphorization reaction is effectively promoted by supplying a medium solvent to the bath surface and causing CaO to exist around the phosphor oxide.

In the method of the present invention, a part of the solvent may be added to the container by a method other than the above-mentioned method (for example, over-the-top charging or injection into a bath). Does not contribute significantly to the above-mentioned effects. Therefore, in the method of the present invention, it is most preferable that the entire amount of the solvent to be added to the container is sprayed onto the bath surface from above the bath surface in the container by using a carrier gas, and the amount of the solvent to be added to the container is It is preferable to spray at least about 1/3 of the bath surface from above the bath surface using a carrier gas. As means for spraying a carrier gas from above the bath surface in the container using a carrier gas, an upper blow lance is generally used, and nitrogen, an inert gas, or gaseous oxygen (pure oxygen gas or oxygen-containing gas) is used as the carrier gas. Is used.

In the method of the present invention, the oxygen source supplied into the container may be either gaseous oxygen or solid oxygen source, or both may be used in combination. The gaseous oxygen used may be either a pure oxygen gas or an oxygen-containing gas, and iron oxide or mill scale can be used as a solid oxygen source. In addition, there is no particular limitation on the method of supplying the oxygen source, and in the case of gaseous oxygen, the acid can be supplied by an arbitrary method such as top blowing by a lance, injection into hot metal, or bottom blowing, and In the case of a solid oxygen source, it can be supplied to the hot metal by any method such as injection or overhead charging. When gaseous oxygen is supplied, the dephosphorization treatment is performed by up-blowing with a lance when the dephosphorization treatment is performed using a converter type vessel or a hot metal pot, and when the dephosphorization treatment is performed using a torpedo, the molten metal is not melted by the lance. Injection is common.

However, in order to obtain the effect of the method of the present invention most effectively, gaseous oxygen is used as at least a part of the oxygen source, and this gaseous oxygen is blown onto the metal bath surface from above the bath surface by an upper blowing lance or the like. It is preferable to spray a medium solvent as a CaO source on the metal bath surface area supplied with the gaseous oxygen. This is because the metal bath surface area to which gaseous oxygen is supplied is a place where FeO is generated by the supply of oxygen, and by adding CaO directly to such a bath surface area, slagging of CaO is effectively promoted. At the same time, the contact efficiency between CaO and FeO is increased, which can significantly promote the dephosphorization reaction efficiency. Also, the medium solvent is in the metal bath surface area supplied with gaseous oxygen.
In particular, it is most preferable to supply the gas to a region called "fire point" generated by the upward blowing of gaseous oxygen. This fire point is a metal bath surface area where the temperature becomes the highest when the gaseous oxygen gas jet collides, and is an area where the oxidation reaction by the gaseous oxygen is concentrated and strongly stirred by the gaseous oxygen gas jet. It can be said that this is a region where the effect of supply is most remarkably obtained. In this sense, it is preferable to use gaseous oxygen (pure oxygen gas or oxygen-containing gas) that becomes at least a part of an oxygen source as a carrier gas for spraying the medium solvent onto the bath surface. Oxygen is blown up onto the bath surface together with the medium solvent, and the medium solvent is directly supplied to the flash point, so that the contact efficiency between CaO and FeO on the metal bath surface is maximized, and the dephosphorization reaction is particularly remarkably promoted. be able to.

When the medium solvent is blown onto the metal bath surface using a carrier gas other than gaseous oxygen (for example, an inert gas such as N ₂ or Ar), a part of the top blow lance (acid feed lance) is used. It is preferable to spray through a nozzle hole, so that a solvent can be supplied to the metal bath surface area to which gaseous oxygen is supplied through another nozzle hole of the upper blowing lance. Specifically, a mode in which a medium other than gaseous oxygen is supplied as a carrier gas from the central nozzle hole at the tip of the upper blowing lance as a carrier gas, and gaseous oxygen is supplied from other nozzle holes around the central nozzle hole is preferable. .

Further, in order to further improve the dephosphorization reaction efficiency, it is preferable to agitate the hot metal with gas. This gas stirring is performed by blowing an inert gas such as a nitrogen gas or an argon gas into the hot metal through an injection lance, a bottom blowing nozzle, or the like. The supply amount of such a stirring gas is 0.02 Nm ³ / min / hot metal ton or more in order to obtain sufficient bath stirring properties.
If the stirring of the bath is too strong, the rate of C reduction in the hot metal to the generated FeO becomes too large, so that 0.3 Nm ³
/ Min / hot metal ton or less.

As the container in which the method of the present invention is carried out, a converter type container is most preferable in that a free board can be sufficiently secured, but other than this, it has a function of spraying a solvent onto the bath surface. There is no particular limitation as long as it is a container. For example, any container such as a hot metal pot or torpedo can be used. FIG. 2 shows one embodiment of the method of the present invention using a converter type container, 1 is a converter type container, 2 is an upper blowing lance, 3 is a bottom blowing nozzle provided at the furnace bottom, In this example, a medium solvent is blown from a top blowing lance 2 to the metal bath surface using gaseous oxygen as a carrier gas, and a stirring gas is blown into the hot metal from a bottom blowing nozzle 3.

Further, the effect of the present invention differs depending on the Si concentration in the hot metal before the dephosphorization treatment,
Particularly remarkable dephosphorization efficiency can be obtained when the method of the present invention is performed on hot metal having a concentration of 0.10 mass% or less. If the Si concentration in the hot metal before the dephosphorization treatment is high, the amount of SiO ₂ generated increases, the amount of CaO for adjusting the basicity increases, and the amount of generated slag increases. Therefore, it is desirable to reduce the amount of Si. In general, when the Si concentration in the hot metal before the dephosphorization treatment is high, the amount of SiO ₂ generated increases, and as a result, not only the amount of slag increases, but also the amount of CaO for adjusting the basicity increases. Therefore, from such a viewpoint, it is preferable that the Si concentration in the hot metal before the dephosphorization treatment is low. On the other hand, when the Si concentration in the hot metal before the dephosphorization treatment is low, the SiO _{2 in the} slag is low.
Since the concentration is reduced, the melting property of CaO is further deteriorated, and the dephosphorization reaction efficiency is reduced. Nevertheless, in the case of the method of the present invention, the lower the concentration of Si in the molten iron before the dephosphorization treatment (preferably 0.10 mass% or less), the more significantly the efficiency of the dephosphorization reaction is improved. This is because, in the method of the present invention, the powder of the medium solvent, which is a CaO source, is sprayed on the bath surface, so that the melting of CaO is promoted by FeO even without the presence of SiO ₂ , thereby contributing to the dephosphorization of CaO. It is thought that this is because the efficiency of the operation is improved.

As described above, the method for producing low-phosphorus hot metal of the present invention is particularly effective when applied to hot metal having a Si concentration of 0.10 mass% or less. When the content exceeds 10 mass%, desiliconization treatment (usually performed by adding oxygen such as solid oxygen source or gaseous oxygen to the hot metal) is performed in a blast furnace cast bed or hot metal pot, etc. It is preferable to perform the dephosphorization treatment after setting the Si concentration to 0.10 mass% or less.

In the conventional dephosphorization treatment, CaF₂F source such as
Although it was essential to add it, in recent years F
Considering the effect, even in refining steel, CaF₂F source such as
There is a growing demand to reduce the use of. In this regard,
Myoho is CaF₂Such as CaO that does not contain F source
High dephosphorization efficiency can be obtained only by using a suitable solvent
This is the biggest feature. However, CaF₂Such as F source
It does not exclude the addition, for example,
To further facilitate, CaF ₂Etc. F
Do not hinder the addition of such. However, even in that case,
CaF contained in solvent₂Is less than 1kg / hot metal ton
Preferably, there is. In the method of the present invention, CaF₂
Only the medium solvent mainly containing CaO that does not contain the F source
When used, the medium solvent does not include the F source.
Means that it is not
For example, a small amount of F source may be included as unavoidable impurities.
Does not prevent.

[0025] The dephosphorization reaction is advantageous when the hot metal temperature is low, and can perform an efficient treatment. On the other hand, when the hot metal temperature after the dephosphorization treatment is low, the heat margin in the next step is reduced. Cause problems. In this regard, according to the method of the present invention, a high dephosphorization reaction efficiency can be obtained even when the dephosphorization temperature is relatively high. In this case, the temperature can be increased to 1360 ° C. or higher, and sufficient heat margin in the next step can be secured.

[0026]

EXAMPLES Example 1 Hot metal from a blast furnace was desiliconized in a casting bed and, if necessary, in a hot metal pot, and then desulfurized in a hot metal pot using mechanical stirring. Dephosphorization was performed in a converter type vessel. The hot metal temperature before and after this dephosphorization treatment was set to 1250 to 1350 ° C. As the dephosphorization medium solvent, calcined lime mainly composed of CaO and sieved with a particle size of 200 mesh or less was used. Is S in the hot metal
5 to 15 kg / hot metal ton according to the i concentration.

In this dephosphorization treatment, as shown in FIG. 2, a medium solvent and an oxygen source are supplied (blowing time: 10 minutes) by blowing a medium solvent through a top blowing lance with oxygen as a carrier gas onto the bath surface. However, at this time, the oxygen supply rate A
(Nm ³ / min / hot metal ton) and the supply rate B of the medium solvent
(Kg / min / hot metal ton) The operation was carried out under various conditions having different ratios A / B. No F source such as fluorite was added to the solvent medium. In addition, nitrogen gas as a stirring gas from the bottom blowing nozzle at the bottom of the furnace was supplied at 0.05 to 0.15 N.
The hot metal was blown into the hot metal at a flow rate of m ³ / min / hot metal ton. The Si concentration in the hot metal subjected to the dephosphorization treatment is tr. ~ 0.3
mass%.

The oxygen supply rate A (Nm ³ / min / hot metal ton) and the medium solvent supply rate B (kg / min / hot metal t)
FIG. 1 shows the relationship between the ratio A / B and the P concentration in the hot metal after the dephosphorization treatment. According to this, in the case of A / B in the range of 0.3 to 7 which is the example of the present invention, the P concentration in the hot metal after the dephosphorization treatment is not more than the target [P] concentration of 0.015 mass% or less. In particular, the Si concentration in the hot metal before the dephosphorization treatment is 0.10 ma
In the case of ss% or less, the low P standard [P] ≦ 0.01
0 mass% is stably achieved. Further, those having an A / B in the range of 1.2 to 2.5 have particularly low [P], which indicates that the highest dephosphorization reaction efficiency can be obtained in this region. On the other hand, A / B is 0.3
In all cases, the P concentration in the hot metal after the dephosphorization treatment is 0.015 mass, which is the target [P] concentration.
% Or less.

[Example 2] Hot metal spouted from a blast furnace was desiliconized in a casting bed and, if necessary, in a hot metal pot, and then desulfurized in a hot metal pot using mechanical stirring. Dephosphorization was performed in a furnace type container. The hot metal temperature at the end of the dephosphorization treatment is 1360 ° C. or higher.
A calcined lime mainly composed of aO and sieved with a particle size of 200 mesh or less was used. In this dephosphorization treatment, as shown in FIG. 2, a medium solvent and an oxygen source were supplied (blowing time: 10 minutes) by blowing oxygen as a carrier gas onto the bath surface through a top blowing lance with a medium solvent. At this time, the ratio A / B between the supply rate A of oxygen (Nm ³ / min / hot metal ton) and the supply rate B of the medium solvent (kg / min / hot metal ton).
Were operated under various conditions. No F source such as fluorite was added to the solvent medium.

Further, nitrogen gas as a stirring gas from the bottom blow nozzle at the bottom of the furnace was supplied to the furnace at 0.05 to 0.15 Nm ³ / mi.
The hot metal was blown into the hot metal at a flow rate of n / hot metal ton. Hot metal components and temperatures before and after the dephosphorization treatment of the present invention examples and comparative examples and A /
Table 1 shows the basic unit of B and CaO. According to this, in the example of the present invention, even when the hot metal temperature at the end of the dephosphorization treatment is 1360 ° C. or higher, the [P] after treatment is stable at a low level (0.015 mass% or less), but in the comparative example, When the hot metal temperature at the end of the phosphorus treatment is 1360 ° C. or higher, the [P] after the treatment is 0.03 mass% or more, and it is understood that only a low dephosphorization reaction efficiency can be obtained at the hot metal temperature after the treatment.

[0031]

[Table 1]

[0032]

As described above, according to the method of the present invention, C
dephosphorization of the hot metal with excellent dephosphorization efficiency even when a medium free solvent F source, such as aF ₂ can be performed.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a ratio A / B of a supply rate A of oxygen and a supply rate B of a CaO-based solvent in an example and a phosphorus concentration in hot metal after a dephosphorization treatment.

FIG. 2 is an explanatory view showing an embodiment of the method of the present invention.

[Explanation of symbols]

 1 ... Converter type container, 2 ... Top blowing lance, 3 ... Bottom blowing nozzle

Continuing from the front page (72) Inventor Yoshiteru Kikuchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Atsushi Watanabe 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock Inside the company (72) Eiji Sakurai, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Inventor Shinichi Wakamatsu 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. F term (reference) 4K014 AA03 AB03 AB04 AB16 AC08 AC14 AC16 AC17 AD01 AD23 AD27

Claims (7)

[Claims] 1. A method for producing a low-phosphorus hot metal in which a medium solvent serving as a CaO source is added to a vessel holding hot metal and a gaseous oxygen and / or a solid oxygen source is supplied as an oxygen source to perform a dephosphorization treatment. At least a part of the medium solvent to be added into the container is added to the container by spraying the bath surface with a carrier gas from above the bath surface in the container, and is sprayed on the bath surface with the carrier gas. The supply rate B (kg / min / hot metal ton) of the medium solvent to be supplied is changed to the supply rate A (Nm
⁽³ / min / hot metal ton), wherein the following formula (1) is satisfied. 0.3 ≦ A / B ≦ 7 (1) 2. A supply rate B (kg) of a medium solvent in terms of CaO.
/ Min / hot metal ton) is the following with respect to the supply rate A (Nm ³ / min / hot metal ton) of the oxygen source in terms of gaseous oxygen.
2. The method for producing low-phosphorus molten iron according to claim 1, wherein the formula (2) is satisfied. 1.2 ≦ A / B ≦ 2.5 (2) 3. The method according to claim 1, wherein gas oxygen is sprayed onto the bath surface from above the bath surface in the container, and a medium solvent is sprayed onto the bath surface region to which the gas oxygen has been supplied.
3. The method for producing low-phosphorus hot metal according to item 1. 4. The production of low-phosphorus hot metal according to claim 1, wherein gaseous oxygen serving as at least a part of an oxygen source is used as a carrier gas for spraying a solvent onto the bath surface. Method. 5. The hot metal having a Si concentration of 0.10 mass% or less is subjected to a dephosphorization treatment.
3. The method for producing low-phosphorus hot metal according to item 1. 6. The medium solvent contains substantially no F source or 1 kg of CaF ₂ contained in the medium solvent / hot metal ton.
The method for producing low-phosphorus molten iron according to claim 1, wherein the method is as follows. 7. The hot metal temperature at the end of the dephosphorization treatment is 1360 ° C.
Claims 1, 2, 3, 4, 5
Or the method for producing low-phosphorus molten iron according to 6.