JP2003328021A - Method for manufacturing low-phosphorus molten pig iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high slag-formation acceleration effect with a smelting agent by supplying gaseous oxygen to the bath surface of molten big iron, in a process for manufacturing low-phosphorus molten pig iron through preliminary phosphorus removal treatment for molten pig iron, and to obtain a high efficiency for a dephosphorization reaction, by controlling the generation of a high-temperature field due to an oxidation reaction in an area of the bath surface of the molten pig iron, onto which the gaseous oxygen is supplied. <P>SOLUTION: In the process for manufacturing the low-phosphorus molten pig iron through the phosphorus removal treatment as the preliminary treatment for the molten pig iron, which adds the smelting agent as an oxygen source and a CaO source into a vessel having retained the molten pig iron, this manufacturing method comprises supplying the gaseous oxygen onto the bath surface of the molten pig iron from above the bath surface, supplying a material absorptive for heat of the molten pig iron through a chemical reaction and/or a thermal decomposition reaction, onto the area on the bath surface of the molten pig iron, onto which the gaseous oxygen is supplied, and controlling a temperature rise in the area of the bath surface of the molten pig iron, to which the gaseous oxygen is supplied. <P>COPYRIGHT: (C)2004,JPO

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 hot metal pretreatment.

[0002]

2. Description of the Related Art In order to manufacture a steel product from hot metal produced in a blast furnace, the impurity components contained in the hot metal are reduced to a predetermined concentration, and necessary components are added to adjust the composition to that required for the steel product. is necessary. Impurity components contained in the hot metal include carbon in an amount of 4 mass% or more, as well as phosphorus and sulfur, and required components for steel materials include manganese and silicon which enhance strength and toughness.

In order to remove phosphorus and carbon from the hot metal, a method of reacting the hot metal with slag or adding a large amount of oxygen to proceed the oxidation reaction is adopted. However, a converter is used to simultaneously remove carbon and phosphorus. In contrast to the conventional method of removing, in recent years, a method in which only phosphorus is previously removed in the hot metal stage (preliminary hot metal dephosphorization treatment) and then converter decarburization blowing is becoming popular. By performing such hot metal preliminary dephosphorization treatment, it is possible to reduce the amount of slag that was required for dephosphorization in converter decarburization blowing. It has become possible to increase the reduction rate of manganese from slag at that time and reduce the amount of manganese alloy iron added during or after tapping.

This hot metal preliminary dephosphorization treatment is carried out by using a hot metal ladle, a converter,
In addition to lime, which is the main refining agent, solid oxygen sources such as sintered powder and scale and gaseous oxygen are added as oxidation sources necessary to accelerate the dephosphorization reaction. The hot metal preliminary dephosphorization treatment performed in this manner is advantageous for dephosphorization in that low-temperature treatment is possible because the target of hot metal treatment is hot metal, but recently hot metal pre-dephosphorization treatment is advantageous from the viewpoint of environmental protection measures. It is required to reduce the slag generated by preliminary dephosphorization to the utmost limit.

As a method for efficiently performing dephosphorization with a small amount of slag, the silicon concentration in the hot metal is reduced to
Possible methods include reducing the amount of silicic acid that reacts with CaO to produce calcium silicate, and controlling the iron oxide concentration of slag that regulates the oxygen potential of the dephosphorization reaction. Can be expected to improve.

On the other hand, in order to enhance the efficiency of dephosphorization reaction, it is also important to produce slag quickly and efficiently. From such a viewpoint, the applicant of the present invention has a low phosphorus content which can effectively promote the production of slag. Japanese Patent Application No. 2001-3896 for manufacturing method of hot metal
Proposed as No. 96. In this method, a refining agent (powdered lime, etc.) is added to the inside of the container by spraying it onto the surface of the bath from above the surface of the bath using the carrier gas, and this carrier gas is also used to spray onto the surface of the bath. The supply rate of the refining agent and the supply rate of the oxygen source supplied into the container are regulated within a predetermined range, and in this method, in particular, the use of gaseous oxygen as a carrier gas for spraying the refining agent onto the bath surface. The refining agent (CaO) is generated by the iron oxide generated when gaseous oxygen is supplied to the bath surface.
Can be slagged most quickly and efficiently.

[0007]

In the method of spraying the refining agent with gaseous oxygen as a carrier gas onto the bath surface as described above, a large amount of iron oxide is produced by the gaseous oxygen colliding with the bath surface. This is a very advantageous condition for promoting chemical conversion. However, on the other hand, there is a problem in that a high temperature field is formed in the bath surface region where gaseous oxygen collides, due to the oxidation reaction, and the generation of such a high temperature field is disadvantageous in promoting the dephosphorization reaction.

Therefore, an object of the present invention is to provide a high slag promoting action of the refining agent by supplying gaseous oxygen to the hot metal bath surface in the method for producing low phosphorus hot metal by the hot metal preliminary dephosphorization treatment, and the gaseous oxygen To provide a method for producing low phosphorus hot metal, which can effectively suppress the formation of a high temperature field due to an oxidation reaction in the supplied hot metal bath surface region and thereby obtain high dephosphorization reaction efficiency. is there.

[0009]

[Means for Solving the Problems] Temperature conditions are important for the dephosphorization reaction, and a lower hot metal temperature is more advantageous for dephosphorization.
As mentioned above, the refining agent (Ca
When gaseous oxygen is supplied to the hot metal bath surface in order to rapidly slag (O), the hot metal temperature rises in the hot metal bath surface region to which the gaseous oxygen is supplied, which becomes a factor inhibiting the dephosphorization reaction. From this point of view, the present inventor has investigated a method of making the hot metal bath surface region to which gaseous oxygen is supplied a temperature condition advantageous for the dephosphorization reaction, and as a result, the molten iron to which gaseous oxygen is supplied is investigated. By supplying a substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction to the bath surface area,
It has been found that the increase in the temperature of the hot metal bath surface region to which the gaseous oxygen is supplied is appropriately suppressed and the high dephosphorization reaction efficiency can be obtained without inhibiting the slagging promoting action of the refining agent by the gaseous oxygen.

The present invention has been made based on the above findings, and its features are as follows. [1] In a method for producing low phosphorus hot metal by adding a refining agent that is an oxygen source and a CaO source into a container holding hot metal and performing a dephosphorization process that is a hot metal pretreatment, a bath is formed on the hot metal bath surface. A low phosphorus hot metal characterized by supplying gaseous oxygen from above the surface and supplying a substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction to the hot metal bath surface region to which the gaseous oxygen is supplied. Production method. [2] In the production method of the above-mentioned [1], the production of low phosphorus hot metal characterized in that a substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is supplied to at least the hot spot of the hot metal bath surface. Method.

[3] In the manufacturing method according to the above [1] or [2],
A method for producing low phosphorus hot metal, which comprises supplying a refining agent to a hot metal bath surface region to which gaseous oxygen is supplied. [4] The method for producing low-phosphorus hot metal according to any one of the above-mentioned [1] to [3], wherein the refining agent is supplied to at least the flash point of the hot metal bath surface. [5] In the manufacturing method according to any one of the above [1] to [4], the substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is carbon dioxide, water vapor, nitrogen oxide, or a metal carbonate. A method for producing a low-phosphorus molten pig iron, which is one or more selected from metal hydroxides.

[6] In the production method of the above-mentioned [5], the substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is a metal carbonate that generates CO ₂ or H ₂ O by thermal decomposition, 1. A method for producing low-phosphorus hot metal, which is one or more selected from hydroxides of metals that generate CO ₂ or H ₂ O by thermal decomposition. [7] In the production method of the above-mentioned [6], the substance that absorbs the heat of the hot metal by chemical reaction and / or thermal decomposition reaction is CaCO
_{3. A} method for producing low-phosphorus hot metal, which is one or more selected from the group consisting of ₃ , Ca (OH) ₂ , and CaMg (CO ₃ ) ₂ . [8] In the production method according to any one of the above [1] to [7], the substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is a powder or granular material having an average particle size of 5 mm or less. A method for producing low-phosphorus hot metal, which is characterized.

[9] In the manufacturing method according to any one of the above [1] to [8], while supplying gaseous oxygen to the surface of the hot metal bath using an upper blowing acid lance, supplying oxygen from the upper blowing acid lance A method for producing low phosphorus hot metal, which comprises supplying a substance that absorbs the heat of hot metal by a chemical reaction and / or a thermal decomposition reaction to part or all of the line. [10] The method for producing low phosphorus hot metal according to the above-mentioned [9], wherein the refining agent is supplied to a part or all of the oxygen supply line of the top-blown acid lance. [11] In the manufacturing method according to any one of the above [1] to [10], a refining agent (provided that CaC is added to the container holding the hot metal
When one or more kinds selected from O ₃ , Ca (OH) ₂ and CaMg (CO ₃ ) ₂ are added, this is included. 50 mass% or more of (1) is supplied to the hot metal bath surface region to which gaseous oxygen is supplied, the method for producing low phosphorus hot metal.

[12] A method for producing a low phosphorus hot metal by adding a substance having a refining action to an oxygen source in a container holding hot metal and performing a dephosphorization treatment which is a hot metal pretreatment, Gas oxygen is supplied from above the bath surface to the hot metal bath surface region to which the gas oxygen is supplied, instead of a part or all of the refining agent which is a CaO source, a refining agent-forming substance and / or a chemical reaction or And CaCO ₃ , Ca (OH) ₂ and C as substances that absorb the heat of the hot metal due to the thermal decomposition reaction.
A method for producing low phosphorus hot metal, which comprises supplying at least one selected from aMg (CO ₃ ) ₂ . [13] In the manufacturing method of the above-mentioned [12], CaCO ₃ , Ca
1 selected from (OH) ₂ and CaMg (CO ₃ ) ₂
A method for producing low-phosphorus hot metal, which comprises supplying at least a hot spot of a hot metal bath surface with at least one seed.

[14] In the manufacturing method according to the above [12] or [13], CaCO ₃ , Ca (OH) ₂ , CaMg (CO ₃ )
1. A method for producing low-phosphorus hot metal, characterized in that one or more selected from ₂ is a powdery material having an average particle diameter of 5 mm or less. [15] In the manufacturing method according to any one of the above [12] to [14],
Gaseous oxygen is supplied to the surface of the hot metal bath by using the top-blown acid lance, and CaCO ₃ , Ca (OH) ₂ , CaM is supplied to part or all of the oxygen supply line of the top-blown acid lance.
A method for producing a low phosphorus hot metal, which comprises supplying at least one selected from g (CO ₃ ) ₂ .

[16] In the manufacturing method according to any one of the above [12] to [15], CaC added in a container holding hot metal
50 mass% or more of the total amount of one or more selected from O ₃ , Ca (OH) ₂ and CaMg (CO ₃ ) ₂ is supplied to the hot metal bath surface region to which gaseous oxygen is supplied. Method for manufacturing hot metal phosphorus. [17] In the manufacturing method according to any one of the above [1] to [16], it is preferable that 50% or more (however, the amount converted to gaseous oxygen) of the oxygen source added to the container holding the hot metal is gaseous oxygen. A method for producing low-phosphorus hot metal, which is characterized.

[18] The method for producing low-phosphorus hot metal according to any one of the above-mentioned [1] to [17], characterized in that hot metal having a silicon concentration of 0.2 mass% or less is subjected to dephosphorization treatment. [19] In any of the production method of the above-mentioned [1] to [18], it CaF ₂ weight refining agent is included in either or refining agent does not contain CaF ₂ substantially is less than 2 kg / molten pig iron ton A method for producing low phosphorus hot metal, which comprises: [20] The method for producing low phosphorus hot metal according to any one of the above [1] to [19], wherein the hot metal temperature at the end of the dephosphorization treatment is 1350 ° C. or higher.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing low phosphorus hot metal of the present invention comprises:
When adding a refining agent that is an oxygen source and a CaO source into the container holding the hot metal and performing dephosphorization treatment, the gas oxygen is supplied (sprayed) from above the bath surface to the hot metal bath surface. A substance that absorbs the heat of the hot metal is supplied to the hot metal bath surface region by a chemical reaction and / or a thermal decomposition reaction. As the refining agent, a CaO-based refining agent such as lime (refining agent mainly composed of CaO) is usually used. Therefore, in the following description, the refining agent serving as a CaO source is referred to as a CaO-based refining agent.

The addition (supply) of a substance that absorbs the heat of hot metal by a chemical reaction and / or a thermal decomposition reaction (hereinafter referred to as "endothermic substance") to the hot metal bath surface is advantageous for dephosphorization when the hot metal temperature is low. Therefore, this is done to prevent the hot metal temperature from rising excessively due to the heat generated by the gaseous oxygen supplied to the hot metal bath surface. Need to supply. Further, among the hot metal bath surface regions to which gaseous oxygen is supplied, it is particularly preferable to supply them to a region called a "fire point" which is generated by the acid feeding by the top blowing acid lance. This hot point is the hot metal bath surface area where the temperature becomes the highest due to the collision of the gaseous oxygen gas jet, and the area where the oxidation reaction (FeO production reaction) by gaseous oxygen is concentrated and is strongly stirred by the gaseous oxygen gas jet. Therefore, it can be said that this is the region where the effect of the addition of the endothermic substance is most significantly obtained.

When acid is fed from above the bath surface using the top-blown acid feeding lance, Ca is added to the hot metal bath surface area (particularly preferably the above-mentioned "fire point" area) to which gaseous oxygen is supplied.
The method of spraying (projecting) the O-based refining agent using gaseous oxygen or another carrier gas is a collision field of the gaseous oxygen gas jet with the hot metal bath surface, that is, the oxidation reaction by the gaseous oxygen is concentrated, and the gaseous oxygen gas By directly supplying the CaO-based refining agent to the region where the jet is strongly stirred (the main product of FeO), the CaO slag is effectively promoted and the contact efficiency between CaO and FeO is increased. The optimum conditions for contact between CaO and FeO can be achieved, which can promote the dephosphorization reaction particularly remarkably.
Therefore, in such a method, the endothermic substance is directly supplied to the region where the oxidation reaction by the gaseous oxygen is concentrated and is strongly stirred by the gaseous oxygen gas jet, and by suppressing the increase in the hot metal temperature in the region, The dephosphorization reaction can be more effectively promoted.

Here, the endothermic substance is not particularly limited as long as it is a substance that removes (absorbs) heat from the hot metal by a chemical reaction when added to the hot metal, a thermal decomposition reaction, or both reactions. Therefore, this endothermic substance may be either a gas or a solid. Examples of the gas that can be used as the endothermic substance include carbon dioxide, water vapor, and nitrogen oxide (NOx), and at least one of them can be used. When supplied to the surface of the hot metal bath, these gas endothermic substances mainly react with Fe (for example, C
O ₂ + Fe → FeO + CO, H ₂ O + Fe → FeO + H
₂ ) At that time, the heat of the hot metal is absorbed. As a result, the heat generated by Fe oxidation (Fe + 1 / 2O ₂ → FeO) due to gaseous oxygen becomes a total heat absorption or the amount of heat generation is significantly reduced. Further, among the above gas endothermic substances, carbon dioxide and water vapor which are generated in large quantities in the ironworks are particularly suitable because they are easily available and have a great thermal effect.
Even if the purity is somewhat low due to the inclusion of nitrogen or the like in these gases, there is no particular problem because the dephosphorization process is not the final steelmaking stage (= decarburization process). Further, CO and H ₂ produced by the reduction of the supplied carbon dioxide and water vapor are recovered as a part of the exhaust gas at the time of the dephosphorization treatment, which also has the effect of increasing the exhaust gas calories.

Further, it can be used as an endothermic substance.
As solids, metal carbonates, metal hydroxides, especially preferred
More preferably, alkali metal, alkaline earth metal carbonate, water
Oxides are mentioned, and it is possible to use one or more of these.
Wear. These solid endothermic substances are supplied to the hot metal bath surface.
This mainly causes a thermal decomposition reaction, at which time the hot metal
It absorbs heat and CO_TwoOr H_TwoO
Generate this CO_TwoOr H_TwoO is an endothermic substance as described above
It has a particularly high endothermic effect because it functions as a quality
Be done. Such metal carbonates include CaCO_Three,
CaMg (CO _Three)_Two, MgCO_Three, NaCO_Three, Fe
CO_Three, MnCO_Three, NaHCO_Three(Natricarbonate
) And the like as a metal hydroxide.
(OH) _Two, Mg (OH)_Two, Ba (OH)_Two, Al (OH)
_ThreeFe (OH)_Two, Mn (OH) n, Ni (OH) n, etc.
And one or more of these can be used.

Among these solid endothermic substances, Ca
CO ₃ , Ca (OH) ₂ and CaMg (CO ₃ ) ₂ are not only easily available, but also have a great advantage that CaO is produced by the above thermal decomposition and this CaO functions as a refining agent. preferable. Usually, these solid endothermic substances are added in the form of uncalcined or semi-calcined limestone or dolomite. If the particle size of the solid endothermic substance is too large, thermal decomposition does not proceed rapidly, so the average particle size is 5 m.
It is preferably a powder or granule having a particle size of m or less. In the present invention, the gas endothermic substance and the solid endothermic substance as described above may be used in combination, and the gas endothermic substance is used as a part or all of the carrier gas when the solid endothermic substance is supplied to the hot metal bath surface. Good.

There is no particular limitation on the method of adding the endothermic substance (gas or / and solid), and it is sprayed onto the surface of the hot metal bath with an acid lance or other lance to be blown, and is placed on top (in the case of a solid endothermic substance). It is possible to add the endothermic substance to the hot metal bath surface region (particularly preferably "fire point") to which gaseous oxygen is supplied, as described above. In order to obtain such an effect, it is preferable to supply it to the surface of the hot metal bath with a lance, and especially to supply it to the surface of the hot metal bath with a top-blown acid lance.

When the endothermic substance is supplied to the surface of the hot metal bath by the top blowing acid lance, the endothermic substance is mixed with gaseous oxygen (in the case of a solid endothermic substance, gaseous oxygen is used as a carrier gas) and the same lance hole is used. Method of supplying to the hot metal bath surface,
A method of supplying the endothermic substance and gaseous oxygen into the lance through separate gas supply lines and supplying them to the hot metal bath surface from different lance holes (for solid endothermic substances, the endothermic substance is supplied by a carrier gas other than gaseous oxygen). Are used).

From the viewpoint of surely supplying the endothermic substance to the hot metal bath surface region to which gaseous oxygen is supplied, the above method is more preferable, but the above-mentioned method also allows the endothermic substance supplied through a predetermined lance hole to Can be supplied to the hot metal bath surface region to which gaseous oxygen has been supplied through the lance holes. Specifically, for example, a gas endothermic substance is supplied from a central lance hole at the tip of the upper blown acid lance, or an endothermic substance is supplied by using a gas other than gaseous oxygen as a carrier gas, and another lance hole around the central lance hole is supplied. It is preferable to supply gaseous oxygen from the above. N ₂ or A as carrier gas
An inert gas such as r is suitable, and a gas endothermic substance (for example, CO ₂ ) may be used as a carrier gas as described later.

Further, in the above-mentioned method, among the plurality of lance holes, only some of the lance holes receive gaseous oxygen, and the other lance holes contain an endothermic substance (in some cases, CaO may be further added).
Gaseous oxygen mixed with a system refining agent) can be supplied to the hot metal bath surface. Further, in any of the above methods, a gas oxygen or a carrier gas other than gas oxygen or a gas endothermic substance is mixed with a CaO-based refining agent alone or with an endothermic substance (gas or / and solid) to form a hot metal bath surface. It can also be supplied.

To supply the endothermic substance (gas or / and solid) or the endothermic substance and the CaO refining agent in the state of being mixed with gaseous oxygen to the surface of the hot metal bath through the top blowing acid lance, for example, the top blowing acid lance The endothermic substance may be supplied to part or all of the oxygen supply line (header, piping, gas oxygen flow path in the lance, etc.) and mixed with gas oxygen. Further, the endothermic substance (gas or / and solid) or the endothermic substance and the CaO-based refining agent may be supplied to the surface of the hot metal bath using a supply means other than the top-blown acid lance (for example, another lance). Good.
As the lance other than the top-blown acid lance, any sub-lance or the like that is normally used for sampling or temperature measurement may be used as long as it can supply the powder or granular material to a predetermined position in the furnace like the top-blown acid lance. Can be used if there is no problem with the cooling capacity in the furnace. Further, even a top-up charging device such as a shooter or a pouring device may be used as long as the durability at high temperature and the accuracy of the charging position do not pose any problem.

Further, as described above, the CaO refining agent is sprayed onto the hot metal bath surface region (particularly preferably the above-mentioned "fire point" region) to which gaseous oxygen is supplied by using gaseous oxygen or another carrier gas. By directly projecting (projecting) the endothermic substance into this region, the dephosphorization reaction can be most effectively promoted. In this case, a method in which gaseous oxygen, a CaO-based refining agent, and an endothermic substance (gas or / and solid) are mixed and sprayed onto the surface of the hot metal bath from the lance hole of the top-blown acid lance can be used. Also, for example, among the plurality of lance holes of the top-blown acid lance, only a part of the lance holes is supplied with gaseous oxygen, and the other lance holes are supplied with gaseous oxygen or a gas other than gaseous oxygen (eg It is also possible to supply the CaO-based refining agent and the endothermic substance (gas or / and solid) to the surface of the hot metal bath using nitrogen, an inert gas such as Ar) as a carrier gas. In addition, in this case, the main lance hole at the center of the lance tip,
Using an upper blown acid lance having a plurality of sub-lance holes around it, gaseous oxygen from the sub-lance hole, from the main lance hole,
It is particularly preferable to supply the CaO-based refining agent and the endothermic substance (gas or / and solid) to the hot metal bath surface, respectively, if necessary, using gaseous oxygen or a gas other than the above-mentioned gaseous oxygen as a carrier gas. Also, spraying of gaseous oxygen and CaO
The spraying of the refining agent and the endothermic substance may be carried out using different top blowing lances. However, in any case, as described above, the CaO-based refining agent and the endothermic substance (gas or / and solid) are sprayed onto the hot metal bath surface together with gaseous oxygen in order to most efficiently slag the CaO-based refining agent. Is particularly desirable.

The gaseous oxygen used in the present invention may be either pure oxygen gas or oxygen-containing gas. Further, as the oxygen source added to the hot metal holding container in the present invention, solid oxygen sources such as iron oxide (for example, sintered powder, mill scale) and the like can be used in addition to gaseous oxygen. It can be added by any method such as injection or injection into a bath. However, in order to perform efficient hot metal dephosphorization by supplying (spraying) gaseous oxygen to the hot metal bath surface as described above, 50% or more, preferably 70% or more of the oxygen source added to the hot metal holding container is preferably used. The above (gas oxygen equivalent) is preferably gaseous oxygen. A part of the gaseous oxygen may be supplied into the bath by a method other than spraying onto the surface of the hot metal bath, for example, injection into the hot metal bath or bottom blowing.

The most preferable form of supplying the gaseous oxygen and the CaO-based refining agent is the hot metal to which the gaseous oxygen is supplied when the oxygen is fed from above the bath surface using the above-blown acid feeding lance. The CaO-based refining agent is sprayed (projected) onto the bath surface area (preferably the above-mentioned "fire point area") using gaseous oxygen or another carrier gas, and therefore, it is added to the hot metal holding container. CaO ₃ , refining agent or solid endothermic substance CaCO ₃ , Ca (OH) ₂ , C
When supplying one or more kinds selected from aMg (CO ₃ ) ₂ , 50% of the total amount of these and CaO-based refining agent is supplied.
Supplying mass% or more to the hot metal bath surface area (preferably the above-mentioned "fire point" area) to which the gaseous oxygen is supplied, and particularly preferably using a top blowing acid lance to the hot metal bath surface together with the gaseous oxygen. It is preferable to supply.

As described above, the refining agent is usually
A CaO-based refining agent such as lime (a refining agent mainly containing CaO) is used. Further, powder is used as the refining agent to be sprayed onto the surface of the hot metal bath through the top blowing lance. Further, the CaO-based refining agent may be partially added by top-up charging, injection into the bath, etc., in addition to spraying onto the hot metal bath surface by top blowing acid lance. The amount of refining agent added by the method is 20 mass% of the total refining agent
The following is desirable. When the proportion of CaO-based refining agent added by a method other than spraying onto the hot metal bath surface by top-blown acid lance exceeds 20 mass%, the CaO-based refining agent is degassed by blowing it onto the hot metal bath surface together with gaseous oxygen. The effect of promoting the phosphorus reaction tends to decrease.

FIGS. 1 (a) to 1 (e) show some examples of supply forms of gaseous oxygen, a CaO-based refining agent and an endothermic substance to the hot metal bath surface by using the top blowing acid lance. Of these, FIG. 1 (a) is a mode in which gaseous oxygen, a CaO-based refining agent, and an endothermic substance (gas or / and solid) are mixed and supplied from a lance hole (sprayed on the hot metal bath surface), FIG. 1 (b). Is gas oxygen and CaO refining agent from some lance holes, and gas oxygen and endothermic substance (gas or / and solid) from other lance holes.
Are supplied (sprayed onto the hot metal bath surface),
In FIG. 1 (c), a carrier gas other than gaseous oxygen and a CaO-based refining agent are supplied from some lance holes, and gaseous oxygen and an endothermic substance (gas or / and solid) are supplied from other lance holes (hot metal). Fig. 1 (d) shows a gas endothermic substance and CaO refining agent from some lance holes and gaseous oxygen and endothermic substance (gas or / and solid) from other lance holes.
Are supplied (sprayed onto the hot metal bath surface),
In FIG. 1 (e), gaseous oxygen and a CaO refining agent are supplied from some lance holes, and a gas endothermic substance or a gas endothermic substance and a solid endothermic substance are supplied from other lance holes (spraying on the hot metal bath surface). It is a form. However, the supply form of the gaseous oxygen, the CaO-based refining agent, and the endothermic substance to the hot metal bath surface is not limited to these.

As mentioned above, among the solid endothermic substances, C
aCO ₃ , Ca (OH) ₂ and CaMg (CO ₃ ) ₂ generate CaO by thermal decomposition, and this CaO functions as a refining agent. Therefore, in the present invention, CaO-based refining agent (mainly quick lime) It is also possible to supply the above solid endothermic substance in place of part or all of it and perform the dephosphorization treatment using CaO generated from this substance as a substantial refining agent. That is, in this case, instead of a part or all of the CaO-based refining agent, heat of the hot metal is generated by the refining agent-forming substance and by a chemical reaction and / or a thermal decomposition reaction in the hot metal bath surface region to which gaseous oxygen is supplied. As a substance that absorbs heat, CaCO ₃ , Ca (O
H) ₂ and one or more selected from CaMg (CO ₃ ) ₂ (hereinafter referred to as “refining agent forming / endothermic substance”).

According to this method, the refining agent generating / endothermic substance supplied to the surface of the hot metal bath is thermally decomposed to endotherm the hot metal, and the thermal decomposition causes CaO and the endothermic substance to be the refining agent. CO ₂ or H ₂ O is formed, and the advantage that CO ₂ or H ₂ O reacts with Fe to further absorb the heat of the hot metal is obtained, and CaO is added to the hot metal bath surface region to which gaseous oxygen is supplied. The same effects as when both the refining agent and the endothermic substance are supplied are obtained, and as a result, high dephosphorization reaction efficiency can be obtained.

In this case as well, for the same reason as described above, the refining agent-producing / endothermic substance has a "fire point" which is generated particularly by the oxygen transfer by the upward blowing acid lance in the hot metal bath surface region to which gaseous oxygen is supplied. It is preferred to supply the area referred to as "". The refining agent generating / endothermic substance is usually added in the form of uncalcined or semi-calcined limestone or dolomite.
The refining agent-producing / endothermic substance is preferably a powder or granule having an average particle size of 5 mm or less because thermal decomposition or the like does not proceed rapidly if the particle size is too large. Further, the refining agent generating / endothermic substance may be used in combination with the gas endothermic substance as described above, and a part or all of the carrier gas at the time of supplying the refining agent forming / endothermic substance to the hot metal bath surface. Alternatively, a gas endothermic substance may be used.

There are no particular restrictions on the method for producing the refining agent and adding the endothermic substance, such as spraying on the surface of the hot metal bath with an acid blowing lance or other lance, and placing charging (charging using a shooter etc.) etc. Can be added with
In order to reliably supply the endothermic substance to the hot metal bath surface region (particularly preferably the "fire point") to which gaseous oxygen is supplied, and to obtain the above-mentioned effect, the endothermic substance should be supplied to the hot metal bath surface by a lance. In particular, it is preferable to supply to the hot metal bath surface by top-blown acid lance.

Further, when the refining agent forming / endothermic substance is supplied to the surface of the hot metal bath by top blowing acid lance, refining agent forming /
A method of mixing an endothermic substance with gaseous oxygen (using gaseous oxygen as a carrier gas) and supplying it to the surface of the hot metal bath from the same lance hole, refining agent generation and supplying the endothermic substance and gaseous oxygen into the lance through separate gas supply lines. And supplying them to the hot metal bath surface through separate lance holes (a carrier gas other than gaseous oxygen is used for refining agent generation and supply of the endothermic substance).

The above method is more preferable from the viewpoint of surely supplying the refining agent generating / endothermic substance to the hot metal bath surface region to which the gaseous oxygen is supplied, but the refining supplied through a predetermined lance hole is also preferable in the above method. Agent generation and endothermic substances,
It can be supplied to the hot metal bath surface region to which gaseous oxygen is supplied through another lance hole. Specifically, for example, a refining agent generating / endothermic substance is supplied from the central lance hole at the tip of the upper blowing acid lance as a carrier gas using a gas other than gaseous oxygen,
A form in which gaseous oxygen is supplied from another lance hole around the central lance hole is preferable. An inert gas such as N ₂ or Ar is suitable as the carrier gas, and a gas endothermic substance (for example, CO ₂ ) may be used as the carrier gas as described later. Further, in the above method, among the plurality of lance holes, only gaseous oxygen is supplied from some of the lance holes, and gaseous oxygen mixed with the refining agent generating / endothermic substance is supplied from the other lance holes, respectively. Can also be supplied to.

To supply the refining agent-producing / endothermic substance in the state of being mixed with gaseous oxygen to the surface of the hot metal bath through the top-blown acid lance, for example, the oxygen-blown line (header, pipe, lance) of the top-blown acid lance is used. It is sufficient to supply the refining agent-producing / endothermic substance to a part or all of the gas oxygen flow path of (1) and mix with the gas oxygen. Further, the refining agent producing / endothermic substance may be supplied to the hot metal bath surface by using a supply means other than the top-blown acid lance (for example, another lance). As the lance other than the top-blown acid lance, any sub-lance or the like that is normally used for sampling or temperature measurement may be used as long as it can supply the powder or granular material to a predetermined position in the furnace like the top-blown acid lance. Can be used if there is no problem with the cooling capacity in the furnace. Further, even a top-up charging device such as a shooter or a pouring device may be used as long as the durability at high temperature and the accuracy of the charging position do not pose any problem.

The gaseous oxygen used may be either pure oxygen gas or oxygen-containing gas. In addition to gaseous oxygen, solid oxygen sources such as iron oxide (for example, sintered powder, mill scale) can be used as the oxygen source added to the hot metal holding container. It can be added by any method such as injection. However, supply (spraying) of gaseous oxygen to the surface of the hot metal bath as described above
In order to carry out the efficient hot metal dephosphorization by means of 50% or more, preferably 70% or more of the oxygen source added to the hot metal holding container.
The above (gas oxygen equivalent) is preferably gaseous oxygen. A part of the gaseous oxygen may be supplied into the bath by a method other than spraying onto the surface of the hot metal bath, for example, injection into the hot metal bath or bottom blowing.

For the same reason as described above, CaCO ₃ , Ca (OH) ₂ and C added in the hot metal holding container are used.
50 mass% or more of the total amount of at least one selected from aMg (CO ₃ ) ₂ is supplied to the hot metal bath surface region (preferably, the above-mentioned “fire point” region) to which gaseous oxygen is supplied. Particularly preferably, it is preferable to supply it to the surface of the hot metal bath together with gaseous oxygen by using a top-blown acid lance.

In the various forms of dephosphorization treatment of the present invention as described above, it is preferable to stir the hot metal with gas in order to further improve the dephosphorization reaction efficiency. The gas agitation is performed by blowing an inert gas such as nitrogen or Ar into the hot metal through an injection lance, a bottom blowing nozzle, or the like. The amount of the stirring gas supplied is 0.02 Nm ³ / in order to obtain sufficient bath stirring property.
min / hot metal ton or more, and if the stirring of the bath is too strong, the rate at which C in the hot metal is reduced is too high, so 0.3 Nm ³ / min / hot metal t
It is preferably on or less. As the container in which the method of the present invention is carried out, a converter type container is most preferable from the viewpoint that a freeboard can be sufficiently secured, but for example, any container such as a hot metal ladle and a torpedo can be used.

Dephosphorization of hot metal is basically carried out by oxidizing phosphorus in the molten metal and fixing the acidic oxide produced thereby with a basic refining agent (CaO refining agent).
In order to efficiently cause such a dephosphorization reaction, it is necessary to maintain the high oxygen potential of the slag by the supplied oxygen source (gaseous oxygen, solid oxygen source) and stabilize the generated phosphoric acid. It is preferable to generate a slag having a high basicity (= a slag having a high dephosphorization ability). Especially for the latter, it will be controlled by the input amount of CaO-based refining agent, but it is possible to secure high basicity with a CaO-based refining agent that produces less silicic acid.
Also, the amount of slag generated can be reduced. here,
In order to reduce the amount of silicic acid produced, it is necessary to reduce the silicon concentration in the hot metal to be dephosphorized. Specifically, the silicon concentration of the hot metal to be dephosphorized is 0.2 mass%
Hereafter, it is preferably 0.1 mass% or less.

The hot metal is supplied from hot metal production equipment such as a blast furnace. As a method for lowering the silicon concentration of the hot metal produced, the total amount of silicic acid content can be reduced by pretreatment of the raw material for hot metal production. It is effective to use low temperature operation or uneven distribution of coke to suppress silicic acid reduction reaction in a furnace such as a blast furnace. Therefore, when the silicon concentration of the hot metal produced in a blast furnace or the like is 0.2 mass% or less, preferably 0.1 mass% or less, dephosphorization is performed on these hot metal without performing the following desiliconization treatment. May be processed.

On the other hand, when the silicon concentration of the hot metal produced in the blast furnace or the like is higher than the above silicon concentration level, desiliconization treatment is carried out in a blast furnace cast bed or a hot metal ladle before the dephosphorization treatment, and the dephosphorization treatment is carried out. It is preferable to perform the dephosphorization treatment after setting the Si concentration in the hot metal to 0.2 mass% or less, preferably 0.1 mass% or less. Usually, desiliconization of hot metal is performed by adding a solid oxygen source or gaseous oxygen to the hot metal.For example, a solid oxygen source such as sintered powder or mill scale is placed on the hot metal bath surface or in the bath. Or by adding gaseous oxygen to the surface of the hot metal bath or by blowing into the bath.

Further, the desiliconization treatment of the hot metal can be carried out by adding an oxygen source to the hot metal flow from the blast furnace cast bed to the carrier container such as the hot metal pan, in addition to the blast furnace cast bed and the hot metal pan. In addition, in order to improve the desiliconization efficiency, stirring gas is blown into the hot metal in the container, and CaO source such as calcined lime is added to adjust the basicity of the slag to reduce the iron oxide in the desiliconized slag as much as possible. It is also possible to increase the reduction efficiency. When performing dephosphorization treatment after hot metal desiliconization treatment, it is necessary to remove slag such as desiliconized slag in advance to suppress the silicic acid content as much as possible for efficient dephosphorization treatment. preferable. For this reason, before the dephosphorization treatment, the slag is separated from the hot metal by a mechanical slag device or manually, and then the dephosphorization treatment is performed.

In the conventional dephosphorization treatment, slag of CaO refining agent is used.
CaF to promote oxidization_TwoAdd (fluorite)
Was actually essential, but in recent years the impact of F on the environment
Considering the sound, CaF is also used in the refining of steel._TwoSuppress the use of
Are being requested. In this respect, the method of the present invention uses CaF
_TwoVirtually no (i.e. unavoidable in refining agents)
Other than those contained as mechanical impurities_TwoIs not added)
Or a small amount of CaF _TwoHigh dephosphorization efficiency simply by adding
Is obtained. Therefore, to promote the slag formation of CaO
To CaF_TwoEven when adding, the addition amount is 2 kg /
Hot metal ton or less, preferably 1 kg / hot metal ton or less
It is desirable to do.

The dephosphorization reaction is advantageous when the hot metal temperature is low, and efficient treatment can be carried out. On the other hand, when the hot metal temperature after the dephosphorization treatment is low, the heat margin in the next step is increased. Cause problems. In this respect, according to the method of the present invention, a high dephosphorization reaction efficiency can be obtained even when the dephosphorization treatment temperature is high. Therefore, the hot metal temperature at the end of the dephosphorization treatment can be controlled while maintaining a low and stable phosphorus concentration after the treatment. It is possible to raise the temperature to 1350 ° C. or higher, which is difficult to achieve, and it is also possible to raise the temperature to 1400 ° C. or higher, which makes it possible to secure a sufficient heat margin in the next step.

[0050]

[Example] [Example 1] Hot metal (150 tons) having a silicon concentration of 0.22 to 0.35 mass% discharged from a blast furnace was subjected to desiliconization treatment in a casting bed, and then the hot metal was received in a hot metal ladle. It was desiliconized in a hot metal ladle and then dephosphorized using a converter. In the desiliconization treatment in the cast bed, sintered ore powder was placed on top and added to react with the hot metal. Moreover, in the desiliconization treatment in the hot metal ladle, 0.02 Nm ³ / min / min was introduced into the hot metal from the immersion lance.
While stirring the hot metal by blowing the stirring gas of hot metal ton,
From top blown acid lance 0.2 Nm ³ / min / hot metal to
Desiliconization was performed by blowing n gaseous oxygen. The silicon concentration of the hot metal after the desiliconization treatment was 0.05 to 0.20 mass%.
After the completion of the desiliconization treatment, the molten iron was charged into a 300-ton converter used for dephosphorization treatment after discharging the slag.

In the dephosphorization treatment, about 0.
While stirring the hot metal by blowing a stirring gas (nitrogen) of 1 Nm ³ / min / hot metal ton, oxygen gas and lime powder (CaO refining agent), and a part of Except for the comparative example, a gas endothermic substance was supplied to the hot metal bath surface. It should be noted that fluorspar (C
aF ₂ ) was not added.

The upper blown acid lance used had one center hole and three peripheral holes as lance holes. The lime powder used is crushed and adjusted to have a particle size of 3 mm or less. Oxygen gas is cut out from the cutting device as a carrier gas, and the lime powder is conveyed in a pipe and supplied to an upper blown acid feeding lance, together with the oxygen gas from the central hole. It was supplied to the hot metal bath surface. On the other hand, oxygen gas was supplied to the top-blown acid lance through another piping line so that it was supplied to the hot metal bath surface from the peripheral holes. The total acid transfer rate is 1.5 Nm ³ / min /
It was hot metal ton.

A gas endothermic substance was added to each of the above oxygen gas lines so as to have a predetermined concentration. Carbon dioxide and water vapor were used as the gas endothermic substance, and the mixing ratio with respect to oxygen gas was 10 to 40% by volume (external number with respect to 100 oxygen gas). The hot metal temperature before and after the dephosphorization treatment is before the dephosphorization treatment is started: 1283 to 1305 ° C, and after the dephosphorization treatment is completed:
It was 1310-1327 degreeC.

Table 1 shows the hot metal components (silicon concentration before dephosphorization treatment, phosphorus concentration before and after dephosphorization treatment), addition conditions of the endothermic substance, amount of refining agent (lime) used, dephosphorization time and the like. As shown in the table, by supplying an endothermic substance (carbon dioxide, water vapor) to the hot metal bath surface region to which oxygen gas has been supplied, it can be seen that low phosphorus hot metal can be produced in a short time even with a small amount of refining agent used. . In addition, No. 11 and No. No. 12 is an example in which the Si concentration in the hot metal before the dephosphorization treatment is high. In these examples, the treatment time is long and the phosphorus concentration in the hot metal after the treatment is high, but an endothermic substance was added. The effect of is obtained. However, from this result, S in hot metal before dephosphorization treatment
It is understood that the i concentration is preferably 0.2 mass% or less.

[0055]

[Table 1]

Example 2 Hot metal (150 tons) with a silicon concentration of 0.20 to 0.33 mass% tapped from a blast furnace was received in a ladle and desiliconized in the ladle. While stirring the hot metal by blowing a stirring gas of 0.02 Nm ³ / min / hot metal ton into the hot metal from the immersion lance, 0.2 Nm ³ / min / hot metal ton of gaseous oxygen is blown from the top blowing acid lance to remove silicon. I went. The silicon concentration of the hot metal after the desiliconization treatment was 0.06 to 0.16 mass%. After the desiliconization treatment was completed, the slag was discharged, and then dephosphorization treatment was performed in the ladle.

In this dephosphorization treatment, nitrogen gas of ³ Nm ³ per minute was blown into the hot metal from one immersion lance to stir the hot metal, and oxygen gas and lime powder ( A CaO-based refining agent) and an endothermic substance were supplied in the following forms. In addition, fluorite (CaF ₂ ), which is expected to have an effect of promoting slag formation of lime, was not added. Example of the present invention: oxygen gas, lime powder,
Supply CO ₂ . Example of the present invention: oxygen gas, lime powder,
Supply CaCO ₃ (limestone) or Ca (OH) ₂ (slaked lime). Example of the present invention: oxygen gas, lime powder,
Supplying CO ₂ and CaCO ₃ (limestone). Inventive Example: Oxygen gas, CaCO 2 by top blowing acid lance
Supply ₃ (limestone) or Ca (OH) ₂ (slaked lime). Comparative Example: Oxygen gas and lime powder are supplied by top-blown acid lance.

Lime powder, CaCO ₃ (limestone), Ca (O
H) ₂ is pulverized and adjusted to have a particle size of 1 mm or less,
Oxygen gas is cut out from the cutting device as a carrier gas to be transported in the pipe, and is combined with oxygen gas supplied through another pipe at the top blowing acid lance inlet, and the three lances at the tip of the top blowing acid lance are connected. Oxygen gas was jetted from the holes to the bath surface. The total amount of acid fed was 6000 Nm ³ / h. Regarding CO ₂ , the mixing ratio with respect to oxygen gas was set to 25% by volume (external number with respect to 100 oxygen gas). Also, lime powder, CaCO ₃ (limestone), and Ca (OH) ₂ are 70 to 80 per minute in terms of CaO.
It was added so that it might become kg. The hot metal temperature before and after the dephosphorization treatment is
1280 to 1310 ° C before dephosphorization treatment, 13 after dephosphorization treatment
It was 05-1325 degreeC.

Table 2 shows the hot metal components (silicon concentration before dephosphorization treatment, phosphorus concentration before and after dephosphorization treatment), addition conditions of the endothermic substance, amount of refining agent (lime) used, dephosphorization time and the like. As shown in the table, by supplying an endothermic substance (carbon dioxide, CaCO ₃ , Ca (OH) ₂ ) to the hot metal bath surface area to which oxygen gas is supplied, even if a small amount of refining agent is used, it can be reduced in a short time. It turns out that phosphorus hot metal can be produced.

[0060]

[Table 2]

[Example 3] Using the same process as in Example 2, the effect of adding an endothermic substance was examined when the hot metal temperature after dephosphorization treatment in a ladle was raised. The dephosphorization conditions in the ladle were the same as those in Example 2 with respect to the conditions for stirring the hot metal by the immersion lance, the conditions for supplying oxygen gas and the lime powder (CaO-based refining agent) by the top blowing acid lance. In the example of the present invention, CaCO ₃ (limestone) is used as an endothermic substance at 2 kg / molton ton
On the other hand, in the comparative example, no endothermic substance was added.
Further, in some of the examples, 1 kg / hot metal ton of fluorite (CaF ₂ ) was added as a part of the refining agent.

Table 3 shows the hot metal components (silicon concentration before dephosphorization treatment, phosphorus concentration before and after dephosphorization treatment), addition conditions of the endothermic substance, amount of refining agent (lime) used, dephosphorization time and the like. As shown in the table, it can be seen that, in the present invention example, low phosphorus hot metal can be produced in a short time even if the hot metal temperature after completion of dephosphorization is high. The ability to supply hot metal with a higher hot metal temperature to the next process in this way increases the heat margin in the next process and expands the degree of freedom in the use of iron ore and manganese ore, as well as iron such as scrap. It is also possible to increase the amount of source used, which is effective in improving yield and environmental measures.

[0063]

[Table 3]

[0064]

As described above, according to the method for producing low phosphorus hot metal of the present invention, by supplying gaseous oxygen to the hot metal bath surface, a high slag formation promoting action of the refining agent is obtained, and gaseous oxygen is supplied. It is possible to effectively suppress the formation of a high temperature field due to the oxidation reaction in the hot metal bath surface region, and thereby to obtain a high dephosphorization reaction efficiency. Therefore, low phosphorus hot metal can be produced in a short time with a small amount of refining agent used, the efficiency of refining treatment can be improved, the production cost of low phosphorus hot metal can be reduced, and the amount of generated slag can be reduced. Also,
The amount of CaF ₂ added is significantly reduced compared to the conventional method, or C
Efficient treatment can be performed without adding aF ₂ .

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

Continued front page    (72) Inventor Tsuyoshi Murai             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4K014 AA03 AB06 AB11 AB12 AC11

Claims (20)

[Claims] 1. An oxygen source and CaO are contained in a container holding hot metal.
In the method of producing low phosphorus hot metal by adding a refining agent as a source and performing a dephosphorization process which is a hot metal pretreatment, while supplying gaseous oxygen from above the hot metal bath surface to the hot metal bath surface,
Chemical reaction or / or chemical reaction in the hot metal bath surface region to which the gaseous oxygen is supplied
And a method for producing low phosphorus hot metal, which comprises supplying a substance that absorbs heat of hot metal by a thermal decomposition reaction. 2. The method for producing low phosphorus hot metal according to claim 1, wherein a substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is supplied to at least the hot spot of the hot metal bath surface. . 3. The method for producing low phosphorus hot metal according to claim 1, wherein the refining agent is supplied to the hot metal bath surface region to which gaseous oxygen is supplied. 4. The method for producing low phosphorus hot metal according to claim 1, 2 or 3, wherein the refining agent is supplied to at least the hot spot of the hot metal bath surface. 5. The substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is one or more selected from carbon dioxide, water vapor, nitrogen oxides, metal carbonates, and metal hydroxides. The method for producing low-phosphorus hot metal according to claim 1, 2, 3, or 4. 6. A chemical reaction and / or a thermal decomposition reaction
A substance that absorbs the heat of hot metal causes CO_TwoOr H
_TwoCarbonate of metal that generates O, CO by thermal decomposition _TwoOr
H_TwoOne selected from hydroxides of metals that generate O
The low phosphorus hot metal according to claim 5, characterized in that
Manufacturing method. 7. A substance which absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is CaCO ₃ , Ca (O).
7. The method for producing low phosphorus hot metal according to claim 6, wherein the method is one or more selected from H) ₂ and CaMg (CO ₃ ) ₂ . 8. The substance which absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is a granular material having an average particle diameter of 5 mm or less. , 6
Or the method for producing low phosphorus hot metal according to item 7. 9. Gaseous oxygen is supplied to the surface of the hot metal bath by using the top-blown acid lance, and a part of or all of the oxygen supply line of the top-blown acid lance is subjected to a chemical reaction and / or a thermal decomposition reaction. A substance that absorbs the heat of the hot metal is supplied, which is characterized in that:
The method for producing low-phosphorus hot metal according to 1. 10. The method for producing low phosphorus hot metal according to claim 9, wherein the refining agent is supplied to a part or all of the oxygen supply line of the top-blown acid lance. 11. A refining agent (provided that CaCO ₃ , Ca (OH) ₂ and CaMg are added in a container holding hot metal.
When one or more selected from (CO ₃ ) ₂ is added, it is included. 50 mass% or more of (1) is supplied to the hot metal bath surface region to which gaseous oxygen is supplied, the low phosphorus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. Method of manufacturing hot metal. 12. A method for producing a low phosphorus hot metal by adding a substance having a refining action to an oxygen source in a container holding hot metal and performing a dephosphorization treatment which is a hot metal pretreatment, wherein a hot metal bath surface is formed. While supplying gaseous oxygen from above the bath surface,
In the hot metal bath surface area to which the gaseous oxygen is supplied, instead of a part or all of the refining agent which is a CaO source, a refining agent-forming substance and a substance that absorbs heat of hot metal by a chemical reaction and / or a thermal decomposition reaction As, CaCO ₃ , Ca (OH) ₂ , CaM
A method for producing a low phosphorus hot metal, which comprises supplying at least one selected from g (CO ₃ ) ₂ . 13. CaCO ₃ , Ca (OH) ₂ , CaM
_2. One or more kinds selected from g (CO ₃ ) ₂ is supplied to at least the fire point of the hot metal bath surface.
2. The method for producing low phosphorus hot metal according to item 2. 14. CaCO ₃ , Ca (OH) ₂ , CaM
13. One or more selected from g (CO ₃ ) ₂ is a powdery material having an average particle diameter of 5 mm or less.
Or the method for producing low phosphorus hot metal according to item 13. 15. Gaseous oxygen is supplied to the surface of the hot metal bath by using an upper blowing acid lance, and CaCO ₃ , Ca is supplied to a part or all of the oxygen supplying line of the upper blowing acid lance.
1 selected from (OH) ₂ and CaMg (CO ₃ ) ₂
15. The method for producing low phosphorus hot metal according to claim 12, 13 or 14, characterized in that at least one kind is supplied. 16. C added to a container holding hot metal
aCO_Three, Ca (OH) _Two, CaMg (CO_Three)_Twoin
50 mass% or more of the total amount of one or more selected from
It is characterized in that oxygen is supplied to the hot metal bath surface area.
The low phosphorus hot metal according to claim 12, 13, 14 or 15.
Manufacturing method. 17. The method according to claim 1, wherein 50% or more of the oxygen source added to the container holding the hot metal (however, in terms of gaseous oxygen) is gaseous oxygen. ,
6, 7, 8, 9, 10, 11, 12, 13, 14, 15
Or the method for producing low phosphorus hot metal according to item 16. 18. The dephosphorization treatment is applied to the hot metal having a silicon concentration of 0.2 mass% or less.
4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1
4. The method for producing low phosphorus hot metal according to 4, 15, 16 or 17. 19. The refining agent is substantially free of CaF ₂ or the amount of CaF ₂ contained in the refining agent is 2 kg / mol ton or less.
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1
3. The method for producing low phosphorus hot metal according to 3, 14, 15, 16, 17 or 18. 20. The hot metal temperature at the end of the dephosphorization treatment is 1350.
C. or higher, claim 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15. The method for producing low phosphorus hot metal according to 15, 16, 17, 18 or 19.