JP2009030102A - Phosphorous removal material and method for producing the same - Google Patents

Abstract

[PROBLEMS] To provide a dephosphorizing iron-making material useful for steel production using reduced slag and to provide a method for producing the dephosphorizing iron-making material.
SOLUTION: Reducing slag 1 generated during refining and refining is taken out, desulfurization step 200 is performed by bringing moisture into contact with the reduced slag 1 to desulfurize to obtain desulfurized reduced slag, and in mixing step 250, desulfurized reduced slag and FeO component are mixed. In the molding step 300, the mixture is molded into a predetermined shape to form a molded product. In the solidification step 400, the molded product is solidified with carbon dioxide to form a slag material 2 made of a CO ₂ solidified body. Used as a slag material for initial phosphorus removal during secondary refining.
[Selection] Figure 1

Description

  The present invention relates to treatment of reduced slag, and relates to a dephosphorized slagging material using reduced slag and a method of manufacturing the dephosphorized slagging material.

  When refining pig iron, scrap, etc. and manufacturing steel by electric furnace steelmaking, a large amount of oxidized slag and reduced slag are generated as by-products. Oxidation slag is generated during oxidation refining, in which oxygen is added to react with carbon in steel to remove unnecessary components. And after oxidation refining, reduction | restoration slag generate | occur | produces at the time of reductive refining which discharges oxidation slag, adds a reducing material, quick lime, etc., and removes oxygen in molten steel. The reduced slag is mainly composed of a CaO component, has expandability, is finely powdered, has high alkalinity (pH 11 to 12), and has an S component.

  Conventionally, oxidized slag has been crushed to an appropriate size and used as a roadbed material. On the other hand, since the reduced slag contains a large amount of CaO component, when used as a roadbed material, there is a possibility that the volume of the road surface expands over time and the road surface swells several years later. Etc. could not be used.

  Therefore, as a method for treating the reduced slag, a method of using the reduced slag as a roadbed material after being subjected to an aging treatment in which the reduced slag is volume-expanded in the presence of water for several months is known (for example, Patent Document 1).

Further, it is known to use, as a stone material for submergence, a stone material obtained by solidifying and agglomerating CaCO ₃ produced by a carbonation reaction as a binder using slag generated in a steel production process as a raw material (for example, Patent Document 2). reference).
Japanese Patent Publication No. 3-21682 JP-A-11-71160

  However, when reducing slag is mixed with oxidized slag as described in Patent Document 1, there is a limit to the mixing ratio of roadbed materials, and there is a problem that not all reduced slag can be used as roadbed materials. It was. Moreover, when performing the process which aged and expand | swells reduced slag, a vast land is required in order to retain reduced slag in one place for several months, but it is difficult to secure a vast land.

  Further, as described in Patent Document 2, even if the reduced slag is used as a stone for subsidence, it is impossible to treat all the generated reduced slag only by its use. At present, the total amount of reducing slag generated in the steelmaking process is not effectively utilized. There is a demand for effective use of reduced slag.

  Since the reduced slag contains a large amount of CaO component, for example, as a method for treating reduced slag, it can be reused as a slagging material in the reduction and refining process of an electric furnace. However, since reduced slag has a high S component content, it is necessary to increase the amount of lime to be added at the same time, resulting in an increase in manufacturing cost. Further, even if the reduced slag is used as a slag material, the reduced slag is in a fine powder form and easily generates dust, so that there is a problem that it is difficult to handle when transporting or charging. Therefore, the reduced slag could not be used as a slag material.

  The present invention has been made in view of the above problems, and the problem to be solved by the present invention is to effectively utilize reduced slag, and for that purpose, a dephosphorization structure useful for steel production using reduced slag. It is to provide a brazing material and to provide a method for producing the dephosphorizing faux-making material.

The dephosphorizing iron-making material according to the present invention is a iron-making material used for dephosphorization of steel refining, and an FeO component is added to desulfurized and reduced slag dehydrated by bringing moisture into contact with the reduced slag, and solidified by carbon dioxide. is CO ₂ consists solidified body was, and the S component 0.5 mass%, FeO component is summarized in that at 30 wt% or less than 10 wt%.

The dephosphorizing material is preferably a scale in which the FeO component is generated in the steel processing step, the CO ₂ solidified body has a compressive strength of 5 MPa or more, and a melting point of 1350 ° C. or less. .

The method for producing a dephosphorizing iron-making material according to the present invention is a method for producing a dephosphorizing iron-making material using reduced slag, wherein the reduced slag is desulfurized by bringing moisture into contact with the reduced slag, and desulfurized. The gist is that a FeO component is added to the reduced slag to obtain a molded product formed into a predetermined shape, and the molded product is solidified with a gas containing carbon dioxide to obtain a slag-forming material comprising a CO ₂ solidified product.

  In the above method for producing a dephosphorizing ironmaking material, it is preferable to desulfurize the reduced slag by bringing water vapor into contact therewith.

The dephosphorizing iron-making material according to the present invention comprises a CO ₂ solidified body obtained by adding a FeO component to desulfurized and reduced slag that has been desulfurized by bringing moisture into contact with the reduced slag, and having an S component of 0.5. By adopting a configuration in which the FeO component is 10% by mass to 30% by mass and less, it can be used as a dephosphorizing iron-making material for steel refining, and reduced slag can be used effectively. is there.

Conventionally, in steelmaking, in the dephosphorization process in secondary refining after leaving the electric furnace, CaO, oxide scale (FeO), and the like have been separately charged as the ironmaking material. However, when these materials are charged separately, the melting point of each material is high, so that they do not dissolve immediately, and it takes time to dissolve. Therefore, conventionally, in the dephosphorization step, fluorite (CaF ₂ ) is simultaneously charged in order to lower the melting point of oxide scale, CaO, etc. to improve the fluidity and promote the reaction with molten steel.

On the other hand, the dephosphorizing iron-making material of the present invention is characterized by having a low melting point because it contains a large amount of CaO component and 10% by mass or more of FeO component because reduced slag is used as a raw material and is a premelt product. There is. Therefore, the dephosphorizing iron-making material of the present invention can be used in place of CaF _{2 in} the dephosphorization process of steelmaking. Compared with the case where the CaO, FeO, and CaF ₂ are separately charged, the present dephosphorizing iron-making material of the present invention has a high melting rate and requires less melting energy when dissolving the iron-making material. There is an advantage of energy saving.

As described above, since the dephosphorizing iron-making material of the present invention has a low melting point, when used as a kneading material, the addition of CaF ₂ , which has been conventionally required to be added, can be added or the addition of CaF ₂ can be reduced. . Conventionally, when CaF ₂ is used in the initial dephosphorization process of secondary refining, a fluorine (F) component is contained in the generated slag. When slag containing a fluorine component is used for a roadbed material or the like, there is a possibility that fluorine may be eluted in soil or groundwater. Therefore, it is required to reduce the fluorine component from the slag. By using the iron removing material for dephosphorization of the present invention in the dephosphorization process of steelmaking, the fluorine component in the generated slag can be reduced. Incidentally, when using the present invention dephosphorization for slag material, it may be added CaF ₂ as in the prior art. Even in that case, at least the effect of reducing the amount of CaO charged can be obtained.

Since the dephosphorizing material of the present invention is a CO ₂ solidified body solidified by carbon dioxide, the interface of the fine particles of the reduced slag is composed of CaCO _3, and the dephosphorizing material was introduced into the molten steel. At this time, when CaCO ₃ comes into contact with the molten steel, it is immediately pyrolyzed, and the particles of the dephosphorizing iron-making material collapse and become fine particles. As a result, the surface area reacting with the molten steel of the dephosphorizing steel is increased, so that the reaction between the dephosphorizing steel and the molten steel is promoted.

The method for producing a dephosphorizing iron-making material according to the present invention is a method for producing a dephosphorizing iron-making material using reduced slag, wherein the reduced slag is desulfurized by bringing moisture into contact with the reduced slag, and desulfurized. By adopting a method of adding a FeO component to reduced slag and forming a molded product formed into a predetermined shape, and solidifying the molded product with a gas containing carbon dioxide to obtain a slagging material made of a CO ₂ solidified product, The dephosphorization iron-making material that has a matrix structure made of CaCO ₃ and that does not require the addition of the FeO component in the steel dephosphorization step can be obtained with certainty.

  As described above, according to the present invention, the slag obtained by treating the reduced slag is reused as the dephosphorized slagging material in the dephosphorization step in the steel making process, so that the reduced slag can be effectively used. At the same time, the burden of processing the reduced slag can be reduced.

Hereinafter, a dephosphorizing iron-making material according to an embodiment of the present invention (hereinafter sometimes simply referred to as a iron-making material) will be described in detail. The ironmaking material of the present invention is a desulfurized and reduced slag that is desulfurized by bringing moisture into contact with the reduced slag, an FeO component is added to the desulfurized and reduced slag, and the molded product is molded into a predetermined shape, and the molded product contains carbon dioxide. It consists of a CO ₂ solidified body that is solidified by contact with gas.

Table 1 shows the component composition of the dephosphorizing ironmaking material. As shown in Table 1, as a characteristic of the composition of the slagging material, since reduced slag is used as a raw material, the CaO component is more than 20% by mass, and the mass ratio of CaO / SiO ₂ (hereinafter referred to as C / S ratio). The C / S ratio is sometimes referred to as basicity.) Is as high as 1.0. Further, the slagging material is added with a FeO component later to the reduced slag, and contains 10% by mass or more and 30% by mass or less of the FeO component. These points are the major characteristics of the ingredient composition

The composition of the ironmaking material depends on the composition of the reduced slag and the composition of the FeO component to be added such as scale. In addition to the components shown in Table 1, the composition of the ironmaking material may contain MnO, Cr ₂ O ₃ , TiO ₂ , C, moisture (crystal water), and the like.

  The reduced slag used as a raw material for the ironmaking material is a by-product mainly composed of CaO in the secondary refining of steelmaking. Specific examples of such reduced slag include LF (Ladle Refining) slag or AOD slag. In addition, since the reduced slag used as the raw material for the slag material is almost completely removed during the oxidative refining, which is the primary refining, the phosphorus component (P) is substantially eliminated even when the slagging material is used. Not included.

  Further, the reduced slag itself as a raw material for the koji material has a high S component content, but since the dehydrated sulfur is brought into contact with the reduced slag, as shown in Table 1, the S component content is 0. It has a low S content of 5% by mass or less. The ironmaking material preferably has an S component of 0.3% by mass or less, and more preferably an S component of 0.1% by mass or less. When the S component is large, it is necessary to add CaO for de-S during secondary refining, but when the S component is small, it is not necessary to add CaO.

When moisture is brought into contact with the reduced slag, as shown in the following formula (1), the calcium sulfide contained in the reduced slag reacts with water and the desulfurization reaction proceeds, and the S component is removed and the calcium hydroxide is removed. The desulfurization reduction slag containing is obtained. When water is brought into contact with the reduced slag, calcium oxide also becomes calcium hydroxide as shown in the following formula (2).
CaS + 2H ₂ O → Ca (OH) ₂ + H ₂ S ↑ (1)
CaO + H ₂ O → Ca (OH) ₂ (2)

The ironmaking material is a solidified body obtained by adding a FeO component to desulfurized and reduced slag and solidifying the molded product formed into a predetermined shape with CO ₂ . In this case, the shape of the molded body is not particularly limited, and can be formed into a predetermined shape such as a tablet shape or a pellet shape. The size of the molded body is not particularly limited, but in the case of a pellet, it is preferably formed to have a diameter of about 10 to 100 mm. Moreover, when the shape is a cylindrical tablet, it is preferable that the diameter is 10 to 100 mm and the height is about 10 to 50 mm. As a preferable shape and size of the koji-making material, for example, a cylindrical tablet having a diameter of 30 to 50 mm and a height of 10 to 20 mm can be mentioned. If the shape of the molded ironmaking material is within the above range, the production of the ironmaking material is easy, and handling when using the steelmaking material when it is transported or put into molten steel is easy.

  When molding the desulfurized and reduced slag, molding is performed using a mixture obtained by adding the FeO component to the desulfurized and reduced slag. The FeO component is not particularly limited, but it is preferable to use a waste containing FeO such as a scale (mill scale) generated in a steel processing step. The scale is formed by peeling off the surface of a steel material that has become hot when subjected to hot working such as rolling or forging of steel, and its components are substantially composed of FeO. The added amount of the FeO component is 10% by mass or more and 30% by mass or less of the FeO component in the slag material.

  If the FeO component in the slag material is less than 10% by mass or exceeds 30% by mass, the effect as a dephosphorizing slagging material is insufficient. The content of the FeO component in the more preferable slag material is in the range of 15% by mass to 25% by mass.

The koji-making material is preferably formed so that the compressive strength of the CO ₂ solidified body is 5 MPa or more. If it has the said compressive strength, there is no possibility that the shape which shape | molded may collapse | crumble and pulverize at the time of handling of a slag material, and it can handle reliably. It is more preferable that the koji material has a compressive strength of 10 MPa or more because it is more difficult to disintegrate during handling. The compressive strength can be measured by a method according to JIS A 1108. The specimen used for the measurement of the compressive strength can be a cylindrical one or a briquette one.

The ironmaking material is carbonized (CO ₂ solidified) by bringing carbon dioxide into contact with a molded body obtained by adding FeO to desulfurized and reduced slag, and as shown in the following formula (3), the water in the desulfurized and reduced slag Calcium oxide is converted to calcium carbonate. In order to bring carbon dioxide into contact with the molded body, a gas containing carbon dioxide gas or the like is used. In addition, as shown in the following formula (4), when water is present when desulfurization-reducing slag is solidified with CO ₂ , CaS reacts with carbonic acid and the desulfurization reaction proceeds.
Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O (3)
CaS + H ₂ CO ₃ → CaCO ₃ + H ₂ S ↑ (4)

The koji-making material has a matrix structure in which Ca (OH) ₂ existing between CaO particles by solidification of CO ₂ reacts with carbon dioxide to form CaCO ₃ as a matrix. Desulfurized and reduced slag that has just been desulfurized by bringing moisture into contact with the reduced slag is in a brittle state by pulverizing with Ca (OH) ₂ , but the slagging material after solidified with CO ₂ is agglomerated by the matrix structure. It is hard to be pulverized and has a strength that is easy to handle.

The steelmaking material is characterized in that it immediately dissolves when it is put into molten steel. As shown in Table 2 below, the individual melting point of each component such as CaO (quick lime) in the reduced slag is 2000 ° C. or higher. On the other hand, the melting point of CaCO ₃ produced by CO ₂ solidification is as low as 1339 ° C. Therefore, when a steelmaking material is thrown into molten steel, when the steelmaking material contacts the molten steel, the binder component CaCO ₃ is instantly pyrolyzed. When CaCO ₃ is decomposed, the particles constituting the slag material are disintegrated, components mainly composed of CaO are atomized to increase the surface area, and the contact interface with the molten steel is increased to promote the reaction with the molten steel.

  The ironmaking material has a melting point of 1350 ° C. or lower and a low melting point. Since the koji-making material is a pre-melt product made from reduced slag, it has a very low melting point compared to the melting point of pure quicklime (2572 ° C.). Therefore, when the steelmaking material is added in the steelmaking process, it dissolves in the molten steel in a short time, and the energy required for melting is small and can be easily dissolved.

  FIG. 1 is a process diagram showing an example of a method for producing a koji material of the present invention. Hereinafter, the manufacturing method of the ironmaking material of this invention is demonstrated. As shown in FIG. 1, the manufacturing method of the ironmaking material of this invention uses the reduction | restoration slag 1 which generate | occur | produces as a by-product in the secondary refining of steelmaking first as a raw material. In the cooling process 100, the reduced slag 1 taken out in a molten state is placed in a predetermined container or the like and allowed to cool. In the cooling step 100, it is preferable to cool the reduced slag until the temperature of the reducing slag reaches about the outside air temperature because it is easy to handle in the next step.

  Next, a desulfurization step 200 is performed in which moisture is brought into contact with the cooled reduced slag and desulfurized to obtain desulfurized reduced slag. In the desulfurization process 200, desulfurization is performed by bringing the reduced slag 1 into contact with water vapor. Desulfurization is performed until at least the S component is 0.5 mass% or less. Desulfurization is preferably performed until the S component is less than 0.3% by mass, and more preferably is performed until the S component is less than 0.1% by mass.

In the desulfurization process 200, the temperature of the water vapor brought into contact with the reduced slag is preferably 100 to 110 ° C. In the case of water vapor at 100 to 110 ° C., it is preferable that the time for bringing water vapor into contact with the reduced slag is about 7 to 10 days. When water vapor is brought into contact with the reduced slag, the content of the S component can be reliably reduced to 0.5% by mass or less under the above conditions. In the desulfurized and reduced slag obtained by performing the desulfurization process 200, the CaS and CaO components of the reduced slag are changed to Ca (OH) ₂ and become from a lump to a fine powder. The particle diameter of the fine powdery desulfurization-reducing slag after the desulfurization step 200 is preferably formed to be 0.2 mm or less.

  Following the desulfurization step 200, a mixing step 250 for mixing the desulfurization-reducing slag and FeO components such as a mill scale is performed. The mixing step 250 is not particularly limited as long as the desulfurization reduction slag and the mill scale can be mixed almost uniformly. Further, the mixing step 250 can be performed at room temperature. The particle size of FeO component particles such as a mill scale to be mixed in the mixing step 250 is preferably 2 mm or less from the viewpoint of increasing the melting speed.

Next, a molding process 300 is performed in which the mixture obtained by mixing desulfurized and reduced slag and the FeO component is molded into a predetermined shape. In the molding step 300, a mixture of finely powdered desulfurized and reduced slag and mill scale is molded using a molding apparatus such as a pressure molding apparatus such as briquette or press molding or a granulation molding apparatus such as pelletizing. In this molding step 300, molding is performed only by the pressure of the molding means without adding other components to the mixture. The strength of the molded body obtained in the molding process 300 is such that the molded body can maintain a predetermined shape as a molded body during handling until the molded body solidifies and develops strength in the subsequent solidification step with CO _2. I just need it. The strength of such a compact before solidification of CO ₂ is preferably 0.2 MPa or more in terms of compressive strength.

Then, perform the solidification step 400 to the molding of the desulfurization reducing slag obtained in the molding step 300 the CO ₂ solid material is solidified by carbon dioxide (CO _2). In the solidification step 400, the desulfurized and reduced slag compact is put in an atmosphere containing CO ₂ gas such as carbon dioxide gas, and the Ca (OH) ₂ component contained in the desulfurized and reduced slag is reacted with CO ₂ to form CaCO ₃ . . In solidifying step 400, the method of the Ca (OH) ₂ component of the molded article is reacted with CO _2, the method for venting a method of exposing the molded body to a gas containing CO _2, a gas containing CO2 to the molded body Is mentioned.

When the Ca component of the desulfurized and reduced slag is in the state of Ca (OH) ₂ , the pH of the desulfurized and reduced slag has a high alkalinity of around 11 to 12. When this solidifies CO ₂ to form CaCO ₃ , the alkalinity decreases to about pH 9-10.

Further, as shown in the above formula (4), when desulfurized and reduced slag is solidified with CO ₂ , if moisture is present, CaS reacts with H ₂ CO ₃ and the desulfurization reaction proceeds, but the reduced slag is solidified with CO ₂ . Since the S component is removed to 0.5% by mass or less in the previous desulfurization process 200, the amount of H ₂ S generated in the CO ₂ solidification process can be reduced as compared with the case where the desulfurization process 200 is not performed.

It is considered that the CO ₂ solidification reaction of the desulfurized and reduced slag in the solidification process 400 proceeds by the following mechanism.
(i) First, as shown in the reaction formula (3), the Ca (OH) ₂ component present in the matrix part reacts with CO ₂ to form CaCO _3, and a partial reaction starts.
(ii) Next, the generated H ₂ O is discharged to the outside by an exothermic reaction.
(iii) The matrix part is depressurized and CO ₂ enters the matrix part.
(iv) By repeating the above (i) to (iii), the formation of CaCO _{3 in} the matrix portion proceeds.
In addition, it is thought that the above reaction proceeds in a gas phase (CO ₂ ) -liquid layer (H ₂ O) -solid phase [Ca (OH) ₂ ].

As the gas containing CO ₂ to be used in the solidification step 400, CO ₂ concentration high gas such as carbon dioxide, boiler, SR, CO ₂ concentration, such as exhaust gas after burning a fuel of the heating furnace or the like 8 any of to 9 vol% of CO ₂ concentration lower gas can be used. High CO ₂ concentration gas, the expression of the intensity of the CO ₂ solidification body be short fast set time, there is an advantage that the strength of the CO ₂ solidification body also increases. In addition, the gas having a low CO ₂ concentration has an advantage that it is economical because a gas generated as an exhaust gas from a boiler of a steelmaking factory can be used.

The gas containing CO ₂ used in the solidification step 400 preferably has a CO ₂ concentration of at least 8% by volume from the viewpoint of obtaining a CO ₂ solidified body having sufficient compressive strength. FIG. 2 is a graph showing the relationship between the solidification time and compressive strength of the solidified CO ₂ when CO ₂ gas (purity 99.99% by volume) and exhaust gas (CO ₂ concentration is 9% by volume) are used. As shown in the graph of FIG. 2, when CO ₂ gas is used, the treatment time is about 1 to 2 hours, and the compressive strength reaches 25 MPa or more. On the other hand, when exhaust gas is used, the treatment time is about 4 hours, the compressive strength exceeds 5 MPa, and reaches 20 MPa in about 50 hours.

FIG. 3 is a graph showing the relationship between the C content and the compressive strength when the carbon (C) content of the CO ₂ solidified body is variously changed. The graph shown in FIG. 3 shows that the compressive strength increases as the CO ₂ solidification progresses and the CaCO ₃ component increases. As shown in the graph of FIG. 3, in order to form the compressive strength of the CO ₂ solidified body at 5 MPa or more, the C component content derived from CaCO ₃ in the solidified body should be 1.5% by mass or more. preferable.

The CO ₂ solidified body obtained by solidifying CO _{2 in the} solidifying step 400 is dried as necessary, and the water content is adjusted to 1.0% by mass or less to obtain the slag material 2.

  FIG. 4 is a process diagram showing an example of a steel making method using the steelmaking material of the present invention. Hereinafter, the processing method of reduced slag and the steel making method will be described. As shown in FIG. 4, in the steelmaking method, first, an oxidative refining (primary refining 500) of molten steel is performed in an electric furnace 10. Next, the molten steel discharged from the electric furnace 10 is transferred to the molten steel pan 14, and the molten oxidized slag 11 generated during the primary refining 500 is discharged into the slag pan 12 to remove the oxidized slag 550. The discharged oxidized slag 11 is transferred to a treatment plant by a dedicated vehicle or the like.

In the reduction refining (secondary refining 600), the molten steel is transferred to the ladle refining furnace 15, and quick refining, CaF ₂ , rolling scale, etc. are charged to adjust the components, and the second refining is performed. Next, degassing is performed by the vacuum degassing device 16. Next, in the continuous casting process 700, the ladle lid 17 is installed in the ladle refining furnace 15, and continuous casting is performed using the continuous casting apparatus 18. When the continuous casting is finished, the reduced slag 1 is taken out and collected in a reduced slag collection step 800. The reduced slag 1 taken out is processed by the following processing method.

The processing method of the reduced slag 1 taken out is the cooling step 100 for cooling the reduced slag, as described in the method for producing the slag material shown in FIG. Desulfurization step 200, mixing step 250 for mixing desulfurized reduced slag and FeO component, molding step 300 for molding the mixture into a predetermined shape to form a molded product, and solidifying the molded product with carbon dioxide to solidify CO ₂ The solidification process 400 is sequentially performed. The CO ₂ solidified body is used as the slag material 2.

  The obtained steelmaking material 2 can be used as a steelmaking material for initial dephosphorization of secondary refining in the steelmaking process. For example, as shown by the arrow R1 in FIG. 4, the slagging material 2 is charged into the ladle smelting furnace 15 as a slagging material for initial dephosphorization in the secondary smelting 600 process, and quick lime, fluorite, and scale are added. Can be used as an alternative. Thus, the reduced slag generated in the steel making process can be reused as a steelmaking material in the steel making process.

Examples of the present invention will be described below.
Example 1
The molten reduced slag generated in the steelmaking process is taken out, cooled to the outside temperature, and then steam desulfurized by contacting with steam at 100 to 110 ° C. for 7 days, and the desulfurized reduced slag having an S component of 0.5% by mass or less. Got. A mill scale was added to the desulfurized and reduced slag and mixed to obtain a mixture. The amount of mill scale added was such that the FeO component was 21% by mass of the ironmaking material. Next, using a briquette molding apparatus 301 as shown in FIG. 1, briquette molding was performed without adding other additives to the above mixture to obtain a cylindrical molded body having a diameter of 35 mm × height of 15 mm. The compression strength of the obtained molded body was 0.2 MPa. Next, this molded body was placed in a container into which an exhaust gas having a CO ₂ concentration of 8% was introduced, and CO _{2 was} solidified in a CO ₂ atmosphere at room temperature for 7 hours to obtain a slag material. Table 3 shows the component composition of the obtained koji-making material. Table 4 shows the compressive strength, C component content, and melting point of this slag material.

  The steelmaking material of Example 1 was used as a steelmaking material for initial dephosphorization in secondary refining of steelmaking (ladder refining), and compared with a conventional steelmaking method. The results are shown in Table 5. In the initial dephosphorization of ladle refining, when 200 kg of lime, 500 kg of fluorite, and 200 kg of rolling scale were charged and refining for dephosphorization was performed, the P component content in the steel before refining was 0.035 mass. %, But decreased to 0.026% by mass after refining. On the other hand, when 800 kg of the ironmaking material of Example 1 was charged instead of the conventional lime, fluorite, and rolling scale and refined in the same manner, the P component content in the steel after refining is It decreased to 0.026 mass% as before. It has been confirmed that the ironmaking material of the present invention has a dephosphorization ability equivalent to that of a conventional dephosphorizing ironmaking material.

It is process drawing which shows an example of the manufacturing method of the iron-making material for phosphorus removal of this invention. CO ₂ gas and the setting time of a CO ₂ solidified in the case of using the exhaust gas as is a graph showing the relationship between the compressive strength. In the case of variously changing the C content of CO ₂ solid material is a graph showing the relationship between compressive strength and the C content. It is process drawing which shows an example of the steel manufacturing method using the steelmaking material for phosphorus removal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reduced slag 2 Slagging material 100 Cooling process 200 Desulfurization process 250 Mixing process 300 Molding process 400 Solidification process 500 Primary refining (oxidation refining) process 550 Oxidation slag removal process 600 Secondary refining (reduction refining) process 800 Reduced slag collection process

Claims (6)

A steelmaking material used for dephosphorization of steel refining, consisting of a CO ₂ solidified body obtained by adding FeO component to desulfurized and reduced slag that is desulfurized by bringing moisture into contact with reduced slag, and containing S component. A phosphatizing material for dephosphorization, characterized in that it is 0.5% by mass or less and the FeO component is 10% by mass to 30% by mass.   2. The dephosphorizing iron-making material according to claim 1, wherein the FeO component is a scale generated in a steel processing step. _2. The dephosphorizing iron-making material according to claim 1, wherein the compressive strength of the CO ₂ solidified body is 5 MPa or more.   Melting | fusing point is 1350 degrees C or less, The ironmaking material for dephosphorization of Claim 1 or 2 characterized by the above-mentioned. A method for producing a dephosphorizing slag material using reduced slag, wherein desulfurization is performed by bringing moisture into contact with reduced slag to form desulfurized reduced slag, and a FeO component is added to the desulfurized reduced slag and molded into a predetermined shape. A method for producing a dephosphorizing iron-making material, wherein the molding is solidified with a gas containing carbon dioxide to obtain a iron-making material comprising a CO ₂ solidified body.   The method for producing a dephosphorizing iron-making material according to claim 4, wherein the reducing slag is desulfurized by bringing water vapor into contact therewith.

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