JP5296359B2 - Manufacturing method of iron making agent for steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slag-making agent for iron and steel, and manufacturing method therefor by which a slag-making property can be improved and desulfurizing reaction can efficiently be performed. <P>SOLUTION: The slag-making agent for iron and steel exists under combining state of calcium fluoride on the surface of granular material composed of lime or light-burnt dolomite and the existing amount of the calcium fluoride is 8-35 mass% to the total amount of the calcium fluoride and the lime or the light-burnt dolomite. As the granular material, the one composed of the lime is desired. Further, it is desirable that the granular material has 2-30 mm grain diameter. Such slag-making agent for iron and steel, is manufactured by contacting the granular material composed of the lime or the light-burnt dolomite with an organic fluorine compound under heating state at 600-1,100&deg;C and decomposing the organic fluorine compound and reacting the fluorine generated by decomposing with the lime or the light-burnt dolomite. As the organic fluorine compound, a hydrofluorocarbon is desirable. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a method for producing a steel making agent used for removing impurities such as sulfur existing in molten steel.

Generally, the following two methods are implemented as a method for removing impurities in molten steel using a steel forging agent. That is, the first method is a method using quicklime as an iron and steel making agent and adding fluorite (calcium fluoride) as a melting point depressant (flux) to promote hatching ( For example, see Patent Document 1). The second method is a method in which powdered quicklime, fluorite, or the like is mixed as a steel making agent, and a molded body is used (see, for example, Patent Document 2).
JP-A-10-102132 (pages 2 to 4) JP 7-126725 A (pages 2 to 5)

  Incidentally, quick lime needs to be hatched (melted) in a short time in order to quickly remove impurities such as sulfur existing in the molten steel. However, in the iron and steel making agent described in Patent Document 1, fluorite added to quicklime may not be uniformly dispersed. In such a case, quicklime hatching becomes uneven, The result is that hatching takes a long time. On the other hand, in the case of the iron and steel making agent described in Patent Document 2, quick lime and fluorite are uniformly mixed, so that quick lime hatching progresses uniformly. However, since the fluorite which is a hatching accelerator is uniformly dispersed throughout the molded body, the content of fluorite on the surface of the molded body is reduced, and there is a problem that the hatchability in the initial stage is lowered. .

The present invention has been made by paying attention to such problems existing in the prior art, and the object of the present invention is to improve hatchability and to efficiently perform desulfurization reaction. It is providing the manufacturing method of the iron-making agent for steel.

Method for producing a steel for slag agent of the invention according to claim 1, in contact with the organic fluorine compound to decompose the organic fluorine compound while heating the granules consisting of quick lime or dolomitic to 600 to 1100 ° C., The fluorine produced by decomposition is reacted with quick lime or light calcined dolomite to bind calcium fluoride to the surface of the granular material, and the abundance of calcium fluoride is determined between calcium fluoride and calcined lime or light calcined dolomite. It is characterized by being 8 to 35 mass% with respect to the total amount.

According to a second aspect of the present invention, there is provided a method for producing a steel making agent according to the first aspect of the present invention, wherein the organic fluorine compound is a hydrofluorocarbon.

  According to the present invention, the following effects can be exhibited.

In the manufacturing method of the iron and steel making agent of the invention which concerns on Claim 1 , the granular material which consists of quicklime or light-burning dolomite is made to contact an organic fluorine compound in the state heated to 600-1100 degreeC, and an organic fluorine compound is decomposed | disassembled, The fluorine produced by decomposition is reacted with quick lime or light calcined dolomite to bind calcium fluoride to the surface of the granular material, and the abundance of calcium fluoride is determined between calcium fluoride and calcined lime or light calcined dolomite. The amount is 8 to 35% by mass with respect to the total amount. Therefore, calcium fluoride can be localized on the surface of the granular material, the hatchability of the granular material can be improved, and an iron and steel making agent that can efficiently perform a desulfurization reaction is easily manufactured. can do.

In the manufacturing method of the iron and steel making agent of the invention which concerns on Claim 2 , an organic fluorine compound is hydrofluorocarbon. For this reason, in addition to the effect of the invention according to claim 1 , fluorine produced by decomposition of hydrofluorocarbon chemically binds to quick lime or light calcined dolomite and binds calcium fluoride as a reaction product to the surface of the granular material. Can be easily localized.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The iron and steel making agent in the present embodiment is one in which calcium fluoride is bonded to the surface of a granular body made of quick lime or light calcined dolomite. The abundance of the calcium fluoride is 10 to 27% by mass with respect to the total amount of calcium fluoride and quicklime or light calcined dolomite. Quick lime constituting the granular material is calcium oxide (CaO), which is obtained by calcination of limestone, and is a compound that is suitably used for desulfurization excluding sulfur contained in molten steel. Light-burned dolomite (CaO · MgO) is obtained by baking dolomite [CaMg (CO ₃ ) ₂ ] at 1000 to 1200 ° C. The CaO content in the light-burned dolomite is usually 55 to 70% by mass.

  As the granular material, quick lime which is involved in the desulfurization reaction, is easily available, and has good handleability is preferable. Moreover, in order to promote the hatching and desulfurization reaction, the granular material preferably has a particle size of 2 to 30 mm, and more preferably has a particle size of 2 to 10 mm. Here, the range of the particle diameter means that the granule has a particle diameter substantially within this range. Further, the granular body may be a molded body molded by a predetermined molding method. When the particle size of the granular material is smaller than 2 mm, it becomes difficult to localize calcium fluoride on the surface of the granular material, and it is powdered to reduce handling properties. Furthermore, when the granular material is used as a steel making agent, it is difficult to use it in powder form. On the other hand, when the particle diameter is larger than 30 mm, the granular material is not easily dissolved in the molten steel, and the surface area of the granular material is reduced, and the desulfurization reaction tends to be reduced.

Next, the manufacturing method of the above-mentioned iron-making agent for iron and steel decomposes and decomposes the organic fluorine compound by bringing the granule made of quick lime or light calcined dolomite into contact with the organic fluorine compound in a state heated to 600 to 1100 ° C. The fluorine produced in this way is reacted with quicklime or light calcined dolomite. Thereby, calcium fluoride is bound and present on the surface of the granular material, and the existing amount of calcium fluoride is 8 to 35% by mass with respect to the total amount of calcium fluoride and quicklime or light calcined dolomite. Can do. Examples of the organic fluorine compound include hydrofluorocarbon (HFC) and perfluorocarbon (PFC). Among these, hydrofluorocarbon (HFC) that can be easily decomposed to generate fluorine is preferably used. The hydrofluorocarbon _{according, HFC-134a (C 2 H} 2 F 4), HFC-152a (C 2 H 4 F 2), fluoromethane _(CH 3 F), difluoromethane _{(CH 2 F} 2), trifluoromethane ( CHF ₃ ) and the like.

When the heating temperature is less than 600 ° C., the heating temperature is too low, which makes it difficult for the organic fluorine compound to decompose and decreases the amount of fluorine produced. On the other hand, when it exceeds 1100 ° C., quick lime (CaO) and calcium fluoride (CaF ₂ ) are eutectic, the melting point is lowered, and quick lime or light-burned dolomite is fused and hardened, making handling difficult.

  As described above, the calcium fluoride bonded to the surface of the granular material is set to 8 to 35% by mass with respect to the total amount of calcium fluoride and quicklime or light calcined dolomite. When the amount of calcium fluoride produced is less than 8% by mass, the effect of promoting the hatching of the granular material by calcium fluoride is insufficient. As a result, the desulfurization rate is low and the desired desulfurization reaction cannot be performed. On the other hand, when it is more than 35% by mass, it is not preferable because the content of quicklime that reacts with the sulfur component decreases when used as a steel making agent.

The reaction between the organic fluorine compound and quicklime or light-burned dolomite takes a reaction temperature of HFC-134a (C ₂ H ₂ F ₄ ) and quicklime as an organic fluorine compound. When the temperature is not higher than ° C., the reaction proceeds as shown in the following reaction formula (1), and calcium fluoride (CaF ₂ , fluorite) is generated. Further, when the heating temperature is 600 to 900 ° C. proceeds as shown by the following reaction formula (2), to produce calcium fluoride (CaF _2, fluorite). This calcium fluoride has a melting point of 1360 ° C., which is lower than the melting point of quicklime (2572 ° C.) and functions as a hatching accelerator.
C ₂ H ₂ F ₄ + 2CaO + 3 / 2O ₂ = 2CaF ₂ + 2CO ₂ + H ₂ O (1)
C ₂ H ₂ F ₄ + 4CaO + 5 / 2O ₂ = 2CaF ₂ + 2CaCO ₃ + H ₂ O (2)
Manufacture of the iron making agent for steel is implemented, for example using the vertical baking furnace 10 shown in FIG. The vertical firing furnace 10 will be described. A cylindrical firing furnace body 12 is supported on a stocker 11 for containing the reaction product, and a hopper 13 is attached to the upper end of the firing furnace body 12. The hopper 13 is continuously charged with quick lime or light dolomite granules 14. A heating unit 16 in which an electric heater 15 is disposed so as to surround the baking furnace main body 12 is provided in an intermediate portion of the baking furnace main body 12, and quick lime or light-burning dolomite granules 14 put into the hopper 13 are provided. It is configured to be heated while descending in the firing furnace body 12. The heating temperature in the baking furnace main body 12 is set so that the quick lime or the light baking dolomite in the baking furnace main body 12 may be 600-1100 degreeC.

  A support frame 18 is suspended from the center of the top plate 17 of the stocker 11, and an oblique guide plate 20 that is rotated by a motor 19 is supported in the support frame 18. And the reaction product which fell from the inside of the baking furnace main body 12 is accommodated equally in the storage container 21 of the inner bottom part of the stocker 11, and is discharged | emitted quantitatively.

  A gas pipe 22 is connected to the upper part of the stocker 11, and the gas pipe 22 is branched into an organic fluorine gas pipe 23 and an air pipe 24. The organic fluorine gas pipe 23 is connected to the organic fluorine gas cylinder 26 via the flow meter 25, and the air pipe 24 is connected to the pump 27 via the flow meter 2525. The organic fluorine gas is supplied from the organic fluorine gas pipe 23, the air is supplied from the air pipe 24, and the organic fluorine gas and air are introduced into the stocker 11 through the gas pipe 22. A discharge pipe 29 is connected to the central portion of the sealed container 28 that accommodates the hopper 13, and an exhaust pump 30 is provided in the discharge pipe 29 to exhaust the gas in the sealed container 28.

  In the heating unit 16, the quick lime or light-burned dolomite granules 14 supplied from above are heated, and at the same time, the organic halogen gas supplied from below is thermally decomposed to generate fluorine. The generated fluorine reacts with quicklime in the presence of oxygen on the surface of the granular material 14 simultaneously with the generation, and calcium fluoride is generated based on the reaction formula (1). The lime or light-burned dolomite granules 14 whose surface has been fluorinated in this manner are guided by the guide plate 20 and accumulated in the storage container 21 of the stocker 11.

  Next, when using the ironmaking agent for iron and steel for desulfurization reaction etc. in molten steel, it is carried out according to a conventional method. For example, there are mainly converter steelmaking methods and electric furnace steelmaking methods in steelmaking methods. In the steelmaking process, steelmaking iron and other ironmaking agents containing quicklime are added to the main raw materials such as pig iron. Some sulfur and phosphorus are removed and components are adjusted. The iron and steel making agent becomes the main component of slag in molten steel and is added to cause desulfurization reaction and dephosphorization reaction. Of these, the desulfurization reaction easily proceeds when the basicity of the slag is high in a reducing atmosphere, and therefore the amount of the iron-making agent for steel is determined by the basicity of the slag.

The operations and effects of the embodiment described in detail above will be described together below.
-In the iron and steel making agent in this embodiment, calcium fluoride is 8 to 35 mass% with respect to the total amount of calcium fluoride and quick lime or light calcined dolomite on the surface of the granular material consisting of quick lime or light calcined dolomite. It is chemically bound to exist as follows. That is, calcium fluoride (melting point 1360 ° C.) is localized on the surface of the granule, and the surface of the granule is easily hatched in molten steel (about 1600 ° C.). The hatching is likely to progress. Accordingly, it is possible to improve the hatchability such as increasing the hatching rate of the granular material and reducing the viscosity of the hatched product (slag), and the desulfurization reaction can be performed efficiently. In addition, impurities such as phosphorus (P) in the molten steel can be removed by this iron and steel making agent.

-By the said granular material being comprised with quick lime, the quick lime which reacts with the sulfur in molten steel rapidly, and can perform a desulfurization reaction more efficiently.
-Moreover, when a granular body has a moderate particle diameter of 2-30 mm, the hatching of a granular body becomes favorable and can accelerate | stimulate the desulfurization reaction in molten steel.

  -In the manufacturing method of the iron and steel making agent, the granular material consisting of quick lime or light calcined dolomite is brought into contact with the organic fluorine compound in a state heated to 600 to 1100 ° C to decompose and decompose the organic fluorine compound (Freon). This is done by reacting the produced fluorine with quick lime or light calcined dolomite. In this case, calcium fluoride, which is a reaction product, exists mainly on the surface of the granular material and slightly permeates from the surface of the granular material to the inside. And the calcium fluoride which concerns is 8-35 mass% couple | bonded with respect to the total amount of calcium fluoride, quicklime, or light-burned dolomite. Therefore, calcium fluoride can be localized not on the inside of the granular material but on the surface thereof, and a steelmaking agent having the above-described effects can be easily produced. That is, the iron-making iron-making agent can be manufactured with the produced | generated fluorine using the decomposition | disassembly process of CFC.

  -The organic fluorine compound is hydrofluorocarbon, so that the fluorine produced by decomposition of hydrofluorocarbon is chemically reacted with quick lime or light calcined dolomite to bond calcium fluoride, which is a reaction product, to the granular surface easily. Can be localized.

Hereinafter, although the said embodiment is described further more concretely by giving an Example and a comparative example, this invention is not limited to the range of these Examples.
Example 1
A vertical calcining furnace 10 shown in FIG. 1 was filled with quicklime granules 14 having a particle diameter of 2 to 4 mm. The granular material 14 is continuously supplied from the hopper 13 and is quantitatively discharged at a rate of 1000 g / hr by the discharge container 21 in the stocker 11. The granule 14 and the atmosphere in the baking furnace body 12 were heated to 800 ° C. by the electric heater 15 of the heating unit 16 located in the center of the baking furnace body 12. On the other hand, HFC-134a (C ₂ H ₂ F ₄ ) was introduced as an organic fluorine compound from the air pipe 24 and from the organic fluorine gas pipe 23, and exhausted from the discharge pipe 29 at the top of the firing furnace. The organic halogen compound in the heating unit 16 at the center of the firing furnace is decomposed to generate fluorine. The generated fluorine reacts with quick lime on the surface of the granular material 14 simultaneously with the generation, and calcium fluoride is generated. The air supply amount at this time was 3.5 L / min, and the supply amount of HFC-134a was 350 mL / min so that the production rate of calcium fluoride was 15% by mass. The granular material 14 thus treated with fluorine is accumulated in the storage container 21 of the stocker 11. Then, the sample accumulated in the container 21 is sampled, and the calcium fluoride content on the surface of quicklime constituting the granule 14, that is, [calcium fluoride / (calcium fluoride + quicklime)] × 100 (mass%). The results are shown in Table 1.
(Example 2)
The same procedure as in Example 1 was performed except that the flow rate of HFC-134a was adjusted to 233 mL / min so that the content of calcium fluoride was 10% by mass.
(Example 3)
It implemented like the said Example 1 except having adjusted the flow volume of HFC-134a to 583 mL / min so that content of a calcium fluoride might be 25 mass%.
Example 4
It implemented similarly to the said Example 1 except the heating temperature of the baking furnace having been 1100 degreeC.
(Example 5)
The same operation as in Example 1 was performed except that light-burned dolomite was used instead of quick lime as the granular material 14 filled in the baking furnace.
(Example 6)
It implemented like the said Example 1 except having adjusted the flow volume of HFC-134a to 700 mL / min so that content of calcium fluoride might be 30.5 mass%.
(Comparative Example 1)
It implemented similarly to the said Example 1 except having introduce | transduced only air from the air piping 24 of the baking furnace lower part.
(Comparative Example 2)
Quicklime powder and calcium fluoride powder were mixed and compression molded. The content of calcium fluoride was adjusted to be the same as in Example 1.

Next, in order to show the use as a steel making agent, the following tests were conducted.
That is, as shown in FIG. 2, the carbon-treated crucible 31 together with the nail 32 as the iron source and the iron sulfide (reagent) 33 as the sulfur source were used for the granules 14 treated in Examples 1 to 6, Comparative Example 1 and Comparative Example 2. And heated and melted in a nitrogen atmosphere using a high-frequency induction heating device. As each material, 50 g of nails, 1.37 g of iron sulfide and 2 g of each sample were used. The amount of iron sulfide added was adjusted so that the sulfur content in iron was 1% by mass. Moreover, about Example 6, it grind | pulverized and used the particle diameter 2-4 mm. The heating temperature in the high frequency induction heating apparatus was about 1600 ° C., and the heating time was 30 minutes. After heating, the inside of the carbon crucible 31 is observed, the surface of the iron lump solidified by melting the nail 32 taken out from the carbon crucible 31 is polished, and the sulfur content (mass%) in the nail 32 is measured by fluorescent X-rays. did.
(Comparative Example 3)
In the case where quicklime was not added, the nail 32 as the iron source and only the iron sulfide 33 as the sulfur source were put into the carbon crucible 31 and heated and melted in the same manner as in Examples 1 to 6 and Comparative Examples 1 and 2.

  As a result of performing the test in the same manner as described above for Comparative Example 3, the sulfur content in the nail 32 was 1.02% by mass, and it was confirmed that the added sulfur component was contained in the nail 32 as scheduled. .

Using these sulfur contents and the following formula (2), the ratio of sulfur removed from the nail 32 (desulfurization rate) was calculated.
Desulfurization rate (%) = [1- (sulfur content in nail of each sample) / (sulfur content in nail of Comparative Example 4)] × 100 (2)
The results of sulfur content and desulfurization rate are summarized in Table 1.

表１に示したように、実施例１ではフッ化カルシウムの含有量が１４．４質量％であり、フッ化カルシウムが表面に存在する生石灰（以下、フッ化カルシウム含有生石灰ともいう）であることを確認した。同様に、実施例２ではフッ化カルシウムの含有量が１０．３質量％、実施例３ではフッ化カルシウムの含有量が２５．１質量％となり、フッ化カルシウムが表面に存在する生石灰であることを確認した。高温（１１００℃）でフロン処理した実施例４ではフッ化カルシウムの含有量が１４．９質量％であった。フッ化カルシウムが表面に存在する生石灰は、加熱温度が８００〜１１００℃の条件で得られた。軽焼ドロマイトを用いた実施例５ではフッ化カルシウムの含有量が１５．１質量％となり、軽焼ドロマイトについても同様にフッ化カルシウムが表面に存在する軽焼ドロマイトであることを確認した。実施例６では、フッ化カルシウムの含有量が３０．５質量％となり、フッ化カルシウム含有生石灰であった。

As shown in Table 1, in Example 1, the content of calcium fluoride is 14.4% by mass, and calcium fluoride is present on the surface (hereinafter also referred to as calcium fluoride-containing quick lime). It was confirmed. Similarly, in Example 2, the content of calcium fluoride is 10.3% by mass, in Example 3, the content of calcium fluoride is 25.1% by mass, and calcium fluoride exists on the surface. It was confirmed. In Example 4 where the Freon treatment was performed at a high temperature (1100 ° C.), the content of calcium fluoride was 14.9% by mass. Quick lime with calcium fluoride present on the surface was obtained under the conditions where the heating temperature was 800 to 1100 ° C. In Example 5 using light-burned dolomite, the content of calcium fluoride was 15.1% by mass, and it was confirmed that light-burned dolomite was also light-burned dolomite with calcium fluoride existing on the surface. In Example 6, the content of calcium fluoride was 30.5% by mass, which was calcium fluoride-containing quicklime.

  On the other hand, in the comparative example 1, it confirmed that it was normal quicklime which does not contain calcium fluoride. In Comparative Example 2 in which quick lime powder and calcium fluoride powder were mixed and compression-molded, it was confirmed to be calcium fluoride-containing quick lime. A desulfurization evaluation test was conducted using these samples.

That is, from the state in the carbon crucible 31 after the test, the hatchability was visually evaluated according to the following criteria. The results are also shown in Table 1.
A: The hatchability was very good, O: The hatchability was good, Δ: The hatchability was insufficient, and X: The hatchability was poor.

  From the results shown in Table 1, it was confirmed that in Example 1, the samples were fused together and the hatching was sufficiently advanced because the shape was not maintained. When Example 2 and Example 3 were compared with Comparative Example 2, the higher the calcium fluoride content, the more the hatching proceeded, and the shape was not maintained in all the samples, and the hatching was sufficient. On the other hand, in Comparative Example 1, the shape of the sample remained almost as it was. From this, it was confirmed that calcium fluoride-containing quicklime having a calcium fluoride content of 10% by mass or more is easier to hatch than ordinary quicklime. Example 4 was about the same hatching condition as Example 1.

  In Example 5, the hatching situation was almost the same as that in Example 1, so that there was no difference in hatchability even when the heating temperature was 1100 ° C. or when lightly burned dolomite was used. In Comparative Example 3, fusion between samples was observed, but the shape of the sample was maintained, and it was not completely melted. Compared to Example 1, hatching did not progress sufficiently. From this, in the calcium fluoride containing quicklime of Examples 1-5, since the calcium fluoride is localized on the surface of the quicklime granule, melting of the granule surface is easy to proceed, and hatchability is improved. I understand.

  Regarding the sulfur content and the desulfurization rate, in Example 1, the sulfur content in the nail 32 showed a low value of 0.44% by mass, and the desulfurization rate showed a high value of 57%. This is probably because the desulfurization reaction proceeded quickly because the hatchability of the sample was good. In Example 2, the desulfurization rate was as high as 60%, and in Example 3, the desulfurization rate was as high as 55%. In Example 6, the desulfurization rate decreased to 39%. The higher the calcium fluoride content, the better the hatchability, but the higher the calcium fluoride content, the lower the desulfurization rate because the amount of calcium that reacts with the sulfur component in iron decreases. It is thought to do. From this, it was found that calcium fluoride-containing quicklime having a calcium fluoride content of 8 to 35% by mass has sufficient desulfurization performance. Example 4 and Example 5 also showed high desulfurization rates of 58% and 62%, so that they were sufficiently high even in the case of calcium fluoride-containing quicklime produced by high-temperature heating or calcium fluoride-containing light-burned dolomite. It was confirmed that it has desulfurization performance.

  On the other hand, in the comparative example 1, it turns out that the hatching rate is slow and desulfurization reaction does not advance. In Comparative Example 2, the sulfur content in the nail 32 was as high as 0.70% than in Examples 1 to 5, and the desulfurization rate was low. From this, the material in which calcium fluoride is localized on the surface of the granular material as in Example 1 is more hatched than the material in which calcium fluoride is uniformly distributed throughout the sample as in Comparative Example 2. It was found that the desulfurization reaction proceeds rapidly and efficiently in a short time.

It should be noted that the embodiment described above can be modified and embodied as follows.
-Quick lime and light-burned dolomite constituting the granular material can be mixed and used.
-Hydrochlorofluorocarbon (HCFC), chlorofluorocarbon (CFC), etc. can be used as the organic fluorine compound.

-It can also set so that the particle size distribution of the said granular material may become narrow, and to improve hatchability.
-The shape of the granular material can be close to a sphere, and the shape can be made uniform to improve hatchability.

Next, the technical idea that can be grasped from the embodiment will be described below.
The method for producing a steel making agent according to claim 1 or 2 , wherein the granule is continuously brought into contact with an organic fluorine compound to cause the reaction to proceed. When comprised in this way, in addition to the effect of the invention which concerns on Claim 1 or Claim 2 , the ironmaking agent for steel can be manufactured continuously, and it is industrially useful.

The method for producing a steel making agent according to claim 1 or 2 , wherein the reaction between the granular material and the organic fluorine compound is performed under supply of air. When comprised in this way, in addition to the effect of the invention which concerns on Claim 1 or Claim 2 , the iron and steel making agent for steel can be manufactured with a sufficient yield.

Schematic explanatory drawing for demonstrating the method to manufacture the iron and steel making agent using a vertical baking furnace. A typical explanatory view for explaining a method of performing desulfurization using a carbon crucible.

Explanation of symbols

  14 ... Granules.

Claims (2)

Granules made of quick lime or light calcined dolomite are brought into contact with the organic fluorine compound in a state heated to 600 to 1100 ° C. to decompose the organic fluorine compound, and the fluorine produced by the decomposition is reacted with quick lime or light calcined dolomite to be granular Calcium fluoride is bonded to the surface of the body, and the calcium fluoride is present in an amount of 8 to 35% by mass with respect to the total amount of calcium fluoride and quicklime or light calcined dolomite. A method for producing a steel making agent. The said organic fluorine compound is hydrofluorocarbon, The manufacturing method of the iron-making agent for steels of Claim 1 characterized by the above-mentioned.

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