JP7522992B2 - Carbon-containing unburned brick refractory and method for producing carbon-containing unburned brick refractory - Google Patents

Description

The present invention relates to a carbon-containing unburned brick refractory material used as an inner lining in high-temperature processes such as iron-making refining equipment, and a method for producing the carbon-containing unburned brick refractory material.

Conventionally, representative examples of carbon-containing brick refractories include MgO-C bricks, Al ₂ O ₃ -C bricks, and Al ₂ O ₃ -SiC-C bricks. In particular, MgO-C bricks have the characteristics of being excellent in corrosion resistance to steelmaking slag and having relatively good thermal shock resistance compared to sintered bricks, and are mainly used as refractory linings in major equipment in the steelmaking process. On the other hand, MgO-C bricks have a higher thermal conductivity than sintered bricks because they contain carbon.

Moreover, for the sake of the global environment, _CO2 emissions reduction activities are being carried out on a global scale. In the steel industry, since a large amount of carbonaceous materials is used, various efforts to reduce _CO2 emissions are important, such as suppressing the loss of thermal energy due to the reduction of the reducing agent ratio in blast furnaces and developing technologies for effective use of heat. In the field of refractories, a measure to create thermal margin is to suppress heat dissipation from the furnace body by reducing the thermal conductivity of refractories. In particular, carbon-containing bricks such as MgO-C bricks have a carbon concentration-dependent thermal conductivity, so reducing the carbon content greatly contributes to suppressing the loss of thermal energy. In addition, reducing the carbon content of bricks also contributes to improving the quality of steel pieces, such as suppressing carbon pickup during refining.

When carbon-containing refractory bricks such as MgO-C bricks are reduced in carbon content, a problem arises: the deterioration of heat spalling resistance. In particular, spalling destruction of refractories (MgO-C bricks) used in the steelmaking process occurs when cracks that occur in the refractory due to repeated thermal loads over a long period of time propagate. In recent years, as a countermeasure, carbon MgO-C bricks that suppress the deterioration of heat spalling resistance have been proposed. For example, Patent Document 1 discloses a technology in which carbon fiber (length 0.13 to 50 mm, diameter 5 μm or more) is added to the refractory in a range of 50% or less as a carbon source.

In recent years, many carbon nanomaterials have been discovered, such as carbon black, carbon nanotubes (hereinafter sometimes referred to as "CNT"), carbon nanofibers (hereinafter sometimes referred to as "CNF"), fullerenes, and graphene, and many technologies have been used to improve mechanical properties, especially spalling resistance, by adding these nanomaterials. For example, Patent Document 2 discloses a technology in which mesophase pitch + thermosetting resin is added to a refractory material, and carbon nanofibers (diameter: maximum 500 nm, length: 100 μm) are generated by thermal decomposition (1000° C. or less) of the mesophase pitch + thermosetting resin, thereby improving corrosion resistance and thermal shock resistance. Patent Document 3 discloses a technology in which fullerenes are added to a refractory material in a range of 5% or less to improve spalling resistance. The principle is that fullerenes react with the binder phenol resin at high temperatures (heat treatment: up to 1500°C), producing carbon nanofibers (CNF). These CNFs act as a bridging effect, improving spalling resistance. One type of spalling resistance is heat spalling resistance.

Patent Document 4 discloses a technology for improving the toughness of refractories by kneading an organic binder, a colloidal or suspension-like solution or dispersion of transition metals or transition metal salts in which fine particles with a particle size of 1000 nm or less are dispersed in a solvent, and refractory raw materials, and heat treating the mixture at a temperature of 600°C to 1200°C to produce a dispersion of fine particles containing a carbon fiber structure and transition metals or transition metal salts with a particle size of 1000 nm or less.

Patent Document 5 also discloses a technology that uses a catalyst-coated refractory raw material, in which the surface of the refractory raw material is coated with one or more metals selected from the group consisting of V, Fe, Co, Ni, Cu, Mo, Pd, Rh, W, and Pt as a catalyst, and an organic polymer resin or its precursor as raw materials, and heat-treats the refractory material to uniformly disperse nanocarbon tubes in the structure and improve toughness.

Furthermore, Patent Document 6 discloses a technology for providing a refractory material with excellent strength and fracture resistance by applying a refractory material made of a refractory material whose surface is coated with CNT or CNF.

These technologies all aim to prevent the growth of cracks that occur in the refractory due to mechanical loads by introducing fibrous materials into the structure of the refractory and using the bridging effect of the fibrous materials. The above-mentioned conventional technologies can be applied not only to low-carbon bricks, but also to bricks with a relatively high carbon content, and contribute to further increasing the strength of the refractory or further improving its spalling resistance.

Japanese Unexamined Patent Publication No. 62-9553 JP 2005-139062 A JP 2006-8504 A Patent No. 4641316 Patent No. 4856513 Patent No. 5192774

However, when a fibrous material is added as in Patent Document 1, the denseness of the refractory material is impaired, and it may become difficult to mold the refractory material. This may also lead to an increase in the manufacturing costs of the refractory material. In the case of Patent Document 2, the added material is mesophase pitch, which is relatively expensive, which poses a problem in terms of manufacturing costs. In the case of Patent Document 3, the added material is fullerene, which is relatively expensive, which may also lead to an increase in the manufacturing costs of the refractory material.

In addition, in the case of Patent Document 4, a colloidal or liquid substance is newly added along with the liquid organic binder. At this time, the fluidity of the kneaded material increases excessively, making it very difficult to mold the refractory material. This results in a restriction on the amount of colloidal substance or suspension added to the binder, which places great restrictions on the manufacture of refractories. Furthermore, the technologies disclosed in Patent Documents 5 and 6 both apply coating technology. This coating technology usually uses a deposition method such as CVD, but this method also has the problem of being very expensive and very difficult to coat in large quantities. Therefore, these technologies cannot be said to be necessarily effective.

The present invention was made in consideration of the above circumstances, and aims to provide a carbon-containing unburned brick refractory material and a manufacturing method for a carbon-containing unburned brick refractory material that can improve the heat spalling resistance of the refractory material by applying the material to a converter and then preheating the converter.

The gist and configuration of the present invention to solve the above problems are as follows.
[1] A carbon-containing unburned brick refractory material comprising a mixture of a transition metal or a transition metal compound containing a transition metal, the transition metal having an average particle size of 1 μm or less, and a liquid binder made of an organic substance, a refractory raw material, and a graphite raw material.
[2] The carbon-containing unburned brick refractory material according to [1], wherein the refractory raw material is composed of at least one compound selected from Al ₂ O ₃ and MgO, and the compound has a particle size range in which, in terms of average particle size, 5 to 40 mass% is 3 mm or more, 10 to 45 mass% is 1 mm or more and less than 3 mm, 15 to 30 mass% is 0.15 mm or more and less than 1 mm, and 5 to 45 mass% is less than 0.15 mm.
[3] The carbon-containing unburned brick refractory material according to [1] or [2], wherein the mass of the binder is from 2 mass% to 5 mass%, with the exception of the total mass of the refractory raw material and the graphite raw material.
[4] The carbon-containing unburned brick refractory material according to any one of [1] to [3], wherein the transition metal compound is a compound containing Fe or Ni.
[5] The carbon-containing unburned brick refractory material according to [4], wherein the compound containing Fe or Ni is any one of Fe ₂ O ₃ , Fe ₃ O ₄ , FeO, NiCO ₃ , and NiO.
[6] The carbon-containing unburned brick refractory material according to any one of [1] to [5], wherein a total mass of the transition metal and the transition metal compound is 0.1 mass% or more and 8.0 mass% or less with respect to the mass of the binder.
[7] A method for producing a carbon-containing unburned brick refractory, comprising: a mixing step of mixing a transition metal or a transition metal compound containing a transition metal, the transition metal having an average particle size of 1 μm or less, with a liquid binder made of an organic substance to prepare a mixture; and a molding step of blending and molding the mixture prepared in the mixing step with a refractory raw material and a graphite raw material.

According to the present invention, by carrying out preheating treatment of the converter after application to the converter, it is possible to efficiently generate fibrous material in the refractory material. This makes it possible to improve the thermal spalling resistance of the refractory material.

FIG. 2 is a diagram showing a heating temperature pattern of a mixture of a binder and a transition metal (transition metal compound). FIG. 1 is a diagram showing a TEM photograph of a phenol resin dry distillation product (CNT) in the case where a transition metal compound (Fe ₂ O ₃ ) is used. FIG. 1 is a diagram showing a TEM photograph of a phenol resin dry distillation product (CNT) in the case where a transition metal compound (NiCO ₃ ) is used. 1 is a graph showing the relationship between load and displacement in normal bricks and _NiCO3- added bricks. 1 is a graph showing the static elastic modulus of normal bricks and _NiCO3- added bricks. FIG. 1 is a schematic diagram showing a CNT production mechanism when FeO is added as a transition metal to a phenol resin.

The present invention will be described below through the embodiments of the present invention. In the present invention, "unfired brick refractory" refers to a brick refractory prior to the firing step, as opposed to a brick refractory manufactured by carrying out a molding step in which refractory raw materials, graphite raw materials, binder, etc. are mixed and molded, and a firing step in which the product molded in the molding step is fired. The molding step may include a treatment for thermally curing the binder as necessary (for example, a treatment (curing treatment) in which the molded product is held at about 150 to 300°C for a long period of time (24 to 72 hours)).

In the steelmaking process, multiple refining processes are carried out in a batch manner, so heat is absorbed and released periodically. When refractory equipment continues to be subjected to repeated thermal loads, the thermal stress generated in the refractory also fluctuates accordingly. This causes cracks to form in the refractory, leading to its destruction. Therefore, if the toughness of the refractory can be improved to improve its durability, it can lead to an increase in the lifespan of refractory equipment in the steelmaking process.

One method for improving the toughness of refractories is to prevent the initiation and propagation of cracks that cause destruction within the material. One method for preventing the initiation and propagation of cracks is to add a material with a high aspect ratio, such as a fibrous material, to the refractory to strengthen bridging. Here, a possible example of a fibrous material would be carbon fiber, which is lightweight and has high tensile strength. However, simply adding a fibrous material can cause problems such as lamination during refractory molding due to volume differences, shapes, and surface conditions.

Refractories, such as MgO-C bricks, are composed of refractory raw materials such as aggregate and fine powder, graphite raw material (flake-like graphite), liquid binders made of organic substances such as phenolic resin, and various other additives. Other additives include, for example, hardeners. Depending on the type of binder, a hardener may or may not be required.

Here, when a liquid binder made of an organic substance is heated, the volatile components are removed, and carbon substances such as amorphous carbon are produced. At this time, if it were possible to produce nano-fibrous substances such as carbon nanotubes during heating using the binder as a raw material, it may be possible to solve problems such as the occurrence of lamination at lower costs. Therefore, the inventors investigated whether carbon nano-fibrous substances could be produced when a binder material (for example, organic resins such as tar, phenolic resin, and pitch) is heated.

When it comes to the generation of carbon nanotubes, if fine particles of transition metals such as Fe or Ni are present, nanotubes are generated and grow from these particles as nuclei. Therefore, the inventors added oxides of Fe and Ni to the binder material and conducted observations, aiming to generate nanotubes from the Fe and Ni particles generated by reduction with the binder material components during heating. The details of the investigation and experiment are described below.

The raw materials used were powdered Fe ₂ O ₃ or NiCO ₃ as a transition metal compound, and phenolic resin as a binder. 10 g of phenolic resin was added to a carbon crucible, and then powdered Fe ₂ O ₃ or NiCO ₃ was added to the crucible. The amount added and the experimental level are shown in Table 1. In each condition, the phenolic resin and the powdered transition metal compound were thoroughly mixed in the crucible and heated in an Ar atmosphere with the temperature pattern shown in FIG. 1. The sample after cooling was observed with a TEM (transmission electron microscope). TEM photos under each condition are shown in FIGS. 2 to 3. From FIGS. 2 to 3, the presence of a pseudo-fibrous phenolic resin dry distillation product of sub-μm size was confirmed. FIG. 2 shows a TEM photo of CNT, which is an example of a phenolic resin dry distillation product when Fe ₂ O ₃ is used as a transition metal compound. FIG. 3 shows a TEM photo of CNT, which is an example of a phenolic resin dry distillation product when NiCO ₃ is used as a transition metal compound.

Based on the results of this investigation and experiment, powdered NiCO ₃ was added to the binder in an amount of 1 mass % to prepare a mixture in which the binder and powdered NiCO ₃ were premixed, and the mixture was mixed with a refractory raw material and a graphite raw material to form a molded product, which was then heat-treated to produce a prototype MgO-10%C brick. Here, the term "MgO-10%C brick" refers to a brick made by mixing magnesia (MgO) and 10 mass % graphite raw material (C). The bending strength (σ: MPa) and static elastic modulus (E: MPa) of the brick were evaluated by a three-point bending test (JIS R2213:2005 Test method for bending strength of refractory bricks). Here, the static elastic modulus (E) was evaluated using the following formula (1). Here, L is the distance between the supports (m), B is the width of the sample (m), W is the height of the sample (m), Δu is the deflection (mm), and ΔP is the maximum load in the linear range (N).

The results are shown in Figures 4 and 5. Figure 4 shows the relationship between the displacement and the load, with the load (N) on the vertical axis and the displacement (mm) on the horizontal axis. Figure 5 shows the static modulus of elasticity (MPa) on the vertical axis. The results of bending strength can be seen from Figure 4, and the results of static modulus of elasticity can be seen from Figure 5. From Figure 5, it can be confirmed that the static modulus of elasticity of the MgO-10%C brick with NiCO ₃ added (NiCO _3- added brick) is almost the same as that of the normal MgO-C brick without NiCO ₃ added (normal brick). Also, from Figure 4, it can be confirmed that the bending strength of the NiCO ₃ -added brick is improved compared to the normal brick. This suggests that the thermal shock fracture resistance R (unit: K) defined by the following formula (2) is improved by applying a binder with added nano-NiCO ₃ .

In formula (2), ν is the Poisson's ratio (a dimensionless number (here, 0.3)) and α is the thermal expansion coefficient of the material (1/K). When the thermal shock resistance R of the two bricks is actually compared, the R of the normal brick is 22, while the R of the _NiCO3 -added brick is 34, showing a large increase in the thermal shock resistance R.

Here, the CNT generation mechanism of the present invention will be described with reference to FIG. 6, taking the case where FeO is added as a transition metal as an example. First, as shown in FIG. 6(a), reducing gas (CxHy, H ₂ , CO) is volatilized from the phenolic resin (resin) by the heat treatment. Then, as shown in FIG. 6(b), the reducing gas and FeO cause an oxidation-reduction reaction to generate metallic Fe. After that, as shown in FIG. 6(c), the reducing gas volatilized from the phenolic resin is decomposed on the surface of metallic Fe, and carbon is generated and diffused with metallic Fe as a nucleus. In response to this, as shown in FIG. 6(d), the carbon diffused on the surface of metallic Fe is bonded (C-C bond) by the catalytic action of metallic Fe, and is generated and grown as CNT.

By utilizing the reaction that occurs during this heat treatment, it is possible to efficiently generate and grow CNTs within the refractory. Taking the construction and operation of a converter as an example, during construction, the refractory before CNT generation is installed in the same way as conventional refractory, and during preheating of the converter (800-1200°C), a reaction occurs according to the principle shown in Figure 6, and CNTs are generated uniformly inside the refractory. The bridging effect of the generated CNTs greatly improves the toughness of the refractory, thereby achieving an improvement in the refractory's lifespan.

Here, the additive (catalyst) to the binder used in the present invention must be a transition metal or a transition metal compound (oxide, carbonate, or other compound) containing a transition metal with an average particle size of 1 μm or less. This is because when the average particle size of the transition metal (transition metal compound) added to the binder exceeds 1 μm, CNTs are difficult to generate. It is most preferable to use transition metal particles as the added particles, but they are relatively expensive and require sufficient attention to safety when handling. Therefore, it is more preferable to add a transition metal compound (oxide, carbonate, or other compound) in the sense that it can ensure safety when handling and has the same effect. The transition metal compound used is preferably a compound containing Fe or Ni, and more preferably NiCO ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , FeO, NiO, or the like. In addition, when used as a transition metal, Fe or Ni is preferable. The additive to the binder may be a mixture of a transition metal and a transition metal compound (e.g., a mixture of Fe and FeO), or a mixture of transition metal compounds (e.g. _, a mixture of _Fe3O4 and FeO).

Here, the present invention is characterized in that a transition metal or transition metal compound having an average particle size of 1 μm or less is mixed with a liquid binder made of an organic substance in advance to form a mixture, which is then added to a refractory raw material or graphite raw material to form a carbon-containing unburned brick refractory. Usually, when metal particles are contained in a refractory, the metal particles are generally added to the refractory raw material. However, when metal particles are added to the refractory raw material, the binder and the metal particles are not mixed well, making it difficult to generate and grow CNTs. In addition, when metal particles are mixed with a binder through a solution as in Patent Document 4, the moldability of the refractory decreases. In contrast, as in the present invention, a process (mixing process) of mixing a transition metal or transition metal compound with a binder in advance to prepare a mixture is provided before a process (molding process) of blending with the refractory raw material and the graphite raw material and molding the mixture, so that the transition metal can be reliably and uniformly dispersed in the binder without reducing the moldability of the refractory, and CNTs can be generated and grown more easily. The transition metal (transition metal compound) and binder can be mixed in a variety of ways, such as using a stirrer such as a mixer or a kneader, and there are no limitations on the method.

The mass of the binder added to the refractory is preferably 2% to 5% by mass relative to the total mass of the refractory raw materials and the graphite raw materials. If it is less than 2% by mass, it will not act as a sufficient binder, and if it exceeds 5% by mass, there will be too much binder and it may seep out during molding of the refractory.

Furthermore, it is desirable to add a transition metal (transition metal compound) having an average particle size of 1 μm or less in an amount of 0.1% by mass to 8.0% by mass relative to the liquid binder made of an organic substance. If it is less than 0.1% by mass, the amount of CNT generated will be suppressed, and if it is added in an amount of more than 8.0% by mass, the effect will be the same as that of 8.0% by mass, and excessive effects cannot be expected. Conversely, it is not preferable because it will affect the close packing of the refractory structure.

The present invention can be applied to various carbon-containing bricks such as MgO-C and Al ₂ O ₃ -C. When at least one compound of Al ₂ O ₃ and MgO is used as the refractory raw material, the particle size range of Al ₂ O ₃ and MgO is preferably 5 to 40 mass% of 3 mm or more, 10 to 45 mass% of 1 mm or more and less than 3 mm, 15 to 30 mass% of 0.15 mm or more and less than 1 mm, and 5 to 45 mass% of less than 0.15 mm in terms of average particle size. Of course, it is not a problem if an antioxidant such as Al or Si is added to these refractories. Rather, since Al and the like contribute to the generation of whiskers, a higher effect can be fully expected. In addition, the present invention can also be applied to refractories with SiC added.

The refractory raw material used in the present invention can be any of electrofused products, sintered products, and natural materials (including seawater MgO). In addition, various graphite raw materials can be used, such as scaly graphite, carbon black, and thin graphite.

MgO-C bricks were manufactured using electrofused MgO aggregate with a maximum size of 5.00 mm, MgO fine powder less than 1.00 mm, and flaky graphite. The carbon concentration in the bricks was 10.0 mass%. The composition of the reference MgO-C brick is shown in Table 2. The MgO-C brick with the composition shown in Table 2 is an example shown as Comparative Example 1 in Tables 3 and 4 described below.

Table 3 shows a list of the invention examples and comparative examples. In invention example 1, _CoCO3 was premixed with the binder at a ratio of 9.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In invention example 2, NiO was premixed with the binder at a ratio of 8.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In invention example 3 _{, Fe3O4} was premixed with the binder at a ratio of 4.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In invention example 4, FeO was premixed with the binder at a ratio of 8.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In invention example 5 _{, Fe2O3} was premixed with the binder at a ratio of 4.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In Example 6, metallic Fe was premixed with the binder at a ratio of 4.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In Example 7, Ni was premixed with the binder at a ratio of 4.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less. In Example 8, Co was premixed with the binder at a ratio of 4.0 mass% relative to the binder as an additive having an average particle size of 1 μm or less.

In contrast, in Comparative Example 1, the materials were mixed according to the composition shown in Table 2, and no additives were added. In Comparative Example 2, the materials were mixed according to the composition shown in Table 2, but Al powder was added to the additives at a ratio of 4.0 mass% separately from the binder. In Comparative Example 3, the materials were mixed according to the composition shown in Table 2, and Si powder was added to the additives at a ratio of 4.0 mass% by mixing with the binder in advance. In Comparative Example 4, NiCO ₃ was added separately from the binder as an additive having an average particle size of 1 μm or less at a ratio of 10.0 mass% relative to the binder. In Comparative Example 5, Fe ₂ O ₃ was added separately from the binder as an additive having an average particle size of 1 μm or less at a ratio of 8.5 mass%. Here, "added separately from the binder" in Comparative Examples 2, 4, and 5 means that metal particles are added directly to the refractory raw material.

In both the invention and comparative examples, the raw materials were mixed and then molded using a friction press. The molded products were held at 230°C for 24 hours for curing, and then held in a reducing atmosphere at 1350°C for 3 hours for firing to obtain evaluation samples. For evaluation, mechanical properties such as bending strength σ (MPa) and elastic modulus (dynamic elastic modulus) E (MPa) were measured, and thermal shock fracture resistance R was derived according to formula (2). The higher this thermal shock fracture resistance R, the more difficult the material is to fracture, and the material can be said to have excellent heat spalling resistance.

The results are shown in Table 4. Inventive Examples 1 to 8, in which a transition metal or transition metal compound having an average particle size of 1 μm or less was mixed in advance with a binder and added, bending strength and elastic modulus were increased compared to Comparative Example 1. Inventive Examples 1 to 8, thermal shock fracture resistance R was improved compared to Comparative Examples 1 to 3. Inventive Examples 1 to 8, thermal shock fracture resistance R was higher than Comparative Examples 4 and 5, and toughness was improved. Furthermore, in Inventive Example 5, in which Fe ₂ O ₃ was adopted as a transition metal compound having an average particle size of 1 μm or less and the amount added was 4.0 mass%, thermal shock fracture resistance R was improved compared to Comparative Example 5, in which Fe 2 O 3 was added at more than 8.0 mass%. In addition, when comparing thermal shock fracture resistance R by type of transition metal or transition metal compound having an average particle size of 1 μm or less using the same addition method (conditions in which an organic binder was mixed in advance and added), no significant difference was observed in Inventive Examples 1 to 8.

From the above, it has become clear that by producing a carbon-containing unburned brick refractory using the carbon-containing unburned brick refractory and the method for producing a carbon-containing unburned brick refractory according to the present invention, and then subjecting the refractory to a preheating treatment after installation in a converter, it is possible to efficiently generate fibrous substances in the refractory. It has also become clear that this has an excellent effect on the thermal shock fracture resistance, i.e., heat spalling resistance, of the carbon-containing brick refractory.

Claims (5)

A carbon -containing brick refractory material comprising a mixture of a liquid binder made of a transition metal or a transition metal compound containing a transition metal, the average particle size of which is 1 μm or less, and an organic substance, a refractory raw material, and a graphite raw material,
The mass of the binder is 2% by mass or more and 5% by mass or less with respect to the total mass of the refractory raw material and the graphite raw material,
a total mass of the transition metal and the transition metal compound is 0.1 mass% or more and 8.0 mass% or less with respect to the mass of the binder,
A carbon-containing brick refractory having a carbon nanofiber material . The refractory raw material is composed of at least one compound selected from the group consisting of Al ₂ O ₃ and MgO,
The compound has a particle size range of 5 to 40% by mass of an average particle size of 3 mm or more, 10 to 45% by mass of an average particle size of 1 mm or more but less than 3 mm, 15 to 30% by mass of an average particle size of 0.15 mm or more but less than 1 mm, and 5 to 45% by mass of an average particle size of less than 0.15 mm.
The carbon -containing brick refractory material according to claim 1 . 3. The carbon -containing brick refractory material according to claim 1 , wherein the transition metal compound is a compound containing Fe or Ni. _4. The carbon -containing brick refractory according to claim 3 , wherein the compound containing _Fe or Ni is any one of _Fe2O3 , _Fe3O4 , FeO, _NiCO3 , and NiO. a mixing step of mixing a transition metal or a transition metal compound containing a transition metal having an average particle size of 1 μm or less with a liquid binder made of an organic substance to prepare a mixture;
a molding step of blending and molding the mixture prepared in the mixing step, a refractory raw material, and a graphite raw material;
A firing step of firing the molded product formed in the molding step to produce a carbon nanofiber material ,
The mass of the binder is 2% by mass or more and 5% by mass or less with respect to the total mass of the refractory raw material and the graphite raw material,
a total mass of the transition metal and the transition metal compound is 0.1 mass % or more and 8.0 mass % or less based on the mass of the binder .

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