JPH08333173A - Monolithic refractory containing isotropic pitch carbon having high softening point - Google Patents

Abstract

PURPOSE: To obtain a monolithic refractory, such as a castable refractory, improved in workability, strength, corresion resistance and slag resistance by adding a specific high softrening point isotropic pitch to refractory aggregates. CONSTITUTION: A coal heavy oil or the pitch or a petroleum heavy oil or the pitch is bubbled with oxygen or ozone gas and simultaneously thermally treated at 300-400 deg.C to obtain a high softening point anisotropic pitch having a softening point of 200-350 deg.C, an optically isotropic texture of <=5vol.%, an immobilized oxygen content of 60-95wt.%, a quinoline insoluble content of 0-60wt.%, a toluene insoluble content of 20-80wt.% and particle diameters of <=2mm. Refractory aggregates are compounded with 0.5-10wt.% of the obtained isotropic pitch, and if necessary, further with a dispersing agent, an antioxidizing agent, a thickening agent, a viscosity-controlling agent, a deforming agent, and a liquid selected from water, an organic solvent, an inorganic solvent, and an organic metal solvent in a total amount of 3-30wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing amorphous refractory having excellent corrosion resistance against molten metal or slag.

[0002]

2. Description of the Related Art Conventionally, amorphous refractory materials, especially castable refractory materials, have been used as lining refractory materials for gutters, hot metal ladles, mixing pig wheels, etc., but corrosion resistance to molten metal or slag, especially slag and hot metal. In order to improve the erosion resistance, spalling resistance, etc. at the interface of the, the carbon source such as pitches has been added.

Particularly in the case of pitch, since it softens and permeates into the pores of the castable refractory, it has a function of preventing and protecting the permeation of the molten metal and slag into the refractory. Further, it is possible to expect formation of a strong refractory structure by carbon bond due to carbonization during heating of pitch or during use or heating.

However, since the pitch itself is hydrophobic, when it is added as a carbon source of the castable refractory, when the water is added and the mixture is kneaded, the castable fluidity is remarkably lowered. Will be done. For this reason,
At the time of kneading, the amount of water added must be greatly increased and the mixture must be kneaded. The cast body made of castable refractory has an increased porosity and is significantly deteriorated in structure, so that a dense structure cannot be obtained. In addition, there is a problem that the oxidation of the carbon raw material remarkably lowers the strength and corrosion resistance, and the original characteristics of the carbon raw material are not utilized.

In order to improve the fluidity at the time of kneading with such a pitch mixture, it has been attempted to use granulated pitch pellets in combination with a surfactant in order to make the hydrophobic surface as small as possible, but it is sufficient. Workability improvement effect is not obtained.

Further, since the pitch is volatilized at a high temperature, if it is used in a granular form, a large cavity is created in the constructed tissue body to deteriorate the tissue, and the pitch is unevenly distributed in the tissue, resulting in corrosion resistance. It is not preferable from the aspect.

In order to eliminate the adverse effects caused by the addition of the pitch, various improvement measures have been proposed. For example, Japanese Examined Patent Publication (Kokoku) No. 60-24072 discloses that the porosity of a refractory material is reduced without adding pitch to make the structure denser, but it is not sufficient in terms of corrosion resistance. In addition, JP-A-5-
No. 330930 discloses that pitch is hydrophilically treated with a surfactant before use, but the corrosion resistance of the construction refractory is not sufficient. Furthermore, JP-A-63-215
Japanese Patent No. 573 discloses that graphite is hot-kneaded with pitch, and the pitch-treated graphite obtained by crushing after kneading is used. However, graphite that is not covered with the pitch generated at the time of crushing is Castable fluidity is significantly impaired.

In addition, pitches having a large amount of optical anisotropy such as mesophase pitch and bulk mesophase are selected in JP-A-2-268953, JP-A-5-4861 and JP-B-6-99182. Refractory,
In particular, it is disclosed that the strength of carbon bond is improved when added to bricks. However, when such a mesophase pitch or bulk mesophase is applied to a castable refractory, it is necessary to increase the added water content during kneading more than the pitch. For this reason,
The strength is not improved as in the case of bricks, and the quality is rather deteriorated by the increase of added water.

[0009]

The object of the present invention is to shorten the deflocculation time during kneading, to obtain a fluidity that can be applied in a short time, and to obtain a compound that can be applied with low water content. Low cost, excellent workability, densified structure of construction body, lower porosity of construction body to improve wettability to slag, and amorphous shape that can fully show the corrosion resistance improvement effect by pitch as carbon raw material To provide refractory materials.

[0010]

The present invention has been completed based on the finding that it is possible to improve the strength by including a high softening point isotropic pitch in an amorphous refractory material.
The refractory aggregate has a softening point of 200 to 350 ° C., an optically anisotropic structure of 5% by volume or less, and a fixed carbon amount of 60 to 95% by weight.
In addition, 0.5 to 10% by weight of a highly soft isotropic pitch having a particle diameter of 2 mm or less is contained.

Pitches are usually classified into three types by showing the degree of softness and hardness by a softening point. A soft pitch is about 700 ° C. or less, a medium pitch is about 70 to 900 ° C., and a 90 ° pitch.
Those having a temperature of 0 ° C. or higher are called hard pitch.

Among these, soft pitch and medium pitch have a low softening point and, in addition, since they have a large amount of volatile matter, when they are used for an irregular shaped refractory material such as casting material, the structure of the construction body is deteriorated due to the volatile matter. At the same time, the amount of residual carbon is small, so improvement in corrosion resistance cannot be expected.

Therefore, the hard pitch and the mesophase pitch obtained by heat-treating the hard pitch are usually used as a carbon raw material for an amorphous refractory.

Hard pitch is optically isotropic when observed with a polarization microscope, but mesophase pitch contains a large amount of optically anisotropic liquid crystal (mesophase) and is also called crystallized pitch. It is advantageous as a raw material for refractory materials in that it has a lower volatile content than hard pitch. However, when hard pitch or mesophase pitch is applied to an amorphous refractory, workability is significantly deteriorated during kneading, as compared with high softening point isotropic pitch.

The high softening point isotropic pitch referred to in the present invention means
It is similar to mesophase pitch in that it has a high softening point and a low volatile content, but it contains almost no anisotropic structure. In this respect, although it is a hard pitch in terms of classification, it is obtained by performing a special treatment of the hard pitch, and such a pitch is usually referred to as “isotropic pitch with a high softening point” (hereinafter, “high softening point isotropic pitch”). It is a pitch widely known as a raw material of carbon fiber.

The high softening point isotropic pitch is 300 to 400 ° C. when a gas containing oxygen or ozone is blown into heavy oil or pitch of petroleum, or heavy oil or pitch of petroleum.
It is obtained by performing heat treatment at. As a property,
Softening point is 200 to 350 ° C., no optically anisotropic structure is contained, quinoline insoluble matter is 0 to 60% by weight, toluene insoluble matter is 20 to 80% by weight, fixed carbon is 60 to 95% by weight.
Is.

In recent years, this high softening point isotropic pitch has been used in a large amount and can be obtained at a relatively low cost.

As the raw material pitch of the carbon fiber, an anisotropic pitch can be mentioned in addition to the high softening point isotropic pitch, but it is unsuitable as a raw material for refractory material because the cost is significantly high in adjusting the properties. Is.

Table 1 shows general properties of the high softening point isotropic pitch, general-purpose hard pitch, and mesophase pitch.

[0020]

[Table 1] The softening point in the above measurement method was measured by the Mettler method, and the solvent analysis (QI, TI) and the fixed carbon were measured according to JIS K2425. Further, the amount of aliphatic carbon is determined by measurement of 13C-NMR spectrum in a molten state using a GX-270 spectrometer manufactured by JEOL Ltd., and the optically anisotropic structure is observed by a polarizing microscope of LEITZ Co., in area ratio. After the calculation, volume conversion was performed.

The high softening point isotropic pitch has a softening point of 200.
Although it is as high as ~ 350 ° C and the amount of fixed carbon is as high as 60 ~ 95% by weight, there is a large difference between the hard pitch and mesophase pitch in the properties of the quinoline insoluble component (hereinafter referred to as α component) contained in the pitch. . The α component of ordinary hard pitch or mesophase pitch includes solid components that do not soften and melt even when heat is applied, such as free carbon and coke, and these components are generally called non-sintered components. There is.

On the other hand, in the case of the high softening point isotropic pitch used in the present invention, the α component in the pitch does not include a solid component and is easily softened and melted by applying heat to form a sintered mixture. It acts as a minute. That is, due to such a difference in the properties of the α component, the isotropic pitch of the present invention is characterized in that all the components in the pitch are easily softened and melted by applying heat.

The reason why the high softening point isotropic pitch differs from a general-purpose hard pitch in terms of components and characteristics is as follows.

The high softening point isotropic pitch is obtained by removing solid components contained in coal tar, that is, non-sintered components insoluble in quinoline, and distilling light components in the process of refining pitch in the manufacturing process. After being removed by (1), a pitch containing oxygen and ozone is blown during the heat treatment, and the pitch is cross-linked and polymerized by the action of the blown oxygen and ozone. During this cross-linking polymerization, the aliphatic carbon component in the pitch,
That is, a methyl group, a naphthene group, a cross-linked methylene, etc.
Since it reacts with oxygen and is removed to the outside of the system, it can be said that the amount of aliphatic carbon in the pitch is smaller than that in normal hard pitch.

When such a high softening point isotropic pitch is added to a refractory material, the high softening point isotropic pitch improves the corrosion resistance as a carbon raw material and, in addition to hard pitch and mesophase pitch, all components are Since it softens and melts, the surface of the refractory aggregate can be uniformly covered, and the fixed carbon is high,
The α component, which is a quinoline-insoluble component, and the β component, which is soluble in quinoline and insoluble in toluene, both act as sintering components. For this reason, carbon bonds are easily formed, and the refractory after sintering has high strength.

Further, as compared with a pitch having a mesophase, a high softening point isotropic pitch is produced while blowing a gas containing oxygen or ozone, so that a component in the pitch which is easily affected by oxygen is a pitch. Since the amount decreases during production, the property becomes low in reactivity to the oxidation reaction. Therefore, when this high softening point isotropic pitch is applied as a casting repair material for an irregular shaped refractory, it has excellent oxidation resistance at high temperatures.

Further, the high softening point isotropic pitch and the mesophase pitch have the following differences at the time of transition from carbonaceous material to graphite material by heating.

When the mesophase pitch is heat-treated, it grows closer to a graphite structure due to the growth of aromatic planes and the development of two-dimensional regularity of plane stacking (called graphitizable carbon). On the other hand, in the high softening point isotropic pitch, the cross-linking structure of the pitch hinders the growth and stacking of the aromatic plane due to the heat treatment, and approaches the structure of glassy carbon (called non-graphitizable carbon).

That is, although there is no difference in that the high softening point isotropic pitch is carbonized from the solid phase once passing through the liquid phase when heated, it is a non-graphitizable carbon because the molecule is a cross-linking bond. Can be said to be a big difference from other pitches.

As described above, a mesophase pitch having an ordinary optically anisotropic structure is inferior in wear resistance because it has a structure similar to graphite when carbonized, but it has a high softening point isotropic property used in the present invention. Since the characteristic pitch is optically isotropic, it becomes a glassy carbon structure when carbonized, so that a refractory having excellent wear resistance can be obtained.

The high softening point isotropic pitch is superior in hydrophilicity to normal pitches and mesophase pitches because it has more hydroxyl groups, carboxylic groups, ether groups, etc. The liquidity is clearly improved by comparison.

The amount of dispersant used is within the customary range of use, for example 0.00 per 100 parts by weight of refractory aggregate.
It is 5 to 1% by weight. If it is less than 0.005% by weight, the effect is not sufficient, and if it exceeds 1% by weight, it is not improved and is industrially meaningless.

The high softening point isotropic pitch has an optically anisotropic structure of 0% by volume as shown in Table 1, but in the case of the present invention, it is not limited to this, and an optically anisotropic structure of 5% is obtained. It can be used without any problem as long as it is less than the volume. However, if the optically anisotropic structure exceeds 5% by volume, the workability is deteriorated like hard pitch and mesophase pitch.

Further, in order to make the high softening point isotropic pitch have a particle size of 2 mm or less, granulation may be carried out at the time of production, or coarse high softening point isotropic pitch may be milled, crusher, breaker or the like. The particle size may be adjusted using the crusher of No. 1. The reason why the particle size is limited to 2 mm or less is that if the particle size is 2 mm or more, the water-reducing effect of the addition of the high softening point isotropic pitch is not sufficient, and the peptization time during kneading becomes long and the workability is deteriorated. Furthermore, the high softening point isotropic pitch is not evenly dispersed in the matrix of the refractory molded body, and if the refractory is used at high temperature for a long period of time, the pitch is oxidized to form a relatively large cavity in the matrix and the structure deteriorates. Corrosion resistance decreases. Further, the addition amount is limited to 0.5 to 10% by weight, when the amount is less than 0.5% by weight, the effect of the addition is not sufficient, and when it exceeds 10% by weight, the particle size composition of the entire formulation is deteriorated. This is because the workability is remarkably lowered and the total volatile content is increased, so that the explosion resistance is lowered. Therefore, the addition amount is preferably 0.5 to 10% by weight, and preferably 0.5 to 5% by weight in view of workability.

Examples of the refractory aggregate used in the present invention include siliceous materials such as silica stone, silica sand, fused silica, hydrous amorphous silica, and anhydrous amorphous silica as a raw material containing oxides, mullite,
Bauxite, van shale, sillimanite, kyanite, sintered alumina, fused alumina, alumina such as calcined alumina, loastone, chamotte, porcelain stone, clay, kaolin, alumina-silica such as bentonite, zircon, Zirconia such as zirconia, electrofused magnesia, sintered magnesia, alumina-magnesia spinel, basic properties such as calcium oxide, spinel, chromium oxide, chrome such as chromite, etc. can be used. Carbides such as silicon carbide, aluminum carbide and zirconium carbide can be used as the carbide, and zirconium nitride, silicon nitride, iron iron nitride, boron nitride, aluminum nitride and the like can be used as the nitride.
As the raw material containing carbon, pitch powder such as coke, natural graphite, artificial graphite, calcined anthracite, hard pitch, mesophase pitch, and carbonaceous material such as carbon brick and electrode scrap can be used. Furthermore, it can be selected from the group consisting of all refractory raw materials such as boride such as boron carbide, silicide such as silicon and ferrosilicon, and if necessary, one kind or two or more kinds can be used in combination.

For the casting material of the present invention, the dispersant used for ordinary casting materials can be used. When a dispersant is used in combination, casting with a low water content is possible, and the characteristics of the amorphous refractory as a carbon raw material can be sufficiently exhibited. Examples of the dispersant include alkali metal phosphates, alkali metal carboxylates, alkali metal humates, polycarboxylates, alkyl sulfonates, aromatic sulfonates, alkali metal silicates and alkali metal carbonates. ,
Lignin sulfonate, sodium salt of anhydrous malein-isobutylene copolymer and ammonium salt thereof, and one or more kinds selected from substances having the same effects as these can be selected and used.

However, when the carbonaceous raw material is used in combination, the flowability of the castable refractory material is remarkably lowered as described above, and therefore the amount and method of use must be carefully considered.

The amorphous refractory material of the present invention further contains various metal fibers, organic fibers, inorganic fibers, metal powder, glass, etc. as antioxidants and strength imparting agents as additives for this type of refractory material for casting. Thickeners, setting regulators, defoaming agents, etc., which are commonly known as additives for mortar, may be added.

The irregular-shaped refractory applied to the present invention is based on the above-mentioned commonly used refractory aggregate, which is adjusted in particle size and added with a binder. It can be applied to a usual castable refractory made by adding one or more of a dispersant and a curing modifier.

As the liquid used at the time of kneading, in addition to water, an organic solvent, an inorganic solvent and an organic metal solvent can be used alone or in combination. In the case of the present invention, the liquid is 3 to 3
Suitable for 0 wt%, especially 3-10 wt% castable refractories. Of course, it is also effective for a so-called semi-wet type amorphous refractory containing about 0.5 to 3% by weight of liquid. That is, the amorphous refractory material of the present invention is not limited to castable refractory materials, and is similarly effective for baking materials, spraying materials, stamp materials, patching materials, and press-fitting materials. Furthermore, the amorphous refractory material of the present invention is not limited to lining furnace refractory materials such as blast furnaces, gutters, hot metal ladles, and mixed pig wheels, but also molten steel ladle, tundish, vacuum degassing furnace, gas blowing lance, electric furnace, transfer furnace. It can be applied as a refractory material for lining of furnaces or for repair.

[0041]

Function: 0.5 to 10 parts by weight of a high softening point isotropic pitch from which the non-sintered substance and other components contained in the pitch have been removed and a particle size of 2 mm or less is added, and a dispersant is added thereto. When used in combination, the fluidity of the castable is not lowered, and casting with a low water content is possible, which makes it possible to sufficiently exhibit the characteristics of the high softening point isotropic pitch.

[0042]

[Examples] Table 2 shows Comparative Example 1 in which the conventional carbon content is not added to the composition of the large gutter casting material for blast furnace, and Comparative Examples 2 to 7 in which hard pitch, mesophase pitch, pitch-coated graphite and hydrophilically treated pitch are added. The formulations of Examples 1 to 3 to which the high softening point isotropic pitch, which is the product of the present invention having the properties shown in Table 1, was added, and the added water content, fluidity and quality results are shown. In addition, the + mark in the table indicates the external weight%.

[0043]

[Table 2] All of these carbon components had a particle size of 2.0 mm or less, and the addition amount was unified to 3% by weight. Also, pitch-coated graphite has a graphite purity of 95 to 98% using medium pitch.
5% by weight and 15% by weight of the scaly graphite obtained in (1) and (2) were hot kneaded and crushed, respectively. As the hydrophilic treatment pitch, a hard pitch is subjected to hydrophilic treatment in advance using an anionic or nonionic surfactant, and is used as the hydrophilic treatment pitches a and b, respectively. The high softening point isotropic pitch was used for the three kinds of components A, B and C shown in Table 1. For the fluidity, the flow value of the kneaded product to which water was added was measured according to JIS R2512. If this value is 130 to 140 mm, it means that the steel is in a standard softness state according to JIS R2553, and that it is in a sufficiently castable state.

The quality sample after drying is 40 × 4 after kneading.
It was made by casting into a size of 0 × 160 mm, curing and deframed, and then drying at 110 ° C. × 24 hrs. The calcined sample was prepared by reducing and calcining 1500 ° C. × 3 hrs in a box containing coke breeze after drying. Here, the added water content and fluidity serve as a guideline for workability during construction,
Apparent porosity is a measure of the compactness of the construction body.

As for the oxidation resistance, a sample of 50φ × 50 mm was fired at 1000 ° C. for 3 hours, cut at the center, and the thickness (mm) of the decarburized layer was measured. The smaller this value is, the better the oxidation resistance is. In Comparative Example 1, since the central portion was oxidized, the total oxidation was performed.

In Comparative Example 1, the corrosion resistance index * 1 shows the hot metal resistance, and the corrosion resistance index * 2 shows the slag resistance.

From the results shown in Table 2, when the high softening point isotropic pitch is added, the added water content in the same fluidity becomes equal to or less than that in the case of no addition, the apparent porosity decreases and the structure becomes dense, Oxidation resistance and corrosion resistance are improved. Furthermore, it was confirmed that the drying and firing strength was improved as compared with other carbons.

Table 3 shows Comparative Example 8 in which the high softening point isotropic pitch used in the present invention for blending the large gutter casting material for blast furnace was adjusted to a particle diameter of 3 to 2.1 mm, and the particle diameter is 2 mm or less. Comparative Examples 9 and 10 added outside the specified range, Examples 4 to added within the specified range
6 shows the composition, added water content and quality.

[0049]

[Table 3] From the results in Table 3, in Comparative Example 8, the water-reducing effect of the high softening point isotropic pitch was not sufficient, the peptization time during kneading was long, and the fluidity of the compounded kneaded product was lowered. Furthermore, the quality is comparable to that of the hard pitch shown in Comparative Example 2 of Table 2, and the corrosion resistance is the same as that of Comparative Example 2 and is not improved.

In Comparative Example 9, a high softening point isotropic pitch was used, but the addition amount was small, so that the effect of improving the corrosion resistance as a carbon raw material could not be obtained. On the contrary, in Comparative Example 10, the addition amount was excessive, the particle size composition of the entire formulation was deteriorated, the workability was significantly reduced, and the added water was excessive and kneading was required, and the curing strength of the cast sample was reduced. And it was impossible to deframe. On the other hand, the quality of Examples 4 and 5 was about the same as the quality of Example 1. In Table 4, the pitch components are adjusted in advance so that the optically anisotropic structure is 1, 5, 6, 10% by volume and the rest is an isotropic structure, and the particle size is 2 mm or less, The following shows the composition and workability comparison when these are added to the composition of the gutter material for blast furnace as pitch D, pitch E, pitch F, and pitch G, respectively.

[0051]

[Table 4] From the results of Table 4, Examples 6 and 7 in which the pitch D and the pitch E in which the optically anisotropic structure is 1, 5% by volume are added are the results of Example 1 in which the high softening point isotropic pitch is used. Similarly, a water reducing effect was recognized, but in Comparative Examples 11 and 12 in which the pitch F and the pitch G in which the optically anisotropic structure was increased were added, the workability was decreased.

Examples 8 to 10 shown in Table 5 are 0.005, 0.5, and
It was set to 1.0% by weight. As a result, the fluidity after kneading was Comparative Example 1
The fluidity was improved in all cases as compared with the composition containing no high softening point isotropic pitch.

[0053]

[Table 5] On the other hand, in Comparative Examples 13 to 15, the addition amount of the dispersant was 0,
0.004 and 1.1% by weight, 0 and 0.0
In the case of 04% by weight, the addition amount of the dispersant was small, so that a sufficient effect was not obtained, and in the case of 1.1% by weight, the fluidity was rather lowered as compared with the case of adding 1.0% by weight.

Next, Table 6 shows a comparison of workability between the high softening point isotropic pitch and the hard pitch in the present invention in which the grain size is adjusted by using magnesia as an aggregate. From this result, in Example 11 using the high softening point isotropic pitch, the water reducing effect was recognized similarly to the result of Table 2 using the mixture of the gutter material.

Further, in Examples 12 and 13 in which a small amount of hard pitch or mesophase pitch was used in combination, the water reducing effect was recognized as in Example 11, but in Comparative Example 18 in which a large amount of hard pitch was used, the fluidity was lowered. .

[0056]

[Table 6] Table 7 shows the composition, the added water content and the quality of Comparative Examples 19 and 20 in which hard pitch was added to the composition for the spraying material and Examples 14 and 15 in which the high softening point isotropic pitch used in the present invention was added.
The adhesion rate is shown. The adhesion rate was 0.000 when heated to 1300 ° C.
Spraying was performed using a dry gun on a sprayed wall surface of 5 m ² magnesia-chromic brick, and the adhesion rate at this time was shown in wt%.

[0057]

[Table 7] As a result, in the case of the sprayed material, water is excessively added and used, so that the water reducing effect by using the high softening point isotropic pitch is difficult to confirm in Example 14, The firing strength at 1000 ° C. was improved. Furthermore, the rebound loss and runoff during spraying were reduced, and the adhesion rate was significantly improved compared to hard pitch.

Similarly, in Example 15, by using a high softening point isotropic pitch, carbon bond
The firing strength at 000 ° C was improved, and the rebound loss and flow-down during spraying were further reduced, and the adhesion rate was significantly improved compared to hard pitch.

The physical properties in the examples and comparative examples were measured by the following methods.

Bulk specific gravity, porosity ... JIS R2205-74 Compressive strength ... JIS R2206-77 Bending strength ... JIS R2213-78 Implementation of the present invention When Examples 1 and 2 were used as a metal zone material for blast furnace tap gutter, the maximum dissolution rate was 100
It becomes 5.5 to 6.0 mm per 0t, and Comparative Examples 1 and 2
Corrosion resistance was significantly improved as compared with 6.5 to 7.0 mm. As a result, the amount of gutter timber that can be fed is approximately 40,000 to 40,000 tons.
Since it has been improved to 1,000 tons, the durability of refractory materials has improved by more than 10%,
The effectiveness of the present invention was confirmed.

[0061]

INDUSTRIAL APPLICABILITY The amorphous refractory material of the present invention not only improves the workability of castable refractory materials, but also promotes the hot bonding of pitches and improves the strength of the refractory molded body by carbon bonding. In addition, the corrosion resistance and slag resistance of the refractory as a carbon raw material when added to the refractory are improved.

Claims (1)

[Claims] 1. A refractory aggregate having a softening point of 200 to 350.
° C, optically anisotropic structure 5% by volume or less, fixed carbon amount 6
A high softening point isotropic pitch carbon-containing amorphous refractory material containing 0 to 95% by weight and 0.5 to 10% by weight of a highly softening isotropic pitch having a particle diameter of 2 mm or less.