JPH0733512A - Carbon-containing refractory manufacturing method - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a method for producing a carbon-containing refractory material which is excellent in heat shock resistance, hot strength, oxidation resistance and corrosion resistance. [Composition] Magnesia-carbon refractory raw material or a mixture of magnesia-carbon refractory raw material to which Al or Al alloy fine particles are added, and a mixture of modified pitch powder and an aromatic compound is dried and pressure-molded. After that, it is fired in a non-oxidizing atmosphere.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a container for treating molten metal,
In particular, the present invention relates to a method for manufacturing a refractory material containing a carbon lining such as a converter.

[0002]

As a binder for carbon-containing refractory materials,
Phenolic resins have been used (for example, Japanese Patent Laid-Open No. Sho 5).
4-16161).

Further, in order to improve the thermal shock resistance of the carbon-containing refractory, a binder to which pitch and a phenol resin are added in combination is used (for example, JP-A-2-180).
753, JP-A-4-55361, JP-A-4-36755
6).

[0004]

When a phenolic resin is used as a binder, curing proceeds due to a polycondensation reaction of a functional group bonded to a benzene ring or a crosslinking reaction with an adjacent benzene ring due to addition of a curing agent. Develops strength.

However, when heated in a non-oxidizing atmosphere, thermal decomposition occurs from the binding site formed by polycondensation or cross-linking reaction, it becomes difficult for condensation between adjacent benzene rings to occur, and the yield remaining as carbon after heating is increased. Get lower.

As a result, the weight loss due to thermal decomposition causes
When a phenol resin is used as a binder for a carbon-containing refractory, the strength is reduced during hot working.

The pitch is composed of various compounds having different molecular weights such as aliphatic compounds and aromatic compounds.

Therefore, when heated in a non-oxidizing atmosphere, the low molecular weight compound contained in the pitch undergoes thermal decomposition, resulting in weight reduction.

As a result, when pitch is used as a binder for a carbon-containing refractory, the reduction in weight due to the thermal decomposition of the low molecular weight compound is large, so that the strength decreases during hot working.

In order to solve this problem, a metal has been added to improve the hot strength, but the thermal shock resistance is deteriorated.

The present invention has the advantages of thermal shock resistance, hot strength,
An object of the present invention is to provide a method for producing a carbon-containing refractory having excellent oxidation resistance and corrosion resistance.

[0012]

The present invention has been made to solve the above problems, and its gist is as follows.

(1) A mixture prepared by adding 2 to 15 wt% of modified pitch powder and an aromatic compound to 100 wt% of a refractory raw material composed of 5 to 30 wt% of carbon and 70 to 95 wt% of magnesia is used at 50 ° C. or above 100. The mixture is mixed at a temperature of not higher than 100 ° C and then dried at a temperature of higher than 100 ° C and lower than 300 ° C with stirring to form a mixed powder, which is then fired at a temperature of 500 ° C or higher and 1400 ° C or lower in a non-oxidizing atmosphere. A method for producing a carbon-containing refractory material characterized by the above.

(2) In addition to the modified pitch powder and aromatic compound of (1), 0.5 to 5.0 wt% of Al or Al
A method for producing a carbon-containing refractory material, characterized in that fine particles of an alloy are added.

(3) The modified pitch powder is a crystalline phase or a mixed phase consisting of a crystalline phase or an amorphous phase, and has a weight loss rate when fired at 800 ° C. in a non-oxidizing atmosphere. Is 30% or less, the carbon-containing refractory material according to 1 or 2 above.

(4) The method for producing a carbon-containing refractory material according to 1 or 2, wherein the amount of the aromatic compound added is 2 to 30 vol% with respect to 100 vol% of the bulk volume of the refractory raw material.

[0017]

The present invention will be described in detail below. The inventors of the present invention have an extremely low weight loss rate of 30% or less when the modified pitch is fired at 800 ° C. in a non-oxidizing atmosphere, as compared with the phenol resin and the pitch, and the aromatic compound. Focusing on the property that the wettability with and is very good, by adding the modified pitch powder and the aromatic compound to the magnesia-carbonaceous refractory, by further adding Al or Al alloy fine particles and firing, The present invention has been accomplished on the assumption that it is effective in improving thermal shock resistance, hot strength, oxidation resistance and corrosion resistance.

The carbon content is set to 5 to 30 wt% because it is excellent in thermal shock resistance and slag infiltration resistance.
This is because if the carbon content is less than 5 wt%, the thermal shock resistance and the slag infiltration resistance are poor, and if the carbon content exceeds 30 wt%, the oxidation resistance is significantly reduced.

As the carbon, natural or artificial graphite, anthracite, mesophase carbon, carbon black and the like can be used, and it is desirable that the purity is 90% or more and the particle size is 500 μm or less.

The magnesia content is set to 70 to 95 wt% because it is excellent in corrosion resistance and thermal shock resistance.

This is because if the magnesia is less than 70 wt%, the corrosion resistance is poor, and if the magnesia exceeds 95 wt%, the thermal shock resistance is poor.

As magnesia, either sintered products or electro-melted products can be used, and it is desirable that the purity is 95% or more and the particle size is 5 mm or less.

The amount of the modified pitch powder added is set to 2 to 15 wt% because it is excellent in hot strength, thermal shock resistance, oxidation resistance and corrosion resistance.

If the added amount of the modified pitch powder is less than 2 wt%, the hot strength, thermal shock resistance, oxidation resistance and corrosion resistance are poor, and if the added amount of the modified pitch exceeds 15 wt%, the refractory shrinks during firing. This causes cracking, resulting in poor strength.

The modified pitch powder preferably has a particle size of 44 μm or less. This is because if the particle size exceeds 44 μm, uniform mixing with the refractory raw material becomes difficult and the hot strength becomes poor.

The modified pitch powder used in the present invention is a crystalline phase or a mixed phase consisting of a crystalline phase or an amorphous phase, and has a reduced weight when fired at 800 ° C. in a non-oxidizing atmosphere. It is desirable that the rate is 30% or less.

The modified pitch powder was added to 80 in a non-oxidizing atmosphere.
If the weight loss rate exceeds 30% when fired at 0 ° C,
This is because the hot strength is poor.

Further, the crystalline content in the modified pitch powder is preferably 60% or more.

The crystalline content in the modified pitch powder is 60%
If it is less than the above range, the strength exhibited when used as a binder is poor.

The amount of fine particles of Al or Al alloy added is 0.5.
The reason why it is set to ˜5.0 wt% is that it is excellent in hot strength, corrosion resistance, and oxidation resistance.

The amount of fine particles of Al or Al alloy added is 0.5.
If it is less than wt%, the hot strength, corrosion resistance and oxidation resistance are poor,
This is because the thermal shock resistance is inferior when the addition amount of Al or Al alloy fine particles exceeds 3.0 wt%.

The grain size of Al or Al alloy is preferably 44 μm or less. However, it is desirable that the particle diameter of a material such as an Al—Mg alloy that spontaneously ignites when mixed in the atmosphere is 250 to 500 μm in order to prevent explosion.

The Al alloy used in the present invention is Al-
Mg, Al-Ca, Al-Si, Al-Mn, Al-F
It is desirable that the alloying elements for Al form oxides or carbides after firing in a non-oxidizing atmosphere, and the melting point of these compounds is high.

In the present invention, the mixing of the refractory raw material and the additive at a temperature of 50 ° C. or higher and 100 ° C. or lower promotes the dissolution of the modified pitch in the aromatic compound and allows the refractory raw material particles to be uniformly dispersed on the surface. This is to improve the sex.

When the heating temperature is lower than 50 ° C., the modified pitch does not dissolve in the aromatic compound and the uniform dispersibility is poor, and when the heating temperature exceeds 100 ° C., the aromatic compound evaporates and the uniform mixing is poor. is there.

To maintain the temperature at 50 ° C. or higher and 100 ° C. or lower, the kneading machine can be appropriately heated and controlled by, for example, electric heat, steam, gas or the like.

The drying of the mixture is carried out at a temperature higher than 100 ° C. and lower than 300 ° C. while stirring so that the boiling point of the aromatic compound is 1.
This is because the temperature is higher than 00 ° C and the segregation phenomenon during drying is prevented.

If the drying temperature is higher than 300 ° C., the modified pitch is softened and melted to form a strong agglomerate during drying, resulting in poor moldability. This is because if it is left to stand and dried, the uniform dispersibility of the modified pitch is poor due to the segregation phenomenon.

The atmosphere for firing the carbon-containing refractory is preferably a non-oxidizing atmosphere such as Ar, N ₂ , CO or CO ₂ . The atmosphere is made non-oxidizing in order to prevent the oxidation of graphite.

The firing temperature of the carbon-containing refractory is set to 500 ° C. or more and 1400 or less because the modified pitch is softened and melted at a temperature of 300 ° C. or more and semi-coke at a temperature of 500 ° C. or more. This is to prevent re-melting of.

If the firing temperature is less than 500 ° C., a creep phenomenon occurs during use, and the stability of the structure having a refractory lining cannot be ensured.

If the firing temperature exceeds 1400 ° C., the reaction between magnesia and carbon or magnesia and CO proceeds, and as a result, magnesia disappears and the refractory structure becomes weakened.

The aromatic compound used in the present invention is a carbocyclic compound having a benzene ring, which is a liquid at room temperature and has a boiling point of more than 100 ° C and less than 300 ° C. The case of using toluene as an example of the aromatic compound will be described.

The amount of toluene added was 10% by volume of the refractory raw material.
The reason why the content is 2 to 30 vol% with respect to 0 vol% is that it is excellent in uniform mixing and dispersibility of the modified pitch on the surface of the refractory raw material particles.

This is because if the addition amount of toluene is less than 2 vol%, the uniform mixing and the dispersibility of the modified pitch are poor, and if the addition amount of toluene exceeds 30 vol%, the uniform mixing is poor.

The modified pitch becomes a carbonized product having a layered structure with a highly developed carbon hexagonal net surface by heating in a non-oxidizing atmosphere, forming a strong carbon bond and comparing with a phenol resin or pitch. Since the rate of weight loss due to thermal decomposition is extremely low, when the modified pitch is used as the binder of the carbon-containing refractory, the strength is less decreased due to thermal decomposition and the hot strength is improved.

By adding the reformed pitch to the refractory raw material together with toluene and mixing them while heating at a temperature of 50 ° C. or higher and 100 ° C. or lower, it becomes possible to uniformly disperse the reformed pitch and to obtain hot strength. Bring about an improvement.

As described above, by using the modified pitch as the binder of the carbon-containing refractory, the hot strength of the carbon-containing refractory is improved, but the carbonized product of the modified pitch is higher than that of the phenolic resin. Has high thermal conductivity,
In addition, the thermal shock resistance is improved because a layered structure capable of relaxing the thermal stress generated by the thermal shock inside the carbon-containing refractory is provided.

Further, the carbon-containing refractory material of the present invention has oxidation resistance due to the following mechanism of added Al or Al alloy,
Brings strength improvement.

Since metal Al has a higher oxygen affinity than carbon in the temperature range of 600 ° C. or higher, it is more easily oxidized than carbon to Al ₂ O ₃ and prevents the oxidation of carbon.

The pores in the refractory structure are closed by the volume expansion when Al ₂ O _{3 is} formed, so that the inflow of the oxidizing gas into the refractory is suppressed and the oxidation resistance is improved.

Further, when firing in a non-oxidizing atmosphere or preheating the furnace, the metallic Al is converted into A by the reaction of the formula (1).
It generates a _{l 4 C 3, Al 2 O} 3 , and MgO · Al ₂ O _3, and accompanied by volume expansion at the time of generation.

[0053]

[Chemical formula 1] MgO + C + Al → MgO + C + Al ₄ C ₃ + Al ₂ O ₃ + MgO.Al ₂ O ₃ ... (1)

Due to this volume expansion, the pores in the refractory structure are closed, the structure is densified, and the strength is improved.

An Al--Mg alloy will be described as an example of the Al alloy. Al-Mg alloys, the 450 ° C. or higher temperature range is readily oxidized than carbon to oxygen affinity higher than carbon MgO, Al ₂ O ₃ and MgO · Al ₂ O ₃
And prevent carbon oxidation.

The volume expansion during the formation of Al ₂ O ₃ and MgO.Al ₂ O ₃ closes the pores in the refractory structure, thereby suppressing the inflow of oxidizing gas into the refractory and improving the oxidation resistance. Improve.

[0057] Also, preheating of firing or furnace in a non-oxidizing atmosphere, Al-Mg alloy during operation will produce an _{Al 4 C 3, Al 2 O} 3 and MgO · Al ₂ O ₃ by reaction (2) In addition, it is accompanied by volume expansion at the time of generation.

[0058]

Embedded image MgO + C + Al—Mg → MgO + C + Al ₄ C ₃ + Al ₂ O ₃ + MgO.Al ₂ O ₃ (2)

Due to this volume expansion, the pores in the refractory structure are closed and the structure is densified, and the strength is improved.

[0060]

EXAMPLES The present invention will be described below based on examples.

[0061]

Example 1 As a refractory lining for a molten metal processing container,
Table 1 shows an example of a method for producing a magnesia-carbonaceous refractory material to which the modified pitch of the present invention is added as a binder.

[0062]

[Table 1]

[0063]

[Table 2]

Electromagnetic fused magnesia was used as magnesia, and natural graphite was used as carbon. The modified pitch is prepared by subjecting coal tar pitch to heat treatment and solvent fractionation.
What was crushed to less than μm was used.

The presence or absence of the crystalline phase contained in the modified pitch was confirmed by X-ray diffraction.

The weight loss rate of the modified pitch was calculated from the weight change before and after firing at 800 ° C. in an Ar atmosphere.

The modified pitch and toluene were added to the raw material compositions shown in Table 1, and mixing was performed while heating the kneader at 80 ° C. by electric heating. Then 150 by electric heat
Drying was performed while raising the temperature to ℃ and mixing.

This mixture was molded by a vacuum friction press and fired under the conditions shown in Table 1 to obtain a magnesia-carbonaceous refractory material.

For comparison, Table 1 also shows the manufacturing conditions of the magnesia-carbonaceous refractory when a phenol resin is used as a binder.

The obtained magnesia-carbonaceous refractory material was subjected to bulk specific gravity, apparent porosity measurement, hot strength evaluation test, thermal shock resistance evaluation test, oxidation resistance test and corrosion resistance test.

The hot strength evaluation test was carried out at 1000 in Ar gas flow.
It was carried out by measuring the bending strength during hot at 1400C.

The thermal shock resistance test was conducted on molten steel at 1600 ° C.
After dipping for 0 second, water cooling was performed for 30 seconds, and then air cooling was repeated for 10 minutes to evaluate thermal shock resistance.

The thermal shock resistance was evaluated as follows: one in which the refractory was cracked in one thermal shock test was bad, and one in which the refractory was cracked in two to four repeated thermal shock tests was good. The case where the refractory did not crack in the thermal shock test was rated as excellent.

The oxidation resistance test was carried out by firing in air at a temperature of 1400 ° C. for 3 hours.

For the oxidation resistance index, the thickness of the decarburized layer after firing was measured, and the refractory to which the phenol resin was added was shown as 100.

The smaller the oxidation resistance index, the better the oxidation resistance. The corrosion resistance test was performed by a high frequency lining method at 1650 ° C. for 3 hours. The composition of slag is CaO / Si
O ₂ = 3.3, T. Fe = 18%.

The corrosion resistance index was measured by measuring the amount of erosion in the maximum erosion part after the erosion test, and measuring the refractory material containing the phenol resin as 1
It is shown as 00. The smaller the corrosion resistance index, the better the corrosion resistance.

The magnesia-carbonaceous refractory to which the modified pitch of the present invention was added as a binder was excellent in thermal shock resistance and excellent in hot strength, oxidation resistance and corrosion resistance.

On the other hand, in Comparative Example 5, since the addition amounts of carbon, modified pitch and toluene and the mixing temperature are not appropriate, the hot strength,
It was inferior in oxidation resistance and corrosion resistance.

Comparative Example 6 was inferior in hot strength, oxidation resistance, corrosion resistance and thermal shock resistance because the added amounts of magnesia, modified pitch and toluene were not proper.

Comparative Example 7 was inferior in hot strength, oxidation resistance and corrosion resistance because the weight reduction rate of the modified pitch used as the binder was large.

In Comparative Example 8, the refractory material after molding was processed in air at 800
Since it was fired at ℃, the apparent porosity became large, and the hot strength, oxidation resistance and corrosion resistance were poor.

Comparative Example 9 was inferior in hot strength, oxidation resistance and corrosion resistance because a phenol resin was used as a binder.

[0084]

Example 2 As a refractory lining for a molten metal processing container,
Table 2 shows an example of a method for producing a magnesia-carbonaceous refractory containing the metal and the modified pitch of the present invention as a binder.

[0085]

[Table 3]

[0086]

[Table 4]

[0087]

[Table 5]

[0088]

[Table 6]

Electro-fused magnesia was used as magnesia, and natural graphite was used as carbon. The modified pitch used was prepared under the same conditions as in Example 1.

The Al-Mg alloy has a component ratio of 1: 1 by weight.
1, the Al-Si alloy has a component ratio of 9:% by weight.
1 was used.

The modified pitch and toluene were added to the raw material compositions shown in Table 2 and mixed while heating to 80 ° C. by electric heating. After that, the temperature was raised to 150 ° C. by electric heating and drying was performed while mixing.

This mixture was molded by a vacuum friction press and fired under the conditions shown in Table 2 to obtain a magnesia-carbonaceous refractory material.

For comparison, Table 2 also shows the manufacturing conditions of the magnesia-carbonaceous refractory when a phenol resin is used as a binder.

With respect to the obtained magnesia-carbonaceous refractory material, measurement of bulk specific gravity and apparent porosity, hot strength evaluation test, thermal shock resistance evaluation test, oxidation resistance test and corrosion resistance test under the same conditions as in Example 1 Was carried out.

For the oxidation resistance, the thickness of the decarburized layer after firing was measured, and the refractory containing metal and phenol resin was added to 10 times.
The value is expressed as an index of 0, and the smaller the oxidation resistance index, the better.

The corrosion resistance was measured by measuring the amount of erosion at the maximum erosion part after the erosion test, and the refractory to which the metal and the phenol resin were added was expressed as an index, and the smaller the corrosion resistance index, the better.

The magnesia-carbonaceous refractory material containing the metal of the present invention and the modified pitch as a binder was excellent in thermal shock resistance and excellent in hot strength, oxidation resistance and corrosion resistance.

On the other hand, Comparative Example 16 was inferior in hot strength, oxidation resistance and corrosion resistance because the amounts of carbon, modified pitch, toluene and metal added and the mixing temperature were not proper.

Comparative Example 17 was inferior in hot strength, corrosion resistance and thermal shock resistance because the addition amounts of magnesia, metal, modified pitch and toluene and the mixing temperature were not proper.

Comparative Example 18 was inferior in hot strength, oxidation resistance, corrosion resistance and thermal shock resistance because the weight reduction rate of the modified pitch used as the binder was large. Comparative Example 19 had a large apparent porosity because the molded refractory was fired at 800 ° C. in air, and was inferior in hot strength, oxidation resistance, corrosion resistance and thermal shock resistance.

In Comparative 20, since the phenol resin was used as the binder, the hot strength, the oxidation resistance, the corrosion resistance and the thermal shock resistance were poor.

[0102]

Industrial Applicability According to the present invention, the thermal shock resistance, hot strength, oxidation resistance, and corrosion resistance are dramatically improved as compared with conventional phenol resins or carbon-containing refractories containing phenol resins and metals. It has become possible to extend body life and reduce furnace material costs.

Continued Front Page (72) Inventor Jun Nakao 20-1 Shintomi, Futtsu City Nippon Steel Corp. Technical Development Division

Claims (4)

[Claims] 1. Carbon 5 to 30 wt% and magnesia 7
A mixture obtained by adding 2 to 15 wt% of modified pitch powder and an aromatic compound to 100 wt% of a refractory raw material consisting of 0 to 95 wt% is mixed at a temperature of 50 ° C. or higher and 100 ° C. or lower, and then over 100 ° C. 300 A method for producing a carbon-containing refractory material, characterized in that the mixture is dried at a temperature of less than 0 ° C while stirring, the mixed powder is molded, and fired at a temperature of 500 ° C or more and 1400 ° C or less in a non-oxidizing atmosphere. . 2. A carbon-containing refractory product, characterized in that, in addition to the modified pitch powder and aromatic compound of claim 1, 0.5 to 5.0 wt% of Al or Al alloy fine particles are added. Method. 3. The modified pitch powder is a crystalline phase or a mixed phase composed of a crystalline phase or an amorphous phase, and has a weight loss rate when fired at 800 ° C. in a non-oxidizing atmosphere. The carbon-containing refractory material according to claim 1 or 2, which is 30% or less. 4. The method for producing a carbon-containing refractory material according to claim 1, wherein the amount of the aromatic compound added is 2 to 30 vol% with respect to 100 vol% of the bulk volume of the refractory raw material.