JPH06287057A - Carbon-containing refractory - Google Patents

Abstract

PURPOSE:To obtain an inexpensive carbon-contg. refractory of prolonged working life, improved in resistance to corrosion, oxidation and mechanical impact and the suppression of joint wear, by incorporating a specified magnesia in a refractory stock comprising alumina, spinel, SiC and graphite. CONSTITUTION:(A) 100 pts.wt. of a refractory stock comprising (1) 30-60wt.% of fused alumina >=95% in purity, (2) 10-85wt.% of fused spinel >=95% in purity, (3) 2-10wt.% of a SiC (e.g. alpha-SiC) <=150mum in crystal grain diameter and >=90% in purity, and (4) 1-20wt.% of graphite (e.g. coke) >=90% in purity and <=500mum in particle diameter is incorporated with (B) 2-10 pts.wt. of fused magnesia >=95% in purity and <=74mum in particle diameter, (C) 2-10 pts.wt. of Al (alloy) and (D) 0.5-3 pts.wt. of glass powder <=150mum in particle diameter (e.g. phosphate glass). The resultant composition is then kneaded, molded, dried, and then cured, thus obtaining the objective carbon-contg. refractory.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a container for treating molten metal,
In particular, it relates to a refractory material containing carbon, which is lined in a hot metal pretreatment furnace.

[0002]

2. Description of the Related Art In a lining structure of a molten metal treatment container made of alumina-silicon carbide-carbonaceous refractory and mortar, the refractory is attached to the center of the joint where the mortar between adjacent refractories is applied. The joint is worn out in a pattern.

In order to suppress the joint damage, in addition to metal and glass, magnesia having a grain size of 0.2 mm or less and a grain size of 1 mm or less containing 10% or less of elevation is added to have residual expansion alumina-silicon carbide-carbon. A high-quality refractory is used (Japanese Patent Laid-Open No. 3-65556).

[0004]

However, in order to further improve the durability of the alumina-silicon carbide-carbonaceous refractory used as the lining refractory of the molten metal processing container, it is necessary to improve the corrosion resistance and to prevent joint wear. It is essential to control and improve mechanical shock resistance.

Metal, glass and magnesia have been added in combination in order to suppress the joint wear of refractory material, but the corrosion resistance and mechanical impact resistance have not been improved yet.

The present invention provides a carbon-containing refractory having excellent corrosion resistance and suppression of joint wear by adding spinel and magnesia to an alumina-silicon carbide-carbonaceous refractory, and spinel, magnesia, metal, It is to provide a carbon-containing refractory having excellent corrosion resistance, suppression of joint wear, oxidation resistance and mechanical shock resistance by adding glass together.

[0007]

The present invention is directed to alumina 30
~ 60 wt%, spinel 10-58 wt%, silicon carbide 2
It is a carbon-containing refractory characterized by adding 2 to 10 wt% of magnesia having a particle size of 74 μm or less to 100 wt% of a refractory raw material composed of 10 to 10 wt% and graphite of 10 to 20 wt%.

Further, the present invention relates to alumina 30-60w.
t%, spinel 10 to 58 wt%, silicon carbide 2 to 10 w
refractory raw material 10 consisting of t% and graphite 10 to 20 wt%
2% magnesia with a particle size of 74 μm or less against 0 wt%
It is a carbon-containing refractory characterized by adding 10 to 10 wt%, 2 to 10 wt% of Al or Al alloy, and 0.5 to 3 wt% of glass powder.

The content of alumina is set to 30 to 60 wt% because it is excellent in corrosion resistance and suppression of joint wear.

When the content of alumina is less than 30% by weight,
This is because the content of alumina in the refractory raw material is small, the amount of spinel produced accompanied by volume expansion due to the reaction with magnesia is small, and as a result, the residual expansion developed is small and the joint wear is poorly suppressed.

If the content of alumina exceeds 60 wt%, the content of spinel in the refractory raw material will be small and the corrosion resistance will be poor. As the alumina, an electro-melted product, a sintered product or the like can be used, but one having a purity of 95% or more is desirable.

The spinel content is set to 10 to 58 wt% because it is excellent in corrosion resistance and suppression of joint wear.

When the content of spinel is less than 10 wt%,
This is because the spinel content in the refractory raw material is small and the corrosion resistance is poor.

When the content of spinel exceeds 58 wt%, the content of alumina in the refractory raw material is small and the amount of spinel produced accompanied by volume expansion due to reaction with magnesia is small, resulting in small residual expansion. This is because the joint wear is poorly suppressed.

As the spinel, an electromelted product, a sintered product or the like can be used, but it is preferable that the purity is 95% or more.

The content of silicon carbide is set to 2 to 10 wt% because it is excellent in corrosion resistance and oxidation resistance.

This is because if the silicon carbide content is less than 2 wt%, the oxidation resistance will be poor, and if it exceeds 10 wt%, the corrosion resistance will be poor.

As the silicon carbide, it is desirable to use α-SiC and have a purity of 90% or more and a crystal grain size of 150 μm or less.

The graphite content is set to 10 to 20 wt% because it is excellent in slag infiltration resistance and thermal shock resistance.

This is because if the graphite content is less than 10 wt%, the slag infiltration resistance and thermal shock resistance are poor, and if it exceeds 20 wt%, the oxidation resistance is poor.

The graphite refers to natural or artificial graphite, messy phase carbon, coke, etc., and preferably has a purity of 90% or more and a particle size of 500 μm or less.

The particle size of magnesia used in the present invention is 74 μm.
The reason for setting m or less is that the reactivity with alumina is excellent and the filling property at the time of molding is excellent.

When the particle size of magnesia exceeds 74 μm,
This is because the reactivity with alumina is poor and the filling property during molding is poor.

The amount of magnesia added is set to 2 to 10 wt% because the volume expansion accompanied by spinel formation due to the reaction with alumina during use causes an appropriate residual expansion.
This is because it is excellent in suppressing joint wear.

If the amount of magnesia added is less than 2 wt%,
This is because the amount of spinel that accompanies volume expansion is small, and as a result, the residual expansion that occurs is small and the control of joint wear is poor.

When the amount of magnesia added exceeds 10 wt%, the amount of spinel produced accompanied by volume expansion increases, and as a result, the residual expansion that is manifested becomes too large and cracking occurs due to the shearing between adjacent refractories. This is because it is inferior in thermal shock resistance.

As magnesia, electro-melted products, sintered products and the like can be used, but those having a purity of 95% or more are desirable.

The amount of Al or Al alloy added is 2 to 10 w.
The reason for setting t% is that it is excellent in oxidation resistance and mechanical shock resistance.

If the added amount is less than 2 wt%, the oxidation resistance and mechanical shock resistance are poor, and if the added amount exceeds 10 wt%, the thermal shock resistance is poor.

The glass powder used in the present invention refers to borosilicate glass, phosphate glass, Li ₂ O-containing glass, etc.,
A particle size of 150 μm or less is desirable.

The glass powder is added in an amount of 0.5 to 3 wt% because it is excellent in oxidation resistance and thermal shock resistance.

If the added amount is less than 0.5 wt%, the oxidation resistance and thermal shock resistance are poor, and if the added amount exceeds 3 wt%, the corrosion resistance is poor.

[0033]

The carbon-containing refractory containing spinel and magnesia of the present invention has improved corrosion resistance due to the following mechanism.
Brings down joint wear.

In a molten metal treatment vessel lined with alumina-silicon carbide-carbonaceous refractory material, particularly in a hot metal pretreatment furnace, desiliconization, dephosphorization and desulfurization treatments have been carried out continuously.

When these hot metal pretreatments are continuously carried out,
The basicity of the generated slag ranges from about 1.0 to about 4.0 and ranges from low basicity to high basicity.

Spinel is superior to alumina in corrosion resistance to such slag having a wide range of basicity.

During use, magnesia reacts with the alumina in the refractory raw material to form spinel, which is more corrosion resistant than alumina.

This spinel formation reaction suppresses the infiltration of slag into the refractory by densifying the structure of the refractory with volume expansion. Due to such an action, the corrosion resistance of the refractory material is greatly improved.

Further, in the lining structure of the molten metal processing container made of alumina-silicon carbide-carbon refractory and mortar, the joint wear of the refractory occurs due to the following mechanism.

During use, a gap is formed between the refractory and the mortar due to the preceding erosion of the mortar between the adjacent refractories and the shrinkage of the refractory surface due to repeated heating and cooling of the refractory.

As a result, corrosion occurs due to corrosion from slag, erosion due to hot metal flow and oxidation from the corners of the refractory surface, and the refractory undergoes joint wear in the shape of a kamaboko.

However, the addition of magnesia causes residual expansion in the refractory material due to volume expansion accompanying spinel formation due to reaction with alumina during use.

As a result, the gap between the refractory material and the mortar generated during use is eliminated, the wear from the corner portion of the refractory material is suppressed, and the joint wear is also suppressed.

Further, the carbon-containing refractory material of the present invention improves the oxidation resistance and mechanical impact resistance by the following mechanism of the added Al or Al alloy and glass powder.

Here, metal Al and borosilicate glass will be described as an example. Since metal Al has a higher oxygen affinity than graphite in the temperature range of 600 ° C. or higher, it is more easily oxidized to graphite and becomes Al ₂ O ₃ to prevent graphite oxidation.

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.

Inside the refractory, metal Al reacts with Al ₄ C ₃ and Al ₂ O ₃ during preheating or operation of the furnace.
Is generated and is accompanied by volume expansion at the time of generation.

Due to this volume expansion, the pores in the refractory structure are closed and the structure is densified, so that the strength and elastic modulus are increased, and the mechanical shock resistance is improved.

Borosilicate glass is softened and melted in a temperature range of 800 ° C. or higher to coat carbon particles and close pores in the refractory structure, thereby improving oxidation resistance.

Further, by softening and melting in the temperature range of 800 ° C. or higher, the thermal stress generated in the refractory due to the temperature fluctuation is relaxed, thereby improving the thermal shock resistance.

[0051]

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

[0052]

Example 1 Al ₂ O ₃ --Si containing spinel and magnesia of the present invention as a refractory lining for a molten metal processing container
Table 1 shows examples of C-carbon refractories.

[0053]

[Table 1]

An appropriate amount of liquid phenolic binder was added to each of the raw material compositions shown in Table 1, and kneading, vacuum friction molding, drying (90 ° C. × 24 h), and curing treatment (2
50 ° C. × 10 h) was carried out to obtain an Al ₂ O ₃ —SiC—carbon refractory.

Here, alumina is electrofused alumina, spinel is electrofused spinel, and silicon carbide is α-.
SiC was used, graphite was 99% pure natural graphite, and magnesia was sintered magnesia.

In Table 1, the particle size of this embodiment is 74 μm.
The ones using the following magnesia are indicated as ◯.

The obtained Al ₂ O ₃ --SiC-carbon refractory material was subjected to bulk specific gravity, apparent porosity measurement, residual expansion evaluation test, and corrosion resistance test.

The residual expansivity evaluation test was carried out by heating in an Ar atmosphere under a load of 1 MPa at a temperature of 1400 ° C. for 3 hours. The residual expansion was evaluated from the linear change rate before and after the measurement.

The corrosion resistance test was conducted by alternately introducing desiliconization slag and dephosphorization slag by a high frequency lining method at 1600 ° C. for 3 hours every 15 minutes.

The composition of the slag is that the desiliconized slag is CaO / S.
iO ₂ = 0.8, T.I. Fe = 8%, dephosphorization slag is CaO
/ SiO ₂ = 3.1, CaF ₂ = 10%, T.I. Fe = 5%
Is.

The corrosion resistance index was determined by measuring the amount of erosion in the maximum erosion portion after the erosion test, and setting the refractories without addition of spinel and magnesia as 100. The smaller the corrosion resistance index, the better the corrosion resistance.

As a comprehensive judgment, the case where the residual expansion was 0.3% or more and the corrosion resistance index was 60 or less was marked with ◯, and the case where either the residual expansion or the corrosion resistance index did not satisfy the above criteria was marked with x.

As shown in Table 1, the Al ₂ O ₃ -SiC-carbon refractory material to which the spinel and magnesia of the present invention were added exhibited excellent residual expansion and excellent corrosion resistance.

On the other hand, Comparative Examples 5 and 8 showed residual shrinkage and were inferior in residual expansion and corrosion resistance because the amount of magnesia added was not an appropriate amount.

Comparative Examples 6 and 7 were excellent in either one of the residual expansion and the corrosion resistance, but were not excellent in the two characteristics of the residual expansion and the corrosion resistance.

In Table 1, the grain sizes of Comparative Examples 5 and 7 are 7
Good using magnesia of 4 μm or less, Comparative Example 7
The magnesia having a particle size of more than 74 μm was marked as ◯, and magnesia was not used in Comparative Example 8.

[0067]

[Example 2] Al ₂ O ₃ -Si containing spinel and magnesia of the present invention as a refractory lining for a molten metal processing container
Examples of C-carbon refractories are shown in Table 2.

[0068]

[Table 2]

[0069]

[Table 3]

An appropriate amount of liquid phenolic binder was added to each raw material composition shown in Table 2, kneading, vacuum friction molding, drying (90 ° C. × 24 h), and curing treatment (2
50 ° C. × 10 h) was carried out to obtain an Al ₂ O ₃ —SiC—carbon refractory.

Here, alumina is electrofused alumina, spinel is electrofused spinel, and silicon carbide is α-.
SiC was used, graphite was 99% pure natural graphite, and magnesia was sintered magnesia.

In Table 2, the particle size of this embodiment is 74 μm.
The ones using the following magnesia are indicated as ◯.

With respect to the obtained Al ₂ O ₃ --SiC--carbon refractory, the bulk specific gravity and the apparent porosity were measured, the residual expansion evaluation test and the corrosion resistance test were conducted under the same conditions as in Example 1, and the mechanical resistance The impact test, the oxidation resistance test, and the thermal shock resistance test were performed.

Here, the mechanical impact resistance test was carried out by measuring the bending strength at room temperature and hot (1400 ° C.).

The bending strength at room temperature was obtained by measuring the obtained Al ₂ O ₃
The SiC-carbon refractory was reduced and fired at a temperature of 1400 ° C. for measurement.

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 having no metal or glass added was set to 100. The smaller the oxidation resistance index, the better the oxidation resistance.

The thermal shock resistance test was conducted by using hot metal 90 at 1600 ° C.
After the second immersion, the sample was cooled with water for 30 seconds and then repeatedly cooled with air for 10 minutes to evaluate the thermal shock resistance.

The thermal shock resistance was evaluated as follows: one in which a crack was formed in the refractory in one thermal shock test was bad, and one in which a crack was formed in the refractory 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.

As a comprehensive evaluation, the residual expansion was 0.3% or more, the corrosion resistance index was 60 or less, and the mechanical shock resistance was room temperature, 1
Bending strength at 400 ° C is 150 (kg / cm ² ) or more,
Oxidation resistance index of 60 or less, excellent thermal shock resistance ○
The case where any one of the residual expansion, the corrosion resistance index, the mechanical shock resistance, the oxidation resistance index and the thermal shock resistance did not satisfy the above criteria was designated as x.

As shown in Table 2, the spinel, magnesia, metal and glass-added Al ₂ O ₃ --SiC-carbon refractory material of the present invention has excellent residual expansion and excellent corrosion resistance and mechanical shock resistance. It showed high resistance, oxidation resistance and thermal shock resistance.

On the other hand, Comparative Example 15 shows residual shrinkage due to a small addition amount of magnesia, is inferior in residual expansion, and has a low corrosion resistance due to a small addition amount of graphite, metal and glass.
It was inferior in mechanical shock resistance, oxidation resistance and thermal shock resistance.

Comparative Example 16 was considerably inferior in thermal shock resistance because the amounts of magnesia and metal added were large.

In Comparative Example 17, since the particle size of magnesia to be added exceeds 74 μm, the amount of spinel produced was small, and the residual expansion and corrosion resistance were poor.

Comparative Example 18 was inferior in residual expansion, corrosion resistance, oxidation resistance, mechanical shock resistance and thermal shock resistance because spinel, magnesia, metal and glass were not added.

In Table 2, those using magnesia having a particle size of 74 μm or less in Comparative Examples 15 and 16 are indicated as ◯, and those using magnesia having a particle size exceeding 74 μm in Comparative Example 17 are indicated as ◯, and in Comparative Example 18, No magnesia was used.

[0087]

INDUSTRIAL APPLICABILITY According to the present invention, the carbon-containing fire resistance having the conventional metal addition, metal / glass combination addition, or metal / glass / magnesia combination addition has the corrosion resistance, the suppression of joint wear, the oxidation resistance, and the mechanical shock resistance. The dramatic improvement of the product is extremely effective as it extends the life of the furnace body and reduces the cost of the furnace material.

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[Procedure amendment]

[Submission date] May 19, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

[0003] In order to suppress this joint loss millimeter, metal, following the addition to the particle size 0.2mm glass also for the addition of 1mm or less magnesia containing 10% or less, alumina having a residual expansion - silicon carbide - carbon A high-quality refractory is used (Japanese Patent Laid-Open No. 3-65556).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026] If the amount of magnesia is more than 10 wt%, becomes large spinel generation amount accompanied by volume expansion, its binding <br/> result, only expressed residual expansion is increased, parsley between the adjacent refractories The reason is that cracking due to cracking occurs and thermal shock resistance is poor.

Claims (2)

[Claims] 1. Alumina 30 to 60 wt%, spinel 1
0-58 wt%, silicon carbide 2-10 wt% and graphite 1
A carbon-containing refractory characterized by adding 2 to 10 wt% of magnesia having a particle size of 74 μm or less to 100 wt% of refractory raw material consisting of 0 to 20 wt%. 2. Alumina 30-60 wt%, spinel 1
0-58 wt%, silicon carbide 2-10 wt% and graphite 1
2 to 10 wt% of magnesia having a particle size of 74 μm or less with respect to 100 wt% of refractory raw material consisting of 0 to 20 wt%,
A carbon-containing refractory containing 2 to 10 wt% of Al or Al alloy and 0.5 to 3 wt% of glass powder.