TITLE OF THE INVENTION
Aluminum oxycarbide composition and production method therefor
TECHNICAL FIELD
[0001]
The present invention relates to an aluminum oxycarbide composition usable as a ceramic
or refractory material, or a raw material therefor, and a production method for the aluminum
oxycarbide composition
BACKGROUND ART
[0002]
As an aluminum oxycarbide, the following two types Al2OC and Al4O4C, have been
known In particular, Al4O4C is stable at high temperatures and excellent in oxidation resistant,
corrosion resistance and thermal shock resistance, so that it is expected as a refractory or ceramic
material, or a raw material therefor Especially, Al4O4C is expected as a raw material for a
carbon-containing refractory material, such as an alumina-carbon based refractory material or a
magnesia-carbon based refractory material, used as a refractory material for use with molten
metal such as molten iron or steel
[0003]
As a production method for Al4O4C, a sintering process of heat-treating a carbon- raw
material and an alumina- raw material in a burning furnace, or a melting process of melting a
carbon- raw material and an alumina- raw material in an arc furnace, are being studied, although
they have not been put to practical use
[0004]
For example, as disclosed in the following Non-Patent Document 1, it has been
experimentally confirmed that Al4O4C is formed by heat-treating powdery alumina and powdery
graphite in an argon atmosphere This production method comprises adding ethanol to
alumina having a mean particle diameter of 0 1 µm and graphite reagent having a particle size of
45 µm or less, mixing them in an agate mortar, drying the obtained mixture, putting the dried

mixture in powder form (2g) into a graphite crucible, setting the crucible in an electric furnace,
forming a vacuum within the electric furnace, and then burning the mixture at 1700°C while
supplying argon gas into the electric furnace
[0005]
The Non-Patent Document 1 says that, in a test carried out under conditions that a mole
ratio C/Al2O3 is set to 0 5, 1 5, 2 and 3, when C/Al2O3 = 1 5, an amount of formation of Al4O4C
was maximized without forming Al2OC and Al4C3, and therefore the best blend ratio for
synthesis of Al4O4C is considered to be 1 5 However, it is mentioned that pure Al4O4C free of
Al2O3 and graphite was not obtained Further, a produced composition had a particle diameter
of about 10 to 100 µm [0006]
In the production method disclosed in the Non-Patent Document 1, it is assumed that the
formation of Al4O4C from a carbon- raw material and an alumina- raw material is progressed
according to chemical reactions expressed by the following Formulas (1) to (3)
2A12O3 (s) + 3C (s) = Al4O4C (s) + 2 CO (g) —- (1)
2Al2O3 (s) + 4CO (g) = Al4O4C (s) + 3 CO2 (g) -- (2)
CO(g) + C(g) = 2CO(g) --(3)
[0007]
However, it is mentioned that, when C/Al2O3 becomes greater than 1 5, Al4C3 is also
formed according to the following Formulas (4) and (5), and the formation of Al4C3 according to
the following Formulas (4) and (5) is facilitated along with an increase in heating time
Al4O4C (s) + 8CO (g) = A14C3 (S) + 6CO2 (g) —- (4)
Al4O4C (s) + 6C (s) = Al4C3 (S) + 4CO2 (g) —- (5)
[0008]
The following Patent Document 1 discloses a method of producing an aluminum
oxycarbide composition using an arc furnace In inventive examples disclosed in the Patent
Document 1, various coarse grain consisting primarily of alumina-aluminum oxycarbide and
having total carbon contents of 0 8 mass%, 1 11 mass%, 176 mass% and 2 13 mass%,
respectively, are obtained by adding carbon to 100 mass parts of Bayer process alumina, in

amounts of 2 5 mass parts, 5 0 mass parts, 10 0 mass parts and 12 5 mass parts, and melting the
obtained mixture in an arc furnace In a comparative example where carbon is added to 100
mass parts of Bayer process alumina, in an amount of 15 mass parts, a refractory aggregate
having a total carbon content of 3 10 mass% is obtained The Patent Document 1 says that a
refractory aggregate having a total carbon content of 3 0 mass% or more is not suitable as a
refractory raw material, because the aggregate is likely to form aluminum carbide (Al4C3) which
easily reacts with water It is also mentioned that, when the aggregate was applied to a
refractory material, hot bending strength was significantly and undesirably deteriorated
[0009]
The Non-Patent Document 2 discloses a technique of producing an aluminum oxycarbide
composition by a method similar to that in the Patent Document 1, wherein the aluminum
oxycarbide composition has an apparent porosity of 0 3 to 1 2%, an apparent specific gravity of
3 24 to 3 87, and an carbon content rate of 0 83 to 3 14 mass% It is mentioned that a sample
prepared in the Non-Patent Document 2 contains Al4C3, because it can react with water to
generate methane gas
[0010]
The following Patent Document 2 discloses a carbon-containing brick containing aluminum
oxycarbide, and the following Patent Document 3 discloses a monolithic refractory material
containing aluminum oxycarbide In the Patent Documents 2 and 3, it is mentioned that
aluminum oxycarbide is produced by heating a mixture of alumina and carbon under an argon
atmosphere or the like at 1400°C or more
LIST OF PRIOR ART DOCUMENTS
[PATENT DOCUMENTS]
[0011]
Patent Document 1 JP 57-061708B
Patent Document 2 JP 09-295857A
Patent Document 3 JP 09-295874A
[NON-PATENT DOCUMENTS]

[0012]
Non-Patent Document 1 REFRACTORIES, Vol 59, p 288, 2007
Non-Patent Document 2 REFRACTORIES, Vol 35, p 316, 1983
SUMMARY OF THE INVENTION
[PROBLEM TO BE SOLVED BY THE INVENTION]
[0013]
In the production method disclosed in the Non-Patent Document 1, the produced
composition is in the form of a powder having a particle diameter of 10 to 100 µm In other
words, this method is incapable of producing a dense and high-strength composition This
causes a problem that versatility as a raw material for refractory materials is limited
Specifically, the composition cannot be use as a raw material for a course particle fraction
having a particle diameter, for example, of 1 mm or more, so that it is impossible to sufficiently
bring out advantageous effects of Al4O4C, 1 e , low thermal expansion coefficient and excellent
corrosion resistance Moreover, the production under an argon atmosphere involves a problem
of poor productivity
[0014]
In the production method disclosed in the Patent Document 1, a refractory aggregate having
a total carbon content of 3 0 mass% or more is not suitable as a refractory raw material, because
it is likely to form Al4C3 which easily reacts with water This means that the production
method disclosed in the Patent Document 1 has a problem that Al4C3 is formed as a by-product
[0015]
In the production method disclosed in the Non-Patent Document 2, Al4C3 is also formed as
a by-product Moreover, although a theoretical formation rate of Al4O4C to be calculated from
a rate of raw materials used therein is 100%, it is actually 57% as calculated from C component
of the sample A-7 in the Table Thus, there is another problem of low yield of Al4O4C
[0016]
Even if Al4C3 is contained in a refractory material only in a small amount, it forms Al
(OH)3 through a hydration reaction, called "slaking", which gives rise to a phenomenon that a

microstructure of the refractory material breaks up Thus, in cases where the composition in the
Non-Patent Document 2 is used as a raw material for a refractory material, a microstructure of
the refractory material becomes brittle due to cracks, which causes a problem of significantly
lowed strength Specifically, there is a problem that Al4C3 develops a hydration reaction with
moisture in the air during storage of the refractory material, and thereby cracks occur in the
refractory material, resulting in deterioration of durability Particularly, it is often the case that
a refractory brick is stored in the air for several months, 1 e , is placed in an environment where
Al4C3 is more likely to undergo slaking, 1 e , react with moisture in the air, for a long period of
time Moreover, the composition in the Non-Patent Document 2 cannot be used for a
monolithic refractory material necessary to use water
[0017]
Production methods disclosed in the Patent Documents 2 and 3 are based on a sintering
process as with the production methods disclosed in the Non-Patent Document 1, so that thee is a
problem that a raw material having a dense microstructure and a large particle size cannot be
obtained
[0018]
It is therefore an object of the present invention to provide an aluminum oxycarbide
composition production method capable of increasing a yield of Al4O4C while reducing a content
rate of Al4C3 and achieving high productivity, and an aluminum oxycarbide composition
[0019]
It is difficult to isolate Al4O4C from a carbon- raw material and an alumina- raw material
used as raw materials in the production method of the present invention, or Al2OC, etc, as
by-products thereof Thus, in this specification, a material produced by the production method
of the present invention will be referred to as "aluminum oxycarbide composition"
[MEANS FOR SOLVING THE PROBLEM]
[0020]
Generally, in cases where a blend of raw materials is melted in an arc furnace, it is not
necessary to homogeneously mix the raw materials in advance. This is because the raw

materials are melted and fluidified in the arc furnace, and a strong convection occurs in the arc
furnace due to heating by an electrode, so that it is possible to obtain a sufficient stirring effect
However, through various researches for increasing the yield of Al4O4C while suppressing
formation of Al4C3, during production of Al4O4C in an arc furnace, the inventor of the present
invention has found that it is extremely effective to homogeneously mix raw materials used for
the production
[0021]
As for Al4O4C, it is considered that a carbon- raw material and an alumina- raw material are
melted while reacting with each other in accordance, primarily, with the following chemical
reaction formula 2Al2O3 + 3C = Al4O4C + 2 CO (Formula (1)) In other words, it is assumed
that a reaction between the carbon- raw material and the alumina- raw material occurs*even
before the melting The stirring effect based on the melting cannot be expected during the
pre-melting reaction In addition, an unreacted part of the carbon- raw material reacts with
formed Al4O4C to form Al4C3 Further, the carbon- raw material and the alumina- raw material
are largely different in specific gravity, and thereby it is quite difficult to homogeneously mix
them Therefore, the preliminary homogeneous mixing is extremely effective in increasing the
yield of Al4O4C while suppressing the formation of Al4C3
[0022]
As used in this specification, the term "homogeneously mixing (homogeneous mixing)"
means a state in which variation is significantly reduced when the mixture is sampled Ifi this
specification, an index of the homogeneous mixing is represented by a variation in C component
The term "variation in C component" means a ratio (%) of a difference between a specific one of
a plurality of analysis values, and a preset target value of the C component, to the preset target
value, wherein the plurality of analysis values are obtained by taking a sample three times from a
mixture of the carbon- raw material and the alumina- raw material, and analyzing respective C
components of the sampled mixtures, and the specific analysis value has the largest difference
with the preset target value In the present invention, the variation in C component is set to fall
within ± 10%, preferably within ± 5% In order to achieve the homogeneous mixing, it is
preferable to perform mixing using a commercially available powder mixer The term "preset

target value (%)" means (a ratio (%) of the carbon- raw material to the blend) x (a content rate
(%) of C component in the carbon- raw material), wherein the content rate (%) of the C
component in the carbon- raw material is a measurement value before the mixing
[0023]
The blend is prepared using fine raw material particles, so that the raw material particles
can be homogeneously dispersed This allows the carbon- raw material and the alumina- raw
material to efficiently react with each other in the arc furnace, which makes it possible to obtain
an aluminum oxycarbide having a high content rate of Al4O4C and containing almost no Al4C3
[0024]
Specifically, an aluminum oxycarbide composition production method of the present
invention comprises preparing a blend substantially consisting of a carbon- raw material having
a mean particle diameter of 0 5 mm or less and an alumina- raw material having a mean particle
diameter of 350 µm or less, wherein a mole ratio of the carbon- raw material to the alumina- raw
material (C/Al2O3) is in a range of 0 8 to 2 0, homogeneously mixing the blend to allow a
variation in C component to fall within ± 10%, and melting the obtained mixture in an arc
furnace at 1850°C or more
[0025]
As above, in the present invention, in order to increase the yield of Al4O4C while
suppressing the formation of Al4C3, the mean particle diameter of the carbon- raw material is set
to 0 5 mm or less, preferably, 200 µm or less If the mean particle diameter is greater than 0 5
mm, a homogeneous reaction with the alumina- raw material is less likely to occur, which causes
a reduction in yield of Al4O4C, and an increase in formation of Al4C3 Preferably, a lower limit
of the mean particle diameter of the carbon- raw material is set to 0 5um If the mean particle
diameter of the carbon- raw material is less than 0 5um, fine particles of the carbon- raw material
in the blend are kicked up during production, due to shock caused by electric discharge, etc , and
generation of CO gas in the course of formation of Al4O4C This worsens working
environment Moreover, if dust-collecting equipment, air ventilating equipment or the like, is
provided as working environment measures, a blend ratio of the carbon- raw material will be
changed, which is likely to cause a reduction in yield of Al4O4C

[0026]
A particle size of the alumina- raw material is set to 350 µm or less, preferably, 60 jam or
less, in terms of a mean particle diameter If the mean particle diameter is greater than 350 urn,
a homogeneous reaction with the carbon- raw material is less likely to occur, which causes a
reduction in yield of Al4O4C, and an increase in formation of Al4C3 Preferably, a lower limit
of the mean particle diameter of the alumina- raw material is set to 0 5um If the mean particle
diameter of the alumina- raw material is less than 0 5um, fine particles of the alumina- raw
material are kicked up during production, due to shock caused by electric discharge, etc, and
generation of CO gas in the course of formation of Al4O4C based on a reaction between Al2O3
and C This worsens working environment Moreover, if dust-collecting equipment, air
ventilating equipment or the like, is provided as working environment measures, a blend ratio of
*
the alumina- raw material will be changed Thus, if the amount of the carbon- raw material
becomes excessive, the formation of Al4C3 is likely to occur
[0027]
As used in this specification, the term "mean particle diameter" is a median size which
means a particle diameter at a mass percentage of 50% in a mass cumulative graph representing
a result of particle diameter measurement The particle diameter measurement may be
performed, for example, by sieving or laser diffractometry As used in this specification, the
term "mesh" as a unit of particle size means an opening size of each Tyler standard sieve For
example, the term "100 mesh or less" means sizes of particles which pass through the Tyler
standard sieve 100 Mesh
[0028]
In the present invention, a blend substantially consists of a carbon- raw material having a
mean particle diameter of 0 5 mm or less and an alumina- raw material having a mean particle
diameter of 350 µm or less The term "substantially" here means that a raw material other than
the carbon- raw material and the alumina- raw material may be used in combination according to
need as long as it does not have any adverse effect on the yield of Al4O4C, or that a binder may
be used when the blend is preliminarily pelletized However, it is preferable that the carbon-
raw material having a mean particle diameter of 0 5 mm or less and the alumina- raw material

having a mean particle diameter of 350 µm or less are included in the blend in a total amount of
95 mass% or more
[0029]
The carbon- raw material and the alumina- raw material are blended such that a mole ratio
of the carbon- raw material to the alumina- raw material (C/Al2O3) is in a range of 0 8 to 2 0 If
the mole ratio of the carbon- raw material to the alumina- raw material is less than 0 8, the yield
of Al4O4C becomes excessively low If the mole ratio is greater than 2 0, the formation of
Al4C3 is more likely to occur Further, in order to obtain an aluminum oxycarbide composition
having a high content rate of Al4O4C, it is preferable that the mole ratio of the carbon- raw
material to the alumina- raw material (C/Al2O3) is set in a range of 1 0 to 1 8
[0030]
Then, the blend of the carbon- raw material and the alumina- raw material is
homogeneously mixed and melted in an arc furnace In this manner, an aluminum oxycarbide
composition having a high content rate of Al4O4C and a low content rate of Al4C3 can be
obtained A melting temperature in the arc furnace is set to 1850°C or more which is greater
than a melting point of the Al4O4C
[0031]
In addition to the above production method, the present invention further provides an
aluminum oxycarbide composition produced using an arc furnace The aluminum oxycarbide
composition has a chemical composition consisting of 95 mass% or more of a total of C and
*
Al2O3, 45 mass% or more of Al4O4C as a mineral phase, and 10 mass% or less of other mineral
phase, with the remainder being corundum The aluminum oxycarbide composition has a
degradation rate of 3 mass% or less as measured in a magnesia clinker slaking test according to
the Gakushin-method 4
[0032]
The aluminum oxycarbide composition of the present invention is produced by melting a
starting raw material in an arc furnace As the starting material, a carbon- raw material and an
alumina- raw material may be used A resulting composition contains a mineral phase
primarily comprising Al4O4C and corundum, and has a chemical composition including 95

mass% or more of a total of C and Al2O3 As the chemical composition, although it is desirable
to set the total amount of C and Al2O3 to a higher value so as to obtain a higher content rate of
Al4O4C, impurities due to the starting raw material may be included in an amount of less than 5
mass%
[0033]
In the aluminum oxycarbide composition of the present invention, it is desirable to set the
content rate of Al4O4C to a higher value The content rate of Al4O4C is at least 45 mass%,
preferably, 70 mass% or more If the content rate is less than 45 mass%, for example, in cases
where the aluminum oxycarbide composition is used as a refractory material, an amount of the
aluminum oxycarbide composition to be added will be inevitably increased Thus, depending
on types of target refractory materials, a content rate of corundum as the remainder is increased,
so that the refractory material has a higher thermal expansion coefficient and a lower oxidation
*
resistance, resulting in limit to versatility of the aluminum oxycarbide composition Most of
the corundum as the remainder is a melt of the alumina- raw material used as the starting
material
[0034]
The "other mineral phase" is a mineral phase, for example, Al4C3, graphite, Al, AbOC,
AlON, and impurities in the starting material Although it is desirable to minimize the "other
mineral phase", the "other mineral phase" may be contained in a total amount of 10 mass% or
less, preferably, 2 mass% or less, to allow the aluminum oxycarbide composition to be used as a
raw material for refractory materials, without any problem
[0035]
It is also assumed that a small amount of Al4C3 is contained in the aluminum oxycarbide
composition, as a by-product However, Al4C3 originally has a small peak in X-ray
diffractometry, and thereby it is difficult to defect a small amount of Al4C3 For this reason, an
amount of Al4C3 is detected as a degradation rate as measured in a magnesia clinker slaking test
When the degradation rate as measured in the magnesia clinker slaking test is 3 mass% or less,
preferably, 1 mass% or less, the aluminum oxycarbide composition is considered to be at a level
usable as a raw material for refractory materials If the degradation rate is greater than 3

mass%, a problem, such as cracks in cases where the aluminum oxycarbide composition is used
as a refractory material, is more likely to occur An upper limit of the degradation rate is set
using the plate brick slaking test disclosed in WO 2009/119683A1 as one reference
[0036]
The aluminum oxycarbide composition of the present invention is melted once, so that it
has a dense microstructure having an extremely low porosity In particular, the aluminum
oxycarbide composition preferably has an apparent porosity of 3 5% or less If the apparent
porosity is greater than 3 5%, for example, in cases where the aluminum oxycarbide composition
is used as a raw material for refractory materials, deterioration in corrosion resistance, or
deterioration in strength and abrasion resistance, is likely to occur
[0037]
The aluminum oxycarbide composition of the present invention has a high content rate of
Al4O4C, and thereby an apparent specific gravity becomes smaller In particular, the aluminum
oxycarbide composition preferably has an apparent specific gravity of 3 20 or less In a
situation where the apparent specific gravity is greater than 3 20, corundum is contained in a
relatively large amount, so that the effects of Al4O4C are impaired
[0038]
In the aluminum oxycaroide composition of the present invention, a content rate of carbon
is preferably in a range of 2 5 to 5 5 mass%, more preferably in a range of 3 2 to 5 5 mass% If
the content rate of carbon is less than 2 5 mass%, the content rate of Al4O4C becomes smaller,
and the content rate of corundum as the remainder becomes excessively large, so that the
oxidation resistant, corrosion resistance and thermal shock resistance become insufficient If
the content rate of carbon is greater than 5 5 mass%, Al4C3 is contained, and thereby
deterioration in slaking resistance will occur
[0039]
The aluminum oxycarbide composition of the present invention has a high content rate of
Al4O4C and contains almost no Al4C3, so that it can be suitably used as a raw material for
carbon-containing refractory materials For example, the carbon-containing refractory
materials may include a magnesia carbon brick, an alumina carbon brick, a taphole mix, a

casting material, and a spraying material
[0040]
The aluminum oxycarbide composition of the present invention can be obtained by the
production method of the present invention
[EFFECT OF THE INVENTION]
[0041]
The production method of the present invention makes it possible to obtain an aluminum
oxycarbide composition having a high content rate of Al4O4C and a low content rate of Al4C3
In addition, the production method of the present invention employs a melting process using an
arc furnace, so that it becomes possible to perform mass production at low cost with high
productivity, and arbitrarily adjust a particle size of the aluminum oxycarbide composition by
adjusting conditions for pulverization after the melting This makes it possible to significantly
improve durability of a carbon-containing refractory material
[0042]
The aluminum oxycarbide composition of the present invention contains Al4O4C at a high
rate of 45 mass% or more, almost without containing Al4C3,1 e , without a problem of slaking,
so that it can be suitably used as a ceramic or refractory material, or as a raw material therefor
In addition, the aluminum oxycarbide composition of the present invention can be obtained by a
melting process using an arc furnace, so that it becomes possible to obtain a massive aluminum
oxycarbide composition having a dense micro structure, differently from an aluminum
oxycarbide composition obtained by a sintering process
DESCRIPTION OF EMBODIMENTS
[0043]
A carbon- raw material for use in the present invention may be one or more selected from
the group consisting of pitch, graphite, coke, carbon black and powdered organic resin, each of
which is commonly used as a raw material for refractory materials Among them, as graphite, it
is possible to use one or more selected from the group consisting of flaky graphite, earthy

(amorphous) graphite, expanded graphite and artificial graphite A content rate of carbon (C
content rate) of the carbon- raw material may be 90 mass% or more, preferably, 95 mass% or
more
[0044]
An alumina- raw material for use in the present invention may be one or more selected from
the group consisting of fused alumina, sintered alumina and calcinated alumina, each of which is
prepared by artificially refining natural bauxite or the like through a Bayer process or the like, to
allow an Al2O3 purity to become 95 mass% or more Further, it is possible to use China
bauxite, bauxite, clay and/or brick dust to an extent that an Al2O3 purity in the entire alumina-
raw material is preferably 90 mass% or more, more preferably, 95 mass% or more
[0045]
The carbon- raw material and the alumina- raw material are weighted and blended at a
given ratio, and the blend is homogeneously mixed before being put in an arc furnace • The
mixing may be performed using a mixer which is commonly used to mix a powder such as a
monolithic refractory material For example, it is possible to use a ball mill, a Henschel mixer,
a blade mixer, a Nauta mixer or a V-Cone mixer In order to homogeneously mix the blend of
the carbon- raw material and the alumina- raw material, it is preferable to mix the blend by a
mixer for 1 minute or more
[0046]
After the mixing or during the mixing, the blend may be subjected to pelletization (size
enlargement) The pelletization has an effect of enhancing efficiency of electric discharge in
the arc furnace and preventing dust generation Preferably, the pelletization is performed to
allow the blend to have a mean particle diameter of 0 1 to 5 mm Further, the mixture may be
formed into a rough block having a given size so as to prevent dust generation during melting
The blend may be subjected to pulverization during the mixing, or may be simultaneously
subjected to pulverization and pelletization during the mixing
[0047]
As the arc furnace, it is possible to use a type which is commonly used to melt magnesia,
alumina or the like so as to produce a refractory material In the arc furnace, the mixture of the

[
carbon- raw material and the alumina- raw material is melted Specifically, the mixture is
melted at a temperature of about 1850 to 2400°C After the melting, the molten mixture is
cooled and pulverized to obtain an aluminum oxycarbide composition
[0048]
The aluminum oxycarbide composition of the present invention is produced by a melting
process using an arc furnace, for example, in the above production method
[0049]
In the aluminum oxycarbide composition production method of the present invention, a
mole ratio of the carbon- raw material to the alumina- raw material (C/Al2O3) is controlled in a
range of 0 8 to 2 0 to allow a content rate of Al4O4C to be controlled When the mole ratio
(C/Al2O3) is set in a range of 1 5 to 2 0, the content rate of Al4O4C is maximized, and
simultaneously an apparent specific gravity is minimized Further, a starting raw material is
prepared to have a small particle size, and homogeneously mixed, so that formation of Al4Q3 can
be suppressed to increase a yield of Al4O4C, and a dense micro structure can be obtained to
reduce an apparent porosity
[0050]
In the aluminum oxycarbide composition obtained in the above manner, Al4O4C and Al2O3
(corundum) are observed as a mineral phase in X-ray diffractometry, and Al2O3 and C are
detected in chemical composition analysis
[0051]
The aluminum oxycarbide composition of the present invention contents Al4O4C at a high
rate almost without containing Al4C3,1 e , without a problem of slaking, so that it can be suitably
used as a ceramic or refractory material, or as a raw material therefor Particularly, the
aluminum oxycarbide composition of the present invention may be used for a carbon-containing
refractor material In this case, it becomes possible to improve oxidation resistant, corrosion
resistance and thermal shock resistance
[0052]
Resistance to slaking due to a hydration reaction is evaluated by a magnesia clinker slaking
test described in the Gakushin-method 4 Specifically, 50g of an aluminum oxycarbide

composition having adjusted to have a particle size of 1 mm to 3 36 mm is put in a 100 mL
beaker, and the beaker is placed within an autoclave under a condition that it is covered by a
watch glass so as to prevent water droplets from entering into the sample Then, the sample is
heated, and, after an internal pressure of the autoclave reaches 5 atm (152°C), held in the state
for 3 hours Then, the dried sample is subjected to sieving using 1 mm sieve to measure a
degradation rate using the following formula
Degradation rate (%) = [(pre-test mass of sample) - (post-test mass of oversize fraction
of sample, on sieve with 1 mm opening)] / pre-test mass of sample x 100
[0053]
The content rate of Al4O4C in the aluminum oxycarbide composition of the present
invention can be calculated according to the following calculation method
[0054]
It is assumed that C to be measured through the chemical composition analysis for the
aluminum oxycarbide composition obtained by the production method of the present invention
includes C components of Al4O4C, Al2OC, Al4C3 and free carbon Among them, the C
component of free carbon is actually seldom or never detected This would be because the C
component of free carbon is changed to Al4O4C, Al2OC or Al4C3 through reaction during
production
[0055]
If a content rate of Al2OC, Al or Al4C3 is 1 mass% or less, it is difficult to detect it by X-ray
analysis Further, Al and Al4C3 have slaking properties Thus, when Al and Al4C3 are not
detected in an aluminum oxycarbide composition by X-ray analysis, and a degradation rate of the
aluminum oxycarbide composition detected by the slaking test is 3 mass% or less, it is deemed
that Al and Al4C3 are not contained in the aluminum oxycarbide composition In Al4O4C, 5 56
mass% of C and 94 4 mass% of Al2O3 are measured as chemical composition analysis values
Thus, on an assumption that Al4O4C is contained in an amount of 100 mass% when C is
measured as 5 56 mass%, the content rate of Al4O4C is calculated from a C component analysis
value of an aluminum oxycarbide composition Further, a content of Al4O4C and a content of
corundum which is substantially an Al2O3 component, can also be quantified by an internal

reference method based on X-ray diffractometry
[EXAMPLES]
[0056]
Table 1 illustrates a verification result of an influence of the preliminary mixing of the
blend before being put into the arc furnace, on the yield (content rate) of Al4O4C
[0057]
Calcinated alumina and flaky graphite were weighted by a total amount of 10 kg and
blended at a ratio illustrated in Table 1 Then, the blend was mixed in a manner illustrated in
Table 1 The obtained mixture was put into an arc furnace and melted at about 2000°C to
produce an aluminum oxycarbide composition After cooling, a measurement sample was cut
out from the massive aluminum oxycarbide composition, or was obtained by pulverizing the
massive aluminum oxycarbide composition, to measure physical properties and chemical
properties
[0058]
As for purity of each raw material used in inventive samples and comparative samples,
calcinated alumina, fused alumina, artificial graphite, flaky graphite, pitch, carbon black, and
earthy graphite, were 99 9 mass% m terms of Al2O3, 99 mass% or more in terms of Al2O3, 99
mass% or more in terms of C, 99 mass% or more in terms of C, 99 mass% or more in terms of C,
99 9 mass% in terms of C, and 95 mass% or more in terms of C, respectively
[0059]
In order to evaluate homogeneity of the mixture, a variation in C component of the mixture
was checked The variation in C component is a ratio (%) of a difference between a specific
one of a plurality of analysis values, and a preset target value of the C component, to the preset
target value, wherein the plurality of analysis values are obtained by taking a sample three times
from the mixture and analyzing respective C components of the sampled mixtures, and the
specific analysis value has the largest difference with the preset target value, as mentioned
above Specifically, Variation in C component = (preset target value of C component - specific
analysis value having largest difference with preset target value of C component) / preset target

value of C component * 100 For example, in the inventive sample 1, the preset target value of
the C component was 14 99 mass%, whereas C components in the result of analysis on the three
sampled mixtures were 15 05 mass%, 15 04 mass% and 14 93 mass% Thus, the variation in C
component is calculated as follows (14 99 - 14 93) /14 99 * 100 = 0 40%
[0060]
The apparent porosity and the apparent specific gravity were measured according to
JIS-R2205 The chemical composition was measured according to JIS-R2212 and JIS-R2216
[0061]
As for the mineral phases, if a content rate of Al2OC, Al or Al4C3 is 1 mass% or less, it is
difficult to detect it by X-ray analysis Therefore, their contents were calculated based on
chemical composition analysis values Specifically, on an assumption that the entire C
component in the chemical composition analysis comes from Al4O4C, an amount of Al4O4C was
calculated Further, corundum was calculated on an assumption that a remaining part other
than Al4O4C is corundum For example, when the C component is 3 mass%, ALtO^C is
calculated as 3 0 / 5 56 * 100 = 54 0 (mass%), and corundum is calculated as 100 - 54 0 = 46 0
(mass%)
[0062]
As for the slaking resistance, a sample having a degradation rate of 3 mass% or less as
measured in the magnesia clinker slaking test according to the Gakushin-method 4 was evaluated
as GOOD (o), and a sample having a degradation rate of greater than 3 mass% was evaluated as
BAD (x)
[0063]
Further, as for a composition produced after the melting in the arc furnace, a mineral phase
was identified by X-ray diffractometry As a result, a major mineral phase was Al4O4C, and
Al2O3 (corundum) Respective content of Al4O4C and Al2O3 (corundum) were quantified by an
internal reference method based on X-ray diffractometry
[0064]
The inventive samples 1 to 3 were subjected to mixing using a V-Cone mixer for a given
period of time Table 1 shows that, as a mixing time becomes linger, the carbon- raw material

and the alumina- raw material more homogeneously reacts with each other to reduce a content
rate of corundum Table 1 also shows that, as the mixture is more homogeneously mixed, the
apparent specific gravity becomes smaller and the content rate of C component becomes larger
[0065]
On the other hand, due to insufficient mixing, the comparative sample 1 has a low yield
(content rate) of Al4O4C, and poor slaking resistance The comparative sample 2 which is not
subjected to mixing has a lower yield (content rate) of Al4O4C Moreover, it is assumed that a
large amount of Al4C3 is formed, and slaking resistance is actually deteriorated
[0066]
Table 2 illustrates a verification result of an influence of respective particle sizes of the
carbon- raw material and the alumina- raw material, on slaking resistance and the yield (content
rate) of Al4O4C The mixing of the carbon- raw material and the alumina- raw material was
performed in the same manner as that in the inventive sample 1 illustrated in Table 1
Aftermentioned samples illustrated in Tables 3 and 4 were also subjected to mixing in the .same
manner
[0067]
In the inventive samples 4 to 6, a particle size of a carbon- raw material (flaky graphite) is
changed within the range of the present invention Table 2 shows that, as the particle size of
the carbon- raw material (flaky graphite) becomes smaller, it become possible to obtain an
aluminum oxycarbide composition having a higher content rate of Al4O4C On the other hand,
in the comparative samples 3 to 5, a particle size of a carbon- raw material (artificial graphite) is
beyond the range of the present invention As a result, the content rate of Al4O4C is relatively
reduced, and the slaking resistance becomes insufficient due to a negative effect of the formation
of Al4C3 Further, it was found that, as the particle size of the carbon- raw material becomes
larger, the content rate of Al4O4C tends to be reduced Thus, it is assumed that, when the
particle size of the carbon- raw material becomes larger, a contact area with the alumina- raw
material becomes smaller, which causes deterioration in reactivity and occurrence of variation in
carbon concentration within the mixture, and thereby Al4C3 is formed in a region having an
excessively high carbon concentration

[0068]
In the inventive samples 6 to 8, a particle size of fused alumina is changed within the range
of the present invention Table 2 shows that, as the particle size of the fused alumina becomes
smaller, it become possible to obtain an aluminum oxycarbide composition having a higher
content rate of Al4O4C On the other hand, in the comparative samples 6 to 8, the particle size
of fused alumina is beyond the range of the present invention As a result, the content rate of
Al4O4C is relatively reduced, and the slaking resistance becomes insufficient Further, it was
found that, as the particle size of the fused alumina becomes larger, the content rate of Al4O4C
tends to be reduced Thus, as in the carbon- raw material, it is assumed that, when the particle
size of the aluminum- raw material becomes larger, a contact area with the carbon- raw material
becomes smaller, which causes occurrence of variation in alumina concentration within the
mixture, and thereby Al4C3 is formed in a region having an excessively high carbon
concentration
[0069]
*
In the inventive samples 9 to 12 in Table 3, the mole ratio of the carbon- raw material to the
alumina- raw material (C/Al2O3) is changed Each of the inventive samples 9 to 12 has a high
yield of Al4O4C, and excellent slaking resistance However, considering the application to a
refractory material, the inventive samples 10 to 12 are more preferable In the comparative
sample 9, the mole ratio is set to a low value of 0 4, and therefore an amount of formed Al4O4C
is small
[0070]
The inventive samples 13 to 18 in Table 4 are examples in which various raw materials are
used as the carbon- raw material and the alumina- raw material In each of inventive sarnples
13 to 18, an aluminum oxycarbide composition having excellent slaking resistance could be
obtained Carbon black used in the inventive sample 15 is a most fine carbon- raw material
However, the extremely fine carbon- raw material is oxidized by oxygen in the air, so that an
amount of formed Al4C3 (corundum) is increased
[0071]
In the inventive samples 7 and 18 in Table 4, an aluminum oxycarbide composition

prepared by mixing fused alumina having a particle size of 100 mesh and flaky graphite having a
particle size of 100 mesh by a V-Cone mixer for 5 minutes (inventive sample 7) was compared
with an aluminum oxycarbide composition prepared by, after the mixing, adding an aqueous
organic solvent to the mixture, and pelletizing it using a high-speed mixer (inventive sample 18)
Table 4 shows that the pelletization makes it possible to improve reactivity between the carbon-
raw material and the alumina- raw material, and therefore increase the yield of Al4O4C
[0072]
TABLE 1
[0073]
TABLE 2
[0074]
TABLE 3
[0075]
TABLE 4
i

WE CLAIM
A method of producing an aluminum oxycarbide composition, comprising
preparing a blend substantially consisting of a carbon- raw material having a
mean particle diameter of 0 5 mm or less and an alumina- raw material having a
mean particle diameter of 350 µm or less, wherein a mole ratio of the carbon-
raw material to the alumina- raw material (C/Al2O3) is in a range of 0 8 to 2 0,
homogeneously mixing the blend to allow a variation in C component to fall
within ± 10%, and melting the obtained mixture in an arc furnace at 1850°C or
more
2 The method as claimed in claim 1, wherein the mean particle diameter of
the carbon- raw material is in a range of 0 5 µm to 0 5 mm, and the mean
particle diameter of the alumina- raw material is in a range of 0 5 µm to 350 urn
3 The method as claimed in claim 1 or 2, wherein the mole ratio of the carbon-
raw material to the alumina- raw material (C/Al2O3) is in a range of 1 0 to 1 8
4 An aluminum oxycarbide composition produced using an arc furnace, which
has a chemical composition consisting of 95 mass% or more of a total of C and
Al2O3,45 mass% or more of Al4O4C as a mineral phase, and 10 rnass% or less

of other mineral phase, with the remainder being corundum, the aluminum
oxycarbide composition having a degradation rate of 3 mass% or less as
measured in a magnesia clinker slaking test according to the Gakushin-method
4
5 The aluminum oxycarbide composition as claimed in claim 4, which has an
apparent porosity of 3 5% or less
6 The aluminum oxycarbide composition as claimed in claim 4 or 5, which has
an apparent specific gravity of 3 20 or less, wherein C as the chemical
component is contained in an amount of 2 5 to 5 5 mass%

ABSTRACT

Title ALUMINUM OXYCARBIDE COMPOSITION AND PRODUCTION METHOD
THEREFOR
A method of producing an aluminum oxycarbide composition, comprising
preparing a blend substantially consisting of a carbon- raw material having a
mean particle diameter of 0 5 mm or less and an alumina- raw material having a
mean particle diameter of 350 µm or less, wherein a mole ratio of the carbon-
raw material to the alumina- raw material (C/Al2O3) is in a range of 0 8 to 2 0,
homogeneously mixing the blend to allow a variation in C component to fall
within ± 10%, and melting the obtained mixture in an arc furnace at 1850°C or
more