JPH04182347A - Production of carbon-containing calcined firebrick - Google Patents

Abstract

PURPOSE:To obtain a carbon-contg. calcined firebrick having superior oxidation and corrosion resistances and superior strength at high temp. by blending a specified carbon-contg. refractory compsn. with a thermosetting resin binder, molding the blend and calcining the molded body while regulating the temp. and atmosphere. CONSTITUTION:Starting material consisting of 11-23wt.% carbonaceous material such as natural graphite, 1-5 wt.% powder of one or more among Mg, Ca, Al-Mg, Ca-Si, Ca-Al and B4C each having >=90% purity and the balance basic refractory aggregate based on MgO, MgO-Al2O3 and/or MgO-CaO is prepd., blended with a thermosetting resin binder and molded. This molded body is calcined by heating to 200-600 deg.C under a reduced pressure of <=10Torr, further heating to 1,000 deg.C in an atmosphere contg. 17-25vol.% oxygen and furnace cooling to 200 deg.C in an inert gaseous atmosphere contg. <=0.1vol.% oxygen to obtain a carbon-contg. calcined firebrick.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing carbon-containing calcined refractory bricks suitable as linings for steelmaking furnaces (converters, electric furnaces, open hearths, various special steelmaking furnaces, etc.) in the steel manufacturing process. The refractory brick obtained by the present invention has particularly excellent oxidation resistance.

[Conventional technology]

The refractory brick lining of a steelmaking furnace is subject to mechanical wear, chemical erosion, and spalling (surface flaking) during steelmaking operations, so it is required to have high durability against these. Carbon-containing firebricks containing carbon materials such as artificial graphite are
The carbon material exhibits good spalling resistance due to its high thermal conductivity, and at the same time exhibits the advantageous property of being difficult to wet with molten metal and slag due to the characteristics of the carbon material. In addition, since the structure formed in bricks during firing or use forms carbon bonds, it has the property of preventing over-sintering of firebricks, and even when coexisting with other fireproof aggregates, they Because it complements the advantages of aggregate, it is widely used not only in steelmaking furnaces but also as a metallurgical refractory. However, carbon materials such as graphite easily oxidize in an oxidizing atmosphere and lose the above-mentioned properties. Therefore, in order to ensure that the characteristics of carbon-containing firebricks are exhibited, it is practically extremely important to minimize the oxidation of carbon materials such as graphite (that is, to make carbon-containing firebricks with excellent oxidation resistance). Important. In steelmaking furnaces, especially converters, MgO-C unfired carbon-containing refractory bricks, which have excellent corrosion resistance, have traditionally been used. However, with the recent development of hot metal pretreatment technology, converter furnaces The refining function of the refining system has changed from desulfurization and dephosphorization functions to simple decarburization and temperature adjustment functions.Such changes in functions reduce the erosion of refractory bricks due to slag, but on the other hand, secondary combustion Due to the increase in the ratio, the oxygen partial pressure inside the furnace increases and the oxidation of graphite in the bricks is promoted. Various attempts have been made, but not enough has been achieved due to insufficient elucidation of the phenomenon.For example, Japanese Patent Publication No. 433.12.1982, Japanese Patent Application Laid-Open No. 163913.1982, No. 55-65348, No. 55-107749, No. 56-5966
In Publication No. 8 and Publication No. 57-166362, Mg to which metal powder has a higher affinity for oxygen than carbon is added.
A 0-C carbon-containing unfired refractory brick composition is proposed. However, these methods only guarantee high corrosion resistance by improving hot strength due to the formation of carbides that occur in the brick during use, and as the phenomenon of the internal structure is not fully understood, it is recommended to use a lining that is suitable for the area where it will be used. It's not something you do. That is,
In the low-temperature region on the skin side of the lining furnace material, strength deterioration due to oxidation of the carbon material in the bricks is significant, often causing buckling and shortening the furnace life. Physical means have also been proposed in which carbon particles are coated with a glassy film of silicates, borates, phosphates, etc. to block contact with oxygen and carbon dioxide gas and prevent oxidation. Although it is effective in preventing oxidation in the low temperature range (500 to 600°C), it is completely insufficient in the high temperature range on the working surface side in contact with the molten metal, as it causes a loss of corrosion resistance.

[Problem to be solved by the invention]

The present inventors have added the various known metal powders mentioned above. IgO
In order to improve the oxidation resistance of -C-based carbon-containing unfired refractory bricks, we carried out laboratory tests, and also collected samples from the converter after it died and examined the changes in properties. As a result, it has been found that the following problems occur with conventional methods, especially in order to strengthen the oxidation-resistant function of Mg0-C refractory bricks for converter lining. 1) Conventional Mg0-C bricks are so-called unfired bricks (
(Simply kneaded raw materials with resin binder and molded)
Therefore, at the initial stage of heating and operation after construction of the furnace, gas containing lI20 is generated due to the thermal decomposition of the binder, and this permeates into the inside of the bricks, resulting in significantly large wear and tear during the initial stage of operation. 2) During operation, oxidation of the blended carbon material is suppressed on the inner working surface in contact with the molten metal due to the effect of adding metal powder. On the other hand, in the outer low-temperature region in contact with the steel shell, oxidation of the carbon material progresses due to the backflow phenomenon of the generated gas, causing a weathering phenomenon and making it easier to buckle. On the other hand, as another carbon-containing refractory brick, there is a fired brick used for immersion nozzles, typified by Al□03-C type. This does not include metal powder, and is fired in a non-oxidizing atmosphere after being formed using an isostatic press such as CIP or IIP, but firing conditions have not been established for carbon-containing refractory compositions with metal powder added. In addition, 31 is sometimes blended in the manufacturing process of Carpon Pronk, but this is a binder for the purpose of forming a silicon-containing connective tissue such as SiC or SiN, and cannot be a useful means for achieving the purpose of the present invention. . The present invention solves the above-mentioned problems with the conventional Mg0-C refractory bricks and uses a carbon base as a refractory brick, which has extremely excellent corrosion resistance, especially oxidation resistance in a low temperature range, and is suitable as the lining of an i-making furnace. The purpose is to provide a manufacturing method.

[Means to solve the problem]

In order to achieve the above object, the present inventors mainly focused on Mg0-
Regarding the oxidation behavior of C-type refractory bricks, we conducted experimental reproduction tests and investigated samples taken from actual furnaces, and as a result, we obtained the following knowledge. 0Mg, Ca, Ca-S
Adding powders of i, Ca-old, pre-Mg or B and C shows better oxidation resistance, and these latter added components become oxides after heat treatment (600-1400°C in 1 atmosphere), An oxide-based boundary layer was formed near the surface at the boundary between the undecarburized part and the decarburized part. ■This boundary layer has a width of 50 to 100 μm, and MgO
It had a dense structure that connected the aggregates. ■ Regarding the samples collected from the actual reactor, Mg, Ca,...
When the element distribution near the working surface of Mg0-C refractory bricks containing Ca-5i, Ca-Al, Al-Mg, or B and C was determined, the formation of a similar oxide-based boundary layer was observed. . Furthermore, the strength of the bricks containing these additive components was only slightly reduced, and the corrosion resistance was also good. However, a buckling phenomenon on the back side of the iron skin was observed in a low temperature range (estimated to be less than 1000°C). (2) A Mg0-C refractory brick containing the above additive components was calcined in an electric furnace. At that time, the inside of the furnace is degassed when the temperature rises from 100 to 600 degrees Celsius, air is introduced between 600 and 1000 degrees Celsius, and after maintaining the temperature for the required time, the atmosphere is replaced with an inert gas such as N2. When we observed a sample that had been cooled to room temperature, we found that a similar oxide-based boundary layer was formed. (2) As a result of an erosion experiment on the sample subjected to the above calcining treatment, the corrosion resistance was better than that of the untreated material. ■The state of formation of the above oxide boundary layer differed depending on the amount of carbon material blended in the brick. From the above, when an IgO-C refractory composition (with a composition adjusted to a specific range) is calcined under specific conditions as a pretreatment, an oxide boundary layer is formed near the surface. The layer acts as a barrier to block ventilation and suppresses the oxidation of carbon substances contained in the bricks inside.
It was found that the corrosion resistance and oxidation resistance of bricks were improved, and the present invention was completed. The gist of the present invention is that the carbonaceous material is 11 to 23% by weight,
・Hg powder, Ca powder, Al-Mg powder, C with purity of 90% or more
Contains 1 to 5% of one or more powders selected from a-5i powder, Ca-Al powder, and B4C powder, and the remainder is
After molding a carbon-containing refractory composition made by blending a thermosetting resin binder into a raw material consisting of a basic refractory aggregate mainly composed of MgO-ΔI2O3 and/or MgO-CaO, ■200'C to 600''C. Temperature range up to 10
Heating under reduced pressure of Torr or less, (2) further 100
Heating in the temperature range up to 0°C in an atmosphere with an oxygen partial pressure adjusted to 17 to 25 vol%, (3) then reducing the oxygen partial pressure to 0
．． A method for producing a carbon-containing calcined refractory brick, which is characterized by calcining by a step of furnace cooling to 200° C. in an inert gas atmosphere of 1 vol % or less. According to the present invention, in the Mg0-C-based refractory brick composition used in steelmaking furnaces such as converters, the surface of the brick is An oxide boundary layer is formed in the vicinity. Thereby, oxidative consumption can be prevented on both the inside and outside of the refractory lining layer of the converter, and the life of the converter is significantly improved.

[Effect]

The structure and operation of the present invention will be explained. In addition, in the following description, % is weight % unless otherwise specified. The raw materials for the refractory composition used in the present invention include basic refractory aggregate, carbon material, Mg, Ca, Al lag,
It contains at least one powder selected from Ca-5i, Ca-Al and B4C. Basic refractory aggregates include MgO (magnesia) and Mg0A.
1203 (spinel) and/or MgO-Ca
It is not particularly limited as long as it is mainly composed of 0 (dolomite). Preferably, the basic refractory aggregate consists of only one or more of these, but other aggregates (eg, magnesite) may be blended in an amount of about 5% or less. The average particle size of the basic refractory aggregate is 0.5 to 0.3 mm.
The degree is within an appropriate range, and it is not preferable that the maximum particle size exceeds 2 mm. If the particle size of the aggregate is too large, the surface condition of the bricks after the calcination treatment according to the present invention will inevitably become rough, resulting in loss of surface smoothness and poor furnace construction workability. The type of carbon material is not particularly limited, and natural graphite such as beaded graphite and flaky graphite, artificial graphite, electrode scrap, carbon black, quiche graphite, and various types of coke for steel manufacturing can be used, but natural graphite is used. This is desirable. The blending amount of the carbon material is within the range of 11 to 23%, preferably 13 to 20% of the total amount of the raw materials. Below 11%,
Although an oxide boundary layer is obtained after calcination, the spalling resistance is poor. If it exceeds 23%, the volume ratio to ml flint becomes too large, and the sealing effect expected of the boundary layer is impaired. Additive powders to be added to refractory aggregates to improve corrosion resistance include Ca, Mg alone or alloys containing these (At
-Mg, Ca-5i, Ca-81) powder and 84G
It has been found that powders (hereinafter collectively referred to as additive metal powders) act more effectively. One of these additive metal powders
One species or two or more species can be used. A1, S
i or Al-Si alloy is heat treated (calcined) in the present invention.
Due to the generation of microcracks due to abnormal expansion during the process, the above-mentioned sealing effect is insufficient and the corrosion resistance of the obtained calcined refractory brick is impaired. The amount of added metal powder is 1 to 5% of the total amount of raw material powder,
Desirably, a range of 2 to 4% is appropriate. If it is less than 1%, there is almost no effect of improving corrosion resistance, and if it exceeds 5%, the cutting and spalling properties will decrease rapidly. Further, the additive metal powder used has a purity of 90% or more. If the purity is less than 90%, durable lag erosion properties will be reduced. Note that the carbon material and the added metal powder react during the calcination process, so the particle size is not particularly limited, but if the particle size is too large, it will not be possible to obtain a uniform raw material mixture, and the calcination will take a long time. . In that sense, the average particle size of carbon materials is 1 mm or less,
The amount of added metal powder is preferably about 100 meshes or less. The remainder of the raw material consists essentially of the basic refractory aggregate described above. A carbon-containing refractory composition is obtained by adding a liquid resin binder to the raw material, which is a powder mixture of the three types of materials mentioned above, and kneading the mixture to bind the powder to a moldable extent. As the binder, any liquid thermosetting resin binder commonly used for unfired bricks can be used. A typical resin binder of this type is a phenol resin, and a phenol resin can also be suitably used in the present invention. The amount of the binder to be used is not particularly limited as long as it is the amount necessary to bind the raw material powder to a moldable extent. Generally, it will be in the range of 5 to 10 parts by weight per 100 parts by weight of the raw powder. When this unfired carbon-containing refractory composition is molded after kneading, it can be used as is as an unfired shaped brick. However, as mentioned above, by heat-treating and calcining this composition under specific conditions, calcined bricks with particularly excellent oxidation resistance can be obtained. It is preferable to use Molding is carried out using a standard method, with no deviations. For example, molding pressure 70
Unfired shaped bricks can be obtained by molding using a hydraulic press, vacuum friction press, etc. at a pressure of about 0 to 1000 kg/cm2. If desired, the molded body may be
The resin binder may be thermoset by heating to 0°C. According to the present invention, calcination after molding the refractory composition involves heating in a temperature range of 0200°C to 600°C for 10
(1) Heating in the temperature range up to 1000°C in an atmosphere with an oxygen partial pressure adjusted to 17 to 25 vol%; (3) After that, the oxygen partial pressure Q, l
It is carried out in three stages: furnace cooling to 200"C in an inert atmosphere of vol% or less. In this way, a feature of the present invention is that calcination is performed by limiting the oxygen partial pressure before and after calcination. That is, in step (2), the resin binder is sufficiently thermally cured, and its thermal decomposition is also completed to form carbon bonds in the brick structure.Thereafter, in step (2), heat treatment in an oxygen-containing atmosphere removes the additive metal. The powder is oxidized. This ensures the formation of the aforementioned oxide boundary layer near the surface of the brick. This boundary layer acts as a barrier to block air flow inside and outside the brick during use in an actual furnace. Suppresses the oxidation of the carbon material blended inside the brick. Cooling after replacing with inert scum in step ① prevents excessive oxidation after the required oxide boundary layer is formed by calcination. As the firing furnace used for this calcination, an electric furnace that can control the atmosphere can be used.
Use a furnace that can provide a degree of vacuum of 0 Torr or less. Therefore, furnaces with gas burners such as tunnel kilns,
It's not appropriate. The first stage of calcination means a temperature range of 200-600°C. During the temperature raising process to 200'C, evacuation to a vacuum level of 10 Torr or less is completed. After checking this exhaust,
1. The temperature is raised from 200° C. to 600° C. while maintaining a vacuum degree of OTorr or less to cause thermosetting, decomposition, and carbonization of the resin binder. The temperature increase rate at this time is 10°
f:/min or less is preferable. The heating rate is 10' (:/
If the temperature exceeds min, the temperature difference between the inside and the surface of the brick becomes large and cracks may occur. During this temperature rise, in order to quickly reduce the oxygen partial pressure, a carbon source such as coke powder may be placed on the bed, and an inert gas such as +12 gas may be filled in combination. The second stage of calcination is heat treatment in a temperature range of 600 to 1000°C. This heat treatment reduces Po2 to 17-25 vol%
It is carried out in an atmosphere adjusted to oxidize the added metal powder,
Forms an oxide boundary layer. Therefore, after the end of the first stage, preferably 0.5 to 1. The atmosphere is replaced with an oxidizing atmosphere having the above oxygen partial pressure within Ohr. For example, air and oxygen gas are blown into the furnace so that Po2 is in the range of 17 to 25 vol% as monitored by an oxygen partial pressure meter. The amount of gas blown depends on the volume of the furnace. When the replacement is completed, preferably 100
The temperature is raised to 1000° C. at a rate of less than° C./hr to advance melting and oxidation of the added metal powder. Po2 is 17 vol
If it is less than %, a boundary layer will not be sufficiently formed in the brick, resulting in a decrease in oxidation resistance. On the other hand, when Po2 exceeds 25 vol%, the inside of the brick deteriorates significantly. Temperature increase rate] At 00℃/hr or more,
Oxidation of the brick surface may be promoted and the decarburized layer may become too large. Further, in order to uniformly heat the brick surface layer and expose it to an atmosphere with the same oxygen partial pressure, it is preferable to stack the test bricks using tool bricks with a porosity of 80 to 90%. When the temperature reaches 1000°C, it is preferable to stop blowing in oxygen gas for soaking, and maintain the temperature at 1000°C for about 1 hour while Po2 is in the range of 10 to 20 vol%. The third stage of calcination means a cooling process from 1000°C. This cooling is performed in an inert gas atmosphere containing 0.1 vol % or less of PO2 to suppress excessive progress of oxidation during cooling. For example, after the temperature is maintained at 1000'C, the vacuum is immediately evacuated to a degree of vacuum of 10 Torr or less, and then
Inert gas such as N2 is filled in to exclude oxygen. Po
After confirming that 2 is 0.1 vol% or less, the furnace is cooled to 200'C. When the PO2 concentration in the furnace cooling atmosphere exceeds 0.1 vol%, oxidation progresses too much and spalling resistance decreases. The temperature decreasing rate at this time is 4°I
:/min or less is preferable. Thereafter, the furnace is opened and allowed to cool, yielding the desired carbon-containing calcined refractory brick. Note that the obtained refractory brick has a decarburized layer with a thickness of about 1 to 2 mm on the surface layer, and the surface is roughened. In particular, in order to improve the workability or joint sealing required during furnace construction, it is preferable to impregnate the bricks with wax, tar, pitch, or resin to improve the surface smoothness. This impregnation treatment can be carried out by soaking in a drain for a short time, but it is desirable to keep the water content in the impregnating liquid to 1% or less to suppress the hydration reaction during the heating process of the actual furnace. Furthermore, if the purpose is to prevent corner breakage, etc., application of the above liquid agent is sufficient.

【Example】

Hereinafter, the present invention will be specifically explained with reference to Examples. Actual picture I: A mixture of fused magnesia clinker and sintered magnesia clinker in a weight ratio of 1:1 was used as the basic refractory aggregate. To this aggregate sized to an average particle size of 0.8 mm, flaky graphite sized to an average particle size of 0.5 mm in the amount listed in Table 1 and a particle size of 150 mesh or less and a purity of 90% are added.
A raw material powder was prepared by blending the above Al-Mg powder. 45 to 6.5% of novolac type liquid phenolic resin was added to this raw material powder, and after kneading at a temperature of 50 to 80°C, it was molded into a sub-mold size using a hydraulic press at a pressure of 800 kg/cmZ. , an Mg0-C based unfired refractory composition was obtained. From this unfired molded brick, a diameter of 100 m
A cylinder with a length of 65 mm was sampled. For comparison, unfired molded bricks were similarly produced using Al-5i powder as the additive metal powder, and samples were obtained. This molded brick sample was calcined by the method of the present invention in a three-step heat treatment in an exhaust type electric furnace to obtain a calcined refractory brick sample. In this calcination step, nitrogen gas was used as an inert gas, the temperature increase rate from 200'C to 600°C was 4°C/min, and the pressure was about 10 Torr;
The temperature increase rate from °C to 1000 °C is 600 °C/hr, Po2
Approximately 21 vol%; Temperature holding time at 1000°C is 1
Time, Po2 approx. 17 vol%; 1000℃→200
Furnace cooling rate to ゛C is 4℃/min, POz 0.1
It was made vol% or less. Samples of the obtained calcined refractory bricks and unfired molded bricks were further heat treated to determine the decarburization status and strength. That is, P
1200° (
: After heat treatment for 3 hours, the thickness of the decarburized layer formed was determined, and a test piece with a diameter of 50 mm and a length of 50 mm was cut out from this sample and its compressive strength was determined. Figure 1 shows the measurement results of the thickness of the decarburized layer, and Figure 2 shows the results of the compressive strength test. The decarburization ratio shown in Figure 1 is
The thickness of the white change layer on the surface of the sample after heat treatment at 1200° C. is expressed as an index, and the worst result is set as 100 for comparison. This decarburization ratio indicates the degree of oxidation of carbon in the brick, and is a relative value with the result of 100. From the results shown in FIGS. 1 and 2, it is clear that the refractory bricks prepared by calcining the MgO-C refractory composition containing Al-Mg alloy powder by the method of the present invention have better strength and oxidation resistance than the comparative ones. It can be seen that it is significantly improved compared to . A mixture of fused magnesia clinker and sintered magnesia clinker with a blending weight ratio of 1:1 was used as basic refractory aggregate sized in the same manner as in Example 1, and 17% of flaky graphite was added to this.
And as additive metal powders, Ca-Al powder, Al-Mg powder, M
Add 3% of g powder, Ca-5i powder, or B, C powder,
It was made into a raw material powder. 7% of novolac type liquid phenol resin was added to this raw material powder, and after kneading with warm air at 50 to 80°C, it was molded into a sub-mold size with a pressure of 1000 kg/cm2 using a hydraulic press to form an MgO-C based fire-resistant composition. Manufactured unfired molded bricks. The calcination process was performed in three stages under the same conditions as in Example 1, and three molded bricks each were heat treated to obtain a decarburized layer thickness of 1.5 to 2.
A 2 mm test brick was obtained. A 15 mm cubic sample containing a decarburized layer on the working surface was cut out from the test brick, and a 30 mm x 140 mm diameter sample without a decarburized layer was cut out, and the samples were heated under a non-oxidizing atmosphere (Ar gas).
The three-point bending strength was measured at 1200°C. In addition, molten steel containing slag was placed in a crucible lined with a 15 mm thick brick sample containing a decarburized layer on the working surface, and slag erosion was performed for 1700'CX 1 hr in a high frequency induction furnace, and the amount of erosion of the brick was measured. . The amount of molten steel used in this test was 50 kg, the amount of slag was 2.5 kg, and the slag basicity (C/S) in the molten steel was 3. As a comparative material, calcined bricks containing Δ1 powder and S] powder were manufactured in the same manner and tested in the same manner. Also shown are the results for conventional bricks that were not subjected to calcining treatment. The test results are summarized in Table 2. Similar to Table 1, the values in Table 2 are relative values obtained by subtracting the value of the example showing the worst results (unfired brick with AI added) by 100. As is clear from the results shown in Table 2, in the Mg0-C based calcined bricks containing Kg-Ca or B according to the present invention, even when subjected to thermal history at 1200°C, the oxidation of the blended graphite is slight. It can be seen that stable and high strength is obtained. ! Table 2 Example 3 Based on the results of Example 2, Mg0-
C-type calcined bricks were manufactured and used in an actual furnace. The blending ratio and particle size of the raw material powder were the same as in Example 2, and 5% of Novolanc type liquid phenol resin was added to this raw material powder, which was kneaded with warm air, and converted into converter bricks with a length of 720 mm using a vacuum friction press. It was molded, calcined in the same manner as in Example 1, and coated with Wanx. The lined part is the straight body part on the trunnion side of the 250-ton converter. Conventionally, MgC1-C unfired bricks containing AI powder have been used. 60 from the 300th charge of furnace operation
When the wear condition up to the 0th charge was summarized, the amount of wear per charge was 0.8 mm in the conventional product, but as a result of using the product of the present invention, the amount of wear was reduced to 0.32 mm. Therefore, it is estimated that the reactor life can be more than doubled. This converter failed at 2,800 charges, but a disassembly investigation revealed that there was no buckling at all on the steel shell side of the product of the present invention.

【Effect of the invention】

The Mg0-C-based refractory composition and calcined refractory brick of the present invention have significantly improved oxidation resistance compared to conventional products, so they maintain stable strength at high temperatures and have good corrosion resistance. Therefore, by lining a steelmaking furnace such as a converter with this material, the life of the lining can be extended, and the overall economic effect on the industry is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the amount of decarburization after an oxidation test at 1200° C. of the present invention and comparative Mg0-C based unfired and calcined bricks containing various amounts of graphite as a carbon material;
and FIG. 2 is a graph showing the compressive strength of the brick after an oxidation test at 1200°C.

Claims (2)

[Claims] (1) Carbonaceous material 11-23% by weight and purity 90%
The above Mg powder, Ca powder, Al-Mg powder, Ca-Si powder,
Contains 1 to 5% of one or more powders selected from Ca-Al powder and B_4C powder, and the remainder is MgO and MgO-Al powder.
After molding a carbon-containing refractory composition in which a thermosetting resin binder is blended into a raw material consisting of a basic refractory aggregate mainly composed of _2O_3 and/or MgO-CaO, (1)2
Heating in the temperature range from 00°C to 600°C under reduced pressure of 10 Torr or less, (2) further heating in the temperature range up to 1000°C in an atmosphere with an oxygen partial pressure adjusted to 17 to 25 vol%, (3) A method for producing a carbon-containing calcined refractory brick, which is then calcined by a step of furnace cooling to 200° C. in an inert gas atmosphere with an oxygen partial pressure of 0.1 vol% or less. (2) After calcination, the resulting brick is coated or impregnated with wax, tar, pitch or resin;
The method according to claim 1.