JP2002362980A - Monolithic refractory containing carbon, and wet spraying method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monolithic refractory which has improved flowability, corrosion resistance and spalling resistance, does not cause the problem of explosive fracture at the time of drying, and exhibits excellent sticking property and adhesion when it is used as a wet-spraying material. SOLUTION: The monolithic refractory containing carbon is produced by using infusible mesophase pitch, which is obtained by heat treating mesophase pitch under an oxygen atmosphere so as to make it infusible and has an average diameter of <=10 μm. Further, it is possible to incorporate the mesophase pitch and/or pitch in an amount of <=5 mass %, and furthermore, it is possible to incorporate carbon black in an amount of not more than 5 mass %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon-containing irregular refractory used for lining or repairing various iron and steel making furnaces and the like, and a wet spraying method using the irregular refractory.

[0002]

2. Description of the Related Art As a refractory material, a carbon-containing refractory to which carbon such as pitch and graphite is added is known. The carbon-containing refractory has excellent effects on corrosion resistance and spalling resistance due to the high thermal conductivity of carbon and the property of being hardly wetted by slag.

[0003]

However, when a carbon material is applied to an irregular-shaped refractory, fluidity during construction is inferior due to the fact that carbon is hardly wetted by water. Therefore, it is necessary to increase the construction moisture to ensure fluidity,
To that extent, the porosity of the refractory structure increases and the strength decreases. In addition, the pores serve as an oxygen supply path to promote the oxidation of carbon, so that the properties of carbon cannot be fully utilized.

[0004] When pitch is used as a carbon material, when the amorphous refractory is heated during drying or the like, it is softened and melted, penetrates into the ventilation holes of the refractory structure, and reduces the permeability of the refractory structure during drying. Inhibit. As a result, the escape path of the water vapor is cut off during drying, and the vapor pressure causes a dry explosion.

In order to prevent carbon from wetting easily with water, Japanese Unexamined Patent Publication (Kokai) No. 63-215573 discloses a method in which graphite particles that are hardly wetted with water are coated with a pitch to prevent a decrease in the fluidity of an amorphous refractory. Proposed. However, since the pitch itself is hard to get wet with water, the effect is not sufficient.

Japanese Patent Application Laid-Open No. 7-17773 proposes the addition of carbon black for the purpose of improving corrosion resistance. However, if only carbon black is used as the carbon source, the refractory structure will have a low bulk specific gravity, and the strength of the refractory structure will decrease the physical impact resistance such as abrasion resistance to the molten metal flow due to the deterioration of the molten metal. I can't.

[0007] As a method of spraying an amorphous refractory, there is known a method of spraying an amorphous refractory kneaded by adding a working moisture while adding a quick-setting agent. Since the spraying is performed by adding the working moisture in advance, as a term for the dry spraying in which the working moisture is added near the nozzle tip to the dry powder and sprayed,
It is called wet spraying.

[0008] This wet spraying method does not require a formwork as in the case of pouring because it is sprayed, and there is no dust generation at the time of spraying because the amorphous refractory is previously kneaded. There are advantages.

[0009] However, the carbon-containing irregular shaped refractory also has problems in dryness, durability and the like in this wet spraying construction for the same reason as described above. Further, in the spraying construction, adhesiveness and adhesiveness are required for its properties, but these properties are not sufficient with conventional materials.

The present invention provides an amorphous refractory which has improved fluidity, corrosion resistance and spalling resistance, has no problem of dry explosion, and has excellent adhesion and adhesion when used as a wet spray material. Is what you do.

[0011]

The carbon-containing amorphous refractory of the present invention is characterized by using an infusible mesophase pitch having an average particle diameter of 10 μm or less, which is obtained by heat-treating mesophase pitch in an oxygen atmosphere. Is to do.

When a petroleum-based or coal-based pitch is heat-treated, free carbon and hydrocarbons are aggregated with an array to produce a liquid crystal having optical anisotropy. This is a sphere of several μm to several tens μm called a micro mesophase. When these are further heated, the fine spheres coalesce to form a mass called bulk mesophase (hereinafter, referred to as mesophase pitch).

The mesophase pitch thus obtained is
By self-sintering by heating to form a carbon bond, when added to a refractory, the refractory structure strength is improved.

The infusible mesophase pitch used in the present invention is obtained by further subjecting the above mesophase pitch to a heat treatment in an oxygen atmosphere such as in the air.

The infusible mesophase pitch has the effect of improving the strength of the amorphous refractory by forming a carbon bond in the refractory structure similarly to the mesophase pitch. In addition, due to the property of infusibility, it does not soften and melt, does not block pores of the refractory structure during drying of the amorphous refractory, and prevents the occurrence of dry explosion.

In the case of the mesophase pitch, a gas is generated by being heated when the amorphous refractory is used. However, the infusible mesophase pitch hardly generates a gas. In addition, since heat treatment is performed in advance in an oxygen atmosphere, the composition has excellent oxidation resistance. Due to these characteristics, the refractory structure becomes dense and high in strength, and the corrosion resistance is improved.

The infusibilized mesophase pitch used in the present invention is an ultrafine powder having an average particle size of 10 μm or less. Due to the bearing effect of the ultrafine powder, the fluidity during refractory construction is improved, and accordingly, the construction moisture can be reduced, and the refractory structure is further densified.

The infusibilized mesophase pitch is less likely to undergo an oxidation reaction, probably because the heat-treated in an oxygen atmosphere has reduced the components that are susceptible to oxygen. Therefore, the use of the infusibilized mesophase pitch is also effective in improving the oxidation resistance of the carbon-containing amorphous refractory.

In the present invention, the carbon source may be only the infusible mesophase pitch, but may be used in combination with the mesophase pitch (mesophase pitch not subjected to infusibilization treatment) and / or the pitch.

The infusibilized mesophase pitch does not exhibit carbon bonding unless the temperature becomes 600 ° C. or higher, at which it becomes graphitizable carbon. For this reason, the strength is inferior in an intermediate temperature range not reaching 600 ° C., and when used under a mechanical shock in this temperature range,
The strength of the refractory will be insufficient.

On the other hand, the mesophase pitch and / or
Alternatively, a carbon bonding structure is formed in a temperature range of 600 ° C. or less. As a result, in combination with the infusibilized mesophase pitch, the amorphous refractory can maintain high strength regardless of the intermediate temperature range or the high temperature range.

The carbon-containing amorphous refractory according to the present invention is applied by pouring or spraying, but when used for wet spraying, it exhibits excellent effects on adhesion and adhesion.

The infusibilized mesophase pitch has a higher oxygen content than the pitch or mesophase pitch, and has a high reactivity with the quick-setting additive added during spraying. In addition, since it is used with ultrafine powder, there is an effect of biting into the bonding surface.
Then, it is considered that the high reactivity with the quick-setting agent and the biting into the bonding surface act synergistically to improve the adhesiveness and the adhesiveness.

The high oxygen content of the infusibilized mesophase pitch is presumably due to the fact that oxygen in the heat treatment atmosphere reacts with the functional groups present in the pitch at the time of its production and oxygen is trapped in the mesophase pitch. It is.

As described above, infusible mesophase pitch is excellent in adhesion and adhesion in wet spraying, but on the other hand, tends to increase the pumping resistance of amorphous refractories in a material hose or at a material discharge port. This is considered to be because the infusibilized mesophase pitch was heat-treated in an oxygen atmosphere, resulting in a surface with large friction. If the refractory of the irregular-shaped refractory has a large pumping resistance, it is difficult to smoothly discharge the material from a material discharge port such as a nozzle, and the spraying efficiency is impaired.

The carbon-containing irregular-shaped refractory of the present invention can solve the problem of the pumping resistance in spraying work by further combining carbon black. This is considered to be due to the fact that the carbon black is spherical and ultra-fine powder, which reduces the pumping resistance due to its sliding action and the effect of reducing the specific gravity of the amorphous refractory kneaded material.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The infusible mesophase pitch used in the present invention is obtained, for example, by subjecting a micro mesophase obtained by further heat treatment to a finer mesophase obtained by pulverization or the like, followed by heat treatment in an oxidizing atmosphere. Manufactured. A method is known in which coal tar is obtained by heat treatment, and micro mesophase is extracted by centrifugation or the like and oxidized and heat-treated.However, the former is manufactured through bulk mesophase from the viewpoint of productivity. Use is preferred.

The treatment in the atmosphere is sufficient for the oxidizing atmosphere. The heat treatment temperature is, for example, 250 to 300 ° C. The particle size of the ultrafine powder is adjusted using a micron separator or the like. The infusibilized mesophase pitch used in the present invention has been conventionally used as a negative electrode raw material for a lithium battery, and is also available from commercial products.

The average particle size of the infusible mesophase pitch is 1
0 μm or less. More preferably, the average is 7 μm or less. The maximum particle size is not limited, but may be 30 μm
The following is preferred.

The infusibility of the pitch is specified, for example, in accordance with “ASTM D3104” of the American Society for Testing and Materials, 37
It can be performed by measuring the softening point up to 5 ° C.
The average particle size can be specified by, for example, measurement using a scattering type particle size distribution meter.

The proportion of the infusible mesophase pitch used is as follows:
The content is set to 1 to 10% by mass in the refractory aggregate. If it is less than 1% by mass, the effect of improving corrosion resistance cannot be obtained. Amorphous refractories have poor adhesion and adhesion when used in spray construction. When the content exceeds 10% by mass, the particle size composition of the entire amorphous refractory becomes excessively fine and the strength is reduced. Also, 10
If the amount is more than 10% by mass, the viscosity of the amorphous refractory after kneading increases, and the filling property or the fluidity decreases. The infusibilized mesophase pitch is higher in cost than a normal pitch, and preferably 1 to 7% by mass in view of economy.

When a mesophase pitch and / or a pitch are used together, the proportion is 5% by mass or less. More preferably, it is 1 to 5% by mass. If it is less than 1% by mass, the strength after drying in a low temperature range is inferior. If it exceeds 5% by mass, the fluidity during construction of the irregular-shaped refractory decreases.

Further, the average grain size 1 defined by the present invention is as follows.
Combinations of infusible mesophase pitches greater than 0 μm can also be used, in which case the average grain size is 10 μm.
It is necessary to make the total amount with the following infusible mesophase pitch 7% by mass or less.

The combined use of carbon black has the effect of reducing the pressure resistance of irregular shaped refractories during spraying.
The proportion is set to 5% by mass or less, more preferably 1 to 5%.
% By mass. When the amount is less than 1% by mass, the effect of reducing the pumping resistance is poor. When the amount exceeds 5% by mass, the particle size balance of the entire amorphous refractory deteriorates, and the fluidity at the time of applying the irregular refractory decreases.

Specific examples of the refractory aggregate other than the pitches described above are not particularly limited. Examples thereof include electrofused or sintered alumina, mullite, synthetic mullite, mullite alumina, magnesia-lime, magnesia, spinel, spinel, zirconia, zirconia-mullite, and the like. Also, bauxite, sillimanite, andalusite, kyanite, ban earth shale, chamotte, rubble and the like. Further, these are used in combination with fused silica, calcined alumina, ultrafine silica, zircon, chromite, silicon carbide, silicon nitride, natural graphite, artificial graphite, anthracite and the like.

The use of binders, dispersants and the like is not particularly different from conventional materials. As the binder, for example, a cement such as alumina cement or Portland cement, or a magnesia-silica hydraulic composition is added in an amount of about 1 to 10% by mass relative to 100% by mass of the refractory aggregate.

Examples of the dispersant include condensed phosphoric acid, polyacrylic acid, polycarboxylic acid, phosphonic acid, humic acid,
One or more of alkyl sulfonic acid, aromatic sulfonic acid, and the like, or a substance having the same effect as those described above can be selected and used. The ratio is preferably about 0.005 to 1% by mass with respect to 100% by mass of the refractory aggregate.

For the purpose of preventing carbon oxidation and improving the strength of the refractory structure, aluminum, aluminum-silicon alloy,
Metal components such as aluminum-magnesium alloy, aluminum-silicon-magnesium alloy, silicon, magnesium, etc., carbides such as boron carbide, borides such as zirconium boride, and glass components such as borosilicate glass are reduced to 100% by mass of fire-resistant aggregate. On the other hand, it can be added up to about 5% by mass.

If necessary, metal fiber,
Fibers such as organic fibers and inorganic fibers, or thickeners such as clay, bentonite, and CMC, as well as setting regulators, defoamers, and refractory coarse particles may be added.

The refractory coarse particles have an effect of imparting spalling resistance. The material is, for example, alumina, spinel, silicon carbide or a refractory waste material containing these as main materials. The particle size is, for example, 10 to 40 mm. The ratio is preferably 1 to 30% by mass with respect to 100% by weight of the refractory aggregate.

In the kneading of the present invention, sufficient fluidity can be obtained when the water used in the kneading is 4 to 10% by mass based on the total amount of the amorphous refractory composition. However, when the kneaded material is fed over a long distance or at a high place, the liquid content may be further increased by about 1 to 5% by mass.

When the amorphous refractory of the present invention is applied by wet spraying, a commonly used sodium silicate solution, for example, SiO ₂ / Na equivalent to JIS No. 1 is used as a quick setting agent. ₂ O molar ratio = 2.1 to 2.3, JIS
- corresponding to the No. 2 _SiO 2 / Na ₂ O molar ratio = 2.4 to
2.6, SiO ₂ / Na ₂ O molar ratio = 3.1-3.3 corresponding to JIS No. 3, or potassium silicate solution, aluminate aqueous solution, chloride aqueous solution and the like can be used. In addition, from the viewpoint of mixing with an amorphous refractory, it is preferable to use a quick-setting agent whose viscosity is adjusted to 50 mPa · sec (25 ° C.) or less.

FIG. 1 shows an example of a spraying apparatus used for wet spraying of an amorphous refractory according to the present invention. Its function is to transport an irregular-shaped refractory kneaded with construction moisture from a pressure pump 1 to a spray nozzle 3 via a material hose 2. On the other hand, the quick-setting agent is added to the irregular refractory in the nozzle from the quick-setting agent pump 4 connected to the compressor 7 via the air hose 6 via the quick-setting agent hose 5. As a result, the preliminarily kneaded amorphous refractory is sprayed while the quick-setting agent is added in the nozzle.

[0044]

EXAMPLES The present invention and comparative examples are shown below. Table 1 shows infusible mesophase pitch, mesophase pitch (not infusibilized), and characteristic values of pitch used in each example. Here, the infusibilized mesophase pitch is infusible by heat treatment at a temperature of 250 to 300 ° C. in the air.

[0045]

[Table 1] The infusible mesophase pitch A having an average particle size of 3 μm among the infusible mesophase pitch is “Product code: MPM-BL4” manufactured by Adchemco.

The average particle size was measured using a scattering type particle size distribution meter LSM-30 manufactured by Seishin Enterprise Co., Ltd. The oxygen content was measured by a method according to the pyrolysis gas chromatography method JIS M8813.

The softening point was measured according to ASTM D3104, and the fixed carbon was measured according to JIS K2425. Since none of the infusibilized mesophase pitches softened, it is displayed as unmeasurable here.

As the carbon black, a fine thermal grade produced by a thermal method was used.

Table 2 shows Examples of the present invention, and Table 3 shows Comparative Examples. Each table also shows the test results. In each case, magnesia was used as the main aggregate. The maximum particle size of magnesia was 5 mm, and was adjusted appropriately to coarse particles, medium particles, and fine particles as in the conventional material so as to obtain a tightly packed structure.

The test method is as follows.

The fluidity was measured by measuring the flow value of a kneaded product to which water was added in accordance with JIS R2521. 13 measured values
If it is 0 to 160 mm, it is in a standard softness state indicated by JIS R2553, and has sufficient fluidity for pouring.

The following tests were conducted by kneading the composition of each example shown in the table with the working moisture and casting the mixture into a mold.
After removing the frame, a molded product obtained by drying at 110 ° C. for 24 hours was used as a test sample.

The bulk specific gravity, apparent porosity, and flexural strength were measured for a sample cast into a size of 40 × 40 × 160 mm after drying and further firing. After the firing, the dried sample was measured at 500 ° C. for 3 hours and at 1500 ° C. for 3 hours in a sheath filled with coke breeze.
A sample fired by reduction in time was measured. Here, the apparent porosity is a measure of the denseness of the construction body. The degree of strength is confirmed by the bending strength.

The oxidation resistance was determined by sintering a sample obtained by casting at 50 mm × 50 mm for 3 hours at 1000 ° C., cutting the center, and measuring the thickness (mm) of the decarburized layer. The smaller this value is, the better the oxidation resistance is. In Comparative Example 1, no carbon material was used, so there was no oxidation.

The corrosion resistance of a sample cast to a size of 95 × 115 × 30 mm was measured by a high frequency induction furnace lining test. The slag of electrolytic iron and CaO / SiO ₂ = 3.1 was used as an erosion agent, and the test was performed at 1700 ° C. × 5 hours.
It is shown as an index when the amount of erosion of Comparative Example 1 is set to 100. The smaller this value is, the better the corrosion resistance is.

The spalling resistance is 50 × 50 × 230.
The sample was measured in mm. 1000 samples
After reduction firing at 3 ° C. × 3 hours, the material was immersed in hot metal at 1600 ° C. for 90 seconds, then water-cooled for 15 seconds, and left to cool at room temperature. This cycle of immersion, water cooling, and standing was repeated until the sample peeled off by spalling. The higher the number of repetitions, the better the spalling resistance.

The explosion resistance test was 235 × 235 × 15
After curing the sample cast to 0 mm for 24 hours, 235
× 235 mm on one side only in a gas burner furnace
It was heated to 1200 ° C. at a heating rate of 0 ° C./hour, and the presence or absence of explosion was confirmed.

Some of the examples and comparative examples were subjected to a spraying test, and the pumping resistance, the adhesion rate, and the adhesiveness were measured. The outline of the spraying device used for the measurement is as shown in FIG. 1, and a power cleaner 10SHP manufactured by Allentown was used as a pressure pump, and the size was 40 A × length 22.
m material hose.

An amorphous refractory to which water has been added and kneaded in advance is pressure-fed to a spray nozzle at a discharge rate of 75 to 85 / kg by a pressure pump, and is used as a quick-setting agent in the nozzle.
0.6% by mass of S.2 sodium silicate solution was externally added with compressed air and sprayed.

The pumping resistance was determined by the pumping pressure delivered by the pump during spraying. If the pumping resistance is low, there is no adverse effect such as clogging of the material discharge port, and the spraying work efficiency is excellent.

The adhesion rate was determined by spraying the material on the vertical wall of the refractory lining.

FIGS. 2A to 2D show the test methods of the adhesiveness. As shown in A, an irregular-shaped refractory 10 is sprayed as shown in B by a spray nozzle 3 on a base 9 made of magnesia-carbon fired brick provided with a groove in a metal frame 8. Next, the measuring part of the groove is removed, and curing is performed in the state of C.
After drying at 10 ° C. for 24 hours, as shown in D, a shearing stress was applied to the sprayed material 10 adhered to the base with a push rod 12 to measure the adhesive strength.

[0063]

[Table 2]

[Table 3] All of the examples of the present invention are excellent in oxidation resistance, corrosion resistance, spalling resistance and dry explosion resistance. Of these, Examples 5 and 9 are those obtained by combining a mesophase pitch or a pitch with the infusible mesophase pitch limited by the present invention, and have excellent strength in the treatment after firing at 500 ° C. in the intermediate temperature range. .

On the other hand, Comparative Examples 1 to 7, which do not use the infusibilized mesophase pitch, are all inferior in corrosion resistance. Further, Comparative Examples 3 and 4 using graphite or pitch were also inferior in oxidation resistance, and due to this, the reduction in corrosion resistance was even more remarkable.

In Comparative Examples 8 and 9 in which the proportion of mesophase pitch or carbon black was large, the corrosion resistance and sporin resistance were all significantly reduced. In Comparative Example 8, dry explosion occurred due to too much mesophase pitch.

Comparative Example 10 uses the infusible mesophase pitch C, but uses the infusible mesophase pitch C having an average particle size larger than the limited range of the present invention, and is inferior in both corrosion resistance and spalling resistance. Comparative Example 11 in which infusibilized mesophase pitch A was excessively added also showed corrosion resistance,
Poor spalling resistance.

Comparative Example 3 is an example in which only the pitch was used as the carbon material. Poor corrosion resistance and oxidation resistance, and dry explosion occurred.

Each of the embodiments of the present invention has sufficient fluidity for pouring work. As a result, the apparent porosity is reduced, and the oxidation resistance and corrosion resistance are improved. On the other hand, Comparative Example 11 in which the infusibilized mesophase pitch was excessively added was inferior in fluidity, so the amount of added water was increased, the apparent porosity was increased, and the corrosion resistance was reduced.

In the spraying construction test, some of the examples were tested. If the test value is not described, it means that the test was not performed.

In this spraying test, Examples 2 and 5 using infusible mesophase pitch A were used.
Is Comparative Example 1 not using infusible mesophase pitch
And the adhesiveness and adhesiveness were improved as compared with Comparative Example 2.

When the material using the infusibilized mesophase pitch is sprayed, as shown in Example 2 and Example 5, the resistance to pumping tends to increase. Will be resolved. For example, it is as in Examples 6 to 8 using carbon black in combination. Reduction of pumping resistance improves spraying efficiency.

In Comparative Example 9 in which carbon black was excessively used, the fluidity was lowered, the amount of added water was increased to secure the fluidity, the porosity of the refractory structure was increased, and the effect of improving corrosion resistance was obtained. Absent.

In the above embodiments, the case where the infusible pitch is added to the magnesia-based amorphous refractory is described. However, the infusible pitch for the amorphous-based refractory such as alumina-magnesia and alumina-silicon carbide is used. Similar effects were confirmed in the addition.

The present invention can be used for lining or repairing various iron and steel making furnaces such as blast furnaces, blast furnace gutters, converters, degassing furnaces, ladles, mixed iron wheels, and mixed iron furnaces.

[0075]

According to the carbonaceous amorphous refractory of the present invention, fluidity, corrosion resistance and spalling resistance are improved by using a specific amount of infusible mesophase pitch having an average particle diameter of 10 μm or less as a carbon material. . There is no problem of dry explosion seen when using pitch as a carbon material.

Further, when used as a wet spraying material, in addition to the above-mentioned effects, excellent effects are also exhibited in adhesion and adhesion.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a layout of a wet spraying machine for carrying out the present invention.

FIG. 2 shows a method for measuring adhesive strength.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pressure pump 2 material hose 3 spray nozzle 4 quick setting pump 5 quick setting hose 6 air hose 7 compressor 8 metal frame 9 magnesia-carbon brick 10 refractory spraying material 11 iron plate 12 Amsler connection pressing jig

Continuing from the front page (72) Inventor Yoichi Tsuji 1 at 7 Tsukiji, Kisarazu-shi, Chiba Pref. No. 1-1 Kurosaki Harima Co., Ltd. Technical Research Institute F term (reference) 4G033 AA03 AA14 AA24 AB01 AB25 4K051 AA01 AA02 AA05 AA06 AB03 AB05 BE03 LA02 LA11

Claims (4)

[Claims] An amorphous carbon-containing refractory comprising 1 to 10% by mass of an infusible mesophase pitch having an average particle size of 10 μm or less obtained by heat-treating a mesophase pitch in an oxygen atmosphere to a refractory aggregate. 2. A refractory aggregate, wherein 1 to 10% by mass of an infusible mesophase pitch having an average particle size of 10 μm or less obtained by heat-treating mesophase pitch in an oxygen atmosphere, and 5% by mass of mesophase pitch and / or pitch. %. The carbon-containing amorphous refractory according to claim 1, wherein the content of the refractory material is not more than 10%. 3. The carbon-containing irregular shaped refractory according to claim 1, wherein the refractory aggregate further contains 5% by mass or less of carbon black. 4. The irregular-shaped refractory according to claim 1, 2 or 3, wherein the irregular-shaped refractory which is kneaded by adding working moisture is sprayed while adding a quick-setting agent. A wet spraying method for carbon-containing irregular shaped refractories using refractories.