JPH0137351B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fire-resistant composition that has excellent workability, strength, and fire resistance. Traditionally, alumina cement has been mixed with refractory aggregate and used as a castable refractory material in furnace materials, etc., but its dispersibility is relatively poor, and even when the amount is increased, the strength does not increase much and the fire resistance decreases. Therefore, the amount of alumina cement in castable refractories was usually 12 to 30% by weight. However, even in this case, the high-temperature strength and high-temperature corrosion resistance deteriorated, and there were problems with fire resistance due to the influence of CaO contained in the alumina cement. In order to improve this, attempts were made to reduce the amount of alumina cement mixed to 5 to 8 parts by weight, but these had the drawback of poor workability during construction and insufficient strength even when molded. . _The present inventor found that in the conventional _product , _the main mineral corresponds to CA _and other Mineral components containing small amounts of substances corresponding to CA ₂ , C ₁₂ A ₇ , C ₄ AF and C ₂ AS) are 30 to 40% by weight, and this is pulverized by a ball mill by staying in the mill for a long time. As a result of extensive research, we found that the particle shape is essentially spherical with little unevenness on the surface, and that many of the particles have internal cracks. Contains 40 to 60% by weight of quality components and 40 to 70% by weight of Al ₂ O ₃ , and when the particle size is measured by the sedimentation balance method,
The particle size is 30μ or less, of which particles with a size of 5μ or less account for 10 to 35% by weight, and the specific surface area is 0.5 to 1.2m ² /g.
The present inventors have discovered that a castable obtained by blending a small amount of alumina cement whose particle shape is not substantially spherical has excellent workability, strength, and fire resistance, and has completed the present invention. In order to produce the alumina cement used in the present invention, clinker is produced by firing or melting a raw material mixture of alumina cement, which is rapidly cooled by contacting with air or water, and the cooling rate is adjusted to form amorphous components. Adjust so that it is 40 to 60% by weight. The raw materials are mixed so that the Al ₂ O ₃ content is 40 to 70% by weight. Next, the alumina cement clinker is pulverized using a rapid pulverizer such as a jet mill or a roller mill, and the particle size is measured using a sedimentation balance method.
It is adjusted to have a specific surface area of 10 to 35% by weight and a specific surface area of 0.5 to 1.2 m ² /g. Jet mills and roller mills are of the forced passage type using air, and the residence time is within about 1 minute. The alumina cement used in the present invention has more amorphous components than conventional products, so when it is ground with a rapid grinder such as the jet mill or roller mill that can grind it rapidly, the surface becomes uneven and has needle-like or prismatic shapes. , a mixture of various angular shapes that were not substantially spherical, such as plate shapes, were obtained, and there were few internal cracks. This material has the particle size and specific surface area described above, has excellent workability such as dispersibility and fluidity, and has high strength when molded. As the amorphous component increases, the content of angular components increases, but if it is less than 40% by weight, the working time is short and the strength is slightly reduced. On the other hand, if it exceeds 60% by weight, curing will be delayed significantly, which is not preferable. Furthermore, if the Al ₂ O ₃ content exceeds 70% by weight, the curing time will be significantly delayed, and if it is less than 40% by weight, the working time will be too short to be practical. In addition, the particle size structure of alumina cement is an important factor in workability. In other words, in normal commercial products, 10 to 20% by weight of particles that do not pass through a 30μ sieve, and 35 to 45% by weight of particles with a particle size of 5μ or less, but coarse particles that do not pass through a 30μ sieve. Since the hydration reaction is slow and the dispersibility is also poor, it is preferable that there are few coarse particles mixed in. Therefore, the particle size (Stokes diameter measured by the sedimentation balance method) of the alumina cement used in the present invention was set to be 30 μm or less. In addition, if particles of 5 μm or less, which have particularly high activity, are present in too large a quantity, workability will be impaired, whereas if they are not present at all, the development of strength will be delayed, so the content of particles of 5 μm or less is preferably 10 to 35% by weight. Depending on the case, materials classified by a classification step may be appropriately blended. In the present invention, the reason why the particle size of alumina cement was measured by the sedimentation balance method (buoyancy balance method) is as follows. Since cement is a hydraulic powder, various dry and wet particle size measurement methods have been studied, but no definitive measurement method has yet been established. Normally, cement is made by grinding clinker in a mill for a long time, and its particle shape is close to spherical.Since it is essentially a spherical fine powder, the sedimentation balance method is adopted as a method for measuring the particle size of cement. ing. On the other hand, the particle shape of the alumina cement of the present invention is a non-spherical fine powder that is different from the particle shape of conventional cement, but the sedimentation balance method was adopted because it allows relative comparison with conventional products and has excellent reproducibility. be. The fireproof composition of the present invention contains (A) the above-mentioned amorphous component.
Contains 40-60% by weight and 40-70% _by weight _Al2O3 ,
The particle size is 30μ when measured by sedimentation balance method.
Hereinafter, 1 to 10 parts by weight of alumina cement whose particle shape is not substantially spherical and whose particle size is 10 to 35% by weight and whose specific surface area is 0.5 to 1.2 m ² /g, and (B) Powder of refractory material with a particle size of 1μ or less 1~
(C) 2 to 10 parts by weight of powder of refractory material with a particle size of 10 μ or less; (D) 75 to 96 parts by weight of refractory aggregate;
(E) Dispersant, consisting of 0.1 to 1.0% by weight based on the total amount of (A), (B), (C) and (D). Although this refractory composition contains a small amount of alumina cement, it exhibits excellent workability, strength, and fire resistance when used in castable refractories such as furnace materials. The refractory material of component (B) is particularly effective in assisting the dispersion of alumina cement. for example,
Siliceous, alumina, zirconia, chromia, and calcia are preferred, and ultrafine siliceous powder is particularly preferred. The particle size is 1 μm or less (average particle size 0.1 to 0.5 μm), preferably 100 μm or less, the shape is preferably spherical, and it must be water-insoluble. If the amount added is less than 1 part by weight, the effect of the dispersion aid will not be sufficient and preferred viscosity will not be obtained when the fireproof composition of the present invention is hydrogenated and kneaded. If it exceeds 5 parts by weight, curing will be delayed,
In addition to having adverse effects such as a decrease in strength, the viscosity during kneading increases more than necessary. The refractory material of component (C) is an important element constituting the refractory matrix, together with the alumina cement and the refractory material of component (B), and improves the strength by increasing the filling properties of the matrix. It also contributes to fire resistance. Examples of the refractory material of component (C) include silica, alumina, zirconia, chromia, and calcia, and the lower the water absorption, the better the results. The particle size is 10 μm or less (average particle size 4 to 9 μm), and it is particularly preferable that the particle size is 80% by weight or more of 5 μm or less. If the amount added is less than 2 parts by weight, no improvement in filling properties can be expected, and if it exceeds 10 parts by weight, the particle size structure will not be appropriate and the filling properties will be impaired. The fire-resistant aggregate of component (D) includes, for example, silica, cypress, alumina, magnesia, maguro, spinel, silicon carbide, and carbon, even if the particle size is 30 mm or less. Bye. For example, it is preferable that particles passing through a 0.5 mm sieve in an amount of about 20% by weight are contained through a 10 mm sieve. Components (A), (B), (C), and (D) are blended in the proportions listed above, but the reason for specifying the amount of each component is that outside this range, a castable with excellent dispersibility cannot be obtained. First, the strength of the refractory material cannot be obtained sufficiently when molded. In the present invention, in addition to the above-mentioned components, the above-mentioned dispersant is also used.
0.1 to 1.0% by weight based on the total amount of (A), (B), (C), and (D)
Contains. Examples of dispersants include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, acidic sodium hexametaphosphate, aluminum phosphate, sodium borate, boric acid, and sodium carbonate;
Examples include organic salts such as sodium citrate, sodium tartrate, and sodium polyacrylate. In the present invention, it goes without saying that one type of dispersant may be used, but preferred results can be obtained by using two or more types in combination. When applying the fireproof composition of the present invention, usually 8
It is used after adding water in an amount of % by weight or less and kneading it. In conventional fireproof compositions, 12 to 25% by weight of water was added, so in the case of the product of the present invention, compared to the conventional product,
A significantly small amount is sufficient, and therefore the obtained molded product has the advantage that there is little increase in porosity and little decrease in strength after dehydration by drying or firing. EXAMPLES The present invention will be explained in more detail with reference to Examples below. The percentages in the examples are percentages by weight unless otherwise specified. In addition, the test was measured by the following method. (1) Flow (mm): According to the method described in JIS R5201,
After filling the flow cone with the kneaded material and smoothing the surface, the flow cone was pulled vertically upward and then vibrated at 8000 RPM using a vibrator.
I gave it 10 seconds. The spread of this kneaded material was measured with a caliper, and the average value (mm) of the major axis and minor axis was taken as the flow measurement value. Note that the larger the flow measurement value, the greater the fluidity of the kneaded material due to vibration. Further, when the same operation was performed 30 minutes later and the flow was measured, and the difference between the flow measurements after 3 minutes and 30 minutes was determined, the smaller the difference, the better the kneading property. Note that kneading property refers to the workability (ease of construction) when left after kneading with water. (2) Curing time: 40×40 while applying vibration to the kneaded material
It was poured into a ×160 (mm) mold and allowed to harden. The time from the addition of water to the composition until it generates heat was defined as the curing time. (3) Strength (Kg/cm ² ): The cured product obtained by pouring into the mold in (2) was used as a test piece, and the strength after being left for 24 hours, the strength after drying at a temperature of 110℃, and the strength after drying at a temperature of 100℃ and
The strength and linear change rate after firing at 1400°C were measured according to the following method. Bending strength: JIS R2553 Compressive strength: JIS R2553 Baking bending strength: JIS R2553 Linear rate of change: JIS R2554 Example 1 Production of alumina cement Bauxite and quicklime were mixed in a molar ratio of CaO and Al ₂ O ₃ of 1: 1 and melted at about 1650°C in a resistance electric furnace. This molten material was blown out at an air pressure of 5 kg/cm ² when tapping from inside the furnace and quenched with air to produce clinkers according to the present invention shown in Tables 1 and 2. The conventional product was made in the same manner except that the air pressure was 2Kg/cm ² . The mineral compositions shown in Table 2 were determined as follows.

【table】

[Table] Mineral components are identified by the peak positions of crystal components by X-ray diffraction. The ratio of the crystalline component to the amorphous component is determined based on the peak of the crystalline component of the mineral component estimated from the raw material composition. That is, a calibration curve of peak heights of known proportions is created in advance,
At that time, the ratio is determined from the height of the crystalline peak at that time. This clinker was ground in a roller mill for the product of the present invention and in a ball mill for the conventional product to produce alumina cement. When the particle shape of each particle was observed using a microscope (SEM) (1000x magnification), it was found that none of the particles of the present invention were substantially spherical as shown in Figure 1, while that of the conventional product was substantially spherical as shown in Figure 2. It was spherical.
In addition, the particle size was measured by a sedimentation balance method using a model "SR-1000" manufactured by Shimadzu Corporation. The particle size distribution was as follows.

[Table] In addition, the specific surface area of the product of the present invention was 0.758 in the gas adsorption method using "QUANTASORB" manufactured by Yuasa Battery.
m ² /g, and the conventional product was 2.505 m ² /g. The following tests were conducted on products of the present invention and conventional products. Using the alumina cement produced in the alumina cement production process, mix it in the proportions shown in Table 4, put it in a mixer, stir it for 3 minutes,
To this, 6.5% water was added and stirred for an additional 3 minutes.The flow was measured and the kneaded product was subjected to various tests, and the results are shown in Tables 5 and 6. Examples 2 to 7 Alumina cement, ultrafine silica, alumina,
The same procedure as in Example 1 was carried out except that the blending ratio of Otabishi Yamamoto was changed. These conditions and results are shown in Tables 7, 8, and 9. Examples 8 to 10 The same procedure as in Example 1 was conducted except that the ratio of the refractory aggregate (A) and the material other than this aggregate (B) was changed to make it castable. These conditions and results are shown in Table 10.
Shown in Tables 11, 12, and 13. Example 11 The same procedure as Example 1 was carried out except that the proportion of dispersant to 100 parts by weight of the castable formulation was changed.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] As detailed above, the present invention is an alumina cement-based refractory composition that has excellent workability, particularly workability in high-temperature atmospheres, hardenability, strength, and fire resistance. It has excellent properties and high strength as a molded product, and conventional castables are difficult to use due to their high temperature strength and corrosion resistance, such as soaking furnaces, heating furnaces, annealing furnaces, etc. related to steel, cement, and non-ferrous metals. This invention is extremely useful as it can be used for furnace materials.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing the particle structure of alumina cement used in an example of the present invention. Second
The figure is a micrograph showing the particle structure of a conventional alumina cement used as a comparative example.

Claims (1)

[Claims] 1 (A) 40 to 60% by weight of amorphous component and Al ₂ O ₃
Contains 40 to 70% by weight, and when measured by the sedimentation balance method, the particle size is 30 μ or less, of which the particles are 5 μ or less.
10-35% by weight, specific surface area 0.5-1.2m ² /g
1 to 10 parts by weight of alumina cement whose particle shape is not substantially spherical, (B) 1 to 5 parts by weight of powder of a refractory material with a particle size of 1 μ or less, and (C) a refractory material with a particle size of 10 μ or less 2 to 10 parts by weight of powder of the substance; and (D) refractory aggregate.
75 to 96 parts by weight and (E) dispersant to (A), (B), (C) and (D)
0.1 to 1.0% by weight based on the total amount of refractory composition.