JP2005162569A - Alumina cement, alumina cement composition and monolithic refractory using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alumina cement having excellent workability and strength development property, an alumina cement composition and a monolithic refractory using the same. <P>SOLUTION: Problems of conventional technology is solved by developing alumina cement having specific particle diameter distribution and shape. The alumina cement contains CaO-Al<SB>2</SB>O<SB>3</SB>as a mineral phase, has peaks of the particle diameter distribution in a particle size ranging from 1 μm to 10 μm and ranging from 10 μm to 200 μm, contains 50-90 vol.% particles having 10-200 μm particle diameter, 10-20 vol.% particles having ≥90 μm particle diameter and has sphericity of 0.5-1.0. The alumina cement composition contains the alumina cement and phosphoric acids and/or boric acids. The monolithic refractory contains the alumina cement or the alumina cement composition and the refractory aggregate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is an irregular refractory mainly used for lining materials such as blast furnace tapping, kneading car, ladle, tundish, etc., and has a specific particle size with little variation in curing time due to variation in temperature. The present invention relates to an alumina cement having a distribution, an alumina cement composition, and an amorphous refractory using the same.

  Conventionally, alumina cement has problems such as poor workability, difficult construction, poor strength development, peeling and cracking, etc. in construction in a high temperature atmosphere of 30 ° C. or higher.

In order to improve these problems, it contains an alumina cement composition obtained by blending hydroxycarboxylate and the like with alumina cement, an alumina cement composition obtained by blending inorganic carbonate and the like, and polymethacrylic acid. There have been proposed an alumina cement to which various additives are added and an alumina cement having a square particle shape, such as an alumina cement composition.
Japanese Patent Publication No. 50-28090 Japanese Patent Publication No.55-45507 Japanese Patent Publication No. 56-22822 Japanese Patent Publication No.57-21499 Japanese Patent Publication No. 60-54897 Japanese Patent Publication No. 60-54898 Japanese Patent Publication No.63-384

  However, the alumina cement to which such an additive is added has a problem that workability and strength development at the time of high temperature construction cannot be sufficiently satisfied.

  Furthermore, if you add an amorphous refractory with a curing retarder added for use in the summer and adjust the curing time, for example, at the time of lower temperatures than expected, such as around autumn, the curing time will be longer, There was a problem that the strength development was reduced and the schedule after curing was delayed such as unframed and dried.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have overcome the problems of the prior art, such as alumina cement having a specific particle size distribution and shape even during high-temperature construction, workability, strength development, etc. As a result, the present invention was completed.

That is, the present invention contains CaO · Al ₂ O ₃ as a mineral phase, has a particle size distribution peak in a particle size range of 1 to 10 μm and a particle size range of 10 to 200 μm, and is contained in a particle size range of 10 to 200 μm. The alumina cement is characterized by containing 50 to 90% by volume of powder and 10 to 20% by volume of particles of 90 μm or more, and the alumina cement having a roundness of 0.5 to 1.0. There is an alumina cement composition comprising the alumina cement and phosphoric acids and / or boric acids, and an amorphous refractory comprising the alumina cement or the alumina cement composition and a refractory aggregate.

  The alumina cement of the present invention has very little temperature dependency of the curing time, is excellent in water reduction effect, fluidity, strength development and corrosion resistance, and has an appropriate pot life, which could not be achieved with conventional products. Excellent performance. In particular, even in a high-temperature construction atmosphere of 30 ° C. or higher, there is an effect of showing excellent workability, strength development, and heat resistance.

  Alumina cement used in the present invention is composed of calcium aluminate (hereinafter referred to as CA), or CA and other, specifically, including finely divided alumina such as α-alumina, It can be obtained by mixing CA with finely divided alumina or by mixing and grinding CA clinker and finely divided alumina.

CA mixes or mixes and grinds natural raw materials such as red bauxite and Al ₂ O ₃ raw materials such as high-purity alumina obtained by refining by a purification method such as the buyer process, and CaO raw materials such as limestone and quicklime. Or, after mixing partly, further mixing and pulverizing, blending so as to have a predetermined component ratio, when manufacturing by melting method, when manufacturing by firing method with equipment such as electric furnace, radiation furnace, flat furnace, etc. The clinker melted or fired by equipment such as a shaft kiln or rotary kiln is pulverized by a pulverizer such as a tube mill, a vibration mill, a jet mill, or a roller mill.

CA is a general term for substances having CaO and Al ₂ O ₃ as main components and having hydration activity, and CaO and / or a part of Al ₂ O ₃ is an alkali metal oxide, an alkaline earth metal oxide, Silicon oxide, titanium oxide, iron oxide, oxides of trivalent metals other than aluminum, P ₂ O ₅ , alkali metal halides, alkaline earth metal halides, alkali metal sulfates, alkaline earth metal sulfates, etc. It is a substance obtained by dissolving these in a substituted compound or a substance mainly composed of CaO and Al ₂ O ₃ .

  Inevitable impurities are contained in the industrial raw materials, and CA containing these impurities can be used in the present invention, but the impurity content is usually preferably about 1% by mass or less.

In the present invention, an alumina cement containing CaO · Al ₂ O _{3 in} which CaO and Al ₂ O ₃ are equimolar is used, but the content of CaO · Al ₂ O ₃ is 30 to 80% by mass. It is preferable. If the content of CaO · Al ₂ O ₃ is less than 30% by mass, the initial fluidity may be insufficient, and the curing time may be delayed due to a delay in curing time. On the other hand, if the content exceeds 80% by mass, the curing time may be decreased. May be shortened and the strength after firing may be reduced.

  In order to obtain good workability and strength development even at high temperature construction, the particle size of the alumina cement of the present invention has a particle size distribution peak in a particle size range of 1 to 10 μm and a particle size range of 10 to 200 μm, The powder contained in a particle size range of 10 to 200 μm is 50 to 90% by volume, and preferably contains 10 to 20% by volume of particles of 90 μm or more. If these conditions are not met, desired characteristics may not be obtained with respect to workability and strength development.

  The particle size distribution measurement can be performed by a general particle size distribution measurement method such as a laser diffraction method, a light scattering method, a photon correlation method, and a sedimentation method.

  The alumina cement of the present invention preferably has a value expressed by roundness of 0.5 to 1.0, more preferably 0.8 to 1.0. The roundness can be measured using a scanning electron microscope (for example, “JSM-T200 type” manufactured by JEOL Ltd.) and an image analysis device (for example, manufactured by Nihon Avionics Co., Ltd.).

The projected area (A) and the perimeter (PM) of the particle are measured from the SEM photograph. When the area of a perfect circle corresponding to the perimeter (PM) is (B), the roundness of the particle can be displayed as A / B. Assuming a perfect circle having the same perimeter as the sample particle (PM), PM = 2πr and B = πr ² , so B = π × (PM / 2π) ² , and the trueness of each particle Circularity (A / B) can be calculated as A × 4π / (PM) ² . In the present invention, 100 particles were measured, and the average value was defined as roundness.

  In the present invention, it is possible to blend a specific admixture in order to reduce the temperature dependency of the setting time of the alumina cement and to impart a water reducing effect and high strength expression. For example, phosphoric acids and / or boric acids are mentioned as preferred admixtures.

  Examples of the phosphoric acids according to the present invention include hexametaphosphoric acid, tripolyphosphoric acid, pyrophosphoric acid, and ultrapolyphosphoric acid, or sodium salts, potassium salts, and calcium salt salts thereof. From the viewpoint of ease of use and industrial production. The use of readily available sodium salts is preferred.

  0.1-1 mass part is preferable with respect to 100 mass parts of alumina cements, and, as for the usage-amount of the phosphoric acids based on this invention, 0.3-0.8 mass part is more preferable. Outside this range, the temperature dependency of the curing time is increased, the water reducing effect, fluidity, and strength development are decreased, and an appropriate pot life may not be obtained.

  The boric acid according to the present invention is boric acid or an alkali salt thereof, and examples of the alkali salt include sodium salt, potassium salt, and calcium salt. Of these, from the viewpoint of industrial production, it is preferable to use boric acid which is easily available.

  0.1-1 mass part is preferable with respect to 100 mass parts of alumina cement, and, as for the usage-amount of the boric acid which concerns on this invention, 0.3-0.8 mass part is more preferable. Outside this range, the temperature dependency of the curing time is increased, the water reducing effect, fluidity, and strength development are decreased, and an appropriate pot life may not be obtained.

  In the present invention, an alumina cement or an alumina cement composition and a refractory aggregate are blended to form an amorphous refractory. Refractory aggregates include fused magnesia, sintered magnesia, natural magnesia, magnesia such as light-burned magnesia, magnesia spinel such as fused magnesia spinel and sintered magnesia spinel, fused alumina, sintered alumina, light-burned alumina, and easy-burning alumina. Alumina such as sintered alumina, ultrafine powder such as silica fume, colloidal silica, light calcined alumina, and easily sintered alumina, other fused silica, calcined mullite, chromium oxide, bauxite, andalusite, sillimanite, chamotte, quartzite, rho Stone, clay, zircon, zirconia, dolomite, perlite, vermiculite, brick katsu, pottery katsu, silicon nitride, boron nitride, silicon carbide, silicon nitride iron, and the like can be used. The proportion of the amorphous refractory according to the present invention should be appropriately determined depending on the construction site, and is not particularly limited, but from the viewpoint of corrosion resistance, durability, and fire resistance, alumina fireproof aggregate is used. It is preferable to use it in combination with other aggregates.

Alumina according to the present invention is obtained by sintering or melting an Al ₂ O ₃ source such as aluminum hydroxide or calcined alumina into a predetermined size by a sintering device such as a rotary kiln or a melting device such as an electric furnace. It is crushed and sieved, and the mineral composition is aluminum oxide indicated as α-Al ₂ O ₃ or β-Al ₂ O ₃ , sintered alumina, calcined alumina, and easily sintered It is called alumina or the like, and usually α-alumina containing 90% by mass or more of Al ₂ O ₃ is preferably used.

  It is also possible to use alumina / zirconia clinker or the like obtained by melting alumina and zirconia and having improved heat spalling properties.

  The particle size of the refractory aggregate is usually 5 to 3 mm, 3 to 1 mm, 1 mm, 200 mesh, 325 mesh or the like depending on the required physical properties. In the present invention, it is desirable to use alumina and ultrafine powder in combination as the refractory aggregate.

Ultra fine powder is a refractory fine powder in which particles with a particle size of 10 μm or less occupy 80% by mass or more, and has an average particle size of 1 μm or less and a specific surface area of 10 m ² / g or more by the BET method. When blended in a refractory, fluidity can be secured and high strength is exhibited, which is preferable. Specifically, inorganic fine powders such as silica fume, colloidal silica, easily sintered alumina, amorphous silica, zircon, silicon carbide, silicon nitride, chromium oxide, and titanium oxide can be used. The use of fume, colloidal silica, and easily sintered alumina is preferred. The mixing ratio of the amorphous refractory according to the present invention should be appropriately determined depending on the construction site, and is not particularly limited, but the content of the refractory aggregate is usually about 80 to 99% by mass.

  The method for producing the amorphous refractory according to the present invention is not particularly limited, and in accordance with the usual method for producing an irregular refractory, the respective materials are blended in a predetermined ratio, and a V-type blender, cone It is also possible to perform uniform mixing using a blender such as a blender, nauta mixer, bread mixer, and omni mixer, or to weigh directly into a kneader when performing kneading at a predetermined ratio.

The amorphous refractory of the present invention is for the purpose of preventing explosion when the cured product is dried, such as foaming agents such as metallic aluminum and magnesium, organic fibers such as vinylon fiber, polypropylene fiber, and vinyl chloride fiber, and aluminum lactate. Basic colloids, N ₂ gas generating decomposition fibers, and explosion prevention materials such as humic acids can be blended as necessary.

  The amorphous refractory of the present invention can be used in combination with a dispersant for the purpose of improving fluidity. The kind of the dispersing agent is not particularly limited, and commercially available ones can be used.

  In order to avoid material separation, the amorphous refractory of the present invention can be blended with a thickener such as methylcellulose, carboxymethylcellulose, a polyacrylamide-modified product or a copolymer thereof, and polyvinyl alcohol.

  The amorphous refractory of the present invention is, as long as the temperature dependence of the curing time does not increase, citric acid, gluconic acid, tartaric acid, malic acid, and salicylic acid or their sodium salts, potassium salts, etc. One or more additives selected from the group consisting of hydroxycarboxylic acid or a salt thereof, polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, and a methacrylic acid-acrylic acid copolymer or a salt thereof are used in combination. It is possible. Further, various additives such as carbonates such as potassium carbonate, sodium carbonate, potassium hydrogen carbonate and sodium hydrogen carbonate, and organic dispersants for ordinary Portland cement can be used in combination.

  The amount of kneading water for the irregular refractory according to the present invention is greatly affected by the particle size composition and the porosity of the refractory aggregate, but is usually about 5 to 8% by mass with respect to the irregular refractory. It is.

  Using high-purity alumina as the alumina source and high-purity calcium carbonate as the calcia source, each raw material was blended so that the mineral composition in the product was a predetermined ratio, and clinker was manufactured by firing in a kiln ( (Baking temperature 1400-1600 ° C). The clinker was pulverized with a vibration mill to prepare alumina cement as shown in Table 1. With respect to 5 parts by mass of this alumina cement, 90 parts by mass of refractory aggregate α parts by mass and 5 parts by mass of silica fume are blended and kneaded at a water / (alumina cement + refractory aggregate) ratio = 0.06. An amorphous refractory was prepared, and the flow value, pot life, curing time, heat generation time, and various strengths at 20 ° C and 35 ° C were measured. The results are shown in Table 2.

<Materials used>
Al ₂ O ₃ raw material: High purity alumina, commercial product
CaO raw material: High-purity calcium carbonate, commercially available fireproof aggregate α: Sintered alumina manufactured by Moralco, particle size 3,360-1190μm is 27 parts by mass, 1,190-590μm is 16 parts by mass, 590-297μm is 16 parts by mass, 297μm below 14 parts by mass, and 44 μm below 17 parts by mass Ultra fine powder: Silica fume, commercial product

<Test method>
Fluidity: Using the kneaded material immediately after kneading for 4 minutes and after standing for 30 minutes, the spread diameter after tapping 15 times with a flow table was measured according to JIS R 2521.
Pot life: The produced amorphous refractory was transferred to a plastic bag, and the time taken for the fluidity to disappear was measured.
Curing time: 500 g of the produced amorphous refractory was transferred to a poly beaker, and the time taken from pouring water to the peak of hydration exotherm was measured with a platinum resistance temperature detector and a dot recording recorder.
Curing strength: The produced amorphous refractory was placed on a 4 × 4 × 16cm mold with stamping sticks, and the surface was flattened with a cement knife, and then the compressive strength after curing for 24 hours was measured. .
Dry strength: A specimen for measuring curing strength was dried at 110 ° C. for 24 hours, allowed to cool to room temperature, and measured for compressive strength.
Firing strength: A specimen for measuring dry strength was placed in a siliconite electric furnace, heated at a rate of 10 ° C./min to 800 ° C., held for 3 hours, allowed to cool to room temperature, and the compressive strength was measured.
Temperature dependence: If the difference in curing time between 20 ° C and 35 ° C was within 3 hours, the temperature dependence was small (◯), and if it exceeded 3 hours, it was judged as impossible (x).

  Experiment No. The same procedure as in Experimental Example 1 was performed except that 1-9 alumina cement was used and the additives shown in Table 3 were added to 100 parts by mass of the alumina cement. The results are also shown in Table 3.

<Materials used>
Additive a: sodium triphosphate
Additive b: Boric acid additive c: Sodium hexametaphosphate
Additive d: Na borate

Claims (5)

50 to 90 powders containing CaO · Al ₂ O ₃ as a mineral phase, having a particle size distribution peak in a particle size range of 1 to 10 μm and a particle size range of 10 to 200 μm, and contained in a particle size range of 10 to 200 μm Alumina cement characterized by containing 10-20% by volume of particles having a volume% of 90 μm or more. The alumina cement according to claim 1, wherein the roundness is 0.5 to 1.0. An alumina cement composition comprising the alumina cement according to claim 1 or 2, and phosphoric acids and / or boric acids. An amorphous refractory comprising the alumina cement according to claim 1 or 2 and a refractory aggregate. An amorphous refractory comprising the alumina cement composition according to claim 3 and a refractory aggregate.