JP4351526B2 - Unshaped refractories for wet spraying with used refractories - Google Patents

Description

  The present invention relates to an amorphous refractory for wet spraying containing a used refractory.

  Conventionally, most of the refractories after being used for the lining of the molten metal are disposed of. Then, the reuse of this used refractory is tried from the viewpoint of effective use of resources.

  In general, the used refractory is pulverized and blended as a part of the refractory raw material of the regular refractory or the irregular refractory. For example, it has been proposed to mix a pulverized product of magnesia-chromic refractory brick after use as the lining of a molten steel refining vessel (see, for example, Patent Document 1).

Examples of use for non-standard refractories include baking repair materials containing used magnesia bricks or dolomite bricks (see, for example, Patent Document 2), and magnesia castable refractories using waste magnesia-carbon bricks. (For example, refer patent document 3), the spray repair material (for example, refer patent document 4) using the waste material of a carbon containing refractory is proposed.
JP-A-7-291718 JP-A-3-251684 JP-A-6-219853 JP-A-9-278548

  The structure of the used refractory contains a plurality of refractory raw materials, and the quality is not constant. Moreover, it is inferior to denseness compared with the unused refractory raw material of baking and electromelting.

  The corrosion resistance, strength, etc. of the refractory depend greatly on the matrix structure. For this reason, it is general that the used refractory having inferior denseness in addition to the fact that the quality is not constant is mainly blended in the coarse portion.

  In the case of using a used refractory of carbon-containing brick such as magnesia carbonaceous material, for example, as described in the inventions of Patent Document 3 and Patent Document 4, the used refractory is previously phosphoric acid, phosphoric acid metal salt, oxidation Impregnation treatment with metal sol, metal alkoxide, etc. The surface treatment by this impregnation improves the hydrophilicity and digestion resistance of the used refractory.

  However, the use of the used refractory is blended in the coarse part and further impregnated, and the properties such as corrosion resistance and strength are inferior to those of the refractory made of an unused refractory raw material. Moreover, the impregnation treatment cannot be denied the high manufacturing cost of refractories due to the addition of the treatment process.

As a lining material such as a molten steel container, there is an alumina-magnesia amorphous refractory material that is constructed by pouring. This material is subjected to the high temperature of the molten steel during use, and alumina and magnesia react to produce spinel (MgO.Al ₂ O ₃ ), and the refractory structure is densified by the lining restraint structure, thereby improving the corrosion resistance. The generated spinel has the effect of resistance to slag penetration.

  On the other hand, as a method for spraying an irregular refractory, there is a wet spraying method in which water is added and an amorphous refractory kneaded in advance is pumped to a nozzle, and a quick setting agent is added before the nozzle or nozzle. is there.

  Among the above-mentioned alumina-magnesia used amorphous refractories, the present inventors selected a material containing spinel generated during use of the amorphous refractories, particularly one of the refractory raw materials for amorphous refractories for wet spraying. When used as a part, the present inventors have found that an effect excellent in adhesion and adhesiveness required for spraying characteristics can be obtained without impairing corrosion resistance, and the present invention has been completed. Moreover, even if it does not perform surface treatment etc. on a used refractory, the said effect is acquired and manufacturing cost high is not caused.

The feature of the present invention is that the amorphous refractory material previously kneaded by adding water is pumped to the nozzle, and the irregular shape used for wet spraying in which the quick setting agent is added and sprayed before the nozzle or the nozzle. Alumina-magnesia used amorphous refractory, which is a refractory and contains a spinel (MgO.Al ₂ O ₃ ) produced during use of the lining of a molten metal container and has a porosity of 18.0% or more Wet product containing used refractory with a composition mainly composed of alumina as a refractory raw material, with 10 to 75% by weight of the pulverized product and particle size adjusted, 3 to 20% by weight of magnesia with a particle size of less than 1 mm It is an irregular refractory for spraying.

  The refractory raw material composition of the irregular refractory applied by spraying is appropriately adjusted to coarse particles, medium particles, and fine particles in consideration of adhesion, adhesive strength, corrosion resistance, and the like. In wet spraying, an irregular shaped refractory is pumped to the nozzle and sprayed with a quick-setting agent added to the nozzle or in front of the nozzle. Specific gravity separation occurs. Of the refractory material, coarse particles are particularly easily separated. When specific gravity separation occurs, adhesiveness, adhesive strength, corrosion resistance, and the like decrease due to unevenness of tissue.

  The amorphous refractory according to the present invention is an alumina-magnesia used amorphous refractory used as a refractory raw material, a sintered alumina or an electrofused alumina generally used as a refractory raw material for wet sprayed amorphous refractories, etc. The specific gravity is small compared to In addition, when the specific gravity is small, the specific gravity separation from water is suppressed during the pumping to the nozzle, the homogenization of the tissue is maintained, and excellent effects in adhesion and adhesiveness are exhibited.

  Used amorphous refractories are porous because of their low specific gravity. Since the amorphous refractory contains a porous refractory raw material, thermal expansion stress that causes separation from the work surface after spraying is reduced, and adhesion is improved.

  Alumina-magnesia amorphous refractories are subjected to the high temperature of molten steel during use, and alumina and magnesia react to produce spinel. It is porous because it is a used refractory, and its use is concerned about a decrease in corrosion resistance. However, the inclusion of spinel having an effect of slag resistance is incompatible with corrosion resistance.

  When an alumina-magnesia used amorphous refractory containing no spinel is used, not only the corrosion resistance is lowered but also the adhesiveness is inferior. The fact that spinel is not included means that after the amorphous refractory is sprayed, the construction body receives heat from molten metal or the like, and leaves room for spinel to be generated by the reaction between alumina and magnesia. When the spinel is formed after spraying the amorphous refractory, the adhesiveness of the present invention is lowered due to the significant volume expansion accompanying the generation.

  Alumina-magnesia spent amorphous refractories do not necessarily contain spinel. For example, even in the lining of a molten steel container, spinel is not generated if it is used on the back side of the lining which does not reach the spinel generation temperature of 1200 ° C. In order to obtain an amorphous refractory having adhesiveness and corrosion resistance, which are the effects of the present invention, it is necessary to selectively use an alumina-magnesia spent amorphous refractory containing spinel.

  Alumina-magnesia used amorphous refractories have a particle size of 8 to 1 mm in a ratio of 10 to 45 mass% and less than 1 mm in a ratio of 0 to 30 mass% in the ratio of the entire refractory raw material. Since specific gravity separation is likely to occur in coarse particles, the effects of adhesion and adhesiveness of the present invention become more remarkable by blending alumina-magnesia used amorphous refractory into the coarse particles.

  In addition, the particle size as used in the field of this invention is classification based on JIS sieve opening. Moreover, the average particle diameter of the ultrafine powder mentioned later is measured by a laser diffraction / diffusion type particle size distribution measuring device.

  The amorphous refractory for wet spraying according to the present invention uses, as a part of the refractory raw material, a material containing spinel produced during use by the amorphous refractory among the alumina-magnesia used amorphous refractories. Thus, an effect excellent in adhesion and adhesiveness required for the characteristics of spraying construction was obtained without impairing the corrosion resistance. Moreover, even if it does not perform surface treatment etc. on a used refractory, the said effect is acquired and manufacturing cost high is not caused. Thereby, the effective utilization of the used amorphous refractory conventionally discarded can be aimed at.

  The alumina-magnesia used amorphous refractory blended with the amorphous refractory of the present invention is used by being lined in a molten steel ladle, tundish, various molten steel processing apparatuses and the like. It is necessary that the material is a material that generates spinel during use, and the presence or absence of spinel can be confirmed by, for example, X-ray diffraction.

  Even if the alumina-magnesia used amorphous refractory is used, the adhesive and corrosion resistance effects of the present invention cannot be obtained with a material that does not generate spinel due to use in a place where the temperature is low.

  Alumina-magnesia used amorphous refractory is the ratio of amorphous refractory to the refractory raw material. If it is less than 10% by mass, the effect of the present invention cannot be obtained in terms of adhesion and adhesive strength. An excessive proportion of the quality refractory raw material causes a decrease in corrosion resistance. A more preferable range is 30 to 60% by mass.

  The particle size of the alumina-magnesia used amorphous refractory is preferably 10 to 45% by mass with a particle size of 8 to 1 mm and 0 to 30% by mass of less than 1 mm as a percentage of the total refractory raw material composition. When the coarse particles of 8 to 1 mm are small, the effect of separation of specific gravity and the effect of relaxation of thermal expansion absorption of magnesia fine powder become insufficient, and a tendency to decrease in adhesion and adhesiveness is observed. Too much is not preferable in terms of corrosion resistance. In addition, if the particle size is less than 1 mm, 0 to 30% by mass is preferable. If the particle size is too large, the ratio of coarse-grained alumina-magnesia used amorphous refractory must be reduced from the balance of the entire particle size composition, and the adhesion Inadequate adhesion.

The used waste materials of the alumina-magnesia amorphous refractory are preferably those having chemical component values of, for example, MgO: 1 to 20% by mass and Al ₂ O ₃ : 97 to 80% by mass.

  The magnesia particles having a particle size of less than 1 mm contribute to the improvement of the corrosion resistance of the matrix portion. As long as the particle size is less than 1 mm, it may be finer, for example, 0.5 mm or less or 0.1 mm or less. If the particle size is too large, the effect of imparting corrosion resistance is poor.

  The specific material of magnesia may be a sintered product or an electromelted product. Also, light-burned magnesia obtained by baking magnesium hydroxide at a relatively low temperature of about 800 to 1200 ° C. may be used.

  The proportion of magnesia in the refractory raw material composition is 3 to 20% by mass. More preferably, it is 5-15 mass%. If it is less, the effect of imparting corrosion resistance is inferior, and if it is too much, the adhesiveness is lowered.

  The remaining alumina in the refractory raw material composition is a refractory raw material excellent in corrosion resistance and volume stability. The specific ratio is preferably 5 to 87% by mass.

  The particle size of alumina is preferably used mainly in the form of fine particles, but when the above-mentioned used waste material is used in a small proportion, it is also used in the coarse portion as necessary in order to balance the particle size of the entire amorphous refractory.

  A specific example of alumina may be either a sintered product or an electromelted product. For use in the fine powder part, calcined alumina which is easily available as fine powder is preferable. Calcinated alumina is an ultrafine powder having an average particle size of 5 μm or less.

  You may combine another refractory raw material with the refractory raw material composition in the range which does not inhibit the effect of this invention. For example, bauxite, porphyry shale, mullite, feldspar, silica, chamotte, andalusite, silica, fused silica, magnesia-calcia, spinel, chromite, sillimanite, zirconia, carbon, silicon carbide, clay, volatile silica , Pitch and the like.

  Of these, the use of volatile silica is particularly effective. Volatile silica is an ultrafine powder, and has the effect of improving the pumpability of the amorphous refractory and preventing the hydration of the magnesia component. The amount used is 5% by mass or less, more preferably 0.5 to 3% by mass, as a percentage of the total refractory raw material composition.

  The feature of the present invention is the above refractory raw material composition, but the amorphous refractory for wet spraying further contains a binder and a dispersant. The types of these binders and dispersants and the amounts used thereof are sufficient by conventional techniques.

  Examples of the binder include alumina cement, magnesia cement, Portland cement, calcium lactate, and aluminum lactate. The addition amount is preferably adjusted in the range of 1 to 15% by mass depending on the kind of the binder with respect to 100% by mass of the refractory raw material composition. Among these, alumina cement having both strength imparting and fire resistance of the construction body is preferable.

  In addition, when a sufficient aggregating action is obtained for the amorphous refractory by using, for example, refractory ultrafine powder such as volatile silica and calcined alumina as a part of the refractory raw material of the amorphous refractory, the binder is used. Is not always necessary.

  The dispersant has the effect of imparting fluidity to the amorphous refractory. Specific examples thereof include sodium tripolyphosphate, sodium hexametaphosphate, sodium polyacrylate, sodium polyacrylate, polycarboxylic acid, sodium lignin sulfonate, and carboxyl group-containing polyether. A preferable addition amount is 0.01 to 1% by mass with respect to 100% by mass of the refractory raw material composition.

  In addition, organic short fibers or inorganic short fibers may be added within a range of, for example, 1% by mass or less to impart effects such as adhesion and drying properties. Examples of the organic short fiber material include nylon, vinylon, PVA, and polyester. Examples of the material of the inorganic short fiber include alumina, silica, alumina-silica, rock wool and the like.

  At the time of construction, the above irregular refractories are kneaded in advance. The kneading water is preferably 10% by mass or less, more preferably 4 to 7% by mass, based on the total amount of the amorphous refractory composition. If too much, the construction body becomes porous and inferior in corrosion resistance.

  During construction, the refractory material after kneading is pumped from a pumping pump such as a piston pump or squeeze pump to a nozzle through a pumping tube, and a quick setting agent is added and sprayed in front of the nozzle or nozzle.

  In order to mix the quick setting agent and to assist the ejection of the amorphous refractory, it is preferable to add the quick setting agent to the amorphous refractory with compressed air as in the past. In addition, when kneading the irregular refractory material, a part of the construction moisture may be used, and the remaining construction moisture may be added and sprayed before the nozzle or the nozzle.

  Examples of the quick setting agent include hydroxides such as calcium hydroxide, sodium hydroxide and potassium hydroxide, alkali aluminates such as sodium aluminate, potassium aluminate and calcium aluminate, sodium silicate, potassium silicate and lithium silicate. Inorganic acid salts such as alkali silicates, phosphoric acid, phosphates, nitric acid, nitrates, hydrochloric acid and chlorides. Moreover, you may combine with flocculating agents, such as a cation system or an anion system, as needed. These quick setting agents can be used in the form of a solution, suspension or powder.

Examples of the present invention and comparative examples thereof are shown below. Table 1 shows the chemical analysis values, X-ray diffraction results, and apparent porosity of the main refractory raw materials used in each example. The apparent porosity was measured according to “Study Method 2. Measurement Method of Apparent Porosity, Apparent Specific Gravity, and Bulk Specific Gravity of Magnesia Clinker” by the Japan Society for the Promotion of Science 124th Test Method Subcommittee.

  The used amorphous refractories A to D shown in Table 1 are obtained from the alumina-magnesia amorphous refractories used for the lining of the molten steel ladle. The used amorphous refractories A to C have a spinel peak in X-ray diffraction. This spinel is produced by heating during use of an alumina raw material and a magnesia raw material. For example, spinel is not generated in the used amorphous refractory D that is not sufficiently heated. In addition, in the table | surface, the numerical value of + has shown the X-ray peak intensity of spinel, and peak intensity is so large that + number is large.

Tables 2 and 3 show the composition of the amorphous refractories in each example and the test results. The test method is as follows.

  The wet spraying equipment is equipped with a 10PRO swing valve double piston pump made by Allentown, and the pressure feed pipe has an inner diameter of 0.051m (2 inches) and a length of 24.48m (100 feet). The tip was connected with a 200 mm long drawn rubber nozzle. The amount of the kneading water was set to 7% by mass with respect to the irregular refractory for spraying.

The quick setting agent was supplied to the amorphous refractory using a monopump having a snake pump, and further compressed air of 0.55 MPa (70 psi) and 8.5 m ³ / min (240 cft) was connected to the rubber nozzle. This was done via a supply tube. As the quick setting agent, a sodium silicate solution was used.

  It was sprayed and tested as a lining repair for a molten steel container that was cast with magnesia-alumina amorphous refractories.

  Specific gravity separation: The degree of specific gravity separation was evaluated in three stages from the cross-sectional structure of the irregular-shaped refractory construction body after spraying (◯: no specific gravity separation, Δ: low specific gravity separation, x: high specific gravity separation).

  Adhesion: The adhesion rate to the vertical repair surface was determined.

  Adhesiveness: After spraying, the bending strength was measured, and the adhesive strength at the boundary between the sprayed material and the repaired material was evaluated.

  Corrosion resistance: Sprayed, test pieces were cut out from the construction, and a rotary erosion test was conducted at 1650 ° C using an erodant consisting of steel and converter slag to determine the rate of erosion.

  Actual machine durability: The number of charges until the construction body after the spraying construction disappeared as the lining repair of the 350t molten steel ladle was obtained.

  In the examples of the present invention, almost no specific gravity separation was observed, and in addition, effects excellent in adhesion, adhesion strength, and spalling resistance were obtained. As a result, these effects showed good durability compared with the conventional materials even in actual machine evaluation.

  On the other hand, Comparative Example 1 which does not use a used amorphous refractory is excellent in corrosion resistance, but has a large specific gravity separation and is inferior in adhesion, adhesion and spalling resistance. Comparative Example 2 uses a used amorphous refractory D having no spinel formation, and is inferior in spalling resistance and corrosion resistance. In Comparative Example 3, the amount of used amorphous refractory is small, specific gravity separation is large, and adhesion, adhesion, and spalling resistance are poor. Comparative Example 4 in which the amount of used amorphous refractory used is large and Comparative Example 5 in which magnesia is not used are both inferior in corrosion resistance. In Comparative Example 6, the amount of magnesia used is too large and the spalling resistance is poor.

  The irregular refractories for wet spraying obtained by the present invention can be used, for example, for molten metal containers such as molten steel pans and tundish, or for lining or repair of incinerators, cement plant furnaces, soaking furnaces, heating furnaces, etc. .

Claims (2)

An amorphous refractory used for wet spraying, in which water is added and kneaded in advance to form an unshaped refractory that is pumped to a nozzle and then added with a quick setting agent in front of the nozzle or nozzle. Alumina-magnesia used amorphous refractory containing a spinel (MgO.Al ₂ O ₃ ) produced during use of the inner lining and having a porosity of 18.0% or more was pulverized and adjusted in particle size An amorphous refractory material for wet spraying containing a used refractory material containing 10 to 75% by mass, 3 to 20% by mass of magnesia having a particle size of less than 1 mm, and the balance mainly composed of alumina as a refractory raw material.   The use according to claim 1, wherein the particle size of the alumina-magnesia used amorphous refractory is 10 to 45 mass% with a particle size of 8 to 1 mm and 0 to 30 mass% with a particle size of less than 1 mm as a percentage of the entire refractory raw material. A non-standard refractory for wet spraying containing finished refractories.