JPH0478585B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is particularly applicable to tap runners, ladles, tundishes,
The present invention relates to castable refractories used for lining soaking furnaces, heating furnaces, pig iron mixers, degasser immersion pipes, etc. (Prior art) Generally, castable refractories have a large amount of alumina cement added as a binder, so the CaO component in the cement forms a liquid phase at high temperatures during use, reducing the strength and fire resistance of castable refractories. It is decreasing. For this reason, it is known that high strength can be achieved by reducing the amount of alumina cement and adding refractory ultrafine powder accordingly, and ultrafine silica powder is particularly frequently used. However, in this case, there is a drawback that during construction, the hardening after kneading with water is rapid, and a sufficient pot life is not obtained until casting. Furthermore, at low temperatures in winter, the hardening of the constructed body often did not proceed. (Problems to be Solved by the Invention) Therefore, various dispersants, water reducing agents, curing retarders, curing accelerators, etc. are added, or cement components are treated with organic solvents, etc., but the pot life and curing Adequate effects have not yet been obtained regarding time adjustment. As a result of extensive research in order to resolve the drawbacks of the conventional materials, the present inventors have reduced the proportion of alumina cement and/or magnesia as binders, and created castable refractories containing ultrafine silica powder. Castable refractories obtained by limiting the particle size and amount of addition, as well as the particle size, amount of addition, and especially PH of ultrafine silica powder, can have sufficient pot life when mixed with water and cast, and can be used in winter. The present invention was completed based on the discovery that curing is guaranteed within the desired time even at low temperatures, and a constructed body with low porosity and high strength can be obtained. (Means for Solving the Problems) The present invention uses alumina cement of 100 to 1μ and/or magnesia of 1 to 8% by weight and a particle size of 5 to 0.01μ.
Ultrafine silica powder 1 to 10 with pH adjusted to 3.5 to 8.5
It is a castable refractory made by adding 0.01 to 0.3% by weight of a refractory powder whose particle size has been adjusted and a deflocculant to the balance. The present invention will be explained in detail below. The particle size of the alumina cement or magnesia used in the binder should be 100 to 1μ; if it is less than 1μ, hydration will be excessive during ripening.
The pot life of castable refractories is shortened. Also
If it exceeds 100μ, the total surface area decreases and a sufficient effect as a binder cannot be obtained. The amount added is preferably from 1 to 8% by weight; if it exceeds 8% by weight, the amount of water required for application will be relatively insufficient, resulting in poor fluidity and premature agglomeration, which is undesirable. Furthermore, the amount of liquid phase produced increases at high temperatures, reducing the fire resistance of castable refractories. This is because if the amount is less than 1% by weight, the desired strength as a construction body cannot be obtained. The ultrafine silica powder used in the present invention has a particle size of 0.01 to 5μ.
It is an amorphous collected dust that is produced as a by-product during the production of metallic silicon, silicon alloys, and zirconia, and is generally known as silica flour. This ultrafine silica powder not only gives castable refractories fluidity during construction, but also creates strong bonds through van der Waals bonds created by Ca ⁺⁺ and Mg ⁺⁺ ions eluted from alumina cement or magnesia as a binder. and the strength of the construction body,
Improve precision. If the particle size is less than 0.01μ, it will coagulate and solidify in the hydration layer of alumina cement or magnesia, reducing its ability to improve fluidity, strength, etc. Moreover, if it exceeds 5μ, the particle size becomes large and the effect as an ultrafine powder is impaired. The proportion of ultrafine silica powder is 1 to 10% by weight,
If it is less than 1% by weight, the amount necessary to obtain close packing will be insufficient and the fluidity will also decrease. On the other hand, if it exceeds 10% by weight, it will be too much and the filling properties will decrease. The pH of ultrafine silica powder used with the above particle size and ratio is
It is necessary to adjust it to 3.5-8.5, preferably 4.0-6.5. The present inventors conducted various studies regarding the pot life and curing time, and found that leaching from alumina cement or magnesia does not occur as usual.
We found that it is effective to control the elution of these cations themselves, rather than reacting Ca ⁺⁺ and Mg ⁺⁺ with a dispersant to control the aggregation of ultrafine silica powder caused by these cations. . It has become clear that when alumina cement or magnesia, which coexists with ultrafine silica powder, is manufactured as a castable refractory, the elution rate of Ca ⁺⁺ and Mg ⁺⁺ is significantly different due to the difference in the pH of the ultrafine silica powder. . That is, PH3.5 to 8.5, which is used in a particularly limited manner in the present invention.
The ultra-fine silica powder has a pot life that is possible for construction and a curing time that does not interfere with construction work. When using PH3.5 or lower, add Ca ⁺⁺ or Mg ⁺⁺ from alumina cement or magnesia after mixing with water.
elutes less, especially when the temperature is low in winter, and when cation elution is inactive, the applied product often remains uncured, although the pot life required for application is sufficient. In addition, in compositions with a pH of 8.5 or higher, Ca ⁺⁺ or Mg ⁺⁺ rapidly dissolves from alumina cement or agnesia after mixing with water, and ultrafine silica powder rapidly aggregates, resulting in a shortened pot life required for construction. It will not be possible to secure it. As mentioned above, by adjusting the pH for limited use to 3.5 to 8.5, preferably 4.0 to 6.0, in winter,
For the first time, it was possible to ensure stable pot life and curing time regardless of the summer season. The above mechanism cannot be said to be fully elucidated, but at present, the alumina cement or magnesia surface becomes hydrated due to trace amounts of water present in these compositions during manufacture or storage after manufacture. The elution of Ca ⁺⁺ or Mg ⁺⁺ is controlled after water-mixing, which fixes the ultrafine silica powder in the hydrated film. It is thought that the degree of immobilization differs depending on the pH of the ultrafine silica powder, resulting in a difference in the elution of Ca ⁺⁺ and Mg ⁺⁺ cations. Adjustment of the pH of the ultrafine silica powder to 3.5 to 8.5 is performed by mixing two or more types of ultrafine silica powder, or by surface treatment of one or more types of ultrafine silica powder, such as pre-mixing treatment with an acid, alkaline solution, etc. As the refractory powder, one or more types selected from basic, neutral, and acidic powders are used. Basic properties include magnesia, dolomite, calcia, and spinel; neutral properties include alumina, chromium, zirconia, and zircon; acidic properties include silica;
These include siliceous, silicate, and clay. Furthermore, carbonaceous materials and carbides may be used. The particle size of these materials is adjusted to coarse, medium, and fine particles in the same way as conventional castable refractories to obtain dense packing. Further, it is also possible to use a material containing ultrafine powder of 5μ or less of one or more of alumina, chromium oxide, zircon, and zirconia. The deflocculant improves the dispersibility of the refractory ultrafine powder and improves the fluidity of the castable refractory. The type is not particularly limited, and examples include inorganic salts such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, acidic sodium hexametaphosphate, aluminum phosphate, sodium borate, and soda carbonate;
One or more organic salts selected from organic salts such as sodium citrate, sodium tartrate, sodium polyacrylate, and sodium sulfonate are used, preferably in accordance with the pH of the ultrafine silica powder. The ratio is 0.01 to 0.01 in terms of the above formulation.
The content shall be 0.3wt%. If it is less than 0.01wt%, the refractory ultrafine powder will have poor dispersibility. If it exceeds 0.3 wt%, the peptizer exhibits thickening properties, and sufficient fluidity cannot be obtained unless the amount of water added is increased. (Example) Examples will be described below. Both the invention examples and comparative examples were kneaded at the proportions and ambient temperature shown in Table 1, and their pot life, curing time, quality, and strength were measured by the following methods. The pot life is determined by measuring the time at which work becomes impossible due to curing after mixing with water during construction.The curing time is determined by measuring the time at which it becomes possible to remove the frame by curing after kneading with water during construction.The apparent porosity is determined by measuring the construction body. JIS after heat treatment at each temperature
- Measured based on R2205. Compressive strength was measured based on JIS-R2206 after heat treatment of the constructed body at each temperature. As is clear from Table 1, the results show that in the examples of the present invention, the pot life was 40 to 120 minutes, and the curing time was 1.5 to 120 minutes.
The required time for implementation was 4.5 hours.
The quality of the constructed body was high, with low porosity and high strength. On the other hand, as shown in Comparative Examples No. 1 and No. 2, ultrafine silica powder with a pH outside the range of the present invention takes 32 hours to harden and a pot life of 15 minutes. Both become shorter and cause problems in construction. In addition, Comparative Examples No. 3 to No. 6 have low strength or compression after heat treatment at 1400°C because the amount of alumina cement as a binder or the amount of ultrafine silica powder added is outside the scope of the present invention. The strength increased significantly compared to that at 110°C, the amount of liquid phase produced at high temperatures was large, and the quality as a refractory deteriorated. As described above, the castable refractory of the present invention has a suitable pot life and curing time and has excellent workability compared to conventional castable refractories, and can provide a constructed body of good quality with low porosity and high strength.

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[Table] Effects of the invention (1) A pot life of at least 30 minutes or more is ensured, and even when casting castable refractories into large construction objects, the pouring surface (if the pot life is short, (The poured material loses its fluidity and does not mix well with the newly cast material, leaving traces of splicing.)
An integrated construction body can be easily obtained without causing any problems. (2) Curing time can be controlled within a few hours even in winter (conventionally, curing time is longer in winter and curing is required for about 12 to 24 hours, and construction is suspended until curing).Construction The construction work will be drastically shortened. (3) As shown in the above (1) and (2), it is possible to obtain a constructed body that has excellent workability and also has good quality as a refractory.

Claims (1)

[Claims] 1 1 to 8% by weight of alumina cement with a particle size of 100 to 1μ and/or magnesia with a particle size of 100 to 1μ,
Add a deflocculant to a mixture consisting of 1 to 10% by weight of ultrafine silica powder with a particle size of 5 to 0.01μ and a pH of 3.5 to 8.5, and the balance of refractory powder with a particle size adjustment of 0.01 to 10%. Castable refractory made by adding 0.3% by weight.