JP2013189322A - Silica-based castable refractory and silica-based precast block refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica-based castable refractory which has excellent thermal shock resistance during heating, suppresses shrinkage under load at high temperatures, exhibits good creep resistance at high temperatures, and hardens within a proper time.SOLUTION: A silica-based castable refractory is obtained by adding, to 100 mass% of a silica-based refractory raw material mixture comprising fused quartz and fired silica stone, 3.0-9.3 mass% (expressed in terms of solid SiO) of colloidal silica and 0.04-0.30 mass% (expressed in terms of solid NaO) of sodium silicate. The fired silica stone consists mainly of tridymite, blending percentages of fused quartz and fired silica stone are 40-100 mass% of fused quartz and 0-60 mass% of fired silica stone, and a total addition amount of sodium components is 0.06-0.32 mass% (expressed in terms of solid NaO) externally relative to 100 mass% of the composition. The fired silica stone may consist mainly of tridymite and cristobalite. In this case, blending percentages of fused quartz and fired silica stone are set to 60-100 mass% of fused quartz and 0-40 mass% of fired silica.

Description

  The present invention relates to a siliceous castable refractory material that is excellent in thermal shock resistance during heating, is suppressed from shrinkage under load at high temperatures, and hardly undergoes creep deformation, and a siliceous precast block refractory using the same.

  Generally, in a coke oven, silica brick is lined for a long period of 30 years or more, and repair of damaged lining parts during long-term use is performed by replacing bricks or spraying refractory materials. . Among these, the repair brick is required to have thermal shock resistance because it is built on the inner wall of the coke oven kept at around 500 ° C.

  Silica brick for lining mainly consists of tridymite and cristobalite as crystal phases, but each crystal has an abnormal volume change due to transition from low temperature type to high temperature type in low temperature region, so thermal shock resistance is inferior. It is not suitable as a hot repair brick. Tridymite undergoes phase transitions at 117 ° C and 163 ° C, resulting in 0.15% and 0.2% linear changes, respectively, and cristobalite transitions at 230 ° C to 270 ° C, with a linear change of approximately 0.4%. Arise.

  Therefore, as a silica brick for hot repair, a brick using a fused silica and a fused silica having a low thermal expansion is usually used. The hot expansion coefficients of cristobalite and tridymite at 1000 ° C. are 1.5% and 1.0%, respectively, whereas that of fused quartz is very small, 0.1%. Can be reduced, and thermal shock resistance is generated. For example, Patent Documents 1 to 5 describe silica impact bricks having thermal shock resistance, which are made of calcined silica mainly composed of cristobalite and / or tridymite and fused silica.

  Fused quartz has the property of crystallizing at a temperature dependent rate regardless of its particle size. The brick is usually fired at 1200 ° C. to 1400 ° C. in the manufacturing process. When the fused quartz blended before firing is crystallized in the firing process, the thermal shock resistance decreases. Since fused quartz is crystallized from the particle surface during the firing process, if it is used in the fine powder part, it will crystallize to the inside during the firing process, and the amorphous part disappears. Thus, complete disappearance of the amorphous part in the firing process is avoided.

Castable refractories, on the other hand, are powder refractories mixed with refractory aggregates and hardeners. They have hydration properties or chemical bonds. Is done. If the temperature rises rapidly after curing, the water vapor pressure inside the construction body may increase and explode. Therefore, it is necessary to raise the temperature stepwise until it reaches several hundred degrees C over several days and dry it.
As a hardener for castable refractories, alumina cement is usually used. However, when alumina cement is used for siliceous castable refractories, CaO · Al ₂ O ₃ which is the main component of alumina cement is the main component of aggregate. Reacts with a certain SiO ₂ to produce a low-melting material of aluminum / calcium silicate (CaO—Al ₂ O ₃ —SiO ₂ ), which loses aggregate particle bonding at a high temperature range and significantly lowers the thermal expansion coefficient under load. Therefore, it is limited to use in a low temperature range.

Portland cement is mainly composed of calcium silicate, and when used in siliceous castable refractories, the amount of CaO-Al ₂ O ₃ —SiO ₂ low melting point product is small and high melting point CaO—SiO ₂ type compound is In order to maintain the function as a binder, it can be used in a higher temperature range than when alumina cement is used as a hardener. For this reason, Portland cement has become the mainstream as a hardener for siliceous castable refractories. For example, Patent Documents 6 and 7 describe a siliceous castable refractory using Portland cement as a curing agent. Patent Document 6 relates to a siliceous castable refractory material containing 2-10% by mass of Portland cement and 1-8% by mass of silica ultrafine powder using fused quartz as a main raw material. Patent Document 7 discloses a post-use silica brick that contains 70% by mass or more of tridymite as a main mineral phase or a non-standard product of a fired silica brick, 2-5% by weight of Portland cement, and 8-22 of fumed silica. The present invention relates to a siliceous castable refractory blended and adjusted by mass%.

However, calcium silicate which is the main component of Portland cement (its main substance is alite (3CaO · SiO ₂ )) is hydrated and contains a large amount of 3CaO · 2SiO ₂ · 3H ₂ O as shown in the chemical reaction formula below. Ca (OH) ₂ is produced, but its hydration rate is slower than that of CaO.Al ₂ O ₃ which is the main material constituting the alumina cement. Moreover, the dehydration temperature of Ca (OH) ₂ is high at 500 ° C to 600 ° C. For this reason, siliceous castable refractories using Portland cement as a curing agent need to take sufficient measures against explosion in addition to means such as adding a curing accelerator.

For example, Patent Documents 8 and 9 describe castable refractories that are cured using the gelation action of colloidal silica. The castable refractory disclosed in Patent Document 8 is 0.05 to 5.0 parts by mass in terms of 100 to part by mass of the refractory composition, with a siliceous chemical binder such as silica sol converted to solid SiO ₂ , and polyacrylic. It is an acid and / or salt thereof blended in an amount of 0.001 to 1.0 parts by mass, and its main use is for the lining of molten metal containers. Polyacrylic acid and / or a salt thereof is used as a regulator for gelation time (curing time), and in the examples, 1N hydrochloric acid or 1N sodium hydroxide aqueous solution is 0.1 to 1 as a gelling agent. 0.0% by mass is used. In the examples, 2% of alumina cement is blended.

The castable refractory described in Patent Document 9 is 0.39 to 5 parts by mass of a hardly soluble sodium silicate as a binder and 0.09 to 0.09 in terms of solid content with respect to 100 parts by mass of a normal refractory raw material. 3 parts by mass is added. This castable refractory has a self-hardening property because the hardly soluble sodium silicate gels the colloidal silica, but the mass of the colloidal silica solid content and the hardly soluble sodium silicate so as to have sufficient curability in a timely manner. The ratio needs to be 5 or less, and the amount of hardly soluble sodium silicate added increases.
Slightly soluble sodium silicate is a pulverized product (cullet) before autoclave treatment in which silica sand and sodium hydroxide are melted at a high temperature and cooled, and a powder or an aqueous solution obtained by dehydration after autoclave treatment generally contains sodium silicate and It is what is called. Although sodium silicate is readily soluble in water, poorly soluble sodium silicate has a much lower dissolution rate in water than sodium silicate.

Japanese Patent Publication No. 1-338073 JP-B-1-38074 JP 05-132355 A JP 2003-55035 A JP 2007-302540 A JP 56-78476 A JP 2006-290657 A JP-A-7-149575 JP-A-55-167182

Silicic castable refractories have the advantage that there is no firing step necessary for the production of silica bricks and no crystallization countermeasures are required in the firing step of the fused quartz compounded to impart thermal shock resistance. Further, when the gelling action of colloidal silica described in Patent Documents 8 and 9 is used as a curing agent for siliceous castable refractories, CaO and Al ₂ O ₃ are used as compared with the case of using alumina cement or Portland cement. Therefore, there is a possibility that a castable refractory having a considerable quality of silica brick can be obtained.
However, Patent Documents 8 and 9 do not describe thermal shock resistance during heating and creep resistance under high temperature, and if the technique of Patent Document 9 is applied to a siliceous castable refractory, gelation occurs. A large amount of poorly soluble sodium silicate is required as an agent, and there is a concern that the heat resistance (shrinkage under load, creep resistance) is lowered.

  The present invention has been made in view of the above-mentioned problems of the prior art relating to siliceous castable refractories, is excellent in thermal shock resistance during heating, and is suppressed from shrinkage under load at high temperatures, An object of the present invention is to provide a siliceous castable refractory and a siliceous precast block refractory having good creep resistance and sufficient curability at the appropriate time.

The siliceous castable refractory according to the present invention is obtained by converting colloidal silica into solid SiO ₂ by 3.0 to 9.9 with respect to 100% by mass of a siliceous refractory raw material composition composed of fused quartz and calcined silica. 3% by mass, sodium silicate in terms of solid Na ₂ O added in an amount of 0.04 to 0.30% by mass, calcined quartz is mainly composed of tridymite, fused quartz and calcined silica of siliceous refractory raw material composition The blending ratio is set to 40 to 100% by mass of fused quartz and 0 to 60% by mass (including 0% by mass) of calcined silica. Further, the total amount of soda components added to the outer shell (the total amount of soda components contained in the colloidal silica or the like) is 0.06 to 0.32% by mass in terms of solid Na ₂ O.

In the siliceous castable refractory according to the present invention, a calcined silica mainly composed of tridymite and cristobalite can be used instead of the calcined silica mainly composed of tridymite. In this case, the blending ratio of the fused silica and the fired silica is 60-100% by weight of fused silica and 0-40% by weight (including 0% by weight) of the fired silica.
The siliceous castable refractory can contain 8% by mass or less of silica flour as a part of the siliceous refractory raw material composition.

  According to the present invention, the thermal shock resistance during heating is excellent, the shrinkage under load at high temperature is suppressed, the creep resistance at high temperature is good, the drying is easy, and the curability is sufficient in a timely manner. A siliceous castable refractory and a siliceous precast block refractory can be provided.

It is a graph of the thermal expansion curve of an Example and a comparative example. It is a graph of the thermal expansion curve under a load of an Example and a comparative example. It is a graph of the thermal expansion curve under load of another Example and a comparative example. It is a graph of the thermal expansion curve of another Example and a comparative example. It is a graph of the thermal expansion curve under load of another Example and a comparative example.

Hereinafter, the siliceous refractory raw material composition and the curing agent of the siliceous castable refractory according to the present invention will be described more specifically.
(Siliceous refractory raw material composition)
The siliceous castable refractory according to the present invention uses fused quartz and calcined silica (crystalline silica) as a siliceous refractory raw material composition (aggregate). As the calcined silica, calcined silica mainly composed of tridymite or calcined silica mainly composed of tridymite and cristobalite is used. As fused quartz, quartz glass, which is a quartz glass melted at a high temperature of 2000 ° C. or higher, is rapidly cooled and solidified, and a porous gel of quartz glass is prepared by a hydrolysis method from a solution of metal alkoxide, which is dried and fired. The high-purity fused quartz obtained in this way can be used.

  In the siliceous refractory raw material composition, the proportion of fused quartz and calcined silica is 40 to 100% by mass of fused quartz and 0 to 60% by mass of calcined silica when the calcined silica is mainly composed of tridymite, and mainly tridymite and cristobalite. When it makes it into a component, it is set as 60-100 mass% of fused quartz, and 0-40 mass% of baked silica. There may be a case where the fused silica is not contained in the fused silica 100 mass%, that is, the siliceous refractory raw material composition. When using calcined silica with tridymite as a main component, the ratio of calcined silica exceeds 60% by mass (the blending ratio of fused silica is less than 40% by mass), or calcined silica with tridimite and cristobalite as main components. When the ratio of calcined silica exceeds 40% by mass (the blending ratio of fused silica is less than 60% by mass), the thermal shock resistance decreases.

  The calcined silica with tridymite as the main component is, for example, one obtained by crushing used siliceous brick and adjusting the particle size. Can be used after crushing and adjusting the particle size. The used siliceous brick has an X-ray diffraction intensity ratio of tridymite and cristobalite of approximately 100 to 10 or more, and in the present invention, the one having such an X-ray diffraction intensity ratio is called a calcined meteorite mainly composed of tridymite. . In addition, the unused siliceous brick has an X-ray diffraction intensity ratio of tridymite and cristobalite generally in the range of 100 to 90 to 140. In the present invention, those having such an X-ray diffraction intensity ratio are treated with tridymite and cristobalite. It is called calcined meteorite with the main component. When the blending ratio of calcined silica is large, it is desirable to use calcined silica in fine and fine powder regions of 1 mm or less and fused quartz in coarse particle regions of more than 1 mm.

  The siliceous refractory raw material composition may contain silica flour as necessary, in addition to fused quartz and calcined silica. In addition, the fused quartz can include fused quartz ultrafine powder having an integrated average particle diameter of less than about 1 μm. Silica flour and fused silica ultrafine powder have the effect of reducing the amount of colloidal silica added and the amount of water added, and improving bulk specific gravity and compressive strength. As the amount of silica flour increases, the flowability and filling properties of the castable refractory after kneading deteriorate, so the blending proportion of silica flour in the siliceous refractory raw material composition is preferably 8% by mass or less.

(Curing agent)
The siliceous castable refractory according to the present invention uses colloidal silica and sodium silicate as a curing agent. Sodium silicate is a colloidal silica gelling agent, and, as described above, is an ordinary product obtained by dehydrating cullet (slightly water-soluble sodium silicate) after autoclaving. This sodium silicate has a SiO ₂ / Na ₂ O molar ratio of 1 to 3.3 and is readily water-soluble, and can be used in the form of a powder or an aqueous solution. Colloidal silica is 3.0-9.3 mass% (converted to solid SiO ₂ ) as an outer shell, and sodium silicate is 0.04-0.30 mass% with respect to 100 mass% of the siliceous refractory raw material composition. (Converted to solid Na ₂ O). In the production of the siliceous castable refractory, for example, sodium silicate is added to the siliceous refractory raw material composition, kneaded with colloidal silica diluted with an undiluted solution or water, cast into a mold, and dried.

Since 99% or more of the solid content of the colloidal silica is SiO ₂ , the chemical component of the siliceous castable refractory according to the present invention has few impurities and is substantially equivalent to the silica brick. Therefore, it is possible to obtain a siliceous castable refractory having a small amount of CaO—Al ₂ O ₃ —SiO ₂ -based low melting point compound, relaxing thermal contraction under load, and having good creep resistance. Moreover, since most of the water | moisture content adsorb | sucked to a silica gel is spin-dry | dehydrated at 100-150 degreeC, it can dry easily and the explosion resistance at the time of a heating is also favorable.

The castable refractory according to the present invention is one in which sodium silicate is added to a siliceous refractory raw material composition, kneaded with a colloidal silica diluted with a stock solution or water, and poured into a formwork. The pot life that can maintain the hardness, and the curing time until it becomes so hard that it can be removed, the more the amount of solid SiO _{2 in} colloidal silica, and the solid Na ₂ O of sodium silicate added as a gelling agent The higher the amount, the shorter. If the pot life is short, pouring becomes difficult, and if the curing time is too long, the construction process is extended. Therefore, the pot life is usually required to be 0.5 hours or more, and the curing time is 72 hours or less. Required. Further, the pot life is preferably 1 hour or longer and the curing time is preferably within 24 hours.

  In addition to the function as a gelling agent for colloidal silica, sodium silicate has the effect of relaxing the shrinkage under load at a high temperature of 1000 ° C. to 1400 ° C. and improving the creep resistance. Colloidal silica gels at room temperature by pH change and addition of electrolyte. Various gelling agents such as ammonium chloride, sodium silicofluoride, ammonium alum, gypsum, magnesium sulfate, etc. are known, and these gelling agents can be used only if gelling colloidal silica. These may be added as appropriate, but they do not have the effect of reducing shrinkage under load at high temperatures.

From the standpoint of obtaining an appropriate pot life and curing time and reducing the shrinkage under load at a high temperature, colloidal silica is 3.0 to 9.3 mass% (in terms of solid SiO ₂ ) as an outer shell, Similarly, sodium silicate was added within a range of 0.04 to 0.30 mass% (in terms of solid Na ₂ O). When the Na ₂ O solid content of sodium silicate is less than 0.04% by mass, the relaxation effect of shrinkage under load at high temperature is small, and when it is more than 0.30% by mass, creep resistance is lowered.
In addition, in the siliceous castable refractory according to the present invention, fused quartz, which occupies most of the siliceous refractory raw material composition, has a property of crystallizing at a temperature of about 1000 ° C. or more. It accelerates in the presence of earth metals, and alkali metals react with SiO ₂ to produce low melting point products. Therefore, technically, the siliceous castable refractory according to the present invention is not strange even if the shrinkage under load at high temperature is increased, but actually the shrinkage under load at high temperature is suppressed.
In order to assist the gelation action of sodium silicate, other gelling agents such as a small amount of ammonium chloride and sodium sulfate can be added. For example, ammonium chloride is suitably 0.2% by mass or less, and sodium sulfate is suitably 0.02% by mass or less in terms of solid Na ₂ O.

In the castable refractory according to the present invention, sodium silicate is added in an amount of 0.04 to 0.30% by mass in terms of solid Na ₂ O, but the soda component contained in a small amount in colloidal silica also acts to alleviate shrinkage under load. It is thought that there is. Therefore, in the present invention, not only the amount of sodium silicate added, but also the total amount of soda components added to the soda component contained in the colloidal silica is 0.06 to 0.32 mass in terms of solid Na ₂ O. %.

(Additional water amount)
As mentioned earlier, in the production of siliceous castable refractories, sodium silicate is added to the siliceous refractory raw material composition (aggregate), kneaded with colloidal silica diluted with stock solution or water, and poured into the mold Install and dry. If castable refractories are too hard during casting, filling will be insufficient, and if they are too soft, the coarse and fine parts of the siliceous refractory raw material composition will be easily separated, especially in the construction method using a vibration table, and the construction will be homogeneous. I can't get a body. The softness of the castable refractory at the time of casting construction can be adjusted by the amount of added water (including that added as a dispersion medium for colloidal silica). The optimum softness of the castable refractory during casting works depends on the construction method such as a stick, vibrator and vibration table, but if the amount of water added suitable for the construction method is experimentally determined within the range of 6 to 12% by mass. Good.

[Common subject matter]
Unused silica bricks that are out of specification or unnecessary are used as fired silica stones that have been collected after a long period of use in a hot-blast furnace as fired silica stones containing tridymite as the main component, and fired silica stones mainly containing tridymite and cristobalite. Waste was used. About 300 kg of used silica brick waste and unused silica brick waste were each randomly collected, crushed and mixed to 3 mm or less, and divided into particle sizes of 3-1 mm, 1-0.150 mm, and 0.150 mm or less.

Randomly sample 2Kg of used silica bricks and unused silica bricks that were crushed and mixed to 3mm or less. The crystal phase was examined. The crystal phase was analyzed by X-ray diffraction method. Table 1 shows chemical components of used silica brick waste and unused silica brick waste, and Table 2 shows crystal phases and X-ray diffraction intensities. As shown in Table 2, low-temperature type tridymite and low-temperature type cristobalite were observed in the crystal layer for both used silica brick waste and unused silica brick waste. In Table 2, the X-ray diffraction intensity (maximum diffraction intensity) of cristobalite is a relative value when the X-ray diffraction intensity (maximum diffraction intensity) of tridymite is 100.
Spent silica brick waste is mainly composed of tridymite, and unused silica brick waste is mainly composed of tridymite and cristobalite.

As the fused quartz, a high-purity amorphous product having a SiO ₂ content of 99.9% by weight or more and divided into particle sizes of 3-1 mm, 1-0.150 mm, and 0.150 mm or less was used.
As colloidal silica, colloidal silica using water as a dispersion medium was used. Table 3 shows the materials of the two types of colloidal silica A and B used in the examples. In the examples, a stock solution of colloidal silica A or colloidal silica B, or a diluted solution thereof was used.

[Example 1]
As the siliceous refractory raw material composition (aggregate), the spent silica brick and fused silica are used, the blending ratio of both aggregates is changed, and sodium silicate is added as an outer shell to 100% by mass of the raw material composition. Obtained by adding 0.14% by mass as solid Na ₂ O, colloidal silica to 6.7% by mass in terms of solid SiO ₂ , and 10.0% by mass of water, kneading, molding, and de-framed. Using the refractory test pieces, physical property values (bulk specific gravity, compressive strength, thermal expansion coefficient, thermal expansion coefficient under load, creep value) and thermal shock resistance evaluation were performed.
For the kneading, a universal kneader manufactured by Dalton Co., Ltd. was used. The softness of the castable refractory after kneading was almost the same in Examples 1 to 6 and Comparative Example 1. Molding was performed using a vibration table manufactured by Hayashi Vibrator Co., Ltd. under conditions of a frequency of 50 Hz and a vibration time of 5 minutes. Using the castable refractories after kneading and molding, the pot life and curing time at room temperature (25 ° C.) were measured.

A part (about 500 g) of the castable refractory after kneading was put in a plastic bag and stored in a thermostat kept at a constant temperature of 25 ° C., and used for measuring the pot life and the curing time. At this time, the bag mouth of the plastic bag was closed with a rubber band and stored in a thermostatic bath so that the castable refractory was not dried. Check the fluidity of castable refractories every 15 minutes with the touch and visual sense, and use the time from kneading until the fluidity is lowered (flowiness is lowered enough to cause insufficient filling by vibration construction method). It was time (assuming T1). If no decrease in fluidity was confirmed after 72 hours had elapsed from the start of the pot life measurement, the subsequent measurement was stopped.
Castable refractories that have been judged to have deteriorated in fluidity are placed on a vibration table with plastic bags and subjected to vibration for 5 minutes to increase the density. Then, the fluidity is confirmed again as described above, and the decrease in fluidity is re-established. When confirmed, the pot life of the castable refractory was determined as T1. This castable refractory was returned to the thermostat for curing time measurement. On the other hand, if fluidity decline was not reconfirmed (fluidity returned), it was returned to the thermostatic bath again, and after 15 minutes, the plastic bag was placed on the vibration table again and subjected to vibration for 5 minutes. Was confirmed in the previous term, and when the fluidity drop was reconfirmed at this time, the pot life of the castable refractory was determined to be T1 + 15 minutes. If the fluidity decline was not reconfirmed, the above process was repeated.

The curing time is the time from when kneading until strength is developed to such an extent that the molded body can be removed without damage. In this embodiment, the strength of the castable refractory for measuring the curing time is confirmed every 15 minutes, and the time until the strength is developed to such an extent that the castable refractory is not crushed or cracked by arm force is defined as the curing time. did.
On the other hand, a part of the castable refractory after the kneading was poured into a mold conforming to the regulations of JISR2553, and the entire mold was cured in the same thermostatic bath as described above, and this was used for confirmation of curing. During curing, the castable refractories were covered with a plastic sheet to prevent drying. When the castable refractory for measuring the curing time reaches the curing time, take out the castable refractory for confirmation of curing from the thermostatic bath and check whether it can be removed normally, and immediately comply with the regulations of JISR2553. The compressive strength was measured accordingly. In addition, about the Example of this invention, and the comparative example, all could be removed normally normally at the time of hardening time arrival, and all the compressive strengths were 4 Mpa or more.

The test piece for bulk specific gravity and compressive strength test was molded using a molding die described in JIS-R-2553. The compressive strength was measured in accordance with JIS-R-2553. Table 4 shows the measured values of bulk specific gravity and compressive strength after drying at 110 ° C. for 24 hours and after baking at 1200 ° C. (heating rate 5 ° C./min) for 3 hours.
The coefficient of thermal expansion was measured in accordance with JIS-R-2207-1 (visible light projection method). Table 4 shows the measured values of the coefficient of thermal expansion at 1000 ° C.

  The thermal expansion coefficient and creep value under load were measured in accordance with JIS-R-2658 using a hot creep test furnace (SRC-15 type) manufactured by Shinagawa Refractories Co., Ltd. with a pressure of 0.2 MPa. did. The thermal expansion coefficient under load was measured by heating the test piece to 1400 ° C. at a heating rate of 5 ° C./min. Table 4 shows the measured values of the coefficient of thermal expansion under load when the temperature reaches 1400 ° C. Then, it kept at 1400 degreeC for 50 hours as it was, and measured the thermal expansion coefficient under the load after holding for 50 hours. Table 4 shows the difference between the thermal expansion coefficient under load after holding at 1400 ° C. for 50 hours and the thermal expansion coefficient under load when reaching 1400 ° C. as a creep value.

  The thermal shock resistance evaluation was performed by using a test body which was molded into a cube having a side of 100 mm, dried at 110 ° C. × 24 hours and then naturally cooled, and placed in an electric furnace maintained at 600 ° C. or 1200 ° C. for 3 hours. After the elapse of time, the electric furnace was turned off and allowed to cool naturally, and then the appearance of the specimen was observed with the naked eye. Thermal shock resistance was evaluated by the presence or absence of cracks. The results are shown in Table 4.

As shown in Table 4, in all of Examples 1 to 6 and Comparative Example 1, the compressive strength is 20 MPa or more, which is the standard for coke oven quartzite brick, and the thermal expansion coefficient under load when reaching 1400 ° C. is −0. It was in the range of 13 to 0.25%, and the creep resistance was also good. In addition, in Examples 1 to 6, the result of the thermal shock resistance evaluation test was also good. On the other hand, in Comparative Example 1, the proportion of the aggregate obtained from used silica brick (fired meteorite composed mainly of tridymite) was excessive, and cracks occurred in the thermal shock resistance evaluation test.
In Examples 2 and 3, the blending ratio of fused silica and used silica brick is the same, but in Example 2, the used silica brick is used in a fine powder area of 0.150 mm or less, and Example 3 is used. Pre-silica brick is used for fine and coarse grained areas of 0.150 mm to 3 mm. The reason why the thermal expansion coefficient at 1000 ° C. of Example 3 is larger than that of Example 2 is considered for this reason.

[Example 2]
As the siliceous refractory raw material composition (aggregate), the above-mentioned unused silica brick and fused quartz are used, the blending ratio of both aggregates is changed, and sodium silicate is added as an outer shell to 100% by mass of the raw material composition. 0.14% by weight as solid Na ₂ O, 6.7% by weight of colloidal silica in terms of solid SiO ₂ and 10.0% by weight of water were added, and kneaded in the same manner as in [Example 1]. Using the refractory test pieces obtained by molding and deframement, the physical property values were measured and the thermal shock resistance was evaluated in the same manner as in [Example 1]. The results are shown in Table 5.

In all of Examples 1, Examples 7 to 10, and Comparative Examples 2 to 3, the compressive strength is 20 MPa or more, which is the standard for coke oven siliceous brick, and the thermal expansion coefficient under load when reaching 1400 ° C. is −0.13. It was in the range of ˜0.32%, and the creep resistance was also good. In addition, in Example 1 and Examples 7 to 10, the result of the thermal shock resistance evaluation test was also good. On the other hand, in Comparative Examples 2 and 3, the proportion of aggregate obtained from unused silica brick (fired meteorite composed mainly of tridymite and cristobalite) was excessive, and cracks occurred in the thermal shock resistance evaluation test. .
In Example 7 and Example 8, the blending ratio of fused quartz and unused siliceous aggregate is the same, but in Example 7, unused silica brick is 20% by mass in a fine powder region of 0.150 mm or less. On the other hand, Example 8 uses 12% by mass of unused silica brick in the fine powder region of 0.150 mm or less and 8% by mass in the fine particle region of 0.150 to 1 mm. The reason why the thermal expansion coefficient at 1000 ° C. of Example 8 is larger than that of Example 7 is considered for this reason.

As shown in Tables 4 and 5, the thermal expansion coefficient at 1000 ° C. tends to increase as the blending ratio of silica brick increases. Moreover, in Comparative Examples 2 and 3 using unused silica brick, the thermal expansion coefficient exceeds 1% with a small blending ratio compared to Comparative Example 1 using used silica brick, and in an impact resistance evaluation test. A crack has occurred.
Comparing Examples 2 and 3 in Table 4 and Examples 7 and 8 in Table 5, the coefficient of thermal expansion at 1000 ° C. also varies depending on the particle size of the silica brick, and Example 2 in which the silica brick is frequently used in the fine powder region. 7 has a lower coefficient of thermal expansion than Examples 3 and 8. On the other hand, it is well known that thermal shock resistance tends to decrease as the coefficient of thermal expansion increases. Therefore, when silica brick is blended in the castable refractory according to the present invention, the blending is small from the viewpoint of impact resistance. In proportion, it is desirable to use in the fine powder region, and it is desirable to use used silica brick (calcined silica with tridymite as the main component).

[Example 3]
As the siliceous refractory raw material composition (aggregate), the unused silica brick and fused quartz are used, the blending ratio of both aggregates is constant, and the amount of colloidal silica added (added in terms of solid SiO ₂ ) and The amount of water added was constant, only the amount of sodium silicate added (added in terms of solid Na ₂ O) was changed, and the relationship between the amount of sodium silicate added and the curability was examined. Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 6.

As shown in Table 6, the pot life and the curing time tended to be shortened as the amount of sodium silicate added increased. In all the examples shown in Table 6 (Examples 11 to 14, 7, and 15), the pot life and the curing time are within the normally required time range. In Examples 12 to 14, Example 7 and Example 15, the amount of sodium silicate added (added in terms of solid Na ₂ O) is 0.08 to 0.16% by mass, which is preferable in this range. A pot life of 1 hour or more and a curing time of 24 hours or less are obtained. At this time, the total soda content (added amount converted to solid Na ₂ O) is 0.10 to 0.18% by mass. In addition, the physical property value of a refractory is substantially the same in all Examples (Examples 11 to 14, 7, and 15), and compressive strength, thermal expansion coefficient under load when reaching 1400 ° C., creep resistance, and thermal shock Resistance was also good.
On the other hand, Comparative Example 4 was not cured within 72 hours because the amount of sodium silicate added (the amount added in terms of solid Na ₂ O) was zero. Therefore, in Comparative Example 4, the physical property value of the refractory is not measured.

[Example 4]
As the siliceous refractory raw material composition (aggregate), the unused silica brick and fused quartz are used, the blending ratio of both aggregates is constant, and the addition amount of sodium silicate (addition amount converted to solid Na ₂ O) The amount of colloidal silica and the amount of curability were examined by changing only the amount of colloidal silica added (the amount added in terms of solid SiO ₂ ). Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 7.

As shown in Table 7, as the amount of colloidal silica added decreased, the pot life and the curing time tended to be extended. In all the examples shown in Table 7 (Examples 16 to 22), the pot life and the curing time are within the normally required time range. In Examples 16 to 21, the colloidal silica addition amount (addition amount converted to solid SiO ₂ ) is 4.2 to 9.3 mass%, and the pot life of 1 hour or more which is preferable in this range is used. And a curing time within 24 hours is obtained. The physical properties of the refractories are almost the same in all Examples (Examples 16 to 22), and the compressive strength, thermal expansion coefficient under load when reaching 1400 ° C., creep resistance and thermal shock resistance are also shown. It was good.

[Example 5]
As a siliceous refractory raw material composition (aggregate), in addition to the unused silica brick and fused quartz, silica flour or fused silica ultrafine powder is used, and the blending ratio of silica flour or fused quartz ultrafine powder is changed, and a curing agent is used. As described above, the addition amount of colloidal silica was adjusted so that the addition amount of sodium silicate (addition amount converted to solid Na ₂ O) was constant and the softness of the castable refractory immediately after kneading became substantially the same. The used fused silica ultrafine powder has a SiO ₂ content of 99.7%, spherical particles having an integrated average particle diameter of 1 μm or less, and silica flour has a SiO ₂ content of 97.1%. Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 8.

Silica flour is a siliceous ultrafine powder, and in siliceous castable and general low cement castable refractory with Portland cement as a hardener, by adding a combination of several mass% silica flour and a small amount of water reducing agent, Since the amount of added water can be reduced and the strength can be increased, it is widely used.
As shown in Example 13 and Examples 23 to 26 in Table 8, as the blending amount of silica flour increases, the amount of colloidal silica added tends to decrease, and the bulk specific gravity and compressive strength tend to increase. The pot life and the curing time are shortened as the amount of silica flour is increased because the trace amount of the electrolyte component is eluted from the silica flour.

Examples 27 and 28 in Table 8 use fused silica ultrafine powder instead of silica flour. The fused silica ultrafine powder is higher in purity than the silica flour and has very little elution electrolyte component. When comparing the examples 24 and 27 and the examples 26 and 28, the fused quartz ultrafine powder uses the fused quartz ultrafine powder rather than the silica flour. By doing so, the amount of colloidal silica added can be reduced, and a molded article having high fluidity and good filling properties during vibration molding can be obtained, and the bulk specific gravity and compressive strength are increased.
Examples 23 to 25 and Examples 27 and 28 shown in Table 8 show significant differences in thermal expansion and creep values under load compared to Example 13 in which neither silica flour nor fused silica ultrafine powder was added. Furthermore, the thermal shock resistance is also good. However, in Example 26 with a large amount of silica flour added, the fluidity at the time of vibration molding is small, so the filling property is relatively poor, the shrinkage under load is large, and the creep deformation is slightly larger than that of Example 13. It was.

[Example 6]
In addition to the unused silica brick and fused quartz, the silica flour or fused silica ultrafine powder is used as the siliceous refractory raw material composition (aggregate), the blending ratio is constant, and the appropriate pot life and hardening The addition amount of colloidal silica and the addition amount of sodium silicate (addition amount converted to solid Na ₂ O) were adjusted so that time was obtained. In the case of using no sodium silicate, ammonium chloride or the hardly soluble sodium silicate described in Patent Document 9 was used as a gelling agent. Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 9.

When Table 9 is seen, Examples 29-32 have high compressive strength, shrinkage | contraction under load is suppressed, and it has creep resistance. Thus, in addition to the function as a gelling agent for colloidal silica, sodium silicate has the effect of alleviating shrinkage under load during heating and heating.
On the other hand, Comparative Examples 5 and 6 in which sodium silicate was not added and ammonium chloride was used as a gelling agent had a small thermal expansion coefficient under load (large shrinkage under load). Further, in Comparative Example 7 in which the amount of sodium silicate added (the amount added in terms of solid Na ₂ O) is excessive, the creep resistance is lowered. Comparative Example 8 to which hardly soluble sodium silicate was added as a gelling agent did not cure within 72 hours, and the refractory physical properties could not be measured.

For Comparative Example 5 and Examples 29, 31, and 32, FIG. 1 shows a graph of thermal expansion curves, and FIG. 2 shows a graph of thermal expansion curves under load. Looking at the thermal expansion curve, there is no significant difference between Comparative Example 5 and Examples 29, 31, and 32. However, when looking at the thermal expansion curve under load, the addition amount of sodium silicate (addition amount converted to solid Na ₂ O) In Examples 29, 31, and 32, which are appropriate), compared with Comparative Example 5 in which no sodium silicate was added, the shrinkage under load from around 900 ° C. was alleviated, and in Examples 31 and 32 in which the amount added was particularly increased. It can be seen that it has been relaxed.

[Example 7]
As the siliceous refractory raw material composition (aggregate), in addition to the unused silica brick and fused quartz, the fused silica ultrafine powder is used, the blending ratio thereof is constant, and the amount of colloidal silica added and sodium silicate The addition amount (addition amount converted to solid Na ₂ O) was kept constant, and ammonium chloride or sodium sulfate was added as a gelling agent. Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 10.

As shown in Table 10, in Example 29, the addition time of sodium silicate as the gelling agent (addition amount converted to solid Na ₂ O) is relatively small, so the curing time is 24 hours. On the other hand, Example 33 using ammonium chloride as a gelling agent and Example 34 using sodium sulfate together have a shorter curing time. Thus, by using another type of gelling agent in combination with sodium silicate, it is possible to give the castable refractory according to the present invention fast hardening. The physical property values of Examples 33 and 34 are almost the same as those of Example 29.

[Example 8]
As the siliceous refractory raw material composition (aggregate), only the fused silica is used, the amount of colloidal silica added is constant, and sodium silicate (Example 1) or ammonium chloride (Comparative Example 9) is added as a gelling agent. did. Using the refractory specimens obtained by kneading, molding, and deframeation in the same manner as in [Example 1], measurement of physical properties and evaluation of thermal shock resistance were performed in the same manner as in [Example 1]. The results are shown in Table 11. Moreover, the graph of the thermal expansion curve under a load of Example 1 and Comparative Example 9 is shown in FIG.

  As shown in Table 11 and FIG. 3, in Comparative Example 9 using ammonium chloride as the gelling agent, the resin contracts significantly under the load from around 900 ° C., but in Example 1 using sodium silicate as the gelling agent, This shrinkage under load is alleviated.

In FIG. 3 and FIG. 2 shown above, Comparative Examples 5 and 9 using ammonium chloride as the gelling agent remarkably shrunk under load from around 900 ° C., whereas examples using sodium silicate as the gelling agent 1, 29, 31, and 32 are relaxed under load from around 900 ° C. Since the soda component produces a Na ₂ O—SiO ₂ low melting point product, when sodium silicate is used as the gelling agent, it is considered technically common that this shrinkage under load increases, but the measured load The lower thermal expansion curve has the opposite result.
The shrinkage under load from around 900 ° C. seen in Comparative Examples 5 and 9 is considered to be caused by the decrease in fine pores accompanying the sintering of silica gel, but in Examples 1, 29, 31, 32, etc. according to the present invention. By using sodium silicate as a gelling agent, the soda component of sodium silicate diffuses and penetrates the surface of the fused silica and adheres to the surface of the fused silica, and the fused quartz and silica gel are subjected to crystallization promoting action by the soda component, It is presumed that the change to high-temperature type cristobalite with a low density progressed rapidly, and this caused the shrinkage under load to be suppressed. Table 12 shows the crystal phase of silica and the density of fused quartz.

[Example 9]
The characteristics of the siliceous castable refractory according to the present invention were compared with those of conventional siliceous castable refractories and silica bricks. In Comparative Example 10, ordinary Portland cement is used as a curing agent, and organic fibers are added as an explosion preventing material. In Comparative Example 11, alumina cement is used as a curing agent. Comparative Example 12 is a normal silica brick actually used in a coke oven. For Examples 35 and 36 and Comparative Examples 10 and 11, refractory specimens obtained by kneading, molding, and deframing were used in the same manner as in [Example 1], and Comparative Example 12 was fired under normal conditions. Using the refractory test piece cut out from the silica brick, the physical property value was measured and the thermal shock resistance was evaluated in the same manner as in [Example 1], and a blast test (excluding Comparative Example 12) was performed.

In the explosion test, a cube-hardened specimen having a side of 100 mm that was cured for 48 hours in a 5 ° C. constant temperature bath was placed in an electric furnace previously held at 800 ° C., and the presence or absence of explosion was observed. During curing, the casting surface at the top of the mold was covered with vinyl to prevent drying.
In thermal shock resistance evaluation, only Comparative Example 10 (because it is easy to explode) was heated to 600 ° C. at a heating rate of 1 ° C./min in an electric furnace for drying, and baked at the same temperature for 3 hours. What was naturally cooled in an electric furnace was used as a test specimen.
The results are shown in Tables 13 and 14. FIG. 4 shows a graph of thermal expansion curve, and FIG. 5 shows a graph of thermal expansion curve under load.

As shown in Tables 13 and 14 and FIGS. 4 and 5, Examples 35 and 36 are CaO, Al ₂ O ₃ compared to Comparative Example 10 using Portland cement as a curing agent and Comparative Example 11 using alumina cement. Therefore, shrinkage under load from around 700 ° C. is suppressed, drying is easy and explosion resistance is excellent. Moreover, while it has the creep resistance substantially equivalent to the comparative example 12 which is a silica brick, it has a thermal expansion coefficient lower than the comparative example 12, and has thermal shock resistance.

Claims (4)

Colloidal silica is converted into solid SiO ₂ by the outer coating with respect to 100% by mass of the siliceous refractory raw material composition composed of fused quartz and calcined silica, and sodium silicate is solid Na ₂ O. It is a siliceous castable refractory added in an amount of 0.04 to 0.30% by mass, and the calcined silica is composed mainly of tridymite, and the blending ratio of the fused quartz and calcined silica of the siliceous refractory raw material composition is Fused quartz 40-100% by mass, calcined silica 0-60% by mass, and the total amount of soda component added to the outer shell is 0.06-0.32% by mass in terms of solid Na ₂ O Silica castable refractory characterized by Colloidal silica is converted into solid SiO ₂ by the outer coating with respect to 100% by mass of the siliceous refractory raw material composition composed of fused quartz and calcined silica, and sodium silicate is solid Na ₂ O. A siliceous castable refractory added in an amount of 0.04 to 0.30% by mass in terms of the above, wherein the calcined silica is composed mainly of tridymite and cristobalite, and the blend of fused quartz and calcined silica of the siliceous refractory raw material composition The ratio is 60 to 100% by mass of fused quartz, 0 to 40% by mass of calcined silica, and the total amount of soda components added to the outer shell is 0.06 to 0.32% by mass in terms of solid Na ₂ O. A siliceous castable refractory characterized by being. The siliceous castable refractory according to claim 1 or 2, wherein the siliceous refractory raw material composition contains 8% by mass or less of silica flour. A siliceous precast block refractory obtained by adding water to the siliceous castable refractory according to any one of claims 1 to 3 and kneading as necessary, pouring into a mold and drying.

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