JPH0687666A - Heat insulating castable refractory containing ceramic fiber - Google Patents

Abstract

PURPOSE:To provide cold-setting castable refractories ensuring satisfactory casting work efficiency and low shrinkage by drying and heating and excellent in fire resistance and heat insulating property. CONSTITUTION:Granular fleece of ceramic fibers having 10-50mm diameter is added to an Al2O3-SiO2 refractory material as a base by 5-20wt.% and a foaming agent is further added by 0.1-0.5wt.% per 100wt.%, in total, of the granular fleece and the refractory material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory heat-insulating castable used as a lining material for furnace walls and furnace lids of various kilns, or as a covering material for skid pipes and posts of heating furnaces, and more particularly to pouring workability. The present invention relates to a refractory heat-insulating castable containing a room temperature curable ceramic fiber, which has good heat resistance and small drying / heating shrinkage.

[0002]

2. Description of the Related Art Ceramic fibers are widely used for various irregular shaped refractories because they have excellent heat insulation, spall resistance, impact resistance, and air permeability. In many cases, materials, inorganic binders, organic thickeners, etc. are used in a secondary manner. For example, Japanese Patent Publication 5
3-43713, Japanese Patent Publication No. 56-26791, Japanese Patent Publication No. 59-174579 and the like are cited as disclosure examples. Since they contain a lot of fibers, they are used by being kneaded into a clay-like form and then applied or stamped, which is unsuitable or at least not good for pouring.
Next, as an example of disclosure of castables, Japanese Patent Publication No. 54-688.
There is a publication No. 16 in which a cotton-like substance and a foaming agent are essential components. And the cotton-like substance has an average fiber length of 10
It is regulated to be not more than mm, and the purpose of the regulation is to improve the dispersibility of the fiber itself. Therefore, the fibers used for this are exemplified by long fibers finely crushed by a fret mill or the like. As pointed out in the publication, such short fibers have good dispersibility,
Castables using it have the drawbacks that they are inferior in light weight heat insulation and that the contraction of the construction body is large as pointed out in JP-B-59-174579. In addition, generally, when the amount of ceramic fiber used is increased for lightweight insulation, the amount of kneading water inevitably increases significantly, resulting in sedimentation and separation of aggregates, and in some cases water floating on the casting surface, A so-called breathing phenomenon occurs and the workability itself deteriorates in fluidity.

Therefore, in the above-mentioned prior art, in order to improve these drawbacks, usually, a measure such as adding a large amount of refractory clay or an organic thickener to increase water retention and viscosity is taken. As for the measures, (1) the drying shrinkage becomes large,
(2) High temperature heat shrinkage increases due to sintering of refractory clay, and (3) a large amount of organic thickener delays the hydration reaction of hydraulic binder.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. The object of the present invention is to have good pouring workability, small drying and heating shrinkage, and fire resistance. It is to provide a room temperature curable castable having excellent heat insulating properties.

[0005]

In order to achieve the above objects, in the refractory heat insulating castable according to the present invention, the main component is Al ₂ O ₃ --SiO ₂ refractory material and the crushed particle size is 10 to 50 mm. 5% to 20% by weight of ceramic fiber granular cotton is added to 100% by weight of a foaming agent of 0.1 to 100% by weight.
0.5% by weight is added.

In the present invention, the ceramic fiber refers to an artificial inorganic fiber having high heat resistance regardless of whether it is crystalline or vitreous, and its composition corresponds to alumina, mullite, alumina-silica, zirconia or the like. . And granular cotton is used as a fiber shape. Dispersion of the fibers alone is rather undesirable here. That is, when the fiber length is short and the dispersibility is good, the fiber and the refractory fine powder are well reacted and sintered to increase the shrinkage, and the porosity is lowered. Therefore, it is necessary that the fibers do not disintegrate or disperse even if they get tired, and form a granular mass. This is because the contact structure between the fibers and the refractory fine powder is suppressed and the voids of the granular cotton are retained by forming a tissue structure in which the granular cotton has a skeleton and the space between the granular cotton is filled with the fire resistant fine powder and the inorganic binder. As a result, sintering of the fibers and the refractory fine powder is suppressed, and castable with a small heat shrinkage and a high heat insulation property can be obtained. A particle size of 10 to 50 mm is suitable. When the particle size is 10 mm or less, heat shrinkage due to the reaction between the fiber and the inorganic binder becomes large and the heat insulating property also deteriorates. On the other hand, when it is 50 mm or more, the castable fluidity is significantly deteriorated and the strength is significantly reduced. Generally, granular ceramic fibers are provided by disintegrating bulk, blanket, or the like.

The purpose of the foaming agent is to improve the fluidity of the castable by the following action of the foaming agent and to provide a uniform construction body with small shrinkage.
That is, (1) the fine spherical bubbles that are entrained during the kneading of the castable work as a ball bearing to improve the fluidity of the castable. (2) Curing / drying shrinkage is reduced due to a decrease in the amount of kneading water entrained by air and a decrease in the surface tension of the kneading water due to the surface action. (3) Fine air bubbles prevent sedimentation and separation of aggregates and water floating (breathing). When the aggregate is separated, the upper part of the construction body, which contains a large amount of fine powder, is more likely to be warped and deformed due to the larger heat shrinkage than the lower part, and the structure of the construction body itself becomes uneven. Therefore, in order to prevent sedimentation and separation of the aggregate, a method of using a large amount of ultrafine particles such as clay and silica flour or an organic thickener is often adopted. There is an adverse effect that the sintering is promoted to increase the heat shrinkage, and the organic thickener delays the hardening of the hydraulic binder. By adding a foaming agent, the amounts of these ultrafine particles and organic thickener used can be greatly reduced, and as a result, the above problems can be solved all at once. When selecting a foaming agent, it is important that the shape of the bubbles is fine and uniform, that the stability to alkali is good, and that the curing characteristics of the binder are not significantly affected. Generally, anionic surfactants such as alkylbenzene sulfonate and alkyl sulfate ester salt are suitable. Proper addition amount is 0.1-0.5%
If the amount is too small, the above effect cannot be exhibited, and if the amount is too large, the amount of bubbles increases and the strength of the construction body decreases.

The Al ₂ O ₃ -SiO ₂ refractory material will be described in detail. As the refractory aggregate, alumina, bauxite,
Mullite, chamotte, zirconia, zircon, silica stone, etc. may be used alone or in admixture of two or more. As fire-resistant fine powder, silica flour, calcined alumina or sintered
One kind or two or more kinds of ultrafine powder (a few microns or less) such as fused alumina is appropriately mixed and used. As the hydraulic inorganic binder, ρ-alumina, alumina cement, alumina sol and the like can be used. Alumina cement is Al ₂ O
_{3 A} content of 70% or more is preferable.

As other auxiliary additives, a small amount of a dispersant such as alkylallyl sulfonate or lignin sulfonate, or an organic thickener such as methyl cellulose or carboxymethyl cellulose is used.

The present inventors changed the particle size and the amount of the ceramic fiber granular cotton based on the basic composition shown in Table 1 and examined their effects on the linear change rate and the kneading water amount. In that case, the ceramic fiber contains high alumina (Al ₂
O ₃ 80%, SiO ₂ 20%), ρ-alumina was used as the binder, and alkylbenzene sulfonate was used as the foaming agent. The preparation of the test piece was carried out by pouring the powder material, kneading with a soft water amount, casting in an iron mold of 4 × 4 × 16 cm, curing for 24 hours, deframed, dried at 110 ° C. for 24 hours, and then subjected to the test.
FIG. 1 shows the relationship between the fiber blending amount and the linear change rate after firing at 1500 ° C. for 3 hours with the fiber particle size as a parameter. The linear change rate increases as the fiber amount decreases (large linear change rate means a large absolute value. The same applies hereinafter), and this tendency becomes more remarkable as the fiber particle size decreases. From the experience of an actual furnace, the upper limit of this value is preferably 2.2% or less, but if this value is applied to a fiber of 50 mm, the compounding amount must be at least 5% or more. In FIG. 2, the effect of the particle size of the fiber granular cotton on the amount of kneading water was examined using the amount of fiber blended as a parameter. The kneading water amount represents an index of good or bad of pouring workability, and the kneading water amount showing good workability is approximately 75% or less. When the fiber particle size becomes large, the upper limit value of the proper fiber blending amount becomes smaller, and the fiber particle size becomes 10 mm.
In the case of, the upper limit is 20%, and in the case of 50 mm, it is 10% or less. Comprehensively judging the appropriate range from the results of FIGS. 1 and 2, the fiber particle size is 10 mm to 50 mm, and the amount used is 5% to 20%.

[0011]

[Table 1]

[0012]

EXAMPLES The present invention will be described in more detail with reference to the following examples. Example The basic composition shown in Table 1 was used, and the material was investigated after firing. The high temperature physical properties are those after firing at each temperature for 3 hours. The results are shown in Table 2. All of them have good workability, and the rate of linear change after drying and after firing at 1200 ° C. and 1400 ° C. is small.
It can be seen that in Examples 1 and 2, the larger the amount of the foaming agent, the smaller the bulk specific gravity and the linear change rate tended to be. In Examples 3 and 4, the influence of the amount and particle size of the ceramic fiber is shown. When the amount of the ceramic fiber is small, the strength after firing becomes large, and the bulk specific gravity and the linear change rate become large accordingly. The compounding material of Example 1 was used as a coating material on the skid and posts of the preheat zone and the heating zone of the heating furnace. The use progress situation is shown in Table 3, and all are good. Comparative Example The composition of the comparative example and the result of material examination after firing are the same as those of the example 2
Shown in. In Comparative Examples 1 to 3, since no foaming agent was added, sedimentation and separation of aggregate occurred, and clay was added to improve it and the amount of the organic thickener was increased, resulting in high viscosity. Resulting in poor workability and a high rate of change in the line after firing. In Comparative Example 4, since the amount of ceramic fibers is small, the bulk specific gravity and the linear change rate are large. In Comparative Example 5, on the contrary, the amount of ceramic fibers is too large and the fluidity is poor, and strength is hardly exhibited. (Below margin)

[0013]

[Table 2]

[0014]

[Table 3]

[0015]

INDUSTRIAL APPLICABILITY As described above, the ceramic fiber-containing refractory heat-insulating castable obtained according to the present invention has a relatively low water content and is excellent in pouring workability.
It is a lightweight, heat-resistant refractory material that has high temperature fire resistance of 500 ° C or higher and has little drying and heat shrinkage. Further, the air entraining action of the foaming agent improves the workability with a low amount of water.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a fiber blending amount and a linear change rate with a fiber particle diameter as a parameter in an example of the present invention.

FIG. 2 is a graph showing the relationship between the fiber particle size and the amount of kneading water with the amount of fiber used as a parameter in Examples of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Tanaka 2-2-17 Osatohigashi, Moji-ku, Kitakyushu, Fukuoka Prefecture (72) Masahiko Sugawara 1-10-8 Nagao, Kokuraminami-ku, Kitakyushu, Fukuoka

Claims (1)

[Claims] 1. A foaming agent based on 100% by weight of a main component of Al ₂ O ₃ --SiO ₂ refractory material to which 5 to 20% by weight of ceramic fiber granular cotton having a crushed particle size of 10 to 50 mm is added. A refractory heat-insulating castable comprising 0.1 to 0.5% by weight.