JPH101373A - Heat insulating monolithic refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain heat insulating monolithic refractories capable of eliminating the hardening retarding property of transition alumina at low temp. and improving strength exhibiting property in a high temp. region, heat insulating property, corrosion and heat resistances and applicability. SOLUTION: A blowing agent is incorporated with 0.05-0.50wt.% to 100wt.%, in total, of 20-40wt.% refractory alumina and/or mullite aggregate, 40-60wt.% transition alumina, 1-5wt.% calcined gypsum, 3-10wt.% superfine silica powder and 1-5wt.% ceramic fibers to obtain the objective heat insulating monolithic refractories.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat insulating furnace for billet rolling, a lining around a beam post and a skid, a cover of a dandysh used for casting molten steel, a molten steel ladle lid, and the like. About things.

[0002]

2. Description of the Related Art Conventionally, as this kind of heat-insulating amorphous refractories, a large amount of alumina cement is added as a binder to heat-insulating aggregates (fire-resistant aggregates) such as hollow alumina and perlite ("Refractory materials"). And its application ”Refractory Technology Association 32
7 to 328), a ceramic fiber aggregate and alumina cement added thereto as a binder (see JP-A-59-174579).
A material obtained by adding a transition alumina having hydraulic properties as a binder to a ceramic fiber as an aggregate (Japanese Unexamined Patent Publication No. 7-6)
No. 9743). The combination of the above-mentioned heat-insulating aggregate and alumina cement has been developed almost at the same time as the castable refractories, and is the most central heat-insulating amorphous refractory among the above three types. In addition, the combination of ceramic fiber and alumina cement is not as good as the one using heat-insulating aggregate, but it was developed from the time ceramic fiber came to be used in industrial furnaces. It is an insulating refractory with a narrow color. Further, the combination of ceramic fiber and transition alumina is an adiabatic refractory developed in consideration of heat resistance.

[0003]

However, in the conventional heat-insulating amorphous refractories made of heat-insulating aggregate and alumina cement, the aggregate is made of a lightweight material in order to lower the thermal conductivity (bulk specific gravity). This lightweight aggregate is used differently according to the rank of the product (construction body). Alumina is mainly used for high-temperature adiabatic refractories, and pearlite is used for low-temperature adiabatic refractories. And artificial lightweight aggregate is generally used. However, since the above aggregate is mostly porous, it requires a large amount of kneading water to mix and fluidize with other raw materials, while adding alumina cement to supplement the strength of the construction body. Need to increase. Therefore, there is a problem in that the heat insulating aggregate and calcia (CaO) in the alumina cement react during the use of the construction body to generate a low melt, thereby significantly reducing the heat resistance of the product. Therefore, for low-temperature use below 1000 ° C,
It is difficult to use as a lining material in high temperature applications,
It is only used as a backing in most cases. On the other hand, in the case of a high temperature of 1600 ° C. or higher, since a refractory raw material such as fused alumina and sintered alumina is added at the same time in addition to hollow alumina, the alumina content of the whole product is increased, and the heat insulating property is increased. It contributes to the decline. In addition, in the case of an adiabatic refractory made of ceramic fiber and alumina cement, the ceramic fiber is inferior in alkali resistance and reacts with calcia (CaO) in alumina cement to significantly lower heat resistance.
While the maximum use temperature of the product is 1000 to 1200 ° C., there is a problem that the mechanical strength characteristics of the product are deteriorated because the ceramic fiber has poor mechanical strength characteristics.
Furthermore, in the case of an adiabatic refractory made of ceramic fiber and hydraulic transition alumina, the transition alumina has a high alumina purity of at least 99% and does not react with the ceramic fiber unlike alumina cement, so that it has excellent heat resistance. Although a product can be obtained, the hydraulic property of the transition alumina greatly varies depending on the temperature, and there is a possibility of causing poor curing particularly at low temperatures. For example, at a temperature of about 5 ° C., about 7 days may be required after the casting until the mold is removed. Incidentally, manufacturers of hydraulic transition alumina and amorphous refractories are currently developing a method by adding a hardening accelerator in order to solve the above-mentioned temperature dependence problem, but all of them work effectively. The fact is that what has to be done has not been obtained. Accordingly, the present invention provides a heat-insulating irregular-shaped refractory that eliminates the transition retardation of transition alumina at a low temperature and improves strength development, heat insulation, corrosion resistance and heat resistance in a high temperature range, and can improve workability. The purpose is to:

[0004]

In order to solve the above-mentioned problems, the heat-insulating amorphous refractory of the present invention comprises 20 to 40% by weight of alumina and / or mullite refractory aggregate and 40 to 60% by weight of transition alumina. Calcined gypsum 1-5 wt%, ultrafine silica powder 3-10 wt%, ceramic fiber 1-5 wt%
And 0.05 with respect to 100 wt% of refractory aggregate, transition alumina, plaster of Paris, silica ultrafine powder and ceramic fiber.
And a foaming agent added to 0.50% by weight. The refractory aggregate preferably has a maximum particle size of 1.0 mm. Preferably, the foaming agent is sodium lauryl sulfate or a powder detergent.

The refractory aggregate is added to increase the corrosion resistance and to reduce the volume stability, that is, to reduce the volume shrinkage.
Alternatively, a mullite material is used. When the particle size of the refractory aggregate exceeds 1.0 mm, sedimentation of the particles to the bottom of the construction body is observed, and not only cannot a uniform construction body be obtained, but also the volume shrinkage, corrosion resistance and heat conduction properties decrease. Is likely to have a significant adverse effect on The amount of refractory aggregate added is 20wt
%, The volumetric shrinkage due to heat increases, which tends to result in a lack of volume stability as a construction body. or,
If it exceeds 40% by weight, the bulk specific gravity increases, and the heat insulating property decreases. The preferable addition amount of the refractory aggregate is 35 to 40.
wt%.

[0006] Transition alumina functions as a binder together with calcined gypsum described later, and a hydraulic material such as ρ-alumina, χ-alumina, η-alumina, γ-alumina, and θ-alumina is used. . It is known that hydraulic transition alumina such as ρ-alumina generates bayerite and boehmite gel by adding water, and develops strength by gelation. Further, it is contained in transition alumina (Al ₂
The amount of O ₃ ) is very large, for example, about 99%, contains almost no CaO affecting ceramic fibers, and contains potassium oxide (K ₂ O) and iron oxide (III) (Fe ₂ O).
_It is characterized by very low impurities such as ₃ ). If the added amount of the transition alumina is less than 40% by weight, the mechanical strength characteristics are remarkably deteriorated, and even the strength required for demolding cannot be obtained. On the other hand, if it exceeds 60% by weight, 600 to 1
The strength is remarkably reduced in the intermediate temperature range of 000 ° C., and it becomes necessary to add a large amount of ultrafine silica powder as a strength developing agent, which will be described later, resulting in an adverse effect on heat resistance. The preferable addition amount of the transition alumina is 40 to 50% by weight.
It is.

[0007] Calcined gypsum (CaSO ₄ .1 / 2H ₂ O)
Used in combination with the above transition alumina, as a binder,
It is added to prevent poor curing at a low temperature of about ° C and to improve mechanical strength characteristics. This is because calcined gypsum has a higher solubility at lower temperatures and generates a large amount of fine gypsum crystals, so that hardening failure does not occur at low temperatures, and mechanical strength increases at lower temperatures. If the amount of calcined gypsum is less than 1 wt%, there is no effect of preventing poor curing at low temperatures. On the other hand, when the content exceeds 5 wt%, the volume shrinkage in a high temperature range of about 1500 ° C. becomes large, which tends to result in a lack of volume stability of the construction body and a remarkable decrease in fluidity. The preferred amount of calcined gypsum is 2 to
4 wt%. As the plaster of Paris, those widely used for ceramic moldings are generally used, but plaster of Paris used for any of the moldings can be used depending on the situation.

[0008] Ultra-fine silica powder is added for improving the fluidity and for developing strength in an intermediate temperature range by heating, and uses micro-silica generated as a by-product accompanying the production of ferrosilicon (Fe-Si). Is done.

That is, since the ultrafine silica powder has a spherical shape, its flowability is remarkably improved, and it is easy to construct a complicated shape or a thin shape. Also, as described above, transition alumina having hydraulic properties generates strength by generating hydrated alumina and gel by hydration. However, dehydration occurs by heating, and extreme transition occurs at an intermediate temperature range of 600 to 1000 ° C. Although the strength is significantly reduced, the strength reduction in the intermediate temperature range is eliminated by the sinterability of the ultrafine silica powder at a low temperature. If the amount of the ultrafine silica powder deviates from the range of 3 to 10% by weight, sufficient mechanical strength cannot be obtained and the volume shrinkage tends to increase. A preferable addition amount of the ultrafine silica powder is 5 to 10% by weight.

The ceramic fiber is formed by preventing bubbles generated by the foaming agent from being released in the slurry-like heat-insulating irregular refractory due to kneading at the time of construction and dispersing independent pores uniformly in the construction. Is added for
Although it depends on the degree of heat resistance required for the product, generally, a mullite component is used, and it may be either crystalline or non-crystalline. That is, in order to form the construction body, when adding the kneading water to the adiabatic irregular refractory and kneading, the slurry-like adiabatic irregular refractory containing the bubbles generated by the foaming agent is constructed as it is. Also, air bubbles float on the construction surface and it is not possible to form independent pores uniformly in the construction body, and the construction body has a large number of independent pores with the lower layer mainly composed of fire-resistant aggregate. The upper layer has a two-layer structure, and is not lightweight and has excellent strength characteristics and the like. However, by uniformly dispersing the ceramic fibers in the adiabatic refractory, the release of bubbles in the adiabatic refractory in the form of a slurry is prevented, and, as a result, independent pores are uniformly distributed in the construction body. It is formed by If the amount of the ceramic fiber is less than 1 wt%, uniform dispersion of bubbles cannot be sufficiently achieved. or,
If it exceeds 4% by weight, the fluidity of the slurry-like adiabatic refractory material is remarkably reduced, and the strength properties are extremely reduced. The preferred addition amount of ceramic fiber is 3-5wt
%.

[0011] The foaming agent is added in order to form spherical independent pores in the construction body to improve heat insulation, and sodium lauryl sulfate or a powder detergent is used.
That is, the foaming agent generates bubbles having a diameter of about 50 to 100 μm in the slurry-like adiabatic refractory in the form of slurry due to kneading during the construction, due to the gelling action of the transition alumina having hydraulic properties, and the construction is performed by the construction. Inside diameter 50 ~ 100μm
To form independent pores. The amount of foaming agent added
0.05wt% for refractory aggregate, transition alumina, calcined gypsum, ultrafine silica powder and 100wt% ceramic fiber
If it is less than 1, the amount of generated bubbles is reduced, and sufficient heat insulation cannot be provided. On the other hand, if it exceeds 0.50% by weight, the mechanical strength decreases. A more preferable addition amount of the foaming agent is 0.1 to 0.2% by weight.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a heat-insulating amorphous refractory according to the present invention will be described with reference to specific examples and comparative examples. Examples 1 to 7, Comparative Examples 1 to 7 Refractory aggregate, transition alumina, calcined gypsum, ultrafine silica powder and ceramic fiber were blended in the proportions shown in Tables 1 and 2, and 100% by weight of these were commercially available. Powder detergents were added at the ratios shown in each table, and mixed with a mixer (Omnimixer (trade name) manufactured by Chiyoda Giken Kogyo Co., Ltd.) for 5 minutes to obtain an adiabatic amorphous refractory. Next, kneading water was added to 100% by weight of each of the adiabatic refractories, and the mixture was stirred at the ratios shown in Tables 1 and 2 for a minute to obtain a slurry-like adiabatic refractories. Is poured into a mold (40 × 40 × 160 mm), cured, demolded and dried (110 ° C.), and heat-treated (1000 ° C., 150 mm).
0 ° C.) to obtain a sample of each construction body. The fluidity (workability) of each of the obtained slurry-like adiabatic irregular-shaped refractories and the curing time at a temperature of 5 ° C. for the samples of each construction body, 11
Tables 1 and 2 show the linear change rate, bulk specific gravity and bending strength at 0 ° C., 1000 ° C. and 1500 ° C.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As described above, according to the adiabatic amorphous refractory of the present invention, by adding calcined gypsum in combination with transition alumina as a binder, curing delay at low temperature when transition alumina alone is used. By adding silica ultrafine powder, it is possible to improve strength development and workability in high temperature range, and by adding ceramic fiber, uniform air bubble distribution Heat insulation can be improved. Therefore,
The construction body can have excellent heat insulation, heat resistance, corrosion resistance, and mechanical strength in a high temperature range, and can be used for various applications.

Claims (3)

[Claims] 1. An alumina and / or mullite refractory aggregate of 20 to 40% by weight and a transition alumina of 40 to 60% by weight.
And calcined gypsum 1-5 wt% and silica ultrafine powder 3-10 wt%
And 1-5 wt% of ceramic fiber and refractory aggregate,
What is claimed is: 1. An adiabatic refractory comprising a transition alumina, calcined gypsum, ultrafine silica powder and a foaming agent added in an amount of 0.05 to 0.50% by weight based on 100% by weight of ceramic fiber. 2. The refractory according to claim 1, wherein the refractory aggregate has a maximum particle size of 1.0 mm. 3. The adiabatic refractory according to claim 1, wherein the blowing agent is sodium lauryl sulfate or a powder detergent.