JP2002179471A - Heat-insulating refractory composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-insulating refractory composition in which a porous heat-insulating aggregate consisting of a hexagonal crystal of a composition SCA6 (CaO.6Al2O3) [SLA-92 aggregate from Alcoa] is used as a component and which is capable of exhibiting stable strength irrespective of the ambient temperature of construction work. SOLUTION: In this composition, the SLA-92 aggregate is used as an heat- insulating aggregate and hydraulic alumina is used as a binder. The content of SiO2 as a chemical component expressed in terms of oxide is <0.5 wt.% on the basis of the weight of the whole composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lining material for a billet heat treatment furnace, a back lining material for a molten metal container, a heat insulating cover material for a molten metal container, a precast heat insulating block, etc. The present invention relates to a heat insulating refractory composition used for lining and repair.

[0002]

2. Description of the Related Art Insulated aggregate of SLA-92 (trade name) manufactured by Alcoa (hereinafter simply referred to as "SLA-92 aggregate").
Is a lightweight heat-insulating aggregate having the composition shown in Table 1, and its use technology is UNITECR'99 in Berlin, an international conference on refractories held from September 6 to 9, 1999.
(Long Term High Temperature Stability of Mic
roporous Calcium Hexaluminate Based Insulating Mat
erials) with 5-30 alumina cement as binder
There is seen a blending example in which a dispersant and an antiseparation agent were appropriately added by weight%.

[Table 1]

[0003]

The compounding of the SLA-92 aggregate with alumina cement as a binder tends to decrease the strength properties after drying as the working atmosphere temperature increases. For example, it has been confirmed that the strength at a working atmosphere temperature of 35 ° C. only exhibits １ ／ to １ ／ of the strength at a working atmosphere temperature of 10 ° C.

[0004] Therefore, when the working atmosphere temperature is high, such as in the summer, the support metal such as anchors do not exhibit the binding force, which may cause them to fall off. This may lead to troubles such as the occurrence of corner breaks and the inability to carry.

[0005] An object of the present invention is to solve the problems of the prior art and to provide a heat-insulating refractory composition capable of obtaining stable strength regardless of the working atmosphere temperature.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the above disadvantages have been solved by using hydraulic alumina without using alumina cement as a binder. I found that it can be resolved. That is, the adiabatic refractory composition of the present invention comprises CA6 (CaO.6).
Al 2 _{O 3)} hexagonal compositional crystal system crystal porous insulation aggregate the (SLA-92 of typically Alcoa) was used as aggregate, using a hydraulic alumina as a binder, the total composition In terms of chemical components, the content of SiO ₂ was calculated to be 0.
It is less than 5% by weight.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The Alcoa SLA-92 aggregate used in the present invention is a porous aggregate, which itself has a high porosity and a high heat insulating property, and is dispersed by scattering like a conventional ceramic fiber. There is no problem of environmental deterioration, and when used as a castable, it has an excellent property that high fluidity can be obtained. However, CaO-Al ₂
Since it is an O ₃ -based composition, the influence of the SiO ₂ component on the fire resistance is large, and a lightweight aggregate rich in the SiO ₂ component, such as a lightweight chamotte or pearlite, which can be used in a conventional heat insulating material, cannot be used together. Further, the use of strength imparting agents such as silica sol and ultrafine silica powder is also restricted.

On the other hand, SiO ₂ such as hollow alumina
The lightweight alumina-based aggregate having a very small component can be used in combination with the SLA-92 aggregate as long as the amount of SiO ₂ in the refractory composition is within a limit of less than 0.5% by weight in terms of oxide. it can. In the heat-insulating refractory composition of the present invention,
Depending on the application, a workability-imparting agent (for example, a dispersant for reducing the amount of water in a casting material, an anti-separation agent, and a coagulant in a coating material) that may be added may be added to a general amorphous refractory. Similar but negatively affecting fire resistance
An increase in the iO ₂ component should be avoided.

The present inventors set the range of the Si content in the refractory composition as long as the fire resistance and the heat insulation during the high temperature firing were not impaired.
The amount of O ₂ is limited to less than 0.5% by weight in terms of oxide. However, when the amount of SiO ₂ is 0.5% by weight or more, the reduction in fire resistance and heat insulation due to sintering and shrinkage occurs. Because you invite. The particle size of the heat-insulating aggregate (SLA-92 aggregate) used in the present invention is not particularly limited, and may be any particle size suitable for operations such as pouring, press-fitting, and painting.

Hydraulic alumina used as a binder
Is powdery and has the property of hydrating when water is added.
, Χ, ρ, γ, δ, κ, θ-alumina, etc.
Transfer alumina. Sumitomo Chemical as a commercial product
BK-103, BK-112 etc., depending on the product
SiO₂Some have many components, and from the point of fire resistance, SiO
₂It is preferable to use one having a small amount of components. In the present invention, hydraulic
The addition amount of the reactive alumina is preferably 10 to 50% by weight.
Good. If it is less than 10% by weight, the strength at the time of demolding cannot be obtained,
If it exceeds 50% by weight, the shrinkage during high-temperature firing becomes large.
An example of the chemical components of the hydraulic alumina used in the present invention
It is shown in the right column of Table 1.

[0011]

EXAMPLES Examples of the present invention and comparative examples are shown below. However, the present invention is not limited by the following examples. Test pieces of Examples and Comparative Examples shown in Tables 2 and 3 were kneaded with a predetermined amount of added water using a mixture and water stored in a constant temperature chamber at a predetermined atmospheric temperature for 24 hours or more, and then mixed with a 40 ×
Pour into a 40 × 160 mm formwork or use Example 7
It was created by painting like this. After curing for 24 hours at a predetermined atmosphere temperature, the frame was removed, dried at 110 ° C. for 24 hours, and then the physical properties were measured. Further, after drying, the test specimen was 1500
C. for 3 hours, and the physical properties and the linear change rate were measured.

[Table 2]

In Examples 1 to 3 shown in Table 2, hydraulic alumina was used as a binder and the working atmosphere temperature was 10
℃, 20 ℃, 35 ℃. Comparative Examples 1-3
Are those in which alumina cement was used as a binder and the working atmosphere temperature was 10 ° C., 20 ° C., and 35 ° C., respectively. In the case of using hydraulic alumina, the strength after drying is high and constant without being affected by the working atmosphere temperature, whereas in the case of using alumina cement, the strength clearly decreases as the working atmosphere temperature increases. Also, Comparative Example 4 shows an example in which alumina cement and hydraulic alumina are used in combination. The combined product has a low strength after drying like the alumina cement alone product.

In Examples 4 to 6 shown in Table 3, the amount of hydraulic alumina added was changed under a working atmosphere of 20 ° C., and in Example 7, a coagulant was added to enable coating or spraying. This is a formulation example, and shrinkage during firing is suppressed to within -1% by using an organic coagulant.

[Table 3] Comparative Examples 4 to 6 are outside the scope of the present invention. In Comparative Example 4, the linear change rate after firing at 1500 ° C. was within −1%, but the strength after drying was too small.
The linear change rate after firing at 500 ° C. exceeds −1%. In Comparative Example 6, the SiO ₂ component in the entire composition was 0.5% by weight.
However, the linear change rate after firing at 1500 ° C. shows a large shrinkage of −4.5%.

[0014]

As described above, the present invention provides the SCA
6 (CaO.6Al ₂O₃) Composition of hexagonal crystal
In heat-insulating refractory compositions using lath insulating aggregates,
Hydraulic adhesive instead of conventional alumina cement as a mixture
Lumina is converted to SiO 2 by the chemical composition of oxide conversion.₂Is the overall composition
Less than 0.5% by weight of
And stable strength independent of the construction atmosphere temperature
Expression can be obtained.

Claims (2)

[Claims] 1. An adiabatic refractory composition obtained by using a porous heat insulating aggregate of hexagonal crystal having a composition of CA6 (CaO.6Al ₂ O ₃ ) as an aggregate and adding hydraulic alumina as a binder. The chemical composition of SiO ₂ is 0.1% of the overall composition.
Insulating refractory composition characterized by being less than 5% by weight. 2. A heat-insulating refractory composition comprising a porous heat-insulating aggregate of hexagonal crystal having a CA6 (CaO.6Al ₂ O ₃ ) composition as an aggregate and 10 to 50% by weight of hydraulic alumina added as a binder. Characterized in that the composition of SiO ₂ is less than 0.5% by weight of the total composition in terms of oxide composition.