JPS6041636B2 - castable refractory formulations - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a castable refractory formulation, and particularly to a castable refractory formulation in which the amount of alumina cement added is reduced and the heat resistance and corrosion resistance are improved.

Castable refractories are not only widely used as materials for various kilns because they are easy to construct and can be used in a relatively short period of time after construction, but in recent years, they have been used not only for kilns but also for construction with fairly complex shapes. It has also been used as an effective material for special linings such as ceramic linings for pipes and pipes.

The present invention is mainly suitable for refractories of specific shapes such as pipes, which can be immediately used for subsequent heat treatment and have sufficient durability for use, but of course can also be used as castable refractories for use in kilns. It is an effective product, and it was developed as a product that is particularly effective for parts and locations that require both heat resistance and corrosion resistance.

That is, the gist of the present invention is a castable refractory composition in which a refractory aggregate is arranged in a small amount of alumina cement containing an alumina sol.

Conventional castable formulations often contain 15 to 40% alumina cement (by weight, the same hereinafter) due to workability and other reasons; however, if a large amount of alumina cement is added, the curing time will be short, but the heat resistance will increase. However, there are many problems with corrosion resistance, and conversely, reducing the amount of alumina cement mixed improves J heat resistance and corrosion resistance, but the curing time is longer and the strength is lower. Conventionally, the required properties were generally within the above range. The amount of alumina cement mixed has been determined while taking into account workability and other factors.

Therefore, the present invention makes it possible to adjust the curing time to a desired time without impairing heat resistance and corrosion resistance, which has been considered difficult in the past, by adding a small amount of alumina cement to the alumina sol. This was done after discovering that it was effective. That is, in castable refractories using alumina cement, the amount of alumina cement is 0.5 to 5%, preferably 1 to 3%, based on the refractory aggregate.
%, it does not impair heat resistance or corrosion resistance.
and an alumina sol selected from aluminum oxychloride or aluminum acetate in a solid content of 0.5 to 10%, preferably 1 to 5%, based on the entire castable formulation.
By adding % and kneading, strength and workability are improved and the curing time can be adjusted to a desired time. If the curing accelerator in this alumina sol exceeds 10%, moldability, dimensional accuracy, etc. will deteriorate, and the fire resistance of the product and the effective properties of the aggregate in the product will be lost. Otherwise, its effectiveness as a binder will be reduced. The refractory aggregate, which is the main component in this castable refractory mixture, is appropriately selected from mullite, fused silica, zircon, zirconia, silicon carbide, etc. depending on the purpose of use of the castable refractory mixture, but most preferably achieves the characteristics of the present invention. Alumina or cordierite is selected when low expansion is required.

Furthermore, various commercially available alumina sols can be used as the binder, but aluminum oxychloride and aluminum acetate are typically preferred.

Furthermore, these binders may be dissolved in water to form a formulation, and in some cases, they may be prepared as a powder and mixed with water on-site to form a castable formulation.

Further, as a forming method, in addition to the above-mentioned casting and on-site casting, it is also possible to reduce the amount of moisture and use vibration forming and ramming to achieve higher strength. Although the reasons for the effectiveness of these sols are not clearly understood, they are not only effective as binders that work together with the alumina cement used to desirably promote the hardening of the formulation, especially enabling instant setting. Depending on how it is used, it may have a remarkable effect, particularly in improving the firing strength of the molded product subsequently obtained.

Furthermore, in order to adjust the curing, it is also effective to add acids such as hydrochloric acid, acetic acid, phosphoric acid, or salts thereof. Generally, if the concentration of these sols as an aqueous solution is increased, the purity of the aggregate components will be lowered, and if the concentration is relatively diluted, the strength after curing will decrease. By changing the combination of the amount of alumina cement and the amount of binder within the range specified herein, the curing time can be changed as appropriate within the range of 1 gin to 1 hour.

Various additives can be used as needed in the composition of the present invention, and it is more desirable to add a viscosity modifier to the composition in order to improve its cast formability. may be carboxymethyl cellulose, polyvinyl alcohol, etc., which are commonly known for that purpose.

The present invention will be explained in more detail below with reference to Examples.

Example alumina aggregate (RW-♀ fine grain manufactured by Showa Denko)
45 parts by weight alumina aggregate (Showa Denko Co., Ltd. RW-Fine Grain)
2 Heel volume tabular alumina (T made by Alcoa)
-60) 32.5 parts by weight alumina cement (CA-25 manufactured by Alcoa)
2.5 parts by weight Alumina sol (aluminum oxychloride manufactured by Taki Chemical Co., Ltd., trade name "Takibain" 20% aqueous solution 11 parts by weight 1st)
Aluminum phosphate (manufactured by Taki Chemical)
0.0 heel weight part The above formulation was mixed for 2 minutes using a universal stirrer, and immediately placed in a vibrating PVC mold (
450 x 250 x 75 = internal volume) and released from the mold after 2 hours, the shape retention was sufficient and the strength required for handling was sufficient.

After drying this material at 110'C for 16 hours, the temperature was raised at a rate of 100'Clhr in a city gas furnace, maintained at 1450°C for 3 hours, and then cooled in the furnace. The physical properties of the obtained fired product were as follows. Bending strength after mold release: 12k
91cIt゛Bending strength after drying 50
k91cT1 Bending strength after firing 18
0kgIc1t Bulk specific gravity after firing
2.86 Apparent specific gravity 3.78
Water absorption rate 17.8% Porosity
24.5% coefficient of thermal expansion [C-1
) 80 x 10 -7 Comparative Example A formulation containing 15% by weight of alumina sol and 5 parts of water, based on the total weight of the formulation, was molded by vibration casting.

Claims (1)

[Claims] 1 The solid content of the alumina sol selected from aluminum oxychloride or aluminum acetate is 0.5 to 10% by weight based on the castable refractory formulation, and the alumina cement is 0.5 to 10% by weight based on the refractory aggregate. A castable refractory formulation containing 10% by weight of alumina cement as a hardening modifier and an alumina sol as a binder.