JPS6213300B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-resistant calcium silicate material that can be machined by cutting or grinding. Machineable calcium silicate-based heat-resistant materials are known and can be used in sheet form as devices for transporting, holding, and dispensing molten metal, such as troughs, troughs, and pouring boxes for molten aluminum. It is used as is or after being processed into various shapes. In such applications,
Calcium silicate-based materials are generally light, have excellent insulation properties, do not get wet with hot water, and do not contaminate hot water, but they also have a high degree of heat resistance and mechanical properties that can withstand contact with high-temperature molten metal in a fluid state. Physical strength and workability that enables precise machining are required. It cannot be used for this purpose. Therefore, for example, a typical commercially available product that has been put to practical use is formed by adding an inorganic binder to amosite asbestos and diatomaceous earth silica, reacting and hardening it by high-pressure steam curing, and then firing it. It is made using a special manufacturing method. By the way, conventional products, not only the above example, contain a large amount of asbestos fiber for reinforcement.
However, inhalation of asbestos fibers is considered to be harmful to health, and therefore, the use of asbestos fibers for reinforcement is not desirable from both manufacturing and product processing standpoints. Therefore, there was a desire for a manufacturing method and product that did not use asbestos fibers, but since the required properties are as high as described above, it is possible to completely replace reinforcing fibers with other fibers. It wasn't long yet. Against this background, the inventors of the present invention have conducted repeated research to find a method for manufacturing a calcium silicate-based heat-resistant material that can be used to store molten metal without using asbestos fibers, and have found the following. This led to the completion of the present invention as described. First, an outline of the present invention will be described. (A) 100 parts by weight of a mixture of lime raw materials and silicic acid raw materials with a CaO/SiO ₂ molar ratio of 0.6 to 1.2 (B) Zonotlite obtained by hydrothermal synthesis (solid content 36 parts by weight or more and less than 50 parts by weight (C) Fibrous wollastonite 15 to 150 parts by weight (D) Water 2 to 8 times the amount of total solids Slurry consisting of a homogeneous mixture of (A) to (D) The obtained molded product is steam-treated under pressurized steam of 6 kg/cm ² or more to react the silicic acid raw material and the lime raw material, and then heated to 330°C or higher under atmospheric pressure and molded. By removing water that separates from objects,
The desired heat-resistant material is obtained. The manufacturing method according to the present invention will be described in detail below. The silicic acid raw material and lime raw material for the above raw material (A) are not particularly limited, and any of those commonly used as raw materials for producing calcium silicate molded bodies can be used. Particularly preferred examples of silicic acid raw materials include diatomaceous earth, silica stone, ferrosilicon dust, silica, etc., and examples of lime raw materials include slaked lime, quicklime, carbide slag, etc. . The blending ratio of these raw materials is such that the CaO/SiO ₂ molar ratio is 0.6 to 1.2.
It is sufficient that the molar ratio is within the range of
It is between 0.7 and 1.0. Although the hydrothermal synthesis of xonotlite may be carried out according to a conventional method, xonotlite is particularly preferable as a raw material in the method of the present invention. 20Kg/ ^cm2
It was obtained by heating and reacting for 2 to 8 hours with stirring under a vapor pressure of . Such xonotlite adsorbs powdered silicic acid raw materials and lime raw materials, and reduces the loss of these powdered raw materials during dehydration molding (when asbestos fibers are used, the fibers adsorb the powdered raw materials, but the fibers Wollastonite does not have this ability. Therefore, the above-mentioned effect of xonotlite in the forming process is important.) Zonotlite also plays many important roles in the manufacturing method of the present invention, such as improving the handling properties of the formed body after dehydration molding and improving the heat resistance and strength of the final product. It goes without saying that if the amount of xonotlite is too small, sufficient effects cannot be expected, but on the other hand, using an excessive amount will make molding difficult and give a product with an unnecessarily low specific gravity and low strength. Undesirable. The preferred amount used is 36 to 170 parts by weight per 100 parts by weight of the mixture of lime raw material and silicic acid raw material.
However, the invention of a similar manufacturing method using 50 to 170 parts by weight of xonotlite is claimed in Japanese Patent Application No. 58689/1989. As the fibrous wollastonite, commercially available products such as NYARD-G manufactured by Interspace Co., Ltd. in the United States,
It can be used as is. It is well known that this fibrous wollastonite is used in the production of calcium silicate-based insulation materials, etc., but although it is fibrous, it is much shorter than asbestos fibers and has a small specific surface area, so it can be used for reinforcement. It cannot be used as a substitute for asbestos fibers as a material. In the manufacturing method of the present invention, the reason why fibrous wollastonite is blended is not because we expect the same reinforcing effect as when asbestos fibers are blended, but because the blend suppresses the occurrence of cracks during the molding firing process. This is because a product having extremely good machinability can be obtained. Furthermore, since fibrous wollastonite does not have crystallization water, one of the advantages of using fibrous wollastonite is that the firing time is shorter than when using asbestos fibers that have crystallization water. be. Although fibrous wollastonite is chemically the same calcium silicate as the matrix part of the product, adding too much of it will cause a decrease in the strength of the product, so it must be avoided. In the manufacturing method of the present invention, if necessary, a small amount of alkali-resistant glass fiber, inorganic fiber such as rock wool may be used for reinforcement, and it also improves the freeness during dehydration molding and the strength of the molded product before firing. To achieve this, organic fibers such as rayon and pulp may be used in combination, but since adding a large amount of organic fibers leads to a decrease in the strength of the final product, it is desirable that the amount of organic fibers be 2% or less of the total solid raw materials. The slurry obtained by uniformly mixing the above raw materials is dehydrated and molded into an appropriate shape. During the molding process, the molding surface ^pressure and It is desirable to adjust the degree of dehydration (the higher the density, the greater the strength, but if the density is too high, the workability and heat insulation properties will deteriorate.If molding is carried out using the raw materials and their blending ratio adopted in the present invention) For example, with the above-mentioned product density, a product with excellent physical properties and processability can be obtained.) Pressurized steam treatment (steam treatment) of dehydrated molded products
involves the formation of a matrix of calcium silicate crystals by reacting the silicic acid raw materials with the lime raw materials and possibly also the reaction of these raw materials with the surfaces of the xonotlite particles. Treatment is 3-10 under steam pressure of 6-20Kg/ ^cm2
Regarding the silicic acid raw material and the lime raw material, the treatment is carried out until tobermorite or xonotlite is produced (it is possible that a part of it becomes CSH- or CSH- to form a mixed crystal). After that, a drying process is performed, and then high-temperature heat treatment (calcination) under atmospheric pressure is performed. Firing is usually at 330-600℃,
If necessary, the temperature is increased to about 1000° C., and the process is carried out with ventilation until the separation of water from the molded product at the processing temperature has substantially ceased. However, when organic fibers are blended, it is necessary to bake at about 500° C. or higher in order to burn out the fibers. In this step, CSH- and CSH- bound water are removed (when the firing temperature is about 700°C or higher, tobermorite crystal water is also removed), and the microstructure of the matrix portion changes accordingly.
The molded product after firing no longer generates gas or deforms even when it comes into contact with high-temperature molten metal, and has excellent stability. The method for producing a heat-resistant material according to the present invention has the advantage that the above-described firing process can be performed at a relatively low temperature and in a short time, and that the molded product is not deformed or cracked during firing, resulting in a high yield. The heat-resistant material produced by the method of the present invention as described above is
It has all the properties necessary as a constituent material for the molten metal processing equipment, and since it does not contain asbestos fibers, it has the advantage of requiring simple environmental measures when performing machining. The present invention will be described below with reference to Examples and Comparative Examples, and in each example, "parts" means parts by weight. The xonotlite used was prepared by mixing silica powder and milk of lime (quicklime digested with 12 times the amount of water) so that the CaO/SiO ₂ (molar ratio) was 0.98, and adding 12 times the amount of water. The wollastonite was then reacted under a water vapor pressure of 16 kg/cm ² with stirring for 5 hours, and the wollastonite was a fibrous one (NYARD-G) manufactured by Interpace, USA. Example 1 20 parts of silica stone, 21 parts of slaked lime, 15 parts of xonotlite (36.6 parts per 100 parts of total amount of silica stone and slaked lime)
), 40 parts of wollastonite (97.6 parts per 100 parts of total amount of silica stone and slaked lime), 4 parts of alkali-resistant glass fiber, and 500 parts of water were mixed under a surface pressure of 15
Kg/cm ² and molded into a plate shape of 30×300×300 mm, and the molded product was steam-treated for 10 hours under a steam pressure of 9 Kg/cm ² .
This treatment caused the silica and slaked lime to react, producing calcium silicate consisting primarily of xonotlite. The molded product was then fired at 550°C for 6 hours.
No warpage, cracking, or change in appearance of the molded product due to firing was observed. The performance values of the product were as shown in Table 1. Example 2 21 parts of silica, 22 parts of slaked lime, 20 parts of xonotlite (46.5 parts per 100 parts of total amount of silica and slaked lime)
A heat-resistant material was produced by treating a mixture of 35 parts of wollastonite (81.4 parts per 100 parts of total amount of silica stone and slaked lime), 2 parts of pulp, and 400 parts of water in the same manner as in Example 1. However, the surface pressure during molding is 10
(changed to Kg/ ^cm2 ). No warpage, cracking, or change in appearance was observed during the firing process. Product performance values are shown in Table 1. Comparative example 1 35 parts of wollastonite, 32 parts of diatomaceous earth, slaked lime
A mixture of 33 parts and 300 parts of water was treated in the same manner as in Example 1, except that the surface pressure during molding was changed to 5 kg/cm ² . Although no warping or cracking was observed during the firing process, the product had low strength and poor heat resistance, as shown in Table 1. Comparative example 2 15 parts of zonotrite, 41 parts of silica, 40 parts of slaked lime,
A mixture of 4 parts of alkali-resistant glass fibers and 500 parts of water was treated as in Example 1. In this case, hair cracks were observed in some of the products (the performance values of which are shown in Table 1). 【table】

Claims (1)

[Claims] 1 A slurry consisting of a homogeneous mixture of the following (A) to (D) is dehydrated and molded, and the resulting molded product is steam-treated under pressurized steam of 6 kg/cm ² or more to form a silicic acid raw material. A method for producing a heat-resistant calcium silicate material, which comprises reacting it with a lime raw material and then heating it to 330°C or higher under atmospheric pressure to remove water released from the molded product. (A) 100 parts by weight of a mixture of lime raw materials and silicic acid raw materials with a CaO/SiO ₂ molar ratio of 0.6 to 1.2 (B) Zonotlite obtained by hydrothermal synthesis
36 parts by weight or more but less than 50 parts by weight (C) Fibrous wollastonite 15 to 150 parts by weight (D) Water 2 to 8 times the amount of total solids