JPS6144773A - Kneaded-clay like basic stamp material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel clay-like basic stamp material that can reliably prevent aging of the stamp material containing magnesia due to the digestion reaction.

In recent years, there has been an increasing trend towards cleaner steel in the steel manufacturing field, and with this trend, conventional refractories used for lining molten steel containers such as ladles and tundishes have been developed to suppress non-metallic inclusions as much as possible. Properties that can withstand higher temperatures and longer periods of time are required compared to other materials. Basic refractories based on magnesia are now attracting attention as refractories that can meet these demands.

By the way, it is well known that the stamping method is superior to the bricklaying method as a refractory construction method, and therefore, the appearance of basic refractories that can be stamped is the next option that is strongly desired in this industry. It is.

However, in order to easily obtain basic refractories that can be stamped, it is necessary to knead a refractory composition containing magnesia with water. In this case, magnesia, the main raw material, undergoes a hydration reaction and A reaction occurs, and as a result, the basic stamping material loses the plasticity necessary for stamping for a short period of time, making it impossible to stamp, which is a serious drawback in practice.

Traditionally, basic stamping materials used in practical use include those used in electric furnace hearths, etc., which use bittern as a binder, but these are kneaded on site immediately before construction. By doing so, it is possible to prevent installation defects due to the above-mentioned digestion reaction of magnesia, and it has been practically impractical to store basic stamp materials in a state where they can be used for stamping.

To prevent the digestion reaction of the magnesia raw material, which causes the aging of basic stamp materials There are some methods that try to achieve the plasticity required during stamp construction by cross-fertilizing only with a non-aqueous solution such as. However, when a coil or pitch is used, it is necessary to carry out heating crosstalk, which is economically disadvantageous and also poses a pollution problem.

In addition, in the case of crosstalk caused by alcohol, manufacturing/1, storage/
There is a risk of ignition during construction and initial drying.

In addition, as another conventionally disclosed anti-digestion technology, by firing the magnesia raw material at a higher temperature and longer time than usual, the particle surface is completely sintered, resulting in so-called dead-burned magnesia, which lowers the particle surface energy and causes a hydration reaction. Some attempts have been made to suppress this, but since this requires secondary calcination, the magnesia raw material becomes expensive, which is economically disadvantageous, and the effect of suppressing the hydration reaction is not so significant.

In other words, it is difficult to pulverize dead burnt magnesia with this method, and when forming a stamp material, untreated magnesia raw materials are used in the fine powder part or crushed dead burnt magnesia products with untreated parts exposed on the particle surface are used. As a result, it is impossible to prevent the digestion reaction caused by the hydration reaction of the fine powder part of the magnesia raw material. Therefore, it is possible to completely prevent the aging of the basic stamp material caused by the digestion reaction. It is impossible to prevent it.

Furthermore, in addition to the conventionally disclosed techniques described above, many techniques have been disclosed in which the surfaces of magnesia particles are coated with various organic and inorganic additives to thereby prevent hydration reactions. By adding additives, it is impossible to completely cover the surface of magnesia particles by kneading, and therefore,
It is not possible to completely prevent digestion due to the hydration reaction of magnesia particles, and it is difficult to suppress aging of the basic stamp material.

The present inventor has proposed that the digestion reaction caused by the hydration reaction of magnesia particles, which could not be prevented by conventional techniques, can be prevented by using unpulverized single-crystal magnesia fine powder that occurs during the normal production stage of sintered magnesia raw materials. Focusing on the fact that this can be effectively and inexpensively prevented, we have completed a new basic stamp material for strings that is less susceptible to fading over time due to the digestive reaction caused by the hydration reaction of the magnesia raw material.

Hereinafter, the present invention will be explained in detail.

The present invention provides an amorphous refractory composition containing a magnesia raw material, characterized in that the fine powder portion contains unpulverized single crystal magnesia fine powder of 20 to 40 weight ji of the amorphous refractory composition. It is a basic stamp material.

The unpulverized single-crystal magnesia fine powder used in the present invention is obtained by collecting single-crystal grains floating in the rotary cooler exhaust gas with a gas cyclone when sintered magnesia is produced in a rotary kiln. suitable. Incidentally, the unpulverized single-crystal magnesia fine powder generated during the production of sintered magnesia has conventionally been collected using a gas cyclone or the like and returned to the rotary kiln.

Particle size distribution of unpulverized single crystal magnesia fine powder according to the present invention,
Table 1 shows a comparison of the specific surface area and digestion resistance with ordinary crushed magnesia fine powder.

In Table 1, the particle size distribution was determined by the wet fractionation method, the specific surface area was determined by the Blaine method, and the digestion resistance was determined by the weight increase determined by the autoclave method.

Table 1 As is clear from Table 1 above, as a result of the unground single crystal magnesia powder being collected by the gas cyclone, 44μ
Although the following ultrafine powder has a smaller particle size distribution than normal crushed magnesia fine powder, it can be conveniently used as a fine powder when used as a component of a stamp material.

In this case, the unpulverized single-crystal magnesia fine powder that constitutes the stamp material is shown in Table 1 above and in Figure 1 showing its crystal structure and in Figure 2 showing the crystal structure of the crushed magnesia fine powder.
As is clear from the comparison with the figure, there are few ultra-fine powder parts, and the grain shape is single crystal, and since it is made into fine powder without going through a crushing process, it is relatively close to spherical, compared to The surface area is much smaller than that of crushed magnesia fine powder, and as a result, it has the property of being difficult to cause digestion reactions due to hydration reactions.

In addition, since unground single-crystal magnesia fine powder does not go through a crushing process, its particle surface is completely covered with impure components such as silicate, and moreover, it exists in a fine powder state even in the rotary kiln. Therefore, magnesia coarse grains・
Compared to medium grains, they receive relatively large thermal energy, and as a result, they become single-crystalline and close to a dead burnt state.

Even with such particle characteristics, unground single-crystal magnesia fine powder is difficult to cause a hydration reaction.

Table 2 shows the pH change when 10 g of unground single crystal magnesia fine powder and crushed magnesia fine powder were reacted with 15Q+n/water. It is clear from the surface of the wood that it is difficult to produce magnesium oxide.

Table 2 Furthermore, the unpulverized single-crystal magnesia fine powder according to the present invention is naturally generated when calcined magnesia is manufactured in a normal manufacturing process, does not require any special treatment such as secondary firing, and is economical. It is also advantageous from a gender perspective.

In the present invention, the reason why the amount of unpulverized single crystal magnesia fine powder used is limited to 20 to 40% by weight of the refractory composition is as follows.
If it is less than 0% by weight, when forming a basic stamp material, ordinary crushed magnesia fine powder other than unpulverized single-crystal magnesia fine powder must be used in the fine powder part, and as a result, the water of crushed magnesia fine powder This is because the change over time due to the digestion reaction increases, and unground single-crystal magnesia fine powder is used in the refractory composition. This is because if more than it% is used, there will be too much fine powder in terms of the particle size structure of the stamp material, which will adversely affect the workability, physical properties, etc.

In order to configure the basic stamp material according to the present invention, in addition to the above-mentioned 20 to 40% by weight of unpulverized single crystal magnesia fine powder in the fine powder part, fused magnesia, sintered magnesia, etc. are added to the coarse and medium grain parts. Magnesia raw materials and/or spinel raw materials such as fused spinel and sintered spinel are used, and plasticity imparting raw materials such as clay raw materials are used to (support) the plasticity necessary for the stamp material. Needless to say, it's a good thing.

Examples of the present invention are shown below.

Example 3 Add the required amount of water to the composition shown in Table 3 and knead it for 15 minutes to obtain a stamp-ready material, then store it in a sealed plastic bag under normal storage conditions and observe changes in bulk specific gravity over time. Table 4 shows the results of confirming the degree of change over time by examining changes to the touch. The molding pressure of the sample for bulk specific gravity measurement was 150 kg/am.

Also, sample No. in Table 3. Table 5 shows the physical properties of samples No. 1, No. 5, immediately after kneading, and samples No. 1, after 2 weeks of aging.

As shown in Table 4, Samples No. 1 and 1 using 30% by weight of unpulverized single crystal magnesia fine powder according to the present invention are Sample No. 1 using 30% by weight of ordinary crushed magnesia fine powder.
However, at the 38th point after the crosstalk, it became impossible to perform stamp work, but the stamp work has remained possible for about 3 weeks. In addition, as shown in Table 5, the physical properties of samples No. 1 and 1 after oral administration for 2 weeks were determined immediately after the crosstalk and for sample no.
, s maintains almost the same physical properties as those immediately after crosstalk.

Sample No. 2 in Table 3 uses a small amount of unground single-crystal magnesia fine powder, and sample No. 004 uses too much fine powder, so when it is configured as a stamp material, the former has an insufficient amount of fine powder, while the latter In either case, there is an excessive amount of fine powder, resulting in poor moldability and filling properties, and in the case of excessive fine powder, cracks occur after molding rests, which is unsuitable in any case.

Also, sample No. in Table 3. 3, when sample No. 62 was made into a stamp material, the fine powder portion that was insufficient due to the unground single-crystal magnesia fine powder content alone was supplemented with ordinary crushed magnesia fine powder, but as is clear from Table 4. In addition, this sample No. 3 had a construction defect about one week after cross-contact, and the prevention of oral change as a basic stamp material was insufficient, which caused practical problems.

As mentioned above, in Table 3, only sample No. 1 according to the present invention, in which 30 weight of the refractory composition contains unpulverized single-crystal magnesia fine powder, can be stored for about 3 weeks in a state ready for stamping. In addition, it is easy to construct, fill, and
In terms of physical properties, it was also possible to maintain them within a range that would not cause any practical problems.

Table 3 Table 4 E 5 Table

[Brief explanation of the drawing]

FIG. 1 (A), (Bl, (01) are all micrographs showing the crystal structure of one example of unpulverized single-crystal magnesia fine powder according to the present invention.
(Both 01 are micrographs showing the crystal structure of one example of crushed magnesia fine powder. Procedural amendment (voluntary) April 10, 1985

Claims (1)

[Claims] 1. An amorphous refractory composition containing a magnesia raw material, characterized in that the fine powder portion contains 20 to 40% by weight of unpulverized single-crystal magnesia fine powder of the amorphous refractory composition. , basic stamp material in the form of clay. 2. The clay-like clay according to claim 1, wherein the unpulverized single-crystal magnesia fine powder is used to collect and use a gas cyclone to collect what is floating in the exhaust gas of a rotary cooler in a rotary kiln during the production of sintered magnesia. Basic stamp material.