JPH0959072A - Fine slaking resistant magnesia powder, its production and monolithic refractory using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably improve the operability in execution without causing a deterioration of the fluidity of a monolithic refractory containing a slaking resistant magnesia fine powder by directly sticking silica particles to the surface of a fine powder and regulating the average particle diameter thereof to a prescribed size. SOLUTION: This slaking resistant magnesia fine powder is obtained by directly sticking silica particles to the surface of a fine powder and regulating the average particle diameter thereof to 20μm size. The method for producing the slaking resistant magnesia fine powder is to mix the silica particles (e.g. fused silica) with a magnesia fine powder having <=20μm average particle diameter (e.g. seawater magnesia) in a mixer having a strong grinding force and/or impulsive force. Otherwise, the fine powder is obtained by pulverizing the magnesia fine powder to a size of <=20μm average particle diameter in the presence of a silica fine powder. The monolithic refractory excellent in slaking resistance and fluidity is obtained by blending 4-30% slaking resistant magnesia fine powder in the fine powder, in the monolithic refractory comprising the aggregate, the fine powder, a dispersing agent and a hardening material blended therein.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnesia fine powder having excellent digestion resistance, an amorphous refractory material containing the magnesia fine powder, which has good fluidity and excellent durability, and a method for producing the same. .

[0002]

2. Description of the Related Art In recent years, refractory bricks used in metallurgical furnaces and the like are shifting to amorphous refractories in order to save labor and energy. Since such an amorphous refractory has a jointless structure formed by integral construction, it has less intrusion of metal and slag. Therefore, it has the advantages of superior heat-resistant spalling and longer life than refractory bricks. A typical example of such an amorphous refractory is a castable refractory which is kneaded with water to give appropriate fluidity and which is constructed by fluid filling or the like.

By the way, in a general castable refractory, it is usual to mix "refractory fine powder" as a constituent. This refractory fine powder plays an important role of imparting self-hardening due to deflocculation-aggregation action, blocking fine pores, and imparting fluidity during construction, and is therefore an extremely important material in the formulation of castable refractories. One of the components.

However, in the case of such a refractory fine powder, for example, in the case of magnesia fine powder, if it is blended into an irregular shaped refractory (castable refractory), it causes a digestion problem caused by a hydration reaction accompanying water addition. Moreover, the smaller the particle size of magnesia, the higher the activity against digestibility, so the generation of magnesium hydroxide accompanying the elution of magnesium ions becomes more intense, and the fatal defect that cracks due to volume expansion frequently occur. was there.

As explained above, the magnesium raw material,
Especially when magnesia fine powder having a particle size of 20 μm or less is used as a raw material for an amorphous refractory, it is indispensable to solve the problem of digestibility. Further, the elution of magnesium ions also promotes the agglomeration of the alumina fine powder and the alumina cement, so that there is another problem that the fluidity is also lost.

Various countermeasures have been conventionally taken against these problems. For example, in Japanese Examined Patent Publication (Kokoku) No. 2-2828 and Japanese Patent Laid-Open No. 5-43279, hydration is achieved by coating the surface of magnesia particles with a phosphate, borate, frit, or a glassy substance such as synthetic resin or pitch. JP-A-58-99177 proposes a method for preventing hydration by adding 0.5 to 40 wt% of amorphous silica fine powder to a magnesia raw material.

[0007]

However, in these known methods, it is not possible to simultaneously satisfy the digestion resistance and the improvement in the properties of the refractory obtained by using the fine powder of magnesia having an average particle size of 20 μm or less. could not.
That is, the former method requires firing for coating, but during this firing, magnesia fine powder is fused and the particle size becomes large. In addition, there is a problem that granulation occurs when using synthetic resin or pitch.
The latter method has a small effect when applied to fine powder having an average particle size of 20 μm or less, and a large amount of fine silica powder must be used in order to satisfy digestion resistance, resulting in reduced strength and reduced corrosion resistance. There is a problem of bringing.

Accordingly, the present invention provides digestion-resistant magnesia fine powder having an average particle size of 20 μm or less, which solves the problems of (1) digestion and (2) deterioration of fluidity due to acceleration of aggregation. It is an object of the present invention to provide a method for advantageously manufacturing, and further densify the structure of a refractory, thereby providing a magnesia-containing amorphous refractory having excellent durability.

[0009]

As a result of intensive studies to solve the above-mentioned problems of the prior art, the inventors have found that the amorphous refractory material containing fine powder magnesia having an average particle size of 20 μm or less. In the production, it was found that it is effective to use the means described below as means for improving the prevention of digestion of magnesia and the prevention of elution of magnesium ions. That is, the present invention is a technique focusing on a method of coating and adhering fine silica powder.

First, in the present invention, the reason for paying attention to the above silica fine powder is that it improves the digestion resistance of magnesia. This is because water reacts with silica and magnesia during kneading, and the reaction product thereof is This is because a coating film is quickly formed on the surface of magnesia. That is,
The inventors have considered that even if the ultrafine magnesia fine powder having an average particle diameter of 20 μm or less is used, if the silica fine powder can be arranged in the vicinity of the magnesia fine powder in advance, the digestion prevention efficiency may be improved. As a result, the fine powder of magnesia is mixed with silica fine powder in advance before being mixed with the aggregate and the like, so that the surface of the fine powder of silica is adhered and coated (coating), thereby improving the digestion prevention efficiency of the fine powder of magnesia. I did. In addition, the above method of coating adhesion can achieve substantially the same effect (silica coating) by adding amorphous silica at the time of crushing magnesia, thereby enhancing the digestion resistance of the magnesia fine powder. It has been found that even magnesia fine powder having an average particle diameter of 20 μm or less can be converted into magnesia fine powder having excellent digestion resistance.

That is, the present invention is a digestion-resistant magnesia fine powder characterized in that silica particles are directly adhered to the surface of the fine powder to have an average particle size of 20 μm, wherein the silica is fused silica or white. It is characterized by being any one kind or a mixture of two or more kinds selected from carbon, silica flour, silica fume and the like.

Further, according to the present invention, silica particles and fine magnesia powder having an average particle size of 20 μm or less are strongly ground and / or
Alternatively, by mixing in a mixer having an impact force, a method for producing a digestion-resistant magnesia fine powder, characterized in that silica particles are directly attached to the surface of the magnesia fine powder without using a binder, wherein the magnesia fine powder is Is a magnesia fine powder in the presence of silica fine powder having an average particle size of 2
It is characterized in that silica particles are directly adhered to the surface of magnesia fine powder by using a particle size of 0 μm or less without using a binder.

Further, according to the present invention, in an irregular shaped refractory material mainly containing an aggregate, a fine powder, a dispersant and a hardening material, the digestive resistant magnesia fine powder is blended in an amount of 4 to 30% in the fine powder. A magnesia-containing amorphous refractory characterized by the following aggregates: alumina, magnesia, spinel, zircon, silica, zirconia, silica, faux stone, shale, chamotte, graphite and silicon carbide. It is characterized by using any one kind or a mixture of two or more kinds selected.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the features of the present invention are as follows.
Among the fine powders to be blended in the refractory composition, the fine powder of magnesia is used after being subjected to digestion resistance treatment in advance. That is, by coating a predetermined amount of fine silica powder on the surface of the magnesia fine powder so that the fine powder of silica is sprinkled on the surface, a film formed by a reaction product with water can be effectively formed during kneading.

As the magnesia fine powder, fine powder of seawater magnesia, sintered magnesia, electrofused magnesia, natural magnesia, or the like is used. The average particle size is 0.1 to 20 μm, preferably 1 to 15 μm. If the average particle size range is larger than 20 μm, there will be a problem in the denseness of the matrix structure of the refractory material.
On the other hand, if the particle size is smaller than 0.1 μm, the particles are remarkably aggregated and the dispersion and fluidity are deteriorated.

As the above silica fine powder, so-called silica flour or silica fume, which is a by-product during the production of fused silica, white carbon or metallic silicon and silicon alloy, can be used. The silica fine powder is preferably as fine as possible, for example, the average particle size is 1 μm or less, preferably 0.5 μm or less. The reason for limiting the particle size to this is that if the particle size of silica is large, adhesion to magnesia does not occur.

The amount of the silica fine powder added is 0.1 to 30% by weight, preferably 1 to 10% by weight, based on the amount of the magnesia fine powder. When the amount of the silica fine powder added is low, the effect of improving the digestion resistance is insufficient. On the other hand, when the amount of the silica fine powder is more than 30 wt%, the strength and fire resistance of the molded product decrease, so the above range Add only within.

The method for forming the digestion-resistant magnesia fine powder used in the present invention is a method in which magnesia fine powder (mother particles) and silica fine powder (child particles) are uniformly mixed in advance at a predetermined mixing ratio. This method may also be carried out by milling magnesia in the presence of finely divided silica. The mixer used at this time is preferably a mixer capable of uniformly mixing the two types of particles without segregation and imparting stronger frictional force, shearing force, and impact force. As such a mixer, a mixer such as an Ongmill, a hybridizer, a theta composer, a high-ex machine, a mechanochemical reformer, or the like can be used. As another method, a crusher such as a ball mill, a vibrating ball mill, a roller mill or a jet mill, or the mechanochemical reformer described in the preceding paragraph may be used.

Next, in the production of the above-mentioned amorphous refractory material according to the present invention, the components to be blended with the above-mentioned digestion-resistant magnesia fine powder are aggregates, other fine powders, dispersants and curing agents.

First, as the refractory aggregate, alumina, magnesia, spinel, zircon, silica, zirconia,
Silica, Wax, Ban Shale, Chamotte, Graphite, SiC
One of them or a combination of two or more thereof can be used. The particle size is adjusted to coarse, medium and fine so as to obtain a tightly packed structure.

As the refractory fine powder used in the present invention, other than the above digestion-resistant magnesia fine powder, it is possible to use alone or in combination with alumina fine powder. Considering the fluidity and the reactivity with the premixed magnesia fine powder, the fine alumina powder preferably has an average particle size of 0.5 to 10 μm. The amount of the fine powder blended, especially the proportion of the digestion-resistant magnesia fine powder in all refractories, is 4 to 30 wt%, preferably 4 to 20.
wt% range. If the amount of fine powder is more than 30%, the viscosity will increase during kneading, making handling difficult, and the strength will decrease due to increased cracking of the molded body. If less than 4%, improved corrosion resistance can be expected. Limited because it does not exist.

The dispersant used in the present invention is a commonly used inorganic salt such as sodium tripolyphosphate, sodium hexametaphosphate, sodium ultrapolyphosphate, sodium acid hexametaphosphate, sodium borate, sodium carbonate, sodium citrate, etc. It is preferable to use one kind or a mixture of two or more kinds of tartaric acid salt, sodium polyacrylate, sodium sulfonate and β-naphthalenesulfonic acid soda formalin condensate.

As the hardening material used in the present invention, one or two kinds of alumina cement, silica sol or alumina sol which are generally used for refractories are used.

The amorphous castable refractory material according to the present invention may further contain known dispersants, fibers, metal powders, binders and the like, in addition to the above-described compounds, within the range that does not impair the effects of the present invention. You may.

[0025]

【Example】

(1) The influence of the modified digestion-resistant magnesia fine powder used in the present invention on the digestibility was tested. In this test, the digestibility was evaluated by the rate of weight increase (Gakushin method) in an autoclave test at 120 ° C., 3 atm × 3 hours. The results are shown in Table 1 together with the production method of each digestion resistant magnesia fine powder. As can be seen from Table 1, the digestion resistant magnesia fine powder (No. 3 to 7) is
It was found that it was much more resistant to digestion than the magnesia fine powder (No. 1). Digestion-resistant magnesia fine powder (No. 3 ~
7) is a simple mixture of silica fume and magnesia fines (
It has much better digestion resistance than No.2).

[0026]

[Table 1]

(2) Next, in order to verify the effect of the amorphous refractory containing the digestion-resistant magnesia fine powder (No. 3 to 7) for premixing used in the above (1), castable for ironmaking. It was tested for its effect when used as. Table 2 shows the test results. As shown in Table 2, this embodiment (No. 1 ~
In 3), even if the particle size of the magnesia fine powder was small, due to the effect of the surface modification, the usable time was not shortened or digested, and good results were obtained. On the other hand, untreated product (Comparative Examples 2, 4, 5)
In this case, not only the workability remarkably deteriorated immediately after kneading, but also the digestibility was remarkable, and swelling and pulverization occurred during the drying of the molded body, and the strength and the like could not be measured.

[0028]

[Table 2]

Further, in both Example 1 and Comparative Example 1,
It was used as a castable for blast furnace gutter,
The example using the magnesia fine powder having an average particle diameter of 20 μm or less is superior to the conventional material (comparative example 1) using the magnesia fine powder having an average particle diameter of 70 μm in both porosity and bending strength. When the castable of Example 1 was used in an actual machine,
The service life was extended to 21 days compared to 14 days of conventional materials.

Example 2 and Comparative Example 3 are examples when applied to castables for steelmaking steel bath parts, and have an average particle size of 20.
Examples using fine powder of less than μm magnesia, porosity,
Both the bending strength is superior to the conventional material (Comparative Example 3) using fine magnesia powder having an average particle size of 70 μm. Example 2
When the castables were used in an actual machine, the durability of the conventional material was extended to 350 charges, which was extended to 350 charges.
Example 3 is a castable for lining a converter brick, and has a durability of 6000 charges per furnace charge.

[0031]

INDUSTRIAL APPLICABILITY As described above, the amorphous refractory material containing the digestion-resistant magnesia fine powder according to the present invention does not cause a decrease in fluidity due to the digestion of the magnesia fine powder, and has no digestibility. The workability at the time is remarkably improved. Moreover, an amorphous refractory having excellent digestibility and fluidity can be easily manufactured at low cost by a simple operation of premixing treatment.

Front Page Continuation (72) Inventor Keiichiro Isomura, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture, within the Technical Research Laboratory, Kawasaki Steel Co., Ltd. (72) Masato Kumagai 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Kawasaki Steel Co., Ltd. Company Technology Research Institute (72) Inventor Kyonobu Toriya 1576, Higashi-oki, Ako-shi, Hyogo, 2 No. 1576, Kawasaki Furnace Co., Ltd. (72) Inventor Junichiro Mori, Ako-shi, Hyogo, Higashi-oki, 1556 No. 2 inside Kawasaki Furnace Co., Ltd. (72) Inventor Katsumi Jono No. 2 at 1576 East Offshore Nakahiro, Ako City, Hyogo Pref.

Claims (6)

[Claims] 1. A digestion-resistant magnesia fine powder, characterized in that silica particles are directly adhered to the surface of the fine powder to have an average particle size of 20 μm. 2. The digestion resistance according to claim 1, wherein the silica is any one kind selected from fused silica, white carbon, silica flour, silica fume and the like, or a mixture of two or more kinds. Fine magnesia powder. 3. The silica particles and the magnesia fine powder having an average particle size of 20 μm or less are mixed in a mixer having a strong grinding force and / or impact force to form a binder for the silica particles on the surface of the magnesia fine powder. A method for producing a digestion-resistant magnesia fine powder, which is characterized in that it is directly attached without using. 4. A method of pulverizing magnesia fine powder to have a mean particle size of 20 μm or less in the presence of silica, whereby silica particles are directly attached to the surface of the magnesia fine powder without using a binder. Method for producing digestion-resistant magnesia fine powder. 5. An amorphous refractory material mainly composed of an aggregate, a fine powder, a dispersant and a hardening material, wherein 4 to 30 of the digestive resistant magnesia fine powder according to claim 1 or 2 is contained in the fine powder. % Magnesia-containing amorphous refractory characterized by being mixed. 6. The aggregate is any one or two selected from alumina, magnesia, spinel, zircon, silica, zirconia, silica, wax, shale, chamotte, graphite and silicon carbide. The amorphous refractory material according to claim 5, wherein a mixture of one or more kinds is used.