JPH0558712A - Production of slaking resistant calcia clinker and production of slaking resistant calcia refractory material - Google Patents

Abstract

PURPOSE:To provide a production method of calcia clinker having excellent slaking resistance and refining effect on a molten steel, and to provide a production method of a slaking resistant calcia refractory material from the slaking resistant calcia clinker. CONSTITUTION:This slaking resistant calcia clinker is produced by compacting and granulating a mixture of 100 pts.wt. of calcium carbonate having <=1mm particle size and 1-6 pts.wt. of alumina powder and then sintering the granulated material at 1400-1700 deg.C. The slaking resistant calcia clinker thus obtd. is mixed with magnesia cement and water to prepare a fluidizing mixture, which is then poured in a die, dried and sintered at 400-800 deg.C to produce the slaking resistant calcia refractory material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a digestion-resistant calcia clinker and a method for producing a calcia refractory having excellent digestion resistance and refining effect from the digestion-resistant calcia clinker obtained by this method. ..

[0002]

2. Description of the Related Art With the recent progress in steelmaking technology, there has been a demand for a refractory having excellent performance under severe conditions as a refractory used in a steelmaking apparatus. Further, from the viewpoint of energy saving and labor saving, the demand for amorphous refractory is larger than that for regular refractory, and in particular, in the tundish used in the continuous casting method, the proportion of irregular refractory increases. ing.

Calcia (CaO) has a very high melting point (2
570 ℃), the dissociation oxygen pressure at high temperature is also low, and it is a refractory of MgO-based refractory for special steel furnace material for producing steel with low oxygen, low sulfur, low phosphorus, etc. It is attracting attention as a promising alternative to basic refractories.

For example, the tundish is provided with a cough to prevent the tundish nozzle from being blocked by the alumina contained in the molten steel from the ladle. That is, as shown in FIG. 1 which is a schematic perspective view of an example of a tundish and FIG. 2 which is a sectional view taken along the line AA of FIG. 1, the tundish 1 has a refractory brick 4 stretched on a wall surface 2 and a bottom surface 3. The bottom surface 3 is provided with a tundish nozzle 5, and a cough 6 for refractory material. Molten steel is supplied to the tundish 1 from an arrow 7, and the molten steel overflows the cough 6 and is discharged from the tundish nozzle 5. Although the molten steel supplied to the tundish 1 has been smelted for some time, impurities such as alumina remain and the alumina floats on the surface of the molten steel while the cough 6 is exceeded and is discharged from the tundish nozzle 5. It reduces the amount of alumina in molten steel.

Conventionally, the cough 6 was made of magnesia or alumina, but when the cough 6 is made of calcia, the alumina in the molten steel reacts with the calcia to produce 3CaO.
A low melting point compound represented by Al ₂ O ₃ is generated, and this compound becomes a liquid and floats on the surface of the molten steel, and the amount of alumina in the molten steel discharged from the tundish nozzle 5 is extremely small, that is, the molten steel is Further refining prevents clogging of the tundish nozzle 5 with alumina.

However, calcia inherently has a problem of poor digestion resistance. The cough 6 as described above is produced by pouring an aqueous slurry of calcia into a mold, drying it, and then calcining it. In this case, calcia reacts with water to form calcium hydroxide, which causes volume expansion. Cause
There is a drawback that the cough 6 is cracked and collapses.

Various proposals have been made for a method of improving the digestion resistance of calcia. For example, JP-A-59-2
In Japanese Patent No. 13668, the core part is a granular material having CaO as a main component and a particle size of 1 to 7 mm, and the surface layer covering the core part is a metal having a high melting point and a high digestion resistance such as iron, titanium, aluminum and chromium. A digestion resistant calcia clinker that is an oxide is shown. In addition, as a manufacturing method thereof, a sintering accelerator and the above-mentioned metal oxide having a high melting point and a high digestion resistance are mixed with a coarse-grained calcareous raw material having a particle size of 1 to 10 mm, and the obtained mixture is heated to 1500 ° C. or higher. The method of baking at is shown.

However, the digestion-resistant calcia clinker described in the above publication completely covers the surface of the core calcia with, for example, alumina, and the calcia is not exposed on the surface of this clinker. Although the digestion resistance is improved, when used as a material for the cough 6 of the tundish as described above, calcia does not react with the alumina in the molten steel, so that the refining action of removing the alumina in the molten steel is performed. Not shown.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a calcia clinker having excellent digestion resistance and having a refining action on molten steel, and a digestion resistance from such a digestion resistant calcia clinker. A method for manufacturing a calcia refractory is provided.

[0010]

According to the present invention, a mixture of 100 parts by weight of calcium carbonate having a particle size of less than 1 mm and 1 to 6 parts by weight of alumina powder is compression-granulated to obtain 1400 particles. A method for producing a digestion-resistant calcia clinker, which comprises firing at a temperature of ˜1700 ° C.

In another aspect of the present invention, a mixture of 100 parts by weight of calcium carbonate having a particle size of less than 1 mm and 1 to 6 parts by weight of alumina powder is compression-granulated, and the obtained granules are mixed with 140 parts by weight.
A flowable mixture of digestion-resistant calcia clinker, magnesia cement, and water obtained by firing at a temperature of 0 to 1700 ° C. was poured into a mold and dried, and then 40
A method for producing a digestive-resistant calcia refractory material, which comprises firing at a temperature of 0 to 800 ° C.

The preferred embodiments of the present invention are as follows. (1) The method for producing the above digestion-resistant calcia clinker, wherein the calcium carbonate has a particle size of 0.5 mm or less.

(2) In the fluid mixture, the amount of magnesia cement is 10 to 50 parts by weight based on 100 parts by weight of digestion-resistant calcia clinker, and the amount of water is that of the digestion-resistant calcia clinker and magnesia cement. 10 in total
30 to 100 parts by weight with respect to 0 parts by weight, The method for producing a digestive-resistant calcia refractory described above.

First, the method for producing the digestive-resistant calcia clinker of the present invention (hereinafter sometimes referred to as the first invention) will be described.

As the calcium carbonate used as one of the raw materials of the first invention, crushed natural limestone can be used. It may be calcium carbonate synthesized by carbonation of calcium hydroxide. The calcium carbonate is preferably as pure as possible, and the content of impurities such as phosphorus, sulfur and silica is preferably 2.0% by weight or less. The raw material calcium carbonate has a particle size of less than 1 mm,
Those having a particle size of 0.5 mm or less, particularly 0.2 mm or less are preferable. Such calcium carbonate can be easily produced by subjecting limestone to treatments such as crushing, washing with water and sieving. When the particle size of calcium carbonate is larger than the above range, the dispersibility of alumina in the obtained calcia clinker becomes poor, and the digestion resistance of the calcia clinker becomes poor.

As the alumina powder which is another raw material of the first invention, a usual aluminum oxide powder can be used without any particular limitation. The particle size of the alumina powder is preferably 150 μm or less, and particularly preferably 50 μm or less. When the particle size of the alumina powder is larger than the above range, the dispersibility of alumina in the obtained calcia clinker becomes poor and the digestion resistance of the calcia clinker becomes poor.

In the first invention, first, 100 parts by weight of calcium carbonate having a particle size of less than 1 mm and 1 to 6 parts by weight, preferably 2 to 5 parts by weight of alumina powder are used in a usual powder mixer. And mix as uniformly as possible to prepare a mixture of the two. If the proportion of the alumina powder is less than the above range, the digestion resistance of the calcia clinker becomes poor, and if it is more than the above range, the refining action of the calcia clinker becomes small.

The above mixture is then compression granulated to produce granules, preferably having a particle size of 2-5 mm. This compression granulation can be performed using a device such as a briquetting roll, a compression roll, and a tableting machine. The shape of the obtained granular material is not particularly limited, for example,
The shape may be spherical, spheroidal, cylindrical, prismatic, or the like. With this granulation operation, the compressive strength is 0.5 kg.
It is desirable to produce granules that are / grain or more. In this specification, the compressive strength is JIS
The values measured for a granulated product having a particle size of 2 mm in accordance with M8718 “Iron and steel stone (pellet) compressive strength measurement method” are shown.

Next, the granular material obtained as described above is calcined at a temperature of 1400 to 1700 ° C. to oxidize calcium carbonate to produce a calcia clinker. When the firing temperature is lower than the above range, the digestion resistance of the calcia clinker is poor, and it is desirable to increase the firing temperature from the viewpoint of the digestion resistance of the calcia clinker, but it is not too high in terms of thermal economy and firing equipment. Is desirable. The calcination needs to be carried out until the calcium carbonate is substantially entirely converted to calcia, and the calcination time is generally 5 to 30 hours, although it varies depending on the calcination temperature. By firing,
The apparent volume of compressed granules of the above mixture is 30 to 60%.
The degree is reduced. This firing operation can be performed using a normal rotary kiln, tunnel furnace, gas furnace, electric furnace, or the like.

The calcia clinker produced in this manner has excellent digestion resistance and should be used as it is or after being crushed into particles of an appropriate size to be used as a raw material for refractories, particularly amorphous refractories. You can The calcia clinker produced by the first invention has alumina dispersed almost uniformly throughout the particles, and like the calcia clinker described in JP-A-59-213668, the surface of the particles of calcia is The surface layer of alumina is not formed. Nevertheless, as shown in the examples, the calcia clinker produced by the first invention exhibits excellent digestion resistance when the mixture of calcium carbonate and alumina in the form of fine particles is calcined. It is thought that this is because calcia has undergone a large amount of growth, and calcia has undergone some modification by alumina.

The digestion-resistant calcia clinker produced by the first invention can be used as an amorphous refractory used by mixing it with water, if necessary, together with other substances. Further, the digestion-resistant calcia clinker produced by the first invention has a uniform dispersion of alumina, and the particles of calcia do not have a core-shell structure covered with a layer of alumina. It can be advantageously used for applications in fields in which not only the property but also the chemical reactivity is utilized.

Next, the method for producing the digestive-resistant calcia refractory material of the present invention (hereinafter sometimes referred to as the second invention) will be described.

The second invention is a digestion resistant calcia clinker, magnesia cement, obtained by the above first invention,
A method for producing a calcia refractory by pouring a fluid mixture containing water and water into a mold, drying the mixture, and then firing it at a temperature of 400 to 800 ° C.

In the second invention, the digestive resistant calcia clinker preferably has a particle size of 1 to 10 mm. Further, as the magnesia cement, a normal magnesia cement can be used. The magnesia cement acts as a binder for calcia clinker, and is preferably used in an amount of 10 to 50 parts by weight, particularly 15 to 30 parts by weight, based on 100 parts by weight of the above-mentioned calcia clinker. The amount of water used may be such that the mixture of digestion-resistant calcia clinker, magnesia cement, and water has sufficient fluidity to be poured into the mold, and generally digestion-resistant calcia. It is 30 to 100 parts by weight based on 100 parts by weight of the total of clinker and magnesia cement.

In the second invention, a predetermined amount of the above-mentioned digestion resistant calcia clinker, magnesia cement and water are added,
Prepare a flowable mixture by mixing using a suitable mixer. At this time, since calcia clinker has digestion resistance, it does not change to calcium hydroxide by digestion.

Next, the flowable mixture is poured into a mold prepared according to the shape of the desired refractory and then dried at a temperature of generally room temperature to 100 ° C, preferably 80 to 100 ° C. This mold is not particularly limited as long as it is a mold used for molding an amorphous refractory, and can be made of, for example, a wooden frame or a metal frame. This drying is carried out until the mixture of the digestion-resistant calcia clinker and magnesia cement can maintain the shape of the mold even after the mold is removed.

Then, the obtained dried molded product is 400 to 8
The calcia refractory is manufactured by firing at a temperature of 00 ° C, preferably 500 to 600 ° C. This calcination can be carried out by putting the dry-molded product obtained as described above in an appropriate calcination furnace. However, the dry-molded product can be burned directly or indirectly from outside the mold with a burner. It can also be fired with a flame such as. The time required for this firing is generally 0.
Five to two hours is sufficient. The obtained calcia refractory has excellent digestion resistance.

According to the second aspect of the invention, for example, a tundish cough as shown in FIGS. 1 and 2 can be provided.
That is, a wooden frame for forming the cough 6 is provided in the tundish 1, and a fluid mixture composed of the digestion-resistant calcia clinker, magnesia cement, and water produced by the first invention is poured and filled in the wooden frame. After that, leave it at room temperature or dry it by blowing hot air, remove the wooden frame, and then calcine the calcia refractory cough by firing the calcia molded product at a predetermined temperature with, for example, a gas burner. You can

The weirs of the calcia refractory produced as described above have the effect of digesting resistance and further refining the molten steel. That is, since the surface of the calcia particles in the cough calcia refractory is not covered with metal oxides, etc., the cough calcia reacts with the alumina in the molten steel entering the tundish to form a compound of 3CaO · Al ₂ O _3. By doing so, the molten steel is refined as described above.

[0030]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Calcium carbonate 1000 passed through a 100-mesh sieve obtained by pulverizing limestone
g and 20 g of alumina that has passed through a 100-mesh sieve were dry-blended using a high-speed stirring mixer, and the obtained powder mixture was compression-granulated using a briquetting roll to obtain a pressing strength ( Spherical granules having a sieved particle diameter of 2 mm (measured) of 0.2 kg / grain and an average particle diameter of 6 mm were produced.

Then, this granulated product was heated using an electric furnace.
A calcia clinker was produced by firing at 1400 ° C. for 10 hours.

[Example 2] Compression granulation was performed in the same manner as in Example 1 except that the amount of alumina was changed to 50 g, and the compressive strength was 0.2 kg / grain and the average particle diameter was 6 mm. A spherical granulate was produced.

Then, the granulated product was calcined at 1600 ° C. for 10 hours using a rotary kiln to produce a calcia clinker.

Example 3 300 g of calcia clinker obtained in Example 1, 90 g of magnesia cement and 200 g of water were mixed by stirring, and the resulting fluid mixture was used as a wooden frame mold of the internal method 20 × 20 × 80 mm. Pour into the inside, 100
The temperature was maintained at 8 ° C. for 8 hours to dry. After that, the wooden frame was removed to obtain a dry molded product of a mixture of calcia clinker and magnesia cement. It was observed that this molded body had neither whitening nor swelling and was not digested by calcia.

Then, the dry molded product was fired at about 600 ° C. for 1 hour using a burner to produce a calcia refractory. It was observed that this refractory material was neither bleached nor swelled and calcia was not digested.

[Example 4] 300 g of calcia clinker obtained in Example 2, 90 g of magnesia cement and 200 g of water were mixed with stirring, and the resulting fluid mixture was used as a wooden frame mold for an internal method of 20 x 20 x 80 mm. Pour into the inside, 100
It was kept at 24 ° C. for 24 hours and dried. After that, the wooden frame was removed to obtain a dry molded product of a mixture of calcia clinker and magnesia cement. It was observed that this molded body had neither whitening nor swelling and was not digested by calcia.

Next, this dry molded product was fired at about 600 ° C. for 1 hour using a burner to produce a calcia refractory. It was observed that this refractory material was neither bleached nor swelled and calcia was not digested.

Comparative Example 1 The calcium carbonate alone used in Example 1 was compression granulated in the same manner as in Example 1, the compressive strength was 0.2 kg / grain, and the average particle diameter was 6.
mm spherical granules were produced, and then the granules were calcined at 1800 ° C. for 2 hours using a tunnel furnace to produce calcia clinker.

300 g of the obtained calcia clinker, 90 g of magnesia cement and 200 g of water were mixed with stirring,
The obtained fluid mixture was poured into a wooden frame mold of an internal method of 20 × 20 × 80 mm, dried at 100 ° C. for 24 hours. After that, when the wooden frame was removed, the molded product was swollen and collapsed, and the shape could not be maintained.

[0041]

INDUSTRIAL APPLICABILITY The method for producing calcia clinker of the present invention has an effect that a calcia clinker excellent in digestion resistance can be produced, and
The method for producing a digestion-resistant calcia refractory material of the present invention has the effect of producing a calcia refractory material having excellent digestion resistance from the above-mentioned digestion-resistant calcia clinker and having a refining action on molten steel. Is.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an example of a tundish.

FIG. 2 is a sectional view taken along the line AA of FIG.

[Explanation of symbols]

 1 Tundish 2 Wall surface 3 Bottom surface 4 Refractory brick 5 Tundish nozzle 6 Cough

Claims (2)

[Claims] 1. A mixture of 100 parts by weight of calcium carbonate having a particle size of less than 1 mm and 1 to 6 parts by weight of alumina powder is compression-granulated, and the obtained granules are 1400 to 1700.
A method for producing a digestion-resistant calcia clinker, which comprises calcination at a temperature of ° C. 2. A mixture of 100 parts by weight of calcium carbonate having a particle size of less than 1 mm and 1 to 6 parts by weight of alumina powder is compression granulated, and the obtained granules are 1400 to 1700.
A flowable mixture of digestion-resistant calcia clinker, magnesia cement, and water obtained by firing at a temperature of ℃ was poured into a mold and dried, and then 400 to 800 ℃
A method for producing a digestive-resistant calcia refractory, which comprises firing at a temperature of.