JPH0459677A - Production of porous refractory material for gas blowing - Google Patents

Abstract

PURPOSE:To obtain a refractory material having excellent resistance to spalling without reducing air permeability by forming a mixture of spherical granules of aluminum titanate derived from burning of mixed powder of alumina and titanium dioxide in a specific ratio and burning. CONSTITUTION:Alumina is mixed with titanium dioxide in a molar ratio of TiO2/Al3O3=0.1-4.0 and resultant mixed powder is spherically granulated, then burned to obtain spherical granules of aluminum titanate, thus a mixture containing said granules as a principal component is formed and burned to afford the aimed refractory material. Said refractory material has sufficient air permeability required to a refractory material for gas blowing and also exhibits excellent resistance to spalling against a large temperature difference exposed in gas blowing. Therefore, said porous refractory material for gas blowing exhibits functions such as stirring of molten steel by gas blowing or clogging inhibition of nozzle corresponding to the use without fear of a serious accident such as run-out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a porous refractory for gas blowing.

[Prior art] A porous plug (for example, JP-A-49-97705) that blows an inert gas into molten metal for the purpose of temperature adjustment, homogenization of components, removal of non-metallic inclusions, etc., or molten steel. A porous commercial product that prevents nozzle clogging by blowing an inert gas into the inner hole of a casting nozzle (for example, Japanese Utility Model Publication No. 54-34342, Japanese Utility Model Application Publication No. 5-1283)
Alumina refractories (e.g., JP-A-50-45810) are used as porous refractories for gas injection, which are used in JP-A No. 17, JP-A-56-148453, etc.
, magnesia refractories, and spinel refractories (for example, JP-A-50-45810) are known.

[Problems to be Solved by the Invention] Alumina refractories are generally known as materials with excellent corrosion resistance and spalling resistance. However, gas-blown refractories in which a significant temperature difference occurs between the refractory and the molten steel contact surface due to the cooling effect of the inert gas do not have sufficient spalling resistance. Moreover, if cracks occur due to spalling, gas permeability decreases due to the intrusion of molten steel, and the function as a refractory for slag injection is lost.

On the other hand, basic materials such as magnesia refractories and spinel refractories have excellent corrosion resistance, or are even worse in terms of spalling resistance than alumina refractories.

It is known that spalling resistance can be improved by adding silica raw materials with a low coefficient of thermal expansion, such as fused silica, or carbon powder, which has the effect of absorbing thermal expansion, to the above conventional materials. There is. However, when the amount of silica raw material added is increased, there is a problem that corrosion resistance and air permeability are reduced due to the formation of low melting point substances. In addition, carbon powder has the effect of clogging the pores of the refractory structure and inhibits the gas blowing function.

An object of the present invention is to provide a porous refractory for gas blowing that has excellent durability against poling without reducing air permeability.

[Means for Solving the Problems] The present invention provides a method for solving the problems by converting alumina and titanium dioxide into a molar ratio of T.
iO□/A cross, 0. A porous refractory for dregs injection, which is made by granulating a mixed powder of 0.1 to 4.0 into a spherical shape and firing it, forming a compound mainly composed of aluminum titanate spherical particles, and firing it. This is the manufacturing method.

The present invention will be explained in more detail below.

Aluminum titanate spherical particles are obtained by mixing alumina and titanium dioxide in a specific ratio, forming them into a spherical shape, and then firing them. Acts as a buffer. The porous refractory for gas blowing according to the present invention is
The above action of the aluminum titanate spherical particles suppresses rapid expansion and provides excellent spalling resistance. In addition, aluminum titanate grains produce less melting point substances and are spherical.
The fine cracks within the particles act as air passages, providing sufficient air permeability necessary for a refractory for slag injection.

Titanium dioxide used in the production of aluminum titanate spherical particles is produced, for example, by refining, firing, and pulverizing ilmenite. The average particle size is preferably 50 μm or less. Due to its properties such as hiding power, coloring power, and insolubility, titanium dioxide has traditionally been used as a filler in paints, inks, paper, and plastics, as well as in porcelain raw materials, abrasives, pharmaceuticals, cosmetics, etc., and is available from commercially available products. We'll also have some manpower. Titanium dioxide is known to have rutile type and anatase type depending on its form, but either form can be used in the present invention.

The alumina to be combined with titanium monoxide is, for example, sintered alumina, fused alumina finely pulverized to an average particle size of 5 μm or less, or light-sintered alumina powder obtained by light-sintering aluminum hydroxide obtained by the Bayer process. is used.

The ratio of the above combination of titanium dioxide and alumina is such that TiO□/AUz03 is 0.1 to 4.0 in terms of molar ratio. If the molar ratio is less than 0.1, the amount of aluminum titanate produced is small due to a lack of TlO2, and the effect of improving spalling resistance is poor. If the molar ratio exceeds 4.0, unreacted T
The amount of iO2 increases, and TiO2 increases in contact with molten metal.
2 produces a slag component, which reacts with Cab, 5in2, etc. to produce a low-melting substance, resulting in a decrease in corrosion resistance.

In the mixed powder for producing aluminum titanate spherical particles, the total proportion of titanium dioxide and alumina is 70 wt% or more. If the amount is less than 7% by weight, the amount of aluminum titanate produced will be small, and the above-mentioned effects of aluminum titanate spherical particles cannot be obtained. When combining other than alumina and titanium dioxide as a mixed powder, for example, zircon, zirconia, magnesia, MgO
-One or more selected from Al2O3 spinel and chromium oxide. The average particle size is preferably 50
It is used as a fine powder of less than μm.

The aluminum titanate spherical particles are formed by adding an appropriate amount of a binder and using any spheroidizing method such as a transfer method or a spray dryer method. Note that the spherical shape in this case may be anything that has no corners and a smooth surface and is considered to be spherical, and does not need to be completely spherical.

The binder used in this spheroidization can be a common inorganic or organic binder known as a binder for refractories.

Firing is performed using any device such as an air flow furnace, rotary kiln, or tunnel kiln, for example, at a temperature of 1300 to 1800°C.
Perform the test at a temperature of Fine cracks in the grain boundaries of aluminum titanate particles are generated during the firing and cooling process in this firing process. The average particle size of the spherical particles after firing is, for example, 0.1 to 2 mm in order to provide the gas blowing refractory with the necessary air permeability.

The present invention is a method for producing a porous refractory for gas injection using the aluminum titanate spherical particles obtained as described above.

Table 1 shows the compositions used in the production of various aluminum titanate spherical particles. All of the spherical particles shown in the same table from ■ to 0 are coated with 7wt% of calcium polyalkylarylsulfonate as a binder.
After adding and kneading, the mixture was spheroidized by the transfer method. Firing is 160
It was fired at a temperature of 0°C. The particle size after firing is 05-1.6
It was mm.

(1) to (2) and (2) to [phase] are spherical particles whose ratio of combination of titanium oxide and alumina is within the range defined by the present invention. In (1) and (2), the ratio of alumina and titanium dioxide (TiO□/AuzO3 in terms of molar ratio) is outside the range. ■ is,
This is an example in which the contents of alumina and titanium dioxide are too small.

Table 2 shows the results of preparing porous large-sized materials by blending the aluminum titanate spherical particles shown in Table 1, and testing the physical properties of the products. In Table 2, for the production of porous trade-resistant products, 5 wt% of calcium lignin sulfonate was added as a binder to the formulation shown in the table, and after kneading,
It was pressure-molded using a friction press and fired at 1600°C.

As shown in the test results in Table 2, refractories using aluminum titanate spherical particles within the range defined by the present invention have excellent spalling resistance and air permeability.

Although refractories using aluminum titanate spherical particles are effective in spalling resistance and forming an air-permeable structure, they have poor mechanical strength due to the presence of fine cracks in the aluminum titanate particles, and are less likely to interact with molten steel. Corrosion resistance tends to be poor at contact areas. Therefore, the proportion of aluminum titanate spherical particles should be 10 wt% or more, preferably 10 to 10 wt%.
90wt% or more, the balance being alumina, magnesia, M
1fi or 2 derived from gO-ALO3 spinel
By molding and firing a compound mainly composed of seeds or more, a porous refractory for gas injection with excellent corrosion resistance can be obtained.

In Table 2, phases ■~[phase] are porous refractories manufactured by combining aluminum titanate spherical particles with a proportion of 88 wt%, and the balance being a combination of alumina, magnesia, and MgO-Auto3 spinel.From the test results, ,
It is confirmed that it has excellent corrosion resistance.

The above-mentioned alumina, magnesia, MgO-A9. in combination with aluminum titanate spherical particles. The aOs-based spinel may be either a fired crystal or an electrified product. Further, the shape of these particles may be either pulverized or spherical.

In addition to the above, the present invention may also include silica powder, clay powder, chromium oxide powder, zirconia powder, Fe, 03 powder, Appropriate amounts of NiO powder, LjO powder, metal powder, etc. may be added.

In the present invention, the above-mentioned mixture is used, and then an inorganic or organic binder is applied to the mixture in a conventional manner.
Add about 5% by weight, knead, and then pressurize into an arbitrary shape. Firing is performed at a temperature of, for example, 1300 to 1800°C.

U implementation example Examples of the present invention and comparative examples thereof are shown in Table 3 below.

The aluminum cutic acid spherical particles in the same table are the first
The aluminum titanate spherical particles shown in the table were used.

In order to obtain a porous refractory structure, each side had a blending composition that contained fewer intermediate-diameter aggregate particles than a normal refractory. In addition, calcium lignin sulfonate is added as a binder to the molding process in a state dissolved in water, and after mixing,
Pressure was applied using a friction press. Firing at 1700℃
I went there in 6 hours.

The test method is as follows.

Spalling resistance...30 x 40 x 120
A test piece of mm in diameter was heated in an electric furnace for 30 minutes, then cooled in air, and this process was repeated to measure the number of times until cracking occurred.

Air permeability...Measurement using room temperature air.

Compressive strength: Measured according to JIS-R2206.

Corrosion resistance: Measured by a rotary erosion test using a steel piece as an eroding agent. After repeating 1650° C. for 30 minutes three times, the erosion loss size was measured and expressed as an index with the erosion loss size of Comparative Example 1 set as 100.

The lower the number, the more corrosion resistant Excellent in sex.

Actual machine test: A porous plug was manufactured, 300 was attached to a molten steel ladle, and the service life was measured. Items with blank data are unused.

[Effect] The porous refractory for dregs injection obtained by the present invention has sufficient air permeability necessary for a refractory for sludge injection, and also exhibits excellent spalling resistance against the significant temperature difference experienced during gas injection. . Therefore, when using this porous refractory for gas injection, there is no need to worry about major accidents such as leakage, and depending on the application,
It can fully perform functions such as stirring molten steel by blowing gas and preventing nozzle clogging.

[Effect 4 others

Claims (1)

[Claims] 1 TiO_ in terms of molar ratio of alumina and titanium dioxide
Porous for gas blowing, which is made by granulating a mixed powder in which 2/Al_2O_3 is 0.1 to 4.0 into a spherical shape and then firing it, forming a compound mainly made of aluminum titanate spherical particles and firing it. Method of manufacturing refractories. 2 TiO_ in terms of molar ratio of alumina and titanium dioxide
10 wt% or more of aluminum titanate spherical particles obtained by granulating a mixed powder in which 2/Al_2O_3 is combined in a range of 0.1 to 4.0 into a spherical shape and firing the mixture, the balance being selected from alumina, magnesia, and MgO-Al_2O_3 spinel. 1
A method for producing a porous refractory for gas blowing, which comprises molding and firing a mixture mainly consisting of seeds or two or more seeds. 3. According to claim 1 or 2, the mixed powder contains alumina and titanium dioxide in a total amount of 70 wt% or more, and the balance is one or more selected from zircon, zirconia, magnesia, MgO-Al_2O_3 spinel, and chromium oxide. A method for manufacturing porous refractories for gas injection.